Дисертації з теми "Transport in porus environment"
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1
Castenson, Catharine M. (Catharine Marie) 1976. "An investigation of bioluminescent microbial transport in porus media." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8988.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (leaves 101-106).
Since bacteria play a significant role in the composition of the subsurface, understanding the transport of microorganisms through groundwater and porous media is of great importance. Recently, increased study of microbial transport in the subsurface has been driven by the development of in-situ remediation techniques utilizing bacteria's natural ability to degrade contaminants in the subsurface. To date, research in microbial transport within soil and groundwater has been conducted extensively without any physical visualization of what is occurring in the subsurface. Because the factors that control the transport of bacteria through soil and groundwater are not well understood, direct visualization of microbial transport in the subsurface would be extremely valuable in understanding soil, microbial, and groundwater interactions. This project sought to investigate and develop a means of visualizing microbial transport through porous media. A system incorporating bioluminescent bacteria, as a visual indicator of both microbial transport and activity, was coupled with a transparent porous medium that allowed the bioluminescent bacteria to be directly visualized as they were transported through a model aquifer system. The investigation of microbial transport was performed at a range of pore fluid velocities, varying from 1.31E-5 m/s to 2.21E-4 m/s. Results acquired from the experimental setup were reproducible at similar flow rates and bacterial cell concentrations. The two main factors controlling microbial transport and activity were found to be flow velocity and oxygen concentration levels. The degradation and consumption of oxygen and contaminants is related to the amount of time microorganisms spend in particular pore spaces. Faster flow rates allow the bacteria to move through the soil without consuming all of the available oxygen, but may not allow the bacteria enough time to degrade the contaminant. Alternately, bacteria traveling through soil at slower flow rates consume all available oxygen before traveling too far. For the flow rates tested with this research, microbial flow was found to follow the flow pattern of a color tracer. However, at the lower flow rates, an oxygen depletion zone developed behind the advancing flow front. The width of this zone was observed to increase with time, resulting in a reduction of bioluminescent activity, and thus, degradation activity, within the system.
by Catharine M. Castenson.
S.M.
2
Neyland, Ryan P. "Colloid Detachment from Rough Surfaces in the Environment." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-050505-114151/.
3
Chan, Matthew Yunho. "Transport, Stability, and Deposition of Gold Nanoparticles in Porous Media." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/64177.
Анотація:
Gold-nanoparticle (AuNP) transport in groundwater is heavily influenced by the intrinsic properties of the nanoparticles and the external parameters of the environment. Batch experimental data indicated that 15 nm AuNP coated by bovine serum albumin (BSA-AuNP) was more stable at high ionic strength compared to citrate-coated AuNP (cit-AuNP) of similar size. It was expected that the stability of these AuNP would be replicated in column studies. Column experiments with varying monovalent and divalent ion concentrations using both types of AuNP yielded breakthrough curves that both adhere and deviate from this hypothesis. BSA-AuNP was found to be more stable relative to cit-AuNP during porous media flow in the presence of increasing concentrations of CaCl2, but the opposite occurred with increasing NaCl concentration. Colloidal filtration theory (CFT) fails to predict and explain this discrepancy. DLVO calculations suggested pore-space destabilization occurred in these experiments that were not accounted by CFT.Master of Science
4
Ha, Quoc Dat. "Modélisation multiéchelle du couplage adsorption-transport-mécanique dans les réservoirs de gaz de charbon : récupération assistée par injection de CO₂." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0194.
Анотація:
Le gaz de charbon est une ressource énergétique dont l'exploitation peut être accélérée par injection de gaz carbonique (CO₂) combinant ainsi production de méthane (CH₄) et stockage du gaz carbonique produit par sa combustion. La structure du réservoir est considérée comme un milieu à double porosité avec des fractures naturelles (cleats) et une matrice contenant une phase solide et des nanopores (de taille inférieure à 2 nm) où le gaz est stocké par adsorption sur la paroi solide. Le CO₂ est plus facilement adsorbé que le CH₄. Un modèle théorique multiéchelle combinant adsorption, transport et poromécanique du réservoir est développé. À la plus petite échelle, les molécules de gaz sont considérées comme des sphères dures interagissant par un potentiel de Lennard-Jones. Une nouvelle méthode numérique utilise la théorie de la fonctionnelle de densité (DFT) et la théorie fondamentale de la mesure (FMT) pour calculer la distribution des densités moléculaires d'un mélange de gaz pour une géométrie quelconque des nanopores. La paroi solide exerce un potentiel extérieur répulsif à très courte distance et attractif à plus grande distance sur les molécules de gaz. À partir des distributions moléculaires des gaz, la force de solvatation exercée par la phase fluide sur la surface des nanopores est calculée précisément. La méthode de l'homogénéisation asymptotique permet de passer de l'échelle du nanopore à l'échelle microscopique et d'obtenir la réponse de la matrice de charbon. Le modèle poroélastique de Biot est modifié par la force de solvatation qui agit comme le principal facteur gouvernant le gonflement ou la contraction de la matrice. Les équations moyennes de conservation de la masse des deux gaz (CH₄ et CO₂) dans la matrice prennent en compte les phénomènes d'adsorption caractérisés par des coefficients de partition et une diffusion effective de type Knudsen. Une seconde homogénéisation vise à obtenir la loi macroscopique à l'échelle du réservoir en combinant le réseau de cleats et la matrice solide. Le contact à l'interface matrice-cleats est caractérisé par la loi hyperbolique de Barton-Bandis qui modifie la rigidité effective ainsi que la perméabilité du réservoir. Après homogénéisation, le réservoir est un milieu hétérogène et anisotrope du fait de la structure des cleats et de la variation spatiale de la pression du fluide. Une équation moyenne macroscopique pour la diffusion des gaz dans la matrice et le transport gaz-eau dans les cleats est développée en considérant l'échange de masse entre la matrice et les cleats gouverné par l'approximation de Warren et Root. Des simulations numériques démontrent la corrélation cruciale entre les distributions de pression de gaz, l'ouverture des cleats et la rigidité du réservoir. L'injection de CO₂ améliore significativement la production de CH₄. Elle permet le stockage souterrain de CO₂ contribuant à réduire les émissions de gaz à effet de serreCoal seam gas is an energy resource whose exploitation can be enhanced by injectingcarbon dioxide (CO₂), thus combining the production of methane (CH₄) and the storage of carbon dioxide produced by its combustion. The structure of the reservoir is considered to be a double-porosity medium with natural fractures (cleats) and a matrix containing a solid phase and nanopores (less than 2 nm in size) where the gas is stored by adsorption on the solid wall. CO₂ is more easily adsorbed than CH₄. A multiscale theoretical model combining adsorption, transport and reservoir poro-mechanics is developed. At the smallest scale, the gas molecules are considered as hard spheres interacting through a Lennard-Jones potential. A new numerical method uses Density Functional Theory (DFT) and Fundamental Measure Theory (FMT) to calculate the distribution of molecular densities of a mixture of gases for any nanopore geometry. The solid wall exerts an external potential that is repulsive at very short distances and attractive at longer distances on the gas molecules. From the molecular distributions of the gases, the solvation force exerted by the fluid phase on the surface of the nanopores is precisely calculated. The asymptotic homogenization method is performed to upscale the nanopore-scale model and to obtain the response of the coal matrix at the microscale. The Biot poroelastic model is modified by the solvation force, which acts as the main factor governing matrix swelling or contraction. The average mass conservation equations for the two gases (CH₄ and CO₂) in the matrix take into account adsorption phenomena characterized by partition coefficients and an effective Knudsen-type diffusion. A second homogenization aims at obtaining the macroscopic law at the reservoir scaleby combining the cleats network and the solid matrix. The joint stiffness at the matrix-cleats interface is characterized by the hyperbolic Barton-Bandis law, which modifies the effective stiffness and the permeability of the reservoir. After homogenization, the reservoir is a heterogeneous and anisotropic medium due to the structure of the cleats and the spatial variation of the fluid pressure. A macroscopic average equation for gas diffusion in the matrix and gas-water transport in the cleats is developed by considering the mass exchange between the matrix and the cleats governed by the Warren and Root approximation. Numerical simulations illustrate the crucial correlation between gas pressure distributions, cleat opening and reservoir stiffness. CO₂ injection significantly improves CH₄ production and enables a underground storage of CO₂, which contributes to reducing green-house gas emissions
5
Chan, Matthew Yunho. "Visualization, Characterization, and Analysis of Gold Nanoparticles Fate and Transport in Aqueous Porous Media Environment with Advanced Photonics Technique." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85437.
Анотація:
Increased proliferation of nanotechnology has led to concerns regarding its implication to the water environment. Gold nanoparticles (AuNP) were used as a model nanomaterial to investigate the fate and dynamics of nanoparticles in the complex water environment. A column study was performed to examine the fate and transport of gold nanoparticles with two different coatings in porous media. The resulting data suggested that gold nanoparticles aggregate significantly in the porespace of the column interior, a finding that is not predicted by traditional colloidal filtration theory or Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surface-enhanced Raman spectroscopy (SERS) was developed as a new technique to investigate AuNP aggregation in water with varying salt levels. The SERS technique proved valuable as an analytical technique, elucidating information about aggregation as well as AuNP surface interactions with dissolved halides in water. A thorough investigation examining Aunt aggregation with monovalent and divalent salts utilizing SERS, ultraviolet-visible light (UV-Vis) spectroscopy, and
dynamic light scattering (DLS) was conducted. Each technique provided data describing different aspects of the dynamic behavior of AuNPs in complex water environments. Results suggest that in addition to
attractive and repulsive interactions described by DLVO theory, chemical interactions between the AuNP surface and dissolved halides were also a significant driving force for aggregation and other
transformative behaviors of AuNPs in water. The SERS technique developed in this work was shown to be a viable tool to help unveil the vastly complex dynamics of nanomaterial in the water environment.Ph. D.
6
Lo, Prete Mariantonia. "Port de commerce et environnement, une relation en évolution : ce que nous apprennent les recours contentieux dans les ports français et italiens en mer Méditerranée." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1178.
