Dissertations / Theses on the topic 'Separation media'

The efficiency of colloidal gas aphron (CGA) flotation for separation of algae from growth media was investigated. Anionic, cationic and non-ionic surfactants were used to generate CGAs. Preliminary batch studies showed that two CGA flotation procedures could be successfully used for algae flotation. CGA flotation without pretreatment of algae was only successful using cationic surfactants. All three types of surfactants yielded promising results while combining CGA flotation with alum flocculation as a pretreatment step. Observed removal efficiencies were above ninety percent for batch applications. “Pure CGA flotation” was studied in countercurrent continuous flow operations. Satisfactory removal of algae could be achieved even at substantially reduced volume ratios of CGAs to algae solution. However, TOC concentrations increased with higher volume ratios and higher flowrates due to carryover of CGA bubbles and diffusion of surfactant molecules into the bulk solution. The cationic surfactant Cetyl Pyrimidinium Chloride, present at very low concentrations in the raffinate and the froth algae mixture, exhibited biostatic and biocidal properties in the microbial activity test.
Master of Science
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008.
Includes bibliographical references (leaves 84-86).
This thesis studies the theory and application of co-channel digital signal separation techniques. We set up a test-bed with the GNU Software Defined Radio (SDR) platform where we implement and experiment with single-antenna signal separation algorithms. We mainly investigate linearly-modulated digital signals. To do this, we design a multiple RFID card reader capable of decoding multiple commodity ID cards simultaneously. These passive RFID cards transmit DBPSK waveforms once activated. A signal separation function at the receiver delivers great convenience to the users without increasing the complexity and cost of the cards. Second, we derive the optimal criteria for deciding the start of an RFID frame. We show that the commonly utilized correlation rule is suboptimal and that a correction term needs to be considered to achieve the best detection performance. Several rules for frame synchronization are proposed and analyzed numerically using Monte Carlo simulation. These signal separation techniques present an opportunity to improve the capacity of wireless systems and combat interference. This thesis documents design issues in the physical and application layers, thereby demonstrating the great flexibility and strength of the GNU SDR system.
by Dawei Shen.
S.M.

This thesis developed a methodology in order to compare the performance of different types of coalescing filters (fibrous, knitted, and foam media) which has not been reported in literature. Moreover, the local optimum in pressure drop curve which identified in this work is a novel contribution to the field of interfacial science and gas-liquid separation which can significantly affect the coalescence filters design in future.

Color printing is traditionally achieved by separating an input image into four channels (CMYK) and binarizing them using halftoning algorithms, in order to designate the locations of ink droplet placement. Multi-channel printing means a reproduction that employs additional inks other than these four in order to augment the color gamut (scope of reproducible colors) and reduce undesirable ink droplet visibility, so-called graininess. One aim of this dissertation has been to characterize a print setup in which both the primary inks CMYK and their light versions are used. The presented approach groups the inks, forming subsets, each representing a channel that is reproduced with multiple inks. To halftone the separated channels in the present methodology, a specific multilevel halftoning algorithm is employed, halftoning each channel to multiple levels. This algorithm performs the binarization from the ink subsets to each separate colorant. Consequently, the print characterization complexity remains unaltered when employing the light inks, avoiding the normal increase in computational complexity, the one-to-many mapping problem and the increase in the number of training samples. The results show that the reproduction is visually improved in terms of graininess and detail enhancement. The secondary color inks RGB are added in multi-channel printing to increase the color gamut. Utilizing them, however, potentially increases the perceived graininess. Moreover, employing the primary, secondary and light inks means a color separation from a three-channel CIELAB space into a multi-channel colorant space, resulting in colorimetric redundancy in which multiple ink combinations can reproduce the same target color. To address this, a proposed cost function is incorporated in the color separation approach, weighting selected factors that influence the reproduced image quality, i.e. graininess and color accuracy, in order to select the optimal ink combination. The perceived graininess is modeled by employing S-CIELAB, a spatial low-pass filtering mimicking the human visual system. By applying the filtering to a large dataset, a generalized prediction that quantifies the perceived graininess is carried out and incorporated as a criterion in the color separation. Consequently, the presented research increases the understanding of color reproduction and image quality in multi-channel printing, provides concrete solutions to challenges in the practical implementation, and rises the possibilities to fully utilize the potential in multi-channel printing for superior image quality.

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2007.
Includes bibliographical references (leaves 51-53).
This thesis presents a Differential Binary Phase Shift Key (DBPSK) source separation system implemented with the GNU Software Defined Radio (SDR) platform and interfaced with the existing MIT community Radio Frequency Identification (RFID) system. Source separation, well studied in the theoretical signal processing setting, presents an opportunity to achieve higher throughput in a practical SDR deployment. While much research has centered around the design of complex multi-input-multi-output (MIMO) and code division multiple access (CDMA) systems, single antenna source separation presents a simple alternative that is suitable in settings such as RFID where sources are naturally synchronized. Motivated by the analysis of physical channel properties with GNU SDR, this thesis documents the complete design process from the physical layer to the application layer and presents a realization of a co-channel DBPSK source separating technique. The result is an intelligent RFID source-separating reader that is capable of decoding multiple "dumb" cards.
by Grace R. Woo.
S.M.

Includes bibliographical references.
To write critically about any given text is very different to writing critically about the process of that text’s creation. Given that this essay will deal closely with representations of the self, perhaps it is not out of place for me to open with an autobiographical confession: while I greatly enjoy the former, relishing opportunities to analyse both literary and filmic texts, I have no such fond feelings for the latter, especially when the situation calls for a critical analysis of my own writing process. The task seems to intrude on a sacred space that I imagine most writers value greatly, a time when what will eventually become the ‘finished product’ is still in formation, is still incomplete. Due to the very nature of the process, it is a time when everything is still in flux, when ideas are still seeking their final form. Therefore, subjecting this tenuous process to critical examination seems somewhat like a betrayal of its nature, a desire to fix in meaning that which has no such absolute meaning. As a result, I have strategically avoided such undertakings in the past as much as possible. It then comes as a surprise to me that after completing the screenplay for Then It Happened, I have the desire to do just that. The reason, I believe, is revealing. It is not the aforementioned final product (the screenplay) that has inspired the ideas that will be discussed in this essay, but the process of creating it, for it is the process that brought me into contact with the three incarnations of the biographical narrative that will be discussed below: autobiography, biography and the biopic (in the form of both the screenplay and the final film). If I have done my job as a storyteller relatively well, then – hopefully – upon reading the screenplay, the reader will receive it as one coherent narrative, with a unity of purpose and style. They will not see it as a collage, composed out of several key sources, namely, Frank Capra’s autobiography The Name Above the Title, Joseph McBride’s biography of Capra, The Catastrophe of Success, as well as six other biographies of the key players: Harry Cohn, Robert Riskin, Clark Gable and Claudette Colbert. The reader might – again, hopefully – glean the sense that a significant amount of research has gone into the screenplay, and from this might infer that multiple sources have been used, but the story should not feel in any way disjointed or 2 fragmented. The purpose of this essay, then, will be precisely to take this story apart and to reveal the collage. In this critical analysis of my writing process, I would like to reverse that very process: instead of stitching together the information gathered through my research, attempting to make the connections invisible, I will magnify those very seams and examine the act of their creation. For I believe that these seams can inform the way that we think about the processes of writing, reading, adaptation as well as the intimate connections between the three, ultimately revealing the importance of narrative in our lives. I will begin, in sections one and two, by examining the forms of autobiography and biography in their own right as well as in their relationships to one another. These sections of the essay will be used to establish a foundation on which the discussion of key questions may be based – questions about subjectivity, interpretation, adaptation and fidelity. Then, in sections three and four, I will look more closely at my own writing process and its intersection with the autobiographical and biographical writings of others. Here I will examine the biopic genre and connect it with reflections on theories of adaptation, furthering this discussion by exploring alternate ways in which both my screenplay, as well as biopics in general, may be read in relation to the contested issue of fidelity.

