Mortalitätssalienz und Angstbewältingung im Kontext einer Krebserkrankung

Doctoral thesis (2008)

Network security through artificial immunity with SANA

Doctoral thesis (2008)

IFDMA for uplink mobile radio communication systems

Doctoral thesis (2008)

An application of interleaved frequency-division multiple-access (IFDMA) for mobile communications has become an active field of research since 1998. The special interest has been given to the uplink of ... [more ▼]

An application of interleaved frequency-division multiple-access (IFDMA) for mobile communications has become an active field of research since 1998. The special interest has been given to the uplink of mobile communication since low peak-to-average power ratio makes IFDMA attractive for hand-held mobile devices allowing an application of cheap amplifiers. The IFDMA signal can be generated simply by compression and repetition of the transmit data sequence, without usage of fast Fourier transformation. Due to the periodic nulls in transmit spectrum, other users may utilize the same frequency band allowing multiple access. This work contributes to the state of the art in the field of IFDMA in the following areas: data detection, PAPR reduction of multi-carrier systems, an estimation of frequency offsets in multicarrier uplink, where many users are simultaneously active. [less ▲]

Les pratiques discursives œnophiles entre normativité et appropriation. Contribution à une sociologie des cultures alimentaires

Doctoral thesis (2008)

Owing to the fact that wine consumption is becoming ever more culturalised, I have adopted a micro-sociological approach to contemporary œnophile discursive practices, in Luxembourg, by concentrating on ... [more ▼]

Owing to the fact that wine consumption is becoming ever more culturalised, I have adopted a micro-sociological approach to contemporary œnophile discursive practices, in Luxembourg, by concentrating on inherent normativity (moral and aesthetic) and ordinary appropriation (ethical and hedonistic). The context for this articulation is provided by wine tasting lessons ‘for beginners’. The analytical tools that food studies offer are pertinent for tracing the historical evolution of œnophile discursive practices – being singularised, aesthetic and reflexive –, viewed through their rationalisation processes (legislative regulation, scientific consolidation and media diffusion). Through this cristallisation, œnophily has brought about a governmentality of consumption ; its concrete institutionalisation, in the form of state-organised evening-classes, conveys a specific type of normativity. It will be shown that the publics of this institution – mainly male and affluent – have both ‘operational’ and ‘hedonistic’ motivations, thus enhancing a form of governmentality and an interior orientation of experiences. Appropriations of the œnophile normativity are reactive – either positively or negatively : interviewees adopt tactical usages of specific dispositions and of tactical courses of action, related to vertical differenciations (social trajectory and position), but also and mainly to horizontal ones (milieus, interactions and experiments carried out through various projects of subjectivation). These dispositions and tactics are linked to the domestic œnophile logics of action – which are active, strategic and hedonistic. Contrasting with the œnophile normativity (focusing on wine), ordinary discursive practices relate to preoccupations with one’s personal and social life, rather than to wine. Nonetheless, it is the aesthetic-based œnophile canonisation that contains essential prerequisites of subjectivation, even if it is appropriated in a hedonistic, socio- or egocentric way. This shows the consubstantial and flexible interweaving of norms and pleasure, leading to a personal and social empowerment (with a potential that is mainly ethical, but also distinctive), via the discursive usage of one particular food item. [less ▲]

Topology control and small-worlds in hybrid wireless networks

Doctoral thesis (2007)

Operations on Finite Sets, Functional Composition, and Ordered Sets

Doctoral thesis (2007)

The unifying theme of this research work is functional composition. We study operations on a nonempty set A, an important particular case being that of Boolean functions when A = {0, 1}. A class of ... [more ▼]

