非洲内罗毕城市变化的遥感监测与驱动因子分析

作为肯尼亚的首都,内罗毕是非洲发展最快的城市之一.本文研究了内罗毕市1988年-2010年城市建成区空间扩展情况.利用1988年Landsat TM、2000年Landsat ETM+以及2010年Landsat TM数据,采用主成分分析与混合分类的方法,提取了1988年-2000年、2000年-2010年、1988年-2010年内罗毕土地覆盖空间变化数据,并分析了城市用地面积扩展的驱动因素.分析结果表明,内罗毕从1988年到2010年总共扩展了141.24km2,扩展面积为1988年城市建成区面积的1.27倍,其中1988年到2000年扩展了60.03km2,2000年到2010年扩展了81.21km2.城市建成区所侵占的地类主要是荒草地和林地,城市建成区的扩展方向是以东西方向为主,并沿着主要交通路线的方向扩展.人口和经济快速增长、便利的交通、地质地形、政府政策是内罗毕城市扩展的驱动因素.     

新疆产业用水变化的驱动效应分解及时空分异

新疆是我国缺水地区,研究水资源合理利用问题有利于新疆提高水资源利用效率.本文通过基于拉斯拜尔指数的完全分解模型,构建产业用水变化的全要素分解模型,测度了2005-2010年新疆经济增长效应、产业结构效应与用水强度效应对产业用水的驱动效应,分析了水资源消耗的反弹效应,计算了各种效应对用水变化的贡献率,并对各种效应进行了时间分异分析,得出2005-2010年新疆经济发展极大地拉动了产业用水量,并且拉动力具有很强的刚性,而用水强度和产业结构则对新疆产业用水起到了抑制作用.新疆应该降低用水强度和调整产业结构以减少水资源的消耗;运用全要素分解模型测度了2005-2010年新疆15个地州经济增长效应、产业结构效应与用水强度效应对产业用水的驱动效应,并对各种效应进行空间聚类,进而对各种效应进行空间分异分析,结果显示:经济增长对各地州产业用水消耗表现为正向驱动效应,产业结构、用水强度对用水量的驱动效应基本表现为减量效应.各地州虽然效应趋势相同,但效应强度却因地而异.因此,政府需要根据各地州的经济发展、产业结构、用水强度的具体情况来制定相应的调控政策.     

警察入职体测4×10m往返跑技术特点分析

4×10m往返跑是人民警察入职体测中的必测项目,其技术动作包括起跑加速、急停、换取木决、转身加速等环节。通过测试成绩与分析技术特点认为：受测者应根据自身能力特点确定适合的起跑姿势并采用合理加速技术迅速起跑提速;形成右脚在前制动,身体侧对端线的急停姿势;运用稳定性较强的双手同时换取木块技术以提高成绩;并在有效急停和换取木块基础上,完成同步转身和加速动作。     

基于案例驱动和积件式实验的单片机课程教学

针对单片机教学传统方式的各种弊病,提出了更加注重实践能力培养的教学方式。使用案例驱动教学能增强学生学习兴趣,避免了枯燥的填鸭式理论教学;为避免过早陷入设计电路细节又不至因高度集成化的实验环境屏蔽掉硬件细节,采用积件式实验让学生在理解模块功能的基础上对模块进行有效控制,即关注底层硬件又不必陷入细节。实践证明,该教学方式有助于提升学习积极性,学生对原理性知识的理解更轻松。     

正确对待汉语字母词及其入典

汉语字母词在日常生活中使用日益频繁,这一现象引起越来越多的语言学家以及大众群体的重视。如何看待汉语字母词现象,词典应不应该收录字母词,这些问题近来争议不断。文章探讨了汉语字母词的相关问题,首先从字母词的分类出发,其次分析了字母词存在价值以及使用过程中存在的问题,提出要正确对待汉语字母词。在承认的前提下规范使用,有选择地录入词典。     

Kinematic analysis of the backstroke start: differences between backstroke specialists and non-specialists

Abstract

The purpose of this study was to clarify factors to perform the hole-entry technique in the backstroke start. A total of 16 well-trained Japanese competitive swimmers were divided into two groups (backstroke specialists and non-specialists) to compare their backstroke start motions. Their backstroke motions were videotaped, and two-dimensional co-ordinates for the swimmers were obtained from the video images using direct linear transformation methods. A non-paired t-test and Mann–Whitney U-test were used to analyse the statistical difference of the kinematic variables between the groups. Backstroke specialists showed a significantly shorter 5 m time (P = 0.009, effect size = –1.54), a significantly higher position of the toe (P = 0.010, effect size = 1.47) at signal and of the hip at toe-off (P = 0.002, effect size = 1.94), a significantly larger hip joint angle at toe-off (P = 0.007, effect size = 1.60) and a significantly higher angular velocities of the hip joints (45–85%; P < 0.05) for the normalised time as compared to that of non-specialists. An earlier initiation of the extension and the maintenance of a higher extension speed at the hip joints were important factors in achieving an arched-back posture, which facilitated and water entrance with a small entry range.     

国有经济布局战略性调整及其路径选择

国有经济布局战略性调整既包括所有制结构的调整，也包括国有资产在不同产业间的调整，“有进有退”是调整思路，而“退出”是关键。     

五个"关键词"的修订与当代文艺思潮的演进

1965年<辞海·未定稿>文艺条目、"文革"期间修订的文艺条目、1979年<辞海(修订稿)>文学分册之文艺条目和1979年版<辞海>文艺条目,形成了一个相对完整的系统,从一个侧面凸现了中国当代文艺思想演变的历史.解读"文艺条目(1976)",兼顾"文艺条目(1965)"、"文艺条目(1979/修订稿)"文艺条目(1979)",不仅对我们理解"文革"文艺思潮,而且对具体把握当代文艺思潮的演变,都是有益的.     

English language learners and kindergarten entry age: Achievement and social-emotional effects

In evaluating the role of kindergarten entry age, previous researchers have not examined the entry-age effects for English language learners (ELL). Additionally, little work has assessed the role of entry age on both achievement and social-emotional outcomes. This study is the first to do both simultaneously. The authors used data from a longitudinal study that followed a national sample of U.S. students from kindergarten through Grade 5. Relying on variation in children's birth dates and in states' kindergarten entrance age cutoffs, the authors estimated how differences in the age at which children enroll in kindergarten are related to their achievement and social-emotional outcomes. Our results show that enrolling in kindergarten as an older entrant is associated with significantly higher achievement and social-behavioral outcomes during the early elementary school years for ELL students, but that these effects largely disappear by the end of elementary school. Policy implications are addressed.     

New insights into the activation mechanism of store-operated calcium channels: roles of STIM and Orai

The activation of Ca2 entry through store-operated channels by agonists that deplete Ca2 from the endoplasmic reticulum (ER)is a ubiquitous signaling mechanism,the molecular basis of which has remained elusive for the past two decades.Store-operated Ca2 -release-activated Ca2 (CRAC)channels constitute the sole pathway for Ca2 entry following antigen-receptor engagement.In a set of breakthrough studies over the past two years,stromal interaction molecule l(STIM1,tbe ER Ca2 sensor) and Orail(a pore-forming subunit of the CRAC channel)have been identified.Here we review these recent studies and the insights they provide into the mechanism of store-operated Ca2 channels(SOCCs).