Browsing by Issue Date, starting with "2006-10-18"

Now showing 1 - 20 of 62576

Magnetoresistance and percolation in Au-p-(PrBa2Cu3O7)(1-p) composites
(2006-10-18)
Le Touze, C.
;
Lin, J. J.
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
We examine the transverse magnetoresistance of three-dimensional bicomponent composites Au-p-(PrBa2Cu3O7)(1-p). This property, seldom measured on percolation systems, has been measured below 5 K and up to 1.5 T. Contrarily to well known transport properties, the magnetoresistance of these compounds exhibits a metal volume fraction's threshold pc linked to the onset of disorder rather than to percolation.
Chirped modulation of molecular vibration in quinoidal thiophene after sub-5 fs excitation
(2006-10-19)
Wang, Zhuan
;
Otsubo, Tetsuo
;
Kobayashi, Takayoshi
;
電子物理學系
;
Department of Electrophysics
Fourier transformation of the real-time trace of sub-5 fs pump-induced molecular vibration in quinoidal thiophene in solution revealed coupled modes to the electronic excitation at 206, 447, and 1466 cm(-1). Spectrogram analysis of 1466 cm(-1) (C=C stretching) mode showed that the amplitude and frequency of the mode are modulated with another low-frequency mode at about 220 cm(-1), which is down chirped being induced by the coupling with modes of even lower frequency, resulting in the irreversible relaxation due to high mode density in the low-frequency range. This Letter thus reports on observation of the modulation of vibrational frequency with a chirped frequency. (c) 2006 Elsevier B.V. All rights reserved.
Transmission method combining trellis coded modulation and low-density parity check code and architecture thereof
(2006-10-19)
Lin, Chien-Ching
;
Chang, Hsie-Chia `
;
Lee, Chen-Yi
The present invention discloses a method combining Trellis Coded Modulation (TCM) and Low-Density Parity Check (LDPC) code and the architecture thereof, which incorporates TCM with LDPC code having better error-correction capability to promote transmission quality and to define TCM of different transmission rates. Further, TCM can utilize less number of states to outperform the conventional spreading so that the hardware complexity in high-speed transmission can be reduced.
Scheduling method for supporting quality of service (QoS) in wireless local area network (WLAN)
(2006-10-19)
Huang, Ching Yao
;
Fan, Yu Long
A method for polling of stations in a Wireless Local Area Network (WLAN), comprising the steps of: obtaining Quality of Service (QoS) information related to the stations; assigning two timers to each WLAN service requiring QoS guarantee, one for uplink transmission and the other for downlink transmission; starting a Controlled Access Period (CAP) when a minimum timer Tm is below the threshold Tthr; polling the station with the minimum timer; updating the minimum timer after a polling message is sent; quitting CAP and permitting the resource contention if the minimum timer Tm is larger than the threshold Tthr.
Method and computer program for constructing complex structure graphic
(2006-10-19)
Chen, Ming-Jang
A general complex structure graph constructing method and the associated computer program is described. The generators and initiators selected by the user are used as the geometrical graphing basis. Using the transformation information of the generators and the operation information between the generators and the initiators, the geometrical transformation and duplication of the objects are performed according to the definitions of duplication objects and connecting objects. This implements the geometrical graphing of complex structures. It is characterized in that: the operations are performed in a visualized way, including graphing operations (e.g., generation of objects), parameter transmissions (e.g., shifted duplications), and data generation (e.g., generation of a geometrical graph). Since the operations are simple and can be implemented on all computer executable platforms and is suitable for artistic designs, graphing, and teaching.
