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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Coherent production of neutral pions on '1'2C and '4'0Ca

Fog, Lotte S. January 2001 (has links)
No description available.
42

Growth, Accumulation, Crisis : With New Macroeconomic Data for Sweden 1800-2000

Edvinsson, Rodney January 2005 (has links)
This dissertation has two main objectives. The first one is to construct historical macroeconomic series for Sweden using a consistent method throughout the relevant periods, and which rely on modern methods of national accounting. The second objective is to investigate patterns of economic growth, accumulation and crisis in Sweden 1800-2000, based on the constructed data series. New annual data series of Gross Domestic Product and its division into activities (type of production) and expenditures (consumption, investment and foreign trade), Net Domestic Product, stocks of produced assets and consumption of fixed assets are constructed for the period 1800-2000; series of employment, wages, imputed labour income of self employed and surplus for the period 1850-2000; and series of worked hours for the period 1950-2000. Summary tables of the main aggregate variables are presented at the end of the dissertation. The intent is to make the data material available online (also at a more disaggregated level) at: http://www.historia.se. Although the present study criticises the somewhat deterministic vision of many long cycle theories, it also demonstrates that the concept of long cycle can be applied when studying long-term fluctuations in GDP per capita, provided that the notion of a fixed periodicity of long cycles is abandoned. Long-term economic fluctuations are irregular, but so is also the short-term business cycle. Different historical tendencies and trends are investigated. The decline of the relative size of industrial activities in the last half of 20th century was not as dramatic, if unpaid household labour is considered and that many services are industry-related. The Marxist theory of a Tendency for the Rate of Profit to Fall is partly confirmed as a secular process up to the 1970s, but profitability has rebounded in the last two decades of the 20th century. During the 1990s, the investment ratio declined to historically low levels and the volume value of the net stock of buildings and structures fell for the first time since the 1830s. A comparison is also made of depressions in Sweden since 1850. During the 19th century, depressions were largely induced by the agricultural sector, and during the 20th century by industrial activities. However, the transition to the modern business cycle was not sudden but rather protracted. Another finding is that the 1990s depression was somewhat deeper than the 1930s depression in terms of GDP contraction.
43

Modelling and Experimental Verification of Direct Drive Wave Energy Conversion : Buoy-Generator Dynamics

Eriksson, Mikael January 2007 (has links)
This thesis is focused on development of models and modelling of a wave energy converter in operation. Through the thesis linear potential wave theory has been used to describe the wave-buoy interaction. The differences lie in the generator models, in the simplest model the generator is a mechanical damper characterized by a damping factor. In the most advanced generator model the magnetic fields is calculated the by a FE-method, which gives detailed description of the electric properties and the effect it has on the buoy dynamics. Moreover, an equivalent circuit description of the generator has been tested. It has the same accuracy as the field based model but with a strongly enhanced CPU time. All models are verified against full scale experiments. The models are intended to be used for design of the next generation wave energy converters. Further, the developed models have also been used to study what effect buoy geometry and generator damping have on the ability to energy absorption. In the spring 2006 a full scale wave energy converter was installed at the west coast of Sweden. It was in operation and collected data during three months. During that period the load resistance was varied in order to study the effect on the energy absorption. These collected data was then used in the verification of the developed models. In the year 2002 a wave energy project started at Uppsala University; this work is a part of that larger project which intendeds to develop a viable wave energy conversion concept.
44

Demoneycrazy : A case study of the United Arab Emirates

Al-Maawaly, Nura January 2008 (has links)
No description available.
45

Optovláknové senzory neelektrický veličin / Non-elektricity Quantities Fiber Optic Sensor

Mytyska, Kamil January 2017 (has links)
This diploma thesis deals with an analysis of the method of propagation of optical fiber by two polarization planes. The method of light propagation is mathematically described using Jones and Stokes vectors. The first part describes wave theory of light divided by Fresnel wave theory, polarization ellipse, degenerate polarization states, parameters of polarization ellipse, Poincaré sphere and degenerated states on Poincaré sphere. Then follows Stokes and Jones polarization parameters, their vectors and Mueller matrix. In addition this paper illustrates the principle of the temperature sensor which is carried out with the help of the polarimeter and its computer program. The following is design of temperature sensor, which is composed of polarizer, photodiode, light output meter and digital multimeter. Another part of the thesis shows the measured values using the current measurement solution using polarimeter and proposed photodiode sensor. At the end of the thesis there is a comparison of the measured values for the three different temperatures that were applied to the optical fiber.
46

