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Zur kontinuierlichen Herstellung von Faser-Kunstoff-Verbunden in Form von Profilen
hat sich das Pultrusionsverfahren seit langem erfolgreich industriell etabliert. Bis jetzt
wurden fast ausschließlich duroplastische Matrizes verwendet. Aufgrund der
zahlreichen Vorteile wecken thermoplastische Faserverbundwerkstoffe zunehmend
das Interesse der Industrie; der Einsatz und die Fertigung von thermoplastischen
Profilen in hohen Stückzahlen werden jedoch bislang wegen mangelnder
Grundkenntnisse noch nicht realisiert.
In der vorliegenden Arbeit wird der Pultrusionsprozess thermoplastischer
Faserverbundwerkstoffe im Hinblick auf Realisierbarkeit und Optimierung von
Prozessparametern untersucht. Ziel war es bereits vorliegende Erkenntnisse zu
erweitern und bestehende Wissenslücken zu schließen. Als Ausgangsmaterial
wurden verschiedene Garntypen verwendet: ein Garn aus Kohlenstoff- und Polyamid
12-Fasern, ein Mischgarn aus Glas- und Polypropylen-Fasern sowie Polypropylen
pulverimprägnierte Glasfasern (sogenannte Towpregs). Besonderes Augenmerk lag
auf dem ersten Garntyp aus CF/PA12, der diskontinuierliche Fasern enthält. Mit
diesen Materialien wurden unidirektional faserverstärkte, rechteckige und runde
Profile hergestellt. Weiterhin wurde der Einfluss von zwei Hauptprozessparametern,
die Temperatur der Vorheizzone und der Heizdüse und die Abzugsgeschwindigkeit,
sowie von der Länge der Heizdüse auf die Profilqualität analysiert. Die jeweils
verwendeten Garntypen, der sich einsstellende Faservolumengehalt sowie der
Feuchtigkeitseinfluss wurden zusätzlich systematisch untersucht. Weiterhin wurde
die Abzugskraft analysiert.
Die Charakterisierung der Pultrudatqualität erfolgte durch mechanische und
morphologische Prüfungen. Der Imprägnierungsgrad, die Biegeeigenschaften und
die Scherfestigkeit, sowie zweitrangig die Charpy-Schlagzähigkeit und die
Zugeigenschaften wurden hierzu ermittelt und anschließend bewertet. Weiterhin
wurde die Oberflächenqualität mittels Laserprofilometrie untersucht.
Einen entscheidenden Faktor stellte die Abzugsgeschwindigkeit dar. Bis auf die
Oberfläche wurden Verschlechterungen der Imprägnierung und der mechanischen
Eigenschaften mit zunehmender Geschwindigkeit beobachtet.
Weiterhin wurde der Abkühlungsprozess untersucht. Die bei der Pultrusion
vorhandenen Abkühlraten sind sehr hoch und werden von der
Abzugsgeschwindigkeit sowie der Kühldüsentemperatur beeinflusst.Die Erstellung eines Verarbeitungsfensters für das Garn aus CF/PA12 wurde
erfolgreich durch Verwendung einer Qualitätskennzahl durchgeführt.
Des Weiteren wurde die Erstarrung und der Prozess der Kristallisation aus der
Schmelze für das CF/PA12 System näher untersucht. Zur Beschreibung der
isothermen sowie nicht-isothermen Kristallisationskinetik wurden verschiedene
Methoden angewandt. In diesem Zusammenhang lieferten das Modell von Chuah
zufriedenstellende Ergebnisse.
Weiterhin erfolgte die Modellierung der Wärmeübertragung zur Vorhersage der
Temperatur im Material während der Pultrusion mit der Finiten Elemente Methode.
Aufbauend hierauf können im Versuchsvorfeld die am besten geeigneten
Werkzeugtemperatur-/Abzugsgeschwindigkeitskombinationen eingestellt werden.
The popularity of composite materials is constantly growing, which can be verified by
the rising number of composite parts in our everyday life. Examples of composite
parts can be found in the Airbus A 380 or the constantly increasing number of wind
turbines which contain composite rotor blades of over 50m length. Because of the
main features of composites, which are light weight combined with high strength and
the possibility of tailoring the strength and the stiffness of the composite according to
the requirements, their application is highly efficient and economic.
In order to manufacture a composite part by employing a Liquid Composite Molding
Process (LCM), it is first necessary to select an appropriate manufacturing process
such as the Resin Transfer Molding Process (RTM) and to design a mold which corresponds
to the requirements of the selected process. Then the stacking sequence of
the individual fibrous reinforcements is designed to withstand the loads on the final
part. To achieve an efficient composite manufacturing process, pre-shaped, handable,
dry reinforcing structures, so called preforms, need to be applied. Such preforms
can be assembled either by using conventional binder technologies or by the
recently developed “cut and sew approach”. A variety of available software simulation
tools support the design engineer in this task. These tools are, on the one hand, a
fast way of gaining information about the expected loads the mold has to endure during
the injection process. On the other hand, they provide the possibility to optimize
the injection process and its process parameters and to identify critical points of incomplete
saturation. With this information at hand, the design of the mold can be adjusted
in order to obtain optimal processing conditions for a slim and efficient production
cycle.
A prerequisite for employing these powerful simulation tools is to obtain thorough
knowledge of the required input parameters concerning the fibrous reinforcement to
be used. The most important input parameters are the compaction behavior and the
permeability of the fibrous stacking sequence. Because of the absence of modelbased
tools to provide this input information experimental determination methods
have to be employed.
This work introduces two semi-automated measurement cells which determine the inplane
permeability of fibrous reinforcements in an efficient manner, i.e. the dielectrical permeability work cell and the optical compaction and permeability work cell. The
latter of which can determine both the required compaction and the permeability information
in one single experiment. The design and manner of operating of the optical
compaction and permeability work cell is described and its functionality is validated
by a comparison of experimental results.
The complexity of modern real-time systems is increasing day by day. This inevitable rise in complexity predominantly stems from two contradicting requirements, i.e., ever increasing demand for functionality, and required low cost for the final product. The development of modern multi-processors and variety of network protocols and architectures have enabled such a leap in complexity and functionality possible. Albeit, efficient use of these multi-processors and network architectures is still a major problem. Moreover, the software design and its development process needs improvements in order to support rapid-prototyping for ever changing system designs. Therefore, in this dissertation, we provide solutions for different problems faced in the development and deployment process of real-time systems. The contributions presented in this thesis enable efficient utilization of system resources, rapid design & development and component modularity & portability.
In order to ease the certification process, time-triggered computation model is often used in distributed systems. However, time-triggered scheduling is NP-hard, due to which the process of schedule generation for complex large systems becomes convoluted. Large scheduler run-times and low scalability are two major problems with time-triggered scheduling. To solve these problems, we present a modular real-time scheduler based on a novel search-tree pruning technique, which consumes less time (compared to the state-of-the-art) in order to schedule tasks on large distributed time-triggered systems. In order to provide end-to-end guarantees, we also extend our modular scheduler to quickly generate schedules for time-triggered network traffic in large TTEthernet based networks. We evaluate our schedulers on synthetic but practical task-sets and demonstrate that our pruning technique efficiently reduces scheduler run-times and exhibits adequate scalability for future time-triggered distributed systems.
