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Item Open Access Towards spin injection into silicon(2007) Dash, Saroj Prasad; Carstanjen, Heinz Dieter (Prof. Dr.)The efficient spin injection into semiconductors could pave the way to a new generation of electronics devices such as spin memories, spin transistors, and spin quantum computers. The most important semiconductor for industrial application, Si has been studied for the purpose of spin injection extensively in this thesis. Three different concepts for spin injection into Si have been addressed: (1) spin injection through a ferromagnet-Si Schottky contact, (2) spin injection using MgO tunnel barriers in between the ferromagnet and Si, and (3) spin injection from Mn-doped Si (DMS) as spin aligner. (1) FM-Si Schottky contact for spin injection: In a heterostructure of a ferromagnetic thin film on a Si substrate, any structural disorder at the interface would drastically reduce the spin polarization at the interface and, hence, the spin injection efficiency. To be able to improve the interface qualities one needs to understand the atomic processes involved in the formation of such silicide phases. In order to obtain more detailed insight into the formation of such silicide phases the initial stages of growth of Co and Fe were studied in situ by HRBS with monolayer depth resolution. As understood, it was important to prohibit the in-diffusion of Co into interstitial sites at the initial stages of growth and the out-diffusion of Si atoms in the latter stages. So in order to control and improve the interface, equilibrium growth conditions were followed (i) by lowering the growth temperature and (ii) by surfactant-mediated growth. Low temperature growth of Co on Si (100): Already at very low coverage Co diffusion into the bulk Si has been observed. The amount of in-diffused Co is, however, less than at room temperature. In contradiction to room temperature growth, Co atoms form layers of pure Co on top of the Si surface already at very low coverage. Every second Si layer, starting with the first Si layer, is Co depleted. This leads to an oscillatory Co distribution in the Si lattice which is preserved up to higher coverages (1.3 ML). Surfactant-mediated growth of Co on Si (100) : The lower surface free energy of Sb in comparison to Co and Si, makes it a potential candidate for surfactant mediated growth. By the use of one monolayer of Sb adsorbed on a Si (100) surface, Co-Si intermixing at the interface is strongly reduced in comparison to the interface without Sb as surfactant. The improved interface quality with Sb-mediated growth is also reflected in magnetic measurements. Co with Sb-mediated growth shows a higher magnetic moment. It was shown that simple solutions can reduce the FM-Si inter diffusion at the interface and improve the interface quality. However these non-equilibrium growth conditions could not stop the silicide formation completely. (2) MgO tunnel barrier for spin injection into Si: On the other hand, using an ultra-thin tunnel barrier between FM and Si will have three advantages: (i) form a chemical barrier between the FM and Si, (ii) circumvent the conductivity mismatch problem, and (iii) in addition act as a spin filter. The fabrication and characterization of ultra-thin crystalline MgO tunnel barriers on Si (100) was presented. Some of the important properties required for tunnel barriers on Si have been addressed. Ultra-thin stoichiometric MgO tunnel barriers with sharp interface with Si (100), very homogeneous, without pin-holes, and crystalline in structure could be fabricated by reactive molecular beam epitaxy. Co and Fe on an ultra thin MgO tunnel barrier were found to have island-like growth with a rough surface. Ultra-thin Co and Fe films are found to be thermally quite stable up to 450 °C. (3) Mn doped Si for spin injection: For spin injection purpose, instead of contacting the Si with a ferromagnetic metal, the contact could be made with another semiconductor, one with ferromagnetic properties. This solves the conductivity mismatch problem by ensuring that the resistivities of the materials on both side of the interface are comparable in magnitude. Si-based diluted magnetic semiconductor samples were prepared by doping Si with Mn by two different methods i) by Mn ion implantation and ii) by in-diffusion of Mn atoms (solid state growth). In the case of implanted samples, Mn atoms do not substitute Si sites. The implanted samples show room temperature ferromagnetism as measured by a SQUID magnetometer. The magnetic moment per Mn atom is found to decrease with increasing implantation dose. It has been observed that the implanted samples show carrier mediated ferromagnetism and, more importantly, mediated by both holes and electrons in contrast to statements in the literature. Solid state growth of Mn doped Si : For evaporation of Mn on Si (100), Mn atoms diffuse deep into the Si bulk already at room