Browsing by Issue Date, starting with "1998-11-10"

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Improvement of mechanical properties of electroplated diamond tools by microwave plasma CVD diamond process
(1998-11-10)
Lin, CR
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The growth and surface modification of irregular diamond grains of electroplated diamond tools have been developed successfully. Results show that the adherence, cutting ability, and wear resistance of diamond grains are improved by this process. In this study, the crystallization and quality of diamond grains were determined by SEM (SE and BSE), Raman spectroscopy, and XRD determination. Tests using a block-on-ring tribotester were also carried out to examine the adherence, cutting ability, and wearing resistance of the electroplated diamond tools, The adherence of diamond grains was also observed on a SEM microphotograph of the cross-section view of specimens. SEM line scanning was performed to determine whether the alloy elements are effectual in promoting the diffusion bonding strength among diamonds, the interlayer and substrate. (C) 1998 Elsevier Science S.A. All rights reserved.
Non-linear dynamics and chaos control of a damped satellite with partially-filled liquid
(1998-11-12)
Ge, ZM
;
Lee, CI
;
Chen, HH
;
Lee, SC
;
機械工程學系
The dynamic behaviors of a damped satellite with partially-filled liquid which is subjected to external disturbance are studied in this paper. The Lyapunov direct method is used to obtain conditions of stability of the equilibrium point of the system. A co-dimension one bifurcation analysis for the autonomous system is carried out near the degenerate point. It is found that Hopf bifurcation occurs in the system by center manifold theory. By applying numerical results, phase diagrams, power spectrum, Poincare maps, and Lyapunov exponents are presented to observe periodic and chaotic motions. The effect of the parameter changes in the system can be found in the bifurcation and parametric diagrams. For global analysis, the basins of attraction of each attractor of the system are located by employing the modified interpolated cell mapping (MICM) method. Finally, several methods, the delayed feedback control, the addition of constant motor torque, the addition of periodic force, and adaptive control algorithm are used to control chaos effectively. (C) 1998 Academic Press.
Non-linear dynamics and chaos control of a damped satellite with partially-filled liquid
(1998-11-12)
Ge, ZM
;
Lee, CI
;
Chen, HH
;
Lee, SC
;
機械工程學系
The dynamic behaviors of a damped satellite with partially-filled liquid which is subjected to external disturbance are studied in this paper. The Lyapunov direct method is used to obtain conditions of stability of the equilibrium point of the system. A co-dimension one bifurcation analysis for the autonomous system is carried out near the degenerate point. It is found that Hopf bifurcation occurs in the system by center manifold theory. By applying numerical results, phase diagrams, power spectrum, Poincare maps, and Lyapunov exponents are presented to observe periodic and chaotic motions. The effect of the parameter changes in the system can be found in the bifurcation and parametric diagrams. For global analysis, the basins of attraction of each attractor of the system are located by employing the modified interpolated cell mapping (MICM) method. Finally, several methods, the delayed feedback control, the addition of constant motor torque, the addition of periodic force, and adaptive control algorithm are used to control chaos effectively. (C) 1998 Academic Press.
Active aperture-coupled leaky-wave antenna
(1998-11-12)
Kao, NA
;
Hu, CC
;
Wu, JJ
;
Jou, CF
;
傳播研究所
An active aperture-coupled leaky-wave antenna which is integrated with a varactor-tuned high electron mobility transistor voltage-controlled oscillator (HEMT VCO) is presented. To excite the first higher mode of the microstrip, the aperture-coupled structure is used and a sequence of covered wire is added at the centre of this antenna to suppress the dominant mode. The measured H-plane main beam can be continuously scanned 10 degrees as the HEMT VCO frequency is varied from 9.05 to 9.5GHz. This feeding structure is very suitable for active phase antenna array applications.
Application of fuzzy control to a road tunnel ventilation system
(1998-11-16)
Chen, PH
;
Lai, JH
;
Lin, CT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper deals with the serious problems of ventilation system in a large road tunnel. Higher visibility and lower concentration of carbon monoxide are the key issues concerning the ventilation system. Prior to designing the fuzzy control model, a configuration layout of the ventilation system including sensing, control and traffic prediction as well is conceptually constructed. Based on the layout that offers assignments of sensors and control elements, a fuzzy logic control model is developed. Membership functions of sensor errors and control increments are physically submitted in order to set up the fuzzy logic rules. Timing and spacing filtering in terms of weighting approaches is employed in the fuzzy logic rules. A dynamic equation describing the concentration of air pollution is also given so as to cooperate with the fuzzy logic rules and to play roles in the computer simulation. The result of computer simulation involving five cases indicates that a multi-level scheme is able to solve the engineering problems. (C) 1998 Elsevier Science B.V. All rights reserved.
