Helmut Schmidt University

Selective etching of material areas modified by femtosecond laser pulses in the volume of lithium tantalate has been applied to produce hollow microchannels. In a fully monolithic approach, microchannels up to 2.5 mm long with cross sections of 2.5 µm × 20 µm were etched into the crystal volume at a depth of 430 µm. The influence of the laser repetition rate, the pulse energy and the writing speed on the etching time and the etching selectivity was investigated as part of a systematic study. Characteristic process parameters, i.e. selectivity and diffusion coefficient were determined by fitting the etch depth versus time using a superdiffusion model. The obtained parameters are suitable for predicting the results of selective etching for certain process parameters, and thus enable the process to be controlled. A similar study was carried out in sapphire for comparison purposes.

The chapter provides two cases of development finance impact evaluation. The first case is focused on evaluating the impact of the multilateral development aid on socio-economic indicators. The second case assesses the FDI as a source of private development finance. In conclusion the issues of evaluating the impacts of private and of public development flows will be compared.

The chapter will focus on private mechanisms for development finance. It starts with international approaches to define private finance for development and related international frameworks. A special emphasis will be placed on M&E of private development finance.

This chapter will focus on official development assistance (ODA) as the greatest source of public development finance in international development cooperation. First, the statistical methodological framework will be considered. Second, statistics on multilateral and bilateral aid will be collected. Third, the statistical issues on climate-related development finance will be discussed.

The chapter analyzes methodological framework for M&E of development finance. It dwells on multilateral and bilateral approaches to establish monitoring and evaluation systems for development finance. The chapter represents the experience both of industrial donor countries and of developing countries, who receive the development finance. It concludes with the best practices for establishing M&E systems for development finance.

This chapter will focus on theoretical dimension of private and public development finance. On the one hand, it will analyze development aid as a public source of development finance. On the other hand, as for the private development finance foreign direct investments (FDI) will be considered. A special emphasis will be made on theoretical preconditions for development finance evaluation.

Corporate actors are more resourceful, more powerful and more capable of influencing their own conditions of action than most other actors. This curated article argues that to imagine the future of corporate actors in a world that is rapidly changing due to the possibilities of digital technology and sustainability challenges, we also need to revisit dominant conceptualizations of the corporate actor in economic or social science research. The four essays included in this article draw on different theories to elaborate on the role that corporate actors play, could play, or should play in the future. The problems that the authors identify in their essays include the power and wrongdoing of corporate actors; the ability of corporate actors to create their environment, not just react to it; the lack of a concept of (corporate) responsibility capable of responding to the desiderata of society; and the accountability of corporate actorhood outside the boundaries of formal organizations. By providing reflections on these problems, this article—written against the background of the historical peculiarities of German business administration research marked by a neglect of collectivist concepts such as corporate actors—shows that research and society actively co-construct the roles and responsibilities of corporate actors. The performativity of theories addressing corporate actors is thus a concern for business administration scholars aiming to contribute to a more sustainable future.

The phenomenon of liquid metal embrittlement (LME) poses safety concerns for welded joints in the manufacturing field. In present study, LME was observed in refill friction stir spot welding (refill FSSW) of dissimilar magnesium (Mg) to galvanized steel. This marks the first reported proof of evidence of LME in the field of solid-state welding. Microstructural characterization of cracks formed during the welding process revealed typical characteristics of LME, specifically the penetration and enrichment of Zn at the Mg alloy grain boundaries and the formation of a liquefied phase. Tensile tests of Zn-coated Mg alloy were conducted at elevated temperatures to validate the LME phenomenon in refill FSSW and to identify the temperature range in which LME occurs. Based on these observations, a mechanism of LME formation for the Mg-Zn system in refill FSSW is proposed. Additionally, strategies to prevent LME are suggested and experimentally validated.

Auxetic materials are characterized by their negative Poisson's ratio, which also leads to several other beneficial properties. For example, a low density, high indentation resistance, and high energy absorption capacity enable applications in lightweight construction, ballistic protection, and shock absorption. A modified auxetic reentrant structure has previously been optimized to maximize its mass‐specific energy absorption capacity for ideal usage in lightweight construction. Yet, the structure is only composed of a single‐material, whereas, a multimaterial approach can improve its ability to exhibit auxetic deformation, if its vertical struts are composed of a material with a higher stiffness than the horizontal struts. Hence, the present contribution shows that the usage of multiple materials combined into the same structure leads to severe improvements of the overall performance. Therefore, quasi‐static experiments are carried out on 3D‐printed samples of a reentrant structure consisting of two different polymers and compared to each individual phase. Additionally, simulations are performed using LS‐DYNA to get a deeper understanding of the deformation process. While the fabrication can be challenging, the characteristic deformation behavior is improved significantly, leading to a 50% lower Poisson's ratio as well as enhanced failure characteristics, which are especially noticeable through digital image correlation analysis.

