Dissertations / Theses on the topic 'Processus de dissolution'
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Azzolini-Manouk, Maryvonne. "Le processus de dissolution des firmes post-industrielles." Aix-Marseille 3, 2001. http://www.theses.fr/2001AIX32014.
Full textThe decline of the "Henry Ford" system of manufacture has led us to make a strategic redefinition of the big business organization, with a view to incorporating in it new parameters which form part of a global process of dematerialisation. The major changes affecting firms - changes that are accentuated by the phenomenom of globalisation - appear to highlight the insufficiency of those key values which come out of materialist doctrines of the previous period : rationalism, cartesianism, mecanism, positivism, etc. , thanks to which the capitalist, institutional business entity was able to form itself in a coherent, orderly, secure and long-lasting, all of which satisfied the prevailing mentality at the time. Various different clear signs enable us to ask questions about the uncertain future of the post-industrial firms. The crisis about sense and legitimacy affecting them is worrying to a point that is has led to reactions amongst researchers, and suggests that this crisis will tend to become a primary and unavoidable fact for anyone studying this matter in depth. .
Desboeufs, Karine. "Processus de dissolution des aérosols atmosphériques au sein des gouttes d'eau nuageuses." Phd thesis, Université Paris-Diderot - Paris VII, 2001. http://tel.archives-ouvertes.fr/tel-00005175.
Full textDesboeufs, Karine. "Processus de dissolution des aerosols atmospheriques au sein des gouttes d'eau nuageuses." Paris 7, 2001. http://www.theses.fr/2001PA077020.
Full textWagener, Thibaut. "Le fer à l'interface océan-atmosphère : Flux et processus de dissolution dans l'eau de mer." Phd thesis, Université de la Méditerranée - Aix-Marseille II, 2008. http://tel.archives-ouvertes.fr/tel-00270558.
Full textDuportal, Malo. "Impact de la concentration en hydrogène sur les processus de dissolution et de passivation d’un acier inoxydable austénitique." Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS024.
Full textDifferent processes can lead to hydrogen absorption on the surface of the materials and can decrease their inherent materials properties, especially their surface characteristics. Interactions between these modifications and corrosion processes have to be more thoroughly studied. In this context, this work aims to investigate the role of hydrogen absorption on the dissolution and passivation mechanisms of the AISI 316L. First, the total absorbed hydrogen concentration has been quantified after an electrochemical charging process. Then, we evaluated the different hydrogen states in the material and its distribution from surface to the bulk. Results suggest a strong concentration gradient and allows to estimate both an apparent coefficient of diffusion and a local hydrogen concentration. In addition, we observed that the local hydrogen increased hardness enhanced the dislocations density and induced an occasionally phase transformation to martensite (γ→ε). In the second time, the influence of hydrogen on anodic processes on the AISI 316L have been investigated. For that purpose, electrochemical tests have been conducted and show an increase of anodic kinetics after hydrogen absorption. Hydrogen induced an increase of the passive current density while the pitting resistance is widely degraded. XPS analyses attest of a similar passive layer (thickness and composition) before and after H-charging even though EIS results show a decrease of the resistance. Inductively Coupled Plasma showed that hydrogen promotes dissolution processes. The modifications induced by hydrogen are partially reversible with hydrogen desorption. Our results illustrate that mobile hydrogen is mainly responsible for the decrease of the properties and that trapped hydrogen and / or metallurgical modifications induced by electrochemical charging have few effects on the corrosion process even they highlight the partial non-reversibility of the observed effects
Saad, Alice. "Influence du changement climatique et des conditions extrêmes sur les massifs fracturés : rôle des fluides (H2O, CO2) dans leur processus d’altération." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1117/document.
Full textThe objective of this work is to understand the weathering process of oolitic limestone and estimate their weathering kinetics under French climatic conditions. Accelerated ageing cycles, based on parameters deduced from a literature review and on temperature and precipitation data, have been defined. Then samples of two oolitic limestones have undergone these ageing. The measurements used to determine damage were chosen based on their metrological characteristics and their relevance. The results were compared with the same measurements performed on naturally weathered limestone. Thus, the relationships between the weathering process of oolitic limestone and their mechanical, physical and microstructural characteristics have been established. This analysis also led to weathering kinetics. The results were validated by the study of another oolitic limestone under different climatic conditions. Finally, the influence of a potential climate change on the weathering kinetics was determined using a statistical tool
Devigne, Vincent. "Ecoulements et conditions aux limites particulières appliquées en hydrogéologie et théorie mathématique des processus de dissolution/précipitation en milieux poreux." Phd thesis, Université Claude Bernard - Lyon I, 2006. http://tel.archives-ouvertes.fr/tel-00132036.
Full textproblèmes de nature phénoménologique nombreux conduisent bien souvent à
l'étude des Équations aux Dérivées Partielles (EDP's) au travers des non
moins nombreux modèles qui en découlent.
Si chaque phénomène physique, mécanique, chimique ou autres pris
indépendamment et à une échelle suffisamment fine est aujourd'hui bien
compris et relativement aisé à modéliser il n'en est pas de même pour les
problèmes multiphysiques, physico-chimique, les écoulements au voisinage de
domaines de structures différentes ou même dans l'appréhension de ces
phénomènes à des échelles plus grandes méso et macroscopique.
La compréhension des conditions aux limites et leur modélisation reste une
étape clef dans l'étude de ces phénomènes naturels.
Nous verrons au travers du (dé)couplage de problèmes multi-domaines par les
lois de paroi (Navier, Beavers et Joseph), des processus chimiques (Modèle de
Duijn-Knabner) ou la dispersion de Taylor comment il est possible de résoudre
numériquement et en partie ces difficultés par des techniques d'analyse
mathématique récentes (homogénéisation, raisonnement multi-échelles et
développements asymptotiques).