應用於視訊編碼／解碼之解塊濾波方法及其裝置
(2006-10-21)
鄭朝鐘
;
張添烜
;
林天虹
一種應用於視訊編碼/解碼之解塊濾波方法，其步驟包含依據一解塊方向，依序讀取相鄰於一垂直邊界之該次區塊，並對該垂直邊界進行該解塊處理；將一目前次區塊之像素資料進行轉置；對該目前次區塊之一平行邊界進行該解塊處理，相鄰於該平行邊界之另一次區塊之像素資料則轉置後輸出；依序儲存多個該目前次區塊；以及在該目前巨集區塊之解塊處理完成後，將該多個目前次區塊之像素資料轉置輸出。
高解析度智慧型階次診斷系統及其診斷方法
(2006-10-21)
白明憲
;
洪銘宏
;
黃嘉閔
;
蘇富誠
本發明係關於一種高解析度智慧型階次診斷系統及其診斷方法，其係用於旋轉設備之頻率階次分析(order analysis) 與診斷，包括：資料擷取裝置，機台資料建立裝置，時頻譜分析和再取樣分析裝置，卡氏濾波器(Kalman filter)或遞迴最小平方演算法(RLS)分析裝置，模糊判斷裝置，視窗介面(GUI)裝置，其中該系統係反覆施行前述各裝置之功能，以隨時獲取該旋轉設備之診斷結果。
無線網路設備進行無線網路基地臺交遞的方法
(2006-10-21)
曾建超
;
謝明燈
;
張弘鑫
;
范榮軒
本發明係揭露一種無線網路設備進行無線網路基地臺交遞的方法，在本方法中，無線網路設備必須取得整個無線網路基地臺的佈置資訊與本身所在之位置資訊，或再計算自己的移動方向，以便在進行無線網路基地臺之交遞時，找出無線網路設備鄰近或靠近中的無線網路基地臺，並直接交遞至該無線網路基地臺。由於本發明乃利用無線網路設備位置資訊、無線網路基地臺佈置資訊與無線網路設備移動方向來快速地決定欲交遞之目標無線網路基地臺，故可節省交遞過程中，探索無線網路基地臺所須的時間，有助於快速的聯接層交遞。
Theoretical treatments of ultrafast electron transfer from adsorbed dye molecule to semiconductor nanocrystalline surface
(2006-10-21)
Liang, Kuo Kan
;
Lin, Chih-Kai
;
Chang, Huan-Cheng
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
In studying ultrafast electron transfer from a dye molecule to a nanosized semiconductor particle, pump-probe experiments are commonly used. In this system the electron transfer (ET) rate is faster than vibrational relaxation so that the ET rate should be described by a single-level rate constant and the probing signal (often in the form of time-resolved spectra) contains the contribution from the dynamics of both population and coherence (i.e., wave packet). In this paper, we shall present the theoretical treatments for femtosecond time-resolved pump-probe experiment and the dynamics of population and coherence by the density matrix method, and the calculation of single-level ET rate constant involved in a pump-probe experiment. As an application, we show the theoretical results using parameters extracted from experiments on a specific dye/semiconductor system. (c) 2006 American Institute of Physics.
利用隨機位元重排獲致精細度可縮放的執行上下文適性二進制算術編碼的方法
(2006-10-21)
彭文孝
;
蔣迪豪
;
杭學鳴
本發明揭露一種利用隨機位元重排架構以執行上下文為本的二進制算術編碼的方法，其在改善基於MPEG-4精細度可縮放(fine granularity scalability, FGS)的位元平面編碼。該方法包括下列步驟：以MPEG-4 AVC(Advanced Video Coding)中的4×4整數轉換係數取代8×8 DCT；將各轉換係數分割為有效位元(significant bit)與精化位元(refinement bit)；根據轉換區塊中的能量分布與鄰近區塊的空間相關性，設定有效位元上下文；利用一估測的拉普拉斯分布 (Laplacian distribution)導出精化位元的編碼機率；以及利用位元平面之間的上下文來分割各有效位元平面，以節省側邊資訊位元。
真空紫外線激發之紅光螢光材料與其製造方法
(2006-10-21)
陳登銘
;
吳佳蓁
本發明係揭露一種真空紫外線激發之紅光螢光材料與其製造方法，此紅光螢光材料組成化學式表示為(Y1-r-sGds)(V1-tPt)O4：rEu，其中0≦r≦0.5，0 < S < 1，0 < t < 1，此紅光螢光材料為可供電漿電視、背光源或照明燈具使用之紅光螢光材料，其具有更高的發光強度與更佳色飽和度。
Characterization of Zr-doped TiO2 nanocrystals prepared by a nonhydrolytic sol-gel method at high temperatures
(2006-10-26)
Chang, Sue-min
;
Doong, Ruey-an
;
環境工程研究所
;
Institute of Environmental Engineering
Highly crystalline and surface-modified Zr-doped TiO2 nanorods were successfully prepared using a nonhydrolytic sol-gel method that involves the condensation of metal halides with alkoxides in anhydrous trioctylphosphine oxide (TOPO) at either 320 or 400 degrees C. In addition, the interaction of the cross-condensation between the Ti and Zr species was studied by characterizing the morphologies, crystalline structures, chemical compositions, surface properties, and band gaps of the nanocrystals obtained at different reaction temperatures and Zr-to-Ti stoichiometric ratios. Increases in the concentration of Zr4+ and in the reaction temperature led to large nanorods and regular shapes, respectively. In addition, only the anatase form was observed in the Zr-doped TiO2 nanorods. The Zr-to-Ti ratios obtained ranged from 0.01 to 2.05, all of which were far below the stoichiometric ratios used during the preparation of the samples (0.25-4). Moreover, the Zr4+ units accumulated mainly at the surface of the TiO2 nanocrystals. The band gaps of the Zr-doped TiO2 nanorods ranged from 2.8 to 3.8 eV, which are smaller than those of pure TiO2 (3.7 eV) or ZrO2 (5.2 eV). The Zr-doped anatase TiO2 nanorods prepared at 400 degrees C at an initial stoichiometric Zr-to-Ti ratio of 2: 3 exhibited the highest photoactivities for the decomposition of rhodamine B because of the presence of trace amounts of Zr4+ (Zr/Ti = 0.03) in the TiO2 and the regular shapes of these particles. DSC analysis indicated that the temperatures for forming nanocrystalline TiO2 and ZrO2 were 207 and 340 degrees C, respectively. Moreover, the reactivities of condensation between the Ti species were reduced when Zr species were involved in the NHSG reactions. The results obtained in this study clearly demonstrate that the faster kinetics for the generation of TiO2 controls the material properties as well as the photoactivities of the nonhydrolytic sol-gel-derived nanocrystals.
