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Neste trabalho analisa-se o problema do transporte do feixe de elétrons em canhões de elétrons, estruturas periódicas de ímãs permanentes e em coletores de simples e múltiplos estágios. Essa análise é de relevância em projetos de dispositivos de micro-ondas de potência dos tipos amplicador klystron e válvula TWT. Determina-se a dinâmica das partículas a partir da solução da equação da trajetória que é derivada da força de Lorentz e da conservação de energia. A equação da trajetória obtida é diferencial de segunda ordem, não-linear e independentemente do tempo para o potencial generalizado. Utiliza-se o método de Runge-Kutta de 4a Ordem para integrar a equação da trajetória das partículas. Obtém-se o potencial escalar elétrico a partir da solução da equação de Poisson. Numericamente, obtêm-se os po- tenciais escalares elétricos e magnéticos, por meio do Método de Elementos Finitos (MEF). Ao longo do movimento de uma partícula, obtida a partir da solução da equação da trajetória, deposita-se carga elétrica. Utilizam-se macropartículas, uma vez que é praticamente impossível modelar cada partícula do problema, a partir do método Partícula na Célula (Particle in Cell - PIC). Neste caso, tem-se um problema acoplado para o potencial escalar elétrico e as trajetórias das macropartículas, uma vez que, as trajetórias das macropartículas dependem dos potenciais e estes, por sua vez, dependem das trajetórias. À convergência deste problema acoplado utiliza-se o Método das Aproximações Sucessivas (MAS). A plataforma desenvolvida, baseada nos métodos acima, compõe-se de duas ferramentas computacionais. A primeira, XMGUN, dedica-se ao projeto de: canhões de elétrons com grades e grades de sombreamento; e coletores de simples e múltiplos estágios considerando, ainda, a emissão de elétrons secundários. A segunda, XMAGUN, volta-se ao projeto de estruturas periódicas com ímãs permanentes. Afere-se o desempenho da ferramenta computacional XMGUN com o diodo plano de Pierce operando na condição em que a corrente é limitada pelas cargas espaciais. Por sua vez, verica-se o desempenho do XMAGUN por meio de simulações com estruturas do tipo PPM separadas pelo vácuo e na presença de pole pieces. Os resultados obtidos em todas as simulações convergiram satisfatoriamente para as soluções analíticas. Utilizando o XMGUN, projeta-se um canhão de elétrons com 30 kV de tensão de anodo e uma perveância de 1,37 Perv com capacidade de fornecer uma corrente elétrica de 7,1 A. Esse canhão tem uma malha com 2796 elementos e 5057 nós. As principais características geométricas do canhão de elétrons são: raio do catodo rc=14,6 mm; raio do disco do catodo rk =6,2 mm; e ângulo do eletrodo de focalização = 37. Neste caso, a velocidade transversal normalizada e o alcance do feixe zw observados são de 0,068 e 26,88 mm respectivamente. Obtém-se uma concordância superior a 93% em corrente e perveância com o EGUN. Utilizando, ainda, o XMGUN, são simulados coletores de simples e múltiplos estágios. O coletor de simples estágio apresenta 1612 nós e 2969 elementos, e o de 4 (quatro) estágios, 2496 nós e 4257 elementos. As tensões dos eletrodos do 1o, 2o, 3o e 4o estágio são de 9,45 kV, 8,65 kV, 6,45 kV e 3,45 kV respectivamente. Durante as simulações, devido à emissão de elétrons secundários, observa-se, para o coletor de simples estágio, macropartículas penetrando na região de deriva, fenômeno este indesejado, e não observado para o coletor de 4 (quatro) estágios. Considerando o XMAGUN, projeta-se um arranjo periódico com pole pieces e 5 (cinco) ímãs permanentes, capaz de fornecer um campo magnético, no centro da estrutura, de 0,42 T. Neste caso, a geometria do arranjo periódico obtida é: raio interno rm1 e externo rm2 do ímã permanente são iguais a 3,5 mm e 7,5 mm respectivamente; raio externo do pole piece r3 = 7,5 mm ; raio interno rf1 e externo rf2 da ponteira do pole piece são 1,6 mm e 3,05 mm respectivamente; espessura do ímã permanente T=2,95 mm; período magnético L =8,5 mm. A remanência do ímã permanente