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Zhang, Xuesong, i n/a. "Punching Shear Failure Analysis of Reinforced Concrete Flat Plates Using Simplified Ust Failure Criterion". Griffith University. School of Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051104.153239.
Pełny tekst źródłaZhang, Xuesong. "Punching Shear Failure Analysis of Reinforced Concrete Flat Plates Using Simplified Ust Failure Criterion". Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365777.
Pełny tekst źródłaThesis (Masters)
Master of Philosophy (MPhil)
School of Engineering
Full Text
Yadav, Priti. "Multiscale Modelling of Proximal Femur Growth : Importance of Geometry and Influence of Load". Doctoral thesis, KTH, Strukturmekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209149.
Pełny tekst źródłaQC 20170616
Rouleau, Léonie. "Endothelial cell response to shear stress in an asymmetric stenosis model". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99535.
Pełny tekst źródłaTucker, Russell P. "Validating a new in vitro model for dynamic fluid shear stress mechanobiology". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:0ea8b159-5cb6-4bf0-9a60-4c580824016a.
Pełny tekst źródłaWillett, Nick J. "Redox signaling in an in vivo flow model of low magnitude oscillatory wall shear stress". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33917.
Pełny tekst źródłaVorobtsova, Natalya. "Computational model of coronary tortuosity". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/51267.
Pełny tekst źródłaMaster of Science
Miller, Leigh Ann. "Wall shear stress distribution and the effects of branch angle on a human coronary artery model". Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16088.
Pełny tekst źródłaEmmott, Alexander. "The effect of wall shear stress in a novel endothelial tissue culture model of arterial curvature". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107873.
Pełny tekst źródłaIl existe une hypothèse spéculant que les variations locales des forces hémodynamiques, particulièrement la contrainte de cisaillement à la paroi (CCP), mènent à un dérèglement important des cellules endothéliales (CEs) causant un environnement pro-inflammatoire. Les observations cliniques d'athérosclérose ont été documentées principalement dans: les bifurcations artérielles, les points de branchement et à la courbure artérielle. Des expériences in vivo et in vitro ont démontré que la CCP peut engendrer une cascade d'interactions biochimiques qui finissent par activer la voie inflammatoire. Les changements fonctionnels incluent : une expression modifiée des molécules d'adhésion inter-vasculaires et-cellulaire (ICAM-1 et VCAM-1, respectivement) de la surface luminale de l'endothélium. Ce changement de phénotype peuvent aider à identifier les premières phases du développement d'une lésion en facilitant l'adhérence des leucocytes en circulation dans le sang.Nous avons créé un modèle tridimensionnel de culture cellulaire en utilisant le nombre adimensionnel de Dean pour modéliser l'hémodynamique physiologique dans une artère courbée (De = 104). La CCP au sein de notre modèle de culture cellulaire est définie par les murs intérieurs et extérieurs en utilisant une méthode de dynamique des fluides computationnelle. Les CEs cultivées dans le modèle sont soumis à des expériences de perfusion pour une durée de 24h et à une CCP a l'entrée de 10 dynes/cm2. Les changements régionaux dans le phénotype des CEs sont évaluées en utilisant des indices de morphologie cellulaire (indice de forme par exemple), l'expression de certaines protéines et l'attachement des leucocytes circulants. L'indice de forme suggère que les CEs tapissant la paroi interne de notre modèle courbé présentent un phénotype atheroprone important par rapport à ceux vus tapissant le mur extérieur observée dans l'ensemble de la courbe de 180°. De même, la distribution des leucocytes favorise le mur interne du modèle de culture cellulaire entre 0°-90°. Cependant, l'analyse Western Blot montre une réduction de 54% en concentration de protéine endothéliale ICAM-1 dans la courbe relative au contrôle interne de droites. Cette étude démontre que le flux à travers un vaisseau courbé donne des résultats avec d'importantes variations locales dans le phénotype des CEs et préférentielles d'adhérence des leucocytes in vitro, donnant un aperçu futur sur le rôle de l'hémodynamique local dans les premiers stades de l'athérosclérose.
Wang, Taige. "Mathematical Analysis on the PEC model for Thixotropic Fluids". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/70907.
Pełny tekst źródłaPh. D.
Ibarra, Sandra. "A model of stress distribution and cracking in cohesive soils produced by simple tillage implements /". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38205.
Pełny tekst źródłaThe problem was solved using fundamental principles of soil mechanics and force equilibrium analyzis. As a result, a mathematical model was developed which describes three failure zones within the cut soil volume. The model can be programmed into a computer to generate maps of normal and shear stresses to visualize the three failure zones.
The failure zones are the shear failure zone, the tensile fracturing zone and the no failure zone. The tensile fracturing zone is delimited by the tensile stress reaching the tensile strength of the soil at the given soil moisture content and soil density. The tensile strength of the soil was measured using an apparatus and method designed in this research.
The mathematical model gives an explanation of the mechanics of crumbling and the shape of the failed volume, but it does not give information concerning soil aggregate quality and arrangement within the soil furrow. Then, a method of analyzing the formed aggregates was developed which considers some soil physical properties of aggregates.
The study concluded that the smaller tool width and the smaller tool rake angle, among the ones used in this research, produced the most efficient geometry in producing the largest amount of soil break up, the most uniform aggregate formation and the most stable aggregate arrangement. The same tool geometry requires less energy per unit volume of soil disturbed. The best performance is produced at the lowest soil water content among those tested.
