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The influence of sleep on human life, including physiological, psychological, and mental aspects, is remarkable. Therefore, it is essential to apply appropriate therapy in the case of sleep disorders. For this, however, the irregularities must first be recognised, preferably conveniently for the person concerned. This dissertation, structured as a composition of research articles, presents the development of mathematically based algorithmic principles for a sleep analysis system. The particular focus is on the classification of sleep stages with a minimal set of physiological parameters. In addition, the aspects of using the sleep analysis system as part of the more complex healthcare systems are explored. Design of hardware for non-obtrusive measurement of relevant physiological parameters and the use of such systems to detect other sleep disorders, such as sleep apnoea, are also referred to. Multinomial logistic regression was selected as the basis for development resulting from the investigations carried out. By following a methodical procedure, the number of physiological parameters necessary for the classification of sleep stages was successively reduced to two: Respiratory and Movement signals. These signals might be measured in a contactless way. A prototype implementation of the developed algorithms was performed to validate the proposed method, and the evaluation of 19324 sleep epochs was carried out. The results, with the achieved accuracy of 73% in the classification of Wake/NREM/REM stages and Cohen's kappa of 0.44, outperform the state of the art and demonstrate the appropriateness of the selected approach. In the future, this method could enable convenient, cost-effective, and accurate sleep analysis, leading to the detection of sleep disorders at an early stage so that therapy can be initiated as soon as possible, thus improving the general population's health status and quality of life.
Nowadays, most digital modulation schemes are based on conventional signal constellations that have no algebraic group, ring, or field properties, e.g. square quadrature-amplitude modulation constellations. Signal constellations with algebraic structure can enhance the system performance. For instance, multidimensional signal constellations based on dense lattices can achieve performance gains due to the dense packing. The algebraic structure enables low-complexity decoding and detection schemes. In this work, signal constellations with algebraic properties and their application in spatial modulation transmission schemes are investigated. Several design approaches of two- and four-dimensional signal constellations based on Gaussian, Eisenstein, and Hurwitz integers are shown. Detection algorithms with reduced complexity are proposed. It is shown, that the proposed Eisenstein and Hurwitz constellations combined with the proposed suboptimal detection can outperform conventional two-dimensional constellations with ML detection.
Nachhaltiges Wirtschaften und insbesondere nachhaltigerer Konsum sind längst als zentrale Herausforderung des 21. Jahrhunderts erkannt worden. Unternehmen und Verbraucher/innen sind dabei gleichermaßen gefordert, sich gegenseitig in Prozessen gemeinsamer Wertschöpfung zu befähigen. Das Potential dieser Prozesse liegt jedoch nicht alleine in einer klugen Mäßigung der Akteure, sondern in einer sichtbaren Aufwertung der vielfältigen nachhaltigen Konsumoptionen. Eine Möglichkeit, dies zu erreichen, liegt darin, Nachhaltigkeit als Qualität für ein breites Spektrum von Konsumgütern erkennbar und erlebbar werden zu lassen. Eine Nachhaltigkeitsdeklarierung kann dabei weit mehr leisten als nur eine weitere visuelle Auszeichnung. Unternehmen können die kulturellen Kontexte von Verbraucher/innen erkennen und zielgerichtet agieren. Dabei können die vielfältigen Möglichkeiten digitaler Medien hilfreich sein. Die vorliegende Arbeit schlägt vor, dies stets mit Blick auf die lebendige Realität auf Anbieter- und Nachfragerseite zu tun.
The main goal of this work was to experimentally characterize the hot air-drying process of agricultural products (Potato, Carrot, Tomato) and verify it with numerical solutions at single layer and industrial scale dryer using Comsol Multiphysics® 5.3.
Input parameters at single layer dryer effects on quality attributes were examined. Two strategies of drying were applied on batch dryer to examine the input effects on quality attributes. Constant input parameters strategy was designed by using central composite design formulation and optimized by Response Surface Methodology (RSM). The second strategy was applied for further optimization of the selected region by using square wave profile of the air temperature and relative humidity. Similarly, numerical method for single layer dryer, unsteady-state partial differential equations have been solved by means of the Finite Elements Method coupled to the Arbitrary Lagrangian-Eulerian (ALE). Also, for batch dryer, the mechanistic mathematical models of coupled heat and mass transfer were developed and solved as solid porous moist material.
