Dissertations / Theses on the topic 'Agglomeration'

In agglomeration using liquid binders, powders are agitated in the presence of liquid to form structured products but the detailed flow fields during processing have not been investigated. Systematic experiments have been performed in a mechanical mixer (diameter 250mm) with ploughshare impellers to examine the effect of processing variables on the velocity fields and torque during agglomeration. Liquid to powder ratio, impeller rotation speed and initial powder volume fill were varied and agglomerate properties were measured. Coincident transitions of the mechanism of agglomeration and type of flow were induced by varying the impeller speed. At around 4Hz the mode of the agglomerate size distribution increased rapidly together with an increase in tap bulk density, a weakening of the agglomerates, and a change in the relationship between torque and time. Tracers were used to show that there was an associated change in the size enlargement mechanism from crushing and layering to coalescence. Detailed velocity information, obtained using a positron camera, showed that at around 4Hz the particle angular velocity increased rapidly while mean axial velocity and the axial dispersion coefficient were greatest. Some particles left the bed as the transition from gravity-dominated to centrifuging flow occurred. For all conditions around 90% of the agglomerates were moving at less than 30% of the impeller tip speed and it is likely that the impeller Froude number (Fr) is not the appropriate criterion to designate the transition from gravity-dominated to centrifuging flow. For instance at 4Hz (Fr=8), around 5% of the agglomerates and none of the sand had a particle Froude number (Fr_p) greater than 1. At 6Hz (Fr=18), 20% of the agglomerates and 5% of the sand had Fr_p>l. Hence the particle Froude number is a better criterion to determine the onset of centrifuging flow. Taken together, the agglomerate properties and velocity distributions were consistent with the current binary collision model for agglomeration. In order to further improve knowledge of agglomeration it is essential to conduct integrated studies of agglomerate properties and flow fields using well-defined systems together with physically-based approaches to modelling.

This article presents a framework within which the effects of demographic change on both agglomeration and growth of economic activities can be analyzed. I introduce an overlapping generation structure into a New Economic Geography model with endogenous growth due to learning spillovers and focus on the effects of demographic structures on long-run equilibrium outcomes and stability properties. First, life-time uncertainty is shown to decrease long-run economic growth perspectives. In doing so, it also mitigates the pro-growth effects of agglomeration resulting from the localized nature of learning externalities. Second, the turnover of generations acts as a dispersion force whose anti-agglomerative effects are, however, dampened by the growth-linked circular causality being present as long as interregional knowledge spillovers are not perfect. Finally, lifetime uncertainty also reduces the possibility that agglomeration is the result of a self-fulfilling prophecy. (author's abstract)
Series: Department of Economics Working Paper Series

Thesis advisor: Richard Arnott
Thesis advisor: Marvin Kraus
Thesis advisor: Stephen Ross
This dissertation comprises three self-contained essays on urban agglomeration economies. The first essay studies the optimal population agglomeration in a city in dynamic contexts. The second essay tests the local labor market agglomeration economies in the Boston metropolitan area, focusing on the effects of social interactions at workplaces on individual earnings. The third essay tests the effects of social interactions at residential locations on housing values
Thesis (PhD) — Boston College, 2005
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Economics

This article investigates agglomeration processes in aging societies by introducing an overlapping generation structure into a New Economic Geography model. Whether higher economic integration leads to spatial concentration of economic activity crucially hinges on the economies' demographic properties. While population aging as represented by declining birth rates strengthens agglomeration processes, declining mortality rates weaken them. This is due to the fact that we allow for nonconstant population size. In particular, we show that population growth acts as an important dispersion force that augments the distributional effects on agglomeration processes resulting from the turnover of generations. (author's abstract)
Series: Department of Economics Working Paper Series

A simple thermodynamic analysis suggests that oil can spontaneously displace water from coal's surface if the coal particle has a water contact angle greater than 90°. However, the clean coal products obtained from laboratory-scale dewatering-by-displacement (DbD) test work assayed moistures substantially higher than expected. These high moisture contents were attributed to the formation of water-in-oil emulsions stabilized by coal particles. Four different approaches were taken to overcome this problem and obtain low-moisture agglomeration products. These included separating the water droplets by screening, breaking emulsions with ultrasonic energy, breaking agglomerates with ultrasonic energy, and breaking agglomerates using vibrating mesh plates. On the basis of the laboratory test work, a semi-continuous test circuit was built and tested using an ultrasonic vibrator to break the water-in-oil emulsions. The most promising results were obtained agglomerates were broken using the ultrasonic probe and the vibrating mesh plates. Tests conducted on flotation feed from the Kingston coal preparation plant gave a clean coal product containing 1% by weigh of moisture with a 94% combustible recovery. The separation efficiency of 93% is substantially higher than results achievable using froth flotation. When agglomerates formed from thermal coal from the Bailey coal preparation plant were broken using either ultrasonic energy or vibrating mesh plates, the obtained results were very similar: clean coal products assayed less than 5% moisture with separation efficiencies of 86% in average.
Master of Science

Clusters are spatial agglomerations of firms in related industries. Although industry clusters have existed for centuries, the cluster concept has only recently been formulated in economic terms and has begun to attract considerable interest from scholars and policymakers over the last 20 years. A vast literature has examined all kinds of clusters and how clustering relates to innovation, growth, and other forms of economic performance of firms and regions. The cluster concept has provided a framework for thousands of national, regional, and local initiatives around the world. Yet, both research and policy efforts have yielded varying and sometimes contradictory results. This dissertation revisits some of the most basic questions about clusters. Using an approach that treats agglomeration and proximity effects as separate but related phenomena, it examines three fundamental aspects of clusters. First, it proposes a way to measure agglomeration more accurately and presents more detailed data on clusters in Europe than have previously been available. Second, it analyses the benefits of clusters for new firms and for regions. Third, it examines how clusters are “organised” through cluster initiatives. The results presented here carry implications for the study of clusters in economic geography, strategic management, and cluster policy research. They also contribute to our knowledge of cluster organisations and are of interest to both policymakers and cluster practitioners. Göran Lindqvist is a researcher at the Center for Strategy and Competitiveness at the Stockholm School of Economics. He has published books and articles about clusters and cluster policy, and he has conducted numerous cluster-related projects for international and national public agencies in Europe and the USA. www.sse.edu/csc

