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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.
161

A Bourdieusian investigation into reproduction and transformation in the field of disability cricket

Kitchin, Paul J. January 2014 (has links)
Disability cricket in England and Wales exists within a constant state of change. This thesis is an organizational analysis of how environmental factors foster reproduction and/or transformation within the field of disability cricket. It is important to examine how these factors are translated across multiple levels of analysis; institutional, organizational, and individual. A layered analysis is important because it attempts to overcome the limitations of previous micro- and macro-approaches to change. A reflexive ethnography that involved three years of fieldwork allowed perceptions and meanings of change to be examined in real-time. This approach is novel in studies of institutional and organizational change. Data was collected through formal and informal interviews, active-member observations, and document analysis. The findings reveal a series of structural and cognitive consequences, which included a greater number of playing opportunities for disabled cricketers and the establishment of an economic market for disability cricket which ensured organizational commitment to accepting accountability and managerial pressures. While change occurred, the nature of organizational responses to these environmental factors varied. Drawing on the theoretical insights of Bourdieu (2005) and the institutional theory of translation (Czarniawska & Sevon, 1996), I demonstrate that these responses varied between organizations because of the relationship between the field, the organization's doxa and the habitus of the individuals employed within. It concludes empirically that the translation of environmental factors is dependent on the interlinking relationships between institutions, organizations and individuals. The use of Bourdieu extends previous institutional analysis in sport management by providing a unique perspective on the role of organizations in reproducing inequality. As this thesis demonstrates institutional change is a recurrent theme in British sport organizations and further work is needed to examine the impact of these changes on the relations between sport organizations and the participants, employees and volunteers within them. As such it reinforces interdisciplinary calls to link sport management and the sociology of sport.
162

Method development for affinity capillary electrophoresis of ß2-glycoprotein I and biological ligands

Bohlin, Maria E. January 2011 (has links)
The final goal of this study is to establish a microscale analysis method that allows solution phase characterization of interactions between β2-glycoprotein I (β2gpI) and some of its ligands. Human β2gpI is a phospholipid- and heparin-binding plasma glycoprotein. The physiological role of the protein in normal blood coagulation is not entirely known, nor is its role in autoimmune diseases characterized by blood clotting disturbances (thrombosis). Quantitative binding data of β2gpI interactions with some of its ligands may help elucidating the mechanisms behind these diseases and in the development of new approaches for diagnostics, prevention, and therapy. In this thesis, capillary electrophoresis (CE) was used as methodological platform for the interaction studies. The analysis of peptides and proteins by CE is desirable due to low sample consumption, possibilities for non-denaturing and highly effective separations. The first objective of this thesis was to find an approach to prevent charge dependent adsorption of β2gpI to the inner surface of the capillaries. Analyte adsorption at the negatively charged inner surface of fused silica capillaries is detrimental to interaction analyses. This phenomenon is especially pronounced in the analysis of basic proteins and proteins containing exposed positively charged domains, such as β2gpI. A new strategy to suppress these solute-wall interactions was devised, investigated and optimized. This strategy exploits the pH hysteresis behavior of fused silica surfaces, by simply performing an acidic pretreatment of the capillary. The results in this thesis show that the acidic pretreatment efficiently prevents protein adsorption. / <p>Papper 4 Estimation of the amount of β<sub>2</sub>-glycoprotein I adsorbed at the inner surface of fused silica capillaries after acidic, neutral and alkaline pretreatment ingick som manuskript i avhandlingen, nu publicerad.</p>
163

Computational modelling for type-II superconductivity and the investigation of high temperature superconducting electrical machines

Barnes, Gary James January 2000 (has links)
No description available.
164

Configuration Optimization of Underground Cables inside a Large Magnetic Steel Casing for Best Ampacity

Moutassem, Wael 22 February 2011 (has links)
This thesis presents a method for optimizing cable configuration inside a large magnetic cylindrical steel casing, from the total ampacity point of view. The method is comprised of two main parts, namely: 1) analytically calculating the electromagnetic losses in the steel casing and sheathed cables, for an arbitrary cables configuration, and 2) implementing an algorithm for determining the optimal cables configuration to obtain the best total ampacity. The first part involves approximating the eddy current and hysteresis losses in the casing and cables. The calculation is based on the theory of images, which this thesis expands to apply to casings having both high magnetic permeability and high electric conductivity at the same time. The method of images, in combination with approximating the cable conductors and sheaths as multiple physical filaments, is used to compute the final current distributions in the cables and pipe and thus the associated losses. The accuracy of this computation is assessed against numerical solutions obtained using the Maxwell finite element program by Ansoft. Next, the optimal cable configuration is determined by applying a proposed two-level optimization algorithm. At the outer level, a combinatorial optimization based on a genetic algorithm explores the different possible configurations. The performance of every configuration is evaluated according to its total ampacity, which is calculated using a convex optimization algorithm. The convex optimization algorithm, which forms the inner level of the overall optimization procedure, is based on the barrier method. This proposed optimization procedure is tested for a duct bank installation containing twelve cables and fifteen ducts, comprising two circuits and two cables per phase, and compared with a brute force method of considering all possible configurations. The optimization process is also applied to an installation consisting of a single circuit inside a large magnetic steel casing.
165

