Spherical agglomerates of benzoic acid crystals have been successfully prepared by drowning-out crystallization in three solvent partial miscible mixtures. Benzoic acid is dissolved in ethanol, bridging liquid is added and this mixture is fed to the agitated crystallizer containing water. Fine crystals are produced by crystallization of the substance, and the crystals are agglomerated by introduction of an immiscible liquid called the bridging liquid. The concentration of solute, agitation rate, feeding rate, amount of bridging liquid and temperature are found to have a significant influence on the physico-mechanical properties of the product. The product particle characterization includes the particle size distribution, morphology and mechanical strength. Many of the solvents such as chloroform, toluene, pentane, heptane, cyclo hexane, diethyl ether and ethyl acetate were used as bridging liquids. Among the selected solvents ethyl acetate and di ethyl ether could not form the spherical agglomerates. Characteristics of the particles are changing with the bridging liquid used. Range of the operation for spherical agglomeration is very narrow and was shown that only at certain conditions the spherical agglomerates are produced. Increased amount of bridging liquid, decrease in feeding rate and temperature causes the particle size to increase. Particle morphology depends on the bridging liquid used, amount of bridging liquid and the temperature. Particles look completely spherical from the experiments where toluene is used as bridging liquid. The mechanical strength of single agglomerates has been determined by compression in a materials testing machine, using a 10N load cell. For single particle compression an approximate estimation of the true stress is presented. Compression characteristics for single agglomerates are compared with data on particle bed compression. Low elastic recovery and high compressibility of the single particles and of bed of particles reveals that the spherical agglomerates prepared in this work have a plastic behavior which is expected to be favorable for direct tabletting. Some of the stress–strain curves are J-shaped with no clear fracturing of the particles, and are well correlated by an exponential–polynomial equation. / QC 20101119

This study examines the determinants of unemployment at the municipal level and as such aims to answer what the place-specific drivers of unemployment in South African cities and towns are. The purpose has been to test the arguments that local economies and labour markets matter for local unemployment. The empirical analysis makes use of a balanced panel data set for the period 1996 to 2012 for across 234 local and metropolitan municipalities to estimate a regression model in which the level of unemployment in a particular place is determined by a range of place-specific explanatory variables. It is found that the place-specific determinants of unemployment are a higher population growth rate and dense populations that are associated with lower unemployment rates, indicating the benefits from agglomeration economies. A large informal sector is negatively associated with unemployment, which supports the sentiments expressed in the literature that without agglomeration, economic opportunities for individuals in informal employment are limited. If people in a city or town are better educated this is associated with lower levels of unemployment on average. High inequality does not necessarily cause high unemployment; however, they do coincide. A positive association between specialisation and unemployment is found. Furthermore, the mining, manufacturing, construction and trade sectors that are locally bigger than in the national economy are associated with lower unemployment. The results support the findings that a link exists between geography and labour market outcomes and therefore the need exists for convergence of the social safety net and integration with the economic opportunities at the thriving cities and towns. / MCom (Economics), North-West University, Potchefstroom Campus, 2015

This study examines the determinants of unemployment at the municipal level and as such aims to answer what the place-specific drivers of unemployment in South African cities and towns are. The purpose has been to test the arguments that local economies and labour markets matter for local unemployment. The empirical analysis makes use of a balanced panel data set for the period 1996 to 2012 for across 234 local and metropolitan municipalities to estimate a regression model in which the level of unemployment in a particular place is determined by a range of place-specific explanatory variables. It is found that the place-specific determinants of unemployment are a higher population growth rate and dense populations that are associated with lower unemployment rates, indicating the benefits from agglomeration economies. A large informal sector is negatively associated with unemployment, which supports the sentiments expressed in the literature that without agglomeration, economic opportunities for individuals in informal employment are limited. If people in a city or town are better educated this is associated with lower levels of unemployment on average. High inequality does not necessarily cause high unemployment; however, they do coincide. A positive association between specialisation and unemployment is found. Furthermore, the mining, manufacturing, construction and trade sectors that are locally bigger than in the national economy are associated with lower unemployment. The results support the findings that a link exists between geography and labour market outcomes and therefore the need exists for convergence of the social safety net and integration with the economic opportunities at the thriving cities and towns. / MCom (Economics), North-West University, Potchefstroom Campus, 2015

