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Портюх, Крістіна Валеріївна. "Цех з виробництва паперу для простирадл з целюлози у системі Публічного акціонерного товариства «Кохавинська паперова фабрика» з розробленням технологічного потоку." Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2019. https://ela.kpi.ua/handle/123456789/29114.
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Дипломний проект: стор.85 , рис.3 , табл.11 , першоджерел 11, додатків 1.
Метою дипломного проекту було розроблення технологічного потоку з виробництва паперу для простирадл з целюлози на основі Публічного акціонерного товариства «Каховинська паперова фабрика».
Наведено стандарти та сертифікати якості на сировину, хімікати та готову продукцію.
Розроблено та описано технологічну схему з виробництва паперу для простирадл.
Розраховано матеріальний баланс води та волокна, а також тепловий баланс контактно-конвективного методу сушіння, для виробництва 1 т продукції.
Проведено розрахунок та вибір основного обладнання.
Описано об’ємно-планувальне і конструктивне рішення будівлі цеху.
Наведені заходи щодо охорони навколишнього середовища.Diploma project: pag. 85, draw. 3, 11 tables, primary sources 11, addition 1 The purpose of the diploma project was to develop a technological flow for the production of paper for a sheet on the basis of the Public Joint Stock Company "Kakhovinsky Paper Mill". The standards and quality certificates for raw materials, chemicals and finished products are given. A technological scheme for the production of sheet metal sheets has been developed and described. The material balance of water and fiber has been calculated, as well as the thermal balance of contact-convection drying method, for the production of 1 ton of product. The calculation and selection of basic equipment has been carried out. The volume-planning and constructive decision of the building of the shop is given. The measures on environmental protection are given.
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Frisby, Brandi N. "Communicative facework in marital dissolution and post-dissolution processes." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11241.
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Thesis (Ph. D.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains viii, 159 p. Includes abstract. Includes bibliographical references (p. 108-125).
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Hougaard, Sunesen Vibeke. "Biorelevant dissolution media to simulate in vivo dissolution of poorly soluble drugs /." Cph. : The Danish University of Pharmaceutical Sciences, 2003. http://www.dfuni.dk/phd/defences/vibekehougaardsunesen.htm.
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Cordara, Théo. "Effet de la présence de produits de fission sur les mécanismes de dissolution de composés modèles à base de dioxyde d'uranium." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT176/document.
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L’étape de dissolution des combustibles nucléaires usés, réalisée en milieu nitrique concentré, est complexe notamment du fait de leur complexité chimique et microstructurale à l’issue de leur passage en réacteur. Ainsi, la présence de produits de fission (PF) localisés au sein des différentes phases cristallines constitutives du combustible usé peut en impacter la vitesse de dissolution. Dans ce cadre, trois systèmes représentatifs du matériau combustible initial UO2, de UO2 contenant des PF dissous au sein de la phase fluorine ou formant de précipités métalliques ont été obtenus par conversion de précurseurs préparés par voie humide (oxalate, hydroxyde). Pour chaque système, des pastilles denses et de microstructures proches de celle retrouvée au sein du combustible usé ont été préparées à l’issue d’une étape de mise en forme suivie d’un traitement thermique à haute température.L’étude multiparamétrique de la dissolution (approche macroscopique) conduite dans plusieurs solutions d’acide nitrique et à diverses températures a souligné l’impact important joué par la composition chimique sur la durabilité chimique des échantillons. Ainsi, l’incorporation d’éléments lanthanide a conduit à une augmentation de la vitesse de dissolution par rapport à l’échantillon UO2 de référence, laquelle est demeurée largement inférieure à celle relevée en présence d’éléments platinoïde. Par ailleurs, les effets de l’acidité et de la température du milieu sur la vitesse de dissolution ont été examinés et des modifications significatives dans le mécanisme de dissolution prépondérant ont été suggérées pour des concentrations d’acide nitrique supérieures à 0,5 mol.L-1.Pour les trois systèmes sélectionnés, l’évolution de l’interface solide/solution a également été suivie en cours de dissolution à travers une étude operando, réalisée par Microscopie Electronique à Balayage en mode Environnemental (approche microscopique). En présence d’éléments lanthanide ou à proximité des éléments platinoïde métalliques, ce suivi a démontré l’existence de zones de dissolution préférentielles dont les joints de grains et les jonctions triples. Le couplage des résultats obtenus à travers ces deux approches a permis de fournir des données complémentaires en vue d’une meilleure compréhension des mécanismes de dissolution mis en jeu en présence des différents PF considérésThe dissolution of spent nuclear fuels, performed in concentrated nitric acid solution, is a complex process due to some chemical and microstructural heterogeneities. As instance, the presence of Fission Products (FP) in various phases constitutive of spent nuclear fuels can affect the chemical durability of the materials. In this context, three systems of interest representing fresh UO2 used as reference material, and UO2 doped with FP products dissolved in the fluorite structure (lanthanide elements) or incorporated as metallic precipitates (platinoids) were prepared by oxalic or hydroxide precipitation. Dense pellets with microstructure representative for spent nuclear fuel were prepared through sintering step at high temperature.The multiparametric study of the dissolution (macroscopic approach) was developed by varying independently several parameters. While incorporation of lanthanide elements induced a significant increase of the normalized dissolution rates, it remained lower compared to that observed for platinoids. Moreover, increase of nitric acid concentration or temperature led to the decrease of the chemical durability of the prepared materials. Additionally, significant modification of the preponderant mechanism of dissolution occurred for nitric acid concentration higher than 0.5 mol.L-1.For the three selected systems, the monitoring of the evolving solid/solution interface (microscopic approach) was performed operando by Environmental Scanning Electron Microscopy. Compared to pure UO2, the presence of FP (lanthanide elements or metallic platinoids) induced preferential dissolution of grain boundaries and triple junctions. Coupling the results obtained from micro- and macroscopic approaches led to complementary data of strong interest in order to improve the understanding of the role of FP during the dissolution of UO2
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Moore, Christopher Michael. "Dissolution Caves of Mississippi." MSSTATE, 2006. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04132006-090433/.
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The purpose of this project was to distinguish between the karst and pseudokarst caves throughout Mississippi, create an inventory and survey of representative caves and karst features, identify the geology of the rocks hosting the caves, and produce a GIS-based digital karst map. The State of Mississippi is not known for its karst features, yet there are three distinct limestone units that contain dissolution caves: 1) Paleozoic (Mississippian) Tuscumbia Formation limestone; 2) Mesozoic carbonate units; and 3) Cenozoic limestone, Marianna Formation. There are a total of 44 caves known within the state based on past documentation, however the caves listed are not always differentiated between karst or pseudokarst features. This study located and mapped 20 caves, of which 18 were karst caves from eight counties and two were pseudokarst caves from two counties. Four of these caves were newly discovered karst caves, increasing the state total to 48; however two separate karst caves were connected, which makes the final state total 47 caves. Of the remaining 28 caves not surveyed, 11 were pseudokarst caves from eight counties and were not studied because the focus was on dissolutional karst caves. The remaining 17 missing karst caves either had been destroyed, access permission could not be obtained, or the caves could not be located. No active caving organizations exist in Mississippi to preserve cave location data or the caves themselves. Mining, deforestation, and other land use procedures have altered the landscape, resulting in concealment of some caves, and completely or partially destroying other caves.
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Feder, Jens. "Diffusion, dissolution and dispersion." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184715.
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Allen, Ansgar. "The dissolution of meritocracy." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540602.
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Chen, Y. "Granule dissolution and disintegration." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597529.
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The increasing use of granular materials in the chemical, petrochemical, food and pharmaceutical industries, both as intermediate and as end products, gives rise to the need for a better understanding of granule dissolution and disintegration (GDD). However, little is understood about the physical principles controlling the release of active ingredients from granules, a crucial knowledge for the design of product structure in order to optimise product performance. The aim of this work is to bring a scientific approach to the study of GDD in a systematic way. which has not been addressed hitherto. The work here is to highlight the testing of these hypotheses and provide insight into GDD mechanisms. The scientific concern in this thesis is to attempt to reveal the unique behaviour of GDD that is different from homogeneous material dissolution. Unlike homogeneous material dissolution, which depends mainly on the chemical properties of the solute and solvent, GDD is more complicated because the heterogeneous system involves mixed insoluble particles and soluble binder. Further complexity lies in the fact that various physical properties such as granule size, primary particle size, binder-solid ratio and internal pore structure play in influencing GDD behaviour. This thesis reports experiments and theoretical analysis of such GDD behaviour. Four hypotheses - reaction-limited consumption of binder, transport limit for binder removal, transport limit for particle removal and additional Hmit for particle and binder removal - were proposed to cover all of the possible GDD mechanisms. Theories were developed and experiments were set up to test the theory and give explanation of various limiting cases of GDD. A bimodal population balance model was developed. Furthermore, a dynamic shrinking-shell and core model was proposed to clarify GDD mechanisms. The analysis, which has its origin in comparing binder and particle transport coefficients, enables prediction of whether particle or binder transport will hmit GDD process. This evolved into a Sherwood number analysis, which provides a direct physical account of the controlling step. Based on a non-synchronous binder and particle transport analysis, a shrinking shell and core model was proposed to highlight that binder transport may be limited by internal particle shell build-up in the granule. A dynamic model was then developed to provide quantitative analysis of the binder Sherwood number, which was tested by experiment. A rigorous deduction of the model provided a clear physical meaning of the parameters in the equations. To demonstrate the theory and test hypotheses, an ionic binder, zeolite-NaLAS was used in high shear granulation, low shear granulation, fluidised bed granulation and spray drying granulation to provide a range of granule structures and to allow investigation of GDD by both PSD and electrical conductivity. Granules were characterised using mercury porosimetry, sieving, bulk density, particle size analyser and SEM to provide information concerning their various properties, such as binder content, internal pore structure and volume fraction, granule size and primary particle size distribution, as well as surface morphology and granule internal structure. Two main methodologies were adopted to investigate GDD behaviour including a): monitoring electrical conductivity and granule diameter simultaneously for a single granule; b) monitoring the evolution of the PSD by laser light scattering. Those results were analysed to support the theory. In general, the phenomena in GDD are quite different from the general cases of dissolution.