Shen, Yao. "A peierls model of dislocation transmission through coherent interfaces and embedded layers". Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1092183192.
Pełny tekst źródłaTitle from first page of PDF file. Document formatted into pages; contains xv, 148 p.; also includes graphics Includes bibliographical references (p. 143-148).
Rouleau, Léonie. "Endothelial cell response and leukocyte adhesion in an asymmetric stenosis model: role of fluid wall shear stress gradients". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86519.
Pełny tekst źródłaL'athérosclérose est une maladie qui se développe localement où le flux sanguin est perturbé. Les cellules endothéliales sont soumises en permanence à des contraintes mécaniques et leur réponse a été reliée au développement et à la progression de l'artériosclérose. Différentes chambres d'écoulement ont été développées in vitro afin d'étudier la réponse des cellules endothéliales aux forces de cisaillement et de grandes avancées ont été faites afin de mieux comprendre les réponses cellulaires à l'écoulement sanguin. Ces modèles ne peuvent reproduire adéquatement la complexité des conditions présentes in vivo. Ainsi, afin de déterminer le lien entre les forces hémodynamiques et la stabilité des plaques artérioscléreuses, des modèles tridimensionnels ont été développés ainsi que les techniques biomoléculaires nécessaire afin d'étudier la fonction des cellules à l'intérieur de ceux-ci. Du dextran a été utilisé comme supplément afin d'augmenter la viscosité du média de culture et son effet sur les cellules a été caractérisé. Des modèles tubulaires ont été utilisés afin d'étudier la réponse à court et à long terme des cellules endothéliales à des forces de cisaillement de diverses magnitudes. La réponse morphologique des cellules endothéliales, suite à l'exposition d'un débit constant, a été étudiée dans des modèles idéalisés de sténoses asymétriques et réalistes anatomiquement. L'expression régionale des cellules endothéliales et l'adhésion locale de neutrophiles dans les modèles sténosés ont été quantifiées en fonction de la durée et de la magnitude des forces de cisaillement. Les résultats obtenus démontrent que le dextran peut affecter la réponse des cellules et ainsi les contrôles appropriés doivent être utilisé. La morphologie des cellules endothéliales varie avec la durée et la force du cisaillement ainsi que dans les régions où des gradients sont présent
Brooks, Zachary Edward. "Mechanical Stresses on Nasal Mucosa Using Nose-On-Chip Model". Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1578492176817977.
Pełny tekst źródłaAltshuler, Angelina E. "Proteolytic receptor cleavage and attenuated endothelial cell response to fluid shear stress in a model for autodigestion in shock". Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/fullcit?p1477880.
Pełny tekst źródłaTitle from first page of PDF file (viewed July 10, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references (leaves 75-85).
Wiesner, Theodore F. "A mathematical model of the dynamics of cytosolic free calcium in cultured vascular endothelial cells responding to shear stress". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/9374.
Pełny tekst źródłaYamanaka, Kenya. "Olprinone Attenuates Excessive Shear Stress Through Up-Regulation of Endothelial Nitric Oxide Synthase in a Rat Excessive Hepatectomy Model". Kyoto University, 2012. http://hdl.handle.net/2433/157435.
Pełny tekst źródłaAbo, Abdulla. "A three-dimensional flow model for different cross-section high-velocity channels". Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/2852.
Pełny tekst źródłaKornuta, Jeffrey Alan. "Characterization of lymphatic pump function in response to mechanical loading". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52208.
Pełny tekst źródłaNishii, Kenichiro. "MICRO-SCALE FLUID DYNAMICS AND ITS EFFECT ON HEPATIC PROGENITOR CELL REGENERATION ACTIVATION". Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1461945701.
Pełny tekst źródłaRicci, Giovanni. "Organic matter deposition/resuspension in a one-dimensional physical-biogeochemical model. A modelling study". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10595/.
Pełny tekst źródłaGrytsan, Andrii. "Abdominal aortic aneurysm inception and evolution - A computational model". Doctoral thesis, KTH, Biomekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-197289.
Pełny tekst źródłaBukaortaaneurysm (AAA) kännetecknas av en utbuktning hos aortaväggen i buken. Tillväxt av en AAA är oftast asymtomatisk, men en sådan utbuktning kan plö̈tsligt brista, vilket har hög dödlighet. Tyvärr finns det inga mediciner som kan förhindra AAA från att expandera eller brista. Patienter med upptä̈ckt AAA hålls därför under uppsikt tills operationskrav är uppnådda, såsom maximal AAA-diameter på 55 mm eller expansionstakt på 1 cm/år. Modeller för AAA-tillväxt kan bidra till att öka förståelsen för sjukdomsförloppet och till att förbättra beslutsunderlaget på en patientspecifik basis. AAA modeller för tillväxt och strukturförändring (G&R) är ganska komplicerade och innan man tar sig an denna utmaning krävs de god klinisk validering. I Artikel A har en befintlig tjockväggig modell för tillväxt av ett skikt av en AAA-skiva utö̈kats till en två-skiktsmodell. Denna modell återspeglar bättre den skiktade strukturen hos kärlväggen. Genom en parameterstudie undersö̈ktes påverkan av mekaniska egenskaper och G&R-parametrar hos en sådan modell för AAA-tillväxt. I Artikel B utvidgades modellen från Artikel A till en organnivå-modell för AAA-tillväxt. Vidare inkorporerades modellen i ett “Fluid–Solid–Growth” (FSG) ramverk. En patientspecifik geometri hos bukaortan användes för att illustrera möjligheterna med modellen. I Artikel C undersöktes utvecklingen av patientspecifika biomekaniska egenskaper hos AAA. Fyra patienter som skannats fem till åtta gånger med “Computed Tomography-Angiography” (CT-A) vid olika tillfällen analyserades. Flera icke triviala statistiska samband konstaterades mellan de analyserade parametrarna. I Artikel D undersöktes effekten av olika tillväxt-kinematik för AAA tillväxt. En modell med transversellt-isotrop-i-tjockleken-tillväxt var den bäst lämpade för AAA tillväxt, medans antagandet om fullt-isotrop-tillväxt och transversellt-isotrop-i-planet-tillväxt producerade orimliga resultat. Dessutom gav modellering av vävnadsvolymsförändring ett förbättrat väggtjockleks resultat men en fortsatt överskattning av väggförtunningen under AAA-expansionen.