In safety critical systems, the certification process also requires strict isolation between independent components. This isolation is enforced by utilizing resource partitioning approach, where different criticality components execute in different partitions (each temporally and spatially isolated from each other). However, existing partitioning approaches use periodic servers or tasks to service aperiodic activities. This approach leads to utilization loss and potentially leads to large latencies. On the contrary to the periodic approaches, state-of-the-art aperiodic task admission algorithms do not suffer from problems like utilization loss. However, these approaches do not support partitioned scheduling or mixed-criticality execution environment. To solve this problem, we propose an algorithm for online admission of aperiodic tasks which provides job execution flexibility, jitter control and leads to lower latencies of aperiodic tasks.
For safety critical systems, fault-tolerance is one of the most important requirements. In time-triggered systems, modes are often used to ensure survivability against faults, i.e., when a fault is detected, current system configuration (or mode) is changed such that the overall system performance is either unaffected or degrades gracefully. In literature, it has been asserted that a task-set might be schedulable in individual modes but unschedulable during a mode-change. Moreover, conventional mode-change execution strategies might cause significant delays until the next mode is established. In order to address these issues, in this dissertation, we present an approach for schedulability analysis of mode-changes and propose mode-change delay reduction techniques in distributed system architecture defined by the DREAMS project. We evaluate our approach on an avionics use case and demonstrate that our approach can drastically reduce mode-change delays.
In order to manage increasing system complexity, real-time applications also require new design and development technologies. Other than fulfilling the technical requirements, the main features required from such technologies include modularity and re-usability. AUTOSAR is one of these technologies in automotive industry, which defines an open standard for software architecture of a real-time operating system. However, being an industrial standard, the available proprietary tools do not support model extensions and/or new developments by third-parties and, therefore, hinder the software evolution. To solve this problem, we developed an open-source AUTOSAR toolchain which supports application development and code generation for several modules. In order to exhibit the capabilities of our toolchain, we developed two case studies. These case studies demonstrate that our toolchain generates valid artifacts, avoids dirty workarounds and supports application development.
In order to cope with evolving system designs and hardware platforms, rapid-development of scheduling and analysis algorithms is required. In order to ease the process of algorithm development, a number of scheduling and analysis frameworks are proposed in literature. However, these frameworks focus on a specific class of applications and are limited in functionality. In this dissertation, we provide the skeleton of a scheduling and analysis framework for real-time systems. In order to support rapid-development, we also highlight different development components which promote code reuse and component modularity.
Asynchronous concurrency is a wide-spread way of writing programs that
deal with many short tasks. It is the programming model behind
event-driven concurrency, as exemplified by GUI applications, where the
tasks correspond to event handlers, web applications based around
JavaScript, the implementation of web browsers, but also of server-side
software or operating systems.
This model is widely used because it provides the performance benefits of
concurrency together with easier programming than multi-threading. While
there is ample work on how to implement asynchronous programs, and
significant work on testing and model checking, little research has been
done on handling asynchronous programs that involve heap manipulation, nor
on how to automatically optimize code for asynchronous concurrency.
This thesis addresses the question of how we can reason about asynchronous
programs while considering the heap, and how to use this this to optimize
programs. The work is organized along the main questions: (i) How can we
reason about asynchronous programs, without ignoring the heap? (ii) How
can we use such reasoning techniques to optimize programs involving
asynchronous behavior? (iii) How can we transfer these reasoning and
optimization techniques to other settings?
The unifying idea behind all the results in the thesis is the use of an
appropriate model encompassing global state and a promise-based model of
asynchronous concurrency. For the first question, We start from refinement
type systems for sequential programs and extend them to perform precise
resource-based reasoning in terms of heap contents, known outstanding
tasks and promises. This extended type system is known as Asynchronous
Liquid Separation Types, or ALST for short. We implement ALST in for OCaml
programs using the Lwt library.
For the second question, we consider a family of possible program
optimizations, described by a set of rewriting rules, the DWFM rules. The
rewriting rules are type-driven: We only guarantee soundness for programs
that are well-typed under ALST. We give a soundness proof based on a
semantic interpretation of ALST that allows us to show behavior inclusion
of pairs of programs.
For the third question, we address an optimization problem from industrial
practice: Normally, JavaScript files that are referenced in an HTML file
are be loaded synchronously, i.e., when a script tag is encountered, the
browser must suspend parsing, then load and execute the script, and only
after will it continue parsing HTML. But in practice, there are numerous
JavaScript files for which asynchronous loading would be perfectly sound.
First, we sketch a hypothetical optimization using the DWFM rules and a
static analysis.
To actually implement the analysis, we modify the approach to use a
dynamic analysis. This analysis, known as JSDefer, enables us to analyze
real-world web pages, and provide experimental evidence for the efficiency
of this transformation.
Das virtuelle, optische Messen wird in der industriellen Anwendung häufig vernachlässigt. Um optische Messergebnisse jedoch vorhersehbar und zuverlässig zu machen, ist es erforderlich, Sensoren zu modellieren und die Resultate, sogenannte virtuelle Messergebnisse, zu analysieren. Die zulässigen Modellvereinfachungen sind dabei vom zugrunde liegenden, physikalischen Messprinzip abhängig. In dieser Arbeit werden zwei virtuelle, optische Sensoren mit unterschiedlichen Messprinzipien unter paraxialen Annahmen modelliert. Zudem werden Untersuchungen zum Übertragungsverhalten der Sensoren angestellt. Beim ersten Sensor handelt es sich um einen winkelauflösenden Streulichtsensor zur Messung der statistischen Verteilung von Gradienten geometrischer Oberflächen. Der zweite Sensor ist ein kurzkohärentes Interferometer zur vertikal hochauflösenden Messung von Topographien. Während dem winkelauflösenden Messprinzip ein inkohärenter Modellansatz zugrunde liegt, werden beim Interferometer kohärente Annahmen getroffen. Mithilfe der Sensormodelle ist es möglich, geometrische Oberflächen virtuell anzutasten und, basierend auf generierten oder real gemessenen Topographiedaten, virtuelle Messungen anzustellen. Auf diese Weise werden umfangreiche Untersuchungen zum Übertragungsverhalten der Sensoren ermöglicht. Darüber hinaus wird ein eigens entwickeltes, VTK-basiertes Programm vorgestellt, das die nichtsequentielle Berechnung optischer Sensoren ermöglicht. Dieses Programm nutzt Ray Tracing zur Simulation nichtsequentieller, optischer Systeme. Des Weiteren werden Ansätze für die parallele Datenverarbeitung mit CUDA® vorgestellt. Der paraxial modellierte, winkelauflösende Streulichtsensor wird demnach zusätzlich nichtsequentiell simuliert und die Ergebnisse der paraxialen und der nichtsequentiellen Berechnung werden gegenübergestellt.