The thesis focuses on the development of new homogeneous gels for the separation of drug enantiomers, peptides, DNA and virus by electrophoresis and electrochromatography in capillaries and microchips. This type of separation media offers high resolution and small zone broadening. Compared to particulate beds the resolution in this type of separation media is high because the eddy diffusion is zero and the resistance to mass transfer is small, since the diffusional distance between two polymer chains in the gel is considerably shorter than that between two beads in a packed bed.

The gels have been characterized in terms of plate heights, plate numbers, resolution, etc. Gels of agarose, polyvinyl alcohol, albumin and polyacrylamide have been employed for electrochromatography or electrophoresis. N,N’-methylene-bisacrylamide, the most widely used crosslinker in polyacrylamide gels, was exchanged for allyl-β-cyclodextrin to get a multi-purpose gel, i.e., a separation medium the separation properties of which is determined not only by the polyacrylamide chains, but also by β-cyclodextrin with its complexation power.

A cost-effective, hybrid microdevice has been designed for fast electrophoretic and electrochromatographic analyses as well as for microchromatography. It consists of a fused silica capillary mounted on a supporting plate which integrates most of the compartments necessary for automation and sensitive detection at short UV wavelengths.

ABSTRACT PRODUCTION OF HEAVY-MEDIA-QUALITY MAGNETITE CONCENTRATE FROM KESiKKÖ
PRÜ
IRON ORE TAILINGS Gü
ngö
r, Kazim M. Sc. Department of Mining Engineering Supervisor: Prof. Dr. M. Ü
mit Atalay May 2010, 91 pages The aim of this research was to investigate the possibility of the production of a magnetite concentrate which is suitable for preparation of heavy media from iron ore tailings of Gü
ncem Mining Company magnetic separation facility. During the study, three different tailings named as low grade, medium grade and high grade with 5.91 % Fe3O4, 19.06 % Fe3O4 and 37.06 % Fe3O4, respectively, were used. Mineralogical analyses of test samples showed that magnetite and hematite were the major ore minerals while pyrite and chalcopyrite were found in trace amounts. Actimolite, tremolite, epidote, chlorite, quartz, calcite, and dolomite were the gangue minerals. The effects of feed particle size and applied magnetic field intensity on the Fe3O4 grade and recovery of concentrate were examined throughout magnetic concentration tests. The highest grade magnetite concentrate with 79.98% Fe3O4 content was obtained with 65.42% recovery from 100% -75 micron size feed at 1000 Gauss magnetic field intensity from high grade tailing.

Pipeline natural gas is the primary fuel of choice for distributed fuel cell-based applications. The concentration of sulfur in odorized natural gas is about 30 ppm, with acceptable levels being <1 ppm for catalyst stability in such applications. Packed bed technology for desulfurization suffers from several disadvantages including high pressure drop and slow regeneration rates that require large unit sizes. We describe a novel Rapid Temperature Swing Adsorption (RTSA) system utilizing hollow fibers with polymer 'binder', impregnated with high loadings of sulfur selective sorbent 'fillers'. Steam and cooling water can be utilized to thermally swing the sorbent during the regeneration cycles. An impermeable, thin polymer barrier layer on the outside of fiber sorbents allows only thermal interactions with the regeneration media, thereby promoting consistent sorption capacity over repeated cycles. A simplified flow pattern minimizes pressure drop, porous core morphology maximizes sorption efficiencies, while small fiber dimensions allows for rapid thermal cycles.

Produced water presents economical and environmental challenges to oil producers. Downhole separation technology is able to separate oil or gas from produced fluid in downhole environment and injects waste water into deeper formations, thus saving energy and reducing waste emission. More than 120 downhole separation systems have been installed worldwide, but only about 60% of the installations achieved success. Most of the failures were due to the injectivity decline under the invasion of impurities in the injected water, such as suspended particles and oil droplets. A reliable model is needed to predict the reaction of reservoir permeability under the invasion of such impurities and serves as a tool to screen appropriate formations for downhole separator installations.Previous experimental studies on particle-induced permeability damage reveal that high particle concentration, low fluid velocity, large particle size lead to more severe damage. The damage mechanisms are attributed to surface interception, bridging and size exclusion of particles in porous media. While for droplets, the resultant permeability decline is mostly due to surface interception. Empirical correlations with key parameters determined by core flooding data are widely applied to the simulation of permeability decline under invasion of particles and droplets. These correlations are developed based on characteristics of certain rocks and fluids, thus their applications are very restricted.A more scientific method is to model the flow and capture of particulates at pore level. Reservoir rocks are porous media composed of pores of various sizes. Pore network models employ certain assumptions to imitate real porous media, and have been proved realistic in simulating fluid flow in porous media. In this study, a 2-dimensional square network model is used to simulate capture of particles and droplets in porous media. Pore bodies are represented by globes and pore throats are imitated with capillary tubes. The flow rates in the network are obtained by simultaneously solving mass balance equations at each pore body. The network model is tuned to match the porosity and permeability of a certain rock and serves as the infrastructure where the capture process takes place.Particles are categorized as Brownian and non-Brownian particles according to size. For Brownian particles, diffusion is dominant and Fick’s law is applied to each pore inside the network to obtain deposition rate. For non-Brownian particles, their trajectories are mainly governed by gravity and drag force acting on them. Besides, the size of each particle is compared with the size of the pore where it is captured to determine the damage mechanism. For particles much smaller than the pore size, surface deposition is dominant and the permeability decline is gradual. For particles with sizes comparable to pore size, bridging and clogging are dominant and the permeability decline is much more severe.Unlike particles, droplets can not be captured on top of each other. Accordingly, a captureequilibrium theory is proposed. Once the pore surface is covered by droplets, equilibrium is reached and droplets flow freely through porous media without being captured. The simulation on capture of oil droplets reveals that the surface wettability has significant influence on the resultant permeability damage. Most natural reservoirs are neutrally or oil wet. It is thus recommended to apply these surface conditions to future simulations.The proposed model is validated with test data and reasonably good agreements are obtained. This new mechanistic model provides more insights into the capture process and greatly reduces the dependence on core flooding data.

Produced water presents economical and environmental challenges to oil producers. Downhole separation technology is able to separate oil or gas from produced fluid in downhole environment and injects waste water into deeper formations, thus saving energy and reducing waste emission. More than 120 downhole separation systems have been installed worldwide, but only about 60% of the installations achieved success. Most of the failures were due to the injectivity decline under the invasion of impurities in the injected water, such as suspended particles and oil droplets. A reliable model is needed to predict the reaction of reservoir permeability under the invasion of such impurities and serves as a tool to screen appropriate formations for downhole separator installations.
Previous experimental studies on particle-induced permeability damage reveal that high particle concentration, low fluid velocity, large particle size lead to more severe damage. The damage mechanisms are attributed to surface interception, bridging and size exclusion of particles in porous media. While for droplets, the resultant permeability decline is mostly due to surface interception. Empirical correlations with key parameters determined by core flooding data are widely applied to the simulation of permeability decline under invasion of particles and droplets. These correlations are developed based on characteristics of certain rocks and fluids, thus their applications are very restricted.
A more scientific method is to model the flow and capture of particulates at pore level. Reservoir rocks are porous media composed of pores of various sizes. Pore network models employ certain assumptions to imitate real porous media, and have been proved realistic in simulating fluid flow in porous media. In this study, a 2-dimensional square network model is used to simulate capture of particles and droplets in porous media. Pore bodies are represented by globes and pore throats are imitated with capillary tubes. The flow rates in the network are obtained by simultaneously solving mass balance equations at each pore body. The network model is tuned to match the porosity and permeability of a certain rock and serves as the infrastructure where the capture process takes place.
Particles are categorized as Brownian and non-Brownian particles according to size. For Brownian particles, diffusion is dominant and Fick’s law is applied to each pore inside the network to obtain deposition rate. For non-Brownian particles, their trajectories are mainly governed by gravity and drag force acting on them. Besides, the size of each particle is compared with the size of the pore where it is captured to determine the damage mechanism. For particles much smaller than the pore size, surface deposition is dominant and the permeability decline is gradual. For particles with sizes comparable to pore size, bridging and clogging are dominant and the permeability decline is much more severe.
Unlike particles, droplets can not be captured on top of each other. Accordingly, a captureequilibrium theory is proposed. Once the pore surface is covered by droplets, equilibrium is reached and droplets flow freely through porous media without being captured. The simulation on capture of oil droplets reveals that the surface wettability has significant influence on the resultant permeability damage. Most natural reservoirs are neutrally or oil wet. It is thus recommended to apply these surface conditions to future simulations.
The proposed model is validated with test data and reasonably good agreements are obtained. This new mechanistic model provides more insights into the capture process and greatly reduces the dependence on core flooding data.

