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Dissertations / Theses on the topic 'Microstructural analysis'
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1
Kok, Kuan Ying. "Microstructural analysis of giant magnetoresistive multilayers." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627229.
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Bolser, Diana. "Microstructural Analysis of Calcium-Aluminum-Rich Inclusions." Thesis, The University of Arizona, 2014. http://hdl.handle.net/10150/339044.
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Refractory materials are among the building blocks of our solar system and their chemistry and structure hold clues to understanding our origins. In this thesis I present a multifaceted approach toward understanding the histories of refractory materials within calcium-aluminum rich inclusions (CAIs) in primitive meteorites. I apply high-spatial resolution techniques including electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and scanning transmission X-ray microscopy (STXM) enabled by focused ion beam scanning electron microscopy (FIB-SEM) to investigate CAI components and the Wark Lovering Rims that surround them to obtain information on microstructure and crystal chemistry in meteorites with varied pre-terrestrial histories. These inclusions possess three-dimensional grain islands, which exhibit crystallographic preferred orientations. The islands formed by high-temperature condensation in the solar nebula in a process driven by surface energy minimization, as shown by density functional theory (DFT) calculations. I also report preliminary results from laboratory experiments designed to synthesize perovskite under controlled temperature and oxygen fugacity (fO₂) conditions. The goal of this project was to develop a calibrated barometer based on changes in the oxidation state of Ti and apply the barometer to measurements of meteoritic samples in order to infer the thermodynamic conditions under which meteoritic perovskite formed in CAIs.
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Lustig, Steven K. "Microstructural analysis of finite deformation in FCC polycrystals." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15916.
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Lemmon, Timothy John. "Microstructural analysis of a liquid-crystalline aromatic copolyester." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317931.
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Minick, Jill Suzanne. "Microstructural analysis of polyethylenes and their blends and copolymers." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058204252.
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Johnson, Lindsay W. "The mechanical and microstructural analysis of the human cornea." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17065.
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Corry, Denis Albert Kenneth. "Mechanistic and microstructural analysis of ring-opening metathesis polymerisation." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266699.
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Abdelaziz, Gamal E. "Microstructural analysis of surface and interface zones in concrete." Thesis, Aston University, 1997. http://publications.aston.ac.uk/13268/.
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Several of OPC paste and concrete specimens, with different mix proportions, were cast against CPF and impermeable formwork (IF) and the profiles of pore structure, microhardness and scratch hardness of the cover zone were established. The chloride ingress and the depth of carbonation of the surface zone of concrete cast against CPF and IF were investigated. The main mechanisms controlling the ECR processes and the factors affecting such treatment were critically reviewed. Subsequently, as a means of restoring passivation of steel embedded in carbonated concrete, such HCP specimens were subjected to ECR. The influence of ECR on the chemistry of the pore solution and the microstructure of the surface and the steel/cement past interface zones were also studied. The main findings of this investigation were as follows: (a) The thickness of the microstructure gradient of cover concrete is significantly decreased with increasing period of water curing but is relatively unaffected by curing temperature, w/e ratio and the use of cement replacement materials. (b) The scratch hardness technique was shown to be potentially useful for characterising the microstructure and microhardness gradients of the surface zone. (c) A relationship between the microstructure gradient and mass transport properties of the surface zone was established. (d) The use of CPF resulted in a significant reduction in porosity of both the cement paste matrix and the aggregate/cement paste transition zone, and a marked improvement in the resistance of the surface zone to carbonation and the ingress of chloride ions. (e) The ECR treatment resulted in a marked densification of the pore structure and in changes to the pore solution chemistry and the cement phases of near-surface and steel/cement paste transition zones. This effect was more pronounced with current density, period of treatment and particularly with the use of sodium phosphate as an electrolyte.
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Inglis, Jeremy David. "P-T-t-d constraints on the early evolution of Cadomia, La Hague region, NW France." Thesis, Oxford Brookes University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251669.
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Badiei, Nafisheh. "Microstructural and rheological studies of fibrin-thrombin gels." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678597.
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Morgan, David Scott. "A microstructural and mechanical analysis of perforation of aluminum alloys." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16361.
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SOBREIRA, GUSTAVO HENRIQUE OLIVEIRA. "EVALUATION OF ELASTIC PROPERTIES OF CARBONATIC ROCKS FROM MICROSTRUCTURAL ANALYSIS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29612@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Reservatórios carbonáticos contêm entre 50 e 60 porcento de petróleo e gás do mundo. No entanto, estas rochas têm apresentado problemas operacionais consideráveis durante as etapas de perfuração e produção. Tais problemas são originados pelas dificuldades na caracterização adequada destas rochas em função da complexa distribuição espacial de suas micro e macro estrutura. Enquanto ambas as escalas possuem importância no entendimento do comportamento de carbonatos, o presente trabalho trata da análise da microestrutura. Nesse âmbito, a proposta deste trabalho integra o processamento e análises de imagens digitais, elaboração de malhas de elementos finitos e simulação numérica de forma a prever propriedades elásticas, com o objetivo de correlacionar a microestrutura e o módulo de Young. Foram utilizadas imagens digitais de amostras de afloramento (travertinos) considerados como possíveis análogas a rochas carbonáticas de reservatório. A metodologia implementada permitiu obter subamostras que incluem uma gama de microestruturas e porosidades numa única amostra para assim simular numericamente o módulo de Young. Conclui-se neste estudo que os poros maiores (vuggys) são os principais responsáveis pelo comportamento do material quando o mesmo é carregado, e também a influência da estrutura porosa nos resultados, foi possível observar que a posição dos poros afeta o módulo de elasticidade do corpo de prova.
Carbonate reservoirs contain between 50 and 60 percent of oil and gas reserves in the world. However, these rocks have presented considerable operating problems during the phases of drilling and production. Such problems are originated by the difficulties in the proper characterization of these rocks due to the complex spatial distribution of its micro and macro structure. While both scales have importance on the carbonate behavior understanding, this paper deals with the analysis of the microstructure. In this context, the aim of this work is part of the processing and digital image analysis, mesh preparation and finite element numerical simulation to predict elastic properties, in order to correlate the microstructure and the Young s modulus. Using digital images of outcrop samples (travertine) considered as possible analogous to carbonate rocks reservoir. The methodology implemented afforded sub-samples that include a range of porosities and microstructures for a single sample well numerically simulate the Young s modulus. It is concluded in this study that the larger pores (vuggys) are mainly responsible for the behavior of the material when it is loaded, and also the influence of the porous structure in the results, it was observed that the position of pores affects the modulus of elasticity of sample.
