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Particularly for manufactured products subject to aesthetic evaluation, the industrial manufacturing process must be monitored, and visual defects detected. For this purpose, more and more computer vision-integrated inspection systems are being used. In optical inspection based on cameras or range scanners, only a few examples are typically known before novel examples are inspected. Consequently, no large data set of non-defective and defective examples could be used to train a classifier, and methods that work with limited or weak supervision must be applied. For such scenarios, I propose new data-efficient machine learning approaches based on one-class learning that reduce the need for supervision in industrial computer vision tasks. The developed novelty detection model automatically extracts features from the input images and is trained only on available non-defective reference data. On top of the feature extractor, a one-class classifier based on recent developments in deep learning is placed. I evaluate the novelty detector in an industrial inspection scenario and state-of-the-art benchmarks from the machine learning community. In the second part of this work, the model gets improved by using a small number of novel defective examples, and hence, another source of supervision gets incorporated. The targeted real-world inspection unit is based on a camera array and a flashing light illumination, allowing inline capturing of multichannel images at a high rate. Optionally, the integration of range data, such as laser or Lidar signals, is possible by using the developed targetless data fusion method.
Stress management is becoming increasingly important in our society. It is evident that stress, whether measured subjectively or physiologically, has a detrimental effect on decision-making abilities and significantly impacts an individual's health and well-being, as well as the private and public economy. While technological advances simplify our daily lives, managing stress is more challenging than ever due to individual perceptions, cultural nuances, and personality traits. The need to respond quickly to workplace challenges, traffic, and the drive to achieve more is making chronic stress more prevalent, underscoring the importance of understanding, measuring, and predicting stress. In this work, stress is defined as the body's response to a stressor. Stressors can be either short-term or long-term, causing the body to function differently than it should, but also helping it respond to and cope with situations. Common ways of measuring stress include two main approaches: the classic method using questionnaires or direct conversations, and the use of physiological signals. In this research, we used questionnaires and heart rate characteristics to determine baseline stress levels, compared stress with physical activity, and studied the relationship between stress, personality traits, and demographics of the participants. It is important to remember that stress cannot be entirely avoided in our lives. Stress optimizes bodily functions and assists in coping with dangerous or challenging situations. However, it is possible to develop a system that helps us understand and detect stress more efficiently, thereby avoiding dangerous or hazardous situations. This could lead to significant improvements in sectors where errors are costly or can influence health. By doing so, a better understanding, better management, and a reduction of the negative long-term effects of stress can be achieved.
The Hadamard product of two matrices of the same order is obtained by entry-wise multiplication of their coefficients. In a similar way, the Hadamard power of a matrix and a polynomial is formed by real powers of their coefficients. Results for the Hadamard product of some important classes of matrices, e.g., positive definite matrices, conditionally negative definite matrices, and matrices with one positive eigenvalue are presented. The results are extended to give sufficient conditions for symmetric matrices to have exactly one positive eigenvalue. A Hurwitz (or stable) polynomial is a real polynomial whose roots are located in the open left half of the complex plane. Results for the Hadamard square root of Hurwitz polynomials of degree five are given. Also, a type of Oppenheim's inequality for Hurwitz matrices is presented. Finally, interval matrices, i.e., matrices with intervals as entries are studied, and new results for the interval property of several classes of matrices, e.g., inverse M-matrices, conditionally positive (negative) semidefinite matrices, and infinitely divisible matrices are given.
Flash memory is essential in modern electronics due to its fast access, high storage density, and cost-effectiveness. As the demand for expanded local storage capacity continues, its appliance is increasing.
This work primarily focuses on enhancing the reliability of flash memories. It begins with a comprehensive characterization of the flash channel, identifying and analyzing various sources of errors. The study delves into different bit-labeling schemes and investigates the achievable capacities associated with them. Additionally, the importance of read reference voltages is explained, particularly in adapting them to the life-cycle condition. The thesis also introduces calibration and adaptation algorithms for this purpose.