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Cha, Minsu. "Mineral dissolution in sediments." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50144.
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Mineral dissolution is an inherent chemo-hydro-mechanical coupled diagenetic process in sediments. This ubiquitous geological phenomenon affects all properties in sediments, however, its engineering impact remains largely unknown. This research centers on the effects of mineral dissolution on sediment behavior with emphasis on dissolution modes in nature and their engineering implications. Five different dissolution modes are identified: homogeneous, pressure-dependent, and localized dissolution, and the dissolution of shallow and deep dissolvable inclusions. The consequences of each dissolution mode are investigated through experiments and discrete element methods. While each dissolution mode triggers unique consequences, it is observed that in all cases 1) significant displacement takes places during dissolution, 2) there is a pronounced effect of internal friction and the extent of dissolution on the evolution of the sediment, 3) the sediment has higher compressibility and exhibits a more contractive tendency after dissolution, 4) a porous honeycomb-shaped internal fabric develops accompanied by contact force concentration along dissolved inclusions, and 5) horizontal stress reduction takes place during dissolution and shear localization may develop under zero lateral strain conditions. Mineral dissolution has important engineering implications, from soil characterization to slope stability and shallow foundations. Pre- and post-dissolution CPT studies show that dissolution decreases the tip resistance proportional to the extent of dissolution. Dissolution in sloping ground induces global settlement as the prevailing deformation pattern, and prominent lateral movements near the slope surface; sudden undrained shear failure may take place during otherwise quasi-static dissolution. While footings experience larger settlements during post-dissolution loading, subsequent dissolution beneath a previously loaded footing causes displacements that are greater than the sum of dissolution-induced and load-induced settlements.
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Feder, Jens. "Diffusion, dissolution and dispersion." Diffusion fundamentals 16 (2011) 19, S. 1, 2011. https://ul.qucosa.de/id/qucosa%3A13748.
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RANGEL, VANESSA GEROSA DA SILVA. "DISSOLUTION OF A MARRIAGE: A STUDY ABOUT THE PROCESS OF DISSOLUTION OF CONJUGALITY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25550@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Esta pesquisa tem como objetivo a investigação do processo de dissolução da conjugalidade, incluindo o luto decorrente desse processo. Para atingir tal objetivo, este estudo analisa os discursos de homens e mulheres sobre a separação conjugal, perpassando seus sentimentos, assim como, sua relação com os ex-cônjuges. Para realização deste trabalho, foram entrevistados 10 homens e 10 mulheres que ainda não tinham recasado, que ficaram casados ao menos 3 anos, que estavam separados há, no mínimo, 1 ano e, no máximo, 7 anos, e que tiveram filhos com os ex-parceiros. Enquanto as mulheres mencionam que os sentimentos seguintes à separação estavam relacionados ao sonho de amor desfeito, os homens relacionam esses sentimentos à perda do contato diário com os filhos. Com relação aos sentimentos atuais decorrentes da separação, embora mais frequentes nas falas femininas, sentimentos de autonomia, autovalorização e crescimento pessoal aparecem tanto no discurso dos homens quanto no depoimento das mulheres. Em contrapartida, sentimentos de tristeza são mencionados somente pelos homens, ainda que não tenham a mesma intensidade e frequência do período pós-separação. No que diz respeito à parentalidade, os dados ratificam a dificuldade dos pais em conversar sobre o processo de separação com os filhos. Por outro lado, os resultados indicam que a maioria dos participantes não teve sua capacidade parental diminuída logo após a separação. Nesta pesquisa, a maioria dos entrevistados manteve o mesmo padrão de relacionamento com o ex-cônjuge ao longo do tempo. A manutenção de um bom relacionamento com o ex-parceiro emerge mais nas falas femininas do que no discurso dos homens. Quanto aos casos de conflito e litígio, foi possível verificar como aspectos conjugais e parentais ficam emaranhados.
This research has the intention of investigating the process of the dissolution of the conjugality, including the mourning derived from this process. To achieve such a goal, this study compares the speeches of men and women about the separation, showing their feelings, and their relationship with their ex-partners. In order to do this work, we interviewed 10 men and 10 women, that haven t remarried. They were married at least 3 years, were separated at least a year and at the most 7 years and had children with the ex-partner. While the women mention their feelings after separation are related to the loss of the dream love, the men relate those feelings to the loss of the contact with their kids. In relation with the feelings resulting of separation, even though more frequent in feminine speeches, feelings of self esteem and personal growth are often heard from men and women. On the other hand, sadness feelings are only mentioned by men, even though they don t have the same intensity and frequency of the period post separation. Related to the parenting, data shows the difficulty of parents to talk about the separation process with their kids. On the other hand, the result shows that the majority of the participants didn t have their parental capacity lowered right after separation. In this research, the majority of the interviewed kept the same relationship with the ex-partner with time. The maintenance of a good relationship with the ex-partner emerges more in feminine speeches than in men. As far as the conflicts and legal, was possible to verify how messy marriage and parenting can be.
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Zafranian, Venus. "The influence of dissolution medium on in vitro dissolution profiles for pulmonary drug delivery." Thesis, Uppsala universitet, Institutionen för farmaceutisk biovetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-454536.
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Today, orally inhaled drugs found on the market suffer from variable and discontinuous pulmonary drug release which lowers efficacy and patience compliance. This is usually a consequence of the poor understanding of the interaction and dissolution behavior of drug particles in the lung environment. Thus, the aim of this project was to investigate the effect of the dissolution medium on dissolution profiles for the well-known orally inhaled drug budesonide (BD) and fluticasone propionate (FP), in order to assess the importance of a proper selection of dissolution media for in vitro dissolution methods. In order to achieve this a modified Andersen Cascade Impactor was used to simulate deposition of particles onto filters. The dissolution was measured using a Transwell set up with polycarbonate membranes that can hold the filters with the deposited drug on it. Different media were prepared, from simple to more biorelevant. The samples taken during the dissolution experiments were analyzed quantitatively using UPLC-UV and the experimental data was processed by fitting to the Weibull function. The aim of this project was successfully achieved and the dissolution media that worked best for both BD and FP was PBS with the addition of 0.5% SDS. On the other hand, the dissolution media that performed the least for both BD and FP was the simulated lung fluid (SLF) with presence of 0.02% (w/v) DPPC. This may be due to the fact that DPPC forms liposomal aggregates which probably results in the media becoming more viscous and hence the dissolution time becomes slower.
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Lucero, Borja Diego Sebastián. "Solubility and Dissolution Rate of Active Pharmaceutical Ingredients: Dissolution Media and Effect of Enhancers." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/671762.
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The present doctoral thesis is focused on the effect of pH, enhancers and biorelevant media in the Solubility and the Dissolution Rates of some selected acidic active pharmaceutical ingredients (API). Because of the effect of these physicochemical parameters in the bioavailability of drugs and their pharmacological action, deepen the knowledge on the factors affecting the dissolution properties is of paramount importance in the drug development process.
Solubility and dissolution rates are examined in different aqueous solutions and buffering systems, accounting for the pH values of main interest in the gastrointestinal tract (2.0, 5.8 and 6.5), together with dissolution media that simulate intestinal fluids in fasted (FaSSIF) and fed states (FeSSIF). It is also determined in these media and discussed the effect of some excipients intended as dissolution enhancers, such as cyclodextrins, polyvinylpyrrolidones and hydroxypropylcellulose. Finally, differential scanning calorimetry was used to identify solid-solid interactions between excipients and APIs. As a complementary investigation, this thesis also presents a comparative study of the reference shake-flask and potentiometric CheqSol methods for the determination of solubility, including APIs with different acid/base properties (acidic, amphoteric and basic).
The study confirms that solubility is pH dependent, and an accurate pKa determination of the drugs is needed to detect the presence of concurrent aggregation or complexation reactions affecting the amount of compound dissolved. As expected, the addition of excipients increases the solubility of APIs, but in different degrees depending on the drug, excipient, and pH conditions. Solubility in simulated intestinal fluids is generally improved, and the addition of excipients might increase, diminish or even cancel the enhancement, depending on the matrix formed. Interestingly, the factors improving the solubility of an API do not necessarily enhance its dissolution rate. The release of the drug from its compressed solid form (tablet) is a complex process, involving an aqueous boundary layer between the solid and the bulk solution.
