非高斯噪声激励下的基因转录调控系统

考虑生物生长过程中受到的不可预知的跳跃性的环境扰动,运用一类非高斯噪声建立了随机的基因转录调控系统. 利用 Monte Carlo 法得到了系统的稳态概率密度函数,研究了非高斯噪声的各个参数对蛋白质浓度的影响,发现噪声强度不能够诱导基因开关,而稳定性指标和偏斜参数能够作为基因开关的控制参量. 进一步研究了非高斯噪声作用下系统从一个态跃迁到另一个态的平均首通时间(MFPT) ,并讨论了各个参数不同的作用机理.     

Alpha稳定分布随机变量的产生

在实际应用中遇到的大量的非高斯信号或噪声具有显著的尖峰脉冲特性,其概率密度函数的衰减过程比高斯分布要慢,表现出显著的拖尾。而基于广义中心极限定理的Alpha稳定分布描述了信号统计分布的非高斯性和重拖尾性。实现服从Alpha稳定分布随机变量的仿真是开展相关研究的基础。该文由S2参数系下的分布模型的仿真算法导出标准参数系下Alpha稳定分布随机变量的仿真算法。并通过仿真实验证实了该仿真算法的可行性。     

任意概率密度信号的盲分离

独立分量分析(ICA)是一种把多维随机矢量转换为尽可能统计独立的分量的统计方法,被广泛用于非高斯信号处理领域.本文给出了一种基于峰度的盲源分离(BSS)算法,也可看作是最大似然方法的扩展,解决了最大似然方法限制过多的缺陷,且与用Comon的方法求解Givens矩阵相比,结构清晰、实现简单.仿真证明了算法的有效性.     

基于统计特征的语音回声隐藏分析

提出了一种基于偏度和峰度的语音回声隐藏分析方法.通过分析回声隐藏导致的语音复倒谱变化,计算出语音复倒谱的统计特征--偏度和峰度.通过对原始语音样本和藏密语音样本复倒谱偏度和峰度的学习和训练,分别得到可用于回声隐藏分析的偏度和峰度阈值.该方法已在计算机上进行了实验.实验结果表明,该方法能够有效地分析多种回声隐藏方法,峰度的隐藏分析结果好于偏度.     

任意概率密度信号的盲分离

独立分量分析(ICA)是一种把多维随机矢量转换为尽可能统计独立的分量的统计方法,被广泛用于非高斯信号处理领域。本文给出了一种基于峰度的盲源分离(BSS)算法,也可看作是最大似然方法的扩展,解决了最大似然方法限制过多的缺陷,且与用Comon的方法求解Givens矩阵相比,结构清晰、实现简单。仿真证明了算法的有效性。     

基于W检验统计量的稳健波达方向估计方法

针对实际环境中广泛存在的脉冲性非高斯噪声会降低基于传统二阶循环统计量的各类算法性能的问题,将混有脉冲噪声的信号样值看作粗差,以稳健估计理论为基础,应用进行高斯检验的W统计量,以自适应方式剔除脉冲样值,得到新的循环互相关函数估计表达式,从而实现了DOA(direction of arrival)的稳健估计.该方法无需噪声统计特性的先验知识,适用于各种非高斯噪声环境,且计算机仿真表明其在不同非高斯噪声条件下的估计性能均优于现有的稳健方法.     

对消处理技术在宽带频谱感知中的应用研究

在高斯噪声背景假设条件下,能量检测的频谱感知性能最优且易于工程实现,但在非高斯噪声背景下,其感知性能大大下降甚至无效。针对这一问题,利用对消处理方法来提高能量检测在非高斯噪声下的频谱感知性能,通过将检测统计量与先验背景噪声进行对消预处理,在降低噪声非高斯度的同时提高了统计量的信噪比,从而提高了检测概率,并进一步提高了宽带频谱感知性能。利用USRP、GNURADIO和MATLAB设计并实现了频谱感知平台,同时验证了该算法的可行性。     

基于QPSO-LMK的自相似性网络流量预测

现在对高性能、高效性流量测量的研究表明网络流量呈现统计上的自相似性.因此,网络预测在网络管理中占据重要地位.使用QPSO(quantum-behaved particle swarm optimization)对预测自相似性网络流量的最小均值峰度(LMK)方法进行优化,能够获得较小的信噪比SNR-1(signal to noise ratio).通过对真实网络流量的仿真实验,表明该方法能比LMK(最小均值峰度)算法更精确的预测网络流量.     

