@unpublished{Kreitmeier2009,
author = {Kreitmeier, Wolfgang},
title = {Error bounds for high-resolution quantization with R{\´e}nyi - \&\#945; - entropy constraints},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-16647},
year = {2009},
abstract = {We consider the problem of optimal quantization with norm exponent r > 0 for Borel probabilities on Rd under constrained R{\´e}nyi-\&\#945;-entropy of the quantizers. If the bound on the entropy becomes large, then sharp asymptotics for the optimal quantization error are well-known in the special cases \&\#945; = 0 (memory-constrained quantization) and \&\#945; = 1 (Shannon-entropy-constrained quantization). In this paper we determine sharp asymptotics for the optimal quantization error under large entropy bound with entropy parameter \&\#945; \&\#8712; [1+r/d, \&\#8734;]. For \&\#945; \&\#8712; [0,1+r/d[ we specify the asymptotical order of the optimal quantization error under large entropy bound. The optimal quantization error decays exponentially fast with the entropy bound and the exact decay rate is determined for all \&\#945; \&\#8712; [0, \&\#8734;].},
subject = {Maßtheorie},
language = {en}
}
@phdthesis{Maydl2005,
author = {Maydl, Walter},
title = {Komponentenbasierte Softwareentwicklung f{\"u}r datenflußorientierte eingebettete Systeme},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-681},
school = {Universit{\"a}t Passau},
year = {2005},
abstract = {Diese Dissertation besch{\"a}ftigt sich mit den Problemen bei der Entwicklung von effizienter und zuverl{\"a}ssiger Software f{\"u}r eingebettete Systeme. Eingebettete Systeme sind inh{\"a}rent nebenl{\"a}ufig, was mit einen Grund f{\"u}r ihre hohe Entwurfskomplexit{\"a}t darstellt. Aus dieser Nebenl{\"a}ufigkeit resultiert ein hoher Grad an Kommunikation zwischen den einzelnen Komponenten. Eine wichtige Forderung zur Vereinfachung des Entwurfsprozesses besteht in der getrennten Modellierung von Kommunikationsprotokollen und eigentlichen Verarbeitungsalgorithmen. Daraus resultiert eine h{\"o}here Wiederverwendbarkeit bei sich {\"a}ndernden Kommunikationsstrukturen. Die Grundlage f{\"u}r die sogenannten Datenflußsprachen bildet eine einfache von Gilles Kahn konzipierte Sprache f{\"u}r Parallelverarbeitung. In dieser Sprache besteht ein System aus einer Menge sequentieller Prozesse (Komponenten), die {\"u}ber Fifokan{\"a}le miteinander kommunizieren. Ein Prozess ist rechenbereit, wenn seine Eingangsfifos mit entsprechenden Daten gef{\"u}llt sind. {\"U}bertragen werden physikalische Signale, die als Str{\"o}me bezeichnet werden. Str{\"o}me sind Folgen von Werten ohne explizite Zeitangaben. Das Einsatzgebiet von Datenflußsprachen liegt in der Entwicklung von Programmen zur Bild- und Signalverarbeitung, typischen Aufgaben in eingebetteten Systemen. Die Programmierung erfolgt visuell, wobei man Icons als Repr{\"a}sentanten parametrisierbarer Komponenten aus einer Bibliothek ausw{\"a}hlt und mittels Kanten (Fifos) verbindet. Ein im allgemeinen dynamischer Scheduler {\"u}berwacht die Ausf{\"u}hrung des fertiggestellten Anwendungsprogramms. Diese Arbeit schl{\"a}gt ein universelleres Modell physikalischer Signale vor. Dabei werden zwei Ziele verfolgt: 1. Effiziente Kommunikation zwischen den Komponenten 2. Entwurfsbegleitende {\"U}berpr{\"u}fung von Programmeigenschaften unter Verwendung komplexerer Komponentenmodelle Zur Effizienzsteigerung werden nur relevante Werte innerhalb von Str{\"o}men {\"u}bertragen. Dies erh{\"o}ht zwar den Mehraufwand zur Kennzeichnung des Aufbaus eines Teilstroms, in praktischen Anwendungen ist die hier vorgestellte Methode jedoch effizienter. Die Einf{\"u}hrung neuer Signalmerkmale erlaubt unterschiedlichste {\"U}berpr{\"u}fungen der Einhaltung von Typregeln durch die Eingangs- und Ausgangsstr{\"o}me einer Komponente. Anstelle einfacher Schaltregeln werden aufwendigere Kommunikationsprotokolle f{\"u}r die verschiedenen Arten von Komponenten eingef{\"u}hrt. Fifomaten (Fifo-Automaten) dienen als formale Grundlage. Mittels eines dezidierten Model-Checking-Verfahrens wird das Zusammenspiel der Fifomaten daraufhin untersucht, ob ein zyklischer Schedule existiert. Die Existenz eines solchen zyklischen Schedules schließt Speicher{\"u}berlauf und Deadlocks aus und garantiert dar{\"u}ber hinaus, daß das Programm nach endlicher Zeit wieder in die Ausgangssituation zur{\"u}ckfindet. Da im allgemeinen die Datenflußprogramme turing{\"a}quivalent sind, kann es allerdings zyklische Schedules geben, die das Verfahren nicht entdeckt. Mit der hier vorgestellten und implementierten Methode wird die Entwicklungszeit korrekter Datenflußprogramme deutlich reduziert. Das neue Modell physikalischer Signale macht zudem die Ausf{\"u}hrung effizienter.},
