Using the Jisan Coalmine's top-coal caving for the 3down coal seam with ascending mining as the project background, the air-leakage characteristics of the goaf wasanalyzed. Through data fitting of the in situ obse...Using the Jisan Coalmine's top-coal caving for the 3down coal seam with ascending mining as the project background, the air-leakage characteristics of the goaf wasanalyzed. Through data fitting of the in situ observation, the models of gas seepage, diffusion and air-leakage in the goaf were established in ascending mining. The ComputationFluid Dynamics software Fluent was used to simulate the air-leakage law of the goaf. Theresults of the numerical simulation provide a basis for the use of the technology of ventilation and fire prevention in the working face of an ascending mining, which ensures thesafety in production in the working face of the top-coal caving for 3_down coal seam in theJisan Coalmine.展开更多
Some long distance air ammunition can be used to attack large still target. According to this character and according to the mathematical description of target-missile relative motion built by the message supplied by ...Some long distance air ammunition can be used to attack large still target. According to this character and according to the mathematical description of target-missile relative motion built by the message supplied by the strapdown inertial navigation system/global position system （SINS/GPS） of air ammunition, optimal guidance law is designed by applying optimal control theory. The simulation is provided to indicate that when the air ammunition reaches the target, its line-of-sight （LOS） and LOS angular rate can nearly equal zero. So the air ammunition can get good terminal attitude, and the air ammunition reaches the target at the expected velocity and heading.展开更多
The haze has become the necessary thing to talk about everywhere for the Chinese people nowadays and the main report object in the news. It becomes increasingly urgent to develop the circular economy and build a beaut...The haze has become the necessary thing to talk about everywhere for the Chinese people nowadays and the main report object in the news. It becomes increasingly urgent to develop the circular economy and build a beautiful China. But there exists secretly a game between the central and local governments when the air protection is enforced. The central government calls for implementing the total control system of the key pollutant emission,but the local governments are blandly ignoring the central government＇s requirement as they have to face the pressures of the assessment and performance. And the games among the local governments at the same level and between the governments and enterprises lead that the existing incentive policy through the legislation is inefficiency in China. The amendment about Environmental Law has laid foundation of the legal system for it.展开更多
In recent years, the large scale and frequency of severe air pollution in China has become an important consideration in the construction of livable cities and the physical and mental health of urban residents. Based ...In recent years, the large scale and frequency of severe air pollution in China has become an important consideration in the construction of livable cities and the physical and mental health of urban residents. Based on the 2016-year urban air quality index(AQI) data published by the Ministry of Environmental Protection of China, this study analyzed the spatial and temporal characteristics of air quality and its influencing factors in 338 urban units nationwide. The analysis provides an effective scientific basis for formulating national air pollution control measures. Four key results are shown. 1) Generally, air quality in the 338 cities is poor, and the average annual values for urban AQI and air pollution in 2016 were 79.58% and 21.22%, respectively. 2) The air quality index presents seasonal changes, with winter > spring > autumn > summer and a u-shaped trend. 3) The spatial distribution of the urban air quality index shows clear north-south characteristic differences and a spatial agglomeration effect; the high value area of air pollution is mainly concentrated in the North China Plain and Xinjiang Uygur Autonomous Region. 4) An evaluation of the spatial econometric model shows that differences in urban air quality are due to social, economic, and natural factors.展开更多
The characteristics of surface maneuver targets are analyzed and a 3-D relative motion model for missiles and targets is established. A variable structure guidance law is designed considering the characteristics of ta...The characteristics of surface maneuver targets are analyzed and a 3-D relative motion model for missiles and targets is established. A variable structure guidance law is designed considering the characteristics of targets. In the guidance law, the distance between missiles and targets as well as the missile-target relative velocity are all substituted by estimation values. The estimation errors, the target＇s velocity, and the maneuver acceleration are all treated as bounded disturbance. The guidance law proposed can be implemented conveniently in engineering with little target information. The performance of the guidance system is analyzed theoretically and the numerical simulation result shows the effectiveness of the guidance law.展开更多
基金Supported by the National Natural Science Foundation of China(50704025)the National Science Fundation of Education Department in Shaanxi Province(07JK318)the Planning Project of Excellent Talented Person of New Century Supported by Ministry of Education of China (NECT050874)
文摘Using the Jisan Coalmine's top-coal caving for the 3down coal seam with ascending mining as the project background, the air-leakage characteristics of the goaf wasanalyzed. Through data fitting of the in situ observation, the models of gas seepage, diffusion and air-leakage in the goaf were established in ascending mining. The ComputationFluid Dynamics software Fluent was used to simulate the air-leakage law of the goaf. Theresults of the numerical simulation provide a basis for the use of the technology of ventilation and fire prevention in the working face of an ascending mining, which ensures thesafety in production in the working face of the top-coal caving for 3_down coal seam in theJisan Coalmine.
文摘Some long distance air ammunition can be used to attack large still target. According to this character and according to the mathematical description of target-missile relative motion built by the message supplied by the strapdown inertial navigation system/global position system （SINS/GPS） of air ammunition, optimal guidance law is designed by applying optimal control theory. The simulation is provided to indicate that when the air ammunition reaches the target, its line-of-sight （LOS） and LOS angular rate can nearly equal zero. So the air ammunition can get good terminal attitude, and the air ammunition reaches the target at the expected velocity and heading.
文摘The haze has become the necessary thing to talk about everywhere for the Chinese people nowadays and the main report object in the news. It becomes increasingly urgent to develop the circular economy and build a beautiful China. But there exists secretly a game between the central and local governments when the air protection is enforced. The central government calls for implementing the total control system of the key pollutant emission,but the local governments are blandly ignoring the central government＇s requirement as they have to face the pressures of the assessment and performance. And the games among the local governments at the same level and between the governments and enterprises lead that the existing incentive policy through the legislation is inefficiency in China. The amendment about Environmental Law has laid foundation of the legal system for it.
文摘In recent years, the large scale and frequency of severe air pollution in China has become an important consideration in the construction of livable cities and the physical and mental health of urban residents. Based on the 2016-year urban air quality index(AQI) data published by the Ministry of Environmental Protection of China, this study analyzed the spatial and temporal characteristics of air quality and its influencing factors in 338 urban units nationwide. The analysis provides an effective scientific basis for formulating national air pollution control measures. Four key results are shown. 1) Generally, air quality in the 338 cities is poor, and the average annual values for urban AQI and air pollution in 2016 were 79.58% and 21.22%, respectively. 2) The air quality index presents seasonal changes, with winter > spring > autumn > summer and a u-shaped trend. 3) The spatial distribution of the urban air quality index shows clear north-south characteristic differences and a spatial agglomeration effect; the high value area of air pollution is mainly concentrated in the North China Plain and Xinjiang Uygur Autonomous Region. 4) An evaluation of the spatial econometric model shows that differences in urban air quality are due to social, economic, and natural factors.
文摘The characteristics of surface maneuver targets are analyzed and a 3-D relative motion model for missiles and targets is established. A variable structure guidance law is designed considering the characteristics of targets. In the guidance law, the distance between missiles and targets as well as the missile-target relative velocity are all substituted by estimation values. The estimation errors, the target＇s velocity, and the maneuver acceleration are all treated as bounded disturbance. The guidance law proposed can be implemented conveniently in engineering with little target information. The performance of the guidance system is analyzed theoretically and the numerical simulation result shows the effectiveness of the guidance law.
