Developing Transport Infrastructure in Sub-Saharan Africa through Public–Private Partnerships: Policy Practice and Implications

In contemporary times, Public–Private Partnership (PPP) in transport infrastructure has gained considerable attention in developing regions following its success in the developed countries. However, Sub-Saharan Africa (SSA) is among the developing regions with few transport PPP projects and among the regions with high number of failed projects. Meanwhile the region's transport infrastructure need far exceeds it current provision. This paper therefore aims to examine the project experiences (success and failure factors) of three highly profiled transport PPP projects, namely the Lekki toll road concession project (Nigeria), N4 toll road (South Africa/Mozambique) and Port of Maputo (Mozambique) in order to develop policy measures for effective future implementation. The experiences of the three projects show that transport PPP policy is indeed feasible in SSA. However, to realise its full applicability, proper policy actions and measures must be carefully observed and these include effective and efficient stakeholder management, transparent and competitive tendering process, high participation of local investors, stable macro-economic conditions and strong government commitment and regulatory framework. The projects experiences and policy actions developed are impactful in accelerating transport infrastructure development through PPP approach in SSA. Hence it is hoped that policy-makers and practitioners would be informed on the key strategies to employ in implementing future projects.     

Reasonable scheduling for arrival–departure track operations in railway stations

We analyze the train types handled at a section station and the factors affecting the scheduling of the arrival–departure track operation, using the following conditions as our optimization goals: operating the arrival–departure tracks in accordance with a fixed operation scheme, and reducing the influence which the departing–receiving operations impose on shunting operations. We establish a 0–1 integer programming model for formulating a track operation plan. By applying modern sequencing theory, this is transformed into a fixed sequencing model of special parallel machines. We then design a heuristic algorithm to solve the model. Finally, the example of Yiyang railway station is used to verify the advantages of the model and the algorithm. A better operation plan is obtained using MATLAB 7.0 by applying the model and the algorithm provided in the paper, indicating the superiority of our study’s approach.     

带脉冲和时滞的二阶微分方程的稳定性

研究了带脉冲和时滞的二阶微分方程的稳定性问题。通过构造合适的Lyapunov函数,利用稳定性理论和脉冲控制方法,证明了对于不稳定的时滞二阶微分方程,可以通过加强一定的脉冲控制使其稳定。获得的结果改进和推广了前人的工作,提供的例子表明了获得结果的有效性。     

港口平面布置对港内波况的影响

开展葫芦岛港绥中港区波浪整体模型试验并运用改进的Boussinesq方程模拟了不同平面布置方案港内波高情况,探讨了防波堤结构形式、口门方向、口门宽度、航道和港池边界结构对港内波高的影响。结果表明从上述影响因素出发,合理地选取港口平面布置形式可以有效地减少港内波高,为港口总平面规划的优化提供了科学依据。此外探讨了物模与数模的局限性,给出了结合两者研究港口规划的思路。     

用一种全非线性Boussinesq方程模拟斜坡上的波浪破碎和爬高

基于一种新的二阶全非线性Boussinesq方程,采用预测-校正格式的有限差分法对该方程进行离散,建立了数值模型.模型中通过“狭槽法“来处理波浪在岸线处的动边界条件,采用涡粘模型来模拟波浪破碎引起的能量耗散.为了验证数值模型的适用性,模拟了斜坡地形上的波浪破碎和爬高.从数值结果和试验结果的比较上看,该模型可以很好地模拟近岸波浪场的实际问题.     

树枝型专用线取送车的模型及算法研究

合理确定取送车作业顺序,有利于减少货车在站非生产时间,加速车辆周转,通过对取送车作业过程的分析,可以将其归纳为一个典型的旅行商问题.运用图论中的哈密尔顿图,可以将树枝型专用线取送车问题,转化为求哈密尔顿图中权值最小的哈密尔顿回路问题.     

三维可压缩Euler方程组经典解的爆破

研究了三维可压缩等熵Euler方程组经典解的爆破。在Sideris T C等研究的基础上,利用局部解具有有限传播速度的性质,通过构造适当的泛函,证明了某些初始数据较大时Cauchy问题的经典解必定在有限时间内爆破的结论。     

Cross-sector Analysis of Four Renegotiated Transport PPPs in Portugal

Abstract

This paper uses the Fertagus renegotiation results as a reference and explores the features that made it such a widely commended case, aiming to identify the best practice to be followed in other cases. The two main questions that this paper aimed to respond were: Was the success of the renegotiation process in the Fertagus contract due to mode-specific factors? Are those factors (mode specific or not) transferable to other modes under public private partnership (PPP) contracts and if so, to what extent? Regarding the mode specificity and transferability analysis, it can be noticed that much of the features were not mode specific in theory, however for the successful transferability to other transport modes, some changes should be made to the PPP model taking into account modal specificities and national contexts.     

TMD design for seismic vibration control of high-pier bridges in Sichuan–Tibet Railway and its influence on running trains

Sichuan–Tibet Railway plays a vital role in China’s transportation system by connecting Tibet and Central China, whose design and construction are extremely difficult due to numerous seismic zones and deep valleys along the railway line. This paper systematically presents a framework to control seismic vibration of T-beam bridges with high-piers in Sichuan–Tibet Railway using tuned mass dampers (TMDs). Firstly, a finite element model of the widely used high-pier bridge is established to reveal its vibration modes subject to earthquakes. On this basis, optimal installation locations and optimal parameters of the TMDs are determined. Then, vibration reduction effects of the designed TMDs on the high-pier bridge subject to actual earthquake samples are investigated and compared with that of using some other vibration absorption measures. Finally, a detailed train-track-bridge dynamic model with attached TMDs is established to study the effects of the designed TMDs on the seismic responses of the running trains. The results indicate that, for the high-pier T-beam bridges, the first bending vibration mode of the high-pier is most likely to be excited by earthquakes, which should be restrained. With the designed optimal parameters, the attached TMDs are effective to control seismic vibrations of the concerned high-pier bridges. Tuned mass damper is the best one among all the investigated measures to absorb vibrations subject to earthquakes from the perspective of vibration absorption performance, installation and maintenance.     

A new method for wheel–rail contact force continuous measurement using instrumented wheelset

With the aim of improving the continuous measurement of wheel–rail contact force by instrumented wheelset, instead of solving the non-linear equations, we proposed a new method based on state space theory. With this new method, the wheel–rail contact force can be calculated by the recurrence relation and the signals from strain gauge bridges on wheel web. The implementation of continuous instrumented wheelset is quite general and simplified, due to the specific bridging scheme is not necessary. It means that continuous measurement of the contact force could be realised with a simple bridging scheme, even as simple as discrete instrumented scheme. In this work, we first demonstrated and discussed the effectiveness and accuracy of this new method by estimation results with the numerical simulations, and we also applied this new method to two field tests, including one was conducted in a loop test line using a high-speed train and the other one was conducted in an urban line with a light rail vehicle. In a word, this new method is proved to be an effective way to monitor the wheel–rail contact force of rail vehicle track system.