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The high-order harmonics caused by traditional fixed switching frequency space vector pulse width modulation (SVPWM) technology cause serious electromagnetic interference problems in electric drive systems. Random switching frequency (RSF) SVPWM can be used to solve the problem of severe electromagnetic interference. The principles of SVPWM technology and RSF-SVPWM technology are introduced, and the influence of the increase of the spread spectrum range in RSF-SVPWM strategy on the system is discussed. To achieve good dispersion of high order harmonics in a small spread spectrum range, a novel RSF-SVPWM strategy based on dual frequency division is proposed. Taking the original central switching frequency as the midpoint, the initial complete variation range is divided into two local frequency bands, and their local central frequency points and local spread spectrum range are set. Taking the positive and negative of the ideal β axis voltage component in the two-phase static α-β coordinate system as the standard, after judging the specific frequency division band of each switching cycle, the switching frequency is randomized around the local central frequency point in the frequency division band. The simulation and experimental results show that compared to the traditional RSF-SVPWM strategy with a wider spread spectrum range, the new RSF-SVPWM strategy has equivalent high order harmonic dispersion effect. At the same time, the new RSF-SVPWM reduces the pulsation of the system current loop and outputs a relatively stable electromagnetic torque. The new RSF-SVPWM promotes the application of electric drive systems in high-end industry fields.

There is growing evidence for the impact of arts engagement on later life cognition. However, confounding by socioeconomic factors may have led to an overestimation of this association. We analyzed data from 4,344 older adults in the Wisconsin Longitudinal Study. We measured participatory (e.g. painting, making music, crafts) and receptive (e.g. concert, play, museum) arts engagement separately. Participants completed six neurocognitive tests measuring two distinct domains of cognitive function (episodic/working memory and executive function/language) concurrently and seven years later. We used inverse probability of treatment weighting (IPTW) to remove confounding by a range of demographic and socioeconomic factors. Engaging in participatory or receptive arts for up to one hour per week (but not more frequently) was associated with better subsequent executive function/language. Similarly, engaging in receptive arts activities for up to three hours per week (but not more frequently) was associated with better subsequent episodic/working memory. These effects were of similar sizes to doing vigorous physical activity for up to one hour per week. However, our findings also highlight key methodological issues when exploring the relationship between arts engagement and cognition that should be considered in future studies, including measurement bias, life-course stage, length of follow-up, variation in outcomes, attrition, and missing data. [ABSTRACT FROM AUTHOR]

Background There has been much research into the mental health impact of the Coronavirus Disease 2019 (COVID-19) pandemic and how it is related to time-invariant individual characteristics. However, there is still a lack of research showing long-term trajectories of mental health across different stages of the pandemic. And little is known regarding the longitudinal association of time-varying factors with mental health outcomes. This study aimed to provide a longitudinal profile of how mental health in adults changed across different stages of the COVID-19 pandemic and to examine their longitudinal associations with time-varying contextual (e.g., COVID-19 policy response and pandemic intensity) and individual level factors. Methods and findings This study used data from a large panel study of over 57,000 adults living in England, who were followed up regularly for 2 years between March 2020 and April 2022. Mental health outcomes were depressive and anxiety symptoms. Depressive symptoms were assessed by the Patient Health Questionnaire (PHQ-9) and anxiety symptoms by the Generalized Anxiety Disorder assessment (GAD-7). Entropy balancing weights were applied to restore sample representativeness. After weighting, approximately 50% of participants were female, 14% from ethnic minority backgrounds, with a mean age of 48 years. Descriptive analyses showed that mental health changes were largely in line with changes in COVID-19 policy response and pandemic intensity. Further, data were analysed using fixed-effects (FE) models, which controlled for all time-invariant confounders (observed or not). FE models were fitted separately across 3 stages of the COVID-19 pandemic, including the first national lockdown (21/03/2020-23/08/2020), second and third national lockdowns (21/09/2020-11/04/2021), and 'freedom' period (12/04/2021-14/11/2021). We found that more stringent policy response (measured by stringency index) was associated with increased depressive symptoms, in particular, during lockdown periods ([beta] = 0.23, 95% confidence interval (CI) = [0.18 to 0.28], p < 0.001; [beta] = 0.30, 95% CI = [0.21 to 0.39], p < 0.001; [beta] = 0.04, 95% CI = [-0.03 to 0.12], p = 0.262). Higher COVID-19 deaths were also associated with increased depressive symptoms, but this association weakened over time ([beta] = 0.29, 95% CI = [0.25 to 0.32], p < 0.001; [beta] = 0.09, 95% CI = [0.05 to 0.13], p < 0.001; [beta] = -0.06, 95% CI = [-0.30 to 0.19], p = 0.655). Similar results were also found for anxiety symptoms, for example, stringency index ([beta] = 0.17, 95% CI = [0.12 to 0.21], p < 0.001; [beta] = 0.13, 95% CI = [0.06 to 0.21], p = 0.001; [beta] = 0.10, 95% CI = [0.03 to 0.17], p = 0.005), COVID-19 deaths ([beta] = 0.07, 95% CI = [0.04 to 0.10], p < 0.001; [beta] = 0.04, 95% CI = [0.00 to 0.07], p = 0.03; [beta] = 0.16, 95% CI = [-0.08 to 0.39], p = 0.192). Finally, there was also evidence for the longitudinal association of mental health with individual level factors, including confidence in government/healthcare/essentials, COVID-19 knowledge, COVID-19 stress, COVID-19 infection, and social support. However, it is worth noting that the magnitudes of these longitudinal associations were generally small. The main limitation of the study was its non-probability sample design. Conclusions Our results provided empirical evidence on how changes in contextual and individual level factors were related to changes in depressive and anxiety symptoms. While some factors (e.g., confidence in healthcare, social support) clearly acted as consistent predictors of depressive and/or anxiety symptoms, other factors (e.g., stringency index, COVID-19 knowledge) were dependent on the specific situations occurring within society. This could provide important implications for policy making and for a better understanding of mental health of the general public during a national or global health crisis., Author(s): Feifei Bu, Andrew Steptoe, Daisy Fancourt * Introduction The Coronavirus Disease 2019 (COVID-19) pandemic has caused unprecedented disruptions to the global economy and people's everyday lives. It has presented [...]

Objectives There is evidence to suggest that leisure engagement may influence self-perceptions of aging, but disentangling potential bidirectionality in this relationship is challenging. A better understanding of the directionality of this association is essential for designing more effective interventions to promote healthy aging. We, therefore, tested concurrent effects and lagged effects in both directions for a univariate measure of leisure engagement as well as specific domains of community, cognitive, creative, and physical activities. Methods A total of 17,753 adults aged 50 or above living in the United States from the Health and Retirement Study were included in the analysis. They provided 32,703 observations over 3 waves between 2008/2010 and 2016/2018. Data were analyzed using structural equation modeling with both concurrent and lagged associations between self-perceptions of aging and leisure engagement, controlling for confounders including age, gender, ethnicity, socioeconomic position, and health conditions. Results We found consistent evidence for leisure engagement as a predictor of self-perceptions of aging. There was also evidence for a reciprocal relationship where leisure engagement was predicted by older adults' self-perceptions of aging. Similar results were observed for specific domains of leisure engagement. Discussion Our findings provide empirical support for the potential benefits of leisure engagement on positive self-perceptions of aging, regardless of the type of activities. Our study also highlights the importance to consider the directionality in researching leisure engagement and self-perceptions of aging. [ABSTRACT FROM AUTHOR]