utilizada é de Br=0,85 T. A malha dessa estrutura periódica magnética apresenta pouco mais de 20.000 nós e 40.000 elementos. / In this paper we analyze the problem of transport of the electron beam in electron guns, periodic arrays of permanent magnets and collectors of simple and multiple stages. This analysis is of relevance in the design of power microwave devices such as klystron amplier and TWT valve. The dynamics of particles is determined from the solution of the equation of the trajectory that is derived from the Lorentz force and energy conservation law. The equation of the trajectory obtained is differential of second-order, non-linear and time independent for the generalized potential. It is used the Runge-Kutta 4th order method to integrate the equation of the trajectory of the particles. The electric scalar potential is obtained from the solution of the Poisson equation. Numerically, we obtain the electric and magnetic scalar potentials, using the Finite Element Method (FEM). Throughout the motion of a particle, obtained from the solution of the equation of the trajectory, electrical charge it is deposited. Macroparticles are used, since it is virtually impossible to model each particle of the problem, based on Particle in Cell scheme (Particle in Cell - PIC). In this case, there is a coupled problem for the electric scalar potential and the trajectories of the macroparticles, since these trajectories depend on the potential and the potential, in turn, depends on the trajectories. In order to abtain the convergence of this coupled problem, it used the Method of Successive Approximations (MSA). The platform developed, based on the above methods, consists of two computational tools. The rst, XMGUN, is dedicated to the project of: electron guns with grids and shadow-grids, and collectors of simple and multiple stages, where secondary electrons emission is considered. The second, XMAGUN, is used to the design of periodic permanent magnets structures. The XMGUN was benchmarked against the plan Pierce diode under space charge limited condiction. In turn, the XMAGUN was benchmarked against PPM like structures, separated by a vacuum and in the presence of pole pieces. The results, in all simulations, converged satisfactorily to the analytical solu- tions. Using XMGUN, it is designed an electron gun with 30 kV anode voltage, 1.37 Perv capable of supplying an electric current of 7.1 A. This gun has a mesh with 2796 elements and 5057 nodes. The main geometric characteristics of the electron gun are: cathode radius rc = 14.6 mm; cathode disc radius rk = 6.2 mm; and half cone angle = 37. In this case, the normalized transverse velocity and beam-waist distance from anode zw are 0.068 and 26.88 mm respectively. An agreement above 93% in current and perveance is found when compared with EGUN. XMGUN is also used to simulate single and multi stage collectors. The single-stage collector has 1612 nodes and 2969 elements, while the 4 (four) stages collector has 2496 nodes and 4257 we elements. The collector electrode voltages of the 1st, 2nd, 3rd and 4th stage are 9.45 kV 8.65 kV 3.45 kV 6.45 kV, respectively. During the simulations, due to yield of secondary electrons, for the single stage collector, it is observed macroparticles entering into the drift region, a phenomenon unwanted, and not observed for the 4 (four) stage collector. Whereas XMAGUN is projected at a periodic arrangement with pole pieces and 5 (ve) permanent magnets, capable of providing a magnetic eld in the center of the structure was 0.42 T. In this case, the geometry of the periodic arrangement is obtained: inner and outer radius of the permanent magnet rm1 = 3.5 mm and 7.5 mm respectively rm2 =; outer radius of the pole piece r3 = 7.5 mm, internal radius and external tip of the pole piece rf1=rf2 =1.6 mm and 3.05 mm respectively; permanent magnet thickness T = 2.95 mm magnetic period L = 8.5 mm. The remanence of the permanent magnet used is Br = 0.85 T. The net periodic structure of magnetic features little more than 20,000 nodes and 40,000 elements.

