以激光散射立体角分布测量表面横向形貌参数

为了利用光学非接触方法测量表面横向形貌参数,从Beckmann-Kirchhoff标量散射理论出发,分析并得到了高斯粗糙表面激光散射能量的立体角分布特征与轮廓均方根斜率之间的关系.提出了散射光的两个特征值:经度及纬度辐射立体角密度矩,用以提取散射光能量立体角分布情况,并给出了利用数字图像信号在非傍轴远场条件下测量和计算特征值的方法.实验证明:给出的特征参数和测量方法能够得到激光散射立体角分布特征并可用于测量粗糙表面轮廓均方根斜率.     

利用散射辐射分布矩测量表面轮廓均方根斜率

为了利用激光散射分布测量表面粗糙度参数,从分析高斯粗糙表面非傍轴散射光能量的角分布特征与轮廓均方根斜率之间的关系,得到了利用散射角分布进行粗糙表面横向粗糙度参数的测量方法。提出了散射光的两个特征值：辐射立体角密度矩M(θ)和M（φ）,用以表征散射光能量立体角分布情况,并给出了在非傍轴远场条件下的测量和计算方法。实验证明,给出的特征参数能够得到散射光能量立体角分布特征并可用于测量粗糙表面横向形貌参数。     

改性离子注入高阻SOI衬底的共面波导特性研究

因良好的射频性能,高阻SOI(High-Resistivity Silicon-on-Insulator,HR-SOI)被广泛应用于射频集成电路(RFICs)。通过提取共面波导传输线(Co-Plane Waveguide,CPW)的射频损耗来表征衬底材料的射频性能。高阻SOI衬底由于表面寄生电导效应(Parasitic Surface Conductance,PSC),射频性能恶化。设计并制备了一种新型的改性结构来优化高阻SOI的射频性能,通过将硅离子注入到绝缘埋层中来消除表面寄生电导效应。在0~8 GHz范围内,传输线损耗优于时下业界最先进的TR-SOI的结果(Trap-Rich Layer Silicon-on-Insulator)。由于工艺简单,易于集成化,是极具潜力的射频SOI材料。     

基于三维真实表面形貌的聚碳酸酯激光透射焊接温度场模拟北大核心CSCD

在三维真实表面形貌分析的基础上,对激光透射焊接过程进行了模拟分析。利用表面粗糙度测量仪对聚碳酸酯(PC)试件的表面粗糙度进行了测量,构建了表面粗糙轮廓的数学模型,并进行了实体建模,通过ANSYS Fluent软件对光滑表面以及真实粗糙表面进行了激光焊接模拟,分析了焊缝断口微观形貌。结果表明,粗糙PC表面的焊接强度要低于光滑表面的。     

THz频段粗糙导体圆锥的极化成像特性

太赫兹频段下粗糙导体表面会对电磁散射回波的幅度、相位、极化状态产生影响,为分析这一影响,以导体圆锥为例,研究了不同粗糙参数表面电磁散射在雷达图像中的表现规律。基于谱方法和坐标变换对粗糙圆锥面进行建模,利用高频电磁计算方法获得不同粗糙度导体圆锥样本多角度、多频点、全极化的单站散射场,基于转台模型,利用二重积分法获得目标二维像。从仿真结果可以看出,粗糙与理想光滑导体的圆锥图像存在明显差异,粗糙圆锥图像中能量分布偏离理想光滑情况下的强散射区域;随着粗糙度的增加,图像能量分布愈加均匀;相比于同极化图像,交叉极化图像更具反映目标轮廓信息的潜力。     

表面处理降低GaAs界面态密度的研究

GaAs材料经机械研磨后，表层形成粗糙界面，用酸碱法表面处理GaAs，使Ga-O、As-O键断裂并修复粗糙界面，处理效果通过电导法测量界面态密度与XPS分析界面化合物价态来表征。结果表明酸碱处理均可降低界面态密度与表面Ga、As氧化物，且酸处理的效果优于碱处理，Ga-O化合物去除率高于As-O化合物去除率，界面态密度的降低可能主要与Ga化合物的减少相关。     

CF_4、SF_6和NF_3反应离子腐蚀硅表面粗糙度的研究

本文采用CF_4、SF_6和NF_3三种腐蚀气体对硅进行反应离子腐蚀,研究了腐蚀表面粗糙度与腐蚀工艺条件(气压、射频功率),附加气体和腐蚀深度等因素之间的关系。并通过SEM和Auger能谱仪分析,探讨了引起腐蚀表面粗糙的原因。     

随机粗糙表面电磁散射特性的双尺度法

介绍了双尺度法计算随机粗糙表面后向散射系数的方法,同时采用蒙特卡洛法仿真了单尺度和双尺度的二维随机粗糙表面。利用基尔霍夫近似、微扰法和双尺度法分别计算了粗糙面的后向散射系数,并且比较了这三种方法计算的结果,显示出了双尺度法在研究粗糙面电磁散射特性的优越性。     

分形粗糙表面涂覆目标太赫兹散射特性

该文采用物理光学法方法研究了具有分形粗糙表面的涂覆目标太赫兹散射特性。基于分形粗糙面建立表面粗糙目标模型,根据菲涅尔反射系数得出表面电流分布进而得到涂覆粗糙目标的雷达散射截面。对比分析了具有粗糙表面和光滑目标的散射结果,详细讨论了不同频率、不同涂层厚度的表面粗糙钝锥目标模型的太赫兹散射特性,计算结果表明在太赫兹波段目标表面的粗糙度对散射有显著的影响。      

三色激光散斑自相关法测量表面粗糙度的分析

为研究表面弯曲对利用多色散斑测量表面粗糙度的影响,引入表面曲率半径,通过模拟粗糙表面以及其形成的多色散斑场,讨论了不同曲率半径的粗糙曲面对模拟散斑场和散斑延长率的影响.结果表明,引入粗糙表面的曲率半径,对三色激光散斑自相关测量法是可行的.粗糙表面曲率半径越大,其模拟的散斑场和计算的散斑延长率与平直的粗糙表面越接近.曲率...     

