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Dissertationen zum Thema „Semi-distribution“
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1
Hong, Jiazheng. „A Semi-Analytical Load Distribution Model of Spline Joints“. The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1426110670.
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2
Kim, Minjoo. „Three essays in semi-parametric modelling of time-varying distribution“. Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/1916/.
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During the last century we have been frustrated by the number of economic crises which trigger extreme uncertainty in the global economic system. Economic agents are sensitive to the uncertainty of inflations, as well as to asset values, for survival in such circumstances. Hence, modern finance and monetary economics emphasise that risk modelling of asset values and inflations are key inputs to financial theory and monetary policy. The risk is completely described by the distribution which is verified to be time-varying and non-normal. Although various parametric and non-parametric approaches have been developed to model the time-varying nature and the non-normality, they still suffer from intrinsic limitations. This study proposes the dynamic modelling of the non-parametric distribution (Functional Autoregressive Model (FAR) and Spatial Distribution Analysis) in order to overcome the limitations. Firstly, we apply FAR to the Value-at-Risk analysis. It forecasts an intraday return density function by the functional autoregressive process and calculates a daily Value-at-Risk by the Normal Inverse Gaussian distribution. It reduces economic cost and improves coverage ability in the Value-at-Risk analysis. Secondly, we apply FAR to forecasting the cross-sectional distribution of sectoral inflation rates, which holds the information of the heterogeneous variation across sectors. As a result, it improves the aggregate inflation rate forecasting. Further, the heterogeneous variation is utilised for constructing the uncertainty band of the aggregate inflation forecast, like the fan-chart of the Bank of England. Thirdly, we apply the spatial distribution analysis to rank investment strategies by comparing their time aggregated utilities over the investment horizon. To this end, we use a spatial dominance test. Since a classical stochastic dominance approach considers only the return distribution at the terminal time point of the investment horizon, it cannot properly evaluate the risk, broken out exogenously or endogenously, in the middle of the investment horizon. However, the proposed spatial dominance approach considers completely the interim risk in evaluating alternative investment strategies.
3
Chopping, M. J. „Linear semi-empirical kernel-driven bidirectional reflectance distribution function models in monitoring semi-arid grasslands from space“. Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262949.
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4
Bianco, Nicola. „Optimal control of particle size distribution in semi-batch emulsion polymerisation“. Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/7474.
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5
Ozger, Sukru Serkan. „A semi-pressure-driven approach to reliability assessment of water distribution networks“. online access from Digital Dissertation Consortium access full-text, 2003. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?3109593.
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6
Sun, Ye. „Peer-assisted semi-persistent online storage and distribution : design, analysis and modeling /“. View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CSED%202009%20SUN.
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7
Hu, Xin. „Distribution, elimination and toxicity assessment of semi-volatile polychlorobiphenyls after inhalation exposure“. Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2523.
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Inhalation exposure to semi-volatile polychlorobiphenyls (PCBs) that ubiquitously exist in the environment has the potential to cause adverse health effects. Recently identified sources of airborne PCBs, especially non-legacy sources, stress the importance of risk assessment for inhalation exposure. However, the fate of inhaled airborne PCBs in biological systems and the resultant toxicity remain unexplored.
The objective of this thesis research was to investigate the distribution and elimination of semi-volatile PCBs in biological systems after inhalation exposure and evaluate the biologic and toxicologic consequences. This objective was achieved by conducting the following inhalation studies in rats: a short-term exposure study of the body burden and elimination; a subchronic exposure toxicity study; an acute exposure study of PCB11 metabolism; and a mass balance study of [14C]PCB11 following lung exposure.
PCBs found in technical Aroclor mixtures and PCB11 were readily absorbed and distributed following nose-only inhalation exposure. PCBs accumulated in adipose tissue, but decayed in other tissues with biological half-lives of several hours. Their elimination was dependent on the structure of the PCB congeners and the metabolic nature of the organ. Lower-chlorinated PCBs exhibited more rapid clearance than higher-chlorinated congeners yet differential rates of elimination were also seen within the homologue. A distinct congener pattern was found in tissues, ranging from tri- to pentachorobiphenyls after subacute and subchronic exposure.
Rapid elimination of PCB11 and its metabolite, 4-OH-CB11, were detected in liver following nose-only inhalation exposure by our established methodology. Further investigation revealed that [14C]PCB11 was 99.8% absorbed in lung. Elimination of the [14C]PCB11 and products consisted of an initial fast phase followed by a slow clearance phase. [14C]PCB11 underwent rapid and extensive metabolism in liver. The major products were phase II metabolites which dominated in the non-adipose tissues and were eliminated via the large intestine and urine.
Overall, differential congener elimination was found after inhalation of airborne PCBs, with minimal toxicity. Lower-chlorinated congeners were rapidly and extensively metabolized to phase II products and eliminated within hours.
8
Crego, Ramiro Daniel. „Modeling the distribution of meadows in arid and semi-arid Patagonia, Argentina: assessing current distribution and predicting response to climate change“. OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/1001.
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Meadows are critical in arid and semi-arid Argentinean Patagonia because of their importance for regional biodiversity. Despite this, little information on the spatial distribution of meadows is available and no analysis of the potential effect of climate change on meadows has been performed, which hampers conservation planning. In this study, I modeled the spatial distribution of meadows and investigated how climate change may affect the current distribution of meadows in arid and semiarid Patagonia by 2050. In addition, I investigated conservation status and areas of desertification vulnerability of those areas predicted to contain meadows. I used high-resolution imagery available in Google Earth software to visually estimate presence and absence of meadows. To model current and future distribution of meadows I used these observations and different socio-environmental predictor variables. I implemented generalized linear, additive, boosting, and random forest models, as the basis for a mean ensemble technique. I predicted future distribution of meadows using four different general circulation models and the A2 SERES scenario. The final ensemble model was an accurate representation of the current distribution of meadows in Patagonia and indicates they are severely under-represented within protected areas. I determined that overall meadow abundance is going to decrease by 2050 given the changes in climate. However, there were two contrasting trends: severe reduction of meadows in northwest Patagonia and Tierra del Fuego Island, and an expansion of suitable areas for meadows in the south and a small section in the northwest. This first regional map of meadow distribution across Argentinean Patagonia and information on meadows vulnerability to climate change represent key information for planning actions to conserve this critical habitat.
9
Shek, Yiu-fai, und 石耀輝. „Electric field distribution in metal/semi-insulating GaAs contacts investigated by positron lifetime technique“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31221579.
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10
Gramlich, Anja. „Development of a semi-quantitative method to determine the distribution of Ni in hyperaccumulator plants“. Zürich : ETH, Swiss Federal Institute of Technology Zurich, ITES - Institute of Terrestrial Ecosystems, 2008. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=365.
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11
Keromnes, Gwen. „Les incidences du droit communautaire sur le droit national français de la distribution semi-intégrée“. Paris 2, 1991. http://www.theses.fr/1991PA020094.
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A la date de l'entree en vigueur du traite de rome, le droit national francais de la concurrence relevait moins d'un systeme de protection de la competition dans l'interet des consommateurs que d'un systeme de protection des concurrents. Ainsi prohibait-il le refus de vendre qui constituait un delit prevu pa l'article 37-1 a) de l'ordonnance no 1483. 45 du 30 juin 1945. Or, tel n'etait pas la conception de la libre concurrence qui presida a l'elaboration et a l'application des articles 85 et 86 du traite cee. C'est pourquoi, nous assistames a un assez long combat d'arriere-garde, qui eut pour cadre les relations entre operateurs places a un stade different du processus economique. Mais les principes de la primaute et de l'effet direct du droit communautaire eurent finalement raison de la resistance du gouvernement francais, lequel depenalisa en 1986 une pratique inherente a l'existence de reseaux de distribution semi-integree : le refus de venteWhen the treaty of rome came into force, french national competition law was more a system to protect the competitor, than a system of competition protecting the consumer's interest. Thus it prohibited the refusal to sell wich constituted a crime provided by article 37-1 a) of the ordinance no 45. 1483 of june 30. 1945. However, this was not the conception of free competition wich existed at the time of the creation and application of articles 85 and 86 of the treaty of rome creating the european economic community. This is why we saw a rather long struggle between operators at the different economic levis. But the principles of primacy and direct effect of european law finally won and the french government decriminalised a practice wich was inherent to the existence of semi-integrated distribution networks in 1986 : the refusal to sell
12
De, Meo Ilaria. „Ecological distribution of semi-demersal fishes in space and time on the shelf of Antalya Gulf“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9030/.
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In this study we provide a baseline data on semidemersal fish assemblages and biology in a heterogeneous and yet less studied portion of the shelf of Antalya Gulf. The distribution of fish abundance in three transects subjected to different fisheries regulations (fishery vs non fishery areas), and including depths of 10, 25, 75, 125, 200 m, was studied between May 2014 and February 2015 in representative months of winter, spring, summer and autumn seasons. A total of 76 fish species belonging to 40 families was collected and semidemersal species distribution was analyzed in comparison with the whole community. Spatial distribution of fish was driven mainly by depth and two main assemblages were observed: shallow waters (10-25; 75 m) and deep waters (125-200 m). Significant differences among transects were found for the whole community but not for the semidemersal species. Analysis showed that this was due to a strong relation of these species with local environmental characteristics rather than to a different fishing pressure over transects. Firstly all species distribute according to the bathymetrical gradient and secondly to the bottom type structure. Semidemersal species were then found more related to zooplankton and suspended matter availability. The main morphological characteristics, sex and size distribution of the target semidemersal species Spicara smaris (Linnaeus, 1758), Saurida undosquamis (Richardson, 1848), Pagellus acarne (Risso, 1827) were also investigated.
