Browsing by Issue Date, starting with "2000-05-20"

Now showing 1 - 20 of 78342

Distribution of dangling bond pairs on partially hydrogen-terminated Si(100) surface observed by scanning tunneling microscopy
(2000-05-20)
Chen, RP
;
Lin, DS
;
物理研究所
;
Institute of Physics
Hydrogen recombinative desorption from a Si2H2 monohydride dimer on the Si(100) surface regenerates a dangling bond (DB) pair on the dimer. In this paper, we investigated the spatial distribution of the regenerated DB pairs on the Si(100)-2 x 1:H and disilane-passivated Si(100) surface using elevated temperature scanning tunneling microscopy (HT-STM) in the temperature range between 590 and 622 K. Experimental results indicate that the ends of one-dimensional (1D) monohydride dimer islands are preferred sites for DB pairs and a repulsive interaction occurs between two neighboring DB pairs in the same dimer row. (C) 2000 Elsevier Science B.V. All rights reserved.
Mesh independence of matrix-free methods for path following
(2000-05-21)
Ferng, WR
;
Kelley, CT
;
應用數學系
;
Department of Applied Mathematics
In this paper we consider a matrix-free path following algorithm for nonlinear parameter-dependent compact fixed point problems. We show that if these problems are discretized so that certain collective compactness and strong convergence properties hold, then this algorithm can follow smooth folds and capture simple bifurcations in a mesh-independent way.
Dielectric relaxation and defect analysis of Ta2O5 thin films
(2000-05-21)
Ezhilvalavan, S
;
Tsai, MS
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The presence of defects in thin-film dielectrics often leads to dielectric relaxation as a function of frequency, in which the dielectric constant decreases and the loss tangent increases with increasing frequency. Dielectric relaxation results in charge storage capacity reduction under dynamic random access memory operating conditions. In this work, the dielectric relaxation behaviour of de reactive sputtered Ta2O5 thin film was investigated. Using dielectric dispersion measurements as a function of frequency (100 Hz less than or equal to f less than or equal to 10 MHz) and temperature (27 degrees C less than or equal to T less than or equal to 150 degrees C), we determined the dielectric relaxation and defect quantity of the films and propose an equivalent circuit on the basis of complex capacitance, admittance and impedance spectral studies.
Time-resolved photoluminescence study of isoelectronic In-doped GaN films grown by metalorganic vapor-phase epitaxy
(2000-05-29)
Huang, HY
;
Shu, CK
;
Lin, WC
;
Chuang, CH
;
Lee, MC
Time-resolved photoluminescence spectra were used to characterize isoelectronically doped GaN:In films. Our results indicate that the recombination lifetime of the donor-bound-exciton transition of undoped GaN exhibits a strong dependence on temperature. When In is doped into the film, the recombination lifetime decreases sharply from 68 to 30 ps, regardless of the measured temperature and In source flow rate. These observations might be related to the isoelectronic In impurity itself in GaN, which creates shallow energy levels that predominate the recombination process. (C) 2000 American Institute of Physics. [S0003- 6951(00)02622-X].
Depth-averaged two-dimensional curvilinear explicit finite analytic model for open-channel flows
(2000-05-30)
Hsu, CT
;
Yeh, KC
;
Yang, JC
;
土木工程學系
;
Department of Civil Engineering
A depth-averaged two-dimensional model has been developed in the curvilinear co-ordinate system for free-surface flow problems. The non-linear convective terms of the momentum equations are discretized based on the explicit-finite-analytic method with second-order accuracy in space and first-order accuracy in time. The other terms of the momentum equations, as well as the mass conservation equation, are discretized by the finite difference method. The discretized governing equations are solved in turn, and iteration in each time step is adopted to guarantee the numerical convergence. The new model has been applied to various flow situations, even for the cases with the presence of sub-critical and supercritical flows simultaneously or sequentially. Comparisons between the numerical results and the experimental data show that the proposed model is robust with satisfactory accuracy. Copyright (C) 2000 John Wiley & Sons, Ltd.
