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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Computation experimental DIC hybrid strategy for robust 3D ductile plastic law identification / Calcul expérimental d'une stratégie hybride DIC pour l'identification de la loi plastique ductile robuste en 3D

Muhibullah, . 27 November 2012 (has links)
La validation du modèle de réponse globale des échantillons ou des structures présente des lacunes qui peuvent être surmontés par l'utilisation de techniques de mesure de plein champ. Les techniques de mesure plein champ offrent la possibilité d'acquérir une quantité importante de données expérimentales qui pourraient être utiles dans le cadre de l'identification des paramètres de la Loi de comportement. Parmi les techniques de mesure de champ complet, le plus populaire est la corrélation d'images mono et stéréo. Les stratégies existantes pour rendre l'utilisation des données de plein champ comme la méthode de champ virtuel, la méthode écart d'équilibre, la méthode de Gap équation Constitutive et la méthode de réciprocité ont été limitées à des applications 2D. Cependant, pour un échantillon d'épaisseur finie, les effets 3D doivent être remplis. Plus important encore, dans le cas de la plasticité, triaxialité du stress joue un rôle important. Son effet doit donc être inscrits dans la modélisation du comportement de la matière. Ainsi, dans cette thèse, nous proposons une méthode pour identifier les paramètres d'une loi de comportement élasto-plastique dans lequel le modèle mécanique peut comporter cinématique 3D. La stratégie s'est avérée être le bruit robuste, presque indépendamment de la conjecture de paramètre initial et de raffinement de maillage et permet de différencier les modèles de comportement avec la même réponse globale sur la base de l'erreur de corrélation moyenne. L'identification est avérée bon pour une ou plusieurs caméras. La validation de la stratégie est faite d'acier inoxydable. La réponse globale du déplacement de charge identifié de la stratégie avec la corrélation d'image mécanique mono et stéréo est très proche des expériences. Enfin, les paramètres du matériau ont été identifiés avec l’estimation initial très différents mais tous convergent vers les mêmes valeurs finales qui montrent la solidité de la stratégie proposée. / The objective of the thesis is to formulate a strategy that gives a robust identification of constitutive law from full-field measurements taking into account 3D effects. Model validation from global response of samples or structures has shortcomings that can be overcome by the use of full-field measurement techniques. Full-field measurement techniques offer the opportunity to acquire large amount of experimental data that might be useful in the context of identification of constitutive law parameters. Among the full field measurement techniques the most popular is digital and stereo image correlation. The existing strategies to make use of full-field data like the Virtual Field Method, the Equilibrium Gap Method, the Constitutive Equation Gap Method and the Reciprocity Method were limited to 2D applications. However, for a specimen with finite thickness 3D effects must be included. Most importantly, for the case of plasticity, stress triaxiality plays an important role. Its effect must therefore be accounted for in the modelling of the constitutive behaviour of the material. Thus in this thesis we propose a method to identify the parameters of an elasto-plastic constitutive law in which the mechanical model can have 3D kinematics. The strategy has been shown to be noise robust, almost independent of initial parameter guess and mesh refinement and allows differentiating between constitutive models with same global response on the basis of mean correlation error. The identification is shown to be good for both single and multiple cameras. The strategy validation is done for stainless steel. The global identified load displacement response of the strategy for mono and stereo mechanical image correlation is very close to the experiments. Lastly, the material parameters have been identified with very different initial guess but all converge to the same final values which show the robustness of the proposed strategy.
12

Transferts couplés chaleur/masse dans les matériaux de construction biosourcés : investigation expérimentale et théorique du non-équilibre local / Coupled heat and mass transfers in biosourced construction materials : experimental and theoretical investigation of local non-equilibrium

