Random vibration of a current carrying circular plate in magnetic field

分析载流圆板在磁场中的磁弹性随机振动问题。根据薄板、薄壳体的磁弹性运动方程和连续体的随机振动理论,导出在磁场环境中圆板的磁弹性随机振动方程。对磁场中的载流圆板进行随机响应分析,得到圆板位移响应的自相关函数、功率谱密度函数及均值函数等数字特征。通过具体算例,对处于外加磁场中通入平稳随机电流的导电圆板,计算其位移响应的功率谱密度函数

Study on Vibrational Spectra of Cypermethrin Based on Density Functional Theory

As a broad-spectrum insecticide,Cypermethrin is widely used in various agricultural products,such as fruits, vegetables and poultry and so on.Because of its large dosage and slow degradation rate,drug residues in fruits,vegetables, livestock and other agricultural products are harmful to human health.In order to avoid human intake,it is very important to detect cypermethrin residues in agricultural products.Among the current detection methods,the vibration spectrum technology has the advantages of being non-destructive and fast.Therefore,this paper uses the density functional theory method combined with the vibration spectrum technology to provide a theoretical basis for the vibration spectrum detection and identification of Cypermethrin,and provide a reference for the application field of pesticide residue detection.The specific research contents and results are as follows:the first step is to construct the molecular space configuration of Cypermethrin by using Gaussian view software.Based on the DFT/B3LYP method of density functional theory,the structure is roughly optimized with a 3-21Gbasis set and then reoptimized with 6-311++G basis set based on coarse structure to obtain the stable configuration and frontier orbital distribution of the molecule.Then,based on the optimized structure,the theoretical infrared and Raman spectra of Cypermethrin were calculated.The theoretical results show that Cypermethrin has obvious infrared activity in the range of 3 300~3 000and 1 700~500cm~(-1).The former is mainly the vibration of functional groups,and the latter is the vibration of the fingerprint region.It can also be seen from the calculation results that the stretching vibration and scissor vibration of methylene hydrocarbon on cyclopropyl at 3 044and 1 459cm~(-1),the wagging vibration of methyne on cyclopropyl at 1 196cm~(-1)and the rocking vibration of hydrocarbon in benzene ring at 1 153cm~(-1)in Raman spectrum have no activity in the infrared spectrum.The cyano group without infrared activity shows a strong band in the Raman spectrum.The benzene ring skeleton vibration is weakly absorbed in the infrared spectrum but shows a strong band in the Raman spectrum.These reflect the complementary advantages of infrared spectroscopy and Raman spectroscopy.The combination of the two spectra is more conducive to the identification and detection of compound structure.In the second step,the natural Raman spectrum of Cypermethrin powder was measured by experimental method.The theoretical calculation error was corrected by the frequency correction factor of 0.973.The experimental results were compared with the theoretical calculation results.The difference in the peak frequency wavenumber was mostly in the range of 4~10cm~(-1),and the theoretical data were consistent with the experimental results.This study provides a theoretical basis for the vibration spectrum detection and structure identification of Cypermethrin,and provides a theoretical reference for its application in pesticide detection

基于激光诱导击穿光谱技术检测分析原铝中硅铁元素含量

利用自行搭建的LIBS装置对原铝中硅铁含量进行了分析测试,测试前对原铝试样进行了微观形貌分析,研究发现原铝中硅元素除有个别区域聚团现象外,其分布相对较为均匀;铁元素多以团状汇聚形态出现,且无明显的分布规律。实验分别考察了激光脉冲能量对激光诱导原铝等离子体光谱的影响,发现随着激光脉冲能量的增大,硅、铁元素信噪比先增加后减小,硅、铁谱线信噪比最大值均出现在160mJ处,实验选取的激光脉冲能量为160mJ。在上述较为合理的实验条件下,以内标法为基础,分别采用两种标样(纯铝标样与自选标样)建立了定标模型;结果表明:相比于纯铝标准试样,采用自选试样建立的定标模型不够理想,且数据的离散程度较大,铁元素直线拟合优度仅为0.921 3,相对标准偏差也较大。采用纯铝标样时,在试样不旋转的情况下,硅、铁元素定标曲线拟合优度分别为0.961 1与0.974 1,相对标准偏差分别为8.85%与9.43%,且误差棒显示误差随定标试样的硅、铁含量升高而增大。当试样台保持转速50r·min~(-1)条件下进行实验,发现硅、铁元素定标曲线的拟合优度分别为0.978 5与0.988,相对标准偏差分别为3.78%与3.4%,相比于试样平台固定情况下的定标结果,拟合优度明显改善,相对标准偏差也有所降低,定标模型明显优于自选试样建立的模型。使用两种定标模型对25个测试样进行了分析测试,比较了两种测试结果的相对误差,纯铝定标试样由于含量梯度较大,跨度较宽,采用该标样建立的定标模型对低铁原铝试样测试适应性相对较差,而自选试样建立的定标模型虽然不够理想,但针对低铁原铝试样的测试适应性相对较好。对激光诱导原铝产生的等离子体进行了诊断,通过镁元素几条离子谱线的玻耳兹曼图,计算出了等离子体温度约为9 163.63K,利用镁元素一条谱线的Stark展宽估算出等离子体电子密度为1.69ⅹ1017 cm~(-3),验证了激光诱导原铝等离子体处于局部热力学平衡状态的假设是成立的