Finite element simulation of the micromagnetic behaviour of nanoelements

Ridley, Philip Harold William January 2000 (has links)
No description available.
166

Glacial geology and glaciology of the Younger Dryas ice cap in Scotland

Golledge, Nicholas Robert January 2009 (has links)
This thesis uses geological field data and numerical ice sheet modelling to study the Younger Dryas ice cap in Scotland. The Younger Dryas stadial is important because it represents the most recent period of high-magnitude global climate change, and was marked by the expansion of ice sheets in North America and Scandinavia, and the regrowth of glaciers in the British Isles. An integrated methodology linking field results and modelling is developed and applied here, specifically focussing on the deposits, landforms, and palaeoglaciology of Younger Dryas glaciers in western Scotland. This combined approach enables data of different scales to be compared, and connected, from local sedimentological investigations and empirically derived reconstructions, to regional ice-sheet simulations from a high-resolution numerical model. Previous geological mapping in western Scotland resulted in contradictory views of the thickness and extent of ice during the Younger Dryas, consequently leading to uncertainty about the dynamics of the former ice cap. By using a ‘landsystem’ method to characterise the terrain, it is argued here that geological evidence in the study area implies a relatively thick central ice cap that fed steep outlet glaciers around its margins. These glaciers oscillated throughout the stadial, and during deglaciation produced suites of moraines that marked successive positions of glacier retreat. Widespread preservation of superimposed landforms, and of sediment sequences pre-dating the Younger Dryas, suggest that, despite being active, the Younger Dryas ice cap was not particularly erosive in its central area and only subtly modified its bed. These geological interpretations are supported by high-resolution numerical modelling of the ice cap, which reveals clear spatial variability in the velocity structure, thermal regime, and flow mechanism of the ice cap; patterns that led to local contrasts in basal processes and diversity in the geological imprint. These model experiments also highlight the non-linear relationship between climate forcing and glacier response, identifying evidence of ice sheet hysteresis and climatically decoupled glacier oscillations – concepts as relevant to geological investigations of former ice masses as they are to the prediction of glacier response under future climate changes.
167

A three-phase hybrid dc-ac inverter system utilizing hysteresis control

White, Terence H. 06 1900 (has links)
Approved for public release; distribution is unlimited / The naval vessels of the future will require lighter, more compact, and more versatile power electronics systems. With the advent of the DC Zonal Electrical Distribution System, more innovative approaches to the conversion of the dc bus power to ac power for motor drives will enhance the efficiency and warfighting capability of tomorrow's ships. This thesis explores the concept of a hybrid dc-ac power converter that combines a hysteresis controlled inverter with a six-step bulk inverter. A six-step bulk inverter is built from discrete components and tested in simulation and hardware. The two inverters are connected in parallel to provide a high-fidelity current source for a three-phase load. The addition of the hysteresis inverter to the bulk inverter adds a closed current loop for more robust control and improves the quality of the output load current. / Major, United States Marine Corps
168

Devenir du séléniate dans les sols : mise en évidence expérimentale et modélisation des phénomènes d'hystérèse de sorption/désorption / Behaviour of selenate in soils : experimental approch and modelisation of hysteresis of sorption/desorption

