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Parametric study of the phase diffusion process in a gain-switched semiconductor laser for randomness assessment in quantum random number generator
Get PDFThe quantum phase noise in a pulsed semiconductor laser is studied thoroughly in the context of its utilization as a quantum entropy source in a quantum random number generator (QRNG) device. We performed a numerical analysis of the phase diffusion process for a semiconductor laser in the continuous-wave operation mode and gain-switched (GS) mode. The result demonstrates the amplification of randomness in the GS mode, which is gauged physically by the variance VarΔϕ. The variance value, which is mathematically related to the temporal distance between the laser pulses used in the experimental setup, also determines the stability of the setup. Furthermore, we show how the QRNG probability distribution is influenced by several experimental factors such as the quality of the interference process and the noise in the detection system
Visible-wavelength polarization-entangled photon source for quantum communication and imaging
Get PDFWe present a polarization-entangled photon pair source operating in the visible light range around 532 nm. Employing a collinear crossed-crystal scheme with type-I degenerate phase matching in barium borate (BBO), our source achieves a brightness of 9.5 k pairs/s/mW and a quantum state fidelity of 98.3%, making it a candidate for integration in microscopes and make use of the advantages of mid-visible optimized single-photon detection technologies. In order to study potential applications, we present a trade-off between source brightness and polarization entanglement visibility and propose use cases for different filtering configurations of the source, capable of a brightness up to 1.23 M pairs/s/mW
Optimization Approach for Long-Term Planning of Charging Infrastructure for Fixed-Route Transportation Systems
Get PDFAs the electrification of the transportation sector advances, fleet operators have to rethink their approach regarding fleet management against the background of limiting factors, such as a reduced range or extended recharging times. Charging infrastructure plays a critical role, and it is worthwhile to consider its planning as an integral part for the long-term operation of an electric vehicle fleet. In the category of fixed route transportation systems, the predictable character of the routes can be exploited when planning charging infrastructure. After a prior categorization of stakeholders and their respective optimization objectives in the sector coupling domain, a cost optimization framework for fixed route transportation systems is presented as the main contribution of this work. We confirm previous literature in that there is no one-fits-all optimization method for this kind of problem. The method is tested on seven scenarios for the public transport operator of Darmstadt, Germany. The core optimization is formulated as a mixed integer linear programming (MILP) problem. All scenarios are terminated by the criterion of a maximum solving time of 48 h and provide feasible solutions with a relative MIP-gap between 7 and 24%
Analyzing the flexibility potential of bus fleet operators in Germany
Get PDFThe transition to smart energy systems is a crucial component for ensuring sustainability and reducing carbon emissions. Electrification is a key factor in achieving these goals, with the transport sector being an integral part of the equation. The integration of the transport sector with the electricity sector will facilitate a reduction in carbon emissions. This paper assesses the potential of electric bus depots to function as smart energy infrastructures. Analyzing the energetic system flexibility of the electrified public transport system is at the core. Previous studies emphasize the importance of identifying and managing the optimal operation strategies of electrified transport to achieve system flexibility. This work concentrates on Germany as a reference market for balancing and electricity markets at the center of the EU. The flexibility potential of a bus fleet with 80 electric buses is analyzed under optimal participation in the short-term electricity and balancing market. The bus fleet operator acts as a storage systems aggregator, which combines mobile and stationary storages to enhance energy flexibility. The study measures the potential contribution for the stability of the electricity grid in Germany. The additional battery degradation that arises with the provision of balancing services is part of the economic equation. The analysis is based on historical data from 2020, 2021, and 2022 and investigates hypothetically lower and higher demand for balancing energy in the load-frequency control area of Germany and Denmark. The paper concludes by demonstrating the feasibility of the electrified bus depot as an integral component of smart energy systems. These findings contribute to a better understanding of the electrification of transport, sector integration, and the role of infrastructures in achieving smart energy systems and showcases the attractiveness of this business model
Application of mobile-macroscale scanning X-ray fluorescence (mobile-MA-XRF) imaging in paleontology: analyses of vertebrate fossil specimens from Messel conserved in different solid and liquid media
