No description available.

Competitive-Consecutive and Competitive-Parallel reactions are both mixing sensitive reactions; the yield of desired product from these reactions depends on how fast the reactants are brought together. Recent experimental results have suggested that the mixing effect may depend strongly on the stoichiometry of the reactions. To investigate this, a 1-D, non-dimensional, reaction-diffusion model at the micro-mixing scale has been developed. Assuming constant mass concentration and diffusivities, systems of PDEs have been derived on a mass fraction basis for both types of reactions. A single general Damkhler number and specific dimensionless reaction rate ratios were derived for both reaction schemes. The resulting dimensionless equations were simulated to investigate the effects of mixing, reaction rate ratio and stoichiometry of the reactions. It was found that decreasing the striation thickness and the dimensionless rate ratio maximizes yield for both types of reactions and that the stoichiometry has a considerable effect on yield. All three variables were found to interact strongly. Phase plots showing the interactions between the three variables were developed.

No description available.

The thesis is dealing with mixing processes havingapplication to ground improvement by deep mixing. The mainobjectives of the thesis is to make a contribution to knowledgeof the basic mechanisms in mixing binding agents into soil andimprove the knowledge concerning factors that influence theuniformity of stabilised soil. A great part of the work consists of a literature surveywith particular emphasis on literature on the processindustries. This review forms a basis for a profounddescription and discussion of the mixing process and factorsaffecting the process in connection with deep mixingmethods. The thesis presents a method for a simple field test for thestudy of influential factors in the mixing process. A number offactors in the installation process of lime-cement columns havebeen studied in two field tests using statistical multifactorexperiment design. The effects of retrieval rate, number ofmixing blades, rotation speed, air pressure in the storagetank, and diameter of the binder outlet on the stabilisationeffect and the coefficient of variation determined byhand-operated penetrometer tests for excavated lime-cementcolumns, were studied. The literature review, the description of the mixingprocess, and the results from the field tests provide a morebalanced picture of the mixing process and are expected to beuseful in connection to ground improvement projects and thedevelopment of mixing equipments. The concept of sufficient mixture quality, i.e. theinteraction between the mixing process and the mechanicalsystem, is discussed in the last section. By means ofgeostatistical methods, the analysis considers thevolume-variability relationship with reference to strengthproperties. According to the analysis, the design values forstrength properties depends on the mechanical system, the scaleof scrutiny, the spatial correlation structure, and the conceptof safety, i.e. the concept of sufficient mixture quality isproblem specific. Key words:Deep Mixing, Lime cement columns, Mixingmechanisms, Mixture quality, Field test, ANOVA, Variancereduction.

Thesis (doctoral)--Delft University of Technology, Delft, The Netherlands. / Description based on print version record. Includes bibliographical references (p. [135]-144).

Resumo: De todas as operações, a agitação de fluidos, a troca de calor em tanques e a mistura de pós são, sem dúvida, as mais usuais, principalmente, na indústria de alimentos. Embora exigindo um estudo em separado, é comum estas operações unitárias estarem presentes, em instantes diferentes, no mesmo processo de fabricação. O propósito deste trabalho é enfatizar procedimentos de projeto para problemas práticos nas indústrias de processos envolvendo estas três operações. O modelo matemático proposto para a agitação de fluidos foi aplicado na substituição das tradicionais âncoras por impelidores de pás retas e inclinadas no processamento do suco concentrado de laranja. Observou-se que o tempo de permanência do suco no tanque de resfriamento caiu de quarenta para cinco minutos em decorrência da maior ação de mistura provocada pelas pás retas. O modelo proposto acompanha bem as exigências de potências requeridas pelo suco na medida em que é resfriado...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In all operations, the fluid agitation, the heat tranfer in tanks and the solids mixing are, undoubtedly the more usual, mainly in the food industry. Although requering a present research, is usual this unitary operations to be process. The purpose of this work is to emphasize design project proceeding for practical problems in the process industry involving this three operations. The mathematical model proposed to fluid agitation, was used in the substitution to the traditionals anchors by pitches flat blades in the concentrated orange in cooling tank reduce in 35 minutes resulting of the greater mixture action of the pitches flat blades. That model follow the required power for the juice...(Complete abstract click electronic access below)

