一种高效的Ad Hoc网络链路层数据级联方法

在Ad Hoc网络条件下,受接入层效率及高误码率等客观因素影响,链路层传输性能较低。针对这一问题,提出了一种高效的链路层数据级联方法,使发端的数据既能更好地匹配接入层协议,得到较高的吞吐量,又能减少高误码率对传输性能的影响。理论及仿真结果表明：与传统的数据级联方法相比,该方法可获得更高的链路层吞吐量,提升了Ad Hoc网络链路层的传输性能。     

Incorporating Driver Behaviors in Network Design Problems: Challenges and Opportunities

The goal of a network design problem (NDP) is to make optimal decisions to achieve a certain objective such as minimizing total travel time or maximizing tolls collected in the network. A critical component to NDP is how travelers make their route choices. Researchers in transportation have adopted human decision theories to describe more accurate route choice behaviors. In this paper, we review the NDP with various route choice models: the random utility model (RUM), random regret-minimization (RRM) model, bounded rationality (BR), cumulative prospect theory (CPT), the fuzzy logic model (FLM) and dynamic learning models. Moreover, we identify challenges in applying behavioral route choice models to NDP and opportunities for future research.     

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高速铁路为人们提供了一种高效的运输方式.本文借鉴弹性系数法的相关理论,首先运用广义费用函数测算样本中高铁开通前后两地区综合客运成本的变化,结合两地区高铁开通前后客运量的变化得到了运输成本弹性系数,用于衡量两地区对于高铁开通的迫切性程度,从而在另一个层面衡量高铁建设的可行性.然后根据运输经济学及新经济地理学的相关理论,从人口、距离、人均GDP差异、平均人均GDP和产业结构相似度5个维度对样本的运输成本弹性系数进行建模,运用神经网络的方法来拟合其对运输成本弹性系数的影响情况,并以此为依据来测算北京市和张家口市对即将开通的京张高铁的迫切性程度.     

An efficient and exact event-based algorithm for solving simplified first order dynamic network loading problems in continuous time

In this paper a novel solution algorithm is proposed for exactly solving simplified first order dynamic network loading (DNL) problems for any generalised network. This DNL solution algorithm, termed eLTM (event-based Link Transmission Model), is based on the seminal Lighthill–Witham–Richards (LWR) model, adopts a triangular fundamental diagram and includes a generalised first order node model formulation. Unlike virtually all DNL solution algorithms, eLTM does not rely on time discretisation, but instead adopts an event based approach. The main advantage of this approach is the possibility of yielding exact results. Furthermore, an approximate version of the same algorithm is introduced. The user can configure an a-priori threshold that dictates the approximation error (measurable a-posteriori). Using this approximation the computational effort required decreases significantly, making it especially suitable for large scale applications. The computational complexity is investigated and results are demonstrated via theoretical and real world case studies. Fixed periods of stationary demands are included adopting a matrix demand profile to mimic basic departure time demand fluctuations. Finally, the information loss of the approximate solution is assessed under different configurations.     

Indicators of reliability and vulnerability: Similarities and differences in ranking links of a complex road system

This article investigates two performance attributes of road networks, reliability and vulnerability, analyzing their similarities as well as the differences that justify distinct definitions, based on consolidation of recent studies. We also discuss the indicators found in the literature for these two performance attributes. Since various authors treat vulnerability as an aspect of reliability instead of a specific attribute, we carried out an application to a complex road network representative of the city of Rio de Janeiro to check the suitability of this approach. The results show that the vulnerability indicators are more strongly affected by the characteristics of alternative routes while the reliability metrics are more sensitive to the congestion level. The conclusion is that reliability and vulnerability should be treated distinctly for evaluating the performance of road network links.     

基于复杂网络的机场群航线网络动态特征分析

随着航空运输和区域经济一体化的快速发展,我国已形成京津冀、长三角和珠三角三大典型机场群。文章以三大典型机场群为研究对象,构建基于滑动时间窗的航线网络拓扑结构,运用复杂网络理论分析机场群航线网络动态特征和同构性。研究结果表明,机场群航线网络具有无标度和小世界网络特征,并表现出显著的波峰和波谷动态性,并且长三角机场群的航班集中度分布明显高于其他两大机场群。文章首次从航线网络视角,运用Dice相似系数衡量了机场群内部各机场之间航线网络同构性程度。     

客运专线铁路隧道高陡坡洞口开裂整治技术研究

以宝兰客运专线塔稍村隧道为依托,分析隧道进口边坡及洞内裂缝的成因,评价边坡的稳定性,并提出具体的处理措施。对该隧道地层岩性、构造属性、围岩等级等进行阐述,针对该边坡建立系统的地表及洞内变形监测网并进行钻孔内位移测量工作,结合详细的地质调查,查明隧道进口处边坡、洞口挡墙、隧道内二衬裂缝的成因和基本特征,结合区段的工程地质特征,提出合理的工程处理措施,为类似工程的调查与处理提供参考。     

物流网络优化中路径问题的研究

在深入分析物流系统化和网络化的基础上,对物流网络优化中物流路径问题进行研究,通过分析物流结构模型和数学模型,提出了最短路径和关键路径物流策略的分析方法,给出了具体的计算方法,并举实例加以说明,为解决现代物流结构中存在的系统设计和运作等问题提供了理论依据和技术方法。     

基于文化粒子群网络优化算法的医学图像研究

文章提出了基于文化粒子群的网络优化算法的医学图像方法，通过在50例唇裂矫正术中运用BP神经网络进行学习．对唇部进行解剖观察和美学分析，在矫正修复手术中不断学习和调整来接近期望输出，并通过实验仿真及客观的图像提出了评估准则。实验结果表明，在美学研究基础上的基于文化粒子群BP神经网络的医学图像研究，适用于唇裂的矫正修复。