Browsing by Issue Date, starting with "2004-04-18"

Now showing 1 - 20 of 70322

Optimizing assembly planning through a three-stage integrated approach
(2004-04-18)
Chen, RS
;
Lu, KY
;
Tai, PH
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
This study proposes a three-stage integrated approach with heuristic working rules to assist the planner to develop a better assembly plan. In the first stage, Above Graph and transforming rules were used to create a correct Explosion Graph of the assembly models. In the second stage, a three-level relational model was developed to create a complete relational model graph and an incidence matrix. In the third stage, a mathematical model, based on a penalty index was formulated, and a revised minimum spanning table method was used to generate and evaluate a feasible assembly sequence. The example of a military system is presented to demonstrate the feasibility of the proposed method. The contribution of this study is based oil a design for assembly potential applications of three-dimensional (313) component models to assist manual or automatic assembly in a virtual environment, and allows the designer to recognize the relative position, constraints and relationships of 3D components using graph-oriented methods: Above Graph, assembly precedent diagram, and relational model graph. (C) 2003 Elsevier B.V. All rights reserved.
A case study on the multistage IC final testing scheduling problem with reentry
(2004-04-18)
Pearn, WL
;
Chung, SH
;
Chen, AY
;
Yang, MH
;
工業工程與管理學系
The integrated-circuit final testing scheduling problem (ICFTSP) with reentry is a variation of the complex flow-shop scheduling problem, which is also a generalization of the classical reentrant flow batch process problem, and the identical parallel machine problem. In this paper, we present a case study on the ICFTSP with reentry, which is taken from a final testing shop floor in an integrated circuit manufacturing factory. For the case investigated, the jobs are clustered by their product types, which must be processed on groups of parallel machines at various process stages following the manufacturing sequence, which must be completed before the due dates. The job processing time depends on the product type, and the machine setup time is sequentially dependent on the orders of jobs processed. The objective is to schedule jobs without violating all constraints, while the total machine workload is minimized. Since the ICFTSP has reentry characteristic, and involves job processing precedence, serial-processing stage, batch-processing stage, job clusters, job-cluster dependent processing time, due dates, machine capacity, and sequence dependent setup time, it is more difficult to solve than the classical flow-shop scheduling problem. We present three fast network algorithms to efficiently solve the ICFTSP with reentry and provide a performance comparison between the three algorithms on eight test problems. (C) 2003 Elsevier B.V. All rights reserved.
Low-temperature fabrication of carbon nanofibers by self-assembling of polycyclic aromatic hydrocarbon molecules
(2004-04-19)
Suen, SC
;
Whang, WT
;
Wu, BW
;
Lai, YF
;
材料科學與工程學系
Carbon nanofibers (CNFs) with diameter similar to66 nm have been synthesized from coronene by low-temperature (similar to45 degreesC) vacuum sublimation without the aid of a catalyst. Our method makes use of the property of polycyclic aromatic hydrocarbon (PAH) molecules, which can self-assemble into columnar aggregates. This polycyclic aromatic hydrocarbon-carbon nanofibers (PAH-CNFs) reveal much better thermal stability than commercial carbon nanotubes and exhibit field-emission characteristics with the onset of an electric field of 5.4 V/mum and field enhancement factor of 1326 cm(-1) for 100 mum interelectrode distance. The relative high thermal stability and easier process open up a possibility to fabricate large-scale field-emission devices in an efficient way and to provide a broad range of applications in nanoscience and technology. (C) 2004 American Institute of Physics.
