基于粒子模拟的磁绝缘传输线等效电容和等效电感的计算

提出了一种基于粒子模拟的磁绝缘传输线等效电容和等效电感计算方法,在层流模型得到的同轴磁绝缘传输线等效电感和等效电容理论公式中引入修正因子,对粒子模拟所得结果进行数值拟合,获得了等效电容和等效电感修正因子依赖于电压的拟合表达式,修正后的等效电容和等效电感理论公式与粒子模拟结果符合较好,所得结果可用于磁绝缘传输线的等效电路建模。     

平行板传输线特性阻抗仿真计算及解析修正

提出了一种基于时域反射原理的平行板传输线特性阻抗仿真计算方法,利用该方法借助CST软件构建模型对平行板传输线的特性阻抗值进行了仿真计算,同时重点研究了下极板展宽结构对特性阻抗值的影响。以仿真计算结果为基础,对原有特性阻抗公式进行了修正,提出了包含下极板展宽结构在内的不对称结构的平行板传输线阻抗计算公式,该公式可作为计算有界波模拟器等电磁脉冲模拟装置特性阻抗的参考公式。     

高纯锗探测器探测效率修正法的研究

探测效率是高纯锗探测器的一个重要指标，实际工作中面对的测试对象经常是一些不规则的辐射体，使得用标准源刻度探测效率难以实现，为此通过理论方法研究刻度体源探测效率有着重要意义。但是理论模拟面对着模型刻画准确性的问题，为此，该项研究针对实验室的两台便携式高纯锗γ谱仪开展了理论计算的验证工作，通过两种方法作为验证基准，即：实验和基准程序计算。针对计算产生的偏差，探索了影响效率差异的各种因素，推导了修正公式，并对修正公式的有效性和适应性进行验证。修正后的理论结果与基准的比较见图1和图2。     

光折变晶体均匀多重全息图存储研究

本文推导了光折变晶体角度编码多重全息存储中写入均匀光栅时的曝光时间递推公式.分析了散射效应对光栅写入时间常数的影响和写入光耦合对光栅振幅的影响,给出了两种因素影响下曝光时间计算的修正递推公式.数值计算结果表明,按照这种修正公式计算所得多重存储中各幅全息光栅振幅不仅均匀性好,而且振幅相对较大,这种曝光方法有利于提高晶体的存储容量.实验中以递推公式所得时间进行曝光记录,在厚度为0.6mm的Fe:LiNbO₃晶体中采用角度编码很容易存储了30幅全息图.     

光谱仪测量窄带宽光源光谱分布的七点修正法

针对光谱仪在测量窄带宽光源的光谱分布时出现的光谱变形现象,提出了一种带宽修正方法—七点修正方法。首先,利用泰勒级数和相关的导数公式,得到了七点修正公式的数学解析式;其次,用光谱线型为正弦函数的模拟光谱对七点修正法进行验证,采用正弦函数来模拟真实光谱,通过光谱仪的带宽函数计算出测量值,然后应用七点修正公式,对测量值进行修正;最后利用中心波长为365 nm的LED光源对七点修正法进行了实验验证,用双光栅单色仪来测量LED光源的光谱辐射照度,光谱仪带宽分别选为5与0.5 nm,将七点修正公式应用于测量值,得到修正值。模拟结果表明： 在选定的模拟条件下,修正后得到的中心波长处的峰值可以达到真实值的99%以上;实验结果表明： 修正后中心波长处的峰值可以达到真实值的95%以上。由模拟结果和实验结果可知,七点修正法与三点修正法和五点修正法相比,修正效果有明显提升,这种带宽修正方法可以广泛应用在光谱测量领域。     

膨胀腔消声器声学仿真的一维修正方法

传统一维方法计算消声器声学性能随频率增加误差加大,本文应用管道末端修正系数改善一维方法的计算结果.应用二维轴对称解析方法计算管道末端修正系数,研究结构因素和频率对修正系数的影响规律,研究表明修正系数随截面半径比增加而降低,随频率增加而增加,超过截止频率后修正系数无效.根据计算结果给出修正系数拟合公式并修正传统一维方法,应用一维修正方法计算膨胀腔消声器的传递损失并和实验结果、三维有限元结果进行比较,证明一维修正方法结果精度有明显提高.     

