Дисертації з теми "NATURAL SOLUTION"
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Konrad, Stephanie, and Daniela Polziehn. "The Natural Solution? : A Qualitative Study on Attitudes towards Natural Care Products for Men of Generation Y." Thesis, Internationella Handelshögskolan, Högskolan i Jönköping, IHH, Företagsekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-30387.
Повний текст джерелаSmethurst, Christopher. "A Finite Element Solution of the Natural Convection Problem in 3D." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517825.
Повний текст джерелаDonini, Mariovane Sabino. "Numerical solution for the droplet combustion." Universidade Federal do Pampa, 2017. http://dspace.unipampa.edu.br:8080/jspui/handle/riu/1955.
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In the present work, vaporization and combustion of an isolated fuel droplet at diferente ambient temperatures are examined numerically in order to analyze the effect of buoyancy force on the flame. Generally, fuel droplets in combustion devices are so small that the influence of buoyancy force on vaporization and combustion of droplets is negligible. On the other hand, fuel droplets in experimental devices are affected by the buoyancy force due to their diameters being around or more than 1 mm. To reduce the buoyancy effects, expensive experimental studies are performed in microgravity ambient (drop-tower or out of space). In normal-gravity conditions, the buoyancy force is induced by temperature gradient on ambient atmosphere. The buoyancy is positive in regions of hot gases and negative in regions of cold gases compared with the ambient atmosphere gas. Hot gases move upward and cold gases downward. Playing with the positive buoyancy force of hot gases around the flame and with the negative (cold) buoyancy force of cold gases around the droplet via ambient atmosphere temperature, it is possible to modify the flame shape. In the numerical simulations, incompressible Navier–Stokes equations along with mixture fraction and excess enthalpy conservation equations are solved using a finite volume technique with a uniform structured grid. An artificial compressibility method was applied to reach steady state solutions. The numerical predictions have been compared with analytical results for a zero gravity condition, showing good agreement. For normal gravity condition the numerical results showed that when the ambient temperature increases, the velocity gradient and buoyancy source term decreases. Despite that, the flame increased in all directions. The results have also shown that increasing the ambient temperature, decreases the temperature gradient in the flame, which ends up affecting the flame position.
No presente trabalho, a vaporização e a combustão de uma gota de combustível isolada a diferentes temperaturas ambiente são examinadas numericamente para analisar o efeito da força de flutuação na chama. Geralmente, as gotículas de combustível em dispositivos de combustão são tão pequenas que a influência da força de flutuação na vaporização e na combustão de gotículas é insignificante. Por outro lado, as gotículas de combustível em dispositivos experimentais são afetadas pela força de flutuabilidade devido ao seu diâmetro em torno de ou mais de 1 mm. Para reduzir os efeitos de flutuabilidade, estudos experimentais caros são realizados em ambiente de microgravidade (drop-tower ou fora do espaço). Em condições de gravidade normal, a força de flutuação é induzida por gradiente de temperatura na atmosfera ambiente. A flutuabilidade é positiva em regiões de gases quentes e negativas em regiões de gases frios em comparação com o gás atmosférico ambiente. Os gases quentes movem-se para cima e os gases frios para baixo. Jogando com a força de flutuação positiva dos gases quentes ao redor da chama e com a força de flutuação negativa (fria) dos gases frios ao redor da gota através da temperatura da atmosfera ambiente, é possível modificar a forma da chama. Nas simulações numéricas, as equações de Navier-Stokes incompressíveis juntamente com a fração de mistura e as equações de conservação de entalpia em excesso são resolvidas usando uma técnica de volume finito com uma grade estruturada uniforme. Foi aplicado um método de compressibilidade artificial para alcançar soluções de estado estacionário. As previsões numéricas foram comparadas com resultados analíticos para uma condição de gravidade zero, mostrando boa concordância. Para a condição de gravidade normal, os resultados numéricos mostraram que, quando a temperatura ambiente aumenta, o gradiente de velocidade e o termo da fonte de flutuação diminuem. Apesar disso, a chama aumentou em todas as direções. Os resultados também mostraram que aumentar a temperatura ambiente, diminui o gradiente de temperatura na chama, o que acaba afetando a posição da chama.
Ogunrobo, Emmanuel Osarumwense. "Analysis of hydrocarbon solubility in amine solution used for natural gas processing." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Знайти повний текст джерелаRhys, Natasha Hazel. "Exploring the structural properties of natural and synthetic biological molecules in aqueous solution." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/11248/.
Повний текст джерелаComuni, Federica. "A natural language processing solution to probable Alzheimer’s disease detection in conversation transcripts." Thesis, Högskolan Kristianstad, Fakulteten för naturvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hkr:diva-19889.
Повний текст джерелаLi, Bo. "Synthesis, Kinetics and Mechanisms of Designer and Natural Product Antioxidants: From Solution to Cells." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34335.
Повний текст джерелаTalbot, James David Ralph. "The conductivity of carbonate and phosphate species in aqueous solution and in some related natural waters." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280559.
Повний текст джерелаJonsson, Åsa. "Enhancement of Dry Content in Coating Solution for Functional Packaging." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16576.
Повний текст джерелаThe main goal for a packaging is to protect the product inside. Typical packaging nowadays is made of layers of paper and barriers consisting of plastics or aluminum foil. A problem with the barrier used today is the environmental thinking. Xylophane® is an environmental friendly and biodegradable alternative to the current barrier material used in packaging. It consists of the natural carbohydrate xylan and additives. Xylophane® is an efficient barrier to oxygen, grease and aroma and can prolong the shelf life of sensitive food.
The raw material xylan is water soluble and Xylophane® can be coated on paper, board and plastics without using other solvents. A problem with the drying process is the amount of energy needed and the consumption needs to be decreased. Also, the drying capacity of the equipment to be used is often limited and the amount of water to be dried off is critical for the success of the coating process. By increasing the dry content of Xylophane® without increasing the viscosity too much, the drying process can be more effective. In this thesis, studies were made of using a filler as an additive to increase the dry content without destroying the barrier properties.
