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Modern decision making in the digital age is highly driven by the massive amount of
data collected from different technologies and thus affects both individuals as well as
economic businesses. The benefit of using these data and turning them into knowledge
requires appropriate statistical models that describe the underlying observations well.
Imposing a certain parametric statistical model goes along with the need of finding
optimal parameters such that the model describes the data best. This often results in
challenging mathematical optimization problems with respect to the model’s parameters
which potentially involve covariance matrices. Positive definiteness of covariance matrices
is required for many advanced statistical models and these constraints must be imposed
for standard Euclidean nonlinear optimization methods which often results in a high
computational effort. As Riemannian optimization techniques proved efficient to handle
difficult matrix-valued geometric constraints, we consider optimization over the manifold
of positive definite matrices to estimate parameters of statistical models. The statistical
models treated in this thesis assume that the underlying data sets used for parameter
fitting have a clustering structure which results in complex optimization problems. This
motivates to use the intrinsic geometric structure of the parameter space. In this thesis,
we analyze the appropriateness of Riemannian optimization over the manifold of positive
definite matrices on two advanced statistical models. We establish important problem-
specific Riemannian characteristics of the two problems and demonstrate the importance
of exploiting the Riemannian geometry of covariance matrices based on numerical studies.
Auf Twitter sind viele Journalisten mit persönlichen Accounts präsent und damit ein potenzieller Interaktionspartner für das Publikum. Untersuchungen aktiver Twitterer zeigen, dass auf der Netzwerkplattform politisch interessierte, persönlichkeitsstarke Nutzer interagieren, die sich vom Durchschnitt typischer Internetnutzer unterscheiden. Nachrichtenjournalisten berichten über negative Erfahrungen im direkten Publikumskontakt auf Twitter. Anders als bei Nutzerkommentaren auf Nachrichtenseiten sind öffentliche Anschriebe und Kontakte zu Journalisten auch unabhängig von einem Beitrag möglich. Zu diesem Phänomen existieren bislang jedoch kaum Studien. Über ein Tracking der Anschriebe wird daher erstens untersucht, wie häufig Politikjournalisten 2017 überhaupt in Tweets erwähnt wurden. Zweitens wurden die Nutzer befragt, die die Journalisten angeschrieben haben. Eine Nutzergruppe aus mehreren zehntausend Accounts nimmt Adressierungen vor. Die Erwähnungen verteilen sich unter den Journalisten ungleich. Die Nutzung von Blogs als alternative Informationsquelle und starke politische Orientierungen erklären das Vorkommen häufiger Interaktionen. Als Hauptmotivationen für Interaktionen zeigen sich das Bedürfnis nach eigener Meinungsäußerung und Kritik sowie das Weitergeben von neuen Informationen und Feedback an Journalisten. Sind diese Motivationen ausgeprägt, tendieren die Nutzer eher zu häufigen Interaktionen.
Stress position in English words is well-known to correlate with both their morphological properties and their phonological organisation in terms of non-segmental, prosodic categories like syllable structure. While two generalisations capturing this correlation, directionality and stratification, are well established, the exact nature of the interaction of phonological and morphological factors in English stress assignment is a much debated issue in the literature. The present study investigates if and how directionality and stratification effects in English can be learned by means of Naive Discriminative Learning, a computational model that is trained using error-driven learning and that does not make any a-priori assumptions about the higher-level phonological organisation and morphological structure of words. Based on a series of simulation studies we show that neither directionality nor stratification need to be stipulated as a-priori properties of words or constraints in the lexicon. Stress can be learned solely on the basis of very flat word representations. Morphological stratification emerges as an effect of the model learning that informativity with regard to stress position is unevenly distributed across all trigrams constituting a word. Morphological affix classes like stress-preserving and stress-shifting affixes are, hence, not predefined classes but sets of trigrams that have similar informativity values with regard to stress position. Directionality, by contrast, emerges as spurious in our simulations; no syllable counting or recourse to abstract prosodic representations seems to be necessary to learn stress position in English.
Trotz des Rückgangs der Einwohner*innenzahl, kommunaler wohnungspolitischer Maßnahmen und der Pandemie steigen die Göttinger Mieten weiterhin. Besonders Menschen mit geringen Einkommen haben nach wie vor große Probleme, eine bezahlbare Wohnung in Göttingen zu finden. In diesem Wohnraumatlas zeigen wir die Entwicklung der Angebotsmieten auf. Zudem verdeutlichen wir, dass der Mietwohnungsmarkt in Teilmärkte segmentiert ist, für deren Identifizierung wir Ansätze liefern. Damit wollen wir stadtpolitisch Aktiven und anderen Interessierten Materialien an die Hand geben, um die Wohnungspolitik der Stadt einordnen zu können.