13
Haworth, Kathryn. „Effects of Quercus emoryi trees on microclimate, precipitation distribution, and herbs in a semi-arid savanna“. FIND on the Web, 1992.
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14
Campbell, M. D. „The distribution of weathering and erosion on an inselberg-pediment system in semi-arid central Sudan“. Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636200.
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A number of geomorphic studies were conducted on Jebel Arashkil, an inselberg and pediment complex in central Sudan. The various explanations of inselbergs are summarised and some testable hypotheses formulated. The environment of central Sudan is described and its variability emphasised. The morphology of the inselberg is described and the slopes analysed using Rock Mass Strength criteria. The inselberg slopes are not simply controlled by bedrock strength characteristics and clearly have a developmental history. Data are also presented concerning drainage density, infiltration capacities and the nature of surface material for the inselberg and pediment. Field and laboratory techniques are used to assess spatial patterns in the nature and intensity of weathering. The techniques employed include descriptive analysis, x-ray diffraction of clay minerals, abrasion pH, quartz:felspar ratios, SEM analysis of quartz grains and gypsum weathering tablets. Weathering indices are produced which show that the most intense weathering is taking place on the inselberg slopes. This is due to both concentration of water and rate of throughput. The concentration of runoff and solution in regolith pockets on the slopes enhances slope microrelief. Schmidt hammer 'R' values were similar for all exposed bare rock surfaces regardless of location. Erosion measurements using simple repeat survey techniques show that significant erosion occured near the break of slope, mainly through headward growth of and lateral erosion by ephemeral gullies. Vertical incision and planar wash are insignificant in comparison. The form of the inselerg is due to the local balances between erosion and weathering and does not require novel explanations. Inselbergs have long evolutionary histories, and may be subject to equifinality.
15
Haworth, Kathryn 1963. „Effects of Quercus emoryi trees on microclimate, precipitation distribution, and herbs in a semi-arid savanna“. Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/192062.
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This study evaluated the effects of individual trees (5-70 m² canopy area) on precipitation distribution, bulk density, soil moisture, soil temperature, elevational gradients, and herbaceous species composition and biomass in a Ouercus emoryi Torr. savanna in southeastern Arizona. Throughfall was influenced by tree size and storm size for precipitation events less than 3 cm. Nonlinear regression showed an exponential relationship between storm size and stemflow; storm size explained 67% of the variability in stemf low. Tree size was linearly related to stemf low, and explained an additional 5% of the variability. Location beneath trees and between-tree variability influenced soil moisture and temperature. These factors influenced soil temperature on more sampling dates than soil moisture. Temperatures were cooler beneath tree canopies in summer and warmer in winter. Herbaceous biomass was reduced by tree canopies, but composition was not influenced by trees.
16
Vessby, Karolina. „Distribution and reproduction of dung beetles in a varying environment : implications for conservation of semi-natural grasslands /“. Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/avh/2001/91-576-5823-4.pdf.
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17
Molotch, Noah P. „ESTIMATING THE SPATIAL DISTRIBUTION OF SNOW WATER EQUIVALENT AND SNOWMELT IN MOUNTAINOUS WATERSHEDS OF SEMI-ARID REGIONS“. Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/191275.
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The processes controlling snowpack mass balance are highly variable in time and space, requiring remote sensing to observe regional processes and intensive field observations to observe hilislope-scale phenomena. This research aims to further understanding of the processes controlling snowpack mass balance through innovative applications of remotely sensed data and statistical interpolations of ground observations. Four advancements were obtained: 1) the sensitivity of regression tree snow distribution models to digital elevation data and independent variables was quanitified; 2) improved ability to upscale point snow water equivalent (SWE) measurements at snow telemetry (SNOTEL) stations was obtained by quantifying the small-scale SWE variability surrounding these stations; 3) spatially distributed snowmelt algorithms were improved by incorporating remotely sensed snow-surface albedo data into snowmelt modeling; and (4) the temporal and spatial continuity of regional-scale estimates of snow covered area (SCA) and SWE were improved by combining remotely sensed data and air temperature data to extend estimates beneath the cloud cover.
18
Thébault, Cyril. „Quels apports d'une approche multi-modèle semi-distribuée pour la prévision des débits ?“ Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS649.
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La prévision des débits dans les cours d’eau est nécessaire pour répondre à divers objectifs, allant de la sécurité des populations dans le cas des inondations, à la gestion de la ressource en eau pour de multiples usages, importante particulièrement en période d’étiage. La production hydroélectrique est également étroitement liée aux débits de nos rivières, comme c’est le cas sur le bassin versant du Rhône où la Compagnie nationale du Rhône (CNR) gère des unités de production hydroélectrique sur tout le cours principal du fleuve. Pour optimiser sa production, la CNR s’appuie en partie sur des modèles hydrologiques, qui transforment l’information météorologique en estimation des débits en rivière. Les modèles hydrologiques existants revêtent des spécificités, dans leur façon de représenter le bassin versant (c’est-à-dire leur structure mathématique) ou leurs modalités d’application, liées aux objectifs ou contextes hydroclimatiques pour lesquels ils ont été conçus. Cela conduit à l’existence d’une très large gamme de modèles hydrologiques, pouvant représenter une variété de relations pluie-débit et fonctionnant à différentes échelles spatiales, avec souvent la difficulté de choisir la structure et la discrétisation spatiale les mieux adaptées aux objectifs visés. Cela reflète également les nombreuses incertitudes affectant la chaîne de modélisation, dont la quantification revêt de forts enjeux pour la gestion opérationnelle et l’aide à la décision. Dans ce contexte, l’objectif de la thèse a été d’évaluer les apports de l’approche multi-modèle dans le cadre d’une modélisation hydrologique semi-distribuée pour la prévision des débits. Pour ce faire, un large échantillon de 643 bassins versants français, regroupant des données hydroclimatiques au pas de temps horaire, a été constitué, et 14 structures de modèles hydrologiques ont été utilisées selon différentes stratégies de calage et pour différentes configurations spatiales. Dans un premier temps, nous avons mis en place le cadre de modélisation hydrologique pour répondre à nos objectifs. Nous avons ensuite testé l’approche multi-modèle semi-distribuée en contexte de simulation, puis dans un objectif de prévision des débits en traitant plus particulièrement le cas des affluents du Rhône. Les résultats montrent que la stratégie d’un modèle unique pour un grand nombre de bassins présente des limites qui peuvent être en partie dépassées par différentes stratégies multi-modèles. Ainsi, l’utilisation de différents modèles hydrologiques selon les bassins versants engendre une amélioration significative de la simulation des débits sur le territoire français. Des performances encore améliorées peuvent être obtenues par une approche multi-modèle plus complexe, en combinant les sorties des modèles hydrologiques. Bien que l’intérêt de la semi-distribution soit difficile à déterminer a priori en contexte de simulation, elle montre des résultats encourageants sur les bassins influencés ou présentant des phénomènes nivaux, tels que sur les cours d’eau alpins du Rhône par exemple. Enfin, la modélisation multi-modèle semi-distribuée améliore également la prévision, que ce soit dans un contexte idéalisé de pluies futures connues ou plus réaliste d’utilisation d’archives de pluies d’ensemble prévues. Bien qu’engendrant des prévisions plus fiables, le chaînage entre les prévisions météorologiques d’ensemble et le multi-modèle probabiliste (créant ainsi un super-ensemble hydrologique) nécessite une phase d’interprétation pour être exploitable d’un point de vue opérationnelStreamflow forecasting is needed to meet various objectives, from the safety of populations in the case of floods, to the management of water resources for multiple uses, particularly important during low flow periods. Hydroelectric production is also closely linked to streamflow, as is the case on the Rhône catchment, where the Compagnie Nationale du Rhône (CNR) manages hydroelectric production units along the main course of the river. To optimize its production, CNR relies in part on hydrological models, which transform meteorological information into streamflow estimates. Hydrological models have their own specificities, in terms of the way they represent the catchment (i.e. their mathematical structure) or the way they are applied, linked to the objectives or hydro-climatic contexts for which they were designed. It leads to a very wide range of hydrological models, representing various rainfall-runoff relationships and operating at different spatial scales, often making it difficult for users to choose the structure and spatial discretization best suited to their objectives. This also reflects the numerous uncertainties affecting the modelling chain, the quantification of which is of major importance for operational management and decision support. In this context, the aim of this PhD is to evaluate the contribution of a semi-distributed multi-model approach for streamflow forecasting. To this end, a large sample of 643 French catchments, with hydro-climatic data at hourly time steps, was compiled, and 14 hydrological model structures were used according to different calibration strategies and for different spatial configurations. First, we set up the hydrological modelling framework to meet our objectives. After that, we tested the semi-distributed multi-model approach in a simulation context, and then for streamflow forecasting purposes, focusing on the case of Rhône tributaries. The results show that the strategy of a single model for a large number of catchments has limitations that can be partly overcome by multi-model strategies. In this way, the use of different hydrological models for different catchment areas leads to an improvement in streamflow simulation over the French territory. Even better performance can be achieved by a more complex multi-model approach, combining the outputs of hydrological models. Although the value of semi-distribution is difficult to determine a priori, it is nevertheless showing encouraging results over several catchments. Finally, semi-distributed multi-model modelling also improves forecasting, whether in an idealized context of known future rainfall, or in a more realistic context of ensemble meteorological forecast. Although generating more reliable forecasts, the chaining between ensemble meteorological forecasts and the probabilistic multi-model approach (thus creating a hydrological superset) requires an interpretation phase to be exploitable from an operational point of view
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Arbelo, Gonzalez Wilmer. „Nouvelles perspectives dans les traitements classique et semiclassique de la dynamique réactionnelle“. Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00942297.