temperature, even for very low coverage (0.25 ML) with an oscillatory concentration depth profile as observed by HRBS with monolayer depth resolution. This results in natural MnxSi1-x/Si digital layers on the surface. Surprisingly, the samples prepared by this solid state diffusion process show room-temperature ferromagnetism having a magnetic moment of 1.8 µB per Mn atom, which is much higher than that of the ion-implanted samples. In contrast to ion-implanted samples the ferromagnetism in these samples does not show any carrier mediation.Item Open Access Funktionalmethoden und Abbildungen dissipativer Quantensysteme(2007) Baur, Holger; Weiß, Ulrich (Prof. Dr.)Im ersten Abschnitt dieser Arbeit versuchen wir, die algebraische Struktur, welche im Rahmen der dissipativen Quantenmechanik unter Verwendung des Influenzfunktionals auftritt, herauszuarbeiten. Dies erlaubt uns einen tieferen Einblick in ansonsten unübersichtliche und langwierige Rechenschritte, speziell im Realzeitformalismus, und ermöglicht uns eine leichtere Identifikation der dabei auftretenden Terme und deren Ursprung aus dem zugrunde liegenden Modell als auch deren physikalische Bedeutung. Die verwendeten Methoden haben wir soweit als möglich in konsistenter und anschaulicher Form eingeführt, so dass diese Arbeit ohne spezielle Kenntnis des Gebietes der dissipativen Quantenmechanik gelesen werden kann. Besonderen Wert haben wir auf den Übergang von der quantenmechanischen auf die klassische Beschreibung von dissipativen Vorgängen gelegt, da ein Verständnis dieses Übergangs eine tiefere Einsicht in den Messprozess liefert. In der selben Weise ist damit auch der Übergang von der mikroskopischen - durch die Quantenmechanik beschriebenen - Welt in die makroskopische Welt verbunden, welche den Gesetzen der klassischen Mechanik folgt. Zusätzlich zeigen wir, wie die Resultate der Influenzfunktionalmethode stochastisch interpretiert werden können, was einen leichteren Vergleich mit der bekannten quantenmechanischen Zeitentwicklung durch die Schrödingergleichung erlaubt. Im weiteren betrachten wir die sogenannte Tight-Binding Näherung von Modellen, bei welchen sich der Hamiltonraum für die Systembeschreibung im wesentlichen durch diskrete Eigenzustände des Ortsoperators ausdrücken lässt und Übergänge zwischen diesen Zuständen unterdrückt sind, wodurch eine Propagation entweder durch ein Tunneln oder durch thermische Anregung erfolgt. Im Rahmen der dissipativen Quantenmechanik bringt diese Methode eine immense Vereinfachung in der effektiven Beschreibung des Systems, da Anstelle einer ganzen Historie von Systempfaden nur noch die Übergangszeiten mit den entsprechenden Übergängen berücksichtigt werden müssen. Im Bild des Pfadintegralformalismus bedeutet dies, dass Anstelle des Integrals über alle Systempfade ein Produkt von Integrationen über alle möglichen Sprungzeiten mit Sprunggewichten entsprechend des Übergangs rückt, welches analytisch als auch numerisch wesentlich einfacher handzuhaben ist. Innerhalb dieser Näherung wurden dadurch in der Vergangenheit viele beeindruckende analytische Resultate abgeleitet. Darüber hinaus beschäftigen wir uns mit der Abbildung und dem Zusammenhang von dissipativen Modellen mit Feldmodellen aus der Quantenfeldtheorie und im besonderen der Feldtheorie statistischer Systeme. Der Reiz dieser Abbildungen liegt besonders darin, dass in den letztgenannten Gebieten schon seit Jahrzehnten sehr intensiv die grundlegenden Modelle bearbeitet wurden und vor allem auch nach neuen Methoden gesucht und Forschung dafür betrieben wurde und noch immer Gegenstand der aktuellen Forschung darstellt. Als Beispiel sei in zwei Dimensionen die Invarianz unter konformen Abbildungen genannt, welche immer dann Anwendung findet, wenn Systeme nur lokal wechselwirken und eine Invarianz unter lokaler Umskalierung der Felder zeigen. Bei statistischen Systemen mit lokaler Wechselwirkung zeigt sich dieses Verhalten immer beim Erreichen eines kritischen Punktes, da hier per Definition keine Längenskala ausgezeichnet ist. In zwei Dimensionen führt dies zu einer immensen Einschränkung der möglichen Form von Korrelationsfunktionen und hat zu dem eigenständigen Gebiet der Konformen Feldtheorie geführt, da konforme Abbildungen per Definition die lokale Struktur erhalten (Winkeltreue) und lokal nur zu einer Unskalierung führen. Während in D>2 Dimensionen nur endlich viele Generatoren für konforme Abbildungen existieren, ist deren Anzahl in 2 Dimensionen unendlich. Dies resultiert in einer unendlichen Anzahl von lokalen Erhaltungsgrößen mit den entsprechenden Folgen. Während solche Techniken sehr schnell unanschaulich werden, erlaubt die Abbildung auf dissipative Modelle hier oftmals eine sehr anschauliche Interpretation.Item Open Access On the compatibility of the Braille code and universal grammar(2007) Lauenstein, Christine; Alexiadou, Artemis (Prof. Dr.)The central question of this work is to investigate whether there are structural