@article{FuhrbergAhrensSchkutowetal.2020, author = {Fuhrberg, Peter and Ahrens, Anja and Schkutow, Andreas and Frick, Thomas}, title = {2.0 μm Laser Transmission Welding}, series = {PhotonicsViews}, volume = {17}, journal = {PhotonicsViews}, number = {2}, publisher = {Wiley}, issn = {2626-1294}, doi = {https://doi.org/10.1002/phvs.202000013}, pages = {64 -- 68}, year = {2020}, abstract = {2.0 μm fiber lasers provide a high beam quality and a high-power output, which makes them ideal for welding and cutting a wide variety of commercially used plastics, as well as marking plastics, metals or even food. At 2.0 μm wavelength the intrinsic absorption of most thermoplastics is high enough to weld or cut without applying any absorbent additives or coatings. Compared to commonly used near-infrared systems, welding with 2.0 μm lasers can improve heat distribution and gap bridging and enable transmission welding for challenging materials.}, language = {en} } @inproceedings{BrostEggerLaietal.2020, author = {Brost, Julian and Egger, Christoph and Lai, Russell and Schmid, Fritz and Schr{\"o}der, Dominique and Zoppelt, Markus}, title = {Threshold Password-Hardened Encryption Services}, publisher = {ACM}, doi = {10.1145/3372297.3417266}, pages = {409 -- 424}, year = {2020}, abstract = {Password-hardened encryption (PHE) was introduced by Lai et al. at USENIX 2018 and immediately productized by VirgilSecurity. PHE is a password-based key derivation protocol that involves an oblivious external crypto service for key derivation. The security of PHE protects against offline brute-force attacks, even when the attacker is given the entire database. Furthermore, the crypto service neither learns the derived key nor the password. PHE supports key-rotation meaning that both the server and crypto service can update their keys without involving the user. While PHE significantly strengthens data security, it introduces a single point of failure because key-derivation always requires access to the crypto service. In this work, we address this issue and simultaneously increase security by introducing threshold password-hardened encryption. Our formalization of this primitive revealed shortcomings of the original PHE definition that we also address in this work. Following the spirit of prior works, we give a simple and efficient construction using lightweight tools only. We also implement our construction and evaluate its efficiency. Our experiments confirm the practical efficiency of our scheme and show that it is more efficient than common memory-hard functions, such as scrypt. From a practical perspective this means that threshold PHE can be used as an alternative to scrypt for password protection and key-derivation, offering better security in terms of offline brute force attacks. CCS CONCEPTS • Security and privacy → Cryptography.}, language = {en} } @inproceedings{WendelKaramanakosDietzetal.2020, author = {Wendel, Sebastian and Karamanakos, Petros and Dietz, Armin and Kennel, Ralph}, title = {Flux Linkage-Based Model Predictive Current Control for Nonlinear PMSM Drives}, series = {IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society}, booktitle = {IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society}, publisher = {IEEE}, doi = {https://doi.org/10.1109/iecon43393.2020.9254484}, year = {2020}, abstract = {In this paper, a flux linkage-based direct model predictive current control approach is presented for small permanent magnet synchronous motor (PMSM) drives. The method aims to minimize the current ripples at steady state by deciding on the optimal switching instant, while exhibiting fast dynamic behavior during transients. To this end, the future trajectory of the stator current is not computed based on the machine inductances or inductance look-up tables, but on the changes of the magnetic flux linkage by utilizing flux linkage maps. As shown, the proposed method can be particularly advantageous for electric drives with a noticeable nonlinearity in terms of saturation and/or cross-coupling effects since it allows for a significantly increased prediction accuracy, which leads to an improved steady-state performance as indicated by the reduced current distortions.