简述了仿真实验设计与分析(design and analysis of simulation experiment,DASE)的几个基本术语和理论框架,在这一理论框架下对国内外物流系统的优化设计案例进行了总结和回顾,展示了实际物流系统与DASE理论相结合所取得的应用成果;通...简述了仿真实验设计与分析(design and analysis of simulation experiment,DASE)的几个基本术语和理论框架,在这一理论框架下对国内外物流系统的优化设计案例进行了总结和回顾,展示了实际物流系统与DASE理论相结合所取得的应用成果;通过与DASE前沿理论的比较指明了两者结合的未来是值得关注的发展方向。本研究为实际仿真问题的优化提供了一定的方法参考,也为方法研究者提供了更丰富的实际素材。展开更多
厘清气候变化和人类活动对植被净初级生产力(NPP)的影响,对区域生态系统变化与可持续发展具有重要意义。基于CASA模型,利用1994—2018年5期Landsat遥感影像及气象数据,通过仿真情景实验研究了人类活动和气候变化对哈萨克斯坦首都圈植被...厘清气候变化和人类活动对植被净初级生产力(NPP)的影响,对区域生态系统变化与可持续发展具有重要意义。基于CASA模型,利用1994—2018年5期Landsat遥感影像及气象数据,通过仿真情景实验研究了人类活动和气候变化对哈萨克斯坦首都圈植被净生产力的影响。结果表明:(1)1994—2018年间,哈萨克斯坦首都圈植被NPP呈波动上升趋势,NPP多年均值为226.21 g C·m^(-2)·a^(-1);(2)首都圈人工造林面积不断增加,对NPP有显著的正增益效果(0.38 Tg C·a^(-1),P<0.01),而气候变化对NPP影响波动比较大,整体上呈现负增益效果(-0.07 Tg C·a^(-1),P=0.34);在土地覆盖变化和气候变化共同作用下,哈萨克斯坦首都圈植被NPP总体上呈显著正增益效果(0.27 Tg C·a^(-1),P<0.1)。相较于气候变化,人类活动对植被净初级生产力影响更加明显,相关性也更强;(3)气候因子中温度、太阳辐射和降水是影响NPP的主要因素。1994—2000年和2006—2012年期间由于温度的升高和降雨量的减少导致NPP损失,分别由218.50 g C·m^(-2)·a^(-1)、201.19 g C·m^(-2)·a^(-1)降到189.00 g C·m^(-2)·a^(-1)、188.48 g C·m^(-2)·a^(-1);2000—2006年和2012—2018年期间随着降水条件的改善,该地区NPP均值显著上升,均值分别达到201.19 g C·m^(-2)·a^(-1)、207.73 g C·m^(-2)·a^(-1)。本文研究结果有助于揭示气候变化和人类活动对植被NPP的影响机制,可为改善荒漠草原区生态环境质量,缓解全球变暖问题和实现哈萨克斯坦2060年碳中和目标提供参考。展开更多
The application of new-designed levitation controller requires extensive validation prior to enter into commercial service. However, huge mounts of approximations and assumptions lead the theoretical analysis away fro...The application of new-designed levitation controller requires extensive validation prior to enter into commercial service. However, huge mounts of approximations and assumptions lead the theoretical analysis away from the engineering practice. The experimental methods are time-consuming and financial expensive, even unrealizable due to the lack of suitable sensors. Numerical simulations can bridge the gap between the theoretical analysis and experimental techniques. A complete overall dynamic model of maglev levitation system is derived in this work, which includes the simple-supported bridges, the calculation of electromagnetic force with more details, the stress of levitation modules and the cabin. Based on the aforementioned model, it shows that the inherent nonlinearity, inner coupling, misalignments between the sensors and actuators, and self-excited vibration are the main issues that should be considered during the design process of controller. Then, the backstepping controller based on the mathematical model of the module with reasonable simplifications is proposed, and the stability proofs are listed. To show the advantage of controller, two numerical simulation experiments are carried out. Finally, the results illustrating closed-loop performance are provided.展开更多
文摘简述了仿真实验设计与分析(design and analysis of simulation experiment,DASE)的几个基本术语和理论框架,在这一理论框架下对国内外物流系统的优化设计案例进行了总结和回顾,展示了实际物流系统与DASE理论相结合所取得的应用成果;通过与DASE前沿理论的比较指明了两者结合的未来是值得关注的发展方向。本研究为实际仿真问题的优化提供了一定的方法参考,也为方法研究者提供了更丰富的实际素材。
文摘厘清气候变化和人类活动对植被净初级生产力(NPP)的影响,对区域生态系统变化与可持续发展具有重要意义。基于CASA模型,利用1994—2018年5期Landsat遥感影像及气象数据,通过仿真情景实验研究了人类活动和气候变化对哈萨克斯坦首都圈植被净生产力的影响。结果表明:(1)1994—2018年间,哈萨克斯坦首都圈植被NPP呈波动上升趋势,NPP多年均值为226.21 g C·m^(-2)·a^(-1);(2)首都圈人工造林面积不断增加,对NPP有显著的正增益效果(0.38 Tg C·a^(-1),P<0.01),而气候变化对NPP影响波动比较大,整体上呈现负增益效果(-0.07 Tg C·a^(-1),P=0.34);在土地覆盖变化和气候变化共同作用下,哈萨克斯坦首都圈植被NPP总体上呈显著正增益效果(0.27 Tg C·a^(-1),P<0.1)。相较于气候变化,人类活动对植被净初级生产力影响更加明显,相关性也更强;(3)气候因子中温度、太阳辐射和降水是影响NPP的主要因素。1994—2000年和2006—2012年期间由于温度的升高和降雨量的减少导致NPP损失,分别由218.50 g C·m^(-2)·a^(-1)、201.19 g C·m^(-2)·a^(-1)降到189.00 g C·m^(-2)·a^(-1)、188.48 g C·m^(-2)·a^(-1);2000—2006年和2012—2018年期间随着降水条件的改善,该地区NPP均值显著上升,均值分别达到201.19 g C·m^(-2)·a^(-1)、207.73 g C·m^(-2)·a^(-1)。本文研究结果有助于揭示气候变化和人类活动对植被NPP的影响机制,可为改善荒漠草原区生态环境质量,缓解全球变暖问题和实现哈萨克斯坦2060年碳中和目标提供参考。
基金Projects(60404003,11202230)supported by the National Natural Science Foundation of China
文摘The application of new-designed levitation controller requires extensive validation prior to enter into commercial service. However, huge mounts of approximations and assumptions lead the theoretical analysis away from the engineering practice. The experimental methods are time-consuming and financial expensive, even unrealizable due to the lack of suitable sensors. Numerical simulations can bridge the gap between the theoretical analysis and experimental techniques. A complete overall dynamic model of maglev levitation system is derived in this work, which includes the simple-supported bridges, the calculation of electromagnetic force with more details, the stress of levitation modules and the cabin. Based on the aforementioned model, it shows that the inherent nonlinearity, inner coupling, misalignments between the sensors and actuators, and self-excited vibration are the main issues that should be considered during the design process of controller. Then, the backstepping controller based on the mathematical model of the module with reasonable simplifications is proposed, and the stability proofs are listed. To show the advantage of controller, two numerical simulation experiments are carried out. Finally, the results illustrating closed-loop performance are provided.
