Browsing by Issue Date, starting with "1992-11-01"

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TWINNED STRUCTURE OF M(6)C CARBIDE IN AN FE-MN-AL-MO-C ALLOY
(1992-11-01)
PENG, SW
;
CHOU, CP
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
OFF-LINE RECOGNITION OF HANDWRITTEN CHINESE CHARACTERS BY ONLINE MODEL-GUIDED MATCHING
(1992-11-01)
HSIEH, CC
;
LEE, HJ
;
資訊工程學系
;
Department of Computer Science
A model-guided structural matching method for recognizing handwritten off-line Chinese characters is presented. According to the stroke writing sequence, each character is described by an on-line model, which is a one-dimensional (1D) string consisting of a stroke sequence interleaved with relationships between two consecutive strokes. After an unknown input is thinned and line approximated, all possible strokes are extracted. A tree is created to represent all possible combinations of the extracted strokes which have the same stroke sequence as the one defined in the model. In the recognition process, we match the strokes with those defined in the on-line model. The matching process is formulated as a tree searching algorithm guided by the relationships in the model. The modelled character is taken to be a candidate if there is a feasible path which satisfies the relationships defined in the on-line model and the number of missing strokes in the input is less than a given threshold. The input is recognized as the character with the greatest number of matched strokes among all candidates. Experimental results on 300 frequently used characters in a database called CCL/HCCR1, which contains 5401 Chinese characters and about 250 variations for each one, show that the recognition rate is over 90%.
ANOMALOUS PR ORDERING IN THE NEW TLBA2PRCU2O7-DELTA COMPOUND
(1992-11-01)
LAI, CC
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CHIOU, BS
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CHEN, YY
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HO, JC
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KU, HC
Magnetic measurements on the new tetragonal Tl(1212) compound TlBa2PrCu2O7-delta (a = 3.910 angstrom and c = 12.53 angstrom) reveal an anomalously high antiferromagnetic Neel temperature T(N) congruent-to 8 K. This transition temperature is higher than T(N) = 2.2 K for isostructural TlBa2GdCu2O7-delta. Corroborative evidence comes from calorimetric studies, in which a magnetic entropy was obtained DELTAS congruent-to 0.5 Rln 2 between 2 and 10 K, as well as a sizeable linear term in specific heat comparable to those found in heavy-fermion systems. Through structural consideration, these observations can not only be correlated to the almost identical but still puzzling features of PrBa2Cu3O7-y, but also remove some ambiguity in the interpretation of earlier results.
BIREFRINGENCE-INDUCED SPECTRAL FEATURES IN CONTINUOUS-WAVE AND PASSIVELY MODE-LOCKED TI-SAPPHIRE LASERS
(1992-11-01)
PAN, CL
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HWANG, CD
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KUO, JC
;
SHIEH, JM
;
WU, KH
We show that the transient spectrum of a continuous-wave Ti:sapphire laser during the initial stage of the buildup, which exhibits multiple clusters (of longitudinal modes), is due to the spectral windowing effect of the Brewster-angle-cut Ti:sapphire crystal, which acts as a birefringent filter in the laser cavity. This effect is also responsible for certain spectral features of a passively mode-locked Ti:sapphire/DDI laser.
ALUMINA-CHROMIUM CARBIDE COMPOSITE THROUGH AN INTERNAL SYNTHESIS METHODS
(1992-11-01)
CHUANG, SC
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KUO, CT
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LEE, CS
;
HO, CT
;
LI, AK
In situ formation of chromium carbide parlicles, through a solid state reaction between Cr2O3 and SiC, for strengthening Al2O3 has been studied. Three kinds of chromium compound, Cr3Si, Cr3C2 and Cr7C3 and mullite were formed in the alumina matrix. The reaction behaviour during hot pressing depends on heating parameters such as temperature and atmosphere. In a vacuum environment, the Cr3Si particles formed first and was the dominant dispersed phase below 1550-degrees-C, while the Cr7C3 phase was only dominant above 1600-degrees-C. The Cr3C2 phase emerged briefly then diminished at temperature greater-than-or-equal-to 1500-degrees-C. In an argon environment, however, the Cr3C2 phase was the main product component at temperatures ranging from 1450-1550-degrees-C. The mullite phase formed concurrently through the diffusion Of SiO2 phase into the A12O3 matrix, which is a by-product from the reaction between Cr2O3 and SiC. Incorporating chromium carbide or silicide particles into the Al2O3 matrix induces a strengthening effect. However, only when the content of dispersed phases is low and is mainly of Cr3C2 particles, is the strengthening effect significant. For instance, the composite, containing 5 vol % chromium carbide and hot-pressed at 1500-degrees-C in argon, gives a flexural strength and fracture toughness up to 600 M Pa and 6.1 MPa m1/2, respectively.
