2024-03-29T10:06:42Zhttps://www.repo.uni-hannover.de/oai/requestoai:www.repo.uni-hannover.de:123456789/562022-12-02T15:02:17Zcom_123456789_1col_123456789_3ddc:004ddc:550doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Integrated GNSS Attitude Determination and Positioning for Direct Geo-Referencing
Nadarajah, Nandakumaran
Paffenholz, Jens-André
Teunissen, Peter J.G.
global navigation satellite system
GNSS
attitude determination
multivariate constrained integer least-squares
MC-LAMBDA
carrier phase ambiguity resolution
direct geo-referencing
laser scanner
Globales Navigationssatellitensystem
GNSS
Lagebestimmung
Kleinste-Quadrate-Methode
MC-LAMBDA
Träger-Phasen-Mehrdeutigkeitsauflösung
Trägerphasen-Mehrdeutigkeitsauflösung
Mehrdeutigkeitsauflösung
Trägerphase
Direkte Georeferenzierung
Laserscanner
Positionsbestimmung
Direct geo-referencing is an efficient methodology for the fast acquisition of 3D spatial data. It requires the fusion of spatial data acquisition sensors with navigation sensors, such as Global Navigation Satellite System (GNSS) receivers. In this contribution, we consider an integrated GNSS navigation system to provide estimates of the position and attitude (orientation) of a 3D laser scanner. The proposed multi-sensor system (MSS) consists of multiple GNSS antennas rigidly mounted on the frame of a rotating laser scanner and a reference GNSS station with known coordinates. Precise GNSS navigation requires the resolution of the carrier phase ambiguities. The proposed method uses the multivariate constrained integer least-squares (MC-LAMBDA) method for the estimation of rotating frame ambiguities and attitude angles. MC-LAMBDA makes use of the known antenna geometry to strengthen the underlying attitude model and, hence, to enhance the reliability of rotating frame ambiguity resolution and attitude determination. The reliable estimation of rotating frame ambiguities is consequently utilized to enhance the relative positioning of the rotating frame with respect to the reference station. This integrated (array-aided) method improves ambiguity resolution, as well as positioning accuracy between the rotating frame and the reference station. Numerical analyses of GNSS data from a real-data campaign confirm the improved performance of the proposed method over the existing method. In particular, the integrated method yields reliable ambiguity resolution and reduces position standard deviation by a factor of about 0.8, matching the theoretical gain of √3/4 for two antennas on the rotating frame and a single antenna at the reference station.
2015-08-19T09:48:07Z
2015-08-19T09:48:07Z
2014-07-17
Article
Text
Nadarajah, Nandakumaran; Paffenholz, Jens-André; Teunissen, Peter J. G.: Integrated GNSS Attitude Determination and Positioning for Direct Geo-Referencing. In: Sensors 14 (2014), Nr. 7, S. 12715-12734. DOI: http://dx.doi.org/10.3390/s140712715
http://www.repo.uni-hannover.de/handle/123456789/56
http://dx.doi.org/10.15488/38
eng
1424-8220
http://dx.doi.org/10.3390/s140712715
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Basel : MDPI AG
oai:www.repo.uni-hannover.de:123456789/582022-12-02T15:04:50Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600ddc:500
Encapsulating Non-Human Primate Multipotent Stromal Cells in Alginate via High Voltage for Cell-Based Therapies and Cryopreservation
Gryshkov, Oleksandr
Pogozhykh, Denys
Hofmann, Nicola
Pogozhykh, Olena
Müller, Thomas
Glasmacher, Birgit
Cross-linking
Cryopreservation
Marmoset
Air flow
Cell staining
Amnion
Flow rate
Cell differentiation
Vernetzung
Kryokonservierung
Callithrix jacchus
Weißbüschelaffe
Marmosetten
Luftstrom
Zellfärbung
Amnion
Flussrate
Durchsatz
Alginate cell-based therapy requires further development focused on clinical application. To assess engraftment, risk of mutations and therapeutic benefit studies should be performed in an appropriate non-human primate model, such as the common marmoset (Callithrix jacchus). In this work we encapsulated amnion derived multipotent stromal cells (MSCs) from Callithrix jacchus in defined size alginate beads using a high voltage technique. Our results indicate that i) alginate-cell mixing procedure and cell concentration do not affect the diameter of alginate beads, ii) encapsulation of high cell numbers (up to 10×106 cells/ml) can be performed in alginate beads utilizing high voltage and iii) high voltage (15–30 kV) does not alter the viability, proliferation and differentiation capacity of MSCs post-encapsulation compared with alginate encapsulated cells produced by the traditional air-flow method. The consistent results were obtained over the period of 7 days of encapsulated MSCs culture and after cryopreservation utilizing a slow cooling procedure (1 K/min). The results of this work show that high voltage encapsulation can further be maximized to develop cell-based therapies with alginate beads in a non-human primate model towards human application.
2015-08-19T11:59:00Z
2015-08-19T11:59:00Z
2014-09-26
Article
Text
Gryshkov, Oleksandr; Pogozhykh, Denys; Hofmann, Nicola; Pogozhykh, Olena; Mueller, Thomas; Glasmacher, Birgit: Encapsulating Non-Human Primate Multipotent Stromal Cells in Alginate via High Voltage for Cell-Based Therapies and Cryopreservation. In: PLoS ONE 9 (2014), Nr. 9. DOI: http://dx.doi.org/10.1371/journal.pone.0107911
http://www.repo.uni-hannover.de/handle/123456789/58
http://dx.doi.org/10.15488/40
eng
http://dx.doi.org/10.1371/journal.pone.0107911.g001
http://dx.doi.org/10.1371/journal.pone.0107911.g002
http://dx.doi.org/10.1371/journal.pone.0107911.g003
http://dx.doi.org/10.1371/journal.pone.0107911.g004
http://dx.doi.org/10.1371/journal.pone.0107911.g005
http://dx.doi.org/10.1371/journal.pone.0107911.g006
http://dx.doi.org/10.1371/journal.pone.0107911.g007
http://dx.doi.org/10.1371/journal.pone.0107911.s001
http://dx.doi.org/10.1371/journal.pone.0107911.s002
1932-6203
http://dx.doi.org/10.1371/journal.pone.0107911
http://creativecommons.org/licenses/by/4.0/
CC BY 4.0 Unported
San Francisco : Public Library of Science
oai:www.repo.uni-hannover.de:123456789/682022-12-02T19:19:55Zcom_123456789_15col_123456789_16doc-type:Articlestatus-type:updatedVersiondoc-type:Textopen_accessddc:380ddc:600
Von der Usability zur Ertragssteigerung
Schneider, Irka
Probst, Gerhard
Öffentlicher Personennahverkehr
Kundenorientierung
Vertrieb
Automatisierung
grafische Benutzeroberfläche
Bedienoberflächen
local public transport
customer focus
distribution
automation
graphical user interface
Obwohl die Automatisierung des Vertriebs im ÖPNV durch Automaten und Abonnementsysteme und moderne Vertriebswege (Handy- und Online-Tickets) für viele Kunden bequeme Formen des Ticketserwerbs darstellen, gibt es zahlreiche Kundengruppen, für die diese neuen Vertriebskanäle ein großes Nutzungshindernis sind. Im Beitrag werden Wege aufgezeigt, wie die sogenannten Gebrauchstauglichkeit (engl. Usability) systematisch verbessert werden kann und dadurch automatisierte Vertriebskanäle zu aktiven Vertriebswegen entwickelt werden können. Erfahrungen dazu lassen sich aus einem Bereich der Wirtschaft übertragen, in dem Usability der zentrale Erfolgsfaktor ist, dem Internet. Damit der Kaufprozess erfolgreich abgeschlossen wird, reicht es nicht, die Kunden auf die Seite zu locken und ihnen die angebotenen Produkte näher zu bringen. Abbruchraten werden systematisch erhoben und ausgewertet. Bei Onlineshops liegen die Abbruchraten zwischen 27 und 66 %. Im ÖPNV gibt es dazu kaum Untersuchungsmaterial.
2015-10-07T16:21:49Z
2015-10-07T16:21:49Z
2011
Article
Text
Schneider, Irka; Probst, Gerhard: Von der Usability zur Ertragssteigerung. In: Nahverkehrspraxis (2011), Nr. 5, S. 30-31. ISSN: 0342-9849
http://www.repo.uni-hannover.de/handle/123456789/68
http://dx.doi.org/10.15488/50
ger
0342-9849
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden.
Dortmund : Arnold
oai:www.repo.uni-hannover.de:123456789/1212022-12-02T16:17:36Zcom_123456789_1col_123456789_6doc-type:Reportdoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Manufacturing and Characterization of Paper-Based Magnetic Coatings : Projects in Engineering and Science Summer 2015
Steggeman, Matthew
Akin, Meriem
Rissing, Lutz
Paper magnetics
Smart paper
Paper-based systems
Papier-basierte Systeme
Intelligentes Papier
Papierbasierte Systeme
Papierbasiertes System
Employing paper as an engineering material is emerging in industry today. Paper-based technology has grown in the last several years. Current technology includes, but is not limited to, foldable paper microscopes, a disk jockey board made from paper, and interactive wallpapers and newspapers. In terms of magnetic paper-based devices, these systems are limited to the use of hard magnetic materials for bitwise writing and reading, and actuating. At the Institute of Micro-Production Technology, embedding soft magnetic materials into the paper itself is being researched to enable a novel paper-based technology such as spintronic devices. This report will show the details of the ongoing research of the characteristics and properties of soft magnetic coatings on paper-based substrates.
2015-11-09T10:05:47Z
2015-11-09T10:05:47Z
2015-11-09
Report
Text
Steggeman, Matthew: Manufacturing and Characterization of Paper-Based Magnetic Coatings : Projects in Engineering and Science Summer 2015. Hannover : Institutionelles Repositorium der Leibniz Universität Hannover, 2015. 18 S. DOI: http://dx.doi.org/10.15488/103
http://www.repo.uni-hannover.de/handle/123456789/121
http://dx.doi.org/10.15488/103
eng
http://creativecommons.org/licenses/by-nc-nd/3.0/de/
CC BY-NC-ND 3.0 DE
Hannover : Institutionelles Repositorium der Leibniz Universität Hannover
oai:www.repo.uni-hannover.de:123456789/1962022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Different cell populations are inducible by BMP-2 covalently covered Bioverit® II implants in rabbit subcutis and middle ear
Kuhnert, E.
Ehlert, Nina
Behrens, Peter
Gross, G.
Lenarz, Thomas
Stieve, Martin
Brandes, Gudrun
TORP
biomaterial
healing
ossification
connective tissue
To optimize the function of implants the formation of surrounding connective tissue should be adapted in dependence to the mechanical conditions. Therefore, with nanostructured silica coated Bioverit® II implants were only partly reacted with recombinant BMP-2. The histology was compared 28, 84 and 301 days after implantation in the rabbit middle ear and subcutis, respectively. The whole tissue blocks were embedded in Epon, sequentially grinded, stained with Toluidine Blue O and Eosin G. The granulation tissue covering the implants varies related to cell types, cell amounts, extracellular matrix and vessels. Whereas the high cell density and the angiogenesis predominated in the subcutis, the formation of new bone could only be recognized in the scar around the implants in the middle ear.
2016-01-25T13:26:17Z
2016-01-25T13:26:17Z
2013-09-07
Article
Text
Kuhnert, E.; Ehlert, N.; Behrens, Peter; Gross, G.; Lenarz, T.; Stieve, M.; Brandes, G.: Different cell populations are inducible by BMP-2 covalently covered Bioverit® II implants in rabbit subcutis and middle ear. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4051
http://www.repo.uni-hannover.de/handle/123456789/196
http://dx.doi.org/10.15488/174
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4051
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin: Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2092022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Comparison between simulation results and DEXA investigation of the bone remodelling after implanting a cementless long stem hip prosthesis
Almohallami, Amer
Bouguecha, Anas
Stukenborg-Colsman, Christina
Lerch, M.
Nolte, I.
Behrens, Bernd-Arno
stress shielding
FEM
bone remodeling
DEXA
periprosthetic femur
Bone remodelling around a femoral prosthesis is one of the main reasons of aseptic loosening of the implant’s stem. The difference in stiffness between the bone tissue and the prosthesis leads to unload the periprosthetic bone and thus to decrease the bone mineral density (BMD), which is known as stress shielding. This paper represents a comparison between measured changes in (BMD) in a periprosthetic Femur with a cementless Bicontact stem by prospective dualenergy X-ray absorptiometry study (DEXA)and calculated changes of the (BMD) using a finite element method (FEM). As a result, it is determined that the total deviation between the two investigations is about 18%.
2016-02-02T12:03:12Z
2016-02-02T12:03:12Z
2013-09-07
Article
Text
Almohallami, A.; Bouguecha, A.; Stukenborg-Colsman, C.; Lerch, M.; Nolte, I.; Behrens, B.-A.: Comparison between simulation results and DEXA investigation of the bone remodelling after implanting a cementless long stem hip prosthesis. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1 . DOI: http://dx.doi.org/10.1515/bmt-2013-4075
http://www.repo.uni-hannover.de/handle/123456789/209
http://dx.doi.org/10.15488/187
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4075
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2112022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
FE-Simulation zur Lokalisierung hoch beanspruchter Bereiche in der Hüftpfanne von Endoprothesen
Behrens, Bernd-Arno
Helms, Gabriele
Poesse, Olaf
Nolte, Ingo
Meyer-Lindenberg, Andrea
Rittmann, Pia
Windhagen, Henning
Pressel, Thomas
FEA
hip prosthesis
load distribution
strain
wear
contact mechanics
joint replacements
force
Dehnung
FEM
Hüftendoprothese
Spannungsverteilung
Verschleiß
The implantation of a total hip prosthesis is an operation which is performed frequently due to advanced hip jointdamage both in humans and in veterinary medicine in dogs. The long-term result of a hip prosthesis is mainly determined by aseptic loosening of the prosthesis; among other causes, abrasion particles of the tribological pairing are responsible for the loosening. For the analysis of the surface stresses with different tribological pairings, a finite element model was generated which was based on the CAD data of a commercial total hip prosthesis. After transmission of a physiological force in the components of the three tribological pairings ceramic/polyethylene, ceramic/ceramic and metal/polyethylene, stresses were calculated. Stresses in the ceramic/ceramic tribological pairings were conspicuously higher than in the other material pairings. In the future adapted prostheses have to be developed that ensure optimal friction and absorption characteristics of the components.
Die Implantation einer Hüfttotalendoprothese ist ein operativer Eingriff, der in Deutschland häufig aufgrund eines fortgeschrittenen Hüftgelenkschadens sowohl beim Menschen als auch in der Veterinärmedizin beim Hund durchgeführt wird. Das Langzeitergebnis einer Hüfttotalendoprothese wird hauptsächlich durch die aseptische Lockerung der Prothese bestimmt; Abriebpartikel der Gleitpaarung sind für eine Lockerung mit verantwortlich. Zur Analyse der Oberflächenspannungen bei unterschiedlichen Gleitpaarungen wurde ein Finite-Element-Modell generiert, das auf den CAD-Daten einer handelsüblichen Hüfttotalendoprothese basiert. Nach Einleitung einer physiologischen Gelenkkraft wurden Spannungen in den Komponenten der drei Gleitpaarungen Keramik/Polyethylen, Keramik/Keramik und Metall/Polyethylen berechnet. Dabei zeigten sich bei der Gleitpaarung Keramik/Keramik deutlich höhere Spitzenspannungen als bei den beiden übrigen Gleitpaarungen. In weiteren Arbeiten sollen angepasste Prothesen entwickelt werden, die optimale Reib- und Dämpfungseigenschaften der Komponenten sicherstellen.
2016-02-02T12:03:12Z
2016-02-02T12:03:12Z
2006-12-07
Article
Text
Behrens, Bernd-Arno; Helms, Gabriele; Poesse, Olaf; Nolte, Ingo; Meyer-Lindenberg, Andrea; Rittmann, Pia; Windhagen, Henning; Pressel, Thomas: FE-Simulation zur Lokalisierung hoch beanspruchter Bereiche in der Hüftpfanne von Endoprothesen : FE-analysis of surface stresses for the tribological system in total hip prostheses. In: Biomedical Engineering / Biomedizinische Technik 51 (2006) Nr. 5-6, S. 367-370. DOI: http://dx.doi.org/10.1515/BMT.2006.071
http://www.repo.uni-hannover.de/handle/123456789/211
http://dx.doi.org/10.15488/189
ger
Biomedical Engineering / Biomedizinische Technik 51 (2006), Nr. 5-6
1862-278X
0013-5585
http://dx.doi.org/10.1515/BMT.2006.071
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2122022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Patient-individual hip cups: simulation-based design and sheet metal forming manufacturing
Betancur Escobar, S.
Bouguecha, Anas
Almohallami, Amer
Niemeier, H.
Nolte, I.
Lucas, K.
Stukenborg-Colsman, Christina
Lerch, M.
Behrens, Bernd-Arno
Patient-individual hip cups
bone remodelling
reverse engineering
process planning
sheet metal forming
The revision of an hip prosthesis can have different reasons. One frequent cause, especialley after implantation of a conventional cup, is the so called stress-shielding effect which can lead to a migration or loosening. Patientspecific hip cups can be used to counteract this. However, individual hip cups are only implanted for the treatment of great deformations or tumours because of the cost-intensive manufacturing. Within this project a patient-specific hip cup prosthesis has to be developed and manufactured. Besides the numerical design by means of a coupling between multi-body simulation (MBS) and finite element method (FEM), an inovative concept for the production of patientindividual hip prosthesis out of titanium sheets is introduced in this study.
2016-02-02T12:03:12Z
2016-02-02T12:03:12Z
2013-09-07
Article
Text
Betancur Escobar, S.; Bouguecha, A.; Almohallami, A.; Niemeier, H.; Nolte, I.; Lucas, K.; Stukenborg-Colsmann, C.; Lerch, M.; Behrens, B.-A.: Patient-individual hip cups: simulation-based design and sheet metal forming manufacturing. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4076
http://www.repo.uni-hannover.de/handle/123456789/212
http://dx.doi.org/10.15488/190
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4076
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2152022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Preparation and Analysis of PCL Spun Chitosan Scaffolds as Guidance Channels for Peripheral Nerve Regeneration
Behrens, Peter
Glasmacher, Birgit
Duda, Sven
Haastert-Talini, Kirsten
nerve guidance channel
oriented solidification
lyophilisation
chitosan
electrospinning of PCL
The results of this work show that the process of oriented solidification and lyophilisation is able to produce porous chitosan scaffolds with appropriate porosity and pore size for nerve regeneration. Interesting in this context are the results of statistical analysis of image analysis from SEM micrographs of uncrosslinked and UV cross-linked samples. The average pore size and mean minimum pore diameter show only small differences if the cooling rate is varied from B = 1…5 K / min and the temperature gradient from G = 1, 1.5, 2.0 K / mm. The average pore size (cross sectional area) of these samples can be estimated with reasonable accuracy, with 2100 μm². The average minimum pore diameter is within the range of 36-38 μm. These values are in a favourable range for the cell growth of nerve regeneration.
2016-02-02T12:03:13Z
2016-02-02T12:03:13Z
2013-09-07
Article
Text
Behrens, Peter; Glasmacher, Birgit; Duda, Sven; Haastert – Talini, Kirsten: Preparation and Analysis of PCL Spun Chitosan Scaffolds as Guidance Channels for Peripheral Nerve Regeneration. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4062
http://www.repo.uni-hannover.de/handle/123456789/215
http://dx.doi.org/10.15488/193
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4062
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2162022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Proof of Concept of a New Glucose Sensing Technology: Color-Changing Hydrogels Including au Nanoparticles
Esch, C.
Galperin, A.
Krolitzki, Benjamin
Glasmacher, Birgit
Shen, A.
Ratner, B.D.
Glucose sensor
Au nanoparticles
hydrogel synthesis
enzyme immobilization
porous scaffolds
This Master thesis provides a proof of concept for a novel, implantable continuous glucose sensing technology. Immobilized glucose oxidase in a poly 2-hydroxyethyl methacrylate hydrogel is used to enzymatically convert an increase in glucose level to a local decrease in pH, which leads to a swelling of the hydrogel. Encapsulated gold nanoparticles in the gel allow an optical readout of the glucose concentration. Experimental methods include hydrogel synthesis, nanoparticle encapsulation and finally glucose sensing with the hydrogel by UV-vis measurements. Two possible readouts, absorbance change and frequency shift, are discussed and tested. While a frequency shift is not detected, results show that the absorbance of the gel is proportional to glucose level, making it a promising concept for continuous glucose monitoring.
2016-02-02T12:03:13Z
2016-02-02T12:03:13Z
2013-09-07
Article
Text
Esch, C.; Galperin, A.; Krolitzki, B.; Glasmacher, Birgit; Shen, A.; Ratner, B. D.: Proof of Concept of a New Glucose Sensing Technology: Color-Changing Hydrogels Including au Nanoparticles. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4063
http://www.repo.uni-hannover.de/handle/123456789/216
http://dx.doi.org/10.15488/194
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4063
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2172022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Solving Biocompatibility Layer by Layer: Designing Scaffolds for Tissues
Zernetsch, Holger
Repanas, Alexandros
Gryshkov, Oleksandr
Al Halabi, Fedaa
Rittinghaus, Tim
Wienecke, Soenke
Müller, Marc
Glasmacher, Birgit
Functional tissue engineering
scaffold
ice templating
electrospinning
mimicking ECM
fibers
New opportunities for the design of artificial tissue structures via ice templating and electrospinning are described. Exemplarily, developments of vascular grafts, heart valves and nerve guides will be presented.
2016-02-02T12:03:13Z
2016-02-02T12:03:13Z
2013-09-07
Article
Text
Zernetsch, H.; Repanas, A.; Gryshkov, A.; Al Halabi, F.; Rittinghaus, T.; Wienecke, S.; Müller, M.; Glasmacher, Birgit: Solving Biocompatibility Layer by Layer: Designing Scaffolds for Tissues. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4065
http://www.repo.uni-hannover.de/handle/123456789/217
http://dx.doi.org/10.15488/195
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4065
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2182022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Magnesium as a biomaterial and its biological interactions
Evertz, F.
Hauser, Hansjörg
Müller, P.P.
Kietzmann, Manfred
Maier, Hans Jürgen
Glasmacher, Birgit
magnesium
degradation
implant
biomaterial
in vitro
To investigate different magnesium alloys as a biodegradable material for implants it is necessary to understand the degradation process in the biological environment. The following study shows interactions of pure magnesium with various physical and chemical environmental parameters according to the parameters within the application area.
2016-02-02T12:03:13Z
2016-02-02T12:03:13Z
2013-09-07
Article
Text
Evertz, F.; Hauser, H.; Müller, P. P.; Kietzmann, M.; Maier, H.J; Glasmacher, Birgit: Magnesium as a biomaterial and its biological interactions. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1 . DOI: http://dx.doi.org/10.1515/bmt-2013-4066
http://www.repo.uni-hannover.de/handle/123456789/218
http://dx.doi.org/10.15488/196
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4066
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2192022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Entwicklung von schichtweise ausgerichteten Faserverbundstrukturen
Rittinghaus, Tim
Zernetsch, Holger
Glasmacher, Birgit
Tissue Engineering
Herzklappenscaffold
ausgerichtete Fasern
Schichtstruktur
Gapspinning
Jedes Jahr müssen tausende defekte Herzklappen ersetzt werden. Die Verwendung von biologischen oder mechanischen Prothesen macht aufgrund der Tatsache, dass diese nicht mitwachsen, gerade bei Heranwachsenden regelmäßige Reimplantationen erforderlich. Eine mögliche Alternative sind Klappenprothesen bestehend aus einer Gerüststruktur, welche mit körpereigenen Zellen besiedelt wird. Das Gerüst wird im Laufe der Zeit vollständig durch lebendes Gewebe ersetzt. Ziel dieser Diplomarbeit ist die Herstellung von schichtweise ausgerichteten Faserverbundstrukturen, um zukünftig den aus mehreren Gewebeschichten bestehenden Aufbau der menschlichen Herzklappen nachahmen zu können und den Zellen so eine optimale Trägerstruktur bereit zu stellen.
