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1
Sun, Binyong. "Matrix coefficients and representations of real reductive groups /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?MATH%202004%20SUN.
Testo completo
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El-Bordany, Refaat. "In orbit calibration of satellite inertia matrix and thruster coefficients". Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/842840/.
Testo completoAbstract (sommario):
In this research study, several new in-orbit algorithms are proposed to improve the performance of Attitude Determination and Control System (ADCS) by estimating the inertia matrix and calibrating the cold gas thruster system of the UoSAT-12 spacecraft. Computer-based simulation models will be constructed using MATLAB and SIMULINK in order to evaluate the expected performance. The first focus is on the identification of the satellite inertia matrix. A new algorithm based on a Recursive Least Square (RLS) estimation technique is proposed for in-orbit use to estimate the inertia matrix (moments and products of inertia parameters) of a satellite. To facilitate this, one attitude axis is disturbed using a reaction wheel whilst the other two axes are controlled to keep their respective angular" rates small. Within a fraction of an orbit three components of the inertia matrix can be accurately determined. This procedure is then repeated for the other two axes to obtain all nine elements of the inertia matrix. The procedure is designed to prevent the build up of momentum in the reaction wheels, whilst keeping the attitude disturbance to the satellite within acceptable limits. It can also overcome potential errors introduced by unmodeled external disturbance torques and attitude sensor noise. The second focus is on a new algorithm for in-orbit use to calibrate thruster coefficients for thrust level and alignment, using three reaction wheel actuators. These algorithms will ensure robustness against modeling errors. The algorithms assume no prior knowledge of the thruster parameters and only an initial guess of the inertia matrix. It is proposed that this calibration can be used during normal mission conditions when the satellite is stabilised. The final goal of this research study was to apply the proposed algorithms in real-time. Firstly, the thruster calibration algorithm was tested on an air-bearing table. Finally, both thruster calibration and moment of inertia algorithms were tested using data generated by UoSAT-12 while in orbit. The practical estimation results proved the feasibility of proposed algorithms.
3
Sternini, Simone. "On the identification of bridge decks aeroelastic coefficients: the covariance block hankel matrix method". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5999/.
Testo completoAbstract (sommario):
Il seguente elaborato si concentra sull'identifi�cazione strutturale di sistemi soggetti a sollecitazioni aeroelastiche e nello speci�fico l'attenzione viene rivolta ad impalcati da ponte. Si analizzano i concetti principali caratterizzanti il campo dell'aeroelasticità indagando i fattori dominanti che entrano in gioco sul piano teorico. In seguito, si considera il metodo di identifi�cazione strutturale chiamato Covariance Block Hankel
Matrix (CBHM) utilizzato come strumento di derivazione
dei coeffi�cienti aeroelastici propri della struttura. Infi�ne, si indaga il comportamento di questo metodo di identi�ficazione al variare di una serie di parametri chiave e all'interno di diversi scenari, visionando risultati ottenuti tramite una serie di test eff�ettuati per provare l'a�dattabilità del metodo stesso al variare delle condizioni che caratterizzano il sistema.
4
Zhebel, Elena. "A multigrid method with matrix-dependent transfer operators for 3D diffusion problems with jump coefficients". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:bsz:105-682918.
Testo completoAbstract (sommario):
Gegeben sei ein lineares Gleichungssystem $Au = f$ mit Koeffizientenmatrix $A$, welche eine spezielle block-tridiagonale Struktur besitzt. Solche lineare Gleichungssysteme entstehen bei der Diskretisierung dreidimensionaler elliptischer Randwertprobleme mit 7- oder 27-Punkte-Stern. In geophysikalischen Anwedungen, insbesondere bei Aufgaben aus der Geoelektrik, haben die Randwertprobleme unstetige Koeffizienten und sind meistens auf nicht-uniformen Gittern diskretisiert. Klassische geometrische Mehrgitterverfahren konvergieren um so langsamer, je stärker die Koeffizientensprünge ausfallen. Außerdem kann die Konvergenz durch die Variation der Gitterabstände beeinträchtigt werden. Zur Lösung wird ein matrix-abhängiges Mehrgitterverfahren vorgestellt. Als Glätter wird eine unvollständige Block LU-Zerlegung verwendet. Die Gittertransferoperationen werden anhand der Einträge der Matrix $A$ ermittelt. Das resultierende Verfahren erweist sich als sehr robust, insbesondere wenn es als Vorkonditionierung für das Verfahren der konjugierten Gradienten eingesetzt wird.
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CHO, Deung-Lyong, Mi-Jung JEEN e Takenori KATO. "Validation of physical parameters in quantitative electron probe microanalysis (EPMA) Part I : mass attenuation coefficients". Dept. of Earth and Planetary Sciences, Nagoya University, 2013. http://hdl.handle.net/2237/20540.
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Kestring, Franciele Buss Frescki. "Análise geoestatística de mapas temáticos da produtividade da soja com diferentes grades amostrais". Universidade Estadual do Oeste do Parana, 2011. http://tede.unioeste.br:8080/tede/handle/tede/359.
Testo completoAbstract (sommario):
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Previous issue date: 2011-07-07Studies on spatial variability of soybeans yield are of great importance for the development of new technologies that improve the world agricultural production. One of methods that allows this study is geostatistics. The geostatistical analysis makes possible the predictions of results and one of its products are thematic maps. Thus, this trial describes some techniques to draw and compare thematic maps using kriging. The analysis was based on data from soybean yield in t ha−1 according to harvest year 2004/2005 in an experimental area with sampling grades whose distances were: 25x25 m, 50x50 m, 75x75 m and 100x100 m plus a harvest monitor. The maps were compared using error matrix and confusion matrix. In addition, there was a better accuracy of the spatial variability maps that were drawn, while the analysis of coefficients of accuracy allows a better planning of sampling mesh for future studies. The measures of accuracy that were obtained by error matrix are significant options to make comparison among thematic maps, once they provide global indices and also by classes.
Com o aumento da produção agrícola mundial, o processo de produção agrícola tornou-se alvo do estudo de diversos pesquisadores. Estudos sobre a variabilidade espacial da produtividade da soja são de grande importância para o desenvolvimento de novas tecnologias, que beneficiam a agricultura. A análise geoestatística torna possível realizar previsões dos resultados, tendo como um de seus produtos os mapas temáticos. Este trabalho descreve algumas técnicas para a construção e comparação de mapas temáticos, utilizando a krigagem. A análise foi realizada com dados da produtividade de soja em t ha−1 do ano agrícola 2004/2005 numa área experimental com grades de amostragem com distâncias de 25x25 m, 50x50 m, 75x75 m, 100x100 m e monitor de colheita, comparando-se os mapas, utilizando a matriz de erros e a matriz de confusão. Além de uma melhor precisão dos mapas de variabilidade espacial gerados, a análise dos índices de acurácia possibilita um melhor planejamento das malhas amostrais para futuros estudos. As medidas de acurácia obtidas por meio da matriz de erros são opções significativas para realizar a comparação entre mapas temáticos, uma vez que fornecem índices globais e também por classes.
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Buenger, Carl D. Buenger. "Quantitative Non-Divergence, Effective Mixing, and Random Walks on Homogeneous Spaces". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462800914.
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Boyer, Adrien. "Sur certains aspects de la propriété RD pour des représentations sur les bords de Poisson-Furstenberg". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4723.
Testo completoAbstract (sommario):
Nous étudions la propriété RD en terme de décroissance de coefficients matriciels de représentations unitaires. Nous nous concentrons en particulier sur des représentations provenant de l'action des groupes de Lie et de groupes discrets sur un "bord" approprié. Ces actions produisent des rerésentations unitaires à normalisation prés. Nous utilisons des techniques d'analyse harmonique et de théorie ergodique pour amorcer une nouvelle approche de la conjecture de ValetteWe study property RD in terms of decay of matrix coefficients for unitary representations. We focus our attention on unitary representations arising from action of Lie groups and discrete groups of isometries of a CAT(-1) space on their appropriate boundary. We use some techniques of harmonic analysis, and ergodic theory to start a new approach of Valette's conjecture
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Maati, Amel. "Mise en œuvre de formalismes pour la modélisation de grands réseaux périodiques d'antennes". Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0009/document.
Testo completoAbstract (sommario):
Cette thèse se place dans le contexte général de la modélisation de réseaux d’antennes de grande taille, avec pour objectif d’atteindre un niveau de précision suffisamment élevé pour permettre une optimisation complète des performances et en particulier une amélioration de l’efficacité énergétique. Partant du constat que l’optimisation électromagnétique de grands réseaux représente un verrou si les couplages doivent être modélisés efficacement, cette thèse propose la mise en œuvre d’une méthode permettant la modélisation fine de grands réseaux d'antennes tout en réduisant les temps de calcul et en conservant un haut degré de précision. L'objectif est de montrer qu'une approche dérivée des formalismes périodiques infinis connus de la littérature permet d'obtenir une matrice [S] complète d'un réseau depuis l'étude d'une cellule unitaire. Après avoir présenté un état de l'art sur les réseaux d'antennes et leurs méthodes d'analyse, l'approche de modélisation proposée est détaillée. Des véhicules de test numériques et expérimentaux, permettant de valider cette méthode de modélisation, sont ensuite réalisés. L'approche est enfin utilisée avec succès pour deux types d'applicationThis thesis is organized in the general context of modeling a large antenna arrays with the aim of achieving a high level of precision. This modeling allows a complete optimization of the performances and an enhancement of the energy efficiency. Given that the electromagnetic optimization of large arrays still represents a challenge if the mutual coupling is not efficiently modeled. This work offers the implementation of a method allowing the precise modeling of large antenna arrays while reducing the computation time and maintaining a high degree of precision. The aim is to demonstrate that the derived approach from the infinite periodic formalisms makes it possible to obtain a full [S] matrix of an array based on the study of a unit cell. After presenting a state of the art of antenna arrays and their methods of analysis, the proposed modeling approach is explained. Numerical and Experimental demonstrators are then made for the validation. Finally, this method is successfully used for two types of applications
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Matta, Sandrine. "Propagation des ondes acoustiques dans une multicouche composée de couches viscoélastiques liquides, solides et poreuses". Thesis, Valenciennes, 2018. http://www.theses.fr/2018VALE0035/document.
Testo completoAbstract (sommario):
Cette thèse propose un formalisme général pour modéliser la propagation des ondes acoustiques dans une multicouche composée de toute combinaison de couches liquides, solides élastiques isotropes et poro-élastiques isotropes, la méthode ayant la flexibilité d'être développée pour inclure d'autres natures de couches. Dans un premier lieu, un algorithme stable est développé, basé sur l'approche récursive de la matrice de rigidité, pour modéliser la propagation d'une onde plane incidente sur la multicouche en fonction de son angle d'incidence et de sa fréquence. Cet algorithme fusionne de manière récursive les matrices de rigidité des couches individuelles de la structure en une matrice de rigidité totale et permet ensuite le calcul des coefficients de réflexion et de transmission, ainsi que les composantes de déplacement et de contrainte à l'intérieur de la multicouche pour chaque direction d'incidence des ondes planes. Deuxièmement, pour modéliser la propagation d'un faisceau délimité d'ondes incidentes, la technique du spectre angulaire est utilisée, basée sur la décomposition de ce faisceau en un spectre d'ondes planes se propageant dans des directions différentes. Par la suite, le faisceau d'onde réfléchi dans le milieu d'incidence et le faisceau d'onde transmis dans le milieu de transmission, ainsi que la distribution des champs (composantes de déplacement et de contrainte) à l'intérieur de la multicouche sont obtenus en superposant la contribution de toutes les ondes planes se propageant dans les différentes directions. Comme application numérique, une tri-couche solide-poreuse-solide immergée dans l'eau est simulée. La réflexion et la transmission qui en résultent, ainsi que les composantes de déplacement et de contrainte dans la multicouche, correspondants à l’onde plane incidente et au faisceau limité incident, révèlent la stabilité du procédé et la continuité des déplacements et des contraintes aux interfacesThis thesis proposes a general formalism to model the acoustic wave propagation in a multilayer consisting of any combination of fluid, isotropic elastic solid, and isotropic poroelastic layers, the method having the flexibility to be extended to include other layer-natures. At a first stage, a stable algorithm is developed, based on the recursive stiffness matrix approach, to model the propagation of a plane wave incident on the multilayer as a function of its incidence angle and frequency. This algorithm merges recursively the structureindividual layers stiffness matrices into one total stiffness matrix and allows then the calculation of the reflection and transmission coefficients, as well as the displacement and stress components inside the multilayer for every incident plane wave direction. Secondly, to model the propagation of a bounded incident wave beam, the angular spectrum technique is used which is based on the decomposition of this beam into a spectrum of plane waves traveling in different directions. The corresponding reflected wave beam in the incidence medium, and the transmitted wave beam in the transmission medium, as well as the fields distributions (displacement and stress components) inside the multilayer are obtained by summing the contribution of all the plane waves traveling in different directions. As a numerical application, a three-layered solid-porous-solid structure immersed in water is simulated. The resulting reflection and transmission as well as the displacement and stress components in the multilayer corresponding to both, the incident plane wave in different directions and the incident bounded beam reveal the stability of the method and the continuity of the displacements and stresses at the interfaces
11
Cissokho, Youssouph. "Extremal Covariance Matrices". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37124.
