Heralded photonic interaction between distant single ions

We establish heralded interaction between two remotely trapped single 40Ca+ ions through the exchange of single photons. In the sender ion, we release single photons with controlled temporal shape on the P_3/2 to D_5/2 transition and transmit them to the distant receiver ion. Individual absorption events in the receiver ion are detected by quantum jumps. For continuously generated photons, the absorption reduces significantly the lifetime of the long-lived D_5/2 state. For triggered single-photon transmission, we observe coincidence between the emission at the sender and quantum jump events at the receiver.Comment: 5 pages, 4 figures. v2: number on p. 3, bottom, correcte

Learning Multiple Defaults for Machine Learning Algorithms

The performance of modern machine learning methods highly depends on their hyperparameter configurations. One simple way of selecting a configuration is to use default settings, often proposed along with the publication and implementation of a new algorithm. Those default values are usually chosen in an ad-hoc manner to work good enough on a wide variety of datasets. To address this problem, different automatic hyperparameter configuration algorithms have been proposed, which select an optimal configuration per dataset. This principled approach usually improves performance, but adds additional algorithmic complexity and computational costs to the training procedure. As an alternative to this, we propose learning a set of complementary default values from a large database of prior empirical results. Selecting an appropriate configuration on a new dataset then requires only a simple, efficient and embarrassingly parallel search over this set. We demonstrate the effectiveness and efficiency of the approach we propose in comparison to random search and Bayesian Optimization

Stochastic Service Network Design for Intermodal Freight Transportation

In view of the accelerating climate change, greenhouse gas emissions from freight transportation must be significantly reduced over the next decades. Intermodal transportation can make a significant contribution here. During the transportation process, different modes of transportation are combined, enabling a modal shift to environmentally friendly alternatives such as rail and inland waterway transportation. However, at the same time, the organization of several modes is more complex compared to the unimodal case (where, for example, only trucks are employed). In particular, an efficient management of uncertainties, such as fluctuating transportation demand volumes or delays, is required to realize low costs and transportation times, thereby ensuring the attractiveness of intermodal transportation for a further modal shift. Stochastic service network design can explicitly consider such uncertainities in the planning in order to increase the performance of intermodal transportation. Decisions for the network design as well as for the mode choice are defined by mathematical optimization models, which originate from operations research and include relevant uncertainities by stochastic parameters. As central research gap, this dissertation addresses important operational constraints and decision variables of real-life intermodal networks, which have not been considered in these models so far and, in consequence, strongly limit their application in everyday operations. The resulting research contribution are two new variants of stochastic service network design models: The "stochastic service network design with integrated vehicle routing problem" integrates corresponding routing problems for road vehicles into the planning of intermodal networks. This new variant ensures a cost- and delay-minimal mode choice in the case of uncertain transportation times. The "stochastic service network design with short-term schedule modifications" deals with modifications of intermodal transportation schedules in order to adapt them to fluctuating demand as best as possible. For both new model variants, heuristic solution methods are presented which can efficiently solve even large network instances. Extensive case studies with real-world data demonstrate significant savings potentials compared to deterministic models as well as (simplified) stochastic models that already exist in literature

Design of a green chemoenzymatic cascade for scalable synthesis of bio-based styrene alternatives

As renewable lignin building blocks, hydroxystyrenes are particularly appealing as either a replacement or addition to styrene-based polymer chemistry. These monomers are obtained by decarboxylation of phenolic acids and often subjected to chemical modifications of their phenolic hydroxy groups to improve polymerization behaviour. Despite efforts, a simple, scalable, and purely (chemo)catalytic synthesis of acetylated hydroxystyrenes remains elusive. We thus propose a custom-made chemoenzymatic route that utilizes a phenolic acid decarboxylase (PAD). Our process development strategy encompasses a computational solvent assessment informing about solubilities and viable reactor operation modes, experimental solvent screening, cascade engineering, heterogenization of biocatalyst, tailoring of acetylation conditions, and reaction upscale in a rotating bed reactor. By this means, we established a clean one-pot two-step process that uses the renewable solvent CPME, bio-based phenolic acid educts and reusable immobilised PAD. The overall chemoenzymatic reaction cascade was demonstrated on a 1 L scale to yield 18.3 g 4-acetoxy-3-methoxystyrene in 96% isolated yield. © 2022 The Royal Society of Chemistry

