基于GA、RBF和改进Cao方法的空中交通流预测方法

针对传统空中交通流量预测方法精度不足、时效性差的问题,考虑空中交通流量时间序列的混沌特征,在相空间重构理论的基础上,研究了结合遗传算法（GA）、径向基（RBF）神经网络与改进Cao方法的空中交通流量预测方法。为降低传统Cao方法人为参数选择引入的误差,提高相空间重构精度,通过判定虚假邻近点,以及迭代比较嵌入维度离差和可接受偏差,确定重构相空间嵌入维度值的选择标准,进而得到重构后的空中交通流量时间序列数据;为提升径向基神经网络预测精度并降低参数误差,使用遗传算法优化RBF神经网络的中心矢量、加权系数和输出层阈值,再通过最优系数标定后的神经网络对重构后的时间序列进行预测;利用实际空中交通流量数据进行仿真以验证方法的有效性,并结合最大Lyapunov指数和预测结果分析了预测的时效性以及时间尺度对精度影响。结果显示：①改进后的预测方法具有更好的非线性拟合能力,提高了交通流量时间序列的预测精度;②以5 min时间间隔预测为例,相比传统RBF神经网络,改进方法的平均绝对误差、均方误差以及平均绝对百分比误差分别降低了19.44%、34.78%和27.21%;③相比反向传播（BP）神经网络和长短期记忆（LSTM）神经网络,所提方法的平均绝对误差分别降低了36.20%和16.10%,运行速度分别提高了27.42%和35.00%。综上所述,所提方法能更好地解析系统的混沌特性,提升空中交通流量预测精度与速度。     

弹性需求下拥挤道路收费的模型与算法研究

拥挤道路收费作为交通需求管理的一种有效措施在许多国家和地区开始提倡。研究了弹性需求下的拥挤道路收费问题, 建立了双层规划模型, 其中上层模型以用户盈余最大化为目标, 下层模型满足弹性需求下的随机用户平衡(SUE)。基于双层模型求解的复杂性, 设计了一个基于步长加速法和惩罚函数法的启发式算法, 实例计算表明该模型与算法是有效的。     

Dynamic pricing for managed lanes with multiple entrances and exits

Priced managed lanes are increasingly being used to better utilize the existing capacity of the roadway to relieve congestion and offer reliable travel time to road users. In this paper, we investigate the optimization problem for pricing managed lanes with multiple entrances and exits which seeks to maximize the revenue and minimize the total system travel time (TSTT) over a finite horizon. We propose a lane choice model where travelers make online decisions at each diverge point considering all routes on a managed lane network. We formulate the problem as a deterministic Markov decision process and solve it using the value function approximation (VFA) method for different initializations. We compare the performance of the toll policies predicted by the VFA method against the myopic revenue policy which maximizes the revenue only at the current timestep and two heuristic policies based on the measured densities on the managed and general purpose lanes (GPLs). We test the results on four different test networks. The primary findings from our research suggest the usefulness of the VFA method for determining dynamic tolls. The best-found objective value from the method at its termination is better than other heuristics for all test networks with average improvements in the objective ranging between 10% and 90% for revenue maximization and 0–27% for TSTT minimization. Certain VFA initializations obtain best-found toll profiles within first 5–50 iterations which warrants computational time savings. Our findings also indicate that the revenue-maximizing optimal policies follow the “jam-and-harvest” behavior where the GPLs are pushed towards congestion in the earlier time steps to generate higher revenue in the later time steps, a characteristic not observed for the policies minimizing TSTT.     

