斗轮堆取料机回转机构定位方式浅析

斗轮堆取料机回转减速机连接螺栓经常松动、断裂,设备运行存在安全隐患。分析了堆取料机回转机构定位方式、定位结构,查找了减速机连接螺栓松动原因。制定可行性解决方案,便于设备进行合理化改造,保障设备安全可靠运行。     

京沪高铁天津西站曲线变宽异型钢箱梁设计实践

在恒载、温度荷载和活载等因素作用下连续曲线钢箱梁会出现支座脱空、梁体侧移和翻转等问题。同时相对直梁桥,弯桥扭转效应明显,应引起重视。该文通过京沪高铁天津西站异型连续曲线钢箱梁的设计实践,探讨该类桥梁设计中应注意的若干问题,使连续曲线钢箱梁设计安全、合理、经济。     

Investigation of particle emission characteristics from a diesel engine with a diesel particulate filter for alternative fuels

Particle number measurement is a new approach to determine emission, which may be more accurate at very low emission levels than when using gravimetric measurements. An experimental study was performed to investigate the effect of fuel properties on the performance, combustion process, regulated gaseous emissions and particle number emissions of a diesel engine with an uncatalyzed diesel particulate filter (DPF). The effect of the filter on the particle size distribution was reported. The DPF number-based filtration efficiency in terms of number efficiency and fractional efficiency for petroleum diesel fuel and two alternative fuels, BTL and GTL, were analyzed. For nearly all test modes, the filter had a higher number efficiency for diesel than for BTL and GTL. The DPF fractional efficiency showed it was highly dependent on fuel type and varied widely at each size range. For diesel, the filter fractional efficiency was sufficiently high and behaved as predicted by filtration theory. For BTL and GTL, the fractional performance of the filter decreased when unexpectedly low efficiencies within the nuclei mode were exhibited. This research will be helpful in understanding DPF number-based filtration performance for alternative fuels and will provide information for the development of particulate emission control technology.     

预防客车超载的智能系统设计

本文介绍了一种基于单片机的预防客车超载的智能系统。系统的核心控制模块采用MC9S12DG256VPV单片机,并利用PLD204E圆板式测力传感器实时检测车内乘客数量,并根据车辆额定载客量对客车是否超载做出判断。若客车超载,则系统发出警报,若客车超载持续时间达到一定值,系统中的MC39IGSM无线通信模块通过GSM网络向交通管理部门的信息接收平台发送超载报警信息,同时单片机向控制开关模块发出指令,切断点火开关的电源,使客车熄火。本文还对系统的程序实现进行了设计。     

装备研制进度风险管理研究

进度风险是新装备研制面临的重要风险之一,它与计划、技术等因素密切相关。该文分析了装备研制进度风险的影响因素,总结了网络计划技术在进度风险评估分析中的应用,并就如何进行风险控制进行了研究。     

列车气密性静态泄漏理论模型与计算

基于一维等熵流动理论推导了列车气密性静态泄漏状态方程, 考虑泄漏孔流量系数, 得到了压降泄漏时间和总泄漏时间计算公式; 数值模拟了列车气密性静态泄漏的动态过程, 并研究了长细比分别为1∶1、1∶4、1∶8和1∶16, 车内初始气压分别为6、5、4和3 kPa时, 泄漏孔长细比和车内初始气压对列车气密性的影响。分析结果表明: 在车内空气压力从3.0 kPa下降到0.8 kPa的过程中, 数值仿真和理论公式计算得到的压降时间分别为20.25、20.23 s, 与试验结果的相对误差分别为1.41%和1.51%;当泄漏孔长细比为1∶8和1∶16时, 列车车厢内空气压力下降时程曲线基本一致, 泄漏孔气流流量保持不变; 泄漏过程中泄漏孔的气流速度呈现中间大周围小的分布特征, 这是由泄漏孔壁面的黏滞作用引起的; 根据出口截面的中心速度和质量流率得到泄漏孔流量系数为0.71, 车内初始气压对相同指定压力下降时间的影响不足1%;若压降范围一致, 随着初始气压的增大, 压降时间减小, 压力从4 kPa下降到1 kPa的时间为24.18 s, 从5 kPa下降到2 kPa的时间为19.80 s; 数值仿真得到的压降泄漏时间与理论计算结果的最大相对误差为1.22%, 表明理论模型与数值仿真计算方法可以用于计算列车泄漏面积或气密性。      

基于月客流量残差的地铁客流季节指数预测方法

为精准反映城市轨道交通的季节性特征,基于月客流残差提出了地铁客流季节区间分类方法.建立趋势方程并计算月客流残差,以月客流残差曲线之间的相似度为基础对月份进行分类,得出基于月客流残差曲线的季节分组区间(SIR).分别以每月进行分类并计算传统月份分组区间(TMC)、以每季度进行分类并计算传统季度分组区间(TQC)以及SIR区间的季节指数并进行预测.预测结果表明,提出的分类方法在相对误差、平均绝对百分比误差、均方根误差三方面都比其他分类方法更小.这说明所提出的分类方法在地铁客流预测中具有更好的适应性,从而可以为地铁运能运力调整以及运营计划的制定提供参考依据.     

基于有限元方法的调距桨桨毂机构强度分析

对受推力、扭力、离心力和螺栓受预紧力联合作用下的某型舰船调距桨完整机构各部件的静强度进行有限元仿真分析;基于ANSYS 12.0软件,考虑完整部件的三维模型以及装配接触关系,对桨毂机构各部件进行有限元建模。有限元分析结果与理论计算和试验结果的对比验证表明,在完整模型和复杂工况下,基于应力应变准则,重点针对如叶根螺栓、曲柄盘和桨毂体等主要受力部件进行分析,更符合实际工程需要。     

Nonlinear buckling analysis of pre-stressed ring-stiffened circular cylindrical shells under external pressure

This paper is concerned with the nonlinear buckling behavior of pre-stressed ring-stiffened thin circular cylindrical shells under external pressure. According to the geometrical nonlinearity, governing equations are derived by incorporating initial stresses based on Donnell-type shell theory. The “smeared stiffeners” approach is used for ring stiffeners. The numerical analyses are conducted by Gelerkin’s method to obtain critical buckling loads of shells. This study shows effects of initial stresses on stability of shells. Moreover, effects of initial stresses on buckling modes of shells are discussed.     

Experimental study on the resistance of a transport ship navigating in level ice

This study investigates the resistance of a transport ship navigating in Arctic waters by conducting a series of model tests in an ice tank at Tianjin University. The laboratory-scale model ship was mounted on a rigid carriage using a one-directional load cell and then towed through an ice sheet at different speeds. We observed the ice-breaking process at different parts of the ship and motion of the ice floes and measured the resistances under different speeds to determine the relationship between the ice-breaking process and the ice resistance. The bending failure at the shoulder area was found to cause maximum resistance. Furthermore, we introduced the analytical method of Lindqvist (1989) for estimating ice resistance and then compared these calculated results with those from our model tests. The results indicate that the calculated total resistances are higher than those we determined in the model tests.