2016-02-02T12:03:13Z
2016-02-02T12:03:13Z
2013-09-07
Article
Text
Rittinghaus, Tim; Zernetsch, Holger; Glasmacher, Birgit: Entwicklung von schichtweise ausgerichteten Faserverbundstrukturen. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4071
http://www.repo.uni-hannover.de/handle/123456789/219
http://dx.doi.org/10.15488/197
ger
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4071
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2202022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Dynamische In-Vitro-Studie zur Strömungsabhängigkeit der Degradationsrate von Magnesium
Quirico, M.
Evertz, F.
Glasmacher, Birgit
Entwicklung
Werkstoff
Implantat
Magnesium
Degradation
Magnesiumdegradation
Strömungsabhängigkeit
in-vitro
dynamisch
Zur Schaffung eines standardisierten Versuchsablaufs für Studien zur Magnesiumdegradation im Rahmen der Entwicklung eines biodegradablen Implantatwerkstoffs, wurde eine Steuerung für einen Prüfstand zur dynamischen in-vitro-Testung programmiert und deren Funktionsfähigkeit mit einer Testreihe bestätigt. Durch die Ergebnisse dieser Versuchsreihe konnte zudem die Strömungsabhängigkeit der Degradationsrate von Magnesium nachgewiesen werden.
2016-02-02T12:03:15Z
2016-02-02T12:03:15Z
2013-09-07
Article
Text
Quirico, M.; Evertz, F.; Glasmacher, Birgit: Dynamische In-Vitro-Studie zur Strömungsabhängigkeit der Degradationsrate von Magnesium. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4103
http://www.repo.uni-hannover.de/handle/123456789/220
http://dx.doi.org/10.15488/198
ger
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4103
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2212022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Antioxidantien als Strategie zur Optimierung der Kryokonservierung von Stammzellen für das Tissue Engineering
Smits, L.
Hofmann, Nicola
Glasmacher, Birgit
Kryokonservierung
Antioxidantien
Kryoadditiv
Stammzellen
α-Tocophero
L-Ascorbinsäure
Kontrolliertes Einfrieren in den Temperaturbereich zwischen – 80 °C und – 196 °C erlaubt es Zellen, bei gleichzeitigem Erhalt ihrer Vitalität nach dem Auftauprozess, langfristig zu lagern. Durch die Verwendung von Antioxidantien sollte in der vorliegenden Arbeit eine Steigerung der Rekultivierbarkeit von mesenchymalen Stammzellen nach der Kryokonservierung erzielt werden. Der Zusatz von 100 μM α–Tocopherol steigerte die Rekultivierungseffzienz der Stammzellen um 117,5 % gegenüber der Kontrolle ohne Antioxidans. Darüber hinaus konnte gezeigt werden, dass eine Reduzierung der DMSO-Konzentration möglich ist, da Versuche mit 200 μM α–Tocopherol und 2,5 % bzw. 5 % DMSO vergleichbare Resultate von ca. 164 % bzw. 170 % Rekultivierbarkeit erzielten.
2016-02-02T12:03:16Z
2016-02-02T12:03:16Z
2013-09-07
Article
Text
Smits, L.; Hofmann, N.; Glasmacher, Birgit: Antioxidantien als Strategie zur Optimierung der Kryokonservierung von Stammzellen für das Tissue Engineering. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1. DOI: http://dx.doi.org/10.1515/bmt-2013-4200
http://www.repo.uni-hannover.de/handle/123456789/221
http://dx.doi.org/10.15488/199
ger
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. S1
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4200
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2222022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Dynamic in vitro hemocompatibility testing – improving the signal to noise ratio
Müller, Marc
Krolitzki, Benjamin
Glasmacher, Birgit
biomaterial
biocompatibility
small vascular implants
hemocompatibility testing
CHANDLER-Loop system
Assigning the hemocompatibility of small vascular implants is one of the great challenges in biomedical engineering. Due to the fact, that there are no widely approved test setups1, we decided to developed a modified CHANDLER-Loop system for dynamic in vitro hemocompatibility tests. The setup allows simultaneous testing of about 30 tube rings with an inner diameter of 2,4 mm. Cardiovascular implants can be placed into these tube rings. After filling them with anticoagulated blood and closing them to loops, they were placed on a rotating disc. While the loop is rotating, the blood remains in the lower part of the loop. The relative movement between the foreign surface and the blood sample induces a blood flow without the need of mechanical pumping. A first test series with the new test setup had been conducted to achieve a highly hemocompatible tube material. The results were compared to hemocompatibility tests done by LEMM, mentioned in the ISO 10993-42,3. We could prove, that Tygon S50HL® and Polyurethane achieve similar hemocompatibility values. In addition, we did in vitro tests of bare metal stents. We recorded a difference in the index of thrombocytes of about 17 % between the loops with three stents and the control. During further experiments the difference decreases to 8 %, which might be due to adhesion processes. The ability to measure these processes demonstrates the high sensitivity and very low background activation of the test setup. This can be assured by the recorded index of hemolysis, which had been less than 0,8 % in all our experiments. By developing and improving our modified CHANDLER-Loop system, we were able to establish a dynamic in vitro test setup for the hemocompatibility testing of small vascular implants. Because of its extremely low background activation and a high variability, the system serves as a benchmark for upcoming test setups.
2016-02-02T12:03:16Z
2016-02-02T12:03:16Z
2012-08-27
Article
Text
Mueller, M.; Krolitzki, B.; Glasmacher, Birgit: Dynamic in vitro hemocompatibility testing – improving the signal to noise ratio. In: Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-D. DOI: http://dx.doi.org/10.1515/bmt-2012-4211
http://www.repo.uni-hannover.de/handle/123456789/222
http://dx.doi.org/10.15488/200
eng
Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-D
1862-278X
http://dx.doi.org/10.1515/bmt-2012-4211
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2232022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Optimization of a test setup for examining blood damage caused by high shear forces
Kortlepel, Rieke
Krolitzki, Benjamin
Müller, Marc
Glasmacher, Birgit
biomaterial
biocompatibility
blood pump
blood damage
human body
If blood pumps are applied in the human body or extracorporeal, blood damage can be caused by shear forces that act on the blood during the delivery. For an accelerated development of blood pumps with help of simulations there is a need for reliable limit values for shear forces. To determine these limit values a shear force test setup was built at the Institute for Multiphase Processes. In the context of the presented master thesis the former test setup peripheral devices were evaluated, possible blood damage mechanisms were considered, blood analysis in different experiments to identify the blood damage caused by different elements were made and peripheral devices were replaced. At the same time the shear chamber was constructional reengineered in a project thesis [1]. We were able to show, that in former works the blood damage caused by test setup peripheral devices had heterodyned the results. Finally the test setup was rebuilt with the results and a test was made. Two findings of the thesis are a reduction of about 60% of the number of components in the blood-conveying tube system and an application of a new fluid seal.
2016-02-02T12:03:16Z
2016-02-02T12:03:16Z
2012-08-27
Article
Text
Kortlepel, R.; Krolitzki, B.; Müller, M.; Glasmacher, Birgit: Optimization of a test setup for examining blood damage caused by high shear forces. In: Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-D. DOI: http://dx.doi.org/10.1515/bmt-2012-4362
http://www.repo.uni-hannover.de/handle/123456789/223
http://dx.doi.org/10.15488/201
eng
Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-D
1862-278X
http://dx.doi.org/10.1515/bmt-2012-4362
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2242022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
In situ optical coherence tomography of percutaneous implant-tissue interfaces in a murine model
Donner, Sabine
Müller, Oliver
Witte, Frank
Bartsch, Ivonne
Willbold, Elmar
Ripken, Tammo
Heisterkamp, Alexander
Rosenhahn, Bodo
Krüger, Alexander
in vivo
motion artifacts
refractive index
scanning scheme
segmentation
human skin
motion
oct
Novel surface coatings of percutaneous implants need to be tested in biocompatibility studies. The use of animal models for testing usually involves numerous lethal biopsies for the analysis of the implant-tissue interface. In this study, optical coherence tomography (OCT) was used to monitor the reaction of the skin to a percutaneous implant in an animal model of hairless but immunocompetent mice. In vivo optical biopsies with OCT were taken at days 7 and 21 after implantation and post mortem on the day of noticeable inflammation. A Fourier-domain OCT was programmed for spoke pattern scanning schemes centered at the implant midpoint to reduce motion artifacts during in vivo imaging. Image segmentation allowed the automatic detection and morphometric analysis of the skin contour and the subcutaneous implant anchor. On the basis of the segmentation, the overall refractive index of the tissue within one OCT data set was estimated as a free parameter of a fitting algorithm, which corrects for the curved distortion of the planar implant base in the OCT images. OCT in combination with the spoke scanning scheme and image processing provided time-resolved three-dimensional optical biopsies around the implants to assess tissue morphology.
2016-02-11T09:04:21Z
2016-02-11T09:04:21Z
2013-05-17
Article
Text
Donner, Sabine; Mueller, Oliver; Witte, Frank; Bartsch, Ivonne; Willbold, Elmar; Ripken, Tammo; Heisterkamp, Alexander; Rosenhahn, Bodo; Krueger, Alexander: In situ optical coherence tomography of percutaneous implant-tissue interfaces in a murine model. In: Biomedical Engineering-Biomedizinische Technik 58 (2013), Nr. 4, S. 359-367. DOI: http://dx.doi.org/10.1515/bmt-2012-0044
http://www.repo.uni-hannover.de/handle/123456789/224
http://dx.doi.org/10.15488/202
eng
Biomedical Engineering-Biomedizinische Technik 58 (2013), Nr. 4
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2012-0044
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2342022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Online measurement and evaluation of the Er:YAG laser ablation process using an integrated OCT system
Fuchs, Alexander
Schultz, M.
Krüger, A.
Kundrat, Dennis
Díaz Díaz, Jesus
Ortmaier, Tobias
laser surgery
oct
Laser surgery has gained clinical importance due to numerous advantages including contact-free processing, arbitrary cutting geometries, and high precision. However, online process control remains a challenge for widespread clinical use. Therefore, we established a combined setup of a pulsed Er:YAG laser ( = 2940 nm) and an optical coherence tomogra-phy (OCT) ( = 930 nm) for in situ monitoring of hard tissue ablation. The optical setup facilitates an interactive control of the laser ablation depth and remaining tissue strength through the depth resolution of OCT. The 3D OCT data-set, which is acquired after ablation, provides contours and layer thicknesses.
2016-02-11T09:04:23Z
2016-02-11T09:04:23Z
2012-08-31
Article
Text
Fuchs, A.; Schultz, M.; Krüger, A.; Kundrat, D.; Díaz Díaz, J.; Ortmaier, T.: Online measurement and evaluation of the Er:YAG laser ablation process using an integrated OCT system. In: Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-H, S. 434-437. DOI: http://dx.doi.org/10.1515/bmt-2012-4231
http://www.repo.uni-hannover.de/handle/123456789/234
http://dx.doi.org/10.15488/212
eng
Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-H
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2012-4231
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2352022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Force measurement at the insertion process of cochlear implant electrodes
Majdani, Omid
Kobler, Jan-Philipp
Beckmann, Daniel
Ortmaier, Tobias
Lenarz, Thomas
Rau, Thomas S.
implant electrodes
cochlear implant
cochlea
inner ear
Several research groups have reported studies on the insertion force measurement at different cochlear implant electrodes. So far, all experimental setups to measure the forces applied to the electrode outside the cochlea (inner ear), ie have measured externally. Our aim was to integrate the sensors into an automatically operating instrument insertion, so that the forces can be measured, which act directly on the electrode, ie an internal force measurement.
2016-02-11T09:04:23Z
2016-02-11T09:04:23Z
2012-08-31
Article
Text
Majdani, Omid; Kobler, Jan-Phillipp; Beckmann, Daniel; Ortmaier, Tobias; Lenarz, Thomas; Rau, Thomas: Force measurement at the insertion process of cochlear implant electrodes. In: Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-H, S. 438-438. DOI: http://dx.doi.org/10.1515/bmt-2012-4484
http://www.repo.uni-hannover.de/handle/123456789/235
http://dx.doi.org/10.15488/213
eng
Biomedical Engineering / Biomedizinische Technik 57 (2012), Nr. SI-1 Track-H
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2012-4484
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2672022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Influence of Heat Treatment on the Degradation Behaviour of Degradable Magnesium Based Implants
Bracht, Katja
Angrisani, Nina
Seitz, J.
Besdo, S.
Reifenrath, Janin
in vitro
in vivo
heat treatment
degradable
magnesium implant
Aim of the study was to characterise the influence of heat treatment on the degradation behaviour and stability of degradable magnesium based implants. For this purpose two groups (untreated/ heat treated) of LAE442 pins were separately analysed in an in vitro and in vivo study. The corrosion behaviour was evaluated during 8 weeks degradation in SBF (in vitro) and 48 weeks degradation intramedullary in the rabbit tibia (in vivo). The analyses were made by using μ-computed tomography and three-point-bending tests. Heat treatment led to altered mechanical and corrosion properties of LAE442.While the initial stability declined significantly a reduction of the degradation rate over either in vitro and in vivo evaluation period is determined. If these alterations are still reasonable for osteosynthesis implants remains to be investigated in further projects.
2016-03-04T11:42:41Z
2016-03-04T11:42:41Z
2013-08
Article
Text
Bracht, K.; Angrisani, N.; Seitz, J.; Besdo, S.; Reifenrath, J.: Influence of Heat Treatment on the Degradation Behaviour of Degradable Magnesium Based Implants. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. Sl-1 Track C. DOI: http://dx.doi.org/10.1515/bmt-2013-4057
http://www.repo.uni-hannover.de/handle/123456789/267
http://dx.doi.org/10.15488/245
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. Sl-1 Track C
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4057
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2682022-12-13T15:12:26Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Finite element study of the accommodation behaviour of the crystalline lens after fs-laser treatment
Besdo, S.
Wiegand, J.
Hahn, J.
Ripken, Tammo
Krüger, A.
Fromm, M.
Lubatschowski, H.
crystalline lens
fs-Laser
lentotomiy
presbyopia
With aging the ability of the crystalline lens to adapt to different viewing distances decreases. Until now there is no satisfying treatment available. It is possible to influence the deformability of the crystalline lens by inducing cuts using femtosecond (fs)-laser. To test the influence of several different cutting geometries is expensive and a huge amount of crystalline lenses is needed. Finit Element Method offers the possibility to test the influence of different cutting geometries on the flexibility. Therefore, it is necessary to develop a method to simulate the cuts in an adequate way. In first simulations cuts were assumed to be isotropic inter layers. Later on, effective material properties for the inter layer were calculated with a homogenization technique. The results confirm the influence of the cuts on the flexibility.
2016-03-04T11:42:41Z
2016-03-04T11:42:41Z
2013-08
Article
Text
Besdo, S.; Wiegand, J.; Hahn, J.; Ripken, T.; Krüger, A.; Fromm, M.; Lubatschowski, H.: Finite element study of the accommodation behaviour of the crystalline lens after fs-laser treatment. In: Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. Sl-1 Track N . DOI: http://dx.doi.org/10.1515/bmt-2013-4337
http://www.repo.uni-hannover.de/handle/123456789/268
http://dx.doi.org/10.15488/246
eng
Biomedical Engineering / Biomedizinische Technik 58 (2013), Nr. Sl-1 Track N
1862-278X
0013-5585
http://dx.doi.org/10.1515/bmt-2013-4337
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Berlin : Walter de Gruyter
oai:www.repo.uni-hannover.de:123456789/2922022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Participatory Patterns in an International Air Quality Monitoring Initiative
Sirbu, Alina
Becker, Martin
Caminiti, Saverio
De Baets, Bernard
Elen, Bart
Francis, Louise
Gravino, Pietro
Hotho, Andreas
Ingarra, Stefano
Loreto, Vittorio
Molino, Andrea
Müller, Jürgen
Peters, Jan
Ricchiuti, Ferdinando
Saracino, Fabio
Servedio, Vito D.P.
Stumme, Gerd
Theunis, Jan
Tria, Francesca
Van den Bossche, Joris
transport microenvironments
exposure
pollution
carbon
The issue of sustainability is at the top of the political and societal agenda, being considered of extreme importance and urgency. Human individual action impacts the environment both locally (e.g., local air/water quality, noise disturbance) and globally (e.g., climate change, resource use). Urban environments represent a crucial example, with an increasing realization that the most effective way of producing a change is involving the citizens themselves in monitoring campaigns (a citizen science bottom-up approach). This is possible by developing novel technologies and IT infrastructures enabling large citizen participation. Here, in the wider framework of one of the first such projects, we show results from an international competition where citizens were involved in mobile air pollution monitoring using low cost sensing devices, combined with a web-based game to monitor perceived levels of pollution. Measures of shift in perceptions over the course of the campaign are provided, together with insights into participatory patterns emerging from this study. Interesting effects related to inertia and to direct involvement in measurement activities rather than indirect information exposure are also highlighted, indicating that direct involvement can enhance learning and environmental awareness. In the future, this could result in better adoption of policies towards decreasing pollution.
2016-06-13T14:30:39Z
2016-06-13T14:30:39Z
2015-08-27
Article
Text
Sirbu, Alina; Becker, Martin; Caminiti, Saverio; De Baets, Bernard; Elen, Bart; Francis, Louise; Gravino, Pietro; Hotho, Andreas; Ingarra, Stefano; Loreto, Vittorio; Molino, Andrea; Mueller, Juergen; Peters, Jan; Ricchiuti, Ferdinando; Saracino, Fabio; Se: Participatory Patterns in an International Air Quality Monitoring Initiative. In: PloS ONE 10 (2015), Nr. 8, e0136763. DOI: http://dx.doi.org/10.1371/journal.pone.0136763
http://www.repo.uni-hannover.de/handle/123456789/292
http://dx.doi.org/10.15488/270
eng
PLoS ONE 10 (2015), Nr. 8
1932-6203
http://dx.doi.org/10.1371/journal.pone.0136763
http://creativecommons.org/licenses/by/4.0/
CC BY 4.0 Unported
San Francisco : Public Library Science
oai:www.repo.uni-hannover.de:123456789/3212022-12-02T15:17:13Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Tile-Based Two-Dimensional Phase Unwrapping for Digital Holography Using a Modular Framework
Antonopoulos, Georgios C.
Steltner, Benjamin
Heisterkamp, Alexander
Ripken, Tammo
Meyer, Heiko
Zhang, Heye
algorithms
holography
polynomial
Gaussian noise
linear algebra
physical mapping
magnetic resonance imaging
machine learning algorithms
A variety of physical and biomedical imaging techniques, such as digital holography, interferometric synthetic aperture radar (InSAR), or magnetic resonance imaging (MRI) enable measurement of the phase of a physical quantity additionally to its amplitude. However, the phase can commonly only be measured modulo 2π, as a so called wrapped phase map. Phase unwrapping is the process of obtaining the underlying physical phase map from the wrapped phase. Tile-based phase unwrapping algorithms operate by first tessellating the phase map, then unwrapping individual tiles, and finally merging them to a continuous phase map. They can be implemented computationally efficiently and are robust to noise. However, they are prone to failure in the presence of phase residues or erroneous unwraps of single tiles. We tried to overcome these shortcomings by creating novel tile unwrapping and merging algorithms as well as creating a framework that allows to combine them in modular fashion. To increase the robustness of the tile unwrapping step, we implemented a model-based algorithm that makes efficient use of linear algebra to unwrap individual tiles. Furthermore, we adapted an established pixel-based unwrapping algorithm to create a quality guided tile merger. These original algorithms as well as previously existing ones were implemented in a modular phase unwrapping C++ framework. By examining different combinations of unwrapping and merging algorithms we compared our method to existing approaches. We could show that the appropriate choice of unwrapping and merging algorithms can significantly improve the unwrapped result in the presence of phase residues and noise. Beyond that, our modular framework allows for efficient design and test of new tile-based phase unwrapping algorithms. The software developed in this study is freely available.
2016-06-13T15:14:01Z
2016-06-13T15:14:01Z
2015
Article
Text
Antonopoulos, Georgios C.; Steltner, Benjamin; Heisterkamp, Alexander; Ripken, Tammo; Meyer, Heiko; Zhang, Heye: Tile-Based Two-Dimensional Phase Unwrapping for Digital Holography Using a Modular Framework. In: PloS ONE 10 (2015), Nr. 11, e0143186. DOI: http://dx.doi.org/10.1371/journal.pone.0143186
http://www.repo.uni-hannover.de/handle/123456789/321
http://dx.doi.org/10.15488/299
eng
PLoS ONE 10 (2015), Nr. 11
1932-6204
http://dx.doi.org/10.1371/journal.pone.0143186
http://creativecommons.org/licenses/by/4.0/
CC BY 4.0 Unported
San Francisco : Public Library Science
oai:www.repo.uni-hannover.de:123456789/4842022-12-02T15:04:49Zcom_123456789_1col_123456789_4ddc:004doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Probabilistic Evaluation of Three-Dimensional Reconstructions from X-Ray Images Spanning a Limited Angle
Frost, Anja
Renners, Eike
Hötter, Michael
Ostermann, Jörn
x-ray
computed tomography
discrete tomography
three-dimensional image reconstruction
limited data
dempster-shafer theory
data fusion
probability calculus
discrete tomography
algorithms
An important part of computed tomography is the calculation of a three-dimensional reconstruction of an object from series of X-ray images. Unfortunately, some applications do not provide sufficient X-ray images. Then, the reconstructed objects no longer truly represent the original. Inside of the volumes, the accuracy seems to vary unpredictably. In this paper, we introduce a novel method to evaluate any reconstruction, voxel by voxel. The evaluation is based on a sophisticated probabilistic handling of the measured X-rays, as well as the inclusion of a priori knowledge about the materials that the object receiving the X-ray examination consists of. For each voxel, the proposed method outputs a numerical value that represents the probability of existence of a predefined material at the position of the voxel while doing X-ray. Such a probabilistic quality measure was lacking so far. In our experiment, false reconstructed areas get detected by their low probability. In exact reconstructed areas, a high probability predominates. Receiver Operating Characteristics not only confirm the reliability of our quality measure but also demonstrate that existing methods are less suitable for evaluating a reconstruction.
2016-08-30T10:20:22Z
2016-08-30T10:20:22Z
2013-01
Article
Text
Frost, Anja; Renners, Eike; Hoetter, Michael; Ostermann, Joern: Probabilistic Evaluation of Three-Dimensional Reconstructions from X-Ray Images Spanning a Limited Angle. In: Sensors 13 (2013), Nr. 1, S. 137-151. DOI: http://dx.doi.org/10.3390/s130100137
http://www.repo.uni-hannover.de/handle/123456789/484
http://dx.doi.org/10.15488/461
eng
Sensors 13 (2013), Nr. 1
1424-8220
http://dx.doi.org/10.3390/s130100137
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Basel : Mdpi Ag
oai:www.repo.uni-hannover.de:123456789/4932022-12-02T15:04:49Zcom_123456789_1col_123456789_4ddc:004doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Analysis of the "Sonar Hopf" Cochlea
Kern, Albert
Martignoli, Stefan
Mathis, Wolfgang
Steeb, Willi-Hans
Stoop, Ralph Lukas
Stoop, Ruedi
artificial cochlea
biomorphic
mathematical analysis
delayed feedback-control
systems
hearing
The "Sonar Hopf" cochlea is a recently much advertised engineering design of an auditory sensor. We analyze this approach based on a recent description by its inventors Hamilton, Tapson, Rapson, Jin, and van Schaik, in which they exhibit the "Sonar Hopf" model, its analysis and the corresponding hardware in detail. We identify problems in the theoretical formulation of the model and critically examine the claimed coherence between the described model, the measurements from the implemented hardware, and biological data.
