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1
Perng, Jia-Der. "Analysis of crack propagation in asphalt concrete using a cohesive crack model". Connect to this title online, 1989. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1094737677.
Testo completo
2
Brahmachari, Koushik, of Western Sydney Hawkesbury University, of Science Technology and Agriculture Faculty e School of Construction and Building Sciences. "Connection and flexural behaviour of steel RHS filled with high strength concrete". THESIS_FTA_CBS_BRAHMACHARI_K.xml, 1997. http://handle.uws.edu.au:8081/1959.7/526.
Testo completoAbstract (sommario):
Steel hollow section members filled with concrete have been frequently used in recent construction industry as columns and beams and beam-columns because of their superior performance and constructability. Previous research demonstrated that such system has large energy absorption capacity which is critical in the event of an earthquake. By filling steel RHS with concrete, the failure of the steel shell due to local buckling can be delayed and the ductility of the concrete core can be improved as a result of the confinement of the steel shell. This type of composite section may be used in various structures including frames of high rise buildings, bridges, offshore structures, cast-in-situ piles in foundation etc. Design methods for concrete-filled steel tubular sections are recommended in a number of code of practices. Due to the significant differences in the material properties between normal strength concrete and high strength concrete, there is a need to study the behaviour of composite sections with higher strength concretes. The study emphasises ultimate strength, ductility, post-failure strength reserve and interface bond. It also emphasises ductility and post-failure strength of the composite beams due to the brittle behaviour of higher strength concretes when compared to normal strength concrete. Spreadsheet graph were used to present the results such as load versus strains, load versus deflections etc. In this thesis analytical study is presented on the calculation of ultimate moment of resistance of the concrete-filled RHS beams. Among the main considerations of the derivation, the steel portion was assumed either elastic-perfectly plastic or perfectly plastic and concrete carries no strength in the tensile zone. At the interface both full bond and partial bond were assumed for comparison. Efforts were also made to calculate the midspan deflections of the composite beams. Simple analytical expressions derived from this study can be coded to a prgrammable calculator or in a small spreadsheet program for design use. Finite element studies were carried out by using a proprietorship software package ANSYS. In the analysis of concrete-filled, three types of elements with large deformation and nonlinear capabilities were used. A plastic shell element, a solid concrete element with cracking and crushing capabilities, and a nonlinear spring contact element were used to model the steel shell, the concrete core and the interface respectively.Doctor of Philosophy (PhD)
3
Lolla, Sri Venkata Tapasvi. "Understanding the Role of Initial Microstructure on Intercritically Reheated Heat Affected Zone Microstructure and Properties of Multi-Pass Welds". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397826410.
Testo completo
4
Cristea, Alex Florian. "Analysis of thermal effects in circumferential groove journal bearings with reference to the divergent zone". Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2313/document.
Testo completoAbstract (sommario):
Ce travail porte sur l'étude des effets thermiques dans un palier hydrodynamique, alimentée par une rainure circonférentielle (CGJB) sous charge statique, en tenant compte des phénomènes de rupture de film dans la zone divergente. La recherche expérimentale a été réalisée à l'Université de Poitiers ; elle a permis une détermination minutieuse des champs de pression et de température sur la portée située à l’avant d’un CGJB et dans la section médiane de sa rainure. Ces mesures sous un régime stationnaire sont originales par rapport celles existantes, quel que le type de palier, de par le grand nombre de points de mesure, 180 pour la pression et 144 pour la température, l'instrumentation de haute précision, la large plage de conditions d'exploitation (pression spécifique variant de 0,125 à 2 MPa et vitesse linéaire de l’arbre allant de 5,25 à 21 m/s). Des études du régime transitoire de démarrage au régime stationnaire établi ont été effectuées pour de faibles charges. Des expériences effectuées à l'Université "Politehnica" de Bucarest ont montré une bonne corrélation entre la perte de portance, anti-portance et la rupture du film sur un patin Rayleigh (RSP), ce qui est essentiel pour l'évaluation des phénomènes de rupture dans les paliers. Quelques modèles théoriques ont été utilisés pour évaluer les risques de serrage au démarrage qui est une instabilité thermoélastique catastrophique. Les principaux résultats sont l’obtention d’une base fiable de données expérimentales permettant le développement des modèles théoriques avancés et l’infirmation d’une répartition de pression constante dans la zone divergente et de pression et température constantes dans la rainure d'alimeThe main objective of the thesis is to study the thermal effects in steadily loaded circumferential groove journal bearings (CGJBs), including cavitation phenomena occurring in the divergent zone of such bearings. Experimental research conducted at University of Poitiers – Institut Pprime – France enabled a thorough determination of film pressure and temperature fields for the front land of a CGJB plus its mid-groove section, and several performance parameters. Measurements of film pressure and temperature fields under steady-state regime surpassed existing works, regardless of journal bearing design, through: sheer number of land measurement locations, 180 for pressure and for 144 temperature; high precision state of art instrumentation; broad range of operating conditions, 0.125 … 2 MPa specific bearing pressure and 5.25 … 21 m/s shaft speeds. Transient start-up to steady-statestabilization regimes have been investigated at low loads. Experiments at University "Politehnica" of Bucharest – Romania showed a correlation between the downforce thrust and film rupture for a Rayleigh step pin (RSP), important in evaluating divergent zone cavitation phenomena. Theoretical research consisted in developing simple models for evaluating CGJBs performance in steady-state and transient start-up regimes. Several theoretical models were employed for assessing start-up seizure, catastrophic transient thermoelastic instability and damage risk. The major result is a reliable experimental data collection that: enables development of advanced theoretical models; disprove flat film pressure distributions in divergent zones, and constant pressure and temperature in the bearing supply groov
5
Brahmachari, Koushik. "Connection and flexural behaviour of steel RHS filled with high strength concrete". Thesis, View thesis, 1997. http://handle.uws.edu.au:8081/1959.7/526.
Testo completoAbstract (sommario):
Steel hollow section members filled with concrete have been frequently used in recent construction industry as columns and beams and beam-columns because of their superior performance and constructability. Previous research demonstrated that such system has large energy absorption capacity which is critical in the event of an earthquake. By filling steel RHS with concrete, the failure of the steel shell due to local buckling can be delayed and the ductility of the concrete core can be improved as a result of the confinement of the steel shell. This type of composite section may be used in various structures including frames of high rise buildings, bridges, offshore structures, cast-in-situ piles in foundation etc. Design methods for concrete-filled steel tubular sections are recommended in a number of code of practices. Due to the significant differences in the material properties between normal strength concrete and high strength concrete, there is a need to study the behaviour of composite sections with higher strength concretes. The study emphasises ultimate strength, ductility, post-failure strength reserve and interface bond. It also emphasises ductility and post-failure strength of the composite beams due to the brittle behaviour of higher strength concretes when compared to normal strength concrete. Spreadsheet graph were used to present the results such as load versus strains, load versus deflections etc. In this thesis analytical study is presented on the calculation of ultimate moment of resistance of the concrete-filled RHS beams. Among the main considerations of the derivation, the steel portion was assumed either elastic-perfectly plastic or perfectly plastic and concrete carries no strength in the tensile zone. At the interface both full bond and partial bond were assumed for comparison. Efforts were also made to calculate the midspan deflections of the composite beams. Simple analytical expressions derived from this study can be coded to a prgrammable calculator or in a small spreadsheet program for design use. Finite element studies were carried out by using a proprietorship software package ANSYS. In the analysis of concrete-filled, three types of elements with large deformation and nonlinear capabilities were used. A plastic shell element, a solid concrete element with cracking and crushing capabilities, and a nonlinear spring contact element were used to model the steel shell, the concrete core and the interface respectively.