Анотація:
Le territoire portuaire est inévitablement un lieu de conflits, notamment dans son processus de prise en compte de l'environnement. L'objet de notre travail de recherche est de voir comment l'environnement s'inscrit dans le développement portuaire à partir de l'analyse des recours contentieux, c'est-à-dire des conflits environnementaux qui engagent des acteurs publics et privés face aux tribunaux. Nous avons ainsi mis en place un outil méthodologique permettant de traiter les arrêts : une grille d'analyse géo-juridique des conflits environnementaux portuaires résolus par le juge qui permet de saisir la variété d'éléments caractérisant chaque conflit, et ainsi d'en faire une analyse quantitative et qualitative. L'originalité de cette thèse réside donc dans son approche de l'aménagement de l'espace par le droit. Travailler sur les contentieux donne en effet des éléments précieux pour comprendre les rapports qui s'établissent entre les différents acteurs dans la fabrique des territoires portuaires lorsque ceux-ci sont confrontés au développement et aux enjeux environnementaux. C'est à cet effet que nous proposons une typologie de la prise en compte de l'environnement dans le développement portuaire. Celle-ci pourrait permettre de mieux comprendre de nouveaux conflits environnementaux en les rapportant aux profils portuaires identifiés, voire de réfléchir aux moyens d'améliorer la prise en compte de l'environnement dans le territoire portuairePorts are inevitably the site of litigation born out of environmental issues. Our research aims to understand how the environment is taken into account in port development. For that purpose, we analysed litigation where public and private players went to court over environmental issues. To do so, we created a method based on a geo-law grid that we used to read and analyse judgements on environmental issues linked to ports, and to grasp the variety of characteristics of these judgements on which we can base a quantitative and qualitative analysis. Our thesis is unique in using a legal approach to study port development. Using the prism of litigation provides valuable information to understand the relationships between private and public players involved in the development of ports as they face environmental issues. As a contribution to this purpose, we provide profiles of how the environment has been taken into account in port development. These port profiles can help us better understand new environmental disputes, and help us find better ways to take the environment into account in port development
7
Kilchherr, Rudolf. "Transport phenomena in porous media." Thesis, Kingston University, 2003. http://eprints.kingston.ac.uk/20729/.
Анотація:
Non-Newtonian flow in heterogeneous media is of enormous theoretical and industrial importance. This phenomenon is studied to reveal macroscopic effects that arise due to the interaction between the non-linear flow behaviour and the spatial variation of the medium through which it is forced to move. The heterogeneity is achieved by using porous granular media, which is naturally non-homogeneous. The non-Newtonian properties of the fluid may have many causes and is an intrinsic property of the fluid that is used: One way of achieving it is by studying dense slurries of neutral particles or naturally occurring magmatic flows. Another way is to study the case where the flow is dominated by its ionic content and where the double layer thickness (the effective size of the ionic entities) is of the order of magnitude of the pore size. All cases studied in this thesis pertain to slow flow (low Reynolds number), though the fluid may be compressible. The variations in the flow are calculated in first order and these turn out to be coupled to the spatial variations in the porous medium. In this way structure formation is predicted. The structures may be either aligned with or may be perpendicular to the mean flow direction. 'Experiments to decide on which regime is relevant have been conducted. The genesis of structure formation is studied as a temporal development by considering a compressible flow. The constitutive equation that is required to couple the compressibility to the flow parameters is investigated. Two possible mechanisms have been identified: compressibility coupled to the pressure field and compressibility associated with the fluctuations in the flow. Using linear analysis the structure formation patterns associated with these two mechanisms are established for the steady state. Flow of ionically laden fluids has also been studied. Experiments done at Loughborough University (Department of Chemical Engineering) on electrowashing of filter cakes has been used to prove a major macroscopic effect. This effect takes place when the ionic diameter (which is approximately twice the double layer thickness) is of the order of magnitude of the pore size. A phenomenological set of transport equations has been set up. These contain coefficients, such as transition probabilities and mean ionic flow rates, that can be obtained from experiments by doing a first order solution of the equations for short times. A more involved numerical solution is also supplied and confirms the initial analytical estimates.
8
Jing, Wen 1966. "Virus transport through porous media." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/291550.
Анотація:
Investigated in laboratory column experiments were the effects of 0.01 M and 0.001 M CaPO₄ concentrations and pH on the attachment-detachment of bacteriophages PRD-1 and MS-2. Bacteriophages PRD-1 and MS-2 exhibited attachment to the soil at concentrations of 0.01M CaPO₄ and 0.5M NaCl. Release of attached phage at 0.001 M CaPO₄ and without NaCl was observed. The pH was also found to affect the attachment-detachment of PRD-1 and MS-2. However, they attached at pH 5.5 and detached at pH 8.0 at a limited extent and over an extented long period of time. The effect of salt concentration on deattachment was greater than the effect of pH. Similar results were obtained when glass beads were used as the adsorbent. These results suggest that changes in pH and ionic strength (as might occur after a rainfall) can result in the rapid release of previously adsorbed virus. (Abstract shortened by UMI.)
9
Du, Plessis Elsa. "Modelling of single phase diffusive transport in porous environments." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4323.
Анотація:
Thesis (MSc (Applied Mathematics))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Macroscopic diffusion through porous media is considered in systems where this process does not occur along with or induce bulk convective flow of the diffusing species. The diffusion coefficient present in the governing equations of suchmacroscopic diffusion is unique to a pair of species in a binary system. This coefficient may be determined experimentally, but such experimentation must be carried out for every different pair of species. Taking this into consideration, a deterministic pore-scale model is proposed to predict the effective diffusivity of homogeneous and unconsolidated porous media which ultimately depends solely on the porosity of the media. The approach taken is to model a porous medium as either a fibre bed or an array of granules through which the diffusive process is assumed to be homogenous and transversally isotropic. The fibre bed and granular modelsmay be viewed as two-dimensional and three-dimensional models respectively, and may also be combined to form a weighted average model which adjusts to differing diffusive behaviour at different porosities. The model is validated through comparison with published analytical and numerical models as well as experimental data available in the literature. A numerical program is implemented to generate further data for various arrangements of homogeneous, anisotropic and transversely isotropic porous media. The numerical results were validated against an analytical model from the literature which proved to be inapplicable to a specific case. The weighted average analytical model is proposed for this case, instead. The results of this study indicate that the weighted average analytical model is in good agreement with the numerical and experimental data and as such may be applied directly to a binary system of which the porosity is known in order to predict the effective diffusivity.
AFRIKAANSE OPSOMMING: Makroskopiese diffusieprosesse deur poreuse media word oorweeg in sisteme waar geen konveksie van die diffunderende stof plaasvind of geïnduseer word nie. Die wiskundige beskrywing van hierdie prossese bevat die sogenaamde diffusiekoëffisïent, ’n konstante wat uniek is tot ’n tweeledige sisteem. Dié konstante kan eksperimenteel bepaal word, maar as gevolg van die uniekhied daarvan tot verskillende sisteme moet dit vir elke tweeledige sisteem bepaal word. Op grond hiervan word ’n deterministiese model voorgestel om die effektiewe diffusiwiteit vir diffusie deur homogene en losstaande poreuse media te voorspel. Die model hang slegs af van die porositeit van die poreuse medium wat benader word as ’n veselbed of korrelstruktuur. Die diffusieproses deur dergelike strukture word beskou as homogeen en isotroop in die dwarsstroomrigting. Die veselbed- en korrelmodelle word beskou as twee- en driedimensionele modelle onderskeidelik en word gekombineer om ’n geweegde gemiddelde model te vorm wat dus by enige porositeit die verlangde porositeit gee. Die model is geverifieer deur vergelyking met analitiese- en numeriese modelle asook eksperimentele data vanuit die literatuur. ’n Numeriese program is gebruik om verdere resultate te verkry vir verskeie skikkings van homogene, anisotrope en dwarsverskuifde poreuse media. Die numeriese resultate is gekontroleer deur vergelyking met ’n analitiese model vanuit die literatuur. ’n Spesifieke geval is uitgewys waarvoor hierdie model nie toepasbaar is nie, maar waarvoor die voorgestelde geweegde gemiddelde model goeie resultate lewer. Die uitkomste dui aan dat die analitiese model goed ooreenstem met die numeriese en eksperimentele data en kan dus direk toegepas word om die effektiewe diffusiwiteit te verkry van ’n tweeledige sisteem waarvan die porositeit bekend is.
10
Kang, Peter Kyungchul. "Anomalous transport through porous and fractured media." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90043.
Анотація:
Thesis: Ph. D. in Hydrology, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 132-144).
Anomalous transport, understood as the nonlinear scaling with time of the mean square displacement of transported particles, is observed in many physical processes, including contaminant transport through porous and fractured geologic media, animal and human foraging patterns, tracer diffusion in biological systems, and transport in complex networks. Understanding the origin of anomalous transport is essential, because it determines the likelihood of high-impact, low-probability events and therefore exerts a dominant control over the predictability of a system. The origin of anomalous transport, however, remains a matter of debate. In this thesis, we first investigate the pore-scale origin of anomalous transport through sandstone. From high-resolution (micron-scale) 3D numerical flow and transport simulation, we find that transport at the pore scale is markedly anomalous. We demonstrate that this anomalous behavior originates from the intermittent structure of the velocity field at the pore scale, which in turn emanates from the interplay between velocity heterogeneity and velocity correlation. Finally, we propose a continuous time random walk (CTRW) model that honors this intermittent structure at the pore scale and captures the anomalous 3D transport behavior at the macroscale. To show the generality of our finding, we study transport through lattice networks with quenched disorder. We again observe anomalous transport originating from the interplay between velocity heterogeneity and velocity correlation. We extend the developed CTRW model to capture the full multidimensional particle transport dynamics for a broad range of network heterogeneities and for both advection- and diffusion-dominated flow regimes. We then study anomalous transport through fractured rock at the field-scale. We show that the interplay between heterogeneity and correlation in controlling anomalous transport can be quantified by combining convergent and push-pull tracer tests because flow reversibility is strongly dependent on correlation, whereas late-time scaling of breakthrough curves is mainly controlled by velocity heterogeneity. Our transport model captures the anomalous behavior in the breakthrough curves for both push-pull and convergent flow geometries, with the same set of parameters. Moreover, the inferred flow correlation length shows qualitative agreement with geophysical measurements. Thus, the proposed correlated CTRW modeling approach furnishes a simple yet powerful framework for characterizing the impact of flow correlation and heterogeneity on transport in porous and fractured media. Finally, we propose a joint flow-seismic inversion methodology for characterizing fractured reservoirs. Traditionally, seismic interpretation of subsurface structures is performed without any account of flow behavior. With the proposed methodology, we reduce the uncertainty by integrating dynamic flow measurements into the seismic interpretation, and improve the predictability of reservoir models by this joint use of seismic and flow data. This work opens up many possibilities of combining geophysical and flow information for improving subsurface characterization.
by Peter Kyungchul Kang.