2016-08-30T10:20:26Z
2016-08-30T10:20:26Z
2011-06
Article
Text
Kern, Albert; Martignoli, Stefan; Mathis, Wolfgang; Steeb, Willi-Hans; Stoop, Ralph Lukas; Stoop, Ruedi: Analysis of the "Sonar Hopf" Cochlea. In: Sensors 11 (2011), Nr. 6, S. 5808-5818. DOI: http://dx.doi.org/10.3390/s110605808
http://www.repo.uni-hannover.de/handle/123456789/493
http://dx.doi.org/10.15488/470
eng
Sensors 11 (2011), Nr. 6
1424-8220
http://dx.doi.org/10.3390/s110605808
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Basel : Mdpi Ag
oai:www.repo.uni-hannover.de:123456789/5092022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
A single theoretical framework for circular features processing in humans: orientation and direction of motion compared
Tzvetanov, Tzvetomir
vision
context
orientation
motion direction
psychophysics
misperception
center-surround
primary visual-cortex
contextual interactions
association field
tilt illusion
psychophysics
suppression
integration
mechanisms
repulsion
contrast
Common computational principles underlie processing of various visual features in the cortex. They are considered to create similar patterns of contextual modulations in behavioral studies for different features as orientation and direction of motion. Here, I studied the possibility that a single theoretical framework, implemented in different visual areas, of circular feature coding and processing could explain these similarities in observations. Stimuli were created that allowed direct comparison of the contextual effects on orientation and motion direction with two different psychophysical probes: changes in weak and strong signal perception. One unique simplified theoretical model of circular feature coding including only inhibitory interactions, and decoding through standard vector average, successfully predicted the similarities in the two domains, while different feature population characteristics explained well the differences in modulation on both experimental probes. These results demonstrate how a single computational principle underlies processing of various features across the cortices.
2016-09-01T09:05:33Z
2016-09-01T09:05:33Z
2012-05-22
Article
Text
Tzvetanov, Tzvetomir: A single theoretical framework for circular features processing in humans: orientation and direction of motion compared. In: Frontiers in Computational Neuroscience 6 (2012), 28. DOI: http://dx.doi.org/10.3389/fncom.2012.00028
http://www.repo.uni-hannover.de/handle/123456789/509
http://dx.doi.org/10.15488/485
eng
Frontiers in Computational Neuroscience 6 (2012)
1662-5188
http://dx.doi.org/10.3389/fncom.2012.00028
https://creativecommons.org/licenses/by-nc/3.0/
CC BY-NC 3.0 Unported
Lausanne : Frontiers Research Foundation
oai:www.repo.uni-hannover.de:123456789/5102022-12-02T15:03:42Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Erratum: A single theoretical framework for circular features processing in humans: orientation and direction of motion compared (vol 6, pg 28, 2012)
Tzvetanov, Tzvetomir
vision
context
orientation
motion direction
psychophysics
misperception
center-surround
primary visual-cortex
contextual interactions
association field
tilt illusion
psychophysics
suppression
integration
mechanisms
repulsion
contrast
Erratum to: A single theoretical framework for circular features processing in humans: orientation and direction of motion compared. In: Frontiers in computational neuroscience 6 (2012), 28
2016-09-01T09:05:34Z
2016-09-01T09:05:34Z
2013-04-04
Article
Text
Tzvetanov, Tzvetomir: Erratum: A single theoretical framework for circular features processing in humans: orientation and direction of motion compared (vol 6, pg 28, 2012). In: Frontiers in Computational Neuroscience 7 (2013), 28. DOI: http://dx.doi.org/10.3389/fncom.2013.00028
http://www.repo.uni-hannover.de/handle/123456789/510
http://dx.doi.org/10.15488/486
eng
Frontiers in Computational Neuroscience 7 (2013)
1662-5188
http://dx.doi.org/10.3389/fncom.2013.00028
Tzvetanov, Tzvetomir: A single theoretical framework for circular features processing in humans: orientation and direction of motion compared. In: Frontiers in Computational Neuroscience 6 (2012), 28. DOI: http://dx.doi.org/10.3389/fncom.2012.00028
https://creativecommons.org/licenses/by-nc/3.0/
CC BY-NC 3.0 Unported
Lausanne : Frontiers Research Foundation
oai:www.repo.uni-hannover.de:123456789/5722022-12-02T15:04:50Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:570ddc:600
A rolling-gliding wear simulator for the investigation of tribological material pairings for application in total knee arthroplasty
Richter, Berna I.
Ostermeier, Sven
Turger, Anke
Denkena, Berend
Hurschler, Christof
Knee joint
Knee joint replacement
Material wear
Motion cycle
Pin on disc
Plane geometry
Promising materials
Ring-on-disc
Rolling movement
Test results
Total knee arthroplasty
User intervention
Wear measurements
Wear rates
Wear simulators
Wear test
Cobalt
Joint prostheses
Joints (anatomy)
Materials testing
Polyethylenes
Surface roughness
Surgery
Thermoplastics
Ceramic materials
cobalt
polyethylene
article
biological model
ceramics
femur
instrumentation
knee arthroplasty
materials testing
methodology
motion
surface property
tibia
Arthroplasty, Replacement, Knee
Ceramics
Cobalt
Femur
Materials Testing
Models, Biological
Motion
Polyethylene
Surface Properties
Tibia
Background: Material wear testing is an important technique in the development and evaluation of materials for use in implant for total knee arthroplasty. Since a knee joint induces a complex rolling-gliding movement, standardised material wear testing devices such as Pin-on-Disc or Ring-on-Disc testers are suitable to only a limited extent because they generate pure gliding motion only.Methods: A rolling-gliding wear simulator was thus designed, constructed and implemented, which simulates and reproduces the rolling-gliding movement and loading of the knee joint on specimens of simplified geometry. The technical concept was to run a base-plate, representing the tibia plateau, against a pivoted cylindrical counter-body, representing one femur condyle under an axial load. A rolling movement occurs as a result of the friction and pure gliding is induced by limiting the rotation of the cylindrical counter-body. The set up also enables simplified specimens handling and removal for gravimetrical wear measurements. Long-term wear tests and gravimetrical wear measurements were carried out on the well known material pairings: cobalt chrome-polyethylene, ceramic-polyethylene and ceramic-ceramic, over three million motion cycles to allow material comparisons to be made.Results: The observed differences in wear rates between cobalt-chrome on polyethylene and ceramic on polyethylene pairings were similar to the differences of published data for existing material-pairings. Test results on ceramic-ceramic pairings of different frontal-plane geometry and surface roughness displayed low wear rates and no fracture failures.Conclusions: The presented set up is able to simulate the rolling-gliding movement of the knee joint, is easy to use, and requires a minimum of user intervention or monitoring. It is suitable for long-term testing, and therefore a useful tool for the investigation of new and promising materials which are of interest for application in knee joint replacement implants.
2016-10-28T09:05:29Z
2016-10-28T09:05:29Z
2010
Article
Text
Richter, B.I.; Ostermeier, S.; Turger, Anke; Denkena, Berend; Hurschler, C.: A rolling-gliding wear simulator for the investigation of tribological material pairings for application in total knee arthroplasty. In: BioMedical Engineering Online 9 (2010) , 24. DOI: http://dx.doi.org/10.1186/1475-925X-9-24
http://www.repo.uni-hannover.de/handle/123456789/572
http://dx.doi.org/10.15488/548
eng
BioMedical Engineering Online 9 (2010)
1475-925X
http://dx.doi.org/10.1186/1475-925X-9-24
https://creativecommons.org/licenses/by/2.0/
CC BY 2.0 Unported
London : BioMed Central Ltd.
oai:www.repo.uni-hannover.de:123456789/5752022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
A test method for analysing disturbed ethernet data streams
Kreitlow, M.
Sabath, F.
Garbe, Heyno
Data communication systems
Electromagnetic pulse
Ethernet
Testing
Data transmission rates
Direct assessment
Electromagnetic attack
Electromagnetic disturbances
Ethernet connections
Measuring method
Physical interactions
Time-domain data
Time domain analysis
Ethernet connections, which are widely used in many computer networks, can suffer from electromagnetic interference. Typically, a degradation of the data transmission rate can be perceived as electromagnetic disturbances lead to corruption of data frames on the network media. In this paper a software-based measuring method is presented, which allows a direct assessment of the effects on the link layer. The results can directly be linked to the physical interaction without the influence of software related effects on higher protocol layers. This gives a simple tool for a quantitative analysis of the disturbance of an Ethernet connection based on time domain data. An example is shown, how the data can be used for further investigation of mechanisms and detection of intentional electromagnetic attacks.
2016-10-28T09:05:31Z
2016-10-28T09:05:31Z
2015
Article
Text
Kreitlow, M.; Sabath, F.; Garbe, Heyno: A test method for analysing disturbed ethernet data streams. In: Advances in Radio Science 13 (2015), 149. DOI: http://dx.doi.org/10.5194/ars-13-149-2015
http://www.repo.uni-hannover.de/handle/123456789/575
http://dx.doi.org/10.15488/551
eng
Advances in Radio Science 13 (2015)
1684-9965
http://dx.doi.org/10.5194/ars-13-149-2015
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/5772022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Advanced parametrical modelling of 24 GHz radar sensor IC packaging components
Kazemzadeh, R.
John, Werner
Wellmann, J.
Bala, U.B.
Thiede, A.
communications
radio
SiP
This paper deals with the development of an advanced parametrical modelling concept for packaging components of a 24 GHz radar sensor IC used in automotive driver assistance systems. For fast and efficient design of packages for system-in-package modules (SiP), a simplified model for the description of parasitic electromagnetic effects within the package is desirable, as 3-D field computation becomes inefficient due to the high density of conductive elements of the various signal paths in the package. By using lumped element models for the characterization of the conductive components, a fast indication of the design's signal-quality can be gained, but so far does not offer enough flexibility to cover the whole range of geometric arrangements of signal paths in a contemporary package. This work pursues to meet the challenge of developing a flexible and fast package modelling concept by defining parametric lumped-element models for all basic signal path components, e.g. bond wires, vias, strip lines, bumps and balls.
2016-10-28T09:05:31Z
2016-10-28T09:05:31Z
2011
Article
Text
Kazemzadeh, R.; John, Werner; Wellmann, J.; Bala, U.B.; Thiede, A.: Advanced parametrical modelling of 24 GHz radar sensor IC packaging components. In: Advances in Radio Science 9 (2011), S. 383-389. DOI: http://dx.doi.org/10.5194/ars-9-383-2011
http://www.repo.uni-hannover.de/handle/123456789/577
http://dx.doi.org/10.15488/553
eng
Advances in Radio Science 9 (2011)
1684-9965
http://dx.doi.org/10.5194/ars-9-383-2011
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/5792022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
An identification procedure of multi-input Wiener models for the distortion analysis of nonlinear circuits
Weng, T.
Stegemann, S.
John, Werner
Mathis, Wolfgang
Black box approach
Correlation analysis
Distortion analysis
Distortion behaviors
Identification procedure
Interfering signals
Nonlinear circuit
System identification procedure
Electromagnetic pulse
White noise
Nonlinear equations
In this contribution, a system identification procedure of a two-input Wiener model suitable for the analysis of the disturbance behavior of integrated nonlinear circuits is presented. The identified block model is comprised of two linear dynamic and one static nonlinear block, which are determined using an parameterized approach. In order to characterize the linear blocks, an correlation analysis using a white noise input in combination with a model reduction scheme is adopted. After having characterized the linear blocks, from the output spectrum under single tone excitation at each input a linear set of equations will be set up, whose solution gives the coefficients of the nonlinear block. By this data based black box approach, the distortion behavior of a nonlinear circuit under the influence of an interfering signal at an arbitrary input port can be determined. Such an interfering signal can be, for example, an electromagnetic interference signal which conductively couples into the port of consideration.
2016-10-28T09:05:32Z
2016-10-28T09:05:32Z
2013
Article
Text
Weng, T.; Stegemann, S.; John, Werner; Mathis, Wolfgang: An identification procedure of multi-input Wiener models for the distortion analysis of nonlinear circuits. In: Advances in Radio Science 11 (2013), S. 165-170. DOI: http://dx.doi.org/10.5194/ars-11-165-2013
http://www.repo.uni-hannover.de/handle/123456789/579
http://dx.doi.org/10.15488/555
eng
Advances in Radio Science 11 (2013)
1684-9965
http://dx.doi.org/10.5194/ars-11-165-2013
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/5962022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Comparison of order reduction algorithms for application to electrical networks
Radić-Weissenfeld, Ljubica J.
Ludwig, Stefan
Mathis, Wolfgang
Computational burden
Electrical models
Electrical networks
FAST model
Order reduction
Computer simulation
Algorithms
This paper addresses issues related to the minimization of the computational burden in terms of both memory and speed during the simulation of electrical models. In order to achieve a simple and computational fast model the order reduction of its reducible part is proposed. In this paper the overview of the order reduction algorithms and their application are discussed.
2016-10-31T07:59:00Z
2016-10-31T07:59:00Z
2009
Article
Text
Radić-Weissenfeld, L.J.; Ludwig, S.; Mathis, W.: Comparison of order reduction algorithms for application to electrical networks. In: Advances in Radio Science 7 (2009), S 119-122. DOI: http://dx.doi.org/10.5194/ars-7-119-2009
http://www.repo.uni-hannover.de/handle/123456789/596
http://dx.doi.org/10.15488/572
eng
Advances in Radio Science 7 (2009)
1684-9965
http://dx.doi.org/10.5194/ars-7-119-2009
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6012022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Coupled coating formation simulation in thermal spray processes using CFD and FEM
Prehm, J.
Xin, L.
Möhwald, Kai
Bach, Friedrich-Wilhelm
Atmospheric plasma spraying
Coating formation
Particle spreading
Pore formation
Simulation
Thermal spraying
Volume of fluid method
This paper deals with the simulation of coating formation in Thermal Spray processes. That means that impingement and flattening of molten metal- or ceramic particles with a diameter of about 50 microns on a rough surface have to be regarded. In this work, this is accomplished use of the Volume of Fluid method. The disadvantage here is that only the pure flattening process can be considered. In order to implicate the shrinking of the particles due to cooling down after solidification, which is responsible for the occurrence of pores and thermal stresses, a Finite Element calculation is done subsequent to the CFD calculation. After the FEM calculation has finished, the newly generated, shrinked particle shape has to be re-imported into the CFD grid. © 2009-2012.
2016-10-31T07:59:01Z
2016-10-31T07:59:01Z
2011
Article
Text
Prehm, J.; Xin, L.; Möhwald, Kai; Bach, F.-W.: Coupled coating formation simulation in thermal spray processes using CFD and FEM. In: CFD Letters 3 (2011), Nr. 2, S. 89-99.
http://www.repo.uni-hannover.de/handle/123456789/601
http://dx.doi.org/10.15488/577
eng
CFD Letters 3 (2011), Nr. 2
2180-1363
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Kuala Lumpur : The International Society for Science & Religion
oai:www.repo.uni-hannover.de:123456789/6042022-12-02T16:16:28Zcom_123456789_1col_123456789_10doc-type:Articledoc-type:Textopen_accessddc:330status-type:publishedVersionddc:600
Determinants of consumers' perceived trust in IT-ecosystems
Wiedmann, Klaus-Peter
Hennigs, Nadine
Varelmann, Dieter
Reeh, Marc-Oliver
Digital environment
It-ecosystems
Man-machine-interaction
Trust
Trustworthiness
Digital ecosystems, or IT-ecosystems (ITEs), are composed of multiple and independent entities such as individuals, organizations, services, software, and applications. Together, these elements create a number of new independent systems that operate and communicate with their own infrastructure (man to machine; machine to machine; person to person), sharing one or several missions. A better understanding of how ITEs and their interconnected components create benefits and added value for different types of consumers is of particular importance to the establishment of digital environments and to managing their resources. Considering different components of perceived trust in ITEs, we rely in this paper on a multi-dimensional framework of trust effects that includes system-centric as well as user-centric determinants of trust. Based on our conceptual model, we develop two sets of propositions. The first ones address technological drivers of trust in ITEs, whereas the second set of propositions considers individual as well as social drivers of trust. The model and propositions are discussed with reference to preliminary empirical results as well as to future research steps and business implications.
2016-10-31T07:59:02Z
2016-10-31T07:59:02Z
2010
Article
Text
Wiedmann, Klaus-Peter; Hennigs, Nadine; Varelmann, Dieter; Reeh, Marc-Oliver: Determinants of consumers' perceived trust in IT-ecosystems. In: Journal of Theoretical and Applied Electronic Commerce Research 5 (2010), Nr. 2, S. 137-154. DOI: http://dx.doi.org/10.4067/S0718-18762010000200009
http://www.repo.uni-hannover.de/handle/123456789/604
http://dx.doi.org/10.15488/580
eng
Journal of Theoretical and Applied Electronic Commerce Research 5 (2010), Nr. 2
0718-1876
http://dx.doi.org/10.4067/S0718-18762010000200009
https://creativecommons.org/licenses/by/4.0/deed.en
CC BY 4.0 Unported
Curico : University of Talca, Faculty of Engineering
oai:www.repo.uni-hannover.de:123456789/6062022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Determination of the input impedance of RFID transponder antennas with novel measurement procedure using a modified on-wafer-prober
Camp, M.
Herschmann, R.
Zelder, T.
Eul, H.
Antenna structures
FEM simulations
Input impedance
Large parts
Measurement procedures
RFID transponders
Electric impedance
Electric impedance measurement
Transponders
Antennas
This paper shows a new method to determine the input impedance of RFID transponder antennas with a combination of on-wafer-prober and network analyzer. It is shown that the results are in a good agreement with FEM simulations (HFSS) for a large part of the examined antenna structures.
2016-10-31T10:06:37Z
2016-10-31T10:06:37Z
2007
Article
Text
Camp, M.; Herschmann, R.; Zelder, T.; Eul, H.: Determination of the input impedance of RFID transponder antennas with novel measurement procedure using a modified on-wafer-prober. In: Advances in Radio Science 5 (2007) S. 115-118. DOI: http://dx.doi.org/10.5194/ars-5-115-2007
http://www.repo.uni-hannover.de/handle/123456789/606
http://dx.doi.org/10.15488/582
eng
Advances in Radio Science 5 (2007)
1684-9965
http://dx.doi.org/10.5194/ars-5-115-2007
https://creativecommons.org/licenses/by-nc-sa/2.5/
CC BY-NC-SA 2.5 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6092022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Differential algebraic equations of MOS circuits and jump behavior
Sarangapani, P.
Thiessen, Tina
Mathis, Wolfgang
Circuit simulators
Differential algebraic equations
Drain current models
Equivalent circuit model
Geometric approaches
Nonlinear electronic circuits
Parasitic inductors
Transient solutions
Bipolar transistors
Circuit simulation
Vibrators
Numerical methods
Many nonlinear electronic circuits showing fast switching behavior exhibit jump effects which occurs when the state space of the electronic system contains a fold. This leads to difficulties during the simulation of these systems with standard circuit simulators. A method to overcome these problems is by regularization, where parasitic inductors and capacitors are added at the suitable locations. However, the transient solution will not be reliable if this regularization is not done in accordance with Tikhonov's Theorem. A geometric approach is taken to overcome these problems by explicitly computing the state space and jump points of the circuit. Until now, work has been done in analyzing example circuits exhibiting this behavior for BJT transistors. In this work we apply these methods to MOS circuits (Schmitt trigger, flip flop and multivibrator) and present the numerical results. To analyze the circuits we use the EKV drain current model as equivalent circuit model for the MOS transistors.
2016-10-31T10:06:39Z
2016-10-31T10:06:39Z
2012
Article
Text
Sarangapani, P.; Thiessen, Tina; Mathis, Wolfgang: Differential algebraic equations of MOS circuits and jump behavior. In: Advances in Radio Science 10 (2012), S. 327-332. DOI: http://dx.doi.org/10.5194/ars-10-327-2012
http://www.repo.uni-hannover.de/handle/123456789/609
http://dx.doi.org/10.15488/585
eng
Advances in Radio Science 10 (2012)
1684-9965
http://dx.doi.org/10.5194/ars-10-327-2012
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6152022-12-02T15:03:42Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Efficient modelling of IC conducted emission for power integrity analysis
Kazemzadeh, Reza
Ludwig, Stefan
Radić-Weissenfeld, Ljubica J.
Mathis, Wolfgang
Complex model
Conducted emissions
Model order reduction
Module-based
Power integrity
Reduced model
Rough estimation
Supply currents
Electronics engineering
Electrical engineering
In this paper two methodologies to reduce the complexity of IC conducted emission models for Power Integrity analysis in ICs are presented. The methodologies differ concerning the applicability in simulation tools, complexity and accuracy of the generated models. The first methodology uses a complex model and reduces its order to generate a model with a fewer number of elements. This methodology therefore involves a model order reduction approach. A second minimum complexity, module based modelling approach is introduced for rough estimations, as the order reduced model is still too complex for some applications. The two methodologies are applied to an IC conducted emission model of two digital modules of a 32 Bit microcontroller. The results of the three models are compared and discussed. Fields of application for the introduced modelling approaches are the estimation of the magnitude and time behaviour of the supply current as well as the determination of the number and position of the IC's supply pins.
2016-10-31T10:06:40Z
2016-10-31T10:06:40Z
2009
Article
Text
Kazemzadeh, R.; Ludwig, S.; Radić-Weissenfeld, Lj.; Mathis, W.: Efficient modelling of IC conducted emission for power integrity analysis. In: Advances in Radio Science 7 (2009), S 123-126. DOI: http://dx.doi.org/10.5194/ars-7-123-2009
http://www.repo.uni-hannover.de/handle/123456789/615
http://dx.doi.org/10.15488/591
eng
Advances in Radio Science 7 (2009)
1684-9965
http://dx.doi.org/10.5194/ars-7-123-2009
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6162022-12-02T15:03:42Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Efficient passive network description of IC conducted emission models for model reduction
Ludwig, Stefan
Radić-Weissenfeld, Ljubica J.
Mathis, Wolfgang
John, W.
Circuit simulators
Conducted emissions
Electrical networks
Independent sources
Model order reduction
Model reduction
Reduced systems
Standard model
Electrical engineering
Electronics engineering
Computer simulation
This article adresses the model reduction of IC conducted emission models. A method to efficiently deal with the high number of independent sources in IC conducted emission models, which are a strong limitation for model order reduction, is presented. A network alteration is proposed, which allows for a much higher model reduction than standard approaches. The system of the altered network can be more efficiently reduced with standard model order reduction algorithms in order to speed up frequency-simulations. Synthesising the reduced system into a passive electrical network enables fast time-simulations to be made with circuit simulators. The whole procedure is validated by reducing an example of an IC conducted emission model of an 32 Bit microcontroller.
