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Urban bio-retention system is meaningful in reducing rainfall runoff and enhancing infiltration capacity. But the moisture migration in bio-retention systems are not clear under climate change. The spatial and temporal distribution of moisture under different rainfall events in bio-retention systems are studied in this paper based on experimental data in Beijing. Richards model is introduced to simulate the spatial and temporal distribution of moisture including pressure head, hydraulic head and water content under different initial and boundary conditions. As a result, we found that from the depth of the node to the lower boundary, the values of pressure head and hydraulic head increase with depth and decrease with time, while the values of water content represent opposite trends relative to the distribution of pressure head and hydraulic head in bio-retention systems. [ABSTRACT FROM AUTHOR]

This study is to analyze the relationship between human settlements system and water resources, select the water resource's carrying capacity index, and construct a system based on the human settlements system theory for the water resource's carrying capacity index. The index weight is determined by the analytic hierarchy process, and the set pair analysis method is used to calculate the connection number and evaluation grade of samples in Beijing, Tianjin, and Hebei Province from 2016 to 2019. The results show that there are differences in water resources carrying capacity from the perspective of human settlements in Beijing, Tianjin, and Hebei Province, and the changing trend of water resources carrying capacity in the three regions is different. The introduction of human settlement theory into the construction of water resource's carrying capacity index system can better reflect the carrying capacity of water resources to human society and can provide a new perspective for other related research in the future. [ABSTRACT FROM AUTHOR]

Taking Beijing metro line 5 as the research vehicle model, the influence of different track structure on subway vibration is analyzed. According to the coupling dynamic equations of vehicle rail, the coupling dynamic equations of vehicle body models under integrated rail bed, plate rail bed and floating plate rail structure are established, respectively, and the vibration response of vehicle body models under three kinds of rail structure is calculated. The evaluation indexes of dynamic characteristics of rail coupling are analyzed. The analysis results show that with the increase of subway speed, the vertical displacement and acceleration between the vehicle and the middle point of the track gradually increase, and the vibration response of the fourth wheel to the maximum wheel-rail force also gradually increases. With the increase of the buried depth of subway tunnel, the maximum vertical displacement and ground motion acceleration of the three tracks gradually decrease, which indicates that this method can accurately analyze the vibration response of subway under different track structures. [ABSTRACT FROM AUTHOR]

The demands of cooling, heating and electricity in residential buildings are varied with seasons. This article presented a seasonal solar combined cooling heating and power (CCHP) system based on evacuated flat-plate collectors and organic Rankine cycle. The heat collected by evacuated flat-plate collectors is used to drive the organic Rankine cycle unit in spring, autumn and winter, and drive the double-effect lithium bromide absorption chiller in summer. The organic Rankine cycle condensation heat is used to yield hot water in spring and autumn, whereas supply heating in winter. The system thermodynamic performance was analyzed. The results show that the system thermal efficiency in spring, autumn and winter, ηsys,I, increases as organic Rankine cycle evaporation temperature, T6, and evacuated flat-plate collectors outlet temperature, T2, decrease. The maximum ηsys,I of 67.0% is achieved when T6 = 80 °C and T2 =100 °C. In summer, the system thermal efficiency, ηsys,II, increases first and then decreases with the increment of T2. The maximum ηsys,II of 69.9% is obtained at T2 =136 °C. The system output performance in Beijing and Lanzhou is better than that in Hefei. The average output power, heating capacity, hot water and cooling capacity are 50-72 kWh per day, 989-1514 kWh per day, 49-57 ton per day and 1812-2311 kWh per day, respectively. The system exergy efficiency increases from 17.8-40.8% after integrating the organic Rankine cycle unit. [ABSTRACT FROM AUTHOR]