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Kayahan, Ahmet. "Compressibility Of Various Coarse-grained Fill Materials In Dry And Wet Loading Conditions In Oedometer Test." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1052539/index.pdf.
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The use of coarse-grained fill materials has grown significantly in recent years especially on account of their use in dams and transportation networks. This study investigates compressibility of various coarse-grained fill materials in dry and wet loading conditions in oedometer test. Four materials were used in the experiments, which falls into GP, GW, GM and GC categories respectively. GP material is a weathered rock obtained from Eymir Lake region. This material was chosen especially to be able to investigate degradation and particle breakage due to compaction and compression. GW, GM and GC materials were obtained by using the material called &lsquobypass&rsquo
which is a fill material used in the construction of metro of Eryaman. Using these four materials, large-scale double oedometer tests were carried out to investigate compressibility in both dry and wet conditions. The double oedometer testing technique is used to investigate the effect of soaking on compressibility behaviour of compacted fill materials. Various compactive efforts were used in the compaction stage to investigate the effect of compactive effort on compressibility and degradation of the four gravelly materials. Gradations of the post-test samples were obtained and particle breakage due to compaction using various compactive efforts and particle breakage due to compression were determined. It is found that amount of compression does not necessarily depend on the dry density of the material and fine fraction is also a dominating property regarding the compressibility in coarse-grained fill materials. The vertical strains induced by soaking are on the order of 12% - 20% of the compression measured in dry loading case for the well-graded coarse-grained fill materials tested. Besides, there is significant particle breakage in the compaction process and no further particle breakage in the oedometer test for GP material.
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Hornbeck, Nicholas C. "Effect of compaction effort on Superpave surface course materials." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5592.
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Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains viii, 73 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 52-54).
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Adamah, Cornelius. "Effect of compaction effort on SuperPave base course materials." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10822.
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Thesis (M.S.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains viii, 79 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 52-54).
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El-Ali, Mohammad Abdullah 1958. "Effect of variations in compaction on asphaltic concrete." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276662.
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In this report the influence of several variables including asphalt content, mixing temperature, compaction temperature and compaction energy on void content, voids-in-the-mineral-aggregate (VMA), density and stability of asphaltic concrete mixtures was established. Straight lines were obtained on double logarithmic paper for each asphalt content when the logarithm of Marshall stability values as ordinate were plotted versus the logarithm of the corresponding number of blows of a Marshall compactor as the abscissa. The straight lines were very nearly parallel and therefore, it was possible to develop a single empirical formula expressing the relationship between stability at any compactive effort, within the range of 20 to 110 blows per face, in terms of the standard stability at 75 blows per face of specimen. Results indicate that void content, VMA, density and stability were significantly affected by compaction temperature, asphalt content, compactive effort and mixing temperature.
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Lemaire, Charles-Éric. "Estimation des efforts de contact cylindre / matériau d'un compacteur vibrant." Nantes, 2005. http://www.theses.fr/2005NANT2135.
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Le compactage des routes est une phase majeure de la construction des routes. Les efforts de contact caractérisent l'action du compacteur, leur estimation est nécessaire à l'amélioration du compactage. La mesure des efforts de contact n'est pas possible, ils sont estimés grâce au modèle dynamique du compacteur. La modélisation revient à considérer le compacteur comme un robot manipulateur. Cette approche a été enrichie par le formalisme mixte eulerien lagrangien qui donne un modèle plus simple. La méthode d'identification retenue est celle des moindres carrés pondérés. Une attention particulière a été portée à la description complète de cette méthode. La partie expérimentale constitue une partie majeure du travail et s'articule autour de trois axes : - Instrumentation d'un compacteur, - Définition et mise en place des essais, - Intégration et validation de la méthode sur un chantier. Pour la première fois le torseur des efforts de contact d'un compacteur a été estimé sur un chantier réel.
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Obousy, Richard K. Cleaver Gerald B. "Investigation into compactifed dimensions Casimir energies and phenomenological aspects /." Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5261.
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Karlstrand, Nils, and Johan Neander. "After-compaction effect on the stiffness modulus of laboratory made samples." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-97217.
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The report is written in research purpose for the Swedish National Road and Transport Research Institute (VTI). The aim has been to find out and to determine after-compaction effect on the stiffness modulus of laboratory made samples with different void content and at various temperatures. With the stiffness modulus the shear modulus can be calculated. With the shear modulus a road structure’s deformation in its different layers can be calculated. The work began with the choice of asphalt mixture (ABb16 160/220) with 5% binder content. This was compacted to sample bodies. These samples were analyzed with a number of methods from FAS (the association for asphalt pavements in Sweden). The results from these tests show among other things bulk density, void content and stiffness modulus. These results have afterwards been analyzed through different calculations developed by VTI. From the results we draw the conclusion that there is a clear connection between void and deformation, i.e. a higher void content gives a bigger deformation because of the low stiffness modulus. What happens is that after-compaction leads to a reduced void content which gives a higher stiffness modulus which gives an asphalt pavement that is more resistant against deformations. If the asphalt mixture has a void content of 5% you get a deformation during the first years that is 20% bigger than at a void content of 2% at 10°C. Is the void content 7% the deformation becomes 40% bigger that with 2% according to this study.Rapporten är skriven i forskningssyfte för Statens väg och transportforskningsinstitut (VTI). Med syftet att ta reda på och klarlägga efterpackningens effekt på styvhetsmodulen hos laboratorietillverkade provkroppar med olika hålrum och vid olika temperaturer. Med hjälp av styvhetsmodulen kan skjuvmodulen räknas fram, under förutsättning att materialet är elastiskt, som man direkt kan härleda till en väg konstruktions deformation i de olika lagren. Arbetet började med val av asfaltmassa (ABb16 160/220) med en 5 % bindehalt, som sedan packades till provkroppar. Dessa provkroppar analyserades med ett antal metoder från FAS´(Föreningen för asfaltbeläggningar i Sverige). Resultatet från dessa metoder visar bland annat kompakt- och skrymdensitet, hålrumshalt och styvhetsmodul. Dessa resultat har sedan analyserats genom olika beräkningar framtagna av VTI. Från dessa resultat drar vi slutsatsen att det finns ett klart samband mellan hålrum och deformation (efterpackning), då en högre hålrumshalt ger en större deformation på grund av den låga styvhetsmodulen. Vad som sker är att efterpackningen leder till en minskad hålrumshalt vilket ger en högre styvhetsmodul vilket i sin tur ger en asfaltbeläggning som är mer motståndskraftig mot deformationer. Packas bindlagret till en hålrumshalt på 5 % får man en deformation under de första åren som är 20 % större än vid en hålrumshalt på 2 %, vid 10ºC. Är hålrumshalten 7 % blir deformationen istället 40 % större än vid 2 % enligt denna undersökning.
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Levina, Marina. "The effect of ultrasonic vibration on the compaction of pharmaceutical powders." Thesis, Liverpool John Moores University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521741.
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Zughaer, Hussien Jasim. "The effect of high strain deformation on the compaction of metal powders." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277591.
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Rajkumar, Arthi D. "The effect of roller compaction and tableting stresses on pharmaceutical tablet performance." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/21418/.
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Wang, ShuHong. "Soil substrate selection for urban trees under deicing salt and compaction conditions." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82446.
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The effects of high sodium chloride (NaCl) levels on Na and nutrient retention of three soil substrates and on littleleaf linden growth in different soil substrates were studied in the laboratory and the greenhouse, within the framework of a substrate selection program for trees planted in downtown Montreal. In addition, the effects of the structural soil (SS) compaction were studied in the first greenhouse experiment. The first greenhouse experiment was established in a factorial arrangement of four soils x four salt levels in a completely randomized design with five replicates. The four soil types were (1) L with a bulk density (BD) of 1.53 g/cm3, (2) LP with a BD of 1.26 g/cm3, (3) SS with a BD of 1.8 g/cm 3 (SS1.8), and (4) SS with a BD of 2.0 g/cm3 (SS2.0). The second greenhouse experiment had a split plot design. Two fertilization levels (with fertilizer and without fertilizer) were randomly arranged as the main plots on ten benches. Within each main plot, the combinations of three NaCl levels (0, 0.5 and 1.0 g NaCl/kg soil) and three soil substrates (L with a BD of 1.40 g/cm3, LP with a BD of 1.13 g/cm 3 and SS2.0) were randomized in the sub-plots. Results from the laboratory leaching experiment indicated that SS had the fastest Na leaching rate and highest Na loss, while LP retained more Na than SS or L. (Abstract shortened by UMI.)
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Ribière, Philippe. "Étude de la compaction des milieux granulaires : de l'échelle locale à l'échelle globale." Rennes 1, 2005. http://www.theses.fr/2005REN1S109.
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La densification lente d'un empilement granulaire sous sollicitations présente un double intérêt. D'une part, la compaction douce est un processus industriel courant. D'autre part la compaction d'un empilement s'avère très analogue à l'évolution d'un système vitreux. La densification a été étudiée expérimentalement par gamma-densimétrie. Conjointement, la visualisation de la position des grains au coeur de l'empilement est possible grâce à une technique d'imagerie en fluide iso indice. Ces études expérimentales furent complétées par diverses simulations numériques de la compaction. L'évolution de la compacité est bien décrite par une loi en exponentielle étendue, issue de la dynamique des verres. Le temps caractéristique de la compaction suit une loi d'Arrhenius ce qui caractérise le comportement des verres forts. Outre la compaction, de la convection est aussi observée dans le milieu et son influence sur la compacité a été étudiée. L'étude menée à l'échelle du grain a permis de montrer que les déplacements des grains présentent des caractéristiques communes à tous les systèmes hors équilibre : distributions des mouvements non gaussiennes, intermittence. . . Elle a établi que certains événements rares, de grandes amplitudes, influent profondément sur la dynamique du système. L'étude de la structuration de l'empilement à l'échelle locale a aussi fourni une explication aux effets mémoire observés dans les milieux granulaires.
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Omar, Chalak S. "Roller compaction : effect of morphology and amorphous content of different types of lactose." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/15964/.
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Truong-Loï, My-Linh. "Potentiels d'un système RSO basse fréquence opérant en polarimétrie compacte." Rennes 1, 2010. https://theses.hal.science/tel-00559529.
