Browsing by Issue Date, starting with "1997-06-01"

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Characteristics of nonalloyed pseudomorphic high electron mobility transistors using InAs/InxGa1-xAs (x=-> 0) AlyGa1-yAs (y=0 -> 0.3) contact structures
(1997-06-01)
Chen, SS
;
Lin, CC
;
Lan, WH
;
Tu, SL
;
Peng, CK
A molecular beam epitaxy InAs/InxGa1-xAs (x = 1 --> 0)/AlyGa1-yAs (y = 0 --> 0.3) heterojunction was used as an ohmic contact structure to the GaAs-based pseudomorphic high electron mobility transistors (PHEMTs). This nonalloyed PHEMT had a specific contact resistance r(c) of 1.05 x 10(-7) Omega . cm(2) and an extrinsic transconductance g(me) of 272 mS/mm for devices with 1 mu m gate-length, microwave measurements shelved a current gain cut-off frequency f(t) of 22 GHz and a maximum oscillation frequency f(max) of 43 GHz. These results are comparable to our best conventional PHEMTs' alloyed at 450 degrees C and 2 min duration. Meanwhile, a small-signal equivalent circuit model of the nonalloyed PHEMT has also been demonstrated.
PACS network signaling using AIN/ISDN
(1997-06-01)
Lin, YB
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
This article describes network signaling for PACS (Personal Access Communications System). One of the distinguishing features of PACS is that the Advanced intelligent Network (AIN) protocol is used, and the general AIN switch and service control point (SCP) provide the flexibility to implement PCS network/service applications. The basic method for providing PCS support transparently to the AIN switch, at least from a call processing point of view, is that PCS-related messages are sent directly from the radio system to the AIN SCP by a sort of ''tunnel'' through the AIN switch. The PACS design has illustrated a new approach, interconnecting the radio system with the PSTN via general AIN switches. However, extra network traffic will be created by the NCA signaling. The performance of PACS network signaling is an open issue for future investigation.
Removal of CO2 greenhouse gas by ammonia scrubbing
(1997-06-01)
Bai, HL
;
Yeh, AC
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
This paper provides preliminary results on the novel study of ammonia scrubbing for the removal of carbon dioxide from flue gas. Experimental results indicated the potential of CO2 reduction by NH3 scrubbing is very promising. The overall CO2 removal efficiencies could be above 95% under proper operation conditions. The absorption capacity of NH3 was around 0.9 kg of CO2/ kg of NH3 reagent being used. This should be higher than that by a MEA solution. The reaction products were analyzed and determined by X-ray diffraction analysis, SEM picture, and pH measurements. All the measurements indicated that an ammonium bicarbonate solution and its crystalline solids are the major products of reaction.
Analytical framework for designing the divided automated guided Vehicles system
(1997-06-01)
Liu, FHF
;
Chen, JT
;
交大名義發表
;
工業工程與管理學系
;
National Chiao Tung University
The purpose of this paper is to present an analytical design framework for an AGV system configuration, called divided AGV system. In the divided AGV system, the pickup/deposit stations are divided into several transportation cells, and each cell has a simple guidepath traversed by a dedicated vehicle. Several transit stations may be set to construct a transit system for handling the intercell transport requirements. Moreover, the guidepaths for all cells are allowed to intersect at the crossroads. A systematic procedure is proposed to consider two important factors, distance and transport requirements (flow) between pickup/deposit stations simultaneously during the dividing procedure. In addition, a mathematical programming model for locating transit stations is integrated in the analytical framework. The divided configuration would not be seriously affected by plant layout, and the bi-directional vehicles would be implemented more effectively. In brief, the divided configuration could keep the simplicity of a control system and improve system feasibility and competition in a practical manufacturing environment.
