Browsing by Issue Date, starting with "1997-04-01"

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VLSI cell placement on arbitrarily-shaped rectilinear regions using neural networks with calibration nodes - Comments
(1997-04-01)
Huang, KY
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
;
Department of Computer Science
D-stability bound analysis for discrete multiparameter singularly perturbed systems
(1997-04-01)
Hsiao, FH
;
Pan, ST
;
Teng, CC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The D-stability (i.e., the stability in the sense that all the poles of a system are lying inside the disk D(alpha, r)) problem for discrete multiparameter singularly perturbed systems is considered in this brief, A two-stage method is first developed to analyze the stability relationship between the discrete multiparameter singularly perturbed systems and their corresponding reduced systems. An upper hound of the singular perturbation parameters is then derived such that the D-stability of the reduced systems implies that of the original systems, provided that the singular perturbation parameters are small enough to be within this bound. This fact enables us to investigate D-stability of the original systems by establishing that of their corresponding reduced systems.
Low-lying exciton states in a type-II broken-gap quantum well structure: A variation-basis-set approach
(1997-04-01)
Chu, CS
;
Chu, KD
;
電子物理學系
;
Department of Electrophysics
The exciton binding energy and the low-lying exciton states in a type-II broken-gap quantum well structure are studied. The conduction electron and the hole that form the exciton are spatially separated and are each confined by a quantum well. A variation-basis-set approach is proposed in which a set of variation basis set wavefunctions are constructed from the eigenstates of a variation Hamiltonian. The calculation of the exciton states can be carried out systematically and the accuracy of the state energies can be estimated. Numerical examples are presented, showing the rapid convergence of the excitonic levels with respect to the size of the variation basis set in and beyond the small well width regime. The effective binding energies for the states are found to increase with the decreasing of the well width. The low-lying exciton states in and beyond the small well width regime are presented.
In0.52Al0.48As/InAs/InxAl1-xAs pseudomorphic HEMT's on InP
(1997-04-01)
Chin, A
;
Liao, CC
;
Tsai, C
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The dc and microwave performance of an InAs channel HEMT is reported. Room-temperature electron mobility as high as 20 200 cm(2)/Vs is measured, with a high carrier concentration of 2.7x10(12) cm(-2). DC extrinsic transconductance of 714 mS/mm is measured and a unity-current-gain cut-off frequency of 50 GHz is obtained for a 1.1-mu m gate length HEMT. The success of achieving superior Hall mobility and device performance is strongly dependent on the InxAl1-xAs buffer layer design that changes the lattice constant from lattice-matched In0.52Al0.48As to In0.75Al0.25As. The multiple In0.52Al0.48As/InAs monolayer superlattices buffer achieves the best performance as compared to the step-graded InxAl1-xAs and the uniform In0.75Al0.25As buffer.
3-D polyhedral face computation from two perspective views with the aid of a calibration plate
(1997-04-01)
Chiu, JM
;
Chen, Z
;
Wang, CM
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
The 3-D reconstruction of visible polyhedral faces from a pair of general perspective views with the aid of a calibration plate is addressed. A polyhedron is placed on a planar calibration plate and two side views of both the polyhedron and the calibration plate are taken. Through proper arrangements we may assume that in the two views a number of polyhedral edges lying on the calibration plate and the whole calibration plate boundary are visible. We present an on-line camera calibration technique with the aid of the calibration plate and a two-stage process to find the vertex/edge correspondences without encountering the ambiguity problem of the conventional epipolar line technique. Then we give a closed form solution to the 3-D polyhedral vertices visible in both images. We also describe other advantages of using our method for the 3-D polyhedron reconstruction. Experimental results show that the obtained 3-D polyhedral vertex coordinates are rather accurate.
Adaptive VSS blind equalizers
(1997-04-01)
Ueng, FB
;
Su, YT
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
It is well known that an adaptive filter with a large step size in the transient period and a small one in the convergence period gives small mean squared steady state error while achieving a fast convergence rate. Based upon this idea, we present two variable step size (VSS) blind equalizers. The first one employs an intersymbol interference (ISI) estimator to control the step size, the second algorithm uses a mean squared error (MSE) estimator to adjust the step size. Both accomplish what has been expected.