6
Kejík, Vít. "Predikce chování stříkaného betonu s využitím elastoplastického materiálového modelu". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409748.
Testo completoAbstract (sommario):
This work is focused on the application of advanced elasto-plastic material model intended for shotcrete. Spatial mathematical models of two laboratory tests are created, where this model is used. The first test is a three-point bending concrete specimen. Next, the behavior of the material is analyzed, in which input parameters are entered. Consequently, two reverse analyzes of the available data are analyzed where a match between prediction and measurement can be obtained. The second test is a modified tensile test, where is describe the material behavior in changing of input parameters. Subsequently, reverse data analysis is created, where an acceptable match between prediction and measurement is possible. In every study, the stress waveform in the fracture process zone is analyzed to more detail.
7
Ben, Salem Naoufel. "Fiabilité des assemblages structuraux collés pour applications spatiales". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14681/document.
Testo completoAbstract (sommario):
Le dimensionnement des joints collés est une préoccupation majeure du CNES pour lesapplications spatiales des futurs lanceurs. Pour dimensionner une structure collée, il est nécessaire depouvoir apprécier les caractéristiques mécaniques du joint collé.Dans cette étude, trois adhésifs structuraux ont été sélectionnés (Hysol®EA 9321, Hysol®EA9394 et Hysol EA® 9395). Après leur caractérisation massique, une étude statistique pour mettre enévidence les effets des différents paramètres (vitesse d’essai, géométrie éprouvette, le degré depolymérisation…) a été entreprise.La deuxième étape a pour objectif de fiabiliser l’analyse des essais de fissuration etd’améliorer la compréhension des mécanismes d’endommagement et de propagation de fissure dansles liaisons collées. Trois types d’essai ont été utilisés, à savoir, l’essai Double Cantilever Beam(DCB), pour l’étude du mode I, l’essai End Notched Flexure (ENF), pour le mode II, et l’essai MixedMode Bending (MMB), pour les chargements en mode mixte I/II. Nous avons développé de nouvellesinstrumentations et méthodologies d’analyse. Pour affiner le protocole de test standard, la techniquedite de « backface strain monitoring » a été utilisée. Elle consiste à positionnées des jauges dedéformation sur les surfaces de l’éprouvette de façon à enregistrer l’évolution du signalextensométrique durant la propagation de la fissure. Cette méthode permet une meilleure estimation dela position front de fissure ainsi que l'étude de la répartition des contraintes le long du joint de colle.La corrélation d'images numériques (DIC) a également été utilisée afin de proposer un nouveauprotocole de calibrage de la longueur de fissure et pour comparer un modèle analytique (poutre deTimoshenko sur fondation élastique) avec les résultats expérimentauxAdhesive bonding is being strongly considered in space applications CNES as anadvantageous assembly technique for future launchers. Correct design of adhesive joints is of majorconcern. Aerospace adhesives are tough viscoelastic matrices (special epoxy resins) reinforced withnano-, or microparticles. Extended use of adhesive joints in structural applications is limited due to thedifficulties in predicting in-service performance, frequently leading to over-conservative design.Three structural adhesives (Hysol®EA 9321, Hysol®EA 9394 and Hysol®EA 9395) wereselected. After their bulk characterization, statistical studies to highlight effects of different parameterse.g. speed, test piece geometry, degree of polymerization were undertaken.In the second stage, fracture mechanics tests were effected employing: the double cantileverbeam (DCB) configuration (mode I characterisation), the three point bending end-notched flexure(ENF) (mode II) and the mixed-mode bending (MMB) (combined mode I/II loading). Crack growth inbonded joints was investigated in a novel way. To refine standard test protocol, the backface strainmonitoring technique was used. Strain gauges were used to measure the strain on the exposed skin ofthe adherends during crack onset and propagation. This method allows better estimation of the crackfront position as well as fine investigation of the stress distribution along the bondline and in the crackfront vicinity. Digital image correlation (DIC) was also used to compare analytical models, e.g.Timoshenko beam on elastic foundation model with experimental results
8
Nikpay, Mitra. "Experimental investigation of the stability of the colmation zone around leaky sewers". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-191137.
Testo completoAbstract (sommario):
Sewage exfiltration from a sanitary and combined sewer systems and its percolation into porous medium results in a clogged or colmation layer in the nearby soil. In order to develop a comprehensive understanding of raw sewage transport mechanisms in porous media, investigations were carried out on the micro-scale properties of the multiphase system. In our laboratory experiments, the role of surfactants as a major organic chemical compound in wastewater was evaluated by using a surfactant solution as an artificial wastewater percolating into a porous media, represented by using columns and Plexiglas model. We studied flows of water and surfactants solution in saturated porous medium to detect the dynamic effects by means of measuring pressure and permeability as well as by visualization of flow regions and consequence for porosity along interfaces between water and surfactants solution.
The tests revealed that mechanisms at interfaces between fluids and solids as well as between water and surfactants solution (i.e. wastewater) are significantly influencing the flow behavior. At the interfaces surfactant molecules are adsorbed or accumulate, respectively, and subsequently inducing electrical charges to those layers, altering the properties of fluids and these interfaces. Depending on the conditions, channels might be narrowed and thus decreasing the flow rate with a later erosion and increase of flow rates, or the flow and thus the erosive capacity might become intensified along the interface between surfactants solution and neighbouring water. In conclusion, the results of tests proved the surfactants to be an important controlling factor in the hydraulic properties of wastewater percolating into soil.
9
Raiss, Mark Edward. "Observation of the development of fracture process zones in concrete under tension". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/47748.
Testo completo
10
Lookingbill, Scott David, e Scott David Lookingbill. "Effects of concentration-dependent surface tension on vadose zone instrumentation". Thesis, The University of Arizona, 1997. http://hdl.handle.net/10150/626774.
Testo completoAbstract (sommario):
Many of the organic compounds of environmental interest which are commonly found
at contaminated sites have the effect of lowering the surface tension of water in proportion
to their aqueous concentration. Laboratory studies were conducted to investigate the
effects of reduced surface tension on instruments commonly used to measure pressure
head in the vadose zone. Gypsum block electrical resistance sensors and heat dissipation
probes were calibrated in tap water and in butanol solutions. A scaling relationship was
used to correct pressure head measurements taken in liquids of reduced surface tension.
The results indicate that the these measurements would be in error in that they would
underestimate pressure head for solutions of lower surface tension to the same factor by
which surface tension was reduced. This would result in pressure head gradient and flux
being underestimated as well. Therefore, surface tension effects on these instruments
should be considered when measuring pressure head in soils contaminated with organic
compounds.
11
Kong, Kok Loon. "Cracking and tension zone behaviour in reinforced concrete flexural members". Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427779.
Testo completo
12
Rocha, Daphne Wojciechowski. "Flexural strengthening by means of a arc overlay in the tension zone". Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/8850.
