连分式算法插值顺序的有效安排

n节连分式算法是一个实用的一维搜索方法。构造连分式插位函数时,部分分母的计算在该算法中占有较大的比重,本文通过对插值点先后顺序的有效安排,使得部分分母的计算量下降近三分之一。最后,对该算法可能遇到的数值困难提供了一个实施方案。     

Conservatism of the Accident Sequence Evaluation Program HRA Procedure

This paper presents a limited assessment of the conservatism of the Accident Sequence Evaluation Program (ASEP) human reliability analysis (HRA) procedure described in NUREG/CR-4772. The data for this study are derived from simulator examination reports from the NRC requalification examination cycle for nuclear power plant operators. The ASEP procedure was used to estimate human error probability (HEP) values for critical tasks, and the HEP results were compared with the failure rates observed in the examinations. The ASEP procedure was applied by PNNL operator license examiners who supplemented the limited information in the examination reports with expert judgment based upon their extensive simulator examination experience. Comparison of the average of the ASEP HEP values with the fraction of the population actually failed and demonstrated that the ASEP HEP values are larger (conservative) by a statistically significant average factor of two. Partitioning of tasks into subgroups based on the ASEP HEP values and comparison of the subgroup average ASEP HEP values with observed subgroup failure rates showed little or no conservatism for small ASEP HEP values, but considerable conservatism for larger ASEP HEP values.     

从12SrRNA部分基因序列探讨鳄的系统发生关系

本文用常规方法测定了雅卡凯门鳄（caiman yacane）、新几内亚鳄（crocodylus novaeguineae）等2种鳄类的约400bp的mtDNA12SrRNA基因片段的部分序列，所测序列与GenBank中的其他18种鳄类的12SrRNA基因相应片段同源序列一起经Clustal X1．8软件进行比对，并以乌龟（chinemys reevesii）为外群，用ClustalX（1．8），Mega2软件以及paup软件将这20种鳄的12SrRNA基因部分序列进行比对后构建了20种鳄的进化关系树，并分别用NJ树，MP树探讨它们之间的系统发生关系。其结果显示：食鱼鳄属Gavialis与马来假食鱼鳄属Tomistoma的亲缘关系较近，构成姐妹群并位于鳄科分支的基部。非洲窄吻鳄（Crocodylus cataphractus）与骨喉鳄（Osteolaemus retraspis）形成姐妹群，它们的亲缘关系比与其它真鳄类的关系更近，赞同非洲窄吻鳄应从鳄属中独土出来归属于长吻鳄属Mecistops的观点，因此鳄科包括鳄属、骨喉鳄属和长吻鳄属，它们的关系为（鳄属（骨喉鳄属，长吻鳄属））。鼍科4属中凯门鳄属与黑鳄属关系最近，接下来的是古鳄属、鼍属，而且鼍属是鼍科中起源最早的类群。扬予鳄（Alligator sinensis）与密河鳄（Alligator mississippiensis）较近的亲缘关系得到支持，但它们并没有形成姐妹群关系。     

Statistical methodology for assessing homology of intronic regions of genes

We consider the problem of statistically evaluating the similarity of DNA intronic regions of genes. Present algorithms are based on matching a sequence of interest with known DNA sequences in a gene bank and are designed primarily to assess homology among exonic regions of genes. Most research focuses on exonic regions because they have a clear biological significance, coding for proteins, and therefore tend to be more conserved in evolution than intronic regions. To investigate whether the intronic features of genes whose expression is highly sensitive to environmental perturbations differ from genes that have a more constant expression, a collection of oncogenes, tumor suppressor genes, and nonregulatory genes involved in energy metabolism are compared. An analysis of the features of these genes' intronic regions result in clustering by regulatory group. In addition, Billingsley's test for Markov structure (1961) suggests that 67% of the intronic regions in this collection of genes show evidence of nonrandom structure, indicating the possibility of a biological function for these regions. The result of Billingsley's test for homology is used as input to a clustering algorithm. The biological significance of this methodology lies in the identification of groups based on the intronic regions from genes of unknown function. With the advent of rapid sequencing techniques, there is a great need for statistical techniques to help identify the purpose of poorly understood portions of genes. These methods can be utilized to assess the functional group to which such a gene might possibly belong.     

直接序列扩频信号PN序列盲估计方法

在非协作信息侦测情况下,提出了一种实用的直接序列扩频(DS-SS)通信信号PN码序列的快速盲估计方法。该方法根据DS-SS基带信号的特点,首先采用二阶循环统计量估计PN码周期,然后利用分段互相关平均估计PN码同步始点;并在准确预估计这2个参数的基础上,将接收信号以PN码周期分成多个时段,利用多重互相关方法估计PN码序列。理论分析与仿真表明,该方法在截获信号信噪比很低的情况下有很好的估计性能,且无需任何先验知识,对PN码码型也没有任何限制,是一种有效的快速盲估计方法。     

无线光通信脉冲位置调制的符号同步技术

讨论了PPM序列的符号同步原理;在分析随机PPM序列的精确符号同步概率上限的基础上,给出了一种在PPM序列中插入同步信号来实现PPM精确符号同步的方案及其数字逻辑电路实现。该方案通过改变PPM调制序列结构,按照一定的间隔在PPM序列中插入脉冲时隙肩并肩的2个相邻符号作为同步符号,通过对同步符号的检测来提取同步信号。理论及仿真实验表明,该方案能实现PPM精确符号同步。     

高校田径运动会新计分方法及其作用的探讨

1999年度绍兴文理学院田径运动会计分方法进行了改进--增设了参赛成绩分(以下简称新方法).弥补了过去仅设名次分的不足之处.具体表现在报名与参赛率比往年提高,竞争外延扩大,项目间竞争激烈.     

文变染乎世情兴废系乎时序——《文心雕龙·时序》的文学史论认识

《文心雕龙.时序》的“质文代变”和“文变染乎世情”是刘勰在共时性框架下的对于历代文学的总结,“崇替在选”揭示了政治教化、社会风尚和统治者好恶对于文学的影响,反映出刘勰的文学史的线索观是完全的他律论模式,并以经典作为主要的文学史的价值评判标准。     

从诗歌中管窥汉英语言文字差异

借助中英诗歌的不同表现 ,本文从语言文字的语音、语形、语义、语法四方面论述了汉英两种语言文字本身的差异。从而说明上述差异仅是汉英两种语言的本色而已 ,并非是绝对的此有彼无 ,而是相对的此强彼弱。民族语言之间的相互渗透 ,相互影响是过去、现在及未来语言发展的规律和趋势。     

大学生心理健康与未来发展--包头师范学院2001级学生心理健康状况调查报告

通过对包头师范学院2001级学生心理健康状况抽查分析,结果得出呈现中等程度心理疾病的人数占总人数的1/3以上;男女生的心理健康状况无明显差异;心理健康的主要问题表现在强迫症、人际关系敏感、抑郁、焦虑、偏执及精神病症.产生以上问题的原因主要在于这一群体的家庭出身、高考影响、学习压力、社会竞争压力等.解决问题的关键在于建立心理健康教育机构;学生工作机构应通过各种途径积极引导学生建立正确的世界观、人生观、价值观.