Thermoplastische Faser-Kunststoff-Verbunde (TP-FKV) rücken aufgrund ihrer guten Verarbeit- und Rezyklierbarkeit immer weiter in den Fokus der Automobilindustrie. Sie können effizient in serientauglichen Fließpress- oder Umformprozessen zu Bauteilen verarbeitet werden und bringen gute chemische, mechanische und thermische Eigenschaften mit. Die resultierenden Bauteile werden anschließend in Baugruppen eingesetzt, deren Strukturbauteile nach wie vor hauptsächlich aus Metallen bestehen. An der Schnittstelle zwischen TP-FKV und Metall entsteht ein Verbindungsproblem, das bisher meist durch Schrauben, Nieten oder Kleben gelöst wird. Allerdings werden diese Verfahren den speziellen Anforderungen der TP-FKV nicht gerecht und bringen zusätzliches Material in das Bauteil ein. TP-FKV eignen sich aufgrund der Schmelzbarkeit der thermoplastischen Matrix für thermische Fügeverfahren. Da die thermoplastische Matrix selbst als Klebstoff genutzt werden kann, entsteht eine flächige Verbindung, ohne dass Bohrungen oder zusätzliches Material notwendig sind. Außerdem kann durch eine geeignete Vorbehandlung der Metalloberfläche ein Formschluss erzielt und so die Festigkeit signifikant gesteigert werden.
In der vorliegenden Arbeit wurden ein diskontinuierlicher und ein kontinuierlicher, induktiver Schweißprozess entwickelt und optimiert. Dazu wurde ein Prüfstand ent-worfen und aufgebaut, der auf beide Prozesse angepasst werden kann. Beim konti-nuierlichen Induktionsschweißen konnte die Prozessgeschwindigkeit durch den Einsatz einer Bauteilkühlung ohne Beeinträchtigung der Fügefestigkeit auf mehr als 1m/min gesteigert werden. Beim diskontinuierlichen Schweißen wurde die bisher verwendete, sehr fehleranfällige temperaturbasierte Prozessregelung durch eine Wegregelung ersetzt. So konnte ein stabiler, voll automatisierter Schweißprozess entwickelt werden. Zum Abschluss wurde die Eignung des Induktionsschweißens für die industrielle Anwendung am Beispiel eines Unterbodenblechs eines Nutzfahrzeuges gezeigt. Hier konnte durch diskontinuierliches Induktionsschweißen in Kombination mit der Vorbehandlung des metallischen Fügepartners durch Laserstrukturierung die gleiche Performance wie bei dem ursprünglichen, genieteten Ansatz erzielt werden. Es steht mit dem Induktionsschweißen also ein Fügeprozess zur Verfügung, der sowohl hinsichtlich Effizienz als auch Festigkeit für die industrielle Anwendung geeignet ist.
Optical Character Recognition (OCR) system plays an important role in digitization of data acquired as images from a variety of sources. Although the area is very well explored for Latin languages, some of the languages based on Arabic cursive script are not yet explored. It is due to many factors: Most importantly are the unavailability of proper data sets and complexities posed by cursive scripts. The Pashto language is one of such languages which needs considerable exploration towards OCR. In order to develop such an OCR system, this thesis provides a pioneering study that explores deep learning for the Pashto language in the field of OCR.
The Pashto language is spoken by more than $50$ million people across the world, and it is an active medium both for oral as well as written communication. It is associated with rich literary heritage and contains huge written collection. These written materials present contents of simple to complex nature, and layouts from hand-scribed to printed text. The Pashto language presents mainly two types of complexities (i) generic w.r.t. cursive script, (ii) specific w.r.t. Pashto language. Generic complexities are cursiveness, context dependency, and breaker character anomalies, as well as space anomalies. Pashto specific complexities are variations in shape for a single character and shape similarity for some of the additional Pashto characters. Existing research in the area of Arabic OCR did not lead to an end-to-end solution for the mentioned complexities and therefore could not be generalized to build a sophisticated OCR system for Pashto.
The contribution of this thesis spans in three levels, conceptual level, data level, and practical level. In the conceptual level, we have deeply explored the Pashto language and identified those characters, which are responsible for the challenges mentioned above. In the data level, a comprehensive dataset is introduced containing real images of hand-scribed contents. The dataset is manually transcribed and has the most frequent layout patterns associated with the Pashto language. The practical level contribution provides a bridge, in the form of a complete Pashto OCR system, and connects the outcomes of the conceptual and data levels contributions. The practical contribution comprises of skew detection, text-line segmentation, feature extraction, classification, and post-processing. The OCR module is more strengthened by using deep learning paradigm to recognize Pashto cursive script by the framework of Recursive Neural Networks (RNN). Proposed Pashto text recognition is based on Long Short-Term Memory Network (LSTM) and realizes a character recognition rate of $90.78\%$ on Pashto real hand-scribed images. All these contributions are integrated into an application to provide a flexible and generic End-to-End Pashto OCR system.
The impact of this thesis is not only specific to the Pashto language, but it is also beneficial to other cursive languages like Arabic, Urdu, and Persian e.t.c. The main reason is the Pashto character set, which is a superset of Arabic, Persian, and Urdu languages. Therefore, the conceptual contribution of this thesis provides insight and proposes solutions to almost all generic complexities associated with Arabic, Persian, and Urdu languages. For example, an anomaly caused by breaker characters is deeply analyzed, which is shared among 70 languages, mainly use Arabic script. This thesis presents a solution to this issue and is equally beneficial to almost all Arabic like languages.
The scope of this thesis has two important aspects. First, a social impact, i.e., how a society may benefit from it. The main advantages are to bring the historical and almost vanished document to life and to ensure the opportunities to explore, analyze, translate, share, and understand the contents of Pashto language globally. Second, the advancement and exploration of the technical aspects. Because, this thesis empirically explores the recognition and challenges which are solely related to the Pashto language, both regarding character-set and the materials which present such complexities. Furthermore, the conceptual and practical background of this thesis regarding complexities of Pashto language is very beneficial regarding OCR for other cursive languages.
The N-containing heterocycles have received strong attention from the organic synthesis field because of their importance for pharmaceutical and material sciences. Nitrogen element plays an important role between inorganic salts and biomolecules, to search convenient methods combine C-N bond together become a hot topic in recent decades.
Since the early beginning of 20th century, transition-metal-catalyzed coupling reactions had been well-known and world widely spread in organic researchs, achieved abundant significant progress. In the other side, the less toxic and more challenging transition metal free coupling method remained further potential value.
With the evolution of amination reactions and oxidants, more and more effective, simplified, and atom economic organic synthesis methods will come soon. And these stories also drove me to think about investigating the novel cross-dehydrogenative-coupling amination methods development as the topics of my PhD research.
Thus, we selected the phenothiazine derivatives as the N-nucleophile reagents and the phenols as the C-nucleophile reagents. To achieve the transition metal-free CDC aminations of phenols with phenothiazines, we scanned the chemical toolbox and tested a series of both common and uncommon oxidants.
Firstly, we start the condition in the presence of cumene and O2. The proposed mechanism initiated by a Hock process, which would form in situ peroxo-species as initiator of the reaction. And the initial infra-red analysis predicted there is a strong O-H..N interaction.
In the second method, a series of iodines with different valance have been tested to achieve the C-N bond formation of phenols with phenothiazines. This time, a simplified and more efficient method had been developed, which also provides a wider scope of phenols. Several controlling experiments had been conducted for the plausible pathway research. Large-scale synthesis of target molecular was also successfully performed.