2016-10-31T10:06:41Z
2016-10-31T10:06:41Z
2008
Article
Text
Ludwig, S.; Radić-Weissenfeld, Lj.; Mathis, W.; John, W.: Efficient passive network description of IC conducted emission models for model reduction. In: Advances in Radio Science 6 (2008), S. 133-137. DOI: http://dx.doi.org/10.5194/ars-6-133-2008
http://www.repo.uni-hannover.de/handle/123456789/616
http://dx.doi.org/10.15488/592
eng
Advances in Radio Science 6 (2008)
1684-9965
http://dx.doi.org/10.5194/ars-6-133-2008
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6192022-12-02T15:04:50Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:570ddc:600
Evaluation of the soft tissue biocompatibility of MgCa0.8 and surgical steel 316L in vivo: A comparative study in rabbits
Erdmann, Nina
Bondarenko, Alexandr
Hewicker-Trautwein, Marion
Angrisani, Nina
Reifenrath, Janin
Lucas, Arne
Meyer-Lindenberg, Andrea
Anti-cd3
B lymphocytes
Cell types
Cellular infiltration
Commonly used
Comparative studies
Fibrous tissue
Follow up
Geometrical conformation
Giant cells
Haematoxylin
Humoral immunity
Implant materials
In-vivo
Magnesium-calcium alloys
Observation Period
Screw head
Semi-quantitative
Soft tissue
Synoviocytes
Time-periods
Tissue necrosis
Antibodies
Calcium alloys
Chemical detection
Magnesium
Magnesium alloys
Muscle
Paraffin waxes
Paraffins
Pathology
Screws
Surgery
Biocompatibility
Oryctolagus cuniculus
Rattus
alloy
biomaterial
calcium
magnesium
steel
animal
article
biodegradable implant
bone screw
chemically induced disorder
chemistry
comparative study
drug effect
female
general surgery
inflammation
materials testing
methodology
pathology
rabbit
radiography
skeletal muscle
tibia
Absorbable Implants
Alloys
Animals
Biocompatible Materials
Bone Screws
Calcium
Female
General Surgery
Inflammation
Magnesium
Materials Testing
Muscle, Skeletal
Rabbits
Steel
Tibia
Background: Recent studies have shown the potential suitability of magnesium alloys as biodegradable implants. The aim of the present study was to compare the soft tissue biocompatibility of MgCa0.8 and commonly used surgical steel in vivo.Methods: A biodegradable magnesium calcium alloy (MgCa0.8) and surgical steel (S316L), as a control, were investigated. Screws of identical geometrical conformation were implanted into the tibiae of 40 rabbits for a postoperative follow up of two, four, six and eight weeks. The tibialis cranialis muscle was in direct vicinity of the screw head and thus embedded in paraffin and histologically and immunohistochemically assessed. Haematoxylin and eosin staining was performed to identify macrophages, giant cells and heterophil granulocytes as well as the extent of tissue fibrosis and necrosis. Mouse anti-CD79α and rat anti-CD3 monoclonal primary antibodies were used for B- and T-lymphocyte detection. Evaluation of all sections was performed by applying a semi-quantitative score.Results: Clinically, both implant materials were tolerated well. Histology revealed that a layer of fibrous tissue had formed between implant and overlying muscle in MgCa0.8 and S316L, which was demarcated by a layer of synoviocyte-like cells at its interface to the implant. In MgCa0.8 implants cavities were detected within the fibrous tissue, which were surrounded by the same kind of cell type. The thickness of the fibrous layer and the amount of tissue necrosis and cellular infiltrations gradually decreased in S316L. In contrast, a decrease could only be noted in the first weeks of implantation in MgCa0.8, whereas parameters were increasing again at the end of the observation period. B-lymphocytes were found more often in MgCa0.8 indicating humoral immunity and the presence of soluble antigens. Conversely, S316L displayed a higher quantity of T-lymphocytes.Conclusions: Moderate inflammation was detected in both implant materials and resolved to a minimum during the first weeks indicating comparable biocompatibility for MgCa0.8 and S316L. Thus, the application of MgCa0.8 as biodegradable implant material seems conceivable. Since the inflammatory parameters were re-increasing at the end of the observation period in MgCa0.8 it is important to observe the development of inflammation over a longer time period in addition to the present study.
2016-10-31T13:37:18Z
2016-10-31T13:37:18Z
2010
Article
Text
Erdmann, N.; Bondarenko, A.; Hewicker-Trautwein, M.; Angrisani, N.; Reifenrath, J.et al.: Evaluation of the soft tissue biocompatibility of MgCa0.8 and surgical steel 316L in vivo: A comparative study in rabbits. In: BioMedical Engineering Online 9 (2010), 63. DOI: http://dx.doi.org/10.1186/1475-925X-9-63
http://www.repo.uni-hannover.de/handle/123456789/619
http://dx.doi.org/10.15488/595
eng
BioMedical Engineering Online 9 (2010)
1475-925X
http://dx.doi.org/10.1186/1475-925X-9-63
https://creativecommons.org/licenses/by/2.0/
CC BY 2.0 Unported
London : BioMed Central Ltd.
oai:www.repo.uni-hannover.de:123456789/6222022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Gold nanoparticle-mediated delivery of molecules into primary human gingival fibroblasts using ns-laser pulses: A pilot study
Krawinkel, Judith
Torres-Mapa, Maria Leilani
Werelius, Kristian
Heisterkamp, Alexander
Rüttermann, Stefan
Romanos, Georgios E.
Gerhardt-Szép, Susanne
Gold nanoparticles
Human gingival fibroblasts
Laser
Laser based cell manipulation
Interaction of gold nanoparticles (AuNPs) in the vicinity of cells' membrane with a pulsed laser (λ = 532 nm, τ = 1 ns) leads to perforation of the cell membrane, thereby allowing extracellular molecules to diffuse into the cell. The objective of this study was to develop an experimental setting to deliver molecules into primary human gingival fibroblasts (pHFIB-G) by using ns-laser pulses interacting with AuNPs (study group). To compare the parameters required for manipulation of pHFIB-G with those needed for cell lines, a canine pleomorphic adenoma cell line (ZMTH3) was used (control group). Non-laser-treated cells incubated with AuNPs and the delivery molecules served as negative control. Laser irradiation (up to 35 mJ/cm2) resulted in a significant proportion of manipulated fibroblasts (up to 85%, compared to non-irradiated cells: p < 0.05), while cell viability (97%) was not reduced significantly. pHFIB-G were perforated as efficiently as ZMTH3. No significant decrease of metabolic cell activity was observed up to 72 h after laser treatment. The fibroblasts took up dextrans with molecular weights up to 500 kDa. Interaction of AuNPs and a pulsed laser beam yields a spatially selective technique for manipulation of even primary cells such as pHFIB-G in high throughput. © 2016 by the authors.
2016-10-31T13:37:19Z
2016-10-31T13:37:19Z
2016
Article
Text
Krawinkel, J.; Torres-Mapa, Maria Leilani.; Werelius, K.; Heisterkamp, Alexander; Rüttermann, S. et al.: Gold nanoparticle-mediated delivery of molecules into primary human gingival fibroblasts using ns-laser pulses: A pilot study. In: Materials 9 (2016), Nr. 5, 397. DOI: http://dx.doi.org/10.3390/ma9050397
http://www.repo.uni-hannover.de/handle/123456789/622
http://dx.doi.org/10.15488/598
eng
Materials 9 (2016), Nr. 5
1996-1944
http://dx.doi.org/10.3390/ma9050397
https://creativecommons.org/licenses/by-nc-sa/4.0/
CC BY-NC-SA 4.0 Unported
Basel : MDPI AG
oai:www.repo.uni-hannover.de:123456789/6282022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510ddc:600
Implementing second-order decision analysis: Concepts, algorithms, and tool
Larsson, Aron
Kuznetsova, Alina
Caster, Ola
Ekenberg, Love
systems sciences
communications system
WINPRE
PRIME method
We present implemented concepts and algorithms for a simulation approach to decision evaluation with second-order belief distributions in a common framework for interval decision analysis. The rationale behind this work is that decision analysis with interval-valued probabilities and utilities may lead to overlapping expected utility intervals yielding difficulties in discriminating between alternatives. By allowing for second-order belief distributions over interval-valued utility and probability statements these difficulties may not only be remedied but will also allow for decision evaluation concepts and techniques providing additional insight into a decision problem. The approach is based upon sets of linear constraints together with generation of random probability distributions and utility values from implicitly stated uniform second-order belief distributions over the polytopes given from the constraints. The result is an interactive method for decision evaluation with second-order belief distributions, complementing earlier methods for decision evaluation with interval-valued probabilities and utilities. The method has been implemented for trial use in a user oriented decision analysis software.
2016-10-31T13:38:59Z
2016-10-31T13:38:59Z
2014
Article
Text
Larsson, A.; Kuznetsova, Alina; Caster, O.; Ekenberg, L.: Implementing second-order decision analysis: Concepts, algorithms, and tool. In: Advances in Decision Sciences 2014 (2014), 519512. DOI: http://dx.doi.org/10.1155/2014/519512
http://www.repo.uni-hannover.de/handle/123456789/628
http://dx.doi.org/10.15488/604
eng
Advances in Decision Sciences 2014 (2014)
2090-3359
http://dx.doi.org/10.1155/2014/519512
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
New York, NY : Hindawi Publishing Corporation
oai:www.repo.uni-hannover.de:123456789/6292022-12-02T15:04:50Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:570ddc:600
In vitro corrosion of ZEK100 plates in Hank's Balanced Salt Solution
Waizy, Hazibullah
Weizbauer, Andreas
Modrejewski, Christian
Witte, Frank
Windhagen, Henning
Lucas, Arne
Kieke, Marc D.K.
Denkena, Berend
Behrens, Peter
Meyer-Lindenberg, Andrea
Bach, Friedrich-Wilhelm
Thorey, Fritz
Corrosion
In vitro study
Magnesium alloy
Plates
Corrosion property
Degradation behavior
Four-point bending test
Hank's balanced salt solutions
In-vitro
Mg content
Natural bone
Orthopedic implant
Physiological condition
Plates
Resorbable materials
Stress shielding
Calcium phosphate
Corrosion
Magnesium
Magnesium alloys
Mechanical properties
Salt removal
Surfaces
Magnesium printing plates
alloy
bicarbonate
biomaterial
Hanks Balanced Salt Solution
isotonic solution
magnesium
article
chemistry
corrosion
hydrodynamics
immersion
mechanics
surface property
Alloys
Bicarbonates
Biocompatible Materials
Corrosion
Hydrodynamics
Immersion
Isotonic Solutions
Magnesium
Mechanical Processes
Surface Properties
Background: In recent years magnesium alloys have been intensively investigated as potential resorbable materials with appropriate mechanical and corrosion properties. Particularly in orthopedic research magnesium is interesting because of its mechanical properties close to those of natural bone, the prevention of both stress shielding and removal of the implant after surgery.Methods: ZEK100 plates were examined in this in vitro study with Hank's Balanced Salt Solution under physiological conditions with a constant laminar flow rate. After 14, 28 and 42 days of immersion the ZEK100 plates were mechanically tested via four point bending test. The surfaces of the immersed specimens were characterized by SEM, EDX and XRD.Results: The four point bending test displayed an increased bending strength after 6 weeks immersion compared to the 2 week group and 4 week group. The characterization of the surface revealed the presence of high amounts of O, P and Ca on the surface and small Mg content. This indicates the precipitation of calcium phosphates with low solubility on the surface of the ZEK100 plates.Conclusions: The results of the present in vitro study indicate that ZEK100 is a potential candidate for degradable orthopedic implants. Further investigations are needed to examine the degradation behavior.
2016-10-31T13:38:59Z
2016-10-31T13:38:59Z
2012
Article
Text
Waizy, H.; Weizbauer, A.; Modrejewski, C.; Witte, F.; Windhagen, H. et al.: In vitro corrosion of ZEK100 plates in Hank's Balanced Salt Solution. In: BioMedical Engineering Online 11 (2012), 12. DOI: http://dx.doi.org/10.1186/1475-925X-11-12
http://www.repo.uni-hannover.de/handle/123456789/629
http://dx.doi.org/10.15488/605
eng
BioMedical Engineering Online 11 (2012)
1475-925X
http://dx.doi.org/10.1186/1475-925X-11-12
https://creativecommons.org/licenses/by/2.0/
CC BY 2.0 Unported
London : BioMed Central Ltd.
oai:www.repo.uni-hannover.de:123456789/6302022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
In vivo degradation behavior of the magnesium alloy land442 in rabbit tibiae
Ullmann, Berit
Reifenrath, Janin
Dziuba, Dina
Seitz, Jan-Marten
Bormann, Dirk
Meyer-Lindenberg, Andrea
μ-Computed tomography
Animal model
Biodegradation
Magnesium alloy
Mechanical stability
Animal model
Bending force
Degradation behaviours
Rare earth compositions
Reproducibilities
Sem examinations
Three-point bending test
Weight loss
Biocompatibility
Biodegradation
Computerized tomography
Corrosion rate
Degradation
Mechanical stability
Pitting
Magnesium alloys
In former studies the magnesium alloy LAE442 showed promising in vivo degradation behavior and biocompatibility. However, reproducibility might be enhanced by replacement of the rare earth composition metal "E" by only a single rare earth element. Therefore, it was the aim of this study to examine whether the substitution of "E" by neodymium ("Nd") had an influence on the in vivo degradation rate. LANd442 implants were inserted into rabbit tibiae and rabbits were euthanized after 4, 8, 13 and 26 weeks postoperatively. In vivo μCT was performed to evaluate the in vivo implant degradation behaviour by calculation of implant volume, density true 3-D thickness and corrosion rates. Additionally, weight loss, type of corrosion and mechanical stability were appraised by SEM/EDS-analysis and three-point bending tests. Implant volume, density and true 3-D thickness decreased over time, whereas the variance of the maximum diameters within an implant as well as the corrosion rate and weight loss increased. SEM examination revealed mainly pitting corrosion after 26 weeks. The maximum bending forces decreased over time.
2016-10-31T13:38:59Z
2016-10-31T13:38:59Z
2011
Article
Text
Ullmann, B.; Reifenrath, J.; Dziuba, D.; Seitz, Jan-Marten; Bormann, Dirk et al.: In vivo degradation behavior of the magnesium alloy land442 in rabbit tibiae. In: Materials 4 (2011), Nr. 12, S. 2197-2218. DOI: http://dx.doi.org/10.3390/ma4122197
http://www.repo.uni-hannover.de/handle/123456789/630
http://dx.doi.org/10.15488/606
eng
Materials 4 (2011), Nr. 12
1996-1944
http://dx.doi.org/10.3390/ma4122197
https://creativecommons.org/licenses/by-nc-sa/3.0/
CC BY-NC-SA 3.0 Unported
Basel : MDPI AG
oai:www.repo.uni-hannover.de:123456789/6342022-12-02T15:19:58Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Irreversibility of pressure induced boron speciation change in glass
Smedskjaer, Marten M.
Youngman, Randalf E.
Striepe, Simon
Potuzak, Marcel
Bauer, Ute
Deubener, Joachim
Behrens, Harald
Mauro, John C.
Yue, Yuanzheng
Solid state NMR
materials science
glass
It is known that the coordination number (CN) of atoms or ions in many materials increases through application of sufficiently high pressure. This also applies to glassy materials. In boron-containing glasses, trigonal BO 3 units can be transformed into tetrahedral BO 4 under pressure. However, one of the key questions is whether the pressure-quenched CN change in glass is reversible upon annealing below the ambient glass transition temperature (T g). Here we address this issue by performing 11 B NMR measurements on a soda lime borate glass that has been pressure-quenched at ∼0.6 GPa near T g. The results show a remarkable phenomenon, i.e., upon annealing at 0.9T g the pressure-induced change in CN remains unchanged, while the pressurised values of macroscopic properties such as density, refractive index, and hardness are relaxing. This suggests that the pressure-induced changes in macroscopic properties of soda lime borate glasses compressed up to ∼0.6 GPa are not attributed to changes in the short-range order in the glass, but rather to changes in overall atomic packing density and medium-range structures.
2016-11-02T08:33:44Z
2016-11-02T08:33:44Z
2014
Article
Text
Smedskjaer, M.M.; Youngman, R.E.; Striepe, S.; Potuzak, M.; Bauer, Ute et al.: Irreversibility of pressure induced boron speciation change in glass. In: Scientific Reports 4 (2014), 3770. DOI: http://dx.doi.org/10.1038/srep03770
http://www.repo.uni-hannover.de/handle/123456789/634
http://dx.doi.org/10.15488/610
eng
Scientific Reports 4 (2014)
2045-2322
http://dx.doi.org/10.1038/srep03770
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
London : Nature Publishing Group
oai:www.repo.uni-hannover.de:123456789/6392022-12-02T16:11:41Zcom_123456789_1col_123456789_8doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Limits of ZnO electrodeposition in mesoporous tin doped indium oxide films in view of application in dye-sensitized solar cells
Dunkel, Christian
Graberg, Till von
Smarsly, Bernd M.
Oekermann, Torsten
Wark, Michael
Dye-sensitized solar cells (DSSC)
Electrodeposition
Indium tin oxide (ITO)
Mesoporous TCO
Zinc oxide
Deposition
Electrodeposition
Mesoporous materials
Photoelectrochemical cells
Polyethylene oxides
Pore size
Reduction
Sol-gel process
Solar cells
Tin
Zinc oxide
Dye-Sensitized solar cell
Dye-sensitized solar cells
Electrochemical deposition
Indium tin oxide
Mesoporous
Photogenerated electrons
Porous current collectors
Tin doped indium oxide films
Conductive films
Well-ordered 3D mesoporous indium tin oxide (ITO) films obtained by a templated sol-gel route are discussed as conductive porous current collectors. This paper explores the use of such films modified by electrochemical deposition of zinc oxide (ZnO) on the pore walls to improve the electron transport in dye-sensitized solar cells (DSSCs). Mesoporous ITO film were dip-coated with pore sizes of 20-25 nm and 40-45 nm employing novel poly(isobutylene)-b-poly(ethylene oxide) block copolymers as structure-directors. After electrochemical deposition of ZnO and sensitization with the indoline dye D149 the films were tested as photoanodes in DSSCs. Short ZnO deposition times led to strong back reaction of photogenerated electrons from non-covered ITO to the electrolyte. ITO films with larger pores enabled longer ZnO deposition times before pore blocking occurred, resulting in higher efficiencies, which could be further increased by using thicker ITO films consisting of five layers, but were still lower compared to nanoporous ZnO films electrodeposited on flat ITO. The major factors that currently limit the application are the still low thickness of the mesoporous ITO films, too small pore sizes and non-ideal geometries that do not allow obtaining full coverage of the ITO surface with ZnO before pore blocking occurs.
2016-11-02T08:33:58Z
2016-11-02T08:33:58Z
2014
Article
Text
Dunkel, Christian; von Graberg, T.; Smarsly, B.M.; Oekermann, Torsten; Wark, Michael: Limits of ZnO electrodeposition in mesoporous tin doped indium oxide films in view of application in dye-sensitized solar cells. In: Materials 7 (2014), Nr. 4, S. 3291-3304. DOI: http://dx.doi.org/10.3390/ma7043291
http://www.repo.uni-hannover.de/handle/123456789/639
http://dx.doi.org/10.15488/615
eng
Materials 7 (2014), Nr. 4
1996-1944
http://dx.doi.org/10.3390/ma7043291
https://creativecommons.org/licenses/by-nc-sa/3.0/
CC BY-NC-SA 3.0 Unported
Basel : MDPI AG
oai:www.repo.uni-hannover.de:123456789/6402022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Macro-modelling via radial basis functionen nets
Wiegand, C.
Fischer, C.
Kazemzadeh, Reza
Hedayat, C.
John, W.
Hilleringmann, U.
Black-box model
Dynamic reconstruction
Efficient simulation
Input and outputs
Macro-modelling
Miniaturisation
Radial basis functions
Transient interactions
Radial basis function networks
Time series
Computer simulation
By the rising complexity and miniaturisation of the device's dimensions, the density of the conductors increases considerably. Referring to this, locally transient interactions between single physical values become apparent. Therefore, for the investigation and optimisation of integrated circuits it is essential to develop suitable models and simulation surroundings which allow for memory and timeefficient calculation of the behaviour. By means of the dynamic reconstruction theory and the radial basis functions nets the so-called black box models are provided. The description of black box models is derived from the input and output behaviour or so-called time series of a dynamic system. Concerning the time series, the black box model adapts its parameters via the extended Kalman filter. This paper provides a modelling approach that enables fast and efficient simulations.
2016-11-02T08:33:59Z
2016-11-02T08:33:59Z
2008
Article
Text
Wiegand, C.; Fischer, C.; Kazemzadeh, R.; Hedayat, C.; John, W. et al.: Macro-modelling via radial basis functionen nets. In: Advances in Radio Science 6 (2008) , S. 139-143. DOI: http://dx.doi.org/10.5194/ars-6-139-2008
http://www.repo.uni-hannover.de/handle/123456789/640
http://dx.doi.org/10.15488/616
eng
Advances in Radio Science 6 (2008)
1684-9965
http://dx.doi.org/10.5194/ars-6-139-2008
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6412022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Matching the termination of radiating non-uniform transmission-lines
Rambousky, R.
Nitsch, J.
Garbe, Heyno
Characteristic impedance
Concentrated load
Cooperative process
Frequency dependent
Line parameters
Local effects
Radiated power
Transmission-line
Characteristic impedance
Concentrated load
Cooperative process
Frequency dependent
Line parameters
Radiated power
Single wire transmission
Transmission-line
Electrical engineering
Electronics engineering
Transmission line theory
Electric lines
Electric lines
In this contribution a concept of matching the termination of radiating non-uniform transmission-lines is proposed. Using Transmission-Line Super Theory, position and frequency dependent line parameters can be obtained. Therefore, a characteristic impedance can be determined which is also position and frequency dependent. For a single wire transmission-line it could be shown that the maximum value of that characteristic impedance is an optimal termination in the sense of minimizing the variation of the current on the line. This indicates that matching is not a local effect at the position of the concentrated load but a cooperative process including the whole non-uniform transmission-line. In addition this choice of termination minimizes the variation of the radiated power over frequency.
2016-11-02T08:33:59Z
2016-11-02T08:33:59Z
2013
Article
Text
Rambousky, R.; Nitsch, J.; Garbe, Heyno: Matching the termination of radiating non-uniform transmission-lines. In: Advances in Radio Science 11 (2013), S. 259-264. DOI: http://dx.doi.org/10.5194/ars-11-259-2013
http://www.repo.uni-hannover.de/handle/123456789/641
http://dx.doi.org/10.15488/617
eng
Advances in Radio Science 11 (2013)
1684-9965
http://dx.doi.org/10.5194/ars-11-259-2013
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6462022-12-02T15:03:42Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Model order reduction of linear time invariant systems
Radić-Weissenfeld, Ljubica J.
Ludwig, Stefan
Mathis, Wolfgang
John, W.
Krylov sub spaces
Linear time invariant systems
Lyapunov equation
Model order reduction
Multiple inputs
Multipoint approximation
Order reduction methods
System matrices
Linear systems
Lyapunov functions
This paper addresses issues related to the order reduction of systems with multiple input/output ports. The order reduction is divided up into two steps. The first step is the standard order reduction method based on the multipoint approximation of system matrices by applying Krylov subspace. The second step is based on the rejection of the weak part of a system. To recognise the weak system part, Lyapunov equations are used. Thus, this paper introduces efficient solutions of the Lyapunov equations for port to port subsystems.
2016-11-02T13:36:01Z
2016-11-02T13:36:01Z
2008
Article
Text
Radić-Weissenfeld, L.J.; Ludwig, S.; Mathis, W.; John, W.: Model order reduction of linear time invariant systems. In: Advances in Radio Science 6 (2008) , S. 129-132. DOI: http://dx.doi.org/10.5194/ars-6-129-2008
http://www.repo.uni-hannover.de/handle/123456789/646
http://dx.doi.org/10.15488/622
eng
Advances in Radio Science 6 (2008)
1684-9965
http://dx.doi.org/10.5194/ars-6-129-2008
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6482022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Modelling dielectric and magnetic properties of ferroconcrete
Frenzel, T.
Koch, M.
Complex permittivity
Dielectric and magnetic properties
Electromagnetic field analysis
Frequency ranges
Method of moments (MOM)
Reflection and transmission
Shielding effectiveness
Electromagnetic fields
Method of moments
This contribution discusses the modelling and parameterization of dielectric and magnetic properties of ferroconcrete by using numerical electromagnetic field analysis software. The software is based on the Method of Moments (MoM). The shielding effectiveness (SE) of the ferroconcrete DUT was already measured in a study by order of the government. According to these results, the ferroconcrete DUT is modelled and calculated. Therefore the DUT is subdivided into two parts. The first part represents the reinforcement mesh; the second part represents the lossy concrete with complex permittivity. Afterwards, the reflection and transmission properties of numerical analysed building materials are validated and compared with the measurement results in a frequency range of 30-1000 MHz.
