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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
301

Factors controlling the sorption of Cs, Ni and U in soil : A statistical analysis with experimental sorption data of caesium, nickel and uranium in soils from the Laxemar area / Faktorer som styr sorptionen av Cs, Ni och U i mark : En statistisk analys med experimentella sorptionsdata för caesium, nickel och uran i jordar från

Johansson, Emilia January 2020 (has links)
In the fall of 2006, soils from three small valleys in the Laxemar/Oskarshamn area were sampled. A total of eight composite samples were characterized for a number of soil parameters that are important for geochemical sorption and were later also used in batch sorption experiments. Solid/liquid partition coefficients (Kd values) were then determined for seven radionuclides in each of the eight samples. To contribute to the interpretation of the sorption results together with the soil characterizations, this study aims to describe the sorption behavior of the radionuclides caesium, nickel and uranium and also discern which parameters that could provide a basis for estimating the strength of sorption of radionuclides in general. The methodology included quantitative methodologies such as compilation of chemical equilibrium diagrams by the software Hydra/Medusa and correlation analyses using the statistical software SPSS statistics. Based on the speciation diagrams of each radionuclide and identified important linear and non-linear relationships of the Kd values with a number of soil parameters, the following soil- and soil solution properties were found to have controlled the sorption of Cs, Ni and U, respectively, in the Laxemar soils. Cs: the specific surface area of the soil coupled to the clay content. Ni: the cation exchange capacity, alkaline solution pH, soil organic matter and dissolved organic matter. U: the cation exchange capacity, soil organic matter, dissolved organic matter, dissolved carbonate and alkaline solution pH. The soil that showed the strongest sorption varied between the nuclides, which can be related to the individual sorption behavior of caesium, nickel and uranium, as well as the different physicochemical properties of the soils. The parameters that should be prioritized in characterizations of soil samples are identified to be: solution pH, the cation exchange capacity, the specific surface area of the soil, soil organic matter and soil texture (clay content). / För att kunna fatta beslut relaterade till hypotetisk framtida kontaminering från slutförvar av radioaktivt avfall är det direkt avgörande att förstå mobiliteten av radioaktiva element i miljön. Sorption är en av de viktigaste kemiska mekanismerna som kan minska spridningen av radionuklider i vatten/jord/bergssystem, där nukliderna fördelar sig mellan vätskefasen och ytor på fasta partiklar i dessa system. Fördelningskoefficienter (Kd värden) används generellt som ett kvantitativt mått på sorptionen, där ett högt Kd värde innebär att en större andel av ämnet i fråga är bundet till den fasta fasen. Under hösten 2006 togs jordprover från tre dalgångar i Laxemar/Oskarshamn. Totalt åtta jordprover karakteriserades för ett antal jordparametrar som är viktiga för geokemisk sorption och användes senare i batchförsök tillsammans med ett naturligt grundvatten. Fördelningskoefficienter (Kd värden) bestämdes för sju radionuklider (Cs, Eu, I, Ni, Np, Sr and U) för vart och ett av de åtta jordproverna. För att bidra till tolkningen av sorptionsresultaten tillsammans med jordprovernas egenskaper syftar denna studie till att beskriva sorptionsbeteendet hos radionukliderna caesium, nickel och uran samt urskilja vilka parametrar som kan fungera som grund för att uppskatta sorptionsstyrkan av radionuklider i allmänhet. För att uppnå detta syfte så har studien följande mål. Identifiera de jord- och marklösningsegenskaper som kontrollerar sorptionen av Cs, Ni respektive U i de åtta Laxemar proverna. Bestämma vilket Laxemar-jordprov som starkast sorberar de tre radionukliderna. Identifiera de jordparametrar som bör prioriteras vid jordkarakteriseringar, baserat på deras sorptionsinflytande, för att kunna uppskatta Kd värden endast med begränsad information om ett jordsystem. Metoden innefattade kvantitativa metoder såsom sammanställning av kemiska jämviktsdiagram med programvaran Hydra/Medusa och korrelationsanalyser med hjälp av statistikprogramvaran SPSS statistics. De kemiska jämviktsdiagrammen bidrog till att beskriva specieringen av respektive nuklid som en funktion av pH och korrelationsanalyserna bidrog till att identifiera linjära samband mellan par av variabler, tex mellan Kd och jordparametrar. Baserat på specieringsdiagrammen för varje radionuklid och identifierade viktiga linjära och icke-linjära förhållanden mellan Kd-värdena och ett antal jordparametrar har följande egenskaper hos jordarna och marklösningen visat sig huvudsakligen kontrollera sorptionen av Cs, Ni respektive U i de åtta Laxemar jordarna: För caesium gäller jordens specifika ytarea kopplad till lerinnehållet, medan för nickel är det katjonbytarkapaciteten, organiskt material, alkaliska pH-värden samt löst organiskt material. Sorptionen av uran befanns kontrolleras av katjonbytarkapaciteten, organiskt material, löst organiskt material, alkaliska pH-värden samt lösta karbonater. Den jord som visade starkast sorption varierar mellan de tre nukliderna, vilket kan relateras till nuklidernas individuella sorptionsbeteende i jord samt jordarnas olika fysikaliska och kemiska egenskaper. Parametrarna som bör prioriteras vid karaktärisering av jordprov identifierades vara: pH, katjonbytarkapaciteten, jordens specifika ytarea, mängden organiskt material samt jordtexturen (lerinnehåll).
302