Diss. Stockholm : Handelshögskolan, 2009 Sammanfattning jämte 7 uppsatser

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 191-199).
My dissertation aims to assess transport infrastructure's influence on the productivity, scale and distribution of urban economic activities through changing intercity accessibility. Standard project-level cost-benefit analysis fails to capture the economy-wide impacts in justifying investments in the transport sector. I propose a research framework that: (1) synthesizes the spatial emphasis of the New Economic Geography theories with the temporal perspective of the growth theories; (2) extends the scope of agglomeration effects by highlighting a city's access to external resources as a partial substitute for its own endowment; and (3) bridges the spatial discontinuity between regional and urban studies by introducing intercity accessibility as a determinant of intra-city land uses. I apply the proposed framework to study the spatial economic impacts of China's high-speed rail system at network, corridor, and node (city) levels. The GIS-based spatial analyses of the network accessibility measured by three alternative indicators consistently illustrate that, the extensive transport investments during 2001-2010 have reduced the disparities in accessibility among cities in China, with the coefficient of variation dropping by nearly 50%. Differently, estimations from the panel data models shed light on the complexity in the relationship between accessibility and economic activities, which consists of both generative and redistributive components and simultaneously leads to convergent and divergent economic outcomes. Yet, empirical evidence denies the saturation effects of accessibility. Extended estimations using different instrument variables (IV) partially relieve the concerns on endogeneity issues. Further analyses of a particular transport corridor reveal that, with HSR, the regional urban hierarchy is evolving towards a more interwoven structure, with major cities reaching for overlapped hinterlands. HSR's short-run influences on the location choice of economic activities vary in terms of spatial coverage and are not necessarily restricted to cities with direct HSR access. The city-level comparative case studies indicate that HSR stations introduce external demand for urbanization, leading to new development once matching land supply exists. A cluster analysis of ten demand-supply-related factors generates three prototypes of station-area development. For each type, public and private sectors have adopted different institutional arrangements, yet common challenges exist in preventing speculative investments and matching the development portfolio with the composition of actual needs. The findings lead to important policy implications for decision-makers in China. First, China has not exhausted the agglomeration benefits dispersing through transport infrastructure given the remarkable regional disparities. From an economic development perspective, HSR lines connecting coastal megacities with lagging inland cities are effective in reducing disparities in accessibility and should be encouraged. Second, for the appraisal of major transport projects including HSR, it is reasonable to extend the standard CBA to include the generative benefits; to evaluate the impacts on regional disparities based on redistributive effects; and to avoid overbuilding through identification of saturation effects. Third, HSR has the potential to reshape the path of urbanization. The evolution of the urban hierarchy towards a more interwoven structure may eventually raise the need for adapting administrative arrangements to fit the actual economic interaction. As to urban configuration, HSR stations may catalyze compact urbanization around transit facilities. However, local governments should avoid using HSR stations as a vehicle for excessive generation of land concession revenues.
by Wanli Fang.
Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 202-205.
by William Shan-chen Fong.
Ph.D.

The main purpose of this thesis is to examine the agglomeration phenomenon in Turkish manufacturing industries in depth. Chapter 1 presents an overall discussion of the thesis. Chapter 2; examines the theoretical background of the agglomeration phenomenon, while the structure of Turkish manufacturing sector is examined in Chapter 3. Chapter 4 investigates the degree of agglomeration in Turkish manufacturing industries. For this purpose, several specialization and concentration indexes are examined and also calculated, however the Ellison and Glaeser index of agglomeration is used throughout this thesis, for reasons described in chapter 4. The results from the Ellison and Glaeser index indicate a declining trend in agglomeration for Turkish manufacturing industries. After investigating the degree of agglomeration, the main theory that describes agglomeration in Turkish manufacturing industries is also investigated in Chapter 5. For this purpose several econometric methods are employed and the results indicate that the Ricardian model of technological differences is the main theory that explains agglomeration patterns in Turkish manufacturing industries. Chapter 6 investigates the relationship between agglomeration and entry-exit. For such investigation a dynamic model, count data models and seemingly unrelated regression techniques are employed. The results from chapter 6 indicate that firms in Turkish manufacturing industries do not want to locate in agglomerated regions. Chapter 7 investigates the relationship between Total Factor Productivity (TFP) and agglomeration. For such analysis, fixed effect method and dynamic estimation methodologies are employed. The results indicate that firms that are located in agglomerated regions in Turkish manufacturing industries face decreasing productivity levels. Finally chapter 8 presents an overall conclusion for the thesis.

This thesis focuses on analyzing agglomeration effects in Ecuador. The thesis is divided into five chapters. The first chapter is an introductory chapter where it is focused on the motivation of the case study and the importance of studying agglomeration economies in developing countries. The chapter two is devoted to identifying the Functional Urban Areas in Ecuador. This identification is important because Ecuador does not follow an adequate definition of economic urban areas. However, Ecuador does not also have information available to identify Functional Urban Areas, the Functional urban area identification is based on population density per squared kilometer and commuting census. Thus, this chapter presents an identification of Functional Urban Areas on the basis of satellite data to get data on population density in grid cells of one squared kilometer and road network system of Ecuador to identify urban center and using the concept of proximity to connect those urban centers from an economic point of view. A function of proximity measured in travel time which varies according to the size of each urban core is estimated to connect the urban cores and to define the final boundaries of the Functional Urban Areas. Chapter three is devoted to analyzing agglomeration effects on labor productivity, analyzing the 28 Functional Urban Areas identified in the previous essay. The data used in this chapter is micro data of workers, called ENEMDU surveys, to evaluate wages as an indicator of labor productivity during the period 2005-2015. In addition, we include the consideration of analyzing the labor market divided in the formal and informal sector. Finding presents that larger cities are more productive in Ecuador. The two variables analyzed are total market size and local specialization index. Findings show that agglomeration effects are positive and significant, with a magnitude lower than other developing economies studied so far. Moreover, it is founded that both sectors, formal and informal benefits from working in larger cities, but informal in less magnitude. The channels of the agglomeration are also studied. Chapter four presents the analysis of city size and slum for the 28 Functional Urban Areas introduced in chapter two. To address slums in Ecuador, it is proxied through several measures that combines bad material of the houses and lack of coverage of basic infrastructure. Moreover, it is going beyond the dichotomy of slum identification, by means of measuring the slum level of the households. Three indexes are built to measure slum level at a micro-level of households. The data is gathered from the national censuses of the population of Ecuador in 1990, 2001 and 2010. It is founded a negative relationship between city size and slum characteristics, indicating that larger cities in Ecuador offer lower level of slum characteristics. Moreover, it is analyzed the new areas created in the largest city of Ecuador, named as Guayaquil, over the period of analysis, results show that new extension are characterized by slum incidents. Chapter five introduces the final conclusions. The conclusion shows that Ecuador presents positive and significant agglomeration effects, that benefit both sectors, formal and informal, but informal in less magnitude. Moreover, it is considered that Functional Urban Areas presents are preferred for urban planning and policy considerations. The importance of improving the quality of the labor force in Ecuador, and the needs of monitoring slums characteristics in Ecuador.

