Based on the hourly precipitation data from 4 observation stations of Xining City from June to September during 2005-2011,the temporal and spatial distribution characteristics of short-time precipitation were analyzed...Based on the hourly precipitation data from 4 observation stations of Xining City from June to September during 2005-2011,the temporal and spatial distribution characteristics of short-time precipitation were analyzed.The results show that the precipitation distribution in Xining region exhibited the less-more-less trend from southwest to northeast,while the torrential rain gradually increased from the northwest and southwest to the middle.The hourly general precipitation in Xining region had obviously seasonal characteristics,and its annual distribution showed wavy changes,but the annual variation of short-time heavy precipitation and rainstorm was very obvious.Furthermore,short-time heavy precipitation was concentrated from 18:00 to 24:00,followed by 03:00-07:00 on the following day.The occurrence time of short-time rainstorm accorded with short-time heavy precipitation.It offers a useful reference for the accurate and timely short-term forecast.展开更多
Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. ...Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. The last four grades together constitute the so called effective precipitation （〉 1 mm d^-1）. The spatial distribution and temporal trend of the graded precipitation days are examined. A decreasing trend in trace precipitation days is observed for the whole of China, except at several sites in the south of the middle section of the Yangtze River, while a decreasing trend in slight precipitation days only appears in eastern China. The decreasing trend and interannual variability of trace precipitation days is consistent with the warming trend and corresponding temperature variability in China for the same period, indicating a possible role played by increased surface air temperature in cloud formation processes. For the effective precipitation days, a decreasing trend is observed along the Yellow River valley and for the middle reaches of the Yangtze River and Southwest China, while an increasing trend is found for Xinjiang, the eastern Tibetan Plateau, Northeast China and Southeast China. The decreasing trend of effective precipitation days for the middle- lower Yellow River valley and the increasing trend for the lower Yangtze River valley are most likely linked to anomalous monsoon circulation in East China. The most important contributor to the trend in effective precipitation depends upon the region concerned.展开更多
Using observed daily precipitation data to classify five levels of rainy days by strength in South China （SC）,with an emphasis on the Pearl River Delta （PRD） region,the spatiotemporal variation of different grades...Using observed daily precipitation data to classify five levels of rainy days by strength in South China （SC）,with an emphasis on the Pearl River Delta （PRD） region,the spatiotemporal variation of different grades of precipitation during the period 1960-2010 was analyzed and the possible link with anthropogenic aerosols examined.Statistical analysis showed that drizzle and small precipitation has significantly decreased,whereas medium to heavy precipitation has increased slightly over the past 50 years （although not statistically significant）.Further data analysis suggested that the decline in drizzle and small precipitation probably has a strong link to increased concentrations of anthropogenic aerosols produced by large-scale human activities related to the rapid socioeconomic development of the PRD region.These aerosols may also have led to the obvious decreasing trend in horizontal visibility and sunshine duration in SC,which is statistically significant according to the t-test.展开更多
Ginseng polysaccharides were extracted by water decoction from Panax ginseng C.A.Meyer(Cultivated Ginseng),named CGPS.Four polysaccharide fractions,CGPS-20,CGPS-40,CGPS-60 and CGPS-80,were precipitated at final ethano...Ginseng polysaccharides were extracted by water decoction from Panax ginseng C.A.Meyer(Cultivated Ginseng),named CGPS.Four polysaccharide fractions,CGPS-20,CGPS-40,CGPS-60 and CGPS-80,were precipitated at final ethanol concentrations of 20%,40%,60%and 80%,respectively.Physicochemical properties,molecular weight,monosaccharide composition and antioxidant capacity of polysaccharide fractions were all investigated.The results indicated that changing the concentration of ethanol could precipitate polysaccharides into fractions with different molecular weights,functional group composition and physicochemical properties,eventually leading to differences in antioxidant activity,which would help to find a simple,efficient,and reliable method for rapid extraction and purification of antioxidant polysaccharides from Panax ginseng C.A.Meyer.Among the four polysaccharide fractions,CGPS-80 had lower molecular weight,higher contents of uronic acid and total phenolic,and stronger scavenging ability on DPPH∙and ABTS∙+radicals.展开更多
Mn-Zn ferrite powders were produced from low-grade manganese ore(LMO) via the chemical coprecipitation method combined with the ceramic method,after the LMO was leached in sulfuric acid and the obtained solution was p...Mn-Zn ferrite powders were produced from low-grade manganese ore(LMO) via the chemical coprecipitation method combined with the ceramic method,after the LMO was leached in sulfuric acid and the obtained solution was purified.The effect of the pH on the magnetic properties of Mn-Zn ferrite was investigated by the varying pH of the co-precipitation system.The crystal structure and phases of the samples were characterized by X-ray diffraction and infrared spectrum,respectively.The magnetic measurements were carried out on a vibrating sample magnetometer.The optimal sample was obtained with a saturation magnetization of 55.02 emu/g,a coercivity of 8.20 G and a remanent magnetization of1.71 emu/g when pH is 7.5.展开更多
基金Supported by the Key Research and Development and Transformation Project of Science and Technology Department of Qinghai Province in 2021(2021-SF-141-2).