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-02-22T18:13:44Z No. of bitstreams: 1 williamdasilvapedretti.pdf: 1030447 bytes, checksum: aee304fa3b25d381a6cc4ad1fe2fd1e5 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-02-26T14:12:49Z (GMT) No. of bitstreams: 1 williamdasilvapedretti.pdf: 1030447 bytes, checksum: aee304fa3b25d381a6cc4ad1fe2fd1e5 (MD5) / Made available in DSpace on 2016-02-26T14:12:49Z (GMT). No. of bitstreams: 1 williamdasilvapedretti.pdf: 1030447 bytes, checksum: aee304fa3b25d381a6cc4ad1fe2fd1e5 (MD5) Previous issue date: 2014-03-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Desde o trabalho de Pomeau e Maneville [27] o estudo de intermitência vem ocorrendo cada vez mais ao longo dos anos. Gaspard e Wang [17] introduziram uma função geradora de sequências de renovação decorrentes da distribuição de tempos de retorno, e a partir disto vários trabalhos vêm sendo desenvolvidos nesse ambiente, devido às ricas propriedades que possuem. Neste trabalho estaremos interessados em obter uma estimativa polinomial exata para o comportamento assintótico da taxa de mixing quando a medida invariante é nita e da taxa de scaling quando a medida é in nita, ambos casos abordados por Isola [20]. Para isto analisaremos o comportamento assintótico dos coe cientes da série de Taylor obtidos da função geradora da sequência de renovação. Esta série de ne uma função holomorfa no disco aberto unitário que converge em todo ponto exceto para z = 1, onde possui uma singularidade não-polar. / Since the work of Pomeau and Maneville [27] the study of intermittency has been happening increasingly over the years. Gaspard and Wang [17] introduced a generating function of renewal sequences arising from the distribution of return times, and from this several studies have been developed in this environment due to the rich properties they have. In this work we are interested to obtain an exact polynomial estimate for the asymptotic behavior of the mixing rate when the invariant measure is nite and of the scaling rate when the measure is in nite, both cases addressed by Isola [20]. For this we analyze the asymptotic behavior of the coe cients of the Taylor series obtained from the generating function of the renewal sequence. This series de nes a holomorphic function in the unit open disk and it converges at every point except for z = 1 where it has a non-polar singularity.

Cópulas tem se tornado uma importante ferramenta para descrever e analisar a estrutura de dependência entre variáveis aleatórias e processos estocásticos. Recentemente, surgiram alguns métodos de estimação não paramétricos, utilizando kernels e ondaletas. Neste contexto, sabendo que cópulas podem ser escritas como expansão em ondaletas, foi proposto um estimador não paramétrico via ondaletas para a função cópula para dados independentes e de séries temporais, considerando processos alfa-mixing. Este estimador tem como característica principal estimar diretamente a função cópula, sem fazer suposição alguma sobre a distribuição dos dados e sem ajustes prévios de modelos ARMA - GARCH, como é feito em ajuste paramétrico para cópulas. Foram calculadas taxas de convergência para o estimador proposto em ambos os casos, mostrando sua consistência. Foram feitos também alguns estudos de simulação, além de aplicações a dados reais. / Copulas are important tools for describing the dependence structure between random variables and stochastic processes. Recently some nonparametric estimation procedures have appeared, using kernels and wavelets. In this context, knowing that a copula function can be expanded in a wavelet basis, we have proposed a nonparametric copula estimation procedure through wavelets for independent data and times series under alpha-mixing condition. The main feature of this estimator is the copula function estimation without assumptions about the data distribution and without ARMA - GARCH modeling, like in parametric copula estimation. Convergence rates for the estimator were computed, showing the estimator consistency. Some simulation studies were made, as well as analysis of real data sets.

