Controlled source electromagnetic (CSEM) geophysics has been used with a fair amount of success in near surface hydrogeological studies. Recently, these investigations have been conducted frequently in human impacted field sites containing cultural conductors such as metal fences and buried pipes. Cultural noise adds an element of complexity to the geological interpretation of this type of data. This research investigates the influence of mutual induction between two buried targets in a CSEM experiment. In particular, it looks at the mutual coupling between a buried cultural conductor and a geological heterogeneity. We attempt to isolate the Hz field induced by tertiary currents in targets caused by mutual coupling. This is achieved with a Texas A&M 3D CSEM finite element code, which calculates the secondary Hz fields emanating from a target buried in a halfspace. Buried geological targets and cultural conductors are modeled as volumetric slabs embedded in a halfspace. A series of models have been simulated to study the effect of varying parameters such as target conductivity, transmitter location and shape of a target on the mutual inductance. In each case, the secondary Hz field is calculated for a model with two slabs, and two models with individual slabs. The mutual coupling is calculated by removing the secondary fields from the individual slab models from the response of a two slab model. The calculations of mutual inductance from a variety of such models suggests a complicated interaction of EM fields between the two targets. However, we can explain most of these complexities by adapting a simple approach to Maxwell’s equations. Although the tertiary Hz field is complicated, it may be useful in the characterization and delineation of electrical heterogeneities in the subsurface, which can then be related to geological features such as fractures or joints. It is seen that the most important factor affecting the mutual coupling is the host conductivity. The results have also shown that mutual coupling is very sensitive to transmitter (TX) location, especially when the TX is positioned near one of the targets.

<p>Controlled radical polymerization has proven to be a viableroute to obtain polymers with narrow polydispersities (PDI's)and controlled molecular weights under simple reactionconditions. It also offers control over the chain-]ends of thesynthesized polymer. Atom transfer radical polymerization(ATRP) is the most studied and utilized of these techniques. Inthis study ATRP has been utilized as a tool to obtain differentcomplex macromolecular structures.</p><p>In order to elaborate a system for which a multitude ofchains can polymerize in a controlled manner and in closeproximity to one another, a multifunctional initiator based onpoly(3-ethyl-3-(hydroxymethyl)oxetane was synthesized. Themacroinitiator was used to initiate ATRP of methyl acrylate(MA). The resulting dendritic-]linear copolymer hybrids hadcontrolled molecular weights and low PDI's. Essentially thesame system was used for the grafting of MA from a solidsubstrate, cellulose. A filter paper was used as cellulosesubstrate and the hydroxyl groups on the cellulose weremodified into bromo-]ester groups, known to initiate ATRP.Subsequent grafting of MA by ATRP on the cellulose made thesurface hydrophobic. The amount of polymer that was attached tothe cellulose could be tailored. In order to control that thesurface polymerization was -eliving-f and hence that thechain-]end functionality was intact, a second layer of ahydrophilic monomer, 2-hydroxyethyl methacrylate, was graftedonto the PMA- grafted cellulose. This dramatically changed thehydrophilicity of the cellulose.</p><p>Dendronized polymers of generation one, two and three weresynthesized by ATRP of acrylic macromonomers based on2,2-bis(hydroxymethyl)propionic acid. In the macromonomerroute, macromonomers of each generation were polymerized byATRP. The polymerizations resulted in polymers with low PDI's.The kinetics of the reactions were investigated, and thepolymerizations followed first-order kinetics when ethyl2-bromopropionate was used as the initiator. In the-egraft-]onto-f route dendrons were divergently attached to adendronized polymer of generation one, that had been obtainedby ATRP.</p>

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves [328]-333).

No description available.

Controlled radical polymerization (CRP) has emerged as a powerful method of creating polymers with tailored molecular architectures under mild reaction conditions. However, production of these polymers efficiently at an industrial scale will likely require them to be synthesized in the dispersed phase. Three types of CRP are explored, Atom Transfer Radical Polymerization (ATRP), Nitroxide Mediated Polymerization (NMP) and Catalytic Chain Transfer (CCT) to elucidate the intricacies of creating these novel polymer colloids. Compartmentalization in an ATRP dispersed phase system is explored theoretically to understand the effects of particle size and catalyst concentration on the polymerization. The results suggest that there is an optimal range of particle sizes where the rate of polymerization is greater than that in an equivalent bulk system while maintaining both a lower PDI (polydispersity index) and higher livingness. All three factors are desirable in ATRP but generally cannot be achieved simultaneously in bulk. Compartmentalization manifests itself differently in CCT dispersed phase systems, where the segregation of the CCT agents into different polymer particles leads to multimodal molecular weight distributions. Control over the particle size is notoriously difficult for nitroxide mediated polymerization, as it is challenging to decouple an increase in the particle size with an increase in target molecular weight using a two stage emulsion polymerization approach. This often leads to colloidally unstable latexes for low molecular weight, high solids conditions which are the result of superswelling. We offer several strategies to minimize this problem and create colloidally stable, high solids, n-butyl acrylate latexes by NMP with moderate to high molecular weight targets (>70 kg/mol). Using this synergy between target molecular weight and particle size, high solids (>40 wt.%), high molecular weight (<200 kg/mol) microemulsions (~20 nm) of methyl methacrylate-co-styrene were prepared. Finally, the monomer type and nucleation mechanisms also play a role in determining the particle size distribution in NMP emulsion systems. Using n-butyl methacrylate in emulsion with surfactant concentrations above the critical micelle concentration yields latexes with bimodal particle size distributions. However a surfactant-free approach allows monomodal latexes to be created. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-12-03 13:30:15.346

No description available.

Cellular metals are a relatively new class of engineering materials that can be fabricated with either a random or controlled cellular structure. A controlled cellular structure allows the precise control of the pore geometry and hence subsequent material properties that can be important for some applications such as orthopathic implants. Recently the interest in using magnesium (Mg) as a biodegradable implant in the body has been growing rapidly. However, current methods for fabricating cellular magnesium typically results in a random arrangement of the cellular structure. A novel processing method is developed for the preparation of cellular metals with controlled open-cellular architectures. In particular, this process has been developed for magnesium due to the difficulties associated with powder processing. The fabrication routine utilises a multistage inverse templating technique implemented with assistance of a rapid prototyping (RP) technique. Rapid prototyped polymer performs of desired architectures were infiltrated using a specially designed slurry of NaCl. Removal of the polymer resulted in an accurate negative NaCl template that could be infiltrated with liquid metal using low pressure die casting. Subsequently, the template material is removed, resulting in a controlled cellular structure within Mg. Prior to metal infiltration, the compressive modulus, strength, grain growth and microstructure of the NaCl structure with and without sintering was examined using compression testing and electron backscattered diffraction (EBSD). For the EBSD analyses a new sample preparation technique for the micro porous samples had to be developed for use in the scanning electron microscopy (SEM). The NaCl and the cellular metal were evaluated using SEM and micro-computed tomography (µ-CT). Furthermore, the relationship between the original CAD model and the final NaCl pore morphology was investigated were the surfaces of the RP scaffold and the NaCl template were analysed and compared to the as-cast Mg.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Toronto, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 148-150).