查看更多>>摘要：Currently,the manual contact rail measurement that was basically adopted in China has low detection efficiency,poor accuracy and poor stability.In order to improve the function of the system,we propose a non-contact measurement method based on the flatness and verticality ruler model.The flatness measurement model was built by employing the string measurement method.In addition,the verticality measurement model was built by the dihe-dral method to measure the rail comprehensively.By extracting curvature information of feature points,in this system,each laser sensor is used to collect rail profile curves.A large number of three-dimensional point clouds data are generated by the unit qua-ternion method of coordinate transformation,and the contour curves of the characteristic points of the four laser sensors are matched with the corresponding point sets one to one,and the rail contour splicing is finally completed.The experimental results show that this method has better measurement effect compared with the traditional manual measurement method.
查看更多>>摘要：The novel coronavirus disease 2019(COVID-19)in human caused by novel severe acute respiratory syndrome coro-navirus 2(SARS-CoV-2)is currently rampant across the world,causing an international concern for public health emergency.At the time of July,2020,about 8 380 000 confirmed cases and more than 450 000 deaths have been reported worldwide.This is the third out-break of severe coronavirus family after the Middle East respiratory syndrome(MERS)and severe acute respiratory syndrome(SARS).Young victims(＜12 years)in clinical course and prognosis of pedi-atric COVID-19 appear symptomatically milder than do teenage and adult patients,and many children with asymptomatic infections or showing only mild symptoms may be transmitter as well.Thus,the children with COVID-19 infection deserve more attention.This review is cautiously designed to report the clinical characteristics and symptoms of three kinds of coronaviruses(SARS-CoV,MERS-CoV,and SARS-CoV-2)in children and to summarize some recom-mended tactics to reduce COVID-19 transmission and/or to attain improved prevention in children.
NETL
NSTL
万方数据
维普