The viscous damping coefficient （VDC） of hydraulic actuators is crucial for system modeling, control and dynamic characteristic analysis. Currently, the resear- ches on hydraulic actuators focus on behavior assessme...The viscous damping coefficient （VDC） of hydraulic actuators is crucial for system modeling, control and dynamic characteristic analysis. Currently, the resear- ches on hydraulic actuators focus on behavior assessment, promotion of control performance and efficiency. However, the estimation of the VDC is difficult due to a lack of study. Firstly, using two types of hydraulic cylinders, behaviors of the VDC are experimentally examined with velocities and pressure variations. For the tested plunger type hydraulic cylinder, the exponential model B = αν-β （α 〉 0, β 〉 0） or B = α1e-β1ν＋α2e-β2ν（α1, α2 〉 0, β1,β2 〉 0）, fits the relation between the VDC and velocities for a given pressure of chamber with high precision. The magnitude of the VDC decreases almost linearly under certain velocities when increasing the chamber pressure from 0.6 MPa to 6.0 MPa. Furthermore, the effects of the chamber pressures on the VDC of piston and plunge type hydraulic cylinders are different due to different sealing types. In order to investi- gate the VDC of a plunger type hydraulic actuator drasti- cally, a steady-state numerical model has been developed to describe the mechanism incorporating tandem seal lubrica- tion, back-up ring related friction behaviors and shear stress of fluid. It is shown that the simulated results of VDC agreewith the measured results with a good accuracy. The pro- posed method provides an instruction to predict the VDC in system modeling and analysis.展开更多
A novel approach to virus-induced post-transcriptional gene silencing for studying the function of the ribulose bisphosphate carboxylase small subunit （rbcS） gene was established and optimized using potato virus X v...A novel approach to virus-induced post-transcriptional gene silencing for studying the function of the ribulose bisphosphate carboxylase small subunit （rbcS） gene was established and optimized using potato virus X vector and Nicotiana benthamiana as experimental material. The analysis of silencing phenomena, transcriptional level, protein expression, and pigment measurement showed that the expression of the rbcS endogenous gene was inactivated by the expression of a 500-bp homologous cDNA fragment carried in the virus vector.展开更多
基金Supported by National Basic Research Development Program of China(Grant No.2011CB706802)Hunan Provincial Foundation for Postgraduate of China(Grant No.CX2013B062)Innovation Driven Program of Central South University of China(Grant No.2015CX002)
文摘The viscous damping coefficient （VDC） of hydraulic actuators is crucial for system modeling, control and dynamic characteristic analysis. Currently, the resear- ches on hydraulic actuators focus on behavior assessment, promotion of control performance and efficiency. However, the estimation of the VDC is difficult due to a lack of study. Firstly, using two types of hydraulic cylinders, behaviors of the VDC are experimentally examined with velocities and pressure variations. For the tested plunger type hydraulic cylinder, the exponential model B = αν-β （α 〉 0, β 〉 0） or B = α1e-β1ν＋α2e-β2ν（α1, α2 〉 0, β1,β2 〉 0）, fits the relation between the VDC and velocities for a given pressure of chamber with high precision. The magnitude of the VDC decreases almost linearly under certain velocities when increasing the chamber pressure from 0.6 MPa to 6.0 MPa. Furthermore, the effects of the chamber pressures on the VDC of piston and plunge type hydraulic cylinders are different due to different sealing types. In order to investi- gate the VDC of a plunger type hydraulic actuator drasti- cally, a steady-state numerical model has been developed to describe the mechanism incorporating tandem seal lubrica- tion, back-up ring related friction behaviors and shear stress of fluid. It is shown that the simulated results of VDC agreewith the measured results with a good accuracy. The pro- posed method provides an instruction to predict the VDC in system modeling and analysis.
基金Supported by the National Natural Science Foundation of China, the Chinese National Program for Changjiang Scholars and Innovative Research Team （PCSIRT） in University （#1RT0519）, Plant Transformation Center and Jilin Provincial Science and Technology Commission. Acknowledgements We thank Dr David Baulcombe, Sainsbury Lab, UK, for providing the PVX vector construct and A.GV3101, and Dr Rachel A. Burton, Department of Plant Science, University of Adelaide, Australia, for providing the IV. benthamiana seeds.
文摘A novel approach to virus-induced post-transcriptional gene silencing for studying the function of the ribulose bisphosphate carboxylase small subunit （rbcS） gene was established and optimized using potato virus X vector and Nicotiana benthamiana as experimental material. The analysis of silencing phenomena, transcriptional level, protein expression, and pigment measurement showed that the expression of the rbcS endogenous gene was inactivated by the expression of a 500-bp homologous cDNA fragment carried in the virus vector.