Testo completoAbstract (sommario):
Dissertação para obtenção do Grau de Mestre em
Engenharia Civil – Perfil de EstruturasReinforced concrete structures may be flexurally strengthened in the tension zone by the addition of a new concrete layer with embedded steel reinforcement. However, the interface between the new and old concrete creates a weak area that may cause failure to occur for loads inferior to the designed. Therefore the success of this technique relies on the interface capacity to transmit stress. Surface treatments and cleanliness are the two main aspects that affect adhesion between different age concretes cast against each other. Nevertheless, the amount of steel reinforcement crossing the interface is a factor that may overcome adhesion and improve shear resistance. In the last years, several studies have been elaborated on this theme. In the present dissertation, an experimental study was conducted in order to evaluate the performance of this strengthening solution, characterize failure modes and shear resistance at the interface. Simply supported beams with a bonded concrete overlay in the tension zone were subjected to a three point bending test, and interfacial failure was forced. Three different solutions for stress transmission across the interface are analyzed. In the first solution, shear transmission relies solely on adherence, whereas the two remaining solutions were developed with the aim of evaluating the contribution of reinforcement crossing the interface. Regarding the strengthening solutions with reinforcement crossing the interface, the difference between the effect of reinforcement concentrated near the borders of the new concrete layer or equally distributed along the interface is studied. During the tests, ultimate load, deflections, steel strains, cracking and rupture modes were analyzed. The obtained values were compared among each other and with the provisions of EC2 and MC2010.
13
Axson, Daniel Peter. "Ultimate Bearing Strength of Post-tensioned Local Anchorage Zones in Lightweight Concrete". Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33711.
Testo completoAbstract (sommario):
Currently, NCHRP Report 356 has published an equation to estimate the ultimate strength of the
local zone in normal weight concrete. The local zone is the area of concrete directly ahead of the
bearing plate. The equation can be broken into two distinct parts: unconfined bearing strength of
concrete enhanced by the A/Ab ratio and the enhancement of strength due to the presence of
confining. Research has shown that the strength enhancement of the A/Ab ratio and confining
reinforcing is less in lightweight concrete than in normal weight concrete.
To determine the strength of the local zone in lightweight concrete 30 reinforced prisms, 2
unreinforced prisms, and concrete cylinders were tested. The dimensions of the prisms were 8
in. x 8 in. x 16 in. and the cylinders were 4 in. x 8 in. cylinders. The simulated reinforcing in the
prisms extended only through the top 8 in. of the prism and consisted of either ties or spirals with
different spacing or pitch, respectively. To determine the effect of the A/Ab ratio for each
spacing or pitch arrangement of the reinforcing, one of two different size bearing plates were
used.
From the testing performed in this research and other research, it is apparent that the NCHRP
equation is unconservative when estimating the ultimate strength of the local zone in lightweight
concrete. By modifying both parts of the NCHRP equation it is possible to conservatively
predict the ultimate strength of the local zone in lightweight concrete.
Also investigated in this thesis are equations to predict the splitting cylinder strength and
modulus of elasticity of lightweight concrete. For a sand-lightweight concrete, as defined by
ACI 318-05 Building code and Commentary, the splitting tensile strength can be accurately
predicted by multiplying the square root of the compressive strength by 5.7.Master of Science
14
Hamodi, Sara, e Sadi Taha Fahandezh. "Analysis of Tension-Zone Resistance in Bolted Steel Connections : Component Method according to Eurocode3". Thesis, KTH, Stålbyggnad, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213723.
Testo completoAbstract (sommario):
In order to predict the behaviour of bolted steel connections, different methods can be applied to calculate the design tension resistance. In this thesis, the tension resistance is evaluated in the context of the so called Component Method according to Eurocode 3 part 1-8. The design approach establishes a unified procedure of modelling steel joints. Each joint configuration is decomposed into its basic components depending on loading type. In order to design the resistance of components subjected to tensile forces, a simple substitute model, the so-called Tstub flange is adopted. The Component Method is rather complicated to apply for all joint configurations. Therefore, the aim of this thesis is to create a brief and facilitated handbook covering the most common types of connections Kadesjös’ engineers deal with. The topic to be studied is rather comprehensive. Thus, this work is only focusing on the resistance calculation of components located in tension zone of HEA-sections in order to go deeper into the equivalent T-stub approach. To get a complete view about the designing procedure, general information about the Component Method are gathered by a literature study. Thereafter, the technical rules for calculation introduced in codes and standards were used to generate a general solution algorithm for two different connection configurations. The calculations have been performed using Mathcad, and the obtained results from a parametric analysis for particular profiles in each example are then summarised in tables and diagrams using Microsoft Excel.Att förutse skruvförbands beteende kan kräva tillämpning av diverse metoder. Metoderna används för att kalkylera den dimensionerande lastkapaciteten. I denna avhandling värderas lastkapaciteten i enlighet med den så kallade Komponentmetoden från del 1-8 i Eurokod 3. Denna dimensioneringsmetod fastslår en enhetlig procedur när det gäller modelleringen av stålförband. Varje förbandstyp bryts ner till sina baskomponenter med avseende på belastningstypen. För att beräkna den dimensionerande lastkapaciteten för dragbelastade komponenter används en förenklad substitutionsmodell en så kallad T-knut. Komponentmetoden är något komplicerad att tillämpa för alla former av skruvförband. Därmed är den huvudsakliga ambitionen med arbetet att skapa en kortfattad handbok vars syfte är att täcka de vanligaste typerna av skruvförband som Kadesjös konstruktörer använder sig av. Ämnet som kommer att studeras är relativt omfattande, således bestämdes det att i huvudsak sätta fokus på bärförmågan hos komponenter i dragzonen för HEA-profiler och därav dyka djupare i den ekvivalenta T-knutmetodiken. För att få en helhetsbild av dimensioneringsprocessen samlades allmän information om komponentmetoden genom litteraturstudier. Därefter användes dimensioneringsreglerna, presenterade i koder och standarder, för beräkning av lastkapacitet. Dessa utnyttjades för att generera en lösningsalgoritm för två skilda förband. Beräkningen genomfördes med hjälp av beräkningsprogrammet Mathcad. De erhållna resultaten, från en parametrisk analys för särskilda profiler i varje exempel, sammanfattades i form av tabeller och diagram med hjälp av Microsoft Excel.
15
Knowles, Kelsey. "Living Pedagogical Moments Between Curriculum as Lived and Curriculum as Plan: A Phenomenological Inquiry Into the Tensions of Teacher Education". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32573.
Testo completoAbstract (sommario):
This master’s research is a phenomenological inquiry into the pedagogical moment in teacher education. This phenomenon is explored through a conceptual lens that draws from the phenomenological pedagogical ideals that are intrinsic to the work of both Ted Aoki and Max van Manen. Following a comprehensive outline of the phenomenological methodology that guides this thesis, the pedagogical moment is described in terms of three phases: tension, opening and pulse. The phenomenon is further explored through several sub themes relating to the lifeworld existentials (time, body, space, relation to other). This research intertwines several phenomenological concepts (such as intentionality, embodiment, consciousness, pedagogy, and motion sensitive phenomenology), within the context of one “living” phenomenon as a way of shedding light on what it is like to experience a pedagogical moment from within the tensions of practicum teaching.
16
Bouchet, Thierry. "Etude de la zone de charge d'espace mixte (ZCEM) dans le drain des MOS haute tension". Aix-Marseille 3, 2001. http://www.theses.fr/2001AIX30087.
