Gaussian peaks decomposing of simple liquids' RDF

According to feasibility of Gaussian peaks decomposing distribution function (DF) 4πrρ(r), radial distribution function (RDF) 4πr~2ρ(r) of simple liquids also is possibly decomposed into Gaussian peaks with r in the size of several atoms. Experimental structure parameters of pure liquid Al and Si were obtained by θ-θ X-ray diffraction measurements and following data processing. Based on Gaussian decomposing liquid aluminun's DF 4πrρ(r), liquid aluminum and silicon's radial distribution function (RDF) 4πr~2ρ(r), it is shown that RDF of simple liquids is able to be decomposed in Gaussian function, compared with decomposing of DF, supplying more physical meaning and better indicating the short range order of liquids, whicb draws a clearer structure picture of simple liquids.     

角度相关函数与径向分布函数分析微组织结构

为了研究纳米加工过程导致材料组织结构的变化,采用分子动力学方法,构建了单晶铜耦合纳动纳米加工模型,并进行了纳米切削过程仿真.提出采用角度相关函数(ADF)结合径向分布函数(RDF)方法,分析单晶铜耦合纳动加工过程中材料亚表面组织结构变化.模拟结果表明,单晶铜(111)表面耦合纳动加工过程中,在材料的亚表面原子存在从密排六方排列转变为面心结构排列的不稳相变.     

环境噪声峰值的空间分布

本文将正态随机过程的峰值分布理论推广到环境噪声峰值的空间分布的计算上。文中分析了杭州市环境噪声的测试数据,发现它们符合正态分布。在这种情况下,容易计算出超过某一峰值的噪声所占的空间比例,并且有可能以较少的测量数据来反映环境噪声的分布规律,从而大大减少噪声测试分析的工作量。     

高斯求积在三维分布源法中的应用

三维分布源法广泛应用于各种海洋结构物的波浪载荷计算 .其中格林函数及其空间导数沿面元的积分和面元上流体力的计算是十分重要的 .首先阐述了基于四边形面元几何特性的二重高斯型求积公式 .接着讨论了如何应用这一公式计算三维分布源法中面元中心诱导速度和面元流体力积分 ,给出了相应的算例 .实际数值计算结果表明 ,在三维分布源法中面元诱导速度及流体力数值计算中采用 2× 2高斯积分 ,一般可以兼顾到计算精度和计算效率两方面的要求 .     

A statistical approach to fit Gaussian part of full-energy peaks from Si(PIN) and SDD X-ray spectrometers

A new statistical fitting approach,named Statistical Distribution-Based Analytic(SDA)method,is proposed to fit single Gaussian-shaped Kαand KβX-ray peaks recorded by Si(PIN)and silicon drift detector(SDD).In this method,we use the discrete distribution theory to calculate standard deviation of energy resolutionσ.The calibration ofσand energy(E)for two detectors between the energy ranges of 4.5–26 keV are also completed by measuring characteristic X-ray spectra of nineteen types of pure elements.With the spectrum fraction(SF)parameter proposed in this paper,the SDA method can be used to resolve overlapping peaks.In measured spectra,the Gaussian part of X-ray peaks can be fitted by a Gaussian function with two parameters,σand SF.This new fitting approach is simpler than traditional methods and it achieves relatively good results when fitting the complex X-ray spectra of national standard alloy samples detected by Si(PIN)and SDD detectors.The2r values are obtained for each spectrum to assess fitting results,and the SDA fitting method gives a preferable fit for the SDD detector.     

Gaussian process assisted coevolutionary estimation of distribution algorithm for computationally expensive problems

In order to reduce the computation of complex problems, a new surrogate-assisted estimation of distribution algorithm with Gaussian process was proposed. Coevolution was used in dual populations which evolved in parallel. The search space was projected into multiple subspaces and searched by sub-populations. Also, the whole space was exploited by the other population which exchanges information with the sub-populations. In order to make the evolutionary course efficient, multivariate Gaussian model and Gaussian mixture model were used in both populations separately to estimate the distribution of individuals and reproduce new generations. For the surrogate model, Gaussian process was combined with the algorithm which predicted variance of the predictions. The results on six benchmark functions show that the new algorithm performs better than other surrogate-model based algorithms and the computation complexity is only 10% of the original estimation of distribution algorithm.     

用X射线吸收谱对多元物质精细结构的研究

基于EXFS的物理机制,我们用EXAFS研究多元物质中任一组元临近结构时,首先由测定的吸收谱求出精细结构函数X(k),根据X(k)确定结构参数.这种方法在结构研究中有其独到之处,本文根据"短程序理论"所构造的物理模型,对用透射法的结果的处理方法进行了深入讨论.     

像素域基于广义高斯分布的WZ帧重构方案设计

为提高分布式视频编码系统解码WZ帧的图像质量,提出了像素域基于广义高斯分布的WZ帧重构方案. 该方案充分考虑了边信息与原始WZ帧间的相关性,以广义高斯分布作为虚拟相关信道模型,提高率失真性能;用广义高斯分布做相关噪声模型,对给定量化区间,计算边信息已知情况下WZ的条件期望作为WZ重构值;为了不过多地增加重构方案的复杂度,将广义高斯分布的形状参数固定为0.5,推导出重构WZ帧的闭式表示. 实验结果表明,基于广义高斯分布的WZ帧重构方案能有效提高率失真性能和改善重构WZ帧的图像质量.     

径向分布函数法关联过量

通过求解ＰＹ积分方程，得到了Ｓｕｔｈｅｒｌａｎｄ位能模型径向分布函数式。由纯物质的蒸发热数据确定位能模型参数，采用二次型混合法则，将导出的径向分布函数和上述参数关联了二元物系的过量焓。关联过程引入两个相互作用参数。计算结果优于局部组成模型。