Cette thèse présente un nouveau modèle SCRAM (Size and Composition Resolved Aerosol Model) pour simuler la dynamique des particules dans l'atmosphère (nucléation, coagulation, condensation / évaporation) en prenant en compte leur état de mélange, et elle évalue la performance de SCRAM dans des simulations 3D de qualité de l'air. Le travail peut être divisé en quatre parties. Premièrement, la notion de mélange externe est introduite, ainsi que la modélisation de la dynamique des aérosols. Ensuite, le développement du modèle SCRAM est présenté avec des tests de validation. Dans SCRAM, pour définir les compositions, on discrétise d'abord en sections les fractions massiques des composés chimiques des particules ou d'ensembles de composés chimiques. Les compositions des particules sont ensuite définies par les combinaisons des sections de fractions massiques. Les trois processus principaux impliqués dans la dynamique des aérosols (la coagulation, la condensation / évaporation et la nucléation) sont inclus dans SCRAM. SCRAM est validé par comparaison avec des simulations « académiques » publiées dans la littérature de coagulation et condensation/évaporation pour des particules en mélange interne. L'impact de l'hypothèse de mélange externe pour ces simulations est notamment étudié. L'impact du degré de mélange sur les concentrations de particules est ensuite étudié dans une simulation 0-D en utilisant des données représentatives d'un site trafic en Ile de France. L'influence relative sur l'état de mélange des différents processus influençant la dynamique des particules (condensation / évaporation, coagulation) et de l'algorithme utilisé pour modéliser la condensation / évaporation (hypothèse d'équilibre entre les phases gazeuse et particulaire, ou bien modélisation dynamique des échanges gaz/particules) est étudiée. Ensuite, SCRAM est intégré dans la plate-forme de qualité de l'air Polyphemus et utilisé pour effectuer des simulations sur l'Ile de France pendant l'été 2009. Une évaluation par comparaison à des observations a montré que SCRAM donne des résultats satisfaisants pour les concentrations de PM2.5/PM10 et l'épaisseur optique des aérosols. Le modèle est utilisé pour analyser l'état de mélange des particules, ainsi que l'impact des différentes hypothèses de mélange (mélange interne MI ou mélange externe ME) sur la formation des particules et leurs propriétés. Enfin, deux simulations, une avec l'hypothèse de MI et une autre avec l'hypothèse de ME, sont effectuées entre le 15 janvier et le 11 février 2010, pendant la campagne hiver MEGAPOLI (Megacities : Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) durant laquelle les compositions des particules individuelles ont été mesurées. Les concentrations simulées de composés chimiques (concentration massique totale de différents composés) et les concentrations des classes de particules individuelles (une classe est définie par sa taille et sa composition chimique) sont comparées avec les observations à un site urbain parisien. Un indicateur de la diversité des particules et de l'état de mélange est calculé à partir des simulations et comparé à celui calculé à partir des mesures. Le modèle se compare bien aux observations avec un état de mélange moyen simulé de 69% contre 59% dans les observations, indiquant que les particules ne sont pas en mélange interne sur Paris / This thesis present a newly developed size-composition resolved aerosol model (SCRAM), which is able to simulate the dynamics of externally-mixed particles in the atmosphere, and it evaluates its performance in three-dimensional air-quality simulations. The main work is split into four parts. First, the research context of external mixing and aerosol modelling is introduced. Secondly, the development of the SCRAM box model is presented along with validation tests. Each particle composition is defined by the combination of mass-fraction sections of its chemical components or aggregates of components. The three main processes involved in aerosol dynamic (nucleation, coagulation, condensation/evaporation) are included in SCRAM. The model is first validated by comparisons with published reference solutions for coagulation and condensation/evaporation of internally-mixed particles. The particle mixing state is investigated in a 0-D simulation using data representative of air pollution at a traffic site in Paris. The relative influence on the mixing state of the different aerosol processes and of the algorithm used to model condensation/evaporation (dynamic evolution or bulk equilibrium between particles and gas) is studied. Then, SCRAM is integrated into the Polyphemus air quality platform and used to conduct simulations over Greater Paris during the summer period of 2009. This evaluation showed that SCRAM gives satisfactory results for both PM2.5/PM10 concentrations and aerosol optical depths, as assessed from comparisons to observations. Besides, the model allows us to analyze the particle mixing state, as well as the impact of the mixing state assumption made in the modelling on particle formation, aerosols optical properties, and cloud condensation nuclei activation. Finally, two simulations are conducted during the winter campaign of MEGAPOLI (Megacities : Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) in January 2010 where the composition of individual particles was measured. One simulation assumes that particles are internally mixed, while the other explicitly models the mixing state with SCRAM. The simulation results of both bulk concentrations of chemical species and concentrations of individual particle classes are compared with the measurements. Then, the single particle diversity and the mixing-state index are computed using a quantification approach based on information-theoretic entropy, and they are compared to those derived from the measurements at a urban site in Paris: the simulated mixing-state index is equal to 69% against 59% from the measurements, indicating that particles are not internally mixed over Paris

