Browsing by Issue Date, starting with "1999-09-24"

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這個日子我們盼了四十年!
(1999-09-24)
应紅
Pseudo-rate TCP: a congestion avoidance scheme with nearly optimized fairness and throughput
(1999-09-25)
Chen, JR
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
As the bandwidth requirement on the Internet grows, the efficiency of networking protocol becomes an important concern. This paper proposes a so-called pseudo-rate TCP, which features both better fairness and higher throughput than TCP Vegas by exponentially increasing the window size to a derived bound. The pseudo-rate TCP avoids the typical problem that sources with shorter round-trip times always get better chance in allocating the bandwidth. We discuss two key mechanisms designed for pseudo-rate TCP, and compare its performance with TCP Vegas through system simulation. (C) 1999 Elsevier Science B.V. All rights reserved.
Solid phase epitaxy for low pressure chemical vapor deposition Si films induced by ion implantation
(1999-09-29)
Chen, PS
;
Hsieh, TE
;
Chu, CH
;
材料科學與工程學系
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Department of Materials Science and Engineering
This work investigated the ion implantation induced solid phase epitaxy (SPE) of Si thin films prepared by low pressure chemical vapor deposition (LPCVD). Previous studies indicate that the residual layer at the interface between the Si thin film and single crystalline substrate is the major obstacle to the SPE process of Si film. In this work, Ge+ and Si+ ion were implanted to completely amorphize the Si film prepared by LPCVD. Ion implantation also mixed the interfacial oxide layer and its effects on subsequent epitaxial growth of Si film subjected to various annealing conditions were discussed as well. In addition, the specimen surface was modified by inductive couple plasma (ICP) process. The ICP modification using nitrogen gas could form a vacancy source on the sample surface to enhance the atomic diffusion rare and change the stress state in the vicinity of surface, thereby accelerating the SPE process. (C) 1999 Elsevier Science S.A. All rights reserved.
Effect of diatomic islands on step morphological stability of a terrace edge in molecular beam epitaxy
(1999-09-29)
Lin, SP
;
Hwang, CC
;
Chu, HS
;
機械工程學系
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Department of Mechanical Engineering
The effect of two-dimensional diatomic-island nucleation on the linear stability of the step morphology during molecular beam epitaxy is investigated numerically via shooting methods. It is found that the effect of diatomic islands on the step morphological stability is significant. The greater the effects of diatomic islands, the more stable the step morphology. increasing capture efficiency can decrease the critical surface capillary length and shift the critical wave number toward short-wavelength regimes. The unstable region is shrunk with increasing capture efficiency. Further, increasing flux coverage and/or surface coverage can decrease the critical surface capillary length and shift the critical wave number toward short-wavelength regimes. (C) 1999 Elsevier Science S.A. All rights reserved.
Quasi-universal switch matrices for FPD design
(1999-10-01)
Wu, GM
;
Chang, YW
;
資訊工程學系
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Department of Computer Science
An FPD switch module M with omega terminals on each side is said to be universal if every set of nets satisfying the dimension constraint (i.e., the number of nets on each side of M is at most omega) is simultaneously routable through M [8]. Chang-et al, have identified a class of universal switch blocks in [8]. In this paper, we consider the design and routing problems for another popular model of switch modules called switch matrices. Unlike switch blocks, we prove that there exist no universal switch matrices. Nevertheless, we present quasi-universal switch matrices which have the maximum possible routing capacities among all switch matrices of the same size and show that their routing capacities converge to those of universal switch blocks. Each of the quasi-universal switch matrices of size omega has a total of only 14 omega - 20 (14 omega - 21) switches if omega is even (odd), omega > 1, compared to a fully populated one which has 3 omega(2) - 2 omega switches. We prove that no switch matrix with less than 14 omega - 20 (14 omega - 21) switches can be quasi-universal. Experimental results demonstrate that the quasi-universal switch matrices improve routabilty at the chip level.