Charge oscillations in coupled quantum wells
(1997-04-01)
Juang, C
;
Tsai, CB
;
Juang, J
;
應用數學系
;
Department of Applied Mathematics
A study of charge oscillations due to electron- and hole-coherent, and mixing tunnelling in coupled quantum well structures is given. The time-dependent picture of coherent tunnelling of an electron and hole wave packet is obtained by the application of the time-development operator of the time-depsndent Schrodinger equation, and the time-dependent Schrodinger equation with the Luttinger Hamiltonian. Detailed physical mechanisms involving resonant coherent tunnelling on electrons, valence-band mixing effects on heavy- and light-hole tunnelling, spatial and mixing multiple tunnelling effects, in coupled quantum wells are described.
Analysis of a liquid crystal Fabry-Perot etalon filter: A novel model
(1997-04-01)
Chen, PL
;
Lin, KC
;
Chuang, WC
;
Tzeng, YC
;
Lee, KY
The authors propose a novel analysis method to investigate the characteristics of an electrically tunable liquid-crystal Fabry-Perot interferometer (LC-FPI), Based on the solution of deformation analysis of liquid crystal in an electric field and the assumption of small refractive index variation in the Fabry-Perot cavity, the voltage-dependent equivalent refractive index of the cavity has been derived. Tuning behaviors of the LC-FPI filter were simulated by means of the dependence, The calculated result and the experimental measured data agree well with each other.
Performance evaluation of a bigrating as a beam splitter
(1997-04-01)
Hwang, RB
;
Peng, ST
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
The design of a bigrating for use as a beam splitter is presented. It is based on a rigorous formulation of plane-wave scattering by a big-rating that is composed of two individual gratings oriented in different directions. Numerical results are carried out to optimize the design of a bigrating to perform 1 x 4 beam splitting in two dimensions and to examine its fabrication and operation tolerances. It is found that a bigrating can be designed to perform two functions: beam splitting and polarization purification. (C) 1997 Optical Society of America.
Electrical and luminescent characteristics of alpha-SiC:H p-i-n thin-film LED's with graded-gap junctions
(1997-04-01)
Jen, TS
;
Shin, NF
;
Laih, LH
;
Chen, YA
;
Hong, JW
A-SiC:H p-i-n thin-film LED's (TFLED's) containing a single graded-gap p-i-n junction (SG) or double graded-gap p-i-n and i-n junctions (DG) have been postulated and fabricated successfully on indium-tin-oxide (ITO)-coated glass substrates, with a plasma-enhanced chemical vapor deposition (PECVD) system, Some important characteristics and related physics of these two types of TFLED's are presented and discussed, At an injection current density (J) of 600 mA/cm(2), the brightness (B) of the SG and DG TFLED's obtained were 30 and 207 cd/m(2), respectively, This significant improvement of brightness, as compared to those of the previously reported TFLED's with a highest brightness of 20 cd/m(2), could be ascribed to the reduced interface states with the graded-gap junctions, lower contact resistance between ITO and p-layer due to a plasma treatment of ITO prior to p-layer deposition, post metallization annealing of thermally evaporated Al on n-layer, and higher optical gaps (E(opt)'s) of the doped layers employed, The slopes of the nearly linear B-J relationships show the diode factor very close to unity for the fabricated SG and DG TFLED's, This implies that the electroluminescence (EL) mechanism of these TFLED's might be a tail-to-tail-state recombination, In addition, the conduction currents of these TFLED's are almost temperature dependent, and that of the DG TFLED might consist of an ohmic current and a space-charge-limited current (SCLC) within the lower and higher applied-bias regions, respectively.
Multilevel secure database encryption with subkeys
(1997-04-01)
Hwang, MS
;
Yang, WP
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資訊工程學系
;
Department of Computer Science
In this paper, we propose a multilevel database encryption system with subkeys. This new system is called the record-oriented cryptosystem which encrypts each record with different field-subkeys according to a security class of the data element. Each field is decrypted individually by the field-subkeys of which security class is higher than or equal to that of the encrypted field-subkeys. This system is based on the Chinese Remainder Theorem. Our scheme can protect the finest level of granularity such as relation level, attribute level, tuple level, or data element level in the relational database model.