Loffredo, Nicolas 07 April 2011 (has links)
Dans le contexte des futurs stockages des matières nucléaires en couches géologiques profondes, le transfert de sélénium 79 des eaux de nappes vers la biosphère, par le biais de l’irrigation, est un des scenarii envisagés par l’ANDRA. Le sol servirait alors d’interface entre la géosphère et la biosphère. Le modèle actuellement utilisé pour évaluer la mobilité de nombreux éléments dans le sol repose sur une représentation simple de leur distribution entre la quantité adsorbée sur le sol et la quantité restante en solution (modèle Kd), considérée comme instantanée, réversible et linéaire avec la concentration de contamination. Ce modèle présente des lacunes vis-à-vis du sélénium puisque ce dernier peut être présent sous différents états redox qui contrôlent sa mobilité et dont les cinétiques de transformation entre ces états sont peu connues (Se(-II), Se(0),Se(IV) et Se(VI)).Dans le but d’améliorer les prédictions faites sur la mobilité du sélénium dans un sol, le séléniate (Se(VI)), qui est la forme la plus mobile, a été utilisé pour étudier ses interactions vis-à-vis de deux sols différents (sol B et sol R).Un modèle cinétique, alternatif au modèle Kd, a été développé pour décrire l’évolution des stocks de Se(VI) en solution, en considérant une fraction de sélénium associée au sol de façon réversible (potentiellement mobile) et une fraction stabilisée sur le sol (fixée pseudo-irréversiblement). Ce modèle intègre des cinétiques de stabilisation biotique et abiotique sur le sol, et une cinétique de réduction en solution. Afin d’acquérir les paramètres des modèles, des expériences en batchs et en réacteurs à flux ouvert avec l’utilisation de sacs à dialyse ont été réalisées. L’acquisition des paramètres a permis de confronter les modèles cinétiques et Kd dans différents scenarii réalistes de contamination (chronique ou séquentielle) d’un sol de surface par du 79Se(VI).De plus, les mécanismes de sorption du Se(VI) au sein des deux sols ont été évalués en batch avec l’ajout de compétiteurs spécifiques vis-à-vis de certains sites pouvant sorber ce dernier (acides humiques et carbonates de calcium). Ceci a été complété avec l’étude de la sorption du Se(VI) sur des phases pures commerciales (silice, hydroxyde d’aluminium, goethite, bentonite, carbonate de calcium et acides humiques) ou extraites d’un sol (substances humiques), pour différentes concentrations en Se(VI) (10-8, 10-6 et/ou 10-3 mol/L), de l’impact de l’ajout de phases pures réactives, dans les sols, sur la sorption du Se(VI).Il a été montré que le Se(VI) était sorbé sous la forme de complexes de sphères externes (CSE) au sein du sol R pour des concentrations inférieures à 10-6 mol/L, tandis que dans le sol B, la majorité était sorbée sous la forme de complexes de sphère internes (CSI). La formation de CSE étant réversible et instantanée, l’utilisation du modèle Kd était donc suffisante pour décrire la sorption du Se(VI) au sein du sol R, dans les expériences en réacteurs à flux ouvert. A contrario, pour le sol B, il a été montré que le modèle Kd, contrairement au modèle cinétique, présentait des lacunes pour décrire la sorption pseudo-irréversible du Se(VI), engendrée par la formation de CSI. Il a été montré que les mécanismes biotiques étaient majoritaires au sein du sol B, en raison de l’apport de nutriments pour les microorganismes, par l’utilisation de sacs à dialyse en cellulose régénérée. Cependant les mécanismes abiotiques ont aussi eu lieux au sein du sol B.14/256. Les études sur les phases pures ont montré que seuls l’hydroxyde d’aluminium (pH 5,2 et 8) et la goethite (pH 5,2) pouvaient sorber le Se(VI) respectivement de manière pseudo-irréversible et réversible (pour [Se(VI)] < 10-6mol/L). Enfin, il a été montré que l’ajout de certaines phases pures (goethite et hydroxyde d’aluminium) au sein des deux sols, pouvait entrainer une augmentation ou une diminution de la sorption du Se(VI) par rapport à celle attendue (additivité réactionnelle). / In the context of future storage of nuclear material in deep geological layers, the transfer of selenium-79 from groundwater to biosphere through irrigation is one of the scenarios considered by the ANDRA (National Agency for Radioactive Waste Management). So, the soil would act as an interface between the geosphere and biosphere. Actually the model adopted to evaluate the element mobility in soil is based on a simple representation of its distribution between the quantity adsorbed on the soil and the amount remaining in the solution (KD model). Such distribution is considered as instantaneous, reversible and linear with the concentration of contamination. This model has some inadequacies with respect to selenium because this latter can be present in different redox states that control its mobility and whose transformation kinetics among states are poorly known (Se(-II), Se(0), Se(IV)and Se(VI)). In order to improve predictions on the mobility of selenium in soil, selenate (Se(VI)) - which is the most mobile form - has been used to study its interactions with respect to two different soils (soil B and soil R). Akinetic model, alternative to the Kd model, has been developed to describe the evolution of stocks of Se(VI) in solution. This model considers that a fraction of selenium is associated with soil in a reversibly way (potentially mobile) and a portion of it is stabilized in soil (pseudo-irreversibly fixed). This model integrates on one hand, in the soil, kinetics of biotic and abiotic stabilization and on the other hand, in solution, a reduction kinetic. With the goal of acquiring the parameters of the models, various experiments using dialysis bags have been effectuated, both in batch and with open-flow reactors. The parameter acquisition has allowed kinetic and Kd models to be compared in different realistic scenarios of contamination (chronic or sequential) of a surface soil with 79Se(VI). In addition, the sorption mechanisms of Se(VI) have been evaluated in the two soils in batch adding specific competitors (humic acid and calcium carbonates) that can sorb on solid sites such as selenate. This study has been completed with the analysis of the sorption of Se(VI) on pure phases available on the market (silica, aluminum hydroxide, goethite, bentonite, calcium carbonate and humic acids) or extracted from a soil (humic substances).This investigation has been carried out at different concentrations of Se(VI) (10-8, 10-6 et/ou 10-3 mol/L). In addition, some pure reactive phases have been added to the soil in order to study the solid-solid interaction having a role on the sorption of Se(VI).This study has underlined that in the R-soil Se(VI) was sorbed in the form of outer sphere complexes (OSC) at concentration slower than 10-6 mol/L, whereas in B-soil, the majority were sorbed as inner sphere complexes (ISC). As the formation of OSC is reversible and instantaneous, in experiments with open-flow reactors, the use of Kd model was sufficient to describe the sorption of Se(VI) in R-soil. On the contrary, for soil B, the study has shown that the Kd model, unlike the kinetic model, was inadequate to describe the pseudo-irreversible sorption of Se(VI), caused by the formation of ISC. Due to the supply of nutrients for microorganisms, it has been shown that biotic mechanisms predominated in soil B, due to the utilization of cellulose dialysis bags. However, abiotic mechanisms took places in soil B, too. The studies on pure phases have shown that only aluminum hydroxide (pH 5.2 and 8) and goethite (pH 5.2) could sorb Se(VI), respectively in a pseudo-irreversible and reversible way (for [Se(VI)] < 10-6 mol/L).Moreover, it has been shown that, in both soils, the addition of some pure phases (goethite and aluminum hydroxide),could cause an increase or a decrease of the sorption of Se(VI) with respect to the one expected (additivity reaction).
169

