SO 2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO 2 at different types of sites in Northern China.The overall average c...SO 2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO 2 at different types of sites in Northern China.The overall average concentrations of SO 2 are （16.8±13.1） ppb,（14.8±9.4） ppb,and （7.5±4.0） ppb at China Meteorological Administration （CMA,Beijing urban area）,Gucheng （GCH,relatively polluted rural area,110 km to the southwest of Beijing urban area）,and Shangdianzi （SDZ,clean background area,100 km to the northeast of Beijing urban area）,respectively.The SO 2 levels in winter （heating season） are 4–6 folds higher than those in summer.There are highly significant correlations among the daily means of SO 2 at different sites,indicating regional characteristics of SO 2 pollution.Diurnal patterns of surface SO 2 at all sites have a common feature with a daytime peak,which is probably caused by the downward mixing and/or the advection transport of SO 2 -richer air over the North China Plain.The concentrations of SO 2 at CMA and GCH show highly significant downward trends （–4.4 ppb/yr for CMA and –2.4 ppb/yr for GCH）,while a less significant trend （–0.3 ppb/yr） is identified in the data from SDZ,reflecting the character of SDZ as a regional atmospheric background site in North China.The SO 2 concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games,suggesting that the SO 2 pollution control has long-term effectiveness and benefits.In the post-Olympics period,the mean concentrations of SO 2 at CMA,GCH,and SDZ are （14.3±11.0） ppb,（12.1±7.7） ppb,and （7.5±4.0） ppb,respectively,with reductions of 26%,36%,and 13%,respectively,compared to the levels before.Detailed analysis shows that the differences of temperature,relative humidity,wind speed,and wind direction were not the dominant factors for the significant differences of SO 2 between the pre-Olympics and post-Olympics periods.By extracting the data being more representative of local or regional characteristics,a reduction of up to 40% for SO 2 in polluted areas and a reduction of 20% for regional SO 2 are obtained for the effect of control measures implemented for the Olympic Games.展开更多
Shape is an important quality index of cold rolling strip. Up to now, many problems in the shape control domain have not been solved satisfactorily, and a review on the research progress in the shape control domain ca...Shape is an important quality index of cold rolling strip. Up to now, many problems in the shape control domain have not been solved satisfactorily, and a review on the research progress in the shape control domain can help to seek new breakthrough directions. In the past 10 years, researches and applications of shape control models, shape control means, shape detection technology, and shape con- trol system have achieved significant progress. In the aspect of shape control models, the researches in the past improve the accuracy, speed and robustness of the models. The intelligentization of shape control models should be strengthened in the future. In the aspect of the shape control means, the researches in the past focus on the roll opti- mization, mill type selection, process optimization, local strip shape control, edge drop control, and so on. In the future, more attention should be paid to the coordination control of both strip shape and other quality indexes, and the refinement of control objective should be strengthened. In the aspects of shape detection technology and shape control system, some new types of shape detection meters and shape control systems are developed and have successfully indus- trial applications. In the future, the standardization of shape detection technology and shape control system should be promoted to solve the problem of compatibility. In general,the four expected development trends of shape control for cold roiling strip in the future are intelligentization, coordi- nation, refinement, and standardization. The proposed research provides new breakthrough directions for improv- ing shape quality.展开更多
Complexity is one of the leading features of modem control systems. It is caused by the complex properties of controlled plants and the varied requirements in controller designs. In dealing with the control problems w...Complexity is one of the leading features of modem control systems. It is caused by the complex properties of controlled plants and the varied requirements in controller designs. In dealing with the control problems with complexity, in the past two decades, a lot of papers have been published that reported fruitful results on different theoretical backgrounds and with different methodologies, such as differential geometry-based design methods, hybrid system theory, switching control, neural network-based intelligent control, etc.展开更多
