Browsing by Issue Date, starting with "1991-03-15"

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FREE-CARRIER ABSORPTION IN N-TYPE GALLIUM-ARSENIDE IN QUANTIZING MAGNETIC-FIELDS
(1991-03-15)
WU, CC
;
TSAI, J
;
LIN, CJ
;
應用數學系
;
電子工程學系及電子研究所
Free-carrier absorption in n-type GaAs in quantizing magnetic fields has been investigated quantum mechanically. It is assumed that the energy gand of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for electrons is acoustic-phonon scattering via deformation-potential coupling. When the radiation field is polarized parallel to the magnetic field, the free-carrier absorption coefficient assumes a complex value due to the ac radiation and phonon fields. Our results show that the real part of the absorption coefficient and the imaginary part of the absorption coefficient oscillate with the magnetic field. However, at very low temperatures, oscillations in the imaginary part are diminished and its value decreases rapidly with increasing magnetic field.
MAGNETIC-FIELD-INDUCED FREEDERICKSZ TRANSITION AND THE DYNAMIC-RESPONSE OF NEMATIC LIQUID-CRYSTAL FILMS WITH A FREE-SURFACE
(1991-03-15)
CHEN, SM
;
HSIEH, TC
;
PAN, RP
;
電子物理學系
;
光電工程研究所
The Freedericksz transition and the dynamic response of homeotropical liquid-crystal films with a free surface (FS) induced by a perpendicular dc magnetic field have been studied theoretically and experimentally for two nematic substances: 4'-n-pentyl-4-cyanobiphenyl (5CB) and 4'-n-octyl-4-cyanobiphenyl (8CB). For either one of these two materials, it is found that the critical magnetic field of these two nematic liquid-crystal (NLC) films with a free surface is equal to that of the NLC film with hard boundaries (HB) of the same thickness. This thus demonstrates a very strong orientational anchoring for 5CB and 8CB at the free surface. The intrinsic structures of FS samples are homeotropic, just as the HB ones are. For the dynamic response, the turn-off rates of FS samples are found to be about two times faster than those of the HB ones. This is interpreted with the backflow theory and the lack of positional anchoring on the free surface. Finally, a sensitive approach to determine the viscosity coefficients, gamma-1 and eta-c, of the NLC film is suggested.
COMPOSITION AND CHEMICAL-REACTIONS OF TITANIUM-OXIDE FILMS DEPOSITED BY LASER EVAPORATION
(1991-03-15)
DAI, CM
;
SU, CS
;
CHUU, DS
;
電子物理學系
;
光電工程學系
Thin films were deposited on Pyrex glass substrates from Ti and TiO2 targets at room temperature by laser evaporation technique. These films were characterized by scanning electron microscopy, Auger electron spectroscopy, and depth profile analysis. The films deposited from Ti target are TiC(x) and TiO(y) matrix, while films from TiO2 target are almost stoichiometric in oxygen. The films have a smooth surface morphology under a laser power density of 5 X 10(6) W/cm2, which is close to the critical intensity for evaporation. The interface reaction of these films is strong, and the Ti atoms diffuse into the substrate.
SCALE-FACTOR-STABILIZED FIBEROPTIC GYROSCOPE BASED ON A SPECTRUM-BROADENED LASER-DIODE SOURCE
(1991-03-15)
CHIEN, PY
;
PAN, CL
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A spectrum-broadened laser-diode source that uses the optical feedback and current-modulation effects has been adopted as the light source of a fiber-optic gyroscope to reduce the inherent phase noise. The scale factor of the gyroscope has also been stabilized.