Ph. D. in Hydrology
11
Lo, Prete Mariantonia. "Port de commerce et environnement, une relation en évolution : ce que nous apprennent les recours contentieux dans les ports français et italiens en mer Méditerranée." Electronic Thesis or Diss., Paris Est, 2012. http://www.theses.fr/2012PEST1178.
Анотація:
Le territoire portuaire est inévitablement un lieu de conflits, notamment dans son processus de prise en compte de l'environnement. L'objet de notre travail de recherche est de voir comment l'environnement s'inscrit dans le développement portuaire à partir de l'analyse des recours contentieux, c'est-à-dire des conflits environnementaux qui engagent des acteurs publics et privés face aux tribunaux. Nous avons ainsi mis en place un outil méthodologique permettant de traiter les arrêts : une grille d'analyse géo-juridique des conflits environnementaux portuaires résolus par le juge qui permet de saisir la variété d'éléments caractérisant chaque conflit, et ainsi d'en faire une analyse quantitative et qualitative. L'originalité de cette thèse réside donc dans son approche de l'aménagement de l'espace par le droit. Travailler sur les contentieux donne en effet des éléments précieux pour comprendre les rapports qui s'établissent entre les différents acteurs dans la fabrique des territoires portuaires lorsque ceux-ci sont confrontés au développement et aux enjeux environnementaux. C'est à cet effet que nous proposons une typologie de la prise en compte de l'environnement dans le développement portuaire. Celle-ci pourrait permettre de mieux comprendre de nouveaux conflits environnementaux en les rapportant aux profils portuaires identifiés, voire de réfléchir aux moyens d'améliorer la prise en compte de l'environnement dans le territoire portuairePorts are inevitably the site of litigation born out of environmental issues. Our research aims to understand how the environment is taken into account in port development. For that purpose, we analysed litigation where public and private players went to court over environmental issues. To do so, we created a method based on a geo-law grid that we used to read and analyse judgements on environmental issues linked to ports, and to grasp the variety of characteristics of these judgements on which we can base a quantitative and qualitative analysis. Our thesis is unique in using a legal approach to study port development. Using the prism of litigation provides valuable information to understand the relationships between private and public players involved in the development of ports as they face environmental issues. As a contribution to this purpose, we provide profiles of how the environment has been taken into account in port development. These port profiles can help us better understand new environmental disputes, and help us find better ways to take the environment into account in port development
12
Essiam, Albert K. "Stochastic flow and transport through multifractal porous media." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84301.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references.
Stochastic theories of flow and transport in aquifers have relied on the linear perturbation approach that is accurate for flow fields with log-conductivity variance cr2 less than unity. Several studies have found that the linear perturbation ignores terms that have significant effects on the spectra of the hydraulic gradient VH and specific discharge q when (Y2 exceeds unity. In this thesis we study flow and transport when the hydraulic conductivity K is an isotropic lognormal multifractal field. Unlike the perturbation approach, results obtained are nonlinear even though several simplifying assumptions are made. The spectral density of F = in (K) for this type of field is SF (k) o kl-D where D is the space dimension. It is found that under this condition, the hydraulic gradient VH and specific discharge q are also multifractal; whose renormalization properties under space contraction involve random scaling and random rotation of the fields. Analytical expressions that are functions of D and the codimension parameter of F, CK 'are obtained for the renormalization properties and marginal distributions of VH and q . Because of the boundary conditions, the fields VH and q are anisotropic at large scales but become isotropic at very small scales. The mean specific flow decreases as the scaling range of F increases, at a rate that is dependent on D and CK. Flow simulations on a plane validate the analytical results. The multifractal properties of VH and q are used to derive their spectral density tensors, the macrodispersivities, and the effective conductivity of the medium. The spectra obtained account for the random rotation of the VH and q at smaller scales. Spectra for VH and q are anisotropic at large scales but become isotropic at small scales.
(cont.) The scale of isotropy depends on D and CK. The linear perturbation approach does not capture this important feature and further gives incorrect amplitudes and power decays of the spectral density tensors. Using the spectra of q the macrodispersivities are computed and compared with results from the linear perturbation approach. Reflecting the properties of the spectral density of q, the macrodispersivities for the nonlinear theory are isotropic at small travel distances and are anisotropic at large travel distances. In the ergodic case when the spatial averages of all fields of interest are close to their ensemble averages, it is found that our expression for effective conductivity Keff corresponds to a formula conjectured by Matheron [1967]. Using the scaling properties of the inverse of the velocity field (also known as slowness), we derive expressions for the first passage time distribution FPTD and mean plume concentration for transport in a multifractal K field. The theoretical results of FPTD for the nonlinear theory are fitted by regression methods to data from field experiments and from numerical simulations and compared with results from the continuous time random walk CTRW and two-phase transport model. Results of the nonlinear theory are found to be more suitable for predicting non-Fickian transport. The CTRW model is more suited for transport in statistically inhomogeneous media. Both the CTRW and two-phase models are suitable for modeling Fickian transport ...
by Albert Essiam.
Ph.D.
13
Kim, Yun Sung 1974. "Simulation of filtration for suspension transport in porous media." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30187.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Page 308 blank.
Includes bibliographical references (p. 295-307).
This thesis describes the development and application of a novel method for analyzing the filtration of particles transported through a granular porous medium. The proposed analysis considers the deposition of particles through discrete simulations of particle-laden flow in a cylindrical model pore. The pore model assumes that particles collect, mound up and ultimately clog the pore under the action of hydrodynamic and gravitational forces. By simulating particle deposition processes at the pore scale, the current analyses provide a more realistic physical framework for interpreting filtration experiments than conventional continuum models that implicitly assume length scales much larger than the pores. A detailed parametric study has established relationships between the collection efficiency, mound height and deposit depth as functions of the model pore dimensions, orientation (relative to the gravitational field) and particle settling velocity for injection at constant flow rate. The results showed that the maximum mound height and deposit depth can be correlated with the pressure difference necessary to maintain flow through the model pore. A quasi one-dimensional network 'bubble' model (Datta and Redner, 1998) was developed to simulate 1-D suspension transport problems. The bubble model comprises a serial linkage of bundles of cylindrical bonds with shared nodes at each end. Bubble model simulations include distribution functions for the pore dimensions. Filtration in an individual bond is characterized by correlations from the model pore simulations.
The bubble model has been applied to interpret filtration data from two sets of column experiments: acrylic particle transport through glass beads by Yoon et al. (2004), and microfine cement suspension through a sand bed by Bouchelaghem and Vulliet (2001). It was found that the collection efficiency obtained from model pore simulations overestimates the measured filtration rates due to detachment process that are not considered in the parametric study. Two empirical parameters, attachment probability and detachment rate were employed to partition the deposited particles between those firmly attached and those detachable, and its rate of re-entrainment. With these parameters, the bubble model produced successful predictions of measured temporal and spatial filtration extent in column tests that have proved difficult to simulate with continuum models.
by Yun Sung Kim.
Ph.D.
14
Cox, Hazel Anne. "Transport Mechanisms of Titanium Dioxide Nanoparticles in Porous Media." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/247277.
Анотація:
Nanoparticles are an emerging contaminant of concern. They are used in many products and industries and, due to a lack of regulation, are entering the natural environment through our waste streams. Studies examining the transport of nanoparticles in porous media have observed divergences between data and theory. Transport data also varies greatly across studies, adding complexity to the determination of the important factors in nanoparticle transport. These main factors and key areas of deviation from theory were determined by comparing and contrasting various studies of nanoparticle transport. To further examine behavior and retention mechanisms of nanoparticles in porous media, nano-sized titanium dioxide (nano-TiO₂) was used in miscible-displacement transport experiments, followed by force measurements by Atomic Force Microscopy (AFM) between the same nanoparticles and porous media. Ionic strength ranged from 0.0015 - 30 mM, and solution chemistries were varied from pH 4.5 (favorable attachment) to 8 (unfavorable attachment). To determine the possible presence of secondary minima attachment, detachment transport experiments were performed for the unfavorable attachment conditions. Calculations were performed using DLVO theory, which is often used to describe colloid and nanoparticle retention, and compared to measured force profiles. Mass recoveries for the transport experiments ranged from 28-80%. Retention under favorable conditions was much greater than under unfavorable conditions, as was anticipated. Detachment was observed, indicating the potential presence of secondary minima. Large adhesive forces were measured by AFM and were affected by solution chemistry. Force profiles were highly variable, especially under unfavorable attachment conditions. Secondary minima were observed, even at a 0.0015 mM ionic strength. DLVO theory, while qualitatively accurate, largely under-predicted attractive and repulsive forces and their range of influence. Variability in the force profile and potential conformational changes of nanoparticle aggregates were postulated to be influential in nanoparticle transport. Retention of the nanoparticles under unfavorable conditions was postulated to involve secondary minima and the effects of surface roughness. These mechanisms, which are not represented in DLVO theory, are likely causes of the observed divergence of experimental results from theory. Improved understanding of retention mechanisms will hopefully enhance our understanding of the potential impacts of nanoparticles on the natural environment.
15
Norwood, Sasha Norien. "Characterization of Nano-scale Aluminum Oxide Transport Through Porous Media." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/981.
Анотація:
Land application of biosolids has become common practice in the United States as an alternative to industrial fertilizers. Although nutrient rich, biosolids have been found to contain high concentrations of emerging contaminants (e.g. pharmaceuticals, personal care products) while containing a significant fraction of inorganic nano-scale colloidal materials such as oxides of iron, titanium, and aluminum.