Fourier series expansion method for plated-structures
(1999-10-01)
Deng, JG
;
Cheng, FP
;
土木工程學系
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Department of Civil Engineering
This work applies a structural analysis method based on an analytical solution from the Fourier series which transforms a half-range cosine expansion into a static solution involving plated structures. Two sub-matrices of in-plane and plate-bending problems are also formulated and coupled with the prescribed boundary conditions for these variables, thereby providing a convenient basis for a numerical solution. In addition, the plate connection are introduced by describing the connection between common boundary continuity and equilibrium. Moreover, a simple computation scheme is proposed. Numerical results are then compared with finite element results, demonstrating the numerical scheme's versatility and accuracy.
Design of QMF banks based on derivative information
(1999-10-01)
Kao, MC
;
Chen, SG
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
New L-2 objective functions for the design of quadrature mirror filter (QMF) banks are proposed. They are based on the derivative information of the reconstruction error Simple and explicit matrix-form formulas for the proposed objective functions are derived. Efficient design methods are proposed by incorporating a separability technique into the derived optimality conditions on prototype filters. The proposed design methods need only solve linear equation iteratively without nonlinear optimisation. Design examples demonstrate that good low-delay QMF banks and linear-phase QMF banks can be obtained in only a few iterations. Compared with the conventional approach, the new approach leads to QMF banks with larger stopband attenuation and smaller reconstruction errors.
Bilevel hysteretic service rate control for bulk arrival queue
(1999-10-01)
Liu, FH
;
Tseng, JW
;
工業工程與管理學系
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Department of Industrial Engineering and Management
This paper concerns M-[X] / M / 1 queue. The number of customers in each arriving unit is a random variable. There is two control threshold values K and N, K is smaller than N. Service rate is switched from u to tu whenever the system size increases to N. The tu rate is switched to u when the system size drops to the value K. We derive the steady-state probabilities of the number of customers in system and the expected number of customers in system. A cost model is introduced for the service cost, queuing cost, and switching cost. (C) 1999 Elsevier Science Ltd. All rights reserved.
A novel Si-B diffusion source for p(+)-poly-Si gate
(1999-10-01)
Chao, TS
;
Kuo, CP
;
Chen, TP
;
Lei, TF
;
電子工程學系及電子研究所
In this paper, we report a novel Si-B diffusion source for p(+)-polySi gate p-metal oxide-semiconductor field effect transistors (pMOSFETs). It is found that boron penetration can br effectively suppressed using this process. All the electrical properties of the MOS capacitors are significantly improved over the conventional BF2+ or B+-implanted samples. This process is very promising for fabrication of future surface-channel p-MOSFETs. (C) 1999 The Electrochemical Society. S0013-4651(99)03-017-7. All rights reserved.
Adaptive variable step-size Griffiths' algorithm for blind demodulation of DS/CDMA signals
(1999-10-01)
Hwang, HC
;
Wei, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The minimum mean-squared error (MMSE) linear detector [1], [2] has been proposed to successfully suppress the multiple access interference and mitigate the near-far problem in direct-sequence code-division multiple access communication systems. In the presence of unknown or time-varying channel parameters, the MMSE linear detector can be implemented by the blind Griffiths' algorithm [3], which uses the desired signal vector instead of a training sequence of symbols for initial adaptation. In this paper, a variable step-size (VSS) Griffiths' algorithm is proposed for accelerating the convergence speed, especially in the presence of strong interference. Numerical results show that the convergence properties of the VSS Griffiths' algorithm are robust against the wide eigenvalue-spread problem of the correlation matrix associated with the received signal vector compared to the Griffiths' algorithm using a fixed step-size.
An overview of a heuristic for vehicle routing problem with time windows
(1999-10-01)
Liu, FHF
;
Shen, SY
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
In this paper, a two-stage metaheuristic based on a new neighborhood structure is proposed to solve the vehicle routing problem with time windows. Our neighborhood construction focuses on the relationship between route(s) and node(s). Unlike the conventional methods for parallel route construction, we construct routes in a nested parallel manner to obtain higher solution quality. Computational results for 60 benchmark problems are reported. The results indicate that our approach is highly competitive with all existing heuristics, in particular very promising for solving problems with large size. (C) 1999 Elsevier Science Ltd. All rights reserved.