Application of fuzzy control to a road tunnel ventilation system
(1998-11-16)
Chen, PH
;
Lai, JH
;
Lin, CT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper deals with the serious problems of ventilation system in a large road tunnel. Higher visibility and lower concentration of carbon monoxide are the key issues concerning the ventilation system. Prior to designing the fuzzy control model, a configuration layout of the ventilation system including sensing, control and traffic prediction as well is conceptually constructed. Based on the layout that offers assignments of sensors and control elements, a fuzzy logic control model is developed. Membership functions of sensor errors and control increments are physically submitted in order to set up the fuzzy logic rules. Timing and spacing filtering in terms of weighting approaches is employed in the fuzzy logic rules. A dynamic equation describing the concentration of air pollution is also given so as to cooperate with the fuzzy logic rules and to play roles in the computer simulation. The result of computer simulation involving five cases indicates that a multi-level scheme is able to solve the engineering problems. (C) 1998 Elsevier Science B.V. All rights reserved.
Phase transition voltage and response time of an aligned phase-change-guest-host mode of liquid-crystal film
(1998-11-23)
Wu, JJ
;
Lee, TY
;
Chen, SH
;
Kuo, CL
;
光電工程學系
We have studied the electro-optical properties of the aligned phase-change-guest-host (PCGH) mode liquid-crystal display. The PCGH material is spread between two glass substrates. Each substrate has previously been coated with a homeotropic alignment layer and has been softly rubbed. Samples with various thickness-to-natural pitch ratio d/p(0) are fabricated. It is found that, in some ranges of the d/p(0) ratio, the response times and phase transition voltage are affected by the rubbing direction. (C) 1998 American Institute of Physics. [S0003-6951(98)04546-X].
A pilot-scale study of the design and operation parameters of a pulse-jet baghouse
(1998-12-01)
Lu, HC
;
Tsai, CJ
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環境工程研究所
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Institute of Environmental Engineering
Filtration curves and pulse-jet cleaning performance of different design and operating conditions of a pilot-scale pulse-jet baghouse are investigated. The effective residual pressure loss is used as an index of bag cleaning effect, while the average pulse overpressure inside the bag is used as an index of bag cleaning intensity. It is found that filtration curves vary with the initial tank pressure and the nozzle diameter of the bag cleaning system. The filtration time increases with increasing initial tank pressure or nozzle diameter. However, a critical value of the tank pressure exists for an effective bag cleaning. It is also found that a critical effective residual pressure loss value exists for the pulse-jet cleaning system. Too large an initial tank pressure and nozzle diameter result in a waste of cleaning energy. The addition of a venturi increases the average pulse overpressure appreciably, hence increasing the cleaning effect. A venturi is suggested to be installed to increase the bag cleaning effect and maximize cleaning energy in this study. (C) 1998 American Association for Aerosol Research.
Recursive wiener filter for motion parameter estimation in three-parameter motion model
(1998-12-01)
Liu, PC
;
Chang, WT
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資訊工程學系
;
Department of Computer Science
Motion compensation is used to reduce the displaced frame difference (DFD) during the video coding. To increase the accuracy of the point correspondence during the compensation, a three-parameter motion model is considered. The matching error can be significantly reduced as compared with that of the two-parameter block matching. To derive the parameters, a partial full search method is used. The full search is used when the zoom value is set at one. Otherwise, the gradient-based algorithm is used, Since the DFD is a nonlinear function of the image gradients and the motion parameters, a linearized model is considered. To eliminate the linearization error, Wiener filtering is used to smoothen the DFD to improve the convergence condition of the iterative gradient search. To make the gradient-based search more robust to the gradient variation, several gradient estimation methods are also compared.
