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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Computational electromagnetic modeling for wireless channel characterization

Lim, Chan-Ping Edwin 22 September 2006 (has links)
No description available.

Microstructural Characterization of Al-Fe Intermetallics in Aluminum Alloy 7xxx during Controlled Solidification

Nagaraj, Kishor January 2018 (has links)
Aluminum 7xxx series alloys have been a major focus for lightweight automotive structural components to achieve the targeted weight reductions by auto industries and, in turn, to increase the vehicle fuel efficiency. AA 7xxx series wrought alloy components have been widely used by the aerospace and automotive industries for many decades due to their low density and high strength. However, although near net shape casting of these alloys has many benefits versus wrought alloys; this processing route has been a challenge for the researchers and the auto industry because of limitations due to castability issues such as like hot tearing and die soldering. One possible mitigation strategy involves the addition of iron (Fe) as one of the major alloying element and then subsequently optimizing the alloy chemistry and solidification parameters in terms of die soldering. The objective of this thesis is to determine the microstructural evolution of any Al-Fe intermetallic phases with respect to cooling rate during solidification for a range of AA 7xxx series alloy compositions. Fe was added at three different levels in a total of nine alloy composition developed from a Taguchi experimental matrix based on the interaction of three composition levels for four alloying elements. The alloys were cast using a custom built casting rig while the cooling rates were measured along the length of a directionally solidifying sample. The thermocouple measurements were analyzed to determine the velocity of the solid/liquid interface, overall cooling rate and thermal arrest points for later correlation to variations in the microstructural development of any Al-Fe intermetallic phase particles present in the experimental alloys. Metallographic samples were taken at locations with iv known cooling rates to determine the resultant microstructure. Scanning electron microscopy (SEM) and energy dispersive X-Ray spectroscopy (EDS) were performed to obtain elemental analyses of the Al-Fe intermetallic phases for present in the samples. The Fe maps obtained by EDS were processed and analyzed using Image-J software to determine the size distribution and area fraction of the Al-Fe intermetallic phases as a function of alloy composition and solidification rates. Also, a regression analysis was used to develop a statistical model to predict the variation of intermetallic particle size and area fraction of the Al-Fe intermetallic phases as a function of alloy composition and cooling rate. Based on the experimental investigation and analysis of the nine Al 7xxx-Fe alloys the results can be summarized as follows: (1) Cooling rate has a strong influence on the chemistry and morphology of the Fe intermetallic particles: It was determined that the dominant intermetallic species changes from the equilibrium Al3Fe to the metastable Al6Fe alloys for cooling rates in excess of approximately10 °C/s. (2) Alloy cooling rate does significantly affect the area fraction of the Fe intermetallic particles. It was determined that the morphology of the Al-Fe particles transitions from a relatively low aspect ratio particles to a high aspect, needle-like particles for cooling rates less than approximately 10 °C/s. (3) Alloying elements such as Zn, Cu, and Mg does not influence the Fe intermetallic chemistry and the area fraction of the intermetallics. / Thesis / Master of Applied Science (MASc)

Static and Dynamic Characterization of Ionic Polymer Metal Composites - 'Artificial Muscles'

Mudigonda, Ashwin 18 April 2006 (has links)
No description available.

Advanced Physical and Chemical Characterization of Stormwater Sediments

Li, Helena 08 1900 (has links)
<p> This work focuses on the advanced physical analysis of stormwater sediments using laser diffraction particle size analyzer and scanning electron microscope and chemical characterization using neutron activation analysis. Since previous studies of sediments from stormwater ponds in the Greater Toronto Area indicated a marginal-to-significant level of pollution by most of the regulated heavy metals, the characteristics of the storm water sediment samples obtained in this study were compared to the sediment quality guidelines of the Ontario Ministry of the Environment. The images from optical microscope showed that the particles in the dried sediment were irregular, and the sizes of each particle vary greatly. Using scanning electron microscope, it was shown that two different structures of particles were present in the storm water sediment. It was also observed that the main compositions (above 1000ppm) of the dried sediment included, in descending order of concentration, Ca >AI> Fe> K > Mg > Na >Ti > Mn. The trace compositions (below 1000ppm) included, also in descending order of concentration, Cl > Zn > Ba > Sr > Cr > V > La > Nd > As > Br > Co > Sc > Th > Sb > Sm > Eu. The concentrations of regulated elements such as Cr, Fe Zn, As and Mn were above the lowest effect level, suggesting that treatment of stormwater sediment may be necessary. A preliminary stormwater sediment treatment experiment using thermal plasma technology was therefore conducted. After the thermal plasma treatment, the percentage of total organic carbon decreased and eight gas compounds including CO, COz, NO, NOz, NOx, SOz, H2S and CxHy emitted during the process. Enrichments of Mg, Cl and Na were observed in the treated sludge while the concentrations of K and Ca decreased. The potential of thermal plasma technology for the treatment of contaminated stormwater sediment was demonstrated. </p> / Thesis / Master of Applied Science (MASc)

