The research reviewed the concept of family farm and analyzed family farm types including unified, facility rental-oriented, employment-oriented, circular and grain＆oil based family farms, as well as corresponding de...The research reviewed the concept of family farm and analyzed family farm types including unified, facility rental-oriented, employment-oriented, circular and grain＆oil based family farms, as well as corresponding demands in technology and policies. Based on the analysis, the research proposed countermeasures and suggestions. It is necessary to define the range and scale on family farm before giving policy supports. It is important to establish access system of industry and commerce capital to rural areas to guarantee the operators in need be benefited from national preferential policies. Meanwhile, new system on land transfer should be established to guarantee security system for family farm, improve socialized service system and promote government-built production facilities operated by farmers.展开更多
In this paper, regarding the actual conditions of a roller compacted concrete dam, three-dimensional finite element relocating mesh method is utilized to simulate and calculate the temperature field of the RCC dam dur...In this paper, regarding the actual conditions of a roller compacted concrete dam, three-dimensional finite element relocating mesh method is utilized to simulate and calculate the temperature field of the RCC dam during the construction stage and operating period. The calculation is well consistent with the actual construction process, the thin-layer pouring process the pouring temperature and all kinds of external loads involved being taken into account, By comparing and analyzing of the impact of the cold wave on the dam stress, important references are provided for the RCCD design and the temperature control during construction.展开更多
This paper proposes an on-site monitoring system for evaporation （Ew） and evapotranspiration （ET） in wetlands called the Compensation Evapotranspiration Observation System. Considering the characteristics of wetla...This paper proposes an on-site monitoring system for evaporation （Ew） and evapotranspiration （ET） in wetlands called the Compensation Evapotranspiration Observation System. Considering the characteristics of wetlands environment and emergent plants, the vertical flux of water loss in wetlands can be separated using the system based on compensation principle. A comparison research on water loss through ET in reed （Phragmites australis） stands between Zhalong wetland and Baiyangdian wetland was carded out in 2004-2009. In Baiyangdian wetland, the ET rates from three reed stands with different leaf area indexes were measured. The results show that annual ET in Zhalong wetland was 739-886 mm during study period. Comparatively, annual ET of the three reed stands in Baiyangdian wetland was 970-1117 mm, 1261-1452 mm and 1759-2035 ram, respectively. The ET rates in Baiyangdian were stronger than in Zhalong because of the effects of geography and climate characteristics. Moreover, seasonal dynamic changes and influence factors of transpiration-acting factor from the two wetlands were also analyzed. It is indicated that the transpirafion-actng factor can be affected by geographic location, aboveground biomass, plant growth and climate conditions.展开更多
Regional gravity field modeling with high-precision and high-resolution is one of the most important scientific objectives in geodesy, and can provide fundamental information for geophysics, geodynamics, seismology, a...Regional gravity field modeling with high-precision and high-resolution is one of the most important scientific objectives in geodesy, and can provide fundamental information for geophysics, geodynamics, seismology, and mineral exploration. Rectangular harmonic analysis （RHA） is proposed for regional gravity field modeling in this paper. By solving the Laplace＇s equation of gravitational potential in local Cartesian coordinate system, the rectangular harmonic expansions of disturbing potential, gravity anomaly, gravity disturbance, geoid undulation and deflection of the vertical are derived, and so are the formula for signal degree variance and error degree variance of the rectangular harmonic coefficients （RHC）. We also present the mathematical model and detailed algorithm for the solution of RHC using RHA from gravity observations. In order to reduce the edge effects caused by periodic continuation in RHA, we propose the strategy of extending the size of computation domain. The RHA-based modeling method is validated by conducting numerical experiments based on simulated ground and airborne gravity data that are generated from geopotential model EGM2008 and contaminated by Gauss white noise with standard deviation of 2 mGal. The accuracy of the 2.5＇×2.5＇ geoid undulations computed from ground and airborne gravity data is 1 and 1.4 cm, respectively. The standard error of the gravity disturbances that downward continued from the flight height of 4 km to the geoid is only 3.1 reGal. Numerical results confirm that RHA is able to provide a reliable and accurate regional gravity field model, which may be a new option for the representation of the fine structure of regional gravity field.展开更多
文摘论述了西安地裂缝勘察场地类型的划分,分析了三类勘察场地隐伏地裂缝识别存在的问题.依据西安地区地形地貌类型及地层沉积差异,将西安地裂缝三类勘察场地划分为3个亚区（Ⅲ-0区、Ⅲ-1区和Ⅲ-2区）.Ⅲ-0区位于西安北郊,地貌单元为渭河河漫滩及Ⅰ级阶地,目前尚未发现地裂缝；Ⅲ-1区位于西安西郊,地貌单元为Ⅰ级洪积台地；Ⅲ-2区位于西安东郊,地貌单元为浐河、灞河Ⅰ级阶地；Ⅲ-1区和Ⅲ-2区地裂缝研究程度低,是西安地裂缝三类勘察场地研究的难点所在.根据Ⅲ-1区和Ⅲ-2区大量地球物理勘探和工程地质钻探,提出Ⅲ-1区宜采用浅层人工地震勘探和工程地质钻探相结合的方法,控制钻孔间距不宜大于40 m,孔深宜为80-100 m；Ⅲ-2区由于存在厚层可对比的卵石（圆砾）层,可仅采用工程地质钻探方法,建议控制钻孔间距为60-80 m,孔深60-70 m.
