L’Alliage à Mémoire de Forme (AMF) est un matériau intelligent ayant de nombreuses applications dans l'industrie aérospatiale, le génie civil, ainsi que dans le domaine biomédical. Dans toutes ces applications, le matériau est soumis à un chargement cyclique ce qui le rend vulnérable vis-à-vis du phénomène de la fatigue. Une des questions importantes dans l'étude de la fatigue de l’AMF polycristallin est l'interaction entre l’endommagement local et la transformation de phase martensitique; cette transformation se déroule dans un mode homogène macroscopique ou un mode hétérogène se traduisant par la formation de bandes de Lüders en raison de la localisation de la déformation et du changement de phase. La formation et l'évolution de ces bandes influence fortement les mécanismes physiques de déformation ainsi que l’endommagement par fatigue du matériau. Dans la littérature, on ne trouve pas d’études permettant de faire le lien entre la formation et l’évolution des bandes de localisation et la fatigue du matériau. Dans cette thèse, des expériences systématiques de fatigue en traction sont réalisées sur les éprouvettes pseudo-élastiques du Nickel-Titane avec des observations optiques in-situ de l’évolution des macro-bandes. Ces observations ont permis de retracer l'histoire de la déformation locale dans les zones où la rupture se produit. Ces résultats expérimentaux permettent de mieux comprendre le comportement de fatigue ainsi que sa dépendance par rapport à la contrainte appliquée ainsi que la fréquence du chargement. En particulier, il a été prouvé que la déformation locale résiduelle représente un meilleur indicateur de l’endommagement du matériau que la déformation résiduelle nominale/globale de la structure. / Shape Memory Alloy (SMA) is a typical smart material having many applications from aerospace industry, mechanical and civil engineering, to biomedical devices, where the material’s fatigue is a big concern. One of the challenging issues in studying the fatigue behaviors of SMA polycrystals is the interaction between the material damage and the martensitic phase transformation which takes place in a macroscopic homogeneous mode or a heterogeneous mode (forming macroscopic patterns (Lüders-like bands) due to the localized deformations and localized heating/cooling). Such pattern formation and evolution imply the governing physical mechanisms in the material system such as the fatigue process, but there is still no fatigue study of SMAs by tracing the macro-band patterns and the local material responses. To bridge this gap, systematic tensile fatigue experiments are conducted on pseudoelastic NiTi polycrystalline strips by in-situ optical observation on the band-pattern evolutions and by tracing the deformation history of the cyclic phase transformation zones where fatigue failure occurs. These experimental results help to better understand the stress- and frequency-dependent fatigue behaviors. Particularly, it is found that the local residual strain rather than the structural nominal/global residual strain is a good indicator on the material’s damage leading to the fatigue failure, which is important for understanding and modeling the fatigue process in SMAs.

In this dissertation I present advances in the studies of artificial lattices with honeycomb topology, called artificial graphene (AG), in nano-patterned GaAs quantum wells (QWs). AG lattices with very small lattice constants as low as 40 nm are achieved for the first time in GaAs. The high quality AG lattices are created by optimized electron-beam (E-beam) lithography followed by inductively coupled plasma reactive-ion etching (ICP-RIE) process. E-beam lithography is used to define a honeycomb lattice etch mask on the surface of the GaAs QW sample and the optimized anisotropic ICP-RIE process is developed to transfer the pattern into the sample and create the AG lattices. Such high-resolution AG lattices with small lattice constants are essential to form AG miniband structures and create well-developed Dirac cones. Characterization of electron states in the nanofabricated artificial lattices is by optical experiments. Optical emission (photoluminescence) yields a determination of the Fermi energy of the electrons. A significant reduction of the Fermi energy is due to the nano-patterning process. Resonant inelastic light scattering (RILS) spectra reveal novel transitions related to the electron band structures of the AG lattices. These transitions exhibit a remarkable agreement with the predicted joint density of states (JDOS) based on the band structure calculation for the honeycomb topology. I calculate the electron band structures of AG lattices in nano-patterned GaAs QWs using a periodic muffin-tin potential model. The evaluations predict linear energy-momentum dispersion and Dirac cones, where the massless Dirac fermions (MDFs) appear, occur in the band structures. Requirements of the parameters of the AG potential to achieve isolated and well-developed Dirac cones are discussed. Density of states (DOS) and JDOS from AG band structures are calculated, which provide a basis to interpret quantitatively observed transitions of electrons involving AG bands. RILS of intersubband transitions