And then, we focus the research on the cross-coupling reaction of pre-oxidized(iminated) phenothiazine with ubiquitous phenols and indoles. In this task, we first regio-selectively synthesized the novel iminated phenothiazine derivatives with the traditional biocide and mild disinfectant, Chloramine T. Then the phenothiazinimine performed an ultra-simple condensation technique with phenol or indole coupling partners in a simplified condition. Parallel reactions were also performed to investigate the plausible pathway.
Nowadays, the increasing demand for ever more customizable products has emphasized the need for more flexible and fast-changing manufacturing systems. In this environment, simulation has become a strategic tool for the design, development, and implementation of such systems. Simulation represents a relatively low-cost and risk-free alternative for testing the impact and effectiveness of changes in different aspects of manufacturing systems.
Systems that deal with this kind of data for its use in decision making processes are known as Simulation-Based Decision Support Systems (SB-DSS). Although most SB-DSS provide a powerful variety of tools for the automatic and semi-automatic analysis of simulations, visual and interactive alternatives for the manual exploration of the results are still open to further development.
The work in this dissertation is focused on enhancing decision makers’ analysis capabilities by making simulation data more accessible through the incorporation of visualization and analysis techniques. To demonstrate how this goal can be achieved, two systems were developed. The first system, viPhos – standing for visualization of Phos: Greek for light –, is a system that supports lighting design in factory layout planning. viPhos combines simulation, analysis, and visualization tools and techniques to facilitate the global and local (overall factory or single workstations, respectively) interactive exploration and comparison of lighting design alternatives.
The second system, STRAD - standing for Spatio-Temporal Radar -, is a web-based systems that considers the spatio/attribute-temporal analysis of event data. Since decision making processes in manufacturing also involve the monitoring of the systems over time, STRAD enables the multilevel exploration of event data (e.g., simulated or historical registers of the status of machines or results of quality control processes).
A set of four case studies and one proof of concept prepared for both systems demonstrate the suitability of the visualization and analysis strategies adopted for supporting decision making processes in diverse application domains. The results of these case studies indicate that both, the systems as well as the techniques included in the systems can be generalized and extended to support the analysis of different tasks and scenarios.
Das 2,2′-Bipyrimidinradikalanion als Brückenligand für Komplexe mit L-N\(_\text{4}\)Me\(_\text{2}\)
(2018)
Im Rahmen dieser Dissertationsschrift gelang es erstmals 3d-Metallionen über ein 2,2′-Bipyrimidinradikalanion zu verbrücken und zu isolieren. Der für sich betrachtet instabile Radikalbrückenligand wurde hierbei in situ durch Reduktion mit Cobaltocen generiert und durch Koordination stabilisiert. Es konnte neben verschiedenen Referenzverbindungen eine Reihe von vier unter Luftausschluss stabilen homodimetallischen Verbindungen mit dem [{M\(^\text{II}\)(L-N\(_\text{4}\)Me\(_\text{2}\))}\(_\text{2}\)(μ-bpym\(^\text{●}\))]\(^\text{3+}\)-Komplexkation (mit M = Zn (\(\textbf{2}\)), Ni (\(\textbf{6}\)), Co (\(\textbf{8}\)) und Fe (\(\textbf{12}\)) synthetisiert, vollständig charakterisiert und miteinander verglichen werden. Durch Gegenüberstellung der strukturellen Parameter des verbrückend koordinierten 2,2′-Bipyrimidinradikalanions in den zweikernigen Verbindungen wurden für dieses charakteristische Bindungslängenbereiche festgestellt. Weiterhin wurden IR- und UV/Vis-spektroskopisch typische Banden des verbrückend koordinierten 2,2′-Bipyrimidinradikalanions gefunden. Durch cyclovoltammetrische und NMR-spektroskopische Untersuchungen wurde der Reaktionspfad zu den dinuklearen Verbindungen aufgeklärt. An \(\textbf{2}\) wurden die intrinsischen ESR-spektroskopischen Eigenschaften der 2,2′-Bipyrimidinradikalanion-Brücke untersucht. Die Elektronendichte des Radikals in \(\textbf{2}\) ist hauptsächlich auf dem Brückenliganden verortet und es liegt ein S = 1/2 System vor. SQUID-magnetometrische Messungen an \(\textbf{6}\) zeigen eine starke ferromagnetische Kopplung zwischen den Nickelionen und der Radikalbrücke, welche zu einem S = 5/2 Spingrundzustand führt. Der S = 5/2 Zustand wurde mittels X-Band-ESR-Spektroskopie bestätigt. Durch Hochfeld-ESR-Spektroskopie wurde ebenfalls die ferromagnetische Kopplung bestätigt und die Nullfeldaufspaltung der Nickelionen in \(\textbf{6}\) eindeutig als schwach negativ bestimmt. Röntgenkristallographische Untersuchungen an \(\textbf{8}\) zeigen bei D\(_\text{2h}\)-Symmetrie einen über einen weiten Temperaturbereich stabilen low-spin/high-spin Zustand der beiden Cobaltionen. Dies alleine ist für Cobaltionen nach bisherigem Kenntnisstand einzigartig. \(\textbf{8}\) ist zudem die erste Verbindung, in welcher diese Begebenheiten mit einem direkt an die Metallzentren koordinierten Radikalbrückenliganden kombiniert vorliegen. Der low-spin/high-spin Zustand wurde weiterhin durch EXAFS- und XANES-Messungen verifiziert. Mit der Verbindung [{Co(L-N\(_\text{4}\)Me\(_\text{2}\))}\(_\text{2}\)(μ-Ph\(_\text{2}\)bpym\(^\text{●}\))](ClO\(_\text{4}\))\(_\text{3}\) (\(\textbf{10}\)) wurde eine weitere radikalverbrückte Verbindung synthetisiert, in der beide Cobaltionen bei identischer Koordinationsumgebung über einen weiten Temperaturbereich in unterschiedlichem Spinzustand vorliegen. SQUID-magnetometrische Untersuchungen an \(\textbf{8}\) und \(\textbf{10}\) zeigen, dass in beiden Verbindungen die low-spin Cobaltionen moderat ferro-, die high-spin Cobaltionen stark antiferromagnetisch mit der jeweiligen Radikalbrücke koppeln, was in beiden Fällen zu einem S = 3/2 Grundzustand führt. Der S = 3/2 Grundzustand wurde ebenfalls durch X-Band-ESR-Spektroskopie bestätigt. In \(\textbf{8}\) und \(\textbf{10}\) konnte jeweils ein Spincrossover des low-spin Cobaltions zum high-spin Zustand festgestellt werden. Dieser wurde mittels XRD-Analytik und SQUID-Magnetometrie für beide Verbindungen und für \(\textbf{8}\) zusätzlich durch EXAFS-Messungen, XANES-Messungen und temperaturabhängige IR-Spektroskopie nachgewiesen. Die Spincrossovereigenschaften sind zusammen mit den anderen vorgenannten Eigenschaften dieser neuen zweikernigen Cobaltverbindungsklasse ein weiteres Alleinstellungsmerkmal. Die einkernigen Referenzverbindungen [Co(L-N\(_\text{4}\)Me\(_\text{2}\))(bpym)](ClO\(_\text{4}\))\(_\text{2}\) (\(\textbf{9a}\)) und [Co(L-N\(_\text{4}\)Me\(_\text{2}\))(Ph\(_\text{2}\)bpym)](ClO\(_\text{4}\))\(_\text{2}\) ∙ MeCN (\(\textbf{11}\)) zeigen jeweils ebenfalls Spincrossovereigenschaften, was mittels SQUID-Magnetometrie und im Fall von \(\textbf{11}\) zusätzlich durch XRD-Analytik und temperaturabhängige IR-Spektroskopie nachgewiesen wurde. In \(\textbf{12}\) liegen beide Eisenionen im low-spin Zustand vor. Dies wurde röntgenkristallographisch und mittels Mößbauer-Spektroskopie bestätigt. X-Band-ESR-spektroskopisch wird ein Signal einer S = 1/2 Spezies gefunden, welches durch das brückenligandzentrierte Radikal hervorgerufen wird.