Kinematic optimization of a modified helical gear train
(1997-06-01)
Chang, SL
;
Tsay, CB
;
Tseng, CH
;
交大名義發表
;
機械工程學系
A mathematical model of a modified helical gear train (MHGT), manufactured with a practical hobbing machine using a curved-template guide, and which takes considerations of center-distance variation and axial misalignment into account, is developed. Tooth contact analysis (TCA) and kinematic errors of a MHGT due to mis-assembly are investigated. A multiple optimization method is applied to reduce the level of MHGT kinematic errors, and to investigate optimal gear tooth modifications. Computer simulation programs for TCA and optimization are also developed. Two numerical examples are presented to illustrate the kinematic optimization of the proposed helical gear train. The results of this study are most helpful in designing and analyzing a MHGT.
Characteristics of nonalloyed pseudomorphic high electron mobility transistors using InAs/InxGa1-xAs (x=-> 0) AlyGa1-yAs (y=0 -> 0.3) contact structures
(1997-06-01)
Chen, SS
;
Lin, CC
;
Lan, WH
;
Tu, SL
;
Peng, CK
A molecular beam epitaxy InAs/InxGa1-xAs (x = 1 --> 0)/AlyGa1-yAs (y = 0 --> 0.3) heterojunction was used as an ohmic contact structure to the GaAs-based pseudomorphic high electron mobility transistors (PHEMTs). This nonalloyed PHEMT had a specific contact resistance r(c) of 1.05 x 10(-7) Omega . cm(2) and an extrinsic transconductance g(me) of 272 mS/mm for devices with 1 mu m gate-length, microwave measurements shelved a current gain cut-off frequency f(t) of 22 GHz and a maximum oscillation frequency f(max) of 43 GHz. These results are comparable to our best conventional PHEMTs' alloyed at 450 degrees C and 2 min duration. Meanwhile, a small-signal equivalent circuit model of the nonalloyed PHEMT has also been demonstrated.
Exchange coupling coefficient and domain wall mobility of (Dy,Tb)FeCo magneto-optical films
(1997-06-01)
Hwang, WK
;
Wu, TH
;
Shieh, HPD
;
交大名義發表
;
光電工程學系
The magnetic properties and recording characteristics of (Dy,Tb)Fr,Co films are dependent upon the anisotropy dispersion of rare earth constituents and the exchange integral between rare earth and transition metal sub networks. The exchange coupling coefficient lambda and the domain wall mobility mu(eff) are found to be interrelated by both measurements and calculations. The higher the lambda or the lower the mu(eff), the higher bias field that is required for magneto-optical recording. The temperature independent lambda is demonstrated to be an important parameter in the assessment of magnetic properties and recording characteristics of sperimagnetic films. (C) 1997 American Institute of Physics.
Implementation of damped-rate resolved-acceleration robot control
(1997-06-01)
Wu, SL
;
Lin, SK
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
The damped least-squares method has frequently been used to solve the singularity problem of resolved-acceleration control schemes. It works by damping only the joint accelerations, so that the joint accelerations in the degenerated directions (the end-effector cannot move along these directions) are zero at a singular point. However, the joint velocities in the degenerated directions may be nonzero in some situations, in which case they will create fluctuations around the singular point. In this paper, a damped-rate resolved-acceleration control scheme (DRRAC) is proposed to overcome this drawback. The paper also shows that the DRRAC is asymptotically stable, and its convergent property is discussed. Experiments were undertaken to verify the proposed control scheme. Copyright (C) 1997 Elsevier Science Ltd.
Optimizing parameters for machining general continuous forms using genetic algorithm
(1997-06-01)
Su, CT
;
Chen, MC
;
交大名義發表
;
工業工程與管理學系
;
National Chiao Tung University
With the widespread application of CNC (computer numerical control) machines in industry, machining condition optimization becomes an important problem. Turning is one of the most widely used metal removal processes. The formulation of turning optimization model for bar components has been investigated extensively in the literature. However, the machined parts in turning operations frequently have general continuous forms. In this paper, we develop a mathematical model to determine the optimal machining parameters for such turned parts. A genetic algorithm (GA) is applied to find the optimal solution. Finally, numerical examples are given to explain the application of developed model and GA.