ACTIVE CONTROL OF AN ASYMMETRICAL RIGID ROTOR SUPPORTED BY MAGNETIC BEARINGS
(1992-11-01)
FAN, YH
;
CHEN, ST
;
LEE, AC
;
交大名義發表
;
機械工程學系
Vibration control of a horizontal rotor with an asymmetrical moment of inertia is investigated. A linear optimal control system is developed to stabilize and control the rotor system by using the mathematical model of a rotor system expressed in the rotating coordinates. An approximated dynamical equation of a long rotor system is derived and used to obtain the compensator in analytical form (which saves much computational effort in control design), and is particularly useful in hardware implementation. Simulation results show the efficiency of the proposed strategy. The influences of weighting matrices and the effects of the asymmetrical moment of inertia on system performance for different controllers are also assessed.
SYNCHRONIZATION OF ELECTRICAL AND OPTICAL SIGNALS BY USING AN OPTOELECTRONIC TIMING DISCRIMINATOR IN A PHASE-LOCK LOOP
(1992-11-01)
PAN, CL
;
WU, HH
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交大名義發表
;
光電工程學系
;
National Chiao Tung University
A GaAs:Cr photoconductive switch is employed as an optoelectronic timing discriminator or phase detector in the phase-lock loop. Timing information is derived from the temporally sloped output of the switch, which is the cross-correlation function of the electrical signal and the photoconductive response induced by the laser pulse train. Optoelectronic synchronization of microwave signals up to 12 GHz in a laser-diode-based system has been demonstrated. The long-term relative timing jitter between the electrical and optical signals is estimated from the error signal in the PLL to be less than 500 fs. This technique can also be used to synchronize lasers.
TRANSIENT ANALYSIS OF AN ASYMMETRIC ROTOR-BEARING SYSTEM DURING ACCELERATION
(1992-11-01)
LEE, AC
;
KANG, Y
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TSAI, KL
;
HSIAO, KM
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交大名義發表
This paper deals with the transient vibration of asymmetric rotor systems during acceleration passing through several critical speeds at which synchronous or super-harmonic resonance occurs. The dynamic equations of the rotor-bearing system are formulated by the finite element model and the resulting dynamic equations are time-varying due to the effects of acceleration and asymmetry. In the formulation, a Timoshenko beam element is employed to simulate the rotating shaft and Eulerian angles are used to describe the orientations of the shaft element and disk. The numerical integration scheme for transient analysis is generated from the finite element model. Numerical examples are presented to illustrate (1) the effects of acceleration on peak amplitude and speed at which the peak occurs as the system passes through critical speeds, (2) the optimal acceleration process, which can be obtained by minimizing the peak response and the period of acceleration, (3) the speed regions where the transient instability exists.
QUANTUM-WELL GEOMETRICAL EFFECTS ON 2-DIMENSIONAL ELECTRON-MOBILITY
(1992-11-01)
WANG, TH
;
HSIEH, TH
;
CHEN, YT
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交大名義發表
;
電控工程研究所
A Monte Carlo analysis to study the quantization effects on the low-field electron mobility in various AlGaAs/GaAs/AlGaAs quantum well structures has been performed. The influence of the electron envelop wave-function and the subband structure on the two-dimensional electron scattering rates was evaluated. Our results showed that a maximum two-dimensional electron mobility can be achieved in a quantum well structure where the energy difference between the first subband and the second subband is about two times the polar optical phonon energy.
