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In this thesis we study structure-preserving model reduction methods for the efficient and reliable approximation of dynamical systems. A major focus is the approximation of a nonlinear flow problem on networks, which can, e.g., be used to describe gas network systems. Our proposed approximation framework guarantees so-called port-Hamiltonian structure and is general enough to be realizable by projection-based model order reduction combined with complexity reduction. We divide the discussion of the flow problem into two parts, one concerned with the linear damped wave equation and the other one with the general nonlinear flow problem on networks.
The study around the linear damped wave equation relies on a Galerkin framework, which allows for convenient network generalizations. Notable contributions of this part are the profound analysis of the algebraic setting after space-discretization in relation to the infinite dimensional setting and its implications for model reduction. In particular, this includes the discussion of differential-algebraic structures associated to the network-character of our problem and the derivation of compatibility conditions related to fundamental physical properties. Amongst the different model reduction techniques, we consider the moment matching method to be a particularly well-suited choice in our framework.
The Galerkin framework is then appropriately extended to our general nonlinear flow problem. Crucial supplementary concepts are required for the analysis, such as the partial Legendre transform and a more careful discussion of the underlying energy-based modeling. The preservation of the port-Hamiltonian structure after the model-order- and complexity-reduction-step represents a major focus of this work. Similar as in the analysis of the model order reduction, compatibility conditions play a crucial role in the analysis of our complexity reduction, which relies on a quadrature-type ansatz. Furthermore, energy-stable time-discretization schemes are derived for our port-Hamiltonian approximations, as structure-preserving methods from literature are not applicable due to our rather unconventional parametrization of the solution.
Apart from the port-Hamiltonian approximation of the flow problem, another topic of this thesis is the derivation of a new extension of moment matching methods from linear systems to quadratic-bilinear systems. Most system-theoretic reduction methods for nonlinear systems rely on multivariate frequency representations. Our approach instead uses univariate frequency representations tailored towards user-defined families of inputs. Then moment matching corresponds to a one-dimensional interpolation problem rather than to a multi-dimensional interpolation as for the multivariate approaches, i.e., it involves fewer interpolation frequencies to be chosen. The notion of signal-generator-driven systems, variational expansions of the resulting autonomous systems as well as the derivation of convenient tensor-structured approximation conditions are the main ingredients of this part. Notably, our approach allows for the incorporation of general input relations in the state equations, not only affine-linear ones as in existing system-theoretic methods.
Structured Eurobonds - Optimal Construction, Impact on the Euro and the Influence of Interest Rates
(2020)
Structured Eurobonds are a prominent topic in the discussions how to complete the monetary and fiscal union. This work sheds light on several issues going hand in hand with the introduction of common bonds. At first a crucial question is on the optimal construction, e.g. what is the optimal common liability. Other questions that arise belong to the time after the introduction. The impact on several exchnage rates is examined in this work. Finally an approximation bias in forward-looking DSGE models is quantified which would lead to an adjustment of central bank interest rates and therefore has an impact on the other two topics.
The present thesis is devoted to a construction which defies generalisations about the prototypical English noun phrase (NP) to such an extent that it has been termed the Big Mess Construction (Berman 1974). As illustrated by the examples in (1) and (2), the NPs under study involve premodifying adjective phrases (APs) which precede the determiner (always realised in the form of the indefinite article a(n)) rather than following it.
(1) NoS had not been hijacked – that was too strong a word. (BNC: CHU 1766)
(2) He was prepared for a battle if the porter turned out to be as difficult a customer as his wife. (BNC: CJX 1755)
Previous research on the construction is largely limited to contributions from the realms of theoretical syntax and a number of cursory accounts in reference grammars. No comprehensive investigation of its realisations and uses has as yet been conducted. My thesis fills this gap by means of an exhaustive analysis of the construction on the basis of authentic language data retrieved from the British National Corpus (BNC). The corpus-based approach allows me to examine not only the possible but also the most typical uses of the construction. Moreover, while previous work has almost exclusively focused on the formal realisations of the construction, I investigate both its forms and functions.
It is demonstrated that, while the construction is remarkably flexible as concerns its possible realisations, its use is governed by probabilistic constraints. For example, some items occur much more frequently inside the degree item slot than others (as, too and so stand out for their particularly high frequency). Contrary to what is assumed in most previous descriptions, the slot is not restricted in its realisation to a fixed number of items. Rather than representing a specialised structure, the construction is furthermore shown to be distributed over a wide range of possible text types and syntactic functions. On the other hand, it is found to be much less typical of spontaneous conversation than of written language; Big Mess NPs further display a strong preference for the function of subject complement. Investigations of the internal structural complexity of the construction indicate that its obligatory components can optionally be enriched by a remarkably wide range of optional (if infrequent) elements. In an additional analysis of the realisations of the obligatory but lexically variable slots (head noun and head of AP), the construction is highlighted to represent a productive pattern. With the help of the methods of Collexeme Analysis (Stefanowitsch and Gries 2003) and Co-varying Collexeme Analysis (Gries and Stefanowitsch 2004b, Stefanowitsch and Gries 2005), the two slots are, however, revealed to be strongly associated with general nouns and ‘evaluative’ and ‘dimension’ adjectives, respectively. On the basis of an inspection of the most typical adjective-noun combinations, I identify the prototypical semantics of the Big Mess Construction.