QC 20161201
Ramesh, Chandra D. S. "Turbulent Mixed Convection". Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/236.
Pełny tekst źródłaShaarbaf, Ihsan Ali Saib. "Three-dimensional non-linear finite element analysis of reinforced concrete beams in torsion : reinforced concrete members under torsion and bending are analysed up to failure : a non-linear concrete model for general states of stress including compressive strength degradation due to cracking is described". Thesis, University of Bradford, 1990. http://hdl.handle.net/10454/3576.
Pełny tekst źródłaJurášek, Lubomír. "Nelineární analýza stěnových železobetonových prvků". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225628.
Pełny tekst źródłaJohnson, Tiffany Lynn. "Endothelial Cell Function Using a Tissue Engineered Blood Vessel Model: A Case Study of Cell-Cell Communication". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04032006-120602/.
Pełny tekst źródłaPollman, Matthew, Committee Member ; Galis, Zorina, Committee Member ; McIntire, Larry, Committee Member ; Taylor, W Robert, Committee Member ; Jo, Hanjoong, Committee Member ; Nerem, Robert, Committee Chair.
Hrabovský, Michal. "Návrh rekonstrukce balvanitého skluzu na toku Lomná v km 1,9". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265698.
Pełny tekst źródłaShamu, John. "On the measurement and application of cement grout rheological properties". Licentiate thesis, KTH, Jord- och bergmekanik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-251745.
Pełny tekst źródłaCementbaserade injekteringsmedels reologiska egenskaper har en stor påverkan på strömning och inträngningslängd i sprickigt berg. Medlens reologi är komplex, inklusive tixotropi, men strömningen beskrivs ändå oftast med den enkla linjära Bingham modellen i injekteringssammanhang. De två parametrarna från denna modell, flytgräns och viskositet, används sedan inom injekteringsdesign, för t.ex. tunnlar och dammar, för att bedöma inträngningen. Eftersom cementbaserade medel är tixoptropa suspensioner försvåras utvärderingen vid mätning med konventionella rotationsviskometrar på grund av glidning vid fasta begränsningsytor, sedimentation/separation av partiklarna och instabila flöden vid låga deformationshastigheter. En systematisk mätprocedur för att studera ovanstående problem med rotationsviskometer och koncentriska cylindrar samt olika vanliga vattencementtal, har utförts inom ramen för detta licentiatarbete. Av särskilt intresse har varit att studera effekten av olika geometrier och tidsintervallet mellan mätningarna, inklusive den instabila delen av flödeskurvan då deformationshastigheten är lägre än ett kritiskt värde. Denna del av kurvan har i litteraturen beskrivits som karakteristisk för tixotropa suspensioner, som t.ex. cementbaserade injekteringsmedel. Praktiskt kan ovanstående kunskap användas för att förbättra mätningen av de reologiska egenskaperna. Existensen av en kritisk deformationshastighet under vilken det inte finns något stabilt flöde, i kombination med glidning vid fasta begränsningsytor, diskuteras särskilt med hänsyn till dess påverkan på faktisk inträngning i släta och råa bergsprickor. Ett annat fokus i licentiatarbetet har varit att studera icke-Newtonska modellvätskors (Carbopol) radiella strömning mellan parallella plattor. Denna typ av strömningsgeometri används ofta som en idealiserad konfiguration för strömning i bergsprickor. I jämförelse med andra enklare geometrier, finns endast en begränsad forskning utförd för denna geometri både då det gäller analytiska och numeriska beräkningar men framförallt då det gäller experiment. Som ett första steg inför en mer systematisk undersökning av icke-Newtonsk radiella strömning presenteras i detta arbete framtagandet av en fysisk laboratoriemodell där hastighetsprofilerna mellan plattorna för första gången visualiserats med hjälp av ultraljud. De utförda mätningarna med tre olika öppningar mellan plattorna sam tre olika värden på det konstanta flödet, visar på en distinkt plugg som är ett resultat av vätskans flytgräns samt glidning i gränsskiktet mellan vätskan och plattornas fasta begränsningsytor. En jämförelse mellan uppmätta hastighetsprofiler och analytiskt beräknade diskuteras där resultaten överensstämmer relativt väl, med beaktande av de långtgående förenklade antaganden som krävs för beräkningarna. Fortsatta studier kommer att fokuseras på att förbättra laboratoriemodellen för en mer detaljerad studie av icke-Newtonska vätskors strömning och hur pluggen utvecklas under den radiella inträngningen, vilket fortsättningsvis är av betydelse för design av injektering i bergsprickor.