Get PDFCutting-edge analytical instrumentation is increasingly being developed and applied to the analysis of fossils. X-ray fluorescence (XRF) imaging spectroscopy is a powerful tool to resolve the elemental chemistry of fossil specimens. Most of the XRF application to study fossils is carried out at dedicated synchrotron radiation XRF beamlines. Recent studies used laboratory scanners, i.e. stationary instruments with a measurement chamber or mobile ones to tackle paleontological questions. The application of these new XRF systems on fossils is still relatively limited and clear protocols for the acquisition and processing of the XRF data are currently lacking. Here, we present the use of mobile-macroscale scanning XRF (mobile-MA-XRF) imaging for the in situ analyses of the elemental chemistry of fossil vertebrates from the Messel biota (∼48 Ma, Eocene), including amphibians, reptiles, mammals and birds. We investigate the usefulness of mobile-MA-XRF to detect tissue-specific elemental signatures in fossils preserved in solid resin, liquid glycerin and water. We found remarkable tissue-specific chemical signatures preserved in almost all specimens analyzed. Hair and feathers are associated with S and Ti, abdominal tissues with Cu and Zn and stomach contents, e.g., seeds, are associated with Ni, Cu, and Zn. We provide a detailed protocol for acquisition and processing of MA-XRF data and a critical discussion of the application of this approach to paleontological research. Our work sets the foundation for applying MA-XRF to the analyses of those fossils that cannot be measured at synchrotron facilities and/or with stationary laboratory scanners due to their dimensions, weights and conservation mode
Solving Bongard Problems With a Visual Language and Pragmatic Constraints
Get PDFMore than 50 years ago, Bongard introduced 100 visual concept learning problems as a challenge for artificial vision systems. These problems are now known as Bongard problems. Although they are well known in cognitive science and artificial intelligence, only very little progress has been made toward building systems that can solve a substantial subset of them. In the system presented here, visual features are extracted through image processing and then translated into a symbolic visual vocabulary. We introduce a formal language that allows representing compositional visual concepts based on this vocabulary. Using this language and Bayesian inference, concepts can be induced from the examples that are provided in each problem. We find a reasonable agreement between the concepts with high posterior probability and the solutions formulated by Bongard himself for a subset of 35 problems. While this approach is far from solving Bongard problems like humans, it does considerably better than previous approaches. We discuss the issues we encountered while developing this system and their continuing relevance for understanding visual cognition. For instance, contrary to other concept learning problems, the examples are not random in Bongard problems; instead they are carefully chosen to ensure that the concept can be induced, and we found it helpful to take the resulting pragmatic constraints into account
A method for approximating high frequency sound radiation - The plane projection Rayleigh integral
Get PDFThe sound radiation of vibrating surfaces can be calculated using integral-based numerical methods. Due to the increasing discretization requirements, the computational effort increases significantly with increasing frequencies. Therefore, approximation methods with less computational effort are desirable. This paper introduces a method called the plane projection Rayleigh integral (PPRI), which combines low computational effort with high precision. The method approximates the sound radiation by applying the Rayleigh integral to a vibrating virtual plane representing the object in two dimensions. The method's performance is evaluated by comparing it to the visible element Rayleigh integral and the high frequency boundary element method (HFBEM), focusing on the accuracy and its dependence on radius of surface curvature, sound frequency, and distance from the surface. Analytical solutions for the breathing and oscillating sphere are used as benchmarks. The PPRI demonstrates the highest accuracy among the methods tested. Error values decrease significantly with larger radii and higher frequencies, falling below a 1% threshold at 4 times smaller Helmholtz numbers (radius-wavelength ratio) than the HFBEM. Additionally, the PPRI requires the least computational time in this consideration. Thus, the PPRI achieves both high precision and efficiency
Eine Methodik zur Analyse und Synthese robuster sensorischer Funktionen
Get PDFDie Bereitstellung verlässlicher Messdaten zu relevanten Zustands- und Prozessgrößen technischer Systeme mittels sensorischer Funktionen ist in der Industrie 4.0 eine wesentliche Voraussetzung für die effektive Funktionserfüllung nachgelagerter Systeme zur Informationsverarbeitung, bspw. zur vorausschauenden Instandhaltung. Störgrößen können dabei einen wesentlichen Einfluss auf die Verlässlichkeit der Messdaten ausüben. Die Unempfindlichkeit einer sensorischen Funktion und somit der bereitgestellten Messdaten gegenüber Störgrößen wird als Robustheit bezeichnet und ist eine wichtige Zielgröße. Deren effektive Absicherung stellt jedoch eine Herausforderung in der Entwicklung sensorischer Funktionen dar, die bislang nur unzureichend methodisch unterstützt wird. Folglich besteht das übergeordnete Ziel dieser Arbeit in der effektiven Absicherung der Robustheit systemindividueller sensorischer Funktionen gegenüber Störgrößen, um die Verlässlichkeit der bereitgestellten Messdaten abzusichern. Dazu wird eine Methodik zur Analyse und Synthese robuster sensorischer Funktionen entwickelt.
