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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Growth and Characterization of Strain-engineered Si/SiGe Heterostructures Prepared by Molecular Beam Epitaxy

Zhao, Ming January 2008 (has links)
The strain introduced by lattice mismatch is a built-in characteristic in Si/SiGe heterostructures, which has significant influences on various material properties. Proper design and precise control of strain within Si/SiGe heterostructures, i.e. the so-called “strain engineering”, have become a very important way not only for substantial performance enhancement of conventional microelectronic devices, but also to allow novel device concepts to be integrated with Si chips for new functions, e.g. Si-based optoelectronics. This thesis thus describes studies on two subjects of such strain-engineered Si/SiGe heterostructures grown by molecular beam epitaxy (MBE). The first one focuses on the growth and characterizations of delicately strain-symmetrized Si/SiGe multi-quantum-well/superlattice structures on fully relaxed SiGe virtual substrates for light emission in the THz frequency range. The second one investigates the strain relaxation mechanism of thin SiGe layers during MBE growth and post-growth processes in non-conventional conditions. Two types of THz emitters, based on different quantum cascade (QC) intersubband transition schemes, were studied. The QC emitters using the diagonal transition between two adjacent wells were grown with Si/Si0.7Ge0.3 superlattices up to 100 periods. It was shown that nearly perfect strain symmetry in the superlattice with a high material quality was obtained. The layer parameters were precisely controlled with deviations of ≤ 2 Å in layer thickness and ≤ 1.5 at. % in Ge composition from the designed values. The fabricated emitter devices exhibited a dominating emission peak at ~13 meV (~3 THz), which was consistent with the design. An attempt to produce the first QC THz emitter based on the bound-to-continuum transition was made. The structures with a complicated design of 20 periods of active units were extremely challenging for the growth. Each unit contained 16 Si/Si0.724Ge0.276 superlattice layers, in which the thinnest one was only 8 Å. The growth parameters were carefully studied, and several samples with different boron δ-doping concentrations were grown at optimized conditions. Extensive material characterizations revealed a high crystalline quality of the grown structures with an excellent growth control, while the heavy δ-doping may introduce layer undulations as a result of the non-uniformity in the strain field. Moreover, carrier lifetime dynamics, which is crucial for the THz QC structure design, was also investigated. Strain-symmetrized Si/SiGe multi-quantum-well structures, designed for probing the carrier lifetime of intersubband transitions inside a well between heavy hole 1 (HH1) and light hole 1 (LH1) states with transition energies below the optical phonon energy, were grown on SiGe virtual substrates. The lifetime of the LH1 excited state was determined directly with pump-probe spectroscopy. The measurements indicated an increase of lifetime by a factor of ~2 due to the increasingly unconfined LH1 state, which agreed very well with the theory. It also showed a very long lifetime of several hundred picoseconds for the holes excited out of the well to transit back to the well through a diagonal process. Strained SiGe grown on Si (110) substrates has promising potentials for high-speed microelectronics devices due to the enhanced carrier mobility. Strain relaxation of SiGe/Si(110) subjected to different annealing treatments was studied by X-ray reciprocal space mapping. The in-plane lattice mismatch was found to be asymmetric with the major strain relaxation observed in the lateral [001] direction. It was concluded that this was associated to the formation and propagation of conventional a/2<110> dislocations oriented along [110]. This was different from the relaxation observed during growth, which was mainly along in-plane [110]. A novel MBE growth process to fabricate thin strain-relaxed Si0.6Ge0.4 virtual substrates involving low-temperature (LT) buffer layers was investigated. At a certain LT-buffer growth temperature, a dramatic increase in the strain relaxation accompanied with a decrease of surface roughness was observed in the top SiGe, together with a cross-hatch/cross-hatch-free transition in the surface morphology. It was explained by the association with a certain onset stage of the ordered/disordered transition during the growth of the LT-SiGe buffer. / Kisel(Si)-baserad mikroelektronik har utvecklats under en femtioårsperiod till att bli basen för vår nuvarande informationsteknologi. Förutom att integrera fler och mindre komponenter på varje kisel-chip så utvecklas metoder att modifiera och förbättra materialegenskaperna för att förbättra prestanda ytterligare. Ett sätt att göra detta är att kombinera kisel med germanium (Ge) bl.a. för att skapa kvantstrukturer av nanometer-storlek. Eftersom Ge-atomerna är större än Si-atomerna kan man skapa en töjning i materialet vilket kan förbättra egenskaperna, ex.vis hur snabbt laddningarna (elektronerna) rör sig i materialet. Genom att variera Gekoncentrationen i tunna skikt kan man skapa skikt som är antingen komprimerade eller expanderade och därmed ger möjlighet att göra strukturer för tillverkning av nya typer av komponenter för mikroelektronik eller optoelektronik. I detta avhandlingsarbete har Si/SiGe nanostrukturer tillverkats med molekylstråle-epitaxi-teknik (molecular beam epitaxy, MBE). Med denna teknik byggs materialet upp på ett substrat, atomlager för atomlager, med mycket god kontroll på sammansättningen av varje skikt. Samtidigt kan töjningen av materialet designas så att inga defekter skapas alternativt många defekter genereras på ett kontrollerat sätt. I denna avhandling beskrivs detaljerade studier av hur töjda i/SiGe-strukturer kan tillverkas och ge nya potentiella tillämpningar ex.vis som källa för infraröd strålning. Studierna av de olika töjda skikten har framför allt gjorts med avancerade röntgendiffraktionsmätningar och transmissionselektronmikroskopi.
252

