The influence of eddy viscosity on the distribution of subtropical quasi-stationary planetary waves in summer is analysed theoretically.It is found that since the basic flow is very weak,the eddy viscosity may play an...The influence of eddy viscosity on the distribution of subtropical quasi-stationary planetary waves in summer is analysed theoretically.It is found that since the basic flow is very weak,the eddy viscosity may play an impor- tant role for the subtropical planetary-scale motion in summer. A linear,quasi-geostrophic,34-level spherical coordinate model is also utilized to calculate the differences of quasi-stationary planetary waves and of quasi-stationary disturbance pattern responding to forcing by topography and heat sources under the different eddy viscosities.The computed results show that the coefficient of eddy viscosity considerably influences the strength of the subtropical planetary-scale circulation in summer.展开更多
A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks...A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks of different depths were detected through the designed detection system. The characteristics of micro-cracks can be clearly showed after signals processing through the short-time Fourier transform（ STFT）. By changing the parameter and its value in detecting process,the factors including the excitation frequency and amplitude,the lift-off effect and the scanning direction were discussed,respectively. The results showed that the differential excitation probe was insensitive to dimension and surface state of the tested specimen,while it had a high degree of recognition for micro-crack detection. Therefore,when the differential excitation detection technology was used for inspecting micro-crack of turbine blade in aero-engine,and smoothed pseudo Wigner-Ville distribution was used for signal processing,micro-cracks of 0. 3 mm depth and 0. 1 mm width could be identified. The experimental results might be useful for further research on engineering test of turbine blades of aero-engine.展开更多
文摘The influence of eddy viscosity on the distribution of subtropical quasi-stationary planetary waves in summer is analysed theoretically.It is found that since the basic flow is very weak,the eddy viscosity may play an impor- tant role for the subtropical planetary-scale motion in summer. A linear,quasi-geostrophic,34-level spherical coordinate model is also utilized to calculate the differences of quasi-stationary planetary waves and of quasi-stationary disturbance pattern responding to forcing by topography and heat sources under the different eddy viscosities.The computed results show that the coefficient of eddy viscosity considerably influences the strength of the subtropical planetary-scale circulation in summer.
基金Supported by the Ministerial Level Advanced Research Foundation(051317030586)Ph.D.Programs Foundation of the Ministry of Education of China(20121101110018)
文摘A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks of different depths were detected through the designed detection system. The characteristics of micro-cracks can be clearly showed after signals processing through the short-time Fourier transform（ STFT）. By changing the parameter and its value in detecting process,the factors including the excitation frequency and amplitude,the lift-off effect and the scanning direction were discussed,respectively. The results showed that the differential excitation probe was insensitive to dimension and surface state of the tested specimen,while it had a high degree of recognition for micro-crack detection. Therefore,when the differential excitation detection technology was used for inspecting micro-crack of turbine blade in aero-engine,and smoothed pseudo Wigner-Ville distribution was used for signal processing,micro-cracks of 0. 3 mm depth and 0. 1 mm width could be identified. The experimental results might be useful for further research on engineering test of turbine blades of aero-engine.
