衡水湖地区气溶胶分布特征的航测研究

利用飞机机载粒子测量系统(PMS)对河北省衡水湖自然保护区上空的大气气溶胶粒子进行观测研究。观测结果表明:下垫面、天气条件、逆温等对气溶胶的分布存在较大的影响;衡水湖上空不同高度的气溶胶平均谱分布均呈现出单峰分布;细粒子谱分布在0.28μm左右处出现峰值;多阶Γ函数对气溶胶粒子谱有较好的拟合效果。     

基于逆非中心分布的初步探究

在非中心分布理论的基础上提出逆非中心分布的概念,并对其性质及推论作了初步性研究。     

声呐图像背景灰度分布特性分析及模型研究

在图像声呐滤波、分割以及目标识别中,像素灰度分布特性及其模型的选择与建立具有非常重要的作用。针对当前声呐图像背景灰度分布模型研究尚不够深入的现状,分别采用威布尔分布和瑞利分布模型对声呐图像背景区域像素点灰度分布进行了仿真验证。结果表明,威布尔分布较瑞利分布来说能够更好地逼近图像声呐灰度分布曲线,且具有较强的自适应性。但在某些情况下,可采用瑞利分布替代威布尔分布,以提高运算效率。     

非瑞利混响背景下接收机工作特性曲线仿真

介绍了高分辨主动声呐的非瑞利分布混响的产生原因及几种典型的混响概率密度分布函数,并通过对混响概率密度分布函数的拖尾分析及其高阶统计量的比较,分析了检测过程中虚警概率增大的原因。此外,在窄带信号检测条件下,利用蒙特卡洛方法对瑞利分布和非瑞利分布混响背景下的接收机工作特性曲线进行了仿真。     

粒径分布对循环床内颗粒速度分布的影响

利用激光相位多普勒粒子分析仪，在截面尺寸为１００ｍｍ＊１５ｍｍ的二维循环流化床实验装置上测量比较了平均粒径基相同的３种不同粒径分布的玻璃珠颗粒在相同操作气上的颗粒时均速度、脉动速度与数量密度的截面分布特性；     

充电桩计量重要性的评价

对某行政区域内随机抽取的6 000台充电桩数据进行了统计分析,表明充电桩的年充电量和交易次数均为长尾分布。尾部3.3%的充电桩,年充电量超过了总充电量的55%;尾部6.7%的充电桩,充电次数超过总充电次数的39%。提出了考虑年充电量和交易次数的充电桩计量重要性因子,作为有重点随机抽样的依据。     

用优化方法求取统计分布参数

统计分布参数的求取是可靠性研究的基础，对于只含有一个或两个参数的统计分布，已有许多方法来求取其参数，但对于具有复杂形式的分布，其多参数求取比较困难。作者提出把求解统计分布参数问题归结为求解非线性优化问题，调用现成的优化程序即可方便地求出具有复杂形式的统计分布的参数。所给出的例题表明，该方法是可行的。     

密相气力输灰管道的设计与应用

对气力输灰工程中密相输灰管道的设计和计算确定管内压力和速度的公式进行整理 ,同时可以得到较合理的管径和不同管径的长度。运行参数当已知时 ,给出的计算公式可作为设计的依据     

Zeta分布及其应用

基于Ｚｅｔａ函数提出一种新的Ｚｅｔａ分布，将Ｚｅｔａ分布分为两种类型（ＺｅｔａⅠ型及ＺｅｔａⅡ型），并指出连续的ＺｅｔａⅠ型分布就是Ｐａｒｅｔｏ分布。最后给出一个实例予以说明。     

条缝式纤维空气分布系统速度压力性能实验

以干冰作为发烟物质可视化研究了条缝式纤维空气分布系统表面空气的流动情况,研究了条缝式纤维空气分布系统表面空气流速和内部空气压力(总压、静压和动压)沿径向和轴向方向的分布特性。实验结果表明:采用条缝式纤维空气分布系统送风时,部分空气以较低的流速从纤维孔隙中向外渗透,其余空气则以较高的流速从孔口处射出,方向垂直于纤维壁面,各股射流流态相似,到达一定射程后开始掺混,形成类似条缝式的气流;表面空气流速(渗透流速和射流流速)沿管长方向(轴向方向)近似均匀分布;空腔内部空气径向总压、静压近似均匀分布,动压呈辐射状向壁面处递减;轴向总压和和动压逐渐减小,静压逐渐增加,且入口处压力梯度较大。     

