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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.
641

Ermittlung bleibender Bodenverformungen infolge dynamischer Belastung mittels numerischer Verfahren

Wegener, Dirk 25 October 2012 (has links)
In der Arbeit wird gezeigt, wie man die Bodensteifigkeit bei sehr kleinen Dehnungen sowie die Abnahme der Steifigkeit mit zunehmender Scherdehnung in Labor- und Feldversuchen ermitteln kann. Dazu werden typische Eigenschaften mineralischer und organischer Böden einschließlich Korrelationen zusammengestellt und wesentliche Unterschiede zum Bodenverhalten bei großen Dehnungen, insbesondere hinsichtlich der Steifigkeit und der Spannungsabhängigkeit aufgezeigt. Weiterhin wird dargelegt, wie man mit dem hypoplastischen Stoffgesetz mit intergranularen Dehnungen das Bodenverhalten bei kleinen Dehnungen wirklichkeitsnah erfassen kann und wie die Stoffparameter zu bestimmen sind. Für die realistische Erfassung des Bodenverhaltens infolge zyklischer Belastung einschließlich der Ausbildung von Hystereseschleifen wird eine Modifizierung des hypoplastischen Stoffgesetzes unter Einführung eines zusätzlichen Stoffparameters vorgenommen. Es wird gezeigt, wie dieser Parameter in zyklischen Laborversuchen bestimmt werden kann und wie damit die Akkumulation von Dehnungen bei drainierten Bedingungen bzw. von Porenwasserdrücken bei undrainierten Bedingungen zuverlässig prognostiziert werden kann. Anhand der dynamischen Beanspruchung eines Eisenbahndammes auf weichem, organischem Untergrund wird das modifizierte hypoplastische Stoffgesetz mit intergranularen Dehnungen für ein bodendynamisches Randwertproblem angewendet und gezeigt, dass damit das Bodenverhalten realistisch abgebildet werden kann. Die Berechnungsergebnisse zeigen eine gute Übereinstimmung mit Ergebnissen von Schwingungsmessungen und Langzeitverformungsmessungen. Es werden bodendynamische Berechnungen zur Wellenausbreitung sowohl eindimensional als auch im Halbraum mit unterschiedlichen Stoffgesetzen geführt und Vergleiche mit analytischen Lösungen vorgenommen. Dazu wird gezeigt, welche Anforderungen an numerische Berechnungen zur Wellenausbreitung, insbesondere hinsichtlich Wahl der Zeitschritte, Elementgröße bzw. Knotenabstände, Größe des FE-Netzes und Modellierung der FE-Ränder erforderlich sind.:1 Einführung 2 Bodensteifgkeit 2.1 Defnition der Scherdehnung und der Schubspannung 2.2 Versuchstechnische Ermittlung der Bodensteifgkeiten 2.3 Ermittlung der Bodensteifgkeiten im Feld 2.4 Ermittlung der Bodensteifgkeiten im Labor 2.5 Bodensteifgkeit bei sehr kleinen Dehnungen 2.6 Abnahme der Steifigkeit mit zunehmender Scherdehnung 2.7 Bodenverhalten und Scherdehnungsgrenzen 2.8 Weitere bodendynamische Eigenschaften 3 Hypoplastisches Stogesetz 3.1 Allgemeine Formulierung der Hypoplastizität 3.2 Intergranulare Dehnungen 3.3 Bereich mit sehr kleinen Dehnungen 3.4 Bereich mit kleinen bis mittleren Dehnungen 3.5 Vergleich der Ergebnisse mit dem HS-Small-Modell 3.6 Zusammenfassung und Wertung der Ergebnisse 4 Numerische Berechnungen zur Wellenausbreitung 4.1 Eindimensionale Wellenausbreitung 4.2 Wellenausbreitung im Halbraum 4.3 Wellenausbreitung im porösen Medium 5 Anwendungsbeispiel 5.1 Geometrische Situation, Baugrundschichtung 5.2 Bodenmechanische und bodendynamische Kennwerte 5.3 Schwingungsmessungen 5.4 Messung von bleibenden Verformungen 5.5 Belastung 5.6 Numerische Modellierung 5.7 Hypoplastische Berechnung 5.8 Vergleich Mess- und Berechnungsergebnisse 5.9 Linear elastische Berechnung 5.10 Vergleich der Ergebnisse mit hypoplastischer und