Browsing by Issue Date, starting with "1993-02-28"

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USE OF CHARACTERISTICS METHOD WITH CUBIC INTERPOLATION FOR UNSTEADY-FLOW COMPUTATION
(1993-02-28)
YANG, JC
;
CHIU, KP
;
交大名義發表
;
土木工程學系
;
National Chiao Tung University
The specified-time-interval (STI) scheme has been used commonly in applying the method of characteristics (MOC) to unsteady open-channel flow problems. However, with the use of STI scheme, the numerical error for the simulation results can always be induced due to the interpolation used to approximate the characteristics trajectory. Hence, in order to remedy the numerical errors caused by the interpolation, one needs to seek some kind of interpolation technique with higher-order accuracy. Instead of the linear interpolation technique, which has been used very commonly and can induce serious numerical diffusion, the Holly-Preissmann two-point method, which is a cubic interpolation technique with fourth-order of accuracy, is proposed here to integrate with the method of characteristics for the computation of one-dimensional unsteady flow in open channel. The concept of reachback and reachout in space and time directions for the characteristics is also introduced to assure the model stability. The computed results from this new model are compared with those computed by using the Preissmann four-point scheme and the multimode method of characteristics with linear interpolation.
EFFECT OF ALUMINUM ON TRIP FE-MN-AL ALLOY-STEELS AT ROOM-TEMPERATURE
(1993-02-28)
CHEN, FC
;
CHOU, CP
;
LI, P
;
CHU, SL
;
機械工程學系
Fe-Mn-Al alloy steel has undergone many significant developments during the past few years, and it is considered to be a steel of high strength and toughness. Studies and test results have shown that Fe-Mn-Al is a good potential replacement for conventional stainless steels which contain expensive nickel and chromium additions. Recently, it has been found that strain-induced martensitic transformation at room temperature is possible in austenitic Fe-Mn-Al alloy. Further study has shown that the alpha' martensite can improve the mechanical properties of these Fe-Mn-Al alloys. However, as the aluminium content increases, the strain-induced phase transformation is inhibited. Moreover, the mechanical properties of these materials are very dependent on the aluminium content.
QUANTUM-THEORY OF SOLITON PROPAGATION - A UNIFIED APPROACH BASED ON THE LINEARIZATION APPROXIMATION
(1993-03-01)
LAI, YC
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
;
Department of Photonics
Based on the linearization approximation, a unified approach to the quantum effects of soliton propagation is developed. The new formulation provides a clearer picture. The real and imaginary parts of the perturbation field are expanded in different basis sets. Orthogonality relations are used to project out the soliton parameters. The new formulation also provides a general numerical approach to the calculation of detection noise. Numerical analyses of fiber ring gyros that use squeezed solitons are presented.
FINDING A COMPLETE MATCHING WITH THE MAXIMUM PRODUCT ON WEIGHTED BIPARTITE GRAPHS
(1993-03-01)
TSENG, FSC
;
YANG, WP
;
CHEN, ALP
;
資訊工程學系
;
Department of Computer Science
The traditional bipartite weighted matching problem is to maximize the largest possible sum of weights. In this paper, we define a bipartite matching problem which maximizes the largest possible product of weights and develop an algorithm to solve it. Although this problem corresponds to a non-linear program, we show this problem can be easily solved by modifying the Hungarian method. Finally, we present an application of this problem.
ELECTRICAL CHARACTERISTICS OF TEXTURED POLYSILICON OXIDE PREPARED BY A LOW-TEMPERATURE WAFER LOADING AND N-2 PREANNEALING PROCESS
(1993-03-01)
WU, SL
;
LIN, TY
;
LEE, CL
;
LEI, TF
;
電子工程學系及電子研究所
A low-temperature wafer loading and N2 preannealing process is used to grow a thin textured polysilicon oxide. The polyoxide grown on the heavily doped polysilicon film exhibits less oxide tunneling leakage current and higher dielectric strength when the top electrode is positively biased.
TOPOLOGICAL OPTIMIZATION OF A COMMUNICATION-NETWORK SUBJECT TO A RELIABILITY CONSTRAINT
(1993-03-01)
JAN, RH
;
HWANG, FJ
;
CHENG, ST
;
資訊工程學系
;
Department of Computer Science
This paper considers network topological optimization with a reliability constraint. The objective is to find the topological layout of links, at a minimal cost, under the constraint that the network reliability is not less than a given level of system reliability. A decomposition method, based on branch & bound, is used for solving the problem. In order to speed-up the procedure, an upper bound on system reliability in terms of node degrees is applied. A numerical example illustrates, and shows the effectiveness of the method. If a*, an important parameter, is close to the minimal number of links in a network which satisfy the reliability constraint, then a better starting solution can be obtained, and many searching steps can be saved. In our method, the lower bound a* is close to its actual value if the operational reliability of the link is close enough to 1. Also, if we can find the maximal increasing value of the reliability when a set of links is added to a specified topology, the efficiency of the branch & bound algorithm is improved.