A finest partitioning algorithm for attribute grammars
(1999-10-01)
Yang, W
;
資訊工程學系
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Department of Computer Science
The attribute dependence graph of a syntax tree may be partitioned into disjoint regions. Attribute instances in different regions are independent of one other. The advantages of partitioning the attribute dependence graph include simplifying the attribute grammar conceptually and allowing the possibility of parallel evaluation. We present a static partitioning algorithm for attribute grammars. The algorithm builds the set of all feasible partitions for every production by analyzing the grammar. After the attributed syntax tree is constructed, one of the feasible partitions is chosen for each production instance in the syntax tree. Gluing together the selected partitions for individual production instances results in a partition of the attribute dependence graph of the syntax tree. No further merging or partitioning is needed at evaluation time. In addition to static partitioning, the algorithm always produces the finest partition of every attribute dependence graph. An application of the partitioning technique is the strictness analysis for a simple programming language that contains no higher-order functions. (C) 2000 Elsevier Science Ltd. All rights reserved.
Bend-flow simulation using 2D depth-averaged model
(1999-10-01)
Lien, HC
;
Hsieh, TY
;
Yang, JC
;
Yeh, KC
;
土木工程學系
The purpose of this paper is to present a 2D depth-averaged model for simulating and examining flow patterns in channel bends. In particular, this paper proposes a 2D depth-averaged model that takes into account the influence of the secondary flow phenomenon through the calculation of the dispersion stresses arisen from the integration of the products of the discrepancy between the mean and the true velocity distributions. The proposed model uses an orthogonal curvilinear coordinate system to efficiently and accurately simulate the flow field with irregular boundaries. As for the numerical solution procedure, the two-step split-operator approach consisting of the dispersion step and the propagation step with the staggered grid is used to numerically solve the flow governing equations. Two sets of experimental data from de Vriend and Koch and from Rozovskii were used to demonstrate the model's capabilities. The former data set was from a mildly curved channel, whereas the latter was from a sharply curved channel. The simulations considering the secondary flow effect agree well with the measured data. Furthermore, an examination of the dispersion stress terms shows that the dispersion stresses play a major role in the transverse convection of the momentum shifting from the inner bank to the outer bank for flows in both mild and sharp bends.
Synthesis, characterization and electrostatic dissipating ability of poly(oxyethylene) block polyesteramides
(1999-10-01)
Lin, JJ
;
Sheen, YC
;
Tseng, FP
;
Chang, FC
;
應用化學系
Poly(oxyethylene)diamines were included in the copolymerization of ethylene glycol and dicarboxylic acids, such as terephthalic, adipic and sebacic acid, to produce a series of hydrophilic polyether-ester-amides. With the addition of poly(oxyethylene)diamines (average molecular weight of 2,000) to PET in the amounts of 3.2, 6.6, 12 and 16 wt%, melting points of these polymers dropped accordingly, from 240 degrees C to around 227 degrees C, and the electronic resistivity decreased from 1x10(13) to approximately 8x10(8) ohm/sq. For comparison, the introduction of hydrophilic PEG-2000 or a low molecular weight diamine, such as triethyleneglycol diamine, has less effect on electronic resistivity. Molecular weight. polymer rigidity and ageing are other factors affecting the surface resistivity. The degree of hydrophilicity was measured by the moisture absorption of the fibers made from these polyether-ester-amides. A weight gain of 0.96% was observed for 12 wt% Poly(oxyethylene)diamine modified polyether-ester-amides in comparison with 0.40% for the unmodified poly(ethylene terephthalate), These results are explained by a mechanism involving moisture absorption on the polymer surface through the formation of hydrogen bonding with amide and -(OCH2CH2)-functionalities on the polymer surface.
High average power mode locked Ti : Sapphire laser with intracavity continuous-wave amplifier and strained saturable Bragg reflector
(1999-10-01)
Liu, TA
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Huang, KF
;
Pan, CL
;
Liu, ZL
;
Ohtake, H
We demonstrate a new scheme for the generation of high average power femtosecond pulses by incorporating an intracavity amplifier and a strained saturable Bragg reflector with low saturation fluence for self-starting mode locking. When the Ti:sapphire oscillator and intracavity amplifier are pumped at 10W and 15W, respectively, the average output power is as high as 1.62 W. The pulse duration is about 145 fs, and the peak power reaches 160 kW at a 68 MHz repetition rate: The pulse-formation time of 400 mu s is sufficiently short to sustain stable mode locking.