elastischer Berechnung 6 Zusammenfassung und Ausblick Summary Literaturverzeichnis Symbolverzeichnis Anhang A Berechnungen zur Wellenausbreitung Anhang B Eingabedateien für Berechnungen mit TOCHNOG Anhang C Herleitungen der Biot-Theorie / In this thesis it is shown how to determine the soil stiffness at very small strains, as well as the decrease in stiffness with increasing shear strain amplitude in laboratory and field tests. Typical properties and empirical correlations of coarse-, fine-grained and organic soils are collected and significant differences in soil stiffness and stress-dependence at small strains compared to large strains are shown. Further it is shown how one can realistically reproduce the soil behaviour at small strains with the hypoplastic constitutive model with intergranular strains and how the material parameters are determined. For a realistic prediction of soil behaviour due to cyclic loading including hysteresis loops in the stress-strain relationship, a modification of the hypoplastic constitutive model is made by using an additional material parameter. It is shown how this additional parameter can be determined in cyclic laboratory tests and how the accumulation of strains in drained conditions and excess pore pressures built up in undrained conditions can be realistically reproduced. Based on the dynamic load on a railway embankment on soft marshy ground, the modified hypoplastic constitutive model with intergranular strains is applied for a boundary value problem. It is demonstrated, that the soil behaviour can be reproduced realistically. Numerical results show a good agreement with results of vibration measurements and measurements of permanent displacements. A dynamical numerical analysis is performed for both one-dimensional and half-space conditions. Different constitutive models have been applied and compared with analytical solutions. The results demonstrate requirements on numerical analysis of wave propagation, in particular with regards to time steps, element size, node spacing, size of the FE mesh and boundary conditions.:1 Einführung 2 Bodensteifgkeit 2.1 Defnition der Scherdehnung und der Schubspannung 2.2 Versuchstechnische Ermittlung der Bodensteifgkeiten 2.3 Ermittlung der Bodensteifgkeiten im Feld 2.4 Ermittlung der Bodensteifgkeiten im Labor 2.5 Bodensteifgkeit bei sehr kleinen Dehnungen 2.6 Abnahme der Steifigkeit mit zunehmender Scherdehnung 2.7 Bodenverhalten und Scherdehnungsgrenzen 2.8 Weitere bodendynamische Eigenschaften 3 Hypoplastisches Stogesetz 3.1 Allgemeine Formulierung der Hypoplastizität 3.2 Intergranulare Dehnungen 3.3 Bereich mit sehr kleinen Dehnungen 3.4 Bereich mit kleinen bis mittleren Dehnungen 3.5 Vergleich der Ergebnisse mit dem HS-Small-Modell 3.6 Zusammenfassung und Wertung der Ergebnisse 4 Numerische Berechnungen zur Wellenausbreitung 4.1 Eindimensionale Wellenausbreitung 4.2 Wellenausbreitung im Halbraum 4.3 Wellenausbreitung im porösen Medium 5 Anwendungsbeispiel 5.1 Geometrische Situation, Baugrundschichtung 5.2 Bodenmechanische und bodendynamische Kennwerte 5.3 Schwingungsmessungen 5.4 Messung von bleibenden Verformungen 5.5 Belastung 5.6 Numerische Modellierung 5.7 Hypoplastische Berechnung 5.8 Vergleich Mess- und Berechnungsergebnisse 5.9 Linear elastische Berechnung 5.10 Vergleich der Ergebnisse mit hypoplastischer und elastischer Berechnung 6 Zusammenfassung und Ausblick Summary Literaturverzeichnis Symbolverzeichnis Anhang A Berechnungen zur Wellenausbreitung Anhang B Eingabedateien für Berechnungen mit TOCHNOG Anhang C Herleitungen der Biot-Theorie
642