The scientific and industrial interest devoted to polymer/layered silicate
nanocomposites due to their outstanding properties and novel applications resulted
in numerous studies in the last decade. They cover mostly thermoplastic- and
thermoset-based systems. Recently, studies in rubber/layered silicate
nanocomposites were started, as well. It was presented how complex maybe the
nanocomposite formation for the related systems. Therefore the rules governing their
structure-property relationships have to be clarified. In this Thesis, the related
aspects were addressed.
For the investigations several ethylene propylene diene rubbers (EPDM) of polar and
non-polar origin were selected, as well as, the more polar hydrogenated acrylonitrile
butadiene rubber (HNBR). The polarity was found to be beneficial on the
nanocomposite formation as it assisted to the intercalation of the polymer chains
within the clay galleries. This favored the development of exfoliated structures.
Finding an appropriate processing procedure, i.e. compounding in a kneader instead
of on an open mill, the mechanical performance of the nanocomposites was
significantly improved. The complexity of the nanocomposite formation in
rubber/organoclay system was demonstrated. The deintercalation of the organoclay
observed, was traced to the vulcanization system used. It was evidenced by an
indirect way that during sulfur curing, the primary amine clay intercalant leaves the
silicate surface and migrates in the rubber matrix. This was explained by its
participation in the sulfur-rich Zn-complexes created. Thus, by using quaternary
amine clay intercalants (as it was presented for EPDM or HNBR compounds) the
deintercalation was eliminated. The organoclay intercalation/deintercalation detected
for the primary amine clay intercalants, were controlled by means of peroxide curing
(as it was presented for HNBR compounds), where the vulcanization mechanism
differs from that of the sulfur curing.
The current analysis showed that by selecting the appropriate organoclay type the
properties of the nanocomposites can be tailored. This occurs via generating different
nanostructures (i.e. exfoliated, intercalated or deintercalated). In all cases, the
rubber/organoclay nanocomposites exhibited better performance than vulcanizates
with traditional fillers, like silica or unmodified (pristine) layered silicates.The mechanical and gas permeation behavior of the respective nanocomposites
were modelled. It was shown that models (e.g. Guth’s or Nielsen’s equations)
developed for “traditional” vulcanizates can be used when specific aspects are taken
into consideration. These involve characteristics related to the platy structure of the
silicates, i.e. their aspect ratio after compounding (appearance of platelet stacks), or
their orientation in the rubber matrix (order parameter).
Benzene is a natural constituent of crude oil and a product of incomplete combustion of petrol
and has been classified as “carcinogenic to humans” by IARC in 1982 (IARC 1982). (E,E)-
Muconaldehyde has been postulated to be a microsomal metabolite of benzene in vitro
(Latriano et al. 1986). (E,E)-Muconaldehyde is hematotoxic in vivo and its role in the
hematotoxicity of benzene is unclear (Witz et al. 1985).
We intended to ascertain the presence of (E,E)-muconaldehyde in vivo by detection of a
protein conjugate deriving from (E,E)-muconaldehyde.
Therefore we improved the current synthetic access to (E,E)-muconaldehyde. (E,E)-
muconaldehyde was synthesized in three steps starting from with (E,E)-muconic acid in an
overall yield of 60 %.
Reaction of (E,E)-muconaldehyde with bovine serum albumin resulted in formation of a
conjugate which was converted upon addition of NaBH4 to a new species whose HPLC-
retention time, UV spectra, Q1 mass and MS2 spectra matched those of the crude reaction
product from one pot conversion of Ac-Lys-OMe with (E,E)-muconaldehyde in the presence
of NaBH4 and subsequent cleavage of protection groups.
Synthetic access to the presumed structure (S)-2-ammonio-6-(((E,E)-6-oxohexa-2,4-dien-1-
yl)amino)hexanoate (Lys(MUC-CHO)) was provided in eleven steps starting from (E,E)-
muconic acid and Lys(Z)-OtBu*HCl in 2 % overall yield. Additionally synthetic access to
(S)-2-ammonio-6-(((E,E)-6-hydroxyhexa-2,4-dien-1-yl)amino)hexanoate (Lys(MUC-OH))
and (S)-2-ammonio-6-((6-hydroxyhexyl)amino)hexanoate (IS) was provided.
With synthetic reference material at hand, the presumed structure Lys(MUC-OH) could be
identified from incubations of (E,E)-muconaldehyde with bovine serum albumin via HPLC-ESI+-
MS/MS.
Cytotoxicity analysis of (E,E)-muconaldehyde and Lys(MUC-CHO) in human promyelocytic
NB4 cells resulted in EC50 ≈ 1 μM for (E,E)-muconaldehyde. Lys(MUC-CHO) did not show
any additional cytotoxicity up to 10 μM.
B6C3F1 mice were exposed to 0, 400 and 800 mg/kg b.w. benzene to examine the formation
of Lys(MUC-OH) in vivo. After 24 h mice were sacrificed and serum albumin was isolated.
Analysis for Lys(MUC-OH) has not been performed in this work.
Collaboration aims to increase the efficiency of problem solving and decision making by bringing diverse areas of expertise together, i.e., teams of experts from various disciplines, all necessary to come up with acceptable concepts. This dissertation is concerned with the design of highly efficient computer-supported collaborative work involving active participation of user groups with diverse expertise. Three main contributions can be highlighted: (1) the definition and design of a framework facilitating collaborative decision making; (2) the deployment and evaluation of more natural and intuitive interaction and visualization techniques in order to support multiple decision makers in virtual reality environments; and (3) the integration of novel techniques into a single proof-of-concept system.