新型激光扫描仪RF620及其应用

RIFFEK公司的RF620系列二维激光位移传感器（二维轮廓扫描仪）问世以来,以其极高的性价比久负盛名。该激光轮廓扫描仪主要应用于物体轮廓、二维尺寸、二维位移的非接触测量与检验,以及目标物体的分拣。本文介绍了此系列扫描仪的原理、接口、配置及软件开发工具。     

Magnetic resonance driven electrical impedance tomography: a simulation study

Magnetic resonance electrical impedance tomography (MREIT) is a method for reconstructing a three-dimensional image of the conductivity distribution in a target volume using magnetic resonance (MR). In MREIT, currents are applied to the volume through surface electrodes and their effects on the MR induced magnetic fields are analyzed to produce the conductance image. However, current injection through surface electrodes poses technical problems such as the limitation on the safely applicable currents. In this paper, we present a new method called magnetic resonance driven electrical impedance tomography (MRDEIT), where the magnetic resonance in each voxel is used as the applied magnetic field source, and the resultant electromagnetic field is measured through surface electrodes or radio-frequency (RF) detectors placed near the surface. Because the applied magnetic field is at the RF frequency and eddy currents are the integral components in the method, a vector wave equation for the electric field is used as the basis of the analysis instead of a quasi-static approximation. Using computer simulations, it is shown that complex permittivity images can be reconstructed using MRDEIT, but that improvements in signal detection are necessary for detecting moderate complex permittivity changes.     

The scattering from curved rough surfaces of an EM wave transmitted through a turbulent medium

A generalized analysis of electromagnetic (EM) wave scattering from rough surfaces yields an expression for mean scattered power flux which is the spatial Fourier transform of the product of three transfer functions: 1) the optical transfer function (OTF) of the propagating medium; 2) the joint characteristic function of the surface roughness; and 3) a coherence involving the mean surface and the wave profile. The solution is applicable to moderately rough surfaces which have rms slopes less than a few degrees. The solution is applied to laser scattering from aluminum and titanium surfaces where the medium is the atmosphere. The randomly rough surface consists of independent "roughness" and "waviness" components which possess a Gaussian autocorrelation. The deterministic surface is quadratic; the laser profile, Gaussian. The atmospheric OTF is modeled into a Gaussian form. For typical parameters, the result decouples into a specular term (depending on turbulence, wave profile, and known surface) and a diffuse component (depending on rough and known surfaces). A slightly spherical incident wave affects only the coherent term.     

平板与正弦型组合粗糙面的电磁波复合散射

分别用正弦型组合粗糙面和正弦型二维粗糙面模拟海洋表面，建立了海上目标电磁散射的简化模型，用物理光的双次反弹来表示目标与组合粗糙面之间的电磁波相互作用。     

Si在SF6＋N2中反应离子刻蚀及其剖面的研究

本文报导了用ＳＦ＿６＋Ｎ＿２混合气体反应离子刻蚀Ｓｉ及其剖面的实验结果，研究了在刻蚀时，混合气体的成份和射频功率密度对Ｓｉ的蚀速影响以及Ｓｉ的负载效应，通过实验得到了一种获得Ｓｉ的腐蚀垂直剖面的方法，该腐蚀技术在制作微机械马达和周期为４６６．８ｎｍ的二级光栅（线宽０．２μｍ）中得到应用。     

再流焊工艺技术研究

随着表面贴装技术的发展,再流焊越来越受到人们的重视。本文介绍了再流焊接的一般技术要求,并给出了典型温度曲线以及温度曲线上主要控制点的工艺参数。同时还介绍了再流焊中常见的质量缺陷,并粗浅地讨论了其产生的原因及其相应对策。     

Electromagnetic scattering from a dielectric cylinder buried beneath a slightly rough surface

An analytical solution is presented for the electromagnetic scattering from a dielectric circular cylinder embedded in a dielectric half-space with a slightly rough interface. The solution utilizes the spectral (plane-wave) representation of the fields and accounts for all the multiple interactions between the rough interface and the. buried cylinder. First-order coefficients from the small perturbation method are used for computation of the scattered fields from the rough surface. The derivation includes both TM and TE polarizations and can be easily extended for other cylindrical buried objects (e.g., cylindrical shell, metallic cylinder). Several scattering scenarios are examined utilizing the new solution for a dielectric cylinder beneath a flat, sinusoidal, and arbitrary rough surface profile. Results indicate that the scattering pattern of a buried object below a slightly rough surface differs from the flat surface case only when the surface roughness spectrum contains a limited range of spatial frequencies. Furthermore, the illuminated area of the incident wave is seen to be a critical factor in the visibility of a buried object below a rough surface.     

GPR phase-based techniques for profiling rough surfaces and detecting small, low-contrast landmines under flat ground

We present a new technique whereby phase variation signatures are used to profile two-dimensional (2-D) rough surfaces and to discern shallowly buried, small, low-contrast landmines under a flat ground. The method has been tested using data measured over a composite surface containing two rough dielectric surface patches, and over a flat ground under which small, low-contrast antipersonnel landmines are shallowly buried. The results show that the phase-based technique is capable of profiling rough surfaces and of detecting small, low-contrast landmines with different internal structures buried underneath a flat ground.