Many efforts have been made to develop time division multiple access （TDMA） slots allocation in a multi-hop converge-cast wireless sensor network （WSN）, however, most of them either use complex algorithm or concer...Many efforts have been made to develop time division multiple access （TDMA） slots allocation in a multi-hop converge-cast wireless sensor network （WSN）, however, most of them either use complex algorithm or concern frames only without simultaneous transmission in a single slot. In this paper, we present a timeslot assignment scheme for cluster-tree-based TDMA WSN, co：＇ering three frequently used working modes in practical applications. The shortest frame formed can guarantee real-time conununication and is also facilitated for message and slot integration, since timeslots allocated to a single node are continuous. During allocation processes, the algorithms are distributed and light-weighted. The experiment resulted from a WSN prototype system shows that our scheme can achieve a good reliability.展开更多
针对无线传感网络在实际应用中网络能耗不均匀、传感器节点容易失效以及网络生命周期短的问题,提出一种基于聚类树的负载平衡算法(load balancing algorithm based on cluster tree, LBACT)。基于聚类树将网络中的节点划分为多层结构,...针对无线传感网络在实际应用中网络能耗不均匀、传感器节点容易失效以及网络生命周期短的问题,提出一种基于聚类树的负载平衡算法(load balancing algorithm based on cluster tree, LBACT)。基于聚类树将网络中的节点划分为多层结构,通过立即转发机制降低聚类树的高度;使用平衡算法对构造的聚类树进行多轮次负载平衡,在汇聚节点的控制下,通过每个节点多次运行负载平衡算法,使网络中的节点负载平衡。仿真结果表明,相比LEACH(low-energy adaptive clustering hierarchy)和CBSHA(component based self-healing approach),提出的算法能够有效均衡节点能耗,延长网络的稳定期、生命周期,提高网络的吞吐量。展开更多
红树林是重要的碳汇生态系统。激光雷达LiDAR (Light Detection And Ranging)是获取林木三维结构参数进行生物量估算的重要技术手段。针对仅利用机载LiDAR难以完整描述红树林三维结构的问题,本文以广东省湛江市英罗港和广西壮族自治区...红树林是重要的碳汇生态系统。激光雷达LiDAR (Light Detection And Ranging)是获取林木三维结构参数进行生物量估算的重要技术手段。针对仅利用机载LiDAR难以完整描述红树林三维结构的问题,本文以广东省湛江市英罗港和广西壮族自治区茅尾海红树林保护区为研究区,利用无人机载和手持式LiDAR获取的点云数据,提出了一种红树冠层下部约束聚类分割方法,对木榄、红海榄、桐花树等不同类型红树的单木分割以及树高、冠幅的进行提取,并与传统单木分割算法进行了对比和分析。结果表明:本文提出的结合空地LiDAR数据的单木分割算法,在不同类型红树单木分割中均取得了较高的单木检出率,与传统的冠层高度模型分割法相比较,单木检出率提升了13.4%—26.7%。其次,有效提高了红树树高的提取精度。3种红树树高参数提取值与实测值之间的R2提高了1.8%—42.2%,RMSE降低了3.4%—55.3%。此外,由于红树冠幅分割结果存在提取值偏小的规律,本研究将能够表征红树冠层交叠密集程度的点云密度变量作为修正因子,经修正后的RMSE降低了45.25%—53.33%。因此,本文提出的联合空地LiDAR的红树林单木生长参数提取方法,可以实现精确的红树单木点云分割并有效提升红树生长参数提取精度,为红树林生物量估算及碳汇能力评估提供了技术和数据支撑。展开更多
基金Supported by the National High Technology Research and Development Programme of China ( No. 2006AA040302 2007AA041201 +1 种基金 2007AA041301 )the National Creative Research Groups Science Foundation of China (No. 60721062)
文摘Many efforts have been made to develop time division multiple access （TDMA） slots allocation in a multi-hop converge-cast wireless sensor network （WSN）, however, most of them either use complex algorithm or concern frames only without simultaneous transmission in a single slot. In this paper, we present a timeslot assignment scheme for cluster-tree-based TDMA WSN, co：＇ering three frequently used working modes in practical applications. The shortest frame formed can guarantee real-time conununication and is also facilitated for message and slot integration, since timeslots allocated to a single node are continuous. During allocation processes, the algorithms are distributed and light-weighted. The experiment resulted from a WSN prototype system shows that our scheme can achieve a good reliability.
文摘针对无线传感网络在实际应用中网络能耗不均匀、传感器节点容易失效以及网络生命周期短的问题,提出一种基于聚类树的负载平衡算法(load balancing algorithm based on cluster tree, LBACT)。基于聚类树将网络中的节点划分为多层结构,通过立即转发机制降低聚类树的高度;使用平衡算法对构造的聚类树进行多轮次负载平衡,在汇聚节点的控制下,通过每个节点多次运行负载平衡算法,使网络中的节点负载平衡。仿真结果表明,相比LEACH(low-energy adaptive clustering hierarchy)和CBSHA(component based self-healing approach),提出的算法能够有效均衡节点能耗,延长网络的稳定期、生命周期,提高网络的吞吐量。
文摘红树林是重要的碳汇生态系统。激光雷达LiDAR (Light Detection And Ranging)是获取林木三维结构参数进行生物量估算的重要技术手段。针对仅利用机载LiDAR难以完整描述红树林三维结构的问题,本文以广东省湛江市英罗港和广西壮族自治区茅尾海红树林保护区为研究区,利用无人机载和手持式LiDAR获取的点云数据,提出了一种红树冠层下部约束聚类分割方法,对木榄、红海榄、桐花树等不同类型红树的单木分割以及树高、冠幅的进行提取,并与传统单木分割算法进行了对比和分析。结果表明:本文提出的结合空地LiDAR数据的单木分割算法,在不同类型红树单木分割中均取得了较高的单木检出率,与传统的冠层高度模型分割法相比较,单木检出率提升了13.4%—26.7%。其次,有效提高了红树树高的提取精度。3种红树树高参数提取值与实测值之间的R2提高了1.8%—42.2%,RMSE降低了3.4%—55.3%。此外,由于红树冠幅分割结果存在提取值偏小的规律,本研究将能够表征红树冠层交叠密集程度的点云密度变量作为修正因子,经修正后的RMSE降低了45.25%—53.33%。因此,本文提出的联合空地LiDAR的红树林单木生长参数提取方法,可以实现精确的红树单木点云分割并有效提升红树生长参数提取精度,为红树林生物量估算及碳汇能力评估提供了技术和数据支撑。