Decision making processes are time-consuming, typically involving several iterations of different options before a generally acceptable solution is obtained. Although, collaboration is an often-applied method, the execution of collaborative sessions is often inefficient, does not involve all participants, and decisions are often finalized with- out the agreement of all participants. An increasing number of computer-supported cooperative work systems (CSCW) facilitate collaborative work by providing shared viewpoints and tools to solve joint tasks. However, most of these software systems are designed from a feature-oriented perspective, rather than a human-centered perspective and without the consideration of user groups with diverse experience and joint goals instead of joint tasks. The aim of this dissertation is to bring insights to the following research question: How can computer-supported cooperative work be designed to be more efficient? This question opens up more specific questions like: How can collaborative work be designed to be more efficient? How can all participants be involved in the collaboration process? And how can interaction interfaces that support collaborative work be designed to be more efficient? As such, this dissertation makes contributions in:
1. Definition and design of a framework facilitating decision making and collaborative work. Based on examinations of collaborative work and decision making processes requirements of a collaboration framework are assorted and formulated. Following, an approach to define and rate software/frameworks is introduced. This approach is used to translate the assorted requirements into a software’s architecture design. Next, an approach to evaluate alternatives based on Multi Criteria Decision Making (MCDM) and Multi Attribute Utility Theory (MAUT) is presented. Two case studies demonstrate the usability of this approach for (1) benchmarking between systems and evaluates the value of the desired collaboration framework, and (2) ranking a set of alternatives resulting from a decision-making process incorporating the points of view of multiple stake- holders.
2. Deployment and evaluation of natural and intuitive interaction and visualization techniques in order to support multiple diverse decision makers. A user taxonomy of industrial corporations serves to create a petri network of users in order to identify dependencies and information flows between each other. An explicit characterization and design of task models was developed to define interfaces and further components of the collaboration framework. In order to involve and support user groups with diverse experiences, smart de- vices and virtual reality are used within the presented collaboration framework. Natural and intuitive interaction techniques as well as advanced visualizations of user centered views of the collaboratively processed data are developed in order to support and increase the efficiency of decision making processes. The smartwatch as one of the latest technologies of smart devices, offers new possibilities of interaction techniques. A multi-modal interaction interface is provided, realized with smartwatch and smartphone in full immersive environments, including touch-input, in-air gestures, and speech.
3. Integration of novel techniques into a single proof-of-concept system. Finally, all findings and designed components are combined into the new collaboration framework called IN2CO, for distributed or co-located participants to efficiently collaborate using diverse mobile devices. In a prototypical implementation, all described components are integrated and evaluated. Examples where next-generation network-enabled collaborative environments, connected by visual and mobile interaction devices, can have significant impact are: design and simulation of automobiles and aircrafts; urban planning and simulation of urban infrastructure; or the design of complex and large buildings, including efficiency- and cost-optimized manufacturing buildings as task in factory planning. To demonstrate the functionality and usability of the framework, case studies referring to factory planning are demonstrated. Considering that factory planning is a process that involves the interaction of multiple aspects as well as the participation of experts from different domains (i.e., mechanical engineering, electrical engineering, computer engineering, ergonomics, material science, and even more), this application is suitable to demonstrate the utilization and usability of the collaboration framework. The various software modules and the integrated system resulting from the research will all be subjected to evaluations. Thus, collaborative decision making for co-located and distributed participants is enhanced by the use of natural and intuitive multi-modal interaction interfaces and techniques.
Due to their superior weight-specific mechanical properties, carbon fibre epoxy composites (CFRP) are commonly used in aviation industry. However, their brittle failure behaviour limits the structural integrity and damage tolerance in case of impact (e.g. tool drop, bird strike, hail strike, ramp collision) or crash events. To ensure sufficient robustness, a minimum skin thickness is therefore prescribed for the fuselage, partially exceeding typical service load requirements from ground or flight manoeuvre load cases. A minimum skin thickness is also required for lightning strike protection purposes and to enable state-of-the-art bolted repair technology. Furthermore, the electrical conductivity of CFRP aircraft structures is insufficient for certain applications; additional metal components are necessary to provide electrical functionality (e.g. metal meshes on the outer skin for lightning strike protection, wires for electrical bonding and grounding, overbraiding of cables to provide electromagnetic shielding). The corresponding penalty weights compromise the lightweight potential that is actually given by the structural performance of CFRP over aluminium alloys.
Former research attempts tried to overcome these deficits by modifying the resin system (e.g. by addition of conductive particles or toughening agents) but could not prove sufficient enhancements. A novel holistic approach is the incorporation of highly conductive and ductile continuous metal fibres into CFRP. The basic idea of this hybrid material concept is to take advantage of both the electrical and mechanical capabilities of the integrated metal fibres in order to simultaneously improve the electrical conductivity and the damage tolerance of the composite. The increased density of the hybrid material is over-compensated by omitting the need for additional electrical system installation items and by the enhanced structural performance, enabling a reduction of the prescribed minimum skin thickness. Advantages over state-of-the-art fibre metal laminates mainly arise from design and processing technology aspects.
In this context, the present work focuses on analysing and optimising the structural and electrical performance of such hybrid composites with shares of metal fibres up to 20 vol.%. Bundles of soft-annealed austenitic steel or copper cladded low carbon steel fibres with filament diameters of 60 or 63 µm are considered. The fibre bundles are distinguished by high elongation at break (32 %) and ultimate tensile strength (900 MPa) or high electrical conductivity (2.4 × 10^7 S/m). Comprehensive researches are carried out on the fibre bundles as well as on unidirectional and multiaxial laminates. Both hybrid composites with homogeneous and accumulated steel fibre arrangement are taken into account. Electrical in-plane conductivity, plain tensile behaviour, suitability for bolted joints as well as impact and perforation performance of the composite are analysed. Additionally, a novel non-destructive testing method based on measurement of deformation-induced phase transformation of the metastable austenitic steel fibres is discussed.
The outcome of the conductivity measurements verifies a correlation of the volume conductivity of the composite with the volume share and the specific electrical resistance of the incorporated metal fibres. Compared to conventional CFRP, the electrical conductivity in parallel to the fibre orientation can be increased by one to two orders of magnitude even for minor percentages of steel fibres. The analysis, however, also discloses the challenge of establishing a sufficient connection to the hybrid composite in order to entirely exploit its electrical conductivity.
In case of plain tensile load, the performance of the hybrid composite is essentially affected by the steel fibre-resin-adhesion as well as the laminate structure. Uniaxial hybrid laminates show brittle, singular failure behaviour. Exhaustive yielding of the embedded steel fibres is confined to the arising fracture gap. The high transverse stiffness of the isotropic metal fibres additionally intensifies strain magnification within the resin under transverse tensile load. This promotes (intralaminar) inter-fibre-failure at minor composite deformation. By contrast, multiaxial hybrid laminates exhibit distinctive damage evolution. After failure initiation, the steel fibres extensively yield and sustain the load-carrying capacity of angularly (e.g. ±45°) aligned CFRP plies. The overall material response is thus not only a simple superimposition but a complex interaction of the mechanical behaviour of the composite’s constituents. As a result of this post-damage performance, an ultimate elongation of over 11 % can be proven for the hybrid laminates analysed in this work. In this context, the influence of the steel fibre-resin adhesion on the failure behaviour of the hybrid composite is explicated by means of an analytical model. Long term exposure to corrosive media has no detrimental effect on the mechanical performance of stainless steel fibre reinforced composites. By trend, water uptake increases the maximum elongation at break of the hybrid laminate.
Moreover, the suitability of CFRP for bolted joints can partially be improved by the integration of steel fibres. While the bearing strength basically remains nearly unaffected, the bypass failure behaviour (ε_{max}: +363 %) as well as the head pull-through resistance (E_{a,BPT}: +81 %) can be enhanced. The improvements primarily concern the load-carrying capacity after failure initiation. Additionally, the integrated ductile steel fibres significantly increase the energy absorption capacity of the laminate in case of progressive bearing failure by up to 63 %.
