Gauss—Markoff估计的协方差改进形式及其在SUR模型中的应用

本文采用并推广Rao[1]的协方差改进原理，证明了线性模型（1．1）的Gauaa－Markoff估计（1．2）具有协方差改进形式＝（X′X）－1X′Y－（X′X）－1X′VN［NVN］＋NY，其中N＝I－X（X′X）－1X′．这一结果用于SUR系统yi＝Xiβi＋εi（i＝1，2，…，m），容易得到Zellner两步估计的有限样本性质．本文得到了一类系统的有限样本方差结果，从而完善了一些已有结果．     

截尾样本下回归函数改良核估计的强相合性

设(Xi,Yi),i=1,,n是从取值于\Rd×R1的随机向量(X,Y)中抽取的i.i.d.样本,E(|Y|)<∞,而以m(x)=E(Y|X=x)表示回归函数。在截尾情况下,观察到的不是诸Yi本身,而是Zi=min(Yi,Ti)及δi=I(YiTi),其中Ti是与(Xi,Yi)独立的随机变量,i=1,2,…,n.当T的分布未知时,在一定条件下,得到了回归函数改良估计的强合性.     

截断情况下独立随机变量样本均值和方差的近似分布

设X1，X2……Xn为非负随机变量，相互独立具有共同的分布函数F(t)，Y1，Y2……Yn是相应的干扰随机变量，非负，相互独立具有共同的分布G(t)，并且Xi与Yi也相互独立，文章在仅能观察到Zi=min(Xi，Yi)．δi=I(Xi≤Yi)，i=1，2……，n和假设G已知的情况下．分别定义了F的均值和方差的估计量，并求出了估计量的近似分布．     

GBVE分布的参数估计

设二元随机变量（Ｘ，Ｙ）的生存函数为可．把它称作ＧＢＶＥ（θ１，θ２，δ）．本文采用把元件和系统（串联）的定时截尾寿命试验数据综合起来进行统计分析的方法，研究ＧＢＶＥ（θ１，θ２，δ）中参数的估计及其性质．在θ１＝θ２＝θ的情况下给出了（θ，δ）的极大似然估计证明了具有强相合性和渐近正态性．在无θ１＝θ２限制时给出了（θ１，θ２，δ）的矩法估计（θ１，θ２，θ３，δ），证明了同样具有强相合性和渐近正态性．     

矩阵损失下多元统计中期望向量的线性Minimax估计

设yi，y2，…，yn，i．i．d，Ey1＝β，Cov（y1）＝∑，这里ε∈RP和∑＞0未知，我们估计β，估计类为L＝｛Liyi：Li为p阶常数方阵，i＝1，2，…，n｝，损失函数为其中V1，V2＞0已知，我们研究β的一个线性估计在L中的Minimax性．主要结果是1．当V2＝kV1，k＞0时，β的唯一的Ⅰ-型线性Minimax估计为Y／（1＋），其中Y＝＝2．当V2＝kV1对所有k＞0不成立，但V1V2＝V2V1时，β的Ⅰ-型线性Minimax估计不存在．3．当V1V2＝V2V1时，β的Ⅱ-型线性Minimax估计为，这个估计在V1，V2满足条件V1V2＝V2V1下变化时，构成了集合｛AY：A对称，A的特征根均在（0，1）中｝．4．对于一般的V1，V2；Y仍是β的Ⅱ-型线性Minimnax估计，这个估计在V1，V2任意变化时，构成了集会｛AY:A的特征根是实的，特征根全在（0，1）中，且A只具有线性初等因子｝．     

一类SUR模型参数两步估计的有限样本结果

对于m（3）SUR模型（1），其设计矩阵满足条件（4），本文得到了回归系数βi（i＝1，…，m）的两步Aitken估计的精确协方差表达式，从而获得了两步估计优于LS估计的有限样本性质．特别是，当m＝3时本文结果可以与Revankar（1974）给出的一类两方程SUR模型结果相比较.     

多元回归系数的所有k—容许估计

对于多元线性模型Y～N（XΘ，）（已知）中的可估函数SXΘ的估计问题，取损失函数为（δ－SXΘ）'（δ－SXΘ）．用风险函数矩阵的前k个顺序特征值之和作为比较不同估计的风险函数大小的标准，我们可定义所谓的"k－容许估计"．本文得到了SXΘ的线性估计AY＋D在一切估计类中k－容许的充要条件．     

污染数据回归分析中估计的强相合性

考虑简单回归模型（Ⅰ）yi＝α＋xiβ＋εi，i＝1，2，…，n，与半参数回归模型（Ⅱ）yi＝xiβ＋g（ti）－εi，i＝1，2，…，n，其中Eεi＝0，Eεi2＝σ12．假定y1，y2，…，yn受到另一独立同分布随机变量序列μ1，μ2，…，μn的污染，且仅能观察到污染数据，｛μi｝与｛yi｝独立．对文[1]，[2]中给出的α，β，g（·）及污染参数v的估计，本文在适当的条件下，证明了它们的强相合性．     

