Mapping regional forest management units:a road-based framework in Southeastern Coastal Plain and Piedmont

Management practices are one of the most important factors affecting forest structure and function.Landowners in southern United States manage forests using appropriately sized areas,to meet management objectives that include economic return,sustainability,and esthetic enjoyment.Road networks spatially designate the socioenvironmental elements for the forests,which represented and aggregated as forest management units.Road networks are widely used for managing forests by setting logging roads and firebreaks.We propose that common types of forest management are practiced in road-delineated units that can be determined by remote sensing satellite imagery coupled with crowd-sourced road network datasets.Satellite sensors do not always capture roadcaused canopy openings,so it is difficult to delineate ecologically relevant units based only on satellite data.By integrating citizen-based road networks with the National Land Cover Database,we mapped road-delineated management units across the regional landscape and analyzed the size frequency distribution of management units.We found the road-delineated units smaller than 0.5 ha comprised 64%of the number of units,but only0.98%of the total forest area.We also applied a statistical similarity test(Warren's Index)to access the equivalency of road-delineated units with forest disturbances by simulating a serious of neutral landscapes.The outputs showed that the whole southeastern U.S.has the probability of road-delineated unit of 0.44 and production forests overlapped significantly with disturbance areas with an average probability of 0.50.

Regeneration Potential of Woody Species at the Side of Secondary Roads Post-Logging of Loundoungou-Toukoulaka Forest Management Unit, Republic of the Congo

Natural regeneration is the basis of a dynamic and demographic balance of plant populations. The objective of this study was to assess the natural regeneration potential of woody species along secondary roads post-logging abandoned since 2008 and 2018. In the two Annual Allowable Cuts (AAC 2008 and AAC 2018), 24 regenerating sub-plots (i.e. 12 sub-plots for AAC 2008 and 12 sub-plots for AAC 2018) with a unit area of 5 m × 5 m were delimited with a total area of 0.06 ha (i.e. 0.03 ha for each AAC). The abundance and diversity of woody species were respectively inventoried and estimated. Two estimators of the specific richness were used to estimate the floristic diversity of each Annual Allowable Cuts (AAC). The results reveal globally 88 woody species in the AAC 2008 and 241 woody species in the AAC 2018, with respective average densities of 2933 stem/ha and 8033 stem/ha. There was a very highly significant difference between the mean densities of the two AAC (Kruskal-Wallis test;H = 2.36, p-value < 0.000). The results also highlight a great diversity and a relatively high abundance of woody species in the 2018 AAC compared to the 2008 AAC. Also, the spatial structuring of the sub-plots on the basis of Principal Component Analysis (PCA) demonstrates that the floristic composition of the two AAC is globally different. The study suggests silvicultural interventions and the long-term assessment of regenerating woody species along abandoned secondary roads in order to guarantee the sustainable management of their population.

Research on the Coverage of the Belt and Road Initiative and a Community with Shared Future for Mankind by Mainstream Media in the United States--Taking the three major mainstream media in the United States as an example

Since China put forward the Belt and Road Initiative and a community with shared future for mankind,mainstream media in the United States such as The Washington Post,The New York Times and The Wall Street Journal have given continuous reports.As the world’s superpower,the United States has a developed media system and a wide range of influence.The study extracted 173 valid texts from May 2015 to March 2020,among which only 5 reports were on a community with shared future for mankind.American media mainly reported from five aspects including economy,politics,cultural,security and environment,although there is no lack of certain sounds,there was more negative reports.It can provide a reference basis for our accurate response and creating a positive international public opinion environment that grasping the reporting trends on the Belt and Road Initiative and a community with shared future for mankind accurately.

基于RSU辅助的车载机会网络通信能力增强方案

针对传统车载机会网络通信能力的有限性及随机化的问题,提出一种通过部署路边单元(RSU)进行辅助通信来增强车载机会网络通信能力的方案。该方案利用RSU稳定的覆盖、存储和传输优势,有效克服传统车载机会网络通信时间间隔长、传输能力有限等缺点。以北京和上海各自一个月的出租车全球定位系统(GPS)数据为基础,对车辆与RSU的相遇特性进行了分析,发现该方案通过合理部署RSU对车辆信息进行缓存,可以极大地提高车辆间的通信概率。理论分析和仿真实验表明,利用RSU可以完成车与车之间大数据的传输,能极大提升车载机会网络的通信能力。

