基于有色Petri网的安全构件模型

安全性是安全苛求软件的重要特性,基于传统构件模型的软件开发技术尚不能满足安全苛求软件的开发需求。安全构件模型是一种既具有功能性需求又具有安全性需求的特殊构件模型。该文提出一种基于有色Petri网的安全构件模型及相应的构件组装算法,以确保系统符合相应的安全性需求并将其应用于CTCS-2级列车控制中心仿真系统建模。     

Random vibration analysis for train–track interaction from the aspect of uncertainty quantification

This work is devoted to constructing a stochastic analysis model for train–track​ interaction. The fundamentals of the modelling framework in the establishment of the dynamic model, simulation of system uncertainties and randomness propagation process have been properly illustrated and unified in detail. For modelling train–track interaction, a matrix representation method is developed to depict the displacement compatibility and force equilibrium between the train and tracks. This dynamic model possesses advantages in computational stability and accuracy. Using uncertainty quantification approaches, the randomness of system geometries and longitudinal inhomogeneity of system properties can be simulated properly. Finally, the probabilistic transmission between the system inputs and response outputs are investigated from physical concepts, and a family of probability density evolution methods is introduced. Following the fundamental framework of train–track stochastic analysis, numerical examples are presented in detail to show the efficiency and accurateness of the proposed model. Moreover, the applications and advancements of this model in reliability assessment, response and frequency analysis, derailment, etc., are illustrated.     

力量博弈与要素组织—— 乌德勒支站城融合发展研究

文章首先从力量博弈的视角，呈现乌德勒支中央站区域的站城融合发展历史，揭示了站城开发过程中的多主体 多利益诉求关系，尝试构建结构化的价值框架，并指出设计师在其中的角色作用。其次，文章梳理了乌站的设计策略， 反映了站城融合需要多尺度的策略衔接。最后，通过中荷语境的分析，指出乌站案例学习中，可以转译为中国所用的 经验教训。     

Safe velocity of on-fire train running in the tunnel

The safety of a running train on fire in a tunnel is a key issue for rescue operations, and the train velocity is mainly related to its safety. In this study, the relationship between the wind velocity and heat release rate (HRR), temperature field around the train, and flame/smoke pervasion rule were investigated under the conditions of variable train velocity, fire location, and fire source location. Beijing Metro was considered as a typical example, in which the safe velocity was estimated to be ∼41.83 km h⁻¹. Assuming the occurrence of fire at the center of the train, the numerical simulations of the flow field using the sliding grid of CFD were performed for a full-scale tunnel under different HRRs. When the fire source reached to the target section, the velocities of all the monitoring points rapidly increased. The velocities increased as the train tail arrived at the target section. The velocities at the measuring points increased with the increase in height, excluding the value of the position with a distance of 0.025 m from the tunnel ceiling. The average temperature and concentration of smoke in the annular space between the train and tunnel ceiling had the minimum values when the running train on fire moved with a speed of 45 km h⁻¹. Thus, the safe velocity of a subway train on fire should be managed between 41.83 km h⁻¹ and 45 km h⁻¹.     

一种新型混合动力城市客车的开发

针对城市公交客车的实际运行工况需要,开发出一种新型混合动力总成装置,用于混合动力城市公交客车。混合动力总成具有高低速双电机模式,能充分发挥串联式和并联式优点。混合动力客车具有纯电、混联、驻车发电和电网充电4种工作模式,使发动机、发电机、电机等部件更优化地匹配工作,在结构上保证了在复杂的工况下系统工作在最优状态,达到更高的节能和减排目标。     

Improvement of Lubrication for Cam and Follower

In order to improve the lubrication between cam and follower of internal combustion engines, the influences of materials or oil viscosity and additives on the friction and scuffing characteristics have been examined with a test rig by increasing the contact load at a constant revolution speed. Also the effects of oil supply through the oil-hole of the camshaft on the reduction of friction and the prevention of scuffing have been examined. From the experiments the following results were made obvious.

Firstly, the effect of the material on the reduction of friction or the prevention of scuffing is dependent upon the combination of cam and follower materials. The follower material of hard sintered metal or silicon nitride ceramics is superior in both effects to chilled cast iron when mating with the cam material of hardened S48C steel cam.

Secondly, as the viscosity of base-oil becomes low, the friction increases or decreases depending on oil additives, but the scuffing resistance always becomes small. The organo-molybdenum compounds, MoDTP and MoDTC, decrease the friction and the zinc dialkyl-dithiophosphates are effective in preventing scuffing. In the case of mixed additive with such Molybdenum friction modifiers, primary ZnDTP and secondary ZnDTP enhance the effect to modif' the friction. when mixed with MoDTP, however primary ZnDTP becomes inferior in scuffing resistance to secondary ZnDTP. Specifically the mixed additive of MoDTC and primary ZnDTP improves the lubrication in both respects of the friction and the anti-scuffing.

Lastly, the oil supply from cam surface oil-hole is an effective means of improving the lubrication. The effect becomes largest when the oil-hole is arranged between the flank and shoulder of the cam-lobe corresponding to the valve opening.     

同时考虑速度和轴跨比影响时铁路钢桥的影响因子的确定

传统桥梁设计方法中,把交通荷载处理为静载乘以影响因子。依据现行规范,该因子仅是跨度或一阶自振频率的函数。分析各种参数对钢桥动力响应的影响,包括:速度、火车轴距、车轴数、桥跨度,并研究影响因子。计算了火车速度100～400km/h,轴距13～20m,桥跨度10,15,20,25m情况下的动力响应和影响因子。动力分析表明,大多数情况下,算得的影响因子高于相关规范中的值。影响因子随火车速度、火车轴距和桥跨度之比而变化,而车轴数仅在共振时产生影响。给出了速度、车轴距、桥跨度与影响因子的关系。     

Positive Train Control (PTC) for railway safety in the United States: Policy developments and critical issues

Nationwide implementation of Positive Train Control (PTC) is underway in the United States. PTC is designed to prevent certain types of train accidents. This paper provides a review of the policy development, operational impact, cost-effectiveness, and critical issues associated with industry-wide PTC implementation. Challenges include interoperability, technological complexity, and limited implementation resources. Emerging critical issues include train operations at restricted speeds, railroad cyber-security risk, broken rail prevention in PTC territories, en route failure of PTC, grade-crossing protection, and opportunities for leveraging PTC-generated big data that require more research from academia, government, and industry.     

Dynamic response of a double-lined shield tunnel to train impact loads

A three-dimensional numerical finite element model was established by Abaqus to study the time-history curves of train-to-tunnel impact forces for impacts at different velocities, train configurations and oblique-impact angles. A concrete plastic-damage model was used to study the dynamic responses of a double-lined shield tunnel to train impacts by the HHT time-integration scheme. Model simulations showed that the impact force was related to the velocity and angle of the train at impact, as well as the train configuration. Two categories of characteristic force vs. time curve were found for the train-to-tunnel impact, and multi-peak Gaussian fitting was used to interpret the first category. The dynamic response increases with greater impact velocity and impact angle, while it greatly reduces when the thickness of the secondary lining is increased. Most of the tensile damage was seen ahead of the impact point (in the direction of travel), and compressive damage was concentrated behind, above and below the impact point. The average maximum tensile damage was found to exceed the compressive damage.     

车用汽油机配气机构噪声的研究

本文介绍了EQ6100型发动机配气机构噪声试验结果。讨论了配气机构噪声形成的机理,指出了影响配气机构噪声的因素及降低配气机构噪声的基本途径。