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In this thesis, unique administrative data, a relevant time of follow-up and advanced statistical measures to handle confounding have been utilized in order to provide new and informative evidence on the effects of vocational rehabilitation programs on work participation outcomes in Germany. While re-affirming the important role of micro-level determinants, the present study provides an extensive example of the individual and fiscal effects that are possible through meaningful vocational rehabilitation measures. The analysis showed that the principal objective, namely, to improve participation in employment, was generally achieved. Contrary to the common misconception that “off-the-job training” is relatively ineffective, this thesis has provided an empirical example of the positive impact of the programs.
Computer graphics research strives to synthesize images of a high visual realism that are indistinguishable from real visual experiences. While modern image synthesis approaches enable to create digital images of astonishing complexity and beauty, processing resources remain a limiting factor. Here, rendering efficiency is a central challenge involving a trade-off between visual fidelity and interactivity. For that reason, there is still a fundamental difference between the perception of the physical world and computer-generated imagery. At the same time, advances in display technologies drive the development of novel display devices. The dynamic range, the pixel densities, and refresh rates are constantly increasing. Display systems enable a larger visual field to be addressed by covering a wider field-of-view, due to either their size or in the form of head-mounted devices. Currently, research prototypes are ranging from stereo and multi-view systems, head-mounted devices with adaptable lenses, up to retinal projection, and lightfield/holographic displays. Computer graphics has to keep step with, as driving these devices presents us with immense challenges, most of which are currently unsolved. Fortunately, the human visual system has certain limitations, which means that providing the highest possible visual quality is not always necessary. Visual input passes through the eye’s optics, is filtered, and is processed at higher level structures in the brain. Knowledge of these processes helps to design novel rendering approaches that allow the creation of images at a higher quality and within a reduced time-frame. This thesis presents the state-of-the-art research and models that exploit the limitations of perception in order to increase visual quality but also to reduce workload alike - a concept we call perception-driven rendering. This research results in several practical rendering approaches that allow some of the fundamental challenges of computer graphics to be tackled. By using different tracking hardware, display systems, and head-mounted devices, we show the potential of each of the presented systems. The capturing of specific processes of the human visual system can be improved by combining multiple measurements using machine learning techniques. Different sampling, filtering, and reconstruction techniques aid the visual quality of the synthesized images. An in-depth evaluation of the presented systems including benchmarks, comparative examination with image metrics as well as user studies and experiments demonstrated that the methods introduced are visually superior or on the same qualitative level as ground truth, whilst having a significantly reduced computational complexity.
Process-dependent thermo-mechanical viscoelastic properties and the corresponding morphology of HDPE extrusion blow molded (EBM) parts were investigated. Evaluation of bulk data showed that flow direction, draw ratio, and mold temperature influence the viscoelastic behavior significantly in certain temperature ranges. Flow induced orientations due to higher draw ratio and higher mold temperature lead to higher crystallinities. To determine the local viscoelastic properties, a new microindentation system was developed by merging indentation with dynamic mechanical analysis. The local process-structure-property relationship of EBM parts showed that the cross-sectional temperature distribution is clearly reflected by local crystallinities and local complex moduli. Additionally, a model to calculate three-dimensional anisotropic coefficients of thermal expansion as a function of the process dependent crystallinity was developed based on an elementary volume unit cell with stacked layers of amorphous phase and crystalline lamellae. Good agreement of the predicted thermal expansion coefficients with measured ones was found up to a temperature of 70 °C.
The initially large number of variants is reduced by applying custom variant annotation and filtering procedures. This requires complex software toolchains to be set up and data sources to be integrated. Furthermore, increasing study sizes subsequently require higher efforts to manage datasets in a multi-user and multi-institution environment. It is common practice to expect numerous iterations of continuative respecification and refinement of filter strategies, when the cause for a disease or phenotype is unknown. Data analysis support during this phase is fundamental, because handling the large volume of data is not possible or inadequate for users with limited computer literacy. Constant feedback and communication is necessary when filter parameters are adjusted or the study grows with additional samples. Consequently, variant filtering and interpretation becomes time-consuming and hinders a dynamic and explorative data analysis by experts.
