Gemstones have fascinated mankind forever,and people traveled far to find them.The Silk Road is one of the most traditional trade routes in the middle ages that was used to bring the precious stones to the European ma...Gemstones have fascinated mankind forever,and people traveled far to find them.The Silk Road is one of the most traditional trade routes in the middle ages that was used to bring the precious stones to the European market.Later,emeralds from Colombia were shipped via the ocean to the Old World.展开更多
The impact trend of rock-coal system was studied by the method of accumulat- ing and releasing of deformation energy and interaction of rock-coal system.The system model of roof-coal-floor was established.Based on the...The impact trend of rock-coal system was studied by the method of accumulat- ing and releasing of deformation energy and interaction of rock-coal system.The system model of roof-coal-floor was established.Based on the RFPA software,rock fracture process analysis system,the numerical test of deformation,fracture and energy transmis- sion of nonlinear and nonhomogeneous rock-coal system,and the numerical test and evaluating method of impact trend of rock-coal system were achieved.When the same coal seam was in different roof and floor conditions,the fracture process of rock-coal sys- tem can be classified as gradual,sudden and delayed fracture three kinds,and their im- pact trend can be classified as void,intense and medium correspondingly.The rock-coal system's impact trend is evaluated by the system impact index μ and burst expanding forms.The criteria μ are μ<1.0,1.0≤μ<1.5 and μ≥1.5 when the impact trend is void,in- tense or medium,which are tested and verified by the No.2 and No.4 coal seams in Sun- cun mine.展开更多
Water pollution is one of the major environmental problems,especially in urban areas.Due to rapid urban expansion and industrialization,water pollution in Zhengzhou City,the capital of Henan Province in central China ...Water pollution is one of the major environmental problems,especially in urban areas.Due to rapid urban expansion and industrialization,water pollution in Zhengzhou City,the capital of Henan Province in central China has become a serious problem for its development.In this study,the surface water quality was evaluated using Nemerow Comprehensive Pollution Index (NCPI),and the change trend was calculated using methods of Mann-Kendall test and Sen's slope estimator,based on the monitoring data from 1998 to 2008.The results show that the NCPI ranged from 3 to 50 in 70% of the monitoring cases,implying that most rivers were seriously polluted.However,this serious polltuon is expected to be gradually improved,as the concentration of water pollutants and NCPI declined significantly in most rivers.Water pollution in reservoirs was much lower than rivers,and the NCPI in the three monitored reservoirs was lower than 3 in most years,and shows a downward trend.Although the surface water quality was gradually improved,great efforts are still needed to enhance the protection and improvement of surface water environment.展开更多
文摘Gemstones have fascinated mankind forever,and people traveled far to find them.The Silk Road is one of the most traditional trade routes in the middle ages that was used to bring the precious stones to the European market.Later,emeralds from Colombia were shipped via the ocean to the Old World.
基金the Ministry of Education Backbone Teachers Funded Projects
文摘The impact trend of rock-coal system was studied by the method of accumulat- ing and releasing of deformation energy and interaction of rock-coal system.The system model of roof-coal-floor was established.Based on the RFPA software,rock fracture process analysis system,the numerical test of deformation,fracture and energy transmis- sion of nonlinear and nonhomogeneous rock-coal system,and the numerical test and evaluating method of impact trend of rock-coal system were achieved.When the same coal seam was in different roof and floor conditions,the fracture process of rock-coal sys- tem can be classified as gradual,sudden and delayed fracture three kinds,and their im- pact trend can be classified as void,intense and medium correspondingly.The rock-coal system's impact trend is evaluated by the system impact index μ and burst expanding forms.The criteria μ are μ<1.0,1.0≤μ<1.5 and μ≥1.5 when the impact trend is void,in- tense or medium,which are tested and verified by the No.2 and No.4 coal seams in Sun- cun mine.
文摘Water pollution is one of the major environmental problems,especially in urban areas.Due to rapid urban expansion and industrialization,water pollution in Zhengzhou City,the capital of Henan Province in central China has become a serious problem for its development.In this study,the surface water quality was evaluated using Nemerow Comprehensive Pollution Index (NCPI),and the change trend was calculated using methods of Mann-Kendall test and Sen's slope estimator,based on the monitoring data from 1998 to 2008.The results show that the NCPI ranged from 3 to 50 in 70% of the monitoring cases,implying that most rivers were seriously polluted.However,this serious polltuon is expected to be gradually improved,as the concentration of water pollutants and NCPI declined significantly in most rivers.Water pollution in reservoirs was much lower than rivers,and the NCPI in the three monitored reservoirs was lower than 3 in most years,and shows a downward trend.Although the surface water quality was gradually improved,great efforts are still needed to enhance the protection and improvement of surface water environment.