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Le but de cette thèse est d’évaluer les capacités d’un système radar à synthèse d’ouverture en basse fréquence opérant en polarimétrie compacte pour des applications polarimétriques et interféropolarimétriques. La polarimétrie compacte (CP) est un cas particulier de la polarimétrie duale consistant en une polarisation d’émission unique et deux polarisations orthogonales à la réception. Les basses fréquences permettent de réaliser des applications telles que l’estimation de paramètres liés à la végétation et l’inversion de paramètres de surface. Cependant, dans un contexte spatial en basse fréquence, le plan de propagation subit une rotation lors de la traversée de la couche ionosphérique appelée rotation de Faraday (RF). Un premier objectif est l’estimation et la correction de la RF reposant sur les propriétés de rétrodiffusion des surfaces nues. La sélection des surfaces nues est basée sur un nouveau paramètre, le coefficient de conformité, construit à partir des mesures en CP. Trois méthodes d’estimation de la RF sont ensuite proposées et des applications sont montrées réalisables, directement avec des données en CP. L’étalonnage d’un tel système est enfin proposéThe aim of this dissertation is to assess the potential of a Synthetic Aperture Radar system operating in compact polarimetry mode at low frequency for polarimetric as well as polarimetry-interferometric applications. The compact polarimetry (CP) mode is a special case of dual polarimetry consisting in a unique polarization in transmission and two orthogonal polarizations in reception. Low frequencies allow applications such as vegetation parameters estimation and inversion of surface parameters. However, in a spatial context at low frequency, the propagation plane is rotated while crossing the ionosphere and this rotation is called the Faraday rotation (FR). A first objective is to deal with the estimation and correction of the FR which relies on the scattering properties of bare surfaces. The selection of the bare surfaces is based on a new parameter, the conformity coefficient, constructed from CP measurements. Once bare surfaces are selected, three methods to estimate the FR are suggested and applications are shown feasible, directly with CP data. Next, the calibration of such a system is suggested
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Christianto, Heru Ari. "Effect Of Chemical And Mineral Admixtures On The Fresh Properties Of Self Compacting Mortars." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605322/index.pdf.
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Fresh properties of mortars are important factors in altering the performance of self compacting concrete (SCC). Measurement of the rheological properties of the fine mortar part of concrete is generally used in the mix design of SCC. It can be stated that SCC rheology can be optimized if the fine mortar part of concrete is designed properly. However, measurement of the rheological properties is often impractical due to the need for complex equipment. Therefore, more practical methods of assessing mortar workability are often preferred.
In this study, four mineral admixtures, three superplasticizers (SP) and two viscosity modifying admixtures (VMA) were used to prepare self compacting mortar (SCM). The mineral admixtures included fly-ash, brick powder, limestone powder, and kaolinite. Two of the SPs were polycarboxylate based and another one was melamine formaldehyde based. One of the viscosity modifying admixtures was based on an aqueous dispersion of microscopic silica and the other one was based on high molecular weight hydroxylated polymer.
Within the scope of the experimental program, 43 mixes of SCM were prepared from different materials with keeping the amount of mixing water constant. Workability of the fresh mortar were determined using V - funnel and slump flow tests. The setting time of the mortars, were also determined. The hardened properties that were determined included the ultrasonic pulse velocity (UPV) and the strength which was determined at 7, 28, and 56 days.
It was concluded that among the mineral admixtures used, only fly-ash and limestone powder increased the workability of the mixes. The two polycarboxylate based SPs yield approximately the same workability and the melamine formaldehyde based SP was not as effective as the other two.
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Little, Lauren M. "INVESTIGATING THE EFFECT OF STRESS, WETTING, AND COMPACTION ON SETTLEMENT POTENTIAL OF MINE SPOILS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_theses/525.
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Strip mining in Kentucky has left large areas of land that could potentially be used for business and housing developments. However, the mine spoils underlying these areas are prone to severe differential settlement due to a variety of factors. Mine spoil from the Gateway Business Park in Jenkins, Kentucky was used for a series of laboratory tests to develop relationships between shear wave velocity, confining stress, compaction energy, and dry unit weight to develop a method to assess settlement potential. It was found that a stress-corrected shear wave velocity of greater than 275 ft/s/psi0.25 typically indicated dry mine spoil, and less than 275 ft/s/psi0.25 typically indicated wet mine spoil. Equations were developed to predict the amount of settlement of a mine spoil profile based on the load, the mine spoil lithology, and the shear wave velocity of the mine spoil. With regards to compaction, it was found that if the mine spoil was compacted to at least 120 pcf (18.8 kN/m3), or a void ratio of 0.45 or less, the mine spoil would suffer little to no volume change when wetted. The results provided herein form the basis of a methodology for screening mine spoil sites for development based on settlement potential.
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VALVERDE, VIVIANA TORRALBA. "EFFECT OF THE COMPACTION METHOD ON THE PERMEABILITY OF AN ORGANIC COMPOUND-COLLUVIONAR SOIL MIXTURE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9632@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO liner é um elemento de extrema importância no processo construtivo de um aterro sanitário, pois funciona como uma barreira capaz de impedir a percolação de agentes contaminantes através do subsolo. Os liners ou camadas impermeabilizantes são geralmente construídos a partir de materiais que possuem baixa permeabilidade. A escolha de um material adequado, assim como o controle dos processos construtivos são indispensáveis para garantir um bom desempenho da camada impermeabilizante. O processo de compactação é de extrema importância neste tipo de obra geotécnica. Os ensaios de compactação realizados em laboratório têm como objetivo reproduzir as condições de campo, no entanto, em numerosos casos há diferenças importantes entre os mecanismos de compactação utilizados, na preparação do material antes do processo de densificação e nas características das amostras, o que gera como conseqüência discrepâncias nos valores de permeabilidade de campo com os de laboratório. O objetivo principal do presente estudo é avaliar experimentalmente a influência de dois mecanismos diferentes de compactação (dinâmico, com o Proctor Normal e estático, com o método de compactação por pisoteamento) nos valores de permeabilidade de um solo coluvionar e de um composto orgânico para seu eventual uso em um liner. Os ensaios foram realizados em corpos de prova com diferentes teores de umidade, preparados com solo coletado no campo Experimental II da PUC-Rio, com composto orgânico produzido a partir do processo de compostagem da grama do Aeroporto Internacional Galeão (RJ), e com misturas em diferentes proporções de ambos os materiais.
The liner is one of the most important elements in a sanitary landfill project, since it works as a barrier capable to impede seepage of pollutant substances through the subsurface. This element is usually built with materials that have low permeability. The choice of the right material as well as the control and supervision of the constructive processes are fundamental to achieve a good liner performance. The compaction process is extremely important in this type of geotechnical impoundment. Laboratory compaction intends to reproduce the field conditions; however, in some cases, there happen to be important differences between the compaction mechanisms used, the preparation of the material before the densification process and the specimens characteristics, which cause discrepancies between the permeability values obtained in the field and the ones obtained in the laboratory. The main objective of this study is to evaluate experimentally the effect of two different compaction mechanisms (dynamic, with standard Proctor and static, with the kneading compaction method) in the hydraulic conductivity of a colluvionar soil and an organic compound for their eventual use in a liner. The tests were executed using specimens with different water contents, prepared with colluvionar soil extracted from the Experimental Field II at the PUC-Rio, with the organic compound, and with mixtures of both materials in different proportions.
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Esnaashari, Esfahani Rashin. "The effect of addition of a dry binder on compaction properties of dry granulated particles." Thesis, Uppsala universitet, Institutionen för farmaceutisk biovetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-451665.
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The purpose of this study was to examine the influence of content of a copovidone binder (0%, 5% and 10% w/w) and its addition method on compression and compaction properties of six MCCformulations following dry granulation. Briquetting was used to form dry granules for furthercharacterization. The mean yield pressure and fracture strength of granules were assessed at 300MPa on the basis of “in-die” Heckel and Adams model respectively. Then tablet tensile strengthof manufactured tablets was determined at 100 and 300 MPa. The results demonstrated thatintragranular addition of further binder (10%) to MCC could increase plasticity. However, therewas a drastic reduction in compactibility of dry granules mostly impacted by binding capacity ofthe binder. Generally, 5% intragranular:5% extragranular binder under a compaction pressure of300 MPa had the greatest binder efficacy on strength of pure MCC tablets while 10%extragranular binder improved tensile strength significantly at 100 MPa. PVP in a level of 5%w/w had no significant impact on tensile strength of tablets compacted at 100 and 300 MPa.
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Adawi, Seif Salim. "The long term effect of compaction and subsoiling on crop yield and soil physical properties." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291062005.
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Abusuwar, Awad Osman Mohmed 1952. "Land imprinting as an effective way of soil surface manipulation to revegetate arid lands." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/191107.
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Research was conducted over a 2-year period at the University of Arizona Campus and Oracle Agricultural Centers to evaluate the effectiveness of surface imprintation in revegetating arid lands. Introduction of forage leguminous species into arid rangelands through land imprintat ion was another objective of this study. The soil at the Campus Center is a Brasito, mixed thermic, typic torripsamment with a sandy-loam texture. This was compared with a White House, fine mixed thermic, Ustollic haplargid with a sandyloam texture at the Oracle Center. Natural rains were the only source of irrigation at Oracle. At the Campus Center, however, a sprinkler irrigation system was installed to match rains with that at the Oracle Center. Three cover treatments together with four surface treatments were used at both sites. The cover treatments included a pure stand of grasses, a pure stand of legumes, and a mixture of both grasses and legumes. The surface treatments were imprinted, mulched, imprinted-mulched, and an untreated surface as a check. Surface imprintation was performed by a land imprinter at Oracle and by a hand imprinter at Campus. The imprinted surface significantly increased soil moisture retention, number of plants per unit area, plant height, plant cover, and biomass compared to the untreated surface. At the Oracle Center, the imprinted surface improved legume germination by 800% over the untreated surface, and by 367% over the mulched one. Corresponding percentages at Campus were 48 and 4% over the untreated and the mulched surfaces, respectively. Increases in biomass production achieved through surface imprintation were 102% over the untreated surface and 35% over the mulched surface at the Oracle Center. Corresponding increases at Campus were 63 and 33% over the untreated and the mulched surfaces, respectively. Plants grown on imprinted surfaces exhibited higher transpiration rates, lower diffusive resistance, and cooler leaf temperature compared to those grown on the untreated surfaces. Addition of mulch to the imprinted surface made no significant differences with respect to the parameters measured when compared to the imprinted surface without mulch. When mulch was used as a separate treatment, however, it significantly increased the parameters measured over the untreated surface. The effect of cover treatments on growth parameters and biomass production was masked by seasonality. Grasses tended to be superior over legumes in samples taken during the fall and the opposite was true during the summer. Mixing legumes with grasses, however, resulted in significantly taller grasses compared to grasses grown as a pure stand.
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Gebremeskel, Kiflat Yohannes. "The effect of filler type and shape on HMA energy dissipation performance." Thesis, KTH, Väg- och banteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-127706.