Pseudopotential (PP)-basierte Lattice-Boltzmann-Methoden werden zunehmend für die Simulation von Mehrphasenströmungen eingesetzt. Da sie auf einem phänomenologischen Ansatz basieren, ist ihr Einsatz mit einem hohen Modellierungsaufwand verbunden. Zudem entstehen an den Phasengrenzen sogenannte Scheingeschwindigkeiten, welche Genauigkeit und numerische Stabilität beeinträchtigen. Daher werden PP-Modelle in dieser Arbeit um drei neue Aspekte erweitert. Erstens wird gezeigt, dass bei der Modellierung unterschiedlicher Kontaktwinkel mit gängigen Methoden in Kombination mit verbesserten Kräfteschemata Scheintröpfchen entstehen. Diese werden durch einen neuartigen Ansatz eliminiert, der auf zusätzlichen Randbedingungen für alle Wechselwirkungskräfte basiert. Diese Technik verhindert nicht nur das Auftreten der Scheintröpfchen, sondern erhöht auch die Stabilität in wandgebundenen Strömungen. Zweitens wird ein neuartiges Verfahren zur Reduktion von Scheingeschwindigkeiten eingeführt. Dabei wird die Diskretisierung der Interaktionskräfte erweitert und die zusätzlichen, freien Koeffizienten in Simulationen statischer Tropfen numerisch optimiert. Die resultierende Diskretisierung wurde in Simulationen stationärer und dynamischer Testfälle validiert, wobei Scheingeschwindigkeiten deutlich reduziert werden konnten. Drittens und letztens wurden die Diffusionseigenschaften in Mehrstoffsystemen detailliert untersucht, wobei eine kritische Abhängigkeit zwischen den makroskopischen Diffusionskoeffizienten und dem Kräfteschema aufgezeigt wird. Diese Analyse bildet die Grundlage für den Vergleich und die zukünftige Entwicklung neuer Potentialfunktionen (für Mehrstoffsysteme) und reduziert den Modellierungsaufwand.
In the field of domestic service robots, recovery from faults is crucial to promote user acceptance. In this context, this work focuses on some specific faults which arise from the interaction of a robot with its real world environment. Even a well-modelled robot may fail to perform its tasks successfully due to external faults which occur because of an infinite number of unforeseeable and unmodelled situations. Through investigating the most frequent failures in typical scenarios which have been observed in real-world demonstrations and competitions using the autonomous service robots Care-O-Bot III and youBot, we identified four different fault classes caused by disturbances, imperfect perception, inadequate planning operator or chaining of action sequences. This thesis then presents two approaches to handle external faults caused by insufficient knowledge about the preconditions of the planning operator. The first approach presents reasoning on detected external faults using knowledge about naive physics. The naive physics knowledge is represented by the physical properties of objects which are formalized in a logical framework. The proposed approach applies a qualitative version of physical laws to these properties in order to reason. By interpreting the reasoning results the robot identifies the information about the situations which can cause the fault. Applying this approach to simple manipulation tasks like picking and placing objects show that naive physics holds great possibilities for reasoning on unknown external faults in robotics. The second approach includes missing knowledge about the execution of an action through learning by experimentation. Firstly, it investigates such representation of execution specific knowledge that can be learned for one particular situation and reused for situations which deviate from the original. The combination of symbolic and geometric models allows us to represent action execution knowledge effectively. This representation is called action execution model (AEM) here. The approach provides a learning strategy which uses a physical simulation for generating the training data to learn both symbolic and geometric aspects of the model. The experimental analysis, performed on two physical robots, shows that AEM can reliably describe execution specific knowledge and thereby serving as a potential model for avoiding the occurrence of external faults.
Miscanthus bietet als nachwachsende Industrie- und Energiepflanze zahlreiche Vorteile, die neben den direkten landwirtschaftlichen Anwendungen wie Verbrennung und Tiereinstreu auch eine stoffliche Nutzung im chemischen Bereich zulassen. Als C4-Pflanze mit gesteigerter Photosynthese-Aktivität weist Miscanthus zudem eine hohe CO2-Fixierrate auf. Aufgrund des geringen Kultivierungsaufwandes sowie der hohen Erträge bietet sich Miscanthus als ausgesprochen attraktiver Rohstoff für die Produktion erneuerbarer Kraftstoffe und Chemikalien an, welche mittels thermo-chemischer Umwandlung gewonnen werden.