Testo completoAbstract (sommario):
The tail dependence coefficient (TDC) is a natural tool to describe extremal dependence. Estimation of the tail dependence coefficient can be performed via empirical process theory. In case of extremal independence, the limit degenerates and hence one cannot construct a test for extremal independence. In order to deal with this issue, we consider an analog of the covariance matrix, namely the extremogram matrix, whose entries depend only on extremal observations. We show that under the null hypothesis of extremal independence and for finite dimension d ≥ 2, the largest eigenvalue of the sample extremogram matrix converges to the maximum of d independent normal random variables. This allows us to conduct an hypothesis testing for extremal independence by means of the asymptotic distribution of the largest eigenvalue. Simulation studies are performed to further illustrate this approach.
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COELHO, Pedro Cézar Pereira. "Modelo insumo-produto nas relações intersetoriais de água no brasil". Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1009.
Testo completoAbstract (sommario):
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PEDRO CÉZAR PEREIRA COELHO - TESE (PPGRN) 2016.pdf: 1878473 bytes, checksum: d39580ba38e3efab805eaccf1049f4a4 (MD5)Made available in DSpace on 2018-06-18T12:11:40Z (GMT). No. of bitstreams: 1 PEDRO CÉZAR PEREIRA COELHO - TESE (PPGRN) 2016.pdf: 1878473 bytes, checksum: d39580ba38e3efab805eaccf1049f4a4 (MD5) Previous issue date: 2016
O modelo insumo-produto é uma teoria amplamente utilizada na economia que ao longo das últimas duas décadas teve sua aplicação estendida a diversas áreas do conhecimento. Nos últimos dez anos alguns pesquisadores usaram esse conceito para mensurar as relações econômicas associadas a demanda de água para setores da economia em cidades com características de escassez de recursos hídricos. Neste trabalho foram mensuradas algumas relações de consumo direto e indireto de água dos setores agropecuário, industrial, comercial e público a nível municipal, estadual e nacional. Na região abastecida pela Barragem Epitácio Pessoa os setores agropecuário e comercial apresentaram elevados percentuais de consumo direto de água, da ordem de 88% e 71%, respectivamente, enquanto o industrial apresentou percentual de 97% de consumo indireto em relação ao total de consumo. Para cada um metro cúbico de aumento de demanda de água, o setor industrial provoca um consumo adicional no agropecuário de 27 m3. No estado da Paraíba para cada aumento de um metro cúbico de água no setor industrial provoca aumento no setor agropecuário de 8 m3. O setor agropecuário apresentou para todos os Estados da federação elevado consumo direto de água, sendo a região Nordeste, a maior consumidora, com 35% do total, enquanto o maior consumo de água na forma virtual (consumo indireto) no Brasil encontra-se no setor industrial. No setor industrial, cada metro cúbico consumido diretamente provoca, no mesmo, a nível nacional um consumo médio adicional de água de 2 m3 e no setor agropecuário de 9 m3.
The input-output model is a theory widely used in the economy over the past two decades which has been applied to various areas of knowledge. Some researchers have used this concept to measure the economic relations associated with water demand for economy areas in with shortages of fresh water. In this work we have measured water relationship (direct and indirect form) from agricultural, industrial, commercial and public sectors for municipal, state and national levels in Brazil. In the Epitácio Pessoa Dan, the agricultural and commercial sectors showed a high percentage of direct water use of 88% and 71%, respectively, while the industrial sector is 97% as indirect consumption. For each one cubic meter increase of water demand, the industrial sector causes an additional water consumption in the agricultural sector of 27 m3. In the state of Paraíba, for each one cubic meter of water increase the industrial sector leads to an increase in agricultural sector of 8 m3. The agricultural sector showed high direct water consumption in all states of Brazil. The Northeast region is the largest water consumer with 35% of the total, while the highest water consumption in virtual form (indirect consumption) in Brazil is the industrial sector. In the industrial sector, for each one cubic meter consumed directly causes an additional national water consumption of 2 m3 while for the agricultural sector is 9 m3.
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Shahzad, Yasser. "Micellar chromatographic partition coefficients and their application in predicting skin permeability". Thesis, University of Huddersfield, 2013. http://eprints.hud.ac.uk/id/eprint/23480/.
Testo completoAbstract (sommario):
The major goal for physicochemical screening of pharmaceuticals is to predict human drug absorption, distribution, elimination, excretion and toxicity. These are all dependent on the lipophilicity of the drug, which is expressed as a partition coefficient i.e. a measure of a drug’s preference for the lipophilic or hydrophilic phases. The most common method of determining a partition coefficient is the shake flask method using octanol and water as partitioning media. However, this system has many limitations when modeling the interaction of ionised compounds with membranes, therefore, unreliable partitioning data for many solutes has been reported. In addition to these concerns, the procedure is tedious and time consuming and requires a high level of solute and solvent purity. Micellar liquid chromatography (MLC) has been proposed as an alternative technique for measuring partition coefficients utilising surfactant aggregates, known as micelles. This thesis investigates the application of MLC in determining micelle-water partition coefficients (logPMW) of pharmaceutical compounds of varying physicochemical properties. The effect of mobile phase pH and column temperature on the partitioning of compounds was evaluated. Results revealed that partitioning of drugs solely into the micellar core was influenced by the interaction of charged and neutral species with the surface of the micelle. Furthermore, the pH of the mobile phase significantly influenced the partitioning behaviour and a good correlation of logPMW was observed with calculated distribution coefficient (logD) values. More interestingly, a significant change in partitioning was observed near the dissociation constant of each drug indicating an influence of ionised species on the association with the micelle and retention on the stationary phase. Elevated column temperatures confirmed partitioning of drugs considered in this study was enthalpically driven with a small change in the entropy of the system because of the change in the nature of hydrogen bonding. Finally, a quantitative structure property relationship was developed to evaluate biological relevance in terms of predicting skin permeability of the newly developed partition coefficient values. This study provides a better surrogate for predicting skin permeability based on an easy, fast and cheap experimental methodology, and the method holds the predictive capability for a wider population of drugs. In summary, it can be concluded that MLC has the ability to generate partition coefficient values in a shorter time with higher accuracy, and has the potential to replace the octanol-water system for pharmaceutical compounds.
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Sarrazin, François. "Caractérisation d'antennes par la méthode du développement en singularités appliquée au coefficient de rétrodiffusion". Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00925409.
Testo completoAbstract (sommario):
Ce manuscrit est consacré à l'étude de la méthode du développement en singularités (SEM) appliquée aux antennes. Dans la première partie de ce travail, trois méthodes d'extraction des pôles de résonance sont présentées et comparées : les méthodes de Prony et Matrix Pencil dans le domaine temporel et la méthode de Cauchy dans le domaine fréquentiel. Une procédure est établie pour optimiser l'extraction avec chaque méthode et une étude de robustesse montre que la méthode Matrix Pencil permet d'obtenir plus de pôles et avec une meilleure précision que les deux autres méthodes en présence de bruit. Dans un second temps, la méthode Matrix Pencil est appliquée sur des réponses d'antennes, obtenues en rayonnement et en Surface Equivalente Radar (SER), et les pôles de résonance extraits sont identiques pour les deux approches. Cette étude valide donc la possibilité d'extraire les pôles de résonance d'une antenne directement à partir de sa SER. La variation de la position des pôles de résonance en fonction des dimensions et de la charge de deux antennes est ensuite étudiée et met en évidence le lien entre l'impédance d'entrée de l'antenne et ses pôles de résonance. Enfin, les mesures de la SER de trois antennes valident expérimentalement l'extraction des pôles de résonance à partir de la SER d'une antenne. Ce travail pose donc les bases de la caractérisation d'antennes à l'aide de la SEM appliquée à la SER de l'antenne.
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Pelletant, Aurelien. "Elaboration de matériaux composites céramiques à faible coefficient de dilatation thermique pour des applications spatiales". Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0018.
Testo completoAbstract (sommario):
Actuellement, la qualité de l’imagerie provenant de systèmes optiques spatiaux est limitée par la taille de leurs miroirs et la masse des structures supportant le miroir. Le développement de systèmes athermiques légers (un seul matériau) constitue le principal challenge dans l’amélioration de ces systèmes. De matériaux légers, résistants mécaniquement (E/ρ3 > 10, σf > 100 MPa) et stables thermiquement (< 2,0.e-6/K) doivent être développés. Dans ce cadre, notre travail porte sur l’élaboration de composites céramiques associant un matériau à coefficient de dilatation thermique (CTE) positif résistant mécaniquement (alumine ou zircone cériée) et un matériau à CTE très négatif (tungstate de zirconium ou β-eucryptite). L'étude du tungstate de zirconium a révélé plusieurs problèmes de décomposition et de réactions avec certaines matrices oxydes, menant à l’abandon de cet oxyde dans l’élaboration des composites. Dans le cas de la β-eucryptite, un phénomène de vermiculation a été mis en évidence, conduisant à la formation d’une porosité intragranulaire. L’optimisation des paramètres de frittage a permis de limiter cette porosité. L’étude du comportement thermique de la β-eucryptite confirme que son CTE très négatif provient principalement d’un phénomène de fissuration, généré par l’anisotropie de dilatation de sa maille cristalline. Cette fissuration est dépendante de la taille des grains mais également de la taille des agrégats de grains dans le cas des poudres. Ainsi, bien que le CTE intrinsèque de la β-eucryptite soit très faible (-0,4.e-6/K), son CTE extrinsèque peut atteindre des valeurs jusqu'à -10,9.e-6/K selon les conditions d’élaboration. Dans ce travail, deux stratégies d’élaboration de composites sont étudiées. Le premier cas consiste à diminuer le CTE des matrices oxydes à partir d’une poudre de β-eucryptite non microfissurée (-0,4.e-6/K) tandis que le second cas consiste à obtenir des matériaux à CTE très faible à partir d’une poudre de β-eucryptite microfissurée (-3,0.e-6/K). Lors de l’utilisation de la matrice en zircone cériée, le taux de dopage au cérium est optimisé afin de limiter la transformation de phase de la zircone. Cette transformation, induite par les contraintes de tension exercées par la β-eucryptite, affecte la linéarité du comportement thermique du composite. Dans les deux cas d’étude, les composites denses montrent une modification du CTE intrinsèque de la β-eucryptite passant de -0,4.e-6/K à plus de +3,2.e-6/K en raison des contraintes de compression appliquées par la matrice (alumine ou zircone cériée). La relaxation de ces contraintes nécessite une sous-densification des composites. A partir de ces observations, différents composites à CTE très faible sont élaborés. Toutefois, le sous-frittage des composites associé à la microfissuration de la β-eucryptite diminuent fortement les propriétés mécaniques des matériaux ainsi élaborésHigh resolution satellite imagery from space optical systems is mainly limited by the mirror size and the mass of structures supporting the mirror. Nowadays, the development of light athermal systems is the major challenge to improve these optical systems. So, light materials having good mechanical properties (E/ρ3 > 10, σf > 100 MPa) and thermal stability (< 2.0e-6/K) are required. Within this context, our project consists in processing new ceramic composites by combining positive thermal expansion coefficient (TEC) materials having good mechanical properties (alumina or ceria doped zirconia) and negative TEC materials (zirconium tungstate or β-eucryptite) The processing of zirconium tungstate-based materials showed several decomposition and chemical reactions with some oxide matrix leading to its giving up. In the case of β-eucryptite, vermicular phenomenon occurs during sintering leading to the formation of intragranular porosity. Sintering parameters optimization can limit this porosity. The study of the thermal behavior of pure β-eucryptite materials shows that the very negative TEC results from microcracking, generated by the TEC anisotropy of its crystal lattice. This microcracking depends on the grain size and the aggregate size in the case of powder materials. Despite the fact that the TEC of its lattice (called intrinsic TE C equals to -0.4e-6/K) is very low, its bulk (or extrinsic) TEC can reach values until -10.9e-6/K according to the processing conditions. In this work, two strategies for developing composites were studied. The first one consists in decreasing the matrix TEC using an uncracked β-eucryptite powder (-0.4e-6/K) while the second one consists in elaborating near zero TEC materials from a microcracked β-eucryptite powder (-3.0e-6/K). When ceria-doped zirconia is used, ceria content must be adjusted in order to limit zirconia phase transformation. This transformation is driven by tensile stresses induced by the β-eucryptite and modifies the composite thermal behavior linearity. In both studied cases, dense composites show a modification of the β-eucryptite intrinsic TEC from -0.4e-6/K to more than +3.2e-6/K as a consequence of compressive stresses applied by the oxide matrix. An uncompleted densification of composites is required to relax these stresses. Taking into account these observations, several very low TEC composites were elaborated. However, the uncompleted densification of composites and the β-eucryptite microcracking greatly decrease the mechanical properties of these materials
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Kumar, Pawan. "Studies of wire-matrix interaction in some tungsten wire reinforced stainless steels". Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/8980.