Based on the climatic data of 580 stations in China during 1956 and 2000, potential evapotranspiration are calculated using the Penman-Monteith Method recommended by FAO. The spatial and temporal distributions of the ...Based on the climatic data of 580 stations in China during 1956 and 2000, potential evapotranspiration are calculated using the Penman-Monteith Method recommended by FAO. The spatial and temporal distributions of the potential evapotranspiration over China and the temporal trends of the regional means for 10 major river basins and whole China are analyzed. Through a partial correlation analysis, the major climate factors which affect the temporal change of the potential evapotranspiration are analyzed. Major results are drawn as follows： 1） The seasonal and annual potential evapotranspiration for China as a whole and for most basins show decline tendencies during the past 45 years; for the Songhua River Basin there appears a slightly increasing trend. 2） Consequently, the annual potential evapotranspirations averaged over 1980-2000 are lower than those for the first water resources assessment （1956-1979） in most parts of China. Exceptions are found in some areas of Shandong Peninsula, western and middle basins of the rivers in Southwest China, Ningxia Hui Autonomous Region as well as the source regions of the Yangtze and Yellow rivers, which may have brought about disadvantages to the exploration and utilization of water resources. 3） Generally, sunshine duration, wind speed and relative humidity have greater impact on the potential evapotranspiration than temperature. Decline tendencies of sunshine duration and/or wind speed in the same period appear to be the major causes for the negative trend of the potential evapotranspiration in most areas.展开更多
Based on defition of desertification in Intematonal Convention toCombat Desertfication. and on China's situation, desenification is found notonly In and and senuand ropons but also in huAnd and subhunud ropons. In...Based on defition of desertification in Intematonal Convention toCombat Desertfication. and on China's situation, desenification is found notonly In and and senuand ropons but also in huAnd and subhunud ropons. InChina the desertified land area has already reached 1,1 17,000kin2, or 11.6percen of China's total land area. Of which 33.2 percent is caused by winderosion, 33.8 percen by water erosion and 33.0 percen by physical andchemical actions. Besides- another 535,000 kin2 of land is susceptible to wind erosion, 875,000 km2 to water erosion and 173,000 km2 to saliruzation.Land desertification in China is the result Of over growth of populahon and irrational human aCtivities, such as abuse of water res ou rces, overculti vati on'overgrazlng. deforestaion, vopation destruCtion and envirormental polluton caused by industry and nurung under fragile ecological conditions.In recat decades, reverse tronds have occurred in mpons under proper conrol.However. on the Whole it has beenexpanding. For instance, sandy desertification develops at an annual rate of 1.39 percen in agropastoral ropons in Northem China. This paper is supposed to evaluate the curren conrol measures and practices of desertification- in ligh of the distributon characteristics and developmedl trend of land desertification in China.展开更多
基金supported by the National Basic Research Program of China (No.2005CB4222002)the National Natural Science Foundation of China (No. 20407001,40775074)+1 种基金the Basic Research Fund of CAMS (No. 2008Z011,2011CX001,2011Z003)the China Meteorological Administration(No. GYHY200706036,GYHY201106050)
文摘SO 2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO 2 at different types of sites in Northern China.The overall average concentrations of SO 2 are （16.8±13.1） ppb,（14.8±9.4） ppb,and （7.5±4.0） ppb at China Meteorological Administration （CMA,Beijing urban area）,Gucheng （GCH,relatively polluted rural area,110 km to the southwest of Beijing urban area）,and Shangdianzi （SDZ,clean background area,100 km to the northeast of Beijing urban area）,respectively.The SO 2 levels in winter （heating season） are 4–6 folds higher than those in summer.There are highly significant correlations among the daily means of SO 2 at different sites,indicating regional characteristics of SO 2 pollution.Diurnal patterns of surface SO 2 at all sites have a common feature with a daytime peak,which is probably caused by the downward mixing and/or the advection transport of SO 2 -richer air over the North China Plain.The concentrations of SO 2 at CMA and GCH show highly significant downward trends （–4.4 ppb/yr for CMA and –2.4 ppb/yr for GCH）,while a less significant trend （–0.3 ppb/yr） is identified in the data from SDZ,reflecting the character of SDZ as a regional atmospheric background site in North China.The SO 2 concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games,suggesting that the SO 2 pollution control has long-term effectiveness and benefits.In the post-Olympics period,the mean concentrations of SO 2 at CMA,GCH,and SDZ are （14.3±11.0） ppb,（12.1±7.7） ppb,and （7.5±4.0） ppb,respectively,with reductions of 26%,36%,and 13%,respectively,compared to the levels before.Detailed analysis shows that the differences of temperature,relative humidity,wind speed,and wind direction were not the dominant factors for the significant differences of SO 2 between the pre-Olympics and post-Olympics periods.By extracting the data being more representative of local or regional characteristics,a reduction of up to 40% for SO 2 in polluted areas and a reduction of 20% for regional SO 2 are obtained for the effect of control measures implemented for the Olympic Games.