With an experimental design, a suitable relationship between the ingredients xylan (X), plasticizer (P) and filler (F) was found. Xylan is the main component and is needed to get a good oxygen barrier. The plasticizer decreases the oxygen barrier properties but is needed to make the material more flexible. The filler is positive for the barrier properties. The chosen composition was X:P = 7:3 and X:F = 1:1. Some extra experiments were made to find a reasonable value of the dry content. Dry contents around 18 % work well with temperatures at and above 45°C, but to manage to perform coating at room temperature the dry content needs to be lower.
Heeren, Alexander Heeren. "Identifying the Problem or Identifying with the Solution?The Role of Motivated Reasoning and Identity Politics in Environmental Science." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1468073451.
Повний текст джерелаNikolkina, Irina. "Modélisation des écoulements de gravité et des ondes longues : application à l'évaluation des risques de catastrophes naturelles dans les Antilles françaises." Thesis, Antilles-Guyane, 2011. http://www.theses.fr/2011AGUY0435/document.
Повний текст джерелаThe dissertation is devoted to research in the field of marine natural hazards (tsunamis, storm surges) in the French West Indies, using analytical and numerical models of fluid mechanics. Emphasis is placed on the development of models of landslide motion and generated tsunami waves. The simple "solid block" model is used to evaluate the characteristics of pyroclastic flow Soufriere Hills volcano (Montserrat). The "fluid model" of a landslide (so called Savage-Hutter model) is studied analytically; within this model a new family of exact solutions that describe the motion of nonlinear gravity flow in a valley or underwater canyon is found: nonlinear Riemann wave, dan break problem, self-similar solutions (M - wave and parabolic cap). In the framework of the linear shallow water theory the process of generation of tsunami waves by landslides of variable volume moving with variable velocity above the basin of variable depth is studied. For the specific bottom profile ("reflectionless" one) the resonant phenomena is investigated in the basin of variable depth. Numerical methods are used to analyze marine hazards: historical (storm surges, caused by Cyclone LILI in 2002; volcanic tsunami 2003 on Montserrat) and possible events (possible tsunami of the coast of Martinique). Various data on marine natural disasters are obtained during field surveys (volcanic tsunami in 2003, stonn surges caused by Hurricane Dean in 2007). Designed catalogs of tsunamis and storm surges are created based on results of numerical modeling and field studies; some statistical analysis is perfomed
Armagan, Emre. "Decomposition algorithms for global solution of deterministic and stochastic pooling problems in natural gas value chains." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/46629.
Повний текст джерелаIncludes bibliographical references (leaves 153-158).
In this thesis, a Benders decomposition algorithm is designed and implemented to solve both deterministic and stochastic pooling problems to global optimality. Convergence of the algorithm to a global optimum is proved and then it is implemented both in GAMS and C++ to get the best performance. A series of example problems are solved, both with the proposed Benders decomposition algorithm and commercially available global optimization software to determine the validity and the performance of the proposed algorithm. Moreover, a two stage stochastic pooling problem is formulated to model the optimal capacity expansion problem in pooling networks and the proposed algorithm is applied to this problem to obtain global optimum. A number of example stochastic pooling problems are solved, both with the proposed Benders decomposition algorithm and commercially available global optimization software to determine the validity and the performance of the proposed algorithm applied to stochastic problems.
by Emre Armagan.
S.M.
Ndayambaje, Guillaume. "Sorption properties of natural zeolites for the removal of ammonium and chromium ions in aqueous solution." University of the Western Cape, 2011. http://hdl.handle.net/11394/5425.
Повний текст джерелаThere are huge amount of natural clinoptilolite available in South Africa which can be utilised for wastewater treatment of ammonia and chromium if their characteristics are properly known. However, these deposits have not been well characterised but in this study, the untreated clinoptilolite materials were fully characterised using techniques such as SEM-EDS, HRTEM-SAED, XRD, XRF, FTIR and BET. After acid pretreatment with several extractions, the pretreated samples were again characterised using the above mentioned techniques. These pretreated materials were used for NH₄⁺ and Cr³⁺ adsorption of wastewater. The three natural South African clinoptilolite samples used in this study were from ECCA Holdings (ESC and EHC samples) and Pratley (PC sample) deposits obtained from Western Cape and KwaZulu-Natal Province respectively. This study revealed that the chemical composition and mineral phases of South African clinoptilolites vary considerably from site to site, even clinoptilolite mined from the same deposit sites. The XRD analyses showed that Pratley clinoptilolite (PC) was the most pure clinoptilolite sample (81.41 %) compared to the purity of EHC (67.88 %) and ESC (44.0 %) sample. The ECCA Holdings untreated clinoptilolite samples contained dense phases such as quartz which was not found in Pratley sample. Quartz was found to be the most dominant impurity in both ECCA Holding sample. The cation exchange capacity (CEC) of ESC, EHC and PC samples were found to be 1.23, 1.81 and 2.90 meq/g respectively and these results were compared to that of XRF analyses. The acid solutions of 0.02 and 1.0 M HCl were used to pretreat natural clinoptilolite to determine the optimum acid concentration and number of extractions required to fully replace the exchangeable cations. The pretreatment results showed that 0.02 M HCl was the optimum acid concentration for acid pretreatment of clinoptilolite samples. Between 7 and 22 extractions were required to remove Na⁺, K⁺, Ca²⁺ and Mg²⁺ without causing much dealumination of the framework. Sodium ion was found to be weakly bound cation in the clinoptilolite framework, since it could be completely exchanged by H⁺ after 7 extractions with 0.02 M HCl acid solution. Potassium ion was found to be strongly bound in the clinoptilolite framework since it could not be completely exchanged during the acid pretreatment process even after 22 extractions. The HRTEM-SAED and BET results showed that ESC, EHC and PC were all polycrystalline and microporous materials respectively. It was found that the adsorption capacity of the treated Pratley clinoptilolite sample was increased by 36 % for NH₄⁺ removal, compared to that of the untreated PC sample. The adsorption study results showed that the pretreatment of clinoptilolite samples using 150 mL volumes of 0.02 M HCl with 7 acid extractions at 25 °C for ESC pretreated and EHC pretreated. The pretreatment of PC sample at 22 extractions could remove high percentage of NH₄⁺ (98.11 %) within a short contact time of 10 min. The pretreated Pratley clinoptilolite sample was found to be the best NH₄⁺ adsorbent (98.11 % NH₄⁺ removal) compared to EHC treated (93.89 % NH₄⁺ removal) and ESC treated (75.00 % NH₄⁺ removal) clinoptilolite samples. However, acid-pretreated Pratley clinoptilolite did not sufficiently remove Cr³⁺ (16.10 %) from synthetic wastewater showing that it is not a good adsorbent for this particular metal ion removal. Despite several studies that have been conducted on clinoptilolite, no study has been carried out on the pretreatment and comparison of sorption capacity of different South African clinoptilolites for the removal of NH₄⁺ from wastewater. This study has been able improve on the acid-pretreatment procedure for clinoptilolite. This study demonstrated that it is not only the acid concentration that is important but also the number of extractions needed to remove all the exchangeable cations from the clinoptilolite framework. This study has also been able to prove that South African clinoptilolite can treated ammonia from wastewater.