Testo completoAbstract (sommario):
Ce mémoire traite de l'analyse du comportement des MOS à canal N de puissance haute tension en mode de certains régimes sévères (tension drain-source Dos élevée et fortes densités de courants). Leurs conception et réalisation, pour une application spécifique, mirent sur la sellette un phénomène limitant le courant du dispositif quelle que soit Ucs la tension grille source. Nous avons attribué ce mécanisme à une Zone de Charge d'Espace Mixte (ZCEM). On bâtit ainsi un modèle plus approprié que celui du TECJ (JFE7) parasite admis jusque-là. La zone de charge d'espace n'est plus " déserte " (matériau N' forte résistivité avec seulement des charges fixes positives) mais " remplie " aussi de charges mobiles (électrons) transitant à une vitesse de saturation V sat # lO 7 cm. S'1. Cette cohabitation " positifs " (fixes et mobiles) et " négatifs " (mobiles) sous fort champ électrique explique l'acronyme ZCEM. Les caractérisations statique et dynamique des MOS haute tension se soldent par une détermination de l'influence de la structure sur la ZCEM (résistivité et épaisseur de la région de tenue en tension, distance intercellulaire). Des simulations en éléments finis (MEDICI, ATLAS) sont venues conforter ces résultats expérimentaux et ont montré le rôle essentiel de la zone N' de drain. On a donc été amené à réaliser un composant spécifique, simple, N'̂N* représentant la partie ZCEM observée dans le transistor MOS. .This thesis deals the analysis of high voltage power MOSFET behavior under extreme conditions (high supply voltages, high current densities). The design and realisation of high voltage MOSFET for a specific application brought forward a phenomenon limiting the current in the device - the mixed space charge layer - that replaces the conventional parasitic JFET model. The space charge layer is not "free" of charges but "filled" with mobile charges (electrons) forwarding through the structure with a limited saturation speed V sat # lO 7 cm. S'1. The static and dynamic characterization of the MOS high voltage makes it possible to determine the influence of the structure (thickness, intercellular distance, resistivity) on the ZCEM. Digital simulations lead to a consolidation of these experimental results and show the fundamental role of the v zone of drain. We carry out a specific simple component N ̂̂representing the ZCEM observed in MOSFET. The results from the impulse electric characterization are in conformity with simulation and show a similar behavior to the one observed in the MOS. .
17
Demassieux, Quentin. "Structural changes in the process zone of a cyclic fatigue crack in filled natural rubber". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066074.
Testo completoAbstract (sommario):
Les caoutchoucs naturels chargés sont largement utilisés pour leurs excellentes propriétés mécaniques comme matériaux structurels dans les pneumatiques. Leurs excellentes performances sont souvent associées à leur capacité à cristalliser sous tension. Dans le cas de la fatigue cyclique, la dissipation induite par la création et fusion de cristallites est souvent donnée comme responsable de la bonne résistance des caoutchoucs naturel à la propagation de fissures. Ce travail de doctorat s'est focalisé sur les divers mécanismes dissipatifs qui sont activé par les grandes déformations rencontrées près d'une pointe de fissure. La diffusion des rayons X a été utilisée pour caractériser les changements de structure à des échelles sub-microniques, tels que la cristallisation sous tension, la création de nano-cavités, ou la réorganisation de la charge. Un premier volet de l'étude s'est focalisé sur des tests uniaxiaux, afin d'étudier l'effet d'un changement de formulation du matériau (taux de charge, densité de réticulation), d'un vieillissement thermique, ou encore d'une élévation de la température sur ces modification de structure. Dans une seconde partie, une caractérisation complète de fissures de fatigue a été effectuée. La corrélation d'image numérique a été utilisée pour mesurer les déformations locales au voisinage d'une pointe de fissure, et les rayons X ont permis d'y associer une mesure locale de la structure du matériau. Les propriétés de fatigue de ces matériaux ont été mit en regard des structures observées afin de discuter leur relation. Il a été mis en évidence que le rôle de la cristallisation dépassait largement sa contribution à la dissipation localeFilled natural rubbers are widely used in structural parts such as tires for their outstanding mechanical properties. Their exceptional behavior is often associated to the ability of natural rubber chains to form a crystalline structure under tension. In the case of cyclic fatigue cracking, the dissipation added through crystallization and melting at the crack tip is often seen as the main reinforcing mechanism that reduces fatigue crack growth. This PhD work focused on all the dissipative mechanisms activated by the strain amplification near a crack tip. An extensive use of X-ray scattering was made to investigate sub-micronic changes in structure (strain-induced crystallization, cavitation, filler network). A study was made in uniaxial tension to understand the effects of material composition and test environment on these structure changes. The effect of filler volume fraction, crosslink density, thermal ageing and test temperature were considered. This study was followed by a complete description of several fatigue crack-tips. Digital image correlation was used to map the strain fields at the vicinity of the cracks, while X-ray mapping of the process zone gave information on the local changes in structure. The cyclic fatigue properties of the materials were then discussed through the knowledge acquired both in uniaxial tension and near crack-tips. It showed that the effect of strain induced-crystallization far outweigh the dissipation added
18
Cisneros, Solis Pereira Cesar Christian. "Cambio del nivel de 10kV A 22,9 kV y su influencia en la subestación tipo interior de la zona registral IX- sede Lima". Bachelor's thesis, Universidad Continental, 2018. http://repositorio.continental.edu.pe/handle/continental/4682.
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Turcotte, Julie. "Traduction de «Las malas juntas» de J.L. Urbina, suivi de la littérature latino-canadienne en traduction: zones de contact, zones de tension". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117061.
Testo completoAbstract (sommario):
The first part of this thesis consists of a translation from Spanish to French of approximately half of the short stories in the book Las malas juntas, by Chilean-Canadian writer José Leandro Urbina. This important book, by a writer renowned in Chile but little known in Canada, was first published in Ottawa in 1978; up to this day, it had not been translated into French. The second part of this thesis takes a postcolonial approach to study the role and importance of translation in the production and dissemination of a Spanish-language literature in both Quebec and Canada, and to describe how this literature calls into question some traditional concepts of translation theory. We then examine the problematic insertion of latino-québécois writers in the literary field of Quebec, by looking at how these books in translation challenge the delimitation of contemporary Quebecois literature.La première partie de ce mémoire consiste en une traduction de l'espagnol au français d'environ la moitié des textes du recueil de nouvelles Las malas juntas, de l'écrivain chileno-canadien José Leandro Urbina. Cette œuvre importante d'un auteur renommé au Chili mais peu connu au Canada, parue pour la première fois en 1978 à Ottawa, n'avait jamais été traduite en français.La seconde partie du mémoire adopte une approche postcoloniale pour examiner dans un premier temps le rôle et la place de la traduction dans la production et la diffusion d'une littérature en espagnol au Québec et au Canada, et la façon dont cette littérature bouscule certains présupposés des théories traditionnelles de la traduction. Dans un deuxième temps, l'insertion problématique des œuvres latino-québécoise dans le corpus littéraire du Québec est examinée sous l'angle des défis que posent ces œuvres en traduction pour la définition des frontières de la littérature québécoise contemporaine.
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Spielman-Davidson, Sylvia Justina. "Collaborative dialogues in the zone of proximal development, grade eight French immersion students learning the conditional tense". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/NQ53714.pdf.
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Saad, Ahmad. "Material properties of concrete used in skewed concrete bridges". Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-54412.
