In this thesis we study Sobolev gradient flows for Perona-Malik style energy functionals and generalizations thereof. We begin with first order isotropic flows which are shown to be regularizations of the heat equation. We show that these flows are well-posed in the forward and reverse directions which yields an effective linear sharpening algorithm. We furthermore establish a number of maximum principles for the forward flow and show that edges are preserved for a finite period of time. We then go on to study isotropic Sobolev gradient flows with respect to higher order Sobolev metrics. As the Sobolev order is increased, we observe an increasing reluctance to destroy fine details and texture. We then consider Sobolev gradient flows for non-linear anisotropic diffusion functionals of arbitrary order. We establish existence, uniqueness and continuous dependence on initial data for a broad class of such equations. The well-posedness of these new anisotropic gradient flows opens the door to a wide variety of sharpening and diffusion techniques which were previously impossible under L2 gradient descent. We show how one can easily use this framework to design an anisotropic sharpening algorithm which can sharpen image features while suppressing noise. We compare our sharpening algorithm to the well-known shock filter and show that Sobolev sharpening produces natural looking images without the "staircasing" artifacts that plague the shock filter. / Thesis (Master, Mathematics & Statistics) -- Queen's University, 2010-08-25 10:44:12.23

Darbo tema yra aktuali tuo, kad tarptautinės reitingų agentūros, įvertindamos skolų krizę Europoje, pastaruoju metu daugeliui šalių mažino valstybės kredito reitingus ar blogino jų perspektyvas. Nors po prieš trejus metus patirto nuosmukio Baltijos šalių reitingai ir stabilizavosi, jų aukštesnių reikšmių išlaikymas Baltijos valstybėms yra svarbus užsienio investicijų pritraukimo ir šių šalių finansų sektoriaus vystymosi veiksnys. Vis dėlto, reitingų gerėjimas gali turėti ir priešingą poveikį.Todėl svarbu išsiaiškinti situaciją Baltijos šalyse. Tiriamojo darbo objektas yra Baltijos šalių ilgalaikio ir trumpalaikio skolinimosi užsienio valiuta reitingai bei ilgalaikio ir trumpalaikio skolinimosi nacionaline valiuta reitingai. Šio darbo tikslas - atlikus teorinę valstybės kredito reitingų ir jų įtakos šalies finansų sektoriaus vystymuisi ir užsienio investicijų srautams analizę, nustatyti valstybės kredito reitingų įtaką finansų sektoriaus vystymuisi ir užsienio investicijų srautams Baltijos šalyse. Darbo tikslui pasiekti buvo suformuluoti uždaviniai: atlikti teorinę valstybės kredito reitingų ir jų įtakos šalies finansų sektoriaus vystymuisi ir užsienio investicijų srautams analizę, išanalizuoti Baltijos šalių finansų sektoriaus išsivystymo lygį bei užsienio investicijų srautų ir kredito reitingų šiose šalyse pokyčių tendencijas, reitingus įtakojusius veiksnius, nustatyti valstybės kredito reitingų įtaką finansų sektoriaus vystymuisi ir užsienio investicijų srautams Baltijos... [toliau žr. visą tekstą] / The topic of the work is relevant due to the fact, that international credit rating agencies, assessing the debt crisis in Europe, recently downgraded credit ratings or their outlook for many countries. Despite the fact that sovereign credit ratings of Baltic states have stabilized after the decline occured three years ago, higher ratings are the essential factor for Baltic states, seeking to attract foreign investment and promote their financial sector development. Though, the improvements of ratings may have the opposite effect. Therefore, it is important to clarify the situation in Baltic states. The object of the research work – the Baltic states‘ short and long term in foreign and local currency ratings. The purpose of this paper is to establish the impact of sovereign credit ratings on the financial sector development and international capital flows in the Baltic states, doing theoretical analysis on sovereign credit ratings and their impact on the financial sector development and international capital flows in a country. In order to achieve an objective, the following tasks have been fomulated: to accomplish above-mentioned theoretical analysis, to analyse the level of financial sector development, changes in trends of international capital flows and sovereign credit ratings in the Baltic states, reveal the main factors, which affected ratings in these countries and ascertain the influence of these ratings on the financial sector development and international capital... [to full text]

Based on an individual longitudinal data on dependent employment we analyse the role of Creative Industries for the employment system of Vienna. We focus on gross job flows and firm dynamics in this priority field of Vienna's urban policy and analyse the characteristics of the different parts of the cluster's production system. We find ample evidence for positive effects of Creative Industries on employment growth and firm birth, but also reveal considerable job turnover and a large heterogeneity of firm growth in the cluster. Especially, we find rather different evolutions along the clusters value chain, which points to weak linkages between upstream and downstream activities in the cluster. (author's abstract) / Series: Creative Industries in Vienna: Development, Dynamics and Potentials

