Acoustic array sensor device for partial discharge detection is widely used in power equipment inspection with the advantages of non-contact and precise positioning compared with partial discharge detection methods su...Acoustic array sensor device for partial discharge detection is widely used in power equipment inspection with the advantages of non-contact and precise positioning compared with partial discharge detection methods such as ultrasonic method and pulse current method.However,due to the sensitivity of the acoustic array sensor and the influence of the equipment operation site interference,the acoustic array sensor device for partial discharge type diagnosis by phase resolved partial discharge(PRPD)map might occasionally presents incorrect results,thus affecting the power equipment operation and maintenance strategy.The acoustic array sensor detection device for power equipment developed in this paper applies the array design model of equal-area multi-arm spiral with machine learning fast fourier transform clean(FFT-CLEAN)sound source localization identification algorithm to avoid the interference factors in the noise acquisition system using a single microphone and conventional beam forming algorithm,improves the spatial resolution of the acoustic array sensor device,and proposes an acoustic array sensor device based on the acoustic spectrogram.The analysis and diagnosis method of discharge type of acoustic array sensor device can effectively reduce the system misjudgment caused by factors such as the resolution of the acoustic imaging device and the time domain pulse of the digital signal,and reduce the false alarm rate of the acoustic array sensor device.The proposed method is tested by selecting power cables as the object,and its effectiveness is proved by laboratory verification and field verification.展开更多
The pulse current method,acoustic and ultrasonic partial discharge(PD)detection,and voiceprint PD detection are commonly used detection methods for the PD detection of power equipment.To study the characteristics of P...The pulse current method,acoustic and ultrasonic partial discharge(PD)detection,and voiceprint PD detection are commonly used detection methods for the PD detection of power equipment.To study the characteristics of PD signals of typical discharge models based on the principles of the above three detection methods,an acoustic detection experimental system consisting of a needle-tip model and a surface model was built.Acoustic tests were carried out on needle-tip models with different curvature radii and surface discharge models with different lengths of conductive paste.The experimental results showed that acoustic and ultrasonic PD detection and voiceprint PD detection exhibited different sensitivities to the needle-tip discharge models,and the combination of acoustic and ultrasonic PD and voiceprint PD detection was more beneficial for the comprehensive detection of cable PD signals.Based on voiceprint recognition technology,this study drew FFT(Fast Fourier Transformation)diagrams of different types of PD acoustic signals and analyzed the differences in the ultrasonic signal frequency distribution.The frequency band of the voiceprint PD signal of the needle-tip discharge models was concentrated in the range 17-27 kHz,and the frequency band of the voiceprint PD signal of the conductive paste discharge models was concentrated in the range 20-25 kHz.The measurement of voiceprint PD signals in these frequency bands were strengthened when the PD of a cable was detected on-site,which provides the basis for the use of the cable model for on-site PD detection.展开更多
There is an urgent demand to explore new approaches of improving the electric breakdown strength of the ferroelectric thin-film capacitor without the degradation of the high dielectric constant.In this work,LaNiO_(3)/...There is an urgent demand to explore new approaches of improving the electric breakdown strength of the ferroelectric thin-film capacitor without the degradation of the high dielectric constant.In this work,LaNiO_(3)/Ba_(0.67)Sr_(0.33)TiO_(3)(LNO/BST) thin film and SrTiO_(3)(STO)/LNO/BST/SrTiO_(3)(STO) were prepared by using radio frequency(RF) magnetron sputtering technique and ultrathin STO insulator layers were inserted between the LNO/BST and metal electrodes(Au or Pt) to improve the electric breakdown strength and the leakage current of the LNO/BST thin film.X-ray diffraction(XRD) and scanning electron microscopy(SEM) investigations revealed that these multilayer thin films show compact,smooth and uniform morphologies.The leakage current density of STO/LNO/BST/STO thin film was decreased by one order of magnitude and breakdown strength of STO/LNO/BST/STO thin film was enhanced from 0.72 to 1.26 MV-cm-1compared with that of LNO/BST thin film.Moreover,the dielectric constant of the STO/LNO/BST/STO thin film keeps at the same level as that of LNO/BST thin film,and dielectric loss of the STO/LNO/BST/STO thin film was decreased slightly compared with that of LNO/BST thin film.展开更多
Mutual influence may be driven by different models and operating mechanisms of grounding systems in multi-in-one substations.Even equipment damage and personal injury will occur in the event of a short-circuit or ligh...Mutual influence may be driven by different models and operating mechanisms of grounding systems in multi-in-one substations.Even equipment damage and personal injury will occur in the event of a short-circuit or lightning strike.To meet the construction requirements of different multi-in-one substations,two typical application modes of grounding systems in multi-in-one substations are analyzed in this paper:plane and longitudinal layout schemes.First,the safety index and withstand voltage of secondary equipment in multi-in-one substations are introduced.Second,the plane layout scheme of grounding grids is examined.Based on a 35-kV multi-in-one substations in Shanghai,it was verified that the overall grounding grid needs to be laid to meet the safety of secondary equipment in the station.Finally,considering that it is feasible to rebuild the upper layer of a substation,the longitudinal layout scheme of the grounding grid in multi-in-one substations is also examined.Safety assessment is carried out in terms of aspects such as short-circuits and lightning strikes,and relevant optimization construction methods are analyzed.In this study,a real 35-kV substation in Shanghai was selected as an example.Simulation and field tests based on Current Distribution,Electromagnetic Fields,Grounding and Soil Structure Analysis(CDEGS)software verified that the proposed construction scheme can achieve safe operation of multi-in-one substations.This construction idea can also serve as a reference for the future construction of multi-in-one substations.展开更多
