推导光栅衍射暗纹和次级亮纹位置公式的一种新方法

用菲涅耳半波带法推出光栅衍射缝间干涉因子暗纹和次极亮纹位置公式,其中次极大位置公式在算次极大强度时有着非常重要的作用。     

矩孔菲涅耳衍射的一种数值计算方法

提出了一种用计算机计算矩孔菲涅耳衍射的方法,通过对菲涅耳衍射积分公式的转换,把矩孔菲涅耳衍射公式用菲涅耳积分来表示,结合MATLAB和MAPLE的优点,在MATLAB中调用MAPLE的积分指令来实现对矩孔菲涅耳衍射场的计算．并给出了计算结果和这种方法用于计算单缝和半平面屏的菲涅耳衍射.     

菲涅耳衍射的计算机模拟研究

光的衍射现象研究,不仅具有重要的理论意义,而且在光学仪器研制和成像分析等方面均有重要价值。文章研究了菲涅耳衍射的计算机模拟问题,先从标量衍射的菲涅耳-基尔荷夫积分入手,导出菲涅耳衍射(积分)的数学公式,并从物理上解释了其意义。然后再对该公式进行变换,得出所需要的菲涅耳积分C(x)和S(x),尝试用菲涅耳积分的简化公式来进行数值计算,并利用Visual Basic 6.0编程绘制其函数图像。再之,进一步研究单缝菲涅耳衍射的计算,利用上面的研究做基础,采用VisualBasic6.0编程绘制单缝衍射的光强分布图和位图,并将此计算机模拟方法同传统的用科纽曲线研究衍射的方法做了对比,得出本文的方法更为简捷和精准。     

正弦振幅光栅菲涅耳衍射光场的空间分布

在三维传感系统中通常采用结构照明光场。产生结构照明光场的方法一般有投影法和双光束干涉法。本文利用平面波衍射理论（角谱理论），分析了正弦振幅光栅在不同照明条件下的菲涅耳衍射光场的空间分布，特别讨论了在发散球面波照明条件下，菲涅耳衍射光场和泰伯像的一些有趣的性质，指出了这些性质在三维传感中的应用前景。     

分数傅里叶变换与菲涅耳衍射的等效性

用波前相因子判断法,分析了分数傅里叶变换频变分布与球面波照明物体的自由空间菲涅耳衍射光场分布的等效性,给出了分数傅里叶变换与菲涅耳衍射相互转化的约束条件。结果表明：分数傅里叶变换是适应于菲涅耳衍射的数学工具。计算机模拟实验证明了结论的可靠与可行。     

有振幅调制和位相畸变光束的聚焦特性

用广义惠更斯－菲涅耳衍射积分和统计光学方法对有振幅调制和位相畸变光束的聚焦特性作了详细研究，并对有位相畸变光束的光束质量Ｍ２因子作了分析     

有振幅调制和位相畸变光束通过光阑的变化

用广义惠更斯-菲涅耳衍射积分和统计光学方法对有振幅调制和位相畸变光束分别通过硬边和软边光阑的传输特性作了详细研究。数值计算结果表明近场和远场光强分布与截断参数、系统菲涅耳数、光束的振幅调制和位相畸变参数均有关。     

多矩孔菲涅耳衍射的数值模拟

本文由衍射积分公式出发,利用数值模拟方法对多矩孔的菲涅耳衍射进行分析,基于菲涅耳衍射积分法,提出了一种针对多矩孔菲涅耳衍射的数值算法,同时给出了相应的Matlab程序以及仿真结果。从数值分析结果可以看出,该研究结果对于实验验证和计算较为复杂的多矩孔菲涅耳衍射现象具有重要的理论参考意义。     

关于标量衍射理论在二元化透镜设计中的应用极限的探讨

本文分别用菲涅耳衍射公式和瑞利－索末菲衍射公式对不同数值孔径的二元化透镜的衍射问题进行了计算机模拟，给出了计算结果，从中得出了菲涅耳衍射公式和瑞利－索末菲衍射公式各自的应用范围。并对大数值孔径二元化透镜设计中的应用严格电磁理论问题作了讨论。     

基于二维彩色图像和深度图的复杂三维场景的计算全息图

提出了利用二维彩色图像和深度图生产计算菲涅耳全息图的方法。把二维彩色图像按深度图分为多层物面信息,并把每层物面深度值转换为菲涅耳衍射距离。根据层析法原理,采用单步菲涅耳衍射算法,即可得到三维场景的计算全息图。研究结果显示该方法可以正确地对复杂三维场景进行全息图的记录和再现。利用强度叠加法对再现像进行散斑去除,提高了再现三维图的质量。     

