Browsing by Issue Date, starting with "1994-02-15"

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THE DOMATIC NUMBER PROBLEM
(1994-02-15)
CHANG, GJ
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交大名義發表
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應用數學系
;
National Chiao Tung University
;
Department of Applied Mathematics
A dominating set of a graph G=(V,E) is a subset D of V such that every vertex not in D is adjacent to some vertex in D. The domatic number d(G) of G is the maximum positive integer k such that V can be partitioned into k pairwise disjoint dominating sets. The purpose of this paper is to study the domatic numbers of graphs that are obtained from small graphs by performing graph operations, such as union, join and Cartesian product.
LOW-TEMPERATURE LUMINESCENT PROPERTIES OF DEGENERATE P-TYPE GAAS GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-02-15)
CHEN, HD
;
FENG, MS
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CHEN, PA
;
LIN, KC
;
WU, CC
Low-temperature (20 K) luminescent properties of heavily carbon- and zinc-doped GaAs grown by low-pressure metalorganic chemical vapor deposition were investigated. The luminescence linewidth became broader at low temperatures when p > 4 X 10(19) cm-3 due to the appearance of a shoulder peak. The main peak shifted to low energy when the dopant concentration was increased; however, the shoulder peak was at around 1.485 eV and was nearly independent of the dopant concentration. The peak of the band-to-acceptor transition occurred at low temperature and dominated the emission spectra of degenerate GaAs. The peak energy of Zn-doped samples was lower than that of C-doped samples because of the existence of defects. The excitation power intensity was varied to investigate the behavior of the shoulder peak for both types of dopants. The shoulder peak was a part of the main peak because of the recombination between the conduction band and the bottom of the impurity band.
THE DOUBLE RESONANT ENHANCEMENT OF OPTICAL 2ND-HARMONIC SUSCEPTIBILITY IN THE COMPOSITIONALLY ASYMMETRIC COUPLED-QUANTUM-WELL
(1994-02-15)
LIEN, CS
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HUANG, YM
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LEI, TF
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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 second harmonic suceptibility due to the intersubband transitions in the three-level GaAs/AlxGa1-xAs/AlyGa1-yAs compositionally asymmetric coupled quantum well (CACQW) under the influence of the applied electric field is investigated theoretically. The subband eigenenergy E(n) of the CACQOW structure could he designed to form an equally spaced energy-level ladder. Since the eigenenergy spacing could be designed to resonate with the pumping source, the second harmonic susceptibility could be greatly enhanced through the double resonance. Based on the theoretical calculations, the second harmonic susceptibility as high as 220 nm/V can be achieved for the CACQW. This is a more than three orders of magnitude enhancement as compared to that of the bulk GaAs. In addition to the design of CACQW structure, the double resonance can also be achieved by biasing the CACQW under a proper electric field. The extinguishment of the second order nonlinear optical effect by the applied electric field has also been studied. This phenomenon is attributed to the symmetry restoration of envelope wave functions of the CACQW structures under the quenching electric field C(off). A simple physical model to estimate the C(off) has also been developed.
ENHANCEMENT OF ELECTRON-WAVE REFLECTION BY SUPERLATTICES WITH MULTIPLE STACKS OF MULTIQUANTUM BARRIERS
(1994-02-28)
YEN, ST
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TSAI, CM
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LEE, CP
;
LIU, DC
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電子工程學系及電子研究所
We report a superlattice (SL) with multiple stacks of multiquantum barriers (MQB), which can reflect electrons more effectively than with a single stack of MQB. The reflectivities are calculated and compared with one another for a variety of potential barrier structures. The multistack SL has a wider energy spectrum within which electrons are reflected. Four types of n-GaAs/i-barrier/n-GaAs diodes were fabricated to confirm the calculated results. The current-voltage characteristics measured at 77 K for these diodes show that the turn-on voltage increases with the number of stacks of MQBs in the SL. This is in agreement with our calculated results.
