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1
Dopler, Thomas. "Low pressure infiltration process modeling". Châtenay-Malabry, Ecole centrale de Paris, 1999. http://www.theses.fr/1999ECAP0673.
Testo completoAbstract (sommario):
Les composites à matrice métallique, une matrice métalliquerenforcée par des fibres ou particlues céramiques, constituent un solution élegante pour obtenir des materiaux à propriétés mécaniques, de résistance à l'usure et à la fatigue exceptionnelles. Leurs applications sonts pour le moment limitées, moins à cause de leur coût, mais plutôt à cause des problème liés à la reproductibilité et à la dispertionde leurs propriétés. Le travail présent contribue au développement d'un code de simulation capable de prédire la cinétique d'infiltration pendant l'infiltration sous pression. Pour la première fois l'écoulement non saturé et le transfert de chaleur incluant la solidification sont traités d'une façon simultanée.
2
Wang, Xuelei. "Level set model of microstructure evolution in the chemical vapor infiltration process". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/29845.
Testo completo
3
Wannasin, Jessada 1977. "Centrifugal infiltration of particulate metal matrix composites : process development and fundamental studies/". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32267.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (p. 118-125).
A high-pressure liquid infiltration process utilizing centrifugal force was designed and laboratory equipment developed. In this process, a mold containing reinforcing materials was located at the end of an elongated runner, which was filled with a molten metal. Rotation of the runner created centrifugal force driving infiltration. To obtain high pressures, the metal head was controlled to be long and constant throughout the process. Threshold pressures required for infiltration of several packed ceramic powders were determined using the laboratory equipment built. Achievable pressures were up to 150 atm for Sn-15 wt% Pb. The pressures allowed SiC, TiC, and A1203 powders ranging in sizes from 25 [mu]m to 300 [mu]m, packed to a high volume fraction, to be infiltrated by Sn-15 wt% Pb. Threshold pressure results obtained agree well with experimental results previously reported, and with calculated values. Observations of the resulting composite structures showed layering and porosity defects. Layering defects, but no porosity defects, were observed in the composite samples containing coarse powders. In contrast, the composites containing fine powders possess porosity defects, but not layering defects. The layering defect was attributed to the depacking mechanism of the powders during the cold pressing process. The porosity defect was attributed to insufficient applied pressures. A new packing process was proposed to avoid layering in coarse powders. Macrosegregation and microsegregation were limited in all samples. The interparticle spacings of these composites were smaller than the dendrite arm spacing would have been at equivalent cooling rates; thus, dendrite formation and microsegregation were effectively suppressed.
(cont.) Commercial viability of the process was assessed. Results show that the centrifugal infiltration process has several attributes, including a higher production rate and larger part size when compared with gas pressure infiltration and a wider variety of part geometry, part sizes, and materials systems capable of being produced when compared with squeeze casting. A feasibility study shows that an industrial-scale centrifuge would be able to fabricate aluminum metal matrix composites (MMCs) containing both coarse and fine reinforcements at a high volume fraction. The process should also be scalable to higher melting point MMCs.
by Jessada Wannasin.
Ph.D.
4
Vaidyaraman, Sundararaman. "Carbon/carbon composites by forced flow-thermal gradient chemical vapor infiltration (FCVI) process". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10028.
Testo completo
5
Hammond, Vincent H. "Verification of a two-dimensional infiltration model for the resin transfer molding process". Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/41537.
Testo completoAbstract (sommario):
A two-dimensional fmite element model for the infiltration of a dry textile preform
by an injected resin has been verified. The model, which is based on the finite
element/control volume technique, determines the total infiltration time and the
pressure increase at the mold inlet associated with the RTM process. Important input
data for the model are the compaction and permeability behavior of the preform
along with the kinetic and rheological behavior of the resin.
The compaction behavior for several textile preforms was determined by experimental methods. A power law regression model was used to relate fiber volume fraction to the applied compaction pressure. Results showed a large increase in fiber volume fraction with the initial application of pressure. However, as the maximum fiber volume fraction was approached, the amount of compaction pressure required to decrease the porosity of the preform rapidly increased.
Similarly, a power law regression model was used to relate permeability to the fiber volume fraction of the preform. Two methods were used to measure the permeability of the textile preform. The first, known as the steady state method, measures the permeability of a saturated preform under constant flow rate conditions. The second, denoted the advancing front method, determines the permeability of a dry preform to an infiltrating fluid. Water, corn oil, and an epoxy resin, Epon 815, were used to determine the effect of fluid type and viscosity on the steady state permeability behavior of the preform. Permeability values measured with the different fluids showed that fluid viscosity had no influence on the permeability behavior of 162 E-glass and TTI IM7/8HS preforms.
Permeabilities measured from steady state and advancing front experiments for the warp direction of 162 E-glass fabric were similar. This behavior was noticed for tests conducted with corn oil and Epon 815. Comparable behavior was observed for the warp direction of the TTl 1M7/8HS preform and corn oil.
Fluid/fiber interaction was measured through the use of the single fiber pull-out test. The surface tension of both the corn oil and Epon 815 was determined. The contact angle between these two fluids and glass and carbon fibers was also measured. These tests indicated that the glass fiber had a lower contact angle than the carbon fiber and therefore is wet out better than the carbon fiber by both fluids. This result is attributed to the sizing commonly used on the carbon fibers.
Mold filling and flow visualization experiments were performed to verify the
analytical computer model. Frequency dependent electromagnetic sensors were used
to monitor the resin flow front as a function of time. For the flow visualization tests,
a video camera and high resolution tape recorder were used to record the
experimental flow fronts. Comparisons between experimental and model predicted
flow fronts agreed well for all tests. For the mold filling tests conducted at constant
flow rate injection, the model was able to accurately predict the pressure increase at
the mold inlet during the infiltration process. A kinetics model developed to predict
the degree of cure as a function of time for the injected resin accurately calculated
the increase in the degree of cure during the subsequent cure cycle.
Master of Science
6
Weideman, Mark H. "An infiltration/cure model for manufacture of fabric composites by the resin infusion process". Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03032009-040744/.
Testo completo
7
Renier, Mark C. "Equipment and process development for fabrication of rhenium-based composites by chemical vapor infiltration". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/18915.
Testo completo
8
Barradas, Martinez Juan Alfredo 1974. "Process-based cost modeling of tool-steels parts by transient liquid-phase infiltration of powder-metal preforms". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28869.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (leaves 74-75).
(cont.) cost between these two processes was related mainly to their powder scrap rates, 15 % for the Pressing-TLI and 80% for the 3DP-TLI. The high scrap rate value of the 3DP process originates from the fact that powder is sieved before printing, eliminating the coarse and very fine particles. A possible option to decrease this value is to recycle or sell the extra powder, which will reduce the fabrication cost significantly. The model also shows that the main cost for both processes is the powder cost. TLI technical parameters such as heating and cooling rates were included in the model in order to predict the cost behavior when those are manipulated. Because the powder cost dominates the total fabrication cost, variations in the heating and cooling rates do not significantly affect the cost.
