We developed a sophisticated method to depict the spatial and seasonal characterization of net primary productivity (NPP) and climate variables. The role of climate variability in the seasonal variation of NPP exerts ...We developed a sophisticated method to depict the spatial and seasonal characterization of net primary productivity (NPP) and climate variables. The role of climate variability in the seasonal variation of NPP exerts delayed and continuous effects. This study expands on this by mapping the seasonal characterization of NPP and climate variables from space using geographic information system (GIS) technology at the pixel level. Our approach was developed in southeastern China using moderate-resolution imaging spectroradiometer (MODIS) data. The results showed that air temperature,precipitation and sunshine percentage contributed significantly to seasonal variation of NPP. In the northern portion of the study area,a significant positive 32-d lagged correlation was observed between seasonal variation of NPP and climate (P<0.01),and the influences of changing climate on NPP lasted for 48 d or 64 d. In central southeastern China,NPP showed 16-d,48-d,and 96-d lagged correlation with air temperature,precipitation,and sunshine percentage,respectively (P<0.01); the influences of air temperature and precipitation on NPP lasted for 48 d or 64 d,while sunshine influence on NPP only persisted for 16 d. Due to complex topography and vegetation distribution in the southern part of the study region,the spatial patterns of vegetation-climate relationship became complicated and diversiform,especially for precipitation influences on NPP. In the northern part of the study area,all vegetation NPP had an almost similar response to seasonal variation of air temperature except for broad crops. The impacts of seasonal variation of precipitation and sunshine on broad and cereal crop NPP were slightly different from other vegetation NPP.展开更多
This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional l...This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional linear variation the rays of quasi-stationary planetary wave may propagate along oblique lines and if the meridional variability of heat source has second order term the rays show distinct deformation as a great circular route. Additionally, the inhomogeneous distribution may cause lower frequency oscillations in mid- and low-latitudes. The combination of zonal and meridional wave numbers and distributive character of heat source may form an inverse mechanism of variational trend of generized wave energy, reflecting in some degree the physical process of transition between meridional and zonal flow patterns.展开更多
Using NDVI data of NOAA-AVHRR in recent 20 years and the temperature and precipitation data of West China, the vegetation activity is discussed by adopting the EOF and REOF decomposed functions. Results show that the ...Using NDVI data of NOAA-AVHRR in recent 20 years and the temperature and precipitation data of West China, the vegetation activity is discussed by adopting the EOF and REOF decomposed functions. Results show that the overall increasing trend of vegetation activity in different seasons reflects an advanced and prolonged growth period of vegetation under the circumstance of climate warming, but the vegetation evolvement has much inconsistency between different regions and seasons. There are four notable regions, eight sub-areas for vegetation evolvement in spring and summer, and nine sub-areas in autumn. The vegetation activity in most sub-areas is increasing. The most notable region is represented by Lhaze station on the Tibetan Plateau. Two other marked stations are represented by Altay station in Xinjiang Uygur Autonomous Region and Pengshui station in Sichuan Province. But the time series analysis of NDVI makes clear that the trends of the other two sub-areas, Turpan station in Xinjiang and Huashan station in Shaanxi Province, are descending. It is an important reason for vegetation evolvement that temperature ascends in most of the regions and descends in the east region in some seasons. But another important reason for vegetation evolvement is that precipitation is ascending in the west and descending in the east of the region.展开更多
地表颗粒物是城市雨水径流的主要污染源,也是多种径流污染物的主要载体,对其污染特征及规律的掌握是有效控制径流污染的关键。采用文献计量学方法,系统梳理2017—2023年国内外城市地表颗粒物研究报道,从物理化学特性、污染时空分布特征...地表颗粒物是城市雨水径流的主要污染源,也是多种径流污染物的主要载体,对其污染特征及规律的掌握是有效控制径流污染的关键。采用文献计量学方法,系统梳理2017—2023年国内外城市地表颗粒物研究报道,从物理化学特性、污染时空分布特征、污染源解析、累积过程与影响因素4个方面归纳总结城市地表颗粒物的研究进展。结果表明:Web of Science和中国知网数据库2017—2023年在城市地表颗粒物领域的发文量均呈现先上升后下降的趋势,中英文文献研究热点集中在重金属、多环芳烃(PAHs)、源解析、风险评价等方面;粒径是影响地表颗粒物携带污染物种类和含量的重要物理特性,地表颗粒物中新污染物如多环芳烃衍生物、微塑料等化学指标逐渐受到关注;城市商业区、交通区和工业区地表颗粒物中重金属、PAHs、微塑料等污染水平较高,而公园绿地中氮和磷含量较高;地表颗粒物污染显著的季节性差异与污染来源和气候因素有关;城市地表颗粒物中重金属来源于自然或人为活动,PAHs主要源于有机物不完全燃烧,氮和磷来源解析尚无定论;幂函数、指数函数、饱和函数等函数形式可较好地描述城市地表颗粒物累积过程。未来研究应重点关注污染物赋存形态及其迁移转化机制,深入探讨不同类型下垫面颗粒物时空演替规律及相应机制,精确解析不同类型污染物来源,并探索地表颗粒物累积过程普适性形式。展开更多
Contaminated or infected patients present a risk of cross-contamination for emergency responders, attending medical personnel and medical facilities as they enter a treatment facility. The controlled conditions of an ...Contaminated or infected patients present a risk of cross-contamination for emergency responders, attending medical personnel and medical facilities as they enter a treatment facility. The controlled conditions of an aerosol test chamber are required to examine factors of contamination, decontamination, and cross-contamination. This study presents the design, construction, and a method for characterizing an aerosol test chamber for a full-sized manikin on a standard North Atlantic Treaty Organization litter. The methodology combined air velocity measurements, aerosol particle counts and size distributions, and computational fluid dynamics modeling to describe the chamber’s performance in three dimensions. This detailed characterization facilitates future experimental design by predicting chamber performance for a variety of patient-focused research.展开更多
