Browsing by Issue Date, starting with "1999-05-08"

Now showing 1 - 20 of 80590

Chain dynamics of concentrated polystyrene solutions studied by depolarized photon-correlation and viscosity measurements
(1999-05-08)
Lai, CS
;
Juang, JH
;
Lin, YH
;
應用化學系
;
Department of Applied Chemistry
Concentrated solutions of nearly monodisperse polystyrene samples in cyclohexane in the theta condition and in the entanglement-free region have been studied by means of the depolarized photon-correlation spectroscopy and viscosity measurements. It is shown that the viscoelastic behavior of the studied systems is described by the Rouse theory and that in agreement with the theoretical analysis the main polymer dynamic process probed by the depolarized Rayleigh scattering is basically the reorientational motion associated with a Rouse segment of the polymer chain, whose relaxation is independent of the scattering angle and the molecular weight. In addition to the main dynamic process, the tail region of a very fast process associated with the sub-Rouse-segmental motions can be observed, whose existence is expected from the theoretical analysis. (C) 1999 American Institute of Physics. [S0021-9606(99)51817-5].
B -> eta ' X-s in the standard model
(1999-05-13)
He, XG
;
Lin, GL
;
物理研究所
;
Institute of Physics
We study B --> eta'X-s within the framework of the Standard Model. Several mechanisms such as b --> eta'sg through the QCD anomaly, and b --> eta's and B --> eta's (q) over bar arising from four-quark operators are treated simultaneously. Using QCD equations of motion, we relate the effective Hamiltonian for the first mechanism to that for the latter two. By incorporating next-to-leading-logarithmic(NLL) contributions, the first mechanism is shown to give a significant branching ratio for B --> eta'X-s, while the other two mechanisms account for about 15% of the experimental value. The Standard Model prediction for B --> eta'X-s is consistent with the CLEO data. (C) 1999 Elsevier Science B.V. All rights reserved.
Common modulus and chosen-message attacks on public-key schemes with linear recurrence relations
(1999-05-14)
Tzeng, WG
;
資訊工程學系
;
Department of Computer Science
We consider the linear recurrence relation V-t(x) = Sigma(i=1)(m) (a(i)x + b(i))Vt-i(x) + cx + f where m greater than or equal to 1, a(i) and b(i), 1 less than or equal to i less than or equal to m, are integers. The RSA and LUC schemes can be defined by this relation. In this paper we show that if the linear recurrence relation has some properties, the public-key scheme based on it cannot withstand the common modulus and chosen-message attacks, no matter what the order in is and what the parameters for a(i) and b(i), 1 less than or equal to i less than or equal to m, are. This implies that the LUC cryptosystem cannot withstand the common modulus attack and the LUC digital signature scheme cannot withstand the chosen-message attack. (C) 1999 Elsevier Science B.V. All rights reserved.
Magnitude of effect of reaction parameters on 2-chlorophenol decomposition by ultrasonic process
(1999-05-14)
Lin, JG
;
Ma, YS
;
環境工程研究所
;
Institute of Environmental Engineering
In the present work, decomposition of o-chlorophenol (2-cp) was carried out using an ultrasonic process. The extent of 2-cp decomposition depends on several parameters such as ultrasound wave energy (ultrasonic amplitude), addition of hydrogen peroxide (H2O2), pH value (H+ concentration), ionic strength, and initial concentration of 2-cp. The experimental results showed that the decomposition of 2-cp was affected by the various reaction conditions. The profiles of 2-cp decomposition fitted well with the first-order kinetic equation. A linear relationship was obtained between the rate constants of 2-cp decomposition and the varying reaction parameters. The magnitude of effect of reaction parameters such as ultrasonic amplitude, H+ concentration, ionic strength, H2O2 and 2-cp initial concentration on 2-cp decomposition were 0.60, 0,48, 0.19, 0.09 and -0.06, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.
子宮是詩誕生的自然也是詩
(1999-05-15)
管管
Spin-dependent tunneling in double-barrier semiconductor heterostructures
(1999-05-15)
Voskoboynikov, A
;
Liu, SS
;
Lee, CP
;
交大名義發表
;
National Chiao Tung University
Spin-dependent tunneling in symmetric and asymmetric double-barrier semiconductor heterostructures is studied. The effective one-band Hamiltonian approximation and spin-dependent boundary conditions approach an used for a theoretical investigation of the influence of electron spin on the tunneling probability. It is shown that spin-orbit splitting in the dispersion relation for electrons in A(III)B(V) semiconductors can provide the dependence of the tunneling transmission probability on the electron-spin polarization without additional magnetic field. The dependence can be controlled by an external electric field, and may be significant for realistic models of double-barrier semiconductor heterostructures. [S0163-1829(99)02320-6].