subject = {Softwareentwicklung},
language = {de}
}
@phdthesis{Schwarzfischer2004,
author = {Schwarzfischer, Thomas},
title = {Quality and Utility - On the Use of Time-Value Functions to Integrate Quality and Timeliness Flexible Aspects in a Dynamic Real-Time Scheduling Environment},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-619},
school = {Universit{\"a}t Passau},
year = {2004},
abstract = {Scheduling methodologies for real-time applications have been of keen interest to diverse research communities for several decades. Depending on the application area, algorithms have been developed that are tailored to specific requirements with respect to both the individual components of which an application is made up and the computational platform on which it is to be executed. Many real-time scheduling algorithms base their decisions solely or partly on timing constraints expressed by deadlines which must be met even under worst-case conditions. The increasing complexity of computing hardware means that worst-case execution time analysis becomes increasingly pessimistic. Scheduling hard real-time computations according to their worst-case execution times (which is common practice) will thus result, on average, in an increasing amount of spare capacity. The main goal of flexible real-time scheduling is to exploit this otherwise wasted capacity. Flexible scheduling schemes have been proposed to increase the ability of a real-time system to adapt to changing requirements and nondeterminism in the application behaviour. These models can be categorised as those whose source of flexibility is the quality of computations and those which are flexible regarding their timing constraints. This work describes a novel model which allows to specify both flexible timing constraints and quality profiles for an application. Furthermore, it demonstrates the applicability of this specification method to real-world examples and suggests a set of feasible scheduling algorithms for the proposed problem class.},
subject = {Echtzeitsystem},
language = {en}
}
@phdthesis{Kreitmeier2006,
author = {Kreitmeier, Wolfgang},
title = {Optimale Quantisierung verallgemeinerter Cantor-Verteilungen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-913},
school = {Universit{\"a}t Passau},
year = {2006},
abstract = {F{\"u}r verallgemeinerte Cantor-Verteilungen, die im Eindimensionalen mittels klassischer Wischkonstruktion bzw. in h{\"o}heren Dimensionen {\"u}ber iterierte Funktionensysteme definiert werden, wird das Problem der optimalen Quantisierung unter bestimmten Voraussetzungen vollst{\"a}ndig gel{\"o}st. Es werden die optimalen Codeb{\"u}cher bestimmt und Formeln f{\"u}r den optimalen Quantisierungsfehler bewiesen. Im eindimensionalen Fall wird eine Existenzcharakterisierung der Quantisierungsdimension gegeben und unter bestimmten Voraussetzungen die Nichtexistenz des Quantisierungskoeffizienten gezeigt. Auch in h{\"o}heren Dimensionen wird f{\"u}r die betrachteten Verteilungen bewiesen, dass der Quantisierungskoeffizient, bei existenter Quantisierungsdimension, nicht existiert. Die gewonnenen Resultate werden auf die Gleichverteilungen von modifizierten klassischen fraktalen Mengen, wie das Sierpinski-Dreieck, die Cantormenge und den Cantor-Staub angewandt.},
subject = {Maßtheorie},
language = {de}
}
@unpublished{Kreitmeier2007,
author = {Kreitmeier, Wolfgang},
title = {Optimal quantization of probabilities concentrated on small balls},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-12010},
year = {2007},
abstract = {We consider probability distributions which are uniformly distributed on a disjoint union of balls with equal radius. For small enough radius the optimal quantization error is calculated explicitly in terms of the ball centroids. We apply the results to special self-similar measures.},
subject = {Maßtheorie},
language = {en}
}
@unpublished{Kreitmeier2007,
author = {Kreitmeier, Wolfgang},
title = {Asymptotic order of quantization for Cantor distributions in terms of Euler characteristic, Hausdorff and Packing measure},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-7374},
year = {2007},
abstract = {For homogeneous one-dimensional Cantor sets, which are not necessarily self-similar, we show under some restrictions that the Euler exponent equals the quantization dimension of the uniform distribution on these Cantor sets. Moreover for a special sub-class of these sets we present a linkage between the Hausdorff and the Packing measure of these sets and the high-rate asymptotics of the quantization error.},
subject = {Maßtheorie},
language = {en}
}
@phdthesis{Ramsauer2005,
author = {Ramsauer, Markus},
