Zirconium is a widely applied material in nuclear industry and characterized by highly anisotropic mechanical behaviour. With the development of the nuclear industry, zirconium alloys have proven to be very important structural material used as pressure tubes in heavy water reactors, and thin-walled tubing in light water reactors due to improved corrosion resistance. To study the special property of zirconium, this thesis will evaluate different numerical models and will present an overview about the deformation mechanisms for zirconium alloys. Twinning and De-twinning (TDT) and Predominant Twin Reorientation (PTR) models are both implemented in the EVPSC polycrystal model. Various self-consistent models as well as TDT and PTR twinning models are evaluated by studying large strain behavior of zirconium alloys slab under different deformation processes. The material parameters for those models are determined by virtue of the experimental uniaxial tension and compression along the normal direction (ND) as well as tension along the rolling direction (RD). The predictability of those models is assumed through comparison of macroscopic deformation behavior (stress strain curves and R values) and microscopic mechanical response (texture coefficients and lattice strain) between the predicted and experimental data. Numerical results reveal that, among the various models examined, the VPSC-TDT model with the Affine self-consistent scheme gives the best overall performance for zirconium alloys slab, TDT twinning model gives the better overall performance than the PTR twinning model. / Thesis / Master of Applied Science (MASc)

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No description available.

No description available.

<p>There have been considerable requirements for improved products of sheet metal in automobile industry. A quick and economical route to new products is to design novel surface textures of varying scales for improved product enhancement in better optical appearance and formability. The critical deformation in the surface texturing is on the order of only a few microns, and can not be accurately predicted by the classical plasticity due to the size effect. The theory of strain gradient plasticity has been developed to capture the size effect based on the concept of geometrically necessary dislocations (GNDs). A selected strain gradient theory has been implemented into the finite element (FE) model to simulate the surface texturing process. A 3D FE model was developed to simulate the rolling process of sheet metal which has band-type feature on the original surface. The numerical results show that a textured roller can efficiently modify the band-type feature without changing the whole mechanical property of the sheet. Size effect has significant contribution to the magnitude of the rolling force. A FE model was developed to simulate the tensile test of the sheet with textured surface. A textured surface of the sheet is prepared through the indention on the sheet surface. The results show that the textured surface becomes harder due to the strain gradient effect, and finally improves the formability of the sheet.</p> / Master of Applied Science (MASc)

Schistosomiasis, a disease of humans caused by helminth parasites of the genus Schistosoma, kills 200 to 500 thousand people annually, endangering over 600 million people world-wide with 200 million people infected in 2003 [1, 2]. Three species of schistosome are primarily responsible for human infections, namely, Schistosoma haematobium, endemic to Africa, India, and the Middle East, S. mansoni, endemic to Africa / South America, and S. japonicum endemic to China and the Philippines [3]. The major pathological effects of schistosomiasis result from the deposition of parasite ova in human tissues and the subsequent intense granulomatous response induced by these eggs. There is a high priority to provide an effective sub-unit vaccine against these schistosome flukes, using proteins encoded by cDNAs expressed by the parasites at critical phases of their development. One technique that may expedite this gene identification is the use of microarrays for expression analysis. A 22,575 feature custom oligonucleotide DNA microarray designed from public domain databases of schistosome ESTs (Expressed Sequence Tags) was used to explore differential gene expression between the Philippine (SJP) and Chinese (SJC) strains of S. japonicum, and between males and females. It was found that 593, 664 and 426 probes were differentially expressed between the two geographical strains when mix sexed adults, male worms and female worms were compared respectively. Additionally, the study revealed that 1,163 male- and 1,016 female-associated probes were differentially expressed in SJP whereas 1,047 male- and 897 female-associated probes were differentially expressed in SJC [4]. Further to this, a detailed real time PCR expression study was used to explore the differential expression of eight genes of interest throughout the SJC life cycle, which showed that several of the genes were down-regulated in different life cycle stages. The study has greatly expanded previously published data of strain and gender-associated differential expression in S. japonicum. Further, the new data will provide a stepping stone for understanding the complexities of the biology, sexual differentiation, maturation, and development of human schistosomes, signaling new approaches for identifying novel intervention and diagnostic targets against schistosomiasis [4].