文摘Based on the hourly precipitation data from 4 observation stations of Xining City from June to September during 2005-2011,the temporal and spatial distribution characteristics of short-time precipitation were analyzed.The results show that the precipitation distribution in Xining region exhibited the less-more-less trend from southwest to northeast,while the torrential rain gradually increased from the northwest and southwest to the middle.The hourly general precipitation in Xining region had obviously seasonal characteristics,and its annual distribution showed wavy changes,but the annual variation of short-time heavy precipitation and rainstorm was very obvious.Furthermore,short-time heavy precipitation was concentrated from 18:00 to 24:00,followed by 03:00-07:00 on the following day.The occurrence time of short-time rainstorm accorded with short-time heavy precipitation.It offers a useful reference for the accurate and timely short-term forecast.
基金This research was supported by the National Natural Science Foundation of China （Grant Nos. 90502001 and 40475032）the National Key Program for Developing Basic Sciences in China （Grant No. 2006CB403602）.
文摘Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. The last four grades together constitute the so called effective precipitation （〉 1 mm d^-1）. The spatial distribution and temporal trend of the graded precipitation days are examined. A decreasing trend in trace precipitation days is observed for the whole of China, except at several sites in the south of the middle section of the Yangtze River, while a decreasing trend in slight precipitation days only appears in eastern China. The decreasing trend and interannual variability of trace precipitation days is consistent with the warming trend and corresponding temperature variability in China for the same period, indicating a possible role played by increased surface air temperature in cloud formation processes. For the effective precipitation days, a decreasing trend is observed along the Yellow River valley and for the middle reaches of the Yangtze River and Southwest China, while an increasing trend is found for Xinjiang, the eastern Tibetan Plateau, Northeast China and Southeast China. The decreasing trend of effective precipitation days for the middle- lower Yellow River valley and the increasing trend for the lower Yangtze River valley are most likely linked to anomalous monsoon circulation in East China. The most important contributor to the trend in effective precipitation depends upon the region concerned.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-EW-QN208)the National Basic Research Program of China (Grant No. 2010CB428502)+3 种基金the open fund of the State Key Laboratory of Remote Sensing Science (Grant No. OFSLRSS201113)the CAS Strategic Priority Research Program (Grant No. XDA05110103)the R&D Special Fund for Public Welfare Industry (meteorology) by the Ministry of Financethe Ministry of Science and Technology (Grant No. GYHY20100601404)
文摘Using observed daily precipitation data to classify five levels of rainy days by strength in South China （SC）,with an emphasis on the Pearl River Delta （PRD） region,the spatiotemporal variation of different grades of precipitation during the period 1960-2010 was analyzed and the possible link with anthropogenic aerosols examined.Statistical analysis showed that drizzle and small precipitation has significantly decreased,whereas medium to heavy precipitation has increased slightly over the past 50 years （although not statistically significant）.Further data analysis suggested that the decline in drizzle and small precipitation probably has a strong link to increased concentrations of anthropogenic aerosols produced by large-scale human activities related to the rapid socioeconomic development of the PRD region.These aerosols may also have led to the obvious decreasing trend in horizontal visibility and sunshine duration in SC,which is statistically significant according to the t-test.
基金This work was granted by the National Key R&D Program of China(2017YFC1702302)LiaoNing Revitalization Talents Program(XLYC1902119).
文摘Ginseng polysaccharides were extracted by water decoction from Panax ginseng C.A.Meyer(Cultivated Ginseng),named CGPS.Four polysaccharide fractions,CGPS-20,CGPS-40,CGPS-60 and CGPS-80,were precipitated at final ethanol concentrations of 20%,40%,60%and 80%,respectively.Physicochemical properties,molecular weight,monosaccharide composition and antioxidant capacity of polysaccharide fractions were all investigated.The results indicated that changing the concentration of ethanol could precipitate polysaccharides into fractions with different molecular weights,functional group composition and physicochemical properties,eventually leading to differences in antioxidant activity,which would help to find a simple,efficient,and reliable method for rapid extraction and purification of antioxidant polysaccharides from Panax ginseng C.A.Meyer.Among the four polysaccharide fractions,CGPS-80 had lower molecular weight,higher contents of uronic acid and total phenolic,and stronger scavenging ability on DPPH∙and ABTS∙+radicals.
基金financed by the Bureau of Land Resources and Housing Management of Chongqing(Scientific & Technologic Program in 2011)the Science and Technology Bureau of Hengyang(Scientific & Technologic Program in 2013)the State Administration of Work Safety(Scientific & Technologic Program in 2013)
文摘Mn-Zn ferrite powders were produced from low-grade manganese ore(LMO) via the chemical coprecipitation method combined with the ceramic method,after the LMO was leached in sulfuric acid and the obtained solution was purified.The effect of the pH on the magnetic properties of Mn-Zn ferrite was investigated by the varying pH of the co-precipitation system.The crystal structure and phases of the samples were characterized by X-ray diffraction and infrared spectrum,respectively.The magnetic measurements were carried out on a vibrating sample magnetometer.The optimal sample was obtained with a saturation magnetization of 55.02 emu/g,a coercivity of 8.20 G and a remanent magnetization of1.71 emu/g when pH is 7.5.