An aperture-coupled linear microstrip leaky-wave antenna array with two-dimensional dual-beam scanning capability
(2000-06-01)
Hu, CC
;
Jou, CF
;
Wu, JJ
;
傳播研究所
;
Institute of Communication Studies
This paper describes an X-band 4 x 1 aperture-coupled series-fed electronically steerable microstrip leaky-wave antenna (LWA) array design, which has dual-beam radiation pattern and two-dimensional (2-D) beam-scanning capability. The LWA array is operated in the first higher order mode and excited by center-fed aperture coupled for dual-beam operation. The varactor-tuned phase shifters are placed between the antenna elements. The measured half-power beamwidth of the H-plane and quasi-E-plane radiation patterns are less than 30 degrees. By tuning the reverse de bias of the varactor diodes, the main beam can be scanned in azimuth plane from -13 degrees to +13 degrees off broadside. In the elevation plane, the beam-scanning angle is close to 20 degrees as the operating frequency tuned from 11.58-12.5 GHz. Taking into account each phase-shifter insertion loss and phase progression, the measured results compared closely with the theoretical prediction, The proposed antenna array is suitable for wireless communication and collision warning radar systems.
Thermocapillary effect on drying of a polymer solution under non-uniform radiant heating
(2000-06-01)
Chen, JJ
;
Lin, JD
;
機械工程學系
;
Department of Mechanical Engineering
This theoretical investigation analyzes the two-dimensional heat and mass transfer characteristics arising from the cion-uniform radiant incidence in polymer solutions whose motion is governed by combined thermocapillary/ buoyancy laminar flow. Also considered herein is the evaporation of solvent at solution surface. The effects of various radiation input, external convective parameters, and important physical properties of solutions on the drying characteristics are investigated and results are presented in terms of flow, thermal, and concentration fields, and rate of water removal. In addition, the influence of thermocapillary effect on drying features is also examined. Numerical results indicate that absorbed energy and distribution of the solvent concentration dominate the drying rate. At larger surface tension Reynolds number, more mass concentration can be transferred by thermocapillary flow from the interior region to the surface, which then increases drying rate. Furthermore, removing the solid wall effect reduces the drying time required for a solution film with two sides of symmetric surfaces, which is irradiated by an array of infrared radiant heaters. (C) 2000 Elsevier Science Ltd. All rights reserved.
Thickness dependent gate oxide quality of thin thermal oxide grown on high temperature formed SiGe
(2000-06-01)
Wu, YH
;
Chin, A
;
Chen, WJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
For thin oxides grown on high temperature formed Si0.3Ge0.7, the gate oxide quality is strongly dependent on oxide thickness and improves as thickness reduces from 50 to 30 Angstrom. The thinner 30 Angstrom oxide has excellent quality as evidenced by the comparable leakage current, breakdown voltage, interface-trap density and charge-to-breakdown with conventional thermal oxide grown on Si. The achieved good oxide quality is due to the high temperature formed Si0.3Ge0.7 that is strain relaxed and stable during oxidation, The possible reason for strong thickness dependence may be due to the lower GeO2 content formed in thinner 30 Angstrom oxide rather than strain relaxation related rough surface or defects.
Study of linear and nonlinear optical properties of distorted Ti-O-6 perovskite structure in BaxSr1-xTiO3
(2000-06-01)
Chen, WK
;
Cheng, CM
;
Huang, JY
;
Hsieh, WF
;
Tseng, TY
We report the linear and nonlinear optical properties of sol-gel prepared BaxSr1-xTiO3 (BST) crystalline powders. The results from powder X-ray diffraction, birefringence, and second-order optical nonlinearity measurements indicate that the paraelectric-ferroelectric phase transition of Ba0.75Sr0.25TiO3 occurs near room temperature. The second-order optical nonlinearity of the ferroelectric BST is about 7.9 pm/V. The index of refraction, n = 2.2, and birefringence, Delta n(B) similar to 0.05, are also appropriate for practical nonlinear optical applications. (C) 2000 Elsevier Science Ltd. All rights reserved.