Quantum transport through a quantum well in the presence of a finite-range time-modulated potential
(1999-10-01)
Chu, CS
;
Liang, HC
;
電子物理學系
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Department of Electrophysics
We have studied the transport of electrons through a quantum well within which a time-modulated potential of amplitude V-2, range a, and frequency w is applied. Our results show that, as the chemical potential mu increases, the de conductance G exhibits Fano-structures when mu is at m (h) over bar w above the bound state energy in the well. As V-2 increases, the Fano-structures are broadened, and higher m (h) over bar w processes emerge. These features are identified as the formation of quasi-bound states. For a fixed but large potential strength V-1 = aV(2), the Fano-structures are broadened and are shifted toward lower electron energies, as a decreases. The dependence of the Fano-structure to the location of the time-modulated potential is also studied.
Joint synchronization in eureka 147 DAB system based on abrupt phase change detection
(1999-10-01)
Huang, YL
;
Sheu, CR
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Huang, CC
;
交大名義發表
;
電信工程研究所
We present a joint symbol, frame, and carrier synchronization method for the Eureka 147 DAB signal in this paper. Symbol timing is determined first by detecting an abrupt change in the phase angle of the complex product between the last quarter of a useful symbol and its cyclic extension in the guard interval. The detection of this abrupt change is based on the maximal likelihood (ML) principle. Frequency offset of fractional carrier spacing is estimated from the phase angle of the autocorrelation after symbol timing is estimated. Coarse frame synchronization and null symbol detection can also be achieved through this correlation information Frequency offset of integral carrier spacing is determined from the convolution outputs between a received phase reference symbol and several locally generated but frequency-shifted phase reference symbols. We found the length of a yard interval is the most important parameter for the synchronization algorithm to work. Simulation results show that the performance of this synchronization method approaches to the ideal synchronization case in both an additive white Gaussian noise (AWGN) channel and a two-path Rayleigh fading channel.
Color quantization by preserving color distribution features
(1999-10-01)
Lin, WJ
;
Lin, JC
;
資訊工程學系
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Department of Computer Science
A color quantization method is proposed. The method hierarchically uses a bisection tool that preserves certain color-distribution features. The preserved features are average color, variance in each color dimension, and average color radius. An algorithm is given that includes the histogram simplification procedure, color palette generation, and pixel mapping. Experiments show that the proposed method usually obtains acceptable quantized images with competitive speed. (C) 1999 Elsevier Science B.V. All rights reserved.
Optimization of OMVPE-grown GaInP/GaAs quantum well interfaces
(1999-10-01)
Chiou, SW
;
Lee, CP
;
Hong, JM
;
Chen, CW
;
Tsou, Y
A new and improved method of growing Al-free GaInP/GaAs quantum wells (QWs) is presented. We found that both interfaces are important for obtaining a high-quality quantum well. With an added H-2 purge and PH3 preflow procedure, we have significantly improved the GaInP on GaAs interface by eliminating the unwanted dark line region at the interface. At the GaAs on GaInP interface, we added a thin GaAsP layer. This layer effectively prevents the In memory effect at the interface. As a result of this new growth procedure, a linewidth of 6.7 meV (at 20 It) for the quantum well emission was achieved. (C) 1999 Elsevier Science B.V. All rights reserved.
Pragmatical asymptotical stability theorem with application to satellite system
(1999-10-01)
Ge, ZM
;
Yu, JK
;
Chen, YT
;
機械工程學系
;
Department of Mechanical Engineering
The motion stability of many actual dynamical systems may not be mathematical asymptotical stability in tradition, but it is actual asymptotical stability, namely, pragmatical asymptotical stability, which can be introduced by the concept of probability. To fill the gap between the tradictional idealized mathematical models and the actual reality of dynamical systems, a pragmatical asymptotical stability theorem is given with application to satellite system.