Reliability analysis of repairable systems using stochastic point processes

In order to analyze the failure data from repairable systems, the homogeneous Poisson process(HPP) is usually used. In general, HPP cannot be applied to analyze the entire life cycle of a complex, re-pairable system because the rate of occurrence of failures (ROCOF) of the system changes over time rather thanremains stable. However, from a practical point of view, it is always preferred to apply the simplest methodto address problems and to obtain useful practical results. Therefore, we attempted to use the HPP model toanalyze the failure data from real repairable systems. A graphic method and the Laplace test were also usedin the analysis. Results of numerical applications show that the HPP model may be a useful tool for the entirelife cycle of repairable systems.     

路段平均行程时间估计方法

为了有效利用线圈检测数据, 精确估计路段平均行程时间, 提出了一种路段平均行程时间估计方法。将路段平均行程时间分为平均行驶时间、平均排队时间和平均通过路口时间三部分。考虑线圈埋设的特点, 通过估计平均行驶速度得到平均行驶时间。用分段时齐Poisson过程描述车辆驶入路段过程和驶离过程, 用Markov排队模型描述车辆排队过程, 用生灭过程描述排队车辆数, 得到车辆排队模型, 计算了路段有、无初始排队的平均排队时间。基于选取与路口相关的饱和流率和平均车长, 计算了平均通过路口时间。计算结果表明: 平均行程时间估计值与实测值的误差小于12%, 说明路段平均行程时间估计方法可行。     

Intermodal and international freight network modeling

The authors describe the development and application of a single, integrated digital representation of a multimodal and transcontinental freight transportation network. The network was constructed to support the simulation of some five million origin to destination freight shipments reported as part of the 1997 United States Commodity Flow Survey. The paper focuses on the routing of the tens of thousands of intermodal freight movements reported in this survey. Routings involve different combinations of truck, rail and water transportation. Geographic information systems (GIS) technology was invaluable in the cost-effective construction and maintenance of this network and in the subsequent validation of mode sequences and route selections. However, computationally efficient routing of intermodal freight shipments was found to be most efficiently accomplished outside the GIS. Selection of appropriate intermodal routes required procedures for linking freight origins and destinations to the transportation network, procedures for modeling intermodal terminal transfers and inter-carrier interlining practices, and a procedure for generating multimodal impedance functions to reflect the relative costs of alternative, survey reported mode sequences.     

地铁站环控系统控制方案的节能对比研究

为明确常见的地铁车站环控系统控制方案的用能表现和节能潜力,为地铁车站节能降碳提供参考和指导,以北京、上海和广州分别作为寒冷、夏热冬冷和夏热冬暖地区的代表性城市,在 TRNSYS 软件中搭建屏蔽门地铁站模型,探究增设自控系统和优化时刻表控制这 2 种优化方案相比于当前常规的时刻表控制方案在站内环境控制、节能潜力、改造成本方面的表现。结果显示,采用 2 种优化方案均可有效提高站内空调控制温度,实现类似的站内温度控制效果。用能方面,相比于当前的时刻表控制方案,增设自控系统可为各气候区地铁站环控系统降低41%～49%的年能耗,优化时刻表控制方案可降低 38%～48%的年能耗。改造成本方面,优化时刻表控制方案仅需要提高管理水平,无需增加设备和系统,而增设自控系统方案的设备成本和后期运维管理成本较高。因此,综合考虑站内环境控制效果、能耗情况和改造成本,建议地铁站采用优化时刻表控制方案进行节能运行优化,以实现节能目标。     

批量控制器在液化气装车系统中的应用

石油二厂每年生产液化气五十万吨,这些液化气产品的出厂一直采用装车后用汽车衡检斤的方式,为了提高出厂产品的计量准确性,避免液化气装车过程中的作弊现象, 2004年石油二厂对液化气装车系统进行改造,采用批量控制器控制质量流量计在线定量装车.系统利用计算机管理系统,采用MODBUS总线方式进行信号采集传输,实现液化气槽车的自动罐装,提高了出厂产品的计量精度.     

舰船信息系统信号接地的电磁兼容性分析

从设备和系统角度对舰船信息系统的接地技术进行详细分析,提出了实用的设计方法和建议,并对数字接地的电磁特性提出了测量建议,给出实用的设计指导原则。     

某轻型汽车离合系统隔振技术的探讨和研究

汽车离合系统作为一类与操控者接触频率较高的元件,其舒适性是一项不可或缺的品质指标[1]。本文以某轻型客车为例,对踏板振动进行测试,并对测试的特性图、频谱以及振动产生的机理进行分析,确定了系统产生振动的原因和解决方案。基于试验数据的对比分析发现,采用螺旋管+限流阀+动态隔振器的方式可有效解决振动问题,以此来大幅提高离合系统的舒适性。最后,还通过实车测试探究了隔振结构对离合系统的影响。     

柴油机气缸盖精密加工技术研究及应用

通过针对某型号柴油机气缸盖气门导管孔与气门座圈锥面的精密加工技术研究,从工艺方案、装夹系统、精密复合刀具的应用、刀片国产化的选用、加工过程中的冷却方式及其切削参数等各个环节进行了改进与优化,并在工艺试验验证的基础上,突破了气缸盖精密加工的关键技术,实现了气缸盖在批量生产加工中高精度加工的要求.     

Alternative fuels for transportation

The alternatives to the oil based fuels for transportation are considered and analysed. These are the synthetic fuels, made from coal, the liquid petroleum gases of propane and butane, compressed natural gas and methanol. The problems associated with the use of electric vehicles are discussed; the main problem being that of range.

The possible use of hydrogen as a fuel is analysed in some detail. Since its supply can be tied directly to nuclear energy sources, rather than hydrocarbon feed stocks, it could be an alternative in the long term. The main problems of the storage of hydrogen on the vehicle and of its propensity to “back‐fire” into the engine intake are discussed. The first can be ameliorated and the second eliminated by dual fuelling; with petrol. It is advocated that the on‐board storage of hydrogen be by the use of hydrides for private cars. However, it is expected that it may be as liquid hydrogen for some forms of transport and will certainly be in this form for aircraft.