Made available in DSpace on 2016-04-26T20:48:46Z (GMT). No. of bitstreams: 1 Dissertacao Adriana Keiko Miyake.pdf: 3746552 bytes, checksum: 6dd1aaa0e7aa880c56b3871870d50940 (MD5) Previous issue date: 2006-06-20 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / As transformações ocorridas nas últimas décadas na economia internacional provocaram graves crises monetárias e fmanceiras em diversos países, resultando em crises cambiais e no abandono do regime de câmbio fixo. O aumento do poder do capital financeiro sobre o produtivo, decorrente da maior abertura e da desregulamentação dos mercados financeiros, foi um dos fatores que aumentou a vulnerabilidade de economias menos preparadas para essas mudanças, como foi o caso de muitos países em desenvolvimento. Ainda, a abertura comercial ocorrida nesses países expôs seu setor produtivo à crescente concorrência externa de grandes empresas multinacionais. Aliada a esses fatores, a forma com que a política foi conduzida por seus respectivos governos contribuiu para a deflagração da cnse. A crise cambial brasileira, ocorrida no início de 1999, acarretou problemas para toda a economia brasileira. Diante disso, este trabalho procurou estudar os fatores que poderiam ser apontados como responsáveis por esse acontecimento, para que, no futuro, situações semelhantes sejam previstas com maior antecedência e para que medidas sejam tomadas para evitar este tipo de desfecho. Foi feito um acompanhamento da economia, ao longo da década de 1990, para se identificar as variáveis que levaram à crise cambial. A partir disso, foi utilizado um instrumental matemático (regressão do tipo Probit) para se chegar a um modelo econométrico que relacionasse essas variáveis à probabilidade de ocorrência de crise. Diferentemente do que ocorreu nos países do leste asiático, que suscitou o desenvolvimento dos modelos chamados de terceira geração, o resultado obtido no caso brasileiro se mostrou em conformidade com aspectos tanto dos modelos de primeira quanto de segunda geração

In this thesis, the structural, optical and electrical properties of crystalline silicon quantum dots (SiQDs) are examined for application to silicon based tandem cells. The approach has been to concentrate on all silicon devices by taking advantage of quantum confinement in low-dimensional Si. RF magnetron co-sputtering provided the capability of creating superlattice structures in conjunction with high temperature annealing, to form Si nanocrystals in an oxide matrix. Structural techniques, including Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Secondary ion mass spectroscopy (SIM) were employed to gather structural information about the SiQD/SiO2 SLs. The result combine presents that the packing density of Si QDs, correlated to the oxygen content of the silicon rich oxide layer can be control independently. The effect of Si nanocrystallite density on Raman scattering is investigated. The preliminary results present that a decrease in the oxygen content (x) results in an increased sharpness of the Strokes-mode peak of nanocrystalline Si, attributed to an increase in the proportion of crystalline Si because of the increased number of SiQDs. However the influence of the surface region on the crystallite core intensity scattering becomes dominant, when SiQD size diameter is very small (less than 3 nm). The present work shows that a decrease in x-content leading to an increase of the SiQD concentration, initially results in the enhancement of the lateral conductivity in the SiQD superlattice material. In this work, the Al contacting scheme, using a prolonged heat treatment technique at elevated temperature less than the eutectic point of Al and Si (577C) has been successfully applied to making Ohmic contacts on both SiQD SLs in oxide and nitride matrices. Activation energy (Ea) of SiQDs, extracted from a linear Arrhenius plot is investigated in the present work in order to expand the understanding of engineering electrical injection in laterally active paths. It is found that a lower barrier height of dielectric matrix influences to the lateral electron transport of the SiQDs in such dielectric matrix. PL results confirm that the band gap of surface oxidized SiQDs widens due to quantum confinement. The present results reveal that the strong peak (Q-peak) due to quantum confinement is more effective in the emission with increasing SiQD concentration. The surface oxide is believed to play an important role in the reduction of SiQD luminescence due to a trapped exiciton. It is concluded that SiQDs surface oxide accompanied by a SiO2 matrix may not provide a good passivation in very small SiQD size. However the energy band gap and conductivity of the SiQDs are tunablity, in the optimum range of SiQD size and concentration. This observation may be important for future nanoelectronics applications.

