Дисертації з теми "Structural permeability"
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1
Rezai, Taha. "Structural permeability relationships of cyclic peptides /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
Повний текст джерела
2
Ioannidou, Sofia. "Structural and functional analysis of vascular permeability." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444750/.
Повний текст джерелаАнотація:
Vascular permeability and its regulation are indispensable for normal circulatory function and tissue homeostasis. When unregulated, vascular permeability contributes significantly to blood vessel related pathologies, such as cancer and diabetic retinopathy. Interposed between blood and tissues, endothelial cells become structurally and functionally differentiated, to mediate controlled permeability. The aim of this thesis work was to develop suitable systems to study two different aspects of vascular permeability, endothelial fenestrae formation and tyrosine phophatase-based regulation of paracellular permeability. Transcellular permeability describes the passage of water and macromolecules across endothelial cells. A route for transcellular permeability is provided by fenestrae, the 60 nm circular pores that span the entire thickness of highly attenuated endothelia encountered in endocrine or filtrating organs. In an attempt to gain insight into the structure and biogenesis of fenestrae I helped set up an in vitro culture system where fenestrae could be rapidly induced in cell biological and biochemical quantities. To understand the molecular composition of fenestrae I established a biochemical method for their enrichment. Subtractive proteomic analysis performed on a subcellular fraction enriched in plasma membranes revealed proteins with roles in actin filament disassembly, plasma membrane remodeling, endocytosis, and membrane to cytoskeleton linkage. One particular candidate, the membrane-cytoskeleton linker moesin, was validated as a component of fenestrae by immunocytochemical means. Paracellular permeability occurs through tight or adherens junctions that join endothelial cells. In order to understand the regulation of paracellular permeability through adherens junctions I focused on Vascular Endothelial Protein Tyrosine Phosphatase (VE-PTP), a demonstrated phosphatase modulator of the junctional protein VE-cadherin. To this end I established transgenic mice with inducible expression of wildtype or mutant VE-PTP in endothelial cells. A correlation between VE-PTP expression at the RNA level and embryonic defects suggests the potential utility of the mice as models of adherens junction dysfunction.
3
Bamforth, P. B. "The structural permeability of concrete at cryogenic temperatures." Thesis, Aston University, 1987. http://publications.aston.ac.uk/14275/.
Повний текст джерелаАнотація:
The thesis describes a programme of research designed to identify concretes for application at cryogenic temperature, in particular for storage of Liquefield Natural Gas which is maintained at a temperature of -165oC. The programme was undertaken in two stages. Stage 1 involved screening tests on seventeen concrete mixes to investigate the effects of strength grade (and water/cement ratio), air entrainment, aggregate type and cement type. Four mixes were selected on the basis of low temperature strength, residual strength after thermal cycling and permeability at ambient temperature. In Stage 2 the selected mixes were subjected to a comprehensive range of tests to measure those properties which determine the leak tightness of a concrete tank at temperatures down to -165oC. These included gas permeability; tensile strength, strain capacity, thermal expansion coefficient and elastic modulus, which in combination provide a measure of resistance to cracking; and bond to reinforcement, which is one of the determining factors regarding crack size and spacing. The results demonstrated that the properties of concrete were generally enhanced at cryogenic temperature, with reduced permeability, reduced crack proneness and, by virtue of increased bond to reinforcement, better control of cracking should it occur. Of the concretes tested, a lightweight mix containing sintered PFA aggregate exhibited the best performance at ambient and cryogenic temperature, having appreciably lower permeability and higher crack resistance than normal weight concretes of the same strength grade. The lightweight mix was most sensitive to thermal cycling, but there was limited evidence that this behaviour would not be significant if the concrete was prestressed. Relationships between various properties have been identified, the most significant being the reduction in gas permeability with increasing strain capacity. The structural implications of the changing properties of the concrete have also been considered.
4
Dunn, A. G. "Bactericidal/permeability-increasing protein, autoimmunity, structural and functional inter-relationships." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598691.
Повний текст джерелаАнотація:
This thesis describes the investigation into the interactions between anti-neutrophil cyptoplasm antibody (ANCA) autoantibodies to Bactericidal/Permeability Increasing Protein (BPI) and BPI. BPI is located in the azurophilic granules of cells of the myeloid lineage and functions to kill gram negative bacteria, neutralise endotoxin and opsonise bacteria for phagocytosis. Autoantibodies to BPI have been discovered in a range of diseases raising interest in their role in pathogenesis, either through perturbation of BPI's biological function, or through their interaction with BPI expressed on the surface of the primed neutrophils. This thesis describes studies which investigate the epitopes recognised by anti-BPI ANCA, their effect on the functions of BPI in vitro, and their relationship to clinical parameters in a population with the unifying diagnosis of cystic fibrosis. Using molecular fusion proteins of BPI, synthesised by recombinant DNA technology it was found that anti-BPI ANCA recognised epitopes located in the carboxyl domain of BPI, but not the amino terminal. Furthermore they inhibited the BPI mediated opsonisation/phagocytosis of bacteria by neutrophils, a recently characterised function of the carboxyl domain. Anti-BPI autoantibodies, had no effect on the amino terminal functions of BPI. In addition anti-BPI ANCA were found to cause primed neutrophils to undergo respiratory burst. When a cystic fibrosis population was investigated for the prevalence of anti-BPI ANCA it was found that anti-BPI antibody levels showed a strong association with patient bacterial colonisation status. These results suggest that anti-BPI ANCA may contribute to chronic infection and inflammation in diseases such as cystic fibrosis by impairing bacterial phagocytosis and activating neutrophils.
5
Reinwald, Yvonne. "Investigation of interconnectivity and permeability in correlation with scaffold structural properties." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574659.
Повний текст джерелаАнотація:
It is widely accepted that pore interconnectivity and permeability are important characteristics effecting cell migration and cell response as well as the transport of nutrients, oxygen and cellular waste products throughout porous tissue engineering scaffolds. Furthermore, it was hypothesized that limited mass transport throughout three-dimensional structures resulted in diminished cell survival and cell distribution being restricted to the scaffold periphery. Several approaches were described for the quantification of scaffold permeability for liquid systems. Up to date, there are only a limited number of quantitative approaches to determine three-dimensional scaffold interconnectivity. This study aims to investigate interconnectivity and permeability in correlation with pore size and porosity. Therefore, tissue engineering scaffolds were fabricated by solvent casting/particulate leaching, supercritical fluid technology and particle sintering. In order to obtain different scaffold architectures, processing conditions were modified. Pore size, pore size distribution and porosity were quantified by MicroCT, and pore windows were analyzed using SEM. A novel interconnectivity algorithm was developed, which allowed the quantification of interconnectivity in 3D throughout the entire scaffold. Permeability of pre-wet scaffolds was determined. Results suggested that scaffolds with larger pore sizes and porosities also exhibited highest interconnectivities and permeabilities. However, these scaffolds showed a heterogeneous pore structure and pore distribution. The distribution of 3T3 fibroblasts through scC02-foamed scaffolds and particulate scaffolds was investigated by MicroCT and MTT staining. Homogenous cell distributions and largest cell volumes were observed on scaffolds with homogenous pore structure and hence smallest pore sizes, porosities, interconnectivities and permeabilities. This study might enable the tailoring of scaffold interconnectivity and permeability by altering scaffold processing conditions. Further, this study might allow the investigation of a minimum interconnectivity that is required for cell migration and proliferation in to order to generate tissues such as bone and cartilage; as well as to promote vascularization.
6
Hapa, Cankat. "Uncertainty In Well Test And Core Permeability Analysis." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12610144/index.pdf.
Повний текст джерелаАнотація:
Reservoir permeability is one of the important parameters derived from well test analysis. Small-scale permeability measurements in wells are usually made using core plugs, or more recently, probe permeameter measurements. Upscaling of these measurements for comparisons with permeability derived well tests (Pressure Build-Up) can be completed by statistical averaging methods. Well Test permeability is often compared with one of the core plug averages: arithmetic, geometric and harmonic. A question that often arises is which average does the well test-derived permeability represent and over what region is this average valid? A second important question is how should the data sets be reconciled when there are discrepancies?
In practice, the permeability derived from well tests is often assumed to be equivalent to the arithmetic (in a layered reservoir) or geometric (in a randomly distributed permeability field) average of the plug measures. These averages are known to be members of a more general power-average solution. This pragmatic approach (which may include an assumption on the near-well geology) is often flawed due to a number of reasons, which is tried to be explained in this study. The assessment of in-situ, reservoir permeability requires an understanding of both core (plug and probe) and well test measurements –
in terms of their volume scale of investigation, measurement mechanism, interpretation and integration. Pressure build-up tests for 26 wells and core plug analysis for 32 wells have valid measured data to be evaluated. Core plug permeabilities are upscaled and compared with pressure build-up test derived permeabilities. The arithmetic, harmonic and geometric averages of core plug permeability data are found out for each facies and formation distribution. The reservoir permeability heterogeneities are evaluated in each step of upscaling procedure by computing coefficient of variation, The Dykstra-Parson&
#8217
s Coefficient and Lorenz Coefficients. This study compared core and well test measurements in South East of Turkey heavy oil carbonate field. An evaluation of well test data and associated core plug data sets from a single field will be resulting from the interpretation of small (core) and reservoir (well test) scale permeability data. The techniques that were used are traditional volume averaging/homogenization methods with the contribution of determining permeability heterogeneities of facies at each step of upscaling procedure and manipulating the data which is not proper to be averaged (approximately normally distributed) with the combination of Lorenz Plot to identify the flowing intervals. As a result, geometrical average of upscaled core plug permeability data is found to be approximately equal to the well test derived permeability for the goodly interpreted well tests. Carbonates are very heterogeneous and this exercise will also be instructive in understanding the heterogeneity for the guidance of reservoir models in such a system.
7
Philit, Sven. "Elaboration d'un modèle structural, pétrophysique et mécanique des failles en milieu gréseux poreux : implication pour la migration et le piégeage des fluides." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT090/document.