DEPOLYMERIZATION OF POLY(ETHYLENE-TEREPHTHALATE) RESIN UNDER PRESSURE
(1991-03-20)
CHEN, JY
;
OU, CF
;
HU, YC
;
LIN, CC
;
應用化學系
The process of depolymerization of PET resin by EG glycolysis under pressure is investigated. The kinetics of this pressurized depolymerization of PET resin is discussed. It was found that the rate of deploymerization is dependent of temperature, pressure, and concentration ratio of EG to PET. The rate of depolymerization is proportional to the square of EG concentration and faster than that under atmospheric pressure. Glycolyzed products under pressure consist of the PET monomer, BHET, and oligomers, mostly dimer and trimer. An equilibrium between BHET and oligomers is attained quickly soon after the deploymerization step is completed in the case of a higher ratio of EG/PET used. In the case of lower ratio of EG/PET, the final product now consists of molecular weight of oligomers rather than monomer, dimer, and trimer.
SCALE-INVARIANCE AND INFLATION
(1991-03-25)
KAO, WF
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
;
Department of Electrophysics
Solving a scale invariant effective theory, we obtain an inflationary solution which is equivalent to an asymptotic boundary condition that has been imposed previously by hand on the scalar field phi, namely, phi-(r --> infinity) --> v. This inflationary solution is unique for a slow roller phi. Possible implications are also discussed. This result signifies the importance of the global scale symmetry.
EVAPORATIVE COOLING OF LIQUID-FILM THROUGH INTERFACIAL HEAT AND MASS-TRANSFER IN A VERTICAL CHANNEL .2. NUMERICAL STUDY
(1991-04-01)
YAN, WM
;
LIN, TF
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A numerical analysis is carried out to investigate the evaporative cooling of liquid falling film through interfacial heat and mass transfer in natural convection channel flows. Results for heat and mass transfer rates are specifically presented for the systems with ethanol film evaporation. The predicted results are also contrasted with the experimental results. The predictions show that the effects of the evaporative latent heat transfer on the cooling of the liquid film depend largely on the inlet liquid film temperature and liquid mass flow rate. Additionally, the results indicate that the heat transfer from the interface to the gas stream is predominated by the transport of the latent heat in conjunction with the liquid film evaporation.
DECOUPLING CONTROLLER-DESIGN FOR LINEAR-MULTIVARIABLE PLANTS
(1991-04-01)
LIN, CA
;
HSIEH, TF
;
電控工程研究所
;
Institute of Electrical and Control Engineering
We study decoupling controller design for linear time-invariant square MIMO plants under the unity-feedback configuration. For plants with no coincidences of unstable poles and zeros, we give a simplified necessary and sufficient condition for closed-loop stability. The simplified condition leads to a simple parametrization of the set of all achievable decoupled I/O maps and an algorithm which allows the design of decoupling controllers to achieve preassigned closed-loop poles.
FABRICATION AND PROPERTIES OF PLZT CERAMICS FROM SPRAY-DRIED AQUEOUS-SOLUTION
(1991-04-01)
CHIOU, BS
;
KUO, JN
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
PLZT ceramics with the composition of 9/62/38 (La/Zr/Ti) were fabricated from spray-dried aqueous solution. Complete crystallization of the spray-dried powder is achieved after 1 hr calcination at 650-degrees-C as compared to 800-degrees-C, 1 hr for conventional mixed-oxide method. Sintering environment plays an important role in the densification of PLZT ceramics. Densities of the atmosphere sintered samples are much higher than those of normal sintered ones. PLZT ceramics derived from spray-dried powders have properties comparable to those derived from sol-gel ones. The spray-dried method presents a less expensive and more effective approach in the synthesis of PLZT ceramics.
2-DIMENSIONAL SIMULATION OF THE DRAIN-CURRENT TRANSIENT EFFECT IN GAAS-MESFETS
(1991-04-01)
LO, SH
;
LEE, CP
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交大名義發表
;
電控工程研究所
;
National Chiao Tung University
A two-dimensional numerical analysis of the drain-current transient behavior of ion-implantation GaAs MESFETs on undoped semi-insulating substrates is presented. It is found that the EL2 traps with slow transient behaviors play an important role in the drain lag effects. Also, the current overshoot and undershoot can be explained by the capture and the emission of electrons through the EL2 traps, respectively.