The Deformation and Fracture Energy of Natural Rubber Under High Strain Rates

Al-Quraishi, Ali Abdul Hussain 02 October 2007 (has links)
No description available.
643

Elastomer-based Cellular Micromechanical Stimulators for Mechanobiological Study

Wang, Qian 16 September 2014 (has links)
No description available.
644

Web-based dynamic material modeling

Nanjappa, Jagdish January 2002 (has links)
No description available.
645

BEHAVIOUR OF DETERIORATED PIPES REHABILITATED WITH GROUTED SLIPLINERS

Simpson, Bryan 29 November 2013 (has links)
The goals of this research are to develop and validate the use of distributed fibre optic sensors for use in strain monitoring of buried culverts, and to use full-scale experiments to evaluate the performance of both deteriorated steel and reinforced concrete culverts rehabilitated with grouted slipliners subjected to surface loading. Bench scale experiments were conducted to evaluate the use of fibre optic sensors against conventional strain sensors. Then, fibre optic sensors were attached to a full-scale culvert that was tested in a buried state as a proof of concept. Finally, fibre optic sensors were used in two large scale buried pipe tests to explore the performance of rehabilitated flexible and rigid culverts. A deteriorated steel culvert was tested in a buried state under surface loading, then rehabilitated with a grouted high density polyethylene (HDPE) slipliner while still in a buried state and tested under surface loading at 0.9 m and 0.6 m burial depths. The rehabilitated steel pipe was tested under service loading, and up to 1250 kN of applied load. The results suggested that the grouted annulus stiffened the overall structure, and increased the capacity of the system to over 3 times the fully factored design load. A deteriorated reinforced concrete culvert was tested and rehabilitated in a similar fashion. The grout in the annulus penetrated the cracks at the crown, invert and joint of the concrete pipeline. The lined concrete pipe was tested to 1200 kN under single axle loading, and to 800 kN under single wheel loading. The results suggested that while the concrete pipe was stiffened by the grout, it remained the primary contributor to structural capacity, with the liner contributing little to the capacity. Repair reduced the diameter change by an average of 90%, with the capacity reaching approximately 3.3 and 4.2 times the design loads for single axle and single wheel pair loading, respectively. The maximum response was under single axle loading over the barrels of the concrete pipe. In no instance did the structures reach an ultimate limit state, and the tests were stopped after bearing failure of the soil occurred. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-11-28 17:24:50.815
646

Změny hladin katecholaminů, serotoninu a laktátu při sportovním lezení na umělé stěně v závislosti na stylu jištění prvolezece / Changes of the catecholamins, serotonine and lactate levels during sport climbing on a climbing wall depending on the leader climber's style of belaying

Kárníková, Kateřina January 2015 (has links)
Title: Changes of the catecholamins, serotonine and lactate levels during sport climbing on a climbing wall depending on the leader climber's style of belaying. Goals: The Goal of this thesis is to build on the bachelor thesis and develop its goals. The research is focused on a detection of blood hormonal changes before performance, right after it and after a 15- minute pacification depending on a style of a personal profile and style of belaying of the climbers. Hormonal changes have been compared during the performance on two climbing routes of the same difficulty and different styles of belaying. Methods: The randomized research sample consisted of 10 women, climbers, who climbed two routes using the OS (on sight) style on the level of maximum effort. One of the routes was climbed with clipping in protection points against the second route, which was climbed without protection points. The research was performed using a blood collection from v. brachialis and spinning off the blood plasma of the collected blood. Lactate was determined on Siemens Adria 1800 in a routine laboratory, serotonine was determined using LS-MS/MS with a gradient elution. Catecholamines were determined using LS-MS/MS with an isocratic elution. The survey composed of three psychological questionnaires (DMV, RCAI, Eysenck's...
647

Entrainement, préparation physique et physiologique cardio-respiratoire appliquée au rugby à XV / Training, physical training and cardiovascular physiology applied to the rugby union

