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Wideband channel modeling for wireless avionics intra-communications
No full textWireless Avionics Intra-Communications (WAIC) has been proposed to partially replace costly wiring in future generations of aircraft. Besides the allocation of a frequency range and several performance figures, there is no standardized transmission scheme so far. For the design of suitable physical layer techniques, comprehensive models are required to perform realistic link-level simulations for the aircraft environment. We present a wideband channel model for in-cabin WAIC systems, that has been derived from channel measurements performed in an Airbus A321 cabin. The model is validated by comparing physically measured frame error rates to simulated error ratesusing the proposed model in an OFDM transmission based on IEEE 802.11a applied to the WAIC frequency band
Hamburg Pluvial flood risk map
No full textThe "Hamburg Pluvial Flood Risk Map" aims to improve our understanding of the drivers, dynamics and interactions of climate-induced risks in Hamburg. Following the risk framework of the IPCC, we calculate a risk index based on hazard, exposure and (social) vulnerability. In this sense, we combine data from the previously published Social Vulnerability Index (von Szombathely et al., 2023) with novel meter-scale hydraulic simulations of urban flooding provided by the heavy rain hazard map of the city of Hamburg (BKG/FHH 2023), developing an integrated urban pluvial flood risk assessment. We enhance the modeling of social vulnerability by applying the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and the Shannon Entropy procedure. We propose high-resolution exposure modeling for residents affected by urban flooding, with two distinct exposure layers influencing well-being on the one hand and restricting mobility and accessibility on the other. We show that fundamentally new spatial patterns emerge for integrated pluvial flood risk in Hamburg, which differ from familiar socio-economic urban structures and at the same time differ clearly from a pure representation of the hazard. Presented through high-resolution spatial maps, this analysis aids in identifying adaptation needs and potential for sustainable transformation in urban areas and in prioritizing policy measures for climate change adaptation.
References:
BKG/FHH 2023. Eine Starkregen-Gefahrenkarte für Deutschland. https://www.business-geomatics.com/2023/02/02/eine-starkregen-gefahrenkarte-fuer-deutschland/
von Szombathely M., Hanf F. S., Janka B., Meier L., Ossenbrügge J., Pohl T. 2023. An Index-Based Approach to Assess Social Vulnerability for Hamburg, Germany: International journal of disaster risk science. 14, 5, p. 782-794 13 p. DOI: 10.1007/s13753-023-00517-
Untersuchungen zum Einspannvorgang von CFK-Werkzeugschnittstellen in konventionelle Werkzeughalter
No full textBundesministerium für Wirtschaft und Energie (BMWE
A network‐based approach to identifying key components in structural vibrations
No full textModeling the dynamics of systems with many interacting components, such as robots, wind turbines, and trusses, remains challenging today. These systems often display complex oscillatory responses to external inputs, and harmful vibrations might be excited along with the desired motion. Understanding the relative importance of individual components or systems aspects to the overall system dynamics could be a vital step towards focused design and maintenance efforts. This work proposes a network‐based approach to studying the dynamics of a mechanical system by representing the system as a network of coupled oscillators, where each node corresponds to a machine component and each link denotes a physical connection, such as a weld or bolt. Inspired by studies of dynamics in biological and social networks, we show how network measures can be used to predict the importance of a single oscillator, or component, for shaping the overall dynamics. We further demonstrate under which conditions these conclusions are possible, and where the metrics fail. This study hopes to contribute to the broader field of network‐based methods in engineering and yield insights that help focus design and maintenance efforts in the future
Covariance-based structural equation modeling (CB-SEM): a SmartPLS 4 software tutorial
No full textCovariance-based structural equation modeling (CB-SEM) enables researchers to estimate models with hypothesized cause-effect relationships between latent variables (i.e., constructs), each of which is operationalized by several items (i.e., indicators). To conduct CB-SEM analyses, researchers can rely on a range of software applications. However, many of these applications require researchers to engage in sometimes complicated and error-prone programming tasks. While IBM SPSS AMOS provides a graphical user interface (GUI), it does not fully meet the expectations of contemporary software. In order to address these challenges, the statistical SmartPLS 4 software has recently introduced a new CB-SEM module, which improves the user experience through a modern and intuitive graphical interface and comprehensive result reports. This tutorial describes the key CB-SEM analysis steps (i.e., model setup, estimation, and results evaluation) using the SmartPLS software
Capacitive deionisation for water desalination review: experimental and simulation