With this work, the process of convective drying of agricultural products could be optimized. Furthermore, important knowledge about the basic mechanisms of the drying process was found and implemented in the numerical models.
Die Fähigkeit zur Erzeugung einer nur wenige Nanometer dicken Passivschicht gelingt nichtrostenden Edelstählen aufgrund deren chemischer Zusammensetzung. Die erzielte Korrosionsbeständigkeit wird allerdings darüber hinaus als Systemeigenschaft von einer Vielzahl von weiteren Faktoren beeinflusst. Die vorliegende Arbeit befasst sich fokussiert mit dem Einfluss der schleiftechnischen Oberflächenbearbeitung von zwei ausgesuchten metastabilen austenitischen Legierungen auf deren Korrosionsverhalten.
Obwohl beide Legierungen eine vergleichbare Beständigkeit gemäß der chemischen Zusammensetzung besitzen, kann gezeigt werden, dass infolge von unterschiedlicher Oberflächenbearbeitung und unterschiedlichem Umformgrad eine starke Variation des Korrosionsverhaltens möglich ist. Es kann ebenfalls nachgewiesen werden, dass die Ausprägung und Anzahl von lokalen Oberflächendefekten hierfür verantwortlich ist. Dem eingesetzten Schleifkornwerkstoff kommt hierbei eine besondere Bedeutung zu.
Algorithms and Architectures for Cryptography and Source Coding in Non-Volatile Flash Memories
(2021)
In this work, algorithms and architectures for cryptography and source coding are developed, which are suitable for many resource-constrained embedded systems such as non-volatile flash memories. A new concept for elliptic curve cryptography is presented, which uses an arithmetic over Gaussian integers. Gaussian integers are a subset of the complex numbers with integers as real and imaginary parts. Ordinary modular arithmetic over Gaussian integers is computational expensive. To reduce the complexity, a new arithmetic based on the Montgomery reduction is presented. For the elliptic curve point multiplication, this arithmetic over Gaussian integers improves the computational efficiency, the resistance against side channel attacks, and reduces the memory requirements. Furthermore, an efficient variant of the Lempel-Ziv-Welch (LZW) algorithm for universal lossless data compression is investigated. Instead of one LZW dictionary, this algorithm applies several dictionaries to speed up the encoding process. Two dictionary partitioning techniques are introduced that improve the compression rate and reduce the memory size of this parallel dictionary LZW algorithm.
Die Entwicklung der Elektromobilität, als alternative Fortbewegungsform ist seit geraumer Zeit eine nicht nur regional, sondern weltweit und unter den verschiedensten Aspekten (Technik, Umwelt, Wirtschaft, Energiewende etc.) intensiv betrachtete und untersuchte Thematik. Hierbei spielt der mögliche positive Effekt auf die Umwelt und die Energiewende hin zu nicht fossilen Energieträgern eine zentrale Rolle für Politik und Forschung bei der Förderung dieser Technologie. Die vorliegende Arbeit untersucht die Elektromobilität im Bodenseetourismus. Ziel der Arbeit ist es, die Potenziale für die Integration der Elektromobilität im Bodenseetourismus darzustellen. Hierfür wird die Elektromobilität im Bodenseetourismus als innovative Mobilitätsform postuliert, verstanden und untersucht. Die Betrachtung der Diffusion der Innovation wird vor dem Hintergrund heterogener Akteursgruppen im Dreiländereck D-A-CH untersucht.
In today's volatile market environments, companies must be able to continuously innovate. In this context, innovation does not only refer to the development of new products or business models but often also affects the entire organization, which has to transform its structures, processes, and ways of working.Corporate entrepreneurship (CE) programs are often used by established companies to address these innovation and transformation challenges. In general, they are understood as formalized entrepreneurial activities to (1) support internal corporate ventures or (2) work with external startups. The organizational design and value creation of CE programs exhibit a high degree of heterogeneity. On the one hand, this heterogeneity makes CE programs a valuable management tool that can be used for many purposes. On the other hand, it can be seen as a reason for the current challenges that companies experience in effectively using and managing CE programs.By systematically analyzing 54 different cases in established companies in Germany, Switzerland, and Austria, this study contributes to a better understanding of the heterogeneity of CE programs. The taxonomic approach provides clearly defined types of CE programs that are distinguished according to their organizational design and the outputs they generate.