特征为2的有限域上正交几何中对偶子空间的维数及类型

设Ｆｑ是一个ｑ元有限域，其中ｑ是２的一个幂，用Ｆｑ＾（ｎ）表示Ｆｑ上的ｎ维正交空间，计算了Ｆｑ＾（ｎ）中任一个空间的对偶子空间的维数，并确定了这种子空间的类型。     

济宁市农村社会养老服务供需的实证研究

本文通过抽样调研,对济宁市农村人口老龄化现状以及社会养老服务供需进行分析,从而对实现该地区农村社会养老服务供需均衡提出相应对策,以促进济宁市养老保障事业发展.     

接触网作业车基础制动装置设计

接触网作业车基础制动装置是作业车制动系统的重要组成部分,文章介绍了其结构特点及主要构成,详细说明了基础制动装置的工作原理及制动方式,以及设计作业车基础制动装置。     

Multifractal analysis of resting state fMRI series in default mode network: age and gender effects

Age-related changes of resting state in default mode network （DMN） may provide new clues to the developing mechanism of normal brain as well as early diagnosis and therapy of some neuropsychiatric disorders. The application of multifractal theory to functional magnetic resonance imaging （fMRI） signals has recently raised increasing attention. We aim to explore the multifractal characteristics underlying the resting state functional magnetic resonance imaging （rs-fMRI） series extracted from DMN, and two issues are mainly discussed： （1） whether there exist multifractals in rs-fMRI series; （2） whether it is possible to distinguish between the different ages or genders by means of multifractal characteristics. Results demon- strated the existence of multifractals in rs-fMRI series in DMN. In addition, slight differences between young subjects and middle-aged or elderly subjects can be successfully detected by △asα, a modified measure we proposed. Furthermore, it is revealed that the rs-fMRI series from young subjects possess smaller averaged scale index and weaker long range correlation, while those from middle-aged or elderly people present increasing averaged scale index andstronger long range correlation. Whereas no significant statistical differences has been found between male and female group. Our results, therefore, highlight the potential useful- ness of multifractal analysis in fMRI series of a certain brain region, and provide important insights into healthy aging in DMN.     

Burn-resistant behavior and mechanism of Ti14 alloy

The direct-current simulation burning method was used to investigate the burn-resistant behavior of Ti14 titanium alloy. The results show that Ti14 alloy exhibits a better burn resistance than TC4 alloy (Ti–6Al–4V). Cu is observed to preferentially migrate to the surface of Ti14 alloy during the burning reaction, and the burned product contains Cu, Cu₂O, and TiO₂. An oxide layer mainly comprising loose TiO₂ is observed beneath the burned product. Meanwhile, Ti₂Cu precipitates at grain boundaries near the interface of the oxide layer, preventing the contact between O₂ and Ti and forming a rapid diffusion layer near the matrix interface. Consequently, a multiple-layer structure with a Cu-enriched layer (burned product)/Cu-lean layer (oxide layer)/Cu-enriched layer (rapid diffusion layer) configuration is formed in the burn heat-affected zone of Ti14 alloy; this multiple-layer structure is beneficial for preventing O₂ diffusion. Furthermore, although Al can migrate to form Al₂O₃ on the surface of TC4 alloy, the burn-resistant ability of TC4 is unimproved because the Al₂O₃ is discontinuous and not present in sufficient quantity.     

煤矿采掘工程的计算机绘图系统

介绍煤矿采掘工程的计算机绘图系统,本系统是将生产矿井的采掘工程图件实现计算机存储和编辑的应用软件,该软件在晋普山煤矿经过了实际应用,效果良好。本文介绍了软件研制的技术路线、系统的整体结构和各模块程序化状况。     

关于四次非协调板元的收敛性

讨论一种三角剖分下的四次非协调元,它是Ｃ０元,在每个单元上的形函数是一个完全四次多项式,由单元三顶点处的函数值与一阶偏导数值,及三边中点处的函数值与法向导数值所决定。将此有限元用于薄板弯曲问题,得出了关于能量模以及Ｌ２模的收敛阶估计。与已知为收敛的Ｍｏｒｌｅｙ元相比,其相应的收敛性结果更强。     

PEMFC输出功率的二自由度PID控制

为提高质子交换膜燃料电池(PEMFC)的输出性能,对于其输出功率的一阶滞后数学模型,进行二自由度PID控制方案设计.针对二自由度PID控制器参数整定过程中存在的不足,提出一种基于自适应遗传算法的二自由度PID控制器设计.仿真结果表明,经优化整定后的二自由度PID控制器,可使PEMFC的输出功率能较好地跟踪给定期望值的变化,同时也可更好地抑制外扰.