Wind erosion is a key global environmental problem and has many adverse effects.The Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually dis...Wind erosion is a key global environmental problem and has many adverse effects.The Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually distributed mosaically,and aeolian activities occur frequently.Vegetation plays a significant role in controlling wind erosion.Artemisia ordosica is the most dominant native plant species in the Mu Us Sandy Land.It is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy Land.This study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes,aeolian sediment transport,and surface change of Artemisia ordosica plots with four coverages(denoted as site A,site B,site C,and site D)in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June 2019.The coverages of Artemisia ordosica at site A,site B,site C,and site D were 2%,16%,29%,and 69%,respectively.The annual average wind speeds at 2.0 m height above the ground for site A,site B,site C,and site D were 3.47,2.77,2.21,and 1.97 m/s,respectively.The annual drift potentials were 193.80,69.72,15.05,and 6.73 VU at site A,site B,site C,and site D,respectively.The total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A,site B,site C,and site D were 4633.61,896.80,10.54,and 6.14 kg/m,respectively.Site A had the largest surface changes,and the surface changes at site B were significantly weaker than those at site A,whereas the surface changes at site C and site D were minimal.The results indicated that Artemisia ordosica significantly reduced the wind speed,drift potential,aeolian sediment transport,and surface changes.The higher the coverage of Artemisia ordosica is,the more obvious the effects of wind-proof and sand-fixing.Wind erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%.These results provide a scientific basis for evaluating the ecosystem service function of Artemisia ordosica and the vegetation protection and construction projects in the Mu Us Sandy Land.展开更多
风速的随机性和风电机组控制系统的非线性导致难以获取风电机组精确的数学模型。鉴于实际的风电工程通常采用简单的比例-积分-微分(proportional integral differential,PID)控制器或比例-积分(proportional integral,PI)控制器达到输...风速的随机性和风电机组控制系统的非线性导致难以获取风电机组精确的数学模型。鉴于实际的风电工程通常采用简单的比例-积分-微分(proportional integral differential,PID)控制器或比例-积分(proportional integral,PI)控制器达到输出恒定功率的控制目标,不涉及复杂的智能控制算法,在风速高于额定风速时,提出了一种基于加性分解原理的方法来规范风力发电机组变桨控制器的设计参数,将风力发电机组变桨控制问题分解为2个简单的子问题,即线性时不变主系统的追踪问题和辅系统的镇定问题。基于该原理,设计出了简单的PI控制器,并在此基础上进行了控制器优化设计,而且通过理论推导给出了该控制器的稳定性证明,最后通过仿真验证优化后的控制器能够大大增加输出功率的平稳性。这将为今后设计风力发电机组变桨控制器设计提供一定的准则。展开更多
基金the Fundamental Research Funds of Chinese Academy of Forestry(CAFYBB2019MA009)the National Natural Science Foundation of China(41701010)+1 种基金the Key Special Project on'Science and Technology Promoting the Development of Inner Mongolia Autonomous Region'(KJXM-EEDS-2020006)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2018459)。
文摘Wind erosion is a key global environmental problem and has many adverse effects.The Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually distributed mosaically,and aeolian activities occur frequently.Vegetation plays a significant role in controlling wind erosion.Artemisia ordosica is the most dominant native plant species in the Mu Us Sandy Land.It is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy Land.This study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes,aeolian sediment transport,and surface change of Artemisia ordosica plots with four coverages(denoted as site A,site B,site C,and site D)in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June 2019.The coverages of Artemisia ordosica at site A,site B,site C,and site D were 2%,16%,29%,and 69%,respectively.The annual average wind speeds at 2.0 m height above the ground for site A,site B,site C,and site D were 3.47,2.77,2.21,and 1.97 m/s,respectively.The annual drift potentials were 193.80,69.72,15.05,and 6.73 VU at site A,site B,site C,and site D,respectively.The total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A,site B,site C,and site D were 4633.61,896.80,10.54,and 6.14 kg/m,respectively.Site A had the largest surface changes,and the surface changes at site B were significantly weaker than those at site A,whereas the surface changes at site C and site D were minimal.The results indicated that Artemisia ordosica significantly reduced the wind speed,drift potential,aeolian sediment transport,and surface changes.The higher the coverage of Artemisia ordosica is,the more obvious the effects of wind-proof and sand-fixing.Wind erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%.These results provide a scientific basis for evaluating the ecosystem service function of Artemisia ordosica and the vegetation protection and construction projects in the Mu Us Sandy Land.
文摘风速的随机性和风电机组控制系统的非线性导致难以获取风电机组精确的数学模型。鉴于实际的风电工程通常采用简单的比例-积分-微分(proportional integral differential,PID)控制器或比例-积分(proportional integral,PI)控制器达到输出恒定功率的控制目标,不涉及复杂的智能控制算法,在风速高于额定风速时,提出了一种基于加性分解原理的方法来规范风力发电机组变桨控制器的设计参数,将风力发电机组变桨控制问题分解为2个简单的子问题,即线性时不变主系统的追踪问题和辅系统的镇定问题。基于该原理,设计出了简单的PI控制器,并在此基础上进行了控制器优化设计,而且通过理论推导给出了该控制器的稳定性证明,最后通过仿真验证优化后的控制器能够大大增加输出功率的平稳性。这将为今后设计风力发电机组变桨控制器设计提供一定的准则。