The results of this thesis point out the need of systematic and detailed dissolution studies in the step of pharmaceutical formulation, as long as the enhancement produced by a particular excipient in a singular dissolution medium can be characteristic of an individual API, and these results cannot be uncritically extended to other drugs.La presente tesis doctoral se enfoca en el efecto del pH, excipientes y medios biorelevantes sobre la solubilidad y velocidad de disolución de algunos principios activos (PA). Dado el efecto de estos parámetros fisicoquímicos en la biodisponibilidad de los fármacos y su acción farmacológica, el profundizar en el conocimiento de los factores que afectan estas propiedades de disolución es de suma importancia en el desarrollo de medicamentos. La solubilidad y velocidad de disolución se examinan en diferentes soluciones y sistemas tamponadores, de acuerdo a valores de pH de interés del tracto gastrointestinal, junto a medios de disolución que simulan fluidos intestinales. También se determina el efecto que puedan tener en estos medios, sustancias como excipientes que aumenten la disolución, tales como ciclodextrinas, polivinilpirrolidonas e hidroxipropilcelulosa. Calorimetría diferencial de barrido fue utilizada para identificar interacciones sólido-sólido entre excipientes y PA. Complementariamente, en esta tesis también se presenta un estudio comparativo entre el método de referencia de equilibrio de fases y el método potenciométrico CheqSol para la determinación de solubilidad, incluyendo PA de diferentes propiedades fisicoquímicas. El estudio confirma la dependencia entre pH y solubilidad, una medición exacta del pKa de los fármacos es necesaria para detectar la presencia de agregados o complejos que afecten la cantidad de muestra disuelta. Como se esperaba, la adición de excipientes incrementa la solubilidad pero en diferente grado dependiendo del compuesto, el excipiente y las condiciones de pH. La solubilidad generalmente es mejorada cuando se usan medios biorelevantes, mientras que el uso de excipientes en estos medios podría incrementar, disminuir o cancelar el efecto de solubilización, dependiendo de la matriz formada. Sorpresivamente, los factores que incrementan la solubilidad no necesariamente lo hacen en la velocidad de disolución. La liberación del compuesto desde la superficie de la tableta es un proceso complejo, relacionado con la capa acuosa intermedia entre la tableta y la solución. Los resultados de esta tesis señalan la necesidad de estudios sistemáticos y detallados en el paso previo de formulación farmacéutica, pues la mejora producida por un excipiente en particular en condiciones singulares del medio, puede ser característica para un PA específico, y estos resultados no deben ser extrapolados sin criterio a otros fármacos.
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Durbin, Tracie L. "Modeling Dissolution in Aluminum Alloys." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6873.
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Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working, annealing, precipitation-hardening, and/or heat-treatments. Heat-treatable aluminum alloys contain one or more soluble constituents such as copper, lithium, magnesium, silicon and zinc that individually, or with other elements, can form phases that strengthen the alloy.
Microstructure development is highly dependent on all of the processing steps the alloy experiences. Ultimately, the macroscopic properties of the alloy depend strongly on the microstructure. Therefore, a quantitative understanding of the microstructural changes that occur during thermal and mechanical processing is fundamental to predicting alloy properties. In particular, the microstructure becomes more homogeneous and secondary phases are dissolved during thermal treatments. Robust physical models for the kinetics of particle dissolution are necessary to predict the most efficient thermal treatment.
A general dissolution model for multi-component alloys has been developed using the front-tracking method to study the dissolution of precipitates in an aluminum alloy matrix. This technique is applicable to any alloy system, provided thermodynamic and diffusion data are available. Treatment of the precipitate interface is explored using two techniques: the immersed-boundary method and a new technique, termed here the sharp-interface method. The sharp-interface technique is based on a variation of the ghost fluid method and eliminates the need for corrective source terms in the characteristic equations. In addition, the sharp-interface method is shown to predict the dissolution behavior of precipitates in aluminum alloys when compared with published experimental results. The influence of inter-particle spacing is examined and shown to have a significant effect on dissolution kinetics. Finally, the impact of multiple particles of various sizes interacting in an aluminum matrix is investigated. It is shown that smaller particles dissolve faster, as expected, but influence the dissolution of larger particles through soft-impingement, even after the smaller particles have disappeared.
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Speer, Rachel L. "Coping with romantic relationship dissolution." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq27380.pdf.
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Hume, Lily Ann. "The dissolution rate of chrysotile." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-06082009-171119/.
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Sanders, Giles. "The dissolution of organic compounds." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362083.
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Curry, Richard M. "Mineral dissolution in silicate melts." Thesis, University of St Andrews, 1990. http://hdl.handle.net/10023/7278.
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Quartz and orthopyroxene in mafic rocks are commonly observed to be surrounded by fringes of granular pyroxene, and of olivine and clinopyroxene, respectively. This study reproduces the conditions of formation of these textures, and investigates their origins, kinetics and phase relations. Pieces of silica glass or crystals of orthopyroxene were dissolved into tholeiitic and slightly alkaline basalts, suspended from wire loops in an atmospheric pressure quenching furnace, and run for 10 minutes to 32 days at subliquidus temperatures between 1120° and 1190°C and oxygen fugacities close to the QFM buffer. Polished sections of charges were examined primarily by backscattered electron imagery and by microprobe analysis. The textures developed in silica dissolution experiments consist of fringes of elongate skeletal pyroxenes radially arranged around the silica. The pyroxenes first nucleate on the surface of the silica. As dissolution continues, growth continues mostly on existing crystals, rather than by the nucleation of additional crystals. Dissolution rates for silica range from 2.8*10⁻¹¹ to 4.4*10⁻¹⁰ms⁻¹, and are time-independent until growth of the pyroxene fringe hinders transport processes in the melt. This causes dissolution to slow down, until it ceases altogether after 3 to 8 days. A silica-rich layer of melt forms around the surface of charges run at higher temperatures, suggesting that convection driven by variations in surface tension may operate in the charges. The textures developed in orthopyroxene dissolution experiments consist of granular olivines, some of which nucleate on the pyroxene surface, whereas others nucleate within the pyroxene as a result of the decomposition of included phases. With time, olivine crystals become connected and form complex grain shapes. Dissolution rates for orthopyroxene range from 1.7*10⁻¹¹ to 1.2*10⁻⁹ ms⁻¹. At higher temperatures dissolution rates are constant, but at lower temperatures dissolution is time-dependent. Unlike silica dissolution, orthopyroxene dissolution does not cease as a result of continued neocryst growth hindering melt transport, indicating that the fringe remains permeable. For both systems, the neocryst compositions are strongly dependent on the chemistry of the melt formed at the interface between the dissolving crystal and the bulk melt, and the neocrysts may be metastable with respect to the bulk melt. Chemical equilibration of olivine neocrysts with time is observed for longer experiments. Textural equilibration of olivine grains occurs by the processes of liquid-phase sintering in runs longer than 12 hours. Subliquidus dissolution data are applied to textures from natural samples collected from dykes, lava flows and lava lakes, to estimate the residence time of reacted crystals; values range from 0.6 to 208 days for reacted quartz, and from 0.7 to 462 days for reacted orthopyroxenes. The rates of cooling of the magma and the size of the magma body in which the reaction occurred are also estimated.
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Daly, P. J. "Dissolution kinetics of calcium carbonate." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372693.
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Conde, Adele. "Multiscale Expression Of Apatite Dissolution." ScholarWorks @ UVM, 2019. https://scholarworks.uvm.edu/graddis/1151.
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The weathering of apatite is the foundation of the phosphorus cycle and essential to life, yet little is known about the nanoscale mechanisms driving apatite weathering. Deciphering nanoscale dissolution in apatite is a significant step to understand phosphate weathering behavior, that was key to the development of life. Determining what controls apatite weathering can impact many areas of environmental and medical mineralogy such as dentistry, contaminant scavenging, geochronology, and paleoenvironment studies. The aim of this study was to characterize apatite dissolution across scales with an emphasis on the nanoscale mechanisms. Recent research on the weathering of silicate minerals at the nanoscale has provided telling evidence of a relatively new chemical weathering model referred to as coupled interfacial dissolution-precipitation (CIDR) mechanism. We hypothesize that this mechanism could be broadened to phosphate minerals.
To investigate crystals of Durango fluorapatite (FAP) and hydroxyl-chlorapatite (HAP) were hydrolyzed in flow-through devices with pH 3 HNO3 solutions. Apatites used in the study were chemically and structurally characterized via Single Crystal-XRD, with particular emphasis on the anion composition and atomic arrangement. Determination of the mechanisms of dissolution was carried at multiple scales using ICP-OES chemical analysis (macroscale), SEM (microscale) and STEM-HAADF-EDS/EELS on FIB liftouts (nanoscale).
At the macroscale, The anionic composition of the apatite controlled its weathering rate. As expected, HAP dissolution occurred at faster rates compared to FAP. SEM characterization of the crystal surfaces pre- and post-dissolution revealed the development of etch pits during dissolution, however, more pronounced for FAP than HAP. Observation of the mineral/solution interface at the nanoscale using STEM-HAADF revealed the development of a nanometric amorphous layer likely depleted in Ca compared to P.