Given their reactivity and small size, there are many questions concerning the potential migration of these nano-sized colloidal materials through the soil column and into our surface and groundwater bodies. Transport of emerging pollutants of concern through the soil column, at minimum, is impacted by colloidal properties (e.g. chemical composition, shape, aggregation kinetics), solution chemistry (e.g. pH, ionic strength, natural organic matter), and water flow velocity. The purpose of this current research was to characterize the long-term transport behavior of aluminum oxide nanoparticles (Al2O3) through a natural porous media with changes in pH, aqueous-phase concentration, pore-water velocity and electrolyte valence. Additionally, deposition rates during the initial stages of deposition were compared to several models developed based on colloid filtration theory and DLVO stability theory. Benchtop column laboratory experiments showed that, under environmentally relevant groundwater conditions, Al2O3 nanoparticles are mobile through saturated porous media. Mobility increased under conditions in which the nanoparticles and porous media were of like charge (pH 9). Changes in linear pore water velocity, under these same high pH conditions, showed similar transport behavior with little mass retained in the system. Deposition is believed to be kinetically controlled at pH 9, as evidenced by the slightly earlier breakthrough as flow rate increased and was further supported by observed concentration effects on the arrival wave following several stop flows.
While lower aqueous-phase concentrations resulted in significantly longer breakthrough times, the total mass retained in the system was found to be independent of concentration. Additionally, experimental deposition rate coefficients (kd), used to describe deposition kinetics under "clean bed" conditions, were similar across the aqueous-phase concentrations studied. The use of calcium chloride electrolyte solution in transport studies resulted in enhanced mobility relative to potassium chloride suggesting that changes in groundwater solution chemistry could impact mobility of contaminants associated with biosolids. Predicted deposition rate coefficients, using three different models, were found to under- or over-predict values relative to those experimentally determined values depending on the model. This current research has shown that nanocolloids associated with biosolids, specifically Al2O3, are mobile through saturated porous media. Given the ubiquity of nanocolloidal materials, particularly engineered nanomaterials, coupled with the expected increase in land-application of biosolids, a clear understanding of their transport and fate is prudent to understanding the potential impact these emerging pollutants may have on our surface and groundwater bodies.
16
Matzner, Robert Allan. "Characterization of aza-arene transport in saturated porous media." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/191179.
Анотація:
Several factors which affect the transport of pyridine, quinoline and acridine (aza-arenes) in saturated porous media were investigated in laboratory experiments in order to provide data for input into coupled models that may be applied to predicting the fate of these compounds in groundwater. The effect of pH and ligand type and concentration on acridine solubility was studied in a series of batch and pH-stat experiments. There was a decrease in acridine solubility below the compound's pKₐ due to acridine/ligand precipitate formation. The reaction stoichiometry and solute/sorbent interactions of aza-arene adsorbed to porous silica were determined from batch adsorption and Raman spectroscopy experiments. The neutral aza-arene was hydrogen bonded to surface sites above the compound's pKₐ and there was a cation/ClO₄⁻ complex interacting with surface sites through dipole-dipole interactions below the pKₐ of the compound. The effect of pH, temperature, ligand type, average linear velocity and initial aqueous phase solute concentration on the adsorption of aza-arenes to porous silica was investigated in a series of column experiments. The extent of adsorption followed the trend pyridine < quinoline < acridine due to greater overlap of the molecule with adsorption sites as the number of rings increases. The extent of adsorption was greater below the compound's pKₐ than above because the complex was able to optimize its orientation with the surface. The extent of adsorption of neutral acridine was enhanced when carbonate was used as a buffer relative to phosphate due to carbonate's more exothermic hydration enthalpy. The isotherms were non-linear above and below the pKₐ of acridine. The enthalpy of the adsorption reaction was less exothermic below the compound's pKₐ than above due to the stronger hydrogen bonds formed between the surface and the neutral molecule compared to the dipole-dipole interactions that bond the complex to the surface below the pKₐ. Non-equilibrium effects on the adsorption reaction were minor. Adsorption-desorption was on the order of seconds to minutes. Kinetic effects became more important as temperature decreased.
17
Ruan, Feng 1965. "Numerical characterization of solute transport in nested two-scale porous media." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10189.
18
Oates, Peter M. (Peter Michael) 1977. "Upscaling reactive transport in porous media : laboratory visualization and stochastic models." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39353.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.Includes bibliographical references.
Solute transport models are essential tools for understanding and forecasting chemical concentrations in groundwater. Advection-dispersion based models can adequately predict spatial averages of conservative solute concentrations without using explicit maps of pore structures or variations in hydraulic conductivity. However, coupling advection-dispersion based transport models to chemical reaction models is inaccurate because it implicitly assumes complete mixing. Mixing in natural porous media is a slow process that can control the overall rate of chemical reactions, and the lack of mixing causes concentrations to be spatially variable. This thesis develops and experimentally validates a new solute transport modeling framework that approximates the correct amount of chemical reaction and provides concentration probability density functions, which are needed to address laws and regulations based on maximum contaminant levels. To study solute mixing and reaction in porous media, we conducted highly detailed lab-scale experiments by digitally imaging the movement of colored dye tracers and colorimetric chemical reactions through illuminated clear homogeneous and heterogeneous porous media.
(cont.) The resulting sequence of solute concentration maps demonstrates the problem of conventional solute transport models and shows that concentrations can be well approximated with Beta distributions. Conservative Beta distributions can be modeled with partial-differential equations for concentration mean and variance. These conservative distributions can then be transformed into joint reactant distributions, which produces product and remaining reactant distributions. This upscaling approach is verified by modeling the product and reactant means, variances, and distributions in heterogeneous media and product means in homogeneous media from our lab-scale experiments. We found that (co)variance production-destruction balances can approximate aqueous species covariance matrixes, which are necessary to form multivariate reactant distributions of complex reactive transport scenarios. Alternatively, these second moments can be used in upscaled reaction expressions derived from a second order Taylor series expansion. Incomplete mixing, parameterized by variance and covariance, causes an upscaled reaction rate to be almost an order of magnitude smaller compared to the conventional reaction rate that implicitly assumes complete mixing.
(cont.) Finally, manipulating the flow field to be perpendicular to its original direction would increase the rate of reactive mixing by an order of magnitude. Thus generating a transient flow field would be a practical way to accelerate natural attenuation and bioremediation.
by Peter M. Oates.
Ph.D.
19
Bai, Guiyun 1964. "Biosurfactant-enhanced nonaqueous phase liquid (NAPL) removal and bacterial transport in porous media." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282451.
Анотація:
The well documented ineffectiveness of traditional pump-and-treat technology on the cleanup of non aqueous phase liquid (NAPL) contaminated sites has incurred an intensive research activities in improving the efficiency of NAPL removal from subsurface. Surfactant enhanced subsurface remediation has been proposed as one such option. In this dissertation, a series laboratory experiments were conducted to investigate the potential application of a microbially produced surfactant (biosurfactant) on NAPL removal and the effect on bacteria transport. Monorhamnolipid biosurfactant, produced by Pseudomonas aeruginosa ATCC 9027, was used in all the studies. Hexadecane was used as model NAPL to represent petroleum based products which are common NAPLs detected in contaminated sites. Results showed that rhamnolipid biosurfactant is effective in removing residual hexadecane from sandy soil. In the surfactant concentration tested in this study (40 to 1500 mg/L), mobilization of hexadecane is the main mechanism of the removal. In addition to displacement of hexadecane droplets from subsurface porous matrixes, dispersion or emulsification of hexadecane into surfactant solution also played an important role in hexadecane removal. The performance of this anionic rhamnolipid surfactant is greatly affected by the addition of electrolytes and the change of pH. Addition of Na⁺ and Mg²⁺ can significantly increase the solubilization capacity of rhamnolipid and reduce the interfacial tension between hexadecane and surfactant solution, while addition of Ca²⁺ has a competing effects of enhanced solubilization and Ca²⁺ induced rhamnolipid precipitation. Control of ionic strength and pH can be used to optimize surfactant systems to enhance the NAPL removal depending on the nature of NAPL (LNAPL or DNAPL). Addition of rhamnolipid can also enhance the transport of three bacterial cells with varying hydrophobicity, P. aeruginosa ATCC 9027, 27853, and 15442, by decreasing cell adsorption. This is because the adsorption of surfactant to the porous medium surface increases the surface negative charge density, hence the adsorption of bacteria to the surface is reduced. No significant influence of rhamnolipid on the bacteria surface properties is observed. The measured bacteria breakthrough curves were simulated by an advection-dispersion transport model incorporating two domain reversible sorption (instantaneous and rate-limited) and with two first order sink terms for irreversible sorption. Model simulation suggests that rhamnolipid mainly affects the irreversible sorption of cells.
20
Morales-Casique, Eric. "Nonlocal and localized analyses of nonreactive solute transport in bounded randomly heterogeneous porous media." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280728.
Анотація:
Solute transport in randomly heterogeneous media is described by stochastic transport equations that are typically solved by Monte Carlo simulation. A promising alternative is to solve a corresponding system of statistical moment equations directly. The moment equations are generally integro-differential and include nonlocal parameters depending on more than one point in space-time [Neuman, 1993; Zhang and Neuman, 1996; Guadagnini and Neuman, 2001]. We present recursive approximations, and a numerical algorithm, that allow computing lead ensemble moments of non-reactive solute transport in bounded, randomly heterogeneous media. Our recursive equations are formally valid for mildly heterogeneous aquifers with σ²ᵧ < 1, where σ²ᵧ is a measure of log-hydraulic conductivity variance, or well-conditioned highly heterogeneous aquifers. Our algorithm utilizes a finite element Laplace transform method (FELT) valid for steady state velocity fields. We solved the recursive moment equations up to second order in σᵧ. We also present an iterative improvement of the recursive equations which allows reaching a solution of order higher than two in σᵧ but does not reach third order accuracy because we do not include third order moments in the computations. Computational results in two spatial dimensions conditioned on synthetic measurements of K , hydraulic conductivity, compare well with Monte Carlo results for σ²ᵧ and Peclet number (in terms of the integral scale of K) as high as 0.3 and 100 respectively for the iterative approach. As these parameters increase, the quality of our iterative moment solution deteriorates. Without conditioning the quality of the solution deteriorates more rapidly as dimensionless time increases. The recursive solution without iteration is much less accurate and deteriorates more rapidly as σ²ᵧ , Peclet number, and/or dimensionless time increase. We infer that this loss in accuracy is due to higher order moments which become important as σ²ᵧ , dimensionless time, and/or Pe increase. We also evaluate a space-localized moment equation and show that the quality of its solution is of inferior accuracy than the iterative solution. In terms of computational efficiency, the recursive and iterative methods require less CPU time than Monte Carlo transport simulations using the same numerical solution method (FELT) and without parallelization.