春花燦爛已逝
(1993-03-01)
管管
SYMMETRY-BREAKINGS FOR SEMILINEAR ELLIPTIC-EQUATIONS OF FINITE CYLINDRICAL DOMAINS
(1993-03-01)
LIN, SS
;
交大名義發表
;
應用數學系
;
National Chiao Tung University
;
Department of Applied Mathematics
We study the existence and multiplicity of asymmetric positive solutions of a semilinear elliptic equation on finite cylinders with mixed type boundary conditions. By using a Nehari-type variational method, we prove that the numbers of asymmetric positive solutions are increasing without bound when the lengths of cylinders are increasing. On the contrary, by using the blow up technique, we obtain an a priori bound for positive solutions and then prove that all positive solutions must be symmetric when the cylinders are short enough.
UNSTEADY THERMOSOLUTAL OPPOSING CONVECTION OF LIQUID WATER MIXTURE IN A SQUARE CAVITY .2. FLOW STRUCTURE AND FLUCTUATION ANALYSIS
(1993-03-01)
CHANG, J
;
LIN, TF
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
Effects of buoyancy ratio on the flow structure and fluctuating characteristics of the velocity, temperature and concentration fields are numerically investigated for a liquid-water mixture cavity subject to opposing horizontal thermal and solutal buoyancies at high thermal and solutal Rayleigh numbers. Three different flow structures, namely, the multilayer, mixed and secondary cell flows, were predicted. Time histories and power spectra for flow variables probed at several locations indicate that the flow is highly unstable. The collision of the thermally and solutally driven cells causes the secondary cell flow to be chaotic. Moreover, flow bifurcation is noted.
春花燦爛已逝
(1993-03-01)
管管
MOLECULAR-BEAM EPITAXY GROWTH OF INAS-ALSB-GASB INTERBAND TUNNELING DIODES
(1993-03-01)
CHEN, JF
;
CHO, AY
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電子物理學系
;
Department of Electrophysics
This paper presents our studies of the growth of InAs/GaAs and GaSb/GaAs heterojunctions by molecular beam epitaxy and their applications in fabricating the InAs-AlSb-GaSb interband tunneling devices. The Hall effect and x-ray diffraction were used to determine the optimum growth conditions for the layers. In addition, the qualities of the InAs and GaSb epilayers, grown under their optimum conditions, were compared. The full width at half maximum (FWHM) from the x-ray diffraction for a GaSb epilayer is about 50 arcsec narrower than an InAs epilayer of the same thickness. The narrower FWHM and excellent surface morphology of the GaSb layer have led us to grow the polytype heterostructure on a p+-GaAs substrate using a p+-GaSb as the buffer layer. The polytype tunneling structures grown on GaAs substrates under these conditions show good negative differential resistance properties. Five different interband tunneling structures are compared and discussed in terms of their peak-current densities and peak-to-valley current ratios.
INSITU DEPOSITION OF SUPERCONDUCTING YBCO FILMS ON SI WITH CERAMIC BUFFER LAYERS
(1993-03-01)
JUANG, JY
;
WU, KH
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LAI, TC
;
LEE, MH
;
HSEIH, MC
Systematic studies on the optimization of depositing superconducting YBCO thin films on Si substrates with YSZ buffer layers by pulsed laser ablation have been carried out. Nearly c-axis oriented YBCO films with T(co) almost-equal-to 85 K were obtained routinely on Si(100) substrates with in-situ deposition of YSZ layers on top. Preliminary measurements on the critical current density Jc of these films showed Jc > 2.0 x 10(4) A/cm2 at 77K and Jc > 1.4 x 10(6) A/CM2 at 20K. The significant improvements on Jc are attributed to the great reduction of microcracks and the crystallinity of YSZ layer, achieved by the in-situ annealing of the buffer layer prior to the YBCO deposition. The effects of oxygen partial pressure and substrate temperature during YSZ deposition on the crystallinity of YSZ layer as well as on the quality of subsequently deposited YBCO films will be discussed. In our most recent attempt the microcracks has been sucessfully eliminated by a process combining the in-situ annealing and slow cooling process.
ROBUST OPTIMIZATION OF MULTIVARIABLE FEEDBACK-SYSTEMS WITH TIME-VARYING NONLINEAR UNCERTAINTIES
(1993-03-01)
TU, MH
;
LIN, CM
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LIN, YP
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電控工程研究所
;
Institute of Electrical and Control Engineering
A design criterion is developed to achieve the input-output decoupling of multivariable feedback systems and the robust stabilization of systems with time-varying nonlinear uncertainties. Moreover, an effective design algorithm is derived to achieve the robust optimization of multivariable feedback systems subjected to time-varying nonlnear uncertainties. The theory of minimum H(infinity)-norm and the optimal interpolation technique are employed to solve this robust optimization problem. Since the requirements of internal stability are satisfied, this design algorithm performs appropriately, even if the plant is unstable and/or non-minimum phase. From the result of the robust optimization, we can predict the maximum sector bounds of nonlinear uncertainties that can be tolerated in the multivariable feedback system.
