Browsing by Issue Date, starting with "1996-11-30"

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Mechanism of transesterification and cyclization of epoxy-polycarbonate blends catalyzed by quarternary ammonium salt
(1996-11-30)
Li, MS
;
Ma, CCM
;
Lu, MS
;
Lin, ML
;
Chang, FC
The reaction of oxirane with carbonate using quarternary ammonium salts as catalyst has been studied. Curing is caused by the transesterification reaction of the oxirane cycle with the carbonate group that proceeds by an ''insertion'' mechanism in the stoichiometric system. The ratio of the reactants is two oxirane groups to one carbonate group. In the nonstoichiometric system, the epoxide content is more than the stoichiometric quantity required. A cyclization reaction is followed by the transesterification reaction. To identify the finished products, a model reaction was proposed using diphenyl carbonate and phenyl glycidyl ether which results in the formation of 4-phenoxymethyl-1,3-dioxolane-2-one (PMD). The mechanism of forming the cyclic structure is assumed to proceed through the chain scission of the network in which the molecular chain crosslinked with carbonate group by a transesterification reaction. (C) 1996 John Wiley & Sons,Inc.
藝術發源地
(1996-11-30)
不詳
Mechanism of transesterification and cyclization of epoxy-polycarbonate blends catalyzed by quarternary ammonium salt
(1996-11-30)
Li, MS
;
Ma, CCM
;
Lu, MS
;
Lin, ML
;
Chang, FC
The reaction of oxirane with carbonate using quarternary ammonium salts as catalyst has been studied. Curing is caused by the transesterification reaction of the oxirane cycle with the carbonate group that proceeds by an ''insertion'' mechanism in the stoichiometric system. The ratio of the reactants is two oxirane groups to one carbonate group. In the nonstoichiometric system, the epoxide content is more than the stoichiometric quantity required. A cyclization reaction is followed by the transesterification reaction. To identify the finished products, a model reaction was proposed using diphenyl carbonate and phenyl glycidyl ether which results in the formation of 4-phenoxymethyl-1,3-dioxolane-2-one (PMD). The mechanism of forming the cyclic structure is assumed to proceed through the chain scission of the network in which the molecular chain crosslinked with carbonate group by a transesterification reaction. (C) 1996 John Wiley & Sons,Inc.
Robust Kalman filter synthesis for uncertain multiple time-delay stochastic systems
(1996-12-01)
Hsiao, FH
;
Pan, ST
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The problem of robust Kalman filter synthesis is considered in this present study for discrete multiple time-delay stochastic systems with parametric and noise uncertainties. A discrete multiple time-delay uncertain stochastic system can be transformed into another uncertain stochastic system with no delay by properly defining state variables. Minimax theory and Bellman-Gronwall lemma are employed on the basis of the upper norm-bounds of parametric uncertainties and noise uncertainties. A robust criterion can consequently be derived which guarantees the asymptotic stability of the uncertain stochastic system. Designed procedures are finally elaborated upon with an illustrative example.
A fast algorithm for computing field radiated by an insulated dipole antenna in dissipative medium
(1996-12-01)
Wu, LK
;
Su, DWF
;
Tseng, BC
;
交大名義發表
;
傳播研究所
A fast algorithm for determining the near-field characteristics of an insulated dipole antenna (IDA) embedded in a homogenous dissipative medium is described in this paper. A thin-wire-approximation type of analysis is followed here. In this case, radiation is considered to originate from a filamentary current flowing along the axis of the dipole, which is surrounded immediately hy the ambient dissipative medium, The translational symmetry inherent in the resultant radiation integrals is then exploited to speed up the computation. In one case studied, the basic thin-wire approach that uses no symmetry property is found to yield accurate results in approximately 380 times less CPU time than the traditional King-Casey approach, In another case, use of symmetry property further reduces the CPU time by a factor of 7; additional reduction in CPU time is possible by taking into account the near-field nature of the problem.