Resource Efficient Parallel VLDB with Customizable Degree of Redundancy

Xiong, Fanfan January 2009 (has links)
This thesis focuses on the practical use of very large scale relational databases. It leverages two recent breakthroughs in parallel and distributed computing: a) synchronous transaction replication technologies by Justin Y. Shi and Suntain Song; and b) Stateless Parallel Processing principle pioneered by Justin Y. Shi. These breakthroughs enable scalable performance and reliability of database service using multiple redundant shared-nothing database servers. This thesis presents a Functional Horizontal Partitioning method with customizable degree of redundancy to address practical very large scale database applications problems. The prototype VLDB implementation is designed for transparent non-intrusive deployments. The prototype system supports Microsoft SQL Servers databases. Computational experiments are conducted using industry-standard benchmark (TPC-E). / Computer and Information Science
303

Applications of Melt Inclusions to Problems in Igneous Petrogenesis

Severs, Matthew Jeremiah 31 July 2007 (has links)
Understanding the different igneous processes that magmas undergo is important for a variety of reasons including potential hazards associated with volcanoes in populated regions, magmatic hydrothermal ore deposition, and tectonic processes. One method of obtaining geochemical data that can help constrain petrogenetic processes is through the study of melt and fluid inclusions. The research presented here examines melt inclusions through experimental, analytical and field studies to better understand igneous petrogenesis. One potential problem associated with melt inclusions is water-loss during laboratory heating. A Raman spectroscopic technique was developed to determine water contents of silicate glasses, and this technique was applied to monitor water loss from natural melt inclusions that were heated for varying lengths of time. The results suggest that water loss is insignificant when heated for less than 12 hours but significant water loss can occur with longer duration heating. The distribution of trace elements between silicate melts and phenocrysts growing from that melt can constrain igneous processes such as fractional crystallization, assimilation, and partial melting. Partition coefficients were determined for syngenetic clinopyroxene, orthopyroxene, and plagioclase in equilibrium with a dacitic melt using the Melt Inclusion-Mineral (MIM) technique. Melt inclusion chemistry is the same regardless of mineral host phase, suggesting that the melt inclusions have not been subjected to re-equilibration processes or boundary layer development. Partition coefficients from this study are similar but typically lower than published values. Three closely-spaced monogenetic eruptive units from the active Campi Flegrei volcanic system (Italy) with similar eruptive styles were examined to better understand the evolution of the magmatic system. Results suggest fractional crystallization as the dominant process taking place over time but that magma mixing was significant for one of the eruptions. Trace element geochemical data suggest a mixed magma source of within-plate and volcanic arc components, and still retain a T-MORB signature from the subducting slab. / Ph. D.
304

Analysis of heat partition ratio in vehicle braking processes.

