Browsing by Issue Date, starting with "2009-04-27"

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RF phase shifter using a distributed feedback laser in microwave transport systems
(2009-04-27)
Peng, Peng-Chun
;
Wu, Fang-Ming
;
Jiang, Wen-Jr
;
Lan, Ruei-Long
;
Lin, Chun-Ting
This work experimentally demonstrates the efficacy of a radio-frequency phase shifter using a distributed feedback laser in a microwave transport system. Phase shifts of about 101 are obtained at 8.75GHz. The proposed phase shifter can amplify microwave signals and thereby improve transmission performance. Additionally, a similar single sideband modulation can be generated by the phase shifter. Experimental results indicate that the proposed phase shifter can be used in future long-distance microwave transport systems and all optical inverters. (C) 2009 Optical Society of America
Electrical properties of single and multiple poly(3,4-ethylenedioxythiophene) nanowires for sensing nitric oxide gas
(2009-04-27)
Lu, Hui-Hsin
;
Lin, Chia-Yu
;
Hsiao, Tzu-Chien
;
Fang, Yueh-Yuan
;
Ho, Kuo-Chuan
The electrical properties of conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), nanowires were studied to develop nitric oxide (NO) gas sensors with low working temperatures. A nanowire with a diameter of 300 nm was fabricated using dip-pen nanolithography (DPN) across a 55 mu m gap between a pair of electrodes. The electrical properties of single or multiple PEDOT nanowires were examined by plotting the current-voltage (I-V) curves in the range -3 V to +3 V at temperatures between 298 K and 393 K. The conductance of parallel wires was normalized with respect to the dimensions of the fabricated nanowires. The single nanowire exhibited nonlinear conductance associated with hysteresis but multiple wires did not. The currents increased with the temperature and the I-V characteristics were consistent with the power lawG(T)alpha T(alpha) with alpha similar to 5.14 and 5.43. The responses to NO were highly linear and reproducible, indicating that sensing using PEDOT nanowires was reliable with a minimal concentration of NO of 10 ppm. (c) 2009 Elsevier B.V. All rights reserved.
Efficiency Enhancement of GaAs Photovoltaics Employing Antireflective Indium Tin Oxide Nanocolumns
(2009-04-27)
Yu, Peichen
;
Chang, Chia-Hua
;
Chiu, Ching-Hua
;
Yang, Chin-Sheng
;
Yu, Jue-Chin
Highly-oriented indium tin oxide nano-columns are prepared by glancing-angle deposition with nitrogen. The tapered column profiles, which function as a graded-refiractive-index layer, offer superior antireflective characteristics. The nano-structured material serves as the conductive antireflective layer for GaAs solar cells, demonstrating a viable efficiency-boosting strategy for next-generation photovoltaics.
Stored don't-care based hierarchical search-line scheme
(2009-04-28)
Chang
;
Shu-Wei
;
Hwang
;
Wei
;
Chang
In the proposed stored don't-care hierarchical search-line scheme, a content-addressable memory (CAM) is divided into several blocks. Each block contains a plurality of local search-lines, a global search-line, a buffer and a memory memory cell. Data are stored in the blocks in order according to the length of the prefix. Data with the longest prefix is stored at the bottommost, and its don't-care state is used as the control signal of the buffer to control whether to transfer the data on the global search-line to the local search-line or not. The local search-line then transfer the value into the memory cell. There is no complex control circuit and extra storage device needed. Moreover, because the control signal directly comes from the don't-care state, power consumption on search-lines can be effectively reduced with no increase of search delay.
Mediation of chain reactions by propagating radicals during halogenation of H-masked Si(100): Implications for atomic-scale lithography and processing
(2009-04-28)
Ferng, Shyh-Shin
;
Wu, Shiao-Ting
;
Lin, Deng-Sung
;
Chiang, Tai C.
;
物理研究所
Scanning tunneling microscopy reveals a free radical-induced surface chain reaction in the chlorination of nanoscale patterns on an otherwise H-passivated (masked) Si (100). While scanning probe methods can be used to pattern active surface regions with single-bond precision, follow-up selective chemical vapor deposition with polyatomic molecules can produce various filling characteristics. On active surface regions, molecular Cl(2) undergoes an atom abstraction reaction in which a Si dangling bond abstracts one atom of the incident Cl(2) molecule while the complementary Cl atom is scattered away from the initial abstraction site either back into the vacuum or to be captured by a second dangling bond and adsorbed there, or to react with a nearby adsorbed H atom to form volatile HCl. In contrast, I(2) undergoes only dissociative adsorption on two immediately neighboring dangling bonds, whereby two I-Si bonds are formed simultaneously upon cleavage of the I(2) bond. The different chemisorption processes of the two model diatomic molecular gases place intrinsic limitations on atomic-scale lithography and processing: Adsorption of Cl(2) results in spillage over the prepatterned regions of active bonds. In contrast, adsorption of I(2) is a pair process and results in under-filling. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3122987]
Net transport due to noise-induced internal reciprocating motion
(2009-04-28)
Makhnovskii, Yurii A.
