Browsing by Issue Date, starting with "2002-02-21"

Now showing 1 - 20 of 74895

最短篇名家展
(2002-02-21)
管管
無線傳輸系統
(2002-02-21)
張瑞川
;
黃良益
;
姜美玲
一種整合Access Point間通信技術與移動式IP技術而成的無線傳輸系統，用來解決移動主機在相同子網域內不同的BSS之間handoff的問題，並使移動主機也能在不同的手網域中任意的移動。本發明利用特殊之設計，以減少不必要或多餘的資料傳輸，以在無線的網路環境有限傳輸頻寬下，提供更有效率的資料傳輸。實驗結果證明了移動主機除了能在不同網域中任意漫遊外，同時也能在相同的網域中任意移動，且順利的進行資料傳輸。
Effects of CH4/SiH4 flow ratio and microwave power on the growth of beta-SiC on Si by ECR-CVD using CH4/SiH4/Ar at 200 degrees C
(2002-02-22)
Lee, WH
;
Lin, JC
;
Lee, C
;
Cheng, HC
;
Yew, TR
The effects of CH4/SiH4 flow ratio and microwave power on the formation of SiC at 200 degreesC by electron cyclotron resonance chemical vapor deposition is investigated. When the CH4/SiH4 flow ratio is varied from 0.5 to 10, crystalline phase of films vary from polycrystalline silicon to polycrystalline P-SiC and finally to amorphous silicon carbide. However, as the microwave power increases from 300 to 1500 W. the film microstructure changes from polycrystalline Si to amorphous SiC. and finally to polycrystalline beta-SiC. The deposition mechanism which controls the film characteristics is also presented. (C) 2002 Elsevier Science B.V. All rights reserved.
Anisotropic diffraction of light by volume holographic grating in birefringent photorefractive crystals with extended wavelength range
(2002-02-25)
Zaitsev, AK
;
Hsu, KY
;
Lin, SH
;
交大名義發表
;
National Chiao Tung University
The properties of anisotropic diffraction of light by volume holographic grating in birefringent photorefractive crystals are discussed. This diffraction takes place when the refractive index for diffracted light is different from the refractive index for incident light. It is found that in some special geometry of wavevector diagram the diffraction becomes less sensitive to the wavelength mismatch of Bragg condition. The wavelength range may extent in several times the range of ordinary isotropic diffraction on the grating of the same spacing and thickness. Theoretical explanation of this phenomena and experimental results of widerange diffraction in BaTiO3 photorefractive crystal are also presented. (C) 2002 Optical Society of America.
Identification of the general acid/base catalyst of a family 3 beta-glucosidase from Flavobacterium meningosepticum
(2002-02-26)
Li, YK
;
Chir, J
;
Tanaka, S
;
Chen, FY
;
應用化學系
beta-Glucosidase from Flavobacterium meningosepticum (Fbgl) (also known as Chryseobacterium meningosepticum) has been classified as a member of the family 3 glycohydrolases. It is a retaining enzyme involving a two-step, double-displacement mechanism. 0247 was shown to function as the nucleophile of the enzymatic reaction [Li, Y.-K., Chir, J., and Chen, F.-Y. (2001) Biochem. J. 355, 835-840]. However, the general acid/base catalyst of this enzyme and of all other family 3 glycohydrolases has not yet been identified. On the basis of amino acid sequence alignment of 15 family 3 enzymes, 11 residues (071, 8129, E132, E136, D137, K168, H169, E177, D247, D458, and E473) are highly conserved. All of these residues are studied by site-directed mutagenesis and kinetic investigation. Analyzing the catalytic power of all mutants reveals E473 residue is the best candidate of the acid/base catalyst. Detailed studies supporting this suggestion are summarized as follows. (1) The k(cat) and K-m values for the hydrolysis of 2,4-dinitrophenyl beta-D-glucopyranoside (2,4-DNPG) by E473G are reduced 3300- and 900-fold, respectively, compared with those of the wild type (WT). (2) The k(cat) values of E473G-catalyzed hydrolysis are virtually invariant with pH over the range of 5.0-9.0. (3) The activity of E473G with 2,4-DNPG is enhanced by the addition of azide, and beta-glucosyl azide is formed. (4) The k(cat) of the reaction of 2-carboxyphenyl beta-glucoside catalyzed by E473G is comparable to that for hydrolysis by wild-type Fbgl and is 100- and 320-fold better than the k(cat) values for the E473G-catalyzed hydrolysis of 4-carboxyphenyl beta-glucoside and the corresponding methyl ester, respectively. (5) The accumulated glucosyl-enzyme intermediate was directly observed by mass analysis in the reaction of 2,4-DNPG with E473G. All of these results confirm that E473 is the general acid/base catalyst of Fbgl.
