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-log...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.展开更多
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...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.展开更多
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 specifical...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.展开更多
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...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.展开更多
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 ...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%’.展开更多
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...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。展开更多
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...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。展开更多
文摘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.
基金funding from the Macrosystems Biology Program Grant EF#1241860 from United States National Science Foundation(NSF)。
文摘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.
文摘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.
基金Postgraduate Innovation Program of Jiangsu Province in 2020:research on the construction of a community of shared future for mankind from the perspective of Marx’s thoery of world history(KYCX20_3060)Key projects in 2017 of The National Social Science Fund of China“The spread of Chinese traditional elementary school among countries in‘the Belt and Road Initiative’”(No.17AZS012)Teaching reform and research topics of Jiangsu University“Research on the construction of the mixed teaching mode of‘Internet+ideological and political courses’”(No.2019JGZD014)。
文摘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.
文摘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%’.
文摘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。
文摘针对车联网(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。