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La théorie de la dynamique des processus chimiques élementaires cherche à décrire quantitativement les collisions réactives à l'échelle atomique. Les mouvements des noyaux étant extrêmement difficiles à traiter dans le formalisme quantique, les tomes sont souvent considérés comme des objets classiques. Cepandant, les effets purement quantiques jouent un rôle majeur dans certaines situations, alors que la description classique les néglige. Cette thèse apporte de nouvelles perspectives sur l'inclusion, dans le formalisme clasique, de forts effets quantiques, à savoir la quantification des mouvements internes des réactifs et produits.
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Smith-Adao, Lindie B. „Links between valley confinement, landforms and vegetation distribution in a semi-arid valley floor environment, Baviaanskloof, South Africa“. Thesis, Rhodes University, 2016. http://hdl.handle.net/10962/953.
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Although a large body of international literature has advanced our understanding of river systems, a considerable amount of gaps exit in the knowledge of dryland systems. River systems reflect complex interactions between biophysical processes and patterns. Understanding how processes generate observed patterns and, in turn, how patterns influence processes is crucial to understanding river structure and function. It requires an interdisciplinary approach in both research and resulting applications. The aim of this thesis was to examine the relationship between valley confinement, fluvial style, valley floor morphology and vegetation in the semi-arid environment of the Baviaanskloof river catchment, South Africa. This interdisciplinary investigation used a mixed method approach that involved desktop analyses and field surveys to understand dynamics at multiple scales, from the whole catchment to local (site, reach and quadrat or sample plot) scales. The desktop analyses included historical rainfall patterns and climate extremes, aerial photograph time-series and remote sensing greenness indices, and the field surveys focussed on cross-valley landform profiles, groundwater depth levels, sediment size distribution and soil chemistry, and vegetation distribution patterns. Based on the integrative assessment of these techniques a framework was developed of the links between valley confinement, surface-groundwater interaction, hydrogeomorphic processes and landforms, vegetation and human activities. Study findings highlighted the fact that very strong links exist between these factors. In this semi-arid area water availability (groundwater and streamflow conditions) was the primary control on valley floor vegetation composition and patterning. One group of species was associated with the wetted channel reaches at confined and semi-confined valley settings, while the other was associated with dry bed channel reaches at unconfined valley settings. The analyses also indicated that the environmental variables which best explained the variation in vegetation at the differing geomorphic landforms were related to landform position (elevation and distance), sediment size (fine and coarse sand) and available phosphorus (i.e. human impacts). The different plants, in turn, also affected landforms through their influence on sediment erosion, transport and deposition. Specially, they build, maintained or modified geomorphic landforms at confined, semi-confined and unconfined valley settings across the valley floor. Valley confinement was a primary control influencing hydrogeomorphic processes and their associated landforms. Alluvial fans and terraces acted as critical additional controls at especially the unconfined valley setting. Implications for restoration efforts in the catchment included strategies that took cognisance of: active revegetation on floodplain surfaces related to former agricultural fields; channel switching associated with the highly dynamic and unpredictable nature of geomorphic features; unstable multi-thread braided channels in the unconfined valley setting; and the selection of representative monitoring sites.
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Van, Waveren E. J. „Land resource distribution under customary tenure in Swaziland : a geographic analysis with special attention to semi-arid land“. Thesis, University of the West of England, Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274679.
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This study aims to contribute to a better understanding of the indigenous management of geographically diverse small-scale agricultural production environments in Africa by investigating the effects of customary land allocation on the use of the land and sustainable agricultural development in Swaziland. This study addresses two questions: (a) to what extent has the heterogeneity of the natural environment been considered in the allocation of land for agricultural purposes; and (b) what are the implications of the existing land allocation system and current land allocation pattern on the development and sustainability of agricultural land use. The study focuses on semi-arid land. The land allocation efficiency is determined by comparing the spatial heterogeneity of the land with the pattern of land allocation. The analysis is carried out at a sub-regional scale, and a local scale in twelve study areas. Changes over time are studied by comparing current land allocation patterns with those at Independence (1968). This study has identified two apparent weaknesses in the customary land management system. The frrst is in the capacity to ensure an efficient land resource distribution at a subregional level. The second is in the ability to ensure consistent land allocation practices at a local level. The study provides evidence that these shortcomings are now affecting the production environment and opportunities for development, and that changes in the tenure system are required. The study findings partly support a recent land po licy initiative proposing a gradual devolution in land management responsibilities to local level management systems, but also raise two major concerns. First, the land policy initiative does not address the shortcomings in sub-regional land management. Second, the inconsistent land distribution found at a local level does not support the notion that devolution will necessarily lead to more sustainable levels of land use within communities. In the wider debate on the agrarian transformation in Africa, this study adds to the body of knowledge in identifying specific shortcomings of indigenous management systems in land distribution, and their effects on sustainable agricultural development and land management. The study thus extends the more critical strand of thought on the role of local and indigenous land management systems in this process, and thus on the effectiveness of the devolution of resource management to community levels. The study also demonstrates that land sufficiency and quality are important issues in the process of sustainable intensification in small-scale land use systems, and question the wider applicability of the optimistic development model, which is primarily based on economic considerations. Lastly, the fmdings support the critical view on the applicability of the evolutionary theory of land rights in conditions similar to those in Swaziland. The fmdings of this study confIrm the importance of considering spatial scale and diversity in land use related studies, and show that any inference from one level of scale to another can be highly misleading.
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Nguyen, Tien Anh. „Instrumentation électronique et diagnostic de modules de puissance à semi-conducteur“. Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00910357.
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Les objectifs de la thèse sont d'élaborer des systèmes d'instrumentation électronique qui permettent une analyse et un diagnostic fins de l'état d'intégrité et du processus de vieillissement des composants de puissance à semi-conducteur. Ces travaux visent à évaluer la variation de la conductivité de la métallisation à l'aide de capteurs à Courant Foucault (CF) mais aussi à estimer l'effet du vieillissement des puces et de leur assemblage sur la distribution de courant dans les puces afin de mieux comprendre les mécanismes de défaillance. Des éprouvettes simplifiées mais également des modules de puissance représentatifs ont été vieillis par les cyclages thermique. Les capteurs développés ont été utilisés afin, d'une part de suivre le vieillissement, mais aussi d'autre part afin de comprendre l'effet de ce vieillissement sur le comportement des puces de puissance. Un banc d'instrumentation dédié a été élaboré et exploité pour la mesure locale de la conductivité électrique par le capteur à courants de Foucault, et l'estimation de la distribution de courants à partir de la mesure de cartographies de champ magnétique par capteurs de champ, ou à partir de la cartographie de la distribution de tension sur la métallisation de source. Ce banc a permis en premier lieu d'évaluer la pertinence et les performances de différents types de capteurs exploitables. Le travail s'est également appuyé sur des techniques de traitement de signal, à la fois pour estimer de manière quantitative les informations de conductivité des métallisations issues des capteurs à courant de Foucault, mais aussi pour l'analyse de la distribution de courant à partir des informations fournies par des capteurs de champ magnétiques. Les modèles utilisés exploitent des techniques de modélisation comportementale (le modèle approché de " transformateur analogique " modélisant capteurs à CF ou bien d'inversion de modèle semi-analytique dans le cas l'estimation de la distribution de courant). Les résultats obtenus à partir de ces modèles nous permettrons, d'une part de mieux comprendre certains mécanismes de défaillance, mais également de proposer une implantation et des structures de capteurs pour le suivi " in situ " de l'intégrité des composants.
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Connell, Kristin Anne. „Factors influencing the spatial distribution and ecological interactions of a habitat specialist, the semi-aquatic water rat (Hydromys chrysogaster)“. Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/16266.
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Semi-aquatic mammals, such as the native Australian water rat (Hydromys chrysogaster), are habitat specialists, often requiring additional adaptations to their environment compared to generalists. While the water rat is widely distributed, it is a species about which we know little. To increase our fundamental ecological and evolutionary knowledge about this species, my research focused on four key areas. First, I examined variation of body and extremity size across its geographical distribution, and found size was curvilinearly related to latitude, consistent with the abundant centre hypothesis. This hypothesis could be expanded to include ambient temperature to help explain extremity size variation. Second, I compared use of environmental factors between two semi-aquatic mammals, the water rat and the platypus (Ornithorhynchus anatinus), using species distribution models at a regional scale. Both species exhibited a similar response to the variables, but differed in magnitude (water rats more generalist, platypus more specialised). The results also showed including biotic factors in species distribution models increased model prediction. Third, I examined habitat use by water rats and found that they exhibited scale-specific responses to their environment. Habitat characteristics used were associated with reduced predation risk across all scales; however, the relative importance of each was strongly modified by spatial scale. Fourth, I tested if chemical cues from the water rat influence the common yabby (Cherax destructor), their prey. Water rat cues increased the time yabbies spent in corners, and influenced walking behaviours, but the exact nature of this response was unclear, requiring further exploration. The results from this thesis further our knowledge of the water rat as a species, but also of how semi-aquatic mammals respond to environmental factors across spatial scales, and it allowed me to answer some fundamental ecological and evolutionary questions.
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Sbai, Youssef. „Analyse semi-classique des opérateurs périodiques perturbés“. Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0270/document.
