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As modern society progresses, waste treatment becomes a pressing issue. Not only are global waste amounts increasing, but there is also an unmet demand for sustainable materials (e.g. bioplastics). By identifying and developing processes, which efficiently treat waste while simultaneously generating sustainable materials, potentially both these issues might be alleviated. Following this line of thought, this dissertation focuses on procedures for treatment of the organic fraction of waste. Organic waste is a suitable starting material for microbial fermentation, where carbohydrates are converted to smaller molecules, such as ethanol, acetic acid, and lactic acid. Being the monomer of the thermoplastic poly-lactic acid, lactic acid is of particular interest with regard to bioplastics production and was selected as target compound for this dissertation. Organic waste acted as substrate for non-sterile batch and continuous fermentations. Fermentations were initiated with inoculum of Streptococcus sp. or with indigenous consortium alone. During batch mode, concentration, yield, and productivity reached maximum values of 50 g L−1, 63%, and 2.93 g L−1 h −1. During continuous operation at a dilution rate of 0.44 d−1, concentration and yield were increased to 69 g L−1 and 86%, respectively, while productivity was lowered to 1.27 g L−1 h −1 . To fully exploit the nutrients present in organic waste, phosphate recovery was analyzed using seashells as adsorbent. Furthermore, the pattern of the indigenous consortium was monitored. Evidently, a very efficient Enterococcus strain tended to dominate the indigenous consortium during fermentation. The isolation and cultivation of this consortium gave a very potent inoculum. In comparison to the non-inoculated fermentation of a different organic waste batch, addition of this inoculum lead to an improved fermentation performance. Lactic acid yield, concentration, and molar selectivity could be increased from 38% to 51%, 49 g L−1 to 65 g L−1, and 46% to 86%, respectively. Eventually, fermentation process data was used to perform techno-economic analysis proposing a waste treatment plant with different catchment area sizes ranging from 50,000 to 1,000,000 people. Economically profitable scenarios for both batch and continuous operation could be identified for a community with as few as 100,000 inhabitants. With the experimental data, as well as techno-economic calculations presented in this dissertation, a profound contribution to sustainable waste treatment and material production was made.
Both sustainability and transdisciplinary research can change academic research, especially with regard to its relevance for, and relationship with, its environments. Transdisciplinary sustainability research (TSR), thus, offers the opportunity to change non-sustainable development paths of sciences themselves. In order to fully exploit this possibility, this PhD project addresses the question of how TSR, in the first place, does conceptualize and, in the second place, could conceptualize knowledge, research, and science. Firstly, this PhD project analyzes, from a discourse studies perspective, the term problem in TSR, against the background of discourses on sustainable development. Secondly, it explores the historical-analytical and transformative concept of the problematic. The results, firstly, show the consequences of a problem-solving focus for TSR, and secondly, differentiate it from a transformative direction of problematic designing, as a more appropriate view on the dimensions of transformation and their qualities of change that matter for TSR. This PhD project aims to contribute to a self-understanding of, and a philosophical communication about, TSR, as a research form in the sustainability sciences.
