High breakdown point robust estimators with missing data

In this paper, we propose a new procedure to estimate the distribution of a variable y when there are missing data. To compensate the presence of missing responses, it is assumed that a covariate vector x is observed and that y and x are related by means of a semi-parametric regression model. Observed residuals are combined with predicted values to estimate the missing response distribution. Once the responses distribution is consistently estimated, we can estimate any parameter defined through a continuous functional T using a plug in procedure. We prove that the proposed estimators have high breakdown point.     

Spatial pattern analysis of the incidence of aster yellows disease in lettuce

The degree of aggregation of lettuce plants infected by aster yellows phytoplasma (AYP) was investigated in 12 fields from three experiments. Position of diseased and healthy plants was mapped in a 6–9×12-m section of each field; for most analyses, fields were divided into 10-plant quadrats. Mean disease incidence (p) ranged from 0.01 to 0.30. The frequency of diseased plants was described by the beta-binomial distribution, with an index of aggregation (θ) ranging from 0 to 0.17, positively correlated withp, and generally increasing over time within a field. Distance-class analysis revealed a core-cluster size of only a few plants. However, spatial autocorrelations ofp between quadrats were not significant, indicating that the scale of spatial pattern was small, generally less than 10 plants. An overall measure of aggregation was given by the slope parameter of the binary form of the power law, in which the log of the calculated variance is regressed on the log of the theoretical variance for a binomial distribution. The slope was 1.18 and significantly different from 1. Results for this “simple-interest” disease are interpreted in relation to the persistent transmission of AYP by its aster leafhopper vector.     

亨利定律及其在环境科学与工程中的应用

亨利定律描述了化合物在气液两相中的分配规律,在环境科学与工程领域中有着广泛的应用.鉴于挥发性有毒化合物在多介质环境中的行为研究的重要性,本文对于亨利定律常数在真实自然环境中应用的最新研究做了评述.此外,本文首次将不同教材的亨利定律常数的定义做了汇编.     

环圈结构的研究

环圈结构这新种型慢波结构具有一系列独特的优点。本文在文献[1]的基础上对它继续进行深入研究,利用格林函数给出了积分方程解,讨论了该结构的色散方程,从这个色散方程出发,研究环结构、介质环圈支持的环圈结构与环杆线。并利用这种系统的场论解导出了环圈结构中的功率流和耦合阻抗的表达式,以及对环圈结构的耦合阻抗进行了详细的讨论。作为其特例,本文还研究了环杆线与环结构的耦合阻抗。本文所得的一系列结果为利用这类慢波结构提供了依据。     

GOODNESS OF FIT FOR THE BINOMIAL DISTRIBUTION

Goodness of fit testing for the binomial distribution can be carried out using Pearson's X²_p statistic and its components. Applications of this technique are considered and compared with recently suggested empirical distribution function tests. Diagnostic use of components is discussed.     

狭缝离轴全息图的色散及单色仪

用白光源再现一狭缝离轴全息图,得到色散的狭缝象;在狭缝实象处加一狭缝光阑,实现了单色输出。计算并测量了谱线半宽度,结果表明单色仪是可行的。     

An exact decomposition for a class of exponential dispersion models: Application to sequential testing

We define the Wishart distribution on the cone of positive definite matrices and an exponential distribution on the Lorentz cone as exponential dispersion models. We show that these two distributions possess a property of exact decomposition, and we use this property to solve the following problem: given q samples (y_il,… y_iNj), i = l,…,q, from a N(μ_i,Σ_i,) distribution, test H:Σ₁ = Σ₂ = … = σ_q. Using the exact decomposition property, the classical test statistic for H, involving q parameters p_i = (N_i, - l)/2, i = 1,…,q, is replaced by a sequence of q - l test statistics for the sequence of tests H_i,:σ₁ =σ₂ = … =σ_i given that H_i-1 is true, i = 2,…,q. Each one of these test statistics involves two parameters only, p._i-1 = p₁ + … + p_i-1 and p_i. We also use the exact decomposition property to test equality of the “direction parameters” for q sample points from the exponential distribution on the Lorentz cone. We give a table of critical values for the distribution on the three-dimensional Lorentz cone. Tables of critical values in higher dimensions can easily be computed following the same method as in dimension three.     

色散控制“呼吸”孤子传输特性的数值研究

采用数值计算方法研究了色散控制“呼吸”孤子传输系统稳定传输的特性,研究结果表明:脉冲的主体或“内核”部分的演化是稳定的,而脉冲所受的周期放大损耗以及色散项的扰动在归一化放大间距Z_d(Z_d)<<1条件下,该扰动对脉冲主体的影响可以忽略,从而证明了色散控制“呼吸”孤子传输是一个稳定的传输方案。     

尘土浓度检测技术研究

本文提出了采用激光分光式传感器的检测技术,并对其温度漂移补偿、抗噪能力等方面进行了改善,提高了其在现场试验中的稳定性和可靠性。     

40 Gb/s单通道光纤传输系统研究

提出了一种比特率为40 Gb/s的单通道传输系统的设计方案,通过大量的数值仿真研究了在单波长传输系统中放大器间隔、脉冲占空比、色散补偿因子、色散补偿系数、光纤的入纤功率等参数对系统传输性能的影响,并根据这些影响关系设计了一个九段的光纤传输系统,其传输距离为928 km。仿真结果对单波长和多波长40 Gb/s光纤传输系统的设计具有指导意义。