Zunächst werden Ansätze der methodischen Produktentwicklung, des Robust Designs und der Messtechnik zur Identifikation, Analyse und Berücksichtigung von Störgrößen bzgl. ihrer Limitierungen vor dem Hintergrund der Zielsetzung dieser Arbeit untersucht. Basierend auf den daraus abgeleiteten Anforderungen wird eine entsprechende Methodik konzeptioniert, die sich aus einem Analyse- und einem Syntheseteil zusammensetzt. Der Analyseteil dient der Ermittlung kritischer Störgrößen einer systemindividuellen sensorischen Funktion, woraus die erste der beiden Forschungsfragen dieser Arbeit abgeleitet wird: Wie können Störgrößen einer systemindividuellen sensorischen Funktion effektiv ermittelt werden, die kritisch für die Verlässlichkeit der bereitgestellten Messdaten sind? Zur Beantwortung wird zunächst ein divergentes Vorgehen verfolgt, wobei eine Störgrößenmatrix zur systematischen Identifikation potenzieller Störgrößen auf Basis der mehrpolbasierten Modellbildung erarbeitet wird. Durch eine systematische Untersuchung deren Wirkungen auf eine sensorische Funktion auf Basis physikalischer Effekte erfolgt im Anschluss eine erste Fokussierung. Hierzu wird ein Effektgraphentool funktional erweitert. Anhand des quantitativen Ausmaßes der Wirkungen von Störgrößen und der verbundenen Unsicherheit erfolgt anschließend deren Bewertung. Auf Basis der Bewertungsergebnisse erfolgt in einer Entscheidung eine abschließende Fokussierung auf kritische Störgrößen. Im Syntheseteil wird die systematischen Berücksichtigung kritischer Störgrößen mittels Maßnahmen forciert, woraus die zweite Forschungsfrage resultiert: Wie kann die Robustheit einer systemindividuellen sensorischen Funktion gegenüber kritischen Störgrößen und somit die Verlässlichkeit der bereitgestellten Messdaten effektiv abgesichert werden? Zur Beantwortung wird zunächst ein divergentes Vorgehen mit der Entwicklung potenzieller Maßnahmen verfolgt. Hierzu wird ein Flussdiagramm erarbeitet, das die Auswahl prinzipiell anwendbarer Ansätze des Robust Designs sowie der Messtechnik ermöglicht. Auf Basis der Ergebnisse einer anschließenden Bewertung anhand eines gewichteten Zielsystems erfolgt abschließend eine Entscheidung hinsichtlich der umzusetzenden Maßnahmen zur Absicherung der Robustheit der sensorischen Funktion und damit der Verlässlichkeit der bereitgestellten Messdaten.