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Knutsen, Robert Douglas. "A microstructural examination of duplex ferrite -martensite corrosion resisting steels." Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/26079.
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This thesis reports a study of the microstructural evolution of chromium containing duplex ferrite-martensite steels and examines the effects of the microstructure on the mechanical properties. Emphasis has been placed on determining the microstructural factors responsible for the persistent occurrence of anisotropy in a modified 12 wt% Cr steel designated 3CR12. in addition an investigation has been carried out in order to refine the grain structure of a ferritic steel containing 16-17 wt % Cr by inducing a duplex ferrite-martensite phase structure. The microstructural evolution of 3CR12 was studied during cooling from a solution heat treatment at 1380°C and the natures of the phase transformations evident were investigated. Energy dispersive X-ray spectroscopy (EDS), in association with a scanning electron microscope (SEM), was used to determine the composition of the phases arising from the solid state δ-ferrite to austenite transformation. It is shown that the high temperature δ-ferrite phase partially decomposes to austenite via a Widmanstatten growth mechanism and consequently a banded two phase structure is produced after hot rolling. The element partitioning which arises during the solid state δ-ferrite decomposition ieads to compositional banding with an indelible nature. A model is proposed for the events leading to the generation of the banded phase structure and the formation of an elongated ferritic microstructure in 3CR12 after sub-critical annealing. The type and distribution of non-metallic inclusions occurring in 3CR12 has also been assessed. Characteristic fracture modes developed during impact testing have been related to the grain morphology and the occurrence of non-metallic inclusions. It is shown that splits form parallel to the rolling plane when Charpy specimens are subjected to impact testing and that both impact energy and mode of fracture are dependent on the directional properties of the 3CR12 microstructure. Splitting is predominantly caused by the low energy crack path provided by long, undulating grain boundaries parallel to the rolling plane, and inclusions, particularly manganese sulphides (MnS), facilitate low energy modes of fracture associated with the splitting phenomenon. MnS inclusions are also found to affect the corrosion resistance of 3CR12 and careful control of the chemistry of the steel permits these inclusions to be restricted to levels at which acceptable impact and corrosion properties are maintained. Refinement of the grain structure of ferritic steels containing 16-17 wt % Cr was carried out by modifying the ratio of ferritising elements to austenitising elements in the steel chemistry. Suitable ruckel additions have been determined which provide alloys with sufficient austenitising ability to refine the high temperature δ-ferrite phase and consequently a duplex ferrite-martensite microstructure is produced. Tempering of these alloys at 700°C results in a lamellar ferrite-martensite structure which gives rise to an attractive combination of impact and tensile properties which may provide a stainless steel with superior cost effectiveness to austenitic grades.
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Gardner, Eric Jesse. "Microstructural and crystallographic fabric analysis of stretched-pebble conglomerates in central Vermont." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12162009-020350/.
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Millan, Cristina. "Microstructural analysis of the Cape Roberts core, western Ross Sea, Antarctica /." Columbus, Ohio : Ohio State University, 2001. http://hdl.handle.net/1811/6111.
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Galbincea, Nicholas D. "Critical Analysis of Dimensionality Reduction Techniques and Statistical Microstructural Descriptors for Mesoscale Variability Quantification." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500642043518197.
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Bayliss, Roger W. "The sintering, microstructural analysis and mechanical properties of two β' MgSiAlON ceramics." Thesis, University of Warwick, 1986. http://wrap.warwick.ac.uk/2823/.
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This work describes the preparation and the determination of some properties of two magnesium SiAlON ceramics, one with a low substitution level and one with a high substitution level ' phase. Each had a specific amount of spinel as second phase which would form on sintering or after a post-sintering heat-treatment. The work was undertaken because (a) the improvement in the properties of pressureless-sintered yttrium SiAlON ceramics was not as high as anticipated and (b) by applying the knowledge gained with the widely researched yttrium system to the MgSiAlON ceramic system, the properties of the magnesium system may be further improved. Under consideration in this thesis were the sintering of these ceramics and some sintering reactions are proposed. Also discussed is the effect on the microstructure of heating the ceramic in both oxidising and inert atmospheres. Some mechanical properties were determined, including fracture toughness and hardness testing at ambient temperature, and creep testing at upto 1300^oC. It was expected that MgSiAlONs would be easier to sinter due to the lower ternary oxide eutectic temperature and from a sintering view-point the high z materials do offer an alternative system to the yttrium system by being easier to sinter, but the low z material was as difficult to sinter as the yttrium system. Whilst the MgSiAlONs that were produced in this project were generally out-performed, encouraging results were obtained for the high z material in oxidation resistance. Low z material had the highest fracture toughness and hardness - both of which increased by heat-treatment. It is proposed that alterations to this heat-treatment would improve matters and would form a useful area for future work.
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Segatori, Antonio <1981>. "Experimental analysis and FE Modeling of Aluminium alloys Microstructural Evolution in Extrusion." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4847/.
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Extrusion is a process used to form long products of constant cross section, from simple billets, with a high variety of shapes. Aluminum alloys are the materials most processed in the extrusion industry due to their deformability and the wide field of applications that range from buildings to aerospace and from design to automotive industries. The diverse applications imply different requirements that can be fulfilled by the wide range of alloys and treatments, that is from critical structural application to high quality surface and aesthetical aspect. Whether one or the other is the critical aspect, they both depend directly from microstructure.
The extrusion process is moreover marked by high deformations and complex strain gradients making difficult the control of microstructure evolution that is at present not yet fully achieved. Nevertheless the evolution of Finite Element modeling has reached a maturity and can therefore start to be used as a tool for investigation and prediction of microstructure evolution.
This thesis will analyze and model the evolution of microstructure throughout the entire extrusion process for 6XXX series aluminum alloys. Core phase of the work was the development of specific tests to investigate the microstructure evolution and validate the model implemented in a commercial FE code. Along with it two essential activities were carried out for a correct calibration of the model beyond the simple research of contour parameters, thus leading to the understanding and control of both code and process. In this direction activities were also conducted on building critical knowhow on the interpretation of microstructure and extrusion phenomena. It is believed, in fact, that the sole analysis of the microstructure evolution regardless of its relevance in the technological aspects of the process would be of little use for the industry as well as ineffective for the interpretation of the results.
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Liu, Xi. "Microstructural characterisation of pearlitic and complex phase steels using image analysis methods." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4842/.
