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Datengestützte Feedbackoptimierung für die Anwendung an Teilchenbeschleunigern
No full textFor many engineering problems involving control systems, finding a good working point for steady-state operation is crucial. Therefore, this paper presents an application of steady-state optimization with feedback on particle accelerators, specifically the European X-ray free-electron laser. In simulation studies, we demonstrate that feedback optimization is able to reach a near-optimal steady-state operation in the presence of uncertainties, even without relying on a priori known model information but purely data-driven through input-output measurements. Additionally, we discuss the importance of including second-order information in the optimization to ensure a satisfactory convergence speed and propose an approximated Hessian representation for problems without second-order knowledge on the plant
Design and implementation of a multi-link modem for future UAS networks
No full textProviding reliable communication services for Unmanned Aircraft Systems (UASs) is one of the remaining challenges hindering the deployment of large-scale UAS operations. In this paper, we describe the design and implementation of a multi-link modem developed to fulfill current and future communication needs. This modem combines LTE/5G with 868MHz based long-range communication, an Iridium satellite connection, and C-V2X to provide direct UAS to UAS communication with a low latency and a high data rate. To realize this, hardware components were selected and integrated into a communication stack. Custom software was developed to operate the hardware and intelligently utilize all available communication links. Real-world flight tests were conducted with the developed modems mounted on state-of-the art commercial UASs. In this work, we present an in-depth analysis of the performance of the direct C-V2X communication which is one of the proposed technologies for future UAS communication. Our results show that a communication range over 2km is achieved at an end-to-end delay of around 60ms
On Schrödinger operators with oblique transmission conditions on non-smooth curves
No full textIn a recent paper Behrndt, Holzmann, and Stenzel introduced a new class of two-dimensional Schrödinger operators with oblique transmissions along smooth curves. We extend most components of this analysis to the case of Lipschitz curves
Concept of manufacturing control for a workstation with sequence-dependent setup times in a make-to-stock production
No full textSequence-dependent setup times pose a challenge for a make-to-stock production. If companies apply setup-optimised sequencing to reduce setup efforts, varying replenishment times of the finished goods warehouse will increase the required safety inventories of the products. This publication presents a comprehensive manufacturing control concept for workstations with sequence-dependent setup times in make-to-stock production. The manufacturing control concept aims to effectively control the workstation and finished goods inventory, thereby enhancing the achievement of logistical objectives. The proposed concept integrates three relevant tasks of manufacturing control: order generation, capacity control, and sequencing. Cumulative Production Figures serve as a superordinate procedure, facilitating order generation and capacity control, while cyclical sequencing reduces setup efforts. Simulation experiments validate and evaluate the manufacturing control concept, demonstrating its effectiveness in managing setup efforts while limiting the negative impacts on required safety inventories. The results align with theoretical modeling and show potential for practical application in companies with make-to-stock production
Does a short journey get me to the food bank? An empirical study on fare-based public transport accessibility and its implications for social equity
No full textFares are a critical barrier for low-income earners towards using public transport (PT). While most literature focuses only on travel time and distance, we introduce the novel indicator of ‘fare accessibility’.
Fare accessibility extends Hansen Accessibility by incorporating pay-as-you-go costs as impedance, counting the amenity destinations reachable within a €2.30 ticket. To assess distributional equity of fare accessibility in the Greater Hamburg region (HVV) we use Lorenz curves. Furthermore, we employ spatial regression models to predict its variation based on eight factors, including PT service level, purchasing power and car availability. We calculate models at three spatial levels (municipality/PT stop/500 m grid) to discuss the influence of the Modifiable Area Unit Problem. In doing so, we assess the sensitivity and suitability of this indicator beyond established metrics.
Fare accessibility shows a significant relationship with centrality at all spatial levels. A single ticket offers the highest accessibility in densely-populated regions with a high PT service index, short travel times, low purchasing power and low car availability. While this hints towards using existing indicators at a regional level, fare accessibility helps to identify local deficits e.g. by quantifying the population without access to a food bank (which we understand as exemplary for any kind of destination). Overall, fare accessibility is less equally distributed than PT service and car availability; the HVV residents holding around half of the purchasing power are not able to reach any destination on a €2.30 budget, which is supposed to connect everyone to the next shopping centre. The share is dependent on spatial resolution, while a finer level improves sensitivity to inequity. With the Modifiable Area Unit Problem in mind, the stop level offers a suitable compromise between precision and computational capacity. Moreover, stop level analysis is compatible with practical PT planning.
