One main challenge for realistic quantum computing and quantum sensing is to combat noise.Three formal strategies including quantum error correction,[1,2]decoherence-free subspace[3,4]and dynamical decoupling[5]have b...One main challenge for realistic quantum computing and quantum sensing is to combat noise.Three formal strategies including quantum error correction,[1,2]decoherence-free subspace[3,4]and dynamical decoupling[5]have been developed for suppressing the noise.Quantum systems can lose their coherence when subjected to fluctuations of the local fields from their surrounding environments.Such decoherence phenomena are a fundamental effect in quantum physics and sometimes are referred to as a back-action from the measured system.As one typical dynamical decoupling technique,spin echo originated from magnetic resonance spectroscopy can average out the noise by flipping the target qubit.展开更多
Subsequent commutation failure(SCF)can be easily generated during the first commutation failure(CF)recovery process in a line-commutated converter-based high voltage direct-current system.SCF poses a significant threa...Subsequent commutation failure(SCF)can be easily generated during the first commutation failure(CF)recovery process in a line-commutated converter-based high voltage direct-current system.SCF poses a significant threat to the safe and stable operation of power systems,and accurate prediction of CF is thus important.However,SCF is affected by the operating characteristics of the main circuit and the coupling effects of sequential control response in the inverter station.These are difficult to predict accurately.In this paper,a new SCF prediction method considering the control response is proposed based on the physical principle of SCF.The time sequence and switching conditions of the controllers at different stages of the first CF recovery process are described,and the corresponding equations of commutation voltage affected by different controllers are derived.The calculation method of the SCF threshold voltage is proposed,and the prediction method is established.Simulations show that the proposed method can predict SCF accurately and provide useful tools to suppress SCF.展开更多
The shipbuilding industry is booming and the health problems of workers caused by the harsh indoor dock environmentforce us to explore efficient and reasonable ventilation methods suitable for large workshops.Due to t...The shipbuilding industry is booming and the health problems of workers caused by the harsh indoor dock environmentforce us to explore efficient and reasonable ventilation methods suitable for large workshops.Due to the strongspecificity of large workshops,general or local ventilation methods cannot be universally applied.It has great potentialand good economy to improve indoor environment by changing natural ventilation design.Computational fluiddynamics(CFD)has gradually become a powerful tool for predicting indoor and outdoor airflow organization andoptimizing indoor ventilation.This paper adopts CFD to study the effect of the inflow wind speed,the position of theside wall shutters,the area ratio and form of roof ventilators on the effectiveness of natural ventilation in a large shipyarddriven by wind pressure.The results show that the influence on total ventilation volume is more obvious whenthe intake side is shaded than the exhaust side.Different incoming wind speeds will affect the wind pressure at theventilation position,which is the decisive external factor affecting the natural ventilation of docks.When the area ratioof roof ventilators increases to a certain extent,its continued increase has an insignificant effect on the total ventilationvolume.The influence of changing the arrangement of the roof ventilator on the natural ventilation effect can beneglected when the area ratio is kept constant.展开更多
A new type of liquid–solid fluidized bed,named circulating conventional fluidized bed(CCFB)which operates below particle terminal velocity was proposed and experimentally studied.The hydrodynamic behavior was systema...A new type of liquid–solid fluidized bed,named circulating conventional fluidized bed(CCFB)which operates below particle terminal velocity was proposed and experimentally studied.The hydrodynamic behavior was systematically studied in a liquid–solid CCFB of 0.032 m I.D.and 4.5 m in height with five different types of particles.Liquid–solid fluidization with external particle circulation was experimentally realized below the particle terminal velocity.The axial distribution of local solids holdup was obtained and found to be fairly uniform in a wide range of liquid velocities and solids circulation rates.The average solids holdup is found to be significantly increased compared with conventional fluidization at similar conditions.The effect of particle properties and operating conditions on bed behavior was investigated as well.Results show that particles with higher terminal velocity have higher average solids holdup.展开更多
文摘One main challenge for realistic quantum computing and quantum sensing is to combat noise.Three formal strategies including quantum error correction,[1,2]decoherence-free subspace[3,4]and dynamical decoupling[5]have been developed for suppressing the noise.Quantum systems can lose their coherence when subjected to fluctuations of the local fields from their surrounding environments.Such decoherence phenomena are a fundamental effect in quantum physics and sometimes are referred to as a back-action from the measured system.As one typical dynamical decoupling technique,spin echo originated from magnetic resonance spectroscopy can average out the noise by flipping the target qubit.
基金supported in part by the National Natural Science Foundation of China under Grant(51877018).
文摘Subsequent commutation failure(SCF)can be easily generated during the first commutation failure(CF)recovery process in a line-commutated converter-based high voltage direct-current system.SCF poses a significant threat to the safe and stable operation of power systems,and accurate prediction of CF is thus important.However,SCF is affected by the operating characteristics of the main circuit and the coupling effects of sequential control response in the inverter station.These are difficult to predict accurately.In this paper,a new SCF prediction method considering the control response is proposed based on the physical principle of SCF.The time sequence and switching conditions of the controllers at different stages of the first CF recovery process are described,and the corresponding equations of commutation voltage affected by different controllers are derived.The calculation method of the SCF threshold voltage is proposed,and the prediction method is established.Simulations show that the proposed method can predict SCF accurately and provide useful tools to suppress SCF.
基金supported by Shanghai 2020“Science and Technology Innovation Action Plan”for Social Development Science and Technology Research Project under the project number of 20DZ1207802.
文摘The shipbuilding industry is booming and the health problems of workers caused by the harsh indoor dock environmentforce us to explore efficient and reasonable ventilation methods suitable for large workshops.Due to the strongspecificity of large workshops,general or local ventilation methods cannot be universally applied.It has great potentialand good economy to improve indoor environment by changing natural ventilation design.Computational fluiddynamics(CFD)has gradually become a powerful tool for predicting indoor and outdoor airflow organization andoptimizing indoor ventilation.This paper adopts CFD to study the effect of the inflow wind speed,the position of theside wall shutters,the area ratio and form of roof ventilators on the effectiveness of natural ventilation in a large shipyarddriven by wind pressure.The results show that the influence on total ventilation volume is more obvious whenthe intake side is shaded than the exhaust side.Different incoming wind speeds will affect the wind pressure at theventilation position,which is the decisive external factor affecting the natural ventilation of docks.When the area ratioof roof ventilators increases to a certain extent,its continued increase has an insignificant effect on the total ventilationvolume.The influence of changing the arrangement of the roof ventilator on the natural ventilation effect can beneglected when the area ratio is kept constant.
文摘A new type of liquid–solid fluidized bed,named circulating conventional fluidized bed(CCFB)which operates below particle terminal velocity was proposed and experimentally studied.The hydrodynamic behavior was systematically studied in a liquid–solid CCFB of 0.032 m I.D.and 4.5 m in height with five different types of particles.Liquid–solid fluidization with external particle circulation was experimentally realized below the particle terminal velocity.The axial distribution of local solids holdup was obtained and found to be fairly uniform in a wide range of liquid velocities and solids circulation rates.The average solids holdup is found to be significantly increased compared with conventional fluidization at similar conditions.The effect of particle properties and operating conditions on bed behavior was investigated as well.Results show that particles with higher terminal velocity have higher average solids holdup.