;
Rozenbaum, Viktor M.
;
Yang, Dah-Yen
;
Lin, Sheng Hsien
;
應用化學系
We consider a system of two coupled Brownian particles fluctuating between two states. The fluctuations are produced by both equilibrium thermal and external nonthermal noise, the transition rates depending on the interparticle distance. An externally induced modulation of the transition rates acts on the internal degree of freedom (the interparticle distance) and generates reciprocating motion along this coordinate. The system moves unidirectionally due to rectification of the internal motion by asymmetric friction fluctuations and thus operates as a dimeric motor that converts input energy into net movement. The properties of the motor are primarily determined by the properties of the reciprocating engine, represented by the interparticle distance dynamics. Two main mechanisms are recognized by which the engine operates: energetic and informational. In the physically important cases where only one of the motion-inducing mechanisms is operative, exact solutions can be found for the model with linearly coupled particles. We focus on the informational mechanism, in which thermal noise is involved as a vital component and the reciprocating velocity exhibits a rich behavior as a function of the model parameters. An efficient rectification method for the reciprocating motion is also discussed. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3116790]
Master curves and radial distribution functions for shear dilatancy of liquid n-hexadecane via nonequilibrium molecular dynamics simulations
(2009-04-28)
Tseng, Huan-Chang
;
Wu, Jiann-Shing
;
Chang, Rong-Yeu
;
應用化學系
;
Department of Applied Chemistry
Shear dilatancy, a significant nonlinear behavior of nonequilibrium thermodynamics states, has been observed in nonequilibrium molecular dynamics (NEMD) simulations for liquid n-hexadecane fluid under extreme shear conditions. The existence of shear dilatancy is relevant to the relationship between the imposed shear rate (gamma) over dot and the critical shear rate (gamma) over dot(c). Consequently, as (gamma) over dot < (gamma) over dot(c), the intermolecular equilibrium distance of the fluid remains unchanged, while the nonequilibrium state of the fluid approaches equilibrium. In contrast to (gamma) over dot > (gamma) over dot(c), the intermolecular distance is lengthened substantially by strong shear deformation breaking the equilibrium thermodynamic state so that shear dilatancy takes place. Notably, a characteristic shear rate (gamma) over dot(m), which depends on the root mean square molecular velocity and the average free molecular distance, is found in nonequilibrium thermodynamics state curves. Studies of the variations in the intermolecular radial distribution function (RDF) with respect to the shear rate provide a direct measure of the variation in the degree of intermolecular separation. Additionally, the variations of the RDF curve in the microscopic regime are consistent with those of the nonequilibrium thermodynamic state in the macroscopic world. By inspecting the overall shape of the RDF curve, it can be readily corroborated that the fluid of interest exists in the liquid state. More importantly, both primary characteristic values, the equilibrium thermodynamic state variable and a particular shear rate of (gamma) over dot(p), are determined cautiously, with (gamma) over dot(p) depending on the (gamma) over dot(m) value and the square root of pressure. Thereby, the nonequilibrium thermodynamic state curves can be normalized as temperature-, pressure-, and density-invariant master curves, formulated by applying the Cross constitutive equation. Clearly, (gamma) over dot(c) occurs at which a reduced shear rate (gamma) over dot/(gamma) over dot(p) approaches 0.1. Furthermore, the trends in the rates of shear dilatancy in both the constant-pressure and constant-volume NEMD systems under isothermal conditions conform to the cyclic rule of pressure, as a function of density and shear rate. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3123171]
METHOD FOR MODULATING REFRACTIVE INDICES OF OPTICAL FIBER GRATINGS
(2009-04-30)
HSU, Kuei Chu
;
Lai, Yin Chieh
The present invention proposes a method for modulating refractive indices of optical fiber gratings, wherein the UV exposure on a least one assigned location of an optical fiber grating is divided into to two UV shots, and the intensities or phases of the two UV shots, which expose the location sequentially, are controlled to make the total exposure intensity of one assigned location maintained at a fixed value, whereby the interference fringes, which are created by a superposition of the two UV shots, have fixed phases and adjustable intensities, and whereby the dc index of the optical fiber grating maintains fixed and the ac index independently adjustable.