Overall, fare accessibility emerges as an informative indicator for planners and policymakers. It can be expressed for numerous amenity destinations, offer insights into the daily struggles faced by low-income earners, and provide a tool to assess and improve accessibility for those most in need.Deutsche Forschungsgemeinschaft (DFG
Continuous-wave radar and motion-derived biomarkers for non-contact vital status classification in end-of-life care: A clinically validated machine learning approach
No full textIn palliative care, effective communication about anticipated death is critical for aligning therapeutic goals, managing family expectations, and ensuring dignified care. However, prognostic uncertainty - particularly regarding the time of death - remains a challenge due to the limited reliability of current methods. This study explores the potential of radar-derived motion biomarkers as a novel approach to distinguish between living and deceased patients, addressing the need for objective decision-support tools in palliative care. Using continuous-wave radar, we recorded the torso displacement (distance signal) of 16 palliative care patients during their dying phase and derived ground-truth annotations from electronic health records (EHR). Machine learning (ML) algorithms processed 5-minute segments of radar-derived motion signals for binary vital status classification. We evaluated the results with balanced accuracy, Gini gain, and SHAP values. Palliative care specialists provided qualitative feedback to ensure clinical relevance. The ML models achieved balanced accuracy of 0.92-0.98 in distinguishing vital states, demonstrating radar technology's potential as an objective monitoring tool. This study is the first to investigate continuous motion biomarkers in end-of-life patients under real-world clinical conditions, capturing physiological changes during this critical phase. Limitations include the challenges in EHR-derived annotation accuracy, as well as the inherent complexity of physiological variability near death. Our findings highlight radar technology's viability for complementary vital status monitoring in palliative care settings. By providing objective data, this approach could reduce prognostic uncertainty while maintaining patient dignity. This work bridges technological innovation with palliative care's humanistic ethos, offering new possibilities for evidence-based end-of-life management
Agriculture’s impact on water–energy balance varies across climates
No full textAgriculture is a cornerstone of global food production, accounting for a substantial portion of water withdrawals worldwide. As the world’s population grows, so does the demand for water in agriculture, leading to alterations in regional water–energy balances. We present an approach to identify the influence of agriculture on the water–energy balance using empirical data. We explore the departure from the Budyko curve for catchments with agricultural expansion and their associations with changes in the water–energy balance using a causal discovery algorithm. Analyzing data from 1,342 catchments across three Köppen-Geiger climate classes—temperate, snowy, and others—from 1980 to 2014, we show that temperate and snowy catchments, which account for over 90% of stations, exhibit distinct patterns. Cropland percentage (CL%) emerges as the dominant factor, explaining 47 and 37% of the variance in deviations from the Budyko curve in temperate and snowy catchments, respectively. In temperate catchments, CL% shows a strong negative correlation with precipitation-streamflow (P-Q) causal strength (Spearman Ƿ = −0.75), suggesting that cropland exacerbates precipitation-driven deviations. A moderate negative correlation with aridity-streamflow (AR-Q) causal strength (Ƿ = −0.42) indicates additional influences of cropland through aridity-driven interactions. In snowy catchments, CL% is similarly influential, with a positive correlation with P-Q causal strength (Ƿ = 0.51). However, the negative correlation with AR-Q causal strength (Ƿ = −0.45) underscores the role of aridity as a secondary driver. While vegetation and precipitation seasonality also contribute to the deviations, their impacts are comparatively lower. These findings underscore the need for inclusion of agricultural activities in changing water–energy balance to secure future water supplies
Higher order constellations for channels with residual phase noise and nonlinear power amplifiers
No full textIn satellite transponders, hardware impairments play a significant role when transmission at very high data rates is desired. Two components in satellite transponders causing
such impairments are the power amplifier and the oscillator. Particularly for high data rates, the power amplifier needs to be driven as close to saturation as possible, as doing so maximizes
transmit power. Operation close to saturation, however, causes clipping effects. The local oscillator, on the other hand, poses challenges to synchronization at the receiver particularly at high data rates. Hence, imperfect synchronizers can result in high residual phase noise which needs to be taken into account as additional hardware impairment. When it comes to designing
optimal transmit constellations, past research has treated these problems individually, resulting in spiral constellations for channels with high phase noise and amplitude and phaseshift
keying (APSK) constellations for channels with amplifiers operating close to saturation. In this work, we optimize high order constellation, i.e., with order 256, for channels with joint
impairment of power amplifier and residual phase noise. We optimize our constellations using neural networks, and propose an extension of spiral constellation optimization using a feedforward
network. We compare our proposed constellations to APSK constellations from DVB-S2X and spiral constellations and provide information rates for different severities of each
impairment
Unforeseen silly errors in network simulations and visualizations
No full textAccurate network simulations are essential for meaningful research. Factors like incorrect parameterization, unsuitable KPIs, or overlooking key aspects in design and modeling may result in misleading conclusions, time- and resource-waste. In this paper, we share our genuine experiences from working with bachelor's, master's and PhD students, with the focus on three scenarios where distinct simulation errors commonly occur. The first two scenarios highlight cases of unjustifiable results, leading to investigations that uncovered "silly errors"in randomization and visualization. The third scenario, though properly modeled, failed to capture the overall picture needed to reflect real-world outcomes. By sharing these lessons learned across experience levels using packet level network simulations, we aim to help students and researchers achieve more credible results while saving valuable time
Computational complexity of unitary and state design propertie
No full textWe investigate unitary and state -designs from a computational complexity perspective. First, we address the problems of computing frame potentials that characterize (approximate) -designs. We present a quantum algorithm for computing frame potentials and establish the following: (1) exact computation can be achieved by a single query to a # oracle and is #-hard; (2) for state vectors, deciding whether the frame potential is larger than or smaller than certain values is -complete, provided that the promise gap between the two values is inverse polynomial in the number of qubits; and (3) for both state vectors and unitaries, this promise problem is -complete if the promise gap is exponentially small. Second, we address the promise problem of deciding whether or not a given set is a good approximation to a design. Given a certain promise gap that could be constant, we show that this problem is -hard, highlighting the inherent computational difficulty of determining properties of unitary and state designs. We further identify implications of our results, including variational methods for constructing designs, diagnosing quantum chaos, and exploring emergent designs in Hamiltonian systems