2016-11-02T13:36:02Z
2016-11-02T13:36:02Z
2008
Article
Text
Frenzel, T.; Koch, M.: Modelling dielectric and magnetic properties of ferroconcrete. In: Advances in Radio Science 6 (2008), S. 289-292. DOI: http://dx.doi.org/10.5194/ars-6-289-2008
http://www.repo.uni-hannover.de/handle/123456789/648
http://dx.doi.org/10.15488/624
eng
Advances in Radio Science 6 (2008)
1684-9965
http://dx.doi.org/10.5194/ars-6-289-2008
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6562022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
On the performance of the time reversal SM-MIMO-UWB system on correlated channels
Nguyen, Hieu
Nguyen, Van Duc
Nguyen, Trung Kien
Maichalernnukul, Kiattisak
Zheng, Feng
Kaiser, Thomas
Channel measurements
Correlated channels
Data stream
Indoor environment
Line-of-sight
Multi-input multi-output
Multiple transmit antennas
Non-line-of-sight
Spatial correlations
Time reversal
Transmit correlation
Antennas
Electrical engineering
MIMO systems
The impact of spatial correlation on the multi-input multi-output ultrawide band (MIMO-UWB) system using the time reversal (TR) technique is investigated. Thanks to TR, several data streams can be transmitted by using only one antenna in a system named virtual MIMO-TRUWB. Since the virtual MIMO-TR-UWB system is not affected by the transmit correlation, under the condition of the high spatial correlation, it outperforms the true MIMO-UWB system with multiple transmit antennas. The channel measurements are performed in short-range indoor environment, both line-of-sight and non-line-of-sight to verify the adopted correlated channel model.
2016-11-03T09:29:49Z
2016-11-03T09:29:49Z
2012
Article
Text
Nguyen, Hieu; Nguyen, V.D.; Nguyen, Trung Kien; Maichalernnukul, Kiattisak; Zheng, F. et al.: On the performance of the time reversal SM-MIMO-UWB system on correlated channels. In: International Journal of Antennas and Propagation 2012 (2012), 929018. DOI: http://dx.doi.org/10.1155/2012/929018
http://www.repo.uni-hannover.de/handle/123456789/656
http://dx.doi.org/10.15488/632
eng
International Journal of Antennas and Propagation 2012 (2012)
1687-5869
http://dx.doi.org/10.1155/2012/929018
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
New York, NY : Hindawi Publishing Corporation
oai:www.repo.uni-hannover.de:123456789/6582022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:600
Optimal design of piezoelectric actuators for shunt damping techniques
Neubauer, Marcus
Piezoelectric energy harvesting
Piezoelectric shunt damping
Piezoelectric transducer
Vibration damping
Damping
Energy harvesting
Piezoelectric ceramics
Piezoelectric transducers
Piezoelectricity
Transducers
Damping performance
Piezoelectric elements
Piezoelectric energy harvesting
Piezoelectric shunt damping
Shunt damping techniques
Strain distributions
Vibration behavior
Vibration-damping
Piezoelectric actuators
In vibration control with piezoceramics, a high coupling of the piezoelement with the structure is desired. A high coupling improves the damping performance of passive techniques like shunt damping. The coupling can be influenced by a the material properties of the piezoceramics, but also by the placement within the structure and the size of the transducer. Detailed knowlegde about the vibration behavior of the structure is required for this. This paper presents an in-depth analysis of the optimal shape of piezoelectric elements. General results for one-dimensional, but inhomogeneos strain distribution are provided. These results are applied to the case of a longitudinal transducer and a bending bimorph. It is obtained that for maximum coupling, only a certain fracture of the volume should be made of piezoelectric material.
2016-11-03T09:29:49Z
2016-11-03T09:29:49Z
2014
Article
Text
Neubauer, Marcus: Optimal design of piezoelectric actuators for shunt damping techniques. In: Archives of Acoustics 39 (2014), Nr. 4, S. 615-622. DOI: http://dx.doi.org/10.2478/aoa-2014-0066
http://www.repo.uni-hannover.de/handle/123456789/658
http://dx.doi.org/10.15488/634
eng
Archives of Acoustics 39 (2014), Nr. 4
2300-262X
http://dx.doi.org/10.2478/aoa-2014-0066
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Warsaw : Polish Academy of Sciences, Institute of Fundamental Technological Research
oai:www.repo.uni-hannover.de:123456789/6592022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:570ddc:600
Outer electrospun polycaprolactone shell induces massive foreign body reaction and impairs axonal regeneration through 3D multichannel chitosan nerve guides
Duda, Sven
Dreyer, Lutz
Behrens, Peter
Wienecke, Soenke
Chakradeo, Tanmay
Glasmacher, Birgit
Haastert-Talini, Kirsten
chitosan
polycaprolactone
biomaterial
chitosan
polycaprolactone
polyester
adult
animal experiment
article
automutilation
controlled study
electric field
electrophysiological procedures
electrospinning
extracellular space
female
foreign body reaction
freeze drying
giant cell
in vivo study
microenvironment
nerve fiber regeneration
nerve transplantation
nociception
nonhuman
peripheral nerve
rat
scanning electron microscopy
sciatic nerve
animal
chemically induced
convalescence
drug effects
electrodiagnosis
foreign body reaction
inflammation
motor activity
muscle
nerve fiber
nerve regeneration
organ size
pathology
pathophysiology
procedures
tissue regeneration
tissue scaffold
Wistar rat
Animals
Axons
Biocompatible Materials
Chitosan
Electrodiagnosis
Female
Foreign-Body Reaction
Guided Tissue Regeneration
Inflammation
Microscopy, Electron, Scanning
Motor Activity
Muscles
Nerve Regeneration
Organ Size
Pain Perception
Polyesters
Rats, Wistar
Recovery of Function
Tissue Scaffolds
We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT). The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts.
2016-11-03T09:29:49Z
2016-11-03T09:29:49Z
2014
Article
Text
Duda, S.; Dreyer, Lutz; Behrens Peter; Wienecke, Soenke; Chakradeo, Tanmay et al.: Outer electrospun polycaprolactone shell induces massive foreign body reaction and impairs axonal regeneration through 3D multichannel chitosan nerve guides. In: BioMed Research International 2014 (2014), 835269. DOI: http://dx.doi.org/10.1155/2014/835269
http://www.repo.uni-hannover.de/handle/123456789/659
http://dx.doi.org/10.15488/635
eng
BioMed Research International 2014 (2014)
2314-6133
http://dx.doi.org/10.1155/2014/835269
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
New York, NY : Hindawi Publishing Corporation
oai:www.repo.uni-hannover.de:123456789/6652022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:600
Polyethylenimine-mediated gene delivery into human bone marrow mesenchymal stem cells from patients
Wang, Weiwei
Li, Wenzhong
Ou, Lailiang
Flick, Eva
Mark, Peter
Nesselmann, Catharina
Lux, Cornelia A.
Gatzen, Hanz-Heinrich
Kaminski, Alexander
Liebold, Andreas
Lützow, Karola
Lendlein, Andreas
Li, Ren-Ke
Steinhoff, Gustav
Ma, Nan
Cardiovascular disease
Gene delivery
Human bone marrow derived mesenchymal stem cells
Non-viral vector
Polyethylenimine
DNA
green fluorescent protein
polyethyleneimine
vasculotropin A
VEGFA protein, human
adult
aged
article
bone marrow cell
cell cycle S phase
cell death
cell survival
cytology
drug effect
female
gene transfer
genetic transfection
human
male
mesenchymal stem cell
metabolism
middle aged
phenotype
Adult
Aged
Aged, 80 and over
Bone Marrow Cells
Cell Death
Cell Survival
DNA
Female
Gene Transfer Techniques
Green Fluorescent Proteins
Humans
Male
Mesenchymal Stem Cells
Middle Aged
Phenotype
Polyethyleneimine
S Phase
Transfection
Vascular Endothelial Growth Factor A
Transplantation of mesenchymal stem cells (MSCs) derived from adult bone marrow has been proposed as a potential therapeutic approach for post-infarction left ventricular (LV) dysfunction. However, age-related functional decline of stem cells has restricted their clinical benefits after transplantation into the infarcted myocardium. The limitations imposed on patient cells could be addressed by genetic modification of stem cells. This study was designed to improve our understanding of genetic modification of human bone marrow derived mesenchymal stem cells (hMSCs) by polyethylenimine (PEI, branched with Mw 25 kD), one of non-viral vectors that show promise in stem cell genetic modification, in the context of cardiac regeneration for patients. We optimized the PEI-mediated reporter gene transfection into hMSCs, evaluated whether transfection efficiency is associated with gender or age of the cell donors, analysed the influence of cell cycle on transfection and investigated the transfer of therapeutic vascular endothelial growth factor gene (VEGF). hMSCs were isolated from patients with cardiovascular disease aged from 41 to 85 years. Optimization of gene delivery to hMSCs was carried out based on the particle size of the PEI/DNA complexes, N/P ratio of complexes, DNA dosage and cell viability. The highest efficiency with the cell viability near 60% was achieved at N/P ratio 2 and 6.0 μg DNA/cm 2. The average transfection efficiency for all tested samples, middle-age group (<65 years), old-age group (>65 years), female group and male group was 4.32%, 3.85%, 4.52%, 4.14% and 4.38%, respectively. The transfection efficiency did not show any correlation either with the age or the gender of the donors. Statistically, there were two subpopulations in the donors; and transfection efficiency in each subpopulation was linearly related to the cell percentage in S phase. No significant phenotypic differences were observed between these two subpopulations. Furthermore, PEI-mediated therapeutic gene VEGF transfer could significantly enhance the expression level.
2016-11-03T09:29:55Z
2016-11-03T09:29:55Z
2011
Article
Text
Wang, W.; Li, W.; Ou, L.; Flick, Eva; Mark, P. et al.: Polyethylenimine-mediated gene delivery into human bone marrow mesenchymal stem cells from patients. In: Journal of Cellular and Molecular Medicine 15 (2011), Nr. 9, S. 1989-1998. DOI: http://dx.doi.org/10.1111/j.1582-4934.2010.01130.x
http://www.repo.uni-hannover.de/handle/123456789/665
http://dx.doi.org/10.15488/641
eng
Journal of Cellular and Molecular Medicine 15 (2011), Nr. 9
1582-1838
http://dx.doi.org/10.1111/j.1582-4934.2010.01130.x
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Chichester : Wiley-Blackwell Publishing Ltd.
oai:www.repo.uni-hannover.de:123456789/6812022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Simulating circuits with impasse points
Thiessen, Tina
Mathis, Wolfgang
Circuit simulators
Co-ordinate system
Configuration space
Geometric approaches
New approaches
Circuit simulators
Co-ordinate system
Configuration space
Geometric approaches
New approaches
Wave functions
Electric network analysis
Wave functions
SPICE
SPICE
In this paper circuits with impasse points, i.e. with jumps in their configuration space will be analyzed. These non-regularized circuits exhibit a fold in their configuration space, which can lead to difficulties during the simulation with standard circuit simulators like SPICE. The former developed geometric approach to simulate these circuits without regularization will be extended by a detailed discussion of which coordinate system has to be chosen. Furthermore, two new approaches for a numerically efficient calculation of the hit points will be shown.
2016-11-04T10:43:02Z
2016-11-04T10:43:02Z
2013
Article
Text
Thiessen, Tina; Mathis, Wolfgang: Simulating circuits with impasse points. In: Advances in Radio Science 11 (2013), S. 113-118. DOI: http://dx.doi.org/10.5194/ars-11-113-2013
http://www.repo.uni-hannover.de/handle/123456789/681
http://dx.doi.org/10.15488/657
eng
Advances in Radio Science 11 (2013)
1684-9965
http://dx.doi.org/10.5194/ars-11-113-2013
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6852022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
State scaling of continuous-time sigma-delta modulators
Zorn, C.
Brückner, T.
Ortmanns, M.
Mathis, Wolfgang
Amplitude distributions
Continuous-time sigma-delta modulators
Multi-bits
Out-of-band
Quantization levels
Sigma Delta modulator
State-space description
Amplitude distributions
Continuous-time sigma-delta modulators
Multi-bits
Out-of-band
Quantization levels
Sigma Delta modulator
State-space description
Modulators
Continuous time systems
Delta modulation
Delta sigma modulation
Radio receivers
Continuous time systems
Modulators
In this paper, the common method of scaling the feedback coefficients of continuous time sigma delta modulators in order to stabilize the system is enhanced. The presented approach scales the different states of the system instead of the coefficients. The new corresponding coefficients are then calculated from the solution of the state space description. Therewith, it is possible to tune the maximum out-of-band gain directly in continuous time. In addition, the input amplitude distribution between each quantization level of multi bit sigma-delta modulator can be adapted.
2016-11-04T10:43:03Z
2016-11-04T10:43:03Z
2013
Article
Text
Zorn, C.; Brückner, T.; Ortmanns, M.; Mathis, W.: State scaling of continuous-time sigma-delta modulators. In: Advances in Radio Science 11 (2013), S. 119-123. DOI: http://dx.doi.org/10.5194/ars-11-119-2013
http://www.repo.uni-hannover.de/handle/123456789/685
http://dx.doi.org/10.15488/661
eng
Advances in Radio Science 11 (2013)
1684-9965
http://dx.doi.org/10.5194/ars-11-119-2013
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/6962022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:610ddc:570ddc:600
The influence of storage and heat treatment on a magnesium-based implant material: An in vitro and in vivo study
Bracht, Katja
Angrisani, Nina
Seitz, Jan-Marten
Eifler, Rainer
Weizbauer, Andreas
Reifenrath, Janin
Degradable
Aluminum
In vitro
In vivo
Magnesium
Storage
Biocompatibility
Computerized tomography
Corrosion
Corrosion resistance
Energy storage
Heat resistance
Heat treatment
Magnesium alloys
Scanning electron microscopy
Degradable
In-vitro corrosions
In-vivo experiments
Initial stabilities
Simulated body fluids
body fluid
Three point bending
Storage (materials)
alloy
lithium
unclassified drug
animal experiment
animal model
biocompatibility
biomechanics
bone mass
controlled study
corrosion
degradation
energy dispersive spectroscopy
evaluation study
ex vivo study
experimental design
grain
heat treatment
implant
in vitro study
in vivo study
micro-computed tomography
nonhuman
precipitation
priority journal
rabbit model
radiography
scanning electron microscopy
spectroscopy
three point bending
Background: Magnesium alloys are recommended as a potential material for osteosynthesis. It is known that storage-induced property modifications can occur in materials like aluminum. Thus the aim of this study was to analyze the influence of storage durations of up to 48weeks on the biomechanical, structural, and degradation properties of the degradable magnesium alloy LAE442. Methods: Extruded implants (n=104; Ø 2.5mm×25mm) were investigated after storage periods of 0, 12, 24, and 48weeks in three different sub-studies: (I) immediately after the respective storage duration and after an additional (II) 56days of in vitro corrosion in simulated body fluid (SFB), and (III) 48weeks in vivo corrosion in a rabbit model, respectively. In addition, the influence of a T5-heat treatment (206°C for 15h in an argon atmosphere) was tested (n=26; 0week of storage). Evaluation was performed by three-point bending, scanning electron microscopy, radiography, μ-computed tomography, evaluation of the mean grain size, and contrast analysis of precipitations (such as aluminum or lithium). Results: The heat treatment induced a significant reduction in initial stability, and enhanced the corrosion resistance. In vivo experiments showed a good biocompatibility for all implants. During the storage of up to 48weeks, no significant changes occurred in the implant properties. Conclusions: LAE442 implants can be safely used after up to 48weeks of storage.
2016-11-09T08:40:17Z
2016-11-09T08:40:17Z
2015
Article
Text
Bracht, K.; Angrisani, N.; Seitz, J.-M.; Eifler, Rainer; Weizbauer, A. Et al.: The influence of storage and heat treatment on a magnesium-based implant material: An in vitro and in vivo study. In: BioMedical Engineering Online 14 (2015), Nr. 1 , 92. DOI: https://doi.org/10.1186/s12938-015-0091-8
http://www.repo.uni-hannover.de/handle/123456789/696
http://dx.doi.org/10.15488/672
eng
BioMedical Engineering Online 14 (2015), Nr. 1
1475-925X
https://doi.org/10.1186/s12938-015-0091-8
http://creativecommons.org/licenses/by/4.0/
CC BY 4.0 Unported
London : BioMed Central Ltd.
oai:www.repo.uni-hannover.de:123456789/7032022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Transformation of passive electrical networks with distributed PWL-sources using a Model Order Reduction
Ludwig, Stefan
Mathis, Wolfgang
Distributed sources
Distributed systems
Electrical networks
High complexity
Independent sources
Model order reduction
Model reduction
Number of sources
Electrical engineering
Electronics engineering
Complex networks
In modeling of distributed systems with distributed sources large networks with RLC-elements and independent sources arise. This high complexity leads to a high effort in simulations. Therefore model reduction can be used to reduce these networks, preserving the behavior at the observed nodes in the networks. For the reduction of networks with a large number of independent sources only a weak reduction is enabled with standard model reduction techniques. In this paper an efficient reduction of networks with a large number of sources with piece-wise-linear waveforms is presented, using the decomposition of piece-wise-linear functions. With the proposed method a higher reduction of the network and/or a higher accuracy can be achieved with model reduction. The validity and efficiency of the proposed method is shown by reducing a RCI-Grid model.
2016-11-09T10:37:57Z
2016-11-09T10:37:57Z
2009
Article
Text
Ludwig, S.; Mathis, W.: Transformation of passive electrical networks with distributed PWL-sources using a Model Order Reduction. In: Advances in Radio Science 7 (2009), S. 113-118. DOI: http://dx.doi.org/10.5194/ars-7-113-2009
http://www.repo.uni-hannover.de/handle/123456789/703
http://dx.doi.org/10.15488/679
eng
Advances in Radio Science 7 (2009)
1684-9965
http://dx.doi.org/10.5194/ars-7-113-2009
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/7382022-12-02T15:04:50Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Uncertainty contribution of a wind turbine to the electric field of a DVOR antenna as a function of wind direction and rotor position
Sandmann, Sergei
Garbe, Heyno
Antennas
Electric fields
Electromagnetic fields
Navigation systems
Omnidirectional antennas
Wind turbines
Field distortions
Field distribution
Omni-directional radios
Rotor diameter
Rotor position
Uncertainty contributions
Very high frequency
The presence of a wind turbine (WT) has the potential to distort electromagnetic fields emitted by terrestrial radio navigation aids. In this paper especially the field distortion of a Doppler Very High Frequency Omnidirectional Radio Range (DVOR) surveillance navigation system is investigated as a function of wind direction and rotor position. Therefor, the field distribution of a DVOR is simulated in the surrounding of a WT for 104 combinations of the angles of wind direction and rotor position. Furthermore, these calculations are executed for two different rotor diameters and 10 steps of distance between DVOR and WT in the range of 10 km. Based on the calculated data a method to estimate the maximum field distortion is developed. It is shown that the presented method allows to approximate the worst case field distortion with the results of two general simulation setups. Eliminating the need of simulating all possible geometric constellations of the WT this method hereby offers the benefit of significantly reduced simulation effort.
2016-11-24T12:51:14Z
2016-11-24T12:51:14Z
2016
Article
Text
Sandmann, Sergei; Garbe, Heyno: Uncertainty contribution of a wind turbine to the electric field of a DVOR antenna as a function of wind direction and rotor position. In: Advances in Radio Science 14 (2016), S. 17-24. DOI: http://dx.doi.org/10.5194/ars-14-17-2016
http://www.repo.uni-hannover.de/handle/123456789/738
http://dx.doi.org/10.15488/714
eng
Advances in Radio Science 14 (2016)
1684-9965
http://dx.doi.org/10.5194/ars-14-17-2016
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/7392022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Implementation of a digital evaluation platform to analyze bifurcation based nonlinear amplifiers
Feldkord, Sven
Reit, Marco
Mathis, Wolfgang
Amplifiers (electronic)
Audition
Bifurcation (mathematics)
Mammals
Andronov-Hopf bifurcation
Control interfaces
DSP implementation
Evaluation platforms
Flexible framework
Input-output behavior
Neimark-Sacker bifurcation
Nonlinear amplifier
Hop
Recently, nonlinear amplifiers based on the supercritical Andronov–Hopf bifurcation have become a focus of attention, especially in the modeling of the mammalian hearing organ. In general, to gain deeper insights in the input-output behavior, the analysis of bifurcation based amplifiers requires a flexible framework to exchange equations and adjust certain parameters. A DSP implementation is presented which is capable to analyze various amplifier systems. Amplifiers based on the Andronov–Hopf and Neimark–Sacker bifurcations are implemented and compared exemplarily. It is shown that the Neimark–Sacker system remarkably outperforms the Andronov–Hopf amplifier regarding the CPU usage. Nevertheless, both show a similar input-output behavior over a wide parameter range. Combined with an USB-based control interface connected to a PC, the digital framework provides a powerful instrument to analyze bifurcation based amplifiers.
2016-11-24T12:51:15Z
2016-11-24T12:51:15Z
2016
Article
Text
Feldkord, Sven; Reit, Marco; Mathis, Wolfgang: Implementation of a digital evaluation platform to analyze bifurcation based nonlinear amplifiers. In: Advances in Radio Science 14 (2016), S. 47-50. DOI: http://dx.doi.org/10.5194/ars-14-47-2016
http://www.repo.uni-hannover.de/handle/123456789/739
http://dx.doi.org/10.15488/715
eng
Advances in Radio Science 14 (2016)
1684-9965
http://dx.doi.org/10.5194/ars-14-47-2016
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/7402022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Adapting the range of validity for the Carleman linearization
Weber, Harry
Mathis, Wolfgang
Differential equations
Linear systems
Linearization
Nonlinear equations
Ordinary differential equations
Polynomials
Carleman linearization
Finite dimensional
Infinite-dimensional linear systems
Infinite-dimensional system
In this contribution, the limitations of the Carleman linearization approach are presented and discussed. The Carleman linearization transforms an ordinary nonlinear differential equation into an infinite system of linear differential equations. In order to transform the nonlinear differential equation, orthogonal polynomials which represent solutions of a Sturm–Liouville problem are used as basis. The determination of the time derivate of this basis yields an infinite dimensional linear system that depends on the considered nonlinear differential equation. The infinite linear system has the same properties as the nonlinear differential equation such as limit cycles or chaotic behavior. In general, the infinite dimensional linear system cannot be solved. Therefore, the infinite dimensional linear system has to be approximated by a finite dimensional linear system. Due to limitation of dimension the solution of the finite dimensional linear system does not represent the global behavior of the nonlinear differential equation. In fact, the accuracy of the approximation depends on the considered nonlinear system and the initial value. The idea of this contribution is to adapt the range of validity for the Carleman linearization in order to increase the accuracy of the approximation for different ranges of initial values. Instead of truncating the infinite dimensional system after a certain order a Taylor series approach is used to approximate the behavior of the nonlinear differential equation about different equilibrium points. Thus, the adapted finite linear system describes the local behavior of the solution of the nonlinear differential equation.
2016-11-24T12:51:15Z
2016-11-24T12:51:15Z
2016
Article
Text
Weber, Harry; Mathis, Wolfgang: Adapting the range of validity for the Carleman linearization. In: Advances in Radio Science 14 (2016), S. 51-54. DOI: http://dx.doi.org/10.5194/ars-14-51-2016
http://www.repo.uni-hannover.de/handle/123456789/740
http://dx.doi.org/10.15488/716
eng
Advances in Radio Science 14 (2016)
1684-9965
http://dx.doi.org/10.5194/ars-14-51-2016
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/7412022-12-02T15:04:50Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Risk analysis with a fuzzy-logic approach of a complex installation
Peikert, Tim
Garbe, Heyno
Potthast, S.
Bayesian networks
Complex networks
Computer circuits
Electromagnetic pulse
Fault tree analysis
Linguistics
Membership functions
Reconfigurable hardware
Risk analysis
Risk assessment
Uncertainty analysis
Electromagnetic environments
This paper introduces a procedural method based on fuzzy logic to analyze systematic the risk of an electronic system in an intentional electromagnetic environment (IEME). The method analyzes the susceptibility of a complex electronic installation with respect to intentional electromagnetic interference (IEMI). It combines the advantages of well-known techniques as fault tree analysis (FTA), electromagnetic topology (EMT) and Bayesian networks (BN) and extends the techniques with an approach to handle uncertainty. This approach uses fuzzy sets, membership functions and fuzzy logic to handle the uncertainty with probability functions and linguistic terms. The linguistic terms add to the risk analysis the knowledge from experts of the investigated system or environment.