Assessment Of Roll-formed Products Including The Cold Forming Effects

Guner, Alper 01 May 2007 (has links) (PDF)
Roll-forming is an efficient sheet forming process that is used in manufacturing long parts with constant cross-section. The theoretical, experimental and numerical analyses of the process are limited since the sheet takes a complex 3D shape during the process. In this study proper finite element method models to simulate the roll-forming process are examined both numerically and experimentally. In addition, the applicability of 2D plane strain models to the simulation of the process is investigated. To reveal the deformation of the sheet, important geometrical parameters of the sheet and the rollers are introduced. The effect of these parameters on the strain hardening and deformation of the sheet is analyzed at distinct parts of the sheet that undergoes different types of deformations. Having revealed the deformation mechanisms, the assumptions behind the theoretical knowledge is criticized. The mentioned studies are verified with a case study in which a roll-formed product is analyzed under service loads. The manufacturing of the product and service load application are simulated and the results are compared with the experiments. In addition, effects of cold forming on the behaviour of the product under service loads are examined. It is concluded that under some conditions, 2D plane strain simulations can be used to predict the strain hardening in the material that occurs during roll-forming and this hardening has a considerable effect on the response of the material under loading.
253

Strain engineering as a method for manufacturing micro- and; nano- scale responsive particles

Simpson, Brian Keith, Jr. 29 April 2010 (has links)
Strain engineering is used as a means of manufacturing micro- and nano- scale particles with the ability to reversibly alter their geometry from three dimensional tubes to two dimensional flat layers. These particles are formed from a bi-layer of two dissimilar materials, one of which is the elastomeric material polydimethylsiloxane (PDMS), deposited under stress on a sacrificial substrate. Upon the release of the bi-layer structure from the substrate, interfacial residual stress is released resulting in the formation of tubes or coils. These particles possess the ability to dramatically alter their geometry and, consequently, change some properties that are reversible and can be triggered by a stimulus. This work focuses on the material selection and manufacturing of the bi-layer structures used to create the responsive particles and methods for characterizing and controlling the responsive nature of the particles. Furthermore, the potential of using these particles for a capture/release application is explored, and a systematic approach to scale up the manufacturing process for such particles is provided. This includes addressing many of the problems associated with fabricating ultra-thin layers, tuning the size of the particles, understanding how the stress accumulated at the interface of a bi-layer structure can be used as a tool for triggering a response as well as developing methods (i.e. experiments and applications) that allow the demonstration of this response.
254

