基于路网分布特征的非均匀地物抽稀

公路电子地图的编绘,需保留观览路网起参照作用的地物等元素,以反映公路布局走向、展示路网的整体联通性。本文基于路网分布特征研究提出了沿公路一定容限范围内,综合考虑点状地物距路网关键节点的距离、聚集度和标注长度等条件和因素的路网非均匀抽稀方案,而对容限范围外的点状地物,仅考虑聚集度和标注长度因素进行逐步抽稀,从而达到保留关键地物的抽稀效果,并以制作甘肃中部交通旱码头定西市公路电子地图为应用场景,验证了算法以市域为单元的公路网中自然村组的抽稀效果,结果表明本算法对点状地物抽稀效果俱佳。

京津雄三角区道路交通路网分布及智能化建设研究

雄安新区作为北京非首都功能的集中疏解地,与京津之间的交通路网信息化、智能化建设与交通畅通运行尤为重要。本文对京-津-雄之间三角区主要道路分布状况进行了调研与阐述,并对三角区道路交通智能化建设的意义和可行性进行了深入分析,为京-津-雄三角区道路交通智能化建设的规划与实施提供决策支持。

城市路网的分布式鲁棒预测控制

针对具有模型不确定的城市路网系统,研究了使闭环系统渐近稳定的分布式鲁棒预测状态反馈控制器设计问题.首先,将由"存储与向前"路段线性模型扩展得到的城市路网拓扑模型分解为分布式模型.同时考虑实际情况中路况变化、测量误差等因素引起的饱和流量、车辆数的不确定性对城市路网系统的影响,得到了具有不确定参数的城市路网分布式模型.然后,提出了一种合作式的分布式鲁棒预测控制算法,并利用线性矩阵不等式(linear matrix inequality,LMI)处理方法在线求解多个凸优化问题,给出了子系统控制器求解方法.最后通过Matlab仿真验证了分布式鲁棒预测控制是一种能有效缓解城市交通拥堵和优化信号灯的控制策略.

基于路网环分布的隐私保护近邻查询方法

位置服务在方便人们生活的同时,也带来了隐私安全问题,路网环境对移动对象运动模式的限制使得位置隐私保护问题更为复杂.基于空间混淆的现有路网隐私保护近邻查询方法存在对重放攻击的抵御能力较弱,位置泛化与查询处理效率低,以及处理效率与位置保护安全强度不可调节,难以支持个性化隐私保护查询的不足.针对上述问题,引入路网环分布概念并设计生成给定路网环分布的算法,在匿名服务器端离线生成路网环分布;通过设置基于路网环分布的子网扩张结束条件,提升所提隐匿环机制对重放攻击的抵御能力;借助子网扩张结束条件调控隐匿环子网规模实现对隐匿环生成效率、近邻查询效率与位置隐私保护强度的调节.进一步,结合隐匿环的组成结构,提出可以有效降低搜索起始边规模的剪枝方法,提升基于隐匿环的近邻POI查询效率.理论分析和实验结果表明,所提方法能有效抵御重放攻击,提升位置泛化处理与近邻查询处理的时效,在此基础上能够兼顾对查询发起者位置信息保护效果、位置泛化处理与近邻查询时效的调节.

前苏联铁路网的形成、发展和布局

前苏联是世界上铁路运输利用率最高的国家。本文从其铁路发展的背景条件出发，分析了铁路成为前苏联最主要运输方式的原因，并进一步探讨了前苏联铁路网的建设、发展和分布特点，对我国正在进行的大规模铁路建设有一定借鉴意义。

基于多源交通数据的路网OD分布动态估计

首先,利用小波(DWT)对交通流进行低频率、高频率的分割;其次,利用BPNN与GRU网络,对高低频序列进行加权累加;最后,将预测结果输入KNN道路状态判别模型中,从而达到交通状况的预报目的。将视频车辆牌照识别、GPS等道路信息与其他路段的交通流数据相结合,利用多源异质数据,建立通用交通网络中的交通量动态估算模型。

基于宏观基本图的突发事件影响下交通流分布不均衡性研究

宏观基本图的提出为城市宏观交通状态分析提供新的思路和方法,但其假设路网交通分布是均衡的。突发事件导致路段通行能力下降会影响城市路网交通分布。为研究突发事件影响下路网交通流分布不均衡性与宏观基本图之间关系,保障路网运行效率,运用路段密度方差指标,提出定量分析突发事件影响下路网交通分布不均衡性与宏观基本图之间关系的方法。使用实际路网和交通需求矩阵进行案例分析,结果表明,在不同突发事件场景中,若路网平均密度相同,则交通分布不均衡性与路网流量之间存在不稳定的负相关关系,即路网交通分布越不均匀,路网流量越小。研究结果为突发事件条件下交通诱导、路网交通管理与控制决策提供一定科学依据。