Romashko, A. S. "Green economy as a solution of ecological problems." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/45223.
Повний текст джерелаBeltz, Morgan. "The Declining Natural Fish Stock: A Proposed Solution to Public Fear and Perceptions of Genetically Modified Fish." Scholarship @ Claremont, 2013. http://scholarship.claremont.edu/cmc_theses/765.
Повний текст джерелаde, las Heras Reverte Víctor. "Evaluation of natural materials in Sustainable Buildings : A potential solution to the European 2050 long-term strategy." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300115.
Повний текст джерелаGumgum, Sevin. "The Dual Reciprocity Boundary Element Method Solution Of Fluid Flow Problems." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611605/index.pdf.
Повний текст джерелаKoller, David. "A Solution Under Pressure: Integrating Facilitative Practices into Water-Related Civil Litigations." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22745.
Повний текст джерелаReséndiz, Marino. "Photochemical decarbonylation of ketones in the solid state and in solution ; Progress towards the total synthesis of natural products." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1790313711&sid=16&Fmt=2&clientId=48051&RQT=309&VName=PQD.
Повний текст джерелаKelly, Sean R. "STRUCTURAL MECHANISMS OF (POLY)ANION SOLID SOLUTION IN SYNTHETIC OH-Cl BINARY APATITE AND NATURAL F-OH-Cl TERNARY APATITE." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1480963439051542.
Повний текст джерелаAlsoy-akgun, Nagehan. "The Dual Reciprocity Boundary Element Solution Of Helmholtz-type Equations In Fluid Dynamics." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615729/index.pdf.
Повний текст джерелаMELLO, Rafael Ferreira Leite de. "A solution to extractive summarization based on document type and a new measure for sentence similarity." UNIVERSIDADE FEDERAL DE PERNAMBUCO, 2015. https://repositorio.ufpe.br/handle/123456789/15257.
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The Internet is a enormous and fast growing digital repository encompassing billions of documents in a diversity of subjects, quality, reliability, etc. It is increasingly difficult to scavenge useful information from it. Thus, it is necessary to provide automatically techniques that allowing users to save time and resources. Automatic text summarization techniques may offer a way out to this problem. Text summarization (TS) aims at automatically compress one or more documents to present their main ideas in less space. TS platforms receive one or more documents as input to generate a summary. In recent years, a variety of text summarization methods has been proposed. However, due to the different document types (such as news, blogs, and scientific articles) it became difficult to create a general TS application to create expressive summaries for each type. Another related relevant problem is measuring the degree of similarity between sentences, which is used in applications, such as: text summarization, information retrieval, image retrieval, text categorization, and machine translation. Recent works report several efforts to evaluate sentence similarity by representing sentences using vectors of bag of words or a tree of the syntactic information among words. However, most of these approaches do not take in consideration the sentence meaning and the words order. This thesis proposes: (i) a new text summarization solution which identifies the document type before perform the summarization, (ii) the creation of a new sentence similarity measure based on lexical, syntactic and semantic evaluation to deal with meaning and word order problems. The previous identification of the document types allows the summarization solution to select the methods that is more suitable to each type of text. This thesis also perform a detailed assessment with the most used text summarization methods to selects which create more informative summaries for news, blogs and scientific articles contexts.The sentence similarity measure proposed is completely unsupervised and reaches results similar to humans annotator using the dataset proposed by Li et al. The proposed measure was satisfactorily applied to evaluate the similarity between summaries and to eliminate redundancy in multi-document summarization.
Atualmente a quantidade de documentos de texto aumentou consideravelmente principalmente com o grande crescimento da internet. Existem milhares de artigos de notícias, livros eletrônicos, artigos científicos, blog, etc. Com isso é necessário aplicar técnicas automáticas para extrair informações dessa grande massa de dados. Sumarização de texto pode ser usada para lidar com esse problema. Sumarização de texto (ST) cria versões comprimidas de um ou mais documentos de texto. Em outras palavras, palataformas de ST recebem um ou mais documentos como entrada e gera um sumário deles. Nos últimos anos, uma grande quantidade de técnicas de sumarização foram propostas. Contudo, dado a grande quantidade de tipos de documentos (por exemplo, notícias, blogs e artigos científicos) é difícil encontrar uma técnica seja genérica suficiente para criar sumários para todos os tipos de forma eficiente. Além disto, outro tópico bastante trabalhado na área de mineração de texto é a análise de similaridade entre sentenças. Essa similaridade pode ser usada em aplicações como: sumarização de texto, recuperação de infromação, recuperação de imagem, categorização de texto e tradução. Em geral, as técnicas propostas são baseados em vetores de palavras ou árvores sintáticas, com isso dois problemas não são abordados: o problema de significado e de ordem das palavras. Essa tese propõe: (i) Uma nova solução em sumarização de texto que identifica o tipo de documento antes de realizar a sumarização. (ii) A criação de uma nova medida de similaridade entre sentenças baseada nas análises léxica, sintática e semântica. A identificação de tipo de documento permite que a solução de sumarização selecione os melhores métodos para cada tipo de texto. Essa tese também realizar um estudo detalhado sobre os métodos de sumarização para selecinoar os que criam sumários mais informativos nos contextos de notícias blogs e artigos científicos. A medida de similaridade entre sentences é completamente não supervisionada e alcança resultados similarires dos anotadores humanos usando o dataset proposed por Li et al. A medida proposta também foi satisfatoriamente aplicada na avaliação de similaridade entre resumos e para eliminar redundância em sumarização multi-documento.