A Novel Offset Fresnel Zone Plate Antenna

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光栅衍射条纹的最小次极大强度研究

本文研究了光栅衍射条纹强度分布的次极大强度，并计算出最小次极大强度，得出最小次极大与光栅缝数无关的重要结论，计算结果与计算机仿真结果完全一致。     

SBR image approach for radio wave propagation in tunnels with andwithout traffic

We propose a deterministic approach to model the radio propagation channels in tunnels with and without traffic. This technique applies the modified shooting and bouncing ray (SBR) method to find equivalent sources (images) in each launched ray tube and sums the receiving complex amplitude contributed by all images coherently. In addition, the vector effective antenna height (VEH) is introduced to consider the polarization-coupling effect resulting from the shape of the tunnels. We verify this approach by comparing the numerical results in two canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high-frequency radio propagation inside tunnels where reflection is dominant. We show that the propagation loss in tunnels can vary considerably according to the tunnel shapes and the traffic inside them. From the results we also find a “focusing” effect, which makes the power received in an arched tunnel higher than that in a rectangular tunnel. Besides, the deep fading that appears in a rectangular tunnel is absent in an arched tunnel. The major effect of the traffic is observed to be the fast fading due to the reflection/obstruction of vehicles. Additional considerations, such as time delay, wall roughness, and wedge diffraction of radio wave propagation in tunnels are left for future studies     

A maximum a posteriori probability expectation maximization algorithm for image reconstruction in emission tomography

The expectation maximization method for maximum likelihood image reconstruction in emission tomography, based on the Poisson distribution of the statistically independent components of the image and measurement vectors, is extended to a maximum aposteriori image reconstruction using a multivariate Gaussian a priori probability distribution of the image vector. The approach is equivalent to a penalized maximum likelihood estimation with a special choice of the penalty function. The expectation maximization method is applied to find the a posteriori probability maximizer. A simple iterative formula is derived for a penalty function that is a weighted sum of the squared deviations of image vector components from their a priori mean values. The method is demonstrated to be superior to pure likelihood maximization, in that the penalty function prevents the occurrence of irregular high amplitude patterns in the image with a large number of iterations (the so-called "checkerboard effect" or "noise artifact").     

Bayesian kernel methods for analysis of functional neuroimages

We propose an approach to analyzing functional neuroimages in which 1) regions of neuronal activation are described by a superposition of spatial kernel functions, the parameters of which are estimated from the data and 2) the presence of activation is detected by means of a generalized likelihood ratio test (GLRT). Kernel methods have become a staple of modern machine learning. Herein, we show that these techniques show promise for neuroimage analysis. In an on-off design, we model the spatial activation pattern as a sum of an unknown number of kernel functions of unknown location, amplitude, and/or size. We employ two Bayesian methods of estimating the kernel functions. The first is a maximum a posteriori (MAP) estimation method based on a Reversible-Jump Markov-chain Monte-Carlo (RJMCMC) algorithm that searches for both the appropriate model complexity and parameter values. The second is a relevance vector machine (RVM), a kernel machine that is known to be effective in controlling model complexity (and thus discouraging overfitting). In each method, after estimating the activation pattern, we test for local activation using a GLRT. We evaluate the results using receiver operating characteristic (ROC) curves for simulated neuroimaging data and example results for real fMRI data. We find that, while RVM and RJMCMC both produce good results, RVM requires far less computation time, and thus appears to be the more promising of the two approaches.     

偏馈FZPA焦区场特性研究

基于菲涅尔原理提出了一种椭圆形相位修正区域的偏馈菲涅尔区相位修正平面反射面天线（ＦＺＰＡ），在正入射和斜入射等不同情形下，利用物理光学法分析了其聚焦平面的场幅分布。有关结果表明，这种新型的ＦＺＰＡ具有良好聚焦特性，达到了设计目的。     

基于逆绕射抛物方程法的辐射源定位技术研究

对非合作辐射源的定位是当前热点及难点问题,逆绕射抛物方程法对于复杂环境下的无源定位有着很好的适用性和稳定性。在理想大气辐射源定位的基础上,分析了标准大气、地形遮蔽条件下一个和两个辐射源的定位问题,提出了数据点取值、误差椭圆绘制等方法,研究了数据点数目、折射指数、地形高度等参数与定位误差之间的关系。通过仿真分析,验证了算法特性并给出了参数取值的方法及建议,提高了算法的定位精度,扩大了算法的应用范围。     

基于TFT-LCD的相位型菲涅尔波带片生成的中空光束

中空光束具有特殊的物理性质,在光信息处理、微电子学、同位素分离和分子光学等领域有着广泛的应用。本文提出采用TFT—LCD制作相位型菲涅尔波带片,平面波经TFTLCD衍射生成中空光束。实验结果表明,基于TFT—LCD的菲涅尔波带片生成的中空光束具有实时可调、快捷和精确等优点。     

光栅衍射条纹次极大强度研究

算出三缝到八缝光栅的各次极大衍射条纹次极大强度。发现单缝衍射因子对各次极大均有调制作用，但其单缝衍射强度的调制系统却不相同。