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1
Wagner, Vanda Doreen. "Effect of a preoperative warming intervention on the acute phase response of surgical stress." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002274.
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Hantsoo, Liisa Victoria. "Interactive Effect of the Serotonin Transporter 5-HTTLPR Genotype and Chronic Stress on Depressive Symptoms in Postmenopausal Women." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1266260369.
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Ward, Allan III. "Residual Stress Effects on Power Slump and Wafer Breakage in GaAs MESFETs." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/30503.
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The objectives of this investigation are to develop a precise, non-destructive single crystal stress measurement technique, develop a model to explain the phenomenon known as 3power slump2, and investigate the role of device processing on wafer breakage. All three objectives were successfully met. The single crystal stress technique uses a least squares analysis of X-ray diffraction data to calculate the full stress tensor. In this way, precise non-destructive stress measurements can be made with known error bars. Rocking curve analysis, stress gradient corrections, and a data reliability technique were implemented to ensure that the stress data are correct. A theory was developed to explain 3power slump2, which is a rapid decrease in the amplifying properties of microwave amplifier circuits during operation. The model explains that for the particular geometry and bias configuration of the devices studied in this research, power slump is linearly related to shear stress at values of less than 90 MPa. The microscopic explanation of power slump is that radiation enhanced dislocation glide increases the kink concentration, thereby increasing the generation center concentration in the active region of the device. These generation centers increase the total gate current, leading to a decrease in the amplifying properties of the device. Passivation layer processing has been shown to both reduce the fracture strength and increase the residual stress in GaAs wafers, making them more susceptible to wafer breakage. Bare wafers are found to have higher fracture strength than passivated wafers. Bare wafers are also found to contain less residual stress than SiON passivated wafers, which, in turn, are found to have less stress than SiN passivated wafers. Topographic imaging suggests that SiN passivated wafers have larger flaws than SiON passivated wafers, and that the distribution of flaw size among SiN passivated wafers is wider than the distribution of flaws in SiON passivated wafers. These flaws are believed to lead to breakage of the device during processing, resulting in low fabrication yield. Both the power slump model and the wafer breakage data show that these phenomena are dependent on residual stress developed in the substrate during device fabrication. Reduction of process-induced residual stress should therefore simultaneously decrease wafer breakage rates and reduce power slump during device fabrication and operation.Ph. D.
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Liu, Xiaodong. "Effects of stress on intergranular corrosion and intergranular stress corrosion cracking in AA2024-T3." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133313637.
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Hengari, Simeon Ngaitungue. "The growth response of Eucalyptus grandis x E. camaldulensis to salt stress, ectomycorrhizae and endomycorrhizae double colonisation /." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/390.
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Reubush, Kimberly J. "The effects of acute handling stress on the secondary stress responses of striped bass (Morone saxtilis) and its hybrid (Morone chrysops x Morone saxtilis)." Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/41933.
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Koh, Cha San. "Poplar oxidoreductases involved in the oxidative stress response : a crystallographic snapshot towards the understanding of the catalytic mechanism." Thesis, Nancy 1, 2008. http://www.theses.fr/2008NAN10028/document.
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La structure de trois oxydoréductases (la glutathion peroxydase (Gpx), la thiorédoxine (Trx) et la glutarédoxine (Grx)) de Populus trichocarpa × deltoides (le peuplier) a été caractérisée par diffraction des rayons X. Les Gpxs forment un groupe d’enzymes qui régulent la concentration des espèces réactives de l'oxygène (ROS) dans les cellules, et qui les protègent des effets d’un stress oxydant. Contrairement à leurs homologues d’origine animale, les Gpxs végétales ne dépendent pas du glutathion (GSH) mais des Trx pour leur fonctionnement. Dans cette étude, j'ai résolu les structures des formes réduite et oxydée de la Gpx5 de peuplier et montré que des changements conformationnels drastiques sont nécessaires pour passer d’une forme à l’autre. Les Trxs régulent diverses protéines cibles par la réduction de leur pont disulfure. Mon objectif était de comprendre le mécanisme catalytique d’une nouvelle isoforme, la PtTrxh4, dont la capacité à accepter des électrons de la Grx a été récemment démontrée. Cette PtTrxh4 contient trois cystéines, la première localisée dans une extension en position N-terminale (Cys4) et deux situées dans le site actif classique (WC1GPC2) de la Trx. Les résolutions des structures de l’enzyme sauvage et du mutant C4S m’ont permis de proposer un mécanisme catalytique en quatre étapes en accord avec les études enzymatiques. Les Grxs sont des protéines qui utilisent des électrons du GSH en particulier pour catalyser des réactions d'échange de thiol-disulfure. Ici, je présente la structure de la PtGrxS12 (en complexe avec le GSH), la première structure de la Grx végétale de sous-classe 1 ayant un site actif de motif atypique 28WCSYS32Three oxidoreductases (glutathione peroxidase, GPX; thioredoxin, Trx and glutaredoxin, Grx) from Populus trichocarpa × deltoides (poplar tree) were characterized using X-ray crystallography approach. GPXs are a group of enzymes that regulate the levels of oxygen species in cells, and protect them against oxidative damage. In this study, I have determined the crystal structures of the reduced and oxidized form of poplar GPX5 (PtGPX5). Comparison of both redox structures indicates that a drastic conformational change is necessary to bring the two distant cysteine residues together to form an intramolecular disulfide bond. Trxs regulate various protein partners through the thiol-disulfide(s) reduction. The aim of this study is thus to precisely describe the catalytic mechanism of a new isoform of Trx, PtTrxh4, since it has been demonstrated recently to be reduced by Grx. PtTrxh4 contains three cysteines; one localized in an N-terminal extension (Cys4) and two in the usual Trx active site (WC1GPC2). Two crystal structures of PtTrxh4 solved in this study, wild-type and C61S mutant, allow us to propose a four-step disulfide cascade catalytic mechanism in accordance with enzymatic studies. Grxs are highly conserved redox-proteins that utilize electrons from GSH particularly to catalyze thiol-disulfide exchange reactions. Here, I present the structure of glutathionylated PtGrxS12, the first structure of plant Grx of subclass 1 with an atypical 28WCSYS32 active site. Protein structures solved here shed lights to our understanding of the redox mechanism in plant and to the enzyme-substrate interactions
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Taylor, Joshua Edward Logan. "Investigating the effects of stress on the microstructure of nuclear grade graphite." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/investigating-the-effects-of-stress-on-the-microstructure-of-nuclear-grade-graphite(eb30164d-7e26-4ef7-a787-8ba2f4563994).html.