Повний текст джерелаАнотація:
La cataclase est un processus de déformation efficace en termes de réduction de porosité et de perméabilité dans les grès poreux, constituant des aquifères et réservoirs d’hydrocarbures classiques. Un enjeu majeur concernant la déformation dans les grès consiste à identifier les processus contrôlant l’évolution des structures cataclastiques et reconnaitre les paramètres influençant l’expression de la déformation à l’échelle microscopique et à l’échelle du bassin.Dans cette étude, nous nous concentrons sur l’analyse structurale des amas (« clusters ») de bande de déformation cataclastiques afin de considérer une déformation suffisamment localisée représentant un potentiel rôle de barrière sur les fluides. Nous choisissons sept sites d’étude présentant des clusters formés en tectonique extensive et contractive, dans différent régimes Andersoniens, à différentes profondeurs d’enfouissement, et dans des grès aux lithologies variées. Nous utilisons une approche analytique afin d’estimer l’évolution de l’état de contrainte des grès jusqu’à la déformation. L’utilisation de modèles numériques permet d’analyser l’influence de certains paramètres physiques sur la structuration de la déformation.Nous montrons que la position de l’enveloppe de rupture du grès (dépendant de sa lithologie) semble déterminer la morphologie de la déformation. D’autre part, les clusters formés en régimes Andersoniens normal, décrochant et inverse semblent respectivement couramment se former sur la même partie de l’enveloppe.Les clusters formés en régime normal montrent des épaisseurs fines à moyennes, des densités de bande importantes et forment, avec d’autres clusters, des réseaux d’échelle kilométrique souvent localisés à proximité d’une faille majeure. Ils représentent une barrière potentielle pour les fluides. Les clusters formés en régime décrochant ont des épaisseurs et des densités de band moyennes. Parce qu’ils semblent éparses, ces clusters ne forment probablement aucun frein pour les fluides. Les clusters formés en régime inverse ont des épaisseurs et des densités de bande moyennes si la rupture est atteinte sur la partie fragile de l’enveloppe. Ils semblent potentiellement plus épais avec des densités de bands faibles voire deviennent de simples réseaux de bandes distribuées si l’enveloppe de rupture est atteinte sur sa partie ductile. Parce qu’ils sont courts et éparses, ces clusters ne représentent pas de frein pour les fluides.Nous relions le développement des clusters et leur morphologie à l’agencement microscopique des clasts dans le matériel déformé. La faible compaction du matériel déformé des clusters créés en régimes normal et décrochant semble être à l’origine de l’étroite localisation des bandes à cause de la présence de plans de faiblesse dans le matériel déformé. Pour le même degré de déformation, la compaction plus élevée du matériel en régime inverse favoriserait la distribution des bandes.Le passage à la faille tel qu’observé dans les clusters en régime normal est permis par la présence entre les grès de niveaux incluant des minéraux fragiles. Ces niveaux permettent l’initiation et la propagation d’une surface de glissement majeure dans les grès adjacents. L’initiation d’une faille est aussi favorisée lorsque des grès poreux sont juxtaposés contre une lithologie indurée.Notre étude montre que la cimentation de quartz des parties les plus déformées des clusters est fréquente, même dans le cas de clusters ayant été enfouis à des profondeurs inférieures à 800 m. Cette cimentation est catalysée par l’intense degré de cataclase, semble être précipitée par « self-healing » et altère les propriétés pétrophysiques des clustersDeformation through cataclasis, which corresponds to grain crushing, is an effective process of porosity and permeability reduction in porous sandstones, classical aquifers and hydrocarbon reservoirs at depth. A major stake concerning the deformation in sandstone is to understand what processes govern the growth of the cataclastic structures and to recognize what parameters influence the expression of the deformation at microscopic scale and at basin scale.In this study, we focus on the analysis of cataclastic deformation band clusters in order to consider a significantly concentrated deformation regarding the potential of fluid flow baffling. We select seven study sites presenting clusters formed in extensional and contractional tectonics, under different Andersonian regimes, at various burial depths and in sandstones of varying lithologies. To complement the structural analysis, we use an analytical approach to estimate the stress-state evolution of the sandstones leading to deformation. Numerical modeling allows the analysis of the influence of physical parameters on the structuring of the deformation.We show that the position of failure along the failure envelope of the sandstone (which depends on its lithology) seems to determine the morphology of deformation. On the other hand, normal, strike-slip and thrust Andersonian regime clusters respectively seem to form frequently on the same part of the envelope.Normal regime clusters (favorably formed in extensional tectonics) have thin to medium thickness, with high band density and form, with other clusters, networks of km-scale length - often localized near a major fault. They are likely to baffle fluid flow. Strike-slip regime clusters (favorably formed in contractional tectonics) have medium thickness with medium band densities. Due to their sparseness, they seem unlikely to form a baffle for fluids. Thrust regime clusters (favorably formed in contractional tectonics) have medium thickness and medium band density if failure is attained on the brittle part of the envelope. They seem potentially thicker, with low band density and tend to form arrays of deformation bands if failure is attained on the cap of the envelope. Because they are short and sparse, they do not represent an effective baffle for fluid flow.We relate the process of cluster growth and their resulting morphology to the microscopic arrangement of the clasts in the deformed material. The minor compaction in the deformed material of normal and strike-slip regime clusters seems to be at the origin of the dense localization of the bands through the presence of weaker planes in the deformed material. For the same degree of deformation, the more compacted material in thrust regime clusters would favor the distribution of the bands.Faulting of normal regime clusters is enhanced by the presence of layers including weak minerals between the sandstones. These weak layers are responsible for the initiation and propagation of major slip-surfaces in the adjacent sandstone from small displacements. The initiation of major slip-surfaces is also favored when porous sandstone is juxtaposed with a hard lithology.We find that the quartz cementation of the most deformed parts of the clusters is common, even in clusters that were never buried below 800 m. This cementation is promoted by an intense degree of cataclasis, seems to form by “self-healing”, and may reduce the petrophysical properties of clusters
8
Barker, Helen Claire. "Antimicrobial peptides derived from the human bactericidal/permeability increasing protein (BPI) : structural determinants and mechanism of action." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241788.
Повний текст джерела
9
Elwood, James Andrew. "Enriching Structural Models of L2 Willingness to Communicate: The Role of Personality, Ego Permeability, and Perceived Distance." Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/134212.
Повний текст джерелаАнотація:
CITE/Language ArtsPh.D.
Willingness to communicate (WTC) in a second language (L2) is crucial to the development of communicative speaking skills. This study is a cross-sectional investigation of the role in models of second language (L2) willingness to communicate of three personality variables hitherto underresearched in the L2 field: extroversion, ego permeability (one's capacity to tolerate ambiguity), and perceived distance from one's core persona. A sample of 252 Japanese university students responded to a set of instruments used to measure individual difference variables and personality variables; the instruments were drawn from the fields of L2 acquisition and psychology as well as a 5-item instrument designed to measure perceived distance in a series of participatory L2 speaking activities. Confirmatory factor analysis, Rasch analysis, and structural equation modeling were utilized to validate the respective instruments. The International Posture instrument was best represented by a two-factor configuration consisting of Intergroup Approach-Avoidance Tendency and Intercultural Friendship Orientation, while the L2 Communicative Confidence was altered to consist of three factors (L2 Anxiety, Perceived L2 Communicative Competence, and Extroversion). The hypothesized additions of Ego Permeability and Perceived Distance failed to improve the measurement models, and the original Ego Permeability variable functioned poorly in this context. The MacIntyre and Charos (1996) model had marginal fit to the data even after undergoing considerable respecification. The models of Yashima (2002) and Yashima, Zenuk-Nishide, and Shimizu (2004) were found to have good fit as originally conceptualized, but the addition of Extroversion and paths from International Posture and L2 Communicative Anxiety improved the fit of both models. Collectively, the results indicate that extroversion plays an important role in models of L2 WTC and that the basic models of Yashima and colleagues are robust. These findings provide crucial insights into the process of L2 WTC, an important factor in the students' acquisition of communicative competence.
Temple University--Theses
10
Angus, Barbara Lee. "Structural and functional studies on the role of the outer membrane of Pseudomonas aeruginosa in resistance and permeability to antibiotics." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26767.
Повний текст джерелаАнотація:
The intrinsic antibiotic resistance of aeruginosa was
examined using an antibiotic hypersusceptible mutant strain. This multiple mutant (M1) was characterised with respect to antibiotic susceptibility, outer membrane permeability and outer membrane structure. It was found to be hypersusceptible to all antibiotics tested. Two spontaneous revertants of the mutant strain were isolated (P1-4 and P1-6), using carbenicillin or gentamicin as the selective agent, and characterised, revealing that these had recovered partial resistance to all antibiotics. Two other strains, for which two genetic loci (apparently responsible for antibiotic hypersusceptibility in the mutant M1) had been separately conjugated into a strain with a wild type genetic background, were also characterised. One of these transconjugants (P2-6) was found to be partially hypersusceptible to a wide range of antibiotics, whereas the other (P2-8) was partially hypersusceptible to B-lactam and aminoglycoside antibiotics but not to the hydrophobic agent, trimethoprim. Outer membrane permeability of the above strains was characterised by three different methods. Using an assay involving periplasmic beta-lactamase, the mutant strain M1 was found to be five-fold more permeable to the chromogenic cephalosporin nitrocefin than its wild type parent WT1. In addition, mutant M1 was much more permeable to the hydrophobic fluorescent compound 1-N-phenyl-N-naphthylamine than was wild type strain WT1. In contrast, mutant strain M1 was less susceptible to permeabilisation of the outer membrane to lysozyme by aminoglycoside antibiotics or ethylenediaminetetraacetate. Partially resistant mutants were used to confirm and clarify these results. It was concluded from these data that the mutations responsible for antibiotic susceptibility in the mutant were acting upon one or more of the outer membrane constituents, protein and lipopolysaccharide.
