Purpose–In this paper,a high-frequency radar test system was used to collect the data of clean ballast bed and fouled ballast bed of ballasted tracks,respectively,for a quantitative evaluation of the condition of rai...Purpose–In this paper,a high-frequency radar test system was used to collect the data of clean ballast bed and fouled ballast bed of ballasted tracks,respectively,for a quantitative evaluation of the condition of railway ballast bed.Design/methodology/approach–Based on original radar signals,the time–frequency characteristics of radar signals were analyzed,five ballast bed condition characteristic indexes were proposed,including the frequency domain integral area,scanning area,number of intersections with the time axis,number of timedomain inflection points and amplitude envelope obtained by Hilbert transform,and the effectiveness and sensitivity of the indexes were analyzed.Findings–The thickness of ballast bed tested at the sleep bottom by high-frequency radar is up to 55 cm,which meets the requirements of ballast bed detection.Compared with clean ballast bed,the values of the five indexes of fouled ballast bed are larger,and the five indexes could effectively show the condition of the ballast bed.The computational efficiency of amplitude envelope obtained by Hilbert transform is 140 s$km1,and the computational efficiency of other indexes is 5 s$km1.The amplitude envelopes obtained by Hilbert transform in the subgrade sections and tunnel sections are the most sensitive,followed by scanning area.The number of intersections with the time axis in the bridge sections was the most sensitive,followed by the scanning area.The scanning area can adapt to different substructures such as subgrade,bridges and tunnels,with high comprehensive sensitivity.Originality/value–The research can provide appropriate characteristic indexes from the high-frequency radar original signal to quantitatively evaluate ballast bed condition under different substructures.展开更多
The world's first known Olympics games took place some 3000 years ago.The historical carbon footprint-a measure of the amount of carbon dioxide released into the atmosphere because of a defined set of activities–...The world's first known Olympics games took place some 3000 years ago.The historical carbon footprint-a measure of the amount of carbon dioxide released into the atmosphere because of a defined set of activities–is not known,but the current emissions represent no small number.According to the International Olympic Committee1.展开更多
基金funded by the National Key R&Dprogram of China[Grant No.2022YFB2603302]the Science and Technology Research and Development Program of China State Railway Group Co.,Ltd[Grant No.K2022G015]the Fund Project of China Academy of Railway Sciences Corporation Limited[Grant No.2022YJ305].
文摘Purpose–In this paper,a high-frequency radar test system was used to collect the data of clean ballast bed and fouled ballast bed of ballasted tracks,respectively,for a quantitative evaluation of the condition of railway ballast bed.Design/methodology/approach–Based on original radar signals,the time–frequency characteristics of radar signals were analyzed,five ballast bed condition characteristic indexes were proposed,including the frequency domain integral area,scanning area,number of intersections with the time axis,number of timedomain inflection points and amplitude envelope obtained by Hilbert transform,and the effectiveness and sensitivity of the indexes were analyzed.Findings–The thickness of ballast bed tested at the sleep bottom by high-frequency radar is up to 55 cm,which meets the requirements of ballast bed detection.Compared with clean ballast bed,the values of the five indexes of fouled ballast bed are larger,and the five indexes could effectively show the condition of the ballast bed.The computational efficiency of amplitude envelope obtained by Hilbert transform is 140 s$km1,and the computational efficiency of other indexes is 5 s$km1.The amplitude envelopes obtained by Hilbert transform in the subgrade sections and tunnel sections are the most sensitive,followed by scanning area.The number of intersections with the time axis in the bridge sections was the most sensitive,followed by the scanning area.The scanning area can adapt to different substructures such as subgrade,bridges and tunnels,with high comprehensive sensitivity.Originality/value–The research can provide appropriate characteristic indexes from the high-frequency radar original signal to quantitatively evaluate ballast bed condition under different substructures.
基金The authors gratefully acknowledge financial support from the EnvironmentalDefense Fund Beijing RepresentativeOffice.We gratefully thank the support from the General Planning Department and the Sustainability Advisory Commission of the Beijing 2022 Organizing Committee.Heartfelt thanks are extended to the Bureau of Ecology and Environment of Beijing Municipality,the Bureau of Ecology and Environment of Yanqing District,relevant enterprises and experts for their assistance in the research,discussion,and data collection.
文摘The world's first known Olympics games took place some 3000 years ago.The historical carbon footprint-a measure of the amount of carbon dioxide released into the atmosphere because of a defined set of activities–is not known,but the current emissions represent no small number.According to the International Olympic Committee1.