title = {Energie- und qualit{\"a}tsbewußte Einplanung von periodischen Prozessen in eingebetteten Echtzeitsystemen},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-628},
school = {Universit{\"a}t Passau},
year = {2005},
abstract = {Mobile Ger{\"a}te dienen immer h{\"a}ufiger zur Ausf{\"u}hrung von Echtzeitanwendungen, sie bieten immer mehr Rechenleistung und sie werden kleiner und leichter. Hohe Rechenleistung erfordert jedoch sehr viel Energie, was im Gegensatz zu den geringen Akkukapazit{\"a}ten, die aus der Forderung nach kleinen und leichten Ger{\"a}ten resultieren, steht. Bei der Echtzeiteinplanung von Rechenprozessen gewinnt daher der Energieverbrauch der Ger{\"a}te neben der rechtzeitigen Beendigung von Anwendungen zunehmend an Bedeutung, weil sie m{\"o}glichst lange unabh{\"a}ngig vom Stromnetz betrieben werden sollen. Andererseits werden auf diesen Ger{\"a}ten rechenintensive Anwendungen ausgef{\"u}hrt, bei denen es w{\"u}nschenswert ist, die maximale mit der verf{\"u}gbaren Rechenleistung erzielbare Qualit{\"a}t zu erhalten. In dieser Arbeit wird ein Systemmodell vorgestellt, das den Design-to-time-Ansatz mit den M{\"o}glichkeiten der dynamischen Leistungsanpassung (Rechenleistung und verbrauchte elektrische Leistung) moderner Prozessoren vereinigt. Der Design-to-time-Ansatz erm{\"o}glicht Energieeinsparungen oder Qualit{\"a}tssteigerungen durch die dynamische Auswahl alternativer Implementierungen, welche dieselbe Aufgabe mit unterschiedlicher Ausf{\"u}hrungsdauer und Qualit{\"a}t bzw. Energieverbrauch erf{\"u}llen. Das Systemmodell umfaßt unter anderem periodische Prozesse mit harten Echtzeitbedingungen, Datenabh{\"a}ngigkeiten und alternativen Implementierungen, sowie Prozessoren mit diskreten Leistungsstufen. Die Einplanung der Prozesse erfolgt in zwei Phasen. In der Offline-Phase wird ein flexibler Schedule berechnet, der f{\"u}r die zur Laufzeit m{\"o}glichen Kombinationen von verstrichener Zeit und noch einzuplanender Prozeßmenge den jeweils einzuplanenden Prozeß, sowie die zu verwendende Implementierung und gegebenenfalls die einzustellende Leistungsstufe beinhaltet. Dieser flexible Schedule wird w{\"a}hrend der Online-Phase mit vernachl{\"a}ssigbarem Zeit- und Energieaufwand von einem Scheduler interpretiert. F{\"u}r die Berechnung der optimalen flexiblen Schedules wurde ein Optimierer entwickelt, der eine Folge von flexiblen Schedules mit monoton steigender G{\"u}te (niedriger Energieverbrauch bzw. hohe Qualit{\"a}t) generiert, und damit der Klasse der Anytime-Algorithmen zuzuordnen ist. Eine Variante der Dynamischen Programmierung dient zur Bestimmung global optimaler, flexibler Schedules, die beispielsweise als Basis f{\"u}r Benchmarks dienen. Eine auf Simulated Annealing basierende Variante des Optimierers erm{\"o}glicht ein schnelleres Auffinden guter, flexibler Schedules f{\"u}r umfangreichere Anwendungen.},
subject = {Echtzeitsystem},
language = {de}
}
@phdthesis{Raitner2005,
author = {Raitner, Marcus},
title = {Efficient visual navigation of hierarchically structured graphs},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-658},
school = {Universit{\"a}t Passau},
year = {2005},
abstract = {Visual navigation of hierarchically structured graphs is a technique for interactively exploring large graphs that possess an additional hierarchical structure. This structure is expressed in form of a recursive clustering of the nodes: in call graphs of telephone networks, for instance, the nodes are identified with phone numbers; they are clustered recursively through the implicit structure of the numbers, e. g., nodes with the same area code belong to a cluster. In order to reduce the complexity and the size of the graph, only those subgraphs that are currently needed are shown in detail, while the others are collapsed, i. e., represented by meta nodes. In such a graph view the subgraphs in the areas of interest are expanded furthest, whereas those on the periphery are abstracted. As the areas of interest change over time, clusters in a view need to be expanded or contracted. First and foremost, there is need for an efficient data structure for this graph view maintenance problem. Depending on the admissible modifications of the graph and its hierarchical clustering, three variants have been discussed in the literature: in the static case, everything is fixed; in the dynamic graph variant, only edges of the graph can be inserted and deleted; finally, in the dynamic graph and tree variant the graph additionally is subject to node insertions and deletions and the clustering may change through splitting and merging of clusters. We introduce a new variant, dynamic leaves, which is based on the dynamic graph variant, but additionally allows insertion and deletion of graph nodes, i. e., leaves of the hierarchy. So far efficient data