Vehicle air temperature affects drivers’ physiology, psychology, and cognitive abilities. However, the effects are difficult to quantify, especially for jobs related to driving tasks. In this research, 10 male subjects were directly exposed to four different vehicle air temperatures of 20, 23, 26, and 30 °C for 160 min. They were asked to perform cognitive tasks and subjective questionnaires, and 16 channels of EEG signals were monitored in a vehicle cabin. Based on the assessment of the EEG characteristics, the impacts of vehicle air temperature on cognitive abilities and EEG were investigated. The results showed that the cognitive ability of drivers decreased with the rising of the ambient temperature. The subjective questionnaire scores for thermal sensation, thermal comfort and brain load increased as ambient temperature rose; meanwhile, the scores for environmental acceptance, job satisfaction and willingness to work declined. As the ambient temperature rose, the normalized power of θ activity and α activity elevated, and the vigilance and frontal EEG asymmetry decreased. At 20 °C, the completion time of cognitive ability test was the shortest, the number of errors was the smallest, and the drivers could maintain high cognitive ability. At this time, the β activity component of the EEG signal increased, and the level of alertness (AL) and prefrontal asymmetry (FEA) also increased. At 23 °C, drivers’ subjective thermal comfort reached its peak: the EEG wavelet entropy values of the two segments before and after the experiment were the largest, and the wavelet entropy difference was also the largest. A suitable vehicle air temperature aroused β activity and motivation, increased driver alertness and thus enhanced cognitive performance. Therefore, to achieve high cognitive ability and thermal comfort, the vehicle air temperature should be maintained between 20 °C and 23 °C. The research results can provide a reference for the design standards of vehicle air temperature and improve the safety of driving.

In this paper, a novel H-shaped radial phononic crystal (H-RPC) structure is proposed to suppress the anchor loss of a Lamb wave resonator (LWR), which has an ultra-high frequency (UHF) and ultra-wideband gap characteristics. Compared to previous studies on phononic crystal (PC) structures aimed at suppressing anchor loss, the radial phononic crystal (RPC) structure is more suitable for suppressing the anchor loss of the LWR. By using the finite element method, through the research and analysis of the complex energy band and frequency response, it is found that the elastic wave can generate an ultra-wideband gap with a relative bandwidth of up to 80.2% in the UHF range when propagating in the H-RPC structure. Furthermore, the influence of geometric parameters on the ultra-wideband gap is analyzed. Then, the H-RPC structure is introduced into the LWR. Through the analysis of the resonant frequency, it is found that the LWR formed by the H-RPC structure can effectively reduce the vibration energy radiated by the anchor point. The anchor quality factor was increased by 505,560.4% compared with the conventional LWR. In addition, the analysis of the LWR under load shows that the LWR with the H-RPC structure can increase the load quality factor by 249.9% and reduce the insertion loss by 93.1%, while the electromechanical coupling coefficient is less affected.

In this paper, a radial gradient seismic metamaterial (RGSM) is proposed. The structural unit cell is composed of an external square soil embedded with a triangular-cross-sectioned steel ring, which is filled at different angles of multiple steel rings to form a supercell. The dispersion curve and attenuation spectrum of the unit cell are calculated by the finite element method, and the opening mechanism of the band gap is explained by analyzing the modes at the band gap boundary. The influence of geometric parameters and material parameters on the band gap is further studied, and the optimized supercell radial gradient seismic metamaterial (OS-RGSM) structure is designed through structure and parameter optimization. The ultra-low broadband excellent band gap in the range of 2.35–20 Hz for seismic Lamb waves is realized, and its three-dimensional frequency response and displacement field diagram are calculated. In addition, the attenuation characteristics of the optimized supercell seismic metamaterial on the seismic surface wave are calculated and analyzed. It is found that the attenuation can reach more than 50% in the ultra-low frequency range of 3.5–9 Hz. The seismic wave barrier is verified by the vibration transmission characteristics of RGSM under finite period and dynamic time history analysis. The results show that RGSM can effectively shield from seismic Lamb waves in the ultra-wideband with the starting frequency of 2.35 Hz and can also effectively attenuate the seismic surface wave in semi-infinite space.

In this paper, a multi-material radial phononic crystal (M-RPC) structure is proposed to reduce the anchor-point loss of piezoelectric micro-electro-mechanical system (MEMS) resonators and improve their quality factor. Compared with single-material phononic crystal structures, an M-RPC structure can reduce the strength damage at the anchor point of a resonator due to the etching of the substrate. The dispersion curve and frequency transmission response of the M-RPC structure were calculated by applying the finite element method, and it was shown that the M-RPC structure was more likely to produce a band-gap range with strong attenuation compared with a single-material radial phononic crystal (S-RPC) structure. Then, the effects of different metal–silicon combinations on the band gap of the M-RPC structures were studied, and we found that the largest band-gap range was produced by a Pt and Si combination, and the range was 84.1–118.3 MHz. Finally, the M-RPC structure was applied to a piezoelectric MEMS resonator. The results showed that the anchor quality factor of the M-RPC resonator was increased by 33.5 times compared with a conventional resonator, and the insertion loss was reduced by 53.6%. In addition, the loaded and unloaded quality factors of the M-RPC resonator were improved by 75.7% and 235.0%, respectively, and at the same time, there was no effect on the electromechanical coupling coefficient.

To deal with the conflict of specific on resistance (RON-sp) and breakdown voltage (BV) in design of SiC LDMOS power devices, a SiC LDMOS power device with low RON-sp is given and its principle is studied in the paper. The proposed structure consists of a conduction cell with several poly plates and a modulation cell with floating electrodes. The modulation cell consists of two opposite diodes in series and does not participate in current conduction. In the on state, gate voltage (V_G ) is delivered to modulation cell, which is held on by P+/N-well junction in drain side. Then the floating electrodes deliver V_G back to the conduction cell for electron attraction. Because a electron accumulation layer is existed on surface of N-drift region, a low resistive current path is formed. The low resistive current path greatly decreases RON-sp of SiC LDMOS. In the off state, modulation cell can be designed to reach a high BV without considering the forward conduction performance. In the conduction cell, thanks to the potential modulation of poly plates connected to floating electrodes, a high BV can also be obtained. Experimental results and comparison analysis show the given SiC LDMOS gains better performance than traditional SiC LDMOS. RON-sp is 34.8% less than traditional SiC LDMOS device without degenerating BV.

This paper studies a fuzzy adaptive PID control method for a quadcopter UAV equipped with an airborne three-coordinate radar operating in autonomous counter-drone mode. A mathematical model of the quadcopter is first established, and a cascade control architecture is adopted in which fuzzy adaptive PID is applied to the outer position control loops to adjust PID parameters online based on the relative attitude and distance deviation detected by the onboard radar. The horizontal position loops generate roll and pitch references tracked by fixed-gain inner PID controllers. Simulation compares outer-loop adaptation with fixed-gain PID and inner-loop fuzzy PID to assess its effect on attitude transients within the cascade. A universe-of-discourse sensitivity analysis is conducted to examine the effect of FIS input domain size on control performance, and a 21-state closed-loop stability verification with Monte Carlo robustness check under parameter uncertainties is presented. An experimental platform consisting of two quadcopters and an STM32-based flight controller is built for validation. The yaw and pitch MAPE values were 0.1235% and 0.1963%, respectively, for the tested trajectory. In addition, dynamic horizontal calibration tests are performed for the airborne radar, and the altitude measurement error characteristics at different ranges are quantitatively analyzed via segmented RMSE, providing empirical support for the sensing link of the countermeasure system.