公路网规划现实思考与新思路

基于公路网规划的研究现状，研究了目前规划理论中规划逻辑与交通预测。指出了规划中存在的突出问题：规划逻辑上存在价值逻辑和因果逻辑的缺陷；规划依据的需求预测置信水平不高。运用系统多维价值导向的共生思维方法和生态进化的演替思想，提出用慢变量决定路网布局，优化路网结构，用快变量改进管理，用广义目标规划实现规划目标的价值导向和公路网功能整合的规划思路。该方法能在很大程度上避免逻辑缺陷和预测模型的不良影响，改善规划的质量。     

一种同步环的改进设计

对手动变速器的一种同步环在换挡过程中出现的问题进行了分析。针对存在的缺陷,提出在满足同步容量的同时,可以通过提高材料的耐磨性和改进设计参数来提高换挡时的同步性能。主要改进了同步环内螺纹参数,提高了其换挡摩擦力,实现了在换档过程中同步器和结合齿完全同步。     

连拱隧道断面型式选型及中墙构型优劣研究

通过对目前在建和已建的连拱隧道的调查和总结,支护结构受力的复杂性和中墙开裂、渗漏水是连拱隧道设计、施工和运营中的突出问题。因此,对连拱隧道断面型式选型及中墙构型进行了分析、研究,得出连拱隧道断面型式在不同情况时的合理选用,同时得出分层式曲中墙是最优的中墙型式,并对其在施工中稳定性相对不足进行了进一步优化,使其能更好地应用到实际工程中去。     

Multiple hub network and high-speed railway: Connectivity,gateway, and airport leakage

This paper considers the relation between the role of airport as gateway (inter–intra transit airport) and the connectivity between air transport and high-speed rail (HSR) transport to discuss the possibility of a multiple gateway system with HSR. We deal with both international and domestic transport markets in the model analysis. In the international markets, only airlines compete against each other, while in the domestic market airlines and HSR compete against each other. The results suggest that the improvement of connectivity between air and HSR at the airport increases its international passengers, and therefore, that strengthens its role as gateway, for example, gathering more inter–intra transit passengers. However, the results also suggest that the demand of the area which the airport belongs to affects the role of airport as gateway.     

调距桨桨毂机构静强度的有限元仿真分析

文章对受推力、扭力、扭矩、离心力和螺栓预紧力联合作用下的某型舰船调距桨桨毂机构静强度进行有限元仿真分析。基于ANSYS 12.0软件平台,考虑桨毂部件几何结构及零件间装配接触关系,对桨毂机构整体及零件进行全六面体和六面体与四面体混合有限元建模,研究了桨毂中各零件在正常工况相互作用下的应力大小及分布。重点针对叶根螺栓的实际结构,采用六面体网格分析螺栓有无螺纹区别,证明螺纹的几何特征在强度校核中不能忽略。     

基于多套载重线的船舶安全监管研究

文中研究了航运业内存在的多套载重线问题,提出借助完善法律制度、加强船检与公司监管、规范文书管理、加大检查力度等手段,加强对多套载重线船舶的安全监管建议。     

Estimation of mean and covariance of stochastic multi-class OD demands from classified traffic counts

This paper proposes a new model to estimate the mean and covariance of stochastic multi-class (multiple vehicle classes) origin–destination (OD) demands from hourly classified traffic counts throughout the whole year. It is usually assumed in the conventional OD demand estimation models that the OD demand by vehicle class is deterministic. Little attention is given on the estimation of the statistical properties of stochastic OD demands as well as their covariance between different vehicle classes. Also, the interactions between different vehicle classes in OD demand are ignored such as the change of modes between private car and taxi during a particular hourly period over the year. To fill these two gaps, the mean and covariance matrix of stochastic multi-class OD demands for the same hourly period over the year are simultaneously estimated by a modified lasso (least absolute shrinkage and selection operator) method. The estimated covariance matrix of stochastic multi-class OD demands can be used to capture the statistical dependency of traffic demands between different vehicle classes. In this paper, the proposed model is formulated as a non-linear constrained optimization problem. An exterior penalty algorithm is adapted to solve the proposed model. Numerical examples are presented to illustrate the applications of the proposed model together with some insightful findings on the importance of covariance of OD demand between difference vehicle classes.     

A static free-floating bike repositioning problem with multiple heterogeneous vehicles,multiple depots,and multiple visits

In this paper, a bike repositioning problem with multiple depots, multiple visits, and multiple heterogeneous vehicles for the free-floating bike-sharing system (FFBSS) is studied. Two types of nodes (i.e., easily and hardly access nodes) with different penalties are defined to represent different convenience levels of getting bikes from the FFBSS. The objective of the repositioning is to minimize the weighted sum of the inconvenience level of getting bikes from the system and the total unmet demand and the total operational time. To solve this problem, an enhanced version of chemical reaction optimization (CRO) is developed. A loading and unloading quantity adjustment procedure with the consideration of the node characteristics, including the type of node and its current state (i.e., in a balanced, surplus, or deficit state) is proposed and incorporated into this version to improve its solution quality. A concept of the nearby-node set is also proposed to narrow the search space. Numerical results are presented and indicate that compared to the traditional CRO and CPLEX, the enhanced CRO improves solution quality and has potential to tackle the repositioning problem for larger, longer repositioning duration, and more vehicle instances. The results also demonstrate the effectiveness of the proposed adjustment procedure.     

How much is too much for tolled road users: Toll saturation and the implications for car commuting value of travel time savings?

The current practice of forecasting the demand for new tolled roads typically assumes that car users are prepared to pay a higher toll for a shorter journey, and they will keep doing so as long as the toll cost is not higher than their current value of travel time savings. Practice ignores the possibility that there could be a point when motorists stop driving on toll roads due to a toll budget constraint. The unconstrained toll budget assumption may be valid in networks where the addition of a new toll road does not result in a binding budget constraint that car users may have for using toll roads (although it could also be invoked for existing tolled routes through a reduction in use of a tolled route). In a road network like Sydney which offers a growing number of (linked) tolled roads, the binding budget constraint may be invoked, and hence including additional toll links might in turn reduce the car users’ willingness to pay for toll roads to save the same amount of travel time. When this occurs, car users are said to reach a toll saturation point (or threshold) and begin to consider avoiding one or more toll roads. Whilst toll saturation has important implications for demand forecasting and planning of toll roads, this type of behaviour has not been explored in the literature. We investigate the influence that increasing toll outlays has on preferences of car commuters to use one or more tolled roads as the number of tolled roads increases. The Sydney metropolitan area offers a unique laboratory to test this phenomenon, with nine tolled roads currently in place and another five in planning. The evidence supports the hypothesis that the value of travel time savings decreases as a consequence of toll saturation.     

石油管螺纹的检测技术

石油专用管螺纹是一种气密性良好、质量要求极高的专用螺纹，因此为保证螺纹的检测质量与了解螺纹的基本扣型，正确选用测量方法、掌握几何精度对于严格按照标准检修和检验钻具而言乃是至关重要的。基于对钻具、油套管螺纹检验的目的、检验内容、方法及存在问题的探讨，较为详尽地阐述了如何在工作中正确应用石油管螺纹检测技术。