Loizou, Andreas, Qi, Hong Sheng, Day, Andrew J. 06 September 2009 (has links)
Yes / An examination of the heat partition ratio between the friction surfaces of a disc braking system is presented using finite element analysis (FEA). This includes a 2D static analysis of two semi-infinite bodies in contact with and without an interface layer which represents the interface tribo-layer (ITL). An analytical approach with a finite difference solution was used for cross-comparison with the static FE models. Results from the static model have provided the boundary conditions for a 2D dynamic model, where one rectangular block slides on another (fixed) rectangular block. The effects of normal loads and real contact area have also been studied. / Institution of Mechanical Engineers
305

On Refinements of Van der Waerden's Theorem

Farhangi, Sohail 28 October 2016 (has links)
We examine different methods of generalize Van der Waerden's Theorem, the Multidimensional Van der Waerden Theorem, the Canonical Van der Waerden Theorem, and other Variants. / Master of Science
306

Design and Implementation of an Ultrabroadband Millimeter-Wavelength Vector Sliding Correlator Channel Sounder and In-Building Multipath Measurements at 2.5 & 60 GHz

Anderson, Christopher R. 21 May 2002 (has links)
Over the past decade, the market for wireless service has grown at an unprecedented rate. The industry has grown from cellular phones and pagers to broadband and ultra-broadband (also called ultra-wideband) wireless services that can provide voice, data, and full-motion video in real time. This growing hunger for faster data rates and larger bandwidths has prompted a need for a deeper understanding of the wireless channels upon which these devices communicate. In order for the visions of real time full-motion video, multimedia, and high speed data delivery inherent in the 3rd and 4th generations of wireless communication standards to be fully realized, system design engineers must have a thorough understanding of the wireless channels upon which these devices operate. Additionally, for these networks to deliver their promised data rates, they must operate at very high microwave and millimeter-wave frequencies, where large segments of spectrum are readily obtained. Unfortunately, little is known about the propagation characteristics at these frequencies and bandwidths. As a consequence, there has been a significant demand for wireless test equipment that is capable of characterizing these new wireless channels. The objective of this research was to design and develop a wireless test instrument that can not only characterize these new wireless channels, but has the portability to be quickly and easily re-located to various measurement sites, as well as the flexibility to characterize a wide variety of frequencies and bandwidths in addition to the ultrawideband channels investigated in this work. This measurement system is also designed to be capable of characterizing both the magnitude and phase response of these wireless channels, which not only provides a more complete channel characteristic, but the potential capability to measure the Doppler spectrum introduced by a dynamic channel. / Master of Science
307

Development of a liquid-liquid extraction method of resveratrol from cell culture media using solubility parameters

Al balkhi, M.H., Mohammad, Mohammad A., Tisserant, L-P., Boitel-Conti, M. 2016 June 1923 (has links)
Yes / The extraction of bioactive compounds, produced by plant cell cultures, directly from their culture medium, which contains other by-products, is a great challenge. Resveratrol extraction from its grapevine cell cultures is considered here as an example to improve the extraction processes from plant cell cultures using solubility parameters. Successive liquid-liquid extraction (LLE) processes were exploited to extract resveratrol from the culture medium with an extraction ratio approaching 100%, high selectivity and minimum amounts of solvents. The calculations of partition coefficients as a function of solubility parameters demonstrated that benzyl benzoate is the most suitable intermediate solvent to extract resveratrol from its aqueous medium. The calculations also illustrated the high ability of methanol and ethanol to extract resveratrol from benzyl benzoate. The physicochemical properties of benzyl benzoate and processing conditions were exploited to separate it from aqueous media and organic solvents. The agitation method, component ratios and extraction time were studied to maximize the extraction yield. Under the best studied conditions, the recovery of resveratrol from different culture media approached ∼100% with a selectivity of ∼92%. Ultimately, the improved extraction processes of resveratrol are markedly efficient, selective, rapid and economical. / Mohammad Amin Mohammad gratefully acknowledges CARA (The Council for At-Risk Academics, Stephen Wordsworth and Ryan Mundy) for providing the financial support for an academic fellowship.
308

Partition of neutral molecules and ions from water to o-nitrophenyl octyl ether and of neutral molecules from the gas phase to o-nitrophenyl octyl ether

Abraham, M.H., Acree Jr, W.E., Liu, Xiangli 2018 February 1916 (has links)
Yes / We have set out an equation for partition of 87 neutral molecules from water to o-nitrophenyl octyl ether, NPOE, an equation for partition of the 87 neutral molecules and 21 ionic species from water to NPOE, and an equation for partition of 87 neutral molecules from the gas phase to NPOE. Comparison with equations for partition into other solvents shows that, as regards partition of neutral (nonelectrolyte) compounds, NPOE would be a good model for 1,2-dichloroethane and for nitrobenzene. In terms of partition of ions and ionic species, NPOE is quite similar to 1,2-dichloroethane and not far away from other aprotic solvents such as nitrobenzene.
309

