In order to improve the accuracy of cable fault position location at a low cost and make the testing results intuitive, a cable fault detector based on wave form reconstruction is designed. In this detector, the cable...In order to improve the accuracy of cable fault position location at a low cost and make the testing results intuitive, a cable fault detector based on wave form reconstruction is designed. In this detector, the cable fault position is located based on the time-domain pulse reflection （TDR） principle. A pulse waveform is injected in the tested cable, and a high-speed comparator with changeable reference voltages is used to binarize the test pulse waveform to a binary sequence on a certain voltage. Through scanning the reference voltage in a full voltage range, multi-sequences are acquired to reconstruct the pulse waveform transmission in the cable, and then the pulse attenuation feature, electrical open circuit fault, electrical short circuit fault, and the fault position of the cable are diagnosed. Experimental results show that the designed cable fault detector can determine the fault type and its position of the cable being tested, and the testing results are intuitive.展开更多
Aiming at the problem of pedestrian bridge vibration measurement,a vibration measurement system of pedestrian bridge with dual magnetic suspension vibrator structure was designed according to absolute vibration measur...Aiming at the problem of pedestrian bridge vibration measurement,a vibration measurement system of pedestrian bridge with dual magnetic suspension vibrator structure was designed according to absolute vibration measurement principle. The relationship between the magnetic repulsion force of vibrator and its displacement was obtained by the experimental method and the least square fitting method. The vibration equations of two magnetic suspension vibrators were deduced respectively,and the measurement sensitivity of the system was deduced. The amplitude-frequency characteristic of the system was studied. A simulation model of vibrator measurement system with double magnetic suspension vibrator was established. The analysis shows that the sensitivity of the vibration measurement system with double magnetic suspension vibrator is higher than that with single magnetic suspension vibrator. The four vibration waveforms were measured,that is,no one passes through a pedestrian bridge,there are cars running under the pedestrian bridge,single pedestrian passes through the pedestrian bridge and multiple pedestrians pass through the pedestrian bridge. The multi-scale one-dimensional wavelet decomposition function was used to analyze the vibration signals. The vibration characteristics were obtained using one dimension wavelet decomposition function under four different conditions. Finally,the vibration waveforms of four cases were reconstructed. The measured results show that the vibration measurement system of pedestrian bridge with double magnetic suspension vibrator structure has high measurement sensitivity. The design has a certain value to monitor a pedestrian bridge.展开更多
With the recent development of diversity electro-optic sampling(DEOS),significant progress has been made in the range of applicability of single-shot EOS measurements,allowing broadband THz waveforms to be captured in...With the recent development of diversity electro-optic sampling(DEOS),significant progress has been made in the range of applicability of single-shot EOS measurements,allowing broadband THz waveforms to be captured in a single shot over large temporal windows.In addition to the decrease in acquisition time compared to standard multishot data acquisition,this technique allows measurements on systems far from equilibrium with large shotto-shot noise or with irreversible or poorly repeatable dynamics.Although DEOS has been demonstrated and verified for linearly polarized THz waveforms,we investigate the effects resulting from the presence of a secondary polarization component.This imposes new challenges for accurate waveform reconstruction,and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field.We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both x-and y-THz fields simultaneously with a single(110)-cut EO crystal for THz polarimetry and ellipsometry over a wide range of frequencies.展开更多
基金The National Natural Science Foundation of China(No.61240032)the Natural Science Foundation of Jiangsu Province(No.BK2012560)+1 种基金the College Scientific and Technological Achievements Transformation Promotion Project of Jiangsu Province(No.JH-05)the Science and Technology Support Program of Jiangsu Province(No.BE2012740)
文摘In order to improve the accuracy of cable fault position location at a low cost and make the testing results intuitive, a cable fault detector based on wave form reconstruction is designed. In this detector, the cable fault position is located based on the time-domain pulse reflection （TDR） principle. A pulse waveform is injected in the tested cable, and a high-speed comparator with changeable reference voltages is used to binarize the test pulse waveform to a binary sequence on a certain voltage. Through scanning the reference voltage in a full voltage range, multi-sequences are acquired to reconstruct the pulse waveform transmission in the cable, and then the pulse attenuation feature, electrical open circuit fault, electrical short circuit fault, and the fault position of the cable are diagnosed. Experimental results show that the designed cable fault detector can determine the fault type and its position of the cable being tested, and the testing results are intuitive.
基金supported by the Chinese National Natural Science Foundation under Grant (51377037)
文摘Aiming at the problem of pedestrian bridge vibration measurement,a vibration measurement system of pedestrian bridge with dual magnetic suspension vibrator structure was designed according to absolute vibration measurement principle. The relationship between the magnetic repulsion force of vibrator and its displacement was obtained by the experimental method and the least square fitting method. The vibration equations of two magnetic suspension vibrators were deduced respectively,and the measurement sensitivity of the system was deduced. The amplitude-frequency characteristic of the system was studied. A simulation model of vibrator measurement system with double magnetic suspension vibrator was established. The analysis shows that the sensitivity of the vibration measurement system with double magnetic suspension vibrator is higher than that with single magnetic suspension vibrator. The four vibration waveforms were measured,that is,no one passes through a pedestrian bridge,there are cars running under the pedestrian bridge,single pedestrian passes through the pedestrian bridge and multiple pedestrians pass through the pedestrian bridge. The multi-scale one-dimensional wavelet decomposition function was used to analyze the vibration signals. The vibration characteristics were obtained using one dimension wavelet decomposition function under four different conditions. Finally,the vibration waveforms of four cases were reconstructed. The measured results show that the vibration measurement system of pedestrian bridge with double magnetic suspension vibrator structure has high measurement sensitivity. The design has a certain value to monitor a pedestrian bridge.
文摘With the recent development of diversity electro-optic sampling(DEOS),significant progress has been made in the range of applicability of single-shot EOS measurements,allowing broadband THz waveforms to be captured in a single shot over large temporal windows.In addition to the decrease in acquisition time compared to standard multishot data acquisition,this technique allows measurements on systems far from equilibrium with large shotto-shot noise or with irreversible or poorly repeatable dynamics.Although DEOS has been demonstrated and verified for linearly polarized THz waveforms,we investigate the effects resulting from the presence of a secondary polarization component.This imposes new challenges for accurate waveform reconstruction,and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field.We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both x-and y-THz fields simultaneously with a single(110)-cut EO crystal for THz polarimetry and ellipsometry over a wide range of frequencies.
