Orientador: Watson Loh / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T12:43:41Z (GMT). No. of bitstreams: 1 Bernardes_JulianadaSilva_D.pdf: 3716800 bytes, checksum: 697cfd08d77b6bb1c1d45598c8324907 (MD5) Previous issue date: 2008 / Resumo: Polieletrólitos associam-se fortemente com surfatantes de carga oposta em meio aquoso, levando a uma separação de fases que resulta em uma fase concentrada, rica em polieletrólito e surfatante, em equilíbrio com uma fase diluída constituída pelos contra-íons. A fase concentrada pode ser constituída de interessantes estruturas supramoleculares advindas das propriedades de auto-organização destes sistemas, que aliadas à possibilidade de modificaremse a geometria da mesofase e as distâncias entre os agregados, tornam estes sistemas ferramentas importantes em processos de fabricação de estruturas micro e mesoporosas e em sistemas de liberação controlada de drogas. O estudo do equilíbrio de fases de sistemas constituídos por polieletrólitos e surfatantes de cargas opostas em água não é tão simples devido ao grande número de componentes presentes no sistema, porém é possível reduzir a quantidade de componentes através da síntese do sal complexo ¿puro¿ (polieletrólito-surfatante), facilitando dessa forma a análise dos diagramas de fases gerados. Neste trabalho o comportamento de fases de sais complexos formados pelo íon surfatante hexadeciltrimetilaônio (CTA) e pelo polieletrólito (PA) em água e na presença de diferentes solventes orgânicos foi investigado. Três efeitos principais foram analisados: efeito da natureza do solvente orgânico; efeito da adição de uma série homóloga de álcoois e efeito da hidrofobicidade do contra-íon polimérico. Os resultados obtidos indicam que a polaridade do solvente orgânico utilizado influencia intensamente nas estruturas formadas pelo sal complexo. Em geral, observou-se a predominância de estruturas lamelares em sistemas contendo co-surfatantes (n-álcoois) e a predominância de estruturas hexagonais em sistemas contendo p-xileno e ciclohexano. A hidrofobicidade do contra-íon polimérico não gerou mudanças significativas nos diagramas de fases obtidos. / Abstrat: Association between charged polymers and oppositely charged surfactants in aqueous solutions may lead to phase separation forming a concentrated phase rich in polyions and surfactant ions, and a more dilute phase, which mostly contains simple ions. The concentrated phases may display a variety of supramolecular structures with diverse and interesting features due to self-assembling properties of these systems, which have found applications in the field of controlled drug delivery and in templating the synthesis of materials with tailored geometries. A complete description of the phase equilibrium in these systems is quite demanding, because addition of polyelectrolyte and oppositely charged surfactant to water leads to the formation of several components, however it is possible to reduce the number of the components by the preparation of the pure complex-salt, which allows to analyze the phase equilibrium in a controlled manner. In this work the phase behavior of complex salts formed by the surfactant ion hexadecyltrimethylammonium (CTA) and the polyacrylate (PA) in water and with different organic solvents were investigated. Three principal effects were analyzed: the effect of the organic solvent nature; the effect of n-alcohol carbon chain length and the effect of the polyelectrolyte hidrophibicity. The obtained results revealed that the organic solvent nature has a strong influence in the structure assumed by the complex salt. From the general analysis, systems containing co-surfactants (n-alcohols) a predominance of lamellar structures was observed, and in systems containing p-xylene and ciclohexane a predominance of hexagonal structures was detected. The polyelectrolyte hidrophobicity did not display significant changes in the obtained phase diagrams. / Doutorado / Físico-Química / Doutor em Ciências

