Browsing by Issue Date, starting with "1994-05-26"

Now showing 1 - 20 of 88278

MEASURING EMISSION CROSS-SECTION PROFILE OF ERBIUM-DOPED FIBER WITH LOW-INPUT POWER
(1994-05-26)
CHEN, CY
;
WEN, S
;
CHI, S
;
光電工程學系
;
電信研究中心
A simple and elegant method is proposed to measure the emission cross-section profile of erbium-doped fibre by using a short piece of erbium-doped fibre with input pump or signal power less than 1mW. Relative error is within 1% over the whole spectrum. The theoretical and experimental results are discussed.
GROWTH OF ZNGA2O4 PHOSPHOR BY RADIO-FREQUENCY MAGNETRON SPUTTERING
(1994-06-01)
HSIEH, IJ
;
FENG, MS
;
KUO, KT
;
LIN, P
;
材料科學與工程學系
ZnGa2O4 films have been prepared by radio frequency (RF) magnetron sputtering at various total pressure, RF power, and substrate temperatures. Microstructure and crystallographic orientation were characterized by x-ray diffraction Surface morphologies were observed by scanning electron microscope. In addition, cathodoluminescence (CL) measurement was employed to observe the emission spectra of ZnGa2O4 films. The influences of various deposition parameters on the properties of grown films were studied. The optimum substrate deposition temperature for luminous characteristics was about 500-degrees-C in this investigation. A blue cathodoluminescent emission peaked at 470 nm was observed. Good luminescent properties were observed in the films which exhibit the standard ZnGa2O4 x-ray diffraction pattern.
VARIABLE FRAME RATE SPEECH CODING USING OPTIMAL INTERPOLATION
(1994-06-01)
CHUNG, CJ
;
CHEN, SH
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電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
A VFR LPC vocoder using optimal interpolation is presented in this paper. In the encoder, some representative frames of an utterance are selected for transmission. In the decoder, LPC parameters of all untransmitted frames are restored by optimal interpolation. Simulation results show that this coding scheme outperforms the conventional VFR vocoder using linear interpolation. By incorporating contour quantization of gain and pitch information, a low variable-rate LPC vocoder is realized. An informal listening test shows that very high intelligible reconstructed speech was obtained at an average data rate of 300 bps.
EFFECTIVE ACTIVE DAMPING DESIGN FOR SUPPRESSION OF VIBRATION IN FLEXIBLE SYSTEMS VIA DISLOCATED SENSOR ACTUATOR POSITIONING
(1994-06-01)
CHEN, ST
;
FAN, YH
;
LEE, AC
;
交大名義發表
;
機械工程學系
In this paper we present a new controller design method that effectively suppresses vibration in flexible systems. The method allows integrated determination of sensor/actuator locations and feedback gain via minimization of an energy criterion which represents the integrated total energy stored in the system. This energy criterion is characterized by an effective representation of vibration, determined via an efficient solution of the Lyapunov equation and minimized with a quasi-Newton or recursive quadratic programming algorithm. The application of this method to a simple flexible structure confirms the direct relationship between our optimization criterion and effectiveness of vibration suppression.
A MODIFIED CRITERION FOR OPTIMAL LINEAR TIME-INVARIANT OBSERVER PROBLEMS
(1994-06-01)
HWANG, MS
;
LEE, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A modified criterion for designing a linear time-invariant observer is studied. This criterion is a compromise between errors due to stochastic and modal-type deterministic signals. The advantage of this criterion is in its design potentiality to take care of both transient and steady-state behavior. Theoretical properties such as existence, uniqueness, and stability of the optimal solution can be guaranteed for detectable systems under a weak stabilizability condition, which is satisfied by any reasonably defined problem. Moreover, under the criterion, relationships with other existing methods are also discussed.
AN ALGORITHM FOR COMPUTING THE RELIABILITY OF WEIGHTED-K-OUT-OF-N SYSTEMS
(1994-06-01)
WU, JS
;
CHEN, RJ
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
This paper constructs a new k-out-of-n model, viz, a weighted-k-out-of-n system, and proposes an O(n . k) algorithm for computing its reliability.