Characterization of some Cu-Al-X alloys

Iqbal, J. January 1985 (has links)
No description available.

Block copolymers : Synthesis, characterization and properties

Parr, K. J. January 1986 (has links)
No description available.

Caractérisation moléculaire de la rétine embryonnaire et larvaire de la lamproie Petromyzon marinus / Molecular characterization in the developing eye of the lamprey Petromyzon marinus

Rocancourt, Claire 09 December 2010 (has links)
La lamproie présente un mode de développement de la rétine très particulier parmi les vertébrés. Elle implique deux processus distincts. Le premier conduit à la formation précoce d’une rétine centrale, qui présente des indications de différenciation dès les stades prolarvaires et ne contient que trois types cellulaires différenciés (photorécepteurs, cellules bipolaires et cellules ganglionnaires). Dans un deuxième temps, au cours des stades larvaires, une rétine périphérique, dont dérive l’essentiel de la rétine adulte, se développe à la marge de la rétine centrale. Elle croît de façon importante jusqu’à la métamorphose, au cours de laquelle la différenciation des différents types cellulaires s’effectue. J’ai engagé une analyse des programmes génétiques qui contrôlent ces processus en étudiant les profils d’expression de trois paralogues de la famille Otx (PmOtxA/B/C), ainsi que des gènes PmFoxG1, PmPax6, PmVax2 et PmSix3 au cours du développement précoce de l’oeil, aux stades prolarvaires. L’analyse de l’expression des gènes PmPax6, PmOtxB et PmOtxC a également été étudiée au cours des stades larvaires et dans la rétine différenciée post-métamorphique. Enfin des traitements pharmacologiques visant à inhiber l’activité du récepteur au FGF ont été effectués, en vue d’évaluer le rôle des signalisations médiées par ce récepteur aux stades prolarvaires. Les résultats mettent en évidence un patron de régionalisation de la cupule optique très semblable entre la lamproie et les gnathostomes. Les traitements pharmacologiques suggèrent également des mécanismes de spécification du pédoncule optique conservés à l’échelle des vertébrés. Au cours de la différenciation de la rétine centrale et de la formation de la rétine périphérique, les gènes PmPax6 et PmOtxB/C présentent également une dynamique d’expression globalement conservée, avec quelques différences. Ces analyses fournissent la première caractérisation des programmes génétiques contrôlant la formation de l’oeil chez la lamproie. A la suite de ces analyses, la formation de la rétine centrale apparaît comme un processus accessible aux caractérisations moléculaires et aux analyses fonctionnelles et d’un intérêt majeur à la fois pour des aspects évolutifs et mécanistiques. / The lamprey presents a very particular way of development of the retina among the vertebrates. It implies two distinct processes. The first lead to the early formation of a central retina, which presents indications of differentiation in prolarval stages and contains only three differentiated cellular types (bipolar cells, photoreceptors and ganglionar cells). Secondly, during larval stages, a peripheral retina, of which the main part of the adult retina derives, develops within the margin of the central retina. It grows in an important way until the metamorphosis, during which the differentiation of the various cellular types is carried out. I engaged an analysis of the genetic programs which control these processes by studying the expression profiles of three paralogues of the Otx family (PmOtxA/B/C), as well as PmFoxG1, PmPax6, PmVax2 and PmSix3 genes during the early development of the eye, at the stages prolarvaires. The expression analysis of PmPax6, PmOtxB and PmOtxC genes was also studied during larval stages and in the post-metamorphic differentiated retina. Finally pharmacological treatments aiming at inhibiting the activity of the FGF receptor were carried out, in order to evaluate the role of the indications mediated by this receptor at the prolarval stages. The results highlight a very similar regionalization pattern of the optical cup between the lamprey and the gnathostomes. The pharmacological treatments also suggest specification mechanisms of the optical stalk preserved at the level of vertebrate. During the differentiation of the central retina and formation of the peripheral retina, the PmPax6 genes and PmOtxB/C also present a conserved dynamic expression, with some differences. These analyzes provide the first characterization of the genetic programs controlling the formation of the eye in the lamprey. Following these analyzes, the formation of the central retina seems to be an accessible process to molecular characterizations and to functional analyzes and it is a major interest for both evolutionary and mechanistic aspects.