Uppsatsen syftar till att beskriva, analysera och förstå kött- och charkindustrins koncentration i Slakthusområdet i Stockholm och vad området innebär för dess företag. Uppsatsen är en fallstudie och bygger på 18 intervjuer med representanter från företag, föreningar och förvaltningar i, och med anknytning till, Slakthusområdet. Vidare bygger den på teorier om agglomerationer och kluster. Utvecklingen av området kopplas till två drivkrafter i form av Stockholms stad och tillgången på råvaror och specialiserade lokaler. Slakthusområdet har kommit att bli ett nav eller en knutpunkt för kött, chark och andra livsmedelsprodukter. Den fysiska och sociala närheten i området medför många positiva egenskaper vilket genererar en trygghet för företagen. Som helhet har det skapat möjligheter och en förmåga hos företagen i Slakthusområdet att hålla en hög flexibilitets- och servicenivå. En förmåga som informanterna framhåller som sina respektive företags främsta konkurrensfördel och framgång.

The purpose of this research is to investigate the determinants of local labour growth in Italian Local labour Systems (LLSs) over the period 1991-2001. Employing a Glaeser et al. (1992) modelling framework we try to assess whether knowledge spills over between firms within the same sector or between firms in different sectors, what is the role of competition as well as introducing new potential determinants of local growth. Our research is also interested in testing the sensitivity of the model to different model specifications, the inclusion of new variables, different levels of sectoral aggregation, and different estimation methods. In particular, in our analysis we propose an innovative estimation technique based on mixed models, which allows exploiting the information coming from our two cross-sectional dimensions, areas and sectors, using both fixed and random effects.

In order to reduce expensive coke usage, blast furnace operators inject coal to replace a portion of the coke. However, the use of some injection coals can result in blast furnace instability and lowered permeability. This thesis is concerned with the injection of coal under entrained flow, high heating rate (104-106 °C/s) blast furnace conditions, namely the possibility of coal particle agglomeration via the use of caking coals. Methods of mitigating agglomeration via blending and pre-oxidation are tested, whilst the resultant performance implications of agglomerated coal chars are considered and analysed. A drop tube furnace (DTF) was used to experimentally test coal injection under conditions that are applicable to the blast furnace 'hot blast' region. Relatable DTF parameters include an operating temperature of 1100°C, and heating rate of 104 °C/s. Four industrial injection coals with varying volatile matter and caking properties were tested at both granulated and pulverised particle size specifications. It was found that coals defined as 'caking coals' showed consistent agglomeration during DTF injection, a potentially problematic effect regarding blast furnace injection. Agglomeration percentages (as defined by sieve classification) for the industrially problematic MV4 coal were 11% and 23% for the granulated and pulverised samples respectively. Blending of whole coals was effective in reducing the amount of agglomerated material in the char, as was sample pre-oxidation prior to injection. Regarding performance, agglomerated chars had greater combustion performance and gasification reactivity than the non-agglomerated samples. With agglomeration shown to be present under high heating rate conditions at temperatures akin to the blast furnace hot blast, it is concluded that agglomeration is a possibility during blast furnace injection. However, due to differing feed systems between the DTF and blast furnace, the precise form and extent of agglomeration in the blast furnace remains uncertain. Based on char combustion and gasification analysis, chars characterised by fine agglomerated material are not likely to be problematic for blast furnace operators relative to 'standard' injection coals.

Agglomeration economies have a relevant impact on local labour markets. The interaction of workers and firms in dense urban areas may generate productivity advantages that result in higher wages. They may be accompanied by an increase in local costs, but the existence of cities that continue to grow is a sign by itself that these gains supersede higher costs. Therefore, large urban areas have an expected positive impact on wages. However, not only the size of the city but also the sectoral composition is relevant to understand locational choices of firms of a specific sector. The industrial scope of agglomeration economies is investigated in the first chapter of this dissertation, and the main results indicate that there is not a unique optimal local industrial mix to foster productivity in different technological sectors. Furthermore, high-tech and low-tech manufacturing sectors benefit more from urban scale in Brazil, followed by services associated with higher knowledge intensity. These sectors are supposed to locate relatively more in large urban areas in order to profit from these advantages. Agglomeration economies may have static and dynamic effects for individuals. These effects are reinforced by a process of sorting of skilled workers into large urban areas. In fact, initial and return migration are mechanisms that select more skilled and more productive workers into large urban areas. Then, cities with a higher percentage of skilled workers attract more of these highly-qualified individuals. Second migration seems to reinforce these relations. The estimation of static agglomeration economies indicate that the inclusion of individual fixed effects decreases density coefficient significantly. Then, dynamic agglomeration economies are estimated considering previous work experience in cities. In this case, static agglomeration advantages become insignificant and whenever years of previous experience are combined with the current place of work, individuals working in less dense cities who had previous experience in denser areas will benefit the most from these gains. Finally, controlling for worker heterogeneity previous experience has a relevant and positive impact on wage growth only in cities with at least the same density level of the current place of work. Finally, city size has an important impact on the relative bargaining power of workers and firms in the labour market. When analysing the relationship of local wages and the business cycle, wage flexibility, measured by the wage curve, is higher in informal sectors in less dense areas. Therefore, large agglomerations are supposed to provide a higher bargaining power for workers, as they have further job opportunities. All these results indicate that agglomeration economies in Brazil are likely to stimulate spatial concentration and increase regional inequalities. Workers and firms self-select themselves into agglomerated urban areas, in which they find a more diversified environment and a larger share of high-skilled individuals. Bigger centres also provide the conditions for workers to bargain for higher wages, even if they are in the informal sector.
Economias de aglomeração possuem um impacto importante sobre o mercado de trabalho. A interação entre trabalhadores e firmas em áreas de elevada densidade pode gerar ganhos de produtividade que resultam em salários mais elevados. Tais áreas também podem possuir custos de vida mais elevados, mas o crescimento recente das cidades parece indicar que os ganhos se sobrepõem aos custos. Portanto, grandes áreas urbanas têm um impacto esperado positivo sobre os salários. No entanto, não só o tamanho da cidade, mas também a composição setorial é relevante para entender as escolhas de localização das empresas de um sector específico. O escopo industrial de economias de aglomeração é investigado no primeiro capítulo desta tese, e os principais resultados indicam que não há um único mix setorial local ótimo para fomentar a produtividade em diferentes setores tecnológicos. Além disso, setores de alta tecnologia e setores industriais de baixa tecnologia se beneficiam mais da escala urbana no Brasil, seguidos de setores de serviços associados a intensidade de conhecimento mais elevado. As economias de aglomeração podem ter efeitos estáticos e dinâmicos. Eles são reforçados por um processo de seleção de trabalhadores qualificados para grandes áreas urbanas. As migrações inicial e de retorno constituem mecanismos essencial para a auto-seleção de trabalhadores mais qualificados e mais produtivos para grandes áreas urbanas. Assim, cidades com maior percentual de trabalhadores mais habilidosos deverão atrais mais indivíduos qualificados. A estimação de economias de aglomeração estáticas indica que a inclusão do efeito fixo individual reduz o coeficiente da densidade de maneira significante. Quando economias de aglomeração dinâmica são estimadas tendo por base a experiência prévia de trabalho em cidades, as vantagens estáticas se tornam não-significantes. Conforme esses anos de experiência são iterados com a densidade do local de trabalho atual, indivíduos trabalhando em cidades menos densas com experiência em cidades mais densas serão os maiores beneficiados. Por fim, a experiência prévia de trabalho tem um efeito positivo sobre o crescimento do salário somente no caso da experiência em cidades com ao menos a mesma densidade da cidade atual. Finalmente, o tamanho da cidade tem um impacto importante sobre o poder de barganha relativo dos trabalhadores e das empresas no mercado de trabalho. Ao analisar a relação dos salários locais e do ciclo de negócios, a flexibilidade salarial, medida pela curva de salário, é maior em setores informais em áreas menos densas. Portanto, as grandes aglomerações supostamente oferecem maior poder de barganha dos trabalhadores, pois eles têm mais oportunidades de emprego. Esses resultados indicam que as economias de aglomeração no Brasil parecem estimular a concentração espacial e ampliar as desigualdades regionais. Trabalhadores e firmas se auto-selecionam para grandes áreas urbanas, nas quais encontram um ambiente mais diversificado e outros trabalhadores altamente qualificados. Adicionalmente, grandes centros proporcionam maior poder de barganha aos trabalhadores em negociações salariais, mesmo que estejam no setor informal