Method for updating check-node of low-density parity-check (LDPC) codes decoder and device using the same
(2006-10-26)
Lee, Chen-Yi
;
Lin, Chien-Ching
;
Lin, Kai-Li
;
Chang, Hsie-Chia
The invention provides a method for updating check-node of low-density parity-check (LDPC) codes decoder. The method comprises the following steps: First of all, sort all data that are input into the check-node of LDPC codes decoder to find a minimum absolute value and a second minimum absolute value. Secondly, compare each of all the data to both of the minimum absolute value. If the compared data is equivalent to the current minimum absolute value, the compared data is updated by the secondary minimum absolute value. Otherwise, the compared data is updated by the minimum absolute value.
Effects of cathode humidification on the gas-liquid interface location in a PEM fuel cell
(2006-10-27)
Lee, Chun-I
;
Chu, Hsin-Sen
;
機械工程學系
;
Department of Mechanical Engineering
This study investigates the location of the gas-liquid interface under various humidity conditions in the cathode gas diffusion layer and the conventional flow field of a polymer electrolyte membrane fuel cell (PEMFC), using commercial computational fluid dynamics (CFDRC) analysis, based on a three-dimensional steady state isothermal model. The effects of the formation of liquid water on the transport of reactant gas are considered in the model. The simulation results indicate that the gas-liquid interface approaches the gas flow channel inlet and the cell performance declines gradually as liquid water obstructs the pores in the porous media as the relative humidity of the cathode is increased. Additionally, the oxygen fraction, the water fraction and the liquid water saturation field along the flow channel are presented. (c) 2006 Elsevier B.V. All rights reserved.
Effect of inlet flow maldistribution on the thermal and electrical performance of a molten carbonate fuel cell unit
(2006-10-27)
Liu, Syu-Fang
;
Chu, Hsin-Sen
;
Yuan, Ping
;
機械工程學系
;
Department of Mechanical Engineering
This study investigates the temperature and current density distributions in a molten carbonate fuel cell unit when the inlet flows of the anode gas and the cathode gas are mal-distributed in eight patterns. The two-dimensional simultaneous partial differential equations of mass, energy and electrochemistry are solved numerically. The results indicate that the maldistribution of anode and cathode gases dominates the current density field and the cell temperature field, respectively. Moreover, the non-uniform inlet flow slightly affects the mean temperature and mean current density, but worsens the distribution of temperature and current density for most maldistribution patterns. According to the results, the variations of the cell temperature in Pattern G and the current density in Pattern D are 12% and 37% greater than those in the uniform pattern when the deviation of the non-uniform profile is 0.25. Consequently, the effect of non-uniform inlet flow on the temperature and current density distribution on the cell plane is evident, and cannot be neglected. (c) 2006 Elsevier B.V. All rights reserved.
Transient behavior of a PEMFC
(2006-10-27)
Chang, Shih-Ming
;
Chu, Hsin-Sen
;
機械工程學系
;
Department of Mechanical Engineering
The transient behavior of a proton exchange membrane fuel cell (PEMFC) with porosity is investigated in this study using a two-phase, half-cell model. The thin film agglomerate approach is used to model the catalyst layer. Both vapor transport and liquid water transport in the PEMFC are examined in this study. Proton transport is much faster than the gaseous and liquid water transport. The ionic potential reaches a steady state level in similar to 10(-1) s but liquid water transport takes similar to 10 s. The variation of the ionic potential loss reaches a critical value, decreasing to a steady state, and is not monotonic. The gas diffusion layer (GDL) and the catalyst layer (CL) porosity, which can affect cell performance, have been carefully investigated. The current density rises rapidly within 10(-2) S, then remaining constant. After I s, this is affected by the cell voltage, GDL porosity, and CL porosity, and if the GDL porosity is below 0.4, the current density drops. For the gas diffusion layer porosity, the current density increases between epsilon(GDL) = 0.2 and epsilon(GDL) = 0.5, with increased GDL porosity. For the catalyst layer porosity, the optimum value appears between epsilon(CL) = 0.06 and epsilon(CL) = 0.1 (c) 2006 Elsevier B.V. All rights reserved.