However, the hybrid composite exhibits a sensitive low velocity/low mass impact behaviour. Compared to conventional CFRP, the damage threshold load of very thin hybrid laminates is lower, making them prone for delamination at minor, non-critical impact energies. At higher energy levels, however, the impact-induced delamination spreads less since most of the impact energy is absorbed by yielding of the ductile metal fibres instead of crack propagation. This structural advantage compared to CFRP gains in importance with increasing impact energy. The plastic deformation of the metastable austenitic steel fibres is accompanied by a phase transformation from paramagnetic γ-austenite to ferromagnetic α’-martensite. This change of the magnetic behaviour can be used to detect and evaluate impacts on the surface of the hybrid composite, which provides a simple non-destructive testing method. In case of low velocity/high mass impact, integration of ductile metal fibres into CFRP enables to address spacious areas of the laminate for energy absorption purposes. As a consequence, the perforation resistance of the hybrid composite is significantly enhanced; by addition of approximately 20 vol.% of stainless steel fibres, the perforation strength can be increased by 61 %, while the maximum energy absorption capacity rises by 194 %.
Due to the steadily growing flood of data, the appropriate use of visualizations for efficient data analysis is as important today as it has never been before. In many application domains, the data flood is based on processes that can be represented by node-link diagrams. Within such a diagram, nodes may represent intermediate results (or products), system states (or snapshots), milestones or real (and possibly georeferenced) objects, while links (edges) can embody transition conditions, transformation processes or real physical connections. Inspired by the engineering sciences application domain and the research project “SinOptiKom: Cross-sectoral optimization of transformation processes in municipal infrastructures in rural areas”, a platform for the analysis of transformation processes has been researched and developed based on a geographic information system (GIS). Caused by the increased amount of available and interesting data, a particular challenge is the simultaneous visualization of several visible attributes within one single diagram instead of using multiple ones. Therefore, two approaches have been developed, which utilize the available space between nodes in a diagram to display additional information.
Motivated by the necessity of appropriate result communication with various stakeholders, a concept for a universal, dashboard-based analysis platform has been developed. This web-based approach is conceptually capable of displaying data from various data sources and has been supplemented by collaboration possibilities such as sharing, annotating and presenting features.
In order to demonstrate the applicability and usability of newly developed applications, visualizations or user interfaces, extensive evaluations with human users are often inevitable. To reduce the complexity and the effort for conducting an evaluation, the browser-based evaluation framework (BREF) has been designed and implemented. Through its universal and flexible character, virtually any visualization or interaction running in the browser can be evaluated with BREF without any additional application (except for a modern web browser) on the target device. BREF has already proved itself in a wide range of application areas during the development and has since grown into a comprehensive evaluation tool.
A fast numerical method for an advanced electro-chemo-mechanical model is developed which is able to capture phase separation processes in porous materials. This method is applied to simulate lithium-ion battery cells, where the complex microstructure of the electrodes is fully resolved. The intercalation of ions into the popular cathode material LFP leads to a separation into lithium-rich and lithium-poor phases. The large concentration gradients result in high mechanical stresses. A phase-field method applying the Cahn-Hilliard equation is used to describe the diffusion. For the sake of simplicity, the linear elastic case is considered. Numerical tests for fully resolved three-dimensional granular microstructures are discussed in detail.
In this thesis we integrate discrete dividends into the stock model, estimate
future outstanding dividend payments and solve different portfolio optimization
problems. Therefore, we discuss three well-known stock models, including
discrete dividend payments and evolve a model, which also takes early
announcement into account.
In order to estimate the future outstanding dividend payments, we develop a
general estimation framework. First, we investigate a model-free, no-arbitrage
methodology, which is based on the put-call parity for European options. Our
approach integrates all available option market data and simultaneously calculates
the market-implied discount curve. We illustrate our method using stocks
of European blue-chip companies and show within a statistical assessment that
the estimate performs well in practice.
As American options are more common, we additionally develop a methodology,
which is based on market prices of American at-the-money options.
This method relies on a linear combination of no-arbitrage bounds of the dividends,
where the corresponding optimal weight is determined via a historical
least squares estimation using realized dividends. We demonstrate our method
using all Dow Jones Industrial Average constituents and provide a robustness
check with respect to the used discount factor. Furthermore, we backtest our
results against the method using European options and against a so called
simple estimate.
In the last part of the thesis we solve the terminal wealth portfolio optimization
problem for a dividend paying stock. In the case of the logarithmic utility
function, we show that the optimal strategy is not a constant anymore but
connected to the Merton strategy. Additionally, we solve a special optimal
consumption problem, where the investor is only allowed to consume dividends.
We show that this problem can be reduced to the before solved terminal wealth
problem.
Sandwichelemente aus Stahlbeton genügen zahlreichen Ansprüchen hinsichtlich
energetischer, wirtschaftlicher, architektonischer und gestalterischer Gesichtspunkte
sowie tragfähiger Konstruktionen. Neben Sandwichwänden können Sandwichelemente auch als biegebeanspruchte Bauteile wie Sandwichdecken oder Sandwichdächer eingesetzt werden. Das große Potential solcher Elemente kann jedoch aufgrund
fehlender Kenntnisse bezüglich des Last-Verformungs-Verhaltens bisher nicht ausgeschöpft werden.
Das Tragverhalten von Stahlbetonsandwichelementen wird maßgeblich durch die
Rissbildung in den Betonschichten beeinflusst. Während die Berücksichtigung der
Rissbildung beispielsweise bei der Verformungsberechnung von biegebeanspruchten
Stahlbetonbauteilen schon intensiv erforscht wurde und realitätsnah beschrieben werden kann, steht die Entwicklung einer abschnittsweisen Berücksichtigung der reduzierten Dehn- und Biegesteifigkeiten infolge der Rissbildung für biegebeanspruchte Sandwichelemente aufgrund der höheren Komplexität noch am Anfang. Bisher existieren
nur Modelle, die die Rissbildung im Beton von Sandwichelementen für die Berechnung
der Teilschnittgrößen und der Verformung näherungsweise berücksichtigen. Die Anwendung dieser Rissmodelle ist aber aufgrund verschiedener Annahmen und Vereinfachungen, die diesen Modellen zugrunde liegen, für die in dieser Arbeit untersuchten
Sandwichelemente mit Stahlbetontragschichten nicht geeignet.
Mithilfe eines realitätsnahen Ansatzes zur Bestimmung des Schubmoduls eines
Dämmstoffes, der Auswahl eines geeigneten Verfahrens zur Berechnung des Last-
Verformungs-Verhaltens eines Stahlbetonbauteils einschließlich der Berücksichtigung
der Rissbildung sowie eines Modellvorschlags zur Nachrechnung der Schubversuche
an Sandwichelementen wird ein eigenes Ingenieurmodell zur Nachrechnung des Last-
Verformungs-Verhaltens von biegebeanspruchten Sandwichelementen entwickelt.