elements of British Braille that are in conflict with language processes, i.e. whether the system of British Braille can be held responsible for poor spelling performance. Especially from the point of view of a print reader braille is a secondary system which requires many extra rules that have to be learnt. Thus it is easily considered more difficult. I do not wish to question the value of braille, whether it is used in contracted or uncontracted form. A detailed analysis of British Braille has shown that it is a seemingly arbitrary compilation of rules that is sensitive to language processes, the most important unit being the ortho-syllable as postulated by Primus (2003) and Weingarten (2004). In chapter 4 I have shown that the apparent compilation of arbitrary British Braille rules be restructured by the underlying implicit use it makes of word structure, most importantly the segmentation of ortho-syllables. This system is not a mere compilation of rules and lists that have to be learnt by rote. The analysis supports the assumption that cognitive processes are not the only possible route to contracted braille and that the way in which the rules of contracted braille have been compiled is far more problematic than the underlying system itself. Many braillists receive a dual education, learning to read and write contracted braille and use full spelling on computer keyboards. Millar (1997) argues that having two orthographic representations for the same letter groups may increase memory load in retrieval. This might indeed make spelling more difficult for braillists. I will focus on possible interferences from contracted braille with natural language without the additional difficulty of mastering full spelling on a computer keyboard. I adopt Millar's (1997) axiom that print and braille are identical in linguistics. Thus models and findings for print can be used for testing hypotheses in braille. Further support for access to language processes comes from a study on braille which I have developed to investigate whether there are structural elements of British Braille that inhibit writing performance. Thus the study is designed to reveal the interaction of braille contractions with natural language, in particular to investigate whether the bridging of syllable or morpheme boundaries by arbitrary contractions influences spelling performance. My study shows that former print readers have different error patterns with respect to both spelling errors and braille code errors than subjects who have no former functional use of print. Regarding the underlying linguistic processes, both groups of braillists show most errors in the categories gemination error and phonetic spelling. Whereas these errors are of equal frequency among the congenitally blind braillists, former print readers follow the pattern of the control group and produce approximately twice as many errors by phonetic spelling than gemination errors. The differing patterns in the group of spelling errors indicate that former knowledge of Standard English Orthography is a relevant factor in braille production. Former print readers have already established an orthographic system, which may interfere with contracted braille. Although there is a wide scope for individual variation within the data, some error patterns obtained in the data can only be explained as interference of those parts of British Braille which require an algorithmic process if the form is not already lexicalised. The resulting braille code errors show that print and braille operate with the same processes but use different underlying units at a subsyllabic level. Only former print readers are sensitive to characteristics of Standard English Orthography. However, both congenitally blind braillists and former print readers produce errors that show a stronger sensitivity for linguistic than for cognitive processes which contradicts the old saying that you need to be clever to learn braille! Both parts, the analysis of British Braille and the study, confirmed that there is an independent unit syllable in the writing system. Furthermore, braille and braillists are more sensitive to this unit than to phonological syllables and morphemes. Questioning the compatibility of braille and Universal Grammar, both the code analysis and the study show that braille takes linguistic units into account. There are very few instances in which braille prescribes rules that can only be accessed via cognitive processes. These rules tend to be ignored in favour of a form consistent with the linguistic structure of the target just as print reading children are insensitive to prescriptive rules in orthography (Weingarten 2004). Yet, there is an interference but it is not between linguistic principles and braille but between two orthographic systems: Standard English Orthography and contracted braille.Item Open Access Investigation of evapotranspiration concepts in hydrological modelling for climate change impact assessment(2007) Hartmann, Gabriele Maria; Bárdossy, András (Prof. Dr.