Tesi sul tema "DLOQ"

Det blir alltmer vanligt att utföra olika typer av geodetiska inmätningar med hjälp av GNSS och grundentill den här studien är att undersöka olika mätmetoder som kan tillämpas på punkter där fixlösning integår att erhålla. Syftet blev således att ta fram ett resultat som visar om och i så fall hur stor skillnad detär mellan tre olika metoder samt vilken noggrannhet respektive metod uppvisar. De två metoderna somtestats i studien är ortogonal inmätning och inmätning med dubbla avstånd. För dessa två metoder krävsutöver den vanliga utrustningen vid inmätning med GNSS endast några stakkäppar och ett mätband. Dentredje metoden är inmätning med totalstation som etablerats med RUFRIS (realtidsuppdaterad fristation)och den baseras på tidigare gjorda undersökningar och jämförs i studien med ortogonal inmätning ochinmätning med dubbla avstånd. Vidare undersöks åtgången av tid och material i jämförelse mednoggrannheten hos respektive mätmetod. Metoderna ortogonal inmätning och inmätning med dubbla avstånd testades 24 gånger vardera genommätning mot sedan tidigare kända punkter med koordinater i SWEREF 99 13 30. Efter att resultatenanalyserats drogs slutsatsen att det i den här studien inte går att skilja dessa två metoder åtkvalitetsmässigt. De uppvisade en medelavvikelse på 32 respektive 33 mm. Den metod som kan vara attföredra sett till material och tidsåtgång är inmätning med dubbla avstånd vilken också är något merflexibel. Jämfört med RUFRIS så erbjuder de andra två metoderna inte lika hög noggrannhet, men ändå tillräckligdär inmätning sker med GNSS. Vid samma antal bakobjekt, vilket är två, går det att anta att en punktkan mätas in via RUFRIS med en noggrannhet på mellan 55,1 och 12,6 mm beroende på geometrin förbakobjekten. Genom ökat antal bakobjekt minskar också osäkerheten i mätningarna vilket gör attRUFRIS ger fler valmöjligheter. Att mäta in den här typen av punkter med RUFRIS ger alltså en bättrenoggrannhet och kontrollerbarhet. Men att använda metoden i dessa situationer kan betraktas somomotiverad då den kräver mer arbete, plats och utrustning samtidigt som de andra två metoderna ger entillräcklig noggrannhet.
GNSS-surveying is common today and it’s interesting to investigate methods that can be applied whenthe ambiguities cannot be fixed to the correct integer on a point that are involved. Three methods arecompared and two of them tested, which are Two distances and backwards bearing and distance. N-RTK(Network- Real Time Kinematic) is used and both methods are measured 24 times each on four knownpoints with coordinates in SWEREF 99 13 30. RUFRIS (Real Time Updated Free Station) is the thirdmethod and earlier studies are the background behind the comparison for this method. The consumptionof time, material and quality are included parts of the comparison. RUFRIS can provide high precision results, but takes more time to establish, more equipment andrequires free sights. An establishment with two back sights can give a precision between 55.1 and 12.6mm depending on the proliferation between the back sights. The result for two distance and backwardsbearing and distance were found equivalent to each other. The mean deviation was 32 and 33 mm.Because of time, material and more flexibility is the method Two distances to prefer.

