In order to reduce the uncertainty of offline land surface model （LSM） simulations of land evapotranspiration （ET）, we used ensemble simulations based on three meteorological forcing datasets [Princeton, ITPCAS （...In order to reduce the uncertainty of offline land surface model （LSM） simulations of land evapotranspiration （ET）, we used ensemble simulations based on three meteorological forcing datasets [Princeton, ITPCAS （Institute of Tibetan Plateau Research, Chinese Academy of Sciences）, Qian] and four LSMs （BATS, VIC, CLM3.0 and CLM3.5）, to explore the trends and spatiotemporal characteristics of ET, as well as the spatiotemporal pattern of ET in response to climate factors over China's Mainland during 1982-2007. The results showed that various simulations of each member and their arithmetic mean （EnsAVlean） could capture the spatial distribution and seasonal pattern of ET sufficiently well, where they exhibited more significant spatial and seasonal variation in the ET compared with observation-based ET estimates （Obs_MTE）. For the mean annual ET, we found that the BATS forced by Princeton forcing overestimated the annual mean ET compared with Obs_MTE for most of the basins in China, whereas the VIC forced by Princeton forcing showed underestimations. By contrast, the Ens_Mean was closer to Obs_MTE, although the results were underestimated over Southeast China. Furthermore, both the Obs_MTE and Ens_Mean exhibited a significant increasing trend during 1982-98; whereas after 1998, when the last big EI Nifio event occurred, the Ens_Mean tended to decrease significantly between 1999 and 2007, although the change was not significant for Obs_MTE. Changes in air temperature and shortwave radiation played key roles in the long-term variation in ET over the humid area of China, but precipitation mainly controlled the long-term variation in ET in arid and semi-arid areas of China.展开更多
We present a systematic investigation of the impact of changing the geometry structure of the SPC/E water model by performing a series of molecular dynamic simulations at 1 bar （1 bar = 105 Pa） and 298.15 K. The geo...We present a systematic investigation of the impact of changing the geometry structure of the SPC/E water model by performing a series of molecular dynamic simulations at 1 bar （1 bar = 105 Pa） and 298.15 K. The geometric modification includes altering the H-O-H angle range from 90° to 115° and modifying the O-H length range from 0.90 A to 1.10 A in the SPC/E model. The former is achieved by keeping the dipole moment constant by modifying the O-H length, while in the latter only the O-H length is changed. With the larger bond length and angle, we find that the liquid shows a strong quadrupole interaction and high tetrahedral structure order parameter, resulting in the enhancement of the network structure of the liquid. When the bond length or angle is reduced, the hydrogen bond lifetime and self-diffusion constant decrease due to the weakening of the intermolecular interaction. We find that modifying the water molecular bond length leading to the variation of the intermolecular interaction strength is more intensive than changing the bond angle. Through calculating the average reduced density gradient and thermal fluctuation index, it is found that the scope of vdW interaction with neighbouring water molecules is inversely proportional to the change of the bond length and angle. The effect is mainly due to a significant change of the hydrogen bond network. To study the effect of water models as a solvent whose geometry has been modified, the solutions of ions in different solvent environments are examined by introducing NaCI. During the dissolving process, NaCI ions are ideally dissolved in SPC/E water and bond with natural water more easily than with other solvent models.展开更多
空间站在轨组装和长期运营阶段涉及到多飞行器独立飞行、飞行器间交会对接、多飞行器组合体融合控制、多飞行器分离过程控制和飞行器返回再入等复杂飞行任务,完整、真实的飞行模拟是必需且至关重要的.基于时间同步、实时数据交换的分布...空间站在轨组装和长期运营阶段涉及到多飞行器独立飞行、飞行器间交会对接、多飞行器组合体融合控制、多飞行器分离过程控制和飞行器返回再入等复杂飞行任务,完整、真实的飞行模拟是必需且至关重要的.基于时间同步、实时数据交换的分布式一体化仿真架构,设计了一种多飞行器协同的通用半物理制导、导航与控制(guidance,navigation and control,GNC)系统飞行模拟平台,可很好地满足复杂系统的飞行模拟需要.平台由若干灵活、可扩展的通用模拟器构成,单个模拟器通过配置可以实现任一飞行器的功能,能够独立对指定飞行器的全任务过程进行仿真.平台通过靶场仪器组B时间码(inter-range instramentation group-B,IRIG-B)信号进行时间同步,利用1553B总线完成动力学仿真数据实时交换,并在多模拟器之间通过协调机制实现热并网后进行协同仿真.该模拟平台成功应用于空间站飞行控制演练.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.4140508391437220 and 41305066)+1 种基金the Natural Science Foundation of Hunan Province(Grant No.2015JJ3098)the Fund Project for The Education Department of Hunan Province(Grant No.14C0897)