structures were known only for the static and the dynamic graph variant, i. e., neither the nodes of the graph nor the clustering could be modified. As this is unsatisfactory in an interactive editor for hierarchically structured graphs, we first generalize the approach of Buchsbaum et. al (Proc. 8th ESA, vol. 1879 of LNCS, pp. 120-131, 2000), in which graph view maintenance is formulated as a special case of range searching over tree cross products, to the new dynamic leaves variant. This generalization builds on a novel technique of superimposing a search tree over an ordered list maintenance structure. With an additional factor of roughly O(log n/log log n), this is the first data structure for the problem of graph view maintenance where the node set is dynamic. Visualizing the expanding and contracting appropriately is the second challenge. We propose a local update scheme for the algorithm of Sugiyama and Misue (IEEE Trans. on Systems, Man, and Cybernetics 21 (1991) 876- 892) for drawing compound digraphs. The layered drawings that it produces have many applications ranging from biochemical pathways to UML diagrams. Modifying the intermediate results of every step of the original algorithm locally, the update scheme is more efficient than re-applying the entire algorithm after expansion or contraction. As our experimental results on randomly generated graphs show, the average time for updating the drawing is around 50 \% of the time for redrawing for dense graphs and below 20 \% for sparse graphs. Also, the performance gain is not at the expense of quality as regards the area of the drawing, which increases only insignificantly, and the number of crossings, which is reduced. At the same time, the locality of the updates preserves the user 's mental map of the graph: nodes that are are not affected stay on the same level in the same relative order and expanded edges take the same course as the corresponding contracted edge; furthermore, expansion and contraction are visually inverse. Finally, our new data structure and the update scheme are combined into an interactive editor and viewer for compound (di-)graphs. A flexible and extensible software architecture is introduced that lays the ground for future research. It employs the well-known Model-View-Controller (MVC) paradigm to separate the abstract data from its presentation. As a consequence, the purely combinatorial parts, i. e., the compound (di-)graph and its views, are reusable without the editor front-end. A proof-of-concept implementation based on the proposed architecture shows its feasibility and suitability.},
subject = {Dynamische Datenstruktur},
language = {en}
}
@phdthesis{Lauren2005,
author = {Lauren, Verena},
title = {Semilineare Approximation in der Bildrekonstruktion},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-730},
school = {Universit{\"a}t Passau},
year = {2005},
abstract = {In der Bildverarbeitung spielen Segmentierungsalgorithmen, bei denen die Art der zu segmentierenden Menge schon im Voraus festgelegt werden kann und nur noch ihre Gr{\"o}ße und Lage angepasst werden muss, eine eher untergeordnete Rolle. Gr{\"u}nde hierf{\"u}r sind vor allem komplizierte Zielfunktionen und daraus resultierende lange Rechenzeiten, die zudem meist kein optimales Ergebnis liefern. Dabei kann eine mengenbasierte Segmentierung durchaus sinnvoll eingesetzt werden, wenn gewisse Rahmenbedingungen eingehalten werden. In dieser Arbeit wird eine Theorie zur allgemeinen mengenbasierten Segmentierung vorgestellt und untersucht, unter welchen Bedingungen optimale Segmentierungsergebnisse erreicht werden k{\"o}nnen. Die anschließenden Anwendungen best{\"a}tigen die N{\"u}tzlichkeit dieser Theorie.},
subject = {Optimale Rekonstruktion},
language = {de}
}
@phdthesis{Streckenbach2005,
author = {Streckenbach, Mirko},
title = {KABA - a system for refactoring Java programs},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-638},
school = {Universit{\"a}t Passau},
year = {2005},
abstract = {Refactoring is a well known technique to enhance various aspects of an object-oriented program. It has become very popular during recent years, as it allows to overcome deficits present in many programs. Doing refactoring by hand is almost impossible due to the size and complexity of modern software systems. Automated tools provide support for the application of refactorings, but do not give hints, which refactorings to apply and why. The Snelting/Tip analysis is a program analysis, which creates a refactoring proposal for a class hierarchy by analyzing how class members are used inside a program. KABA is an adaption and extension of the Snelting/Tip analysis for Java. It has been implemented and expanded to become a semantic preserving, interactive refactoring system. Case studies of real world programs will show the usefulness of the system and its practical value.},