reveal intriguing satellite peaks that are not present in the as-grown QWs. These additional peaks are interpreted as combined intersubband transitions with simultaneous change of QW subband and AG band index. The calculated JDOS for the electron transitions within the AG lattice model provide a remarkably accurate description of the combined intersubband excitations. Novel low-lying excitation peaks in RILS spectra, interpreted as direct transitions between AG bands without change in QW subband, provide a more direct insight on the AG band structures. We discovered that RILS transitions around the Dirac cones are resonantly enhanced by varying the incident photon energies. The spectral lineshape of these transitions provides insights into the formation of Dirac cones that are characteristic of the honeycomb symmetry of the AG lattices. The results confirm the formation of AG miniband structures and well-developed Dirac cones. The realization of AG lattices in a nanofabricated high mobility semiconductor offers the advantage of tunability through methods suitable for device scalability and integration. The last part of this thesis describes the growth of nanocrystalline single layer and bilayer graphene on sapphire substrates by molecular beam epitaxy (MBE) with a solid carbon source. Raman spectroscopy reveals that fabrication of single layer, bilayer or multilayer graphene crucially depends on MBE growth conditions. Etch pits revealed by atomic force microscopy indicate a removal mechanism of carbon by reduction of sapphire. Tuning the interplay between carbon deposition and its removal, by varying the incident carbon flux and substrate temperature, should enable the growth of high quality graphene layers on large area sapphire substrates.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-10-24T18:46:15Z No. of bitstreams: 1 2013 - Gisele Santos de Meireles.pdf: 16741114 bytes, checksum: 1d4b03cbd2287a0984257f70efb149da (MD5) / Made available in DSpace on 2018-10-24T18:46:15Z (GMT). No. of bitstreams: 1 2013 - Gisele Santos de Meireles.pdf: 16741114 bytes, checksum: 1d4b03cbd2287a0984257f70efb149da (MD5) Previous issue date: 2013-02-27 / CAPES / FAPERJ / This study aimed to determine from the protein profile of oocysts of Cystoisospora felis recovered from the sequential use of various purification techniques adapted for specific use in sporulated oocysts of C. felis. With the aid of SDS-PAGE 12% resulted in identification of 25 groups of protein: 266, 240, 186, 165, 140, 119, 112, 105, 98, 90, 78, 55, 47, 42, 37, 35, 30, 27-28, 25, 22, 19, 18, 16, 14 kDa belonging to the structure of sporulated oocysts and sporozoites of C. felis. Based on this results and heterologous bovine serum anti-C. felis was possible to determine polypeptides dominant relevant to diagnostic immunoassay technique with "Western Blotting", these being immunodominant bands: P208, P138, P113, p106, p62, p56, p51, p48, p44, p38, p36, and p33 p27. In order to avoid misdiagnosis from cross-reactivity a positive control serum anti-C. felis was compared to with positive serum anti-Toxoplasma and Neospora in order to exclude the common protein bands, probably markers of gender and group to identify cattle infected naturally or experimentally with C. felis. As showed, the following specific antigenic protein units: p 206-208, P137-139, p112- 113, p104-107, p27-28 are responsible for determining the animal tested positive or not for Cystoisospora felis. Of the analysis of the variables could be observed that the presence of felines related to the handling, size and type of milking properties facilitates dispersion C. felis. / Este trabalho teve por objetivo, diagnosticar a infec??o por Cystoisospora felis em bovinos atrav?s do Western Blotting, apartir de oocistos obtidos com o uso sequencial de v?rias t?cnicas de purifica??o adaptadas para o uso em oocistos esporulados de C. felis. Com o aux?lio do SDS-PAGE a 12 % resultou na identifica??o de 25 grupos proteicos de: 266; 240; 186; 165; 140; 119, 112, 105, 98, 90, 78, 55, 47, 42, 37, 35, 30, 27-28, 25, 22, 19, 18, 16, 14 KDa, pertencentes a estrutura dos oocistos esporulados e esporozoitas de C. felis. Com base nesse resultado e em soro de bovino heter?logo anti-C. felis foi poss?vel determinar os polipept?deos dominantes relevantes ? t?cnica de diagn?stico imunoenzimatico com ?Western Blotting?, sendo estas, as bandas imunodominantes: p208, p138, p113, p106, p62, p56, p51, p48, p44, p38, p36, p33 e p27. A fim de evitar o diagn?stico equivocado a partir de rea??es cruzadas foi feita a compara??o do soro controle positivo anti-C. felis com o soro positivo anti-Toxoplasma e Neospora com o intuito de excluir as bandas proteicas comuns, prov?veis marcadoras de g?nero e grupo para identifica??o de bovinos infectados de maneira natural ou experimental com C. felis. Sendo evidenciadas, as seguintes unidades proteicas antig?nicas espec?ficas: p 206-208, p137-139, p112-113, p104-107, p27-28 respons?veis por determinar a positividade dos animais testados para C. felis. A partir das an?lises das vari?veis foi poss?vel observar que a presen?a de felinos associados, ao manejo, tipo de ordenha e tamanho das propriedades facilita a dispers?o de C. felis.