-Ing. habil. Dr. rer. nat. )Climate change (CC) will impact water resources. Assessing the extent of these impacts in due time is an important task, as it forms the basis for decision making. Unfortunately, the extent of this forecasted impact depends very much on data and tools used for this task. Although such methods might work well with present climatic conditions, it has to be doubted whether their results can still be relied upon in a changed climate. The uncertainties in the forecasts are partly of meteorological and partly of hydrological origin. Whereas the uncertainties of GCMs are well known and often discussed, the problems of hydrological models in this context are seldom investigated. In particular the uncertainty in process representation within the hydrological models must be revised. This dissertation focuses on the representation of the evapotranspiration (ET) process, because this process will be strongly influenced by CC. For this purpose, the suitability of nine different ET models was investigated. In a theoretical investigation, the sensitivity of the ET models to only a small change in temperature was found to be very different. Thus the question had to be raised as to how the resulting ET from these models will change with the entire predicted CC. Therefore a spatially distributed hydrological model based on the HBV concept was set up and the results of the different ET models were used consecutively as input to the hydrological model. The modelling was applied on the Upper Neckar catchment, a mesoscale river in southwestern Germany with a basin size of about 4,000 km2. This catchment was divided into 13 subcatchments with different subcatchment characteristics. The suitability of the different ET approaches was checked by calibrating the hydrological model on different climatic periods and then applying the model on other climatic periods. Thus, different 10-year periods with different climatic conditions were compiled: 10 cold, 10 warm, 10 wet and 10 dry years from the time series 1961–1990 were collected. The first step was to adapt the model to the same period it was calibrated to. Then the model was applied to other 10 years, i.e. the model calibrated on for example, the cold years was used on the warm years. The transferability was also checked by applying the models on the period 1991–2000. For the investigation of the impact of CC, the calibration of the model must meet special requirements. Apart from the selection of proper periods for calibration and validation, this also concerns the establishment of a suitable objective function. Such a function is the Nash Sutcliffe efficiency. Usually it is calculated comparing observed and modelled daily values. In this study it is shown that problems in the transfer from one climatic condition to the other cannot be detected on the base of daily values. Therefore parameter sets were optimized by an automatic calibration procedure based on Simulated Annealing, which considered the model performance on different time scales simultaneously (days up to years). As the results show, some of the ET models, which work well under stationary conditions, are not able to reproduce changes in a realistic manner. The results also show that calibrating a hydrological model that is supposed to handle short as well as long term signals becomes an important task; the objective function especially has to be chosen very carefully.Item Open Access Using spin polarised positive muons for studying guest molecule partitioning in soft matter structures(2007) Martyniak-Stronczek, Aleksandra; Roduner, Emil (Prof. Dr.)The intention of this thesis is to explore the effect of guest molecules on the structure of diverse soft matter architectures, and thus the stability of the entire systems. More specifically, we focus on the determination of the factors that affect partitioning of fragrance components in emulsions and microemulsions, including various lyotropic liquid crystalline mesophases of cationic and anionic surfactants. It is well known that the most common fragrance materials are created based on the mixtures of aliphatic alcohols or/and phenyl alcohols. Until recently, however, qualitative and quantitative studies of the guest molecule partitioning into the surfactant membrane have been performed mostly for short, medium and long chain aliphatic alcohols. In consequence, in the literature arose a gap of information on the distribution of alcohols containing an aromatic group into colloidal surfactant dispersions. Hence, to fill at least partly this gap, the probes used in this work are muoniated cyclohexadienyl radicals derived from five different phenyl alcohols: 2-Phenylethan-1-ol (n = 2), 3-Phenylpropan-1-ol (n = 3), 4-Phenylbutan-1-ol (n = 4), 5-Phenylpentan-1-ol (n = 5) und Para-propyl-2-phenylethan-1-ol (n = 2 + 3). The variation of