Nous étudions expérimentalement différentes configurations du transport de particules solide dans le réseau de canaux fluides (bords de Plateau) d’une mousse liquide. Dans un premier temps, la perméabilité de la mousse est mesurée à l’échelle d’un canal fluide puis de l’ensemble du réseau de canaux pour deux solutions moussantes conférant des mobilités interfaciales significativement différentes. Un modèle d’écoulement, basé sur une description fine de la géométrie des canaux de la mousse ainsi que sur un nombre de Boussinesq constant pour une solution donnée, permet de rendre compte de tous les résultats expérimentaux sur une large gamme de fraction volumique de liquide. Dans un second temps nous mesurons, à l’échelle d’un canal fluide, la vitesse d’une particule convectée par le liquide pour différents rapports d’aspect particule / canal. Pour des petits rapports d’aspects, nous mesurons des vitesses de particules anormalement faibles. Ces mesures nous permettent de mettre en évidence des contre-écoulement à la jonction du bord de Plateau et des films. Pour expliquer cet effet, nous proposons un modèle de recirculation du tensioactif faisant intervenir l’élasticité de Gibbs. Nous abordons ensuite le cas d’une particule piégée dans le réseau de canaux de la mousse. Nous abordons ensuite le cas d’une particule piégée dans le réseau de canaux de la mousse. Nous montrons que le seuil de rétention de la particule est déterminé par l’équilibre des forces hydrodynamique et capillaire. Finalement, le cas du colmatage d’un nœud de mousse est abordé / We study experimentally different particle transport configurations in fluid microchannels network (Plateau borders) of aqueous foams. At first, foams permeability is measured at the scale of a single channel and of the whole foam network for two soap solutions known for their significant different interface mobility. Experimental data are well described by a model that takes into account the real geometry of the foam and by considering a constant value of the Boussinesq number for each soap solutions. Secondly, the velocity of one particle convected in a single foam channel is measured for different particle / channel aspect ratio. For small aspect ratio, counterflows that are taking place at the channel’s corners slow down the particle. A recirculation model in the channel foam films is developed to describe this effect. To do this, the Gibbs elasticity is introduced. Then, the threshold between trapped and released of one particle in liquid foam are carried out. This threshold is deduced from hydrodynamic and capillary forces equilibrium. Finally, the case of a clog foam node is adressed

This diploma thesis deals with the question of whether do public subsidies cause wasteful use of pharmaceuticals, and if so then to what extent. The hypothesis is tested on the Czech republic data for the years 2005-2012. The biggest contributions are defining the health system as an intra-temporal problem, which tells us that lower values of discount rate implies higher level of wasteful use. I express the environmental issues, which are caused by unprofessional pharmaceutical disposal. You can find the price (-0,11), the income (-0,2) and the cross-price (-0,14) elasticity of demand for pharmaceuticals in the empirical part. These estimates are obtained with the help of the Kuhn-Tucker method. Using the 2OLS method Model 2 comes with the major findings. With 10% increase of public subsidies, consumers tend to waste 13,2% more pharmaceuticals.

Most colleges and universities invest substantial resources in an effort to strategically plan for a sound financial base. The revenue for the financial base is dependent on student enrollment that must be effectively managed. Increases in the price of tuition and fees can lead to decreased enrollment and negatively impact the revenue of an institution. The increases can also impact the enrollment of certain student populations such as minority students and high school graduates enrolling in college for the first time. Many studies have analyzed the price elasticity and student price response models that have been developed over time by reviewing historical price increases and enrollment across institutions. Few studies have used the models to predict changes in the enrollment of students for one college or university after the increases in the cost of attendance are imposed on students. This study sought to analyze the effectiveness of the most commonly reviewed student price response and price elasticity models in predicting changes in undergraduate enrollment at one metropolitan academic university. The three models introduced by Leslie and Brinkman, St. John and Heller were used to analyze the tuition and fee increases and to identify the likely percentage of increase or decrease in student enrollment at the University of North Texas for the fall 2004 semester. The study predicted the change in undergraduate enrollment among Caucasian, Hispanic, African American and Asian student populations. The price elasticity among full-time students, part-time students, undergraduate transfer students and new from high school students entering the University of North Texas were also analyzed in the research study. The results of the study found the student price response developed by Heller accurately predicted decreases in enrollment among first-time undergraduate students, continuing undergraduate students and undergraduate Caucasian students. The model introduced by Heller accurately predicted increases in enrollment among first-time Asian undergraduate students, first-time African American undergraduate students, continuing Asian undergraduate students and continuing African American undergraduate students. The study found an inelastic demand to price elasticity among full-time and part-time students and undergraduate transfer students. New from high school students were found to have an elastic demand to price elasticity.