QC 20190521
McKellar, Dougan Kelk. "A dislocation model of plasticity with particular application to fatigue crack closure". Thesis, University of Oxford, 2001. http://ora.ox.ac.uk/objects/uuid:45183b90-017f-4ac1-9550-94772a0ca88b.
Pełny tekst źródłaWu, Zexiang. "Modélisation du comportement des sables sous la condition de cisaillement simple et applications au calcul des pieux". Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0045/document.
Pełny tekst źródłaThe thesis aims to study the mechanical behaviour of sand under simple shear condition and to apply the results to the numerical simulation of pile foundation. First, a recently developed critical state sand model (SIMSAND) is introduced with a straight forward procedure of parameters determination, implemented into a finite element code and then subjected to a series of validations. Then, the model is enhanced by considering the inherent anisotropy during the principal stress rotation under the simple shear condition and validated by using results of both triaxial tests and simple shear tests on Fontainebleau sand. Simple shear tests are analysed by simulating in three-dimensions the real conditions imposed by the simple shear apparatus. The inhomogeneity of the samples with the effect of sample size is also investigated. Furthermore, undrained and drained cyclic simple shear tests on Fontainebleau sand are conducted to investigate the cyclic responses, such as the effective normal stress degradation and the volumetric strain accumulation, respectively, considering some impact factors such as the initial void ratio, the normal stress, the cyclic shear stress ratio and the average shear stress ratio. Based on these results, two analytical models are proposed to predict the long-term degradation of the effective normal stress and the accumulation of the volumetric strain with the number of cycles. Moreover, the cyclic simple shear tests are simulated by the enhanced SIMSAND model by incorporating the stress reversal technique. Finally, a series of model pile tests under monotonic and cyclic loadings are simulated based on which the cone resistance of the piles is evaluated as well as the response of the soil surrounding the pile
Duffrene, Lucas. "Comportement viscoélastique d'un verre silico-sodocalcique dans le domaine des températures intermédiaires : approche phénoménologique et modélisation en triaxialité". Paris, ENMP, 1994. http://www.theses.fr/1994ENMP0515.
Pełny tekst źródłaShabani, Behnam. "Wave-Associated Seabed Behaviour near Submarine Buried Pipelines". University of Sydney, 2008. http://hdl.handle.net/2123/3532.
Pełny tekst źródłaSoil surrounding a submarine buried pipeline consolidates as ocean waves propagate over the seabed surface. Conventional models for the analysis of soil behaviour near the pipeline assume a two-dimensional interaction problem between waves, the seabed soil, and the structure. In other words, it is often considered that water waves travel normal to the orientation of pipeline. However, the real ocean environment is three-dimensional and waves approach the structure from various directions. It is therefore the key objective of the present research to study the seabed behaviour in the vicinity of marine pipelines from a three-dimensional point of view. A three-dimensional numerical model is developed based on the Finite Element Method to analyse the so-called momentary behaviour of soil under the wave loading. In this model, the pipeline is assumed to be rigid and anchored within a rigid impervious trench. A non-slip condition is considered to exist between the pipe and the surrounding soil. Quasi-static soil consolidation equations are then solved with the aid of the proposed FE model. In this analysis, the seabed behaviour is assumed to be linear elastic with the soil strains remaining small. The influence of wave obliquity on seabed responses, i.e. the pore pressure and soil stresses, are then studied. It is revealed that three-dimensional characteristics systematically affect the distribution of soil response around the circumference of the underwater pipeline. Numerical results suggest that the effect of wave obliquity on soil responses can be explained through the following two mechanisms: (i) geometry-based three-dimensional influences, and (ii) the formation of inversion nodes. Further, a parametric study is carried out to investigate the influence of soil, wave and pipeline properties on wave-associated pore pressure as well as principal effective and shear stresses within the porous bed, with the aid of proposed three-dimensional model. There is strong evidence in the literature that the failure of marine pipelines often stems from the instability of seabed soil close to this structure, rather than from construction deficiencies. The wave-induced seabed instability is either associated with the soil shear failure or the seabed liquefaction. Therefore, the developed three-dimensional FE model is used in this thesis to further investigate the instability of seabed soil in the presence of a pipeline. The widely-accepted criterion, which links the soil liquefaction to the wave-induced excess pressure is used herein to justify the seabed liquefaction. It should be pointed out that although the present analysis is only concerned with the momentary liquefaction of seabed soil, this study forms the basis for the three-dimensional analysis of liquefaction due to the residual mechanisms. The latter can be an important subject for future investigations. At the same time, a new concept is developed in this thesis to apply the dynamic component of soil stress angle to address the phenomenon of wave-associated soil shear failure. At this point, the influence of three-dimensionality on the potentials for seabed liquefaction and shear failure around the pipeline is investigated. Numerical simulations reveal that the wave obliquity may not notably affect the risk of liquefaction near the underwater pipeline. But, it significantly influences the potential for soil shear failure. Finally, the thesis proceeds to a parametric study on effects of wave, soil and pipeline characteristics on excess pore pressure and stress angle in the vicinity of the structure.
Zagzoule, Mokhtar. "Modelisation mathematique de la circulation sanguine cerebrale : aspects instationnaires et non-newtoniens". Toulouse 3, 1987. http://www.theses.fr/1987TOU30144.
Pełny tekst źródłaDesombre, Jonathan. "Modélisation vof de l’écoulement de jet de rive en surface et dans une plage perméable". Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3038/document.
