Browsing by Issue Date, starting with "1998-09-01"

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On the stability of the hybrid-damped resolved-acceleration control
(1998-09-01)
Lin, SK
;
Wu, SL
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper points out that the stability analysis of the hybrid-damped resolved-acceleration control in our earlier work is incomplete, since the stability was concluded directly from the fact that the joint velocities come to rest as time approaches infinity. A similar incomplete technique was also used in the work of Wampler and Leifer to prove the stability of a damped least-squares resolved-acceleration control scheme. In this paper, we use LaSalle's invariance principle rigorously to show that the solution trajectory of the hybrid-damped resolved-acceleration control will eventually come to the target without steady-state error or will stay at a kinematic singular point with some steady-state error. Discussions on the case of staying at a singular point are also given. (C) 1998 John Wiley & Sons, Inc.
Dilation to the unilateral shifts
(1998-09-01)
Takahashi, K
;
Wu, PY
;
應用數學系
;
Department of Applied Mathematics
The classical result of Foias says that an operator power dilates to a unilateral shift if and only if it is a C-.o contraction. In this paper, we consider the corresponding question of dilating to a unilateral shift. We show tht for contractions with, at least one defect index finite, dilation and power dilation to some unilateral shift amount to the same thing. The only difference is on the minimum multiplicity of the unilateral shift to which the contraction can be (power) dilated. We also obtain a characterization of contractions which are finite-rank perturbations of a unilateral shift, generalizing the rank-one perturbation result of Nakamura.
羅漢床上數羅漢
(1998-09-01)
管管
Diatomic molecule under pulsed field: One-dimensional versus full-dimensional studies
(1998-09-01)
Lin, JT
;
Chuu, DS
;
Jiang, TF
;
電子物理學系
;
物理研究所
This work investigates the dissociation dynamics of a diatomic molecule under the chirped pulse with the vibrational and rotational degrees of freedom. Results obtained herein are also compared with those of the conventionally used one-dimensional (ID) model. According to the comparison, the 1D model still provides valuable information such as dissociation dynamics. Meanwhile, predictions such as harmonic generation spectrum from the 1D model are impractical.
On stationarizability for nonstationary 2-D random fields using discrete wavelet transforms
(1998-09-01)
Wu, BF
;
Su, YL
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
The emphasis in this correspondence is on the study of nonstationary two-dimensional (2-D) random fields with wide-sense stationary increments, wide-sense stationary jumps, and 2-D fractional Brownian motion (fBm) fields. The effort made in this work is to develop a realizable method of stationarization provided for nonstationary 2-D random fields. We also present the correlation functions of the discrete wavelet transform relating to 2-D fBm fields that will decay hyperbolically fast.
ZK-type dual-lead worm and worm gear drives: Contact teeth, contact ratios and kinematic errors
(1998-09-01)
Bair, BW
;
Tsay, CB
;
機械工程學系
;
Department of Mechanical Engineering
Contact ratio is an important gear design parameter for gear bending and contact stresses. A higher contact ratio may reduce the stresses and kinematic errors of the gear set. In this study, we calculate the kinematic error of the ZK-type dual-lead worm gear set by applying the tooth contact analysis (TCA) method. Two kinds of contact ratios, the instantaneous contact teeth (ICT) and the average contact ratio (ACR), are investigated and calculated by applying TCA method. ICT is an important design parameter for a dual-lead worm gear set when the gear set is used in a machine subjected to large impact forces. ACR is also a useful design factor for assessing gear tooth strength and dynamic load. If gear surface elastic deformation 3 mu m is allowed for the worm gear set, the ICT may have 2, 3 or 4 teeth and the ACR reveals that the ZK-type dual-lead worm gear drive is a high-contact-ratio gear set. It is found that this type of worm gear set with a shorter center distance assembly can increase the value of ACR during the gear meshing. Illustrative examples presented herein demonstrate the effects of gear parameters on contact teeth, contact ratios, average contact ratios and kinematic errors under various conditions.
