A research on the stability of repair-welding for a great truss under the load

 In this paper, we developed the direct repair welding method without eliminating the load when the repair welding of the great steel truss is going. According to the information about the process and data systematized, working for eliminate defect of welding joint and analyzing used FEM on the stability of the process and result of welding-repair were scientific more than the last time at the great structure.  When do this we did not eliminate defect from the part of joint and so it’s not necessity to use any Jackie and turning back. The result of analysis and construction show that this method is very useful in the practice and by then the problem of stability solved clearly and perfectly and the time and efforts had consumed

Influence of geometric structure, convection, and eddy on sound propagation in acoustic metamaterial with turbulent flow

The problem of reducing noise in the transportation is an important research field to prevent accidents and to provide a civilized environment for people. A material that has recently attracted attention in research to reduce noise is acoustic metamaterial, and most of the research projects so far have been limited to the case of static media without flow. We have studied the sound transmission properties of acoustic metamaterial with turbulent flow to develop acoustic metamaterial that be used in transportation. In this paper, the effect of geometrical structure, the convective effect, and the eddy effect on sound propagation in acoustic metamaterial with turbulent flow are investigated, and the relationships between them are analyzed. The convective effect and the eddy effect both reduce the resonant strength of sound transmission loss resulting from the unique geometry of the acoustic crystal, but shift the resonant frequencies in opposite directions. In addition, when the convective effect and the eddy effect of the airflow, as well as the intrinsic interaction effect generated from the unique geometrical structure of the acoustic metamaterial cannot be ignored, they exhibit competition phenomena with each other, resulting in a widening of the resonance peak. As a result, these three effects cause the shift of the resonance frequency of the sound transmission loss and the widening of the resonance peak. The results of this study show that even in the case of turbulent flow, acoustic metamaterial can be used for transportation by properly controlling the geometric size and shape of the acoustic metamaterial.Comment: 19 pages, 17 figure