The term "Metal Matrix Nano-Composites (MMNCs)" broadly refers to a composite system that is based on metal or alloy substrate, combined with metallic or non-metallic nano-scale reinforcements. The main advantages of MMNCs include excellent mechanical performance, feasible to be used at elevated temperatures, good wear resistance, low creep rate, etc. In the recent past, MMNCs have been extensively studied, especially the method of fabrication as the processing of such composites is quite a challenge. Though a variety of processing methods have been explored and studied over the years, none have emerged as the optimum-processing route. The major issue that needs to be addressed is the tendency of nano-sized particles to cluster and also the challenge as to how to disperse them in the bulk melt. This work explored the feasibility of utilizing Lorentz forces to address both of these critical issues: clustering and dispersion. The work was carried out both theoretically as well as with accompanying validation experiments. The results indicate that Lorentz Forces may be viable and should be considered in the processing of MMNCs.

Depuis quelques années, les nanomatériaux sont de plus en plus utilisés dans les processus industriels. Afin de protéger la population et l'environnement des possibles conséquences lors de rejets accidentels de ces produits dans l'atmosphère, des analyses de risques ont permis d'identifier des scénarios accidentels dans le cas du transport, de la manipulation et du stockage. Parmi les cas de fuite non intentionnelle dans l'atmosphère libre, la fuite accidentelle sur un convoyeur peut générer un relargage massif de nanoparticules. Afin d’évaluer les conséquences de ce type de scénario accidentel, notre étude s’intéresse à la prédiction des propriétés du nuage de particules dispersées dans l’air, par exemple la concentration en nombre et la distribution des diamètres. La première étape de l’étude consiste à synthétiser les phénomènes physiques des nanoparticules dans l’air afin de choisir les phénomènes physiques les plus pertinants à modéliser. Les phénomènes physiques à modéliser sont la forme complexe des agglomérats, la force de traînée des agglomérats, la fragmentation des agglomérats par le fluide, la collision et l'agglomération des agglomérats. Ensuite, la modélisation des phénomènes physiques est développée dans l'outil CFD Code\_Saturne. Pour chaque phénomène physique, un cas de simulation numérique est réalisé pour vérifier le développement de la modélisation dans l'outil CFD. Une bonne comparaison des résultats CFD avec les résultats de modèle 0D de Scilab et les modèles dans la littérature est obtenue. Egalement dans notre étude, un nouveau modèle de la probabilité de collision des agglomérats est proposé. Ces nouveaux modèles sont validés par les expérimentations numériques. Ensuite, l'outil CFD développé est appliqué dans une simulation d'une fuite de canalisation de transport. La zone proche de la fuite est simulée par Code\_Saturne. Les résultats du Code\_Saturne sont utilisés comme les données entrées pour ADMS, un outil numérique de la dispersion des particules à grande échelle. Les résultats montrent que les particules sont dispersées plus de 1 km par rapport au terme source, ce qui est en accord avec la distance observée. En perspective, l'influence de plusieurs paramètres comme la vitesse du vent, les propriétés des particules comme la distribution de taille ou la concentration en agglomérats pourrait être testé. Une expérimentation de rejet des microparticules est réalisée à l'INERIS pour ensuite pouvoir étudier les rejets des nanoparticules à l'échelle laboratoire. / Since a few years, nanomaterials are more and more used in industrial process. In order to protect the population and the environment from the consequences of an accidental release into the atmosphere, the risk assessment allowed to identify the accidental scenario in transport, manipulation and storage of those products. The accidental leakage of the conveying pipe may lead to a massive release of nanoparticles. In order to evaluate the consequences of this type of accident, our study focuses on the prediction of particles properties dispersed into the air, for example the particle number concentration and the particle diameter distribution. The first step of the study consists in the analyse of physical phenomena related to nanoparticles in order to choose the most predominant physical phenomena to model. The relevant physical phenomena in the present configuration are the agglomerate complex shape, the drag force on agglomerates, the agglomerate breakage by gas, the agglomerate collision and the agglomeration. After that, the modelling of physical phenomena chosen is developed in CFD tool Code\_Saturne. For each physical phenomenon, a simulation test case is realized in order to verify the development in CFD tool. A good agreement between CFD tool Code\_Saturne and 0D tool from Scilab and model in the literature is obtained. Also in the present study, new model for the collision probability of agglomerates is proposed. This new model is validated with the numerical experiment. After that, the numerical tool developed is applied in a simulation of an accidental pipe leakage. The field near the leakage is simulated by Code\_Saturne. The results from Code\_Saturne is used as the input data for ADMS tool, a simulation tool for the particle dispersion in large scale. The results show that the particles are dispersed more than 1 km from the release source, which is in agreement with the distance observed. In perspective, the influences of different parameters as the wind field and the particle properties, on the agglomerate size and number distribution can be tested. An experiment of the microparticle jet is realized at INERIS in order to be able to assess the nanoparticle jet experiment in the laboratory scale.