The unifying theme of this research work is functional composition. We study operations on a nonempty set A, an important particular case being that of Boolean functions when A = {0, 1}. A class of operations is a subset of the set of all operations on A. A clone on A is a class of operations on A that contains all projection maps and is closed under functional composition. The first part of this thesis is a study of compositions of the clones of Boolean functions. The clone of all Boolean functions can be decomposed in various ways into minimal clones, and we observe that such decompositions correspond to different normal form systems: the disjunctive normal form (DNF), conjunctive normal form (CNF), Zhegalkin polynomial, dual Zhegalkin polynomial, and so-called median normal form. These normal form systems are compared in terms of efficiency, and we establish that the median normal form system provides in a certain sense more efficient representations than the other four normal form systems mentioned above. The second part of this thesis is a study of certain order relations on the set of all operations on A. For a fixed class C of operations on A, we say that f is a C-subfunction of g, if f can be obtained by composing g from inside with operations from C. We say that f and g are C-equivalent, if f and g are C-subfunctions of each other. The C-subfunction relation is a quasiorder (a reflexive and transitive relation) on the set of all operations on A if and only if the parametrizing class C is a clone. The simplest example of C-subfunction relations is obtained when C is the smallest clone I of projections on A. Forming I-subfunctions corresponds to simple manipulation of variables, namely addition and deletion of dummy variables, permutation of variables, and identification of variables. None of these operations increases the number of essential variables, and only variable identification may decrease this number. We study more carefully the effect of variable identification on the number of essential variables of operations on finite base sets. We then study certain order-theoretical properties of various C-subfunction partial orders defined by larger clones C on finite base sets A. We are mostly concerned about the descending chain condition and the existence of infinite antichains, and as it turns out, these properties on the defining clone C. Homomorphisms of labeled posets (or k-posets) are applied in our analysis of subfunction relations defined by clones of monotone functions. The third part of this thesis is a study of the homomorphicity order of finite k-posets on its own right. We establish that this order is a distributive lattice, and furthermore, it is universal in the sense that every countable poset can be embedded into it. This result implies universality of the subfunction partial orders defined by clones of monotone functions on finite sets of more than two elements. In this way, we also obtain a new proof for the well-known universality of the homomorphicity order of graphs. [less ▲]

Prudent ranking rules: Theoretical contributions and applications

Doctoral thesis (2007)

The subject of this PhD thesis is about ordinal ranking rules. An ordinal ranking rule is a procedure which combines several initial rankings into a global ranking. Given the difficulty and ambiguity of ... [more ▼]

The subject of this PhD thesis is about ordinal ranking rules. An ordinal ranking rule is a procedure which combines several initial rankings into a global ranking. Given the difficulty and ambiguity of aggregating ordinal data, it is worthwhile studying ranking rules which, depending on the initial data, do not lead to one, but to several global rankings, hence leaving some indeterminateness about the final result. It appears that the concept of a prudent order, initially introduced by Arrow and Raynaud, is a possible answer from such a perspective. In this approach, pairwise majority margins are computed which count for any two alternatives the number of initial rankings that prefer the first over the second alternative. A prudent order is then defined as a linear order which maximizes the smallest pairwise majority margin. It was our main objective in this thesis to gain a better understanding of the family of prudent ranking rules. According to our definition, a prudent ranking rule is a rule which outputs only prudent orders. To achieve this goal, we pursued different strategies: i) axiomatic characterizations which highlight the distinctive features of a ranking rule, ii) comparison of the properties or results of prudent ranking rules to those of other ranking rules, and iii) empirical simulations allowing for more quantitative conclusions. The thesis is divided into 3 parts. Part I contains an introduction to the ordinal ranking problem. Our main theoretical contributions can be found in Part II. Finally, Part III illustrates the use of prudent ranking rules in two fields of applications. [less ▲]

Sécurité des architectures de calcul distribué : Authentification et certification de résultats

Doctoral thesis (2007)

Strafgesetzlichkeit als völkerstrafrechtliches Legitimationsprinzip

Doctoral thesis (2007)

Global and Local Gravity Field Recovery from Satellite-to-Satellite Tracking

Doctoral thesis (2007)

The main objective of this thesis is the gravity field recovery using satellite-to-satellite tracking methods. Based on new technologies like the global positioning system and accelerometers satellite-to ... [more ▼]

