自适应跌倒前实时检测方法

为了能利用单一传感器在跌倒撞击前实时检测出跌倒即将发生,结合支持向量机(SVM)和阈值法设计了一种自适应跌倒前实时检测方法.实验结果表明,该方法能在跌倒撞击前实时检测出跌倒即将发生,且比人工阈值法和SVM方法有更长的间隔时间,比SVM方法有更高的召回率和特异度.     

产后早期肛提肌裂孔扩张程度及相关因素分析

目的 分析产后早期肛提肌裂孔扩张的影响因素.方法 盆底超声测量产后早期女性肛提肌裂孔面积,其中研究组为105名肛提肌裂孔扩张者,对照组为145名肛提肌裂孔正常者,对肛提肌裂孔扩张的相关因素进行二元Logistic回归分析.结果 研究组中盆底疾病的发生率高于对照组(P＜0.05),Logistic回归分析显示第二产程时间、胎儿体重、催产素使用和盆腔器官脱垂与肛提肌裂孔扩张显著相关(P＜0.05).结论 第二产程时间延长、催产素增加和胎儿体重增加是肛提肌裂孔扩张的影响因素,对预测和精确诊断盆底疾病有临床意义.     

一种改进的基于人体静电冲击模型应力的瞬态功率模型

提出一种改进的基于人体静电冲击模型(Human Body Model, HBM)应力的瞬态功率模型。利用HSPICE仿真软件, 模拟MOS管遭受的HBM应力, 得到对应的等效直流电压。HBM电路的预充电电压与MOS管对应的等效直流电压值的散点图表明, 两者保持线性关系, 并通过拉普拉斯变化得到证明。与现有的瞬态功率模型相比, 改进后的模型降低了在HBM应力作用下的计算复杂度, 可以更加简便地从统计学上预测MOS管栅氧击穿的发生, 给HBM冲击作用下MOS管栅氧化层可靠性的评估提供参考。     

Facile synthesis of flake-like dihydrate zinc oxalate particles

Monodispersed dihydrated zinc oxalate(ZnC_2O_4·2H_2O) particles with characteristic morphology were synthesized by aging a mixed solution of zinc nitrate(Zn(NO_3)_2) and sodium oxalate(Na_2C_2O_4) in the presence of a citrate ligand, with an average flat size of approximately 10–15 μm. The important parameters, including the solution pH values and the concentration of the zinc ions and citrate ligand, were investigated using a series of experiments. It is verified that the citrate ligand significantly affects the morphology of zinc oxalate particles, probably via its multiple roles of chelating, dispersing, and selective absorption. Thermodynamic equilibrium of the distribution of zinc species in an aqueous solution of Zn(Ⅱ)-citrate-oxalate-H_2O was estimated to explain the experimental results and to clarify the size and morphological evolution mechanism of the precipitated particles.     

基于效率和经济价值的期货套期保值二次决策准则

基于不同风险测度得到的期货套期保值策略不同，利用套期保值效率可以对比分析不同风险测度下的套期保值效果。然而，当考虑套保成本时，套保效率大的套保策略不一定是“最优”的。为兼顾套保效率和套保成本，引入经济价值进一步对比不同套保策略的效用，提出期货套期保值二次决策准则。首先，构建方差、VaR和 CVaR等风险测度下的期货套期保值模型，给出最优套保头寸和套保效率的显式表达式，提出模型驱动下的最优套保策略决策准则；然后，考虑套保成本，基于经济价值提出不同套保策略的二次决策准则；最后，针对Brent原油期货套期保值进行实证分析，实证研究结果与理论研究相吻合。基于一次准则的最优套保策略的经济价值并不恒大于零，即当考虑套保成本时，基于套保效率最大的套保策略可能使投资者得不偿失，这也进一步体现了本文所构建的套保二次准则的有效性。     

液中放电沉积技术研究进展

液中放电沉积是一种新型的表面改性技术，起源于电火花加工技术，可在金属表面制备出具有高硬度、高耐磨性以及高结合力等优良性能的沉积层。此外，该技术不污染环境，有望替代部分常用但具有污染性的表面改性技术。液中放电沉积技术的核心内容为沉积层形成机制、工具电极材料以及介电流体成分。简单介绍了液中放电沉积技术的特点，重点阐述了沉积层的形成机制以及缺陷优化工艺，并从工具电极材料、介电流体成分和实际生产应用三个方面总结了液中放电沉积技术的国内外研究进展，展望了该技术的发展方向。     

Guaranteed Cost Finite-Time Control of Fractional-Order Nonlinear Positive Switched Systems with D-Perturbations via MDADT

This paper is concerned with the problem of guaranteed cost finite-time control of fractionalorder nonlinear positive switched systems(FONPSS) with D-perturbation. Firstly, the proof of the positivity of FONPSS with D-perturbation is given, the definition of guaranteed cost finite-time stability is firstly given in such systems. Then, by constructing linear copositive Lyapunov functions and using the mode-dependent average dwell time(MDADT) approach, a static output feedback controller is constructed, and sufficient conditions are derived to guarantee that the corresponding closed-loop system is guaranteed cost finite-time stable(GCFTS). Such conditions can be easily solved by linear programming. Finally, an example is provided to illustrate the effectiveness of the proposed method.     

Prediction of end-use energy consumption in a region of Northwest China

End-use energy consumption can reflect the industrial development of a country and the living standards of its residents. The study of end-use energy consumption can provide a solid basis for industrial restructuring, energy saving, and emission reduction. In this paper, we analyzed the end-use energy consumption of a region in Northwestern China, and applied the Markov prediction method to forecast the future demand of different types of end-use energy. This provides a reference for the energy structure optimization in the Northwestern China.     

Two Innovative Coalition Formation Models for Dynamic Task Allocation in Disaster Rescues

This paper addresses the problem of multi-objective coalition formation for task allocation. In disaster rescue, due to the dynamics of environments, heterogeneity and complexity of tasks as well as limited available agents, it is hard for the single-objective and single (task)-to-single (agent) task allocation approaches to handle task allocation in such circumstances. To this end, two multi-objective coalition formation for task allocation models are proposed for disaster rescues in this paper. First, through coalition formation, the proposed models enable agents to cooperatively perform complex tasks that cannot be completed by single agent. In addition, through adjusting the weights of multiple task allocation objectives, the proposed models can employ the linear programming to generate more adaptive task allocation plans, which can satisfy different task allocation requirements in disaster rescue. Finally, through employing the multi-stage task allocation mechanism of the dynamic programming, the proposed models can handle the dynamics of tasks and agents in disaster environments. Experimental results indicate that the proposed models have good performance on coalition formation for task allocation in disaster environments, which can generate suitable task allocation plans according to various objectives of task allocation.     

国际上运动对人体骨骼影响的知识基础及研究热点

目的:探讨当前国际上运动对骨骼影响研究的知识基础及研究热点.方法:利用计算机检索Web of Science数据库中2010-2016年运动与骨骼相关文献4587篇,运用CitespaceⅢ可视化软件绘制共现图谱,分析研究国家机构分布、高被引文献及高频关键词.结果:美国、英国、澳大利亚是该研究领域的中坚力量;研究热点主要集中在不同运动干预对绝经妇女、发育期青少年儿童及老年人三类人群骨骼的影响;知识基础方向主要为骨骼功能适应性理论的实验与发展.结论:以客观数据和图谱为依据,透析运动对骨骼影响研究领域的知识基础和热点,为该领域的后续研究提供参考.