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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 [...]

High-performance overmodulation strategies for voltage source inverters (VSIs) can further broaden the operation range of machines. Among them, Space Vector Pulse Width Modulation (SVPWM) is worth researching as it performs well in digital implementation. This paper presents a detailed comparison of various SVPWM overmodulation strategies and analysis of their performance. It firstly briefly elaborates fundamental laws of two subspaces of five-phase VSIs. Then, it focuses on several overmodulation strategies. Their corresponding basic principles and main characteristics are researched, and conclusions are given. In addition, differences and relationships between them are proved and summarized. Lastly, comparative simulations and experiments were carried out and verify that in the overmodulation region, the output voltage distortion degree increases with the increase in modulation ratio, and strategies with more control degrees of freedom (CDFs) are capable of better controlling the third harmonic subspace, which means that higher-quality output voltage waveforms would be obtained. [ABSTRACT FROM AUTHOR]

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]

Aims: Due to a prolonged period of national and regional lockdown measures during the coronavirus (COVID-19) pandemic, there has been an increase reliance on informal care for informal carers. In light of this, the current study compared the experiences of carers and non-carers on various mental health and wellbeing measures across six key time points during the pandemic. Methods: Data analysed were from the University College London (UCL) COVID -19 Social Study. Our study focused on six time points in England: (1) the first national lockdown (March–April 2020); (2) the beginning of first lockdown rules easing (May 2020); (3) the second national lockdown (November 2020); (4) the third national lockdown (January 2021); (5) the easing of the third lockdown (March 2021); and (6) the end of restrictions (July–August 2021). We considered five mental health and wellbeing measures: depressive symptoms, anxiety symptoms, loneliness, life satisfaction, and sense of being worthwhile. Propensity score matching was applied for the analyses. Results: We found that informal carers experienced higher levels of depressive and anxiety symptoms than non-carers across much of the pandemic. During the first national lockdown, carers also experienced a higher sense of life being worthwhile. No association was found between informal caring responsibilities and levels of loneliness and life satisfaction. Conclusion: Given that carers are an essential national healthcare support, especially during a pandemic, it is crucial to integrate carers' needs into healthcare planning and delivery. These results highlight that there is a pressing need to provide adequate and targeted mental health support for carers during and following this pandemic. [ABSTRACT FROM AUTHOR]

To Bourdieu, interaction with culture has symbolic power and drives the manifestation of social stratification. Many have adapted his theory and methodology, developing new models of cultural engagement. Here, to further integrate these theoretical and methodological approaches, Bourdieu's tools were used to operationalise and interpret a Latent Class Analysis of cultural engagement in the Understanding Society dataset. Six classes of increasing engagement were established, and were increasingly correlated with youth, capital and social advantage. However, some qualitative differences in engagement were also seen. The classes also varied by which characteristics correlated with membership. For example, economic capital was associated with sports engagement, while advantaged social position was associated with broad-scale engagement. Overall, this analysis combined Bourdieusian theory with contemporary methodology in the largest representative UK dataset and highlights the broader relevance of cultural engagement patterns in indicating (and possibly generating) status, identity, capital and social position. [ABSTRACT FROM AUTHOR]

Background: The coronavirus disease 2019 (COVID-19) pandemic has brought about significant behavioural changes, one of which is increased time spent at home. This could have important public health implications. This study aimed to explore longitudinal patterns of 'home confinement' (defined as not leaving the house/garden) during the COVID-19 pandemic, and the associated predictors and mental health outcomes. Methods: Data were from the UCL COVID-19 Social Study. The analytical sample consisted of 25 390 adults in England who were followed up for 17 months (March 2020–July 2021). Data were analysed using growth mixture models. Results: Our analyses identified three classes of growth trajectories, including one class showing a high level of persistent home confinement (the home-confined, 24.8%), one changing class with clear alignment with national containment measures (the adaptive, 32.0%), and one class with a persistently low level of confinement (the unconfined, 43.1%). A range of factors were associated with the class membership of home-confinement trajectories, such as age, gender, income, employment status, social relationships and health. The home-confined class had the highest number of depressive (diff = 1.34–1.68, p < 0.001) and anxiety symptoms (diff = 0.84–1.05, p < 0.001) at the end of the follow-up than the other two classes. Conclusions: There was substantial heterogeneity in longitudinal patterns of home confinement during the COVID-19 pandemic. People with a persistent high level of confinement had the worst mental health outcomes, calling for special attention in mental health action plans, in particular targeted interventions for at-risk groups. [ABSTRACT FROM AUTHOR]