Fornasier Santos, Charly 20 December 2018 (has links)
Le rugby à XV est un sport collectif qui se caractérise en match par des courses et des collisions de hauteintensité très variables selon les positions. La première partie des travaux, qui s’est centrée sur l’analyse del’activité par centrale d’analyse cinématique, a mis en évidence une activité de haute intensité plus importante enCoupe d’Europe qu’en TOP14 qui varie selon les cinq postes de jeu en termes de répétitions d’efforts et dedistances parcourues à haute intensité notamment chez les avants. De plus, ces activités de haute intensitédiminuent en première et deuxième mi-temps et sont différentes selon les positions. En effet, une diminution plusprécoce est observée chez les avants et les trois-quarts ailes, qui est majorée au niveau des accélérations entre lesdeux dernières périodes d’un match pour les avants démontrant un impact de la fatigue. A l’inverse, les arrièresarrivent globalement à maintenir une intensité élevée. Ainsi, au regard des résultats de la première partie, ladeuxième partie des travaux a consisté en la mise en place d’un entraînement par répétition de sprints en hypoxieinduite par hypoventilation à bas volume pulmonaire. Celui-ci a permis une amélioration significative de lacapacité à répéter des sprints après sept séances d’entraînement par hypoventilation chez les joueurs très entraînés,alors qu’aucun changement n’a été observé dans le groupe normoxie. L’entraînement en rugby à XV se caractérisepar la répétition d’efforts de haute intensité à dominante dynamique (courses) et statique (musculation, phases decombat) qui vont impacter le remodelage du ventricule gauche de manière spécifique. La troisième partie a montré,à partir d’échocardiographies de repos en mode 2D-strain, une hypertrophie physiologique majorée chez les avantscomparativement aux arrières. Cette hypertrophie s’accompagne d’une augmentation des pressions de remplissageet une diminution de la relaxation lors de la diastole, notamment chez les avants. Enfin, malgré une torsionventriculaire inchangée, les rotations et les vitesses de rotation sont plus grandes au niveau basal et plus faibles auniveau apical chez les joueurs de rugby à XV. Ainsi, cette thèse CIFRE apporte de nouvelles données au niveaude l’analyse de l’activité, des méthodes d’entraînement facilement applicables pour l’entraîneur, ainsi que desdonnées plus spécifiques à l’évaluation cardiaque de repos pour le clinicien. / Rugby union is a team sport characterized by high-intensity collisions and running efforts during gameswhich are position-dependent. Accounting for the five different positional groups, the first part of this thesisdemonstrated greater high-intensity activity in European cup when compared to the TOP14 rugby unioncompetition; with position-dependent variations in the frequency of repeated high-intensity efforts and the relativedistance of high-speed movements in forwards. A decrease in high-intensity movement parameters was observedduring the first and second halves of a competitive rugby union match. Indeed, the decrease in high-intensitymovements was earlier in forwards and outside backs who peaked in high-intensity accelerations between the lasttwo periods of the game, while backs were able to maintain their high-intensity activity throughout the match.Collectively, the capacity for a player to repeat high-intensity efforts during a rugby union game varied by thelevel of competition and was influenced by the onset of fatigue. In this context, the second part of this thesis was to conduct a repeated-sprint training in hypoxia. Hypoxia was induced by voluntary hypoventilation at low lungvolume. This training protocol has largely improved the repeated-sprint ability performance in highly-trainedrugby union players after seven training sessions of hypoventilation, whereas it was unaltered in the controlnormoxic group. Such training demands in rugby union (characterised by repeated high-intensity efforts indynamic (running) and static (weightlifting, fighting)) have a specific impact on left ventricular remodelling. Thelast part of this thesis, using 2D-speckle-tracking resting echocardiography, demonstrated that LV hypertrophywas greater in forwards when compared to backs and to control group. Systolic function remained unchanged, butdiastolic function was altered, mainly in forwards, with an increase in filling pressures and a decrease in leftventricular relaxation. Finally, left ventricular twisting was similar while rugby union players exhibited lowerapical and higher basal rotations velocities compared to controls. Collectively, this CIFRE research programprovided new data in activity analysis and training methods that are widely applicable to a range of rugby unionprograms and data on left ventricular morphology, function and mechanics for the clinician.
648

Avaliação da deformação média gerada nos intermediários e na região peri-implantar durante as etapas de confecção da prótese parcial fixa parafusada: análise com strain gauges / Evaluation of abutment and simulated bone tissue mean deformation around dental implants, during fabrication stages of screw-retained fixed partial prostheses: strain gauges analysis