21
Li, Wei Ph D. Massachusetts Institute of Technology Department of Civil and Environmental Engineering. "Experimental and theoretical studies of reactive transport processes in soluble porous rocks." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123229.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 207-219).
Underground reactive transport processes involve fluid flow and reactions (dissolution, precipitation, and pressure solution) driving the evolution of the rock-fluid systems, which may result in favorable processes such as increased oil production by reservoir acid stimulation, or undesired processes such as caves and subsidence. Flow and reaction in the rock matrix often induce wormholes, which are long, finger-like channels that form due to the dissolution heterogeneity in the matrix. These wormholes become major flow pathways, which greatly increase the permeability of the rock. To study the reactive transport processes and the formation of wormholes, experimental and theoretical studies were conducted. More specifically, a new experimental setup and data analysis methods were introduced to the tube flow tests and core flood tests to experimentally study the evolution of the rock-fluid system. Theoretical studies with analytical and numerical models were used to simulate the experimental results and provide theoretical explanation for the experimental observations. Through the experimental and theoretical studies, this research improved the fundamental understanding of reactive transport processes in rock-fluid systems. This in turn provided accurate prediction of the evolution of the rock-fluid systems driven by the reactive transport processes.
by Wei Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
22
Li, Zhen. "Transport of reactive solutes in heterogeneous porous media: Heterogeneous rate-limited mass transfer." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284040.
Анотація:
The transport of reactive solutes in the subsurface is influenced by a variety of physical and chemical processes. The processes are characteristically heterogeneous and often operate simultaneously at different temporal and spatial scales. In modeling reactive solute transport different models take different approaches, dependent on the scale of the system and the objective of the study. Two major approaches have been used to incorporate heterogeneous rate-limited mass transfer into mathematical models for solute transport. One focuses on processes operative at the microscopic scale and associated grain-scale heterogeneity, while the other stresses the macroscopic variability of the medium and the field-scale behavior of solute transport. In this work, I first examine the conceptual framework and model formulation of these two approaches in an attempt to evaluate potential commonality, then present a two dimensional numerical model that integrates the first approach with traditional stochastic modeling for reactive transport. In this model multiple processes are explicitly accounted for, including spatially variable flow, spatially variable sorption, locally heterogeneous diffusive mass transfer, locally heterogeneous rate-limited sorption, and locally heterogeneous first-order degradation. Finally, the model is used to (1) examine the individual and concurrent effects of multiple heterogeneous processes on reactive transport, and (2) evaluate the impact of microscopic-scale mass transfer heterogeneity on field-scale transport in systems for which hydraulic conductivity is spatially variable. The comparison of the two approaches shows that despite differences in conceptualization and formulation, both microscopic and macroscopic based models produce comparable behavior for smaller-scale systems. However, greater deviations are observed at larger scales. This suggests that caution should be taken when using mathematical modeling for elucidating the specific processes that may be influencing reactive-solute transport for a given system. Results from 2-D simulations of the new model reveal that inclusion of locally heterogeneous mass transfer does not appear to significantly influence the mean transport behavior for systems with field-scale heterogeneity. However, it does appear to influence low-concentration tailing. For simulations of reactive transport over extended distances, models with locally heterogeneous mass transfer may "preserve" the non-equilibrium effects associated with rate-limited mass transfer better than the models incorporating locally uniform mass transfer when both pore-scale and field-scale heterogeneity coexist.
23
Zhai, Guiming, and 翟桂明. "Nanoparticle transport in porous medium and nanosized zero-valent iron(nZVI) for environmental remediation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44907199.
24
Dagher, Jessica M. "The fate and one-dimensional transport of Creighton colloidal silver nanoparticles through saturated porous media." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1527531069401526.
25
Chornewich, Cristina. "Bacterial transport in granular porous media: the effects of cell concentration and media pre-coating." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67039.
Анотація:
Column transport experiments were conducted under saturated conditions to examine the effects of cell concentration and media pre-coating. Two strains of E. coli were used in the study; the commonly studied laboratory organism E. coli K12 D21 and a mutant of the waterborne pathogen E. coli O157:H7. Column experiments were conducted with both clean sand and sand that was pre-coated with bacteria. The influent concentration of the E. coli strains was varied over several orders of magnitude to examine the effect of cell concentration. Concentration dependent removal rates were observed for both organisms in both the clean and media pre-coated sand columns. It was also found that the media pre-coating either does not influence the transport behavior or it decreases the attachment efficiency. Although differences in transport are observed, these differences are not large enough to have a significant influence on the predicted travel distances.Des expériences de transport par colonne ont été menées afin d'examiner les effets de la concentration des cellules et du pré-revêtement de média. Deux souches de bactéries ont été utilisées: E. coli K12 D12 et une souche mutante E. coli O157:H7. Les expériences par colonne ont été menées avec du sable propre et du sable qui a été préalablement enduit de bactéries. La concentration de l'influent en bactérie a été variée sur plusieurs ordres de grandeur pour examiner l'effet de la concentration cellulaire. Une dépendance du taux d'élimination à la concentration a été observée pour les deux souches de bactéries dans les deux types de sable. De plus, le pré-revêtement de média n'influence d'aucune façon le comportement du transport ni en réduit l'efficacité d'adhésion. Bien que des différences dans le transport ont été observées, celles-ci n'ont eu aucun effet significatif sur la prédiction de la distance à parcourir.
26
Li, Jing. "Multi-scale investigations of carboxymethyl cellulose- coated nanoscale zero valent iron particle transport in porous media." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123130.
Анотація:
Subsurface injection of nano scale zero valent iron (NZVI) particles is an emerging technology for in situ remediation of the sites contaminated by toxic contaminants such as chlorinated organic dense non aqueous phase liquids (DNAPLs) and heavy metals. One of the key challenges in applying NZVI particles for remediation at the field scale is that NZVI particles are not readily transported in subsurface porous media. The overall objective of this research is to address this challenge by conducting a number of column experiments and 2-D pilot scale tank experiments as well as by exploring the deposition mechanics of metal nanoparticles theoretically. Although numerous studies have focused the stability and transport of polymer/polyelectrolyte coated NZVI particles, the comparison of the effect of the same type of polyelectrolyte stabilizer with different molecular weight on the stability and transport of the corresponding coated NZVI particles has not been systematically conducted to date. Varying molecular weights of homologous polyelectrolytes can cause changes in viscosity and rheology in free solution, and alter the extent of colloidal stability when coated on the nanoparticles. Furthermore, most of the studies on NZVI particle transport have been conducted in the vertically placed columns, which are not representative with the actual flow orientation in field, leading to a potential difference of transport performance of NZVI particles between the commonly used vertical flow orientation and the horizontal flow model. In addition, the scale-up effects (from laboratory-scale column to pilot-scale or field-scale demonstrations) on NZVI transport are reported. In this study, a thorough investigation on NZVI transport is conducted in a 2-D pilot-scale tank to shed some light on the transport performance of NZVI particles under conditions that are more close to actual circumstances. Finally, to calculate the deposition rate coefficient of metal nanoparticles during transport, a considerable number of studies on NZVI particles transport employed equations for predicting the single collector contact efficiency that are developed on the basis of the numerical calculations for common colloidal particles such as latex particles, which have smaller densities than those of metal particles. Taking the horizontal flow mode and the density effects for metal nanoparticles into consideration, a new methodology is developed in three dimensions (3-D) to more precisely predict the single collector efficiency of NZVI particles.In the first study, the influence of the molecular weight of the polyelectrolyte grafted on NZVI particle on its stability and transport was investigated. Three carboxymethyl celluloses (CMC) with different molecular weights (90,000 Da, 250,000 Da and 700,000 Da) were used to stabilize NZVI particles. The comparison of the results revealed that the stability and transport of NZVI particles were improved significantly by CMC with high molecular weight, due to its high viscosity property. In the second study, the effects of gravity on NZVI particle during its transport were extensively assessed in vertical and horizontal placed columns under different conditions (mean sand diameters and NZVI concentrations). The results indicated that the gravity forces significantly reduced NZVI particles transport in coarse sand and at high NZVI concentration in horizontally placed columns. To thoroughly study the impact of horizontal orientation flow on the transport of NZVI particles at a larger scale, a series of transport experiments were conducted in a pilot-scale 2-D tank. Furthermore, to address the challenges met in predicting the single collector efficiency in horizontal orientation flow mode, a methodology based on trajectory analysis of particles around a Happel sphere-in-cell model for porous media in 3-D was developed.L'injection souterraine des nanoparticules de fer à zéro valence (NZVI) est une technologie émergente pour l'assainissement in situ des sites contaminés par des polluants toxiques comme les solvants chlorés et les métaux lourds. L'un des principaux défis dans l'application des particules de NZVI à des fins de rémédiation est que les particules de NZVI ne sont pas facilement transportées dans des milieux poreux souterrains. L'objectif général de cette recherche est de relever ce défi en réalisant un certain nombre d'expériences en colonnes et en 2-D sur desbassins à l'échelle pilote ainsi que par l'analyse de la mécanique de dépôt de nanoparticules métalliques en théorie. Bien que de nombreuses études ont porté sur la stabilité et le transport de nanoparticules de fer (NZVI) revêtues de polymère / poly-électrolyte, la comparaison de l'effet du même type de stabilisant en polyélectrolyte ayant des poids moléculaires différents, sur la stabilité et le transport des particules de NZVI enrobées n'ont pas été effectués systématiquement à ce jour. Des poids moléculaires variables des polyélectrolytes homologues peuvent provoquer des variations de viscosité en solution libre et dans l'étendue de la stabilisation colloïdale électrostérique de NZVI en s'attachant sur la surface des nanoparticules. Des études antérieures sur le transport des particules NZVI ont été menées dans les colonnes placées verticalement, qui souvent ne sont pas représentatifs de l'orientation de l'écoulement réel sur le champ, ce qui conduit à une différence de potentiel de performance du transport de particules NZVI entre l'orientation de l'écoulement vertical couramment utilisé et le modèle à flux horizontal. Outre, les effets à l'échelle grandissante (de la colonne à l'échelle de laboratoire, pilote ou des manifestations à l'échelle du champ) sur le transport de NZVI sont rapportés. Dans cette étude, une enquête approfondie sur le transport de NZVI est effectuée dans un réservoir en 2-D à l'échelle pilote afin de faire la lumière sur la performance du transport des particules de NZVI dans des conditions qui sont plus près de la situation réelle. Enfin, pour calculer le coefficient de vitesse de dépôt des nanoparticules de métal en cours de transport, un nombre considérable d'études sur les particules de NZVI ont été effectué en employant des équations de transport à fin de prédire le contact de rendement du capteur unique qui sont mis au point sur la base des calculs numériques pour les particules colloïdales communes moins denses tels que des particules de latex, qui ont des densités plus inferieures que celles des particules de métal. Prenant le mode d'écoulement horizontal et les effets de la densité de nanoparticules métalliques en considération, une nouvelle méthode est développée en trois dimensions (3-D) afin de prédire plus précisément l'efficacité du collecteur unique de particules NZVI .