关于密立根油滴实验中的几个问题探究

通过建立密立根油滴实验中油滴下落的动力学数学模型，解释了油滴从开始下落便可视作为匀速的“合理性”。同时从微观分子碰撞角度解释了空气黏滞系数修正因子“b”的物理意义。最后使用直接代入公式法、修正R公式法和迭代运算法三种实验数据处理方法计算元电荷值，并得出迭代运算的方法得出的数据更稳定且误差小的结论。     

火箭发动机热力计算中修正温度和压力的牛顿迭代公式

火箭发动机热力计算对于温度、压力的修正大多采用插值法,但插值法仪仪对于一个变量进行修正是方便的,而且收敛较慢.本文根据牛顿法和热力学微分关系式推导了各种热力计算情况下修正温度、压力的牛顿迭代公式. 有了这些公式,便可对喷管任一截面进行热力计算。文中还给出了算例。     

分层介质中p偏振光透射系数的修正

通过理论计算获得了全反射时分层介质中p偏振光的透射系数计算公式,并采用时域有限差分(FDTD)方法进行了验证。计算所获得的公式与传统的采用分层介质的特性矩阵法计算获得的相似,不同之处在于当发生全反射时,公式多了一个全反射修正因子。此外,采用FDTD模拟的两层介质的全反射结构及表面等离子体共振(SPR)膜系结构的结果与修正后的公式符合得很好。该修正公式是对分层介质中电磁波传播的完善,是对一些有影响力的文献关于场增强因子的修正,它对SPR及倏逝场的研究具有参考价值。     

机场跑道临时关闭警示装置可见性计算研究

为了快速得到机场跑道临时关闭警示装置整体光强的准确值和该装置可见距离与空气浑浊度T的关系。提出了利用虚拟点计算装置整体光强的方法,得到了装置的整体光强。相对于叠加得到装置整体光强值的方法,该方法提高了计算的准确性。然后根据Rayleigh散射和Mie散射公式建立了空气浑浊度T与跑道视程（RVR）的关系,并修正了点光源视距公式。修正后的公式考虑的入射光波长的影响并与RVR联系起来,使公式更具有实际意义。通过计算可知,在满足机场最低运行标准的情况下,该装置的可见距离仍为280 m~370 m,该距离能使飞行员识别并安全复飞。该公式为判断机场跑道临时关闭警示装置在空中的可见性提供了计算方法,也从理论上验证了该装置可以满足可见性要求并通过实验初步验证了该计算方法的正确性。     

Solving the direct problem of quantitative electron microprobe analysis for binary alloys with a known composition

The results of solving the direct problem of quantitative electron microprobe analysis (calculation of the relative intensities of analyzed lines in a material with a known composition up to an accuracy of 2–5%) are presented. An additional matrix correction caused by the difference in the concentrations of atoms in the reference and sample is shown to be necessary for the microanalysis results and the value of this new fundamental correction is determined. The obtained solution of the direct problem is used to refine the value of an important parameter in electron microprobe analysis, i.e., the mass absorption factor of the analyzed X-ray line.     

Single-cell analysis using Fourier transform infrared microspectroscopy

Fourier transform infrared spectroscopy (FTIR) is a well-established, non-destructive method of obtaining chemical information from biological samples such as tissues and cells. This review focuses specifically on the development of infrared spectroscopic microanalysis at the single-cell level. Technological developments, including that of the infrared microscope, synchrotron radiation FTIR, and focal plane array detectors, and their impact on the field are discussed along with the various data processing procedures that are currently used to extract meaningful information. There is then an emphasis on live cell infrared (IR) imaging, including developments in water correction and microfluidic device design. The review concludes with look to future directions, highlighting the potential impact of quantum cascade lasers.     

Electron-probe X-ray microanalysis of individual particles of solid snow sediment with size factor correction

A technique is proposed for X-ray electron-probe microanalysis (EPMA) of individual particles of solid snow sediment. Two sample preparation procedures were used to analyze the sediments. The PAP-method and the original bi-exponential model were used for matrix correction and the calculation of elemental composition. A method of calculating composition has been developed for approximately spherical individual particles, comparable in size with an area of X-ray generation. An analytical expression is proposed for determining the composition of these particles, taking account of their size. Including the size factor reduces the error of composition determination from 0.5-45 to 0.2-22% relative percent, for particles in the size range 1-3 microm.     