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The measurement of properties is very important for both material design and quality control. As materials’ properties are determined by the microstructure of the materials such as grain size or the volume fraction of the present phases, microstructural characterisation is a powerful tool for property prediction. Unfortunately, microstructural characterisation has not been widely applied with all steels such as pearlitic steels or complex multi-phase steels due to their complex microstructures. These microstructures may contain features that cannot be resolved by optical microscopy, and in which important information is contained in their texture rather than simply their grey level. These microstructures were investigated in this study using image texture analysis. Fourier transform-based analysis was applied to pearlitic microstructures to extract the image orientation information. The orientation information as well as the grey value of low pass filtered image was used as predicates in a split-merge algorithm to segment the pearlitic colonies. A supervised classification method based on various statistical measures including a number of 2-point statistics (Grey Level Co-occurrence Matrix measures) was developed to distinguish the bainite (upper bainite and lower bainite), martensite and ferrite phases in steels. The influence of etching on the analysis results was also investigated.
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Şenöz, Ceylan Akkurt Sedat. "Microstructural Analysis of The Corrosion of Al2O3 And Zro2 İn Frit Melts/." [s.l.]: [s.n.], 2007. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000638.pdf.
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Марченко, Станіслав Вікторович, Станислав Викторович Марченко, Stanislav Viktorovych Marchenko, Є. А. Петренко, and І. О. Варуха. "Особливості структуроутворення наплавленого білого титанвмісного чавуну, легованого азотом." Thesis, Вид-во СумДУ, 2010. http://essuir.sumdu.edu.ua/handle/123456789/6468.
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Dong, S., Y. Wang, Ashraf F. Ashour, B. Han, and J. Ou. "Nano/micro-structures and mechanical properties of ultra-high performance concrete incorporating graphene with different lateral sizes." Elsevier, 2020. http://hdl.handle.net/10454/17889.
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YesThe performance of cement-based materials can be controlled and tailored by adjusting the characteristics of reinforced nano inclusions. Therefore, the lateral size effect of graphene on the nano/micro-structures of ultra-high performance concrete (UHPC) was explored, and then the mechanical properties were investigated to analyze the structure–property correlation of composites in this paper. The test results show that due to nucleation site effect and the formation of core–shell elements, incorporating graphene with lateral size of > 50 µm improves the polymerization degree and mean molecule chain length of C-S-H gel by 242.6% and 56.3%, respectively. Meanwhile, the porosity and average pore volume of composites is reduced by 41.4% and 43.4%. Furthermore, graphene can effectively inhibit the initiation and propagation of cracks by crack-bridging, crack-deflection, pinning and being pulled-out effect, and the wrinkling characteristic is conductive to the enhancement of pinning effect. These improvements on nano- and micro- structures result in that the compressive strength, compressive toughness and three-point bending modulus of UHPC are increased by 43.5%, 95.7% and 39.1%, respectively, when graphene with lateral size of > 50 µm and dosage of 0.5% is added. Compared to graphene with lateral size of > 50 µm, graphene with average lateral size of 10 µm has less folds and larger effective size, then reducing the distance between core–shell elements. Hence, the addition of graphene with average lateral size of 10 µm leads to 21.1% reduction for Ca(OH)2 crystal orientation index, as well as 30.0% increase for three-point bending strength. It can be, therefore, concluded that the lateral size of graphene obviously influences the nano/micro-structures of UHPC, thus leading to the significantly different reinforcing effects of graphene on mechanical behaviors of UHPC.
The full-text of this article will be released for public view at the end of the publisher embargo on 11 Jun 2021.
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Coleman, Rashadd L. "Microstructural Analysis of Ti-6Al-4V Components Made by Electron Beam Additive Manufacturing." Thesis, The University of Alabama, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10603400.
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Electron Beam Additive Manufacturing (EBAM) is a relatively new additive manufacturing (AM) technology that uses a high-energy electron beam to melt and fuse powders to build full-density parts in a layer by layer fashion. EBAM can fabricate metallic components, particularly, of complex shapes, in an efficient and cost-effective manner compared to conventional manufacturing means. EBAM is an enabling technology for rapid manufacturing (RM) of metallic components, and thus, can efficiently integrate the design and manufacturing of aerospace components. However, EBAM for aerospace-related applications remain limited because the effect of the EBAM process on part characteristics is not fully understood. In this study, various techniques including microhardness, optical microscopy (OM), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and electron backscatter diffraction (EBSD) were used to characterize Ti-6Al-4V components processed using EBAM. The results were compared to Ti-6Al-4V components processed using conventional techniques. In this study it is shown that EBAM built Ti-64 components have increased hardness, elastic modulus, and yield strength compared to wrought Ti-6Al-4V. Further, it is also shown in this study that the horizontal build EBAM Ti-6Al-4V has increased hardness, elastic modulus, and yield strength compared to vertical build EBAM due to a preferential growth of the β phase.
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Nagaraja, Srinidhi. "Microstructural Stresses and Strains Associated with Trabecular Bone Microdamage." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14093.
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Bone is a composite material consisting of hydroxyapatite crystals deposited in an oriented manner on a collagen backbone. The arrangement of the mineral and organic phases provides bone tissue with the appropriate strength, stiffness, and fracture resistance properties required to protect vital internal organs and maintain the shape of the body. A remarkable feature of bone is the ability to alter its properties and geometry in response to changes in the mechanical environment. However, in cases of metabolic bone diseases or aging, bone can no longer successfully adapt to its environment, increasing its fragility. To elucidate the mechanisms of bone microdamage, this research project developed a specimen-specific approach that integrated 3D imaging, histological damage labeling, image registration, and image-based finite element analysis to correlate microdamage events with microstructural stresses and strains under compressive loading conditions. By applying this novel method to different ages of bovine and human bone, we have shown that the local mechanical environment at microdamage initiation is altered with age. We have also shown that formation of microdamage is time-dependent and may have implications in age-related microdamage progression with cyclic and/or sustained static loading. The work presented in this dissertation is significant because it improved our understanding of trabecular bone microdamage initiation and unlocked exciting future research directions that may contribute to the development of therapies for fragility diseases such as osteoporosis.
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Neilson, Henry Jathuren. "Mechanical Behavior and Microstructural Evolution during Hot Deformation of Aluminum 2070." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case152302739582634.
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Pauskar, Praveen M. "An integrated system for analysis of metal flow and microstructural evolution in hot rolling /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487951907958535.