Orientador: Martín Aznar / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T15:48:19Z (GMT). No. of bitstreams: 1 Barbosa_MarianaRicken_M.pdf: 3140781 bytes, checksum: ce61206a4ab10df4d9f58d21d2faa257 (MD5) Previous issue date: 2012 / Resumo: Os líquidos iônicos são compostos químicos cujas propriedades termofísicas têm sido estudadas a fim de aplicá-los em diversos processos, tais como o de separação. No caso da destilação, para realizar o projeto, otimização e a operacao do sistema, necessita-se conhecer o equilíbrio liquida-vapor, cujo calculo pode ser realizado por equações de estado cúbicas. Essas expressões contêm parâmetros de atração e repulsão que são dependentes de propriedades críticas, as quais não são possíveis de determinar experimentalmente para os líquidos iônicos, mas podem ser estimadas por grandezas mensuráveis, como, por exemplo, a velocidade do som. Neste trabalho, as propriedades críticas, temperatura de ebulição e os termos atrativo e repulsivo de equações de estado cúbicas para os líquidos iônicos baseados no íon imidazólio [C2mim] [EtSO4], [C2mim] [NTf2], [C6mim] [NTf2], [C5mim] [NTf2], [C4mim] [PF6], [C2mim] [PF6], [C6mim] [PF6], [C8mim] [NTf2], [C8mim] [PF6], [C8mim] [BF4], [C4mim] [BF4], [C6mim] [BF4] e [C4mim] [NTf2], foram determinados a partir de dados de velocidade do som, volume molar e capacidades caloríficas, minimizando uma função objetivo atraves do algoritmo genético PIKAIA. As frações molares da fase liquida do equilíbrio liquida-vapor de sistemas binários incluindo imidazólios foram calculadas pelo software Phase Equilibrium 2000 e comparadas com os dados experimentais. Os líquidos iônicos com anions [BF4]- e [NTf2]- apresentaram resultados similares de ELV para a maioria das equações de estado e regras de mistura quando se utilizou os valores de temperatura normal de ebulição, pressão e temperatura criticas obtidos pelo processo de otimização e pelo método de contribuição de grupo proposto por Valderrama e Rojas (2009). Para os imidazólios contendo íons [PF6]- e [EtSO4]-, os desvios médios relativos para as frações molares na fase liquida foram menores quando se utilizaram as propriedades termofísicas calculadas por velocidade do som e regra de mistura de van der Waals / Abstract: Ionic liquids are chemical compounds whose thermophysical properties have been studied in order to apply them in a large amount of processes, for example, separation process. In case of distillation, one needs to know liquid-vapor equilibria whose determination can be done through cubic equations of state in order to design, optimize and operate the system. In those equations, there are attractive and repulsive parameters which are dependent on critical properties that, for ionic liquids, cannot be experimentally determined but can be estimated by measurable variables, such as speed of sound. In this work, the critical properties, boiling temperature and the attractive and repulsive parameters of cubic equations of state for ionic liquids based on imidazolium [C2mim] [EtSO4], [C2mim] [NTf2], [C6mim] [NTf2], [C5mim] [NTf2], [C4mim] [PF6], [C2mim] [PF6], [C6mim] [PF6], [C8mim] [NTf2], [C8mim] [PF6], [C8mim] [BF4], [C4mim] [BF4], [C6mim] [BF4] e [C4mim] [NTf2], were determined using speed of sound, molar volume and heat capacities data, minimizing an objective function using PIKAIA genetic algorithm. Liquid mole fractions of binary liquid-vapor equilibria with imidazolium were calculated by Phase Equilibrium 2000 software and then compared with experimental data. Ionic liquids with [BF4]- and [NTf2]- anions showed similar results for most of the equations of state and mixing rules when the normal boiling temperature, critical pressure and temperature were used and estimated by an optimization procedure and group contribution method proposed by Valderrama and Rojas (2009). Imidazolium-based ionic liquids with [PF6]- and [EtSO4]- ions had the smallest relative mean deviations of liquid mole fractions when the thermophysical properties were calculated by speed of sound and the van der Waals's mixing rule were used / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Based on Ian Steedman's seminal contribution "Consumption Takes Time", we propose a formal activity-based model for consumer behaviour. The model simultaneously incorporates choices over consumption time, as well as quantities and qualities of products consumed. We identify and examine preconditions for satiation with products and draw implications for economic policy. Satiation with products explains the limited effects of price or income changes on demand and questions the pertinence of economic growth for development. It further highlights the relevance of working time reductions for well-being. (authors' abstract)

No description available.