The observation of a sharp crystalline/amorphous transition and 5 to 15 nanometers thick amorphous surface altered layer, associated with a depletion in Ca suggests that similar to silicate, apatite is subject to a coupled interfacial dissolution-reprecipitation mechanism. This potential discovery could transform our understanding of phosphate behavior in medical and environmental mineralogy fields.
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Li, Changdong. "Dissolution behaviours of structured particles." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7954/.
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The work presented in this thesis aims at the fundamental understanding and investigation of dissolution behaviors of structured particles. This topic is relevant to numerous industrial applications including detergent, pharmaceutical, agrochemical and energy products. Both experimental works and theoretical analyses were carried out in this work. The particles of several different materials including sodium carbonate and polymers with specific characteristic and structure were used into the experimental works in this thesis. Polymers used in this thesis included carboxymethyl celluslose, croscarmellose sodium and crospovidone. The studies on characteristics of these particles included the determination of particle size, shape and structure with several measurement techniques. The dissolution process was measured with experimental methods under different solution conditions including temperature, stirring speed and pH. Based on these measured data, the dissolution kinetics such as dissolution rate constant were quantified with mathematical models and analyzed with theoretical studies. In this way, the dissolution behaviors of different structured particles could be finally identified and analyzed with the quantified data of dissolution process and dissolution kinetics. Additionally according to the quantification process, the effects of these solution conditions on dissolution kinetics could also be determined and identified that how these conditions impact dissolution kinetics. Main conclusions of my work on dissolution experiments in this thesis were simply summarized as the following that: • An increasing in the temperature and stirring speed leads to the increases of dissolution rate and dissolution rate constant of sodium carbonate particles in all cases. • The dissolution rate and the rate constant decreases with the increasing of pH value of solution. • Carboxymethyl cellulose and crospovidone show a clear effect to enhance the dissolution rate and the rate constant of sodium carbonate-polymer composite tablets. • Cropovidone also has a stronger effect to enhance the dissolution process and kinetics than carboxymethyl cellulose • Croscarmellose sodium shows a clear effect to weaken the dissolution rate and the rate constant of sodium carbonate-polymer composite tablet.
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Wang, Ying. "Cellulose fiber dissolution in sodium hydroxide solution at low temperature dissolution kinetics and solubility improvement /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26632.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Deng, Yulin; Committee Member: Banerjee, Sujit; Committee Member: Frederick, James; Committee Member: Hsieh, Jeffery; Committee Member: Ragauskas, Arthur J.. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Gausse, Clémence. "Synthèse et dissolution de matrices phosphatées de structure monazitique." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT217/document.
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Dans le cadre de la loi du 30 décembre 1991 relative à la gestion à long terme des déchets nucléaires, plusieurs matrices de confinement spécifique des actinides, dont la monazite et la solution solide monazite/chéralite associée ont été étudiées au cours de ce travail en vue de leur stockage en formation géologique profonde. Ainsi, différentes monazites LnPO4 (Ln = La → Gd) ont été préparées par conversion thermique de rhabdophanes, LnPO4 , 0,667H2O, précipitées à basse température. Sur la base d’expériences menées sous rayonnement synchrotron, la structure cristallographique de la rhabdophane a d’abord été résolue dans un système monoclinique (groupe d’espace C2) tout comme la monazite (groupe d'espace P21/n) puis sa conversion thermique en monazite a été étudiée. Une étude multiparamétrique de la vitesse de dissolution de la monazite LnPO4 (Ln = La → Gd) dans l’acide nitrique a été réalisée en conditions dynamiques. Les valeurs de vitesses de dissolution normalisées sont demeurées très faibles quelles que soient l'acidité du milieu, la température et la nature de l’élément lanthanide, confirmant l’excellente durabilité chimique des matériaux préparés. Des ordres partiels relatifs à l'activité du proton compris entre 0,7 ± 0,2 et 1,5 ± 0,3 ont été relevés. Parallèlement, la diminution de l’énergie d’activation apparente pour T ≥ 313 K a souligné une modification de l’étape cinétiquement limitante du mécanisme de dissolution, liée à l'impact de l’indice de saturation de la solution par rapport à la précipitation de la phase rhabdophane.Les produits de solubilité des rhabdophanes (La → Dy) ainsi que les grandeurs thermodynamiques associées ont été déterminés via des expériences de sur- et de sous-saturation. Le bon accord entre les valeurs obtenues par ces deux approches a confirmé la réversibilité de l’équilibre de solubilité associé à la rhabdophane. Une faible variation du produit de solubilité et des grandeurs thermodynamiques de formation de la rhabdophane a été observée le long de la série des éléments lanthanide (-2151±13 ≤ Df H^o (298K) ≤ -2130±12 kJ.mol-1, -2004±2 ≤ Df G^o (298K) ≤ -1984±2 kJ.mol-1 et -504±11≤ DS^o (298K)≤ -473±12 J.mol-1.K-1), à l’exception de l’europium qui présente des valeurs nettement supérieures d'énergie libre (-1896 ± 2 kJ.mol-1), d'enthalpie (-2057 ± 9 kJ.mol-1) et d'entropie (–538 ± 11 J.mol-1.K-1) de formation. Par ailleurs, une relation directe entre les enthalpies obtenues pour les rhabdophanes et les monazites a été démontrée ; les données associées aux rhabdophanes étant obtenues par simple ajout de la contribution de 0,667 molécule d'eau. Cette observation corrobore aussi bien la structure monoclinique de la rhabdophane que le nombre de molécules d'eau constitutionnelles.Parallèlement, l'évolution structurale et microstructurale de la surface de monazites frittées a été suivie en cours de dissolution par plusieurs techniques complémentaires (MEBE, AFM, XRR, et DRX en mode d’incidence rasante). La très bonne durabilité chimique de ces céramiques préparées a été confirmée : seulement 0,04% et 0,3% en masse de matériau ont été dissous après 300 jours de lixiviation, respectivement dans HNO3 0,1M et 0,25M à 363K. Des analyses de surface, il est apparu que les défauts préexistants (fissures, défauts liés au polissage, pores) constituaient des zones préférentielles de dissolution tandis qu’aucune phase secondaire n'a été clairement mise en évidence malgré un indice de saturation en solution traduisant un état proche de l'équilibre de précipitation de la rhabdophane.Enfin, un protocole original de synthèse d’échantillons de rhabdophane dopés en thorium (Nd1-2xCaxThxPO4 , 0,667H2O) par voie humide a été développé au cours de ce travail. Les premières expériences de solubilité, menées en conditions de sous-saturation dans HCl 0,25 M, ont conduit à une estimation des produits de solubilité apparents, lesquels présentent une faible variation sur l’intervalle de températures considéréIn the context of the French research law dedicated to the radioactive waste management, several ceramics were proposed for the specific conditioning of actinides. Among them, monazites and monazite/cheralite solid solutions were particularly considered in this work.Thus, monazites LnPO4 (Ln = La → Gd) were prepared by thermal conversion of low-temperature rhabdophane precursors, LnPO4•0.667H2O. From synchrotron experiments, the crystal structure of rhabdophane was solved. It was found to be monoclinic (space group C2) as monazite (space group P21/n).The multiparametric study of the kinetics of dissolution of monazites LnPO4 (Ln = La → Gd) was performed in nitric acid solutions and using dynamic conditions. The normalized dissolution rates remained very low whatever the acidity, the temperature, and the lanthanide element considered. The partial order of the reaction related to the protons activity varied from 0.7 ± 0.2 to 1.5 ± 0.3. Moreover, the apparent activation energy of the dissolution mechanism was found to vary with temperature, suggesting a change in the rate-limiting step. The decrease of the apparent activation energy for T ≥ 313 K was assigned to the impact of saturation processes with respect to the rhabdophane.Thus, the solubility products as well as thermodynamic data associated to the formation of rhabdophanes were evaluated from over- and under-saturation conditions. The similar values obtained by both approaches confirmed the reversibility of the equilibrium associated to the rhabdophane precipitation. Solubility products as well as thermodynamic data only slightly varied along the lanthanide elements series : -2151±13 ≤ Df H^o (298K) ≤ -2130±12 kJ.mol-1, -2004±2 ≤ Df G^o (298K) ≤ -1984±2 kJ.mol-1 and -504±11 ≤ Df S^o (298K) ≤ -473±12 J.mol-1.K-1, excepted for europium that presented the highest values of free energy (-1896 ± 2 kJ.mol-1), enthalpy (-2057 ± 9 kJ.mol-1) and entropy (–538 ± 11 J.mol-1.K-1) of formation. The comparison of the data obtained for rhabdophanes and monazites showed that the values associated to rhabdophane can be deduced from those of monazite by adding the contribution of 0.667 water molecule. It confirms either the monoclinic structure of the rhabdophane and the number of water molecules present in the structure.For the first time, structural and microstructural evolution of monazite pellets was monitored during dissolution thanks to several complementary surface analysis techniques (ESEM, AFM, GI-XRR and GI-XRD). This study confirmed the very good chemical durability of these ceramics (only 0.04 wt.% and 0.3 wt.% of dissolved ceramic in 0.1 M HNO3 and 0.25 M HNO3, respectively, at 363 K after 300 days of dissolution). These different techniques also highlighted that pre-existing defects (pores, cracks, polishing marks) acted as preferential dissolution zones. However, no secondary phase was clearly evidenced onto the surface of the samples even if the solutions were found to be close to equilibrium with rhabdophane.Finally, an original protocol of precipitation of Th-doped rhabdophanes, Nd1-2xCaxThxPO4•0.667H2O, was developed during this work. The first estimation of the apparent solubility constants, performed in under-saturated conditions in 0.25 M HCl solution, did not evidence any significant variation in the temperature range investigated
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Stork-Hestad, Nicole B. "A NON-MARITAL, ROMANTIC RELATIONSHIP DISSOLUTION STUDY." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/38.