Elastocaloric technology is currently the most promising alternative air conditioning technology, in terms of environmental friendliness and efficiency. To optimize an elastocaloric machine in its entity, it is essential to research and improve all components, from the material to efficient load concepts. This work is dedicated to the evaluation of triply periodic minimal surface (TPMS) structures for use as heating/cooling element within an elastocaloric machine. TPMS structures have promising properties such as a high surface/volume ratio, which offers great potential for the exchange of generated thermal energy with the environment. They consist of continuous curved surfaces without notches, which act as nucleation points for fatigue cracks under cyclic loading, commonly found in continuous operating cooling devices. The structures Gyroid, Diamond, Schwarz, and FischerKochS are compared by simulating compression tests. The elastocaloric efficiency, defined as the quotient of generated thermal energy and invested mechanical work and the heat exchange potential, are used as evaluation criteria. To illustrate the improvement that can be achieved by using TPMS structures instead of conventional geometries, a tube is used as a comparative geometry. The observed deformation mechanisms are correlated with the results of a geometric analysis to determine optimization strategies for the investigated structures.

Hopes and fears about algorithmic predictions are often rooted in the assumption that they represent a particularly actionable form of knowledge. Algorithmic predictions, the story goes, turn historical data into anticipatory actions instantly and on a large scale. Recent empirical evidence, however, casts doubt on whether algorithmic predictions are best understood as being inherently actionable. In this study, we draw on adjacent debates about actionable knowledge and reconceptualize the actionability of predictions as an active and deliberate construction accomplished by the designers of algorithmic systems. We demonstrate the value of this new perspective using material from an ethnographic research project on predictive policing in Germany. Over a 12-month period, we followed the work of designers in a police research unit responsible for developing an algorithmic system that generates crime predictions. We found that an important part of the designers' work is calibrating the predictions. When engaging in calibration work, the designers adjust the form of the statistically calculated predictions-their volume, time, and space-to reflect their assumptions of what is most actionable knowledge for frontline police officers. Our study highlights a type of work on algorithmic systems that has received little attention, but which can have a significant impact on how the intended effects of algorithmic predictions are translated into their users' actions.

A major limitation of laser interferometers using continuous wave lasers are parasitic light fields, such as ghost beams, scattered or stray light, that can cause nonlinear noise. This is especially relevant for laser interferometric ground-based gravitational wave detectors. Increasing their sensitivity, particularly at frequencies below 10 Hz, is threatened by the influence of parasitic photons. These can up-convert low-frequency disturbances into phase and amplitude noise inside the relevant measurement band. By artificially tuning the coherence of the lasers, using pseudo-random-noise (PRN) phase modulations, this influence of parasitic fields can be suppressed. As it relies on these fields traveling different paths, it does not sacrifice the coherence for the intentional interference. We demonstrate the feasibility of this technique experimentally, achieving noise suppression levels of 40 dB in a Michelson interferometer with an artificial coherence length below 30 cm. We probe how the suppression depends on the delay mismatch and length of the PRN sequence. We also prove that optical resonators can be operated in the presence of PRN modulation by measuring the behavior of a linear cavity with and without such a modulation. By matching the resonators round-trip length and the PRN sequence repetition length, the classic response is recovered. Published by the American Physical Society 2025

Abstrakt Eine zentrale Aufgabe von BauingenieurInnen ist die Auswahl geeigneter Werkstoffe für neue Bauwerke und Instandhaltung der bestehenden Bausubstanz. Neben Festigkeits‐ und Verformungsverhalten sind Langlebigkeit und geringe Umweltauswirkungen essenziell. Daher sind fundierte Kenntnisse über Eigenschaften, Herstellung und Verarbeitung verschiedener Werkstoffe wie Beton, Stahl, Mauerwerk, Holz, Asphalt oder Polymere erforderlich. Neben der etablierten Materialcharakterisierung gewinnen datenbasierte Analysemethoden – wie Künstliche Intelligenz (KI) und Machine Learning (ML) – zunehmend an Bedeutung. Gleichzeitig führt die wachsende Relevanz von Materialrecycling und der Wiederverwendung von Bauteilen zu einer zusätzlichen Zunahme der Komplexität. Werkstoffe spielen eine Schlüsselrolle für Nachhaltigkeit und Ressourcenschonung, sodass BauingenieurInnen ökologische, ökonomische und soziale Aspekte auf Projekt‐ und Systemebene berücksichtigen müssen, um nachhaltige Entscheidungen zu treffen. Das Memorandum zur Hochschullehre „Werkstoffe im Bauwesen“ verankert diese Kompetenzen im Bauingenieurstudium, um künftige Generationen zu befähigen, nachhaltige, langlebige und klimaresiliente Bauwerke zu schaffen und die Lebensdauer des Bauwerksbestandes zu verlängern. Es lädt dazu ein, bestehende Curricula zu reflektieren und an veränderte Rahmenbedingungen anzupassen.