Neste trabalho analisa-se o problema do transporte do feixe de elétrons em canhões de elétrons, estruturas periódicas de ímãs permanentes e em coletores de simples e múltiplos estágios. Essa análise é de relevância em projetos de dispositivos de micro-ondas de potência dos tipos amplicador klystron e válvula TWT. Determina-se a dinâmica das partículas a partir da solução da equação da trajetória que é derivada da força de Lorentz e da conservação de energia. A equação da trajetória obtida é diferencial de segunda ordem, não-linear e independentemente do tempo para o potencial generalizado. Utiliza-se o método de Runge-Kutta de 4a Ordem para integrar a equação da trajetória das partículas. Obtém-se o potencial escalar elétrico a partir da solução da equação de Poisson. Numericamente, obtêm-se os po- tenciais escalares elétricos e magnéticos, por meio do Método de Elementos Finitos (MEF). Ao longo do movimento de uma partícula, obtida a partir da solução da equação da trajetória, deposita-se carga elétrica. Utilizam-se macropartículas, uma vez que é praticamente impossível modelar cada partícula do problema, a partir do método Partícula na Célula (Particle in Cell - PIC). Neste caso, tem-se um problema acoplado para o potencial escalar elétrico e as trajetórias das macropartículas, uma vez que, as trajetórias das macropartículas dependem dos potenciais e estes, por sua vez, dependem das trajetórias. À convergência deste problema acoplado utiliza-se o Método das Aproximações Sucessivas (MAS). A plataforma desenvolvida, baseada nos métodos acima, compõe-se de duas ferramentas computacionais. A primeira, XMGUN, dedica-se ao projeto de: canhões de elétrons com grades e grades de sombreamento; e coletores de simples e múltiplos estágios considerando, ainda, a emissão de elétrons secundários. A segunda, XMAGUN, volta-se ao projeto de estruturas periódicas com ímãs permanentes. Afere-se o desempenho da ferramenta computacional XMGUN com o diodo plano de Pierce operando na condição em que a corrente é limitada pelas cargas espaciais. Por sua vez, verica-se o desempenho do XMAGUN por meio de simulações com estruturas do tipo PPM separadas pelo vácuo e na presença de pole pieces. Os resultados obtidos em todas as simulações convergiram satisfatoriamente para as soluções analíticas. Utilizando o XMGUN, projeta-se um canhão de elétrons com 30 kV de tensão de anodo e uma perveância de 1,37 Perv com capacidade de fornecer uma corrente elétrica de 7,1 A. Esse canhão tem uma malha com 2796 elementos e 5057 nós. As principais características geométricas do canhão de elétrons são: raio do catodo rc=14,6 mm; raio do disco do catodo rk =6,2 mm; e ângulo do eletrodo de focalização = 37. Neste caso, a velocidade transversal normalizada e o alcance do feixe zw observados são de 0,068 e 26,88 mm respectivamente. Obtém-se uma concordância superior a 93% em corrente e perveância com o EGUN. Utilizando, ainda, o XMGUN, são simulados coletores de simples e múltiplos estágios. O coletor de simples estágio apresenta 1612 nós e 2969 elementos, e o de 4 (quatro) estágios, 2496 nós e 4257 elementos. As tensões dos eletrodos do 1o, 2o, 3o e 4o estágio são de 9,45 kV, 8,65 kV, 6,45 kV e 3,45 kV respectivamente. Durante as simulações, devido à emissão de elétrons secundários, observa-se, para o coletor de simples estágio, macropartículas penetrando na região de deriva, fenômeno este indesejado, e não observado para o coletor de 4 (quatro) estágios. Considerando o XMAGUN, projeta-se um arranjo periódico com pole pieces e 5 (cinco) ímãs permanentes, capaz de fornecer um campo magnético, no centro da estrutura, de 0,42 T. Neste caso, a geometria do arranjo periódico obtida é: raio interno rm1 e externo rm2 do ímã permanente são iguais a 3,5 mm e 7,5 mm respectivamente; raio externo do pole piece r3 = 7,5 mm ; raio interno rf1 e externo rf2 da ponteira do pole piece são 1,6 mm e 3,05 mm respectivamente; espessura do ímã permanente T=2,95 mm; período magnético L =8,5 mm. A remanência do ímã permanente utilizada é de Br=0,85 T. A malha dessa estrutura periódica magnética apresenta pouco mais de 20.000 nós e 40.000 elementos. / In this paper we analyze the problem of transport of the electron beam in electron guns, periodic arrays of permanent magnets and collectors of simple and multiple stages. This analysis is of relevance in the design of power microwave devices such as klystron amplier and TWT valve. The dynamics of particles is determined from the solution of the equation of the trajectory that is derived from the Lorentz force and energy conservation law. The equation of the trajectory obtained is differential of second-order, non-linear and time independent for the generalized potential. It is used the Runge-Kutta 4th order method to integrate the equation of the trajectory of the particles. The electric scalar potential is obtained from the solution of the Poisson equation. Numerically, we obtain the electric and magnetic scalar potentials, using the Finite Element Method (FEM). Throughout the motion of a particle, obtained from the solution of the equation of the trajectory, electrical charge it is deposited. Macroparticles are used, since it is virtually impossible to model each particle of the problem, based on Particle in Cell scheme (Particle in Cell - PIC). In this case, there is a coupled problem for the electric scalar potential and the trajectories of the macroparticles, since these trajectories depend on the potential and the potential, in turn, depends on the trajectories. In order to abtain the convergence of this coupled problem, it used the Method of Successive Approximations (MSA). The platform developed, based on the above methods, consists of two computational tools. The rst, XMGUN, is dedicated to the project of: electron guns with grids and shadow-grids, and collectors of simple and multiple stages, where secondary electrons emission is considered. The second, XMAGUN, is used to the design of periodic permanent magnets structures. The XMGUN was benchmarked against the plan Pierce diode under space charge limited condiction. In turn, the XMAGUN was benchmarked against PPM like structures, separated by a vacuum and in the presence of pole pieces. The results, in all simulations, converged satisfactorily to the analytical solu- tions. Using XMGUN, it is designed an electron gun with 30 kV anode voltage, 1.37 Perv capable of supplying an electric current of 7.1 A. This gun has a mesh with 2796 elements and 5057 nodes. The main geometric characteristics of the electron gun are: cathode radius rc = 14.6 mm; cathode disc radius rk = 6.2 mm; and half cone angle = 37. In this case, the normalized transverse velocity and beam-waist distance from anode zw are 0.068 and 26.88 mm respectively. An agreement above 93% in current and perveance is found when compared with EGUN. XMGUN is also used to simulate single and multi stage collectors. The single-stage collector has 1612 nodes and 2969 elements, while the 4 (four) stages collector has 2496 nodes and 4257 we elements. The collector electrode voltages of the 1st, 2nd, 3rd and 4th stage are 9.45 kV 8.65 kV 3.45 kV 6.45 kV, respectively. During the simulations, due to yield of secondary electrons, for the single stage collector, it is observed macroparticles entering into the drift region, a phenomenon unwanted, and not observed for the 4 (four) stage collector. Whereas XMAGUN is projected at a periodic arrangement with pole pieces and 5 (ve) permanent magnets, capable of providing a magnetic eld in the center of the structure was 0.42 T. In this case, the geometry of the periodic arrangement is obtained: inner and outer radius of the permanent magnet rm1 = 3.5 mm and 7.5 mm respectively rm2 =; outer radius of the pole piece r3 = 7.5 mm, internal radius and external tip of the pole piece rf1=rf2 =1.6 mm and 3.05 mm respectively; permanent magnet thickness T = 2.95 mm magnetic period L = 8.5 mm. The remanence of the permanent magnet used is Br = 0.85 T. The net periodic structure of magnetic features little more than 20,000 nodes and 40,000 elements.

Bakgrund & Problemformulering: Momentumeffekten på fondmarknaden är ett relativt outforskat område där dess existens på senare tid har blivit omtvistad. Eftersom kunskapen om pensionssparande och det svenska pensionssystemet är låg, samtidigt som de sociala skyddsnäten i samhället minskar är det viktigt att undersöka om momentumstrategier kan ge överavkastning för privatpersoners pensionssparande. Således ställs frågan: Kan momentumstrategier skapa överavkastning på fondmarknaden? Syfte: Syftet med uppsatsen är att undersöka momentumeffekten på fondmarknaden och om momentumstrategier kan utnyttjas av svenska pensionssparare för att skapa överavkastning i PPM-systemet. Metod: Uppsatsen har ett kvantitativt tillvägagångssätt och en deduktiv utgångspunkt tillämpas. För att undersöka momentumeffekten på fondmarknaden tillämpas en multipel regressionsanalys med Fama French-Trefaktormodell, samt Sharpekvot. Uppsatsens urval är PPM-fonder under perioden 2010-2017. Slutsatser: Uppsatsen finner inget statistiskt stöd för en momentumeffekt på fondmarknaden genom Fama French-Trefaktormodell. Detta är ett tecken på att fondmarknaden kan vara svagt effektiv då historisk information inte har kunnat användas för att skapa riskjusterad överavkastning. Uppsatsen finner således ingen momentumeffekt för fondmarknaden efter finanskrisen 2008, trots att en momentumeffekt har kunnat påvisas dessförinnan inom tidigare forskning. Med hänsyn till det har författarna anledning att misstänka att marknadens effektivitet kan variera, vilket skulle kunna förklaras av den Adaptiva Marknadshypotesen. / Background & Problem: The momentum effect in the fund market is relatively unexplored were its existence has been controversial. Due to the lack of knowledge in retirement savings and the Swedish Premium Pension Agency system, alongside the weakening of a social safety net, it is important to examine if momentum strategies give excess returns and can be used for retirement savings. Therefore, the authors question: Do momentum strategies give excess returns in the fund market? Purpose: The aim of the thesis is to examine the momentum effect in the fund market and if momentum strategies can be used to create excess return in the Premium Pension Agency system. Method: The thesis takes a deductive research approach with a quantitative methodology. To examine the momentum effect in the fund market, a multiple regression analysis model from Fama French-Three factor model is applied, and the Sharpe ratio. The sample for the study is Swedish Premium Pension Agency funds, which is examined over the period of 2010-2017. Conclusions: The thesis does not find support for a momentum effect in the fund market through the Fama French-Three factor model. This indicates that the fund market is weak form efficient, as historical information cannot be used to create risk adjusted excess return. Thus, the thesis does not find a momentum effect for the fund market after the financial crisis in 2008, even though a momentum effect is proven to exist before then. In view of this, the authors have reason to suspect the market efficiency to vary, which could be explained by the Adaptive Market Hypothesis.

