Browsing by Issue Date, starting with "1991-06-10"

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2-DIMENSIONAL ELECTRON GASES IN DELTA-DOPED GAAS/IN0.25GA0.75AS/GAAS HETEROSTRUCTURES
(1991-06-10)
LIN, W
;
HSU, WC
;
WU, TS
;
CHANG, SZ
;
WANG, C
Delta-doped (delta-doped) GaAs/In0.25Ga0.75As/GaAs strained-layer modulation-doped field-effect transistor (delta-SMODFET) structures grown by the low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique have been studied for the first time. The delta-doped GaAs, adopted as the electron supplier, was obtained by a stop-growth process so that a very thin and heavily doped layer (1.9 X 10(13) cm-2) can be realized. Experimental results show that a structure with an 80 angstrom In0.25Ga0.75As layer as the active channel and an 80 angstrom spacer layer demonstrated the highest two-dimensional electron gases mobility of 26 800 cm2/V s. This structure is easy to achieve by the LP-MOCVD method because the growth of AlGaAs is avoided and is promising for high performance FETs.
EXCITON BINDING-ENERGY AND SUBBAND STRUCTURES OF GAAS/ALXGA1-XAS SUPERLATTICES
(1991-06-15)
CHUU, DS
;
LOU, YC
;
電子物理學系
;
Department of Electrophysics
The subband structure and the binding energy of an exciton in the GaAs/Al(x)Ga(1-x)As superlattice are studied by a simple approximation method. Both the exciton binding energy and the subband energy are expressed as a function of well width, barrier width, and Al composition. The influence of the effective-mass mismatch is taken into account. The energy spacings between interband or intersubband transitions are calculated and compared with the observed data. Good agreement is obtained.
RAMAN INVESTIGATIONS OF THE SURFACE-MODES OF THE CRYSTALLITES IN CDS THIN-FILMS GROWN BY PULSED LASER AND THERMAL EVAPORATION
(1991-06-15)
CHUU, DS
;
DAI, CM
;
HSIEH, WF
;
TSAI, CT
;
電子物理學系
CdS films have been grown on Corning glass by pulsed laser evaporation (PLE) and thermal evaporation (TE) techniques at a substrate temperature between room temperature and 250-degrees-C. The quality of these films is investigated by resonance Raman scattering, x-ray diffraction and optical transmittance. Our results reveal that the Raman shifts of the surface phonon mode are observed with 300 and 297 cm-1 by PLE and TE techniques, respectively, and as many as four overtones are obtained by PLE method. The difference of Raman shift between these two techniques are caused by the discrepancy of crystallite sizes which is larger for PLE technique. The crystallite sizes are in the range of 200-500 angstrom in diameter. Highly oriented films have been grown by both of the techniques even when the substrate is at room temperature.
THE K-NEIGHBOR DOMINATION PROBLEM
(1991-06-17)
HWANG, SF
;
CHANG, GJ
;
應用數學系
;
Department of Applied Mathematics
As a model of certain location problem, we consider the following domination problem. The k-neighbor domination problem is to select a minimum cardinality vertex set D of a graph G = (V, E) such that every vertex x not in D is adjacent to at least k vertices in D. This paper presents a linear algorithm to solve the problem for block graphs. For any fixed k, we also prove that the k-neighbor domination problem is NP-complete for some classes of graphs.
隱者
(1991-06-17)
管管
現代野馬詩人
(1991-06-22)
管管
MACHINABLE VOLUMES EXTRACTION - NON-BLOCK TYPE RAW-MATERIAL INPUT
(1991-07-01)
LI, RK
;
TZIENG, SD
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
A method for automatically extracting machinable volumes by considering non-blank type raw material input is proposed. The method takes CSG input (both raw material and finished part) and determine relative shifting origins of the finished part to ensure its machinability. CSG to DSG transformation is performed to extract DSG primitives of raw material and finished part. Both DSG primitives are mapped to find removing volumes based on geometrical definition. The geometrical definition removing volumes are further reorganized into a set of machinable volumes by considering the influence of process information. A prototype system to implement the method is developed on a SUN/260 computer system. An example is evaluated to demonstrate the success of the system.
ANALYTIC SOLUTION FOR DYNAMIC LOADING ON HALF-SPACE MEDIUM
(1991-07-01)
LIOU, GS
;
LEE, GC
;
KETTER, RL
;
土木工程學系
;
Department of Civil Engineering
A systematic procedure for generating impedance matrices for foundations resting on an elastic half-space medium is presented. The prescribed harmonic loading due to the foundation is decomposed into an infinite Fourier series with respect to the azimuth. For each Fourier component an analytic solution is found. Then, provided that the interaction stresses due to excitation of the foundation can be assumed to be piecewise linear in the r-direction of the cylindrical coordinates, the impedance matrix of the foundation can be generated using the variational principle and the reciprocal theorem. A simple example of a rigid circular plate, rigidly attached to the half-space medium, and subjected to torsional, vertical, rocking, and horizontal exitation is used to demonstrate the effectiveness and efficiency of the procedure.