我國在電信開放自由化後，行動通訊發展的腳步就一直以極快的速度成長，而第三代行動通訊則是目前行動通訊的大熱門，其擁有以往GSM系統所沒有的高速傳輸速度、以封包的方式傳輸資料等的特點、在搭配更優良的通訊品質，使得第三代行動通訊深受投資人的期待，而本論文則將針對我國未來第三代行動通訊市場，提出市場成形條件與關鍵成功因素。 本研究採定性分析之方法，除了探討相關文獻外，再以個案訪談之方式，希望能對第三代行動通訊市場做個完整的分析。個案對象包括行動通訊系統商、終端設備製造商、以及欲加入第三代行動通訊事業之新進入者。 本論文研究中，對於市場成形條件列出以下十點：傳輸技術的發展、消費者消費行為的了解、定價合理化、終端設備的出現、電信系統業者的存在、尋找適用於行動通訊網路的內容、行動整合平台的出現、網路安全問題的解決、行動通訊內容的蓬勃發展、網站使用者付費機制的形成。 而關鍵成功因素也列出下列十點，分別是找出殺手級應用服務、電信業者注意系統的穩定性、安全性及網路管理能力、行動終端設備的功能提升及與其他技術的整合、提供顧客個人化、客制化的第三代行動通訊服務、電信系統商與其他業者間拆帳問題的解決、政府的法令規定、行動終端供應速度必須滿足市場需求、針對企業用戶提供其所需要的服務內容、網路外部性的運用。 而市場成形條件與關鍵成功因素之間的關聯，則以兩者之關聯圖表做解釋。又未來的第三代行動通訊服務中，行動顧客關係管理(Mobile CRM)所扮演的角色將格外重要，這部份必須與行動整合平台間有著緊密的關聯，以行動顧客關係管理為基礎，結合未來WAP之PUSH機制的成熟，將更能夠達到主動行銷的概念，又利用行動終端設備屬於個人化產品的特性，將能夠讓一對一行銷的概念在未來第三代行動通訊中實現，再輔以本論文所提之市場關鍵成功因素，未來我國第三代行動通訊服務市場的發展將是值得期待的。

Since its introduction in 1993, the turbo coding error-correction technique has generated a tremendous interest due to its near Shannon-limit performance. Two key innovations of turbo codes are parallel concatenated encoding and iterative decoding. In its IMT-2000 initiative, the International Telecommunication Union (ITU) adopted turbo coding as a channel coding standard for Third-Generation (3G) wireless high-speed (up to 2 Mbps) data services (cdma2000 in North America and W-CDMA in Japan and Europe). For battery-powered hand-held wireless terminals, energy consumption is a major concern. In this thesis, a new design for an energy-efficient turbo decoder that is suitable for 3G wireless high-speed data terminals is proposed. The Log-MAP decoding algorithm is selected for implementation of the constituent Soft-Input/Soft-Output (SISO) decoder; the algorithm is approximated by a fixed-point representation that achieves the best performance/complexity tradeoff. To attain energy reduction, a two-stage design approach is adopted. First, a novel dynamic-iterative technique that is appropriate for both good and poor channel conditions is proposed, and then applied to reduce energy consumption of the turbo decoder. Second, a combination of architectural-level techniques is applied to obtain further energy reduction; these techniques also enhance throughput of the turbo decoder and are area-efficient. The turbo decoder design is coded in the VHDL hardware description language, and then synthesized and mapped to a 0. 18<i>&mu;</i>m CMOS technology using the standard-cell approach. The designed turbo decoder has a maximum data rate of 5 Mb/s (at an upper limit of five iterations) and is 3G-compatible. Results show that the adopted two-stage design approach reduces energy consumption of the turbo decoder by about 65%. A prototype for the new turbo codec (encoder/decoder) system is implemented on a Xilinx XC2V6000 FPGA chip; then the FPGA is tested using the CMC Rapid Prototyping Platform (RPP). The test proves correct functionality of the turbo codec implementation, and hence feasibility of the proposed turbo decoder design.