Tool steels are iron-based alloys that are melted and processed to develop characteristics useful in the working and shaping of other metals. Tools for such processes must withstand high loads without breaking and without undergoing excessive wear or deformation. Fabrication of direct tool steel parts with complex geometry is possible using Transient Liquid-Phase Infiltration (TLI) in conjunction with Three-Dimensional Printing (3DP). Tool steel parts can also be manufactured using TLI in combination with Cold Powder Methods such as Uniaxial Pressing. Both approaches produce a final part of homogenous composition without significant dimensional change, offering advantages over-traditional infiltration and full-density sintering [1]. Now that the expertise in the TLI has been developed in the MIT laboratories, an economic evaluation represents a complementary action for introducing TLI in the commercial market of Rapid Prototyping and Powder Metallurgy. A process-based cost model was developed to describe and measure the performance of the 3DP-TLI and Pressing-TLI combined processes. Operating conditions such as cycle time, material cost, labor cost, production volume and financial parameters were introduced into the model in order to calculate a total fabrication cost per part. Different charts showing cost behaviors and their relations with production volume, batch size, effectiveness in the powder utilization, and weight of the part are presented. The results show that the optimum point in the cost-production volume curve was located at 13,000 parts per year with a fabrication cost of $19.90 per part, for the Pressing-TLI case, and $61.73 per part for the 3DP-TLI alternative (based on a one-half pound D2 tool steel part). The difference in cost
by Juan Alfredo Barradas Martinez.
M.Eng.
9
馬, 賢鎬, Hyun-Ho MA, 法美 水谷, Norimi MIZUTANI, 周. 江口 e Shu EGUCHI. "礫浜斜面上の流速場と漂砂移動機構に関する研究". 土木学会, 2005. http://hdl.handle.net/2237/8607.
Testo completo
10
Kütemeyer, Marius [Verfasser], e D. [Akademischer Betreuer] Koch. "Development of Ultra High Temperature Matrix Composites using a Reactive Melt Infiltration Process / Marius Kütemeyer ; Betreuer: D. Koch". Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1230475699/34.
Testo completo
11
Tsai, Ching Yi. "Modeling and analysis of the forced-flow thermal gradient chemical vapor infiltration process for fabrication of the ceramic matrix composites". Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-165804/.
Testo completo
12
Higashino, Fumiko. "Infiltration process of brine in the deep crust constrained from multi-scale major and trace element zonings in high-grade metamorphic rocks". 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215324.
Testo completo
13
Alam, Muhammad Faisal. "Squeeze Casting as Alternative Fabrication Process for Carbon Fiber Reinforced Aluminium Matrix Composites". Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24361.
Testo completoAbstract (sommario):
Aluminium matrix composites are among the most promising candidate materials for light weight and high strength applications such as transportation and armour. In a previous study 6061 aluminum matrix composites reinforced with plain weave carbon fiber preform (AS4 Hexcel) were successfully fabricated by squeeze casting using the laminate fabrication technique. This research aims at optimizing the fabrication process in order to achieve improved strength and mechanical properties. It focuses on the liquid infiltration squeeze casting method. Good mechanical bonding between fiber and aluminium is achieved thanks to improved infiltration and impregnation of the fabric by liquid aluminium. Oxidation products at fiber/aluminium interface and porosity are reduced. As a result, composites are produced with overall improved mechanical properties. The flexural strength is increased by up to 19.9% and 15.4% compared to the laminate approach and the reference 6061 aluminium alloy squeeze cast under identical conditions, respectively. Similarly, overall hardness is improved. However, the impact strength is reduced by 7.76% and 25.78% when compared to casts fabricated by the laminate method and the reference aluminium alloy, respectively. The thesis constitutes a good basis for further research on fiber and particle reinforced aluminium matrix composites with the goal of further improving fracture toughness, particularly for gradient materials used in armour applications.
14
Palma, Janaina Barrios. "Avaliação integrada em diferentes escalas dos atributos que controlam a dinâmica das águas: aplicação para análise de risco de contaminação das águas subsuperficiais na região entre São Carlos e Ribeirão Preto". Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-04102017-144907/.
Testo completoAbstract (sommario):
O trabalho avalia a importância dos atributos que afetam a dinâmica da água subsuperficial, em 4 níveis de escala, para a região entre São Carlos e Ribeirão Preto, nordeste do Estado de São Paulo. A área é constituída, principalmente, por arenitos da formação Botucatu e basaltos da formação Serra Geral, recobertos por materiais inconsolidados, com espessura variando de 1 a 20 m. O estudo na escala 1:100.000 considerou 27 atributos, incluindo características dos materiais geológicos, geomorfologia, precipitações e fontes de contaminação. A técnica AHP (Analytic Hierarchy Process) foi utilizada para determinar o potencial relativo em termos de contaminação das águas subsuperficiais. Os resultados indicaram que o risco atual de contaminação das águas subsuperficiais é relativamente baixo, devendo ser analisado com maior detalhe para algumas bacias consideradas de risco mais acentuado. Foram realizados levantamentos em escala 1:10.000 e 1:20.000 para as bacias hidrográficas do córrego do Vaçununga (cidade de Luis Antônio) e Ribeirão do Tamanduá (próximo às cidades de Cravinhos e Serrana), respectivamente. Estas bacias foram selecionadas a partir do estudo em escala 1:100.000 devido as suas características ambientais. Foram selecionados 12 cenários de chuvas para avaliar a relação entre infiltração e escoamento superficial utilizando os modelos de infiltração de Morel - Seytoux & Khanji (1976) e Chu (1978). Os valores de descarga nos exutório e análise de recessão nestas bacias foram medidos por 2 anos. A bacia hidrográfica do córrego do esgoto (próximo a Ribeirão Preto) foi selecionada para a modelagem numérica (escala 1:1.000) por apresentar o maior índice potencial ao evento de contaminação das águas subsuperficiais na escala 1:100.000. A modelagem auxiliou na definição da direção do fluxo e indicou tendências de migração dos contaminantes oriundos do lixão instalado nesta bacia (modelagem de fluxo e de transporte).This work presents the results obtained from integrated assessment of the attributes related to groundwater dynamic in 4 scales in the São Carlos and Ribeirão Preto region, northeast of State of São Paulo, Brazil. This area is constituted of sandstones of the Botucatu formation and basalt of the Serra Geral formation. Unconsolidated materials cover these rocks with thickness varying from 1 to 20 m. For 1:100.000 scale were considered 27 attributes of the geological materials, geomorphology, rainfall and pollutant sources. The AHP method (Analytic Hierarchy Process) was used to determine the relative degree in terms of groundwater contamination potential. The results show that the risk level for groundwater contamination is predominately low, and few basins are classified with high risk level. Studies were developed in 1:20.000 and 1:10.000 scales for córrego do Vaçununga (city of Luis Antônio) and ribeirão do Tamanduá (near to cities of Cravinhos e Serrana) basins, respectively. These basins were selected from the study in 1:100.000 scale due to environmental characteristics. It were considered 12 rainfall scenarios to evaluate the infiltration and overland flow rates using the Morel - Seytoux & Khanji (1976) and Chu (1978) model\'s, and recession and discharge rates were measured for 2 years. The córrego do esgoto basin (next to city of Ribeirão Preto) was selected for numerical modelling at 1:1.000 scale to simulate the groundwater flow and contaminantplumes, because it presented highest risk level in the 1:100.000 study.
15
Saintonge, Arnaud. "Élaboration d’un composite oxyde/oxyde à matrice d'aluminosilicate de baryum et fibres d'alumine". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0243.