Automatic Macro- and Micro-Facial Expression Spotting and Applications

Shreve, Matthew Adam 01 January 2013 (has links)
Automatically determining the temporal characteristics of facial expressions has extensive application domains such as human-machine interfaces for emotion recognition, face identification, as well as medical analysis. However, many papers in the literature have not addressed the step of determining when such expressions occur. This dissertation is focused on the problem of automatically segmenting macro- and micro-expressions frames (or retrieving the expression intervals) in video sequences, without the need for training a model on a specific subset of such expressions. The proposed method exploits the non-rigid facial motion that occurs during facial expressions by modeling the strain observed during the elastic deformation of facial skin tissue. The method is capable of spotting both macro expressions which are typically associated with emotions such as happiness, sadness, anger, disgust, and surprise, and rapid micro- expressions which are typically, but not always, associated with semi-suppressed macro-expressions. Additionally, we have used this method to automatically retrieve strain maps generated from peak expressions for human identification. This dissertation also contributes a novel 3-D surface strain estimation algorithm using commodity 3-D sensors aligned with an HD camera. We demonstrate the feasibility of the method, as well as the improvements gained when using 3-D, by providing empirical and quantitative comparisons between 2-D and 3-D strain estimations.
255

The role of extension during the evolution of the NW Indian Himalaya

Hintersberger, Esther January 2013 (has links)
The evolution of most orogens typically records cogenetic shortening and extension. Pervasive normal faulting in an orogen, however, has been related to late syn- and post-collisional stages of mountain building with shortening focused along the peripheral sectors of the orogen. While extensional processes constitute an integral part of orogenic evolution, the spatiotemporal characteristics and the kinematic linkage of structures related to shortening and extension in the core regions of the orogen are often not well known. Related to the India-Eurasia collision, the Himalaya forms the southern margin of the Tibetan Plateau and constitutes the most prominent Cenozoic type example of a collisional orogen. While thrusting is presently observed along the foothills of the orogen, several generations of extensional structures have been detected in the internal, high-elevation regions, both oriented either parallel or perpendicular to the strike of the orogen. In the NW Indian Himalaya, earthquake focal mechanisms, seismites and ubiquitous normal faulting in Quaternary deposits, and regional GPS measurements reveal ongoing E-W extension. In contrast to other extensional structures observed in the Himalaya, this extension direction is neither parallel nor perpendicular to the NE-SW regional shortening direction. In this study, I took advantage of this obliquity between the trend of the orogen and structures related to E-W oriented extension in order to address the question of the driving forces of different extension directions. Thus, extension might be triggered triggered by processes within the Tibetan Plateau or originates from the curvature of the Himalayan orogen. In order to elaborate on this topic, I present new fault-kinematic data based on systematic measurements of approximately 2000 outcrop-scale brittle fault planes with displacements of up to several centimeters that cover a large area of the NW Indian Himalaya. This new data set together with field observations relevant for relative chronology allows me to distinguish six different deformation styles. One of the main results are that the overall strain pattern derived from this data reflects the regionally important contractional deformation pattern very well, but also reveals significant extensional deformation. In total, I was able to identify six deformation styles, most of which are temporally and spatially linked and represent protracted shortening, but also significant extensional directions. For example, this is the first data set where a succession of both, arc-normal and E-W extension have been documented in the Himalaya. My observations also furnish the basis for a detailed overview of the younger extensional deformation history in the NW Indian Himalaya. Field and remote-sensing based geomorphic analyses, and geochronologic 40Ar/39Ar data on synkinematic muscovites along normal faults help elucidate widespread E-W extension in the NW Indian Himalaya which must have started at approximately 14-16 Ma, if not earlier. In addition, I documented and mapped fault scarps in Quaternary sedimentary deposits using satellite