Land cover change in Ningbo and its surrounding area of Zhejiang Province,1987～2000

INTRODUCTION Land use and land cover change (LUCC) has become an increasingly important aspect of global environmental change and is a multi-disciplinary subject where geophysicist, bio-physicists and socio-economists meet one another. Land cover is an expression of human activities and, as such, changes with changes in land use and management (Louisa and Antonio, 2001), and land cover change could be regarded as change in biotic diversity, actual and potential productivity, soil quality…     

Application of the Bayes＇ theory to the failure rate evaluation of electrical apparatus

The Weibull distribution has been widely used in reliability fields. A mixed Weibull distribution represents a population that consists of several Weibull subpopulations. In this paper, a new approach which combines the least-squares method with Bayes＇ theorem, takes advantage of the parameter estimation for single Weibull distribution is developed to estimate the parameters of each subpopulation. The estimates given by this paper also satisfy the maximum likelihood equation. The estimates of the failure rate of the mixed Weibull population are given. An actual test data is computed by using the proposed method. The Kolmogorov-Smirnov goodness-of-fit test turns out that the proposed method yields more accurate result.     

最优停止规则在多种选择中的应用

众所周知,在n种物品中选择k种优秀物品是常发生的事。问题是按怎样的选择方式才能使选到的优秀物品的可能性最大。本文应用最优停时定理给出了在n种物品中选择k种物品的一般数学模型及最优选择规则的求解方程;本文还就k等于2给出了最优规则τ_1~α,n及按此规则进行选择所能得到的概率P~2——在n种物品中选择2种优秀物品的最大概率。     

太阳电池发电系统的最佳功率流控制

本文提出一种实现太阳电池输出最大功率的跟踪控制方法,给出实验结果,证实这一控制方法的可行性和有效性。文中还讨论了太阳电池发电系统最佳功率流控制的实现方法以及补偿无功功率和谐波失真等问题.     

均匀分布中参数θ的估计量的比较

结合教学中遇到的问题,举例分析和说明了仅有无偏性不足以判定一个估计的好坏。     

New Ways to Evaluate Goodness of Fit: A Note on Using Equivalence Testing to Assess Structural Equation Models

Structural equation models are typically evaluated on the basis of goodness-of-fit indexes. Despite their popularity, agreeing what value these indexes should attain to confidently decide between the acceptance and rejection of a model has been greatly debated. A recently proposed approach by means of equivalence testing has been recommended as a superior way to evaluate the goodness of fit of models. The approach has also been proposed as providing a necessary vehicle that can be used to advance the inferential nature of structural equation modeling as a confirmatory tool. The purpose of this article is to introduce readers to key ideas in equivalence testing and illustrate its use for conducting model–data fit assessments. Two confirmatory factor analysis models in which a priori specified latent variable models with known structure and tested against data are used as examples. It is advocated that whenever the goodness of fit of a model is to be assessed researchers should always examine the resulting values obtained via the equivalence testing approach.     

最大模原则的推广及应用

主要讨论了Phragmen-Lindelof原则在有界区域边界上有不解析点的函数;在无界区域上满足适当条件函数的最大模的状态;对在有界区域上的解析函数f(z),其实部或虚部有界,则在该区域内|f(z)|有界.     

矩法估计与极大似然估计的比较

以二项分布为例,讨论了其分布参数的矩法估计与极大似然估计,并比较了两种估计的优良性质,主要讨论它们的一致性、无偏性和有效性．     

光栅衍射次极大条纹相对强度分布的仿真研究

根据惠更斯-菲涅耳原理,应用Matlab软件编程,模拟了光栅衍射条纹次极大强度的分布图形,通过改变缝数、光栅常数和缝宽等参数,观察到次极大衍射条纹的相应变化,得出了缝数越多,则次极大的相对强度越小,而光栅常数和缝宽则只能改变次极大的分布。计算机仿真方法扩展了光栅衍射问题的研究途径与方法,具有一定的应用价值,尤其对于教学具有直观作用。     

两种Zipf定律拟合方法的对比实证研究

采用普通最小二乘法和最大似然估计两种方法分别对Zipf定律的分布进行拟合比较研究。普通最小二乘法是目前曲线拟合中普遍采用的方法,而最大似然估计是曲线拟合更为合理的方法。分别利用三组中文和三组英文语料,对两种方法进行对比实证研究,结果发现最大似然估计方法的拟合更合理,对Zipf定律的拟合比普通最小二乘法好,同时发现英文词汇比中文更好地符合Zipf定律分布,即中文语料不严格符合经典的Zipf定律分布。本研究可以为幂律拟合的研究提供一些参考。