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。     

三阶色散效应对色散控制孤子传输的影响

采用分步快速傅里叶数值计算方法研究三阶色散对高速色散控制孤子传输特性的影响,通过对比不同系统条件下数值模拟的传输演化图,表明色散控制孤子系统比普通孤子系统的传输性能更优越,且对色散控制孤子系统设计具有参考价值。     

苯那普利对原发性高血压左室肥厚与QT离散度的干预

目的 :探讨苯那普利对原发性高血压 (EH)左室肥厚 (LVH)与QT离散度 (QTd)的干预作用。方法 :对 36例EH伴有LVH患者给予口服苯那普利 10mg/日 ,1次 /日 (qd) ;服药 4周时若患者BP≥ 16 0 /10 0mmHg ,则苯那普利剂量增加至 2 0mgqd ,总疗程 2 6周。治疗前后用彩色超声多普勒检测左室相关参数 ,并计算出左室重量指数 (LVMI) ;用ECG计算出QTd、校正的QTd(QTcd)。结果 :(1)治疗后的LVMI、QTd和QTcd分别较治疗前显著降低 ,差别具有显著性 (P <0 .0 1)。 (2 )治疗前的QTd、QTcd分别与治疗前的LVMI呈显著正相关 (r =0 .79,P <0 .0 1及r =0 .77,P <0 .0 1) ,治疗后的QTd和QTcd的降低程度分别与LVMI降低程度呈显著正相关 (r =0 .77,P <0 .0 1及r =0 .75 ,P <0 .0 1)。结论 :苯那普利能有效地逆转EH患者LVH ,降低QTd、QTcd ;QTd与QTcd可作为LVH逆转的评估指标。     

网络市场效率与价格离散研究

网络市场是一个新兴的市场,最近十年获得了飞速的发展.网络市场的效率是学者们一直争论的问题,价格离散可以用来表征网络市场效率的高低,网上价格离散具有多种动因.不同的网络零售商具有不同的发展战略,具有不同战略目标的网络零售商在定价战略和定价方面的选择具有明显的不同.     

Influence diagnostics in nonlinear reproductive dispersion mixed models

The class of nonlinear reproductive dispersion mixed models (NRDMMs) is an extension of nonlinear reproductive dispersion models and generalized linear mixed models. This paper discusses the influence analysis of the model based on Laplace approximation. The equivalence of case-deletion models and mean-shift outlier models in NRDMMs is investigated, and some diagnostic measures are proposed via the case-deletion method. We also investigate the assessment of local influence of various perturbation schemes. The proposed method is illustrated with an example.     

Asymptotic properties of the score test for varying dispersion in exponential family nonlinear models

Wei et al. [B.C. Wei, J.Q. Shi, W.K. Fung, and Y.Q. Hu, Testing for varying dispersion in exponential family nonlinear models, Ann. Inst. Statist. Math. 50 (1998), pp. 277–294.] developed the score diagnostics for varying dispersion in exponential family nonlinear models, such as the normal, inverse Gaussian, and gamma models, and investigated the powers of these tests through Monte Carlo simulations. In this paper, the asymptotic behaviours, including asymptotic chi-square and approximate powers under local alternatives of the score tests, are studied and examined by Monte Carlo simulations. The methods to estimate local powers of the score tests are illustrated with Grass yield data [P. McCullagh, and J.A. Nelder, Generalized Linear Models, Chapman and Hall, London (1989).].