Testo completoAbstract (sommario):
There is potential for improving creep properties of stainless steels by reinforcing them with tungsten (W) wires. Past studies have shown that a detrimental factor that impairs the mechanical properties of tungsten wire reinforced superalloy composites is the formation of brittle intermetallic phases due to the interaction between W wire and constituents of the alloy matrices. Formation and growth of the intermetallic phases strongly depends on the matrix chemistry and for the retention of creep strength, matrix compositions that do not form intermetallic phases with tungsten are desirable for fabricating W wire reinforced composites for high temperature applications.
This research investigated the formation and growth of reaction phases in W wire reinforced 316L (W/316L) stainless steel and HP alloy steel (W/HP) that were fabricated by casting method. Additionally, the effect of composition on the evolution and kinetics of reaction phases was studied in some W wire reinforced experimental alloys based on Fe-Ni-Cr only (W/Fe-Ni-Cr). The fabricated composites were diffusion annealed in the temperature range 1000-1200°C for 25-500 hours. Microstructure and chemistry of the reaction phases in the as-cast and diffusion annealed composites were studied using scanning electron microscopy, energy dispersive spectroscopy and electron backscattered diffraction techniques. Growth kinetics of the reaction layers and average effective interdiffusion coefficients in the layers were determined for the composites.
Results showed that an intermetallic phase isostructural with µ-phase formed in the as-cast W/316L and W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratios. In W/HP a phase M12C with crystal structure similar to η-carbide was formed. These phases developed and formed brittle reaction layers around the W wires during diffusion annealing. A parabolic relationship between the µ-phase and η-carbide growth and diffusion annealing time indicated that the growth of reaction layers was diffusion controlled. In the W/Fe-Ni-Cr composites, formation of intermetallic phases did not occur in the matrices with 0.5Fe:Ni ratio, instead some isolated tungsten particles were observed in the matrix adjacent to the wires after diffusion annealing. In W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratio, the growth of µ-phase reaction layers during annealing was observed to be dependent on the matrix composition. It was found that with an increase in the Ni content in the matrix, growth of µ-phase reaction layer decreased.
The study presented in this thesis gives first-hand information on phase formation and growth kinetics of the reaction layers in W/316L and W/HP composites. It revealed that the interaction of W with 316L and HP alloy matrices leads to formation of cracked intermetallic and carbide reaction layers which are not desirable in the composites designed for high temperature applications. It has also been shown in this study that in W/Fe-Ni-Cr composites, intermetallic phase formation can be suppressed by increasing Ni content in the matrix. In the composite with high Ni contents in the matrix (0.5Fe:Ni ratio) intermetallic phases do not form even after diffusion annealing at 1200°C. This intermetallic free W/Fe-Ni-Cr composite can further be studied for its creep strength.
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Tomek, Peter. "Approximation of Terrain Data Utilizing Splines". Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2012. http://www.nusl.cz/ntk/nusl-236488.
Testo completoAbstract (sommario):
Pro optimalizaci letových trajektorií ve velmi malé nadmorské výšce, terenní vlastnosti musí být zahrnuty velice přesne. Proto rychlá a efektivní evaluace terenních dat je velice důležitá vzhledem nato, že čas potrebný pro optimalizaci musí být co nejkratší. Navyše, na optimalizaci letové trajektorie se využívájí metody založené na výpočtu gradientu. Proto musí být aproximační funkce terenních dat spojitá do určitého stupne derivace. Velice nádejná metoda na aproximaci terenních dat je aplikace víceroměrných simplex polynomů. Cílem této práce je implementovat funkci, která vyhodnotí dané terenní data na určitých bodech spolu s gradientem pomocí vícerozměrných splajnů. Program by měl vyčíslit více bodů najednou a měl by pracovat v $n$-dimensionálním prostoru.
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Lisboa, Luana. "Matriz de coeficientes técnicos de recursos hídricos para o setor industrial brasileiro". Universidade Federal de Viçosa, 2010. http://locus.ufv.br/handle/123456789/3627.
Testo completoAbstract (sommario):
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Previous issue date: 2010-07-30Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The water is one essential to guarantee the life quality, is a factor that restrict the economic and social development in many regions. Despite of Brazil have a privileged situation because of the disponibility of the water, the geographical variability and the growth population have caused conflicts of use behind the sectors that use. From this perspective, one should highlight those economic activities whose uses of water resources are more intensive, like the industrial sector. To estimate water use in this sector there are several methods, though, the most part of this methods are based on data reported and compiled in the seventies in the United States reflecting, outdated technology and environmental of the production process, besides, this do not represent the Brazilian local conditions. Noting that technological developments of the recent decades has altered the use of natural resources in the production processes; there is a need for a more comprehensive, updated and specific study in Brazil, providing subsidies to companies and governing agencies for an appropriate planning and management program of water resources in the industrial sector. Thus, considering the importance of this matter and of the technical coefficients in the use of the water, this study aimed the construction of technical coefficients of water resources for the industrial sector in Brazil. To be successful in the objective, firstly was done exploration of dada of withdraw, of generation of effluents and consume by product (m3/produced unit), the dada of water flow and production, that allow prepare the coefficients. After this phase, the structure of the dada bank was composed and filled. The structure consider fields refer to name of the company, type, coefficients of capitation, consume and generation of effluents, allowing classify the information regarding many criteria. To classification of the type of the industries was considered the National Classification of Economic Activities (CNAE), version 2.0. After the cadastre of the information in the dada bank, were analyzed the difference of the dada in the same segment, trying explain this differences. The last phase was the validation of the coefficients, with discussion with public agencies, private institutions and others relevant entities of the industrial sector, aim to finish the dada and add pertinent contributions. The dada obtained in the research summarize 148 companies or associations, representing 51 types of economics activities. After the analyses and comparison of the results of the group of technical coefficients with dada of others methodologies, based in international dada, verify that the adoption of such values overestimates the coefficient of withdraw, consume and effluent associated with the Brazilian companies. It was realized that the dada presented by Integrated Pollution Prevention and Control (IPPC, 2009), comparing with other fonts, are the more indicated to represent the reality of the Brazilian industrial sector, when there isn t specific dada of the national industries. It is concluded that the CNAE allow define in a clear way as type associated with the main economics activities of the Brazilian industrial sector. The group of technical coefficient of water resources obtained in the present study reflects, in a consistent and correct way, the present situation of the Brazilian industries studies providing subsidies to companies and governing agencies for an appropriate planning and management program, controlling the rational use of water resources in the industrial sector brazilian.
A água é um elemento essencial para a garantia da qualidade de vida, sendo fator restritivo ao desenvolvimento econômico e social em muitas regiões. Apesar de o Brasil possuir uma situação privilegiada no que diz respeito à sua disponibilidade, sua variação geográfica, temporal e o crescimento populacional tem gerado conflitos pelo seu uso em diversos setores usuários. Nessa perspectiva, merecem destaque aquelas atividades econômicas cujos usos dos recursos hídricos sejam mais intensivos, por exemplo, o setor industrial. Para estimativa do uso da água neste setor, diversas são as metodologias utilizadas. No entanto a maior parte delas tem como base valores reportados e compilados na década de setenta nos Estados Unidos refletindo, desta forma, defasagem tecnológica e ambiental dos processos produtivos, além de não representar especificamente as condições brasileiras. A evolução tecnológica das últimas décadas alterou profundamente o uso dos recursos naturais nos processos produtivos, verificando-se assim a necessidade de um estudo mais abrangente, atualizado e específico para o Brasil. Tal estudo fornecerá subsídios às empresas e órgãos gestores para um adequado programa de planejamento e gestão dos recursos hídricos neste setor. Considerando o tema apresentado e a importância de se ter coeficientes técnicos de uso da água, o presente trabalho teve como objetivo a construção de matriz de coeficientes técnicos de recursos hídricos para o setor industrial brasileiro. Para se atingir o objetivo do trabalho, inicialmente fez-se um levantamento de dados sobre os coeficientes de retirada, de geração de efluentes e consumo por produto (m3/unidade produzida), ou dados de vazão e produção, possibilitando, dessa forma, o cálculo dos coeficientes. Após esta etapa, foi estabelecida a estrutura do banco de dados e feito seu preenchimento. A estrutura contempla campos referentes ao nome da indústria, tipologia, coeficientes de captação, consumo e de geração de efluentes, entre outros, permitindo assim classificar as informações de acordo com vários critérios. Para o enquadramento das tipologias das indústrias foi utilizada a Classificação Nacional de Atividades Econômicas (CNAE), versão 2.0. Após o cadastro das informações no banco de dados, fizeram-se análises para observar, por exemplo, as discrepâncias existentes entre os dados, dentro de um mesmo segmento buscando-se com isso, justificativas plausíveis para tais diferenças. A última etapa do trabalho foi a validação da matriz, com discussões junto aos órgãos públicos, instituições privadas e outras entidades relevantes do setor industrial, com o intuito de consolidar os dados e incorporar as contribuições pertinentes. Os dados obtidos nas pesquisas contemplaram um total de 148 empresas ou associações/federações, representando 51 tipologias de atividades econômicas. Após a análise e comparação dos resultados da matriz de coeficientes técnicos com dados de outras metodologias, baseadas em dados internacionais, verifica-se que, de modo geral, a adoção de tais valores superestima os coeficientes de retirada, consumo e efluentes associados às indústrias brasileiras. Comprovou-se, também, que os dados apresentados pelo Integrated Pollution Prevention and Control (ITPS, 2009), comparado às outras fontes disponíveis, são mais indicados para representar a realidade do setor industrial brasileiro quando da inexistência de dados específicos das indústrias nacionais. Conclui-se, portanto, que a CNAE permitiu definir de maneira clara e objetiva as tipologias associadas às principais atividades econômicas do setor industrial brasileiro e que a matriz de coeficientes técnicos de recursos hídricos obtida no presente trabalho retrata de forma mais consistente e precisa a atual situação das indústrias brasileiras, fornecendo subsídios indispensáveis às empresas e aos órgãos gestores para um adequado programa de gestão, planejamento, controle e uso racional dos recursos hídricos para o setor industrial do Brasil.
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Suo, Xinkun. "Réalisation et caractérisation des revêtements à base magnésium élaborés par projection à froid". Phd thesis, Université de Technologie de Belfort-Montbeliard, 2012. http://tel.archives-ouvertes.fr/tel-00864186.
Testo completoAbstract (sommario):
Le procédé de projection à froid a démontré ses avantages uniques dans la préparation de revêtements métalliques, composites et céramiques. Parmi ces revêtements, ceux constitués de magnésium pur ou de composites à matrice métallique à base de magnésium font partie des matériaux les plus prometteurs en raison de leur excellente résistance spécifique. Pourtant, les mécanismes de fabrication, par ce procédé de projection, des revêtements magnésium et composites à base de magnésium n'ont pas été étudiés. C'est le sujet de cette thèse. Les recherches menées dans cette étude s'articulent autour de plusieurs domaines, à savoir: La science des matériaux avec des études sur l'effet de la granulométrie des particules de magnésium, l'effet de la taille et de la teneur (15% vol. - 60 % vol.) des particules de renforcement (SiC) ; La mécanique des fluides avec des modélisations de géométrie de buse, d'écoulement de gaz et des vitesses des particules de magnésium et alliage de magnésium (AZ91D) ; Les caractérisations des dépôts avec des analyses de microstructure et des mesures de microdureté, d'adhérence et de comportement au frottement des revêtements;Les résultats montrent que la projection à froid peut être utilisée pour fabriquer des revêtements de magnésium purs ou composites sans aucune oxydation ou transformation de phase. La taille de ces particules doit rester dans une fourchette acceptable pour égaler la vitesse critique (entre 653 m*s-1 et 677 m*s-1) permettant la déposition. Concernant plus spécifiquement les résultats sur les revêtements de magnésium pur, le maximum de rendement de dépôt est obtenu par projection d'une poudre de granulométrie comprise entre 22 μm et 64 μm. L'adhérence atteint 11.6 ± 0.5 MPa lorsque le substrat est préchauffé à 200 oC. Pour le cas des revêtements AZ91D, la construction du dépôt s'effectue par effet de verrouillage mécanique. Le type de frottement observé sur ces revêtements est une usure adhésive. Dans les revêtements composites d'AZ91D - SiC, la teneur en particules de renforcement SiC présentes dans le dépôt diminue avec leur taille dû à l'effet "onde de choc". Le rendement de dépôt augmente avec la teneur en SiC de 15 vol.% à 30 vol.%, puis diminue au-delà de 30 vol%. Le type de frottement correspond à une usure par abrasion.