Testo completoAbstract (sommario):
This thesis has discussed both properties and geometry of concrete slabs used in bridges. It gave understanding on behavior of concrete in both tension and compression zones and how crack propagates in specimens by presenting both theory of fracture and performing concrete tests like tension splitting, uniaxial compression and uniaxial tension tests. Furthermore, it supported experimental tests with finite elements modelling for each test, and illustrated both boundary conditions and loads. The thesis has used ARAMIS cameras to observe crack propagations in all experimental tests, and its first study at LNU that emphasized on Brazilian test, because of importance of this test to describe both crushing and cracking behavior of concrete under loading. It’s an excellent opportunity to understand how concrete and steel behave individually and in combination with each other, and to understand fracture process zone, and this has been discussed in theory chapter. The geometry change that could affect stresses distributions has also described in literature and modelled to give good idea on how to model slabs in different angles in the methodology chapter. Thus, thesis will use finite elements program (Abaqus) to model both experimental specimens and concrete slabs without reinforcement to emphasize on concrete behavior and skewness effect. This means studying both properties of concrete and geometry of concrete slabs. This thesis has expanded experimental tests and chose bridges as an application.
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Clark, Tad Dee. "An Analysis of Microstructure and Corrosion Resistance in Underwater Friction Stir Welded 304L Stainless Steel". Diss., BYU ScholarsArchive, 2005. http://contentdm.lib.byu.edu/ETD/image/etd872.pdf.
Testo completo
23
Bernier, Mahana. "solutions smart grid innovantes pour l’intégration massive de la production photovoltaïque au réseau public de distribution en zone rurale". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT036.
Testo completoAbstract (sommario):
Les réseaux électriques de distribution évoluent et doivent faire face à de nouvelles problématiques, dont l’insertion massive d’énergie décentralisée et la modification des usages de consommation. Ces changements de paradigmes provoquent de nouvelles contraintes, qui impactent le dimensionnement et l’exploitation des réseaux électriques, ainsi que les études de planification ou de raccordement associées. Nous progressons alors vers des réseaux plus instrumentés et intelligents : les Smart Grids. Dans le projet SMAP en particulier, nous comparons des solutions pour améliorer l’insertion massive de production photovoltaïque dans les réseaux de distribution basse tension ruraux.Dans ce contexte, nous développons des modèles et des algorithmes permettant d’intégrer les différentes incertitudes sur les 35 prochaines années dans les méthodes de planification des réseaux de distribution. Quatre solutions alternatives aux solutions classiques de renforcement sont également modélisées : deux types de contrôle local des onduleurs PV, un bridage des onduleurs PV et un transformateur HTA/BT équipé d’un régleur en charge. Différents indicateurs sont définis afin d’évaluer la performance des solutions en termes de coûts et d’efficacité. Les développements effectués sont validés sur deux périmètres géographiques ce qui permet de tracer des premières conclusions qui devront être validées sur d’autres périmètres. Un des résultats intéressants de la thèse est notamment le gain important des solutions de type contrôle local de la tension par rapport à l’utilisation d’un régleur en charge. Les nombreux algorithmes ont été développés sous PowerFactory afin de pouvoir être directement réutilisés et complétés par EnedisDistribution grids are evolving and facing new challenges, including the massive insertion of distributed energy resources and the modification of consumer uses. These paradigm shifts are creating new constraints that affect the design and operation of electricity grids, as well as the planning and interconnection studies. We are now moving towards more instrumented and intelligent networks called Smart Grids. In the SMAP project in particular, we compare solutions to improve the massive insertion of photovoltaic production in rural low voltage distribution networks.In this context, we develop models and algorithms to integrate different uncertainties over the next 35 years into distribution network planning methods. Four alternative solutions compared to conventional reinforcement solutions are also modeled: two types of local control of PV inverters, the active power limitation of the PV inverters and an MV/LV transformer equipped with an on load tap changer. We define different indicators in order to evaluate the performance of the solutions in terms of costs and efficiency. The developments carried out are validated on two geographical perimeters, which makes it possible to draw first conclusions that will have to be validated on other perimeters. One of the important results of the thesis is in particular the significant gain of the solutions based on local voltage control of the inverter compared to the use of an on load tap changer. The many algorithms have been developed with PowerFactory so that they can be reused and completed by Enedis
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Owen, John. "DEVELOPMENT OF PHYSIOLOGIC CONTACT MODELS FOR ARTICULAR SURFACES". VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2444.
Testo completoAbstract (sommario):
The superficial tangential zone (STZ) plays a significant role in normal articular cartilage’s ability to support loads and retain fluids. To date, tissue engineering efforts have not replicated normal STZ function in cartilage repairs. Finite element models were developed to examine the STZ’s role in normal and repaired articular surfaces under different contact conditions. Models were developed by incrementally adding improvements which culminated in contact loading of curved models by permeable and impermeable rigid surfaces and a normal cartilage layer. In the normal STZ, permeability was strain-dependent on volumetric strain; tension-compression nonlinearity modeled collagen behavior. Nonlinear geometry accounted for finite deformation. Results showed that STZ properties of sufficient quality maybe critical for the survival of transplanted constructs in vivo. As compared to rigid surfaces, loading via normal cartilage provided more physiologic results. These models can provide guidance in identifying critical features for the design of tissue engineered articular cartilage constructs.
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Conand, Clément. "Etude tectonique, pétrographique et géochimique de la zone de transition subduction-collision à Taïwan : rôle de l'héritage et de l'obliquité de la convergence". Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30262.
Testo completoAbstract (sommario):
La chaîne de Taïwan est un exemple unique où il est possible d’étudier une transition subduction/collision active. L’obliquité de la convergence permet en effet d’observer du Sud vers le Nord les stades initiaux de l’accrétion continentale en mer jusqu’au stade mature de la collision. Je montre que la Chaîne Centrale au Sud de Taiwan, située la zone de transition, exhume des assemblages pétrographiques de grades croissants vers le Nord, dans un couloir décrochant senestre qui résulte du partitionnement de la convergence. Dans ce couloir l’extension sub-parallèle à la chaîne accommode une partie de l’exhumation. A proximité de la zone de suture principale, des assemblages de haute pression (12-15 kbars et 380-420 °C) associés à des blocs exotiques de serpentinites se sont mis en place dans un encaissant d’âge Miocène HT-BP associé à une intense déformation cisaillante senestre. Les analyses pétrologiques et géochimiques des mélanges ophiolitiques de Kenting et Lichi montrent que ces mélanges proviennent de deux sources situées à l’origine au pied de la marge continentale et dans la croûte océanique. Enfin, je propose, un nouveau modèle tectonique 3D du sud de Taïwan qui tient compte de l’architecture de la marge continentale, et qui met en avant la formation de la chaîne de Taiwan en contexte décrochantThe Taiwan collision is the unique example where to examine ongoing tectonic processes at the subduction/collision transition. The oblique convergence setting allows observations of first continental accretion offshore to the mature stage of collision onshore. I show that the southern Central Range, located at the transition, exhumed petrographic assemblages with peak metamorphism increasing northwards, in a corridor characterized by left-lateral transcurrent deformation. Extension sub-parallel to the belt is also understood as a major ingredient of rock exhumation. Near the suture zone, HP rocks (12-15 kbars and 380-420 °C) associated with isolated serpentinite bodies were emplaced in association with intense ductile strain localization in the strike-slip corridor. Petrographc and geochemical analyses of the Kenting and Lichi ophiolitic mélanges reveal that these mélanges originated from the distal rifted margin and the oceanic crust of the South China Sea. I propose a 3D geodynamic model of the evolution of the Taiwan orogen in which the rifted margin architecture is taken into account and the strike-slip kinematic component of the convergence is the main driver of mountain building
26
Treasurer, Paul James. "Characterization and Analysis of Damage Progression in Non-Traditional Composite Laminates With Circular Holes". Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13989.
