A course of study for developing voice and articulation on a second grade level.

Thesis (Ed.M.)--Boston Universit

Towards Predictive Rendering in Virtual Reality

The strive for generating predictive images, i.e., images representing radiometrically correct renditions of reality, has been a longstanding problem in computer graphics. The exactness of such images is extremely important for Virtual Reality applications like Virtual Prototyping, where users need to make decisions impacting large investments based on the simulated images. Unfortunately, generation of predictive imagery is still an unsolved problem due to manifold reasons, especially if real-time restrictions apply. First, existing scenes used for rendering are not modeled accurately enough to create predictive images. Second, even with huge computational efforts existing rendering algorithms are not able to produce radiometrically correct images. Third, current display devices need to convert rendered images into some low-dimensional color space, which prohibits display of radiometrically correct images. Overcoming these limitations is the focus of current state-of-the-art research. This thesis also contributes to this task. First, it briefly introduces the necessary background and identifies the steps required for real-time predictive image generation. Then, existing techniques targeting these steps are presented and their limitations are pointed out. To solve some of the remaining problems, novel techniques are proposed. They cover various steps in the predictive image generation process, ranging from accurate scene modeling over efficient data representation to high-quality, real-time rendering. A special focus of this thesis lays on real-time generation of predictive images using bidirectional texture functions (BTFs), i.e., very accurate representations for spatially varying surface materials. The techniques proposed by this thesis enable efficient handling of BTFs by compressing the huge amount of data contained in this material representation, applying them to geometric surfaces using texture and BTF synthesis techniques, and rendering BTF covered objects in real-time. Further approaches proposed in this thesis target inclusion of real-time global illumination effects or more efficient rendering using novel level-of-detail representations for geometric objects. Finally, this thesis assesses the rendering quality achievable with BTF materials, indicating a significant increase in realism but also confirming the remainder of problems to be solved to achieve truly predictive image generation

Water management improvements for agriculture by applying efficient crop schedules in the highland forest of Vilcabamba, Peru

The current work is aimed to improve the water management for agriculture, by applying efficient crop schedules in Vilcabamba -and similar areas of the Andean highland forest-, which can satisfy most of the water requirements with rainfed irrigation and maximise the crops yield.  For this purpose, two field practices were carried out during the dry (September 2012) and wet season (February 2013) to measure rivers and canals flows with the velocity/area method.  Nineteen soil samples were collected on-site and analysed, presenting prevalent sandy loam and loam textures.  Cropwat programme and data on climate, crops and soil were used to estimate crop water requirements and scheme irrigation requirements, indicating that crop evapotranspiration is low due to humidity and cool temperature.  Crops did not need any water during the rainy season (December to April), although irrigation requirements occur in the dry season, with a maximum flow capacity of 1.72 L/s in May.  The flow capacity can be satisfied, since small ditches convey approximately 2 L/s to 6 L/s on the same season.  Rainfed farming can be practised, but an initial pre-irrigation that needs to be applied for crops should not be water stressed.  However, if soil is not pre-irrigated the production can be affected, with vegetables and potato crop yields reduced by 4.7% and 1.4%, respectively.  To minimise these effects, both crops are suggested to be planted one month later, adapting their growth period to the rainy season.   Keywords: Crop scheduling, crop water requirements, rainfed irrigation, water management for agriculture, Cropwa