On etudie la planification du reseau electrique dans une grande agglomeration. L'ensemble du reseau present est pris en compte, les influences entre les reseaux de differents niveaux de tension sont etudiees. Une application est effectuee pour le reseau de bordeaux. Le critere retenu est economique: on minimise la depense totale (cout d'investissements et le cout des pertes). La chute de tension etant tres faible dans une grande agglomeration, seule la contrainte thermique est consideree. Le critere n-1 est appliquee comme le critere de securite, soit tous les consommateurs peuvent etre alimentes en cas ou un element elementaire est hors service. L'etude theorique comprend une etude statique et une etude dynamique. On etudie deux transformations de tensions: 400 kv/225 kv/20 kv/400 v et 400 kv/90 kv/20 kv/400 v et les reseaux souterrains. Dans l'etude statique, quatre densites de charges sont etudiees: 2, 5, 8 et 12 mw par km carre. Dans l'etude dynamique, toutes les strategies sont etudiees pendant 20 ans. L'etude pratique est effectuee pour le reseau de bordeaux, la consommation initiale est de 348 mw, et elle atteint 774 mw dans 20 ans

Thesis (M.S.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains xii, 91 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 76-78).

Agglomeration (the sticking together of particles) is often the major growth mechanism in granulation processes. The population balance equation (PBE) is a mathematical framework that is often applied to systems to describe how the particle size distribution changes as a function of time. Different kinetic terms are included in the PBE to describe the different particle growth mechanisms. In this work, a new kinetic model framework is proposed for the growth mechanism binary agglomeration. Binary agglomeration means that only two particles are involved in an agglomeration event. The generality of the new model framework is an advantage over the previous coalescence kernel framework. It is shown that an existing coalescence kernel model can be expressed by means of the new framework.

The new model framework is then adapted to the special case of fluidized bed granulation (FBG) by proposing/choosing expressions for the three submodels in the model framework. An advantage of the new FBG model is that a maximum number of agglomeration events per unit time can be estimated. This means that the model is one step closer to being used predictively. At the moment, no population balance models can predict granulation processes where agglomeration is the dominant growth mechanism. It is shown that both the new FBG model and an existing model could fit experimental data well, however, the new model reflects the situation that the presence of surface liquid is rate limiting for the agglomeratio process.

Experiments in a laboratory batch fluidized bed granulator were carried out. Samples of the particle size distribution were taken at intervals during an experiment. These data were used to fit the model parameters of the FBG model. The dissertation includes a discussion of the effect of certain operating conditions such as bed temperature and liquid spray rate on a model parameter.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH
Bibliography: leaves 142-149.
by Sunwoong Kim.
Ph.D.

Since the 21st century, with the further development of globalization, innovation resources came into an open innovation era. Innovation resources can flow freely in a global scale. In the process of flow, innovation resources agglomeration in some cities, makes these cities become the global science and technology innovation center. Innovation has become the most important source of competitive advantage, and building innovative capacity can provide a strong impetus for the comprehensive competitiveness and economic prosperity (Porter & Stern, 2001). Innovation resources agglomeration makes innovation happen continuously, thus makes the global science and technology innovation center becomes the new engine and important support of national comprehensive strength. After two major industrial structure shift, the traditional development advantages are vanishing. The current economic growth of Shanghai is below the national average; the traditional development advantage is gradually weakening. At the same time, China's economy is faced with an L-shaped recession (Lei, 2016). Therefore, to become the global science and technology innovation center is not only necessary for Shanghai’s own transformation and development, but also accordance with the national development strategy. The aim of the Chinese government is to preliminarily finishes the work of develop Shanghai into the global science and technology innovation center during the period of 13th Five-Year Development Plan1 (from 2016 to 2020). Improve the innovation resources agglomeration capacity of Shanghai, and maximum accumulate innovation resources is the key to success. The existing studies have shown that innovation resources agglomeration has the characteristic of self-organizing, and there is the Matthew effect in this process: the better the innovation foundation, the more obvious the agglomeration effect, and vice versa. This research will from the perspective of the innovation system theory, using DEA method to study the R&D resources utilization efficiency of Shanghai’s industrial enterprises above designated size, demonstrates the deficiencies of Shanghai’s innovation resources agglomeration foundation, and put forward suggestions for improvement.

In this thesis, both the wettability and the agglomeration characteristics of non-metallic inclusions in liquid iron/steel were studied by using both experimental results and thermodynamic considerations. The mechanisms of the wettability of different types of inclusions were discussed. Also, the agglomeration behaviors of the inclusions were analyzed. Firstly, the wettability of different types of inclusions (including Al2O3, MgO, Ti2O3, TiO2 and TiN) in contact with the liquid iron/steel was studied. For the TiNcase, there is no reaction formation at the interface between TiN and pureiron/steel. In the caseo f pure Fe, the oxygen increase is the main factor for a contact angle decrease. As for the steel case, a sharp decrease of the contact angle is due to the effects of both an increased oxygen content in the liquid steel and a formation of a Ti(N,C,O) phase at the interface. For the Al2O3 and MgO cases, the formation of a FeAl2O4 and a MgO-FeO reaction layer at the interface, respectively, lead to a contact angle decrease. In the case of the Ti2O3/pure Fe case, the reaction at the interface cannot be identified. For the Ti2O3/steel case, the formation of an Al2TiO5 reaction layer is the main reason for a steep decrease of the contact angle. In the TiO2 case, the melting region appears at the temperature below the melting point of pure iron. This is due to the strong formation of a solid solution TiOx-FeO. The main source of the oxygen for the solid solution formationis due to a TiO2 substrate decomposition and a low partial pressure of oxygen in the chamber. Regarding to the non-metallic particle additions (TiO2 and TiN) into the molten steel, the steel composition should be controlled to have a small Al content (<0.005mass%) and a high Ti content (>0.035mass%), so as togeta high number of Ti-rich oxide inclusions with a small size. This conclusionis supported from the view point of the van der Waals force, liquid-capillary force and wettability. Regarding the Ti/Al complex deoxidation in the melt, the “mainly occupied clustered inclusions” with spherical shape is due to a TiOx-FeO liquid inclusion precipitation after an addition of Ti as a pre-deoxidizer. The much lower cluster number in the Ti/Al case than that in the Al case is mainly due to a coagulation of single TiOx-FeO liquid inclusions. Also, the cluster formation in a complex Ti/Al deoxidation is started after an Al addition rather than after a Ti addition. Regarding the Al2O3 cluster formation in deoxidation, the cavity bridge forceis larger than the van der Waals force. However, the difference between them is smaller than 7 times. In the reoxidation process, the influence of the cavity bridge force due to the wettability decreased, and became similar to that of the liquid-capillary force.

