Browsing by Issue Date, starting with "1997-03-27"

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Reflection-type normally-on two-wavelength modulator
(1997-03-27)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The authors demonstrate a novel reflection-type normally-on two-wavelength modulator by combining two quantum-well structures with different operating wavelengths in a coupled cavity structure. Reflection spectra show simultaneous modulations at wavelengths of 856 and 886 nm in the device consisting of GaAs/A1GaAs and InGaAs/A1GaAs quantum wells for each wavelength. Under separate applied voltages, maximum reflectivity changes of 70 and 54% were obtained for the two wavelengths. To the best of the authors' knowledge, this is the First two-wavelength reflection modulator ever reported.
Development of a feedforward active noise control system by using the H-2 and H infinity model matching principle
(1997-03-27)
Bai, MR
;
Chen, HP
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
Two novel active noise control techniques on the basis of feedforward H-2 and H-infinity optimal model matching principle are proposed. These methods effectively overcome the problem of unstable inverse plant resulting from the inherent non-minimum phase property of the cancellation path. The proposed algorithms are implemented by using a digital signal processor. The experimental results obtained by using H-2 and H-infinity feedforward techniques show attenuation for stationary noise in a duct as comparable to those of conventional methods. The proposed methods also have potential in suppressing transient noises that have been the major difficulty in adaptive methods. Comparisons of the methods are summarized. (C) 1997 Academic Press Limited.
Development of a feedforward active noise control system by using the H-2 and H infinity model matching principle
(1997-03-27)
Bai, MR
;
Chen, HP
;
機械工程學系
;
Department of Mechanical Engineering
Two novel active noise control techniques on the basis of feedforward H-2 and H-infinity optimal model matching principle are proposed. These methods effectively overcome the problem of unstable inverse plant resulting from the inherent non-minimum phase property of the cancellation path. The proposed algorithms are implemented by using a digital signal processor. The experimental results obtained by using H-2 and H-infinity feedforward techniques show attenuation for stationary noise in a duct as comparable to those of conventional methods. The proposed methods also have potential in suppressing transient noises that have been the major difficulty in adaptive methods. Comparisons of the methods are summarized. (C) 1997 Academic Press Limited.
MOS magnetic current sensor based on standard CMOS process
(1997-03-27)
Yang, HM
;
Lei, TF
;
Huang, YC
;
Lee, CL
;
電子工程學系及電子研究所
A novel current sensor is proposed. The current sensor consists of one MOS magnetic sensor and a flat coil in an industrial CMOS process, An experimental device demonstrated a sensitivity of 8.4mV/A.
Reflection-type normally-on two-wavelength modulator
(1997-03-27)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The authors demonstrate a novel reflection-type normally-on two-wavelength modulator by combining two quantum-well structures with different operating wavelengths in a coupled cavity structure. Reflection spectra show simultaneous modulations at wavelengths of 856 and 886 nm in the device consisting of GaAs/A1GaAs and InGaAs/A1GaAs quantum wells for each wavelength. Under separate applied voltages, maximum reflectivity changes of 70 and 54% were obtained for the two wavelengths. To the best of the authors' knowledge, this is the First two-wavelength reflection modulator ever reported.
MOS magnetic current sensor based on standard CMOS process
(1997-03-27)
Yang, HM
;
Lei, TF
;
Huang, YC
;
Lee, CL
;
電子工程學系及電子研究所
A novel current sensor is proposed. The current sensor consists of one MOS magnetic sensor and a flat coil in an industrial CMOS process, An experimental device demonstrated a sensitivity of 8.4mV/A.
Elastic interaction between screw dislocations and a circular surface crack
(1997-03-31)
Lin, KM
;
Lin, HC
;
Chen, KC
;
Chang, HL
;
材料科學與工程學系
The behaviour of a screw dislocation around a circular surface crack was analyzed using the conformal mapping method. The effects of the crack length l and its radius of curvature R on the shielding effect and the strain energy were discussed in detail. It was found that for a dislocation being fixed at a constant distance from the crack tip and located on a plane tangent to crack surface at the tip, there exists a critical crack length l* corresponding to a maximum shielding effect induced by the dislocation on the circular surface crack. The l* increases with R and approaches infinity as the crack becomes planar (i.e. R --> infinity). The shielding effect vanishes as the crack disappears. It increases rapidly with l if 0 < l much less than l*, regardless of R. After reaching the maximum, it decreases slightly for larger R but significantly for smaller R as the crack becomes longer. The shielding is more pronounced for larger R than that for smaller R, with the difference increasing with crack length. As a result, a surface microcrack propagates initially in a rather brittle manner then becomes more ductile. When the crack gets longer, it still keeps ductile for a less curved or a planar crack but becomes relatively brittle for a severely curved crack. In addition, the strain energy is also significantly influenced by crack length and increases rapidly with l when l is rather small, regardless of R. With increasing l, it becomes less affected by l, and the variation with R is still not obvious, with larger R corresponding to a slightly higher strain energy. (C) 1997 Elsevier Science S.A.
Elastic interaction between screw dislocations and a circular surface crack
(1997-03-31)
Lin, KM
;
Lin, HC
;
Chen, KC
;
Chang, HL
;
材料科學與工程學系
The behaviour of a screw dislocation around a circular surface crack was analyzed using the conformal mapping method. The effects of the crack length l and its radius of curvature R on the shielding effect and the strain energy were discussed in detail. It was found that for a dislocation being fixed at a constant distance from the crack tip and located on a plane tangent to crack surface at the tip, there exists a critical crack length l* corresponding to a maximum shielding effect induced by the dislocation on the circular surface crack. The l* increases with R and approaches infinity as the crack becomes planar (i.e. R --> infinity). The shielding effect vanishes as the crack disappears. It increases rapidly with l if 0 < l much less than l*, regardless of R. After reaching the maximum, it decreases slightly for larger R but significantly for smaller R as the crack becomes longer. The shielding is more pronounced for larger R than that for smaller R, with the difference increasing with crack length. As a result, a surface microcrack propagates initially in a rather brittle manner then becomes more ductile. When the crack gets longer, it still keeps ductile for a less curved or a planar crack but becomes relatively brittle for a severely curved crack. In addition, the strain energy is also significantly influenced by crack length and increases rapidly with l when l is rather small, regardless of R. With increasing l, it becomes less affected by l, and the variation with R is still not obvious, with larger R corresponding to a slightly higher strain energy. (C) 1997 Elsevier Science S.A.
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
;
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.