Photovoltaics with Silicon Nanoparticles

Photovoltaik mit Siliziumnanopartikeln Bislang besteht der Lichtabsorber nahezu aller installierter photovoltaischer (PV) Module aus ein- oder multikristallinem Silicium (c-Si oder mc-Si). Wegen ihrer geringeren Kosten pro installierter Leistung existiert jedoch seit einigen Jahren ein Trend hin zu Dünnschichtzellen. Das Fernziel der dieser Arbeit zugrundeliegenden Untersuchungen besteht deswegen darin, druckbare PV Zellen zu realisieren, deren Dünnfilm-Absorberschicht aus Si Nanopartikeln (NP) hergestellt wird. Si bietet sich an, da es ungiftig ist und eine nahezu unbegrenzt verfügbare Ressource darstellt. Die Partikelform wurde gewählt, weil NP dispergiert und somit materialeffizient verdruckt werden können. In einem ersten Schritt wurden in dieser Arbeit c-Si Substrate mit hoch dotierten Si NP beschichtet und mittels Laser-Temperns eine dotierte Substratschicht erzeugt. Für das Tempern standen ein infraroter (IR, Wellenlänge λ = 808nm) Dauerstrahllaser und ein gepulster, ultravioletter (UV, λ = 248nm) Laser zur Verfügung. Für beide Laser konnte durch elektrische (Vierpunkt-Leitfähigkeit) und analytische (SIMS / ECV) Messungen nachgewiesen werden, dass Dopanden in das Substrat eingebracht werden. Während der IR-Laser Dotiertiefen von ca. 100µm erzeugte, betrugen sie für den UV-Laser lediglich ca. 200nm. Durch Anwenden dieser Technik auf dotierte Substrate mit komplementär dotierten NP, konnten pn-Übergange geschaffen werden, die einen PV Effekt zeigen. Die dünnere Emitterschicht (≈Dotiertiefe) ist ein wichtiger Grund dafür, dass die maximalen Konversionseffizienzen η der UV-Laser behandelten Proben (η ≈ 6%) deutlich über denen der IR-Laser behandelten Proben (η ≈ 2%) liegen. Als Hauptgrund für die für c-Si PV vglw. niedrigen Konversionseffizienzen werden chemische und strukturelle Defekte vermutet. Ihre Reduktion lässt eine deutliche Effizienzsteigerung erwarten. Wegen der zu großen Dotiertiefe wurde der IR-Laser für weitere Experimente ausgeschlossen. Für die Produktion von PV Zellen kann die UV-Laser NP Dotiermethode weiterhin interessant sein, um das Aluminium (Al) aus dem Standardrückseitendotierprozess zu verdrängen: Bei einer Reduktion der Substratdicke zukünftiger Generationen von PV Zellen würde das Al wegen des von Si abweichenden, temperaturabhängigen Ausdehnungskoeffizienten zu einer Substratverbiegung führen. Mit der präsentierten Technik konnte eine Rückseitendotierung von mc-Si Solarzell-Halbzeugen realisiert werden; bislang ist aber nicht klar, ob die Technik wirklich zu einer ähnlichen oder sogar höheren Effizienz als der Standardprozess führen kann. Diese Methode könnte bereits heute für die PV-Industrie interessant sein, weil sie eine Verbiegung verhindern sollte und ein unabhängiges Bearbeiten von Vorder- und Rückseite ermöglicht. Nachdem es möglich war, Si Substrate umzudotieren, wurden in einem zweiten Schritt grundlegende Versuche durchgeführt, um pn-Übergänge nur aus Si NP herzustellen. So wurden pn-Proben einerseits durch Spark-Plasma-Sintern (SPS) von p- auf n-typ NP-Schüttungen und andererseits durch sukzessive Schleuderbeschichtung von p- auf n-typ Dispersionen und deren Lasertemperung hergestellt. Während die SPS-Versuche primär das Ziel verfolgten, einen direkteren Einblick in den nur aus NPn erzeugten pn-Übergang zu ermöglichen, stellt die Schleuderbeschichtungsmethode eine deutlich anwendungsnahere Methode dar. In beiden Fällen wurde eine elektromotorische Kraft gemessen, wobei nicht abschließend geklärt werden konnte, ob deren