Au/Ge/Pd ohmic contacts to n-GaAs with the Mo/Ti diffusion barrier
(1996-12-01)
Chai, CY
;
Huang, JA
;
Lai, YL
;
Wu, JW
;
Chang, CY
The influences of the As-outdiffusion and Au-indiffusion on the performances of the Au/Ge/Pd/n-GaAs ohmic metallization systems are clarified by investigating three different types of barrier metal structures Au/Ge/Pd/GaAs, Au/Ti/Ge/Pd/GaAs, and Au/Mo/Ti/Ge/Pd/GaAs. The results indicate? that As-outdiffusion leads to higher specific contact resistivity, whereas Au-indiffusion contributes to the turnaround of the contact resistivity at even higher annealing temperature. For Au/Mo/Ti/Ge/Pd/n-GaAs samples, they exhibit the smoothest surface and the lowest specific contact resistivity with the wildest available annealing temperature,range, Moreover, Auger electron spectroscopy depth profiles show that the existing Ti oxide for the Mo/Ti bilayer can very effectively retard Au-indiffusion, reflecting the onset of the turnaround point at much higher annealing temperature.
沒有臍帶的詩論大鏢客和老頑童
(1996-12-01)
管管
Growth and fatigue properties of pulsed laser deposited Pb1-xLax(ZryTiz)O-3 thin films with [001] preferred orientation
(1996-12-01)
Lin, WJ
;
Tseng, TY
;
Wu, YZ
;
Lin, SP
;
Tu, SL
Growth of [00/] preferentially oriented Pb1-xLax(ZryTiz) O-3 (PLZT) thin films was carried out by using targets of either tetragonal or rhombohedral structure. The tetragonal films grew in a similar manner to the rhombohedral films. Both the substrate temperature (500 or 550 degrees C) and oxygen pressure (0.1 mbar, 10 Pa) required stringent control in order to deposit [00/]-textured PLZT thin films. The ferroelectric and fatigue properties were examined. The films deposited on YBa2Cu3O7-x and CeO2 coated silicon (YBCO/CeO2/Si) substrates possessed substantially lower remanent polarization than those grown on YBCO coated SrTiO3 (YBCO/STO) substrates; this is ascribed to inferior crystallinity of the PLZT/BCO/CeO2/Si films. The remanent polarization of tetragonal PLZT films was degraded insignificantly up to 10(8) polarization switching cycles, whereas that of rhombohedral PLZT films was already reduced to 80% of the initial value after 10(8) cycles. Low endurance of rhombohedral films was ascribed to the periodic stress induced when the inclined spontaneous polarization vector (P=[111]) switched. On the other hand, high endurance of tetragonal films was explained by the fact that the spontaneous polarization vector (P=[001]) lies along the film's normal such that switch cycles cause no lateral stress.
Growth and characterization of Cd1-x-yZnxMnyTe crystals
(1996-12-01)
Chou, WC
;
Chen, FR
;
Chiang, TY
;
Shin, HY
;
Sun, CY
The Cd1-x-yZnxMnyTe crystals, having potential in the development of magnetic field sensitive devices, were grown by the temperature gradient solution method at 940 degrees C. All crystals were p-type with resistivity of 10(7) Omega . cm. They have novel magneto-optical properties, and could be substitutes for the Cd1-xZnxTe ternary compounds in certain optoelectronic/integrated-optical device applications.
Suppression of boron penetration in BF2+-implanted poly-Si gate
(1996-12-01)
Chao, TS
;
Chu, CH
;
Wang, CF
;
Ho, KJ
;
Lei, TF
In this paper, a comprehensive study of gate engineering to suppress the penetration of boron in p-type metaloxide-semiconductor held-effect transistor (MOSFET) with the p(+)-poly-Si-gate is reported. Four types of poly-Si gate structure, two types of gate dielectrics were investigated to suppress the boron penetration. Among the different gate structures, the stacked amorphous silicon structure was found to be the most effective way to retard the boron penetration. N2O oxide exhibited a better retarding of the boron diffusion as compared with the O-2 oxide. It was found that a combination of stacked amorphous silicon with N2O oxide is the most effective way to suppress the boron penetration. Thermal stability, oxide integrity, and D-it of this sample are superior to all the other samples.