QC 20160301

Particulate emissions from road transportation are known to have an adverse impact on human health as well the environment. As the effects become more palpable, stricter legislation have been proposed by regulating bodies. This puts forward a challenge for the automotive industry to develop after treatment technologies to fulfil the progressively stricter legislation. At present, the most common after-treatment technologies used for particulates are the diesel and gasoline particulate filters. The typical size distribution of the particles is such that the smallest particles in terms of size are in numbers the largest, although they are not influencing the total particle mass significantly. The most recent legislation have included restrictions on the particle number as well as particle mass. In this thesis numerical tools for studying the transport and interaction of particles in an exhaust flow are evaluated. The specific application is particle agglomeration as a mean to reduce the number of particles and manipulate the size distribution. As particles agglomerate the particle number distribution is shifted and larger sized agglomerates of particles are created reducing the number of ultra-fine particles. The particle agglomeration is obtained by forcing sudden acceleration and deceleration of the host gas carrying the particles by variations in the cross sectional areas of the geometry it is passing through. Initially, a simplified one dimensional model is utilized to assess the governing parameters of particle grouping. Grouping here means that the particles form and are transported in groups, thus increasing the probability for agglomeration. The lessons learned from the 1D-model are also used to design the three dimensional geometry: an axisymmetric corrugated pipe. Two different geometries are studied, they both have the same main pipe diameter but different diameter on the corrugations. The purpose is to find the potential onset of flow instabilities and the influence of 3D-effects such as recirculation on the agglomeration. The CFD simulations are performed using DES methodology. First the simulations are run without particles in a non pulsatile flow scenario. Later particles are added to the setup in a one way coupled approach (no particle-particle interaction). The main results were: 1) An additional criterion for grouping to the ones given in previous work on the 1D model is proposed. It is found that grouping is more likely if the combination of the pulse frequency and geometric wavelength is large. Furthermore, smooth pulse forms (modelling the modulation in the flow due to the geometry) yielded more grouping than other more abrupt pulse shapes. However, idealised inlet pulses underestimate the extent of grouping compared to actual engine pulses. 2) For the geometry with larger maximum cross sectional area stronger flow separation was observed along with higher turbulent kinetic energy. 3) Particles were added in the flow field and a reduction in the particle count was observed in the initial simulations for particles going from the first corrugated segment to the last. Natural extensions of the present work would be to consider pulsatile flow scenarios, particle-particle interaction and a polydisperse setup for the particles

QC 20181008

This licentiate thesis provides an economic analysis of the retail sector, focusing on the factors influencing sales and thus the retail performance of regions and shopping centers. The two essays presented in this thesis can be read independently of each other, but both rest on the theoretical framework of agglomeration economies in addition to consumer demand and supply theory. Chapter one deals with a theoretical exploration of these issues and presents an overview of the retail industry, specifically from a Swedish point of view. The second chapter, “Determinants of Regional Retail Performance”, analyses which factors influence the level of retail sales, within both durables and non-durables, in Swedish regions over a seven-year period. The study shows that agglomeration and retail diversity are influential factors when explaining why some regions perform better than others in terms of retail turnover. The last chapter, “External versus internal shopping center characteristics – which is more important?”, investigates whether external or internal factors explain the performance of shopping centers. The results capture a higher overall effect from the internal factors, especially the tenant mix. However, agglomeration economies also play a role in explaining center performance. In both chapters, novel and detailed data over a whole country, in this case Sweden, are used. To sum up, the empirical results show that the success factor at a regional or a shopping center level in terms of boosting retail sales depends on the regional market size. However, even more important is the amount of product diversity available to the consumer, either at the regional or the shopping center level. This is also a feature that policy makers as well as center management can influence, as oppose to regional size, which must be seen as a more fixed or consistent factor.

