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Albert-Ludwigs-Universität Freiburg Fakultät für Angewandte Wissenschaften

Overview
Works: 271 works in 275 publications in 2 languages and 1,783 library holdings
Roles: Degree grantor, Contributor, his, Other
Publication Timeline
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Most widely held works by Albert-Ludwigs-Universität Freiburg
Polymerbasierte Dehnmessstreifen zur intra- und extrakorporalen Applikation by Johannes Ruhhammer( )

2 editions published in 2017 in German and held by 35 WorldCat member libraries worldwide

Distributed processing of navigational query languages for RDF by Martin Przyjaciel-Zablocki( )

2 editions published in 2017 in English and held by 20 WorldCat member libraries worldwide

Approaches to safe and efficient robot navigation by Benjamin Suger( )

1 edition published in 2017 in English and held by 19 WorldCat member libraries worldwide

Interdependenzen in Prozessarchitekturen : Simulation gegenseitiger Beeinflussung sicherheitsorientierter Geschäftsprozesse by Richard Markus Zahoransky( )

1 edition published in 2017 in German and held by 19 WorldCat member libraries worldwide

Abstract: Sowohl der globale Wettbewerb als auch die sich verschärfende Gesetzeslage, setzen Unternehmen unter zunehmenden ökonomischen und regulatorischen Druck. Einerseits erfordert die Globalisierung die Effizienzsteigerung durch automatisierte Geschäftsprozesse, anderseits führten vermehrte Wirtschaftskriminalitätsdelikte zu neuen Anforderung an sichere Geschäftsprozesse aufgrund regulatorischer Vorgaben. Damit die Einhaltungen dieser Anforderungen dem unternehmerischen Effizienzstreben nicht zuwiderlaufen, wird in dieser Arbeit ein Simulationsverfahren vorgestellt, welches erstmals den Einfluss von Sicherheitskontrollen auf simultan ablaufende, gegenseitig abhängige Geschäftsprozesse aufdeckt. Dieses Simulationsverfahren stellt Zeitaspekte als zentrale Determinante in den Mittelpunkt der Betrachtung.Prozessentwickler können mit dieser Lösung die Auswirkungen ihrer Prozessänderungen a priori, vor der tatsächlichen Ausführung, prognostizieren. Dabei wird das Ziel verfolgt, eine zeit- und kostenminimierende Umsetzung der geforderten Anpassungen zu finden.<br><br>Allgemeine Trends wie Industrie 4.0 tragen zur weiteren Automatisierung von Geschäftsprozessen bei, welche so aufeinander abgestimmt sind, dass Produkte, Dienstleistungen und Waren mit hoher Taktzahl bearbeitet oder ausgeliefert werden. Prozessänderungen können wegen den wachsenden Abhängigkeiten der automatisierten Geschäftsprozesse das Zusammenspiel auf bisher unquantifizierbare Weise stören. Maßnahmen zur Stärkung der Sicherheit können deswegen von Einflussnehmern abgelehnt werden, da sich monetäre Auswirkungen auf Grund der Interdependenzen zwischen den Geschäftsprozessen bisher nicht beziffern lassen.<br><br>Das im Rahmen dieser Arbeit entwickelte Simulationsverfahren berücksichtigt die Abhängigkeiten zwischen Prozessen, deren Zugriffsrechten und die benötigte Zeit zur Abarbeitung von Einzelschritten. Dies ermöglicht die Aufdeckung der Auswirkungen einer Prozessänderung auch auf abhängige Geschäftsprozesse um die Gesamtkosten einer Änderung zu ermitteln und unterstützt hiermit Prozessentwickler, Sicherheitsmaßnahmen kosteneffizient durchzuführen. Dadurch lassen sich Bedürfnisse der Interessengruppen, die Unternehmensziele und die Sicherheit miteinander vereinen
Entwicklung und Evaluierung eines adaptiv-prädiktiven Algorithmus' für thermoaktive Bauteilsysteme by Martin Schmelas( )

1 edition published in 2017 in German and held by 19 WorldCat member libraries worldwide