The analyses of the constructional functions centre on two distinct functional areas. First, I investigate Bolinger’s (1972) hypothesis that the construction fulfils functions in line with the Principle of Rhythmic Alternation (e.g. Selkirk 1984: 11, Schlüter 2005). It is established that rhythmic preferences co-determine the use of the construction to some extent, but that they clearly do not suffice to explain the phenomenon under study. In a next step, the discourse-pragmatic functions of the construction are scrutinised. Big Mess NPs are demonstrated to perform distinct information-structural functions in that the non-canonical position of the AP serves to highlight focal information (compare De Mönnink 2000: 134-35). Additionally, the construction is shown to place emphasis on acts of evaluation. I conclude the construction to represent a contrastive focus construction.
My investigations of the formal and functional characteristics of Big Mess NPs each include analyses which compare individual versions of the construction to one another (e.g. the As Big a Mess, Too Big a Mess and So Big a Mess Constructions). It is revealed that the versions are united by a shared core of properties while differing from one another at more abstract levels of description. The question of the status of the constructional versions as separate constructions further receives special emphasis as part of a discussion in which I integrate my results into the framework of usage-based Construction Grammar (e.g. Goldberg 1995, 2006).
The dissertation includes three published articles on which the development of a theoretical model of motivational and self-regulatory determinants of the intention to comprehensively search for health information is based. The first article focuses on building a solid theoretical foundation as to the nature of a comprehensive search for health information and enabling its integration into a broader conceptual framework. Based on subjective source perceptions, a taxonomy of health information sources was developed. The aim of this taxonomy was to identify most fundamental source characteristics to provide a point of reference when it comes to relating to the target objects of a comprehensive search. Three basic source characteristics were identified: expertise, interaction and accessibility. The second article reports on the development and evaluation of an instrument measuring the goals individuals have when seeking health information: the ‘Goals Associated with Health Information Seeking’ (GAINS) questionnaire. Two goal categories (coping focus and regulatory focus) were theoretically derived, based on which four goals (understanding, action planning, hope and reassurance) were classified. The final version of the questionnaire comprised four scales representing the goals, with four items per scale (sixteen items in total). The psychometric properties of the GAINS were analyzed in three independent samples, and the questionnaire was found to be reliable and sufficiently valid as well as suitable for a patient sample. It was concluded that the GAINS makes it possible to evaluate goals of health information seeking (HIS) which are likely to inform the intention building on how to organize the search for health information. The third article describes the final development and a first empirical evaluation of a model of motivational and self-regulatory determinants of an intentionally comprehensive search for health information. Based on the insights and implications of the previous two articles and an additional rigorous theoretical investigation, the model included approach and avoidance motivation, emotion regulation, HIS self-efficacy, problem and emotion focused coping goals and the intention to seek comprehensively (as outcome variable). The model was analyzed via structural equation modeling in a sample of university students. Model fit was good and hypotheses with regard to specific direct and indirect effects were confirmed. Last, the findings of all three articles are synthesized, the final model is presented and discussed with regard to its strengths and weaknesses, and implications for further research are determined.
Es wird ein Workshopkonzept dargelegt, um das im Rahmen des PODMAN-Projektes entwickelte DIAMANTModell zur Implementierung einer institutionellen FDM-Servicelandschaft kennenzulernen. Anhand von Beispielen erfahren die Teilnehmenden, wie die entwickelten Instrumente auf die eigene Forschungseinrichtung angewendet werden. Primär wird das Konzept für den Initial-Workshop vorgestellt, der alle FDM-Akteur*innen
einer Forschungseinrichtung zusammenbringt, um das DIAMANT-Modell zunächst auf die gesamte Forschungseinrichtung zu applizieren. Daraus wurde ein weiteres Workshopkonzept abgeleitet, das insbesondere für die fach- oder abteilungsspezifische Bedarfserhebung vorgesehen ist.