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Graphite is used as a moderating material and as a structural component in a number of current generation nuclear reactors. During reactor operation stresses develop in the graphite components, causing them to deform. If significant numbers of graphite components were to fail in this manner, the material’s effectiveness as a neutron moderator will be reduced, and the reactor’s safe operation may be compromised. It is therefore important to understand how the microstructure of graphite affects the material’s response to these stresses. Despite much research into the effects of stress on nuclear grade graphite, there remain gaps in our understanding of this process, and there are a number of frequently observed limitations in the current research. Many existing studies either focus on the bulk material, ignoring the important changes at the microlevel; or focus on residual stresses due to the lack of available in-situ data. An experimental programme was designed to study stress-induced changes to the microstructures of Gilsocarbon and Pile Grade A graphite used in UK nuclear reactors. Particular focus was paid to the deformation of the pore structure, since graphite is highly porous and the porosity has a significant effect on the strength and structural integrity of the graphite components. A compression rig was used to simulate the build-up of operational stresses, during which confocal laser microscopy and X-ray tomography were performed to quantify changes to the pore structure at the microlevel; while X-ray diffraction was performed to study deformation of the crystal lattice and quantify the build-up of lattice strains. Pore properties of interest included pore area, surface area, volume, eccentricity, orientation, angularity and separation. Crystal lattice properties of interest included layer spacing, unit cell and crystallite size parameters, lattice strains and Bacon Anisotropy Factor. The experimental and analytical techniques were designed to significantly enhance our current understanding of how graphite responds to stress, with each observation made using a novel technique or improving the effectiveness of existing techniques. These studies have enabled significant novel observations and discussions of the stress-induced deformation behaviour of nuclear grade graphite to be made.
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Galitz, Christopher Lee. "The Effects of Early-Age Stress on the Elastic and Viscoelastic Behavior of Cement Paste." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56988.
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The viscoelastic behavior of concrete, nearly completely attributable to changes in properties in the cement paste, is an ongoing area of research with the objective of avoiding unpredictable response and potentially failure of concrete structures. This research explores the elastic and viscoelastic response in cement paste beams using relaxation testing, with and without strain reversals in the load history. It was seen that strain reversal imparts significant changes in mechanical response, retarding load relaxation. Companion beams were tested for chemical composition at varying depths in the beam section and the results were compared to those of control specimens not subject to stress. Results indicate significant variations in composition implying that stress accelerates the hydration process. The reasons behind the acceleration are discussed and incorporated into a preliminary solidification-dissolution model for beam relaxation. The model, though in need of improvement through further research, shows promise in potentially predicting relaxation in cement paste and by extension, in concrete structures.Ph. D.
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Khan, Munhammad Kashif. "Scribe Marks at Fuselage Joints-Determination of Residual Stress and Effects of Fatigue Loading using Nanoindention and Synchrotron X-ray Diffraction." Thesis, Open University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518174.
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Fayyaz, Payam. "Effects of salt stress on ecophysiological and molecular characteristics of Populus euphratica Oliv., Populus x canescens (Aiton) Sm. and Arabidopsis thaliana L. /." Göttingen : Cuvillier, 2008. http://d-nb.info/987899864/04.
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DEY, SONAL. "ELASTICITY OF MAIN CHAIN LIQUID CRYSTAL ELASTOMERS AND ITS RELATIONSHIP TO LIQUID CRYSTAL MICROSTRUCTURE." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1385403238.
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Anderoglu, Osman. "Residual stress measurement using X-ray diffraction." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1507.
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This paper briefly describes the theory and methods of x-ray residual stress
measurements.
Residual stresses can be defined as the stresses which remain in a material in the
absence of any external forces. There are many stress determination methods. Some of
those methods are destructive and some are nondestructive. X-ray residual stress
measurement is considered as a nondestructive method.
X-ray diffraction together with the other diffraction techniques of residual stress
measurement uses the distance between crystallographic planes as a strain gage. The
deformations cause changes in the spacing of the lattice planes from their stress free
value to a new value that corresponds to the magnitude of the residual stress. Because of
Poissons ratio effect, if a tensile stress is applied, the lattice spacing will increase for
planes perpendicular to the stress direction, and decrease for planes parallel to the stress
direction. This new spacing will be the same in any similarly oriented planes, with
respect to the applied stress. Therefore the method can only be applied to crystalline,
polycrystalline and semi-crystalline materials.
The diffraction angle, 2θ, is measured experimentally and then the lattice spacing
is calculated from the diffraction angle, and the known x-ray wavelength using Bragg's
Law. Once the d-spacing values are known, they can be plotted versus 2 sin ψ, ( ψ is the
tilt angle). In this paper, stress measurement of the samples that exhibit a linear behavior
as in the case of a homogenous isotropic sample in a biaxial stress state is included. The
plot of d vs. 2 sin ψ is a straight line which slope is proportional to stress. On the other
hand, the second set of samples showed oscillatory d vs. 2 sin ψ behavior. The oscillatory
behavior indicates the presence of inhomogeneous stress distribution. In this case the xray
elastic constants must be used instead of E and ν values. These constants can be
obtained from the literature for a given material and reflection combination. It is also
possible to obtain these values experimentally. Calculation of the residual stresses for
these samples is beyond the scope of this paper and will not be discussed here.
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Junior, Luciano Gomes de Medeiros. "Efeitos magnetocalórico e barocalórico em Mn[As(1-x) Sb(x)] e La[Fe(x) Si(1-x)]13." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1521.
