Browsing by Issue Date, starting with "1992-02-15"

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ELECTRICAL TRANSPORT AND SUPERCONDUCTIVITY IN THE AU-BI2SR1.8CA1.2CU2OY COMPOSITE SYSTEM
(1992-02-15)
LIN, WY
;
LIN, JJ
;
CHEN, TM
;
應用化學系
;
Department of Applied Chemistry
We have measured the resistivity-rho of the Au-Bi2Sr1.8Ca1.2Cu2Oy composite system with Au volume fraction p(Au) ranging from 0.00 to 1.00. We find, for the samples with p(Au) less-than-or-equal-to 0.4, that the addition of Au does not disturb the superconducting transition temperature of Bi2Sr1.8Ca1.2Cu2Oy. For the samples with p(Au) greater-than-or-equal-to 0.6, no zero-resistivity state is observed. The variation of rho(300 K) with p(Au) indicates a three-dimensional percolating Au matrix occurring at p(Au) almost-equal-to 0.18.
AN ACCURATE COMPUTATION FOR RAPIDLY VARIED FLOW IN AN OPEN CHANNEL
(1992-02-15)
YANG, JC
;
CHEN, KN
;
LEE, HY
;
土木工程學系
;
Department of Civil Engineering
A new method combining the Preissmann four-point scheme and the Holly-Preissmann reach-back scheme is introduced to solve the rapidly varied flow problem in an open channel. The Preissmann four-point scheme is well known for the computation of one-dimensional unsteady flow. The Holly-Preissmann reach-back scheme integrates the Holly-Preissmann two-point scheme with the concept of reach-back characteristics, which allows the characteristics to project several time steps beyond the current time level. A spontaneous surge formation case is used to demonstrate and evaluate the applicability of the new method. It has been found that the results from this method are quite compatible with those of Preissmann four-point scheme. In addition, with the appropriate choice of the number of reach-back time steps, this new method can always avoid the numerical oscillation which usually exists when one uses the Preissmann four-point scheme for the condition of Courant number not close to unity.
詩是最美麗的毒藥
(1992-02-18)
管管
A GENERAL EXPRESSION FOR THE TOTAL RELEASE OF DIFFUSANT THROUGH HETEROGENEOUS MEMBRANES
(1992-02-19)
CHEN, JS
;
ROSENBERGER, F
;
應用化學系
;
Department of Applied Chemistry
An expression for the total amount of diffusant Q(t) released into a receiver by diffusion through a heterogeneous membrane is rigorously derived for time-dependent boundary conditions and a position-dependent initial condition. The heterogeneity of the membrane is characterized by a position-dependent diffusivity and partition coefficient. Two examples are given to demonstrate the utility of this general expression. It is shown that the expression for Q(t) proposed by Keister [ J. Membrane Sci., 29 (1986) 333-3441 is only valid when the asymptotic concentration of the diffusant within the membrane is zero.
DATA FLOW REPRESENTATION OF ITERATIVE ALGORITHMS FOR SYSTOLIC ARRAYS
(1992-03-01)
JEN, CW
;
KWAI, DM
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
An algebraic representation is proposed for regular iterative algorithms that can be described as bundles of data flows with different wavefronts. Modeling data flows with a generating function of power series, this form corresponds to the geometric representation such as a dependence graph. The main attributes of systolic algorithms and arrays are revealed by a unique data flow representation. This provides the ability to pipeline two or more systolic arrays solving different subproblems without intermediate buffering. We use an example to show the case with which our technique can be used.
SPATIAL REASONING AND SIMILARITY RETRIEVAL OF IMAGES USING 2D C-STRING KNOWLEDGE REPRESENTATION
(1992-03-01)
LEE, SY
;
HSU, FJ
;
資訊科學與工程研究所
;
電信研究中心
;
Institute of Computer Science and Engineering
The data structure called 2D string to represent symbolic pictures was proposed by Chang et al. It allows a natural way to construct iconic indexes for pictures. A new spatial knowledge representation of a 2D C-string with accompanying cutting mechanism and a set of spatial operators are proposed. 2D C-string is more characteristic of spatial knowledge in images and is more efficient in representation and manipulation of images. Since a spatial relationship is a fuzzy concept, the capability of similarity retrieval is essential in image database systems. The spatial query and spatial reasoning based on a 2D C-string representation are presented. The similarity measure is defined and the algorithm for similarity retrieval of iconic images is also proposed.
TRANSPORT AND DEPOSITION OF WEAR PARTICLES IN COMPUTER DISK DRIVES
(1992-03-01)
TSAI, CJ
;
PUI, DYH
;
LIU, BYH
;
環境工程研究所
;
Institute of Environmental Engineering
To understand the roles that wear particles play in disk crashes, analytical and numerical approaches have been used to study three dimensional fluid flow and wear particle transport and deposition in computer disk drives. The study shows that wear particles are flying very close to the disk surface. They can deposit on the disk surface and cause damage to disk drives. Cooling air flow through the disk hub of corotating disks has been found to play important roles in removing wear particles from disk drives. Parametric study has shown that the optimum cooling air flow rate is 12 slpm for 8" disk with the Reynolds number of 150,000.