Syfte – Studiens syfte var att analysera hur uppkomsten av defekta produkter och omarbeten kan minska i kundorderstyrd montering genom effektivare material- och informationsflöden. Som hjälp till att besvara syftet har det brutits ned i två frågeställningar: I. Vilka möjliga orsaker till defekta produkter och omarbeten kan identifieras i kundorderstyrd montering? II. Hur kan förändringar i material- och informationsflöden minska uppkomsten av defekta produkter och omarbeten i kundorderstyrd montering? Metod – Studiens tillvägagångssätt pågick i en iterativ process och innefattade litteraturstudier samt en fallstudie. I samarbete med det kundorderstyrda företaget JELDWEN Sverige AB i Forserum, genomfördes fallstudien på deras monteringsavdelning. Fallstudien innefattade intervjuer, observationer samt dokumentstudier. Resultatet i studien har uppnåtts genom analysering och jämförelse av insamlad empiri och teori. Resultat – Studien identifierar orsaker till defekta produkter och omarbeten i form av brister i material- och informationsflöden. Orsakerna delas in i fyra huvudrubriker; informationsunderlag, rutiner, personal samt material, som i sin tur bryts ned i elva underrubriker. Samtliga orsaker bidrar till icke värdeskapande aktiviteter och bör därför minskas. En kombination av kanban och kittning är ett förändringsalternativ till nuvarande materialhantering, som säkerställer att rätt material är på rätt plats vid rätt tidpunkt. Informationsunderlag och upplärning bör tydliggöras för att minska osäkerheter hos operatörerna inom montering och därmed minska uppkomst av defekta produkter och omarbeten. Implikationer – I denna studie fastställs att förändringar i material- och informations– flöden kan effektivisera kundorderstyrd montering. För att åstadkomma detta måste bristande orsaker specifikt för varje tillverkande verksamhet identifieras. De förändringsalternativ som presenteras kan kräva vissa investeringar för tillverkande verksamheter och aspekter relaterade till kostnad bör därmed beaktas. Begränsningar – Fallstudien som genomfördes var av enskild karaktär vilket innebär begränsningar i studiens generaliserbarhet. Studien hade till avsikt att identifiera möjliga orsaker till problemet som presenterats, kopplat till material- och informationsflöden. Utifrån denna avgränsning kan väsentliga orsaker utöver detta försummats. / Purpose – The purpose of the study was to analyse how the occurrence of defect products and rework can decrease within customer-order-driven assembly through more efficient material- and information flows. In order to help answering the purpose, the purpose has been decomposed into two questions: I. What possible causes of defective products and rework can be identified in customer-order-driven assembly? II. How can changes in the material- and information flows decrease the occurrence of defect products and rework in customer-order-driven assembly? Method – The approach of the study was iterative and included literature studies and a case study. In cooperation with JELD-WEN Sverige AB in Forserum, which has a high degree customer-order-driven manufacturing, the case study was conducted on their assembly department. The case study included interviews, observations and document studies. The result of the study has been achieved through comparison and analysis of empirical data and theory. Findings – The study identifies the causes of defect products and rework in forms of flaws in material- and information flows. The causes are divided into four headlines; information base, routines, employees as well as material which in turn are broken down into eleven subheadings. All causes contribute to non-value adding activities and should therefore be minimized. A combination of kanban and kitting is an alternative to current strategy for handling the material, which ensures that the right material is in the right place, at the right time. Information base and training should be clarified in order to minimize uncertainty among the operators in the assembly, thus minimizing the occurrence of defect products and rework. Implications – This study establish that customer-order-driven assembly can improve efficiency with changes in material- and information flows. To achieve this, the causes for flaws need to be identified for each specific manufacturing business. The possibilities for change that is presented may require certain investments for the manufacturing business, therefore aspects related to cost should be considered. Limitations – The performed case study had a single character, thus limiting the generalizability of the study. The intention of the study was to identify possible causes to the presented problem, connected to material- and information flows. Due to this limitation, other significant causes may have been neglected.

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This thesis deals with questions concerning spatial agglomeration of economic activities. The object of study is the Internet industry in central Stockholm. Through the use of statistical data and an interview study the Internet industry is described, measured, and analyzed through theories concerning agglomerations, social network relations, and knowledge and information flows. These theories are interpreted through five agglomeration themes related to the role of customers, subcontractors and partners, competitors, financing, and labour market, respec-tively. The research has recognized the importance of proximity to create and maintain social networks, and to spread information and knowledge, especially tacit knowledge. The thesis also shows how social networks, and information and knowledge flows have an essential role in all the five agglomeration themes that are analyzed. The results of this analysis show that the proximity to customers is the most important factor for the location of the Internet indus-try. Also, the local labour market and access to suppliers and partners are important factors. Competitors and rivals have a role to play when it comes to the diffusion of knowledge and information, although its importance as a location factor is hard to estimate. The analysis of the firms’ financing demonstrate that this factor hardly has been of crucial importance for the location of the Internet industry, but access to (venture) capital might have been of indirect importance for the location and the pace of the development of the Internet industry.

