Konceptet kring kluster har fått mycket uppmärksamhet de senaste årtiondena. Dels beskrivet som ett viktigt fenomen, dels som ett bidrag till effektiva nationella ekonomier. I denna kandidatuppsats ämnar vi undersöka några viktiga drivkrafter som driver koncentrationerna av svenska bankers etablering inom kluster för Private Banking i Luxemburg. Finansklustret lever kvar trots ändrade förutsättningar och hårdare regleringar. Genom en kvalitativ studie av två svenska banker som har enheter i finanscentrum i Luxemburg, undersöker vi drivkrafter bakom etableringarna. Totalt har tre semi-strukturerade djupintervjuer ägt rum. De viktigaste identifierade drivkrafterna visade sig vara horisontella och vertikala nätverk genom personlig integration samt lägre kostnader genom rekrytering av kompetent personal och gemensamma IT-lösningar.

The primary objective of this thesis was to develop a nucleation regime map to determine the controlling nucleation mechanism as a function of material properties and operating parameters. Two distinct regimes of nucleation were identified. The drop controlled nucleation regime occurs when nucleation conditions are ideal and one drop produces one nucleus granule and the controlling property is the droplet size. The nuclei formation kinetics are fast and the binder droplets penetrate into the powder bed pores almost immediately. In this region, the nuclei distribution reflects the drop size distribution as one drop tends to form one granule provided that (a) drops hitting the powder surface do not overlap - low spray flux Ya and (b) the drop must wet into the bed completely before bed mixing brings it into contact with another partially absorbed drop on the bed surface - low penetration time tp. If either criterion is not met, powder mixing characteristics will dominate. In the mechanical dispersion regime, the viscous or poorly wetting binder is slow to flow through the powder pores and form nuclei and good mixing is required for binder dispersion. The kinetics of nuclei formation were characterised using a simple drop penetration time test. A single drop of binder fluid was placed on a loosely packed powder bed and the time taken for the fluid to penetrate completely was measured for a range of powder and binder combinations. Loosely packed powder beds contain large macrovoids which are included in the existing Kozeny approach to estimating pore size. However it was found that these pores do not participate in liquid flow. A new two phase model was proposed where the total volume of the macrovoids was assumed to be the difference between the bed porosity and the tap porosity. A new parameter, the effective porosity eeff, was defined as the tap porosity multiplied by the estimated fraction of pores that terminate at a macrovoid and are effectively blocked pores. The pore sizes and drop penetration times were recalculated using the effective porosity and the predicted tp values were generally within an order of magnitude of the experimental results for all powders. The drop penetration time is reduced by small drops, low viscosity fluids, porous powders (but without macrovoids), large powder pores, high surface tension, low contact angle and pre-wetting of the powder bed. A new dimensionless group, the dimensionless spray flux Ya was defined to characterise the three most important operating variables in binder dispersion: liquid binder flowrate, drop size and powder flux through the spray zone. At low Ya, the majority of drops land on the powder sufficiently well separated to allow ideal “drop controlled” nucleation where one drop forms one granule. As Ya increases, the probability of drop footprints overlapping to give larger agglomerate nuclei increases. Monte-Carlo simulations were performed to validate the spray flux theory. The proportion of nuclei formed from single drops falls exponentially as Ya increases and to remain in the drop controlled regime Ya must be kept below 0.1. Analytical solutions based on the Poisson distribution for the fraction of single drop nuclei as a function of Ya were an excellent match with the Monte-Carlo data. Further validation experiments in carefully designed ex-granulator experiments and in an industrial granulator were performed. The results matched the theoretical solutions and demonstrated the ability of Ya to describe the nucleation zone in a real granulator. The proposed nucleation regime map demonstrated the interaction between drop penetration time and spray flux in nucleation. At short penetration times, such as the water and lactose system, decreasing Ya causes a shift towards the drop controlled regime and a narrower nuclei distribution. When penetration time is long, the nuclei size distribution is always larger and broader. Granulation may still be successful if the mechanical dispersion forces are able to break up the binder clumps and distribute the binder through the powder. The nucleation regime map should prove to be a useful tool for maintaining effective liquid distribution during scale-up as well as a useful trouble-shooting tool. It allows the dominant mechanism controlling the nucleation process to be easily identified using relatively simple parameters and a rational approach can then be used to control the properties of the nuclei.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [127]-137).