Wireless Communication Receiving System and Apparatus and Method for Deciding a Transmitted Signal Corresponding to a Received Signal Thereof
(2009-04-30)
Wu, Wen-Rong
;
Wu, Jiun-Ying
A wireless communication receiving system and an apparatus and a method for deciding a transmitted signal corresponding to a received signal thereof are provided. The transmitted signal comprises a plurality of sub-transmitted signals. The system selects at least one of the sub-transmitted signals as a reference signal group, wherein each of a plurality of candidate values of the reference signal group forms a candidate geometric space respectively. The received signal is projected to each of the candidate geometric spaces to generate a projection signal respectively. In each of the candidate geometric space, the corresponding projection signal is quantized to generate a quantized projection signal having a projection distance to the corresponding projection signal. Finally, the transmitted signal is decided according the quantized projection signal and the candidate signal value corresponding to the shortest projection distance.
Method and Apparatus for Deciding a Channel Impulse Response
(2009-04-30)
Wu, Wen-Rong
;
Kao, Shiang-Lun
Method and apparatus for deciding a channel impulse response for an OFDM system are provided. First, a channel frequency response is generated by using a plurality of pilot tones of a signal. A channel impulse response is generated by applying the IFFT to the channel frequency response. A plurality of selected channel taps are derived by comparing a plurality of channel taps related to the channel impulse response with a reference threshold. Finally, the channel impulse response is generated by calculating channel impulse respose according to the selected channel taps. This method calculates the channel impulse response in time domain and frequency domain so that the calculation complexity can be reduced, and the system efficiency can be enhanced.
Wireless Communication Systems, Apparatus and Method for Encoding and Decoding a Plurality of Information Bits
(2009-04-30)
Wu, Wen-Rong
;
Shen, Shih-Chi
;
Lin, Yu-Cheng
Wireless transmitted system and apparatus and method for encoding a plurality of information bits to a plurality of transmitted signals thereof, and wireless received system and apparatus and method for decoding a received signal to a plurality of information bits thereof are provided. The wireless transmitted system encodes a plurality of information bits to a plurality of transmitted signals by two logic operation modules, an interleaving module, and a combination module. The wireless received system decodes a received signal to a plurality of information bits by a division module, two probability generation modules, two status calculation modules, a signal generation module and a combination module.
Prediction of O(2) Dissociation Kinetics on LaMnO(3)-Based Cathode Materials for Solid Oxide Fuel Cells
(2009-04-30)
Choi, YongMan
;
Lynch, Matthew E.
;
Lin, M. C.
;
Liu, Meilin
;
應用化學系分子科學碩博班
First-principles and statistical-theory calculations were applied to examine the interactions between oxygen molecules and the (100) surfaces of LaMnO(3) and La(0.5)Sr(0.5)MnO(2.75), one of the most-used cathode materials in solid oxide fuel cells (SOFCs). To predict the rate constants for the interactions between O(2) and LaMnO(3) or La(0.5)Sr(0.5)MnO(2.75), potential energy profiles were constructed using the nudged elastic band (NEB) method. Predicted rate constants for the dissociation of adsorbed oxygen species on LaMnO(3) (lm) and La(0.5)Sr(0.5)MnO(2.75) (lsm) can be expressed as k(diss,lm) = 2.35 x 10(12) exp(-0.50 eV/RT) s(-1) and k(diss,lsm) = 2.15 x 10(12) exp(-0.23 eV/RT) s(-1), respectively, in the temperature range of 873-1273 K at 1 atm. Because the activation energy for oxygen dissociation on La(0.5)Sr(0.5)MnO(2.75) (0.23 eV) is much smaller than that on LaMnO(3) (0.50 eV), oxygen vacancies greatly enhance O(2) dissociation kinetics. The kinetic and mechanistic studies for the interactions at the molecular level are imperative to gaining a fundamental understanding of oxygen reduction kinetics on cathode materials and to providing important insight into the rational design of more catalytically active cathode materials for SOFCs.
Prediction of O-2 Dissociation Kinetics on LaMnO3-Based Cathode Materials for Solid Oxide Fuel Cells
(2009-04-30)
Choi, YongMan
;
Lynch, Matthew E.