Bakgrund: Illikviditetsrabatten (DLOM) är en omdiskuterad rabatt som ofta leder till konflikt vid värdering. DLOM uppstår i en brist på säljbarhet och problematiken ligger i att denna rabatt inte är observerbar och kan även anses subjektiv. DLOM beror också på flertalet ofta unika faktorer vilket medför att rabatten kan skilja sig kraftigt från fall till fall. DLOM kan anta allt från negativa värden upp till 90 % vilket medför att bolagets slutgiltiga värde i stor grad beror av denna rabatt. Således blir det relevant att bestämma en korrekt nivå för denna rabatt utifrån vetenskaplig litteratur och praxis. Fallföretaget för denna studie, PwC, har efterfrågat en ny modell för att estimera DLOM. Detta på grund av ett ökat fokus från Skatteverket och Fallföretagets kunder att kontrollera om estimeringar av DLOM har utförts på ett korrekt och argumenterbart sätt. I dagsläget hävdar Fallföretaget att ämnet har givits bristande uppmärksamhet i branschen, varför en uppdatering av deras nuvarande metodik för att estimera DLOM är kritisk för sitt fortsatta arbete. Syfte: Denna studies syfte är att analysera och skapa en modell, grundad i validitet och praktisk genomförbarhet, som estimerar illikviditetsrabatten. Genomförande: På grund av att rabatten inte är observerbar uppstår ett behov av att identifiera substitut för rabatten och förstå sambandet mellan dessa och DLOM. Till hjälp har en omfattande sammanställningsstudie gjorts i ämnet tillsammans med en fallstudie av Fallföretagets nuvarande metodik. Baserat på detta och triangulering har en modell sedan utvecklats. Denna modell har sedan tillämpats på fyra värderingsfall som tillhandahållits av Fallföretaget. Utifrån detta följer sedan en analys på Fallföretagets metodik, den framtagna modellen och en jämförelse av dessa. Resultat: EMQ-modellen är en modell som bygger på tre metoder för att estimera DLOM. De tre metoderna är en empirisk metod, en matematisk metod och en kvalitativ metod. Två intervall för vad DLOM kan anta för värden utifrån bolagsspecifika data skapas utifrån den empiriska och matematiska metoden. Dessa intervall viktas sedan ihop till ett intervall med avseende på inlåsningsperioden för innehavet som ska värderas. Slutligen undersöks kvalitativa faktorer som ger ett bestämt värde inom intervallet för DLOM. De tre metoderna är valda utifrån att ta hänsyn till de faktorer som påverkar DLOM för att sedan överföra dessa till ett faktiskt värde för DLOM. Modellen är även skapad för att vara anpassningsbar till varje specifikt värderingsfall.
Background: The marketability discount (DLOM) is a controversial discount that has often led to conflict in valuation. DLOM is derived from a lack of marketability and the problem lies in the fact that DLOM is not observable and also considered subjective. Furthermore, DLOM depends on multiple often unique factors, which means that the discount can differ greatly from case to case. DLOM can assume values ranging from negative values and up to as much as 90%, which means that the company's final value to a great extent depends on this discount. Thus, it becomes relevant to determine a reasonable level of this discount based on scientific literature and practice. The case company for this study, PwC, has requested a new model to estimate DLOM. The reason behind the request is that the Swedish Tax Agency and customers of the case company have increased its effort on controlling whether estimates of DLOM have been carried out in a correct and arguably manner. Currently, the case company claims that the subject has been given a lack of attention in the industry, which is why an update of their current methodology for estimating DLOM is critical for their continued work. Aim: The aim of this report is to create and analyze a model, based on validity and practical feasibility, which estimates the marketability discount. Completion: Due to the fact that the discount is not observable creates a need for identifying proxies for the discount and an understanding of the connection between these and DLOM. An extensive literature study together with a case study on the case company has been made in order to achieve this. A model is then developed based on this and triangulation. The model is then used on four valuation cases, provided by the case company. After that follows an analysis of the methodology of the case company, the model of this study and a comparison between these two. Findings: The EMQ-model is a model that is based on three methods for estimating DLOM. The three methods are an empirical method, a mathematical method and a qualitative method. Two possible intervals for DLOM is created based on company-specific data by the empirical and mathematical method. These intervals are then weighted together into one interval with respect to the restriction period for the holding to be valued. Finally, qualitative factors that provide a definite value are investigated within the interval of DLOM. The three methods are chosen based on considering the factors affecting DLOM. The model is also created to enable adaptability to each specific valuation case.