Zugl.: Berlin, Humboldt-Universiẗat, Diss., 2008. / Zsfassung in engl. Sprache. - Anhang teils dt., teils portugies. - Online-Ausg. im Internet.

Worker exposure to coal dust in underground mines remains a major health hazard. This research has: 1) Analyzed the wetting characteristics of less than 10 micron dust particles using a novel micro-emulsion technology (MET) at bench scale and prototype scale with emphasis on agglomeration of dust particles, and 2) Simulate airflow and dust dispersion patterns on a longwall mining face using CFD modeling techniques to compare the current and proposed spatial distributions of water sprays around a longwall shearer. With the “Final Dust Rule” adopted by MSHA in 2014 and slated to go into full effect August 16, 2016, this research is a significant contribution to the coal industry. A suitable micro-emulsion containing 0.2% oil and 0.0125% didodecyl-dimethyl-ammonium bromide (DDAB) was identified. For assessing the wettability of coal dusts, a slightly modified version of “Fixed Time Wettability” or FTW (Chugh et al., 2004) was employed. These wettability tests however, did not yeild true wettability using the MET. An analysis for both unwetted and wetted portions of coal dust using particle size distribution curves (PSD) confirmed agglomeration when treated with the emulsion. For the unwetted portion, 96.6% of the particles had sizes greater than 25 μm after treatment with MET. Similar data for wetted dust was 100%. Experiemental studies in a 4 ft x 4ft x 10 ft chamber showed 12-15% improvement in respirable dust when using MET as compared to water alone.. Validated computational fluid dynamics (CFD) models were used to study airflow patterns and the interaction between sprays and airflow for designing both engineering and administrative controls around a longwall face. Two important zones – low air velocity (LAV) and recirculation (RC) – were identified around the model of a longwall face. These zones were located: 1) Behind the headgate drum and 2) Above the shearer chassis. Analysis of a modified geometric configuration of sprays on the shearer chassis showed improved coverage for wetting the dust on the longwall face. Numerical modeling comparisons were made between current spray systems and spray systems proposed by Dr. Y. P. Chugh using the concepts of “Continuous and Discrete Phase Modeling”. Analyses included changes in airflow patterns caused by spray systems and dust dispersion tracks generated from the cutting face. Chugh’s spray system was able to effectively eliminate RC zones existing above the shearer body, thereby minimizing the extent to which coal dust enters the walkway of the longwall face where workers are located. The proposed spray system used concepts of multiple wetting points for dust, air-locks, and venturi to wet the dust and direct the dust-laden air from mine workers. These improvements can be used in longwall mines as engineering controls for meeting new dust control standards.

Zugl.: Frankfurt(Oder), Universiẗat Viadrina, Diss., 2005.

The aim of this work is to look into the applicability of Discrete Element Modelling (DEM) coupled to Computational Fluid Dynamics (CFD) to simulate micro-scale colloidal particles immersed in fluid. Numerical methods were implemented through the commercial framework of EDEM2.3. As opposed to dissolved matter, which behaves as a continuum within the fluid medium, particulate matter is made of discrete entities that interact amongst themselves, and with the fluid and any physical boundaries. Particulate matter is ubiquitous in many purification processes that would beneficiate from having an easy way to model particle dynamics immersed in water. In an effort to understand better the dynamics of particle deposition under surface forces and hydraulic forces, a micro-scale numerical model was built adopting both a mechanistic and a statistical approach to represent the forces involved in colloidal suspension. The primary aim of the model was to simulate particle aggregation, deposition and cluster re-suspension in real world micro-systems. Case studies include colloidal flocculation in a constricted tube, and colloidal fouling around membrane filtration feed spacers. This work used a DEM-CFD coupling method that combined the DEM particle flow simulation with hydrodynamics forces from a velocity field computed through CFD. It also implemented boundary-particle and particle-particle interactions by enabling the modelling of surface and interfacial forces. Two kinds of coupling method were considered: two-way and one-way coupling. Two-way coupling is suitable for high particle concentration flow where particle loading affects the hydrodynamics. One-way coupling is suitable for dispersed particle configuration where the flow field is assumed to be undisturbed by the particles. The advantages and drawbacks of both techniques for micron-size particles were investigated. EDEM 2.3 was customised with plug-ins to implement Van der Waals forces and Brownian forces and its post-processing features offered the ability to investigate easily the microparticles behaviour under the influence of fluid forces. In this context, DEM-CFD modelling using EDEM 2.3 represents an improvement on previously published works as it enables higher visibility and reproducibility along with increasing the number of potential users of such modelling. Emphasis was given in presenting original findings and validation results that illustrate DEMCFD applicability, with respect to modelling of hydraulically mediated colloidal surface interaction; while highlighting factors that limit the ability of the technique. For instance, the effect of particle disturbance on the surrounding medium currently proves difficult to model.