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Hot mix asphalt pavements require adequate compaction to achieve the required density to resist rutting. The amount of energy required to achieve the optimum degree of compaction depends on the type of gradation, bitumen content, filler type and shape, type of compaction equipment etc. In this study, the net energy required to reduce the specimen volume (size) after each gyration of the superpave gyratory compactor is used as the compaction energy index (CEI) to measure the compactability of the samples. Samples with different filler types and content are used for the analysis. Effect of fillers on the viscosity of the mastic has been studied previously. Viscosity of mastics in return affects the compactability of the mix in general. In this regard this paper tries to study the effect of fillers on the compaction of hot mix asphalt with the help of the superpave gyratory compactor. Moreover, resistance of the asphalt mix samples against rutting is evaluated using the simple performance test. In this test, the sample is subjected to a hydraulic loading while strain transducers attached to the sample measure the displacement. A computer program receives the displacement data at various frequencies and calculates the dynamic modulus and flow number which are used for the evaluation of the pavement performance. :
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Regmi, Sanjeev. "EFFECT OF PLASTICITY AND INITIAL COMPACTION CONDITIONS ON SOIL WATER CHARACTERISTICS CURVE OF FINE-GRAINED SOILS." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2625.
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The soil water characteristics curve (SWCC) of a soil plays an important role in study of unsaturated soil mechanics. The behavior of unsaturated soil is a complex phenomenon to understand and the direct measurement of unsaturated soil properties in laboratory or in field is costly and time consuming. Knowing the SWCC of a soil is useful in estimating the unsaturated property of a soil, which is close to the natural soil conditions and can be used in effective design procedure. The present study deals with the effect of plasticity and initial compaction conditions of a soil in the SWCC by using SWC-150 (Fredlund SWCC device) and WP4C dewpoint potentiometer. The test data obtained from both the device were best fitted using Fredlund and Xing (1994) equation (FX), Van Genutchen (1980) equation (VG), Burdine (1958) equation, and Mualem (1976) equation.
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Kim, Chang Hyun. "APPROCHE PHYSIQUE DE LA MODÉLISATION COMPACTE POUR LES COMPOSANTS ÉLECTRONIQUES ORGANIQUES." Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00844519.
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En dépit de progrès impressionnants dans les performances des dispositifs électroniques organiques, il n'existe toujours pas de modèle théorique complet pour décrire leur mode opératoire. Cette thèse se propose d'établir une description théorique opérationnelle pour ces dispositifs, avec en ligne de mire leur modélisation physique et compacte. Des exemples typiques de structure de diodes et de transistors organiques avec différentes architectures ont été étudiés, avec une attention constante pour présenter les effets du transport et de l'injection des porteurs de charge sur les caractéristiques observables des dispositifs. Une attention particulière est donnée à l'intégration de ces modèles dans des outils de simulation de circuit, mettant ainsi en relation le dispositif isolé et son intégration dans un circuit. Les différentes approches comprennent la modélisation de circuit par spectroscopie d'impédance, le développement analytique d'équations physiques, la simulation numérique bi-dimensionnelle par éléments finis et leur validation expérimentale. Les résultats apportent une compréhension significative des effets des pièges et de la barrière d'injection sur les caractéristiques courant-tension. Nous proposons des modèles compacts entièrement analytiques pour les diodes redresseuses et les transistors à effet de champ dont la fiabilité numérique et expérimentale est prouvée.
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Ghomsheh, Habib Nadian. "Effects of soil compaction on growth and P uptake by Trifolium subterraneum colonised by VAM fungi /." Title page, Contents and Summary only, 1997. http://web4.library.adelaide.edu.au/theses/09ASOP/09asopg427.pdf.
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McDaniel, Christopher George. "The Dendritic Effect on Enantioselectivity of Organocatalytic Reactions and the Effect of Local Compaction on a Titanium Mediated Allylation of Aldehydes." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281293828.
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Ohu, John Olutunde. "Peatmoss influence on strength, hydraulic characteristics and crop production of compacted soils." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=71960.
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The quantitative effects of increasing the organic matter contents of three soils upon their susceptibility to compaction, the recovery of tilth after compaction and the fertility of the soils were investigated. These effects were further studied on the production of bush bean (Phaseolus vulgaris).Soil consistency limits, soil water status, applied pressure and organic matter contents were used to predict shear strength, penetration resistance and water retention characteristics of compacted soils, with the aim of meeting the widespread demand for possible techniques of soil compaction prediction.
Soil compaction increased the ability of the soils to retain moisture, increased penetration resistance, shear strength and decreased the available water capacity of soils. On the other hand, organic matter increased the ability of the soils to retain moisture, expanded the available water capacity and decreased the penetration resistance and shear strength of compacted soils.
Although soil compaction increased the stem diameter of bush bean; the height, yields and root dry matter of the crop decreased with higher compaction levels. On the contrary, higher organic matter levels increased the plant and yield parameters of the crop.
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Lokre, Chinmay Vivekananda. "Effect of Density, Initial Water Content, Drying Temperature, Layer Thickness, and Plasticity Characteristics on Shrinkage Crack Development in Clay Soils: An Experimental Study." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1557423451910154.
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Cousin, Bastien. "Modélisation compacte de transistors à effet de champ nanofils pour la conception de circuits." Grenoble INPG, 2010. http://www.theses.fr/2010INPG0064.
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L'objectif de ce travail de thèse s'articule autour du développement d'un modèle compact du transistor GAA nanofil cylindrique. L'objectif est ici de reproduire le comportement électrique du transistor à travers un modèle afin que celui-ci soit utilisable en conception de circuits. Le transistor est considéré tout d'abord comme idéal c'est-à-dire sans effets parasites afin de constituer le cœur du modèle compact. L'étude porte ensuite sur la modélisation des effets de confinement quantique. Une correction quantique avec prise en compte à la fois des confinements structurels et électriques des porteurs dans le silicium est alors proposée et insérée dans le cœur du modèle compact. L'étude concerne ensuite la modélisation des effets de canaux courts, phénomènes parasites associés à la réduction de longueur de grille du transistor. Puis, plusieurs effets physiques spécifiques tels que les courants de fuite de grille, le GIDL, la résistance série et la dégradation de la mobilité sont traités et implémentés dans le cœur du modèle. Enfin, des résultats de mesures expérimentales permettent la validation du modèle completThe aim ofthis the sis is to develop a compact model for the cylindrical GAA MOSFET transistor. The objective is to reproduce the electrical behavior of the transistor through a predictive model which could be used for circuit simulations. The transistor is considered first as an ideal device that is to say without any parasitic effects in order to form the model core. Subsequently, the study focuses on the modeling of quantum-mechanical effects. A quantum correction, which takes into account both structural and electrical confinement of carriers in silicon, is then proposed and implemented into the model core. Afterwards, the study concerns the modeling of short channel effects, which are associated to the reduction of the transistor gate length. Moreover, several parasitic effects such as gate leakage currents, GIDL, series resistance and mobility degradation are modeled separately and implemented into the model core. Finally, experimental data measurements lead to the validation of the whole compact model
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Jung, Sungyeop. "Physically-Based Compact Modelling of Organic Electronic Devices." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX115/document.
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En dépit d'une amélioration remarquable de la performance des composants électroniques organiques, il y a encore un manque de compréhension théorique rigoureux sur le fonctionnement du composant. Cette thèse est consacrée à la création de modèles pratiques pour composants électroniques organiques à base physique complet, à savoir un modèle compact à base physique. Un modèle compact à base physique d'un élément de circuit est une équation mathématique qui décrit le fonctionnement du composant, et est généralement évaluée par trois critères: si elle est suffisamment simple pour être incorporé dans des simulateurs de circuits, précise pour rendre le résultat des simulateurs utile les concepteurs de circuits et rigoureux pour capturer des phénomènes physiques se produisant dans le composant. Dans ce contexte, les caractéristiques distinctives de l'injection de porteurs de charge et de transport dans les semi-conducteurs organiques sont incorporés dans les modèles avec un effort particulier pour maintenir la simplicité mathématique. L'effet concomitant sur les caractéristiques courant-tension des diodes et des transistors organiques prototypiques sont étudiés. Les méthodes d'extraction des paramètres cohérents aux modèles sont présentés qui permettent la détermination univoque des paramètres de le composant utilisé pour le fonctionnement du composant de modélisation et l'évaluation des performances de le composant et les propriétés des couches minces et des interfaces organiques. Les approches englobent le developement analytique des équations physiques, la simulation numérique à deux dimensions basé sur la méthode des éléments finis et la validation expérimentale. Les modèles compacts originaux et entièrement analytiques et des méthodes d'extraction de paramètres fournissent une compréhension fondamentale sur la façon dont le désordre énergétique dans une couche mince de semi-conducteur organique, décrit par la densité d’etats Gaussienne, affecte les caractéristiques courant-tension observables des composants.Mots-clés : Electronique organique, physique des composants électroniques, modélisation analytique, diodes, transistors à effet de champ, densité d’etats GaussienneIn spite of a remarkable improvement in the performance of organic electronic devices, there is still a lack of rigorous theoretical understanding on the device operation. This thesis is dedicated to establishing practical models of organic electronic devices with a full physical basis, namely a physically-based compact model. A physically-based compact model of a circuit element is a mathematical equation that describes the device operation, and is generally assessed by three criteria: whether it is sufficiently simple to be incorporated in circuit simulators, accurate to make the outcome of the simulators useful to circuit designers, and rigorous to capture physical phenomena occuring in the device. In this context, distinctive features of charge carrier injection and transport in organic semiconductors are incorporated in the models with a particular effort to maintain mathematical simplicity. The concomitant effect on the current-voltage characteristics of prototypical organic diodes and transistors are studied. Parameter extraction methods consistent to the models are presented which enable unambiguity determination of device parameters used for modeling device operation and assessing device performance and properties of organic thin-films and interfaces. The approaches encompass analytical developement of physical equations, two-dimensional numerical simulation based on finite-element method and experimental validation. The original and fully analytical compact models and parameter extraction methods provide fundamental understanding on how energetic disorder in an organic semiconductor thin-film, described by the Gaussian density of states, affects the observable current-voltage characteristics of the devices.Keywords : Organic electronics, device physics, analytical modeling, diodes, field-effect transistors, Gaussian density-of-states
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Sylla, Diaguely 1951. "EFFECT OF MICROPHYTIC CRUST ON EMERGENCE OF RANGE GRASSES." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276554.
