Three-Dimensional Cooperative Localization via Space-Air-Ground Integrated Networks

The space-air-ground integrated network(SAGIN)combines the superiority of the satellite,aerial,and ground communications,which is envisioned to provide high-precision positioning ability as well as seamless connectivity in the 5G and Beyond 5G(B5G)systems.In this paper,we propose a three-dimensional SAGIN localization scheme for ground agents utilizing multi-source information from satellites,base stations and unmanned aerial vehicles(UAVs).Based on the designed scheme,we derive the positioning performance bound and establish a distributed maximum likelihood algorithm to jointly estimate the positions and clock offsets of ground agents.Simulation results demonstrate the validity of the SAGIN localization scheme and reveal the effects of the number of satellites,the number of base stations,the number of UAVs and clock noise on positioning performance.

Possible Sustainability of Intermodal Transportation in Africa

The lack of adequate and modern transport infrastructures makes the cost of transport in Africa higher than the rest of the world. Most of the transport infrastructures that exist were constructed during the colonial era which makes inter-regional connectivity difficult. The African Union in collaboration with other organization has committed to bridge the transport gap in Africa but still, face some challenges. This paper discusses the main issues that contribute for the weak nature of transportation in Sub-Saharan Africa with regards to the main transport modes and seeks to establish the possibility of sustainable intermodal transport through the integration of the different transport modes. Some policy reforms and other bilateral agreements such as deregulating the transport markets in West and Central Africa have been suggested to facilitate the development of an effective and efficient transport network in the Sub-Saharan African region.

Transportation Network Density,Domestic Market Integration and Excess Sensitivity of Household Consumption

From the perspective of domestic market integration,this paper systematically examines the impact of transportation infrastructure conditions on excess sensitivity of household consumption based on the China Family Panel Survey(CFPS)and multi-level matching panel data of transportation network density.The results show that the fast-growing development of the transportation infrastructure network has a significant alleviating effect on excess sensitivity of household consumption along the route,and the conclusion is still robust after the use of the multi-dimensional instrumental variable method and a series of robustness tests.According to the heterogeneity tests,in terms of the alleviating effect of transportation infrastructure,railroads rank the first,highways the second,substandard roads the third,waterways the fourth,and roads of other grades at the bottom.The mechanism test reveals that the improvement of domestic market integration is an important channel for transportation infrastructure to alleviate excess sensitivity of household consumption.This paper confirms that improving the transportation infrustructure system is conducive to the construction of a unified national market,alleviating excess sensitivity of consumption and stimulating consumption.This paper provides suggestions for implementing the strategy of boosting domestic demand,and helps the government understand households'consumption decision-making from a broader perspective.This study also provides a theoretical basis for the economic spillover effect of transportation infrastructure.

Multi-stage Dynamic Post-disaster Recovery Strategy for Distribution Networks Considering Integrated Energy and Transportation Networks

To improve the resilience of distribution networks(DNs),a multi-stage dynamic recovery strategy is proposed in this paper,which is designed for post-disaster DN considering an integrated energy system(IES)and transportation network(TN).First,the emergency response quickly increases the output of gas turbines(GTs)in the natural gas network(NGN),and responsively reconfigures the DN in microgrids,to maximize the amount of loads to be restored.The single-commodity flow model is adopted to construct spanning tree constraints.Then,in the second stage of energy storage recovery,mobile energy storage systems(MESSs)are deployed to cover the shortages of power demands,i.e.,to further restore the loads after evaluating the load recovery situation.The Floyd algorithm based dynamic traffic assignment(DTA)is selected to obtain the optimal path of the MESSs.In the third stage,the outputs of various post-disaster recovery measures are adjusted to achieve an economically optimized operation.Case studies demonstrate the effectiveness of the proposed dynamic post-disaster recovery strategy.

Energy management of hybrid electric propulsion system: Recent progress and a flying car perspective under three-dimensional transportation networks

The hybrid electric propulsion system(HEPS)holds clear potential to support the goal of sustainability in the automobile and aviation industry.As an important part of the three-dimensional transportation network,vehicles and aircraft using HEPSs have the advantages of high fuel economy,low emission,and low noise.To fulfill these advantages,the design of their energy management strategies(EMSs)is essential.This paper presents an in-depth review of EMSs for hybrid electric vehicles(HEVs)and hybrid electric aircraft.First,in view of the main challenges of current EMSs of HEVs,the referenced research is reviewed according to the solutions facing real-time implementation problems,variable driving conditions adaptability problems,and multi-objective optimization problems,respectively.Second,the existing research on the EMSs for hybrid electric aircraft is summarized according to the hybrid electric propulsion architectures.In addition,with the advance in propulsion technology and mechanical manufacturing in recent years,flying cars have gradually become a reality,further enriching the composition of the three-dimensional transportation network.And EMSs also play an essential role in the efficient operation of flying cars driven by HEPSs.Therefore,in the last part of this paper,the development status of flying cars and their future prospects are elaborated.By comprehensively summarizing the EMSs of HEPS for vehicles and aircraft,this review aims to provide guidance for the research on the EMSs for flying cars driven by HEPS and serve as the basis for knowledge transfer of relevant researchers.