Testo completoAbstract (sommario):
Dans l’industrie de l’aéronautique et de la défense, les applications thermostructurales nécessitent des matériaux toujours plus performants, alliant résistance mécanique, réfractarité et légèreté. Pour répondre à ces exigences, les matériaux composites à matrice céramique tout oxyde (OCMC) sont prometteurs. Parmi les matrices de ces OCMC, l'aluminosilicate de baryum (BAS) se distingue par ses propriétés physiques intéressantes, notamment en tant que matériau pour radômes. Cependant, pour rendre ce matériau fonctionnel à haute température, proche de sa température de fusion (1750°C), il est essentiel de le renforcer avec un matériau thermochimiquement stable et doté d'une architecture adaptée. Plusieurs thèses antérieures ont permis de maîtriser la phase hexagonale du BAS. La nature chimique du renfort présentant la stabilité souhaitée avec le BAS a été identifiée et des OCMC Al2O3/BAS à renfort fibreux 1D, 2D ont commencé à être élaborés. Toutefois, pour obtenir des matériaux ayant des propriétés accrues pour des conditions thermostructurales sévères, il est nécessaire de réaliser ces OCMC avec une architecture « 3D » du renfort. Le sujet présenté porte sur la réalisation d'un tel composite avec une architecture complexe (3D) du renfort fibreux et sur l'évaluation de ses propriétés. Pour répondre à cet objectif, ces travaux de recherche incluent : l'étude du frittage du BAS-H afin d’anticiper son comportement en tant que matrice, l'amélioration de son comportement rhéologique en suspension afin de favoriser son infiltration dans une préforme de renforts fibreux, et la mise en place d'un procédé d'imprégnation adapté aux renforts 3D. À la suite de ces études, la fabrication d'OCMC Al2O3/BAS a été réalisée, mettant en évidence des caractéristiques prometteuses en lien avec l'applicationIn the aerospace and defense industry, thermostructural applications require increasingly high-performance materials, combining mechanical strength, refractoriness, and lightness. To meet these demands, all-oxide ceramic matrix composites (OCMC) are considered promising candidates. Among the matrices for these OCMCs, barium aluminosilicate (BAS) stands out due to its advantageous physical properties, particularly as a material for radomes. However, to make this material functional at high temperatures, close to its melting point (1750°C), it is essential to reinforce it with a thermochemically stable material that has an appropriate architecture. Previous theses have successfully mastered the hexagonal phase of BAS. The chemical nature of the reinforcement, which offers the desired stability with BAS, has been identified, and OCMC Al2O3/BAS composites with 1D and 2D fibrous reinforcements have been developed. However, to achieve materials with enhanced properties under severe thermostructural conditions, these OCMCs need to be produced with a "3D" reinforcement architecture. This work focuses on the development of such a composite with a complex (3D) fiber reinforcement architecture and the evaluation of its properties. To achieve this, the research involves studying the sintering of BAS-H to predict its behavior as a matrix, improving its rheological behavior in suspension to facilitate infiltration into the fibrous reinforcement preform, and implementing an impregnation process suitable for 3D reinforcements. Following these studies, the fabrication of OCMC Al2O3/BAS was completed, demonstrating promising characteristics for the intended application
16
Ledain, Olivier. "Elaboration de matrices céramiques par un nouveau procédé hybride : imprégnation de poudres et CVI réactive". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0177/document.
Testo completoAbstract (sommario):
Les composites à matrice céramique ont initialement été développés pour des applications aérospatiales, aéronautiques militaires ou énergétiques en raison de leurs bonnes propriétés à haute température. Ils sont généralement fabriqués par le procédé CVI (Chemical Vapour Infiltration). Un nouveau procédé hybride combinant l’imprégnation de poudre au sein de préformes, suivie de la CVI Réactive(RCVI), est proposé afin de réduire les temps de production. Cette voie est basé sur l’adaptation du procédé RCVD à l’infiltration en milieu poreux. En RCVD, l’absence d’une partie des éléments du dépôt de carbure dans la phase gazeuse implique une consommation/conversion du substrat solide. Dans cette étude, la croissance et la consommation associée ont été étudiées en fonction de divers paramètres dans le système chimique Ti-H-Cl-C. Cette étude est accompagnée d’analyses (DRX, XPS, IRTF) des produits issus de la réaction chimique de formation du TiC. Ensuite, la conversion partielle d’une poudre de carbone submicronique enTiC et la consolidation des zones compactes de poudre par l’infiltration RCVI utilisant le mélange gazeux H2/TiCl4 a été étudiée. La porosité résiduelle et la teneur en TiC ont été mesurées par analyse d’image à différentes distance de la surface des matériaux. Selon la température, plusieurs centaines de micromètres infiltrés ont été obtenus. Finalement, les résultats ont été transposés à l’infiltration RCVI de préformes type CMC. Malgré une teneur minimale de 25% de TiC dans l’ensemble de la préforme, les résultats montrent une mauvaise homogénéité d’infiltration et une mauvaise cohésion des blocs de poudre consolidés avecles fibres de leurs environnementsCeramic matrix composites were originally developed for aerospace,military aeronautics or energyapplications thanks to their good properties at high temperature. They are generally made by ChemicalVapor Infiltration (CVI). A new short hybrid process combining fiber preforms lurry impregnation ofceramic powders with an innovative Reactive CVI (RCVI) route is proposed to reduce the productiontime. This route is based on the combination of Reactive Chemical Vapour Deposition (RCVD), whichis often used to deposit coatings on fibres, with the Chemical Vapor Infiltration (CVI).In RCVD, the absence of one element of the deposited carbide in the initial gas phase involves theconsumption/conversion of the solid substrate. In this work, the RCVD growth and the associatedconsumption were studied with different parameters in the Ti-H-Cl-C chemical system. The study hasbeen completed with the chemical products analysis, combining XRD, XPS and FTIR. Then, the partialconversion of sub-micrometer carbon powders into titaniumcarbide and the consolidation of greenbodies by RCVI from H2/TiCl4 gaseous infiltration were studied. The residual porosity and the final TiCcontent were measured in the bulk of the infiltrated powders by image analysis from scanning electronmicroscopy. Depending on temperature, few hundred micrometers-depth infiltrations are obtained.Finally, the results have been transposed to the RCVI into CMC-type preforms. Despite aminimalTiC content of 25% in the overall preform, the results shown a bad homogeneity of the infiltration anda poor cohesion of fibres with RCVI consolidated powder of their environment
17
Gomes, Dirlene Moreira. "Mapeamento geotécnico para análise de feições erosivas concentradas na bacia do Ribeirão do Meio, São Pedro/SP, na escala 1:20.000". Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-01042016-101454/.
Testo completoAbstract (sommario):
A bacia do Ribeirão do Meio é uma área com sérios problemas associados ao processo de erosão hídrica. A carta de susceptibilidade à erosão foi obtida a partir do uso combinado de um conjunto de ferramentas de trabalhos como: mapeamento geológico-geotécnico e o geoprocessamento; fundamentais para a definição das potencialidades e limitações do meio físico. Os procedimentos adotados durante o mapeamento geológico-geotécnico permitiram obter informações de caráter qualitativo e quantitativo dos materiais inconsolidados, os quais foram submetidos a um processo de análise para a sua caracterização. Dentre as técnicas de trabalho merece destaque o ensaio de infiltração in situ tanto pela qualidade e importância das informações obtidas, quanto pelo baixo custo financeiro. Os critérios estabelecidos para avaliação dos principais fatores associados ao fenômeno de erosão, foram: índice de erodibilidade, declividade do terreno, espessura dos materiais inconsolidados, textura do material, condutividade hidráulica, origem do material, presença ou não da cobertura vegetal e processo de ocupação das terras. Durante o processo de análise das informações as características hidráulicas e os índices de erodibilidade foram correlacionados a todas outras propriedades dos materiais inconsolidados, e revelaram-se fortes parâmetros de avaliação frente aos processos erosivos. Todas essas informações, foram introduzidas no sistema de tratamento de dados do geoprocessamento para a apresentação em forma de documentos cartográficos e cruzamento das informações que culminaram no reconhecimento de cinco classes susceptíveis à erosão por escoamento concentrado.This research proposes the elaboration of the Ribeirão do Meio river\'s basin erosion susceptibility map. This area was chosen due to serious problems related to the gully erosion observed on the site. This cartographic document was obtained using tools such as the Geological-Geotechnical Mapping and Geoprocessament; essential to define the physical environment\'s potentialities and limitations. The procedures adopted during the geological-geotechnical mapping made it possible to obtain qualitative and quantitative information of the unconsolidated material, which were analyzed and characterized. The in situ infiltration test must be emphasized among the other work techniques due to its quality, low cost and importance of the obtained information. The criteria established to evaluate the main factors were: erodibility index, declivity, the unconsolidated material\'s thickness, material texture, hydraulic conductivity, the material\'s source, possible presence of vegetable covering and antropic activity process. During the information analysis process, the hydraulic characteristics and the erodibility indexes were correlated to all other properties of the unconsolidated materials, and among the parameters used to evaluate the erosive process the hydraulic characteristics and erodibility indexes provided the most consistent results. Cartographic documents and the other information were crossing culminating on the recognition of five susceptibility classes of erosion for concentrated drainage.