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Ivan, Jokić. "Анализа мел-фреквенцијских кепстралних коефицијената као обележја коришћених при аутоматском препознавању говорника". Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2014. https://www.cris.uns.ac.rs/record.jsf?recordId=88036&source=NDLTD&language=en.
Testo completoAbstract (sommario):
Рад је окренут ка анализи мел-фреквенцијских кепстралних коефицијената као обележја говорника која се користе при аутоматском препознавању говорника. Испитан је утицај промене облика чујних критичних опсега као и модификације енергије у њима на тачност препознавања говорника. Такође испитане су и неке трансформације ради умањења временске променљивости модела истих говорника.Rad je okrenut ka analizi mel-frekvencijskih kepstralnih koeficijenata kao obeležja govornika koja se koriste pri automatskom prepoznavanju govornika. Ispitan je uticaj promene oblika čujnih kritičnih opsega kao i modifikacije energije u njima na tačnost prepoznavanja govornika. Takođe ispitane su i neke transformacije radi umanjenja vremenske promenljivosti modela istih govornika.
The work is oriented towards the analysis of mel-frequency cepstralcoefficients as speaker features used in automatic speaker recognition. Theinfluence of the shape of auditory critical bands as well as the proposedenergy modification inside them is tested. Also, some transformations forreducing of time variability of models of the same speakers are proposed.
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Balvay, Daniel. "Qualité de la modélisation en imagerie dynamique de la microcirculation avec injection d'un agent de contraste : nouveaux critères et applications en multimodalité". Paris 11, 2005. http://www.theses.fr/2005PA112147.
Testo completoAbstract (sommario):
L'imagerie dynamique de microcirculation dispose d'un potentiel important pour l'étude de nombreuses pathologies in vivo, en complément à l'imagerie conventionnelle. Or pour obtenir des cartes de paramètres microcirculatoires à partir des données dynamiques, une modélisation doit être effectuée. Les méthodes actuelles pour vérifier la qualité de cette modélisation n'étant pas satisfaisantes, le potentiel de l'imagerie dynamique en est fortement réduit. Nous montrons ici que pour étudier la modélisation, tant qualitativement que quantitativement, il est nécessaire de traiter séparément les questions de qualité d'ajustement et de robustesse,. Nous avons mis au point une nouvelle méthode, basée sur l'autocorrélation, pour estimer les amplitudes des composantes corrélées et non corrélées des signaux. Cette méthode nous a permis de corriger le coefficient de corrélation R² et la matrice de covariance, et ainsi de définir de nouveaux critères de fiabilité et une matrice de covariance corrigée pour les remplacer. L'amélioration apportée par les nouveaux critères est démontrée sur simulations et sur données IRM dynamiques réelles. La matrice de covariance corrigée estime la robustesse et la redondance locale des paramètres. Elle peut être calculée conjointement pour compléter les nouveaux critères de fiabilité. Les améliorations apportées par les nouveaux indicateurs doivent faciliter le développement de l'imagerie de la microcirculation. L'intérêt des nouveaux indicateurs est illustré sur un grand panel de données d'imagerie. Ils constituent plus généralement de nouveaux outils de traitement du signalThe microcirculation dynamic imaging could be a relevant imaging when used in addition with more conventional medical imaging. The dynamic data are modeled, pixel by pixel, to provide microcirculation parameters maps. However there is no efficient tool to assess the modeling quality. The relevance of the parametric maps provided by the dynamic imaging is then limited. Here, we show that a qualitative and quantitative study of the modeling quality needs first to distinguish two questions : the quality of the data fits and the robusness for the random noise. To separate the questions, we designed a new autocorrelation based method which is able to estimate the amplitude of both the correlated and not correlated component of a signal. This method allowed us to correct the correlation coefficient R² and the covariance matrix estimation. It allowed us to define new reliability criteria and a corrected covariance matrix to replace the more conventional indicators. It was shown, on simulated data and in MR data, that new reliabily criteria are obviously better than the R² to assess fit quality. The corrected covariance matrix which assess the robustness and the redoundancy can be calculated in addition to the reliability criteria unlike conventional one which is limited to good data fits. Thus the modeling quality is obviously improved by the new indicators. It should improve the clinical use of microcirculation dynamic imaging where guaranties are needed against artefact. The interest of the new criteria is showed on many different dynamic data. More generaly the new indicators appear as new efficient tools for signal analysis
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Arduini, Tommaso. "Volumetric mass transfer coefficient in viscous batch in mechanically agitated fermenters". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Cerca il testo completoAbstract (sommario):
L’industria di processo è basata su diverse operazioni unitarie, le quali possono essere divise in due gruppi principali: il primo contenente quelle volte alla produzione vera e propria dei prodotti, mentre le rimanenti hanno come scopo la separazione dei prodotti d’interesse da quelli ritenuti di scarto. Per questo motivo, un corretto dimensionamento delle apparecchiature coinvolte è strettamente consigliato. Tuttavia, in situazioni complesse come i sistemi bifase, ciò non è sempre possibile. Infatti, lo scambio di materia che avviene tra il liquido e il gas non può essere calcolato analiticamente con formule puramente teoriche, ma al contrario, diversi dati sperimentali sono richiesti. Per questo motivo, spesso il dimensionamento di questo tipo di reattori è spesso fatto a tentativi, senza seguire una procedura ingegnerizzata. Per risolvere questo problema, diversi studi stanno cercando di costruire una corretta procedura per predire, in modo più accurato possibile il valore del coefficiente di scambio volumetrico. Il valore di questo parametro, infatti, è strettamente richiesto nella soluzione dei bilanci di materia che permettono il dimensionamento dell’apparecchiatura. In particolare, questo parametro può essere ricavato da misurazioni sperimentali. Tuttavia, diverse metodologie impiegate restituiscono risultati differenti. Per questo motivo, la letteratura contiene numerosi articoli con risultati significativamente diversi tra di loro.
Tuttavia, metodi di misurazione più efficaci sono stati introdotti. Tra questi si ricorda il Dynamic Pressure Method, il quale sarà utilizzato in questo elaborato per la valutazione del coefficiente di trasporto di materia volumetrico. Inoltre saranno proposte diverse correlazioni come un utile strumento per il dimensionamento di fermentatori industriali con più di una girante.
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weathers, jeffrey wayne. "COMBINING THE MATRIX TRANSFORM METHOD WITH THREE-DIMENSIONAL FINITE ELEMENT MODELING TO ESTIMATE THE INTERFACIAL HEAT TRANSFER COEFFICIENT CORRESPONDING TO VARIOUS MOLD COATINGS". MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04072005-143359/.
Testo completoAbstract (sommario):
The interfacial heat transfer coefficient is an important variable regarding the subject of metal castings. The error associated with the experimental temperature data must be dealt with appropriately so that they do not significantly affect the resulting interfacial heat transfer coefficient. The systematic and random errors are addressed using a combination of three-dimensional finite element modeling and the matrix transform method, respectively. Experimentally obtained A356 permanent mold casting data was used to estimate the interfacial heat transfer coefficient corresponding to common industrial mold coatings.
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Santos, Josiane Alexandrino dos. "Desenvolvimento e caracterização de compósitos piezoelétricos de PZT com matriz cimentícia e borracha natural /". Ilha Solteira, 2018. http://hdl.handle.net/11449/153992.
Testo completoAbstract (sommario):
Orientador: Jose Antonio MalmongeResumo: O uso de materiais inteligentes tem sido cada vez mais utilizado pelo ramo de engenharia civil, devido à crescente demanda por construções que têm como função não só atenderem ao crescente aumento populacional, como agirem também como facilitadores da vida humana. Dentro dos estudos em desenvolvimento nesta área, o que vem ganhando destaque é o desenvolvimento de sensores compósitos de materiais piezoelétricos à base de cimento, que sejam capazes de atuar no monitoramento e detecção de possíveis falhas nas estruturas civis em tempo real e contínuo. Alguns dos grandes problemas encontrados no desenvolvimento de sensores piezoelétricos baseados em matrizes cimentícias, encontram se na degradação das propriedades dos sensores frente às condições ambientais em tempo contínuo a que estes são submetidos, bem como, a possibilidades de as fases de preenchimento interferirem diretamente no processo de cura da matriz, reduzindo suas propriedades mecânicas desejáveis. Buscando resolver tais problemas, o presente trabalho teve como objetivo a obtenção e caracterização de compósitos piezoelétricos utilizando como matriz o cimento modificado com borracha natural (BN) e titanato zirconato de chumbo (PZT) como fase piezoelétrica. O PZT foi escolhido como fase piezoelétrica devido seu alto valor do coeficiente piezoelétrico enquanto a inserção da BN buscou garantir aos compósitos, resistência à passagem de água, umidade e a resistência a soluções nocivas ao cimento, atuando no aumento da dura... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The use of intelligent materials has been increasingly used by the civil engineering industry, in response to the increasing demand for constructions that serve, not only to attend to the increasing population, but also to act as facilitators of human life. Within the studies under development in this area, the one that has being gaining prominence is the development of composite sensors of cement-based piezoelectric materials, that can act in the monitoring and detection of possible failures in civil structures in real and continuous time. Some of the major problems encountered in the development of piezoelectric sensors based on cementitious matrices lie in the degradation of the properties of the sensors, both as against the environmental conditions in continuous time to which they are subjected, as well as the possibility that filling phases interfere directly in the process of curing the matrix, reducing its desirable mechanical properties. In order to solve such problems, the present study aimed to obtain and characterize of a composite piezoelectric array of modified cement with natural rubber (NR) and lead zirconate titanate (PZT) as the piezoelectric layer. The PZT was chosen as the piezoelectric phase because of its high piezoelectric coefficient, while the BN insertion sought to guarantee the resistance of the composites to the passage of water, moisture and noxious solutions to the cement, in order to increase not only the durability, as well the piezoeletric prop... (Complete abstract click electronic access below)
Mestre
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SILVA, THAIANA ALVIM. "EVALUATION OF THE INFLUENCE OF MATRIC SUCTION AND DEGREE OF WEATHERING ON THE COEFFICIENT OF EARTH PRESSURE AT REST (K0) IN RESIDUAL SOIL". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31407@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
A necessidade da determinação do comportamento tensão-deformação de solos sob carregamento para fins de projeto de Engenharia exige o conhecimento prévio do estado natural de tensões ao que o solo está imposto. Quando se trata de solos residuais tropicais, este desafio amplia-se ainda mais devido à ação do intemperismo e variação de umidade. O estado natural do solo é usualmente expresso pelo coeficiente de empuxo no repouso (K0). Para a determinação de K0 três classes de métodos são utilizadas: métodos de correlação, de determinação in situ e em laboratório. Neste estudo, é utilizada uma célula rígida com sistema de controle de sucção para a obtenção de K0 em laboratório. Foram analisadas três amostras de solo residual de Gnaisse com diferentes graus de intemperismo, provenientes de São Conrado, Rio de Janeiro, denominadas: solo residual jovem (SRJ); solo residual de transição (SRT); e solo residual maduro (SRM). Para a análise da influência da sucção no valor do coeficiente de empuxo, cada amostra de solo foi ensaiada sob três diferentes condições de umidade, que tentaram representar as seguintes condições: mais úmida, com sucção de 10 kPa; intermediária, com 40 kPa de sucção; e mais seca, com 100 kPa. Os valores de K0 obtidos nos ensaios variaram de 0,50 a 0,65. Os resultados seguiram, em parte, a tendência esperada. Entretanto, devido à heterogeneidade do material estudado, é necessário realizar repetições dos ensaios a fim de obter dados representativos.
The necessity to determine the stress-strain behavior of soils under loading for the purpose of engineering projects requires early knowledge of the natural state of stress that acting on the mass of soil. When it comes to tropical residual soils, this challenge is even greater due to weathering and moisture variation. The natural state of the soil is usually expressed by the coefficient of earth pressure at rest (K0). For the determination of K0 three classes of methods can be used: correlation meth-ods, in situ determination and laboratory tests. On this research, one rigid cell with system of suction control is used to obtain values of K0 in laboratory tests. Were analyzed three samples of Gneiss residual soil with different degrees of weathering. The samples were provenient to São Conrado, Rio de Janeiro and namely: young residual soil (SRJ), transition residual soil (SRT) and mature residual soil (SRM). To evaluate the influence of suction on the value of coefficient of earth pressure at rest, each sample of soil were tested into three different levels of moisture which correspond of following conditions: more humid, with suction of 10 kPa; interme-diate, with 40 kPa of suction; and more dry, with 100 kPa. The K0 values obtained in the tests ranged from 0,50 to 0,65. In general, the results attended the expected trend. However, due to the great heterogeneity of the studied material, it is neces-sary to perform repetitions of tests in order to obtain representative data.