;
Lin, M. C.
;
Liu, Meilin
;
應用化學系分子科學碩博班
First-principles and statistical-theory calculations were applied to examine the interactions between oxygen molecules and the (100) surfaces of LaMnO3 and La0.5Sr0.5MnO2.75, one of the most-used cathode materials in solid oxide fuel cells (SOFCs). To predict the rate constants for the interactions between O-2 and LaMnO3 or La0.5Sr0.5MnO2.75, potential energy profiles were constructed using the nudged elastic band (NEB) method. Predicted rate constants for the dissociation of adsorbed oxygen species on LaMnO3 (lm) and La0.5Sr0.5MnO2.75 (lsm) can be expressed as k(diss,lm) = 2.35 x 10(12) exp(-0.50 eV/RT) s(-1) and k(diss,lsm) = 2.15 x 10(12) exp(-0.23 eV/RT) s(-1), respectively, in the temperature range of 873-1273 K at 1 atm. Because the activation energy for oxygen dissociation on La0.5Sr0.5MnO2.75 (0.23 eV) is much smaller than that on LaMnO3 (0.50 eV), oxygen vacancies greatly enhance O-2 dissociation kinetics. The kinetic and mechanistic studies for the interactions at the molecular level are imperative to gaining a fundamental understanding of oxygen reduction kinetics on cathode materials and to providing important insight into the rational design of more catalytically active cathode materials for SOFCs.
單端多埠之儲存裝置
(2009-05-01)
楊皓義
;
黃威
本發明係有關於一種單端多埠之儲存裝置,其藉由一第一反相器之第一輸入端耦接於一第二反相器之第二輸出端,第一反相器之第一輸出端耦接於第二反相器之第二輸入端,一均衡器,耦接該第一反相器與該第二反相器,以控制該第一反相器與該第二相器之電位,使耦接於第一反相器與於第二反相器之複數存取埠可存取資料。如此,可降低資料寫入儲存裝置所消耗的功率,並加快資料寫入儲存裝置的速度。
The Inductance Enhancement Study of Spiral Inductor Using Ni-AAO Nanocomposite Core
(2009-05-01)
Hsu, M. C.
;
Chao, T. Y.
;
Cheng, Y. T.
;
Liu, C. M.
;
Chen, C.
The letter presents the fabrication and characterization of on-chip spiral inductors with Ni-anodic alumina oxide (Ni-AAO) nanocomposite core. Ni nanorods with 70 nm diameter are deposited and isolated in an AAO matrix to form a layer of nanocomposite on silicon substrate. About 3% inductance enhancement to the inductor with the nanocomposite core has been observed and the enhancement can be kept up more than 6 GHz. Because the proposed inductance enhancement scheme using ferromagnetic-AAO-based nanocomposite as inductor core employs a CMOS-compatible fabrication process with the characteristics that can be further improved, it is our belief that the scheme has a great potential application for future radio frequency integrated circuitry (RFIC) manufacture.
Asymptotic Critical Transmission Radii for Greedy Forward Routing in Wireless Ad Hoc Networks
(2009-05-01)
Wan, Peng-Jun
;
Yi, Chih-Wei
;
Wang, Lixin
;
Yao, Frances
;
Jia, Xiaohua
In wireless ad hoe networks, greedy forward routing is a localized geographic routing algorithm in which one node discards a packet if none of its neighbors is closer to the destination of the packet than itself, or otherwise forwards the packet to the neighbor closest to the destination. If all nodes have the same transmission radii, the critical transmission radius for greedy forward routing is the smallest transmission radius which ensures packets can be delivered by greedy forward routing through any source-destination pair. In this paper, we study asymptotic critical transmission radii of randomly deployed wireless ad hoc networks. Assume network nodes are represented by a Poisson point process of density n over a unit-area convex compact region whose boundary curvature is bounded. We show that the ratio of critical transmission radii to root ln n/pi n is asymptotically almost surely equal to root 1/(2/3 - root 3/2 pi) approximate to 1.6.