One- and two-electron transitions in slow C5+-He collisions: Total and angle-differential cross sections and coherence parameters
(1996-12-01)
Fritsch, W
;
Lin, CD
;
物理研究所
;
Institute of Physics
Transitions of one or two electrons in C5+-He collisions are studied within the semiclassical close-coupling description of atomic collisions, at impact energies of 1-35 keV/u. Angle-integrated cross sections are determined for single-transfer, double-transfer, and transfer-excitation channels. For single capture to 3p states and for two final states in the two-electron transfer channel, angle-differential cross sections are derived and a number of coherence parameters that depend on the quantum-mechanical phases are calculated. The results are compared with recent data on angle-differential two-electron transfer and with results from an earlier theoretical study.
An impact control scheme inspired by human reflex
(1996-12-01)
Weng, SW
;
Young, KY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this article, we propose a control scheme to deal with unexpected impacts. Impact is inevitable when robot manipulators interact with the environment. Undesirable impacts may induce large interaction forces harmful to robot manipulators and the environment. Impacts may also excite oscillations, and even result in manipulator instability. When unexpected impacts occur, a very limited amount of time is available for control. Thus, a reflex mechanism, which emulates the functioning of human reflexes, is included in the proposed scheme. Human reflex is a kind of human action that requires no conscious effort; consequently, it responds to external stimuli without much delay. Simulations are performed to verify the effectiveness of the proposed scheme under a wide range of environmental variations and impact velocities. (C) 1996 John Wiley & Sons, Inc.
Growth and characterization of Cd1-x-yZnxMnyTe crystals
(1996-12-01)
Chou, WC
;
Chen, FR
;
Chiang, TY
;
Shin, HY
;
Sun, CY
The Cd1-x-yZnxMnyTe crystals, having potential in the development of magnetic field sensitive devices, were grown by the temperature gradient solution method at 940 degrees C. All crystals were p-type with resistivity of 10(7) Omega . cm. They have novel magneto-optical properties, and could be substitutes for the Cd1-xZnxTe ternary compounds in certain optoelectronic/integrated-optical device applications.
A high-performance thin-film transistor with a vertical offset structure
(1996-12-01)
Chang, CY
;
Lin, CW
;
交大名義發表
;
電子工程學系及電子研究所
;
National Chiao Tung University
In this study, we propose a novel device structure combined with conventional hydrogenated amorphous silicon (a-Si:H) for the source and drain regions and microcrystalline silicon (mu c-Si:H) for the channel region to obtain a high-performance thin-film transistor (TFT), This is a vertical a-Si:H offset structure used to suppress OFF-state current to a small value which is comparable to the conventional a-Si:H TFT's with a much higher drivability. The fabrication process is simple, low temperature (less than or equal to 300 degrees C), and low cost, with a potential for high reliability.
In situ compatibility of polystyrene and liquid crystalline polymer blends
(1996-12-01)
Chiou, YP
;
Chang, DY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The styrene-glycidyl methacrylate (SG) copolymer can be used to compatibilize the immiscible and incompatible blends between polystyrene (PS) and liquid crystalline polymer (LCP) copolyester. The epoxy functional groups present in the SG copolymer can react with the carboxylic and/or the hydroxyl terminal groups of the LCP at interface to form the SG-g-LCP copolymer during melt processing. This in situ-formed graft copolymer tends to reside along the interface to reduce the interfacial tension in the melt state and to increase the interphase adhesion in the solid state. However, the compatibilized PS/LCP blends reduce the number of LCP fibrils formed and have a tendency to form droplet LCP domains. The overall mechanical properties, stiffness and toughness of the blends improved after compatibilization, but the extent of the improvement is not very significant. It appears that the gain from the adhesion enhancement is more than offset by the loss due to the reduction in LCP fibril formation. The ethyl triphenylsphosponium bromide catalyst can further improve the compatibility of the blends by increasing the rate of the graft reaction. Copyright (C) 1996 Elsevier Science Ltd.