Tableau d'honneur de la Faculté des études supérieures et postdorales, 2016-2017
Ce projet de recherche en développement international est ancré dans une perspective féministe postcoloniale. Celui-ci vise à reconnaître et approfondir la multiplicité et les complexités du pouvoir, dans un but d’empowerment, auprès des femmes de Lhomond, une communauét rurale en Haïti. Cette étude a documenté les discours de femmes (n=10) à propos de l’actualisation de leur propre empowerment au quotidien. Le cadre conceptuel choisi relatif à l’empowerment décline le pouvoir en quatre types : le « pouvoir intérieur », le « pouvoir de », le « pouvoir avec » et le « pouvoir sur » (Charlier, 2006b, 2006a; Oxaal et Baden, 1997; Rowlands, 1997). La collecte de données s’est déroulée sur une période de trois mois. La méthodologie utilisée a mis en place des entrevues (individuelles et de groupe) ainsi qu’une observation participante. Les résultats ont mis en lumière les descriptions des femmes de plusieurs situations de leur vie quotidienne au sein desquelles se manifestaient ces quatre types de pouvoir. De plus, les participantes ont fait part de nombreuses interactions ayant lieu entre différents types de pouvoir. Ces résultats ont reconfirmé des recherches antérieures sur les différents types de pouvoir et leur lien avec le processus d’empowerment. Par exemple, un « pouvoir de » limité (dépendance financière, analphabétisme, accès difficile à l’emploi, etc.) tend à freiner le processus d’empowerment, alors qu’un « pouvoir avec » renforcé (solidarité, partage, action collective, etc.) tend à favoriser le processus d’empowerment malgré la faiblesse d’autres types de pouvoir. À partir des résultats obtenus, cette étude amène quelques nuances ainsi qu’une complexité additionnelle au cadre conceptuel adopté au départ et met en lumière d’autres aspects du pouvoir à considérer dans de futures recherches portant sur l’empowerment des femmes.
This research project in the field of international development and the empowerment of women is rooted in a postcolonial feminist perspective. This research attempts to recognize and foreground the multiplicity and complexities of power – within the goal of empowerment – for the women of Lhomond, a rural community in Haiti. The study documented women’s discourse (n=10) with respect to their own sense of empowerment in their daily lives. The conceptual model chosen portrays power along four lines : “power within”, “power to”, “power with” and “power over” (Charlier, 2006b, 2006a; Oxaal & Baden, 1997; Rowlands, 1997). Data collection occurred over a three month period. Principal methodology included interviews (individual and group) and participant observation. Results showcase the women’s descriptions of multiple situations in their daily life in which these four types of power were occurring. Moreover, these women articulated numerous interactions taking place between these four types of power. These results reaffirm previous research with respect to differing types of power and their relationship with empowerment. For example, a limited sense of “power to” (financial dependance, illiteracy, poor access to employment, etc.), tends to diminish the process of empowerment, whereas an enhanced sense of “power with” (solidarity, sharing, collective action, etc.), tends to enhance the process of empowerment (and this even when the other types of power are weak). Based on the results, this study offers some nuances – additional complexity – to the conceptual model and highlights some additional aspects of power to be considered for future research in regards to the empowerment of women.
Pwojè rechèch sa a, ki nan sijè devlòpman entènasyonal, li gen yon pèspèktiv feminist ak poskolonyalis. Li vle konnen pi byen konplèksite ak miltiplikasyon pouvwa a nan yon objèktif ranfòsman pouvwa a pou fanm Lonmon, yon zòn ki andeyò an Ayiti. Etid sa a te fèt sou pawòl fanm yo (n=10) sou ki jan yo wè ranfòsman pouvwa pa yo nan lavi chak jou yo. Modèl ranfòsman pouvwa a gen 4 jan pouvwa yo: “pouvwa nan ou a”, “pouvwa de”, “pouvwa avèk” ak “pouvwa sou” (Charlier, 2006b, 2006a; Oxaal ak Baden, 1997; Rowlands, 1997). Kolèksyon done yo te fèt sou yon peryòd 3 mwa. Fason etid la te fèt se ak entèvyou (endividyèl ak an gwoup) epi tou ak obsèvasyon a patisipasyon. Rezilta yo te pèmèt wè, ak pawòl fanm Lomon yo, kijan 4 jan pouvwa yo reyalize nan lavi yo. Epi tou, fanm yo te montre entèraksyon yo ki rive ant 4 jan pouvwa yo. Etid sa a te vin konfime ki sa lòt etid lòt moun yo te fèt anvan yo te jwenn sou jan pouvwa yo ak ranfòsman pouvwa a. Pou ègzanp, yon “pouvwa de” ki fèb (lè ou sou kont on moun, lè ou pa konn li ak ekri, lè ou pa ka jwenn djòb, elatriye) ka bloke pwosesis ranfòsman pouvwa, menm jan ak yon “pouvwa avèk” ki fò (tèt ansanm, youn ede lòt, pataj, aksyon kolèktif, elatriye) ka ede pwosesis sa a menm si lòt jan pouvwa yo fèb. Ak rezilta etid sa a te genyen, li pote kèk presizyon ak pi fò konplèksite nan modèl ranfòsman pouvwa a epi tou li mete nan limyè lòt aspè pouvwa yo lòt pwojè rechèch sou ranfòsman pouvwa fanm yo ta ka etidye nan jou kap vini yo.