27
Yoon, Joon Sik 1973. "Discrete particle transport in porous media : discrete observations of physical mechanisms influencing particle behavior." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30194.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Page 362 blank.
Includes bibliographical references.
An understanding of how discrete particles in the micron to submicron range behave in porous media is important to a number of environmental problems. Discrete particle behavior in the interior of a porous medium is complex and influenced by various physical and chemical factors. This work aimed to provide new insight into the physical factors influencing discrete particle movement and attachment in a uniform, saturated porous medium. As part of this aim, a new technique for visualizing discrete particle transport in the interior of a porous medium has been developed. The technique, which includes the construction of a translucent medium and the use of laser induced fluorescence for particle tracking, was used to examine the behavior of a 50 mg/L suspension of negatively charged, micron-size, non-Brownian particles in the interior of a porous medium constructed from water saturated, mono-size 4mm diameter glass beads. Particle behavior as a function of pore fluid velocity and solid surface roughness was imaged at both the macroscopic and microscopic level. Experimental results revealed two interactions between the discrete particles and the solid phase of the medium. One, particle entrapment, resulted in the firm collection of particles at solid-solid contact points and asperities on the solid surfaces. The other, particle hindrance, resulted in non-firm interactions between the particles and the solid's contact points and surfaces. Both entrapment and hindrance were driven by gravity. Hence, the discrete particles were entrapped and hindered at the top surface of the glass beads comprising the medium, and at the upper portion of the contact points.
(cont.) The entrapment mechanism was physical interlocking on surface roughness and physical straining at the contact points. Particle sedimentation and particle re-entrainment as a result of flow field perturbations were the main mechanisms contributing to the hindrance of particles. Changes in the concentrations of particles that were entrapped or hindered were observed with distance from the particle injection point. These changes, which became more significant as the fluid velocity decreased, were attributed to particle size distribution effects. Experiments conducted with an upward pore fluid velocity supported the hypothesis that particle entrapment and hindrance are driven by gravity. The comparison of the experimental results with particle transport models based on macroscopic mass balance equations demonstrated some of the short-comings of these models. Drainage tests performed using the geotechnical centrifuge and the new visualization technique e also provided initial insight into discrete particle behavior in an unsaturated porous medium. The results of these tests show that particles were scavenged by the air-water interface, adsorbed on the air-water interface of the pendular rings, and were retained by film straining. Thus, it is believed that the visualization technique developed during this work can be used to further investigations of discrete particle transport behavior in partially saturated porous media.
by Joon Sik Yoon.
Ph.D.
28
Чорток, Юлія Володимирівна, Юлия Владимировна Чорток, Yuliia Volodymyrivna Chortok, R. M. Nechyporenko, and A. O. Yaskevich. "Smart transport and logistics environment." Thesis, Sumy State University, 2020. https://essuir.sumdu.edu.ua/handle/123456789/80929.
Анотація:
Автори дослідили вплив ІКТ та логістики на формування розумних міст. Проаналізували особливості розумних міст.Авторы исследовали влияние ИКТ и логистики на формирование умных городов. Проанализировали особенности умных городов.
The authors investigated the impact of ICT and logistics on the formation of smart cities. The authors analyzed the features of smart cities.
29
Heinse, Robert. "Measurement and Modeling of Reduced-Gravity Fluid Distribution and Transport in Unsaturated Porous Plant-Growth Media." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/243.
Анотація:
The effect of reduced gravity on the balanced management of liquid, gaseous and ionic fluxes in unsaturated porous media remains a central challenge for plant-based bio-regenerative life support systems needed for long-duration space missions. This research investigated how shifting capillary and gravitational forces alter the sample-scale transport and distribution of fluids in mm-sized porous ceramic aggregates. Measurements in variably saturated media conducted on the International Space Station in microgravity ($sim1cdot10^{-3} g_{earth}$) and measurements during parabolic flight in variable gravity encompassing microgravity, terrestrial gravity and hypergravity ($sim1.8 g_{earth}$) were supported by numerical modeling based on fundamental, earth-derived soil-physical relationships. Measurements of water fluxes in rigid saturated media suggested Darcian flow unaffected by gravity. Observations of hydraulic potential and sample water content were used to estimate the primary draining and wetting water-retention characteristic (WRC). Terrestrial parameterizations of the WRC were largely unaffected by reduced gravity. However, because the WRC is hysteretic, heterogenous water-content distributions resulted within the confines of the primary draining and wetting characteristics. Ensuing distributions were fundamentally different from terrestrial observations and were stable in the absence of a significant gravity gradient. We showed that these distributions, though unexpected, could be predicted using the Richards equation. One consequence of altered water distribution could be the reduction in, and increased tortuosity of, continuous gas-filled pathways for diffusive transport compared to terrestrial estimates. Measurements of oxygen diffusion in microgravity suggested reduced diffusivities during draining. These observations, particularly for the smaller particle-sized media, were suggestive of the delayed formation of critical air-filled pathways at lower water contents. This dissertation further uses a case history of a stratified root-zone developed based on water-retention characteristics of different particle-sized media. The root-zone design provided a more uniform water-content distribution at terrestrial gravity suggested to provide more optimal conditions for root growth. Additionally, the design and testing of a novel integrated sensor for measurements of water content based on the dissipation of heat and estimation of nutrient status based on electrical resistivity are discussed. These results should provide insights into microgravity fluid distribution and transport contributing to the design and implementation of controllable plant-growth systems for use in microgravity and future planetary habitats.
30
El, Badawy Amro. "Assessment of the Fate and Transport of Silver Nanoparticles in Porous Media." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1312481545.
31
Li, Bailing. "Unconditional and conditional analysis of flow and solute transport in variably saturated porous media." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282729.
Анотація:
A numerical first order approach is proposed to conduct stochastic analyses of head and concentration under variably saturated conditions. The approach is based on a first-order Taylor series expansion and an adjoint state method. To implement the approach in different flow and transport regimes, numerical models are adopted to evaluate sensitivities of head and concentration with respect to hydrological parameters. This provides the possibility of conducting stochastic analyses of flow and transport problems with any kind of boundary and initial conditions. As a result, limitations of analytical approaches such as the spectral/perturbation approach can be avoided. In addition, the use of adjoint state method also alleviates the computational burden encountered in Monte Carlo simulation by allowing us to evaluate the sensitivities of head and concentration only at interesting/measurement locations. Several numerical simulations are performed to examine the sensitivities and moments of head and concentration under different flow conditions. The results show that the existence of water tables in the simulation domain can have a significant impact on the moment calculation of head and concentration. The calculated statistical moments are used to estimate log-conductivity by cokriging. The conditioning effect of head, concentration, and arrival time in estimating log-conductivity is investigated under different flow conditions. The results show steady state head is the best secondary information compared to solute concentration and arrival time in estimating conductivity by providing stable and consistent results. Estimates can be error prone when concentration measurements are used to estimate LnKs because of the nonlinear relationship between concentration and LnKs and the large variability in the simulated solute plumes. A sequential estimating technique is shown to be able to overcome some of these inadequacies of using concentration measurements. Arrival time, requiring a large amount of CPU time, does not show any advantage over concentration and head in estimating conductivity.
32
Nasir, Sharin. "Intermodal container transport logistics to andfrom Malaysian ports : Evaluation of Customer requirements and environmental effects." Doctoral thesis, KTH, Trafik och logistik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158972.
Анотація:
Malaysian ports’ container volumes are expected to increase to 36.6 million TEUs in 2020 compare to 12 million TEUs in 2005. Almost 45% of the container volumes are local containers entering the Malaysian hinterland. The hinterland container transport movements are dominated by road haulage (90%), alongside road-rail intermodal that currently handles the remaining 10%. The aim of this research is to develop possible strategies for improving the logistics of the intermodal hinterland container transport system based on customer demand, cost-efficiency, environmental impacts and quality. Intermodal began to capture more container volumes from ports, especially Port Klang, in 1989. This was initiated by the opening of Ipoh Cargo Terminal (ICT). Other inland terminals such as Padang Besar (Perlis), Nilai Inland Port (Negeri Sembilan), Segamat Inland Port (Johore) and three other ICDs have seen a good share of intermodal movements during that time. But for the past 10 years, the intermodal share has declined. The government is concerned with the congestion, greenhouse gas (GHG) emissions from road haulage and security issues. The Prime Minister has pledged that by the year 2020, Malaysia will reduce its CO2 emissions by 40% and it is believed that intermodal could be one of the solutions to achieve this. The need to shift from road haulage to road-rail intermodal has been mentioned in Industrial Master Plan 3 (2006) and the Logistics Road Map (2009) to alleviate these problems. Intermodal hinterland container transport is a trend in many European ports to solve road haulage problems. The current hinterland container transport in Malaysia showed that the share of intermodal in Malaysia is still low. Most of the inland terminals in Malaysia are underutilised. Based on a customer survey, the major issues for customers to shift to intermodal is not only cost but also service quality. The lack of strategic policies and effective institutional aspects also contributes to make intermodal services less attractive. The Port Klang-Ipoh Corridor has a huge potential to be the main intermodal corridor in Malaysia. The case study showed that this corridor has the container volume to support intermodal services. The case study indicated a cost saving of 51% compared to direct road haulage, whereby CO2 emissions would be reduced by 36%. However, all the cost savings and reductions in CO2 emissions are not viable if there is no implementation of the most effective strategies to promote intermodal movement. The strategies include 1) introducing the Intermodal Transport Department and new policies, 2) introducing specific intermodal services, 3) setting up the green corridor concept, 4) developing a reward system for actors in intermodal transportation, 5) collaboration and coordination issues and 6) quality of service monitoring. Implementations of these strategies is vital to enhance the intermodal share in the Malaysian environment.QC 20150116
33
Nicolai, Andreas. "Modeling and numerical simulation of salt transport and phase transitions in unsaturated porous building materials." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
34
Wang, Wenbin. "Uncertainty analysis of groundwater flow and solute transport in unsaturated-saturated porous medium: Maricopa case." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280222.