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Dotti, Massimo. "Analisi dei coefficienti di auto induzione di dispersione nelle macchine elettriche rotanti di tipo multifase". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amslaurea.unibo.it/713/.
Testo completoAbstract (sommario):
L’obiettivo di questa tesi è l’analisi e la modellizzazione dei flussi dispersi statorici nelle macchine multifase utilizzando la teoria dei vettori di spazio multipli. L’analisi ed il calcolo del coefficiente di auto induzione di dispersione statorica nei vari spazi è cruciale nella progettazione e nel controllo delle macchine elettriche multifase in quanto, per esempio, essa limita il ripple di corrente quando la macchina non è alimentata con una tensione perfettamente sinusoidale. Il fine è pertanto di giungere alla scrittura di un’equazione che leghi il generico vettore di spazio dei flussi dispersi ai vettori di spazio delle correnti che alimentano la macchina elettrica tramite una costante che contenga i coefficienti di auto e mutua induzione di dispersione in cava degli avvolgimenti statorici.
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Liénard, E. "Mesures du coefficient de corrélation angulaire B-v dans les transitions B nucléaires". Habilitation à diriger des recherches, Université de Caen, 2010. http://tel.archives-ouvertes.fr/tel-00577620.
Testo completoAbstract (sommario):
Les mesures de corrélation dans les transitions B sont des mesures de précision effectuées à basse énergie dans le but de mettre en évidence une physique au-delà du Modèle Standard. Le groupe Interactions fondamentales du LPC Caen a développé dans ce cadre un dispositif de piégeage d'ions, LPCTrap, installé sur la ligne LIRAT au GANIL. Le projet initial, dont l'objectif était de mesurer précisément le coefficient de corrélation angulaire B-v dans la décroissance B des noyaux 6He, arrive à son terme. Ce coefficient est sensible aux constantes de couplage de l'interaction faible et l'expérience permet donc de tester l'existence éventuelle d'un couplage exotique rejeté par le Modèle Standard. L'objectif du travail présenté est de donner l'état des lieux de l'expérience 6He en fin de parcours en la resituant dans son cadre théorique et expérimental, et de présenter les perspectives du groupe dans le domaine à court et moyen termes.
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Silva, Paulo Maria de Oliveira e. "Estudo dos efeitos da adiÃÃo de ZnO e Nb2O5 nas propriedades dielÃtricas da matriz cerÃmicas BaBi4Ti4O15 (BBT) e suas aplicaÃÃes em antenas". Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=10945.
Testo completoAbstract (sommario):
nÃo hÃCom o rÃpido crescimento das indÃstrias de telecomunicaÃÃes criou-se uma forte necessidade por materiais cerÃmicos para aplicaÃÃes em micro-ondas. Devendo estes materiais apresentar alta permissividade dielÃtrica (εr), elevado fator de qualidade (Q), boa estabilidade tÃrmica (τf Â10 ppm/ÂC) e baixo custo. Com a invenÃÃo de telefones celulares portÃteis, o campo da comunicaÃÃo sem fio passou por um crescimento inovador nas Ãltimas dÃcadas. O sucesso da terceira geraÃÃo (3G) dos serviÃos de comunicaÃÃo de telefonia celular, motiva o desenvolvimento de banda larga de quarta geraÃÃo (4G) de telefones celulares e outros produtos e serviÃos sem fio, como por exemplo, o Bluetooth. Este trabalho consiste no desenvolvimento e caracterizaÃÃo da cerÃmica de titanato de bÃrio-bismuto (BaBi4Ti4O15) com adiÃÃo de Ãxido de niÃbio (Nb2O5) ou Ãxido de zinco (ZnO), visando a diminuiÃÃo da temperatura de sinterizaÃÃo e possivelmente melhorar a densificaÃÃo, e posteriormente, verificar as modificaÃÃes ocorridas nas propriedades do material, como por exemplo, o coeficiente de temperatura da frequÃncia ressonante (τf). As sÃries cerÃmicas foram produzidas usando a reaÃÃo no estado sÃlido, com o uso de moagem mecÃnica de alta energia e tratamento tÃrmico. A caracterizaÃÃo estrutural foi realizada com base na Microscopia EletrÃnica de Varredura (MEV) e Picnometria. As densidades relativas das amostras adicionadas com (ZnO) a de maior concentraÃÃo teve valor de 77% enquanto que o BBT puro o valor foi de 56%. As densidades relativas das amostras adicionadas com (Nb2O5) a de maior concentraÃÃo teve valor de 61% em relaÃÃo ao BBT puro. Foram realizados experimentos para avaliaÃÃo do comportamento elÃtrico e dielÃtrico das amostras, na faixa de Micro-ondas e RadiofrequÃncia (temperatura ambiente e com variaÃÃo de temperatura). Por fim, o material foi testado como uma DRA, e posteriormente os resultados obtidos foram simulados atravÃs do programa HFSS. As caracterÃsticas da DRA da cerÃmica pura sÃo 1,12dBi de ganho e 32,51% de eficiÃncia. A DRA que foi adicionada com 2% de (ZnO) apresentou ganho de 1,16dBi com 33,96% de eficiÃncia, enquanto a que foi adicionada com 5% de (Nb2O5) apresentou 1,41dBi de ganho com 42,21% de eficiÃncia.
With the rapid growth of the telecommunications industry created a strong need for ceramic materials for applications in microwave. These materials should exhibit high dielectric permittivity (εr), high quality factor (Q), good thermal stability (τf Â10 ppm/ÂC) and low cost. With the invention of mobile phones, the field of wireless communication has undergone a revolutionary growth in recent decades. The success of the third generation (3G) services in mobile communication, motivates the development of broadband fourth generation (4G) of mobile phones and other wireless products and services, such as Bluetooth. Nowadays it is well known the use of tablets, which are increasingly gaining market and encouraging the development of new technologies to improve the flow of information. This work involves the development and characterization of the barium bismuth titanate ceramic, (BaBi4Ti4O15) with addition of niobium oxide (Nb2O5) or zinc oxide (ZnO) in order to decrease the sintering temperature and possibly improve the densification and subsequently check the modifications on material properties, such as the temperature coefficient of resonant frequency (τf). The series ceramics were produced using the solid state reaction with the use of high energy mechanical milling and heat treatment. The structural characterization was performed based on Scanning Electron Microscopy (SEM) and Measurement by Pycnometer. The relative densities of the samples with added (ZnO) had the highest concentration value of 77% pure BBT while the value was 56%. The relative densities of the samples spiked with (Nb2O5) had the highest concentration value of 61% compared to pure BBT. Experiments were conducted to evaluate the electrical and dielectric behavior of the samples in the range of Microwave and Radio Frequency (temperature and temperature variation). Finally, the material was tested as a DRA, and then the results were simulated using the HFSS program. The characteristics of the pure ceramic DRA are 1,12dBi gain and 32,51% efficiency. The DRA added with 2% (ZnO ) showed 1.16dBi gain with 33,96% efficiency , while the one that was added with 5% (Nb2O5) showed gain of 1.41dBi with 42,21% efficiency.
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Totò, Matteo. "Studio delle proprietà reometriche di compound a matrice poliolefinica espandibile e reticolabile e ricerca di possibili correlazioni con il coefficiente di espansione". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21672/.
Testo completoAbstract (sommario):
Il compound a matrice poliolefinica studiato è un materiale espandibile e reticolabile, usato per la produzione di manufatti espansi a celle chiuse mediante stampaggio ad iniezione. In questo progetto di tesi il compound viene studiato dal punto di vista reologico, per cercare di prevedere il grado di espansione del manufatto stampato. La correlazione tra l’analisi reometrica e il coefficiente di espansione del manufatto finale potrebbe essere sfruttata per un controllo di qualità del materiale, permettendo così di prevedere il comportamento e le dimensioni finali del manufatto prima dello stampaggio. Lo scopo dello studio è quello di prevedere le dimensioni del manufatto finale partendo da un campione derivante dai granuli del compound a matrice poliolefinica. La prima parte dello studio si concentra sull’analisi del materiale in condizioni ideali, cioè campioni che contengono solo agente reticolante e campioni che contengono esclusivamente agente espandente, valutando l’influenza di questi additivi singolarmente.
La seconda parte si concentra sull’analisi del materiale in condizioni reali, co-presenza di reticolante ed espandente, e sulla ricerca di una correlazione tra le analisi reometriche e il coefficiente di espansione.
L’ultima parte dello studio si focalizza sull’applicazione di un metodo di previsione lineare delle dimensioni di manufatti stampati, partendo da mescole incognite. Le tecniche di analisi impiegate spaziano da quelle termogravimetriche (TGA), calorimetriche (DSC) a quelle reometriche sui provini derivanti dai granuli, mentre sui campioni stampati sono state eseguite prove dimensionali, prove di densità, prove di durezza (SHORE A e Ascker C) e prove di abrasione.
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Brooks, Josh Daniel. "Nested (2,r)-regular graphs and their network properties". Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etd/1471.
Testo completoAbstract (sommario):
A graph G is a (t, r)-regular graph if every collection of t independent vertices is collectively adjacent to exactly r vertices. If a graph G is (2, r)-regular where p, s, and m are positive integers, and m ≥ 2, then when n is sufficiently large, then G is isomorphic to G = Ks+mKp, where 2(p-1)+s = r. A nested (2,r)-regular graph is constructed by replacing selected cliques with a (2,r)-regular graph and joining the vertices of the peripheral cliques. For example, in a nested 's' graph when n = s + mp, we obtain n = s1+m1p1+mp. The nested 's' graph is now of the form Gs = Ks1+m1Kp1+mKp. We examine the network properties such as the average path length, clustering coefficient, and the spectrum of these nested graphs.
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Santos, Anna Rita Marcondes dos. "Efeito da densidade de marcadores e do tipo de matriz de parentesco genômico na acurácia da seleção genômica em milho tropical". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11137/tde-09082016-155117/.
Testo completoAbstract (sommario):
A seleção genômica (Genomic Selection - GS) permite identificar indivíduos superiores com base no seu método genômico e apresenta a possibilidade de incorporação do melhoramento quantitativo à genética molecular. O melhor preditor linear não viesado (Best Linear Unbiased Prediction - BLUP) é um método de predição dos efeitos aleatórios do modelo com base nos componentes de variância obtidos por meio do método máxima verossimilhança restrita (Restricted maximum likelihood - REML). A eficiência do REML\\BLUP pode ser incrementada por meio da incorporação de matrizes de parentesco genômico nos modelos de seleção genômica, uma vez que os efeitos genéticos genômicos aditivos dos indivíduos avaliados constituem os componentes aleatórios dos modelos mistos abordados. Dentre os algoritmos disponíveis para estimá-las, a partir de dados de polimorfismo de nucleotídeo único (Single-nucleotide polymorphism - SNP\'s) há as matrizes de Vanraden (2008) Astle e Balding (2009) e as de Yang et al. (2010) (matriz de parentesco unificado e matriz de parentesco unificado ajustado). Adicionalmente ao método de estimação da matriz de parentesco, a acurácia da GS depende da densidade de marcadores e da extensão e padrão de desequilíbrio de ligação (Linkage desequilibrium - LD) que existe no painel. Com isto, os objetivos foram: i) investigar o efeito da redução nas densidades de marcadores SNP\'s, por meio do LD, na estimativa do parentesco genético dos indivíduos e, consequentemente, na acurácia preditiva da GS; ii) estudar o efeito do uso de diferentes tipos de matrizes de parentesco genômico na acurácia da seleção genômica para linhagens e híbridos de milho tropical. Para isso, foram considerados dois painéis distintos de milho tropical: uma composta por 64 linhagens endogâmicas e a outra, por 452 híbridos. Estas foram avaliadas para o caráter produtividade de grãos, em oito e cinco ambientes, respectivamente. As linhagens e os híbridos foram genotipados com a plataforma Affymetrix® Axiom® Maize Genotyping Array, com cerca de 600 mil marcadores. Foram construídos diferentes cenários de GS quanto ao tipo de painel (linhagens e híbridos), densidade de marcadores (400k, 60k, 9586 e 1304 para linhagens e 50k, 4458 e 495, para híbridos) e tipos de matrizes de parentesco (citadas acima). Em cada um destes cenários foi estimada a herdabilidade, acurácia, capacidade preditiva e a coincidência de seleção. A partir dos resultados conclui-se que: tanto para híbridos como para linhagens, a densidade de marcas pode ser reduzida significativamente por meio do LD existente entre os SNP\'s, sem gerar prejuízos quanto à acurácia da GS, mas reduzindo os custos com genotipagem e a demanda computacional. Para predição genômica das linhagens, a matriz de Vanraden (2008) apresenta o melhor custo benefício, pois tem menor demanda computacional e proporciona resultados satisfatórios quanto à acurácia e coincidência de seleção. Para a predição genômica de híbridos, as matrizes de Yang et al. (2010) são superiores em relação às demais testadas, quanto à acurácia preditiva e coincidência de seleção.The efficiency of the Best Linear Unbiased Prediction (BLUP), along with the Restricted maximum likelihood (REML) methods, can be increased by incorporating genomic kinship matrices to Genomic Selection models (GS). Among the available algorithms to estimate these matrices from single-nucleotide polymorphism (SNP) data there are Vanraden (2008), Astle e Balding (2009) and Yang et al. (2010) (unified relationship matrix and adjusted unified relationship matrix). In addition to the estimation method of the relationship matrix, the accuracy of GS depends on the density of markers and the extent and pattern of linkage disequilibrium (LD) that there is in the panel. Thus, the aims were: i) assess the effect of marker density reduction, based on LD, on the estimative of the genetic relationship of individuals and, consequently, on the predictive accuracy of GS; ii) study the effects of types of genomic relationship matrices on the accuracy of genomic selection for tropical maize lines and hybrids. In order to achieve there, two distinct panel of tropical maize were used: the first consisting of 64 inbred lines and latter of 452 hybrids. These panels were evaluated in field trials for grain yield in eight and five environments, respectively. The lines and hybrids were genotyped by the Affymetrix® Axiom® Maize Genotyping Array platform with 612 thousand markers. Distinct scenarios of GS were comprised considering panel type (lines and hybrids), marker density (400k, 60k, 9586 and 1304 for lines and, 50k, 4458 and 495 for hybrids) and, types of kinship matrices cited aboved. In each of these scenarios heritability, accuracy, predictive capacity and the selection coincidence were estimated. From the results it was concluded that: for both, hybrids and lines, marker density can be significantly reduced based on LD between SNP\'s without affecting the accuracy. Furthermore, this reduction also decreases genotyping costs and computational requirements. For genomic prediction of lines, Vanraden (2008) matrix shows the best cost-benefit, because it demands less computer resources and provides satisfactory results in terms of accuracy and selection coincidence. On the other hand, for genomic prediction of hybrids, the matrices of Yang et al. (2010) yielded higher predictive accuracies and selection coincidences.
