Browsing by Issue Date, starting with "1991-07-04"

Now showing 1 - 20 of 91212

EXTINCTION RATIO DEGRADATION IN RAMAN AMPLIFIED OPTICAL COMMUNICATION-SYSTEM
(1991-07-04)
KAO, MS
;
CHI, S
;
電信工程研究所
;
光電工程學系
;
電信研究中心
The extinction ratio of a Raman amplified optical fibre system is investigated. The results show that serious extinction ratio degradation occurs at high pump level. Because the Raman gain increases with pump power, there exists a trade-off between the extinction ratio and the achievable amplifier gain. A design rule to estimate the suitable pump power is presented.
A STUDY OF UPSTREAM-WEIGHTED HIGH-ORDER DIFFERENCING FOR APPROXIMATION TO FLOW CONVECTION
(1991-07-05)
TSUI, YY
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
;
Department of Mechanical Engineering
This paper is concerned with a number of upstream-weighted second- and third-order difference schemes. Also considered are the conventional upwind and central difference schemes for comparison. It commences with a general difference equation which unifies all the given first-, second- and third-order schemes. The various schemes are evaluated through the use of the general equation. The unboundedness and accuracy of the solutions by the difference schemes are assessed via various analyses: examination of the coefficients of the difference equation, Taylor series truncation error analysis, study of the upstream connection to numerical diffusion, single-cell analysis. Finally, the difference schemes are tested on one- and two-dimensional model problems. It is shown that the high-order schemes suffer less from the problem of numerical diffusion than the first-order upwind difference scheme. However, unboundedness cannot be avoided in the solutions by these schemes. Among them the linear upwind difference scheme presents the best compromise between numerical diffusion and solution unboundedness.
長江圖卷
(1991-07-11)
管管
NONLINEAR-WAVE PROPAGATION IN AN ASYMMETRIC CONVERGING Y-JUNCTION
(1991-07-15)
SHI, TT
;
CHI, S
;
光電工程學系
;
電信研究中心
;
Department of Photonics
Nonlinear wave propagation in an asymmetric converging Y junction, which consists of a nonlinear cladding, a linear film, and a linear substrate, is studied. The nonlinear dispersion curves of the successive sections of the Y junction are calculated to be used to illustrate the evolutions of the eigenmodes. The field incident from the nonlinear thinner branch can evolve into the symmetric mode of the stem with a high coupling efficiency. An insertion coupler for a time-multiplexed loop is suggested.
OXIDATION OF GAAS SURFACE BY OXYGEN PLASMA AND ITS APPLICATION AS AN ANTIREFLECTION LAYER
(1991-07-15)
LOONG, WA
;
CHANG, HL
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The optical reflectivity of a GaAs wafer is found to decrease from about 45% down to about 5% for both the g-line and i-line by oxidation in low-power oxygen plasma at 300-degrees-C for 4 hours. The oxide layer on the GaAs top surface used as an in situ antireflection layer for optical microlithography is demonstrated to be effective.
ELECTRICAL TRANSPORT IN THE AG-BI2SR1.8CA1.2CU2OY COMPOSITE SYSTEM
(1991-07-15)
LIN, JJ
;
CHEN, TM
;
應用化學系
;
Department of Applied Chemistry
We have measured the resistivity of the Ag-Bi2Sr1.8Ca1.2Cu2O(y) composite system with Ag volume fraction p(Ag) ranging from 0.00 to 1.00. We find, for the samples with p(Ag) < 0.6, that the addition of Ag slightly decreases the superconducting transition temperature of Bi2Sr1.8Ca1.2Cu2O(y). For the samples with p(Ag) > 0.6, no zero-resistivity state is observed. The variation of the room-temperature resistivity with p(Ag) indicates a three-dimensional percolating Ag matrix occurring at p(Ag) almost-equal-to 0.17.
杜甫草堂
(1991-07-15)
管管
杜甫草堂
(1991-07-15)
管管
A MEASURING METHOD OF A CONCAVE MIRROR BY DEFOCUSING A SCATTER PLATE
(1991-07-15)
SU, DC
;
SHYU, LH
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
Based on the fact that the phase variation is linearly proportional to the defocusing amount of the scatter plate, the additional phase shift can be achieved by defocusing the scatter plate in a controlled manner. Consequently, a method of how the phase shifting interferometric technique can be applied to the scatter plate interferometer is described. It has both the merits of a conventional scatter plate interferometer and the phase shifting interferometric technique. The validity of this method is demonstrated.
杜甫草堂
(1991-07-15)
管管
INFRARED UP-CONVERSION WITH BETA-BARIUM BORATE CRYSTAL
(1991-07-15)
LU, MH
;
LIU, YM
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
An IR up-conversion with a beta barium borate (beta-BBO) crystal as an upconverter has been made. The IR source at wavelengths 2.45-mu-m and 2.69-mu-m was provided by the lithium vapor excited by a pulsed dye laser tuned to the 2S-4S two-photon resonance of lithium atom. The phase matching angles for the type I phase matching has been measured and compared with the calculated values. Based on this comparison, the accuracy of various refractive index formulae extrapolated to the IR region is discussed. The IR up-conversion efficiency has also been measured which agrees reasonably with the calculation under a plane-wave approximation. The up-conversion with the beta-BBO crystal provides an effective approach for the IR detection in the 1-3-mu-m wavelength region.
杜甫草堂
(1991-07-15)
管管
K-BAND SUSPENDED SUBSTRATE STRIPLINE TAPPED COMBLINE FILTER
(1991-07-18)
LO, WT
;
TZUANG, CKC
;
交大名義發表
;
傳播研究所
;
National Chiao Tung University
A newly developed 19.5-20.5 GHz combline bandpass filter realised by multiple coupled suspended substrate striplines (MCSSSs) and metal-insulator-metal (MIM) capacitors is presented. The filter design uses an iterative field-theory-based algorithm to account for the composite effects of multiple dominant quasi-TEM modes of the MCSSS and the couplings through the nonadjacent lines. A prototype is built and tested. The measured and theoretical filter characteristics are in good agreement for the combline filter without any tuning.
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.