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Numerical Simulations on the Formation of Speckles in Nanofluids Illuminated by a TEM00 Laser Beam 下载免费PDF全文
On the basis of a Rayleigh scattering model for a single nanoparticle illuminated by a TEMoo laser beam, we theoretically and numerically study the speckle formation when nanofluids are illuminated by a TEMoo laser beam. The results show that the laser speckles possess a Gaussian distribution, which are in agreement with the experimental results. The results may be useful for using a laser speckle velocimetry to determine the velocitiies of nanoparticles in nanofluids. 相似文献
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The ultraviolet (UV) light excited fluorescence spectra of ethanol-water mixture with different concentrations are investigated by derivative fluorimetry. It is found that there are 8 types of luminescent cluster molecules, formed by ethanol and water molecules in different ways, existing in the solution. The peak wavelengths of all these clusters' fluorescence spectra are measured and their contents are obtained by measuring the peak values in the second derivative fluorescence spectra. The spectra corresponding to the 8 types of clusters are obtained by Gaussian decomposition. It is found that two kinds of cluster molecules whose peak wavelengths are 330 and 345 nm have an optimal excitation wavelength located at (236 4- 3) nm. This research contributes to the study of ethanol-water cluster structures and their physical and chemical characteristics. 相似文献
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The applied laser energy absorbed in a local area in laser thermal stress cleaving of brittle materials using a controlled fracture technique produces tensile thermal stress that causes the material to separate along the moving direction of the laser beam. The material separation is similar to crack extension, but the fracture growth is controllable. Using heat transfer theory, we establish a three-dimensional (3D) mathematical thermoelastic calculational model containing a pre-existing crack for a two-point pulsed Nd:YAG laser cleaving silicon wafer. The temperature field and thermal stress field in the silicon wafer are obtained by using the finite element method (FEM). The distribution of the tensile stress and changes in stress intensity factor around the crack tip are analyzed during the pulse duration. Meanwhile, the mechanism of crack propagation is investigated by analyzing the development of the thermal stress field during the cleaving process. 相似文献
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空间想象能力是指对空间形式的观察、分析和抽象思维的能力,它包含三个方面的要求:能根据条件画出正确的图形,根据图形想象出直观形象;能正确地分析出图形中基本元素及其相互关系;能对图形进行分解、组合与变形.高考对空间想象能力的考查常常依托一些基本的几何体(如正方体、长方体、正四面体、球等)来进行,球是一种基本而重要的几何体, 相似文献
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创新试题是近年来高考数学试题中“抢眼”的一种题型,它多姿多彩的格调、清新优美的风采、发散开放的形式,构成了高考试题中一道亮丽的风景线。它突出考查学生的探究能力、创新意识和继续学习的潜能,体现了较好的育人和评价功能。本文将对07年高考数学试题中的部分创新试题归类解析,仅供参考。1情境创新——突出信息迁移这类试题常常在题目中给定一些新信息,如新的概念、新的关系、新的运算等,要求学生通过观察分析、阅读理解,并与已有认知结构中的知识进行同化,探索获取有用的信息,从而创造性的解决问题。对学生的独立思考问题、加工提取信… 相似文献
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血液静态荧光偏振光谱研究 总被引:5,自引:0,他引:5
报道了用408 nm的LED偏振光诱导浓度为0.3%的人全血溶液在350800 nm波段的静态荧光偏振光谱,讨论了其光谱的结构特征和红移现象并给出了机理解释;检测了不同浓度全血溶液荧光偏振光谱中在490nm和610 nm附近处两个各主要荧光区的偏振度,实验结果表明,当血液浓度为1.0%时,在两个主要荧光区的偏振度分别为0.4796和0.4344,当浓度增加到8.0%时,相应的偏拓坟墓分别为0.2064和0.0538。研究了偏振度随浓度的变化规律,用能量转移理论分析了在不同荧光区、不同浓度下,血液中各荧光团之间的不同能量转换机理及偏振度的变化现象。研究结果对光诱导生物组织自体荧光诊断技术有一定的参考价值。 相似文献
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