20005 research outputs found
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Joint training of predistortion, power back-off and constellation for satellite power amplifiers using neural networks
No full textThe deployment of satellite mega constellations may enable global coverage, even for direct transmission from satellite to handheld device. Such transmissions come with increased
demands in power efficiency. The traveling wave-tube amplifier (TWTA) in satellite payloads fundamentally limits the transmit power and causes distortions to the transmit signal when power efficient transmission close to amplifier saturation is desired. This work introduces a novel joint training paradigm of constellation, amplifier power back-off and data predistortion to maximize the throughput of single carrier transmission over transparent satellite links. The joint design is enabled by means of communication autoencoders, where transmitter and receiver components are adapted together to achieve the lowest bit error rate (BER). We show how constrained constellation optimization can improve performance on selected configurations from the broadcasting standard DVB-S2X. Results are presented in terms of coded BER and information rates
Decentralized real-time iterations for distributed NMPC
No full textThis article presents a Real-Time Iteration (RTI) scheme for distributed Nonlinear Model Predictive Control (NMPC). The scheme transfers the well-known RTI approach, a key enabler for many industrial real-time NMPC implementations, to the setting of cooperative distributed control. At each sampling instant, one outer iteration of a bi-level decentralized Sequential Quadratic Programming (dSQP) method is applied to a centralized optimal control problem. This ensures that real-time requirements are met and it facilitates cooperation between subsystems. Combining novel dSQP convergence results with RTI stability guarantees, we prove local exponential stability under standard assumptions on the MPC design with and without terminal constraints. The proposed scheme only requires neighbor-to-neighbor communication and avoids a central coordinator. A numerical example with coupled inverted pendulums demonstrates the efficacy of the approach
Interfacial ion hydration and electrostatics govern salt precipitation and crystal morphology
No full textSalt precipitation, a phenomenon central to processes such as soil salinization, water treatment, and energy storage, is dictated by nanoscale hydration and electrostatic interactions at crystal interfaces. Understanding how their interplay gives rise to salt-specific growth behaviors and morphologies remains a critical challenge. Combining large-scale molecular dynamics simulations with free energy calculations, we investigate the precipitation behavior of three common salts, namely, NaCl, KCl, and Na2SO4, on their respective crystal surfaces. While all crystals grow steadily under controlled supersaturation, their surface morphologies differ markedly. KCl grows in a nearly ideal layer-by-layer mode, whereas NaCl and Na2SO4 develop increasingly rough, defect-rich surfaces. This roughening is accompanied by an early-stage charge imbalance at the crystal surface, characterized by preferential cation adsorption. The resulting local electrostatic environment modifies the structuring and dynamics of interfacial water, which in turn facilitates the premature growth of subsequent layers. We further find that ion adsorption is strongly defect-dependent: kinks provide stabilizing environments, whereas steps are energetically unfavorable due to their distinct hydration. Our study offers molecular-level insight into the coupled roles of ion-specific adsorption and interfacial hydration in shaping crystal morphology for different salts
Ganzheitliche Nachhaltigkeitsbewertung und -optimierung unter Nutzung kartografischer Generalisierung
No full textThis paper presents an extension of the Process Atlas System (PAS) to enable holistic sustainability assessment in industrial processes. By integrating Life Cycle Assessment (LCA), Life Cycle Costing (LCC), and Social Life Cycle Assessment (SLCA), the new S-PAS method visualizes ecological, economic, and social impacts at process level. A case study on disposable paper cup production demonstrates how S-PAS supports early-stage decision-making in product development through clear, process-specific sustainability visualization
Towards safe Bayesian optimization with Wiener kernel regression