<p>Urban problems have several features that make them inherently dynamic. Large transaction costs all but guarantee that homeowners will do their best to consider how a neighborhood might change before buying a house. Similarly, stores face large sunk costs when opening, and want to be sure that their investment will pay off in the long run. In line with those concerns, different areas of Economics have made recent advances in modeling those questions within a dynamic framework. This dissertation contributes to those efforts.</p><p>Chapter 2 discusses how to model an agent’s location decision when the agent must learn about an exogenous amenity that may be changing over time. The model is applied to estimating the marginal willingness to pay to avoid crime, in which agents are learning about the crime rate in a neighborhood, and the crime rate can change in predictable (Markovian) ways.</p><p>Chapters 3 and 4 concentrate on location decision problems when there are externalities between decision makers. Chapter 3 focuses on the decision of business owners to open a store, when its demand is a function of other nearby stores, either through competition, or through spillovers on foot traffic. It uses a dynamic model in continuous time to model agents’ decisions. A particular challenge is isolating the contribution of spillovers from the contribution of other unobserved neighborhood attributes that could also lead to agglomeration. A key contribution of this chapter is showing how we can use information on storefront ownership to help separately identify spillovers.</p><p>Finally, chapter 4 focuses on a class of models in which families prefer to live</p><p>close to similar neighbors. This chapter provides the first simulation of such a model in which agents are forward looking, and shows that this leads to more segregation than it would have been observed with myopic agents, which is the standard in this literature. The chapter also discusses several extensions of the model that can be used to investigate relevant questions such as the arrival of a large contingent high skilled tech workers in San Francisco, the immigration of hispanic families to several southern American cities, large changes in local amenities, such as the construction of magnet schools or metro stations, and the flight of wealthy residents from cities in the Rust belt, such as Detroit.</p> / Dissertation

The thesis deals with the description and evaluation of the cluster analysis methodology and cluster policies as an adequate tool of growth in a region. Special emphasis is given to the work of M. Porter, which can be looked upon as a genesis of earlier research in the field and represents the current state of affairs in theoretical background and practical application. Also, the Czech republic as a case study is given a special section.

The disintegration of agglomerates of solid charge used in a nickel flash furnace has been investigated. The in-flight agglomerate size of solid charge with different characteristics has been measured using turbulent conditions similar to a full-scale flash furnace. Plant observations indicated that under certain conditions solid charge was able to pass through the furnace shaft unreacted. The motivation for this work was to improve the understanding and the modelling of a flash furnace. A review of the literature revealed that the disintegration of agglomerates of solid charge is very important to the performance of a flash furnace, however, there has been no detailed study of the factors governing the disintegration of in-flight agglomerates of solid charge.A laboratory-scale experimental rig was constructed to non-intrusively measure the in-flight agglomerate size distribution of solid charge and to visualise the powder injection process, while using turbulent conditions similar to a flash furnace. A high-speed video technique and a laser diffraction technique were used to measure the wide range of in-flight agglomerate sizes present during powder injection. A range of variables including the particle size, turbulence level, packing density, particle shape, solid concentration, and moisture content were investigated.