@inproceedings{HaenninenNiemetzSchoepe, author = {H{\"a}nninen, Risto and Niemetz, Michael and Schoepe, Wilfried}, title = {Transition to turbulence in oscillatory superflows}, series = {ETC 2013 - 14th European Turbulence Conference 2020: 2 September 2013 - 4 September 2013, Lyon, France}, booktitle = {ETC 2013 - 14th European Turbulence Conference 2020: 2 September 2013 - 4 September 2013, Lyon, France}, abstract = {The flow of superfluid helium-4 at very low temperatures around an oscillating microsphere has been studied in detail. At small oscillation amplitudes the drag force is linear in velocity amplitude. Above a critical velocity amplitude vc a transition from potential flow to turbulent flow is signaled by a large and nonlinear drag force that scales as (v2 - v2 c ), where vc is found to be independent of temperature (below 1 K) and of driving force. Interestingly, the critical velocity is found to scale as vc ~ √κω, where κ = h/m ≈ 10-7 m2/s (h is Planck's constant and m is the mass of a helium-4 atom) is the circulation quantum of the superfluid vortices and ω/2π is the oscillation frequency ranging from about 120 Hz to 700 Hz. We also observe slightly above vc that the flow pattern is unstable and switches intermittently between potential flow and turbulence. From time series recorded at constant drive and temperature we have investigated the statistical properties of this switching phenomenon. In this talk the universal law vc ~ √κω will be discussed in detail. It can be derived theoretically in various ways: firstly, from a qualitative but very general argument based on the "superfluid Reynolds number" Rs = vl/κ where v is the flow velocity and l is a characteristic length scale, secondly, and in more detail, from Kopnin's equation of the time dependence of the vortex line density, and, finally, we have obtained this law rigorously by dynamical scaling of the equations of motion of vortex dynamics.}, language = {en} } @inproceedings{RiegerMuehlbauerRabletal., author = {Rieger, Anna and M{\"u}hlbauer, Christian and Rabl, Hans-Peter and Weber, Rainer}, title = {Dissonanz als Bewertungskriterium multi-tonalen Schalls}, series = {Fortschritte der Akustik - DAGA 2020: 46. Deutsche Jahrestagung f{\"u}r Akustik}, booktitle = {Fortschritte der Akustik - DAGA 2020: 46. Deutsche Jahrestagung f{\"u}r Akustik}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, pages = {788 -- 791}, language = {de} } @inproceedings{MuehlbauerRablRottengruber, author = {M{\"u}hlbauer, Christian and Rabl, Hans-Peter and Rottengruber, Herrmann}, title = {Development of a Methodology for Acoustic Analysis and Optimization of Mechatronic Fuel Injection Systems}, series = {Automotive Acoustics Conference 2019: Proceedings, 5. Internationale ATZ-Fachtagung Fahrzeugakustik}, booktitle = {Automotive Acoustics Conference 2019: Proceedings, 5. Internationale ATZ-Fachtagung Fahrzeugakustik}, editor = {Siebenpfeiffer, Wolfgang}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-27668-3}, doi = {10.1007/978-3-658-27669-0_15}, pages = {211 -- 225}, abstract = {To identify the sound quality of fuel injection systems as a frontloading measure, a system test bench has been developed that simulates the structure and airborne noise emission. The setup of the system test bench includes an assembly of the acoustical relevant engine parts and an encapsulated drive for the high-pressure pump. A specific control unit enables a high variability for the operation strategy of the injection system. The focus of this study is on the development of a methodology to analyze and optimize the sound quality of gasoline direct injectors in critical operation points by suitable active means. For this, the injection parameters in engine idle have been identified and subsequently transferred to the system test bench. Additionally, the injection parameters have been optimized acoustically and the impacts on the key functions regarding injection rating and shot-to-shot scattering of the injected fuel mass are discussed.}, language = {en} } @inproceedings{ReindlMeierNiemetz, author = {Reindl, Andrea and Meier, Hans and Niemetz, Michael}, title = {Scalable, Decentralized Battery Management System Based on Self-organizing Nodes}, series = {Architecture of computing systems - ARCS 2020: 33rd international conference, Aachen, Germany, May 25-28, 2020, proceedings}, volume = {12155}, booktitle = {Architecture of computing systems - ARCS 2020: 33rd international conference, Aachen, Germany, May 25-28, 2020, proceedings}, editor = {Brinkmann, Andr{\´e} and Karl, Wolfgang and Lankes, Stefan and Tomforde, Sven and Pionteck, Thilo and Trinitis, Carsten}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-030-52793-8}, doi = {10.1007/978-3-030-52794-5_13}, pages = {171 -- 184}, abstract = {Due to the transition to renewable energy sources and the increasing share of electric vehicles and smart grids, batteries are gaining in importance. Battery management systems (BMSs) are required for optimal, reliable operation. In this paper, existing BMS topologies are presented and evaluated in terms of reliability, scalability and flexibility. The decentralisation of BMSs and associated advantages are shown. A scalable, reconfigurable BMS based on a distributed architecture of self-organized, locally controlled nodes is proposed. For distributed system control, producers, batteries and consumers each are equipped with a local microcontroller based control unit, which monitors and controls the local parameters with its own computing and communication resources. Features, advantages and challenges to overcome of the proposed approach are described.