Forced responses of the electromechanical integrated magnetic gear system

The electromechanical integrated magnetic gear (EIMG) is a new type of the magnetic gears, in which the traditional field modulated magnetic gear, drive and control are integrated. Considering the torque wave, the dynamic model of the EIMG system with four subsystems was founded and the resonance responses were discussed. The results show that the strong resonances will occur when the excited frequency is close to the natural frequencies of the inner rotor, the outer ferromagnetic pole-piece and the outer stator torsional modes. The resonances hardly happen when the excited frequency is close to other natural frequencies

Forced vibration frequency response for a permanent magnetic planetary gear

The time and frequency forced responses for the permanent magnetic planetary gear drive were computed and analyzed. The influence of air gap between sun gear and planetary gear to frequency forced responses is discussed. Results show that the changes of air gap have obvious effects on the low frequency vibration amplitude of elements. When air gap is too large or too small, it will seriously affects the dynamic performance of the system. So, selecting rational system structure parameters is very important, which can avoid system elements generating larger vibration

Combination resonances of parametric vibration system of the field modulated magnetic gear

Considering the time-varying magnetic coupling stiffness caused by the component eccentricity, the parametric vibration model of the field modulated magnetic gear (FMMG) system is founded and the corresponding dynamic differential equations are deduced. The expressions of the combination resonances are worked out when the excited frequency is close to the combination frequency between the meshing frequency and the natural frequencies, and the resonance responses are discussed. The results show that the resonance amplitudes are much bigger when the excited frequency is close to the combination frequency between the meshing frequency and the natural frequency of the inner rotor torsional mode than when the frequency is close to other combination frequencies. Meanwhile, because the magnetic coupling stiffnesses are much smaller than the supporting stiffness, the resonance displacement of only one degree of freedom is always much bigger than the displacements of other degrees of freedom. The combination resonances make the stability regions of the FMMG system decrease and worsen the dynamic characteristics. All these can lay the foundation for the parameter optimization of the FMMG system

Dynamic model of field modulated magnetic gear system

Considering the special working principle and the structure of field modulation magnetic gear (FMMG), the magnetic coupling stiffnesses (MCS) are calculated and analyzed by finite element method. A magnetic coupling dynamic model is presented and the dynamic differential equations are founded. The natural frequencies and mode shapes of FMMG system are investigated. The effects of main design parameters on the natural frequencies are discussed. The results show that MCS are much smaller than the meshing stiffnesses of mechanical gears and are affected greatly by system parameters. Six modes of FMMG system have distinctive features, and six natural frequencies change differently as main parameters increase

Free vibration of the electromechanical integrated magnetic gear system

The electromechanical integrated magnetic gear (EIMG), in which the field modulated magnetic gear, drive and control are integrated, is proposed in this paper. The dynamic model of the EIMG system with four subsystems is founded and the model assumptions are given. Then, the electromagnetic coupling stiffnesses are calculated by the finite element method and the dynamic differential equations are deduced. On the basis of the modal analyses of the EIMG system, the changes of the natural frequencies with the system parameters are discussed. The results show that the electromagnetic coupling sitffnesses change periodically with the relative rotation angles. The EIMG system has five torsional modes and five transverse modes, which have entirely different modal characteristics. The natural frequencies of the EIMG system are affected greatly by the system parameters

Risk factors of infection after transarterial chemoembolization for hepatocellular carcinoma: A protocol for systematic review and meta-analysis

Background:Transarterial chemoembolization (TACE) has the characteristics of minimally invasive, strong repeatability and good curative effect, so it is commonly used in the non-operative treatment of hepatocellular carcinoma (HCC). However, infection will occur after TACE, which not only increases the hospitalization time and medical expenses, but also affects the efficacy of TACE treatment. At present, there is a lack of analysis of the risk factors of infection after TACE of patients with HCC. In this study, meta-analysis was used to further explore the risk factors of postoperative infection in patients with HCC after TACE, and to provide strategies for infection prevention and intervention. Methods:To search the literatures about the influencing factors of post-TACE infection in patients with HCC published from the establishment of PubMed, Embase, The Cochrane Library, Web of Science, China Biology Medicine Database, China National Knowledge Infrastructure, China Science and Technology Journal Database, and WANFANG to April 2021. Screening was carried out according to inclusion criteria and exclusion criteria. A meta-analysis was performed using RevMan 5.3 software. Results: We disseminated the findings of this systematic review and meta-analysis via publications in peer-reviewed journals. Conclusion: This study systematically reviewed the existing evidence and determined the incidence and predictors of infection after TACE of patients with HCC

