移动式放射性惰性气体监测仪对不同能量的γ射线存在不同的能量响应,为了提高其测量γ射线的准确性,需要对该监测仪进行能量响应补偿。利用MCNP(Monte Carlo N Particle Transport Code)软件模拟监测仪中的Na I(Tl)晶体在不同铅孔模型...移动式放射性惰性气体监测仪对不同能量的γ射线存在不同的能量响应,为了提高其测量γ射线的准确性,需要对该监测仪进行能量响应补偿。利用MCNP(Monte Carlo N Particle Transport Code)软件模拟监测仪中的Na I(Tl)晶体在不同铅孔模型下的能量响应,通过比较不同模型下的标准偏差,选出屏蔽铅孔的最佳尺寸。模拟得出补偿铅孔的半径为3.0 cm、厚度为0.5 cm时,该监测仪的能量响应得到较好补偿。展开更多
Evaluation of the ecological effects of eco-compensation policies helps analyze policy rationality and feasibility and provides scientific and practical bases for perfecting eco-compensation systems. Taking the key ec...Evaluation of the ecological effects of eco-compensation policies helps analyze policy rationality and feasibility and provides scientific and practical bases for perfecting eco-compensation systems. Taking the key ecological function area of the Loess Plateau, China as a case study, we have evaluated ecosystem responses to the Grain-for-Green Project that commenced in 1999. Six indicators were selected to assess changes in ecosystem structure, quality and function. The results showed that implementation of the Grain-for-Green Project has reduced sloping cropland by 1571 km2 and increased ecological land by 1337 km2. The increase in ecological land alters ecosystem structures across the study area and the decline in sloping cropland reduces farming activity interference; both of these are conducive to the restoration of natural vegetation. From 2000 to 2010, the vegetation cover of grassland, desert and forest ecosystems increased 10.89%, 8.34% and 4.24% respectively and average NPP rose 51%, with an average annual growth rate of around 5%. This indicates that eco-compensation has promoted the improvement of ecosystem quality. Total biomass of ecosystems increased two times on average from 2000 to 2010, meaning that the carbon sequestration capacity of ecosystems also increased. The reduction in the area of water loss and soil erosion and the increase in retained runoff by forests indicate an improvement in ecosystem function and services on the Loess Plateau.展开更多
Land fallow is of great significance for undertaking land reclamation, safeguarding national food security, promoting environmental improvements and ensuring the sustainable use of land resources. This paper reviews t...Land fallow is of great significance for undertaking land reclamation, safeguarding national food security, promoting environmental improvements and ensuring the sustainable use of land resources. This paper reviews the important achievements in three areas of research on the land fallow system. It reviews and compares the land fallow system in different countries and regions of the world; it examines the response of farmers to the land fallow system and ecological environment; and it looks at the economic effects of the land fallow system. Based on Chi- na＇s rotation system for cultivated land, some relevant policy implications are put forward. Based on the different degrees of land damage, the evaluation system and the subsidy accounting standard for fallow land are formulated, and the compulsory fallow and voluntary participation of the niche fallow are targeting. The land fallow system should improve both the regulatory and the restraint mechanisms, improve the environmental awareness and en- vironmental protection skills of farmers, change the production behaviors of farmers, and encourage farmers to change to high coverage crops to protect the land. In view of the negative effects produced by implementation of the fallow system should take corresponding management and compensation measures.展开更多
When the envelope of the conducting strips for the input transducer of magnetostatic surface wave(MSSW) device is designed according to the wavelet-function envelope,the impulse-response function of the input transduc...When the envelope of the conducting strips for the input transducer of magnetostatic surface wave(MSSW) device is designed according to the wavelet-function envelope,the impulse-response function of the input transducer for MSSW device is equal to the wavelet function,so that single-scale wavelet-transform processor of MSSW type is fabricated.First,according to the envelope function of the wavelet,the length function of the conducting strips is defined,then,the lengths of the conducting strips can be calculated from the length function of the conducting strips,finally,the input transducer can be designed according to the lengths and widths for the conducting strips.The compensation method of the insertion loss for single-scale wavelet trans-form processor of MSSW type is also given in the paper.When the output end of single-scale wavelet transform processor of MSSW type is connected to the amplifier,its insertion loss can be compensated.展开更多
