人口年龄结构对中国城乡居民消费率及消费差距的影响——基于省级面板数据的实证分析

在对中国人口年龄结构、消费率与城乡消费差距现状分析的基础上,基于2000-2014年中国省级面板数据,综合时空尺度,建立动态面板及空间面板数据模型,探究人口年龄结构对城镇消费率、农村消费率及城乡消费差距的影响.结果显示,少儿抚养比与老年抚养比对城镇居民消费率均具有正向影响,而对农村地区居民消费率则分别产生负效应和正效应;城乡少儿抚养系数比、城乡老年抚养系数比对城乡消费差距均具有正效应,且城乡居民消费差距存在空间集聚格局,呈现正的空间依赖性;"全面两孩"生育政策将改善人口年龄结构,从而有利于缩小城乡消费差距.     

The green June beetle (Cotinis nitida) (Coleoptera: Scarabaeidae): local variation in the beetle’s major avian predators and in the competition for mates

The green June beetle (Cotinis nitida) was observed in northern Virginia for a second and third flight season. The study yielded some results that were consistent with earlier findings, namely that mate-locating beetles were vulnerable to attack by avian predators and matings occurred primarily early in the flight season. Novel findings included the following: (1) blue jays (Cyanocitta cristata) were the major predators, not common grackles (Quiscalus quiscala), (2) some jays appeared to selectively prey on female beetles, (3) competition for mates among male beetles could be so intense that some males attempted to copulate with already mated (unreceptive) females, and (4) the sex ratio of the beetle population feeding on wild blackberries remained near equality late in the flight season despite the fact that the sex ratio of the population of beetles at the emergence site became highly female-biased over time.     

Population biology of Sphaeroma serratum Fabricius (Isopoda,Flabellifera) at the Port of Mar del Plata,Argentina

Variations in size distribution, sex ratio, fecundity and morph frequencies in a population of Sphaeroma serratum were studied year-round. Changes in size distribution are most marked during the breeding season. Growth is arrested during the winter months. Young are produced throughout the summer; these overwinter, reproduce and then die. Differences in size of mature males suggest an effect of the timing of birth on life-span. Females are able to produce two broods. Offspring number is positively correlated with female size. Brood pouch mortality is estimated at 39%. Marked changes in sex ratio within the breeding season are thought to be artifacts due to sexual differences in behaviour. Comparison of reproductive traits of this, and other, populations shows a latitudinal pattern related to the duration of the warm season. Analysis of morph frequencies revealed similarities with European populations so far studied.     

数码卷绕的概念和技术

数码卷绕是在精密卷绕的基础上，引入导丝机构的数字控制方式，得到张力更稳定、纱管成形更完善的最新卷绕技术。文章介绍了高速精密数码卷绕技术的概念、实现原理和应用现状。     

泡桐木夹层梁的弯曲疲劳试验

对采用真空导入工艺的泡桐木夹层梁进行4点弯曲疲劳试验,研究发现泡桐木夹层梁的破坏形式主要有界面的脱黏、芯材的剪切破坏、面板分层等。试验过程中采集试件的S-N曲线,采用3种寿命预测公式对其进行线性拟合,得到该泡桐木夹层梁的寿命预测公式。基于S-N曲线在实际工程中的应用,引入失效率的概念,采用双参数的Weibull函数分布,对不同应力等级下的失效率进行研究,从而得到泡桐木夹层梁P-S-N曲线。     

不同应变率和温度下AFRP力学性能试验研究

利用MTS液压伺服高速试验机测试芳纶纤维(Kevlar 29)增强复合材料(AFRP)在不同应变率(25,50,100和200s-1)和温度(-25,0,25,50和100℃)条件下的力学性能.结果表明,在相同温度(25℃)下,随着应变率的增大,杨氏模量和拉伸强度先增大(25~50s-1)后减小(50~200s-1),而韧性则表现为相反的趋势.在相同应变率(25s-1)下,温度的升高会造成杨氏模量出现波动,拉伸强度上升,而韧性则没有明显的改变.不同试验条件下AFRP破坏形态没有明显区别,均为较平整断裂面.最后,通过Weibull分析,量化了破坏强度在不同应变率和温度下的离散程度.     

浅析高校图书馆电子阅览室的现状与对策——以山东师范大学图书馆为例

以山东师范大学图书馆为例,介绍了电子阅览室的兴起,阐述了电子阅览室现状及存在的问题,提出了提高电子阅览室使用效率的对策,指出了电子阅览室亟待改进的地方。     

基于双响应曲面的精密产品子集模拟可靠稳健优化设计

针对不确定性场景下小失效概率的精密产品可靠性问题,提出了基于双响应曲面法(dual response surface methodology,DRSM)与子集模拟的可靠稳健优化方法。首先,建立精密产品多失效模式极限状态的RSM模型和以质量特性均值-方差为优化目标的功能函数DRSM模型。其次,在此基础上运用子集模拟法进行可靠性分析,将精密产品小失效概率描述成一系列较大的条件失效概率之积。最后,将极值事件的优化问题视作稀有事件的可靠性问题的特例,基于该转换思想采用子集模拟法将优化问题在可靠性问题的框架内进行求解。案例分析及验证结果表明所提方法的有效性。     

谢桥煤矿综采工作面“人—机—环境”系统研究与应用

综采工作面是煤矿生产系统的重要组成部分,其"人—机—环境"相互作用关系直接影响着煤矿的安全生产。本文以谢桥煤矿综采面"人—机—环境"系统为研究对象,并从这三个组成要素出发,对各类影响因素进行了研究和评价,为人、机、环境各子系统的改进提供理论基础和决策支持。继而结合采煤生产循环实际过程,提出"以人为本"的人机工程匹配完善方案,提高人机互动准确度,克服设备三大故障。将研究结果应用到谢桥煤矿13116综采工作面的实际生产,并提出相应的改进措施,使系统功能趋于完善。     

纤维金属层板的拉伸性能研究

GLARE是一种先进的混杂层板材料,由高韧度薄铝合金层和高强度玻璃纤维/环氧树脂层交替铺设而成,具有独特的轻质、耐疲劳、耐冲击、高阻燃性和耐腐蚀属性.系统地对GLARE层板进行了静力拉伸测试,展示了铺层结构和铺层类型对其静力学性能的影响,并对混杂模型的适用性进行了验证.结果显示:采用混杂模型法预测GLARE层的轴向弹性模量具有较高的精度,但进行强度预测时对于部分类型的层板需要考虑纤维的桥接作用.