傳送和包裝訊號的數位編碼方法與結構
(2004-04-21)
劉啟民
;
李文傑
一種數位編碼的方法，將輸入音訊轉換成頻率樣本序列，以代表該音訊的一種頻譜合成；並且根據一種位元分配程序，將此頻率樣本序列量化成量化值。藉由一個遮罩門檻值，此位元分配程序利用一個參數預估器來預估量化參數。此量化值被編碼成包含複數個位元的已編碼資料。如果此已編碼資料的位元數超過此已編碼資料的一個預定的可用位元數，則一個反覆比率控制迴圈會調整量化參數和量化間隔大小。在量化頻率樣本序列之前，此方法也會根據一個砍除頻率，將輸入音訊的高頻率分量砍除，此砍除頻率是由反覆比率控制迴圈來決定的。
Analysis of thermal and water management with temperature-dependent diffusion effects in membrane of proton exchange membrane fuel cells
(2004-04-22)
Yan, WM
;
Chen, FL
;
Wu, HY
;
Soong, CY
;
Chu, HS
In the present work, the detailed thermal and water management in the membrane of proton exchange membrane fuel cells (PEMFC) is investigated numerically. The coupling effects of mass diffusion and temperature gradient on the water distribution in the membrane are taken into account with consideration of the temperature-dependent diffusivity. Thermal and water transport equations with various boundary conditions are solved by the control volume finite difference method. Predictions show that under the conditions of fixed water concentration at the cathode side, the effect of cathode temperature, T-c, on the water concentration is significant. Increases in T-c may lead to an increase in membrane dehydration. At the water-flux condition on the cathode side, the influence of the operating temperature on the water distribution in the membrane shows a similar trend. The effects of the anode temperature, T-a, on the water management in the membrane are also examined. It is found that T-a has considerable impact on the water content in the membrane. In addition, high current density may cause non-uniformity of the temperature distribution in the membrane. (C) 2003 Elsevier B.V. All rights reserved.
Reply to comment by A.F. Moench on "Aquifer parameter identification using the extended Kalman filter''
(2004-04-28)
Leng, CH
;
Yeh, HD
;
環境工程研究所
;
Institute of Environmental Engineering
A solution to the forest leave problem for partial 6-cycle systems
(2004-04-28)
Ashe, DJ
;
Fu, HL
;
Rodger, CA
;
應用數學系
;
Department of Applied Mathematics
In this paper, we find necessary and sufficient conditions for the existence of a 6-cycle system of K-n - E(F) for every forest F of K-n. (C) 2003 Published by Elsevier B.V.
Gate structure of metal oxide semiconductor field effect transistor
(2004-04-29)
Bing-Yue, Tsui
;
Chih-Feng, Huang
The present invention provides an alloy system as metal gate material of MOSFET devices that can solve the issue of work function incompatibility of metal gate and then can achieve low threshold voltage of surface channel MOSFETs effectively to satisfy the requirement of low voltage and high performance operation. To achieve this purpose, a chemically inert and thermally stable element, platinum (Pt), with high work function is selected as the basic component, which is doped with low work function element, such as tantalum (Ta), or titanium (Ti) to various atomic ratios. The work function can be adjusted to arbitrary value depends on the atomic ratio of element. The metal alloy can be deposited with co-sputtering or co-evaporation method of physical vapor deposition to synthesize the suitable alloy of platinum (Pt) by adjustment of deposition rate of platinum (Pt) target and relative low work function metallic target, that can also be employed by simple sputtering on pre-formed platinum (Pt)—alloy target.
Development and evaluation of a generic evolutionary method for protein-ligand docking
(2004-04-30)
Yang, JM
;
生物科技學系
;
生物資訊及系統生物研究所
;
Department of Biological Science and Technology
;
Institude of Bioinformatics and Systems Biology
We have developed a generic evolutionary method with an empirical scoring function for the protein-ligand docking, which is a problem of paramount importance in structure-based drug design. This approach, referred to as the GEMDOCK (Generic Evolutionary Method for molecular DOCKing), combines both continuous and discrete search mechanisms. We tested our approach on seven protein-ligand complexes, and the docked lowest energy structures have root-mean-square derivations ranging from 0.32 to 0.99 Angstrom with respect to the corresponding crystal ligand structures. In addition, we evaluated GEMDOCK on crossdocking experiments, in which some complexes with an identical protein used for docking all crystallized ligands of these complexes. GEMDOCK yielded 98% docked structures with RMSD below 2.0 Angstrom when the ligands were docked into foreign protein structures. We have reported the validation and analysis of our approach on various search spaces and scoring functions. Experimental results show that our approach is robust, and the empirical scoring function is simple and fast to recognize compounds. We found that if GEMDOCK used the RMSD scoring function, then the prediction accuracy was 100% and the docked structures had RMSD below 0.1 Angstrom for each test system. These results suggest that GEMDOCK is a useful tool, and may systematically improve the forms and parameters of a scoring function, which is one of major bottlenecks for molecular recognition. (C) 2004 Wiley Periodicals, Inc.
