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Aufsatz
Effect of Auger recombination and leakage on the droop in InGaN/GaN quantum well LEDs
(Optical Society of America, 2014)
We investigate the effect of the epitaxial structure and the acceptor doping profile on the efficiency droop in InGaN/GaN LEDs by the physics based simulation of experimental internal quantum efficiency (IQE) characteristics. The device geometry is an integral part of our simulation approach. We demonstrate that even for single quantum well LEDs the droop depends critically on the acceptor doping profile. The Auger recombination was found to increase stronger than with the third power of the carrier density and has ...
Dissertation
Verfahren zur echtzeitfähigen Simulation dynamischer Emissionsverläufe ausgewählter Schadstoffe von Ottomotoren
(2011-09-14)
Im Rahmen dieser Arbeit werden Modellbildungsverfahren zur echtzeitfähigen Simulation wichtiger Schadstoffkomponenten im Abgasstrom von Verbrennungsmotoren vorgestellt. Es wird ein ganzheitlicher Entwicklungsablauf dargestellt, dessen einzelne Schritte, beginnend bei der Ver-suchsplanung über die Erstellung einer geeigneten Modellstruktur bis hin zur Modellvalidierung, detailliert beschrieben werden. Diese Methoden werden zur Nachbildung der dynamischen Emissi-onsverläufe relevanter Schadstoffe des Ottomotors angewendet. ...
Dissertation
Regelbasiertes Reasoning auf massiv paralleler Hardware
(2015-10-15)
Eine wesentliche Funktionalität bei der Verwendung semantischer Technologien besteht in dem als Reasoning bezeichneten Prozess des Ableitens von impliziten Fakten aus einer explizit gegebenen Wissensbasis. Der Vorgang des Reasonings stellt vor dem Hintergrund der stetig wachsenden Menge an (semantischen) Informationen zunehmend eine Herausforderung in Bezug auf die notwendigen Ressourcen sowie der Ausführungsgeschwindigkeit dar. Um diesen Herausforderungen zu begegnen, adressiert die vorliegende Arbeit das Reasoning ...
Technischer Report
On CD-systems of stateless deterministic R-automata with window size one
(2010-04-27)
We study cooperating distributed systems (CD-systems) of restarting automata that are very restricted: they are deterministic, they cannot rewrite, but only delete symbols, they restart immediately after performing a delete operation, they are stateless, and they have a read/write window of size 1 only, that is, these are stateless deterministic R(1)-automata. We study the expressive power of these systems by relating the class of languages that they accept by mode =1 computations to other well-studied language ...
Technischer Report
CD-Systems of Stateless Deterministic R(1)-Automata Governed by an External Pushdown Store
(2011-01-06)
We study cooperating distributed systems (CD-systems) of stateless deterministic restarting automata with window size 1 that are governed by an external pushdown store. In this way we obtain an automata-theoretical characterization for the class of context-free trace languages.
Dissertation
Dynamic Injection of Scribble Features into Graphical Diagram Editors
(2015-05-20)
Almost everyone sketches. People use sketches day in and day out in many different and heterogeneous fields, to share their thoughts and clarify ambiguous interpretations, for example. The media used to sketch varies from analog tools like flipcharts to digital tools like smartboards. Whereas analog tools are usually affected by insufficient editing capabilities like cut/copy/paste, digital tools greatly support these scenarios. Digital tools can be grouped into informal and formal tools. Informal tools can be ...
Technischer Report
On Globally Deterministic CD-Systems of Stateless R-Automata with Window Size One
(2011-03-30)
It is known that cooperating distributed systems (CD-systems) of stateless deterministic restarting automata with window size 1 accept a class of semi-linear languages that properly includes all rational trace languages. Although the component automata of such a CD-system are all deterministic, in general the CD-system itself is not, as in each of its computations, the initial component and the successor components are still chosen nondeterministically. Here we study CD-systems of stateless deterministic restarting ...
Dissertation
A probabilistic approach to the estimation of regional photovoltaic power generation using meteorological data
(2016-09-05)
In Germany the upscaling algorithm is currently the standard approach for evaluating the PV power produced in a region. This method involves spatially interpolating the normalized power of a set of reference PV plants to estimate the power production by another set of unknown plants. As little information on the performances of this method could be found in the literature, the first goal of this thesis is to conduct an analysis of the uncertainty associated to this method. It was found that this method can lead to ...
Dissertation
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 ...
Dissertation
Zweiachsige Hybriderregung von Synchronmaschinen
(2017-04-25)
Neue Anwendungsfelder von geregelten elektrischen Antrieben, wie beispielsweise die Windenergie und die Elektromobilität, führen zu einer stetig steigenden Nachfrage nach wartungsfreien Systemen mit langen Betriebszeiten. Der Preisverfall der Leistungselektronik bei immer höheren Wirkungsgraden ermöglicht durch geeignete Topologien und entsprechende Regelung deutliche Energieeinsparung beim Betrieb elektrischer Antriebe.
In der Elektromobilität stellen im Besonderen gegensinnige Anforderungen, wie hohe Effizienz bei ...