In 2015, the area of first and second class land in Tongnan Distdct of Chongqing was 221.646 km2, accounting for 30% of the total cultivated area, and the area of the third, fourth and fifth class land was 517.861 km2...In 2015, the area of first and second class land in Tongnan Distdct of Chongqing was 221.646 km2, accounting for 30% of the total cultivated area, and the area of the third, fourth and fifth class land was 517.861 km2, accounting for 70% of the total cultivated area. The quality of cultivated land was at a low level. Comparison with the Second Soil Census in 2015 showed that the soil pH value has been improved; the organic matter content in the tillage layer showed a slight upward trend; the contents of available nitrogen, available phosphorus and available potassium in the topsoil increased. Countermeasures were proposed as follows： vig- orously promote the construction of high-standard farmland; adjust the industrial structure of agriculture and implement farming reform; combine organic and inorgan- ic fertilization to reduce the amount of fertilizers; popularize soil testing and formu- lated fertilization to change farmers＇ traditional fertilization habits; improve pollution control to ensure the sustainable productivity of farmland; strictly promote the quality management of cultivated land and strengthen the construction of quality monitoring system; increase investment and improve the monitoring mechanism; vigorously publicize and enhance the awareness of all citizens in protecting cultivated land; im- prove the law of cultivated land protection and enhance the seriousness of the law on the protection of cultivated land.展开更多
Scheduling is a major concern in construction planning and management, and current construction simulation research typically targets the shortest total duration. However, uncertainties are inevitable in actual constr...Scheduling is a major concern in construction planning and management, and current construction simulation research typically targets the shortest total duration. However, uncertainties are inevitable in actual construction, which may lead to discrepancies between the actual and planned schedules and increase the risk of total duration delay. Therefore, developing a robust construction scheduling technique is of vital importance for mitigating disturbance and improving completion probability. In the present study, the authors propose a robustness analysis method that involves underground powerhouse construction simulation based on the Markov Chain Monte Carlo(MCMC) method. Specifically, the MCMC method samples construction disturbances by considering the interrelationship between the states of parameters through a Markov state transition probability matrix, which is more robust and efficient than traditional sampling methods such as the Monte Carlo(MC) method. Additionally, a hierarchical simulation model coupling critical path method(CPM) and a cycle operation network(CYCLONE) is built, using which construction duration and robustness criteria can be calculated. Furthermore, a detailed measurement method is presented to quantize the robustness of underground powerhouse construction, and the setting model of the time buffer is proposed based on the MCMC method. The application of this methodology not only considers duration but also robustness, providing scientific guidance for engineering decision making. We analyzed a case study project to demonstrate the effectiveness and superiority of the proposed methodology.展开更多
文摘In 2015, the area of first and second class land in Tongnan Distdct of Chongqing was 221.646 km2, accounting for 30% of the total cultivated area, and the area of the third, fourth and fifth class land was 517.861 km2, accounting for 70% of the total cultivated area. The quality of cultivated land was at a low level. Comparison with the Second Soil Census in 2015 showed that the soil pH value has been improved; the organic matter content in the tillage layer showed a slight upward trend; the contents of available nitrogen, available phosphorus and available potassium in the topsoil increased. Countermeasures were proposed as follows： vig- orously promote the construction of high-standard farmland; adjust the industrial structure of agriculture and implement farming reform; combine organic and inorgan- ic fertilization to reduce the amount of fertilizers; popularize soil testing and formu- lated fertilization to change farmers＇ traditional fertilization habits; improve pollution control to ensure the sustainable productivity of farmland; strictly promote the quality management of cultivated land and strengthen the construction of quality monitoring system; increase investment and improve the monitoring mechanism; vigorously publicize and enhance the awareness of all citizens in protecting cultivated land; im- prove the law of cultivated land protection and enhance the seriousness of the law on the protection of cultivated land.
基金supported by the Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51321065)the National Natural Science Foundation of China(Grant Nos.9121530151439005)
文摘Scheduling is a major concern in construction planning and management, and current construction simulation research typically targets the shortest total duration. However, uncertainties are inevitable in actual construction, which may lead to discrepancies between the actual and planned schedules and increase the risk of total duration delay. Therefore, developing a robust construction scheduling technique is of vital importance for mitigating disturbance and improving completion probability. In the present study, the authors propose a robustness analysis method that involves underground powerhouse construction simulation based on the Markov Chain Monte Carlo(MCMC) method. Specifically, the MCMC method samples construction disturbances by considering the interrelationship between the states of parameters through a Markov state transition probability matrix, which is more robust and efficient than traditional sampling methods such as the Monte Carlo(MC) method. Additionally, a hierarchical simulation model coupling critical path method(CPM) and a cycle operation network(CYCLONE) is built, using which construction duration and robustness criteria can be calculated. Furthermore, a detailed measurement method is presented to quantize the robustness of underground powerhouse construction, and the setting model of the time buffer is proposed based on the MCMC method. The application of this methodology not only considers duration but also robustness, providing scientific guidance for engineering decision making. We analyzed a case study project to demonstrate the effectiveness and superiority of the proposed methodology.