Submitted by admin tede (tede@pucgoias.edu.br) on 2018-04-02T17:32:33Z No. of bitstreams: 1 DENYA PEREIRA DO NASCIMENTO.pdf: 1293394 bytes, checksum: b4851d8e33b06dbacb027be04f51e04f (MD5) / Made available in DSpace on 2018-04-02T17:32:33Z (GMT). No. of bitstreams: 1 DENYA PEREIRA DO NASCIMENTO.pdf: 1293394 bytes, checksum: b4851d8e33b06dbacb027be04f51e04f (MD5) Previous issue date: 2017-08-01 / The commercial cluster of Avenida 44 in Goiânia, located in Setor Norte Ferroviário, currently consists of hundreds of commercial galleries, shopping malls, free markets, hotels and also includes the Bus Terminal in the capital of Goiás. This area is notable for being a huge shopping center, well-endowed with infrastructure, and for this reason is considered as the second largest agglomeration of popular commerce in Brazil, both in number of activities developed and in number of visitors. This territory had another form of use and occupation in the period of construction and implantation of the capital of Goiás, it was a railroad surrounded by illegal subdivisions occupied by employees of the enterprise itself. From the second half of the twentieth century, this space began to undergo intense changes that culminated in the formation of the Commercial Cluster of Avenida 44. The present research aims to understand the urban transformations and the formation process of the Cluster and, Adopted a methodological systematization composed by bibliographical review, documentary analysis and field activities, and interviews were carried out in this last phase. It was concluded that the commercial agglomeration is characterized by concentrating fundamental attractives to the process of buying and selling, such as logistics facility, great diversity of products, quality of manufacture, affordable prices and infrastructure. It is hoped that this research will make possible the elaboration of Public Policies for Regional Development that will provide greater benefits to the users and shopkeepers of the Avenida 44 Cluster in Goiânia, Goiás. / A aglomeração comercial da Avenida 44 em Goiânia, localizada no Setor Norte Ferroviário, atualmente é composta por centenas de galerias comerciais, shoppings centers, feiras livres, hotéis e comporta também o Terminal Rodoviário da capital goiana. Este espaço chama atenção por constituir um enorme centro de compras, bem-dotado de infraestrutura, e por este motivo é considerado como a segunda maior aglomeração de comercio popular do Brasil, tanto em número de atividades desenvolvidas, como em número de visitantes. Esse território possuía outra forma de uso e ocupação no período da construção e implantação da capital goiana, tratava-se de uma Ferrovia envolta por loteamentos ilegais ocupados por funcionários do próprio empreendimento. A partir da secunda metade do século XX, este espaço começou a sofrer modificações intensas que culminaram na formação do Cluster Comercial da Avenida 44. A presente investigação que tem por objetivo compreender as transformações urbanas e o processo de formação do Cluster e, para tal, adotou uma sistematização metodológica composta por revisão bibliográfica, análise documental e atividades de campo, sendo que entrevistas foram realizadas nesta última fase. Concluiu-se que a aglomeração comercial se caracteriza por concentrar atrativos fundamentais ao processo de compra e venda, tais como facilidade logística, grande diversidade de produtos, qualidade da manufatura, preços acessíveis e infraestrutura. Espera-se que a presente investigação torne possível a elaboração de Políticas Públicas de Desenvolvimento Regional que contemplem maiores benefícios para os usuários e lojistas do Cluster da Avenida 44 em Goiânia, Goiás.