Empirische Studien aus dem Bereich der Lehrerbildungsforschung haben gezeigt, dass die Arbeit mit Unterrichtsvideos eine wirksame Möglichkeit darstellt, um professionelle Kompetenzen von Lehramtsstudierenden zu erweitern. In der Unterrichtsforschung werden Unterrichtsvideos darüber hinaus auch als Messinstrument zur Wahrnehmung von Unterrichtsqualität genutzt. Dabei werden meist Filmaufnahmen verwendet, die mit einer Überblicks- oder Lehrerkamera gefilmt wurden. In diesem Kontext äußern Bildungswissenschaftler die Annahme, dass die gefilmte Kameraperspektive einen Effekt auf die Beobachtung und Beurteilung der Unterrichtsvideos haben kann. Empirische Befunde sind zu dieser Hypothese bisher wenig vorhanden. Die vorliegende Dissertation hat sich daher - in der Tradition standardisierter Videostudien - das Ziel gesetzt, das bisherige standardisierte Kamerasetting inhaltlich-konzeptionell durch die Installierung mehrerer Schülerkameraperspektiven weiterzuentwickeln. Auf dieser Grundlage wurde geprüft, ob die Rater durch den Einsatz multiperspektivischer Videos in ihrer Einschätzung der Unterrichtsqualität zu unterschiedlichen Ergebnissen gelangen. Die Befunde belegen, dass Rater ein Unterrichtsgeschehen mit den etablierten Perspektiven der Überblicks- oder Lehrerkamera nahezu ähnlich einschätzen. Mit weiteren Kameraperspektiven, die auf die Schüler gerichtet sind, wird jedoch eine deutlich breitere Beurteilung in den Dimensionen "Kognitive Aktivierung", "Klassenmanagement" und "Individuelle Förderung" deutlich. Mehrere Kameraperspektiven ermöglichen detaillierte Aussagen über Unterricht. Von diesem Ergebnis können auch Studierende in der Lehrpersonenausbildung profitieren. Schülerkameraperspektiven eröffnen Dozierenden insbesondere zur Thematik "heterogene Schülerschaft" ein didaktisches Lehrmittel und Werkzeug, das eine Videoanalyse zu Mikrointeraktionen zwischen Schüler-Lehrpersonen-Interaktionen dynamisch und simultan erlaubt.
Technological development made it possible to store and process data on a scale not imaginable decades ago — a development that also includes network data. A particular characteristic of network data is that, unlike standard data, the objects of interest, called nodes, have relationships to (possibly all) other objects in the network. Collecting empirical data is often complicated and cumbersome, hence, the observed data are typically incomplete and might also contain other types of errors. Because of the interdependent structure of network data, these errors have a severe impact on network analysis methods. This cumulative dissertation is about the impact of erroneous network data on centrality measures, which are methods to assess the position of an object, for example a person, with respect to all other objects in a network. Existing studies have shown that even small errors can substantially alter these positions. The impact of errors on centrality measures is typically quantified using a concept called robustness. The articles included in this dissertation contribute to a better understanding of the robustness of centrality measures in several aspects. It is argued why the robustness needs to be estimated and a new method is proposed. This method allows researchers to estimate the robustness of a centrality measure in a specific network and can be used as a basis for decision making. The relationship between network properties and the robustness of centrality measures is analyzed. Experimental and analytical approaches show that centrality measures are often more robust in networks with a larger average degree. The study of the impact of non-random errors on the robustness suggests that centrality measures are often more robust if missing nodes are more likely to belong to the same community compared to missingness completely at random. For the development of imputation procedures based on machine learning techniques, a process for the evaluation of node embedding methods is proposed.
Thermal energy storage systems have a high potential for a sustainable energy management. Low temperature thermochemical energy stores based on gas-solid reactions represent appealing alternative options to sensible and latent storage technologies, in particular for heating and cooling purposes. They convert heat energy provided from renewable energy and waste heat sources into chemical energy and can effectively contribute to load balancing and CO2 mitigation. At present, several obstacles are associated with the implementation in full-scale reactors. Notably, the mass and heat transfer must be optimized. Limitations in the heat transport and diffusions resistances are mainly related to physical stability issues, adsorption/desorption hysteresis and volume expansion and can impact the reversibility of gas-solid reactions. The aim of this thesis was to examine the energy storage and cooling efficiency of CaCl2, MgCl2, and their physical salt mixtures as adsorbents paired with water, ethanol and methanol as adsorbates for utilization in a closed, low level energy store. Two-component composite adsorbents were engineered using a representative set of different host matrices (activated carbon, binderless zeolite NaX, expanded natural graphite, expanded vermiculite, natural clinoptiolite, and silica gel). The energetic characteristics and sorption behavior of the parent salts and modified thermochemical materials were analyzed employing TGA/DSC, TG-MS, Raman spectroscopy, and XRD. Successive discharging/charging cycles were conducted to determine the cycle stability of the storage materials. The overall performance was strongly dependent on the material combination. Increase in the partial pressure of the adsorbate accelerated the overall adsorbate uptake. From energetic perspectives the CaCl2-H2O system exhibited higher energy storage densities than the CaCl2 and MgCl2 alcoholates studied. The latter were prone to irreversible decomposition. Ethyl chloride formation was observed for MgCl2 at room and elevated temperatures. TG-MS measurements confirmed the evolution of alkyl chloride from MgCl2 ethanolates and methanolates upon heating. However, CaCl2 and its ethanolates and methanolates proved reversible and cyclable in the temperature range between 25°C and 500°C. All composite adsorbents achieved intermediate energy storage densities between the salt and the matrix. The use of carbonaceous matrices had a heat and mass transfer promoting effect on the reaction system CaCl2-H2O. Expanded graphite affected only moderately the adsorption/desorption of methanol onto CaCl2. CaCl2 dispersed inside zeolite 13X showed excellent adsorption kinetics towards ethanol. However, main drawback of the molecular sieve used as supporting structure was the apparent high charging temperature. Despite variations in the reactivity over thermal cycling caused by structural deterioration, composite adsorbents based on CaCl2 have a good potential as thermochemical energy storage materials for heating and cooling applications. Further research is required so that the storage media tested can meet all necessary technical requirements.