The spatially-distributed recording of the composite filter using the pixelated liquid crystal display
(1999-05-15)
Tsai, J
;
Lin, SH
;
Hsieh, TC
;
Hsu, K
;
電子物理學系
A new recording method using a liquid crystal display (LCD) as an input device to synthesize a composite filter is presented. The filter in the optical correlator makes use of the multiple diffraction orders from the pixelated structure of the LCD panel. During the recording stage, each training pattern is sequentially recorded as a sub-filter at different diffracted order by holographic technology. After that, an input pattern could be simultaneously processed with all sub-filters in parallel such that the composite filter can be achieved. This recording method with spatial distribution could avoid the low efficiency of the conventional multi-exposure. The simulations and experimental results show that this system can perform invariant correlation as a composite filter. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
七十當老爸
(1999-05-15)
蘇嫻雅
Elimination of dynamic instabilities in the plus c-face incident photorefractive BaTiO3 mutually pumped phase conjugator
(1999-05-15)
Chang, CC
;
Chen, TC
;
Tang, LC
;
Yau, HF
;
光電工程學系
Experimental observations of the dynamic instabilities in the +c-face incident mutually pumped phase conjugator (MPPC) of a BaTiO3 crystal are reported for the first time. Experiments show that it is possible to stabilize the phase-conjugate output by choosing a proper geometry formed from the crystal and two incident beams. By choosing the proper geometry the essential configuration of the MPPC attained is a "kite" rather than a "fish head". Data also indicate that the phase-conjugate output can reach a very steady state with a high value (similar to 32%) and is insensitive to angular and positional variations.
給小孩起個好名字看著順眼 ,叫著舒服
(1999-05-22)
管管
Robust SBR method for adverse Mandarin speech recognition
(1999-05-27)
Hong, WT
;
Chen, SH
;
電信工程研究所
;
Institute of Communications Engineering
An RNN-based robust signal bias removal (RRSBR) method is proposed for improving both the recognition performance and the computational efficiency of the SBR method fbr adverse Mandarin speech recognition. It differs from the SBR method in using three broad-class sub-codebooks to encode the feature vector of each frame and combining the three encoding residuals to form the frame-level signal bias estimate. A novel approach involving softly combining the board-class encoding residuals using dynamic weighting functions generated by an RNN is applied. Experimental results show that the RRSBR method significantly outperforms the SBR method.
Foundation of direct perturbation method for dark solitons
(1999-05-28)
Huang, NN
;
Chi, S
;
Chen, XJ
;
光電工程學系
;
Department of Photonics
The foundation of the direct perturbation theory for solitons is a complete set of the squared Jest functions. With a suitable definition of the adjoint functions and inner products which yields orthogonal relations, the expansion of the the unity is obtained and the completeness is shown by a generalized Marchenko equation. The direct perturbation method for dark solitons is generalized to the multi-soliton case.
Two design patterns for data-parallel computation based on master-slave model
(1999-05-28)
Huang, KC
;
Wang, FJ
;
Tsai, JH
;
資訊工程學系
;
Department of Computer Science
This paper presents two design patterns useful for parallel computations of master-slave model. These patterns are concerned with task management and parallel and distributed data structures. They can be used to help addressing the issues of data partition and mapping, dynamic task allocation and management in parallel programming with the benefit of less programming efforts and better program structures. The patterns are described in object-oriented notation, accompanied with illustrative examples in C++. We also provide our experience in applying these patterns to two scientific simulation programs simulating Ising model and plasma physics respectively. Since master-slave model is a widely used parallel programming paradigm, the design patterns presented in this paper have large potential application in parallel computations. (C) 1999 Elsevier Science B.V. All rights reserved.
An efficient algorithm for computing quantiles of the noncentral chi-squared distribution (vol 29, pg 253, 1999)
(1999-05-28)
Ding, CG
;
管理科學系
;
Department of Management Science
大家都愛騙子
(1999-05-29)
管管
The application of laser metrology and resonant optical cavity techniques to the measurement of G
(1999-06-01)
Ni, WT
;
Liu, DK
;
Liu, TT
;
Mei, HH
;
Pan, SS
Our goal is to measure the gravitational constant G to within 1-10 ppm using a high-finesse Fabry-Perot optical cavity. The two high-reflectivity mirrors of the Fabry-Perot cavity will be suspended separately by two nearly identical simple pendulums of length about 1 m. For the source of attraction, we have built a rotating mass source with 12 lead bricks (each brick is of mass 11.5 kg) on each of two opposite sides of a rotating table. The period of rotation can be adjusted. We normally use a rotation period of 200 s. For this rotating mass, the relative equilibrium displacement of the two mirrors is over 10 nm and we are working for a preliminary measurement of this distance to one part in 10(4). Auxiliary quantities such as the positions of the test mass and the positions of Fabry-Perot cavity mirrors can be monitored using real-time laser metrology. The stability and real-time monitoring of the pendulums, building stability, and the compensation or averaging of mass inhomogeneity need special considerations.