The main objective of this thesis is the gravity field recovery using satellite-to-satellite tracking methods. Based on new technologies like the global positioning system and accelerometers satellite-to-satellite tracking yields a dramatic improvement in the de- termination of the Earth gravity field. Two dedicated satellite missions, namely the CHAllenging Minisatellite Payload (CHAMP) and the Gravity Recovery And Climate Experiment (GRACE) are underway. This work describes the processing of the satel- lite data from CHAMP and GRACE based on the energy balance approach. The first part discusses the global gravity field recovery from CHAMP. Specifically, it aims at a reprocessing of kinematic position data and at a refinement of the data processing strategies. Although the energy balance approach is theoretically simple, its imple- mentation proved to be quite challenging. By refining the processing techniques an improvement of up to 30\% is reached for the low degree spherical harmonic coefficients. Nevertheless, the solutions still depend strongly on the variability of the groundtrack. The quality of the monthly solutions can vary up to one order of magnitude. To ad- dress this challenge, an in-depth analysis gives new insight into the phenomenon, and a new and unique combination method with GRACE data is presented, which yields a more homogeneous set of solutions and reaches the edge of the recoverability of a time-variable gravity signal from high-low satellite-to-satellite tracking missions. In the second part the energy balance approach is applied to the GRACE mission. Pre- vious attempts of expressing the kinetic energy in terms of the K-band measurement make use of an approximation. In this work, an exact representation is introduced and is validated by simulations. In the third part, the aim is to make optimal usage of the data distribution in the high latitude area. For this, interpolation and downward continuation techniques are investigated and an improvement, compared to the global solutions, is achieved. Overall, the analysis provides new and valuable insight into the data processing of satellite-to-satellite tracking data using the energy balance approach. [less ▲]

La somministrazione di manodopera. Duplicità di datori di lavoro e tecniche di tutela

Doctoral thesis (2007)

Relating to Nature: The Performative Spaces of Icelandic Tourism

Doctoral thesis (2007)

Use of commercial simulation software for analyzing the dynamics of an injection-molding clamp unit

Doctoral thesis (2006)

Today, the interest in integrated dynamic analysis of mechatronic systems increases. Different approaches are possible depending on the nature of the system, on the required complexity of the model, or ... [more ▼]

Today, the interest in integrated dynamic analysis of mechatronic systems increases. Different approaches are possible depending on the nature of the system, on the required complexity of the model, or simply on the tools available to the engineer. During this work, the aim was to implement specialized commercial simulation software packages and to combine them in order to simulate the dynamic behavior of mechatronic systems as for example an injection molding machine. The multi-body simulation software is the backbone of the current analysis as it inherently models large non-linear motions. It is possible to account for the flexibility of components in the MBS model if necessary. Furthermore, other simulation codes were used to model the hydraulic and controls systems. The case studies show the interest and the potential of a combined analysis of mechatronic systems. Once the different sub-models, generated with the adequate simulation tool, have been successfully linked and validated by measurements, various scenarios can be simulated and analyzed. The model provides the engineer with an additional insight into the overall system and thus with a better understanding of its dynamic characteristics. The interactions between the subsystems, which may be of very distinctive nature, can be investigated. Generally, it is difficult to predict such relations intuitively. Finally, the model allows to simulate with different design parameters and to asses the effect of modifications to these on the overall performance of the machine. This helps to identify the significant parameters that are crucial for an optimized functioning. [less ▲]

Eignet sich die semi-konkrete Darstellungsform Pfeilsprache als nonverbale Kommunikationsmöglichkeit im aktiv-entdeckenden Mathematikunterricht?

Doctoral thesis (2005)

Corrupting Cooks: Domestic Service and Expertise in Eighteenth-Century France

Doctoral thesis (2005)

Sens et symboles en mathématiques : Etude de l'utilisation du signe moins dans les réductions polynomiales et la résolution d'équations du premier degré à une inconnue

Doctoral thesis (2005)

Barriers to Inclusion: The Institutionalization of Special Education in the United States and Germany

Doctoral thesis (2004)

Comprendre la trajectoire scolaire : l’influence des processus intra-familiaux et de l’engagement parental. Une approche transversale et longitudinale

Doctoral thesis (2003)

Anticipatory discourses : constructing futures of action in a vocational program for long-term unemployed

Doctoral thesis (2003)

Design and Implementation of Decision Making Checkers for Industrial Production Scheduling, Control, and Maintenance

Doctoral thesis (2002)

Benetzung in ternären Flüssigkeitsmischungen

Doctoral thesis (2001)

Autorité publique et conscience dynastique. Etudes sur les représentations du pouvoir entre Meuse et Moselle. Les origines du comté de Luxembourg (Xe - début XIIe s.)