Des résultats de simulations réalisées au moyen d'un logiciel de résolution
d'EDP's baptisé SciFEM (Scilab Finite Element Method) conçu pour les besoins
de la thèse illustreront notre démarche.
Devigne, Vincent. "Écoulements et conditions aux limites particulières appliquées en hydrogéologie et théorie mathématique des processus de dissolution / précipitation en milieux poreux." Lyon 1, 2006. http://tel.archives-ouvertes.fr/docs/00/13/20/36/PDF/UCBL_manuscrit.pdf.
Full textRembert, Flore. "Development of geo-electrical methods to characterize dissolution and precipitation processes in a carbonate context." Electronic Thesis or Diss., Sorbonne université, 2021. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2021SORUS114.pdf.
Full textPrecipitation and dissolution of calcite are key processes in carbonate rocks and being able to monitor them in situ is a major issue. Hydrogeophysical methods are based on the development of appropriate geophysical techniques for monitoring hydrological and biogeochemical processes in a non-intrusive and low-cost manner. Among the existing techniques, electrical methods have already proven their ability to monitor such processes. For this reason, the methods of self-potential (SP) and spectral induced polarization (SIP) were chosen to investigate the processes of dissolution and precipitation of calcite. SP is a passive technique consisting in measuring the natural electric field generated by water flows and concentration gradients, while SIP is an active method measuring the complex electrical conductivity at low frequencies (mHz-kHz). Its real and imaginary components can be related respectively to the microstructure and surface state of the minerals constituting it. This thesis presents experimental and theoretical developments in order to improve the interpretation of SP and SIP methods. A new electrical conductivity model is developed and shows a good fit with the numerical results of dissolution and precipitation. Remarkable SP data have been obtained and could be quantitatively linked through reactive transport modeling. The SIP results provide further insights into the mechanisms responsible for the polarization variations caused by the reactivity of calcite
Pauwels, Hélène. "Etude theorique et experimentale du comportement des elements traces lors des processus d'interaction eau-roche." Paris 7, 1988. http://www.theses.fr/1988PA077136.
Full textDevigne, Vincent Graillot Didier Mikelic Andro Batton-Hubert Mireille. "Écoulements et conditions aux limites particulières appliquées en hydrogéologie et théorie mathématique des processus de dissolution / précipitation en milieux poreux = Flows and Particular Boundary Conditions applied in Hydrogeology and Mathematical Theory of Dissolution/Precipitation process in porous media." Lyon : [s.n], 2006. http://tel.archives-ouvertes.fr/docs/00/13/20/36/PDF/UCBL_manuscrit.pdf.
Full textDavranche, Mélanie. "Impacts des processus aux interfaces solide/liquide sur la mobilité des éléments : Observations de terrain-Expérimentation-modélisation." Habilitation à diriger des recherches, Université Rennes 1, 2008. http://tel.archives-ouvertes.fr/tel-00289457.
Full textLaveuf, Cédric. "Les terres rares et le zinc comme traceurs des processus pédogénétiques : application à une séquence de sols issue de calcaires minéralisés." Phd thesis, Université d'Orléans, 2009. http://tel.archives-ouvertes.fr/tel-00452682.
Full textDaviray, Maxime. "Fonctionnement biogéochimique des écosystèmes transitionnels colonisés par les bactéries filamentaires électriques : réponse des biocénoses et thanatocénoses de foraminifères benthiques." Electronic Thesis or Diss., Angers, 2024. http://www.theses.fr/2024ANGE0031.
Full textThis thesis aims to assess the effect of acidification caused by cable bacteria activity on the sediment geochemistry in intertidal environments, and the consequences of this dissolution process on benthic foraminiferal communities and the preservation of their shell in sediments. This study combines intertidal mudflats monitoring in various estuaries on the Atlantic coast and in the English Channel (France) using high-resolution approaches and incubation under controlled conditions in the laboratory.. The cable bacteria activity varies according to the season, with maximum activity during the summer-autumn period, and strongly structures the vertical oxic-suboxic-anoxic redox zone succession. Bioturbation associated with macrofauna or the eelgrass roots introduces late--ral heterogeneity into this system and generate microhabitats. The structuring effect of pH on the successive distribution of foraminiferal species within sediment has been demonstrated. The response of foraminifera to the acidification of their environment seems to depend on the species and involves both their metabolic and behavioural characteristics. The activity of the cable bacteria results in a significant loss of calcareous shells in the sedimentary record. Their residence time is estimated about a dozen days. The accumulation of agglutinated shells and organic linings despite of calcareous shells could be used to provide a historical review of dissolution processes in marine sediments
Chen, Tao. "Evolution de la perméabilité d'agrégats de sels sous contrainte liée à des circulations de fluides : dissolution, colmatage, déformation." Phd thesis, Université Joseph Fourier (Grenoble), 1994. http://tel.archives-ouvertes.fr/tel-00743930.
Full textSaad, Alice. "Influence du changement climatique et des conditions extrêmes sur les massifs fracturés : rôle des fluides (H2O, CO2) dans leur processus d'altération." Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00657462.
Full textFrisby, 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.
Full textTitle from document title page. Document formatted into pages; contains viii, 159 p. Includes abstract. Includes bibliographical references (p. 108-125).
Moune, Severine. "Volatils mineurs (S, Cl, F) et éléments traces dans les magmas pré-éruptifs et les gaz volcaniques. Etude des processus de dégazage magmatique sur les volcans Hekla (Islande) et Masaya (Nicaragua)." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2005. http://tel.archives-ouvertes.fr/tel-00011542.
