竖直圆管中超临界压力CO2对流换热实验研究

本文对超临界压力CO2在竖直加热圆管内的对流换热进行了实验研究,比较了不同流向、不同热流密度等对流动和换热的影响。实验结果表明,管内径为2mm时,在低进口Re条件下,由于浮升力影响导致层流向湍流提前转变, 对流换热增强;与向上流动相比,向下流动更易由层流转变为湍流;向下流动的换热要强于向上流动,表明浮升力对换热有很大影响。对于管内径为0．27 mm的微细圆管,当进口Re高于104时,浮升力的影响可以忽略,对流换热系数的变化完全由物性的变化尤其是cp的变化导致。     

一定条件下样本函数极值的重采样方法

本文对一定条件下样本函数极值的重采样方法进行了研究,给出了γ~2估计的几种方法,包括减-d折刀法、减-1折刀法和自助法；并对得到的统计量的性质进行了分析．     

高温核磁共振探头

本文设计研制了一种用于动态核磁共振研究的高温探头,它适用于磁铁极间距离为30mm的核磁共振波谱仪,探头中样品处的温度从室温至1300K连续可变,探头既可用于质子(¹H)也可用于其它核(如¹¹B,³¹P,²³Na等),并给出了高温探头的结构、指标及实际应用于测量的例子。     

分布自由的回归函数近邻核估计的相合性

本文获得了基于混合，α－混合样本的回归函数核估计，随机窗宽核估计，近邻核估计的强相合性，积分绝对误差的强相合性与平均相合性，所得结果对所有ｘ的分布μ均成立，其中核函数的支撑可以无界，甚至可以是不可积的。     

Exponential bounds of mean error for the kernel estimates of regression functions

Let (X, Y), (X₁, Y₁), …, (X_n, Y_n) be i.d.d. R^r × R-valued random vectors with E|Y| < ∞, and let Q_n(x) be a kernel estimate of the regression function Q(x) = E(Y|X = x). In this paper, we establish an exponential bound of the mean deviation between Q_n(x) and Q(x) given the training sample Zⁿ = (X₁, Y₁, …, X_n, Y_n), under conditions as weak as possible.     

How to optimize discrete-event systems from a single sample path by the score function method

We present a method for deriving theoptimal solution of a class of mathematical programming problems, associated with discrete-event systems and in particular with queueing models, while using asingle sample path (single simulation experiment) from the underlying process. Our method, called thescore function method, is based on probability measure transformation derived from the efficient score process and generating statistical counterparts to the conventional deterministic optimization procedures (e.g. Lagrange multipliers, penalty functions, etc.). Applications of our method to optimization of various discrete-event systems are presented, and numerical results are given.Research supported by the L. Edelstein Research Fund at the Technion-Israel Institute of Technology.     

新疆骆驼蓬属药用植物种类、生长环境与分布调查

对新疆骆驼蓬属药用植物的种类、生长环境和分布进行了调查。通过野外实地考察和采样，制作植物标本，并测定和采集生长地的海拔高度、经度、纬度等地理参数和年平均气温、年降水量等气象参数。结果表明，骆驼蓬在全疆各地均有分布；骆驼蒿仅在哈密地区有少量分布，并与骆驼蓬混生，新疆境内未见有多裂骆驼蓬生长。可见骆驼蓬属耐干旱植物，新疆资源丰富，具有药用、绿化和水土保持等作用。     

On the equivalence of three types of blocking in non-Markovian tandem queues

Definitions of blocking types for tandem queueing systems are given where each stage consists of multiple servers. Some of them are shown to be identical with respect to service initiation epochs at each stage. Such identical relationships are proved using sample path correspondence, and are therefore valid irrespective of the arrival process and the service time distributions.     

广义非参数回归的B样本贝叶斯估计

本文主要研究广义非参数模型B样条Bayes估计 .将回归函数按照B样条基展开 ,我们不具体选择节点的个数 ,而是节点个数取均匀的无信息先验 ,样条函数系数取正态先验 ,用B样条函数的后验均值估计回归函数 .并给出了回归函数B样条Bayes估计的MCMC的模拟计算方法 .通过对Logistic非参数回归的模拟研究 ,表明B样条Bayes估计得到了很好的估计效果     

Bartlett's formulae—Closed forms and recurrent equations

We show that the entries of the asymptotic covariance matrix of the sample autocovariances and autocorrelations of a stationary process can be expressed in terms of the square of its spectral density. This leads to closed form expressions and fast computational algorithms.This research has been partly supported by contract No. MM 440/94 with the Bulgarian Ministry of Science and Education and by the Division of Quality Technology and Statistics, Luleå University, Sweden.