为了探究中国土地利用变化驱动机制和未来土地利用状况,该文利用中国科学院资源环境科学数据库中的2000年和2005年土地利用数据,结合区域土地利用变化与影响模型CLUE-S(the conversion of land use and its effects at small regional e...为了探究中国土地利用变化驱动机制和未来土地利用状况,该文利用中国科学院资源环境科学数据库中的2000年和2005年土地利用数据,结合区域土地利用变化与影响模型CLUE-S(the conversion of land use and its effects at small regional extent)和面向地理过程动态环境模型Dinamica EGO(environment for geoprocessing objects)模拟2000-2020年中国土地利用状况,并借助于Logistic回归结果和贝叶斯估计结果,探讨了中国2000-2005年土地利用适宜性和土地利用变化的驱动力空间特征。以2005年土地利用数据对模拟结果进行验证表明,CLUE-S模型和Dinamica EGO模型在LUCC预测上与实际结果一致性较好,并且CLUE-S模型在预测总体精度上优于Dinamica EGO模型。但在土地利用变化类型的数量预测上,Dinamica EGO模型的Markov过程可以准确预测,并且Dinamica EGO模拟的土地利用变化在空间分布上与经验结果较一致。从2020年中国土地利用预测结果来看,耕地、林地、水域和建设用地将会增加,草地会出现大面积的缩减,未利用地在CLUE-S模型预测中出现增加,而在Dinamica EGO模型中减少。该文可为国土资源规划和耕地资源保护政策的制定提供科学依据。展开更多
Based on the pipe transportation of paste-like backfilling system of a certain deep coal mine,its dynamics process was simulated and analyzed.A two-dimensional dynamic model of extraordinary deep and lone pipe was bui...Based on the pipe transportation of paste-like backfilling system of a certain deep coal mine,its dynamics process was simulated and analyzed.A two-dimensional dynamic model of extraordinary deep and lone pipe was built by GAMBIT,on the basis of which the simulation was done by implicit solver of FLUENT 2ddp.The results show that hydraulic loss of pipe transportation is less than the pressure produced by gravity,which means the backfilling material can flow by itself.When the inlet velocity is 3.2 m/s,the maximum velocity of 4.10 m/s is at the elbow and the maximum velocity in the horizontal pipe is 3.91 m/s,which can both meet the stability requirement.The results of the simulation are proved to be reliable by the residual monitor plotting of related parameter,so it can be concluded that the system of pipe transportation is safe.展开更多
A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mas...A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mass to solution volume, flow velocity and temperature on Cr（Ⅵ） leaching. The optimal parameters were obtained for Cr（Ⅵ） leaching and a fitting model was established to describe the procedure of Cr（Ⅵ） leaching. The results show that Cr（Ⅵ） concentration in leachate increases with decreasing pH and increasing flow velocity and temperature. Moreover, Cr（Ⅵ） leaching percentage increases with increasing ratio of solid mass to solution volume. The optimal parameters for Cr（Ⅵ） selective leaching are as follows： pH=3.0, 1：5 of ratio of solid mass to solution volume, 180 mL/min of flow velocity and 40 ℃ of temperature. The procedure of Cr（Ⅵ） leaching fits well with the model： v= 1.87t^-0.54, indicating that the leaching rate of Cr（Ⅵ） declines in an exponential order of-0.54.展开更多
In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process(dynamic programming) model for railway freight reservation was formulated and the overbooking limit ...In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process(dynamic programming) model for railway freight reservation was formulated and the overbooking limit level was proposed as a control policy. However, computing the dynamic programming treatment needs six nested loops and this will be burdensome for real-world problems. To break through the calculation limit, the properties of value function were analyzed and the overbooking protection level was proposed to reduce the calculating quantity. The simulation experiments show that the overbooking protection level for the lower-fare class is higher than that for the higher-fare class, so the overbooking strategy is nested by fare class. Besides, by analyzing the influence on the overbooking strategy of freight arrival probability and cancellation probability, the proposed approach is efficient and also has a good application prospect in reality. Also, compared with the existing reservation(FCFS), the overbooking strategy performs better in the fields of vacancy reduction and revenue improvement.展开更多