General solution of contradirectional two-wave mixing with partially coherent waves in photorefractive crystals
(1997-06-01)
Yi, XM
;
Yang, CX
;
Yeh, PC
;
Lin, SH
;
Hsu, KY
We investigate contradirectional two-wave mixing with partially coherent waves in photorefractive crystals. By use of a statistical theory on linear systems, a general formulation of the problem in the space and frequency domain is derived and implemented numerically. We obtain results on beam intensity and mutual coherence. The results on the enhancement of mutual coherence are compared with previous theoretical results on simpler cases and with experimental measurements. Excellent agreements are achieved. The results also indicate that the effective interaction length can be significantly longer than the coherence length of the waves. (C) 1997 Optical Society of America.
Analytical framework for designing the divided automated guided Vehicles system
(1997-06-01)
Liu, FHF
;
Chen, JT
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The purpose of this paper is to present an analytical design framework for an AGV system configuration, called divided AGV system. In the divided AGV system, the pickup/deposit stations are divided into several transportation cells, and each cell has a simple guidepath traversed by a dedicated vehicle. Several transit stations may be set to construct a transit system for handling the intercell transport requirements. Moreover, the guidepaths for all cells are allowed to intersect at the crossroads. A systematic procedure is proposed to consider two important factors, distance and transport requirements (flow) between pickup/deposit stations simultaneously during the dividing procedure. In addition, a mathematical programming model for locating transit stations is integrated in the analytical framework. The divided configuration would not be seriously affected by plant layout, and the bi-directional vehicles would be implemented more effectively. In brief, the divided configuration could keep the simplicity of a control system and improve system feasibility and competition in a practical manufacturing environment.
Efficiency improvement in charge pump circuits
(1997-06-01)
Wang, CC
;
Wu, JC
;
交大名義發表
;
電子工程學系及電子研究所
;
National Chiao Tung University
Conventional charge pump circuits use a fixed switching frequency that leads to power efficiency degradation for loading less than the rated loading. This paper proposes a level shifter design that also functions as a frequency converter to automatically vary the switching frequency of a dual charge pump circuit according to the loading. The switching frequency is designed to be 25 kHz with 12 mA loading on both inverting and noninverting outputs. The switching frequency is automatically reduced when loading is lighter to improve the power efficiency. The frequency tuning range of this circuit is designed to be from 100 Hz to 25 KHz. A start-up circuit is included to ensure proper pumping action and avoid latch-up during power-up. A slow turn-on, fast turn-off driving scheme is used in the clock buffer to reduce power dissipation, The new dual charge pump circuit was fabricated in a 3-mu m p-well double-poly single-metal CMOS technology with breakdown voltage of 18 V, the die size is 4.7 x 4.5 mm(2), For comparison, a charge pump circuit with conventional level shifter and clock buffer was also fabricated. The measured results show that the new charge pump has two advantages: 1) the power dissipation of the charge pump is improved by a factor of 32 at no load and by 2% at rated loading of 500 Omega and 2) the breakdown voltage requirement is reduced from 19.2 to 17 V.
A synthesis of alpha-cuparenone based on symmetry considerations
(1997-06-01)
Ho, TL
;
Chang, MH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
A ring expansion approach to alpha-cuparenone was accomplished in 5 or 6 steps. The key intermediate is 3-methyl-3-(4-methylphenyl)cyclobutanone, which was derived from a [2+2]cycloaddition of dichloroketene on a styrene derivative, followed by dechlorination.
七絕
(1997-06-01)
管管
A video information system for sport motion analysis
(1997-06-01)
Chang, CW
;
Lee, SY
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
In this paper, we present several important methods in a video information system for sport motion analysis. We first describe an efficient method for computing the position of one or more moving objects in a video sequence. We utilize computer vision routines for both target object tracking and feature value extraction. Then, we propose a multiple subsequence matching mechanism for comparing the difference in object motion between two video sequences. A mapping function, penalty table and the overall distance between two video sequences have been defined. We use the prominent feature points as our segmentation positions and separate the sequence into several subsequence groups. After an alignment process, we can find the mapping of the best matching and get an evaluation report between the two video sequences for motion analysis. The video information system described in this paper has successfully analysed several examples of sport motion, and is representative of techniques commonly used in practice. (C) 1997 Academic Press Limited.