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Portais, Mathilde. "Matrice de diffusion en interaction de configuration : résonances orbitalaires et électronique moléculaire quantique". Phd thesis, Université Paul Sabatier - Toulouse III, 2013. http://tel.archives-ouvertes.fr/tel-00957409.
Testo completoAbstract (sommario):
La miniaturisation des circuits électroniques, qui pourraient à terme être réalisés par une seule molécule placée entre des électrodes, tout comme l'amélioration des techniques expérimentales pour mesurer le courant dans une jonction moléculaire, nous oblige à développer des techniques de calcul du courant tunnel et de ses variations toujours plus précises. Nous développons dans cette thèse une méthode de calcul multi-électronique du coefficient de transmission qui est en fait une généralisation de la méthode mono-électronique ESQC. Celle-ci repose sur l'écriture de la matrice de diffusion de la jonction moléculaire dans une base de configurations à m+1 particules: 1 particule incidente, et m électrons localisés, mais non figés, sur la molécule. Cette méthode, nommée CI-ESQC, est par la suite utilisée pour comprendre les mécanismes multi-électroniques de transfert de charges dans la jonction tunnel aux énergies résonantes. Dans la suite, les interférences entre plusieurs résonances sont étudiées, de même que la décroissance du coefficient de transmission avec la longueur d'un fil moléculaire contenu dans la jonction. Finalement la méthode est appliquée à une jonction moléculaire susceptible de réaliser des portes logiques contrôlées en fréquence.
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Lalet, Grégory. "Composites aluminium/fibres de carbone pour l'électronique de puissance". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00538480.
Testo completoAbstract (sommario):
L'étude a pour objectif l'amélioration de la fiabilité des assemblages électroniques à travers la mise en œuvre de drains composites aluminium/fibres de carbone. Le travail a consisté à 1) modéliser, par la méthode des éléments finis, l'influence des propriétés thermiques et mécaniques du matériau de semelle sur l'assemblage életronique ; 2) élaborer (par frittage sous charge uniaxiale, frittage flash et extrusion à chaud) des matériaux composites aluminium/fibres de carbone ; et 3) lier les microstructures observées aux paramètres des procédés d'élaboration ainsi qu'aux propriétés thermiques et mécaniques mesurées.
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Trochmann, Jose Luiz Lino. "Simulação atomistica como ferramenta para investigação dos mecanismos de difusão : coeficientes de autodifusão de gases simples em matriz polimerica". [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266175.
Testo completoAbstract (sommario):
Orientador: Sergio Persio RavagnaniTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-07T03:49:14Z (GMT). No. of bitstreams: 1 Trochmann_JoseLuizLino_D.pdf: 1070584 bytes, checksum: 3407aee7ad6d88d9de0a1326aaf3d29d (MD5) Previous issue date: 2006
Resumo: Neste trabalho de tese foi realizado um estudo do potencial de predição de propriedades de transporte em matrizes poliméricas de poli - imidas, utilizando a simulação dinâmica molecular de gases simples como Oxigênio, Nitrogênio e Dióxido de Carbono. A propriedade de transporte de interesse prático, a permeabilidade de uma membrana polimérica a um dado penetrante, envolve a determinação de propriedades de ordem cinética e termodinâmica, respectivamente a determinação do coeficiente de difusão e da solubilidade deste penetrante na matriz polimérica. Atenção especial foi conferida à propriedade cinética, pela predição do coeficiente de autodifusão dos penetrantes. Num procedimento experimental clássico é de vital importância para significância das conclusões derivadas dos experimentos, o uso de amostras de membranas poliméricas adequadamente preparadas quanto à composição química, estrutura física e morfologia. Analogamente, quando se utiliza a simulação molecular para a predição de propriedades, tais como o coeficiente de autodifusão, também é de fundamental relevância para os resultados obtidos, a qualidade dos modelos moleculares das matrizes poliméricas, que serão usados como base. Assim para a preparação de modelos moleculares com o adequado empacotamento, um procedimento para a obtenção de modelos bem equilibrados foi desenvolvido neste trabalho. Os modelos moleculares desenvolvidos foram usados para a obtenção dos valores de massa específica em função da temperatura, e comparados aos valores experimentais disponíveis e quando necessário a, valores preditos por meio da expressão de massa específica em função da temperatura, acima e abaixo da temperatura de transição. A capacidade do modelo molecular desenvolvido em predizer a massa especifica e temperatura de transição vítrea foi usada como critério para a validação da adequação do empacotamento proposto para o referido modelo molecular da matriz polimérica. Os modelos validados de empacotamento, células amorfas, foram utilizados para o cálculo do coeficiente de autodifusão dos gases acima mencionados, através do da simulação dinâmica molecular. A comparação dos coeficientes de autodifusão obtidos das poli-imidas aromáticas e éster imidas, BAAF, 6FDA-ODA, PMDA-ODA e BA-20DA, para os gases O2, N2 e CO2, com os dados experimentais, permitiu concluir a adequação das células amorfas e do esquema de simulação dinâmica molecular para a predição do coeficiente de autodifusão.. A versão preditiva de Vrentas e Duda, baseada na teoria do volume livre, foi utilizada para a predição dos coeficientes de autodifusão da água e do etanol para as poli-imidas acima. , Estes valores, quando comparados com os valores obtidos através da simulação dinâmica molecular mostram a validade de ambas as teorias para a predição da cinética de difusão de penetrantes em matrizes poliméricas complexas
Abstract: In this thesis a study of the predictive potential of the molecular dynamic simulation was performed for transport properties of light gases in polyimide matrix. From de practical point of view permeability is the property of most interest, and involves kinetics as well as thermodynamics properties, diffusion coefficient and solubility of the penetrants molecule in the bulk polymeric matrix, this work will be focus in the former. As important as is in as experimental work, a well prepared polymeric membrane is essential for the significance of the draw conclusions. Therefore a special attention was take in the preparation of the bulk molecular polymeric model, the so called amorphous cell, in order to obtain well-equilibrated molecular packing models for the polyimide matrixes. The amorphous cells were prepared throughout thermodynamic transforms, using one or more of the statistical ensembles and cell specific volume obtained as a function of temperature, this data was compared against the experimental data available, and when necessary to data obtained via predictive methods. The molecular packing model ability to predict the glass transition temperature was used as criteria to validate de amorphous cell, to be used in the molecular dynamic' simulations allow the matrix to be locally flexible and coupled to the classic molecular dynamics simulation. The resulting self diffusion coefficients for the polyimide, BAAF, 6FDA-ODA, PMDAODA and BA-20DA for the gases O2, N2 e CO2 were compared to the experimental data. The lack of quality experimental diffusion data available for polyimide membranes for larger penetrants as water and ethanol, showed up as a good opportunity to assess the predictive capability of the molecular dynamic simulation for self diffusion coefficients, considering the relevant technological relevance of polyimide membranes for pervaporation process. The data of self diffusion coefficient produced by the predictive version of free-volume theory after Vrentas and Duda, was compared with the data produced via coupled molecular dynamic simulation for the water and ethanol penetrants, showing the relevance of both theories for the prediction of penetrants kinetic in complex polymeric matrixes
Doutorado
Ciencia e Tecnologia de Materiais
Doutor em Engenharia Química
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Pritchard, Joshua D. "Design, Fabrication, and Analysis of a Multi-Layer, Low-Density, Thermally-Invariant Smart Composite via Ultrasonic Additive Manufacturing". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406284899.
Testo completo
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Troadec, Carole. "Composite à matrice métallique Al-AlN : de la poudre au matériau". Grenoble INPG, 1996. http://www.theses.fr/1996INPG4205.
Testo completoAbstract (sommario):
Cette etude s'inscrit dans le cadre de l'elaboration de composites a matrice metallique aluminium/nitrure d'aluminium, par metallurgie des poudres. Deux types de poudres sont utilisees: une poudre dite composite synthetisee par nitruration directe de l'aluminium par l'azote et une poudre dite melange obtenue a partir d'un melange de poudres commerciales elementaires aluminium et nitrure d'aluminium. Ces deux types de poudres subissent un broyage hautement energetique par melangeur planetaire sous argon, puis sont frittes par compression a chaud en phase solide. La microstructure de ces materiaux, etudiee en met et nanoanalyse edx, est relativement heterogene, constituee de zones denses polycristallines et de zones a forte porosite constituees de nanocristaux. La taille de ces zones microporeuses est superieure dans les materiaux melanges et varie en fonction du taux de nitrure d'aluminium et du temps de broyage. Les zones denses sont composees de grains d'aluminium entoures de nanocristaux de nitrure d'aluminium, avec des aiguilles d'alumine et quelques cristaux d'oxynitrure d'aluminium. L'ordre de grandeur des cristaux (<1 m) est confirme par diffraction des rayons x. Les proprietes physico-chimiques (coefficient de dilatation, conductivites thermique et electrique) et mecaniques (durete, module de young, limite d'elasticite, contrainte a la rupture) different en fonction du type des poudres de depart et evoluent avec la teneur en aln. Le comportement des deux types de materiaux differe egalement en usure et en corrosion. Ces nouveaux materiaux ont dans l'ensemble, a teneur en renfort similaire, des proprietes equivalentes a celles des materiaux al/sic ou al/al#2o#3
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Monsef, Anton Jorgen Adel Youssef. "Etude des problèmes inverses pour l'équation de Sturn-Liouville à coefficients discontinus. Estimation du noyau de la résolvante près des seuils pour opérateur S-\nablaS où Sb S est une matrice". Aix-Marseille 1, 2004. http://www.theses.fr/2004AIX11035.
