Browsing by Issue Date, starting with "2001-09-16"

Now showing 1 - 20 of 76236

Improvement of machining accuracy by fuzzy logic at corner parts for wire-EDM
(2001-09-16)
Lin, CT
;
Chung, IF
;
Huang, SY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Wire electrical discharge machining (wire-EDM) has always occupied an important position in some production fields, due to its capability of machining hard materials and intricate shapes. However, the machining accuracy, especially at corner parts, may be destroyed because of some phenomena such as wire deflection and vibration, etc. The purpose of this paper is to develop a control strategy based on fuzzy logic so that the machining accuracy at corner parts for wire-EDM can be improved. The fuzzy rules based on the wire-EDM's physical characteristics, experimental data, and operator's experience are constructed, so that the reduced percentage of sparking force can be determined by a multi-variables fuzzy logic controller. The objective of the total control is to improve the machining accuracy at corner parts, but still keep the cutting feedrate at fair values. As a result of experiments, machining errors of corner parts, especially in rough-cutting, can be reduced to less than 50% of those in normal machining, while the machining process time increases not more than 10% of the normal value. (C) 2001 Elsevier Science B.V. All rights reserved.
An algorithm for generalized fuzzy binary linear programming problems
(2001-09-16)
Yu, CS
;
Li, HL
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Fuzzy binary linear programming (FBLP) problems are very essential in many fields such as assignment and assembly line balancing problems in operational research, multiple projects, locations, and candidates selection cases in management science, as well as representing and reasoning with prepositional knowledge in artificial intelligence. Although FBLP problems play a significant role in human decision environment, not very much research has focused on FBLP problems. This work first proposes a simple means of expressing a triangular fuzzy number as a linear function with an absolute term. A method of linearizing absolute terms is also presented. The developed goal programming (GP) model weighted by decision-makers' (DMs) preference aims to optimize the expected objective function and minimize the sum of possible membership functions' deviations. After presented a novel way of linearizing product terms, the solution algorithm is proposed to generate a crisp trade-off promising solution that is also an optimal solution in a certain sense. Three examples, equipment purchasing choice, investment project selection, and assigning clients to project leaders, illustrate that the proposed algorithm can effectively solve generalized FBLP problems. (C) 2001 Elsevier Science B.V. All rights reserved.
Activated diffusion brazed repair for IN738 hot section components of gas turbines
(2001-09-24)
Su, CY
;
Lih, WC
;
Chou, CP
;
Tsai, HC
;
機械工程學系
The wide-clearance activated diffusion brazing (ADB) techniques with various brazing alloys, namely DF4B and Nicrobraz 150 were applied to restore worn areas of IN738 components. In this study, the microstructure of an ADB joint and the results of thermal cyclic tests as well as tensile tests within the temperature range of from 25 to 980 degreesC were investigated and discussed. The results of the tensile tests showed that ADB specimens brazed by 40 wt.% DF4B at 1190 degreesC exhibited 85% tensile strength of the IN738 base materials at room temperature and retained the same strength as that of the base material at 980 degreesC. However, the ductility of the ADB specimens with both brazing alloys was reduced. The results of cyclic-oxidation tests showed that ADB specimens with Nicrobraz 150 as the brazing alloy decayed after 150 cycles. However, the ADB specimens with DF4B had no obvious weight change until 205 cycles. (C) 2001 Elsevier Science B.V. All rights reserved.
Effect of side chain alkyl length on the electroluminescence characteristics of carbazole-based light emitting polymers
(2001-09-28)
Chao, CS
;
Whang, WT
;
Hung, CH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Three carbazole-based copolymers with different long side chains were synthesized using the Wittig reaction. These three copolymers and model compound were characterized by nuclear magnetic resonance (NMR) spectroscopy to determine the cis/trans ratio. The cis/ trans ratios decrease with the side chain length due to the variation in the degree of steric hindrance in the Wittig reaction. They affect the electroluminescence (EL) characteristics of the carbazole-based light emitting polymers. As the length of the side chain increases the wavelength of the emitted light increases proportionally whereas a decrease in the threshold voltages, 5.2, 4.8, 2.5 V was observed. However, EL intensity at same applied voltage creases with the length of the side chain. The energy levels of these three copolymers were also investigated to account for the phenomenon.
Additive multiplicative increasing functions on nonnegative square matrices and multidigraphs
(2001-09-28)
Chang, CH
;
Chuang, YC
;
Hsu, LH
;
資訊工程學系
;
Department of Computer Science
It is known that if f is a multiplicative increasing function on N, then either f(n) = 0 for all n is an element of N or f (n) = n(alpha) for some alpha greater than or equal to 0. It is very natural to ask if there are similar results in other algebraic systems. In this paper, we first study the multiplicative increasing functions. over nonnegative square matrices with respect to tensor product and then restrict our result to multidigraphs and loopless multidigraphs. (C) 2001 Elsevier Science B.V. All rights reserved.