Models in nonlinear condensed-matter optics: From theory to experiment

Voit, Kay-Michael 12 April 2013 (has links)
Cumulative Dissertation on models in nonlinear condensed-matter optics. In chapter 2, the coupled-wave theory first introduced by Kogelnik is reviewed and extended with emphasis on out-of-phase mixed holographic gratings. This class of gratings becomes increasingly important due to novel methods of hologram recording and new classes of materials and metamaterials like holographic polymer dispersed liquid crystals. Additionally, advances in laser technology suggest a stronger spectro- scopic view on holography. The model presented in this thesis accounts for both of these demands and provides a closed analytical solution. Chapter 3 contributes to the field of space-charge waves (SCW), which provides powerful tools for material analysis, especially in semiconductor technology. Although the underlying theory is generally understood, recent improvements of the ex- perimental techniques required extensions of the model and the interpretation of new effects. In this thesis, the existing formalism is adapted to a new method of excitation, which not only simplifies the experimental setup, allowing for easier adoption into industrial environments, but also provides insight into the direction of carrier motion. Furthermore, the model is extended to describe the influence of an external magnetic field, adding the possibility to examine the Hall mobility of carriers. Eventually, chapter 4 studies the dynamics of light induced absorption in pho- tochromic [Ru(bpy)2 (OSO)]+ . Compared to other photofunctional compounds, this molecule is nontoxic and exhibits exceptional photochromic reactions. These properties make it a promising candidate for important industrial and technological applications, ranging from data storage to non-electronic computation. For a profound analysis, the models used for the description of photofunctional molecules have been completely revised to account for the pronounced absortion changes in the material. Furthermore, a setup with orthogonal pump and probe beams is modeled and exper- imentally tested. This novel geometry is introduced to resemble common industrial setups.
47

Theories, experiments, and human agents: the controversy between emissionists and undulationists in Britain, 1827-1859

Chen, Xiang 22 May 2007 (has links)
This dissertation is an interdisciplinary study of scientific change. The undulatory theory of light replaces the emission theory of light in the early nineteenth century, triggering an "optical revolution" and vigorous debates among physicists in British from the 1830s to the 1850s. In this study I give the first full account of this extended episode of scientific change, drawing on methods and concepts from history, sociology and philosophy of science. The interdisciplinary account of the episode provides a basis for criticizing the existing models of scientific change in the philosophy of science. Previous historical studies of the “optical revolution" pay little attention to the period after the 1830s. Because the cognitive superiority of the undulatory theory had become obvious in the early 1830s, some historians have implicitly assumed that any controversy would soon come to a natural end. I, however, document that intensive debates continued from the 1830s until the end of the 1850s, and that emissionists even enjoyed temporary victories in their fights with undulationists. The narrative reveals the historical complexities of this episode: the debates extended long after the cognitive superiority of the undulatory theory should have become apparent by modern standard, the results of the debates did not necessarily coincide with modern cognitive judgements, and individual agents played decisive roles in determining how long a debate lasted and how it would end. On the basis of the historical narrative, I provide a philosophical analysis of the practices of theory appraisal and experiment appraisal that constituted the main theme of the controversy. Instead of merely identifying the criteria of evaluation employed in this episode, I pay special attention to how individual agents actually applied these criteria in concrete situations, what kinds of strategies or tactics they employed for the applications of these criteria, and how they created favorable conditions, both cognitive and social, for successfully applying these criteria. Individual agents’ efforts in selecting application strategies and in creating favorable conditions made the practices of appraisal complicated, exhibiting various features that are incomprehensible if we limit ourselves merely to studying the criteria of evaluation. I finally discuss a different approach to scientific change. The existing philosophical models of scientific change merely analyze the final product of science -- scientific theories, and ignore the impact of social factors and the role of individual agents. I suggest we concentrate on the process of knowledge production, and pay attention to individual agents’s practices in this process, as well as to the relevant cognitive and social factors that influence individual agents. Following this new approach, scientific change is understood as an evolution that involves interactions among three elements: theory, experiment, and human agent. / Ph. D.
48

Interpretação de resultados do ensaio SPT com base em instrumentação dinâmica / Interpretation of SPT test results based on dynamic instrumentation

