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Dissertation
Simulationen und Experimente im Schwellenwertbereich zur Aufklärung der Risswachstumsmechanismen in einer Aluminiumlegierung
(2020)
Lange Risse, die bei Belastungen nahe des Schwellenwerts wachsen, können Ausbreitungscharakteristika zeigen, welche denen kurzer Stadium I-Risse ähneln. Neben einer lokalen Blockade der Rissfront durch Teilchen einer zweiten Phase ist ein schubspannungsgesteuerter Rissfortschritt ein interessanter Effekt, der bei diesen Belastungsbedingungen auftritt. Das berichtete Verhalten wird im Rahmen dieser Arbeit auf das Rissspitzenfeld zurückgeführt. Zu diesem Zweck wurden Risswachstumsexperimente mit angerissenen Flachproben ...
Dissertation
A new perspective to strongly-interacting lattice fermions in the framework of density functional theory
(2020)
Die in dieser Arbeit formulierte Theorie betrachtet das Vielteilchenproblem wechselwirkender Fermionen auf einem Gitter aus einem neuen Blickwinkel.
Dissertation
Combining crop growth models with the Precision Agriculture concept of yield gap analysis to evaluate yield limiting and reducing factors
(2022)
The agricultural sector is considered as one of the main elements of a “functional” society and its welfare for providing means to fulfil the most basic human need for food. In the past, an improved overall welfare of developed countries was directly related to early investment in conventional farming machinery parallel to the industrial development. With the expected future population increase and climate change, farm yield gaps are expected to increase and become more volatile. The awareness of negative externalities ...
Dissertation
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Optimal Control of Quantum Information Tasks in Open Quantum Systems
(2020-07-30)
Every quantum system inevitably interacts with its environment. This is a fundamental requirement that allows us to control, measure and, in general, interact with quantum systems. In that respect, a quantum system's openness can be interpreted as prerequisite that enables quantum technologies in the first place. The latter are built to harness the intrinsic quantum mechanical behavior of quantum devices in order to build new, powerful technologies. However, a quantum system's openness also causes it to interact ...
Dissertation
High temperature-stable InGaAs QDs for the monolithic integration in external-cavity surface-emitting lasers
(2021)
Optically pumped vertical external-cavity surface-emitting lasers (VECSELs), also called semiconductor disk lasers (SDLs), benefit from the flexibility and versatility of the semiconductor material. With a simple cavity layout, fundamental transverse mode operation with a circular output beam and high beam quality is possible. They have excellent heat-sink properties and only require inexpensive multimode diode lasers for pumping. The complete VECSEL structure is only a few micrometers thick which leads to a strong ...
Dissertation
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Managing Risk, Performance and Sustainability in Textile & Apparel Supply Chains.
(2023)
The thesis at hand analyzes sustainability prerequisites, practices, risk and performance in textile and apparel (T&A) supply chains (SCs). Given the growing awareness of sustainability risks by various stakeholders, T&A firms are required to implement and adapt sustainability practices along their SCs, while at the same time measuring their performance to counteract the (re)emergence of risks. Appropriate management strategies are therefore needed to ensure sustainable transformation in T&A SCs. While the state of ...
Dissertation
Synthese und Reaktivität eines cyclischen (Alkyl)(amino)carbens mit 1,1'-Ferrocenylen-Rückgrat
(2023-01)
Ziel der vorliegenden Arbeit war es, cyclische (Alkyl)(amino)carbene mit einem 1,1‘ Ferrocenylen-Rückgrat (fcCAACs) darzustellen und zu charakterisieren und somit eine Kombination aus bekanntermaßen jeweils höchst ambiphilen CAACs und N-heterocyclischen Carbenen mit 1,1‘-Ferrocenylen-Rückgrat (fcNHCs) zu schaffen. Durch das fc-Rückgrat sollten die Zielverbindungen eine im Vergleich zu bisher zugänglichen CAACs noch ausgeprägtere Ambiphilie besitzen und somit eine nochmals gesteigerte Reaktivität zeigen, insbesondere ...
Dissertation
Designing Breeding Programs For Improving Milk Yield Performance Of Indigenous Genous Dairy Cattle In Sudan
(2022)
The overall aim of the present study was to design appropriate breeding programs for the sustainable improvement of Butana cattle in Sudan. Four studies were conducted, beginning with a comprehensive review of literature on indigenous dairy cattle breeding strategies in sub-Saharan Africa with a focus on the factors that contribute to their success or failure. It showed that crossbreeding of indigenous breeds with exotic breeds has been widely used for genetic improvement, but it largely failed under low-input ...
Dissertation
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Taking a Closer Look at the Desirability of Desirable Difficulties - Additionally Focusing on Required Prerequisites, Negative Side-Effects, and Negative Consequences
(2022)
As the title of my dissertation already indicates, the main purpose of the following work was to take a closer, more thorough, and encompassing look at the desirability of desirable difficulties. The term desirable difficulties thereby subsumes varying types of difficult, demanding, and challenging learning strategies—like the application of (learning/practice) tests and generation tasks: Working on and successfully solving those difficult tasks requires more (cognitive) effort compared to working on easier learning ...
Dissertation
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Validation of a generalized model for the description of polycrystalline exchange-biased magnetic thin films
(2022)
Applications based on nano- and microscaled systems have become indispensable in many aspects in everyday life, industry, research and medicine. In this regard, thin film technology plays a crucial role with the physical properties of solids changing significantly when they are reduced to thin layers with thicknesses in the nanometer range. In this regime, a solid’s microstructure as well as boundary and surface effects start to dominate. A prominent example is the exchange bias effect, which results due to the ...