The current sound absorption theory which is based on Rayleigh model believes that fibrous material absorb sound by the fluid frictional energy dissipation between the air and the solid fibers. However, Rayleigh model...The current sound absorption theory which is based on Rayleigh model believes that fibrous material absorb sound by the fluid frictional energy dissipation between the air and the solid fibers. However, Rayleigh model is only useful for a quanlitative understanding of effects In a porous material but not for calculation of the acoustical properties of real absorbent. In this paper, a new vibration sound absorption theory which is totally different from classical theory was put forward. The specific acoustic impedance of fiber layers have been derived from the membrane vibration equation and the sound absorption coefficient calculated agree with test results. The new theory can explaIn the phenomenon that thIn fiber layers exhibit less sound absorption coefficient when it was as the cover fabric of sound absorber, but it is more efficient to sound absorption when it was hang as the curtains or have back cavity behind it.展开更多
Design of composites and usage of new polymer materials allows for improvement of constructional properties of belts. Different applications： transmission, conveying or controlling have different meshing in gear. The...Design of composites and usage of new polymer materials allows for improvement of constructional properties of belts. Different applications： transmission, conveying or controlling have different meshing in gear. The work presents meshing model between timing belt and pulley and constructional features of transmission timing belts depending on materials used for their production. While designing timing belt, much attention should be paid to selection of materials, which has significant influence on mechanical properties of belts. This paper attempts to identify the model material and the nature of cooperation of timing belt-pulley; this is basic knowledge for the development of timing belt gear.展开更多
基金Key Laboratory Items of Shanxi Province (No.05JS07)
文摘The current sound absorption theory which is based on Rayleigh model believes that fibrous material absorb sound by the fluid frictional energy dissipation between the air and the solid fibers. However, Rayleigh model is only useful for a quanlitative understanding of effects In a porous material but not for calculation of the acoustical properties of real absorbent. In this paper, a new vibration sound absorption theory which is totally different from classical theory was put forward. The specific acoustic impedance of fiber layers have been derived from the membrane vibration equation and the sound absorption coefficient calculated agree with test results. The new theory can explaIn the phenomenon that thIn fiber layers exhibit less sound absorption coefficient when it was as the cover fabric of sound absorber, but it is more efficient to sound absorption when it was hang as the curtains or have back cavity behind it.
文摘Design of composites and usage of new polymer materials allows for improvement of constructional properties of belts. Different applications： transmission, conveying or controlling have different meshing in gear. The work presents meshing model between timing belt and pulley and constructional features of transmission timing belts depending on materials used for their production. While designing timing belt, much attention should be paid to selection of materials, which has significant influence on mechanical properties of belts. This paper attempts to identify the model material and the nature of cooperation of timing belt-pulley; this is basic knowledge for the development of timing belt gear.