>Magister Scientiae - MSc / During the course of this study iron oxide nanoparticles, which have been researched for drug-targeted delivery, were synthesised via the co-precipitation method and characterised using various methods. This study focused on the role of relevant capping agents for the inhibition of agglomeration of the particles; chitosan, polyvinyl alcohol (PVA) and poly lactic glycolic acid (PLGA) were the capping agents of interest. The study is an assessment of the effects brought about the different capping agents used for this work. The prepared particles were then capped with the different capping agents followed by the loading of the drug curcumin. Various analytical methods were used to analyse the particles such as High resolution transmission electron microscopy (HR-TEM), Superconducting quantum interference device (SQUID), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and zeta potential. PVA, chitosan and PLGA capped SPIONS were successfully prepared and verified by FT-IR spectrometry, various sizes were prepared almost ranging the same for the successfully prepared particles verified by XRD. The resultant particles were found to be spherical with an average particles size between 13- 22 nm. From the study it was concluded that the addition of the different capping agents resulted in the reduction of the intensity of the peaks in XRD, it was also found out the presence of the capping agents did not alter the crystalline phase of the particles. From the study it was also observed that higher saturation magnetization was experienced where PVA was used as the capping agents.

Particle motion, clustering and agglomeration play an important role in natural phenomena and industrial processes. In classical computational fluid dynamics (CFD), there are three major methods which can be used to predict the flow field and consequently the behavior of particles in flow-fields: 1) direct numerical simulation (DNS) which is very expensive and time consuming, 2) large eddy simulation (LES) which resolves the large scale but not the small scale fluctuations, and 3) Reynolds-Averaged Navier-Stokes (RANS) which can only predict the mean flow. In order to make LES and RANS usable for studying the behavior of small suspended particles, we need to introduce small scale fluctuations to these models, since these small scales have a huge impact on the particle behavior. The first part of this dissertation both extends and critically examines a new method for the generation of small scale fluctuations for use with RANS simulations. This method, called the stochastic vortex structure (SVS) method, uses a series of randomly positioned and oriented vortex tubes to induce the small-scale fluctuating flow. We first use SVS in isotropic homogenous turbulence and validate the predicted flow characteristics and collision and agglomeration of particles from the SVS model with full DNS computations. The calculation speed for the induced velocity from the vortex structures is improved by about two orders of magnitude using a combination of the fast multiple method and a local Taylor series expansion. Next we turn to the problem of extension of the SVS method to more general turbulent flows. We propose an inverse method by which the initial vortex orientation can be specified to generate a specific anisotropic Reynolds stress field. The proposed method is validated for turbulence measures and colliding particle transport in comparison to DNS for turbulent jet flow. The second part of the dissertation uses DNS to examine in more detail two issues raised during developing the SVS model. The first issue concerns the effect of two-way coupling on the agglomeration of adhesive particles. The SVS model as developed to date does not account for the effect of particles on the flow-field (one-way coupling). We focused on examination of the local flow around agglomerates and the effect of agglomeration on modulation of the turbulence. The second issue examines the microphysics of turbulent agglomeration by examining breakup and collision of agglomerates in a shear flow. DNS results are reported both for one agglomerate in shear and for collision of two agglomerates, with a focus on the physics and role of the particle-induced flow field on the particle dynamics.