Effect of growth temperature on the electric properties of In0.12Ga0.88As/GaAs p-i-n multiple-quantum-well diodes
(2000-06-01)
Chen, JF
;
Wang, PY
;
Wang, JS
;
Wong, HZ
;
電子物理學系
The electric properties of In0.12Ga0.88As/GaAs p-i-n multiple-quantum-well (MQW) diodes, with the MQW layer grown at different temperatures by molecular beam epitaxy, have been investigated. Temperature-dependent current-voltage studies reveal a trap-filled limit current at a low temperature and a generation-recombination current via deep levels at high temperature for a 300 degrees C-grown sample. Frequency-dependent capacitance and deep-level transient spectroscopy reveal one majority trap at 0.73 eV and two minority traps at 0.71 and 0.43 eV. The 0.73 eV trap is also detected in 550 degrees C-grown samples, suggesting that it is a common defect in relaxed InGaAs/GaAs MQWs and probably originates from the defect states related to the strain relaxation. The 0.71 eV trap is believed to be the dominating deep level that governs the current conduction due to the activation energy observed in the current-voltage characteristics. (C) 2000 American Institute of Physics. [S0021-8979(00)00711-8].
Personal rules generation for intelligent e-mail service system
(2000-06-01)
Tsai, CJ
;
Tseng, SS
;
Cheng, HT
;
資訊工程學系
;
Department of Computer Science
As E-mail becomes more popular over network, the problem of receiving a lot of undesired E-mails arise. All of the previous systems, which have been developed to solve this problem, may be divided into two different categories, client-side, and server-side, from the view of location of filter. The former case always causes waste of network traffic and the latter case results that ail users may only share a small predefined set of filtering rules. In this paper, we propose a new architecture of E-mail service system, called Intelligent E-mail Service System (IESS), integrating client-side and server-side to help users manage their E-mails. A data mining approach is used in client to find managing rules from user's behavior of reading E-mail automatically. Then these rules would be stored in rule base for predicating E-mail at server. The prediction of the E-mail is made before transferring it to client; therefore, the undesired E-mails can be filtered at server to save network traffic. In addition, the feedback mechanism is provided to refine the prediction accuracy based on each user's decisions for reading E-mails. Experimental results show that IESS can infer E-mail reading preference of individual users correctly up to the accuracy about 80%. We may conclude that IESS can help users manage their E-mails effectively.
Comments on "Reliability and component importance of a consecutive-k-out-of-n system" by Zuo
(2000-06-01)
Hwang, FK
;
Cui, LR
;
Chang, JC
;
Lin, WD
;
應用數學系
Zuo claimed that the comparison of Birnbaum importance between two components for a consecutive-k-out-of-n:G system is the same as that for the F-system. We show that this is not the case and give a correct relation between the two systems. (C) 2000 Elsevier Science Ltd. All rights reserved.
A FIFO-based buffer management approach for the ATM GFR services
(2000-06-01)
Chan, CT
;
Hu, SC
;
Wang, PC
;
Chen, YC
;
資訊工程學系
We investigate the TCP packet transmission over the ATM Guaranteed Frame Rate (GFR) service using a selective packet-discard with buffer vacancy tracking strategy and a packet-based push-out buffering scheme. Our approach is based on FIFO queueing discipline, it features fair sharing of available resources as well as feasibility in hardware implementation.