The present study was largely concerned with measuring accurate absolute values for the electronic state excitation cross sections in H2O, in the incident electron energy range 15eV to 50eV. It is hoped that these data will eventually help to improve the current state of electron - molecule scattering theory, as well as being useful in various fields of modelling. As an illustration of this latter point, the cross sections determined here were used to calculate quantities of importance in atmospheric modelling, namely, electron energy transfer rates and rates for the excitation of water molecules by auroral secondary electrons.

該篇文章中提出一個新的交易方式：條件機率交易模型conditional probability trading model。 這個模型應用了三個主要的基本假設： （1）總體經濟因子和股價指數間有相關性。因此可以透過總經指標來衡量股市應有的合理價位。 （2）股價具有回歸均數的特質。亦即股價一旦過度偏離基本價值，理論上會傾向回復到基本價值之上。 （3）股價指數相對於基本價值線的距離，將會影響偏態係數的大小。 根據以上三個性質，試圖建構出一個能夠捕捉股價指數變動的模型，並用以進行交易模擬，觀察其是否能獲取正報酬。 / The trading strategy, conditional probability trading model(CPTM), is presented in this article. We’ve tried to develop a new trading strategy which is built up by the combination of the properties which includes 1)the relationship between macroeconomic factors and stock market. 2) mean reversion and 3) conditional skewness. The conclusion implies that we may successfully find out a method to combine fundamental and technical analysis, if this method is proved effective. The former hypothesis is assumed that the different level of stock market index may stand for a specific condition of macroeconomic environment. Meanwhile, a better fundamental economic condition could reasonably create a higher stock market index, vice versa. By observing the fundamental value, we can figure out the market ,currently, is over-priced or under-priced. Next, we construct a trading model which is graphed like Bollinger bands. According to specific rules, it provides buying or selling signals. In some special situations, it can also forecast the turning points of the stock market precisely. 3) Skewness also plays a very important role in CPTM, because one of the hypothesis assumes that overpriced /underpriced stock market probably accompanies with left-skewed / right-skewed distribution of daily stock return. The hypothesis of dynamically adjusted skewness implies the concept that over-priced/under-priced stock market has higher propensity to decline/rise. To judge the trading timing is the core value in this model.