Costa, Max Dória 30 May 2011 (has links)
A adaptação passiva e estabilidade têm se tornado os dois pré-requisitos de maior importância na escolha dos materiais e técnicas de confecção em prótese implantossuportada. A proposta deste trabalho foi avaliar, com auxílio dos strain gauges ou extensômetros lineares elétricos, a deformação média ocorrida nos intermediários e na região peri-implantar mediante a instalação da infraestrutura parafusada durante sete etapas de confecção da prótese parcial fixa. Para a investigação, foi utilizado um modelo experimental homogêneo à base de poliuretano com dois implantes hexágono externo paralelos entre si. Sobre os implantes foram acoplados pilares Multi-unit de 5 mm de altura que receberam na sua superfície três strain gauges dispostos de maneira eqüidistante entre si. Também foram colados na superfície superior do bloco experimental quatro strain gauges para cada implante, posicionados nas faces mesial, distal, vestibular e lingual visando medir as tensões nestas áreas. Os testes foram realizados parafusando os corpos de prova sobre os intermediários utilizando-se para isto um dispositivo eletrônico de torque com força máxima de 10 Ncm. As leituras foram realizadas em sete momentos, obtendo os valores médios de deformação no poliuretano e no intermediário respectivamente: 1) cilindros de cobalto-cromo pré-fabricados usinados como grupo controle (36,4µε e 87,5µε), 2) infraestrutura sobrefundida em monobloco com liga de níquel-cobalto-cromo (340,3µε e 131,4µε), 3) em seguida seccionada com espaço livre para solda (43,2µε e 66,6µε), 4) seccionada com espaço para solda preenchida com resina acrílica quimicamente ativada (Duralay) (74µε e 86,8µε), 5) seccionada e soldada (280µε e 146,2µε), 6) soldada com aplicação de cerâmica (288,7µε e 151,1µε) e 7) finalizada com aplicação do glaze, acabamento e polimento (359,9µε e 197,8µε). Estes resultados mostraram um aumento crescente da deformação média tanto nos intermediários como no poliuretano durante todas as etapas de confecção, com excessão da fundição em monobloco que atingiu altos valores, próximos da prótese finalizada. Desta forma, o procedimento de soldagem diminuiu os níveis de derformação, enquanto a aplicação da cobertura cerâmica, glaze, acabamento e polimento, aumentaram as deformações. / Passive fit and stability have become the most important prerequisites during the choice of materials and techniques to implant-supported prostheses. Therefore, the aim of this study was to verify the mean deformation in abutments and simulated bone tissue around dental implants, with the use of strain gages, during framework screw retention, analyzing seven fabrication stages of the fixed partial denture. For this research, an experimental model based on homogeneous polyurethane with two external hexagon implants parallel to each other, provided with 5 mm height multi-unit abutments. For each, abutment surface received three equidistant strain gauges and the experimental block received upper surface four strain gauges, positioned on the mesial, distal, buccal and lingual aspects. The tests were performed screwing the specimens on the abutment using an electronic torque with 10 Ncm maximum force. The readings were made in seven moments, with abutment and polyurethane mean deformation, respectively: 1) control group: cobalt-chromium prefabricated machined cylinder (36,4µε e 87,5µε), 2) framework fabricated by 1-piece method in nickel-cobalt-chromium alloy (340,3µε e 131,4µε), 3) framework sectioned with space for welding (43,2µε e 66,6µε), 4) weld space filled with chemically activated acrylic resin (Duralay) (74µε e 86,8µε), 5) framework sectioned and soldered (280µε e 146,2µε), 6) framework welded and ceramic application (288,7µε e 151,1µε) and 7) framework concluded applying glaze, finishing and polishing (359,9µε e 197,8µε). The results showed the mean strain increase in abutment and polyurethane over fabrication stages, except that framework fabricated by 1-piece method reached high values close to finished prostheses. Thus, the welding procedure decreased strain levels in simulated bone tissue around dental implants, while ceramic and glaze application, finishing and polishing procedures, increased strain.
649

Identificação de lesões coronárias graves por meio do strain bidimensional longitudinal do ventrículo esquerdo na síndrome coronariana aguda sem elevação do segmento ST / Severe coronary artery stenosis identification by two dimensional strain in non-ST- elevation acute coronary syndrome