Characterisation of outer membrane proteins by SDS-polyacrylamide gel electrophoresis showed no observable differences between outer membrane proteins of the wild type and mutant strains. Further examination showed that the lipopolysaccharide in the mutant strain M1 was altered with respect to its composition, mobility on SDS-polyacrylamide gels and in its Mg++-binding properties. From these data, it appeared that at least three separate mutations existed in the mutant which contributed to antibiotic susceptibility. Two of these mutations were responsible for separate alterations to lipopolysaccharide, while the third mutation could not be characterised. It was proposed that the chief alteration leading to antibiotic susceptibility in strain M1 involved partial loss of an outer membrane-stabilising, Mg++-binding site on lipopolysaccharide.
In another portion of the study, native oligomers of
three P. aeruginosa outer membrane proteins and one E. coli
porin were demonstrated using a chemical crosslinking
technique. P. aeruginosa protein F, the major constitutive outer membrane porin, was crosslinked to dimers in outer membranes and whole cell crosslinking experiments. Purified preparations of P. aeruginosa proteins F, P (phosphate starvation-induced) and coli protein PhoE (Ic) were also
crosslinked to reveal dimers and trimers upon two-dimensional SDS-polyacrylamide gel electrophoretic analysis. Crosslinking of protein F was abolished by pretreatment of the protein with SDS, indicating that the crosslinked products were due to native associations in the outer membrane.Science, Faculty of
Microbiology and Immunology, Department of
Graduate
11
DeValve, Caleb Joshua. "Investigations on Void Formation in Composite Molding Processes and Structural Damping in Fiber-Reinforced Composites with Nanoscale Reinforcements." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19290.
Повний текст джерелаАнотація:
Fiber-reinforced composites (FRCs) offer a stronger and lighter weight alternative to traditional materials used in engineering components such as wind turbine blades and rotorcraft structures. Composites for these applications are often fabricated using liquid molding techniques, such as injection molding or resin transfer molding. One significant issue during these processing methods is void formation due to incomplete wet-out of the resin within the fiber preform, resulting in discontinuous material properties and localized failure zones in the material. A fundamental understanding of the resin evolution during processing is essential to designing processing conditions for void-free filling, which is the first objective of the dissertation. Secondly, FRCs used in rotorcraft experience severe vibrational loads during service, and improved damping characteristics of the composite structure are desirable. To this end, a second goal is to explore the use of matrix-embedded nanoscale reinforcements to augment the inherent damping capabilities in FRCs.The first objective is addressed through a computational modeling and simulation of the infiltrating dual-scale resin flow through the micro-architectures of woven fibrous preforms, accounting for the capillary effects within the fiber bundles. An analytical model is developed for the longitudinal permeability of flow through fibrous bundles and applied to simulations which provide detailed predictions of local air entrapment locations as the resin permeates the preform. Generalized design plots are presented for predicting the void content and processing time in terms of the Capillary and Reynolds Numbers governing the molding process.
The second portion of the research investigates the damping enhancement provided to FRC\'s in static and rotational configurations by different types and weight fractions of matrix-embedded carbon nanotubes (CNTs) in high fiber volume fraction composites. The damping is measured using dynamic mechanical analysis (DMA) and modal analysis techniques, and the results show that the addition of CNTs can increase the material damping by up to 130%. Numerical simulations are conducted to explore the CNT vibration damping effects in rotating composite structures, and demonstrate that the vibration settling times and the maximum displacement amplitudes of the different structures may be reduced by up to 72% and 50%, respectively, with the addition of CNTs.
Ph. D.
12
Stanek, Martin. "Structural and petrophysical characterisation of granite : intended for radioactive waste stocking." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01019915.
Повний текст джерелаАнотація:
Structural and petrophysical analysis have been conducted within the Melechov massif with focus on structures controlling the porosity, permeability and thermal conductivity of the rock. The structure of the massif has been constrained based on extensive dataset including AMS and field structural measurements of ductile and brittle structures. The fracture system of the massif has been described by four sets of fractures. The measured petrophysical data have been used to characterize the effect of fracturing and alteration on pore space geometry and in turn on permeability, thermal conductivity and elastic properties of the studied granite. Distinct petrophysical properties have been identified for pristine granite, for fractured fresh granite as well as for fractured granite altered by Fe-oxide, chlorite and clay minerals. A detailed microstructural study combined with multidirectional P-wave velocity measurements at high confining pressure and with AMS analysis has been conducted on a schlieren bearing sample of Lipnice granite. The granite VP anisotropy at low confining pressure was controlled by intergranular cracks interconnecting schlieren-subparallel cleavage cracks in micas and feldspars and by exfoliation fracture-subparallel intra- or trans-granular cracks in cleavage-free quartz. Major closing of the crack porosity linked to the schlieren granite below depth of 500 m has been interpreted in terms of crack compliance reflected by rapid increase in VP with confining pressure.
13
Nyflött, Åsa. "Structural Studies and Modelling of Oxygen Transport in Barrier Materials for Food Packaging." Licentiate thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-34468.
Повний текст джерелаАнотація:
The requirements of food packages are to ensure food safety and quality, to minimize spoilage, and to provide an easy way to store and handle food. To meet these demands for fibre-based food packages, barrier coatings are generally used to regulate the amount of gases entering a package, as some gases are detrimental to food quality. Oxygen, for example, initiates lipid oxidation in fatty foods. Bakery products may also be sensitive to oxygen. This thesis focused on mass transport of oxygen in order to gain deeper knowledge in the performance of barrier coatings and to develop means to optimize the performance of barrier coatings. This experimental study along with computer modelling characterized the structure of barrier materials with respect to the mass transport process.This project was performed as part of the multidisciplinary industrial graduate school VIPP (www.kau.se/en/vipp) - Values Created in Fibre Based Processes and Products – at Karlstad University, with the financial support from the Knowledge Foundation, Sweden, and Stora Enso.Artikel 2 "The influence of clay orientation..." ingick som manuskript i avhandlingen, då med titeln: "Influence of clay orientation in dispersion barrier coatings on oxygen permeation". Nu publicerad.
14
Gülyüz, Nilay. "Textural and structural characteristics of the Kestanelik epithermal vein system, NW Turkey : implications for permeability enhancement mechanisms and gold exploration in epithermal systems." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28902.
Повний текст джерелаАнотація:
It has long been known that faults and fracture provide a critical role in multiphase epithermal mineralization, however the mechanisms of permeability enhancement after a conduit becomes sealed up over time has been less well studied. The research in this thesis investigates the vein-scale permeability enhancement mechanisms in epithermal gold deposits through a detailed study of geology, dimensions, geometry, textures and breccias of the well-exposed Kestanelik gold deposit (NW Turkey). New mapping of the deposit and its host rocks show that the Late Eocene mineralization is associated with regional Cenozoic calc-alkaline magmatism. Vein textures and breccia components indicate repeated sealing and subsequent brecciation of wall rock and pre-existing vein infill. Kinematic analyses together with macroscopic and petrographic analyses of vein textures characterize E-W trending veins as left lateral faults, whilst NE-SW trending veins are extensional (Mode I) fractures. Although two phases of mineralization were picked up from E-W trending veins, at least three were determined from NE-SW trending veins. Cataclasite and tectonic breccia of wall rocks and early quartz, hydrothermal crackle breccias, and cement supported chaotic breccias of pre-existing vein infill, all of which are cemented by late-stage quartz, indicate that coseismic rupturing and hydraulic fracturing are two major permeability enhancement mechanisms. Faults were reactivated along the vein footwall-wall rock contact, while extensional veins were opened along their either margin. Transient local stress variation also has the potential to enhance permeability on mis-oriented surfaces and at locations where the dip changes. Constructed 3D vein geometries show subsurface vein bends are more favorable structural locations for gold to precipitate than smooth, planar segments, and the host rock schist host the majority of gold. This study emphasizes the importance of detailed structural and textural studies for gold exploration and 3D orebody modelling.
15
Bonsu, Mensah. "Structural stability and surface sealing as related to organic matter depletion of a shallow organic soil." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26961.
Повний текст джерелаАнотація:
A physically based model describing the mechanism of surface sealing of soil was evaluated in the context of aggregate stability. The intent of the model study was to better understand the effect of mixing fine-textured mineral subsoil with organic surface soil on structural stability and surface seal formation. The mixing results from tillage and harvesting operations, and management practices such as levelling. The index derived from the model showed that sealing of the shallow organic soil increased with an increase of mineral matter content.
The mathematical formulation of the model was based on the principle of conservation of mass and Darcy's law for flow of water through a layered soil column. Assuming convective flow, it was shown theoretically that the rate of surface seal formation is proportional to the flux density of the filtrate, as assumed by Scheidegger (1974). In the model it was further assumed that the pore necks at the soil surface clog first before the seal develops. The assumption that convective flow alone was responsible for the movement of the suspension is likely incorrect for suspensions derived from medium or coarse textured soils, since sedimentation does influence the movement of larger particles. However, introducing a constant sedimentation parameter into the convective flow model did not improve the model. Therefore, it is likely a non-constant sedimentation parameter could improve the model considerably.
The model showed that for sufficiently large times the flux density of a filtrate flowing through a soil column at a constant hydraulic head is proportional to inverse square root of time. Testing the model experimentally showed a good agreement between theory and experiment. A highly significant correlation between the soil stability factor derived from the model and aggregate stability suggests that the index is a soil structural attribute. The soil stability factor was exponentially related with aggregate stability and mineral matter content. However, whereas the relationship between the soil stability factor and aggregate stability gave a positive exponent, a negative exponent was obtained with mineral matter content.
Further studies showed that structural stability and saturated hydraulic conductivity of the aggregate beds were positively and significantly correlated exponentially. However, saturated hydraulic conductivity and mineral matter content were negatively and significantly correlated exponentially. Collateral to the results of the model, the strong negative correlation between wet-sieved aggregate stability and mineral matter content confirmed the deleterious effect of mixing fine-textured mineral soil on the structure of the shallow organic soil.