their hydrocarbon chain length (distinguished by the number, n, of CH2 groups in their hydrocarbon chain) changes their hydrophobicity, and this is expected to affect their partitioning between the aqueous and the hydrocarbon moiety of the surfactant dispersion, which is the main focus of the present study. Furthermore, a detailed understanding of solvation thermodynamic properties and reorientational dynamics of the chosen species, including Heisenberg spin exchange in order to confirm the interpretation of particular aspects, is also presented here. Common methods for the investigation of a variety of soft matter structures, such as spherical micelles, vesicles, lamellar, rectangular, hexagonal and cubic phases or bi-continuous sponge type structures include light, X-ray and neutron scattering, and measurements of calorimetric and rheological properties. Nuclear magnetic resonance is a powerful tool for the study of the dynamics of specific molecules or groups, or also of the entire structures. For the same purpose but with higher sensitivity, fluorescent dye molecules or spin labels are introduced as guests or bound to the amphiphile in specific positions, permitting optical spectroscopy (UV-Vis) or electron spin resonance studies, respectively. Technical applications may require other types of guest molecules to be introduced into these structures. Prominent examples are drug molecules for their delivery to specific sites in the body, or skin care, dyes and fragrance molecules in day care products or additives to food. They are often needed in low concentrations (because of the limited solubility or high toxicity, etc.) that makes it difficult to monitor them with conventional methods at a molecular level. For these reasons we used here a special experimental technique which permits highly sensitive spectroscopy, the Avoided Level Crossing Muon Spin Resonance (ALC-mSR). ALC-mSR relies on a unique property of the positive muon, i.e. where it becomes attached to a C=C double bond or phenyl group via addition of the muonium atom (Mu), which can be regarded as a light hydrogen isotope. Mu addition to unsaturated molecules produces radicals that contain the muon as a fully polarized spin label which reveals information about the structure, kinetics, distribution and solvation thermodynamics of such radicals even under extremely dilute conditions in different colloidal dispersions. Moreover, the high spin polarisation and the single particle counting technique make the muon an exceptionally sensitive probe. It has been already shown that ALC-mSR has so far found applications for the investigation of muonium-substituted free radicals in various environments, for example in the gas phase, in polymers, in liquid crystals, in zeolites, and also for Mu in semiconductors and for muons in metals. This time, however, to prove that this method is also suitable to apply in more complex (multicomponent) systems than described above, the ALC-mSR serves here as a tool for sensitive monitoring of the local environment and reorientational dynamics of muoniated radicals (kept at very low concentrations) in ternary and quaternary surfactant mixtures. Thus, it is a successive challenge of these studies to show that the muoniated radical can be treated as a spectator of the changes in the properties of diverse surfactant systems at a molecular level.Item Open Access In-situ radiation grafting of polymer films and degradation studies of monomers for applications in fuel cell membranes(2007) Mitov, Svetlin; Roduner, Emil (Prof. Dr.)The present work consists of three parts which deal with the optimization of the properties of polymers finding application as proton exchange membranes in PEMFCs. The focus is the oxidative and photochemical stability of non-fluorinated polymer membranes, as well as the radiation-induced grafting of commercially available fluoropolymer films. The use of the ESR technique is common for the first two parts of the dissertation. The third part comprises the results and discussions of DFT calculations for non-fluorinated and fluorinated fragments. In order to predict hydroxyl radical initiated degradation of new proton conducting polymer membranes based on sulfonated polyetherketones and polysulfones, five non-fluorinated aromatics (4,4'-sulfonyldiphenol, bisphenol A, 4,4'-diphenol, 4,'-dihydroxybenzophenone and sulfonated 4,4'-dichlorodiphenylsulfone) are chosen as model compounds for ESR experiments, aiming at the identification of products of HO· radical reactions with these monomers. Direct photolysis of aqueous solutions of H2O2 was chosen as the source of HO· radicals. In order to distinguish HO· radical attack from direct photolysis of the monomers, experiments were carried out in the presence and absence of H2O2. In the second part of the present work three different electron beam irradiated fluoropolymers - poly(ethylene-alt-tetrafluoroethylene), poly(tetrafluoroethylene-co-hexafluoropropylene) and