A RIPPLE FREE SAMPLED-DATA ROBUST SERVOMECHANISM CONTROLLER USING EXPONENTIAL HOLD
(1994-06-01)
WU, YC
;
YEN, NZ
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In a general command tracking and disturbance rejection problem, it is known that a sampled-data controller using zero-order hold may only guarantee the asymptotic tracking at the sampling instances, but cannot smooth out the ripples between the sampling instances. In this paper, a sampled-data robust servomechanism controller using exponential hold is developed for guaranteeing the asymptotic tracking not only at, but also between, the sampling instances In this development, a so called ''internally-reducible'' condition to characterize a class of robust servomechanism controllers is derived first, then the proposed controller is shown to be contained in this class. Generally speaking, a sampled-data structure using exponential hold can provide more design freedoms so that it tends to simplify the construction of a robust servomechanism controller and facilitate the implementation on digital computers. An example for a dc motor control is presented to illustrate the advantages of this approach.
CONSTRAINED OPTIMIZATION OF ACTIVE NOISE-CONTROL SYSTEMS IN ENCLOSURES
(1994-06-01)
YANG, TC
;
TSENG, CH
;
LING, SF
;
機械工程學系
;
Department of Mechanical Engineering
An effective software design tool is proposed for solving active noise control problems associated with constraints in which the complex strength and location of the secondary source of an active noise control system in an enclosed space are simultaneously optimized. The boundary element method is adopted to evaluate the sound field in enclosures. Furthermore, the boundary used could be of pressure, velocity, or impedance; in addition, the primary source may be at an arbitrary position. An optimizer based on sequential quadratic programming is selected for its accuracy, efficiency, and reliability. Bounds for design variables and proper constraints on the sound field and secondary source can be specified as required. The powerfulness of the proposed tool is demonstrated by optimizing an active control system for an enclosure. For a rectangular cavity, the optimal location of the secondary source is confirmed by observed simulations as always forming a dipole with the primary source situated at off-resonance excitations and subsequently approaching a mirror image position of the primary source at resonance excitations. The optimal location of the controller is found to change with varied upper bounds of the strength of the secondary source. These findings show a discrepancy from those reported in previous researches based on an unconstrained formulation. Sensitivity analysis at the optimum is also included to provide information of practical concern for implementing optimized active noise control systems.
FAST CLOSEST CODEWORD SEARCH ALGORITHM FOR VECTOR QUANTIZATION
(1994-06-01)
LEE, CH
;
CHEN, LH
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
One of the most serious problems for vector quantisation is the high computational complexity of searching for the closest codeword in the codebook design and encoding phases. The authors present a fast algorithm to search for the closest codeword. The proposed algorithm uses two significant features of a vector, mean value and variance, to reject many unlikely codewords and saves a great deal of computation time. Since the proposed algorithm rejects those codewords that are impossible to be the closest codeword, this algorithm introduces no extra distortion than conventional full search method. The results obtained confirm the effectiveness of the proposed algorithm.
ANALYSIS OF AN ELECTROHYDRAULIC SERVO SYSTEM SUBJECT TO STRIBECK-TYPE FRICTION
(1994-06-01)
CHIN, JH
;
FU, WC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
The main objective of this paper is to study the phenomena of the electrohydraulic servo system under the influence of the Stribeck-type friction. Owing to the nonlinear nature of this friction, a sustained oscillation, or limit cycle, might appear in the system behaviour. The system is first divided into two parts, the linear and the nonlinear. For the nonlinear Stribeck-type friction, a flexible model is proposed to represent the whole friction family, and the describing function of this nonlinear friction is generated. The system characteristic equation is established by correlating the frequency response of the linear part and the describing function of the nonlinear part. The existence and stability of the limit cycle are predicted based on the characteristic equation. Finally, by using the sinusoidal, step and ramp input, respectively, the numerical simulation is adopted to observe the system response. All predicted limit cycles can be verified by the simulation results, and the effects of stable and unstable limit cycles are clarified. The dynamic characteristics obtained in this study help to bring insight into this important engineering configuration and throw some light on the possibilities for improvement.
A MODEL OF THE TIME-DEPENDENT INTERACTION BETWEEN ROCK AND SHOTCRETE SUPPORT IN A TUNNEL
(1994-06-01)
PAN, YW
;
HUANG, ZL
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交大名義發表
;
土木工程學系
;
National Chiao Tung University
A viscoelastic model is developed to simulate the tunnel-support interaction of a circular tunnel in a viscoelsatic rock mass. This model accounts for the time-dependent stiffness and the yielding strain of shotcrete support. This model is formulated to analyze the effects of the time -dependence of support characteristics on tunnel convergence, support pressure, and tunnel-support interaction. Results of a parametric study reveal that the time-dependence of shotcrete stiffness has a strong influence on tunnel convergence and support pressure. Ignoring the yield strain of shotcrete may lead to the underestimation of tunnel convergence and the overestimation of the ultimate capacity of shotcrete support.