Optimization Processes of Tangible and Intangible Networks through the Laplace Problems for Regular Lattices with Multiple Obstacles along the Way

A systematic approach is proposed to the theme of safety,reliability and global quality of complex networks(material and immaterial)by means of special mathematical tools that allow an adequate geometric characterization and study of the operation,even in the presence of multiple obstacles along the path.To that end,applying the theory of graphs to the problem under study and using a special mathematical model based on stochastic geometry,in this article we consider some regular lattices in which it is possible to schematize the elements of the network,with the fundamental cell with six,eight or 2(n+2)obstacles,calculating the probability of Laplace.In this way it is possible to measure the“degree of impedance”exerted by the anomalies along the network by the obstacles examined.The method can be extended to other regular and/or irregular geometric figures,whose union together constitutes the examined network,allowing to optimize the functioning of the complex system considered.

空铁综合运输网络结构特征实证分析

为探究中国空铁综合运输网络结构特性,以城市为节点,若城市间有航班或高铁则连边,以航班数量和高铁数量为权重,分别建立了3个加权网络:高铁子网络、航空子网络和空铁综合运输网络。首先,通过均值关联、三角中介中心度、加权谐波中心度指标对比研究了不同网络的关键节点;其次,通过聚类系数和平均最短路径长度研究了三个网络的小世界特性;再次,通过Newman算法研究了三个网络的社团结构;最后,通过加权网络效率为指标,研究了三个网络的鲁棒性。研究结果表明,北上广深是三个网络的三种不同加权中心度的排名都很靠前,是共有的最为关键的节点。三个网络都具有小世界特性,但只有高铁子网络的模块度值大于0.3,存在明显的社团结构,并被划分为了10个社团。空铁综合运输网络具有更好的加权网络效率,约为0.32,为三个网络中最高,节点失效时的加权效率变化最小,鲁棒性最强。可见空铁综合运输网络集成了高铁网络、航空网络的互补优势,网络结构特征优于单一运输网络。

循环神经网络模型下道路碳排放浓度预测

以湖南省永州市永州大道基本路段CO_(2)浓度时序数据为研究对象,旨在实现道路CO_(2)浓度的实时预测。测得用于模型训练和预测精度计算的路段CO_(2)浓度数据,利用Savitzky-Golay滤波器对数据进行平滑去噪,在调试并建立循环神经网络最优模型结构的基础上,引入多元预测模型(MLR、SVR、BP)和时序预测模型(BP、RF、RNN、LSTM、GRU)进行预测性能对比,为路段CO_(2)浓度的实时预测提供参照。结果表明:时序预测模型相比于多元预测模型具有更好的预测效果,特别是循环神经网络模型中的GRU表现出较高的预测精度,其次是LSTM,最后是RNN;循环神经网络模型在处理路段CO_(2)浓度时序数据的训练和预测任务中具备突出性能,能够实时且精准预测道路路段CO_(2)浓度。

空铁综合运输网络互补作用分析

为更好地发挥航空运输和高铁运输的优势,本文研究了空铁综合运输网络的互补作用。首先,以城市为节点,以航线/高铁线路为边,以单日航班频率/高铁班次频率为权值,构建了航空网络、高铁网络和空铁综合运输网络。其次,采用枚举法和遗传算法,基于网络加权效率研究了网络的鲁棒性,并识别出网络关键节点组合。再次,针对随机节点失效和关键节点失效两种情况,分别从鲁棒性、互补强度两个方面研究了高铁网络和航空网络的互补作用。结果显示:空铁综合运输网络的加权效率为0.317,明显高于航空网络0.268和高铁网络0.209,当独立的高铁网络不连通时,空铁综合运输网络仍然连通;当随机节点和关键节点失效时,高铁子网络对航空子网络的互补强度平均值分别为0.072和0.435,航空子网络对高铁子网络的互补强度平均值分别为0.217和0.368,关键节点失效时的互补作用更强。结果表明,空铁综合运输网络结合了航空网络和高铁网络的优势,具备更好的鲁棒性,航空网络和高铁网络能够发挥互补作用,且当关键节点失效时,互补作用更为明显。