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Estudos experimentais recentes revelaram que os compostos Mn[As(1-x) Sb(x)] e La[Fe(x) Si(1-x)]13 apresentam grandes valores para a variação isométrica da entropia e para a variação adiabática da temperatura. Estudos experimetais também mostram que o efeito magnetocalórico nestes compostos pode ser facilmente controlado através da dopagem e da pressão externa. Logo, tais dados experimentais, que necessitam de uma descrição teórica, indicam que estes compostos são bons candidatos para se estudar também o efeito barocalórico. Nesta tese, estudamos do ponto de vista teórico o efeito magnetocalórico nos compostos La[Fe(x)Si(1-x)]13 e Mn[As(1-x) Sb(x)], a pressão ambiente e a pressões externas. Estudamos também o efeito barocalórico, para alguns valores fixos do campo magnético. Este estudo teórico foi feito utilizando três modelos, a saber: (1) um modelo itinerante, de uma única rede.(2) um modelo itinerante mais elaborado com duas subredes incluindo a desordem química em uma das subredes. (3) um modelo de monentos localizados. Nossos resultados mostram que os dados experimentais dos potenciais magnetocalóricos são bem explicados pelos três modelos. Entretanto, o modelo com duas subredes é o que melhor descreve os mecanismos físicos envolvidos no efeito magnetocalórico dos compostos estudados. O modelo de monentos magnéticos localizados falha na explicação da entropia magnética a altas temperaturas e na magnetização de saturação a T= 0 K. O modelo itinerante, com uma única rede, não descreve corretamente a transferência eletrônica entre as subredes.Recent experimental data revealed that the compounds La[Fe(x)Si(1-x)]13 and Mn[As(1-x)Sb(x)], present great values for the isothermal entropy change and the adiabatic temperature change. They also showed that the magnetocaloric effect in these compounds can be easily tuned through doping and external pressure. Therefore, such experimental data, which need a theoretical description indicate that these compounds are also good candidates to study the barocaloric effect. In this PhD thesis, we studied from the theoretical point of view the magnetocaloric effect in the compounds La[Fe(x)Si(1-x)]13 and Mn[As(1-x)Sb(x)], at ambient pressure and upon external pressures. We also studied the barocaloric effect,for some fixed values of the model, of only one lattice.(2)a more elaborated itinerant model with two sublattices including the chemical disorder in one sulattice. (3) model of localized magnetic moments. Our results show that the available experimental data of the magnetocaloric potentials are well explained by the three models. However, only the two sublattice itinerant model properly describes the physical mechanisms involved in the magnetocaloric effect of the studied compounds.The localized magnetic moment model fails in explaining the magnetic entropy at high temperatures and the saturation magnetization at T = 0 K. The effective one lattice itinerant model does not properly describe the eletronic transfer between the sublattices.
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OLIVEIRA, RENE R. de. "Estudo do efeito da tensão residual na microdeformação da rede cristalina e no tamanho de cristalito em aço Cr-Si-V jateado com granalhas de aço." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27497.
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No presente trabalho foram estudados alguns efeitos causados pelo jateamento por granalhas no aço Cr-Si-V, processo que tem por objetivo aumentar a resistência à fadiga. Para este estudo a variação de parâmetros no processo são ferramentas para melhor compreender os mecanismos que influenciam esta propriedade. Os parâmetros utilizados neste trabalho foram a variação da granalha e o pré tensionamento das amostras aplicados em lâminas utilizadas em feixe de molas automobilísticas de aço de liga cromo silício vanádio (SAE 9254+V). Inicialmente foi realizada a avaliação do perfil de tensão residual, efetuada por difração de raios-x pelo método do sen2 ao longo da espessura na região onde a tensão é compressiva. Nos resultados nota-se um efeito anômalo em relação ao perfil característico da distribuição de tensão residual com a perda de compressão nas camadas iniciais em relação à superfície jateada. Com o uso da microscopia eletrônica de varredura foi observado a região afetada pelo jateamento por granalhas notando que as regiões plasticamente deformadas se encontram nas mesmas regiões onde ocorre a diminuição da tensão residual compressiva. O perfil obtido pela difração de raios-x fornece as informações necessárias com o propósito de conjugar os efeitos que a microtensão (microdeformação) influenciam na macrotensão (tensão residual). Esta relação foi comprovada pela sobreposição dos resultados encontrados na distribuição da microdeformação da rede cristalina com a tensão residual ao longo da espessura na região plasticamente deformada. Os resultados dos perfis das difrações de raios-x mostraram a existência de anisotropia de tensões entre os planos, geradas por defeitos de empilhamento e pela densidade de discordâncias. Assim sendo, para obter os valores das microtensões devem ser considerados os fatores das constantes elásticas (conforme o módulo das direções) e dos planos cristalográficos. O método aplicado foi o Williamson-Hall modificado. Além deste método outros também foram utilizados, tais como: método de Warren-Averbach e o método Single Line, este aplicando a série de Fourier, porém, ao observar os resultados, nota-se a diferença entre os valores obtidos nas deformações, tanto aos métodos quanto aos planos cristalográficos, porém a ênfase deste trabalho foi dada às características dos perfis da distribuição e não aos valores absolutos. Somando a isto, foi proporcionado o estudo da distribuição do tamanho médio de cristalito ao longo da espessura no perfil das difrações de raios-x e os resultados mostraram que esta distribuição varia de forma inversa a microdeformação. A relação entre o tamanho médio de cristalito e a variação das distâncias interplanares corresponde diretamente a alterações das densidades de discordâncias ocorridas no material que por sua vez estão ligadas às microdeformações da rede cristalina. Como complemento ao trabalho foram analisados o fator de concentração de tensão e ensaios de fadiga do material. O fator de concentração de tensão não variou conforme a utilização das granalhas S330 e S390, ambas sendo aplicadas no mesmo regime de jateamento. Os ensaios de fadiga indicaram que o pré tensionamento aumenta a vida útil nas tensões cíclicas do material estudado.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Hendriks, Erika Erna. "Streservarings van die onderwyser met betrekking tot leerders met gedrags- en emosionele probleme in die klas." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-11192007-083026/.
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Durand, Thomas. "Approche protéomique des stress abiotiques chez Populus tremula x P. alba." Phd thesis, Université d'Orléans, 2009. http://tel.archives-ouvertes.fr/tel-00520792.
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Les contraintes environnementales dans un monde en changement remettent en cause la survie des plantes ; les plus drastiques sont les contraintes abiotiques, comme les stress hydriques, thermiques, ou la pollution par les métaux lourds. Les mécanismes inductibles de la tolérance des plantes sous stress ont été étudiés par une approche physiologique combinée à une analyse protéomique. Des plants de Populus tremula x P. alba genotype 717-1B4 ont été exposés à plusieurs contraintes en chambre phytotronique : 1) un sol contenant des concentrations importantes de Cd2+ ou Zn2+, 2) une sécheresse induite par arrêt d'arrosage, 3) une contrainte thermique par élévation subite ou graduelle de 22 à 42°C. Les paramètres physiologiques des plantes ont été suivis au cours des traitements ainsi que durant la période de recouvrement qui a suivi les contraintes hydriques et thermiques. La réponse de stress a été caractérisée par ces paramètres physiologiques et par les changements dans les profils protéomiques du tissu foliaire et de la zone cambiale. Les aspects communs et particuliers du stress induit par chaque contrainte ont été décrits. Les données rassemblées dans cette étude, en enrichissant les connaissances sur la gamme de réponse des essences ligneuses, contibuent à déterminer la frontière entre le stress générique et les réponses plus spécifiques ; elles apportent également des éléments de réponse à l'utilisation du peuplier en phytoremédiation des sols pollués par les métaux.