Lukiantchuki, Juliana Azoia 27 July 2012 (has links)
O ensaio de simples reconhecimento do solo (SPT) e usualmente utilizado para estimar a resistência do solo, atraves do índice NSPT, que representa a resistencia a penetração dinâmica do amostrador no solo. Esse índice é usado diretamente em correlações empíricas ou semi-empíricas na determinação da capacidade de suporte e recalque das fundações. Entretanto, esse ensaio tem sido alvo de críticas devido a utilização dessas correlações empíricas, geralmente baseadas em observações práticas e sem nenhum fundamento científico. Críticas também estão relacionadas com a dispersão dos resultados, devido a utilização de diferentes tipos de equipamentos e procedimentos executivos. O índice NSPT depende da parcela de energia que e efetivamente transmitida ao amostrador durante a queda do martelo. Assim, análises racionais dos resultados de ensaios SPT dependem essencialmente da estimativa da quantidade dessa energia. Por esse motivo, tem sido desenvolvidas diversas pesquisas relacionados com a energia envolvida no ensaio SPT. Este trabalho apresenta interpretações dos resultados do ensaio SPT a partir das quantidades de energia envolvidas durante a queda do martelo. Essas quantidades de energia são determinadas indiretamente, através dos sinais de força normal e aceleração durante a propagação da onda de tensão ao longo da composição de hastes. Para isso, foi desenvolvido um equipamento que inclui uma instrumentação capaz de registrar esses sinais de força normal e aceleração. Uma série de ensaios SPT foi realizada com instrumentação instalada tanto no topo como na base da composição de hastes. Esse arranjo permitiu estimar as quantidades de energia disponíveis no topo e na base da composição de hastes. Assim, foi possível determinar a eficiência dos equipamentos SPT com base na quantidade de energia que efetivamente atinge o amostrador. A partir dos sinais registrados, também foi possível determinar a resistência dinâmica mobilizada no sistema solo-amostrador. Os resultados experimentais foram comparados com resultados obtidos através de métodos teóricos, baseados no Princípio de Hamilton, para a determinação da resistência estática e dinâmica do solo. Essas análises mostraram que equações teóricas podem ser adequadas para a determinação da resistência do solo, desde que seja considerada a quantidade de energia que efetivamente atinge o amostrador. Desta forma, essas equações teóricas podem ser facilmente incorporadas na prática de projeto de fundações, contribuindo para o desenvolvimento de métodos baseados na quantidade de energia necessária para a penetração do amostrador no solo. / The standard penetration test (SPT) is usually used to estimate the soil strength through the NSPT index which represents the dynamic reaction force of the sampler penetration into the soil. This index is directly used in empirical or semi-empirical correlations for the determination of the bearing capacity and foundation settlements. However, this test has been criticized due to the use of these empirical correlations, often based on practical observation without any scientific basis. Criticism is also related to result dispersion due to the use of different types of equipment and execution procedures. The NSPT index depends on the amount of energy that is effectively transmitted to the sampler during the hammer fall. Thus, rational analyses of the SPT test results essentially depend on the estimation of this amount of energy. For this reason, several studies related to the energy involved in SPT test have been developed. This research presents interpretations of the SPT test results from the amounts of energy involved during the hammer fall. These amounts of energy are indirectly assessed by means of normal force and acceleration signals during the stress wave propagation along the string of rods. For this reason, a device that includes instrumentation capable of registering these signals of normal force and acceleration was developed. A series of tests was performed with the instrumentation installed at the top and the bottom of the string of rods. This arrangement allowed estimating the amount of energy available at the top and bottom of the string of rods. Thus, it was possible to estimate the efficiency of the SPT equipment basing on the amount of energy that actually reaches the sampler. From the recorded signals, it was also possible to assess the dynamic reaction force mobilized in the soil-sample system. The results were compared with other results obtained by theoretical methods, based on the Hamilton´s Principle, for evaluating the static and dynamic reaction force of the soil. These analyzes have shown that theoretical equations may be suitable for the determination of the soil strength, provided that the amount of energy that actually reaches the sampler be considered. Thus, these theoretical equations can be easily incorporated into the practice of foundation designs contributing to the development of methods based on the amount of energy required for the penetration of the sampler into the soil.
49

Theoretical Studies of Two-Dimensional Magnetism and Chemical Bonding

Grechnyev, Oleksiy January 2005 (has links)
<p>This thesis is divided into two parts. In the first part we study thermodynamics of the two-dimensional Heisenberg ferromagnet with dipolar interaction. This interaction breaks the conditions of the Mermin-Wagner theorem, resulting in a finite transition temperature. Our calculations are done within the framework of the self-consistent spin-wave theory (SSWT), which is modified in order to include the dipolar interaction. Both quantum and classical versions of the Heisenberg model are considered.</p><p>The second part of the thesis investigates the chemical bonding in solids from the first principles calculations. A new chemical bonding indicator called balanced crystal orbital overlap population (BCOOP) is developed. BCOOP is less basis set dependent than the earlier indicators and it can be used with full-potential density-functional theory (DFT) codes. We apply BCOOP formalism to the chemical bonding in the high-T_c superconductor MgB2 and the theoretically predicted MAX phase Nb3SiC2. We also study how the chemical bonding results in a repulsive hydrogen–hydrogen interaction in metal hydrides. The role of this interaction in the structural phase transition in Ti3SnHx is investigated.</p>
50

Theoretical Studies of Two-Dimensional Magnetism and Chemical Bonding

Grechnyev, Oleksiy January 2005 (has links)
This thesis is divided into two parts. In the first part we study thermodynamics of the two-dimensional Heisenberg ferromagnet with dipolar interaction. This interaction breaks the conditions of the Mermin-Wagner theorem, resulting in a finite transition temperature. Our calculations are done within the framework of the self-consistent spin-wave theory (SSWT), which is modified in order to include the dipolar interaction. Both quantum and classical versions of the Heisenberg model are considered. The second part of the thesis investigates the chemical bonding in solids from the first principles calculations. A new chemical bonding indicator called balanced crystal orbital overlap population (BCOOP) is developed. BCOOP is less basis set dependent than the earlier indicators and it can be used with full-potential density-functional theory (DFT) codes. We apply BCOOP formalism to the chemical bonding in the high-T_c superconductor MgB2 and the theoretically predicted MAX phase Nb3SiC2. We also study how the chemical bonding results in a repulsive hydrogen–hydrogen interaction in metal hydrides. The role of this interaction in the structural phase transition in Ti3SnHx is investigated.

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