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Cette thèse traite de certaines propriétés spectrales de deux classes spécifiques des opérateurs périodiques. Nous nous intéressons tout d’abord à un modèle périodique perturbée par un opérateur dépendant d’un petit paramètre semi-classique. Nous obtenons alors le comportement asymptotique de la fonction du comptage des valeurs propres dans les gaps spectrales avec une estimation optimale du reste. Le second modèle étudié dans cette thèse est un modèle elliptique périodique d’ordre deux perturbée par un opérateur dépendant d’une grande constante de couplage. Nous donnons également la description de la fonction de compactage des valeurs propres lorsque la constante de couplage tend vers l’infini. La dernière partie de cette thèse discute l’étude du spectre discret de l’opérateur de Schrödinger avec un potentiel très oscillent dépendant d’un petit paramètre semi-classiqueThis Ph.D thesis deals with some spectral properties of two specific classes of two periodic operators. We are firstly interested in the model periodic perturbed by operator depending on a small semi-classical constant. We obtain an asymptotic behavior of the eigenvalue counting function in the spectral gaps with scharp remainder estimate. The second model studied in this thesis is a two-dimensional periodic elliptic second order opera-tor perturbed by operator depending on a large coupling constant. We also give the description of the counting function of eigenvalues when the coupling constant tends to infinity. The last part of this thesis highlights the study the spectrum of a Schrödinger operator perturbed by a fast oscillatingdecaying potential depending on a small parameter
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Pesee, Chatchai. „Stochastic modelling of financial processes with memory and semi-heavy tails“. Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16057/2/Chatchai%20Pesee%20Thesis.pdf.
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This PhD thesis aims to study financial processes which have semi-heavy-tailed marginal distributions and may exhibit memory. The traditional Black-Scholes model is expanded to incorporate memory via an integral operator, resulting in a class of market models which still preserve the completeness and arbitragefree conditions needed for replication of contingent claims. This approach is used to estimate the implied volatility of the resulting model. The first part of the thesis investigates the semi-heavy-tailed behaviour of financial processes. We treat these processes as continuous-time random walks characterised by a transition probability density governed by a fractional Riesz- Bessel equation. This equation extends the Feller fractional heat equation which generates a-stable processes. These latter processes have heavy tails, while those processes generated by the fractional Riesz-Bessel equation have semi-heavy tails, which are more suitable to model financial data. We propose a quasi-likelihood method to estimate the parameters of the fractional Riesz- Bessel equation based on the empirical characteristic function. The second part considers a dynamic model of complete financial markets in which the prices of European calls and puts are given by the Black-Scholes formula. The model has memory and can distinguish between historical volatility and implied volatility. A new method is then provided to estimate the implied volatility from the model. The third part of the thesis considers the problem of classification of financial markets using high-frequency data. The classification is based on the measure representation of high-frequency data, which is then modelled as a recurrent iterated function system. The new methodology developed is applied to some stock prices, stock indices, foreign exchange rates and other financial time series of some major markets. In particular, the models and techniques are used to analyse the SET index, the SET50 index and the MAI index of the Stock Exchange of Thailand.
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Pesee, Chatchai. „Stochastic Modelling of Financial Processes with Memory and Semi-Heavy Tails“. Queensland University of Technology, 2005. http://eprints.qut.edu.au/16057/.
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This PhD thesis aims to study financial processes which have semi-heavy-tailed marginal distributions and may exhibit memory. The traditional Black-Scholes model is expanded to incorporate memory via an integral operator, resulting in a class of market models which still preserve the completeness and arbitragefree conditions needed for replication of contingent claims. This approach is used to estimate the implied volatility of the resulting model. The first part of the thesis investigates the semi-heavy-tailed behaviour of financial processes. We treat these processes as continuous-time random walks characterised by a transition probability density governed by a fractional Riesz- Bessel equation. This equation extends the Feller fractional heat equation which generates a-stable processes. These latter processes have heavy tails, while those processes generated by the fractional Riesz-Bessel equation have semi-heavy tails, which are more suitable to model financial data. We propose a quasi-likelihood method to estimate the parameters of the fractional Riesz- Bessel equation based on the empirical characteristic function. The second part considers a dynamic model of complete financial markets in which the prices of European calls and puts are given by the Black-Scholes formula. The model has memory and can distinguish between historical volatility and implied volatility. A new method is then provided to estimate the implied volatility from the model. The third part of the thesis considers the problem of classification of financial markets using high-frequency data. The classification is based on the measure representation of high-frequency data, which is then modelled as a recurrent iterated function system. The new methodology developed is applied to some stock prices, stock indices, foreign exchange rates and other financial time series of some major markets. In particular, the models and techniques are used to analyse the SET index, the SET50 index and the MAI index of the Stock Exchange of Thailand.
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Harrington, Rhidian. „The effects of artificial watering points on the distribution and abundance of avifauna in an arid and semi-arid mallee environment“. Connect to this title online, 2002. http://repository.unimelb.edu.au/10187/2874.
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The role of artificial watering points in the avifaunal dynamics of the semi-arid mallee woodlands of southeast Australia was examined. Species richness and abundance were monitored throughout the year at different distances from water to determine how birds were distributed around water points and how this changed in relation to environmental factors such as climate. Vegetation attributes were also measured to determine which factors explained patterns in the avifauna with distance from water, and also to allow a description of the vegetation in relation to the water points. Water points were monitored throughout the year to determine which species were utilising them, under which environmental circumstances and for what purposes. Knowledge of the water utilisation behaviour of individual bird species allowed some explanation of their distribution patterns, as well as an ability to predict the likely effects of water point closure on those bird species. The closure of two water points during the study allowed an assessment of the immediate effects of water point closure on avifauna (For complete abstract open document)
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Dressler, Kevin Andrew. „Estimating the Spatial Distribution of Snow Water Equivalent and Simulated Snowmelt Runoff Modeling in Headwater Basins of the Semi-arid Southwest“. Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1063%5F1%5Fm.pdf&type=application/pdf.
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Bondesson, Carl. „Modelling of Safety Concepts for Autonomous Vehicles using Semi-Markov Models“. Thesis, Uppsala universitet, Signaler och System, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353060.
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Autonomous vehicles is soon a reality in the every-day life. Though before it is used commercially the vehicles need to be proven safe. The current standard for functional safety on roads, ISO 26262, does not include autonomous vehicles at the moment, which is why in this project an approach using semi-Markov models is used to assess safety. A semi-Markov process is a stochastic process modelled by a state space model where the transitions between the states of the model can be arbitrarily distributed. The approach is realized as a MATLAB tool where the user can use a steady-state based analysis called a Loss and Risk based measure of safety to assess safety. The tool works and can assess safety of semi-Markov systems as long as they are irreducible and positive recurrent. For systems that fulfill these properties, it is possible to draw conclusions about the safety of the system through a risk analysis and also about which autonomous driving level the system is in through a sensitivity analysis. The developed tool, or the approach with the semi-Markov model, might be a good complement to ISO 26262.
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Xu, Fang [Verfasser]. „Land-cover change and the distribution pattern of natural and semi-natural alluvial vegetation remnants along the Upper Danube River / Fang Xu“. Gießen : Universitätsbibliothek, 2019. http://d-nb.info/1189066041/34.
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Liang, Longjuan. „A semi-parametric approach to estimating item response functions“. Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180453363.
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Gibellato, Marilisa Gail. „Stochastic modeling of the sleep process“. The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1110318321.
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Ramires, Thiago Gentil. „A distribuição beta semi-normal generalizada geométrica“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11134/tde-22082013-154605/.
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Com o avanço tecnológico aprimorado, diferentes comportamentos do tempo de vida vem sendo estudados, e com isso é necessário a criação de novos modelos, muitas vezes mais complexos, para melhor ajuste e inferência sobre a população em estudo. A distribuição beta semi-normal generalizada é útil para modelagem de tempos de vida, e com isso propomos neste trabalho uma distribuição mais ampla chamada distribuição beta semi-normal generalizada geométrica, cuja função de risco pode assumir as formas crescente, decrescente, forma de banheira ou modal. A função densidade da nova distribuição é escrita como uma combinação linear da função densidade da distribuição beta semi-normal generalizada, sendo assim, algumas importantes propriedades da nova distribuição foram obtidas, como: momentos, assimetria, curtose, função geradora de momentos, desvios médios, função quantíl e curvas de Lorenz e de Bonferroni. Para a estimação dos parâmetros, é utilizado o método de máxima verossimilhança. Também foi proposto no trabalho, o novo modelo de regressão baseado na distribuição beta semi-normal generalizada geométrica, os quais podem ser muito úteis em análise de dados reais por serem mais flexíveis.Due to the technological improved advances, different behaviors of the lifetime has been studied and for this reason, it is necessary to create new statistical models, many times more complex, for the better fit and inferences about the population under study. The beta generalized half-normal distribution is useful for modeling lifetime data, and in this sense, we propose, in this work, a wider distribution called the geometric beta generalized half-normal distribution in which the hazard function takes the forms increasing, decreasing, bathtub and unimodal. The density function of the new distribution can be written as a linear combination of the beta generalized half-normal densities, and thereby, some properties of the new distribution can be obtained such as the moments, skewness, kurtosis, moment generating function, mean deviations, quantile function and Lorenz and Bonferroni curves. For the estimation of the parameters, we use the maximum likelihood method considering the presence of censored data. We also propose a new regression model based on the geometric beta generalized half-normal distribution, which can be very useful in the analysis of real data due to their flexibility.
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BREESE, DAVID RYAN. „MODELING THE EFFECTS OF SOLID STATE ORIENTATION ON BLOWN HIGH MOLECULAR WEIGHT HIGH DENSITY POLYETHYLENE FILMS: A COMPOSITE THEORY APPROACH“. University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1107958634.
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Dagher, Gulnar. „Mesure directe et non destructive de la distribution de charges d'espace à l'échelle nanométrique dans les isolants et les semi-conducteurs : application à la microélectronique“. Paris 6, 2008. http://www.theses.fr/2008PA066573.
