RÉSUMÉ
Objective@#To explore the relationship between mobile phone dependence (MPD) and academic burden among junior middle school students in Guizhou Province, under the "double reduction" policy by using a multi level model, so as to provide a basis for preventing the occurrence of MPD.@*Methods@#From December 2021 to January 2022, 7 868 students from grade 1 to grade 3 in 3 cities (prefecture) of Guizhou Province were selected by multi stage stratification random sampling method, and on site investigation was conducted by self compiled questionnaire and Self rating Questionnaire for Adolescent Problematic Mobile Phone Use(SQAPMPU). Using MLwiN 2.30 to fit a multi level model of the relationship between MPD and academic burden among junior middle school students.@*Results@#The MPD detection rate of junior middle school students in Guizhou Province was 20.9%. The multi level model revealed that MPD of junior middle school students was clustered at the level of school and class ( χ 2= 1 565.32 , P <0.01), and high perceived academic pressure had a positive predictive effect on MPD among junior middle school students ( β =1.96). Homework duration ≥90 min/d at weekends had a negative predictive effect on MPD ( β =-0.55), while participation in off campus training on learning days had a positive predictive effect ( β =1.66)( P <0.05).@*Conclusion@#The MPD occurrence level is higher among junior middle school students in Guizhou Province. Perceived academic pressure, time spent on homework during weekends, off campus training and other academic burdens have an impact on MPD among junior middle school students, which should be a cause of concern for schools, families and social departments.
RÉSUMÉ
Objective To discuss the value of radiation dose reduction with directed digital radiography application in chest X-ray. Methods Patients were in posterior-anterior standing posture for test. To compare DR exposure parameters with traditional roentgenography in the same exposure condition of 125 kVp, automatic mAs, 180cm focus-film distance. Patients' thoracic thickness was 22-25cm. Results DR can reduce exposure dose by 44.2%. Conclusion Directed digital radiography can improve the quality of chest images,make working flow more reasonable, enhance the working efficiency and reduce patient's x-ray dose as well.