Die vorliegende Arbeit untersucht erstmals systematisch die Intonation des Luxemburgischen, mit dem Ziel, ein Inventar der gängigsten Intonationskonturen sowie deren Funktion zu erstellen und damit Vergleiche mit Intonationssystemen anderer Sprachen zu ermöglichen. Datengrundlage für diese formale sowie funktionale Analyse bildet sowohl geskriptetes als auch ungeskriptetes Sprachmaterial von zwölf luxemburgischen Muttersprachlern in monologischer und dialogischer Form. Insgesamt können sechs verschiedene Konturen ermittelt werden, wobei vier davon in mehr als einer Funktion vorkommen. Auf diesem Ergebnis basierend werden die Unterschiede bzw. Ähnlichkeiten zu den Intonationssystemen der beiden weiteren Landessprachen in Luxemburg – Deutsch und Französisch – erarbeitet. Die kontrastive Analyse zeigt, dass sich beide Systeme substanziell von dem des Luxemburgischen unterscheiden, auch wenn die Unterschiede zum Deutschen aufgrund ähnlicherer prosodischer Strukturen leichter zu vergleichen und damit eindeutiger sind. In einem weiteren Schritt wird der Transfer luxemburgischer Strukturen in die beiden Fremdsprachen untersucht, um mögliche Interferenzen aufzeigen zu können. Die Ergebnisse zeigen, dass die Sprecher häufig muttersprachliche Konturen in die Fremdsprachen importieren.
This study scrutinizes press photographs published during the first 6 weeks of the Russian War in Ukraine, beginning February 24th, 2022. Its objective is to shed light on the emotions evoked in Internet-savvy audiences. This empirical research aims to contribute to the understanding of emotional media effects that shape attitudes and actions of ordinary citizens. Main research questions are: What kind of empathic reactions are observed during the Q-sort study? Which visual patterns are relevant for which emotional evaluations and attributions? The assumption is that the evaluations and attributions of empathy are not random, but follow specific patterns. The empathic reactions are based on visual patterns which, in turn, influence the type of empathic reaction. The identification of specific categories for visual and emotional reaction patterns are arrived at in different methodological processes. Visual pattern categories were developed inductively, using the art history method of iconography-iconology to identify six distinct types of visual motifs in a final sample of 33 war photographs. The overarching categories for empathic reactions—empty empathy, vicarious traumatization and witnessing—were applied deductively, building on E. Ann Kaplan's pivotal distinctions. The main result of this research are three novel categories that combine visual patterns with empathic reaction patterns. The labels for these categories are a direct result of the Q-factorial analysis, interpreted through the lense of iconography-iconology. An exploratory nine-scale forced-choice Q-sort study (Nstimuli = 33) was implemented, followed by self-report interviews with a total of 25 participants [F = 16 (64%), M = 9 (36%), Mage = 26.4 years]. Results from this exploratory research include motivational statements on the meanings of war photography from semi-structured post-sort-interviews. The major result of this study are three types of visual patterns (“factors”) that govern distinct empathic reactions in participants: Factor 1 is “veiled empathy” with highest empathy being attributed to photos showing victims whose corpses or faces were veiled. Additional features of “veiled empathy” are a strong anti-politician bias and a heightened awareness of potential visual manipulation. Factor 2 is “mirrored empathy” with highest empathy attributions to photos displaying human suffering openly. Factor 3 focused on the context. It showed a proclivity for documentary style photography. This pattern ranked photos without clear contextualization lower in empathy than those photos displaying the fully contextualized setting. To the best of our knowledge, no study has tested empathic reactions to war photography empirically. In this respect, the study is novel, but also exploratory. Findings like the three patterns of visual empathy might be helpful for photo selection processes in journalism, for political decision-making, for the promotion of relief efforts, and for coping strategies in civil society to deal with the potentially numbing or traumatizing visual legacy of the War in Ukraine.
Survey data can be viewed as incomplete or partially missing from a variety of perspectives and there are different ways of dealing with this kind of data in the prediction and the estimation of economic quantities. In this thesis, we present two selected research contexts in which the prediction or estimation of economic quantities is examined under incomplete survey data.
These contexts are first the investigation of composite estimators in the German Microcensus (Chapters 3 and 4) and second extensions of multivariate Fay-Herriot (MFH) models (Chapters 5 and 6), which are applied to small area problems.
Composite estimators are estimation methods that take into account the sample overlap in rotating panel surveys such as the German Microcensus in order to stabilise the estimation of the statistics of interest (e.g. employment statistics). Due to the partial sample overlaps, information from previous samples is only available for some of the respondents, so the data are partially missing.
MFH models are model-based estimation methods that work with aggregated survey data in order to obtain more precise estimation results for small area problems compared to classical estimation methods. In these models, several variables of interest are modelled simultaneously. The survey estimates of these variables, which are used as input in the MFH models, are often partially missing. If the domains of interest are not explicitly accounted for in a sampling design, the sizes of the samples allocated to them can, by chance, be small. As a result, it can happen that either no estimates can be calculated at all or that the estimated values are not published by statistical offices because their variances are too large.