Interfacial reactions of Ni/Si0.76Ge0.24 and Ni/Si1-x-yGexCy by vacuum annealing and pulsed KrF laser annealing
(2000-06-01)
Luo, JS
;
Lin, WT
;
Chang, CY
;
Shih, PS
;
電子工程學系及電子研究所
Interfacial reactions of Ni on Si0.76Ge0.24 and Si1-x-yGexCy. films by vacuum annealing and pulsed KrF laser annealing were studied by transmission electron microscopy (TEM) in conjunction with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). For the Ni/Si0.76Ge0.24 and Ni/Si1-x-yGexCy films annealed at a temperature of 200-600 degrees C Ge segregation and agglomeration occurred at an extent becoming more severe at higher temperatures. Upon pulsed KrF laser annealing the agglomeration structure was improved. The retardation of phase transformation in the Ni/Si1-x-yGexCy system was observed upon either vacuum annealing or pulsed laser annealing. Multiple-pulse annealing is an effective method to fabricate smooth Ni(Si0.76Ge0.24)(2) and Ni(Si1-x-yGexCy)(2) films without inducing Ge segregation to the remaining substrates and strain relaxation. (C) 2000 Elsevier Science B.V. All rights reserved.
Analogical process in hypothesis-testing skill acquisition: The modulatory effect of language
(2000-06-01)
Huang, LF
;
Horng, RY
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
唱詩
(2000-06-01)
管管
Correlates of sex-role egalitarianism on employment: A study in Taiwan
(2000-06-01)
Horng, RY
;
Chen, PH
;
交大名義發表
;
National Chiao Tung University
High capacity image steganographic model
(2000-06-01)
Lee, YK
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
Steganography is an ancient art of conveying messages in a secret way that only the receiver knows the existence of a message. So a fundamental requirement for a steganographic method is imperceptibility; this means that the embedded messages should not be discernible to the human eye. There are two other requirements, one is to maximise the embedding capacity, and the other is security. The least-significant bit (LSB) insertion method is the most common and easiest method for embedding messages in an image. However, how to decide on the maximal embedding capacity for each pixel is still an open issue. An image steganographic model is proposed that is based on variable-size LSB insertion to maximise the embedding capacity while maintaining image fidelity. For each pixel of a grey-scale image, at least four bits can be used for message embedding. Three components are provided to achieve the goal. First, according to contrast and luminance characteristics, the capacity evaluation is provided to estimate the maximum embedding capacity of each pixel. Then the minimum-error replacement method is adapted to find a grey scale as close to the original one as possible. Finally, the improved grey-scale compensation, which takes advantage of the peculiarities of human visual system, is used to eliminate the false contouring effect. Two methods, pixelwise and bitwise, are provided to deal with the security issue when using the proposed model. Experimental results show effectiveness and efficiency of the proposed model.
Analysis of dielectric breakdown patterns in parallel-plate capacitors
(2000-06-01)
Sheu, CR
;
Cheng, CY
;
Wang, PS
;
Lee, CY
;
Pan, RP
The parallel-plate capacitor cells are used as model systems for studying the dielectric breakdown (DB) patterns. Air, a liquid crystal and several kinds of oils are used as the dielectric material sandwiched between the plates. We study the types of patterns formed with different materials, voltages and cell thickness. The fractal dimensions and the conditions for getting each type of DB pattern are obtained for the first time. In addition, the fractal dimensions of patterns simulated by using the active walker model (AWM) are also analyzed and compared with the experimental DB patterns.
Construction of complex-valued wavelets and its applications to scattering problems
(2000-06-01)
Leou, JL
;
Huang, JM
;
Jeng, SK
;
Li, HJ
;
電信工程研究所
This paper introduces the construction of a Family of complex-valued scaling functions and wavelets with symmetry/antisymmetry, compact support, and orthogonality from the Daubechies polynomial, and applies them to solve electromagnetic scattering problems. For simplicity, only two extreme cases in the family, maximum-localized complex-valued wavelets and minimum-localized complex-valued wavelets are investigated. Regularity of root location of the Daubechies polynomial in spectral Factorization are also presented to construct these two extreme genus of complex-valued wavelets. When wavelets are used as basis functions to solve electromagnetic scattering problems by the method of moment (MoM), they often lead to sparse matrix equations. We will compare the sparsity of MoM matrices by the real-valued Daubechies wavelets, minimum-localized complex-valued Daubechies and maximum-localized complex-valued Daubechies wavelets. Our research summarized in this paper shows that the wavelets with smaller signal width will result in a more sparse MoM matrix, especially when the scatterer is with many corners.