Challansonnex, Arnaud 19 March 2019 (has links)
L’intérêt croissant pour les matériaux biosourcés dans le domaine de la construction se heurte à des difficultés quant à la simulation de leur comportement hygrothermique. En particulier, les matériaux isolants tels que les panneaux de fibres concentrent toutes les difficultés car ils sont peu conducteurs thermiquement, très hygroscopiques et très diffusifs à la vapeur d’eau. Conséquemment, en régime transitoire le couplage chaleur masse est exacerbé et les phases de l’eau ne sont pas à l’équilibre localement.Afin de mettre en évidence ce second phénomène, un nouveau dispositif expérimental a été développé. Il permet de soumettre un échantillon de quelques centimètres d’épaisseur à une perturbation de l’humidité relative sur sa face avant puis de mesurer simultanément l’évolution de l’humidité relative sur sa face arrière et de sa masse. En situation de non-équilibre, il existe un déphasage entre ces deux grandeurs que la formulation de transferts couplés classique n’arrive pas à prédire. Afin d’obtenir une prédiction correcte, une nouvelle formulation a été utilisée. Celle-ci se base sur l’emploi de fonctions mémoires caractérisant la diffusion microscopique. De manière à démontrer la capacité prédictive de la nouvelle formulation, ces fonctions ont été déterminées avec des essais gravimétriques réalisés sur de très petits échantillons à l’aide d’une balance à suspension magnétique. En parallèle, une analyse rigoureuse du couplage chaleur masse dans ces matériaux a permis de souligner l’impact sur leur caractérisation de différents paramètres macroscopiques.L’utilisation de la nouvelle formulation alimentée par les fonctions mémoires et les différents paramètres macroscopiques permet une excellente prédiction de l’humidité relative et de la masse. Cette nouvelle formulation validée expérimentalement est désormais utilisable dans des logiciels de simulation énergétique du bâtiment. / The growing interest in biosourced materials in the construction sector is confronted with difficulties in simulating their hygrothermal behavior. Insulating materials such as fiberboard concentrate all the difficulties because they are not very thermally conductive, very hygroscopic and very diffusive to water vapor. Consequently, in transient state, heat and mass coupling is exacerbated, and the phases of water are not in equilibrium locally.In order to highlight this second phenomenon, a new experimental device has been developed. It allows to subject a sample a few centimeters thick to a disturbance of relative humidity on its front face and then to simultaneously measure the evolution of relative humidity on its back face and its mass. In a situation of non-equilibrium, there is a phase shift between these two quantities that the classic coupled transfer formulation cannot predict. In order to obtain a correct prediction, a new formulation was used. It is based on the use of memory functions characterizing microscopic diffusion. In order to demonstrate the predictive capacity of the new formulation, these functions have been determined with gravimetric tests performed on very small samples using a magnetic suspension balance. In parallel, a rigorous analysis of the heat and mass coupling in these materials made it possible to highlight the impact of different macroscopic parameters on their characterization.The use of the new formulation fed by the identified memory functions and the various macroscopic parameters allows an excellent prediction of relative humidity and mass. This new formulation, experimentally validated, can now be used in energy simulation of the building.
13

Development and Validation of Methods for Characterization of Multi-Component Systems in Preparative LC / Utveckling och Validering av Metoder för Karaktärisering av Flerkomponentsystem vid Preparativ Vätskekromatografi

Arnell, Robert January 2006 (has links)
<p>This thesis concerns the development and validation of methods for characterization of multi-component preparative LC systems. Measurements of competitive adsorption isotherms are performed to gain detailed information about the interactions inside the chromatography column. This information increases our understanding of the separation process and makes it possible to perform computer simulations and numerical optimizations to find optimal operating conditions.</p><p>The methods under focus are called “the tracer-pulse method”, “the inverse method”, and “the inverse method on plateaus”. They are extensions of existing methods, with new experimental and numerical procedures to enable rapid and accurate multi-component adsorption isotherm determination. In the validation it was shown that they can produce results agreeing with traditional methods and that the acquired adsorption isotherm parameters can be used in simulations to accurately predict the outcome of preparative LC separations.</p><p>The methods were used to characterize several complex LC systems and two phenomena were discovered and theoretically treated: 1) The presence of invisible deformed peaks in single-component systems. 2) Peak deformations encountered with modern chiral stationary phases, caused by strongly adsorbed eluent additives. The latter type of deformation was highly tuneable and it was possible to adjust the enantiomer peak shapes so that the peaks tailed in opposite directions with the sharp sides in between, yielding baseline resolution at remarkably high sample loads.</p><p>In a final applied study both the LC-based perturbation peak method and a biosensor method based on surface plasmon resonance (SPR) were used for the first time for detailed characterization of chiral drug-protein interactions. The fundamental properties of the two very different methods were compared and it was found that the LC method is more suitable for multi-component analysis and that the SPR method is more suitable for stronger interactions.</p>
14

Development and Validation of Methods for Characterization of Multi-Component Systems in Preparative LC / Utveckling och Validering av Metoder för Karaktärisering av Flerkomponentsystem vid Preparativ Vätskekromatografi

