In this paper, we develop a linear sampling method for the inverse scattering of timeharmonic plane waves by open arcs. We derive a characterization of the scatterer in terms of the spectral data of the scattering matrix analogously to the case of the scattering by bounded open domains. Numerical examples show that this theoretical result also leads to a very fast visualization technique for the unknown arc.

The inverted classroom is a teaching model, where the students prepare for classroom by watching video lectures. The classroom time is then dedicated to individual practice. We evaluated a mathematics course for electrical engineering students throughout three semesters, where 20% of the topics were taught using the inverted classroom model. The aim was to find out whether the model can help to better address groups with large differences in prior knowledge in mathematics. We report mainly positive feedback from the students, although the opinions vary greatly between the groups. The students appreciate the increased amount of practice in the classroom as well as the possibility to learn at their own pace. Exam performance remained constant in the topics taught using the inverted classroom compared to previous semesters. The exam performance of weaker students also remained constant.

We study a dual Monte-Carlo two-chain fragmentation model for hadron-hadron collisions. A comparison of the model with data from proton-proton, pion-proton and kaon-proton interactions is presented. This includes inclusive x-distributions in the fragmentation region, resonance production and forward-backward correlations.(To be published in z. Physik C) *) Permanent address: Karl-Marx-Universitat, Leipzig, GDR 1. INTRODUCTIONParticle production in high-energy hadron-hadron and hadronnucleus collisions is actively studied at present, but serious predictions from quantum chromodynamics (QCD) are lacking. Therefore different models are used to interpret the data. Models such as the one we consider here are constructed in the framework of the parton model together with dynamical assumptions motivated by QCD. We study the multi-chain fragmentation model, which starts from the dual topological unitarization (DTU) scheme [1]. Capella and Tran Thanh Van developed a two-chain model for hadron-hadron interactions [2] on the basis of the DTU scheme and generalized it to a multi-chain model for hadron-nucleus interactions [3]. This is the approach we already followed in Ref. [4]. There we presented a two-chain Monte-Carlo fragmentation model for hadron-hadron interactions and a multi-chain Monte-Carlo fragmentation model for hadron-nucleus collisions. The two-chain model for hadron-hadron scattering processes has the following features:(i) We construct two parton chains built up only from valence quarks of the projectile and the target particle.(ii) Going into the centre of mass system of the chains we fragment them into hadrons or hadron resonances using a Monte-Carlo chain decay fragmentation model developed earlier by the authors [5][6][7]. This model has been tested in comparison with data from e+e-annihilation [6] and from lepton-hadron interactions [8]. In order to apply such a hadronization scheme also to soft hadron-hadron interactions, we have to make the basic assumption that quark and antiquark jets from e+e-annihilation or diquark jets from lepton-hadron scattering processes do not differ strongly from the ones produced in hadron-hadron collisions. This jet universality is not derived theoretically, but experimental data strongly suggest such an assumption, see [9] for a review.(iii) For chains of very low invariant mass we slightly modify the kinematics and create directly stable hadrons or hadron resonances.-2 -(iv) Transforming all created hadrons and hadron resonances back into the laboratory system, we obtain a complete final hadronic state.Since we use a Monte-Carlo method we are able to generate exclusive events conserving exactly energy momentum and all additive quantum numbers.(v) The subsequent decay of hadron resonances into stable final hadrons is realized using the Monte-Carlo code DECAY [10].Since we are only interested in multiparticle production in the energy range from 5 or 10 GeV up to 1 TeV, it is sufficient to consider two chains containing only the valence quarks in hadron-hadron collisions....

Utility-scale battery storage systems typically consist of multiple smaller units contributing to the overall power dispatch of the system. Herein, the power distribution among these units is analyzed and optimized to operate the system with increased energy efficiency. To improve the real-life storage operation, a holistic system model for battery storage systems has been developed that enables a calculation of the energy efficiency. A utility-scale Second-Life battery storage system with a capacity of 3.3 MWh/3 MW is operated and evaluated in this work. The system is in operation for the provision of primary control reserve in combination with intraday trading for controlling the battery state of charge. The simulation model is parameterized with the system data. Results show that losses in power electronics dominate. An operational strategy improving the energy efficiency through an optimized power flow distribution within the storage system is developed. The power flow distribution strategy is based on the reduction of the power electronics losses at no-load/partial-load by minimizing their in-operation time. The simulation derived power flow distribution strategy is implemented in the real-life storage system. Field-test measurements and analysis prove the functionality of the power flow distribution strategy and reveal the reduction of the energy throughput of the units by 7%, as well as a significant reduction of energy losses in the units by 24%. The cost savings for electricity over the system's lifetime are approximated to 4.4% of its investment cost.

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