18
Durin, Bertrand. "Transfert et transport colloïdal de polluants métalliquesApplications en assainissement routier". Phd thesis, Université de Nantes, 2006. http://tel.archives-ouvertes.fr/tel-00104567.
Testo completoAbstract (sommario):
L'impact des infrastructures de transport sur l'environnement est une des préoccupations du ministère en charge de l'environnement. Le ruissellement des eaux de pluie sur les surfaces urbanisées engendre un effluent complexe plus ou moins pollué. L'objet de ce travail était de préciser le rôle de la fraction colloïdale sur la mobilité des éléments traces en assainissement routier. Pour cela nous avons procédé à deux échelles, d'une part d'une manière globale en instrumentant un bassin d'infiltration des eaux pluviales, afin de collecter et de qualifier l'effluent au cours de la chaîne d'infiltration depuis la route jusqu'aux eaux interstitielles ; d'autre part en simulant à l'échelle de la colonne de laboratoire, les sollicitations subies par le sédiment au cours de l'année, c'est à dire des variations de force ionique et des variations de charge hydraulique. L'isolement de la fraction colloïdale a été assurépar un protocole d'ultrafiltration et la caractérisation a été réalisée en couplant les analyses physicochimiques (ICP-AES, SAA, MEB, MEBE, MET, XPS) et un code de calcul géochimique. Les résultats obtenus sur le terrain mettent en évidence l'existence et la grande variabilité de la fraction colloïdale. Seul le cuivre y est toujours présent entre 4 et 59 % de sa concentration totale. Une méthodologie visant à réduire l'incertitude a été mise au point. La chute de la force ionique entraîne une mobilisation colloïdale d'aluminium, de cuivre, de plomb et de matière organique, alors que les cycles d'arrêt-reprise du débit mobilisent le cuivre, le fer, le zinc, le nickel et des composés organiques. La caractérisation colloïdale des éluats montre que les éléments traces sont associés à des oxydes d'aluminium et de fer accompagnés de substances organiques issues de la dégradation biologique mais qui sont à identifier.
19
Frigo, Jianice Pires. "Infiltração da água em latossolo vermelho distroférrico utilizando infiltrômetros de cilíndro único". Universidade Estadual do Oeste do Paraná, 2017. http://tede.unioeste.br/handle/tede/3015.
Testo completoAbstract (sommario):
Submitted by Neusa Fagundes (neusa.fagundes@unioeste.br) on 2017-09-05T12:35:02Z
No. of bitstreams: 1
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The infiltration process understanding and its relationship with soil properties is essential for the efficient management of soil and water. Thus, this paper aimed at evaluating water infiltration in an area of Oxisol, using single ring infiltrometers with different diameters. In addition, it also aimed at comparing the performance of 7 cm (A7) and 15 cm (A15) cylinders, matching soil moisture and bulk density to water infiltration and evaluating spatial distribution of infiltration. For this purpose, 24 data points were evaluated, placed in 8 plots of a circular area prepared for permaculture cropping, named as Mandala. Shewhart graphs and process capability index were used to compare cylinders and the inverse of distance square for data interpolation. It was observed that the average stable infiltration rate, determined with A7 cylinder, was 196.79 mm h-1 and with A15 cylinder was 187.30 mm h-1, consequently, there was a difference of 5.6%. The process capacity was estimated at 0.61 for A7 and 1.62 for A15, considered adequate for A15 and inadequate for A7 cylinder. Thus, it was concluded that the infiltration rates that were stabilized and determined by the cylinders were compatible with the rates determined by other methods in other papers. Regarding the performance of single-ring infiltrometers, it is concluded that, although both cylinders presented controlled processes, and did not differ statistically, cylinder A15 presented less variability on data, and may be considered adequate due to its process capability index.
O entendimento do processo de infiltração e das suas relações com as propriedades do solo é fundamental para o eficiente manejo do solo e da água. Assim, este trabalho teve como objetivo avaliar a infiltração de água em uma área de latossolo vermelho, para tanto, foram utilizados infiltrômetros de único cilindro, de diferentes diâmetros. Além disso, objetivou-se comparar o desempenho desses cilindros de 7 (A7) e de 15 cm (A15), relacionar a umidade e a densidade aparente do solo à infiltração da água e avaliar a distribuição espacial da infiltração. Foram avaliados 24 pontos de coleta de dados, alocados em 8 parcelas de um talhão circular preparado para plantio em regime de permacultura, denominado mandala. Gráficos de Shewhart e o índice de capacidade de processo foram utilizados para a comparação entre os cilindros e inverso do quadrado da distância para interpolação de dados. Verificou-se que a taxa de infiltração estável média, determinada com o cilindro A7, foi de 196,79 mm h-1 e com o cilindro A15 foi de 187,30 mm h-1, cuja diferença foi de 5,6 %. A capacidade de processo foi estimada em 0,61 para A7 e 1,62 para A15, a qual foi considerada adequada para o cilindro A15, porém inadequada para cilindro A7. Desta forma, neste trabalho, concluiu-se que as taxas de infiltração estáveis e determinadas pelos cilindros foram compatíveis com as taxas determinadas por outros métodos em outros trabalhos. Em relação ao desempenho dos infiltrômetros de cilindros únicos, conclui-se que, embora ambos os cilindros tenham apresentado processos controlados e não tenham diferido estatisticamente, o cilindro A15 apresentou menos variabilidade dos dados, e pode ser considerado adequado em função do seu índice de capacidade de processo.
20
Deumier, François. "Formulation et déshydratation de viande de volaille par immersion. Étude des transferts de matière à pression atmosphérique et sous vide". Phd thesis, ENSIA (AgroParisTech), 2000. http://tel.archives-ouvertes.fr/tel-00709458.
Testo completoAbstract (sommario):
L'application du procédé de Déshydratation-Imprégnation par Immersion (DII) dans des solutions ternaires (eau, NaCl, sirop de glucose) à basse température a été proposée pour la transformation de la viande de dinde. La connaissance des propriétés des solutions utilisées conjuguée à celle des transports de matière entre le produit et la solution ont permis de dégager un domaine d'applications rationnelles du procédé de DII à la viande de dinde, en fonction des caractéristiques finales du produit transformé souhaité. Afin de s'affranchir en partie de la lenteur des mécanismes diffusifs qui régissent les transports de matière en DII et également d'élargir la gamme potentielle des produits pouvant être obtenus par immersion de viande de volaille dans des solutions concentrées, le procédé d'Immersion sous Vide Pulsé dans une solution saturée en sel a été proposé. Il s'agit d'immerger le produit dans une solution et de le soumettre à un traitement alternant des phases sous pression résiduelle et des phases à pression atmosphérique. L'IVP a pour effet une forte augmentation du gain en sel et une diminution de la perte en eau, ce qui a pour conséquence une augmentation du rendement massique. Les principales variables de commande de ce procédé ont été identifiées et leurs effets sur les transports de matière ont été quantifiés. Cette étude a montré l'importance de la structure de la viande et de la présence de gaz occlus et/ou dissous dans la viande. Les essais conduits sur viande et sur gels modèles ont permis de proposer un modèle de représentation des phénomènes intervenant dans les transports de matière en IVP. Ainsi, le traitement sous vide permet-il de dégazer les pores de la viande et la remise à pression atmosphérique se traduit par une infiltration de solution dans ces pores, les gaz encore présents dans ces pores étant alors comprimés. Cette infiltration se traduit également par une augmentation de la surface d'échanges entre la viande et la solution. Cependant, la solution infiltrée est très rapidement diluée et cette dilution diminue notablement, voire inverse, les transports d'eau. Enfin, le séquençage des opérations de DII et/ou d'IVP a été proposé pour obtenir plus rapidement certains produits et pour formuler d'autres produits, impossibles à obtenir par DII dans des conditions satisfaisantes.