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Field and greenhouse studies were conducted in 1986 and 1987 to determine the impact of disturbance of microphytic soil crust on emergence of two warm season grass species. In the greenhouse, emergence of seedlings sown on the top of undisturbed crust, under the crust, on disturbed crust, and on bare soil was studied. The mean number of seedlings of "Cochise" lovegrass (Eragrostis lehmanniana x Eragrostis tricophora) and Kleingrass (Panicum coloratum) was higher on disturbed field plots than undisturbed plots. Disturbance reduced the microphytic crust cover, and the crust did not recover throughout the growing season. Presence of seedlings in samples of litter washed off the plots and observation on ants showed that all the seeds sown did not remain on the plots during the growing season. In greenhouse flats the emergence of seedlings of both species was greater on disturbed microphytic crust and bare soil than when seeded on top of or under an intact crust. Undisturbed crust restricted penetration of roots and shoots when seeds were placed on or under the crust.
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Enferad, Shirin. "Compactage et vieillissement des poudres : influence de la formulation." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0214.
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Cette étude est menée dans le cadre du projet "PowderReg", financé par le programme européen Interreg VA GR dans le cadre de l'axe prioritaire 4 "Renforcer la compétitivité et l'attractivité de la Grande Région / Groβregion". La compréhension du lien entre l'organisation microscopique et le comportement de l'écoulement des poudres est une avancée majeure dans l'établissement de critères pour optimiser leurs propriétés de transport, de stockage et de traitement. Ainsi, une meilleure compréhension du comportement de l'écoulement des poudres évite aux industries d'énormes pertes économiques. Il est donc essentiel d'évaluer leur aptitude à l'écoulement. Ce travail consiste à étudier expérimentalement l'influence de la formulation des poudres, de la taille des particules, ainsi que l'influence des conditions environnementales telles que l'humidité sur les comportements d'écoulement des poudres. Cinq types de formulations ont été analysés: la bille de verre témoin a été utilisée comme poudre de référence et trois types de formulations de surface consistant en un enrobage hydrophile, hydrophobe et de lactose ainsi qu'une poudre de lactose agglomérée ont été préparés. Tout d'abord, l'influence de deux tailles différentes, 100 et 500 µm, sur le comportement d'écoulement des poudres a été analysée. Ensuite, le comportement de l'écoulement des poudres a été étudié avec différents équipements expérimentaux: FT4, Granutools et rhéomètre Discover HR3. Y compris différentes techniques, telles que la cellule de cisaillement, la compressibilité, l'angle de rotation du repos, etc. L'objectif était de déterminer le comportement des poudres dans différentes conditions de traitement. Les résultats ont montré que le passage d'une technique à l'autre peut modifier la classification de la fluidité des poudres. Comme les poudres subissaient des contraintes mécaniques différentes. Dans la dernière partie de cette thèse, nous avons observé l'influence impressionnante de l'humidité après 80 % sur le comportement d'écoulement de deux tailles différentes de billes de verre de contrôle (40 et 100 µm). Les perles de verre de petit diamètre ont montré une fluidité plus faible qui est due au plus grand nombre de contacts de surface de ces particules. De plus, la comparaison du comportement d'écoulement des billes de verre de contrôle et hydrophobes de taille 100 µm à un taux de cisaillement élevé a révélé la même fluidité pour les deux échantillons. Alors qu'à faible taux de cisaillement, les mesures par rhéologie vibratoire ont révélé une fluidité plus élevée dans les billes de verre de contrôle. La fluidité de la perle de verre témoin a diminué de façon spectaculaire après 80 % de contrôle de l'humidité, mais la perle de verre hydrophobe a conservé son comportement d'écoulement comme auparavant avec une très faible sensibilité à l'humidité. Enfin, l'influence de l'ajout d'une petite quantité d'eau sur le comportement d'écoulement de la bille de verre de contrôle a été étudiéeThis study is conducted in the framework of the “PowderReg” project, funded by the European program Interreg VA GR within the priority axis 4 “Strengthen the competitiveness and the attractiveness of the Grande Région Groβregion”. Understanding the link between microscopic organization and powders flow behavior is a major step forward in establishing criteria for optimizing their transport, storage and processing properties. Whereby, better understating of powder flow behavior saves the industries from huge economic loss. Therefore, it is essential to evaluate their flowability. This work consists in experimentally studying the influence of powder formulation, particle size, as well as influence of environmental condition such as humidity on flow behaviors of powders. Five types of formulations have been analyzed: control glass bead has been used as reference powder and three types of surface formulations consisting of hydrophilic, hydrophobic and lactose coating as well as agglomerated lactose powder have been prepared. First, influence of two different sizes 100 and 500 µm on flow behavior of powders has been analyzed. Then, the powders flow behavior has been considered with different experimental equipements: FT4, Granutools and Rheometer Discover HR3. Including different techniques, such as shear cell, compressibility, rotating angle of repose, etc. The objective was to figure out the behavior of powders under different processing conditions. The, results reported that the transition from one technique to another can modify the classification of the powder flowability. Since the powders were experiencing different mechanical stresses. At the last part of this thesis, we observed the impressive influence of humidity after 80 % on flow behavior of two different size of control glass beads (40 and 100 µm). Small diameter glass bead showed lower flowability which is due to the more surface contacts of these particles. Furthermore, the comparison of flow behavior of control and hydrophobic glass beads with 100 µm size at high shear rate reported the same flowability for both samples. While at low shear rate measurements by vibrational rheology revealed higher flowability in control glass bead. The flowability of control glass bead decreased dramatically after 80 % of humid control, however hydrophobic formulated glass bead kept its flow behavior like as before with very low sensitivity to humidity. Finally, influence of addition of small quantity of water on flow behavior of control glass bead has been investigated
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Philipson, Harald. "The effect of thickness and compaction on the recovery of aluminium in recycling of foils in salt flux." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280048.
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In Norway, more than 40.000 tonnes of aluminum (Al) in food packaging goes to incineration annually. Recycling this waste would save more than 1.5 TWh of energy and several hundred thousand tonnes of CO2 emissions. However, recycling thin aluminum foil in small packaging is more difficult than recycling of larger and cleaner scrap. In this thesis, properties of compacted coating-free Al foil with five different thicknesses (15, 30, 100, 200, 300 𝜇𝜇m) were investigated and related to percentage Al recovery during remelting in salt flux. This thesis consists of five main parts. Two initial studies involved shredding of the foil into a controlled chip size and compaction of these chips to briquettes of a wide range of bulk densities using three types of compaction techniques. In the following two studies, relevant briquette properties and oxidation behavior were determined. Finally, chips and briquettes were melted in salt flux and the percentage Al recovery was calculated. The bulk density, porosity and surface areas of the briquettes were significantly influenced by the type of compaction technique. Applied torque and heat in addition to uniaxial pressing were found to be effective measures to increase bulk density. Oxidation was higher for thin Al foil due to higher specific surface area and micro roughness. However, the oxidation of briquettes significantly decreased as the bulk density exceeded 2.4 g/cm3. Briquetting led to significantly increased recovery of the two thinnest foils. For the three thickest foils the effect of briquetting was smaller. For the thinnest foil, recovery increased with compaction. For this foil, even significantly oxidized chips compacted to bulk density 2.6 g/cm3 resulted in 99-100 % recovery. The specific surface area of the aluminum was the most important material property influencing recovery. It is expected that an optimum amount of salt flux and fluoride contentrelated to specific surface area of the scrap can be developed.I Norge förbränns mer än 40 000 ton aluminiumförpackningar årligen. Återvinning av denna mängd aluminiumförpackningar skulle spara 1,5 TWh energi och hundratusentals ton av koldioxidutsläpp. Det mycket svårare att återvinna tunn aluminiumfolie i förpackningar än större och renare aluminiumskrot. I denna uppsats har egenskaper hos komprimerad beläggningsfri aluminiumfolie med fem olika tjocklekar (15, 30, 100, 200, 300 𝜇𝜇m) bestämts. Dessa egenskaper är sedan till kopplade till återvinningsgraden efter smältning i saltfluss. Uppsatsen består av fem huvuddelar. I de två inledande delarna strimlas foliet till en bestämd spånstorlekt varpå dessa komprimeras med tre olika presstekniker till briketter av olika bulkdensiteter. I de nästa två delarna bestäms relevanta brikettegenskaper och oxidationsbeteendet. I den sista delen bestäms återvinningsgraden av spån och briketter som smälts i saltfluss. Briketternas bulkdensitet, porositet och ytarea varierade beroende på pressningsteknik. Högtryckvridning under tillförd värme var ett effektivt sätt att öka bulkdensiteten. Tunnare folie oxiderade mera på grund av stor specifik ytarea och hög mikrosträvhet. Oxidationsgraden för briketter med bulkdensitet över 2.4 g/cm3 var betydligt lägre än briketter med lägre bulkdensitet. Briketter av de två tunnaste folierna ledde till högre återvinningsgrad jämfört med motsvarande spån. Effekten av kompression på återvinningsgraden var mindre för de tre tjockaste folierna. Återvinningsgraden ökade med ökad kompression för det tunnaste foliet. Trots att denna folie oxiderades relativt mycket var återvinningsgraden 99-100 % efter kompression till 2.6 g/cm3. Resultatet indikerar på att främst specifika ytarean påverkar återvinningsgraden av aluminiumet. Baserat på den föreslagna teorin borde ett optimum avsaltmängd, fluorinnehåll och ytarea skrot kunna utvecklas för att maximera återvinningsgraden.
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Tricot, Francois. "Analyse et réduction des sources d'instabilitè de fréquence dans une horloge CPT compacte." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS037/document.
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Ce travail de thèse effectué dans le cadre d’un contrat CIFRE-Défense porte sur l’étude des sources d’instabilité de fréquence d’une horloge atomique basée sur le piégeage cohérent de population. L’objectif est de démontrer une stabilité de fréquence d’horloge de l’ordre de 10-13 tau-1/2 jusque 10 000 s. Une cellule de vapeur de césium est utilisée avec un schéma d’excitation à fort contraste en utilisant des polarisations linéaires croisées et avec une interrogation impulsionnelle de type Ramsey. Un chapitre d’abord consacré aux sources de bruit à court terme présente les travaux réalisés pour réduire le bruit de phase et le bruit de puissance laser, limitant tous deux les performances de l’horloge à 1 s d’intégration. L’optimisation de la chaine micro-onde avec un nouvel oscillateur local, et la réalisation d’un asservissement de puissance performant ont permis d’améliorer la stabilité de fréquence à 2,3x10-13 à 1 s. L’analyse des fluctuations des paramètres de fonctionnement (puissance laser, champ magnétique, température, etc.) et la mesure de la fréquence d’horloge montrent que les variations de fréquence à moyen terme sont majoritairement limitées par les variations de puissance laser et celles du champ magnétique à 2x10-14 à 2 000 s. Ces analyses démontrent aussi que les fluctuations de puissance laser, malgré l’asservissement, sont liées aux fluctuations de polarisation via les fluctuations de température de l’expérience. Pour finir, les études d’un laser bifréquence et bipolarisation pour une horloge CPT compacte sont présentées, ouvrant la voie vers l’industrialisation en réduisant le banc optiqueThis thesis work has been granted by a CIFRE-Défense contract to study the frequency stabilities of an atomic clock based on coherent population trapping. The objective is to demonstrate a frequency stability in the range of 10-13 tau-1/2 up to 10 000 s. A caesium vapour cell is used with a high-contrast excitation scheme using cross linear polarisations and a Ramsey interrogation. The short-term frequency stability is presented with the reduction of the phase and the laser power noise, both limiting clock performance at 1 s integration time. The optimisation of the microwave chain with a new local oscillator, and the implementation of a very low noise power lock loop have improved the frequency stability down to 2,3x10-13 at 1 s integration time. The fluctuations analysis of the operating parameters (laser intensity, magnetic field, temperature, etc.) and the measurement of the clock frequency show that the medium-term frequency instability is mostly limited by laser power and magnetic field fluctuations at the level of 2x10-14 at 2 000 s integration time. These analyses also show that laser power fluctuations, despite servo loop control, are related to polarisation fluctuations through temperature fluctuations inside the experiment isolation box. Finally, the studies of a dual-frequency and dual-polarisation laser for a compact CPT clock are presented, paving the way to industrialisation by reducing the optical bench
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Truong-Loi, My-Linh. "Potentiels d'un système RSO basse fréquence opérant en polarimétrie compacte." Phd thesis, Université Rennes 1, 2010. http://tel.archives-ouvertes.fr/tel-00559529.