Doctoral thesis (1999)

Premiers espaces de cohomologie de l'algèbre de Lie des opérateurs différentiels sur une variété, à coefficients dans les fonctions

Doctoral thesis (1998)

Ästhetik und Kompositionsweise der Gruppe der Six. Studien zu ihrer Kammermusik aus den Jahren 1917-1921

Doctoral thesis (1996)

Discrete element analysis of granular materials

Doctoral thesis (1996)

Discrete Element Analysis of Granular Materials During oil and gas production, several years after drilling a borehole, sand particles and small sandstone particles start to break away from the borehole ... [more ▼]

Discrete Element Analysis of Granular Materials During oil and gas production, several years after drilling a borehole, sand particles and small sandstone particles start to break away from the borehole surface. These particles can damage the transport pipes and other equipment in a short period of time. By simulating this borehole behaviour with the thick-walled cylinder test, four phenomena were found which cannot be explained by conventional continuum mechanics: 1. Despite the compressive stress, failure occurs on the micro level due to tension cracks. 2. These cracks are not diagonal to, but parallel to, the borehole surface. 3. These cracks cause two diametrically opposite breakouts. 4. The functional failure of the borehole starts at a higher radial pressure than predicted. In 1979, Cundall developed a computer model, based on the basic elements of granular materials, i.e. the grains themselves and their interactions, to describe the behaviour of these materials. Lindhout tried, in 1992, to use this model to describe the cylinder test. Due to compaction problems, stability problems and the large computational time, this could not be achieved. Therefore a new model was developed by the author, which does not use the equations of motion, but the equations of equilibrium, to calculate the new grain positions. This model can be used both for non-cohesive grains (sand) and for cohesive grains (sandstone). The results can generally be described by an advanced Mohr-Coulomb model. However, there are a few exceptions. Firstly, during loading of a granular structure, many contacts between the grains will collapse, not due to shear deformation as Coulomb suggests, but due to tension failure. Secondly, these micro cracks always occur in the direction of the major principal stress, which might be another direction than the observed failure surface. In this way, the axial micro cracks form a diagonal failure surface during a biaxial test, but the axial micro cracks in a cylinder test may form a failure surface parallel to the borehole surface. During the formation of natural sandstone, the difference between the horizontal and vertical stress causes anisotropy in the strength behaviour of this material. This or other anisotropies may explain the diametrically opposite breakouts. The conclusion that a borehole fails at a higher radial pressure than predicted, originates from the definition difference between local failure and functional failure and the large rest capacity of a thick-walled cylinder. [less ▲]

Sequenz und Sequenz-Struktur Vergleiche und deren Anwendung für die Struktur- und Funktionsvorhersage von Proteinen

Doctoral thesis (1994)

Zusammenfassung der Inaugural-Dissertation Name: Reinhard Schneider Titel: Sequenz und Sequenz-Struktur Vergleiche und deren Anwendung für die Struktur- und Funktionsvorhersage von Proteinen Betreuer ... [more ▼]

