The estimation of gross flows in the presence of measurement error using auxiliary variables

Classification error can lead to substantial biases in the estimation of gross flows from longitudinal data. We propose a method to adjust flow estimates for bias, based on fitting separate multinomial logistic models to the classification error probabilities and the true state transition probabilities using values of auxiliary variables. Our approach has the advantages that it does not require external information on misclassification rates, it permits the identification of factors that are related to misclassification and true transitions and it does not assume independence between classification errors at successive points in time. Constraining the prediction of the stocks to agree with the observed stocks protects against model misspecification. We apply the approach to data on women from the Panel Study of Income Dynamics with three categories of labour force status. The model fitted is shown to have interpretable coefficient estimates and to provide a good fit. Simulation results indicate good performance of the model in predicting the true flows and robustness against departures from the model postulated.     

基于空簧气动响应的高速列车交会动力学分析

空气弹簧的动态特性受其内部压力影响较大，为了更深入地分析动车组高速交会时的运行安全性，需要考虑空气弹簧在交会流场下的气动响应。将空气弹簧的气动流体力学模型与某型动车组的整车动力学模型相结合，以列车交会气动流场压力的时间历程作为空气弹簧与车体的外部激励，分析了动车组以不同车速交会时的动力学特性。研究结果表明，交会车速越高，空气弹簧的内压波动幅度越大；会车中车体的垂向平稳性优于横向平稳性；轮轨垂向力与轮重减载率受会车流场的影响较小，在会车时有较大的安全余量；当两车以450 km/h车速交会时，空气弹簧内压波动     

On the Breakdown Properties of Some Multivariate M‐Functionals*

Abstract. For probability distributions on ? ^q, a detailed study of the breakdown properties of some multivariate M‐functionals related to Tyler's [Ann. Statist. 15 (1987) 234] ‘distribution‐free’ M‐functional of scatter is given. These include a symmetrized version of Tyler's M‐functional of scatter, and the multivariate t M‐functionals of location and scatter. It is shown that for ‘smooth’ distributions, the (contamination) breakdown point of Tyler's M‐functional of scatter and of its symmetrized version are 1/q and , respectively. For the multivariate t M‐functional which arises from the maximum likelihood estimate for the parameters of an elliptical t distribution on ν ≥ 1 degrees of freedom the breakdown point at smooth distributions is 1/( q + ν). Breakdown points are also obtained for general distributions, including empirical distributions. Finally, the sources of breakdown are investigated. It turns out that breakdown can only be caused by contaminating distributions that are concentrated near low‐dimensional subspaces.     

新型冷藏陈列柜测试室气流组织模拟与试验分析

据新欧洲标准EN441-2要求,设计并建造了一套全自动陈列柜热工性能测试试验室.在环境测试室气流组织的设计中结合实际情况,对各种气流组织形式进行了分析,用FLUENT流体计算软件进行模拟验证与辅助设计,在试验区域内实现了标准中规定的技术要求,并进行了相应试验.     

上海市高架道路车辆密度与污染物浓度的实测研究

通过对上海市高架道路上车辆的车速、流量进行实测统计，计算出最大的车流量和最佳车速．并对高架道路上的空气污染物进行分析，研究了车辆密度与流量、车速和污染物之间的关系．结果表明，通过降低车密度，不但提高了通行效率，缓解了交通堵塞，而且还减少了高架道路上的空气污染．     

Book Reviews

Books reviewed: S. Moolgavkar, D. Krewski, L. Zeise, E. Cardis, and H. Møller, Quantitative Estimation and Prediction of Human Cancer Risks Jacqueline Karnell Corn, Environmental Public Health Policy for Asbestos in Schools: Unintended Consequences Andrew Ford, Modeling the Environment. An Introduction to System Dynamics Modeling of Environmental Systems James Hamilton and W. Kip Viscusi, Calculating Risks? The Spatial and Political Dimensions of Hazardous Waste Policy Sharon M. Friedman, Sharon Dunwoody, and Carol L. Rogers, Communicating Uncertainty: Media Coverage of New and Controversial Science     

航空运输业的自由化:动因、趋势、对策

世界航空运输业自由化的新发展主要表现为管理的自由化和产业的自由化 ,自由化的网络经济基础和政府管制理论的演变是其发展的动因。未来的航空运输业自由化将影响到全球范围内的产业重组。我国民航可以从政府管制和企业重组方面进行改革与创新。     

红江橙黄龙病热治疗的研究

本试验通过对红江橙二年生带黄龙病的苗木进行50-54℃湿热空气脱毒处理，不仅完全杀死材体内的病原菌，使树体恢复健康，而且提高病苗处理后的成活率，使湿热空气处理这种有效的脱毒方法，大面积推广到生产中去．     

航空物流园区规划及设施布局研究

物流园区在我国是一个新生事物 ,物流园区设施的合理布局是物流园区规划的主要内容。目前 ,有关物流园区设施布局方面的研究较少 ,航空物流园区规划及设施布局方面的文献更是难以见到 ,几乎没有可参照的模式。文章从物流园区的主要功能出发 ,根据现代物流理念、航空物流的特点以及最优化方法 ,研究航空物流园区规划及设施布局的最优化     

北京远期能源需求与大气环境目标及近期对策探讨

北京市为实现本世纪前半叶建成世界一流国际化大都市的战略目标及实施能源结构调整规划 ,需要研究远期能源需求和大气环境目标。文章根据北京市的发展战略和规划 ,并与国际上的发展进行比较 ,测算了届时的能源需求 ,探讨了应达到的大气环境目标 ,分析了达到未来大气环境目标的不同进程对能源系统成本的影响。建议在保证大气环境质量整体效果情况下 ,采用渐近进程减少能源引起的大气污染 ,以降低能源系统成本 ;并在考虑远期能源与大气环境要求下 ,分析了近期发展热电联产和煤炭利用对策问题。