Die Geburt des Genies aus dem Eigenrecht der Jugend

in Jahrbuch für Historische Bildungsforschung, 11 (2005)

Global geometric deformations of current algebras as Krichever-Novikov type algebras

in Communications in Mathematical Physics (2005), 260(3), 579-612

Dramatischer Bilderdienst. "Zur Trilogie des Wiedersehens" von Botho Strauß

in Heimböckel, Dieter; Werlein, Uwe (Eds.) Der Bildhunger der Literatur. Festschrift für Gunter E. Grimm (2005)

Aufschwung und Niedergang des Steinkohlenbergbaus im Saarrevier

in Becker, Christoph (Ed.) Grenztouren - Exkursionen zwischen Maas, Mosel, Saar und Rhein (2005)

Mobile Satellite Broadcast and Multichannel Communications Analysis and Design

Book published by KTH (2005)

In this thesis, analytical analysis and design techniques for wireless communications with diversity are studied. The impact of impairments such as correlated fading is analyzed using statistical models ... [more ▼]

In this thesis, analytical analysis and design techniques for wireless communications with diversity are studied. The impact of impairments such as correlated fading is analyzed using statistical models. Countermeasures designed to overcome, or even exploit, such effects are proposed and examined. In particular two applications are considered, satellite broadcast to vehicular terminals and communication using transmitters and receivers equipped with multiple antennas. Mobile satellite broadcast systems offer the possibility of high data rate services with reliability and ubiquitous coverage. The design of sys- tem architectures providing such services requires complex trade-offs involving technical, economical, and regulatory aspects. A satisfactory availability can be ensured using space, terrestrial, and time diversity techniques. The amount of applied diversity affects the spectral efficiency and system performance. Also, dedicated satellite and terrestrial networks represent significant investments and regulatory limitations may further complicate system design. The work presented in this thesis provides insights to the technical aspects of the trade-offs above. This is done by deriving an efficient method for estimating what resources in terms of spectrum and delay are required for a broadcast service to reach a satisfactory number of end users using a well designed system. The results are based on statistical models of the mobile satellite channel for which efficient analytical design and error rate estimation methods are derived. We also provide insight to the achievable spectral efficiency using different transmitter and receiver configurations. Multiple-element antenna communication is a promising technology for future high speed wireless infrastructures. By adding a spatial dimension, radio resources in terms of transmission power and spectrum can be used more efficiently. Much of the design and analysis work has focused on cases where the transmitter either has access to perfect channel state information or it is blind and the spatial channels are uncorrelated. Herein, systems where the fading of the spatial channels is correlated and/or the transmitter has access to partial channel state information are considered. While maintaining perfect channel knowledge at the transmitter may prove difficult, updating parameters that change on a slower time scale could be realistic. Here we formulate analysis and design techniques based on statistical models of the multichannel propagation. Fundamental properties of the multi-element antenna channel and limitations given by information theory are investigated under an asymptotic assumption on the number of antennas on either side of the system. For example, limiting normal distributions are derived for the squared singular values of the channel matrix and the mutual information. We also propose and examine a practical scheme capable of exploiting partial channel state information. In both applications outlined above, by using statistical models of the channel characteristics in the system design, performance can be improved. The main contribution of this thesis is the development of efficient techniques for estimating the system performance in different scenarios. Such techniques are vital to obtain insights to the impact of different impairments and how countermeasures against these should be designed. [less ▲]

Robot planning in partially observable continuous domains

in Proc. Robotics: Science and Systems (2005)

We present a value iteration algorithm for learning to act in Partially Observable Markov Decision Processes (POMDPs) with continuous state spaces. Mainstream POMDP research focuses on the discrete case ... [more ▼]

We present a value iteration algorithm for learning to act in Partially Observable Markov Decision Processes (POMDPs) with continuous state spaces. Mainstream POMDP research focuses on the discrete case and this complicates its application to, e.g., robotic problems that are naturally modeled using continuous state spaces. The main difficulty in defining a (belief-based) POMDP in a continuous state space is that expected values over states must be defined using integrals that, in general, cannot be computed in closed from. In this paper, we first show that the optimal finite-horizon value function over the continuous infinite-dimensional POMDP belief space is piecewise linear and convex, and is defined by a finite set of supporting α-functions that are analogous to the α-vectors (hyperplanes) defining the value function of a discrete-state POMDP. Second, we show that, for a fairly general class of POMDP models in which all functions of interest are modeled by Gaussian mixtures, all belief updates and value iteration backups can be carried out analytically and exact. A crucial difference with respect to the α-vectors of the discrete case is that, in the continuous case, the α-functions will typically grow in complexity (e.g., in the number of components) in each value iteration. Finally, we demonstrate PERSEUS, our previously proposed randomized point-based value iteration algorithm, in a simple robot planning problem with a continuous domain, where encouraging results are observed. [less ▲]

A Glance at Some Fundamental Public Economics Issues Through a Parametric Lens

in Schmidt, Ulrich; Traub, Stefan (Eds.) Advances in Public Economics: Utility, Choice and Welfare, 38 (2005)

Le profilage multidimensionnel des chômeurs

in Bulletin Luxembourgeois de Psychologie (2005), 2(4), 1-4

Transition école - vie active : une typologie des mesures pour les jeunes sans qualification

in Actes de l'Université européenne d'été de la FREREF (2005)

Comme dans tous les pays européens, un grand nombre de mesures à destination des jeunes sortis du système scolaire sans qualification ont été mises en place au Luxembourg. Une étude systématique par ... [more ▼]

Comme dans tous les pays européens, un grand nombre de mesures à destination des jeunes sortis du système scolaire sans qualification ont été mises en place au Luxembourg. Une étude systématique par interview semi-dirigée a été réalisée auprès des responsables formation de l'ensemble des 32 dispositifs répertoriés au Luxembourg, en distinguant les mesures spécifiquement destinées aux jeunes et celles destinées pour tout âge, jeunes compris. L'enquête visait surtout à déterminer les caractéristiques des pratiques pédagogiques mises en oeuvre avec les publics concernés. A partir du dépouillement du matériel recueilli, une typologie en trois catégories a été élaborée. Celle-ci est construite sur 10 indicateurs importants : pré-requis, statut de l'apprenant, profil de l'apprenant, activités de remotivation, description de la formation (contenus et méthodes), suivi, stages, formateurs, qualification/certification, débouchés. Elle distingue les formations par le travail (formation "sur le tas" permettant d'apprendre des tâches professionnelles spécifiques ainsi que des compétences sociales de base), les formations d'insertion socio-professionnelle (formations se basant sur un programme de formation défini et donnent droit à une attestation en fonction d'une évaluation) et les formations qualifiantes (formations permettant d'obtenir un diplôme ou un certificat officiel du ministère et donnant droit à un barème salarial légal). Chacun de ces dispositifs a une logique de fonctionnement propre, une certaine cohérence en fonction du profil du groupe cible, des objectifs visés et de la démarche socio-pédagogique adoptée. Chacun de ces dispositifs correspond à des possibilités de travail avec une certaine partie du groupe cible. Situées à des distances spécifiques sur l'axe de transition entre la formation initiale et la vie active, ces types de mesures combinent de façon variable des caractéristiques spécifiques du champ scolaire et du champ professionnel. [less ▲]

Knowledge production and democracy in educational research: The case of evidence-based education.

in South African Journal of Higher Education (2005), 19