It is pointed out that the damping matrix deduced by active members in the finite element vibration equation of a truss adaptive structure generally can not be decoupled, which leads to the difficulty in the process o...It is pointed out that the damping matrix deduced by active members in the finite element vibration equation of a truss adaptive structure generally can not be decoupled, which leads to the difficulty in the process of modal analysis by classical superposition method. This paper focuses on the computational method of the dynamic response for truss adaptive structures. Firstly, a new technique of state vector approach is applied to study the dynamic response of truss adaptive structures. It can make the coeffic lent matrix of first derivative of state vector a symmetric positive definite matrix, and particularly a diagonal matrix provided that mass matrix is derived by lumped method, so the coefficient matrix of the first derivative of state vector can be exactly decomposed by CHOLESKY method. In this case, the proposed technique not only improves the calculation accuracy, but also saves the computing time. Based on the procedure mentioned above, the mathematical formulation for the system response of truss adaptive structures is systematically derived in theory. Thirdly, by using FORTRAN language, a program system for computing dynamic response of truss adaptive structures is developed. Fourthly, a typical 18 bar space truss adaptive structure has been chosen as test numerical examples to show the feasibility and effectiveness of the proposed method. Finally, some good suggestions, such as how to choose complex mode shapes practically in determining the dynamic response are also given. The new approach can be extended to calculate the dynamic response of general adaptive structures.展开更多
An analytical solution of the guided wave propagation in a multilayered twodimensional decagonal quasicrystal plate with imperfect interfaces is derived.According to the elastodynamic equations of quasicrystals(QCs),t...An analytical solution of the guided wave propagation in a multilayered twodimensional decagonal quasicrystal plate with imperfect interfaces is derived.According to the elastodynamic equations of quasicrystals(QCs),the wave propagating problem in the plate is converted into a linear control system by employing the state-vector approach,from which the general solutions of the extended displacements and stresses can be obtained,These solutions along the thickness direction are utilized to derive the propagator matrix which connects the physical variables on the lower and upper interfaces of each layer.The special spring model,which describes the discontinuity of the physical quantities across the interface,is introduced into the propagator relationship of the multilayered structure.The total propagator matrix can be used to propagate the solutions in each interface and each layer about the multilayered plate.In addition,the traction-free boundary condition on the top and bottom surfaces of the laminate is considered to obtain the dispersion equation of wave propagation,Finally,typical numerical examples are presented to illustrate the marked influences of stacking sequence and interface coeficients on the dispersion curves and displacement mode shapes of the QC laminates.展开更多
We investigate the decay of a_1^+(1260) →π^+π^+π^-with the assumption that the a_1(1260) is dynamically generated from the coupled channel ρπ and KK~*interactions. In addition to the tree level diagrams that pro...We investigate the decay of a_1^+(1260) →π^+π^+π^-with the assumption that the a_1(1260) is dynamically generated from the coupled channel ρπ and KK~*interactions. In addition to the tree level diagrams that proceed via a_1^+(1260) →ρ~0π^+→π^+π^+π^-, we take into account also the final state interactions of ππ→ππ and KK →ππ. We calculate the invariant π^+π^-mass distribution and also the total decay width of a_1^+(1260) →π^+π^+π^-as a function of the mass of a_1(1260). The calculated total decay width of a_1(1260) is significantly different from other model calculations and tied to the dynamical nature of the a_1(1260) resonance. The future experimental observations could test of model calculations and would provide vary valuable information on the relevance of the ρπ component in the a_1(1260) wave function.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 10472007)
文摘It is pointed out that the damping matrix deduced by active members in the finite element vibration equation of a truss adaptive structure generally can not be decoupled, which leads to the difficulty in the process of modal analysis by classical superposition method. This paper focuses on the computational method of the dynamic response for truss adaptive structures. Firstly, a new technique of state vector approach is applied to study the dynamic response of truss adaptive structures. It can make the coeffic lent matrix of first derivative of state vector a symmetric positive definite matrix, and particularly a diagonal matrix provided that mass matrix is derived by lumped method, so the coefficient matrix of the first derivative of state vector can be exactly decomposed by CHOLESKY method. In this case, the proposed technique not only improves the calculation accuracy, but also saves the computing time. Based on the procedure mentioned above, the mathematical formulation for the system response of truss adaptive structures is systematically derived in theory. Thirdly, by using FORTRAN language, a program system for computing dynamic response of truss adaptive structures is developed. Fourthly, a typical 18 bar space truss adaptive structure has been chosen as test numerical examples to show the feasibility and effectiveness of the proposed method. Finally, some good suggestions, such as how to choose complex mode shapes practically in determining the dynamic response are also given. The new approach can be extended to calculate the dynamic response of general adaptive structures.
基金supported by the National Natural Science Foundation of China(Grant Nos.11972365,12102458,and 11972354)China Agricultural University Education Foundation(No.1101-2412001).
文摘An analytical solution of the guided wave propagation in a multilayered twodimensional decagonal quasicrystal plate with imperfect interfaces is derived.According to the elastodynamic equations of quasicrystals(QCs),the wave propagating problem in the plate is converted into a linear control system by employing the state-vector approach,from which the general solutions of the extended displacements and stresses can be obtained,These solutions along the thickness direction are utilized to derive the propagator matrix which connects the physical variables on the lower and upper interfaces of each layer.The special spring model,which describes the discontinuity of the physical quantities across the interface,is introduced into the propagator relationship of the multilayered structure.The total propagator matrix can be used to propagate the solutions in each interface and each layer about the multilayered plate.In addition,the traction-free boundary condition on the top and bottom surfaces of the laminate is considered to obtain the dispersion equation of wave propagation,Finally,typical numerical examples are presented to illustrate the marked influences of stacking sequence and interface coeficients on the dispersion curves and displacement mode shapes of the QC laminates.
基金Project supported by the National Natural Science Foundation of China(Nos.11472299 and 51704015)the China Agricultural University Education Foundation(No.1101-240001)
基金Supported by the National Natural Science Foundation of China under Grant Nos.11475227 and 11735003supported by the Youth Innovation Promotion Association CAS(No.2016367)
文摘We investigate the decay of a_1^+(1260) →π^+π^+π^-with the assumption that the a_1(1260) is dynamically generated from the coupled channel ρπ and KK~*interactions. In addition to the tree level diagrams that proceed via a_1^+(1260) →ρ~0π^+→π^+π^+π^-, we take into account also the final state interactions of ππ→ππ and KK →ππ. We calculate the invariant π^+π^-mass distribution and also the total decay width of a_1^+(1260) →π^+π^+π^-as a function of the mass of a_1(1260). The calculated total decay width of a_1(1260) is significantly different from other model calculations and tied to the dynamical nature of the a_1(1260) resonance. The future experimental observations could test of model calculations and would provide vary valuable information on the relevance of the ρπ component in the a_1(1260) wave function.
