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Milling processes are often limited by self-excited vibrations of the tool or workpiece, generated by the regenerative effect, especially when using long cantilevered tools or machining thin-walled workpieces. The regenerative effect arises from a periodic modulation of the uncut chip thickness within the frequencies of the eigenmodes, which results in a critical excitation in the consecutive cuts or tooth engagements. This paper presents a new approach for disturbing the regenerative effect ...
In dieser Dissertation betrachten wir die parallele Konstruktion von Text-Indizes. Text-Indizes stellen Zusatzinformationen über Texte bereit, die Anfragen hinsichtlich dieser Texte beschleunigen können. Ein Beispiel hierfür sind Volltext-Indizes, welche für eine effiziente Phrasensuche genutzt werden, also etwa für die Frage, ob eine Phrase in einem Text vorkommt oder nicht. Diese Dissertation befasst sich hauptsächlich, aber nicht ausschließlich mit der parallelen Konstruktion von Text-Indi...
In this thesis, a contribution to explainable artificial intelligence is made. More specifically, the aspect of artificial intelligence which focusses on recreating the human perception is tackled from a previously neglected direction. A variant of human perception is building a mental model of the extents of semantic objects which appear in the field of view. If this task is performed by an algorithm, it is termed image segmentation. Recent methods in this area are mostly trained in a superv...
Vaporizing Foil Actuators (VFA) can be employed as an innovative, extremely fast sheet metal forming method. An ultimate goal in forming technologies is generally to be flexible and rely on as few part-specific tools as possible. Therefore, various realizable VFA pressure distributions were investigated with a focus on the free forming result. Fundamental experiments including laser-based dynamic velocity measurements were conducted to discuss some key forming characteristics of the process. ...
Forming processes influence the mechanical properties of manufactured workpieces in general and by means of forming-induced initial damage in particular. The effect of the latter on performance capability is the underlying research aspect for the investigations conducted. In order to address this aspect, fatigue tests under compressive, tensile and compressive-tensile loads were set-up with discrete block-by-block increased amplitudes and constant amplitudes, and performed up to fracture or d...
We explore if the corona-crash 2020 was driven by news attention or rational expectations about the pandemic’s economic impact. Using a sample of 64 national stock markets covering 94% of the world’s GDP, we find the stock markets’ decline to be mainly associated with higher news attention and less with rational expectation. We estimate the economic cost from the news hype to amount to USD 3.5 trillion for the US and USD 200 billion on average for the rest of the G8 countries.
Varied teaching techniques are an important aspect of a successful classroom. Student and classroom factors such as ability level, lower socioeconomic status, and/or native language can interact with teaching techniques. Previous work suggests that each teaching technique may be more effective for different students or in different classroom situations, but few studies have directly examined which factors relate to effective teaching techniques. This study uses data for early secondary school...
In the mitotic spindle microtubules attach to kinetochores via catch bonds during metaphase, and microtubule depolymerization forces give rise to stochastic chromosome oscillations. We investigate the cooperative stochastic microtubule dynamics in spindle models consisting of ensembles of parallel microtubules, which attach to a kinetochore via elastic linkers. We include the dynamic instability of microtubules and forces on microtubules and kinetochores from elastic linkers. A one-sided mode...
Forming technology and in particular cold forward rod extrusion is one of the key manufacturing technologies with regard to the production of shafts. The selection of process parameters determines the global and local material properties. This particularly implies forming-induced initial damage in representation of pores. On this background, this study aims on describing the influence of these pores in the performance of the material 16MnCrS5 (DIN 1.7139, AISI/SAE 5115) under a torsional load...
In continuous casting processes, inevitable voids (damage) are generated inside the material. The subsequent forming process of hot flat rolling offers the potential of healing these defects by closing the voids and bonding the internal surfaces. In this paper, different forming conditions from hot flat rolling process were characterized with micromagnetic measurement techniques and the influence of the damage evolution on the fatigue behavior was investigated. To characterize the reduction o...
Durch den gesellschaftlichen Wandel hat eine Verschiebung des Diskurses vom monolingualen Selbstverständnis zur migrationsbedingten sprachlichen Diversität im Bildungskontext stattgefunden (Gogolin, 2008). Dieser Paradigmenwechsel bringt Chancen sowie auch Herausforderungen mit sich, die neue didaktische Modelle und Förderansätze zur Unterstützung der sprachlichen Entwicklung erfordern. Der Umgang mit Mehrsprachigkeit in Bildungseinrichtungen ist nicht zuletzt durch die Integration von Kinder...