MODELING HOT-ELECTRON GATE CURRENT IN SI MOSFETS USING A COUPLED DRIFT-DIFFUSION AND MONTE-CARLO METHOD
(1992-11-01)
HUANG, CM
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WANG, TH
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CHEN, CN
;
CHANG, MC
;
FU, J
A coupled two-dimensional drift-diffusion and Monte Carlo analysis is developed to study the hot-electron-caused gate leakage current in Si n-MOSFET's. The electron energy distribution in a device is evaluated directly from a Monte Carlo model at low and intermediate electron energies. In the portion of high electron energy where the distribution function cannot be resolved by the Monte Carlo method due to limited computational resources, an extrapolation technique is adopted with an assumption of a Boltzmann tail distribution. This assumption is based on the simulation result that although the distribution function at a high electric field shows a markedly non-Maxwellian feature globally, it has approximately an exponential decay in an energy region much above average electron energy. A particular averaging method is employed to extract the effective electron temperature in the extrapolation. Our result shows that the electron temperature obtained in this approach is about three times lower than that derived from average electron energy by means of [E] = 3/2 kT(e) in the high-field domain of a device. Channel hot electron injection into a gate via quantum tunneling and thermionic emission is simulated. Electron scattering in gate oxide is also taken into account. The calculated values of gate current are in good agreement with experimental results. In the simulation, the most serious hot electron injection occurs about 200-300 angstrom behind the peak of average electron energy due to a delayed heating effect.
THROUGHPUT PERFORMANCE OF A CLASS OF CONTINUOUS ARQ STRATEGIES FOR BURST-ERROR CHANNELS
(1992-11-01)
LEE, TH
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電信工程研究所
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電信研究中心
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Institute of Communications Engineering
;
Center for Telecommunications Research
This paper studies the throughput performance of a class of continuous automatic repeat request (ARQ) strategies for burst-error channels modeled by two-state Markov chains. The operation of the investigated ARQ strategies can be described as follows. A chunk of m or fewer copies of each data block is transmitted contiguously to the receiver. Whenever a repeat request is received, the transmitter goes back to and retransmits that data block and all successive ones. However, the maximal number of copies transmitted is equal to n in each retransmission. It is proved that the optimal repetition sequence which maximizes the throughput efficiency among a more general set of ARQ schemes falls in the class of investigated strategies. Numerical results reveal that throughput efficiency is very likely to be maximized at m = n.
A NEW APPROACH TO INEXACT REASONING FOR RULE-BASED SYSTEMS
(1992-11-01)
CHEN, SM
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交大名義發表
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資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
This paper presents a new algorithm for dealing with inexact reasoning problems, where the certainty factors of the rules and the truth values of the conditions appearing in the rules are represented by linguistic terms. The algorithm performs inexact reasoning via repeatedly transforming an augmented linguistic truth state vector T by an augmented linguistic rule matrix F. Given the linguistic truth values of some conditions, the algorithm can perform inexact reasoning to evaluate the linguistic truth values of other conditions automatically.
THE EFFECT OF GRAIN-BOUNDARIES ON THE ELECTRICAL-PROPERTIES OF ZINC OXIDE-BASED VARISTOR
(1992-11-01)
BAI, SN
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TSENG, TY
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The ac response of ZnO-based varistors was measured as a function of temperature and applied electric field. Conductivity-frequency measurements indicated that the grain boundaries of the ZnO varistors were amorphous. The device resistance was found to decrease as the temperature/applied field increased. This was attributed to deterioration of the insulating property of the grain boundaries due to generation of conduction carriers in the ZnO grains. As a large amount of these charge carriers passed through the grain boundaries, the ZnO varistors remarkably revealed a non-Debye characteristic that can be modeled by a capacitance to simulate the behavior of the grain boundaries
LINK ENHANCEMENT USING CONSTRAINED RANGE AND REDUCED CANDIDATE SET SEARCHES
(1992-11-01)
YANG, C
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管理科學系
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資訊管理與財務金融系註：原資管所+財金所
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Department of Management Science
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Department of Information Management and Finance
A communication network's survivability and routability are primarily based on the degree of interconnection between the existing nodes of the network Enhancement of these characteristics can be obtained by adding direct communication links between nodes of the network. This process is generally subject to a budget constraint We show that the link enhancement problem, for a given investment, is NP-complete. Explanation of the proposed heuristic, for near-optimal solution, is presented with several examples. Improvements on previous work using constrained range and reduced candidate set searches are introduced and clarified A review of pertinent previous work, problem formulation, algorithm presentation, and discussion of computational issues are also provided.