Forecasting short-term subway passenger flow under special events scenarios using multiscale radial basis function networks

Reliable and accurate short-term subway passenger flow prediction is important for passengers, transit operators, and public agencies. Traditional studies focus on regular demand forecasting and have inherent disadvantages in predicting passenger flows under special events scenarios. These special events may have a disruptive impact on public transportation systems, and should thus be given more attention for proactive management and timely information dissemination. This study proposes a novel multiscale radial basis function (MSRBF) network for forecasting the irregular fluctuation of subway passenger flows. This model is simplified using a matching pursuit orthogonal least squares algorithm through the selection of significant model terms to produce a parsimonious MSRBF model. Combined with transit smart card data, this approach not only exhibits superior predictive performance over prevailing computational intelligence methods for non-regular demand forecasting at least 30 min prior, but also leverages network knowledge to enhance prediction capability and pinpoint vulnerable subway stations for crowd control measures. Three empirical studies with special events in Beijing demonstrate that the proposed algorithm can effectively predict the emergence of passenger flow bursts.     

一般边界条件下矩形薄板振动声辐射特性分析

基于改进傅立叶级数方法,将矩形板振型函数表示为包含正弦三角级数的改进傅立叶级数,从而有效地克服结构在边界处存在的不连续性,建立了一般边界条件下矩形薄板结构振动声辐射的分析方法,并对薄板结构的振动声辐射特性进行了研究。文中还建立了薄板结构的位移容许函数,然后基于最小势能原理求解了系统的Lagrange函数,最后利用Rayleigh-Ritz法对方程求解从而获得薄板自由振动的模态信息;在此基础上,基于Rayleigh积分公式推导出了薄板振动、辐射声压和声功率的表达式,研究了结构特性参数及边界条件对薄板振动声辐射的影响,通过有限元软件和参考文献的比对分析,验证了改进方法的正确性和有效性。     

Local Polynomial Estimation of Distribution Functions

Introduction It is always a focus for statisticians to estimateand predict the function and the related informationusing sample data in the situation without knowing thedistribution function. LetX1,X2,…,Xnbe a samplefrom a population with distribution fu…     

船舶非线性横摇运动方程的线性化研究

考虑阻尼力矩和恢复力矩的非线性,运用能量法对正横规则波中船舶非线性横摇运动方程进行等效线性化,导出等效线性系数表达式,并验证其工程实用性,为船舶横摇预报提供理论分析计算模型。     

彩色多普勒评价正常胎儿心功能的研究

用彩色多普勒技术对50例正常胎儿心脏收缩及舒张功能的各种参数全面、系统地观测分析，评价正常胎儿心脏收缩和舒张功能。结果表明：胎儿时期，胎儿肺循环处于高阻力状态，肺动脉平均压高于主动脉，肺循环阻力高于体循环阻力；胎儿心室舒张顺应性低下，心房的收缩对胎儿心脏维持正常功能有着重要的作用；胎儿时期心脏不仅存在着结构上的右心优势而且存在着功能上的右心优势。     

Time-domain strip method with memory-effect function considering the body nonlinearity of ships in large waves

A time-domain strip method with memory-effect function considering body nonlinearity is presented. In small waves, results from conventional linear strip theory and the present method for a modified Wigley model were compared with the results of linear theories and with experiments, and they were found to be in good agreement. In large waves, a 716 TEU containership was used to compare time histories of motions and vertical bending moments calculated using the present method with experimental results. The time histories of motion were not strongly distorted, but those of the vertical bending moments were extremely distorted, especially for the fore part, and were far from sinusoidal signals. The time histories of the calculations and the experimental results were found to be, qualitatively and quantitatively, in good agreement. A post-Panamax containership was also used as an example of an up-to-date large bow-flare ship, and the calculated results were also found to be in good agreement with the experimental results.     

一种新的混沌系统的优化控制

描述了一种新的混沌系统及其基本动力学行为。随参数的不同,该系统能同时显示2个单漩涡混沌吸引子,或同时显示2个双漩涡混沌吸引子。基于Lyapunov稳定性理论和Krasovskii理论,结合坐标平移变换,对该混沌系统设计了一优化控制器,将混沌吸引子渐近稳定到它的不稳定的平衡点。理论分析和数值仿真都表明了该控制器的有效性。