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The assessment of pedal forces is one of the more sophisticated methods applied on the sports sciences to accomplish cycling performance tests. With information of pedal forces the pedaling technique is evaluated based on the ability of the cyclists to produce and apply forces on the pedals. Several variables concerning the performance can be monitored with the application of instrumented pedals, but there is a lack of studies that consider the differences between the lower limbs on the force generation, what can occur due instrumentation limitation on the laboratories because the instrumented pedal are not commercial available and it is manufactured by research laboratories. The purpose of this study was to develop an instrumented pedals system that permit the evaluation of the pedal forces for each lower limb, with characteristics that no modify the normal pattern of pedaling and able to be used on different bicycle geometries and cycle ergometers. For the instrumentation, spindles of two (right and left) Shimano SPD pedals were modified to mounting 8 strain-gage sensors on each spindle, disposed on two rows and connected on two Wheatstone complete-bridges to measure strain in response to horizontal (Fx, tangential bridge) and vertical loads (Fz, normal bridge). With the spindles mounted on the pedal body, a piece for connection with the crank was manufactured. These pieces (right and left) are the house for ball bearings that permit the movement of the pedal relative to crank and not commit the strain-gages wires. These pieces permit the application of the pedal on different bicycles and cycle ergometers. The system was calibrated and presents a linear relationship between the load applied and the signal output from the full-bridges that monitor the horizontal and vertical efforts on the spindles. A calibration matrix was developed to transform the output signal to force magnitudes, and also an interference matrix was mounted to correct the mechanical interference between the horizontal and vertical measures. For the two pedals, the hysteresis was lower than 0,60%. For the right pedal, the sensitivity of the normal bridge was 2.5 mV/N, the tangential bridge present sensitivity of 2.6 mV/N. The left pedal presents a sensitivity of 2.4 mV/N and 2.7 mV/N for normal and tangential bridges, respectively. The resolution of the system was, for both pedals, lower than 0.5 N, while the error calculated from the calibrated data was 1% for the right normal bridge and 2% for the right tangential bridge and left normal and tangential bridges. It can be concluded that the system present characteristics that permits the application on the athlete s evaluations due the low error, satisfactory resolution and good linearity observed between the applied loads and the signal output on the normal and tangential full-bridges. / A medida das forças envolvidas na pedalada é uma das mais sofisticadas metodologias aplicadas nas ciências do esporte para avaliação da técnica de pedalada. A técnica de pedalada é avaliada com base na habilidade dos ciclistas em produzir e aplicar força aos pedais. Diversas variáveis de controle de desempenho podem ser monitoradas com a aplicação de pedais instrumentados. No entanto, observa-se que um pequeno número de estudos considera as diferenças entre os membros na capacidade de gerar força, o que possivelmente ocorre devido a limitações de instrumentação, pois pedais instrumentados são normalmente unilaterais e construídos por laboratórios de pesquisa, não sendo disponíveis comercialmente. O objetivo deste estudo foi desenvolver um sistema de pedais instrumentados que possibilitem o monitoramento das forças aplicadas nos pedais direito e esquerdo, com características que não modifiquem o padrão normal de movimento e que possam ser utilizados em diferentes bicicletas e ciclo ergômetros. Para a instrumentação, os eixos dos pedais (direito e esquerdo) modelo Shimano SPD para ciclismo mountain-bike foram modificados a fim de que fossem montados 8 extensömetros em cada eixo e dispostos em duas colunas e conectados em duas pontes de Wheatstone completas, sendo uma para o monitoramento da deformação do eixo decorrente da força aplicada no sentido horizontal e outra para medir a deformação decorrente das forças aplicadas no sentido vertical ao plano do pedal. Com o eixo fixo ao corpo do pedal, uma peça foi especialmente desenvolvida para abrigar rolamentos que permitem a conexão e o movimento relativo do pedal com o pé-de-vela, a fim de permitir a montagem dos fios dos extensômetros. Esta peça permite o uso do sistema de diferentes bicicletas e ciclo ergômetros. O sistema foi calibrado e apresentou relação linear entre as cargas aplicadas e as tensões de saída nas pontes de Wheatstone que monitoram esforços horizontais e verticais em ambos os pedais. Uma matriz de calibração foi desenvolvida para a conversão das tensões em magnitudes de força, assim como uma matriz de interferência foi montada para corrigir o acoplamento entre as medidas verticais e horizontais devido ao desalinhamento entre os sensores. Para ambos os pedais a histerese foi menor que 0,6%. Para o pedal direito, a sensibilidade na ponte normal foi de 2,5 mV/N e na ponte tangencial foi de 2,6 mV/N. Para o pedal esquerdo a sensibilidade foi de 2,4 mV/N e 2,7 mV/N para a ponte normal e tangencial respectivamente. A resolução do sistema, para ambos os pedais, foi sempre menor que 0,5 N, enquanto que o erro estimado a partir da matriz de calibração foi de 1% para a ponte normal direita e 2% para a ponte tangencial direita, e pontes normal e tangencial esquerdas. Conclui-se que o sistema apresentou características estáticas que permitem sua aplicação prática na avaliação de atletas devido ao baixo erro, satisfatória resolução e linearidade observada entre as cargas aplicadas e as tensões de saída nas pontes tangenciais e normais.