那是一種現代味的唐詩或離騷
(2001-09-30)
管管
那是一種現代味的唐詩或離騷
(2001-09-30)
管管
那是一種現代味的唐詩或離騷
(2001-09-30)
管管
An automatic macro program for radio frequency MOSFET characteristics analysis
(2001-10-01)
Su, CY
;
Chang, SJ
;
Chen, LP
;
Ho, YP
;
Huang, GW
The parameter extraction language (PEL) in Agilent IC-CAP software is used to develop an automatic macro program for the analysis of the characteristics of RF MOSFETs. By using this powerful macro program, the time spent on the measurement of the MOSFET characteristics and the related analysis is effectively reduced. This macro program permits a fast and accurate method to obtain the DC and RF characteristics of MOSFETs with different device geometries and operating conditions. It is also suitable for high volume measurements and analyses of MOSFET, and provides a solid jou 71 dation for RF circuit design.
Sensitivity of the photo-crosslinkable polyimide for liquid crystal alignment
(2001-10-01)
Lee, WC
;
Hsu, CS
;
Wu, ST
;
應用化學系
;
Department of Applied Chemistry
Two methods were developed for enhancing the photosensitivity of the cinnamates-contained polyimide (PICA), One is to increase the content of cinnamate side chain in PICA main chain and another is to blend some photosensitizer into PICA films. Our experimental results show that increasing the rate of photo-dimerization decreases the alignment ability of the PICA films. Using the molecular simulation method, we successfully describe the photoalignment mechanism of the PICA films. It is also found that photo-induced LC alignment ability of the PICA film could be enhanced through choosing a proper coating solvent.
Internet heavy use and addiction among Taiwanese college students: An online interview study
(2001-10-01)
Chou, C
;
教育研究所
;
Institute of Education
This paper presents empirical qualitative results of Internet heavy-use and addiction among some college students in Taiwan. It offers in-depth, online interviews of student-subjects in order to facilitate an interdisciplinary understanding of Internet heavy use, addiction and its potential impacts. A total of 83 subjects were interviewed, both as individuals and in chat-room groups. The analysis of qualitative data presented in six major themes: (1) Internet use and reasons; (2) Internet features; (3) the Internet as replacement for other media; (4) impact of Internet overuse; (5) controlling Internet use; and (6) coping with Internet withdrawal. Discussions, explanations, along with examples and quotes from subjects, are provided in each section. Implications for student affairs administrators and further research directions are also addressed.
Improving the RF performance of 0.18 mu m CMOS with deep n-well implantation
(2001-10-01)
Su, JG
;
Hsu, HM
;
Wong, SC
;
Chang, CY
;
Huang, TY
The radio-frequency (RF) figures of merit of 0.18 mum complementary metal-oxide-semiconductor (CMOS) technology are investigated by evaluating the unity-current-gain cutoff frequency (F-t) and maximum oscillation frequency (F-max). The device fabricated with an added deep n-well structure is shown to greatly enhance both the cutoff frequency and the maximum oscillation frequency, with negligible dc disturbance. Specifically, 18% increase in F-t and 25% increase in F-max are achieved. Since the deep n-well implant can be easily adopted in a standard CMOS process, the approach appears to be very promising for future CMOS RF applications.
The dispersive approach to electroweak processes in the dackground magnetic field
(2001-10-01)
Lin, GL
;
物理研究所
;
Institute of Physics
We propose a new method to compute amplitudes of electroweak processes in the strong background magnetic field, using gamma --> e(+)e(-) as an example. We show that the moments of gamma --> e(+)e(-) width are proportional to the derivatives of photon polarization function at the zero energy. Hence, the pair-production width can be easily calculated from the latter by the inverse Mellin transform. The prospects of our approach are commented.
A performance criterion for the depth estimation with application to robot visual servo control
(2001-10-01)
Fang, CJ
;
Lin, SK
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This article deals with the depth observability problem of a robot visual system with a moving camera. In the visual system, the unknown depth of a feature point is estimated from the input of the camera velocity and the output of the image of the feature point. Although it is well known that the linear velocity of the camera must satisfy some constraints for successful depth estimation, this proposes a criterion to measure the performance of the depth estimation, which is a heuristic extension from an estimation result of a linear system. This performance criterion depends on both the image position and the linear velocity of the camera. Some simulation and experiment examples demonstrate and verify the proposed performance criterion. Furthermore, this criterion is used to develop a new visual servo control scheme that has good performance in both the depth estimation and the visual control. This control scheme is also verified by a simulation example. (C) 2001 John Wiley & Sons, Inc.
Utilization of a dispersion-shifted fiber for simultaneous measurement of distributed strain and temperature through Brillouin frequency shift
(2001-10-01)
Lee, CC
;
Chiang, PW
;
Chi, S
;
光電工程學系
;
Department of Photonics
In this letter, we propose and realize a new method that utilizes a dispersion-shifted fiber having compound compositions with different temperature coefficients in core to simultaneously measure the distributed strain and temperature based on Brillouin frequency shift. In a 3682-m sensing length of large-effective-area nonzero dispersion-shifted fiber, a temperature resolution of 5 degreesC, a strain resolution of 60 mu epsilon, and a spatial resolution of 2 in are achieved simultaneously.