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Magnant, Jérôme. "Composites fibreux denses à matrice céramique autocicatrisante élaborés par des procédés hybrides". Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14105/document.
Testo completoAbstract (sommario):
L'élaboration de composites à matrice céramique denses et à fibres continues multidirectionnelles par de nouveaux procédés hybrides a été étudiée. Les procédés développés reposent sur le dépôt d'interphases autour des fibres par Infiltration Chimique en phase Vapeur (CVI) puis sur l'introduction de poudres céramiques au sein de préformes fibreuses par infusion de suspensions aqueuses colloïdales concentrées et stables, et enfin sur la consolidation des préformes soit par frittage flash, soit par imprégnation réactive de métaux liquides.La consolidation des composites par frittage flash est très rapide (palier de maintien en température inférieure à 5 minutes) et permet d'obtenir des composites denses. Durant le frittage, la dégradation des fibres de carbone a pu être évitée en adaptant le cycle de pression afin de limiter l'évolution des gaz au sein du système.La densification totale des composites par imprégnation de métaux liquides a été obtenue en contrôlant attentivement les paramètres d'imprégnation afin d'éviter de piéger des espèces gazeuses au sein des préformes fibreuses.Les composites à fibres de carbone consolidés par frittage flash ou par imprégnation réactive de métaux liquide possèdent un comportement mécanique de type élastique endommageable ainsi qu'une contrainte à rupture en flexion voisine de 300 MPa. Ces composites ont montré leur capacité à s'autocicatriser dans des conditions oxydantes. Comparés aux composites à matrice céramiques élaborés par CVI, les composites densifiés par imprégnation de métaux liquide sont eux parfaitement denses et ont un comportement mécanique en traction à température ambiante similaire avec notamment une contrainte à rupture en traction de 220 MPaThe fabrication of multidirectional continuous carbon fibers reinforced dense self healing Ceramic Matrix Composites by new short time hybrid processes was studied. The processes developed are based, first, on the deposition of fiber interphase and coating by chemical vapor infiltration, next, on the introduction of ceramic powders into the fibrous preform by Slurry Impregnation and, finally, on the densification of the composite by liquid-phase Spark Plasma Sintering (SPS) or by Reactive Melt Infiltration of silicon (RMI).The homogeneous introduction of the ceramic particles into the multidirectional fiber preforms was realized by slurry impregnation from highly concentrated (> 32 %vol.) and well dispersed aqueous colloid suspensions. The densification of the composites by spark plasma sintering was possible with a short (< 5 minutes) dwelling period in temperature. The chemical degradation of the carbon fibers during the fabrication was prevented by adapting the sintering pressure cycle to inhibit gas evolution inside the system. The composites elaborated are dense. The fully densification of the composites by RMI was realised by carefully controlling the impregnation parameters to avoid to entrap some gaseous species inside the fiber preforms. Our carbon fiber reinforced ceramic matrix composites processed by Spark Plasma Sintering or Reactive Melt Infiltration have a damageable mechanical behaviour with a room temperature bending stress at failure around 300 MPa and have shown their ability to self-healing in oxidizing conditions. Compared to the CMC processed by CVI, the composites processed with a final consolidation step by RMI are fully dense and have a similar room temperature tensile test behaviour with an ultimate tensile stress around 220 MPa
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Schneider, Christine. "Etude du procede d'elaboration de composites a matrice metallique par inflitration moyenne pression. : Elaboration et caracterisation microstructurale et mecanique du composite unidirectionnel A9/Al203". Lyon, INSA, 1994. http://www.theses.fr/1994ISAL0071.
Testo completoAbstract (sommario):
Ce travail de thèse s'est articule autour de deux pôles principaux: la mise au point de l'élaboration par infiltration moyenne pression appliquée aux composites a matrice métallique et la caractérisation microstructurale et mécanique du composite unidirectionnel A9/Al2O3 obtenu par ce procédé. La première phase de cette étude a été consacrée a la conception de moules et de préformés adaptés à ce nouveau procédé puis à la détermination de conditions d'élaboration pertinentes. La deuxième phase a consiste à évaluer l'influence de ces conditions sur la qualité du matériau par une étude de la microstructure (défauts d'élaboration et répartition du renfort dans la matrice) et des propriétés mécaniques. Ces dernières ont été déterminées dans le cas d'une sollicitation en traction parallèlement et perpendiculairement aux fibres. Les résultats concernant l'ensemble des caractéristiques mécaniques du matériau ont été interprétées a partir de modèles théoriques existantsThis study dealt with : the optimization of pressure infiltration casting elaboration for Metal Matrix Composites and the microstructural and mechanical characterization of the unidirectionnal A9/ Al203 composites obtained with this process. In the first part of this study, moulds were conceived and preforms were manufactured to be adapted to the new processing system. Than the optimal elaboration conditions were determined. The second part consisted to evaluate the influence of these conditions on the material quality with a study of the microstructure (elaboration defects and fibres repartition in the matrix) and of the mechanical properties. This properties were determined with axial and transverse tension tests. The result of the whole mechanical properties of the composite were interpreted on the basis of theoretical existing models
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CORDEIRO, Valéria Vital. "Aproveitamento de resíduo de zircônia oriundo do processo CAD/CAM visando aplicação em prótese odontológica". Universidade Federal de Campina Grande, 2015. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1025.
Testo completoAbstract (sommario):
Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-06-21T13:47:08Z
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VALÉRIA VITAL CORDEIRO - TESE (PPGCEMat) 2015.pdf: 2501691 bytes, checksum: b4f2ef7029d9c18c87c96cc0bbba39e8 (MD5)Made available in DSpace on 2018-06-21T13:47:08Z (GMT). No. of bitstreams: 1 VALÉRIA VITAL CORDEIRO - TESE (PPGCEMat) 2015.pdf: 2501691 bytes, checksum: b4f2ef7029d9c18c87c96cc0bbba39e8 (MD5) Previous issue date: 2015-02-27
CNPq
As indicações das cerâmicas odontológicas se devem as propriedades estéticas. O sistema CAD/CAM permite realizar restaurações cerâmicas, gerando uma elevada quantidade de resíduos, na forma de pó, durante o desbaste e fresa da peça cerâmica, que atualmente é descartado. Este trabalho tem por objetivo estudar o reaproveitamento dos resíduos de zircônia obtidos através do sistema CAD/CAM visando sua aplicação em prótese odontológica. Foi estudado o resíduo proveniente da fresagem de blocos comerciais de zircônia estabilizada com 3% de ítria (3Y-TZP), (sistema Zirkonzahn®), o resíduo caracterizado através da determinação da composição química, difração de raios X, determinação de tamanho de partículas e análise térmica diferencial/gravimétrica. O resíduo beneficiado seguiu duas rotas: desaglomeração em moinho de bolas e sem desaglomeração. Ambos os materiais foram utilizados para confecção de corpos de prova de zircônia queimados a 1180oC em seguida infiltrou-se o vidro de lantânio a 1140oC, os corpos para densificação e os corpos confeccionados extraídos das placas comerciais (Zirkonzahn®) foram queimados em temperaturas de 1300, 1400 e 1500oC após sinterização caracterizados com a determinação da porosidade aparente, microscopia eletrônica de varredura, resistência à flexão em três pontos e microdureza Vickers. Observou-se nos resultados que o resíduo é constituído por zircônia estabilizada com 3% de ítria (3Y-TZP) e matéria orgânica. A desaglomeração diminui o tamanho dos agregados e favoreceu o processo de sinterização, os corpos infiltrados não apresentam resistência adequada para infraestruturas, os corpos sinterizados a 1500oC apresentaram porosidade próxima da obtida pelos corpos de referência. A resistência e a microdureza dos corpos do resíduo atingiram o valor máximo de 1079 HV para os corpos com zircônia não desaglomerada (ZSD) e de 1523 HV para os corpos com zircônia desaglomerada (ZCD), após queima a 1500oC.