Full textUne étude sur les inclusions magmatiques (MIs) a permis de suivre l'évolution des volatils dissous dans le système volcanique d'Hekla au cours de la différenciation magmatique (cristallisation fractionnée). Ceci a permis d'estimer les concentrations en volatils dissous "attendues" dans le liquide pré-éruptif. Cette approche permet donc de ne pas sous-estimer les concentrations des liquides piégés dans les MIs et améliore ainsi les contraintes sur la masse de volatils émise dans l'atmosphère. Cette étude indique que, lors de l'éruption de février 2000, Hekla a émis dans l'atmosphère 0.1 Mt de HCl, 0.2 Mt de HF et 3.8 Mt de SO2. La chimie de la phase sub-Plinienne de cette éruption a été étudiée, de façon plus approfondie, grâce aux averses neigeuses qui ont traversé le panache volcanique. L'étude de ces neiges a montré que l'enrichissement des éléments volatils est lié à un processus de dégazage sous forme de chlorures, fluorures et sulfates. En revanche, l'enrichissement des éléments réfractaires est expliqué par un processus de dissolution non-stoechiométrique des téphras par la phase gazeuse riche en fluor au sein du panache éruptif.
Une étude basée sur les MIs a permis de confirmer la théorie de Walker et al. (1993) selon laquelle la différenciation des magmas tholéiitiques du Masaya se produit à basse pression à partir d'un magma relativement "sec" de composition homogène dans le temps. La caractérisation physico-chimique des aérosols par MEB et la chimie de la phase éruptive du volcan Masaya suggèrent que la plupart des éléments traces sont dégazés sous forme de chlorures, mais aussi sous forme de sulfates et chloro-sulfates. De plus, la quantification des flux de matière a montré que le dégazage au Masaya est une source importante de pollution atmosphérique.
Najjar, Denis. "Compétition entre les mécanismes de dissolution anodique et de fragilisation par l'hydrogène dans le processus de fissuration par corrosion sous contrainte de l'alliage Al-Zn-Mg-Cu 7150 sollicité en traction lente en milieu chlorure (NaCl 3)." Lille 1, 1994. http://www.theses.fr/1994LIL10098.
Full textPritchard, Keith L. "Fundamental processes governing calcite dissolution at high pH." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238178.
Full textAdobes, Vidal Maria. "Quantitative and holistic views of crystal dissolution processes." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/95498/.
Full textParker, Alexander S. "Quantitative crystal investigations : surface dissolution and nucleation processes." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/88282/.
Full textMitchell, Mark J. "Mathematical modelling of carbon dioxide dissolution and reaction processes." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/14502/.
Full textPerry, Amelia Ruth. "Quantitative microscopic methods for crystal growth and dissolution processes." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/73865/.
Full textNoiriel, Catherine. "Contribution à la détermination expérimentale et à la modélisation des différents processus contrôlant l'évolution géochimique, structurale et hydrodynamique des roches fissurées carbonatées." Phd thesis, École Nationale Supérieure des Mines de Paris, 2005. http://tel.archives-ouvertes.fr/tel-00012048.
Full textRheinheimer, Vanessa. "A nanoscale study of dissolution and growth processes in cement hydrates." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/285965.
Full textAquesta tesi té per objectiu proporcionar nous coneixements sobre els mecanismes, abans poc coneguts, que operen durant la hidratació de les fases de ciment i la dissolució dels seus hidrats a escala molecular. Per tal d'aconseguir aquest objectiu, un nou enfocament ha estat seguit amb l'elaboració d'un nou procediment per sintetitzar pel·lícules primes de silicats de calci, la seva caracterització en temps real del creixement del gra i de la dissolució amb les cel·les de líquid al microscopi de forces atòmiques i el seguiment de l'evolució de la seva composició química per espectroscòpia de fotoelectrons de raigs X de pel·lícules primes hidratades in-situ, evitant la seva contaminació atmosfèrica. S'han preparat pel·lícules nanomètriques de les fases del clínquer utilitzant l'evaporació per feix d'electrons. Després de la deposició en substrats de silici, es van caracteritzar el gruix mitjançant la microscòpia de forces atòmiques (AFM) i la perfilometria mecànica i la composició mineralògica amb la difracció de raigs X d'angle rasant (GAXRD). La composició química es va determinar per espectroscòpia fotoelectrònica de raigs X (XPS). Els resultats del GAXRD i d'XPS mostren que els aluminats no són adequats per a ser evaporats utilitzant l'evaporació assistida amb feix d'electrons. No obstant això, anàlisis quantitatives de les mostres de silicats de calci mostren que la relació Ca:Si de la pel·lícula dipositada és la mateixa que en el material de partida, el que confirma la idoneïtat de la tècnica per a la síntesi d'aquests materials. Les pel·lícules primes de silicat càlcic de gruixos diferents van ser sotmeses a hidratació de diferents maneres. Els resultats d`XPS descriuen canvis químics clars quan les mostres estan exposades al vapor d'aigua com s'infereix dels canvis en el pic del silici, l'eixamplament del pic del calci i la disminució en la relació Ca:Si, que es relaciona amb la polimerització del silici degut ala formació de C-S-H. La hidratació in situ en aigua o solució saturada d'hidròxid de calci a la cel·la de fluid de l'AFM permet observar la formació de partícules de C-S-H. La hidratació ocorre molt ràpidament en el C3S, que després es dissol, i és més lenta en el C2S. Finalment, la microscòpia de transmissió i escaneig de raigs X (STXM) de les mostres hidratades in situ amb aigua permet observar la formació de partícules amb diferents concentracions de calci i silici i, en alguns casos, la variació de l'estat químic . El desenvolupament d'aquesta tècnica de síntesi i els resultats obtinguts en la hidratació permeten millorar el coneixement de la hidratació de les fases del clínquer en estadis inicials a nivell molecular i entendre millor el comportament d'aquests materials, ajudant a aclarir el complex problema dels mecanismes d'hidratació dels materials del ciment
Hammons, Joshua Aaron. "A study of precipitated films formed during electrochemically driven dissolution processes." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3165/.