Nanomechanical properties of TiC, TiN and TiCN thin films using scanning probe microscopy and nanoindentation
(2004-04-30)
Fang, TH
;
Jian, SR
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
TiC, TiN and TiCN thin films deposited on silicon (1 0 0) substrates using plasma enhanced chemical vapor deposition (PECVD) was investigated by scanning probe microscopy (SPM) and nanoindentation techniques. Results showed that the TiC film exhibits lower surface roughness and friction coefficient than the TiN and the TiCN films. Young's modulus and hardness both decreased as the indentation depth increased for all the films and the TiC film exhibited a higher hardness and Young's modulus. Additionally. the contact stress-strain relationships and fractal dimension were also analyzed. (C) 2004 Elsevier B.V. All rights reserved.
Adaptive asymptotic Bayesian equalization using a signal space partitioning technique
(2004-05-01)
Chen, RJ
;
Wu, WR
;
電信工程研究所
;
Institute of Communications Engineering
The Bayesian solution is known to be optimal for symbol-by-symbol equalizers; however, its computational complexity is usually very high. The signal space partitioning technique has been proposed to reduce complexity. It was shown that the decision boundary of the equalizer consists of a set of hyperplanes. The disadvantage of existing approaches is that the number of hyperplanes cannot be controlled. In addition, a state-search process, that is not efficient for time-varying channels, is required to find these hyperplanes. In this paper, we propose a new algorithm to remedy these problems. We propose an approximate Bayesian criterion that allows the number of hyperplanes to be arbitrarily set. As a consequence, a tradeoff can be made between performance and computational complexity. In many cases, the resulting performance loss is small, whereas the computational complexity reduction can be large. The proposed equalizer consists of a set of parallel linear discriminant functions and a maximum operation. An adaptive method using stochastic gradient descent has been developed to identify the functions. The proposed algorithm is thus inherently applicable to time-varying channels. The computational complexity of this adaptive algorithm is low and suitable for real-world implementation.
Schottky-barrier S/D MOSFETs with high-K gate dielectrics and metal-gate electrode
(2004-05-01)
Zhu, SY
;
Yu, HY
;
Whang, SJ
;
Chen, JH
;
Shen, C
This letter presents a low-temperature process to fabricate Schottky-barrier silicide source/drain transistors (SSDTs) with high-kappa gate dielectric and metal gate. For p-channel SSDTs (P-SSDT) using PtSi source/drain (S/D), excellent electrical performance of I-on/I-off similar to 10(7) - 10(8) and subthreshold slope of 66 mV/dec have been achieved. For n-channel SSDTs (N-SSDTs) using DySi2-x S/D, I-on/I-off can reach similar to 10(5) at V-ds of 0.2 V with two subthreshold slopes of 80 and 340 mV/dec. The low-temperature process relaxes the thermal budget of high-kappa dielectric and metal-gate materials to be used in the future generation CMOS technology.