Testo completoAbstract (sommario):
Les mémoires non volatiles de type EEPROM sont de plus en plus sujettes à des problèmes de fiabilité dus essentiellement à la réduction des dimensions de la cellule mémoire. Cette réduction est imposée par un accroissement de la densité d'intégration au niveau de la matrice de cellules du plan mémoire. Il devient donc nécessaire de disposer d'outils permettant un diagnostic fiable et rapide des défauts affectant ces dispositifs. Dans ce contexte, l'objectif de cette thèse est de proposer une méthodologie de test, orientée diagnostic, de défauts spécifiques aux mémoires EEPROM. Cette méthodologie cible tout d'abord la cellule mémoire EEPROM isolée. L'approche utilisée se base sur l'obtention d'une équation mathématique qui permet d'évaluer l'impact des variations d'un ou de plusieurs des paramètres géométriques du transistor mémoire sur les signatures électriques de la cellule (tensions de seuil). Dans un deuxième temps, la mise en place d'une méthodologie de diagnostic qui vise la matrice de cellules mémoires EEPROM a pour objectif d'établir une corrélation entre des signatures électriques représentatives de défauts simulés et les signatures électriques obtenues sur silicium après la phase de test. Cette étude passe par une connaissance précise du processus de fabrication dans le but d'extraire une bibliothèque de fautes réalistes, basée sur étude du dessin de masques du circuit. Ces défauts sont modélisés puis pris en compte dans le circuit de simulation qui décrit un composant mémoire EEPROM élémentaire. Les résultats des deux études précédentes ont montré la nécessité de disposer de signatures électriques analogiques (tensions ou courants de seuil) représentatives de chaque cellule du plan mémoire. L'obtention de ces signatures électriques passe par l'intégration, au niveau du circuit mémoire, de structures embarquées qui permettent l'extraction des valeurs de seuil. Cela entraîne une modification du flot de test standard des mémoires EEPROM. Il en résulte une analyse plus efficace du comportement analogique de chaque cellule du plan mémoire (" bitmap analogique " et distributions en courant), permettant d'améliorer le processus de diagnostic de défauts. Ainsi, grâce à l'utilisation de ces dispositifs, il est possible de remonter rapidement à l'origine d'une défaillance responsable d'une baisse de rendementAs the memory cell design rule is scaled down and the memory array density is increased, EEPROM non volatile memories are faced with reliability issues. Therefore, it becomes mandatory to have tools available to diagnose quickly and safely defect that affect this kind of device. Knowing that, the objective of this thesis is to propose a specific EEPROM diagnosis methodology. This methodology targets in a first time an isolated EEPROM cell. The technique used is based on a mathematical equation witch allows the evaluation of the impact of any geometrical parameter variation of the floating gate transistor on electrical signatures (threshold voltages). The aim of the development of a defect diagnosis methodology, which targets the memory array, is to establish a correlation between electrical signatures collected after the simulation of a circuit netlist containing faults (these faults are modelled for simulation purposes) and process steps responsible for the apparition of these defaults. This study requires a prerequisite knowledge of the fabrication process in order that provides a list of faults that can occur for a given physical implementation of the circuit. Since the list of faults is generated, based on the layout of the circuit, only the realistically possible faults are reported. The results of the two last studies showed the necessity to collect analogical signatures representative of each memory cell of the array (voltage or threshold values). To do that, extraction threshold values structures are embedded within the memory circuit and a modification of the EEPROM standard test flow is done. It results in a more efficient analysis of the analogical behaviour of each memory cell (analogical bitmap, threshold current distributions) witch improves the defect diagnosis process. The final aim is to identify quickly the root cause of an EEPROM failure mechanism that limit manufacturing yield
38
Černý, Ondřej. "Stanovení druhé viskozity kapaliny z měřených tlakových pulsací". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229379.
Testo completoAbstract (sommario):
Diploma thesis deals with problem of assessment of the second viscosity and acoustic velocity coefficients by the different liquid´s flow in pipe from measured pressure pulstation created by diaphragm pulsator. For the solution is used a transfer matrix model and for the data evaluation a genetic algorithm in „Facharp.exe“ program. Modal analysis in problematic part of the measured stand is realized to find a wave shapes and natural frequency of a pipe. The results are for the reason of clearness processed into „MS Excel“ program and fetched to the charts which shows depedence of a second viscosity and acoustic velocity coefficients on a various flow as the final result.
39
Thomas, Benjamin. "Matériaux composites Argent/Carbone à propriétés thermiques adaptatives". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0140.
Testo completoAbstract (sommario):
Du fait leur conductivité thermique élevée, les matériaux composites à matrice métallique et renfort carbone possèdent un fort potentiel d’application pour la gestion thermique en électronique. Ces travaux présentent le développement d’un nouveau procédé pour la synthèse de matériaux composites Ag/rGO (argent / « reduced Graphene Oxide ») et Ag/GF (argent / « Graphite Flakes ») par métallurgie des poudres. Ce procédé, inspiré des méthodes de « molecular level mixing », permet d’obtenir des poudres composites Ag/rGO dans lesquelles les nano-renforts sont individualisés jusqu’à une concentration volumique de 1 %. Lorsqu’il est appliqué à la synthèse de matériaux composites Ag/GF, ce dernier permet l’élaboration de matériaux composites denses avec une concentration volumique en graphite jusqu’à 70 % et une conductivité thermique jusqu’à 675 W.m-1.K-1 (426 W.m-1.K-1 pour l’argent pur). En outre, il a été montré que le procédé d’élaboration des poudres composites Ag/GF a une forte influence sur l’anisotropie structurale des matériaux massifs ainsi que sur la résistance thermique d’interface extrinsèque Ag-graphite. Le procédé d’élaboration développé dans ces travaux permet ainsi d’obtenir des matériaux ayant une conductivité thermique jusqu’à 19 % supérieure à celle des matériaux obtenus par un procédé de mélange conventionnel. Néanmoins, comme la plupart des matériaux composites métal/GF (à matrice Cu, Al, Mg et Fe), la dilatation thermique des matériaux composites Ag/GF présente des « anomalies ». En effet, l’anisotropie de leur coefficient d’expansion thermique (CTE) est opposée à leur anisotropie structurale, leur CTE a une dépendance anormalement élevée vis-à-vis de la température et ces matériaux présentent une instabilité dimensionnelle en cyclage thermique. S’il est communément admis dans la littérature que ces anomalies sont la conséquence des contraintes internes générées lors de l’élaboration des matériaux (du fait de la différence de CTE entre matrice et renfort), ce phénomène reste mal compris et difficile à maitriser. Une part importante de ces travaux est consacrée à l’étude de ces « anomalies » et en particulier à l’étude de l’influence des propriétés mécaniques de la matrice d’argent sur la dilation thermique des matériaux composites. Grâce à la combinaison des caractérisations d’EBSD, de DRX, de microdureté instrumentée et de microscopie, des phénomènes clés responsables des propriétés thermomécaniques des matériaux composites Ag/GF ont pu être identifiés. En particulier, il a été montré qu’une part importante des contraintes internes est relaxée via la déformation plastique de la matrice d’argent et la déformation pseudo plastique du graphite lors du refroidissement post-densification des matériaux composites. Ainsi, le contrôle des propriétés mécaniques de la matrice métallique (en particulier de sa limite d’élasticité) permet d’atténuer les anomalies en CTE et confère une meilleure stabilité dimensionnelle aux matériaux composites Ag/GF lors d’un cycle thermique. L’addition de rGO dans la matrice d’argent des matériaux composites Ag/GF a également permis de réduire l’instabilité dimensionnel des matériaux jusqu’à 50 % grâce aux propriétés d’amortissement du rGODue to their high thermal conductivity, metal matrix composite materials reinforced with carbon allotropes exhibit a high potential application for thermal management in electronics. This work deals with the elaboration of new synthesis process to produce Ag/rGO (silver/reduced Graphene Oxide) and Ag/GF (silver/Graphite Flakes) composite materials. This process, based on “molecular level mixing” methods, makes it possible to obtain Ag/rGO composite powders with individualized nano-reinforcements up to a concentration of 1 % in volume. Applied to the synthesis of Ag/GF composite materials, it allows to synthesize dense composite materials with a graphite concentration up to 70 % in volume and with a thermal conductivity up to 675 Wm-1.K-1 (426 Wm-1.K-1 for pure silver). Moreover, it has been shown that Ag/GF powders elaboration process has a strong influence on the structural anisotropy of bulk materials as well as on the extrinsic thermal boundary resistance Ag-graphite. The process developed in this work allows Ag/GF composite materials to reach thermal conductivity up to 19 % higher than the same materials synthesized by conventional mixing powder process. However, like most metal/GF composite materials (with Cu, Al, Mg and Fe matrix), thermal expansion of Ag/GF composite materials shows “anomalies”. Indeed, the anisotropy of their coefficient of thermal expansion (CTE) is opposed to their structural anisotropy, their CTE has an abnormally high dependence on temperature and these materials exhibit dimensional instability during thermal cycling. While it is commonly admit in literature that these “anomalies” are the consequence of internal stresses generated during materials densification (because of CTE mismatch between matrix and reinforcement), this phenomenon remains poorly understood and difficult to control. A significant part of this work is devoted to the study of these anomalies and especially to the study of the influence of matrix mechanical properties on composite materials thermal expansion. Thanks to EBSD, XRD, instrumented microhardness and microscopy analysis, key phenomena responsible of thermomechanical behavior of Ag/GF composite materials have been identified. Especially, it has been shown that a large part of the internal stresses is relaxed by plastic deformation of silver matrix and pseudo-plastic deformation of graphite during the post-densification cooling step of the materials. Thus, the control of mechanical properties of metallic matrix (especially of its elastic limit) makes it possible to attenuate the anomalies in CTE and confers a better dimensional stability to Ag / GF composite materials during thermal cycling. Finally, the addition of rGO in silver matrix of Ag/GF composites materials has also reduced material dimensional instability by up to 50 % thanks to the damping properties of rGO
40
Saïd, Didier. "Étude théorique et numérique des vibrations de structures soumises à des chocs pyrotechniques". Cachan, Ecole normale supérieure, 1998. http://www.theses.fr/1998DENS0020.
Testo completoAbstract (sommario):
L'étude s'inscrit dans le cadre de la prévision des niveaux vibratoires induits par les chocs pyrotechniques lors de la phase de séparation des étages du lanceur Ariane 5, et plus particulièrement de la prévision des niveaux vibratoires dans la case a équipements. On développe une approche simplifiée permettant de déterminer la réponse dynamique de la structure à partir du calcul de matrices de rigidité dynamique exactes. Cette approche est réservée a des structures de type guides d'ondes dans lesquelles la direction de propagation des ondes est connue. On s'intéresse également a la prise en compte de liaisons entre structures ; on montre qu'il est possible de déterminer la matrice de rigidité dynamique des liaisons a partir de la connaissance des coefficients de réflexion et de transmission des ondes et des relations force-déplacement dans les éléments relies a la liaison.
41
Versini, Francesca. "Analisi del processo di dissoluzione in reattori agitati utilizzati nell'industria farmaceutica". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Cerca il testo completoAbstract (sommario):
La descrizione del processo di dissoluzione in recipienti agitati presenta notevoli difficoltà e fattori di incertezza, dovuti alla grande quantità di variabili coinvolte e a una comprensione non ancora completa sia del fenomeno che del regime di flusso turbolento; ne risultano criteri di scale-up e correlazioni per la predizione del coefficiente di trasferimento spesso inadeguati per sistemi diversi da quelli indagati. Inoltre, poca attenzione è stata rivolta alla possibilità di operare in condizioni di sospensione parziale, la quale d’altro canto consentirebbe di ottenere un notevole risparmio energetico.
Nell'elaborato di tesi si riporta un’analisi del processo di dissoluzione di sali inorganici in acqua, condotto in condizioni di diluizione e di sospensione sia completa che parziale e in diverse configurazioni geometriche recipiente-girante. L’evidenza sperimentale dimostra che, nel campo di condizioni esaminato, il processo scala secondo un criterio di uguaglianza della velocità di punta della girante, poiché in tale situazione la velocità d’insieme del liquido prevale su quella relativa tra esso e il solido. Si propone dunque la correlazione di seguito riportata per la predizione del coefficiente di trasferimento in funzione di tale velocità; essa è ricavata sfruttando l’analogia tra il trasporto di materia e di quantità di moto e riconoscendo l’uguaglianza tra il fattore di attrito e il coefficiente di trascinamento delle particelle:
Sh_p=2+0,0096CfRe_p^(2/3)Sc^(1/3)Ar^0,16
Sh_p, Re_p, Sc, Ar sono rispettivamente i numeri di Sherwood e di Reynolds della particella, il numero di Schmidt e il numero di Archimede. Il fattore Cf consente di valersi della medesima equazione anche per sistemi geometricamente diversi da quello utilizzato per ricavarne i coefficienti numerici; esso ha un’origine assolutamente empirica ed è calcolabile come: Cf=0,66[D/T-C/T]+1, dove T, D, C sono rispettivamente il diametro del recipiente e il diametro e la clearance della girante.
42
Konečný, Zdeněk. "Náklady vlastního kapitálu jako měřítko rizik během životního cyklu podniku". Doctoral thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2015. http://www.nusl.cz/ntk/nusl-233780.
Testo completoAbstract (sommario):
In this doctoral thesis is suggested the methodics for determination the risk structure depending on the corporate life cycle with considering the sector sensitivity to the economic cycle. The share of the operational and financial risk is calculated using the beta coefficient, in which the selected measuring quantities are included. The phases of the corporate life cycle are identified according to the quadrants of the Boston matrix and the sector sensitivity to the economic cycle is determined using the Spearman´s rank correlation coefficient describing the relation between the gross domestic product and sales of the sector. The methodics is applicable for both managers and investors.