Radio frequency identification (RFID) is a versatile wireless technology usedworldwide. The fields of applications are many and its popularity constantlygrows due to smaller in size, better and less expensive components. RFID isused to identify, track or share information about an object using radio waves. This master thesis describes the process of designing and implementing ahandheld UHF RFID reader. The goal was to, based on a UHF RFID-chipdesign a fully functional, small in size and power efficient device. Amicrocontroller provides the user interface and is also used to control theRFID-chip and a Bluetooth device. A Bluetooth- and GPRS-compatible mobilephone will be used to forward data to a server connected to the Internet. Allparts of the design are described, such as the printed circuit board design aswell as the software for the micro controller and the mobile phone. Because the extent of this thesis it is neither possible nor necessary to dig toodeep into the Bluetooth- or GPRS-protocol. The focus will be on designingsoftware and hardware for the handheld unit. / Radio frekvens identifiering (RFID) är en mångsidig trådlös teknik somanvänds över hela världen. Områdena där tekniken används är många och dess popularitet växer konstant tack vare mindre storlek, bättre och billigarekomponenter. RFID används för att identifiera, spåra eller dela med siginformation om ett objekt med radiovågor. Det här examensarbetet beskriver processen av design och implementering aven handburen UHF RFID läsare. Målet har varit att, baserat på ett UHF-RFIDchip, designa en fullt fungerande, liten och strömsnål enhet. En microcontroller förser dels användaren med ett användargränssnitt och sköter delskommunikationen med RFID chip och en blåtandsmodul. En blåtands- ochGPRS- eller 3G-kompatibel mobiltelefon används for att skicka vidare data tillen server kopplad till Internet. Alla delar av designen är beskrivna, så som PCB design, mjukvara för micro controllern och mobiltelefonen. På grund av omfattningen av det här examensarbetet så har det inte varitmöjligt eller nödvändigt att gräva för djupt i Blåtands- eller GPRS/3Gprotokollen. Fokus är på att designa hårdvara och mjukvara för den handhållna enheten.

Since its introduction in 1993, the turbo coding error-correction technique has generated a tremendous interest due to its near Shannon-limit performance. Two key innovations of turbo codes are parallel concatenated encoding and iterative decoding. In its IMT-2000 initiative, the International Telecommunication Union (ITU) adopted turbo coding as a channel coding standard for Third-Generation (3G) wireless high-speed (up to 2 Mbps) data services (cdma2000 in North America and W-CDMA in Japan and Europe). For battery-powered hand-held wireless terminals, energy consumption is a major concern. In this thesis, a new design for an energy-efficient turbo decoder that is suitable for 3G wireless high-speed data terminals is proposed. The Log-MAP decoding algorithm is selected for implementation of the constituent Soft-Input/Soft-Output (SISO) decoder; the algorithm is approximated by a fixed-point representation that achieves the best performance/complexity tradeoff. To attain energy reduction, a two-stage design approach is adopted. First, a novel dynamic-iterative technique that is appropriate for both good and poor channel conditions is proposed, and then applied to reduce energy consumption of the turbo decoder. Second, a combination of architectural-level techniques is applied to obtain further energy reduction; these techniques also enhance throughput of the turbo decoder and are area-efficient. The turbo decoder design is coded in the VHDL hardware description language, and then synthesized and mapped to a 0. 18<i>&mu;</i>m CMOS technology using the standard-cell approach. The designed turbo decoder has a maximum data rate of 5 Mb/s (at an upper limit of five iterations) and is 3G-compatible. Results show that the adopted two-stage design approach reduces energy consumption of the turbo decoder by about 65%. A prototype for the new turbo codec (encoder/decoder) system is implemented on a Xilinx XC2V6000 FPGA chip; then the FPGA is tested using the CMC Rapid Prototyping Platform (RPP). The test proves correct functionality of the turbo codec implementation, and hence feasibility of the proposed turbo decoder design.

