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多集采样和非线性最小二乘估计的频谱感知 被引量:3
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作者 宁宏新 《电子测量与仪器学报》 CSCD 北大核心 2018年第11期58-64,共7页
针对认知无线电和网络中可用频带的感知,提出了一种基于多集采样和非线性最小二乘估计的宽带频谱感知方法.首先,基于多集采样器,把可用的频带划分为有限数量的频道,得到一种基于采样参数和噪声功率的检测阈值的理论表达式,并计算出采样... 针对认知无线电和网络中可用频带的感知,提出了一种基于多集采样和非线性最小二乘估计的宽带频谱感知方法.首先,基于多集采样器,把可用的频带划分为有限数量的频道,得到一种基于采样参数和噪声功率的检测阈值的理论表达式,并计算出采样数据的相关矩阵;然后,采用一个非线性最小二乘估计器来估计被占用的频道和空闲频道,同时,采用顺序前向选择算法来降低估计器实现的复杂性;仿真实验结果表明,相比于传统的基于能量检测和其他常用的频谱感知方法,新方案不仅在采样率方面有可观的节省,而且在相同的信噪比(SNR)下能获得更好的检测概率和虚警概率。 展开更多
关键词 认知无线电 频谱感知 多集采样 相关矩阵 最小二乘估计器 检测概率 虚警概率
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An ecological perspective on Joseph Rock’s(1884-1962)plant collection activities in China
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作者 Jifan Luo Ruozhi Huang +7 位作者 Hai Yan Renwu Wu Shuai Liao Zhoubing Xiang Yongxi Zou Liangchen Shi Ke Wang Zhiyi Bao 《Journal of Plant Ecology》 SCIE CSCD 2024年第4期100-113,共14页
In the early 20th century,numerous western botanists,often referred to as‘plant hunters’,embarked on ambitious expeditions to China,playing a crucial role in the study of botany and botanical diversity.Despite their... In the early 20th century,numerous western botanists,often referred to as‘plant hunters’,embarked on ambitious expeditions to China,playing a crucial role in the study of botany and botanical diversity.Despite their contributions,comprehensive assessments of their explorations are lacking.To bridge this gap,this article focuses on the work of Joseph Charles Francis Rock,a notable figure in that era.Our work revisits Rock’s botanical expeditions within the broader context of botanical diversity conservation.It outlines his historical experiences in collecting plants in China and enumerates the species composition and phenotypic traits of the plants he collected.Additionally,it also analyzes the spatial distribution of the species,the completeness of his collection and the α-and β-diversity of the plants he collected.Our findings reveal that Rock led four major botanical expeditions in China between 1922 and 1933,amassing a total of 28184 sheets and 16608 numbers across 204 families,1081 genera and 4231 species.His focus was predominantly on ornamental species,which exhibit a variety of flower colors and inflorescences.His collection work spanned 5 provinces,35 cities and 72 counties,with a notable concentration in the Hengduan Mountains,a current biodiversity hotspot.This study not only reconstructs Rock’s botanical legacy but also offers valuable historical data and fresh analytical insights for understanding contemporary plant diversity.It contributes to the ongoing discourse on the importance of preserving plant diversity as a cornerstone of environmental sustainability. 展开更多
关键词 Joseph Charles Francis Rock plant specimen collection history plant diversity plant collector
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