PRODUCTS OF UNIPOTENT MATRICES OF INDEX-2
(1991-04-01)
WANG, JH
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WU, PY
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交大名義發表
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應用數學系
;
National Chiao Tung University
We show that an n x n complex matrix T is the product of two unipotent matrices of index 2 if and only if T is similar to a matrix of the form D + D-1 + (I + N) + (- I + SIGMA-i(m) = 1 + J(i)), where 0 and +/- 1 are not eigenvalues of D, N is nilpotent, and each J(i) is a nilpotent Jordan block of even size. On the other hand, T is the product of finitely many unipotent matrices of index 2 if and only if det T = 1. In this case, the minimal number of required unipotents is 1 if n = 1, 3 if n = 2, and 4 if n greater-than-or-equal-to 3.
WEIGHTED D-FILTERING
(1991-04-01)
WU, WR
;
KUNDU, AL
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友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper, we have proposed a new type of filter which has the most desirable properties of an image smoothing filter. These properties are 1) robust smoothing efficiency, 2) edge preservation, and 3) thin-line detail preservation. The new filter computes its output as the median of weighted averages, instead of plain averages as used in the Hodges-Lehman D-filter, of symmetrically placed order statistics. One particular weighting scheme is considered in details for experiments. The experimental and comparison results are included verifying the useful properties of the proposed filter.
COMPLEX-SURFACE MODELING WITH BIAS AND TENSION
(1991-04-01)
CHEN, DP
;
LIN, TL
;
HSU, CC
;
交大名義發表
;
機械工程學系
The concept of applying bias and tension to cubic-spline curves for shape adjustment has been discussed in many papers in the literature, but few of them have mentioned any practical use of the parameter-controlled curves in surface modelling or mechanical-component design. In the paper, the influence of bias and tension on the shaping of the conventional cubic spline is investigated, and the tested values of the parameters are used in the surface models of various machine parts.
A NEW COMPOSITE BODY METHOD FOR MANIPULATOR DYNAMICS
(1991-04-01)
LIN, SK
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
;
Institute of Electrical and Control Engineering
This article presents a new composite body method for numerically forming the inertia matrix and the bias vector of manipulators, which is more efficient than the other two existing types of composite body methods. The main discrepancy of this one from the existing ones is that all points in a manipulator are observed from the origin of the base frame and the distances are all measured from this origin. The required computations of the present method for the inertia matrix and the bias vector of a manipulator with n rotational joints are (10.5n2 + 38.5n - 85)M + (6n2 + 39n - 70)A and (12.5n2 + 5.5n + 3)M + (9n2 + n)A, respectively, where "M" denotes multiplications, "A" does additions. In numerically forming the inertia matrix, the present method is more efficient than other methods in the literature for a manipulator with five or more joints; whereas this method is also superior to the recursive Newton-Euler formulation in computing the bias vector for a manipulator with six or less joints.
EVAPORATIVE COOLING OF LIQUID-FILM THROUGH INTERFACIAL HEAT AND MASS-TRANSFER IN A VERTICAL CHANNEL .1. EXPERIMENTAL-STUDY
(1991-04-01)
YAN, WM
;
LIN, TF
;
TSAY, YL
;
交大名義發表
;
機械工程學系
An experimental study is performed to study the evaporative cooling of the falling liquid film through interfacial heat and mass transfer in a vertical channel. The measured wall temperature, heat and mass transfer rates are specifically presented for the systems with water film evaporation and ethanol film evaporation over wide ranges of liquid mass flow rate, channel width and liquid inlet temperature. The results show that the influences of the evaporative latent heat transfer on the cooling of the liquid film depend largely on the inlet liquid film temperature and liquid mass rate. Effective evaporative cooling results for a higher inlet liquid film temperature and a smaller liquid mass flow rate.
