The construction of number fields with given Galois group fits into the framework of the inverse Galois problem. This problem remains still unsolved, although many partial results have been obtained over the last century. Shafarevich proved in 1954 that every solvable group is realizable as the Galois group of a number field. Unfortunately, the proof does not provide a method to explicitly find such a field. This work aims at producing a constructive version of the theorem by solving the following task: given a solvable group $G$ and a $B\in \mathbf N$, construct all normal number fields with Galois group $G$ and absolute discriminant bounded by $B$. Since a field with solvable Galois group can be realized as a tower of abelian extensions, the main role in our algorithm is played by class field theory, which is the subject of the first part of this work. The second half is devoted to the study of the relation between the group structure and the field through Galois correspondence. In particular, we study the existence of obstructions to embedding problems and some criteria to predict the Galois group of an extension.

Mussel-inspired catechol-containing polymers provide a promising basis for developing strong biogenic adhesives (see chapter 1). In order to develop a biomimetic adhesive, solvent stable laccases were investigated for their application as biochemical catalyst for the functionalization of natural polymers (see chapter 2), such as chitosan and lignin, with catechols. Investigation of the laccase-catalysed C–N bond formation between primary amines and catechols, such as protocatechuic acid (PCA) and dihydrocaffeic acid (DHC), suggest that the reaction is promoted by a low pKa value of the primary amine used and a neutral or mildly acidic reaction pH. Since the pKa of chitosan’s amine groups is below 7, spontaneous reactions with catechols were possible, resulting in a PCA-functionalized chitosan, which achieved a tensile strength of 4.56 MPa ± 0.54 MPa on aluminum surfaces blasted with corundum (see chapter 3). For the functionalization of lignin, which was extracted with the Organosolv (OS) process, a two-step concept was required, where first L-lysine and subsequently DHC and PCA were grafted onto lignin. For DHC-lignin, a tensile strength of 169.3 kPa ± 130.6 kPa was measured (see chapter 4). Since the functionalization and curing processes use naturally occurring substances exclusively and are free of toxic chemicals, novel and sustainable bioadhesives were developed. Moreover, differential scanning calorimetry (DSC) analysis was used to characterize the mussel-inspired chitosan adhesive (see chapter 5). Furthermore, DSC measurements were validated for monitoring biodegradation quantitatively using small sample quantities and simple sample preprocessing. Using only DSC measurements, quantifiable detection of degradation progress was possible, while at the same time qualitative assessment of changes in crystallinity (indicating incomplete biodegradation) was obtained. The implemented method is recommended for the quantification of the biodegradability of the PCA-chitosan adhesive. This work introduces novel bio-based adhesives, as well as a new measuring technique for measuring biodegradability of various material.

The present work investigates the role of higher education experience in the process of students’ adult identity formation. In the broadest sense, adult identity is “seeing oneself as an adult” (Macmillan, 2007: 20), and it lays in the core of intensive processes of personal identity formation in the years following adolescence, which are for an increasing number of youth over the past decades spent in higher education. Approaches to adulthood in prior studies reveal ongoing discussions and attempts at re-conceptualisation against changing conditions and regimes of transition to adulthood. Traditionally, the so-called “objective markers” of adulthood have dominated the discourses for a long time, emphasising role transitions and demographic features as criteria for adulthood. The new research venues adding biographical approaches and subjective experiences reveal significance of inner, psychological processes of becoming an adult. However, the problem of the role of higher education in the process of students’ adult identity has not been fully illuminated thus far. The reason for this might be sought within the domain of disciplinary orientation of the field of higher education and Educational Sciences. Higher education research focuses on the overall, “grand” effects of education, while traditional Educational Sciences have not been showing much interest in higher education topics. Substantial work has been produced from developmental sciences, psychology in particular, which has revealed an intricate forest of today’s adulthood and conditions for its attainment, leaving open a whole set of educational, social, economic, cultural antecedents, correlates and experiences affecting transition to adulthood. Besides, as analyses presented in Chapter 2 show, students’ position in dominant discourses marked by political and economic imperatives is marginal. Their experiences and voices are in a sense excluded, making it almost impossible to infer on actual students’ personal benefits of the higher education process. The theoretical framework for this research consists of Erikson’s (Erikson, 1959; 1963; 1968) positions on human development in post-adolescent years, and McAdams’s model of narrative identity (1988; 2011; 2018), which also arose from Eriksonian tradition. Psychosocial theory (Erikson, 1959; 1963; 1968) assumes that social institutions provide structure and guidance to personal development, whereby they create a niche for psychosocial moratorium enabling youth a period of “identity work” before taking on long-term adult commitments. Research over recent decades reporting that higher education provides opportunities for students’ self-growth, exploration and resolving key identity questions in a variety of fields (e.g., Adams and Fitch, 1983; Arnett, 2004a; Berman, Kennerley, Kennerley, 2008; Mayhew, Rockenbach, Bowman, Seifert, Wolniak, Pascarella, Terenzin, 2016) supports such theoretical stances. The present research intends to extend existing knowledge raising the central question: What role of higher education experience students perceive in their adult identity formation? The empirical part reports on biographical research into senior year students’ lived experiences of their developmental path and their meaning to the higher education process. Students’ experiences are approached using the qualitative technique of problem-centred interviewing (PCI), which helps focus participants’ narration on the researcher’s interest and subsequent in-depth analysis of collected experiences. In total, 40 senior year students coming from diverse backgrounds were interviewed. Data were analysed in Atlas.ti software, which enabled the coding system’s better organization and browsing through transcripts. The qualitative analysis process consisted of both inductive and deductive approaches, wherein open and thematic coding techniques were performed interchangeably. Research findings indicate that in certain groups of students – but not in all – higher education experience facilitates and enriches the process of adult identity formation granting orientation and guidelines. Students identify experiences with the highest adult identity formational potential organised in the four broad categories: relationships with teachers and peers, respectively, teaching approach and study material, and extra-curricular activities. Based on the obtained findings, four patterns of thinking about the role of higher education in students’ adult identity formation have been identified: generator of adult identity formation, a safe-zone for exploration processes, interim phase leading to adulthood, and higher education suspending adult identity formation. This formed the basis for constructing the four student types; proactive, explorer, comfort-zone and atypical student. Research findings give the rationale for rethinking the educative potential of higher education in terms of its relevance for diverse students personally – for their self-growth and forming their personal identities, in addition to the professional ones.