Le Soil-Mixing consiste à traiter le sol avec un liant hydraulique en le mélangeant mécaniquement en place pour améliorer ses propriétés mécaniques. Son coté économique ainsi que son faible impact environnemental ont fait de cette méthode jusque là cantonnée à l'amélioration de sols compressibles ou à forte teneur en matière organique une alternative attrayante aux méthodes traditionnelles de renforcements des sols, de soutènements (temporaires voire définitifs), de fondations et de travaux d'étanchéités. Mais avec cette augmentation de la demande, les exigences nouvelles concernant la méthode et le matériau sont apparues.De nombreuses études permettent d'apporter des éléments de réponses. Cependant, il n'existe pas d'étude paramétrique globale étudiant à la fois l'impact du type de sol et de la quantité d'eau sur la caractérisation du matériau Soil-Mixing et qui permettrait d'améliorer les méthodes de dosage ainsi que les méthodes de dimensionnement des ouvrages en Soil-Mixing.Un mélange sol-ciment est composé majoritairement de sol. Le ciment ne représentera au maximum que 30% du mélange. L'approche adoptée est donc plutôt celle du domaine de la géotechnique que des bétons hydrauliques. Nous avons pris le parti de baser notre travail sur une étude de laboratoire, en réalisant des mélanges dits “de référence”. Trois sables et cinq sols fins ont été traités en faisant varier à chaque fois les quantités de ciment et d'eau, afin d'observer l'influence de la granulométrie, de l'argilosité et de la quantité d'eau présente dans le mélange sur la résistance, la rigidité et la déformation à la rupture du matériau. Par ailleurs, des sols reconstitués à base de sable et de sol fin ont été traités afin d'étudier l'impact des fines et de leur nature sur la résistance du matériau. En parallèle, le suivi de différents chantiers nous a permis d'étudier la mise en œuvre de la méthode, l'homogénéité du matériau réalisé in situ, et de comparer les résultats obtenus avec ceux de l'étude paramétrique. Les retombées de ce travail sont la création d'abaques reliant la résistance au dosage en ciment et au rapport C/E, ainsi qu'un tableau de synthèse de données expérimentales des différentes propriétés mécaniques du matériau Soil-Mixing (en fonction de la nature du sol rencontré), et des formules permettant pour les sols grenus de prédire la résistance à 7 et 28 jours en fonction du pourcentage de fines dans le sol et du dosage en ciment / The Soil-Mixing consists in mixing a hydraulic binder into the soil mechanically in order to improve its mechanical properties. Because of its economical as well as its sustainable advantages, this method so far confined to the improvement of compressible or high organic content soils has become an attractive alternative to traditional methods for soil reinforcement, retaining walls (temporary or final), foundations and cutoff walls. But these new applications imply new requirements on the method as well as on the material. Many studies on the subject provide some answers. However, there is no comprehensive parametric study examining both the impact of soil type and the amount of water on the characterization of the Soil-Mixing material and would improve the testing methods and methods for design of structures in Soil-Mixing.Soil-cement mixtures are predominantly composed of soil. The cement will represent at most 30% of the mixture. That is why we have chosen to follow a geotechnical approach rather than the concrete approach for this project.We followed an experimental program based on a laboratory study, realizing mixes called "reference" mixes. Three sand soil and five fine soils were treated by varying each time the quantities of cement and water to observe the influence of particle size, clay content and the amount of water present in the mixes on the resistance of the material, stiffness and failure strain. In addition, soils made from sand and fine soils were reconstituted and treated to study the impact of fines and their nature on the strength of the material.In parallel, monitoring of various projects has enabled us to study the implementation of the method, the homogeneity of the material produced in situ, and to compare the results with those of the parametric study. The results of this work are the creation of abaci connecting the resistance to the cement content and C/E ratio, and a summary table of experimental data of different mechanical properties of the Soil-Mixing material (depending on the nature of the soil), and formulas for granular soils predicting the strength after 7 and 28 days of curing depending on the percentage of fines in the soil and on cement content