}, language = {en} } @inproceedings{GerstnerMaerzDietz2020, author = {Gerstner, Michael and Maerz, Martin and Dietz, Armin}, title = {Reconfigurable Transformer for Wide Input Voltage Range DC/DC Converters}, series = {2020 IEEE 9th International Power Electronics and Motion Control Conference (IPEMC2020-ECCE Asia)}, booktitle = {2020 IEEE 9th International Power Electronics and Motion Control Conference (IPEMC2020-ECCE Asia)}, publisher = {IEEE}, doi = {https://doi.org/10.1109/ipemc-ecceasia48364.2020.9367869}, year = {2020}, abstract = {A transformer with variable primary windings for wide input voltage range DC/DC converters is presented. This transformer structure allows three states of the primary winding to be converted by only two individual windings. Based on the evaluations of a two-switch flyback converter, the potential of DC/DC converters with variable structures, the implementation of such a transformer and the advantages and disadvantages are shown and discussed. Real measurement results demonstrate the noticeable increase in efficiency and the reduction in component stress, having a positive influence on the operation of the converter and the component selection during the design process.}, language = {en} } @article{WeilandLuberSeewaldetal.2020, author = {Weiland, J. and Luber, M. and Seewald, R. and Schiebahn, A. and Engelbrecht, R. and Reisgen, U.}, title = {Structural Health Monitoring of Adhesively Bonded Joints: Proposing a new Method by use of Polymer Optical Fibers}, series = {Procedia Structural Integrity}, volume = {28}, journal = {Procedia Structural Integrity}, publisher = {Elsevier BV}, issn = {2452-3216}, doi = {https://doi.org/10.1016/j.prostr.2020.11.106}, pages = {1249 -- 1257}, year = {2020}, abstract = {According to the current state of the art, adhesively bonded joints cannot be tested completely non-destructively. This is the main motivation to permanently monitor adhesively bonded joints in order to record their structural integrity and - as a result - to ensure safe load transmission. By the use of permanent non-destructive Structural Health Monitoring (SHM) methods, structural damages in the adhesive bond can be detected at an early stage. This paper presents a new method for monitoring the structural integrity of adhesively bonded joints by integrating a Polymer Optical Fiber (POF) into the adhesive layer. The sensor concept is based on a deformation transfer from the adhesive to the POF, which results in a change in the cross-sectional shape of the POF. The cross-sectional shape influences the optical light propagation in the POF, which can be detected by simple optical measuring devices. The paper describes the general principle and first results of investigations on a structural adhesive (3M Scotch-Weld DP 609). The sensor signal is in a good relation to the stress state of the adhesive layer.}, language = {en} } @article{HeenemannMilletGirgsdiesetal.2020, author = {Heenemann, Maria and Millet, Marie-Mathilde and Girgsdies, Frank and Eichelbaum, Maik and Risse, Thomas and Schl{\"o}gl, Robert and Jones, Travis and Frei, Elias}, title = {The Mechanism of Interfacial CO2 Activation on Al Doped Cu/ZnO}, series = {ACS Catalysis}, volume = {10}, journal = {ACS Catalysis}, number = {10}, publisher = {American Chemical Society (ACS)}, issn = {2155-5435}, doi = {https://doi.org/10.1021/acscatal.0c00574}, pages = {5672 -- 5680}, year = {2020}, abstract = {We report on a combined quantitative charge carrier and catalytic activity analysis of Cu/ZnO(:Al) model catalysts. The promoting effect of Al3+ on the ZnO support for CO2 activation via the reverse water-gas-shift reaction has been investigated. The contact-free and operando microwave Hall Effect technique is applied to measure charge carriers in Cu/ZnO(:Al) based model catalysts under reverse water-gas shift reaction conditions. This method allows us to monitor the electrical conductivity, charge carrier mobility, and absolute number of charge carriers. An increase in charge carrier concentration with increasing Al3+ content and its direct correlation with the catalytic activity for CO formation is found. We conclude that the increased availability of charge carriers plays a key role in CO2 activation and CO formation, which finds additional support in a concurrent decrease of the apparent activation energy and increase in the reaction order of CO2. In combination with comprehensive DFT calculations, the impact of the interfacial charge transfer, coupled to oxygen defect sites in ZnO and CO2 adsorption properties, is elucidated and highlighted. In conclusion, the results from this operando investigation combined with DFT calculations demonstrate the importance of charge transfer processes as decisive descriptors for understanding and explaining catalytic properties.