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Gislason-Lee, Amber Jill. "The effect of X-ray system settings on perception in cardiac X-ray imaging." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15568/.
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Cardiologists use coronary angiograms to diagnose and treat cardiac patients during percutaneous coronary interventions (PCI). The X-ray photon fluence used to capture an X-ray image is directly related to image noise, whereby more fluence improves image quality; however exposure to X-rays can be harmful, therefore fluence level must be optimised. Digital image processing (DIP) may enhance image quality such that it allows for lower levels of photon fluence during image capture. The effect of changes in photon fluence and DIP on perception of coronary angiograms by clinicians was determined. Computer-generated quantum noise was added to five unprocessed patient angiograms to simulate incremental reductions in photon fluence, followed by state-of-the-art DIP. The noise adding software was calibrated for clinically-relevant settings, and validated using standard objective and subjective measurements. The degraded images were viewed next to corresponding original (not degraded) images in a staircase psychophysics experiment, with and without DIP; 12 observers selected their preferred angiogram until the point of subjective equality (PSE), i.e. level of degradation at which the observer could not perceive a difference between the original and degraded images, was determined. The PSEs were 33±15% and 34±15% reductions in fluence for unprocessed and processed images respectively. In a second psychophysics experiment angiograms representing selected fluence levels, with and without DIP, were scored individually by 16 observers on a continuous scale. Scores were analysed by a statistical regression model to quantify the fluence reduction facilitated by DIP. The DIP facilitated 25% [19%, 31%] reduction in fluence compared to no processing for the same image quality score. A significant amount of image noise can be added to coronary angiograms without being perceived, indicating potential for a significant reduction in radiation exposure exclusive to that which can be facilitated by DIP. These reductions would benefit both PCI patients and personnel.
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Casanova, i. Fernàndez Fèlix. "Magnetocaloric Effect In Gd5(SixGe1-x)4 Alloys." Doctoral thesis, Universitat de Barcelona, 2004. http://hdl.handle.net/10803/1789.
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This Ph.D. Thesis has been devoted to the preparation and characterisation of bulk Gd5(SixGe1-x)4 alloys and to the study of the magnetocaloric effect at the first-order magnetostructural transition appearing in these compounds. We summarise the most relevant results from this research:- Bulk Gd5(SixGe1-x)4 samples with 0¡Âx ¡Â0.5 have been prepared by using our home-made arc-melting furnace. Characterisation techniques (SEM, microprobe, XRD, DSC, magnetisation, ac susceptibility) show that the 5:4 phase with the desired x is obtained. Some spread around the nominal value and secondary 5:3 and 1:1 phases are detected. Heat treatment favour the segregation of these secondary phases, but also reduce the spread in the x value. A treatment at 920 ¨¬C for 4 hours in a 10-5 mb vacuum furnace enables a trade-off between phase segregation and removal of x spread.
- A new differential scanning calorimeter (DSC), which operates under applied magnetic fields of up to 5 T and within the temperature range 10-300 K, has been developed. This calorimeter enables an accurate determination of the entropy change associated with a magnetostructural phase transition. The transition can be induced by sweeping either T or H.
- It has been shown that the Clausius-Clapeyron equation and DSC measurements yield the entropy change associated with the first-order magnetostructural transition, ∆S. If the Maxwell relation is evaluated only within the field range over which the transition takes place, the same value is obtained. When the Maxwell relation is evaluated over the whole field range, the T and H dependences of the magnetisation in each phase outside the transition region yield an additional entropy change to that associated with that of the actual first-order transition. The transition temperature Tt must significantly shift with the applied field, in order to achieve a large MCE taking advantage of ∆S.
- DSC under H has been used to measure ∆S for Gd5(SixGe1-x)4, x ¡Â0.5. ∆S scales with Tt, which is a direct consequence of the fact that Tt is tuned by x and H and it is thus expected to be universal for any material showing a field-induced transition. The specific shape of ∆S vs. Tt will depend on the details of the phase diagram, Tt(x). The scaling of ∆S shows the equivalence of magnetovolume and substitution-related effects in Gd5(SixGe1-x)4 alloys.
- The variation of the transition field with the transition temperature, dHt/dTt, has been studied in Gd5(SixGe1-x)4 for 0¡Âx ¡Â0.5. It is shown that dHt/dTt governs the scaling of ∆S with Tt. Two distinct behaviours for dHt/dTt have been found on the two compositional ranges where the magnetostructural transition occurs, showing the difference in the strength of the magnetoelastic coupling in this system.
- It has been shown that an unreported field-induced magnetic phase transition exists from the AFM phase to a phase which presents short-range correlations (SRAFM). The results suggest that the transition results from the breaking of the long-range AFM correlations when a magnetic field is applied, which leads to competing FM and AFM short-range correlations. FM correlations are also relevant in the whole long-range AFM phase. The expected transition from the SRAFM to the PM phase takes place at ~240 K at zero field, being widened and smoothed under applied field. This finding in the Ge-rich Gd5(SixGe1-x)4 alloys arises from the competition between the intraslab FM interactions and the interslab AFM interactions.
- The dynamics of the first-order transition in Gd5(SixGe1-x)4 alloys has been studied by cycling virgin samples. The field-induced entropy change increases during the first cycles, then reaching a stationary value. This behaviour is related to the avalanche distribution, which also evolves with cycling. The structure of avalanches becomes repetitive after a few cycles tending towards a power-law distribution, unveiling the athermal character of the transition.
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Dicken, Anthony. "Diffraction enhanced kinetic depth effect X-ray imaging." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/8046.
