Red turpentine beetle （RTB）, Dendroctongs valens LeConte, is a destructive forest invasive species in China, it mainly attacks Pings tabuliformis and P. bungeana. So far it has spread rapidly to the provinces of Sha...Red turpentine beetle （RTB）, Dendroctongs valens LeConte, is a destructive forest invasive species in China, it mainly attacks Pings tabuliformis and P. bungeana. So far it has spread rapidly to the provinces of Shanxi, Hebei, Henan, Shanxi and Beijing since its first outbreak in Shanxi Province in 1998, and has caused extensive tree mortality. Space-time dynamics of D. valens population and spatial sampling technique based on its spatial distribution pattern were ana- lyzed using geostatistical methods in the pure P. tabuliforis forests and mixedwood stands which were at different damage levels. According to the spatial distribu- tion of D. valeas population, the specific spatial sampling technique was also studied, and then was compared with traditional sampling technique. The spatial sam- piing technique combined with sampling theory and the biological characteristics of D. valens population, which not only could calcnlate the error of the sampling, but also could discuss the optimal sampling number and the optimum size of plot according to different damage levels and different stand types. This helps to explain population expansion and colonization mechanism of D. valens, and to provide a good reference for adopting snitable control measures.展开更多
In this paper, Beam Pattern Scanning (BPS), a transmit diversity technique, is compared with two well known transmit diversity techniques, space-time block coding (STBC) and space-time trellis coding (STTC). In BPS (a...In this paper, Beam Pattern Scanning (BPS), a transmit diversity technique, is compared with two well known transmit diversity techniques, space-time block coding (STBC) and space-time trellis coding (STTC). In BPS (also called beam pattern oscillation), controlled time varying weight vectors are applied to the antenna array elements mounted at the base station (BS). This creates a small movement in the antenna array pattern directed toward the desired user. In rich scattering environments, this small beam pattern movement creates an artificial fast fading channel. The receiver is designed to exploit time diversity benefits of the fast fading channel. Via the application of simple combining techniques, BPS improves the probability-of-error performance and network capacity with minimal cost and complexity. In this work, to highlight the potential of the BPS, we compare BPS and Space-Time Coding (i.e., STBC and STTC) schemes. The comparisons are in terms of their complexity, system physical dimension, network capacity, probability-of-error performance, and spectrum efficiency. It is shown that BPS leads to higher network capacity and performance with a smaller antenna dimension and complexity with minimal loss in spectrum efficiency. This identifies BPS as a promising scheme for future wireless communications with smart antennas.展开更多
O·Henry is living in the time when novelists are in the great pursuit of narrative pattern research. Hence his works is inevitably influenced. Beside his humorous language, surprising ends and expressions, O·...O·Henry is living in the time when novelists are in the great pursuit of narrative pattern research. Hence his works is inevitably influenced. Beside his humorous language, surprising ends and expressions, O·Henry's novels in my opinion is also marvelous for his outstanding narrative patterns arrangement. In this article, a research will be conducted onto his narrative pattern in the aspects of narrative perspectives, narrative space and narrative time. By this research, more information and references is intended to obtain for the further study on this area.展开更多
多功能雷达(Multi Function Radar,MFR)通过波形捷变与波束自适应调度实现多任务协同,这给雷达工作模式识别带来了诸多挑战。现有识别方法依赖脉冲序列局部时域特征,难以有效解析不同工作模式的生成机理,面对脉冲丢失、脉内参数相近等...多功能雷达(Multi Function Radar,MFR)通过波形捷变与波束自适应调度实现多任务协同,这给雷达工作模式识别带来了诸多挑战。现有识别方法依赖脉冲序列局部时域特征,难以有效解析不同工作模式的生成机理,面对脉冲丢失、脉内参数相近等复杂情况,识别性能急剧下降。考虑到多功能雷达波束扫描过程对脉冲组序列幅值信息的影响,提出一种基于空时联合图卷积网络的多功能雷达工作模式识别方法。该网络模型首先通过引入动态规整模块量化相邻波位信号的辐射特性相似度,构造具有物理可解释性的空域邻接矩阵;然后将一维脉冲组序列映射为二维图结构,融合脉冲频率、信号幅度等节点特征,形成空时联合表征;最后,设计分层图卷积核,通过多层信息传递机制,提取深层空时特征,完成雷达工作模式识别。对比实验表明,在脉冲丢失等非理想情况下所提方法的平均识别率仍能达到93.38%,具有更好的泛化性和鲁棒性。展开更多