非参数回归函数核估计的Lp收敛速度

在p≥1和适当的条件下，给出了回归函数m(x)＝E（Y|X＝x）的核估计的若干种Lp收敛速度，改进并推广了韦来生（1984）的结果。     

生存率终检模型

1引言．终检病人的生存经历是临床上最感兴趣的．通过建立观测到的和未观测到的生存经历之间的关系[1]可给出一个笼统的生存率估计，如kaplan－Meier[2]或Berkson－gage估计值．利用生存率终检模型[4]可给出终检病人生存专率；并经累积死亡数的分解得以实现．本文说明其原理并提出另外两种实现方法：Kanlan－Meier估计值的自相容性[5]和记分函数[6]．2．原理．令随机变量X是检验条件下的真正生存时间．其分布为F（t）＝P（XS心即病人到州的累积死亡概率，其补为F川一l一月（小令随机变量Y代表终检时间．其分布为E（t）＝P（y＜i）；其…     

RECENT PROGRESS ON SPHERICAL HARMONIC APPROXIMATION MADE BY BNU RESEARCH GROUP ——In memory of Professor Sun Yongsheng

As early as in 1990, Professor Sun Yongsheng, suggested his students at Beijing Normal University to consider research problems on the unit sphere. Under his guidance and encouragement his students started the research on spherical harmonic analysis and approximation. In this paper, we incompletely introduce the main achievements in this area obtained by our group and relative researchers during recent 5 years （2001-2005）. The main topics are： convergence of Cesaro summability, a.e. and strong summability of Fourier-Laplace series; smoothness and K-functionals; Kolmogorov and linear widths.     

On a class of self-similar processes with stationary increments in higher order Wiener chaoses

We study a class of self-similar processes with stationary increments belonging to higher order Wiener chaoses which are similar to Hermite processes. We obtain an almost sure wavelet-like expansion of these processes. This allows us to compute the pointwise and local Hölder regularity of sample paths and to analyse their behaviour at infinity. We also provide some results on the Hausdorff dimension of the range and graphs of multidimensional anisotropic self-similar processes with stationary increments defined by multiple Wiener–Itô integrals.     

A REPRESENTATION FORMULA RELATED TO SCHR(O)DINGER OPERATORS

Schr(o)dinger operator is a central subject in the mathematical study of quantum mechanics.Consider the Schrodinger operator H = -△ V on R, where △ = d2/dx2 and the potential function V is real valued. In Fourier analysis, it is well-known that a square integrable function admits an expansion with exponentials as eigenfunctions of -△. A natural conjecture is that an L2 function admits a similar expansion in terms of "eigenfunctions" of H, a perturbation of the Laplacian (see [7], Ch. Ⅺ and the notes), under certain condition on V.     

On a class of Riemann surfaces

It is considered the class of Riemann surfaces with dimT1 = 0, where T1 is a subclass of exact harmonic forms which is one of the factors in the orthogonal decomposition of the spaceΩH of harmonic forms of the surface, namely The surfaces in the class OHD and the class of planar surfaces satisfy dimT1 = 0. A.Pfluger posed the question whether there might exist other surfaces outside those two classes. Here it is shown that in the case of finite genus g, we should look for a surface S with dimT1 = 0 among the surfaces of the form Sg\K , where Sg is a closed surface of genus g and K a compact set of positive harmonic measure with perfect components and very irregular boundary.     

CONTENTS OF VOLUME 30

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Instructions for contributions

正Applied Mathematics-A Journal of Chinese Universities,Series B(Appl.Math.J.Chinese Univ.,Ser.B)is a comprehensive applied mathematics journal jointly sponsored by Zhejiang University,China Society for Industrial and Applied Mathematics,and Springer-Verlag.It is a quarterly journal with     

Journal of Mathematical Research with Applications Guide for Authors

正Journal overview:Journal of Mathematical Research with Applications(JMRA),formerly Journal of Mathematical Research and Exposition(JMRE)created in 1981,one of the transactions of China Society for Industrial and Applied Mathematics,is a home for original research papers of the highest quality in all areas of mathematics with applications.The target audience comprises:pure and applied mathematicians,graduate students in broad fields of sciences and technology,scientists and engineers interested in mathematics.     

Staircase transportation problems with superadditive rewards and cumulative capacities

A cumulative-capacitated transportation problem is studied. The supply nodes and demand nodes are each chains. Shipments from a supply node to a demand node are possible only if the pair lies in a sublattice, or equivalently, in a staircase disjoint union of rectangles, of the product of the two chains. There are (lattice) superadditive upper bounds on the cumulative flows in all leading subrectangles of each rectangle. It is shown that there is a greatest cumulative flow formed by the natural generalization of the South-West Corner Rule that respects cumulative-flow capacities; it has maximum reward when the rewards are (lattice) superadditive; it is integer if the supplies, demands and capacities are integer; and it can be calculated myopically in linear time. The result is specialized to earlier work of Hoeffding (1940), Fréchet (1951), Lorentz (1953), Hoffman (1963) and Barnes and Hoffman (1985). Applications are given to extreme constrained bivariate distributions, optimal distribution with limited one-way product substitution and, generalizing results of Derman and Klein (1958), optimal sales with age-dependent rewards and capacities.To our friend, Philip Wolfe, with admiration and affection, on the occasion of his 65th birthday.Research was supported respectively by the IBM T.J. Watson and IBM Almaden Research Centers and is a minor revision of the IBM Research Report [6].     

Boundedness for commutators of multipliers on Hardy type spaces

In this paper, we study the commutators generalized by multipliers and a BMO function. Under some assumptions, we establish its boundedness properties from certain atomic Hardy space Hb^p（R^n） into the Lebesgue space L^p with p 〈 1.