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Le but de ce travail de thèse est d'évaluer le potentiel d'un système Radar à Synthèse d'Ouverture (RSO) ou Synthetic Aperture Radar (SAR) en anglais, opérant en mode de polarimétrie compacte à basse fréquence pour des applications polarimétriques et interféro-polarimétriques. Cette thèse s'inscrit dans le projet de mission BIOMASS de l'Agence Spatiale Européenne qui propose la mise en orbite d'un instrument SAR en bande P pour suivre la dynamique de la biomasse terrestre à l'échelle globale, et d'autres missions spatiales futures dont l'objectif est d'étudier les changements environnementaux globaux telles que DESDynI (Deformation, Ecosystem Structure and Dynamics of Ice) et SMAP (Soil Moisture Active and Passive) pour le Jet Propulsion Laboratory (JPL) et Saocom (SAtélite Argentino de Observación COn Microondas) pour l'Agence Spatiale Argentine. La polarimétrie compacte est un cas particulier de la polarimétrie duale consistant en une polarisation d'émission unique et deux polarisations orthogonales à la réception. Trois configurations ont été suggérées : le mode π/4, le mode π/2 et le mode hybride (cas particulier du mode π/2). Il est important de noter qu'il s'agit ici d'un mode dual-pol spécifique où la phase relative entre les deux canaux de réception est conservée. La première partie de cette thèse introduit les concepts de base du système SAR, les notions de polarimétrie, interférométrie, interférométrie SAR polarimétrique, polarimétrie compacte et les motivations justifiant la volonté de mettre en œuvre un système compact-pol. Les basses fréquences permettent de réaliser des applications telles que l'estimation de paramètres liés à la végétation et l'inversion de paramètres de surface. Cependant, dans un contexte spatial en basse fréquence, le plan de propagation subit une rotation lors de la traversée de la couche ionosphérique appelée rotation de Faraday (RF). L'objectif de la deuxième partie de cette thèse est donc d'étudier l'estimation et la correction de la RF reposant sur les propriétés de rétrodiffusion des surfaces nues, avec un système opérant en polarimétrie compacte. La sélection des surfaces nues est basée sur un nouveau paramètre, appelé coefficient de conformité et construit à partir des mesures compact-pol. Une fois les sols nus sélectionnés, trois méthodes d'estimation de la RF utilisant des données compact-pol sont proposées. La troisième partie de cette thèse porte sur la possible inversion de l'humidité du sol, et l'estimation de la biomasse et la hauteur de la végétation à partir de données compact-pol. Nous montrons que l'algorithme standard de Dubois et al. de 1995 peut être directement appliqué à l'aide des données en polarimétrie compacte sur des surfaces nues afin d'y estimer l'humidité. Ensuite, l'estimation de la biomasse aérienne des forêts à partir de données en polarimétrie compacte est testée. Finalement, le concept d'interférométrie est ajouté à la polarimétrie compacte afin d'évaluer le potentiel d'un système compact-PolInSAR à estimer la hauteur de la végétation. Après avoir démontré le potentiel de la polarimétrie compacte pour certaines applications, nous analysons les implications système. Pour cela, les possibilités d'étalonner un tel système sont étudiées en considérant le déséquilibre de canal et la mauvaise isolation entre les canaux associés à la rotation de Faraday, et une procédure utilisant trois cibles externes est proposée. Enfin, l'équivalence entre les données compact-pol simulées à partir des données complètes et les données compact-pol construites à partir de données brutes est démontrée, confirmant la propriété de linéarité du processeur SAR. Ce travail et les techniques présentées tout au long de cette étude ont été simulés et testés à l'aide de données RAMSES en bande P et L, SETHI en bande L, PALSAR en bande L et AIRSAR en bande L.
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Najari, Montassar. "Modélisation compacte des transistors à nanotube de carbone à contacts Schottky et application aux circuits numériques." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00560346.
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Afin de permettre le développement de modèles manipulables par les concepteurs, il est nécessaire de pouvoir comprendre le fonctionnement des nanotubes, en particulier le transport des électrons et leurs propriétés électroniques. C'est dans ce contexte général que cette thèse s'intègre. Le travail a été mené sur quatre plans : • Développement de modèles permettant la description des phénomènes physiques importants au niveau des dispositifs, • Expertise sur le fonctionnement des nano-composants permettant de dégager les ordres de grandeurs pertinents pour les dispositifs, les contraintes, la pertinence de quelques procédés de fabrication (reproductibilité, taux de défauts), • Collection de caractéristiques mesurées et développement éventuel d'expériences spécifiques, • Expertise et conception des circuits innovatifs pour l'électronique numérique avec ces nano-composants. Mots clés — Modélisation compacte, transistor Schottky à nanotube de carbone, simulation circuit, cellule mémoire SRAM, effet tunnel, WKB.
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Lu, Thanh-Chi. "Structure superficielle des poudres de superalliages base nickel et mécanismes intervenant au cours de la densification." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0074.
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Role de la structure des surfaces de poudre avant la compaction isostatique a chaud et son evolution au cours de la consolidation. Influence des caracteristiques morphologiques et microstructurales sur la cinetique de consolidation et sur le comportement mecanique des materiaux compactes
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Rostand, Neil. "Modélisation compacte de l'effet des radiations naturelles des dispositifs sub-28nm pour des applications automobiles et aéronautiques." Thesis, Toulouse, ISAE, 2019. http://www.theses.fr/2019ESAE0035.
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L’objectif de cette thèse était le développement de modèles SET (Single Event Transient) et TID (Total Ionizing Dose) pour les MOSFETs de technologies fortement intégrées, reposant notamment sur la technologie SOI. Ces modèles devaient respecter les standards de la modélisation compacte afin d’assurer leur utilisation dans les simulateurs de circuits SPICE (ELDO, SPECTRE, PSPICE …) tout en assurant la justesse du contenu physique. Le langage d’implémentation est alors le Verilog-A. En 1A, l’investigation physique des SET a été effectuée à l’aide de simulations TCAD. Cette tâche a supporté le développement d’un premier modèle physique SET (validé par la TCAD) adapté aux technologies BULK.En 2A, le modèle physique a été rendu compact et implémenté en Verilog-A. Ce travail a nécessité le développement d’une méthode d’implémentation faisant appel à la considération d’un circuit électrique équivalent au phénomène SET. Le modèle ainsi implémenté en SPICE a été capable de prédire l’occurrence de SEUs (Single Event Upset) dans les mémoires et des erreurs plus fonctionnelles dans les registres à décalage. En parallèle, l’investigation physique du TID a été effectuée à l’aide simulations TCAD. Par ailleurs, les effets TID ont été modélisés et implémentés dans le modèle standard compact LETI – UTSOI décrivant le fonctionnement des transistors FDSOI. Le modèle a été validé à l’aide de simulations TCAD et a été utilisé pour extraire les paramètres TID sur des MOSFETs FDSOI irradiés au CEA/DAM.En 3A, un modèle compact SET pour technologies fortement intégrées (reposant sur la technologie SOI) a été développé. Ce modèle prend en compte l’amplification bipolaire inhérente à ce type de structure ainsi que la morphologie 3D de la charge générée par la particule ionisante. Des validations TCAD de ce modèle ont été effectuées. Par ailleurs, ce modèle SET a été interfacé avec le simulateur multi-physiques MUSCA SEP3 afin d’estimer le risque SEE sur des matrices mémoires FDSOI. L’apport du modèle SET a été mis en évidence dans la fiabilité de cette estimationThe purpose of the PhD was to develop "Single Event Transient"(SET) and "Total Ionizing Dose" (TID) models for sub-28nm MOS technologies. These models have been developed according to standards of compact modeling in order to be used into SPICE simulators (ELDO, SPECTRE, PSPICE ...) while main physical features are taken into account. The implementation has been done in Verilog-A langage.During the first year, SET physical investigation has been done performing TCAD simulations. It supported model development of SET applied to BULK technologies. During the second year, this model has been turned into a compact model and implemented in Verilog-A, which required the development of an implementation method involving equivalent electrical circuit. The resulting model has been able to predict "Single Event Upsets" (SEUs) in memories and functional errors in shift registers. Moreover, physical investigation of TID has been performed through TCAD simulations of FDSOI MOSFETs. TID effects have been included into standard FDSOI transistor model LETI-UTSOI. The model has been validated through TCAD simulations and has been used to extract TID parameters on experimental devices irradiated in CEA/DAM. The third year has been partly dedicated to SET model development for very integrated technologies (relying on SOI technology).This model takes bipolar amplification into account as well as 3D charge deposit morphology induced by the ionizing particle. TCAD validations have been performed in order to validate the model. Moreover, this model has been included into multi-physics simulator MUSCA SEP3 in order to assess SEE risk in FDSOI memory matrix. it has been found that the physical features the model is able to model can influence reliability of this assessment
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Wang, Zhaohao. "Modélisation compacte et conception de circuit à base de jonction tunnel ferroélectrique et de jonction tunnel magnétique exploitant le transfert de spin assisté par effet Hall de spin." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS036/document.