Orientadores: Paulo Sollero, Eder Lima de Albuquerque / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-28T12:08:28Z (GMT). No. of bitstreams: 1 Shaterzadeh-Yazdi_MohammadHossein_M.pdf: 5411191 bytes, checksum: 83da697ff892a31af99059f3e88bd338 (MD5) Previous issue date: 2015 / Resumo: Em problemas de contato mecânico entre dois corpos elásticos, o cálculo de tensões e deformações dos componentes é de grande importância. Em casos particulares os corpos estão sujeitos a cargas normal e tangencial na presença de atrito, o qual aumenta a complexidade do problema. O estudo do fenômeno e a modelagem do problema, empregando o método dos elementos de contorno (MEC), é apresentado neste trabalho. Devido à presença de atrito e restrições de contato, esse problema torna-se um caso não linear. A não linearidade do problema foi contornada com a aplicação incremental de carga e o uso de um método de resolução de sistemas não lineares. A zona de contato é uma das variáveis do problema e pode conter estados de adesão e escorregamento, simultaneamente. Esses estados dependem dos esforços normais e tangenciais no componente e podem variar durante o processo de aplicação de carga. Dessa forma, cada incremento de carga pode perturbar em relação ao estado anterior. Portanto, o cálculo de variáveis e a atualização do sistema de equações em cada iteração é indispensável. Por este motivo, um algoritmo robusto para definição dos estados de contato é proposto. Como o sistema de equações obtido é não linear, o uso de um método numérico adequado é exigido. Para a solução deste sistema, o método de Newton foi aplicado, o qual permite a verificação do estado de contato em cada incremento. A análise é feita com o uso de elementos quadráticos contínuos, apresentando resultados contínuos e sem oscilação. A comparação dos resultados com as soluções analíticas de Hertz e Mindlin-Cattaneo mostram boa concordância / Abstract: The computation of stresses and strains on the components is of great importance, when the contact mechanics problems between two elastic bodies are analyzed. In particular cases, bodies are subjected to normal and shear loading in the presence of friction, which increases the complexity of the problem. The study of the phenomenon and modeling of the problem, using the boundary element method (BEM), are presented in this work. Due to the presence of friction and natural restrictions, this problem becomes non-linear. The non-linearity of the problem was solved with an incremental applied load and with the use of solvers to non linear systems. The contact zone can contain stick and slip states, simultaneously. These states are dependent on the normal and shear forces on the component and can vary during the application load process. Thus, each load increment can violate the previous state and therefore, the evaluation of variables and the updating of the system of equations after each iteration is indispensable For this reason, a robust algorithm for contact state definition is suggested. Since a non linear system of equations is obtained, an appropriate numerical method is required. To solve this system, Newton¿s method is applied, which allows the verification of the state of contact at each increment. The analysis is done with the use of quadratic continuous elements and provides continuous and non-oscillatory results. Comparisons of the results with the analytical solutions of Hertz and Mindlin-Cattaneo show good agreement / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

A gestão eficaz de recursos computacionais em nuvem está diretamente ligada a gerir corretamente o desempenho das aplicações hospedadas na Máquina Virtual (Virtual Machine - VM), criando um ambiente capaz de controlá-la e redimensionar recursos de Memória, Disco, CPU e outros que se façam necessários, individualmente em resposta a carga de trabalho. Neste trabalho considera-se também a gestão eficaz a qual é possível realizar o retorno sobre o investimento realizado para a contratação do serviço de IaaS. Nesta pesquisa de mestrado, foi proposto o gerenciamento da infraestrutura computacional em nuvem, através de dois modelos que facilitam o provisionamento auto-adaptativo de recursos em um ambiente virtualizado: alocação de recursos utilizando modelo para previsão da carga de trabalho futura e a gestão auto-adaptativa de capacidade utilizando agentes computacionais para monitorarem constantemente as VMs. Além disso, é proposto o retorno do investimento, que trata a relação entre o valor que o cliente contratou do serviço de IaaS e o quanto efetivamente ele está utilizando. Desta forma, a cada período é contabilizado a taxa do valor gasto em unidades monetárias. Para contemplar esta proposta, foram desenvolvidos algoritmos que são o núcleo de todo gerenciamento. Também foram realizados experimentos e os resultados mostram a capacidade do autogerenciamento das máquinas virtuais, com reconfiguração dinâmica da infraestrutura através de previsões baseadas em histórico e também da reconfiguração e monitoramento com o uso de agentes computacionais. Após a análise e avaliação dos resultados obtidos nos experimentos, é possível afirmar que houve uma significativa melhora da reconfiguração dos recursos com agentes computacionais se comparado a reconfiguração com previsão de carga