The characteristics of typical AE signals initiated by mechanical component damages are analyzed. Based on the extracting principle of acoustic emission(AE) signals from damaged components,the paper introduces Wigner ...The characteristics of typical AE signals initiated by mechanical component damages are analyzed. Based on the extracting principle of acoustic emission(AE) signals from damaged components,the paper introduces Wigner high-order spectra to the field of feature extraction and fault diagnosis of AE signals. Some main performances of Wigner binary spectra,Wigner triple spectra and Wigner-Ville distribution (WVD) are discussed,including of time-frequency resolution,energy accumulation,reduction of crossing items and noise elimination. Wigner triple spectra is employed to the fault diagnosis of rolling bearings with AE techniques. The fault features reading from experimental data analysis are clear,accurate and intuitionistic. The validity and accuracy of Wigner high-order spectra methods proposed agree quite well with simulation results. Simulation and research results indicate that wigner high-order spectra is quite useful for condition monitoring and fault diagnosis in conjunction with AE technique,and has very important research and application values in feature extraction and faults diagnosis based on AE signals due to mechanical component damages.展开更多
Objective To evaluate the efficacy of minimally invasive perventricular device closure of ventricular septal defect(VSD). Methods Between September 2011 and February 2013, we collected 40 patients who underwent perven...Objective To evaluate the efficacy of minimally invasive perventricular device closure of ventricular septal defect(VSD). Methods Between September 2011 and February 2013, we collected 40 patients who underwent perventricular closure via a small lower sternal incision(minimally invasive group), aged 15.5±3.5 years(12 months to 32 years) with a body weight of 24.2±7.5 kg(10.8-58.0 kg). The mean size of VSD was 5.6±0.5 mm(2-14 mm). Another 40 patients were included as the surgical group, receiving the conventional surgical repair of VSD. The device of the minimally invasive group was released under the guidance of transesophageal echocardiography. Success rate, cardiac indicators, and clinical outcomes of the 2 groups were compared. Results The patients in the surgical group and those in the minimally invasive group showed similar results in success rate(both 97.5%). The procedure time, intensive care unit stay, hospital stay, and postoperative recovery time in the minimally invasive group were significantly shorter than those in the surgical group(58±21 minutes versus 145±26 minutes, 2±1 days versus 8±3 days, 5±1 days versus 16±6 days, 3±1 days versus 90±20 days, all P<0.05). The minimally invasive group had a higher incidence of conduction anomalies(17.5% versus 2.5%, P<0.05). In the follow-up period of 3-12 months, there was no new residual shunt, noticeable aortic regurgitation, significant arrhythmias, or device failure except for new complications in the surgical group. Conclusions The success rate of minimally invasive perventricular device closure of VSD under transesophageal echocardiography guidance is similar to that of conventional surgical repair, but the short-term outcomes of the minimally invasive approach is much better. Long-term follow-up is necessary to confirm the effectiveness of this technique.展开更多
Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power tr...Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power transformers, and the differentiation from other sources of acoustic emission is of the utmost importance. This paper reports the development of a new sensor concept - a fiber laser sensor based on a phase-shifted chirped fiber grating - for the acoustic emission detection of incipient faults in oil-filled power transformers. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure and improving fault detection and location. The performance of the sensing head is characterized and compared for different surrounding media： air, water, and oil. The results obtained indicate the feasibility of this sensing approach for the industrial development of practical solutions.展开更多
基金Supported by the Project of Hunan Provincial Science and Technology Research (2007FJ3025)
文摘The characteristics of typical AE signals initiated by mechanical component damages are analyzed. Based on the extracting principle of acoustic emission(AE) signals from damaged components,the paper introduces Wigner high-order spectra to the field of feature extraction and fault diagnosis of AE signals. Some main performances of Wigner binary spectra,Wigner triple spectra and Wigner-Ville distribution (WVD) are discussed,including of time-frequency resolution,energy accumulation,reduction of crossing items and noise elimination. Wigner triple spectra is employed to the fault diagnosis of rolling bearings with AE techniques. The fault features reading from experimental data analysis are clear,accurate and intuitionistic. The validity and accuracy of Wigner high-order spectra methods proposed agree quite well with simulation results. Simulation and research results indicate that wigner high-order spectra is quite useful for condition monitoring and fault diagnosis in conjunction with AE technique,and has very important research and application values in feature extraction and faults diagnosis based on AE signals due to mechanical component damages.
文摘Objective To evaluate the efficacy of minimally invasive perventricular device closure of ventricular septal defect(VSD). Methods Between September 2011 and February 2013, we collected 40 patients who underwent perventricular closure via a small lower sternal incision(minimally invasive group), aged 15.5±3.5 years(12 months to 32 years) with a body weight of 24.2±7.5 kg(10.8-58.0 kg). The mean size of VSD was 5.6±0.5 mm(2-14 mm). Another 40 patients were included as the surgical group, receiving the conventional surgical repair of VSD. The device of the minimally invasive group was released under the guidance of transesophageal echocardiography. Success rate, cardiac indicators, and clinical outcomes of the 2 groups were compared. Results The patients in the surgical group and those in the minimally invasive group showed similar results in success rate(both 97.5%). The procedure time, intensive care unit stay, hospital stay, and postoperative recovery time in the minimally invasive group were significantly shorter than those in the surgical group(58±21 minutes versus 145±26 minutes, 2±1 days versus 8±3 days, 5±1 days versus 16±6 days, 3±1 days versus 90±20 days, all P<0.05). The minimally invasive group had a higher incidence of conduction anomalies(17.5% versus 2.5%, P<0.05). In the follow-up period of 3-12 months, there was no new residual shunt, noticeable aortic regurgitation, significant arrhythmias, or device failure except for new complications in the surgical group. Conclusions The success rate of minimally invasive perventricular device closure of VSD under transesophageal echocardiography guidance is similar to that of conventional surgical repair, but the short-term outcomes of the minimally invasive approach is much better. Long-term follow-up is necessary to confirm the effectiveness of this technique.
文摘Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power transformers, and the differentiation from other sources of acoustic emission is of the utmost importance. This paper reports the development of a new sensor concept - a fiber laser sensor based on a phase-shifted chirped fiber grating - for the acoustic emission detection of incipient faults in oil-filled power transformers. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure and improving fault detection and location. The performance of the sensing head is characterized and compared for different surrounding media： air, water, and oil. The results obtained indicate the feasibility of this sensing approach for the industrial development of practical solutions.