Orientadores: Reginaldo Guirardello, Charlles Rubber de Almeida Abreu / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T16:13:40Z (GMT). No. of bitstreams: 1 Borghi_DanieladeFreitas_D.pdf: 3030117 bytes, checksum: b4aac454256a7b9c27deaa4219de53e7 (MD5) Previous issue date: 2014 / Resumo: Atualmente, a produção de biodiesel tem sido objeto de estudo em diversos países devido à previsão de exaustão das fontes petrolíferas e também às suas características, já que este combustível possui vantagens ambientais em relação à emissão de gases poluentes. Trata-se de uma fonte de energia renovável e as matérias-primas para a sua produção são abundantes no Brasil. O biodiesel é produzido através da transesterificação de gordura animal ou óleo vegetal. Porém, os reagentes (óleo e etanol/metanol) e os produtos (éster metílico/etílico de ácidos graxos e glicerol) são parcialmente solúveis durante o processo. Assim, o conhecimento do equilíbrio de fases das misturas envolvidas em sua produção é um fator importante na otimização das condições da reação e da separação final dos produtos. Dentro deste contexto, o presente trabalho teve como objetivo realizar cálculos de equilíbrio de misturas de compostos envolvidos nos processos de produção de biodiesel, utilizando técnicas de otimização global. A modelagem matemática requer o conhecimento de propriedades termoquímicas de todas as espécies envolvidas e do equilíbrio de fases do sistema. Tais informações foram obtidas a partir do uso de uma metodologia utilizando o software Gaussian 03 e o método COSMO-SAC. E o equilíbrio de fases foi realizado através da minimização da energia de Gibbs do sistema. Foram obtidos perfis sigma a serem utilizados no método COSMO-SAC através do software MOPAC. Eles foram comparados com os perfis sigma de um banco de dados do grupo Virginia Tech (VT-2005) e percebeu-se que, apesar de apresentarem diferenças, qualitativamente eles possuem muitas semelhanças. Foi verificada a eficiência do modelo COSMO-SAC em predizer os coeficientes de atividade de uma mistura binária de metanol e glicerol e observou-se que os desvios médios absolutos entre os valores experimentais e os calculados estão acima de 27%, o que é um desvio muito alto. Além disso, utilizou-se a metodologia da minimização da energia de Gibbs para a realização do cálculo de equilíbrio de fases de misturas binárias contendo água, metanol e glicerol, com o auxílio da ferramenta computacional GAMS. Os desvios médios absolutos obtidos variaram de 1,55 a 7,96%, dependendo da mistura. Portanto, este modelo ainda precisa de refinamentos para se tornar uma ferramenta confiável / Abstract: Biodiesel production has been studied in several countries due to the forecast of petroleum sources depletion and to its characteristics, since this fuel has environmental advantages due to lower pollutant gas emissions. It is a renewable source of energy and raw materials for its production are abundant in Brazil. Biodiesel is produced by transesterification of vegetable oils or animal fat. However, reagents (oil and ethanol/methanol) and products (fatty acids ethyl/methyl ester and glycerol) are partially soluble in the process. Therefore, knowledge of the phase equilibrium mixtures involved in its production is an important factor in optimizing the reaction conditions and separation of the final products. In this context, this work aims to perform equilibrium calculations of mixtures of compounds involved in the biodiesel production process using global optimization techniques. Mathematical modeling requires the knowledge of thermochemical properties of all the species involved and the phase equilibrium of the system. Such information was obtained with a methodology using the Gaussian 03 software and COSMO-SAC method. The phase equilibrium was achieved by minimizing the Gibbs energy of the system. Sigma profiles to be used in COSMO-SAC method were obtained using the MOPAC software. It was compared with the sigma profiles from Virginia Tech group database (VT-2005) and it was realized that, despite having differences, qualitatively it is similar. The efficiency of COSMO-SAC model to predict the activity coefficients of a binary mixture of methanol and glycerol was verified and it was found that the average absolute deviation between experimental and calculated values are above 27%, a very high value. In addition, a methodology of Gibbs energy minimization we used to perform the calculation of the phase equilibrium of binary mixtures containing water, methanol and glycerol, with the GAMS software. The mean absolute deviations obtained ranged from 1.55 to 7.96% depending on the mixure. Therefore, this model still needs refinements to become a reliable tool / Doutorado / Engenharia Química / Doutora em Engenharia Quimica