Un milieu poreux ou un matériau poreux comprend deux régions interconnectées : une perméable par un gaz ou un liquide et l’autre imperméable. Beaucoup de substances naturelles comme les roches, le sol et les tissus biologiques (par exemple, os, bio-membranes) sont poreuses ainsi que les matériaux manufacturés comme les ciments et les céramiques, etc. Les matériaux poreux ont des applications technologiques importantes et nombreuses, par exemple, comme tamis moléculaires, catalyseurs ou senseurs chimiques. Il existe un nombre très important d’études en expérience et en théorie pour comprendre la structure des matériaux poreux ainsi que les propriétés des substances confinées dans ces matériaux. Dans leur travail de pionnier, Madden et Glandt ont proposé un modèle très simple pour l’adsorption de fluide dans des milieux poreux désordonnés. Dans ce modèle, on forme la matrice en prenant une configuration figée instantanément d’un système à l’équilibre (“quench” en anglais) et puis un fluide est introduit dans une telle matrice. Récemment, T. Patsahan, M. Holovko et W. Dong ont généralisé la “scaled particle theory” (SPT) aux fluides confinés et obtenu ainsi des équations d’état analytiques pour un fluide de sphère dure dans plusieurs modèles de matrice. Dans un premier temps, j’ai développé la version de la SPT pour un mélange de sphères dures additives confiné en milieu poreux. Les expressions pour les valeurs au contact de différentes fonctions de distribution ont été obtenues également. J’ai effectué aussi des simulations de Monte Carlo. Les résultats de ces simulations sont utilisés pour valider les résultats théoriques. Ensuite, j’ai étudié aussi la séparation de phase d’un mélange binaire des sphères dures non additives confiné dans un milieu poreux. Pour obtenir l’équation d’état, nous avons utilisé une théorie de perturbation en prenant un fluide de sphères dures additive comme système de référence. Les résultats donnés par cette théorie sont en bon accord avec les résultats de simulation Monte Carlo
A porous medium or a porous material (called as frame or matrix also) usually consists of two interconnected rejoins: one permeable by a gas or a liquid, i.e., pore or void, and the other impermeable. Many natural substances such as rocks, soils, biological tissues (e.g., bio membranes, bones), and manmade materials such as cements, foams and ceramics are porous materials. Porous materials have important technological applications such as molecular sieve, catalyst, chemical sensor, etc. In recent years, there have been considerable investigations for understanding thoroughly the structure of these materials as well as the behavior of substances confined in them. Much effort (both experimental and theoretical) has been devoted to the study of porous materials. In their pioneering work, a very simple model for the fluid adsorption in random porous media was proposed by Madden and Glandt. The matrix in Madden-Glandt model is made by quenching an equilibrium system. Then, a fluid is adsorbed in such a matrix. Recently, T. Patsahan, M. Holovko and W. Dong have extended the scaled particle theory (SPT) to confined fluids and derived analytical equations of state (EOS) for a hard sphere (HS) fluid in some matrix models. In this thesis, using SPT method, I obtained the equation of state of additive hard-sphere (AHS) fluid mixtures confined in porous media. The contact values of the fluid-fluid and fluid-matrix radial distribution functions (RDF) were derived as well. The results of the contact values of the RDFs and the chemical potentials of different species were assessed against Monte Carlo simulations. Moreover, I analyzed also the fluid-fluid phase separation of non-additive hard sphere (NAHS) fluid confined in porous media. An equation of state is derived by using a perturbation theory with a multi-component fluid reference. The results of this theory are in good agreement with those obtained from semi grand canonical ensemble Monte Carlo simulations

Dans le cadre de ce travail de thèse, la polymérisation de type RAFT a été exploitée pour synthétiser des particules de latex magnétiques décorées de polymères stimulables. Cinq (co)polymères hydrophiles ont tout d'abord été préparés via la (co)polymérisation RAFT en solution d'acide acrylique (AA) et de méthacrylate de 2-diméthylaminoéthyle (MADAME). Les agents macromoléculaires obtenus (macroRAFT) : des homopolymères de PAA ou PMADAME ainsi que des copolymères P(AA-co-MADAME), présentent une sensibilité au pH et à la température. Ces macroRAFT hydrophiles ont ensuite été utilisés dans des réactions d’extension de chaîne avec du styrène conduisant à la formation de copolymères à blocs amphiphiles bien définis. Puis, des dispersions aqueuses d’agrégats (clusters) de nanoparticules d’oxyde de fer (OF) ont ensuite été préparées via un procédé de mini-émulsification/évaporation de solvant, en utilisant les copolymères à blocs comme stabilisants. Après optimisation des conditions expérimentales (sonication, concentration de macroRAFT, pH), des agrégats de taille contrôlée (45 à 300 nm) ont pu être obtenus. Ces clusters ont ensuite été utilisés comme semence lors de la polymérisation en émulsion du styrène, conduite en présence d’un agent de réticulation. Les clusters d'OF ont été individuellement encapsulés par une couche de polymère, formant des particules magnétiques stabilisées par le segment hydrophile des copolymères à blocs. Enfin, les particules magnétiques décorées de copolymères de P(AA-co-MADAME) ont été utilisées avec succès pour la capture et le relargage de bactéries grâce à la modulation de leurs propriétés de surface en fonction du pH
In this work reversible addition-fragmentation chain transfer (RAFT) polymerization was exploited to synthesize magnetic latex particles decorated with stimuli-responsive polymer brushes. First, five hydrophilic (co)polymers with various compositions were successfully prepared by RAFT solution (co)polymerization of acrylic acid (AA) and 2-dimethylaminoethyl methacrylate (DMAEMA) for different AA to DMAEMA molar ratios. The obtained macromolecular RAFT agents (macroRAFTs), PAA or PDMAEMA homopolymers and P(AA-co-DMAEMA) copolymers, displayed interesting pH- and thermo-responsive properties. These hydrophilic macroRAFTs were then chain extended with styrene leading to the formation of well-defined amphiphilic block copolymers. An aqueous dispersion of iron oxide clusters was next prepared using a strategy based on emulsification/solvent evaporation in which the block copolymers were used as stabilizers. By varying the experimental conditions (sonication power, macroRAFT concentration and pH of the medium), the cluster size could be controlled from 45 up to 300 nm. These clusters were then used as seeds in styrene emulsion polymerization in the presence of a crosslinker. The iron oxide clusters were individually encapsulated into a polymer shell generating latex particles, stabilized by the hydrophilic segment of the block copolymers, and displaying interesting magnetic properties. At last, these magnetic beads were evaluated as carriers in the magnetic separation of bacteria. The magnetic latex particles decorated with P(AA-co-DMAEMA) copolymers were successfully employed for the capture and trigger release of bacteria, allowing their concentration in a biological sample

Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: In this thesis, the recovery of RhIII from both synthetically prepared and authentic industrial PGM-containing solutions was systematically investigated via organic precipitation methods using several commercially available, N-containing organic receptors including (amongst others) diethylenetriamine (Deta), triethylenetetramine (Teta), tetraethylenepentamine (Tepa) and tris(2-aminoethyl)amine (Tren). These organic receptors act as precipitating agents in the presence of an appropriate protonating agent (HCl) by lowering the solubility of the PGM chlorido-anions through an ion-pairing mechanism. The recovery of RhIII from synthetically prepared PGM (RhIII and PtIV) containing solutions using these precipitants was excellent, while poor Rh recovery from authentic industrial process solutions was achieved. The poor Rh recovery from these process solutions was ascribed to the species distribution of the [RhCln(H2O)6-n]3-n complexes. In order to validate the proposition that RhIII speciation effects are responsible for the poor Rh recovery observed during the precipitation studies, attempt were made to describe the species distribution of the [RhCln(H2O)6-n]3-n (n=3-6) by means of high-resolution 103Rh NMR spectroscopy. A detailed high-resolution 103Rh NMR spectroscopic study of the series of [RhCln(H2O)6-n]3-n (n=3-6) complexes was conducted. During this study, all six RhIII aqua chlorido-complexes have unambiguously been characterized by means of high-resolution 103Rh NMR spectroscopy, proving the powerful analytical capability of this technique. Characterization of these complexes is based on the detailed analysis of the 35Cl/37Cl isotope effects which is observed in the 19.11 MHz 103Rh NMR resonances of the [RhCln(H2O)6-n]3-n (n=3-6) complexes in aqueous HCl solutions at 292 K. These resonances show that the “finestructure” of each of the 103Rh resonances may be understood in terms of its unique isotopologue, and in certain cases, the isotopomer distribution of each complex, which manifests as a result of its statistically expected 35Cl/37Cl isotopologue and isotopomer distributions. As a result, the 103Rh NMR resonance structure serves as a unique “NMRfingerprint”, which allows for the unambiguous assignment of [RhCln(H2O)6-n]3-n (n=3-6) complexes, without the reliance on accurate δ(103Rh) chemical shifts. Furthermore, this study reports the first direct species distribution diagram for the [RhCln(H2O)6-n]3-n (n=3-6) series of complexes (in aqueous HCl solutions at 292 K) as a function of the “free” (unbound) chloride concentration, constructed from 103Rh NMR measurements. The need for a revised speciation diagram of [RhCln(H2O)6-n]3-n (n=3-6) complexes is clearly reflected by the vast differences observed in the literature reported species distribution diagrams, which makes it difficult to decide which set of experimental conditions (if any) is required for the quantitative and “selective” recovery of RhIII from aqueous HCl solutions containing associated PGMs (Pt, Pd, Ir, Ru) as well as other transition metals. The documented species distribution diagrams for RhIII have been generally constructed via data from indirect (kinetic and spectrophotometric) measurements using dilute RhIII solutions at relatively high HCl concentrations, which implies that the RhIII:Clmole ratio is higher than what may be expected in authentic process solutions – an important aspect to consider when optimizing RhIII recovery methods. In addition, RhIII kinetic investigations reported in this study shows that ionic strength and temperature effects are important factors that dramatically influences the rate of RhIII ligand exchange (i.e. RhIII aquation reactions) which, in turn, have contributing effects on the species distribution of [RhCln(H2O)6-n]3-n complexes. Notable differences exist between the speciation diagram reported in this study and those documented in literature, especially at a “free” chloride concentration of 1.0 M. At this “free” chloride concentration, the [RhCl5(H2O)]2- complex anion was found to have an abundance of 34%, while literature reports an abundance of 80%. In order to ascertain its practical relevance, the proposed 103Rh NMR speciation method was extended, for the first time, to authentic industrial Rh feed solutions (Anglo Platinum PLC). Each of the 103Rh resonances was unambiguously assigned, and each species quantified. Moreover, the RhIII species distribution of the industrial Rh feed solution was accurately predicted by the “direct” speciation diagram constructed form 103Rh NMR measurements. After careful optimization of the Heraeus industrial feed solutions (optimal chloride concentration followed by thermal treatment for enhancing RhIII chloride anation reactions), the recovery of Rh via precipitation was repeated. In this instance, Rh recovery improved dramatically, with up to 95% of Rh removed from solution. This improvement is ascribed primarily to the increased “free” (unbound) chloride concentration. The presence of associated PGMs as well as other transition metals would lower the effective “free” chloride concentration, since these metals would act as “chloride binders”. By adjusting the total chloride concentration, RhIII chloride anation reactions is enhanced which leads to the [RhCln(H2O)6-n]3-n (n=5,6) complex anions being the dominant species in solution, therefore leading to improved Rh recovery. Moreover, it was shown that, under carefully controlled conditions, “selective” recovery of Rh is achieved using tris(2-aminoethyl)amine (Tren). Considering the fact that Rh is the last precious metal recovered in all PGM refineries, this can possibly provide a cost-effective route for the “upfront” (early stage) recovery of Rh from industrial PGM feed solutions.
AFRIKAANSE OPSOMMING: In hierdie tesis word die herwinning van RhIII uit laboratorium voorbereide sowel as ware industriële PGM-bevattende oplossings sistematies ondersoek deur middel van organiese neerslag metodes, deur gebruik te maak van verskeie kommersieël beskikbare, Nbevattende organiese reseptore insluitende dietileentriamien (Deta), tri-etileentetramien (Teta), tetra-etileenpentamien (Tepa) en tris(2-aminoetiel)amien (Tren). Hierdie organiese reseptore tree op as neerslag-agente in die teenwoordigheid van 'n geskikte protoneringsagent (in hierdie geval HCl) deur 'n verlaging van die oplosbaarheid van die PGM chloriedanione deur middel van 'n ioon parings meganisme. Die herwinning van RhIII vanuit laboratorium voorbereide PGM (RhIII en PtIV) oplossing met behulp van hierdie organiese neerslag-agente was uitstekend, terwyl Rh herwinning vanuit ware industriële oplossings swak was. Die onvolledige Rh herwinning uit hierdie industriële oplossings word toegeskryf aan die spesie-verspreiding van die [RhCln(H2O)6-n]3-n komplekse. Ten einde die effek van RhIII spesie-verspreiding op die herwinning van Rh te bestudeer, is gepoog om die spesieverspreiding van [RhCln(H2O)6-n]3-n (n=3-6) komplekse, deur middel van hoë resolusie 103Rh KMR spektroskopie, te beskryf. 'n Gedetailleerde hoë resolusie 103Rh KMR spektroskopiese studie van die reeks van [RhCln(H2O)6-n]3-n (n=3-6) komplekse was uitgevoer. Tydens hierdie studie was al ses RhIII aqua chlorido-komplekse ondubbelsinnig gekarakteriseer deur middel van hoë resolusie 103Rh KMR spektroskopie, wat bewys lewer van die kragtige analitiese vermoë van hierdie tegniek. Karakterisering van hierdie komplekse is gebaseer op die gedetailleerde analise van die 35Cl/37Cl isotoop effekte wat waargeneem word in die 19.11 MHz 103Rh KMR resonansies van die [RhCln(H2O)6-n]3-n (n=3-6) komplekse in HCl oplossings by 292 K. Hierdie resonansies toon dat die "fyn struktuur" van elk van die 103Rh resonansies verstaan kan word in terme van die unieke isotopoloog, en in sekere gevalle, die isotopomeer verspreiding van elke kompleks, wat manifesteer as 'n gevolg van die die statisties verwagte 35Cl/37Cl isotopoloog en isotopomeer verspreiding. Die 103Rh KMR resonansie-struktuur kan sodoende dien as 'n unieke "KMR-vingerafdruk", wat voorsiening maak vir die ondubbelsinnige karakterisering van [RhCln(H2O)6-n]3-n (n=3-6) komplekse, sonder om vertroue op akkurate δ(103Rh) chemiese verskuiwings te plaas. Hierdie studie rapporteer verder die eerste direkte spesie-verspreiding-diagram vir die [RhCln(H2O)6-n]3-n (n=3-6) reeks komplekse (in HCl oplossings by 292 K) as 'n funksie van die "vrye"(ongebonde) chloried-konsentrasie, verkry van 103Rh KMR metings. Die behoefte vir 'n aangepasde spesiasie-diagram vir die [RhCln(H2O)6-n]3-n (n=3-6) komplekse word duidelik weerspieël deur die groot verskille waargeneem in die literatuur gerapporteerde verspreidings diagramme, wat dit moeilik maak om te besluit watter stel eksperimentele toestande (indien enige) benodig word vir die kwantitatiewe en “selektiewe” herwinning van RhIII in HCl oplossings in die teenwoordigheid van gepaardgaande PGM (Pt, Pd, Ir, Ru) sowel as ander oorgangsmetale. Die gedokumenteerde spesie-verspreiding-diagramme vir RhIII is oor die algemeen verkry via data vanaf indirekte (kinetiese en spektrofotometriese metings) deur gebruik te maak van verdunde RhIII oplossings in relatiewe hoë HCl konsentrasies, wat impliseer dat die RhIII:Cl mol verhouding hoër is as wat verwag kan word in ware industriële proses oplossings - 'n belangrike aspek om te oorweeg gedurende die optimalisering van RhIII herwinning-metodes. Verder, die RhIII kinetiese ondersoeke gerapporteer in hierdie studie toon dat ioniese sterkte sowel as temperatuur effekte belangrike faktore is wat die tempo van RhIII ligand uitruiling (d.w.s. RhIII “aquation” reaksies), wat ‘n betekenisvolle invloed hê op die spesie-verspreiding van [RhCln(H2O)6-n]3-n komplekse. Aansienlike verskille bestaan tussen die spesiasie-diagram gerapporteer in hierdie studie en dit gedokumenteer in die literatuur, veral by 'n "vrye" chloried-konsentrasie van 1.0 M. By hierdie "vrye" chloried-konsentrasie was die [RhCl5(H2O)]2- komplekse anioon gevind om in 34% teenwoordig te wees (hierdie studie), terwyl die publiseerde verslae 80% rapporteer. Ten einde die praktiese toepaslikheid van die voorgestelde 103Rh KMR spesiasiemetode te bepaal, was (vir die eerste keer) ware industriële Rh oplossings (Anglo Platinum PLC) gebruik. Elk van die 103Rh resonansies was ondubbelsinnig gekarakteriseer, en elke Rh spesie teenwoordig gekwantifiseer. Daarbenewens is die RhIII spesie-verspreiding van die industriële Rh oplossing deur die "direkte" spesiasie-diagram saamgestel vanuit 103Rh KMR metings akkuraat voorspel. Die berekende RhIII spesie-verspreiding van die industriële Rh oplossings was akkuraat voorspel deur die voorgestelde “direkte” spesiasie-diagram soos saamgestel vanuit die 103Rh KMR metings. Na deeglike optimalisering van Heraeus industriële oplossings (optimale chloriedkonsentrasie gevolg deur termiese behandeling vir effektiewe RhIII chloried anasie reaksies), is die herwinning van Rh via neerslag metodes herhaal. In hierdie geval, het die Rh herwinning dramaties verbeter, met tot 95% van die Rh uit oplossing verwyder. Hierdie verbetering is hoofsaaklik toegeskryf aan die verhoogde "vry" (ongebonde) chloriedkonsentrasie. Die teenwoordigheid van geassosieerde PGM's sowel as ander oorgangsmetale sal die effektiewe "vrye" chloried-konsentrasie verlaag, aangesien hierdie metale sou optree as "chloried-binders". Deur die aanpassing van die totale chloried-konsentrasie, word RhIII chloried anasie reaksies verbeter, wat daartoe lei dat [RhCln(H2O)6-n]3-n (n = 5,6) komplekse anione die dominante spesies in oplossing word, en dus lei tot verbeterde Rh herwinning. Daarbenewens word verder aangetoon dat, onder noukeurig gekontroleerde voorwaardes, "selektiewe" herwinning van Rh bereik word deur gebruik te maak van tris(2-aminoetiel)amien (Tren). Met inagneming van die feit dat Rh die laaste edelmetaal is wat verhaal word in alle PGM-raffinaderye, kan dit 'n koste-effektiewe roete word vir die "vooraf" (vroeë-stadium) herwinning van Rh vanuit industriële PGM bevattende oplossings.