Die Beantwortung der Forschungsfragen und die Erreichung der Zielsetzung dieser Arbeit werden in einer Verifikation gezeigt. Dazu werden die Ergebnisse aus einer beispielhaften Anwendung der Methodik auf eine sensorische Funktion zur Versatz- und Drehfrequenzmessung einer Lamellenpaketkupplung und die Ergebnisse aus einer Probandenstudie herangezogen
Decentralized Singular Value Decomposition of Symmetric and non-Symmetric Matrices for Large-scale Sensor Networks
Get PDFThe Eigenvalue Decomposition (EVD) and the Singular Value Decomposition (SVD) are fundamental matrix factorization techniques that play crucial roles in various application areas such as signal processing, data mining, and machine learning. Efficient and numerically stable implementations of the EVD and SVD have been long-established research topics of interest, e.g., in sensor array processing. As the number of measurements increases drastically nowadays, the conventional approaches that collect all sample measurements in a fusion center to perform the EVD and SVD often become impractical or even impossible. To this end, scalable solutions are preferred, such as the decentralized approaches that involves only peer-to-peer communication and utilize local computation and storage resources.
In this thesis, we first propose a communication efficient decentralized EVD algorithm that addresses the EVD as the sum of the rank-one components. The proposed algorithm utilizes a local lightweight rational function approximation approach and parallel averaging consensus algorithms to estimate and track the eigenvalues and eigenvectors in a fully decentralized online manner. To further reduce the overall communication cost and local computational overhead, e.g., in applications of Principal Component Analysis, a novel and non-trivial truncation technique is proposed. Based on the proposed decentralized EVD algorithm, two types of important application examples are examined: the online EVD of a sample covariance matrix over the network with the application in decentralized Direction-of-Arrival estimation and tracking, and the online computation of the spectra of the graph Laplacian matrix that is important, e.g., in Graph Fourier Analysis and graph dependent filter design.
Second, we extend the proposed decentralized EVD algorithm to non-symmetric/non-Hermitian matrices to perform the decentralized SVD. Based on the availability of the matrix under consideration, two scenarios of the decentralized SVD are examined. While in the first scenario, the matrix of interest is row-wisely available in each local node in the network, in the second scenario, the matrix of interest implicitly forms an outer product generated from two different series of measurements. Combining the lightweight local rational function approximation approach and parallel averaging consensus algorithms, two decentralized implementations of the SVD are proposed to cope with the two aforementioned scenarios. In addition, two respective application examples in extremely large-scale sensor array systems are examined with the proposed decentralized SVD algorithms, i.e., the decentralized sensor localization via low-rank matrix completion for the first scenario and the decentralized passive radar detection for the second scenario.
All simulation results show that our proposed decentralized EVD and decentralized SVD algorithms benefit from the rank-one expressions and thus admit low overall communication cost compared with the state-of-the-art decentralized power method. By employing the truncation technique, both communication costs and local computational overhead are significantly reduced, while a performance comparable to that of the centralized approach is achieved, when principal components are present and of interest
Controlling Temporally and Spatially Homogeneous Temperature Distribution of Paper Substrates by Biogenic Phase Change Hybrid Material Coatings
Get PDFHere the performance of phase change material (PCM)‐coated paper made from unbleached kraft pulp is introduced. The applied PCM consists of a mixture of ethylene glycol distearate (EGDS), a well‐known PCM wax material, and a fully substituted cellulose stearoyl ester (CSE). Transfer of the PCM material onto/into paper is achieved by spray as well as blade coating of EGDS + CSE mixture. It is shown that the kind of coating method used does not interfere with observed PCM properties. The significantly higher melt viscosity of the EGDS + CSE blends ensures that the EGDS wax is not bleeding out of the paper, which avoids the use of further encapsulation processes. The PCM behavior, as observed by thermal load measurements, and the thermal buffering of the coated paper is a function of the applied mass of the PCM material applied. The thermal retention exhibited a quasi‐isothermal behavior at ≈65 °C with EGDS + CSE coatings. These effects can offset fluctuations in temperature, and the PCM papers can be employed to achieve a more uniform temperature setting. PCM‐modified papers are therefore interesting candidates for paper‐based packaging or for use in paper‐based sensors, where overheating can strongly affect reliability of results