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Les isolants et les semi-conducteurs sont les principaux constituants des circuits intégrés, dont les performances croissantes sont notamment dus à la miniaturisation des composants, mais au prix d’une plus grande vulnérabilité : un champ électrique élevé favorise l’accumulation de charges, modifiant les caractéristiques du composant. Au contraire, les charges introduites par dopage contribuent à son bon fonctionnement. Pour une connaissance précise du profil de charges dans les isolants et les semi-conducteurs, un instrument de mesure directe et non destructive à l’échelle nanométrique est alors étudié dans ce mémoire. Une implémentation fondée sur une méthode pompe-sonde utilisant un laser femtoseconde permet d’obtenir une résolution spatiale inférieure à 50 nm. Une détection interférométrique ou électro-optique et l’accumulation d’un grand nombre de mesures sont nécessaires pour améliorer les signaux. Des mesures valident les premières étapes de la réalisation expérimentale.
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Gabillet, Pauline. „Les entreprises locales de distribution à Grenoble et Metz : des outils de gouvernement énergétique urbain partiellement appropriés“. Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1178/document.
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L'action publique comme la recherche développent un intérêt croissant pour les relations entre ville et énergie. Cette thèse porte sur la manière dont les opérateurs énergétiques de réseaux participent à l'élaboration et à la mise en œuvre de politiques énergétiques locales et sur la capacité des acteurs politiques urbains à les piloter en ce sens. La question est abordée à partir d'acteurs alternatifs de la distribution d'énergie en France, les entreprises locales de distribution (ELD). Celles-ci assurent depuis plus de cent ans la distribution et la fourniture d'électricité et parfois de gaz et de chaleur dans les territoires de communes qui les possèdent. Elles apparaissent aujourd'hui comme des leviers d'action innovants à la disposition des villes pour développer des politiques énergétiques urbaines. Centrée sur les opérateurs urbains, la thèse examine les situations de GEG à Grenoble et d'UEM à Metz. Malgré leur implantation locale, les ELD accordent depuis quelques années seulement une place importante à l'échelle urbaine dans leurs stratégies d'entreprises. L'organisation sectorielle et centralisée du service public de l'électricité a pendant longtemps happé les ELD, freinant l'émergence d'une approche spécifique de leurs territoires de concession. Les recompositions du modèle économique qu'impose la libéralisation amènent toutefois les ELD à rechercher de nouveaux relais de croissance. Se saisissant d'opportunités liées à la mise à l'agenda de politiques énergie-climat, elles font preuve d'une forte adaptabilité et élaborent de nouvelles stratégies valorisant davantage leur ancrage urbain. Longtemps dominées par des logiques sectorielles d'ordre national, les entreprises locales participent ainsi de plus en plus au développement d'actions énergétiques urbaines. Cet ancrage urbain ne fait pas pour autant des ELD des outils de gouvernement d'une politique énergétique urbaine, qui supposerait une capacité d'initiative et de pilotage des acteurs politiques municipaux en fonction d'objectifs propres. Par l'analyse des exemples de Grenoble et Metz, nous montrons que la construction de l'énergie comme enjeu politique local est à la fois progressive et hétérogène, remettant en cause une approche jusque-là essentiellement économique et industrielle du pilotage des ELD. La politisation en cours se heurte cependant à une expertise limitée des communes sur l'énergie, qui ne parviennent que très imparfaitement à intégrer leurs préoccupations énergético-climatiques dans le pilotage stratégique de leurs entreprises locales. Les changements sont en revanche beaucoup plus importants sur le plan opérationnel, dans des projets qui impliquent des relations partenariales autour d'enjeux énergétiques : plans climat-énergie territoriaux, réponses à appels d'offres nationaux et européens, coordination des réseaux de distribution…L'analyse du modèle énergétique territorial alternatif des ELD proposée dans la thèse montre que le statut local des opérateurs ne suffit pas au développement d'un gouvernement énergétique urbain, lequel procède aussi de la politisation des questions énergétiques et de la construction d'une expertise adaptée au sein des systèmes politico-administratifs urbainsPublic action, like research, is becoming increasingly interested in the relationship between cities and energy. This thesis focuses on the ways in which energy network operators participate in the development and implementation of local energy policies and in the capacity of urban political stakeholders to drive these operators in this sense. The question is approached through local public utilities (LPU) as alternative energy distribution stakeholders in France. These companies have ensured supply and distribution of electricity and sometimes gas and heat in the areas where they are present for over one hundred years. They appear today to be innovative levers to action available to cities to develop urban energy policies. Centred on urban operators, this thesis examines the cases of GEG in Grenoble and UEM in Metz. Despite their local roots, LPUs have only in recent years granted an important place in their business strategies to the urban scale. The sectoral and centralised organisation of the electricity public services have for a long time limited the capacities of the LPUs, impeding the emergence of approaches specific to their particular areas. Reconfigurations of the economic model which impose liberalisation cause the ELDs to constantly search for new growth sources. Seizing opportunities from emerging energy-climate policies, they are proving their great adaptability and have devised new strategies valorising to a greater extent their urban roots. These urban roots alone are not enough to make the LPUs governmental tools for urban energy policy, which supposes a capacity for initiative and control by the political stakeholders of their own objectives. Through analysis of the Grenoble and Metz examples, we demonstrate that presenting energy as a local political issue is both progressive and heterogeneous, calling into question an approach to LPU control which until now has been essentially economic and industrial. Politicisation is being hindered by the lack of energy expertise in the communes, which only very infrequently manage to integrate their energy-climate concerns into strategic plans for their local businesses. In contrast, changes in operational plans are much greater in projects which involve partnerships around energy issues: regional climate-energy plans, responses to national and European calls for public tenders, coordination of distribution networks…The analysis of an alternative regional energy model from the LPUs proposed in this thesis demonstrates that the local status of operators is insufficient for the development of urban energy governance, which also operates in the politicisation of energy issues and the development of specially adapted expertise within urban political and administrative systems
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Blanchard, Olivier. „Exposition aux composés organiques semi-volatils reprotoxiques et neurotoxiques dans l'habitat“. Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S088/document.
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Les composés organiques semi-volatils (COSVs) regroupent un grand nombre de composés chimiques utilisés notamment comme substances actives ou additifs dans les matériaux de construction, de décoration et dans de nombreux produits de consommation. Les COSVs sont omniprésents dans les environnements intérieurs et fréquemment détectés dans les poussières sédimentées et dans le compartiment aérien. Cette thèse a permis de documenter les concentrations de 57 composés dans 30 logements français et d'utiliser ces mesures pour tester un modèle d'équilibre visant à prédire leur répartition dans les différents compartiments de l'environnement intérieur. De ce travail, il ressort une forte ubiquité des COSVs dans les logements étudiés. Les concentrations les plus élevées ont été observées pour les phtalates et dans une moindre mesure pour le bisphénol A, les muscs synthétiques et certains pesticides et HAPs. Ces résultats confirment l'intérêt de mieux caractériser l'exposition de la population générale aux COSVs dans l'habitat français. Les travaux portant sur le modèle d'équilibre ont montré que le coefficient de partage entre l'air et l'octanol (Koa) peut être un bon prédicteur pour estimer la concentration d'un composé donné dans un ensemble de logements. Cependant, certaines limites ont été identifiées et une meilleure caractérisation des paramètres utilisés est recommandéeSemivolatile organic compounds (SVOCs) include a large number of chemicals compounds used as active substances or additives in building materials and in many consumer products. SVOCs are ubiquitous in indoor environments and frequently detected in settled dust and indoor air. This work has investigated indoor concentrations of 57 target compounds in 30 French dwellings and measurements were used to test an equilibrium model to predict their partitioning in indoor compartments. The results showed a strong ubiquity of SVOCs in French dwellings. The highest concentrations were measured for phthalates and to a lesser extent for bisphenol A, synthetic musks, some pesticides and PAHs. These results confirm the interest to assess human exposure to SVOCs in the French dwellings. The work on the predictive model showed that octanol/air partitioning coefficient (Koa) is a good predictor to estimate SVOC concentrations in a large number of buildings. However, some limits were identified and a better estimation of the parameters used in these models is required
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Cowley, Robyn Anne. „The effect of changing water distribution from linear to point source on vegetation and soil following piping of an artesian bore in a semi-arid mulga paddock /“. [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16636.pdf.
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Teodorescu, Catalin Stefan. „Commande de systèmes d'isolation antisismique mixte“. Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00904280.
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Nous nous intéressons aux méthodes de contrôle de vibrations de modèles réduits de structures à n degrés de liberté, sismiquement isolées au niveau de la base par des systèmes d'isolation mixte.Le mouvement provoqué par une sollicitation sismique horizontale a lieu dans le plan vertical.Nous avons construit un problème de contrôle semi-actif de systèmes incertains soumis à des perturbations inconnues, mais bornées. Dans le langage de l'automatique, il s'agit d'un problème d'atténuation de perturbations.Le résultat principal de cette thèse porte sur la construction d'une version modifiée des résultats de Leitmann et de ses collaborateurs sur la stabilisation de systèmes non linéaires incertains. Le théorème proposé repose sur une loi de commande par retour d'état qui assure en boucle fermée les propriétés de "uniform boundedness" et "uniform ultimate boundedness".En particulier, il peut être appliqué à la résolution de problèmes de contrôle semi-actif, qui sont actuellement traités en génie parasismique.L'objectif du contrôle est d'améliorer le comportement (i.e. la réponse) de structures isolées pour faire face aux perturbations externes, c'est-à-dire les séismes. Plusieurs points différencient notre problème de la majorité que l'on trouve dans la littérature: (i) on ne s'intéresse pas seulement à la protection de la structure isolée, mais aussi aux équipements situés à l'intérieur de la structure, et (ii) au lieu d'utiliser des indicateurs de performance habituels exprimés en termes de déplacement relatif de la base versus des accélérations absolues des planchers, nous utilisons uniquement le spectre de plancher en pseudo-accélération, comme il a été proposé dans des travaux précédents par Politopoulos et Pham. Ce travail est une tentative d'utiliser explicitement les spectres de plancher comme critère de performance.Concernant la procédure d'application, plusieurs étapes intermédiaires ont été détaillées:(i) modélisation de signaux sismiques;(ii) réglage des paramètres de la loi de commande utilisant la théorie des vibrations;(iii) validation et test du comportement en boucle fermée à travers des simulations numériques: pour des raisons de simplicité, on se limite au cas n=2.Cette procédure peut être utilisée sur des structures en industrie nucléaire, mais aussi en génie civil.D'autres sujets traités incluent une tentative d'utiliser les outils temps-fréquence, et en particulier la distribution de Wigner-Ville, pour la synthèse de lois de commande, en espérant pouvoir mieux contrôler les composants transitoires des signaux de perturbation (les entrées) et des variables d'état (les sorties).