This thesis has focused on color reproduction processes in the graphics field and is based on theoretical research and practical studies. The purpose of this thesis was to investigate how new tools and tools adapted to a specific production set-up can be used to raise awareness regarding the quality and workflow of images and image processing for sheet-fed offset within the graphic industry. The work is divided in to the following three study areas with several sub-studies: 1) The first research goal of the thesis is to identify knowledge levels regarding color separation of images and demand specifications within printing houses. 2) The second research goal is to investigate whether novel tools and new terminology can help to increase the knowledge level regarding color management 3) The third goal is to investigate whether process specific adaptation of key color control tools can improve quality levels Three surveys about color reproduction (focusing on level of knowledge concerning color separation, the use of ICC-profiles and demand specifications for controlled color reproduction) at printing companies in Sweden were made between 2000 and 2004. The surveys indicated a serious problem in the graphic arts industry, involving both an insufficient understanding of color management and a lack of communication. An important part of the work was to assist in make color management understandable for users and thereby optimize printing. For this purpose, digital test forms have been developed. The developed tools, together with descriptive material, will facilitate the understanding of color management issues. Definitions within the field of color separations have been examined, and changes have been suggested. A new term for separation “Compensation by Black”, CB, has been suggested, instead of e.g. GCR and UCR. Is it possible to adapt the different parts of the process chain in order to achieve an improved production? Yes! This work has developed the method for adaptation of the scanne rtest chart, the printing test chart for image categorization and the control strip forsheet-fed offset using gray balance. This thesis suggests that it is possible to produce a custom-made IT8 target test chart for scanners and achieve a result at least similar to or even better than the standard test charts on the market. This work has also shown that itis possible to adapt the test chart for printing to image category. The result showed that low-key image separated by the image-adapted test chart showed more detail in the dark areas than a low-key image separated by the standard test chart, in the prints on a coated paper. The result from the adaptation of a control strip for sheet-fed offset showed that gray balance can be used as a control parameter for quality control in sheet-fed offset.
QC20100617

The objective of this thesis is to analyze the authoritarian Karimov regime in post-Soviet Uzbekistan on a comprehensive basis and shed light on the domestic and international factors that has shaped this regime. The thesis consists of three main parts. The first part of the study defines the concepts of democracy and authoritarianism and provides the criteria to determine if a regime is democratic or authoritarian. The second part applies the theoretical framework developed in the first part to Uzbekistan. The third part deals with the factors that helped Karimov to strengthen his authoritarian rule in the country. The main argument of this study is that the incumbent leadership in Uzbekistan has failed to take steps to establish democracy in the country in post-Soviet period. The changes that were introduced proved to be only decorative, they lacked substance. The president of the country, Islam Karimov, has aimed at consolidating his own authority rather than establishing democracy and that his attempts to realize this aim resulted in the strengthening of executive branch in Uzbekistan at the expense of legislative and judiciary, silencing of the opposition forces, curtailment of the civil and political rights of the citizens, restriction of autonomy of civil society organizations and media.