Objective： To study the possibility of using portions of deepithelialized myocutaneous flaps to the reconstruction of thoracic tracheal defects after resection of a large tumor. Methods： From June 2007 to June 2012,...Objective： To study the possibility of using portions of deepithelialized myocutaneous flaps to the reconstruction of thoracic tracheal defects after resection of a large tumor. Methods： From June 2007 to June 2012, five cases of defects of the thoracic trachea were reconstructed by applying portions of deepithelialized myocutaneous flaps. The patients were 27-61 years old with 4 male cases and 1 female. The cervical trachea ranged in diameter from 4-8.5 cm with circumferences of approximately 1/3-2/5 of the bronchial circumference. Results： M1 five patients with thoracic tracheal defects after resection of a large tumor were cured of portions of deepithelialized myocutaneous flaps, with no tracheal stricture remaining and vomica successfully eliminated. During the first 1 to 3 months after the operation, bronchoscopy showed that the tracheal lumens were smooth, and the visible skin of the musculocutaneous flaps became gray and exhibited a small amount of white discharge. Conclusions： Despite this being a small series and short follow-up, this thoracic tracheal reconstruction with portions of deepithelialized myocutaneous flaps shows encouraging preliminary results and could be an alternative to other methods for the treatment of carefully selected patients with thoracic tracheal defects.展开更多
Strategic management oriented enterprise internal control is an inevitable choice after the enterprise develops to a certain scale,and it is also an important starting point for enterprises to adjust their own strateg...Strategic management oriented enterprise internal control is an inevitable choice after the enterprise develops to a certain scale,and it is also an important starting point for enterprises to adjust their own strategic layout and resource allocation.With the continuous expansion of the scope of internal control supervision,the traditional mode of internal control supervision has become more and more restricted.In view of this,the present study started from the necessity of internal control supervision from the overall and top-level perspectives,and analyzed the current problems in the internal control of enterprises from the perspective of strategic management.The problems include the lack of methods and tools of strategic management,insufficient awareness of strategic risk management,insufficient expansion of internal control objects,insufficient prior intervention in internal control supervision,etc.Finally,it came up with the idea of constructing strategic enterprise internal control,in order to provide an effective reference for the study of enterprise internal control.展开更多
基金This work was supported by the science and technology project of State Grid Shanghai Municipal Electric Power Company(No.52090020007F)National Key R&D Program of China(2017YFB0902800).
文摘Acoustic array sensor device for partial discharge detection is widely used in power equipment inspection with the advantages of non-contact and precise positioning compared with partial discharge detection methods such as ultrasonic method and pulse current method.However,due to the sensitivity of the acoustic array sensor and the influence of the equipment operation site interference,the acoustic array sensor device for partial discharge type diagnosis by phase resolved partial discharge(PRPD)map might occasionally presents incorrect results,thus affecting the power equipment operation and maintenance strategy.The acoustic array sensor detection device for power equipment developed in this paper applies the array design model of equal-area multi-arm spiral with machine learning fast fourier transform clean(FFT-CLEAN)sound source localization identification algorithm to avoid the interference factors in the noise acquisition system using a single microphone and conventional beam forming algorithm,improves the spatial resolution of the acoustic array sensor device,and proposes an acoustic array sensor device based on the acoustic spectrogram.The analysis and diagnosis method of discharge type of acoustic array sensor device can effectively reduce the system misjudgment caused by factors such as the resolution of the acoustic imaging device and the time domain pulse of the digital signal,and reduce the false alarm rate of the acoustic array sensor device.The proposed method is tested by selecting power cables as the object,and its effectiveness is proved by laboratory verification and field verification.
基金supported by the science and technology project of State Grid Shanghai Municipal Electric Power Company (No. 52090020007F)National Key R&D Program of China (2017YFB0902800)。
文摘The pulse current method,acoustic and ultrasonic partial discharge(PD)detection,and voiceprint PD detection are commonly used detection methods for the PD detection of power equipment.To study the characteristics of PD signals of typical discharge models based on the principles of the above three detection methods,an acoustic detection experimental system consisting of a needle-tip model and a surface model was built.Acoustic tests were carried out on needle-tip models with different curvature radii and surface discharge models with different lengths of conductive paste.The experimental results showed that acoustic and ultrasonic PD detection and voiceprint PD detection exhibited different sensitivities to the needle-tip discharge models,and the combination of acoustic and ultrasonic PD and voiceprint PD detection was more beneficial for the comprehensive detection of cable PD signals.Based on voiceprint recognition technology,this study drew FFT(Fast Fourier Transformation)diagrams of different types of PD acoustic signals and analyzed the differences in the ultrasonic signal frequency distribution.The frequency band of the voiceprint PD signal of the needle-tip discharge models was concentrated in the range 17-27 kHz,and the frequency band of the voiceprint PD signal of the conductive paste discharge models was concentrated in the range 20-25 kHz.The measurement of voiceprint PD signals in these frequency bands were strengthened when the PD of a cable was detected on-site,which provides the basis for the use of the cable model for on-site PD detection.