Caritey, Jean-Philippe. "Relation entre la modification chimique de précurseurs hydrophiles d'origine naturelle et leurs propriétés en solution diluée et semi-diluée." Rouen, 1994. http://www.theses.fr/1994ROUES013.
Повний текст джерелаDe, Pietro Júlia [UNESP]. "Fisiologia pós-colheita de rosas cortadas cv. Vega." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/96947.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Face à carência de estudos relacionados à fisiologia pós-colheita de flores, a presente pesquisa teve como finalidade estudar a fisiologia e conservação póscolheita de flores cortadas de rosas cv. Vega, considerando os fatores associados à senescência floral e perda de vida decorativa. Os experimentos foram conduzidos em delineamento inteiramente casualizado, em esquema fatorial. Em todos os experimentos, as rosas foram mantidas em ambiente de laboratório com 20±2ºC e 67±3% UR, padronizadas em 50 cm e realizadas as seguintes avaliações (exceto para o experimento 5): perda de massa fresca, massa seca, taxa respiratória, notas de qualidade (escurecimento, turgescência e curvatura), conteúdo relativo de água, carboidratos solúveis e redutores, antocianina e coloração. Para o experimento 5 foi avaliada a quantidade de água absorvida e transpirada das rosas. No primeiro experimento, as flores foram colocadas dentro de uma câmara hermética e expostas ao 1-MCP, por um período de seis horas, nas seguintes concentrações: 1) Água destilada (controle); 2) 1-MCP 100 a ppb; 3) 1-MCP a 250 ppb; 4) 1-MCP a 500 ppb. Ao contrário do tratamento com água destilada, todas as concentrações de 1-MCP foram eficientes para retardar a senescência das flores, com destaque para a de 500 ppb que melhor manteve a qualidade, além de prolongar a vida de vaso das rosas até 19 dias. No segundo experimento, as flores permaneceram nas seguintes soluções de manutenção: 1) Água destilada (Controle); 2) 8-HQC (200 mg.L-1); 3) Sacarose (2%) + 8-HQC (200 mg.L-1); 4) Ácido Cítrico (75 mg.L-1); 5) Sacarose (2%) + Ácido Cítrico (75 mg.L-1); 6) 6- BA (60 mg.L-1); 7) Sacarose (2%) + 6-BA (60 mg.L-1). As rosas foram muito sensíveis à 6-benziladenina, associada ou não à sacarose, e perderam a qualidade aos seis dias de vida de vaso. Em contrapartida, o tratamento com 8-hidroxiquinolina...
Given the lack of studies on postharvest physiology of flowers, this research aims to study the postharvest physiology and keeping quality of Vega cut rose, were observed the factors associated with floral senescence and loss of decorative life. The experiments followed complete randomized design, in factorial arrangement. In all experiments, the roses were kept at room temperature with 20 ± 2ºC and 67±3% UR, standardized at 50 cm and it were analysis (except the fifth experiment): weight loss, dry weight, rate respiratory, quality (browning, turgidity and curvature), relative water content, soluble and reducing carbohydrates, anthocyanin, color and longevity. On the fifth experiment was to evaluation the water absorbed and transpired roses. On the first experiment, the flowers were placed inside an airtight chamber and exposed to 1-MCP for a period of six hours, in these concentrations: 1) Distilled water (control); 2) 1-MCP (100 ppb); 3) 1-MCP ( 250 ppb); 4) 1-MCP (500 ppb). Unlike treatment with distilled water, all concentrations of 1-MCP were effective in delaying the senescence of flowers, however, the concentration of 500 ppb of 1-MCP induced better maintenance of quality and extended vase life of roses to 19 days. On the second experiment, the flowers remained in these following holding solutions: 1) Distilled water (Control); 2) 8-HQC (200 mg.L-1); 3) Sucrose (2%) + 8-HQC (200 mg.L-1); 4) Citric Acid (75 mg.L-1); 5) Sucrose (2%) + Citric Acid (75 mg.L-1); 6) 6-BA (60 mg.L-1); 7) Sucrose (2%) + 6-BA (60 mg.L-1). The roses were very sensitive to 6-benzyladenine, with or without sucrose, and lost quality of six days of vase life. In contrast, treatment with 8-hydroxyquinoline has proved the most promising to maintain the quality of the flowers, for ten days. On the third experiment, the roses were treated this way: 1) Distilled water (Control), 2) STS (1 mM) ... (Complete abstract click electronic access below)
Pires, Plínio Ferreira. "Estudo da carbonatação avançada em concretos contendo adições minerais." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6319.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The carbonation phenomenon consists in a physicochemical process which reduces the alkalinity of concrete. Carbonation can destabilize the protective layer of the steel, leaving it susceptible to corrosion, which is one of the most significant and costly causes of deterioration in reinforced concrete. Accordingly, chemical analysis of the pore solution has been held for about 60 years, but few studies are focused on types of concrete containing mineral additions subjected to carbonation, due to the difficulty of obtaining the pore solution, given its structure densification under these conditions. Depending on the concrete composition, the natural carbonation process can take several years to present sufficient analyzable data, therefore, most of the studies on this topic use accelerated tests to simulate this phenomenon. However, even with full control of the laboratory environment, it is not possible to reproduce the randomness of the variables responsible for the degradation that occur in real situations. This study aims to evaluate the process of natural carbonation in 36 different types of concrete or analysis conditions, which cover a wide range of characteristics and properties of concrete that represent the various service situations of the structures, after about 14 years of exposure, in typical urban environment. The results are presented for types of concrete with and without mineral additions (silica fume, rice husk ash, metakaolin, fly ash and blast furnace slag); three water/binder (0.40, 0.55 and 0.70) and two curing conditions (dry-cured and moist-cured). The study was conducted by the application of simplified models of carbonation and statistical analysis on an extensive experimental database (over 2000 measurements) obtained by eight evaluations of carbonation carried at different ages, through 14 years of natural exposure prototypes of concrete beams. In addition, chemical analysis of pH, ionic strength and conductivity of the pore solution - obtained through innovative method - were conducted in both the carbonated layer and the non-carbonated layer of concrete. The results indicate that the empirically-analytical model proposed by Tuutti, has an excellent representativity of carbonated depth over time. The use of a coefficient of carbonation, from Tuutti’s model, calculated from early ages, can generate mistaken conclusions: underestimating the dry-cured concrete and overestimating the moist-cured concrete. In the overall analysis of the natural carbonation coefficients obtained by ANOVA showed that the water/binder ratio is the most significant factor, followed by curing type and, finally, the type of addition. The best performances as the carbonation are observed to the lower water/binder concretes, subjected to wet cure. Under the method used to obtain the pore solution, it was possible to compare the difference between the chemical properties of non-carbonated and carbonated layers of each type of concrete analyzed.