Zusammenfassung Die praxeologisch-wissenssoziologische Professionstheorie fokussiert die organisatorischen und interaktionalen Fundamente professionellen Handelns. Mit ihren empirischen Anschlüssen und einer ausgefeilten Grundlagentheorie hat sie in wenigen Jahren breite Anwendung nicht nur in der erziehungswissenschaftlichen Forschung gefunden. Mit ihrem Kernbegriff der „konstituierenden Rahmung“ und der Unterscheidung von „Erst-“ und „Zweitcodierung“ nimmt sie die Bedingungen der Möglichkeit professionalisierten pädagogischen Handelns und dessen Scheitern in den Blick. Hieran kritisch anknüpfend, wird in dem Aufsatz erstens vorgeschlagen, der polysozialen Ebene , auf der sich professionalisierte Interaktionen vollziehen, mit dem Begriff des habituierten Interaktionsraums Rechnung zu tragen, zweitens das pädagogische Handeln begrifflich (nach Erziehung, Lehre, Sorge, etc.) zu differenzieren und drittens den „pädagogischen Grundmodus“ (Thomsen 2025), in dem es sich vollzieht, zu bestimmen.

This mixed-methods study examined Japanese and German viewers’ aesthetic appreciation of Bugaku, a traditional Japanese court dance performed in religious ceremonies for over a millennium. In Study 1, we administered questionnaires to German Bugaku practitioners and interviewed a Japanese Bugaku instructor in Germany. The findings revealed cultural differences in the perception of Bugaku’s characteristic movements—described as slow, flowing, and grounded—in contrast to Western dance forms. German participants reported feelings of awe and sublimity when viewing Bugaku, emphasizing the dance’s transcendent qualities. In Study 2, Japanese ( N = 392) and German ( N = 409) participants viewed a professional Bugaku performance and evaluated it along five aesthetic dimensions derived from Study 1: Preference, Transcendent Experience, Gracefulness, Harmony and Structure, and Movement Comprehension. Japanese participants gave higher ratings for Preference, Transcendent Experience, Gracefulness, and Harmony and Structure. German participants reported higher levels of Movement Comprehension. Hierarchical multiple regression analyses, controlling for demographics and other individual differences, revealed two significant cultural interactions. First, cultural background moderated the relationship between Movement Comprehension and Preference: Higher comprehension predicted lower Preference among German but not Japanese participants. Second, cultural background moderated the influence of Harmony and Structure on perceived Gracefulness. This relationship was stronger among German participants. These cultural differences may be explained by variations in cognitive processing styles (holistic vs. analytical) and culturally shaped schemata. The findings demonstrate that traditional performing arts are interpreted through culturally specific cognitive frameworks, while simultaneously evoking universal emotional responses such as awe and transcendence.

We demonstrate dual-comb spectroscopy in the deep UV at 257 nm with an etalon, supported by molecular spectroscopy of iodine at 515 nm. Our free-running thin-disk oscillator provides an average power of 25 W at 1030 nm that is frequency doubled and quadrupled to generate up to 15 W in green and 1.5 W in deep UV. The peak and average power levels in the deep UV generated from the thin-disk oscillator are one order of magnitude higher than in previous systems. The compact frequency conversion setup enables parallel dual-comb spectroscopy in the spectral bands. We use a self-referenced digital correction scheme to achieve a high signal-to-noise ratio (SNR) via coherent interferogram averaging. In the deep UV, our 62 MHz oscillator achieves a SNR of 69 dB at GHz resolution within a 1 s measurement time, covering a spectral span of 2 THz. Our free-running system presents a straightforward solution for precise deep UV dual-comb spectroscopy.

Neural Ordinary Differential Equations (Neural ODEs) have emerged as a promising approach for learning the continuous-time behaviour of dynamical systems from data. However, Neural ODEs are black-box models, posing challenges in interpreting and understanding their decision-making processes. This raises concerns about their application in critical domains such as healthcare and autonomous systems. To address this challenge and provide insight into the decision-making process of Neural ODEs, we introduce the eXplainable Neural ODE (XNODE) framework, a suite of eXplainable Artificial Intelligence (XAI) techniques specifically designed for Neural ODEs. Drawing inspiration from classical visualisation methods for differential equations, including time series, state space, and vector field plots, XNODE aims to offer intuitive insights into model behaviour. Although relatively simple, these techniques are intended to furnish researchers with a deeper understanding of the underlying mathematical tools, thereby serving as a practical guide for interpreting results obtained with Neural ODEs. The effectiveness of XNODE is verified through case studies involving a Resistor–Capacitor (RC) circuit, the Lotka–Volterra predator-prey dynamics, and a chemical reaction. The proposed XNODE suite offers a more nuanced perspective for cases where low Mean Squared Error values are obtained, which initially suggests successful learning of the data dynamics. This reveals that a low training error does not necessarily equate to comprehensive understanding or accurate modelling of the underlying data dynamics.