ENHANCEMENT OF ELECTRON-WAVE REFLECTION BY SUPERLATTICES WITH MULTIPLE STACKS OF MULTIQUANTUM BARRIERS
(1994-02-28)
YEN, ST
;
TSAI, CM
;
LEE, CP
;
LIU, DC
;
電子工程學系及電子研究所
We report a superlattice (SL) with multiple stacks of multiquantum barriers (MQB), which can reflect electrons more effectively than with a single stack of MQB. The reflectivities are calculated and compared with one another for a variety of potential barrier structures. The multistack SL has a wider energy spectrum within which electrons are reflected. Four types of n-GaAs/i-barrier/n-GaAs diodes were fabricated to confirm the calculated results. The current-voltage characteristics measured at 77 K for these diodes show that the turn-on voltage increases with the number of stacks of MQBs in the SL. This is in agreement with our calculated results.
管管作品兩首
(1994-03-01)
管管
NOVEL SUPERVISORY TECHNIQUE USING WAVELENGTH-DIVISION-MULTIPLEXED OTDR IN EDFA REPEATERED TRANSMISSION-SYSTEMS
(1994-03-01)
LAI, YW
;
CHEN, YK
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WAY, WI
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電信工程研究所
;
光電工程學系
A wavelength-division-multiplexed optical-time-domain-reflectometry (OTDR) supervisory technique is experimentally demonstrated in a 200-km transmission system. The technique can simultaneously achieve in-line EDFA performance monitoring and diversity protection, and fault location in optical fibers.
PATH FEASIBILITY AND MODIFICATION BASED ON THE PUMA 560 WORKSPACE ANALYSIS
(1994-03-01)
SHAO, KC
;
YOUNG, KY
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電控工程研究所
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Institute of Electrical and Control Engineering
Robot paths are planned according to different industrial tasks. Their kinematic feasibility is restrained by the structure of the given robot manipulator. In order to design feasible paths under kinematic constraints and different task requirements, we propose first to utilize the geometry of the given robot to generate the geometric boundaries of different regions corresponding to kinematic constraints in the robot workspace. Geometric expressions are then derived to describe the relationship about the planned path and the robot workspace. Finally, by applying the developed modification strategies based on different task requirements, feasible paths can be obtained by modifying the infeasible portions of the paths. To demonstrate the proposed feasibility and modification schemes, the PUMA 560 robot manipulator is selected as a case study due to its complexity and practical application. The results are then extended to general wrist-partitioned types of industrial robot manipulators.
A NEW GLOBAL APPROACH FOR 0-1 POLYNOMIAL PROGRAMS
(1994-03-01)
LI, HL
;
交大名義發表
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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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National Chiao Tung University
;
Department of Information Management and Finance
Given a 0-1 polynomial expression SIGMA(k=1)N-1 SIGMA(m=k+1)N x(k)x(m), where x(k) and x(m) are 0-1 variables, the famous Glover and Woolsey method required to use N(N - 1)/2 additional continuous variables and 2N(N - 1) linear constraints to transform this expression into a linear form. This paper proposes a method which first reformulates the above expression as a new expression SIGMA(k=1)N x(k)y(k), y(k) = SIGMA(m=k+1)N x(m); then to transform the expression into a linear form where x(k) and y(k) are separated. The proposed transformation method only required to use 2(N - 1) additional continuous variables and 8(N - 1) linear constraints. Based on the new transformation, a 0-1 polynomial program can be more effectively solved to obtain a global optimum.