AN ESTIMATION OF GROUND SETTLEMENT DUE TO SHIELD TUNNELING BY THE PECK-FUJITA METHOD
(1994-06-01)
FANG, YS
;
LIN, JS
;
SU, CS
;
交大名義發表
;
土木工程學系
In this paper, an empirical method based on Peck and Fujita's study is proposed to estimate the magnitude and extent of surface settlement associated with shield tunnelling. It is found that the ground-settlement curves calculated with the proposed method for various types of shields, ground conditions, tunnel diameters, and depths are in reasonably good agreement with field measurements. For open shields tunnelled through clayey soils, the stability ratio has a significant influence on the surface settlement induced. Field measurement data suggest that the Peck-Fujita method may be used to estimate the ground subsidence associated with the construction of parallel tunnels.
EFFICIENT WIDE-BAND SOURCE LOCALIZATION USING BEAMFORMING INVARIANCE TECHNIQUE
(1994-06-01)
LEE, TS
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
;
Institute of Communications Engineering
A novel scheme for wideband direction-of-arrival (DOA) estimation is proposed. The technique performs coherent signal subspace transformation by a set of judiciously constructed beamforming matrices. The beamformers are chosen to transform each of the narrowband array manifold vectors into the one corresponding to the reference frequency, regardless of the actual spatial distribution of the sources. The focused data correlation matrix can thus be obtained without any preliminary DOA estimation or iteration. A simplified version of the beamspace Root-MUSIC algorithm is developed and used in conjunction with the proposed method to efficiently localize multiple wideband sources with a linear, equally spaced array. Numerical simulations are conducted to demonstrate the efficacy of the new scheme.
NEW DESIGN METHODOLOGY AND NEW DIFFERENTIAL LOGIC-CIRCUITS FOR THE IMPLEMENTATION OF TERNARY LOGIC SYSTEMS IN CMOS-VLSI WITHOUT PROCESS MODIFICATION
(1994-06-01)
HUANG, HY
;
WU, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new design methodology is proposed and analyzed for the design of ternary logic systems. In the new ternary logic systems, no conversions among radices are required and only the two-state ternary literals associated with the ternary signals are transmitted in the whole system. With the new design methodology, the ternary systems can be realized by the dynamic CMOS logic circuits which are simple and fully compatible with those of the conventional binary logic circuits in process, power supply, and logic levels. A new dynamic differential logic called the CMOS Redundant Differential Logic (CRDL) is also developed to increase the logic flexibility and the circuit performance. Using the new design methodology and the CRDL circuits, the multiplier with redundant binary addition tree is designed in both non-pipelined and pipelined systems. The experimental chip has been fabricated and measured, which successfully verifies the correctness of the logic functions and the speed performance of the designed circuits.
INVESTIGATION OF NEW NARROW-BANDWIDTH A-SI-H PHOTODETECTOR
(1994-06-01)
SHIN, NF
;
HONG, JW
;
WU, YF
;
JEN, TS
;
CHANG, CY
A narrow-bandwidth hydrogenated amorphous silicon (a-Si : H) photodetector with a basic structure of Al/n+-i-p+-i-n-i-p-i-n+/ITO/glass has been investigated. The spectral response of this new photodetector was found to be affected by the absorption coefficient of a-Si:H material, surface recombination current, device layer thicknesses, and applied bias. The spectral response of this device reveals a measured minimum FWHM of 58 nm at zero volt bias. The peak wavelength in the visible spectrum can be shifted from 400 nm (purple) to 550 nm (green) by decreasing the bias voltage from 5 to 0 V. The optoelectronic characteristics of this photodetector fit theoretically using suitable quantitative estimates.
A TERMINATION SCHEME FOR HIGH-SPEED PULSE-PROPAGATION ON A SYSTEM OF TIGHTLY COUPLED COPLANAR STRIPS
(1994-06-01)
KUO, JT
;
TZUANG, CKC
;
傳播研究所
;
電信工程研究所
;
Institute of Communication Studies
A realistic termination scheme is proposed for closely coupled N-conductor microstrips. The design aims to achieve satisfactorily low signal reflection and good fabrication feasibility for the planar MMIC (Monolithic Microwave Integrated Circuit) process. The matched termination network (MTN) for a lossless three-line coupled microstrip structure is presented. High-speed pulse transmission along terminated tightly coupled microstrip lines is analyzed using modal analysis in the frequency domain. Theoretical results for the propagating and reflected waveforms are obtained by applying the inverse discrete Fourier transform (IDFT) to the system responses. These responses are obtained by applying the theory of multiconductor transmission lines to a dispersive database which has been computed using the spectral-domain approach (SDA). The response of a six-line closely coupled microstrip circuit terminated by the proposed termination scheme is measured using the HP8510D network analyzer. The measured results show that the reflected signal is below -30 dB and the results are in good agreement with the theoretical waveforms.