futura. / The efficient management of computational resources in the cloud is directly linked to correctly manage the performance of the applications hosted in the virtual machine (Virtual Machine - VM), creating an environment able to control it and resize features Memory, Disk, CPU and others resources, individually in response to workload. This work is also considered effective management which is possible to realize the return on investment for hiring the IaaS service. This Master thesis, is proposed the management of computing infrastructure in the cloud, using two models that facilitate self-adaptive resource provisioning in a virtualized environment using resource allocation model to predict the future workload and adaptive self-management capacity utilizing computational agents to continuously monitor the VMs. Furthermore, it is proposed return on investment, which is the ratio between the value that the client hired the IaaS service and how effectively it is using. Thus, each period is accounted for the rate of the amount spent in monetary units. To address this proposal, were developed algorithms that are the core of all management. Experiments were also conducted and the results show the ability of self-management for virtual machines with dynamic reconfiguration of infrastructure through predictions based on historical and also the reconfiguration and monitoring with the use of computational agents. After the analysis and evaluation of the results obtained in the experiments, is possible say that there was a significant improvement in reconfiguration of resources with computational agents compared with the workload forecast.

Made available in DSpace on 2017-06-01T17:57:34Z (GMT). No. of bitstreams: 1 larissa_marques_cunha_cabral.pdf: 1240575 bytes, checksum: 527cd5d555a68768c684554d8e1cccd1 (MD5) Previous issue date: 2014-06-09 / The work involved studying the behavior and adjustment of dosage diagram of concrete with respect to static and dynamic elastic modulus. Furthermore, it compares the models of the static elastic modulus based on the compressive strength, German, European, American and Brazilian ABNT NBR 6118 (2014) prediction - Design of Concrete Structures: procedure. Two concrete were produced with different consistency; plastic and other fluid (selfcompacting). Three traits were developed for each consistency, totaling six traits. These dosages were as varying the water / cement and cement consumption; the rebate was kept constant. A comparative analysis of the experimental results with those predicted by some standards was carried out to evaluate the level of accuracy of the same. ACI 318 (2014) was the standard that had their closest results compared to NBR 6118 (2014). Have the Eurocode and DIN 1045 standards -2 showed similar results. And the standard fib CEB - 2010, showed overestimated values in relation to other standards. Thus, we can say that the determination of elasticity of the concrete module proved consistent with the materials and dosages used. However, it is very sensitive to the composition of the trace variable, even when kept the materials. The compressive strength is one of the variables that affect the results. However, it also has great influence to change the nature of the coarse aggregate and the relative folder / coarse aggregate, for example. The dynamic ultrasonic waves through the module was also measured and compared with the static module, showing a rapid and non-destructive option to evaluate the modulus of elasticity of the concrete. / O trabalho em questão estuda o comportamento e adequação do diagrama de dosagem do concreto com relação ao módulo de elasticidade estático e dinâmico. Além disso, compara os modelos de previsão do módulo de elasticidade estático baseados na resistência à compressão das normas americana, alemã, européia, fib e a brasileira ABNT NBR 6118 (2014) - Projeto de Estruturas de Concreto: procedimento. Foram produzidos dois concretos com consistências distintas; uma plástica e outra flúida (auto adensável). Foram desenvolvidos três traços para cada consistência, totalizando assim seis traços. Essas dosagens tiveram como variáveis a relação água/cimento e o consumo de cimento; o abatimento foi mantido constante. Uma análise comparativa entre os resultados experimentais com os valores previstos por algumas normas foi realizada, avaliando o nível de precisão das mesmas. A ACI 318 (2014) foi a norma que teve seus resultados mais próximos em relação a NBR 6118 (2014). Já as normas EUROCODE 2 (2004) e DIN 1045 apresentaram resultados semelhantes. E a norma fib CEB 2010, apresentou valores superestimados em relação às demais normas. Assim, é possível afirmar que a determinação do módulo de elasticidade do concreto se mostrou coerente com os materiais e dosagens utilizadas. Contudo, é uma variável muito sensível à composição do traço, mesmo quando mantidos os materiais. A resistência à compressão é uma das variáveis que interfere nos resultados. Entretanto, tem também grande influência a variação da natureza dos agregados graúdos e a relação pasta/agregado graúdo, por exemplo. O módulo dinâmico através de ondas ultrassônicas, também foi medido e comparado com o módulo estático, mostrando-se uma opção rápida e não destrutiva de avaliar o módulo de elasticidade do concreto.