基金Supported by Research Project of Jiangsu Entry-Exit Inspection and Quarantine Bureau(2015KJ49)Project of Beijing Municipal Education Commission(JD100220888)+2 种基金Project of Beijing Excellent Talents Funding(D Class)Project of Beijing Municipal Education Commission(JD100220888)Beijing Excellent Talents Funding(D Class)Project "Study on Prevention and Control Technology of Dendroctonus valens"
文摘Red turpentine beetle （RTB）, Dendroctongs valens LeConte, is a destructive forest invasive species in China, it mainly attacks Pings tabuliformis and P. bungeana. So far it has spread rapidly to the provinces of Shanxi, Hebei, Henan, Shanxi and Beijing since its first outbreak in Shanxi Province in 1998, and has caused extensive tree mortality. Space-time dynamics of D. valens population and spatial sampling technique based on its spatial distribution pattern were ana- lyzed using geostatistical methods in the pure P. tabuliforis forests and mixedwood stands which were at different damage levels. According to the spatial distribu- tion of D. valeas population, the specific spatial sampling technique was also studied, and then was compared with traditional sampling technique. The spatial sam- piing technique combined with sampling theory and the biological characteristics of D. valens population, which not only could calcnlate the error of the sampling, but also could discuss the optimal sampling number and the optimum size of plot according to different damage levels and different stand types. This helps to explain population expansion and colonization mechanism of D. valens, and to provide a good reference for adopting snitable control measures.
文摘In this paper, Beam Pattern Scanning (BPS), a transmit diversity technique, is compared with two well known transmit diversity techniques, space-time block coding (STBC) and space-time trellis coding (STTC). In BPS (also called beam pattern oscillation), controlled time varying weight vectors are applied to the antenna array elements mounted at the base station (BS). This creates a small movement in the antenna array pattern directed toward the desired user. In rich scattering environments, this small beam pattern movement creates an artificial fast fading channel. The receiver is designed to exploit time diversity benefits of the fast fading channel. Via the application of simple combining techniques, BPS improves the probability-of-error performance and network capacity with minimal cost and complexity. In this work, to highlight the potential of the BPS, we compare BPS and Space-Time Coding (i.e., STBC and STTC) schemes. The comparisons are in terms of their complexity, system physical dimension, network capacity, probability-of-error performance, and spectrum efficiency. It is shown that BPS leads to higher network capacity and performance with a smaller antenna dimension and complexity with minimal loss in spectrum efficiency. This identifies BPS as a promising scheme for future wireless communications with smart antennas.
文摘O·Henry is living in the time when novelists are in the great pursuit of narrative pattern research. Hence his works is inevitably influenced. Beside his humorous language, surprising ends and expressions, O·Henry's novels in my opinion is also marvelous for his outstanding narrative patterns arrangement. In this article, a research will be conducted onto his narrative pattern in the aspects of narrative perspectives, narrative space and narrative time. By this research, more information and references is intended to obtain for the further study on this area.
文摘多功能雷达(Multi Function Radar,MFR)通过波形捷变与波束自适应调度实现多任务协同,这给雷达工作模式识别带来了诸多挑战。现有识别方法依赖脉冲序列局部时域特征,难以有效解析不同工作模式的生成机理,面对脉冲丢失、脉内参数相近等复杂情况,识别性能急剧下降。考虑到多功能雷达波束扫描过程对脉冲组序列幅值信息的影响,提出一种基于空时联合图卷积网络的多功能雷达工作模式识别方法。该网络模型首先通过引入动态规整模块量化相邻波位信号的辐射特性相似度,构造具有物理可解释性的空域邻接矩阵;然后将一维脉冲组序列映射为二维图结构,融合脉冲频率、信号幅度等节点特征,形成空时联合表征;最后,设计分层图卷积核,通过多层信息传递机制,提取深层空时特征,完成雷达工作模式识别。对比实验表明,在脉冲丢失等非理想情况下所提方法的平均识别率仍能达到93.38%,具有更好的泛化性和鲁棒性。