A study on seamless tube in the planetary rolling process
(2002-02-28)
Shih, CK
;
Hsu, RQ
;
Hung, CH
;
機械工程學系
;
Department of Mechanical Engineering
In this paper, the finite element method and the dual-stream functions upper bound method are selected to analyze the tube rolling process with a planetary rolling mill. Three-dimensional elastic-plastic finite element simulations with special emphasis on the determination of the roller profile and realistic contact conditions between the rollers, workpiece and mandrel are used to reveal the deformation characteristics of seamless tube during the rolling process. In addition, the kinematically admissible velocity field of the deforming tube is described in terms of two stream functions so that the velocity components of the deforming tube can be obtained through the upper bound analysis. In both analysis methods, the equation of meshing is used to determine the contact condition between the rollers and the workpiece. The results from both methods with different variables are observed and compared. (C) 2002 Elsevier Science B.V. All rights reserved.
Polarized blue emission based on a side chain liquid crystalline polyacrylate containing bis-tolane side groups
(2002-03-01)
Chang, SW
;
Li, AK
;
Liao, CW
;
Hsu, CS
;
應用化學系
A novel side chain liquid crystalline (LC) polyacrylate (1P) containing highly conjugated bis-tolane side groups was synthesized and used for polymer light emitting diodes application. Polymer 1P shows a nematic phase at room temperature. It exhibits a UV absorption peak at 330 run and emits a blue light at 425 inn. Polyimide (PI), polyaniline (PA) and poly(3,4-diethylenedioxythiophene) (PEDOT) were used as alignment materials for polymer 1P. The photoluminescence dichroic ratios of 1P on rubbed PI, PA and PEDOT films are 10.4, 8.3 and 7.3, respectively. The electroluminescence dichroic ratio of IP aligned on a PEDOT film is 6.1.
Effective strategy for porous organosilicate to suppress oxygen ashing damage
(2002-03-01)
Liu, PT
;
Chang, TC
;
Mor, YS
;
Chen, CW
;
Tsai, TM
Photoresist stripping with oxygen plasma ashing destroys numerous functional groups in porous organosilicate glasses (OSGs), This impact makes the porous OSG relatively hydrophilic and causes low-k dielectric degradation, To mitigate these issues, various strategies are investigated to enhance oxygen plasma resistance of the porous OSG. These include physical and chemical procedures. Both structural and electrical analyses are used to determine their efficiency. In addition, an optimum prescription that consists of H, plasma and chemical trimethylchlorosilane treatment is developed in this work. The enhancement of oxygen plasma resistance can provide the porous OSG for practical application in the multilevel interconnection. (C) 2002 The Electrochemical Society.
Design and fabrication of fiberlenses for optical recording applications
(2002-03-01)
Tien, CH
;
Lai, YC
;
Milster, TD
;
Shieh, HPD
;
光電工程學系
The novel design and fabrication of a microlens on the front end of a single-mode fiber is described. The beam quality and spot size for optical recording applications are analyzed. A hyperbolic-shaped microlens on a single-mode fiber with focused spot of 1/e(2) = 0.82 mum (x-direction) and 0.89 mum (y-direction) at similar to 145 mum working distance was achieved by a simple fabrication procedure.
A release combined scheduling scheme for non-uniform dependence loops
(2002-03-01)
Pean, DL
;
Chua, HT
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
In general, synchronization mechanisms can be used to preserve dependence constraints in any nested loop, and can be combined with a loop scheduling scheme to form a uniform framework to obtain the correct execution order and balance workload distribution. Most current scheduling mechanisms cannot handle non-uniform dependence loops. In this paper, we propose a new combined scheduling scheme called Release Combined Scheduling for Non-uniform Dependence Loops (RCS) to schedule non-uniform dependence doubly-nested loops in multiprocessor systems. It combines both static and dynamic scheduling mechanisms in order to optimize the system performance. In our approach, initialisation of a set of scheduling information is based on the concept of the minimum dependence distance. During runtime, scheduling information is used to adjust the number of parallelizable iterations. Our method is able to discover more parallelism from a given non-uniform dependence doubly-nested loop than is possible with previous approaches. The experimental results show that the RCS method reliably exploits parallelism and outperforms most of the existing non-uniform dependence loop scheduling schemes by 20.29%, on average.