文摘为了探究中国土地利用变化驱动机制和未来土地利用状况,该文利用中国科学院资源环境科学数据库中的2000年和2005年土地利用数据,结合区域土地利用变化与影响模型CLUE-S(the conversion of land use and its effects at small regional extent)和面向地理过程动态环境模型Dinamica EGO(environment for geoprocessing objects)模拟2000-2020年中国土地利用状况,并借助于Logistic回归结果和贝叶斯估计结果,探讨了中国2000-2005年土地利用适宜性和土地利用变化的驱动力空间特征。以2005年土地利用数据对模拟结果进行验证表明,CLUE-S模型和Dinamica EGO模型在LUCC预测上与实际结果一致性较好,并且CLUE-S模型在预测总体精度上优于Dinamica EGO模型。但在土地利用变化类型的数量预测上,Dinamica EGO模型的Markov过程可以准确预测,并且Dinamica EGO模拟的土地利用变化在空间分布上与经验结果较一致。从2020年中国土地利用预测结果来看,耕地、林地、水域和建设用地将会增加,草地会出现大面积的缩减,未利用地在CLUE-S模型预测中出现增加,而在Dinamica EGO模型中减少。该文可为国土资源规划和耕地资源保护政策的制定提供科学依据。
基金Project(2008BAB32B03) supported by the National Science and Technology Pillar Program during the 11th Five-year Plan Period of China
文摘Based on the pipe transportation of paste-like backfilling system of a certain deep coal mine,its dynamics process was simulated and analyzed.A two-dimensional dynamic model of extraordinary deep and lone pipe was built by GAMBIT,on the basis of which the simulation was done by implicit solver of FLUENT 2ddp.The results show that hydraulic loss of pipe transportation is less than the pressure produced by gravity,which means the backfilling material can flow by itself.When the inlet velocity is 3.2 m/s,the maximum velocity of 4.10 m/s is at the elbow and the maximum velocity in the horizontal pipe is 3.91 m/s,which can both meet the stability requirement.The results of the simulation are proved to be reliable by the residual monitor plotting of related parameter,so it can be concluded that the system of pipe transportation is safe.
基金Projects(2006AA06Z374 2007AA021304) supported by the National High-Tech Research and Development Program of China
文摘A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mass to solution volume, flow velocity and temperature on Cr（Ⅵ） leaching. The optimal parameters were obtained for Cr（Ⅵ） leaching and a fitting model was established to describe the procedure of Cr（Ⅵ） leaching. The results show that Cr（Ⅵ） concentration in leachate increases with decreasing pH and increasing flow velocity and temperature. Moreover, Cr（Ⅵ） leaching percentage increases with increasing ratio of solid mass to solution volume. The optimal parameters for Cr（Ⅵ） selective leaching are as follows： pH=3.0, 1：5 of ratio of solid mass to solution volume, 180 mL/min of flow velocity and 40 ℃ of temperature. The procedure of Cr（Ⅵ） leaching fits well with the model： v= 1.87t^-0.54, indicating that the leaching rate of Cr（Ⅵ） declines in an exponential order of-0.54.
基金Project(2010QZZD021)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2015F024)supported by China Railway Science and Technology Research Development Program
文摘In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process(dynamic programming) model for railway freight reservation was formulated and the overbooking limit level was proposed as a control policy. However, computing the dynamic programming treatment needs six nested loops and this will be burdensome for real-world problems. To break through the calculation limit, the properties of value function were analyzed and the overbooking protection level was proposed to reduce the calculating quantity. The simulation experiments show that the overbooking protection level for the lower-fare class is higher than that for the higher-fare class, so the overbooking strategy is nested by fare class. Besides, by analyzing the influence on the overbooking strategy of freight arrival probability and cancellation probability, the proposed approach is efficient and also has a good application prospect in reality. Also, compared with the existing reservation(FCFS), the overbooking strategy performs better in the fields of vacancy reduction and revenue improvement.
