Pantograph-catenary electrical contact system of high-speed railways:recent progress,challenges,and outlooks

As the unique power entrance,the pantograph-catenary electrical contact system maintains the efficiency and reliability of power transmission for the high-speed train.Along with the fast development of high-speed railways all over the world,some commercialized lines are built for covering the remote places under harsh environment,especially in China;these environmental elements including wind,sand,rain,thunder,ice and snow need to be considered during the design of the pantograph-catenary system.The pantograph-catenary system includes the pantograph,the contact wire and the interface—pantograph slide.As the key component,this pantograph slide plays a critical role in reliable power transmission under dynamic condition.The fundamental material characteristics of the pantograph slide and contact wire such as electrical conductivity,impact resistance,wear resistance,etc.,directly determine the sliding electrical contact performance of the pantograph-catenary system;meanwhile,different detection methods of the pantograph-catenary system are crucial for the reliability of service and maintenance.In addition,the challenges brought from extreme operational conditions are discussed,taking the Sichuan-Tibet Railway currently under construction as a special example with the high-altitude climate.The outlook for developing the ultra-high-speed train equipped with the novel pantograph-catenary system which can address the harsher operational environment is also involved.This paper has provided a comprehensive review of the high-speed railway pantograph-catenary systems,including its progress,challenges,outlooks in the history and future.

Rapid and non-destructive detection method for water status and water distribution of rice seeds with different vigor

In this study,newly harvested and aged rice seeds were analyzed to determine their aging process,identify the difference between artificially and naturally aged seeds,and develop a rapid,accurate,and non-destructive detection method for water status and water distribution of rice seed with different vigor.To this end,an artificially accelerated aging test was conducted on the newly harvested rice seeds.Then,low-field nuclear magnetic resonance(LF-NMR)technology was applied to test the new(Shennong No.9816,2018),old(Shennong No.9816,2017),and artificially aged seeds(Shennong No.9816,2018).A standard germination test was conducted for three types of seeds.Finally,the differences of water status and distribution between rice seeds of different vigor were analyzed based on the standard germination test results and wave spectrometry information collected using LF-NMR.The results indicated that new seeds,old seeds,and the artificially accelerated aging rice seeds all exhibited two water phases,and the vigor of rice seeds after the artificial accelerated aging test was lower than that of new seeds.There were significant differences between the frequencies of bound water at the time of the peak and the time at the end of the peak for the three types of seeds.The two times showed an increasing trend for rice seeds with poor vigor,indicating that the ability of the water in the rice seeds having poor vigor to combine with other substances was weakened.There were significant differences between the distributions of free water peak end time for the three types of seeds.All the rice seeds with poor vigor exhibited a decreasing trend at this time,indicating that the freedom of free water inside the rice seed samples with poor vigor was weakened.The total water content of the artificially aged seeds and the aged seeds was higher than that of the new seeds,but the free water content increased from artificially aged seeds to new seeds to aged seeds.This indicates that LF-NMR technology is an effective detection method that can simply compare the differences in seed vitality with respect to water distribution as well as differentiate the seed internal water content of artificially aged and naturally aged seeds.