Testo completoAbstract (sommario):
Carbon Fiber / Epoxy Laminates are increasingly being used in the primary structure of aircraft. To make effective use these materials, it is necessary to consider the ability of a laminate to resist damage, as well as material strength and stiffness. A possible means for improving damage tolerance is the use of non-traditional composite laminates, in which the longitudinal 0 plies are replaced with 5 or 10 plies. The main objectives of this collaborative Georgia Tech / Boeing research was the characterization of these non-traditional laminates, and the determination of appropriate lamina-level analytical techniques that are capable of predicting the changes caused by the use of slightly off-axis longitudinal plies. A quasi-isotropic [45/90/-45/theta/45/90/-45/-theta]s and hard [45/theta/-45/theta/90/45]s lay-up, where theta =0,5 or 10, were tested in open hole tension, filled hole tension, open hole compression, single shear bearing, and unnotched tension. These coupon level tests illustrated the effects of lay-up, notch constraint, and load type on traditional and non-traditional laminates. Die penetrant enhanced in-situ radiography was performed to determine the extent of damage suppression. The use of non-traditional laminates was found to reduce longitudinal ply cracking and delamination, with significant effect on the stress distribution around the notch. The use of non-traditional laminates also resulted in a 15%-20% improvement in bearing strength of the traditional laminates. Several predictive techniques were implemented to evaluate their ability to predict the effect of slight changes in ply orientations. A progressive damage model was written to compare Tsai-Wu, Hashin, and Maximum Stress unnotched strength criterion. Additionally, several semi-empirical failure theories for notched strength prediction were compared with linear and bi-linear cohesive zone models to determine applicability to non-traditional laminates.
27
Turetta, Maxime. "Development of an innovative U-shaped steel-concrete composite beam solution : experimental and numerical studies on the mechanical behaviour". Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0203.
Testo completoAbstract (sommario):
Une solution innovante de poutre mixte acier-béton a été développée en tenant compte des problématiques de résistance au feu et de montage sur chantier. La poutre est composée d'une partie métallique en U connectée à une partie en béton armé. En phase de construction, la poutre métallique supporte la dalle et constitue un coffrage pour la retombée en béton armé. La poutre en U résiste aux charges de construction sans système d’étaiement temporaire. Lors du coulage du béton, la poutre en acier est remplie en même temps que la dalle, ce qui permet un gain de temps considérable sur chantier. En phase d'exploitation, la poutre est mixte acier-béton. La connexion entre les deux matériaux est réalisée par des goujons à tête soudée en partie inférieure de la poutre en U. En situation d'incendie, la poutre mixte répond aux durées de stabilité au feu conventionnelles grâce aux armatures longitudinales à l'intérieur de la retombée avec des enrobages suffisants. Un état de l'art sur les solutions existantes répondant aux critères de la thèse est réalisé afin de proposer une solution innovante et optimisée. En phase de construction, sans présence de maintien, la poutre métallique en U est sujette à l’instabilité globale de déversement. Afin de caractériser la stabilité de la poutre, un test à échelle réelle est effectué au Laboratoire de l'Université du Luxembourg. Les résultats de l’essai sont comparés à des simulations numériques et à des études analytiques. Une étude paramétrique portant sur 200 configurations géométriques de la poutre en U est réalisée afin de valider l'utilisation de la courbe « b » pour le dimensionnement au déversement selon l’Eurocode 3. En phase d'exploitation, une fois le béton durci, la poutre présente un comportement mixte acier-béton assuré par la connexion. Pour des raisons de fabrication, la connexion est située dans une zone où le béton est soumis à des efforts de traction induits par la flexion de la poutre. Le béton dans cette zone est potentiellement fissuré, l’efficacité de la connexion et par conséquent le comportement mixte acier-béton sont étudiés. Un autre test, à échelle réelle, est effectué dans le Laboratoire de l'Université du Luxembourg. La ruine de la poutre mixte, par effort tranchant, se produit à très grands déplacements. Cependant, l’échantillon présente un réel comportement mixte avec une ductilité élevée, la connexion est donc très efficace. Les résultats de l’essai sont comparés à des simulations numériques afin de valider le modèle par éléments finis développé. A partir des résultats numériques et des résultats d’essais, une méthode de conception pour déterminer la résistance à la flexion de cette poutre, basée sur l’Eurocode 4, est proposée en tenant compte de la plastification partielle des parois de la section en U. Une méthode de conception analytique globale est proposée pour la solution développée basée sur les Eurocodes, avec des considérations supplémentaires et des conseils de mise en œuvreAn innovative solution of steel-concrete composite beam was developed taking into consideration the fire situation and the construction stage. The beam is composed of a U-shaped steel part connected to a reinforced concrete part. In the construction phase, the beam is supporting the slab and constitutes a formwork for the reinforced concrete part. The U-shaped beam withstands the construction loads without any temporary propping system. When casting concrete, the steel beam is filled at the same time as the slab, this allows considerable time-saving on site. In exploitation stage, the beam behaves as a steel-concrete composite beam. The connection between the two materials is made by welded headed studs on the lower part of the U-shaped beam. In fire situations, the composite beam satisfies conventional fire stability durations due to the longitudinal reinforcements inside the concrete downstand part with sufficient covers. A literature review focuses on modern solutions that fulfils the criteria of the thesis is performed in order to develop an innovative solution optimised. In construction stage, the U-shaped steel beam without restraints is prone to lateral torsional buckling instability. In order to characterise the stability of the beam, a full-scale test is carried out at the Laboratory of the University of Luxembourg. The test clearly showed the lateral torsional buckling of the steel beam. The test results are compared to numerical simulations and analytical studies. A parametrical study, covering 200 geometrical configurations of the U-shaped beam, is carried out to validate the use of the curve "b" for the design of the steel beam for lateral torsional buckling according to Eurocodes 3. In the exploitation phase, once the concrete hardens, the beam has a steel-concrete composite behaviour provided by the shear connection between the two materials. For manufacturing reasons, the connection is located in a zone where the concrete is subjected to tension forces induced by the bending of the beam. The concrete in this zone is potentially cracked, thus the efficiency of the connection and therefore the mechanical steel-concrete composite behaviour is investigated. Another test is therefore carried out in the Laboratory of the University of Luxembourg, this time the specimen tested is made of concrete and steel. The failure mode is a shear mechanism of the composite beam at very large displacements. However, the beam specimen exhibited a real steel-concrete composite behaviour with high ductility, the connection is therefore very efficient. The test results are compared to numerical simulations in order to validate the finite element model developed. From numerical results and test results, an analytical method, based on EN 1994-1-1, is proposed to find the bending resistant of this composite beam by taking into account the partial yield of the side plates of the U-shaped steel section. A global analytical design method is proposed for the developed solution based on the Eurocodes with additional considerations and constructional guidelines
28
Seppecher, Pierre. "Les fluides de Cahn-Hilliard". Habilitation à diriger des recherches, Université du Sud Toulon Var, 1996. http://tel.archives-ouvertes.fr/tel-00522242.
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29
Šťastný, Radek. "Studie odpočívky a velkokapacitního záchytného parkoviště pro TIR na dálnici D1". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225916.
Testo completoAbstract (sommario):
The task of my diploma work is the study of the parking area on the motorway D1 near Vyškov. This place will be connected with the motorway D1 between the present exit Vyškov – West (226) and Vyškov – East (230/1) in the direction to Kroměříž. The parking area (the parking place, the petrol station, the restaurant) and the truckpark will be designed with the reason of the high intensity of cars and lorries on the motorway D1 and with the reason of the lack of the parking places for the lorries.
