介质的非均匀性对高次谐波影响的研究

讨论了气体介质的非均匀性对飞秒激光高次谐波产生过程的可能影响.计算结果表明,采用喷阀技术所提供的气体介质的密度梯度和气体原子运动速度的影响很小,不会产生实验上可观测的效果.这一结果支持了喷气靶在高次谐波产生中的广泛应用 关键词： 高次谐波 气体介质 各向异性 飞秒激光     

Approximation by modified Szasz—Mirakjan operators on weighted spaces

The theorems on weighted approximation and the order of approximation of continuous functions by modified Szasz—Mirakjan operators on all positive semi-axis are established.     

不同含水量条件下树种叶片光谱差异分析

叶片含水量是影响树种光谱特征的一个重要因素,探索不同叶片含水量条件下相同树种叶片光谱特征的变化规律及相同叶片含水量条件下不同树种叶片的光谱差异,不仅是高光谱植被遥感信息识别的关键,也为研究植被光谱随着叶片含水量变化产生的差异提供理论支撑。利用地物光谱仪对6个树种叶片进行观测,获取了不同含水量叶片的反射光谱,同时进行一阶微分光谱变换,从而分析不同叶片含水量条件下各树种叶片的光谱变化特征,对比了相同叶片含水量条件下不同树种叶片的光谱差异,探索高光谱遥感识别树种叶片含水量的可能波段。结果表明：各树种叶片光谱都随着叶片含水量的改变而产生较大差异,但变化规律各有不同;相同叶片含水量条件下,不同树种叶片的光谱在部分波长范围差异较大,为实现树种高精度识别提供了可能。本研究旨在为植被叶片光谱库的构建以及植被的高光谱识别提供理论支撑和基础数据。     

On Tensor Products of l-Operators and bo-Operators

It is proved that the tensor product of two linear operators is a cone summing operator (respectively, order bounded operator) if and only if both operators are cone summing (respectively, order bounded).     

Bootstrapping Autoregressive and Moving Average Parameter Estimates of Infinite Order Vector Autoregressive Processes

We consider anr-dimensional multivariate time series {y_t, tZ} which is generated by an infinite order vector autoregressive process. We show that a bootstrap procedure which works by generating time series replicates via an estimated finitek-order vector autoregressive process (k→∞ at an appropriate rate with the sample size) gives asymptotically valid approximations to the joint distribution of the growing set of estimated autoregressive coefficients and to the corresponding set of estimated moving average coefficients (impuls responses).     

Third order efficiency implies fourth order efficiency: A resolution of the conjecture of J. K. Ghosh

Under suitable regularity conditions, it is shown that a third order asymptotically efficient estimator is fourth order asymptotically efficient in some class of estimators in the sense that the estimator has the most concentration probability in any symmetric interval around the true parameter up to the fourth order in the class. This is a resolution of the conjecture by Ghosh (1994, Higher Order Asymptotics, Institute of Mathematical Statistics, Hayward, California). It is also shown that the bias-adjusted maximum likelihood estimator is fourth order asymptotically efficient in the class.     

Lifetime distribution and estimation problems of consecutive-k-out-of-n:F systems

Explicit formula is given for the lifetime distribution of a consecutive-k-out-of-n:F system. It is given as a linear combination of distributions of order statistics of the lifetimes of n components. We assume that the lifetimes are independent and identically distributed. The results should make it possible to treat the parametric estimation problems based on the observations of the lifetimes of the system. In fact, we take up, as some examples, the cases where the lifetimes of the components follow the exponential, the Weibull, and the Pareto distributions, and obtain feasible estimators by moment method. In particular, it is shown that the moment estimator is quite good for the exponential case in the sense that the asymptotic efficiency is close to one.This research was partially supported by the ISM Cooperative Research Program (94-ISM-CRP-5).     

液态铝基合金微观结构及其性质的分子动力学模拟研究(英文)

利用分子动力学研究了液态铝基合金Al80Fe20和Al80Cu20在800~2200K温度范围内的微观结构和性质的变化.扩散系数的计算结果显示两合金有着不同的动力学行为.温度大约1400K以下液态Al80Cu20的扩散系数随温度的变化比Arrhenius关系所预期的要慢些,所得结果与Brillo研究小组的实验结果基本一致.当液态铝基合金的动力学发生异常变化时,其微观二十面体短程序的含量和作用也发生相应的变化.因此,熔体的奇特动力学行为可能由于其微观局域结构短程序随着温度的变化而异常地改变而引起的.     

MOMENT GENERATING FUNCTIONS OF RANDOM VARIABLES AND ASYMPTOTIC BEHAVIOUR FOR GENERALIZED FELLER OPERATORS

1. Introduction and NotationsThe generalized Feller operators which include many famous operators, such ajsBernstein, Szasz-Mirakjan, BaskakoV, Meyer--K5nig and Zeller operators, can be constructed by making use of the probabilistic method. In the paper [1][2], Xu JihuaPr(--lvjdetl a general scheme f(,r its construction, and Zhao Jillghui showed that theFeller type operators are of good approximations f'or unbounded functions.Our purpose is to present representation of moment generating …     

自然序Dubreil-Jacotin富足半群

本文考虑Ｄｕｂｒｅｉｌ－Ｊａｃｏｔｉｎ富足半群,给出若干特征后,建立了自然序Ｄｕｂｒｅｉｌ－Ｊａｃｏｔｉｎ富足半群的结构,作为应用,给出了具有正则性条件的自然序Ｄｕｂｒｅｉｋｌ－Ｊａｃｏｔｉｎ富足半群的结构,并将结果推广到具有最大幂等元的自然序的偏序富足半群上。