Vegetation is an important factor linking the atmosphere,water,soil,and biological functions,and it plays a specific role in the climate change response and sustainable development of regional economies.However,little...Vegetation is an important factor linking the atmosphere,water,soil,and biological functions,and it plays a specific role in the climate change response and sustainable development of regional economies.However,little information is available on vegetation vulnerability and its driving mechanism.Therefore,studying temporal and spatial change characteristics of vegetation and their corresponding mechanisms is important for assessing ecosystem stability and formulating ecological policies in the Kherlen River Basin.We used Moderate-resolution Imaging Spectroradiometer(MODIS)normalized difference vegetation index(NDVI)remote sensing images from 2000 to 2020 to analyse temporal changes in NDVI with the autoregressive moving average model(ARMA)and the breaks for additive season trend(BFAST)in the basin and to assess natural,anthropogenic and topographic factors with the Geodetector model.The results show that:1)the long NDVI time series remained stable in the Kherlen River Basin from 2000 to 2020,with a certain significant mutation period from 2013 to 2017;2)the coefficient of variation(CV)in the analysis of the spatial NDVI was generally constant,mainly at the level of 0.01–0.07,and the spatial NDVI change was minimally impacted by external interference;and 3)temperature and precipitation are the key factors affecting the NDVI in the basin,and changes in local hydrothermal conditions directly affect the local NDVI.The results of this study could provide a scientific basis for the effective protection of the ecological environment and will aid in understanding the influence of vegetation change mechanisms and the corresponding factors.展开更多
目的研究某型飞行人员单人漂浮装置在强风浪海况下的漂浮姿态及漂浮稳定性,指导结构优化。方法构建基于重叠网格的多自由度运动仿真计算方法,在非定常雷诺平均Navier-Stokes方程基础之上引入流体体积(volume of fluid,VOF)多相流模型和...目的研究某型飞行人员单人漂浮装置在强风浪海况下的漂浮姿态及漂浮稳定性,指导结构优化。方法构建基于重叠网格的多自由度运动仿真计算方法,在非定常雷诺平均Navier-Stokes方程基础之上引入流体体积(volume of fluid,VOF)多相流模型和湍流模型,对漂浮装置进行结构简化建模,模拟并分析5级海况上限条件下波浪周期内漂浮装置的运动姿态。结果在自由漂浮状态下,装置主要受到横浪的影响而发生侧向倾覆;通过船底下沉式设计、在两侧浮筒下方中心位置增加平衡水袋以及在浮筒外侧增加辅助气囊可以有效提高装置在横浪冲击下抗侧倾的能力,且装置绕垂直轴发生的偏摆角度随水袋数量增加而减小,辅助气囊尺寸的增加也可进一步抑制装置侧向倾覆的角度。结论利用计算流体动力学(computational fluid dynamic,CFD)数值仿真模拟法研究漂浮装置漂浮姿态及稳定性具有可行性,提升装置载人后重心与浮心空间位置的一致性、增加装置绕垂直轴的转动惯量、增大装置产生侧倾趋势后的恢复力矩以及增加其抗倾覆力矩,可有效提升漂浮装置整体漂浮稳定性。展开更多
基金Under the auspices of Project of Inner Mongolia Normal University to Introduce High-level Talents to Start Scientific Research (No.1004021709)Key Special Project of Inner Mongolia (No.2020ZD0028)Science and Technology Planning Project of Inner Mongolia Autonomous Region (No.2022YFSH0027)。
文摘Vegetation is an important factor linking the atmosphere,water,soil,and biological functions,and it plays a specific role in the climate change response and sustainable development of regional economies.However,little information is available on vegetation vulnerability and its driving mechanism.Therefore,studying temporal and spatial change characteristics of vegetation and their corresponding mechanisms is important for assessing ecosystem stability and formulating ecological policies in the Kherlen River Basin.We used Moderate-resolution Imaging Spectroradiometer(MODIS)normalized difference vegetation index(NDVI)remote sensing images from 2000 to 2020 to analyse temporal changes in NDVI with the autoregressive moving average model(ARMA)and the breaks for additive season trend(BFAST)in the basin and to assess natural,anthropogenic and topographic factors with the Geodetector model.The results show that:1)the long NDVI time series remained stable in the Kherlen River Basin from 2000 to 2020,with a certain significant mutation period from 2013 to 2017;2)the coefficient of variation(CV)in the analysis of the spatial NDVI was generally constant,mainly at the level of 0.01–0.07,and the spatial NDVI change was minimally impacted by external interference;and 3)temperature and precipitation are the key factors affecting the NDVI in the basin,and changes in local hydrothermal conditions directly affect the local NDVI.The results of this study could provide a scientific basis for the effective protection of the ecological environment and will aid in understanding the influence of vegetation change mechanisms and the corresponding factors.
文摘目的研究某型飞行人员单人漂浮装置在强风浪海况下的漂浮姿态及漂浮稳定性,指导结构优化。方法构建基于重叠网格的多自由度运动仿真计算方法,在非定常雷诺平均Navier-Stokes方程基础之上引入流体体积(volume of fluid,VOF)多相流模型和湍流模型,对漂浮装置进行结构简化建模,模拟并分析5级海况上限条件下波浪周期内漂浮装置的运动姿态。结果在自由漂浮状态下,装置主要受到横浪的影响而发生侧向倾覆;通过船底下沉式设计、在两侧浮筒下方中心位置增加平衡水袋以及在浮筒外侧增加辅助气囊可以有效提高装置在横浪冲击下抗侧倾的能力,且装置绕垂直轴发生的偏摆角度随水袋数量增加而减小,辅助气囊尺寸的增加也可进一步抑制装置侧向倾覆的角度。结论利用计算流体动力学(computational fluid dynamic,CFD)数值仿真模拟法研究漂浮装置漂浮姿态及稳定性具有可行性,提升装置载人后重心与浮心空间位置的一致性、增加装置绕垂直轴的转动惯量、增大装置产生侧倾趋势后的恢复力矩以及增加其抗倾覆力矩,可有效提升漂浮装置整体漂浮稳定性。
