Haonan Zou

The bonding performance between new and old concrete affects the reliability and service life of the repair structure. However, the bonding interface is complex and has many influencing factors, so selecting appropriate repair materials and evaluation methods for repair structures under different service environments is important. This paper presents a comprehensive overview of the factors that influence bonding properties. These include the choice of repair materials, the condition of the existing concrete, the type of interfacial agents used, the service environment, and the testing methods employed. The paper concludes by examining the challenges and opportunities in developing interface bonding properties to provide insights and research directions for future theoretical analysis and experimental research.

BACKGROUND: Since 2002, the Chinese Ministry of Education has conducted reform in the physical education (PE) curriculums of schools in China, with a focus on shifting from sports skills to regular participation in physical activity (PA) and promoting health. The aim of the study, therefore, is to examine the effects of school PE on the exercise habits of children and adolescents in China over time. METHODS: Data based on 5941 observations of 3708 individuals aged 6 to 17 were collected from the China Health and Nutrition Survey (CHNS) for the period 2004 to 2015. The data were analyzed using the fixed-effect Logit model and the random-effect Tobit model. RESULTS: The likelihood of exercising outside of school is 20.2% higher for students who have school PE than those who do not. Our study found that increasing the duration of PE at school by 100%, increases the duration of out-of-school PA by 22.3%. The variety of the types of sports schools offer encourages students to participate in out-of-school physical activity. The likelihood of students exercising outside of school increases by 5.6% when 1 more exercise type is provided in school PE. In addition, soccer, basketball, badminton, and volleyball education increases students' participation in after-school exercises. Soccer and basketball education, in particular, improves the duration of after-school PA. CONCLUSIONS: To form exercise habits in children and adolescents, we encourage the promotion of a variety of physical activities in schools, especially team sports such as soccer and basketball.

With the increase of the speed of bearingless doubly salient electromagnetic motor (BDSEM), the armature currents affect the suspension force characteristics, thus affecting the suspension performance. In this article, first, the influence of suspension currents on torque characteristics is deduced. Second, the suspension force characteristics at high-speed are analyzed and illustrated under different drive control methods. Third, a suspension force control method is proposed to achieve stable suspension during advanced angle drive control and commutation at high-speed. The finite element (FE) results verify the effectiveness of the proposed suspension control method. An experimental platform of 12/8-pole BDSEMs is built. A system including a drive controller, a suspension controller, and a power generation unit is also developed. The experimental results show that the suspension performance is significantly improved.

Increase of electromagnetic load is an important way for bearingless doubly salient electromagnetic (BDSEM) motor to improve torque density, but this leads to core saturation, resulting in a non-linear gain between the suspension force and current. This paper proposes a new equivalent magnetic circuit model based on the material characteristics of iron core, and reveals the mechanism of the influence of core saturation on BDSEM motor suspension force. Finally, an experimental platform is developed and the analysis results are preliminarily validated.

The new bearingless doubly salient electromagnetic (BDSEM) has the advantage of robust structure, and is suitable for high speed application. However, the armature current commutation of the BDSEM brings peaks in the ideal suspension current, and poor current tracking at high speed affects suspension control, even leads to suspension failure. In this paper, the ideal suspension current generating stable suspension force is derived, and the factors affecting the current characteristics are analyzed. The influence of current tracking performance on suspension control and its mechanism are studied. Finally, the simulation verified the accuracy of the analysis.