CONSIDERING THE EFFECT OF BODY FORCE FOR REGIONAL LAND DISPLACEMENTS
(1994-03-01)
LU, RH
;
YEH, HD
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土木工程學系
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環境工程研究所
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Department of Civil Engineering
In this study, a general mathematical model was developed for land displacements that occur as a result of the pressure decline in confined and/or phreatic aquifers. Two equations were developed by employing the equilibrium (force balance) equation and the flow equation in a deforming aquifer system. Both of these equations were integrated over the thickness of the aquifer system once a regional model had been formulated. The change of the body force in saturated and unsaturated zones of aquifers was considered in the derivation of the equilibrium equation. It was assumed that no external loading or force acting on the aquifer system was present. Two coupled equations expressed in terms of the averaged dilation and pressure were then obtained. The pumping data sets given in the papers of Bear and Corapcioglu1,2 in 1981 and 1983 were analysed. Drawdown and displacements in a confined aquifer were demonstrated to be identical to those estimated by Bear and Corapcioglu.1 In the case of a phreatic aquifer, however, the results estimated by the present approach were slightly different from those obtained by Corapcioglu and Bear.2 The discrepancies in the results are possibly due to errors in the equations presented by Corapcioglu and Bear.2 The present approach was able to avoid several assumptions and complex procedures used by Bear and Corapcioglu,1,2 especially in the case of a phreatic aquifer, by taking into account the change in the body force.
PATH FEASIBILITY AND MODIFICATION BASED ON THE PUMA 560 WORKSPACE ANALYSIS
(1994-03-01)
SHAO, KC
;
YOUNG, KY
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
Robot paths are planned according to different industrial tasks. Their kinematic feasibility is restrained by the structure of the given robot manipulator. In order to design feasible paths under kinematic constraints and different task requirements, we propose first to utilize the geometry of the given robot to generate the geometric boundaries of different regions corresponding to kinematic constraints in the robot workspace. Geometric expressions are then derived to describe the relationship about the planned path and the robot workspace. Finally, by applying the developed modification strategies based on different task requirements, feasible paths can be obtained by modifying the infeasible portions of the paths. To demonstrate the proposed feasibility and modification schemes, the PUMA 560 robot manipulator is selected as a case study due to its complexity and practical application. The results are then extended to general wrist-partitioned types of industrial robot manipulators.
AN AUTHENTICATION-COMBINED ACCESS-CONTROL SCHEME USING A ONE-WAY FUNCTION
(1994-03-01)
WU, TC
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CHANG, CC
;
YEH, YS
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
In this paper, we propose an authentication-combined access control scheme for information protection systems. Let a(ij) be the access privilege of User i to File j. Initially, by the Diffie-Hellman public key distribution scheme, the system and the users are assigned distinct secret keys, and their corresponding public keys, respectively. Let K(s) be the secret key and y(s) be the public key of the system, and let K(i) be the secret key and y(i) be the public key of the User i. By using a predefined one-way function F, we compute r(ij) = F(K(i), y(s), a(ij)). Reversely, the access privilege can be retained as a(ij) = F(K(s), y(i), r(ij)). Being different from the previously proposed schemes, our scheme is safer and the user's secret key is used not only for computing the corresponding access privilege to the intended file, but also for authenticating the requesting user not to illegitimately access the protected files. The proposed scheme is simple to establish. Besides, it can perform the access control in dynamic environments, such as change access privileges and insert/delete users or files.
THE CAST STRUCTURE OF A 7075 ALLOY PRODUCED BY A WATER-COOLING CENTRIFUGAL CASTING METHOD
(1994-03-01)
YEH, JW
;
JONG, SH
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交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
A water-cooling centrifugal casting method was applied to cast the 7075 Al alloy to generate a much finer cast structure than that produced by conventional ingot casting methods. The effects of casting parameters, i.e., rotation speed, pouring temperature, water flow, and grain refiner, on casting structure were systematically studied so that the optimum casting condition and the solidification mechanism could be established. The typical cast structure along the thickness direction of a cast ring could be divided into four equiaxed zones, including the chill zone which is in contact with the mold wall. All zones have their characteristic grain size, morphology, and relative thickness, which are all dependent on the casting condition. The optimum casting condition yielding the finest structure available was found to be 3000 rpm, 650-degrees-C, and sufficient water cooling. A uniform portion occupying 90 pct of the whole thickness and having a grain size of 17 mum could be achieved under such a casting condition. When a grain refiner was added, the whole ring became further concentrated with grains of fine structure. A mechanism concerning the overall effects of rapid solidification, turbulent flow, and centrifugal force has been proposed for the present casting method and might explain the zone-structure formation and the effects of the casting parameters on microstructural features.