Frequency estimation of phase-modulated carriers
(1998-12-01)
Su, YT
;
Wu, RC
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電信工程研究所
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Institute of Communications Engineering
Conventional approach for frequency estimation usually assume a single tone without data modulation. In many applications such an assumption, realized by using either a separate pilot beacon or synchronization preamble is not feasible. This paper deals with frequency estimation of phase-modulated carriers in the absence of timing information and known data pattern. We introduce new frequency estimators that are based on the generalized maximum likelihood principle. The communication channels under consideration include both additive white Gaussian noise (AWGN) channels and correlated Rician fading channels. For the latter class, we distinguish between the case when the fading (amplitude) process is tracked and that when it is not tracked.
Three electrodes touch-mode capacitive pressure sensor
(1998-12-01)
Chang, KM
;
Hwang, GJ
;
Hsien, YL
;
電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
A three-electrode capacitive pressure sensor for touch-mode operation with sensitivity of 0.030 pF/kPa (or 10.4 mV/kPa using CP-10 C/V converter circuit) in the pressure range of 170-280 kPa is presented with theoretical explanation of experimental results. A special ring structure is designed to integrate a sensing capacitor and a reference capacitor into the same cavity to partially cancel out the temperature effect. A third electrode is included to eliminate two-level connections without reducing its pressure sensitivity. The sensor offers the advantages of simple fabrication processes, planar connections, as well as high sensitivity, near-linear output, and large over-range pressure.
Time-constrained distributed program reliability analysis
(1998-12-01)
Chen, DJ
;
Chang, MS
;
Sheng, MC
;
Horng, MS
;
資訊科學與工程研究所
In this paper, we propose an approach to the reliability analysis of distributed programs that addresses real-time constraints. Our approach is based on a model for evaluating transmission time, which allows us to find the time needed to complete execution of the program, task, or mission under evaluation. With information on time-constraints, the corresponding Markov state space can then be defined for reliability computation. To speed up the evaluation process and reduce the size of the Markov state space, several dynamic reliability-preserving reductions are developed. A simple distributed real-time system is used as an example to illustrate the feasibility and uniqueness of the proposed approach.
Classifying and alleviating the communication overheads in matrix computations on large-scale NUMA multiprocessors
(1998-12-01)
Wang, YM
;
Wang, HH
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Large-scale, shared-memory multiprocessors have non-uniform memory access (NUMA) costs. The high communication cost dominates the source of matrix computations' execution. Memory contention and remote memory access are two major communication overheads on large-scale NUMA multiprocessors. However, previous experiments and discussions focus either on reducing the number of remote memory accesses or on alleviating memory contention overhead. In this paper, we propose a simple but effective processor allocation policy, called rectangular processor allocation, to alleviate both overheads at the same time. The policy divides the matrix elements into a certain number of rectangular blocks, and assigns each processor to compute the results of one rectangular block. This methodology may reduce a lot of unnecessary memory accesses to the memory modules. After running many matrix computations under a realistic memory system simulator, we confirmed that at least one-fourth of the communication overhead map be reduced. Therefore, we conclude that rectangular processor allocation policy performs better than other popular policies, and that the combination of rectangular processor allocation policy with software interleaving data allocation policy is a better choice to alleviate communication overhead. (C) 1998 Elsevier Science Inc. All rights reserved.
Analysis of a partially sealed package for microstrip-line circuits
(1998-12-01)
Chen, HH
;
Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
A partially sealed package formed by two metal diaphragms with or without an absorber is proposed and analyzed for shielded microstrip-line circuits. The mode-matching method, method of lines, and finite-element method are mixed appropriately to investigate the package. For a specific analysis, an electric current filament and a microstrip-line gap are chosen to simulate, respectively, an active circuit element (CE) and a passive CE to be packaged. The suppression effect of the package on the spurious (higher order) modes and the influence on the dominant mode are fully studied by comparing the excitation and scattering characteristics of the CE's with and without the package.
The impact of rate control algorithms on system-level VLSI design
(1998-12-01)
Cheng, SC
;
Hang, HM
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper presents an evaluation of rate control algorithms from a system-level VLSI design viewpoint. Rate control in video coding has a significant influence on the coded bit rate and image quality. Many rate control algorithms have been proposed mainly focusing on the optimal rate-distortion performance without considering their performance on the VLS implementation. The purpose of this study is not to propose a hardware architecture for any specific algorithm but to study the algorithm impact on hardware design. Based on our finding, a system designer should choose an algorithm not only good in rate control performance but also good in hardware implementation. When implementing and comparing a few rate control algorithms using a generic processor structure, we found that, in addition to the ordinary computational complexity, the internal buffer size is also very critical in VLSI realization. Several picture sequences have been tested including one sequence constructed specifically to simulate a difficult case for rate control. In this paper, three different types of popular rate control algorithms have been analyzed based on their picture quality, the internal buffer size, and the hardware cost. The methodology and results presented here provide useful guidelines for selecting an appropriate rate control algorithm for system-level VLSI designers.