Arnell, Robert January 2006 (has links)
This thesis concerns the development and validation of methods for characterization of multi-component preparative LC systems. Measurements of competitive adsorption isotherms are performed to gain detailed information about the interactions inside the chromatography column. This information increases our understanding of the separation process and makes it possible to perform computer simulations and numerical optimizations to find optimal operating conditions. The methods under focus are called “the tracer-pulse method”, “the inverse method”, and “the inverse method on plateaus”. They are extensions of existing methods, with new experimental and numerical procedures to enable rapid and accurate multi-component adsorption isotherm determination. In the validation it was shown that they can produce results agreeing with traditional methods and that the acquired adsorption isotherm parameters can be used in simulations to accurately predict the outcome of preparative LC separations. The methods were used to characterize several complex LC systems and two phenomena were discovered and theoretically treated: 1) The presence of invisible deformed peaks in single-component systems. 2) Peak deformations encountered with modern chiral stationary phases, caused by strongly adsorbed eluent additives. The latter type of deformation was highly tuneable and it was possible to adjust the enantiomer peak shapes so that the peaks tailed in opposite directions with the sharp sides in between, yielding baseline resolution at remarkably high sample loads. In a final applied study both the LC-based perturbation peak method and a biosensor method based on surface plasmon resonance (SPR) were used for the first time for detailed characterization of chiral drug-protein interactions. The fundamental properties of the two very different methods were compared and it was found that the LC method is more suitable for multi-component analysis and that the SPR method is more suitable for stronger interactions.
15

Calibração de redes de distribuição de água pelo método inverso aplicado a escoamento transiente / not available

Araújo, John Kenedy de 24 January 2003 (has links)
Desenvolve-se um método para estimar os parâmetros de uma rede hidráulica a partir de dados observados de cargas hidráulicas transientes. Os parâmetros físicos da rede como fatores de atrito, rugosidades absolutas, diâmetros e a identificação e quantificação de vazamentos são as grandezas desconhecidas. O problema transiente inverso é resolvido utilizando uma abordagem indireta que compara os dados disponíveis de carga hidráulica transiente observados com os calculados através de um método matemático. O Método Transiente Inverso (MTI) com um Algoritmo Genético (AG) emprega o Método das Características (MOC) na solução das equações do movimento para escoamento transiente em redes de tubos. As condições de regime permanente são desconhecidas. Para avaliar a confiabilidade do MTI-AG desenvolvido aqui, uma rede-exemplo é usada para os vários problemas de calibração propostos. O comportamento transiente é imposto por duas manobras distintas de uma válvula de controle localizada em um dos nós da rede. Analisam-se, ainda, o desempenho do método proposto mediante a variabilidade do tamanho do registro transiente e de possíveis erros de leitura nas cargas hidráulicas. Ensaios numéricos realizados mostram que o método é viável e aplicável à solução de problema inverso em redes hidráulicas, sobretudo recorrendo-se a poucos dados observados e ao desconhecimento das condições iniciais de estado permanente. Nos diversos problemas de identificação, as informações transientes obtidas da manobra mais brusca produziu estimações mais eficientes. / A method for estimation of parameters of existing hydraulic networks on the basis of observed transients pressures. Such parameters include pipe friction factors or absolute roughness, their diameters and the leakage locations and discharges. The inverse transient problem in terms of unknown parameters is solved through an indirect calibration procedure, which compares the calculated and observed hydraulic heads. The search method for optimal parameters employs the Method of Characteristics for the solution equations of transient motions in pipes and Genetic Algorithms. The initial conditions in the state of equilibrium are supposed unknown and the observed transient behavior of the network is in response to a valve maneuver composed of partial closure and reestablishment of flow in a pipe. In order to validate the transient calibration method, an example network is used to test various proposed calibration problems. The results show that the proposed method can be used with confidence for determination of various kinds of parameters. The transient inverse method is capable of network calibration using transient data collected at few locations in response to a quick valve maneuver.
16

Utilisation de méthodes inverses pour la caractérisation de matériaux à changement de phase (MCP) / Use of inverse methods for the characterization of phase change materials (PCM)