This thesis explores the use of single-photon avalanche diodes (SPADs) for visible light communications (VLC). The high sensitivity of SPADs can potentially enhance the performance of VLC receivers. However, a SPAD-based system has challenges that need to be addressed before it can be considered as a viable option for VLC. The first challenge is the susceptibility of SPAD-based receivers to variations in ambient light. The high sensitivity of SPADs is advantageous for signal detection, but also makes SPADs vulnerable to variations in ambient light. In this thesis, the performance of a SPAD-based receiver is investigated under changing lighting conditions. Analytical expressions to quantify performance are derived, and an experiment is conducted to gain further understanding of system performance. It is shown that a SPAD-based receiver is highly sensitive to illumination changes when on-off keying (OOK) is employed, and that pulse-position modulation (PPM) is a preferred modulation scheme as it is more robust. The second challenge is broadcasting to SPAD-based receivers with different capabilities. A traditional broadcasting scheme is time-sharing, whereby a transmitter sends data to receivers in an alternating manner. Broadcasting to SPAD-based receivers is challenging as receivers may have diverse capabilities. In this thesis, a new multiresolution modulation scheme is proposed, which can potentially improve system performance over the traditional timesharing approach. The performance of the proposed scheme is analyzed, and a proof-of-concept experiment is performed to demonstrate its viability.

<p>Informationsteknologin (IT) fortsätter att utvecklas snabbt. Det ger möjlighet för företag och organisationer att kostnadseffektivisera sina processer och hitta alternativa lösningar som ökar konkurrenskraften. Den höga utvecklingstakten och de stora kostnader som är inbegripna skapar samtidigt en genuin beslutsosäkerhet vid investering i IT. Företagare ställs inför en rad dilemman: var, när och hur ska investeringar göras? I de situationer där utfallen av ett beslut är oklara eller motstridiga befinner sig beslutsfattaren i ett dilemma. Syftet med denna studie är att beskriva och analysera beslutsdilemman som beslutsfattare har vid dessa IT-investeringar.</p><p>Studien bygger på beslutsteori, där referensramen bestäms av såväl den rationella skolans mycket bestämda beslutskedja som av mer socialkonstruktivistiska beslutsmodeller. Beslutsperspektiven varierar med kontexten och intressenterna. Företaget är en koalition mellan olika aktörer, alla med sitt perspektiv på företagets beteende i den specifika branschen.</p><p>Empirin utgörs av två myndigheter (fallstudier), Skatteverket respektive Premiepensionsmyndigheten (PPM). Genom intervjuer, studier av arkivmaterial samt deltagande observation har jag samlat information om två beslutsprocesser: PPM:s val mellan att köpa ett färdigt IT-system och att utveckla ett eget samt Skatteverkets val mellan ett proprietärt IT-verktyg och ett baserat på öppen källkod.</p><p>Analysen av det empiriska materialet har resulterat i en typologi med tre typer av beslutsdilemman vid IT-investeringar. Den första typen av dilemman är de beslutspunkter som uppstår i samband med investeringar. Jag kallar dessa för (a) dilemmapunkter. Den andra typen av dilemman beror av att resultat och konsekvenser ofta är svårbestämda. Det leder till en hög beslutsosäkerhet och jag benämner därför det (b) konsekvensdilemman. Beslutsdilemmat kan också betyda att man ställs inför flera beslutsalternativ med både förväntat önskat och möjliga, oönskade resultat. Det ställer beslutsfattaren inför valet att balansera mellan alternativen. Jag kallar dessa för (c) balansaktsdilemman.</p> / <p>Summary: The rapid progress of Information Technology (IT) continues. IT can make processes more cost-effective and be a tool when identifying alternative solutions to increase competitiveness. However, the rapid pace of development and the high costs attached, creates a genuine uncertainty when it comes to IT-investments. Eventually, the organization will be confronted with dilemmas such when decisions or their outcomes are unclear or contradictory, you have a dilemma.</p><p>The purpose of this study is to describe and analyze balance acts (dilemmas) of IT-investments. The base of study is decision theory, from the traditional rational way of reasoning to more socially constructed models. The perspective varies with the contexts and actors. The company is a coalition of actors, all with a different perspective on a specific part of the business.