浅论桥头跳车现象的预防与治理

通过对路桥相接处不均匀沉降的危害性、引起跳车主要原理的分析 ,提出设计及施工相应的预防与治理措施     

Data-driven ferry network design with candidate service arcs: the case of Zhuhai Islands in China

ABSTRACT

We investigate a ferry network design problem with candidate service arcs (FNDP-SA), which is a new variant motivated by areal-world case from Zhuhai Islands. In this research, the design of a ferry schedule must conform to strict constraints including technical feasibility, safety issues, environmental impacts and moreover, avoid conflicting with ferries from neighboring cities (i.e. HongKong, Shenzhen and Macao). Therefore, a set of cautiously approved service arcs are firstly given, based on which the ferry service network is optimized. This study is among the first to formally describe the FNDP-SA and model it as an integer program. A hybrid variable neighborhood descent (VND)-based algorithm is developed. Two sets of instances are generated based on the case of Zhuhai Islands, where the first set is based on historical ticket sales data while the second set is derived by incorporating increased demands in the future according to a questionnaire survey. Numerical studies have shown that 59% cost reduction on the first set can be achieved by the proposed VND algorithm when compared with manual results. Research outcomes of this study have been adopted and implemented to facilitate the sustainable development of the ferry service of Zhuhai Islands.     

Distance-dependent congestion pricing for downtown zones

A growing literature exploits macroscopic theories of traffic to model congestion pricing policies in downtown zones. This study introduces trip length heterogeneity into this analysis and proposes a usage-based, time-varying congestion toll that alleviates congestion while prioritizing shorter trips. Unlike conventional trip-based tolls the scheme is intended to align the fees paid by drivers with the actual congestion damage they do, and to increase the toll’s benefits as a result.The scheme is intended to maximize the number of people that finish their trips close to their desired times. The usage-based toll is compared to a traditional, trip-based toll which neglects trip length. It is found that, like trip-based tolls, properly designed usage-based tolls alleviate congestion. But they reduce schedule delay more than trip-based tolls and do so with much smaller user fees. As a result usage-based tolls leave most of those who pay with a large welfare gain. This may increase the tolls’ political acceptability.     

The split-demand one-commodity pickup-and-delivery travelling salesman problem

This paper introduces a new vehicle routing problem transferring one commodity between customers with a capacitated vehicle that can visit a customer more than once, although a maximum number of visits must be respected. It generalizes the capacitated vehicle routing problem with split demands and some other variants recently addressed in the literature. We model the problem with a single commodity flow formulation and design a branch-and-cut approach to solve it. We make use of Benders Decomposition to project out the flow variables from the formulation. Inequalities to strengthen the linear programming relaxation are also presented and separated within the approach. Extensive computational results illustrate the performance of the approach on benchmark instances from the literature.     

A distributed VNS algorithm for optimizing dial-a-ride problems in large-scale scenarios

These days, transportation and logistic problems in large cities are demanding smarter transportation services that provide flexibility and adaptability. A possible solution to this arising problem is to compute the best routes for each new scenario. In this problem, known in the literature as the dial-a-ride problem, a number of passengers are transported between pickup and delivery locations trying to minimize the routing costs while respecting a set of prespecified constraints. This problem has been solved in the literature with several approaches from small to medium sized problems. However, few efforts have dealt with large scale problems very common in massive scenarios (big cities or highly-populated regions). In this study, a new distributed algorithm based on the partition of the requests space and the combination of the routes is presented and tested on a set of 24 different scenarios of a large-scale problem (up to 16,000 requests or 32,000 locations) in the city of San Francisco. The results show that, not only the distributed algorithm is able to solve large problem instances that the corresponding sequential algorithm is unable to solve in a reasonable time, but also to have an average improvement of 9% in the smaller problems. The results have been validated by means of statistical procedures proving that the distributed algorithm can be an effective way to solve high dimensional dial-a-ride problems.     

The flying sidekick traveling salesman problem: Optimization of drone-assisted parcel delivery

Once limited to the military domain, unmanned aerial vehicles are now poised to gain widespread adoption in the commercial sector. One such application is to deploy these aircraft, also known as drones, for last-mile delivery in logistics operations. While significant research efforts are underway to improve the technology required to enable delivery by drone, less attention has been focused on the operational challenges associated with leveraging this technology. This paper provides two mathematical programming models aimed at optimal routing and scheduling of unmanned aircraft, and delivery trucks, in this new paradigm of parcel delivery. In particular, a unique variant of the classical vehicle routing problem is introduced, motivated by a scenario in which an unmanned aerial vehicle works in collaboration with a traditional delivery truck to distribute parcels. We present mixed integer linear programming formulations for two delivery-by-drone problems, along with two simple, yet effective, heuristic solution approaches to solve problems of practical size. Solutions to these problems will facilitate the adoption of unmanned aircraft for last-mile delivery. Such a delivery system is expected to provide faster receipt of customer orders at less cost to the distributor and with reduced environmental impacts. A numerical analysis demonstrates the effectiveness of the heuristics and investigates the tradeoffs between using drones with faster flight speeds versus longer endurance.     

依靠技术手段,防止客车电气火灾

铁路客运量的剧增给铁路的安全运输生产提出了更高的要求 ,不断增加的高技术装备使得电气系统发生火险的可能性在不断增大 ,旅客列车安全用电与防火问题也面临着严峻的挑战。为此 ,必须加强对空调客车电气系统的制造、维修、保养中的防火安全意识 ,以及对火灾事故的预想和防范 ,坚决杜绝此类事故的发生 ,以保证旅客列车的绝对安全     

浅谈透水土质路堤边坡滑坡的预防

本文结合作者实际施工体验,根据渗水性土质路堤的特点,对滑坡的现象及成因进行了深入分析,并提出了预防滑坡的两种方法,即将薄弱区移入安全区和将分界面外移。以供进行此类工作的人员参考。     

城市轨道交通噪声问题概述

分析了轨道交通中噪声的类别，产生的原因及传播方式，并从衰减振源、避免结构共振、隔离传播途径、吸声等方面提出了噪声的防治措施。     

铝基牺牲阳极阴极保护在海船压载水舱中的应用研究

海船压载舱使用海水压载，引起船体板的腐蚀，焊缝处会产生蚀孔漏水。采用铝基牺牲阳极阴极保护系统可大为降低腐蚀速率，使压载水舱的保护度在７８％～９５％，保护与未作保护的试片腐蚀率相差８倍，效果明显。