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The present study examines three non-marital, romantic relationship dissolution types: (1) normal dyadic dissolution, (2) fatal attraction dissolution, and (3) social allergen dissolution among a sample of 321 emerging adults, who are between ages eighteen and twenty-nine. Results of an online survey revealed that normal dyadic dissolution occurred in 62%, social allergen dissolution occurred in 27%, and fatal attraction dissolution occurred in 11% of the participants’ relational demises. Results also revealed that there is a surprising amount of overlap between the three dissolution types, and that age is not specifically correlated with a particular dissolution type. However, there are two predicators of dissolution type within an emerging adult population: perceived family support and whether or not the couple cohabitate.
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Felton, David Scott. "Theoretical dissolution coefficient for rock fractures." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/21505.
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Adamcik, Ingrid Alexandra. "Embodying movement from dissection to dissolution." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0001/MQ42300.pdf.
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Ekeroth, Ella. "Radiation induced oxidative dissolution of UO₂ /." Stockholm : Nuclear Chemistry, School of Chemical Science and Engineering, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3891.
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Lloyd, Michael Charles. "The dissolution of soluble phosphate glasses." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293799.
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Lu, Jun. "Petroleum coke slags : characterization and dissolution /." Diss., This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-10022007-144734/.
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Jones, Christopher. "France and the dissolution of Yugoslavia." Thesis, University of East Anglia, 2015. https://ueaeprints.uea.ac.uk/58570/.
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This thesis examines French relations with Yugoslavia in the twentieth century and its response to the federal republic’s dissolution in the 1990s. In doing so it contributes to studies of post-Cold War international politics and international diplomacy during the Yugoslav Wars. It utilises a wide-range of source materials, including: archival documents, interviews, memoirs, newspaper articles and speeches. Many contemporary commentators on French policy towards Yugoslavia believed that the Mitterrand administration’s approach was anachronistic, based upon a fear of a resurgent and newly reunified Germany and an historical friendship with Serbia; this narrative has hitherto remained largely unchallenged. Whilst history did weigh heavily on Mitterrand’s perceptions of the conflicts in Yugoslavia, this thesis argues that France’s Yugoslav policy was more the logical outcome of longer-term trends in French and Mitterrandienne foreign policy. Furthermore, it reflected a determined effort by France to ensure that its long-established preferences for post-Cold War security were at the forefront of European and international politics; its strong position in all significant international multilateral institutions provided an important platform to do so. Therefore, it was imperative for France that Yugoslav dissolution, and recognition of its successor states, be firmly anchored within a strongly European and international framework. Moreover, it was absolutely essential that the Yugoslav crisis did not threaten the Maastricht Treaty in 1991 nor the national referendum on its passing into law in September 1992. Therefore, French diplomacy stressed the primacy of a unified common European approach to the dissolution of Yugoslavia. Many of the methods employed in diplomacy towards, and peacekeeping within, Yugoslavia thus bore the hallmark of French initiative. In addressing these issues, this dissertation demonstrates that France played a far greater role in shaping the international response to the dissolution of Yugoslavia than previously acknowledged.
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Gnamou-Petauton, Dandi. "Dissolution et succession entre organisations internationales." Paris 11, 2006. http://www.theses.fr/2006PA111008.
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Djelali, Nacer-Eddine. "Electropolymérisation cationique amorcée par dissolution anodique." Grenoble 1, 1992. http://www.theses.fr/1992GRE10142.
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La polymerisation cationique est amorcee par certains cations metalliques generes par dissolution anodique. La reaction peut se propager meme en presence de tres fortes concentrations d'anions pourvu que ceux-ci ne soient ni basiques ni nucleophiles. C'est le cas des anions pf#6#, clo#4#, sbf#6# et bf#4# quoique ce dernier peche par son instabilite. Le degre d'oxydation des cations metalliques obtenus electrochimiquement en milieu non complexant a ete determine par coulometrie, gravimetrie et spectrophotometrie d'absorption atomique. Il se forme v#4#+, cr#6#+; le mercure donne hg#+ en milieu non complexant et hg#2#+ en milieu complexant. Als+ forme est oxyde en al#3#+ par l'ion clo#4#. Divers monomeres ont ete testes: pi-donneurs (styrene, isoprene, methylstyrene) n, pi-donneurs (isobutylvinylether, allylglycidylether), n donneurs (lactones, hexamethylcyclotrisiloxane, 1,3-dioxolane). Les polymeres obtenus ont ete analyses et leurs masses sont comparables avec celles que l'on obtient habituellement dans les polymerisations cationiques malgre les conditions defavorables a ce type de reaction
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Qiu, Yang. "Dissolution mechanisms: theoretical and experimental investigations." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1892.
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The dissolution behavior of a drug substance is an important part of its bioavailability. Three solid dissolution mechanisms are recognized: transport control, interface control and mixed-kinetic control. The mixed-kinetic control mechanism is not well studied as the majority of dissolution phenomena in pharmaceutical research are assumed to be transport-controlled. A phenomenological model for mixed-kinetic control was developed in which the interfacial step comprises molecular detachment and re-deposition and is described by chemical kinetic theory. This model encompasses interface control and transport control as limiting cases.
Experimental studies on three organic compounds showed that they dissolved by transport control at 37°C, but exhibited certain degrees of interface control at lower temperatures (10°C and 3°C), which, according to the model, indicates that reducing the dissolution temperature slowed down re-deposition more than transport. Using mathematical approaches derived from the model, up to 27% interface control was calculated from the experimental results.
The second experimental investigation showed significant degrees of interface control in benzoic acid dissolution in sodium dodecyl sulfate (NaDS) solutions at 25°C. The dissolution behavior was well described by the mixed-kinetic control model and up to 73% interface control was calculated. An extension of the model was proposed to describe a potential micelle-interface interaction mechanism indicated by the model-fitted parameters.
The third investigation showed that FD&C Blue #1, a water-soluble dye, inhibited sulfathiazole dissolution in acidic media but not in water. The inhibition was attributed to the blocking of dissolution sites by dye adsorption. A potential pH-dependent adsorption mechanism was proposed in which protonation at sulfathiazole solid surface gives rise to preferential dye adsorption on detachment rates and thus reduced dissolution rates.
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Lee, Hong-Guann. "Mechanistic studies of cocrystal dissolution behavior." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/5548.
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The objective of this study is to investigate cocrystal solubility and dissolution behavior to elucidate the factors affecting these processes in various media. Six cocrystals with xanthines (theophylline (THP), caffeine (CAF) and theobromine (THB)) were prepared and characterized by powder X-ray diffraction and thermal methods. Two cocrystals (CAFCA I and THBSA) are new solids and their crystal structures were determined by single crystal X-ray diffraction.
Cocrystal solubility behavior depended on the dissolving complex solubility and its dissociation behavior in solution. Two THP cocrystals - one with acetaminophen (ACE) and one with citric acid (CA) created different degrees of free THP supersaturation in solubility and dissolution studies. High transient THP supersaturation caused almost immediate THP hydrate crystallization from THPCAH and led to non-congruent solubility behavior. Such behavior was not observed with the ACETHP because free THP supersaturation was not sufficient to induce rapid crystallization but did so over longer equilibration times.
Three salicylic acid (SA) cocrystals with xanthines (THP, CAF, and THB) were prepared; two (THPSA and CAFSA) had low aqueous solubility compared to their pure components and one (THBSA) had higher solubility. Both cocrystal components in these cocrystals produced higher solubility/dissolution rates in alkaline media due to ionization. Also, at higher pH, THB precipitated from THBSA solutions because of higher THB supersaturation under alkaline conditions.
Caffeine (CAF) and theophylline (THP) both form cocrystals with citric acid (CA) which is a highly water-soluble cocrystal former. Both CAFCA Form I and II solubility and dissolution behavior were studied. THPCAH exhibited non-congruent dissolution because of rapid precipitation of THP hydrate on the dissolving cocrystal surface. CAFCA exhibited congruent dissolution because it did not produce sufficient supersaturation to precipitate CAF hydrate during dissolution. CA cocrystals also have the unusual behavior of high viscosities produced in the dissolution boundary layer due to CA’s high solubility. These viscosities alter diffusion coefficients which reduce dissolution rates from that expected based purely on solubility.