</p><p>The empirical data consist of two public authorities (case-studies), Swedish Tax Authority and Premium Pension Authority (PPM). I have collected data by conducting interviews, taking part of archived material and being an observant participator. PPM’s dilemma is whether to buy or to develop a system and Swedish Tax Authority’s dilemma is whether to use open source or a proprietary development tool.</p><p>The analysis of the empiric material have resulted in a typology of dilemmas in conjunction with IT-investments. The typology consists of:</p><p>(a) dilemma points - events where the dilemmas originate.</p><p>(b) dilemma consequences – dilemmas that are hard to discern and thus associated with a great deal of risk.</p><p>(c) balancing acts dilemmas - the decision maker must balance between multiple choices in order to reach a satisfying outcome. Each choice has its pros and cons.</p>

Informationsteknologin (IT) fortsätter att utvecklas snabbt. Det ger möjlighet för företag och organisationer att kostnadseffektivisera sina processer och hitta alternativa lösningar som ökar konkurrenskraften. Den höga utvecklingstakten och de stora kostnader som är inbegripna skapar samtidigt en genuin beslutsosäkerhet vid investering i IT. Företagare ställs inför en rad dilemman: var, när och hur ska investeringar göras? I de situationer där utfallen av ett beslut är oklara eller motstridiga befinner sig beslutsfattaren i ett dilemma. Syftet med denna studie är att beskriva och analysera beslutsdilemman som beslutsfattare har vid dessa IT-investeringar. Studien bygger på beslutsteori, där referensramen bestäms av såväl den rationella skolans mycket bestämda beslutskedja som av mer socialkonstruktivistiska beslutsmodeller. Beslutsperspektiven varierar med kontexten och intressenterna. Företaget är en koalition mellan olika aktörer, alla med sitt perspektiv på företagets beteende i den specifika branschen. Empirin utgörs av två myndigheter (fallstudier), Skatteverket respektive Premiepensionsmyndigheten (PPM). Genom intervjuer, studier av arkivmaterial samt deltagande observation har jag samlat information om två beslutsprocesser: PPM:s val mellan att köpa ett färdigt IT-system och att utveckla ett eget samt Skatteverkets val mellan ett proprietärt IT-verktyg och ett baserat på öppen källkod. Analysen av det empiriska materialet har resulterat i en typologi med tre typer av beslutsdilemman vid IT-investeringar. Den första typen av dilemman är de beslutspunkter som uppstår i samband med investeringar. Jag kallar dessa för (a) dilemmapunkter. Den andra typen av dilemman beror av att resultat och konsekvenser ofta är svårbestämda. Det leder till en hög beslutsosäkerhet och jag benämner därför det (b) konsekvensdilemman. Beslutsdilemmat kan också betyda att man ställs inför flera beslutsalternativ med både förväntat önskat och möjliga, oönskade resultat. Det ställer beslutsfattaren inför valet att balansera mellan alternativen. Jag kallar dessa för (c) balansaktsdilemman. / Summary: The rapid progress of Information Technology (IT) continues. IT can make processes more cost-effective and be a tool when identifying alternative solutions to increase competitiveness. However, the rapid pace of development and the high costs attached, creates a genuine uncertainty when it comes to IT-investments. Eventually, the organization will be confronted with dilemmas such when decisions or their outcomes are unclear or contradictory, you have a dilemma. The purpose of this study is to describe and analyze balance acts (dilemmas) of IT-investments. The base of study is decision theory, from the traditional rational way of reasoning to more socially constructed models. The perspective varies with the contexts and actors. The company is a coalition of actors, all with a different perspective on a specific part of the business. The empirical data consist of two public authorities (case-studies), Swedish Tax Authority and Premium Pension Authority (PPM). I have collected data by conducting interviews, taking part of archived material and being an observant participator. PPM’s dilemma is whether to buy or to develop a system and Swedish Tax Authority’s dilemma is whether to use open source or a proprietary development tool. The analysis of the empiric material have resulted in a typology of dilemmas in conjunction with IT-investments. The typology consists of: (a) dilemma points - events where the dilemmas originate. (b) dilemma consequences – dilemmas that are hard to discern and thus associated with a great deal of risk. (c) balancing acts dilemmas - the decision maker must balance between multiple choices in order to reach a satisfying outcome. Each choice has its pros and cons.