Does regional science matter nowadays? Several researchers have tried - and are still trying - to answer this question at the light of the fact that fast connections and communication technologies allow economic actors to easily interact and do business with global partners. Anyhow, the local and global dimensions seem to play a complementary role in influencing firms' economic performance and behaviour rather than being substitute factors. In fact, there are many cases of excellence among Italian industrial districts, high-tech clusters, and innovative milieus which suggest the relevance of the local dimension for firms to grow and compete. The analysis of the local economic dimension dates back to the pioneering contribution of MARSHALL on the industrial district concept (Principles of Economics, 1890, Macmillan, London), which highlights the peculiar advantages for a firm from being located in an industrially specialised local system. According to MARSHALL's (1890) analysis, firms operating in a spatially bounded - and specialised - area can benefit from both tangible and intangible effects. Tangible effects are mainly related to the local availability of inputs' suppliers and specialised workers, the reduction of transportation costs, and the emerging of external-scale economies. On the contrary, intangible effects are related to the reduction of transaction costs (favoured by face-to-face and repeated interactions which increase trust, reputation, and reciprocity among the local actors), and the spread of knowledge and (tacit) information flows concerning production processes, technologies, and innovation practices. Moving from these intuitions, economists started to analyse the role played by local forces in influencing the economic performance of regional systems and individual actors (i.e. firms). Attention has also been paid to local-based phenomena other than specialised agglomerated areas. Among these, the role of urban areas and the advantages related to the location in large and industrially diversified cities have been deeply analysed by geographers and regional economists. In particular, agglomeration forces concerning - and arising from - the spatial concentration of the economic activity received great attention in both the theoretical and the empirical literature. The contribution of GLAESER, KALLAL, SCHEINKMAN and SHLEIFER ("Growth in Cities", Journal of Political Economy, 1992, Vol. 100, No. 6, pp. 1126-1152) represented the first attempt to empirically analyse the causal relationship between agglomeration externalities and local economic performance, and it began a wide cross-county literature on the topic. This Thesis moves in this direction and tries to contribute to the debate concerning the relationship between spatial agglomeration forces and firms' economic performance. Specifically, it comes as a collection of three empirical papers dealing with this topic from very different perspectives. The first chapter of the Thesis is entitled "Productivity, Credit Constraints and the Role of Short-Run Localization Economies: Micro-Evidence from Italy". This chapter is single-authored and is forthcoming in Regional Studies (doi:10.1080/00343404.2015.1064883). This paper investigates whether Italian manufacturing firms' productivity is affected by credit constraints, and whether short-run localisation economies foster productivity both directly and indirectly, moderating the negative effects of credit rationing via inter-firm credit relationships. The empirical exercise is based on a sample of 12,524 firms observed over the period 1999-2007 and drawn from the AIDA databank (Bureau Van Dijk), and it is carried out in three steps. First, Total Factor Productivity is estimated at the firm level through the approach proposed by WOOLDRIDGE ("On Estimating Firm-Level Production Functions Using Proxy Variables to Control for Unobservables", Economics Letters, 2009, Vol. 104, No. 3, pp. 112-114). Second, dynamic investment equations are estimated to investigate whether firms are credit constrained, and to test the potential moderation effect of short-run localisation economies on the investment-to-cash flow sensitivity. Third, an instrumental-variable approach is employed to test whether firms' productivity is negatively affected by credit constraints (i.e. the marginal effect of cash flow on investments), and whether short-run localisation economies positively affect productivity both directly and indirectly, downsizing the negative effects of credit rationing. The results suggest that firms are affected by credit rationing, and that localisation economies positively moderate the investment-to-cash flow sensitivity favouring inter-firm trade credit. It emerges a negative effect of credit rationing on firms' productivity, while localisation economies have both a direct and an indirect positive effect on productivity. In fact, short-run localisation economies seem to reduce the negative credit constraints-productivity relationship by about 4.5%. Finally, the results suggest a complementary effect between localisation economies and the local banking structure: the positive moderation effect of localisation economies on both firms' investment-to-cash flow sensitivity and the credit constraints-productivity relationship increases as the density of bank branches in the local system increases. The second chapter is entitled "Industrial Clusters, Organised Crime and Productivity Growth in Italian SMEs" and is co-authored with Andrés Rodríguez-Pose (LSE). This paper empirically investigates whether organised crime (namely, mafia-type criminality) affects a firm's performance (defined in terms of Total Factor Productivity growth) both directly and indirectly, downsizing positive externalities arising from the geographic concentration of (intra- and inter-industry) market-related firms. Therefore, this paper investigates the simultaneous role played by - and the interplay of - market-based agglomeration economies and organised crime in influencing manufacturing small and medium sized firms' productivity growth. On the one hand, firms operating in a local system characterised by a high density of horizontally- and vertically-interconnected firms (in terms of input-output relationships) may benefit from both tangible (e.g. the reduction of transportation costs, the local availability of inputs' suppliers) and intangible (e.g. the reduction of transaction costs) agglomeration externalities which are likely to foster their productivity growth. On the other hand, organised crime is likely to negatively affect both the socio-economic environment and firms' performance, for instance imposing protection rackets, altering market rules and competition processes. In particular, criminal organisations may break established economic networks among firms, for instance imposing to local firms the acquisition of inputs from "illicit" firms controlled by the criminal organisation itself. The empirical analysis covers a large sample of Italian manufacturing small and medium sized firms observed over the period 2008-2011, and it employs a two-step sample-selection model to control for firm exit over the three-year growth period. The robustness of the results is tested controlling for potential endogeneity of the variables capturing industrial clustering and organised crime, as well as using two different approaches to estimate Total Factor Productivity. The results suggest a negative direct effect of organised crime on firms' productivity growth, while location in a dense local industrial system fosters productivity growth. Moreover, the positive effect of industrial clustering on productivity growth decreases as the level of organised crime increases in the local system, and that this negative moderation effect of organised crime is greater for smaller than for larger firms. Finally, the results suggest that the extortion crime has a very strong incidence in weakening a firm's performance. The third chapter is entitled "Agglomeration, Heterogeneity and Firm Productivity" and is co-authored with Giulio Cainelli (University of Padova). This paper analyses the relationship between agglomeration (i.e. localisation- vs. diversification-type) economies and firms' short-run productivity growth using Italian manufacturing firm-level data. The analysis deals with two key issues. First, it deals with the Modifiable Areal Unit Problem (MAUP) using distance-based agglomeration measures computed for each firm in the sample over a continuous space, thus avoiding the use of pre-defined spatial units of analysis. Second, it explicitly tests the hypothesis of firm heterogeneity in the context of agglomeration phenomena, i.e. it considers the firms located within a given geographic area as heterogeneous units which may contribute to the production of the agglomeration externalities in different ways, and with a different intensity, according to their specific characteristics (defined in terms of size and Total Factor Productivity). This means that firms can be seen both as receivers of the agglomeration externalities, and as producers of these externalities. The results suggest that intra-industry (i.e. localisation-type) externalities have a positive effect on firms' productivity growth at short distances, while a negligible effect at a longer distance (i.e. after 15 km). Moreover, this positive effect seems to decrease as the distance increases. On the contrary, inter-industry (i.e. diversification-type) externalities have a negative effect on firms' productivity growth at a very short distance (i.e. within 5 km), while a positive effect at a longer distance (i.e. after 15 km). Therefore, it emerges a sort of substitution effect between intra- and inter-industry externalities at different distances. It also emerges that firm heterogeneity (in terms of size and productivity) matters in the generation of intra-industry externalities: in fact, the decreasing-with-distance pattern characterising their positive effect changes to an increasing-with-distance pattern when neighbour firms' characteristics are accounted for. It follows an attenuation of the substitution effect between intra- and inter-industry externalities. In fact, they seem to have opposing effects at short distances (i.e. within 15 km), while both types of externalities seem to foster firms' productivity growth at a longer distance (i.e. after 15 km). Moreover, inter-industry externalities seem to have a greater effect on short-run productivity growth than intra-industry externalities.
