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Aufsatz
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Processing effects on tensile superelastic behaviour of Fe43.5Mn34Al15 ± XNi7.5∓X shape memory alloys
(2019)
Fe₄₃.₅Mn₃₄Al₁₅Ni₇.₅ was introduced in the current decade as a new superelastic alloy with great applicative potential due to: (i) superelastic behaviour over a thermal range of 200°C and (ii) recoverable strains up to 9.7 %. One of the key factors in enhancing the superelastic response of several shape memory alloys (SMAs) is the formation of an oligocrystalline structure, i.e. without triple junctions between grains, which is the result of an abnormal grain growth (AGG) process that can be induced by cyclic heat ...
Aufsatz
Shape memory effect and superelasticity in high-strength FeNiCoAlTi single crystals hardened by nanoparticles
(2019-11-19)
For [001]-oriented single crystals of Fe-28Ni-17Co-11.5Al-2.5Ti (at %) alloy in tension, it was shown that particles of the γ’-phase with a size of 4–6 nm lead to the appearance of superelasticity, with a strain of εSE=4.5% and a shape memory effect of εSME=5.9%. Increasing the particle size to 10–12 nm reduces εSE to 3.6% and εSME to 3.5%. The paper discusses the causes of the influence of particle size on the reversible strain.
Aufsatz
Understanding the emergence and evolution of pastoral community groups from the perspective of community members and external development actors in northern Kenya
(Kassel University Press, 2019-01-15)
Whereas there is abundance of information on community groups that engage in income generation in rural agricultural and peri-urban areas, information on community groups in pastoral areas still remains scarce. However, in the recent past, a growing trend of such groups has been observed in the pastoral areas in northern Kenya. This study therefore explores how these groups have emerged since Kenya’s independence in 1963 to date, and which factors have contributed to their evolution. A full survey on all income-generating ...
Dissertation
Buffered Simulation for Büchi Automata
(2019)
Wir stellen eine neue Familie von Simulationsrelationen zwischen zwei nicht deterministischen Büchi Automaten (NBA), genannt gepufferte Simulation vor. Wir erweitern das Spiel-Framework der üblichen fairen Simulation, so dass Duplicator ihren Spielzug überspringen und die Buchstaben, die Spoiler gelesenen hat, vorübergehend in einem Puffer speichern kann. Duplicator kann diese Buchstaben in ihrer Struktur dann später ausführen. Duplicator hat damit eine Vorschau in die Bewegungen von Spoiler und somit mehr Chancen, ...
Dissertation
The Fatigue and Corrosion Fatigue Behavior of Austenitic Stainless Steel AISI 304 after Deep Rolling at Various Temperatures
(2019-09)
The austenitic stainless steel AISI 304 was deep rolled at 20 °C (RTDR), -195 °C (CTDR), and 550 °C (HTDR). The deep rolling pressures used for each deep rolling temperature were 1.0, 1.7, and 2.4 bar. From microstructural investigation, the largest compressive residual stress field was found in RTDR, and the highest amount of martensitic content and plastic deformation were found in CTDR. The strain aging effect was only found in HTDR.
In the rotating bending fatigue tests, the strain aging effect after HTDR is ...
Dissertation
![Open Access](/themes/Mirage2/images/Open_Access_logo_PLoS_transparent.svg)
Hybrid Branching-Time Logics
(2019)
We introduce and study an extension of the well-known and well-studied branching-time logics CTL, CTL+, FCTL+, CTL* and the modal μ-calculus with the so called "hybrid framework". This framework borrows ideas from first-order logic to enable more precise "structural" reasoning which is known to be impossible in the original logics. In particular, the extension with this framework enables these logics to uniquely name, reference and test for certain states, similarly to the concepts of variables and constants in ...
Preprint
Existence of parameterized BV-solutions for rate-independent systems with discontinuous loads
(2019-09-25)
We study a rate-independent system with non-convex energy and in the case of a time-discontinuous loading. We prove existence of the rate-dependent viscous regularization by time-incremental problems, while the existence of the so called parameterized BV-solutions is obtained via vanishing viscosity in a suitable parameterized setting. In addition, we prove that the solution set is compact.
Buch
Statik und Einflussfunktionen - vom modernen Standpunkt aus
(2019-01-15)
In dem Buch werden die Grundlagen der klassischen Statik in einer modernen, zeitgemäßen Form dargestellt. Dabei wird auf Präzision und Prägnanz in der Darstellung Wert gelegt. Spezielles Gewicht wird auf Einflussfunktionen gelegt, da diese die Basis der finiten Elemente bilden. Das Rechnen mit finiten Elementen ist, wie in dem Buch gezeigt wird, ein Rechnen mit genäherten Einflussfunktionen. Der Text geht ausführlich auf die Fragen der Modellierung von Tragwerken mit finiten Elementen und der Genauigkeit der numerischen ...
Dissertation
![Open Access](/themes/Mirage2/images/Open_Access_logo_PLoS_transparent.svg)
Towards Effective Natural Language Application Development
(2019)
There is a current trend that more and more computer programs analyze written or spoken natural language. For example, DVAs, IE systems, machine translation systems, and many other types of programs process natural language in order to solve specific use cases when interacting with humans via natural language. Amazon, Google, and Mycroft AI are just some of the companies that have produced DVAs capable of interacting with humans via voice. Such NLP applications use techniques from computer science and artificial ...
Aufsatz
![Open Access](/themes/Mirage2/images/Open_Access_logo_PLoS_transparent.svg)
Promoting abnormal grain growth in Fe-based shape memory alloys through compositional adjustments
(2019-05-28)
Iron-based shape memory alloys are promising candidates for large-scale structural applications due to their cost efficiency and the possibility of using conventional processing routes from the steel industry. However, recently developed alloy systems like Fe–Mn–Al–Ni suffer from low recoverability if the grains do not completely cover the sample cross-section. To overcome this issue, here we show that small amounts of titanium added to Fe–Mn–Al–Ni significantly enhance abnormal grain growth due to a considerable ...