Improving myopia awareness via school-based myopia prevention health education among Chinese students

AIM:To investigate the myopia awareness level,knowledge,attitude,and skills at baseline and to implement and evaluate the efficacy of myopia prevention health education among Chinese students.METHODS:A total of 1000 middle school students from 2 middle schools were invited to participate in the study,and myopia prevention health education was conducted.The students were assessed at baseline,followed by a survey.The efficacy of health education was evaluated using the self-comparison method pre-and post-health education.RESULTS:The study included 957 and 850 pre-and post-health education par ticipants,respectively.The baseline knowledge of all respondents on myopic symptoms(87.5%),myopia is a risk of eyes(72.9%),myopia prevention(91.3%),myopia increases with age(86.7%),performing periodic eye examinations(92.8%),and one first,one foot,and one inch(84.8%)significantly increased after health education(P<0.001 for all).However,the percentage of students who still did not think it necessary to take breaks after 30-40min of continuous near work was 27.0%.The opinion that“myopia can be cured”was still present in 38.3%.CONCLUSION:Implementing school-based myopia prevention health education improves knowledge,attitudes,and skills regarding myopia among Chinese middle school students.

Identification of the unknown shielding parameters with gammaray spectrum using a derivative-free inverse radiation transport model

Identifying the unknown geometric and material information of a multi-shield object by analyzing the radiation signature measurements is always an important problem in national and global security. In order to identify the unknown shielding layer thicknesses of a source/shield system with gamma-ray spectra, we have developed a derivative-free inverse radiation transport model based on a differential evolution algorithm with global and local neighbourhoods(IRT-DEGL). In the present paper, the IRT-DEGL model is further extended for estimating the unknown thicknesses with random initial guesses and material mass densities of multi-shielding layers as well as their combinations. Using the detected gamma-ray spectra,the illustration of inverse studies is implemented and the main influence factors for inverse results are also analyzed.

An enhanced differential evolution-based inverse radiation transport model for identification of unknown shielding layer thicknesses with gamma-ray spectrum

Identifying the geometric information of an object by analyzing the detected radiation fields is an important problem for national and global security.In the present work,an inverse radiation transport model,based on the enhanced differential evolution algorithm with global and local neighborhoods(IRT-DEGL),is developed to estimate the unknown layer thickness of the source/shield system with the gamma-ray spectrum.The framework is briefly introduced with the emphasis on handling the enhanced differential evolution algorithm.Using the simulated gamma-ray spectra,the numerical precision of the IRT-DEGL model is evaluated for one-dimensional source systems.Using the detected gamma-ray spectra,the inverse investigations for the unknown thicknesses of multiple shielding layers are performed.By comparing with the traditional gamma-ray absorption method,it is shown that the IRT-EDGL model can provide a much more accurate result and has great potential to be applied for the complicated systems.

Electrical properties of Ca3-xSmxCo4O9+δceramics prepared under magnetic field

We fabricate Sm-doped Ca3Co4O9+δ(CCO)bulk materials in magnetic field during both processes of chemical synthesis and cold pressing.The structure and electrical performance of the samples are investigated.With the increasing Sm concentration,the electrical conductivity 1/ρ decreases and the Seebeck coefficientαincreases.As a result,the power factor(PF=α^2/ρ)is raised slightly.After applying magnetic field,the extent of texture,grain size and density of all the bulk materials are improved obviously,thereby an enhanced electrical conductivity can be gained.Additionally,the degeneracy of Co^4+ state in the CoO2 layer of CCO is also increased as the magnetic field is used in the preparing process,which results in an enhancedα.The Ca2.85Sm0.15Co4O9+δ prepared in magnetic field shows the largest power factor(0.20 mW·m^-1·K^-2 at 1073 K).