Quanto contano gli studi regionali oggigiorno? Molti ricercatori hanno cercato - e ancora cercano - di rispondere a questa domanda alla luce dello sviluppo di mezzi e tecnologie di comunicazione che consentono agli attori economici di interagire e condurre affari con partner globali. Ad ogni modo, le dimensioni locale e globale sembrano avere ruoli complementari, anziché sostitutivi, nell'influenzare la performance e le scelte economiche delle imprese. Ciò emerge chiaramente se si considerano casi di successo tra i distretti industriali italiani, i cluster high-tech e i sistemi locali innovativi, che evidenziano la rilevanza della dimensione locale nel promuovere la crescita e la competitività delle imprese. L'analisi della dimensione economica locale trova origine nello studio pioneristico di MARSHALL (Principles of Economics, 1890, Macmillan, London) sul concetto di distretto industriale, in cui sono messi in evidenza i vantaggi peculiari che un'impresa può trarre dall'essere localizzata in un sistema industriale locale altamente specializzato. Nello specifico, MARSHALL (1890) sottolinea come un'impresa che operi in una località geograficamente delimitata - e specializzata in termini di produzione industriale - possa trarre beneficio sia da fattori tangibili, sia da fattori intangibili. I primi riguardano la disponibilità "locale" di fornitori e lavoratori altamente specializzati, la riduzione dei costi di trasporto, e l'emergere di economie di scala esterne. I secondi, al contrario, riguardano la riduzione dei costi di transazione, che risulta facilitata da interazioni dirette e ripetute (tali da accrescere il livello di fiducia, reputazione e reciprocità) tra gli attori economici locali, e la diffusione di conoscenza e flussi di informazioni (tacite) riguardanti processi produttivi, tecnologie e pratiche innovative. L'analisi di MARSHALL (1890) ha spinto molti economisti ad analizzare la relazione tra fattori legati alla dimensione locale e performance economica, sia a livello di sistemi regionali che di imprese. Nel tempo, diverse tipologie di "forze" locali sono state oggetto di studio, oltre ai conglomerati produttivi altamente specializzati. Ad esempio, economisti regionali e geografi hanno rivolto la loro attenzione verso la dimensione urbana e i vantaggi legati alla localizzazione in città caratterizzate da un'ampia diversificazione della struttura industriale. In particolare, numerosi contributi teorici ed empirici hanno sottolineato la rilevanza di esternalità agglomerative legate alla concentrazione spaziale delle attività economiche. Il contributo di GLAESER, KALLAL, SCHEINKMAN and SHLEIFER ("Growth in Cities", Journal of Political Economy, 1992, Vol. 100, No. 6, pp. 1126-1152) è stato il primo tentativo di analizzare empiricamente la relazione di causalità tra esternalità agglomerative e performance economica locale, dando il via ad un'ampia letteratura sul tema. Il presente elaborato (Tesi) si basa su questa letteratura, e cerca di contribuire al dibattito avente ad oggetto la relazione tra forze legate all'agglomerazione spaziale delle attività economiche e performance delle imprese. Nello specifico, questa Tesi è costituita da tre capitoli (papers) che analizzano la suddetta relazione da punti di vista molti differenti. Il primo capitolo della Tesi è intitolato "Productivity, Credit Constraints and the Role of Short-Run Localization Economies: Micro-Evidence from Italy". Questo capitolo è a firma singola, ed è stato accettato per pubblicazione dalla rivista Regional Studies (doi:10.1080/00343404.2015.1064883). Questo capitolo analizza la relazione tra produttività di impresa, razionamento creditizio ed economie di localizzazione di breve termine. Nello specifico, analizza gli effetti diretti di razionamento creditizio ed economie di localizzazione sulla produttività di impresa, così come il potenziale effetto di moderazione (positivo) che le economie di localizzazione possono avere sulla relazione (negativa) tra razionamento creditizio e produttività, promuovendo fenomeni di "inter-firm trade credit". L'analisi empirica utilizza dati di fonte AIDA (Bureau Van Dijk) relativi ad un campione di 12.524 imprese osservate nel corso del periodo 1999-2007. L'analisi è condotto in tre fasi. In primo luogo, la Produttività Totale dei Fattore è stimata a livella di impresa utilizzando l'approccio proposto da WOOLDRIDGE ("On Estimating Firm-Level Production Functions Using Proxy Variables to Control for Unobservables", Economics Letters, 2009, Vol. 104, No. 3, pp. 112-114). Successivamente, una serie di funzioni di investimento dinamiche sono stimate al fine di analizzare se le imprese del campione siano oggetto di razionamento creditizio, e di testare il potenziale effetto di moderazione delle economie di localizzazione di breve termine sulla relazione tra investimenti e cash flow di impresa. Infine, sono stimati una serie di modelli per variabili strumentali al fine di analizzare se la produttività di impresa sia influenzata negativamente dal razionamento creditizio (definito come effetto marginale del cash flow sugli investimenti), e se le economie di localizzazione di breve termine abbiano sia un effetto positivo diretto sulla produttività, sia un effetto positivo indiretto tale da ridurre gli effetti negativi legati al razionamento creditizio. I risultati empirici suggeriscono che le imprese del campione siano oggetto di razionamento creditizio, e che le economie di localizzazione abbiano un effetto positivo tale da moderare la dipendenza degli investimenti dal cash flow favorendo fenomeni di "inter-firm trade credit". Emerge inoltre un effetto negativo del razionamento creditizio sulla produttività di impresa, mentre le economie di localizzazione sembrano avere un effetto diretto positivo sulla produttività. Allo stesso modo, le economie di localizzazione sembrano avere anche un effetto indiretto positivo sulla produttività: infatti, i risultati mostrano che l'effetto negativo del razionamento creditizio sulla produttività diminuisce del 4,5% quando l'effetto di moderazione delle economie di localizzazione è preso in considerazione. Infine, i risultati mostrano un effetto di complementarietà tra economie di localizzazione e struttura bancaria a livello locale. Infatti, l'effetto indiretto positivo delle economie di localizzazione risulta crescente al crescere della densità di filiali bancarie nel sistema locale di appartenenza dell'impresa. Il secondo capitolo è intitolato "Industrial Clusters, Organised Crime and Productivity Growth in Italian SMEs", ed è co-autorato con Andrés Rodríguez-Pose (LSE). Questo secondo capitolo analizza il ruolo della criminalità organizzata (di tipo mafioso) sulla performance di impresa (definita in termini di crescita della Produttività Totale dei Fattori), considerando anche il suo potenziale effetto indiretto (negativo) sulla relazione (positiva) tra esternalità agglomerative legate alla co-localizzazione di imprese fornitrici (industrial clustering) e crescita della produttività di un campione di piccole e medie imprese manifatturiere italiane. Pertanto, sono presi in esame due differenti (e contrastanti) fattori definiti a livello locale: la criminalità organizzata e la concentrazione spaziale di imprese connesse da relazioni di mercato. Da una parte, imprese che operano in sistemi locali caratterizzati da un'alta densità di imprese potenzialmente connesse (orizzontalmente e verticalmente) da relazioni di mercato possono beneficiare di esternalità agglomerative sia tangibili (ad esempio, la riduzione dei costi di trasporto, la disponibilità di fornitori a livello locale) che intangibili (ad esempio, la riduzione dei costi di transazione), che tendono a favorire la crescita di impresa. Dall'altra parte, la presenza di organizzazioni criminali tende ad avere conseguenze negative sia per l'ambiente socio-economico, sia per la performance di impresa, ad esempio a causa dell'imposizione del pagamento del pizzo, di azioni lesive delle regole di mercato e dei processi competitivi tra imprese. In particolare, la criminalità organizzata opera nel mercato per mezzo di imprese "illegali" direttamente controllate, la cui presenza ed attività (ad esempio, l'imposizione dell'acquisto di input alle imprese "legali") tendono ad indebolire le relazioni di mercato esistenti tra le imprese locali. L'analisi empirica è basata su un campione di piccole e medie imprese manifatturiere italiane osservate nel periodo 2008-2011. L'analisi è condotta applicando modelli di tipo "sample selection", e la robustezza dei risultati è testata controllando per la potenziale endogeneità delle variabili che catturano i fenomeni di criminalità organizzata e agglomerazione industriale, così come stimando la Produttività Totale dei Fattori a livello di impresa per mezzo di due approcci econometrici differenti. I risultati mostrano un effetto diretto negativo della criminalità organizzata sulla crescita della produttività di impresa. AL contrario, la crescita della produttività trae beneficio da un'alta densità di imprese circostanti potenzialmente connesse da relazioni di mercato. I risultati suggeriscono inoltre un effetto negativo indiretto della criminalità organizzata, la cui presenza nel sistema locale sembra ridurre sensibilmente gli effetti positivi dell'agglomerazione di imprese sulla crescita della produttività. Questo risultato sembra particolarmente accentuato per le imprese di più piccole dimensioni. Inoltre, il crimine di estorsione sembra giocare un ruolo chiave in questo scenario. Il terzo capitolo è intitolato "Agglomeration, Heterogeneity and Firm Productivity", ed è co-autorato con Giulio Cainelli (Università di Padova). Questo capitolo analizza la relazione tra economie di agglomerazione (nello specifico, economie di localizzazione e di diversificazione) e crescita della produttività di breve periodo utilizzando un campione di imprese manifatturiere italiane. Nello specifico, due aspetti chiave sono presi in considerazione. Il primo riguarda il cosiddetto "Modifiable Areal Unit Problem (MAUP)", che è trattato costruendo variabili di agglomerazione "distance-based" a livello di impresa e assumendo lo spazio come continuo, e cioè evitando l'uso di aree geografiche pre-definite come unità spaziali di analisi. Il secondo riguarda l'ipotesi di eterogeneità di impresa, che nel contesto dei fenomeni agglomerativi si riferisce all'idea che le imprese co-localizzate nello spazio siano unità eterogenee in grado di contribuire alla produzione delle esternalità agglomerative in maniera (e con intensità) differente in base alle loro specifiche caratteristiche (nello specifico, dimensione e Produttività Totale dei Fattori). Assumere eterogeneità di impresa implica assumere che le imprese non solo traggano beneficio dalle esternalità agglomerative, ma anche agiscano come loro "generatori". I risultati suggeriscono che le esternalità intra-industriali (economie di localizzazione) abbiano un effetto positivo sulla crescita della produttività nella breve distanza, mentre un effetto statisticamente non significativo per distanze maggiori (oltre i 15 km). Inoltre, questo effetto positivo risulta inversamente proporzionale rispetto alla distanza. Al contrario, le esternalità inter-industriali (economie di diversificazione) hanno un effetto negativo nella breve distanza (entro i 5 km), mentre un effetto positivo nella lunga distanza (oltre i 15 km). Pertanto, sembra emergere un effetto di sostituzione tra economie di localizzazione e di diversificazione a distanze differenti. I risultano mostrano inoltre l'importanza di considerare l'eterogeneità di impresa (in termini di dimensione e produttività) nel processo di generazione delle esternalità intra-industriali: infatti, quando si tiene conto delle caratteristiche specifiche delle imprese co-localizzate, emerge un effetto positivo delle economie di localizzazione che risulta crescente al crescere della distanza. Emerge quindi un'attenuazione dell'effetto di sostituzione tra esternalità intra- e inter-industriali, che sembrano avere effetti opposti nella breve distanza (entro i 15 km), mentre entrambe sembrano avere un effetto positivo sulla crescita della produttività nella lunga distanza (oltre i 15 km). Inoltre, le economie di diversificazione sembrano avere un effetto maggiore sulla crescita della produttività di breve termine rispetto alle economie di localizzazione.