Er-Yb Codoped Ferroelectrics for Controlling Visible Upconversion Emissions
(2009-05-01)
Huang, Tung-Ching
;
Hsieh, Wen-Feng
;
光電工程學系
;
Department of Photonics
Under a 980 nm laser pumping, quenching of green upconversion (UC) emission accompanied with enhancement of red UC emission observed was dominated by the energy back-transfer (EBT) process in Er(3+) and Yb(3+) codoped PbTiO(3), BaTiO(3), and SrTiO(3) polycrystalline powders. The efficiency of the EBT process depends not only on Yb(3+) concentration but also on level match of the doped Er(3+) and Yb(3+) ions caused by the crystal fields with different symmetries. Our UC emission spectra and X-ray diffraction confirm that the centrosymmetric crystal field arising from reducing tetragonality causes level match of transition (4)S(3/2) -> (4) I(13/2) of Er(3+) and (2)F(7/2) -> (2) F(5/2) of Yb(3+). This level match is responsible for enhancing red UC emission.
Location Classification of Nonstationary Sound Sources Using Binaural Room Distribution Patterns
(2009-05-01)
Hu, Jwu-Sheng
;
Liu, Wei-Han
;
電控工程研究所
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Institute of Electrical and Control Engineering
This paper discusses the relationships between the nonstationarity of sound sources and the distribution patterns of interaural phase differences (IPDs) and interaural level differences (ILDs) based on short-term frequency analysis. The amplitude variation of nonstationary sound sources is modeled by the exponent of polynomials from the concept of moving pole model. According to the model, the sufficient condition for utilizing the distribution patterns of IPDs and ILDs to localize a nonstationary sound source is suggested and the phenomena of multiple peaks in the distribution pattern can be explained. Simulation is performed to interpret the relation between the distribution patterns of IPD and ILD and the nonstationary sound source. Furthermore, a Gaussian-mixture binaural room distribution model (GMBRDM) is proposed to model distribution patterns of IPDs and ILDs for nonstationary sound source location classification. The effectiveness and performance of the proposed GMBRDM are demonstrated by experimental results.
Effect of Pulsed Electromagnetic Field on the Proliferation and Differentiation Potential of Human Bone Marrow Mesenchymal Stem Cells
(2009-05-01)
Sun, Li-Yi
;
Hsieh, Dean-Kuo
;
Yu, Tzai-Chiu
;
Chiu, Hsien-Tai
;
Lu, Sheng-Fen
Pulsed electromagnetic fields (PEMFs) have been used clinically to slow down osteoporosis and accelerate the healing of bone fractures for many years. The aim of this study is to investigate the effect of PEMFs on the proliferation and differentiation potential of human bone marrow mesenchymal stem cells (BMMSC). PEMF stimulus was administered to BMMSCs for 8 h per day during culture period. The PEMF applied consisted of 4.5 ms bursts repeating at 15 Hz, and each burst contained 20 Pulses. Results showed that about 59% and 40% more viable BMMSC cells were obtained in the 2 PEMF-exposed Cultures at 24 h after plating for the seeding density of 1000 and 3000 cells/cm(2) respectively. Although, based on the kinetic analysis, the growth rates of BMMSC during the exponential growth phase were not significantly affected, 20-60% higher cell densities were achieved during the exponentially expanding stage. Many newly divided cells appeared from 12 to 16 h after the PEMF treatment as revealed by the cell cycle analysis. These results Suggest that PEMF exposure Could enhance the BMMSC cell proliferation during the exponential phase and it possibly resulted from the shortening of the lag phase. In addition, according to the cytochemical and immunofluorescence analysis performed, the PEMF-exposed BMMSC showed multi-lineage differentiation potential similar to the control group. Bioelectromagnetics 30:251-260, 2009. (C) 2009 Wiley-Liss. Inc.
Effect of bump size on current density and temperature distributions in flip-chip solder joints
(2009-05-01)
Kuan, Wei-Chih
;
Liang, S. W.
;
Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Three dimensional thermo-electrical analysis was employed to simulate the current density and temperature distributions for eutectic SnAg solder bumps with shrinkage bump sizes. It was found that the current crowding effects in the solder were reduced significantly for smaller solder joints. Hot-spot temperatures and thermal gradient were increased upon reducing the solder. The maximum temperature for solder joint with 144.7 mu m bump height is 103.15 degrees C which is only 3.15 degrees C higher than the substrate temperature due to joule heating effect. However, upon reducing the bump height to 28.9 mu m, the maximum temperature in the solder increased to 181.26 degrees C. Serious joule heating effect was found when the solder joints shrink. The higher Joule heating effect in smaller solder joints may be attributed to two reasons, first the increase in resistance of the Al trace, which is the main heating source. Second, the average and local current densities increased in smaller bumps, causing higher temperature increase in the smaller solder bumps. (C) 2009 Published by Elsevier Ltd.