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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.
291

Grandeurs cinématiques et mesures locales et de champs dans l'intéraction homme - structure

Rus, Mariana 27 November 2010 (has links) (PDF)
La thématique de la thèse est très vaste. Sont présentées les grandeurs cinématiques locales ou régionales qui agissent sur le corps humain. La deuxième partie de la thèse décrit les méthodes optiques, par lesquelles on peut mesurer les vibrations produites par les machines-outils sur le système humain main-bras au cours de l'activité au travail. Dans la troisième partie sont donnés les effets négatifs des vibrations qui se produisent sur le système humain main-bras pendant l'exposition aux vibrations. La quatrième partie de cette thèse contient la base théorique des techniques optiques utilisées pour mesurer les vibrations. Le chapitre cinq présente la méthodologie d'expérimentation pour mesurer les vibrations. Les résultats des mesures sont indiqués dans le sixième chapitre de la thèse. Dans le chapitre sept on présente la modélisation mécanique et mathématique du système humain main-bras avec trois degrés de liberté et le dernier chapitre contient les conclusions finales.
292

Art, culture, and urban revitalization: a case study of The Edge Artist Village

Besner, Barbara 07 April 2010 (has links)
This research explores culture-led regeneration; specifically, how and why small, community-based culture-led regeneration projects potentially affect their respective communities. Methodology is founded on an in-depth case study of The Edge Artist Village in Winnipeg, supported by a literature review, quantitative research examining property values, and archival research. The practicum shows that The Edge Artist Village has had a tremendous impact on the community of North Main Street. While various stakeholders interpreted The Edge‘s impact in different ways, perceptions of safety in the community have improved, and long vacant buildings in the neighbourhood are finding new tenants. This study makes recommendations as to how planners can potentially play a role in encouraging culture-led regeneration projects such as The Edge Artist Village, and suggests ways in which private developers and municipal government can collaborate more effectively to support their communities.
293

Small Molecule Activation and Transformation using Aluminum-based Frustrated Lewis Pairs

Menard, Gabriel 09 August 2013 (has links)
While hundreds of papers have been published on frustrated Lewis pairs (FLPs) – the combination of bulky Lewis acids and bases which cannot form adducts – few of these use aluminum-based Lewis acids. The research outlined in this thesis expands the small molecule activation chemistry of FLPs to include Al.Combinations of bulky phosphines and AlX3 (X = halide or C6F5) with CO2 leads to the rapid activation to form the complexes R3P(CO2)(AlX3)2 (R = otol, Mes). Subsequent treatment with ammonia borane (AB) results in the rapid reduction of the CO2 fragment to methanol after water quench. Subsequent reactivity studies have established that AB adducts of AlX3, which react with CO2, are key intermediates in this chemistry. Further studies with Mes3P(CO2)(AlX3)2 revealed that these can reduce exogenous CO2 to CO, along with the generation of Mes3P(C(OAlX2)2O)(AlX3) and [Mes3PX][AlX4]. Detailed experimental and theoretical mechanistic investigations outline a possible mechanism involving direct CO2 insertion into free AlX3, followed by nucleophilic attack by PMes3 resulting in the expulsion of CO. Reactions with olefins were also investigated. While addition products of the type R3P(CH2CH2)AlX3 could be obtained with ethylene, C–H bond activation occurred with bulkier olefins. The resulting allyl species underwent subsequent C–C bond forming reactions with other olefins or CO2. Hydrogen was also activated using PR3/AlX3 FLPs to form species of the general formula, [R3PH][(H)(AlX3)2] (X = I, C6F5). These were found to reduce unactivated olefins, generating the redistributed products [R3PH][AlX4] and RAlX2 (R = alkyl). Attempts to circumvent this redistribution and favour alkyl protonation, thus generating a catalytic hydrogenation catalyst, are also discussed. Finally, the activation of N2O was also examined. While addition products could be formed, unexpected aromatic or benzylic C–H bond activation chemistry occurred in the presence of excess Al. A radical reaction pathway is proposed
294

