无线层析成像(radio tomographic imaging,RTI)技术作为无设备目标定位(device-free localization,DFL)的主要方式之一,在被定位目标不携带任何定位装置的情况下仍能实现定位,具有广泛的应用前景.但由于接收信号强度(received signal st...无线层析成像(radio tomographic imaging,RTI)技术作为无设备目标定位(device-free localization,DFL)的主要方式之一,在被定位目标不携带任何定位装置的情况下仍能实现定位,具有广泛的应用前景.但由于接收信号强度(received signal strength,RSS)信息容易受到环境变化和噪声的影响,RTI成像图上往往不可避免地存在着背景噪点,有时甚至还有伪目标出现在图像上.为了提高RTI成像质量,本文提出一种基于核主成分分析(kernel principal component analysis,KPCA)的增强型RTI方法,该方法利用KPCA的学习能力来提取有效受目标影响的链路特征信息,从而达到克服噪声影响和提高定位精度的目的.室内外实验结果表明,该方法的成像质量和定位精度都要优于现有RTI方法.展开更多
The permafrost region is one of the most sensitive areas to climate change.With global warming,the Mongolian Plateau permafrost is rapidly degrading,and its vegetation ecosystem is seriously threatened.To address thi...The permafrost region is one of the most sensitive areas to climate change.With global warming,the Mongolian Plateau permafrost is rapidly degrading,and its vegetation ecosystem is seriously threatened.To address this challenge,it is essential to understand the impact of climate change on vegetation at different permafrost degradation stages on the Mongolian Plateau.Based on the general permafrost distribution,in this study,we divided different permafrost regions and explored the response of vegetation to climate change at different stages of permafrost degradation by the idea of“space instead of time”from 2014 to 2023.The results of the study showed that:(1)Normalized difference vegetation index(NDVI)values showed a decreasing trend,and the proportion of the decreasing region was in the order of sporadic permafrost region>isolated and sparse permafrost region>continuous and discontinuous permafrost regions.(2)The main controlling factors of vegetation growth in permafrost regions are different,air temperature is the main controlling factor of vegetation growth in isolated and sparse permafrost region(r=-0.736)and sporadic permafrost regions(r=-0.522),and precipitation is the main controlling factor of vegetation growth in continuous and discontinuous permafrost region(r=-0.498).(3)The response of NDVI to climate change varies at different stages of permafrost degradation.In the early stages of permafrost degradation,increased land surface temperature(LST)and air temperature favored vegetation growth and increased vegetation cover,whereas increased precipitation impeded vegetation growth;as the permafrost degraded,increased LST and air temperature impeded vegetation growth,whereas increased precipitation promoted vegetation growth.展开更多
文摘无线层析成像(radio tomographic imaging,RTI)技术作为无设备目标定位(device-free localization,DFL)的主要方式之一,在被定位目标不携带任何定位装置的情况下仍能实现定位,具有广泛的应用前景.但由于接收信号强度(received signal strength,RSS)信息容易受到环境变化和噪声的影响,RTI成像图上往往不可避免地存在着背景噪点,有时甚至还有伪目标出现在图像上.为了提高RTI成像质量,本文提出一种基于核主成分分析(kernel principal component analysis,KPCA)的增强型RTI方法,该方法利用KPCA的学习能力来提取有效受目标影响的链路特征信息,从而达到克服噪声影响和提高定位精度的目的.室内外实验结果表明,该方法的成像质量和定位精度都要优于现有RTI方法.
基金The National Natural Science Foundation of China(32161143025)The Science&Technology Fundamental Resources Investigation Program of China(2022FY101905)+4 种基金The National Key R&D Program of China(2022YFE0119200)The Mongolian Foundation for Science and Technology(NSFC_2022/01,CHN2022/276)The Key R&D and Achievement Transformation Plan Project in Inner Mongolia Autonomous Region(2023KJHZ0027)The Key Project of Innovation LREIS(KPI006)The Construction Project of China Knowledge Center for Engineering Sciences and Technology(CKCEST-2023-1-5)。
文摘The permafrost region is one of the most sensitive areas to climate change.With global warming,the Mongolian Plateau permafrost is rapidly degrading,and its vegetation ecosystem is seriously threatened.To address this challenge,it is essential to understand the impact of climate change on vegetation at different permafrost degradation stages on the Mongolian Plateau.Based on the general permafrost distribution,in this study,we divided different permafrost regions and explored the response of vegetation to climate change at different stages of permafrost degradation by the idea of“space instead of time”from 2014 to 2023.The results of the study showed that:(1)Normalized difference vegetation index(NDVI)values showed a decreasing trend,and the proportion of the decreasing region was in the order of sporadic permafrost region>isolated and sparse permafrost region>continuous and discontinuous permafrost regions.(2)The main controlling factors of vegetation growth in permafrost regions are different,air temperature is the main controlling factor of vegetation growth in isolated and sparse permafrost region(r=-0.736)and sporadic permafrost regions(r=-0.522),and precipitation is the main controlling factor of vegetation growth in continuous and discontinuous permafrost region(r=-0.498).(3)The response of NDVI to climate change varies at different stages of permafrost degradation.In the early stages of permafrost degradation,increased land surface temperature(LST)and air temperature favored vegetation growth and increased vegetation cover,whereas increased precipitation impeded vegetation growth;as the permafrost degraded,increased LST and air temperature impeded vegetation growth,whereas increased precipitation promoted vegetation growth.