Made available in DSpace on 2015-05-14T12:36:32Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1384872 bytes, checksum: 17a26f8a3828692a7cd893ffaf2ff3f9 (MD5) Previous issue date: 2010-04-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The usage of mammographic image databases in digital form and the practice of telemedicine require to store and to transmit large amounts of data. The image digitization from a single mammographic exam with appropriate resolution can take up to 120MB of space in disk, which becomes even more critical when considering the large number of exams per day on a clinic. Thus, efficient data compression techniques are needed to reduce storage and transmission costs. This document describes the development of a high-performance lossless compressor based on Prediction by Partial Matching (PPM) algorithm with modules for segmentation, mapping, gray code, bit planes decomposition and move-to-front transform, for mammographic image compression. The compressor developed was efficient in both compression ratio and processing time, and compresses 27MB images in about 13 seconds with an average compression ratio of 5,39. / A utilização de bancos de dados de imagens mamográficas em formato digital e as práticas de telemedicina exigem que se armazene e transmita grandes quantidades de dados. A digitalização das quatro imagens de um único exame mamográfico com resolução adequada pode ocupar até 120MB de espaço em disco. Esta quantidade de dados leva a uma situação ainda mais crítica ao considerar-se o grande número de exames diários efetuados rotineiramente em uma clínica. Assim, técnicas eficientes de compressão de dados são necessárias para reduzir os custos relativos ao armazenamento e à transmissão destas imagens. O presente trabalho descreve o desenvolvimento de um sistema de alto desempenho para compressão sem perdas de imagens mamográficas baseado no algoritmo Prediction by Partial Matching (PPM), em conjunto com módulos para segmentação, mapeamento, codificação com Código Gray, decomposição em planos de bits e transformada move-to-front (MTF). O sistema desenvolvido mostrou-se eficiente tanto no que tange à razão de compressão quanto ao tempo de processamento, comprimindo imagens de 27MB em aproximadamente 13 segundos com razão de compressão média de 5,39.

Made available in DSpace on 2015-05-14T12:36:57Z (GMT). No. of bitstreams: 1 parte1.pdf: 1278902 bytes, checksum: c1a877f74ec783e6525701070c717a4d (MD5) Previous issue date: 2010-03-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The image segmentation problem is present in various tasks such as remote sensing, object detection in robotics, industrial automation, content based image retrieval, security, and others related to medicine. When there is a set of pre-classified data, segmentation is called supervised. In the case of unsupervised segmentation, the classes are extracted directly from the data. Among the image properties, the texture is among those that provide the best results in the segmentation process. This work proposes a new unsupervised texture segmentation method that uses as the similarity measure between regions the bit rate obtained from compression using models, produced by the Prediction by Partial Matching (PPM) algorithm, extracted from them. To segment an image, it is split in rectangular adjacent regions and each of them is assigned to a different cluster. Then a greedy agglomerative clustering algorithm, in which the two closest clusters are grouped at every step, is applied until the number of remaining clusters is equal to the number of classes (supplied by the user). In order to improve the localization of the region boundaries, the image is then split in shorter regions, that are assigned to the cluster whose PPM model results in lower bit rate. To evaluate the proposed method, three image set were used: Trygve Randen, Timo Ojala and one created by the author of this work. By adjusting the method parameters for each image, the hit rate obtained was around 97% in most cases and 100% in several of them. The proposed method, whose main drawback is the complexity order, is robust to regions with different geometric shapes, grouping correctly even those that are disconnected. / O problema da segmentação de imagens está presente em diversas tarefas como sensoriamento remoto, detecção de objetos em robótica, automação industrial, recuperação de imagens por conteúdo, segurança, e outras relacionadas à medicina. Quando há um conjunto de padrões pré-classificados, a segmentação é denominada supervisionada. No caso da segmentação não supervisionada, as classes são extraídas diretamente dos padrões. Dentre as propriedades de uma imagem, a textura está entre as que proporcionam os melhores