Bifunctional Systems in the Chemistry of Frustrated Lewis Pairs

Zhao, Xiaoxi 08 January 2013 (has links)
Three classes of bifunctional compounds related to frustrated Lewis pair chemistry were studied. The first class, alkynyl-linked phosphonium borates, was strategically synthesized and the corresponding neutral alkynyl-linked phosphine boranes generated in solution. They were reacted with THF, alkenes and alkynes to undergo either ring-opening or multiple bond addition reactions, giving rise to zwitterionic macrocycles. In two select alkynyl-linked phosphonium borates, thermolysis resulted in unique rearrangements transforming the phosphino- and boryl-substituted alkynyl moieties into C4 chains. The alkynyl-linked phosphine boranes were further demonstrated to coordinate as η3-BCC ligands in Ni(0) complexes. The rigid nature of the coordination was confirmed by dimerization without cleavage of the Ni–B interaction upon the addition of acetonitrile or carbon monoxide. Moreover, reactions with Al-, Zn- and B-based Lewis acids prompted hydride transfer within the alkynyl-linked phosphonium borate and interesting functional group transfer reactions. The second class of the bifunctional systems, a series of gem-substituted bis-boranes, was subjected to reactions with tBu3P and CO2. The O-linked bis-borane was shown to coordinate the phosphino-carboxylate moiety with one B, while the methylene-linked bis-boranes were demonstrated to chelate the carboxyl group. The third bifunctional system class, vinyl-group tethered boranes, was examined to elucidate the mechanism of the frustrated Lewis pair addition reaction to olefins. Using a bis(pentafluorophenyl)alkylborane, the close proximity of the olefinic protons and the ortho-fluorine nuclei were evident by both NOE measurements and DFT calculations. Moreover, its reactions with phosphine bases suggested that an initial interaction between the highly electrophilic borane and the olefinic fragment precedes such frustrated Lewis pair addition reaction. Furthermore, a bis(pentafluorophenyl)alkoxyborane was synthesized and reacted with P-, N-, C- and H-based nucleophiles, demonstrating the wide range of Lewis bases that can be applied in olefin addition reactions with complementary regioselectivity.
295

Small Molecule Activation and Transformation using Aluminum-based Frustrated Lewis Pairs

Menard, Gabriel 09 August 2013 (has links)
While hundreds of papers have been published on frustrated Lewis pairs (FLPs) – the combination of bulky Lewis acids and bases which cannot form adducts – few of these use aluminum-based Lewis acids. The research outlined in this thesis expands the small molecule activation chemistry of FLPs to include Al.Combinations of bulky phosphines and AlX3 (X = halide or C6F5) with CO2 leads to the rapid activation to form the complexes R3P(CO2)(AlX3)2 (R = otol, Mes). Subsequent treatment with ammonia borane (AB) results in the rapid reduction of the CO2 fragment to methanol after water quench. Subsequent reactivity studies have established that AB adducts of AlX3, which react with CO2, are key intermediates in this chemistry. Further studies with Mes3P(CO2)(AlX3)2 revealed that these can reduce exogenous CO2 to CO, along with the generation of Mes3P(C(OAlX2)2O)(AlX3) and [Mes3PX][AlX4]. Detailed experimental and theoretical mechanistic investigations outline a possible mechanism involving direct CO2 insertion into free AlX3, followed by nucleophilic attack by PMes3 resulting in the expulsion of CO. Reactions with olefins were also investigated. While addition products of the type R3P(CH2CH2)AlX3 could be obtained with ethylene, C–H bond activation occurred with bulkier olefins. The resulting allyl species underwent subsequent C–C bond forming reactions with other olefins or CO2. Hydrogen was also activated using PR3/AlX3 FLPs to form species of the general formula, [R3PH][(H)(AlX3)2] (X = I, C6F5). These were found to reduce unactivated olefins, generating the redistributed products [R3PH][AlX4] and RAlX2 (R = alkyl). Attempts to circumvent this redistribution and favour alkyl protonation, thus generating a catalytic hydrogenation catalyst, are also discussed. Finally, the activation of N2O was also examined. While addition products could be formed, unexpected aromatic or benzylic C–H bond activation chemistry occurred in the presence of excess Al. A radical reaction pathway is proposed
296

Redeveloping the Avenues

Micacchi, Robert 15 December 2010 (has links)
The goal of this thesis is to investigate and propose housing that increases density while offering a better quality of life for citizens inhabiting Toronto’s Avenues. This thesis compares three different building prototypes, all of varying scales and typological characteristics. The viability of each prototype is discussed with regards to the current economic and regulatory conditions within the city, as well as the varying quality of life that each prototype creates.
297

Schiff's bases as solvent extraction reagents

Richardson, Ralph Alan January 1972 (has links)
The solvent extraction of metal chelates has been used for a long time for separation and determination of metal ions. The first quantitative description of the extraction process was, however, not made until 1941 when Kolthoff and Sandell compared experimental data with theoretical predictions for the extraction of metal dithizonates. They found that the theory they proposed was valid under wide experimental conditions. However, the systems used by Kolthoff and Sandell were simple ones and hence relatively simple theory was used to successfully explain their behaviour. In practice solvent extraction systems are complicated by other factors, e.g. hydrolysis, polymerisation and complex formation in the aqueous phase. It has subsequently become apparent that such factors have an important influence on the solvent extraction of chelates. Several authors have published reports since 1941 on the theory of solvent extraction of metal chelates which take these factors into account. In particular two publications by Irving, Rossotti and Williams and Stary (chapter 3) should be noted for their comprehensive treatment of the subject. The influence of these factors will be discussed in the following sections.
298