In the context of industrial robotics, manipulating rigid objects have been studied quite deeply. However, Handling deformable objects is still a big challenge. Moreover, due to new techniques introduced in the object detection literature, employing visual data is getting more and more popular between researchers. This thesis studies how to exploit visual data for detecting the end-point of a deformable linear object. A deep learning model is trained to perform the task of object detection. First of all, basics of the neural networks is studied to get more familiar with the mechanism of the object detection. Then, a state-of-the-art object detection algorithm YOLOv3 is reviewed so it can be used as its best. Following that, it is explained how to collect the visual data and several points that can improve the data gathering procedure are delivered. After clarifying the process of annotating the data, model is trained and then it is tested. Trained model localizes the end-point. This information can be used directly by the robot to perform tasks like pick and place or it can be used to get more information on the form of the object.

Interest in wide bandgap semiconductors such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga 2 O 3 ) and diamond has increased due to their ability to deliver high power, high switching frequency and low loss electronic devices for power conversion applications. To meet these requirements, semiconductor material defects, introduced during growth and fabrication, must be minimized. Otherwise, theoretical limits of operation cannot be achieved. In this dissertation, the non-ideal current- voltage (IV) behavior of GaN-based Schottky diodes is discussed first. Here, a new model is developed to explain better the temperature dependent performance typically associated with a multi-Gaussian distribution of barrier heights at the metal-semiconductor interface [Section 3.1]. Application of this model gives researches a means of understanding not only the effective barrier distribution at the MS interface but also its voltage dependence. With this information, the consequence that material growth and device fabrication methods have on the electrical characteristics can be better understood. To show its applicability, the new model is applied to Ru/GaN Schottky diodes annealed at increasing temperature under normal laboratory air, revealing that the origin of excess reverse leakage current is attributed to the low-side inhomogeneous barrier distribution tail [Section 3.2]. Secondly, challenges encountered during MOCVD growth of low-doped GaN drift layers for high-voltage operation are discussed with focus given to ongoing research characterizing deep-level defect incorporation by deep level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS) [Section 3.3 and 3.4]. It is shown that simply increasing TMGa so that high growth rates (>4 µm/hr) can be achieved will cause the free carrier concentration and the electron mobilities in grown drift layers to decrease. Upon examination of the deep-level defect concentrations, it is found that this is likely caused by an increase in 4 deep level defects states located at E C - 2.30, 2.70, 2.90 and 3.20 eV. Finally, samples where the ammonia molar flow rate is increased while ensuring growth rate is kept at 2 µm/hr, the concentrations of the deep levels located at 0.62, 2.60, and 2.82 eV below the conduction band can be effectively lowered. This accomplishment marks an exciting new means by which the intrinsic impurity concentration in MOCVD-grown GaN films can be reduced so that >20 kV capable devices could be achieved.