The use of ceramics in dental prosthesis is due to the aesthetic properties. The CAD/CAM system allows making ceramic restorations, generating a large amount of waste, in powder form, during the roughing and milling cutter of the ceramic piece, which currently is thrown away. The aim of this work is to study the reuse of the waste obtained from zirconia CAD/CAM system for its application in dental prosthesis. It was studied the residue from the milling of commercial stabilized zirconia blocks with 3% of yttria (3Y-TZP). The residue was characterized by chemical composition, X-ray diffraction, particle size and differential and gravimetric thermal analysis. The improvement residue followed two routes: deagglomeration in a ball mill and without deagglomeration. Both materials were used for preparation of specimens of zirconia. It were sintered at 1180oC then infiltrated with lanthanum glass at 1140oC. The infiltrated specimens and the specimens extracted from the commercial blocks (Zirkonzahn ®) were sintered at temperatures of 1300, 1400 and 1500oC.After sintering its were characterized by apparent porosity, scanning electron microscopy, flexural strength in three points and Vickers micro hardness. It was observed in the results that the residue consists of stabilized zirconia with 3% yttria (3Y-TZP) and organic matter. The deagglomeration decreases the size of the aggregates and favored the sintering process. The infiltrated specimens do not have adequate resistance to infrastructures, the sintered bodies to 1500oC presented close porosity obtained by the scanbodies. Resistance and micro hardness of bodies of waste reached the maximum value of 1079 HV for the bodies with no deagglomeration zirconia (ZSD) and 1523 HV for the bodies with zirconia desaglomerada (ZCD), after burning the 1500oC.
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Klein, Christian. "Etude du procédé de densification par caléfaction de composites C/C, modélisation, optimatisation du contrôle et du bilan énergétique". Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0231.
Testo completoAbstract (sommario):
Le présent travail est réalisé dans le cadre de l’étude d’un procédé industriel de densification de matériaux composites carbone/carbone (C/C) destinés aux freins d’avion. Une préforme poreuse de fibres de carbone baigne dans un précurseur liquide et elle est chauffée par induction électromagnétique radio-fréquence. Le précurseur porté à ébullition dans l’espace poral crée un dépôt de carbone dans les zones les plus chaudes ; ce dépôt constitue la matrice du composite. On propose une modélisation physico-chimique de ce procédé afin d’en assurer le contrôle et l’optimisation. Le travail a consisté à développer un solveur couplant l’induction électromagnétique avec les transferts de masse, de chaleur, de mouvement et d’espèces chimiques, en incluant l’ébullition et le dépôt chimique. Le modèle inclut le circuit électrique complet permettant d’effectuer le chauffage : il permet donc de suivre en temps réel et de façon non destructive l’avancement de la densification par l’évolution des grandeurs électriques. Une formulation originale adaptée à la représentation simultanée du liquide, du gaz et de la zone en ébullition a été développée et implémentée avec succès dans un logiciel commercial d’éléments finis. Les résultats de la simulation sont comparés avec les données obtenues sur le moyen expérimental, avec un bon accord. Enfin, la simulation est utilisée pour proposer des pistes d’amélioration du procédé, en altérant la géométrie du dispositif de chauffage par induction et en modifiant la stratégie de pilotage en puissanceThis work has been carried out in the frame of the study of an industrial process for the manufacturing of carbon/carbon (C/C) composite aircraft brake discs. A porous preform made of carbon fibres is immersed in a liquid precursor and is heated by Radio-Frequency electromagnetic induction. The boiling precursor enters the porous preform and yields a carbon deposit in the hottest zones; this deposit will be the carbon matrix of the composite. A physico-chemical process model is proposed in the aim of ensuring its control and optimisation. The work consisted in developing a numerical solver coupling electromagnetic induction heating with heat, mass and species balances accounting for boiling, diffusion and chemical deposition reactions. The model includes the complete electrical circuit of the heating device: it therefore allows real-time, non-destructive monitoring of the infiltration progress through the evolution of the electrical properties. An original formulation has been designed to simultaneously describe the liquid, the gas and the boiling zone; it has been implemented in a commercial Finite Element software package and validated physically with respect to experimental data, with a good agreement. Finally, the simulation software has been used to propose directions for process improvements, through alterations of the inductive heating device geometry or of the heating power supply program
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LIMA, Cícero Aurélio Grangeiro. "Estudo da variabilidade espacial da infiltração: aspectos teóricos e experimentais". Universidade Federal de Campina Grande, 1992. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/2165.
Testo completoAbstract (sommario):
Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-11-10T13:49:36Z
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CÍCERO AURÉLIO GRANGEIRO LIMA - DISSERTAÇÃO PPGECA 1992..pdf: 25126677 bytes, checksum: 344ec8cc3722c36124b4e9b1b88b50b3 (MD5)Made available in DSpace on 2018-11-10T13:49:36Z (GMT). No. of bitstreams: 1 CÍCERO AURÉLIO GRANGEIRO LIMA - DISSERTAÇÃO PPGECA 1992..pdf: 25126677 bytes, checksum: 344ec8cc3722c36124b4e9b1b88b50b3 (MD5) Previous issue date: 1992-11-12
Testes de infiltração com infiltrômetro duplo anel de nível constante foram efetuados em 32 pontos de uma malha retangular de uma parcela agrícola da Fazenda Experimental da EMEPA - Pb. Ajustamentos as Leis de Philip e de Green e Ampt foram efetuados. Medições da granulometria, densidade aparente seca do solo e umidade volumétrica antes e depois dos testes foram também efetuadas. Utilizou-se a seguir técnicas de análises estatística clássica e geoestatística para caracterizar a variabilidade espacial dos parâmetros de infiltração obtidos pelos ajustamentos. Nenhum dos parâmetros estudados apresentou estrutura espacial definida. Correlações simples e múltiplas evidenciaram dependência da percentagem de Argila + Silte com o espaço físico, e independência entro os parâmetros de infiltração. Ilustrações sobre o efeito da variabilidade espacial sobro o ponto de vista agronômico o hidrológico são mostradas.
Infiltration tests with double-ring infiltrometers were performed in a 33 paint reiangular regular]y spaced grid of an agri cultural site. Fitting of the infiltration curve obtained by Philip and Green and Ampt laws allowed to obtain the sorptivity, the infiltration rate at steady state and the suction parameters of Green and Ampt,for each point. Measurements of pre- and post-humidi ty, granulometry and dry density were also performed. Classical statistical and geo-statistical techniques were used to characterize spatial variability. None of the parameters studied showed a defined spatial structure. Single and muitiple correlations showed a dependence between Cclay + siltD percentage with space but no correlation between parameters was obtained. I11ustrative considerations about spatial variability were ma de with agronomic and hydrologic applications.