subject = {Java },
language = {en}
}
@phdthesis{Fischer2005,
author = {Fischer, Andreas},
title = {Peano-differentiable functions in O-Minimal structures},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-673},
school = {Universit{\"a}t Passau},
year = {2005},
abstract = {We discuss several aspects of Peano-differentiable functions which are definable in an o-minimal structure expanding a real closed field. After recalling some already known results about o-minimal structures we develop techniques for the intrinsic study of differentiable functions in these structures. After this we study (ordinary) differentiable functions definable in an o-minimal structure and their continuiuty properties along curves of different differentiability classes. Then we generalise (ordinary) differentiability to Peano-differentiability. We study differentiability of certain Peano-derivatives of definable functions and characterise the sets of non-continuity of these derivatives. In the end we study extendability of these functions defined on closed sets and give sufficient conditions by which we can extend functions as Peano-differentiable functions.},
subject = {Semialgebraische Menge},
language = {en}
}
@phdthesis{Wuechner2013,
author = {W{\"u}chner, Patrick},
title = {Energy-Efficient and Timely Event Reporting Using Wireless Sensor Networks},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-27159},
school = {Universit{\"a}t Passau},
year = {2013},
abstract = {This thesis investigates the suitability of state-of-the-art protocols for large-scale and long-term environmental event monitoring using wireless sensor networks based on the application scenario of early forest fire detection. By suitable combination of energy-efficient protocol mechanisms a novel communication protocol, referred to as cross-layer message-merging protocol (XLMMP), is developed. Qualitative and quantitative protocol analyses are carried out to confirm that XLMMP is particularly suitable for this application area. The quantitative analysis is mainly based on finite-source retrial queues with multiple unreliable servers. While this queueing model is widely applicable in various research areas even beyond communication networks, this thesis is the first to determine the distribution of the response time in this model. The model evaluation is mainly carried out using Markovian analysis and the method of phases. The obtained quantitative results show that XLMMP is a feasible basis to design scalable wireless sensor networks that (1) may comprise hundreds of thousands of tiny sensor nodes with reduced node complexity, (2) are suitable to monitor an area of tens of square kilometers, (3) achieve a lifetime of several years. The deduced quantifiable relationships between key network parameters — e.g., node size, node density, size of the monitored area, aspired lifetime, and the maximum end-to-end communication delay — enable application-specific optimization of the protocol.},
subject = {Drahtloses Sensorsystem},
language = {en}
}
@phdthesis{Limbeck2013,
author = {Limbeck, Jan},
title = {Computation of Approximate Border Bases and Applications},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-27197},
school = {Universit{\"a}t Passau},
year = {2013},
abstract = {This thesis addresses some of the algorithmic and numerical challenges associated with the computation of approximate border bases, a generalisation of border bases, in the context of the oil and gas industry. The concept of approximate border bases was introduced by D. Heldt, M. Kreuzer, S. Pokutta and H. Poulisse in "Approximate computation of zero-dimensional polynomial ideals" as an effective mean to derive physically relevant polynomial models from measured data. The main advantages of this approach compared to alternative techniques currently in use in the (hydrocarbon) industry are its power to derive polynomial models without additional a priori knowledge about the underlying physical system and its robustness with respect to noise in the measured input data. The so-called Approximate Vanishing Ideal (AVI) algorithm which can be used to compute approximate border bases and which was also introduced by D. Heldt et al. in the paper mentioned above served as a starting point for the research which is conducted in this thesis. A central aim of this work is to broaden the applicability of the AVI algorithm to additional areas in the oil and gas industry, like seismic imaging and the compact representation of unconventional geological structures. For this purpose several new algorithms are developed, among