This thesis studies a problem that has been proposed as a novel way to disrupt communication networks: the load maximization problem. The load on a member of a network represents the amount of communication that the member is forced to be involved in. By maximizing the load on an important member of the network, we hope to increase that member's visibility and susceptibility to capture. In this thesis we characterize load as a combinatorial property of graphs and expose possible connections between load and spectral graph theory. We specifically describe the load and how it changes in several canonical classes of graphs and determine the range of values that the load can take on. We also consider a connection between load and liquid paint flow and use this connection to build a heuristic solver for the load maximization problem. We conclude with a detailed discussion of open questions for future work.

Unsteady shock wave propagation through ducts has many applications, ranging from blast wave shelter design to advanced high-speed propulsion systems. The research objective of this study was improved fundamental understanding of the transient flow structures during unsteady shock wave propagation through rectangular ducts with varying cross-sectional area. This research focused on the fluid dynamics of the unsteady shock-induced flow fields, with an emphasis placed on understanding and characterizing the mechanisms behind flow compression (wave structures), flow induction (via shock waves), and enhanced mixing (via shock-induced viscous shear layers). A theoretical and numerical (CFD) parametric study was performed, in which the effects of these parameters on the unsteady flow fields were examined: incident shock strength, area ratio, and viscous mode (inviscid, laminar, and turbulent). Two geometries were considered: the backward-facing step (BFS) geometry, which provided a benchmark and conceptual framework, and the splitter plate (SP) geometry, which was a canonical representation of the engine flow path. The theoretical analysis was inviscid, quasi-1D and quasi-steady; and the computational analysis was fully 2D, time-accurate, and viscous. The theory provided the wave patterns and primary wave strengths for the BFS geometry, and the simulations verified the wave patterns and quantified the effects of geometry and viscosity. It was shown that the theoretical wave patterns on the BFS geometry can be used to systematically analyze the transient, 2D, viscous flows on the SP geometry. This work also highlighted the importance and the role of oscillating shock and expansion waves in the development of these unsteady flows. The potential for both upstream and downstream flow induction was addressed. Positive upstream flow induction was not found in this study due to the persistent formation of an upstream-moving shock wave. Enhanced mixing was addressed by examining the evolution of the unsteady shear layer, its instability, and their effects on the flow field. The instability always appeared after the reflected shock interaction, and was exacerbated in the laminar cases and damped out in the turbulent cases. This research provided new understanding of the long-term evolution of these confined flows. Lastly, the turbulent work is one of the few turbulent studies on these flows.

The objective of this thesis is to accomplish the three dimensional parallel thin-layer Navier-Stokes solutions for low aspect ratio rectangular flat wings in compressible flow. Two block parallel Navier Stokes solutions of an aspect ratio 1.0 flat plate with sharp edges are obtained at different Mach numbers and angles of attack. Reynolds numbers are of the order of 1.0E5-3.0E5. Two different grid configurations, the coarse and the fine grids, are applied in order to speed up convergence. In coarse grid configuration, 92820 total grid points are used in two blocks, whereas it is 700,000 in fine grid. The flow field is dominated by the vortices and the separated flows. Baldwin Lomax turbulence model is used over the flat plate surface. For the regions dominated by the strong side edge vortices, turbulence model is modified using a polar coordinate system whose origin is at the minimum pressure point of the vortex. In addition, an algebraic wake-type turbulence model is used for the wake region behind the wing. The initial flow variables at the fine grid points are obtained by the interpolation based on the coarse grid results previously obtained for 40000 iterations. Iterations are continued with the fine grid about 20000-40000 more steps. Pressures of the top surface are predicted well with the exception of leading edge region, which may be due to unsuitable turbulence model and/or grid quality. The predictions of the side edge vortices and the size of the leading edge bubble are in good agreement with the experiment.

The study of turbulence has been dominated historically by a bottom-up approach, with a much stronger emphasis on the physical structure of flows than on that of the dynam- ical state space. Turbulence has traditionally been described in terms of various visually recognizable physical features, such as waves and vortices. Thanks to recent theoretical as well as experimental advancements, it is now possible to take a more top-down approach to turbulence. Recent work has uncovered non-trivial equilibria as well as relative periodic orbits in several turbulent systems. Furthermore, it is now possible to verify theoretical results at a high degree of precision, thanks to an experimental technique known as Particle Image Velocimetry. These results squarely frame moderate Reynolds number Re turbulence in boundary shear flows as a tractable dynamical systems problem. In this thesis, I intend to elucidate the finer structure of the state space of moderate Re wall-bounded turbulent flows in hope of providing a more accurate and precise description of this complex phenomenon. Computation of new undiscovered equilibria, relative equilibria, and their heteroclinic connections provide a skeleton upon which a numerically accurate description of turbulence can be framed. The behavior of the equilibria under variation of Reynolds number and cell aspect ratios is also examined. It is hoped that this description of the state space will provide new avenues for research into nonlinear control systems for shear flows as well as quantitative predictions of transport properties of moderate Re fluid flows.