No full textCapacitive Deionization (CDI) has emerged as an energy-efficient and environmentally friendly technology for water desalination. This review provides a comprehensive analysis of CDI, covering both experimental and simulation approaches. It introduces the background, definition, and diverse applications of CDI, from water desalination to environmental monitoring and resource recovery. The review highlights CDI’s advantages, such as low energy consumption and operational simplicity, as well as its limitations, particularly its design-specific operating window favoring low-to-moderate salinity waters and sensitivity to organic-rich conditions. Strategies such as hybrid CDI systems and electrode surface functionalization are discussed to mitigate these challenges. Key working principles and advancements, including innovations in electrode materials, synthesis methods, and reactor design, are examined to improve ion removal efficiency, selectivity, energy use, and system durability. Material modification strategies are presented in the context of structure–performance relationships, emphasizing rational design principles. The review also explores simulation methods, including reactor modeling, computational fluid dynamics, molecular dynamics, and numerical approaches, and machine learning highlighting their synergy with experiments in optimizing CDI performance and guiding scale-up. Coupling CDI with other systems and its applications in water purification, particularly for ion and organic compound removal are also discussed. Finally, challenges in both experimental and simulation efforts, such as material cost, model complexity, computational demands, and scalability, are discussed. While CDI shows promise for sustainable water desalination and resource recovery, further research on hybrid configurations, predictive modeling, and pilot-scale validation is needed to address its limitations and enable large-scale adoption
Comparative analysis of impedance-based and eigenvalue-based approaches for stability assessment
No full textVarious methods for assessing the stability of power systems and components are available, with the most prominent small-signal techniques being eigenvalue-based and impedance-based approaches. Each method offers specific advantages and faces inherent limitations. This paper examines a small Direct Current (DC) grid and compares the applicability, accuracy, and key differences between these two stability assessment techniques, revealing novel insights regarding the imprecise results of the impedance-based approach. These results are relevant for stability investigations of Alternating Current (AC) and DC grids. As an example, a DC grid with a Dual-Active Bridge (DAB) converter feeding an inductive load via a transmission line modeled as a pi equivalent circuit is considered. The eigenvalue-based approach provides precise insight into the system's dynamic behavior at a given operating point by calculating participation factors for each state and mode in the system. Conversely, the impedance-based approach exhibits sensitivity to the partitioning of the system into source and load subsystems, which can lead to inaccuracies or misinterpretations. Additionally, the estimation of system impedance is influenced by the operating point, requiring careful analysis. The applicability of these methods to AC grids is also discussed
Neuordnung der industriellen M+E-Berufe – Etappen und Tragweite der Modernisierungen in den vergangenen vier Jahrzehnten
No full textAusgehend von vier Paradigmen der vergangenen vier Jahrzehnte, welche die Veränderungen in der Arbeitswelt der Metall- und Elektroindustrie charakterisieren, wird diskutiert, wie zukünftig die Metall- und Elektroberufe gestaltet werden sollen, um Veränderungsprozesse zu unterstützen. Im Mittelpunkt der Betrachtungen stehen dabei die strukturellen Veränderungen der vergangenen Jahrzehnte, die Relevanz der Arbeits- und Geschäftsprozesse, die Lernfelder in der Berufsschule sowie die Prüfungsgestaltung. Mit einer kritischen Reflexion der Teilnovellierung von 2018 werden die Ausführungen mit einem Blick in zukünftige Notwendigkeiten abgeschlossen
Investigation of the influence of thermal overloads on mechanical properties of S500 high-strength structural steel using electromagnetic testing technology
No full textHigh-strength steels are mostly realized via a very fine-grained microstructure by a thermomechanical manufacturing process. If the temperature of the steels exceeds a critical range, e.g., due to a fire or inappropriate flame straightening, coarse grain formation, and thus local damage in the form of softening of the structure can occur. This results in a lower fatigue strength. Currently, there is no possibility to inspect the mechanical properties directly on the structure after thermal exposure. To investigate the influence of thermal overloads on mechanical properties and the qualification of non-destructive electromagnetic testing technology for the detection of thermal damage, tensile and fatigue specimens of S500G1+M high-strength structural steel were subjected to different heat treatments in a preheated chamber furnace at temperatures of 550, 1000 and 1300 °C. The resulting changes in microstructure, hardness, yield strength, tensile strength, elastic modulus, fatigue strength and electromagnetic signals were compared to the initial state. The combined results show that thermal damage leading to a degradation of the mechanical properties can be detected using harmonic analysis of eddy current signals. Referencing the initial state in the impedance plane of the third harmonic, a deviation can be detected directly on the component or structure using rapid and non-destructive testing, thus indicating a change in the fatigue strength. In addition, the amplitudes of the first and third harmonics show an inverse correlation to hardness, yield strength and tensile strength