Blind and semiblind detections of OFDM signals in fading channels
(2004-05-01)
Chang, MX
;
Su, YT
;
電信工程研究所
;
Institute of Communications Engineering
This paper considers the problem of blind joint channel estimation and data detection for orthogonal frequency-division multiplexing (OFDM) systems in a fading environment. Employing a regression model for a time-varying channel, we convert the problem into one that finds the data sequence x whose associated least-squares'(LS) channel estimate z(x) is closest to the space of some regression curves (surfaces). We apply the branch-and-bound principle to solve the nonlinear integer programming problem associated with finding the curve that fits a subchannel in the LS sense. A recursive formula for fast metric update is obtained by exploiting the intrinsic characteristic of our objective function. The impacts of reordering the data sequence and selective detection are addressed. By employing a preferred order along with a selective detection method, we greatly reduce the detector complexity while giving up little performance loss. Both the complete and the reduced-complexity algorithms can be used for blind and semiblind detections of OFDM signals in a subchannel-by-subchannel manner. To further reduce the complexity and exploit the frequency-domain channel correlation, we suggest a two-stage approach that detects a few selected positions in some subchannels first, and then, treating the detected symbols as pilots, determines the remaining symbols within a properly chosen time-frequency block by a two-dimensional model-based pilot-assisted algorithm. The proposed methods do not require the information of the channel statistics like signal-to-noise ratio or channel correlation function. Performance of differential modulations like differential quaternary phase-shift keying and STAR 16-ary quadrature amplitude modulation are provided. Both blind and semiblind schemes yield satisfactory performance.
一種鐵電層電極結構及製造方法
(2004-05-01)
曾俊元
;
李顯億
本案係指一種鐵電層電極結構及製造方法，其製造方法係包含下列步驟：(a)提供一基板；(b)形成一絕緣層於該基板上；(c)形成複數個氧化物電極於該絕緣層之上；(d)形成一鐵電層於該絕緣層及該複數個氧化物電極之上；以及(e)相對於該複數個氧化物電極形成複數個金屬電極於該鐵電層之上。
GEMDOCK: A generic evolutionary method for molecular docking
(2004-05-01)
Yang, JM
;
Chen, CC
;
生物科技學系
;
Department of Biological Science and Technology
We have developed an evolutionary approach for flexible ligand docking. This approval, GEMDOCK, uses a Generic Evolutionary Method for molecular DOCKing and an empirical scoring function. The former combines both discrete and continuous global search strategies with local search strategies to speed up convergence, whereas the latter results in rapid recognition of potential ligands. GEMDOCK was tested on a diverse data set of 100 protein-ligand complexes from the Protein Data Bank. In 79% of these complexes, the docked lowest energy ligand structures had root-mean-square derivations (RMSDs) below 2.0 Angstrom with respect to the corresponding crystal structures. The success rate increased to 85% if the structure water molecules were retained. We evaluated GEMDOCK on two cross-docking experiments in which each ligand of a protein ensemble was docked into each protein of the ensemble. Seventy-six percent of the docked structures had RMSDs below 2.0 Angstrom when the ligands were docked into foreign structures. We analyzed and validated GEMDOCK with respect to various search spaces and scoring functions, and found that if the scoring function was perfect, then the predicted accuracy was also essentially perfect. This study suggests that GEMDOCK is a useful tool for molecular recognition and may be used to systematically evaluate and thus improve scoring functions. (C) 2004 Wiley-Liss, Inc.
Single- and multiepoch analyses of global positioning system baseline network: Application to coordinate and velocity determinations in Central Taiwan
(2004-05-01)
Hwang, CW
;
Lee, LH
;
Yu, SB
;
Chen, HY
;
土木工程學系
Theories and computer programs are developed for single- and multiepoch analyses of a global positioning system (GPS) baseline network using the datum-free and weighted constraint solutions. Single-epoch analysis is for evaluating data quality, removing outliers, examining network precision, and estimating coordinates. Multiepoch analysis is for simultaneously determining epoch coordinates and station velocities. The datum-free solution yields estimable data residuals and relative coordinates and is suitable for adjusting data only and for detecting changes of relative coordinates. The weighted constraint solution allows a lower-order network to be attached to an existing, higher-order network. The analysis methods are applied to a multiepoch GPS baseline network in central Taiwan, which was hit by the 1999 Chi-Chi earthquake measuring 7.3 on the Richter scale. The velocities computed by the methods developed in this study are consistent with those from the Bernese GPS software. The result of the multiepoch analysis indicates that, in the first year after the Chi-Chi earthquake, the crust east of the Chelungpu Fault moved northwestwards at a mean rate of about 10 cm/year, while the crust west of the Chelungpu Fault moved in the opposite direction at a much lower speed.