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An increasing number of fields would benefit from a single analytical probe that can characterise bulk objects that vary in morphology and/or material composition. These fields include security screening, medicine and material science. In this study the X-ray region is shown to be an effective probe for the characterisation of materials. The most prominent analytical techniques that utilise X-radiation are reviewed. The study then focuses on methods of amalgamating the three dimensional power of kinetic depth X-ray (KDFX) imaging with the materials discrimination of angular dispersive X-ray diffraction (ADXRD), thus providing KDEX with a much needed material specific counterpart. A knowledge of the sample position is essential for the correct interpretation of diffraction signatures. Two different sensor geometries (i.e. circumferential and linear) that are able to collect end interpret multiple unknown material diffraction patterns and attribute them to their respective loci within an inspection volume are investigated. The circumferential and linear detector geometries are hypothesised, simulated and then tested in an experimental setting with the later demonstrating a greater ability at discerning between mixed diffraction patterns produced by differing materials. Factors known to confound the linear diffraction method such as sample thickness and radiation energy have been explored and quantified with a possible means of mitigation being identified (i.e. via increasing the sample to detector distance). A series of diffraction patterns (following the linear diffraction appoach) were obtained from a single phantom object that was simultaneously interrogated via KDEX imaging. Areas containing diffraction signatures matched from a threat library have been highlighted in the KDEX imagery via colour encoding and match index is inferred by intensity. This union is the first example of its kind and is called diffraction enhanced KDEX imagery. Finally an additional source of information obtained from object disparity is explored as an alternative means of calculating sample loci. This offers a greater level of integration between these two complimentary techniques as object disparity could be used to reinforce the results produced by the linear diffraction geometry.
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Yaman, Mecit. "Scientific visualization of stress tensor information with applications to stress determination by X-ray and neutron diffraction." Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/6507.
Full textAbstract:
Includes bibliographical references (leaves 232-249).The visual analysis of mechanical stress facilitates physical understanding of the tensor quantity which is concealed in scalar and vector methods. In this study, the principles and techniques of scientific visualization are used to develop a visual analysis of mechanical stresses. Scientific visualization is not only applied to the final tensorial quantity obtained from the diffraction measurements, but the visual methods are developed from, and integrated into current residual stress analysis practices by relating the newly developed visual techniques to the conventional techniques, highlighting its advantages. This study consists of the mathematical analysis of the tensor character of mechanical stresses, discussion of the principles and techniques of scientific visualization (visual data analysis) in physical research, and tensor determination, visual analysis and presentation of residual stresses obtained from diffraction measurements.
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Quetz, Abdiel. "PHASE TRANSITIONS AND MAGNETOCALORIC EFFECT IN MnNiGe1−xAlx, Ni50Mn35(In1−xCrx)15 AND (Mn1−xCrx)NiGe1.05." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1514.
Full textAbstract:
The magnetocaloric and thermomagnetic properties of the MnNiGe1-xAlx, Ni50Mn35(In1−xCrx)15 and (Mn1−xCrx)NiGe1.05 systems have been studied by x-ray diffraction, differential scanning calorimetry (DSC), and magnetization measurements. Partial substitution of Al for Ge in MnNiGe1−xAlx results in a first-order magnetostructural transition (MST) from a hexagonal ferromagnetic to an orthorhombic antiferromagnetic phase at 186 K (for x = 0.09). A large magnetic entropy change of ∆SM = -17.6 J/kg K for ∆H = 5 T was observed in the vicinity of TM = 186 K for x = 0.09. This value is comparable to those of well-known giant magnetocaloric materials, such as Gd5Si2Ge2, MnFeP0.45As0.55, and Ni50Mn37Sn13 [1]. The values of the latent heat (L = 6.6 J/g) and corresponding total entropy changes (∆ST = 35 J/kg K) have been evaluated for the MST using DSC measurements. Large negative values of ∆SM of -5.8 and -4.8 J/kg K for ∆H = 5 T in the vicinity of TC were observed for x = 0.09 and 0.085, respectively. Partial substitution of Cr for Mn in(Mn1−xCrx)NiGe1.05 results in a MST from a hexagonal paramagnetic to an orthorhombic paramagnetic phase near TM ~ 380 K (for x = 0.07). Partial substitution of Cr for In in Ni50Mn35(In1−xCrx)15 shifts the magnetostructural transition to a higher temperature (TM ~ 450 K) for x = 0.1. Large magnetic entropy changes of ∆SM = -12 (J/kgK) and ∆S = -11 (J/kgK), both for a magnetic field change of 5 T, were observed in the vicinity of TM for (Mn1−xCrx)NiGe1.05 and Ni50Mn35(In1−xCrx)15, respectively. The concentration-dependent (T-x) phase diagram of transition temperatures (magnetic, structural, and magnetostructural) has been generated using magnetic, XRD, and DSC data. The role of magnetic and structural changes on transition temperatures are discussed.
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Ku, Yao-Ching. "Fabrication of distortion free x-ray masks using low stress tungsten." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/39038.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (leaves 113-115).
by Yao-Ching Ku.
Ph.D.
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Dölle, Michael. "Field effect transistor based CMOS stress sensors /." Tönning ; Lübeck Marburg : Der Andere Verlag, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016086105&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Maliphant, Paula. "The effect of pesticide stress on diatoms." Thesis, University of Hertfordshire, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309720.
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Chung, Samwon. "The effect of internal stress on diffusion." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058210791.
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SUZUKI, Kenji, Keisuke TANAKA, and Yoshiaki AKINIWA. "Estimation of Spalling Stress in Thermal Barrier Coatings Using Hard Synchrotron X-Rays." The Japan Society of Mechanical Engineers, 2004. http://hdl.handle.net/2237/9176.
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MACHADO, VERONICA MIQUELIN. "EFFECT OF ELASTIC-PLASTIC STRESS IN THE DEFECT TOLERANCE UNDER STRESS CORROSION CRACKING." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33679@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Corrosão sob tensão (SCC), que consiste na iniciação e propagação de trincas devido ao efeito combinado de tensões mecânicas e o ambiente corrosivo, é um dano potencial para estruturas e componentes. Além do mais, SCC pode ser explicado por diferentes mecanismos dependendo do par material ambiente corrosivo considerado, o que dificulta o uso de um modelo geral para predizer o comportamento de trincas em SCC. Sendo assim, projetos frequentemente utilizam um critério conservativo que desqualifica materiais susceptíveis à SCC sem analisar de maneira apropriada a influência dos campos de tensão que a induzem. O objetivo deste trabalho é avaliar o efeito de tensões elastoplásticas na corrosão sob tensão. Esta abordagem mecânica considera que todos os efeitos corrosivos envolvidos na corrosão sob tensão podem ser apropriadamente quantificados pelas tradicionais resistências do material à iniciação e propagação de trincas para um ambiente corrosivo específico. Corpos de prova de flexão em Alumínio fragilizados por Gálio líquido serão utilizados para prever o efeito de tensões residuais induzidas por deformações plásticas na iniciação de trincas por corrosão sob tensão. Além disso, uma análise quantitativa baseada no comportamento de trincas não propagantes a partir de entalhes será usada para estimar a tensão necessária para iniciar e propagar trincas em corpos de prova entalhados em aço AISI 4140 sujeitos à corrosão por sulfeto de hidrogênio em ambiente aquoso. O comportamento de trincas curtas e a carga máxima suportada pelos corpos de prova entalhados são analisadas considerando campos de tensões lineares elástico e elastoplásticos através do modelo proposto que será validado através de dados experimentais.
