Impact maturity times and citation time windows: The 2-year maximum journal impact factor

Journal metrics are employed for the assessment of scientific scholar journals from a general bibliometric perspective. In this context, the Thomson Reuters journal impact factors (JIFs) are the citation-based indicators most used. The 2-year journal impact factor (2-JIF) counts citations to one and two year old articles, while the 5-year journal impact factor (5-JIF) counts citations from one to five year old articles. Nevertheless, these indicators are not comparable among fields of science for two reasons: (i) each field has a different impact maturity time, and (ii) because of systematic differences in publication and citation behavior across disciplines. In fact, the 5-JIF firstly appeared in the Journal Citation Reports (JCR) in 2007 with the purpose of making more comparable impacts in fields in which impact matures slowly. However, there is not an optimal fixed impact maturity time valid for all the fields. In some of them two years provides a good performance whereas in others three or more years are necessary. Therefore, there is a problem when comparing a journal from a field in which impact matures slowly with a journal from a field in which impact matures rapidly. In this work, we propose the 2-year maximum journal impact factor (2M-JIF), a new impact indicator that considers the 2-year rolling citation time window of maximum impact instead of the previous 2-year time window. Finally, an empirical application comparing 2-JIF, 5-JIF, and 2M-JIF shows that the maximum rolling target window reduces the between-group variance with respect to the within-group variance in a random sample of about six hundred journals from eight different fields.     

The use of training days: finding time for teachers’ professional development

This study was designed to compare the relative efficiency of three methods of presenting and teaching fractions to slow learners at the secondary stage of education.

Thirty‐six first‐year pupils took part in the experiment and were divided into three groups of 12 for instruction in fractions for 14 periods of 40 minutes. Each group was taught by a different method, viz:

Group A, was taught in a formal, traditional method

Group B, used the Cuisenaire (unimodel) material

Group C, used multi‐model materials specially constructed for teaching fractions to slow learners.

At the beginning of the experiment the groups were equivalent in age, intelligence, arithmetical attainment, attainment in fractions, conceptual understanding of fractions, in adjustment to school, attitudes to learning fractions, and socio‐economic status. On re‐assessment on six of the variables at the end of the experiment it was found that each group had improved in each of the six variables tested.

When considering all the results obtained it was concluded that the multi‐model method was the most effective method of teaching fractions to slow learning children at the secondary stage. This method was found to have particular advantage in creating a favourable attitude to learning fractions and in promoting a sound conceptual understanding of fractions. It also produced the greatest mean gain in fraction computation, and seemed to have some slight advantage in aiding the adjustment of pupils to school.     

优秀运动员大赛前竞技状态调控的时间学规律研究（上）——赛前训练时间调控的科学意义及影响因素的分析

在竞技运动训练中存在着许多时间学规律，尤其优秀运动员在大赛前竞技状态调控方面的要求越来越高，对这一课题的研究将对运动员竞技状态的科学调控有着十分重要的现实意义。这一课题的研究将包括赛前训练时间调控的科学意义及影响因素、赛前训练阶段构成的时间学特征的界定及其时间构成模式，以及中短期赛前训络中各相关训练学因素的时间学特征及其全过程的总体时域模型的确立等内容。     

新的假期制度对旅游业的影响

以带薪休假为代表的闲暇时间作为决定个人旅游消费需求的两个重要的因素之一,在经济发展迅速的今天,对旅游业的发展起着越来越大的作用。2007年12月16日国务院对外公布了新的休假制度,将给我国旅游业带来新的发展机遇与挑战。     

对少年运动员推铅球技术的节奏分析

运动员背向滑步推铅球技术,在A.C.D.三个动作阶段呈现出时间节奏短成绩高的相关性。其滑步后左脚下压的时间节奏长,虽然与成绩呈正相关,但这是一明显的错误定型。如果缩短滑步的时间,改进左腿过渡步动作阶段的错误动作定型,其铅球成绩将取得长足的进步。     

论娱乐性身体活动在全民健身中的作用

根据全民健身的需要,结合现代休闲的概念和理论,通过对娱乐性身体活动的特点的讨论分析,阐述了娱乐性身体活动及其在全民健身中的作用,认为娱乐性身体活动理应成为人们全民健身最佳的活动方式之一。     