Resonant rutherford backscattering studies of cerium oxide thin films deposited by RF sputtering
(1997-06-01)
Chin, CC
;
Lin, RJ
;
Yu, YC
;
Wang, CW
;
Lin, EK
We have studied the stoichiometry of cerium oxide films deposited by RF sputtering on sapphire and MgO as a function of deposition conditions using the resonant Rutherford backscattering method. We found that some films have the off-stoichiometry of CeOy with y greater than 2.0. Such an off-stoichiometry cannot be due to a mixture of the known phases of bulk cerium oxide samples. This may be due to either cerium vacancies or interstitial oxygen atomic impurities. The cerium ion x-ray photoemission spectra of those films cannot determine the vacancy of the cerium ions. The c-axis YBaCuo thin flims deposited by sputtering on the CeO3.3 buffer layer on saphhire was found to be epitaxial. The T-c was 86 K with Delta T-c less than 1 K.
Multiplicative, congruential random-number generators with multiplier +/-2(k1)+/-2(k2) and modulus 2(p)-1
(1997-06-01)
Wu, PC
;
交大名義發表
;
National Chiao Tung University
The demand for random numbers in scientific applications is increasing. However, the most widely used multiplicative, congruential random-number generators with modulus 2(31) - 1 have a cycle length of about 2.1 X 10(9). Moreover, developing portable and efficient generators with a larger modulus such as 2(61) - 1 is more difficult than those with modulus 2(31) - 1. This article presents the development of multiplicative, congruential generators with modulus m = 2(p) - 1 and four forms of multipliers: 2(k1) - 2(k2), 2(k1) + 2(k2), m - 2(k1) + 2(k2), and m - 2(k1) - 2(k2), k1 > k2. The multipliers for modulus 2(31) - 1 and 2(61) - 1 are measured by spectral tests, and the best ones are presented. The generators with these multipliers are portable and very fast. They have also passed several empirical tests, including the frequency test, the run test, and the maximum-of-t test.
七絕
(1997-06-01)
管管
General equations of a helical spring with a cup damper and static verification
(1997-06-01)
Wu, MH
;
Ho, JY
;
Hsu, W
;
機械工程學系
;
Department of Mechanical Engineering
In this study, we derive the general equations of motion for the helical spring with a cup damper by considering the damper's dilation and varying pitch angle of the helical spring. These dynamic equations are simplified to correlate with previous models. The static force-displacement relation is also derived. The extra stiffness due to the damper's dilation considered in the force-displacement relation is the first such modeling in this area. In addition, a method is presented to predict the compressing spring's coil close length and is then verified by experimental data. Moreover, the simulation results of the static force-displacement relation are found to correspond to the experimental data. The maximum error is around 0.6 percent.
Video content representation, indexing, and matching in video information systems
(1997-06-01)
Chang, CW
;
Lee, SY
;
交大名義發表
;
資訊科學與工程研究所
;
National Chiao Tung University
Changing between frames is one of the most obvious information in video data. This frame-by-frame time series data is essential to many application areas. However, how to extract and compare video contents in a video information system is still an important problem to be solved. In this paper, we focus on the problem of design a fast searching method in a video information system to locate video segments that match a content-based query, approximately by time series feature values. The idea is to extract video contents via low-level feature extraction and/or high level semantic retrieval mechanisms according to a specific point of view, then segment video contents into bounding boxes via a box segmentation mechanism by their time series feature values. Video content indexing is constructed by the characteristics of prominent points that accompany bounding boxes. We also propose an efficient and effect:ive video content matching algorithm to find similar sequences. With the help of the video indexing and matching mechanisms, several high level box-to-box and low level point-to-point query types can be requested. The implementation and performance evaluation of our video information prototype system is described. (C) 1997 Academic Press.