SOME COMBINATORIAL ASPECTS OF PARALLEL ALGORITHM DESIGN FOR MATRIX MULTIPLICATION
(1992-03-01)
TSAY, JC
;
SY, Y
;
工學院
;
College of Engineering
In this paper, some combinatorial characteristics of matrix multiplication on regular two-dimensional arrays are studied. From the studies, we are able to design many efficient varieties of the cylindrical array and the two-layered mesh array for matrix multiplication. To design a cylindrical array for matrix multiplication, a systematic design procedure is proposed. In this design procedure, Latin square (a special type of matrix) plays an important role. To design a two-layered mesh array, we find that there is a transformation procedure to transform a cylindrical array to a two-layered mesh array.
龍磐之雲雀變調之研究
(1992-03-01)
管管
MEASUREMENT OF RESIDUAL-STRESSES IN WELDED STEEL JOINTS USING HOLE DRILLING METHOD
(1992-03-01)
WENG, CC
;
LO, SC
;
交大名義發表
;
土木工程學系
;
National Chiao Tung University
An experimental investigation of the residual stresses in three types of welded structural steel joint is presented. A total of twelve specimens was tested. In this investigation, the blind hole-drilling method of ASTM E837 was used - adapted and improved for determination of residual stresses. To account for the effect of local plasticity due to stress concentration near the drilled hole, new calibration coefficients were obtained by carrying out a series of calibration tests. Then, the residual stresses in the welded joints were determined using the new coefficients. The improved hole drilling method presented in this paper was found to be much less time consuming than the conventional sectioning (saw cutting) method for residual stress measurement. The final results obtained in this study showed good agreement with the residual stresses obtained by previous researchers using the sectioning method.
龍磐之雲雀變調之研究
(1992-03-01)
管管
COROTATIONAL TOTAL LAGRANGIAN FORMULATION FOR 3-DIMENSIONAL BEAM ELEMENT
(1992-03-01)
HSIAO, KM
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
;
Department of Mechanical Engineering
A corotational total Lagrangian formulation of beam element is presented for the nonlinear analysis of three-dimensional beam structures with large rotations but small strains. The nonlinear coupling among the bending, twisting, and stretching deformations is considered. All of the element deformations and equations are defined in body-attached element coordinates. Three rotation parameters are proposed to determine the orientation of the element cross section. Two sets of element nodal parameters termed explicit nodal parameters and implicit nodal parameters are introduced. The explicit nodal parameters are used in the assembly of the system equations from the element equations and chosen to be three components of the incremental translation vector and three components of the incremental rotation vector. The implicit nodal parameters are used to determine the deformations of the beam element and chosen to be three components of the total displacement vector and nodal values of the three rotation parameters. The element internal nodal forces corresponding to the implicit nodal parameters are obtained from the virtual work principle. Numerical examples are presented and compared with the numerical and experimental results reported in the literature to demonstrate the accuracy and efficiency of the proposed method.
DIRECTOR-CONFIGURATION DIAGRAM FOR A CLOSED-CYLINDER NEMATIC LIQUID-CRYSTAL
(1992-03-01)
LIANG, BJ
;
CHEN, SH
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交大名義發表
;
光電工程學系
;
National Chiao Tung University
This study reports that the director configuration diagram of a closed cylinder of nematic liquid crystal (CC NLC) with normal orientation at the walls may contain four kinds of stable director configurations. Sample cells were prepared by treating all walls of a closed cylindrical cavity with DMOAP (N,N-dimethyl-N-octadecyl-3-aminopropyltrimethoxysilyl-chloride) and then filling with NLC 5CB. The optical patterns of the CC NLCs were observed between crossed linear polarizers. A theory explaining these observations was developed by calculating the spatial distribution of the nematic director fields. The stable director configurations depend not only on the ratio of the splay and bend Frank elastic constant (K11/K33), but also on the aspect ratio of the cylinder. In general, the occurrence of a transformation between the radial and the hyperbolic type is determined by a critical transformation ratio K11/K33; there is also a critical aspect ratio remarking the transformation between the point and the ring structure. The calculations predict that the characteristic lengths of both the radial and the hyperbolic ring structure are nearly invariant with respect to K11/K33 and the aspect ratio of the cylinder.
TRANSIENT NATURAL-CONVECTION HEAT AND MASS-TRANSFER OVER A VERTICAL PLATE OF FINITE HEIGHT
(1992-03-01)
CHANG, J
;
LIN, TF
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
A detailed numerical analysis has been carried out to study transient natural convection in a binary mixture adjacent to a vertical plate of finite height with the simultaneous presence of temperature and concentration gradients. The full elliptic Navier-Stokes equations and the energy and species diffusion equations were solved together by the projection method with the convective terms treated by the QUICK scheme. Computations were performed for a mixture with Pr = 0.7, Sc = 3.5, and thermal Grashof number fixed at 10(6). Both the augmenting and opposing flows were investigated with the buoyancy ratio varied from - 5 to 5 and the concentration ratio, an interface velocity parameter, from 10 to 1000. Results are presented to illustrate, in particular, the effects of combined thermal and solutal buoyancy forces on the temporal evolution of the flow pattern and the associated heat and mass transfer. Representative transient velocity, temperature, and concentration profiles are presented, along with the transient local and average Nusselt and Sherwood numbers. In the initial transient, the interface velocity at the plate induced by the concentration gradient dominates the flow patterns. After the initial period, the recirculating flows generated by the two buoyancy forces in the fluid are prevalent. In opposing flows, countercurrent flows may result at a high buoyancy ratio.