四网融合条件下以客流需求为导向的市域铁路运输组织优化建议

[目的]区域一体化建设对区域多层次轨道交通网络的融合发展提出了更高的要求。在四网融合趋势下,应充分考虑客流需求,以客流需求为导向进行市域铁路的运输组织优化。[方法]从长江三角洲等区域轨道交通四网融合背景和市域铁路在其中的功能定位出发,明确了轨道交通互联互通的内涵。从客运需求总量、市域铁路客流分担率、运力供给和客运需求的匹配性3个方面阐述了当前市域铁路面临的运输组织困境。以客流需求为导向,从战略层、策略层及运营层3个层面提出了市域铁路运输组织的优化建议。[结果及结论]当前市域铁路运输组织的3大制约因素分别为线路规划建设与客运需求的差异、市域铁路与其他运输方式竞争优势不明显、缺少客流导向的列车开行方案调整机制及方法。从战略层角度应强化顶层设计,形成一体化运输组织体系;从策略层角度应化竞为合,发挥多模式轨道交通网络化效应;从运营层角度应以人为本,实行多样化行车组织模式。

低轨卫星与5G-R融合网络架构设计

由于地面网络覆盖不均匀,信号质量不够稳定,无法实现铁路交通网络的全程、快速、实时监测,阻碍了我国铁路交通网络的快速发展。同时,低轨卫星通信与地面5G的融合成为热点,二者的融合能够使卫星网络作为地面网络的有效补充。当前星地融合较少用于5G-R技术场景中。本文梳理了铁路卫星通信以及星地融合网络的研究现状与发展趋势;分析了铁路通信系统中各业务的通信需求。在此基础上,提出低轨卫星与5G-R融合网络架构。在弥补铁路通信网络覆盖盲区的同时,提供大容量的信息回传,有效保障铁路交通的安全运行,实现铁路交通的信息化、智能化管理。

基于加边策略的城市群客运网络韧性优化

研究城市群客运网络韧性及韧性优化的问题有助于提高城市群应对突发事件的能力。以韧性城市和复杂网络理论构建考虑城市群客运网络吸收、适应、恢复3种能力的模型,以呼包鄂乌城市群路网数据为基础,利用不同攻击策略与加边策略考虑城市群客运网络韧性的优化问题,借助Python分析,找到最佳的加边策略。结果表明:不同的攻击方式对城市群客运网络韧性的影响不同,按低度数加边对韧性提升较为显著,为之后城市群韧性的提高提出了建议。

长江经济带综合交通运输体系铁路货运发展对策研究

长江经济带覆盖长江上中下游重庆、湖北、上海等省(市),区域内基本形成了由铁路、公路、水运等多种交通方式构成的综合交通运输体系,服务区域经济社会的发展。通过分析长江经济带综合交通运输体系铁路、公路和水运的网络结构和货运量现状,存在干线通道能力仍显紧张、交通运输结构不尽合理、多式联运体系有待完善、部分铁路线路能力利用趋紧等问题,铁路大运量、低排放等优势还没有得到充分发挥。在此基础上,提出长江经济带铁路货运发展对策,即:提质改造通道瓶颈区段,推动铁路多式联运发展,加强铁路运输资源分配,积极争取国家政策支持,为推进长江经济带综合交通运输体系建设提供研究依据。

高速公路源网荷储一体化绿色供电系统规划方法与应用

集成应用分布式新能源、新型储能、柔性直流输配电等源网荷储技术装备,构建适用于高速公路长线型特点的绿色柔性供电系统,是交通用能低碳转型的重要路径。本文提出一种高速公路源网荷储一体化绿色供电系统规划方法,考虑交通负荷可扩展性和新能源出力随机性,通过全生命周期仿真模拟和边际效益分析对系统容量进行最优化配置。某典型高速服务区算例表明,所提方法兼顾规划准确性与计算可行性,实现交通动态增长的用能需求与随机波动的新能源供应之间的最优匹配,有效提升投资净收益。

一种空铁联运枢纽节点选择与分级的综合方法

空铁联运枢纽节点的选取与发展定位对构建完善合理的空铁运输网络至关重要。为此,文章基于复杂网络、熵权Topsis与系统聚类理论等提出了一种综合性评价方法,即熵权Topsis-Q型聚类法,同时全面考虑城市的运输能力与社会经济发展水平,对我国空铁联运枢纽城市的选择与分级问题进行了系统研究。首先,以36个国家级流通节点城市为研究对象,构建了有向非加权的空铁联运网络,明确并计算出反映城市运输能力的节点中心性指标。其次,进一步考虑城市社会经济发展水平指标,建立了一个三级综合评价指标体系。再次,应用熵权Topsis-Q型聚类分析法进行枢纽城市筛选与分级,最终确定出2个全国性枢纽城市和7个区域性枢纽城市。文章结论与经济、社会发展高度一致,提出的方法可用于不同模式交通枢纽节点分级评价研究。