The challenges related to error correction codes are addressed extensively, focusing on algorithms designed to reduce decoding complexity. The research delves into low-complexity decoding techniques, particularly for scenarios involving small code lengths. Another area of investigation is concatenated codes based on small cyclic codes.
Furthermore, the thesis explores the advantages of joint processing of NAND flash pages, highlighting improvements in hard-decision decoding to minimize the need for additional read-out operations. This joint processing approach is thoroughly compared with conventional processing methods to assess its effectiveness and potential benefits.
Overall, this thesis contributes to enhancing the reliability of flash memories while proposing optimizations for their decoding processes.
Torsionsschwingungen von Radsätzen mit torsionssteif gekoppelten Radkörpern können beträchtliche Torsionsmomente in der Radsatzwelle von Schienenfahrzeugen verursachen. Die Anregung der Schwingung erfolgt durch einen mit zunehmender Gleitgeschwindigkeit abfallenden Kraftschluss im Rad-Schiene-Kontakt. Messergebnisse zeigen, dass die entstehenden dynamischen Torsionsmomente in der Radsatzwelle ein Vielfaches des quasistatischen Nennmoments betragen können.
Die vorliegende Arbeit beschreibt verschiedene Berechnungsverfahren die realistische, maximale, dynamische Torsionsmomente der Radsatzwelle ermitteln. Außerdem werden Konstruktionspotentiale identifiziert, die das dynamische Torsionsmaximum reduzieren. Auf Grundlage der Rad-Schiene-Kontaktmechanik und der Analyse von Messdaten werden einerseits kritische, schwingungsanregende Kraftschlussfunktionen ermittelt und andererseits die relevanten Eigenfrequenzen der Antriebssysteme festgestellt. Die modellierten Mehrkörpersysteme ermöglichen durch Modalanalysen ein tieferes Verständnis der Schwingungssysteme im Hinblick auf die zu untersuchende Radsatz-Torsions-schwingung. Parameterstudien und Stabilitätsuntersuchungen zeigen die Einflüsse auf die Dämpfung und des damit verbundenen dynamischen Torsionsmoments, wodurch mehrere Optimierungsmaß-nahmen aufgezeigt werden können. Der entwickelte Berechnungsansatz führt schließlich durch gezielte Vereinfachungen auf ein analytisches Verfahren, welches im Vergleich zu den numerischen Berechnungen akzeptable Ergebnisse hinsichtlich des dynamischen Torsionsmaximums erreicht und in der Vorauslegung von Radsätzen und Antriebssystemen verwendet werden kann.
IT-Compliance in KMU
(2023)
Trotz des dringenden Erfordernisses einer nachhaltigen und unabhängigen Energieerzeugung und bereits steigender Anteile photovoltaisch erzeugten Stroms stockt die Verbreitung der bauwerkintegrierten Photovoltaik (BIPV). Zahlreiche „Leuchtturm“-Projekte zeigen das große ästhetische Potential solaraktiver Bauteile und dennoch werden insbesondere von Architekt/innen-Seite neben vermeintlichen Einschränkungen in der planerischen Freiheit immer wieder auch gestalterische Vorbehalte angeführt.
Bisher wurde im Zusammenhang mit PV-Bauteilen schwerpunktmäßig die technische und konstruktive Einfügung thematisiert. Um einen Beitrag zur Diskussion um die Entwicklung visuell überzeugender Ergebnisse zu leisten, die verhindern, dass photovoltaische Bauteile am Gebäude als Fremdkörper wahrgenommen werden, ermittelt die vorliegende Arbeit auf der Grundlage ästhetischer Architekturtheorien allgemeingültige Kriterien für architektonische Wirkungsqualität und transferiert diese auf den Bereich der BIPV-Gestaltung.
Dabei werden zum Verständnis erforderliche Grundlagen der BIPV-Systemtechnik vermittelt sowie verfügbare Bauteile und die unterschiedlichen Akteure und Ziele bei der Gestaltung von BIPV aufzeigt. Auch die speziellen funktionalen und technischen Anforderungen, die PV-Bauteile als „aktive“ Bauteile stellen, werden berücksichtigt und hinsichtlich ihrer hemmenden oder synergetischen Wechselwirkungen differenziert.
