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In order to study the magnetic field model and transmission characteristics of radial solid permanent magnet coupler deeply, an 11 kW experimental prototype of solid permanent magnet coupler is taken as the object, its operation principle is analyzed in detail, and based on moving magnetic field theory and transient eddy current equation, a complete magnetic field model is established by finite element difference method, distribution of electromagnetic field is solved and the mechanical characteristics curve is drawn, the rated torque, starting torque and maximum torque of the experimental prototype are obtained, operating parameters of the experimental prototype meet the design objectives and have certain overload protection functions. Based on the theory analysis, the structural design and processing assembly of the experimental prototype are completed. An experimental platform was built, the correctness of electromagnetic torque calculation process was verified by dynamic loading experiments. Furthermore, the fluctuating load buffering experiment was performed, and the load fluctuation was reduced to 30%, which proved the flexible transmission characteristics and impact relieved function.

China’s rapid urbanization has greatly boosted the quality of life of its traditionally impoverished regions. Research into the spatial distribution characteristics, evolution and spatial correlation of the quality of life in impoverished regions can help illuminate the experience of successful development and construct a knowledge base for authorities to devise development strategies. This study focuses its attention on the historically impoverished districts and counties (which are designated as parallel administrative units in China) of Guizhou Province in southwestern China. Extensively citing official statistics on districts and counties released by China’s National Bureau of Statistics and local governments, it assesses the quality of life of those places in the 3 years of 2000, 2010, and 2020 from the four dimensions of economy, society, culture, and environment. The aim is to illustrate the distribution characteristics and the evolution of quality of life in Guizhou’s historically impoverished districts and counties. In order to understand the characteristics of spatial clustering as well as the patterns of evolution of the quality of life of Guizhou’s impoverished districts and counties, the study incorporates spatial autocorrelation analysis into a spatio-temporal analysis of local quality of life. It could presumably help enrich the knowledge base that local authorities draw on to formulate development strategies that are scientific and adapted to local conditions. The study found that while the overall quality of life in all the impoverished districts and counties of Guizhou Province has improved, large gaps in quality of life between eastern and western regions of the province persisted. In addition, the driving force behind the evolution in the overall quality of life of those places changed with time, as did the characteristics of the spatial aggregation in quality of life.

Abstract This paper presents a study of bidirectional permanent magnet excited machine (BPMEM) based on the study of field-modulation permanent magnetic gear machine (FPGM). The BPMEM structure includes the installation of consequent-pole permanent magnets (PMs) on both the stator and rotor sides of the FPGM so that the stator and rotor can be bidirectionally excited to increase the working airgap flux density amplitude, reduce the flux leakage between poles, and increase the torque density. Therefore, the paper first analysis the influence of different airgap structures and PM arrangements on the airgap flux density and studies the winding slot–pole combination and the resulting working flux density harmonics to analyse the electromagnetic torque generation mechanism. By using the finite element analysis (FEA), the quantitative analysis and comparison of the FPGM, slot-wedge-less FPGM (SWL-FPGM), consequent-pole FPGM (CP-FPGM) and BPMEM verify the superiority of BPMEM in improving electromagnetic torque. In addition, the paper also studies the key performance of BPMEM’s overload capacity, power factor and flux-weakening capability. Finally, no-load and independent load experiments are carried out on the FPGM prototype to verify the correctness of the FEA model and analysis method of the machine in this paper.

Background: A goal of 10,000 steps per day is widely advocated, but there is little evidence to support that goal. Our purpose was to examine the dose–response relationships between step count and all-cause mortality and cardiovascular disease risk. Methods: Cochrane Central Register of Controlled Trials, EMBASE, OVID, PubMed, Scopus, and Web of Science databases were systematically searched for studies published before July 9, 2021, that evaluated the association between daily steps and at least 1 outcome. Results: Sixteen publications (12 related to all-cause mortality, 5 related to cardiovascular disease; and 1 article contained 2 outcomes: both all-cause death and cardiovascular events) were eligible for inclusion in the meta-analysis. There was evidence of a nonlinear dose–response relationship between step count and risk of all-cause mortality or cardiovascular disease (p = 0.002 and p = 0.014 for nonlinearity, respectively). When we restricted the analyses to accelerometer-based studies, the third quartile had a 40.36% lower risk of all-cause mortality and a 35.05% lower risk of cardiovascular event than the first quartile (all-cause mortality: Q1 = 4183 steps/day, Q3 = 8959 steps/day; cardiovascular event: Q1 = 3500 steps/day, Q3 = 9500 steps/day; respectively). Conclusion: Our meta-analysis suggests inverse associations between higher step count and risk of premature death and cardiovascular events in middle-aged and older adults, with nonlinear dose–response patterns.

As a new type of magnetic transmission structure, asynchronous permanent magnet coupling has wide prospect application in mechanical transmission field. This paper proposes a squirrel cage asynchronous permanent magnet coupling combined with structural characteristics of permanent magnet motor and asynchronous motor. In order to study its magnetic field model and transmission characteristics, according to coupling and nonlinear characteristics of its magnetic field, a separate analytical iterative method is proposed to decompose air gap magnetic field, on one hand, as magnetic source, permanent magnet magnetomotive force is analyzed by equivalent magnetic circuit, on the other hand, as induction armature, reaction magnetomotive force of squirrel cage rotor is analyzed by magnetic induction principle. Then, based on time-varying electromagnetic field theory, the analytical model of air gap magnetic field is established, the accurate electromagnetic torque equation is deduced, and detailed calculation process is summarized. An 18.5kW prototype is designed. According to prototype parameters, magnetic field simulation model is established by finite element simulation software, correctness of theoretical analysis is verified by simulation. The transmission performance and speed regulation characteristics are further analyzed and discussed individually according to conditions of constant torque, constant power and centrifugal load. Finally, the experimental prototype is developed and loading experimental platform is built, correctness of theoretical analysis and calculation results is verified by experiments.