Hochschulen und außeruniversitäre Forschungseinrichtungen werden heute zunehmend in die Pflicht genommen, für ihre Forschenden Strukturen und Services für ein nachhaltiges Forschungsdatenmanagement (FDM) bereit-zustellen. Da es vor allem für disziplin- oder datenspezifische Bedarfe nicht für jede Forschungseinrichtung möglich ist, die dafür notwendigen Dienste selbst vorzuhalten, müssen sie externe Dienstleistungen in ihre FDM-Servicestrukturen integrieren. Das erfolgreiche Management der Schnittstelle zwischen den kooperierenden Insti-tutionen bedeutet einen erheblichen Organisationsaufwand, für den der vorliegende Praxisleitfaden eine Hilfe-stellung bietet. Er soll die Einrichtungen in die Lage versetzen, fremdbezogene FDM-Dienstleistungen erfolgreich in ihr eigenes FDM-Serviceangebot bzw. ihre übergeordnete FDM-Strategie zu integrieren. Der Leitfaden dient insbesondere als Anleitung für die erfolgreiche Steuerung der Zusammenarbeit und Kommunikation der invol-vierten internen und externen Mitarbeiter*innen. Über eine Reihe von Steuerungsmechanismen, die in diesem Leitfaden ausführlich erläutert werden, lässt sich der Prozess des Schnittstellenmanagements bestmöglich hand-haben. Der Praxisleitfaden versteht sich als Arbeitsgrundlage für alle Akteur*innen einer Forschungseinrichtung, die an der Erstellung eines institutionellen FDM-Konzeptes beteiligt sind.
Das DIAMANT-Modell wurde im Rahmen des BMBF-geförderten Projekts „Prozessorientierte Entwicklung von Managementinstrumenten für Forschungsdaten im Lebenszyklus“ (PODMAN) entwickelt. Das grundsätzliche Ziel des Modells besteht darin, Hochschulen und außeruniversitäre Forschungseinrichtungen zu befähigen, eine integrierte Informationsarchitektur für die optimierte Bereitstellung und Weiterentwicklung von Forschungsdatenmanagement (FDM)-Technologien und -services aufzubauen und zu pflegen, sodass die Forschenden ihre Forschungsdatensätze zu „hochkarätigen Diamanten“ schleifen können. Das DIAMANTModell besteht zum einen aus dem FDM-Referenzprozess, der – angelehnt an die ARIS-Prozessmodellierung – den gesamten FDM-Prozess und die zugehörigen Akteur*innen darstellt und ihren Grad der Beteiligung / Verantwortung an einem FDM-Service benennt. Der FDM-Referenzprozess sieht die Etablierung einer zentralen FDM-Steuerungseinheit vor, die den Informationsfluss zwischen allen am FDM beteiligten Organisationseinheiten steuert. Ein weiterer Bestandteil des DIAMANT-Modells ist die FDM-Kompetenzmatrix, die sich aus dem FDM-Referenzprozess ableitet. Sie dient der IST- / SOLL-Analyse, um den Referenzprozess auf die eigene Institution übertragen zu können. Abgeleitet wurde auch ein Beschreibungsmodell für FDMServices, um einen FDM-Service- /-Anforderungskatalog zu entwickeln und institutsspezifisch fortzuschreiben. Letzter Teil des DIAMANT-Modells sind Empfehlungen, welche Aspekte hinsichtlich der Personalführung und des Organisationsmanagements bei der Implementierung der FDM-Servicelandschaft berücksichtigt werden sollten.
Der Tagungsbericht fasst die Vorträge, Workshops und Ergebnisse der Abschlusstagung des BMBF-Projektes PODMAN: „Forschung + Datenmanagement = Forschungsdatenmanagement – Wann geht die Gleichung auf?“ vom 27. und 28. März 2019 an der Universität Trier zusammen. Ihm sind die Vortragsfolien, die Präsentationen der Workshops sowie die zugehörige Fotodokumentation der Arbeitsgruppen im Anhang beigefügt.
« Je n’ai rien à cacher... quoique ?! » Un guide pratique pour mener des discussions en classe
(2020)
L’interaction entre les grands volumes de données (big data) et l’intelligence artificielle ouvre de nouveaux horizons, et cela également dans le domaine de la sécurité publique. De plus en plus de villes dans le monde entier y ont recours et installent des caméras à reconnaissance faciale. Tout le monde n’est pas d’accord avec cette pratique. Comment peut-on discuter avec les jeunes du débat social actuel sur la sécurité publique et la vie privée ?
Cet article présente une méthode qui permet aux enseignant(e)s de se faire une idée de l’expérience que les élèves ont des médias numériques et de leur maîtrise du numérique. Elle demande peu de préparation et n’exige pas de connaissances préalables de la part des enseignant(e)s. Cet exercice permet de détendre l’atmosphère en classe et de déterminer dans quelle mesure les élèves réfléchissent déjà à l’usage qu’ils/elles font des médias numériques.