<p>Radio frequency identification (RFID) is a versatile wireless technology usedworldwide. The fields of applications are many and its popularity constantlygrows due to smaller in size, better and less expensive components. RFID isused to identify, track or share information about an object using radio waves.</p><p>This master thesis describes the process of designing and implementing ahandheld UHF RFID reader. The goal was to, based on a UHF RFID-chipdesign a fully functional, small in size and power efficient device. Amicrocontroller provides the user interface and is also used to control theRFID-chip and a Bluetooth device. A Bluetooth- and GPRS-compatible mobilephone will be used to forward data to a server connected to the Internet. Allparts of the design are described, such as the printed circuit board design aswell as the software for the micro controller and the mobile phone.</p><p>Because the extent of this thesis it is neither possible nor necessary to dig toodeep into the Bluetooth- or GPRS-protocol. The focus will be on designingsoftware and hardware for the handheld unit.</p> / <p>Radio frekvens identifiering (RFID) är en mångsidig trådlös teknik somanvänds över hela världen. Områdena där tekniken används är många och dess popularitet växer konstant tack vare mindre storlek, bättre och billigarekomponenter. RFID används för att identifiera, spåra eller dela med siginformation om ett objekt med radiovågor.</p><p>Det här examensarbetet beskriver processen av design och implementering aven handburen UHF RFID läsare. Målet har varit att, baserat på ett UHF-RFIDchip, designa en fullt fungerande, liten och strömsnål enhet. En microcontroller förser dels användaren med ett användargränssnitt och sköter delskommunikationen med RFID chip och en blåtandsmodul. En blåtands- ochGPRS- eller 3G-kompatibel mobiltelefon används for att skicka vidare data tillen server kopplad till Internet. Alla delar av designen är beskrivna, så som PCB design, mjukvara för micro controllern och mobiltelefonen.</p><p>På grund av omfattningen av det här examensarbetet så har det inte varitmöjligt eller nödvändigt att gräva för djupt i Blåtands- eller GPRS/3Gprotokollen. Fokus är på att designa hårdvara och mjukvara för den handhållna enheten.</p>

In this thesis, the structural, optical and electrical properties of crystalline silicon quantum dots (SiQDs) are examined for application to silicon based tandem cells. The approach has been to concentrate on all silicon devices by taking advantage of quantum confinement in low-dimensional Si. RF magnetron co-sputtering provided the capability of creating superlattice structures in conjunction with high temperature annealing, to form Si nanocrystals in an oxide matrix. Structural techniques, including Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Secondary ion mass spectroscopy (SIM) were employed to gather structural information about the SiQD/SiO2 SLs. The result combine presents that the packing density of Si QDs, correlated to the oxygen content of the silicon rich oxide layer can be control independently. The effect of Si nanocrystallite density on Raman scattering is investigated. The preliminary results present that a decrease in the oxygen content (x) results in an increased sharpness of the Strokes-mode peak of nanocrystalline Si, attributed to an increase in the proportion of crystalline Si because of the increased number of SiQDs. However the influence of the surface region on the crystallite core intensity scattering becomes dominant, when SiQD size diameter is very small (less than 3 nm). The present work shows that a decrease in x-content leading to an increase of the SiQD concentration, initially results in the enhancement of the lateral conductivity in the SiQD superlattice material. In this work, the Al contacting scheme, using a prolonged heat treatment technique at elevated temperature less than the eutectic point of Al and Si (577C) has been successfully applied to making Ohmic contacts on both SiQD SLs in oxide and nitride matrices. Activation energy (Ea) of SiQDs, extracted from a linear Arrhenius plot is investigated in the present work in order to expand the understanding of engineering electrical injection in laterally active paths. It is found that a lower barrier height of dielectric matrix influences to the lateral electron transport of the SiQDs in such dielectric matrix. PL results confirm that the band gap of surface oxidized SiQDs widens due to quantum confinement. The present results reveal that the strong peak (Q-peak) due to quantum confinement is more effective in the emission with increasing SiQD concentration. The surface oxide is believed to play an important role in the reduction of SiQD luminescence due to a trapped exiciton. It is concluded that SiQDs surface oxide accompanied by a SiO2 matrix may not provide a good passivation in very small SiQD size. However the energy band gap and conductivity of the SiQDs are tunablity, in the optimum range of SiQD size and concentration. This observation may be important for future nanoelectronics applications.

