Institutionelles Repositorium der Leibniz Universität Hannover
Das digitale Repositorium erfasst, speichert, erhält, erschließt und verbreitet digitale Forschungsergebnisse.
http://www.repo.uni-hannover.de:80
2017-05-14T03:19:32Z
2017-05-14T03:19:32Z
Transient measurement results of pulse propagation in large GTEM cells
Thye, H.
Armbrecht, G.
Koch, M.
http://www.repo.uni-hannover.de/handle/123456789/1546
2017-05-12T01:00:41Z
2008-01-01T00:00:00Z
Transient measurement results of pulse propagation in large GTEM cells
Thye, H.; Armbrecht, G.; Koch, M.
This contribution deals with the results of a transient measurement campaign incorporating ultra-wideband (UWB) pulses applied to a large GTEM cell. The main purpose is to analyse the distortion effects on such a feeding pulse when transformed into a field pulse inside the cells testing volume. We will investigate if the TEM field distribution is interfered by multimode propagation, that may lead to location-dependent pulse distortion and ringing. Finally, conclusions on the applicability of GTEM cells for standardized transient EMC measurements will be drawn. © Author(s) 2008.
2008-01-01T00:00:00Z
Theoretical study of the electronic states of hollandite vanadate K 2V8O16
Horiuchi, S.
Shirakawa, T.
Ohta, Y.
http://www.repo.uni-hannover.de/handle/123456789/1545
2017-05-12T01:00:41Z
2009-01-01T00:00:00Z
Theoretical study of the electronic states of hollandite vanadate K 2V8O16
Horiuchi, S.; Shirakawa, T.; Ohta, Y.
Electronic states of hollandite vanadate K2V8O 16, a one-dimensional zigzag-chain system of t2g orbitals in a mixed valent state, are considered. We calculate the Madelung energies to determine the most stable charge-ordering pattern that is consistent with the observed superlattice structure. We then develop the strong-coupling perturbation theory to derive the effective spin-orbit Hamiltonian, starting from the triply-degenerate t2g orbitals in the VO6 octahedral structure. An exact-diagonalization technique is used on small clusters of this Hamiltonian to determine the orbital-ordering pattern and spin structures in the ground state. We thereby discuss the electronic and magnetic properties of K2 V8O16. © 2009 IOP Publishing Ltd.
2009-01-01T00:00:00Z
Trend tests for the evaluation of exposure-response relationships in epidemiological exposure studies
Hothorn, L.A.
Vaeth, M.
Hothorn, T.
http://www.repo.uni-hannover.de/handle/123456789/1547
2017-05-12T01:00:42Z
2009-01-01T00:00:00Z
Trend tests for the evaluation of exposure-response relationships in epidemiological exposure studies
Hothorn, L.A.; Vaeth, M.; Hothorn, T.
One possibility for the statistical evaluation of trends in epidemiological exposure studies is the use of a trend test for data organized in a 2 × k contingency table. Commonly, the exposure data are naturally grouped or continuous exposure data are appropriately categorized. The trend test should be sensitive to any shape of the exposure-response relationship. Commonly, a global trend test only determines whether there is a trend or not. Once a trend is seen it is important to identify the likely shape of the exposure-response relationship. This paper introduces a best contrast approach and an alternative approach based on order-restricted information criteria for the model selection of a particular exposure-response relationship. For the simple change point alternative H1 : 1 =.= q <q+1 =. = k an appropriate approach for the identification of a global trend as well as for the most likely shape of that exposure-response relationship is characterized by simulation and demonstrated for real data examples. Power and simultaneous confidence intervals can be estimated as well. If the conditions are fulfilled to transform the exposure-response data into a 2 × k table, a simple approach for identification of a global trend and its elementary shape is available for epidemiologists.
2009-01-01T00:00:00Z
Usage of the contactless vector network analysis with varying transmission line geometries
Zelder, T.
Geck, B.
Rolfes, I.
Eul, H.
http://www.repo.uni-hannover.de/handle/123456789/1548
2017-05-12T11:55:23Z
2008-01-01T00:00:00Z
Usage of the contactless vector network analysis with varying transmission line geometries
Zelder, T.; Geck, B.; Rolfes, I.; Eul, H.
The scattering parameters of embedded devices can be measured by means of contactless vector network analysis. To achieve accurate measurement results, the contactless measurement setup has to be calibrated. However, if the substrate material or the planar transmission lines on the substrate changes, a new calibration is necessary. In this paper a method will be examined, which reduces the number of calibration cycles by using a database. Analytical results show that by using this database method, errors occur which depend on the coupling coefficients and on the load impedances of the contactless probes. However, the measurement results show deviations smaller than 7% in comparison to the conventional vector network analysis, which is sufficient for the most pratical applications.
2008-01-01T00:00:00Z