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Vishwanathan, Krishnan. "Process development and microstructural analysis of capacitor filter assemblies using lead free solder preforms." Diss., Online access via UMI:, 2007.
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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2007.Includes bibliographical references.
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Shah, Vatsal. "Pb-free process development and microstructural analysis of capacitor filter assemblies using solder preforms." Diss., Online access via UMI:, 2005.
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Harrison, Ryan K. S. "Investigating the Relationships Between Material Properties and Microstructural Shapes as Quantified by Moment Invariants." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1162.
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The analysis of microstructural shapes is an underutilized tool in the field of materials science. Typical observations of morphology are qualitative, rather than quantitative, which prevents the identification of relationships between shape and the mechanical properties of a material. Recent advances in the fields of computer vision and high-dimensional analysis have made computer-based shape characterization feasible on a variety of materials. In this work, the relationship between microstructural shapes, and the properties and function of the material as a whole, is explored using moment invariants as global shape descriptors. A diifferent relationship is examined in each of three material systems: how the three-dimensional shapes of cells in the cotyledons of the plant Arabidopsis Thaliana can be used to identify cell function; the two-dimensional shapes of additive manufacturing feedstock powder and the ability to distinguish between images of powders from different samples; and the two-dimensional shapes of ' precipitates and their influence on the creep resistance of single crystal nickel-base superalloys. In the case of Arabidopsis Thaliana cotyledon cells, three-dimensional Zernike and Cartesian moment invariants were used to quantify morphology, and combined with size and orientation information. These feature sets were then analyzed using unsupervised and supervised machine learning methods. Moderate success was found using unsupervised methods, indicating that natural delineations in the data correlate to cell roles to some degree. Using supervised methods, a success rate of 90% was possible, indicating that these features can be used to identify cell function. The ability of two-dimensional Cartesian moment invariants to distinguish meaningful features in particles of additive manufacturing feedstock was tested by using these features to classify images of feedstock. Ultimately, simple histogram matching methods were unsuccessful, likely because they rely on the most common particles to draw conclusions. A bag-of-words method was used, which uses high-dimensional visualization and clustering techniques to classify individual particles by common features. Histograms of particle clusters are then used to represent each image. This method was far more successful, and a correct classification rate of up to 90% was found, and comparable rates were discovered using invariants which describe the shapes only broadly. This indicates that moment invariants are an effective measure of the morphologies of these types of particles, and can be used to classify powder shapes, which control many properties which are relevant to the additive manufacturing process. In the case of the superalloys, it has been shown that the shape distribution of ' precipitates can be tracked using second order moment invariants. In addition, several loworder moment invariants are shown to correlate to creep resistance in four alloys examined, which supports the idea that the shape of precipitates plays role in determining creep resistance in these alloys.
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Bargraser, Carmen. "Fatigue lifetime approximation based on quantitative microstructural analysis for air plasma sprayed thermal barrier coatings." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4731.
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The durability of thermal barrier coatings (TBCs) affects the life of the hot section engine components on which they are applied. Fatigue is the general failure mechanism for such components and is responsible for most unexpected failures; therefore it is desirable to develop lifetime approximation models to ensure reliability and durability. In this study, we first examined the microstructural degradation of air plasma sprayed ZrO[sub2]-8wt.%Y[sub2]O[sub3] TBCs with a low-pressure plasma sprayed CoNiCrAlY bond coat on an IN 738LC superalloy substrate. The durability of TBCs were assessed through furnace thermal cyclic tests carried out in air at 1100[degrees]C with a 1-, 10-, and 50-hour dwell period, preceded by a 10-minute heat-up and followed by a 10-minute forced-air-quench. Failure mechanisms of the TBCs were thoroughly investigated through materials characterization techniques including: X-Ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive X-Ray Spectroscopy. Quantitative microstructural analyses were then carried out to document the growth of the thermally grown oxide (TGO) scale, the depletion of the Al-rich [Beta]-NiAl phase in the bond coat, and the population and growth of micro-cracks near the YSZ/bond coat interface. Trends in the TGO growth and the [Beta]-phase depletion in the bond coat followed those of diffusion-controlled processes—parabolic growth of the TGO and exponential depletion of the [Beta]-phase. Formation and propagation of cracks within the YSZ resulted in complete spallation of the YSZ topcoat from the bond-coated superalloy substrate. Evolution in these microstructural features was correlated to the lifetime of TBCs, which showed cracking within the YSZ to be the cause of failure; thus a lifetime approximation model was developed, via modification of Paris Law, based on the experimental data. The model predicted the TBC lifetime within 10% of the experimental lifetime.ID: 030646175; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.M.S.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 67-69).
M.S.M.S.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering; Accelerated BS to MS Track
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Roschkow, Slawa. "Empirical analysis of microstructural dynamics across cross-listed stocks on the London and Moscow exchanges." Thesis, City University London, 2013. http://openaccess.city.ac.uk/2438/.
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Smith, Michael Philip. "Microstructural analysis of plates with large strains as a result of central localised blast loading." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9600.
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Includes bibliographical references.The defonnation response and subsequent tearing of built in plates subjected to central impulsive loading has been investigated experimentally in the past. Theoretical predictions of the structural response have also been made and compared to these experiments. In this thesis, a new method is developed whereby the strains within the defonned plates were measured using micrographs of the grain structure of the plate. The aim of the thesis was to gain a fuller understanding of the internal defonnation of blast loaded plate so as to enable more accurate theoretical predictions of plate defonnation and tearing. The dimensions of the grains of the plate material both in the virgin state and after defonnation were measured by image analysis of scanning electron micrographs. These measurements were processed and averaged at various points within the structure. This enabled the strain distribution throughout the defonned plate to be analysed. Tensile tests were undertaken in order to calibrate this method of strain measurement. The tests were arrested during the loading, after the specimen had undergone a known amount of strain. The strain measured from the microstructure was then compared to the strain measured during the tensile tests. The method was found to give a satisfactory measurement of the strain in the tensile tests.
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Prent, Alexander Martijn. "Microchemical and Microstructural Analysis of Major and Accessory Minerals During Fluid-Rock Interactions and Deformation." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/77367.
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In order to improve our understanding of the relation between fluid-rock interactions and deformation, deep crustal rocks that show evidence of hydration reactions have been analyzed, using microchemical and microstructural analysis techniques. Monazite from the Reynolds Range, proved capable of recording hydrous melt evolution. The combination of monazite and apatite determined timing of shear zone activity in central Australia and the analyses of pyroxene showed its recrystallization was dependent on the fluid flux present.