ROBUST OBSERVER SYNTHESIS FOR NONLINEAR LARGE-SCALE SYSTEMS
(1994-06-01)
CHENG, CF
;
WANG, WJ
;
LIN, YP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The observer synthesis of nonlinear large-scale systems is discussed. The non-linearities satisfy the Lipschitz conditions instead of any matching conditions and exist on the interconnection terms and local system matrices. With the aid of the solution of the Riccati-type equation, the relationship between the nonlinearity bounds and the observer gains is derived. Moreover, the existence condition and seeking algorithm for the solution of the Riccati equation are investigated. An example with simulations is given to illustrate the application of our results.
A MULTIPLE PURPOSE SOIL TESTING APPARATUS
(1994-06-01)
HUANG, AB
;
HSU, SP
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KUHN, HR
;
交大名義發表
;
土木工程學系
A relatively compact soil testing system that is capable of performing monotonic/cyclic triaxial and torsional simple sheaf tests has been developed. A high-torque direct-drive, servo/stepper motor is used to provide the driving force. Under the servo mode, the motor could be controlled to provide a constant torque, which is used in stress-controlled tests. Strain-controlled tests are conducted using the stepper control mode. To perform triaxial tests, the rotational motion of the motor is transformed into linear motion using a preloaded ball screw shaft. A preloaded ball spline shaft directly attached to the motor is used to perform torsional simple shear tests. Because there are no gears in the driving system, there is no backlash during reversals of loading directions. The motor is equipped with an encoder and an indexer. The extremely rigid driving system and high resolution of the encoder enable the linear and rotational displacement to be monitored through the encoder/indexer system. Test control and data logging are fully automated using a personal computer. This paper provides details of the apparatus. A set of strain-controlled test data are presented to demonstrate capabilities of the new apparatus.
ROOM-TEMPERATURE SELECTIVE GROWTH OF DIELECTRIC FILMS BY LIQUID-PHASE DEPOSITION
(1994-06-01)
YEH, CF
;
CHEN, CL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In multilevel interconnection processes, because thermal stress affects device characteristics and wiring reliability, low-temperature deposition has been required for interlayer dielectrics (SiO2). This research investigated high growth rate and selective growth conditions of room-temperature interlayer dielectrics formed using the liquid-phase deposition method. The dependence of deposition rate on growth temperature and H3BO3 concentration is confirmed, and a concentration of 3.8 mol l-1 of H2SiF6 is used to achieve a high deposition rate of 1250 angstrom h-1. The degree of supersaturation of silica of the immersing solution is found to define three ranges of growth conditions: the non-deposition range, selective deposition range, and conformal deposition range. A selective deposition model is proposed to clarify the mechanism of room-temperature selective SiO2 growth,
LOW-TEMPERATURE FORMATION OF PALLADIUM SILICIDED SHALLOW P(+)N JUNCTIONS USING IMPLANT THROUGH METAL TECHNOLOGY
(1994-06-01)
LIN, CT
;
CHOU, PF
;
CHENG, HC
;
奈米中心
;
Nano Facility Center
Excellent silicided shallow pin junctions have been successfully achieved by the implantation of BF: ions into thin Pd films on a Si substrate to a dose of 5 x 10(15) cm(-2) and subsequent low-temperature (as low as 500 degrees C) furnace annealing. The formed junctions have been characterized for the respective implantation conditions. In this experiment, the implant energy plays the key role in obtaining a low leakage diode. Reverse current density of about 1 nA/cm(2) and the ideality factor of about 1.03 can be attained by the implantation of BF2+ ions at 100 keV and subsequent annealing at 600 degrees C. The junction depth is about 0.08 mu m, measured by the spread resistance method. As compared with the results of unimplanted specimens, the implantation of BF2+ ions into a thin Pd layer can stabilize the Pd silicide film and prevent it from forming islands during high-temperature annealing. High-temperature stability of palladium silicides and the leakage current mechanism are also discussed in this report.