imagery and field inspection. Furthermore, I made field observations of regional normal faults, compiled structures from geological maps and put them in a regional context. Finally, I documented seismites in lake sediments close to the currently most active normal fault in the study area in order to extend the (paleo) seismic record of this particular fault. Taken together, this data sets document that E-W extension is the dominant active deformation style in the internal parts of the orogen. In addition, the combined field, geomorphic and remote-sensing data sets prove that E-W extension occurs in a much more larger region toward the south and west than the seismicity data have suggested. In conclusion, the data presented here reveal the importance of extension in a region, which is still dominated by ongoing collision and shortening. The regional fault distribution and cross-cutting relationships suggest that extension parallel and perpendicular to the strike of the orogen are an integral part of the southward propagation of the active thrust front and the associated lateral growth of the Himalayan arc. In the light of a wide range of models proposed for extension in the Himalaya and the Tibetan plateau, I propose that E-W extension in the NW Indian Himalaya is transferred from the Tibetan Plateau due the inability of the Karakorum fault (KF) to adequately accommodate ongoing E-W extension on the Tibetan Plateau. Furthermore, in line with other observations from Tibet, the onset of E-W normal faulting in the NW Himalaya may also reflect the attainment of high topography in this region, which generated crustal stresses conducive to spatially extensive extension. / Die Hauptaufgabe von MHC-kodierten Proteinen ist die Erkennung von körperfremden Molekülen sowie das Einleiten einer adäquaten Immunantwort, womit sie eine Schlüsselrolle im Immunsystem der Wirbeltiere einnehmen. Man nimmt an, dass ihre außergewöhnliche Vielfalt eine Antwort auf die sich ständig anpassenden Parasiten und Krankheitserreger ist, durch adaptive Selektion erhalten wird und dass die individuelle Allelausstattung einen Großteil der Parasitenbelastung erklärt, wofür bereits zahlreiche MHC-Studien Hinweise gefunden haben. Trotzdem ist unser Verständnis über die wirkenden Mechanismen teilweise noch lückenhaft. Ein stark vernachlässigter Aspekt hierbei sind z.B. eventuelle Unterschiede in der Genexpression der MHC-Allele und eine geringere Expression wäre gleichbedeutend mit einer geringeren Aktivierung des Immunsystems. Ich habe hierzu zwei frei lebende Kleinsäugerarten (Delomys sublineatus, Apodemus flavicollis) unter natürlichen Selektionsbedingungen untersucht. Dabei habe ich neben der genotypischen Diversität von MHC-Genen auch deren Expression, sowie die Genexpression immunregulativer Zytokine mit in Betracht gezogen und in Relation zur individuellen Belastung mit gastrointestinalen Helminthen Das gleichzeitige Auftreten von Verkürzung und Dehnung (Extension) ist ein charakteristisches Kennzeichen bei der Bildung von Kollisionsgebirgen. Eine bis heute gängige These beinhaltet ein weit verbreitetes Auftreten von bschiebungen jedoch erst in späteren Stadien der Gebirgsbildung, bzw. nach deren Abschluÿ. Verkürzung ist hingegen während der gesamten Gebirgsbildung zu beobachten. Auch wenn Extensionsprozesse einen wesentlichen Bestandteil der Gebirgsbildung darstellen, ist deren räumlichen und zeitlichen Abfolge sowie ihre kinematische Kopplung zu Verkürzungstrukturen nur wenig gesichert. Der Himalaja, durch die Kollision von Indien und Eurasien entstanden, bildet den südlichen Rand des tibetischen Hochplateaus und stellt ein typisches aktives Kollisionsgebilde dar. Während heutzutage an der Gebirgsfront Überschiebungen beobachtet werden, können mehrere Generationen an Extensionsstrukturen in den hochgelegenen Regionen des Himalajas dokumentiert werden, die sowohl parallel als auch senkrecht zur Gebirgsfront verlaufen. Im NW Indiens zeugen Erdbebendaten sowie regionale GPS-Daten von andauernder E-W-Extension. Im Gegensatz zu anderen im Himalaja beschriebenen Extensionsstrukturen ist diese Extensionsrichtung jedoch weder parallel noch senkrecht zur NE-SW orientierten regionalen Verkürzungsrichtung. In der vorliegenden Arbeit nutze ich diesen schiefen Winkel zwischen der Ausrichtung des Gebirges einerseits und den mit E-W-Extension assoziierten Strukturen andererseits, um mögliche Ursachen für verschiedene Extensionsarten differenzieren zu können. So könnte Extension entweder durch Prozesse innerhalb des tibetischen Hochplateaus gesteuert werden, oder durch die Krümmung des Himalajas, der bogenförmig verläuft. Um dies zu untersuchen, verwende ich einen neuen störungskinematischen Datensatz aus systematischen Messungen von ca. 2000 spröden Störungsflächen im Aufschlussmaßstab über den gesamten Bereich des Himalajas in NW