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The strain rate dependent behaviour of fine grained soils is an important aspect of geotechnical engineering. During dynamic or rapid events such as earthquakes and rapid pile testing, a fine grained soil will display significantly different behaviour than may be observed over the long life span of a structure. There is currently little understanding of the factors which influence the behaviour of fine grained soils during dynamic events (extremely high strain rates), making their response difficult to predict. This research investigates the behaviour of fine grained soils subjected to a wide range of constant strain rates in monotonic triaxial compression testing. Each test is conducted under drained conditions to observe the behaviour of soils as they transition from a drained response at lower strain rates, through to an undrained or viscous response at higher strain rate tests. Where the response of soils is drained or partially drained, higher strain rate tests measure a decrease in strength. The point of transition from partially drained to undrained behaviour corresponds to the lowest strain rate dependent strength. Further tests at higher strain rates measure consistently greater strength. The strain rate dependence of three fine grained soils is investigated, enabling a comparison of strain rate effects with soil index properties. The influence of initial state on the strain rate dependence of these Kaolin based model soils is also evaluated. The drained to partially drained response of the soils to strain rate increase is controlled by the coefficient of consolidation. Tests at high strain rates show the undrained or viscous strain rate effect on strength is related to liquidity index. Local strain instrumentation allowed comparison of strain rate effects on small strain stiffness. At higher strain rate the soils display increasingly linear behaviour. At non-linear elastic strains, liquidity index appears to control the magnitude of the strain rate effects on stiffness.

L’analyse de la fonction systolique en échocardiographie représente un challenge majeur depuis une vingtaine d’années dans le but d’améliorer la détection et la quantification des anomalies de la contraction myocardique. L’analyse des déformations myocardiques consiste à étudier le pourcentage d’étirement ou de raccourcissement myocardiques au cours du cycle cardiaque. Après le grand pas en avant dans ce domaine, consécutif à l’avènement du Doppler tissulaire il y a un quinzaine d’années, ces 4 dernières années ont vu naître une nouvelle technique d’analyse bidimensionnelle des déformations, porteuse de grands espoirs car s’affranchissant de la limitation liée à l’angle d’incidence Doppler et basée sur le suivi des marqueurs acoustiques de la paroi myocardique : le « speckle tracking echocardiography » ou « 2D strain ». Cette thèse rapporte tout d’abord une série de travaux orientés sur la validation de ce nouvel outil. Nous avons ensuite appliqué expérimentalement cette technique pour évaluer sa capacité à détecter l’ischémie myocardique lors d’un examen de stress sous dobutamine en comparaison à l’analyse de perfusion myocardique en échographie de contraste. Enfin, nous exposons plusieurs expériences cliniques qui témoignent de quelques applications potentielles de cette technique dans la prise en charge des patients porteurs de cardiopathies diverses : myocardiopathie hypertrophique, fibrillation auriculaire paroxystique et recherche de viabilité sous faibles doses de dobutamine chez les patients porteurs d’une cardiopathie ischémique. / For 20 years, analysis of systolic myocardial function by echocardiography is a major challenge to improve the detection and the quantification of myocardial contractility abnormalities. The principle of myocardial deformation analysis consists in evaluating the percentage of myocardial thickening or shortening during the cardiac cycle. After a big step forward with the advent of tissue Doppler imaging for 15 years, the 4 last years have seen the apparition of a new technique of bidimensional analysis, without angle dependency, based on the tracking of the acoustic markers of the myocardial wall, and called « speckle tracking echocardiography » or « 2D strain ». This thesis reports serial studies oriented on the validation of this new tool and on the experimental application of this technique in the detection of myocardial ischemia during pharmacological dobutamine stress echocardiography, in comparison with myocardial perfusion analysis by contrast echocardiography. Finally, we report some clinical experiences using the speckle tracking echocardiography which attest of some clinical potential applications of this technique in the management of the patients with different cardiomyopathies: hypertrophic cardiomyopathy, lone paroxysmal atrial fibrillation, and analysis of myocardial regional deformation during low doses dobutamine infusion to investigate viability in patients with ischemic cardiomyopathy.