一类具有动态领导者和时滞的多主体系统的一致性

研究了一类具有动态领导者并且存在时变耦合时滞的多主体系统的一致性问题．在所考虑的模型中,领导者的速度不能被精确量测．为了跟踪这样一个领导者主体,将对每个跟随者主体构造分散式状态估计器以及设计基于邻居的控制器;同时,由于耦合时滞的存在,基于邻居的控制器和状态估计器均包含了时变时滞的作用．当多主体系统的耦合拓扑是固定的或切换的有向图时,跟随者与领导者之间的跟踪误差得到了估计．特别地,可以证明,当动态领导者的速度可以被精确量测时,每一个跟随者都能够跟踪上领导者．     

不同持续时间低氧后训练对大鼠海马组织细胞凋亡的影响

目的:观察不同持续时间低氧后训练对大鼠海马组织细胞凋亡的影响,探讨低氧训练对海马神经细胞凋亡的影响,为科学地指导运动员进行低氧训练提供实验依据。方法:雄性SD大鼠60只,随机分为6组,每组10只,正常对照组(A组),低氧8 h组(B组),低氧12h组(C组),训练对照组(D组),低氧8 h训练组(E组),低氧12 h训练组(F组)。采用零坡度跑台的训练方式,对D、E和F三组以25 m/min的速度在常氧环境中每天训练1 h。将B、C、E和F组放入低氧舱内,氧浓度为12.5%(相当于4 000 m海拔高度),过8 h和12 h后,分别将B、E组和C、F组取出放入正常氧浓度环境。训练共持续4周,每周5 d。最后一次训练至力竭后24 h断头处死,取大鼠海马组织,测定Bax和Bcl-2蛋白表达的阳性细胞个数和凋亡指数。研究结果显示:在低氧训练过程机体对低氧刺激的适应性改变,使得在停止运动后,海马组织的损害减小。随着低氧时间的延长,低氧训练使大鼠海马组织CA1区的细胞凋亡有减少的趋势,从而起到神经保护作用。     

不同时间运动骨骼肌AMP/ATP比值及AMPK活性的变化特点

目的:研究不同时间一次性运动大鼠腓肠肌AMP、ATP含量及AMPK活性,旨在阐明不同时间运动AMPK的变化特点及机制。方法:62只雄性SD大鼠分为4大组:安静对照组(n=8)、30 min运动组(n=18)、60 min运动组(n=18)9、0 min运动组(n=18),其中运动组又各分为3小组(n=6),分别在运动后即刻、1 h和6 h取材。运动速度18 m/min,坡度10%。结果:和安静组相比,各组ATP运动后无显著改变;AMP在60和90min运动后即刻显著升高(0.183,0.212 Vs 0.158,P<0.05),AMP/ATP比值在60、90 min显著升高(0.048,0.053 Vs 0.037,P<0.05,0.01),1 h回到安静水平;各组AMPK在运动后即刻均显著升高(4.16,4.79,5.26 Vs3.18,P<0.05,0.01,0.01),其中60、90 min组至1h仍保持升高,6 h回到安静水平。结论:骨骼肌AMPK在运动中的激活具有时间依赖性,其机制与AMP/ATP比值升高有关。     

嫩江流域径流量多时间尺度特征分析

目前在全球气候变化与人类活动的双重影响下,陆地水文循环发生了深刻的变化,近50年来,嫩江流域径流过程发生了巨大变化,加剧了水资源的短缺和时空变异性,并带来一系列突出的水与生态环境问题.本文根据嫩江、石灰窑、同盟、江桥、大赉水文站1956年～2006年51a的径流资料,采用Morlet小波对嫩江流域径流序列进行了多时间尺度研究,结果表明:流域径流演变过程存在明显的多时间尺度特征,具有8a、20a、45a多尺度的周期变化规律,且以45a尺度的年代周期信号最强,表明45a尺度的年代周期变化最为明显;嫩江、江桥气象站的降水周期与上述径流资料基本一致,说明降水的变化是流域径流演变过程的重要自然控制因素.