基于流量的车载网络路边单元RSU部署方案

针对目前车载移动容迟网络中的路边单元(RSU)部署问题,提出一种基于车流量的车载网络路边单元RSU部署方案,该方案通过对车载网中路口的车流量的统计行为进行分析,在城市重要交通枢纽和交叉路口部署路边单元RSU来进行辅助通信,从而有效提高车载移动网络的通信效率。根据北京和上海两地实际的车载移动数据,进一步对所提方案进行分析和评估。研究结果表明:在辅助车辆与车载之间的通信时,密集部署RSU可以创造连续的通信机会,从而有效提高网络性能。

路网环境下基于Unit模型的位置隐私保护方法

基于位置的服务(LBS)为人们的日常生活带来很大便利,然而由此引起的用户隐私泄露问题也同样受到人们的关注.用户向LBS提交查询时必须提供确切位置信息,攻击者可根据用户的位置信息推断出该用户的私人信息进而做出一些违背道德法律的事情.为解决这个问题,现有的大部分空间匿名技术将用户的位置进行泛化,然后再发送到LBS服务器.本文基于路网环境提出一种新的路网模型,并以该路网模型提出一种新的路网匿名方法.首先,针对路网环境提出Unit路网模型,将道路网络划分为小的匿名单元,然后对匿名单元采用希尔伯特编码进行排序,为后面产生匿名区域和匿名区域扩展打下基础.其次,提出基于Unit路网模型的位置隐私保护算法.为保证服务质量,匿名区域的总长度不能超过一定的长度限制.因此在扩展匿名区域的时候只考虑有活跃用户的匿名单元.第三,提出在匿名区域内添加假用户的方法来提高匿名成功率.最后,基于理论分析和实验验证,证明了上述算法的有效性.

车载自组织网络中RSU协调的多信道MAC协议

提出了一种车载自组织网络中路侧单元(RSU, road side unit)协调的多信道MAC(RMM, RSU-coordinated multichannel MAC)协议,以支持非安全(如运输效率、娱乐应用等)消息的高效传输。在路侧单元的协调下,节点有更多机会在控制信道上进行预约,以实现服务信道上无竞争的传输。同时,RMM协议支持在整个同步间隔内传输服务分组,从而提高了服务信道的饱和吞吐量和利用率,并减少了时延。与现有的其他协议相比,仿真结果证实了所提协议的优越性。

车联网中RSU动态接入选择问题的研究

车联网中车与车以及车与基础设施间的实时通信问题越来越受到关注,而车辆的高速移动性和无线通信的不可靠性大大降低了数据传输效率。为了解决这个问题,针对路边单元(Road Side Unit, RSU)接入选择问题进行了研究,并提出了一种新的RSU接入选择算法,来合理调配车辆与RSU的连接。车辆选择RSU进行接入的常规方法是基于车辆的接收信号强度,但它未充分考虑车辆的高速移动性,这会导致接入RSU的车辆的数目大幅度变化。所以采用实时监测和预测相结合的方法合理调配RSU上连接的车辆,让每一RSU上连接的车辆数目波动幅度达到最小,并且保证RSU得到充分利用。仿真结果表明,此算法能够有效降低数据包碰撞、增强无碰撞传输概率、提高成功传包率。

VANET中基于模糊逻辑的RSU自适应数据更新方案

在基于路边基站(RSU)的车载自组网(VANET)路由协议中,RSU以固定周期更新数据导致交通控制中心(TCC)的部分数据容易失效,造成数据包丢失,严重影响路由协议性能。为此,提出一种基于模糊逻辑的RSU自适应数据更新周期计算方案。RSU根据自身服务范围内车辆节点的运动状况,利用注册表中数据量和数据更新速率参数,设计模糊逻辑控制系统,自适应计算数据更新周期,从而提高TCC中数据的有效性。实验结果表明,与BUS-VANET路由协议相比,基于该方案的VANET路由协议能够提升通信链路的稳定性和可靠性,并降低数据更新包数量和传输时延。

