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Inverter-fed motors are damaged due to pulse voltage. The situation leads to early failure of insulation. Polyimide is an important insulating material in the inverter-fed motors. Its insulation aging process and failure mechanism are different from traditional ac and dc voltage. In this paper, structure change of polyimide film aging under pulse voltage above partial discharge inception voltage (PDIV) is investigated through scanning electron microscopy (SEM), thermally stimulated current (TSC) and lifetime test. It reveals that the degradation of structure in polyimide propagates from surface to interior with continuous aging, creating three layers in section. In the TSC spectrum, two main well-resolved peaks, namely α and β, exist in the 20-200°C range. The configuration corresponding to α peak in polyimide is damaged more severely than the configuration corresponding to β peak and its degradation is accelerated with increase in frequency. [ABSTRACT FROM AUTHOR]

As a core component of ac drive electric locomotive, performance of inverter-fed motor directly influences the stability and reliability of locomotive running. However, insulation early failures occur frequently. Presently, polyimide film, as a special type of engineering plastic film, widely applied in turn to turn insulation and turn to ground insulation of inverter-fed motors is a kind of basic insulating material. This paper investigates charge transport mechanism and space charge characteristics of polyimide films based on measuring and comparing space charge accumulation threshold field between corona-resistant and common polyimide films and analyzing the effect of temperature on space charge distribution. The results reveal that space charge accumulation threshold field of corona-resistant polyimide film is higher than that of common polyimide film; the adding of nano-particles effectively increases dielectric properties of corona-resistant film. Additionally, raising temperature promotes the electrode injecting charge and increases the charge energy and conductivity which gradually enhances space charge number and extends trapping position into the bulk, closely related to polyimide film insulation aging and breakdown which is an important characteristic. [ABSTRACT FROM AUTHOR]

We report on a coupling method, which transfers energy of a light beam from free space into a symmetrical metal-cladding optical waveguide from the top surface without employing the prism, grating, tapered film, and other coupling components. In the experiment, a glass flat with a thickness about 100 μm, sandwiched between two gold films is used as a guiding layer. A top gold film of 46 nm thick serves as a coupling layer as well as the cladding and a base gold film of 200 nm serves as the substrate of the waveguide. Up to 50% of the incident light energy fed into the waveguide has been demonstrated. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Objective: To verify the safety and efficacy of the domestic 3D cardiac electrophysiological mapping system for catheter ablation of persistent atrial fibrillation (AF)., Methods: From December 2011 to April 2014, 255 patients (184 male) with persistent AF in 13 centers were enrolled in this multicenter prospective controlled study.The patients were allocated to catheter ablation group (experiment group) and antiarrhythmics drugs cardioversion group (control group) with the ratio 2∶1 according to the patients' intention. Left atria were constructed with 3D cardiac electrophysiology mapping system, magnetic sensored saline irrigated radiofrequency ablation catheter (FireMagic™ Cool 3D) and surface reference (Columbus™). Pulmonary vein isolation and left atrial roof line, mitral annulus isthmus line, three tricuspid annulus isthmus line, superior vena cava, the coronary sinus and complex atrial fragmented potentials were targeted if necessary under the guidance of the 3D mapping system. Antiarrhythmics drugs (except amiodarone) were applied to patients for 2 to 3 months after ablation. The patients were followed up for 9 months after 3 months blanking period. The patients in the control group underwent cardioversion with amiodarone and electrical cardioversion if needed. Patients in the control group were also followed up for 9 months., Results: Of the 255 patients, 167 cases were in the experiment group and 88 cases were in the control group. In per protocol set (PPS), 155 cases were in the experiment group, 79 cases in the control group. Catheter ablation was successful for all patients in the experiment group under the guidance of the 3D cardiac electrophysiological mapping system. Pumononary veins isolation was achieved in all patients. After 9 months follow-up beyond blanking period, in full analysis set, the success rate was 66.5% (111/167) in the experiment group, which was significantly higher than that in the control group (21.6% (19/88), P<0.001). In PPS, the success rate was also significantly higher in the experiment group than in the control group (67.1% (104/155) vs. 22.8%(18/79), P<0.001). The incidence of adverse events was 19.8% in the experiment group and 13.6% in the control group(P=0.223). The adverse events associated with catheter ablation included 1 case of left subclavian hematoma, 1 case of left subclavian bleeding and 1 case of pericardial effusion, which was alleviated by pericardiocentesis. No pulmonary vein stenosis occurred., Conclusion: Domestic 3D cardiac electrophysiological mapping system can safely and effectively guide catheter ablation of persistent AF.