基金Supported by National Key Technology Support Program of China (Grant No. 2011BAF15B00)Hebei Provincial Natural Science Foundation of China (Grant No. E2016203482)+1 种基金Hebei Provincial Science and Technology Research Foundation of China (Grant No. ZD2014034)Youth Independent Research Program of Yanshan University of China (Grant No. 14LGA003)
文摘Shape is an important quality index of cold rolling strip. Up to now, many problems in the shape control domain have not been solved satisfactorily, and a review on the research progress in the shape control domain can help to seek new breakthrough directions. In the past 10 years, researches and applications of shape control models, shape control means, shape detection technology, and shape con- trol system have achieved significant progress. In the aspect of shape control models, the researches in the past improve the accuracy, speed and robustness of the models. The intelligentization of shape control models should be strengthened in the future. In the aspect of the shape control means, the researches in the past focus on the roll opti- mization, mill type selection, process optimization, local strip shape control, edge drop control, and so on. In the future, more attention should be paid to the coordination control of both strip shape and other quality indexes, and the refinement of control objective should be strengthened. In the aspects of shape detection technology and shape control system, some new types of shape detection meters and shape control systems are developed and have successfully indus- trial applications. In the future, the standardization of shape detection technology and shape control system should be promoted to solve the problem of compatibility. In general,the four expected development trends of shape control for cold roiling strip in the future are intelligentization, coordi- nation, refinement, and standardization. The proposed research provides new breakthrough directions for improv- ing shape quality.
文摘Complexity is one of the leading features of modem control systems. It is caused by the complex properties of controlled plants and the varied requirements in controller designs. In dealing with the control problems with complexity, in the past two decades, a lot of papers have been published that reported fruitful results on different theoretical backgrounds and with different methodologies, such as differential geometry-based design methods, hybrid system theory, switching control, neural network-based intelligent control, etc.
基金Chinese Ministry of Water Resources: Special Study to Water Resources Comprehensive Planning of China Ministry of Science and Technology of China, No.2001BA611B, Sida and STINT
文摘Based on the climatic data of 580 stations in China during 1956 and 2000, potential evapotranspiration are calculated using the Penman-Monteith Method recommended by FAO. The spatial and temporal distributions of the potential evapotranspiration over China and the temporal trends of the regional means for 10 major river basins and whole China are analyzed. Through a partial correlation analysis, the major climate factors which affect the temporal change of the potential evapotranspiration are analyzed. Major results are drawn as follows： 1） The seasonal and annual potential evapotranspiration for China as a whole and for most basins show decline tendencies during the past 45 years; for the Songhua River Basin there appears a slightly increasing trend. 2） Consequently, the annual potential evapotranspirations averaged over 1980-2000 are lower than those for the first water resources assessment （1956-1979） in most parts of China. Exceptions are found in some areas of Shandong Peninsula, western and middle basins of the rivers in Southwest China, Ningxia Hui Autonomous Region as well as the source regions of the Yangtze and Yellow rivers, which may have brought about disadvantages to the exploration and utilization of water resources. 3） Generally, sunshine duration, wind speed and relative humidity have greater impact on the potential evapotranspiration than temperature. Decline tendencies of sunshine duration and/or wind speed in the same period appear to be the major causes for the negative trend of the potential evapotranspiration in most areas.
文摘Based on defition of desertification in Intematonal Convention toCombat Desertfication. and on China's situation, desenification is found notonly In and and senuand ropons but also in huAnd and subhunud ropons. InChina the desertified land area has already reached 1,1 17,000kin2, or 11.6percen of China's total land area. Of which 33.2 percent is caused by winderosion, 33.8 percen by water erosion and 33.0 percen by physical andchemical actions. Besides- another 535,000 kin2 of land is susceptible to wind erosion, 875,000 km2 to water erosion and 173,000 km2 to saliruzation.Land desertification in China is the result Of over growth of populahon and irrational human aCtivities, such as abuse of water res ou rces, overculti vati on'overgrazlng. deforestaion, vopation destruCtion and envirormental polluton caused by industry and nurung under fragile ecological conditions.In recat decades, reverse tronds have occurred in mpons under proper conrol.However. on the Whole it has beenexpanding. For instance, sandy desertification develops at an annual rate of 1.39 percen in agropastoral ropons in Northem China. This paper is supposed to evaluate the curren conrol measures and practices of desertification- in ligh of the distributon characteristics and developmedl trend of land desertification in China.