Indien. Zusammen mit Geländebeobachtungen, aus denen eine relative Altersabfolge abgeleitet werden konnte, ermöglicht mir dieser Datensatz zwischen sechs einzelnen Deformationsarten zu differenzieren. Die meisten dieser Deformationsarten sind zeitlich und räumlich verbunden und zeigen fortschreitende Verkürzung an, gleichzeitig werden auch signifikante Extensionsrichtungen dokumentiert. Unter anderem kann ich hier zum ersten Mal eine separierte Abfolge von Extension parallel zum Himalaja-Bogen bzw. E-W-Extension dokumentieren. Ein weiteres Ziel dieser Studie ist es, einen detaillierten Überblick über die E-W-Extension im NW indischen Himalaja zu erhalten. Basierend auf Kartierung von jungen Bruchstufen sowie geomorphologische Auswertungen, 40Ar/39Ar-daten von synkinematisch gewachsenen Muskoviten auf Abschiebungen, sowie einer Kompilierung von eigene Geländebeobachtungen gröÿerer Abschiebungen mit schon publizierten Strukturen, konnte ich die räumliche Ausdehnung der E-W-Extension sowie deren zeitliche Einordnung als jüngstes Deformationsereignis belegen. Schlussendlich konnte ich anhand von Deformation in Seeablagerungen in der Nähe der momentan aktivsten Abschiebung im Untersuchungsgebiet den Nachweis an paläoseismologischen Ereignissen entlang dieser Störung ausweiten. Mit diesem Datensatz kann ich nachweisen, dass E-W-Extension in einem wesentlich ausgedehnteren Gebiet nach Süden und Westen hin auftritt, als bisher vorhandene Daten dies vermuten lassen, und dass E-W-Extension vor 14-16 Ma begann, wenn nicht sogar noch früher. Zusammenfassend bezeugen die hier präsentierten Daten die Relevanz von Extension in einer von Verkürzung geprägten Region. Die räumliche Verteilung von Störungen sowie Überschneidungskriterien lassen vermuten, dass Extension sowohl parallel wie auch senkrecht zum Himalaja-Bogen ein essentieller Teil des südwärts gerichteten Wanderns der aktiven Überschiebungsfront und des damit assoziierten lateralen Wachstums des Gebirges ist. Nach Abwägung der groÿen Bandbreite an Modellen für Extension im Himalaja und im tibetischen Hochplateau, bin ich der Meinung, dass E-W-Extension im NW indischen Himalaja ihren Ursprung im tibetischen Hochplateau hat. Grund dafür ist, dass die Bewegung entlang der Karakorum-Störung nicht ausreichend ist, um die fortdauernde E-W-Extension im tibetischen Hochplateau zu kompensieren. In Übereinstimmung mit anderen Beobachtungen in Tibet ist es auÿerdem möglich, dass das Einsetzen von E-W-Extension im NW Himalaja ebenfalls Erreichen der hohen Topographie in dieser Gegend widerspiegelt, durch die krustale Prozesse in Gang gesetzt werden, die wiederum zu räumlich ausgedehnten Extensionsprozessen führen können.. Anhand von Leber und Milzproben beider Arten habe ich die Methode der ‚real-time PCR‘ zur relativen Quantifizierung von mRNA im Labor etabliert. Bereits für die Labormaus etablierte PCR-Primersysteme wurden an beiden Arten getestet und so konnten stabile Referenzgene gefunden werden, die Grundvoraussetzung für zuverlässige Genexpressionsmessungen. Für D. sublineatus konnte gezeigt werden, dass Helminthenbefall eine typische Th2 Immunantwort induziert, und dass der Zytokin Il4 Gehalt mit Befallsintensität strongyler Nematoden zunimmt. Es wurde für D. sublineatus kein signifikanter Zusammenhang zwischen MHC Expression oder anderen Zytokinen mit Helminthenbefall gefunden. In A. flavicollis wurde ein negativer Zusammenhang zwischen haptischer MHC-Expression und dem parasitären Nematoden Heligmosomoides polygyrus festgestellt, was auf eine Immunvermeidungsstrategie des Nematoden hindeutet. Ich fand typische positive und negative Assoziationen zwischen MHC-Allelen und anderen Helminthenarten, sowie Zeichen eines positiven Selektionsdruckes auf den MHC-Sequenzen, was sich durch eine erhöhte Rate aminosäureverändernder Mutationen zeigte. Diese nicht-synonymen Veränderungen waren auf Positionen innerhalb des zweiten Exons des DRB-Genes beschränkt, wohingegen die untersuchten Bereiche des ersten und dritten Exons stark konserviert vorlagen. Diese variablen Positionen kodieren Schlüsselstellen im Bereich der Antigenbindungsstelle im MHC Molekül. Zusammenfassend zeigt diese Arbeit, dass Genexpressionsstudien auch an Wildtieren durchgeführt und verlässliche Daten erzeugt werden können. Zusätzlich zur strukturellen Vielfalt sollten zukünftig auch mögliche Genexpressionsunterschiede bei MHC-Studien berücksichtigt werden, um ein kompletteres Bild der koevolutiven Wirt-Parasiten-Beziehungen zeichnen zu können. Dies ist vor allem dann von evolutiver Bedeutung, wenn die Parasiten in der Lage sind die MHC Expression aktiv zu beeinflussen. Die Studien konnten nicht die exakte Bedeutung von MHC-Genexpression in der antagonistischen Koevolution definieren, aber sie konnten zeigen dass diese Bedeutung stark von den jeweils beteiligten Partnern abzuhängen vermag.
256