}, language = {en} } @inproceedings{AndersBriemNovaketal., author = {Anders, M. and Briem, Ulrich and Novak, G. and Steinbach, G.}, title = {Neue VDI-Richtlinie f{\"u}r die Seiltriebauslegung}, series = {28. Internationale Kranfachtagung 2020 "Kran 4.0: Potenziale der Digitalisierung", 4. und 5. M{\"a}rz 2020, Magdeburg}, booktitle = {28. Internationale Kranfachtagung 2020 "Kran 4.0: Potenziale der Digitalisierung", 4. und 5. M{\"a}rz 2020, Magdeburg}, editor = {Katterfeld, Andr{\´e} and Krause, Friedrich and Pfeiffer, Dagmar and Richter, Klaus}, publisher = {LOGiSCH GmbH}, address = {Magdeburg}, isbn = {978-3-947068-08-1}, pages = {59 -- 72}, language = {de} } @inproceedings{DiamantidisSykora, author = {Diamantidis, Dimitris and S{\´y}kora, Miroslav}, title = {Reliability Differentiation and Uniform Risk in Standards}, series = {Scientific Symposium Future Trends in Civil Engineering, Zagreb,Croatia, 17 October 2029}, booktitle = {Scientific Symposium Future Trends in Civil Engineering, Zagreb,Croatia, 17 October 2029}, doi = {10.5592/CO/FTCE.2019.11}, pages = {241 -- 260}, abstract = {Reliability of structures and infrastructures is a major issue in structural engineering. Structural standards have traditionally been mainly concerned with public safety preventing loss of life or injury; this view has been shifting in recent years towards minimisation of economic loss. This contribution discusses the reliability differentiation principle in modern standards. Its aim is to achieve uniform risk levels for the various classes of structures. Codified criteria for reliability differentiation and risk informed decisions inherent in standards and especially in the Eurocodes are critically reviewed. It is shown that the classification of structures based on consequences of failure is an approach that has not been widely implemented in everyday design. Practical rules for the classification and implementation in design are needed and related proposals are presented.}, language = {en} } @inproceedings{Roesel, author = {R{\"o}sel, Birgit}, title = {A concept of a mainly digitalized course on control theory including problembased practical units and digital supported exams}, series = {HEAd'20: Sixth International Conference on Higher Education Advances, June 2 - June 5 2020, Valencia (Spain)}, booktitle = {HEAd'20: Sixth International Conference on Higher Education Advances, June 2 - June 5 2020, Valencia (Spain)}, doi = {10.4995/HEAd20.2020.11112}, abstract = {This paper decribes the concept of a course on control theory as a minor subject in the department of electrical engineering at the OTH Regensburg. The basis for a new concept is the idea of contructive alignment. The whole teaching module is devided in two blocks. The first block contains the teaching of the knowledge about control theory with an integrated approach for lectures, exercises and practical sessions. In the second block the students attent a practical work package to have the possibility to applicate and deepen their knowledge. To foster active participation the students are asked to document and reflect their work with the course context in an electronic portfolio. The exam of this module consists of three parts with respect to the different competencies obtained during the module. This concept develops not only the knowledge on control theory but personal and social competencies which are of growing interest. The aim of the paper is to present the idea of the concept. Following papers will illustrate the development process and the results obtained later on.}, language = {en} } @article{MalzKrenkelSteffens, author = {Malz, Sebastian and Krenkel, Walter and Steffens, Oliver}, title = {Infrared Reflective Wall Paint in Buildings: Energy Saving Potentials and Thermal Comfort}, series = {Energy and Buildings}, volume = {224}, journal = {Energy and Buildings}, number = {October}, publisher = {Elsevier}, issn = {0378-7788}, doi = {10.1016/j.enbuild.2020.110212}, abstract = {The reduction of the energy demand of existing buildings is the main objective of building refurbishment. Managing the heat radiation properties of the wall construction is a possible way to develop highly effective and resource efficient insulation materials and concepts. The application of infrared reflective wall paints and coatings has been studied since the latter half of the 20th century. A brief review of the literature gives an account of the current research status. One has to realise that the conclusions are not uniformly consistent but depend strongly on the specific boundary conditions and investigated parameters. The study presented here discusses the usage of infrared reflective wall paint in conjunction with heat insulation for historic brick masonry. The possible energy savings are linked to the resulting thermal comfort. We identify critical parameters that must be taken into account when using infrared reflective wall paint and derive recommended design rules for the refurbishment of such building types. The findings prove that infrared reflective wall paint can decrease heat losses by 18\% and up to 22\% if comfort conditions are considered. Increasing energy savings can also cause the negative effect of high radiative asymmetry. Thus, each configuration must be observed in detail.