It was theorized that aggregates stabilized through clay-organic complexing are likely to be much stronger than aggregates stabilized through other mechanisms. This implies that whenever the mineral matter content is much higher than the organic matter content, the surplus mineral matter that does not interact with organic matter will be most dispersible. The high silt content of the mineral matter fraction is likely to be an important factor contributing to the decrease in structural stability with increasing mineral matter content. Once the clay and the organic colloids have interacted, the silt that remains is not capable of forming stable aggregates without colloids (Baver et al. 1972).
From measurements of the air to water permeability ratio, the decrease in saturated hydraulic conductivity of the aggregate beds with increasing mineral matter content was attributed to slaking of the mineral matter fraction. However, it is possible for the soil with high mineral matter content to be stable if the mineral matter is allowed to be in contact with the organic matter for a long period of time.Land and Food Systems, Faculty of
Graduate
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Li, Yuqin. "Factors Affecting the Structural Integrity of Wood-Based Composites: Elevated Temperature and Adhesive Bonding." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/102927.
Повний текст джерелаАнотація:
This study focuses on factors that affect the structural integrity of wood-based composites. Wood-based composites exposed to fire may decompose due to the elevated temperatures, resulting in a degradation in performance. Thermal modelling can only predict the structural integrity of construction materials in fire if it is given accurate inputs. Consequently, methods for the characterization of the thermal, physical, and mechanical behaviors of wood and wood-based composites are selected, designed, and benchmarked. The relevant thermal and physical responses characterized includes porosity, permeability and thermal diffusivity. Common construction materials (white pine board, medium density fiberboard and spruce 24) are characterized from room temperature to complete decomposition. The characterization techniques and processes are based on existing literature and relevant ASTM standards. To reduce the number of experiments required for future material characterization, estimates based upon the degree of decomposition and the measured values for the virgin and charred materials are used. For porosity and thermal diffusivity, these models allow values at intermediate temperatures to be estimated with measurements at room temperature and complete decomposition and thermogravimetric analysis (TGA). We find that permeability depends heavily on the microstructure of materials and should be measured independently at the conditions of interest.
An additional important aspect of the performance of wood-based composites is the fracture behavior of wood/adhesive systems. Adhesive bonding enables many engineered wood products such as furniture and structural wood joints and the adhesive fracture toughness often determines the durability. The conventional characterization method for wood/adhesive fracture resistance relies on samples with machined grain angles designed to funnel cracks to the adhesive interface. This method of sample preparation is difficult and time-consuming for certain wood species. In this work, a practical and efficient method is developed to characterize adhesive fracture energy of adhesively bonded veneer systems. In the method, auxiliary aluminum adherends are bonded to the veneers in an effort to drive the crack to the wood/adhesive interface. The method is applied to rotary-peeled veneers and saw-cut veneers produced from three species of wood bonded with three commonly used adhesives. The new tests method yields a high interfacial failure rate and successfully identifies differences in the performance of the three adhesives. SPG (one species of the rotary-peeled veneers) demonstrates a rising R-curve behavior (an increase in the fracture toughness with crack length) when bonded on the loose side. This increase in fracture toughness is observed to be a result of adhesive-substrate interaction, which is a developing process zone behind the crack tip consisting of bridged wood ligaments.Doctor of Philosophy
Construction materials exposed to elevated temperatures from fires may reach temperatures where the material decomposes from the original material to a char. Protected and unprotected structural timber products exposed to fires may exhibit this behavior resulting in a degradation of performance. Understanding the thermal and physical responses of these materials is crucial in evaluating the materials behavior in fire. Additionally, many wood-based products (such as furniture) rely on adhesive bonds. Consequently, their usefulness is determined by the performance of those bonds. In this work, methods are developed to measure key properties impacting the behavior of wood-based systems at elevated temperatures, such as that experienced in fires and when they are subjected to forces attempting to debond one wood material from another. These techniques are demonstrated on common building materials (white pine board, medium density fiberboard and spruce 24) and wood veneers from three different species bonded with three different adhesives. Mathematical models are developed to expand the use of the data beyond the specific conditions for which it is measured.
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Kneedy, Jason Lynn. "Stratigraphic and Structural Analysis of Coals in the Ferron Sandstone Member of the Mancos Shale and Fruitland Formation: Relationship to Coal Reservoir Permeability and Coalbed Methane Production." DigitalCommons@USU, 2005. https://digitalcommons.usu.edu/etd/6042.
Повний текст джерелаАнотація:
Coal reservoir quality in the Ferron Sandstone Member of the Mancos Shale, and in the Fruitland Formation is dependent on coal cleat characteristics. Coal reservoir permeability increases as a result of high cleat density. From careful outcrop examination, we were able to identify several factors that increase cleat density. Vitrain coal typically has the highest fracture density as a result of having well-developed face cleats and conchoidal fractures. Clarain coal contains face and butt cleats. Cleat density in clarain is also controlled by mechanical layer thickness. As mechanical layer thickness decreases, cleat density increases. Durain and fusain coals typically contain no welldeveloped cleat system, although their presence can affect mechanical layer thickness in adjacent coals, as they may form bounding units. Cleat density increases in the damage zone of faults and in the hinge-line of folds. Cleat-controlled reservoir permeability has beneficially affected methane production in one portion of the Drunkards Wash Gas Field, Utah, and appears to have negatively influenced methane production in the coalbed methane field.
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Williams, Randolph T. "A Combined Experimental and Numerical Approach to Understanding Quartz Cementation in Sandstones." Bowling Green State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1339354653.
Повний текст джерела
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Plantier, Jean-Luc. "La thrombine dans la physiopathologie vasculaire : une étude structure-fonction." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10179.
Повний текст джерелаАнотація:
La thrombine est une glycoproteine de la famille des proteases a serine. Comparee a celles des autres membres de sa famille, sa structure tertiaire possede une serie de boucles d'insertion particulierement exposees, organisees autour du site actif. Parce que la specificite restreinte de la thrombine pour ses substrats semble faire appel a des interactions a la surface de la molecule, il nous est apparu interessant de determiner quels etaient les roles de ces boucles dans certaines des activites de l'enzyme. Des mutations ponctuelles ont ete realisees dans deux de ces boucles (la boucle b et la boucle ) ainsi que sur la serine du site actif. L'analyse des resultats nous a permis de conclure qu'une thrombine dont le site actif est mutee est denuee de toute activite catalytique. La boucle b est confirmee dans son role de determinant majeur lors de la reconnaissance de tous les substrats testes. En revanche, les mutants que nous avons realises dans la boucle ne modifient que subtilement la poche de specificite primaire et peu les interactions avec les substrats macromoleculaires. En plus de cette etude structurale, nous avons etudier le mecanisme d'augmentation de la permeabilite de l'endothelium induite par la thrombine. La variation de permeabilite depend exclusivement du clivage du recepteur et necessite donc une enzyme catalytiquement active. La reponse des cellules endotheliales depend aussi de l'activation de la proteine kinase c et de phosphorylation sur les tyrosines. Le retour d'une sensibilite a l'enzyme requiere la synthese de nouveaux recepteurs. L'utilisation de nos outils moleculaires nous a permis de montrer que l'activite catalytique de l'enzyme est necessaire pour activer les megacaryocytes et inhiber specifiquement la pousse de leurs progeniteurs, ces deux mecanismes etant medies par le recepteur de la thrombine
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Halihan, Todd. "Permeability structure in fractured aquifers /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
Повний текст джерела
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Ayt, Ougougdal Mohamed. "Contrôles magmatiques, structuraux et hydrothermaux de la formation des épisyénites de la marche occidentale." Vandoeuvre-les-Nancy, INPL, 1994. http://docnum.univ-lorraine.fr/public/INPL_T_1994_AYT_OUGOUGDAL_M.pdf.
Повний текст джерелаАнотація:
La reconstruction de la succession de percolations hydrothermales dans les granites a été menée sur l'exemple des zones d'altérations subsolidus de type épisyénite, et minéralisées en uranium (marche occidentale). Une étude des contrôles magmatiques, structuraux précoces de la formation des altérations grâce à une cartographie structurale, pétrographique et géochimique a montré que les épisyénites se sont formées dans les zones de contact entre leucogranites et des intrusions de leucogranite à biotite. L’étude quantitative des déformations ductiles et cassantes à l'échelle macro et microscopique a montré le rôle des anisotropies liées à la déformation ductile sur l'orientation et l'intensité de la microfracturation. Grâce à la mise au point d'une méthode de calcul des paléotenseurs de perméabilité, les données sur les réseaux de plans d'inclusions fluides ont permis d'estimer les perméabilités maximales caractérisant les stades hydrothermaux. Les concentrations d'uranium se sont formées grâce à trois facteurs : i) la formation d'un drain majeur, résultant d'une forte altération du granite (dissolution du quartz) sous l'effet de la percolation des fluides aqueux de haute température dans des réseaux denses de microfractures NNE, probablement sous l'effet d'un réchauffement local à basse pression lié aux intrusions tardives. Ii) le maintien de la perméabilité ; iii) jusqu'aux stades de minéralisation à percolation de fluides tardifs
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Loendersloot, Richard. "The structure-permeability relation of textile reinforcements." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/55931.
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Schmitt, Mayka. "Pore structure characterization of low permeability rocks." reponame:Repositório Institucional da UFSC, 2014. https://repositorio.ufsc.br/xmlui/handle/123456789/128792.