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Zedde, Nicola. "Dynamic mechanical-thermal, microstructural and mechanical analysis of ultra-light polymer-metal composites: influence of forming." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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A really particular and innovative metal-polymer sandwich material is Hybrix. Hybrix is a product developed and manufactured by Lamera AB, Gothenburg, Sweden. This innovative hybrid material is composed by two relatively thin metal layers if compared to the core thickness. The most used metals are aluminum and stainless steel and are separated by a core of nylon fibres oriented perpendicularly to the metal plates. The core is then completed by adhesive layers applied at the PA66-metal interface that once cured maintain the nylon fibres in position. This special material is very light and formable. Moreover Hybrix, depending on the specific metal which is used, can achieve a good corrosion resistance and it can be cut and punched easily. Hybrix architecture itself provides extremely good bending stiffness, damping properties, insulation capability, etc., which again, of course, change in magnitude depending in the metal alloy which is used, its thickness and core thickness. For these reasons nowadays it shows potential for all the applications which have the above mentioned characteristic as a requirement. Finally Hybrix can be processed with tools used in regular metal sheet industry and can be handled as solid metal sheets.
In this master thesis project, pre-formed parts of Hybrix were studied and characterized. Previous work on Hybrix was focused on analyze its market potential and different adhesive to be used in the core. All the tests were carried out on flat unformed specimens. However, in order to have a complete description of this material also the effect of the forming process must be taken into account. Thus the main activities of the present master thesis are the following: Dynamic Mechanical-Thermal Analysis (DMTA) on unformed Hybrix samples of different thickness and on pre-strained Hybrix samples, pure epoxy adhesive samples analysis and finally moisture effects evaluation on Hybrix composite structure.
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Chin, Brown. "Finite element analysis of the rolling of hot steel rods and its application to microstructural prediction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37259.pdf.
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Huang, Yi. "Mechanical property, microstructural development and constitutive analysis associated with the high temperature deformation of Inconel 718." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368453.
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Yan, Miaolei. "Defect Analysis and Microstructural Effects on the Surface Exchange Properties of La0.7Sr0.3MnO3(LSM) Epitaxial Thin Films." Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/650.
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La0.7Sr0.3MnO3 (LSM) is a perovskite oxide material that possesses many interesting electromagnetic and electrochemical properties, making it desirable as magnetic tunnel junction (MTJ) and solid oxide fuel cell (SOFC) electrodes.
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Fellah, Clémentine. "Influence de la nature des interfaces carbonées au sein des composites SiC/SiC à renfort Hi-Nicalon S et Tyranno SA3 sur leur comportement mécanique." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM078.
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Les composites SiC/SiC à interphase pyrocarbone (PyC) sont des candidats prometteurs en tant que matériau de gainage du combustible et de structure des réacteurs à neutrons rapides, constituant une alternative aux alliages métalliques. Leur comportement sous irradiation neutronique et leur caractère réfractaire sont de sérieux atouts en milieu irradiant. Néanmoins, les fibres et la matrice en carbure de silicium (SiC) sont, individuellement, des céramiques fragiles. L’intégrité des structures ne peut donc être assurée que si le composite acquiert une tolérance aux déformations. Cette tolérance n’est possible que grâce à la présence d’une interphase de pyrocarbone, entre la matrice et les fibres, assurant le rôle de déviateur de fissures. La capacité des composites SiC/SiC à résister à l’endommagement est dictée par le couplage fibre/matrice (F/M). L’intensité de ce couplage peut être influencée par de nombreux paramètres, tels que la rugosité et la physicochimie de surface du renfort. Les travaux faisant l’objet de cette thèse ont mis en évidence une couche de carbone en surface des fibres par microscopie électronique en transmission à haute résolution (METHR) et via des analyses physicochimiques de surface. Les caractéristiques de cette couche de carbone varient avec le procédé de fabrication des fibres. Son impact sur le couplage F/M a été appréhendé par l’observation des mécanismes locaux d’endommagement. La décohésion fibre/matrice a été étudiée en analysant par METHR les régions interfaciales des composites SiC/SiC ayant subi un essai mécanique. La compréhension de l’origine de cette couche de surface de fibres a permis de mieux connaitre les mécanismes locaux d’interaction. Ces mécanismes dépendent de la structure du carbone de surface des fibres dont découle le mode d’adhésion entre ce carbone de surface et l’interphase de pyrocarbone. Un traitement de surface sur un type de fibres a alors été développé, suggérant une légère amélioration du comportement mécanique des composites SiC/SiC élaborés à partir de ces renforts fibreuxSiC/SiC composites including the third generation SiC fibers with pyrocarbon interphase (PyC) are promising candidates to improve the safety of nuclear reactors, especially for core materials such as cladding and to replace metallic alloys for these applications. Their intrinsic refractory properties, their neutron transparency and their microstructural stability when irradiated or exposed to high temperatures make them attractive for nuclear applications. However SiC fibers and SiC matrix are brittle ceramics. The integrity of the structures can be fulfilled only if the composite is damage tolerant and can acquire a pseudo-ductile mechanical behavior. An interphase is deposited between the fibers and the matrix to provide this damage tolerance of SiC/SiC composites.The ability of SiC/SiC composites to sustain damage is dictated by the fiber/matrix (F/M) coupling mode. The intensity of this coupling can be related to many parameters such as the roughness and the chemistry of the surface of the reinforcement. A carbon layer on the fiberssurface was highlighted by High Resolution Transmission Electronic Microscopy (HRTEM) and by physico-chemical analyses. The characteristics of this carbon layer vary with the fabrication process of the fibers. The impact of this carbon layer on the F/M coupling was investigated by the observation of the local damage mechanisms. To elucidate the local bonding modes governing the damage mechanisms at the F/M interface of these SiC/SiC composites, macroscopic mechanical tests have been coupled with observations of structural modifications occurring in the interface region after loading. Understanding the origin of this carbon layer allowed elucidating the local interaction mechanisms according to these studied materials. These mechanisms depend on the carbon structure of the SiC fibers surface which in turn governs the adhesion between this carbon and the PyC interphase. Thanks to this study, a surface treatment on fibers was developed to optimize the mechanical behavior of SiC/SiC composites, whatever the fibrous reinforcement chosen
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Severs, John. "Microstructural characterisation of novel nitride nanostructures using electron microscopy." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6229b51e-70e7-4431-985e-6bcb63bd99d1.