Magnetism and electronic structure of Fe chains and nano-wires
(2004-05-01)
Yang, TJ
;
Zhao, YJ
;
Freeman, AJ
;
電子物理學系
;
Department of Electrophysics
The electronic and magnetic structures of an Fe linear chain and FCC and BCC nano-wires were determined by accurate first-principles self-consistent full potential linearized augmented plane wave calculations. The one-dimensional nature of the systems results in dramatic changes in their properties-as expected from the early predictions of Weinert and Freeman (J. Mag. Magn. Mater. 38 (1983) 23) for linear transition metal chains: a high density of states arising from van Hove singularities, large s-d-exchange splittings (larger in the chain than in the wires) and filled majority d bands (i.e., a "strong Stoner" ferromagnet) and strikingly enhanced Fe magnetic moments that depend on their coordination number. These unusual and distinctive properties are expected to invite somewhat unique experimental characterizations. (C) 2004 Elsevier B.V. All rights reserved.
Electronic-based procedure for managing unbalanced bids
(2004-05-01)
Wang, WC
;
土木工程學系
;
Department of Civil Engineering
Construction lump sum lowest bid procurement is one of the most prevalent methods of awarding construction contracts. For a lump sum bidding practice in Taiwan, after the lowest bidder is awarded a construction project contract, the contractual unit price for each cost item is taken as the product of the owner's estimated unit price and a discounting ratio equal to the total bid price divided by the owner's project cost estimate. This owner-based approach is inequitable because the bidder is denied the right to allocate the risks associated with the costs of performing the work. In U.S. practice, while the unit prices submitted by the bidder are usually considered as the contractual ones, unbalanced bids may occur. This work presents a bidder-based quantitative procedure, built on an electronic-based bidding process for effectively and efficiently supporting reviewing and adjusting the bidder's proposed unit prices for a lump sum procurement project. The advantages of this procedure include that the unit prices electronically obtained front the owner and all qualified bidders are included in analyses during unit-price evaluation, and that rules for unit-price adjustment along with maintaining the total contractual price are included. The novel procedure has been successfully applied to several construction projects in Taiwan and the results have been greatly appreciated by both governments and contractors.
Matching effect and flux pinning force in a Nb superconducting thin film with a triangular lattice of artificial pinning centers
(2004-05-01)
Horng, Lance
;
Wu, J. C.
;
Kang, P. C.
;
Wu, T. C.
;
Yang, T. J.
A strong pinning force in a Nb superconducting thin film is formed by a triangular lattice of defects due to the structural corrugation that acts as pinning centers. The magnetoresistance measurement close to the transition temperature shows a set of minima of magnetoresistance at equal external field intervals. A crossover in current-voltage relations with matching field and half-integer matching field occurs for currents exceeding a certain threshold value. The phenomenon is related to the presence of pinning structures at matching fields. (C) 2003 Elsevier B.V. All rights reserved.
Ballistic transport through coupled T-shaped quantum wires
(2004-05-01)
Lin, YK
;
Lin, KC
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
The ballistic conductance of a coupled T-shaped semiconductor quantum wire (CTQW) is studied. Two types of CTQW are considered, one of which is a H-shaped quantum wire (PiQW) which consists of two vertical arms on the same side of the horizontal arm and the other a Pi-clone quantum wire (PiCQW) which consists of two vertical armes on the opposite sides of the horizontal arm. The mode matching method and Landauer-Buttiker theory are employed to study the energy dependence of the ballistic conductance. Most of transmission profiles of PiQW and PiCQW are found to be distinguishable for large separation d between the two vertical arms. The transmission probability manifests oscillatory behavior when d is increased. When a potential is applied to the connection region, it results in decoupling or coupling effects between the two T-shaped quantum wires according to whether it is positive or negative. When magnetic field is applied to CTQW, the transmission profiles are found to be affected prominently even if the electron passes through the field free region only. (C) 2003 Elsevier B.V. All rights reserved.