Maréchal, William 24 April 2014 (has links)
Avec le développement des énergies intermittentes et la raréfaction des énergies fossiles, le sujet du stockage de l’énergie prend de plus en plus d’ampleur. Une des voies étudiée est le stockage thermique par utilisation de matériaux à changement de phase (MCP). Cette voie est en outre développée pour améliorer l’inertie thermique dans le secteur du bâtiment. Pour utiliser au mieux ces matériaux il est nécessaire de pouvoir prévoir leur comportement énergétique. Cela nécessite une connaissance précise des propriétés thermophysiques, et en premier lieu de la fonction enthalpie massique . Actuellement, il est souvent proposé d'approximer cette enthalpie par l'intégration directe des thermogrammes de la calorimétrie utilisant notamment la notion de capacité calorifique "équivalente". Cette approche est cependant fausse car le thermogramme n’est qu'une représentation en fonction du temps de phénomènes complexes faisant intervenir non seulement les propriétés énergétique du matériaux mais également les transferts thermiques au sein de la cellule du calorimètre. Il en résulte, par exemple, que la forme des thermogrammes, et donc l’enthalpie apparente, dépend de la vitesse de réchauffement et de la masse de l'échantillon ce qui n'est pas le cas de l'enthalpie des MCP qui ne dépend, à pression fixe, que de la température ou de la concentration (pour les solutions). On propose de comparer la sortie d’un modèle numérique direct avec des thermogrammes expérimentaux. L’objectif principal de cette thèse est alors d’utiliser ce modèle dans le cadre d’une méthode inverse permettant l’identification des paramètres de l’équation d’état permettant alors de calculer l’enthapie massique . Dans un premier temps, il est donc présenté le détail d'un modèle 2D dit enthalpique qui néglige la convection, validé par l'expérience, permettant de reconstituer les thermogrammes de corps purs ou de solutions binaires dont les enthalpies sont connues. Il en est déduit une étude de l'influence des différents paramètres ( , , , ...) sur la forme des thermogrammes pour en déduire leurs sensibilités. Une réduction de ce modèle est ensuite effectuée pour réduire le temps de calcul du modèle direct en vue de l’utilisation dans une méthode inverse. Cette dernière est décrite ainsi que les algorithmes d’optimisation correspondants (de Levenberg-Marquardt, génétique ou du simplexe qui s'est avéré le plus rapide) dans un second temps. Nous appliquerons ensuite cet algorithme pour identifier, à partir d'expériences, la fonction enthalpie de corps purs ou de solutions binaires. Les résultats obtenus montrent qu’il est possible d’identifier une fonction independante de la vitesse de réchauffement et de la masse, ce qui valide la méthode. Une analyse des différentes sources d’erreurs dans le processus d’identification et leurs influences sur le résultat permet d’évaluer la qualité de la fonction enthalpie que l’on identifie. Enfin, cette même approche a été utilisée pour analyser une expérience réalisée sur un échantillon d’un matériau composite utilisé dans le bâtiment (ciment avec inclusion de MCP micro-encapsulé). Dans ce cas encore, nos méthodes permettent une caractérisation énergétique pertinente. / With the development of intermittent sources of energy and the depletion of fossil fuels, the subject of energy storage is becoming an important topic. One of the studied options is tthe latent hermal storage using of phase change materials (PCM). One application for this type of energy storage is to improve the thermal insulation in buildings. To make the best use of these materials it is necessary to be able to predict their energy behavior. This requires a precise knowledge of their thermophysical properties, first of all of the specific enthalpy function of the material . Currently, it is often suggested to approximate the enthalpy by the direct integration of the thermograms obtained through calorimetry experiments (notion of "equivalent" calorific capacity). This approach is false because thermograms are only a time related representation of complex phenomena where thermal transfers arise in the cell of the calorimeter acting with the thermophysical properties. As a result, for example, the shape of thermograms depends on the heating rate and on the mass of the sample, which is not the case for the enthalpy of the PCM, which depends, at constant pressure, only on the temperature or on the concentration (for the solutions). We propose to compare the results given by a of a numerical direct model with experimental thermograms. The main objective in this thesis is then to use this direct model in an inverse method in order to identify the parameters of the equation of state, which enables us to calculate the specific enthalpy . First of all, the detail of an enthalpy model is presented, and then validated by comparison with experiments, allowing us to reconstruct the thermograms of pure substances or of salt solutions, of which the enthalpies are known. A study of the influence of the various parameters ( , , , .,..) on the shape of thermograms is also undertaken in order to deduce their sensibilities. A reduced model is then developed in order to reduce the calculating time of the direct model. This optimized model allows the use of inverse methods with acceptable durations. Several inverses algorithms are then presented: Levenberg-Marquardt, evolutionary and Simplex which has proved to be the fastest). We shall then apply this algorithm to identify, from calorimetric experiments, the enthalpy function of pure substances or of salt solutions. The results that we obtain show that it is possible to identify a function independent of the heating rate and of the mass, which validates the method. An analysis of the various sources of errors in the identification process and of their influences on the result allows us to estimate the quality of the enthalpy function that we identify.
17