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Novel semiconductor nanostructures possess a range of notable properties that have the potential to be harnessed in the next generation of optical devices. Electron microscopy is uniquely suited to characterising the complex microstructure, the results of which may be related to the growth conditions and optical properties. This thesis investigates three such novel materials: (1) GaN/InGaN core/shell nanowires, (2) n-GaN/InGaN/p-GaN core/multi-shell microrods and (3) Zn3N2 nanoparticles, all of which were grown at Sharp Laboratories of Europe. GaN nanowires were grown by a Ni-catalysed VLS process and were characterised by various techniques before and after InGaN shells were deposited by MOCVD. The majority of the core wires were found to have the expected wurtzite structure and completely defect free – reflected in the strong strain-free photoluminescence peak –with a- and m- axis orientations identified with shadow imaging. A small component, <5%, were found to have the cubic zinc-blende phase and a high density of planar faults running the length of the wires. The deposited shells were highly polycrystalline, partially attributed to a layer of silicon at the core shell interface identified through FIB lift-out of cross section samples, and accordingly the PL was very broad likely due to recombination at defects and grain boundaries. A high throughput method of identifying the core size indirectly via the catalyst particle EDX signal is described which may be used to link the shell microstructure to core size in further studies. An n-GaN/InGaN/p-GaN shell structure was deposited by MOCVD on the side walls of microrods etched from c-axis GaN film on sapphire, which offers the possibility of achieving non-polar junctions without the issues due to non-uniformity found in nanowires. Threading dislocations within the core related to the initial growth on sapphire were shown to be confined to this region, therefore avoiding any harmful effect on the junction microstructure. The shell defect density showed a surprising relationship to core size with the smaller diameter rods having a high density of unusual 'flag' defects in the junction region whereas the larger diameter sample shells appeared largely defect free, suggesting the geometry of the etched core has an impact on the strain in the shell layers. The structure of unusual 'flag' defects in the m-plane junctions was characterised via diffraction contrast TEM, weak beam and atomic resolution ADF STEM and were shown to consist of a basal plane stacking faults meeting a perfect or partial dislocation loop on a pyramidal plane, the latter likely gliding in to resolve residual strain due to the fault formed during growth. Zn3N2 has the required bandgap energy to be utilised as a phosphor with the additional advantage over conventional materials of its constituent elements not being toxic or scarce. The first successful synthesis of Zn3N2 nanoparticles appropriate to this application was confirmed via SAD, EDX and HRTEM, with software developed to fit experimental polycrystalline diffraction patterns to simulated components suggesting a maximum Zn3N2 composition of ~30%. There was an apparent decrease in crystallinity with decreasing particle size evidenced in radial distribution function studies with the smallest particles appearing completely amorphous in 80kV HRTEM images. A rapid change in the particles under the electron beam was observed, characterised by growth of large grains of Zn3N2 and ZnO which increased with increasing acceleration voltage suggesting knock-on effects driving the change. PL data was consistent with the bandgap of Zn3N2 blue shifted from 1.1eV to around 1.8eV, confirming the potential of the material for application as a phosphor.
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Deshmukh, Pushkarraj Vasant. "STUDY OF SUPERPLASTIC FORMING PROCESS USING FINITE ELEMENT ANALYSIS." UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_theses/367.
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Superplastic forming (SPF) is a near net-shape forming process which offers many advantages over conventional forming operations including low forming pressure due to low flow stress, low die cost, greater design flexibility, and the ability to shape hard metals and form complex shapes. However, low production rate due to slow forming process and limited predictive capabilities due to lack of accurate constitutive models for superplastic deformation, are the main obstacles to the widespread use of SPF. Recent advancements in finite element tools have helped in the analysis of complex superplastic forming operations. These tools can be utilized successfully in order to develop optimized superplastic forming techniques. In this work, an optimum variable strain rate scheme developed using a combined micromacro stability criterion is integrated with ABAQUS for the optimization of superplastic forming process. Finite element simulations of superplastic forming of Ti-6Al-4V sheet into a hemisphere and a box are carried out using two different forming approaches. The first approach is based on a constant strain rate scheme. The second one is based on the optimum variable strain rate scheme. It is shown that the forming time can be significantly reduced without compromising the uniformity of thickness distribution when using the proposed optimum approach. Further analysis is carried out to study the effects of strain rate, microstructural evolution and friction on the formed product. Finally the constitutive equations and stability criterion mentioned above are used to analyze the forming of dental implant superstructure, a modern industrial application of superplastic forming.
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Muwanguzi, Abraham Judah Bumalirivu, Andrey Karasev, Byaruhanga K. Joseph, and Jönsson G. Pär. "Characterization of chemical composition and microstructure of natural iron ore from Muko deposits." KTH, Tillämpad processmetallurgi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-123054.
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The study aimed at investigating the chemical composition and microstructure of raw iron ore from the deposits in Muko area (south-western Uganda). The quality of this iron ore was evaluated to establish its suitability to serve as a raw material for iron production. Samples were taken from the six hills of Muko ore deposits and tests carried out to establish their composition and properties. X-ray diffraction and scanning electron microscopy were employed in the investigation and chemical analysis performed to determine the compounds constituting the ore. The quality of this ore was compared to generalized world market standards and ores from other nations. It was found that Muko ore is a rich hematite grade with Fe content above 65%. It has little gangue (<6% SiO2 and 3-4% Al2O3) and low contents of the deleterious elements (P ~ 0.02% and S < 0.006%), which correspond to acceptable levels for commercial iron ores.QC 20130531
Sustainable Technology Development in the Lake Victoria Region
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Yang, Shichen. "Development of digital image analysis and stereological techniques to incorporate microstructural information in finite element based simulations." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19137.
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Castles, Megan Erin. "Determining the Geometry and Former Extent of the North Mountain Thrust from Fluid Inclusion and Microstructural Analysis." Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1269223700.
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Buskirk, Stephanie R. "Testing of biomimetic plates with a hole and a microstructural analysis of the bovine metacarpus nutrient foramen." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001119.
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Livingston, Jason James. "The Microstructural Evolution and Constitutive Analysis For A Phisical Simulation of Friction Stir Processing of Ti-6Al-4V." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306419621.
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Love, Ryan. "A microstructural analysis of the effects of news on order flows and on price discovery in foreign exchange markets." Thesis, London School of Economics and Political Science (University of London), 2005. http://etheses.lse.ac.uk/1788/.