resultados no processo de segmentação. Este trabalho propõe um novo método de segmentação não supervisionada de texturas que utiliza como medida de similaridade entre regiões as taxas de bits resultantes da compressão utilizando modelos produzidos pelo algoritmo Prediction by Partial Matching (PPM) extraídos das mesmas. Para segmentar uma imagem, a mesma é dividida em regiões retangulares adjacentes e cada uma delas é atribuída a um grupo distinto. Um algoritmo aglomerativo guloso, que une os dois grupos mais próximos em cada iteração, é aplicado até que o número de grupos seja igual ao número de classes (fornecido pelo usuário). Na etapa seguinte, cujo objetivo é refinar a localização das fronteiras, a imagem é dividida em regiões ainda menores, as quais são atribuídas ao agrupamento cujo modelo PPM resulta na taxa de bits mais baixa. Para avaliar o método proposto, foram utilizados três bancos de imagens: o de Trygve Randen, o de Timo Ojala e um criado pelo autor deste trabalho. Ajustando-se os parâmetros do método para cada imagem, a taxa de acerto obtida foi em torno de 97% na maioria dos casos e 100% em vários deles. O método proposto, cuja principal desvantagem é a ordem de complexidade, se mostrou robusto a regiões de diferentes formas geométricas, agrupando corretamente até mesmo as desconexas.

Retirement is one part of life that everybody will sooner or later come too. It is very important to prepare and plan for it by looking for the best possible alternative(s) to save and invest money in order to get enough capital to live on when it is time to retire. In Sweden like in many other countries women tend to have lower wages than men and the maternity leave is a life event that can affect the income of women during their labour time. This can then result in women having less disposable income during the retirement period. In general, women are living longer than men therefore they should get more money to live on but this is not the case in most of the time. In finance taking high risk can be rewarded by high return. Several researches that have been conducted in different fields came to the same conclusion that women are more risk averse than men. This risk averse can be explained by physiological, psychological, social and intellectual aspects. In this thesis I study the investment behaviour of both genders in Premium Pension Funds managed by the Swedish Pension Authority (PPM). In contrary to what many researches in several fields have come to, I found that men tend to invest less than women when the risk level involved in investing in Premium Pension Funds increases. This observation can be seen as an attempt of the women to increase their pension capital in a shorter of time by investing in riskier pension funds. A further study on this subject will be suitable in order to confirm if the women’s attempt to increase their pension capital by engaging in riskier pension funds is rewarded by a higher return by including annually returns as an additional independent variable / Pensionering är en del av livet som alla förr eller senare kommer också. Det är mycket viktigt att förbereda och planera för det genom att leta efter bästa möjliga alternativ (s) för att spara och investera pengar i för att få tillräckligt med kapital för att leva på när det är dags att gå i pension. I Sverige liksom i många andra länder kvinnor tenderar att ha lägre löner än män och moderskapsledigheten är en händelse i livet som kan påverka inkomster kvinnor under sin arbetstid. Detta kan sedan leda till att kvinnor har mindre disponibel inkomst under pensionstiden. I allmänhet, kvinnor lever längre än män och därför bör de få mer pengar att leva på, men detta är inte fallet i större delen av tiden. I finans ta hög risk kan belönas med hög avkastning. Flera undersökningar som har genomförts inom olika områden kom till samma slutsats att kvinnor är mindre riskbenägna än män. Denna riskaversion kan förklaras av fysiologiska, psykologiska, sociala och intellektuella aspekter. I denna avhandling studerar jag investeringsbeteende båda könen i Premiepensionsfonder som förvaltas av Svenska Pensionsmyndigheten (PPM). I motsats till vad många forskare inom flera områden har kommit till, fann jag att män tenderar att investera mindre än kvinnor när risknivån med att investera i Premiepensionsfonderna ökar. Denna observation kan ses som ett försök av kvinnor att öka sitt pensionskapital i en kortare tid genom att investera i mer riskfyllda pensionsfonder. En påbyggande studie i detta ämne kommer att vara lämplig för att bekräfta om kvinnornas försök att öka sitt pensionskapital genom att delta i riskfyllda pensionsfonder belönas med en högre avkastning genom att inkludera avkastning som en ytterligare oberoende variabel.