基于卡尔曼滤波和AR参数的非平稳杂波仿真

分析了天基雷达地面杂波的统计分布特性和功率谱特性,研究了基于零记忆非线性变换法仿真天基雷达地面杂波相关随机序列的方法.该方法用AR过程模型产生相关杂波,但是,在实现线性滤波器时仿真的相关杂波与实际非平稳杂波存在误差,仿真效率低.提出了基于卡尔曼滤波递归AR参数实现线性滤波器的方法,推导了仿真相关对数正态分布杂波的原理和方法,进行了杂波仿真实验和分析,仿真的杂波能够很好地符合幅度分布和功率谱特性要求,可以提高探测概率,验证了该方法仿真杂波的准确性和有效性.     

认知无线电中非高斯噪声下主用户信号的协作检测方法

本文研究了非高斯噪声情况下主用户的频谱检测问题,采用混合高斯模型拟合了非高斯噪声背景,并采用矩估计方法对混合高斯模型的混合系数等参数进行了估计。在此基础上,将混合高斯Rao检测方法应用于主用户的频谱检测,推导了混合高斯Rao检测的检测统计量和检测性能公式,分析比较了混合高斯Rao检测与高斯Rao检测的性能。此外,建立了多用户协作的检测模型并推导了基于改进的OR准则的协作检测性能公式。通过理论分析和蒙特卡罗仿真说明了在虚警概率一定的情况下,基于混合高斯Rao检测的方法能有效地提高非高斯噪声下主用户的检测性能。     

Application of tilt modulation of the scatter cross-sections to distinguish between different non-Gaussian rough surfaces: unified full wave approach

The tilt modulations of the like- and cross-polarized cross-sections for arbitrarily oriented resolution cells are determined using the unified full-wave approach. A broad family of non-Gaussian rough surfaces characterized by the gamma surface height probability density functions of order K are considered. Furthermore a Pearson-Moskowitz surface height spectral density function is assumed for the sea surface. The surface height autocorrelation function is also assumed to be non-Gaussian. An arbitrarily oriented mean plane associated with the resolution cell is characterized by tilt angles in and perpendicular to a fixed reference plane of incidence. The ‘tilt modulation’ of the scattering cross-sections is determined as functions of the wavelength of the incident field 𝛌₀ and the backscatter angle 0ⁱ ₀. Each resolution cell represents the real (or synthetic) radar footprint. The size of the resolution cell, orientation, and the statistical characteristics of the non-Gaussian surface determine the radar cross-section. Radar remote sensing options are discussed to distinguish between random rough surfaces characterized by different probability density functions.     

The generation of surface targets with specified surface statistics

Abstract

The analysis of scatter from rough surfaces has been of interest to researchers for many years. The comparison between theory and measurement has not always produced results that instill confidence in either the theory or the measurements. One would like to be able to construct the required surfaces to have control of the target as well as the measurements. There has been some work in the past to construct target surfaces, however, the statistics of the surface could only be determined after the fact. This paper presents some results of work to generate physical surfaces from known (i.e. desired) surface statistical properties. This study extends previous work on the generation of random surfaces for use in computer simulation approaches. The known statistical surface is extended using a bicubic spline technique and these results are interfaced to a numerically-controlled machine to generate the physical surface. A portion of a complete surface with Gaussian statistics was constructed and tested to measure conformity to the desired statistics.     

基于Gauss Ball+的二次曲面细分解与识别

首先利用主曲率对网格进行粗分解,然后利用Gauss Ball 方法对每片子区域进行二次曲面的类型检测、细分解和重聚合,最后对细分的子网格区域中的二次曲面进行参数识别.实验结果表明,利用该方法可以自动、快速、准确地分解出零件中存在的二次曲面,可以很好地应用于逆向工程中二次曲面参数反求.     