To further understand cocrystal dissolution, a diffusion-convection-reaction (DCR) model was developed to predict cocrystal dissolution rates in various media. This model predicted concentration profiles of all species (complex, free components and reactive species) in the diffusion layer of a rotating disk intrinsic dissolution system. Predicted dissolution rates had varying degrees of agreement with experimental data depending on the cocrystal model and the medium into which the cocrystal dissolved.
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Molière, Aurélien. "Dissolution des couples et compensation patrimoniale." Thesis, Lyon 3, 2012. http://www.theses.fr/2012LYO30095.
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L’union juridique formée par deux personnes qui vivent en couple se fonde sur l’existence d’une communauté de vie, dont le droit français consacre trois modes d’organisation : le mariage, le pacte civil de solidarité et le concubinage. L’intensité de cette communauté varie selon le mode de conjugalité et chacun constitue, par conséquent, une inégale source de solidarité. Ce soutien, à la fois matériel et moral, ne résiste pas à la dissolution de l’union qui constitue dès lors, dans certains cas, la source d’un préjudice ou d’un état de besoin.Dans le but de les compenser, le droit met en œuvre une indemnisation, lors de la rupture. Ce transfert de valeurs prend la forme de dommages-intérêts, d’une prestation compensatoire et d’une indemnité in rem verso. Toutefois, après avoir assisté au recul de la faute, ainsi qu’à l’avènement d’une responsabilité objective, c’est tout le système de la compensation-indemnisation qui décline et ne semble plus adapté à l’union telle qu’on la conçoit, libéralisée dans sa dissolution et émancipatrice des individus. Ce déclin incite à rechercher l’existence d’une autre méthode de compensation.L’extinction du lien conjugal dissout la communauté de vie, sans que les effets déjà produits ne soient remis en cause. Or, tout au long de la vie commune, l’union provoque la mutualisation d’un certain nombre de richesses, qu’il convient de partager. Cette redistribution, réalisée par l’intermédiaire d’une communauté, d’une indivision ou d’une société a pour effet de compenser l’éventuelle disparité patrimoniale. Lorsque cette compensation est insuffisante ou ne permet pas à l’un des conjoints de subvenir à ses besoins, c’est une redistribution minimale que le droit organise, en tirant profit des biens présents dans le patrimoine de l’un, pour attribuer des droits utiles à l’autre, notamment sur l’immeuble affecté au logement. Ces deux formes de distribution constituent les manifestations d’un nouveau modèle : la compensation-distributionThe legal union formed by two persons living as a couple is based on the existence of a joint living for which French Law sanctions three modes of organization: marriage, civil partnership and cohabitation. The intensity of this community depends on the nature of conjugality. As a consequence, each of the presented modes of organization consists of an uneven source of solidarity. Solidarity is both material and moral, and does not survive the dissolution of the union, which therefore denotes, in some cases, a source of damage or a state of necessity. In order to compensate this situation, French Law provides for compensation when couples break up. This transfer of value takes the form of damages, of a spousal support or of an in rem verso compensation. However, as a consequence of the decline of fault and the accession of an objective liability, the whole compensation system is deteriorating and no more seems suitable for the union the way it is understood, i.e. liberal in its break up and liberated from individuals. This decline encourages us to look for the existence of other compensation methods. The termination of the marital bond dissolves the joint living without prejudice to the effects already produced. Yet, throughout the shared life, the union causes a certain mutual wealth that needs to be divided. This redistribution, made trough a community, a joint ownership or a company, ends up compensating the possible disparity in property. When the compensation is insufficient or cannot permit one of the spouses to support themselves, the Law organizes a minimal redistribution, taking into account the present assets of a spouse in order to grant a useful right to the other, especially concerning accommodation. Those two forms of distribution represent the expression of a new model: the distributive compensation
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Cao, Hui. "Simulations of dissolution of structured particles." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/9531/.
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This thesis presents a new modelling framework for the simulation of detergent powder dissolution. Focusing on population of particles containing multi ingredients with porous structure, the general model framework links mixing system power and particle dissolution behaviour by combining convective dissolution equations and computational fluid dynamics simulation. Particle dissolves in a variety way due to many factors for example particle shape and size, pore structure, agitation speed, solvent material and temperature. It is difficult to quantitatively conclude these factors on dissolution. As a result, detailed simulations based on Lattice-Boltzmann method are carried out to investigate factors for instance particle shape, surface area to volume ratio and pore structure separately. Later on, both experiment and simulation methods have been studied to explore the effects of agitation and particle wetting process. Results show that surface area to volume ratio plays a more important role in terms of particle related properties. Results also indicate that agitation affects dissolution significantly comparing to the other studied factors. The new dissolution model, expressed as a coupled system of numerical and computational issues, is used to predict particle dissolution behaviour in a well mixed system. Simple case study of single ingredient non porous particle sodium carbonate (provided by Proctor and Gamble) successfully shows the capability of the model by validating modelling results with experimental results. Later on, more complicated case study of multi ingredients porous detergent powder (PANDORA, one of the semi product in Proctor and Gamble) suggests that this model can predict porous particle dissolution while the particles are treated as spheres with envelope density. Based on the good agreements between modelling and experiment data, this model can be applied for predicting bulk particle dissolution behaviour in different mixing systems, or the same mixing system but different bulk particle.
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Pereira, Nunes Joao Paulo. "Pore-scale modelling of carbonate dissolution." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/34683.
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High resolution micro-CT images of porous rocks provide a very useful starting point to the development of pore-scale models of fluid flow and transport. Following a literature review covering recent results on the applicability of tomographic imaging to study reaction phenomena at the pore and core scales, this thesis presents a pore-scale streamline-based reactive transport model to simulate rock dissolution. The focus is on carbonate dissolution in CO2-saturated fluids. After injecting CO2-rich fluids into carbonate reservoirs, chemical reactions between the acidic fluid and the host rock are to be expected. Such reactions may cause significant variations in the flow and transport properties of the reservoir, with possible consequences for field development and monitoring. The interplay between flow and reaction exhibits a very rich behaviour that has not yet been fully understood, especially in the case of carbonate rocks, which possess a complex pore structure. The model is developed within a Lagrangian framework, where the advective displacement employs a novel streamline tracing method which respects the no-flow boundary condition at the pore walls. The method is implemented in the pore-space geometry reconstructed from micro-CT images of sedimentary rocks. Diffusion is incorporated with a random walk and fluid-solid reactions are defined in terms of the diffusive flux of reactants through the grain surfaces. To validate the model, simulation results are compared against a dynamic imaging experiment where a carbonate sample was flooded with CO2-saturated brine at reservoir conditions. The agreement is very good and a decrease of one order of magnitude in the average dissolution rate, compared to the rate measured in an ideal reactor, is explained in terms of transport limitations arising from the flow field heterogeneity. The impact of the flow heterogeneity in the reactive transport is illustrated in a series of simulations performed in rocks with different degrees of complexity. It is shown that more heterogeneous rocks, in the sense of flow heterogeneity, may exhibit a decrease of up to two orders of magnitude in the sample-averaged reaction rates, and that the flow rate is also an important factor when studying carbonate dissolution.
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Hewitt, Paul. "Second phase dissolution in aluminium alloys." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38032.
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Agostini, Sabine. "Etude de la vitesse de dissolution de la trinitrine à partir de microgranules." Paris 5, 1988. http://www.theses.fr/1988PA05P180.
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Olsen, Amanda Albright. "Forsterite Dissolution Kinetics: Applications and Implications for Chemical Weathering." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28213.
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Silicate minerals are the most common mineral group in the earth's crust so it is not surprising that their weathering reactions dominate the chemistry of many earth surface processes. This project used forsterite as a model system to identify the important factors that affect silicate mineral dissolution rates and grain lifetimes in the weathering environment.
I determined an empirical rate law for forsterite dissolution of forsterite in oxalic acid solutions: based on a series of 124 semi-batch reactor experiments over a pH range of 0 to 7 and total oxalate concentrations between 0 and 0.35 m at 25°C. These experiments show that oxalate-promoted dissolution rates depend upon both oxalate concentration and pH. I propose a reaction mechanism in which a hydrogen ion and an oxalate ion are simultaneously present in the activated complex for the reaction that releases H4SiO4 into solution. By analogy, I propose that water acts as a ligand in the absence of oxalate.
I also ran 82 batch reactor experiments in magnesium and sodium sulfate and magnesium and potassium nitrate solutions. These experiments show that ionic strength up to 12 m, log mMg up to 4 m, and log mSO4 up to 3 m have no effect on forsterite dissolution rates. However, decreasing aH2O slows forsterite dissolution rates. The effect of decreasing dissolution rates with decreasing aH2O is consistent with the idea that water acts as a ligand that participates in the dissolution process.Forsterite dissolution rate data from previously published studies were combined with results from my experiments and regressed to produce rate laws at low and high pH. For pH < 5.05 or and for pH > 5.05 or I then developed a diagram that shows the effect rate-determining variables on the lifetime of olivine grains in weathering environments using these rate laws.Ph. D.
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Godinho, José Ricardo Assunção. "A surface approach to understanding the dissolution of fluorite type materials : Implications for mineral dissolution kinetic models." Doctoral thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89257.