OBJETIVOS: 1) Avaliar os parâmetros de biomecânica ocular provenientes do Corvis ST (Oculus Corvis ST, Scheimpflug Technology; Wetzlar, Germany) obtidos de olhos saudáveis de uma população de pacientes brasileiros. 2) Correlacionar os parâmetros derivados do Corvis ST com a idade de pacientes jovens saudáveis. 3) Verificar se as técnicas de facoemulsificação (FC) e do laser de femtosegundo (LFS), empregadas na correção cirúrgica de catatara, influenciam os parâmetros de biomecânica ocular provenientes do Corvis ST. 4) Analisar as alterações da deformação da córnea observadas em um caso de ectasia pós LASIK com flap espesso. MÉTODOS: 1) Estudo clínico transversal conduzido em 90 pacientes (90 olhos saudáveis). Foram avaliados 11 parâmetros derivados do sistema de tonometria de não contato integrado com a câmera ultrarrápida de Scheimpflug (Oculus Corvis ST, Scheimpflug Technology; Wetzlar, Germany), a saber: deformidade de amplitude (DA); pressão intraocular; 1st A time; tempo de concavidade máxima; 2nd A time; 1st A Length (tempo da primeira aplanação); 2nd A Length (tempo da segunda aplanação); raio de curvatura de maior alcance; raio de curvatura normal; velocidade de entrada (Vin) e de saída (Vout). Estes parâmetros foram correlacionados com a espessura central corneana mensurada pela Tomografia de Córnea e Segmento Anterior (Pentacam® - Oculus, Wetzlar, Germany). 2) Estudo clínico observacional, retrospectivo, conduzido em 89 pacientes (89 olhos saudáveis). Os parâmetros derivados do Corvis ST foram correlacionados com a idade dos pacientes. 3) Estudo clínico prospectivo, envolvendo 151 olhos de 127 pacientes com diagnóstico de catarata nuclear. Setenta e cinco olhos de 65 pacientes foram submetidos à técnica do laser de femtosegundo (AlconLenSx, Aliso Viejo, USA) e 76 olhos de 62 pacientes à facoemulsificação convencional (Alcon Infinit, Fort Worth, USA). Foram avaliados os 11 parâmetros de biomecânica ocular derivados do Corvis ST antes (Pré) e após as cirurgias de catarata (D1, primeiro dia de pósoperatório). A densitometria do cristalino (scattering) foi realizada pelo PNS (Pentacam Nucleus Staging). 4) Avaliação com tomografia de coerência óptica de espessura dos flaps corneanos pós Lasik e análise dos parâmetros biomecânicos provenientes do Corvis ST em uma córnea com ectasia pós Lasik. RESULTADOS: 1) A média de idade dos pacientes foi de 35,80 ± 12,83 anos. A média do equivalente esférico foi de -3,29 ± 3,69 dioptrias. A média da espessura central corneana foi de 547,50 ± 32,00 ?m Os valores dos 11 parâmetros biomecânicos obtidos de olhos saudáveis, foram os seguintes: deformidade de amplitude 1,05 ± 0,08 mm; tempo de concavidade máxima 18,38 ± 0,93 ms; pressão intraocular 16,43 ± 2,15 mmHg; tempo da primeira aplanação (1st A time) 8,32 ± 0,33 ms; tempo da segunda aplanação 23,80 ± 0,44 ms; raio de curvatura de maior alcance 11,09 ± 2,06 mm; raio de curvatura normal 7,59 ± 0,67 mm; tempo da primeira aplanação (1st A Length) 2,07 ± 0,38 mm; tempo da segunda aplanação (2nd A Length) 2,37 ± 0,47 mm; velocidade de entrada (Vin) 0,21 ± 0,05 m/s e velocidade de saída (Vout) -0,33 ± 0,07 m/s. 2) A média de idade dos pacientes foi de 27,50 ± 6,30 anos. O tempo de concavidade máxima alcançada da córnea (HC-time) foi o único dos 11 parâmetros que apresentou correlação significativa com a idade (p=0,04, rs=0,18). 3) A média de idade dos pacientes dos grupos LFS (laser de femtosegundo) e FC (facoemulsificação convencional) foram, respectivamente, 67,6 ± 9,9 anos e 68,4 ± 11,8 anos. No grupo LFS, 9 dos 11 parâmetros foram estatisticamente significativos entre o Pré e D1; e no grupo FC, 7 dos 11 parâmetros foram estatisticamente significativos entre o Pré e D1. Entre os 11 parâmetros biomecânicos avaliados, somente o tempo de concavidade máxima da córnea (HC-time) foi significativamente diferente entre os dois grupos em D1 (p=0,0387). 