Les monoamides sont étudiés depuis quelques années comme extractants alternatifs au TBP dans le procédé de retraitement du combustible irradié. Ces molécules possèdent une affinité modulable pour le plutonium(IV), selon la nature de leur chaîne alkyle et selon l’acidité. Comme le TBP, les monoamides, solvants immiscibles extraient de l’eau et de l’acide nitrique lorsqu’ils sont mis en contact avec ce dernier. L’acide nitrique étant un composé instable vis-à-vis de la radiolyse, il dismute en plusieurs composés azotés dont l’acide nitreux (HNO2) qui par sa présence pourrait entrainer la formation du couple redox HNO3/HNO2 susceptible de provoquer des réactions redox parasites et perturber le procédé. Il est donc important de connaitre la spéciation redox des actinides (An) en particulier dans la phase organique d’extraction afin d’assurer une bonne maitrise du procédé.Le comportement électrochimique du couple Ce(IV)/Ce(III) a été étudié par voltampérométrie cyclique à 25 et 40°C à une électrode de carbone vitreux dans trois N,N-dialkylamides : le DEHBA (N,N-di-(2-éthylhexyl)-n-butanamide), le DEHiBA (N,N-di-(2- éthylhexyl)-iso-butanamide) et le DEHDMBA (N,N-di-(2-éthylhexyl)-3,3- diméthyl-n-butanamide) pré-équilibrés à l’eau et à l’acide nitrique (HNO3 5M). Les résultats ont montré que le processus électrochimique du couple Ce(IV)/Ce(III) est celui d’un couple redox quasi-rapide limité par la diffusion. Cette étude préalable sur le cérium analogue chimique non radioactif du plutonium a été réalisée dans le but d’identifier la nature du système électrochimique du couple Ce(IV)/Ce(III) et les difficultés liées à la réalisation de mesures électrochimiques dans ces milieux organiques très visqueux et très peu conducteurs. Le couple redox Pu(IV)/Pu(III) a ensuite été étudié à 40°C dans le DEHBA à une électrode de carbone vitreux à différentes concentrations d’acide nitrique (0,6 M < [HNO3]org < 3,7 M). Une étude préalable de la spéciation du plutonium (IV) dans la phase organique DEHBA après extraction a révélé la formation de deux types de complexes avec les ligands DEHBA et dont la prépondérance dans le milieu organique varie avec l’acidité. Les mesures de voltampérométrie cyclique ont montré que la nature des complexes de plutonium dans le DEHBA peut avoir un impact notable sur l’électroactivité du couple redox Pu(IV)/Pu(III). Il a été observé aux faibles acidités en phase organique que le processus électrochimique du couple redox Pu(IV)/Pu(III) est celui d’un couple quasi-rapide limité par la diffusion. Aucune électroactivité du couple Pu(IV)/Pu(III) n’a été observée aux fortes acidités.Cette étude a permis de déterminer les caractéristiques physico-chimiques des couples redox Ce(IV)/Ce(III) et Pu(IV)/Pu(III) tels que le potentiels redox et le coefficient de diffusion dans les milieux N,N-dialkylamides ; des données qui jusque-là, sont quasi-inexistantes dans la littérature. À l’issu de cette étude, une méthode permettant le dosage par voltampérométrie cyclique de cations métalliques en milieu organique a été élaborée
Monoamides extractants are being studied in recent years as alternate extractants to TBP for irradiated nuclear fuels reprocessing. Their extracting strength and selectivity toward Pu(IV) can be tuned depending on the nature of their alkyl chain and the nitric acid concentration. Like TBP, monoamides can extract water and nitric acid while in contact. However, nitric acid is unstable in both aqueous and organic phases. Due to radiolysis, it can be disproportionate in nitrous acid (HNO2) which is known to possess redox properties. It could lead to the formation of the HNO3/HNO2 redox couple which may cause several parasitic redox reactions and affect the recycling process. Meaningful the redox speciation of actinides (An) in an organic phase is important for acute control of the recycling processes. The electrochemical behavior of the Ce(IV)/Ce(III) couple have been studied at 25 and 40°C by cyclic voltammetry at a vitreous carbon working electrode in three N,N-dialkylamides solvents (DEHBA (N,N-di-(2-ethylhexyl)-n-butanamide), DEHiBA (N,N-di-(2-ethylhexyl)-iso-butanamide) and DEHDMBA (N,N-di-(2-ethylhexyl-)3,3-dimethylbutanamide)) pre-equilibrated with aqueous nitric acid solutions (HNO3 5M). Results showed that the Ce(IV)/Ce(III) redox process exhibits a well-defined reversible couple with a diffusion-controlled electrochemical behavior. This initial study on the Ce(IV)/Ce(III) couple, a "non-radioactive model" of the Pu(IV)/Pu(III) couple has been an entry to the direct electrochemical characterization of plutonium in these extractants aiming to identify the nature of the electrochemical process of the Ce(IV)/Ce(III) couple and the difficulties associated with carrying out electrochemical measurements in these viscous and low conductive media. The Pu(IV)/Pu(III) couple has been studied at 40°C in DEHBA at a vitreous carbon working electrode at different concentrations of nitric acid (0,6 M < [HNO3]org < 3,7 M). The study of the speciation of plutonium (IV) in the organic DEHBA phase after extraction showed the presence of two types of plutonium(IV) complexes with variable predominance due to the nitric acid concentration. Cyclic voltammetry measurements showed an significant effect of the speciation of plutonium in the organic phase on the electroactivity of the Pu(IV)/Pu(III) couple. At low nitric acid concentrations, the Pu(IV)/Pu(III) redox process exhibits a well-defined reversible couple with a diffusion-controlled electrochemical behavior. At higher nitric acid concentrations, no electrochemical response of the Pu(IV)/Pu(III) couple is observed. This study enabled the determination of physic and chemical characteristics of the Ce(IV)/Ce(III) and Pu(IV)/Pu(III) couples in N,N-dialkylamides media as the redox potential and the diffusion coefficient that were not previously studied. This study validates the implementation of electrochemical method for the quantification of tetravalent metallic cation in organic phases

The hippocampus is thought to be involved in memory formation and consolidation, with computational models proposing the process of pattern separation as a means for encoding overlapping memories. Previous research has used semantically related targets and lures to investigate hippocampal responses to mnemonic interference. Here, we attempted to define the response function of the hippocampus and its inputs during pattern separation by parametrically varying target-lure similarity in a continuous recognition task. We also investigated the effect of task demands (intentional versus incidental encoding) on pattern separation processes. We collected functional magnetic resonance imaging (fMRI) data while participants were shown a series of objects. In the intentional paradigm, participants identified objects as "new" (novel stimuli), "old" (exact repetitions), or "rotated" (previously seen objects that were subsequently rotated by varied degrees). In the incidental paradigm, participants were shown the same stimuli but identified objects as "toy" or "not toy". Activation in the hippocampus was best fit with a power function, consistent with predictions made by computational models of pattern separation processes in the hippocampus. The degree of pattern separation was driven by the information most relevant to the task—pattern separation was seen in the left hippocampus when semantic information was more important to the task and seen in the right hippocampus when spatial information was more important. We also present data illustrating that top-down processes modulate activity in the ventral visual processing stream.

