Browsing by Issue Date, starting with "1999-09-03"

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Cycloadditions of 16-electron 1,3-dipoles with ethylene. A density functional and CCSD(T) study
(1999-09-03)
Su, MD
;
Liao, HL
;
Chung, WS
;
Chu, SY
;
應用化學系
The 1,3-dipolar cycloaddition (DC) reactions of ethylene with nitrile ylide (CNC), nitrile imine (CNN), nitrile oxide (CNO), diazomethane (NNC), azine (NNN), and nitrous oxide (NNO) in the gas phase were examined using the density functional theory and CCSD(T) calculations. All of the structures, including the precursor complexes;and the transition structures, were completely optimized at the B3LYP/6-31G* level with single-point energies evaluated at CCSD(T)/6-311G**. The theoretical results suggest that the activation energies for the DC reactions of nitrile-type molecules (CNC, CNN, and CNO) are small (5.1-11 kcal/mol) and these reactions are very exothermic (-77 to -46 kcal/mol). In contrast, the DC reactions of NNC, NNN, and NNO are less exothermic (-39 to -6.0 kcal/mol) and have larger activation barriers (13-29 kcal/mol). Moreover, this work shows that the configuration mixing (CM) model based on Press and Shaik's theory can successfully predict the relative ordering of the activation energy and reaction enthalpies of DC reactions; Combining our theoretical calculations and the CM model, the following conclusion emerges: a 16-electron 1,3-dipole reactant with more electropositive substituents at the terminal positions will possess a smaller singlet-triplet splitting. This will facilitate cycloaddition with the dipolarophile and will result in a larger exothermicity.
我們的捉影子詩人
(1999-09-04)
管管
Polymer blends of PET-PS compatibilized by SMA and epoxy dual compatibilizers
(1999-09-06)
Lu, MY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Poly(ethylene terephthalate) (PET) and polystyrene (PS) are immiscible and incompatible and have been well recognized. In this study, styrene maleic anhydride random copolymer (SMA-8 wt % MA) and tetra-glycidyl ether of diphenyl diamino methane (TGDDM) are employed as reactive dual compatibilizers in the blends of PET-PS. The epoxy functional groups of the TGDDM can react with PET terminal groups (-OH and -COOH) and anhydride groups of SMA at the interface to produce PET-co-TGDDM-co-SMA copolymers. SMA with low MA content is miscible with PS, whereas the PET segments are structurally identical with PET phase. Therefore, these in-situ-formed copolymers tend to anchor at the interface and act as effective compatibilizers of the blends. The compatibilized blends, depending on the amounts of TGDDM and SMA addition, result in smaller phase domain, higher viscosity, and improved mechanical properties. This study demonstrates that SMA and TGDDM dual compatibilizer can be utilized effectively in compatibilizing polymer blends of PET and PS. (C) 1999 John Wiley & Sons, Inc.
Effect of oxygen to argon ratio on defects and electrical conductivities in Ba0.47Sr0.53TiO3 thin-film capacitors
(1999-09-07)
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 ionic and electronic conductivity characteristics and defects in the Ba0.47Sr0.53TiO3 (BST) thin films that were rf-sputtered at 450 degrees C on a Pt bottom electrode at various O-2/(Ar + O-2) mixing ratios (OMR) were studied. The dielectric properties specific to the BST films can be explained by considering the influence of the dielectric relaxation phenomenon. Through the measurement of the dielectric dispersion 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 studied the dielectric relaxation and obtained the defect quantity of the films, on the basis of the capacitance, admittance and impedance spectra. The defect density of BST films decreases with an increase of OMR. The majority of electrical conductivity is carried by electrons (electronic conductivity) and not the ionic defects (ionic conductivity).
Synthesis of cuparene and herbertene via a common intermediate
(1999-09-07)
Ho, TL
;
Chang, MH
;
應用化學系
;
Department of Applied Chemistry
A dihydroisobenzofuran (13) was obtained from beta-ionone in 10 steps via an intramolecular Diels-Alder reaction. On further oxidation, reductive ring opening and decarboxylation, cuparene and herbertene were synthesized.
An error evaluation technique for the angle of incidence in a rotating element ellipsometer using a quartz crystal
(1999-09-07)
Chao, YF
;
Wang, MW
;
Ko, ZC
;
交大名義發表
;
National Chiao Tung University
The error in the angle of incidence for a rotating element ellipsometer is evaluated using a uniaxial quartz crystal. At a fixed angle of incidence with respect to the surface of reflection, the ratio of reflectance in the parallel to that in the perpendicular electromagnetic field is measured by rotating the quartz crystal through a full cycle. We determine the deviation in the angle of incidence by comparing: the experimentally measured reflectance ratio to its calculated value.