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Les mémoires non-volatiles (MNV) sont l'objet d'un effort de recherche croissant du fait de leur capacité à limiter la consommation statique, qui obère habituellement la réduction des dimensions dans la technologie CMOS. Dans ce contexte, cette thèse aborde plus spécifiquement deux technologies de mémoires non volatiles : d'une part les jonctions tunnel ferroélectriques (JTF), dispositif non volatil émergent, et d'autre part les dispositifs à transfert de spin (TS) assisté par effet Hall de spin (EHS), approche alternative proposée récemment pour écrire les jonctions tunnel magnétiques (JTM). Mon objectif est de développer des modèles compacts pour ces deux technologies et d'explorer, par simulation, leur intégration dans les circuits non-volatiles.J'ai d'abord étudié les modèles physiques qui décrivent les comportements électriques des JTF : la résistance tunnel, la dynamique de la commutation ferroélectrique et leur comportement memristif. La précision de ces modèles physiques est validée par leur bonne adéquation avec les résultats expérimentaux. Afin de proposer un modèle compatible avec les simulateurs électriques standards, nous j'ai développé les modèles physiques mentionnés ci-dessus en langue Verilog-A, puis je les ai intégrés ensemble. Le modèle électrique que j'ai conçu peut être exploité sur la plate-forme Cadence (un outil standard pour la simulation de circuit). Il reproduit fidèlement les comportements de JTF. Ensuite, en utilisant ce modèle de JTF et le design-kit CMOS de STMicroelectronics, j'ai conçu et simulé trois types de circuits: i) une mémoire vive (RAM) basée sur les JTF, ii) deux systèmes neuromorphiques basés sur les JTF, l'un qui émule la règle d'apprentissage de la plasticité synaptique basée sur le décalage temporel des impulsions neuronale (STDP), l'autre mettant en œuvre l'apprentissage supervisé de fonctions logiques, iii) un bloc logique booléen basé sur les JTF, y compris la démonstration des fonctions logiques NAND et NOR. L'influence des paramètres de la JTF sur les performances de ces circuits a été analysée par simulation. Finalement, nous avons modélisé la dynamique de renversement de l'aimantation dans les dispositifs à anisotropie perpendiculaire à transfert de spin assisté par effet Hall de spin dans un JTM à trois terminaux. Dans ce schéma, deux courants d'écriture sont appliqués pour générer l'EHS et le TS. La simulation numérique basée sur l'équation de Landau-Lifshitz-Gilbert (LLG) démontre que le délai d'incubation de TS peut être éliminé par un fort EHS, conduisant à la commutation ultra-rapide de l'aimantation, sans pour autant requérir une augmentation excessive du TS. Nous avons appliqué cette nouvelle méthode d'écriture à la conception d'une bascule magnétique et d'un additionneur 1 bit magnétique. Les performances des circuits magnétiques assistés par l'EHS ont été comparés à ceux écrits par transfert de spin, par simulation et par une analyse fondée sur le modèle théoriqueNon-volatile memory (NVM) devices have been attracting intensive research interest since they promise to solve the increasing static power issue caused by CMOS technology scaling. This thesis focuses on two fields related to NVM: the one is the ferroelectric tunnel junction (FTJ), which is a recent emerging NVM device. The other is the spin-Hall-assisted spin-transfer torque (STT), which is a recent proposed write approach for the magnetic tunnel junction (MTJ). Our objective is to develop the compact models for these two technologies and to explore their application in the non-volatile circuits through simulation.First, we investigated physical models describing the electrical behaviors of the FTJ such as tunneling resistance, dynamic ferroelectric switching and memristive response. The accuracy of these physical models is validated by a good agreement with experimental results. In order to develop an electrical model available for the circuit simulation, we programmed the aforementioned physical models with Verilog-A language and integrated them together. The developed electrical model can run on Cadence platform (a standard circuit simulation tool) and faithfully reproduce the behaviors of the FTJ.Then, using the developed FTJ model and STMicroelectronics CMOS design kit, we designed and simulated three types of circuits: i) FTJ-based random access memory (FTRAM), ii) two FTJ-based neuromorphic systems, one of which emulates spike-timing dependent plasticity (STDP) learning rule, the other implements supervised learning of logic functions, iii) FTJ-based Boolean logic block, by which NAND and NOR logic are demonstrated. The influences of the FTJ parameters on the performance of these circuits were analyzed based on simulation results.Finally, we focused on the reversal of the perpendicular magnetization driven by spin-Hall-assisted STT in a three-terminal MTJ. In this scheme, two write currents are applied to generate spin-Hall effect (SHE) and STT. Numerical simulation based on Landau-Lifshitz-Gilbert (LLG) equation demonstrates that the incubation delay of the STT can be eliminated by the strong SHE, resulting in ultrafast magnetization switching without the need to strengthen the STT. We applied this novel write approach to the design of the magnetic flip-flop and full-adder. Performance comparison between the spin-Hall-assisted and the conventional STT magnetic circuits were discussed based on simulation results and theoretical models
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Mattsson, Sofia. "Pharmaceutical binders and their function in directly compressed tablets : Mechanistic studies on the effect of dry binders on mechanical strength, pore structure and disintegration of tablets." Doctoral thesis, Uppsala University, Department of Pharmacy, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-533.
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In this thesis, the strength-enhancing mechanisms of dry binders in direct compression were studied. The systems investigated were binary mixtures containing various compounds and binders. Among the binders used were a series of different molecular weights of polyethylene glycol. The proposed simplified tablet model describing the fracture path in a tablet during strength testing offers an explanation for the increase in tablet strength caused by the binder. The model and results in this thesis indicate that fractures will usually propagate around the tablet particles and through the interparticulate voids during tablet strength testing.
One important characteristic of the binder is its ability to be effectively and evenly distributed through the interparticulate voids in a compound tablet. Characteristics such as high plasticity, low elasticity and a small particle size were associated with a more even distribution and a consequent pronounced effect on pore structure and marked improvement in tablet strength. The strength of tablets containing less plastic binders was governed more by the compactibility of the binder. The tablet porosity, bonding mechanisms and volume reduction mechanisms of the compound also influenced the effect of the binder. For example, the plasticity and particle size of the binder had the most significant effects on tablet strength when the tablet porosity of the com-pound was relatively low. A combination of the plasticity and the compactibility of the binder determined the strength of tablets when the tablet of a compound was more porous. The positive effect of a binder on pore structure and tablet strength resulted in an increase in the disintegration time. Although addition of a superdisintegrant generally improved the disintegration time, the effect was decreased when the formulation included more deformable binders.
The choice of a suitable binder for a tablet formulation requires extensive knowledge of the relative importance of binder properties for enhancing the strength of the tablet and also of the interactions between the various materials constituting a tablet. Thus, the increased knowledge of the functionality of a binder obtained in this thesis enables a more rational approach to tablet formulation.
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Almuwbber, Omar Mohamed. "The effect of different Ordinary Portland cement binders, partially replaced by fly ash and slag, on the properties of self-compacting concrete." Thesis, Cape Peninsula University of Technology, 2015. http://hdl.handle.net/20.500.11838/1040.
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Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Civil Engineering in the Faculty of Engineering at the Cape Peninsula University of TechnologySelf-compacting concrete (SCC) is a flowable self-consolidating concrete which can fill formwork without any external vibration. A self-compacting concrete mix requires the addition of superplasticiser (SP), which allows it to become more workable without the addition of excessive water to the mixture. The effect of different CEM I 52.5N cements produced by one company at different factories on self-compacting concrete was investigated. The properties of SCC are highly sensitive to changes in material properties, water content and addition of admixtures. For self-compacting concrete to be more accepted in South Africa, the effect that locally sourced materials have on SCC, partially replaced with extenders, needs to be investigated. The European guidelines for SCC (2005) determined the standard, through an extensive study, for the design and testing of self-compacting concrete. Using these guidelines, the properties of self-compacting concrete with the usage of local materials were investigated. The effect on SCC mixes was studied by using four cements; two types of SPs – partially replaced with two types of fly ash; and one type of slag. Mix design and tests were done according to the European Specification and Guidelines for Self-Compacting Concrete (2005). Using locally sourced materials (different cements, sand, coarse aggregate, fly ashes and slag), mixes were optimised with different SPs. Optimisation was achieved when self-compacting criteria, as found in the European guidelines, were adhered to, and the binders in these required mixes were then partially replaced with fly ash and slag at different concentrations. Tests done were the slump flow, V-funnel, L-box, sieve segregation resistance as well as the compressive strength tests. The results obtained were then compared with the properties prescribed by the European guidelines. The cements reacted differently when adding the SPs, and partially replacing fly ash and slag. According to the tests, replacing cement with extenders – in order to get a sufficient SCC – seemed to depend on the chemical and physical properties of each cement type, including the soluble alkali in the mixture, C3A, C3S and the surface area. The range, in which the concentration of these chemical and physical cement compounds should vary – in order to produce an acceptable SCC partially replaced by extenders – was determined and suggested to the cement producer. The main conclusion of this project is that cement properties vary sufficiently from factory to factory so as to influence the performance of an SCC mix. The problem becomes even bigger when such cements are extended with fly ash or slag, and when different SPs are used. When designing a stable SCC mix, these factors should be taken into account.
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Ederer, Leslie. "The effect of zinc stearate on the compaction and sintering characteristics of a Ti-6%A1-4%V hydride-dehydride powder /." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29857.
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Powder metallurgy (P/M) processing has become an important technique replacing many casting applications, especially for the fabrication of refractory metals where very high melting temperatures are required. Improvement in powder production, cleanliness and characterization techniques, combined with an increased understanding of basic compaction and sintering principles and a need for metals with high strength to weight ratios has led to an increased interest in titanium powder utilization. P/M techniques for Ti-6Al-4V powder can enable the production of high quality parts at lower processing temperatures and cost. For most applications prealloyed powder produced by the hydride-dehydride process (HDH) is used, due to the lower cost of this powder as compared to Ti-6Al-4V powder produced by other methods.General characterization of a Ti-6Al-4V HDH powder and the effects of using a zinc stearate on the green and sintered density were examined at different compaction pressures and sintering temperatures. (Abstract shortened by UMI.)
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Ederer, Leslie. "The effect of zinc stearate on the compaction and sintering characteristics of a Ti-6% Al-4%V hydride-dehydride powder." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/MQ55021.pdf.
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Pérez, Gago Ana [Verfasser], and Peter [Akademischer Betreuer] Kleinebudde. "Roll Compaction Scale-Up: Impact of Material, Effect of Scale and Modelling of The Process Transfer / Ana Pérez Gago ; Betreuer: Peter Kleinebudde." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2017. http://d-nb.info/1129357279/34.
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Naserkhaki, Mostafa. "Effet de la succion matricielle des sols non saturés sur leur compressibilité." Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24160/24160.pdf.
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Muhea, Wondwosen Eshetu. "Characterization and Compact Modeling of Flicker Noise and Piezoelectric Effect in Advanced Field Effect Transistors." Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/668270.