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Traditional dissolution models are based in the analyses of bulk solution compositions and ignore the fact that different sites of a surface dissolve at different rates. Consequently, the variation of surface area and surface reactivity during dissolution are not considered for the calculation of the overall dissolution rate, which is expected to remain constant with time. The results presented here show the limitations of this approach suggesting that dissolution rates should be calculated as a function of an overall surface reactivity term that accounts for the reactivity of each of the sites that constitute the surface. In contrast to previous studies, here the focus is put on studying the surface at different dissolution times. Significant changes in surface topography of CaF2 were observed during the initial seconds and up to 3200 hours of dissolution. The observed changes include the increase of surface area and progressive exposure of the most stable planes, with consequent decrease in overall reactivity of the surface. The novelty of a proposed dissolution model for fluorite surfaces, when compared with traditional dissolution models, is that it differentiates the reactivity of each characteristic site on a surface, e.g. plane or step edge, and considers the time dynamics. The time dependency of dissolution rates is a major factor of uncertainty when calculating long term dissolution rates using equations derived from dissolution experiments running for short periods of time and using materials with different surface properties. An additional factor of uncertainty is that the initial dissolution times are the most dynamic periods of dissolution, when significant variations of surface area and reactivity occur. The results are expected to have impact in the field of nuclear waste management and to the larger geological and material science community.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted.
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Bezerra, Karelayne de Assis Coelho. "Um anjo dissoluto." Florianópolis, SC, 2005. http://repositorio.ufsc.br/handle/123456789/102494.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-Gaduação em Literatura.Made available in DSpace on 2013-07-16T01:06:29Z (GMT). No. of bitstreams: 1 221341.pdf: 601487 bytes, checksum: 11888b03134ae435faad44704c8cca91 (MD5)
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Tocino, Florent. "Contrôle microstructural des réactions rédox à l'interface solide/solution lors de la dissolution d'oxydes mixtes à base d'uranium (IV)." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS247/document.
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Dans le cadre de l’utilisation potentielle d’oxydes mixtes d’actinides au sein des réacteurs nucléaires de 3ème et 4ème générations, des solutions solides de formules générales U1-xThxO2, U1-xCexO2-y, U0,75Nd0,25O1,875, U0,75Gd0,25O1,875 et Th0,75Nd0,25O1,875 ont été préparées par conversion thermique de précurseurs oxalate. Préalablement à l’évaluation de la durabilité chimique des matériaux, une étape de frittage a été entreprise afin d’obtenir des pastilles denses présentant diverses propriétés physico-chimiques et microstructurales d’intérêt (composition, homogénéité, taux de densification, …) L’étude multiparamétrique de la dissolution, conduite en milieux nitrique, sulfurique et chlorhydrique a souligné l’impact important de la composition chimique au sein du matériau sur la durabilité chimique des échantillons. En effet, plusieurs paramètres (ordres partiels par rapport à l’activité en protons, énergie d’activation apparente, …) ont confirmé une modification significative du mécanisme de dissolution prépondérant pour les échantillons enrichis en uranium. Par ailleurs, le rôle important joué par certaines espèces azotées à l’interface solide/solution a également été démontré. L’évolution de l’interface solide/solution (surface réactive, composition) en cours de dissolution a également été suivie à travers une étude operando par Microscopie Electronique à Balayage en mode Environnemental. Cette étude a souligné l’existence de zones préférentielles de dissolution (jonctions triples, joints de grains, porosités inter- et intragranulaires) pour les échantillons les moins riches en uranium ; laquelle s’accompagne d’une forte augmentation de la surface réactive. En raison d’un phénomène prépondérant d’oxydation de l’uranium(IV) à l’interface, la dissolution des échantillons enrichis en uranium apparaît nettement plus homogèneIn the field of the use of actinides mixed oxides as potential fuels for the Gen(III) and Gen(IV) nuclear reactors, solid solutions with general formula U1-xThxO2, U1-xCexO2-y, U0.75Nd0.25O1.875, U0.75Gd0.25O1.875 and Th0.75Nd0.25O1.875 were prepared by thermal conversion of oxalate precursors. Dense pellets exhibiting various physico-chemical and microstructural properties (in terms of composition, homogeneity, densification rate, …) were prepared through sintering then submitted to dissolution tests.The multiparametric study of the dissolution, performed in nitric, sulfuric and hydrochloric media clearly underlined the important effect of the chemical composition on the chemical durability of the samples. Indeed, several parameters (including partial order related to proton activity, apparent activation energy) confirmed the significant modification of the preponderant dissolution mechanism for uranium-enriched samples. Moreover, the role of various nitrogen-based species was evidenced at the solid/solution interface.The evolving of solid/solution interfaces (reactive surface area, composition) during dissolution was monitored by the means of operando ESEM experiments. Preferential dissolution zones (triple junctions, grain boundaries, inter- and intra-granular porosities) were clearly observed for uranium-depleted samples. They induce a significant increase of the reactive surface area even for short progress of the reaction. On the contrary, the dissolution appeared more homogenous for uranium-enriched samples due to the existence of a preponderant mechanism associated to the oxidation of the uranium(IV) at the interface
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El, Koubi Charles. "Modélisation des cinétiques de dissolution des formes orales : application informatique." Paris 5, 1989. http://www.theses.fr/1989PA05P055.
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Alkattan, Marwan Mahmood. "Contribution à l'étude de la cinétique de dissolution des minéraux très solubles : cas de la halite et de la calcite en milieu acide." Toulouse 3, 1996. http://www.theses.fr/1996TOU30163.
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Ce travail a pour but de mieux quantifier les possibilites de stockage des dechets chimiques et nucleaires dans des formations geologiques d'evaporites et les processus d'acidification des reservoirs petroliers carbonates. A cette fin, nous avons determine les vitesses de dissolution de la halite a proximite de l'equilibre et de roches carbonatees en milieu acide, en utilisant la methode du disque tournant. Les essais de dissolution de la halite ont ete realises a 25, 50 et 80c, a vitesse de rotation et indices de saturation variables et en presence de metaux et anions en trace. Ils ont permis de determiner les valeurs des constantes de vitesse et de transport et l'energie d'activation de la dissolution (ea = 16 kj/mol). En presence de metaux et anions en trace, la vitesse de dissolution est diminuee et la reaction n'est plus controlee par le transport, mais par la reaction chimique. Ces resultats ont ete interpretes dans le cadre d'un modele combinant la theorie de l'etat transitoire et les isothermes d'adsorption de langmuir. La cinetique de dissolution de calcite et de calcaires a ete etudiee en fonction du ph, du regime hydrodynamique et de la temperature entre 25 et 80c. Dans le domaine de ph -1 a 3, la vitesse de dissolution de la calcite est controlee par la diffusion (ea = 19 kj/mol) et proportionnelle a l'activite du proton. L'effet d'agents retardateurs a ete teste. Il s'est avere que les ions magnesium et orthophosphates n'ont qu'un tres faible effet dans le domaine de ph etudie. Les ions metaphosphates ont un effet inhibiteur important, quasi-proportionnel a leur concentration, dans le domaine 0-10#-#1 m
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Garcia, Eric. "Etude de la dissolution et de la croissance de principes actifs." Aix-Marseille 3, 2000. http://www.theses.fr/2000AIX30051.
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Dans l'industrie pharmaceutique, la dissolution de principes actifs est un phenomene important qui peut determiner la vitesse d'adsorption de ceux-ci dans le corps humain. Dans ce travail nous avons etudie la dissolution de deux principes actifs, l'irbesartan present sous deux formes polymorphiques et l'amiodarone, en fonction de differents parametres. Les phenomenes rencontres sont la dissolution, la nucleation et la croissance. Dans un premier temps, nous avons developpe un montage experimental de suivi in situ et en continu de la dissolution de suspensions de cristaux de principes actifs en utilisant la technique de conductimetrie. Ceci nous a permis de presenter une etude qualitative de la transition de phase de l'irbesartan ou nous mettons en evidence les differentes etapes qui caracterisent cette transition ainsi que l'influence du facies et de la distribution de taille des cristaux utilises. Ensuite nous presentons l'etude de la dissolution d'une forme d'irbesartan et de l'amiodarone. En travaillant sur les vitesses de dissolution initiales nous mettons en evidence deux comportements en dissolution. Pour de fortes sousaturations, la dissolution est controlee par le transfert de matiere tandis que pour les faibles sousaturations la dissolution est controlee par les phenomenes de surface. On a caracterise l'influence de la masse, de l'agitation du milieu et de la temperature sur le comportement en dissolution. Enfin dans la derniere partie nous modelisons les resultats experimentaux de la dissolution du principe actif irbesartan par la methode des bilans de population. En ajoutant a notre modele de dissolution un terme de fragmentation des cristaux on a pu modeliser de facon satisfaisante la dissolution.
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Nilsson, Sara. "Radiation induced dissolution of model compounds for spent nuclear fuel : mechanistic understanding of oxidative dissolution and its inhibition." Doctoral thesis, KTH, Kärnkemi (stängd 20110630), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95433.