Kinetics and curing mechanism of epoxy and boron trifluoride monoethyl amine complex system
(1999-09-15)
Li, YS
;
Li, MS
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The kinetics of cationic polymerization of epoxy resin has been studied. Due to multiple reaction exotherms and irregular baselines involved in this system, the ASTM E 698 method was chosen to determine the kinetic parameters of this epoxy/BF3-MEA system. The DER 332/BF3-MEA system follows the first order active chain end (ACE) reaction mechanism. The adding of the hydroxyl group into the system is prone to decrease the activation energy and shifts the curing into the activated monomer (AM) mechanism due to the stronger nucleophilicity of the hydroxyl group than the epoxide group. On the other hand, the DER 331/BF3-MEA system possesses lower activation energy because the DER 331 contains more hydroxyl groups-alpha-glycol and secondary alcohol. The former is the major contributor in lowering the activation energy. The hydroxyl group also can act as a chain transfer agent by retarding the propagation process, thus the reaction rate of the DER 332/BF3-MEA system is higher than the DER 331/BF3-MEA system. The DER 332/BF3-MEA system shows good correlation between the experimental data (FT-IR, DSC, and GPC) and the simulation curve based on ASTM E 698 before gelation, while a larger deviation is observed in the DER 331/BF3-MEA system. After gelation, the hydroxyl group also acts as an active site to react with residual epoxy monomers and obtain a more condense matrix. (C) 1999 John Wiley & Sons, Inc.
The self-defocusing of a diffraction beam in a photorefractive crystal and its application in a Fourier plane multiple beam splitter
(1999-09-15)
Tsai, J
;
Chiou, A
;
Hsieh, TC
;
Hsu, K
;
電子物理學系
We propose using a diffraction beam to induce a self-defocusing lens and applying it in a Fourier plane multiple beam splitter (FPMBS). The self-induced lens array in the FPMBS can increase the splitting ratio, which is generated by inserting a photorefractive crystal at the Rayleigh distance of the diffraction beam from each pixel. (C) 1999 Elsevier Science B.V. All rights reserved.
Hydrogen-desorption kinetic measurement on the Si(100)-2x1 : H surface by directly counting desorption sites
(1999-09-15)
Lin, DS
;
Chen, RP
;
物理研究所
;
Institute of Physics
The desorption kinetics of hydrogen from the Si(100)-2x1:H monohydride surface was investigated by means of variable-temperature scanning-tunneling microscopy (STM) in the temperature range between 590 and 668 K. By directly counting the number of desorption sites in the STM images for various annealing time at several temperatures, an activation barrier of E-d = 2.22+/-0.20 eV and a pre-exponential factor of nu(d) = 3.4 x 10(13+/-0.3) s(-1) for the H-2 recombinative desorption are deduced. The sequential images acquired in real times show that hydrogen desorbs in a random manner and the interaction between two neighboring paired dangling bond sites is repulsive.
Transformation from 512-point transform coefficients to 256-point transform coefficients for Dolby AC-3 decoder
(1999-09-16)
Lee, SW
;
Liu, CM
;
資訊工程學系
;
Department of Computer Science
The Dolby AC-3 standard defines 512-point and 256-point transforms to provide high audio quality when signals rapidly change in time. This authors provide theoretical derivations and proofs for the transformation from. 512-point transform coefficients to 256-point transform coefficients.
Decomposition of hydrogen peroxide in a catalytic fluidized-bed reactor
(1999-09-20)
Chou, SS
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
The decomposition of H2O2 by a novel supported gamma-FeOOH catalyst was performed in a continuous fluidized-bed reactor. This catalyst has been successfully used in the treatment of organic contaminants with H2O2 in our previous work. In this study, we attempted to determine the effects of pH, H2O2 concentration, and catalyst concentration on the decomposition of H2O2 An approach, we regarded this reactor as a continuous-flow stirred-tank reactor, was applied to investigate the kinetic behavior. At low H2O2 concentration, the decomposition rate of H2O2 was found to be proportional to both H2O2 and catalyst concentrations. At high H2O2 concentration, however, the rate decreased with the increasing H2O2 concentration. This can be explained by the substrate inhibition model. The large difference in the observed first-order rate constants under various pH values was also modeled. The model agreed well with the experimental results. (C) 1999 Elsevier Science B.V. All rights reserved.
Compact microstrip meander antenna
(1999-09-20)
Wang, CJ
;
Jou, CF
;
傳播研究所
;
Institute of Communication Studies
An electrically small microstrip meander antenna incorporating the folded technology is fabricated and experimental results ale presented in this paper. This antenna has the advantages of compact size, ease of manufacturing, broad bandwidth, and multiband characteristics. Different-feed and different-length antennas are tested. Techniques to reduce the antenna size are presented, and performance trends are established. The measured results show that the variation of the return loss can be easily tuned by changing the feeding points and the microstrip-line length. The maximum measured bandwidth is approximately 770 MHz (12.6% operational bandwidth around 6.115 GHz) when the middle feeding point is chosen. (C) 1999 John Wiley & Sons, Inc.
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
;
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
;
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
;
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
;
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
;
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.