This study focuses on the determinants of agglomerations, natural advantages, spillovers, and transaction costs respectively, and intends to form a location choice model with those agglomerative factors. Besides, we examine the geographic concentration scope overall and by region with the data set of manufacturing industries in Taiwan in 2003. We also explore some interesting empirical results. First, the overall geographic concentration level is slightly decreasing through 1996 to 2003. Second, the plants in the South and Middle regions of Taiwan are more concentrated than those in the North region. And each region has its own specific characteristic that draws different types of industries to locate. Third, with OLS regression we find that outsourcing dependence variable applied to proximate transaction costs effect is the most significant of all and represents that transaction costs have large influence to agglomeration scope. Finally this model can be improved from some aspects of involving distance into consideration and extending to entrepreneur across countries.

The multigrid technique is one of the most effective techniques to achieve the reduction of the CPU cost for flow solvers. The multigrid strategy uses the multilevel grids which are the coarsening subsets of fine grid. An explicit solver rapidly reduces the high frequency errors on the computational grids. Since high frequency errors on coarse grids correspond to low frequency errors on fine grids, cycling through the coarse grid levels rapidly reduces the errors ranging from high-to-low frequency. The aim of this study is, therefore, to accelerate SENSE3D solver developed by TUBITAK-SAGE by implementating multigrid concept. In this work, a novel grid coarsening method suitable for cell-centered hybrid/unstructured grids is developed to provide the cells with high aspect ratio. This new grid coarsening technique relies on the agglomeration of cells based on their distribution on octree data structure. Then, the multigrid strategy is implemented to the baseline flow solver. During this implementation, the flux calculation along the face loops is modified without changing cell-centered scheme. The performance of the coarsening algorithm is investigated for all grid types in two and three dimension. The grid coarsening algorithm produces well defined, nested, body fitted coarser grids with aspect ratios of one and the coarse grids have similar characteristics of Cartesian grids. Then, the multigrid flow solutions are obtained at inviscid, laminar and turbulent flows. It is shown that, the convergence accelerations are up to 14 times for inviscid flows and in a range of 4 to 110 fold for turbulent flow solutions.

Title from PDF of title page. / Document formatted into pages; contains 313 pages. / Thesis (M.S.Ch.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The characterization of fine particles is an area of immense significance to many industrial endeavors. It has been estimated that 70% of all industrial processes deal with fine particles at some point in the process. A natural phenomenon occurring in these processes is colloidal aggregation. This study examines aggregation in colloidal systems in order to characterize, examine, and control this occurrence in industrial processes. The study of particle aggregation has been broken into many different areas, such as collision mechanisms, interaction energy etc, but a complete model that integrates these different aspects has never been fully realized. A new model is required to accurately predict the aggregation behavior of colloidal particles. In this work, a new model is developed that integrates Smoluchowski kinetics, total interaction energy between particles, and stability ratios for perikinetic and orthokinetic collision mechanisms. / ABSTRACT: The total particle interaction energy necessary for the calculation of stability ratios is represented by the summation of electrostatic and van der Waals interactions. The electrostatic interactions are modeled using DLVO theory, the linear Poisson-Boltzmann equation, and a numerical solution for the non-linear Poisson-Boltzmann Equation, while the van der Waals interactions are represented by Hamaker theory. The mathematical model is solved using an adjustable discretion technique, which is tested against a specific analytic solution, and yields an assessment of the error intrinsic in the discretization method. The basis of the mathematical model is a population balance framework. The model developed in this study is general in many respects, but could be readily applied to many different aggregation systems with minor modification. / ABSTRACT: A comparison of the mathematical model with previous experiments conducted by Scott Fisher (1998) is carried out for the perikinetic and orthokinetic transport-limited aggregation regimes. The fractal nature of solid-sphere aggregates is considered when comparing the mathematical model predictions with experimental measurements. The previous experiments that are used for comparison utilized polystyrene particles ranging from 100 nm to 500 nm in initial diameter, several initial particle concentrations, and various stirring rates. Zeta potential measurements are presented in order to set the range of transport-limited aggregation. An assessment of the results of the mathematical model with the experimental results show good agreement for transport-limited aggregation within the perikinetic and orthokinetic transport-limited aggregation, with average particle sizes ranging from 100 nm to well over 2 microns. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

