基于云理论的航空兵电子战作战能力评估

通过对航空兵电子战飞机在造成目标信息损失的实际能力与航空兵战术运用上的分析,建立了其电子战作战能力指标体系,既符合电子战原理同时又体现了航空兵作战特点;通过运用云重心理论,将定性与定量相结合,建立了航空兵电子战作战能力评估模型,并给出了具体算例和步骤。     

渔船非线性横摇理论研究分析

为讨论船舶在波浪中的非线性横摇,应用非线性动力学的方法对现象进行理论分析,得到主共振情况下船舶运动稳态响应的解析解,并对实船进行稳定性分析。通过不同波浪条件下船舶非线性横摇运动的模拟计算,预报船舶在横浪中的横摇运动,预报结果与试验结果比较一致。     

船体特征曲线光顺算法研究

在以特征曲线为船体NURBS曲面控制线的基础上,通过特征曲线的几何要素和光顺准则自动生成NURBS控制点,为此需要求解一个非线性规划问题,针对该非线性规划的特点,运用现代内点理论作为数值最优化算法,解决了带几何约束的船体特征曲线光顺问题。     

混流泵叶轮轴面流道设计及轴面速度场的求解

基于Ωu=0的二元理论,用Matlab编程实现轴面速度场求解。采用五点四次Bezier曲线绘制混流泵叶轮的轮缘、轮毂轴面流线。轴面流道的进出口边取为垂直于旋转轴线的直线,采用等分进出口边间隔的方法划分准正交线,最后采用等分准正交线绕旋转轴一周所得圆环面积的方法获得了初始轴面流线。采用流线迭代法求解轴面流线,引入松弛因子T,有效地保证了计算的收敛。该方法可提高轴面流道的设计效率,较为精确地求解轴面速度场,为叶轮叶片的快速准确绘型奠定技术基础。     

基于图论的舰船水消防系统故障诊断顺序确定方法

快速地准确诊断出舰船水消防系统的故障,可以显著改善舰船损管水平,提出了一种图论与经验公式相结合的方法,将故障抢修时间为准则的经验公式值作为诊断路径中弧的权值,运用"反向追踪"算法计算从故障现象到具体可修理的故障部件的最短路径,以确定水消防系统的故障诊断顺序。实验数据表明:该方法不仅综合权重各潜在故障对水消防系统的重要性,所确定的故障诊断顺序与损管的经验做法相符。     

Social networks as a source of private-vehicle transportation: The practice of getting rides and borrowing vehicles among Mexican immigrants in California

We examine the role of social networks in enabling access to private-vehicle transportation, through getting rides and borrowing cars. Based on qualitative findings from ten focus group discussions with recent Mexican immigrants to California, half of whom have no car, we describe the extent to which participants depend on rides and borrowed cars for transportation. We highlight the unique aspects of informal access to cars, drawing on social exchange theory and related research to characterize the procurement process and likely levels of exchange. We discuss the implications of these findings for transportation services that might serve this and other community groups.     

Embedding risk attitude and decision weights in non-linear logit to accommodate time variability in the value of expected travel time savings

In recent years we have seen important extensions of logit models in behavioural research such as incorporation of preference and scale heterogeneity, attribute processing heuristics, and estimation of willingness to pay (WTP) in WTP space. With rare exception, however, a non-linear treatment of the parameter set to allow for behavioural reality, such as embedded risk attitude and perceptual conditioning of occurrence probabilities attached to specific attributes, is absent. This is especially relevant to the recent focus in travel behaviour research on identifying the willingness to pay for reduced travel time variability, which is the source of estimates of the value of trip reliability that has been shown to take on an increasingly important role in project appraisal. This paper incorporates, in a generalised non-linear (in parameters) logit model, alternative functional forms for perceptual conditioning (known as probability weighting) and risk attitude in the utility function to account for travel time variability, and then derives an empirical estimate of the willingness to pay for trip time variability-embedded travel time savings as an alternative to separate estimates of time savings and trip time reliability. We illustrate the richness of the approach using a stated choice data set for commuter choice between unlabelled attribute packages. Statistically significant risk attitude parameters and parameters underlying decision weights are estimated for multinomial logit and mixed multinomial logit models, along with values of expected travel time savings.     

基于凝集质量法的海洋缆索动态响应建模与仿真

提出了一种基于凝集质量法的海洋缆索动态响应研究的模型,该模型采用Kane方法以广义主动力与广义惯性力相平衡的方式得到缆索运动的控制方程。模拟了以拖船-落锚方式布放次水面浮标的时间历程。对浮标结构设计与布放作业有一定的参考价值。     

模拟直流电动机

本章主要研究设计直流电动机的电路原理图.根据直流电动机的转速公式n=(U-IaRa)/CeΦ,对电动机和负载参数进行比例缩小,运用电路理论和电机拖动的相关知识,实现了电动机转速的可调.