Designing optimal autonomous vehicle sharing and reservation systems: A linear programming approach

Autonomous vehicle (AV) technology holds great promise for improving the efficiency of traditional vehicle sharing systems. In this paper, we investigate a new vehicle sharing system using AVs, referred to as autonomous vehicle sharing and reservation (AVSR). In such a system, travelers can request AV trips ahead of time and the AVSR system operator will optimally arrange AV pickup and delivery schedules and AV trip chains based on these requests. A linear programming model is proposed to efficiently solve for optimal solutions for AV trip chains and required fleet size through constructed AVSR networks. Case studies show that AVSR can significantly increase vehicle use rate (VUR) and consequentially reduce vehicle ownership significantly. In the meantime, it is found that the actual vehicle miles traveled (VMT) in AVSR systems is not significantly more than that of conventional taxis, despite inevitable empty hauls for vehicle relocation in AVSR systems. The results imply huge potential benefits from AVSR systems on improving mobility and sustainability of our current transportation systems.     

A stability analysis of tandem offloading systems at sea

In this article, we analyze the linear stability of tandem offloading systems in wind, current, and waves. The wind and current forces are evaluated with the help of published experimental data, while the hydrodynamic coefficients and wave drift forces are rigorously estimated by using a three-dimensional singularity distribution method based on potential theory. The bow hawser and mooring lines are described quasistatically by elastic catenary equations. In order to examine the linear static and dynamic stability of the system, the equations for surge, sway, and yaw are linearized. The effect of design parameters such as turret position, mooring stiffness, and hawser length and stiffness on stability is investigated based on linearized model. The stability analysis clarifies the mechanism of the limit cycle for tandem offloading systems, which is known as fishtailing motion. The theoretical results of the shape and amplitude of the limit cycle are found to be in good agreement with those of simulations and experiments.     

量规长度测量中温度影响情况的分析

通过对量规测量中可能面对的不同温度影响情况的分析，并应用实例对于量规测量所应选取的较为合理的条件进行初步判定。     

滤纸波纹深度及全高测定仪

介绍了一种测量汽车滤清器滤纸的专用仪器，它可测量各种规格波纹滤纸的厚度、波纹深度及全高等参数。仪器采用了三角法无法接触激光位置传感器、步进电机和单片微机等技术，可实现非接触和自动测量，因而具有操作简便、测量速度快、重复性好及滤纸无变形等优点。     

A dual decomposition method for sector capacity constrained traffic flow optimization

An aggregate air traffic flow model based on a multicommodity network is used for traffic flow management in the National Airspace System. The problem of minimizing the total travel time of flights in the National Airspace System of the United States, subject to sector capacity constraints, is formulated as an Integer Program. The resulting solution achieves optimal delay control. The Integer Program implemented for the scenarios investigated has billions of variables and constraints. It is relaxed to a Linear Program for computational efficiency. A dual decomposition method is applied to solve the large scale Linear Program in a computationally tractable manner. A rounding algorithm is developed to map the Linear Program solution to a physically acceptable result, and is implemented for the entire continental United States. A 2-h traffic flow management problem is solved with the method.     

基于先验信息的自适应核函数设计

针对多分量线性调频信号，提出一种新的自适应核函数，并给出了有效的核参数估计方法。相对于自适应高斯核函数而言，该核函数既能获得更好的交叉项抑制效果，又避免了较大的信号能量损失，因而是一种更好的核函数。计算机仿真结果验证了其有效性。     

Operational surface drift prediction using linear and non-linear hyper-ensemble statistics on atmospheric and ocean models

Multimodel super-ensemble forecasts, which exploit the power of an optimal local combination of individual models usually show superior forecasting skills when compared to individual models because they allow for local correction and/or bias removal. Deterministic approaches to the problem of surface drift are often limited by strong assumptions on the underlying physics. A new approach based on linear and non-linear optimization is proposed, using hyper-ensemble deduced statistics to forecast at short time scale Lagrangian drifts from combined atmospheric and ocean operational models and local observations that were made available during the MREA04 field experiment along the West coast of Portugal. Optimization methods are based on a training/forecast cycle. The performance and the limitations of the hyper-ensembles and the individual models are discussed. Results suggest that our statistical methods reduce the position errors significantly for 12 to 48 h forecasts and hence compete with pure deterministic approaches.     

基于运行速度的高速公路危险路段鉴别及处置对策探讨

高速公路是国民经济发展的重要运输通道,其线形设计的安全性不容忽视.根据高速公路的设计线形要素计算高速公路未来可能车型的自由运行速度曲线,对线形设计的不合理进行鉴别,找寻危险路段,并提出处置对策以加强重点防治,有助于提高高速公路整体安全性.     

Lightweight Occupancy Estimation on Freeways Using Extended Floating Car Data

Advanced traffic management systems rely heavily on technology to perform accurate estimations of the current state of the traffic as well as its short-term evolution. The objectives are improving traffic flow and enhancing road safety. Their success is based on accurate monitoring of two key variables, specifically speed and occupancy. The latter of the two has, to date, received significantly less attention from the scientific community. In this work we present a lightweight method to perform “on-line” occupancy estimation. We first propose three occupancy measurements calculated from data collected by a floating car: vehicle count, percentage of stop time, and headway. We then extend these discrete values to a continuous estimation of occupancy in space and time. The proposed estimators are based on a pairwise linear regression of each of the previously calculated measurements over certain references obtained from other floating cars or magnetic loop detectors. The method has been calibrated and validated under real traffic conditions and data. Despite the ease of implementation, the method is able to reproduce the occupancy values generated by the actual loop detectors, achieving promising results, with estimation errors down to 6.52%, even before multivehicle systems are considered.     

联合线性和模糊逻辑控制的4自由度主动悬架

文中提出了联合线性和模糊逻辑控制的4自由度汽车主动悬架。该主动悬架以线性控制为主，模糊逻辑控制为辅，前者以车身加速度作为控制量，后者以车身的垂直速度与俯仰速度的线性组合和车身位移作为模糊控制规则的输入变量。最后用Simulink进行仿真，并把所得结果与被动的结果进行比较，说明该系统对提高汽车的平顺性是非常有效的。