Purpose: Although arts engagement holds promise for reducing loneliness and enhancing social support, previous research has focussed on older adults. We investigated whether arts engagement was associated with loneliness and social support during adolescence. Methods: We included 11,780 adolescents aged 11–21 years from the National Longitudinal Study of Adolescent to Adult Health, a nationally representative cohort study. We measured whether adolescents engaged in school-based arts activities (band, book club, chorus, choir, cheerleading, dance, drama club, newspaper, orchestra) at wave one (1994–1995). Loneliness and perceived social support from peers were measured at waves one and two (1996). We used logistic regression to test whether arts engagement was associated with concurrent and subsequent loneliness and social support. Results: Arts engagement was not associated with concurrent or subsequent loneliness. Compared to not engaging, doing one or more school-based arts activities was associated with 59% higher odds of high social support concurrently (odds ratio [OR] = 1.59, 95% CI = 1.32–1.91). However, this cross-sectional association was attenuated after adjusting for demographic, socioeconomic, and health-related covariates (adjusted OR [AOR] = 1.16, 95% CI = 0.95–1.42). In contrast, doing arts activities was associated with 28% higher odds of reporting high social support one year later (AOR = 1.28, 95% CI = 1.03–1.59), independent of covariates and previous social support. Conclusions: Extracurricular arts activities are associated with increased odds of reporting good subsequent social support from peers. This may be because they provide opportunities for social engagement, developing friendships, and building a sense of community. Exploring these associations in more detail should be a priority, enabling better understanding of this strategy for enhancing social ties during adolescence. [ABSTRACT FROM AUTHOR]

This paper studies a method for high-precision acquisition of position signals for permanent magnet direct drive servo motors at low speed. First of all, the problem of poor position feedback accuracy and sensor feedback delay in the low-speed operation of the permanent magnet direct drive servo motor is analyzed. Secondly, through analysis and simulation, it is found that the interpolation method can play a certain role in compensating the rotor position signal. However, when the speed is close to 0, the output signal of the sensor will fluctuate in a short time, which will affect the speed control accuracy. Therefore, this paper uses the observer method to achieve high-precision acquisition of the position signal of the permanent magnet direct drive servo motor at low speed. The observer method adopts the idea of combining the system model and closed-loop control. Additionally, it makes full use of the parameter information of the motor system. The control performance of the motor can be better guaranteed through the design of the observer parameters and the accuracy of the rotor position estimation result has been greatly improved. Finally, an experimental platform for permanent magnet direct drive servo motors is built, and the rotor position signal acquisition method based on the observer method is verified to have good performance through simulation and experiments. Not only the accuracy of the rotor position estimation result is improved, but also the motor control performance is improved, realizing the stable operation of the permanent magnet direct drive servo motor at low speed. [ABSTRACT FROM AUTHOR]

Objectives: There is a social gradient in both arts engagement and wellbeing that may have led to an overestimation of the impact of arts engagement on wellbeing. We tested whether participation in community arts groups was associated with wellbeing after removing confounding by demographic, socioeconomic, and health-related factors. Methods: Using propensity score matching, we analyzed data from 12,055 older adults in the Health and Retirement Study. We measured community arts groups participation and concurrent life satisfaction (evaluative wellbeing), positive and negative affect (experienced wellbeing), and purpose in life, constraints on personal control, and mastery (eudaimonic wellbeing). Results: After matching, arts group participation was associated with higher positive affect (average treatment effect on the treated [ATT] = 0.18, 95% CI = 0.12–0.24), life satisfaction (ATT = 0.09, 95% CI = 0.04–0.15), purpose in life (ATT = 0.07, 95% CI = 0.02–0.13), and mastery (ATT = 0.07, 95% CI = 0.01–0.14) than not participating. Participation was not associated with negative affect or constraints on personal control. In sensitivity analyses, these associations were maintained four years later. Conclusion: Arts group participation was associated with the positive elements of evaluative, experienced, and eudaimonic wellbeing. Facilitating participation in community arts groups could help to promote healthy aging, enabling a growing segment of the population to lead more fulfilling and satisfying lives. [ABSTRACT FROM AUTHOR]