Doctor of Philosophy

Interest in wide bandgap semiconductors such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga 2 O 3 ) and diamond has increased due to their ability to deliver high power, high switching frequency and low loss electronic devices for power conversion applications. To meet these requirements, semiconductor material defects, introduced during growth and fabrication, must be minimized. Otherwise, theoretical limits of operation cannot be achieved. In this dissertation, the non-ideal current- voltage (IV) behavior of GaN-based Schottky diodes is discussed first. Here, a new model is developed to explain better the temperature dependent performance typically associated with a multi-Gaussian distribution of barrier heights at the metal-semiconductor interface [Section 3.1]. Application of this model gives researches a means of understanding not only the effective barrier distribution at the MS interface but also its voltage dependence. With this information, the consequence that material growth and device fabrication methods have on the electrical characteristics can be better understood. To show its applicability, the new model is applied to Ru/GaN Schottky diodes annealed at increasing temperature under normal laboratory air, revealing that the origin of excess reverse leakage current is attributed to the low-side inhomogeneous barrier distribution tail [Section 3.2]. Secondly, challenges encountered during MOCVD growth of low-doped GaN drift layers for high-voltage operation are discussed with focus given to ongoing research characterizing deep-level defect incorporation by deep level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS) [Section 3.3 and 3.4]. It is shown that simply increasing TMGa so that high growth rates (>4 µm/hr) can be achieved will cause the free carrier concentration and the electron mobilities in grown drift layers to decrease. Upon examination of the deep-level defect concentrations, it is found that this is likely caused by an increase in 4 deep level defects states located at E C - 2.30, 2.70, 2.90 and 3.20 eV. Finally, samples where the ammonia molar flow rate is increased while ensuring growth rate is kept at 2 µm/hr, the concentrations of the deep levels located at 0.62, 2.60, and 2.82 eV below the conduction band can be effectively lowered. This accomplishment marks an exciting new means by which the intrinsic impurity concentration in MOCVD-grown GaN films can be reduced so that >20 kV capable devices could be achieved.
Doctor of Philosophy

Aufgrund der großen Bedeutung technischer Gummiwerkstoffe in industriellen Anwendungen ist die Vorhersage des Materialverhaltens ein aktuelles Forschungsgebiet. Insbesondere die Veränderung der Eigenschaften, die durch chemische Prozesse herbeigeführt werden, spielen eine große Rolle, da aufgrund gestiegener Anforderungen an die Haltbarkeit von Bauteilen diese Alterungseffekte verstanden, vorhergesagt und abgeschwächt werden müssen. Im Rahmen dieser Arbeit wird ein mathematisches Modell hergeleitet, das die chemischen Vorgänge vorhersagt und deren Auswirkungen auf wichtige Eigenschaften in einem mechanischen Materialmodell beachtet. Insbesondere der Oxidation durch Luftsauerstoff wird Rechnung getragen. Das mechanische Materialverhalten alternder Gummiwerkstoffe wird mit Hilfe eines neuartigen Ansatzes modelliert. Das in dieser Arbeit vorgestellte Dynamische-Netzwerk-Modell betrachtet die Auswirkungen der chemischen Reaktionen auf das mechanische Verhalten als einen kontinuierlichen Netzwerkumbau durch das Entfernen und neue Einsetzen von Verbindungen zwischen Polymerketten. Basierend auf experimentellen Erkenntnissen werden Hypothesen formuliert, die eine Kopplung zwischen den Oxidationsreaktionen und der Veränderung des mechanischen Verhaltens herstellen. Durch Beachtung von Diffusion und Reaktion kann die lokale Sauerstoffverteilung in großvolumigen Bauteilen berechnet und der Effekt der diffusionslimitierten Oxidation (DLO-Effekt) vorhergesagt werden. Um eine Bestimmung der Modellparameter zu ermöglichen, werden verschiedene Experimente vorgeschlagen, mathematisch modelliert und deren Eignung zur Parameteridentifikation analysiert. Mit einer vergleichsweise geringen Anzahl von Experimenten können sowohl die chemischen als auch die mechanischen Modellparameter sicher identifiziert werden. In dieser Arbeit wird zudem ein sogenannter gestaffelter Lösungsalgorithmus vorgeschlagen, der das Alterungsproblem nach einer mathematischen Entkopplung unterschiedlicher Feldprobleme über geeignete Kopplungsvariablen effizient berechnen kann. Mit Hilfe dieses Algorithmus kann eine Simulation effizient durchgeführt und das Alterungsverhalten komplexer Strukturen vorhergesagt werden. Die Simulation anwendungsnaher Strukturen zeigt, dass die abgeleiteten Modelle und Algorithmen problemlos in einem industriellen Umfeld einsetzbar sind