Zusammenfassung der Inaugural-Dissertation Name: Reinhard Schneider Titel: Sequenz und Sequenz-Struktur Vergleiche und deren Anwendung für die Struktur- und Funktionsvorhersage von Proteinen Betreuer: Prof. Dr. K. C. Holmes (MPI für medizinische Forschung, Heidelberg) Durch die sogenannten Genomprojekte wird es in den nächsten Jahren zu einer enormen Vergrößerung der biologischen Sequenzdatenbanken kommen. Eine unabdingbare Voraussetzung zur Nutzung dieses Rohmaterials stellt dabei die Analyse dieser Sequenzdaten mit Hilfe rechnergestützter Methoden dar. Eines der Hauptanwendungsgebiete von Rechnern für die Funktions- und Strukturvorhersage von Proteinen werden dabei selektive Datenbanksuche nach biologisch signifikanten Ähnlichkeiten sein. Zur Signifikanzabschätzung eines Proteinsequenzvergleiches (Alignment) wurde ein empirisch abgeleiteter Homologieschwellenwert definiert. Wichtigstes Merkmal ist dabei eine starke Abhängigkeit von der Länge des betreffenden Alignments. Diese Signifikanzabschätzung ermöglicht sowohl den Ausschluß von nicht verwandten Proteinen, wie auch die Detektion von schwachen Sequenzverwandtschaften. Aufgrund der Allgemeingültigkeit des Homologieschwellenwertes kann er als einfacher und effizienter zusätzlicher Filter für andere Methoden, wie z.B. schnelle Datenbanksuchen, verwendet werden. Es wurde ein neuer Algorithmus für den multiplen Sequenzvergleich entwickelt, der eine relativ geringe rechnerische Komplexität besitzt. Das Hauptmerkmal dieses Algorithmus besteht in der Ableitung von sogenannten positionsabhängigen Konservierungsgewichten, die als zusätzliche Parameter im dynamischen Programmieralgorithmus verwendet werden und zu einer deutlich gesteigerten Sensitivität bei Datenbanksuchen führt. Die programmiertechnische Auslegung des Algorithmus erlaubt die zukünftige Erweiterung auf den Vergleich einer Sequenz gegen ein Sequenzprofil bzw. den Vergleich zweier Sequenzprofile. Um auch zukünftig sensitive Datenbanksuchen in einer vertretbaren Rechenzeit durchführen zu können,, wurde das Programm auf parallele Rechner portiert. Die Ergebnisse zeigen, daß mit den heute verfügbaren massiv parallelen Rechnern ein beinahe interaktives Arbeiten möglich ist. Aufbauend auf dieser Arbeit wird derzeit im Rahmen eines europäischen Projektes die Implementierung der Profilmethoden auf Parallelrechner der neuesten Generation durchgeführt und der Nutzen für das industrielle “Protein design” bestimmt. Mit Hilfe des Homologieschwellenwertes konnte eine Datenbank für homologie-abgeleitete Proteinstrukturen (HSSP) entwickelt werden. Diese Datenbank wird der Öffentlichkeit auf verschiedenen Wegen zugänglich gemacht und hat sich als ein gewisser Standard etabliert. Die Datenbank findet dabei Verwendung im automatisierten dreidimensionalen Modellbau von Proteinstrukturen, sowie als Hilfsmittel und Datengrundlage für ein weitgestecktes Feld von statistischen und anderen theoretischen Arbeiten. Die Verwendung der Datenbank hat einen entscheidenden Beitrag bei der Entwicklung des derzeit besten Programms zur Vorhersage der Sekundärstruktur von Proteinen geleistet. Diese Vorhersagemethode basiert auf einem neuronalen Netzwerk, das die Informationen eines multiplen Sequenzvergleichs ausnutzt. Zur Berechnung der multiplen Sequenzalignments und der dazu notwendigen Datenbanksuche wird das in dieser Arbeit entwickelte Programm verwendet. Die Methode wurde in Form eines Vorhersagedienstes, der über internationale Datenleitungen verfügbar ist, der Öffentlichkeit zugänglich gemacht. Einen neuen Ansatz für die Vorhersage von Proteinstruktur bei fehlender Sequenzverwandtschaft zu einer bereits bekannten Struktur stellt die Methode für das Sequenz-Strukturalignment (“threading”) dar. Dazu wird eine dreidimensionale Struktur in Form von interatomaren Kontakten beschrieben und mit Hilfe von Präferenzparametern die Tauglichkeit einer Sequenz in eine Struktur bewertet. Die Ergebnisse zeigen, daß sowohl eine Verbesserung der abstrahierten Beschreibung für eine dreidimensionale Proteinstruktur, wie auch ein verbesserter Alignmentalgorithmus notwendig ist. Ein in der Praxis vielversprechender Ansatz ist die Verwendung von Methoden, die einerseits eine abstrahierte 3D-Beschreibung zulassen und zusätzlich einen gewissen Grad an Sequenzinformation, etwa in Form eines Sequenzprofils mit einbeziehen. Am Beispiel eines kompletten Chromosoms aus Hefe wurde eine komplexe funktionelle Genomanalyse durchgeführt. Hierbei konnten eine Reihe von biologisch interessanten Sequenzverwandtschaften aufgedeckt werden, waren jedoch mit einem hohen Arbeitsaufwand verbunden. Dabei stellte sich die ungenügende Integration der vorhanden Methoden und heterogenen Datenbanken als Hauptproblem heraus. Die dabei gesammelten Erfahrungen fließen derzeit in die Entwicklung eines integrierten Softwarepackets ein, mit dessen Hilfe es möglich sein wird, den Arbeitsaufwand, der zur Analyse von großen Datenmengen notwendig ist, drastisch zu reduzieren. [less ▲]

Modelle der dreimodalen Faktorenanalyse

Doctoral thesis (1991)

Durch Phasenumwandlungen bedingte Hysterese- und Oszillationserscheinungen an festen Katalysatoren

Doctoral thesis (1987)

L'indisponibilité des droits de la personnalité. Une approche critique de la théorie des droits de la personnalité

Doctoral thesis (1978)