Повний текст джерелаАнотація:
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2014.Made available in DSpace on 2015-02-05T20:21:04Z (GMT). No. of bitstreams: 1 328189.pdf: 16197737 bytes, checksum: ef7484371ab3bfb4817957e38ea6adb5 (MD5) Previous issue date: 2014
Hoje as pesquisas em rochas de baixa permeabilidade (grande tendência no mundo e em breve na indústria petrolífera brasileira) se voltam à escala de poros seja para investigação petrofísica, morfológica, de distribuição de tamanhos de grãos ou poros ou escoamento de fluidos, prática descrita pelos valores de permeabilidade. A avaliação destas propriedades por sua vez, é essencial ao desenvolvimento e exploração de reservas de hidrocarbonetos. No entanto, a determinação de parâmetros do sistema poroso nessas rochas, arenitos de baixa permeabilidade (TGS) e rochas selantes (SR), continua a ser um grande desafio devido à extrema variabilidade de ambientes deposicionais e complexa microestrutura composta por argilas e tamanhos de poros de submícrons a ångströms. Nesta tese empregou-se um conjunto de técnicas experimentais para a caracterização da estrutura porosa de TGS e SR. De tal modo, o trabalho foi dividido em dois tópicos principais: (i) Caracterização do sistema poroso e propriedades petrofísicas em TGS utilizando-se as técnicas de permeabilidade por decaimento de pulso (PDP), NMR de baixo campo, adsorção gasosa N2 (N2GA), porosimetria por intrusão Hg (MICP), nano- e microtomografia de raios X (res. <0,7 µm); (ii) Estudo por espectrometria fotoacústica (PAS) em SR de distintos campos geológicos para a determinação de porosidade e difusividade térmica (TD), de forma a estimular a exploração segura de gás e óleo, o armazenamento de CO2, bem como a caracterização de folhelhos. Para SR os valores de TD variaram entre 0,0167 e 0,0930 (cm2/s) e a porosidade entre 1,42 e 9%; para TGS a caracterização 3D da estrutura porosa forneceu valores de tortuosidade e fator de forma entre 2,19-5,47 e 3,2-8,5. As distribuições de tamanho de poros mostraram-se bimodais nos ensaios MICP, trimodais na multiescala 3D e tetramodais na NMR, enquanto a porosidade pela combinação N2GA e MICP variou entre 1,94 e 11,96% e a permeabilidade PDP de 0,036 a 0,00066 mD. Alguns dos parâmetros microestruturais obtidos em TGS foram correlacionados na estimativa de permeabilidade utilizando-se modelos como Carman-Kozeny (Dullien, 1992) e Coates (1999). O conjunto de técnicas e metodologias aplicado nesta tese mostrou ser ferramenta imprescindível na caracterização de rochas de baixa permeabilidade, uma vez que permitem integrar atributos da rede de poros que influenciam nas macro-propriedades das rochas analisadas.
Abstract : Nowadays, significant research effort in low-permeability rocks (a wide tendency elsewhere and soon in the Brazilian petroleum industry) has been focused on pore-scale petrophysics, morphologies and distributions, as well as fluid flow circulation described by the values of permeability. The evaluation of these properties in turn is essential for the assessment and exploitation of hydrocarbon reserves; however, determining pore system parameters in such rocks as tight gas sandstones (TGS) and seal rocks (SR) remains challenging because of the extreme variability in depositional environments resulting in complex pore structures comprised by clays and length scales from sub-microns to Angstroms. In this work we applied a set of techniques to characterize submicron-pore structures in TGS and SR. Therefore it was divided into two main topics of interest: (i) Characterization of petrophysical properties and pore systems in very low permeability TGS using Pulse-Decay Permeability (PDP), Low Field Nuclear Magnetic Resonance (LFNMR), Nitrogen Gas Adsorption (N2GA), Mercury Intrusion Capillary Pressure (MICP) and Multi-scale 3D X-ray Nano- and MicroCT (down to 0.7 µm resolution) techniques; (ii) Study of Photoacoustic Spectrometry (PAS) for determining thermal diffusivity (TD) and porosity in three seal rocks originating from dissimilar fields as a key issue for safe exploration, storage purposes (CO2 sequestration) and developments in shale characterization. The values obtained for TD were between 0.01667 and 0.09298 (cm2/s) while porosity ranged from 1.42 to 9%. For the analyzed TGS the 3D pore-structure characterization lead to pore tortuosity and shape factors ranges of 2.19-5.47 and 3.2-8.5, respectively, and pore size distributions tended to be bimodal for MICP, trimodal for 3D multi-scale and tetramodal for LFNMR measurements. The porosity values ranged from 1.94 to 11.96% obtained by the combination of N2GA and MICP techniques and permeability from 0.036 to 0.00066 mD by PDP technique. The measured pore-structure parameters were also used to predict empirical permeability in TGS (using e.g. Carman-Kozeny (Dullien, 1992) and Coates (1999) models). The set of applied methods has shown to be a useful tool for the unconventional reservoir characterization since it allows obtaining pore morphological and quantitative parameters which account for the permeability values.
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Agirtopcu, Yasin. "Investigations On The Permeability Of Acrylic Powder Structures." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1045343/index.pdf.
Повний текст джерелаАнотація:
There are many examples where creation and usage of porous substrates
play important roles in various fields of application in material science and
technology. In the manufacture of ceramic products, as an alternative to the plaster molds, porous resin molds are used in order to resolve the drawbacks that result A porous substrate can be produced by various ways. In this study, porous polymeric matrices of poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate-co-2-hydroxyethyl methacrylate) [poly(MMA-HEMA)] polymers were prepared by connecting the polymer microspheres to each other by an epoxy adhesive. To improve the surface properties, methyl methacrylate (MMA) was copolymerized with 2-hydroxyethyl methacrylate (HEMA). The microspheres used were synthesized by suspension polymerization and characterization was
done by Nuclear Magnetic Resonance (NMR), Particle Size Analyzer and
Scanning Electron Microscope (SEM). The porous samples were prepared with
PMMA and poly(MMA-HEMA) copolymer microspheres with two different HEMA contents and their surface energies were measured. In addition, the effect of mean particle diameter of the microspheres used and the epoxy content of the solution used to bind the microspheres, on the impregnation capacity, morphology
and the impact strength of the porous samples prepared, were studied.
Inclusion of HEMA into the formulation improved the impregnation capacity of the samples. Using microspheres with narrower particle size distribution resulted in larger representative capillary radii and higher rate of impregnation of the samples. Increasing the epoxy content of the solution used to bind the beads, increased the impact strengths of the samples prepared.
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Kurek, Mia. "Comprehensive study of the effects of formulation and processing parameters on structural and functional properties of active bio-based packaging films." Thesis, Dijon, 2012. http://www.theses.fr/2012DIJOS095/document.
Повний текст джерелаАнотація:
Cette étude porte sur l’analyse du mécanisme de transfert du carvacrol (molécule antimicrobienne volatile) au travers de films à base de chitosan. La composition, la structure, les paramètres de procédés et de séchage de la couche de chitosan ont été corrélés aux propriétés physico-chimiques et fonctionnelles des films. La compréhension de ces facteurs et de leurs influences est cruciale à l’optimisation de la production de films actifs à base de polyéthylène enduits de chitosan. En effet, composition, microstructure et condition environnementale (température, humidité) conditionnent la rétention puis la libération contrôlée du carvacrol. La présence d’humidité induit absorption, gonflement, et plastification du chitosan, et par conséquent influe sur la structure, ses propriétés thermiques et de surface. L’absorption d’humidité, due au changement de structure, entraîne une forte augmentation de la perméabilité aux gaz et à la vapeur d’eau, et favorise ainsi la libération du carvacrol, nécessaire à une efficacité antimicrobienne rapide. Cette dernière, ainsi que l’impact sensoriel sur l’aliment emballé, sont directement corrélés aux aspects cinétiques et de partage des vapeurs de carvacrol. Ces travaux ont ainsi mis en évidence l’importance le compréhension de mécanismes de transfert dans les emballages à base de bio-polymères sur leur production et application industriellesThe aim of this study is the analysis of structure and transfer mechanisms through chitosan based food packaging materials with incorporated carvacrol as a model of antimicrobial active substance. Integration of composition parameters, structure, processing and drying of chitosan systems is correlated to its physico chemical and functional properties. Understanding and detailed analyses of processing parameters is crucial in production of active chitosan coatings applied on conventional materials such as polyethylene. So, the knowledge of composition and microstructure in association to environmental conditions, control the retention and the release kinetics of carvacrol from chitosan film. Water vapour was crucial parameter that strongly influenced adsorption, swelling and plasticization of chitosan based films, as well as thermal, surface and mechanical properties. By changing the matrix structure, penetrating water molecules decreased gas barrier efficiency and increased release of carvacrol. Furthermore, release of carvacrol in the headspace was correlated to the antimicrobial efficiency and to the organoleptic impact on packed food products. Such investigation highlights the transfer mechanism within bio-based materials, prior to efficiency prediction for their industrial development.In dry conditions, all chitosan films were fairly good gas barriers (about 10 17 g/m∙s∙Pa). Chitosan coated polyethylene films were up to 10000 times less permeable than uncoated PE. Increase in the environmental humidity above 60% and up to 96% (that represents the conditions of a real fresh food packaging system), significantly increased gas permeability of all chitosan films. Mechanical tests confirmed that when relative humidity increased, structural changes were induced. Therefore, extensive water plasticization of chitosan matrix was observed.Diffusion coefficients of carvacrol from chitosan film increased up to 1000 times when humidity increased from 0% to 100%. Water vapour triggers the release of carvacrol in the vapour phase. This indicates the importance of controlling the environmental conditions in the packaging at the time of the application but also during the active film storage.Films with carvacrol concentrations in the vapour phase above 2x10-7 g/mLair were efficient against large spectrum of bacteria, including some Gram-positive bacteria, Gram-negative bacteria and fungi. In some instances the concentration that was required for carvacrol antimicrobial efficiency was not organoleptically acceptable to consumers
Cilj ovog rada je analiza strukture i mehanizama prijenosa tvari kroz ambalažne materijale za pakiranje hrane na bazi kitozana s inkorporiranim karvakrolom kao modelnom aktivnom antimikrobnom tvari. Integrirani sastavni parametri, struktura, proizvodnja i sušenje kitozanskog sustava korelirani su sa njegovim fizikalno-kemijskim i funkcionalnim svojstvima. Razumijevanje i detaljna analiza procesnih parametara predstavlja ključan korak u proizvodnji aktivnih kitozanskih prevlaka na konvencionalnim materijaima kao što je polietilen. Dakle, poznavanje sastava i mikrostrukture u ovisnosti o okolnim uvjetima, osnovni je preduvjet za kontrolirano zadržavanje i otpuštanje karvakrola iz filmova na bazi kitozana. Vodena para predstavlja ključni parametar koji značajno utječe na adsorpciju, bubrenje i plastifikaciju kitozanskih filmova, kao i na njegova toplinska, površinska, i mehanička svojstva. Penetracijom (prodiranjem) molekula vode dolazi do promjene strukture matriksa, smanjuje se učinkovitost barijernih svojstava prema plinovima i povećava otpuštanje karvakrola. Otpuštanje karvakrola u zračnom prostoru u korelaciji je sa antimikrobnom učinkovitosti i organoleptičkim svojstvima upakiranih prehrambenih proizvoda. Ovo istraživanje prije svega naglašava značaj poznavanja mehanizma prijenosa tvari unutar biomaterijala koji je neophodan za predviđanje učinkovite primjene na industrijskoj razini
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Bernabé, Yves. "Permeability and pore structure of rocks under pressure." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/57818.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1986.Microfiche copy available in Archives and Science
Includes bibliographies.