26
Kai-Chieh, Yeh, e 葉凱潔. "Densification in Carbon-Carbon Composites Prepared by Chemical Vapor Infiltration Process". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/28291835529020419878.
Testo completoAbstract (sommario):
碩士國防大學理工學院
化學工程碩士班
103
Carbon fiber reinforced carbon matrix composites, which are called carbon/carbon composites (C/C), are made of carbon fiber, fabric or woven fabrics as reinforcing phase material and the carbon matrix phase. They are often used in the military or aerospace industries. In addition to the advantages of low density, high strength, high wearing resistance, low ablation rate, high thermal shock resistance and low coefficient of thermal expansion, its mechanical strength at high temperature is unmatched by most of the metals. Therefore the development of the material and process technology for C/C composites is very important to our industry. However, carbon/carbon composites are usually porous materials. In order to improve its durability characteristics for applications in high-temperature environments such as rocket nozzles, usually these pores must be filled. Chemical vapor infiltration (CVI) is the most accepted and practically adopted method for the mass production of dense C/C materials. It is a process for producing densified carbon-carbon composites. In CVI, the carbon fiber workpiece is placed in the furnace and heated to high temperature. A hydrocarbon gas is then introduced into the furnace as the carbon precursor which will be decomposed into carbon and hydrogen. The pyrolytic carbon atoms will diffuse into the space between fibers and deposit on the fibers, thereby filling the gaps and densifying the material. The C/C composites can thus be densified through this process. However, the manufacturing process and its parameter adjustment are usually classified as industrial and defense secrets, and are not publicly available. Therefore, in order to set up an independent research and development capacity for our defense industry, the polymer nano palladium (Pd) particles were used as the catalyst and the acetylene or methane as a carbon source to carry out the CVI process. Using this Pd-catalyzed CVI process, in addition to successfully densifing the C/C composites, the man-hours and costs can be greatly saved compared with the traditional CVI process. The process parameters such as the hydrogen flow, the impregnated and CVI times, the process temperature and the process period were evaluated to know their effect on the CVI result and find out the optimal process parameters. The results show that adding small amount of hydrogen can efficiently enhance the activity of Pd catalysts. When methane was used as the carbon source, at the methane flow rate of 100 sccm, the temperature of 600℃ and the growth time of 12 h, the porosity of C/C composite was reduced from original 95% to 65% and the weight gain ratio was enhanced to 558%. On the other hand, when acetylene was used as the carbon source, at the acetylene flow rate of 5 sccm, the temperature of 600℃and the growth time of 12 hr, the porosity of C/C composite was reduced from original 95% to 70% and the weight gain was increased to 176%. Keywords: Chemical vapor infiltration, Carbon/carbon composite, Densification
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CHUN, YANG DAI, e 楊岱錞. "A Study On The Infiltration Process Of Organized Crime Into School In Taipei". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/96850061752535672947.
Testo completoAbstract (sommario):
碩士國立臺北大學
犯罪學研究所
99
The purpose of this research lies in: analyzing the regional distribution, formation and activities at present of gang’s constitution in Taipei city. 2. Investigating guilt gangs to understand the mode and method they used to intrude into the campus. 3. To probe the juvenile crime related theory. 4. To know juvenile gangs’ causes and their progress. 5. To understand the motives for teenagers to join the gang. 6. The characteristics of juvenile gangs. 7. The risk factors for teenagers to join the gang, etc. finally, the research finding will bring up specific suggestions for police organization as reference for investigating and controlling organized crimes. The main research method is in-depth interview. There are 4 criminal investigators who have practical campus gang’s crackdown experiences and 2 gang members were interviewed. My interview finds that gang groups are all using peripheral elements to recruit drop-out or school student in the beginning, and then students exploit peer and friend relationship to attract new member one by one. The most attracting way for student is “sports lottery website”, after making money, the underworld gang students give money back in return by their rank so as to strengthen gang’s chest. The police authorities also find that there’s a tendency of increase in juvenile crime in recent years. If we can’t curb it effectively, perhaps campus vicious power will turn into more and more serious. This study suggests that: 1.we should take the following 3 levels preventive efforts for adolescent: General prevention (1) protective measures (2) educational measures (3) consultative measures. 2. Special prevention: (1) consultation of deviant tendency. (2) Prevention and intervention toward deviant behaviors. (3) Transfer for special treatment, placement and Counseling. 3. Prevention of Recidivism :( 1) Probation measures. (2) Corrective treatment. (3)After-care system. Bring together all the useful social resources, and we should commit ourselves mind and energy mutually to prevent campus plagued by gangs and to ensure the clean environment of campus, let the future master of our nation free from going astray and can grow up healthily to become a useful people of our country.
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Hsu, Pai-Ching, e 徐百慶. "Methods of Simulating the Infiltration Process of Watershed of Tsengwen Reservoir During Raining Season". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/12065761111630231180.
Testo completoAbstract (sommario):
碩士國立成功大學
水利及海洋工程學系碩博士班
93
In the rainfall runoff process, infiltration is an important point to decide how many capacities into the river when a rainstorm is stopped. Therefore, the paper considers using several different methods to compare the part of soil infiltration. Using the inflow and rainfall data of Tsengwen reservoir, make the rainfall runoff analysis of the long-term continuing storms which are taken by plum rains or typhoon. Then, we get the unit hydrograph by linear programming. This paper is compared the method suggested by Bauer and curve number method. The result of the method suggested by Bauer is conformed to the condition of the actual soil moisture content. Therefore, we try using this contention to make up the short of curve number method. The result of simulating the rainstorm cases of watershed of Tsengwen reservoir isn't well, but the tendency is similar. The possible reason is that the base-flow separation to the river flow isn't made well. Because the excess rainfall is transformed by the unit hydrograph, the capacity should be equal to direct runoff. If the base-flow is estimated unreasonable, the transformed excess rainfall may be occurred larger or smaller situation.
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Yan, Beng-Xian, e 顏伻憲. "The Effect of Wax Infiltration by Vacuum on the Milling Process of Zirconia Green Body". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/4pn35d.
Testo completo
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Lee, Mu-Chou, e 李牧洲. "Study of Carbon Nanotubes and Graphene Doping on Three-Dimensional Needled Carbon/Carbon Composites Prepared Through Liquid Infiltration and Fast Carbonization Process". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/3evh4j.
Testo completoAbstract (sommario):
碩士義守大學
材料科學與工程學系
103
This study begins to fabricate carbon fiber skeletons by needled punch method. Secondly, the impregnation process was operated through the vacuum impregnation method and carbon fiber skeletons were impregnated with liquid phenolic resin doped different proportions of carbon nanotube and graphene. After impregnation, hot pressing and carbonization processes were adopted to prepare porous carbon performs. Subsequent densification cycles and impregnation processes were adopted to fabricate the carbon/carbon composites respectively. The objective of this study is to investigate interrelationships among adding proportions of carbon nanotube and graphene, impregnation method, graphitization process and properties of carbon/carbon composites. The results indicate that, addition of carbon nanotube and graphene can enhance the mechanical, wear and thermal conductive properties of the specimens. Properties of the specimens were improved significantly as the additive amount of carbon nanotube and graphene increased. The performances of specimens prepared through densification cycle processes were superior to those specimens prepared through repeatedly impregnation method. The mechanical properties of the specimens prepared through densification cycle process with further graphitization process will decrease slightly. However, the wear and thermal conductive properties of these specimens were improved significantly. Furthermore, graphitization drgree of specimens were enhance significantly with the addition of carbon nanotube and graphene. Especially, specimens added with graphene showed better graphitization drgree than that of specimens added with carbon nanotube.