Vilela, Andréa de Andrade 20 October 2014 (has links)
Estimativas nacionais e internacionais indicam que a síndrome coronariana aguda é uma das principais causas de internação hospitalar e óbito. A maioria desses pacientes tem diagnóstico de síndrome coronariana aguda sem supradesnivelamento do segmento ST (SCASSSST) e possui amplo espectro de gravidade, que varia de acordo com características clínicas e laboratoriais. A estratificação de risco é essencial para auxiliar na decisão clínica, discriminando quais pacientes se beneficiam de estratégias mais agressivas. Os escores TIMI e GRACE são os mais utilizados e com valor prognóstico estabelecido por estudos de coorte prospectiva. O strain longitudinal bidimensional (S2DL) permite a quantificação da deformidade miocárdica por meio do rastreamento de \"marcas acústicas\" naturais do músculo cardíaco pelo ultrassom, apresentando valores reduzidos na presença de isquemia miocárdica. O objetivo principal desse trabalho foi identificar, por meio do S2DL do ventrículo esquerdo, quais pacientes com SCASSSST apresentam estenose coronariana maior ou igual a 70%. Os objetivos secundários foram: 1) Identificar a porcentagem de pacientes categorizados como de baixo risco e moderado risco, segundo os escores TIMI e GRACE, que apresentaram estenose coronária maior ou igual a 70%; 2) Determinar um valor de corte do S2DL e número mínimo de segmentos adjacentes acometidos que se correlacionem com o território irrigado pela coronária comprometida (com estenose maior ou igual a 70%) nos pacientes portadores de SCASSSST. Total de 100 pacientes com Idade de 60±11,4, 62% do sexo masculino e predomínio de pacientes (p) de baixo e moderado risco cardiovascular (80% pelo escore TIMI e 99% pelo escore GRACE). Divididos em grupo A (34p) com estenose coronária < 70% e grupo B (66p) com estenose coronária >=70%. Os escores clínicos foram maiores no grupo B (TIMI 3,59±1,4; p=0,008 e GRACE 88,7±24,18; p=0,040). O strain longitudinal global (SLG) permitiu identificar os pacientes com estenose coronária >=70% (AUC=0,72, sensibilidade=50%, especificidade=90%, valor preditivo positivo= 75,1% e valor preditivo negativo=74,9%). No grupo B, 72,8% e 98,5% foram categorizados como de baixo e moderado risco pelos escores TIMI e GRACE, respectivamente. O strain longitudinal segmentar (SLS) permitiu identificar a coronária culpada pelo evento isquêmico, com valor de cut-off e número mínimo de segmentos estimados em: -14 e 4 segmentos para coronária descendente anterior, -16 e 3 segmentos para a coronária circunflexa e coronária direita. Concluímos que o SLG mostrou ser acurado em discriminar pacientes com estenose coronária grave, mesmo naqueles com escore de risco baixo e moderado pelos escores TIMI e GRACE. O SLS permite estimar a área de miocárdio isquêmico por meio do número de segmentos com deformidade alterada, e conhecer a coronária culpada mais provável. / National and international estimates indicate that acute coronary syndrome is one of the major causes of hospitalization and death. Most of these patients have a diagnosis of non-ST-elevation acute coronary syndrome (NSTE-ACS) and have wide spectrum of severity. Risk stratification is essential to assist in clinical decision. The TIMI and GRACE risk scores are the most used and the prognostic values were established by prospective cohort study. Myocardial strain by speckle tracking is a technique based on widely available two-dimensional grayscale echocardiography, enabling the accurate evaluation of global and regional myocardial function, and it is has been shown to be sensitive to abnormalities caused by ischemia. The main objective of this study was to identify, through global longitudinal strain, whose patients (p) with NSTE-ACS had >= 70 % coronary stenosis. The secondary objectives were: 1) Identify the percentage of p categorized as low or moderate risk according to the TIMI and GRACE risk scores , who showed coronary stenosis >= 70 % ; 2) Determine a cutoff value of regional strain and the minimum number of segments allowing the identification of the culprit coronary artery in p with NSTE-ACS. Hundred (p) with diagnosis NSTE-ACS were stratified according to TIMI and GRACE risk scores, and all p underwent coronary angiography. Global longitudinal strain (GLS) and territorial strain (TS) were calculated. Age 60 ± 11.4, 62% male. Majority were low and moderate cardiovascular risk (TIMI score by 80 % and 99 % by the GRACE score). They were divided into group A (34p) with coronary stenosis < 70 % and group B (66p) with coronary stenosis >= 70 %. Clinical scores were higher in group B (TIMI 3.59 ± 1.4, p = 0.008 and 88.7 ± GRACE 24.18, p = 0.040). SLG was accurate identifying p with coronary stenosis >= 70 % (AUC = 0.72, p=0.001, sensitivity = 50 %, specificity = 90 %, positive predictive value = 75.1 % and negative predictive value = 74.9 %). Group B were low and moderate cardiovascular risk 72.8 % by TIMI risk score and 98.5 % by GRACE risk scores. TS was able to identify the culprit coronary in an ischemic event with cutoff values and minimum number of damaged segments as follow: -14 and 4 segments for anterior descending coronary, -16 and 3 segments to the circumflex coronary and right coronary. SLG has proved accurate in discriminating patients with severe coronary stenosis, even in those with low and moderate risk by TIMI and GRACE risk scores. TS estimates the area of ischemic myocardium by the number of segments with abnormal deformity, and suggests the most likely culprit coronary.
650