by Yves Bernabe.
Ph.D.
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Xiao, Xueliang. "Modeling the structure-permeability relationship for woven fabrics." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12895/.
Повний текст джерелаАнотація:
The performance of woven fabric in many technical applications, such as airbags or reinforced composites, relates to fabric through-thickness permeability. A unified analytical model for woven fabric through-thickness permeability is proposed. It involves flow through gaps between yarns and within the yarns in terms of fabric porosity. The yarn permeability is a combination of flow along and transverse to unidirectional fibres. It is a function of fibre radius, fibre volume fraction, fibre array and crimp angle of interwoven yarns. The gap permeability is developed based on viscous and incompressible Hagen-Poiseuille flow in the gaps at low R_e values. The gap is simplified as a smooth fluid channel at the centre with slowly varying circular cross-section. The shape of the channel is approximated by a parabolic function. Volumetric flow rate is formulated as a function of pressure drop and flow channel geometry for the gap. The gap permeability is calculated thereafter according to Darcy’s law. For a woven fabric subjected to a high pressure load, an energy-based model is developed to predict the fabric out-of-plane deformation using minimum energy theory and an isotropic assumption for woven fabric. The model can predict the fabric maximum displacement and corresponding deflected profile across a diameter given a pressure load. The fabric deflection can be used to obtain the fabric elongation (strain) which results in the change of gap size, yarn width, yarn shape and fabric thickness in loose fabric (clear gaps between yarns) and the change of fibre volume fraction and crimp angle in tight fabric (overlapping yarns). The deformed fabric permeability is calculated by the unified permeability model based on the assumptions of the variation of geometric factors with deformation. If a woven fabric is subjected to a high decreasing pressure drop by air discharge, the fabric permeability is obtained by fitting pressure history and corresponding flow velocity using the Forchheimer equation. A nonlinear relationship is found between the pressure and velocity where the corresponding permeability is also called the dynamic permeability. The high pressure causes the shape of flow streamlines to vary in the gap between yarns (viewed as a converging-diverging duct). This flow behaviour is modelled by adding a non-Darcy term to Darcy’s law according to continuity theory and the Bernoulli equation. Therefore, a predictive Forchheimer equation is given for flow behaviour in a woven fabric based on the fabric geometry, structure and flow situation. The developed analytical models were verified by CFD simulations and experiments in this thesis. The comparisons showed good agreements. Sensitivity studies were conducted to understand the effects of geometric factors and mechanical properties on the fabric deformation and permeability. In this thesis, two pieces of equipment in particular were introduced for measuring the fabric dynamic permeability and fabric out-of-plane deformation. The measurements agreed well with their corresponding analytical predictions. Finally, the comparison of fabric deformation and non-Darcy flow showed the importance of fabric deformation in affecting the final fabric permeability.
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Васильченко, А. О. "Удосконалення фізико-хімічних методів збереження стійкості стінок свердловин в процесі буріння". Thesis, Івано-Франківський національний технічний університет нафти і газу, 2001. http://elar.nung.edu.ua/handle/123456789/3910.
Повний текст джерелаАнотація:
Розроблено ентропоосмотичну модель руйнування стінок свердловин, яка полягає у тому, що вода у системі буровий розчин - привибійна зона свердловини внаслідок самодовільного руху проти градієнту своєї структурної організованості надходить у пори і тріщини гірських порід, утворює високоорганізовані структури в яких нагромаджується механічна енергія. Коли напруження перевищують дорівнюють межі міцності гірських порід, відбувається руйнування стінок свердловин. Запропоновано використовувати параметр діелектричної проникності для оцінки інгібуючих (осмотичних) властивостей бурових розчинів під час їх розробки та застосування. Розроблені і успішно застосовуються рецептури високоінгібуючих бурових розчинів - вапняного і гуматноакрилово-калієвого.Диссертация посвящена вопросам совершенствования физико -химических методов предупреждения нарушения устойчивости стенок скважин. В диссертации разработана и обоснована гипотеза об энтропоосмосе, которая состоит в следующем: жидкость (растворитель) самопроизвольно движется против градиента своей структурной организованности (СО). На основе гипотезы об энтропоосмосе предложена физико --химическая модель разрушения стенок скважины, которая состоит из следующих положений: - вода в системе БР-ПЗС самопроизвольно движется в поры и трещины горных пород, где уровень СО более высокий; в соответствии с синергетическим принципом в призабойной зоне скважины происходит самоорганизация вещества и энергии, что обусловливает накопление напряжений; когда напряжения в массиве горных пород достигают предела прочности, просходит разрушение стенок. Для предупреждения разрушения стенок скважин необходимо: - понизить уровень СО воды в буровом растворе (использование коллоидов, полимеров); - повысить уровень СО воды в порах и трещинах горных пород (использование неорганических электролитов); - разорвать гидродинамическую связь между водой в буровом растворе и горных породах (известкование, гидрофобизация стенок скважины). Предложено использовать параметр диэлектрической проницаемости для оценки уровня ингибирующих (осмотических) свойств буровых растворов. Показано, что параметр диэлектрической проницаемости хорошо коррелирует с величинами осмотических давлений растворов солей. Диэлектрическая проницаемость не является аддитивной величиной в случае многокомпонентных буровых растворов. Если органические гидрофильные вещества и коллоидные глинистые частицы увеличивают структурную организованность воды, то добавление неорганических электролитов приводит к общему увеличению диэлектрической проницаемости вследствие разрушающего действия на гидратные слои вокруг коллоидных частиц. При разработке рецептур ингибированных буровых растворов параметр диэлектрической проницаемости можно использовать для подбора оптимальных соотношений органических и неорганичеких веществ. Предложены непротиворечивые объяснения механизмов ингибирующего действия гидроксида кальция и хлористого калия: молекулы и коллоидные частицы гидроксида кальция образует с алюминатами и силикатами горных пород вяжущее вещество, которое заполняет поры и трещины и закрепляет стенки скважины; ионы калия благодаря тому, что в гидратированной форме имеют меньший чем другие ионы размер, проникают в самые тонкие поры и трещины горных пород, разрушают там высокоорганизованную структуру воды, замедляя тем самым энтропооосмотический поток. Разработаны рецептуры буровых растворов - известкового и гуматноакрилокалиевого. Известковый буровой раствор на основе органической коллоидной фазы предназначен для бурения в условиях, когда в одном разрезе встречаются несовместимые пласты - терригенные, хемогенные, с аномально низкими пластовыми давлениями и чувствительные к водной среде. В экологически безопасном исполнении известковый буровой раствор может использоваться в морском бурении. При разработке рецептуры гуматноакрилокалиевого бурового раствора учитывался параметр диэлектрической проницаемости.Гуматноакрилокалиевый буровой раствор имеет высокие ингибирующие свойства, а также термо- и солестойкость. Промышленное применение известкового бурового раствора на основе органической коллоидной фазы и гуматноакрилокалиевого бурового раствора при бурении скважин в сложных горно - геологических условиях показало высокую их эффективность.
There has been worked out the entropoosmotic model of borehole wall instability which consist in the following statements: 1) water spontaneously moves in the opposite direction to the gradient of water structural organization from drilling fluids into pores and fractures of rocks and causes increase of pressure; 2) well walls break down when entropoosmotic pressure goes over a limit of rock strength. There is proposed the parameter of dielectric permeability for evaluation of inhibitive (osmotic) property of drilling fluids. There has been designed the systems of lime - based and lignite - acryl -potassium - based drilling fluids and introduced in gas industry.
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Hay, Stephen John. "Permeability - past and present - in continental crustal basement." Thesis, University of Glasgow, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278258.
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Edling, Hans Eliot. "Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/95029.
Повний текст джерелаАнотація:
Polyesters are an attractive class of polymer that can be readily modified with a wide range of different comonomers, during polymerization or with melt blending, to achieve a wide variety of physical properties. This research primarily focuses on polyesters that incorporate rigid aromatic structures that have excellent potential to enhance thermal and mechanical properties. Copolyesters were prepared through melt polycondensation of diesters and diols in the presence of an exchange catalyst. Monomer incorporation was verified with nuclear magnetic resonance (NMR) and molecular weights were obtained by measuring inherent viscosity (ninh). Physical properties were assessed with thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rheology. Mechanical properties were assessed with tensile and impact testing.