Due to the great importance of rubber materials in industrial applications, the prediction of the material behavior is a current research field. Particularly the property changes that are induced by chemical processes play a major role, as these aging effects must be understood, predicted and reduced due to the increased requirements regarding the durability of components. In the context of this thesis, a mathematical model that predicts and considers the chemical processes and their effects on important properties in a mechanical material model is derived. Oxidation through atmospheric oxygen is specifically examined in this work. The mechanical material behavior of aging rubber materials is modeled using a novel approach. The dynamic network model introduced in this paper considers the effects of the chemical reactions on the mechanical behavior as a continuous restructuring of the network by removing and inserting new crosslinks between polymer chains. Based on experimental obervations a coupling between the oxidation reactions and a change of the mechanical material behavior is proposed. By taking into account the diffusion and reaction the local distribution of oxygen in large sized components can be computed. Thus, the effect of diffusion limited oxidation (DLO effect) can be predicted. In order to make an identification of the model parameters possible, different experiments are suggested, modeled mathematically and their suitability for parameter identification is analyzed. Not only the chemical, but also the mechanical model parameters can be identified reliably using a comparably few number of experiments. Moreover, a so-called staggered solution algorithm that can calculate the aging problem efficiently after a mathematical uncoupling of the field problems using a suitable coupling variable is introduced. This algorithm can perform a simulation efficiently and predict the aging behavior of complex structures. The simulation of application oriented structures proofs the applicability of the derived models and algorithms within an industrial environment

A private company lacks a direct observable market value and several situations may require a practitioner to compute the value of a private company. Since most of the valuation methods in use are based on data derived from the public stock markets certain adjustments may be appropriate when valuing a private company. Marketability and liquidity is said to be one of the more observable differences between a public and a private company. This implies that the shares in a private company have a lack of marketability and liquidity in comparison to the shares in a public company, which practitioners may have to adjust for. Several quantitative studies are conducted on the subject in order reassure price differences between public and private companies, namely a private company discount (PCD). Furthermore, several quantitative studies strive to establish a general and standardized cost for lack of marketability (liquidity) expressed as the illiquidity discount or the discount for lack of marketability (DLOM). These studies have different perceptions and use different hypothesis to identify illiquidity, which in turn will lead to a large span of different discounts. Essentially, earlier research examines assets marketability and liquidity with the assumption of them being equal in all other aspects. Professional practitioners constantly seek guidance in these studies to justify their estimated and applied illiquidity discount/DLOM when performing a valuation on a privately held company. Furthermore, we have also observed survey-studies adopting a more qualitative method in order to appreciate the level of discounts applied in a valuation by professional practitioners. Consequently, this sea of studies provides the practitioner with a discount that ranges from 5% to 60% to take a stand on. The impossibility to determine the most adequate theory contributes to the inconsistency of how this issue is handled in reality by market participants and courts. In our study we first provide the reader with a rigorous literature study, which describes earlier research on the subject of illiquidity discount/DLOM. We conclude that research has gone one step too far when conducting all of these quantitative studies. This is why we conduct our own empirical data through semi-structured in-depth interviews with professional valuation experts on the Swedish market. This makes our approach a retake on the issue in order to generate suggestions to further studies. What we find is that all of the independent consultants, primarily, does not apply a discount when valuing a majority interest due to the paradigm on the Swedish market. In contrast, the private equity fund manager, which only acquires majority interest, can use this type of discounts in their dependent valuation of majority interests. However, when valuing a minority interest the independent valuation consultants use quantitative empirical studies to derive a starting point of the discount. The level of the discount is then estimated upon the purpose of the valuation and firm-specific variables, which all of the participant’s states to be the most important ones when estimating a illiquidity discount/DLOM. Based on these results we argue that one should be very careful when taking guidelines from quantitative empirical studies. Our interpretation is that the level of illiquidity/DLOM applicable depends on the level of attractiveness, which in turn has a bearing on all firm-specific variables. When it comes to applying the appropriate discount all of the participants argue in favor for a discount-on-value and not as some research suggest; a risk premium added to the discount rate. We also generate adequate suggestions to further studies based on these interviews. Since courts and in particular the Swedish tax-court is inconsistent when approving or rejecting illiquidity discounts/DLOM we suggest legal actions on the issue. Furthermore we suggest a survey-like study in order to catch consensus take on how to estimate the level of discount. In fact, this can be done every year in a similar way as PwC’s market risk premium study is conducted.