30
Rau, C. David, e 饒啟文. "A Study of Micromechanucs and Deformed Zone During Tensile Test of Low Carbon Steel". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/63308299638049852366.
Testo completo
31
Hsiao, Yu-wei, e 蕭喻瑋. "The Tensile Behavior of Composite Adhesive Bonded Single Lap Joint by Using Cohesive Zone Model". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/40654522273840130642.
Testo completoAbstract (sommario):
碩士逢甲大學
機械與電腦輔助工程學系
101
Abstract Composite materials have excellent specific stiffness, and specific strength, that can both reinforce the structure effectively and make it lightweight. As the production technology is becoming more and more advanced, composite materials have been widely applied in many industries. Ifmechanical connection is applied during the process of combination, there must be an opening on the structure of multiple materials. But the opening might destroy the continuity of material, decreasing the strength of structure, and the ability of loading. Therefore, by using bonded joint technology, the damage during combination can be avoided, and we can improve stress concentration to let stress distributeuniformly and obtain a more lightweight structure. The bonded joint technology in composite structural, is now a common technology that has replaced mechanical connection. The study is aimed at the Adhesive Bonded interface of Delamination and mechanical behavior when the composite Adhesive Bonded single lap joint supports Tensile load. In the process, it considers the geometric nonlinear behavior that the load caused. With adhesive Bonded interface matching up with Quadratic nominal stress criterion and energy release rate by cohesive zone model, it can model Adhesive Bonded interface Initial delamination, delamination expansion and the condition of corresponding Stress distribution.
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Kirking, Bryan. "Exploring the Effects of Crosslinking on the Intervertebral Disc". Thesis, 2012. http://hdl.handle.net/1969.1/148231.
Testo completoAbstract (sommario):
Crosslinking soft tissue has become more common in tissue engineering applications, and recent studies have demonstrated that soft tissue mechanical behavior can be directly altered through crosslinking, but increased understanding of how crosslinking affects intervertebral disc mechanical behavior is needed. In vitro testing of bovine disc and motion segments was used to characterize several important aspects of disc behavior in response to crosslinking after both soaking and injection treatment.
The first study was a comparison of different crosslinkers to determine the effect on tensile properties of disc tissue. Circumferential specimens were taken from bovine annulus and then soak treated with an optimized crosslinking formulation or sham solution. A non-contacting laser micrometer was used to measure cross sectional area, after which tension testing until failure was performed to determine yield strain, yield stress, ultimate stress, peak modulus, and resilience. The crosslinkers were observed to produce different changes in the properties, with the measured properties generally increasing.
The second study used bilateral annular injections to simulate a clinically relevant delivery method. The dose response of the motion segment’s neutral zone stability metrics against injection concentration was mapped. Concentrations of 20 mM and less had no significant effects on the stability metrics. 40mM demonstrated a change in neutral zone stiffness, while at least 80mM was required to significantly affect neutral zone length. Thus, meaningful changes in joint neutral zone stability were demonstrated using clinically relevant injection and chemical formulations.
The third study used combinations of biochemical and accelerated mechanical cyclic loading to degrade gelatin and annulus fibrosus specimens with and without genipin treatment. Genipin crosslinking attenuated changes during cyclic loading to specimen geometry and compliance relative to control samples. Full recovery of genipin treated samples appeared to be hampered, at least partially from continued crosslinking during the accelerated testing.
The fourth study tested the effect of genipin crosslinking to resist interlamellar shearing of the annulus lamella. Using a recently reported test method that shears adjacent lamella, crosslinked specimens were noted to have significantly higher yield force, peak force, and resilience compared to sham treated controls, supporting the hypothesis that crosslinking would increase the load bearing ability of the interface.
33
Aouar, Leila. "Les propriétés mécaniques du réseau cellulose/xyloglucanes dans la croissance apicale du tube pollinique". Thèse, 2007. http://hdl.handle.net/1866/8143.
Testo completo
34
Ferrer, Rodrigo Sebastián, e Pablo Javier Mangieri. "Planificación de nuevos distribuidores para alimentación de proyectos inmobiliarios en la zona de Nueva Córdoba, Alta Córdoba y Alberdi en media tensión (13,2 [kV]) y baja tensión (0,4 [kV])". Bachelor's thesis, 2016. http://hdl.handle.net/11086/2452.
Testo completoAbstract (sommario):
Proyecto Integrador (IME)--FCEFN-UNC, 2016Trata el planeamiento eficiente de nuevas redes eléctricas en media tensión (13,2[kV] y baja tensión (0,4[kV]), con base en criterios de diseño para brindar una solución óptima al alimentar eléctricamente a nuevos desarrollos inmobiliarios de cierta envergadura, cumplimentando con la expansión del sistema y satisfaciendo los requerimientos de nuevas demandas, garantizando las exigencias que imponene las normativas
35
Goudarzi, Ali. "Modeling conformance control and chemical EOR processes using different reservoir simulators". Thesis, 2015. http://hdl.handle.net/2152/31338.
Testo completoAbstract (sommario):
Successful field waterflood is a crucial prerequisite for improving the performance before EOR methods, such as ASP, SP, and P flooding, are applied in the field. Excess water production is a major problem in mature waterflooded oil fields that leads to early well abandonment and unrecoverable hydrocarbon. Gel treatments at the injection and production wells to preferentially plug the thief zones are cost-effective methods to improve sweep efficiency in reservoirs and reduce excess water production during hydrocarbon recovery. There are extensive experimental studies performed by some researchers in the past to investigate the performance of gels in conformance control and decreasing water production in mature waterflooded reservoirs, but no substantial modeling work has been done to simulate these experiments and predict the results for large field cases.
We developed a novel, 3-dimensional chemical compositional and robust general reservoir simulator (UTGEL) to model gel treatment processes. The simulator has the capability to model different types of microgels, such as preformed particle gels (PPG), thermally active polymers (TAP), pH-sensitive microgels, and colloidal dispersion gels (CDG). The simulator has been validated for gel flooding using laboratory and field scale data. The simulator helps to design and optimize the flowing gel injection for conformance control processes in larger field cases.
The gel rheology, adsorption, resistance factor and residual resistance factor with salinity effect, gel viscosity, gel kinetics, and swelling ratio were implemented in UTGEL. Several simulation case studies in fractured and heterogeneous reservoirs were performed to illustrate the effect of gel on production behavior and water control. Laboratory results of homogeneous and heterogeneous sandpacks, and Berea sandstone corefloods were used to validate the PPG transport models. Simulations of different heterogeneous field cases were performed and the results showed that PPG can improve the oil recovery by 5-10% OOIP compared to waterflood.
For recovery from fractured reservoirs by waterflooding, injected water will flow easily through fractures and most part of reservoir oil will remain in matrix blocks unrecovered. Recovery from these reservoirs depends on matrix permeability, wettability, fracture intensity, temperature, pressure, and fluid properties. Chemical processes such as polymer flooding (P), surfactant/polymer (SP) flooding and alkali/surfactant/polymer (ASP) flooding are being used to enhance reservoir energy and increase the recovery. Chemical flooding has much broader range of applicability than in the past. These include high temperature reservoirs, formations with extreme salinity and hardness, naturally fractured carbonates, and sandstone reservoirs with heavy and viscous crude oils.
