China’s railway train speed,density and weight in developing

Purpose–This study aims to analyze the development direction of train speed,density and weight in China.Design/methodology/approach–The development of China’s railway in the past 40 years can be divided into 3 stages.At the stage of potential tapping and capacity expansion,it is important to improve the train weight and density by upgrading the existing lines,and improving transportation capacity rapidly.At the stage of railway speed increase,the first priority is to increase train speed,reduce the travel time of passenger train,and synchronously take into account the increase of train density and weight.At the stage of developing high-speed railway,train speed,density and weight are co-developing on demand.Findings–The train speed of high-speed railway will be 400 km h
1,the interval time of train tracking will be 3 min,and the traffic density will be more than 190 pairs per day.The running speed of high-speed freight EMU will reach 200 km h
1 and above.The maximum speed of passenger train on mixed passenger and freight railway can reach 200 km h
1.The minimum interval time of train tracking can be compressed to 5 min.The freight train weight of 850 m series arrival-departure track railway can be increased to 4,500–5,000 t and that of 1,050 m series to 5,500–6,400 t.EMU trains should gradually replace ordinary passenger trains to improve the quality of railway passenger service.Small formation trains will operate more in intercity railway,suburban railway and short-distance passenger transportation.Originality/value–The research can provide new connotations and requirements of railway train speed,density and weight in the new railway stage.

Assessment of wind and photovoltaic power potential in China

Decarbonization of the energy system is the key to China’s goal of achieving carbon neutrality by 2060.However,the potential of wind and photovoltaic(PV)to power China remains unclear,hindering the holistic layout of the renewable energy development plan.Here,we used the wind and PV power generation potential assessment system based on the Geographic Information Systems(GIS)method to investigate the wind and PV power generation potential in China.Firstly,the high spatial-temporal resolution climate data and the mainstream wind turbines and PV modules,were used to assess the theoretical wind and PV power generation.Then,the technical,policy and economic(i.e.,theoretical power generation)constraints for wind and PV energy development were comprehensively considered to evaluate the wind and solar PV power generation potential of China in 2020.The results showed that,under the current technological level,the wind and PV installed capacity potential of China is about 56.55 billion kW,which is approximately 9 times of those required under the carbon neutral scenario.The wind and PV power generation potential of China is about 95.84 PWh,which is approximately 13 times the electricity demand of China in 2020.The rich areas of wind power generation are mainly distributed in the western,northern,and coastal provinces of China.While the rich areas of PV power generation are mainly distributed in western and northern China.Besides,the degree of tapping wind and PV potential in China is not high,and the installed capacity of most provinces in China accounted for no more than 1%of the capacity potential,especially in the wind and PV potential-rich areas.

Response of spatial structure of cotton root to soil-wetting patterns under mulched drip irrigation

The matching relationship between the spatial structure of cotton cluster root systems and soil-wetting patterns under mulched drip irrigation forms the theoretical basis for the technical design of mulched drip irrigation.A 2-year field experiment was conducted,in which different soil-wetting patterns were produced by setting different emitter discharge rates.The envelopes of cotton cluster root length densities were derived using the topological methodology and used to examine the effects of different soil-wetting patterns on the spatial structure of root systems and water uptake capacity within row spaces.The results showed that the root systems in rows of cotton grown under narrower and deeper soil-wetting patterns exhibited a single-peak distribution,while those under wider and shallower soil-wetting patterns exhibited a two-peak distribution.Furthermore,cotton rows grown near mulch edges experienced lower moisture stress,and wider and shallower soil-wetting patterns contributed to greater root growth rates in the vertical direction and resulted in more even potential water uptake capacities.The findings of this study revealed that wider and shallower soil-wetting patterns were more desirable for mulched drip irrigation of cotton and should be considered in the technical design of drip irrigation systems.