This dissertation expands on the economic geography literature on how and why innovation clusters spatially by taking a closer look at two correlated phenomena: regional specialization and firm clustering. While existing studies note that innovative regions are often highly specialized and highly clustered, further research is needed on the relative contributions of specialization and clustering to regional innovation. I examine these contributions by focusing on one key element of any regional innovation project: the labor market for scientific and technical professionals. The foundation for this study is a typology of regions based on regional specialization and firm clustering. I use this typology to answer one key research question: how specialization and clustering affect wages and recruitment methods in science-based industries. I create my typology using firm location data from the Photonics Buyers’ Guide, a leading trade publication in the photonics industry; I use the standardized location quotient and the average nearest neighbor distance as metrics of regional specialization and firm clustering, respectively. I investigate small firms’ labor market strategies using job search and wage data from the 2011 and 2012 SPIE salary surveys of employees in the photonics industry. I also examine how people-based and place-based policies for strengthening scientific and technical labor markets change when viewed through the lens of specialization and clustering. I selected the photonics industry as an example of a science-based industry for three reasons: its diversity of applications, its policy importance, and its unique colocation of design and manufacturing. Regional specialization and firm clustering, while correlated, do not always go hand in hand. By disentangling the effects of specialization versus clustering, this dissertation contributes to the literature on the spatial analysis of innovation. It also offers policymakers a heuristic for deciding on the importance of being known for a particular industry (regional specialization) and creating dense innovation districts (firm clusters) through preferential zoning or other mechanisms.

No description available.

This study examines the determinants of economic growth at sub-national level in South Africa, and investigates cross-locality medium-term (five-year) growth rate differentials between 354 magisterial districts. The period in question is 1998 to 2002. A dynamic panel data regression model is used that includes measures of geography (distance and natural resources) as well as recent estimates of physical and human capital. It is found that the significant determinants of local economic growth are distance from internal markets, human capital, export propensity, and the capital stock of municipalities (reflecting institutional quality and governance on local government level). Distance from international harbours, as a measure of transport costs, and urban agglomeration (or density) affects growth indirectly through its significant effect on the ability of a region to export. Overall, these results indicate that geography is important for economic growth, independent of its effects in institutions. Bearing in mind the medium-term focus of the work, no evidence of absolute convergence could be found over a five-year period, rather the tentative evidence suggests slow beta convergence. / Thesis (Ph.D. (Economics))--North-West University, Potchefstroom Campus, 2005.

Methane hydrate formation and dissociation studies from high water content (>60 vol% water) – crude oil emulsions were performed. The hydrate and emulsion system was characterized using two particle size analyzers and conductivity measurements. It was observed that hydrate formation and dissociation from water-in-oil (W/O) emulsions destabilized the emulsion, with the final emulsion formulation favoring a water continuous state following re-emulsification. Hence, following dissociation, the W/O emulsion formed a multiple o/W/O emulsion (60 vol% water) or inverted at even higher water cuts, forming an oil-in-water (O/W) emulsion (68 vol% water). In contrast, hydrate formation and dissociation from O/W emulsions (≥71 vol% water) stabilized the O/W emulsion.