The subject of this thesis is the probabilistic reliability assessment of notched metallic components under periodic constant-amplitude loads with respect to the failure mode of high-cycle fatigue. The latter refers to the crack initiation within the considered component caused by a high number, typically millions, of load cycles characterized by their small magnitude in terms of the material's static strength. In order to estimate the probability of failure due to high-cycle fatigue for a specified component under given loads, a new empirical model based on weakest-link theory is developed which describes a probabilistic and component specific constant-life diagram with respect to the anticipated design life. A conventional, non-probabilistic constant-life diagram reflects a discrete design boundary in terms of mean stress and stress amplitude, typically based on test results with respect to unnotched coupons made from the material of interest. Its application to the design of a notched component is established by identifying the stress conditions at the component's hot spot with those acting in the smooth coupons during the tests, and comparing those hot-spot conditions with the design boundary described in the constant-life diagram. Disregarded influences, such as notch and statistical size effect have to be incorporated by respective correction factors. The proposed probabilistic model on the other hand describes a continuous field of failure probabilities in the design stress plane, taking into account not only the hot-spot stresses, but the entire cyclic stress field acting throughout the component. In this way, the methodology directly accounts for notch and statistical size effects. Responsible for providing this greater scope is the weakest-link concept, which represents a non-local stochastic approach for quantifying the failure probability of loaded solids. The four model parameters can be calibrated with fatigue test data sets containing entirely unrelated test results on arbitrary specimen geometries, obliterating the constraining need for test data following staircase or probit schemes. This work contains the formulation, analysis, validation and application of the proposed model. After its introduction and a comparison with existing methods, it is analyzed in terms of its numerical properties when applied to finite element models, its efficient calibration and the corresponding model uncertainty. The validation is split into two parts. In a first analysis, the model is fitted to test data, containing results on several types of notched specimens, reflecting predominantly elastic material behavior. In a second step, this restriction is lifted and the model is used in order to predict the failure behavior of notched test specimens experiencing notch root plasticity due to high mean stresses. In both validation studies, the derived model predictions are, for the most part, well in line with the experimentally observed failure behavior of the test specimens. Finally, the applicability of the proposed probabilistic methodology in a design context is demonstrated on the example of a gas turbine compressor blade and the corresponding compressor stage.

To improve efficiency of memory accesses, modern multiprocessor architectures implement a whole range of different weak memory models. The behavior of performance-critical code depends on the underlying hardware. There is a rising demand for verification tools that take the underlying memory model into account. This work examines a variety of prevalent problems in the field of program verification of increasing complexities: testing, reachability, portability and memory model synthesis. We give efficient tools to solve these problems. What sets the presented methods apart is that they are not limited to some few given architectures. They are universal: The memory model is given as part of the input. We make use of the CAT language to succinctly describe axiomatic memory models. CAT has been used to define the semantics of assembly for x86/TSO, ARMv7, ARMv8, and POWER but also the semantics of programming languages such as C/C++, including the Linux kernel concurrency primitives. This work shows that even the simple testing problem is NP-hard for most memory models. It does so using a general reduction technique that applies to a range of models. It examines the more difficult program verification under a memory model and introduces Dartagnan, a bounded model checker (BMC) that encodes the problem as an SMT-query and makes use of advanced encoding techniques. The program portability problem is shown to be even harder. Despite this, it is solved efficiently by the tool Porthos which uses a guided search to produce fast results for most practical instances. A memory model is synthesized by Aramis for a given set of reachability results. Concurrent program verification is generally undecidable even for sequential consistency. As an alternative to BMC, we propose a new CEGAR method for Petri net invariant synthesis. We again use SMT-queries as a back-end.