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Rustand, Denis. „Modèles conjoints pour un biomarqueur semi-continu et un événement terminal avec application aux essais cliniques en cancérologie“. Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0252.
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Evaluer l’efficacité des traitements dans les essais cliniques en oncologie soulève de multiples problèmes méthodologiques qui doivent être correctement traités afin de produire une estimation fiable des effets du traitement. Le but de ce projet de recherche est de proposer une nouvelle stratégie de modélisation dans le cadre de la modélisation conjointe pour étudier simultanément l’évolution de la taille tumorale (biomarqueur) et le risque de décès (évènement terminal). Un excès de zéros caractérise la distribution des mesures de taille tumorale, correspondant à des patients ayant une réponse au traitement qui se traduit par la disparition des tumeurs. Le modèle two-part a été proposé avec l’idée de décomposer la distribution du biomarqueur en une partie binaire (zéros vs. valeurs positives) et une partie continue, les deux étant généralement modélisés avec des modèles de régression à effets mixtes. Nous avons développé un modèle conjoint two-part pour lequel la partie binaire donne l’effet de covariables sur la probabilité de valeur nulle du biomarqueur tandis que la partie continue donne l’effet de covariables soit sur la valeur du biomarqueur parmi les positifs (forme conditionnelle) ou la valeur marginale du biomarqueur (forme marginale), tous deux répondant à différentes questions cliniques d’intérêt. Nous avons établi à l’aide de simulations que ce modèle fournit des estimations de paramètres non biaisées et nous l’avons comparé avec des approches alternatives telles qu’ignorer l’excès de zéro en ne décomposant pas la distribution du biomarqueur ou considérer les zéros comme des valeurs censurées (i.e., trop petites pour être mesurées). Nous montrons comment l’approche two-part est plus appropriée en présence de vrais zéros (i.e., non censurés). Ce nouveau modèle permet d’utiliser à la fois les mesures répétées de taille tumorale et les temps de survie pour comparer plusieurs lignes de traitement, ce qui pourrait impacter les décisions cliniques finales. Nous avons illustré ces développements sur la base de données réelles issues d’essais cliniques randomisés en cancérologie. Enfin, nous avons étendu l’estimation fréquentiste que nous avons implémentée dans le package R frailtypack à un cadre Bayésien avec le package R INLA afin de réduire le temps de calcul et résoudre les problèmes de convergence observés pour des structures de corrélation plus complexes. Les logiciels et codes pour l’estimation fréquentiste et Bayésienne de ce nouveau modèle sont publiquement disponibles pour s’assurer que ces outils sont facilement diffusés aux épidémiologistes, aux statisticiens ou chercheurs en sciences biomédicales. Les distributions semi-continues sont courantes dans la recherche biomédicale, par exemple lorsque l’on quantifie une exposition ou mesure les symptômes d’une maladie, notamment en génomique (microbiome, épigénétique), de sorte que le modèle proposé pourrait ouvrir un large spectre d’applications au-delà de la recherche relative au cancerAssessing the effectiveness of cancer treatments in clinical trials raises multiple methodological problems that need to be properly addressed in order to produce a reliable estimate of treatment effects. The purpose of this research project is to propose a new modeling strategy within the joint modeling framework to study simultaneously the evolution of tumor size (biomarker) and the risk of death (terminal event). An excess of zero values characterize the distribution of the tumor size measurements, corresponding to patients responding well to a treatment that observe a complete shrinkage of their tumors. The two-part model has been proposed with the idea to decompose the distribution of the biomarker into a binary outcome (zero values vs. positive values) and a continuous outcome, both outcomes usually being modeled with mixed effects regression models. We developed a two-part joint model for which the binary part captures the effect of covariates on the probability of zero value of the biomarker while the continuous part gives the effect of covariates either on the expected value of the biomarker among positives (conditional form) or the marginal expected value of the biomarker (marginal form), both answering different clinical questions of interest. We established it provides unbiased parameter estimations by simulations and compared this new model with alternative approaches such as ignoring the zero excess by not decomposing the biomarker’s distribution or considering zeros as censored values (i.e., too small to be measured). We show how the two-part approach is more appropriate in presence of true zeros (i.e., not censored). This new model allows to use both the tumor size repeated measurements and the survival times to compare several treatment lines, which could impact the final clinical decisions. We illustrated these developments on the basis of real data from randomized cancer clinical trials. Finally, we extended the frequentist estimation that we implemented into the R package frailtypack to a Bayesian framework within the R package INLA in order to reduce the computation time and solve convergence issues when dealing with more complex correlation structures. The software and code for both the frequentist and Bayesian estimations of this new model are freely available to ensure that these tools are easily disseminated to epidemiologists, statisticians or biomedical researchers. Semicontinuous distributions are common in biomedical research, e.g., when quantifying exposure or measuring symptoms of a disease, in genomics (microbiome, epigenetics), so that the proposed work could lead to a wide spectrum of applications beyond cancer research
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Wongrod, Suchanya. „Biochars from solid digestates as sorbing materials for metal(loid)s removal from water“. Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2023.
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Les digestats des boues d'épuration (SSD) et les digestats de la fraction organique des déchets ménagers (OFMSWD) ont été récemment considérés comme des sources potentielles pour la production de biochars en raison des quantités grandissantes de digestats solides restant à la fin de la digestion anaérobie. La pyrolyse des digestats solides est connue comme une technique pour promouvoir le recyclage des déchets organiques et générer des bio-produits à valeur ajoutée (i.e. biochar). En outre, en raison d'une capacité de sorption des métal(loïde)s des biochars moins bonnes par rapport aux charbon actifs traditionnels, la modification chimique des biochars bruts est considérée comme une alternative pour améliorer les propriétés de surface des biochars et induire ainsi une meilleure capacité de sorption des métal(loïde)s. Les biochars ont été traités avec 2 M de KOH ou 10% de H2O2, suivis d'un lavage en batch seul ou batch combiné avec un lavage en colonne à l’aide d'eau ultrapure. Les analyses des propriétés de biochar, le pH du point de charge nulle, la surface spécifique et la capacité d'échange cationique ont été effectuées sur les biochars bruts et modifiés afin de relier leurs propriétés de surface au comportement de sorption vis-à-vis des métal(loïde)s. Tous les biochars ont ensuite été utilisés pour étudier l'influence du traitement chimique et de la procédure de lavage des biochars sur le comportement de sorption du Pb(II), Cd(II) et As(III, V) à travers l’étude de la cinétique et des isothermes de sorption. De plus, l’évolution de l'état redox As (i.e. As(III, V)) pendant la sorption de l'As(III) sur la surface du biochar et en solution liquide a été déterminée par extraction solide-liquide suivie d'une analyse en chromatographie liquide.Les résultats ont montré des augmentations de la capacité de sorption pour le Pb(II), le Cd(II) et l’As(V) après traitement chimique du biochar. Par exemple, la capacité de sorption maximale (Qm) (Cd(II)) a été augmentée de 15,4 µmol g−1 sur le biochar de SSD brut à 306,1 µmol g−1 après le traitement au KOH (au pH initial de 5,0). De même, la valeur de Qm du Pb(II) a augmenté de 6,5 mg g−1 (biochar de SSD) à 25 mg g−1 sur le biochar modifié par H2O2. Néanmoins, la capacité de sorption du biochar SSD modifié par KOH n'a pas été déterminée en raison de l’impossibilité de modéliser les données expérimentales avec le modèle de l’isotherme de Langmuir. Cela indique qu'un lavage insuffisant du biochar SSD modifié par KOH peut inhiber la sorption de Pb(II) en raison de la libération de composés organiques dissous de ce biochar pouvant interagir avec Pb2+ et ainsi former des complexes Pb-ligand dans la solution. Ceci met en évidence le rôle important de la procédure de lavage sur l’efficacité de la sorption du Pb(II) sur le biochar. L’étude de la distribution de l’état redox de l'arsenic a montré une oxydation importante (70%) de As (III) en As (V) dans le biochar SSD traité au KOH avec lavage par batch, tandis que l'As(III) a été partiellement oxydé (7%) dans le biochar SSD traité au KOH avec un lavage en colonne. L'extraction de l’arsenic fixé par les biochars suivie d'une analyse par chromatographie en phase liquide a été établie avec succès pour récupérer quantitativement de l'As(III, V) Il a été montré que l'oxydation de As(III) était fortement induite par le biochar et, dans une moindre mesure, par des composés dissous libérés par les biochars.En résumé, les biochars de digestat modifiés par traitement chimique suivi d'une procédure de lavage appropriée du biochar peuvent être utilisés avec succès comme sorbants de Pb(II), Cd(II) et As(III, V). En outre, l'évolution de la distribution redox de l’arsenic dans les biochars et les solutions liquides à l'aide de l'extraction de liquide solide et de l'analyse chromatographique a été déterminée. Cela permet de mieux comprendre la transformation entre As(III) et As(V) lors la sorption de l’arsenic sur les biocharsSewage sludge digestate (SSD) and the organic fraction of municipal solid waste digestate (OFMSWD) are currently considered as alternative feedstocks for biochar production due to the high amount of the organic solid waste remaining at the end of the treatment. The pyrolysis of solid digestate is known as an alternative to promote the recycling of organic wastes and generate added-value bio-products (e.g. biochar). Generally, the digestate biochar has a much lower sorption capacity for metal(loid)s compared to activated carbons. Therefore, chemical treatment is considered as a potential option to improve the biochar surface properties and thus inducing a better sorption ability for metal(loid)s on the biochar surface. The biochars were treated with 2 M KOH or 10% H2O2 followed by batch washing or batch and subsequent column washings with ultrapure water. The physicochemical properties including the pH of point of zero charge, the