Group testing in bipartite graphs
(2002-03-01)
Juan, ST
;
Chang, GJ
;
應用數學系
;
Department of Applied Mathematics
This paper investigates the group testing problem in graphs as follows. Given a graph G = (V, E), determine the minimum number t(G) such that t(G) tests are sufficient to identify an unknown edge e with each test specifies a subset X subset of or equal to V and answers whether the unknown edge e is in G[X] or not. Damaschke proved that [log(2) e(G)] less than or equal to t(G) less than or equal to [log(2) e(G)] + 1 for any graph G, where e(G) is the number of edges of G. While there are infinitely many complete graphs that attain the upper bound, it was conjectured by Chang and Hwang that the lower bound is attained by all bipartite graphs. This paper verifies the conjecture for bipartite graphs G with e(G) less than or equal to 2(4) or 2(k-1) < e(G) less than or equal to 2(k-1) + 2(k-3) + 2(k-6) + 19(.)2(k-7/2) -1 for k greater than or equal to 5.
An electro-thermally driven microactuator with two dimensional motion
(2002-03-01)
Wu, CT
;
Hsu, W
;
機械工程學系
;
Department of Mechanical Engineering
In previous literatures, most of the microactuators were designed to deflect in one dimension only. Here, an electro-thermally driven microactuator with out-of-plane and in-plane two dimensional motion is designed, fabricated and tested. This microactuator comprised of a series of bimorph beams, a moving plate, a lateral driven unit, and contact pads. The out-of-plane motion is produced due to the bimorph effect and residual stress between the layers of Au and polysilicon when they are heated. The in-plane motion is obtained by heating the lateral driven unit which consists of two adjacent beams with different cross sections but the same length, then the asymmetrical thermal expansions in two adjacent beams lead to lateral deflection. The microactuator proposed here is fabricated by surface micromaching technique. A twostep releasing method is used here to free the microactuator successfully. The testing results show that the lateral driven unit can produce 10 mum lateral displacements at input voltages of 5 V, and bimorph structures at the same voltage can produce about 12 mum downward displacement. It is also found that this two dimensional motion can be controlled almost independently.
Diamond deposition on Si (111) and carbon face 6H-SiC (0001) substrates by positively biased pretreatment
(2002-03-01)
Chang, TF
;
Chang, L
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The growth of textured diamond films on Si (111) and carbon face 6H-SiC (0001) has been achieved by positive bias-enhanced-nucleation in microwave plasma chemical vapor deposition. A bias voltage of + 100 to +300 V, 3% CH4 concentration in bias step, and 0.33% CH4 concentration in growth step were used to synthesize diamond films on Si and carbon face 6H-SiC. Highly oriented diamond films were observed by scanning electron microscopy and X-ray diffraction patterns. Cross-sectional transmission electron microscopy showed that the interface between diamond and Si substrate was smooth, while it was rough between diamond and SiC. It also showed that diamond films were directly grown on both substrates. (C) 2002 Elsevier Science B.V. All lights reserved.
The removal selectivity of titanium and aluminum in chemical mechanical planarization
(2002-03-01)
Hsu, JW
;
Chiu, SY
;
Wang, YL
;
Dai, BT
;
Tsai, MS
The removal selectivity control of aluminum and titanium metal barrier during aluminum chemical mechanical polishing in the Damascene process is known to be critical for surface planarity without metal dishing and dielectric erosion. Unfortunately, the electrochemical behaviors of aluminum and titanium are dissimilar, as one may expect. In this study, in situ electrochemical impedance spectroscopy was carried out to investigate the influences of H(2)O(2) concentration, slurry pH, and metal oxide formation through the passivation on aluminum and titanium. As H(2)O(2) concentration increases, the measured impedance of aluminum and titanium decreases, or the oxidation rates of these two metals are enhanced upon increasing the oxidizer concentration. As the slurry pH increases, the removal rate of polished titanium increases, but it decreases for polished aluminum. The removal rate of titanium was limited to its oxidation rate and aluminum was limited to its oxide dissolution rate. (C) 2002 The Electrochemical Society.