Le travail de thèse portant sur « le rôle d’un champ électrique intense sur les phénomènes thermodynamiques et cinétiques mis en jeu au cours de la croissance cristalline d’oxydes », consiste à mettre en œuvre une nouvelle voie de croissance de monocristaux d’oxydes aux propriétés remarquables. A travers l’utilisation d’un champ électrique intense au cours du processus de solidification, nous souhaitons agir sur les équilibres thermodynamiques propres à la cristallisation ainsi que moduler les conditions cinétiques de formation des cristaux dans le but d’obtenir des phases nouvelles, des structures particulières et ainsi obtenir des matériaux aux propriétés nouvelles, exacerbées ou contrôlées. Pour cela, un dispositif spécifique a été conçu dans le but d’introduire, au sein d’un bâti de croissance existant (le four à image), une source de champ électrique intense (plusieurs kV/cm). Des études de modélisation, des observations in situ à la croissance et des analyses de la microstructure et des propriétés des matériaux ont été menées en vue d’appréhender les mécanismes d’influence du champ électrique sur les processus de germination-croissance des cristaux. Ces études soulèvent la grande complexité des interactions entre le champ électrique externe et les milieux ioniques solide et liquide portés à hautes température (conducteurs polarisables). Une influence particulière de l’énergie électrostatique sur les équilibres de phases a été démontrée, notamment à travers une élévation significative de la température de fusion des matériaux en présence du champ électrique [1]. Les résultats associés révèlent que les modèles établis jusqu’à présent [2-4], à savoir une perturbation de l’énergie libre à travers la polarisation des milieux, ne rendent pas compte de l’ensemble des mécanismes sous-jacents à la présence du champ électrique externe. Un modèle de double couche électrique à l’interface de croissance où un champ local intense est créé par des distributions surfaciques de charges semble correspondre au mieux à la description de la nouvelle organisation chimique induite sous champ électrique de manière à rétablir l’équilibre électrostatique. De fait, à l’interface de croissance, les potentiels chimiques des espèces sont principalement influencés par la différence de potentiel électrique locale, déterminée par la nature de la double couche. Par ailleurs, les analyses des microstructures de croissance, notamment ciblées sur l’étape de germination, révèlent que des mécanismes dynamiques de transport de charges couplés aux transferts de chaleur (effets thermoélectriques) agissent très certainement sur les conditions de formation des cristaux. Des analyses élémentaires de cristaux dopés formés sous champ électrique démontrent la capacité de ce dernier à agir sur la ségrégation des espèces et donc, sur les conditions d’équilibres électrostatiques à l’interface de croissance. On distingue ici la possibilité de contrôler, dans une certaine mesure, la stœchiométrie des cristaux formés ainsi que l’incorporation d’espèces qui confèrent aux matériaux des propriétés particulières. En outre, des effets observés sur des orientations de croissance privilégiées sous champ électrique ou encore la formation de défauts par la création de charges d’espace laissent à penser qu’une polarisation in situ de matériaux piézoélectriques ou ferroélectriques serait un objectif atteignable à terme. / This thesis work named “Role of an intense electric field on thermodynamic and kinetic conditions of oxides' crystal growth” lies on the elaboration of a novel way to conduct crystal growth of bulk functional oxides. With the use of an intense electric field during growth, we wish to act on the thermodynamic equilibria taking place during the solidification process and to modulate the kinetic conditions of crystals’ formation with the aim to achieve new crystal phases and structures in order to produce materials with novel, enhanced or controlled properties. Therefore, a specific device of intense electric field production (several kV/cm) that fits inside a mirror furnace has been conceived. The interactions between the external electric field and the ionic solid and liquid media have been investigated through modeling studies, growth in situ observations and analysis of materials’ structure that reveal a complex situation where multiple mechanisms of influence act on the nucleation and growth processes. A notable impact of the electrostatic energy on thermodynamic equilibria has been evidenced, especially on materials’ melting temperature [1]. Moreover, results suggest that the existing models that describe the shifts in thermodynamic equilibria due to displacements of phases’ free energies through a polarization mechanism [2-4] are not sufficient because of the variety of mechanisms