In recent years there has been a growing demand to produce lightweight high pressure die cast (HPDC) parts for structural applications to decrease vehicle mass and to reduce manufacturing costs. Due to the coupled rapid heat flow and complex flow/deformation that occur in the process, the formation of microstructure and defects in HPDC are still not fully understood. Developing a better understanding of microstructure formation is essential to enable advances in die design and process optimisation, as well as alloy development, to improve the quality and productivity of HPDC components. Therefore, this thesis aims to enhance this understanding by conducting detailed microstructural analysis of samples produced in controlled HPDC experiments. In the first series of experiments, various microstructure characterisation techniques were used to study salient HPDC microstructural features. The microstructures of castings were characterised at different length scales, from the scale of the casting to the scale of the eutectic interlamellar spacing. The results show that the salient as-cast microstructural features, e.g. externally solidified crystals (ESCs), defect bands, surface layer, grain size distribution, porosity and hot tears were similar for both two HPDC-specific Al alloys used, AlSi4MgMn and AlMg5Si2Mn. The formation of these features has been explained by considering the influence of flow and solidification during each stage of the HPDC process. The formation of defect bands is further studied by investigating the ratio between band thickness ( ) and average grain size in the band ( ). Suitable methods for measuring w and dsb in HPDC have been developed. The w/dsb relationship of defect bands has been investigated in HPDC specimens from a range of alloys, casting geometries and band locations within castings. The bands were measured to be 7-18 mean grains wide. This is substantial evidence that defect bands form due to strain localisation in partially solidified alloys during cold-chamber and hot-chamber HPDC. At the end of solidification, dilatant shear bands contain a higher eutectic volume fraction and/or porosity content than adjacent material. In the cross-section of the AM50 Mg alloy, the centrally-located band contains a much higher volume fraction of concentrated porosity than the second-outermost band and insignificant porosity was found in the outermost band. The level of porosity in bands was attributed to the relative difficulty of feeding shrinkage for each band location. As the feeding of material during the intensification stage is important for the reduction of porosity, the influence of intensification pressure (IP) and gate thickness on the transport of material through the gate during the latter stages of HPDC were investigated. Microstructural characterisation of the gate region indicated a marked change in feeding mechanism with increasing IP and gate size. Castings produced with a high IP and/or thick gate contained a relatively low fraction of total porosity and shear band-like features existed through the gate, suggesting that semi-solid strain localisation in the gate is involved in feeding during the pressure intensification stage. When a low IP is combined with a thin gate, no shear band was observed in the gate and feeding was less effective, resulting in a higher level of porosity in the HPDC component. As equiaxed primary crystals are subjected to intense shear during HPDC, their agglomeration and bending behaviour were investigated in the last series of experiment. Samples produced by near-static cooling, HPDC and Thixomoulding®, where the solidifying crystals experience different levels of mechanical stresses, were characterised. The electron backscatter diffraction (EBSD) technique was used to acquire grain misorientation data which is linked to the crystal agglomeration and bending behaviour during solidification. The number fraction of low-energy grain boundaries in HPDC and Thixomoulded samples was substantially higher than in ‘statically cooled’ samples. This is attributed to the much higher shear stresses and pressure applied on the solidifying alloy in HPDC and Thixomoulding, which promote crystal collisions and agglomeration. In-grain misorientations were found to be significant only in branched dendritic crystals which were subjected to significant shear stresses. This is related to the increased bending moment acting on long protruding dendrite arms compared to more compact crystal morphologies.

The purpose of this study was to describe the role of the C.E.O. (Education Coordinator) in Band Controlled Schools on selected Indian reserves in Saskatchewan. A number of key functions and leadership components were identified from the literature and were formulated into a structural framework. In this framework, the C.E.O. position was explored and studied under three major components: role, autonomy, and contextual conditions. The aspects of role which were examined were the identifying of the C.E.O., role expectations, role tasks, and obstacles. The functions related to autonomy were identified as performance, overlaps, perceptions, and organizations. Job satisfaction, personal qualities and attributes, and politics were related to contextual conditions.<p> The population was five administrative teams working on Indian reserves in Northern Saskatchewan. These teams consisted of a Chief Executive Officer, the Principal, and, where applicable, the Administrative Assistant. The schools were selected because two have been Band operated for five years or more, whereas the other three were Band operated for less than two years when this study began.<p> A case study approach was used. Data were collected through semi-structured interviews with the C.E.O.s, Principals, and Administrative Assistants. An interview guide containing 18 questions designed for the Education Coordinator, and 18 questions designed specifically for Principals was used.<p> It was concluded that broad, general similarities existed from Band to Band. However, the role was influenced by the needs, wants, and thrusts of the individual Bands. The personality, background, and interests of the individual C.E.O. had an impact upon how the role was enacted. It was difficult to isolate and compartmentalize the job of the C.E.O. on an Indian reserve.<p> Although this study was limited in scope, a number of conclusions were reached and some implications were discussed. The C.E.O. position is a relatively new one and is in many ways unique. It would be of benefit for administrators to learn more about this position since nearly every on-reserve school in Saskatchewan is controlled by the Band. The C.E.O. position will grow and develop and have a great impact upon the future of Indian Education.

