Browsing by Author "CHEN, WJ"

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ADDITION POLYMERIZATION IN A NEMATIC MEDIUM - EFFECTS OF AN ANISOTROPIC SOLVENT IN A KINETIC GELATION MODEL
(1995-10-01)
CHEN, WJ
;
CHEN, SH
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光電工程研究所
;
Institute of EO Enginerring
A kinetic gelation model with rodlike anisotropic solvent is used to study the addition polymerization in a nematic medium. The structure of the polymer network is extended in the direction of the director of anisotropic solvent, since the order parameter of the anisotropic solvent is not zero. Finite-size scalings show that there is no change in the universal behavior of the sol-gel transition in the presence of the anisotropic solvent.
DIGITAL TANLOCK LOOP FOR TRACKING PI/4-DQPSK SIGNALS IN DIGITAL CELLULAR RADIO
(1994-08-01)
WEI, CH
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CHEN, WJ
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電控工程研究所
;
電信研究中心
;
Institute of Electrical and Control Engineering
A digital tanlock loop (DTL) is a nonuniform-sampling digital phase-locked loop (DPLL) whose phase error detector, using the tan-1[.] function with in-phase and quadrature samples of incoming signal, has a linear characteristic with a period of 2pi. In this paper, we study the application of an N-phase DTL in digital cellular radio with pi/4-DQPSK modulation. The performance degradation due to fading effect is investigated in terms of bit error rate and steady state phase error variance by computer simulation. It is shown that, in the digital cellular radio system, the performances on both bit error rate and phase error variance using DTL are far better than that using the traditional digital N-phase I-Q loop.
KINETICS OF POLYMERIZATION-INDUCED PHASE-SEPARATION
(1995-11-15)
CHEN, SH
;
CHEN, WJ
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交大名義發表
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光電工程學系
;
National Chiao Tung University
We have stud led a Monte Carlo computer simulation on a mo del for polymerization-induced phase separation. The time evolution of the structure factor are found to preserve the scaling law obtained from the thermally quenched phase separation, A novel peaking behavior of the mean cluster size of solvent molecules has been found and can be explained by the irreversibility of polymerization. The simulation results are in agreement with experimental observations.
SCALING BEHAVIORS OF PINNING IN POLYMERIZATION-INDUCED PHASE-SEPARATION
(1995-11-01)
CHEN, WJ
;
CHEN, SH
;
光電工程研究所
;
Institute of EO Enginerring
A dynamical model for the phase separation induced by polymerization has been developed and studied by Monte Carlo simulations. The model shows a pinning of the structure factor and exhibits scaling relations and exponents. We propose a theoretical argument to predict the pinning exponents, which are in agreement with simulation values. For a different concentration ratio of bifunctional to tetrafunctional monomers, the simulation results are also found to be consistent with the theoretical predictions.