Pełny tekst źródłaA 2D numerical modeling of flows in the swash zone is proposed using a Volume-Of- Fluid code. The detailed flow structure of a bore-driven swash event over an impermeable beach is first studied. The numerical model is then developed to account for porous media flow within the beach. The unique VARANS momentum equation and 1-fluid method used allow to solve simultaneously both surface and subsurface flows of air and water phases in the swash zone. This model is validated against a series of analytical tests cases and confronted to recent experimental measurements. The numerical results highlight the ability of the VOF-VARANS model to reproduce swash flows over and within a permeable beach
Sincos, Igor Rafael. "Determinação do impacto do oversizing da endoprótese sobre a aorta torácica. Estudo experimental em porcos". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/5/5132/tde-22012013-160615/.
Pełny tekst źródłaIntroduction: The use of endovascular techniques to treat the various disorders of the aorta has supplanted traditional open techniques, and is particularly promising in trauma1. The traumatic rupture of the aorta is the second leading cause of death by traffic accident2, 3, and repair of these lesions with endoluminal stents has showed lower mortality and paraplegia when compared to open surgery, however the long-term results are not yet available2-7. The endoprosthesis approved and commercially available during this study were designed to aneurysmal disease, with a diameter greater than the diameter of the aorta of young people ( ) \" z \" prosthesis with the aortic wall, affecting the vascularization and raising the risk of complications related to stent-graft implantation8-12. Purpose: Analyze, from an experimental animal model, the biomechanical and histological effects of four different levels of stents-graft oversizing in non-atherosclerotic aortas; such as those aorta found in young individuals who undergo stent-graft repair for traumatic aortic injuries. Methods: The diameter of the porcine thoracic aorta is similar to the aorta of young adults (18-20 mm), so 25 pigs were randomized into 5 groups: 1 control (without stent-graft) and 4 oversizing groups (A: 10%-19%, B: 20%-29%, C: 30%-39%, and D: .40%). Two types of biomechanical tests were performed on all aortas 4 weeks after endoprosthesis deployment: The \"detachment\" of the stent, and the biomechanics test of aortic fragments collected. The fragments were submitted to a histological and an immunohistochemistry analysis. Results: The results of the detachment test, which analyzed the strength necessary to remove the stent-graft from the aorta, were similar in the 4 groups (A: 42 N, B: 41 N, C: 46 N e D: 46 N, p= 0,881204). The second test was performed in 3 aortic segments. Maximum strength, maximum stress, and maximum tension supported by the aortic wall had a negative and linear correlation with oversizing. There were significant differences in all 4 groups when compared with the control group. The maximum deformation and strain, which reflect the elastic properties of the aortic wall, were very similar in all 4 groups. But a significant decrease in elasticity was found when compared each group with the control group (p = 0.0000001). Histological and immunohistochemistry analysis supported that the aortic wall has a signifi-?-actin by increasing the oversize (p = 0.000198 p = 0.002031, respectively). The amount of elastic fiber showed a significant drop regardless of the oversizing (p = 0.0000001). Conclusion: The four levels of oversizing studied did not show significant differences in the detachment test. Biomechanical tests of the fragments of the aorta showed a decrease in resistance of the aortic wall with increase in oversize. The elasticity of the aortic wall undergoes significant change independent of the oversizing used. The histopathological and immunohistochemical examinations confirmed the breakdown in the structure of the aortic wall with the use of stents-graft, resulting in decreased amount of elastic and muscle fibers.
Vlach, Jakub. "Porovnání návrhů monolitické konstrukce bez a se zohledněním postupu výstavby". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227302.
Pełny tekst źródłaVouaillat, Guillaume. "Analyse de la fatigue de contact d'engrenages aéronautiques". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI035.
Pełny tekst źródłaGears and rolling elements that are parts of transmissions are sometimes subjected to rolling contact fatigue failures as micro-pitting. It usually results from a lubrication loss or an uncontrolled surface finishing. First layers of the material are consequently overstressed. Microscopic material wrenching then occurs and is called micro-pitting. Such transmission parts failures may potentially lead to the whole system dysfunction. Several studies have already been performed in the literature concerning this topic. However, few of them take into account both surface roughness and material microstructure analyses which impact rolling contact fatigue mechanisms. Thus, a model with those characteristics is developed from literature theories and tools and presented in this thesis. A parametrical study is then conducted so as to estimate the influence of specific contact parameters (among sliding, friction, pressure and roughness) on three fatigue criteria results. However the use of an additional criterion is necessary in order to give more accurate conclusions. Intergranular shear stresses are subsequently studied and make the analysis of the complete stress history possible. Moreover, a life expectancy to micro-cracks nucleation is computed. An identification of sliding-linked local shear stress oscillations which result from successive rough peaks passing over the material surface is also made. Finally, numerical results are compared to an experimental investigation conducted on FZG-type gears. The most at risk areas regarding micropitting in the relevant applications are thus identified among the addendum, the dedendum and the pitch
Andersson, Harald. "Numerical and experimental study of confluent jets supply device with variable airflow". Licentiate thesis, Högskolan i Gävle, Energisystem och byggnadsteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-29271.