EFFECT OF INORGANIC ELECTROLYTES ON THE RHEOLOGICAL PROPERTIES OF THE AQUEOUS YTTRIUM-OXIDE COLLOIDAL ZIRCONIA BINDER SOLS SYSTEM
(1991-04-01)
FRAN, YS
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TSENG, TY
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LIN, YL
;
CHANG, CP
;
交大名義發表
Multivalent ions such as La3+, Mg2+ function as surface-active counter ions for Y2O3 particles in aqueous solution. Due to the addition of these electrolytes, the solid content of Y2O3/ZrO2 binder sols slurry was increased and the stability of the slurry was improved. Both ion valence and ion size of electrolytes added into the slurry are expected to influence the slurry rheological flow behaviour.
A THERMAL PHASE-LOCKED LOOP FOR FREQUENCY STABILIZATION OF INTERNAL-MIRROR HE-NE LASERS (LAMBDA=0.633 MU-M)
(1991-04-01)
CHIEN, PY
;
PAN, CL
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A new servo circuit based on the thermal phase-locked loop (TPLL) has been developed for frequency stabilization of internal-mirror He-Ne laser. A feedback signal proportional to the fluctuation in the frequency of the laser is down-converted through a voltage-controlled oscillator (VCO) and compared in a phase/frequency circuit with that of a frequency reference. The detected phase difference then drives a heater wrapped around the laser tube for tuning the laser cavity length. The frequency stability achieved is +/- 1.0 x 10(-9) over a period of several hours.
NEW PHYSICAL TIMING MODELS OF BIPOLAR NONSATURATION LOGIC USING CURRENT DOMAIN ANALYSIS TECHNIQUE
(1991-04-01)
WU, CY
;
WU, TS
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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
A new large-signal equivalent circuit with input and output current signals for a nonsaturated bipolar junction transistor has been developed. Based upon this equivalent circuit, physical timing models of direct-coupled transistor logic (DCTL) and nonthreshold logic (NTL) have been derived through a general modeling methodology. It is shown from extensive comparisons with SPICE simulation results that the models have a maximum error of 25% in single-stage delay calculation and 10% in multi-stage delay calculation. Experimental results on NTL ring oscillators also partly substantiate the developed current-domain large-signal equivalent circuit and physical timing models. Good accuracy, wide applicable ranges of device/circuit parameters and input waveforms, and less CPU time and memory consumption than full transient simulations make the physical timing models feasible in optimization and CAD of high-speed bipolar ICs.
ELECTRICAL CHARACTERISTICS OF DOUBLE-BARRIER RESONANT TUNNELING STRUCTURES WITH DIFFERENT ELECTRODE DOPING CONCENTRATIONS
(1991-04-01)
WU, JS
;
CHANG, CY
;
LEE, CP
;
CHANG, KH
;
LIU, DG
The electrical characteristics of AlGaAs/GaAs double-barrier resonant tunneling structures with various electrode doping concentrations have been studied. It was found that the peak current and the valley current are not sensitive to the change in the doping level of the electrodes. The peak-current voltage and the valley-current voltage, however, increase when the electrode doping level is lowered. These behaviors are explained using the band-bending effect in the electrodes. For devices with lightly doped or undoped electrodes, the quantum size effect in the accumulation layer due to the strong band bending causes additional kinks in the current-voltage characteristics. They are attributed to the resonant tunneling of electrons from the quantized levels in the accumulation layer. The quantum effect also accounts for the improved negative differential resistance behavior.
A BALANCED DUAL-PHOTODETECTOR OPTICAL RECEIVER FOR DAYLIGHT OPERATION
(1991-04-01)
CHIEN, PY
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
;
Department of Photonics
A balanced dual-photodetector optical receiver with an active optical feedback circuit suitable for daylight operation has been developed. This receiver is suitable for laser range finder or fuse systems operating under high level of sunlight illumination. The design and operation of the receiver is discussed.