Stress Corrosion Cracking (SCC), which consist in the initiation and propagation of cracks due to the combined attack of mechanical stresses and a corrosive environment is a potential danger for structures and components. Moreover, SCC can be explained by different mechanisms depending on the metal environmental pair, what makes difficult to create a generalized analytical approach to predict the crack behavior in SCC. Therefore, projects often use an over-conservative design criteria that disqualify a material susceptible to SCC without properly evaluate the influence of the stress fields that drive them. The aim of this work is to evaluate the effect of elastic-plastic stress in SCC. This mechanical approach assumes that all chemical effects involved in SCC problems can be appositely described and quantified by traditional material resistances to crack initiation and propagation at under specific environment. Aluminum bending specimens in Gallium environment are used to predict the effect of the residual stress induced by plastic deformation in the crack initiation under SCC conditions. Furthermore, a quantitative analysis based on the non-propagating crack behavior departing from notch tips are used to calculate the necessary stress to initiate and propagate SCC in AISI 4140 steel notched specimens under aqueous hydrogen sulfide environment. The non-propagating crack behavior and the maximum load supported by notched specimens are analyzed under linear elastic and elastic-plastic stress field through the proposed model that will be validated by experimental data.
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Iyer, Venkatramani S. "Effect of residual stress gradients in austenitic stainless steels on stress corrosion cracking." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/42119.
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The effect of the residual stresses developed during simulated weld heat affected zone in
austenitic stainless steel specimen on the stress corrosion cracking susceptibility was studied.
Residual stresses was measured using X-ray diffraction technique. Boiling Magnesium
Chloride was used as corrosive environment. Compressive stresses developed in the HAZ of
the specimen and in regions away from the HAZ stress free values were obtained. The magnitude
of the stress gradient decreased as the peak temperature attained during simulated
welding decreased. Transgranular cracks were observed in the compressive stress gradient
region and time to cracking decreased with increasing stress gradient. Higher nickel content
alloys took longer to crack as opposed to lower nickel content alloys at approximately the
same stress gradient.
Master of Science
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Mankowski, Jean Boswell Simeonsson Rune J. Hatton Deborah Dominey. "Mood, anxiety, and stress in mothers of children with Fragile X syndrome, autism, and Fragile X syndrome and autism." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,772.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Dec. 18, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Education (School Psychology)." Discipline: Education; Department/School: Education.
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Patton, Kirralee Anne. "The effect of cell culture on X chromosome mosaicism." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/134.
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The effects of cell culture on X chromosome aneuploidy in young women with established fertility were investigated. Fluorescence in situ hybridisation was performed on paired samples of mitogen stimulated and uncultured lymphocytes using probes for the X and 9 chromosomes. All participants had <5% X aneuploidy in both preparations. X chromosome loss occurred more frequently than gain. These results provide important information when interpreting the low levels of X mosaicism seen in routine cytogenetic practice.
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Dehan, Christophe F. "An intelligent workstation for reliable residual stress determination using x-ray diffraction." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43086.
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Recent hardware developments of automated, high speed, portable X-ray diffraction instrumentation
have not yet resulted in widespread use of the technique in industry despite its potentials. We suggest
that these hardware developments require an equivalent development in the training of instrument
operators in order to guarantee the integrity of the resulting data, as well as to enhance the
understanding of such materials characterization data. The hurdle to date is the variety of skills
necessary in a wide range of scientific and engineering disciplines and which are not commonly found
in a single individual. We suggest that a computer-based system, integrating visualization tools,
knowledge bases and analysis-capabilities and which isfocused on the operator performance can provide an efficient solution to this problem, as it changes the enactment of the stress determination work process.Master of Science
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Del, Fierro Avila Jacqueline. "Stress and Marital Satisfaction of Parents With Children With Fragile X Syndrome." ScholarWorks, 2017. https://scholarworks.waldenu.edu/dissertations/3488.
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Raising a child with a pervasive developmental disorder (PDD), particularly that of Fragile X Syndrome (FXS), is challenging, as it comes with parental stressors for both mothers and fathers. Research on these stressors has been limited to only the stressors that mothers of children with a PDD experience and has failed to thoroughly examine the experiences and stressors of fathers of children with a PDD, particularly that of FXS. Using Hill's ABC-X family stress theory, this quantitative research study investigated the effects of marital satisfaction due to the amount of shared childcare responsibilities and parental stress among the mothers and fathers of children diagnosed with FXS. This study also examined whether significant differences exist among these parents, who were recruited through the use of flyers, notices, and handouts that were randomly passed out to parents at the FXS Alliance of Texas located in the southwest region of Texas. Participants for this study were 128 parents of children with FXS, each of whom completed a demographic questionnaire, the Kansas Marital Satisfaction Scale, and The Sharing of Childcare Responsibilities Scale and Parental Stress Level Scale. An independent samples t test and multiple linear regression statistical analysis was employed. The results of the study indicated that parental stress associated with the amount of shared childcare responsibilities accounted for a significant degree of the variance in marital satisfaction. Yet the study did not find a significant mean difference in the level of parental stress that was experienced uniquely across gender. Potential social changes may include future development and improvements in treatment, therapeutic approaches, and predicted outcomes in efforts to enhance parental stress interventions so as to improve stress-related outcomes for parents of children with FXS.
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Литвиненко, Ярина Миколаївна, Ярина Николаевна Литвиненко, Yaryna Mykolaivna Lytvynenko, and V. A. Siruk. "The effect of annealing on the magnetoresistive properties of (FeNi)[x]Co[1-x] thin films." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/44298.
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Thin films of soft magnetic alloys (FeNi or his alloys with addition of third elements) are widely used as sensing elements for magnetic field detection applications, for example, in magnetic recording read heads or low
field measuring devices.
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Barsoum, Imad. "The effect of stress state in ductile failure." Doctoral thesis, Stockholm : Hållfasthetslära, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4667.
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Bogart, Robert William. "The effect of stress on global cerebral ischemia." Connect to resource, 2008. http://hdl.handle.net/1811/32235.