Pełny tekst źródłaUnder senare tid har applikation av Confluent jets för design av tilluftsdon studerats. Många studier har även utförts över potentialen av att applicera variabelt luftflöde (VAV) för att minska energianvändningen i ventilationssystem. Denna studie undersöker möjligheten att kombinera Confluent jets-don med VAV, både med avseende på den lokala flödesbilden och dess påverkan på termisk komfort, luftkvalitet och energieffektivitet i en klassrumsmiljö där luftflödes varieras. Denna studie baseras dels på en experimentell fältstudie där tilluftsdon baserade på Confluents jets jämfördes med befintliga deplacerande tilluftsdon. Fältstudien utvärderade energieffektiviteten, den termiska komforten och luftkvaliteten för båda typerna av tillluftsdon. Confluent jets-donen testades under varierat luftflöde för att se påverkan av flödesvariationen på ventilationens prestation under de olika flödena. Utöver fältstudien testades Confluent jets-donen experimentellt och numeriskt i ett välisolerat test-rum för få den detaljerade flödeskarakteristiken för den här typen tilluftsdon vid varierat luftflöde. Resultaten från fältstudien visar på en jämn fördelning av den lokala luftsmedelåldern i vistelsezonen, även för fallen med relativt låga luftflöden. Luftflöden har ingen signifikant effekt på omblandningen. Den termiska komforten i klassrummet ökade när luftflödet anpassades efter värmelasten jämfört med de deplacerande donen. Slutsatsen från fältstudien är att kombinationen av VAV och Confluent jets-don kan användas för att minska energianvändningen på skolan och bevara luftkvaliteten och den termiska komforten i vistelsezonen. Resultaten från den experimental och numeriska studien visar luftflödet och lufthastigheten i varje enskild dysa är direkt beroende på det totala luftflödet genom donet. Dock är flödesfördelningen mellan dysorna oberoende av de tre olika luftflödena. Den numeriska undersökningen visar att flödesprofilen för varje dysa är konstant trots att flödet varieras, men amplituden för varje profil ökar med en höjning av luftflödet. Det betyder att tilluftsdon av den här typen kan användas med VAV för att producera Confluent jets för olika luftflöden. Resultaten från båda studierna visar att luftflöde inte påverkar fördelningen av luften vare sig längs luftdonen eller på rumsnivå. Fördelningen av luften är nästan helt jämn längs donen och på rumsnivå är omblandningen och luftkvalitet den samma för varje luftflöde. Det betyder att det finns potential för att kombinera det här två teknikerna för att designa luftdistribueringssystem med hög energieffektivitet och hög termisk komfort med god luftkvalitet.
Chovet, Rogelio. "Caractérisation expérimentale et numérique du comportement rhéologique d'un fluide complexe : application à une mousse en écoulement dans un canal horizontal droit avec et sans singularités". Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0021/document.
Pełny tekst źródłaThis work is an experimental and numerical study of aqueous foam flow inside a horizontal square duct, with and without flow disruption devices (fdd). It is especially devoted to determine the pertinent parameters of the flow: longitudinal pressure losses, velocity fields of foam flow near the walls, liquid film thickness (thick and thin), and the wall shear stress evolution, for an aqueous foam with a void fraction range between 55 and 85%, for a mean foam flow velocity of 2, 4 and 6 cm/s. Once they were determined, inside the horizontal channel, we carried out measurements over different geometries: half-sudden expansion, vertical fence and foam flow around a cylinder. The goal was to study the foam flow reorganization to well understand the rheological behavior of aqueous foam flow in the vicinities of different fdd. Finally, a numerical simulation (CFD), using the Bingham behavior model of non-Newtonian fluid, was undertaken to test its capacity to represent the aqueous foam flow inside the horizontal duct with flow disruption devices. First of all, we verified the static longitudinal pressure evolution, which varies linearly upstream and downstream far from the fdd. The singular pressure loss remains constant for a given mean foam velocity and a foam quality (void fraction). From the Particle Imaging Velocimetry (PIV) technique (2D), we determined the two velocity components in the immediate vicinities of the disruption devices. They allowed us to put into evidence the different foam flow regimes and to observe the foam flow reorganization and rheological behavior through the studied fdd. The slip-layer thickness analysis, obtained using the conductimetry method, shows that the wall presents a liquid film thick enough to apply an electrochemical technique (polarography). Thus, the polarographic signals, obtained for the foam flow, present important fluctuations. They were compared to the wall shear stress deducted from the measurement of pressure losses, showing a good similarity between them. The numerical study (CFD), carried out for aqueous foam flow with a void fraction of 70% and a mean foam flow velocity of 2 cm/s, shows that the Bingham rheological model can be adapted to this kind of aqueous foam flow which is flowing like a block
Goudot, Guillaume. "Applications innovantes des ultrasons en pathologie vasculaire : utilisation de l'imagerie ultrarapide dans l'analyse de la rigidité artérielle et des ultrasons pulsés en thérapie Arterial stiffening assessed by ultrafast ultrasound imaging gives new insight into arterial phenotype of vascular Ehlers–Danlos mouse models Aortic wall elastic properties in case of bicuspid aortic valve Segmental aortic stiffness in bicuspid aortic valve patients compared to first-degree relatives Wall shear stress measurement by ultrafast vector flow imaging for atherosclerotic carotid stenosis Pulsed cavitational therapy using high-frequency ultrasound for the treatment of deep vein thrombosis in an in vitro model of human blood clot". Thesis, Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2215&f=13951.
Pełny tekst źródłaBaumgarten, Lars. "Gesteinsmechanische Versuche und petrophysikalische Untersuchungen – Laborergebnisse und numerische Simulationen". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-202612.