Dviraračio šakės stiprumo ir standumo tyrimas / Analysis of bacycle fork‘s strength and solidity

Rūkas, Alvydas 04 August 2011 (has links)
Dviračių šakių stiprumo ir standumo bandymai atliekami vadovaujantis reikalavimais, aprašytais standarte LST EN 14764. Norėdami nustatyti dviračio šakėje bandymo metu atsirandančius įtempimus ir deformacijas galime naudoti matavimo sistemą ,,Spider 8“ valdomą programine įranga ,,Catman“. Taip pat įtempimus ir deformacijas galima nustatyti naudojant virtualaus modeliavimo programas, tokias kaip SolidWorks. Darbe išnagrinėti matavimo sistemos ,,Spider 8“ veikimo principai. Gauti bandymų rezultatai pateikti lentelėse, grafikuose ir paveikslėliuose. Dviračio šakės bandymo rezultatai gauti naudojant folinius tenzodaviklius. Aprašytas daviklių klijavimas ant bandomos šakės, bei jų žymėjimas. Darbe išnagrinėta mechaninių dydžių matavimo metodai. Palyginti SolidWorks ir Catman programomis gauti bandymo rezultatai. / Bicycle fork’s strength and solidity tests are carried out under the conditions described in the standard LST EN 14764. To identify stresses and strains values in the bicycle fork’s test we can use a measuring system ,,Spider 8" controlled by software Catman. Also, the stresses and strains can be determined by using virtual simulation software such as SolidWorks. Operating principles of measurement system ,,Spider 8 " is described in this project. Test results are presented in tables, graphs and pictures. Bicycle fork test results obtained by using strain gages. In this project is described how to bond strain gages and it’s marking. In this project described measurement values of mechanical methods. Compared test results received by using SolidWorks and Catman programs.
257

Using General Strain Theory to Understand Drug and Alcohol Use in Canada: An Examination of how Strain, its Conditioning Variables and Gender are Interrelated