4) Paciente do sexo feminino, 45 anos, submetida à Lasik em ambos os olhos. Com a utilização da tomografia de coerência óptica (OCT Rtvue, OptoVue, Fremont, CA,USA) foram identificados: um flap com espessura central de 392 ?m no OD e dois cortes, sendo um flap incompleto profundo e o outro mais fino superiormente, no OE. Os parâmetros derivados do Corvis ST como a deformidade de amplitude são diferentes em ambos os olhos. CONCLUSÕES: 1) Os valores de 8 dos 11 parâmetros derivados do Corvis ST foram influenciados pela espessura central da córnea, porém esta influência foi baixa. 2) Em olhos saudáveis de pacientes jovens foi obtida correlação significativa entre a idade e o tempo de concavidade máxima, que é o tempo do início de aplanação até a concavidade máxima alcançada da córnea. 3) O laser de femtosegundo para cirurgia de catarata e a técnica de facoemulsificação convencional induziram alterações nas propriedades biomecânicas da córnea no D1. Dos 11 parâmetros biomecânicos estudados apenas o tempo de concavidade máxima da córnea apresentou diferença significativa entre os grupos (LFS e FC) no D1. 4) A ectasia unilateral após LASIK pode ocorrer devido a flap espesso com falência biomecânica da córnea / PURPOSE: 1) To evaluate ocular biomechanical metrics given by the CorVis ST (Oculus, Inc., Berlin, Germany) in a population of healthy Brazilian patients. 2) To correlate parameters derived from corneal deformation resulting from non-contact tonometry integrated with an ultra-high-speed (UHS) Scheimpflug camera (Oculus Corvis ST, Scheimpflug Technology; Wetzlar, Germany) with age in normal eyes from young patients. 3) To evaluate the changes of corneal biomechanical after femtosecond laser - assisted cataract (FS) and to compare the parameters derived by Corvis ST between standard phacoemulsification (SP) and femtosecond laser - assisted in cataract surgery. 4) To report a case of post-LASIK corneal ectasia due to a thick flap, while the contralateral eye did not develop ectasia after an incomplete deep flap cut, followed by a thinner flap Lasik procedure. METHODS: 1) An observational and cross-sectional study involving 1 eye randomly selected from 90 healthy patients. Studied parameters (including deformation amplitude, first applanation time, highest concavity time, second applanation time, first applanation length, second applanation length, curvature radius highest concavity, curvature radius normal, velocity in, and velocity out) derived from the CorVis ST were correlated to central corneal thickness from the Pentacam (Oculus, Inc.). Differences between data on the basis of gender were evaluated. 2) Observational, retrospective study involving one eye randomly selected from study participants, totaling 89 healthy eyes. The Scheimpflug images were taken with an ultra-high-speed camera during each measurement by the Corvis ST. The deformation amplitude (DA) and other parameters (e.g., pachy apex, intraocular pressure, 1st A time, highest concavity-time, 2nd A time, 1st A Length, 2nd A Length, Wing-Dist, curvature radius highest concavity, curvature radius normal, Vin, Vout) measured by the corvis ST were correlated with age. 3) Prospective study: 151 eyes of 127 patients were underwent cataract surgery. 75 eyes of 65 patients were with femtosecond laser-assisted (FS)(Alcon Len Sx, Aliso Viejo,USA) and 76 eyes of 62 patients with standard phacoemulsification (SP) (Alcon Infinit, FortWorth, USA). 