Background: Adolescents are the primary target population for human papillomavirus (HPV) vaccination. The objective of this study is to explore the acceptability of HPV vaccines and evaluate factors related to willingness to be vaccinated among Chinese adolescents. Methods: A nation-wide survey was conducted across 14 schools in mainland China. The questionnaire consisted of questions relating to socio-demographic characteristics, knowledge of adolescent sexual health, cervical cancer, HPV and HPV-related disease, and students' willingness to be vaccinated. Chisquare tests and multivariable logistic regression were conducted in the data analysis. Results: A total of 4,062 students participated in this study. Among them, only 17.1% of students reported having heard of HPV vaccines; however, 67.3% were willing to receive the HPV vaccine. Multivariable regression analysis showed that students who were from rural areas, have received sexual health education, have heard of cervical cancer or HPV vaccine, have a positive attitude toward vaccination, reported they were at the risk of developing cervical cancer, and those who value their parents' and teachers' opinions were more willing to receive HPV vaccination. Conclusions: Awareness about the HPV vaccine is low among Chinese adolescents. The factors that most related to willingness to vaccinate among Chinese adolescents were school location, education about vaccination, HPV, and HPV vaccines. Integrating health education on HPV vaccination into existing school-based sexual health curricula may be an effective way to increase HPV vaccination coverage in mainland China.

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The Hall sensor is the most commonly used position sensor of the permanent magnet brushless direct current (PMBLDC) motor. Its failure may lead to a decrease in system reliability. Hence, this article proposes a novel methodology for the Hall sensors fault diagnosis and fault-tolerant control in PMBLDC motor drives. Initially, the Hall sensor faults are analyzed and classified into three fault types. Taking the Hall signal as the system state and the conducted MOSFETs as the system event, the extended finite state machine (EFSM) of the motor in operation is established. Meanwhile, a motor speed observer based on the super twisting algorithm (STA) is designed to obtain the speed signal of the proposed strategy. On this basis, a real-time Hall sensor fault diagnosis strategy is established by combining the EFSM and the STA speed observer. Moreover, this article proposes a Hall signal reconstruction strategy, which can generate compensated Hall signal to realize fault-tolerant control under single or double Hall sensor faults. Finally, theoretical analysis and experimental results validate the superior effectiveness of the proposed real-time fault diagnosis and fault-tolerant control strategy.

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This paper proposes a backstepping fuzzy sliding mode control method for the antiskid braking system (ABS) of unmanned aerial vehicles (UAVs). First, the longitudinal dynamic model of the UAV braking system is established and combined with the model of the electromechanical actuator (EMA), based on reasonable simplification. Subsequently, to overcome the higher-order nonlinearity of the braking system and ensure the lateral stability of the UAV during the braking process, an ABS controller is designed using the barrier Lyapunov function to ensure that the slip ratio can track the reference value without exceeding the preset range. Then, a power fast terminal sliding mode control algorithm is adopted to realize high-performance braking pressure control, which is required in the ABS controller, and a fuzzy corrector is established to improve the dynamic adaptation of the EMA controller in different braking pressure ranges. The experimental results show that the proposed braking pressure control strategy can improve the servo performance of the EMA, and the hardware in loop (HIL) experimental results indicate that the proposed slip ratio control strategy demonstrates a satisfactory performance in terms of stability under various runway conditions.