Pełny tekst źródłaTsai, Yu-Lin, i 蔡育霖. "Pulsatile Flows and Wall Shear Stress in Human Aortic Arch Model". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/vzsswd.
Pełny tekst źródła國立臺灣科技大學
機械工程系
95
Pulsatile flow characteristics and evolution processes in a model simulating the aortic arch of human being is diagnosed by using the particle tracking flow visualization method (PTFV) and the particle image velocimeter (PIV). The aortic arch model is made of transparent Plexiglas U-tube with three main branches (brachiocephalic artery, left common carotid artery, and left subclavian artery). Water is used as the working fluid. Pulsatile flows simulating the output of a human heart beat is supplied by a “pulsatile blood pump”. The results of this study are obtained using a 72 strokes/minute (1.2 Hz) stroke rate, a 75 ml/stroke (5.4 L/minute) stroke volume, and a 35%/65% systole/diastole ratio, all of which simulate the general conditions of the human cardiovascular system. The Womersley parameter, Dean number, and time-averaged Reynolds number are measured as 12.94, 2493, and 3697, respectively. The temporal/spatial evolution processes of the flow pattern, velocity distribution, and wall shear stress during systolic and diastolic phases are presented and discussed. It is found that the flows evolve complicatedly into three dimensional structures during the processes of acceleration, deceleration, and reversing. During the systole phase, the boundary layer on the inner wall separates from the area near the turning arch to the descending thoracic aorta. The induced reverse flow has low speed and would increase the probability of plaque deposition. During the diastolic phase, strong reverse flow is produced in the arch. Measured shear stresses show low values around the branch junctions and particularly high values around the outer wall of ascending aorta and descending thoracic aorta. These results correlate with the widely accepted clinic observation that the vessel segments that appear to be at the highest risk for development of atherosclerosis are around the junctions of the three branches and the aneurysms are tentatively found around the outer wall of ascending aorta and descending thoracic aorta. The oscillatory flow separation and shear stress distribution are apparently the primary causes leading to the atheroma and dissection/aneurysm.
Wang, Teng, i 王騰. "Pulsatile Flows and Wall Shear Stress in Renal Arterial System Model". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/98216540397202801179.
Pełny tekst źródła國立臺灣科技大學
機械工程系
97
The pulsatile flow characteristics and evolution process in a model which simulate the renal artery of human being is diagnosed by using the particle tracking flow visualization method (PTFV) and the particle image velocimeter (PIV). The renal artery model is made of transparent plexiglas material which has different dimension with three tubes (abdominal artery, left renal artery and right renal artery). Mixture of glycerol and water at 37oC is used in the experiment as a working fluid to mimic the blood flow. To simulate the pulsating blood as it came out from the human heart, a “pulsatile blood pump” is used. A 72 strokes/minute (1.2Hz) stroke rate, with a volume flow rate of 4 L/min and a 45%/55% systole/diastole ratio is adopted in this study. The temporal/spatial evolution processes of the flow pattern, velocity distribution, and wall shear stress during systolic and diastolic phases are presented and discussed. During the systole stroke, the separation of boundary layer from the inner wall near the branch is shown in the PIV results. These characteristic flow structures induce reverse and low speed flows therefore would increase the probability of plaque deposition around the inner wall of the renal artery. The measured shear stresses around the branch junctions are low while the measured shear stresses at the outer wall of the renal artery are high. The high shear stress at the outer wall of the renal artery might crack the fibrolipid plaque and collagenous cap of atherosclerotic. This would induce rapid assembling of platelets on the exposed connective tissues which form the thrombosis. Furthermore it diminishes the transport of oxygen and metabolites supplied to the organ.
Lai, Tzung-Chi, i 賴宗祺. "Prediction on Shear Stress-Strain Curve of Beam-Column Joint without Shear Reinforcement by Means of Softened Truss Model". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/48637099010730042354.
Pełny tekst źródła國立中央大學
土木工程研究所
92
This thesis comes from an idea of Hakuto’s shear degradation curve provided in 1990’s, proposing a rationally theoretical model verified basing on experimental data. The purpose of this study is to simulate the beam-column joint using a panel truss model via present concrete softened theories to find out the degradation curve of joint. Meanwhile, the analytical results of shear. Degradation on curves of beam-column joints can offer a tool for the seismic assessment of building structures. Results show, in order to predict the ultimate joint stress, the ratio of joint reinforcement have to properly reduce, restricting to the assumption of distributed joint reinforcement of the panel analysis. To obtain joint shear degradation curve, previous softened concrete models are adopted. According to data fitting, 1995’s Belarbi and Hsu softened model with Thorefeldt can simulate the behavior of beam-column joint well. However, it needs more experimental verification.
Shih, Chien-Hung, i 施建宏. "The Plastic Model of Shear Energy Dissipation Device Using Low-yield-stress Steel". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/04946621035025660204.
Pełny tekst źródła中原大學
土木工程研究所
94
The low yield strength steel plate is materials developed newly in recent years, and it possesses large ductility, low yield strength, and small yield ratio. The researches of using shear energy dissipation device using low-yield-stress steel are very much in domestic and foreign. There are many models which can successful simulate disappears energy. It is necessary to find real response of the model can descript this material rightly. The studies is using isotropic-kinematic harden model with Ramberg-Osgood model in Nakashima【1,2】,and finds the model which has a good way of choseing parameters easily . The main purposes of this research are: (1) uses the model to simulate the disappear energy of shear energy dissipation device using low-yield-stress steel in the load tests, and finds five suitable parameters of model. They are the initial yield stress, the initial elastic stiffness, parameterα, parameterη, parameterβ. (2) simulates the capacity of disappear energy in different amplitude of load tests and discusses it.