Etude biomécanique de l’action des Bas Médicaux de Compression sur les parois veineuses du membre inférieur / Biomechanical response of lower leg veins to Medical Elastic Compression

Rohan, Christian Pierre-Yves 03 December 2013 (has links)
La compression élastique est la thérapeutique conservatrice la plus efficace pour la prise en charge de l'insuffisance veineuse et pour le traitement de la maladie veineuse chronique et de ses complications. Malheureusement, en pratique, les objectifs thérapeutiques ne sont pas toujours atteints ce qui souligne le manque de connaissance actuel concernant les mécanismes qui permettent aux Bas Médicaux de Compression (BMC) d'apporter les bienfaits thérapeutiques. Pour apporter des éléments de réponse, une étude numérique de l’action des BMC sur les veines a été réalisée. Dans un premier temps, une nouvelle méthodologie a été développée pour prévoir les pressions transmises aux parois des veines superficielles et pour quantifier la diminution de la pression transmurale et du calibre que la compression engendre. Une étude de sensibilité réalisée à partir du modèle Eléments Finis développé a permis de mettre en évidence les principaux paramètres qui conditionnent l’action des BMC. Il a ensuite été utilisé pour simuler différents scénarios d’application en lien avec la compression en post-sclérothérapie pour répondre à des problématiques industrielles. Dans une deuxième phase de l’étude, une méthode de modélisation numérique de la réponse des veines profondes à la contraction musculaire lors du port d’un BMC a été développée. Une étude de sensibilité a permis d’apporter des éléments de réponse quant à l’influence relative des aponévroses musculaires, de la contraction musculaire et du port d’un BMC. Ces travaux ouvrent des perspectives d’études nouvelles sur le développement d’outils pour permettre aux fabricants de BMC d’adapter le niveau de compression à chaque patient. / Compression therapy is a highly effective modality for treating venous disorders of the lower leg and is considered as the “gold standard” for non-operative therapy. However the mechanisms by which Medical Compression Stockings (MCS) benefit the control and treatment of venous insufficiency are neither clearly understood nor have they been conclusively demonstrated. In the present study, the biomechanical response of the lower leg veins to elastic compression is modelled in order to address some of the issues relating to the mechanisms by which it achieves its medical function. First, a new methodology has been developed in order to predict the pressure transmitted to the superficial vein wall during external compression and to quantify the resulting variations of transmural pressure and of the vein cross sectional area. A parametric study was performed to study the influence of the model parameters on the response of the vein. The developed model was also used to simulate different scenarii related to the use of elastic compression after sclerotherapy. In a second step, a numerical approach was developed to model the biomechanical response of deep veins to elastic compression. A parametric study was performed to evaluate the relative influence of the muscular aponeurosis, muscular contraction and external compression applied by MCS. The obtained results bring a new insight on MCS mechanical action and its possible benefits. They also open up new perspectives, especially, regarding the development of new tools to assist MCS manufacturers in adapting the level of compression to the location of the deep vein, the morphology of the patient and the severity of the disease.
18

The Use operator elitism in calibration diameter water distribution networks using transient data and genetic algorithm. / O Uso do operador elitismo na calibraÃÃo de diÃmetro de redes de distribuiÃÃo de Ãgua utilizando dados transientes e algoritmo genÃtico.