The purpose of this study was to describe the role of the C.E.O. (Education Coordinator) in Band Controlled Schools on selected Indian reserves in Saskatchewan. A number of key functions and leadership components were identified from the literature and were formulated into a structural framework. In this framework, the C.E.O. position was explored and studied under three major components: role, autonomy, and contextual conditions. The aspects of role which were examined were the identifying of the C.E.O., role expectations, role tasks, and obstacles. The functions related to autonomy were identified as performance, overlaps, perceptions, and organizations. Job satisfaction, personal qualities and attributes, and politics were related to contextual conditions.<p> The population was five administrative teams working on Indian reserves in Northern Saskatchewan. These teams consisted of a Chief Executive Officer, the Principal, and, where applicable, the Administrative Assistant. The schools were selected because two have been Band operated for five years or more, whereas the other three were Band operated for less than two years when this study began.<p> A case study approach was used. Data were collected through semi-structured interviews with the C.E.O.s, Principals, and Administrative Assistants. An interview guide containing 18 questions designed for the Education Coordinator, and 18 questions designed specifically for Principals was used.<p> It was concluded that broad, general similarities existed from Band to Band. However, the role was influenced by the needs, wants, and thrusts of the individual Bands. The personality, background, and interests of the individual C.E.O. had an impact upon how the role was enacted. It was difficult to isolate and compartmentalize the job of the C.E.O. on an Indian reserve.<p> Although this study was limited in scope, a number of conclusions were reached and some implications were discussed. The C.E.O. position is a relatively new one and is in many ways unique. It would be of benefit for administrators to learn more about this position since nearly every on-reserve school in Saskatchewan is controlled by the Band. The C.E.O. position will grow and develop and have a great impact upon the future of Indian Education.

M-type barium hexaferrite powders doped with titanium and/or cobalt have been synthesized according to the stochiometric formulations BaFe(12 &amp / #8211 / (4/3)x)TixO19, BaFe12-xCoxO19 , BaFe12-2xTixCoxO19 (x varying from 0 to 1.5 with an increment of 0.5) by the mixed oxide approach. The powders were used to manufacture small ceramic tiles by sintering each composition at 1250 &deg / C with soaking times ranging from 1 to 16 hours. XRD work revealed formation of the magnetoplumbite crystal structure in all ceramics. The variations in processing parameters led to differences in microstructure and various dielectric and magnetic properties of the ceramic tiles. The interaction of the ceramics with electromagnetic waves was characterized by using a vector network analyzer in the X and Ku bands. The results revealed that, undoped barium hexaferrite ceramics and those doped with low titanium exhibited good microwave absorption properties.

In several practical applications, hot-finished steel pipe that exhibits Lüders bands is bent to strains of 2-3%. Lüders banding is a material instability that leads to inhomogeneous plastic deformation in the range of 1-4%. This work investigates the influence of Lüders banding on the inelastic response and stability of tubes under rotation controlled pure bending. It starts with the results of an experimental study involving tubes of several diameter-to-thickness ratios in the range of 33.2 to 14.7 and Lüders strains of 1.8% to 2.7%. In all cases, the initial elastic regime terminates at a local moment maximum and the local nucleation of narrow angled Lüders bands of higher strain on the tension and compression sides of the tube. As the rotation continues, the bands multiply and spread axially causing the affected zone to bend to a higher curvature while the rest of the tube is still at the curvature corresponding to the initial moment maximum. With further rotation of the ends, the higher curvature zone(s) gradually spreads while the moment remains essentially unchanged. For relatively low D/t tubes and/or short Lüders strains, the whole tube eventually is deformed to the higher curvature entering the usual hardening regime. Subsequently it continues to deform uniformly until the usual limit moment instability is reached. For high D/t tubes and/or materials with longer Lüders strains, the propagation of the larger curvature is interrupted by collapse when a critical length is Lüders deformed leaving behind part of the structure essentially undeformed. The higher the D/t and/or the longer the Lüders strain is, the shorter the critical length. This class of problems is analyzed using 3D finite elements while the material is modeled as an elastic-plastic solid with an “up-down-up” response over the extent of the Lüders strain, followed by hardening. The analysis reproduces the main features of the mechanical behavior provided the unstable part of the response is suitably calibrated. The uniform curvature elastic regime terminates with the nucleation of localized banded deformation. The bands appear in pockets on the most deformed sites of the tube and propagate into the hitherto intact part of the structure while the moment remains essentially unchanged. The Lüders-deformed section has a higher curvature, ovalizes more than the rest of the tube, and develops wrinkles with a characteristic wavelength. For every tube D/t there exists a threshold of Lüders strain separating the two types of behavior. This bounding value of Lüders strain was studied parametrically. / text