A generalized planck distribution

We introduce a generalization of the standard Planck distribution discussed by Johnson and Kotz (1970, Section 33.6.1). This generalization results in a very flexible family which contains the gamma distribution as a particular case. In this paper we provide a comprehensive treatment of the mathematical properties of the family. We derive expressions for thenth moment, moment generating function, characteristic function, mean deviation about the mean, mean deviation about the median, Rényi entropy, Shannon entropy and the asymptotic distribution of the extreme order statistics. Estimation and simulation issues are also considered.     

A Universal Distribution for Component Failure Times

It is proposed to use a mixture of Weibull and exponential distributions to describe component reliability on the basis of a realistic model for resource consumption.     

随机过程下的生产配送策略对比

通过研究生产线物料配送的具体流程,考虑信息和物料停滞造成的线边工位等待,以及配送中心的执行费用,运用随机过程理论分别建立定量配送、定时配送和即时配送的成本模型,并对3种配送方式的最优策略进行定量分析。通过实例研究,从成本最优的角度和管理实现的角度对比分析3种配送方式,发现定量配送的一般最优性,以及定时配送和即时配送的特殊适用情况,从而为实际运营中,企业选择合适的配送方式提供科学依据。     

Equipment failure rate updating-Bayesian estimation

The paper presents a Bayes' method for augmenting generic equipment failure data with a prior distribution - predicated on the evidence, e.g., plant data - resulting in a posterior distribution. The depth of the evidence is significant in shaping the characteristics of the posterior distribution. In conditions of insufficient data about the prior distribution or great uncertainty in the generic data sources, we may use "constrained non-informative priors". This representation of the prior preserves the mean value of the failure rate estimate and maintains a broad uncertainty range to accommodate the site-specific event data. Although the methodology and the case study presented in this paper focus on the calculation of a time-based (i.e., failures per unit time) failure rate, based on a Poisson likelihood function and the conjugate gamma distribution, a similar method applies to the calculation of demand failure rates utilizing the binomial likelihood function and its conjugate beta distribution.     

Lifetime test evaluation with mathcad®: Automated weibull parameter and plotting point estimate with arbitrary confidence interval and graphics

This application note describes a computer-based method for automated evaluation of Weibull-distributed life-time data. It uses comercially available software, MathCad, to set up equations and graphs. The computer application is a simple and non-expensive way of evaluating and displaying your life-time data taking into consideration both parametric and non-parametric confidence intervals. It is valid for arbitrarily censored data.     

Reliability demonstration test for a finite population

In many situations, we want to accept or reject a population with small or finite population size. In this paper, we will describe Bayesian and non‐Bayesian approaches for the reliability demonstration test based on the samples from a finite population. The Bayesian method is an approach that combines prior experience with newer test data in the application of statistical tools for reliability quantification. When test time and/or sample quantity is limited, the Bayesian approach should be considered. In this paper, a non‐Bayesian reliability demonstration test is considered for both finite and large population cases. The Bayesian approach with ‘uniform’ prior distributions, Polya prior distributions, and sequential sampling is also presented. Copyright © 2001 John Wiley & Sons, Ltd.     

On the statistical distribution of primary and secondary dendrite arm spacing in cast metals

Statistical distributions of dendrite arm spacing have not been addressed in the literature. Two histograms for primary dendrite arm spacing in a cast nickel-based superalloy, and four histograms from a chill cast 5182 aluminium alloy ingots for secondary dendrite arm spacing have been analysed. For all datasets, lognormal distribution provided excellent fits to the data. Moreover, the Lifshitz–Slyozov–Wagner distribution was found to have systematic error in the fits to the secondary arm spacing data.