O crescente aumento da demanda de tráfego nas redes celulares vem aumentando a necessidade de uma melhor utilização dos recursos do sistema, já que sua expansão é custosa. Nas estações rádio base (ERB), a disponibilidade de largura de faixa de freqüências é limitada e desta maneira, em uma rede de comunicação móvel celular, o controle de admissão de chamadas exerce grande influência no desempenho do sistema, pois determina a utilização de banda das ERBs e se uma determinada quantidade de recursos (banda) será alocado ou não para uma determinada chamada. O desempenho da rede pode ser atrelado a determinados parâmetros, como a probabilidade de bloqueio de novas chamadas, probabilidade de bloqueio de chamadas handoff e a utilização de banda da rede. Este trabalho propõe um controle de admissão de chamadas que, no atendimento de uma chamada, faz o empréstimo de banda de chamadas em andamento na célula no caso de banda insuficiente. O sistema adota um mecanismo heurístico que determina a banda disponível para novas chamadas conforme os valores de certos parâmetros do sistema. O empréstimo de banda é realizado em chamadas em andamento nas células até níveis mínimos estabelecidos para cada tipo de chamada, que se diferenciam pelas necessidades de banda de cada uma. O algoritmo foi aplicado às bandas e características de uma rede de terceira geração (3G), que possui chamadas de voz, videoconferência, interação multimídia, e-mail, downloads e transferência de arquivos e a uma rede GSM/GPRS (global system for mobile communications/ general packet radio service), que possui chamadas de voz e de dados. Os resultados mostram melhorias na probabilidade de bloqueio de novas chamadas, probabilidade de bloqueio de handoff e na utilização de banda do sistema. / The recent growth in traffic loads in cellular networks has seen the need for a better use of system resources as its expansion is expensive. In the base transceiver station (BTS), the bandwidth availability is limited. Thus, in cellular networks the call admission control greatly influences the system performance because it determines the bandwidth use of the BTSs and if an amount of resources will or will not be allocated to a call. The network performance can be evaluated by parameters such as blocking probability of new calls, dropping probability of handoff calls and bandwidth use. This work proposes a call admission control that carries out the bandwidth borrowing when a call arrives and there is not enough bandwidth. The system makes use of a heuristic mechanism that determines the available bandwidth for the new calls according to some parameter values of the system. The bandwidth borrowing is applied to the cell ongoing calls until the minimum levels for each type are met. The algorithm was applied to the bandwidths and characteristics of a third generation cellular network, which supports voice calls, videoconference, multimedia interaction, e-mails, downloads and file transfers. It was also applied to a GSM/GPRS (global system for mobile communications/ general packet radio service), which supports voice and data calls. The results show improvements in the blocking probability of new calls, dropping probability of handoff calls and in the bandwidth use of the system.