文摘移动式放射性惰性气体监测仪对不同能量的γ射线存在不同的能量响应,为了提高其测量γ射线的准确性,需要对该监测仪进行能量响应补偿。利用MCNP(Monte Carlo N Particle Transport Code)软件模拟监测仪中的Na I(Tl)晶体在不同铅孔模型下的能量响应,通过比较不同模型下的标准偏差,选出屏蔽铅孔的最佳尺寸。模拟得出补偿铅孔的半径为3.0 cm、厚度为0.5 cm时,该监测仪的能量响应得到较好补偿。
基金the National Science and Technology Support Program(2013BAC03B05)National Natural Science Foundation of China(41371486)
文摘Evaluation of the ecological effects of eco-compensation policies helps analyze policy rationality and feasibility and provides scientific and practical bases for perfecting eco-compensation systems. Taking the key ecological function area of the Loess Plateau, China as a case study, we have evaluated ecosystem responses to the Grain-for-Green Project that commenced in 1999. Six indicators were selected to assess changes in ecosystem structure, quality and function. The results showed that implementation of the Grain-for-Green Project has reduced sloping cropland by 1571 km2 and increased ecological land by 1337 km2. The increase in ecological land alters ecosystem structures across the study area and the decline in sloping cropland reduces farming activity interference; both of these are conducive to the restoration of natural vegetation. From 2000 to 2010, the vegetation cover of grassland, desert and forest ecosystems increased 10.89%, 8.34% and 4.24% respectively and average NPP rose 51%, with an average annual growth rate of around 5%. This indicates that eco-compensation has promoted the improvement of ecosystem quality. Total biomass of ecosystems increased two times on average from 2000 to 2010, meaning that the carbon sequestration capacity of ecosystems also increased. The reduction in the area of water loss and soil erosion and the increase in retained runoff by forests indicate an improvement in ecosystem function and services on the Loess Plateau.
基金Key projects of the National Social Science Fund of China(No.15AZD075)National Natural Science Foundation of China(No.41561040)+2 种基金Natural Science Foundation of Jiangxi Province(No.20143ACB21023)Technology Foundation of Jiangxi Education Department of China(No.KJLD14033&GJJ160431)Fok Ying-Tung Fund(No.141084)
文摘Land fallow is of great significance for undertaking land reclamation, safeguarding national food security, promoting environmental improvements and ensuring the sustainable use of land resources. This paper reviews the important achievements in three areas of research on the land fallow system. It reviews and compares the land fallow system in different countries and regions of the world; it examines the response of farmers to the land fallow system and ecological environment; and it looks at the economic effects of the land fallow system. Based on Chi- na＇s rotation system for cultivated land, some relevant policy implications are put forward. Based on the different degrees of land damage, the evaluation system and the subsidy accounting standard for fallow land are formulated, and the compulsory fallow and voluntary participation of the niche fallow are targeting. The land fallow system should improve both the regulatory and the restraint mechanisms, improve the environmental awareness and en- vironmental protection skills of farmers, change the production behaviors of farmers, and encourage farmers to change to high coverage crops to protect the land. In view of the negative effects produced by implementation of the fallow system should take corresponding management and compensation measures.
基金supported by the National Natural Science Foundation of China (Grant No 60976058)
文摘When the envelope of the conducting strips for the input transducer of magnetostatic surface wave(MSSW) device is designed according to the wavelet-function envelope,the impulse-response function of the input transducer for MSSW device is equal to the wavelet function,so that single-scale wavelet-transform processor of MSSW type is fabricated.First,according to the envelope function of the wavelet,the length function of the conducting strips is defined,then,the lengths of the conducting strips can be calculated from the length function of the conducting strips,finally,the input transducer can be designed according to the lengths and widths for the conducting strips.The compensation method of the insertion loss for single-scale wavelet trans-form processor of MSSW type is also given in the paper.When the output end of single-scale wavelet transform processor of MSSW type is connected to the amplifier,its insertion loss can be compensated.
