Browsing by Issue Date, starting with "1991-08-01"

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THE EFFECT OF ALUMINUM AND CARBON ON THE STRUCTURAL-CHANGES AND STRAIN-HARDENING OF AUSTENITIC FE-MN-AL ALLOY-STEELS DURING PLASTIC-DEFORMATION
(1991-08-01)
LI, P
;
CHU, SL
;
CHOU, CP
;
CHEN, FC
;
機械工程學系
A HIGH-SPEED NEURAL ANALOG CIRCUIT FOR COMPUTING THE BIT-LEVEL TRANSFORM IMAGE-CODING
(1991-08-01)
CHANG, PR
;
HWANG, KS
;
GONG, HM
;
電信工程研究所
;
Institute of Communications Engineering
This paper presents a Hopfield-type neural network approach which leads to an analog circuit for implementing the bit-level transform image. Different from the conventional digital approach to image coding, the analog coding system would operate at a much higher speed and requires less hardware than digital system. In order to utilize the concept of neural net, the computation of a two-dimensional DCT-based transform coding should be reformulated as minimizing a quadratic nonlinear programming problem subject to the corresponding 2's complement binary variables of 2-D DCT coefficients. A novel Hopfield-type neural net with a number of graded-response neurons designed to perform the quadratic nonlinear programming would lead to such a solution in a time determined by RC time constants, not by algorithmic time complexity. A fourth order Runge-Kutta simulation is conducted to verify the performance of the proposed analog circuit. Experiments show that the circuit is quite robust and independent of parameter variations and the computation time of an 8 x 8 DCT is about 1ns for RC = 10(-8). In practice, programmable hybrid digital-analog MOS circuits are required to implement the neural-based DCT optimizer. The circuit techniques are based on extremely simple and programmable analog parameterized MOS modules with such attractive features as reconfigurability, input/output compatibility, and unrestricted fan-in/fan-out capability.1
SLIDING-MODE CONTROL OF MULTILINK FLEXIBLE MANIPULATORS
(1991-08-01)
CHEN, YP
;
YEUNG, KS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper is a continuation of the research efforts reported recently in Yeung and Chen (1989) and Yeung and Chen (1991). This present work presents an extension of the sliding-mode control design method to multi-link flexible manipulators. There are two main steps in the design procedure, linearization and stabilization. In the linearization step, the sliding-mode technique is used to replace the rigid part of the dynamic equations by a set of linear equations which are determined by the switching surfaces. In the stabilization step, conventional PD/PID compensations are adopted to stabilize the linearized time-invariant system in the following three cases: (1) first-link ramp-tracking of the manipulator on a horizontal plane, (2) first-link parabola-tracking of the manipulator on a horizontal plane, and (3) first link regulation of the manipulator in a vertical plane. The developed sliding-mode controller is simple and requires no inertia matrix inversion, no modal estimation and no payload forecast. Simulation studies have been conducted to demonstrate the robustness of the controller against both input disturbances and payload variations.
PERFORMANCE EVALUATION OF COHERENT SUBCARRIER MULTIPLEXED OPTICAL-DISTRIBUTION SYSTEMS WITH COMMON LOCAL OSCILLATORS
(1991-08-01)
KAO, MS
;
WU, J
;
電信工程研究所
;
Institute of Communications Engineering
Coherent subcarrier multiplexed local distribution systems using a common local oscillator (LO) in which the LO is provided by a distribution centre instead of locally generated at the subscriber premise are described. Both single and multiple optical carrier systems are considered. Because of the low path loss in a local optical network, a common LO system is possible with a LO shared by many subscribers, and indeed provides many advantages. First, a simplified receiver is achievable which eliminates a tunable LO, an automatic frequency control (AFC) circuit, a polarisation controller, and an optical coupler. Secondly, the system cost is decreased due to the reduction of components. Thirdly, laser phase noise and intermediate frequency (IF) drift are expected to be minimised. Fourthly, because no active optical components are placed at the subscriber premises, the system reliability is increased. Fifthly, the common LO system can be expanded with optical amplifiers without increasing the number of LO and simultaneous amplification of the message, and LO signals are achievable. By sharing high power, highly frequency stabilised, and very narrow linewidth LO lasers provided by the centre, it is expected that a simple and reliable coherent optical distributing network can be constructed by using common LO.
THE MEMOIRS OF WITTE,COUNT - HARCAVE,S
(1991-08-01)
TUAN, CK
;
交大名義發表
;
National Chiao Tung University
BANYAN NETWORK NONBLOCKING WITH RESPECT TO CYCLIC SHIFTS
(1991-08-01)
LEE, TH
;
LIU, SJ
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
The nonblocking property of banyan network with respect to cyclic shifts is proved. The property is used to design a fair nonblocking copy network for multicast packet switching. The performance of the designed copy network is evaluated.