4) Case Report. RESULTS: 1) About the first study: Mean patient age was 35.80 ± 12.83 years (range: 21.07 to 78.84 years). Mean central corneal thickness was 547.50 ± 32.00 ?m (range: 490 to 647 ?m) and mean spherical equivalent refraction was -3.29 ± 3.69 diopters (range: -9.50 to +10.37 diopters). Mean deformation amplitude was 1.05 ± 0.08 mm (range: 0.91 to 1.26 mm). Highest concavity time was 18.38 ± 0.93 ms (range: 16.95 to 21.07 ms). Intraocular pressure was 16.43 ± 2.15 mm Hg (range: 11.50 to 21.0 mm Hg). First applanation time was 8.32 ± 0.33 ms (range: 7.53 to 9.12 ms) and second applanation time was 23.80 ± 0.44 ms (range: 22.76 to 24.95 ms). First applanation length (max) was 2.07 ± 0.38 mm (range: 1.20 to 3.10 mm) and second applanation length (max) was 2.37 ± 0.47 mm (range: 1.33 to 4.12 mm). Curvature radius highest concavity was 11.09 ± 2.06 mm (range: 7.58 to 15.98 mm) and curvature radius normal was 7.59 ± 0.67 mm (range: 6.82 to 11.02 mm). Velocity in was 0.21 ± 0.05 m/s (range: 0.16 to 0.72 m/s) and velocity out was -0.33 ± 0.07 m/s (range: - 0.72 to -0.20 m/s). Studied parameters were not associated with gender. 2) Mean patient age was 27.50 ± 6.30 years. The highest concavity-time was the only studied parameter statistically significantly correlated to age (i.e., p=0.04, rs=0.18). 3) In relation the surgery of cataract: In group of FS, 9 of 11 parameters derived from Corvis ST were statistically significant (ss). In group of SP, 7 of 11 parameters derived from Corvis ST were ss. Only the HC - time was statistically significant between two groups (FS;SP) with p = 0.0387. 4) Corneal OCT identified a deep meniscos-shaped Lasik flap, with a central thickness of a 392 ?m in the right eye, and a incomplete deep peripheral cut in the left eye with a thinner meniscos-shaped LASIK flap. CONCLUSIONS: 1) Eight of 11 ocular biomechanical metrics given by the CorVis ST were associated with central corneal thickness, but the influence of central corneal thickness on these measurements was low. 2) In healthy eyes, age and pressure or biomechanics as derived from the Corvis ST parameters were not associated with exception to highestconcavity-time, i.e., the time from starting until the highest concavity is reached. 3) The use of the femtosecond laser- assisted system for cataract surgery and standard phacoemulsification induzed changes of biomechanical properties of the cornea by Corvis ST. Only 1 of 11 parameters studied was different statistically in two groups. 4) Unilateral ectasia after LASIK may occur due to a thick flap which leads to biomechanical failure of the cornea

<p>U radu su prvi put za proveru teorija nastajanja i gumolike elastičnosti polimernih mreža primenjeni modelni poliuretanski sistemi čiji su čvorovi veoma stabilni izocijanurat(heksahidro-1,3,5-triazin- 2,4,6-trion) prstenovi. Rad obuhvata: (1) Sintetezu nekoliko serija homogenih poli(uretan-izocijanuratnih) mreža, na bazi 2.4-TDI i poli(oksipropilen)diola, dvoetapnim postupkom u masi, tj. ciklotrimerizacijom teleheličnih diizocijanata uz katalizator Polycat 41. (2) Sintezu manje savr&scaron;enih mreža sa nekom definisanom koncentracijom visećih lanaca koja je postignuta uvodenjem monoola dietilenglikol- monometiletra u toku pripreme prepolimera. (3) Odredivanje povoljnih reakcionih uslove svih etapa sinteze uz primenu i modifikaciju postojećih analitičkih postupaka za karakterizaciju svojstava reakcionih komponenti i praćenja reakcija umrežavanja. (4) Procenu mogućih bočnih reakcija u toku nastajanja mreža jer one mogu značajno uticati na raspodelu različitih fragmenata u mrežama praćenjem koncentracija reakcionih proizvoda kod modelnih reakcija u rastvoru uz isti diol i isti katalizator i odgovarajuće mono-funkcionalne izocijanatne komponente. (5) Karakterizaciju svojstava i strukturnih parametara modelnih mreža i to primenom postupaka ekstrakcije i bubrenja, diferencijalne skanirajuće kalorimetrije, fotoelastičnih merenja, dinamičko-mehaničke spektroskopije i merenja napon-istezanje. Izborom nominalne Mn diola od 400 do 4000 postigne gustina umreženja 0.1x10^-4mol/cm³ do 10x10^-4mol/cm³ sa rasponom temperatura staklastog prelaza od -60&deg;C do +30&deg;C. Za procenu strukturnih parametara mreža primenjena je teorija granajućih procesa sa kaskadnom zamenom za slučaj nastajanja mreža ciklotrimerizacijom i dvoetapni postupak. U zavisnosti od konverzije NCO grupa u mrežama izračunate