poly(vinylidenefluoride), as well as their grafting reactions with styrene, 25% styrene in benzene and 25% styrene in ethanol are investigated by means of ESR. Firstly, it was possible to compare the radiation chemistry of the three fluoropolymers that have been irradiated using the same irradiation source, doses and atmospheres. Secondly, it was possible to compare the decay of radicals in the different fluoropolymers by carrying out in-situ ESR measurements in a similar systematic manner during the radiation grafting process, aiming at an understanding of the influence of the irradiation atmosphere and of the diluent. In addition, in the radiation grafting of polymer films with styrene for fuel cell applications it is important to control whether the polystyrene chain is grafted onto a peroxy or a carbon centered radical. Thus thermodynamic properties of small alkyl and alkyl-peroxy radicals are studied to model primary, secondary and tertiary radicals in non-fluorinated and perfluorinated polymers and a comparative DFT study is conducted. Furthermore, it is shown based on DFT calculations that pronounced spin polarization effects lead to unexpected behavior of the hyperfine anisotropy. This is demonstrated by comparison of the parameters of CF3·CF2, both in its fully optimized non-planar and in a forced planar conformation, with those of the analogous non-fluorinated and essentially planar CH3·CH2 radical. A B3LYP or UB3LYP hybrid functional and 6-311+G** or EPR-II basis sets are used, and all calculations are performed with the Gaussian package.Item Open Access Modellierung der Adhäsion und Deformation von Mikrokapseln(2007) Graf, Peter; Seifert, Udo (Prof. Dr.)Mikrokapseln spielen eine wichtige Rolle beim Einschluß und der kontrollierten Freisetzung von Substanzen sowohl in industriellen Anwendungen als auch in der Medizin und den Biowissenschaften. Sie dienen ebenso als Modellsysteme für biologische Objekte wie Zellen oder Viruskapseln. Bei vielen dieser Anwendungen sind gute Kenntnisse über die mechanischen Eigenschaften nötig. Typischerweise wird die Kapsel zu diesem Zweck verformt und die dazu benötigten Kräfte werden gemessen. Die Deformation kann auf verschiedene Arten hervorgerufen werden, z. B. durch Adhäsion, äußere Kräfte oder Druckunterschiede zwischen der Innen- und Außenseite der Kapsel. In Experimenten wurde der Adhäsionsradius der Kapsel oder die zum Zusammendrücken der Kapsel benötigte Kraft gemessen. In der vorliegenden Dissertation wird die Adhäsion von Mikrokapseln und die Deformation durch äußere Kräfte auf theoretischem Wege untersucht. Es wird mit Mitteln der Elastizitätstheorie ein Modell entwickelt, mit dem sich die Deformation der Kapsel in Abhängigkeit von den angreifenden Kräften beschreiben läßt. In einer systematischen Untersuchung werden die Vorhersagen des Modells mit experimentellen Daten verglichen, um daraus die elastischen Parameter zu extrahieren.Item Open Access Übertragbarkeit von Vorkenntnissen bei der Zuverlässigkeitstestplanung(2007) Hitziger, Tillmann; Bertsche, Bernd (Prof. Dr.-Ing.)Der Zuverlässigkeit neuer Produkte wird immer mehr Aufmerksamkeit der potentiellen Kunden zu Teil. Zuverlässigkeit ist zu einem der entscheidenden Kaufargumente geworden, sowohl im Konsum- als auch im Industriegüterbereich. Im Entwicklungsprozess ist die Produktzuverlässigkeit daher von zentraler Bedeutung. Auf Grund der immer kürzer werden Entwicklungszeiten und dem allgemein herrschenden Kostendruck findet die Erprobung neuer Produkte mit einem sehr engen Zeit- und Budgetplan statt. Es besteht daher ein großes Interesse, den zum Nachweis der Produktzuverlässigkeit notwendigen Stichprobenumfang auf ein Nötiges zu beschränken. Davon motiviert, wurden in den letzten Jahren verstärkt Analyseverfahren erarbeitet, die es erlauben, bei der Planung von Zuverlässigkeitstests Vorkenntnisse anderer, ähnlicher Produkte einzubinden. Dadurch kann es gelingen, den statistisch geforderten Stichprobenumfang in der Produkterprobung zu reduzieren. Ein mögliches Verfahren zur Berücksichtigung von Vorinformationen zur Zuverlässigkeit wurde von Krolo vorgestellt. Diese Vorgehensweise zeichnet sich unter anderem dadurch aus, dass bei der Übertragung der Vorkenntnisse ein so genannter Transformationsfaktor eingebunden wird. Dieser Faktor ermöglicht es, die bekannte, zusätzliche Information nur zu einem bestimmten Anteil zu nutzen. Einer eventuell unzureichenden, statistischen Absicherung der Zuverlässigkeit wird dadurch entgegengewirkt. Die vorliegende Arbeit beschäftigt sich mit Möglichkeiten zur Bestimmung dieses, von Krolo eingeführten, Transformationsfaktors. Nach dem Einstieg in die Planung von Zuverlässigkeitstests auf Basis der klassischen Testplanung, wurde daher zunächst das Krolo-Verfahren mit den für diese Arbeit maßgeblichen mathematischen Grundlagen vorgestellt. Der Einstieg in die eigentliche Thematik stellt die Übersicht über mögliche Ansätze