EFFECTS OF CARBON CONTENTS ON THE TENSILE PROPERTIES AND DEFORMED MICROSTRUCTURES OF AUSTENITIC FE-28MN-9AL-XC ALLOYS
(1992-11-01)
CHOU, JS
;
CHAO, CG
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機械工程學系
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材料科學與工程學系
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Department of Mechanical Engineering
A STUDY OF THE INTERFACIAL LAYER OF AL AND AL(1-PERCENT SI)-SI CONTACTS USING A ZERO-LAYER ELLIPSOMETRY MODEL
(1992-11-01)
CHAO, TS
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LEE, CL
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LEI, TF
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this work, the interfacial layer of the Al-Si and Al(1% Si) Si contacting system annealed at different temperatures have been studied using ellipsometry incorporated with a zero-layer model. The results show that the thickness of the interfacial P+ layer between Al or Al(1% Si) and the Si-substrate increases with the annealing temperature and the thickness of the P+-layer of the Al(1% Si)-Si system is generally lower than that of the Al-Si system. Also, the fraction of Al in the interfacial layer decreases with the annealing temperature for the Al-Si system, but increases for the Al(1% Si)-Si system. The electrical measurements show that the interface of the Al(1% Si)-Si contact is more stable than that of the Al-Si contact.
COMPLETE DECOMPOSITION ALGORITHM FOR NONCONVEX SEPARABLE OPTIMIZATION PROBLEMS AND APPLICATIONS
(1992-11-01)
LIN, SY
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交大名義發表
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電控工程研究所
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National Chiao Tung University
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Institute of Electrical and Control Engineering
In this paper, we present a complete decomposition algorithm for nonconvex separable optimization problems applied in the optimal control problems. This complete decomposition algorithm combines recursive quadratic programming with the dual method. When our algorithm is applied to discretized optimal control problems, a simple and parallel computation and a simple and regular data flow pattern between consecutive computational steps results. This paper also suggests an approach for developing a hardware implementation of our algorithm and gives an estimation of the execution time needed to solve a practical example.
A PARALLEL ADAPTIVE ALGORITHM FOR MOVING TARGET DETECTION AND ITS VLSI ARRAY REALIZATION
(1992-11-01)
LIU, CM
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JEN, CW
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交大名義發表
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電控工程研究所
;
National Chiao Tung University
The application of an innovations-based detection algorithm (IBDA) in moving target detector (MTD) radars has been shown to be efficient. In this correspondence, an adaptive algorithm for the IBDA is derived. This algorithm behaves well in numerical properties and computational complexity. Also, it possesses high computing parallelism and data locality which lead to the feasibility of VLSI array realization. A systolic array is designed with the iteration time being (2n + 1) and the number of processing elements being [(n2 + 3n)/2], where n is the length of the adaptive filter.
COMPUTER-SIMULATION OF A DIRECT SEQUENCE SPREAD SPECTRUM CELLULAR RADIO ARCHITECTURE
(1992-11-01)
HUANG, CC
;
交大名義發表
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電信工程研究所
;
National Chiao Tung University
;
Institute of Communications Engineering
This paper describes a computer simulation study to evaluate the channel capacity of a direct sequence spread spectrum cellular radio architecture which is based on code division. The cellular radio architecture utilizes the processing pin provided by a wide-band multipath RAKE receiver to suppress multicell/multiuser interference. As a result, the same piece of radio spectrum can be reused in every cell. We use a step-by-step approach to verify the basic idea behind the spread spectrum cellular radio architecture. Computer simulations are used to calculate the distributions of signal-to-reference ratio (SIR). From SIR distributions, we can easily calculate the channel capacity of the cellular radio architecture. Technical requirements to fulfill potential system performance are also discussed. Finally, an 800 MHz system example is given for cellular mobile radio telephone application.
COMBINED RADIATION AND NATURAL-CONVECTION EFFECTS ON GRAETZ PROBLEM IN HORIZONTAL ISOTHERMAL CIRCULAR TUBES
(1992-11-01)
HUANG, JM
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LIN, JD
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交大名義發表
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機械工程學系
;
National Chiao Tung University
A numerical analysis is performed on the combined thermal radiation and mixed convection for a gray fluid flow in a horizontal isothermally-heated circular tube. The governing equations of vorticity-velocity form are employed and solved by DuFort-Frankel method. The contribution of radiation is formulated by integral expression and solved by finite element nodal approximation. The effects of radiation and convection on local Nusselt number and the developing of bulk temperature are presented. The result shows that the heat transfer can be significantly enhanced by the effects of radiation and secondary flow induced by buoyancy. Besides, the fluctuation in local Nusselt number curve which is caused by the existence of secondary flow is reduced by the effect of thermal radiation.