基金Supported by Jiangsu Agricultural Science and Technology Independent Innovation(CX(13)5016)Jiangsu Social Science Research Subject(13SQC-002)~~
文摘The research reviewed the concept of family farm and analyzed family farm types including unified, facility rental-oriented, employment-oriented, circular and grain＆oil based family farms, as well as corresponding demands in technology and policies. Based on the analysis, the research proposed countermeasures and suggestions. It is necessary to define the range and scale on family farm before giving policy supports. It is important to establish access system of industry and commerce capital to rural areas to guarantee the operators in need be benefited from national preferential policies. Meanwhile, new system on land transfer should be established to guarantee security system for family farm, improve socialized service system and promote government-built production facilities operated by farmers.
文摘In this paper, regarding the actual conditions of a roller compacted concrete dam, three-dimensional finite element relocating mesh method is utilized to simulate and calculate the temperature field of the RCC dam during the construction stage and operating period. The calculation is well consistent with the actual construction process, the thin-layer pouring process the pouring temperature and all kinds of external loads involved being taken into account, By comparing and analyzing of the impact of the cold wave on the dam stress, important references are provided for the RCCD design and the temperature control during construction.
基金supported by the National Natural Science Foundation of China (Grant No. 50139020)the National Basic Research Program of China ("973" Program) (Grant No. 2006CB403405)
文摘This paper proposes an on-site monitoring system for evaporation （Ew） and evapotranspiration （ET） in wetlands called the Compensation Evapotranspiration Observation System. Considering the characteristics of wetlands environment and emergent plants, the vertical flux of water loss in wetlands can be separated using the system based on compensation principle. A comparison research on water loss through ET in reed （Phragmites australis） stands between Zhalong wetland and Baiyangdian wetland was carded out in 2004-2009. In Baiyangdian wetland, the ET rates from three reed stands with different leaf area indexes were measured. The results show that annual ET in Zhalong wetland was 739-886 mm during study period. Comparatively, annual ET of the three reed stands in Baiyangdian wetland was 970-1117 mm, 1261-1452 mm and 1759-2035 ram, respectively. The ET rates in Baiyangdian were stronger than in Zhalong because of the effects of geography and climate characteristics. Moreover, seasonal dynamic changes and influence factors of transpiration-acting factor from the two wetlands were also analyzed. It is indicated that the transpirafion-actng factor can be affected by geographic location, aboveground biomass, plant growth and climate conditions.
基金jointly supported by the National Basic Research Program of China (Grant No. 2013CB733301)the National Science and Technology Support Program of China (Grant No. 2012BAB16B01)+1 种基金the National Natural Science Foundation of China (Grant No. 41204008)the Basic Research Program of National Administration of Surveying, Mapping and Geoinformation of China
文摘Regional gravity field modeling with high-precision and high-resolution is one of the most important scientific objectives in geodesy, and can provide fundamental information for geophysics, geodynamics, seismology, and mineral exploration. Rectangular harmonic analysis （RHA） is proposed for regional gravity field modeling in this paper. By solving the Laplace＇s equation of gravitational potential in local Cartesian coordinate system, the rectangular harmonic expansions of disturbing potential, gravity anomaly, gravity disturbance, geoid undulation and deflection of the vertical are derived, and so are the formula for signal degree variance and error degree variance of the rectangular harmonic coefficients （RHC）. We also present the mathematical model and detailed algorithm for the solution of RHC using RHA from gravity observations. In order to reduce the edge effects caused by periodic continuation in RHA, we propose the strategy of extending the size of computation domain. The RHA-based modeling method is validated by conducting numerical experiments based on simulated ground and airborne gravity data that are generated from geopotential model EGM2008 and contaminated by Gauss white noise with standard deviation of 2 mGal. The accuracy of the 2.5＇×2.5＇ geoid undulations computed from ground and airborne gravity data is 1 and 1.4 cm, respectively. The standard error of the gravity disturbances that downward continued from the flight height of 4 km to the geoid is only 3.1 reGal. Numerical results confirm that RHA is able to provide a reliable and accurate regional gravity field model, which may be a new option for the representation of the fine structure of regional gravity field.