43
Shen, Zhengyan. "Elaboration, caractérisation et nouvelle architecture de matériaux composites Al/plaquettes de carbone pour des applications thermiques". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0268.
Testo completoAbstract (sommario):
Dans l'industrie microélectronique, l'augmentation constante de la densité de puissance due à la miniaturisation des composants électroniques nécessite un matériau de dissipation thermique ayant une conductivité thermique élevée (CT), un faible coefficient de dilatation thermique (CTE) et des propriétés mécaniques (PM) appropriées pour une dissipation efficace de la chaleur. Des métaux purs, tels que Al et Cu, ont déjà été utilisés. Cependant, ils ont des CT limitées (ex. 240 W/m.K pour Al) et leurs CTE sont trop élevés (ex. 23 10-6/K pour Al), ce qui est incompatible avec ceux des composants électroniques (ex. 4 10-6/K pour Si), conduisant à une défaillance en service due à la fatigue thermique. À cet égard, les composites à matrice métallique se sont révélés être un matériau prometteur. Les matériaux en carbone, comme le graphite, le diamant et la fibre de carbone, ayant été introduits comme renforts en raison de leurs excellentes propriétés thermiques (c'est-à-dire un CT très élevé et un faible CTE) dans une matrice Al. Dans ces travaux de thèse, des matériaux composites à matrice en Al renforcé par des plaquettes de graphite peu coûteuses et facilement usinables (ci-après appelé composite Al/Gf) ont été développés dans le but de maximiser le CT, d'adapter le CTE proche de 6 10-6/K, ainsi que d'améliorer les PM.La CT intrinsèque du Gf est hautement anisotrope, c'est-à-dire 1000 W/m.K dans le plan et 5-10 W/m.K hors du plan. Il est donc clair que la bonne orientation de Gf dans la matrice d'Al assure un CT élevée, dans la direction du plan du graphite, ainsi qu’à l’échelle du matériau produit dans cette même direction. Dans cette étude, un procédé de remplissage des poudres étape par étape, a été appliquée avec succès afin d’obtenir cet arrangement 1D conventionnel. Ainsi, les valeurs de CT théoriques prévues les plus élevées peuvent être atteintes expérimentalement. En outre, les matériaux composites 2D et 3D de Gf ont été élaborés à l'aide de pistons spécialement conçus afin d'adapter le CTE anisotrope des Gf (c'est-à-dire -1 10-6/K dans le plan et 28 10-6/K hors plan). La structure 2D permet de réduire la CTE, qui est alors compatible avec celui du matériau du substrat (voisin de 8 10-6/K), tout en maintenant une CT élevée. Enfin, les efforts ont été consacrés à renforcer la matrice Al en intégrant des nanoparticules dispersées (ex-situ) de SiC et (in-situ) de TiB2 pour améliorer les PM globales du composite Al/GfIn the microelectronic industry, the ever increase in power density due to miniaturization of electronic components requires heat sink materials with a high thermal conductivity (TC), a low coefficient of thermal expansion (CTE), and specific mechanical properties (MP). Pure metals, such as Al and Cu, have been previously used. However, they have limited TCs (e.g. 240 W/m.K for Al) and their CTEs are too high (e.g. 23 × 10-6/K for Al), being incompatible with those of electronic components (e.g. 4 × 10-6/K for Si), leading to failures in service due to thermal fatigue. Regarding this, metal matrix composites have been proven to be promising material where carbon materials, such as graphite, diamond, and carbon fibres, have been introduced as reinforcements because of their excellent thermal properties (i.e. very high TC and low CTE). In this Ph.D. project, Al matrix composites reinforced with low-cost and easily machinable graphite flakes (hereafter called Al/Gf composite) were developed with the aim to maximize TCs, tailor CTEs close to 6×10-6/K, as well as improve MPs.The intrinsic TCs of Gf are highly anisotropic, i.e. in-plane TC of 1000 W/m.K and out-of-plane TC of 5-10 W/m.K, respectively. It is thus clear that the strong orientation of Gf in the Al matrix ensures the high TCs, along the direction of graphite plane, in the as-produced composite. In this study, a new approach to combining flake powder metallurgy with a step-by-step powder filling process was successfully applied to achieve this conventional 1D arrangement. As such, the highest TC values theoretically predicted can be achieved experimentally. Further, the 2D and 3D arrangements of Gf were made using specifically designed punches in order to tailor the anisotropic CTEs of Gf (i.e. in-plane CTE of -1 × 10−6/K and out-of-plane CTE of 28 × 10−6/K), being unavailable in the 1D arrangement. The 2D arrangement allows to achieve the reduced CTEs being compatible with those of the substrate materials while maintaining a high TCs, demonstrating the strong potential for applications. Finally, the efforts were devoted to strengthen the Al matrix by integrating dispersed (ex-situ) SiC and (in-situ) TiB2 nanoparticles to improve the overall MPs of the Al/Gf composites
44
Merelli, Elisa. "Calcolo del Pagerank: una formulazione basata sulla risoluzione di sistemi lineari". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23202/.
Testo completoAbstract (sommario):
L'obiettivo di questo elaborato è introdurre il problema del calcolo del vettore di PageRank, mostrare come è tradizionalmente risolto e esporre una formulazione alternativa che richiede la risoluzione di sistemi lineari. La trattazione di conclude mostrando i risultati di un'analisi sperimentale volta ad applicare le conoscenze teoriche ad un caso reale.
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Cassiani-Ingoni, Lionel. "Etude d'un hydrogel, copolymere (mma-co-vp) utilise comme precurseur de lentilles de contact : caracterisation du gel, diffusion et activite du lysozyme dans la matrice". Paris 6, 1987. http://www.theses.fr/1987PA066299.
Testo completo
46
Booso, Benjamin David. "The Growth of Columnar Thin Films and Their Characterization Within the Visible and Near Infrared Spectral Bands". University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1272587327.
Testo completo
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Nascimento, Flávia Rodrigues do. "Programação diária da operação de sistemas termoelétricos de geração utilizando otimização bio-inspirada em colônia de formigas". Universidade Federal de Juiz de Fora (UFJF), 2011. https://repositorio.ufjf.br/jspui/handle/ufjf/3038.
Testo completoAbstract (sommario):
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A programação diária da operação de sistemas termoelétricos de geração consiste em determinar uma estratégia de despacho das unidades geradoras para atender a demanda de energia, satisfazendo as restrições operacionais e funcionais do sistema elétrico de potência. O problema pode ser dividido em dois subproblemas: (i) referente à determinação das unidades que devem estar em operação mediante a demanda solicitada, “Thermal Unit Commitment” e (ii) referente à determinação da potência gerada por cada uma das unidades colocadas em serviço, “Despacho Econômico”. Devido à variação de carga ao longo do tempo, a programação da operação envolve decisões do sistema de geração a cada hora, dentro do horizonte de um dia a duas semanas. Os estudos relacionados às técnicas de otimização bio-inspiradas, utilizadas na resolução da programação diária da operação de sistemas termoelétricos de geração, apontam que a combinação entre os métodos computacionais biologicamente inspirados com outras técnicas de otimização tem papel importante na obtenção de melhores soluções em um menor tempo de processamento. Seguindo esta linha de pesquisa, o presente trabalho faz uso de uma metodologia baseada na otimização por colônia de formiga para a minimização do custo da programação diária de operação de unidades termoelétricas. O modelo proposto utiliza uma Matriz de Sensibilidade (MS) baseada nas informações fornecidas pelos multiplicadores de Lagrange a fim de melhorar o processo de busca bio-inspirado. Desta forma, um percentual dos indivíduos da colônia faz uso destas informações no processo evolutivo da colônia. Os resultados alcançados através das simulações indicam que a utilização da MS resulta em soluções de qualidade com um número reduzido de indivíduos.
The daily schedule of thermoelectric systems consists of determining the strategy to set the generation units to be put in operation to meet the load, meeting also the operational and functional constraints of the respective power system. This problem can be split into two subproblems: (i) schedule of units that must operate in accordance with a given load, or Thermal Unit Commitment and (ii) set the power generation for each committed unit, or Economical Schedule. Due to load variations the schedule involves hourly generation decisions, in a horizon that varies from one day to two weeks. Researches related to bio-inspired optimization strategies applied to the daily thermal system operation show that the combination between bio-inspired computing techniques and other optimization methods has an important role in order to obtain better solutions in a shorter computing time. Following this, the present work makes use of a methodology based on Ant Colony Optimization to minimize the costs of the thermal system daily scheduling. This proposed method uses a Sensitivity Matrix (SM) based on information from Lagrange Multipliers related to the problem in order to improve the bio-inspired process. In this way, a percentage of the individuals make use of the provided information in the colony evolution process. The results obtained through those simulations indicate that the use of the SM presents better quality solutions with a reduced number of individuals.
48
Rämmal, Hans. "Studies of flow duct acoustics with applications to turbocharged engines". Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10590.
Testo completoAbstract (sommario):
A number of experimental and theoretical studies, performed in the field of technical flow duct acoustics are presented in this thesis. The acoustical methods treated are implemented on turbocharged IC-engines and engine gas exchange system components. A new method based on the well-known two-load technique has been developed. The method was applied to characterise the source data of various piston-engines with non-linear behaviour including a 6 cylinder turbo-charged truck diesel engine. The source characterisation results were compared to the results obtained using the linear two-load technique. It was demonstrated that the new non-linear multi-load technique gives improved results when the source is slightly non-linear. The use of active one-port models has been tested to characterize an air terminal device (ATD) as a source of flow generated noise. In order to predict the noise generation at different operating points of the device a scaling law was derived and verified. In the experimentally derived scaling law a flow speed dependence of 3 was found for the narrow band spectra, corresponding to a dipole-like behavior of the source in the plane wave range. The proposed technique was validated successfully and the results indicated a good prediction of in-duct sound generation by the air terminal device. Sound reflection from hot flow duct openings has been investigated experimentally. The reflection coefficient was measured for flow temperatures up to 500 ºC and jet velocities up to 108m/s. The results have been compared with famous Munt’s theory. It was concluded that at low Mach number and Helmholz number cases the results agree well with the Munt’s model. This was the first experimental validation of the theory for hot flow conditions. Experimental procedures to determine the sound transmission through automotive turbo-charger compressors were developed and described in detail. An overview of a unique turbocharger testing facility established at KTH CICERO in Stockholm is given. The facility can be used to measure acoustic two-port data for turbo-compressors. Results from measurements on a passenger car turbo-compressor are presented and the influence of operating conditions on the sound transmission is discussed. Current wave action models developed in CMT for computation of the gas exchange processes in I.C. engines have been implemented to determine the acoustic wave transmission through the turbo- compressor. The models are validated with the experimental data and the results are presented for different operating conditions of a Volvo passenger car turbo-compressor.QC 20100809
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Hanusek, Lubomír. "Míry kvality klasifikačních modelů a jejich převod". Doctoral thesis, Vysoká škola ekonomická v Praze, 2003. http://www.nusl.cz/ntk/nusl-77091.
Testo completoAbstract (sommario):
Predictive power of classification models can be evaluated by various measures. The most popular measures in data mining (DM) are Gini coefficient, Kolmogorov-Smirnov statistic and lift. These measures are each based on a completely different way of calculation. If an analyst is used to one of these measures it can be difficult for him to asses the predictive power of a model evaluated by another measure. The aim of this thesis is to develop a method how to convert one performance measure into another. Even though this thesis focuses mainly on the above-mentioned measures, it deals also with other measures like sensitivity, specificity, total accuracy and area under ROC curve. During development of DM models you may need to work with a sample that is stratified by values of the target variable Y instead of working with the whole population containing millions of observations. If you evaluate a model developed on a stratified data you may need to convert these measures to the whole population. This thesis describes a way, how to carry out this conversion. A software application (CPM) enabling all these conversions makes part of this thesis. With this application you can not only convert one performance measure to another, but you can also convert measures calculated on a stratified sample to the whole population. Besides the above mentioned performance measures (sensitivity, specificity, total accuracy, Gini coefficient, Kolmogorov-Smirnov statistic), CPM will also generate confusion matrix and performance charts (lift chart, gains chart, ROC chart and KS chart). This thesis comprises the user manual to this application as well as the web address where the application can be downloaded. The theory described in this thesis was verified on the real data.
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Abbout, Adel. "Transport thermoélectrique dans des contacts quantiques ponctuels et de cavités chaotiques : effets thermiques et fluctuations". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00793816.
Testo completoAbstract (sommario):
Dans cette thèse, on s'intéresse au transport quantique des électrons dans des nano-systèmes et des cavités chaotiques . En particulier, on apporte dans un premier temps la base théorique qui permet d'expliquer les expériences de microscopie à effet de grille dans des contacts quantiques ponctuels.