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In order to improve the restraint ability of electromagnetic energy in space and improve the coupling efficiency, a magnetic coupler structure with composite magnetic shield is proposed. Firstly, the model is established by using the finite-element simulation software. Then, according to the limit of public exposure to time-varying electromagnetic fields pointed out in ICNIPR (International Commission on Non-Ionizing Radiation Protection) guidelines, the characteristics and spatial magnetic field distribution of magnetic couplers with a single shielding structure, double shielding structure, and composite shielding structure are compared and analyzed. Finally, the experimental results show that the structure of magnetic couplers with a composite magnetic shield has a good effect in strengthening magnetic field concentration and reducing the electromagnetic interference of wireless charging systems to the external environment. It also has the advantages of smaller volume, lighter weight, and lower cost, and can effectively improve the transmission efficiency and enhance the stability of wireless charging systems.

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Objectives How does risk preference change across the life span? We address this question by conducting a coordinated analysis to obtain the first meta-analytic estimates of adult longitudinal age differences in risk-taking propensity in different domains. Methods We report results from 26 longitudinal samples (12 panels; 187,733 unique respondents; 19 countries) covering general and domain-specific risk-taking propensity (financial, driving, recreational, occupational, health) across three or more waves. Results Results revealed a negative relation between age and both general and domain-specific risk-taking propensity. Furthermore, females consistently reported lower levels of risk taking across the life span than males in all domains but there is little support for the idea of an age by gender interaction. Although we found evidence of systematic and universal age differences, we also detected considerable heterogeneity across domains and samples. Discussion Our work suggests a need to understand the nature of heterogeneity of age differences in risk-taking propensity and recommends the use of domain-specific and population estimates for applications interested in modeling heterogeneity in risk preference for economic and policy-making purposes.

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The traditional wireless power transfer circuit uses the full-bridge or half-bridge inverter, which has complex circuit and control and low reliability. To solve these problems, a single-switch LC resonant circuit is proposed, which is simple in structure and can realize zero voltage switching (ZVS) without the problem of shoot-through. The circuit parameters and working process are modeled and analyzed. However, due to the influence of resonance, the common Si devices can not meet the demand because of the high blocking voltage of the switch. For this purpose, the circuit characteristics of SiC-based devices are studied, and the differences of driving and temperature characteristics between SiC MOSFET and Si MOSFET are compared. Finally, a single switch wireless power transfer (WPT) platform based on SiC MOSFET is built, which proves that SiC devices have great advantages in the field of WPT.