Durch die Neufassung des § 68f Abs.1 Satz 1 StGB tritt die Führungsaufsicht bei vollverbüßter Strafe von zwei Jahren oder bei schwerwiegenden Taten gemäß § 181b StGB nach einem Jahr kraft Gesetzes ein. Diese Reform im Jahr 2007 hat zu einem enormen Anstieg von Führungsaufsichten nach vollverbüßter Jugendstrafe geführt. Die Regelungen und Aufgaben der Verantwortlichen der Führungsaufsicht nach Jugendstrafe sind vielfältig und anders als beispielsweise bei der Führungsaufsicht nach einer Maßregel der Besserung und Sicherung (gem. §§ 63f). Für die Arbeit mit straffälligen Jugendlichen und Heranwachsenden unter Führungsaufsicht nach vollverbüßter Jugendstrafe gibt es für die Justizsozialarbeitenden keine explizite Handreichung. Im Vordergrund der Arbeit liegt die Frage: Welche Faktoren können, aus Sicht der beteiligten Akteure, die Legalbewährung jugendlicher und heranwachsender Vollverbüßer unter Führungsaufsicht begünstigen? Die Praxisforschung wird anhand von 15 Interviews mit den Verantwortlichen der Führungsaufsicht dargestellt und nimmt Bezug auf das in der Praxis erprobte Modellprojekt RESI und das Lebenslagenkonzept.
Die Energiewende steht im Zentrum aktueller gesellschaftlicher Debatten. Die Frage ist: Wie kann die gegenwärtige Klimakrise aufgehalten und gleichzeitig der Energiebedarf gedeckt werden? Einigkeit besteht darüber, dass eine Strategie zur Energiewende die Umstellung auf erneuerbare Energieträger beinhalten muss. Das Problem ist: Zentrale Begriffe wie "erneuerbare Energieträger " sind uneindeutig und deshalb besonders für naturwissenschaftliche Laien missverständlich. Ihnen wird dadurch die gesellschaftliche Teilhabe an der Debatte erschwert. Wie kann der naturwissenschaftliche Unterricht dazu beitragen, die oben benannten Missverständnisse aufzuklären? Er muss die Schüler dabei unterstützen, die naturwissenschaftlichen Schlüsselprinzipien der verschiedenen Energieträger und darauf aufbauend die Energiewende angemessen zu verstehen. Zu diesem Zweck muss der Unterricht entsprechend strukturiert werden. Welche Leitlinien sowohl die Lehrkräfte der Naturwissenschaften als auch die Entwickler der Unterrichtsmaterialien dabei beachten sollten: Das klärt die vorliegende Studie. Hierfür wird das Modell der didaktischen Rekonstruktion als Forschungsrahmen genutzt. Ausgehend von einem gemäßigt konstruktivistischen Lehr-Lernverständnis werden drei Unterfragen beantwortet: (1) Welche vorunterrichtlichen Vorstellungen bringen Schüler in den Unterricht mit? (2) Welche Vorstellungen haben Wissenschaftler? (3) Welche Unterschiede ergeben sich im Vergleich der Vorstellungen? Für die Beantwortung dieser Fragen wurden in der Erhebung problemzentrierte, leitfadengestützte Interviews mit 27 Achtklässlern geführt und Auszüge aus zwei wissenschaftlichen Gutachten ausgewählt. Mit einer qualitativen Inhaltsanalyse konnten in der Auswertung Inhaltsaspekte identifiziert werden, die Potenzial für die unterrichtliche Vermittlung haben. Mit dem so reduzierten Datenmaterial wurde eine systematische Metaphernanalyse durchgeführt. Damit wurden erfahrungsbasierte Muster hinter den Vorstellungen rekonstruiert. Aus dem systematischen Vergleich der Ergebnisse lassen sich Lernchancen und Lernhindernisse für das Verstehen von naturwissenschaftlichen Hintergründen der Energiewende ableiten. Diese werden in Form von Leitlinien für den naturwissenschaftlichen Unterricht zusammengefasst. Diese Leitlinien können von Lehrpersonen und Entwicklern von Lehrmaterialien genutzt werden, um ein fachlich angemessenes Verstehen der naturwissenschaftlichen Schlüsselprinzipien der Energieträger und der Energiewende zu fördern.