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This thesis brings together a number of studies using high frequency foreign exchange (FX) data. The first part examines the effects of scheduled, publicly released macroeconomic news, while the final chapter considers another, related, aspect of FX microstructure. Chapter 1 provides an introduction to the thesis and reviews the literature in high frequency empirical FX research. In Chapter 2, I use up to ten months of FX transactions and quote data to analyse foreign exchange activity around times of scheduled news releases. The effects of news on exchange rate levels are examined, as well as the effects on spreads, trading volume and volatihty. Chapter 3 extends this analysis, asking how public information enters prices. Under rational expectations and efficient markets hypotheses, the news contained in public information announcements should be impounded directly, with there being no role for trades in this process of information assimilation. However, the results suggest that up to two thirds of the price relevant information enters via trading (order flow in particular). Chapter 4 provides an explanation why order flow is so important around public news releases and also examines the effects of news on market depths. In Chapter 5 I examine how much information is carried in trades by looking at the price impact of order flow when feedback trading is allowed. The model that is often used in the literature is proved to be misspecified when temporally aggregated data are employed and Chapter 5 introduces a method to estimate the otherwise unidentified model. Using impulse response functions, I show that trades actually carry more information than previous estimates suggest.
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知紀, 山口, and Tomonori Yamaguchi. "Microstructural analysis of three-dimensional canal network in the rabbit lumbar vertebral endplate using high-resolution micro-computed tomography." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12908294/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12908294/?lang=0.
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椎間板変性を引き起こす要因として、骨性終板内の栄養管狭小および軟骨終板の石灰化による椎間板への栄養供給の低下が推察されているが、椎体終板内栄養管の3次元微細構造は未だ明確にされていない。本論文は高解像度マイクロCTを用いて家兎腰椎骨性終板内栄養管の3次元微細構造を明らかにする事を目的とし、各栄養管の長さ,直径,配向及び表面からの深さを定量的に解析することでその多層構造を定量的に評価することができた。Insufficient nutrient supply through vertebral canal structures to the intervertebral disc (IVD) has been considered as an important contributor for disc degeneration. In spite of this, three-dimensional (3D) topology inside the vertebral endplate remains poorly understood. This study aims to characterize the 3D canal structure in the rabbit lumbar vertebral endplate using micro computed tomography (µCT), and revealed a distinct depth-dependent structure of the canal in the rabbit vertebral endplate characterized by length, diameter and orientation of the individual canals.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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Gilbert, John Bennett. "Crustal Deformation During Arc-Flare Up Magmatism: Field And Microstructural Analysis Of A Mid-Crustal, Melt Enhanced Shear Zone." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/699.
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This study combines structural field data with microstructural observations in an analysis of a mid-crustal shear zone related to the emplacement of the Misty pluton during a high-flux magmatic event in Northern Fiordland, New Zealand. These high-flux magmatic events transport massive amounts of heat and material as they develop along accretionary continental margins, and represent a primary source of continental crust. Fiordland, New Zealand possesses, perhaps, the most extensive middle and lower crustal exposure of these systems on earth. Therefore, this study area provides a significant opportunity to understand processes of continental crust formation in the mid-crust and how these events relate to the broader construction of continents.
Herein, I document the four-stage geologic history of the Cozette Burn field area. Pre-existing structures along the Gondwana accretionary margin hosted a regional flare-up magmatic event that produced the Misty pluton and several other large plutons of the West Fiordland Orthogneiss (WFO). This study primarily focuses on the mid-crustal emplacement of the Misty pluton during oblique convergence along the accretionary margin, forming the upper-amphibolite facies Misty Shear Zone (MSZ). The exposures of the MSZ within the Cozette Burn preserve rare structural relationships between host rock and the intrusive Misty pluton. Together, these structures developed during end-stage contractional tectonics that constructed a long-lived (~270+ Ma) composite batholith.
Heterogeneous ductile shearing defines the MSZ, with microstructural evidence indicating an interplay of high-temperature crystal plastic deformation along with partial melting of host rock and melt channeling. This resulted in focused, melt-assisted shearing under regional transpressive deformation. These accommodative processes provided an efficient mechanism for moving heat, fluids and magma sourced from the lower crust/mantle boundary into the mid-crust during 15-25 km of crustal thickening related to arc flare-up magmatism.
This flare up magmatism and MSZ formation occurred during the final stages of crustal thickening along Gondwana continental margin. High-strain, mylonitic- ultramylonitic shear zones developed in a later phase of deformation, cutting MSZ fabrics near contacts between the Misty pluton and host rock. These more localized shear zones can be attributed to either accommodation of localized melt-pressure buildup or the shift to extensional tectonics. Brittle faulting cut these structures with oblique-thrust in the Tertiary. These mid-crustal structures carry economic relevance: thickened-crust events along accretionary continental margins produce deep-crustal sourced, metal-bearing magmas that are transferred into mid-crust prior to their hydrothermal emplacement as ore deposits in the upper crust. The lasting influence of these processes warrants consideration when assessing continental crust architecture at all scales.
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Apreutesei, Mihai. "Temperature impact on thermal evolution of advanced PVD ceramic and metallic glass thin films : Physico-chemical and microstructural analysis." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0009/document.