CONFORMAL GRAVITY WITH TORSION
(1991-08-01)
HAN, P
;
KAO, WF
;
PEN, UL
;
交大名義發表
;
光電工程學系
We study a conformal effective theory in the presence of the torsion field. A power-law inflationary solution in the constant gauge is obtained in k = 0 Friedman-Robertson-Walker space. If k not-equal 0, a formal result is also presented. Some technique details are discussed and remarked. It appears that the low energy relic from the torsion field deserves more study.
NUMERICAL-ANALYSIS OF THE FREQUENCY-DEPENDENT OUTPUT CONDUCTANCE OF GAAS-MESFETS
(1991-08-01)
LO, SH
;
LEE, CP
;
物理研究所
;
電控工程研究所
;
Institute of Physics
The small-signal output conductance of GaAs MESFET's on semi-insulating substrate has been studied using two-dimensional numerical analysis. Frequency-, temperature-, and drain-bias-dependent behaviors of the output conductance are analyzed. It is confirmed that the bulk EL2 traps contribute significantly to the low-frequency-dependent behavior of the output conductance. Devices with different background trap concentration and acceptor concentration have been analyzed and compared. For devices with higher trap concentration and higher acceptor concentration, the output conductance is lower but exhibits stronger frequency dependence.
MINIMUM MEAN-SQUARED ERROR DECISION-FEEDBACK EQUALIZATION FOR DIGITAL SUBSCRIBER LINE TRANSMISSION WITH POSSIBLY CORRELATED LINE CODES
(1991-08-01)
LIN, DW
;
電子工程學系及電子研究所
;
電信研究中心
;
Department of Electronics Engineering and Institute of Electronics
;
Center for Telecommunications Research
Most of the published theory on the optimal performance of decision-feedback equalization under the MMSE criterion addresses the transmission of i.i.d. symbol sequences only. This paper presents a theory which accommodates the case of correlated symbol sequences. It also considers the use of a fractionally spaced forward filter in the decision-feedback equalizer (DFE). Two limiting conditions are discussed in some detail, both concerning having an infinite-length DFE feedback filter. In one of them the forward filter is of finite length and in the other it is noncausal infinite. Several numerical examples are given, in which we apply the theory to the study of the MMSE transmission performance, at ISDN basic access rates, of a few example subscriber lines using some well-known line codes. In these examples, the near-end crosstalk from identical digital transmission systems is assumed to be the only significant noise. Throughout the study, we ignore the effects of error propagation in a DFE.
THE OPTICAL SOLITON TRANSMISSION AMPLIFIED BY BIDIRECTIONAL RAMAN PUMPS WITH NONCONSTANT DEPLETION
(1991-08-01)
WEN, SF
;
WANG, TY
;
CHI, S
;
光電工程學系
;
電信研究中心
A numerical method is proposed to solve the coupled equations between the soliton and bidirectional Raman pump waves. The pump depletion due to the soliton is obtained without using the constant depletion approximation. With this method, the soliton propagation in a Raman-pumped fiber can be solved accurately. It is found that the constant depletion approximation is valid at a small depletion rate, which requires low soliton power (or long pulsewidth), small material loss, and a short-pump period. In a periodically Raman-pumped fiber, there exists a stable signal energy, which is very sensitive to the pump intensity. We have also studied the stability of the soliton propagation with nonconstant pump depletion. It is found that the stability predicted by nonconstant depletion (NCD) and constant depletion assumption (CDA) are generally different.
A REAL-TIME C-V MEASUREMENT CIRCUIT FOR MOS CAPACITORS UNDER CURRENT STRESSING
(1991-08-01)
LEE, CL
;
LEI, TF
;
HO, JH
;
WANG, WT
;
電子工程學系及電子研究所
A dynamic large signal C-V measurement circuit is presented to measure real time C-V characteristics of a MOS structure under current stressing conditions. The real time information on the generation and filling of traps and surface states can thus be obtained. With this circuit it has been shown that, for an Al-gate MOS structure, charges on traps and interface surface states recover immediately after the stressing is removed.
GAIN MARGINS AND PHASE MARGINS FOR MULTIVARIABLE CONTROL-SYSTEMS WITH ADJUSTABLE-PARAMETERS
(1991-08-01)
TAO, CS
;
CHANG, CH
;
HAN, KW
;
交大名義發表
;
National Chiao Tung University
This paper presents a method for finding the boundaries of gain margins and phase margins of multivariable control systems with adjustable parameters. The considered systems are first decomposed into the augmented open-loop transfer functions modified by adding an analytical gain-phase margin tester, then the characteristic equations are formulated, and finally the stability equations are used to find the boundaries of constant gain margins and phase margins. The main advantage of the proposed method is to obtain complete information about the effects of adjustable parameters on gain margins and phase margins; thus it is a useful tool for analysis and design of robust control systems.
