THEORETICAL INVESTIGATION OF COLLISION ENERGY EFFECT ON REACTION O(?) BARIUM WITH METHYL BROMIDE

The reac dynamics on Ba+BrCH_3→BaBr+CH_3 has been investigated in the first proposed potential energy surface of the generalized LEPS type,using the quasiclassical trajectory method.In simulation of the conditions in molecular beam experiments,the results of the present study show significant effect of the reagent collision energy on the dynamics of the reaction,and are in good agreement with the experimental ones.

Advances in polymer-stabilized Au nano-cluster catalysis : Interplay of theoretical calculations and experiments

Polymer‐stabilized Au nano clusters （NCs） with mean diameters of 2–10 nm exhibit unique catalytic properties. Several studies have shown that the key factors affecting the catalytic activity of poly‐mer‐stabilized Au NCs are control of the Au NC size, appropriate selection of polymers and optimi‐zation of the reaction conditions. This is because polymer‐stabilized Au NCs exhibit a clear size effect in several catalytic reactions, and the catalytic activity differs with the type of polymer used and the reaction conditions. In order to elucidate the reason underlying the catalytic activity of the polymer‐stabilized Au NCs, much attention is being devoted to the interplay of theoretical calcula‐tions and experiments in catalysis by polymer stabilized Au NCs. The present article mainly summa‐rizes our progress in understanding this interplay in polymer‐stabilized Au NC catalysis.

Impact of multipath effects on theoretical accuracy of TOA-based indoor VLC positioning system

This paper discusses the time-of-arrival(TOA) based indoor visible light communication(VLC) positioning system in a non-line-of-sight environment. The propagation delay is assumed to be gamma distributed. The generalized Cramer–Rao lower bound for multipath propagation is derived as the theoretical accuracy limitation. The performance of the positioning system is affected by the shape parameter and the scale parameter of gamma distribution.The influences on positioning accuracy of multipath effects are analyzed through discussing the physical meaning of the gamma distribution parameters. It is concluded that the lower bound of positioning accuracy is attained when variance of the non-line-of-sight propagation-induced path lengths is zero. The simulation result provesthat the theoretical positioning accuracy is in the order of centimeters with the given scenario.

Effective electromechanical properties of cellular piezoelectret:A review

Due to the large quasi-piezoelectric d33 coefficient in the film thickness direction, cellular piezoelectret has emerged as a new kind of compliant electromechanical transducer materials. The macroscopic piezoelectric effect of cellular piezoelectret is closely related to the void microstructures as well as the material constants of host polymer. Complex void microstmctures are usually encountered in the optimum design of cellular piezoelectret polymer film with ad- vanced piezoelectric properties. Analysis of the effective electromechanical properties is generally needed. This article presents an overview of the recent progress on theoretical models and numerical simulation for the effective electromechanical properties of cellular piezoelectret. Emphasis is placed on our own works of cellular piezoelectret published in past several years.

THEORETICAL STUDY ON EFFECT OF QINGHAI-XIZANG PLATEAU UPON COLD SURGE

Starting from the linear shallow-water wave equations including in themselves the effect of a large-scale orograpny, two types of gravity wave solutions are derived on the assumption that the Qinghai-Xizang Plateau serves as an orography in question inclined from west to east at the same slope. One type contains two solutions of high-frequency inertia-gravitational waves and the other solution of low-frequency topography-excited gravity waves, bearing some similarity to Kelvin mode. Both types are similar, respectively, to the gravity waves of the front of the cold surge during the rapid southward advance, and to the strong velocity center of the surge when it propagates southward slowly along the east brim of the Plateau, as shown by the numerical study. Results indicate that the low-frequency wave vanishes whereas its counterpart remains especially in the absence of the orography. In addition, we find that the propagation of the gravity-wave rays is in the form of a trochoid equation, a result in good agreement with the curved path of the strong velocity center going down the east fringe of the Plateau as shown by the numerical study. And probably a waveguide tube of topographic gravity mode is present in the coastwise area downstream of the orography.

Theoretical studies on the substitution effect of fluorine on ethylene

The substitution effect of fluorine on ethylene is investigated by means of studying the properties of the charge distribution at the bond critical points with the theory of atoms in molecules.It is found that fluorine atom acts not only as a σ electron acceptor,but also as a π electron donor,and these double effects are reflected in the quantity of ellipticity,Lap- lacian and the charge density of charge distribution at the bond critical points.For C—C,C—F bonds,the major axis of elliptical contours is perpendicular to the molecular plane,but for C—H bond,it is parallel to the molecular plane.Other effects originating from the substi- tution have also been discussed.

New Central Axis for Guangzhou City

This paper summarizes the entire construction process of Guangzhou's new central axis, including planning, design, and decisionmaking. The relationships among master plan, action plan and urban design are discussed in a practical case. And design principles which should be followed and factors relevant to desirable effect in the urban design for key areas are also explored.