zur Bestimmung des Transformationsfaktors dar. Im Anschluss daran, wurde ein qualitatives, auf der so genannten Fuzzy-Technik aufbauendes, Verfahren aufgezeigt. Diese expertenbasierte Vorgehensweise ermittelt an Hand der, die spätere Zuverlässigkeit maßgeblich bestimmenden, Einflussgrößen den Transformationsfaktor zwischen einem neuen Produkt und einem ähnlichen Produkt, beispielsweise einem Vorgänger. Es eignet sich daher insbesondere dazu, zu Beginn der Erprobung, wenn noch keine Testergebnisse des neuen Produkts vorhanden sind, eine erste qualitative Aussage über den vermutlich notwendigen Stichprobenumfang zu treffen. Sind jedoch Testergebnisse für beide Produkte bekannt, kann der Transformationsfaktor mittels so genannter Anpassungstests exakter bestimmt werden. Den Kern dieser Arbeit stellen daher die erarbeiteten, quantitativen Vorgehensweisen dar. Sie basieren auf dem Anpassungstest nach Kolmogorov und Smirnov. An Hand der Summenfunktionen der betrachteten Stichproben wird eine Wahrscheinlichkeit dafür ermittelt, dass beide Stichproben aus einer ihnen gemeinen Grundgesamtheit stammen. Der Transformationsfaktor wurde in dieser Arbeit mit jener Wahrscheinlichkeit angenommen. Um diese Annahmen zu verifizieren wurden verschiedene Simulationen durchgeführt. Es zeigte sich, dass die vorgeschlagene Vorgehensweise zur Ermittlung des Transformationsfaktors in Verbindung mit dem Verfahren nach Krolo sehr gute Ergebnisse liefert. Es kann daher davon ausgegangen werden, dass der auf diese Weise ermittelte, zum Nachweis der Produktzuverlässigkeit notwendige Stichprobenumfang mit sehr hoher Wahrscheinlichkeit korrekt ist. Einen weiteren Schwerpunkt der Arbeit stellt die praktische Ermittlung des Transformationsfaktors mittels der erarbeiteten Vorgehensweise dar. Es wurde aufgezeigt wie auf verschiedene Datensituationen eingegangen werden muss. Dabei wurden sowohl zensierte als auch unzensierte Produktinformationen in Betracht gezogen. Außerdem wurde auf den Einsatz der Methodik bei der Planung und Analyse von Systemtests hingewiesen. Den Abschluss der Arbeit bildet die beispielhafte Anwendung des vorgestellten quantitativen Verfahrens. Für Achsgetriebe von Nutzfahrzeugen wurde durch den Einsatz der Methode eine deutliche Reduzierung des Versuchsaufwands erzielt. Es konnte eine bezüglich der Anzahl an Probanden optimierte Teststrategie entwickelt werden. Insbesondere bei Baureihenprodukten ist die Anwendung des Verfahrens nach Krolo im Zusammenspiel mit dem in dieser Arbeit vorgestellten Verfahren zur Bestimmung des Transformationsfaktors sehr effektiv. Nicht zu letzt dieses Beispiel zeigt den Vorteil der Verfahren zur Berücksichtigung von Vorkenntnissen. Im Gegensatz zu den klassischen Vorgehensweisen ist mit derartigen Verfahren eine hinsichtlich Zeit und Kosten optimierte Planung von Zuverlässigkeitstests möglich.Item Open Access Modelling of endogenous technological learning of energy technologies - an analysis with a global multi-regional energy system model(2007) Rout, Ullash Kumar; Voß, Alfred (Prof. Dr.-Ing.)The modelling of energy systems, which coevolved from socio-technological interactions and their interplay with the economy, plays a key role in the development of national and international policies to solve the problem of energy poverty. The other important issues addressed by energy system modelling are change in energy infrastructure, develop energy strategies, paving pathways towards technological sustainability and predicting future energy demand. Almost all energy system models are based on optimization of the lowest energy production cost, where the total cost is contributed jointly by the energy carrier's price and the cost of the associated technology subject to technical parameters. Minimizing the investment cost associated with a given technology is extremely important to sustain the surge in energy demand of the global market. Therefore, how the model applies endogenous investment costs to forecast the future benefit associated with the current knowledge subject to uncertainty in learning rates is an important aspect of energy system modelling and analysis. The influence of uncertainties in learning rates on global learning concepts without and with a technology gap (knowledge gap and time lag) is of concern in order to identify the road map of the technologies across regions. In this modelling study, five regional global models based on TIMES have been developed (TIMES is a model generator and stands for "The Integrated MARKAL EFOM System"). The regions are defined as 25 European nations (EU25), Rest of OECD (R_OECD), Rest of Non-OECD (R_NOECD), India and China, according to the nations included inside each region and also on their economic categorisation. It is a demand driven, bottom-up and technology abundant model, where GDP, population, and traffic demands are the main drivers for the development of energy demand in the past, present and future. It is a long-term