Full textYau, Sze Tai. "Electrochemical recovery of copper from waste catalyst residues." Thesis, University of Huddersfield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327142.
Full textRomero, Joseph Vincent 1977. "Experimental analysis and modeling of transient dissolution of RDX through mass transfer processes." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29957.
Full textIncludes bibliographical references (leaves 79-80).
A simulation study was performed to model the transient behavior of the dissolution of hexahydro-1, 3,5-trinitro-1, 3,5-triazine (RDX) in Composition B. Composition B, also referred to as CompB. CompB is made up of three parts: 54% RDX, 6% HMX and 40% TNT. A numerical simulation was employed to model the overall solute transport equation. The solute transport equation takes into account advection, dispersion, sorption, degradation, mobile-immobile sorption, and a mass transfer source term. Numerical code was developed and this model simulated the following: (1) flow rate, (2) initial mass loading, (3) particle size and (4) field oil. The simulation model results verified laboratory experiments provided by Phelan et. al. [2003] by applying the governing advection-dispersion equation with a linear-driving-force source term of the form kf (C, - C) . The variable k represents the lumped mass transfer coefficient [1/day], which implicitly incorporates specific surface area. The concentration denoted as C [mg/L], represents the effluent chemical concentration present in water at a given time while C, [mg/L] represents the concentration at equilibrium. The mass transfer source term was evaluated by correlating k to the modified Sherwood number. The modified Sherwood number was fitted with a least-squares method that approximated non-aqueous phase liquid (NAPL) dissolution [Miller et. al., 1990]. This study adjusted the constants developed with the obtained modified Sherwood number to model RDX. Modeling development used a modified Sherwood number in the form: ... The simulation code effectively modeled RDX effluent profiles.
by Joseph Vincent Romero.
S.M.
Grant, Gavin P. "The evolution of complex DNAPL releases : rates of migration and dissolution." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/2155.
Full textZaim, Christiane Yuriko Hamai. "Avaliação do perfil de dissolução de comprimidos de glibenclamida 5 mg obtidos por diferentes processos." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/9/9139/tde-10042015-143023/.
Full textSlightly soluble drugs are one of the largest challenges found in tablet formulation, once, if not appropriately formulated, they can present dissolution and bioavailability problems. The present work had as objective to produce 5 mg glibenclamide (practically insoluble hipoglicemic drug) tablets using different processes which aim at enhancing drug dissolution and to compare the in vitro release (dissolution profile) of these formulations with each other as well as with the reference medicine in Brazil, Daonil®. 19 diferent formulations were obtained through direct compression using solid dispersion, cyclodextrin complexion or micronization of the drug. The tablets were also analyzed in relation to aspect, medium weight, hardness, friability, assay and dissolution eficiency. The results indicated that, among the studied processes, an enhancement of the dissolution rate of the drug have arisen from the use of the glibenclamide-β-cyclodextrin complex and the micronized glibenclamide. The disintegrant Explocel® promoted enhancement in the dissolution rate in all the formulations in which it was present. The use of the glibenclamide-β-cyclodextrin complex with Explocel® have presented the best dissolution profile, statistically similar to Daonil®, besides accomplishing the other physico-chemical requirements.
Brown, Eric Vincent. "Incinerator ash dissolution model for the system : plutonium, nitric acid and hydrofluoric acid." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/12166.
Full textStoor, T. (Tuomas). "Air in pulp and papermaking processes." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514280784.
Full textLorenzen, Leon. "A fundamental study of the dissolution of gold from refractory ores." Thesis, Stellenbosch : Stellenbosch University, 1992. http://hdl.handle.net/10019.1/69492.
Full textENGLISH ABSTRACT: The dissolution of gold from refractory ores is a complex kinetic problem involving a number of chemical, mass transport and mineralogical factors. In most Witwatersrand ores in South Africa more than 97 % of the gold is dissolved in cyanide medium after a residence time of about 16 hours in pachuca tanks. This high percentage may be the reason why so little fundamental research has been done into the mechanism and kinetics of the leaching process. With the increasingly lower grades of ore mined, the introduction of backfill mining, and the reduction of profit margins, it has become imperative to increase the efficiency of gold dissolution. The effects of the chemistry and particle size on the dissolution of gold in each sample of ore were studied in detail. The emphasis in this study is on the effect of the leaching behaviour of various ore constituents on the rate of gold dissolution. Interferences with the leaching of gold in contact with other minerals or metals could be attributed to the galvanic interaction (electrical conductivity) between the gold and the mineral and to the formation of a surface film on the gold surface. Sulphide minerals and their oxidation products cause the largest decrease in gold dissolution rate. Galena enhances the rate of gold dissolution owing to dissolved Pb(II)-ions. Gold in contact with conductive minerals passivates as a result of the enhanced magnitude of the cathodic cu1Tent. In all experiments the rotating disc of gold passivated so that the rate of dissolution was much slower than that predicted by a mass-transport limiting model. The various films that form on the surface of the gold and associated minerals, as well as the galvanic interaction, depend largely on the pretreatment of the ore. Pre-elimination of host minerals from the gold bearing ore increases the dissolution rate of gold, and explains the kinetics of reaction on the gold surface to a large extent. The selective destruction of the various minerals with oxidative acid leaches destroys and/or decomposes certain minerals which may form films on the gold surface by precipitation. The chemical composition of these films and precipitates depends on the mineralogy of the sample. These films may be oxides, sulphides, carbonates and cyanide complexes. The complexes can be destroyed, depending on the nature of the film, by interstage dilute acid and/or cyanide washes in an agitated vessel. The destruction of the films exposes the gold surface for cyanidation. A simple distribution function similar to the King liberation model is proposed and tested to describe the dissolution step in the multi-step leaching mechanism. For the King model, good agreement is shown with experimental results. For the liberation results obtained by leaching in this study, the trend is co1Tect, but calibration is required for a close fit. A potentially important use for the liberation model by leaching is to predict the leachable or free gold in an ore from the free gold in the complete sample. This approach for studying the leaching behaviour of different gold bearing minerals has provided reasons why some ores leach better than others.