Filipe Lopes 29 May 2015 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / One of the steps in the technical analysis of water supply systems are simulations of the conditions of equilibrium a distribution network. In order to estimate the parameters of a hydraulic network, from observed data hydraulic loads, there is developed a computational method. In general, the physical parameters of the network as unknown friction factors, the absolute roughness, diameter and the identification and quantification of leaks are unknown quantities. In this study, the focus will be on the identification of diameters through a combination Transient Reverse method - Genetic Algorithm with the MTI - AG using the method of characteristics - MOC the solution of equations of motion for a transient flow in ducting . The use of elitism operator is used to evaluate the effects on the identification of the diameter transient conditions. The steady state conditions are known. The accuracy of the MTI model developed AG are evaluated by two-networks example, used in the proposed calibration problem. The effect of the transient is achieved by changing demand of the nodes of the distribution network. The performance of the proposed method is verified by evaluating the variability of the transient size of the record and possible reading errors in the hydraulic loads and diameters / Uma das etapas na anÃlise tÃcnica de sistemas de abastecimento de Ãgua sÃo as simulaÃÃes das condiÃÃes de equilÃbrio de uma rede de distribuiÃÃo. A fim de se estimar os parÃmetros de uma rede hidrÃulica, a partir de dados observados de cargas hidrÃulicas, desenvolve-se um mÃtodo computacional. Em geral, os parÃmetros fÃsicos da rede desconhecidos como fatores de atrito, rugosidades absolutas, diÃmetros e a identificaÃÃo e quantificaÃÃo de vazamentos sÃo grandezas desconhecidas. Nessa pesquisa, o enfoque serà dado na identificaÃÃo dos diÃmetros, atravÃs de uma combinaÃÃo do MÃtodo Transiente Inverso - MTI com o Algoritmo GenÃtico â AG, utilizando o MÃtodo das CaracterÃsticas â MOC na soluÃÃo das equaÃÃes do movimento para escoamento de transiente em rede de tubos. A utilizaÃÃo do operador elitismo serà utilizada para avaliar os efeitos produzidos na identificaÃÃo dos diÃmetros em condiÃÃes transientes. As condiÃÃes de regime permanente sÃo conhecidas. A precisÃo do modelo MTI com AG desenvolvidos sÃo avaliados atravÃs de duas redes-exemplo, utilizado no problema de calibraÃÃo proposto. O efeito do transiente à alcanÃado atravÃs da mudanÃa de demanda de um dos nÃs da rede de distribuiÃÃo. O desempenho do mÃtodo proposto à verificado avaliando-se a variabilidade do tamanho do registro transiente e de possÃveis erros de leituras nas cargas hidrÃulicas e nos diÃmetros
19

Estimação de Parâmetros de Secagem de Alimentos- Formulação de Luikov e uso da Transformada Integral Generalizada

Silva, Cristiane Kelly Ferreira da 22 December 2010 (has links)
Made available in DSpace on 2015-05-08T15:00:06Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1410495 bytes, checksum: 297a35ec22dfac08098347ad18406247 (MD5) Previous issue date: 2010-12-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Drying is one of the most widely used commercial processes for the preservation of agricultural products, whose maximum objective is to maintain its qualities. On the other hand, for the optimal design and control of processes and equipments it is necessary a clear understanding of the involved phenomena and the transport properties of the product being handled. In this sense two mathematical models were developed, in the configuration of an infinite plane plate, with the aim of studying the process of drying food. The first model was based on Fick's second law, to model the process of mass transfer, treated by the Classical Integral Transform Technique (CITT). The second model was developed for the analysis of the simultaneous heat and mass transfer using the equations of Luikov, where the distributions of temperature and moisture content inside the food were obtained following the formalism inherent to the Generalized Integral Transform Technique (GITT). In both models, the thermophysical properties are considered constant. The results obtained in the two models were compared and found that they are able to describe the process of drying food. The influence of thermophysical parameters relating to the simultaneous heat and mass transfer was also analyzed. The accuracy of the calculations of a heat and mass balance depends on the precision as that is known the properties of the product and the choice of reliable data for these properties is an important part to any careful analysis engineering. Thus, an inverse problem of parameters estimation, for the mass transfer, was solved through the Levenberg-Marquardt's minimization algorithm. The results obtained through the solution of the inverse problem for the effective mass diffusivity are the same order magnitude of those reported in the literature. Key words - food drying, Fick law, Luikov, GITT, inverse method. / A secagem é um dos processos comerciais mais usados na conservação de produtos agropecuários, cujo objetivo máximo é a manutenção de suas qualidades. Por outro lado, para o dimensionamento e controle ótimos dos processos e dos equipamentos é necessário um claro entendimento dos fenômenos envolvidos e das propriedades de transporte do produto que está sendo manuseado. Neste sentido, foram desenvolvidos dois modelos matemáticos, na configuração de uma placa plana infinita, com o objetivo de se estudar o processo de secagem de alimentos. O primeiro modelo foi baseado na segunda lei de Fick, para modelar o processo de transferência de massa, tratado através da Técnica da Transformada Integral Clássica (CITT). O segundo modelo foi desenvolvido para a análise da transferência simultânea de calor e massa usando-se as equações de Luikov, onde as distribuições de temperatura e teor de umidade no interior do alimento foram obtidas segundo os formalismos inerentes à Técnica da Transformada Integral Generalizada (GITT). Em ambos os modelos as propriedades termofísicas são consideradas constantes. Os resultados obtidos nos dois modelos foram comparados e constatou-se que os mesmos são capazes de descrever o processo de secagem de alimentos. Avaliou-se também a influência dos parâmetros termofísicos referentes à transferência simultânea de calor e massa. A exatidão dos cálculos de um balanço de calor e massa depende da precisão com que se conhecem as propriedades do produto e, a escolha de dados confiáveis dessas propriedades é uma parcela importante para qualquer análise cuidadosa de engenharia. Desta forma, um problema inverso de estimação de parâmetros, para a transferência de massa, foi resolvido através do algoritmo de minimização de Levenberg-Marquardt. Os resultados obtidos através da solução do problema inverso para a difusividade efetiva de massa são da mesma ordem de grandeza dos reportados na literatura.
20