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Poirier, Patrick. "Effect of chronic stress on prefrontal cortical function." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86861.
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The prefrontal cortex (PFC) is a brain region thought to mediate cognitive functions such as working memory. Chronic stress has been shown to reduce working memory. In this thesis study, the effect of chronic stress on PFC functions was assessed in adult rats.First, contrary to previous evidences, chronic stress induces working memory performance alterations differentially in two populations of rats. One group displayed a decrease of performance only at 30 second delay, while the other had a decrease and increase at 0 and 30 seconds respectively.
Then, the effect of chronic stress on synaptic plasticity induction in the hippocampus-PFC network was investigated. High-frequency tetanic stimulation (HFS) of the dorsal hippocampus that induced long-term potentiation (LTP) in the prelimbic and infralimbic cortex in normal conditions was unable to induce LTP after chronic stress in the infralimbic cortex, whereas long-term depression (LTD) instead of LTP was induced in the prelimbic cortex.
Given that synaptic plasticity has been shown to depend on NMDA receptors in the PFC, NMDA subunit expressions before and after chronic stress was examined. There was a decrease of NR1 subunits expression in the prelimbic, but not infralimbic cortex. In contrast, the NR2A/NR2B ratio was increased in the infralimbic, but not prelimbic cortex. These results suggest that chronic stress disrupts PFC functions through dynamic modulation of distinct neural networks within the PFC.
Le cortex préfrontal (PFC) est une région du cerveau qui contrôle les fonctions cognitives comme la mémoire de travail. Dans cette thèse, l'effet du stress chronique sur des fonctions du PFC a été analysé chez des rats adultes.
Premièrement, les performances de la mémoire de travail ont été mesurées avant et après exposition au stress chronique. Nous avons constaté que le stress chronique induit des changements de performances de la mémoire de travail différemment selon deux populations de rats. Une des populations a démontré une diminution de performance seulement à 30 secondes de délai. Au contraire, l'autre a démontré une diminution de performance à 0 seconde et une amélioration de performance à 30 secondes.
En plus, nous avons évalué l'effet du stress chronique sur l'induction de la plasticité synaptique dans le réseau reliant l'hippocampe au PFC. Dans les conditions initiales, une stimulation tétanique à haute fréquence (HFS) dans l'hippocampe dorsal provoquait une potentialisation à long terme (LTP) dans le cortex prélimbique et infralimbique Or après exposition au stress chronique, une stimulation tétanique à haute fréquence n'a pas entraîné de potentialisation à long terme dans le cortex infralimbique. De plus, une exposition au stress chronique a provoqué l'apparition dans le cortex prélimbique d'une dépression à long terme (LTD) plutôt qu'une potentialisation à long terme.
Étant donné que la plasticité synaptique dépend des récepteurs de NMDA dans le PFC, nous avons examiné l'expression de sous-unité de NMDA avant et après exposition au stress chronique. En accord avec les changements synaptiques distincts de plasticité entre le cortex prélimbique et infralimbique après exposition au stress chronique, nous avons observé que l'expression de la sous-unité NR1 a diminué dans le prélimbique, mais non dans l'infralimbique. En revanche, le ratio de NR2A/NR2B a augmenté dans le cortex infralimbique, mais non dans le prélimbique. Ces résultats suggèrent que le stress chronique perturbe les fonctions du PFC par la modulation dynamique des réseaux distincts neurologiques dans le PFC.
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Picton, S. "The effect of heat-stress on tomato ripening." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233614.
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Mathers, John F. "The effect of stress on golf putting performance." Thesis, University of Strathclyde, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431793.
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Yeh, Lestter. "The Effect of Stress Coping Techniques in Sports." Scholarship @ Claremont, 2016. http://scholarship.claremont.edu/cmc_theses/1240.
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The first part of this literature review goes over the biological and psychological aspects of stress. The cause of stress can be linked back to a primitive instinct known as “fight or flight.” The “fight or flight” instinct is triggered by several chemical reactions in the body starting from a signal from the amygdala to the sympathetic nervous system. Stress can also be categorized into internal and external stress. Further research links stress to sports. Many studies show that stress coping techniques such as meditation, self-talk, rituals, etc. are beneficial to athletes during competition. Suggested avenues of further research are to develop a standardized way to incorporate practicing stress coping techniques into a younger athlete’s routine, discover whether the same stress coping techniques can be used throughout all sports, and whether certain stress coping techniques will benefit people of different personality types equally. Keywords: Stress, Coping, Sports, Psychology, Athlete
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Kumsta, Caroline. "The effect of oxidative stress on C. elegans." kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/678556/678556.pdf.
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Hoskin, Robert. "The effect of psychological stress on auditory perception." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/6193/.
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Psychological stress appears to precede instances of auditory hallucinations in those vulnerable to them. This suggests that psychological stress acts on the auditory perceptual system in such a way as to encourage the generation of false percepts. This thesis investigated the impact of psychological stress on the perception of emotionally neutral sounds with the aim of identifying a potential mechanism to explain the influence of stress on the occurrence of auditory hallucinations. Two interconnected hypotheses, arising from the theory that stress reduces attentional control and therefore the ability to inhibit distracting information, were tested. An auditory signal detection task was created to test whether stress would reduce the ability of the auditory-perceptual mechanism to accurately detect signals. Instead of reducing discrimination ability, stress was found to bias responding towards reporting a signal in highly anxious individuals. A number of passive oddball tasks were designed to test the hypothesis that stress would increase the distraction caused by emotionally neutral sounds. Once again this hypothesis was largely refuted, with stress appearing to reduce, rather than increase, the impact of distracting auditory information on task performance. On the basis of these findings a revised model of how stress may encourage auditory hallucinations was proposed. This model suggests that, through a strengthening of selective attention, stress may mal-adaptively bias auditory perception towards misinterpreting internal signals as external. Further research proposals, designed to test the predictions of this model, are suggested.
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Followell, Timothy B. "Effect of Dental Treatment on Parental Stress as Measured by the Parenting Stress Index." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276567183.
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Brattos, Alexandra. "The Effect of Stress Presentation Mode on Stress Acquisition Among Advanced Learners of Russian." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3140.