Abstract: Der Gebäudesektor ist einer der Hauptverbraucher von Energie und somit mitverantwortlich für einen wesentlichen Anteil an CO2-Emissionen. Heiz- und Kühlkonzepte, die erneuerbare Energiequellen nutzen können, gewinnen daher immer mehr an Bedeutung. Hierfür besonders geeignet sind Niedertemperatursysteme, wie beispielsweise Thermoaktive Bauteilsysteme (TABS). Die große thermische Trägheit und die geringe Leistung dieser Systeme verhindern eine schnelle Reaktion auf Raumtemperaturänderungen. Bisherige Steuer- und Regelstrategien für TABS können nur sehr schlecht mit der thermischen Trägheit umgehen, da diese in der Regel keine Prädiktionen verwenden. Hinzu kommt eine aufwändige Parametrierung dieser TABS-Strategien, was in der Praxis zu Inbetriebnahmephasen von oft mehreren Jahren führt. Die Möglichkeit TABS als einen Kurzzeitenergiespeicher für das durch die wachsende Einspeisung aus fluktuierenden erneuerbaren Energiequellen belastete Stromnetz nutzbar zu machen, spielt bei diesen Standard-TABS-Strategien bisher keine Rolle.<br><br>In dieser Arbeit wurde ein neuartiger Algorithmus für die Steuerung von TABS entwickelt, der hier durch die Abkürzung AMLR gekennzeichnet wird. Die AMLR nutzt Vorhersagen der Hauptstörgrößen einer TABS-Zone zur Berechnung eines innerhalb des nächsten Tages zuzuführenden Energiepaketes. Zu den Hauptstörgrößen zählen die tagesgemittelte Außentemperatur, die tagesgemittelte globale Einstrahlung sowie ein Belegungsplan jeder TABS-Zone. Die AMLR verwendet ein dynamisches und ein stationäres Widerstands-Kapazitäten(RC)-Modell mit einem Verzögerungsglied erster Ordnung (PT1). Das stationäre TABS- und Raummodell wird für eine Adaptionsfähigkeit und das dynamische Modell für die zeitdiskrete Berechnung von Leistungen genutzt. Es wird gezeigt, dass die Genauigkeit eines Modells mit PT1-Glied für die Steuerung von TABS ausreichend ist. Durch die Adaptionfähigkeit kann sich der Algorithmus automatisiert an unterschiedliche Gebäude, Standorte und Nutzungsprofile anpassen. Auf die Erstellung eines Gebäudemodells inklusive dessen technischer Gebäudeausrüstung (TGA), der Wärmelasten sowie der Wettereinflüsse kann somit verzichtet werden. Weiterhin können mit der AMLR mittlere Soll-Raumtemperaturen pro TABS-Zone vorgegeben werden, was bei Standard-TABS-Strategien nicht möglich ist. Dem Autor stehen als Testumgebungen zur Evaluierung der AMLR die Triple
Identification and optimization of an airborne wind energy system by Giovanni Licitra( )

1 edition published in 2018 in English and held by 18 WorldCat member libraries worldwide

A methodology for numerical fatigue analysis of Carbon Fiber Reinforced Plastics by Peter Wagner( )

1 edition published in 2017 in English and held by 18 WorldCat member libraries worldwide

Abstract: The main focus of this thesis is the development of a non-linear, energy dependent fatigue damage model for carbon fiber reinforced plastics (CFRPs). To achieve this task, the fatigue behavior of carbon fiber reinforced plastics was investigated using online stiffness measurments.<br>Existing quasi-static and fatigue models were assessed based on their potential to accurately describe the observed phenomenology. As a result, the proposed, strain damage energy based, fatigue model combines the statistics of an S-N curve with modified versions of the quasi-static strain damage energy model of Ladevèze and the phenomenological fatigue life model of Van Paepegem. All required material parameters were calibrated using quasi-static and constant amplitude loading experiments.<br><br>To validate the proposed fatigue model, load block experiments were conducted. Those experiments were specially designed pure tension, pure compression and mixed load experiments with constant and changing ratio R. The resualts obtained of the validation experimets are promising.<br><br>To further understand the fatigue behavior of carbon fiber reinforced plastics and to link the observed stiffness degradation to physical damage mechanisms, destructive and nondestructive characterization methods such as microscopy and X-ray tomography were used.<br><br>To conclude, this work displays an overview of the damage mechanims, quasi-static and fatigue models for carbon fiber reinforced plastics. It also displays the experimental techniques to conducte fatigue experiments, online measurments and non-destructive characterization methodes. But most importantly it proposes a new promising strain damage energy based fatigue model for carbon fiber reinforced plastics
Motion imitation and generation for mobile robotic systems by Felix Burget( )