su masa po monomernoj jedinici, maseni udeo, broj po monomernoj jedinici, koncentracija po jedinici zapremine, Mn, Mw, Mz i Mw/Mn kako za elastično aktivne, osnovne i viseće lance tako i zamolekule sola. Ključni ekspehmentalni podaci koji su kori&scaron;ćeni za proveru teorija nastajanja bio sadržaj gela dobijen vi&scaron;estrukim ekstrakcijama, a za teorije gumolike elastičnosti ravnotežni modul dobijen iz fotoelastičnih merenja. Provera teorija gumolike elastičnosti se zasnivala se u nalaženje vrednosti pred- faktora 3 (tzv. faktora pamćenja) u jednačini koja daje vezu ravnotežnog modula elastičnosti i koncentracije elastično aktivnih lanaca mreže koji ukazuje na način fluktuacije cvorova mreže. Fotoelastična merenja su omogućila da se preko njih parameter pred-faktor 3 proceni pri malim deformacijama. Potvrden je koncept stvarnih mreža sa delimično potisnutim fluktuacijama čvorova uz aditivni doprinos zapletenosti lanaca modulu elastičnosti prema Langley-Graesley konceptu zarobljenih prepletaja.</p> / <p>In this thesis polymer network formation theories and rubber elasticity of polymer networks on model polyurethane systems having as a junction very stable isocyanurate(hexahidro-1,3,5-tгiazin-2,4,6- trion) rings are for the first time investigated. The work contains: (1) Synthesis of homogenious series of several poly(urethane-isocyanurate) networks based on poly(oxypropylene)diol and 2.4-TDI by two stages procedures in bulk i.e. cyclotrimerization of telechelic diisoicyanates with Polycat 41 as catalyst. (2) Synthesis of less perfect networks with some concentration of dangling chains obtained by introduction of monofunctional component diethyleneglycolmonomethylether during prepolymer formation. (3) Determination of optimal reaction conditions for both stages of the synthesis. (4) Estimation of possible side reaction during network formation because of theirs important influence on nework fragment distribution. (5) Caracterization of networks structure and properties by swelling and multiply extraction, differential scanning calorimetry, photoelastical measurements, dynamic-mechanical spectroscopy and stress-strain measurements. By using the different Mn of diols (400 - 4000) the network density from<br />0.1x10^-4mol/cm³ to 10x10^-4mol/cm³ and glass transition temperatures from -60&deg;C to +30&deg;C was achieved. For network structure determinations the theory of branching processes with cascade substitution was used. Mass per monomer unit, mass fraction, number per monomer unit, concentration per unit volume, Mn, Mw, Mz and Mw/Mn for elastically active network chains, backbone chains, dangling chains and sol molecules In the dependence on NCO groups conversion are calculated. Crucial experimental data for examination of network formation theories was the gel content and for rubber<br />elasticity theories the equilibrium modulus received from photoelastical measurement. The estimation of rubber elasticity theories was based on the analysis of the front factor 3 in the equation which gives the relation between the equilibrium modulus and concentration of elastically active network chains. It is estimated the additive contribution of chain entanglements to the equilibrium modulus, especially in the case of high networks density according to Langley-Graesley theory of trapped entanglements.</p>

The Master’s thesis is focused on the research influence the dose and type of scattered reinforcement in a reference concrete on physical and mechanical properties of the resulting composite. The investigated properties of composite belongs compressive strength, tensile strength in the flexural and tensile strength in the transverse, static modulus of elasticity in compressive strength, dynamic modulus of elasticity determined using NDT tests. The reference concrete mixture is certified as structural concrete of the class, which is commonly used on construction sites.