GRAIN-BOUNDARY PRECIPITATION IN AN FE-28.6MN-9.8AL-0.8SI-1.0C ALLOY
(1991-07-01)
CHAO, CY
;
LIU, TF
;
交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
RESTRUCTURING OPERATIONS FOR DATA-FLOW DIAGRAMS
(1991-07-01)
CHEN, MJ
;
CHUNG, CG
;
交大名義發表
;
資訊科學與工程研究所
;
National Chiao Tung University
When defining and designing software with structured analysis and design methods, we need to restructure data-flow diagrams. Using basic editing operations to restructure large systems with voluminous data-flow diagrams is tedious, laborious and error-prone. It is necessary to have data-flow diagram editors that provide editing operations specific for restructuring. This paper proposes and formally specifies a set of operations sufficient for all restructuring needs. It also confirms that the properties of consistency and completeness are observed by all the restructuring operations, and that both models of data-flow diagrams are equivalent, before and after each of the restructuring operations.
A NEW IMAGE COMPRESSION METHOD USING DYNAMIC PREDICTOR BASED ON CURRENT CONTEXT
(1991-07-01)
CHEN, LH
;
WENG, SF
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
In this paper, a new image compression method is proposed. The approach first provides a decomposition method to segment the gray values of an image into several parts called buckets. The decomposition rule is to make, as much as possible, each bucket contain only one nearly-homogeneous region or edge area. For each pixel P, if the gray values of its three neighbors (top-left, top, left) belong to buckets B1, B2, and B3, respectively, then (B1, B2, B3) is referred to as P's context. An individual predictor is then derived for each set of pixels with the same context. The gray value of each pixel is then estimated by the predictor corresponding to its context. Some degree of distortion is allowed. A pixel with prediction error less than a preset value is considered as a redundant point. An image is finally coded by the prediction errors of nonredundant pixels and by the number of consecutive redundant pixels. Both of these two kinds of values are quantized and coded by their own adaptive Huffman codes. Experimental results show that the proposed method not only possesses high-speed computing property but also provides high compression ratio and good quality.
MAXIMUM INDEPENDENT NUMBER FOR SERIES-PARALLEL NETWORKS
(1991-07-01)
HSU, LH
;
WANG, SY
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
A series-parallel network is used as a model of electric circuits. Usually, we use a series-parallel graph to represent a series-parallel network. However, there are a lot of different graph representations for a single series-parallel network. For a given graph, a subset of V(G) is called an independent set if there are no edge of G joining two vertices in S. An independent set S of G is maximum if G has no independent set S' with S' > S. The number of vertices in a maximum independent set of G is called the independent number of G and is denoted by alpha-(G). The maximum independent number alpha-(N) for a series-parallel network N is defined to be the maximum alpha(G[N]) among all possible graph representations G[N]. In this paper, we are going to present a linear time algorithm to compute alpha(N) for any series-parallel network N.
QUANTUM EFFECT IN THE ACCUMULATION LAYER ON FIELD-INDUCED PHOTOLUMINESCENCE OF DOUBLE-BARRIER RESONANT TUNNELING STRUCTURES
(1991-07-01)
WU, JS
;
CHANG, KH
;
LEE, CP
;
CHANG, CY
;
LIU, DG
The photoluminescence (PL) of double-barrier resonant tunneling structures (DBRTSs) with undoped electrodes under bias has been studied. The strong band bending across the cathode causes the quantum size effect in the accumulation layer. The resonant tunneling of electrons from the first excited quantum level in the accumulation layer produces a kink in the current-voltage characteristic. It is found that the PL intensity from the quantum well (QW) as a function of bias sharply peaks at the voltage corresponding to the kink. This provides evidence of the interaction between the first excited quantum state in the accumulation layer and the resonant state in the QW.
SHALLOW DONOR IMPURITY STATES OF A SEMICONDUCTOR IN A UNIFORM MAGNETIC-FIELD
(1991-07-01)
DAI, CM
;
CHUU, DS
;
電子物理學系
;
光電工程學系
;
Department of Electrophysics
The perturbative-variational method is used to study the hydrogen-like shallow donor impurity states of the isotropic semiconductor under a uniform magnetic field from a spherical symmetry approach. Using a magnetic field dependent parameter, which is added in the simple hydrogenic wave functions, the eigenvalues can be determined by optimizing the parameter. The results we obtained are in good agreement with the previous works up to gamma = 5 (e.g., 10(6) T for atoms) for the ground state. The extension to the transitional region by this method is considerably higher than other approaches.
