考虑时间因素的运输方式选择问题

本文先对各类运输方式做了概括论述,在着重考虑时间因索的前提下对运输方式的选 择进行了定量分析,提出了利用最小花费来完成运输任务的运输方式选择模型,并分析了该摸 型的求解过程,有助干运输消费者选择经济、合理的运输方式。     

A pattern recognition algorithm for assessing trajectory completeness

Vehicular trajectories are widely used for car-following (CF) model calibration and validation, as they embody characteristics of individual driving behaviour (each trajectory reflects an individual driver). Previous studies have highlighted that the trajectories should contain all the major vehicular interactions (driving regimes) between the leader and the follower for reliable CF model calibration and validation. Based on Dynamic Time Warping and Bottom-Up algorithms, this paper develops a pattern recognition algorithm for vehicle trajectories (PRAVT) to objectively, accurately, and automatically differentiate different driving regimes in a trajectory and then select the most complete trajectories (i.e. trajectories containing a maximum number of regimes). PRAVT is rigorously tested using synthetic data and then applied to the NGSIM data. We have observed that the NGSIM data are dominated by the trajectories which contain only three regimes, namely acceleration, deceleration, and following, 77% of the trajectories lack the standstill regime, and no trajectory in the NGSIM data is complete. These findings’ impact on how to properly utilize NGSIM data can be profound. Given the extensive use of the NGSIM data in the traffic flow community, this paper also provides insights about the types of regimes contained in each trajectory of the NGSIM data.     

Origin-destination pattern estimation based on trajectory reconstruction using automatic license plate recognition data

Origin-destination (OD) pattern estimation is a vital step for traffic simulation applications and active urban traffic management. Many methods have been proposed to estimate OD patterns based on different data sources, such as GPS data and automatic license plate recognition (ALPR) data. These data can be used to identify vehicle IDs and estimate their trajectories by matching vehicles identified by different sensors across the network. OD pattern estimation using ALPR data remains a challenge in real-life applications due to the difficulty in reconstructing vehicle trajectories. This paper proposes an offline method for historical OD pattern estimation based on ALPR data. A particle filter is used to estimate the probability of a vehicle’s trajectory from all possible candidate trajectories. The initial particles are generated by searching potential paths in a pre-determined area based on the time geography theory. Then, the path flow estimation process is conducted through dividing the reconstructed complete trajectories of all detected vehicles into multiple trips. Finally, the OD patterns are estimated by adding up the path flows with the same ODs. The proposed method was implemented on a real-world traffic network in Kunshan, China and verified through a calibrated microscopic traffic simulation model. The results show that the MAPEs of the OD estimation are lower than 19%. Further investigation shows that there exists a minimum required ALPR sampling rate (60% in the test network) for accurately estimating the OD patterns. The findings of this study demonstrate the effectiveness of the proposed method in OD pattern estimation.     

Comparison of numerical and experimental results of nonlinear wave-induced vertical ship motions and loads

 A nonlinear time-domain procedure is presented which is used to calculate the vertical responses of a container ship advancing in head waves. The method assumes linear radiation forces represented by time convolution of memory functions, infinite frequency added masses, and radiation restoring coefficients. The nonlinear hydrostatic restoring and Froude–Krilov forces are computed exactly over the instantaneous wetted surface of the ship's hull. Forces due to green water on deck are calculated using the momentum method. Nonlinear effects are identified on different vertical ship responses, namely on the heave and pitch motions, the vertical accelerations, and the vertical bending moment. These non-linear effects are expressed by the variation of the transfer function with the wave amplitude, the higher-order harmonics of the time signals, the offset of the time series, and the asymmetry of the peaks. The numerical results and the quantified nonlinear effects are compared with experimental results showing an ability to reproduce the main nonlinear effects. Received: December 17, 2001 / Accepted: January 31, 2002     

舰船风浪中航行及操纵系统

基于风浪中经验航法和理论航法相结合的观点；汲取耐波性等领域的研究成果，提出了一种实用的风浪航行操纵系统，集合3个子系统（海浪计算子系统，航向航速优选子系统，摇荡短期时历预子系统）的计算结果，合理组合，可满足风浪航行及转向时机，舰载直升机起降时同，海上补给及拖带航向航速选择等决策的需求。     

浅谈船舶铅封管理

目前,船舶铅封工作正在全国范围内深入开展,本文结合笔者自己的工作实践,以某大型远洋船舶为例,着重介绍了如何阅读机舱油污水管系图以及如何对其实施铅封管理工作。     

城市轨道交通移动闭塞列车安全间隔时间分析

在引入移动闭塞概念的基础上,比较移动闭塞和准移动闭塞的技术差异,提出城市轨道交通列车安全间隔时间计算方法,推导出移动闭塞和准移动闭塞列车安全间隔时间计算公式,对两者进行仿真计算及分析。可知,列车以相同的速度运行,列车安全间隔越大,移动闭塞列车安全间隔时间比准移动闭塞列车安全间隔时间缩短得越多;列车安全间隔距离一定时,列车的运行速度越大,移动闭塞列车安全间隔时间和准移动闭塞列车安全间隔时间越接近。     

浅谈网络计划的工期—成本优化在公路工程管理中的应用

介绍网络计划中的工期、成本优化及在公路工程管理中的应用。     

公交车在站停靠时间建模研究

本文在实际调查统计的基础上,研究公交车在站停靠的流程及其影响因素,对公交车在站停靠时间建立数学模型,并对其科学性和实用性进行检验。     

Investigation of Discretionary Lane-Change Characteristics Using Next-Generation Simulation Data Sets

In this article, we investigate discretionary lane change (DLC) characteristics using Next Generation SIMulation (NGSIM) data sets. We first develop a set of heuristic rules to automatically filter out abnormal samples from a massive trajectory data set and identify DLC trajectories from a mixture of mandatory lane change (MLC) and DLC trajectories. Then, we investigate a variety of DLC characteristics. We demonstrate that the kernel part of every normal DLC trajectory can be approximately depicted by a certain fifth-order polynomial. Moreover, we discuss the definition of begin/end points of DLC actions and show that the duration time of DLC actions follows a log-normal distribution with respect to navigation speed. All the findings can help promote temporal and spatial accuracy of lane changing models.