Improved output ESD protection by dynamic gate floating design
(1998-09-01)
Chang, HH
;
Ker, MD
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A dynamic gate Boating design is proposed to improve ESD robustness of the CMOS output buffers with small drive capability. By using this novel design, the human-body-model (machine-model) ESD failure threshold of a 2-mA CMOS output buffer has been practically improved from 1 KV (100 V) to greater than 8 KV (1500 V) in a 0.35-mu m CMOS process.
A new algorithm for lossless still image compression
(1998-09-01)
Chuang, TJ
;
Lin, JC
;
資訊工程學系
;
Department of Computer Science
This paper presents a spatial domain method for lossless still image compression using a new scheme: base switching (BS). The given image is partitioned into non-overlapping fixed-size subimages. Different subimages then get different compression ratios according to the base values of the subimages. In order to increase the compression ratio, a hierarchical technique is also used. It is found that the compression ratio of the proposed algorithm can compete with that of the VBSS and the international standard algorithms known as JBIG and Lossless JPEG. In addition, when the BS method is compared with the S + P method, which is an excellent frequency domain method that used EZW, although S + P method gains about 9% increase in the compression ratio, its encoding time (excluding I/O) is about three times longer than ours. The math theory needed to build up the proposed compression scheme is also provided. (C) 1998 Published by Elsevier Science Ltd on behalf of the Pattern Recognition Society. All rights reserved.
A logical fault model for library coherence checking
(1998-09-01)
Tung, SW
;
Jou, JY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A library is the basis of modularized design now. Most operations of CAD tools are based on cell definitions in a library. In this paper, we first give a definition of a library and describe the complexity of library verification. A unified automatic test pattern generation and verification environment is then proposed. The amount of library data coherence checking is reduced to functional simulation on different views of the cells. In order to reduce the number of lest vectors and the amount of simulation time, a Port Order Fault (POF) model is proposed. Using the POF model and the sensitized path approach [1] to generate test vectors, the proposed approach could effectively reduce the complexity of the functional test vectors from O(2(n)) to O(n) for cells with n inputs. Using the POF model, the test sequence can also detect timing inconsistency under the verification environment.
Influence of thermal boundary resistance on bolometric response of high-T-c superconducting films
(1998-09-01)
Wu, JP
;
Shih, CU
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
This work presents a thermal analysis on predicting the temperature increase and the voltage response of high-T-c superconducting bolometers. To consider the thermal boundary resistance between film and substrate, an acoustic mismatch model (AMM), a diffusive mismatch model (DMM), and an interfacial layer model (ILM) are employed. The thermal boundary resistance significantly influences the voltage response. Additionally, several common substrates are examined. SrTiO3 (100) or LaAlO3 (100) is a better substrate for high-T-c superconducting bolometers. Furthermore, we demonstrated that there are several factors to affect the voltage response, such as the pulse duration for a constant total incident energy or a fixed highest incident heat flux, the pulse distribution function in time, optical penetration depth, the thermal conductivities of the film and substrate, initial operating temperature, thickness ratio, and the amount of incident heat flux. One interesting finding was that when compared with experimental data, all the theoretical values from the present study as well as the other previously theoretical treatment overestimate the voltage response near the transition temperature. (C) 1998 Elsevier Science Ltd. All rights reserved.
The path-partition problem in bipartite distance-hereditary graphs
(1998-09-01)
Yeh, HG
;
Chang, GJ
;
應用數學系
;
Department of Applied Mathematics
A path partition of a graph is a collection of vertex-disjoint paths that cover all vertices of the graph. The path-partition problem is to find a path partition of minimum size. This paper gives a linear-time algorithm for the path-partition problem in bipartite distance-hereditary graphs.
