AIM: To measure and analysis axial length(AL)/corneal radius of curvature(CRC) ratio and other refractive parameters, provide a medical reference range for refractive development evaluation and earlier visual impairme...AIM: To measure and analysis axial length(AL)/corneal radius of curvature(CRC) ratio and other refractive parameters, provide a medical reference range for refractive development evaluation and earlier visual impairment screening of 3 to 4 y kindergarten students.METHODS: Between April and June 2017, a total of 4350 participants aged 3-to 4-year-old(8700 eyes) from 10 cluster random sampling kindergartens in Shanghai, Pudong District were involved. According to the measurement and analysis of the unaided visual acuity(VA), AL, CRC, AL/CRC ratio, astigmatism and other refractive parameters, the data distribution and reference range were obtained.RESULTS: Uncorrected VA of examined children was 0.23±0.08(logMAR, mean±SD) [95% confidence interval(CI) range ≤0.36];AL was 22.10±0.79 mm(95%CI 20.55-23.65);CRC was 7.86±0.26 mm(95%CI, 7.35-8.37);AL/CRC ratio was 2.81±0.12(95%CI, 2.57-3.05). The median of astigmatism was-0.5 D, a total of 56.3% had astigmatism <-0.50 D, 85.3%<-1.00 D, 6.7%>-1.50 D;71% were astigmatism with the rule. Eye-specific analyses were conducted. Statistical difference of VA was in right and left eyes. There were no significant differences between two eyes of AL, CRC, AL/CRC ratio and astigmatism(P>0.05).CONCLUSION: VA and AL/CRC ratio reference could be used to assess refractive development in children and screening uncorrected refractive errors or amblyopia. Astigmatism needs to be considered in the diagnosis.展开更多
The excitation system of the homopolar inductor machine(HIM)is analyzed and designed to establish the design approach and evaluation criteria of the excitation system.The finite element method is used to calculate the...The excitation system of the homopolar inductor machine(HIM)is analyzed and designed to establish the design approach and evaluation criteria of the excitation system.The finite element method is used to calculate the three-dimensional electromagnetic field in the HIM,and the distribution and characteristics of the magnetic field are described.The analytical method is applied to investigate the design process of the excitation winding.The ratio of the axial length of the armature winding to the excitation winding and the ratio of the axial length of the working air-gap to the non-working air-gap are investigated by the numerical calculation method.A prototype HIM is designed and manufactured,and some experiments are implemented to verify the correctness of the theoretical analysis and numerical calculation results.The research results show that the established design method of the excitation winding is practical and feasible.Under the conditions of constant excitation magnetomotive force or constant excitation power,the optimum range of the axial length ratio of the armature winding and the excitation winding is 0.45 to 0.5.The optimal axial length of the non-working air-gap can be determined by the ratio of the stator inner diameter and pole-pairs.展开更多
基金Supported by the National Natural Science Foundation of China(No.81371040)Shanghai Smart Medical Special Research Project(No.2018ZHYL0221)+1 种基金Shanghai Municipal Education Commission-Gaofeng Clinical Medicine Grant Support(No.20181810)the Science and Technology Commission of Shanghai(No.17DZ2260100)
文摘AIM: To measure and analysis axial length(AL)/corneal radius of curvature(CRC) ratio and other refractive parameters, provide a medical reference range for refractive development evaluation and earlier visual impairment screening of 3 to 4 y kindergarten students.METHODS: Between April and June 2017, a total of 4350 participants aged 3-to 4-year-old(8700 eyes) from 10 cluster random sampling kindergartens in Shanghai, Pudong District were involved. According to the measurement and analysis of the unaided visual acuity(VA), AL, CRC, AL/CRC ratio, astigmatism and other refractive parameters, the data distribution and reference range were obtained.RESULTS: Uncorrected VA of examined children was 0.23±0.08(logMAR, mean±SD) [95% confidence interval(CI) range ≤0.36];AL was 22.10±0.79 mm(95%CI 20.55-23.65);CRC was 7.86±0.26 mm(95%CI, 7.35-8.37);AL/CRC ratio was 2.81±0.12(95%CI, 2.57-3.05). The median of astigmatism was-0.5 D, a total of 56.3% had astigmatism <-0.50 D, 85.3%<-1.00 D, 6.7%>-1.50 D;71% were astigmatism with the rule. Eye-specific analyses were conducted. Statistical difference of VA was in right and left eyes. There were no significant differences between two eyes of AL, CRC, AL/CRC ratio and astigmatism(P>0.05).CONCLUSION: VA and AL/CRC ratio reference could be used to assess refractive development in children and screening uncorrected refractive errors or amblyopia. Astigmatism needs to be considered in the diagnosis.
基金The National Natural Science Foundation of China(No.51977035)。
文摘The excitation system of the homopolar inductor machine(HIM)is analyzed and designed to establish the design approach and evaluation criteria of the excitation system.The finite element method is used to calculate the three-dimensional electromagnetic field in the HIM,and the distribution and characteristics of the magnetic field are described.The analytical method is applied to investigate the design process of the excitation winding.The ratio of the axial length of the armature winding to the excitation winding and the ratio of the axial length of the working air-gap to the non-working air-gap are investigated by the numerical calculation method.A prototype HIM is designed and manufactured,and some experiments are implemented to verify the correctness of the theoretical analysis and numerical calculation results.The research results show that the established design method of the excitation winding is practical and feasible.Under the conditions of constant excitation magnetomotive force or constant excitation power,the optimum range of the axial length ratio of the armature winding and the excitation winding is 0.45 to 0.5.The optimal axial length of the non-working air-gap can be determined by the ratio of the stator inner diameter and pole-pairs.