Asselin, Nicolas, Robert, Pierre 03 September 2009 (has links)
This thesis uses the Canadian Drugs and Alcohol survey conducted in 1994 by Statistics Canada to explore how Agnew’s (1992, 2001, 2006) general strain theory can help to understand drug and alcohol use in Canada. Agnew argues that experiences of strain, which include an array of negative life events, produce a negative emotional response which creates pressure for corrective action. In postulating why certain individuals are more likely to react to strain with deviant behaviour, Agnew (1992, 2001, 2006) emphasizes the importance of variables that condition the effects of strain on deviance. It is argued that people are less likely to respond to strain with deviant coping strategies depending upon their levels of social control, constraint, social support and deviant peers and values (Agnew 1992; Broidy and Agnew 1997; Agnew 2006). Results are very supportive of GST as measures of objective and subjective strains as well measures of the conditioning variables are consistently associated with drug and alcohol use in hypothesized directions; strain measures also tended to interact with conditioning variables in associations with substance use. Hypotheses surrounding gender differences were also supported as females generally scored higher than males on measures argued to protect against the effects of strain and lower on measures argued to encourage deviant coping. Additionally, objective financial strain tended to have a stronger effect on male substance use while subjective strains tended to be more important in the prediction of female substance use. Avenues for further research are discussed including ways to ameliorate the adaptation of GST to gendered substance use patterns. / Thesis (Master, Sociology) -- Queen's University, 2009-08-31 12:12:25.288
258

Damage Detection in Tires From Strain Values Calculated Using Digital Image Correlation

Kotchon, Amanda Christine Unknown Date
No description available.
259

Analysis of structural development during superdrawing of poly(ethylene terephthalate) fibers

Jain, Vibhor 09 January 2009 (has links)
A comprehensive experimental study was conducted to determine the limitations in processing conditions for superdrawing. Experimental studies were carried out by uniaxial drawing tests at temperatures from 90 to 120°C and at strain rates ranging from 0.008/s to 0.425/s. Crystallinity and orientation of the drawn samples were evaluated using differential scanning calorimetry and birefringence measurements. This study revealed that increasing temperature from 110°C to 120°C leads to more crystallization at low strain rates (0.001/s), and less crystallization at high strain rates (0.1/s). Furthermore, it was shown for the first time that the mechanism of crystallinity development in PET undergoes a transition at draw temperature of 113°C and strain rate of 0.17/s. A new one-dimensional constitutive model was developed to predict the stress-strain behavior of PET fibers as they are drawn to very large draw ratios (up to 10) over a wide range of temperature (90-120°C) and strain rate (0.008-0.425/s). The model was based on the rubber elasticity theory and non-linear viscoelasticity.
260

Left Ventricular Strain and Strain Rate Responses to Submaximal Exercise in Prostate Cancer Patients Treated with Androgen Deprivation Therapy

Post, Hunter January 1900 (has links)
Master of Science / Department of Kinesiology / Carl Ade / Background: Androgen Deprivation Therapy (ADT) is a commonly used treatment for prostate cancer with controversy currently surrounding its association with long-term cardiovascular disease risk. Therefore, the aim of the current investigation was to non-invasively measure left ventricular mechanics at rest and during submaximal exercise in human prostate cancer survivors with and without a history of ADT. Methods: Eighteen prostate cancer survivors, 9 with a history of ADT and 9 matched (1:1) non-ADT controls, completed the protocol. Standard and tissue Doppler echocardiography were used to evaluate left ventricular systolic and diastolic function at rest and during submaximal cycling exercise. Results: At rest, there were no differences between groups. Ejection fraction was not different between groups at rest or during exercise (rest p=0.7; exercise p=0.8). During exercise, systolic left ventricular longitudinal strain and strain rate failed to increase in the ADT group (p=0.4; p=0.07), but significantly increased in the non-ADT group (p=0.03; p=0.02). During exercise, systolic strain was significantly different between groups (p=0.02). Diastolic longitudinal strain increased with exercise in both groups (p=0.003; p=0.003). In the ADT group during exercise, mitral valve deceleration time was not significantly different from rest (p=0.8) and was slower compared to non-ADT (p=0.03). Conclusion: In prostate cancer survivors with a history of ADT, there are significant abnormalities of left ventricular systolic function that become apparent with exercise. These findings may hold significant value beyond the standard resting characterization of ventricular function, in particular as part of a risk-stratification strategy.

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