Copolyesters of poly(ethylene terephthalate) (PET) were synthesized by substituting dimethyl terephthalate (DMT) with dimethyl 4,4'-biphenyldicarboxylate (4,4'BB) resulting in enhanced glass transition (Tg) temperatures relative to PET while affording melting temperatures (Tm) low enough to allow facile melt processing. Further modification with dimethyl isophthalate (DMI) or dimethyl 3,4'-biphenyldicarboxylate (3,4'BB) slowed crystallization sufficiently to allow biaxial orientation, leading to further studies assessing the permeability of oriented films.
Novel amorphous polyesters were synthesized with 3,4'BB or 4,4'BB in combination with neopentyl glycol (NPG), 1,4-cyclohexandimethanol (CHDM) and ethylene glycol (EG). Use of multiple diols produced clear, amorphous copolyesters with Tgs as high at 129 C.
A series of novel high temperature(Tm) copolyesters were synthesized from dimethyl 2,6-naphthalenedicarboxylate (DMN) and 4,4'BB combined with CHDM. Studies were performed with standard DSC and thin film calorimetry to show the convergence of multiples melting endotherms in an effort to determine their origin. Preliminary work was performed on the modification of poly(1,4-cyclohexylenedimethylene terephthalate) (PCT), poly(1,4-cyclohexylenedimethylene 2,6-naphthalate) (PCN) and poly(1,4-cyclohexylenedimethylene 4,4'-bibenzoate) (PCB) with dimethyl p-terphenyl-4,4''-dicarboxylate.PHD
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Werrett, M. R. "The structure-function relationships in laminated barrier films." Thesis, De Montfort University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376563.
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Rinkevich, A. B., M. I. Samoylovich, and A. F. Belyanin. "Effective Conductivity and Magnetic Permeability of Nanostructured Materials in Magnetic Field." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35340.
Повний текст джерелаАнотація:
The problem of homogenization the nanostructured materials placed in DC magnetic field has been discussed. The experimental data are obtained using metallic superlattices, metal-dielectric thin films and 3D-nanostructured materials. All these materials contain ferro- or ferrimagnetic component. The trans-mission and reflection coefficients were measured on the waves of millimeter waveband. It has been shown that the experimental frequency spectra of the coefficients in zero magnetic field can be described by the effective conductivity and dielectric permittivity. The spectra of ferromagnetic resonance, however, cannot be calculated correctly with the averaged magnetization.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35340
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Bubacz, Monika. "Permeability and Flammability Study of Composite Sandwich Structures for Cryogenic Applications." ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/418.
Повний текст джерелаАнотація:
Fiber reinforced plastics offer advantageous specific strength and stiffness compared to metals and has been identified as candidates for the reusable space transportation systems primary structures including cryogenic tanks. A number of carbon and aramid fiber reinforced plastics have been considered for the liquid hydrogen tanks. Materials selection is based upon mechanical properties and containment performance (long and short term) and upon manufacturing considerations. The liquid hydrogen tank carries shear, torque, end load, and bending moment due to gusts, maneuver, take-off, landing, lift, drag, and fuel sloshing. The tank is pressurized to about 1.5 atmosphere (14.6psi or 0.1MPa) differential pressure and on ascent maintains the liquid hydrogen at a temperature of 20K. The objective of the research effort is to lay the foundation for developing the technology required for reliable prediction of the effects of various design, manufacturing, and service parameters on the susceptibility of composite tanks to develop excessive permeability to cryogenic fuels. Efforts will be expended on developing the materials and structural concepts for the cryogenic tanks that can meet the functional requirements. This will include consideration for double wall composite sandwich structures, with inner wall to meet the cryogenic requirements. The structure will incorporate nanoparticles for properties modifications and developing barriers. The main effort will be extended to tank wall’s internal skin design. The main requirements for internal composite stack are: • introduction of barrier film (e.g. honeycomb material paper sheet) to reduce the wall permeability to hydrogen, • introduction of nanoparticles into laminate resin to prevent micro-cracking or crack propagation. There is a need to characterize and analyze composite sandwich structural damage due to burning and explosion. Better understanding of the flammability and blast resistance of the composite structures needs to be evaluated.
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Chow, Hon-nin, and 周漢年. "Computer aided modelling of porous structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39848929.
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Goldhawk, Donna E. "Guinea pig fetal membrane structure and permeability to steroids and their conjugates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21287.pdf.
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Zhang, Minhui. "Investigation of structure and permeability of surfaces modified with self-assembled monolayers." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-08222008-063703/.
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Lock, Peter Alex. "Estimating the permeability of reservoir sandstones using image analysis of pore structure." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/37117.
Повний текст джерелаАнотація:
In this thesis, a method is developed for predicting the permeabilities of a core using only a small number of SEM images, without resorting to computationally intensive procedures. The pore structure is idealised as consisting of a cubic network of pore tubes having an arbitrary distribution of cross-sectional areas and shapes. The areas and perimeters of the individual pores are estimated from image analysis of scanning electron micrographs of thin sections, with appropriate stereological corrections introduced to infer the true cross sections of the pores. Effective medium theory is used to find the effective single-tube conductance, based on the measured distribution of individual conductances, thereby allowing a prediction of the permeability. The methodology has been applied to several reservoir sandstones from the North Sea, and also an outcrop sample from Cumbria, UK, yielding predictions that fall within a factor of two of the laboratory measurements in most cases. The procedure, although based on Kirkpatrick's intrinsically isotropic effectivemedium approximation, is not only capable of yielding reasonably accurate estimates of the permeabilities, but also gives a qualitatively correct indication of the anisotropy ratio. It also found that the use of an Bernasconi's anisotropic effective-medium approximation does not lead to a systematic improvement in the results, perhaps because the samples used in this study were insufficiently anisotropic for the approaches to yield different results. The validity of the effective medium approximation was also tested against exact pore network calculations. For the rocks examined in this study, with pore conductance distributions having log-variances less than 3, the effective medium approximation was found to be accurate to within a few percent.
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Pareek, Mamta School of Biological Earth & Environmental Sciences UNSW. "Structure and role of rhizomorphs of Armillaria luteobubalina." Awarded by:University of New South Wales. School of Biological, Earth and Environmental Sciences, 2006. http://handle.unsw.edu.au/1959.4/24353.
Повний текст джерелаАнотація:
Two different types of rhizomorphs were produced by A. luteobubalina in vitro conditions - aerial and submerged. They differed in growth rate, amount of mucilage, extent of peripheral hyphae, degree of pigmentation and in the structure of inner cortex. Otherwise they had a similar internal structure comprising 4 radial zones, namely, peripheral hyphae, outer cortex, inner cortex and medulla. Two membrane permeant symplastic fluorescent tracers, carboxy-DFFDA and CMAC which ultimately sequestered in vacuoles, behaved in a similar fashion in aerial and submerged rhizomorphs regardless of whether pigment was present in the outer cortical cell walls or in the extracellular material. Rhizomorphs appeared to be mostly impermeable to these probes with exception of a few fluorescent patches that potentially connected peripheral hyphae to inner cortical cells. In contrast, the apoplastic tracer HPTS which was applied to fresh material and its localisation determined in semi-thin (dry) sections following anhydrous freeze substitution appeared to be impeded by the pigmentation in cell walls and/or the extracellular material in the outer cortical zone. Structures identified as air pores arose directly from the mycelium and grew upwards into the air. A cluster of rhizomorph apices is initiated immediately beneath the air pores. As air pores elongated they differentiated into a cylindrical structure. Mature air pores became pigmented as did also the surface mycelium of the colony. The pigmented surface layer extended into the base of air pores, where it was elevated into a mound by tissue inside the base of the air pore. Beneath the pigmented surface layer there was a region of loose hyphae with extensive gas space between them. This gas space extended into the base of the air pore and was continuous with the central gas canal of rhizomorphs. Oxygen is conducted through the air pores and their associated rhizomorph gas canals into the oxygen electrode chamber with a conductivity averaging 679??68x10-12 m3s-1. The time averaged oxygen concentration data from the oxygen electrode chamber were used to compare three different air pore diffusion models. It was found that the widely used pseudo-steady-state model overestimated the oxygen conductivity. Finally, a model developed on the basis of fundamental transport equations was used to calculate oxygen diffusivities. This model gave a better comparison with the experimental data.
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Scott, Anthony Stephen John. "Processes of sand injection : relationships with host strata, internal structures, and permeability implications." Thesis, University of Aberdeen, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=92505.
Повний текст джерелаАнотація:
Large-scale sandstone injectite complexes located in California and in Tunisia have exposures of external geometries and sedimentary structures. Substantial macroscale erosion occurred along the margins between the injected sandstones and host mudstones that include scalloped upper margins that cut up to 5 m into the overlying host mudstones. Sedimentary structures preserved in the sandstone injectite complexes record fluid-flow, sedimentation and post-sedimentation processes. Bedload layers moving in traction along fluid-sediment interfaces is identified as a significant transport mechanism of grains in sills, low-angle dykes, and irregular injectites, as evidenced by laminae defined by differences grain size, grain composition, and grain packing. High-angle sandstone dykes are characterised by a distinct suite of sedimentary structures that include horizontal bands and pipes. Horizontal bands record the movement of fluidised sand as bands during the waning phase of sand injection. Pipes are interpreted to have formed due to post-sand-injection consolidation and fluid-escape. The distinct sedimentary structures and microtextures that characterise each intrusive element reflect the coupled relationships between the fluid-flow and sedimentation processes and the element type. Sedimentation, post-sedimentation, and diagenetic processes thereafter, resulted in the formation of heterogeneous permeabilities; values vary three-orders-of-magnitude. The heterogeneity is predictable and correlates with the type of intrusive element and its primary and secondary microfabrics. This link demonstrates the influence of primary sedimentation processes and secondary diagenetic processes on the injected sandstone permeability. By constraining the permeability heterogeneity of injected sandstones, it is possible to accurately quantify and thereby anticipate their impact on fluid flow in sedimentary basins.
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Ezzedine, el Dandachy Mohamad. "Characterization and modelling of permeability of damaged concrete : application to reinforced concrete structures." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI075/document.