The design of rotation-invariant pattern recognition using the silicon retina
(1997-04-01)
Chiu, CF
;
Wu, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new rotation-invariant pattern recognition system is proposed and analyzed, In this system, silicon retina cells capable of image sensing and edge extraction are used so that the system can directly process images from the real world without an extra edge detector, The rotation-invariant discrete correlation function is modified and implemented in the silicon retina structure by using the current summation. Simulation results have verified the correct function of the proposed system, Moreover, an experimental chip to implement the proposed system with a 32 x 32 cell array has been designed and fabricated in 0.8-mu m n-well CMOS process, Experimental results have successfully shown that the system works well for the arbitrary orientation pattern recognition.
Numerical analysis of nonuniform Bragg gratings
(1997-04-01)
Wu, JJ
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
;
Department of Photonics
The characteristics of guided waves scattered by nonuniform Bragg waveguide gratings are systematically investigated by using a staircase approximation, which isa combination of the building blocks of the multimode network theory acid a rigorous mode-matching procedure. The bent dielectric waveguides, periodically with Bragg gratings of rectangular profile and chirped waveguide gratings, are taken as an example of the presented approach. Extensive numerical data are obtained to develop guidelines for integrated optical applications.
A three-parameters-only MOSFET subthreshold current CAD model considering back-gate bias and process variation
(1997-04-01)
Chen, MJ
;
Ho, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper we introduce a new subthreshold conduction CAD model for simulation of VLSI subthreshold CMOS analog circuits and systems, This model explicitly formulates the back-gate bias effect and preserves the original advantages of the existing four-parameter model while reducing the fitting parameter number down to three, A transparent relationship between the fitting parameters and the process parameters has been derived, and its correlation with a recently widely used CAD model as well as with a well-known two-parameter model has been established, Our extensive measurement work on n-channel MOSFET's has highlighted the potential of the model in handling the variations in the subthreshold I-V characteristics at different back-gate biases arising from process variations, The mismatch analysis has further been successfully performed with emphasis on the reverse back-gate bias effect. In summary, the proposed model can serve as a promising alternative in the area of VLSI subthreshold CMOS analog circuit simulation.
Low-lying exciton states in a type-II broken-gap quantum well structure: A variation-basis-set approach
(1997-04-01)
Chu, CS
;
Chu, KD
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
The exciton binding energy and the low-lying exciton states in a type-II broken-gap quantum well structure are studied. The conduction electron and the hole that form the exciton are spatially separated and are each confined by a quantum well. A variation-basis-set approach is proposed in which a set of variation basis set wavefunctions are constructed from the eigenstates of a variation Hamiltonian. The calculation of the exciton states can be carried out systematically and the accuracy of the state energies can be estimated. Numerical examples are presented, showing the rapid convergence of the excitonic levels with respect to the size of the variation basis set in and beyond the small well width regime. The effective binding energies for the states are found to increase with the decreasing of the well width. The low-lying exciton states in and beyond the small well width regime are presented.
Laboratory evaluation of NH3 injection technology to reduce HCl emissions from incinerators
(1997-04-01)
Bai, H
;
Chu, C
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
A laboratory-scale experimental study is conducted to investigate the fundamental properties of NH3-HCl reaction in a simulated incinerator duct system. The NH3 injection technology is a dry HCl removal process which produces solid products. The test results showed that under typical incineration operation conditions, the outlet concentration of HCl can meet the emission standards for incinerators in Taiwan. An excessive injection of NH3 above stoichiometric requirement may not lead to the NH3 slip problem. This is because that the excessive amount of NH3 would probably diffuse onto the product particles. However, the enhancement of NH3 utilization is economically not feasible. The outlet concentrations of HCl and NH3 are almost independent of their inlet concentrations for residence time longer than I second. Moisture content and the NH3/HCl injection ratio are two of the most important factors which affect the HCl removal and NH3 utilization.