Dominated by Heisenberg's uncertainty principle, vacuum is not quantum mechanically an empty void, i.e. virtual pairs of particles appear and disappear persistently. This nonlinearity subsequently provokes a number of phenomena which can only be practically observed by going to a high-intensity regime. Pair production beyond the so-called Sauter-Schwinger limit, which is roughly the field intensity threshold for pairs to show up copiously, is such a nonlinear vacuum phenomenon. From the viewpoint of Dirac's front form of Hamiltonian dynamics, however, vacuum turns out to be trivial. This triviality would suggest that Schwinger pair production is not possible. Of course, this is only up to zero modes. While the instant form of relativistic dynamics has already been at least theoretically well-played out, the way is still open for investigating the front form. The aim of this thesis is to explore the properties of such a contradictory aspect of quantum vacuum in two different forms of relativistic dynamics and hence to investigate the possibility of finding a way to resolve this ambiguity. This exercise is largely based on the application of field quantization to light-front dynamics. In this regard, some concepts within strong field theory and light-front quantization which are fundamental to our survey have been introduced, the order of magnitude of a few important quantum electrodynamical quantities have been fixed and the basic information on a small number of nonlinear vacuum phenomena has been identified. Light-front quantization of simple bosonic and fermionic systems, in particular, the light-front quantization of a fermion in a background electromagnetic field in (1+1) dimensions is given. The light-front vacuum appears to be trivial also in this particular case. Amongst all suggested methods to resolve the aforementioned ambiguity, the discrete light-cone quantization (DLCQ) method is applied to the Dirac equation in (1+1) dimensions. Furthermore, the Tomaras-Tsamis-Woodard (TTW) solution, which expresses a method to resolve the zero-mode issue, is also revisited. Finally, the path integral formulation of quantum mechanics is discussed and, as an alternative to TTW solution, it is proposed that the worldline approach in the light-front framework may shed light on different aspects of the TTW solution and give a clearer picture of the light-front vacuum and the pair production phenomenon on the light-front.

Das Halbleitermaterial Zinkselenid (ZnSe) wurde mit Deep Level Transient Spectroscopy (DLTS) untersucht. Fuer planar N-dotierte, MO-CVD-gewachsene ZnSe-Schichten auf p-GaAs wurden vorwiegend breite Zustandsverteilungen, aber auch tiefe Niveaus gefunden. In kristallin gezuechtetem, undotiertem ZnSe wurden tiefe Stoerstellen nachgewiesen.

Celem pracy jest znalezienie odpowiedzi na pytania dotyczące specyfiki procesów uczenia się małych i średnich firm technologicznych, które wyrażają się w innowacyjnych produktach, usługach i rozwiązaniach technologicznych, oferowanych przez badane firmy. Prezentowany projekt badawczy składa się z dwóch części, opartych odpowiednio na ilościowych i jakościowych technikach badawczych. Część ilościowa pracy opiera się na zastosowaniu do badania małych i średnich firm technologicznych zaadaptowanego kulturowo narzędzia badawczego organizacji uczących się Dimensions of a Learning Organization Questionnaire (Watkins, Marsick 2003) i analizie zebranych danych statystycznych. Część jakościowa opiera na opracowaniu charakterystyki procesów uczenia się i ich uwarunkowań w małych i średnich firmach technologicznych. Wyniki badań jakościowych prezentują formalne i nieformalne możliwości uczenia się pracowników w badanych firmach.