O fenômeno da carbonatação consiste em um processo físico-químico que leva à redução de alcalinidade do concreto. Isto pode desestabilizar a camada protetora do aço, deixando-o passível de corrosão, que é uma das mais importantes e onerosas causas de deterioração do concreto armado. Nesse sentido, a análise química da solução do poro tem sido realizada há cerca de 60 anos, contudo raros trabalhos focam em concretos submetidos à carbonatação contendo adições minerais, dada a dificuldade de se obter a solução devido à densificação na estrutura porosa nessas condições. Dependendo da composição do concreto, o processo de carbonatação natural pode levar vários anos para apresentar dados passíveis de análise, diante disso, a maioria dos estudos nesse tema utilizam ensaios acelerados para simular tal fenômeno, contudo, mesmo com todo controle do ambiente de laboratório, não se pode reproduzir a aleatoriedade das variáveis que ocorre em situações reais de degradação. Este trabalho tem como objetivo avaliar o processo de carbonatação natural em 36 diferentes concretos ou condições de análise, os quais cobrem uma ampla faixa de características e propriedades dos concretos, representando as mais diversas situações de serviço para as estruturas, após cerca de 14 anos de exposição, em ambiente típico urbano. São, portanto, apresentados resultados de concretos sem e com adições minerais (sílica ativa, cinza de casca de arroz, metacaulim, cinza volante e escória de alto-forno); três relações água/ligante (0,40; 0,55 e 0,70) e duas condições de cura (seca e úmida). O estudo se deu por meio de aplicações de modelos simplificados de carbonatação e análises estatísticas em um extenso banco de dados experimentais (mais de 2000 medidas) obtido por oito avaliações da frente de carbonatação realizadas em diferentes idades, durante 14 anos de exposição natural de protótipos de vigas de concreto. Foram realizadas também análises químicas de pH, força iônica e condutividade da solução do poro, obtida através de método inovador, tanto da camada carbonatada quanto da camada não carbonatada dos concretos. Os resultados indicam que o modelo empírico-analítico, proposto por Tuutti, possui excelente representatividade da profundidade carbonatada ao longo do tempo. A utilização de um coeficiente de carbonatação, do modelo de Tuutti, calculado a partir de idades iniciais pode gerar conclusões equivocadas: subestimando os concretos sem cura e superestimando os de cura úmida. A análise global dos coeficientes de carbonatação, obtidos pela ANOVA, demonstrou que a relação água/ligante é o fator mais significativo, seguido do tipo de cura e, por último, o tipo de adição. Os melhores desempenhos quanto à carbonatação são observados para os concretos de menor relação água/ligante, submetidos à cura úmida. De acordo com o método empregado para obtenção da solução do poro, foi possível comparar a diferença entre as propriedades químicas da camada não carbonatada e a carbonatada, para toda a família de concretos analisada.
Blachot, Jean-François. "Étude des propriétés rhéologiques des solutions cellulose/monohydrate de N-oxyde de N-méthylmorpholine (NMMO) : filage de cellulose extraite de paille de blé : structure et fibrillation des fils obtenus." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10189.
Повний текст джерелаCai, Zhemin. "A High-order Discontinuous Galerkin Method for Simulating Incompressible Fluid-Thermal-Structural Problems." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20961.
Повний текст джерелаSalov, Aleksandar. "Towards automated learning from software development issues : Analyzing open source project repositories using natural language processing and machine learning techniques." Thesis, Linnéuniversitetet, Institutionen för medieteknik (ME), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-66834.
Повний текст джерелаDe, Pietro Júlia. "Fisiologia pós-colheita de rosas cortadas cv. Vega /." Jaboticabal : [s.n.], 2009. http://hdl.handle.net/11449/96947.
Повний текст джерелаAbstract: Given the lack of studies on postharvest physiology of flowers, this research aims to study the postharvest physiology and keeping quality of Vega cut rose, were observed the factors associated with floral senescence and loss of decorative life. The experiments followed complete randomized design, in factorial arrangement. In all experiments, the roses were kept at room temperature with 20 ± 2ºC and 67±3% UR, standardized at 50 cm and it were analysis (except the fifth experiment): weight loss, dry weight, rate respiratory, quality (browning, turgidity and curvature), relative water content, soluble and reducing carbohydrates, anthocyanin, color and longevity. On the fifth experiment was to evaluation the water absorbed and transpired roses. On the first experiment, the flowers were placed inside an airtight chamber and exposed to 1-MCP for a period of six hours, in these concentrations: 1) Distilled water (control); 2) 1-MCP (100 ppb); 3) 1-MCP ( 250 ppb); 4) 1-MCP (500 ppb). Unlike treatment with distilled water, all concentrations of 1-MCP were effective in delaying the senescence of flowers, however, the concentration of 500 ppb of 1-MCP induced better maintenance of quality and extended vase life of roses to 19 days. On the second experiment, the flowers remained in these following holding solutions: 1) Distilled water (Control); 2) 8-HQC (200 mg.L-1); 3) Sucrose (2%) + 8-HQC (200 mg.L-1); 4) Citric Acid (75 mg.L-1); 5) Sucrose (2%) + Citric Acid (75 mg.L-1); 6) 6-BA (60 mg.L-1); 7) Sucrose (2%) + 6-BA (60 mg.L-1). The roses were very sensitive to 6-benzyladenine, with or without sucrose, and lost quality of six days of vase life. In contrast, treatment with 8-hydroxyquinoline has proved the most promising to maintain the quality of the flowers, for ten days. On the third experiment, the roses were treated this way: 1) Distilled water (Control), 2) STS (1 mM) ... (Complete abstract click electronic access below)
Orientador: Ben-Hur Mattiuz
Coorientador: Teresinha de Jesus Deléo Rodrigues
Coorientador: Claudia Fabrino Machado Mattiuz
Banca: Kathia Fernandes Lopes Pivetta
Banca: Regina Maria Monteiro de Castilho
Mestre
Kalyva, Maria. "Fate of pharmaceuticals in the environment - A review-." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-132995.