普通干线公路布局规划要点分析

为解决现阶段我国普通干线公路布局和规划期间存在的主要问题,例如等级结构需要提升、路网结构分布不合理、与重要节点之间的衔接需要加强等,文章对普通干线公路的重要作用进行梳理,结合普通干线公路布局规划现状,提出普通干线公路的布局规划要点,以期保证普通干线公路可靠运行,促进我国公路行业的可持续发展。

特殊地形城市道路交通面临问题研究

具有特殊地形、地貌特征的城市道路交通由于受到了山脉、河流、特殊的固定自然物的限制,城市的布局往往形成分散、组团式和带状的特点,呈现出了各种交通模型的非线性、非周期性等特征,该文详细研究了该类城市道路交通面临的问题,重点分析了特殊地形、路网分布、传统的交通指挥系统对特殊地形城市道路交通的影响。以河谷型城市兰州市的地貌特征为例,分析了这些问题及因素,并提出了解决这些问题的方法。

依托铁路编组站建设现代物流中心的构想

根据铁路编组站自身的特点,论述了建设编组站物流中心的意义及其可行性,提出了建设铁路编组站物流中心发展现代物流的对策与建议。

对杭州市公路交通流量特征的研究与分析

通过对近几年杭州市公路交通流量特征进行的分析,指出本地区交通结构的状况和发展趋势,为公路建设规划、建设决策和公路养护管理提供了参考意见。

A Novel Distributed LDoS Attack Scheme against Internet Routing

LDoS （Low-rate Denial of Service） attack, exploiting the flaws in the congestion avoidance mechanism of TCP protocol,is periodic, stealthy, and with high efficiency. Since BGP uses TCP as a transport protocol, it is subject to LDoS attacks as well. LDoS attacks can cause table reset, route flapping of BGP protocol. A deliberately constructed distributed low-rate DOS attacks can even generate surge of updates throughout the Internet. In this paper, we investigate the promotion of attack efficiency of this novel attack, and then propose an attack model to simulate the LDoS attack. Experiments prove that this attack model can exponentially lower the attack costs and improve the attack effect.

Spatial Analysis of Commuting Mode Choice in Guangzhou, China

Metropolitan cities in China are commonly confronted with unresolved traffic congestion issues, primarily due to rapidly increasing traffic demand. Group disparity between commuting mode choice and its spatial distribution on road networks has enabled us to examine the factors that give rise to the discrepancies and the fundamental spatial causes of traffic congestion. In recent years, mi- cro-perspective, individual, and behavior-based spatial analysis have mushroomed and been facilitated with effective tools such as tem- poral geographic information systems （T-GIS）. It is difficult to study the interrelations between transport and space on the basis of commuting mode choice since the mode choice data are invisible in a specific space such as a particular road network. Therefore, in the field of transport, the classical origin destination （OD） four-stage model （FSM） is usually employed to calculate data when studying commuting mode choice. Based on the relative principles of T-GIS and the platform of ArcGIS, this paper considers Guangzhou as a case study and develops a spatio-temporal tool to examine the daily activities of residents. Meanwhile, the traffic volume distribution in rush hours, which was analyzed according to commuting modes and how they were reflected in the road network, was scrutinized with data extracted from travel diaries. Moreover, efforts were made to explain the relationship between traffic demand and urban spatial structure. Based on the investigation, this research indicates that traffic volumes in divergent groups and on the road networks is driven by： l） the socio-economie characteristics of travelers; 2） a jobs-housing imbalance under suburbanization; 3） differences in the spatial supply of transport modes; 4） the remains of the Danwei （work unit） system and market development in China; and 5） the transition of urban spatial structure and other factors.

Location of anemometer along Lanzhou-Xinjiang railway

Using structured mesh to discretize the calculation region, the wind velocity and pressure distribution in front of the wind barrier under different embankment heights are investigated based on the Detached Eddy Simulation(DES) with standard SpalartAllmaras(SA) model. The Reynolds number is 4.0×105 in this calculation. The region is three-dimensional. Since the wind barrier and trains are almost invariable cross-sections, only 25 m along the track is modeled. The height of embankment ranges from 1 m to 5 m and the wind barrier is 3 m high. The results show that the wind speed changes obviously before the wind barrier on the horizontal plane, which is 4.5 m high above the track. The speed of wind reduces gradually while approaching the wind barrier. It reaches the minimum value at a distance about 5 m before the wind barrier, and increases dramatically afterwards. The speed of wind at this location is linear with the speed of far field. The train aerodynamic coefficients decrease sharply with the increment of the embankment height. And they take up the monotonicity. Meanwhile, when the height increases from 3 m to 5 m, they just change slightly. It is concluded that the optimum anemometer location is nearly 5 m in front of the wind barrier.