Gomez, Elizondo Carlos Arturo 1981. "Turbulence Modeling for Compressible Shear Flows". Thesis, 2012. http://hdl.handle.net/1969.1/148160.
Pełny tekst źródłaHung, Chien-Min, i 洪健閔. "Effects of Stent on Pulsatile Flows and Wall Shear Stress in Human Aortic Arch Model". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/27520110313673929894.
Pełny tekst źródła國立臺灣科技大學
機械工程系
98
The pulsatile flow characteristics in a human stent aortic arch has been studied experimentally using particle tracking flow visualization method (PTFV) and the particle image velocimeter (PIV). Such an aortic arch is modeled using transparent Plexiglas U-tube with three main branches (brachiocephalic artery, left common carotid artery, and left subclavian artery) while the working fluid used to mimic the blood is a mixture by water and glycerol. Pulsatile flows simulating the output of a human heart beat is supplied by a “pulsatile blood pump”. The results of this study are obtained using a 72 strokes/minute (1.2 Hz) stroke rate, a 70 ml/stroke (5 L/minute) stroke volume, and a 45% / 55% systole/diastole ratio. The temperature, Womersley parameter and time-averaged Reynolds number are set at 37oC, 16.28 and 1148 respectively. The temporal/spatial evolution processes of the flow pattern, velocity distribution, and wall shear stress during systolic and diastolic phases are presented and discussed. During the systole phase, the boundary layer at the inner wall separates from the area near the turning arch where the thoracic aorta descends. The induced reverse flow increases the probability of plaque deposition while the strong reverse flow during diastolic phase is produced in the arch. Measured shear stresses show low values around the branch junctions and particularly high values around the outer wall of ascending aorta and descending thoracic aorta. These results showed a potential risk of atherosclerosis around the junctions of the three branches and aneurysms at the outer wall of ascending aorta. The benefit of placing the stent at the descending thoracic aorta is the decrease of wall shear stress along the aortic arch and three main branches. Furthermore, shaking of wall shear stress decreases with time during systole and diastole cycle due to the present of stent. The present result would be useful for further improvements in placing of stent technology.
Kun, Lan-Yi, i 藍益坤. "Effects of Fluid Influence of Atherosclerosis on Pulsatile Flows and Wall Shear-Stress in Human Aortic Arch Model". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/67831041773328249451.
Pełny tekst źródła國立臺灣科技大學
機械工程系
96
Pulsatile flow characteristics and evolution processes in a model simulating the aortic arch of human being is diagnosed by using the particle tracking flow visualization method (PTFV) and the particle image velocimeter (PIV). The aortic arch model is made of transparent Plexiglas U-tube which has different ratio with three main branches (brachiocephalic artery, left common carotid artery, and left subclavian artery). Working fluid is used as the mixture by water and glycerol. Pulsatile flows simulating the output of a human heart beat is supplied by a “pulsatile blood pump”. The results of this study are obtained using a 72 strokes/minute (1.2 Hz) stroke rate, a 70 ml/stroke (5 L/minute) stroke volume, and a 45%/55% systole/diastole ratio. The temperature, Womersley parameter and time-averaged Reynolds number are measured as 37℃, 17.31, 2869. During systole stroke, the boundary layer on the inner wall separates from the area near the turning arch to the descending thoracic aorta and three dimensional secondary flows are observed. These characteristic flow structures induce reverse and low speed flows and therefore would increase the probability of plaque deposition around the inner wall of the arch. When the stenosis increases, the separation point would be deferred a little to the downstream area and the timing for separation would be advanced. During the diastolic phase, strong reverse flow is produced in the arch. Measured shear stresses show low values around the branch junctions and particularly high values around the outer wall of ascending aorta and descending thoracic aorta. In the aortic arch model with the atherosclerotic, the maximum wall shear stress appears on the inner wall of the arch might crack fibrolipid plaque and collagenous cap of atherosclerotic plaque and therefore would induce rapid assembling of platelets on the exposed connective tissues, form the thrombosis, and therefore diminish the transport of oxygen and metabolites to the organs.
Tait, Simon J., J. Heald, I. K. McEwan, M. Soressen, G. Cunningham, B. Willetts i D. Goring. "Probabilistic modelling of bed-load composition". 2009. http://hdl.handle.net/10454/2850.
Pełny tekst źródłaThis paper proposes that the changes which occur in composition of the bed load during the transport of mixed-grain-size sediments are largely controlled by the distributions of critical entrainment shear stress for the various size fractions. This hypothesis is examined for a unimodal sediment mixture by calculating these distributions with a discrete particle model and using them in a probabilistic calculation of bed-load composition. The estimates of bed-load composition compare favorably with observations of fractional transport rates made in a laboratory flume for the same sediment, suggesting that the hypothesis is reasonable. The analysis provides additional insight, in terms of grain mechanics, into the processes that determine bed-load composition. These insights strongly suggest that better prediction methods will result from taking account of the variation of threshold within size fractions, something that most previous studies have neglected.
Fiddes, Lindsey. "A Study of the Flow of Microgels in Patterned Microchannels". Thesis, 2011. http://hdl.handle.net/1807/29719.
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