Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non-desingularized technique.Free surface and seabed surface profiles are represented by continuous panels rather th...Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non-desingularized technique.Free surface and seabed surface profiles are represented by continuous panels rather than a discretization by isolated points.These panels are positioned exactly on the fluid boundary surfaces and therefore no desingularization technique is required.Space increment method is applied for both free surface source and seabed source arrangements to reduce computational cost and improve numerical efficiency.Fourth order Runge-Kutta iteration scheme is adopted on the free surface updating at every time step.The finite water depth effect is studied quantitatively for a series of cylinders with different B/T ratios.The accuracy and efficiency of the proposed model are validated by comparison with published numerical results and experimental data.Numerical results show that hydrodynamic coefficients vary for cylinder bodies with different ratios of B/T.For certain set of B/T ratios the effect of finite water depth increases quickly with the increase of motion frequency and becomes stable when frequency is relatively large.It also shows that water depths have larger hydrodynamic effects on cylinder with larger breadth to draft ratios.Both the heave added mass and damping coefficients increase across the frequency range with the water depths decrease for forced heave motion.The water depths have smaller effects on sway motion response than on heave motion response.展开更多
In order to improve the navigation accuracy of human occupied vehicle(HOV)precisely and efficiently,an innovative hybrid approach based on unscented Kalman filter(UKF)and support vector machine(SVM)is proposed to fuse...In order to improve the navigation accuracy of human occupied vehicle(HOV)precisely and efficiently,an innovative hybrid approach based on unscented Kalman filter(UKF)and support vector machine(SVM)is proposed to fuse integrated navigation data.HOV is generally equipped with long baseline(LBL)acoustic positioning system and dead reckoning(DR)as an integrated navigation system.UKF is adopted to estimate the state of the dynamic model because of its good performance in filtering nonlinear problems.An accurate and stable filtering result can be obtained when both LBL and DR are online.At the same time,SVM is utilized to train DR information with the result when LBL outrages,and the particle swarm optimization(PSO)algorithm is employed for SVM parameters optimization.Therefore,the integrated navigation system can maintain a good performance when the LBL is off-line.Simulation results with the real navigation data of Jiaolong HOV show that the methodology proposed here is able to meet the needs of HOV application.展开更多
A novel free-cutting unleaded brass containing antimony and magnesium was prepared by gravity casting and hot extrusion. Microstructure of the hot extruded Sb-Mg brass was studied with scanning electron microscope (SE...A novel free-cutting unleaded brass containing antimony and magnesium was prepared by gravity casting and hot extrusion. Microstructure of the hot extruded Sb-Mg brass was studied with scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). Its mechanical properties were measured by tensile test, and cutting performance was investigated by lathe turning experiment. Results showed that microstructure of the hot extruded Sb-Mg brass was composed of α, β phases and Sb-Mg containing intermetallic compounds. The newly developed brass was compared with the HPb59-1 brass for its mechanical property. Its cutting performance was close to that of a German free-cutting unleaded brass. Sb-Mg brass has potential to replace HPb59-1 brass so as to reduce cost and protect environment.展开更多
基金the support by the National Natural Science Foundation of China(No.11372184)
文摘Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non-desingularized technique.Free surface and seabed surface profiles are represented by continuous panels rather than a discretization by isolated points.These panels are positioned exactly on the fluid boundary surfaces and therefore no desingularization technique is required.Space increment method is applied for both free surface source and seabed source arrangements to reduce computational cost and improve numerical efficiency.Fourth order Runge-Kutta iteration scheme is adopted on the free surface updating at every time step.The finite water depth effect is studied quantitatively for a series of cylinders with different B/T ratios.The accuracy and efficiency of the proposed model are validated by comparison with published numerical results and experimental data.Numerical results show that hydrodynamic coefficients vary for cylinder bodies with different ratios of B/T.For certain set of B/T ratios the effect of finite water depth increases quickly with the increase of motion frequency and becomes stable when frequency is relatively large.It also shows that water depths have larger hydrodynamic effects on cylinder with larger breadth to draft ratios.Both the heave added mass and damping coefficients increase across the frequency range with the water depths decrease for forced heave motion.The water depths have smaller effects on sway motion response than on heave motion response.
基金National High Technology Development Program of China(2009AA093302,2014AA09A110)the Chinese Academy of Strategic Leading Science and Technology Special(XDA11040104)
文摘In order to improve the navigation accuracy of human occupied vehicle(HOV)precisely and efficiently,an innovative hybrid approach based on unscented Kalman filter(UKF)and support vector machine(SVM)is proposed to fuse integrated navigation data.HOV is generally equipped with long baseline(LBL)acoustic positioning system and dead reckoning(DR)as an integrated navigation system.UKF is adopted to estimate the state of the dynamic model because of its good performance in filtering nonlinear problems.An accurate and stable filtering result can be obtained when both LBL and DR are online.At the same time,SVM is utilized to train DR information with the result when LBL outrages,and the particle swarm optimization(PSO)algorithm is employed for SVM parameters optimization.Therefore,the integrated navigation system can maintain a good performance when the LBL is off-line.Simulation results with the real navigation data of Jiaolong HOV show that the methodology proposed here is able to meet the needs of HOV application.
文摘A novel free-cutting unleaded brass containing antimony and magnesium was prepared by gravity casting and hot extrusion. Microstructure of the hot extruded Sb-Mg brass was studied with scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). Its mechanical properties were measured by tensile test, and cutting performance was investigated by lathe turning experiment. Results showed that microstructure of the hot extruded Sb-Mg brass was composed of α, β phases and Sb-Mg containing intermetallic compounds. The newly developed brass was compared with the HPb59-1 brass for its mechanical property. Its cutting performance was close to that of a German free-cutting unleaded brass. Sb-Mg brass has potential to replace HPb59-1 brass so as to reduce cost and protect environment.