An understanding of the mechanism for hydrate formation from water-in-oil emulsions is integral for progressing from preventing hydrate formation through expensive thermodynamic means to hydrate blockage prevention. This work presents hydrate formation and agglomeration in a stirred system studied using two complementary particle size analysis techniques, a Particle Video Microscope (PVM) and a Focused Beam Reflectance Measurement (FBRM). The PVM provides qualitative visual information through digital images in the black oil illuminated by a series of lasers. The FBRM provides a quantitative chord length distribution of the particles/droplets in the system. Three sets of experiments were performed using two different Crude oils, Conroe with a very small asphaltene content and poor emulsion stability, and Caratinga with a much higher asphaltene content and emulsion stability. The first experiments looked at ice as an analogy to hydrates, studying the morphology with both the PVM and FBRM. The second experiments looked at the effect of droplet size on hydrate formation and agglomeration, and the third set of experiments studied the dissociation process using a combination of the PVM and in situ conductivity measurements to determine the continuous phase. For hydrate formation, droplet size was found to have a major effect on whether or not agglomeration will occur. During dissociation agglomeration is extremely dramatic due to the creation of surface water on the particles. The dissociation of these agglomerates results in a significant destabilization of the suspension into a water/hydrate phase at the bottom of the cell until dissociation is complete. The dissociation conceptual picture presented illustrates an important implication when operating a flow line with hydrates present; dissociation within the pipeline should be prevented until the hydrates are out of the flow line.

This work deals with the problem of pipeline plugging by gas hydrates during oil production. Gas hydrates are crystals resulting from water and gas molecules association under high pressure and low temperature conditions. Such thermodynamical conditions are generally encountered during oil production and transport, particularly in deep offshore fields or in cold areas. Due to an agglomeration process which is still debated, hydrate occurrence can lead to plug formation. This study aims at improving the understanding in this mechanism process, in the case of water-in-oil emulsions. Therefore, ice or hydrate particle agglomeration is compared. Ice or trichlorofluoromethane (CCl3F) hydrate particles dispersed in xylene with asphaltenes as surfactant is chosen as a model system. As CCl3F hydrates are stable under atmospheric pressure, it allows us to apply different techniques without being limited by high pressure conditions. The Nuclear Magnetic Resonance (NMR) technique is used. The very different relaxation rate for solids or liquids is used to monitor in situ the ratio between solid and total hydrogen or fluorine as a function of time with controlled shearing conditions. Thus, a kinetic study is realized, that enabled to know the amount of ice formed. The apparent viscosity of the system, during crystallization and plugging, is also followed with rheometry in order to characterize agglomeration. This experimental approach allows us to highlight that physico-chemistry of interface water/oil has an important role in agglomeration. It enables us to discuss different mechanisms of agglomeration of ice and hydrate particles in a hydrocarbon phase.

An underinhibited system is defined as a system where an insufficient amount of thermodynamic inhibitor is present to prevent hydrate formation. Underinhibition might occur due to malfunctioning of equipment, temporary limitations in the inhibitor supplies or operational limitations or errors. Understanding the plugging risk of such systems is important in order to take the correct precautions to avoid blocked flowlines. In this paper we summarize the experimental efforts for the last decade within StatoilHydro on the hydrate plugging risk in underinhibited systems. The flow simulator has been used as the main experimental equipment. The overall results for systems underinhibited with ethylene glycol or methanol show that the plugging potential increases up to a maximum at concentrations around 10-15 wt%. At higher concentrations the plugging potential reduces compared to the uninhibited system. The results can be explained as follows: As water is converted to hydrates in a system containing a thermodynamic inhibitor, the inhibitor concentration will increase until the remaining aqueous phase is inhibited. This self-inhibited aqueous phase will wet the hydrate particles, giving raise to the characteristic term of “sticky” hydrate particles. The aqueous layer surrounding the hydrate particles will form liquid bridges, by capillary attractive forces, upon contact with other hydrate particles or the pipe wall. During the hydrate formation period, there is also a possibility that some of the liquid bridges are converted to solid ones, strengthening the agglomerates. Depending on the oil-water interfacial tension, the phase ratio between the aqueous phase and the solid hydrates and the conversion of liquid bridges to solid ones, this leads to increased plugging risk at lower concentrations of inhibitor (< 20 wt%) and reduced risk at higher concentrations as compared to the uninhibited system.