若尔盖高原作为全国三大草原牧区之一,牧草资源丰富,但受放牧的影响,该地区的生态环境相继出现了湿地和草地的退化、土地沙化等现象。为准确、快速估测若尔盖区域尺度放牧情况,合理安排人类活动,为保护生态环境提供数据与理论支持,本研...若尔盖高原作为全国三大草原牧区之一,牧草资源丰富,但受放牧的影响,该地区的生态环境相继出现了湿地和草地的退化、土地沙化等现象。为准确、快速估测若尔盖区域尺度放牧情况,合理安排人类活动,为保护生态环境提供数据与理论支持,本研究利用MODIS-NDVI数据,结合地面实测数据及气象数据,分别模拟了地上生物量及净初级生产力(aboveground net primary productivity,ANPP),并在此基础上分析了2010−2019年若尔盖高原放牧强度。结果表明:模拟放牧强度的模型效果较好,R2值为0.7813,达到极显著相关水平(P<0.05),且均方根误差(root mean square error,RMSE)较小,精度可达到70%以上,能将不同放牧程度的区域区分开;若尔盖高原2019年平均放牧强度为1.87 AU·hm^(−2),处于过度放牧状态,且整体放牧强度呈现出东南部偏高、西北部偏低的分布态势。在时间变化上,若尔盖高原2010−2019年放牧强度整体呈增加趋势,在2010−2014、2014−2019年分别出现先增加后减少的变化过程;地上净初级生产力和地上生物量的分布态势与放牧强度的大小具有一定的关联性。展开更多
Harmonic wavelets not only possess the traditional advantages of a wavelet function,they also have other merits such as clear expressions,more flexible time-frequency divisions,a simple transformation algorithm,a fine...Harmonic wavelets not only possess the traditional advantages of a wavelet function,they also have other merits such as clear expressions,more flexible time-frequency divisions,a simple transformation algorithm,a finer box-like frequency spectrum and others.Given the frequency distribution characteristics of the nondestructive testing signals from a rockbolt support system and based on the discrete harmonic wavelet transformation theory,we have effectively abstracted signals from frequency ranges concerned by removing useless high and low frequency signals from the testing signals of the rockbolt support system and obtained filtered signals with a reconstruction algorithm of harmonic wavelets.Finally,we applied the harmonic wavelet transformation in filtering analog signals and measured response signals of rockbolts.The results indicate that harmonic wavelets also have excellent filtering characteristics.展开更多
文摘若尔盖高原作为全国三大草原牧区之一,牧草资源丰富,但受放牧的影响,该地区的生态环境相继出现了湿地和草地的退化、土地沙化等现象。为准确、快速估测若尔盖区域尺度放牧情况,合理安排人类活动,为保护生态环境提供数据与理论支持,本研究利用MODIS-NDVI数据,结合地面实测数据及气象数据,分别模拟了地上生物量及净初级生产力(aboveground net primary productivity,ANPP),并在此基础上分析了2010−2019年若尔盖高原放牧强度。结果表明:模拟放牧强度的模型效果较好,R2值为0.7813,达到极显著相关水平(P<0.05),且均方根误差(root mean square error,RMSE)较小,精度可达到70%以上,能将不同放牧程度的区域区分开;若尔盖高原2019年平均放牧强度为1.87 AU·hm^(−2),处于过度放牧状态,且整体放牧强度呈现出东南部偏高、西北部偏低的分布态势。在时间变化上,若尔盖高原2010−2019年放牧强度整体呈增加趋势,在2010−2014、2014−2019年分别出现先增加后减少的变化过程;地上净初级生产力和地上生物量的分布态势与放牧强度的大小具有一定的关联性。
基金Financial support for this work provided by the National Basic Research Program of China (No.2007CB209400)the 111 Project of China (No.B07028)+2 种基金the Key Program of National Natural Science Foundation of China(No.50834004)the National Natural Science Foundation of China (No.50874104)the Natural Science Foundation of Jiangsu Province(No.BK2006040)
文摘Harmonic wavelets not only possess the traditional advantages of a wavelet function,they also have other merits such as clear expressions,more flexible time-frequency divisions,a simple transformation algorithm,a finer box-like frequency spectrum and others.Given the frequency distribution characteristics of the nondestructive testing signals from a rockbolt support system and based on the discrete harmonic wavelet transformation theory,we have effectively abstracted signals from frequency ranges concerned by removing useless high and low frequency signals from the testing signals of the rockbolt support system and obtained filtered signals with a reconstruction algorithm of harmonic wavelets.Finally,we applied the harmonic wavelet transformation in filtering analog signals and measured response signals of rockbolts.The results indicate that harmonic wavelets also have excellent filtering characteristics.