2016-11-24T12:51:15Z
2016-11-24T12:51:15Z
2016
Article
Text
Peikert, Tim; Garbe, Heyno; Potthast, S.: Risk analysis with a fuzzy-logic approach of a complex installation. In: Advances in Radio Science 14 (2016), S. 91-96. DOI: http://dx.doi.org/10.5194/ars-14-91-2016
http://www.repo.uni-hannover.de/handle/123456789/741
http://dx.doi.org/10.15488/717
eng
Advances in Radio Science 14 (2016)
1684-9965
http://dx.doi.org/10.5194/ars-14-91-2016
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/7422022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Extended measurement setup for transient TEM waveguide characterization
Briest, Niklas
Garbe, Heyno
Potthast, S.
Correlation methods
Frequency bands
Field homogeneity
Frequency domains
Higher-order modes
Measurement setup
Pearson correlation coefficients
Propagation direction
Transmission characteristics
Uncertainty contributions
Frequency domain analysis
This paper discusses a field measurement method, based on a two-antenna setup, to qualify the transmission of transient signals inside a GTEM cell. The transmission characteristic of the GTEM1250 is evaluated by the Pearson correlation coefficient (PCC) and is presented with a heatmap. Due to deviations of the uncertainty contribution of the field homogeneity, the frequency band around 100 MHz is evaluated and its effect to the PCC is discussed. Therefore, a comparable narrowband transient signal, a damped sinusoidal (DS) is used. Furthermore, a detailed discussion focussing on nonlinear and distorting effects of the GTEM1250 is performed. The measurements in time domain (TD) identify comparable high secondary E-field components in the propagation direction, which are characteristic for higher order modes. Based on the same setup, another measurement is performed in frequency domain (FD) and relates the phase response of the GTEM cell to the above mentioned effects. According to the measured phase response the propagation time is discussed to investigate the distorting effects caused by higher order modes.
2016-11-24T12:51:15Z
2016-11-24T12:51:15Z
2016
Article
Text
Briest, Niklas; Garbe, Heyno; Potthast, S.: Extended measurement setup for transient TEM waveguide characterization. In: Advances in Radio Science 14 (2016), S 115-120. DOI: http://dx.doi.org/10.5194/ars-14-115-2016
http://www.repo.uni-hannover.de/handle/123456789/742
http://dx.doi.org/10.15488/718
eng
Advances in Radio Science 14 (2016)
1684-9965
http://dx.doi.org/10.5194/ars-14-115-2016
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/7442022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Modeling and simulation aspects of AC machines
Popp, Michael
Laza, Patrick
Mathis, Wolfgang
AC Machines
MATLAB
ODE and DAE Solvers
State Space Modeling
Differential equations
Equations of state
MATLAB
Ordinary differential equations
State space methods
AC machine
Algebraic constraints
Efficient simulation
Model and simulation
ODE and DAE Solvers
State - space models
State space representation
In the field of power and drive systems, electrical AC machines are mostly modeled using a set of explicit ordinary differential equations in a state space representation. It is shown, that by using other equation types for simulation, algebraic constraints arising from aggregating several machines to a more complex system can directly be considered. The effects of different model variants on numerical ODE/DAE solvers are investigated in the focus of this work in order perform efficient simulations of larger systems possessing electrical AC machines.
2016-11-24T12:51:16Z
2016-11-24T12:51:16Z
2016
Article
Text
Popp, Michael; Laza, Patrick; Mathis, Wolfgang: Modeling and simulation aspects of AC machines. In: Archives of Electrical Engineering 65 (2016), Nr. 2, S. 315-326. DOI: http://dx.doi.org/10.1515/aee-2016-0023
http://www.repo.uni-hannover.de/handle/123456789/744
http://dx.doi.org/10.15488/720
eng
Archives of Electrical Engineering 65 (2016), Nr. 2
0004-0746
http://dx.doi.org/10.1515/aee-2016-0023
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Warsaw : De Gruyter Open Ltd
oai:www.repo.uni-hannover.de:123456789/7452022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Ambiguities in input-output behavior of driven nonlinear systems close to bifurcation
Reit, Marco
Berens, Michael
Mathis, Wolfgang
ambiguities
Andronov-Hopf
bifurcation
nonlinear amplifier
Amplifiers (electronic)
Audition
Bifurcation (mathematics)
Mammals
ambiguities
Andronov-Hopf
Andronov-Hopf bifurcation
Input-output characteristics
Mathematical formulation
Nonlinear amplifier
Sinusoidal input signals
Technical applications
Since the so-called Hopf-type amplifier has become an established element in the modeling of the mammalian hearing organ, it also gets attention in the design of nonlinear amplifiers for technical applications. Due to its pure sinusoidal response to a sinusoidal input signal, the amplifier based on the normal form of the Andronov-Hopf bifurcation is a peculiar exception of nonlinear amplifiers. This feature allows an exact mathematical formulation of the input-output characteristic and thus deeper insights of the nonlinear behavior. Aside from the Hopf-type amplifier we investigate an extension of the Hopf system with focus on ambiguities, especially the separation of solution sets, and double hysteresis behavior in the input-output characteristic. Our results are validated by a DSP implementation.
2016-11-24T12:51:17Z
2016-11-24T12:51:17Z
2016
Article
Text
Reit, Marco; Berens, Michael; Mathis, Wolfgang: Ambiguities in input-output behavior of driven nonlinear systems close to bifurcation. In: Archives of Electrical Engineering 65 (2016), Nr. 2, S. 337-347. DOI: http://dx.doi.org/10.1515/aee-2016-0025
http://www.repo.uni-hannover.de/handle/123456789/745
http://dx.doi.org/10.15488/721
eng
Archives of Electrical Engineering 65 (2016), Nr. 2
0004-0746
http://dx.doi.org/10.1515/aee-2016-0025
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Warsaw : De Gruyter Open Ltd
oai:www.repo.uni-hannover.de:123456789/7512022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
A raspberry pi based portable endoscopic 3D measurement system
Schlobohm, Jochen
Pösch, Andreas
Reithmeier, Eduard
Endoscopy
Fringe projection
Measurement
Optics
Triangulation
Endoscopy
Measurements
Optical data processing
Optics
Projection systems
Triangulation
3-D measurement systems
Contactless operation
Fringe projection
Fringe projection system
Geometry measurements
Measurement system
Optical measurement system
Geometry measurements are very important to monitor a machine part’s health and performance. Optical measurement system have several advantages for the acquisition of a parts geometry: measurement speed, precision, point density and contactless operation. Measuring parts inside of assembled machines is also desirable to keep maintenance cost low. The Raspberry Pi is a small and cost efficient computer that creates new opportunities for compact measurement systems. We have developed a fringe projection system which is capable of measuring in very limited space. A Raspberry Pi 2 is used to generate the projection patterns, acquire the image and reconstruct the geometry. Together with a small LED projector, the measurement system is small and easy to handle. It consists of off-the-shelf products which are nonetheless capable of measuring with an uncertainty of less than 100 μ m
2016-11-25T08:33:28Z
2016-11-25T08:33:28Z
2016
Article
Text
Schlobohm, Jochen; Pösch, Andreas; Reithmeier, Eduard: A raspberry pi based portable endoscopic 3D measurement system. In: Electronics (Switzerland) 5 (2016), Nr. 3, 43. DOI: http://dx.doi.org/10.3390/electronics5030043
http://www.repo.uni-hannover.de/handle/123456789/751
http://dx.doi.org/10.15488/727
eng
Electronics (Switzerland) 5 (2016), Nr. 3
2079-9292
http://dx.doi.org/10.3390/electronics5030043
https://creativecommons.org/licenses/by-nc-sa/4.0/
CC BY-NC-SA 4.0 Unported
Basel : MDPI AG
oai:www.repo.uni-hannover.de:123456789/7662022-12-02T15:03:41Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Evaluation of a Novel Radar Based Scanning Method
Fritsche, Paul
Wagner, Bernardo
Mapping
Robotics
Scanning
Laser scanner
Mapping and localization
Mobile robotic
Monostatic radar
Multiple sensors
Research groups
Scanning methods
Ultra wideband radars
Radar
The following paper introduces a novel scanning method for mapping and localization purposes in mobile robotics. Our method is based on a rotating monostatic radar network, which determines the positions of objects around the scanner via a continuously running lateration algorithm. The estimation of surfaces with ultrawideband radar networks has been studied experimentally in lab environments, especially with lateration, envelopes of spheres, and SEABED algorithms. But we do not see a link to the field of mapping and localization of mobile robots, where laser scanners are dominating. Indeed, only few research groups use radars for mapping and localization, but their applied sensor principle is based on a rotating focused radar beam. Consequently, only 2D radar scanners are known inside the robotic world and methods for 3D scanning with radars need to be investigated. This paper will derive the theoretical background of the sensor principle, which is based on a radar network on a rotating joint, and discuss its erroneous influences. We were performing first scans of standard geometries and deriving a model in order to compare theoretical and experimental measurement results. Furthermore, we present first mapping approaches and a simulation of a scanner with multiple sensors.
2016-11-29T09:28:09Z
2016-11-29T09:28:09Z
2016
Article
Text
Fritsche, Paul; Wagner, Bernardo: Evaluation of a Novel Radar Based Scanning Method. In: Journal of Sensors 2016 (2016), 6952075. DOI: http://dx.doi.org/10.1155/2016/6952075
http://www.repo.uni-hannover.de/handle/123456789/766
http://dx.doi.org/10.15488/742
eng
Journal of Sensors 2016 (2016)
1687-725X
http://dx.doi.org/10.1155/2016/6952075
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
New York, NY : Hindawi Publishing Corporation
oai:www.repo.uni-hannover.de:123456789/8032022-12-02T15:09:32Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Single image geometry inspection using inverse endoscopic fringe projection
Matthias, Steffen
Ohrt, Christoph
Pösch, Andreas
Kästner, Markus
Reithmeier, Eduard
Endoscopy
Fiberscopy
Inverse fringe projection
Sheet bulk metal forming
Fringe projection is an important technology for the measurement of free form elements in several application fields. It can be applied to measure geometry elements smaller than one millimeter. In combination with deviation analysis algorithms, errors in fabrication lines can be found promptly to minimize rejections. However, some fields cannot be covered by the classical fringe projection approach. Due to shadowing, filigree form elements on narrow or internal carrier geometries cannot be captured. To overcome this limitation, a fiberscopic micro fringe projection sensor was developed [1]. The new device is capable of resolutions of less than 15 m with uncertainties of about 35 m in a workspace of 3x3x3 mm. Using standard phase measurement techniques, such as Gray-code and cos-patterns, measurement times of over a second are too long for in-situ operation. The following work will introduce an approach of applying a new single image measuring method to the fiberscopic system, based on inverse fringe projection [2]. The fiberscopic fringe projection system employs a laser light source in combination with a digital micro-mirror device (DMD) to generate fringe patterns. Fiber optical image bundles (FOIB) are used as well as gradient-index lenses to project these patterns on the specimen. This advanced optical system creates high demands on the pattern generation algorithms to generate exact inverse patterns for arbitrary CAD-modelled geometries. Approaches of optical simulations of the complex beam path and the drawbacks of the limited resolutions of the FOIBs are discussed. Early results of inverse pattern simulations using a ray tracing approach of a pinhole system model are presented.
2016-11-30T08:58:08Z
2016-11-30T08:58:08Z
2015
Article
Text
Matthias, S.; Ohrt, C.; Pösch, A.; Kästner, M.; Reithmeier, E.: Single image geometry inspection using inverse endoscopic fringe projection. In: Acta IMEKO 4 (2015), Nr. 2, S. 4-9
http://www.repo.uni-hannover.de/handle/123456789/803
http://dx.doi.org/10.15488/779
eng
Acta IMEKO 4 (2015), Nr. 2
Acta IMEKO
0237-028X
http://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Budapest : International Measurement Confederation (IMEKO)
oai:www.repo.uni-hannover.de:123456789/8062022-12-02T15:03:40Zcom_123456789_1col_123456789_3doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Probabilistic fatigue analysis of jacket support structures for offshore wind turbines exemplified on tubular joints
Kelma, Sebastian
Schaumann, Peter
fatigue design
generalized Pareto distribution
jacket substructure
offshore wind energy
peak-over-threshold method
probabilistic analysis
tubular joints
Design
Fatigue damage
Joints (structural components)
Maximum likelihood
Maximum likelihood estimation
Offshore wind turbines
Pareto principle
Structural design
Time series
Time series analysis
Wind power
Wind turbines
Fatigue design
Generalized Pareto Distributions
jacket substructure
Off-shore wind energy
Peak over threshold method
Probabilistic analysis
Tubular joints
Probability distributions
The design of offshore wind turbines is usually based on the semi-probabilistic safety concept. Using probabilistic methods, the aim is to find an advanced structural design of OWTs in order to improve safety and reduce costs. The probabilistic design is exemplified on tubular joints of a jacket substructure. Loads and resistance are considered by their respective probability distributions. Time series of loads are generated by fully-coupled numerical simulation of the offshore wind turbine. Especially the very high stress ranges that rarely occur during a period with constant conditions are decisive for the fatigue design. The peak-over-threshold method is applied to find the probability distribution of the very high stress ranges. The method of maximum-likelihood estimation is used to determine the parameters of the underlying generalized Pareto distribution. Further analysis shows that especially the number of the very high stress ranges, scattering for different time series, has a significant impact on the resulting fatigue damage.
2016-11-30T08:58:10Z
2016-11-30T08:58:10Z
2015
Article
Text
Kelma, S.; Schaumann, P.: Probabilistic fatigue analysis of jacket support structures for offshore wind turbines exemplified on tubular joints. In: Energy Procedia 80 (2015), S. 151-158. DOI: 10.1016/j.egypro.2015.11.417
http://www.repo.uni-hannover.de/handle/123456789/806
https://doi.org/10.15488/782
eng
Energy Procedia 80 (2015)
Energy Procedia
1876-6102
10.1016/j.egypro.2015.11.417
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8072022-12-02T15:17:13Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Numerical Modeling of c-Si PV Modules by Coupling the Semiconductor with the Thermal Conduction, Convection and Radiation Equations
Vogt, Malte R.
Holst, Hendrik
Winter, Matthias
Brendel, Rolf
Altermatt, Pietro P.
dielectric rear side mirror
Ray tracing
simlation
solar module temperature;field measurements
thermal solar module behaviour
Finite element method
Heat convection
Heat radiation
Mirrors
Photovoltaic cells
Ray tracing
Semiconducting silicon
Silicon nitride
Solar cells
Electrical power output
Field measurement
Finite element method simulation
Operating temperature
Rear side
Semiconductor equations
simlation
Thermal solar
Solar cell arrays
Commonly, the thermal behavior of solar cell modules is calculated with analytical approaches using non wavelength-dependent optical data. Here, we employ ray tracing of entire solar modules at wavelengths of 300-2500 nm to calculate heat sources. Subsequently, finite element method (FEM) simulations are used to solve the semiconductor equations coupled with the thermal conduction, thermal convection, and thermal radiation equations. The implemented model is validated with measurements from an outdoor test over the period of an entire year. Our ray tracing analysis of different solar modules under the AM.15G spectrum shows that, for a standard module about 18.9% of the sun's intensity becomes parasitically absorbed. A loss analysis shows that the biggest parasitic heat source is the cell's full-area rear side metallization. We hence propose the use of a SiNx layer as rear side mirror to reduce the parasitic absorption to 11.7%. This change can lead to a 3.2 °C lower module operating temperature, which results in an about 5 W higher electrical power output when considering a typical 260 W module.
2016-11-30T08:58:10Z
2016-11-30T08:58:10Z
2015
Article
Text
Vogt, M.R.; Holst, H.; Winter, M.; Brendel, R.; Altermatt, P.P.: Numerical Modeling of c-Si PV Modules by Coupling the Semiconductor with the Thermal Conduction, Convection and Radiation Equations. In: Energy Procedia 77 (2015), S. 215-224. DOI: https://doi.org/10.1016/j.egypro.2015.07.030
http://www.repo.uni-hannover.de/handle/123456789/807
http://dx.doi.org/10.15488/783
eng
Energy Procedia 77 (2015)
Energy Procedia
1876-6102
10.1016/j.egypro.2015.07.030
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8082022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Assessing the Device-performance Impacts of Structural Defects with TCAD Modeling
Needleman, David Berney
Wagner, Hannes
Altermatt, Pietro P.
Buonassisi, Tonio
dislocation
grain boundary
modeling
photovoltaics
silicon
Solar cell
Architecture
Calculations
Dislocations (crystals)
Electric currents
Electronic design automation
Grain boundaries
Heterojunctions
Impurities
Inverse problems
Models
Silicon
Solar cells
Solar power generation
Device architectures
Electron-beam-induced current
First-principles calculation
Heterojunction with intrinsic thin layers
Multicrystalline silicon (mc-Si)
Numerical simulation studies
Photovoltaics
Solar cell performance
Defects
Advanced solar cell architectures like passivated emitter and rear (PERC) and heterojunction with intrinsic thin layer (HIT) are increasingly sensitive to bulk recombination. Present device models consider homogeneous bulk lifetime, which does not accurately reflect the effects of heterogeneously distributed defects. To determine the efficiency potential of multicrystalline silicon (mc-Si) in next-generation architectures, we present a higher-dimensional numerical simulation study of the impacts of structural defects on solar cell performance. We simulate these defects as an interfacial density of traps with a single mid-gap energy level using Shockley-Read-Hall (SRH) statistics. To account for enhanced recombination at the structural defects, we apply a linear scaling to the majority-carrier capture cross-section and scale the minority-carrier capture cross-section with the inverse of the line density of traps. At 300 K, our simulations of carrier occupation and recombination rate match literature electron-beam-induced current (EBIC) data and first-principles calculations of carrier capture, emission, and recombination for all the energy levels associated with dislocations decorated with metal impurities. We implement our model in Sentaurus Device, determining the losses across different device architectures for varying impurity decoration of grain boundaries.
2016-11-30T08:58:10Z
2016-11-30T08:58:10Z
2015
Article
Text
Needleman, D.B.; Wagner, H.; Altermatt, P.P.; Buonassisi, T.: Assessing the Device-performance Impacts of Structural Defects with TCAD Modeling. In: Energy Procedia 77 (2015), S. 8-14. DOI: https://doi.org/10.1016/j.egypro.2015.07.003
http://www.repo.uni-hannover.de/handle/123456789/808
http://dx.doi.org/10.15488/784
eng
Energy Procedia 77 (2015)
Energy Procedia
1876-6102
10.1016/j.egypro.2015.07.003
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8102022-12-02T15:17:13Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Organic-silicon Solar Cells Exceeding 20% Efficiency
Zielke, Dimitri
Niehaves, Claudia
Lövenich, Wilfried
Elschner, Andreas
Hörteis, Matthias
Schmidt, Jan
Organic-silicon
PEDOT:PSS
solar cell
surface passivation
Carrier lifetime
Conducting polymers
Efficiency
Electric resistance measurement
Heterojunctions
Open circuit voltage
Passivation
Quantum theory
Silicon
Silicon wafers
Solar cells
Surface treatment
3 ,4-ethylenedioxythiophene
Carrier lifetime measurements
Internal quantum efficiency
Numerical device simulation
PEDOT:PSS
Saturation current densities
Sheet resistance measurements
Surface passivation
Silicon solar cells
Aftera briefreview of therecent evolvement oforganic-silicon heterojunction solar cells,we present here our latest measurements of the saturation current densities (J0) and contact resistances (RC) of crystalline silicon (c-Si)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) junctions. We determine the J0values by means of contactless carrier lifetime measurements and theRCvalues by comparing sheet resistance measurements with numerical device simulations of the corresponding test structure. Application of an adopted PEDOT:PSS blend and an optimized silicon surface treatmentresults in a minimalJ0value of46 fA/cm2, limiting the solar cell open-circuit voltage to Voc-limit=708 mV, and a minimal RCvalue of 100 m?cm2. Our optimized silicon surface pre-treatment in combination with the adapted PEDOT:PSS blendare successfully implemented into a cell process with the PEDOT:PSS layer located at the rear surface (the so-called 'BackPEDOT concept'). Record-high efficiencies of 18.3% and of 20.6% are achieved onn-type silicon and onp-type silicon wafers, respectively. Finally, we compare the internal quantum efficiency of our champion BackPEDOT solar cell with that of a state-of-the-art Al2O3/SiNx-passivated PERC solar cell.
2016-11-30T08:58:10Z
2016-11-30T08:58:10Z
2015
Article
Text
Zielke, D.; Niehaves, C.; Lövenich, W.; Elschner, A.; Hörteis, M.; Schmidt, J.: Organic-silicon Solar Cells Exceeding 20% Efficiency. In: Energy Procedia 77 (2015), S. 331-339. DOI: https://doi.org/10.1016/j.egypro.2015.07.047
http://www.repo.uni-hannover.de/handle/123456789/810
http://dx.doi.org/10.15488/786
eng
Energy Procedia 77 (2015)
Energy Procedia
1876-6102
10.1016/j.egypro.2015.07.047
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8462022-12-02T15:09:32Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Simulation-based planning of production capacity through integrative roadmapping in the wind turbine industry
Denkena, Berend
Winter, F.
Decision making
Planning
Simulation
Decision making
Gears
Manufacture
Planning
Wind turbines
Interdisciplinary planning
Manufacturing technologies
Planning phase
Production capacity
Production strategy
Simulation
Software implementation
Wind turbine industry
Turbomachine blades
The development and effective implementation of a production strategy requires an interdisciplinary planning of products, manufacturing technologies and factory concepts. The integrative roadmapping allows the merging of these planning areas and takes into account the occurring interactions. This article shows the concept and software implementation of the integrative roadmapping for a systematic creation of roadmaps using the example of rotor blade production in the wind turbine industry. To reduce planning time and cost the workflow in the rotor blade production has been transferred to a material flow simulation to estimate the mutual impact on the production capacity by product, technology and factory within the planning phase.
2016-12-16T07:23:11Z
2016-12-16T07:23:11Z
2015
Article
Text
Denkena, B.; Winter, F.: Simulation-based planning of production capacity through integrative roadmapping in the wind turbine industry. In: Procedia CIRP 33 (2015), S. 105-110. DOI: https://doi.org/10.1016/j.procir.2015.06.020
http://www.repo.uni-hannover.de/handle/123456789/846
http://dx.doi.org/10.15488/822
eng
Procedia CIRP 33 (2015)
22128271
https://doi.org/10.1016/j.procir.2015.06.020
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8482022-12-02T15:06:07Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Investigation of the skive hobbing process by applying a dexel-based cutting simulation
Böß, Volker
Denkena, Berend
Henning, S.
cutting simulation
dexel-based approach
skive hobbing
Life cycle
Machining
Analytical description
Cartesian coordinate
Cutting simulation
dexel-based approach
Hobbing
Position dependents
Process Modeling
Undeformed chip thickness
Gears
In this paper, a novel approach for cutting simulation of skive hobbing is presented. Skive hobbing is a process applied for finishing of already hardened gears. The process is characterized by varying tool engagements and very small chip thicknesses. The paper describes the process-modeling and the analysis of the workpiece-tool contact. For efficient modeling, a novel dexel-based method is presented for the description of a gear segment with discretized stock allowance. Characteristic of the method is an analytical description of the target workpiece contour which allows to describe points of the surface by Cartesian coordinates on the winding off. Dexel are oriented orthogonal to the surface of the final workpiece contour. The initial lengths of the dexel describe the stock allowance. By cutting these dexel with a tool, a time- and position-dependent prediction of material removal values, e.g. width of undeformed chip or undeformed chip thickness, is possible. Selected results are presented and interpreted.
