This work aims to investigate the application of ultrasound Doppler velocimetry in multiphase flow.The experimental results show that in the homogeneous liquid-solid system,the amplitude of the received echo energy de...This work aims to investigate the application of ultrasound Doppler velocimetry in multiphase flow.The experimental results show that in the homogeneous liquid-solid system,the amplitude of the received echo energy decreases exponentially with measurement depth,and attenuation rate increases with increase of solid holdup monotonously.A model based on the ultrasound reflection and refraction law and scatter characteristics of particles is proposed to predict the relationship between received echo energy and solid holdup.In the gas-liquid system,liquid velocity and bubble rise velocity can be directly obtained from the velocity profile by Dop 2000 when the bubble number is small,while in medium gas velocity range,FFT must be executed to calculate velocity distribution, resulting in a two-peak distribution,which in turn can be used to obtain liquid velocity and bubble velocity by further data processing.展开更多
Liquid metal flow behavior in round strands continuous casting under intermittently reversing direction electromagnetic stirring was measured by ultrasonic Doppler velocity-meter in a physical simulation system in ord...Liquid metal flow behavior in round strands continuous casting under intermittently reversing direction electromagnetic stirring was measured by ultrasonic Doppler velocity-meter in a physical simulation system in order to investigate the effects of time interval(t_i)of periodically reversed magnetic field on the spatial and temporal flow.The results show that under electromagnetic stirring with direction reserved magnetic field,there's a periodically change of the metal flow velocity and rotation direction with the periodically direction changing of the magnetic field.From both the experimental and mathematical model calculation results,it is found that when t_i is nearly equal to the time required for the metal flow speeding to the maximum velocity from still and decreases to zero again,there is a critical value of the rate of dynamic pressure,which means the wash effect of the liquid metal flow.On this point,rate of dynamic pressure was proposed to be a criterion for optimization the processing of electromagnetic stirring.展开更多
Option is a promising method to discover the hierarchical structure in reinforcement learning （RL） for learning acceleration. The key to option discovery is about how an agent can find useful subgoals autonomically ...Option is a promising method to discover the hierarchical structure in reinforcement learning （RL） for learning acceleration. The key to option discovery is about how an agent can find useful subgoals autonomically among the passing trails. By analyzing the agent＇s actions in the trails, useful heuristics can be found. Not only does the agent pass subgoals more frequently, but also its effective actions are restricted in subgoals. As a consequence, the subgoals can be deemed as the most matching action-restricted states in the paths. In the grid-world environment, the concept of the unique-direction value reflecting the action-restricted property was introduced to find the most matching action-restricted states. The unique-direction-value （UDV） approach is chosen to form options offline and online autonomically. Experiments show that the approach can find subgoals correctly. Thus the Q-learning with options found on both offline and online process can accelerate learning significantly.展开更多
文摘This work aims to investigate the application of ultrasound Doppler velocimetry in multiphase flow.The experimental results show that in the homogeneous liquid-solid system,the amplitude of the received echo energy decreases exponentially with measurement depth,and attenuation rate increases with increase of solid holdup monotonously.A model based on the ultrasound reflection and refraction law and scatter characteristics of particles is proposed to predict the relationship between received echo energy and solid holdup.In the gas-liquid system,liquid velocity and bubble rise velocity can be directly obtained from the velocity profile by Dop 2000 when the bubble number is small,while in medium gas velocity range,FFT must be executed to calculate velocity distribution, resulting in a two-peak distribution,which in turn can be used to obtain liquid velocity and bubble velocity by further data processing.
基金Item Sponsored by National Natural Science Foundation of China(No.50874133)
文摘Liquid metal flow behavior in round strands continuous casting under intermittently reversing direction electromagnetic stirring was measured by ultrasonic Doppler velocity-meter in a physical simulation system in order to investigate the effects of time interval(t_i)of periodically reversed magnetic field on the spatial and temporal flow.The results show that under electromagnetic stirring with direction reserved magnetic field,there's a periodically change of the metal flow velocity and rotation direction with the periodically direction changing of the magnetic field.From both the experimental and mathematical model calculation results,it is found that when t_i is nearly equal to the time required for the metal flow speeding to the maximum velocity from still and decreases to zero again,there is a critical value of the rate of dynamic pressure,which means the wash effect of the liquid metal flow.On this point,rate of dynamic pressure was proposed to be a criterion for optimization the processing of electromagnetic stirring.
基金supported by the National Basic Research Program of China (2013CB329603)the National Natural Science Foundation of China (61375058, 71231002)+1 种基金the China Mobile Research Fund (MCM 20130351)the Ministry of Education of China and the Special Co-Construction Project of Beijing Municipal Commission of Education
文摘Option is a promising method to discover the hierarchical structure in reinforcement learning （RL） for learning acceleration. The key to option discovery is about how an agent can find useful subgoals autonomically among the passing trails. By analyzing the agent＇s actions in the trails, useful heuristics can be found. Not only does the agent pass subgoals more frequently, but also its effective actions are restricted in subgoals. As a consequence, the subgoals can be deemed as the most matching action-restricted states in the paths. In the grid-world environment, the concept of the unique-direction value reflecting the action-restricted property was introduced to find the most matching action-restricted states. The unique-direction-value （UDV） approach is chosen to form options offline and online autonomically. Experiments show that the approach can find subgoals correctly. Thus the Q-learning with options found on both offline and online process can accelerate learning significantly.