基金Project supported by the National High-Tech Research and Development Program (863) of China (No. 2006AA120101)the National Natural Science Foundation of China (Nos. 40871158 and 40875070)the Key Technologies Research and Development Program of China (No. 2006BAD10A01)
文摘We developed a sophisticated method to depict the spatial and seasonal characterization of net primary productivity (NPP) and climate variables. The role of climate variability in the seasonal variation of NPP exerts delayed and continuous effects. This study expands on this by mapping the seasonal characterization of NPP and climate variables from space using geographic information system (GIS) technology at the pixel level. Our approach was developed in southeastern China using moderate-resolution imaging spectroradiometer (MODIS) data. The results showed that air temperature,precipitation and sunshine percentage contributed significantly to seasonal variation of NPP. In the northern portion of the study area,a significant positive 32-d lagged correlation was observed between seasonal variation of NPP and climate (P<0.01),and the influences of changing climate on NPP lasted for 48 d or 64 d. In central southeastern China,NPP showed 16-d,48-d,and 96-d lagged correlation with air temperature,precipitation,and sunshine percentage,respectively (P<0.01); the influences of air temperature and precipitation on NPP lasted for 48 d or 64 d,while sunshine influence on NPP only persisted for 16 d. Due to complex topography and vegetation distribution in the southern part of the study region,the spatial patterns of vegetation-climate relationship became complicated and diversiform,especially for precipitation influences on NPP. In the northern part of the study area,all vegetation NPP had an almost similar response to seasonal variation of air temperature except for broad crops. The impacts of seasonal variation of precipitation and sunshine on broad and cereal crop NPP were slightly different from other vegetation NPP.
文摘This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional linear variation the rays of quasi-stationary planetary wave may propagate along oblique lines and if the meridional variability of heat source has second order term the rays show distinct deformation as a great circular route. Additionally, the inhomogeneous distribution may cause lower frequency oscillations in mid- and low-latitudes. The combination of zonal and meridional wave numbers and distributive character of heat source may form an inverse mechanism of variational trend of generized wave energy, reflecting in some degree the physical process of transition between meridional and zonal flow patterns.
基金National Natural Science Foundation of China, No.40205014 No.40175004+2 种基金 Project of Gansu Province, No.3ZS051-A25-011 Item of the Ministry of Science and Technology, No.2004BA901A16 No.2004DIB5J192
文摘Using NDVI data of NOAA-AVHRR in recent 20 years and the temperature and precipitation data of West China, the vegetation activity is discussed by adopting the EOF and REOF decomposed functions. Results show that the overall increasing trend of vegetation activity in different seasons reflects an advanced and prolonged growth period of vegetation under the circumstance of climate warming, but the vegetation evolvement has much inconsistency between different regions and seasons. There are four notable regions, eight sub-areas for vegetation evolvement in spring and summer, and nine sub-areas in autumn. The vegetation activity in most sub-areas is increasing. The most notable region is represented by Lhaze station on the Tibetan Plateau. Two other marked stations are represented by Altay station in Xinjiang Uygur Autonomous Region and Pengshui station in Sichuan Province. But the time series analysis of NDVI makes clear that the trends of the other two sub-areas, Turpan station in Xinjiang and Huashan station in Shaanxi Province, are descending. It is an important reason for vegetation evolvement that temperature ascends in most of the regions and descends in the east region in some seasons. But another important reason for vegetation evolvement is that precipitation is ascending in the west and descending in the east of the region.
文摘地表颗粒物是城市雨水径流的主要污染源,也是多种径流污染物的主要载体,对其污染特征及规律的掌握是有效控制径流污染的关键。采用文献计量学方法,系统梳理2017—2023年国内外城市地表颗粒物研究报道,从物理化学特性、污染时空分布特征、污染源解析、累积过程与影响因素4个方面归纳总结城市地表颗粒物的研究进展。结果表明:Web of Science和中国知网数据库2017—2023年在城市地表颗粒物领域的发文量均呈现先上升后下降的趋势,中英文文献研究热点集中在重金属、多环芳烃(PAHs)、源解析、风险评价等方面;粒径是影响地表颗粒物携带污染物种类和含量的重要物理特性,地表颗粒物中新污染物如多环芳烃衍生物、微塑料等化学指标逐渐受到关注;城市商业区、交通区和工业区地表颗粒物中重金属、PAHs、微塑料等污染水平较高,而公园绿地中氮和磷含量较高;地表颗粒物污染显著的季节性差异与污染来源和气候因素有关;城市地表颗粒物中重金属来源于自然或人为活动,PAHs主要源于有机物不完全燃烧,氮和磷来源解析尚无定论;幂函数、指数函数、饱和函数等函数形式可较好地描述城市地表颗粒物累积过程。未来研究应重点关注污染物赋存形态及其迁移转化机制,深入探讨不同类型下垫面颗粒物时空演替规律及相应机制,精确解析不同类型污染物来源,并探索地表颗粒物累积过程普适性形式。
文摘Contaminated or infected patients present a risk of cross-contamination for emergency responders, attending medical personnel and medical facilities as they enter a treatment facility. The controlled conditions of an aerosol test chamber are required to examine factors of contamination, decontamination, and cross-contamination. This study presents the design, construction, and a method for characterizing an aerosol test chamber for a full-sized manikin on a standard North Atlantic Treaty Organization litter. The methodology combined air velocity measurements, aerosol particle counts and size distributions, and computational fluid dynamics modeling to describe the chamber’s performance in three dimensions. This detailed characterization facilitates future experimental design by predicting chamber performance for a variety of patient-focused research.