surface area and cation exchange capacity were determined for all the biochars in order to link their improved surface properties to the enhanced sorption ability for metal(loid)s. All the biochars were then used to study the influence of chemical treatment and biochar washing procedure on the sorption behavior of Pb(II), Cd(II) and As(III, V) through the batch sorption kinetics and isotherms. Moreover, the As redox state distribution (i.e. As(III, V)) during the As(III) sorption onto the biochar surface and in liquid solution was determined by using solid-liquid extraction followed by liquid chromatographic analysis. Results showed increases of the sorption ability for Pb(II), Cd(II) and As(V) after chemical treatment. For instance, the maximum sorption capacity (Qm) of Cd(II) was increased from 15.4 µmol g−1 on the raw SSD biochar to 306.1 µmol g−1 after the KOH treatment (at initial pH 5.0). Similarly, the Qm of Pb(II) was also increased from 6.5 mg g⁻1 (raw SSD biochar) to 25 mg g⁻1 on the H2O2 modified SSD biochar. However, the sorption capacity for Pb(II) was not determined after KOH treatment due to the failing of the Langmuir isotherm model to fit the experimental data. This indicates that insufficient washing of the KOH-modified SSD biochar can hinder the Pb(II) sorption due to the release dissolved organic compounds from this biochar that may interact with Pb2+ and thereby forming Pb-ligand complexes in the solution. This highlights an important role of washing procedure for Pb(II) sorption by the biochar. The As redox distribution showed a large oxidation (70%) of As(III) to As(V) in KOH-modified SSD biochar with batch washing, while As(III) was partially oxidized (7%) in the KOH-modified SSD biochar with batch and subsequent column washings. The As extraction followed by liquid chromatographic analysis was successfully established to quantitatively recover arsenic (i.e. As(III, V)). The oxidation of As(III) was strongly induced by the biochar and to a lesser extent by the release of dissolved compounds from the biochar. In summary, digestate biochars with the chemical treatment followed by a proper biochar washing procedure can be successfully used as potential sorbents to enhance the Pb(II), Cd(II) and As(III, V) sorption capacity. Moreover, the determination of As redox distribution on the biochars and in liquid phase during the sorption process can be achieved through the As extraction and chromatographic analysis, providing a better understanding of the transformation between As(III) and As(V) in the biochar-liquid sorption system
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Woodhead, Erik. „Imperfections and self testing in prepare-and-measure quantum key distribution“. Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209185.
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Quantum key distribution (QKD) protocols are intended to allow cryptographic keys to be generated and distributed in way that is provably secure based on inherent limitations, such as the no-cloning principle, imposed by quantum mechanics. This unique advantage compared with classical cryptography comes with an added difficulty: key bits in QKD protocols are encoded in analogue quantum states and their preparation is consequently subject to the usual imprecisions inevitable in any real world experiment. The negative impact of such imprecisions is illustrated for the BB84 QKD protocol. Following this, the main part of this thesis is concerned with the incorporation of such imprecisions in security proofs of the BB84 and two semi-device-independent protocols against the class of collective attacks. On a technical level, by contrast with the vast majority of security proofs developed since the turn of the century, in which recasting the protocol into an equivalent entanglement-based form features heavily in the analysis, the main results obtained here are approached directly from the prepare-and-measure perspective and in particular the connection with the no-cloning theorem and an early security proof by Fuchs et al. against the class of individual attacks is emphasised.This thesis also summarises, as an appendix, a separate project which introduces and defines a hierarchy of polytopes intermediate between the local and no-signalling polytopes from the field of Bell nonlocality.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Pertsinidou, Christina Elisavet. „Stochastic models for the estimation of the seismic hazard“. Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2342.
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Dans le premier chapitre, la notion d'évaluation des risques sismiques est définie et les caractéristiques sismotectoniques de la région d'étude sont brièvement présentés. Un examen rigoureux des modèles stochastiques, appliqués au domaine de la sismologie est fourni. Dans le chapitre 2, différents modèles semi-Markoviens sont développés pour étudier la sismicité des îles Ioniennes centrales ainsi que le Nord de la mer Egée (Grèce). Les quantités telles que le noyau semi-Markovien et les probabilités de destination sont évaluées, en considérant que les temps de séjour suivent les distributions géométrique, discrète Weibull et Pareto. Des résultats utiles sont obtenus pour l'estimation de la sismicité. Dans le troisième chapitre un nouvel algorithme de Viterbi pour les modèles semi-Markoviens cachés est construit, dont la complexité est une fonction linéaire du nombre d'observations et une fonction quadratique du nombre d'états cachés, la plus basse existante dans la littérature. Une extension de ce nouvel algorithme est développée pour le cas où une observation dépend de l'état caché correspondant, mais aussi de l'observation précédente (cas SM1-M1). Dans le chapitre 4 les modèles semi-Markoviens cachés sont appliquées pour étudier la sismicité du Nord et du Sud de la mer Égée. La séquence d'observation est constituée des magnitudes et des positions d’un tremblement de terre et le nouvel algorithme de Viterbi est mis en œuvre afin de décoder les niveaux des tensions cachés qui sont responsables pour la sismogenèse. Les phases précurseurs (variations des tensions cachées) ont été détectées en avertissant qu’un tremblement de terre pourrait se produire. Ce résultat est vérifié pour 70 sur 88 cas (le score optimal). Les temps de séjour du processus caché étaient supposés suivre les distributions Poisson, logarithmique ou binomiale négative, tandis que les niveaux de tensions cachés ont été classés en 2, 3 ou 4 états. Les modèles de Markov caché ont également été adaptés sans présenter des résultats intéressants concernant les phases précurseurs. Dans le chapitre 5 un algorithme de Viterbi généralisé pour les modèles semi-Markoviens cachés, est construit dans le sens que les transitions au même état caché sont autorisées et peuvent également être décodées. De plus, une extension de cet algorithme généralisé dans le contexte SM1-M1 est présentée. Dans le chapitre 6 nous modifions de manière convenable le modèle Cramér-Lundberg y compris des sinistres négatifs et positifs, afin de décrire l'évolution avec le temps des changements de contraintes de Coulomb (valeurs ΔCFF) calculées pour sept épicentres (M ≥ 6) du Nord de la mer Egée. Formules pour les probabilités de ruine sont définies sous une forme générale. Corollaires sont également formulés pour la distribution exponentielle et Pareto. L'objectif est de mettre en lumière la question suivante qui pose la problématique dans la Sismologie: Au cours d'une année pourquoi un tremblement de terre s’est produit dans une position précise et pas dans une autre position, aux régions sismotectoniquement homogènes ayant valeurs ΔCFF positives. Les résultats montrent que les nouvelles formules de probabilité peuvent contribuer à répondre au problème susmentionnéIn the first chapter the definition of the seismic hazard assessment is provided, the seismotectonic features of the study areas are briefly presented and the already existing mathematical models applied in the field of Seismology are thoroughly reviewed. In chapter 2, different semi-Markov models are developed for studying the seismicity of the areas of the central Ionian Islands and the North Aegean Sea (Greece). Quantities such as the kernel and the destination probabilities are evaluated, considering geometric, discrete-Weibull and Pareto distributed sojourn times. Useful results are obtained for forecasting purposes. In the third chapter a new Viterbi algorithm for hidden semi-Markov models is developed, whose complexity is a linear function of the number of observations and a quadratic function of the number of hidden states, the lowest existing in the literature. Furthermore, an extension of this new algorithm is introduced for the case that an observation depends on the corresponding hidden state but also on the previous observation (SM1-M1 case). In chapter 4, different hidden semi-Markov models (HSMMs) are applied for the study of the North and South Aegean Sea. The earthquake magnitudes and locations comprise the observation sequence and the new Viterbi algorithm is implemented in order to decode the hidden stress field associated with seismogenesis. Precursory phases (variations of the hidden stress field) were detected warning for an anticipated earthquake occurrence for 70 out of 88 cases (the optimal model’s score). The sojourn times of the hidden process were assumed to follow Poisson, logarithmic or negative binomial distributions, whereas the hidden stress levels were classified into 2, 3 or 4 states. HMMs were also adapted without presenting significant results as for the precursory phases. In chapter 5 a generalized Viterbi algorithm for HSMMs is constructed in the sense that now transitions to the same hidden state are allowed and can also be decoded. Furthermore, an extension of this generalized algorithm in the SM1-M1 context is given. In chapter 6 we modify adequately the Cramér-Lundberg model considering negative and positive claims, in order to describe the evolution in time of the Coulomb failure function changes (ΔCFF values) computed at the locations of seven strong (M ≥ 6) earthquakes of the North Aegean Sea. Ruin probability formulas are derived and proved in a general form. Corollaries are also formulated for the exponential and the Pareto distribution. The aim is to shed light to the following problem posed by the seismologists: During a specific year why did an earthquake occur at a specific location and not at another location in seismotectonically homogeneous areas with positive ΔCFF values (stress enhanced areas). The results demonstrate that the new probability formulas can contribute in answering the aforementioned question
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Smit, Izak Petrus Johannes. „Artificial surface-water provision in a semi-arid savanna : a spatio-temporal analysis of herbivore distribution patterns in relation to artificial waterholes under different habitat, rainfall and management scenarios in the Kruger National Park, South Africa“. Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612119.
