A visible magnified and simulated nozzle was designed and installed on a winding machine according to the similarity principle of Reynolds number, to study the yarn motion track in hairiness-reducing nozzle. High-spee...A visible magnified and simulated nozzle was designed and installed on a winding machine according to the similarity principle of Reynolds number, to study the yarn motion track in hairiness-reducing nozzle. High-speed photography was used to observe the yam instantaneous motion state in the nozzle. The results show that the yarn motion track seems to be a cylindrical helix which is close to inner wall in the twisting chamber and kept the same with different technical parameters, such as diameter of the twisting chamber and jet pressure in orifices. According to simulation results and reasonable simplification, the motion track equation and the rotational equation of the yarn could be derived. The velocity of the swirl and hairiness is faster than that of the yarn balloon, so there is enough time for hairiness to be wrapped into the main body of yarn and hence the hairiness is reduced.展开更多
Point return orbit(PRO) of manned lunar mission is constrained by both lunar parking orbit and reentry corridor associated with reentry position.Besides,the fuel consumption and flight time should be economy.The patch...Point return orbit(PRO) of manned lunar mission is constrained by both lunar parking orbit and reentry corridor associated with reentry position.Besides,the fuel consumption and flight time should be economy.The patched conic equations which are adaptive to PRO are derived first,the PRO is modeled with fuel and time constraints based on the design variables of orbit parameters with clear physical meaning.After that,by combining analytical method with numerical method,a serial orbit design strategy from initial value design to precision solution is proposed.Simulation example indicates that the method has excellent convergence performance and precision.According to a great deal of simulation results by the method,the PRO characteristics such as Moon centered orbit parameters,Earth centered orbit parameters,transfer velocity change,etc.are analyzed,which can supply references to the manned lunar mission orbit scheme.展开更多
A frequency and amplitude dependent model is used to describe the complex behavior of rail pads. It is implemented into the dynamic analysis of three dimensional coupled vehicle-slab track （3D-CVST） systems. The veh...A frequency and amplitude dependent model is used to describe the complex behavior of rail pads. It is implemented into the dynamic analysis of three dimensional coupled vehicle-slab track （3D-CVST） systems. The vehicle is treated as a 35-degree- of-freedom multi-body system, and the slab track is represented by two continuous Bernoulli-Euler beams supported by a se- ries of elastic rectangle plates on a viscoelastic foundation. The rail pad model takes into account the influences of the excita- tion frequency and of the displacement amplitude through a fractional derivative element, and a nonlinear friction element, re- spectively. The Granwald representation of the fractional derivatives is employed to numerically solve the fractional and non- linear equations of motion of the 3D-CVST system by means of an explicit integration algorithm. A dynamic analysis of the 3D-CVST system exposed to excitations of rail harmonic irregularities is primarily carried out, which reveals the dependence of stiffness and damping on excitation frequency and displacement amplitude. Subsequently, sensitive analyses of the model parameters are investigated by conducting the dynamic analysis of the 3D-CVST system subjected to excitations of welded rail joint irregularities. Following this, parameters of the rail pad model are optimized with respect to experimental values. For elu- cidation, the 3D-CVST dynamic model incorporated with the rail pads model is used to calculate the wheel/rail forces induced by excitations of measured random track irregularities. Further, the numerical results are compared with experimental data, demonstrating the reliability of the proposed model.展开更多
Consider a three-dimensional system having an invariant surface. By using bifurca- tion techniques and analyzing the solutions of bifurcation equations, the authors study the spacial bifurcation phenomena of a k multi...Consider a three-dimensional system having an invariant surface. By using bifurca- tion techniques and analyzing the solutions of bifurcation equations, the authors study the spacial bifurcation phenomena of a k multiple closed orbit in the invariant surface. The su?cient conditions of the existence of many closed orbits bifurcate from the k multiple closed orbit are obtained.展开更多
基金Tianjin Science and Technology Planning Projects,China(No.04310471)
文摘A visible magnified and simulated nozzle was designed and installed on a winding machine according to the similarity principle of Reynolds number, to study the yarn motion track in hairiness-reducing nozzle. High-speed photography was used to observe the yam instantaneous motion state in the nozzle. The results show that the yarn motion track seems to be a cylindrical helix which is close to inner wall in the twisting chamber and kept the same with different technical parameters, such as diameter of the twisting chamber and jet pressure in orifices. According to simulation results and reasonable simplification, the motion track equation and the rotational equation of the yarn could be derived. The velocity of the swirl and hairiness is faster than that of the yarn balloon, so there is enough time for hairiness to be wrapped into the main body of yarn and hence the hairiness is reduced.
基金supported by the Open Research Foundation of Science and Technology on Aerospace Flight Dynamics Laboratory (Grant No.2012afdl005)
文摘Point return orbit(PRO) of manned lunar mission is constrained by both lunar parking orbit and reentry corridor associated with reentry position.Besides,the fuel consumption and flight time should be economy.The patched conic equations which are adaptive to PRO are derived first,the PRO is modeled with fuel and time constraints based on the design variables of orbit parameters with clear physical meaning.After that,by combining analytical method with numerical method,a serial orbit design strategy from initial value design to precision solution is proposed.Simulation example indicates that the method has excellent convergence performance and precision.According to a great deal of simulation results by the method,the PRO characteristics such as Moon centered orbit parameters,Earth centered orbit parameters,transfer velocity change,etc.are analyzed,which can supply references to the manned lunar mission orbit scheme.
基金supported by the National Basic Research Program of China("973"Project)(Grant Nos.2013CB036202 and 2013CB036206)the Science and Technology Development Program of China Railway Corporation(Grant No.2014G002-B)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2682013CX029)the 2013 Cultivation Program for the Excellent Doctoral Dissertation of Southwest Jiaotong University
文摘A frequency and amplitude dependent model is used to describe the complex behavior of rail pads. It is implemented into the dynamic analysis of three dimensional coupled vehicle-slab track （3D-CVST） systems. The vehicle is treated as a 35-degree- of-freedom multi-body system, and the slab track is represented by two continuous Bernoulli-Euler beams supported by a se- ries of elastic rectangle plates on a viscoelastic foundation. The rail pad model takes into account the influences of the excita- tion frequency and of the displacement amplitude through a fractional derivative element, and a nonlinear friction element, re- spectively. The Granwald representation of the fractional derivatives is employed to numerically solve the fractional and non- linear equations of motion of the 3D-CVST system by means of an explicit integration algorithm. A dynamic analysis of the 3D-CVST system exposed to excitations of rail harmonic irregularities is primarily carried out, which reveals the dependence of stiffness and damping on excitation frequency and displacement amplitude. Subsequently, sensitive analyses of the model parameters are investigated by conducting the dynamic analysis of the 3D-CVST system subjected to excitations of welded rail joint irregularities. Following this, parameters of the rail pad model are optimized with respect to experimental values. For elu- cidation, the 3D-CVST dynamic model incorporated with the rail pads model is used to calculate the wheel/rail forces induced by excitations of measured random track irregularities. Further, the numerical results are compared with experimental data, demonstrating the reliability of the proposed model.
基金Project supported by the Ministry of Education of China (No.20010248019, No.20020248010) and theNational Natural Science Foundation of China (No.10371072).
文摘Consider a three-dimensional system having an invariant surface. By using bifurca- tion techniques and analyzing the solutions of bifurcation equations, the authors study the spacial bifurcation phenomena of a k multiple closed orbit in the invariant surface. The su?cient conditions of the existence of many closed orbits bifurcate from the k multiple closed orbit are obtained.