In this dissertation, advanced nonlinear control strategies and nonlinear minimum-variance observation are combined, in order to improve the estimation and/or tracking quality within control and fault detection tasks, for several types of systems from the fields of electromobility and conventional drivetrain technology that have some potential for sustainability or performance improvements. The application-specific innovations in terms of nonlinear Kalman filter methods are: (1) Improved state of charge estimation for Lithium-ion battery cells, powered by a novel self-adaptive EKF that uses a high-order polynomial curve fit as a decomposition of the uncertain nonlinear output equation with intentionally redundant bases, and with a reduced number of polynomial parameters that are adapted online by the EKF itself. (2) Online estimation of the time delay between two periodic signals of roughly the same shape that have pronounced uncorrelated noise, based on a fractional-order approximation of the transcendent transfer function of the time delay which is used as a model in a novel kind of EKF. (3) Using two (E)KFs (one for the linear subsystem and one for the nonlinear subsystem of a new kind of multi-stage piezo-hydraulic actuator) in a cascaded loop structure in order to reduce the computation load of the estimation, by appropriate 'interfacing' between the two observers (using one shared system model equation, among other aspects). - The innovations in terms of nonlinear control methods are powered by observation, as well: (1) Sliding mode velocity control of a DC drive that is subject to nonlinear friction and unknown load torques, enhanced by an equivalent control law, and with a new intelligent switching gain adaptation scheme (for reduced control chattering and, thus, less energy consumption and actuator wear), which is powered by Taylor-linearized model predictive control, which in turn requires observer-based disturbance compensation (by a KF with a double-integrator disturbance model) for model-matching purposes in order to function correctly. (2) Direct speed control of permanent-magnet three-phase synchronous motors that have a high power-to-volume ratio, based on sliding mode control in a rotating d,q coordinate system, with a new equivalent control method that exploits both system inputs and with a secondary sliding surface to ensure compliance with the current-trajectory of maximum efficiency for the required torque, and which works without measurement of the rotor angle (thanks to a new kind of EKF that estimates all states in the stationary α,β coordinate system, as well as the disturbance/load torque and its derivative). In all instances, improvements (compared to methods existing in the literature) in terms of control and estimation performance have been achieved and confirmed using simulation studies or real experiments.
