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Cooperative geographic routing with radio coverage extension for SER-constrained wireless relay networks
No full text[[abstract]]Cooperative communication for wireless networks has been extensively investigated from the perspective of physical-layer design. However, the impact of physical-layer cooperation on the network-layer routing design still remains unclear. In this paper, we examine the potential benefit of radio coverage extension from cooperation, and present how to incorporate this feature into the routing design. Specifically, with a series of mathematical formulations and derivations, we quantitatively identify direct and cooperative radio coverages based on the average symbol error rate (SER) performance requirement, elucidating how cooperative diversity gain can be translated into radio coverage extension. We then propose a cooperative geographic routing protocol with cross-layer design, namely the Relay-Aware Cooperative Routing (RACR) protocol, that exploits the merit of radio coverage extension for improving the non-cooperative geographic routing. Simulation results show that the RACR protocol performs significantly better than the non-cooperative geographic routing in terms of the average path length in dense ad hoc networks.[[fileno]]2030102010061[[department]]電機工程學
Effects of pair correlation on mean-field theory of BTW sand pile model
No full text[[abstract]]We extend the mean-field calculation of BTW sand pile model to one that includes the correlation between pairs of nearest neighbors. Specifically, we derive dynamical equations of both one-site and two-site densities, and solve the equations order by order starting with the mean-field solution. The investigation provides analytical results for both stationary and dynamic states of the sand pile near the critical point, which are valid in the regime where h << epsilon(2) << 1 (h = incoming rate of sand grains, e = bulk dissipation rate of sand grains). In the stationary case, we evaluate the pair correlation and the correction to the mean-field single-site densities due to the correlation. The correction is found to be of the same order as the mean-field solution. In the dynamic case, the initial state deviates from the stationary state by a small fluctuation, which subsequently decays exponentially, with the time constant being reduced from the corresponding mean-field value. Again, the correction to the time constant in this case is found comparable to the mean-field value itself.[[fileno]]2030120010050[[department]]電機工程學
LCD 面板之LED 背光燈色序法驅動系統
No full text[[abstract]]本論文是針對液晶面板之發光二極體背光燈色序法驅動系統所做的研究與探討。近年來，由於發光二極體之發光效率提昇，且其具有色彩範圍廣、壽命長、以及容易驅動等優點，因此逐漸取代冷陰極管，成為新一代背光模組之發光源。本論文所提出之LED背光燈驅動系統採用色序法，其所搭配之面板不需彩色濾光片，因而改善光利用率，進而降低背光燈之必v。此外，我們提出一系列無漣波輸出電流之直流轉換器，以提升LED之色度準確度與可靠度；並且也提出發光二極體之旁路電路以防止其串列開路，以及加入一個驅動電壓重置電路防止瞬間電流突波，此兩種電路大幅提升系統可靠度與可行性。文中依據電路分析與設計，以及相關實務考量，製作一個LED背光燈色序法驅動系統，並藉由硬體量測結果驗證其效能及可行性。[[fileno]]2030197010024[[department]]電機工程學
A Structural Approach to Synthesizing Soft Switching PWM Converters
No full text[[abstract]]This paper presents a structural approach to synthesizing soft switching PWM converters based on the concept of basic converter units (BCUs). With a proper reconfiguration, several families of passive and active soft switching PWM converters can be synthesized from either buck BCU or boost BCU plus certain linear networks. These typical soft switching. converters include the well known topologies of buck, buck-boost, Zeta, boost, 'Cuk and Sepic. It has been shown that analysis of the converters can be conveniently performed from the derived general configurations, reducing the complexity significantly. Therefore, using the structural approach not only can explore more physical insights into the converters in a family, but can reveal more relationships among these soft switching converters over conventional approaches. These merits have made the proposed approach become uniquely valuable.[[fileno]]2030197010050[[department]]電機工程學
Improved Start-up Scenario of Single-Stage Electronic Ballasts
No full text[[abstract]]This paper presents improved start-up scenario for single-stage electronic ballast derived with synchronous switch technique (SST), Based on the SST, the derivation of a single-stage inverter (SSI) used for realizing the ballast is then addressed. The SSI can achieve both high power factor and ballasting function. During lamp start-up transition, power imbalance may exist between the power factor correction semi-stage and the ballast semi-stage, and filament preheating is an important issue. Power imbalance usually results in a high de-link voltage which, in turn, imposes high stress on the switching devices. Investigation of the ballast operation is conducted, from which control strategies for reducing component stresses and hot resistance detection circuits for minimizing electrode sputtering are therefore proposed. Hardware measurements have verified that on-off tests are higher than 18 000 times without significant sputtering.[[fileno]]2030197010056[[department]]電機工程學
Analysis and Design of an Isolated Single-Stage Converter Achieving Power Factor Correction and Fast Regulation
No full text[[abstract]]This paper presents the analysis and design of an isolated single-stage converter achieving high-power-factor correction and fast regulation. By using the technique suggested by Wu et at, a buck-boost converter and a flyback converter can be integrated to form the discussed converter. The buck-boost semistage working in the discontinuous conduction mode (DCM) functions as a power-factor corrector, and the flyback semistage operating in the DCM is a voltage regulator which is controlled, theoretically, to be independent of load variation. An approximated small-signal model of the converter operating in the DCM is developed, Design of a peak-current feedback loop with an optimal proportional integral controller is also presented. A prototype is implemented to verify that the analysis and design are effective and feasible.[[fileno]]2030197010075[[department]]電機工程學