FAST ORTHOGONALIZATION ALGORITHM AND PARALLEL ARCHITECTURE FOR AR SPECTRAL ESTIMATION BASED ON FORWARD - BACKWARD LINEAR PREDICTION
(1993-03-01)
LIU, KJR
;
HSIEH, SF
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電信工程研究所
;
Institute of Communications Engineering
The truncated QR methods have been shown to be comparable to the SVD-based methods for the sinusoidal frequency estimation based on the forward-backward linear prediction (FBLP) model. However, without exploiting the special structure of the FBLP matrix, the QR decomposition (QRD) of the FBLP matrix has the computational complexity on the order of 2(6m - n)n2/3 + O(n2) for a 2m x n FBLP matrix. Here we propose a fast algorithm to perform the QRD of the FBLP matrix by exploiting its special Toeplitz-Hankel form. The computational complexity is then reduced to 10n2 + 4mn + O(n). The fast algorithm can also be easily implemented onto a linear systolic array. The number of time steps required is further reduced to 2m + 5n - 4 by using the parallel implementation.
A 3-DIMENSIONAL ANALYSIS OF ELECTROOPTIC MODULATORS BY THE METHOD OF LINES
(1993-03-01)
CHUNG, SJ
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交大名義發表
;
傳播研究所
;
National Chiao Tung University
;
Institute of Communication Studies
A 3-dimensional analysis using the method of lines is developed to study the electrostatic field within an electrooptic switch/modulator. The effect of the ends of the electrodes is investigated by considering the distributions of the electric field along the transverse and longitudinal directions. Also, the capacitance related to the abrupt ends is calculated for several parameters of the structure.
仙人掌與黑白貓
(1993-03-01)
管管
MINIMAL PERIODIC REALIZATIONS OF TRANSFER-MATRICES
(1993-03-01)
LIN, CA
;
KING, CW
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Periodic controllers designed based on the so-called lifting technique are usually represented by transfer matrices. Real-time operations require that the controllers be implemented as periodic systems. We study the problem of realizing an Nn(o) X Nn(i) proper rational transfer matrix as an n(i)-input n(o)-output N-periodic discrete-time system. We propose an algorithm to obtain periodic realizations which have a minimal number of states. The result can also be used to remove any redundant states that exist in a periodic system.
PREPARATION AND AC ELECTRICAL RESPONSE ANALYSIS FOR (BA,PB)TIO3 PTCR CERAMICS
(1993-03-01)
LAI, CH
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TSENG, TY
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
For those PTCR materials with higher Pb content, the thermodynamic derivation of increasing values for ''inversion temperature'' and cation vacancy diffusion rate accounts for the increases in the calculated acceptor-state densities N(s) (cm-2). The influence of frequency-dependent properties for the dielectric constant on the calculation of acceptor-state densities is also presented. Applying the concept of suitable value for N(s) to obtain a strong PTC effect, (Ba,Pb)TiO3 PTCR ceramics with Curie point T(c) over 340-degrees-C up to 420-degrees-C have been successfully prepared by adopting higher cooling rates.
春花燦爛已逝
(1993-03-01)
管管
VLSI NEUROPROCESSORS FOR VIDEO MOTION DETECTION
(1993-03-01)
LEE, JC
;
SHEU, BJ
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FANG, WC
;
CHELLAPPA, R
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交大名義發表
The system design of a locally connected competitive neural network for video motion detection is presented. The motion information from a sequence of image data can be determined through a two-dimensional multiprocessor array in which each processing element consists of an analog neuroprocessor. Massively parallel neurocomputing is done by compact and efficient neuroprocessors. Local data transfer between the neuroprocessors is performed by using an analog point-to-point interconnection scheme. To maintain strong signal strength over the whole system, global data communication between the host computer and neuroprocessors is carried out in a digital common bus. A mixed-signal very large scale integration (VLSI) neural chip that includes multiple neuroprocessors for fast video motion detection has been developed. Measured results of the programmable synapse, and winner-take-all circuitry are presented. Based on the measurement data, system-level analysis on a sequence of real-world images was conducted. A 1.5 x 2.8-cm2 chip in a 1.2-mum CMOS technology can accommodate 64 velocity-selective neuroprocessors. Each chip can achieve 83.2 giga connections per second. The intrinsic speed-up factor over a Sun-4/75 workstation is around 180.