AFRIKAANSE OPSOMMING: Die loging van goud vanuit weerbarstige ertse is 'n komplekse kinetiese probleem wat verskeie faktore soos massa-oordrag, chemiese aspekte en mineralogiese ingeweefdheid insluit. Goud ekstraksies so hoog as 97 % in sianied oplossings in Pachuca reaktore na ongeveer 16 uur logingstyd word behaal in die meeste Witwatersrand ertse in Suid-Afrika. Hierdie hoë ekstraksies mag dalk die rede wees vir die min fundamentele navorsing oor die ekstraksie van goud vanuit minerale in 'n spesifieke erts. Die dalende erts grade, die verlaging van winsgrense en die terugplaas van geloogde erts in die myn noodsaak verbeterde goud ekstraksie. Verkeie faktore nl., chemie, diffusie, partikelgrootte en oplosbaarheid van goud in elke monster erts is in hierdie studie ondersoek. Die sentrale tema was om die logingsgedrag van goud vanuit verskeie minerale in 'n erts te bepaal. Galvaniese interaksie (hou verband met elektriese geleidingsvermoeë) en film vorming is die belangrikste faktore wat die loging van goud in kontak met minerale nadelig beïnvloed. Sulfied minerale en hul oksidasie produkte speel die grootste rol in die verlaging van die tempo van goudloging. Galena verhoog die tempo van goudloging as gevolg van die Pb (II)- ione in oplossing. Goud in kontak met geleidende minerale passiveer as gevolg van die verhoogde katodiese stroomdigtheid. In alle eksperimente met die roterende skyf (goudskyf) apparaat, passiveer die goudskyf in so 'n mate dat die logingstempo baie stadiger is as wat voorspel word met die massa-oordrags model. Die onderskeie films wat vorm op die goud- en geassosieerde minerale se oppervlaktes, asook die galvaniese interaksies, is 'n funksie van die voorafbehandeling van die erts. Die selektiewe eliminering van minerale vanuit 'n gouddraende erts verhoog die tempo van goudloging drasties en dit beskryf die kinetika van goudloging op die goudoppervlak in 'n groot mate. Die selektiewe eliminering van minerale deur gebruik te maak van oksiderende suurlogings, vernietig sekere van die minerale wat films op die goudoppervlakte kan veroorsaak deur middel van presipitasie. Die chemiese samestelling van hierdie films hang af van die mineralogie van die monster. Dit bestaan meestal uit oksiedes, sulfiedes, karbonate en sianiedkomplekse en hulle kan vernietig word deur middel van inter-stadia verdunde suur-en/of sianied wasse. 'n Eenvoudige distribusiefunksie, soortgelyk aan die King bevrydingsmodel word voorgestel en eksperimenteel getoets om die logingstap in die multi-stadia logingsmeganisme te beskryf. Vir bevryding deur loging, is die neiging van King se model korrek, maar kalibrasie word benodig vir goeie passing. 'n Potensiele gebruik van die aangepaste model is om vrye of loogbare goud in 'n spesi fieke partikel grootte fraksie van 'n erts te voorspel as die vry goud in die totale fraksie bekend is. Die resultate uit hierdie studie kan gebruik word om die logingsgedrag van gouddraende minerale te voorspel en te beskryf, en dus veduidelik hoekom goud uit sekere ertse beter loog as uit ander.
Espriu, Alexandra. "Study of near field processes involved in the oxidative dissolution of the spent nuclear fuel and radionuclides release." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461973.
Full textActualmente en España, las centrales nucleares están acumulando el combustible nuclear gastado (CNG) y apenas disponen de espacio suficiente para seguir almacenando el residuo generado por la actividad de la central. En consecuencia, es necesario adoptar una solución definitiva a la gestión de los residuos nucleares. La opción aceptada internacionalmente para almacenar definitivamente el CNG como la más segura y viable es el Almacenamiento Geológico Profundo (AGP) basado en el confinamiento y la protección del residuo mediante un sistema de multibarrera. Dicho sistema considera el CNG como primera barrera donde están contenidos los radionúclidos (RN) debido a las propiedades físicas y químicas del propio combustible. Con el objetivo de evaluar la seguridad del AGP y determinar el comportamiento del CNG en condiciones relevantes para su almacenamiento definitivo, en el presente trabajo se han planteado cuatro posibles escenarios que podrían provocar la alteración del combustible. Dichos escenarios se han estudiado mediante análogos no irradiados del CNG. En el proceso de alteración de las barreras que componen el AGP, la corrosión anaeróbica de la capsula metálica produce una elevada presión de hidrógeno que podría entrar en contacto con el CNG. A su vez, la entrada de agua en el repositorio y la temperatura a la que se encuentra el CNG podrían hacer aumentar la humedad en las proximidades del residuo. Por lo tanto, en este trabajo se ha estudiado el efecto del vapor de agua en contacto con el UO2 en atmósfera de H2. Los resultados obtenidos muestran que se produce la oxidación del uranio tanto en condiciones anaeróbicas como en condiciones reductoras en función de la temperatura usada. Por otro lado, en presencia de nanopartículas de paladio, análogas a las partículas épsilon del CNG, no se observó oxidación alguna del UO2 en presencia de H2. En el momento en que el agua entre en contacto con el CNG, los RN segregados de la matriz más volátiles y solubles serán lixiviados de forma prácticamente instantánea (IRF) provocando un aumento significativo de radiación en las aguas subterráneas. Con el objetivo de predecir la liberación de dichos RN se ha diseñado un modelo y un algoritmo matemático que ha permitido predecir la liberación de los RN disueltos en la matriz e identificar y cuantificar los RN que forman parte de la IRF de un combustible real. Los resultados obtenidos de la aplicación del modelo concuerdan con resultados experimentales publicados anteriormente. Por lo tanto, se puede concluir que el modelo y el algoritmo cumplen con los objetivos marcados de identificación, predicción y cuantificación de la distribución de los RN en el CNG. Debido a que los mecanismos de alteración del UO2 podrían variar dependiendo de la composición del agua subterránea, se ha estudiado la corrosión del CNG en contacto con aguas de cemento. Para ello se ha usado un electrodo de SIMFUEL con el que se han realizado ciclovoltamogramas, experimentos potenciostáticos y mediciones del potencial de corrosión en condiciones hiperalcalinas y en presencia de calcio y silicato como símil de aguas de cemento. Los resultados muestran una disminución de la corrosión en presencia de calcio y silicato que podría ser provocada por la precipitación de fases sólidas en la superficie del SIMFUEL o por la estabilización de las fases reducidas. Por último, la precipitación de fases sólidas podría ayudar a reducir la concentración de los RN liberados por el CNG. En este contexto, se han estudiado y determinado las capacidades de retención de dos fases sólidas de uranio; la soddiita y la uranofana, en contacto con Cs y Sr en disolución. Se ha determinado que ambos sólidos son capaces de adsorber ambos iones en su superficie, siendo la soddiita el sólido con mayor capacidad de retener Cs y la uranofana la fase sólida con mayor capacidad de retención de Sr. Por tanto, la formación de estas fases podría disminuir la concentración de estos RN liberados a la geosfera.
