[Objective]The paper aimed to study effect of shallow groundwater at different depths on crop water requirement and crop evaporation in spring wheat field.[Method]Five treatments of shallow groundwater table at differ...[Objective]The paper aimed to study effect of shallow groundwater at different depths on crop water requirement and crop evaporation in spring wheat field.[Method]Five treatments of shallow groundwater table at different depth were designed to do evaporation experiment for spring wheat in 2008-2009.[Result]The groundwater at different depths had great impact on crop growth and field evaporation;its supply accounted for 0-52% of actual evapotranspiration.Atmospheric evaporation and crop rooting depth were the major factors to affect the uptake of groundwater at shallow table,and the supply of deep groundwater was controlled by groundwater table.[Conclusion]The study reveled the pattern of evapotranspiration of spring wheat and evaporation of shallow groundwater at different depth,in order to supply basis for the rational and effective utilization of shallow groundwater as well as optimization of the irrigation scheduling for spring wheat.展开更多
Variable ballast systems are necessary for manned submersibles to adjust their buoyancy.In this paper,the design of a variable ballast system for a manned submersible is described.The variable ballast system uses a su...Variable ballast systems are necessary for manned submersibles to adjust their buoyancy.In this paper,the design of a variable ballast system for a manned submersible is described.The variable ballast system uses a super high pressure hydraulic seawater system.A super high pressure seawater pump and a deep-sea brushless DC motor are used to pump seawater into or from the variable ballast tank,increasing or decreasing the weight of the manned submersible.A magnetostrictive linear displacement transducer can detect the seawater level in the variable ballast tank.Some seawater valves are used to control pumping direction and control on-off states.The design and testing procedure for the valves is described.Finally,the future development of variable ballast systems and seawater hydraulic systems is projected.展开更多
This paper addresses the need for systematic evaluation of the station keeping systems of deepwater drilling semi-submersibles.Based on the selected drilling semi-submersible configuration, the mooring systems were an...This paper addresses the need for systematic evaluation of the station keeping systems of deepwater drilling semi-submersibles.Based on the selected drilling semi-submersible configuration, the mooring systems were analyzed and designed for a range of water depths using different mooring line materials.These were steel wire rope, polyester rope and HMPE (high modulus poly ethylene).The mooring analysis was carried out using the advanced fully coupled time domain analysis method in the computer software package HARP.Diffraction analysis was first applied to solve the hydrodynamic properties of the vessel and then the motion equations of the complete dynamic system including the drilling rig, the mooring lines and risers were developed and solved in the time domain.Applying the advanced analysis method, a matrix of mooring systems was developed for operating in water depths of 1000 m, 1500 m, and 2 000 m using various mooring materials.The development of mooring systems was conducted in accordance with the commonly adopted mooring design code, API RP 2SK and API RP 2SM.Fresh attempts were then made to comparatively evaluate the mooring system's characteristics and global performance.Useful results have been obtained in terms of mooring materials, water depths, and key parameters of mooring configurations.The results provide in-depth insight for the design and operation of deepwater mooring systems in the South China Sea environment.展开更多
基金Supported by Science Research Project of Ningxia Higher Education~~
文摘[Objective]The paper aimed to study effect of shallow groundwater at different depths on crop water requirement and crop evaporation in spring wheat field.[Method]Five treatments of shallow groundwater table at different depth were designed to do evaporation experiment for spring wheat in 2008-2009.[Result]The groundwater at different depths had great impact on crop growth and field evaporation;its supply accounted for 0-52% of actual evapotranspiration.Atmospheric evaporation and crop rooting depth were the major factors to affect the uptake of groundwater at shallow table,and the supply of deep groundwater was controlled by groundwater table.[Conclusion]The study reveled the pattern of evapotranspiration of spring wheat and evaporation of shallow groundwater at different depth,in order to supply basis for the rational and effective utilization of shallow groundwater as well as optimization of the irrigation scheduling for spring wheat.
基金Supported by the "863" Foundation under Grant No.2002AA401000
文摘Variable ballast systems are necessary for manned submersibles to adjust their buoyancy.In this paper,the design of a variable ballast system for a manned submersible is described.The variable ballast system uses a super high pressure hydraulic seawater system.A super high pressure seawater pump and a deep-sea brushless DC motor are used to pump seawater into or from the variable ballast tank,increasing or decreasing the weight of the manned submersible.A magnetostrictive linear displacement transducer can detect the seawater level in the variable ballast tank.Some seawater valves are used to control pumping direction and control on-off states.The design and testing procedure for the valves is described.Finally,the future development of variable ballast systems and seawater hydraulic systems is projected.
基金Supported by China National 111 Project under Grant No.B07019
文摘This paper addresses the need for systematic evaluation of the station keeping systems of deepwater drilling semi-submersibles.Based on the selected drilling semi-submersible configuration, the mooring systems were analyzed and designed for a range of water depths using different mooring line materials.These were steel wire rope, polyester rope and HMPE (high modulus poly ethylene).The mooring analysis was carried out using the advanced fully coupled time domain analysis method in the computer software package HARP.Diffraction analysis was first applied to solve the hydrodynamic properties of the vessel and then the motion equations of the complete dynamic system including the drilling rig, the mooring lines and risers were developed and solved in the time domain.Applying the advanced analysis method, a matrix of mooring systems was developed for operating in water depths of 1000 m, 1500 m, and 2 000 m using various mooring materials.The development of mooring systems was conducted in accordance with the commonly adopted mooring design code, API RP 2SK and API RP 2SM.Fresh attempts were then made to comparatively evaluate the mooring system's characteristics and global performance.Useful results have been obtained in terms of mooring materials, water depths, and key parameters of mooring configurations.The results provide in-depth insight for the design and operation of deepwater mooring systems in the South China Sea environment.
