Double-and triple-cropping in a year have played a very important role in meeting the rising need for food in China.However,the intensified agricultural practices have significantly altered biogeochemical cycles and s...Double-and triple-cropping in a year have played a very important role in meeting the rising need for food in China.However,the intensified agricultural practices have significantly altered biogeochemical cycles and soil quality.Understanding and mapping cropping intensity in China′s agricultural systems are therefore necessary to better estimate carbon,nitrogen and water fluxes within agro-ecosystems on the national scale.In this study,we investigated the spatial pattern of crop calendar and multiple cropping rotations in China using phenological records from 394 agro-meteorological stations(AMSs)across China.The results from the analysis of in situ field observations were used to develop a new algorithm that identifies the spatial distribution of multiple cropping in China from moderate resolution imaging spectroradiometer(MODIS)time series data with a 500 m spatial resolution and an 8-day temporal resolution.According to the MODIS-derived multiple cropping distribution in 2002,the proportion of cropland cultivated with multiple crops reached 34%in China.Double-cropping accounted for approximately 94.6%and triple-cropping for 5.4%.The results demonstrat that MODIS EVI(Enhanced Vegetation Index)time series data have the capability and potential to delineate the dynamics of double-and triple-cropping practices.The resultant multiple cropping map could be used to evaluate the impacts of agricultural intensification on biogeochemical cycles.展开更多
Organic anticorrosive aviation coatings are an effective guarantee for aviation structure,since aircraft corrosion can lead to great economic losses.Whether it is during ground parking or air cruises,organic aviation ...Organic anticorrosive aviation coatings are an effective guarantee for aviation structure,since aircraft corrosion can lead to great economic losses.Whether it is during ground parking or air cruises,organic aviation coatings are important barriers to the corrosion of aviation structure.With the vigorous development of the aviation industry,organic aviation coatings continue to meet the challenges of diverse,complex,and harsh service environments.This review analyzes and summarizes the research status of the types and development of organic aviation coatings,influencing factors and mechanisms,experimental methods,calendar life research methods,and modification methods.It also summarizes the research results that have been achieved to date.The current research deficiencies in the equivalence relationship between atmospheric exposure and artificial acceleration,failure criteria and life prediction were pointed out,and nano-modification technology,and future research strategies and directions that need breakthroughs are discussed.展开更多
基金Under the auspices of Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues of Chinese Academy of Sciences(No.XDA05050602)Major State Basic Research Development Program of China(No.2010CB950904)+1 种基金National Natural Science Foundation of China(No.40921140410,41071344)Land Cover and Land Use Change Program of National Aeronautics and Space Administration,USA(No.NAG5-11160,NNG05GH80G)
文摘Double-and triple-cropping in a year have played a very important role in meeting the rising need for food in China.However,the intensified agricultural practices have significantly altered biogeochemical cycles and soil quality.Understanding and mapping cropping intensity in China′s agricultural systems are therefore necessary to better estimate carbon,nitrogen and water fluxes within agro-ecosystems on the national scale.In this study,we investigated the spatial pattern of crop calendar and multiple cropping rotations in China using phenological records from 394 agro-meteorological stations(AMSs)across China.The results from the analysis of in situ field observations were used to develop a new algorithm that identifies the spatial distribution of multiple cropping in China from moderate resolution imaging spectroradiometer(MODIS)time series data with a 500 m spatial resolution and an 8-day temporal resolution.According to the MODIS-derived multiple cropping distribution in 2002,the proportion of cropland cultivated with multiple crops reached 34%in China.Double-cropping accounted for approximately 94.6%and triple-cropping for 5.4%.The results demonstrat that MODIS EVI(Enhanced Vegetation Index)time series data have the capability and potential to delineate the dynamics of double-and triple-cropping practices.The resultant multiple cropping map could be used to evaluate the impacts of agricultural intensification on biogeochemical cycles.
基金co-supported by the National Science and Technology Major Special Funding,China(No.J2019-I-0016-0015)the National Natural Science Foundation of China(No.52175155)the Supported Fund for Excellent Doctoral Dissertation of Air Force Engineering University,China(No.KGD082520001).
文摘Organic anticorrosive aviation coatings are an effective guarantee for aviation structure,since aircraft corrosion can lead to great economic losses.Whether it is during ground parking or air cruises,organic aviation coatings are important barriers to the corrosion of aviation structure.With the vigorous development of the aviation industry,organic aviation coatings continue to meet the challenges of diverse,complex,and harsh service environments.This review analyzes and summarizes the research status of the types and development of organic aviation coatings,influencing factors and mechanisms,experimental methods,calendar life research methods,and modification methods.It also summarizes the research results that have been achieved to date.The current research deficiencies in the equivalence relationship between atmospheric exposure and artificial acceleration,failure criteria and life prediction were pointed out,and nano-modification technology,and future research strategies and directions that need breakthroughs are discussed.