2016-12-16T07:23:11Z
2016-12-16T07:23:11Z
2015
Article
Text
Böß, V.; Denkena, B.; Henning, S.: Investigation of the skive hobbing process by applying a dexel-based cutting simulation. In: Procedia CIRP 37 (2015), S. 182-187. DOI: https://doi.org/10.1016/j.procir.2015.08.062
http://www.repo.uni-hannover.de/handle/123456789/848
http://dx.doi.org/10.15488/824
eng
Procedia CIRP 37 (2015)
22128271
https://doi.org/10.1016/j.procir.2015.08.062
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8492022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessddc:330status-type:publishedVersionddc:600
Enabling an Industrial Robot for Metal Cutting Operations
Denkena, Berend
Lepper, Thomas
compensation
force measurement
machining robot
process monitoring
Aerospace industry
Compensation (personnel)
Cost effectiveness
Cutting
Force measurement
Industrial robots
Process monitoring
Robots
Cost effective
Cutting forces
Cutting operations
Machining robot
Measurement device
Positioning error
Static deflections
Tool deflection
Metal cutting
This paper focuses on a cost-effective manufacturing of large frame parts for aerospace industries with an industrial robot. The main challenge is the low stiffness of a serial kinematic, resulting in positioning errors due to gravity and cutting forces. Therefore, an approach is presented to optimize positioning of a robot by compensation of tool deflection. A static deflection model of the robot is built up to calculate the deflection caused by forces acting on the spindle. To detect these forces a suitable measurement device is presented. This sensing spindle holder is calibrated to detect cutting forces.
2016-12-16T07:23:12Z
2016-12-16T07:23:12Z
2015
Article
Text
Denkena, B.; Lepper, T.: Enabling an Industrial Robot for Metal Cutting Operations. In: Procedia CIRP 35 (2015), S. 79-84. DOI: https://doi.org/10.1016/j.procir.2015.08.100
http://www.repo.uni-hannover.de/handle/123456789/849
http://dx.doi.org/10.15488/825
eng
Procedia CIRP 35 (2015)
22128271
https://doi.org/10.1016/j.procir.2015.08.100
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8542022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Influence of the cutting tool compliance on the workpiece surface shape in face milling of workpiece compounds
Denkena, Berend
Hasselberg, E.
Milling
Workpiece compound
Frequency response
Lunar surface analysis
Machining centers
Milling (machining)
Surface analysis
Surface roughness
Cutting edges
Cutting forces
Cutting properties
Frequency response analysis
Machining test
New approaches
Shape deviations
Workpiece
Cutting tools
A currently common method to design high-performance workpieces is to combine two or more materials to one compound. In this way, workpieces can be composed of the most qualified materials according to local loads. When machining high-performance workpiece compounds high quality requirements concerning the accuracy of dimension and shape as well as surface roughness must be fulfilled. However, in case of parallel machining, where the cutting edge moves from one material into the other within one cutting tool revolution, unequal cutting properties have a significant negative influence on tool wear and surface quality. Shape deviations of the surface occur, which are not detected when machining the single materials. The four most significant shape deviations that affect the workpiece quality are the material height deviation, transition deviation at the material joint as well as surface roughness deviation. This paper contains new approaches on the prediction of the surface shape that is generated by a face milling process. The focus is on the transition deviation at the material joint. It arises from a force impulse that is applied on the cutting tool and creates a wavy surface on the workpiece. This shape is predicted via cutting force prediction as well as frequency response analysis of the cutting tool and workpiece in relation to different tool holders. Furthermore, deviations between calculated surface shapes and measured surface shapes subsequent to machining tests are evaluated.
2016-12-16T07:50:11Z
2016-12-16T07:50:11Z
2015
Article
Text
Denkena, B.; Hasselberg, E.: Influence of the cutting tool compliance on the workpiece surface shape in face milling of workpiece compounds. In: Procedia CIRP 31 (2015), S. 7-12. DOI: https://doi.org/10.1016/j.procir.2015.03.074
http://www.repo.uni-hannover.de/handle/123456789/854
http://dx.doi.org/10.15488/830
eng
Procedia CIRP 31 (2015)
22128271
https://doi.org/10.1016/j.procir.2015.03.074
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8602022-12-02T15:06:07Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Prediction of temperature induced shape deviations in dry milling
Denkena, Berend
Schmidt, A.
Maaß, P.
Niederwestberg, D.
Niebuhr, C.
Vehmeyer, J.
Deformation
Dry milling
Finite element method (FEM)
Forecasting
Heat flux
Machining centers
Milling (machining)
Geometric modelling
Material removal
Simulation
Thermal error
Finite element method
In this paper a model for a simulation based prediction of temperature induced shape deviations in dry milling is presented. A closed loop between Boolean material removal, process forces, heat flux and thermoelastic deformation is established. Therefore, an efficient dexel based machining simulation is extended by a contact zone analysis to model the local workpiece load. Based on the computed contact zone the cutting forces and heat flux are calculated using a semi-empirical process model. For a detailed consideration of the loads they are discretized and localized on the dexel-represented workpiece surface. A projection of the localized workpiece loads on the boundary of the finite element domain, taking into account the Boolean material removal during the process, allows the calculation of the current temperature and deformation of the workpiece. By transforming these thermomechanical characteristics back to the dexel-model a consideration in the machining simulation is possible. An extended contact zone analysis is developed for the prediction of the localized shape deviations. Finally, the results of the simulation are compared with measured data. The comparison shows that workpiece temperatures, workpiece deformation and shape deviations in different workpiece areas are predicted accurately.
2016-12-16T07:50:14Z
2016-12-16T07:50:14Z
2015
Article
Text
Denkena, B.; Schmidt, A.; Maaß, P.; Niederwestberg, D.; Niebuhr, C.; et al.: Prediction of temperature induced shape deviations in dry milling. In: Procedia CIRP 31 (2015), S. 340-345. DOI: https://doi.org/10.1016/j.procir.2015.03.072
http://www.repo.uni-hannover.de/handle/123456789/860
http://dx.doi.org/10.15488/836
eng
Procedia CIRP 31 (2015)
22128271
https://doi.org/10.1016/j.procir.2015.03.072
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8612022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Ultrafast Feed Drilling of Carbon Fiber-Reinforced Thermoplastics
Kakinuma, Yasuhiro
Ishida, Takuki
Koike, Ryo
Klemme, Heiner
Denkena, Berend
Aoyama, Tojiro
CFRTP
Drilling
High-performance drilling
Aerospace industry
Fiber reinforced plastics
Reinforcement
Thermoplastics
Carbon fiber reinforced
Dry condition
Feasibility studies
Feed-rates
Rotational drilling
Through-hole drilling
Ultra-fast
Reinforced plastics
Carbon fiber-reinforced thermoplastics (CFRTP) are just beginning to be utilized for various applications such as aerospace, automobiles, and sporting goods in place of CFRPs, and the demand for through-hole drilling of CFRTPs is increasing. In this study, the machinability in drilling of CFRTPs under various conditions was experimentally analyzed in terms of the material properties, and a feasibility study of ultrafast feed drilling was conducted. The results showed that delamination at the outlet surface can be significantly suppressed during high rotational drilling when the feed rate is set to more than 3000 mm/min. By providing appropriate drilling conditions to prevent polymers in CFRTPs from softening, ultra-fast drilling of CFRTPs was successfully achieved under dry conditions.
2016-12-16T07:50:14Z
2016-12-16T07:50:14Z
2015
Article
Text
Kakinuma, Y.; Ishida, T.; Koike, R.; Klemme, H.; Denkena, B.; et al.: Ultrafast Feed Drilling of Carbon Fiber-Reinforced Thermoplastics. In: Procedia CIRP 35 (2015), S. 91-95. DOI: https://doi.org/10.1016/j.procir.2015.08.074
http://www.repo.uni-hannover.de/handle/123456789/861
http://dx.doi.org/10.15488/837
eng
Procedia CIRP 35 (2015)
22128271
https://doi.org/10.1016/j.procir.2015.08.074
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/8872022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Cyclic degradation of titanium-tantalum high-temperature shape memory alloys - The role of dislocation activity and chemical decomposition
Niendorf, T.
Krooß, P.
Somsen, C.
Rynko, R.
Paulsen, A.
Batyrshina, E.
Frenzel, J.
Eggeler, Gunther
Maier, Hans Jürgen
decomposition
Microstructure
phase transformation
training
ω-phase
Alloys
Grain boundaries
Shape memory effect
Tantalum
Titanium
Chemical decomposition
Cyclic degradations
Dislocation activity
Elevated temperature
High temperature
High temperature shape memory alloy
Structural degradation
Thermo-mechanical loading
Titanium-tantalum shape memory alloys (SMAs) are promising candidates for actuator applications at elevated temperatures. They may even succeed in substituting ternary nickel-titanium high temperature SMAs, which are either extremely expensive or difficult to form. However, titanium-tantalum alloys show rapid functional and structural degradation under cyclic thermo-mechanical loading. The current work reveals that degradation is not only governed by the evolution of the ω-phase. Dislocation processes and chemical decomposition of the matrix at grain boundaries also play a major role.
2016-12-16T09:39:07Z
2016-12-16T09:39:07Z
2015
Article
Text
Niendorf, T.; Krooß, P.; Somsen, C.; Rynko, R.; Paulsen, A. et al.: Cyclic degradation of titanium-tantalum high-temperature shape memory alloys - The role of dislocation activity and chemical decomposition. In: Functional Materials Letters 8 (2015), Nr. 6, 1550062. DOI: https://doi.org/10.1142/S1793604715500629
http://www.repo.uni-hannover.de/handle/123456789/887
http://dx.doi.org/10.15488/863
eng
Functional Materials Letters 8 (2015), Nr. 6
17936047
https://doi.org/10.1142/S1793604715500629
https://creativecommons.org/licenses/by/4.0/
CC BY 4.0 Unported
Singapore : World Scientific Publishing Co. Pte Ltd
oai:www.repo.uni-hannover.de:123456789/8892022-12-02T15:06:07Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Electromagnetic levitation guide for use in ultra-precision milling centres
Denkena, Berend
Dahlmann, Dominik
Krueger, R.
machine tool
ultra-precision machining
Electromagnetic propulsion
Levitation melting
Life cycle
Milling (machining)
Precision engineering
Productivity
Cutting parameters
Deterministic methods
Electromagnetic levitation
Engineering process
Magnetic guide
Precision machines
Ultra precision millings
Ultraprecision machining
Machine tools
Today's machine tools for ultra-precision machining are generally characterised by low productivity. Above all, practical cutting parameters are limited due to uncontrollable disturbance forces. Therefore, it is necessary to pursue the qualification of new technologies to overcome current limitations in productivity. In this paper, an approach for the design of a novel electromagnetic levitation guide for use in ultra-precision milling centres is presented. Design and arrangement of the magnetic guide's components are considered with regard to requirements and design principles of precision machines. Deterministic methods are utilised throughout the engineering process to ensure high stiffness and high dynamics. As a result, a concept for the electromagnetic ultra-precision linear guide is derived.
2016-12-16T10:43:00Z
2016-12-16T10:43:00Z
2015
Article
Text
Denkena, B.; Dahlmann, D.; Krueger, R.: Electromagnetic levitation guide for use in ultra-precision milling centres. In: Procedia CIRP 37 (2015), S. 199-204. DOI: https://doi.org/10.1016/j.procir.2015.08.008
http://www.repo.uni-hannover.de/handle/123456789/889
http://dx.doi.org/10.15488/865
eng
Procedia CIRP 37 (2015)
22128271
https://doi.org/10.1016/j.procir.2015.08.008
https://creativecommons.org/licenses/by-nc-nd/4.0/
CC BY-NC-ND 4.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9252022-12-02T15:04:49Zcom_123456789_1col_123456789_4ddc:000doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Systematic design of output filters for audio class-D amplifiers via Simplified Real Frequency Technique
Hintzen, E.
Vennemann, T.
Mathis, Wolfgang
Active filters
Audio systems
Broadband networks
Complex networks
Design
Frequency response
High electron mobility transistors
Impedance matching (electric)
Loudspeakers
MATLAB
Numerical methods
Passive filters
Power amplifiers
Broad band matching
Complex load impedance
Design and calculation
Linear frequency response
Numerical approximations
Real frequency technique
Reconstruction filters
Simplified real frequency techniques
Audio frequency amplifiers
In this paper a new filter design concept is proposed and implemented which takes into account the complex loudspeaker impedance. By means of techniques of broadband matching, that has been successfully applied in radio technology, we are able to optimize the reconstruction filter to achieve an overall linear frequency response. Here, a passive filter network is inserted between source and load that matches the complex load impedance to the complex source impedance within a desired frequency range. The design and calculation of the filter is usually done using numerical approximation methods which are known as Real Frequency Techniques (RFT). A first approach to systematic design of reconstruction filters for class-D amplifiers is proposed, using the Simplified Real Frequency Technique (SRFT). Some fundamental considerations are introduced as well as the benefits and challenges of impedance matching between class-D amplifiers and loudspeakers. Current simulation data using MATLAB is presented and supports some first conclusions.
2016-12-21T12:09:01Z
2016-12-21T12:09:01Z
2014
Article
Text
Hintzen, E.; Vennemann, T.; Mathis, W.: Systematic design of output filters for audio class-D amplifiers via Simplified Real Frequency Technique. In: Advances in Radio Science 12 (2014), S. 49-52. DOI: https://doi.org/10.5194/ars-12-49-2014
http://www.repo.uni-hannover.de/handle/123456789/925
http://dx.doi.org/10.15488/901
eng
Advances in Radio Science 12 (2014)
16849965
https://doi.org/10.5194/ars-12-49-2014
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/9262022-12-02T15:03:41Zcom_123456789_1col_123456789_4ddc:000doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Increasing the time resolution of a pulse width modulator in a class D power amplifier by using delay lines
Weber, M.
Vennemann, T.
Mathis, Wolfgang
In this paper, we present a method to increase the time resolution of a pulse width modulator by using delay lines. The modulator is part of an open loop class D power amplifier, which uses the ZePoC algorithm to code the audio signal which is amplified in the class D power stage. If the time resolution of the pulse width modulator is high enough, ZePoC could also be used to build an high accuracy AC power standard, because of its open loop property. With the presented method the time resolution theoretically could be increased by a factor of 16, which means here the time resolution will be enhanced from 5 ns to 312.5 ps.
2016-12-21T12:09:01Z
2016-12-21T12:09:01Z
2014
Article
Text
Weber, M.; Vennemann, T.; Mathis, W.: Increasing the time resolution of a pulse width modulator in a class D power amplifier by using delay lines. In: Advances in Radio Science 12 (2014), S. 91-94. DOI: https://doi.org/10.5194/ars-12-91-2014
http://www.repo.uni-hannover.de/handle/123456789/926
http://dx.doi.org/10.15488/902
eng
Advances in Radio Science 12 (2014)
16849965
https://doi.org/10.5194/ars-12-91-2014
https://creativecommons.org/licenses/by/3.0/
CC BY 3.0 Unported
Göttingen : Copernicus GmbH
oai:www.repo.uni-hannover.de:123456789/9272022-12-02T15:04:49Zcom_123456789_1col_123456789_4doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:620ddc:600
Ancillary services analysis of an offshore wind farm cluster-technical integration steps of a simulation tool
Hennig, Tobias
Löwer, Lothar
Faiella, Luis Mariano
Stock, Sebastian
Jansen, Malte
Hofmann, Lutz
Rohrig, Kurt
Ancillary services
Cluster control, reserve, balancing power
EERA-DTOC
HVDC technology
Offshore wind farms
In this publication, the authors present methodology and example results for the analysis of ancillary services of an offshore wind farm cluster and its electrical power system. Thereby the operation tool Wind Cluster Management System (WCMS) is used as simulation tool to evaluate certain planning scenarios. Emphasis is made on two topics: 1) the integration of high voltage direct current (HVDC) technology to the WCMS, 2) the ancillary service analysis. As examples, voltage source converter based HVDC (VSC-HVDC) and the provision of reserve respectively balancing power are discussed in detail. The analyzed study case considers the Kriegers Flak area while the associated power system connects wind farms to Sweden, Denmark and Germany.
2016-12-21T12:09:02Z
2016-12-21T12:09:02Z
2014
Article
Text
Hennig, T.; Löwer, L.; Faiella, L.M.; Stock, S.; Jansen, M.; et al.: Ancillary services analysis of an offshore wind farm cluster-technical integration steps of a simulation tool. In: Energy Procedia 53 (2014), Nr. C, S. 114-123. DOI: https://doi.org/10.1016/j.egypro.2014.07.220
http://www.repo.uni-hannover.de/handle/123456789/927
http://dx.doi.org/10.15488/903
eng
Energy Procedia 53 (2014)
18766102
https://doi.org/10.1016/j.egypro.2014.07.220
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9322022-12-02T15:09:32Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
The influence of deep rolling on the surface integrity of AISI 1060 high carbon steel
Abrão, A.M.
Denkena, Berend
Köhler, Jens
Breidenstein, Bernd
Mörke, Tobias
Deep rolling
Integrity
Residual stress
Mechanical properties
Rolling resistance
High carbon steels
Microhardness and microstructure
Roughness parameters
Surface integrity
Tensile residual stress
Ultimate tensile stress
Carbon steel
The aim of this work is to study the influence of selected deep rolling parameters (rolling pressure and number of passes) on the surface integrity of fully annealed AISI 1060 high carbon steel. In addition to the mechanical properties, a comprehensive investigation on surface integrity is carried out. The findings indicate that despite the increase in surface hardness and ultimate tensile stress, deep rolling can negatively affect the yield strength. The amplitude and functional roughness parameters show a considerable reduction after deep rolling, however, increasing rolling pressure and number of passes leads to poorer surface finish. Finally, the tensile residual stress generated by turning shifts to compressive values after deep rolling and the microhardness and microstructure analyses indicate that the depth of the layer affected by deep rolling depends on both the rolling pressure and number of passes.
2016-12-21T13:00:33Z
2016-12-21T13:00:33Z
2014
Article
Text
Abrão, A.M.; Denkena, B.; Köhler, J.; Breidenstein, B.; Mörke, T.: The influence of deep rolling on the surface integrity of AISI 1060 high carbon steel. In: Procedia CIRP 13 (2014), S. 31-36. DOI: https://doi.org/10.1016/j.procir.2014.04.006
http://www.repo.uni-hannover.de/handle/123456789/932
http://dx.doi.org/10.15488/908
eng
Procedia CIRP 13 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.04.006
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9332022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Recent progress in turbine blade and compressor blisk regeneration
Aschenbruck, Jens
Adamczuk, Rafael R.
Seume, Jörg R.
Compressor blisks
Jet-engine overhaul
Turbine blade repair
Compressors
Engines
Fighter aircraft
Jet engines
Manufacture
Repair
Turbine components
Turbines
Flexible manufacturing
Functional simulations
High pressure turbine blade
Hot gas path components
Regeneration
Regeneration process
Structural mechanics
Turbine blade
Turbomachine blades
The regeneration process of jet engines is a highly complex, expensive and time-consuming. Especially the regeneration of high pressure turbine blades and compressor blisks are at the border of what is technically feasible. These components are highly loaded and thus substantial wear occurs. The blades and blisks must be overhauled or replaced regularly. The existing repair methods for these parts are inflexible and cannot be applied in many cases, resulting in a large number of scrapped parts. Therefore a new turbine blade regeneration process is presented. The goal of the improved process is to reduce the scrap rate and cost. This process includes an early evaluation of the condition of the hot-gas path components before disassembly, new detection methods for defects on the turbine blades surfaces, and more flexible manufacturing processes. The process is supported by production process simulations and functional simulations to predict the optimal regeneration path depending on the blade condition and the business model of the customer. The paper also presents a new approach for compressor blisk regeneration. This process will be developed and validated in the next years. New challenges in structural mechanics, aerodynamics, and manufacturing must be addressed due to the complexity of blisks. As part of the ongoing research, three new blisks will be designed and subjected to the complete regeneration path, which is also supported by simulations. In order to validate the simulations, their results will be compared to experimental results of the regenerated components on a compressor test rig.
2016-12-21T13:00:33Z
2016-12-21T13:00:33Z
2014
Article
Text
Aschenbruck, J.; Adamczuk, R.; Seume, J.R.: Recent progress in turbine blade and compressor blisk regeneration. In: Procedia CIRP 22 (2014), Nr. 1, S. 256-262. DOI: https://doi.org/10.1016/j.procir.2014.07.016
http://www.repo.uni-hannover.de/handle/123456789/933
http://dx.doi.org/10.15488/909
eng
Proceedings of the 3rd International Conference in Through-life Engineering Services, 2014, 4-5 November 2013
Procedia CIRP 22 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.07.016
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9342022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Approaches for improving cutting processes and machine too in re-contouring
Denkena, Berend
Boess, V.
Nespor, D.
Rust, F.
Floeter, F.
Machine tool
Process simulation
Re-contouring
Aircraft engines
Fighter aircraft
Repair
Cutting tools
Advanced process
Aircraft engine blades
Experimental investigations
Geometrical accuracy
Machine tool technology
Machined surface
Re-contouring
Re-contouring in the repair process of aircraft engine blades and vanes is a crucial task. Highest demands are made on the geometrical accuracy as well as on the machined surface of the part. Complexity rises even more due to the unique part characteristic originating from the operation and repair history. This requires well-designed processes and machine tool technologies. In this paper, approaches for coping with these challenges and improving the re-contouring process are described and discussed. This includes an advanced process simulation with its capabilities to accurately depict different material areas and predict process forces. Beyond, experimental investigations on workpiece-tooldeflection are presented. Finally, a machine tool prototype with a novel electromagnetic guiding system is introduced and the benefits of this technology in the field of repair are outlined.
2016-12-21T13:00:33Z
2016-12-21T13:00:33Z
2014
Article
Text
Denkena, B.; Boess, V.; Nespor, D.; Rust, F.; Floeter, F.: Approaches for improving cutting processes and machine too in re-contouring. In: Procedia CIRP 22 (2014), Nr. 1, S. 239-242. DOI: https://doi.org/10.1016/j.procir.2014.06.148
http://www.repo.uni-hannover.de/handle/123456789/934
http://dx.doi.org/10.15488/910
eng
Proceedings of the 3rd International Conference in Through-life Engineering Services, 2014, 4-5 November 2014
Procedia CIRP 22 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.06.148
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9382022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Development and analysis of microstructures for the transplantation of thermally sprayed coatings
Freiburg, D.
Biermann, D.
Peuker, A.
Kersting, P.
Maier, Hans Jürgen
Möhwald, Kai
Knödler, Patrick
Otten, Maik
Coating
Microstructure
Milling
Aspect ratio
Automotive industry
Coatings
Milling (machining)
Plasma jets
Plasma spraying
Sprayed coatings
Tribology
Wear resistance
Adhesive strength
Development process
Lightweight materials
Micromilling process
Plasma-sprayed coatings
Point of interest
Thermally sprayed coatings
Tribological surfaces
Thermally sprayed coatings and tribological surfaces are a point of interest in many industrial sectors. They are used for better wear resistance of lightweight materials or for oil retention on surfaces. Lightweight materials are often used in the automotive industry as a weight-saving solution in the production of engine blocks. For this, it is necessary to coat the cylinder liners to ensure wear resistance. In most cases, the coating is sprayed directly onto the surface. Previous research has shown that it is possible to transfer these coatings inversely onto other surfaces. This was achieved with plasma sprayed coatings which were transplanted onto pressure-casted surfaces. These transplanted surfaces exhibited better adhesive strength, smoother surfaces, and lower form deviation compared to directly coated surfaces. Additionally, it was shown that even microstructures of a surface coated by plasma spraying can be transferred to pressure-casted surfaces. This paper presents the development and micromilling of different microstructures for transferring thermally sprayed coatings onto pressure-casted surfaces. In the development process, microstructures with different shapes and aspect ratios as well as thin tribological surfaces are designed in order to evaluate the advantages and limitations of the transplantation process. In subsequent experiments, the micromilling process and a simulation of the coating transplantation are presented and analyzed.
