A synthetic semi-empirical physical model of secondary electron yield of metals under E-beam irradiation

Calculations of secondary electron yield（SEY） by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface contamination states of real sample result in notable difference between simulations and experiments. In this paper, in order to calculate SEY of metal under complicated surface state accurately, we propose a synthetic semi-empirical physical model. The processes of excitation of internal secondary electron（SE） and movement toward surface can be simulated using this model.This model also takes into account the influences of incident angle and backscattering electrons as well as the surface gas contamination. In order to describe internal electronic states accurately, the penetration coefficient of incident electron is described as a function of material atom number. Directions of internal electrons are set to be uniform in each angle. The distribution of internal SEs is proposed by considering both the integration convergence and the cascade scattering process.In addition, according to the experiment data, relationship among desorption gas quantities, sample ultimate temperature and SEY is established. Comparing with experiment results, this synthetic semi-empirical physical model can describe the SEY of metal better than former formulas, especially in the aspect of surface contaminated states. The proposed synthetic semi-empirical physical model and presented results in this paper can be helpful for further studying SE emission, and offer an available method for estimating and taking advantage of SE emission accurately.

Analysis of the Physical Education Teaching Path in Primary and Secondary Schools Under the Guidance of Core Literacy

Since the 2018 National Education Conference in China,physical education has gained importance as a whole,and the development of physical literacy education and teaching has been promoted.In order to ensure high-quality physical education teaching in primary and secondary schools in the new era,it is necessary to take core literacy as the guide to further improve the level of physical education in primary and secondary schools.This article emphasizes the importance of physical education in primary and secondary schools in the new era and analyzes the need of primary and secondary schools for core literacy-oriented physical education.On this basis,targeted suggestions are proposed from three aspects:new concept,new technology,and new evaluation.

Teaching Strategies for Physical Education in Primary and Secondary Schools Under the Background of National Sports

By the end of 2021,the proportion of people participating in normalized physical exercise in China has reached up to 37.2%,contributing to the transformation of competitive sports into national sports.This has significantly affected the teaching quality of physical education in primary and secondary schools.In the critical period of the“14th Five-Year Plan”construction,it is necessary to deepen the physical education work in primary and secondary schools concertedly with high-quality development goals.Taking this as the starting point,the paper outlines the basic content and main influence of national sports as well as analyzes the new demands of physical education in primary and secondary schools under the background of national sports.On this basis,several targeted teaching strategies are put forward from three aspects:teaching concept,information technology,and teaching goals.

Conceptual physical education: A course for the future

The conceptual physical education(CPE)innovation began in the mid-20th century as an alternative approach to college-level,activity-only basic instruction classes.In addition to physical activity sessions,CPE courses(classes)use text material and classroom sessions to teach kinesiology concepts and principles of health-related fitness and health-enhancing physical activity.CPE courses are now offered in nearly all college programs as either required or electives classes.Two decades later,the high school CPE innovation began,and Kindergarten-8 programs followed.In this commentary,I argue that historian Roberta Park was correct in her assessment that physical education has the potential to be the renaissance field of the 21st century.Scientific contributions of researchers in kinesiology will lead the way,but science-based CPE and companion fitness education programs that align with physical education content standards and fitness education benchmarks will play a significant role.CPE courses have been shown to be effective in promoting knowledge,attitudes,and out-of-school physical activity and have the potential to elevate physical education as we chart the course of our future.