合作储存与文献剔旧的甄别标准及交互机制研究

从区分低利用率文献与剔旧文献的动因入手,分别从内涵外延、选择标准及处理方式等几个角度对低利用率文献与剔旧文献的异同点进行详细阐述,为正确认识两者之间的关系,以便规范合理地处理低利用率文献提供一定借鉴和参考。并在此基础上构建低利用率文献合作储存与文献剔旧之间的交互机制模型,揭示合作储存与文献剔旧之间的交互关系。     

一种二用户协作HARQ通信方案

针对协作通信(cooperative communication)的重传问题,提出了在2个用户和基站之间的通信过程中,用户之间如何协作进行混合ARQ(hybrid ARQ)的方案. 通过分时发送机制,每个用户都保存对方上一次发送的数据,在收到基站的ACK/NACK后,根据基站的指示,从存储的上一次发送数据包中,寻找需要重传的数据包,并插入自己需要传送的新数据包,在下一个发送时隙中进行传输. 通过协作通信系统所实现的空间分集增益,提高了HARQ的性能. 比较2个用户分别独立与基站通信和相互协作与基站通信的HARQ方案,并通过理论分析和仿真,比较不同信噪比(SNR)下的吞吐量(throughput)和误包率(PER)以及平均时延,证实了本系统在可提高系统传输时延的前提下,具有更高的吞吐量和更低的PER.     

我国乳制品业的集中度、布局与绩效分析

分析了我国乳制品业的集中度与布局及其对绩效的影响,结果显示,乳制品业的集中度较低,但呈不断上升的态势;乳制品业的布局已经由资源导向型向市场导向型转变,提高乳制品业的集中度及合理的布局将会改善其绩效水平。     

棒球投手专项训练引起盂肱关节旋转肌力变化的研究

目的:通过对参加夏季集训的23名高校棒球运动员(11名女性,12名男性)进行了阶段性盂肱关节内旋、外旋等长肌力测试,探讨棒球投手专项训练引起的盂肱关节旋转肌力特征的变化趋势,结果:盂肱关节内旋(IR)肌力在整个棒球集训过程中显著增长,盂肱关节外旋(ER)肌力在从训练前到训练中期显著增长,而从训练中期到训练后无明显变化,盂肱关节内旋/外旋肌力(IR/ER)比值也因此增大。提示棒球投手专项训练中为了预防肩部损伤的发生,应注重发展盂肱关节外旋肌力。     

Understanding the concepts of proportion and ratio constructed by two grade six students

The purpose of this study was to construct an understanding of two grade six students' proportional reasoning schemes. The data from the clinical interviews gives insight as to the importance of multiplicative thinking in proportional reasoning. Two mental operations, unitizing and iterating play an important role in student's use of multiplicative thinking in proportion tasks. Unitizing a composite unit and iterating it to its referent point enables one to preserve the invariance of a ratio. Proportions involved the coordination of two number sequences, keeping the ratio unit invariant under the iteration. In the iteration process, one needed to explicitly conceptualize the iteration action of the composite ratio unit to make sense of ratio problems and to have sufficient understanding of the meaning of multiplication and division and its relevance in the iteration process. One needed to have constructed multiplicative structures and iteration schemes in order to reason proportionally. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modeling educational choices. A binomial logit model applied to the demand for Higher Education

This paper presents a microeconomic analysis of the choice of universitydegree course that individuals make on finishing their Secondary studies(four-year university degree or three-year university degree), andcontains the theoretical framework as well as empirical results. Themodel selected for our analysis is a binomial logit model. This model,which can be seen as a special case of a general model of utilitymaximization, deals with those aspects of the economics of educationalchoice that are regarded as important in the literature of this subject:academic aptitude, the social background in which the students havegrown up, family income, employment prospects, etc. By using survey dataon educational choices of Spanish High School graduates (cross-sectionaldata), we investigate to what extent the theoretical determinants areconfirmed in practice. The results of the estimation by maximumlikelihood of the logit model, and which allow us to analyze theinfluence of the explanatory variables on the probability of choosing afour-year university degree, show how social background, family earningsand scholastic ability explain, mainly, the educational choice ofstudents. The students from higher socioeconomic status as well as thosewith the best High School curricula are more likely to follow auniversity degree of greater duration.     

极限的等比定理

给出有关极限的几个结论 ,它们类似于比例的等比定理     

利用相对位置冗余度提高文件的压缩比

提出了相对位置冗余度的概念 ,利用被压缩文件中存在的相对冗余度 ,给出了一种变换方法 ,提高了现有压缩软件 (如Arj exe,Pkzip exe等 )对文件压缩的压缩比 .同时还给出一个实例 .     

查全率与查准率之间关系的理论研究

作者在《从检索实例看查全率与查准率之间的关系》一文中揭示了查全率与查准率之间不仅存在互逆关系,而且还可以存在互顺关系和其他关系。本文则对这些关系进行理论上的分析论证,以证实这些关系的普遍性与客观性。     

20世纪90年代河北省人口出生性别比真实水平的统计推断

普查资料显示,我国各省、市、自治区之间的人口出生性别比存在很大的差异性。通过对河北省"四普"和"五普"中同批人的统计资料分析表明,低年龄人口的漏报、瞒报现象是造成河北省出生性别比统计偏高的主要因素,但20世纪90年代出生人口性别比的真实水平仍然明显高于国际公认的正常水平。