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This doctoral thesis is focused on radiation induced oxidative dissolution of UO2, Pd-doped UO2, SIMFUEL (as model substances for spent nuclear fuel) and UN (a possible future fuel) and inhibition of the oxidative dissolution. H2O2 is assumed to be the most important oxidant for spent nuclear fuel dissolution under deep repository conditions. The dissolution of uranium has been studied by oxidation by added H2O2 and by gamma irradiation in the presence and absence of carbonate. In carbonate free solutions very low amounts of uranium are dissolved from UO2 due to formation of metastudtite, UO4·2H2O on the UO2 surface which blocks the surface from further oxidation. Metastudite formation was confirmed with Raman spectroscopy. In the presence of carbonate, the concentration of dissolved uranium increases linearly over time for UO2 and UN, due to the complex formation between carbonate and oxidized uranium. For SIMFUEL a large fraction of H2O2 is consumed by catalytic decomposition under all conditions examined. This results in very low amounts of uranium released. Metastudtite formation was not observed on SIMFUEL. The oxidation during gamma radiolysis shows a larger difference in dissolution rates between UO2 and UN in carbonate solutions compared to upon oxidation by added H2O2. UN was found to have a lower dissolution rate, most probably because 50 % more oxidant is needed to reach the soluble U(VI). It was shown that the redox reactivity of UO2 appears to increase ~1.3 times, after being irradiated at doses > 40 kGy. The effect is permanent and delayed. The presence of sulfide shows an inhibiting effect on radiation induced dissolution due to scavenging of radiolytic oxidants and reduction of U(VI). The catalytic properties of Pd (as a model for the noble metal particles containing Mo, Ru, Tc, Pd and Rh, formed by the fission products) are examined. It was found that Pd has a catalytic effect on the reaction between H2O2 and H2 and the second order rate constant is determined to (2.1±0.1)x10-5 m s-1. The reaction between UO2 and H2O2 is catalyzed by Pd. Pd also has a catalytic effect on the reduction of U(VI) by H2 both in aqueous solution, rate constant (1.5±0.1)x10-5, and in the solid phase, rate constants 4x10-7 m s-1 and 7x10-6 m s-1 for pellets with 1 and 3 % Pd respectively. These values are very close to the diffusion limit for these systems. The catalytic effect was not influenced by the presence of sulfide. The catalytic effect in the solid phase reduction shows that the expected conditions in a deep repository, 40 bar H2 and 1 % noble metal particle content, is sufficient to stop the dissolution.QC 20120530
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Joulié, Marion. "Mécanisme de dissolution de matériaux actifs d'électrodes de type LiNi1/3Mn1/3Co1/3O2 d'accumulateurs Li-ion en vue de leur recyclage." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0011/document.
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La voie hydrométallugique représente une alternative pour la récupération des métaux de valeur tels que le nickel et le cobalt contenus dans les batteries Li-ion usagées. La première étape du procédé hydrométallurgique, l'étape de lixiviation a été optimisée grâce à l'étude du comportement du matériau actif d'électrode positive LiNi1/3Mn1/3Co1/3O2 (NMC) qui s'avère être le candidat idéal pour les batteries de véhicules électriques. Tout d'abord, l'étude des aspects thermodynamiques de la réaction de dissolution a permis de prédire le comportement du NMC dans divers acides. Puis, l'approche cinétique a conduit à l'élucidation du mécanisme se produisant lors de l'étape de lixiviation et à la mise en évidence de l'étape cinétiquement déterminante de la dissolution. Ce mécanisme a par la suite été généralisé aux autres matériaux couramment rencontrés dans les batteries Li-ion. L'impact d'agents réducteurs minéraux, organiques et métalliques pour promouvoir la dissolution du NMC a été évalué. Cette approche compare l'effet de réactifs à faible (acides sulfurique et chlorhydrique) et fort (acides citrique, oxalique et formique et peroxyde d'hydrogène) pouvoir réducteur ainsi que celui du cuivre et de l'aluminium provenant des collecteurs de courants des batteries Li-ion. Cette étude soulève le fort intérêt de l'emploi des collecteurs de courant présents de manière inhérente dans la fraction traitée par hydrométallurgieBasic hydrometallurgical routes represent an alternative to recover valuable metals such as nickel and cobalt from spent Li-ion batteries. The first step of hydrometallurgical process, lixiviation step is optimized by studying the behaviour of LiNi1/3Mn1/3Co1/3O2 (NMC) positive electrode active material, due to its good performances which make it an adequate candidate for the electric vehicles. First of all, the study of thermodynamic aspects allows predicting the behaviour of NMC material in various acidic media. Then, the kinetic approach leads to define the mechanism occurring during the leaching step and to outline the rate-limiting step of the dissolution. The reductive effect of mineral, organic and metallic reducing agents to promote leaching of NMC material is evaluated. The approach comparatively evaluates the reducing power impact of weak (sulfuric and hydrochloric acids), strong reducing agents (citric, oxalic and formic acids and hydrogen peroxide) and copper and aluminum from Li-ion batteries current collectors. This work points out the strong interest to advantageously use current collectors inherently present in the fraction treated by hydrometallurgy
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Golfier, Fabrice. "Dissolution des roches carbonatées par injection d'acide." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2001. http://tel.archives-ouvertes.fr/tel-00634112.
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Les traitements d'acidification sont généralement utilisés pour stimuler l'injection et/ou la productivité des puits dans les formations de carbonates. Cependant, de nombreux traitements ne produisent pas les résultats attendus en terme de gain de productivité à cause de la mauvaise modélisation autour du puits des mécanismes physiques intervenant durant le processus d'injection acide. La nature instable du phénomène de dissolution en milieu poreux entraîne la formation de canaux fortement conductifs appelés wormholes, qui sont difficiles à modéliser quantitativement. Un modèle de dissolution à l'échelle de Darcy est proposé comprenant une équation de Darcy-Brinkman pour la partie écoulement couplée avec un modèle de dissolution en non-équilibre local. Un simulateur numérique 3D a été développé pour résoudre ce système d'équations en utilisant une méthode de pas fractionnaire et des schémas TVD. Les résultats sont présentés sur des configurations 2D et 3D aussi bien pour des systèmes homogènes qu'hétérogènes. Les résultats numériques sont discutés d'un point de vue qualitatif et quantitatif par rapport à la littérature et comparés aux résultats expérimentaux. Les expériences ont été réalisées sur un massif de sel quasi 2D dans lequel on a injecté une solution d'eau salée sous-saturée. Les instabilités de dissolution, le développement des canaux et la propagation des wormholes ont été enregistrés à l'aide d'une caméra vidéo. En se basant sur les résultats 2D, la possibilité d'une description du phénomène à l'échelle de la section, c'est-à-dire en effectuant des moyennes sur des sections du domaine, a été explorée. Plusieurs approches sont utilisées, tels que les modèles à une équation, où le milieu considéré incorpore la physique du wormhole et la matrice poreuse environnante, et les modèles à deux équations pour lesquels les wormholes sont traités séparément. Les implications théoriques sont discutées en se basant sur les résultats numériques.
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Lee, Sung Oh School of Chemical Engineering & Industrial Chemistry UNSW. "Dissolution of iron oxides by oxalic acid." Awarded by:University of New South Wales. School of Chemical Engineering & Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/23924.
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The iron content of industrial minerals can be reduced by physical and chemical processing. Chemical processing is very efficient to achieve a high degree of iron removal at minimum operating cost. Both inorganic acids and organic acids have been used for clay refining. However, due to environmental pollution and contamination of products with the SO42- and Cl-, inorganic acids should be avoided as much as possible. This research investigated the use of oxalic acid to dissolve iron oxides and the dissolution characteristics of natural iron oxides. The dissolution of iron oxides in oxalic acid was found to be very slow at temperatures ranging from 25??? to 60???, but increased rapidly at a temperature above 90oC with increasing oxalic acid concentration, whereas the pH caused the reaction rate to decrease at pH>2.5 and improved the rate from pH 1 to pH 2.5. The iron oxides such as goethite (??-FeOOH), lepidocrocite (??-FeOOH) and iron hydroxide (Fe(OH)3) can be dissolved faster at the presence of magnetite which exhibits an induction period at the initial stage and showed the bell-shaped curves for the dissolution. In titration tests, however, the increase of temperature causes an increase in solubility of the oxalate complexes, resulting in an increased stability of ionized species in solution. During the addition of NaOH, NaHC2O4???H2O was precipitated without forming Na2C2O4???H2O, but it was re-dissolved at pH>4.0. On the other hand with NH4OH, NH4HC2O4???H2O and (NH4) 2C2O4???H2O co-precipitated at pH 0.93, but also re-dissolved at over pH 2.03. The reaction temperature was found not to affect the removal of iron from the ferric oxalate complex solution using lime. Iron is removed as iron hydroxide and calcium oxalate is then precipitated during the iron removal step. The formation of Fe(OH)3 in the solution was affected by the dissociation of Ca(OH)2. The thermodynamics of sodium, ammonium and iron oxalate complexes were investigated and the standard free energy, ??Go was calculated using thermodynamic data and solubility products. The dissolution of pure hematite by oxalate was found to follow a shrinking core model of which the kinetic step of the reaction is the controlled mechanism.