Charge oscillations in coupled quantum wells
(1997-04-01)
Juang, C
;
Tsai, CB
;
Juang, J
;
應用數學系
;
Department of Applied Mathematics
A study of charge oscillations due to electron- and hole-coherent, and mixing tunnelling in coupled quantum well structures is given. The time-dependent picture of coherent tunnelling of an electron and hole wave packet is obtained by the application of the time-development operator of the time-depsndent Schrodinger equation, and the time-dependent Schrodinger equation with the Luttinger Hamiltonian. Detailed physical mechanisms involving resonant coherent tunnelling on electrons, valence-band mixing effects on heavy- and light-hole tunnelling, spatial and mixing multiple tunnelling effects, in coupled quantum wells are described.
Droplet ignition in a high-temperature convective environment
(1997-04-01)
Huang, LW
;
Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
The behaviors of n-heptane droplet ignition in a high-temperature convective environment are studied numerically. Two cases are considered wherein one is a purely forced convection, and the other is a mixed convection. The ignition process can be divided into a heating-up evaporation, a nearly constant droplet-temperature evaporation and a constant droplet-temperature burning. During the heating-up evaporation stage, the droplet temperature rises sharply and the square of the diameter decreases slightly with time. In the next stage, the droplet remains at nearly constant temperature in a pure vaporization process. After ignition, an envelope flame appears and the droplet is in an augmented vaporization process. The d(2)-law still holds. In the mixed convection case, where the gravity effect is taken into consideration, the location of initiation of chemical reaction is closer to the droplet, the ignition takes place earlier, and the flame is subjected to more stretch. The fuel accumulation phenomenon is also identified and it results in a suppression of the fuel evaporation rate. Finally, several future extensions are proposed to further modify the combustion model. (C) 1997 by The Combustion Institute.
Supervised adaptive hamming net for classification of multiple-valued patterns
(1997-04-01)
Hung, CA
;
Lin, SF
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A Supervised Adaptive Hamming Net (SAHN) is introduced for incremental learning of recognition categories in response to arbitrary sequences of multiple-valued or binary-valued input patterns. The binary-valued SAHN derived from the Adaptive Hamming Net (AHN) is functionally equivalent to a simplified ARTMAP, which is specifically designed to establish many-to-one mappings. The generalization to learning multiple-valued input patterns is achieved by incorporating multiple-valued logic into the AHN. In this paper, we examine some useful properties of learning in a P-valued SAHN. In particular, an upper bound is derived on the number of epochs required by the P-valued SAHN to learn a list of input-output pairs that is repeatedly presented to the architecture. Furthermore, we connect the P-valued SAHN with the binary-valued SAHN via the thermometer code.
Interfacial reactions of the Co/Si1-xGex system
(1997-04-01)
Luo, JS
;
Lin, WT
;
Chang, CY
;
Tsai, WC
;
Wang, SJ
Thermal reactions of Co(200 Angstrom)/Si0.76Ge0.24(1500 Angstrom)/Si and Co(200 Angstrom)/Si0.54Ge0.46(1000 Angstrom)/Si systems in a vacuum of 1-2 X 10(-6) Ton. were studied. At temperatures above 200 degrees C Ge segregation appeared even though no silicides and/or germanosilicides were formed. At a temperature of 225-550 degrees C Co(Si1-yGey) was formed, in which the Ge concentration was deficient, The formation temperatures of CoSi2 in the Co/Si1-xGex systems, where x = 0.24 and 0.46, were above 575 degrees C, being relatively higher than that in the Co/Si system. At temperatures above 500 degrees C the island structure, Ge segregation to the surface of the exposed Si1-xGex films, and the penetration of reacted layer into the Si substrate occurred, At temperatures above 700 degrees C a SiC layer was grown on the film surface. For the Si0.54Ge0.46 films the penetration of the reacted layer into the Si substrate occurred even at 350 degrees C owing to the wave structure of the as-grown Si0.54Ge0.46 films. A Si layer interposed between Co and Si0.76Ge0.24 films is an effective scheme to grow a continuous CoSi, contact at 550-600 degrees C without inducing Ge segregation and hence the strain relaxation in the Si0.76Ge0.24 films.