Synthesis and characterization of liquid crystalline multiblock copolyesters of oxybenzoate and ethylene terephthalate
(1999-06-01)
Ho, JC
;
Lin, YS
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Multiblock copoly(oxybenzoate-p-ethylene terephthalate) (POB-PET) was synthesized by a direct reaction of poly(hydroxybenzoic acid) (PHBA), acetoxybenzoic acid and poly(ethylene terephthalate). The synthesized multiblock POB-PET becomes more blocky and less soluble in the mixed solvent of trifluoroacetic acid and chloroform when the degree of polymerization of PHBA used in the synthesis is higher as evidenced in the solid-state and liquid-state nuclear magnetic resonance study. The thermal curves displayed by the synthesized multiblock 20/80 and 40/60 POB-PET contained distinctive contributions from both PET blocks and POB blocks in the copolymers when the degree of polymerization of PHBA used in the synthesis is seven. Only 20 mol% of POB is needed to form liquid crystalline phase in these multiblock POB-PET as opposed to a minimum of 40 mol% of POB is required to form liquid crystalline phases for random POB-PET. (C) 1999 Elsevier Science Ltd. All rights reserved.
Obstacle avoidance for autonomous land vehicle navigation in indoor environments by quadratic classifier
(1999-06-01)
Ku, CH
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A vision-based approach to obstacle avoidance for autonomous land vehicle (ALV) navigation in indoor environments is proposed. The approach is based on the use of a pattern recognition scheme, the quadratic classifier, to find collision-free paths in unknown indoor corridor environments. Obstacles treated in this study include the walls of the corridor and the objects that appear in the way of ALV navigation in the corridor. Detected obstacles as well as the two sides of the ALV body are considered as patterns, A systematic method for separating these patterns into two classes is proposed. The two pattern classes are used as the input data to design a quadratic classifier, Finally, the two-dimensional decision boundary of the classifier, which goes through the middle point between the two front vehicle a heels, is taken as a local collision-free path, This approach is implemented on a real ALV and successful navigations confirm the feasibility of the approach.
A 2-V, 1.8-GHz BJT phase-locked loop
(1999-06-01)
Chen, WZ
;
Wu, JT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper describes the design of a bipolar junction transistor phase-locked loop (PLL) for Sigma Delta fractional-N frequency-synthesis applications. Implemented in a 0.8-mu m BICMOS technology, the PLL can operate up to 1.8 GHz while consuming 225 mW of power from a single -2-V supply. The entire LC-tuned negative-resistance variable-frequency oscillator is integrated on the same chip. A differential low-voltage current-mode logic circuit configuration is used in most of the PLL's functional blocks to minimize phase jitter and achieve low-voltage operation. The multimodulus frequency divider is designed to support multibit digital modulation. The new phase and frequency detector and loop filter contain only npn transistors and resistors and thus achieve excellent resolution in phase comparison. When phase locked to a 53.4-MHz reference clock, the measured phase noise of the 1.6-GHz output is -91 dBc/Hz at 10-kHz offset, The frequency switching time from 1.677 to 1.797 GHz is 150 mu s. Die size is 4300 x 4000 mu m(2), including the passive loop filter.
Application of selective liquid-phase deposition to fabricate contact holes without plasma damage
(1999-06-01)
Yeh, CF
;
Liu, CH
;
Su, JL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work develops an alternative method, selective liquid-phase deposition (S-LPD), to fabricate contact holes instead of reactive ion etching. In preliminary experiments, deep n(+)/p junction diodes with contact holes prepared by S-LPD exhibit much less reverse current, unity ideality factor, larger forward current, lower contact resistance, and higher thermal stability than those prepared by reactive ion etching. Further superiority of plasma damage-free near-surface regions is also investigated using Schottky and ultrashallow junction diodes. Experimental results indicate that S-LPD can be applied to the submicron contact-hole process. The data after reverse bias temperature stress reveals the satisfactory reliability of S-LPD contact holes. This work demonstrates that the S-LPD technology is a highly promising means of replacing reactive ion etching processes to form submicron contact holes as reliably as those by wet-etching. (C) 1999 The Electrochemical Society. S0013-4651(98)08-119-1. All rights reserved.