ransmitted-light coherence-controlled holographic microscope (CCHM) based on an off-axis achromatic and space-invariant interferometer with a diffractive beamsplitter has been designed, constructed and tested. It is capable to image objects illuminated by light sources of arbitrary degree of temporal and spatial coherence. Off-axis image-plane hologram is recorded and the image complex amplitude (intensity and phase) is reconstructed numerically using fast Fourier transform algorithms. Phase image represents the optical path difference between the object and the reference arms caused by presence of an object. Therefore, it is a quantitative phase contrast image. Intensity image is confocal-like. Optical sectioning effect induced by an extended, spatial incoherent light source is equivalent to a conventional confocal image. CCHM is therefore capable to image objects under a diffusive layer or immersed in a turbid media. Spatial and temporal incoherence of illumination makes the optical sectioning effect stronger compared to a confocal imaging process. Object wave reconstruction from the only one recorded interference pattern ensures high resistance to vibrations and medium or ambience fluctuations. The frame rate is not limited by any component of the optical setup. Only the detector and computer speeds limit the frame rate. CCHM therefore allows observation of rapidly varying phenomena. CCHM makes the ex-post numerical refocusing possible within the coherence volume. Coherence degree of the light source in CCHM can be adapted to the object and to the required image properties. More coherent illumination provides wider range of numerical refocusing. On the other hand, a lower degree of coherence makes the optical sectioning stronger, i.e. the optical sections are thiner, it reduces coherence-noise and it makes it possible to separate the ballistic light. In addition to the ballistic light separation, CCHM enables us to separate the diffused light. Multi-colour-light

Le but de cette thèse est de développer et d’analyser les méthodes Hybrides d’Ordre Élevé (HHO: Hybrid High-Order, en anglais) pour des problèmes d’interfaces. Nous nous intéressons à deux types d’interfaces (i) les interfaces diffuses, et (ii) les interfaces traitées comme frontières internes du domaine computationnel. La première moitié de ce manuscrit est consacrée aux interfaces diffuses, et plus précisément aux célèbres équations de Cahn–Hilliard qui modélisent le processus de séparation de phase par lequel les deux composants d’un fluide binaire se séparent pour former des domaines purs en chaque composant. Dans la deuxième moitié, nous considérons des modèles à dimension hybride pour la simulation d’écoulements de Darcy et de transports passifs en milieu poreux fracturé, dans lequel la fracture est considérée comme un hyperplan (d’où le terme hybride) qui traverse le domaine computationnel
The purpose of this Ph.D. thesis is to design and analyse Hybrid High-Order (HHO) methods on some interface problems. By interface, we mean (i) diffuse interface, and (ii) interface as an immersed boundary. The first half of this manuscrit is dedicated to diffuse interface, more precisely we consider the so called Cahn–Hilliard problem that models the process of phase separation, by which the two components of a binary fluid spontaneously separate and form domains pure in each component. In the second half, we deal with the interface as an immersed boundary and consider a hybrid dimensional model for the simulation of Darcy flows and passive transport in fractured porous media, in which the fracture is considered as an hyperplane that crosses our domain of interest

In present finite element study, the dynamics of incompressible isothermal flows of Newtonian and two generalised non-Newtonian models through complex mixing-separating planar channel and circular pipe filled with and without porous media, including Darcy's term in momentum equation, is presented. Whilst, in literature this problem is solved only for planar channel flows of Newtonian and viscoelastic fluids. The primary aim of this study is to examine the laminar flow behaviour of Newtonian and inelastic non-Newtonian fluids, and investigate the robustness of the numerical algorithm. The rheological properties of non-Newtonian fluids are defined utilising a range of constitutive equations, for inelastic non-Newtonian fluids non-linear viscous models, such as Power Law and Bird-Carreau models are used to capture the shear thinning behaviour of fluids. To simulate such complex flows, steady-state solutions are sought employing time-dependent finite element algorithm. Temporal derivatives are discretised using second order Taylor series expansion, while, spatial discretisation is achieved through Galerkin approximation in combination to deal with incompressibility a pressure-correction scheme adopted. In order to achieve the algorithm of semi-implicit form Darcy's-Brinkman equation is utilized for the conversion in Darcy's terms and diffusion, while Crank-Nicolson approach is adopted for stability and acceleration. Simple and complex flows for various complex flow bifurcations of the combined mixing-separating geometries, for both two-dimensional planar channel in Cartesian coordinates, as well as axisymmetric circular tube in cylindrical polar coordinates system are investigated. These geometries consist of a two-inverted channel and pipe flows connected through a gap in common partitions, initially filled with non-porous materials and later with homogeneous porous materials. Computational domain is having variety it has been investigated with many configurations. These computational domains have been appeared in industrial applications of combined mixing and separating of fluid flows both for porous and non-porous materials. Fully developed velocity profile is applied on both inlets of the domain by imposing analytical solutions found during current study for porous materials. Numerical study has been conducted by varying flow rates and flow direction due to a variety in the domain. The influence of varying flow rates and flow directions are analysed on flow structure. Also the impact of increasing inertia, permeability and power law index on flow behaviour and pressure difference are investigated. From predicted solution of present numerical study, for Newtonian fluids a close agreement is realised between numerical solutions and experimental data. During simulations, it has been noticed that enhancing fluid inertia (flow rates), and permeability has visible effects on the flow domains. When the Reynolds number value increases the size and power of the vortex for recirculation increases. Under varying flow rates an early activity of vortex development was observed. During change in flow directions reversed flow showed more inertial effects as compared with unidirectional flows. Less significant influence of inertia has been observed in domains filled with porous media as compared with non-porous. The power law model has more effects on inertia and pressure as compared with Bird Carreau model. Change in the value of permeability gave significant impact on pressure difference. Numerical simulations for the domain and fluids flow investigated in this study are encountered in the real life of mixing and separating applications in the industry. Especially this purely quantitative numerical investigation of flows through porous medium will open more avenues for future researchers and scientists.

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 1999.
Includes bibliographical references (p. 111-114).
This thesis investigates how a digital system can recognize and isolate individual sound sources, or audio objects, from an environment containing several sounds. The main contribution of this work is the application of object-based audio capture to unconstrained real-world environments. Several potential applications for object-based audio capture are outlined, and current blind source separation and deconvolution (BSSD) algorithms that have been applied to acoustically-mixed sounds are reviewed. An explanation of the acoustics issues in object-based audio capture is provided, including an argument for using overdetermined mixtures to yield better source separation. A thorough discussion of the difficulties imposed by a real-world environment is offered, followed by several experiments which compare how different filter configurations and filter lengths, as well as reverberant environments, all have an impact on the performance of object-based audio capture. A real-world implementation of object-based audio capture in a conference room with two people speaking is also discussed. This thesis concludes with future directions for research in object-based audio capture.
Alexander George Westner.
S.M.

This dissertation explores the reconfiguration of religion in modern global society with a focus on Koreans’ use of the category of religion. Using textual and structural analysis, this study examines how the notion of religion is structurally and semantically contextualized in the public sphere of modern Korea. I scrutinize the operation of the differentiated communication systems that produces a variety of discourses and imaginaries on religion and religions in modern Korea. Rather than narrowly define religion in terms of the consequence of religious or scientific projects, this dissertation shows the process in which the evolving societal systems such as politics, law, education, and mass media determine and re-determine what counts as religion in the emergence of a globalized Korea. I argue that, ever since the Western notion of religion was introduced to East Asia in the eighteenth and nineteenth centuries, religion was, unlike in China and Japan, constructed as a positive social component in Korea, because it was considered to be instrumental in maintaining Korean identity and modernizing the Korean nation in the new global context. In twentieth century Korea, the conception of religion was manifest in the representation of the so-called world religions such as Buddhism and Christianity, which were largely re-imagined as resisting colonialism and communism as well as contributing to the integration and democratization of the nation-state. The phenomenal clout and growth of Korea’s mainstream religions can be traced to an established twofold understanding that religion is distinctive, normal, and versatile, while indigenous traditions and new religious groups are abnormal, regressive, and even harmful. I have found that, since the late 1980s, a negative re-formation of religion has been widespread in the public sphere of South Korea, with a growing concern that religion may harbor a parochial attitude against the nation’s new strategies of development. Religion has been increasingly signified as antisocial, conflictual, and sectarian in newly globalized South Korea, because structuralized religious power, in particular that of Protestantism, gets in the way of autonomous evolvement of the secular societal institutions. As such, I conclude by suggesting that the definition of religion was multiply appropriated by the differences in local particularization in contemporary global society. Insofar as religion is regarded as incompatible with the changed location of the national society in the new global society, the semantics assigned to what is called religion continues to be degraded in contemporary South Korea.