管管作品兩首
(1994-03-01)
管管
BENCHMARKING AND ANALYSIS OF SUPERSCALAR ARCHITECTURE
(1994-03-01)
SHIAU, YH
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CHUNG, CP
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
Superscalar processing can improve the performance of a single CPU beyond that of traditional RISC machines by exploiting instruction-level parallelism. It is the objective of this study to design a superscalar system which will best exploit a given program's instruction-level parallelism. Three different architectural models, XPCB, XXPB, and X4P2, are used as vehicles in evaluating system performance and the degree of utilization of each individual functional unit. The XPCB model is used as a preliminary model to analyze the loading breakdowns of the various function types. It was found that the performance improvement of the XPCB model relative to a single-instruction stream model is only about 4.3 percent. In addition, the fixed-point operations are in great demand, and dominate the behavior as well as performance of the processor. Two enhanced models, the XXPB and the X4P2, are suggested to improve on the performance of the XPCB model by distributing fixed-point, and even floating-point operation loads among multiple functional units of the same type(s). Simulations show that the XXPB and X4P2 models can improve the performance of the sequential model by 50.8 and 61.6 percent, respectively.
管管作品兩首
(1994-03-01)
管管
管管作品兩首
(1994-03-01)
管管
AN OPTIMAL PARALLEL ALGORITHM FOR GENERATING PERMUTATIONS IN MINIMAL CHANGE ORDER
(1994-03-01)
TSAY, JC
;
LEE, WP
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交大名義發表
;
工學院
;
National Chiao Tung University
Permutation generation is an important problem in combinatorial computing. In this paper we present an optimal parallel algorithm to generate all N! permutations of N objects. The algorithm is designed to be executed on a very simple computation model that is a linear array with N identical processors. Because of the simplicity and regularity of the processors, the model is very suitable for VLSI implementation. Another advantageous characteristic of this design is that it can generate all the permutations in minimal change order.
MONTE-CARLO SIMULATION FOR CORRELATED VARIABLES WITH MARGINAL DISTRIBUTIONS
(1994-03-01)
CHANG, CH
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TUNG, YK
;
YANG, JC
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土木工程學系
;
Department of Civil Engineering
As computation speed increases, Monte Carlo simulation is becoming a viable tool for engineering design and analysis. However, restrictions are often imposed on multivariate cases in which the involved stochastic parameters are correlated. In multivariate Monte Carlo simulation, a joint probability distribution is required that can only be derived for some limited cases. This paper proposes a practical multivariate Monte Carlo simulation that preserves the marginal distributions of random variables and their correlation structure without requiring the complete joint distribution. For illustration, the procedure is applied to the reliability analysis of a bridge pier against scouring.
BENCHMARKING AND ANALYSIS OF SUPERSCALAR ARCHITECTURE
(1994-03-01)
SHIAU, YH
;
CHUNG, CP
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Superscalar processing can improve the performance of a single CPU beyond that of traditional RISC machines by exploiting instruction-level parallelism. It is the objective of this study to design a superscalar system which will best exploit a given program's instruction-level parallelism. Three different architectural models, XPCB, XXPB, and X4P2, are used as vehicles in evaluating system performance and the degree of utilization of each individual functional unit. The XPCB model is used as a preliminary model to analyze the loading breakdowns of the various function types. It was found that the performance improvement of the XPCB model relative to a single-instruction stream model is only about 4.3 percent. In addition, the fixed-point operations are in great demand, and dominate the behavior as well as performance of the processor. Two enhanced models, the XXPB and the X4P2, are suggested to improve on the performance of the XPCB model by distributing fixed-point, and even floating-point operation loads among multiple functional units of the same type(s). Simulations show that the XXPB and X4P2 models can improve the performance of the sequential model by 50.8 and 61.6 percent, respectively.