Estudo da formação e reversão de martensita induzida por deformação na austenita de dois aços inoxidáveis dúplex. / The study of formation and reversion of the strain induced alpha-prime martensite in duplex and super duplex stainless steels

Aguiar, Denilson José Marcolino de 17 August 2012 (has links)
No presente trabalho foram estudados os fenômenos de encruamento e, principalmente, a formação e reversão da martensita alfa-linha (a\', cúbica de corpo centrado, CCC, ferromagnética) induzida por deformação em um aço inoxidável dúplex UNS S31803 e um super dúplex UNS S32520. Inicialmente, as microestruturas dos dois materiais na condição solubilizada foram caracterizadas com auxílio de várias técnicas complementares de análise microestrutural. Foram determinadas fração volumétrica, estrutura cristalina, composição química, tamanho e morfologia das duas fases (ferrita e austenita). Posteriormente, os dois aços foram deformados por dois métodos: a laminação a frio, dividida em vários estágios, com menores graus de deformação e a limagem, sendo que o cavaco limado resultante apresenta altos graus de deformação. Algumas amostras deformadas foram recozidas. Os fenômenos de encruamento, formação e reversão de martensita induzida por deformação na austenita, recuperação, recristalização da austenita e da ferrita no cavaco limado foram estudados predominantemente por difratometria de raios X e usando o método de Rietveld. A difratometria de raios X também foi utilizada para determinação das microdeformações residuais e tamanhos de cristalito (subgrão), calculadas a partir do alargamento dos picos de difração causado pelas deformações. Desta forma, puderam-se comparar os níveis de deformação da laminação e limagem. Qualitativamente, a formação e reversão da martensita induzida por deformação também foi estudada por meio de medidas magnéticas utilizando-se dados de saturação magnética das curvas de histerese obtidas com o auxílio de um magnetômetro de amostra vibrante. Observou-se que para o aço inoxidável dúplex, tanto a laminação quanto a limagem causaram a formação de martensita induzida por deformação e para o aço inoxidável super dúplex, apenas a limagem promoveu essa transformação. Em comparação com o aço dúplex, o aço super dúplex apresentou maior resistência à formação de martensita induzida por deformação, pois apresenta uma austenita mais rica em nitrogênio e uma maior propensão à formação de fase sigma durante o recozimento, pois apresenta uma ferrita mais rica em cromo e nitrogênio. / In the present work the phenomena of strain hardening, formation and reversion of the strain induced alpha-prime martensite (a\', body centered cubic, BCC, Ferromagnetic) in an UNS S31803 duplex and UNS S32520 super duplex stainless steels have been studied. Firstly, the microstructures of both materials in the solution annealed condition were characterized with the aid of several microstructural analysis complementary techniques. The volume fraction, crystalline structure, chemical composition, size and morphology of the two phases (ferrite and austenite) have been determined. Further, both steels were deformed by two methods: cold rolling, divided into several stages, with lower strain levels than filing, which the chips resulting had higher strain levels. The phenomena of strain hardening, formation and reversion of strain induced martensite in the austenite phase, recovery and recrystallization of austenite and ferrite phases have been studied, mainly using X-ray diffraction and the Rietveld method. X-ray diffraction was also used to determine the residual microstrain and crystallite size (sub grain), calculated from the diffraction peak broadening caused by straining. Thus, the levels of cold rolling and filing strains could be compared. Qualitatively, the formation and reversion of strain induced martensite was also studied by magnetic measurements using data from magnetic saturation of hysteresis curves obtained with the aid of a vibrating sample magnetometer. It has been observed that for the duplex stainless steel, both filing as well as cold rolling promoted strain induced martensite. On the other hand, for the super duplex stainless steel, just filing promoted this transformation. In the comparing with duplex, the super duplex stainless steel austenite is more stable that is why is richer in nitrogen, so, the strain induced martensite formation is more difficult. The easier sigma phase precipitation during annealing as well in the super duplex stainless steel is due higher levels of chrome and molybdenum than the duplex stainless steel.

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