Institutionelles Repositorium der Leibniz Universität HannoverDas digitale Repositorium erfasst, speichert, erhält, erschließt und verbreitet digitale Forschungsergebnisse.https://www.repo.uni-hannover.de:4432024-03-18T08:45:15Z2024-03-18T08:45:15ZEnergetic evaluation and optimization of hydrogen generation and compression pathways considering PEM water electrolyzers and electrochemical hydrogen compressorsZachert, LarsSuermann, MichelBensmann, BorisHanke-Rauschenbach, Richardhttps://www.repo.uni-hannover.de/handle/123456789/167742024-03-18T08:00:18Z2021-01-01T00:00:00ZEnergetic evaluation and optimization of hydrogen generation and compression pathways considering PEM water electrolyzers and electrochemical hydrogen compressors
Zachert, Lars; Suermann, Michel; Bensmann, Boris; Hanke-Rauschenbach, Richard
Electrochemical hydrogen compression is seen as a promising alternative to mechanical compression in the context of power-togas plants. It can be carried out either as direct co-compression in a water electrolyzer (WE) or via a separate electrochemical hydrogen compressor (EHC). This study analyzes the specific energy demand of different hydrogen generation and compression pathways using WEs and EHCs, both based on proton exchange membrane (PEM) technology, for pressures up to 1000 bar. The energy demand is systematically investigated as a function of design parameters such as pressure, current density, temperature and membrane thickness and presented in overpotential-specific and gas-crossover dependent shares. The analysis reveals intrinsic differences in the compression behavior of WEs and EHCs. In the EHC, permeated hydrogen is simply re-compressed back to the cathode. In the WE, instead, water has to be split again to compensate for the hydrogen loss, causing energetic disadvantages with increasing hydrogen pressure. Moreover, using an EHC enables design parameters to be optimized separately regarding hydrogen generation and compression. Therefore, at low current densities, compression via EHC is already favorable to co-compression via WE for pressures above 4 bar. With increasing current density, however, this intersection point shifts up to pressures above 200 bar.
2021-01-01T00:00:00ZDigital pioneers in the periphery? Toward a typology of rural Hidden Champions in times of digitalizationRietmann, Carstenhttps://www.repo.uni-hannover.de/handle/123456789/167722024-03-18T08:00:17Z2021-01-01T00:00:00ZDigital pioneers in the periphery? Toward a typology of rural Hidden Champions in times of digitalization
Rietmann, Carsten
We unravel dimensions, conditions, and outcomes of digitalization for Hidden Champions (HCs) in rural areas in Germany. As highly innovative small- and medium-sized market leaders, HCs are challenged to maintain their niche dominance but are endowed with significant resources. However, firms in rural areas face resource constraints related to digitalization and innovation. Based on qualitative interviews with 28 companies, we develop a typology of HCs with four firm types differing in their handling of digitalization: Digital HCs, HCs of Digitalization, Traditional HCs, and Digitalization-Skeptical HCs. Their digitalization-related potential and risk assessment, resource availability, strategy, and innovation types are portrayed. We provide evidence that innovative market leaders in rural areas are not necessarily also digitalization front-runners. We contribute to a deeper understanding of the nexus of digitalization, SMEs, and rural areas. Our findings have managerial and policy implications. Less innovative SME can emulate HCs’ handling of digitalization. Regional policymakers should expand firm type-specific digitalization policy formulation.
2021-01-01T00:00:00ZErratum: The construction problem for Hodge numbers modulo an integer in positive characteristic (Forum Math. Sigma 8 (2020) E45 DOI: 10.1017/fms.2020.48)van Dobben de Bruyn, RemyPaulsen, Matthiashttps://www.repo.uni-hannover.de/handle/123456789/167732024-03-18T08:00:17Z2021-01-01T00:00:00ZErratum: The construction problem for Hodge numbers modulo an integer in positive characteristic (Forum Math. Sigma 8 (2020) E45 DOI: 10.1017/fms.2020.48)
van Dobben de Bruyn, Remy; Paulsen, Matthias
The original publication of this article includes an error introduced during the publication process. On three occasions, Remark 4.4 has been incorrectly referred to as Theorem 4.4. Please find listed below the corrected paragraphs containing the errors in the original publication along with the page number of where they occur.
2021-01-01T00:00:00ZLimSt – Ein Fragebogen zur Erhebung von Lernstrategien im mathematikhaltigen StudiumLiebendörfer, MichaelGöller, RobinBiehler, RolfHochmuth, ReinhardKortemeyer, JörgOstsieker, LauraRode, JanaSchaper, Niclashttps://www.repo.uni-hannover.de/handle/123456789/167712024-03-18T08:43:12Z2020-01-01T00:00:00ZLimSt – Ein Fragebogen zur Erhebung von Lernstrategien im mathematikhaltigen Studium
Liebendörfer, Michael; Göller, Robin; Biehler, Rolf; Hochmuth, Reinhard; Kortemeyer, Jörg; Ostsieker, Laura; Rode, Jana; Schaper, Niclas
Learning strategies are important in students’ learning. Several studies in tertiary mathematics education focused on learning strategies. Yet, there is no instrument that adequately covers the specialties of learning university mathematics. We present a newly developed questionnaire to fill this gap. It has been developed and validated in eight quantitative and two qualitative studies. On both scale and item level, specialties of university mathematics are taken into account. The instrument is still general in the sense that it allows to measure students’ use of learning strategies across mathematics courses of different study programs like mathematics major programs, engineering and economics, as well as teacher education.
2020-01-01T00:00:00Z