A frequency invariant response algorithm is proposed for getting over the signal distortion in high frequency when the beamformer receives the broadband signals. In this method, the weight vector of the reference beam...A frequency invariant response algorithm is proposed for getting over the signal distortion in high frequency when the beamformer receives the broadband signals. In this method, the weight vector of the reference beam pattern is designed firstly, then the weight vectors when the beam response in the frequency sub-bands approaching the reference response mostly are computed by optimized method or adaptive method. By this method, the beam pattern in each sub-band can be almost kept invariable. As a result, the receiving chirp signal can be improved. Owing to the adoption of the adaptive method to approach the optimized vectors, it has no restricting of the array format and the element directivity, and the method can be used widely.展开更多
In this paper the problem of a circular beam subjected to radial impact by a rigid mass at its lip in its own plane is investigaleil on the basis of rigid-perfectly plastic assumption. The analytical solution of the p...In this paper the problem of a circular beam subjected to radial impact by a rigid mass at its lip in its own plane is investigaleil on the basis of rigid-perfectly plastic assumption. The analytical solution of the particle velocities is obtained as the junction of travelling plastic hinge location. Ky analysing the solution, some special properties oj circular beam problem are found.展开更多
China railways track structure II (CRTS II) slab ballastless track on bridge is one kind of track structures unique to China. Its main bearing component of longitudinal force is the continuous base plate rather than ...China railways track structure II (CRTS II) slab ballastless track on bridge is one kind of track structures unique to China. Its main bearing component of longitudinal force is the continuous base plate rather than rail. And the track-bridge interaction is weakened by the sliding layer installed between base plate and bridge deck. In order to study the dynamic response of CRTS II slab ballastless track on bridge under seismic action, a 3D nonlinear dynamic model for simply-supported bridges and CRTS II track was established, which considered structures such as steel rail, fasteners, track plate, mortar layer, base plate, sliding layer, bridge, consolidation, anchors, stoppers, etc. Then its force and deformation features under different intensities of seismic excitation were studied. As revealed, the seismic response of the system increases with the increase of seismic intensity. The peak stresses of rail, track plate and base plate all occur at the abutment or anchors. Both track plate and base plate are about to crack. Besides, the rapid relative displacement between base plate and bridge deck due to the small friction coefficient of sliding layer is beneficial to improve the seismic performance of the system. During the earthquake, a large vertical displacement appears in base plate which leads to frequent collisions between stoppers and base plate, as a result, stoppers may be damaged.展开更多
基金Supported by the 863 Foundation under Grant No.2002AA602230.
文摘A frequency invariant response algorithm is proposed for getting over the signal distortion in high frequency when the beamformer receives the broadband signals. In this method, the weight vector of the reference beam pattern is designed firstly, then the weight vectors when the beam response in the frequency sub-bands approaching the reference response mostly are computed by optimized method or adaptive method. By this method, the beam pattern in each sub-band can be almost kept invariable. As a result, the receiving chirp signal can be improved. Owing to the adoption of the adaptive method to approach the optimized vectors, it has no restricting of the array format and the element directivity, and the method can be used widely.
文摘In this paper the problem of a circular beam subjected to radial impact by a rigid mass at its lip in its own plane is investigaleil on the basis of rigid-perfectly plastic assumption. The analytical solution of the particle velocities is obtained as the junction of travelling plastic hinge location. Ky analysing the solution, some special properties oj circular beam problem are found.
基金supported by the National Natural Science Foundation of China (Grant No. 51608542)Project of Science and Technology Research and Development Program of China Railway Corporation (Grant No.2015G001-G)
文摘China railways track structure II (CRTS II) slab ballastless track on bridge is one kind of track structures unique to China. Its main bearing component of longitudinal force is the continuous base plate rather than rail. And the track-bridge interaction is weakened by the sliding layer installed between base plate and bridge deck. In order to study the dynamic response of CRTS II slab ballastless track on bridge under seismic action, a 3D nonlinear dynamic model for simply-supported bridges and CRTS II track was established, which considered structures such as steel rail, fasteners, track plate, mortar layer, base plate, sliding layer, bridge, consolidation, anchors, stoppers, etc. Then its force and deformation features under different intensities of seismic excitation were studied. As revealed, the seismic response of the system increases with the increase of seismic intensity. The peak stresses of rail, track plate and base plate all occur at the abutment or anchors. Both track plate and base plate are about to crack. Besides, the rapid relative displacement between base plate and bridge deck due to the small friction coefficient of sliding layer is beneficial to improve the seismic performance of the system. During the earthquake, a large vertical displacement appears in base plate which leads to frequent collisions between stoppers and base plate, as a result, stoppers may be damaged.