Remaining Useful Life Prediction of High-Frequency Swing Self-Lubricating Liner

The remaining useful life (RUL) prediction of self-lubricating spherical plain bearings is essential for replacement decision-making and the reliability of high-end equipment. The high-frequency swing self-lubricating liner (HSLL) is the key component of self-lubricating spherical plain bearings under high-frequency oscillation conditions. In this study, a RUL prediction method was proposed based on the Wiener process and grey system theory. First, the predictive processing of the wear depth was carried out using the grey model GM(1,1) to reduce the randomness and enhance the inherent regularity of the life test data. A degradation process model was established and the RUL was predicted online with the model parameter estimates based on the Bayesian updating strategy. Finally, examples were provided to elaborate the RUL prediction of the HSLL. The results show that the prediction accuracy of the proposed RUL prediction model is higher than that of the simple Wiener process during the entire residual life cycle of the HSLL. Based on the original wear data, the prediction accuracy of the RUL exhibited a strong dependence on prior samples and was relatively low owing to the larger deviation of the wear rate between the test sample and prior samples

Inhaled Long-Acting β2-Agonists Do Not Increase Fatal Cardiovascular Adverse Events in COPD: A Meta-Analysis

<div><p>Background</p><p>The cardiovascular safety of inhaled long-acting β₂-agonists (LABAs) in patients with chronic obstructive pulmonary disease (COPD) is a controversial problem. Certain studies have suggested that inhaled LABAs lead to an increased risk of cardiovascular events in patients with COPD. This meta-analysis aimed to assess the cardiovascular safety of inhaled LABAs in COPD.</p><p>Methods</p><p>A meta-analysis of randomized, double-blind, parallel-group, placebo-controlled trials for LABA treatment of COPD with at least 3 months of follow-up was performed. The fixed-effects model was used to evaluate the effects of LABAs on fatal cardiovascular adverse events. Adverse events were collected for each trial, and the relative risk (RR) and 95% confidence intervals (CI) for LABA/placebo were estimated.</p><p>Results</p><p>There were 24 trials included in this meta-analysis. Compared with placebo, inhaled LABAs significantly decreased fatal cardiovascular adverse events in COPD patients (RR 0.65, 95% CI 0.50 to 0.86, P = 0.002). In sensitivity analysis, there was still no increased risk of fatal cardiovascular events (RR 0.68, 95%CI 0.46 to 1.01, P = 0.06) after excluding the trial with the largest weight. Among the different types of LABAs, only salmeterol had a significant effect (RR 0.64, 95% CI 0.46 to 0.90). In subgroup analyses, inhaled LABAs were able to significantly decrease fatal cardiovascular events in long-term trials (RR 0.64, 95% CI 0.47 to 0.87) and in trials with severe COPD patients (RR 0.69, 95% CI 0.50 to 0.96).</p><p>Conclusion</p><p>Inhaled LABAs do not increase the risk of fatal cardiovascular events in COPD patients.</p></div

A Multi-Objective Semantic Segmentation Algorithm Based on Improved U-Net Networks

The construction of transport facilities plays a pivotal role in enhancing people’s living standards, stimulating economic growth, maintaining social stability and bolstering national security. During the construction of transport facilities, it is essential to identify the distinctive features of a construction area to anticipate the construction process and evaluate the potential risks associated with the project. This paper presents a multi-objective semantic segmentation algorithm based on an improved U-Net network, which can improve the recognition efficiency of various types of features in the construction zone of transportation facilities. The main contributions of this paper are as follows: A multi-class target sample dataset based on UAV remote sensing and construction areas is established. A new virtual data augmentation method based on semantic segmentation of transport facility construction areas is proposed. A semantic segmentation model for the construction regions based on data augmentation and transfer learning is developed and future research directions are given. The results of the study show that the validity of the virtual data augmentation approach has been verified; the semantic segmentation of the transport facility model can semantically segment a wide range of target features. The highest semantic segmentation accuracy of the feature type was 97.56%

Results of Meta-analysis of different inhaled LABAs on fatal cardiovascular events.

<p>Abbreviations: CI, confidence interval; RCT, randomized controlled trials; RR, relative risk</p><p>Results of Meta-analysis of different inhaled LABAs on fatal cardiovascular events.</p