Повний текст джерелаMorris, Graham Peter. "Parameter recovery in AC solution-phase voltammetry and a consideration of some issues arising when applied to surface-confined reactions." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:1b1d40f3-ef1a-4f64-b500-17ce34630c43.
Повний текст джерелаBose, Sweta. "Dissolution Kinetics of Sulfate Minerals: Linking Environmental Significance of Mineral-Water Interface Reactions to the Retention of Aqueous CrO42- in Natural Waters." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1207285064.
Повний текст джерелаFenger, Julie-Anne. "Les anthocyanes acylées en tant que colorants naturels : réactivité en solution aqueuse, complexation métallique et stabilisation pour des applications alimentaires The chemical reactivity of anthocyanins and its consequences in food science and nutrition The influence of acylation and metal binding on the thermal stability of red cabbage anthocyanins The fate of acylated anthocyanins in neutral solution." Thesis, Avignon, 2020. http://www.theses.fr/2020AVIG0278.
Повний текст джерелаAnthocyanins are ubiquitous plant pigments that exhibit bright colors from red to blue. Thus, they are good candidates to replace the synthetic food colors. However, the low stability of anthocyanin colors is a real hurdle to their industrial applications, especially under near neutral conditions required to express the blue color. A promising perspective is to resort to anthocyanins acylated by p-hydroxycinnamic acids, as these pigments develop colorstabilizing mechanisms (intramolecular copigmentation, self-association) based on strong stacking interactions between the anthocyanidin chromophore and the acyl residues. Therefore, this work investigates the structural transformations of acylated anthocyanins (proton transfer, water addition), their affinity to metal ions and their resistance to thermal degradation in the presence or absence of added metal ions. To that purpose, kinetic and thermodynamic studies by UV-visible spectroscopy are combined with the identification of degradation products by UPLC-DAD/MS. The impact of the acyl residues (number, location, type) was deciphered from a series of isolated pigments from red cabbage and purple sweet potato. With the former, the acyl residue bound to the external glucose of the sophorose moiety provides a) optimal protection against attacks by H2O, H2O2 and sulfite, b) improved affinity for metal ions, c) enhanced resistance against thermal degradation (for anthocyanins and their metal complexes). By contrast, caffeic acid, whether free or as an acyl residue (in purple sweet potato), accelerates the degradation of anthocyanins in spite of stabilizing the color. Under moderate heating at pH 7, red cabbage anthocyanins were degraded into acylsophoroses, phloroglucinaldehyde-2-O-glucoside, protocatechuic acid, 3,5,7trihydroxycoumarin derivatives, and 2,4,6-trihydroxyphenylacetic acid derivatives. Intramolecular acyl migration was also evidenced. The anionic base, a major colored form at pH 7, appears most vulnerable to autoxidation. The hydrogen peroxide thus produced is further involved in anthocyanin degradation. Overall, the tight binding of acylated anthocyanins to iron and aluminum ions and possibly the addition of natural antioxidants (e.g., N-acetylcysteine) are promising perspectives for the development of stable natural blue colors
Ji, Yuefei. "Photochemical and photocatalytic degradation of pharmaceutical and personal care products (PPCPS) in aqueous solution : a case study of atenolol and 2-phenylbenzimidazole-5-sulfonic acid." Phd thesis, Université Claude Bernard - Lyon I, 2014. http://tel.archives-ouvertes.fr/tel-01058226.
Повний текст джерелаParks, David William. "Sub-sea gas processing." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/2588.
Повний текст джерелаCapacci, Christian. "Resistenza idraulica del rivestimento arginale vegetato: sperimentazione in canaletta e velocimetria doppler." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Знайти повний текст джерелаNatali, Andrea. "Double Dyke System - Natural engineering solutions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21243/.
Повний текст джерелаCorrales, Juliana. "Modeling a Phosphorus Credit Trading Program in the Lake Okeechobee Watershed." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2294.
Повний текст джерелаMacken, Stephen. "Integrated Optical Solutions for Ubiquitous Sensing." Doctoral thesis, Linköpings universitet, Tillämpad Fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-63709.
Повний текст джерелаFahs, Amin. "Modeling of naturel convection in porous media : development of semi-analytical and spectral numerical solutions of heat transfer problem in special domains." Thesis, Strasbourg, 2021. https://publication-theses.unistra.fr/restreint/theses_doctorat/2021/Fahs_Amin_2021_ED269.pdf.