Distribution network planning based on shortest path

In order to form an algorithm for distribution network routing,an automatic routing method of distribution network planning was proposed based on the shortest path.The problem of automatic routing was divided into two steps in the method:the first step was that the shortest paths along streets between substation and load points were found by the basic ant colony algorithm to form a preliminary radial distribution network,and the second step was that the result of the shortest path was used to initialize pheromone concentration and pheromone updating rules to generate globally optimal distribution network.Cases studies show that the proposed method is effective and can meet the planning requirements.It is verified that the proposed method has better solution and utility than planning method based on the ant colony algorithm.

Inter-domain routing and wavelength assignment based on source routing in ASON

The inter-domain and intra-domain routings are treated jointly with dynamically distributed algorithms in automatically switched optical networks （ASON） based on source routing. The proposed algorithms are discussed through numerical calculations. The routing loops can be avoided efficiently and the inter-domain signaling complexity is reduced significantly. The performance of the blocking probability is also improved.

Norton equivalent circuit for current control loop of grid-connected system

Modeling method for the current control loop of a grid-connected PWM inverter with the LCL output filter was discussed.Firstly,the current control loop with the LCL inverter-side current as feedback was established.Then,parameters of PI controller were calculated on the basis of an equivalent controlled object.Finally,Norton equivalent circuit for the current control loop of grid-connected system was derived by integrating one control equation,which connected the PWM inverter output voltage and the LCL inverter-side current,with two circuit equations,separately using the LCL inverter-side current and the injected current as loop currents.With the induced Norton equivalent circuit,system-level resonant and unstable issues on real grid-connected system applied in weak distributed power systems can be easily analyzed.The validity of substituting Norton equivalent circuit for grid-connected system is verified by simulation and experiment.

Performance Analysis of WLAN Medium Access Control Protocols in Simulcast Radio-Over-Fiber-Based Distributed Antenna Systems

The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where multiple remote antenna units(RAUs) are connected to one access point(AP) with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function(DCF) in basic access mode,DCF in request/clear to send(RTS/CTS) exchange mode,and point coordination function(PCF).In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.

A new measure for evaluating spatially related properties of traffic information credibility

With the wide applications of sensor network technology in traffic information acquisition systems,a new measure will be quite necessary to evaluate spatially related properties of traffic information credibility.The heterogeneity of spatial distribution of information credibility from sensor networks is analyzed and a new measure,information credibility function(ICF),is proposed to describe this heterogeneity.Three possible functional forms of sensor ICF and their corresponding expressions are presented.Then,two feasible operations of spatial superposition of sensor ICFs are discussed.Finally,a numerical example is introduced to show the calibration method of sensor ICF and obtain the spatially related properties of expressway in Beijing.The results show that the sensor ICF of expressway in Beijing possesses a negative exponent property.The traffic information is more abundant at or near the locations of sensor,while with the distance away from the sensor increasing,the traffic information credibility will be declined by an exponential trend.The new measure provides theoretical bases for the optimal locations of traffic sensor networks and the mechanism research of spatial distribution of traffic information credibility.

HHR:Hierarchical Hybrid Routing Scheme for Information-Centric Network

Publish/subscribe(pub/sub) paradigm is the main communication model for Information-Centric Network(ICN) proposals.A key issue for pub/sub system is how to route the content objects to the correct subscribers,and ICN is no exception.ICN network would be divided into core domain and many edge domains as today's internet does.HHR(Hierarchy Hybrid Routing scheme) is presented for ICN:A Chord-like routing scheme is used in core domain,while edge domains routing structure can be classified into three categories,Local Routing(LR),Delivery of Local Publication to Core domain(DLPC),and Remote Publication Routing into edge domain(RPR).LR can be decided by each edge domain,which determined by many factors,such as locality characteristic for pub/sub information and local policies.A hierarchical routing algorithm is proposed to solve DLPC and RPR simultaneously.Simulation results demonstrate that HHR can be fast deployed,and can be applied in large scale network or dynamic subscription environment.