Aspects of the chemistry of titanium dioxide in fused salt solvents

Udy, David John January 1973 (has links)
An investigation into the chemistry of solutions of titanium dioxide in fused alkali metal borates has been made, with the emphasis on the ability of the alkali borate melts to dissolve TiO2 and subsequently crystallize TiO2 and/or complex alkali metal titanates. The preparation and properties of potassium titanates with K2O/TiO2 mol ratio ≤1 has been studied. In addition the thermal decomposition of potassium hexafluorotitanate monohydrate (reported to yield potassium tetratitanate) has been investigated. The decomposition product has been identified as an oxyfluorotitanate. The compounds crystallized on slow cooling of alkali borate + TiO2 melts have been identified. The titanium containing product(s) have been correlated with the concentration of borate groups containing non-bridging oxygens, which depends on the alkali metal cation. Phase diagrams for the M2O.B2O3 + TiO2 (M = Na, K) systems have been obtained. Mass transport in M2O.2B2O3 + TiO2 (M = Li, Na, K) systems has been studied, via measurements of electrical conductivity, as a function of temperature and TiO2 concentration. Additional information on the alkali borate melts has been obtained from measurements of the optical basicity of M2O + B2O3 (M = Li, Na, K, Rb, Cs) glasses, using Pb(II) as probe ion. The results of these measurements have confirmed that the nature of the alkali metal cation significantly affects the basicity of fused alkali borate solvents. Extraction of TiO2 from ilmenite and titaniferous slag, using selected low-basicity alkali borate solvents has been attempted. The results indicate that TiO2 may be separated from ilmenite in essentially a one-step process.
299

Schiff's bases as solvent extraction reagents

Richardson, Ralph Alan January 1972 (has links)
The solvent extraction of metal chelates has been used for a long time for separation and determination of metal ions. The first quantitative description of the extraction process was, however, not made until 1941 when Kolthoff and Sandell compared experimental data with theoretical predictions for the extraction of metal dithizonates. They found that the theory they proposed was valid under wide experimental conditions. However, the systems used by Kolthoff and Sandell were simple ones and hence relatively simple theory was used to successfully explain their behaviour. In practice solvent extraction systems are complicated by other factors, e.g. hydrolysis, polymerisation and complex formation in the aqueous phase. It has subsequently become apparent that such factors have an important influence on the solvent extraction of chelates. Several authors have published reports since 1941 on the theory of solvent extraction of metal chelates which take these factors into account. In particular two publications by Irving, Rossotti and Williams and Stary (chapter 3) should be noted for their comprehensive treatment of the subject. The influence of these factors will be discussed in the following sections.
300

Aspects of the chemistry of titanium dioxide in fused salt solvents

Udy, David John January 1973 (has links)
An investigation into the chemistry of solutions of titanium dioxide in fused alkali metal borates has been made, with the emphasis on the ability of the alkali borate melts to dissolve TiO2 and subsequently crystallize TiO2 and/or complex alkali metal titanates. The preparation and properties of potassium titanates with K2O/TiO2 mol ratio ≤1 has been studied. In addition the thermal decomposition of potassium hexafluorotitanate monohydrate (reported to yield potassium tetratitanate) has been investigated. The decomposition product has been identified as an oxyfluorotitanate. The compounds crystallized on slow cooling of alkali borate + TiO2 melts have been identified. The titanium containing product(s) have been correlated with the concentration of borate groups containing non-bridging oxygens, which depends on the alkali metal cation. Phase diagrams for the M2O.B2O3 + TiO2 (M = Na, K) systems have been obtained. Mass transport in M2O.2B2O3 + TiO2 (M = Li, Na, K) systems has been studied, via measurements of electrical conductivity, as a function of temperature and TiO2 concentration. Additional information on the alkali borate melts has been obtained from measurements of the optical basicity of M2O + B2O3 (M = Li, Na, K, Rb, Cs) glasses, using Pb(II) as probe ion. The results of these measurements have confirmed that the nature of the alkali metal cation significantly affects the basicity of fused alkali borate solvents. Extraction of TiO2 from ilmenite and titaniferous slag, using selected low-basicity alkali borate solvents has been attempted. The results indicate that TiO2 may be separated from ilmenite in essentially a one-step process.

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