Coastal erosion describes the displacement of land caused by destructive sea waves,
currents or tides. Due to the global climate change and associated phenomena such as
melting polar ice caps and changing current patterns of the oceans, which result in rising
sea levels or increased current velocities, the need for countermeasures is continuously
increasing. Today, major efforts have been made to mitigate these effects using groins,
breakwaters and various other structures.
This thesis will find a novel approach to address this problem by applying shape optimization
on the obstacles. Due to this reason, results of this thesis always contain the
following three distinct aspects:
The selected wave propagation model, i.e. the modeling of wave propagation towards
the coastline, using various wave formulations, ranging from steady to unsteady descriptions,
described from the Lagrangian or Eulerian viewpoint with all its specialties. More
precisely, in the Eulerian setting is first a steady Helmholtz equation in the form of a
scattering problem investigated and followed subsequently by shallow water equations,
in classical form, equipped with porosity, sediment portability and further subtleties.
Secondly, in a Lagrangian framework the Lagrangian shallow water equations form the
center of interest.
The chosen discretization, i.e. dependent on the nature and peculiarity of the constraining
partial differential equation, we choose between finite elements in conjunction
with a continuous Galerkin and discontinuous Galerkin method for investigations in the
Eulerian description. In addition, the Lagrangian viewpoint offers itself for mesh-free,
particle-based discretizations, where smoothed particle hydrodynamics are used.
The method for shape optimization w.r.t. the obstacle’s shape over an appropriate
cost function, constrained by the solution of the selected wave-propagation model. In
this sense, we rely on a differentiate-then-discretize approach for free-form shape optimization
in the Eulerian set-up, and reverse the order in Lagrangian computations.
In spite of the wide agreement among linguists as to the significance of spoken language data, actual speech data have not formed the basis of empirical work on English as much as one would think. The present paper is intended to contribute to changing this situation, on a theoretical and on a practical level. On a theoretical level, we discuss different research traditions within (English) linguistics. Whereas speech data have become increasingly important in various linguistic disciplines, major corpora of English developed within the corpus-linguistic community, carefully sampled to be representative of language usage, are usually restricted to orthographic transcriptions of spoken language. As a result, phonological phenomena have remained conspicuously understudied within traditional corpus linguistics. At the same time, work with current speech corpora often requires a considerable level of specialist knowledge and tailor-made solutions. On a practical level, we present a new feature of BNCweb (Hoffmann et al. 2008), a user-friendly interface to the British National Corpus, which gives users access to audio and phonemic transcriptions of more than five million words of spontaneous speech. With the help of a pilot study on the variability of intrusive r we illustrate the scope of the new possibilities.
This paper tested the ability of Mandarin learners of German, whose native language has lexical tone, to imitate pitch accent contrasts in German, an intonation language. In intonation languages, pitch accents do not convey lexical information; also, pitch accents are sparser than lexical tones as they only associate with prominent words in the utterance. We compared two kinds of German pitch-accent contrasts: (1) a “non-merger” contrast, which Mandarin listeners perceive as different and (2) a “merger” contrast, which sounds more similar to Mandarin listeners. Speakers of a tone language are generally very sensitive to pitch. Hypothesis 1 (H1) therefore stated that Mandarin learners produce the two kinds of contrasts similarly to native German speakers. However, the documented sensitivity to tonal contrasts, at the expense of processing phrase-level intonational contrasts, may generally hinder target-like production of intonational pitch accents in the L2 (Hypothesis 2, H2). Finally, cross-linguistic influence (CLI) predicts a difference in the realization of these two contrasts as well as improvement with higher proficiency (Hypothesis 3, H3). We used a delayed imitation paradigm, which is well-suited for assessing L2-phonetics and -phonology because it does not necessitate access to intonational meaning. We investigated the imitation of three kinds of accents, which were associated with the sentence-final noun in short wh-questions (e.g., Wer malt denn Mandalas, lit: “Who draws PRT mandalas?” “Who likes drawing mandalas?”). In Experiment 1, 28 native speakers of Mandarin participated (14 low- and 14 high-proficient). The learners’ productions of the two kinds of contrasts were analyzed using General Additive Mixed Models to evaluate differences in pitch accent contrasts over time, in comparison to the productions of native German participants from an earlier study in our lab. Results showed a more pronounced realization of the non-merger contrast compared to German natives and a less distinct realization of the merger contrast, with beneficial effects of proficiency, lending support to H3. Experiment 2 tested low-proficient Italian learners of German (whose L1 is an intonation language) to contextualize the Mandarin data and further investigate CLI. Italian learners realized the non-merger contrast more target-like than Mandarin learners, lending additional support to CLI (H3).