Vergleich von Schülervorstellungen zur Elektrizitätslehre in Hessen und Weißrussland

Schülervorstellungen zur Elektrizitätslehre sind bereits lange Gegenstand physikdidaktischer Forschung. Im Rahmen einer Staatsexamensarbeit wurde untersucht, inwieweit typische Schülervorstellungen nach dem Elektrizitätslehreunterricht der gymnasialen Sek. I in Hessen und Weißrussland auftreten. Genutzt wurde hierzu das Testinstrument zum Verständnis der Elektrizitätslehre nach Urban-Woldron, das zu diesem Zweck auch ins Russische übersetzt wurde. Der Test besteht aus 22 Items und ermöglicht eine gezielte Analyse der spezifischen Schülervorstellungen und Lernschwierigkeiten. An der Untersuchung nahmen in Hessen sechs Lehrkräfte mit 154 Schülerinnen und Schülern sowie in Weißrussland vier Lehrkräfte mit 145 Schülerinnen und Schülern teil. Die Ergebnisse der Untersuchung deuten auf erhebliche Unterschiede im Fachwissen der GymnasiastInnen in Hessen und Weißrussland hin, da die SchülerInnen aus Weißrussland bei allen Testitems eine höhere Lösungshäufigkeit als ihre Mitschüler aus Hessen zeigten. Während hessische Schüler im Mittel μHessen= 7,8 Items korrekt beantworten konnten, lag dieser Wert für weißrussische Schüler bei μWeißrussland= 12,9. Die Unterschiede zwischen den beiden Schülergruppen sind hoch signifikant und werfen die Frage auf, wie diese zu erklären sind

Vergleich von Schülervorstellungen zur Elektrizitätslehre in Hessen und Weißrussland

Schülervorstellungen zur Elektrizitätslehre sind bereits lange Gegenstand physikdidaktischer Forschung. Im Rahmen einer Staatsexamensarbeit wurde untersucht, inwieweit typische Schülervorstellungen nach dem Elektrizitätslehreunterricht der gymnasialen Sek. I in Hessen und Weißrussland auftreten. Genutzt wurde hierzu das Testinstrument zum Verständnis der Elektrizitätslehre nach Urban-Woldron, das zu diesem Zweck auch ins Russische übersetzt wurde. Der Test besteht aus 22 Items und ermöglicht eine gezielte Analyse der spezifischen Schülervorstellungen und Lernschwierigkeiten. An der Untersuchung nahmen in Hessen sechs Lehrkräfte mit 154 Schülerinnen und Schülern sowie in Weißrussland vier Lehrkräfte mit 145 Schülerinnen und Schülern teil. Die Ergebnisse der Untersuchung deuten auf erhebliche Unterschiede im Fachwissen der GymnasiastInnen in Hessen und Weißrussland hin, da die SchülerInnen aus Weißrussland bei allen Testitems eine höhere Lösungshäufigkeit als ihre Mitschüler aus Hessen zeigten. Während hessische Schüler im Mittel μHessen= 7,8 Items korrekt beantworten konnten, lag dieser Wert für weißrussische Schüler bei μWeißrussland= 12,9. Die Unterschiede zwischen den beiden Schülergruppen sind hoch signifikant und werfen die Frage auf, wie diese zu erklären sind

Simulation and Validation of an Incremental Bending Process for Cylindrical Fuselage Components

In the aviation industry, a large number of processes are not digitalised. Simultaneously, many special processes are used in production, such as incremental bending. In order to model and efficiently design multi-stage processes with methods such as FEM, automation and linking of the individual simulations are necessary. This paper therefore presents a method for automatically simulating and evaluating a complete incremental bending process with 24 strokes in LS-Dyna using a Python framework with cfiles. The final validation of the force–displacement relationships and inner radii of the generated scaled fuselage shell show high prediction accuracies of about 90%. Thus, the presented methodology enables a FEM-based process design of incremental bending in the aviation industry