Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thi...Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thickness measurement limits its widespread application. This paper proposes a method that utilizes cylindrical shear horizontal(SH) guided waves to estimate pipeline thickness without prior knowledge of shear wave velocity. The inversion formulas are derived from the dispersion of higher-order modes with the high-frequency approximation. The waveform of the example problems is simulated using the real-axis integral method. The data points on the dispersion curves are processed in the frequency domain using the wave-number method. These extracted data are then substituted into the derived formulas. The results verify that employing higher-order SH guided waves for the evaluation of thickness and shear wave velocity yields less than1% error. This method can be applied to both metallic and non-metallic pipelines, thus opening new possibilities for health monitoring of pipeline structures.展开更多
The sensitivities of the normal modes arrival time to solitary internal waves （IWs） are analyzed by using the SW06 environments. Simulation results show that the arrival time of mode 1 is relatively stable. But, the...The sensitivities of the normal modes arrival time to solitary internal waves （IWs） are analyzed by using the SW06 environments. Simulation results show that the arrival time of mode 1 is relatively stable. But, there are some higher-order normal modes which arrive earlier than mode 1, and fluctuate with the appearance of solitary IWs. Explanation of the phenomenon is given based on ray theory. It is shown that, when thermocline falls down to some depths, those higher-order modes with a group of definite grazing angles mainly propagate above the thermocline and arrive earlier.展开更多
Energy recovery linacs are promising for achieving high average current with superior beam quality.The key component for accelerating such high-current beams is the superconducting radio-frequency cavity.The design of...Energy recovery linacs are promising for achieving high average current with superior beam quality.The key component for accelerating such high-current beams is the superconducting radio-frequency cavity.The design of a 1.3 GHz five-cell high-current superconducting cavity has been carried out under cooperation between Peking University and the Argonne National Laboratory.The radio-frequency properties,damping of the higher order modes,multipacting and mechanical features of this cavity have been discussed and the final design is presented.展开更多
This paper illustrates the design and simulation of a unique 500 MHz single-cell superconducting radio frequency cavity with a fluted beam pipe and a coaxial-type fundamental power coupler. The simulation results show...This paper illustrates the design and simulation of a unique 500 MHz single-cell superconducting radio frequency cavity with a fluted beam pipe and a coaxial-type fundamental power coupler. The simulation results show that the cavity has a high r/Q value, a low peak surface field and a large beam aperture, so it can be a candidate cavity for high current accelerators. With the help of a fluted beam tube, almost all the higher order modes can propagate out of the cavity, especially the first two dipole modes, TE 111 and TM 110 , and the first higher monopole mode, TM 011 . The external quality factor of the coaxial fundamental power coupler is optimized to 1.2 × 10 5 , which will be useful when it is applied in the light source storage ring.展开更多
基金Project supported by the Natural Science Foundation of Jilin Province of China(Grant Nos.20240402081GH and 20220101012JC)the National Natural Science Foundation of China(Grant No.42074139)the State Key Laboratory of Acoustics,Chinese Academy of Sciences(Grant No.SKLA202308)。
文摘Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thickness measurement limits its widespread application. This paper proposes a method that utilizes cylindrical shear horizontal(SH) guided waves to estimate pipeline thickness without prior knowledge of shear wave velocity. The inversion formulas are derived from the dispersion of higher-order modes with the high-frequency approximation. The waveform of the example problems is simulated using the real-axis integral method. The data points on the dispersion curves are processed in the frequency domain using the wave-number method. These extracted data are then substituted into the derived formulas. The results verify that employing higher-order SH guided waves for the evaluation of thickness and shear wave velocity yields less than1% error. This method can be applied to both metallic and non-metallic pipelines, thus opening new possibilities for health monitoring of pipeline structures.
基金supported by the National Natural Science Foundation of China(11174312,11125420)the Office of Naval Research,USA
文摘The sensitivities of the normal modes arrival time to solitary internal waves （IWs） are analyzed by using the SW06 environments. Simulation results show that the arrival time of mode 1 is relatively stable. But, there are some higher-order normal modes which arrive earlier than mode 1, and fluctuate with the appearance of solitary IWs. Explanation of the phenomenon is given based on ray theory. It is shown that, when thermocline falls down to some depths, those higher-order modes with a group of definite grazing angles mainly propagate above the thermocline and arrive earlier.
基金Supported by National High Technology Research and Development Program 863 (2009AA03Z206)
文摘Energy recovery linacs are promising for achieving high average current with superior beam quality.The key component for accelerating such high-current beams is the superconducting radio-frequency cavity.The design of a 1.3 GHz five-cell high-current superconducting cavity has been carried out under cooperation between Peking University and the Argonne National Laboratory.The radio-frequency properties,damping of the higher order modes,multipacting and mechanical features of this cavity have been discussed and the final design is presented.
文摘This paper illustrates the design and simulation of a unique 500 MHz single-cell superconducting radio frequency cavity with a fluted beam pipe and a coaxial-type fundamental power coupler. The simulation results show that the cavity has a high r/Q value, a low peak surface field and a large beam aperture, so it can be a candidate cavity for high current accelerators. With the help of a fluted beam tube, almost all the higher order modes can propagate out of the cavity, especially the first two dipole modes, TE 111 and TM 110 , and the first higher monopole mode, TM 011 . The external quality factor of the coaxial fundamental power coupler is optimized to 1.2 × 10 5 , which will be useful when it is applied in the light source storage ring.