Growth behaviour of Ge nano-islands on the nanosized Si{111} facets bordering on two {100} planes
(2006-10-28)
Ferng, Shyh-Shin
;
Yang, Tsung-Hsi
;
Luo, Guangli
;
Yang, Kai-Ming
;
Hsieh, Ming-Feng
Si( 100) substrates were used to fabricate various nanosized {111} facets between the ( 100) planes using photolithography and anisotropic wet chemical etching. Following simultaneous Ge chemical vapour deposition on the neighbouring ( 100) and {111} facets, the Ge nano-island formation and distribution was observed on both the ( 100) terraces and the {111} side walls using a dynamical atomic force microscope. The nano-island formation on the nanosized {111} strip facets was found to be strongly suppressed upon reducing the strip width due primarily to the interaction of adatoms on the neighbouring facets. Specifically, the difference in the effective chemical potential of Ge adatoms on the two neighbouring facets leads to the depletion of nano-islands on the {111} strip with width < 500 nm under the growth condition used in this study.
Experimental and theoretical investigation of rate coefficients of the reaction S(P-3)+OCS in the temperature range of 298-985 K
(2006-10-28)
Lu, Chih-Wei
;
Wu, Yu-Jong
;
Lee, Yuan-Pern
;
Zhu, R. S.
;
Lin, M. C.
The reaction S(P-3)+OCS in Ar was investigated over the pressure range of 50-710 Torr and the temperature range of 298-985 K with the laser photolysis technique. S atoms were generated by photolysis of OCS with light at 248 nm from a KrF excimer laser; their concentration was monitored via resonance fluorescence excited by atomic emission of S produced from microwave-discharged SO2. At pressures less than 250 Torr, our measurements give k(298 K)=(2.7 +/- 0.5)x10(-15) cm(3) molecule(-1) s(-1), in satisfactory agreement with a previous report by Klemm and Davis [J. Phys. Chem. 78, 1137 (1974)]. New data determined for 407-985 K connect rate coefficients reported previously for T >= 860 and T <= 478 K and show a non-Arrhenius behavior. Combining our results with data reported at high temperatures, we derived an expression k(T)=(6.1 +/- 0.3)x10(-18) T-1.97 +/- 0.24 exp[-(1560 +/- 170)/T] cm(3) molecule(-1) s(-1) for 298 <= T/K <= 1680. At 298 K and P >= 500 Torr, the reaction rate was enhanced. Theoretical calculations at the G2M(CC2) level, using geometries optimized with the B3LYP/6-311+G(3df) method, yield energies of transition states and products relative to those of the reactants. Rate coefficients predicted with multichannel Rice-Ramsperger-Kassel-Marcus (RRKM) calculations agree satisfactorily with experimental observations. According to our calculations, the singlet channel involving formation of SSCO followed by direct dissociation into S-2(a (1)Delta(g))+CO dominates below 2000 K; SSCO is formed via intersystem crossing from the triplet surface. At low temperature and under high pressure the stabilization of OCS2, formed via isomerization of SSCO, becomes important; its formation and further reaction with S atoms partially account for the observed increase in the rate coefficient under such conditions. (c) 2006 American Institute of Physics.
Pulse retrieval from interferometric autocorrelation measurement by use of the population-split genetic algorithm
(2006-10-30)
Chen, Ching-Wei
;
Huang, Jung Y.
;
Pan, Ci-Ling
;
光電工程學系
;
Department of Photonics
The population-split genetic algorithm ( PSGA) was successfully applied to retrieve femtosecond optical fields from interferometric autocorrelation traces. PSGA strikes a balance between diversity and the size of population in the genetic algorithm. As a result, PSGA is less likely prematurely converging to sub-optimal solutions. Theoretical and experimental studies indicate that the PSGA can yield more accurate results in shorter time compared with conventional genetic algorithm and the iterative method. (c) 2006 Optical Society of America.
Monolithic red-green-blue laser light source based on cascaded wavelength conversion in periodically poled stoichiometric lithium tantalate
(2006-10-30)
Gao, Z. D.
;
Zhu, S. N.
;
Tu, Shih-Yu
;
Kung, A. H.
;
光電工程學系
A compact, pulsed, red, green, and blue laser source based on cascaded quasi-phase-matched wavelength conversion in two periodic superlattices set in tandem in a single stoichiometric LiTaO3 crystal and pumped by a laser source at 532 nm is reported. The white light equivalent flux obtained was 80 lm per 1 W input with a green to white light power conversion efficiency of > 30%. Unity power conversion is feasible in this monolithic approach. (c) 2006 American Institute of Physics.