Im Rahmen einer Projektstudie finden die oben genannten Kriterien Anwendung auf 13 „best practice“-Beispiele aktueller Wettbewerbsgewinner des vom Solarenergieförderverein Bayern e. V. (SeV) ausgelobten „Architekturpreis Gebäudeintegrierte Solartechnik“, die in Form von Steckbriefen vergleichend dargestellt werden.
Das Ergebnis ist die Synthese eines Kriterienkatalogs als Orientierungs-, Planungs- und Kommunikationswerkzeug, in dem alle Ergebnisse systematisiert zusammengestellt werden.
Ergänzend wird in einem kurzen Exkurs auf von der Hauptuntersuchung ausgenommene, für die Praxis aber relevante Schnittstellen zu wirtschaftlichen Aspekten eingegangen.
Public-key cryptographic algorithms are an essential part of todays cyber security, since those are required for key exchange protocols, digital signatures, and authentication. But large scale quantum computers threaten the security of the most widely used public-key cryptosystems. Hence, the National Institute of Standards and Technology ( NIST ) is currently in a standardization process for post-quantum secure public-key cryptography. One type of such systems is based on the NP-complete problem of decoding random linear codes and therefore called code-based cryptography. The best-known code-based cryptographic system is the McEliece system proposed in 1978 by Robert McEliece. It uses a scrambled generator matrix as a public key and the original generator matrix as well as the scrambling as private key. When encrypting a message it is encoded in the public code and a random but correctable error vector is added. Only the legitimate receiver can correct the errors and decrypt the message using the knowledge of the private key generator matrix. The original proposal of the McEliece system was based on binary Goppa codes, which are also considered for standardization. While those codes seem to be a secure choice, the public keys are extremely large, limiting the practicality of those systems. Many different code families were proposed for the McEliece system, but many of them are considered insecure since attacks exist, which use the known code structure to recover the private key. The security of code-based cryptosystems mainly depends on the number of errors added by the sender, which is limited by the error correction capability of the code. Hence, in order to obtain a high security for relatively short codes one needs a high error correction capability. Therefore maximum distance separable ( MDS ) codes were proposed for those systems, since those are optimal for the Hamming distance. In order to increase the error correction capability we propose q -ary codes over different metrics. There are many code families that have a higher minimum distance in some other metric than in the Hamming metric, leading to increased error correction capability over this metric. To make use of this one needs to restrict not only the number of errors but also their value. In this work, we propose the weight-one error channel, which restricts the error values to weight one and can be applied for different metrics. In addition we propose some concatenated code constructions, which make use of this restriction of error values. For each of these constructions we discuss the usability in code-based cryptography and compare them to other state-of-the-art code-based cryptosystems. The proposed code constructions show that restricting the error values allows for significantly lower public key sizes for code-based cryptographic systems. Furthermore, the use of concatenated code constructions allows for low complexity decoding and therefore an efficient cryptosystem.
This thesis presents the development of two different state-feedback controllers to solve the trajectory tracking problem, where the vessel needs to reach and follow a time-varying reference trajectory. This motion problem was addressed to a real-scaled fully actuated surface vessel, whose dynamic model had unknown hydrodynamic and propulsion parameters that were identified by applying an experimental maneuver-based identification process. This dynamic model was then used to develop the controllers. The first one was the backstepping controller, which was designed with a local exponential stability proof. For the NMPC, the controller was developed to minimize the tracking error, considering the thrusters’ constraints. Moreover, both controllers considered the thruster allocation problem and counteracted environmental disturbance forces such as current, waves and wind.The effectiveness of these approaches was verified in simulation using Matlab/Simulink and GRAMPC (in the case of the NMPC), and in experimental scenarios, where they were applied to the vessel, performing docking maneuvers at the Rhine River in Constance (Germany).