Ursprung die PV ist. Dass es aber gelang, leitfähige Schichten auf isolierenden Substraten zu realisieren, stellt einen ersten Schritt in Richtung druckbarer Si PV aus NP dar.Today, the light absorber of almost all installed photovoltaic (PV) modules is made of single or multi crystalline silicon (c-Si or mc-Si). However, due to the reduced costs per installed power, a trend exists towards thin film cells since a few years. Thus, the future's aim of this work's investigations is to realize printable PV cells with a thin film absorber made from Si nanoparticles (NP) solely. Si is chosen, because it is non-toxic and an abundant resource. The particle form is selected, because NP can be dispersed, thus making them printable, resulting in a high material-efficiency for the future application. As a first step, in this work c-Si substrates were coated with highly doped Si NP and via laser annealing, a doped substrate layer was created. For the annealing, a continuous wave, infra red (IR, wave length λ = 808nm) and a pulsed, ultra violet (UV, λ = 248nm) laser were available. For both lasers, electrical (four point conductance) and analytical (SIMS / ECV) measurements proved a successful incorporation of dopants into the substrate. While the IR laser created doping depths of approx. 100µm, for the UV laser they were determined to be approx. 200nm. By applying this method on doped substrates and complementary doped NP, pn-junctions could be realized that exhibit a PV effect. The thin emitter layer (≈doping depth) is one important reason for the higher maximum conversion efficiencies η of the UV laser annealed samples (η ≈ 6%) when compared to the IR laser annealed ones (η ≈ 2%). Chemical and structural defects are supposed to be the major reason for the low conversion efficiencies when compared with c-Si PV. By reducing them, a considerable efficiency increase is expected. Due to the too big doping depth, the IR laser was excluded from further experiments. For the production of PV cells, the UV laser NP doping method may also be interesting to replace the aluminium (Al) from the standard back surface doping process: A reduction of the substrate thickness of future PV generations, would lead to a bending of the substrate due to the different thermal expansion coefficients of Si and Al. Using the presented technique, a back surface doping could be realized on semi-finished mc-Si PV cells; however, so far it is not certain, whether this technique can really create similar or even higher efficiencies as the standard process. Nevertheless, this method can be interesting for the PV industry already today, because a substrate bending should be prevented and an independent handling of the front and the back side is possible. After the feasibility of Si substrates doping, fundamental experiments were conducted to create pn-junctions form Si NP solely, in a second step. Thus, pn-samples were created by spark-plasma sintering (SPS) of p- on n-type NP material on the one hand and by successive spin coating of p- and n-type dispersions and their laser annealing on the other hand. While the SPS experiments primary aimed to get a directer insight of the pn-junction created only from NP, the spin coating method represents a much more application oriented way. In both cases, an electromotive force was measured, whereas it is not finally clarified, whether its origin really is PV. However, the success to realize conductive layers on insulating substrates is interpreted as a first step towards the future's aim of printable Si PV from NP