InfluÃncia de manobras de vÃlvulas na identificaÃÃo das rugosidades em tubulaÃÃes de redes de distribuiÃÃo de Ãgua / Influence valves maneuvers in the identification of roughness in networks of pipes water supply

JoÃosuà de ArÃa LeÃo 28 November 2014 (has links)
Atualmente, com base na anÃlise computacional, avaliaÃÃes mais precisas vÃm sendo possÃveis em estudos de dimensionamento de redes de abastecimento de Ãgua. O transiente hidrÃulico à um fenÃmeno que pode afetar toda rede de escoamento forÃado. A compreensÃo deste fenÃmeno e a constante busca de soluÃÃes para evitar seus efeitos danosos acarretam avanÃos tecnolÃgicos significativos, principalmente atravÃs da aplicaÃÃo dos mÃtodos computacionais. O presente trabalho consiste em utilizar o MÃtodo Transiente Inverso (MTI) com um algoritmo genÃtico para a calibraÃÃo das rugosidades absolutas das tubulaÃÃes de duas redes de distribuiÃÃo de Ãgua utilizando quatro tipos de manobras diferentes, atravÃs de parÃmetros genÃticos. O estudo foi feito em duas redes fictÃcias, mas com caracterÃsticas fÃsicas de redes reais. Foi analisado a influencia de manobras de vÃlvulas na identificaÃÃo das rugosidades em tubulaÃÃes de redes de distribuiÃÃo de Ãgua. As simulaÃÃes foram feitas variando dois tipos de seleÃÃo: com elitismo e sem elitismo, considerando os indicadores de eficiÃncia: Erro MÃdio Relativo (EMR), Erro Relativo (ER) e FunÃÃo Objetivo (FO), onde os resultados da Rede A se mostraram melhores para o Erro Relativo (ER) com elitismo nas quatro manobras. Na rede B, o melhor indicador de eficiÃncia para a calibraÃÃo das quatro manobras foi o Erro MÃdio Relativo (EMR) com elitismo e que os indicadores Erro Relativo (ER) e FunÃÃo Objetiva (FO) variam conforme a manobra analisada. / Currently, based on computational analysis, more accurate assessments have been possible in studies of design of water supply networks. The hydraulic transient is a phenomenon that can affect all forced drainage system. Understanding this phenomenon and the constant search for solutions to avoid its harmful effects cause significant technological advances, principally through the application of computational methods. The present work is to use the Transient Inverse Method (TIM) with a genetic algorithm to calibrate the absolute roughness of pipes of two water distribution networks using four different types of maneuvers through genetic parameters. The study was done in two fictitious networks, but with physical characteristics of real networks. We analyzed the influence of valves maneuvers in the identification of roughness in pipes of water distribution networks. The simulations were made by varying two types of selection: elitism with and without elitism, considering the efficiency indicators: Average Relative Error (EMR), Relative Error (RE) and Objective Function (OF), where the results of the Network proved best for the relative error (RE) with elitism in four maneuvers. In network B, the best indicator of efficiency for the calibration of the four maneuvers was the mean relative error (EMR) with elitism and the indicators Relative Error (RE) and Objective Function (OF) vary according to the analyzed maneuver.

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