A Petri net approach to early failure detection and isolation for preventive maintenance
(1998-09-01)
Yang, SK
;
Liu, TS
;
機械工程學系
;
Department of Mechanical Engineering
To improve preventive maintenance, this study uses a hybrid Petri net modelling method coupled with parameter trend and fault tree analysis to perform early failure detection and isolation. A Petri net arrangement is proposed that facilitates alarm, early failure detection, fault isolation, event count, system state description and automatic shutdown or regulation. These functions are very useful for health monitoring and preventive maintenance of a system. A fault diagnosis system for district heating and cooling facilities is employed as an example to demonstrate the proposed method. (C) 1998 John Wiley Br Sons, Ltd.
A study of tilt angle effect on Halo PMOS performance
(1998-09-01)
Su, JG
;
Wong, SC
;
Huang, CT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The Halo structure is usually adopted in deep submicrometer MOS devices for punchthrough prevention. The tilt angle of the Halo implant determines the dopant distribution which induces anti-punchthrough operation. In this paper, we investigate the impact of the tilt angle on the Halo PMOS device performance via two-dimensional (2D) simulations. We find that the ratio of on-current to off-current is constant for all tilt angles of Halo implant, implying an equivalent DC performance for all tilt angles. The equivalence can be traced back to a self compensation between the body factor and source resistance. The result :implies that a low tilt angle should be adopted for Halo devices, for it gives a small threshold voltage and thus a high noise margin. The methodology used in analyzing body factor and source resistance can also be applied to analyze other devices. (C) 1998 Elsevier Science Ltd. All rights reserved.
The characteristics of chemical vapor deposited amorphous-like tungsten film as a gate electrode
(1998-09-01)
Chang, KM
;
Deng, IC
;
Shih, CW
;
Lain, KD
;
Fu, CM
Tungsten films are often advantageously formed by the chemical vapor deposition system which using WF6 gas through SiH4 or H-2 reduction. The fluorine species will diffuse into poly-Si/SiO2/[Si] multilayers by a driving force which is the reaction of WF6 and poly-Si gate. When too many fluorine atoms diffused into the gate oxide, the fluorine atoms will cause more strain in the gate oxide and the electrical characteristics of device will shift. An amorphous-like tungsten layer was deposited at a flow rate ratio of 2.5 of SiH4/WF6. The driving force in the amorphous-like tungsten film deposition is far less than that in selective tungsten film deposition; therefore, the concentration of fluorine atoms in the amorphous-like tungsten film is much less than in the selective tungsten film. We proved that only few fluorine atoms were incorporated in amorphous-like tungsten film which has good characteristics in the application of gate electrode.
Effects of buoyancy and orientation on the flow in a duct preceded with a double-step expansion
(1998-09-01)
Tsui, YY
;
Shu, SJ
;
機械工程學系
;
Department of Mechanical Engineering
A numerical method, employing nonstaggered grid arrangement, is incorporated to deal with mixed convection flow in a duct with a double-step expansion at inlet. The walls downstream of the expansion are maintained at a uniform temperature. In the first series of tests, the duct is placed vertically (gamma = 0 degrees), and the buoyancy effect is examined via gradually increasing Grashof number until no converged solution is obtained. With the aid of buoyancy force the recirculating flows behind the sudden expansion attach to the two step walls when the Grashof number is large enough. In the meanwhile, reversed flow is detected in the centerline region. At Re = 56 the flow remains symmetric throughout the Grashof numbers tested whereas for Re = 114 the flow held may be symmetric or asymmetric, depending on the Grashof number. Also examined is the effect of inclination angle gamma for Ga = 1000 and 3000. In the horizontal position (gamma = 90 degrees), two recirculations exist behind the two step walls. When gamma > 90 degrees, a number of recirculations are formed on the two side walls and the main stream exhibits a wavy structure. The wavy how helps enhance heat transfer. The above results for different duct orientations are equally applicable to both heating and cooling hows. (C) 1998 Elsevier Science Ltd. All rights reserved.