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El'objectiu d'aquesta tesi és el modelatge compacte basat en la física dels transistors de pel·lícula prima i d'alta mobilitat d'electrons (TFTs, HEMTs). En primer lloc, s'ha realitzat la caracterització del soroll de DC i de baixa freqüència de ESL a-IGZO i TFTs orgànics polimèrics per identificar l'origen físic del soroll 1 / f. L'anàlisi experimental de dades ha revelat un intercanvi aleatori de portadores entre les trampes d'òxid de porta i el canal és la font del soroll Flicker en ambdós tipus de TFTs. Mentre que en les regions d'alta corrent dels TFTs a-IGZO s'ha observat soroll procedent de la dispersió remota de portadors de Coulomb, les resistències de contacte no tenen cap contribució en tots dos dispositius. Basant-se en aquests resultats, es deriven models de soroll DC i 1 / f per als TFTs de a-IGZO utilitzant els mètodes d'extracció de paràmetres UMEM DC i de modelatge de soroll Flicker unificat. En segon lloc, s'ha realitzat el modelatge d'efectes piezoelèctrics en HEMTs de Algan / GaN. Resolent l'equació de Poisson en cada capa de l'estructura de HEMT i assumint que els electrons 2DEG s'originen a partir d'estats superficials presents a la part superior de Algan, s'han desenvolupat les expressions analítiques de l'altura de la barrera Schottky i del llindar de voltatge (Vth). S'han considerat els efectes de la capa d'Algan Contingut d'alumini, la capa GaN-cap i la capa intermèdia de ALN. Els models Vth s'ha implementat en un model I-V prèviament desenvolupat per a la simulació de característiques de DC.
Finalment, dispositius diversos a-IGZO TFT i HEMT s'han utilitzat per validar els models proposats de DC, soroll 1 / f i Vth. Les dades dels models experimentals han donat excel·lents resultats en tots els règims de funcionament dels dispositius.El objetivo de esta tesis es el modelado compacto basado en la física de los transistores de TFTs, y HEMTs. En primer lugar, se ha realizado la caracterización del ruido de DC y de baja frecuencia de ESL a-IGZO y TFTs orgánicos poliméricos para identificar el origen físico del ruido 1/f. El análisis experimental de datos ha revelado un intercambio aleatorio de portadoras entre las trampas de óxido de puerta y el canal es la fuente del ruido Flicker en ambos tipos de TFTs. Mientras que en las regiones de alta corriente de los TFTs a-IGZO se ha observado ruido procedente de la dispersión remota de portadores de Coulomb, las resistencias de contacto no tienen ninguna contribución en ambos dispositivos. Basándose en estos resultados, se derivan modelos de ruido DC y 1/f para los TFTs de a-IGZO utilizando los métodos de extracción de parámetros UMEM DC y de modelado de ruido Flicker unificado. En segundo lugar, se ha realizado el modelado de efectos piezoeléctricos en HEMTs de AlGaN/GaN. Resolviendo la ecuación de Poisson en cada capa de la estructura de HEMT y asumiendo que los electrones 2DEG se originan a partir de estados superficiales presentes en la parte superior de AlGaN, se han desarrollado las expresiones analíticas de la altura de la barrera Schottky y del umbral de voltaje. Se han considerado los efectos de la capa de AlGaN Contenido de aluminio, la capa GaN-cap y la capa intermedia de AlN. Los modelos Vth se han implementado en un modelo I-V previamente desarrollado para la simulación de características de DC. Finalmente, dispositivos varios a-IGZO TFT y HEMT se han utilizado para validar los modelos propuestos de DC, ruido 1/f y Vth. Los datos de los modelos experimentales han dado excelentes resultados en todos los regímenes de funcionamiento de los dispositivos.
Physically-based compact modeling of Thin Film and High Electron Mobility Transistors (TFTs, HEMTs) is targeted in this thesis. Firstly, DC and low-frequency noise characterization of ESL a-IGZO and polymeric organic TFTs have been performed for identifying the physical origin of 1/f noise. The experimental data analysis reveal random carrier exchange between gate oxide traps and the channel is the source of the Flicker noise in both types of TFTs. While noise from remote Coulomb scattering of carriers is observed at high current regions in the a-IGZO TFTs, the contact resistances have no contribution in both devices. Based on these results, DC and 1/f noise models are derived for the a-IGZO TFTs using the UMEM DC parameter extraction and unified Flicker noise modeling approaches. Secondly, piezoelectric effect modeling in AlGaN/GaN HEMTs is performed. By solving Poisson’s equation in each layer of the HEMT structure and assuming that the 2DEG electrons originate from surface states present on the AlGaN top, analytical Schottky barrier height and threshold voltage (Vth) expressions are developed. Effects of the AlGaN layer Aluminum content, GaN-cap layer, and AlN interlayer are considered. The Vth models are implemented in a previously developed I-V model for DC characteristics simulation. Finally, Various a-IGZO TFT and HEMT devices are employed to validate the proposed DC, 1/f noise, and Vth models. Model-experimental data gives excellent results in all operating regimes of the devices.
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O'Keefe, Sorche. "The recovery of soils after compaction : a laboratory investigation into the effect of wet/dry cycles on bulk density and soil hydraulic functions." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4493.
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Van den Akker et al. (2003) stated that “European subsoils are more threatened than ever in history” in an editorial referring to the results of the European Union concerted action “Experiences with the impact of subsoil compaction on soil crop growth and environment and ways to prevent subsoil compaction”. Compaction of agricultural soils not only reduces yields but can lead to pollution of surface waters and the release of greenhouse gases. Understanding, therefore, how, and to what extent, subsoil compaction may be reversed seems of vital importance. The literature suggests that soils with a range of textures could recover structural properties such as total and macro-porosity, infiltration rate and stability, although the extent and depth of these changes varies greatly. Factors affecting the extent and depth of changes are the rate of wetting and drying and the matric potentials achieved during drying (influenced by crop cover and irrigation practices as well as climate), organic matter content and tillage history. There is, however, a limited amount of information regarding changes to the pore-size distribution and unsaturated hydraulic conductivity of soils with wet/dry cycles. Although there are models able to predict the compaction that would occur for a given set of conditions, as well as the compactibility of soils and surface crack generation, there are no predictive models that describe structural changes due to wet/dry cycles. The aims of this study were to assess the changes in bulk density and hydrological parameters of a range of soils, of varying texture and other physical and chemical properties, with wet/dry cycles and to explore the relationships between any measured changes and the measured soil properties. A series of laboratory experiments were designed to measure changes to the total porosity and pore size distribution and hydraulic functions of soil samples. Changes to bulk density and moisture content of undisturbed soil cores at field capacity with wet/dry cycles were monitored. Changes to the moisture release curve and hydraulic conductivity curve (as well as bulk density) of remoulded clayey subsoil samples, with wet/dry cycles, were estimated using the multi-step outflow method. The surface cracking of the samples during the wetting and drying process was also explored. Changes to these parameters were statistically compared between soils and between initial bulk densities, and related to soil properties such as texture, organic matter content and Atterberg limits with a general linear model for repeated measures. Changes to the bulk density of the soils after three wet/dry cycles were found to be significantly different (at the 95 % probability level) between soils and between initial bulk densities. It was found that 90 % of the changes in bulk density could be predicted from the initial bulk density and the liquid limit of soils alone. The porosity gained or lost during wet/dry cycles was not confined to the macro-pore region, but included changes to pores that were undrained at pressures up to and including 100 m of water. Changes in the pore size distribution, as described by the parameters of the water release curve, modelled with the van Genuchten-Mualem equation, were found to be statistically related to soil texture and Atterberg limits. Changes to the hydraulic conductivity function of the soils were found to be affected by changes to the connectivity of the pore network, not just to changes in the volume of conducting pores. This was particularly true of the saturated hydraulic conductivity which was found to increase the most in soil samples that experienced a concomitant increase in bulk density and decrease in macro-porosity. Changes to the area of surface cracks were found to be significantly related to changes in the saturated hydraulic conductivity and to changes in the parameters of the van Genuchten-Mualem equation. It was also found that cracks did not close up entirely when the samples were saturated and there were many instances where wetting increased the area of surface cracks, relative to the preceding dry event, implying that the wetting phase was as important in structural formation as the drying phase. There is a strong suggestion that it would be possible to construct a relatively simple model, based on easily measurable parameters, which could be used to predict the changes to soil structure achievable with wet/dry cycles. Further research is needed, therefore, that extends the data set upon which the predictive model designed in this study was constructed. Refinement of the model to include information on the rates of wetting and drying would also contribute greatly to its applicability to the field situation. However, important steps have been made by this study towards a more comprehensive understanding of soil structural dynamics.
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Azizipesteh, Baglo Hamid Reza. "Effect of various mix parameters on the true tensile strength of concrete." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12560.
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The primary aim of this research was to develop a method for determining the true uniaxial tensile strength of concrete by conducting a series of cylinder splitting, modulus of rupture (MOR) and cylinder/cube compression tests. The main objectives were: • Critically reviewing previous published research in order to identify gaps in current knowledge and understanding, including theoretical and methodological contributions to the true uniaxial tensile strength of concrete. In order to maintain consistency and increase the reliability of the proposed methods, it is essential to review the literature to provide additional data points in order to add additional depth, breathe and rigor to Senussi's investigation (2004). • The design of self compacting concrete (SCC), normal strength concrete (NSC) and high strength concrete (HSC) mixes and undertaking lab-based experimental works for mixing, casting, curing and testing of specimens in order to establish new empirical evidence and data. • Analysing the data, presenting the results, and investigating the application of validity methods as stated by Lin and Raoof (1999) and Senussi (2004). • To draw conclusions including comparison with previous research and literature, including the proposal of new correction factors and recommendations for future research. 29 batches of NSC, 137 batches of HSC, 44 batches of fly ash SCC and 47 batches of GGBS SCC were cast and their hardened and fresh properties were measured. Hardened properties measured included: cylinder splitting strength, MOR, cylinder compressive strength and cube compressive strength. A variety of rheological tests were also applied to characterise the fresh properties of the SCC mixes, including: slump flow, T50, L-box, V-funnel, J-ring and sieve stability. Cylinders were also visually checked after splitting for segregation. The tensile strength of concrete has traditionally been expressed in terms of its compressive strength (e.g. ft = c x c f ). Based on this premise, extensive laboratory testing was conducted to evaluate the tensile strength of the concretes, including the direct tension test and the indirect cylinder splitting and MOR tests. These tests however, do not provide sufficiently accurate results for the true uniaxial tensile strength, due to the results being based upon different test methods. This shortcoming has been overcome by recently developed methods reported by Lin and Raoof (1999) and Senussi (2004) who proposed simple correction factors for the application to the cylinder splitting and MOR test results, with the final outcome providing practically reasonable estimates of the true uniaxial tensile strength of concrete, covering a wide range of concrete compressive strengths 12.57 ≤ fc ≤ 93.82 MPa, as well as a wide range of aggregate types. The current investigation has covered a wide range of ages at testing, from 3 to 91 days. Test data from other sources has also been applied for ages up to 365 days, with the test results reported relating to a variety of mix designs. NSC, SCC and HSC data from the current investigation has shown an encouraging correlation with the previously reported results, hence providing additional wider and deeper empirical evidence for the validity of the recommended correction factors. The results have also demonstrated that the type (size, texture and strength) of aggregate has a negligible effect on the recommended correction factors. The concrete age at testing was demonstrated to have a potentially significant effect on the recommended correction factors. Altering the cement type can also have a significant effect on the hardened properties measured and demonstrated practically noticeable variations on the recommended correction factors. The correction factors proved to be valid regarding the effects of incorporating various blended cements in the HSC and SCC. The NSC, HSC and SCC showed an encouraging correlation with previously reported results, providing additional support, depth, breadth and rigor for the validity of the correction factors recommended.