La lumière du soleil est un bon candidat comme source propre et abondante d'énergie renouvelable. Cette source d'énergie écocompatible peut être exploitée pour répondre aux besoins croissants en énergie du monde. Plusieurs générations de cellules photovoltaïques ont été utilisées pour convertir directement la lumière solaire en énergie électrique. La troisième génération de type multijonction des cellules photovoltaïques est caractérisée par un niveau d'efficacité plus élevé que celui de tous les autres types de cellules photovoltaïques. Des dispositifs optiques, tels que des concentrateurs optiques, des séparateurs optiques et des dispositifs optiques réalisant simultanément la séparation du spectre et la concentration du faisceau ont été utilisés dans des systèmes de cellules solaires. Récemment, les Eléments Optiques Diffractifs (EOD) font l'objet d'un intérêt soutenu en vue de leur utilisation dans la conception de systèmes optiques appliqués aux cellules photovoltaïques. Cette thèse est consacrée à la conception d'un EOD qui peut réaliser simultanément la séparation du spectre et la concentration du faisceau pour des cellules photovoltaïques de type multijonction latéral ou similaire. Les EOD qui ont été conçus ont une structure sous-longueur d'onde et fonctionnent en espace lointain pour implanter la double fonction séparation du spectre et concentration du faisceau. Pour cette raison, des outils de simulation ont été développés pour simuler le comportement du champ magnétique à l'intérieur de l'EOD à structure sous-longueur d'onde. De plus, un propagateur hybride rigoureux a aussi été développé, il est basé sur les deux théories de la diffraction, à savoir la théorie scalaire et la théorie rigoureuse. La méthode FDTD (Finite Difference Time Domain) ou méthode de différences finies dans le domaine temporel a été utilisée pour modéliser la propagation du champ magnétique en champ proche c'est-à-dire à l'intérieur et autour de l'EOD. La méthode ASM (Angular Spectrum Method) ou méthode à spectre angulaire a été utilisée pour modéliser de façon rigoureuse la propagation libre en champ lointain. Deux EOD différents ont été développés permettant d'implanter les fonctions souhaitées (séparation du spectre et concentration du faisceau) ; il s'agit d'une part d'un composant diffractif intitulé G-Fresnel (Grating and Fresnel lens) qui combine un réseau avec une lentille de Fresnel et d'autre part d'une lentille hors-axe. Les composants proposés réalisent la séparation du spectre en deux bandes pour une plage visible-proche infrarouge du spectre solaire. Ces deux bandes peuvent être absorbées et converties en énergie électrique par deux cellules photovoltaïques différentes et disposées latéralement par rapport à l'axe du système. Ces dispositifs permettent d'obtenir un faible facteur de concentration et une efficacité de diffraction théorique d'environ 70 % pour les deux bandes séparées. Grâce à une distance de focalisation faible, ces composants peuvent être intégrés dans des systèmes compacts de cellules solaires. La validation expérimentale du prototype fabriqué montre une bonne correspondance entre les performances expérimentales et le modèle théorique / Sunlight represents a good candidate for an abundant and clean source of renewable energy. This environmentally friendly energy source can be exploited to provide an answer to the increasing requirement of energy from the world. Several generations of photovoltaic cells have been successively used to convert sunlight directly into electrical energy. Third generation multijunction PV cells are characterized by the highest level of efficiency between all types of PV cells. Optical devices have been used in solar cell systems such as optical concentrators, optical splitters, and hybrid optical devices that achieve Spectrum Splitting and Beam Concentration (SSBC) simultaneously. Recently, diffractive optical elements (DOE’s) have attracted more attention for their smart use it in the design of optical devices for PV cells applications.This thesis was allocated to design a DOE that can achieve the SSBC functions for the benefit of the lateral multijunction PV cells or similar. The desired design DOE's have a subwavelength structure and operate in the far field to implement the target functions (i.e. SSBC). Therefore, some modelling tools have been developed which can be used to simulate the electromagnetic field behavior inside a specific DOE structure, in the range of subwavelength features. Furthermore, a rigorous hybrid propagator is developed that is based on both major diffraction theories (i.e. rigorous and scalar diffraction theory). The FDTD method was used to model the propagation of the electromagnetic field in the near field, i.e. inside and around a DOE, and the ASM method was used to model rigorously propagation in the free space far field.The proposed device required to implement the intended functions is based on two different DOE’s components; a G-Fresnel (i.e. Grating and Fresnel lens), and an off-axis lens. The proposed devices achieve the spectrum splitting for a Vis-NIR range of the solar spectrum into two bands. These two bands can be absorbed and converted into electrical energy by two different PV cells, which are laterally arranged. These devices are able to implement a low concentration factor of “concentrator PV cell systems”. These devices also allow achieving theoretically around 70 % of optical diffraction efficiency for the both separated bands. The impact distance is very small for the devices proposed, which allows the possibility to integrate these devices into compact solar cell systems. The experimental validation of the fabricated prototype appears to provide a good matching of the experimental performance with the theoretical model.