No full textBayesian Optimization (BO) is a data-driven strategy for minimizing/maximizing black-box functions based on probabilistic surrogate models. In the presence of safety constraints, the performance of BO crucially relies on tight probabilistic error bounds related to the uncertainty surrounding the surrogate model. For the case of Gaussian Process surrogates and Gaussian measurement noise, we present a novel error bound based on the recently proposed Wiener kernel regression. We prove that under rather mild assumptions, the proposed error bound is tighter than bounds previously documented in the literature, leading to enlarged safety regions. We draw upon a numerical example to demonstrate the efficacy of the proposed error bound in safe BO
FISH–FACS enabled targeted recovery of genomes from uncultivated environmental microbial populations
No full textAs most microbial diversity on Earth remains uncultivated, metagenomics and single-cell genomics have been established as crucial approaches for studying microbial assemblages. While these methodologies provide invaluable insights into the genetic makeup of microbial community members, the genomes recovered most often represent the abundant microorganisms or cells randomly captured. This limits the targeted recovery of genetic material from specific taxa of interest. We here present a comprehensive protocol for the targeted recovery of genomes from uncultivated environmental microorganisms by combining fluorescence in situ hybridization (FISH) with cell sorting. The protocol consists of (i) fixation of cells; (ii) labeling with hybridization chain reaction-FISH; (iii) fluorescence-activated cell sorting (FACS) of labeled populations. The genomic DNA of sorted cells can then be amplified and sequenced using previously established protocols. This procedure can be performed with standard molecular biology and fluorescence imaging equipment, including a FACS machine, and completed within 24 h. This protocol can be adapted for any bacterial or archaeal taxonomic group of interest with available 16S rRNA sequence information
Approach for investigation of CFRP tribological stressed interfaces through levels of abstraction
No full textCarbon Fiber Reinforced Plastics (CFRP) offer high lightweight potential, particularly for dynamic machine components due to their strength-to-weight ratio and low thermal expansion. However, integrating CFRP into stressed interfaces, such as tool spindles, poses challenges like anisotropic properties and tribological complexity. This study presents a multi-level approach to investigate and transfer tribological parameters in CFRP systems. Using the hierarchical product component test pyramid, it bridges product, structure and meterial levels, e.g. through simplified block-on-plate, as well as block-on-tube tests. Through abstracted and application-oriented test setups, key influencing factors can be identified and analyzed. The hierarchical test pyramid allows for stepwise knowledge transfer between abstraction levels, reducing testing effort without sacrificing relevant information
Sustainable sheet-metal design: employing the Product Carbon Footprint as support for engineers in developing new roduct generations
No full textThis study investigates a data-driven approach for integrating sustainability criteria into the design process to reduce the Product Carbon Footprint (PCF) of sheet-metal parts. In a Live-Lab research environment, the design solutions of four engineering teams were analyzed at each iteration to assess how immediate PCF feedback and detailed sustainability information impacted both the design process and the final Product Carbon Footprint of the sheet-metal parts. The findings show that understanding the influencing factors of sustainable sheet-metal design and receiving PCF feedback led to PCF reductions of over 30 %, highlighting the importance of quantifiable sustainability metrics in industrial design practices
Risikomanagement in Supply Chains : Compliance und resiliente Lieferketten – Realisierung von Chancen durch Risikosteuerung
No full textDie zunehmende Vernetzung globaler Lieferketten, technologischer Wandel und volatile Marktbedingungen stellen Unternehmen vor immer komplexere Entscheidungen. Das Risikomanagement in Supply Chains wird damit zur hoch dynamischen, proaktiv zu gestaltenden Kernfunktion, um langfristig wettbewerbsfähig und resilient zu bleiben. Orientiert am global anerkannten COSO-Rahmenwerk entwickelt das Expertenteam um Oliver Bungartz hierfür einen prägnanten Leitfaden: - Grundlagen und Prozess des Risikomanagements: Betriebswirtschaftlich, regulatorisch und methodisch - Governance und Kultur: Zu einer risikobewussten Unternehmenskultur und ihrer Implementierung - Risiken in der Ausführung: Analyse und Steuerung operationeller Risiken entlang der Wertschöpfungskette - Risikoinformation, -kommunikation und -berichterstattung: Insbesondere zum Stellenwert der Nachhaltigkeitsberichterstattung - Überwachung der Leistung: Prüfung, Evaluierung und kontinuierliche Prozessverbesserung Der anschließende Methodenteil stellt konkrete Instrumente und Techniken des Risikomanagements vor, mit denen sich Lieferketten nachhaltig stärken lassen