Direct power control (DPC) has gained increasing attention in recent years as a simple and efficient control strategy for pulse width modulation (PWM) rectifiers. In this paper, the idea of DPC is introduced into the three-phase coupled inductor-based bipolar-output active rectifier (TCIBAR) for the first time, and a virtual vector-based direct power control (VVB-DPC) strategy is proposed for TCIBAR to realize the bipolar DC power supply for more electric aircraft (MEA). First, the mathematical model of the TCIBAR is deduced, and the basic principle of the classic DPC strategy is reviewed. On this basis, the limitations of the classic DPC strategy in TCIBAR control are analyzed. Second, a set of virtual vectors are derived to establish a novel virtual-vector switching table. Based on the virtual-vector switching table, the hysteresis power control of TCIBAR can be realized without affecting the DC-side neutral-point potential of TCIBAR. Finally, a neutral-point potential control method based on DPC architecture is studied and integrated into the VVB-DPC strategy to maintain the bipolar DC voltage balance of TCIBAR under unbalanced load conditions. The VVB-DPC strategy is experimentally studied on a TCIBAR prototype, and the experimental results verify the feasibility and effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper presents a novel direct power control (DPC) strategy based on an optimized sector division for a three-phase coupled inductor-based bipolar output active rectifier (TCIBAR) applied in more electric aircraft (MEA). First, based on the instantaneous power theory, the power model of the TCIBAR is built in the synchronous rotating coordinate system. Second, to implement the hysteresis power control of TCIBAR without causing the runaway of the zero-sequence current in the three-phase coupled inductor (TCI), a set of new voltage vectors that have the same zero-sequence voltage (ZSV) component are synthesized and adopted in the proposed DPC strategy. Third, by quantitatively analyzing the effect of the new synthesized voltage vectors on the power variation of TCIBAR, an optimized sector division method is proposed to improve the accuracy of power control and reduce the phase current harmonics in TCIBAR. Finally, to maintain the voltage balance of the bipolar dc ports in TCIBAR, voltage balance control is studied in the proposed DPC strategy. The proposed DPC strategy is researched on an experimental platform of TCIBAR, and the results show that the proposed DPC strategy is feasible and has good static and dynamic performance. [ABSTRACT FROM AUTHOR]

Electric transportation has made rapid developments and significant steps toward the full electrical powertrain systems. With the increased use of electric vehicles energy conversion systems several technologies have been developed and reached a high degree of performance. Since electric vehicles and hybrid are the more cost competitive technology available today, the evolution toward a more reliable powertrain combining different electric powertrain systems is needed. Induction machine and permanent magnet generators/motors integrated powertrains have some significant advantages over other types of systems such as no need of excitation, low volume and weight, high precision, and no use of a complex gearbox for torque/speed conversion. A electric vehicle powertrain for EV propulsion with a induction motor and a matrix converter is proposed in this paper. The induction motor is controlled using the direct torque flux algorithm. The traditional power conversion stages consist of a rectifier followed by an inverter and bulky DC link capacitor. It involves 2 stages of power conversion and, subsequently, the efficiency of the overall EV is reduced because of power quality issues mainly based on total harmonic distortion. The proposed solution incorporates a matrix converter is mainly utilized to control the induction electric motor for propulsion. The matrix converter is a simple and compact direct AC-AC converter. The proposed EV with matrix converter is modeled using PSIM.

Background: There is a growing global awareness of the psychological consequences of long COVID, supported by emerging empirical evidence. However, the emergence and long-term trajectories of psychological symptoms following the infection are still unclear.Aims: To examine when psychological symptoms first emerge following infection with SARS-CoV-2 and the long-term trajectories of psychological symptoms comparing long- and short-COVID groups.Method: We analysed longitudinal data from the UCL COVID-19 Social Study (March 2020 to November 2021). We included data from adults living in England who reported contracting SARS-CoV-2 by November 2021 (n = 3115). Of these, 15.9% reported having had long COVID (n = 495). They were matched to participants who had short COVID using propensity score matching on a variety of demographic, socioeconomic and health covariates (n = 962 individuals with 13 325 observations) and data were further analysed using growth curve modelling.Results: Depressive and anxiety symptoms increased immediately following the onset of infection in both long- and short-COVID groups. But the long-COVID group had substantially greater initial increases in depressive symptoms and heightened levels over 22 months follow-up. Initial increases in anxiety were not significantly different between groups, but only the short-COVID group experienced an improvement in anxiety over follow-up, leading to widening differences between groups.Conclusions: The findings support work on the psychobiological pathways involved in the development of psychological symptoms relating to long COVID. The results highlight the need for monitoring of mental health and provision of adequate support to be interwoven with diagnosis and treatment of the physical consequences of long COVID. [ABSTRACT FROM AUTHOR]