1 edition published in 2018 in English and held by 18 WorldCat member libraries worldwide

Toward ultra-thin nanocrystalline diamond film growth: electrostatic self-assembly of non-aggregated diamond nanoparticles onto substrate surfaces by Taro Yoshikawa( )

1 edition published in 2017 in English and held by 18 WorldCat member libraries worldwide

Development and investigation of metal oxide nanostructures for sensing applications by Markus Hubertus Jakob( )

1 edition published in 2018 in English and held by 18 WorldCat member libraries worldwide

Robust monocular camera-based localization under challenging perceptual conditions by Tayyab Naseer( )

1 edition published in 2017 in English and held by 18 WorldCat member libraries worldwide

Abstract: Visual localization of autonomous vehicles is imperative to their safe navigation in particular scenarios. The paradigm of monocular camera localization encompasses broad range of applications like place recognition, loop closure detections within a SLAM framework, 6-DoF metric camera pose estimation and augmented reality. To achieve accurate and reliable pose estimates, camera-based localization approaches need to cope with wide variety of challenging perceptual conditions. These methods should be robust to variation in illumination due to day-night changes, different weather conditions and seasonal variations. An autonomous robot should be able to cope with all such variations that enables it to operate over long periods of time. In this thesis, we primarily focus on novel robust methods for long term camera-based visual localization that cope with wide variety of viewing conditions. We highlight the shortcomings of state-of-the-art feature-based methods for monocular cameras and present novel approaches to achieve reliable localization. Although, cameras provide an cost effective solution for autonomous navigation, image data is highly vulnerable to environmental conditions. The rich texture and color information in the images vary drastically over long periods of time. In this work, we develop distinctive and repeatable feature descriptions of images that allow robots to localize under a great spectrum of perceptual conditions. We also develop novel methods that leverage semantics of the environment to imitate human-like behavior in autonomous systems during localization. These methods also scale well with the large map sizes. At first, we discuss both the advantages and shortcomings of the visual information from the cameras for longterm localization. We identify the drawbacks of traditional sparse feature-based methods for longterm localization and propose dense feature descriptions to cope with the pitfalls. We show that by leveraging the sequential nature of the recorded and live data stream from the robot within a network flow graph framework enables to remove false loop closure hypothesis and achieve more precise location estimates. This enables the robot to achieve robust topological localization in a place recognition framework. Although, our approach can handle natural driving maneuvers, the restricted graph connectivity limits its advantages for short, fragmented and more complex trajectories. We discuss a novel approach to h
Serving online requests with mobile resources by Abdolhamid Ghodselahi( )

1 edition published in 2018 in English and held by 18 WorldCat member libraries worldwide