Aufgrund der großen Bedeutung technischer Gummiwerkstoffe in industriellen Anwendungen ist die Vorhersage des Materialverhaltens ein aktuelles Forschungsgebiet. Insbesondere die Veränderung der Eigenschaften, die durch chemische Prozesse herbeigeführt werden, spielen eine große Rolle, da aufgrund gestiegener Anforderungen an die Haltbarkeit von Bauteilen diese Alterungseffekte verstanden, vorhergesagt und abgeschwächt werden müssen. Im Rahmen dieser Arbeit wird ein mathematisches Modell hergeleitet, das die chemischen Vorgänge vorhersagt und deren Auswirkungen auf wichtige Eigenschaften in einem mechanischen Materialmodell beachtet. Insbesondere der Oxidation durch Luftsauerstoff wird Rechnung getragen. Das mechanische Materialverhalten alternder Gummiwerkstoffe wird mit Hilfe eines neuartigen Ansatzes modelliert. Das in dieser Arbeit vorgestellte Dynamische-Netzwerk-Modell betrachtet die Auswirkungen der chemischen Reaktionen auf das mechanische Verhalten als einen kontinuierlichen Netzwerkumbau durch das Entfernen und neue Einsetzen von Verbindungen zwischen Polymerketten. Basierend auf experimentellen Erkenntnissen werden Hypothesen formuliert, die eine Kopplung zwischen den Oxidationsreaktionen und der Veränderung des mechanischen Verhaltens herstellen. Durch Beachtung von Diffusion und Reaktion kann die lokale Sauerstoffverteilung in großvolumigen Bauteilen berechnet und der Effekt der diffusionslimitierten Oxidation (DLO-Effekt) vorhergesagt werden. Um eine Bestimmung der Modellparameter zu ermöglichen, werden verschiedene Experimente vorgeschlagen, mathematisch modelliert und deren Eignung zur Parameteridentifikation analysiert. Mit einer vergleichsweise geringen Anzahl von Experimenten können sowohl die chemischen als auch die mechanischen Modellparameter sicher identifiziert werden. In dieser Arbeit wird zudem ein sogenannter gestaffelter Lösungsalgorithmus vorgeschlagen, der das Alterungsproblem nach einer mathematischen Entkopplung unterschiedlicher Feldprobleme über geeignete Kopplungsvariablen effizient berechnen kann. Mit Hilfe dieses Algorithmus kann eine Simulation effizient durchgeführt und das Alterungsverhalten komplexer Strukturen vorhergesagt werden. Die Simulation anwendungsnaher Strukturen zeigt, dass die abgeleiteten Modelle und Algorithmen problemlos in einem industriellen Umfeld einsetzbar sind.
Due to the great importance of rubber materials in industrial applications, the prediction of the material behavior is a current research field. Particularly the property changes that are induced by chemical processes play a major role, as these aging effects must be understood, predicted and reduced due to the increased requirements regarding the durability of components. In the context of this thesis, a mathematical model that predicts and considers the chemical processes and their effects on important properties in a mechanical material model is derived. Oxidation through atmospheric oxygen is specifically examined in this work. The mechanical material behavior of aging rubber materials is modeled using a novel approach. The dynamic network model introduced in this paper considers the effects of the chemical reactions on the mechanical behavior as a continuous restructuring of the network by removing and inserting new crosslinks between polymer chains. Based on experimental obervations a coupling between the oxidation reactions and a change of the mechanical material behavior is proposed. By taking into account the diffusion and reaction the local distribution of oxygen in large sized components can be computed. Thus, the effect of diffusion limited oxidation (DLO effect) can be predicted. In order to make an identification of the model parameters possible, different experiments are suggested, modeled mathematically and their suitability for parameter identification is analyzed. Not only the chemical, but also the mechanical model parameters can be identified reliably using a comparably few number of experiments. Moreover, a so-called staggered solution algorithm that can calculate the aging problem efficiently after a mathematical uncoupling of the field problems using a suitable coupling variable is introduced. This algorithm can perform a simulation efficiently and predict the aging behavior of complex structures. The simulation of application oriented structures proofs the applicability of the derived models and algorithms within an industrial environment.