}, language = {en} } @article{SchulzSchwarz, author = {Schulz, Carsten and Schwarz, Colin}, title = {Drivetrain fatigue strength characteristics of model-predictive control for wind turbines}, series = {Wind Energy}, volume = {23}, journal = {Wind Energy}, number = {12}, publisher = {Wiley}, doi = {10.1002/we.2520}, pages = {2137 -- 2149}, abstract = {Wind turbines play a crucial role in the revolution towards renewable resources. They need to be economically competitive to be sustainable. This still requires to lower the cost of energy (COE). To this end, nonlinear model predictive control (NMPC) is used within this paper. As known from literature, NMPC significantly improves the energy extracting performance as well as the mitigation of tower loads of wind turbines. As it is shown in this paper, the drivetrain fatigue strength drops disproportionally in parallel, which either increases the demands on the turbine design or decreases the lifetime of drivetrain components. Without additional boundary conditions to the underlying optimal control problems (OCPs), the application of energy-maximizing NMPC might so even raise the COE. Only penalizing axial torque oscillations by quadratic terms decreases energy-extracting performance below the level of classical wind turbine controllers. This makes more sophisticated conditions necessary. In this paper, the increase of the drivetrain damage by NMPC is analyzed, and appropriate boundary conditions are derived, to balance the two contradicting objectives of energy maximization and drivetrain load mitigation. An NMPC approach based on indirect methods is used, to obtain a solution of the OCPs very efficiently. It applies the Hamilton equations and Pontryagin's maximum principle. Its accuracy and efficiency to solve OCPs was presented over the last decades.}, language = {en} } @inproceedings{SippenauerBrueckl, author = {Sippenauer, Thomas and Br{\"u}ckl, Oliver}, title = {Verankerung von Flexibilit{\"a}t in der Netzplanung}, series = {ScienceLab (begleitender Workshop zur Konferenz Zuk{\"u}nftige Stromnetze: 29.-30. Januar 2020, Berlin)}, booktitle = {ScienceLab (begleitender Workshop zur Konferenz Zuk{\"u}nftige Stromnetze: 29.-30. Januar 2020, Berlin)}, publisher = {Conexio GmbH}, address = {Pforzheim}, isbn = {978-3-948176-07-5}, doi = {10.35096/othr/pub-5559}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-55592}, pages = {77 -- 81}, abstract = {Im Rahmen des Projektes C/sells wurden mehrere Mittelspannungsnetze modelliert, um die aktuellen Spannungsverh{\"a}ltnisse und Leitungsauslastungen nachbilden zu k{\"o}nnen. Zudem wurden, angelehnt an den Netzentwicklungsplan, Szenarien f{\"u}r den zuk{\"u}nftigen PV-Zubau und die potenzielle Entwicklung der Elektromobilit{\"a}t entworfen. Auf Basis der Ergebnisse l{\"a}sst sich eine Netzanalyse hinsichtlich Spannungs- und Stromgrenzwert{\"u}berschreitungen sowie zu deren potenziellen Auftrittszeitpunkten und Auftrittsdauern durchf{\"u}hren. Parallel wurde anhand von Sensitivit{\"a}tsanalysen untersucht, welche Wirksamkeit Flexibilit{\"a}tseins{\"a}tze an den verschiedenen Netzknoten auf den Engpass haben. Dadurch kann bestimmt werden, wie effektiv die verf{\"u}gbaren, in der Regel {\"o}rtlich gebundenen Flexibilit{\"a}tsanbieter eingesetzt werden k{\"o}nnen. Da die Sensitivit{\"a}ten arbeitspunktabh{\"a}ngig sind, wurden verschiedene Zeitpunkte im Jahresverlauf berechnet und die jeweilige {\"A}nderungen der Wirksamkeit ausgewertet. Neben der H{\"o}he der Leistungsabweichung wurde die Flexibilit{\"a}tsanforderung auch anhand der Einsatzzeitpunkte und Einsatzdauer sowie anhand der H{\"a}ufigkeit der n{\"o}tigen Flexibilit{\"a}tseins{\"a}tze charakterisiert. Aus den gewonnenen Erkenntnissen soll abgeleitet werden, inwiefern sich der flexible Einsatz der Verbrauchsanlagen in der Netzplanung verankern l{\"a}sst. Besonders relevant ist deshalb, mit welcher Verl{\"a}sslichkeit die Flexibilit{\"a}t abgerufen werden kann. Eine sehr hohe Verl{\"a}sslichkeit l{\"a}sst sich je nach Flexibilit{\"a}tsanbieter m{\"o}glicherweise nicht oder nur zu sehr hohen Preisen gew{\"a}hrleisten. Die Eignung der Flexibilit{\"a}tseins{\"a}tze wird somit sowohl aus technischer als auch aus wirtschaftlicher Sicht bewertet. Da eine vollst{\"a}ndige Verl{\"a}sslichkeit ohnehin nicht sichergestellt werden kann (technische St{\"o}rungen einer Anlage, Wettereinfl{\"u}sse, etc.), werden auch Fallback-Strategien, z. B. Einspeisespitzenkappung, in die Analyse einbezogen.}, language = {de} }