车用发动机废气再循环装置的检修

简述了废气再循环装置的作用和工作原理 ,针对其共性结构 ,较为详细地总结出检修该装置的基本方法     

准周期强迫园映象中两频率准周期吸引子分形测度

用数值计算方法计算了准周期强迫园映象中两频率准周期吸引子的无穷多维数Ｄq、奇性强度α(q)的点集维数f(α)，并给出了相应的图线。     

图像边界检测区域对比度模糊增强算法在轮廓提取中的运用

分析了图像边界检测的区域对比度模糊增强算法的特点，通过实验验证了该算法的正确性和可行性，并指出了算法的一些不足之处和待改进的地方，提出了一种适用轮廓提取的新广义算子。     

Influence of polygonal wear of railway wheels on the wheel set axle stress

The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen–Hedrick–Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions.     

高速铁路客运专线砂浆车供电可靠性分析

针对砂浆车经常发生电气故障的问题，对其供电系统中柴油发电机组的选择、配电系统及接地系统等几方面进行了详细分析，重点分析了影响供电可靠性的因素，提出了提高砂浆车供电可靠性的措施及方法，为砂浆车的设计开发及使用维护提供了参考依据。     

地下工程排烟口部流体动力学数值仿真分析

利用FLUENT对沿着排烟口部附近排烟管内壁引入冷气流进行了数值模拟,分析了不同冷气流速度、不同管径以及不同冷气流进口宽度下的排烟管内温度分布情况,对于排烟口部掺冷装置的设计提供了重要的参考依据。     

Sampling of alternatives for route choice modeling

This paper presents a new paradigm for choice set generation in the context of route choice model estimation. We assume that the choice sets contain all paths connecting each origin–destination pair. Although this is behaviorally questionable, we make this assumption in order to avoid bias in the econometric model. These sets are in general impossible to generate explicitly. Therefore, we propose an importance sampling approach to generate subsets of paths suitable for model estimation. Using only a subset of alternatives requires the path utilities to be corrected according to the sampling protocol in order to obtain unbiased parameter estimates. We derive such a sampling correction for the proposed algorithm.Estimating models based on samples of alternatives is straightforward for some types of models, in particular the multinomial logit (MNL) model. In order to apply MNL for route choice, the utilities should also be corrected to account for the correlation using, for instance, a path size (PS) formulation. We argue that the PS attribute should be computed based on the full choice set. Again, this is not feasible in general, and we propose a new version of the PS attribute derived from the sampling protocol, called Expanded PS.Numerical results based on synthetic data show that models including a sampling correction are remarkably better than the ones that do not. Moreover, the Expanded PS shows good results and outperforms models with the original PS formulation.     

沈阳动车所进口在线式动车组轮对诊断系统应用

对引进进口动车组轮对诊断系统设备的构成、原理进行分析及对设备安装的建议,便于设备使用、维修人员对系统有深入的了解,确保设备真正发挥预测轮对何时需要再仿形加工或更换进行全自动测量、诊断的作用,并使之经常处于良好的使用状态。     

NEW METHOD FOR DERIVING OPTIMAL REDUCT

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基于图论的造船供应链构建

供应链管理的思想和方法适合现代造船模式的需要,能够反映未来造船模式的方向和趋势,供应链的构建是造船供应链管理的前提和基础.本文应用离散数学中的集合、图论方法构建造船供应链模型,并用运筹学中的标号法对模型进行优化,从而给出了寻找、选择、优化供应链合作伙伴的新方法.