}, language = {en} } @inproceedings{SchindlerDietz2020, author = {Schindler, Tobias and Dietz, Armin}, title = {Real-Time Inference of Neural Networks on FPGAs for Motor Control Applications}, series = {2020 10th International Electric Drives Production Conference (EDPC)}, booktitle = {2020 10th International Electric Drives Production Conference (EDPC)}, publisher = {IEEE}, doi = {https://doi.org/10.1109/edpc51184.2020.9388185}, pages = {1 -- 6}, year = {2020}, abstract = {Machine learning algorithms are increasingly used in industrial applications for a multitude of use-cases. However, using them in control tasks is a challenge due to real-time requirements and limited resources. In this paper, an implementation scheme for real-time inference of multilayer perceptron (MLP) neural networks on FPGAs is proposed. Design constraints for using MLPs in reinforcement learning agents for motor control applications are derived and accounted for in the implementation. Two MLP architectures are evaluated on an FPGA, and the timing and resource-usage data are reported. The real-time capability of the implementation for motor control applications is investigated for standard control frequencies. It is shown by experimental validation that real-time interference with an area-efficient implementation for motor control applications is achievable. Therefore, the proposed implementation scheme can be applied to deep reinforcement learning controllers with hard real-time requirements.}, language = {en} } @incollection{Dernbach2020, author = {Dernbach, Beatrice}, title = {Ern{\"a}hrung als Medienthema}, series = {Ern{\"a}hrungskommunikation}, booktitle = {Ern{\"a}hrungskommunikation}, publisher = {Springer Fachmedien Wiesbaden}, address = {Wiesbaden}, isbn = {9783658273156}, doi = {http://dx.doi.org/10.1007/978-3-658-27315-6_15-1}, pages = {1 -- 14}, year = {2020}, language = {de} } @inproceedings{GerstnerMaerzDietz2020, author = {Gerstner, Michael and Maerz, Martin and Dietz, Armin}, title = {Design of a Wide Input Voltage Range Current-Fed DC/DC Converter Within a Reduced Duty-Cycle Range}, series = {2020 22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe)}, booktitle = {2020 22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe)}, publisher = {IEEE}, doi = {https://doi.org/10.23919/epe20ecceeurope43536.2020.9215825}, pages = {10}, year = {2020}, abstract = {A design of a current-fed push-pull converter for wide input voltage ranges within a reduced duty-cycle range is presented. Based on the converter conversion ratios of three different clamping configurations, the potential of the input clamping is shown analytical, simulative and by measurements. A differentiation is made between the four possible operating modes, which can be distinguished in the control of the semiconductors and the magnetomotive force in the reactor. By optimizing the turn ratios of both transformers, the wide input voltage range capability of the input clamped current-fed push-pull converter was improved, which has been proved by measurements on a real prototype.}, language = {en} } @article{WeilandLuberSeewaldetal.2020, author = {Weiland, J. and Luber, M. and Seewald, R. and Schiebahn, A. and Engelbrecht, R. and Reisgen, U.}, title = {Structural Health Monitoring of Adhesively Bonded Joints: Proposing a new Method by use of Polymer Optical Fibers}, series = {Procedia Structural Integrity}, volume = {28}, journal = {Procedia Structural Integrity}, publisher = {Elsevier BV}, issn = {2452-3216}, doi = {http://dx.doi.org/10.1016/j.prostr.2020.11.106}, pages = {1249 -- 1257}, year = {2020}, abstract = {According to the current state of the art, adhesively bonded joints cannot be tested completely non-destructively. This is the main motivation to permanently monitor adhesively bonded joints in order to record their structural integrity and - as a result - to ensure safe load transmission. By the us e of permanent non-destructive Structural Health Monitoring (SHM) methods, structural damages in the adhesive bond can be detected at an early stage. This paper presents a new method for monitoring the structural integrity of adhesively bonded joints by integrating a Polymer Optical Fiber (POF) into the adhesive layer. The sensor concept is based on a deformation transfer from the adhesive to the POF, which results in a change in the cross-sectional shape of the POF. The cross-sectional shape influences the optical light propagation in the POF, which can be detected by simple optical measuring devices. The paper describes the general principle and first results of investigations on a structural adhesive (3M Scotch-Weld DP 609). The sensor signal is in a good relation to the stress state of the adhesive layer.}, language = {en} }