Spatial disorder of cellular neural networks with biased term
(2002-03-01)
Ban, JC
;
Lin, SS
;
Hsu, CH
;
應用數學系
;
Department of Applied Mathematics
This study describes the spatial disorder of one-dimensional Cellular Neural Networks (CNN) with a biased term by applying the iteration map method. Under certain parameters, the map is one-dimensional and the spatial entropy of stable stationary solutions can be obtained explicitly as a staircase function.
Fuzzy modeling employing fuzzy polyploidy genetic algorithms
(2002-03-01)
Wu, MD
;
Sun, CT
;
資訊工程學系
;
Department of Computer Science
Fuzzy modeling generally comprises structure identification and parameter identification. The former determines the structure of a rule-base, whereas the latter determines the contents of each rule. Applying neural networks or genetic algorithms to identify the parameter sets and structures of a fuzzy system is increasingly popular owing to their ability to learn and adapt. However, most conventional approaches cannot integrate structure identification and parameter identification efficiently. This work presents a general approach to fuzzy modeling, i.e. fuzzy polyploidy genetic algorithms which integrate structure identification and parameter identification in a single evolution process. Capable of simulating the structural adaptation process of natural evolution, the proposed model is a generalized model for simultaneously optimizing both structure and parameters of fuzzy rule-bases. The structural adaptation proposed herein provides complete structural operations to simulate structural variation process and simple to complex life form of natural evolution. Illustrative examples involving typical FLCs, such as Mamdani and TSK models, demonstrate the effectiveness of applying the polyploidy scheme.
Effect of annealing on electron dephasing in three-dimensional polycrystalline metals
(2002-03-01)
Lin, JJ
;
Zhong, YL
;
Li, TJ
;
電子物理學系
;
物理研究所
We have studied the effect of thermal annealing on electron dephasing times in three-dimensional polycrystalline metals. Measurements are performed on as-sputtered and annealed AuPd and Sb thick films, using the weak-localization method. In all samples, we find that possesses an extremely weak temperature dependence as T --> 0. Our results show that the effect of annealing is non-universal, and it depends strongly on the amount of disorder quenched in the microstructures during deposition. The observed saturation behavior of cannot be easily explained by magnetic scattering. We suggest that the issue of saturation can be better addressed in three-dimensional, rather than lower-dimensional, structures.
Adaptive-feedrate interpolation for parametric curves with a confined chord error
(2002-03-01)
Yeh, SS
;
Hsu, PL
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Recently, modern manufacturing systems have been designed which can machine arbitrary parametric curves while greatly reducing data communication between CAD/CAM and CNC systems. However, a constant feedrate and chord accuracy between two interpolated points along parametric curves are generally difficult to achieve due to the non-uniform map between curves and parameters. A speed-con trolled interpolation algorithm with an adaptive feedrate is proposed in this paper. Since the chord error in interpolation depends on the curve speed and the radius of curvature, the feedrate in the proposed algorithm is automatically adjusted so that a specified limit on the chord error is met. Both simulation and experimental results for non-uniform rational B-spline (NURBS) examples are provided to verify the feasibility and precision of the proposed interpolation algorithm. (C) 2001 Elsevier Science Ltd. All rights reserved.
Developing the e-Delphi system: a web-based forecasting tool for educational research
(2002-03-01)
Chou, C
;
教育研究所
;
Institute of Education
On the distribution of the estimated process yield index S-pk
(2002-03-01)
Lee, JC
;
Hung, HN
;
Pearn, WL
;
Kueng, TL
;
統計學研究所
This paper considers an asymptotic distribution for an estimate (S) over cap (pk) of the process yield index S-pk proposed by Boyles (1994). The asymptotic distribution of (S) over cap (pk) is useful in statistical inferences for S-pk. An illustrative example is given for hypothesis testing and for interval estimation on the yield index S-pk. Copyright (C) 2002 John Wiley Sons, Ltd.