Nitschke, Fabian [Verfasser], and T. [Akademischer Betreuer] Kohl. "Numerical and Experimental Characterization of Dissolution and Precipitation Processes in Deep Geothermal Reservoirs / Fabian Nitschke ; Betreuer: T. Kohl." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1151938637/34.
Full textTähtinen, J. (Jaana). "The dissolution process of a business relationship:a case study from tailored software business." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514265300.
Full textWilson, Tony Keith. "The dissolution of Ag(111) electrodes investigated by in situ scanning tunnelling microscopy." Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364612.
Full textPotysz, Anna. "Copper metallurgical slags : mineralogy, bio/weathering processes and metal bioleaching." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1201/document.
Full textProblem statement: Copper pyrometallurgical slags are inevitable waste by-products of Cu smelting operations. These waste are considered to be important due to their production volume and high residual metal content that are inefficiently recovered during industrial process. Due to the lack of sustainable practices in the past, tremendous volumes of Cu-slags have been disposed in many industrial districts, regardless of the weathering and associated environmental risk. Consequently, there are many areas where slags have been proven to be a source of metallic pollution for the surrounding environment. At the present time, the outstanding contradiction between the sustainable development and environmental pollution encourages to undertake the action regarding this aspect. For this reason, slags are currently being used as supplementary materials for civil engineering purposes (e.g. cement and concrete additives, road bed filling materials, hydraulic construction materials) rather than disposed. Additionally, modern-day management strategies require slags to be thoroughly evaluated with respect to their environmental stability prior undertaking any reuse action. Main objectives were to evaluate environmental stability of Cu-metallurgical slags resulting from different periods of industrial activities and different smelting technologies. Those included: historical crystalline slag (HS) as well as modern: shaft furnace slag (SFS), granulated slag (GS) and lead slag (LS). Different approaches undertaken in this PhD work considered: i) chemical and mineral phase compositions of slags, ii) leaching susceptibility of slags under exposure to different pH-stat conditions, iii) slags weathering under exposure to organic acids commonly found in soil environment, iv) bacterially (Pseudomonas aeruginosa) mediated weathering of slags and v) future application of studied slags for metal recovery by implementing the bioleaching method. Crucial results: The results of the pH-dependent leaching tests showed a higher metal release in strong acidic conditions (pH 2 and 4), whereas leachability at alkaline conditions (pH 10.5) revealed a lower importance for all the slags analyzed. The study considering soil weathering scenario demonstrated that Cu-slags are susceptible to dissolution in the presence of artificial root exudates (ARE), humic (HA) and fulvic acids (FA), whereby ARE were found to have stronger contribution than HA and FA. According to data collected, the different behavior of individual slags is strictly related to their characteristics (chemical and phase composition) reflecting various susceptibilities to dissolution under the investigated conditions. The study considering bio-weathering scenario revealed that Pseudomonas aeruginosa considerably enhances the release of major (Si and Fe) and metallic (Cu, Zn, Pb) elements compared to the effects of abiotic factors, regardless of the slags chemistry and structure. Furthermore, a high gain (up to 90%) of metals (Cu, Zn, Fe) could be credited to bioleaching with Acidithiobacillus thiooxidans under laboratory conditions. General conclusions: The environmental stability of slags depends on both, their bulk chemistry and mineralogy. However, mineral phases harbouring the metals are the key players in metal leachability intensity. For, this reason consideration of individual slags behaviour is important for preventing environmental contamination and should be regarded as priority branch of sustainable slag management. Optimization of operating parameters for bioleaching following development of industrial scale technology is an incentive scheme for future management of Cu-metallurgical slags
Hupfer, Sarah [Verfasser], Andreas [Akademischer Betreuer] Weller, and S. [Akademischer Betreuer] Kruschwitz. "Spectral induced polarisation for an enhanced pore-space characterisation and analysis of dissolution processes of carbonate rocks / Sarah Hupfer ; Andreas Weller, S. Kruschwitz." Clausthal-Zellerfeld : TU Clausthal, 2020. http://d-nb.info/1231362642/34.
Full textDamian, Alexis. "In situ STM study of the growth and dissolution processes on bimetallic Pd/Au(111) substrates and of ultrathin alloy layers on Au(111)." Phd thesis, Ecole Polytechnique X, 2009. http://pastel.archives-ouvertes.fr/pastel-00005915.