Dynamic analysis of rotating beams with nonuniform cross sections using the dynamic stiffness method
(2001-10-01)
Huang, KJ
;
Liu, TS
;
機械工程學系
;
Department of Mechanical Engineering
This study develops dynamic analysis based on the dynamic stiffness method for a rotating beam of nonuniform cross-section. To deal with nonuniform beams, coefficients related to material and geometric properties in the equation of motion are expressed in a polynomial form. A dynamic stiffness matrix is accordingly formulated in terms of power series. The dynamic response of the rotating beam is calculated by performing modal analysis. It is demonstrated that the present method provides an alternative to the finite element method in dealing with nonuniform rotating beams.
Research into two source-based control algorithms for Internet traffic flows
(2001-10-01)
Yang, CY
;
Fu, CH
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
TCP and UDP are the major applications over the Internet, the characteristics of them lead to different network transmission behaviors. Two source-based mechanisms are proposed in this paper to regulate TCP and UDP flows. One is the-congestion control mechanism, which uses TCP flows' congestion signal to regulate the flows at the source node. The other is the time slot mechanism, which is a time-sharing application to control their flow transmission, Based on the priorities of flows, different bandwidth proportions are allocated and differential services are provided for flows. Several scenarios are simulated to observe the transmission operations of these two mechanisms. Simulation results show some insights into two mechanisms. Moreover, the several simulation parameters that may impact the performance of these two mechanisms are summarized. (C) 2001 Elsevier Science B,V, All rights reserved.
Design and analysis of a merging algorithm for multipoint-to-point ABR service in ATM networks
(2001-10-01)
Lee, CL
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a merging algorithm, which can provide efficient support for multipoint-to-point ABR service in ATM networks. By forwarding the FRM cells belonging to the VC with the largest FRM-cell arrival rate in a merge point, the proposed algorithm can achieve better link utilization than existing merging algorithms. In addition, the proposed algorithm reduces the number of FRM cells forwarded by a C merge point. As a result, it can reduce the control overhead of ABR service. Most importantly, it does not incur extra complexity in switches. We also discuss the impact of different network topologies on our algorithm. Simulation results show that the proposed algorithm is able to achieve better performance while requiring significantly fewer RM cells. (C) 2001 Elsevier Science B.V. All rights reserved.
Electronic stopping powers of solids for slow atoms
(2001-10-01)
Kwei, CM
;
Chou, JJ
;
Yao, J
;
Tung, CJ
;
電子工程學系及電子研究所
Based on the dielectric response theory, electronic stopping powers of solids for slow atoms have been studied. Using a local-field-correction dielectric function, we have calculated these stopping powers by including the correlation and exchange effects. The screening of shellwise electron charge densities of slow atoms by the conduction electrons in solids was estimated using a Thomas-Fermi screening model. In this model, atomic shellwise electron densities were constructed by a superposition of several Yukawa potentials. Stopping powers of Al, Ni, Ag, and Au were calculated for atoms with atomic number between 6 and 18. Calculated results showed that stopping powers oscillated with atomic number consistent with experimental data. Present results also indicated that our approach is much improved over other theoretical calculations. A comparison of presently calculated results with available theoretical and experimental data was made and discussed.
An accurate integral-based scheme for advection-diffusion equation
(2001-10-01)
Tsai, TL
;
Yang, JC
;
Huang, LH
;
土木工程學系
;
Department of Civil Engineering
This paper proposes an accurate integral-based scheme for solving the advection-diffusion equation. In the proposed scheme the advection-diffusion equation is integrated over a computational element using the quadratic polynomial interpolation function. Then elements are connected by the continuity of first derivative at boundary points of adjacent elements. The proposed scheme is unconditionally stable and results in a tridiagonal system of equations which can be solved efficiently by the Thomas algorithm. Using the method of fractional steps, the proposed scheme can be extended straightforwardly from one-dimensional to multi-dimensional problems without much difficulty and complication. To investigate the computational performances of the proposed scheme five numerical examples are considered: (i) dispersion of Gaussian concentration distribution in one-dimensional uniform flow; (ii) one-dimensional viscous Burgers equation; (iii) pure advection of Gaussian concentration distribution in two-dimensional uniform flow; (iv) pure advection of Gaussian concentration distribution in two-dimensional rigid-body rotating flow; and (v) three-dimensional diffusion in a shear flow. In comparison not only with the QUICKEST scheme, the fully time-centred implicit QUICK scheme and the fully time-centred implicit TCSD scheme for one-dimensional problem but also with the ADI-QUICK scheme, the ADI-TCSD scheme and the MOSQUITO scheme for two-dimensional problems, the proposed scheme shows convincing computational performances. Copyright (C) 2001 John Wiley & Sons, Ltd.