The visual appearance of building structures is an important attribute which reflects the character and identity of a region. Due to the influence of weathering, the surfaces of building stones alter, leading to aesthetic changes of the material surface such as discoloration or darkening. In this study, near-surface regions of weathered Baumberger (BST), Schleeriether (SST), and Obernkirchener Sandstones (OKS) have been analyzed at the microscopic scale in order to investigate the intensi...
Evidenced based planning is a salient issue and evokes questions about the role of expertise and scientific policy advice in spatial planning. The paper considers recent trends in the debate on scientific policy advice (crises of expertise, privatization/democratization of expertise, blurring of boundaries between science and policy) and reflects upon these trends against the background of the particular situation of scientific policy advice in spatial planning in Germany. Many insights ...
Electron paramagnetic resonance (EPR) is a spectroscopic technique to study the interaction between free electrons and the local molecular environment. Over the past 60 years, EPR instrumentation and methodology has been developed to study, for example, the structure and dynamics of proteins, chemical reactions of organic-based radicals, transition-metal chemistry, catalytic reactions, electron transfer processes, and metalloenzymes. Because of these past developments, EPR has become a p...
Biocatalysis offers a broad spectrum of possible ecological and economic advantages over conventional chemical catalysis processes, e.g., lower energy consumption and high enantio selectivity. The focus of this work is on gas‐liquid reactions. These are of great importance in the chemical and biochemical industry and subject of current research since they are often limited by mass transfer or show low selectivity. Different suitable biocatalytically gas‐liquid reaction systems were tested in ...
Tropane alkaloids (TA) are important and valuable secondary plant metabolites which occur in the families of Solanaceae, Erythroxylaceae, as well as Convolvulaceae, Moraceae, and Brassicaceae. These plant families produce the TAs hyoscyamine and scopolamine, cocaine, or calystegines, respectively. Due to the medicinal and pharmacological properties of hyoscyamine, scopolamine and cocaine, TA containing plants have been used for thousands of years. Even today, many drugs are derived from TAs ...
Die Identifikation von EGFR-Mutationen in Exon19 und Exon21 als prädiktive Biomarker, die mit einer erhöhten Sensitivität gegenüber EGFR-Inhibitoren der ersten Generation assoziiert werden konnten, leitete einen Paradigmenwechsel in der Behandlung von NSCLC-Patienten ein.[1-2] In entsprechenden Studien konnte retrospektiv gezeigt werden, dass lediglich Tumore auf die Behandlung mit Gefitinib ansprachen, wenn eine somatische EGFR-Mutation vorlag und im Umkehrschluss Patienten ohne die entsprec...
Die Mitochondrien der Hefe besitzen über 1000 Proteine, von denen mehr als 99% durch nukleäre DNA und nur der Rest durch mitochondriale DNA kodiert wird. Um das Mitochondrium erreichen zu können, ist eine effiziente Protein-Zell-Signalweiterleitung notwendig, um die Moleküle nicht nur an das Organell selbst, sondern auch an eines der vier Subkompartimente des Mitochondriums korrekt zu adressieren. Mitochondriale Protein-Fehlzuordnung ist mit verschiedenen Krankheiten wie Alzheimer und Parkins...
Housing is a global phenomenon and is the heartbeat of almost everyone. It is seen as one of the fundamental needs of mankind and the long term focus of many developments across the world. In housing markets research it has been long established that location does matter. That suggests that real estate goods and services place a premium on location. Although this is the case, such location and neighbourhood characteristics are not traded explicitly and their contribution cannot be directly ob...
Die Frage nach dem Verhalten magnetischer Störstellen in Materialien bei tiefen Temperaturen ist aktueller als je zuvor bedingt durch den Schritt hin zu Nanotechnologie und Spintronik. Im ersten Teil dieser Arbeit befassen wir uns mit Störstellen in Graphen motiviert durch experimentelle Arbeiten. Die angesprochenen Störstellen entstehen, wenn einzelne Kohlenstoffatome aus der Gitterstruktur gelöst werden. Wir fassen zusammen, wie in solchen Defekten magnetische Momente entstehen, und,...