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Ces dernières années, les exigences de l'industrie dans le développement de nouveaux matériaux fonctionnels en mesure de résister aux conditions difficiles pendant l'opération d'usinage sont en constante augmentation. Les chercheurs doivent donc trouver de nouvelles solutions pour répondre aux besoins industriels de plus en plus sévères. L’utilisation de revêtement protecteur à la surface de l’outil de coupe est une solution très efficace. Des nouveaux matériaux architecturés sont étudiés pour leurs propriétés mécaniques, physiques et chimiques uniques assurant une résistance aux dégradations de surface dues à la corrosion, l'usure, le frottement; en particulier lorsque ces outils sont utilisés dans des environnements hostiles. Dans le cadre de cette thèse de doctorat, l'influence de la température sur la stabilité structurale de deux types de films minces déposés par PVD a été étudiée. Des films céramiques et de verre métallique ont été envisagés. Afin de préparer et optimiser ces films, le projet s’est axé sur l'étude de l'influence des conditions de dépôt sur les caractéristiques de croissance du film: composition chimique, structure, morphologie, puis sur les changements ultérieurs des principales propriétés des films minces, à savoir la résistance à l’oxydation et à la cristallisation lors de leur utilisation à hautes températures. Une démarche multi-échelle a été développée pour caractériser au mieux les couches. La première partie du travail est liée aux revêtements céramiques à base de CrN pour donner de nouvelles fonctionnalités et améliorer la surface des outils de coupe dans le but essentiel d'accroître leur durée de vie. La seconde partie du manuscrit est dédiée aux films minces de verres métalliques de Zr-Cu préparés par un procédé de co-pulvérisation magnétron PVD. Le but de cette partie consiste en l’étude de la relation entre la structure amorphe de ces films et leurs propriétés mécaniques. La conservation du caractère amorphe de ces films en température présente également un caractère essentiel. Les verres métalliques ont récemment attiré un fort intérêt car ils présentent des propriétés mécaniques intéressantes à température ambiante. Ils présentent, de ce fait, un grand potentiel pour des applications d'ingénierie en raison de leurs caractéristiques mécaniques et physico-chimiques uniques (haute limite élastique, résistance à la corrosion ...). Pour relier les propriétés mécaniques des couches à l’évolution de leurs microstructures, une partie importante de ce travail a porté sur l’observation de l’évolution de la couche au cours du chauffage au moyen de techniques de caractérisation in situ. Les films minces proposés au cours de ce travail peuvent être envisagées pour un large gamme d’application dans l’ingénierie de surface pour protéger les surfaces et améliorer la durée de vie des matériauxIn the recent years the industrial requirements to develop new functional materials able to overcome the severe conditions during machining operation are continuously increasing. Researchers then must find novel solutions to respond to their severe industrial requirements. To coat the tool surface with advanced coatings is the most efficient solution. New nanostructured materials may nowadays exhibit unique mechanical, physical and chemical properties ensuring notable degradation resistance where the surface protection of materials against corrosion, wear, friction or oxidation is a key issue, particularly when operating in hostile environments. Within the scope of this Ph.D. thesis the influence of the temperature on the structural stability of two different PVD ceramic and metallic glass thin films is proposed. The main goal consists in the development of two distinct classes of thin films, with a wide range of properties. In order to prepare these films, the project will be focused on the study on the influence of PVD deposition conditions in the particular film’s growth characteristics: chemical composition, structure, morphology and the subsequent changes in the main properties of the thin films, namely oxidation and crystallization resistance, especially. For that purpose we adopted the multiscale approach. The first part is related to the ceramic CrN-based coatings to give new functionalities and improve the tools’ surface with the primary aim to increase their lifetime. Secondly, new protective materials able to better protect the exposed surfaces against high temperature oxidation have been proposed, namely CrAlN and CrAlYN coatings as will be evidenced in this manuscript. The second part of the manuscript is dedicated to the innovative Zr-Cu thin films metallic glasses prepared by a PVD magnetron co-sputtering method with the objective to investigate the amorphization ability and their structural properties. Their excellent properties at room temperature have recently attracted attention as a new class of materials with great potential for engineering applications due to unique mechanical and physico-chemical characteristics (high elastic strain limit, corrosion resistance…). Finally, an important approach during the course of this thesis was the real time observation of the structure and surface modifications during heating by means of in situ methods. The thin films proposed during the course of the work could be straightforward used as surface engineering solutions to protect and extend the lifetime of the materials and components
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Caccuri, Vincenzo. "Etude des propriétés mécaniques de technologies de report de puce pour électronique de puissance : influence du vieillissement." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2014. http://www.theses.fr/2014ESMA0002/document.
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Les contraintes environnementales imposent de trouver des solutions pour limiter les émissions gazeuses (gaz à effet de serre) ainsi que d’éliminer les matériaux nocifs dans les produits de consommation. L’étude de solutions alternatives devient donc un point clé au développement des produits futurs. Dans ce contexte, les véhicules électriques et hybrides sont en forte progression sur le marché mais leur développement commercial reste fortement lié à leur fiabilité, plus particulièrement à celle des organes contrôlés par l’électronique de puissance. Notre étude s’inscrit dans ce cadre et se focalise sur la pâte d’argent micrométrique, matériau candidat au remplacement des solutions à base de plomb pour le report des puces. Si la pâte d’argent est assez bien caractérisée pour ses propriétés électriques, peu de données sont reportées dans littérature quant à ses propriétés mécaniques, pourtant indispensables pour appréhender la durée de vie des assemblages complets. Dans la thèse, une méthode originale d’élaboration des échantillons a été développée. Basée sur les recommandations d’utilisation donnée par le fournisseur, elle a été adaptée afin de d’obtenir des échantillons massifs dont la microstructure brute et après vieillissement en température est identique à celle des brasures réelles. Après élaboration, le taux porosité, compris entre 15 % et 20 %, n’évolue pas au cours de vieillissements représentatifs des conditions d’utilisation réelles. Seule la morphologie des pores évolue, pour laquelle un grossissement, respectant les cinétiques du mûrissement d’Ostwald, et une évolution de la distribution spatiale est observée. Les propriétés mécaniques sont une fonction de la densité à l’état brut. Après vieillissement des échantillons massifs, si les propriétés élastiques ne varient pas (à densité constante), la dispersion des propriétés plastiques sont reliées à la modification de la distribution spatiale des pores. L’évolution des propriétés élastiques sur les échantillons représentatifs des brasures est attribuée aux mécanismes de relaxation des contraintes d’élaboration. Une fois celles-ci relaxées, les propriétés sont identiques pour les deux états (massif et couche mince) et sont donc intrinsèques au matériauThe requirement for reducing the use of harmful materials in convenience goods hasprompted investigation into alternative solutions. Along with the need to drastically limit theemission of greenhouse gases, the increase of electric or hybrid vehicles in the market reliesmostly on their dependability with a specific focus on reliability of the embedded powerelectronics. The study of alternative materials to lead (Pb) or Pb-based alloys for die bondingis a critical step towards realising an environmentally friendly solution. Micrometric silverpaste was chosen as a candidate because of its excellent electrical properties. However, fewdata are available in the literature concerning its mechanical properties, mandatory to modelthe entire electronic system for service life assessment. The processing route, based on thesintering of micrometric powder, provides a material with significant porosity that is knownto alter the mechanical properties when compared to the dense material. In this thesis, anoriginal processing route was developed in order to obtain bulk samples with the samemicrostructure of real solder joints either before or after ageing. The mechanical properties vsdensity was established prior to or after aging. After aging, the elastic properties do not varywhile the dispersion observed for the plastic properties is connected with the microstructureevolution. The evolution of the elastic properties on the representative samples of solder jointsafter aging is attributed to the mechanisms of stress relaxation. Once these relaxed, theproperties are identical for both states (bulk and thin layer) and are thus intrinsic in thematerial