Opportunistic preventive maintenance optimization for multi-unit series systems with combing multi-preventive maintenance techniques

This paper proposes a dynamic opportunistic preventive maintenance (PM) optimization policy for multi-unit series systems by integrating multi PM techniques. Two PM techniques, periodic PM and sequential PM, are considered. Whenever one of the units reaches its reliability threshold, a PM action has to be performed on that unit. At that time the whole system has to be stopped and PM opportunities arise for the other units of the system. An optimal PM practice is determined by maximizing the short-term cumulative opportunistic maintenance (OM) cost savings for the whole system. Numerical examples are given to show how this approach works. Finally, a comparison between the proposed PM policy and the other policies is given.     

On the algorithms of adaptive neural network-based speed control of switched reluctance machines

AbstractA switched reluctance machine(SRM)drive is a time-varying,strongly nonlinear system.High performance control can no longer be achieved by using linear techniques.This paper describes the back-propagation (BP)neural network-based proportional-integral-derivative(PID)speed control of the SRM.It’s the interest of this paper to explore the utilization of the prior empirical knowledge as guidance in the initializing and training of the neural networks.The purpose is to make the networks less sensitive on the initial weights.Two modified algorithms are presented and simulation experiments show some interesting findings about their control effects and their corresponding sensitivity on the initial weights of the networks.     

3D Numerical simulation of non-isothermal resin transfer molding filling process using unstructured tetrahedron mesh

We present a numerical formulation for resin flow based on the concept of quasi-steady state situation at the flow front. To be fit for complicated product shapes, we use the four-node unstructured tetrahedron mesh based on which the numerical formulation of temperature and degree of cure is developed. The validity of our method is established in the case where flexible meshes are used. The results show that the numerical procedure, tested on known data, provides numerically valid and reasonably accurate predictions.     

轨道交通车辆车轮踏面短波不平顺测试与分析

城市轨道交通轮轨表面短波不平顺是激发线路沿线振动与噪声的主要原因,准确而高效的测量轮轨表面短波不平顺是振动噪声预测、评估及源头控制的重要条件。通过对上海城市轨道交通2号线部分车辆轮踏面不平顺进行现场测试,利用统计分析、1/3倍频和功率谱分析研究了轮踏面不平顺时、频域组成特性。结果表明所测试的轨道交通车辆轮踏面不平顺水平是比较低的,大部分不平顺幅值积聚在3~13μm;在短波范围内,波长大于4.0 cm时不平顺状态比ISO3095标准要好,小于2.5 cm时不平顺状态较标准差;主要波长分布在57.7~95.2 cm,且大部分集中在70~80 cm,平均值为72.1 cm。     

A novel mutation-L539fs/47 of hERG in a Chinese long QT syndrome family

Objective To identify the mutation of human ether-a-go-go-related gene (hERG) and analyze the clinical characteristics of a Chinese family with long ST syndrome (LQTS). Methods The electrocardiogram and DNA samples were obtained from a Chinese LQTS family of 26 members. Genotype was performed with polymorphic short tandem repeat (STR) markers at the known LQT1, LQT2, and LQT3 loci. SSCP analysis was used to find aberrant conformers. hERG mutation was confirmed by cloning and sequencing. Results Three gene carriers were linked to chromosome 7q35-36, where the potassium channel gene hERG was encoded. A 19-base pair deletion was identified. The mutation was located at nucleotide position 1 619-1 637 between transmembrane domains S4 and S5. Furthermore, A1692G polymorphism was found both in the normal control and patients. Conclusion A novel 19 bp deletion mutation of hERG is identified in a Chinese family. All gene carriers are demonstrated to be typical LQT2 ECG phenotype.     

钢—混凝土组合梁抗弯性能研究进展

钢—混凝土组合梁与传统的钢筋混凝土梁相比,具有跨度大、节省模板、减轻结构自重和较好的延性等优点,具有十分广阔的应用前景。系统总结了钢—混凝土组合梁抗弯性能(包括正弯矩作用下和负弯矩作用下)的研究现状,并指出了目前研究存在的问题与不足。     

深水高桩承台轻型吊箱施工方法的探讨

处于深水中的桥梁基础在施工上存在一定的难题,针对深水桩基作业提出了改进的轻型高桩承台吊箱施工方法,与传统的钢围堰砌筑承台相比能节省大量钢材,取得了显著的经济效益。该轻型吊箱施工方法经过辽河特大桥深水施工作业的实践检验,证明其具有施工操作方便、定位准、经济效益高等特点。     

坝陵河大桥主缆缠丝导入力计算

悬索桥主缆缠丝主要是利用导入较大拉力的缠绕钢丝圈在主缆表面构成一个具有足够压力的套箍,以保证涂装防护效果,使主缆不受大气腐蚀。针对坝陵河大桥施工特点,为优化施工工序,合理利用资源,在借鉴已有研究成果的基础上,对主缆拉力增量因素、缠丝工况等进行研究,对缠丝导入力的计算方法进行完善,并根据现有材料技术,确定该桥的缠丝施工工艺,可供类似桥梁参考。     

压力螺旋型喷嘴雾化特性及灭火有效性实验

为了优化压力螺旋型喷嘴参数,设计了压力螺旋型细水雾灭火喷嘴并进行了实验,分析了压力螺旋型喷嘴设计参数、系统压力和添加剂对雾化特性的影响.结果表明:当系统压力从0.5 MPa增加到1.5 MPa时,细水雾的索太尔直径减少8%;水中的添加剂可以降低雾的索太尔直径1.3%~15%;雾场中雾的索太尔直径越大,粒径分布越宽;粒径体积分数分布曲线有向大粒径方向移动的趋势;雾的速度与系统压力成近似线性增大关系;当喷嘴结构设计不合理时,喷嘴下游平面上的雾通量分布会不均匀,对熄灭火灾不利.     

综合客运枢纽车道边通行能力分析

基于对南京火车站车道边出租车流、社会车流的调查,通过分析车道边交通流特性,运用交通流理论建立一定条件下的车道边通行能力计算方法.提出了车道边基本通行能力的定义,分析调查数据获得车辆落客时间的统计分布规律,运用可接受间隙理论计算车辆汇入等待时间,完成对车辆占用停车位时间的调整;接着考虑停车及入口选择行为的影响,对车道边通行能力计算公式进行修正,并将其应用于郑州市综合客运交通枢纽车道边的规划设计.结果表明,当枢纽车道边到达车流服从泊松分布时,方法能够有效定量的计算综合客运枢纽车道边的通行能力.