型钢混凝土结构构件的研究

型钢混凝土指钢筋混凝土构件内含型钢的结构(SRC),在我国的应用和研究从上世纪八十年代开始。本文对目前的型钢混凝土设计理论、计算方法、试验研究的现状进行了整体的综述,简要介绍了设计理论中的容许应力计算法、一般极限状态计算法和概率极限状态设计法、正常使用极限状态计算中的变形、裂缝、刚度计算方法,以及和实验的对比结果,最后简要介绍了一个配螺旋箍SRC短梁试验。     

A 3‐D unconditionally stable precise integration time domain method for the numerical solutions of Maxwell's equations in circular cylindrical coordinates

An unconditionally stable precise integration time‐domain method is extended to 3‐D circular cylindrical coordinates to solve Maxwell's equations. In contrast with the cylindrical finite‐difference time‐domain method, not only can it remove the stability condition restraint, but also make the numerical dispersion independent of the time‐step size. Numerical results are presented to demonstrate the effectiveness of this method. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Three‐dimensional direct simulation of a droplet impacting onto a solid sphere with low‐impact energy

In this paper, a numerical model is developed for direct simulation of droplet impinging onto a spherical surface on a fixed Eulerian mesh. The model couples the level‐set method and the interfacial cell immersed boundary method to the single‐fluid formulation of the Navier–Stokes equations which are solved by a finite‐volume projection technique. Moving contact lines are modelled here with a simple static contact angle model. The model is shown to converge, and to agree with previous work in the literature. The model is then applied to investigate the impact behaviour of a droplet onto solid sphere of different diameters at low Weber number and low Reynolds number. The simulation results show that the droplet used in present study seems to deposit on different spherical surfaces through oscillating. The simulated results also suggest that the impacted‐sphere size has a significant effect on the impact dynamics of the droplet. A local breakage phenomenon may be found in the centre of the droplet collision with a smaller sphere during the first recoiling stage. A regime map is then established to provide quantitative analysis for the breakage mode of the current impacting process.     

Spectroscopic analysis of iron-oxide minerals in aerosol particles from northern China

Diffuse reflectance spectrometry was used to study iron-oxide minerals and to investigate the reflectance characteristics of eolian dust collected during the spring of 2001 and 2002 on bulk filters from three sites in northern China. The first derivatives of the reflectance spectra were consistent with signals from two iron-oxide minerals, hematite and goethite, at wavelengths of 565 and 435 nm, respectively, and these values varied with the iron concentrations in the samples. The percent reflectances for the yellow, orange and red bands increased with the iron concentrations and with the first derivative values representing hematite and goethite while those for violet, blue and green bands decreased correspondingly. The results show that iron-oxide minerals play an important role in determining the aerosol particles' color and reflectance properties. Moreover, the relative amounts of the two iron-oxides in Asian dust apparently differ from those in African dust, suggesting that the iron-oxides may provide another tool for tracing the origins of eolian dust on a global scale.     

基于遗传算法的分形图像压缩

数字图像压缩日益引起人们的重视。利用图像中的局部分形特征进行压缩，取得了好的效果，但其虚拟码书的搜索匹配，计算量十分庞大。本文提出将遗传算法应用于分形图像压缩，大大降低了压缩编码的复杂性，与穷尽搜索匹配的算法相比，搜索范围在Ｏ（１０＾－２）量级，解码图像的峰值信噪比得到很好地保持，实验结果证实了算法的有效性。