Aufbauend auf diesem Ingenieurmodell erfolgt die Erstellung eines Berechnungswerkzeuges. Anhand der Nachrechnung zahlreicher Versuchsergebnisse kann gezeigt
werden, dass mit diesem Berechnungswerkzeug eine sehr gute Übereinstimmung der
rechnerisch ermittelten mit den im Versuch bestimmten Last-Verformungs-Kurven erzielt werden kann. Das neue Ingenieurmodell berücksichtigt sowohl die reduzierten
Dehn- und Biegesteifigkeiten infolge der Rissbildung als auch abschnittsweise unterschiedlich große Schubsteifigkeiten der Kernschicht, die sich aus der Anordnung von
stiftförmigen Verbundmitteln ergeben.
Basierend auf dem Ingenieurmodell sowie den umfangreichen experimentellen Untersuchungen zum Last-Verformungs-Verhalten von Sandwichelementen wird ein Berechnungswerkzeug sowie ein Bemessungskonzept für Stahlbetonsandwichelemente
mit stiftförmigen Verbundmitteln vorgestellt. Damit konnte ein Fortschritt erzielt und die
Grundlage für den Einsatz von Sandwichelementen mit Stahlbetontragschichten sowie
einer Kernschicht aus Dämmstoffplatten und stiftförmigen Verbundmitteln gelegt werden.
In this thesis, we deal with the finite group of Lie type \(F_4(2^n)\). The aim is to find information on the \(l\)-decomposition numbers of \(F_4(2^n)\) on unipotent blocks for \(l\neq2\) and \(n\in \mathbb{N}\) arbitrary and on the irreducible characters of the Sylow \(2\)-subgroup of \(F_4(2^n)\).
S. M. Goodwin, T. Le, K. Magaard and A. Paolini have found a parametrization of the irreducible characters of the unipotent subgroup \(U\) of \(F_4(q)\), a Sylow \(2\)-subgroup of \(F_4(q)\), of \(F_4(p^n)\), \(p\) a prime, for the case \(p\neq2\).
We managed to adapt their methods for the parametrization of the irreducible characters of the Sylow \(2\)-subgroup for the case \(p=2\) for the group \(F_4(q)\), \(q=p^n\). This gives a nearly complete parametrization of the irreducible characters of the unipotent subgroup \(U\) of \(F_4(q)\), namely of all irreducible characters of \(U\) arising from so-called abelian cores.
The general strategy we have applied to obtain information about the \(l\)-decomposition numbers on unipotent blocks is to induce characters of the unipotent subgroup \(U\) of \(F_4(q)\) and Harish-Chandra induce projective characters of proper Levi subgroups of \(F_4(q)\) to obtain projective characters of \(F_4(q)\). Via Brauer reciprocity, the multiplicities of the ordinary irreducible unipotent characters in these projective characters give us information on the \(l\)-decomposition numbers of the unipotent characters of \(F_4(q)\).
Sadly, the projective characters of \(F_4(q)\) we obtained were not sufficient to give the shape of the entire decomposition matrix.
Wird Rotwein im Holzfass gelagert, kommt es meist zu einer Intensivierung und Stabilisierung der Weinfarbe. Ursache ist der durch die Fassdauben diffundierende Sauerstoff, der Ethanol zu Acetaldehyd oxidiert. Dieses bildet Ethylidenbrücken zwischen Anthocyanen und Flavanolen, wodurch intensiv violett gefärbte Pigmente entstehen. Bisher wurden nur die dimeren ethyliden-verbrückten Anthocyan-Flavanol Addukte umfassend erforscht, die jedoch im Wein nicht stabil sind und zu Folgeprodukten reagieren. Deren Struktur ist bisher wenig erforscht. Ein Ziel dieser Arbeit bestand daher darin, die Reaktionsprodukte der ethyliden-verbrückten Anthocyan-Flavanol Dimere im Rotwein zu untersuchen. Dabei wurden erstmals Polyphenoladdukte mit bis zu drei Ethylidenbrücken massenspektrometrisch nachgewiesen. Dies zeigt, dass Weinpigmente durch die Bildung mehrerer Ethylidenbrücken polymerisieren können. Es wurden außerdem mehrere Pigmente gefunden, bei denen ein Anthocyan über zwei Ethylidenbrücken mit anderen Polyphenolen verbunden war. Dies widerlegt die bisherige Annahme, dass sich Anthocyane nur in terminalen Positionen eines polymeren Pigments befinden können. Durch die Quantifizierung ethyliden-verbrückter Di- und Trimere mittels Massenspektrometer wurde deutlich, dass diese Pigmente in höheren Konzentrationen im Rotwein vorliegen als bisher publiziert. Es zeigte sich außerdem, dass bis zu 50 % der durch den Sauerstoff bewirkten Abnahme von Anthocyanen und Flavanolen auf die Bildung ethyliden-verbrückter Di- und Trimere, sowie Vitisin B zurückführen lassen.
Heute werden in der Weinbereitung häufig Edelstahltanks eingesetzt, bei denen es, anders als in Holzfässern, kaum zu Sauerstoffeinträgen kommt. Eine Farbstabilisierung kann somit nicht stattfinden. Dem Rotwein können stattdessen durch das Verfahren der Mikrooxygenierung geringe Mengen Sauerstoff kontrolliert zugesetzt werden. Bei manchen Weinen führt dies jedoch zu einer verringerten Farbintensität statt zu einer Farbvertiefung. Anhand der insgesamt 21 im Rahmen dieser Arbeit untersuchten Weine zeigte sich, dass Sauerstoff nur dann zu einer intensiveren Weinfarbe führt, wenn das Verhältnis von Tanninen zu Anthocyanen (TAV) unter einem Wert von 3 lag. Die Zunahme der Farbintensität war außerdem negativ mit den spektralphotometrisch zu bestimmenden kleinen (SPP) und großen polymeren Pigmenten (LPP) korreliert, sodass Sauerstoff nur bei geringen Konzentrationen dieser Pigmente zu höheren Farbintensitäten führte. Zudem wurde während der Mikrooxygenierung keine weitere Intensivierung der Weinfarbe erzielt, wenn der Gehalt der LPP den der SPP überstieg. Da LPP aufgrund ihrer Molekülgröße auch eine geringere Löslichkeit aufweisen, sollte ihre übermäßige Bildung vermieden werden. Die Bestimmung von TAV, SPP und LPP erlaubt es somit, die Wirkung von Sauerstoff auf die Weinfarbe vor der Anwendung der Mikrooxygenierung einschätzen und den Sauerstoffzusatz zu beenden, wenn aufgrund der analytischen Daten eine weitere Steigerung der Farbintensität nicht zu erwarten ist.
In einem weiteren Teil der Arbeit wurde untersucht, wie sich die Mikrooxygenierung auf die Lagerfähigkeit der Rotweine auswirkt, da Sauerstoff zu einer beschleunigten Reifung führen kann. Dabei zeigte sich, dass die Farbe des mikrooxygenierten Weines auch nach einer 12-monatigen Flaschenlagerung noch stabiler war als in der entsprechenden Kontrollvariante und der Effekt damit nachhaltig. In Geruch und Geschmack unterschied sich der mikrooxygenierte Wein hingegen nicht von der Kontrolle. Mikrooxygenierte Weine sind damit ebenso lagerfähig, wie ohne Sauerstoffzugabe erzeugte Weine.