The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea...The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea level （ASL）, and annual reservoir regulation has caused a 30-m water level difference after impoundment of the TGR since September 2008. This paper first presents the spatiotemporal distribution of landslides in six periods of 175 m ASL trial impoundments from 2008 to 2014. The results show that the number of landslides sharply decreased from 273 at the initial stage to less than ten at the second stage of impoundment. Based on this, the reservoir-induced landslides in the TGR region can be roughly classified into five failure patterns, i.e. accumulation landslide, dip-slope landslide, reversed bedding landslide, rockfall, and karst breccia landslide. The accumulation landslides and dip-slope landslides account for more than 90%. Taking the Shuping accumulation landslide （a sliding mass volume of 20.7 × 106 m^3） in Zigui County and the Outang dip-slope landslide （a sliding mass volume of about 90 × 106 m^3） in Fengjie County as two typical cases, the mechanisms of reactivation of the two landslides are analyzed. The monitoring data and factor of safety （FOS） calculation show that the accumulation landslide is dominated by water level variation in the reservoir as most part of the mass body is under 175 m ASL, and the dip-slope landslide is controlled by the coupling effect of reservoir water level variation and precipitation as an extensive recharge area of rainfall from the rear and the front mass is below 175 m ASL. The characteristics of landslide-induced impulsive wave hazards after and before reservoir impoundment are studied, and the probability of occurrence of a landslide-induced impulsive wave hazard has increased in the reservoir region. Simulation results of the Ganjingzi landslide in Wushan County indicate the strong relationship between landslide-induced surge and water variation with high potential risk to shipping and residential areas. Regarding reservoir regulation in TGR when using a single index, i.e. 1-d water level variation, water resources are not well utilized, and there is also potential risk of disasters since 2008. In addition, various indices such as 1-d, 5-d, and 10-d water level variations are proposed for reservoir regulation. Finally, taking reservoir-induced landslides in June 2015 for example, the feasibility of the optimizing indices of water level variations is verified.展开更多
Purpose–The quad-rotor is an under-actuation,strong coupled nonlinear system with parameters uncertainty,unmodeled disturbance and drive capability boundedness.The purpose of the paper is to design a flight control s...Purpose–The quad-rotor is an under-actuation,strong coupled nonlinear system with parameters uncertainty,unmodeled disturbance and drive capability boundedness.The purpose of the paper is to design a flight control system to regulate the aircraft track the desired trajectory and keep the attitude angles stable on account of these issues.Design/methodology/approach–Considering the dynamics of a quad-rotor,the closed-loop flight control system is divided into two nested loops:the translational outer-loop and the attitude inner-loop.In the outer-loop,the translational controller,which exports the desired attitude angles to the inner-loop,is designed based on bounded control technique.In consideration of the influence of uncertain rotational inertia and external disturbance,the backstepping sliding mode approach with adaptive gains is used in the inner-loop.The switching control strategy based on the sign functions of sliding surface is introduced into the design procedure with respect to the input saturation.Findings–The validity of the proposed flight control system was verified through numerical simulation and prototype flight experiment in this paper.Furthermore,with relation to the flying,the motor speed is kept in the predetermined scope.Originality/value–This article introduces a new flight control system designed for a quad-rotor.展开更多
To improve the seismic performance of reinforced concrete core walls,reinforced concrete com-posite core walls with concealed steel truss were proposed and systemically investigated.Two 1/6 scale core wall specimens,i...To improve the seismic performance of reinforced concrete core walls,reinforced concrete com-posite core walls with concealed steel truss were proposed and systemically investigated.Two 1/6 scale core wall specimens,including a normal reinforced concrete core wall and a reinforced concrete composite core wall with concealed steel truss,were designed.The experimental study on seismic performance under cyclic loading was carried out.The load-carrying capacity,stiffness,ductility,hysteretic behavior and energy dissipation of the core walls were discussed.The test results showed that the seismic performance of core walls is improved greatly by the concealed steel truss.The calculated results were found to agree well with the actual measured ones.展开更多