Scattering cross sections for composite surfaces with large mean square slopes—full wave analysis

Abstract

In this work the full wave approach to rough surface scattering is applied to composite models of rough surfaces with large mean square slopes. It is shown that both specular point scattering as well as Bragg scattering are accounted for in the analysis and the results are compared with earlier solutions based on a combination of physical optics and perturbation theories. Using the full wave approach it is not essential to decompose the rough surface into individual surfaces with different roughness scales unless it is desired to separate the specular point contribution from the Bragg contribution to the scattering cross sections. Shadowing is accounted for in the analysis.     

An approximate model for the microwave brightness temperature of the sea

Abstract

A modified two-scale model is proposed for scattering and emissivity calculations for certain classes of random rough surfaces. It is based on an approach by Burrows and by Brown, but it has been extended to bistatic scattering by lossy dielectric surfaces, and it incorporates modified Fresnel reflection coefficients and a simple correction for multiple-scattering effects. The method is shown to be applicable to the ocean surface for light and moderate winds. A contracted form of the radiative-transfer equation is proposed and the included Wentz correction for surface scattering is discussed. This could lead to a method that could be both simple and accurate enough for real-time inversion algorithms in microwave remote sensing.     

基于随机粗糙样本的统计学习理论研究

介绍随机粗糙理论的基本内容。提出随机粗糙经验风险泛函,随机粗糙期望风险泛函,随机粗糙经验风险最小化原则等概念。最后证明基于随机粗糙样本的统计学习理论的关键定理并讨论学习过程一致收敛速度的界。     

三维CAD曲面模型距离-曲率形状分布检索算法

产品三维CAD模型检索对实现产品设计信息的有效重用具有重要意义和作用.针对在工程应用中存在大量含有曲面的产品,提出一种基于距离-曲率形状分布的三维CAD曲面模型检索算法.首先在模型表面随机取点,计算出所取点的曲率以及该点到模型质心的距离;然后以模型质心为球心,统计处在不同半径球壳间所取随机点的曲率分布,分别以球壳半径和曲率为坐标轴构建距离-曲率平面网格,并统计每个网格中随机点出现的频次,从而形成距离-曲率矩阵;最后利用特定的规则计算矩阵的相似值,用该值衡量2个模型的相似程度,实现模型的相似性检索.实验结果表明,文中算法的检索性能比传统的形状分布算法有较大提高,尤其适用于自由曲面模型的检索.     

Effects of surface roughness and interface wettability on nanoscale flow in a nanochannel

Non-equilibrium molecular dynamics simulations have been carried out to investigate the effect of surface roughness and interface wettability on the nanorheology and slip boundary condition of simple fluids in a nanochannel of several atomic diameters width. The solid surfaces decorated with periodic nanostrips are considered as the rough surface in this study. The simulation results showed that the interface wettability and the surface roughness are important in determining the nanorheology of the nanochannel and fluid slip at solid–fluid interface. It is observed that the presence of surface roughness always suppresses the fluid slip for hydrophilic and hydrophobic surface nanochannels. For fluids over smooth and hydrophobic surfaces, the snapshots of fluid molecules show that an air gap or nanobubble exists at the fluid–solid interface, resulting in the apparent slip velocity. For a given surface with fixed interface wettability, the fluid velocities increase by increasing the driving force, while the driving force has no significant influence on the density structure of fluid molecules. The fluid slip and the flow rate are measured for hydrophilic and hydrophobic nanochannels. The flow rates in rough surface nanochannels are smaller than those of smooth surface walls due to the increase of drag resistance at the solid–fluid interface. The dependence between fluid slip and flow rate showed that the slip length increases approximately linearly with the flow rate for both the hydrophobic and hydrophilic surface nanochannels.     

一种非线性非高斯随机系统的故障诊断方法

针对非线性非高斯随机系统在线故障诊断的问题,运用粒子滤波器提出了一种基于方差自适应粒子滤波器的非线性非高斯随机系统的故障诊断方法,可以用来解决系统的参数偏差型故障诊断问题。通过对连续搅拌釜式反应器(CSTR)的仿真研究,可以看出,该算法实现简单,易于对系统进行在线估计,对于发生缓变和突变的参数偏差型故障的检测与估计均较为有效。