Raman and X-ray studies of InN films grown at different temperatures by metalorganic vapor phase epitaxy
(1998-09-01)
Chen, WK
;
Lin, HC
;
Pan, YC
;
Ou, J
;
Shu, CK
We used Raman scattering and X-ray diffraction (XRD) methods to investigate the properties of InN films deposited at temperatures ranging from 325 to 600 degrees C by metalorganic vapor phase epitaxy (MOVPE). Significant line broadening, softening and intensity evolution were observed from films at growth temperatures between 375 and 450 degrees C. This can be attributed to the formation of mixed hexagonal and cubic structures and related dislocation defects. As the growth temperature was further increased, the hexagonal phase tvas found to be dominant in the deposited InN film.
A combined channel assignment mechanism for hierarchical cellular systems
(1998-09-01)
Lo, KR
;
Chang, CJ
;
Chang, C
;
Shung, CB
;
電子工程學系及電子研究所
This paper proposes a combined channel assignment (CCA) mechanism for hierarchical cellular systems with overlaying macrocells and overlaid microcells. The proposed CCA mechanism combines overflow, underflow, and reversible schemes, where new or handoff calls having no available channel to use in the overlaid microcell can overflow to use free channels in the overlaying macrocell, handoff calls from a neighboring macrocell can underflow to use free channels in the overlaid microcell, and handoff attempts from a macrocell-only region to an overlaid microcell can be reversed to use free channels in the microcell. We apply the CCA mechanism in two different hierarchical cellular systems of Strip type and Manhattan type and compare the CCA with the overflow channel assignment (OCA) scheme. Simulation results show that the CCA mechanism outperforms the OCA scheme by once in forced termination probability, by several times in new call blocking probability, and by 4.7% in system utilization for a hierarchical cellular system, and the CCA mechanism is more suitable for the Manhattan type than for the Strip type. (C) 1998 Elsevier Science B.V.
Passivation of Cu by sputter-deposited Ta and reactively sputter-deposited Ta-nitride layers
(1998-09-01)
Chuang, JC
;
Chen, NC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Sputter-deposited tantalum (Ta) and reactively sputter-deposited Ta-nitride films were studied with respect to the passivation capability against copper (Cu) oxidation in thermal O-2 ambient. A 200 Angstrom Ta or Ta-nitride film was sputter-deposited on a 2000 Angstrom Cu film using a Ta target in an Ar/N-2 gas mixture. With Ta passivation, Cu was not oxidized at temperatures up to 400 degrees C, which can be further improved by using passivation of an amorphous Ta-nitride film deposited in an appropriate condition. The absence of long-range defects in the Ta-nitride film was presumably responsible for this improvement. However, sputtering-induced surface damage by excess N-2 in the sputter gas mixture may reduce the passivation capability of Ta-nitride films. When the passivated Cu was oxidized, the Cu oxides always resided in the top sur face region. That is, in the oxidation process, Cu diffused through the defects of the passivation layers to the outer surface.
A common buffer-based approach to buffer management for a wafer fabrication factory
(1998-09-01)
Huang, JY
;
Sha, DY
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper presents a buffer management method for a wafer fabrication factory. A pull-based production control system (PPCS) is adopted to handle production activity control (PAC) and reduce the work-in-progress (WIP) level. In addition, a common buffer approach is used to further control WIP conditions and utilize limited storage space effectively. Simulation results show that the proposed buffer management method significantly reduces buffer storage space. Besides, it also maintains the manufacturing system's performance roughly equal to that provided by a local buffer scheme. Significance: The proposed buffer management method can handle production activity control, reduce the WIP level, control WIP conditions, and effectively utilize limited storage space. In addition, the method is easy to implement in a practical application.
Alignment error evaluation of the dial pattern
(1998-09-01)
Chang, YH
;
Huang, YC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
To achieve smooth etched sidewall surface at minimal time expense and reduce undercut etching are basic disciplines of the task of accurate alignment. When aligning etch-masks to [110] crystal orientation on a [100] Si wafer, a consideration is proposed by Schroder who uses a dial pattern for pre-etching to determine [110] crystal orientation. But that performance depends strongly on the resolution of the mask pattern generator. In this paper, we analyse Schroder's method by mathematical modeling and computer simulation. Finally, we propose an improvement for the Schroder limitation according to our analytic results.