X射线发射深度分布φ(ρz)计算与电子探针定量分析

本文利用Monte Carlo方法和修改了的原子散射总截面公式,计算了在合金中产生X射线的深度分布φ(ρz),并用于电子探针定量分析。对12种二元合金、一种三元合金和碳化硅中的碳作了计算,结果比ZAF方法和Shimizu方法好。尤其对碳的计算结果比ZAF方法更好,表明本文的计算方法用于轻元素定量分析是可行的。 关键词：     

Improvement of sensitivity using principal component analysis by dual focused ion beam time-of-flight secondary ion mass spectrometry

It is important to develop and to practically use the method to analyze a micro-nanometer order area. Especially, three-dimensional microanalysis for minute structure that consists of the organic compounds and the polymer is difficult. We developed a novel three-dimensional microanalysis method by means of focused ion beam (FIB) for section processing and ToF-SIMS for mapping method. For the purpose of realization of three-dimensional microanalysis and a chemical and structural analysis of the organic matter, the sensitivity improvement of ToF-SIMS in the three-dimensional analysis device and the method of the spectral analysis are examined. To improve the sensitivity of ToF-SIMS, the sample stage was modified to arrange perpendicularly with the ToF optical axis, and the distortion of electric field was corrected. And, by analyzing the fragment ions by using the principal component analysis (PCA) to raise the efficiency of the spectrum analysis, spatial resolution has improved. As a result, the resolution of the device improved to sub micrometer order, and advanced to the achievement of the three-dimensional microanalysis.     

Quantification of surface-sensitive electron spectroscopies

Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were introduced in late 1960s as routine tools for surface analysis. Despite a long history, both techniques are still very useful in different new areas of surface science. The number of publications involving AES or XPS well exceeds 5000 per year, and is still growing.The present paper compiles recent advances in quantitative applications of both techniques. Due to the considerable volume of published material, stress is put on the determination of surface composition. Three groups of subjects are addressed here. At first, typical experimental procedures for quantitative analysis are outlined. For this purpose, we briefly review the common formalism of AES and XPS. Secondly, information is provided on the correction approach in AES and XPS, similar to electron probe microanalysis (EPMA). Next, methods for determination and sources of the correction parameters are reviewed. Finally, we discuss physical parameters needed for calculation of corrections. Much attention is devoted to the problem of determination of the differential elastic-scattering cross sections for signal electrons. This parameter is of crucial importance for describing the electron trajectories in the solid. We also approach further prospects for improved quantification of AES and XPS.     

Invariant embedding approach for electron probe microanalysis. Tilt factor,atomic number and energy of the incident electrons

Electron probe microanalysis (EPMA) is a well‐established and practical technique for the microchemical analysis of materials. Although the physical processes that take place in microprobe analysis are relatively well understood, most of the commercially available approaches for data correction are still empirical or semi‐empirical or make use of numerical calculations. Recently, a so‐called Invariant Embedding Approach to Microanalysis, which is free of the disadvantage of the empirical methods, has been reported. This paper critically assesses the capabilities and limitations of this new approach when different values for the energies of the incident electrons, the atomic number and size and the sample tilt are considered. The theoretical results follow the general trends of the experimental data and Monte Carlo calculations, although a more in‐depth study of the physical parameters involved in the model is still needed. Copyright © 2005 John Wiley & Sons, Ltd.     

Monte Carlo study of quantitative EPMA analysis of a non‐conducting sample with a coating film

Generally, the ZAF method has been used for quantitative electron probe microanalysis (EPMA) analysis of conducting samples. However, the ZAF method is not applied to non‐conducting samples with coating films, mainly because the x‐ray intensity and the primary electron energy are both attenuated within the coating films. In this study, for application to the ZAF method we tried to correct the x‐ray attenuation and the primary electron energy attenuation by Monte Carlo simulation. As calculation models, we selected carbon coating as a light element and gold coating as heavy element and selected four kinds of materials, Al₂O₃, BN, AlN and Al₄C₃, as non‐conducting targets. After the correction we compared the calculated results and theoretical compositions. The calculated results were in good agreement with theoretical compositions. Finally, to verify the method we measured standard Al₄C₃ coated with gold (100 Å thickness). The experimental result showed good agreement with the theoretical composition. In conclusion, we confirmed that this method is useful for the quantitative analysis of non‐conducting samples with coating films. Further, by combining this method with appropriate standard compounds, we can obtain the hypothetical pure x‐ray intensities of gaseous pure elements. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis and Luminescent Properties of Gadolinium Tantalum Niobates Gd(NbxTa1 – x)O4

Optics and Spectroscopy - The feasibility of synthesizing gadolinium tantalum niobates by the liquid-phase method was demonstrated. The methods of X-ray diffraction, electron probe microanalysis,...     

使用位置环的惯性稳定系统中陀螺漂移误差软件修正方法

针对使用位置环的惯性稳定系统中存在因陀螺固有温度漂移特性引起的系统跟随位置误差,首先提出一种软件修正方法,给出此软件修正方法的理论基础及软件修正的具体实现过程,最后对此修正方法进行了实验验证。实验结果表明：在没有振动的情况下,修正程序能将漂移完全校正,效果良好;在存在振动的情况下,修正程序也能较好地校正漂移,但校正后存在1个或2个码值的误差。