This dissertation investigates the mechanisms underlying pattern separation, using rodent models and behavioural tasks that assess the use of representations for similar stimuli. Pattern separation is a theoretical mechanism involving the transformation of inputs into output representations that are less correlated to each other. Because of this orthogonalizing process, similar experiences are stored as discrete non-overlapping representations. Studying pattern separation emphasizes the important but often overlooked fact that successful memory involves more than just remembering events over a period of time, but also differentiating between similar memories. Through a series of experiments this dissertation adds support to the literature that the dentate gyrus (DG) subregion of the hippocampus is important for pattern separation when encoding spatial and contextual inputs. Using the Spontaneous Location Recognition (SLR) task it is shown the brain-derived neurotrophic factor (BDNF) can improve performance by acting via N-methyl-D-aspartate (NMDA) glutamate receptors in the DG and adult-born hippocampal neurons. Manipulating the level of neurogenesis by inhibiting Wnt signalling or by administering acyl-ghrelin systemically is shown to impair and enhance performance on SLR, respectively. Using a novel exposure paradigm in combination with SLR, it is demonstrated for the first time that the relationship between pattern separation and neurogenesis may be reciprocal, such that inhibiting neurogenesis impairs pattern separation, enhancing neurogenesis improves pattern separation, and performing pattern separation enhances the production or survival of adult-born hippocampal neurons. Finally, it is shown that the $TgTau^{P301L}$ mouse model of dementia exhibits spatial and object recognition memory impairments once aged, recapitulating a dementia-like phenotype. Understanding the mechanisms that contribute to effective pattern separation may help elucidate the processes underlying the memory impairment experienced by AD patients. This dissertation concludes with a critical discussion about whether pattern separation can be studied using behavioural paradigms.

Hydrogen isotope separation systems using palladium (Pd) are currently being designed for both reactor designs with the aim of separating and purifying the reactor exhaust products which contain valuable unspent hydrogen isotopes. Hydrogen isotope exchange in Pd offers an efficient, ambient condition process that can produce pure isotopic species in a process far simpler and less costly than the current state of the art cryogenic distillation processes. The method is applicable whether separating hydrogen (protium), deuterium or tritium and any combination of these. If practical fusion devices are ever to be realised it is essential to produce an economical and efficient fuel cycle capable of separating and purifying hydrogen isotopes. Hydrogen isotope exchange in Pd is also of interest to the waste separation and purification industries, in particular those using hydrogen separation membranes which used Pd and Pd-alloy membranes. Understanding hydrogen isotope exchange, with particular regard to the formation of the intermediate (and often unwanted) hydrogen deuteride (HD), will aid significantly in future designs of hydrogen isotope separation systems. Novel hydrogen isotope exchange experiments involving hydrogen and deuterium at a number of temperatures (208 K, 293 K and 373 K) and pressures (1.3 bar – 8 bar) not yet explored are presented in this thesis. The experiments were carried out on a unique piece of laboratory apparatus provided to and further developed at the University of Bath. Alongside experimentation, a novel comprehensive multidimensional multi-physics model has been created to analyse the experimental data obtained using the new apparatus and elucidate the kinetics and mechanisms of the reactions occurring between hydrogen isotopic species and Pd during hydrogen isotope exchange based on Langmuir-Hinshelwood surface reaction mechanism. The surface reaction rates, kinetic rate constants and heat effects have been examined in detail, and in tandem, for the first time.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The pre-ictal epileptiform discharges can hardly be distinguished from the scalp Electroencephalogram (EEG). However, detecting them from the intracranial EEG is much easier. On the other hand, the drawback of using intracranial EEG is the invasive insertion of electrodes into the brain's tissue. Furthermore, for recording these signals patients have to be in hospital under anaesthesia. Conversely, scalp EEG can be recorded easily from normal people as well as patient awaiting surgery under much simpler circumstances. In this work the focus is on extraction of pre-ictal epileptiform discharges from scalp EEG by developing a suitable blind source separation (BSS) algorithm. The first proposed method is based on creating a template from intracranial data, which is then used in the form of a constraint in a BSS algorithm. To generate a suitable template, the segments during which the brain discharges are labelled are used to generate the necessary templates. Approximate entropy (ApEn) is used for detecting these segments using chaoticity measurement. Constrained BSS using independent component analysis (ICA) is then applied to the scalp data to extract the desired source and to evaluate its effect on scalp electrodes. The effectiveness of such a constrained approach has been demonstrated by comparing its outcome with that of the unconstrained method. Such a BSS model can be later directly used to separate the desired components from the scalp EEG only. Exploiting sparsity is known to be very beneficial in BSS. Even if data is not sparse in its current domain, it can be modelled as sparse linear combinations of atoms of a chosen dictionary. This brings up the idea of having a dictionary of the waveforms for almost all possible epileptic discharges. This is a generalisation of the previous method by increasing the number of template from one template to a number of them. The suitable combination of atoms which would best approximate the source of interest are determined. This forms the basis of the second part of the work. The results of applying this method have been compared with that of the conventional BSS. In the final part of the work, the dictionary is partly pre-specified based on chirplet modelling of various kinds of real epileptic discharges, and partly learned using a dictionary learning algorithm. The learned part is added to account for other sources which are are present in the EEG as well as the desired epileptic discharges. The dictionary which includes a fixed and a variable (i.e. learned) part, is incorporated into a source separation framework to extract the closest source to the source of interest from the mixtures. Experiments on synthetic mixtures of real data consisting of epileptic discharges, and on real scalp recordings are used to evaluate the proposed methods, and the results are compared with those of traditional BSS algorithms. In addition, the importance and significance of the method has been tested for a number of cases to validate it for clinical purposes. The detection rate of the proposed method is compared to the clinician's scorings from scalp EEG, which shows a significant improvement. Applying the proposed method helps reduce the number of invasive brain insertions for recording purposes prior to surgery.

Problemformulering och Syfte: Ämnet som huvudsakligen har undersökts i studien är kommunikation i online communities, digitala grupper på internet. Problemet som vi stött på och avgränsade oss till under detta ämne var sexism inom digital kommunikation. Utifrån ett medie- och kommunikationsvetenskapligt perspektiv var studiens syfte att observera på hur tonaliteten kring samtalet om aktier och privatekonomi utspelat sig i en kvinnlig respektive en könsblandad facebookgrupp. Utifrån resultaten och med utgångspunkt i feministisk teori, praxisgemenskaper och social marginalisering har vi dragit slutsatser om huruvida tonaliteten i grupperna kan ha påverkat kvinnors intresse för aktier och privatekonomi. Huvudresultat: Ur ett medie- och kommunikationsvetenskapligt perspektiv har vi genomfört kvantitativa innehållsanalyser vilket gav ett resultat som visar att den könsblandade facebookgruppen hade en mindre uppmuntrande tonalitet jämfört med den kvinnliga. Det visar sig också att den könsblandade gruppen är mansdominerade och har skapat en effekt av separatism där kvinnor väljer att avlägsna sig till andra forum där de får mer utrymme att vara en del av samtalet. Metod: För att kunna besvara syfte och frågeställningar har en kvantitativ innehållsanalys genomförts genom datainsamling från totalt 252 facebookinlägg med tillhörandekommentarer. Detta gjordes med hjälp av ett kodschema som behandlade 93 variabler.