发动机排气门用钢5Cr21Mn9Ni4N中的M7C3相与热裂纹原因探讨

分析和测定了５Ｃｒ２１Ｍｎ９Ｎｉ４Ｎ钢中Ｍ７Ｃ３相的形貌特征及化学组成，并对钢中钙含量与Ｍ７Ｃ３相及铸，锻件裂纹关系进行了探讨。当该钢中钙含量大于０．００６８％及铸锭冷却过地，就易在该钢中形成大而脆的Ｍ７Ｃ３的晶界薄膜，使铸，锻件常常出现热裂纹。     

基于标准研究横风下车辆运行安全性简化方法

为了探究一种分析车辆在横风作用下运行安全性的简化方法。基于标准EN14067-6中简化三质量模型和气动系数的预测公式,编制Matlab程序绘制国内某速度160 km/h动力车的风特性表,对该动力车在横风作用下运行安全性做出评估。三质量模型力矩平衡公式表明若未平衡力方向和横风风向同向,车辆运行时更容易被倾覆;由风特性表可知,该动力车在横风风速为33 m/s作用下,车辆不受未平衡力时,安全运行速度可达到200 km/h。因此该动力车过曲线遇到恶劣的横风时,应及时调整车辆运行速度到均衡速度附近,可以保证运行安全。利用三质量模型力矩平衡公式和预测公式可以简化地评价车辆在横风作用下的运行安全性。     

合肥地铁6号线设计规模和速度目标值的选择

REN Junhui(Shaanxi Provincial Key Laboratory of Railway and Underground Traffic Engineering (FSDI), 710043, Xi′an, China)     

M3919b型司机控制器摩擦力机构问题分析及解决方案

对HXD1C型7200 kW电力机车用M3919b型司机控制器在生产和使用过程中牵引/制动手柄鼓轮摩擦力机构的缺陷进行研究,分析主要基于现有的设计结构和生产操作实际情况.在已有设计基础上根据实际工作情况提出了新的设计方案.新设计方案可以提高产品生产效率,提高机车运行稳定性.     

基于MIH的PMIPv6垂直切换增强机制

当前的代理移动IPv6 (PMIPv6,Proxy Mobile IPv6)仅考虑了基本的注册、解注册和切换管理,并不能很好地支持具有多个异构网络接口的移动节点(MN,Mobile Node)的垂直切换.由于在基本PMIPv6的垂直切换过程中,本地移动锚点(LMA,Local Mobility Anchor)和移动接入网关(MAG,Mobile Access Gateway)在绑定更新完成时,移动节点可能并未配置好有效的地址,从而会引起严重的切换时延和数据包丢失.通过扩展介质独立切换(MIH,Media Independent Handover)原语和参数,可以支持高效的PMIPv6垂直切换.理论分析结果表明,所提机制能够有效减小垂直切换时延.     

基于M/G/c/c模型的地铁车站楼梯通道疏散能力瓶颈分析

乘客疏散能力及服务水平是地铁车站设计与站内客流组织的重要组成部分,也是保证安全运营的重要影响因素。M/G/c/c网络排队模型适用于各种空间内行人运动过程分析及相应指标的计算。本文在乘客运动特性分析基础上,结合车站空间结构特征,构建基于M/G/c/c的地铁车站楼梯与通道乘客疏散能力瓶颈分析模型。以北京地铁2号线与4号线的西直门换乘站为例开展研究,计算分析该站在乘客到达率发生变化时楼梯、通道的疏散能力瓶颈点,验证模型的有效性与实用性。     

基于M3车辆悬浮架结构方案的曲线通过能力研究

为实现城市磁浮快捷交通工程化,提高功率因数和效率,降低建造成本,文章对美国磁动力公司提出的M3中低速直线同步驱动永磁悬浮与导向的单悬浮架车辆系统的走行机构方案的曲线通过能力进行分析,特别对两侧悬浮电磁铁在通过曲线引起的间距缩短问题和在小曲线上的悬浮力分量用于导向的能力问题进行研究,并提出针对性结构改进意见。     

Development of a generalised equivalent estimation approach for multi-axle vehicle handling dynamics

This paper devotes analytical effort in developing the 2M equivalent approach to analyse both the effect of vehicle body roll and n-axle handling on vehicle dynamics. The 1M equivalent vehicle 2DOF equation including an equivalent roll effect was derived from the conventional two-axle 3DOF vehicle model. And the 1M equivalent dynamics concepts were calculated to evaluate the steady-state steering, frequency characteristics, and root locus of the two-axle vehicle with only the effect of body roll. This 1M equivalent approach is extended to a three-axle 3DOF model to derive similar 1M equivalent mathematical identities including an equivalent roll effect. The 1M equivalent wheelbases and stability factor with the effect of the third axle or body roll, and 2M equivalent wheelbase and stability factor including both the effect of body roll and the third-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the three-axle vehicle. By using the recursive method, the generalised 1M equivalent wheelbase and stability factor with the effect of n-axle handling and 2M equivalent generalised wheelbase and stability factor including both the effect of body roll and n-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the n-axle vehicle. The 2M equivalent approach and developed generalised mathematical handling concepts were validated to be useful and could serve as an important tool for estimating both the effect of vehicle body roll and n-axle handling on multi-axle vehicle dynamics.     

帕金森病模型大鼠杏仁基底外侧核神经元电活动的研究

目的观察单侧黑质纹状体通路毁损后杏仁基底外侧核(basolateral nucleus of amygdala,BLA)投射神经元电活动的变化。方法应用6-羟多巴胺单侧毁损黑质致密部建立帕金森病(Parkinson s disease,PD)大鼠模型。采用玻璃微电极细胞外记录法,记录BLA投射神经元的电活动。结果对照组和PD组大鼠BLA投射神经元的放电频率分别是(0.66±0.13)Hz(0.08-2.73 Hz,n=25)和(0.46±0.1)Hz(0.08-2.34 Hz,n=24),PD组大鼠的放电频率较正常组降低,但无统计学差异(P>0.05)。对照组大鼠96%的BLA投射神经元呈现爆发式放电,4%为不规则放电;PD组大鼠90%的投射神经元显示爆发式放电,10%为不规则放电。PD组大鼠BLA投射神经元的放电形式与对照组相比无明显差异(P>0.05)。结论帕金森病大鼠BLA投射神经元的放电频率和放电形式未发生改变。     

Measurement of Swarm Parameters of c-C4F8/CO2 and Its Insulation Characteristics Analysis

In c-C4F8 and c-C4F8/CO2 mixtures, the swarm parameters including ionization coefficient, attachment coefficient and effective ionization coefficient were obtained at the ratio of the electric field strength to the gas density between 150-550 Td by the steady-state Townsend (SST) method. Static breakdown voltages at each ratio were also measured at the SST condition. The limiting field strengths were obtained by two methods:computing the density-normalized effective ionization coefficient as a function of the overall density-reduced electric field strength; and measuring static breakdown voltages as a function of the product of gas density and electrode separation. Good agreement was obtained by these two methods, which ensures the correctness of the former method. The limiting field strengths of c-C4F8 and c-C4F8/CO2 mixtures were compared with those ofpure SF6, SF6/CO2 mixtures and pure c-C4Fs. It is found that buffer gas CO2 does not reduce the limiting field strengths of c-C4F8 greatly, the limiting field strengths of c-C4F8/CO2 mixtures are higher than those of SF6/CO2 mixtures or even pure SF6, and so c-C4F8/CO2 mixtures are suggested to be possible substitutes for SF6.