Abstract: Resource allocation problems have a large variety of applications in different areas of computer science and operations research. A resource allocation problem seeks to find an optimal allocation of a given type of expensive or limited resource to a set of clients that request the services of the given resource. Some of these problems have an online nature: The requests sequence is not revealed at the beginning, but the requests arrive in an online fashion. An algorithm for an online resource allocation problem must make its decision in response to a newly arriving request in an online fashion, i.e., typically before the subsequent request arrives. Depending on the definition of an online resource allocation problem, it might be allowed to postpone serving a request or to change an already made decision. However in this case, postponing a service and changing a decision come at a cost. In this thesis, we also study online allocation problems in the distributed setting, where in contrast to a centralized system, there is no central unit that controls everything and that is aware of the global state of the system. In addition to the uncertainty about the request sequence arising from the online arrivals, there is also uncertainty at each node in the network because the node does not directly learn about requests arriving in other parts of the network. The nodes of a distributed system therefore need to communicate in order to coordinate their actions and one typically assumes that this communication does not come for free. Two online problems are mainly studied in this thesis. First, we consider the distributed queuing problem as a basic problem that coordinates mutually exclusive access to shared data in distributed systems. We devise a randomized distributed queuing algorithm with an expected competitive ratio of O(log n) on general network topologies. We utilize the well-known probabilistic tree embedding of Fakcharoenphol, Rao, and Talwar [STOC 2003] that approximates the distances of a general metric space by mapping it to a special family of tree topologies known as hierarchically well-separated trees and often just referred to as HSTs. Our randomized distributed queuing algorithm is obtained by running the ARROW algorithm--a well-known distributed queuing algorithm--on top of the HST that is produced by applying the above embedding to the distances of the underlying network. It is shown that (under some assumptions) the simple and elegant ARROW algorithm outperforms all existing significantly more complicated distributed queueing algorithms. The second main problem that is studied in a centralized setting is the online facility location problem. We introduce the online mobile facility location (OMFL) problem, where the facilities are mobile. A lower bound for the OMFL problem that even holds on uniform metrics is provided. A natural approach to solve the OMFL problem for general metric spaces is to again use the above embedding into an HST and to directly solve the OMFL problem on HSTs. In this thesis, we provide a first step in this direction by solving a generalized version of the OMFL problem on uniform metrics. A simple deterministic online algorithm is devised and a tight analysis is provided for the algorithm. The second step remains as an open question. We further introduce and study another variant of the OMFL problem that is closer to the k-server problem, arguably one of the most influential problem in the area of online algorithms and competitive analysis
Zur Methodenentwicklung im Entwurf automobiler Strukturkonzepte in FVK-Metall-Hybridbauweise unter Crashbelastung by Michael Dlugosch( )

1 edition published in 2018 in German and held by 18 WorldCat member libraries worldwide

Abstract: Hybride Materialsysteme aus FVKs und Metallen sind ein vielversprechender Ansatz, um den stetig steigenden Anforderungen an die passive Sicherheit und die energetische Effizienz im Betrieb zukünftiger Fahrzeuggenerationen durch effektive Leichtbaumaßnahmen in der Rohkarosserie gerecht zu werden. Für die erfolgreiche, technische Implementierung neuartiger Materialsysteme ist ein profundes Verständnis der Mechanismen unter Last und Versagen durch experimentelle Untersuchungen, Methoden zur gezielten Materialauswahl für eine spezielle Strukturanwendung und prognosefähige Auslegungsmethoden mithilfe numerischer Simulation nötig. Bisherige wissenschaftliche Studien beschränken sich in der Regel auf die Untersuchung Metall-intensiver Hybridsysteme und zeichnen sich, aufgrund des allgemein großen Parameterraums und ihrer meist sehr spezifischen Fragestellungen, durch eine mangelnde Vergleichbarkeit aus. Weiterhin fehlt die integrative Herangehensweise an die drei nötigen Disziplinen, um die Vorteile einer konsistenten Datenbasis und Synergien nutzbar zu machen.<br>Die, in dieser Arbeit vorgestellte, multidisziplinäre Gesamtmethodik verfolgt erstmalig diesen integrativen Ansatz und bearbeitet gleichzeitig wissenschaftliche Fragestellungen in den Einzeldisziplinen. Die umfangreichen experimentellen Untersuchungen erschließen dabei neue<br>Parameterräume FVK-intensiver Hybridsysteme unter quasistatischer und dynamischer Last mit einem konsistenten Materialspektrum über mehrere Ebenen der Strukturkomplexität. Diese Datenbasis nutzt eine neue, objektive Methode zur Eignungsbewertung und Auswahl hybrider<br>Materialsysteme für eine spezielle Strukturanwendung auf Basis ihres überlagerten Beanspruchungsprofils aus den relevanten Crash-Lastfällen. Weiterhin dienen diese Daten als Grundlage zur Analyse und Bewertung vereinfachter, effizienter Modellierungsmethoden für die Simulation des Crashverhaltens hybrider Strukturen in der Konzeptphase mittels Komplexitäts- und Sensitivitätsstudien. Ein neues Phänomen des nichtlokalen Schädigungsverhaltens im Klebstoff-Interface von FVK-Metall-Hybridsystemen unter Zugbelastung wird beschrieben, experimentell<br>untersucht und in ein prognosefähiges, analytisches Modell überführt. Die Ergebnisse der numerischen Studien indizieren, dass die Erweiterung eines stark vereinfachten, starren Interface-Modells um das entwickelte Modell der nicht-lokalen Schädigung einen zielführenden Kompromiss zwischen Modellgenauigkeit und Ressourceneffizienz darstellt. Die Umsetzung der multidisziplinären Gesamtmethodik auf ein reales Fahrzeugsubsystem mit experimentellen alidierungsversuchen belegt ihre generell Anwendbarkeit, offenbart jedoch gleichzeitig vielseitige Potenziale zur Weiterentwicklung und Achtungspunkte bei der Anwendung
Towards precise and convenient semantic search on text and knowledge bases by Elmar Haussmann( )