model (1990-2100) consisting of 19 periods with unequal period lengths (5, 8 and 10 years). Each year is divided into three seasons and each season is further divided into day and night, as the smallest time resolution. The entire Reference Energy System (RES) is represented in the Global TIMES G5 model by extraction; inter-regional exchange; refineries; hydrogen (H2) production; synthetic fuel production; bio-fuel production; electricity and heat production; Carbon Capture and Storage (CCS); and sector-wise energy demands of industry, commerce, residential and transport, non-energy use and finally an integrated climate module. In the extraction sector, hard coal, lignite, crude oil and natural gas are modelled in four steps with the help of default cost-potential curves. Inter-regional exchanges of ten commodities are modeled for each region inside the TIMES G5 model. The final energy demand of end-use sectors such as industry, commerce and residential are modelled by different end use technologies to satisfy the users' energy demand. Natural and artificial carbon pools are included in the modelling aspect for the abatement of CO2 or carbon concentrations in the atmosphere to reduce climate warming. Two climate stabilization scenarios of CO2emissions of 500-ppmv and 550-ppmv have been used in order to estimate the sectoral restructuring of the energy system across different regions as well as its effect on atmospheric and deep ocean layer temperature rise. The phaseout of polluting fuels and the integration of non-polluting or less polluting fuels and renewable energy sources inside the sectoral energy system predominate across all regions. Sectoral energy demand and total final energy demand decreases in individual regions. Technologies such as fuel cells, fusion technology, Integrated Gasification Combined Cycle (IGCC) with CO2 sequestration, Combined Cycle Gas Turbine (CCGT) with CO2 sequestration and hydrogen production with CO2 sequestration are selected in the stabilization scenarios. The CO2 emission by fossil fuels, by sectors and by regions decreases. The atmospheric temperature rises by a maximum of 2.41oC and the ocean bed temperature rises by a maximum of 0.33oC up to the year 2100. The TIMES G5 global model has been developed to test global learning processes for the effect of uncertainties on learning rates of innovative technologies, i.e., technology diffusion across world regions subject to uncertainty in LRs for three PRs has been considered on implementation of floor cost approach The global learning process considering technology gap methodologies (knowledge gap and time lag) has been developed and tested for three different progress ratios of each technology for uncertainty of the technological return. Knowledge gap represents higher specific cost of the technology for developing regions and time lag approach presents a time lag in capacity transfer to developing regions compared to developed regions. This study shows the penetration and integration of new technologies such as IGCC, CCGT, solar photovoltaic (PV), wind onshore, wind offshore and geothermal heat pumps inside the energy system of different regions. Variations result observed by the inclusion of global learning without and with technology gaps in the form of higher specific cost (knowledge gap) and time lag. IGCC technology reaches its maximum potential in all scenarios across the globe. IGCC technology is preferred in the case of global learning without knowledge gap and time lag across developing regions compared to global learning with knowledge gap. CCGT technology development in manufacturing region decreases in global learning with technology knowledge gap compared to without knowledge gap concept. Wind onshore penetrates more in EU25 and R_OECD regions and in energy systems in a global learning concept without knowledge gap. Developed regions use more learning technology in the global learning with time lag concept because of the advantage of early investment cost reduction of learning technologies contributed by developing regions. Geothermal Heat Pump (geothermal HP) penetrates more across all regions and in all scenarios as the technology is modeled for global learning without knowledge gap and time lag. Bio-gasification, solid oxide fuel cells and molten carbonate fuel cells do not enter any energy system under any scenario. It is observed that learning technology diffuses more in higher learning rates and less in lower learning rates across the regions and the globe. The development of specific costs of innovative technologies is observed differently by period for developing and developed regions in global learning with technology gap in the form of higher specific cost approach.Item Open Access Nutzung elektronischer Bücher an der ETH Zürich : E-Book-Seminar Stuttgart, 23. April 2007(2007) Piguet, ArletteDas Angebot und die Nutzung des E-Book-Angebotes der ETH Zürich werden vorgestellt.