Повний текст джерелаАнотація:
Pour les structures de génie civil avec un rôle d'étanchéité lors d'un accident grave, la perméabilité structurelle est une question clé. Dans ce contexte, cette thèse porte sur la modélisation numérique du taux de fuite à travers une structure en béton fissurée. Deux approches hydromécaniques dans un cadre continu sont proposés, une entièrement continu et une autre qui nécessite une analyse semi-discrète. L'approche semi-discrète est basée sur une méthode permettant de trouver le chemin de la fissure. Une fois le chemin de la fissure est trouvé, l’ouverture de fissure peut être calculée le long de la surface de la fissure discrétisé par équivalence d’une discontinuité forte. La dernière étape consiste à prescrire la loi de Poiseuille modifié le long de la surface de la fissure pour estimer le taux de fuite tout en imposant un gradient de pression. L'approche entièrement continue peut être appliquée directement dans le sens où aucun suivi de la fissure n’est nécessaire. C’est une combinaison de la perméabilité des endommagements diffus et de la perméabilité de Poiseuille modifiée. Ici, la déformation principale positive est choisie pour conduire la perméabilité de Poiseuille modifiée. Les deux approches proposées sont validées sur une campagne expérimentale de disque béton sec chargé dans un essai de fendage où la perméabilité aux gaz est réalisée. La validation est effectuée sur le taux de fuite dans la direction longitudinale. Les résultats obtenus avec les approches proposées par rapport aux données expérimentales montrent une bonne estimation de la conductivité hydraulique. En outre, l'approche continue est appliquée pour estimer le taux de fuite à travers un élément en béton armé soumis à une charge de traction où la multi-fissuration en mode I se produit (essai tirant). La comparaison avec l'expérience est effectuée sur le taux de fuite dans la direction perpendiculaire à la charge appliquée. Celui-ci montre un bon accord entre les débits estimé et mesuré si le même nombre de fissures est obtenu par le modèle mécanique.Cette thèse porte aussi sur l'effet des chargements thermomécaniques et de fluage sur la conductivité hydraulique du béton. Un système de perméabilité est développé et construit au cours de cette thèse sur la base du programme expérimental. Une campagne expérimentale est effectuée pour étudier l'effet couplé du fluage thermique et / ou mécanique sur la perméabilité à l’air sec du béton. Les propriétés de transfert dans les directions longitudinale et radiale par rapport à l'axe de charge sont étudiées. L’anisotropie de la perméabilité induite par la charge appliquée est analysée. En outre, la détermination de la perméabilité structurelle le long de l'interface acier-béton à différentes charges de cisaillement est encore une question ouverte. Un programme expérimental est réalisé qui porte sur le comportement mécanique du béton armé soumis à un essai de type push-in, ainsi que sur l’analyse de la perméabilité le long de l'interface acier-béton à des niveaux de charge différents. Une première tentative pour simuler le test en utilisant l'approche continue proposée est effectuée.Cette thèse a été l’occasion de réaliser une nouvelle campagne expérimentale, de produire de résultats originaux, d’effectuer de la modélisation numérique et de confronter les 2 approches proposées pour valider les modèles afin de les appliquer à l’échelle structurelleFor civil engineering structures with a tightness role during a severe accident, structural permeability is a key issue. In this context, this PhD deals with the numerical modelling of leakage rate through a cracked concrete structure. Two hydro-mechanical models in a continuous framework are proposed, a fully continuous one and another one that requires a semi-discrete analysis. The semi-discrete approach is based on a crack tracking method allowing to find the crack path. Once the crack path is found, the Crack Opening Displacement (COD) can be computed along the discretized crack surface by equivalence with strong discontinuity approach. The final step is to prescribe a modified Poiseuille’s law along the crack surface to estimate the leakage rate while imposing a pressure gradient. The fully continuous approach can be directly applied in a sense that no crack tracking is needed. It is a combination of permeability of diffuse damage and modified Poiseuille’s permeability. Herein, the positive principal strain is chosen to drive the modified Poiseuille’s permeability. The two proposed approaches are validated on an experimental campaign of dry concrete disk loaded in a splitting setup where gas permeability is performed. The validation is performed on the flow rate in the longitudinal direction. The results obtained with the proposed approaches compared to experimental data show a good estimation of the hydraulic conductivity. Furthermore, the fully continuous approach is applied to estimate the flow rate through a reinforced concrete element subjected to tensile loading where multi-cracking in Mode I occurs (tie-beam test). The comparison with the experiment is performed on the flow rate in the perpendicular direction to the applied loading. The latter shows a good agreement between the estimated flow rate and the measured one if the same number of cracks is obtained.This PhD deals as well with the effect of the delayed thermo-mechanical loadings on the hydraulic conductivity of concrete. A permeability system is developed and constructed during this PhD based on the experimental program. An experimental campaign is carried out to study the effect of thermal and/or mechanical creep on dry gas permeability of concrete. Permeabilities in longitudinal and radial directions with respect to load axis are addressed. The loading induced anisotropic permeability is analyzed. Furthermore, the determination of the structural permeability along the steel-concrete interface at different shear loadings is still an open issue. An experimental program is carried out which deals with the mechanical behavior of reinforced concrete subjected to a push-in test, as well as with a permeability analysis along the steel-concrete interface at different load levels. A first attempt to simulate the test using the proposed continuous approach is performed.This thesis was the occasion to conduct a new experimental campaign, to produce original results, to perform numerical modeling and to compare two proposed approaches to validate the models in order to apply them at the structural scale
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Adham, Tarek Abbas. "The development of test procedure to determine the potential durability of concrete structures." Thesis, Coventry University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342255.
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42
Khansari, Hossein. "An investigation of one-dimensional compression and consolidation of intact and reconstituted Bothkennar soft soil." Thesis, University of the West of England, Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337381.
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Phillips, Matthew David. "The effect of pore structure on gas and liquid permeability in crystalline rocks." Thesis, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252227.
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Uehara, Shin-ichi. "Permeability Structure of the Median Tectonic Line in Ohshima, Nagano Prefecture, central Japan." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/86470.
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Mathews, Tobias John. "Void structure, colloid and tracer transport properties of stratified porous media." Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2794.
Повний текст джерелаАнотація:
The characterisation of the properties of porous materials is of great importance in the effective management of natural and manmade systems. A sophisticated network model, 'Pore-Cor', of some of these properties has been previously developed. The present study has significantly extended the scope of the model's predictive capabilities. Flow and transport behaviour was examined in laboratory sand columns of various depths. These experiments examined unsaturated flow of water and conservative solute tracer transport through homogeneous sand samples. Flow through these was not homogeneous or repeatable. Experimental observations found that this may have been due to subtle random variations in packing, and the network model was shown to be able to simulate these. Solute transport of bromide was studied, applied both uniformly and from a point source. Both scenarios were modelled using a convection-dispersion equation, and it was demonstrated that the lateral component of such transport was highly significant. It was shown how convection-dispersion equation predictions of uniformly applied tracer transport might be improved by the application of the network model and a method for improving predicted lateral solute transport was outlined. It has been shown that levels of correlation in the distribution of differently sized voids within porous material may be responsible for large variations in permeability. This can make accurate modelling of permeability very difficult. A technique was developed for assessing the degree and nature of such correlations. The new method was tested on a variety of artificial and real samples and demonstrated to provide a quantitative assessment of such correlations. A method by which this could be used to improve network model simulations of materials possessing such correlation was described.
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Pilatos, George, Eleni Vermisoglou, Anastasios Labropoulos, Charitomeni Veziri, George N. Karanikolos, and Nick K. Kanellopoulos. "Pore structure evaluation of carbon nanotube and inorganic membranes through sorption and permeability studies." Diffusion fundamentals 16 (2011) 33, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13766.
Повний текст джерела
47
Pilatos, George, Eleni Vermisoglou, Anastasios Labropoulos, Charitomeni Veziri, George N. Karanikolos, and Nick K. Kanellopoulos. "Pore structure evaluation of carbon nanotube and inorganic membranes through sorption and permeability studies." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184893.
Повний текст джерела
48
Horta, Alen. "Evaluation of Self-Consolidating Concrete for Bridge Structure Applications." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7159.
Повний текст джерелаАнотація:
The goal of this research was to determine whether precast prestressed bridge elements with congested reinforcement could be cast using self-consolidating concrete (SCC) without vibration and yet comply with all parameters of strength, no honeycombing, and void-free surface finish. Eight wall panels and eight BT-72 13-ft long girder sections were fabricated in two precast plants. A qualitative and quantitative evaluation of the surface finish, and homogeneity of the concrete throughout the specimens was performed. Strength, creep, shrinkage and chloride permeability of the SCC field mixes were investigated. Good quality SCC mixes were produced for the walls and the BT-72 girder sections, which completely filled the specimens without the need of internal or external vibration, and resulted in a superior surface finish and a homogenous distribution of the aggregate throughout the section.
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Uddin, Md Jasim. "Synthesis and analysis of metamaterial structure for microwave frequency applications." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/107850/1/Md.%20Jasim_Uddin_Thesis.pdf.
Повний текст джерелаАнотація:
This thesis involves analysis of artificial materials to investigate metamaterial behavior and characteristics. Extraction techniques are used to validate the electromagnetic properties and different microwave applications are investigated. A new geometric structure is designed using dual star split ring resonator, which introduces a sharp, wide rejection band. A metamaterial microwave absorber suitable for dual-band operation and insensitive to incident polarization was also developed.
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Song, Chenlu. "Long-term observation of rock fracture permeability and structure under various pressure and temperature conditions." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/253256.
Повний текст джерелаАнотація:
京都大学0048
新制・課程博士
博士(工学)
甲第22420号
工博第4681号
新制||工||1731(附属図書館)
京都大学大学院工学研究科都市社会工学専攻
(主査)教授 岸田 潔, 教授 三村 衛, 准教授 肥後 陽介
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DFAM