Minimum mean-squared error estimation of stochastic processes by mutual entropy
(1996-12-01)
Wu, BF
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
;
Institute of Electrical and Control Engineering
An upper bound on the con elation coefficients in terms of the mutual entropy is developed for a general estimation problem. This upper bound may be reached by means of a nonlinear transformation such that, after the transformation, the processes are jointly gaussian. In order to minimize globally the mean-squared estimation error, we use an approach based on the Calculus of Variations to find the vector nonlinear functions whose elements turn out to be the eigenfunctions of two vector integral operators that could be concurrently solved from two vector integral equations. The relationship between the minimum mean-squared error (MMSE) and the mutual entropy is discussed. Since the MMSE error is linear with the number of experimental data, we consider the mutual entropy rate, which is the average of the mutual entropy, to evaluate she average MMSE error. This rate is related to the average MMSE error and it is show that a mutual entropy rate of 0.5 is the critical threshold for the MMSE problem. Moreover, given a correlation coefficient, ergodic and jointly gaussian signals can be generated easily by computer. An approach to create these signals is also presented.
A simple fabrication process of T-shaped gates using a deep-UV/electron-beam/deep-UV tri-layer resist system and electron-beam lithography
(1996-12-01)
Lai, YL
;
Chang, EY
;
Chang, CY
;
Yang, HPD
;
Nakamura, K
A new fabrication process of T-shaped gates has been developed using a deep-UV/electron-beam/deep-UV (DUV/EB/DUV) tri-layer resist system and electron-beam lithography for the first time. The simple process accomplished a submicron T-shaped gate by a single exposure and a single development step. The narrow/wide/narrow opening of the DUV/EB/DUV resist structure can be accurately controlled by the e-beam dosage and the development conditions. Differences in the sensitivities of the DUV resist and the EB resist were investigated. Due to the lower sensitivity of the adopted DUV resist to the electron beam, the smaller opening of the DUV resist layer was obtained. The higher sensitivity of the EB resist resulted in a wider opening in the middle resist layer. A 0.15-mu m-gate-length T-shaped gate can be easily formed by the short-process-time and low-production-cost hybrid DUV/EB/DUV resist approach.
Magnetic force acting on a magnetic dipole over a superconducting thin film
(1996-12-01)
Wei, JC
;
Chen, JL
;
Horng, L
;
Yang, TJ
;
電子物理學系
The magnetostatic interaction energy and corresponding magnetic force acting on a magnetic point dipole placed above a type-II thin superconducting film in the mixed state with a single vortex are calculated using electromagnetics coupled with the London theory of superconductivity. If a vortex is trapped by a circular defect of radius b much less than Lambda, the magnetic forces, caused by the vortex, differ from the results of free from defect pinning by the factor (1 - b/Lambda), where Lambda is the effective penetration depth. The possibility of formation of the vortex in the thin film only in the field of the magnetic point dipole is investigated. The critical position of the dipole for creating the first vortex under the electromagnetic pinning of a circular defect and that position in the absence of defect pinning are obtained for comparison. In particular, in the limit of a/Lambda much greater than 1, where a is the separation between the dipole and the thin film, the only difference between two results is in the cutoff length, i.e., in the case of a circular defect the only difference in the critical position calculation is the cutoff at radius b rather than at coherence length xi. The pinning force of a single vortex by a circular defect is also calculated. Further, we investigate the conditions of the vortex creation for various cases (including the first, second, and third vortices) for a free of pinning center in the examining region. It is found that the creation of a new single vortex in the thin film causes an abrupt change in vertical levitation force: the force changed discontinuously.
Preparation and characterization of PLZT thin films by sol-gel processing
(1996-12-01)
Kuo, YF
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effect of acid catalysts on the sol-gel preparation of ferroelectric lead lanthanum zirconium titanate (PLZT) thin films was studied. High quality thin films were successfully produced by using suitable amounts of the drying control chemical additive formamide and also catalyst acids during the sol-gel processing followed by various annealing conditions. The dielectric constants of the PLZT (8/65/35) thin films produced in this study varied between 540 (100 kHz) for a film annealed at 600 degrees C for 30 mins to a maximum 870 degrees C (1 kHz), 700 (100 kHz) for a film annealed at 650 degrees C for 20 mins.
Mobility management for cellular telephony networks
(1996-12-01)
Lin, YB
;
資訊工程學系
;
Department of Computer Science
Cellular telephony provides voice and data services to mobile users. To deliver these services, the cellular network can track the locations of the users, and can allow user movement during the conversations. It achieves these capabilities through small-scale (handoff) and large-scale (roaming) mobility management. In this tutorial, the authors describe mobility management in cellular networks, including the details of different handoff schemes, location-tracking schemes, and call-delivery procedures.