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Santos, Jeferino Manuel dos. „Aplicação da Teoria de Valores Extremos à actividade seguradora“. Master's thesis, Instituto Superior de Economia e Gestão, 2003. http://hdl.handle.net/10400.5/652.
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Mestrado em Ciências ActuariaisO objectivo principal deste trabalho é realçar a importância da Teoria de Valores Extremos na actividade seguradora. São apresentados de uma forma sucinta alguns dos principais resultados ligados a esta teoria. São apresentadas algumas estatísticas que possibilitam a simplificação do processo de reconhecimento de dados de cauda pesada. A modelação da cauda é um assunto de particular interesse, são apresentados dois métodos de modelação da cauda, um pelo ajustamento de uma distribuição de Pareto Generalizada, outro pela aplicação de um método semi-paramétrico adaptativo. No fim, os resultados obtidos por cada um dos modelos são integrados como módulo num modelo de solvência.
The main purpose of this dissertation is to enhance the importance of Extreme Value Theory in the insurance sector. A short introduction to the main results inherent in this theory is presented. Also, a set of statistics to simplify the recognition process of heavy tailed data is provided. Tail modelling is a subject of particular interest in this dissertation, two approaches are presented, one by fitting a Generalized Pareto Distribution, other by modelling by means of a semi-parametric adaptive method. In the last part, the results of these approaches are integrated as a module in a broader solvency model.
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Chebbi, Houssem. „Méthode des coordonnées curvilignes pour la modélisation électromagnétique des matériaux complexes : application au contrôle non destructif par courants de Foucault des matériaux composites The fast computation of eddy current distribution and probe response in homogenized composite material based on semi-analytical approach Investigation of layer interface model of multi-layer structure using semi-analytical and FEM analysis for eddy current pulsed thermography“. Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST004.
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Ce travail de thèse de doctorat, effectué au sein de Laboratoire de Simulation et Modélisation Électromagnétique (LSME) du CEA List, s’intègre dans le cadre du projet européen « NDTonAir » financé sous l'action « H2020-MSCA-ITN-2016- GRANT 722134 ». Le principal objectif est le développement d’un outil de simulation rapide et précis dédié au contrôle non destructif par courants de Foucault des matériaux composites homogénéisés. Comme cas d’application, on s’intéresse particulièrement à l’orientation des fibres d’une part, et d’autre part, à des défauts de type délaminage et ondulation des fibres qui se manifestent par une déformation géométrique locale des interfaces. Les méthodes semi-analytiques existantes dans la littérature, basées sur le formalisme des Dyades de Green, sont limitées jusqu’au là à des structures planes multicouches. Pour introduire des variations locales de géométrie aux interfaces, nous proposons une approche innovante basée sur un changement de coordonnées adapté au profil de la pièce et des interfaces. On propose un modèle numérique performant basé sur le formalisme covariant des équations de Maxwell. Ce formalisme unificateur englobe l'anisotropie du spécimen et les déformations locales des interfaces. La méthode de coordonnées curvilignes est usuellement utilisée pour résoudre des problèmes de diffraction sur des surfaces rugueuses dans le domaine des hautes fréquences (diffraction sur des réseaux). Ce travail de thèse s’inspire des méthodes de Fourier modale et propose de nouveaux outils adaptés au domaine des courants de Foucault. L’extension de la méthode des coordonnées curvilignes au domaine du contrôle des composites par courants de Foucault constitue l’innovation de ce travail. Deux modèles numériques ont été développés pour le calcul de l’interaction du champ émis par un capteur à courants de Foucault avec un matériau composite multicouches. Le modèle numérique développé pour le contrôle des composites plans exploite les structures particulières des matrices creuses pour réduire le temps de calcul sans limitation de nombre de modes utilisés pour la représentation du champ. Dans le cas des profils curvilignes des interfaces, le modèle permet de traiter des interfaces parallèles et quelques cas particuliers des profils non parallèles. Ce cas général présente quelques limitations qui nécessitent le développement des outils numériques complémentaires. Enfin, plusieurs configurations de contrôle ont été envisagées et les résultats numériques produits par les modèles ont été confrontés à des données de simulation par éléments finis. Quelques expérimentations ont été effectuées dans des laboratoires partenaires étrangers pour accroître notre expérience sur la validation expérimentaleThis doctoral thesis work, carried out within the Laboratory of Simulation and Modeling for Electromagnetics (LSME) of CEA List, is part of the “NDTonAir” European project funded under the action “H2020-MSCA-ITN -2016- GRANT 722134”. The main goal of the project is the development of a fast and accurate simulation tool for the non-destructive eddy current testing of homogenized composite materials. As an application case, we are particularly interested in the orientation of the fibers on the one hand, and on the other hand, in defects as delamination which are manifested by a local geometrical deformation of the interfaces. The semi-analytical methods existing in the literature, based on Green's Dyad formalism, have been limited so far to multilayered and planar structures. To introduce local variations in geometry at the interfaces, we propose an innovative approach based on a change of coordinates adapted to the profile of the local perturbation. We propose a powerful numerical model based on the covariant formalism of Maxwell's equations. This unifying formalism takes in the anisotropy of specimen and the local deformations of the interfaces. The curvilinear coordinate method is usually used to solve diffraction problems on rough interfaces in the high frequency domain (diffraction on gratings). This thesis work is inspired by Fourier Modal Methods and proposes new tools which have been adapted to the field of eddy currents. The extension of the curvilinear coordinate method to the field of eddy currents non-destructive testing technique of composites constitutes the innovation of this work. Two numerical models have been developed to calculate the interaction of the field emitted by an eddy current probe with a multilayered composite material. The numerical model developed for the evaluation of planar composite exploits the particular structures of sparse matrices to reduce the computation time without limiting the number of modes used for the modal expansion of the field. In the case of the curvilinear profiles of the interfaces, the model makes it possible to treat parallel interfaces and some particular cases of non-parallel profiles. The general case of non-identical profiles presents some limitations which require the development of complementary numerical tools. Finally, several testing configurations were considered and the numerical results produced by the models were compared to finite element simulated data. Some experiments were carried out in foreign partner laboratories to increase our experience on experimental validation
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Opoku-Agyeman, Bernice. „Complexities in Nonadiabatic Dynamics of Small Molecular Anions“. The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503094708588515.
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Karki, Hemanta D. „Investigation of flow characteristics in an open channel with one-line semicircular vegetation patches“. Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2595.
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Experiments are conducted in an open channel with semi-circular patches distributed on one sidewall of the channel in which velocity distribution, turbulent intensity, and vortex generation are analyzed. The resistance force offered by a vegetation patch causes the change in water depth which have a broader application in river management, bank stabilization, and flood control.
The measurement is conducted in the laboratory with the help of different measuring devices like Laser doppler velocimeter, particle image velocimeter, measuring scale, and so on. From the experiment, the velocity distribution in a longitudinal direction suggests that the flow is fully developed after a certain distance from a channel inlet. When the flow passes through the vegetation patch, it forms three different regions, i.e., canopy region, interference zone, and canopy free region. The flow velocity is maximum at the interference zone because of canopy patches to the flow. Wake formation is observed behind the canopy patch, which plays a vital role in sediment deposition; further moving away in the flow direction, wake formation decreases. Velocity is unstable and very low inside the canopy region due to the resisting force. It increases while moving away from the canopy patch in the transverse direction and becomes stable in canopy free region until it reaches the sidewall. A dip phenomenon is observed for both wide and narrow channels, but a dip phenomenon for narrow channels always lies lower from the surface than for wider channels. Turbulent intensities vary with different factors like the nature of the channel, vegetation density, and vegetation stem diameter. Turbulent intensity for a wide channel is comparatively higher than the narrow channel in a canopy-free region. Also, turbulent intensity is minimum just behind the midpoint of the canopy patches, whereas it is lower for dense vegetation than sparse vegetation behind the patch. Furthermore, turbulent intensity for smaller stem diameters is lower than for larger stem diameters behind the canopy patch.
Kelvin-Helmholtz instabilities are visualized due to the change in velocity in an interference zone and play a vital role in eradicating sediments. Also, the size of instabilities depends on the dimension of patches which shows the importance of vortex generation. The width of the vortex structure is more significant in a narrow channel than in a wide channel due to the substantial flow divergence by vegetation patches. Investigation of velocity distribution, turbulent intensity, and vortex generation with canopy patches on both sides of the channel is left for future work.
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Jaiswal, Vinay Kumar. „Finite element modeling of electric field distributions around a resistive glazed post station insulator covered with ice = Modélisation par éléments finis de la distribution du champ électrique autour d'un isolateur de poste avec une couche semi-conductrice recouvert de glace /“. Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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KANTHA, SAMY MADHAN KUMAR. „FIELD TEST AND ANALYSIS OF TWO PRESTRESSED CONCRETE BRIDGES AFTER DECK REPLACEMENT WITH FRP PANELS“. University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1187271654.
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