Повний текст джерелаThe problem of the porous square cavity is extensively used as a common benchmark case for Natural convection (NC) problem in porous media. It can be used for several numerical, theoretical, and practical purposes. All the existing high accurate solutions are developed under steady-state conditions. However, it is well known that the processes of NC in porous media occurs naturally in a time-dependent procedure, as boundary conditions can be variable in time. Also, the convergence of the steady-state solution is known to be difficult. To overcome this difficulty, the steady-state solution is often simulated as a transient solution that evolves until reaching the steady-state condition. These time-dependent modes are very efficient to detect the effects of the parameter variations on the physical process of NC, especially for the subject of interest in this thesis: the domain inclination level and hot wall temperature variation in time. For this purpose, three goals are identified in this Thesis: 1. Developing a time-dependent solution of natural convection in porous media using the Darcy model in two modes: Transient and unsteady. 2. Investigating the time-dependent behavior of natural convection in porous media having the domain inclination level as a variable parameter in two modes: Transient and unsteady. 3. Developing a time-dependent solution of natural convection in porous media using the Darcy-Lapwood-Brinkman model in two modes: Transient and unsteady. To do so, according to the high accuracy in the simply connected domains, one of the Galerkin spectral weighted residual method is chosen to develop a space-time dependent solution for NC problem in a square porous cavity. Applying the Fourier-Galerkin (FG) procedure, two configurations dealing with transient and unsteady regimes are considered where each solution is derived for a wide range of Rayleigh numbers with other special conditions. This work of thesis is explained in details as five chapters.The NC physical process with the time-dependent variations is described in the transient mode to reach the steady-state solution and for the unsteady mode during a one period using periodic sinusoidal boundary conditions on the cavity hot wall. Finally, the work of this thesis is described in details in five chapters; while the sixth and last chapter is devoted to the summary and conclusion.The results in this thesis work provide a set of high-accurate data that are published in three papers to be used for testing numerical codes of heat transfer in time-dependent configurations
Johansson, Maria. "Natural Light, Space and Perception." Thesis, KTH, Arkitektur, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280168.
Повний текст джерелаRae, Ian Black. "Natural biosorbents for the removal of metals from aqueous solutions." Thesis, Open University, 2008. https://pure.uhi.ac.uk/portal/en/studentthesis/natural-biosorbents-for-the-removal-of-metals-from-aqueous-solutions(02780c75-a23e-41e9-aaae-071f211efafd).html.
Повний текст джерелаPanesar, Kulvinder. "Conversational artificial intelligence - demystifying statistical vs linguistic NLP solutions." Universitat Politécnica de Valéncia, 2020. http://hdl.handle.net/10454/18121.
Повний текст джерелаThis paper aims to demystify the hype and attention on chatbots and its association with conversational artificial intelligence. Both are slowly emerging as a real presence in our lives from the impressive technological developments in machine learning, deep learning and natural language understanding solutions. However, what is under the hood, and how far and to what extent can chatbots/conversational artificial intelligence solutions work – is our question. Natural language is the most easily understood knowledge representation for people, but certainly not the best for computers because of its inherent ambiguous, complex and dynamic nature. We will critique the knowledge representation of heavy statistical chatbot solutions against linguistics alternatives. In order to react intelligently to the user, natural language solutions must critically consider other factors such as context, memory, intelligent understanding, previous experience, and personalized knowledge of the user. We will delve into the spectrum of conversational interfaces and focus on a strong artificial intelligence concept. This is explored via a text based conversational software agents with a deep strategic role to hold a conversation and enable the mechanisms need to plan, and to decide what to do next, and manage the dialogue to achieve a goal. To demonstrate this, a deep linguistically aware and knowledge aware text based conversational agent (LING-CSA) presents a proof-of-concept of a non-statistical conversational AI solution.
Breckel, Alex Cade. "Regulating electricity and natural gas in Peru : solutions for a sustainable energy sector." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90029.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 57-59).
Peru is one of the fastest growing countries in Latin America, thanks in part to industry fueled by generous endowments of hydro power capacity and natural gas reserves. However, investment in electricity generation capacity has not kept pace with the rapid increase in demand and threatens to stymie future economic growth. A flawed regulatory environment is to blame, and specific roadblocks to increased generation investments include a dysfunctional capacity payment system, low administratively determined gas prices, and structural barriers to investment in hydro. This thesis provides an overview of the design, functioning and historical context for energy regulation in Peru; identifies the key barriers to generation investment; analyzes two potential regulatory reforms; and recommends the specific reform that has the most promise for reigniting investment in hydro. Two reforms strike at the root of the current problem: The first, increasing the price of natural gas for power generators up to the economic netback value of LNG exports, would make hydro a viable investment but would hit consumers with very large increases in their electricity bills. An alternative approach, a reform to the capacity payment mechanism, could provide the same benefits in terms of drawing new generator investment but at a much lower cost to consumers. It would also offer benefits for regulatory discretion in the future evolution of the grid.
by Alex Cade Breckel.
S.M. in Technology and Policy
Marzo, i. Grimalt Núria. "Natural Language Processing Model for Log Analysis to Retrieve Solutions For Troubleshooting Processes." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300042.
Повний текст джерелаEn av de mest tidskrävande uppgifterna inom telekommunikationsindustrin är att felsöka och hitta lösningar till felrapporter (TR). Denna uppgift kräver förståelse av textdata, som försvåras as att texten innehåller företags- och domänspecifika attribut. Texten innehåller typiskt sett många förkortningar, felskrivningar och tabeller blandat med numerisk information. Detta examensarbete ämnar att förenkla inhämtningen av lösningar av nya felsökningar på ett automatiserat sätt med hjälp av av naturlig språkbehandling (NLP), specifikt modeller baserade på dubbelriktad kodrepresentation (BERT). Examensarbetet föreslår en textrankningsmodell som, givet en felbeskrivning, kan rangordna de bästa möjliga lösningarna till felet baserat på tidigare felsökningar. Modellen hanterar avvägningen mellan noggrannhet och fördröjning genom att implementera den dubbelriktade kodrepresentationen i två faser: en initial inhämtningsfas och en omordningsfas. För industrianvändning krävs att modellen uppnår en given noggrannhet med en viss tidsbegränsning. Experimenten för att utvärdera noggrannheten och fördröjningen har utförts på Ericssons felsökningsdata. Utvärderingen visar att den föreslagna modellen kan hämta och omordna data för felsökningar med signifikanta förbättringar gentemot modeller utan dubbelriktad kodrepresentation.
Mayer, Timothy David. "Interactions of phosphorus and colloidal iron oxides in model solutions and natural waters /." Full text open access at:, 1995. http://content.ohsu.edu/u?/etd,214.
Повний текст джерелаHERZOG, PATRICIA. "Macrostructure des asphaltenes de petrole, leur comportement en milieu naturel et en solution." Paris 6, 1990. http://www.theses.fr/1990PA066545.
Повний текст джерелаDai, Xiang. "Recognising Biomedical Names: Challenges and Solutions." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25482.
Повний текст джерелаWalsh, Jessica Claire. "Barriers and solutions to implementing evidence-based conservation." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709460.