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The purpose of this research was to test the effect of stress presentation mode on stress acquisition of advanced learners of Russian. The study attempted to determine if advanced learners of Russian are able to place stress more correctly on words in specific texts after receiving various treatments or receiving no treatment. Participants were Brigham Young University students studying Russian as a second language at the third-year level or higher. They were randomly assigned into three groups: a group that received no treatment, a treatment group that read words with graphically marked stress, and a treatment group that heard texts read by a native speaker. All participants completed a pretest, a treatment (in the second and third groups), and a posttest. The pretest and the posttest consisted of a reading task: the participants read 12 sentences taken from 12 different texts. The same words from the texts were used in the treatment to expose the participants to the sentences again in order to determine if the treatment made a difference in the acquisition of correct stress. The treatment was different for each group. Group 1 (A) read texts marked with stress, Group 2 (B) read the same texts but without stress marked; rather, they heard a native speaker of Russian read the texts on a recording, and Group 3 (C) read the same texts but without stress marked graphically or hearing a native speaker. The results of the research reject the hypothesis that aural presentation of stress as opposed to a visual only presentation leads to improved acquisition of stress. However, based on the analyses of the data, overall findings rendered some interesting and unexpected results and observations. First, although the treatment for group A appears to be more effective than that for groups B and C, all groups showed improvement after completing the treatment. This strongly suggests that reading, whatever form it takes, can be a useful tool in facilitating control of stress. Second, group A had more participants that fell into the "fast" reading category, and fast readers scored significantly higher than slow or medium speed readers. This suggests that the faster one reads the better one controls stress, or the better one controls stress the faster one reads.
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Nourifard, Nazanin. "Effect of Stress Magnitude and Stress Rate on Elastic Properties of the Reservoir Rocks." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/77386.
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We studied the effect of stress magnitude and stress rate on elastic properties of the reservoir rocks. We designed and developed experiments to study: (i) the dynamic and static elastic moduli of reservoir rocks, (ii) quantifying the effects of wave’s amplitude on the longitudinal and transverse velocities in porous media, and (iii) anisotropy of sandstone subjected to stress in dry and saturated statuses.
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Cesaretti, Juan Manuel. "Mechanical stress and stress compensation in Hall sensors." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/28202.
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Swartz, Craig H. "Hall effect and photoconductivity lifetime studies of GaN, InN, and Hg₁-[subscript x]Cd[subscript x]Te." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4450.
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Thesis (Ph. D.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains ix, 72 p. : ill. Includes abstract. Includes bibliographical references (p. 68-72).
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Ananthaviravakumar, Nada. "Investigation of residual stresses in engineering components using neutron and synchrotron x-ray diffraction techniques." Thesis, University of Salford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248906.
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Rachwal, James D. "X-ray diffraction applications in thin films and (100) silicon substrate stress analysis." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/1745.
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Silicon is used as a substrate for X-ray mirrors for correct imaging. The substrate needs to be mechanically bent to produce a certain curvature in order to condition and focus the X-ray beam. The X-rays impinge a mirror at very shallow angles, in order to reduce the amount of intensity loss in the diffraction process. The X-ray mirrors need to be bent to an extremely precise profile, and even small distortions from this profile can reduce the effectiveness of the X-ray mirrors. The X-rays that impinge on the mirror also produce large amounts of heat that can change the temperature of the substrate, resulting in its thermal expansion and distortion. By measuring the distortions in-situ caused by these temperature changes it may be possible to correct for these errors. A four-point bending fixture was designed for in-situ X-ray bending experiments in order to measure the distortions to the (100) silicon sample caused by the bending setup.
By being able to measure the distortion caused by the setup, in like manner it would be possible to measure distortion caused by thermal expansion. Several alignments were needed in order to obtain accurate results, including adding copper powder on top of the sample. The copper powder that was added is not under stress, and therefore will not shift its reflection peak when the sample is under bending stress, thus serving as a reference in order to make corrections. The strain results were then compared to values calculated from mechanical deflections from bending. Despite the efforts to control accuracy, a significant variation appeared in the values when the top surface was in compression. As an alternative an IONIC stress-gauge was used to measure the deflections of the sample rather than calculate them.
Another alternative was to calculate the deflection of the substrate by first determining the stress in the layer deposited onto the mirror's substrate by using sin²psi technique, then using Stoney's equation to determine the change in curvature of the substrate, with the stress in the layer being known. Several tests were performed to demonstrate the ability to measure these deflections.
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Polatidis, Efthymios. "Residual stress and phase characterisation on zirconium oxides using synchrotron X-ray diffraction." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/residual-stress-and-phase-characterisation-on-zirconium-oxides-using-synchrotron-xray-diffraction(b0bc325a-2a94-4323-8739-7ea9b04727f3).html.
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The present work was produced as part of the MUZIC consortium, a collaboration between a multi-university team from the UK and industrial partners working on the field of nuclear energy, fabrication of alloys and nuclear research. The aim of the project is to establish a multidiscipline mechanistic understanding of the corrosion and breakaway processes of zirconium alloys used as fuel cladding materials in the nuclear industry. A better understanding of the corrosion mechanism of zirconium alloys will not only aid the development of better performing alloys, but will also allow more accurate models to be developed to reliably predict the service life of existing alloys. This could lead to higher burn-up, increase of energy production and reduction of nuclear waste produced.This work seeks to provide a better understanding of the role of residual stresses in the oxide, which are produced during oxidation due to high Pilling-Bedworth ratio and their impact on oxide phase transformation and oxidation kinetics by employing high energy synchrotron X-ray diffraction techniques. This is achieved by observing how stresses change as oxide growth approaches and passes through transition of the corrosion kinetics, their evolution across the oxide thickness, in situ characterising stresses and phase growth early in oxidation process and how stress changes can affect corrosion properties.It was found that relatively high compressive stresses in the two oxide crystal structures are present. The stresses relax with time up to moments before transition where a possible threshold stress magnitude is reached to aid an extensive tetragonal to monoclinic phase transformation. This generalised tetragonal to monoclinic transformation is believed to produce highly stressed monoclinic crystal structure grains and cause defects in the oxide. The above observation is further supported by a decrease of the tetragonal zirconia content. This is the moment that the oxide looses its protective character and a transition of the corrosion kinetics occurs. By comparing different materials it was observed that the minimum magnitude of the tetragonal phase is lower in better performing alloys while the tetragonal content is some cases was relatively low. It is suggested that the amount of the tetragonal phase, in the oxide layer, is not as important as the rate of it transforming into monoclinic. The extent of tetragonal to monoclinic transformation, that introduces defects in the oxide, defines how protective an oxide layer is. The present work provides a contribution to the available knowledge of the importance of residual stresses in the oxide layer and metal substrate of zirconium alloys and how they can affect corrosion rates or act as a precursor to the corrosion transition.