The dissertation contains four journal articles which are embedded within a framework manuscript that interconnects the individual articles and provides relevant background information. The dissertation's overall objective is to provide a multilayered and critical in-depth engagement with the timely phenomenon of integrated reporting (IR), a new reporting concept that is envisaged to revolutionize firms' present reporting infrastructure. While extant corporate reports (e.g., annual financial- and CSR report) often are criticized for being disconnected and to suffer from a lack of coherence, IR intends to provide all information that is material to a firm's short-, medium- und long-term value creation within one single, succinct document. To contribute to a set of previously defined relevant research gaps in literature, the dissertation makes use of a combined empirical-quantitative and explorative-qualitative research design. The first article entitled investigates a set of different IR-, corporate governance and financial accounting-specific factors that are expected to determine European and South African firms' materiality disclosure quality. To this purpose, an original, hand-collected materiality disclosure score was developed. The second article explores IR perceptions of SME managers that have not embarked on IR, but are potential candidates to do so in future. Based on a review of extant literature, the article develops a theoretical framework to subsequently discuss motives for and barriers to IR adoption. The critical discussion contributes to the academic debate on incentives for and barriers to voluntary IR adoption. The third article investigates whether voluntary IR adoption among European firms is associated with lower cost of public debt. While earlier studies suggest that IR leads to lower information asymmetries, increases analyst forecasts, and decreases cost of equity, corresponding evidence for the debt market is largely missing. Subsequent analyses test as to whether such an association is even more pronounced by a firm's environmental, social and governance (ESG) performance or its belonging to an environmentally sensitive industry. The fourth article uses an experimental design to investigate nonprofessional investors' reactions to an IR assurance. To this purpose, two separate experiments with two different groups of nonprofessional investors were carried out: one with Masters students and one with managers of large corporations. Results help to answer the question as to whether an IR assurance as well as its determinants, namely the assurance provider and the assurance level, affect nonprofessional investors' financial decision-making. In the second step, subsequent in-depth interviews reveal an IR assurance-critical attitude among managers, who draw upon their practical experience with assurance engagements.
It is understood among research and policy makers that addressing unsustainable individual consumption patterns is key for the vision of sustainable development. Education for Sustainable Consumption (ESC) is attributed a pivotal role for this purpose, aiming to improve the capacity of individuals to connect to and act upon knowledge, values and skills in order to respond successfully and purposefully to the demands of sustainable consumption. Yet despite political, scientific, and educational efforts and increasing awareness in the general population, little has been achieved to substantially change behavioral patterns so far. As part of the explanation for this shortcoming, it has been argued that current ESC practices have neglected the personal dimension of sustainable consumption, especially the affective-motivational processes underlying unsustainable consumption patterns. Against this background, this cumulative thesis is guided by the question how personal competencies for sustainable consumption can be defined, observed, and developed within educational settings. Special attention is given to mindfulness practices, describing the practice of cultivating a deliberate, unbiased and openhearted awareness of perceptible experience in the present moment. Drawing upon an explorative, qualitative research methodology, the thesis looks at three different mindfulness-based interventions aiming to stimulate competencies for sustainable consumption, reaching out to a total number of 321 participants (employees and university students). In this thesis, the author suggests to define personal competencies for sustainable consumption as abilities, proficiencies, or skills related to inner states and processes that can be considered necessary or sufficient to engage with sustainable consumption (SC). These include ethics, self-awareness, emotional resilience, selfcare, access to and cultivation of personal resources, access to and cultivation of ethical qualities, and mindsets for sustainability. The thesis holds that the observation of personal competencies benefits from a combination of different methodological and methodical angles. When working with self-reports as empirical data, a pluralistic qualitative methods approach can help overcoming shortcomings that are specifically related to individual methods while increasing the self-reflexivity of the research. Moreover, it is suggested to let learners analyze their own personal statements in groups, applying scientific methods. The products of the group analyses represent data based on an inter-subjectively shared perspective of learners that goes beyond self-estimation of personal competencies. In terms of developing personal competencies for SC, it can be concluded that mindfulness practice alone is not sufficient to build personal competencies for SC. While it can stimulate generic personal competencies, individuals do not necessarily apply these competencies within the domain of their consumption. Nevertheless, mindfulness practice can play an important role in ESC, insofar as it lays the inner foundation to engage with sustainability-related issues. More precisely, it allows learners to experience the relevance of their inner states and processes and the influence they have on actual behaviors, leading to a level of selfawareness that would not be accessible solely through discursive-intellectual means. Furthermore, participants experience mindfulness practice as a way to develop ethical qualities and access psychological resources, entailing stronger emotional resilience and improved well-being. In order to unleash its full potential for stimulating personal competencies for SC, however, the findings of the thesis suggest that mindfulness practice should be (a) complemented with methodically controlled self-inquiry and (b) related to a specific behavioral change. In this vein, self-inquiry-based and self-experience-based learning – two pedagogical approaches developed during the period of research for this thesis – turned out to be promising pedagogies for educational settings striving to stimulate the development of personal competencies for SC.