Erziehungswissenschaft - Systemtheorie - Empirische Forschung: methodologische Überlegungen zur empirischen Rekonstruktion pädagogischer Ordnungen

"Die Systemtheorie wird als Metatheorie empirischer Sozialforschung in der Soziologie inzwischen breit diskutiert. Zu verzeichnen ist eine Normalisierung in der Diskussion um eine Empirisierung ihrer als abstrakt geltenden Theoriearchitektur. Dennoch sind systemtheoretisch argumentierende Projekte und eine entsprechende methodologische Diskussion in der Erziehungswissenschaft bislang die Ausnahme geblieben. Der Autor schlägt vor, die Systemtheorie für die Entwicklung einer reflexiven erziehungswissenschaftlichen Methodologie des Pädagogischen zu nutzen. Er zeigt, wie es mit ihr gelingen kann, ein zentrales Bezugsproblem erziehungswissenschaftlicher Forschung methodologisch zu kontrollieren: die Aufgabe, ein soziales Geschehen, an das hohe normative Erwartungen geknüpft werden, mit sozialwissenschaftlichen Mitteln gegenstandstheoretisch und empirisch in den Blick zu bekommen. Weder darf durch zu viel Nähe zu diesen Erwartungen pädagogisches Wissen verdoppelt werden noch durch zu viel sozialwissenschaftliche Distanz der Gegenstand aus den Augen geraten. Die Leistungsfähigkeit dieser Forschungsperspektive wird an einem Ausschnitt aus einem Transkript verdeutlicht, das den Besuch einer 9. Realschulklasse in einer KZ-Gedenkstätte dokumentiert. Gezeigt wird, wie es mit dieser Perspektive gelingen kann, neue Sichtweisen auf die normative Aufgabenstruktur pädagogischer Handlungsfelder zu werfen und Bezugsprobleme des Pädagogischen zu spezifizieren." (Autorenreferat)"Systems theory is now being widely discussed as a meta-theory for empirical research in sociology. Visible is certain normalization in the discussion about how to open up the presumably abstract architecture of systems theory to empirical research. However, in education science most research projects applying systems theory and the corresponding methodological debates have so far remained the exception. The present contribution suggests using systems theory for the development of a reflexive methodology of the pedagogical. It shows how a central reference problem in educational research methodologies can be successfully controlled: namely, the task of taking account of a social phenomenon - to which high normative expectations are linked - as a subject-matter and empirically by means of the social sciences without doubling the pedagogical knowledge through too much closeness to these expectations or losing the object from sight due too much distance. The fruitfulness of this research perspective will be illustrated by an excerpt from a transcript recorded during a 9th grade class visit to a concentration camp Memorial. It shows how this perspective may succeed in throwing new perspectives on the normative structure of pedagogical fields of action, thus generating a new description for a specification of educational reference problems." (author's abstract

Siegfried Bernfelds "Grenzen der Erziehung" revisited. Eine systemtheoretische Betrachtung

Der Beitrag thematisiert die Grenzen der Erziehung systemtheoretisch als systeminternen Konflikt selbst- und fremdreferentieller Normierungen. Die ambivalenten Strukturen und Spannungen zwischen der Annahme einer relativ autonomen pädagogischen Sphäre und den Bedingungen einer gesellschaftlichen Verfasstheit öffentlicher Erziehung führen zu Grenzziehungen zwischen Pädagogischem und Nicht-Pädagogischem. Diese Abgrenzungsbemühungen werden in dem Beitrag als Konstitutionsmerkmal öffentlicher Erziehung analytisch in den Blick genommen. (DIPF/Orig.

Bayesian Optimization for recurring, simulation-based decision-making in production and logistics (Poster PhD Colloquium WSC 2024)

The thesis proposes a framework to accelerate Bayesian Optimization (BO) for recurrent simulation-based decision-making in production and logistics. BO is recognized for its sample efficiency but is often hindered by computational intensity, making it less suitable for scenarios requiring short-term decisions. The proposed framework TMPBO seeks to integrate transfer learning, meta-learning, and parallel computation to reduce optimization times and enhance convergence rates to make BO practical for operational decisions. The research will focus on leveraging historical optimization data and modern computing capabilities to improve BO's efficiency, making it viable for high-dimensional, multi-objective problems. The framework will be evaluated through a multi-stage process. The thesis aims to demonstrate that the TMPBO framework can offer significant advantages over classic BO and evolutionary algorithms in optimizing recurrent decision-making tasks

Optimization of a stochastic MRP simulation using Bayesian optimization

This paper explores whether the Bayesian optimization algorithms GPEI, TurBO and SAASBO are effective for stochastic material requirements planning simulations. It includes a comparison of other methods, with a focus on the convergence speed, a key factor in simulation-based optimization. The study uses a simple material requirement planning simulation model that is progressively expanded in complexity by adding products and levels to the bill of materials. This results in a high-dimensional optimization problem, which poses a significant challenge for simulation-based optimization. The Bayesian optimization methods are compared at each level of complexity to determine if they produce satisfactory results. Additionally, the convergence speed is analyzed in relation to method and complexity. A genetic algorithm, CMA-ES, and Sobol serve as benchmarks for the Bayesian optimization methods