2016-12-21T13:00:34Z
2016-12-21T13:00:34Z
2014
Article
Text
Freiburg, D.; Biermann, D.; Peuker, A.; Kersting, P.; Maier, H.-J.; et al.: Development and analysis of microstructures for the transplantation of thermally sprayed coatings. In: Procedia CIRP 14 (2014), S. 245-250. DOI: https://doi.org/10.1016/j.procir.2014.03.054
http://www.repo.uni-hannover.de/handle/123456789/938
http://dx.doi.org/10.15488/914
eng
Procedia CIRP 14 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.03.054
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9392022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Forward variance planning and modeling of multi-variant products
Gembarski, Paul Christoph
Lachmayer, Roland
Complexity management
Product configuration
Product customization
Product structure
Shape-DoFs
Specification technique
Computer aided design
Computer aided manufacturing
Degrees of freedom (mechanics)
Design
Product development
Specifications
Structural design
Complexity management
Product design
Planning multi-variant products in the early stage of the design process is still a challenge. In the present paper, a specification technique is introduced in order to define multi-variant products using degrees of freedom of shape attributes (in the following shape-DoFs) within the product structure. Our goal is to plan variety actively at the beginning of product development and not to describe variety by change of parameter values of the product's components as introduced in variant trees. Shape-DoFs are classified in the fields of shape attributes (dimension, position, shape as well as their combinations) on the one hand and mandatory or optional components on the other hand. Set up on this taxonomy graphical symbols are introduced to be used in product modeling. As application example, a welded pipe rack based upon the assembly structure modeling the product structure in this way is visualized in the first step. The second step is to translate the shape-DoFs into design parameters and identify relationships between them. The result is a parameter plan, as well as a configuration concept. Both can be seen as basis for CAD-modeling the product as design template which is the third step. In case of our example, Autodesk Inventor (without the ETO-Environment) is used to create the CAD-data. Discussing the effects of the proposed method, it will be shown that different shape-DoFs may cause various impacts in the whole product development process. Regarding these effects, scenarios can be performed in order to identify the cost and resource optimal variation possibilities of the product. In addition, it will be shown that different kinds of modularity according to PINE (e.g. cut-to-fit-modularity) can be predefined in the product model by using shape-DoFs.
2016-12-21T13:00:35Z
2016-12-21T13:00:35Z
2014
Article
Text
Gembarski, P.C.; Lachmayer, R.: Forward variance planning and modeling of multi-variant products. In: Procedia CIRP 21 (2014), S. 81-86. DOI: https://doi.org/10.1016/j.procir.2014.03.161
http://www.repo.uni-hannover.de/handle/123456789/939
http://dx.doi.org/10.15488/915
eng
Procedia CIRP 21 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.03.161
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9402022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Prediction of process forces and stability of end mills with complex geometries
Grabowski, R.
Denkena, Berend
Köhler, Jens
Chatter
Milling
Process forces
Serrated end mills
Stability charts
Unequal helix angles
Discrete event simulation
Milling (machining)
Stability
Helix angles
Serrated end mills
Geometry
In order to optimize the cutting performance of end mills, the geometry of such cutters is optimized by toolmakers constantly. As a result of geometric changes, process forces can be reduced, i.e. by serrated end mills. Tools with unequal helix angles can lead to an increase of process stability. In this paper, a method to calculate the process forces of end mills with complex geometries is presented. The method for calculating the process forces is designed for the application for stability analysis of end mill cutters with complex geometries. A basic introduction of the method for the stability prediction of such tools is given. Cutting forces of end mills are analyzed at incremental axial depth of cuts to show the influence of the tool geometry on the process forces. The comparison with experimental data verifies this method and shows the influence of further effects on the process forces. Furthermore, stability charts obtained with the Semi-Discretization Method are presented to show the potential of end mills with complex geometries regarding stability improvement.
2016-12-21T13:00:35Z
2016-12-21T13:00:35Z
2014
Article
Text
Grabowski, R.; Denkena, B.; Köhler, J.: Prediction of process forces and stability of end mills with complex geometries. In: Procedia CIRP 14 (2014), S. 119-124. DOI: https://doi.org/10.1016/j.procir.2014.03.101
http://www.repo.uni-hannover.de/handle/123456789/940
http://dx.doi.org/10.15488/916
eng
Procedia CIRP 14 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.03.101
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9412022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Residual stresses in milled β-annealed Ti6Al4V
Grove, Thilo
Köhler, Jens
Denkena, Berend
Indirect measurement method
Milling
Residual stress
Titanium
Aerospace industry
Materials science
Milling (machining)
X ray diffraction
Electrochemical materials
Grained materials
Indirect measurement method
Material removal
Residual stress state
Stress determination
Titanium alloy Ti6Al4V
Workpiece materials
Residual stresses
Residual stresses can cause part distortion especially in the case of large components such as structural parts in aerospace industry. Therefore, this paper investigates the machining induced residual stresses for milling of a workpiece material with increasing usage in industry, the β-annealed titanium alloy Ti6Al4V. This thermal treatment results in a large grained material structure. For this reason X-ray diffraction, the standard residual stress measurement method, cannot be used for stress determination. In this paper an adopted indirect measurement method, the layer removal method is discussed. With respect to the material removal, two different methods are investigated, electrochemical material removal and laser ablation. Finally, the influence of the tool wear on the residual stress state after face milling is analyzed.
2016-12-21T13:00:36Z
2016-12-21T13:00:36Z
2014
Article
Text
Grove, T.; Köhler, J.; Denkena, B.: Residual stresses in milled β-annealed Ti6Al4V. In: Procedia CIRP 13 (2014), S. 320-326. DOI: https://doi.org/10.1016/j.procir.2014.04.054
http://www.repo.uni-hannover.de/handle/123456789/941
http://dx.doi.org/10.15488/917
eng
Procedia CIRP 13 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.04.054
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9422023-02-08T10:06:45Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Automation concepts and gripping solutions for bonding with reactive multilayer systems
Heyn, J.
Blumenthal, P.
Hemken, G.
Fiedler, S.
Walz, C.
Raatz, Annika
Dröder, Klaus
Automated Assembly
Automated bonding
Gripping
Handling
Process Automation
Reactive multilayer systems
Automation
Multilayers
Multi-layer system
Process automation
Assembly
Reactive multilayer systems (RMS) represent an innovative heat source for the establishment of solder joints. They offer fast bonding processes that introduce very little thermal input and internal stress on the bonded parts. The current application process of RMS is predominantly manual labor. There are a couple of challenges to be overcome to automate this process, a requirement for its introduction into industrial production. In this paper we evaluate the requirements for an automated joining process with RMS and devise a concept of a modular assembly system for different product structures. Furthermore we show our results in gently and reliably gripping and handling of RMS.
2016-12-21T13:00:36Z
2016-12-21T13:00:36Z
2014
Article
Text
Heyn, J.; Blumenthal, P.; Hemken, G.; Fiedler, S.; Walz, C.; et al.: Automation concepts and gripping solutions for bonding with reactive multilayer systems. In: Procedia CIRP 23 (2014), Nr. C, S. 13-18. DOI: https://doi.org/10.1016/j.procir.2014.03.198
http://www.repo.uni-hannover.de/handle/123456789/942
http://dx.doi.org/10.15488/918
eng
Procedia CIRP 23 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.03.198
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9432022-12-02T15:06:07Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Form-flexible handling and joining technology (formhand) for the forming and assembly of limp materials
Löchte, Christian
Kunz, Holger
Schnurr, Raphael
Langhorst, Sören
Dietrich, Franz
Raatz, Annika
Dilger, Klaus
Dröder, Klaus
Assembly
Automation
Form-Flexible Handling and Joining
Handling of Objects with Different Characteristics
Preforming
Process Design
End effectors
Joining
Machine tools
Automated process
Granular fillers
Handling of Objects with Different Characteristics
Handling tools
Joining technology
Material behavior
On-line sensor
Working state
Materials handling
The assembly of limp, elastic or differently shaped objects poses a huge challenge which needs to be met by machine tools and the corresponding processes of handling, forming and joining. These processes are often carried out manually. This technological gap triggered the present work at the Technische Universität Braunschweig. A novel form-flexible handling tool (FormHand) is presented which focuses on the automation of these production steps taking into consideration the material behavior. The combination of the flexibility of both industrial robot and the FormHand end-effector allows for new processes appropriate for these materials. This article investigates the used materials of the granular filler and the cushion textile, the working states of FormHand and the use of online sensors for an automated process application.
2016-12-21T13:00:36Z
2016-12-21T13:00:36Z
2014
Article
Text
Löchte, C.; Kunz, H.; Schnurr, R.; Langhorst, S.; Dietrich, F.; et al.: Form-flexible handling and joining technology (formhand) for the forming and assembly of limp materials. In: Procedia CIRP 23 (2014), Nr. C, S. 206-211. DOI: https://doi.org/10.1016/j.procir.2014.10.086
http://www.repo.uni-hannover.de/handle/123456789/943
http://dx.doi.org/10.15488/919
eng
Procedia CIRP 23 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.10.086
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9442022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessddc:330status-type:publishedVersionddc:620ddc:600
Multiscale optical inspection systems for the regeneration of complex capital goods
Schlobohm, Jochen
Li, Yinan
Pösch, Andreas
Langmann, Benjamin
Kästner, Markus
Reithmeier, Eduard
Borescope
Fringe projection
Inline measurement
Metrology
Michelson interferometer
Mulstiscale
White light interferometer
Computer generated holography
Geometry
Inspection
Inspection equipment
Interferometers
Interferometry
Measurements
Michelson interferometers
Optical data processing
Optical testing
Borescope
Mulstiscale
White-light interferometer
Projection systems
The inspection of capital goods with complex geometries is a challenging task due to the limited maneuvering and measuring space available. We developed a set of optical measurement systems for the inline inspection of such machines and capital goods. At first we introduce a borescopic fringe projection system based on of-the-shelf components. It is capable of detecting geometric variances in hard to reach areas, e.g. inside machines or in between parts with highly complex geometries like blade integrated discs (blisks). Single parts like compressor blades are measured with an inverse fringe projection system, which uses fully adaptable fringe patterns. The adaptable patterns lead to a high sensitivity and high speed. Results can be achieved with only one fringe pattern per measurement. In order to perform microscopic measurements and surface characterizations, we use a michelson interferometer with advanced 3D reconstruction algorithms to detect microscopic variances of the objects surface. These newly developed algorithms lead to higher sensitivity and improved results. Together these three inspection systems enable us to detect and to quantify geometric defects or variances of different industrial parts. Based on this information the prediction of the reliability of a part can be improved and the lifetime of an industrial part can be extended leading to a reduction of maintenance costs.
2016-12-21T13:00:36Z
2016-12-21T13:00:36Z
2014
Article
Text
Schlobohm, J.; Li, Y.; Pösch, A.; Langmann, B.; Kästner, M.; et al.: Multiscale optical inspection systems for the regeneration of complex capital goods. In: Procedia CIRP 22 (2014), Nr. 1, S. 243-248. DOI: https://doi.org/10.1016/j.procir.2014.07.019
http://www.repo.uni-hannover.de/handle/123456789/944
http://dx.doi.org/10.15488/920
eng
Proceedings of the 3rd International Conference in Through-life Engineering Services, 4-5 November 2013
Procedia CIRP 22 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.07.019
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9452023-02-08T10:06:01Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:670ddc:600
Battery system development - Assembly planning between lightweight design and high volume production
Tornow, Alexander
Raatz, Annika
Dröder, Klaus
Assembly planning
Battery System
Design for Assembly
Computer aided design
Design
Electric batteries
Secondary batteries
Automated generation
Geometrical complexity
High-volume production
Passenger vehicles
Peripheral components
Assembly
Battery systems of electric vehicles suffer from low energy densities as well as high masses and geometrical complexity. The absence of standards for battery cells and peripheral components in combination with large and distributed design spaces within passenger vehicles open up innumerable possibilities to design battery systems. The results are product specific and uneconomical assembly systems. This paper describes the work of the TU Braunschweig to create a methodology that generates and evaluates modular and easy to assemble battery systems based upon user requirements. This methodology gathers and links requirements between the priorities "lightweight design" and "high volume production" including a partly automated generation of CAD data. The generated concepts are directly used for assembly planning. The presented methodology therefore represents a simultaneous engineering approach that shortens development time and supports design engineers as well as process planners.
2016-12-21T13:00:37Z
2016-12-21T13:00:37Z
2014
Article
Text
Tornow, A.; Raatz, A.; Dröder, K.: Battery system development - Assembly planning between lightweight design and high volume production. In: Procedia CIRP 23 (2014), Nr. C, S. 143-148. DOI: https://doi.org/10.1016/j.procir.2014.10.101
http://www.repo.uni-hannover.de/handle/123456789/945
http://dx.doi.org/10.15488/921
eng
Procedia CIRP 23 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.10.101
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9462022-12-02T15:06:09Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Disassembly of electric vehicle batteries using the example of the Audi Q5 hybrid system
Wegener, Kathirn
Andrew, Stefan
Raatz, Annika
Dröder, Klaus
Herrmann, Christoph
Disassembly
Planning approach
Recycling
Traction batteries
Electric batteries
Electric traction
Electric vehicles
Hybrid systems
Hybrid vehicles
Lithium
Planning
Secondary batteries
Vehicles
Battery recycling
Disassembly sequence
Disassembly systems
Electric vehicle batteries
Li-ion batteries
Traction battery
Work station
Lithium batteries
The rising number of electric vehicles comes along with an increasing demand for Li-Ion batteries. As resources such as lithium are valuable it is economically worthwhile to recycle EV batteries. One of the first steps of every battery recycling process is the disassembly, which can be a quite time and cost consuming process and hence has to be planned properly. Using the battery of the hybrid car Audi Q5 as a case study, a planning approach for the disassembly will be discussed in this paper. Therefore, disassembly sequences will be derived from a priority matrix and a disassembly graph will be drawn up. Finally, recommendations for the design of the disassembly system and work stations will be given.
2016-12-21T14:07:22Z
2016-12-21T14:07:22Z
2014
Article
Text
Wegener, K.; Andrew, S.; Raatz, A.; Dröder, K.; Herrmann, C.: Disassembly of electric vehicle batteries using the example of the Audi Q5 hybrid system. In: Procedia CIRP 23 (2014), Nr. C, S. 155-160. DOI: https://doi.org/10.1016/j.procir.2014.10.098
http://www.repo.uni-hannover.de/handle/123456789/946
http://dx.doi.org/10.15488/922
eng
Procedia CIRP 23 (2014)
22128271
https://doi.org/10.1016/j.procir.2014.10.098
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9472022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Hot stamping of load adjusted structural parts
Behrens, Bernd-Arno
Bouguecha, Anas
Gaebel, Christoph Michael
Moritz, Jörn
Schrödter, Jens
Hot stamping
Masked austenitization
Press hardening
Spray cooling
Tailored properties
Accidents
Automobile manufacture
Cooling
Forging machines
Hardening
High strength steel
Manufacture
Plasticity
Presses (machine tools)
Stress analysis
Austenitization
Tailored properties
Stamping
The importance of high-strength steel concepts for car bodies has increased in recent years due to the necessity of weight reduction and improved crash safety. By using hot stamping or also known as press hardening of boron alloyed heat-treatable steels, it is possible to produce parts with a much higher strength than by cold forming processes. Depending on the stress profile of a structural part, it might be desirable to have different material rigidity in the part, with some high strength and other more ductile areas, so called "Tailored properties". There are a variety of methods to produce such parts, but all of these methods have currently still major challenges. Two methods to manufacture parts with tailored properties, these challenges and corresponding approaches are presented in this paper. This is on the one hand subsequently cooling in a spray field, which currently is still in the development phase because of challenges related to distortion. And on the other hand, the masked austenitization, which is used by only a few manufacturers due to the lack of experience, the impairments of coating condition and the great demands on the process management concerning re-cooling of the mask. Both variants are forward-looking and deliver high potential for further research.
2016-12-21T14:07:22Z
2016-12-21T14:07:22Z
2014
Article
Text
Behrens, B.-A.; Bouguecha, A.; Gaebel, C.M.; Moritz, J.; Schrödter, J.: Hot stamping of load adjusted structural parts. In: Procedia Engineering 81 (2014), S. 1756-1761. DOI: https://doi.org/10.1016/j.proeng.2014.10.227
http://www.repo.uni-hannover.de/handle/123456789/947
http://dx.doi.org/10.15488/923
eng
Procedia Engineering 81 (2014)
18777058
https://doi.org/10.1016/j.proeng.2014.10.227
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9482022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Numerical and experimental determination of cut-edge after blanking of thin steel sheet of DP1000 within use of stress based damage model
Behrens, Bernd-Arno
Bouguecha, Anas
Vucetic, Milan
Krimm, Richard
Hasselbusch, Tobias
Bonk, Christian
Blanking
Damage
Dual phase steel
FE-simulation
Stack-compression test
Tensile test
Compression testing
Finite element method
Fracture
Fracture mechanics
Plasticity
Tensile testing
Dual-phase steel
Elevated temperature
Experimental determination
Experimental investigations
Stress-based damage
Steel sheet
The proposed study focuses on blanking of thin steel sheets of Dogal1000DP +Z100MBO. Numerical and experimental investigations of the influence of clearance and punch speed on the cutting force and the geometry of the sheared edge were done. Tensile and stack compression test at elevated temperatures has been chosen to determine the flow and fracture behavior of Dogal1000DP +Z100MBO at different stress states. It is shown that the flow curve determined by stack compression test leads to better results in force - displacement prediction of a blanking process compared to determination of flow curve by tensile test. Stress based fracture criterion were chosen to describe damage behaviour. Moreover significant influence of fracture locus for negative stress triaxialities on the geometry of the numerically predicted sheared edge is shown.
2016-12-21T14:07:22Z
2016-12-21T14:07:22Z
2014
Article
Text
Behrens, B.-A.; Bouguecha, A.; Vucetic, M.; Krimm, R.; Hasselbusch, T.; et al.: Numerical and experimental determination of cut-edge after blanking of thin steel sheet of DP1000 within use of stress based damage model. In: Procedia Engineering 81 (2014), S. 1096-1101. DOI: https://doi.org/10.1016/j.proeng.2014.10.200
http://www.repo.uni-hannover.de/handle/123456789/948
http://dx.doi.org/10.15488/924
eng
Procedia Engineering 81 (2014)
18777058
https://doi.org/10.1016/j.proeng.2014.10.200
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9492022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Forming sheets of metal and fibre-reinforced plastics to hybrid parts in one deep drawing process
Behrens, Bernd-Arno
Hübner, Sven
Neumann, André
Deep drawing
Hybrid parts
Sheet metal forming
Drawing (forming)
Elastomers
Materials properties
Metal drawing
Metal forming
Metals
Plasticity
Reinforced plastics
Reinforcement
Sheet metal
Chemical and physical properties
Deep-drawing process
Fabrication Technologies
Fibre reinforced plastic (FRP)
Labour-intensive
Metal components
Metallic material
Fiber reinforced plastics
Each material has its own advantages and disadvantages in terms of its mechanical, chemical and physical properties. Metallic materials are comparatively ductile and easy to process. Fibre reinforced plastics are very stiff and endure high tensile stresses based on their weight. By intelligent combination of these materials into one overall-part light but strong components may be established. However, the conventional production of a separate fibre reinforced plastic (FRP)-component and a metal component and a subsequent joining is time- And labour-intensive and therefore not economical in mass-production. Thus in this paper a new fabrication technology is presented.
2016-12-21T14:07:22Z
2016-12-21T14:07:22Z
2014
Article
Text
Behrens, B.-A.; Hübner, S.; Neumann, A.: Forming sheets of metal and fibre-reinforced plastics to hybrid parts in one deep drawing process. In: Procedia Engineering 81 (2014), S. 1608-1613. DOI: https://doi.org/10.1016/j.proeng.2014.10.198
http://www.repo.uni-hannover.de/handle/123456789/949
http://dx.doi.org/10.15488/925
eng
Procedia Engineering 81 (2014)
18777058
https://doi.org/10.1016/j.proeng.2014.10.198
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9502022-12-02T15:06:08Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Properties and application of high-manganese TWIP-steels in sheet metal forming
Busch, Christian
Hatscher, Ansgar
Otto, Manuel
Huinink, Stefan
Vucetic, Milan
Bonk, Christian
Bouguecha, Anas
Behrens, Bernd-Arno
FEM-simulation
Formability
Sheet metal forming
Twip-steel
Deep drawing
Drawing (forming)
Finite element method
Formability
Manganese
Metal drawing
Metal forming
Sheet metal
Steel
Tensile testing
Dual-phase steel
FEM simulations
Forming limit diagrams
Forming limits
Multiaxial stress
Stretch formability
Uniaxial tensile test
Plasticity
Within this work uniaxial tensile tests have been performed with high-manganese TWIP-steel and different dual-phase steels to determine mechanical properties. The transfer of the results form uniaxial tensile tests to multi-axial stresses has been made with deep drawing experiments to describe and assess deep and stretch formability of the analysed materials. Forming limits of materials are demonstrated by forming limit diagrams. FE-simulation systems have been applied to predict deep drawing and spring-back behaviour of high-manganese TWIP in comparison to dual-phase steels. The simulation results are discussed between the different materials.
2016-12-21T14:07:23Z
2016-12-21T14:07:23Z
2014
Article
Text
Busch, C.; Hatscher, A.; Otto, M.; Huinink, S.; Vucetic, M. et al.: Properties and application of high-manganese TWIP-steels in sheet metal forming. In: Procedia Engineering 81 (2014), S. 939-944. DOI: https://doi.org/10.1016/j.proeng.2014.10.121
http://www.repo.uni-hannover.de/handle/123456789/950
http://dx.doi.org/10.15488/926
eng
Procedia Engineering 81 (2014)
18777058
https://doi.org/10.1016/j.proeng.2014.10.121
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
oai:www.repo.uni-hannover.de:123456789/9512022-12-02T15:09:32Zcom_123456789_1col_123456789_6doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:620ddc:600
Sandwich rolling of twin-roll cast aluminium-steel clad strips
Stolbchenko, Mykhailo
Grydin, Olexandr
Nürnberger, Florian
Samsonenko, Andrii
Schaper, Mirko
Aluminium-steel clad strips
Mechanical properties
Twin-roll casting
Aluminum
Cold rolling
Hot rolling
Metal cladding
Microstructure
Plasticity
Electron probe
Interface layer
Pure aluminium
Rolled strips
Sandwich rollings
Strain values
Twin roll cast
Twin roll casting
Steel castings
In the present study experimental results of twin-roll cast aluminium-steel clad strips of a thickness of 2.0 mm using the example of pure aluminium and an austenitic steel are presented. Electron probe measurements of the bonding area revealed the presence of a continuous interface layer of about 2 μm. To verify the formability of the twin-roll cast clad strips, sandwich samples were cold rolled with up to 66% strain. Furthermore, the sandwich samples were hot rolled at the temperature of 300 °C with different strain values. Mechanical properties, the microstructure and the surface quality of the deformed compound after rolling were analysed. To test ductility and formability of the rolled strips these were cold deep drawn.
2016-12-21T14:07:24Z
2016-12-21T14:07:24Z
2014
Article
Text
Stolbchenko, M.; Grydin, O.; Nürnberger, F.; Samsonenko, A.; Schaper, M.: Sandwich rolling of twin-roll cast aluminium-steel clad strips. In: Procedia Engineering 81 (2014), S. 1541-1546. DOI: https://doi.org/10.1016/j.proeng.2014.10.187
http://www.repo.uni-hannover.de/handle/123456789/951
http://dx.doi.org/10.15488/927
eng
Procedia Engineering 81 (2014)
18777058
https://doi.org/10.1016/j.proeng.2014.10.187
https://creativecommons.org/licenses/by-nc-nd/3.0/
CC BY-NC-ND 3.0 Unported
Amsterdam : Elsevier
rdf///ddc:600/100