The function and services are the important components of the life-support system in theplanet, as well as the basic elements for sustainable development of environment and society. It is a must to evaluate it for inc...The function and services are the important components of the life-support system in theplanet, as well as the basic elements for sustainable development of environment and society. It is a must to evaluate it for incorporating it with the social-economic system. It is also an important approach to draw the public attention on the environmental and ecosystem conservation. In this study, the ecosystem function and services in China were estimated by employing the classification and economic parameters from Costanza et al. The type and area of terrestrial ecosystems were extracted from Vegetation Map of China (1:4 000 000), and then the distribution map of ecosystem services of China was drawn. According to our calculation, the total value of ecosystem services in China is 77 834.48×108 RMB yuan per annum. The value for terrestrial ecosystem is 56 098.46×108 yuan per annum, and that for marine ecosystem is 21 736.02×108 yuan per annum. The value of ecosystem services in China is 1.73 times bigger展开更多
BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satel...BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satellites in Inclined Geosynchronous Orbit （IGSO）, and 4 satellites in Medium Earth Orbit （MEO）. In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision （PDOP） value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential position- ing and ambiguity resolution （AR） performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alolae in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accu- racy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements.展开更多
Background:Gastric cancer mortality decreased substantially over the last decades in most countries worldwide.This study aimed to assess the most recent national trend of gastric cancer mortality and examine the dispa...Background:Gastric cancer mortality decreased substantially over the last decades in most countries worldwide.This study aimed to assess the most recent national trend of gastric cancer mortality and examine the disparity of gastric cancer mortality between rural and urban areas in China.Methods:The crude mortality data of gastric cancer by sex,age group,and area were obtained from China Health Statistical Yearbooks(2003-2015)covering 10%of Chinese population.The age-standardized rates of mortality(ASRM)of gastric cancer in rural and urban areas were estimated using the 2010 Chinese Census population stratified by age,sex,and area.The trend of mortality of gastric cancer was assessed by using Joinpoint analysis.Results:During the 13-year period,the ASRM was reduced from 31.5/100,000 in 2003 to 20.9/100,000 in 2015 in rural areas and from 18.9/100,000 in 2003 to 14.5/100,000 in 2015 in urban areas.In the male population,the annual percent changes of mortality were−2.2%in urban areas(95%confidence interval[CI]−3.8%to−0.6%;P<0.001)and−3.4%in rural areas(95%CI−5.1%to−1.8%;P<0.001).In the female population,the annual percent changes of mortality were−2.7%in urban areas(95%CI−4.2%to−1.2%;P<0.001)and−4.6%in rural areas(95%CI−5.5%to−3.7%;P<0.001).Conclusions:The declining trend of mortality of gastric cancer was presented from 2003 to 2015 in both rural and urban areas in China.The decrease in gastric cancer mortality is greater in rural areas than in urban areas in China.展开更多
文摘The function and services are the important components of the life-support system in theplanet, as well as the basic elements for sustainable development of environment and society. It is a must to evaluate it for incorporating it with the social-economic system. It is also an important approach to draw the public attention on the environmental and ecosystem conservation. In this study, the ecosystem function and services in China were estimated by employing the classification and economic parameters from Costanza et al. The type and area of terrestrial ecosystems were extracted from Vegetation Map of China (1:4 000 000), and then the distribution map of ecosystem services of China was drawn. According to our calculation, the total value of ecosystem services in China is 77 834.48×108 RMB yuan per annum. The value for terrestrial ecosystem is 56 098.46×108 yuan per annum, and that for marine ecosystem is 21 736.02×108 yuan per annum. The value of ecosystem services in China is 1.73 times bigger
基金sponsored by the National Natural Science Foundation of China(Grant Nos.41020144004,41374019,41104022)the National High Technology Research and Development Program of China(Grant No.2013AA122501)
文摘BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satellites in Inclined Geosynchronous Orbit （IGSO）, and 4 satellites in Medium Earth Orbit （MEO）. In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision （PDOP） value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential position- ing and ambiguity resolution （AR） performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alolae in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accu- racy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements.
基金This work was supported in part by National Natural Science Foundation of China (Grant 31870983).
文摘Background:Gastric cancer mortality decreased substantially over the last decades in most countries worldwide.This study aimed to assess the most recent national trend of gastric cancer mortality and examine the disparity of gastric cancer mortality between rural and urban areas in China.Methods:The crude mortality data of gastric cancer by sex,age group,and area were obtained from China Health Statistical Yearbooks(2003-2015)covering 10%of Chinese population.The age-standardized rates of mortality(ASRM)of gastric cancer in rural and urban areas were estimated using the 2010 Chinese Census population stratified by age,sex,and area.The trend of mortality of gastric cancer was assessed by using Joinpoint analysis.Results:During the 13-year period,the ASRM was reduced from 31.5/100,000 in 2003 to 20.9/100,000 in 2015 in rural areas and from 18.9/100,000 in 2003 to 14.5/100,000 in 2015 in urban areas.In the male population,the annual percent changes of mortality were−2.2%in urban areas(95%confidence interval[CI]−3.8%to−0.6%;P<0.001)and−3.4%in rural areas(95%CI−5.1%to−1.8%;P<0.001).In the female population,the annual percent changes of mortality were−2.7%in urban areas(95%CI−4.2%to−1.2%;P<0.001)and−4.6%in rural areas(95%CI−5.5%to−3.7%;P<0.001).Conclusions:The declining trend of mortality of gastric cancer was presented from 2003 to 2015 in both rural and urban areas in China.The decrease in gastric cancer mortality is greater in rural areas than in urban areas in China.