STUDY ON THE INTRINSIC THERMAL-STABILITY OF ANISOTROPIC THIN-FILM SUPERCONDUCTORS WITH A LINE HEAT-SOURCE
(1991-08-01)
CHEN, RC
;
CHU, HS
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper presents an analytical method to investigate the intrinsic thermal stability of anisotropic thin film superconductors. A three-dimensional analysis is introduced to consider an instantaneous release of energy in the form of a finite length line source. Through the transformation of coordiantes, an isotropic form of heat conduction equation is obtained. To solve this initial and boundary value problem, the method of separation of variables is employed, which gives an exact solution. The results of limiting cases of this study are compared with those of two previous investigations. Results from this study also show that the anisotropy of highly orientated films of superconductors has a great impact on the thermal stability. The stability parameter also depends on the location of the line source, the length of the line source, the magnitude of disturbance energy, the Biot number and the aspect ratio in the plane of thin film and normal to it.
INTERFERENCE CANCELLATION MATRIX BEAMFORMING FOR 3-D BEAMSPACE ML/MUSIC BEARING ESTIMATION
(1991-08-01)
ZOLTOWSKI, MD
;
LEE, TS
;
電信工程研究所
;
Institute of Communications Engineering
In conventional monopulse radar, the bearing of a single target within the mainlobe of the transmitted beam is estimated via a ML procedure based in a 2-D beamspace defined by sum and difference beams. For the case of two closely spaced targets angularly located within the mainlobe of the transmitted beam, 3D-BDML is a computationally simple ML bearing estimation scheme which operates in a 3-D beamspace generated by three orthogonal, classical beamformers. The presence of strong interferers angularly located outside the mainlobe encompassing the two targets of interest necessitates the use of adaptively formed left, center, and right beams. Let M denote the number of elements comprising the array. Novel procedures are developed for the construction of an M x 3 interference cancellation matrix beamformer which retains those properties of the M x 3 classical matrix beamformer critical to the computational simplicity of 3D-BDML. The most important of these is commonality of M - 3 nulls among the left, center, and right beams. Simulations are presented demonstrating the excellent performance of both single frequency and multifrequency 3D-BDML incorporating interference cancellation in a simulated low-angle radar tracking environment.
HALF-BAND FILTER DESIGN WITH ODD-POLYNOMIAL CHEBYSHEV-APPROXIMATION
(1991-08-01)
CHANG, WT
;
LIN, MS
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
An efficient method for the design of the half-band filter is described. Both the characteristics of the time response and the frequency response of the half-band filter are fully utilised to reduce the computation time and to increase the computation accuracy. The algorithm is based on the Chebyshev approximation criterion and uses only odd-symmetry polynomials for frequency interpolation to meet the required frequency response of the half-band filter.
杜甫草堂之
(1991-08-06)
管管
THEORETICAL CALCULATION OF THE LASER CHARACTERISTICS OF A TRANSVERSELY EXCITED CO2-LASER
(1991-08-14)
WU, KH
;
LIE, CS
;
電子物理學系
;
光電工程學系
;
Department of Electrophysics
This paper presents a theoretical model of a transversely excited CW CO2 laser. The laser rate equations, as well as the basic hydrodynamic and thermodynamic equations, have been used to describe the whole laser system. The spatial distributions of small signal gain and saturation intensity along the gas flow direction have been calculated for a given set of initial conditions, namely, pumping rate, gas mixture, total pressure, gas temperature and gas flow velocity. The dependence of laser output power on discharge and flow parameters is in good agreement with the experimental data, confirming the usefulness of this model and understanding of the laser performance.
SYNTHESIS OF SIDE-CHAIN LIQUID-CRYSTALLINE POLYSILOXANES CONTAINING TRANS-CYCLOHEXANE BASED MESOGENIC GROUPS
(1991-08-25)
HSU, CS
;
LU, YH
;
應用化學系
;
Department of Applied Chemistry
ETHYLIMIDOTANTALUM COMPLEX AS PRECURSOR TO TANTALUM NITRIDE THIN-FILMS
(1991-08-25)
CHIU, HT
;
CHANG, WP
;
應用化學系
;
Department of Applied Chemistry
THE MAGNETIC AND TRANSPORT-PROPERTIES OF HIGH-CRITICAL-CURRENT TL2BA2CA2CU3OX SUPERCONDUCTING THIN-FILMS
(1991-08-26)
CHU, ML
;
CHANG, HL
;
WANG, C
;
JUANG, JY
;
UEN, TM
Highly c-axis-oriented Tl2Ba2Ca2Cu3O(x) superconducting thin films with the critical current density as high as 1 X 10(7) A/cm2 at 87 K were obtained by single-target dc sputtering on LaAlO3 (100) substrates followed by encapsulated compensate annealing. The strong linear temperature dependence of zero-field critical current at low temperatures suggests a creep-dominated behavior. Preliminary field dependence studies on the critical current density in low-field regime (< 2 kOe) shows no evidence of hysteresis commonly encountered in films with higher granularity. The scaling behavior of the global pinning force density exhibits strong resemblance to conventional type-II superconductors with the pinning force density of the same order of magnitude as that in strong pinned NbN thin films.