车联网中基于休眠机制部署RSUs方案

针对车联网(vehicular ad hoc networks,VANETs)中路边设施单元(road side units,RSUs)部署问题,提出部署RSU的新方案,记为P_RSU方案。P_RSU方案以保证必要的数据包传输率(packet delivery ratio,PDR)为前提,以降低所有RSUs消耗总能量为目的。P_RSU方案引用休眠机制,并采用太阳能作为RSUs能量供给的补充。首先将P_RSU方案进行形式化表述,形成约束条件、多目标函数。然后,通过RPR(rainbow product ranking)算法求解目标函数,从而获取部署RSUs的最优位置。仿真结果表明,提出的P_RSU方案能有效地降低能量消耗、优化RSUs数量。

RSU辅助的V-NDN数据转发机制

V-NDN(vehicular named data networking)是一种使用命名数据网络架构的车辆自组织网络(vehicular Ad-hoc network,VANET),主要用来连接移动车辆之间的通信。提高网络中兴趣包的命中率是研究领域急待解决的难题。文章研究了城市道路环境下V-NDN的数据转发策略,考虑到城市道路环境下路侧单元(road side unit,RSU)被均匀广泛部署的特点,提出了一种基于RSU辅助的V-NDN数据转发策略(RSU aided V-NDN)。通过实验仿真与传统的V-NDN和基于蜂窝网络辅助的V-NDN进行对比,结果表明该文提出的数据转发策略有效地提高了网络的服务质量(quality of service,QoS)。

基于GPS轨迹数据的RSU部署方案

车载自组网络(VANET)高度动态变化的拓扑结构,使其存在频繁的网络分割。为此,提出一种基于出租车GPS轨迹数据在真实城市环境下的路边单元(RSU)综合部署方案。采用区域连通性的RSU位置部署策略,提高交通分布不均情形下城市VANET的连通性能,利用基于马尔科夫聚类的热点检测算法确定城市路网中的热点,对其部署RSU,同时兼顾区域连通性和热点区域,设计RSU综合部署方案。以真实出租车GPS轨迹数据为基础进行仿真实验,结果表明该方案可有效提高城市VANET的连通性能。

Short-Term Traffic Flow Prediction Based on Road Network Topology

Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous researches mostly focus on shallow traffic prediction models, which performances were unsatisfying since short-term traffic flow exhibits the characteristics of high nonlinearity, complexity and chaos. Taking the spatial and temporal correlations into consideration, a new traffic flow prediction method is proposed with the basis on the road network topology and gated recurrent unit (GRU). This method can help researchers without professional traffic knowledge extracting generic traffic flow features effectively and efficiently. Experiments are conducted by using real traffic flow data collected from the Caltrans Performance Measurement System (PEMS) database in San Diego and Oakland from June 15, 2017 to September 27, 2017. The results demonstrate that our method outperforms other traditional approaches in terms of mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE) and root mean square error (RMSE).

Ruppert's Delaunay Triangulation Refinement Scheme for Optimal RSUs Placement in Vehicle to Infrastructure Communication Network

Road Side Units(RSUs)are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation.RSUs are generally deployed at the roadside and more specifically at the intersections in order to collect traffic information from the vehicles and disseminate alarms and messages in emergency situations to the neighborhood vehicles cooperating with the network.However,the development of a predominant RSUs placement algorithm for ensuring competent communication in VANETs is a challenging issue due to the hindrance of obstacles like water bodies,trees and buildings.In this paper,Ruppert’s Delaunay Triangulation Refinement Scheme(RDTRS)for optimal RSUs placement is proposed for accurately estimating the optimal number of RSUs that has the possibility of enhancing the area of coverage during data communication.This RDTRS is proposed by considering the maximum number of factors such as global coverage,intersection popularity,vehicle density and obstacles present in the map for optimal RSUs placement,which is considered as the core improvement over the existing RSUs optimal placement strategies.It is contributed for deploying requisite RSUs with essential transmission range for maximal coverage in the convex map such that each position of the map could be effectively covered by at least one RSU in the presence of obstacles.The simulation experiments of the proposed RDTRS are conducted with complex road traffic environments.The results of this proposed RDTRS confirmed its predominance in reducing the end-to-end delay by 21.32%,packet loss by 9.38%with improved packet delivery rate of 10.68%,compared to the benchmarked schemes.