文摘In order to reduce the uncertainty of offline land surface model （LSM） simulations of land evapotranspiration （ET）, we used ensemble simulations based on three meteorological forcing datasets [Princeton, ITPCAS （Institute of Tibetan Plateau Research, Chinese Academy of Sciences）, Qian] and four LSMs （BATS, VIC, CLM3.0 and CLM3.5）, to explore the trends and spatiotemporal characteristics of ET, as well as the spatiotemporal pattern of ET in response to climate factors over China's Mainland during 1982-2007. The results showed that various simulations of each member and their arithmetic mean （EnsAVlean） could capture the spatial distribution and seasonal pattern of ET sufficiently well, where they exhibited more significant spatial and seasonal variation in the ET compared with observation-based ET estimates （Obs_MTE）. For the mean annual ET, we found that the BATS forced by Princeton forcing overestimated the annual mean ET compared with Obs_MTE for most of the basins in China, whereas the VIC forced by Princeton forcing showed underestimations. By contrast, the Ens_Mean was closer to Obs_MTE, although the results were underestimated over Southeast China. Furthermore, both the Obs_MTE and Ens_Mean exhibited a significant increasing trend during 1982-98; whereas after 1998, when the last big EI Nifio event occurred, the Ens_Mean tended to decrease significantly between 1999 and 2007, although the change was not significant for Obs_MTE. Changes in air temperature and shortwave radiation played key roles in the long-term variation in ET over the humid area of China, but precipitation mainly controlled the long-term variation in ET in arid and semi-arid areas of China.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11635003,11025524,and 11161130520)the National Basic Research Program of China(Grant No.2010CB832903)the European Commission’s 7th Framework Programme(Fp7-PEOPLE-2010-IRSES)(Grant Agreement Project No.269131)
文摘We present a systematic investigation of the impact of changing the geometry structure of the SPC/E water model by performing a series of molecular dynamic simulations at 1 bar （1 bar = 105 Pa） and 298.15 K. The geometric modification includes altering the H-O-H angle range from 90° to 115° and modifying the O-H length range from 0.90 A to 1.10 A in the SPC/E model. The former is achieved by keeping the dipole moment constant by modifying the O-H length, while in the latter only the O-H length is changed. With the larger bond length and angle, we find that the liquid shows a strong quadrupole interaction and high tetrahedral structure order parameter, resulting in the enhancement of the network structure of the liquid. When the bond length or angle is reduced, the hydrogen bond lifetime and self-diffusion constant decrease due to the weakening of the intermolecular interaction. We find that modifying the water molecular bond length leading to the variation of the intermolecular interaction strength is more intensive than changing the bond angle. Through calculating the average reduced density gradient and thermal fluctuation index, it is found that the scope of vdW interaction with neighbouring water molecules is inversely proportional to the change of the bond length and angle. The effect is mainly due to a significant change of the hydrogen bond network. To study the effect of water models as a solvent whose geometry has been modified, the solutions of ions in different solvent environments are examined by introducing NaCI. During the dissolving process, NaCI ions are ideally dissolved in SPC/E water and bond with natural water more easily than with other solvent models.
文摘空间站在轨组装和长期运营阶段涉及到多飞行器独立飞行、飞行器间交会对接、多飞行器组合体融合控制、多飞行器分离过程控制和飞行器返回再入等复杂飞行任务,完整、真实的飞行模拟是必需且至关重要的.基于时间同步、实时数据交换的分布式一体化仿真架构,设计了一种多飞行器协同的通用半物理制导、导航与控制(guidance,navigation and control,GNC)系统飞行模拟平台,可很好地满足复杂系统的飞行模拟需要.平台由若干灵活、可扩展的通用模拟器构成,单个模拟器通过配置可以实现任一飞行器的功能,能够独立对指定飞行器的全任务过程进行仿真.平台通过靶场仪器组B时间码(inter-range instramentation group-B,IRIG-B)信号进行时间同步,利用1553B总线完成动力学仿真数据实时交换,并在多模拟器之间通过协调机制实现热并网后进行协同仿真.该模拟平台成功应用于空间站飞行控制演练.