A method for measuring Brewster's angle by circularly polarized heterodyne interferometry
(1998-12-01)
Lee, JY
;
Su, DC
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光電工程學系
;
Department of Photonics
A new method for determining Brewster's angle is proposed based on the effect that the phase difference produced by a simple reflection from the test medium, for a two-frequency circularly polarized light source, is exactly equal to zero when the incident angle equals Brewster's angle. Its best resolution is 10(-3) deg and the validity of the method was demonstrated.
Finding space-optimal linear array for uniform dependence algorithms with arbitrary convex index sets
(1998-12-01)
Ke, JY
;
Tsay, JC
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資訊工程學系
;
Department of Computer Science
The mapping of an n-dimensional uniform dependence algorithm onto a linear processor array can be considered as a linear transformation problem. However, to find a linear space-optimal transformation is difficult because the conditions for checking a correct mapping and the space cost function do not have closed-form expressions, especially when the index set J of an n-dimensional algorithm is of an arbitrary bounded convex index set. In this paper, we propose an enumeration method to find a space-optimal PE allocation vector for mapping an n-dimensional uniform dependence algorithm with an arbitrary bounded convex index set onto a linear processor array, assuming that a linear schedule is given a priori.
Bound-mode resonance improving the input matching of a dual-mode leaky guiding structure
(1998-12-01)
Lin, CC
;
Tzuang, CKC
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電信工程研究所
;
Institute of Communications Engineering
A novel approach of incorporating the bound-mode resonance in a uniform micro-CPW (coplanar waveguide) line that shows excellent input matching is presented. The matrix-pencil signal analyses of the CPW-fed micro-CPW guide confirm that two modes, namely, the bound CPW mode and the leaky second higher order microstrip mode, dominate, whereas the microstrip mode contributes too little to be detected. Both theoretical analyses and experimental measurements of the CPW-fed micro-CPW guide show that two well-matched input return losses regions are directly related to the resonances of the CPW mode within the guide.
Sputtered Cr and reactively sputtered CrNx serving as barrier layers against copper diffusion
(1998-12-01)
Chuang, JC
;
Tu, SL
;
Chen, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The barrier capability of sputter deposited Cr and reactively sputter deposited CrNx films against Cu diffusion in a structure of Cu/barrier/p(+)n junction diodes was investigated by means of thermal annealing at elevated temperatures in conjunction with electrical measurements and material analysis. For a 500 Angstrom thick barrier layer, the barrier capability of a pure Cr layer was limited to temperatures up to 500 degrees C, while CrNx films sputter deposited in a gas mixture of Ar and N-2 showed improved barrier capabilities. With Ar/N-2 flow rates of 24/6 to 24/12 standard cubic centimeters per minute, the deposited CrNx films possessed a much improved barrier capability. In particular, the Cu/CrNx (24/9)/p(+)n junction diodes were capable of sustaining 30 min of thermal anneal at temperatures up to 700 degrees C without degradation of the diodes' electrical characteristics. The failure of Cu/Cr/p(+)n and Cu/CrNx/p(+)n junction diodes under extreme thermal treatment was presumed to arise from two mechanisms: grain boundary diffusion for lightly nitrogen doped CrNx and pure Cr barriers, and localized defect (microcrack) diffusion for excessively nitrogen doped CrNx barriers.
Effects of ligand chain length and terminal N-alkylation on the protonation constants and stability constants of some transition metal complexes of linear tetraaza and pentaaza ligands
(1998-12-01)
Chang, CA
;
Shieh, FK
;
Liu, YL
;
Chung, CS
;
生物科技學系
A number of terminal N-alkylated linear tetraaza and pentaaza ligands were prepared. Their ligand protonation constants and some transition and post-transition metal (Ni2+, Cu2+, Zn2+, and Cd2+) complex stability constants were determined by potentiometric titration methods. In general, methylation and ethylation at the terminal nitrogen atoms caused the corresponding ligand nitrogen basicity to increase; however, the corresponding metal complex stabilities were decreased compared to the non-alkylated structural analogs, presumably due to a steric effect.