面向车路协同的RSU运维管理平台实践

当前V2X正处于试点探索运营阶段,通过产业示范推动V2X发展。随着三部委政策的出台,V2X芯片、模组、终端、CA平台等均已可实现跨厂商互通,产品技术正在走向规模验证阶段。RSU位于路侧,是车路协同的核心单元,其管理运维要求自动化、批量化、远程化。通过行业调研,研究当前车路协同路侧设备RSU对运维管理的需求,分析RSU运维管理平台需要支持的功能需求,梳理不同RSU厂商需支持的基本数据能力和通信协议,通过研发实践实现可落地平台产品,支撑异厂家RSU与运维管理平台的互联互通。

A New System for Road Traffic Optimisation Using the Virtual Traffic Light Technology

Large cities suffer from traffic congestion,particularly at intersections,due to a large number of vehicles,which leads to the loss of time by increasing carbon emissions,including fuel consumption.Therefore,the need for optimising the flow of vehicles at different intersections and reducing the waiting time is a critical challenge.Conventional traffic lights have been used to control traffic flow at different intersections and have been improved to become more efficient by using different algorithms,sensors and cameras.However,they also face some challenges,such as high-cost installation,operation,and maintenance issues.This paper develops a new system based on the Virtual Traffic Light(VTL)technology to improve traffic flow at different intersections and reduce the encountered loss of time and vehicles’travel time.Additionally,it reduces the costs of installation,maintenance and operation over various conventional traffic light systems.Consequently,the system proposes algorithms for traffic scheduling and lane identification by using vehicle ID,priority and time of arrival.To evaluate the system,four scenarios were presented where each scenario uses a different number of vehicles consisting of three types(emergency vehicles,public buses and private vehicles),each given a different priority.The proposed system is evaluated by integrating two simulators,namely,(OMNeT++)and(SUMO),and two frameworks,namely,(VEINS)and(INET)to prepare an appropriate working environment.the results prove that an improvement in the average travel time for several vehicles reaches 44.43%–49.76%compared with conventional traffic lights.Further,it is proven from the obtained results that the average waiting time for emergency vehicles is enhanced by 96.63%–97.63%,while the average waiting time for public buses is improved by 94.81%–97.23%.On the other hand,the waiting time for private vehicles‘improved by 87.14%to 89.71%’.

车路协同RSU软件系统的设计与实现

提出了一种车路协同路侧单元(RSU)软件系统的设计方案,论述了RSU在车路协同系统中的位置及功能,提出功能架构设计、系统架构设计、安全服务设计等若干需要解决的核心问题。详细阐述了解决这些问题用到的关键技术和设计方案,对车路协同系统进行测试,并在实际工程项目进行应用和功能验证,证明了该系统设计的可行性和合理性。

基于多传感器融合技术的智慧路侧单元设计

基于多传感器融合技术,设计了一种智慧路侧单元。通过二维视觉感知和三维点云感知设计获取优质的交通信息;并在此基础上,完成点云和视觉的决策级融合。该智慧路侧单元可满足智慧交通领域实时路况检测需求,为车路协同的实现提供了切实可行的参考方案。

车载社交网中基于密文属性加密的车队车辆数据共享方案

针对车载社交网(VSN)中车队车辆数据共享过程中存在的隐私泄露问题,提出一种基于密文属性的加密方案。利用基于属性的加密技术,保证仅授权的车辆可访问数据,防止车队车辆数据共享过程中发生隐私泄露;针对车队车辆数据共享时生成访问策略时间开销大、数据共享效率低的问题,通过构造访问树实现对访问策略的设计,利用路侧单元将访问树转化为访问矩阵,实现访问策略的快速生成。仿真分析结果表明,该方案能够实现对VSN中车队车辆的数据安全共享,所构建的访问策略生成方案能够有效降低车辆的计算开销。

美国国家道路安全战略简析及启示

随着我国人民生活水平的不断提高,居民出行需求不断增加,道路交通事故数量和伤亡人数也不断上升,道路交通安全治理的重要性日益凸显。道路交通安全治理已成为世界各国社会管理的重中之重,美国交通部于2022年发布的《国家道路安全战略》对我国有极其重要的借鉴意义。首先梳理了我国道路交通安全治理中存在的问题及成因,然后简述了美国国家道路安全战略中构建交通安全系统的原则和总体方略,分析了美国国家道路安全战略及其相关文件的特点与核心思想,最后结合我国国情提出了四个方面的具体措施。研究结果对提升我国道路交通安全管理水平具有借鉴意义。