基金The"Twelfth Five-Year Plan"of the National Science and Technology Support Project(Grant No.2012BAK10B01)the National Natural Science Foundation of China(Grant Nos.41372321 and 41502305)China Geological Survey Projects(Grant No.121201009000150018)
文摘The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea level （ASL）, and annual reservoir regulation has caused a 30-m water level difference after impoundment of the TGR since September 2008. This paper first presents the spatiotemporal distribution of landslides in six periods of 175 m ASL trial impoundments from 2008 to 2014. The results show that the number of landslides sharply decreased from 273 at the initial stage to less than ten at the second stage of impoundment. Based on this, the reservoir-induced landslides in the TGR region can be roughly classified into five failure patterns, i.e. accumulation landslide, dip-slope landslide, reversed bedding landslide, rockfall, and karst breccia landslide. The accumulation landslides and dip-slope landslides account for more than 90%. Taking the Shuping accumulation landslide （a sliding mass volume of 20.7 × 106 m^3） in Zigui County and the Outang dip-slope landslide （a sliding mass volume of about 90 × 106 m^3） in Fengjie County as two typical cases, the mechanisms of reactivation of the two landslides are analyzed. The monitoring data and factor of safety （FOS） calculation show that the accumulation landslide is dominated by water level variation in the reservoir as most part of the mass body is under 175 m ASL, and the dip-slope landslide is controlled by the coupling effect of reservoir water level variation and precipitation as an extensive recharge area of rainfall from the rear and the front mass is below 175 m ASL. The characteristics of landslide-induced impulsive wave hazards after and before reservoir impoundment are studied, and the probability of occurrence of a landslide-induced impulsive wave hazard has increased in the reservoir region. Simulation results of the Ganjingzi landslide in Wushan County indicate the strong relationship between landslide-induced surge and water variation with high potential risk to shipping and residential areas. Regarding reservoir regulation in TGR when using a single index, i.e. 1-d water level variation, water resources are not well utilized, and there is also potential risk of disasters since 2008. In addition, various indices such as 1-d, 5-d, and 10-d water level variations are proposed for reservoir regulation. Finally, taking reservoir-induced landslides in June 2015 for example, the feasibility of the optimizing indices of water level variations is verified.
文摘Purpose–The quad-rotor is an under-actuation,strong coupled nonlinear system with parameters uncertainty,unmodeled disturbance and drive capability boundedness.The purpose of the paper is to design a flight control system to regulate the aircraft track the desired trajectory and keep the attitude angles stable on account of these issues.Design/methodology/approach–Considering the dynamics of a quad-rotor,the closed-loop flight control system is divided into two nested loops:the translational outer-loop and the attitude inner-loop.In the outer-loop,the translational controller,which exports the desired attitude angles to the inner-loop,is designed based on bounded control technique.In consideration of the influence of uncertain rotational inertia and external disturbance,the backstepping sliding mode approach with adaptive gains is used in the inner-loop.The switching control strategy based on the sign functions of sliding surface is introduced into the design procedure with respect to the input saturation.Findings–The validity of the proposed flight control system was verified through numerical simulation and prototype flight experiment in this paper.Furthermore,with relation to the flying,the motor speed is kept in the predetermined scope.Originality/value–This article introduces a new flight control system designed for a quad-rotor.
文摘To improve the seismic performance of reinforced concrete core walls,reinforced concrete com-posite core walls with concealed steel truss were proposed and systemically investigated.Two 1/6 scale core wall specimens,including a normal reinforced concrete core wall and a reinforced concrete composite core wall with concealed steel truss,were designed.The experimental study on seismic performance under cyclic loading was carried out.The load-carrying capacity,stiffness,ductility,hysteretic behavior and energy dissipation of the core walls were discussed.The test results showed that the seismic performance of core walls is improved greatly by the concealed steel truss.The calculated results were found to agree well with the actual measured ones.