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Vieira, Gustavo Fonseca. "Uma abordagem processual penal do Regime Jurídico das Acções Encobertas - Em especial da infiltração de agentes". Master's thesis, 2019. http://hdl.handle.net/10316/90339.
Testo completoAbstract (sommario):
Dissertação de Mestrado em Direito apresentada à Faculdade de DireitoThe present work has as objective to produce a critical criminal procedural analysis to the Legal Regime of Covered Actions and, in particular, to the institute of agent infiltration. After a history of legislative developments, and in addition to the considerations developed regarding the application of the principles of legality and proportionality to the covert actions, it was concluded that the current Legal Regime, inaugurated by Law 101/01 of 25 August, although has made significant progress in dealing with the matter, it still lacks important regulations. In this sense, it was concluded that the law should require the submission of periodic reports on the operation, either undercover or infiltrated, as a way to enable effective control of the actions developed by the agent by the responsible authorities. In addition, we also consider it fundamental that the law should include the requirement to present an infiltration plan so that the authorities of the Public Prosecutor's Office and the Judiciary can be able to decide with objective data the admissibility of the operation. Finally, it was also concluded that, although the law does not provide for a maximum time limit for an infiltration operation, judicial prudence and the principle of proportionality must be applied in order to prevent endless extensions which may ultimately lead not to simple restriction of fundamental rights, guarantees and individual freedoms, but the very negation of such freedoms, affected continuously and for long periods of time by state action.
O presente trabalho tem como objetivo produzir uma análise processual penal crítica ao Regime Jurídico das Acções Encobertas e, em especial, ao instituto da infiltração de agentes. Após histórico da evolução legislativa e a par das considerações desenvolvidas acerca da aplicação dos princípios da legalidade e da proporcionalidade ao campo das ações encobertas, concluiu-se que o atual Regime Jurídico, inaugurado pela lei nº 101/01, de 25 de Agosto, embora tenha consubstanciado avanços significativos no trato da matéria, ainda carece de regulamentações importantes. Neste sentido, concluiu-se que a lei deveria exigir a apresentação de relatórios periódicos sobre a operação, seja ela encoberta ou infiltrada, como forma de possibilitar controle efetivo das ações desenvolvidas pelo agente por parte das autoridades responsáveis. Ademais, julgamos também fundamental que a lei contemple a exigência de apresentação de um plano de infiltração para que as autoridades do MP e do Poder Judiciário tenham condições de avaliar com dados objetivos a admissibilidade ou não da operação. Por fim, concluiu-se também que, embora a lei não preveja prazo máximo para uma operação de infiltração, a prudência judicial e o princípio da proporcionalidade devem ter aplicação no sentido de impedir infinitas prorrogações que podem ocasionar, em última análise, não a simples restrição dos direitos, garantias e liberdades individuais fundamentais, mas a própria negação de tais liberdades, afetadas de forma continuada e por longos períodos de tempo pela ação estatal.
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Barui, Srimanta. "Understanding quantitative process physics of 3D binderjet printing with validation in Ti-6Al-4V and inkjet bioprinting of mammalian cells". Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4615.
Testo completoAbstract (sommario):
In the field of additive manufacturing, laser or electron beam based 3D printing is widely investigated for biomedical applications. However, much less explored is the binderjet 3D printing, which allows processing of biomaterials at physiologically relevant conditions. In this context, this thesis presents a set of experimental and theoretical analysis to develop a quantitative understanding of the transient process physics of the binderjet 3D printing. In the first part, maltodextrin based aqueous binder, deployed to ‘direct’ print Ti-6Al-4V powder with the achieved mechanical properties ranged between cortical and cancellous bone are described. The adopted process induced ~99% interconnectivity in the 3D microstructure, probed using quantitative micro-CT analysis. Finite Element-based analysis was developed to predict the stress-strain response of various designed porous architectures, while assigning an ‘effective’ material property obtained from microporous models without designed porosity.
In the broad second part of the thesis, the formulation of an in situ polymerisable acrylic binder/ink for printing implantable metallic biomaterials is highlighted. The modification of the printable Ti-6Al-4V powders using persulfate, allowed localised polymerisation during the 3D binderjet printing of with the on-demand deposited acrylic ink, In order to establish the theoretical perspective, Washburn’s theory was used to understand the transient kinetics of the ink/binder infiltration phenomena in ~100 µm thick powder bed layers,. The combinatorial experimental/analytical approaches enabled to predict the time required for the transient phenomena involved in binderjet printing. A pertinent combination of statistically reliable strength properties (Weibull modulus, compressive, flexural strength and compressive modulus of ~8, 222 MPa, 93 MPa and 4 GPa, respectively) of Ti-6Al-4V scaffolds was recorded along with ~98% interconnected microporous 3D microstructure. The cytocompatibility of the Ti-6Al-4V 3D architectures was established using mammalian fibroblasts and osteoblasts. In developing a better quantitative insight into ink infiltration kinetics, in the third part of this thesis, real time ink infiltration phenomena in the porous ceramic powder bed was investigated under high brilliance synchrotron X-Ray in refraction based phase contrast mode. An ethylene glycol-DI water based simulated ink was allowed to deposit ‘on-demand’ through a piezoelectric inkjet printhead and the post-impact ink infiltration behaviour through the porous alumina powder bed was captured real-time at a rate of 500 fps. Using a rigorous interactive image analysis, the real time wetting contours were extracted and penetration depth, lateral spread, transformed wetting volume was quantified. Denesuk and Holman’s models based on Washburn’s theory were adapted to develop a theoretical model of wetting volume in real time which was established to be dependent on powder bed porosity.
In the fourth part of this thesis, the experimental results related to the piezoelectric inkjet bioprinting of mammalian cells and the post-printing cell functionalities are demonstrated. Cell laden ‘printable’ bioink was printed through a 60 µm orifice printhead using three driving voltages of 80, 90 and 100 V at 3k Hz frequency. Post-printing proliferation (Alamar blue) of the cells was higher, when printed using higher voltage endorsing the positive effect of smooth and uninterrupted droplet ejectionat higher voltage. Propidium iodide (PI) and Texas red conjugated dextran based hierarchical set of molecular probes (3 kDa, 10 kDa, 40 kDa, and 70 kDa) were used to probe the post-printing cell membrane permeation in real time. An interesting observation is the cell membrane damage, which persisted only for few hours after the printing operation in lower voltage (80V). Importantly, the total area of pores and the maximum pore size are found to vary in accordance with the actuating voltage. As the viability and proliferation are uncompromised in higher printing voltage, the higher lifetime of the finite sized membrane pores can be potentially useful for intra-cellular molecular transfections like gene, protein deliveries for cell engineering applications.Department of Science and Technology (DST), Govt. of India, and particularly FIST funding; Department of Biotechnology ( DBT), Govt. of India; National Network for Mathematical and Computational Biology (NNMCB), SERB, Govt. of India; Commonwealth Scholarship Commission, UK; The cell printing and culture facility of Department of Materials, University of Manchester and Diamond Synchrotron facility (DLS, Oxfordshire), UK
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Almeida, Streitwieser Daniela [Verfasser]. "Kinetic investigation of the chemical vapor infiltration and reaction (CVI-R) process for the production of SiC and TiC biomorphic ceramics from paper preforms = Kinetische Untersuchung der chemischen Gasphaseninfiltration und Reaktion zur Hertsellung von SiC- und TiC-biomorphen Keramiken aus Papier-Vorformen / Daniela Almeida Streitwieser". 2005. http://d-nb.info/974205966/34.
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