Les origines de l'hystérésis de potentiel dans les batteries Li-ion / The origin of voltage hysteresis in Li-ion batteries

Khatib, Rémi 05 April 2013 (has links)
Dans les années 2000, les matériaux de conversion sont apparus comme une alternative intéressante aux matériaux d'insertion actuellement utilisés dans les batteries Li-ion. Ils réagissent avec le lithium pour former une électrode constituée de nanoparticules métalliques encapsulées dans une matrice lithiée. Pour comprendre ces réactions, le phosphure de cobalt (CoP) a été étudié au moyen de techniques théoriques et expérimentales. La complexité de ces systèmes nanocomposites n'a pas permis de caractériser toutes les espèces présentes dans l'électrode. Cependant, les calculs DFT ont prédit la formation de composés intermédiaires dont les potentiels de formation sont cohérents avec l'expérience. De plus, ces travaux ont mis en évidence l'importance de la réactivité de surface quant à l'origine de l'hystérésis de potentiel qui nuit au rendement énergétique de ce type d'électrode. La méthodologie développée spécialement pour les réactions de conversion, mais transférable vers d'autres réaction électrochimique, a été validée par les mesures expérimentales. / In the 2000s, conversion materials appeared as an interesting alternative to the insertion materials currently used in Li-ion batteries. They react with lithium to form an electrode constituted of metallic nanoparticles embedded into a lithiated matrix. To understand those reactions, cobalt phosphide (CoP) has been studied by theoretical and experimental techniques. The complexity of those nanocomposite systems does not allow to characterize all the species present inside the electrode. However, DFT calculations predicted the formation of intermediate compounds whose the formation potentials are in agreement with the experiment. Moreover, these studies have highlighted the importance of surface reactivity about the voltage hysteresis which harms to the electrode efficiency.The methodology especially developed for conversion reactions, but transferable to others electrochemical reaction, was validated by experimental measures.
170

Hystereze nezaměstnanosti v České republice / Unemployment hysteresis in the Czech Republic

Bechný, Jakub January 2016 (has links)
This thesis presents an empirical analysis of the unemployment hysteresis in the Czech Republic on quarterly data from 1999 to 2015. The hysteresis is modelled by allowing for: (i) impact of the cyclical unemployment on the NAIRU; (ii) impact of the long-term un- employment on the NAIRU. Models are written in state space form and estimated using Bayesian approach. The main contributions of this thesis are as follows. The results pro- vide robust evidence in favour of the hysteresis in the Czech Republic, but precise size of the hysteresis effect is surrounded by relatively large uncertainty. Posterior mean estimates of key parameters indicate that in response to increase in the cyclical unemployment of 1 percentage point, the NAIRU increases by 0.15 percentage points. The first specification of the hysteresis implies that the hysteresis induced changes in the Czech Republic's NAIRU of at most 1 percentage point. The hysteresis specified as impact of the long-term unemploy- ment on the NAIRU then implies even weaker effect, inducing changes in the NAIRU of at most 0.6 percentage points. The models are estimated jointly with the hybrid Phillips curve identified using survey forecasts as proxies for the expectations. Estimate of the expecta- tions' parameter 0.65 indicates the forward-looking nature of the Czech...

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