Full textVillinski, John Eugene. "Reductive dissolution of manganese (IV) oxides and precipitation of iron (III) : implications for redox processes in an alluvial aquifer affected by acid mine drainage." Diss., The University of Arizona, 2001. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2001_96_sip1_w.pdf&type=application/pdf.
Full textCRISAFULLI, RUDY. "Preparação de eletrocatalisadores PtSnCu/C e PtSn/C e ativação por processos de Dealloying para aplicação na oxidação eletroquímica do Etanol." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10183.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
Calapa, Kayla. "Hydrologic alteration and enhanced microbial reductive dissolution of Fe(III) (hydr)oxides under flow conditions in Fe(III)-rich rocks: contribution to cave-forming processes." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619628782604003.
Full textMokni, Nadia. "Deformation and flow driven by osmotic processes in porous materials." Doctoral thesis, Universitat Politècnica de Catalunya, 2011. http://hdl.handle.net/10803/6279.
Full textFor deep storage of high-level nuclear waste osmotic flows can be significant and so require a careful analysis. In Belgium, The bituminized nuclear waste (BW) named Eurobitum contained in metallic drums will be placed inside a tunnel or a shaft excavated in the Boom Clay, which is 100 m thick marine clay presenting favourable properties to limit and delay the migration of the leached radionuclides over extended periods of time. In Geological disposal conditions, contact of the bituminized radioactive waste which contains high amounts of highly soluble salt (NaNO3) with groundwater will result in water uptake and swelling of the waste and in subsequent diffusion of the dissolved salt through the host clay formation. Basically, two types of disturbance can be distinguished: A geo-mechanical perturbation, caused by the swelling of the waste and the increase of the pressure in and around the waste and a physico-chemical perturbation by the release of large amounts of NaNO3 and other soluble salts. In this context the aim of this thesis is: (i) to improve the understanding of the processes controlling the water uptake and the subsequent swelling of bituminized waste containing soluble salts (NaNO3), and (ii) to investigate of the possible effects of the increase of pore fluid concentration on swelling, compressibility and shear behaviour of Boom Clay. A formulation has been proposed for the analysis of deformation induced by dissolution of salts in porous media in contact with water. The equations include the effect of coupled transport phenomena and the formulation has been included as an extension in the coupled THM program CODE_BRIGHT. A theoretical and experimental work aiming at understanding the mechanical behaviour of the Bituminized Waste has been presented.This material is considered for this purpose as a mixture of bitumen and crystals of NaNO3. An elasto-viscoplastic model has been developed that describes the creep behaviour of BW considering the constituents' creep behaviour. The elasto-viscoplastic constitutive model has been implemented into CODE_BRIGHT. The modelling results have been compared with the experimental data. The impact of osmotic forces on the swelling of the material has been investigated by simulating water uptake swelling tests under confined conditions and comparing the predictions with experimental results. The numerical analysis has proven to be able to furnish a satisfactory representation of the main observed patterns of the behaviour. In regard to the second objective of this thesis, a formulation has been proposed for the analysis of deformations induced by osmotic processes in double structure porous media. The formulation is based on the distinction within the material of a microstructural and a macrostructural levels with chemical changes having a significant effect on the microstructure. A macroscopic description of the system is provided. Then the basic equations describing coupled flows of water and solutes and the transport of its components through macropores and mass balance equations for water and solute in macro and micro pores have been obtained. The proposed formulation has been particularly applied to analyze qualitatively the effect of osmotic suction on swelling of clayey soils. Transient and long term effects have been analyzed. The influence of pore fluid concentration on the geotechnical properties and behavior of Boom Clay under partially saturated conditions has been investigated. A systematic experimental research program involving osmotic suction and matric suction controlled experiments has been carried to investigate the effect of the increase of pore fluid concentration on shear strength and on the volume change behaviour under odometer stress state conditions. It has been observed that under partially saturated conditions a change in salinity causes a decrease in compressibility and shear strength.
Ramstedt, Madeleine. "Chemical Processes at the Water-Manganite (γ-MnOOH) Interface." Doctoral thesis, Umeå universitet, Kemi, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-253.
Full textMartins, Inês da Costa. "Desenvolvimento dos relacionamentos entre as agências e os seus clientes." Master's thesis, Instituto Superior de Economia e Gestão, 2017. http://hdl.handle.net/10400.5/15635.
Full textO crescimento da indústria da publicidade tem sido acompanhado por um igual desenvolvimento da sua complexidade, resultando numa crescente tensão nas relações entre agência e cliente. Neste sentido o estudo pretende compreender o desenvolvimento dos relacionamentos entre as agências de publicidade e os seus clientes, nomeadamente os critérios de seleção de uma agência, os processos de interação, troca, adaptação e coordenação. Pretende também averiguar quais os fatores que levam à continuidade e/ou dissolução dos relacionamentos. Foi estudado o modelo de Håkansson et al. (1982), Möller & Wilson (1988) e Baptista (2013) por forma a criar um modelo conceptual de desenvolvimento dos relacionamentos entre agência e cliente. O estudo seguiu uma metodologia qualitativa, e a recolha de dados foi executada através de recurso a entrevistas em profundidade semi-estruturadas junto de uma amostra, não-probabilística, por conveniência. Através dos resultados identificou-se que a troca de informação é feita por ambas as partes, independentemente do relacionamento; que os processos de adaptação são mais evidentes quando existe um relacionamento forte; que dependendo do relacionamento será mais provável a adaptação de novos serviços por parte da agência; para um relacionamento ser duradouro é crucial que exista confiança e que nenhuma das partes se acomode, que exista qualidade e abrangência do serviço e capacidade de dar respostas criativas e inovadoras; e que a insatisfação com o desempenho da agência e os fatores pessoais continuam a ser uma das principais razões para a mudança de agência.
