机器视觉在激光干涉测量d31中的应用

提出一种应用机器视觉技术的激光干涉法, 可以研究压电材料的逆压电系数. 在传统干涉测量法中引入机器视觉实现干涉图像灰度最佳估计, 使用数字图像处理技术, 一方面应用降噪算法有效去除激光干涉图样中的噪声, 从而确定激光干涉场的光强分布, 另一方面将干涉图样的明暗变化进一步转化为可量度的灰度变化以提高测量分辨力. 通过合理设计算法, 该方法中对位移的理论测量分辨力可以提高达一个数量级, 为干涉光波长的1/1024, 因此在逆压电系数d₃₁ 的实验测量中可以有效提高分辨力. 关键词： 机器视觉 逆压电系数 双光束干涉 数字图像处理     

A universal kinetic equation for characterising the fractal nature of delignification of lignocellulosic materials

A kinetic model was developed, based on the power law of growth and Avrami’s nuclei growth concepts, to describe the heterogeneous nature of pulping kinetics, taking into account the effects of chemical concentration and temperature. The general form of the kinetic equation is first order with a time-dependent rate coefficient. The model was statistically tested using published data obtained from delignification of lignocellulosic materials (hemp woody core, giant reed, wheat straw, cottonwood, bamboo and flax fibres). The activation energies of the delignification range from 71 to 136 kJ/mol. The p-values obtained from the regression analysis are significantly small indicating that all the estimates of the model parameters were significant with very high levels of confidence. The correlation coefficients R ² for these models range from 0.76 to 0.98.     

Synthesis of tetraarylthiophenes by regioselective Suzuki cross-coupling reactions of tetrabromothiophene

Tetraarylthiophenes were prepared by regioselective Suzuki cross-coupling reactions of tetrabromothiophene.     

Treatment of vortex sheets for the transonic full-potential equation

This paper summarizes a combined analytical-computational technique which models vortex sheets in transonic potential-flow methods. In this approach, the inviscid nature of discontinuities across vortex sheets is preserved by employing the step function to remove singularities at these surfaces. The location and strength of the vortex sheets are determined by satisfying the flow-tangency boundary condition and the vorticity transport equation. The theory is formulated for the general three-dimensional case, but its application is confined to the problem of computing slipstreams behind propellers with free-vortex blading in axisymmetric flows.     

同时发射和接收纵波和横波的压电复合材料换能器

通过控制压电复合材料中压电相的分布形式，本文具有在百度模振动的１－３型压电复合材料和具有扭转模振动的拼接２－２型压电复合材料组合在一起，构成一种混俣模式压电材料，并测试了这种压电材料晶片的性能参数，使用这种晶片作的换能器可以根据使用者的要求，单独产生纵波或横波，也可同时产生这两种波。     

Cohaerins C-F, four azaphilones from the xylariaceous fungus Annulohypoxylon cohaerens

Four azaphilones named cohaerins C-F, along with 4,5,4′,5′-tetrahydroxy-1,1′-binaphthyl were isolated from the methanolic extract of the stromata of Annulohypoxylon cohaerens (Ascomycetes, Xylariaceae). Cohaerins C-E constitute typical azaphilones, bearing a γ-lactone ring, while cohaerin F has an unprecedented carbon skeleton, lacking the lactone ring of the azaphilones and with an aliphatic side chain being attached directly to the azaphilone backbone by a C-C bond. Their structures were determined by 2D NMR, IR, UV, and CD spectroscopy. They showed moderate inhibitory activity of nitric oxide production in RAW cells, and strong and nonselective antimicrobial effects.     

非掺杂GaN的黄光发射模型确定

提出了一种新的光谱———吸收归一化光致发光激发谱,并用这种光谱研究了非掺杂GaN的黄光发射.实验上首次直接测量出了黄光发射的初始态的共振吸收峰位,从而解决了长期争论的有关黄光发射的发光模型问题 关键词： GaN薄膜 黄光发射 吸收归一化光致发光激发谱     

Nontrivial periodicity in discrete delay models of population growth

In this paper, we will study the periodicity in discrete model An+1=λAn+F(An−m) of population growth, where the delay m is large enough and the nonlinearity F is unimodal function. Actually, we prove that there is a slowly oscillated periodic solution. Our method is Browder nonextremal fixed point theorem.     

关于非线性Molodensky问题的解在H^2＋ε中的唯一性

本文研究了物理大地测量中的非线性Molodensky问题.在Holder空间H~(2+ε)中得到了非线性Molodensky问题的解具有局部唯一性,将Hormander关于存在性与唯一性的结果统一在H~(2+ε)中.     

A modified trust region method with Beale’s PCG technique for optimization

It is well-known that the conjugate gradient method is widely used for solving large scale optimization problems. In this paper a modified trust-region method with Beale’s Preconditioned Conjugate Gradient (BPCG) technique is developed for solving unconstrained optimization problems. The modified version adopts an adaptive rule and retains some useful information when an unsuccessful iteration occurs, and therefore improves the efficiency of the method. The behavior and the convergence properties are discussed. Some numerical experiments are reported. This work was partially supported by Grant of the National Natural Science Foundation of China, Grant: 20040319003 of the Doctoral Site of the Education Ministry of China, and SRG: 7001428 of City University of Hong Kong.