INTEGRAL VARIABLE STRUCTURE CONTROL APPROACH FOR ROBOT MANIPULATORS
(1992-03-01)
CHERN, TL
;
WU, YC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
An integral variable structure control (IVSC) approach for robot manipulators is presented to achieve accurate servo-tracking in the presence of load variations, parameter variations and nonlinear dynamic interactions. A procedure is proposed for choosing the control function so that it guarantees the existence of the sliding mode and for determining the coefficients of the switching plane and the integral control gain such that the IVSC approach has the desired properties. Furthermore, a modified proper continuous function is introduced to overcome the chattering problem. The proposed IVSC approach has been simulated for the first three links of a PUMA 560 robot arm as an illustration. The simulation results demonstrate the potential of the proposed scheme.
龍磐之雲雀變調之研究
(1992-03-01)
管管
KNOWLEDGE-GUIDED VISUAL-PERCEPTION OF 3-D HUMAN GAIT FROM A SINGLE IMAGE SEQUENCE
(1992-03-01)
CHEN, Z
;
LEE, HJ
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
A computer vision method is presented to determine the 3-D spatial locations of joints or feature points of a human body from a film recording the human motion during walking. The proposed method first applies the geometric projection theory to obtain a set of feasible postures from a single image, then it makes use of the given dimensions of the human stick figure, physiological and motion-specific knowledge to constrain the feasible postures in both the single-frame analysis and the multi-frame analysis. Finally a unique gait interpretation is selected by an optimization algorithm. Computer simulations are used to illustrate the ideas presented.
A NEURAL NETWORK APPROACH TO MVDR BEAMFORMING PROBLEM
(1992-03-01)
CHANG, PR
;
YANG, WH
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CHAN, KK
;
交大名義發表
;
電信工程研究所
A Hopfield-type neural network approach which leads to an analog circuit for implementing the real-time adaptive antenna array is presented. An optimal pattern of the array can be steered by updating the weights across the array in order to maximize the output signal-to-noise ratio (SNR). Furthermore, it is shown that the problem of adjusting the array weights can be characterized as a constrained quadratic nonlinear programming. Practically, the adjustment of settings is required to respond to a rapid time-varying environment. Many numerical algorithms have been developed for solving such problems using digital computers. The main disadvantage of these algorithms is that they generally converge slowly. To tackle this difficulty, a neural analog circuit solution is particularly attractive in real-time applications with minimization of a cost function subject to constraints. A novel Hopfield-type neural net with a number of graded-response neurons designed to perform the constrained quadratic nonlinear programming would lead to such a solution in a time determined by RC time constants, not by algorithmic time complexity. The constrained quadratic programming neural net has associated it with an energy function which the net always seeks to minimize. A fourth-order Runge-Kutta simulation is conducted to verify the performance of the proposed analog circuit. It shows that the circuit operates at a much higher speed than conventional techniques and the computation time of solving a linear array of 10 elements is about 0.1 ns for RC = 5 x 10(-9).
A NEW ON-CHIP ESD PROTECTION CIRCUIT WITH DUAL PARASITIC SCR STRUCTURES FOR CMOS VLSI
(1992-03-01)
WU, CY
;
KER, MD
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LEE, CY
;
KO, J
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電控工程研究所
A new CMOS on-chip electrostatic discharge (ESD) protection circuit which consists of dual parasitic SCR structures is proposed and investigated. Experimental results show that with a small layout area of 8800-mu-m2, the protection circuit can successfully perform negative and positive ESD protection with failure thresholds greater than +/- 1 and +/- 10 kV in machine-mode (MM) and human-body-mode (HBM) testing, respectively. The low ESD trigger voltages in both SCR's can be readily achieved through proper circuit design and without involving device or junction breakdown. The input capacitance of the proposed protection circuit is very low and no diffusion resistor between I/O pad and internal circuits is required, so it is suitable for high-speed applications. Moreover, this ESD protection circuit is fully process compatible with CMOS technologies.
QUANTUM CONFINEMENT EFFECT ON THE IMPURITY STATES OF A SPHERICAL CONFINING SYSTEM
(1992-03-01)
HSIAO, CM
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MEI, WN
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CHUU, DS
;
電子物理學系
;
Department of Electrophysics
Whittaker function and scattering Coulomb wave function are used to calculate the eigen-energies of an impurity in a spherical confining system. Variation of the state energies with the radii of the confining system is obtained.