The growth of the advertising industry has been accompanied by an equal development of its complexity, resulting in increasing stress in agency-client relationships. In this sense, the objective of this study is to understand the development of relationships between advertising agencies and their clients, the criteria for selecting an agency, the processes of interaction, exchange, adaptation and coordination. It also investigates which factors lead to the continuity and / or dissolution of relationships. The model of Håkansson et al. (1982), Möller & Wilson (1988) and Baptista (2013) was used in order to create a conceptual model for the development of agency-client relationships. The study followed a qualitative methodology, and data collection was executed using semi-structured in-depth interviews with a non-probabilistic sample, for convenience. The results show that the exchange of information is made by both parts, independently of the relationship; adaptation processes are more evident when there is a strong relationship; depending on the relationship, the adaptation of new services by the agency is the most likely scenario; for a relationship to be long-lasting, it is crucial that there is trust and that neither party settles down, that the service has good quality and scope and that there is an ability to respond creatively and innovatively; and that the dissatisfaction with the performance of the agency and personal factors remain the main reasons for the change of agency.
info:eu-repo/semantics/publishedVersion
Castro, Pollyana Souza. "Desenvolvimento de microssensores eletroquímicos e aplicações no estudo de processos dinâmicos interfaciais utilizando microscopia eletroquímica de varredura." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-06042016-145742/.
Full textThe study reported in this thesis shows in details the fabrication and characterization of different electrochemical microsensors which have been employed as probes in SEPM. Thus, the characterization of surfaces can be performed by exploiting different interfacial phenomena that are relevant to life sciences. In this sense, the interfaces of crystalline materials such as hydroxyapatite (dental materials) and calcite were the focus of this study. Thus, different SEPM techniques were explored in order to obtain relevant information related to dental materials processes such as acid erosion and hypersensitivity. Initially, platinum microelectrodes were developed employing conventional methodology that utilizes microfibers encapsulated in glass capillaries. Amperometric SECM mode was used to obtain information regarding the topography changes of tooth enamel caused by contact with acid chemicals. In addition, SECM was used to study the transport of electroactive species in dentin samples. Investigations related to the treatment of dental hypersensitivity and dental whitening were also evaluated. SECM results were compared with SEM images obtained under the same experimental conditions. Ion-selective microelectrode (ISME) based on the ionophore membrane sensitive to calcium ions were also developed and characterized followed by application in SECM potentiometric mode. The acid dissolution of bovine enamel (dental erosion) was investigated at different pH values (2.5; 4.5; 6.8). In addition, the transport of calcium ions through synthetic porous membranes was evaluated at a tip/substrate distance of 300µm. Changes in calcium ion flux were studied in the presence and absence of magnetic fields generated by magnetite nanoparticles incorporated into the porous membrane. Calcite microcrystals easily synthesized by precipitation method were used as a model of an interfacial surface for investigations which can be correlated to the dental materials. Thus, glass nanopipette filled with supporting electrolyte was fabricated and used as SICM probe. The high resolution topographic mapping of the calcite microcrystal was obtained using hopping mode. Additionally, ISME-SICM multifunction probes were developed and characterized for simultaneous investigations related to the topographical changes and quantification of local calcium ions on the surface of a calcite microcrystal. The addition of acidic reagents in the SICM channel promoted the dissolution of the microcrystal surface and dissolution kinetic data were obtained. Investigations in neutral medium were also studied using the ISME-SICM multifunctional probe. The experimental results were also compared with those obtained by computer simulation.
Serris, Eric. "Influence des conditions de compression sur les propriétés physico-chimiques des comprimés issus de poudres organiques." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2002. http://tel.archives-ouvertes.fr/tel-00089185.
Full textDans un premier temps, nous avons caractérisé tous les phénomènes (réarrangement granulaire, fragmentation, déformations plastiques et visqueuses) qui se déroulent lors du cycle de compression grâce à l'étude de l'émission acoustique produite lors de la compression. L'étude des trois poudres différentes utilisées dans ce travail (aspirine, amidon et produit A) a donné des résultats montrant que la fragmentation et réarrangement granulaire initial sont es responsables majeurs de l'émission acoustique en cours de compression.
L'étude du cycle de compression a été menée pour dégager l'influence de chaque partie du cycle (montée en pression, palier isobare, descente en pression et temps avant démoulage) sur les propriétés (la porosité relaxée et la résistance à la rupture) des comprimés de produits purs, ou de mélanges. De plus, cette étude nous a permis d'améliorer les modèles existants avec notamment une modélisation de l'évolution de la porosité lors du palier isobare ainsi qu'une modélisation géométrique de l'élasticité.
Pour finir une étude de la dissolution des comprimés de mélanges aspirines / amidons a été menée. Comme l'aspirine comprimée seule se dissout lentement, il faut lui adjoindre un délitant comme l'amidon de maïs. Nous avons vérifié que le principal paramètre qui joue sur la vitesse de dissolution des comprimés de mélanges est la fraction massique en amidon. Un modèle de prévision du délitement des comprimés utilisant l'analyse d'image permet de prévoir la taille initiale des fragments d'aspirine en contact avec l'eau et donc de mener à bien une étude cinétique.
Hauck, Judith [Verfasser], Dieter [Akademischer Betreuer] Wolf-Gladrow, and Birgit [Akademischer Betreuer] Schneider. "Processes in the Southern Ocean carbon cycle: Dissolution of carbonate sediments and inter-annual variability of carbon fluxes / Judith Hauck. Gutachter: Dieter Wolf-Gladrow ; Birgit Schneider. Betreuer: Dieter Wolf-Gladrow." Bremen : Staats- und Universitätsbibliothek Bremen, 2012. http://d-nb.info/1071993844/34.
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