基金financially supported by the National Natural Science Foundation of China(Nos.u1601208,51802204)。
文摘There is an urgent demand to explore new approaches of improving the electric breakdown strength of the ferroelectric thin-film capacitor without the degradation of the high dielectric constant.In this work,LaNiO_(3)/Ba_(0.67)Sr_(0.33)TiO_(3)(LNO/BST) thin film and SrTiO_(3)(STO)/LNO/BST/SrTiO_(3)(STO) were prepared by using radio frequency(RF) magnetron sputtering technique and ultrathin STO insulator layers were inserted between the LNO/BST and metal electrodes(Au or Pt) to improve the electric breakdown strength and the leakage current of the LNO/BST thin film.X-ray diffraction(XRD) and scanning electron microscopy(SEM) investigations revealed that these multilayer thin films show compact,smooth and uniform morphologies.The leakage current density of STO/LNO/BST/STO thin film was decreased by one order of magnitude and breakdown strength of STO/LNO/BST/STO thin film was enhanced from 0.72 to 1.26 MV-cm-1compared with that of LNO/BST thin film.Moreover,the dielectric constant of the STO/LNO/BST/STO thin film keeps at the same level as that of LNO/BST thin film,and dielectric loss of the STO/LNO/BST/STO thin film was decreased slightly compared with that of LNO/BST thin film.
基金supported by National Natural Science Foundation of China(No.92067105)the science and technology project of State Grid Shanghai Municipal Electric Power Company(No.5209211900VD).
文摘Mutual influence may be driven by different models and operating mechanisms of grounding systems in multi-in-one substations.Even equipment damage and personal injury will occur in the event of a short-circuit or lightning strike.To meet the construction requirements of different multi-in-one substations,two typical application modes of grounding systems in multi-in-one substations are analyzed in this paper:plane and longitudinal layout schemes.First,the safety index and withstand voltage of secondary equipment in multi-in-one substations are introduced.Second,the plane layout scheme of grounding grids is examined.Based on a 35-kV multi-in-one substations in Shanghai,it was verified that the overall grounding grid needs to be laid to meet the safety of secondary equipment in the station.Finally,considering that it is feasible to rebuild the upper layer of a substation,the longitudinal layout scheme of the grounding grid in multi-in-one substations is also examined.Safety assessment is carried out in terms of aspects such as short-circuits and lightning strikes,and relevant optimization construction methods are analyzed.In this study,a real 35-kV substation in Shanghai was selected as an example.Simulation and field tests based on Current Distribution,Electromagnetic Fields,Grounding and Soil Structure Analysis(CDEGS)software verified that the proposed construction scheme can achieve safe operation of multi-in-one substations.This construction idea can also serve as a reference for the future construction of multi-in-one substations.
文摘Objective： To study the possibility of using portions of deepithelialized myocutaneous flaps to the reconstruction of thoracic tracheal defects after resection of a large tumor. Methods： From June 2007 to June 2012, five cases of defects of the thoracic trachea were reconstructed by applying portions of deepithelialized myocutaneous flaps. The patients were 27-61 years old with 4 male cases and 1 female. The cervical trachea ranged in diameter from 4-8.5 cm with circumferences of approximately 1/3-2/5 of the bronchial circumference. Results： M1 five patients with thoracic tracheal defects after resection of a large tumor were cured of portions of deepithelialized myocutaneous flaps, with no tracheal stricture remaining and vomica successfully eliminated. During the first 1 to 3 months after the operation, bronchoscopy showed that the tracheal lumens were smooth, and the visible skin of the musculocutaneous flaps became gray and exhibited a small amount of white discharge. Conclusions： Despite this being a small series and short follow-up, this thoracic tracheal reconstruction with portions of deepithelialized myocutaneous flaps shows encouraging preliminary results and could be an alternative to other methods for the treatment of carefully selected patients with thoracic tracheal defects.
文摘Strategic management oriented enterprise internal control is an inevitable choice after the enterprise develops to a certain scale,and it is also an important starting point for enterprises to adjust their own strategic layout and resource allocation.With the continuous expansion of the scope of internal control supervision,the traditional mode of internal control supervision has become more and more restricted.In view of this,the present study started from the necessity of internal control supervision from the overall and top-level perspectives,and analyzed the current problems in the internal control of enterprises from the perspective of strategic management.The problems include the lack of methods and tools of strategic management,insufficient awareness of strategic risk management,insufficient expansion of internal control objects,insufficient prior intervention in internal control supervision,etc.Finally,it came up with the idea of constructing strategic enterprise internal control,in order to provide an effective reference for the study of enterprise internal control.