1 edition published in 2017 in English and held by 18 WorldCat member libraries worldwide

Abstract: In this dissertation, we consider the problem of making semantic search on text and knowledge bases more precise and convenient. In a nutshell, semantic search is search with meaning. To this respect, text and knowledge bases have different advantages and disadvantages. Large amounts of text are easily available on the web, and they contain a wealth of information in natural language. However, text represents information in an unstructured form. It follows no pre-defined schema, and without further processing, a machine can understand its meaning only on a superficial level. Knowledge bases, on the other hand, contain structured information in the form of subject-predicate-object triples. The meaning of triples is well defined, and triples can be retrieved precisely via a query language. However, formulating queries in this language is inconvenient and compared to text only a small fraction of information is currently available in knowledge bases.<br><br>In this document, we summarize our contributions on making semantic search on text and knowledge bases more precise and convenient. For knowledge bases, we introduce an approach to answer natural language questions. A user can pose questions conveniently in natural language and ask, for example, "who is the ceo of apple?", instead of having to learn and use a specific query language. Our approach applies learning-to-rank strategies and improved the state of the art on two widely used benchmarks at the time of publication. For knowledge bases, we also describe a novel approach to compute relevance scores for triples from type-like relations like profession and nationality. For example, on a large knowledge base, a query for "american actors" can return a list of more than 60 thousand actors in no particular order. Relevance scores allow to sort this list so that, e.g., frequent lead actors appear before those who only had single cameo roles. In a benchmark that we generated via crowdsourcing, we show that our rankings are closer to human judgments than approaches from the literature. Finally, for text, we introduce a novel natural language processing technique that identifies which words in a sentence "semantically belong together". For example, in the sentence "Bill Gates, founder of Microsoft, and Jeff Bezos, founder of Amazon, are among the wealthiest persons in the world", the words "Bill Gates", "founder", and "Amazon" do not belong together, but the words "Bill Gates", "founder", and "Microsoft" do. We show that when query keywords are required to belong together in order to match, search results become more precise.<br><br>Given the characteristics of text and knowledge bases outlined above, it is promising to consider a search that combines both. For example, for the query "CEOs of U.S. companies who advocate cryptocurrencies", a list of CEOs of U.S. companies can be retrieved from a knowledge base. The information who is advocating cryptocurrencies is rather specific and changes frequently. It is, therefore, better found in full text. As part of this thesis, we describe how a combined search could be achieved and present and evaluate a fully functional prototype. All of our approaches are accompanied by an extensive evaluation which show their practicability and, where available, compare them to established approaches from the literature
Infrastrukturkonzepte für virtualisierte wissenschaftliche Forschungsumgebungen by Konrad Meier( )

1 edition published in 2017 in German and held by 18 WorldCat member libraries worldwide

Tubular optofluidics by Daniel Kopp( )

1 edition published in 2017 in English and held by 18 WorldCat member libraries worldwide

