No abstract

No abstract

IntroductionTo understand the features of sedentary behavior of Chinese children and adolescents and its relationship with poor visual acuity, a self-administered “Questionnaire on Sedentary Behavior of Children and Adolescents” was used to survey 4,203 students in grades 4–12 in six administrative regions of China.Results(1) The average time spent in sedentary behaviors (SB) of Chinese children and adolescents was about 8.1 h per day, of which the academic sedentary time was the longest, accounting for 79.2% of total sedentary time. The total time spent on SB and the time spent on studying SB were more in the upper grades and less in screen SB and cultural leisure SB, respectively. There were significant sex differences in total SB time (p < 0.05) and weekend sedentary behaviors time (SB-WD) (p < 0.01) among Chinese children and adolescents, with girls being more likely to be higher than boys. There were also significant differences in sedentary time across different regions (p < 0.05), and the longest total sedentary time in East China. (2) Reduction parents' sedentary time and limitation of sedentary behaviors and the use of electronics among children and adolescents can effectively reduce sedentary time among Chinese children and adolescents. (3) Sedentary time was significantly higher in children and adolescents with poor vision than in those with normal vision (p < 0.01), and study SB and screen SB were important independent factors affecting vision. (4) Timing of breaks in SB can play a positive role in promoting vision health.ConclusionThere were significant grade, sex, and regional differences in the SB of Chinese children and adolescents, and sedentary time was strongly related to the prevalence of poor vision detection rate.

This paper presents a novel fabrication method of PZT micro-fibers using activated carbon template with the aim of manufacturing PZT/epoxy 1-3 composites. Porous carbon was first prepared by chemical activation technology. The pore diameter formed in an activated carbon template is of several microns and lengths are up to several millimeters. These pores provide a basic platform to grow PZT fibers inside. Then the carbon template is removed at high calcination temperatures to form PZT micro-fibers. Subsequently, thermo-gravimetric analysis (TG) and differential scanning calorimetry (DSC) were performed to analyze the process of removing the template as temperature changing. For manufacturing 1-3 piezo-composites, the PZT fibers were carefully aligned in one direction and infiltrated by epoxy resin. Based on the observation from X-ray diffraction (XRD) the fibers show a pure pervoskite phase at low sintering temperature of 950°C. The fibers embedded orderly in the epoxy matrix are smoothly distributed and straightened which were observed using a scanning electron microscopy (SEM). The diameter of fibers is around several microns with the length up to a few millimeters, matching well with pores in the template. The new micro-fiber composite material can be potentially used in a sensor with high directivity in structural health monitoring.