成德眉资经济圈轨道交通一体化发展对策研究

经济圈是都市圈发展进程中寻求更高标准、更高质量的城市形态,不仅能够更好地优化城市资源配置,还能够提升城市整体竞争力,促进经济的持续健康发展。成德眉资经济圈轨道交通一体化建设,不断促进多层次轨道交通初步成网,轨道交通半小时通勤圈和“两环三射”框架初步形成。通过阐释成德眉资经济圈轨道交通发展现状,从线网布局、运营管理、协同机制等方面,分析成德眉资经济圈轨道交通一体化发展存在的问题,提出完善轨道交通线网布局、加强运营管理一体化、强化组织协同管理等对策,以推动成德眉资经济圈协同发展。

复杂网络理论在综合客运建模及网络评价领域的应用综述

随着中国综合运输网的持续完善,各种运输方式的不断持续、融合发展给综合客运网络提出了新要求,研究综合客运网络模型和网络性能很有必要。首先结合文献计量分析法,对比分析交通网络和运输网络研究热点的不同。其次通过综述复杂网络理论在综合客运建模及网络评价领域应用的研究现状,给出不同模型下网络构建的差异,从静、动态两个角度剖析综合客运网络的研究,总结刻画网络特征的方法。对于网络的评价,从整体网络和节点两个角度进行。一方面,梳理脆弱性、抗毁性、可靠性、鲁棒性和韧性5个典型复杂网络评价指标的相关研究;另一方面,总结研究节点影响力常用的方法。最后,总结现有研究所面临的主要问题与挑战,并从网络建模改进、客流再分配、乡村客运网络模型探索和超网络应用等方面对未来综合客运的发展方向与研究趋势进行分析。

云网融合时代下的运营商传送网云化发展浅析

在云网融合时代下,运营商若要为用户提供高品质的云服务,其传统网络也需积极进行转型升级。传送网作为用户至云专网传输接入的基础网络,也需进行云化改造。针对传送网急需云化改造的目的,讨论了面向云网融合的OTN、PON、SPN的主要云化策略,提出了通过在OTN网络部署超100G波分并引入OXC技术、PON网络从10G PON向50G PON演进、为SPN网络引入10M小颗粒切片技术的方案,可满足用户安全、高效、灵活的接入需求,并助力运营商转型升级。

算存融合的天基承载网架构

面向“网络无所不达、计算无处不在”的新一代泛在通信和服务一体化网络,多样化的业务应用存在对计算、存储与网络资源等多种维度资源的需求。与此同时,在卫星网络高动态、弱连接场景下,如何高效调度统筹天、地多元异构的算存资源,协同优化组网、传输、存储机制,建立天基计算、存储、网络联合的资源优化模型,提供高质量的天基承载网服务是一个亟须解决的重要问题。针对该问题,在研究天基算存融合技术的发展现状的基础上,研究和分析其对天基承载网架构的影响,并在此基础上提出一种算存融合的天基承载网架构,从组网优化、传输优化、存储优化、服务优化等4个方面系统分析算存融合的天基承载网架构相较于传统天基承载网架构的优势,总结相关关键技术,以期为后续卫星网络的研究、建设和标准化提供有价值的建议和参考。

线网规划级绿色城轨理论框架体系研究

为贯彻“交通强国”“双碳目标”要求,以《中国城市轨道交通绿色城轨发展行动方案》为指导,从城市空间、综合交通、轨道交通3个层面探讨线网规划阶段的绿色低碳分析与评价方法,系统性搭建了从宏观到微观层面的理论框架。分析过程采用建立模型、空间计量学、地理分析、客流预测等研究方法,通过“定量+定性”建立轨道交通绿色低碳效果理论架构。研究提出一种“城市-交通-轨道”三位一体绿色发展的框架,形成以定量分析为主的评价指标体系,能够有效落实并提升绿色出行占比的目标,在承接上位规划的同时,结合轨道交通自身特征,指导下阶段绿色城轨的实施、相关研究专题编制。研究结果表明,将轨道交通线网规划涉及的各要素与城市、综合交通结合,能全面、有效、量化反映绿色发展的要求,最终形成各指标计算方法,具备可实施性、可操作性、可对比性,不但能落实国土空间、综合交通规划的要求与目标,也能对后续建设规划、工可、初设等阶段的绿色发展提供指导,与轨道交通全过程规划设计流程较为匹配,分析结论与建议也能够较好地反馈并纳入国土空间规划、综合交通规划,确保规划一张蓝图。