Анотація:
Various methods are used to postulate, compare and rank alternative conceptual-mathematical models of unsaturated flow and transport during infiltration and tracer experiments at the Maricopa Agricultural Center (MAC) near Phoenix, Arizona. The models include one- and two-dimensional flow and transport in a uniform soil, a soil consisting of uniform layers, and a stratified soil having laterally varying properties. Characterization of the soil as a uniform medium is based on information obtained from public sources. Characterization of the soil as a layered medium is based on site data. Soil hydraulic properties are estimated from pedologic data. Uniform soil hydraulic properties are ascribed to each layer on the basis of soil type using mean values of three generic databases. Variable soil hydraulic properties are ascribed to individual soil samples using pedotransfer models based on site soil data. By treating these variable hydraulic property estimates as measurements, Bayesian updates of their mean values together with the variance of each estimate are obtained. Geostatistical analysis of soil pedologic and hydraulic properties provides support for a layered conceptual model with relatively large-scale lateral variability in each layer. The above conceptual-mathematical models and hydraulic parameter estimates are applied to analyze flow and transport under uncertainty and to compare simulated and observed water contents during one of the infiltration experiments at the MAC. It is shown that in order to reproduce observed behavior, it is necessary to further modify the hydraulic parameter estimates through inverse modeling. Various conceptual-mathematical models and parameter estimates are compared and ranked using likelihood-based model discrimination criteria. The inverse results are confirmed by using those to simulate the flow of an earlier experiment. Finally, the inverse estimates of soil hydraulic parameters based on one infiltration experiment are used for solute transport modeling. An advection-dispersion model with linear mass transfer to and from a zone of immobile water, or anion exclusion, is employed in forward and inverse modes. The study illustrates how a combination of methods and data sets can be used sequentially and in tandem to improve one's understanding of unsaturated flow and transport conditions at a site.
35
Avila-Palencia, Ione 1985. "Urban environment, transport behaviours, and health." Doctoral thesis, Universitat Pompeu Fabra, 2018. http://hdl.handle.net/10803/665298.
Анотація:
Urban environments are very complex systems with a myriad of factors intricately related. Built environment, transport, physical activity and sedentary behaviours, air pollution, and social contacts and feelings of loneliness can have effects on urban population’s health and well-being. Also, some of these determinants can be associated and can interact between them modifying their effects on health. According to the World Health Organisation (WHO), health is “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”. Taking into account this comprehensive health definition, this thesis covered different layers of health: general, mental, and physical. With four different studies, the results of the present thesis suggest that it is possible to design urban environments that can increase physical activity levels, mainly through active transport, and that the crime-safety perceptions can have an important role in terms of reinforcing the effects of the built environment on physical activity and sedentary behaviours. Furthermore, active transport, mainly bicycle use, seems to be a source of good mental health and well-being, and a tool to boost social capital production. Increasing physical activity levels also seems to be a good way to improve cardiovascular health through blood pressure levels reduction.
The present thesis suggests that urban and transport planning have a great potential to promote healthy behaviours and ensure mental and physical health of city dwellers, mainly through active transport promotion. In order to improve the health promotion through urban environment, more research about aesthetics urban attributes, urban social capital production, effects on mental health and well-being, and effectiveness of urban interventions is needed.Los entornos urbanos son sistemas muy complejos con una miríada de factores intrincadamente relacionados. El entorno construido, el transporte, la actividad física y los comportamientos sedentarios, la contaminación del aire y los contactos sociales y los sentimientos de soledad pueden tener efectos en la salud y el bienestar de la población urbana. Además, algunos de estos determinantes se pueden asociar y pueden interactuar entre ellos modificando sus efectos sobre la salud. Según la Organización Mundial de la Salud (OMS), la salud es "un estado de completo bienestar físico, mental y social y no simplemente la ausencia de enfermedades o dolencias". Teniendo en cuenta esta definición integral de salud, esta tesis cubre diferentes niveles de salud: general, mental y física. Con cuatro estudios diferentes, los resultados de la presente tesis sugieren que es posible diseñar entornos urbanos que puedan aumentar los niveles de actividad física, principalmente a través del transporte activo, y que las percepciones de seguridad con respecto al crimen pueden tener un papel importante en términos de reforzar los efectos del entorno construido sobre la actividad física y los comportamientos sedentarios. Además, el transporte activo, principalmente el uso de bicicletas, parece ser una fuente de buena salud mental y bienestar, y una herramienta para impulsar la producción de capital social. El aumento de los niveles de actividad física también parece ser una buena forma de mejorar la salud cardiovascular a través de la reducción de los niveles de presión arterial. La presente tesis sugiere que la planificación urbana y de transporte tienen un gran potencial para promover comportamientos saludables y garantizar la salud mental y física de los habitantes de las ciudades, principalmente a través de la promoción del transporte activo. Para ir mejorando la promoción de la salud a través del entorno urbano, se necesita más investigación sobre los atributos urbanos estéticos, la producción de capital social urbano, los efectos sobre la salud mental y el bienestar, y la efectividad de las intervenciones urbanas
36
Piatt, Joseph John 1966. "Sorption and Biodegradation of Organic Solutes Undergoing Transport in Laboratory-scale and Field-scale Heterogeneous Porous Media." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/191215.
Анотація:
The first study focused on the magnitude and rate of sorption of hydrophobic organic compounds by two, well-characterized soils. The composition of organic matter had a small effect on the magnitude of the organic carbon normalized equilibrium distribution coefficients. The sorbates sorbed more strongly to the humic-coated soil, most likely due to the organic matter's less polar nature as compared to the fulvic material. The molecular solute descriptor, ¹Xᵛ, performed slightly better than the empirical solute descriptor, K(ov), in evaluating equilibrium sorption coefficients. Thus, sorbate structure may have a secondary influence on the overall magnitude of equilibrium sorption. Sorbate structure exhibited a greater influence on sorption kinetics than on sorption equilibrium. Distinct differences in the magnitudes of mass transfer coefficients for the humic and fulvic soils were observed when relating them to the molecular solute descriptor, ¹Xᵛ. The differences in mass transfer coefficients were attributed to both sorbate structure and the quantity and morphology of soil organic matter. The intrasorbent diffusion coefficients were believed to be the same for both the humic and fulvic material. The second study focused on using a biodegradable solute to measure processes that affect in-situ biodegradation during well-controlled field and laboratory experiments. Specifically, this study investigated how residence time and scale influence the extent and rate of in-situ biodegradation of an organic solute undergoing transport. The transport of the biodegradable solute was compared to that of bromide and/or pentafluorobenzoic acid, which are conservative, non-degradable tracers. Laboratory experiments were conducted to simulate both the flow velocity and residence time conditions existent in the field. Mass recovery the biodegradable solute decreased as the residence time increased, ranging from 14 to 95 percent for the field sites. Mass recoveries in the laboratory experiments were approximately 30% to 40 % less than in the field experiments. The first-order biodegradation rate constants did not vary with residence time for either field site. In addition, the average rate constant value for both field sites was very similar (0.21 d⁻¹).
37
Petosa, Adamo. "Transport, deposition and aggregation of metal oxide nanoparticles in saturated granular porous media: role of water chemistry, collector surface and particle coating." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119416.
Анотація:
As a multitude of engineered nanomaterials (ENMs) are being incorporated into a growing number of consumer products, the potential release of these reactive and potentially toxic constituents into natural aquatic environments and soils is inevitable. Nanosized metal oxides such as cerium dioxide (nCeO2), titanium dioxide (nTiO2) and zinc oxide (nZnO) are examples of ENMs currently appearing in consumer products. Upon the release of such ENMs into natural and engineered aquatic environments, particle aggregation and deposition behavior will determine the particle transport potential and thus the environmental fate and potential ecotoxicological impacts of the released materials. The objective of this research was to examine the transport behavior of select nanosized metal oxides (namely, nCeO2, nTiO2 and nZnO) in saturated granular porous media using laboratory-scale column experiments. The influence of water chemistry (pH, ionic strength (IS) and cation type (Na+, Ca2+, or Mg2+)) and particle coating (uncoated (bare) and poly(acrylic acid) (PAA)-coated ENMs) on particle deposition was examined in quartz sand or loamy sand-packed columns. Select particle transport studies in natural groundwater were also conducted, and PAA-coated metal oxide transport was compared to that of an analogous nanosized PAA polymeric capsule (nCAP). All ENM suspensions were characterized over a range of environmentally relevant water chemistries using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) to establish aggregate size and laser Doppler velocimetry to determine particle surface potential. To investigate aggregate morphology, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images were obtained under select conditions. Overall, bare ENMs exhibited high retention within water-saturated quartz sand-packed columns at NaNO3 solution IS as low as 0.1 mM for nTiO2 and 0.01 mM for nZnO. Furthermore, bare nTiO2 was found to exhibit extensive aggregation, regardless of pH and IS. At lower salt concentrations, the particle attachment efficiency (α) for the nTiO2 aggregates onto quartz sand increased with increasing IS. At higher IS, α (pH 7) > α (pH 3) > α (pH 9), likely due to enhanced particle aggregation at pH 7 and subsequent physical straining within the granular matrix. Bare nTiO2 and nZnO displayed dynamic (time-dependent) deposition behaviors under selected conditions. In contrast, PAA-coated nTiO2 and nZnO were less prone to aggregation and exhibited significant transport potential at IS as high as 100 mM NaNO3 or 3 mM CaCl2. Likewise, PAA-coated nCeO2 particles suspended in NaNO3 were highly mobile in quartz sand-packed columns. Nonetheless, heightened nCeO2 and nCAP particle retention and dynamic transport behavior was observed with increasing divalent salt concentrations and in natural groundwater. Moreover, enhanced particle retention was encountered in loamy sand in comparison to quartz sand. Finally, the nCAPs proved to be a good surrogate particle for the PAA-coated nCeO2. These findings illustrate the importance of considering the extent and type of particle surface modification when investigating metal oxide contamination potential in granular aquatic environments. Furthermore, the results obtained emphasize the need to consider the nature of the granular medium, along with the water chemistry, when evaluating ENM contamination risks.Actuellement, des différents types de nanomatériaux manufacturés (NMM) sont intégrées dans un nombre croissant de produits de consommation. Par conséquent, la libération de ces matériaux réactifs et potentiellement toxiques dans le sol et les milieux aquatiques naturels est inévitable. Lors de la décharge dans l'environnement, l'agrégation et la déposition déterminent le potentiel de transport des particules, influencent les éventuels effets écotoxicologiques des matières rejetées. Les oxydes métalliques de taille nanométrique, tels que le dioxyde de cérium (nCeO2), dioxyde de titane (nTiO2) et l'oxyde de zinc (nZnO) ne font pas exception, nécessitant une meilleure compréhension de leur comportement dans les milieux aquatiques naturels et artificiels. L'objectif de cette recherche était d'examiner le comportement de transport de certains oxydes métalliques de taille nanométrique (en particulier le nCeO2, nTiO2 et nZnO) dans les milieux poreux granulaires saturés. Ceci a été réalisé dans le laboratoire en utilisant des expériences contrôlées en colonne. L'influence de la chimie de l'eau (pH, force ionique (FI) et le type de cations (Na+, Ca2+ ou Mg2+)), et le revêtement des NMM (non revêtus ou revêtus de poly(acide acrylique), PAA) sur la déposition des particules a été examiné dans des colonnes remplis de sable de quartz ou de sable loameux. Des études examinent le transport des particules suspendus dans les eaux souterraines naturelles ont également été menées. Finalement, le transport des oxydes de métal a été comparée à celle d'une capsule nanométrique (nCAP) analogue composer de PAA. Dans l'ensemble, les oxydes métalliques non revêtus démontrent une rétention élevé dans les colonnes remplies de sable de quartz et saturées avec des solutions de NaNO3. Avec ces particules, une forte rétention est observée à des FI aussi faibles que 0.1 mM pour le nTiO2 et 0.01 mM pour le nZnO. En outre, le nTiO2 démontre une agrégation extensive, peu importe le pH et la FI. À des concentrations de NaNO3 inférieures, l'efficacité de filtration (α) des agrégats de nTiO2 dans le sable de quartz augmente en augmentant la FI. À des plus hautes FI, α (pH 7) > α (pH 3) > α (pH 9). Ceci est probablement due à une augmentation d'agrégation à pH 7, causant les particules de devenir prises entres les grains de sable de la colonne. Finalement, le nTiO2 et nZnO non revêtus démontrent des comportements de déposition dynamiques (dépendant du temps) dans certaines conditions analysées. En revanche, le nTiO2 et nZnO revêtus de PAA étaient moins enclins à l'agrégation et démontrent un potentiel de transport important à des FI assez élevées (100 mM NaNO3 ou 3 mM CaCl2). De même, les particules de nCeO2 revêtus de PAA suspendus dans des solutions de NaNO3 étaient très mobiles dans le sable de quartz, peu importe la FI. Néanmoins, le nCeO2 et les particules nCAP démontrent une déposition rehaussée, parfois dynamique avec l'augmentation des concentrations de sels divalents et dans les eaux souterraines naturelles. Une déposition rehaussée est également rencontrée dans le sable loameux comparativement au sable de quartz. Enfin, les particules nCAP se sont avérées être un bon substitut expérimental pour les particules de nCeO2 revêtus de PAA. Ces résultats illustrent l'importance de considérer l'étendue et le type de revêtement des NMM en examinant le potentiel de contamination des oxydes métalliques dans les milieux granulaires et poreux saturés. En outre, les résultats obtenus soulignent la nécessité de tenir compte de la nature du milieu granulaire, ainsi que la chimie de l'eau, lors de l'évaluation des risques de contamination des NMM.
38
Polanowski, Piotr, and Andrzej Sikorski. "Simulation of diffusion in a crowded environment." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183392.
39
Kim, Wongee. "Phenol removal from saturated porous media using horseradish peroxidase mediated oxidative polymerization process." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/383.
40
Xuankun, Li. "Effect of Surfactants on the Behaviors and Transport of Metal Oxide Nanomaterials in Aqueous Matrices and Porous Media." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225578.
41
Goosen, E. (Eduan). "The future of rail transport in South Africa in a deregulated transport environment." Thesis, Stellenbosch : Stellenbosch University, 1997. http://hdl.handle.net/10019.1/55720.
Анотація:
Thesis (MEcon)--Stellenbosch University, 1997.ENGLISH ABSTRACT: On 31 March 1990 the South African Transport Services (SATS) ceased to exist and on 1 April 1990 in its place emerged Transnet, a diversified transport company wholly owned by the South African government. Transnet was founded on the understanding that the government might eventually choose to sell it to the private sector. This study project report discusses the history and events leading up to the creation of Transnet. Thereafter the advantages and disadvantages of privatisation are identified, followed by international privatisation case studies which provide the basis for a discussion of some of the economic issues behind railway privatisation. The separation of infrastructure from operations, which was identified through the case studies as one of the most controversial and far-reaching concepts of railway privatisation, is also examined. Lastly, the study project focuses on the marketing strategy Spoornet ought to pursue in order to ensure sufficient high-value freight in the future.
AFRIKAANSE OPSOMMING: Op 31 Maart 1990 het die Suid-Afrikaanse Vervoerdienste ophou bestaan en is dit op 1 April 1990 vervang deur Transnet, 'n gediversifiseerde vervoermaatskappy wat deur die Suid-Afrikaanse regering besit word. Van meet afwas dit die bedoeling dat die regering die keuse het om Transnet aan die privaatsektor te verkoop. Die werkstuk bespreek die geskiedenis en gebeure wat aanleiding gegee het tot die ontstaan van Transnet. Daarna word die voor- en nadele van privatisering bespreek, gevolg deur internasionale spoorwegprivateriseringsgevallestudies. Daarna word die ekonomiese teorie wat privatisering onderle, bespreek. Die skeiding van infrastruktuur en bedryf, wat deur die gevallestudies as een van die mees omstrede en verreikende aspekte van spoorwegprivatisering ge"identifiseer is, word ook bespreek. Laastens fokus die werkstuk op die bemarkingstrategie wat Spoornet behoort na te streef om hoe-waarde vragte te bekom.
42
Han, Wan Yi. "Real-time transport protocol in a wireless environment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0013/MQ61438.pdf.
43
Darmawan, Hariyanto. "Transport of a pathogenic bacterium and its non-pathogenic variant strain through a granular porous medium: from a simple system to a real system." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104768.
Анотація:
The attachment efficiency of two strains of Escherichia coli O157:H7 – one pathogenic strain and another non-pathogenic strain – was measured over a range of solution ionic strengths and in two different granular systems: a simple system made of clean quartz sand and a real system made of natural subsurface soil. In this study, the relevance of the non-pathogenic strain of E. coli O157:H7 as a potential surrogate for its pathogenic counterpart was investigated. The results suggest that it is not straightforward to find an appropriate surrogate for the pathogenic strain. Different porous media begets different attachment efficiency of the potential surrogate strain relative to the attachment efficiency of the toxigenic strain. A modest attempt was also made to build an artificial system that mimics the natural soil, by coating the clean granular sand with humic acids and adding clay component.Pour étudier la contamination d'eaux souterraines, l'efficacité d'adhésion de deux variétés d'E. coli O157:H7 – une pathogène et une autre non-pathogène – a été mesurée sur une gamme de force ionique dans deux systèmes granulaires : un système simple fait de sable de quartz propre et un système naturel de sol souterrain. Dans cette étude, la pertinence de la variété non-pathogène (E. coli O157:H7) comme substitut potentiel pour sa contrepartie fut étudiée. Les résultats suggèrent qu'il est très difficile de trouver un substitut approprié de la variété pathogène pour ce type d'études, car différents médias porreaux engendrent différentes efficacités d'adhésion de la variété substitut potentielle. Une tentative a aussi été faite de construire un système artificiel dans le labo qui imite le sol naturel, en enrobant le sable de quartz avec des acides humiques et par l'addition d'un composé d'argile.
44
Wong, Wai-sum May. "Public light bus service in a challenging transport environment." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B31633109.
45
Zhou, Weiguo. "Cabin environment and air quality in civil transport aircraft." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7305.
Анотація:
The cabin environment of a commercial aircraft, including cabin layout and the quality of air supply, is crucial to the airline operators. These aspects directly affect the passengers’ experience and willing to travel. This aim of this thesis is to design the cabin layout for flying wing aircraft as part of cabin environment work, followed by the air quality work, which is to understand what effect the ECS can have in terms of cabin air contamination.
The project, initially, focuses on the cabin layout, including passenger cabin configuration, seat arrangement and its own size due to the top requirements, of a conventional aircraft and further into that of a flying wing aircraft. The cabin work in respect of aircraft conceptual design is discussed and conducted by comparing different design approaches. Before the evaluation of cabin air quality, an overall examination of the main ECS components involved in the contaminants access will be carried on and, therefore, attempt to discover how these components influence the property of the concerned contaminants. By case study in the B767 ECS, there are some comments and discussions regarding the relationship between the cabin air contaminations and the passing by ambient environment. The thesis ends up with a conclusion explaining whether or not the contaminated air enters the occupants’ compartments on aircraft and proposing some approaches and engineering solutions to the continue research.
46
黃蔚琛 and Wai-sum May Wong. "Public light bus service in a challenging transport environment." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31633109.
47
Morillon, Anne-Marie. "Modelling of radionuclide transport in a simulated PWR environment." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14659.
48
Grazi, Fabio <1972>. "Agglomeration, transport and environment: the economics of spatial sustainability." Doctoral thesis, Università Ca' Foscari Venezia, 2007. http://hdl.handle.net/10579/120.
49
Soltanian, Mohamad Reza. "RELATING REACTIVE TRANSPORT TO HIERARCHICAL AND MULTISCALE SEDIMENTARY ARCHITECTURE." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1428521270.
50
Veilleux, Douglas L. "Melting in a low gravity environment with applied electromagnetic fields /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3186925.