During the past decades, the establishment of external shopping centers have been increasing, causing debates on how they affect the viability and vitality of city centers. Instead of studying them as individual actors that are in competition with each other, it is interesting to examine them as components that together make cities complete trading destinations.  The purpose of this thesis is to study the coexistence and collaboration between different retail agglomerations. Retail agglomeration attributes are implemented to distinguish existing strengths and weaknesses for each trading venue, in order to identify where they complement each other. The research method is qualitative with an abductive approach. Six semi-structured interviews were conducted with respondents who represent different associations.  The findings of the research revealed that city centers and external shopping establishments are able to coexist if they complement each other through their individual offerings and experiences. Different retail agglomerations attract contrasting customer groups, allowing them to coexist. Collaboration between retail agglomerations can be implemented in several ways and can enhance the attractiveness of cities as trading destinations. The collaboration can occur by implementing shared marketing, shuttle bus services or collective events.  This research is limited to only investigating one medium sized city and three retail agglomeration formats. Furthermore, the choice of participants did not include consumers and store owners, which could have provided additional perspectives. The findings contribute to the study field by highlighting how retail agglomerations can coexist and collaborate and can be useful for other medium sized cities.

Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed August 6, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

As a post-Soviet economy, Ukraine has inherited substantial production assets and qualified personnel. However, the economy was dominated by large-scale enterprises designed for much bigger markets. After the collapse of the Soviet Union Ukrainian firms faced lack of planning, breaks in contacts with their former suppliers and customers, and distortion of prices. There was a clear need in restructuring of the entire economy. Restructuring included splitting firms into smaller parts and privatization. The first phase of transition was completed by 2000 when the output grew for the first time after a long recession in nineties, and most firms became private property. In this work I explore trends in geographic and industrial concentration of Ukrainian manufacturing firms over the period of 2001 to 2005. I found that this period was characterized by relocation of firms between sectors and between regions, as well as by an increase in economic concentration of industries. The speed of adjustment was different for various sectors and even for different industries within manufacturing. Even though the economy is still dominated by large firms, the average firm size decreases due to a rapid growth in the number of new firms. Geographically, manufacturing tends to increasingly concentrate mostly around a few big cities, apparently at the expense of other regions. I also estimate the external scale effects and compare them with Western studies. In particular I focus on machinery and high tech. I found strong localization and urbanization effects in both industry groups. An important contribution of this work is the analysis of the effect of ownership structure on agglomeration economies. I found that private firms tend to enjoy external scale effects to a greater extent than state owned, and foreign owned firms appear to be the most efficient in extracting benefits form agglomeration. Aggregation of the data may distort the estimates of agglomeration effects. I show that most effects take place at the nearest neighborhoods. When the physical distance between firms increases agglomeration effects attenuate quickly. However, localization effects reveal themselves at different level of industrial aggregation for various industries. This may reflect more complicated relationships within sectors and requires further analysis.