that are in stake. The picture of an electric double layer formed at the growth interface where an intense local electric field is created by surface charge distributions seems to be the most reliable conceptualization of the induced chemical organization taking place in order to restore the electrostatic equilibrium under the influence of an external electric field. Thus, at the growth front, the chemical potential of species is mostly influence by the local electric potential that depends upon the electric double layer’s nature. Besides, analysis of the growth microstructures, especially during the nucleation process, reveal that coupling of dynamic charges and heat transports, therefore thermoelectric flux, act upon the growth conditions of crystals. Chemical analysis of doped crystals grown under electric field show that the latter is capable of influencing the segregation of species, which reveals its action on the electrostatic conditions of equilibrium at the interface. Herein, we notice the possibility to control, in a certain extent, the stoichiometry of crystals and the incorporation of chemical elements that impart crystals particular properties. Moreover, some observations of enhanced growth orientations under electric field or some defects formation creating space charges give insights on the possibilities to, at term, conduct in situ polarization of piezoelectric or ferroelectric materials throughout growth under electric field. Finally, an opening on hydrodynamic effects bound to the external electric field reveal the great potentials of the use of an external electric field as an additional parameter to the crystal growth of functional oxides.

Congestion charging is a now accepted means of influencing traffic to behave in a more socio-economic optimal way, like e.g. in the Stockholm project. Already early work, in the 1920’s, showed that road use can be inefficient due externalities, i.e. that users don’t experience their own (negative) effect on other users: an extra car on a traffic link causes delays for other cars, but the driver himself does not experience this cost.In the 1950’s it was further shown - for a congested road network with homogeneous users – that if each user is charged a toll equal to the total value of time loss incurred on other users of the network, then -if we have fixed travel demand - this will induce an equilibrium that is system optimal in the sense that the total cost of network usage is minimal (assuming that all users have fixed and identical time values).  But toll charges need to be levied in monetary units, and different travelers have different values of time. Therefore, to account for the effects of tolls, and to be able to compute equilibria, one needs to introduce different user classes, differing in their time values. In this thesis, consisting of four papers, we study congestion pricing of road networks with users differing only in their time values. In particular, we analyze marginal social cost (MSC) pricing, a tolling scheme that charges each user a penalty corresponding to the value of the delays inflicted on other users, as well as its implementation through fixed tolls. Paper III contains the main theoretical work of the thesis. In that paper we show that the variational inequalities characterizing the equilibria in question can be stated in symmetric or non-symmetric forms. The symmetric forms correspond to optimization problems, convex in the fixed-toll case and non-convex in the MSC case, which hence may have multiple equilibria. The objective of the latter problem is the total value of travel time, which thus is minimized at the global optima of that problem. Implementing close-to-optimal MSC tolls as fixed tolls leads to equilibria with possibly non-unique class specific flows, but with identical close-to-optimal values of the total value of travel time. Finally we give an adaptation, to the MSC setting, of the Frank-Wolfe algorithm, which is further applied to some test cases, including Stockholm. Paper I is an early application using Frank-Wolfe, after having realized the possibility to symmetrize the problem. Paper II gives a convexification of non-convex equilibrium problem for MSC tolls. We have used these convexifications to compute lower bounds when computing equilibria. Paper IV is a short note commenting some flaws in two papers by Dial on MSC tolls. / <p>QC 20100610</p>

No description available.

In this work, we will present experimental and theoretical results concerning adsorption und phase equilibria being influenced by kinetic effects.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20153号 / 理博第4238号 / 新制||理||1609(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)教授 坂上 貴之, 教授 上田 哲生, 教授 國府 寛司 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM