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Benzoni, Séverin. "Classification des filtrations dynamiques et étude des systèmes d'entropie positive." Electronic Thesis or Diss., Normandie, 2024. https://theses.hal.science/tel-04835404.
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Dans cette thèse, nous explorons les structures possibles des systèmes dynamiques de la forme $\bfX :=(X, \A, \mu, T)$ et leurs tribus facteur $\B \subset \A$. Les deux premiers chapitres étudient les différentes façons dont une tribu facteur $\B$ peut s'inclure dans un système dynamique $\bfX :=(X, \A, \mu, T)$, c'est-à-dire que nous étudions certaines structures possibles de l'\emph{extension} $\A \arr \B$. Dans le premier chapitre, nous considérons les concepts de \emph{super-innovations} et de \emph{standardité} des extensions, inspirés de la théorie des filtrations. Un point important est l'introduction de la notion d'\emph{extensions confinées}, qui nous intéressent parce qu'elles n'ont pas de super-innovation. Nous donnons plusieurs exemples et étudions des propriétés supplémentaires de ces extensions, y compris des résultats de relèvement. Ensuite, nous montrons notre résultat principal : l'existence d'extensions non-standard. Enfin, ce résultat trouve une application dans l'étude des filtrations dynamiques, qui sont les filtrations de la forme $(\F_n)_{n \leq 0}$ telles que chaque $\F_n$ est une tribu facteur. Nous montrons qu'il existe des \emph{filtrations dynamiques I-confortables non standard}.Le deuxième chapitre approfondit l'étude des extensions confinées en trouvant un nouveau type de telles extensions, dans le cadre des suspensions de Poisson : nous prenons un système dynamique $(X, \mu, T)$ en mesure $\s$-finie infinie et une extension compacte $(X \times G, \mu \otimes m_G, T_\phi)$, puis nous considérons l'extension de Poisson correspondante $((X \times G)^*, (\mu \otimes m_G)^*, (T_\phi)_*) \to (X^*, \mu^*, T_*)$. Nous donnons des conditions sous lesquelles cette extension est confinée et construisons un exemple qui correspond à ces conditions.Enfin, le troisième chapitre se concentre sur une famille de filtrations dynamiques : les \emph{filtrations de Pinsker faible}. L'existence de ces filtrations sur tout système ergodique provient d'un résultat récent d'Austin \cite{austin}, et elles se présentent comme un outil potentiel pour décrire les systèmes à entropie positive. Nous explorons les liens entre la structure asymptotique des filtrations de Pinsker faible et les propriétés du système dynamique sous-jacent. Naturellement, nous demandons aussi si, sur un système donné, la structure des filtrations de Pinsker faible est unique à isomorphisme près. Nous donnons une réponse partielle, dans le cas où le système sous-jacent est un schéma de Bernoulli. Nous concluons notre travail en donnant deux exemples explicites de filtrations de Pinsker faible<br>In this thesis, we explore the possible structures of measure preserving dynamical systems of the form $\bfX :=(X, \A, \mu, T)$ and their factor $\s$-algebras $\B \subset \A$. The first two chapters investigate various ways in which a factor $\s$-algebra $\B$ can sit in a dynamical system $\bfX :=(X, \A, \mu, T)$, i.e. we study some possible structures of the \emph{extension} $\A \arr \B$. In the first chapter, we consider the concepts of \emph{super-innovations} and \emph{standardness} of extensions, which are inspired from the theory of filtrations. An important focus of our work is the introduction of the notion of \emph{confined extensions}, which first interested us because they have no super-innovation. We give several examples and study additional properties of confined extensions, including several lifting results. Then, we show our main result: the existence of non-standard extensions. Finally, this result finds an application to the study of dynamical filtrations, i.e. filtrations of the form $(\F_n)_{n \leq 0}$ such that each $\F_n$ is a factor $\s$-algebra. We show that there exist \emph{non-standard I-cosy dynamical filtrations}.The second chapter furthers the study of confined extensions by finding a new kind of such extensions, in the setup of Poisson suspensions: we take an infinite $\s$-finite measure-preserving dynamical system $(X, \mu, T)$ and a compact extension $(X \times G, \mu \otimes m_G, T_\phi)$, then we consider the corresponding Poisson extension $((X \times G)^*, (\mu \otimes m_G)^*, (T_\phi)_*) \to (X^*, \mu^*, T_*)$. We give conditions under which that extension is confined and build an example which fits those conditions.Lastly, the third chapter focuses on a family of dynamical filtrations: \emph{weak Pinsker filtrations}. The existence of those filtrations on any ergodic system comes from a recent result by Austin \cite{austin}, and they present themselves as a potential tool to describe positive entropy systems. We explore the links between the asymptotic structure of weak Pinsker filtrations and the properties of the underlying dynamical system. Naturally, we also ask whether, on a given system, the structure of weak Pinsker filtrations is unique up to isomorphism. We give a partial answer, in the case where the underlying system is Bernoulli. We conclude our work by giving two explicit examples of weak Pinsker filtrations
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Lanthier, Paul. "Aspects ergodiques et algébriques des automates cellulaires." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR034.
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La première partie de ce manuscrit entre dans le cadre de la théorie des probabilités, et est consacrée à l’étude de filtrations engendrées par des automates cellulaires. On étudie deux versions d’un automate algébrique agissant sur des configurations dont les états sont à valeurs dans un groupe abélien fini : l’une est déterministe, et consiste à additionner les états de deux cellules consécutives, et la seconde est une perturbation aléatoire de la première. À partir de ces automates, on construit des processus aléatoires markoviens et on étudie les filtrations engendrées par ces processus. On montre en utilisant le critère de I-confort que les deux filtrations sont standards au sens développé par Vershik. Cependant, les automates cellulaires ont comme particularité de commuter avec l’opérateur de décalages des coordonnées, appelé « shift ». Dans cette thèse, on introduit une nouvelle classification des filtrations dite « dynamique » qui tient compte de l’action de cette transformation. Les filtrations sont définies non plus sur des espaces de probabilité mais sur des systèmes dynamiques, ce sont dans ce cas des filtrations « facteurs » : chaque tribu est invariante par la dynamique du système. Le pendant de la standardité du point de vue dynamique est étudié. On crée ainsi un critère nécessaire pour la standardité dynamique appelé « I-confort dynamique ». La question de savoir si le I-confort dynamique est suffisant reste ouverte mais un premier résultat dans cette direction est donné, en montrant qu’une version renforcée du I-confort dynamique entraîne la standardité dynamique. En établissant qu’elle ne satisfait pas le critère de I-confort dynamique, on prouve que la filtration facteur engendrée par l’automate déterministe n’est pas dynamiquement standard, et donc que la classification dynamique des filtrations diffère de la classification développée par Vershik. L’automate probabiliste dépend d’un paramètre d’erreur, et on montre par un argument de percolation que la filtration facteur engendrée par cet automate est dynamiquement standard pour des valeurs assez grandes de ce paramètre. 0n conjecture qu’elle ne sera pas dynamiquement standard pour les valeurs très petites de ce paramètre. La deuxième partie de ce manuscrit, plus algébrique, tire son origine d’une problématique musicale, liée au calcul d’intervalles dans une ligne mélodique périodique. Les travaux présentés ici poursuivent les recherches du compositeur roumain Anatol Vieru et de Moreno Andreatta et Dan Vuza mais d’une manière originale en se plaçant du point des vue des automates cellulaires. On étudie l’action sur des suites périodiques de deux automates cellulaires algébriques, dont l’un est identique à celui de la première partie. Les questions sur la caractérisation des suites réductibles et reproductibles ainsi que les temps associés ont été approfondies et améliorées pour ces deux automates. Le calcul des antécédents et des images via les deux automates a été explicité. La question de l’évolution des périodes a été traitée avec la création d’un outil appelé « caractéristique » qui permet de décrire et de contrôler l’évolution de la période dans les temps négatifs. Des simulations permettent de voir que l’évolution des périodes lorsque l’on tire au hasard des antécédents suit un motif presque régulier, et l’explication de ce phénomène reste une question ouverte. Les résultats mathématiques de cette deuxième partie ont été utilisés dans le module « automaton » d’un logiciel de composition gratuit, nommé « UPISketch. Ce module permet à un compositeur de créer des lignes mélodiques en itérant les images ou en prenant des antécédents successifs d’une ligne mélodique de départ<br>The first part of this manuscript falls within the framework of probability theory, and is devoted to the study of filtrations generated by some cellular automata. We study two versions of an algebraic automaton acting on configurations whose states take values in a finite Abelian group: one is deterministic, and consists in adding the states of two consecutive cells, and the second is a random perturbation of the first one. From these automata, random Markovian processes are constructed and the filtrations generated by these processes are studied. Using the I-cosiness criterion, we show that the two filtrations are standard in the sense developed by Vershik. However, cellular automata have the particularity of commuting with the coordinate shift operator. In this thesis, we introduce a new classification of the filtrations called "dynamic" which takes into account the action of this transformation. Filtrations are no longer defined on probability spaces but on dynamical systems, and are in this case "factor" filtrations: each sigma-algebra is invariant by the dynamics of the system. The counterpart of standardity from the dynamic point of view is studied. This creates a necessary criterion for dynamic standardity called "dynamic I-cosiness". The question of whether the dynamic I-cosiness is sufficient remains open, but a first result in this direction is given, showing that a strengthened version of the dynamic I-cosiness leads to dynamic standardity. By establishing that it does not satisfy the criterion of dynamic I-cosiness, it is proved that the factor filtration generated by the deterministic automaton is not dynamically standard, and therefore that the dynamic classification of the filtrations differs from the classification developed by Vershik. The probabilistic automaton depends on an error parameter, and it is shown by a percolation argument that the factor filtration generated by this automaton is dynamically standard for large enough values of this parameter. It is conjectured that it will not be dynamically standard for very small values of this parameter. The second part of this manuscript, more algebraic, has its origin in a musical problem, linked to the calculation of intervals in a periodic melodic line. The work presented here continues the research of the Romanian composer Anatol Vieru and of Moreno Andreatta and Dan Vuza, but in an original way from the point of view of cellular automata. We study the action on periodic sequences of two algebraic cellular automata, one of which is identical to that of the first part. The questions on the characterization of reducible and reproducible sequences as well as the associated times have been deepened and improved for these two automata. The calculation of preimages and images via the two automata was explained. The question of the evolution of the periods was treated with the creation of a tool called "characteristic" which allows to describe and control the evolution of the period in negative times. Simulations show that the evolution of the periods when the preimages are drawn at random follows an almost regular pattern, and the explanation of this phenomenon remains an open question. The mathematical results of this second part have been used in the "Automaton" module of a free composing software called "UPISketch ». This module allows a composer to create melodic lines by iterating images or taking successive preimages of a starting melodic line
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Khan, Muhammad Waleed. "Dynamic filtration at soil-geotextile interfaces." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39882/.
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The soil-geotextile filtration mechanism is a complex process which depends on physical compatibility between the geotextile and the soil to be retained. Geotextiles often perform well under steady state conditions like those found in dams. However, when the soil-geotextile interface is subjected to dynamic loading, the requirements for successful filtering are uncertain and/ or conservative as the controlling factors are not well understood in these circumstances. There are few filter design criteria available for dynamic flow conditions. These criteria do not properly address the internal instability of soils for which the rearrangement of particles adjacent to the filter interface is complex. Unstable soils may exist in roadway bases adjacent to pavement edge drain. Therefore, this research work was carried out to better understand the filtration behaviour of non-woven geotextiles with internally stable and unstable soils beneath roads. To carry out the filtration tests, a flexible wall gradient ratio (GR) apparatus was developed. The GR tests were performed to investigate the effect of different factors on the filtration performance of the soil-geotextile interface under dynamic conditions. The factors included hydraulic gradient, vertical stress and frequency of loading, soil gradation and geotextile properties. Test results were interpreted in terms of head loss within the soil and across the geotextile, GR values, permeability ratio, mass and gradation of particles passed through geotextiles, microscopic images of geotextiles after test, partial geotextile clogging levels and hydrometer sieve analyses of soil samples to compare the gradation of samples after test with the original gradation. All the tests were performed under a hydraulic gradient of five. The internal stability of soil samples were evaluated by three geometric criteria. The test results showed that a high hydraulic gradient has the ability to lead to the internal instability of soils which resulted in migration of fines towards the geotextiles. The dynamic loading resulted in increase of soil migration within the base soil as well as washing out of soil particles through geotextiles. No significant effect of increase in frequency and vertical stress was observed on filtration behaviour of soil-geotextile combinations. The geotextile pore size was found to be the main factor controlling the filtration behaviour as compared to other geotextile properties. The Kenney and Lau (1985) and the Kezdi (1979) criteria predicted well the internal instability of soils under dynamic conditions. In this research study, a new method was suggested which is able to measure the pore sizes along the entire thickness of geotextiles. The filtration tests showed that geotextiles having the same large openings but different pore size distributions may result in different filtration performances. Based on the test results, filter design criteria were suggested for piping and blinding limits which were compared with the existing design criteria. These new filter criteria were found to be more appropriate in terms of piping and blinding limit states.
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Turkson, Abraham K. "Electro-ultrafiltration with rotating dynamic membranes." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72036.
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In axial electrofiltration, a DC electric field is imposed between a rotating inner cylinder and a stationary outer cylinder giving rise to four mechanisms which act to minimize solute accumulation at the filter surface: turbulence, centrifugal force, electrophoresis and shear stress which removes solute aggregates.<br>Four dynamic membranes, Zr(IV) oxide, calcium oleate, poly-2-vinylpyridine and cadmium sulfide, were used to filter bovine serum albumin (BSA) in a disodium phosphate solution at pH = 8 and Prussian blue in distilled water. Prussian blue is a particle of 0.01(mu)m diameter with a zeta potential of -41mV while BSA is a macromolecule of 69,000 molecular weight, a Stokes-Einstein radius of 0.0038(mu)m and a zeta potential of -23.3mV at pH = 8. For BSA, the flux declined with time while the rejection increased. Filtrate fluxes increased with rotation rate and electric field and declined with concentration for both feeds. The flux declined beyond N = 2000rpm and was constant above C(,0) = 5.0wt%. For Prussian blue, the rejection was greater than 90% at all levels of E, N and C(,0). For BSA, the rejection increased with rotation rate and declined with concentration. The BSA rejection declined above N = 2000rpm and was constant beyond C(,0) = 0.5wt%.<br>A mathematical model was derived to predict the time variation of filtrate flux and a rejection model was used to predict the effect of surface concentration on BSA rejection.
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Schousboe, Frederik Carl. "Media Velocity Considerations in Pleated Air Filtration." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6632.
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Asset protection in the form of fluid filtration makes up an ever-increasing part of the civilized and industrialized world. Fluid filtration applications in the conditioned environment and life sciences are affording the world’s population a chance to better realize their potential, while industrial applications help ensure that high demand processes can be carried out safely, reliably, and effectively.
In the present work, a tool has been developed, using the computational fluid dynamics package FLUENT, to allow the designer to better predict the magnitude of geometric imperfections within a given pleat configuration.
Pleated rectangular filters, intended to improve the quality of air for human occupants, with a U-shaped pleat form have been chosen as the focus of this study. A simulation study is developed to investigate the maximum local velocity normal to the filtration surface and to characterize the magnitude of the pleatwise velocity distribution across a range of pleated geometries and flow conditions. The geometry of the U-shaped pleat form can be characterized by, amongst other parameters, the width of the pleat channel, the overall height of the individual pleat, as well as the thickness of the filtration medium. The various geometries of the current study were developed by changing the width of the pleat channel, as well as the channel height, while keeping the medium thickness constant throughout. Changing the width of the pleat channel allows the designer to achieve varying pleat densities, expressed as a number of pleats along a one inch section of the overall pleated pack. Pleat densities of 6.5, 7, 7.5, 8, and 8.5 pleats per inch are considered in the current study. Pleat heights of 1.0, 0.75, and 0.50 inches are also investigated in the current study. Furthermore, the filter velocity can be characterized by the free stream velocity at the face of the filter pack, termed the face velocity, and by the velocity of the fluid at the interface with the filtration medium, referred to as media velocity. In the present work, the face velocity was adjusted in each case to achieve the desired media velocities across the study, which are 10.5, 9.0, 7.5, and 6.0 feet per minute.
In an effort to more clearly communicate the results of the study, the results are presented in the form of a non-dimensionalized plots which present the designer with a way to quickly gauge the effect of pleat geometry on maximum velocity. Additionally, two tools are presented to aid the designer in more accurately predicting the maximum filtration velocity. These tools are then evaluated for effectiveness using the method of absolute relative percent error. The assumption of uniform flow through the filtration media leads to an average absolute relative percent error of 27%. The first tool the reader is presented with is a simple correction factor which predicts the maximum filtration velocity with an average absolute relative percent error of 10% over the study domain. The second tool, which takes a slightly more complicated y-intercept form, characterizes the maximum filtration velocity as a function of average velocity and aspect ratio. This approach further reduces the average absolute relative percent error to 4%.
The results of the simulation herein are successfully employed to develop a set of simple yet effective tools that allow the filter designer to more accurately predict maximum velocities through a pleated air filter.
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Wang, Yuyan. "Simulation of pulsatile flow in baffled permeable channel for membrane filtration system." Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332793.
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FLEISCHMAN, GREGORY JOSEPH. "FLUID FILTRATION FROM CAPILLARY NETWORKS (MICROCIRCULATION, MATHEMATICAL MODELING)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187998.
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A mathematical model has been developed which describes the fluid exchange from a capillary network of realistic topology, and calculates the spatial distribution of extravascular pressure. In this model, the capillaries are represented by a superposition of sources and sinks, resulting from a D'Arcy's Law description of flow in tissue of uniform fluid conductivity. The combination of this representation and Starling's Hypothesis, which relates the forces influencing transmural fluid exchange, yields an integral equation of the second kind which is solved numerically for the source strength distribution. Two important features of this approach are that: (i) it allows for interaction between the local tissue pressure field and fluid exchange (the model is called, therefore, the tissue pressure interaction model); and (ii) complex network morphologies are easily modeled. In single capillaries, this interaction, which decreases the predicted fluid exchange, increases with the magnitude of the ratio of capillary wall to extravascular fluid conductivities. For multiple capillaries, in addition to the "self" interaction of a capillary with the local extravascular pressure field, there is the possibility of interaction between capillaries ("capillary-capillary" interaction). The ratio of conductivities, and the additional factors of intercapillary distance and the number of capillaries, also affect interaction in capillary networks. Although interaction is only a weak function of intercapillary distance, it depends strongly on the number of capillaries. The major result from this work is that for the entire physiological range of conductivity ratios, interaction cannot be neglected in predicting fluid exchange. Although tissue pressure interaction affects the magnitude of fluid exchange, it does not greatly alter the pattern of extravascular flow. Therefore, previous models which neglected interaction are not invalidated by the present findings. The effect of interaction on planar capillary networks within a semi-infinite tissue space was also investigated. Flow boundary conditions were imposed at opposed planar boundaries, parallel with the capillary network. Interaction was found to decrease with decreasing distance between the boundary and plane of the capillaries. It still exerted a large effect, however, for distances greater than one-fourth the reference capillary length.
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Cao, Shiya. "Analysis of Household Water Filtration in China: A System Dynamics Model." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1268.
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As the economy has been growing fast in China, Chinese people have more incomes and then higher standard of living. In the case of household water treatment, more and more urban residents in China use bottled water or water filtration system instead of tap water because people start to worry about polluted tap water. According to a survey from China Water Supply Services Promotion Alliance in 2014, 59% of urban residents drinking water is from tap water (after being boiled), 41% from bottled water and water filtration system. The 41% participants prefer bottled water as the first choice over a water filtration system.
The comparative advantages and disadvantages of home water filtration system and bottled water are analyzed using comparative analysis. The reasons why home water filtration industry has grown slowly in urban China even though it is less expensive and has environmental benefits are analyzed using a system dynamics model. The model focuses on the physical system of home water filtration industry. The study shows that order delivery delay and service time are key factors to the adoption rate of home water filtration system. However, initial cost becomes a limiting factor to the growth of the market of home water filtration system. The study proposes the according market policy, demand policy, and supply policy to improve the current scenario.
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Arthur, Kevin Gordon. "An experimental and theoretical study of the filtration characteristics of water-based drilling muds." Thesis, Heriot-Watt University, 1986. http://hdl.handle.net/10399/1082.
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Roberts, Mark. "Assessment of glomerular dynamics in human pregnancy using theoretical analysis and dextran sieving coefficients." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336811.
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Hameiri, Avikam. "Soil/geotextile filtration behavior under dynamic conditions of cyclic flow and vibration." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0016/NQ48642.pdf.
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Zhang, Wenxiang. "Optimization of protein concentration from alfalfa juice by high shear rate dynamic filtration." Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2281/document.
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Les protéines extraites des feuilles de luzerne sont une source importante de protéines. La filtration membranaire, technologie de séparation respectueuse de l’environnement avec une productivité élevée et de faible coût a été utilisée pour séparer et concentrer les protéines des feuilles de luzerne à partir de leur jus. Cependant le phénomène du colmatage de la membrane qui réduit sérieusement le flux et la séparation des protéines est un facteur limitant important dans l'application de la filtration membranaire. Pour améliorer la récupération des protéines et amenuiser le phénomène du colmatage, la filtration membranaire associée à fort cisaillement a été utilisée pour la filtration du jus de luzerne. Toujours dans l’objectif d'optimiser le processus de la filtration, "le mode de la filtration" et "les paramètres de fonctionnement" ont été étudiés pour réduire le colmatage de la membrane et améliorer le rendement de la filtration. Puis, l’effluent du jus de luzerne a été filtré par des membranes dans des conditions de fort cisaillement afin de recycler les protéines. En outre, le mécanisme du colmatage a été étudié et a permis d’évaluer les stratégies de contrôle du colmatage. L'optimisation du procédé membranaire, via l’étude du "mode de filtration" et des "paramètres de fonctionnement" a été conduit dans le but d’améliorer la séparation et la concentration des protéines et de réduire le colmatage. Trois types de « mode de filtration » ont été testés : la filtration frontale sur le module de la cellule amicon (DA), la filtration tangentielle dynamique sur le module à disque rotatif (CRDM) et la filtration frontale sur le module à disque rotatif (DRDM)). Les « paramètres de fonctionnement » qui ont été étudiés sont les suivants : le type de membranes (ultrafiltration (UF) et microfiltration (MF)), la vitesse de rotation, la température et la pression transmembranaire (TMP). Le comportement du débit (évolution du flux du perméat au cours de la filtration), les performances de la séparation (taux de clarification et de concentration), l’efficacité du nettoyage de la membrane (récupération de la perméabilité membranaire) et la productivité lors des tests de recyclage et de concentration ont été étudiés dans le but de définir des stratégies dans le contrôle du colmatage. Puis, l’effluent de luzerne a été filtré par UF afin de séparer et purifier les protéines. Le mécanisme du phénomène du colmatage des membranes lors de la filtration du jus de luzerne a été étudié. Le processus du colmatage de la membrane a montré une tendance d’un colmatage multi-site progressif. Le modèle du colmatage multisite progressif selon la loi de Darcy (SMDM) a été proposé afin de mieux décrire et comprendre le processus du colmatage. Les effets de la composition du fluide d’alimentation, du choix de la membrane et des conditions hydraulique ont joué un rôle important dans le processus progressif du colmatage. De plus, les coefficients de résistance et de compressibilité dans les différentes étapes et sites ont été calculés afin d’expliquer le processus complexe du colmatage et d’évaluer l'efficacité des stratégies du contrôle du colmatage. Une série d'essais avec de longues durées de filtration a été réalisée pour étudier le déclin du flux et le colmatage de la membrane à diverses étapes du processus. Ces résultats présentent une utilité pour améliorer la récupération des protéines et contrôler le colmatage dans le processus de la filtration membranaire à fort cisaillement du jus de luzerne. Ces résultats sont aussi utiles pour la conception et la mise en place des technologies membranaires dans les processus industriels<br>Alfalfa leaf proteins extracted from plants are an important protein source. As an environmentally friendly separation technology with high productivity and low cost, membrane filtration was used to separate and concentrate leaf protein from alfalfa juice. However membrane fouling seriously reduces flux and protein separation and is an important limitation in the application of membrane filtration. To improve protein recovery and fouling control, dynamic shear-enhanced membrane filtration with high shear rate on membrane surface and excellent anti-fouling capacity was used for alfalfa juice filtration in this work. In order to optimize filtration process, filtration mode and operation parameters were investigated to reduce membrane fouling and improve separation performance. Then, alfalfa wastewater was also treated by dynamic shear-enhanced membrane filtration to recycle proteins. Furthermore, the fouling mechanism was studied and served as a valuable evaluation for fouling strategies. In this study, process optimization including “Filtration mode” and “Operation parameters” was studied to improve protein recovery and fouling control. In “Filtration mode”, three types of filtration modules (dead end filtration using laboratory Amicon cell (DA), dynamic cross filtration using rotating disk module (CRDM) and dead end filtration using rotating disk module (DRDM)) were used to investigate the filtration performance. As for “Operation parameters”, the operation parameters including membranes (ultrafiltration (UF) and microfiltration (MF)), rotating speed, temperature and transmembrane pressure (TMP) were studied to optimize the filtration process. Flux behavior (permeate flux and flux decline), separation performance (clarification and concentration capacity), membrane cleaning efficiency (permeability recovery) and productivity in full recycling tests and concentration tests were utilized to evaluate the various operation strategies. In addition, alfalfa wastewater was treated by UF membrane, while waste proteins were recycled. Fouling mechanism for alfalfa juice filtration was investigated. The fouling process showed significantly stepwise multisite patterns. Based on Darcy’s law, the stepwise multisite Darcy’s law model (SMDM) was proposed to better describe and understand the fouling process. The effects of feed composition, membrane and hydraulic conditions played an important role in stepwise fouling process. Moreover, the resistance coefficient and compressibility for different steps and sites were calculated to explain the complex fouling process and estimate the efficiency of flux decline control strategies. Besides, a series of long tests were utilized to study flux decline and membrane fouling at various fouling step process. These results can be used to understand the protein recovery and fouling control during shear-enhanced membrane filtration process of alfalfa juice. They have important implications for process design of membrane technology in industrial scale
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Lukins, Halcyon Josephine. "Dynamics of the waterborne stage of Myxobolus cerebralis estimated directly by packed-bed filtration." Thesis, Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/lukins/LukinsH0805.pdf.
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Al-Hajeri, Mohammad Hamad. "Characterization of the fluid flow associated with ceramic candle filters." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323258.
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Azadi, Azin. "A 'dynamic' tissue model of glomerular filtration barrier maintenance, adaptation and potential pathways to failure." Thesis, Azadi, Azin (2022) A 'dynamic' tissue model of glomerular filtration barrier maintenance, adaptation and potential pathways to failure. PhD thesis, Murdoch University, 2022. https://researchrepository.murdoch.edu.au/id/eprint/66252/.
Full textAbstract:
The glomerular filtration barrier (GFB), within the kidney, is known to act as a filter. It must work effectively over its lifespan, avoiding common filter problems such as clogging. Previous mathematical studies mostly just considered how the GFB acts as a size and charge selective barrier. In contrast, here the aim is how the GFB continues to work long-term, despite its environmental changes. The overarching hypothesis presented here is that the tissue is continuously renewing, as podocyte-synthesized molecules are transported ‘upstream’ against the filtrate across the glomerular basement membrane (GBM) to exit via endothelial fenestrae. We refer to this as a ‘dynamic’ tissue, rather than the common static view of the GFB as a simple filter. This then provides a conceptual model to understand how the GFB works long-term. We use computational modelling to (i) test this conceptual model, (ii) integrate and quantify the various biological, biochemical and biophysical processes involved and (iii) predict key model parameter values that are linking to the structural/functional features of GFB. This approach helped identify potential control mechanisms to maintain GFB functional properties against a constant challenges. It also reveals potential pathways to GFB ‘failure’ or pathology. We found there is a constant gradient in the negative fixed charge (NFC) from podocytes to endothelial, which is the main driver for rapid transport of heperan sulfate proteoglycans (HSPGs) against plasma flow. This HSPG flux is a potential anti-clogging mechanism and may enable podocytes-to-endothelial cell upstream crosstalk. We demonstrated that the existence of a constant gradient NFC distribution is beneficial to albumin sieving rate compared to a constant NFC (as assumed in past models). We argue that the role of podocytes slit diaphragms is to retain GBM extracellular matrix proteins, rather than albumin-exclusion barrier. Results are significant in terms of understanding GFB maintenance, adaption and pathology.
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Sendekie, Zenamarkos Bantie. "Clogging dynamics of particles and bacteria in microfluidic systems mimicking microfiltration processes." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30355/document.
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L'objectif de cette thèse est de progresser dans la compréhension du colmatage lors de la filtration de la matière molle (particules colloïdales et bactéries) et d'étudier l'efficacité et la faisabilité de séparateurs microfluidiques. Ces recherches sont réalisées avec des puces microfluidiques constituées de canaux dont la taille est du même ordre de grandeur que les objets filtrés. Ces puces, conçues pour représenter les processus ayant lieu en microfiltration frontale et tangentielles, permettent d'observer in-situ sous microscope les mécanismes de colmatage. Le système est instrumenté avec des capteurs de débit et de pression et permet ainsi une analyse croisée entre les observations et les variations de perméabilité. Les expériences ont été réalisées pour différentes conditions hydrodynamiques (débit, mode de filtration) et conditions d'interactions colloïdales (en changeant la force ionique). Les résultats mettent en évidence l'importance de la dynamique du blocage de pore par des agrégats de particules et du réentrainement de ces agrégats lorsqu'ils sont fragilisés par l'écoulement. La dynamique de ces évènements provoque des fluctuations de perméabilité. Les interactions particule-particule ou particule-paroi jouent également un rôle important sur la dynamique du colmatage. Trois scenarios sont discutés par analogie anthropomorphique : un scenario panique (0.01 mM) où les répulsions entre les particules induit un phénomène de poussée entre particules qui engendre la formation d'arches à l'entrée des canaux ; un scenario instinct de troupeau (10 mM) où l'attraction entre particules (dans un minimum DLVO secondaire) facilite le transport dans le canal et retarde le colmatage ; un scenario sacrificiel (100 mM) où l'efficacité de capture des particules par les parois est élevée mais les agrégats formés sont très fragiles et fréquemment réentraînés par l'écoulement. Cette analyse illustre l'importance des phénomènes collectifs lors du colmatage par des particules inter-agissantes. Le mécanisme de colmatage par des particules biologiques (bactéries) et notamment la création de panaches bactériens en aval des canaux sont ensuite analysés. Ces phénomènes sont étudiés pour différentes conditions de culture (ratio carbone-azote dans le substrat) afin d'examiner l'effet de la production de substances polymériques extracellulaires (EPS) sur le colmatage. Les résultats montrent que les EPS (et donc les conditions de cultures) jouent un rôle crucial sur le développement de panaches bactériens lors d'écoulement dans des constrictions. Il est montré également que la filtration d'un mélange entre des bactéries produisant peu d'EPS et des bactéries produisant d'EPS favorise la formation des panaches bactériens. Des filtrations de mélange de bactéries et de particules montrent que la présence de bactérie modifie la dynamique du blocage des canaux ; de façon surprenante l'ajout de bactérie permet de retarder le colmatage et de former des dépôts de particules plus fragiles. Des systèmes microfluidiques avec un design spécifique ont également été développés pour réaliser un fractionnement par taille de dispersions sous un écoulement tangentiel. Des résultats préliminaires ont permis d'optimiser leur fonctionnement en trouvant des conditions permettant de filtrer en évitant le blocage des canaux ; leur utilisation pour réaliser des fractionnements continus dans des puces microfluidiques peut être envisagée<br>The aim of the PhD is to progress in the understanding of the fouling phenomena during filtration of soft matter (colloidal particles and bacteria) and to examine the efficiency and feasibility of microfluidic separators. These studies are realized with microfluidic devices constituted of micrometric channels having the same size range as the materials being filtered. These devices, which mimic membrane dead-end and cross-flow microfiltration processes, allow in-situ and direct microscopic observations of the fouling mechanisms. The microfluidic system is equipped with flow rate and pressure measurement devices allowing a dynamic cross analysis of the observations with the variations of permeability. Experiments have been realized for different hydrodynamic conditions (flow rate, filtration mode) and for different colloidal interactions (by varying the ionic strength) in order to analyse their interplay in the clogging mechanism by soft matter (interacting particles). The results evidenced the importance of clogs formation, fragility and sweeping out dynamics during the fouling process. These dynamic events at bottlenecks induce important permeability fluctuations. The particle-particle and particle-wall interactions also play important roles on the clogging dynamics. Three different scenarios are discussed by analogy to crowd swarming: panic scenario (0.01 mM) where repulsion between particles induce pushing effects leading to the creation of robust arches at pore entrances; herding instinct scenario (10 mM) where the attraction (in secondary minima) between particles enhances the transport in pores and delays clogging; sacrifice scenario (100 mM) where the capture efficiency is high but the aggregates formed at the wall are fragile. These analyses illustrate the importance of collective behaviour exhibited by interacting particles during fouling. The fouling phenomena by biological particles (bacteria) are analysed in terms of the streamer formation conditions and mechanisms. The streamer formation phenomena are in turn analysed by playing with the cultivation conditions (the carbon to nitrogen ratio in the substrate) in order to study the effect of extracellular polymeric substances (EPS) on the process. The results show that EPS (and hence the bacterial cultivation conditions) play crucial role in streamer formation by microorganisms under flow in constrictions. Furthermore, the presence of non-EPS producing bacterial species along with EPS producing species in a mixed culture enhances the streamer formation. On the other hand, filtration of mixed particles and bacteria suspensions show that the presence of bacteria substantially modifies the clogging dynamics. Microfluidic devices with specific configurations have also been developed for fractionation in order to maximize performances of these processes. The preliminary results with these chips in cross-flow conditions show that it is possible to limit the clogging impact by working below a critical flux; their use for continuous microparticles fractionation could be then considered
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Saleem, Mubbshir. "Application of dynamic membranes in wastewater treatment." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3422308.
Full textAbstract:
The research highlighted the performance of dynamic membrane (DM) in most challenging conditions where advanced technologies like MBR etc. have been successfully applied. In this regard, treatment of old landfill leachate, production of bio hydrogen and enrichment of Anammox bacteria was mostly focused. The research also presented the strategies to expedite the formation of DM under both aerobic and anaerobic conditions. Pneumatic In situ cleaning mechanism was also proposed and proved to be effective in speedy and effective permeability recovery of excessively fouled DM under anaerobic conditions without chemical cleaning. Similarly, the effect of feed characteristics on development and performance of DM was also highlighted for the first time and the associated role of mesh porosity of underlying support was also discussed.<br>La ricerca ha evidenziato le prestazioni della membrana dinamica (DM) nelle condizioni più difficili in cui sono state applicate con successo tecnologie avanzate come MBR ecc. A questo proposito, il trattamento del percolato di discarica precedente, la produzione di bio idrogeno e l'arricchimento dei batteri Anammox sono stati principalmente concentrati. La ricerca ha anche presentato le strategie per accelerare la formazione di DM in condizioni sia aerobiche che anaerobiche. È stato anche proposto un meccanismo di pulitura in situ pneumatico che si è dimostrato efficace nel recupero rapido ed efficace della permeabilità del DM eccessivamente sporco in condizioni anaerobiche senza pulizia chimica. Allo stesso modo, l'effetto delle caratteristiche del mangime sullo sviluppo e sulle prestazioni del DM è stato anche evidenziato per la prima volta e anche il ruolo associato della porosità della mesh del supporto sottostante è stato discusso.
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Abdullah, Syed Zaki. "Investigation of effect of dynamic operational conditions on membrane fouling in a membrane enhanced biological phosphorus removal process." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/264.
Full textAbstract:
The membrane bioreactor (MBR) is becoming increasingly popular for wastewater treatment, mainly due to its capability of producing high quality effluent with a relatively small footprint. However, high plant maintenance and operating costs due to membrane fouling limit the wide spread application of MBRs. Membrane fouling generally depends on the interactions between the membrane and, the activated sludge mixed liquor, which in turn, are affected by the chosen operating conditions. The present research study aimed to explore the process performance and membrane fouling in the membrane enhanced biological phosphorus removal (MEBPR) process under different operating conditions by, (1) comparing two MEBPRs operated in parallel, one with constant inflow and another with a variable inflow, and by, (2) operating the MEBPRs with different solids retention times (SRT).
On-line filtration experiments were conducted simultaneously in both MEBPR systems by using test membrane modules. From the transmembrane pressure (TMP) data of the test membrane modules, it was revealed that fouling propensities of the MEBPR mixed liquors were similar in both parallel reactors under the operating conditions applied, although the fouling propensity of the aerobic mixed liquors of both reactors increased when the SRT of the reactors was reduced.
Routinely monitored reactor performance data suggest that an MEBPR process with a varying inflow (dynamic operating condition) performs similarly to an MEBPR process with steady operating conditions at SRTs of 10 days and 20 days. Mixed liquor characterization tests were conducted, including critical flux, capillary suction time (CST), time to filter (TTF) and, bound and soluble extracellular polymeric substances (EPS) were quantified, to evaluate their role on membrane fouling. The tests results suggest that the inflow variation in an MEBPR process did not make a significant difference in any of the measured parameters.
With decreased SRT, an increase in the concentrations of EPS was observed, especially the bound protein, and the bound and soluble humic-like substances. This suggests that these components of activated sludge mixed liquors may be related to membrane fouling. No clear relationship was observed between membrane fouling and other measured parameters, including critical flux, normalized CST and normalized TTF.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
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Abdullah, Syed. "Investigation of effect of dynamic operational conditions on membrane fouling in a membrane enhanced biological phosphorus removal process." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/264.
Full textAbstract:
The membrane bioreactor (MBR) is becoming increasingly popular for wastewater treatment, mainly due to its capability of producing high quality effluent with a relatively small footprint. However, high plant maintenance and operating costs due to membrane fouling limit the wide spread application of MBRs. Membrane fouling generally depends on the interactions between the membrane and, the activated sludge mixed liquor, which in turn, are affected by the chosen operating conditions. The present research study aimed to explore the process performance and membrane fouling in the membrane enhanced biological phosphorus removal (MEBPR) process under different operating conditions by, (1) comparing two MEBPRs operated in parallel, one with constant inflow and another with a variable inflow, and by, (2) operating the MEBPRs with different solids retention times (SRT).
On-line filtration experiments were conducted simultaneously in both MEBPR systems by using test membrane modules. From the transmembrane pressure (TMP) data of the test membrane modules, it was revealed that fouling propensities of the MEBPR mixed liquors were similar in both parallel reactors under the operating conditions applied, although the fouling propensity of the aerobic mixed liquors of both reactors increased when the SRT of the reactors was reduced.
Routinely monitored reactor performance data suggest that an MEBPR process with a varying inflow (dynamic operating condition) performs similarly to an MEBPR process with steady operating conditions at SRTs of 10 days and 20 days. Mixed liquor characterization tests were conducted, including critical flux, capillary suction time (CST), time to filter (TTF) and, bound and soluble extracellular polymeric substances (EPS) were quantified, to evaluate their role on membrane fouling. The tests results suggest that the inflow variation in an MEBPR process did not make a significant difference in any of the measured parameters.
With decreased SRT, an increase in the concentrations of EPS was observed, especially the bound protein, and the bound and soluble humic-like substances. This suggests that these components of activated sludge mixed liquors may be related to membrane fouling. No clear relationship was observed between membrane fouling and other measured parameters, including critical flux, normalized CST and normalized TTF.
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SANTOS, PAULO ROBERTO DA FONSECA. "EVALUATING CHARACTERISTICS OF STATIC AND DYNAMIC FILTRATION OF A FLUID USED IN HYDRAULIC FRACTURING AT ROOM TEMPERATURE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1989. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33262@1.
Full textAbstract:
Este trabalho teve como objetivo estudar as características de filtração estática e dinâmica de um fluido
usado em fraturamento hidráulico à temperatura ambiente. Para sua realização foi projetado, desenvolvido e qualificado metrologicamente um simulador que permitisse efetuar testes de filtração estática e dinâmica. Foram realizadas filtrações com um fluido newtoniano (água) e um não newtoniano (HPGUAR-BO lbm/1000gal).<br>This research intended to study the characteristcs of dynamic and static leakoff of a fluid in hydraulic
fracturing at room temperature. A test apparatus was designed, constructed and metrologically qualified in order to carry out dynamic and stactic leakoff test. Leakoffs with a Newtonian fluid (water) and with a non-Newtonian one (HPGUAR-BO lbm/1000 gal) were performed.
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Mentesidis, Anastasios. "Experimental Evaluation of the Effects of Dynamic Pressure on Improving Cement-based Grout Penetrability : A study performed with the short slot." Thesis, KTH, Jord- och bergmekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-165034.
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The increasing need for watertight underground works, such as tunnel excavations, has sparked an interest in a number of research studies with grout penetrability being the focus. The research has so far contributed to a deeper understanding regarding the assessment of a successful grouting operation from different perspectives such as choice of equipment, material properties, phase planning and performance. It is well established that several crucial factors influence the penetrability of grouts with pressure type and magnitude being two of them. Researchers have examined this issue from different perspectives and with different instruments. Previous research has shown that the increase of pressure has yielded better grout penetration both in the laboratory and the field. According to studies that dealt with dynamic pressure application, superimposed oscillatory pressure of high frequency resulted in grouts with decreased viscosity and better penetration. However, there is still need for further investigation in terms of lower frequencies, different pressure profiles and magnitudes and possible alternatives regarding the filtration and erosion mechanism. The present study aims to examine the penetrability of grouts under dynamic conditions of predefined peak and rest pressure intervals with frequencies lower than 0.5 Hz. The mechanism of action assumes active decomposition of any partially built plug in the vicinity of a narrowing in a rock fracture caused by the change in flow type before the constriction. The chosen method included the development of a laboratory grout injection system with a pneumatic valve and a pressure control rig. Tests were performed with both constant and varying pressure utilizing different periods of peak and rest intervals. The results showed an overall improvement of penetrability under dynamic conditions compared to the static. The decrease in peak – rest durations from [2 – 2] to [4 – 8] s yielded almost 11 times more material penetrating the 30μm aperture size. The developed method utilized a pneumatic injection system which culminated in better penetration when tuned at [2 – 2] s of [peak – rest] durations with specific material properties. This study presents an indication that further research towards the direction of dynamic pressure application could be proven beneficial in the grouting industry.
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Khan, Wasiq. "A Novel Approach for Continuous Speech Tracking and Dynamic Time Warping. Adaptive Framing Based Continuous Speech Similarity Measure and Dynamic Time Warping using Kalman Filter and Dynamic State Model." Thesis, University of Bradford, 2014. http://hdl.handle.net/10454/14802.
Full textAbstract:
Dynamic speech properties such as time warping, silence removal and background noise interference are the most challenging issues in continuous speech signal matching. Among all of them, the time warped speech signal matching is of great interest and has been a tough challenge for the researchers. An adaptive framing based continuous speech tracking and similarity measurement approach is introduced in this work following a comprehensive research conducted in the diverse areas of speech processing. A dynamic state model is introduced based on system of linear motion equations which models the input (test) speech signal frame as a unidirectional moving object along the template speech signal. The most similar corresponding frame position in the template speech is estimated which is fused with a feature based similarity observation and the noise variances using a Kalman filter. The Kalman filter provides the final estimated frame position in the template speech at current time which is further used for prediction of a new frame size for the next step. In addition, a keyword spotting approach is proposed by introducing wavelet decomposition based dynamic noise filter and combination of beliefs. The Dempster’s theory of belief combination is deployed for the first time in relation to keyword spotting task. Performances for both; speech tracking and keyword spotting approaches are evaluated using the statistical metrics and gold standards for the binary classification. Experimental results proved the superiority of the proposed approaches over the existing methods.
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Xie, Xiaomin. "Investigation of Local and Global Hydrodynamics of a Dynamic Filtration Module (RVF Technology) for Intensification of Industrial Bioprocess." Thesis, Toulouse, INSA, 2017. http://www.theses.fr/2017ISAT0020/document.
Full textAbstract:
Cette thèse porte sur la compréhension et le contrôle des interactions dynamiques entre les mécanismes physiques et biologiques en considérant un procédé alternatif de séparation membranaire pour les bioprocédés industriels. L’objectif premier est un apport de connaissances scientifiques liées à la maîtrise de la bioréaction en considérant l'hydrodynamique complexe et les verrous rétention-perméation. Une technologie de filtration dynamique, appelée Rotating and Vibrating Filtration (RVF), a été spécifiquement étudiée. Elle se compose de cellules de filtration en série comprenant deux membranes circulaires planes fixées sur des supports poreux au voisinage d'un agitateur à trois pales planes attachées à un arbre central. Ce dispositif mécanique simple fonctionne en continu et génère une contrainte de cisaillement élevée ainsi qu'une perturbation hydrodynamique dans un entrefer étroit (pale-membrane). Les verrous scientifiques et techniques qui motivent ce travail, sont la caractérisation et la quantification (i) des champs de vitesse locaux et instantanés, (2) des contraintes pariétales de cisaillement à la surface de la membrane et (3) l'impact mécanique sur les cellules microbiennes.Dans ce but, des expériences et des simulations numériques ont été réalisées pour étudier l'hydrodynamique à des échelles globales et locales, en régimes laminaire et turbulent avec des fluides newtoniens dans des environnements biotique et abiotique. Pour l'approche globale, la distribution des temps de séjour (RTD) et le bilan thermique ont été réalisés et comparés aux précédentes études globales (courbes de consommation de puissance et de frottement). Une étude analytique des fonctions de distribution a été effectuée et les moments statistiques ont été calculés et discutés. Une analyse systémique a été utilisée pour décrire les comportements hydrodynamiques du module RVF. En combinant la simulation des écoulements (CFD) et les observations (RTD), les conditions et les zones de dysfonctionnement des cellules de filtration sont éclairées. Pour l'approche locale, la vélocimétrie laser (PIV) a été réalisée dans les plans horizontaux et verticaux et comparée à la simulation numérique (CFD). Une étude préliminaire basée sur une synchronisation entre la prise d’image et la position de l’agitateur (résolution angulaire) a permis d’accéder aux champs de vitesse moyens. Une campagne de mesure PIV a été réalisée sans synchronisation afin d’appliquer une décomposition orthogonale aux valeurs propres (POD) pour 'identifier les composantes moyennes, organisées et turbulentes des champs de vitesse (énergie cinétique). Pour l'application aux bioprocédés, un travail exploratoire a caractérisé l'effet de la filtration dynamique sur des cellules procaryotes (E. coli) en quantifiant l'intégrité cellulaire ou leur dégradation en fonction du temps et de la vitesse de rotation<br>This thesis focuses on the understanding and the control of dynamic interactions between physical and biological mechanisms considering an alternative membrane separation into industrial bioprocess. It aims to carry scientific knowledge related to the control of bioreaction considering complex hydrodynamics and retention-permeation locks specific to membrane separation. A dynamic filtration technology, called Rotating and Vibrating Filtration (RVF), was investigated. It consists of filtration cells in series including two flat disc membranes fixed onto porous substrates in the vicinity of a three-blade impeller attached to a central shaft. This simple mechanical device runs continuously and generates a high shear stress as well as a hydrodynamic perturbation in the narrow membrane-blade gap. Several scientific and technical locks motivating this work are to characterize and to quantify (i) the velocity fields locally and instantaneously, (2) the shear stresses at membrane surface and (3) the mechanical impact on microbial cells.To this end, experiments and numerical simulations have been performed to investigate the hydrodynamics at global and local scales under laminar and turbulent regimes with Newtonian fluids under biotic and abiotic environment. For global approach, investigation of Residence Time Distribution (RTD) and thermal balance was carried out and compared to the previous global study (power consumption and friction curves). Analytical study of distribution functions was conducted and statistical moments were calculated and discussed. A systemic analysis was used to describe the hydrodynamic behaviors of the RVF module. Combining Computational Fluid Dynamics (CFD) and RTD observations, it leads to demonstrate dysfunctioning conditions and area. For the local approach, Particle Image Velocimetry (PIV) was be carried out in both horizontal and vertical planes and compared to CFD simulation. PIV preliminary study was conducted with a trigger strategy to access through angle-resolved measurements to an averaged velocity field. PIV further study were performed with a non-trigger strategy and applied to Proper Orthogonal Decomposition (POD) analysis in order to identify the coherent structure of the flow by decomposing the organized and turbulent fluctuations. For the bioprocess application, an exploratory work characterized the effect of Dynamic Filtration on prokaryote cell population (Escherichia coli) by quantifying cell integrity or damage as a function of time and rotation speed during filtration process in turbulent regime
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Zoccola, Gregg. "Effect of conditioning on the performance of a plate and frame filter press." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43077.
Full textAbstract:
Experiments were performed on samples of alum,
anaerobically digested, and aerobically digested sludges
to determine optimum polymer dosages for various mixing
intensities produced during conditioning by a high-stress
mixing unit. Mean velocity gradient (G) values were
established for each of the mixing speeds used ranging
from 250 sec -1 to 4,000 sec-1. Using the optimum
conditioning dosages determined each mixing speed,
batches of optimally, conditioned sludge were introduced
into a pilot scale plate and frame filter press. Filtrate
volume per unit time and final cake solids were used to
characterize the press performance. Results indicated
that filter press, performance can be optimized by
selecting mixing. speeds during conditioning that simulate
the shear conditions produced in the filter press during
operation. It was shown that press performance was
substantially reduced using sludge conditioned at a mixing
speed of 200 rpm, corresponding to a Gt equal to 17,000.
Tests using mixing speeds of 400 rpm and 1800 rpm
corresponding to Gt values of 32,000 and 230,000,
respectively indicated better performance and, thus, the
filter press is thought to generate Gt values within this
range. A substantial increase in polymer requirements is shown for sludge conditioned at
a mixing speed of 1800 rpm, and therefore,
it was concluded that sludge
conditioned at mixing speed of 400 rpm best
characterized the filter press producing optimum
operational conditions. It was also postulated that the
filter press may not be characterized by a single Gt
value, but, by a range of values dependent on press run time.<br>Master of Science
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Meng, Bowen. "State of the Art Report on Cement Based Grout Properties and Dynamic Grouting." Thesis, KTH, Jord- och bergmekanik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302699.
Full textAbstract:
Dynamic grouting in rock mass has been studied since 1985 while desired penetration in rock masses with fine fractures is still a challenge because of uncertainty and complexity in the grouting process. This has attracted the attention of researchers in different countries and regions, especially in some Nordic countries such as Sweden. This study presents a comprehensive review of grouting relevant research, including factors that influence penetration, different evaluation systems (equipment, and methods), and a variety of grouting techniques. Filtration as the main obstacle is a tendency that particles of suspensions would gradually separate from the flow and block the flow path. Hence, the effects of various factors on filtration are discussed in detail based on previous research and experiments. Factors such as temperature, grain size, and w/c ratio were found to have a dominant influence on filtration stability and rheology. This means rheology and filtration are highly coupled and brings more difficulties in penetration investigation with dynamic grouting. Therefore, the influence of each factor on rheology and filtration was discussed to help with the understanding of the mechanism in different grouting techniques. Then a review of dynamic grouting methods from 1985 is made in chronological order to find the limitations on existing equipment and evaluation methods. Even it is difficult to conclude the most efficient grouting method in micro-fractures without the quantitative comparison of efficiency, this review paves the way to a more systematic exploration of novel grouting equipment and techniques. Meanwhile, a contradiction regarding the influence of high-frequency oscillatory pressure on viscosity was revealed. Rather than rapid dissipation of pressure in the slots, the thermal effect caused by high-frequency oscillatory grouting is introduced to explain its adverse impact on penetration in fractures (250 and 100μm). The potential reason is the faster hydration of grouts resulted from the increased temperature and the speed of molecular motion. In the end, by evaluating the benefits from different combinations of grouting methods. It was found that the ultrasound dispersing method along with low-frequency rectangular pressure impulse would contribute to the rheology and filtration stability in the mixing and grouting phase respectively. With the application of CDF simulation, this proposal and the assumption of the thermal effect of high-frequency oscillatory pressure can be better verified in future research.<br>Dynamisk injektering i bergmassa har studerats sedan 1985. Önskad tätning av bergmassor med fina sprickor är dock fortfarande en utmaning på grund av osäkerhet och komplexitet i injekteringsprocessen. Detta har uppmärksammats av forskare i olika länder och regioner, särskilt i nordiska länder såsom Sverige. Denna studie presenterar en omfattande granskning av relevant forskning, inklusive faktorer som påverkar penetration, olika utvärderingssystem (utrustning och metoder) och en mängd olika injekteringstekniker. Filtrering som ett huvudsakligt hinder är en tendens att partiklar av cementsuspensioner gradvis separerar och blockerar flödesbanan, främst i små sprickor. Därför diskuteras effekterna av olika faktorer på filtrering i detalj baserat på tidigare forskning och experiment. Faktorer som temperatur, kornstorlek och vattencementtal har en dominerande påverkan på filtreringsstabilitet och reologi. Detta innebär att reologi och filtrering är starkt kopplade och medför fler svårigheter vid injektering. Därför diskuteras varje faktors påverkan på reologi och filtrering för att hjälpa till att förstå mekanismen i olika injekteringstekniker. Därefter görs en översyn av dynamiska injekteringsmetoder från 1985 i kronologisk ordning för att hitta begränsningarna för befintlig utrustning och utvärderingsmetoder. Även om det är svårt att avgöra den mest effektiva injekteringsmetoden vid mikrofrakturer, utan den kvantitativa jämförelsen av effektivitet, banar denna översyn vägen för en mer systematisk studie av ny injekteringsutrustning och teknik. Samtidigt påvisades en motsättning angående påverkan av högfrekvent oscillerande tryck på viskositeten. I stället för en snabb tryckförlust i sprickor introduceras den termiska effekten som orsakas av högfrekvent oscillerande injektering för att förklara dess negativa inverkan på penetration i tunna sprickor (250 och 100μm). Den potentiella orsaken är den snabbare hydratiseringen av injekteringsmedel som beror på den ökade temperaturen och hastigheten på molekylär rörelse. Genom att i slutändan utvärdera fördelarna med olika kombinationer av injekteringsmetoder. Det har visat sig att metoden med ultraljud för att dispergera injekteringsbruket tillsammans med lågfrekvent rektangulär tryckimpuls påverkar reologin och filtreringsstabiliteten i blandnings- och injekteringsfasen. Med tillämpningen av CDF-simulering kan antagandet om den termiska effekten av högfrekvent oscillerande tryck verifieras bättre i framtida forskning.
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Francis, Patrick. "Modeling of controlled-shear affinity filtration using computational fluid dynamics and a novel zonal rate model for membrane chromatography." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/39128.
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Controlled-shear affinity filtration (CSAF) is a novel integrated bioprocessing technology that positions a rotor directly above an affinity membrane chromatography column to permit protein capture and purification directly from cell culture. The rotor provides a tunable shear stress at the membrane surface that inhibits membrane fouling and cell cake formation allowing for a uniform filtrate flux that maximizes membrane column performance. However, the fundamental hydrodynamics and mass transfer kinetics within the CSAF device are poorly understood and, as a result, the industrial applicability of the technology is limited.
A computational fluid dynamic (CFD) model is developed that describes the rotor chamber hydrodynamics of the CSAF device. Once evaluated the model is used to show that a rotor of fixed angle does not provide uniform shear stress at the membrane surface. This results in the need to operate the system at unnecessarily high rotor speeds to reach a required shear stress threshold across the membrane surface, compromising the scale-up of the technology. The CFD model is then used to model design improvements that result in an in silico design of a preparative CSAF device capable of processing industrial feedstocks.
To describe mass transfer in stacked-membrane chromatography a novel zonal rate model (ZRM) is presented that improves on existing hold-up volume models. The ZRM radially partitions the membrane stack and external hold-up volumes to better capture non-uniform flow distribution effects. Global fitting of model parameters is first used under non-retention conditions to build and evaluate the appropriate form of the ZRM. Through its careful accounting of transport non-idealities within and external to the membrane stack, the ZRM is then shown to provide, under protein retention conditions, a useful framework for characterizing putative protein binding models, for predicting breakthrough curves and complex elution behavior, and for simulating and scaling separations using membrane chromatography.
By elucidating the intrinsic physical processes ongoing in CSAF the mathematical models presented in this thesis represent essential theoretical tools for the further development of the technology; a technology which has the potential to increase productivity and decrease costs in the downstream processing of biopharmaceuticals.
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Braak, Etienne. "Aération pour le décolmatage dans les bioréacteurs à membranes immergées pour le traitement des eaux usées : impact sur le milieu biologique et la filtration." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/8859/1/braak.pdf.
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Cette étude présente les travaux réalisés pour comprendre l'effet de l'aération sur le milieu
biologique et sur la filtration dans les bioréacteurs à membranes immergées pour une gamme de paramètres opératoires proche de celles utilisées sur stations réelles. Notre démarche fait le lien entre paramètres opératoires (débit d'aération), hydrodynamique à l'échelle macroscopique (tailles et vitesses de bulles), hydrodynamique à l'échelle locale (contraintes de cisaillement) et propriétés du milieu biologique (taille de flocs et substances polymériques extracellulaires solubles). De moins bonnes performances de filtration à plus forte aération pourraient être expliquées par une plus grande déstructuration des boues sur le court terme. Par ailleurs tout effet d'évolution des boues sur le long terme en fonction des conditions d'aération a été écarté.
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Kampel, Guido. "Mathematical modeling of fines migration and clogging in porous media." Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19764.
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Thesis (Ph.D)--Mathematics, Georgia Institute of Technology, 2008.<br>Committee Chair: Goldsztein, Guillermo; Committee Member: Dieci, Luca; Committee Member: McCuan, John; Committee Member: Santamarina, Juan; Committee Member: Zhou, Haomin.
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Günther, Jan. "Caractérisation et optimisation des phénomènes de transfert dans un double bioréacteur à membranes." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT047G/document.
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L'idée de base est de permettre à deux microorganismes de partager le même environnement tout en les maintenant séparées à l'aide d'une membrane perméable les retenant sélectivement. La principale contrainte résulte du transfert des composées d'intérêts limité par l'écoulement dans et autour des fibres ainsi que dans module et par le colmatage. Le double bioréacteur a membrane étudié dans cette thèse, de par son fonctionnement, alterne les cycles de filtration et rétrofiltration (ou rétrolavage), limitant ainsi en partie le colmatage. Ce travail de thèse s'est donc attaché à approfondir la connaissance des mécanismes de limitation au transfert mis en jeu lors de la filtration de fluide biologique complexes et évolutifs en fonction des conditions opératoires et des caractéristiques géométriques du module de filtration à fibres creuses. Dans cet objectif, sur la base des choix de configuration de module membranaire proposés dans cette étude, et afin de tendre vers une optimisation rationnelle de l'utilisation de ce dispositif, l'étude s'appuya sur l'utilisation d'outils de mécanique des fluides numériques, complétée par une approche expérimentale menée dans des conditions modèles. Les simulations réalisées par cette approche ont ainsi mis en évidence de grandes variations des vitesses de filtration le long de la fibre et ceci en lien direct avec une augmentation de la perte de charge à l'extérieur des fibres due au confinement induisant une baisse des performances de filtration. De manière similaire, un modèle numérique de formation de dépôt nous a permis d'évaluer l'effet du confinement de fibres. Il entraine une augmentation de pression dans la partie fluide externe induisant une forte variation de pertes de charges entrainant une répartition du dépôt le long de la fibre beaucoup plus inhomogène. Le retour du numérique à l'expérimental réalisé s'est attaché à décrire l'influence des conditions de mise oeuvre sur les performances de filtration du pilote. L'analyse méthodique de l'influence du sens de filtration et de la compacité dans le cas de fluides modèles (suspension de différents microorganismes / solutions de protéines modèles) et dans le cas de fluides biologiques évolutifs (milieux de fermentation + micro organismes) fut réalisée. L'ensemble de ces résultats nous permettent de donner des recommandations aux futurs utilisateurs du double bioréacteur à membranes<br>This work presents a specific bioreactor previously designed to study microbial interactions. In this process, the microbial species in two tanks are physically separated by a microfiltration membrane. In order to give to the microorganisms a molecular environment in each compartment similar to the one that would be obtained if the microbial cells were cultivated in the same reactor, two criteria have to be considered: (i) the flow rates between compartments have to be sufficient with respect to the microbial kinetics and (ii) all the molecular compounds of the medium that have an effect on the microorganism behaviour must pass through the membrane. The main constrain is due to transfer of component limited by the fluid flow in and around the fiber of the filtration module. This thesis has therefore committed to deepening the understanding of the mechanisms limiting the transfer involved during the filtration of biological fluid complex according to operating conditions and geometric characteristics of the hollow fiber module of filtration. For this purpose, based on the choice of membrane module configuration proposed in this study, and to strive for a rational optimization of the use of this device, the study relied on the use of CFD tools, supplemented by an experimental approach conducted under models conditions. The numerical simulations of fluid flow have shown a modification of the axial filtration velocity profile with packing density. Similarly, a numerical model of cake deposit was developed and show difference of cake growth along the fiber with packing density. Two experimental hollow fiber modules with two packing densities were tested with clean water and biological fluid, and showed good agreement with the numerical data. These results underline the variations of filtration velocity along the fiber that will allow some predictions on fouling deposit to be done
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Smith, Everhardus Johannes. "A numerical analysis of the hydrodynamic mixing characteristics of a rectangular versus a cylindrical mixing crystallizer tank for a membrane distillation apparatus." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2827.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2018.<br>A membrane distillation crystallization (MDC) experimental setup was designed, constructed and commissioned with rectangular mixing crystallizer tanks. The advantages and disadvantages of a rectangular mixing tank are compared to the traditional cylindrical mixing tank with baffling by means of a computational fluid dynamic (CFD) analysis in Ansys Fluent. The effect of tank configuration and geometry on the hydrodynamic and mixing characteristics for efficient momentum, solid suspension, heat and mass transfer were investigated. The hydrodynamic conditions in a crystallizer-mixing tank determine the quality of fluid mixing essential for optimal crystallization. Forty-five degree pitched blade turbines (PBT) were used to provide the agitation in the stainless steel rectangular jacketed tanks. Clear polycarbonate replicas of the rectangular tanks were manufactured to visually observe the mixing process in the tanks. Silica particles were used to represent the calcium carbonate crystals in the experiment. The data gathered from these experiments showed that the tanks should be operated between 600 to 750 rpm in the CFD simulations to simulate partial to complete suspension. In the numerical simulations a rectangular tank was compared to a cylindrical tank with baffling of the same volume. The partial differential equations solved in the numerical simulation were the conservation of mass (continuity), conservation of momentum and additional turbulence equations. In order to solve the turbulent fluid flow characteristics, the industry standard two-equation model, namely the K-epsilon model was used. This model was refined by the addition of the Wen-Yu drag model, the Simonin turbulent dissipation and the Simonin et al. turbulence interaction models. The RANS based RNG (k-ε), derived from the instantaneous Navier-Stokes equation was selected as the preferred model to analyse the hydrodynamic flow fields in the tanks. The 3D sliding mesh method was used to compute a time accurate solution. The Eulerian-granular multiphase model was used to predict the degree of solids suspension in the tanks. The efficiency of mixing within the tank was measured by the tank’s ability to keep the crystals in suspension and preventing any particle from settling at the bottom for more than 1-2 second(s). The mixing tanks were initially loaded with 5% v/v, which equates to a loaded height of approximately 10 mm. The simulations were done with the use of the volume fraction function to visually observe the cloud height and gauge the homogeneity and distribution of the particulates within the fluid flow fields. The results from the experimental setup were compared to the CFD simulations to qualify the use of CFD simulations for the comparison of the geometrically different tanks. Lastly, the findings from the CFD simulations were used to compare the tanks and determine if the rectangular tank built for the MDC experiment perform satisfactorily to replace a standard cylindrical tank with baffling for this application.
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Zachar, Carrie L. "Pharmaceutically Relevant Microemulsions with Potential Topical, Ophthalmic, and Parenteral Applications." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271273404.
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El, Rayess Youssef. "Microfiltration tangentielle appliquée à l'oenologie : compréhension et maîtrise des phénomènes de colmatage." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0089/document.
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La clarification des vins par procédés membranaires en particulier la microfiltration tangentielle a toujours été limitée par le colmatage, générant des flux de perméation faibles incompatibles avec la rentabilité économique. La compréhension, la maîtrise, ainsi que l'anticipation des phénomènes de colmatage font l'objet de ce travail. Dans un premier temps, la contribution individuelle puis en mélange des composés du vin (tannins, pectines, mannoprotéines et levures) au colmatage d'une membrane céramique multicanaux a été évaluée. Une approche fondamentale a permis de proposer des mécanismes de colmatage : la présence des pectines induit les flux de perméation les plus faibles en formant un gel à la surface de la membrane tandis que les levures semblent au contraire avoir un effet protecteur dans le cas d'un vin brut. Parce qu'il représente le flux au-delà duquel un colmatage irréversible apparaît à la surface de la membrane, le flux critique pour l'irréversibilité est un paramètre clef pour contrôler le colmatage. Dans le cas de la filtration de vin, aucun flux critique n'a pu être déterminé ce qui a conduit à définir un critère identifiant une zone de travail où le degré de colmatage reste acceptable. La dernière partie de cette thèse est consacrée à l'étude de la filtration dynamique (RVF) pour une éventuelle application dans le secteur vinicole. Cette technique est testée en présence de deux membranes organiques différentes: PES (hydrophile) et PTFE (hydrophobe). Les observations ont permis de mettre en évidence l'efficacité du système contre le colmatage des membranes PES induite par l'action de l'agitateur. Le colmatage des membranes PTFE est énormément affecté par les interactions molécules/membrane rendant la filtration dynamique inefficace pour lutter contre le colmatage de ces membranes<br>Wine clarification by membrane processes mainly cross-flow microfiltration has been limited by membrane fouling generating low permeate fluxes with economic efficiency. Understanding, controlling and anticipation of fouling are the main goals of this work. In a first time, the individual contribution of wine compounds (tannins, pectins, mannoproteins and yeasts) to a multichannel ceramic membrane fouling was evaluated. The fouling mechanisms were analyzed using a fundamental approach. The presence of pectins induce the lowest fluxes by a gel-type formation at the membrane surface while yeasts presence tends to reduce fouling in the case of crude wine (case of mixed components). Because it represents the flux beyond which irreversible fouling appears on the membrane surface, the critical flux for irreversibility is a key parameter to control fouling. No critical flux for irreversibility could be measured, hence a criterion that identifies a range of operating conditions where the degree of fouling remains acceptable was proposed. The last part of this work was devoted to the study of dynamic filtration (RVF) for further application in wine sector. This technique was tested with two different membranes: hydrophilic PES and hydrophobic PTFE. Results have allowed to demonstrate the efficiency of the system to reduce fouling in the case of PES membrane. Fouling of PTFE membrane is greatly influenced by molecules / membrane interaction making dynamic filtration ineffective in reducing of membrane fouling
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Křížová, Aneta. "Vývoj biofyzikální interpretace dat kvantitativního fázového zobrazování." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401606.
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This doctoral thesis deals with biophysical interpretation of quantitative phase imaging (QPI) gained with coherence-controlled holographic microscope (CCHM). In the first part methods evaluating information from QPI such as analysis of shape and dynamical characteristics of segmented objects as well as evaluation of the phase information itself are described. In addition, a method of dynamic phase differences (DPD) is designed to allow more detailed monitoring of cell mass translocations. All of these methods are used in biological applications. In an extensive study of various types of cell death, QPI information is compared with flow cytometry data, and preferably a combination of QPI and fluorescence microscopy is used. The DPD method is used to study mass translocations inside the cell during osmotic events. The simplified DPD method is applied to investigate the mechanism of tumor cell movement in collagen gels.
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Škutková, Helena. "Vyhodnocení příbuznosti organismů pomocí číslicového zpracování genomických dat." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-239861.
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This dissertation deals with alternative techniques for analysis of genetic information of organisms. The theoretical part presents two different approaches for evaluation of relationship between organisms based on mutual similarity of genetic information contained in their DNA sequences. The first approach is currently standardized phylogenetics analysis of character based records of DNA sequences. Although this approach is computationally expensive due to the need of multiple sequence alignment, it allows evaluation of global and local similarity of DNA sequences. The second approach is represented by techniques for classification of DNA sequences in a form of numerical vectors representing characteristic features of their genetic information. These methods known as „alignment free“ allow fast evaluation of global similarity but cannot evaluate local changes. The new method presented in this dissertation combines the advantages of both approaches. It utilizes numerical representation similar to 1D digital signal, i.e. representation that contains specific trend along x-axis. The experimental part of dissertation deals with design of a set of appropriate tools for genomic signal processing to allow evaluation mutual similarity of taxonomically specific trends. On the basis of the mutual similarity of genomic signals, the classification in the form of dendrogram is applied. It corresponds to phylogenetic trees used in standard phylogenetics.
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Nejad, Ghafar Ali. "An Experimental Study to Measure And Improve the Grout Penetrability." Licentiate thesis, KTH, Byggvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184511.
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An essential demand in any underground facility is to seal it against the water ingress to reduce the time and cost of the construction and the corresponding environmental hazards. To achieve this, obtaining sufficient grout spread is of great importance. Among the grouts, cement grouts with lower costs and environmental issues have been more reliable, whereas their main problem is filtration that restricts the grout spread. Several investigations have been therefore aimed to develop instruments to measure the grout penetrability as a fundamental means to improve the grout spread. Due to the difference in assumptions, limitations, and test conditions, and the deficiency in design their results are occasionally in contradiction. The question here is how to measure the grout penetrability more realistic? To answer this, two of the most frequently used instruments, Filter pump and Penetrability meter, were adjusted to approach the test conditions in Short slot. The results were discussed with respect to the origins of contradictions to better evaluate the reliability and functionality of the instruments. Among the influencing parameters on grout spread, applied pressure is a key element. The stepwise pressure increment is the method currently used to improve the grout spread in rock. Application of dynamic grouting has been studied as a solution to improve the grout spread for almost three decades. Despite some promising results, the method has not been yet industrialized due to the limited efficiency and issues in the type and frequency of the applied pressure, and the geometry of the test equipment. Therefore, finding a more efficient alternative of the applied pressure was the second goal of this study. A pneumatic pressure control system was consequently employed to examine the efficiency of the method in Short slot. The results conclusively revealed the effectiveness of the method and provided a strong basis for further development of the dynamic grouting.<br>Ett viktigt krav när man bygger under mark är att konstruktionen blir tillräckligt tät, så att inläckage av grundvatten minimeras. Detta minskar både projektkostnaden och eventuell miljöpåverkan. För att skapa en tät konstruktion måste injekteringsbruket spridas tillräckligt i bergmassan. Kemiska injekteringsmedel har ofta bättre spridning i bergmassan än cementbaserade bruk, men cementbaserade bruk är både billigare och ger mindre miljöpåverkan. Det finns dock en del problem med cementbaserade bruk, nämligen att cementpartiklarna filtreras och att brukets reologiska egenskaper begränsar brukets utbredning. Ett antal studier har därför utförts för att studera dessa egenskaper hos cementbaserade bruk och utveckla metoder och instrument för att mäta brukets inträngningsförmåga. Detta i syfte att förbättra brukets utbredning. Dagens metoder och instrument ger nämligen ibland motsägelsefulla resultat på grund av de olika antaganden, begränsningar och förutsättningar som används i de olika testerna. Huvudfrågan är alltså hur man kan mäta brukets inträngningsförmåga på ett mer realistiskt sätt. För att undersöka detta modifierades två vanliga mätinstrument – filterpumpen och filterpressen – för att passa förhållandena i testanordningen Short slot. Resultaten diskuterades med avseende på olika typer av skillnader mellan metoderna i syfte att utröna dels vad som påverkar inträngningsförmågan, dels instrumentens tillförlitlighet och funktionalitet. Bland de parametrar som påverkar brukets spridning i bergmassan har injekteringstrycket en central roll. I dagsläget används stegvis tryckökning för att förbättra brukets spridning i sprickigt, hårt berg. Hur man kan använda dynamisk injektering för att förbättra brukets spridning har dock undersökts under snart tre decennier. Trots lovande resultat av denna metod ännu inte börjat användas i praktiken. Ett problem är svårigheten att ta försök på labb till fältmässiga förhållanden. Ett exempel är att man använde ett tryck som varierade med hög frekvens i en spricka som modellerades med två parallella skivor utan förträngningar, vilket är mycket annorlunda jämförelse med en riktig bergspricka. I modellen blir nämligen brukets spridning starkt beroende av brukets reologiska egenskaper, medan det snarare är filtrering som är problemet i en naturlig spricka på grund av förträngningarna. Dessutom fokuserade tidigare studier endast på sprickor med en sprickvidd större än 100 μm, trots att god spridning av bruket även i de smala sprickorna med mindre än 70 μm bredd är mycket viktigt när det är höga krav på anläggningens täthet. Ett annat mål med denna licentiatuppsats var därför att hitta nya sätt att förbättra brukets spridning i berget. Därför övervakades trycket med ett pneumatiskt kontrollsystem vid tester i Short slot för att studera hur effektiv denna metod är under mer realistiska förhållanden med förträngningar på mindre än 70 μm. Resultaten visade att metoden är effektiv, vilket utgör en bra bas för att fortsätta utveckla dynamisk injektering.<br><p>QC 20160413</p>
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Kampel, Guido. "Mathematical Modeling of Fines Migration snd Clogging in Porous Media." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19764.
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Mathematical Modeling of Fines Migration and Clogging in Porous Media
Guido Kampel
87 Pages
Directed by Dr. Guillermo H. Goldsztein
A porous medium is a material that contains regions filled with fluid embedded in a solid matrix. These fluid filled regions are called pores or voids. Suspensions are fluids with small particles called fines. As a suspension flows through a porous material, some fines are trapped within the material while others that were trapped may be released.
Filters are an example of porous media. We model filters as networks of channels.
As a suspension flows across the filter, particles clog channels. We assume that there is no flow through clogged channels. In the first part of this thesis, we compute a sharp upper bound on the number of channels that can clog before fluid can no longer flow through the filter.
Soil mass is another example of porous media. Fluid in porous media flows through tortuous paths. This tortuosity and inertial effects cause fines to collide with pore walls.
After each collision, a particle looses momentum and needs to be accelerated again by hydrodynamic forces. As a result, the average velocity of fines is smaller than that of the fluid. This retardation of the fines with respect to the fluid may lead to an increase of the concentration of fines in certain regions which may eventually result in the plugging of the porous medium. This effect is of importance in flows near wells where the flow has circular symmetry and thus, it is not macroscopically homogeneous. In the second part of this thesis we develop and analyze a mathematical model to study the physical effect described above.
In the third and last part of this thesis we study particle migration and clogging as suspension flows through filters by means of numerical simulations and elementary analysis. We explore the effect that network geometry, probability distribution of the width of the channels and probability distribution of the diameter of the particles have on the performance of filters.
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Suttisansanee, Uthaiwan. "Biochemistry in Bacterioferritin." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2983.
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Bacterioferritin, an iron storage protein having a 24-subunit quaternary structure, was used as a model for the study of host-guest interactions and guest encapsulation, making use of its spherical cage-like structure. A hexahistidine-affinity tag fused to the C-terminus of each bacterioferritin subunit was constructed. The C-terminus of each subunit points toward the inside of the cavity, while the N-terminus is exposed on the surface of the protein. The hexaHistag was able to form strong interactions with a nickel-nitrilotriacetic acid linked dye molecule (guest) and this interaction was used in attempts to develop a principle to control guest molecule encapsulation within the spherical cavity of the 24-mer bacterioferritin protein molecule. The procedure involved (1) subunit dissociation under acidic pH, (2) affinity controlled dye-Histag binding with exposed C-terminal hexahistidine residues and (3) reassociation of the subunits at neutral pH. The encapsulation conditions involving step 1 and 3 were studied preliminarily using laser light scattering to measure size (hydrodynamic radius) of the protein particle with apoferritin as a model system as it resembles the size and structure of bacterioferritin. In order to encapsulate guest molecules, the emptied shell of bacterioferritin was generated by site-directed mutagenesis resulting in ferroxidase- as well as heme-free bacterioferritin mutants (E18A/M52L/E94A), and these mutants were used to examine protein stability before conducting encapsulation experiments. However, wild-type bacterioferritin possessed highest stability in maintaining its multisubunit structure; hence, it was used for the encapsulation studies. It was found that 100% bacterioferritin with hexahistidine tag at the C-terminus, and a combination of 60% bacterioferritin with hexahistidine tag at the C-terminus and 40% bacterioferritin without hexahistidine tag at the C-terminus yielded similar amounts of encapsulated guest molecules. This suggested that all hexahistidine at the C-terminus were not equally available for dye molecule binding.
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Rainey, Thomas James. "A study into the permeability and compressibility of Australian bagasse pulp." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/30394/1/Tom_Rainey_Thesis.pdf.
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This is an experimental study into the permeability and compressibility properties of bagasse pulp pads. Three experimental rigs were custom-built for this project. The experimental work is complemented by modelling work. Both the steady-state and dynamic behaviour of pulp pads are evaluated in the experimental and modelling components of this project. Bagasse, the fibrous residue that remains after sugar is extracted from sugarcane, is normally burnt in Australia to generate steam and electricity for the sugar factory. A study into bagasse pulp was motivated by the possibility of making highly value-added pulp products from bagasse for the financial benefit of sugarcane millers and growers. The bagasse pulp and paper industry is a multibillion dollar industry (1). Bagasse pulp could replace eucalypt pulp which is more widely used in the local production of paper products. An opportunity exists for replacing the large quantity of mainly generic paper products imported to Australia. This includes 949,000 tonnes of generic photocopier papers (2). The use of bagasse pulp for paper manufacture is the main application area of interest for this study. Bagasse contains a large quantity of short parenchyma cells called ‘pith’. Around 30% of the shortest fibres are removed from bagasse prior to pulping. Despite the ‘depithing’ operations in conventional bagasse pulp mills, a large amount of pith remains in the pulp. Amongst Australian paper producers there is a perception that the high quantity of short fibres in bagasse pulp leads to poor filtration behaviour at the wet-end of a paper machine. Bagasse pulp’s poor filtration behaviour reduces paper production rates and consequently revenue when compared to paper production using locally made eucalypt pulp. Pulp filtration can be characterised by two interacting factors; permeability and compressibility. Surprisingly, there has previously been very little rigorous investigation into neither bagasse pulp permeability nor compressibility. Only freeness testing of bagasse pulp has been published in the open literature. As a result, this study has focussed on a detailed investigation of the filtration properties of bagasse pulp pads. As part of this investigation, this study investigated three options for improving the permeability and compressibility properties of Australian bagasse pulp pads. Two options for further pre-treating depithed bagasse prior to pulping were considered. Firstly, bagasse was fractionated based on size. Two bagasse fractions were produced, ‘coarse’ and ‘medium’ bagasse fractions. Secondly, bagasse was collected after being processed on two types of juice extraction technology, i.e. from a sugar mill and from a sugar diffuser. Finally one method of post-treating the bagasse pulp was investigated. The effects of chemical additives, which are known to improve freeness, were also assessed for their effect on pulp pad permeability and compressibility. Pre-treated Australian bagasse pulp samples were compared with several benchmark pulp samples. A sample of commonly used kraft Eucalyptus globulus pulp was obtained. A sample of depithed Argentinean bagasse, which is used for commercial paper production, was also obtained. A sample of Australian bagasse which was depithed as per typical factory operations was also produced for benchmarking purposes. The steady-state pulp pad permeability and compressibility parameters were determined experimentally using two purpose-built experimental rigs. In reality, steady-state conditions do not exist on a paper machine. The permeability changes as the sheet compresses over time. Hence, a dynamic model was developed which uses the experimentally determined steady-state permeability and compressibility parameters as inputs. The filtration model was developed with a view to designing pulp processing equipment that is suitable specifically for bagasse pulp. The predicted results of the dynamic model were compared to experimental data. The effectiveness of a polymeric and microparticle chemical additives for improving the retention of short fibres and increasing the drainage rate of a bagasse pulp slurry was determined in a third purpose-built rig; a modified Dynamic Drainage Jar (DDJ). These chemical additives were then used in the making of a pulp pad, and their effect on the steady-state and dynamic permeability and compressibility of bagasse pulp pads was determined. The most important finding from this investigation was that Australian bagasse pulp was produced with higher permeability than eucalypt pulp, despite a higher overall content of short fibres. It is thought this research outcome could enable Australian paper producers to switch from eucalypt pulp to bagasse pulp without sacrificing paper machine productivity. It is thought that two factors contributed to the high permeability of the bagasse pulp pad. Firstly, thicker cell walls of the bagasse pulp fibres resulted in high fibre stiffness. Secondly, the bagasse pulp had a large proportion of fibres longer than 1.3 mm. These attributes helped to reinforce the pulp pad matrix. The steady-state permeability and compressibility parameters for the eucalypt pulp were consistent with those found by previous workers. It was also found that Australian pulp derived from the ‘coarse’ bagasse fraction had higher steady-state permeability than the ‘medium’ fraction. However, there was no difference between bagasse pulp originating from a diffuser or a mill. The bagasse pre-treatment options investigated in this study were not found to affect the steady-state compressibility parameters of a pulp pad. The dynamic filtration model was found to give predictions that were in good agreement with experimental data for pads made from samples of pretreated bagasse pulp, provided at least some pith was removed prior to pulping. Applying vacuum to a pulp slurry in the modified DDJ dramatically reduced the drainage time. At any level of vacuum, bagasse pulp benefitted from chemical additives as quantified by reduced drainage time and increased retention of short fibres. Using the modified DDJ, it was observed that under specific conditions, a benchmark depithed bagasse pulp drained more rapidly than the ‘coarse’ bagasse pulp. In steady-state permeability and compressibility experiments, the addition of chemical additives improved the pad permeability and compressibility of a benchmark bagasse pulp with a high quantity of short fibres. Importantly, this effect was not observed for the ‘coarse’ bagasse pulp. However, dynamic filtration experiments showed that there was also a small observable improvement in filtration for the ‘medium’ bagasse pulp. The mechanism of bagasse pulp pad consolidation appears to be by fibre realignment. Chemical additives assist to lubricate the consolidation process. This study was complemented by pulp physical and chemical property testing and a microscopy study. In addition to its high pulp pad permeability, ‘coarse’ bagasse pulp often (but not always) had superior physical properties than a benchmark depithed bagasse pulp.
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Rainey, Thomas James. "A study into the permeability and compressibility of Australian bagasse pulp." Queensland University of Technology, 2009. http://eprints.qut.edu.au/30394/.
Full textAbstract:
This is an experimental study into the permeability and compressibility properties of bagasse pulp pads. Three experimental rigs were custom-built for this project. The experimental work is complemented by modelling work. Both the steady-state and dynamic behaviour of pulp pads are evaluated in the experimental and modelling components of this project. Bagasse, the fibrous residue that remains after sugar is extracted from sugarcane, is normally burnt in Australia to generate steam and electricity for the sugar factory. A study into bagasse pulp was motivated by the possibility of making highly value-added pulp products from bagasse for the financial benefit of sugarcane millers and growers. The bagasse pulp and paper industry is a multibillion dollar industry (1). Bagasse pulp could replace eucalypt pulp which is more widely used in the local production of paper products. An opportunity exists for replacing the large quantity of mainly generic paper products imported to Australia. This includes 949,000 tonnes of generic photocopier papers (2). The use of bagasse pulp for paper manufacture is the main application area of interest for this study. Bagasse contains a large quantity of short parenchyma cells called ‘pith’. Around 30% of the shortest fibres are removed from bagasse prior to pulping. Despite the ‘depithing’ operations in conventional bagasse pulp mills, a large amount of pith remains in the pulp. Amongst Australian paper producers there is a perception that the high quantity of short fibres in bagasse pulp leads to poor filtration behaviour at the wet-end of a paper machine. Bagasse pulp’s poor filtration behaviour reduces paper production rates and consequently revenue when compared to paper production using locally made eucalypt pulp. Pulp filtration can be characterised by two interacting factors; permeability and compressibility. Surprisingly, there has previously been very little rigorous investigation into neither bagasse pulp permeability nor compressibility. Only freeness testing of bagasse pulp has been published in the open literature. As a result, this study has focussed on a detailed investigation of the filtration properties of bagasse pulp pads. As part of this investigation, this study investigated three options for improving the permeability and compressibility properties of Australian bagasse pulp pads. Two options for further pre-treating depithed bagasse prior to pulping were considered. Firstly, bagasse was fractionated based on size. Two bagasse fractions were produced, ‘coarse’ and ‘medium’ bagasse fractions. Secondly, bagasse was collected after being processed on two types of juice extraction technology, i.e. from a sugar mill and from a sugar diffuser. Finally one method of post-treating the bagasse pulp was investigated. The effects of chemical additives, which are known to improve freeness, were also assessed for their effect on pulp pad permeability and compressibility. Pre-treated Australian bagasse pulp samples were compared with several benchmark pulp samples. A sample of commonly used kraft Eucalyptus globulus pulp was obtained. A sample of depithed Argentinean bagasse, which is used for commercial paper production, was also obtained. A sample of Australian bagasse which was depithed as per typical factory operations was also produced for benchmarking purposes. The steady-state pulp pad permeability and compressibility parameters were determined experimentally using two purpose-built experimental rigs. In reality, steady-state conditions do not exist on a paper machine. The permeability changes as the sheet compresses over time. Hence, a dynamic model was developed which uses the experimentally determined steady-state permeability and compressibility parameters as inputs. The filtration model was developed with a view to designing pulp processing equipment that is suitable specifically for bagasse pulp. The predicted results of the dynamic model were compared to experimental data. The effectiveness of a polymeric and microparticle chemical additives for improving the retention of short fibres and increasing the drainage rate of a bagasse pulp slurry was determined in a third purpose-built rig; a modified Dynamic Drainage Jar (DDJ). These chemical additives were then used in the making of a pulp pad, and their effect on the steady-state and dynamic permeability and compressibility of bagasse pulp pads was determined. The most important finding from this investigation was that Australian bagasse pulp was produced with higher permeability than eucalypt pulp, despite a higher overall content of short fibres. It is thought this research outcome could enable Australian paper producers to switch from eucalypt pulp to bagasse pulp without sacrificing paper machine productivity. It is thought that two factors contributed to the high permeability of the bagasse pulp pad. Firstly, thicker cell walls of the bagasse pulp fibres resulted in high fibre stiffness. Secondly, the bagasse pulp had a large proportion of fibres longer than 1.3 mm. These attributes helped to reinforce the pulp pad matrix. The steady-state permeability and compressibility parameters for the eucalypt pulp were consistent with those found by previous workers. It was also found that Australian pulp derived from the ‘coarse’ bagasse fraction had higher steady-state permeability than the ‘medium’ fraction. However, there was no difference between bagasse pulp originating from a diffuser or a mill. The bagasse pre-treatment options investigated in this study were not found to affect the steady-state compressibility parameters of a pulp pad. The dynamic filtration model was found to give predictions that were in good agreement with experimental data for pads made from samples of pretreated bagasse pulp, provided at least some pith was removed prior to pulping. Applying vacuum to a pulp slurry in the modified DDJ dramatically reduced the drainage time. At any level of vacuum, bagasse pulp benefitted from chemical additives as quantified by reduced drainage time and increased retention of short fibres. Using the modified DDJ, it was observed that under specific conditions, a benchmark depithed bagasse pulp drained more rapidly than the ‘coarse’ bagasse pulp. In steady-state permeability and compressibility experiments, the addition of chemical additives improved the pad permeability and compressibility of a benchmark bagasse pulp with a high quantity of short fibres. Importantly, this effect was not observed for the ‘coarse’ bagasse pulp. However, dynamic filtration experiments showed that there was also a small observable improvement in filtration for the ‘medium’ bagasse pulp. The mechanism of bagasse pulp pad consolidation appears to be by fibre realignment. Chemical additives assist to lubricate the consolidation process. This study was complemented by pulp physical and chemical property testing and a microscopy study. In addition to its high pulp pad permeability, ‘coarse’ bagasse pulp often (but not always) had superior physical properties than a benchmark depithed bagasse pulp.
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Neal, Peter Ross Chemical Sciences & Engineering Faculty of Engineering UNSW. "An examination of the nature of critical flux and membrane fouling by direct observation." Awarded by:University of New South Wales. School of Chemical Sciences and Engineering, 2006. http://handle.unsw.edu.au/1959.4/30584.
Full textAbstract:
Securing water in the right quantities at the right quality for the right price is a major issue around the world. Membranes are making an increasingly important contribution to meeting this need; however their performance is limited by fouling. This thesis reports on an investigation into the fouling of systems related to water treatment using the Direct Observation Through the Membrane (DOTM). The investigation focused on the measurement of critical flux and observation of particle behaviour under a variety of conditions and for a number of different particles. The range of meanings attributed to critical flux in the literature was analysed and several proposals made for the improved use of the concept. In particular, critical flux determination techniques were classified by whether they measure resistance changes or particle deposition; leading to the definition of Critical Resistance and Critical Deposition Fluxes. In this thesis the deposition definition is used exclusively. The effect of Reynolds number and spacer orientation on critical flux was correlated for spacer-filled channels. The heterogeneous deposition patterns observed with regions of heavy deposition next to areas of little or no deposition. This pattern was related to the local hydrodynamics of spacer cells (a few mm2 in size). The correlations developed for critical flux in spacer-filled channels were adjusted for submicron particle size and incorporated into a SpiralWound Module (SWM) leaf model and then used to simulate the fouling of SWM leaves under a range of operating conditions and operating policies. The Mass Balance technique of critical flux determination was also briefly assessed. The applicability of critical flux criteria to SWM arrays was discussed. Fouling, particle behaviour and critical flux were also investigated in air-sparged systems. The post-cleaning water flux was found to be enhanced when the membrane is fouled in the presence of bubbles. The rate of flux decline was reduced by bubbles. Critical flux increased with air flowrate, and decreased with increased liquid flowrate and concentration. Bubbles caused particles to periodically deposit on the membrane. Particles were observed to stream past the membrane under the influence of back-diffusive forces. Video clips of particulate fouling are provided.
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Milučká, Daniela. "INFLATION DYNAMICS IN THE CZECH REPUBLIC: ESTIMATING THE NEW KEYNESIAN PHILLIPS CURVE." Master's thesis, Vysoká škola ekonomická v Praze, 2013. http://www.nusl.cz/ntk/nusl-199272.
Full textAbstract:
Recent breakthrough studies by Gali and Gertler (1999), Sbordone (2002) and Roberts (2001) argue that the New Keynesian Phillips curve (based on Calvo pricing model) is empirically valid concept and they conclude that the real marginal costs are preferred driving force to output gap in inflation dynamics for open economies. Neiss and Nelson (2002) and Gali, Gertler and Salido (2001), in turn, contradict that to date, there has been only little empirical evidence to support this statement. Neiss and Nelson (2002) add that "once output gap is defined consistently with economic theory, the gap-based New Keynesian Phillips curve has a fit with data which is at least as good as the real marginal costs-based one". For this purpose, my study investigates relationship between output gap and inflation described in the hybrid New Keynesian Phillips curve. Study estimates key coefficients of the hybrid gap-based New Keynesian Phillips curve, with both forward- and backward-looking inflation components, in the Czech Republic for periods 2000Q1 - 2012Q4 using Kalman filtration. My findings suggest that (i) output gap has a significant impact on Czech inflation dynamics (ii) share of forward-looking agents predominates to backward-looking agents in the Czech Republic and (iii) Czech inflation seems to be significantly driven by change in import prices.
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Куц, Юрій Вікторович, та Yurii Kuts. "Метод підвищення точності вимірювань радіосигналів при адаптивній фільтрації". Master's thesis, ТНТУ ім. І. Пулюя, Факультет прикладних інформаційних технологій та електроінженерії, кафедра біотехнічних систем, 2021. http://elartu.tntu.edu.ua/handle/lib/36525.
Full textAbstract:
В кваліфікаційній роботі розроблено алгоритм адаптивного пошуку оптимальних параметрів фільтра, зокрема, проведений аналіз досліджуваної системи на основі трьох вхідних сигналів: синусоїдальний, функція Хевісайду, імпульсний, та визначено що найбільш якісно та ефективно фільтрує сигнал фільтр Чебишева. Динамічна похибка із застосуванням цього фільтру зменшилася до 2 разів.<br>The qualification work developed an algorithm for adaptive search of optimal filter parameters, in particular, the analysis of the studied system based on three input signals: sinusoidal, Heaviside function, pulse, and determined that the most efficient and effective filtering signal Chebyshev filter. The dynamic error with this filter has been reduced up to 2 times.<br>ВСТУП 9
РОЗДІ 1. ОСНОВНА ЧАСТИНА 11
1.1. Загальна характеристика та визначення динамічної похибки 11
1.2. Спектральні методи фільтрації вимірювальних сигналів 15
1.2.1. Фільтрація вимірювальних сигналів методом поліноміальної
ортогоналізації 15
1.2.2. Фільтрація вимірювальних сигналів формуванням рядів Фур'є 15
1.3. Екстремальний метод фільтрації вимірювальних сигналів 21
1.4. Метод введення в структуру коригувальних ланок 22
1.5. Висновки до розділу 1 23
РОЗДІЛ 2. ОСНОВНА ЧАСТИНА 24
2.1. Загальні уявлення про фільтри 24
2.2. Необхідність дискретних фільтрів 29
2.3. Обмеження точності дискретних фільтрів 30
2.4. КІХ-фільтри з лінійною фазово-частотною характеристикою 31
2.5. Проектування КІХ-фільтрів 31
2.6. Типи дискретних фільтрів 32
2.7. Порівняння між КІХ- та БІХ-фільтрами 34
2.8 Порівняння аналогових та дискретних фільтрів 34
2.9 Висновки до розділу 2 35
РОЗДІЛ 3. НАУКОВО-ДОСЛІДНА ЧАСТИНА 36
3.1. Постановка задачі 36
3.2. Використання програмного середовища MATLAB 37
3.3. Поняття адаптивного фільтра 38
3.4. Алгоритм корекції динамічної похибки 39
3.5. Розрахунок СКВ 39
3.6. Критерій мінімуму СКВ 41
3.7. Безперервна модель 42
3.8. Фільтрація сигналів 43
3.9. Математичне моделювання системи 47
3.10. Прямокутне вікно 48
3.10.1. Перевірка роботи вимірювальної системи на основі функції
Хевісайду на вході ВП 48
3.10.2. Перевірка роботи вимірювальної системи на основі імпульсного
сигналу на вході ВП 54
3.11. Трикутне вікно 60
3.11.1. Перевірка роботи вимірювальної системи на основі функції
Хевісайду на вході ВП 60
3.11.2. Перевірка роботи вимірювальної системи на основі імпульсного
сигналу на вході ВП 65
3.12. Висновки до розділу 3 73
РОЗДІЛ 4. ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ
СИТУАЦІЯХ 74
4.1. Охорона праці 74
4.2. Безпека в надзвичайних ситуаціях 76
4.3. Висновки до розділу 4 80
ВИСНОВКИ 81
СПИСОК ВИКОРИСТАНИХ ДЖЕРЕЛ 82
Додаток А. Лістинг програми прямокутного вікна 84
Додаток Б. Лістинг програми трикутного вікна 86
Додаток В. Лістинг програми прямокутного вікна 88
Додаток Г. Копія тези конференції 90
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Akhlaq, Monis. "Improved performance high speed network intrusion detection systems (NIDS) : a high speed NIDS architectures to address limitations of packet loss and low detection rate by adoption of dynamic cluster architecture and traffic anomaly filtration (IADF)." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5377.
Full textAbstract:
Intrusion Detection Systems (IDS) are considered as a vital component in network security architecture. The system allows the administrator to detect unauthorized use of, or attack upon a computer, network or telecommunication infrastructure. There is no second thought on the necessity of these systems however; their performance remains a critical question. This research has focussed on designing a high performance Network Intrusion Detection Systems (NIDS) model. The work begins with the evaluation of Snort, an open source NIDS considered as a de-facto IDS standard. The motive behind the evaluation strategy is to analyze the performance of Snort and ascertain the causes of limited performance. Design and implementation of high performance techniques are considered as the final objective of this research. Snort has been evaluated on highly sophisticated test bench by employing evasive and avoidance strategies to simulate real-life normal and attack-like traffic. The test-methodology is based on the concept of stressing the system and degrading its performance in terms of its packet handling capacity. This has been achieved by normal traffic generation; fussing; traffic saturation; parallel dissimilar attacks; manipulation of background traffic, e.g. fragmentation, packet sequence disturbance and illegal packet insertion. The evaluation phase has lead us to two high performance designs, first distributed hardware architecture using cluster-based adoption and second cascaded phenomena of anomaly-based filtration and signature-based detection. The first high performance mechanism is based on Dynamic Cluster adoption using refined policy routing and Comparator Logic. The design is a two tier mechanism where front end of the cluster is the load-balancer which distributes traffic on pre-defined policy routing ensuring maximum utilization of cluster resources. The traffic load sharing mechanism reduces the packet drop by exchanging state information between load-balancer and cluster nodes and implementing switchovers between nodes in case the traffic exceeds pre-defined threshold limit. Finally, the recovery evaluation concept using Comparator Logic also enhance the overall efficiency by recovering lost data in switchovers, the retrieved data is than analyzed by the recovery NIDS to identify any leftover threats. Intelligent Anomaly Detection Filtration (IADF) using cascaded architecture of anomaly-based filtration and signature-based detection process is the second high performance design. The IADF design is used to preserve resources of NIDS by eliminating large portion of the traffic on well defined logics. In addition, the filtration concept augment the detection process by eliminating the part of malicious traffic which otherwise can go undetected by most of signature-based mechanisms. We have evaluated the mechanism to detect Denial of Service (DoS) and Probe attempts based by analyzing its performance on Defence Advanced Research Projects Agency (DARPA) dataset. The concept has also been supported by time-based normalized sampling mechanisms to incorporate normal traffic variations to reduce false alarms. Finally, we have observed that the IADF has augmented the overall detection process by reducing false alarms, increasing detection rate and incurring lesser data loss.
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Oxarango, Laurent. "Transferts de Chaleur et de Masse dans des Structures Poreuses Multi-échelles : Application à l'étude des Filtres à Particules Diesel." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2004. http://tel.archives-ouvertes.fr/tel-00007594.
Full textAbstract:
Les filtres céramiques sont des dispositifs prometteurs pour diminuer les émissions de particules carbonées par les moteurs Diesel et respecter les futures normes environnementales. L'analyse et la modélisation des phénomènes physiques intervenant dans leur fonctionnement est indispensable pour améliorer leurs performances et leur durabilité. Dans une première partie, l'écoulement du gaz, le transport et la capture des particules au sein d'un filtre présentant une structure poreuse multi-échelle sont étudiés. Une approche de type « milieu poreux effectif» est adoptée pour simuler l'étape de filtration à l'échelle du filtre. Le modèle s'appuie sur des équations 1D, développées pour un élément unitaire de filtre, préservant le caractère inertiel de l'écoulement. Dans une deuxième partie, le comportement thermique du filtre est étudié. Les transferts de chaleur convectif et diffusif sont pris en compte dans un modèle macroscopique à une température obtenu par la méthode de prise de moyenne volumique. Un terme source de combustion permet de considérer la réaction d'oxydation des particules collectées, intervenant dans l'étape de régénération du filtre.
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Цюра, Надія Ярославівна. "Сумісний процес фільтрування та сушіння дисперсних матеріалів". Diss., Національний університет "Львівська політехніка", 2021. https://ena.lpnu.ua/handle/ntb/56692.
Full textAbstract:
Дисертаційна робота присвячена теоретичним та експериментальним дослідженням фільтраційного сушіння дисперсних матеріалів, зокрема Fe(II) сульфат гептагідрату, відпрацьованого деревного
борошна й залізоокисного пігменту з метою проектування енергоощадного обладнання. Встановлені основні фізико-механічні характеристики стаціонарного шару досліджуваних матеріалів, а саме: насипна густина, пористість, питома поверхня, еквівалентний діаметр каналів, крізь якіфільтрується тепловий агент, усереднений діаметр частинок. На основі узагальнення результатів досліджень гідродинаміки запропоновані рівняння для встановлення гідравлічного опору стаціонарного шару за різних параметрів теплового агенту, які можуть бути використані на етапі проектування нового сушильного обладнання.
Експериментальним шляхом досліджений теплообмін під час фільтраційного сушіння й запропоновані критеріальні залежності у вигляді безрозмірних комплексів для визначення коефіцієнтів тепловіддачі від
теплового агенту до шару Fe(II) сульфат гептагідрату. Встановлений характер впливу висоти стаціонарного шару Fe (II) сульфат гептагідрату, відпрацьованого деревного борошна й залізоокисного пігменту, а також температури теплового агенту й швидкості фільтрування на інтенсивність
фільтраційного сушіння та запропоновані розрахункові залежності для прогнозування процесу висушування вказаних матеріалів в періодах повного та часткового насичення теплового агенту вологою.
Розроблена схема сушильної установки для зневоднення дисперсних матеріалів в стаціонарному шарі шляхом профільтровування теплового агенту крізь пористу структуру, на яку отриманий патент України на винахід. Наведена методика розрахунку та проведені технологічні обчислення, які дали змогу розрахувати основні розміри сушарки та встановити параметри процесу фільтраційного сушіння. The work deals with the filtration method for drying Fe (II) sulfate of heptahydrate, the exhausted wood flour and iron oxide pigment. This method is elected as the most effective according to the critical analysis of literature data. The work is dedicated to the theoretical and experimental researches of filtration drying of dispersed materials, in particular Fe (II) sulfate of heptahydrate, the exhausted wood flour and iron oxide pigment for the purpose of designing of the energy saving equipment. The basic physical and mechanical characteristics of
the stationary layer of the studied materials are determined, such as: bulk density, porosity, specific surface area, averaging of particles size, equivalent diameter of the channels through which the heat agent is filtered. On the basis of obtained experimental data of hydrodynamics research, the equations for establishing the
hydraulic resistance of the stationary layer at variable parameters of the heat agent are proposed. Heat transfer during filtration drying is investigated experimentally and criterion dependences in the form of dimensionless complexes for determination of heat transfer coefficients from heat agent to Fe (II) sulfate heptahydrate layer are proposed. The nature of the influence of the height of the stationary layer of Fe (II) sulfate heptahydrate, exhausted wood flour and iron oxide pigment, as well as the temperature of the heat agent and filtration rate on
the intensity of filtration drying and the proposed dependences for predicting the drying process of these materials. The basic scheme of the drying installation for dehydration of dispersed materials, a technique of its calculation are developed and the basic technological calculations are carried out. The patent of Ukraine for
the invention has protected the plant.
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PEREZ, Wanderlei Elias. "Avaliação do desempenho da filtração em múltiplas etapas (FiME) no tratamento da água do Ribeirão Sozinha em Goianápolis - Estado de Goiás." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/631.
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Previous issue date: 2009-08-17<br>This work presents an evaluation of the performance of a multi-stage filtration system (FiME) in pilot-plant scale to treat surface water from the Ribeirão Sozinha stream which supplies the city of Goianápolis-GO, Brazil. The arrangement of the installation used in this study consisted of a dynamic roughing filter (PFD), a up-flow roughing filter (PFA) and two slow sand filters, being one with sand (FLA) and the other with sand and granular activated carbon (FLACAG). The filtration rates varied from 24 to 48 m3/m2.d in the PFD, 12 to 18 m3/m2.d in the PFA, and 3 to 4 m3/m2.d in the FLA and FLACAG. The performance of each unit was evaluated for removal of color, turbidity, total iron, suspended solids, oxygen consumption, total coliforms and E.coli, and the development of headloss. Results showed that the PFD and PFA are important units in the preparation of affluent water to the slow sand filters, allowing relatively long filtration runs resulted from the removal of larger particles by these units, reducing significantly the turbidity of raw water. The slow sand filters presented larger than 90% of removal efficiency of color, turbidity, suspended solids and total iron, removal over 80% of consumed oxygen and above 95% for coliforms removal. Overall, the slow sand filters showed satisfactory performance in removing turbidity, iron and total coliforms. In particular, the slow sand filter with sand and granular activated carbon layers was more efficient in removing true color and consumed oxygen than the filter with single sand layer. Although peaks of color and turbidity during the fourth and last filtration runs, the FiME system proved to be efficient in removing total coliforms and E.coli in the last three weeks of operation. In the last filtration run, a comparison of the effluent water quality between the FiME system and a conventional full scale treatment plant was carried out for the removal of turbidity and color. Results showed that the FiME system produced similar water quality to the conventional treatment plant when turbidity was < 1,0. In general, results suggest that the FiME is an effective system to produce water quality from surface water with high levels of total coliforms and E.coli and peaks of color and turbidity according to the recommendations of the Portaria 518/2004 of the Ministry of Health, Brazil<br>Este trabalho apresenta uma avaliação do desempenho de um sistema de Filtração em Múltiplas Etapas (FiME), em escala piloto, no tratamento da água bruta retirada do manancial superficial (Ribeirão Sozinha) que abastece a cidade de Goianápolis-GO. O arranjo da instalação utilizado nessa pesquisa constituiu de 1 pré-filtro dinâmico (PFD), 1 pré-filtro ascendente (PFA) e 2 filtros lentos, sendo um com areia (FLA) e outro com areia e carvão ativado granular (FLACAG). As taxas de filtração utilizadas foram de 24, 48, 24 e 24 m3/m2.d para o PFD; 12, 18, 12 e 12 m3/m2.d para o PFA; e 3, 4, 3 e 3 m3/m2.d para o FLA e FLACAG. O desempenho de cada unidade foi avaliado quanto à remoção de cor, turbidez, ferro total, sólidos suspensos, oxigênio consumido, coliformes totais e termotolerantes, e o desenvolvimento da perda de carga. Os resultados obtidos demonstraram que o PFD e o PFA são unidades importantes na preparação da água afluente aos filtros lentos, possibilitando carreiras relativamente longas em função da retenção de partículas maiores, diminuindo consideravelmente a turbidez da água bruta. Os filtros lentos apresentaram eficiência superior a 90% na remoção de cor, turbidez, sólidos suspensos e ferro total, remoção de oxigênio consumido superior a 80% e de coliformes acima de 95%. Na última carreira de filtração foi realizada uma comparação da qualidade da água produzida pela tecnologia da FiME com a ETA de ciclo completo, na remoção de cor e turbidez, comprovando que a qualidade da água produzida na FiME é compatível com a qualidade da água produzida pela tecnologia de ciclo completo. De maneira geral, os filtros lentos apresentaram rendimento satisfatório na remoção de turbidez, ferro total e coliformes, sendo que o filtro lento com camada intermediária de carvão ativado granular foi mais eficiente na remoção de cor verdadeira e oxigênio consumido do que os filtro lento com camada simples de areia. Embora tenha ocorrido picos de cor e turbidez durante a quarta e última carreira de filtração, o sistema FiME mostrou-se eficiente na remoção de coliformes totais e termotolerantes nas três últimas semanas de operação. A verificação da existência de correlação na remoção de cor, turbidez, sólidos suspensos, oxigênio consumido, coliformes totais e termotolerantes, demonstrou a existência de uma boa correlação na remoção dos parâmetros cor e turbidez nos efluentes dos filtros lentos, apresentando um coeficiente de correlação igual a 0,92. Os resultados obtidos sugerem que o sistema FiME é eficiente no tratamento de águas superficiais com elevados teores de coliformes totais e termotolerantes e com picos de cor e turbidez, produzindo, quando operado adequadamente, água com baixos teores de cor, turbidez e bactérias do grupo coliforme, atendendo as recomendações da Portaria 518/2004 do Ministério da Saúde, evidenciando a viabilidade de aplicação dessa tecnologia na produção de água para consumo humano
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Falahati, Hamid. "The Characterization of Bimodal Droplet Size Distributions in the Ultrafiltration of Highly Concentrated Emulsions Applied to the Production of Biodiesel." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/19585.
Full textAbstract:
A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor.<br>Natural Sciences and Engineering Research Council of Canada (NSERC)
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Callegaro, Giorgia. "Credit risk models under partial information." Doctoral thesis, Scuola Normale Superiore, 2010. http://hdl.handle.net/11384/85658.
Full textAbstract:
This Ph.D. thesis consists of five independent parts (Introduction included) devoted to the modeling and to studying problems related to default risk, under partial information.
The first part constitutes the Introduction.
The second part is devoted to the computation of survival probabilities of a firm, conditionally to the information available to the investor, in a structural model, under partial information. We exploit a numerical hybrid technique based on the application of the Monte Carlo method and of optimal quantization. As an application, we trace the credit spreads curve for zero coupon bonds for different maturities, showing that (as in practice on the market) the spreads in the neighborhood of the maturity are not null, i.e., under partial information there is some residual risk on the market, even if we are close to maturity.
Calibration to real data completes this second part.
In the third part we deal, by means of the Dynamic Programming, with a discrete time maximization of the expected utility from terminal wealth problem, in a market where defaultable assets are traded. Contagion risk between the default times is modeled, as well as model uncertainty, by working under partial information. In the part devoted to numerics we study the robustness of the solution found under partial information.
In the fourth part we are interested in studying the problem linked to the uncertainty of the investment horizon. In particular, in a complete market model subject to default risk, we solve, both with a direct martingale approach and with the Dynamic Programming, three different consumption maximization problems. More specifically, denoting by the default time, where is an exogenous positive random variable, we consider three problems of maximization of expected utility from consumption: when the investment horizon is fixed and equal to T, when it is finite, but possibly uncertain, equal to T ^, and when it is
infinite. First we consider the general stochastic coefficients case, then, in order to obtain explicit results in the logarithmic and power utility cases, we pass to the constant coefficients case.
Finally, in the fifth part we deal with a totally different problem, given that it is purely theoretical. In the context of enlargement of filtrations our aim is to retrieve, in a specific setting, the already known results on martingales’ characterization, on the decomposition of
martingales with respect to the reference filtration as semi-martingales in the progressively and in the initially enlarged filtrations and the Predictable Representation Theorem. Some of these results were used in the fourth part of this thesis. The interest in this study is pedagogical: in our specific context most of the results are found more easily, by exploiting "basic" tools, such as Girsanov’s Theorem and by computing conditional expectations.
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友一, 吉田, та Yuichi Yoshida. "微粒子スラリーのろ過設計に関する研究". Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13071668/?lang=0, 2018. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13071668/?lang=0.
Full textAbstract:
粉体の微粒子化に伴い，固液分離操作の中でも高精度かつ多量処理が可能なろ過の重要性はますます高まっている．しかしながら，微粒子スラリーのろ過抵抗は非常に大きく，所望の処理能力を得られないことが多い．本論文では，ろ過操作設計におけるろ材抵抗，スラリー凝集・分散状態，ケークろ過抵抗の予測に関して数値シミュレーションを利用した検討を行うことで，微粒子スラリーのろ過抵抗の低減に有用な知見を得ることができた．<br>著者名の「吉」は「土」の下に「口」の置き換え<br>博士(工学)<br>Doctor of Philosophy in Engineering<br>同志社大学<br>Doshisha University
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ZHUANG, GING-RONG, and 莊清榮. "Study on filtration characteristics of rotating disk type dynamic filters." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/68112638437839782070.
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