Partitions spectrales optimales pour les problèmes aux valeurs propres de Dirichlet et de Neumann

Péloquin-Tessier, Hélène 10 1900 (has links)
Les façons d'aborder l'étude du spectre du laplacien sont multiples. Ce mémoire se concentre sur les partitions spectrales optimales de domaines planaires. Plus précisément, lorsque nous imposons des conditions aux limites de Dirichlet, nous cherchons à trouver la ou les partitions qui réalisent l'infimum (sur l'ensemble des partitions à un certain nombre de composantes) du maximum de la première valeur propre du laplacien sur tous ses sous-domaines. Dans les dernières années, cette question a été activement étudiée par B. Helffer, T. Hoffmann-Ostenhof, S. Terracini et leurs collaborateurs, qui ont obtenu plusieurs résultats analytiques et numériques importants. Dans ce mémoire, nous proposons un problème analogue, mais pour des conditions aux limites de Neumann cette fois. Dans ce contexte, nous nous intéressons aux partitions spectrales maximales plutôt que minimales. Nous cherchons alors à vérifier le maximum sur toutes les $k$-partitions possibles du minimum de la première valeur propre non nulle de chacune des composantes. Cette question s'avère plus difficile que sa semblable dans la mesure où plusieurs propriétés des valeurs propres de Dirichlet, telles que la monotonicité par rapport au domaine, ne tiennent plus. Néanmoins, quelques résultats sont obtenus pour des 2-partitions de domaines symétriques et des partitions spécifiques sont trouvées analytiquement pour des domaines rectangulaires. En outre, des propriétés générales des partitions spectrales optimales et des problèmes ouverts sont abordés. / There exist many ways to study the spectrum of the Laplace operator. This master thesis focuses on optimal spectral partitions of planar domains. More specifically, when imposing Dirichlet boundary conditions, we try to find partitions that achieve the infimum (over all the partitions of a given number of components) of the maximum of the first eigenvalue of the Laplacian in all the subdomains. This question has been actively studied in recent years by B. Helffer, T. Hoffmann-Ostenhof, S. Terracini and their collaborators, who obtained a number of important analytic and numerical results. In the present thesis we propose a similar problem, but for the Neumann boundary conditions. In this case, we are looking for spectral maximal, rather than minimal, partitions. More precisely, we attempt to find the maximum over all possible $k$-partitions of the minimum of the first non-zero Neumann eigenvalue of each component. This question appears to be more difficult than the one for the Dirichlet conditions, since many properties of Dirichlet eigenvalues, such as domain monotonicity, no longer hold in the Neumann case. Nevertheless, some results are obtained for 2-partitions of symmetric domains, and specific partitions are found analytically for rectangular domains. In addition, some general properties of optimal spectral partitions and open problems are also discussed.
310

Surface reconstruction based on forest terrestrial LiDAR data / Reconstruction de surface à partir de données LiDAR terrestre acquises en forêt

Morel, Jules 17 February 2017 (has links)
Au cours des dernières années, la capacité de la technologie LiDAR à capturer des informations détaillées sur la structure des forêts a attiré une attention croissante de la part de la communauté des écologues et des forestiers. Le LiDAR terrestre, notamment, apparaît comme un outil prometteur pour recueillir les caractéristiques géométriques des arbres à une précision millimétrique.Cette thèse étudie la reconstruction de surface à partir de nuages de points épars et non structurés, capturés en environnement forestier par un LiDAR terrestre. Nous proposons une suite d’algorithmes dédiés à la reconstruction de modèles d’attributs de placettes forestières : le sol etla structure ligneuse des arbres (i.e. troncs et branches principales). En pratique, nos approches modélisent le problème par des surfaces implicites construites à partir de fonctions à base radiale pour faire face à la forte hétérogénéité spatiale du nuage de points Lidar terrestre. / In recent years, the capacity of LiDAR technology to capture detailed information about forests structure has attracted increasing attention in the field of forest science. In particular, the terrestrial LiDAR arises as a promising tool to retrieve geometrical characteristics of trees at a millimeter level.This thesis studies the surface reconstruction problem from scattered and unorganized point clouds, captured in forested environment by a terrestrial LiDAR. We propose a sequence of algorithms dedicated to the reconstruction of forests plot attributes model: the ground and the woody structure of trees (i.e. the trunk and the main branches). In practice, our approaches model the surface with implicit function build with radial basis functions to manage the homogeneity and handle the noise of the sample data points.

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