This thesis consists of four self-contained essays on the topic of entrepreneurship. [Essay I] uses a unique and detailed Swedish dataset to explore firm, regional, and industry determinants that stimulate spin-offs using the choice of the individuals as the level of analysis. The most important results are that the size of the region and of the local entrepreneurial culture (the relative number of SMEs) has a positive effect on the propensity of the individual to set up a new venture corroborating the results of past firm- and regional-level studies. Industrial specialization is shown to have a positive impact on spin-offs, albeit only in high-tech manufacturing and in knowledge intensive business service sectors. Moreover, using an entropy measure to disentangle unrelated and related variety, it is found that the former has a significantly negative while the latter a significantly positive effect on the propensity of the individual to start a spin-off. [Essay II] asks how localisation (MAR) and diversity (Jacobs) externalities affect opportunity-based entrepreneurship across all industry sectors in Sweden’s private economy in the period 1999-2005. MAR externalities are found to positively affect entrepreneurship across all sectors. Jacobs externalities, measured as related variety using an entropy measure, positively affect entrepreneurship in high-tech manufacturing and in knowledge intensive business services but have no significant effect on low-tech manufacturing and other services. The results suggest that previous studies that find no evidence of entrepreneurship benefiting from a diverse local market composition might be using too broad measures of variety. [Essay III] analyses how different R&D strategies of incumbent firms affect the quantity and quality of their entrepreneurial spawning. By examining entrepreneurial ventures of ex-employees of firms with different R&D strategies three things emerge: First, firms with persistent R&D investments with a general superiority in sales, exports, productivity, profitability and wages are less likely to generate entrepreneurs than firm with temporary or no R&D investments. Second, start-ups from knowledge intensive business service (KIBS) firms with persistent R&D investments have a significantly increased probability of survival.  No corresponding association between the R&D strategies of incumbents and survival of entrepreneurial spawns is found for incumbents in manufacturing sectors. Third, spin-outs from KIBS-firms are more likely to survive if they start in the same firm, indicating the importance of inherited related knowledge. The findings suggest that R&D intensive firms spur fewer entrepreneurs, but their entrepreneurial spawns tend to be of higher quality. [Essay IV] investigates how universities may affect regional entrepreneurship through the localisation decisions of entrepreneurial alumni. Empirically, a comprehensive, individual-level dataset from Sweden is used for the period 2003-2005. The results suggest that even when controlling for their spatial history, individuals have an increased propensity to set up in the region where they studied. This effect is found to substitute for both urbanisation economies and localisation economies as drivers of regional-level entrepreneurship. Thus, the analysis provides evidence on how universities affect regional economic development that complements the strong focus on spin-off activities by university researchers in previous studies. / QC20100622

This is a quantitative study aimed at analyzing the migration patterns across the fifty United States of America and the determinants thereof. This research is founded upon the theories and study of agglomeration economies and institutional factors to evaluate each state in terms of creativity and freedom. Values for creativity and institutional freedom serve as the independent variables. The dependent variable is actual state to state migration data during the 2004-2008 period from the Internal Revenue Service. Measures for education, climate, population, distance, and crime rates serve as control variables in this study. All 34 models of this study were analyzed via multivariate linear regression using the SPSS 17.0 software package. All models were highly significant with high coefficients of determination. The results show that creativity is highly significantly and positively correlated with circulatory migration flows. Economic, personal, and overall freedom were very significant predictors of migration in terms of attraction and circulation. Apart from education, all the control variables examined were significant predictors of migration flows. This study also creates a new measure of overall freedom: the FRASERMPFI, which outperformed all other independent variables. The results of this study have several implications for workers, businesses, and policy makers. It is hoped that the results of this study can serve as a reference for future economic growth and promotion of freedom in the U.S.