others the so-called Approximate Buchberger M{\"o}ller (ABM) algorithm and the Extended-ABM algorithm. The numerical aspects and the runtime of the methods are analysed in detail - based on a solid foundation of the underlying mathematical and algorithmic concepts that are also provided in this thesis. It is shown that the worst case runtime of the ABM algorithm is cubic in the number of input points, which is a significant improvement over the biquadratic worst case runtime of the AVI algorithm. Furthermore, we show that the ABM algorithm allows us to exercise more direct control over the essential properties of the computed approximate border basis than the AVI algorithm. The improved runtime and the additional control turn out to be the key enablers for the new industrial applications that are proposed here. As a conclusion to the work on the computation of approximate border bases, a detailed comparison between the approach in this thesis and some other state of the art algorithms is given. Furthermore, this work also addresses one important shortcoming of approximate border bases, namely that central concepts from exact algebra such as syzygies could so far not be translated to the setting of approximate border bases. One way to mitigate this problem is to construct a "close by" exact border bases for a given approximate one. Here we present and discuss two new algorithmic approaches that allow us to compute such close by exact border bases. In the first one, we establish a link between this task, referred to as the rational recovery problem, and the problem of simultaneously quasi-diagonalising a set of complex matrices. As simultaneous quasi-diagonalisation is not a standard topic in numerical linear algebra there are hardly any off-the-shelf algorithms and implementations available that are both fast and numerically adequate for our purposes. To bridge this gap we introduce and study a new algorithm that is based on a variant of the classical Jacobi eigenvalue algorithm, which also works for non-symmetric matrices. As a second solution of the rational recovery problem, we motivate and discuss how to compute a close by exact border basis via the minimisation of a sum of squares expression, that is formed from the polynomials in the given approximate border basis. Finally, several applications of the newly developed algorithms are presented. Those include production modelling of oil and gas fields, reconstruction of the subsurface velocities for simple subsurface geometries, the compact representation of unconventional oil and gas bodies via algebraic surfaces and the stable numerical approximation of the roots of zero-dimensional polynomial ideals.},
subject = {Computeralgebra},
language = {en}
}
@phdthesis{Stegmaier2014,
author = {Stegmaier, Florian},
title = {Unified Retrieval in Distributed and Heterogeneous Multimedia Information Systems},
url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-27317},
school = {Universit{\"a}t Passau},
year = {2014},
abstract = {Multimedia retrieval is an essential part of today's world. This situation is observable in industrial domains, e.g., medical imaging, as well as in the private sector, visible by activities in manifold Social Media platforms. This trend led to the creation of a huge environment of multimedia information retrieval services offering multimedia resources for almost any user requests. Indeed, the encompassed data is in general retrievable by (proprietary) APIs and query languages, but unfortunately a unified access is not given due to arising interoperability issues between those services. In this regard, this thesis focuses on two application scenarios, namely a medical retrieval system supporting a radiologist's workflow, as well as an interoperable image retrieval service interconnecting diverse data silos. The scientific contribution of this dissertation is split in three different parts: the first part of this thesis improves the metadata interoperability issue. Here, major contributions to a community-driven, international standardization have been proposed leading to the specification of an API and ontology to enable a unified annotation and retrieval of media resources. The second part issues a metasearch engine especially designed for unified retrieval in distributed and heterogeneous multimedia retrieval environments. This metasearch engine is capable of being operated in a federated as well as autonomous manner inside the aforementioned application scenarios. The remaining third part ensures an efficient retrieval due to the integration of optimization techniques for multimedia retrieval in the overall query execution process of the metasearch engine.},
subject = {Abfrage},
language = {en}
}