The synthesis and charcterization of poly [ oxy(2-methyl-1,3- phenylene) oxyisophthaloyl-b-ox y(2-methyl-1, 3-phenylene)- oxyterephthaloyl]

Onwumere, Fidelis C. 01 July 1983 (has links)
No description available.

Chemical Changes in Hydrothermal Carbon with Reaction Time

McKeogh, Brendan James 07 September 2017 (has links)
"The increasing global demands for materials and energy directly contributes to the devastating ecological, toxicological, and climate consequences currently observed. Biomass-derived energy and materials offers a sustainable option to meeting current needs and developing novel materials. Hydrothermal carbonization is a promising green platform to valorize biomass by forming Hydrochar, a carbon solid. Hydrothermal carbonization converts biomass using liquid phase water at elevated temperatures (180-350 °C), forming organic intermediates, which dehydrate and polymerize to form the solid material on time scales of several hours. Hydrochar shows promise for a wide variety of applications, including aqueous heavy-metal adsorption. The complexity of the hydrochar prevents reliable characterization, hindering a full understanding of how to optimize the material. The focus of this study was to develop spectroscopic methods better understand the material as it changes with reaction time (ex-situ). This study developed IR and Raman Spectroscopy and Mass Spectrometry (MS) methods. Hydrochars were prepared from glucose (a model for biomass) and were prepared at different reaction times between 3 and 24 hours to understand the formation of the material and how it matures under process conditions (180 °C, autogenous pressure). IR and MS identified hydroxyl and ketone functionalities and aliphatic, furanic, and aromatic moieties, and both techniques indicated decreasing hydroxyl and furan content and increasing methyl and aromatic content. The Raman spectra were consistent with aldehyde-functionalized 1- and 2-ring arenes and aldehyde-functionalized furans, and indicated increasing 2-ring arene content relative to 1-ring arenes. MS showed a significant increase in the aromatic to furan ratio, and MS confirmed the increase in 2-ring arenes relative to 1-ring arenes seen in the Raman. These spectroscopic methods are in good agreement and will allow for greater chemical information in the hydrochar, which will inform the link between material modification under process conditions and application performance."

Characterization of the Germania Spraberry unit from analog studies and cased-hole neutron log data

Olumide, Babajide Adelekan 01 November 2005 (has links)
The need for characterization of the Germania unit has emerged as a first step in the review, understanding and enhancement of the production practices applicable within the unit and the trend area in general. Petrophysical characterization of the Germania Spraberry units requires a unique approach for a number of reasons ?? limited core data, lack of modern log data and absence of directed studies within the unit. In the absence of the afore mentioned resources, an approach that will rely heavily on previous petrophysical work carried out in the neighboring ET O??Daniel unit (6.2 miles away), and normalization of the old log data prior to conventional interpretation techniques will be used. A log-based rock model has been able to guide successfully the prediction of pay and non-pay intervals within the ET O??Daniel unit, and will be useful if found applicable within the Germania unit. A novel multiple regression technique utilizing non-parametric transformations to achieve better correlations in predicting a dependent variable (permeability) from multiple independent variables (rock type, shale volume and porosity) will also be investigated in this study. A log data base includes digitized formats of gamma ray, cased hole neutron, limited resistivity and neutron/density/sonic porosity logs over a considerable wide area.

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