Abstract: This thesis describes a novel technology for realizing tunable optofluidic elements andsystems inside a tubular cavity, actuated by Electrowetting-on-Dielectrics (EWOD). The technology allows the implementation of diameter tunable apertures, focustunable and astigmatism-tunable lenses, tunable and rotatable prisms, and the combination of multi-element systems.The new approach allows the deposition and structuring of materials on the innersidewall of the tubular cavity. This is achieved by using flexible polymeric foils fabricated in standard micro-fabrication processes, which includes embedded EWODactuators showing excellent tuning characteristics. By a sophisticated assembly technique, the foils are mounted on the inner sidewall of the tubular cavity. Therefore,the combination of planar fabricated structures converted into a three-dimensionalshape offers completely new design opportunities for realizing more complex optofluidic components and systems.In contrast to conventional optofluidic components, the actuators can be designedin arbitrary shapes, which allows manipulating the liquid interfaces in an entirelynew manner. By this technique, tip and tilt from 0 ° to 45 °, defocus from ≈ 10 mmto infinity for the concave as well as the convex lens shape, oblique and vertical astigmatism and a reversible and linear aperture opening from ≈ 3.2 mm to ≈ 1.3 mm areachieved. Furthermore, the realized elements feature low electrical power consumption of several mW and switching times of several hundreds of ms. The possibility ofrealizing multi-element systems is demonstrated by the first all-liquid optical zoomsystem, with remarkable optical quality.The extensive characterization of the realized elements reveals the excellent performance of the elements and technology, opening up new possibilities and opportunities for highly integrated and miniaturized tunable optofluidic systems
Luminescence properties of SiV-centers in diamond diodes by Björn Tegetmeyer( )

1 edition published in 2018 in English and held by 18 WorldCat member libraries worldwide

Abstract: The silicon-vacancy center (SiV-center) is a promising candidate for quantum-physical applications due to its physical properties. Besides its narrowband photon emission at 738 nm wavelength, it shows a high photo-stability already at ambient conditions. Con- trary to the well-known and extensively studied nitrogen-vacancy center (NV-center), the physical properties of the silicon-vacancy center are not known well enough at the moment for actual applications in the area of quantum-computing or quantum- communication. Especially the possibility of electrical excitation and the luminescence properties of different charge-states of the SiV-center are not sufficiently proven. The present work intends to narrow this gap. Therefore, after initial optimization of the diamond growth-processes in ellipsoidal cavity Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD) reactors developed at Fraunhofer IAF, diamond PIN- and Schottky-diodes with in-situ incorporated as well as implanted silicon-vacancy cen- ters, respectively, were fabricated. With these devices, the electrical excitability of the luminescence of silicon-vacancy centers was studied. Additionally, experiments for exploring the luminescence properties of the silicon-vacancy center at different surface terminations (hydrogen-, oxygen-, and fluorine-termination) influencing its charge-state were performed. For a more detailed investigation of the SiV charge states, a two- dimensional Schottky-diode was fabricated from diamond, allowing to control the charge states actively and examine the resulting optical properties of the silicon-vacancy center. An ATLAS-simulation of the luminescence behavior observed in the two-dimensional Schottky-diode was performed to explain the physical processes and the experimental observation. The simulation indicates, that a charge state shift between SiV0 and SiV− (possibly even to SiV2−, which have been predicted theoretically), could be observed in the present experiment. Thereby, it could be shown, that a shift of the charge state of the SiV-centers from neutral to negative charge state could qualitatively explain the lu- minescence behavior observed. The methods as well as the obtained results, embedded in the physical backgrounds are extensively discussed and interpreted in the present thesis
A logic-based approach to system testing by Tobias Morciniec( )

1 edition published in 2017 in English and held by 18 WorldCat member libraries worldwide

State estimation, calibration, and self-calibration for accelerometer arrays by Patrick Schopp( )

1 edition published in 2018 in English and held by 18 WorldCat member libraries worldwide

 
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Alternative Names
Fakultät für Angewandte Wissenschaften

Languages
English (16)

German (6)