Élasticité, viscoélasticité et transition vitreuse de liquides vitrifiants et de solides modèles sont étudiés par des simulations moléculaires à l'équilibre en utilisant le formalisme de fluctuation de contraintes. Les systèmes modèles étudiés sont composés de systèmes de Lennard-Jones à deux et trois dimensions, un mélange binaire de Lennard-Jones (LJ) des particules constituant la version 2d du modèle bien connu de Kob-Anderson (modèle KA2d), un mélange binaire AB13 de particules répulsives et un mélange ternaire de sphères dures. Nous étudions principalement l'effet de la température T sur les propriétés mécaniques des systèmes, en particulier les transitions de phase telles que la cristallisation ou la transition vitreuse. Les résultats sont présentés en deux parties, à savoir les propriétés statiques et les propriétés dépendant du temps. Les propriétés statiques que nous avons étudiées sont essentiellement le module de cisaillement G et le module de compression K. Utilisation des simulations de dynamique moléculaire proposées par le code LAMMPS, nous avons caractérisé G et K du modèle KA2d vitrifiant, et comparé les résultats avec un système de LJ2d monodisperse. Alors que ce dernier représente un saut significatif en G à la cristallisation, le système KA2d affiche un comportement de type « corne » continu à la transition vitreuse Tg, suivant la loi G (T) ~ (1-T/Tg)^a avec a = 0,6, confirmant qualitativement les résultats des simulations sur le système KA3d en 2013, mais en contradiction avec les prédictions basées sur la théorie de couplage de mode. Nous avons également comparé les constantes élastiques d'un cristal LJ cfc avec ceux d'un solide plus complexe, la structure AB13. Cette étude montre que, bien que la contribution non-affine disparaisse à la température nulle pour la structure cfc, ce n'est pas le cas pour la structure AB13. Cette constatation indique que nous ne pouvons pas utiliser systématiquement l'approximation de l'élasticité affine à T = 0 pour les cristaux à plusieurs composants. Dans la partie consacrée aux propriétés dépendant du temps, nous avons étudié plusieurs aspects et fonctions. Tout d'abord, nous avons exploré la dépendance du temps d'échantillonnage de nos résultats statiques, et montré que cette influence est forte pour les fluctuations de contrainte. Deuxièmement, la dynamique d'équilibre est étudiée par le biais de l'autocorrélation des contraintes de cisaillement et déplacement quadratique moyen de la contrainte, ainsi que la relation entre ces deux fonctions temporelles. L'objet principal, cependant, est le module de relaxation de la contrainte de cisaillement G(t) et les modules dynamique associée G'(w) et G'(w), avec w la fréquence. Ces fonctions caractérisent la viscoélasticité de nos systèmes. En utilisant une formule proposée récemment (Wittmer et al, Phys. Rev. E 2016), nous avons pu déterminer ces fonctions avec précision et étudier leur comportement pour nos systèmes en états liquide, cristallin et vitreux / Elasticity, viscoelasticity and glass transitions of glass-forming liquids and model solids are investigated by computer simulations at equilibrium using the stress fluctuation formalism. The models systems studied include Lennard-Jones systems at two and three dimensions, a binary mixture of Lennard-Jones (LJ) particles constituting the two-dimensional version of the well known glass-former Kob-Andersen model (KA2d model), a AB13 binary mixture of repulsive particles and a ternary mixture of hard spheres. Our studies aim mainly at the effect of the temperature T on the mechanical properties of the systems under investigation, with special focus on phase transitions such as the crystallization, or the glass transition. Our results are presented in two parts, namely static properties and time-dependent properties. The static properties we studied are essentially the shear modulus G and the bulk modulus K. Using molecular dynamics simulations provided by the LAMMPS code, we characterized G and K of the glass-former KA2d model, and compared the results with a one component LJ2d system. While the latter shows a significant jump in G at the freezing transition, the former displays a continuous cusp-type behavior at the glass transition Tg, following the law G(T) ~ (1-T/Tg)^a with a=0.6, confirming qualitatively previous simulation results carried out on KA3d system in 2013, but in contradiction to predictions based on mode-coupling theory. We also compared the elastic constants of a LJ fcc crystal with those of a more complex solid, the AB13 structure. This study shows that while the non-affine contribution vanishes at zero temperature for the fcc structure, it is not the case for the AB13 structure. This finding points out that we cannot use systematically the approximation of affine elasticity at T=0 for crystals of more than one component. In the part devoted to time-dependent properties, we investigated several aspects and functions. First, we explored the sampling-time dependence of our static results, and show that this influences strongly the stress fluctuations. Secondly, equilibrium dynamics are studied via the shear-stress autocorrelation and the shear-stress mean square displacement, and the relation between them. The main focus, however, is the shear-stress relaxation modulus G(t) and the associated dynamic moduli G'(w) and G''(w), with w the frequency. These functions characterize the viscoelasticity of our systems. Using a recently proposed formula (Wittmer at al, Phys. Rev. E 2016), we were able to determine these functions quite accurately and study their behavior in liquid, crystal and glassy states