Повний текст джерелаDonado, Garzón Leonardo David. "On multicomponent reactive transports in porous media: from the natural complexity to analitycal solutions." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/5918.
Повний текст джерелаEsta disertación doctoral estudia el transporte en medios heterogéneos cubriendo diferentes y tipos de acuíferos. Primero, el flujo y el transporte se analizan en rocas fracturadas, las cuales poseen baja permeabilidad. Estas formaciones son estudiadas usando como modelo conceptual las Redes Discretas de Fracturas, donde se considera el medio como una densa red de fracturas que se interconectan y conducen agua. Este modelo de es una alternativa válida para conceptualizar el transporte de solutos en el medio fracturado, pero tradicionalmente no se ha utilizado para analizar ni el transporte ni el flujo en una modelación de tipo problema inverso, debido a su alto costo computacional.
El transporte de solutos conservativos en medios heterogéneos puede modelarse con una ecuación efectiva que involucre un término de transferencia de masa entre la zona móvil y la zona inmóvil. La segunda parte de la disertación explora la posibilidad de extender esta idea para tener en cuenta las especies reactivas. Se parte de la consideración de que las especies están en equilibrio químico local, el cual es alcanzado instantáneamente. El impacto de la heterogeneidad del medio en el transporte efectivo es representado por un modelo de tasa de transferencia múltiple de masa (MRMT), el cual aproxima el medio a un multicontinuo de una región móvil y varias regiones inmóviles, las cuales se relacionan por una transferencia de masa cinética. Partiendo del hecho de que todas las regiones están bien mezcladas, el equilibrio global no se preserva. Esta imposición implica que las reacciones tomen lugar en todo el dominio, y sean dominadas tanto por la dispersión local como por la transferencia de masa. Se derivaron expresiones explícitas para calcular las tasas de reacción en las regiones móvil e inmóvil y se estudió el impacto de la transferencia de masa en el transporte reactivo. Las tasas de reacción pueden cambiar significativamente comparadas con aquellas que se obtendrían en un medio homogéneo. Para una amplia distribución de tiempos de residencia en las zonas inmóviles, el sistema podría tomar mucho más tiempo para equilibrar globalmente el medio comparado que para un medio homogéneo.
El último tema abordado en esta disertación es el análisis del transporte de especies bajo condiciones de cinética química o equilibrio no instantáneo. El transporte reactivo a escala local es analizado bajo dos situaciones: (i) con una reacción sencilla y (ii) con dos reacciones simultáneas: una considerada instantánea y la otra como lenta respecto al tiempo característico de transporte. En la primera situación de las dos planteadas, es posible concluir que el problema puede ser reescrito sólo en términos del estado inicial del sistema más una ecuación diferencial para la tasa de reacción.
El resultado clave es que la tasa de reacción en equilibrio depende de un término relativo a la mezcla y a la reacción cinética, la cual es de hecho el factor que controla la disponibilidad de reactantes en el sistema, y la distribución de las combinaciones lineales de las concentraciones acuosas de las especies, llamadas componentes tanto conservativas como cinéticas. Desde un punto de vista operacional, estas expresiones permiten el cálculo directo de las tasas de reacción en equilibrio sin la necesidad de calcular las concentraciones de las especies acuosas.
Transport of non-conservative species or solutes in porous or fractured media is highly influenced by heterogeneity. Additional complexity is added to the processes due to the presence of different types of chemical reactions that control the fate of species concentrations in the medium. Many of these chemical reactions are governed by mixing of waters with different geochemical signature. Mixing yields instantaneous chemical disequilibrium in the resulting mixed water, and reactions take place to re-equilibrate the system.
This dissertation studies transport in heterogeneous media covering different problems (flow, conservative transport and reactive transport) and in different aquifer types. First, we analyze flow and transport in low permeable highly fractured massifs. These are studied using the Discrete Fracture Network (DFN) approach, where a dense network of water-conducting intersecting fractures is considered. The DFN approach traditionally has lacked the possibility of analyzing transport (as well as flow) in an inverse problem framework. The actual tracer test, performed with a conservative solute (deuterium), evidences Non-Fickian behavior, characterized by tailing in the breakthrough curve.
As a consequence, transport of conservative solutes in heterogeneous media can be modeled with an effective equation involving a mass transfer term between the mobile and some immobile zones. In the second part of the thesis we explore the possibility of extending this idea to account for transport of reactive species. We start by considering species where local chemical equilibrium conditions are reached instantaneously. The impact of the medium heterogeneity on effective transport is represented by a multi rate mass transfer approach, which models the medium as a multiple continuum of one mobile and multiple immobile regions, which are related by kinetic mass transfer. Even though all regions (mobile and immobile) are assumed to be well mixed (local equilibrium), globally equilibrium is not preserved. The imposition of local equilibrium at all points implies the need for reactions to take place all through the domain, driven by both local dispersion and mass transfer. We derive explicit expressions for the reaction rates in the mobile and immobile regions and study the impact of mass transfer on reactive transport. The reaction rates can change significantly compared with the ones that would be obtained in a homogeneous media. For a broad distribution of residence times in the immobile zones, the system may take much more time to equilibrate globally than for a homogeneous medium.
The last topic addressed in this Thesis is the analysis of transport of species undergoing non-instantaneous (kinetic) chemical equilibrium. Reactive transport at the local scale is analyzed under two situations: (i) with a single kinetic reaction and (ii) with two simultaneous reactions: one considered instantaneous and the other one being slow related to the transport characteristic time. In the first problem of these problems, we find that the problem can be rewritten only in terms of the initial state of the system plus a non-linear partial differential equation for the reaction rate.
The key result is that the equilibrium reaction rate depends on a mixingrelated term, the kinetic reaction rate, which is actually controlling the availability of reactants in the system, and the distribution of (conservative and kinetic) linear combinations of aqueous species concentrations. From an operational standpoint, our expressions allow direct computation of equilibrium reaction rates without the need to calculate aqueous species concentrations. To illustrate the results, the dissolution of calcite in the presence of precipitating gypsum in a one-dimensional fully saturated system is analyzed. The example highlights the highly nonlinear and non monotonic response of the system to the controlling input parameters.