Objective: To investigate the long-term effect of biventricular (BIV) and right ventricular apical (RVA) pacing on cardiac function in patients with high-degree atrioventricular block (AVB) and left ventricular ejection fraction(LVEF)over 35%., Methods: A total of 118 consecutive patients with high-degree AVB in six hospitals from East China between May 2009 and December 2012 were enrolled in this randomized, double-blind and parallel controlled study. Patients were randomly assigned to BIV and RVA pacing with or without LV lead on after one-week cardiac resynchronization therapy (CRT). Cardiac function including New York Heart Association(NYHA), 6 minute walking distance (6MWD), Minnesota living with heart failure (MLHF) score, LVEF, left ventricular end-diastolic volumes/diameters (LVEDV/LVEDD) and other echocardiography parameters, as well as N-terminal pro-B-type natriuretic peptide (NT-proBNP)were assessed at 6 months and 12 months., Results: A total of 114 patients were successfully implanted with CRT. Cardiac function was significantly improved after one-week BIV pacing (n=57) compared with pre-CRT: rate of patients with NYHA Ⅲ (25.44%(29/114) vs. 9.65%(11/114)), MLHF score (17.1±13.6 vs. 26.9±21.6), 6MWD ((315.4±121.8)m vs. (291.8±102.9)m) and NT-proBNP (157.0(70.0, 639.0) ng/L vs. 444.7(144.0, 1 546.0)ng/L, all P<0.05). In BIV group, 6MWD extended from (314.8±142.7)m to (332.7±117.5)m at 6 months (P<0.05), LVEF increased from (60.7±7.9)% at 1 week to (56.6±10.7)% at 6 months(P<0.05), both LVEDV and LVEDD decreased at 12 months compared with at 1 week ((116.2±39.5)ml vs. (131.4±49.6)ml and (50.2±5.6)mm vs. (52.5±6.8)mm, P<0.05). In RVA group (n=57), 6MWD increased at 6 months compared that at 1week ((342.4±109.9)m vs. (310.2±105.1)m, P<0.05), NT-proBNP was higher at 12 months than that at 1 week (349.5(191.8, 884.3)ng/L vs. 127.0(70.3, 336.7)ng/L, P<0.05). Compared with RVA group, BIV group had a bigger shrink in LVEDV decrease at 12 months was more significant in BIV group ((-16.68±24.30)ml vs. (9.09±29.30)ml, P<0.05)., Conclusions: Cardiac pacing could acutely improve the cardiac function in patients with high-degree AVB and LVEF over 35%. Improvements on cardiac function and remodeling are more significant after 12-month BIV pacing than that of RVA pacing. Clinical Trail Registry: Chinese Clinical Trial Registry, ChiCTR-TRC-10000832.

To investigate whether circadian or any other temporal pattern(s) exist in the occurrence of acute myocardial infarction (AMI) in a Chinese population, we analyzed 428 patients with confirmed AMI for temporal patterns of AMI occurrence. The patients admitted to the Affiliated Hospital of Shandong Medical University during 1991-95 were from Jinan, the capital city of Shandong Province of China, which has a population of 2.5 million. The chi-square test for goodness of fit was used to test the difference among the frequencies of AMI occurrence in 4 equal intervals (01.00-07.00 h, 07.00-13.00 h, 13.00-19.00 h, 19.00-01.00 h) during the day and among those on 7 days during the week. The results showed that AMI occurrence exhibited significant circadian (p<0.001) and septadian (day of the week) (p=0.046) periodicity, with a peak at 01.00-07.00 h and a trough at 13.00-19.00 h during the day, and a peak on Saturday and a trough on Wednesday during the week. The peak to trough ratio of risk was 2.7 during the day and 2.1 during the week. It is concluded that there were circadian and septadian biorhythms in AMI occurrence in the Chinese population and that these were different from those observed in Western populations. Further investigation of the underlying mechanisms may shed further light on the trigger mechanisms of AMI and thus be helpful in the prevention and treatment of AMI.