PICTURE ALGEBRA FOR SPATIAL REASONING OF ICONIC IMAGES REPRESENTED IN 2D C-STRING
(1991-07-01)
LEE, SY
;
HSU, FJ
;
資訊科學與工程研究所
;
電信研究中心
;
Institute of Computer Science and Engineering
A new spatial knowledge representation 2D C-string with accompanied cutting mechanism and a set of spatial operators are proposed. 2D C-string is characteristic of spatial knowledge embedded in images and is efficient in representation and manipulation of images. In this paper, transitive laws, distributive laws and manipulation laws of picture algebra are presented. All the binary relationships among objects in an image can be derived from 2D C-string. The picture algebra provides the theoretic basis for spatial reasoning and pictorial query inference.
APPROXIMATE SOLUTIONS FOR TRANSIENT-RESPONSE OF A SHELL AND TUBE HEAT-EXCHANGER
(1991-07-01)
TAN, KS
;
SPINNER, IH
;
應用化學系
;
Department of Applied Chemistry
Approximate solutions for the transient response of a shell and tube heat exchanger to step change in shell fluid temperature and tube fluid velocity are derived. It has been shown that other previously published limited or approximate solutions are derivable from the exact solutions. The limiting asymptotic "no wall" solutions for both response to shell fluid temperature and tube fluid velocity change are also deducible from a limiting tube wall time constant solution. Some of the approximate solutions presented include the use of simple exponential forms of equations that enable the quick estimation of the time required to reach a given degree of approach to the final steady state. The error between the exact and the approximate exponential form of solutions are in most cases less than 2%. All the previous derived exact and approximate solutions presented here are applicable to crosscurrent, cocurrent, or countercurrent flow heat exchangers with one infinite thermal capacitance rate fluid.
NEAR-INFRARED TRANSMISSION MEASUREMENT OF EL2 CONCENTRATION IN SEMIINSULATING GAAS WAFERS WITH A LASER DIODE (LAMBDA=1.3-MU-M)
(1991-07-01)
PAN, CL
;
WU, HH
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HSIEH, TR
;
交大名義發表
;
光電工程學系
We demonstrated a near-infrared transmittance setup for EL2 concentration mapping in undoped semi-insulating (SI) GaAs wafers. The light source was a power-stabilized laser diode (lambda = 1.3-mu-m) operating in the light emitting diode (LED) mode. The sensitivity of the apparatus was as low as 10(14) cm-3 for typical commerical wafers 350-mu-m in thickness.
TECHNIQUE OF OPTIMUM DESIGN OF CONTROL-SYSTEMS WITH LARGE PLANT UNCERTAINTY
(1991-07-01)
CHIEN, CM
;
WANG, BC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A modified technique for optimum design with significant plant uncertainty is presented using Wiener's least-square optimization with a quadratic constraint in the frequency domain. The plant uncertainty is transformed into an external disturbance and the procedures of the optimum design problem become much simpler. Examples are used to illustrate the design process. Computer simulations are performed to show that the designed results meet the specifications.
THEORY OF PHASE-CONJUGATE OSCILLATORS .2.
(1991-07-01)
LEE, WS
;
CHI, S
;
YEH, P
;
SAXENA, R
;
光電工程學系
This paper is the second in a series describing propagation of electromagnetic radiation in phase-conjugate oscillators. We apply the formulation developed in the first paper to study the phase-conjugate resonator (PCR) and the Fabry-Perot cavity with an intracavity phase-conjugate mirror (PCM). Our results show that nondegenerate oscillation occurs in the PCR for large parametric gains and fixed separation between the conventional reflector and the PCM. The bandwidth is considerably reduced from that of a PCM alone. In the phase-conjugate oscillator, oscillation will occur at the pump frequency only if there is no separation between the conventional mirrors and the phase-conjugate element and if the nonlinear medium fills the entire Fabry-Perot cavity.
BROADCASTING CRYPTOSYSTEM IN COMPUTER-NETWORKS USING INTERPOLATING POLYNOMIALS
(1991-07-01)
CHANG, CC
;
WU, TC
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Based on the characteristics of the interpolating polynomials and some properties of the Euclidean geometry, a cryptosystem for broadcasting secrets in computer networks is presented. It is assumed that there is a central authority server (CAS) in a network system. Each principal of the network owns a secret point, known only to the principal and the CAS. When a secure broadcasting request is initiated, the CAS computes an interpolating polynomial P(x) on the secret points owned by the originator and the legal recipient(s). The CAS then cleverly reveals some public points to let the originator and legal recipient(s) reconstruct P(x), whereas illegal recipients are unable to do so. With these public points and a value c, the originator has P(c) as the encryption/decryption key, and can broadcast c and the message encrypted by P(c) in the network. For the legal recipients, P(x) can be reconstructed, and thus P(c) obtained. Since the legal recipients cannot obtain the exact P(x), they have no way of finding the decryption key.