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Favier, Pierre. "Etude et conception d'une cavité Fabry-Perot de haute finesse pour la source compacte de rayons X ThomX." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS412/document.
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La diffusion Compton inverse est un moyen unique pour produire des rayons X quasi-monochromatiques via l'interaction entre des électrons relativistes et une impulsion laser. Ce processus présente l'avantage de produire des flux très élevés de rayons X avec des énergies supérieures à quelques dizaines de keV. De plus, la divergence du faisceau de sortie est beaucoup plus grande que dans les sources de lumière synchrotron classiques et le faisceau de rayons X est donc plus facile à manipuler. Nous présentons une source de rayons X en construction à l'Université Paris-Sud, ThomX. Cette source utilise un faisceau d'électrons de 50 MeV qui interagit à 16,7 MHz avec une impulsion laser de quelques picosecondes dont la puissance moyenne est à l'état de l'art avec 600 kW, permettant de produire des rayons X entre 30 et 50 keV avec un flux de 10^{13} ph/s. Cette gamme d'énergie ainsi que la dépendance énergie-angulaire provenant du processus physique conviennent aux applications sociétales comme la radiothérapie ou l'histoire de l'art.Une cavité optique de très haute finesse (> 24000) est utilisée comme prototype pour effectuer des travaux de R&D pour la source ThomX. 400 kW de puissance laser moyenne ont été stockés avec succès dans cette cavité, en utilisant un faisceau laser d'entrée de seulement 40 W. Ce résultat, unique au monde, permet d'envisager l'achèvement de la source de rayons X de faible coût et de haut flux ThomX. Cette thèse explique les études expérimentales et analytiques qui ont été réalisées pour atteindre cette performance, dont une généralisation du processus d'empilement des impulsions laser pour les faisceaux laser ayant une fréquence de répétition différente de celle de la cavité, et les méthodes développées pour l'amélioration expérimentale du couplage spatialInverse Compton Scattering provides a unique way to produce quasi-monochromatic X-rays via the interaction of relativistic electrons with a laser pulse. This process has the advantage of producing very high fluxes of X-rays with energies above a few tens of keV. In addition the output beam divergence is much larger than in classical synchrotron light sources and the X-ray beam is thus easier to manipulate. We present an X-ray source under construction at Paris-Sud University, ThomX. This source uses a 50 MeV electron beam that collides at 16.7 MHz with a few picoseconds pulsed laser beam whose power is enhanced at the state of the art 600 kW average power to produce X-rays between 30 and 50 keV with a flux of 10^{13} ph/s. This energy range as well as the energy-angular dependence coming from the physical process are suitable for societal applications like radiotherapy or art history.A very high finesse optical cavity (> 24000) is used as a prototype to perform R&D for the ThomX source. 400 kW of average laser power have been successfully stored in this cavity, using an input laser beam of only 40 W. This result, unique in the world, is a pathway towards the completion of the low-cost, compact, high flux X-ray source ThomX. This thesis explains the experimental and analytical studies that have been performed to reach this performance, including a generalization of the process of laser pulse stacking to frequency-detuned laser beams, and the methods developped for experimental spatial coupling enhancement
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He, Rui. "Systematic Tire Testing and Model Parameterization for Tire Traction on Soft Soil." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/104386.
Full textAbstract:
Tire performance over soft soil influences the performance of off-road vehicles on soft soil, as the tire is the only force transmitting element between the off-road vehicles and soil during the vehicle operation. One aspect of the tire performance over soft soil is the tire tractive performance on soft soil, and it attracts the attention of vehicle and geotechnical engineers. The vehicle engineer is interested in the tire tractive performance on soft soil because it is related to vehicle mobility and energy efficiency; the geotechnical engineer is concerned about the soil compaction, brought about by the tire traffic, which accompanies the tire tractive performance on soft soil. In order to improve the vehicle mobility and energy efficiency over soft soil and mitigate the soil compaction, it's essential to develop an in-depth understanding of tire tractive performance on soft soil.
This study has enhanced the understanding of tire tractive performance on soft soil and promoted the development of terramechanics and tire model parameterization method through experimental tests. The experimental tests consisted of static tire deflection tests, static tire-soil tests, soil properties tests, and dynamic tire-soil tests. The series of tests (test program) presented herein produced parameterization and validation data that can be used in tire off-road traction dynamics modeling and terramechanics modeling.
The 225/60R16 97S Uniroyal (Michelin) Standard Reference Test Tire (SRTT) and loamy sand were chosen to be studied in the test program. The tests included the quantification or/and measurement of soil properties of the test soil, pre-traffic soil condition, the pressure distribution in the tire contact patch, tire off-road tractive performance, and post-traffic soil compaction. The influence of operational parameters, e.g., tire inflation pressure, tire normal load, tire slip ratio, initial soil compaction, or the number of passes, on the measurement data of tire performance parameters or soil response parameters was also analyzed. New methods of the rolling radius estimation for a tire on soft soil and of the 3-D rut reconstruction were developed. A multi-pass effect phenomenon, different from any previously observed phenomenon in the available existing literature, was discovered.
The test data was fed into optimization programs for the parameterization of the Bekker's model, a modified Bekker's model, the Magic Formula tire model, and a bulk density estimation model. The modified Bekker's model accounts for the slip sinkage effect which the original Bekker's pressure-sinkage model doesn't. The Magic Formula tire model was adapted to account for the combined influence of tire inflation pressure and initial soil compaction on the tire tractive performance and validated by the test data. The parameterization methods presented herein are new effective terramechanics model parameterization methods, can capture tire-soil interaction which the conventional parameterization methods such as the plate-sinkage test and shear test (not using a tire as the shear tool) cannot sufficiently, and hence can be used to develop tire off-road dynamics models that are heavily based on terramechanics models.
This study has been partially supported by the U.S. Army Engineer Research and Development Center (ERDC) and by the Terramechanics, Multibody, and Vehicle (TMVS) Laboratory at Virginia Tech.Doctor of Philosophy
Big differences exist between a tire moving in on-road conditions, such as asphalt lanes, and a tire moving in off-road conditions, such as soft soil. For example, for passenger cars commonly driven on asphalt lanes, normally, the tire inflation pressure is suggested to be between 30 and 35 psi; very low inflation pressure is also not suggested. By contrast, for off-road vehicles operated on soft soil, low inflation pressure is recommended for their tires; the inflation pressure of a tractor tire can be as low as 12 psi, for the sake of low post-traffic soil compaction and better tire traction. Besides, unlike the research on tire on-road dynamics, the research on off-road dynamics is still immature, while the physics behind the off-road dynamics could be more complex than the on-road dynamics. In this dissertation, experimental tests were completed to study the factors influencing tire tractive performance and soil behavior, and model parameterization methods were developed for a better prediction of tire off-road dynamics models. Tire or vehicle manufacturers can use the research results or methods presented in this dissertation to offer suggestions for the tire or vehicle operation on soft soil in order to maximize the tractive performance and minimize the post-traffic soil compaction.
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Zhang, Yue. "Modélisation compacte et conception de circuit hybride pour les dispositifs spintroniques basés sur la commutation induite par le courant." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01058504.
Full textAbstract:
La miniaturisation du nœud technologique de CMOS en dessous de 90 nm conduit à une forte consommation statique pour les mémoires et les circuits logiques, due aux courants de fuite de plus en plus importants. La spintronique, une technologie émergente, est d'un grand intérêt pour remédier à ce problème grâce à sa non-volatilité, sa grande vitesse d'accès et son intégration facile avec les procédés CMOS. Comparé à la commutation induite par le champ magnétique, le transfert de spin (STT), une approche de commutation induite par le courant, non seulement simplifie le processus de commutation mais aussi permet un fonctionnement sans précédent en termes de consommation et de vitesse. Cette thèse est consacrée à la modélisation compacte et la conception de circuit hybride pour les dispositifs spintroniques basés sur la commutation induite par le courant. La jonction tunnel magnétique (JTM), élément fondamental de la mémoire magnétique (MRAM), et la mémoire racetrack, nouveau concept fondé sur la propagation des parois de domaine induites par le courant, sont particulièrement étudiés. Ces dispositifs et circuits spintroniques sont basés sur les matériaux à anisotropie magnétique perpendiculaire (AMP) qui ouvrent la perspective d'une miniaturisation submicronique tout en conservant une grande stabilité thermique. De nombreux modèles physiques et paramètres réalistes sont intégrés dans la modélisation compacte pour obtenir une bonne cohérence avec les mesures expérimentales. En utilisant ces modèles compacts précis, certaines applications pour la logique et les mémoires magnétiques, tels que l'additionneur complet magnétique (ACM) et la mémoire adressable par contenu (CAM), sont conçues et simulées. Nous analysons et évaluons leur potentiel de performance en termes de surface, vitesse et consommation d'énergie par rapport aux circuits classiques. Enfin, afin de lutter contre la limitation de capacité entravant la large application, nous proposons deux optimisations de conception : la mémoire multivaluée (MLC) pour la STT-MRAM et l'assistance par champ magnétique pour la mémoire racetrack. Ce concept de MLC utilise le comportement stochastique des STT pour atteindre une haute vitesse tout en augmentant la densité de STT-MRAM. La mémoire racetrack assistée par champ magnétique est fondée sur l'observation d'une propagation des parois de domaine en dessous du courant critique, propagation est attribué à l'effet " Walker breakdown ". Ceci ouvre une nouvelle voie pour réduire le courant de propagation et augmenter la capacité des mémoires racetrack au-delà des améliorations des circuits périphériques et des matériaux.