The recovery from fractured carbonate reservoirs is frequently considered to be dominated by spontaneous imbibition. Therefore, any chemical process which can enhance the rate of imbibition has to be studied carefully. Wettability alteration using chemicals such as surfactant and alkali has been studied by many researchers in the past years and is recognized as one of the most effective recovery methods in fractured carbonate reservoirs. Injected surfactant will alter the wettability of matrix blocks from oil-wet to water-wet and also reduce the interfacial tension to ultra-low values and consequently more oil will be recovered by spontaneous co-current or counter-current imbibition depending on the dominant recovery mechanism.
Accurate and reliable up-scaling of chemical enhanced oil recovery processes (CEOR) are among the most important issues in reservoir simulation. The important challenges in up-scaling CEOR processes are predictability of developed dimensionless numbers and also considering all the required mechanisms including wettability alteration and interfacial tension reduction. Thus, developing new dimensionless numbers with improved predictability at larger scales is of utmost importance in CEOR processes. There are some scaling groups developed in the past for either imbibition or coreflood experiments but none of them were predictive because all the physics related to chemical EOR processes (interfacial tension reduction and wettability alteration) were not included.
Furthermore, most of commercial reservoir simulators do not have the capability to model imbibition tests due to lack of some physics, such as surfactant molecular diffusion. The modeling of imbibition cell tests can aid to understand the mechanisms behind wettability alteration and consequently aid in up-scaling the process. Also, modeling coreflood experiments for fractured vuggy carbonates is challenging. Different approaches of random permeability distribution and explicit fractures were used to model the experiments which demonstrate the validity and ranges of applicability of upscaled procedures, and also indicate the importance of viscous and capillary forces in larger scales. The simulation models were then used to predict the recovery response times for larger cores.
36
Marquez, Alberto C. "Finite element analysis of welds attaching short doubler plates in steel moment resisting frames". Thesis, 2014. http://hdl.handle.net/2152/28259.
Testo completoAbstract (sommario):
A number of recent research studies have investigated the performance of panel zones in seismic-resistant steel Special Moment Resisting Frames (SMF). These recent studies investigated various options for attaching doubler plates to the column at beam-column joints in SMF for purpose of increasing the shear strength of the panel zone. This previous work was primarily focused on doubler plates that extend beyond the top and bottom of the attached beams, and considered cases both with and without continuity plates. As an extension to this previous research, this thesis explores the situation when a doubler plate is fitted between the continuity plates. The objective of this research was to evaluate various options for welding fitted doubler plates to the column and continuity plates through the use of finite element analysis, and to provide recommendations for design. The development and validation of the finite element model are described, along with the results of an extensive series of parametric studies on various panel zone configurations and attachment details for fitted doubler plates. Based on the results of these analyses, recommendations are provided for design of welds used for attaching fitted doubler plates in the panel zone of SMF systems.text
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Kanzenbach, Lars. "Experimentell-numerische Vorgehensweise zur Entwicklung von Probekörper-Setups für die Charakterisierung technischer Elastomere". 2019. https://monarch.qucosa.de/id/qucosa%3A36514.
Testo completoAbstract (sommario):
Für die Materialcharakterisierung und Parameteridentifikation von technischen Elastomeren werden homogene Probekörper benötigt. Eine besonders wichtige Beanspruchungsart ist dabei der einachsige Zug/Druck. Für Versuche dieser Art findet die Standard-Hantel Anwendung, die für kombinierte Zug-/Druckversuche geeignet ist. Allerdings lässt sich hier schon bei geringen Druckbelastungen ein inhomogener Messbereich detektieren. Ein Ziel dieser Arbeit besteht in der Entwicklung eines neuen und verbesserten Probekörpers, der für hochpräzise Zug-/Druckversuche geeignet ist. Im Gegensatz zur Standard-Hantel wird der für Messungen zugänglich gemachte homogene Messbereich deutlich verbessert. Darüber hinaus soll der Bereich der maximal erreichbaren Stauchung signifikant erhöht werden. Der Probekörper selbst weist dabei eine verhältnismäßig einfache Hantelgeometrie mit verlängertem Mittelteil auf. Durch ein spezielles Design der Halterungsgeometrie kann sowohl ein homogenes Verzerrungsfeld erreicht als auch eine hohe Knickstabilität gewährleistet werden. Die Grundidee besteht dabei darin, dass der Probekörper mit zunehmender Stauchung immer weiter mit der Halterungsgeometrie in Kontakt tritt und dadurch seine knickgefährdete Länge reduziert wird. Mit Hilfe eines speziellen Halterungsalgorithmus kann eine neue, verbesserte Halterungsgeometrie berechnet werden. Mit dem entwickelten Probekörper-Setup (bestehend aus Hantel- und Halterungsgeometrie) lassen sich dann eine Vielzahl phänomenologischer Eigenschaften von technischen Elastomeren wie Payne-
Effekt, Mullins-Effekt, Erholungs- und Relaxationsverhalten vorzugsweise bei extremen Stauchungen (bis zu 70 %) untersuchen.
Ein weiteres Ziel dieser Arbeit besteht in der Entwicklung eines Scherprobekörpers zur Realisierung präziser Schermessungen. Das Design soll dabei auf einem flächigen Probekörper (Elastomermatte) beruhen, um Alterungsuntersuchungen, Untersuchungen mit faserverstärkten Materialien und Versuche mit Vorreckungen realisieren zu können. Im Gegensatz zu herkömmlichen Scherprobekörpern soll dabei auf eine stoffschlüssige Verbindung mittels Kleben oder Anvulkanisieren aufgrund von Materialirritationen oder Schrumpf verzichtet werden. Im Rahmen dieser Arbeit wurde diesbezüglich ein spezielles Fixierdesign mit Stiften entwickelt, welches zur Ausbildung nahezu homogener Scherdeformationen führt. Damit lassen sich eine Vielzahl wichtiger Eigenschaften bei einer annähernd homogenen Scherdeformation untersuchen.Homogeneous test specimens are required for material characterization and model parameter identification. An important kind of loading is uniaxial tension/compression. For this, a standard dumbbell is available for combined tension-compression tests. But even for small compressive strains the standard dumbbell leads to an inhomogeneous stress state in the measuring zone. One aim of this work is the development of a new test specimen, which is suitable for high-precision tension/compression tests. In comparison to the standard dumbbell the homogeneity in the measuring zone is significantly improved. Furthermore, the range of maximal compression is increased substantially. The test specimen itself consists of a slender dumbbell structure. By a special design of the mounting geometry, homogeneous stress and strain fields as well as a high stability can be achieved. For an increasing compression, the test specimen comes into contact with the mounting geometry and the critical length is reduced. By means of dynamic analysis, the mounting geometry was calculated and optimized. This method is a powerful tool for developing new mounting geometries, by taking into account both the stability and the homogeneity characteristic. With the developed specimen-setup (consisting of dumbbell and mounting geometry), the phenomenological characteristics of rubber like Payne effect, Mullins effect, recovery and relaxation behavior can be investigated up to a compressive strain of 70 %. Another aim of this work is the development of a shear specimen, which enables precision shear measurements for large shear values. The design is based on a planar test specimen (rubber mat) in order to enable ageing tests, tests with fibre-reinforced materials and tests with pre-stretching. In contrast to other shear specimens, a material-locking connection by gluing or vulcanizing sould be avoided in consequence of material irritation or shrinkage. For this, a special fixing design was developed, which enables a uniform initiation of shear deformation for different rubber thicknesses. Finally, the new shear specimen enables the investigation of typical rubber properties.