The effects of an external electric field on the structure and stability of the nitrogen hydrate confined in a single-walled carbon nanotube(CNT)were studied by using molecular dynamics(MD)simulations.It was found tha...The effects of an external electric field on the structure and stability of the nitrogen hydrate confined in a single-walled carbon nanotube(CNT)were studied by using molecular dynamics(MD)simulations.It was found that the structure of the nitrogen hydrate,the occupancy and distribution of the nitrogen molecules inside the nanotube depend sensitively on the direction of the external electric field.A parallel electric field can destabilize the nitrogen hydrate and cause the release of nitrogen molecules from the ice nanotube of the hydrate.While a vertical electric field can redistribute the nitrogen molecules from the core to the shell of the hydrate.The occupancy of the nitrogen molecules of the hydrate follows a sigmoid-like function as the direction of the electric field changes.Our findings may aid in the development of methods to control gas release and encapsulation by using electric fields.展开更多
Owing to the large-scale grid connection of new energy sources, several installed power electronic devices introduce sub-/supersynchronous inter-harmonics into power signals, resulting in the frequent occurrence of su...Owing to the large-scale grid connection of new energy sources, several installed power electronic devices introduce sub-/supersynchronous inter-harmonics into power signals, resulting in the frequent occurrence of subsynchronous oscillations(SSOs). The SSOs may cause significant harm to generator sets and power systems;thus, online monitoring and accurate alarms for power systems are crucial for their safe and stable operation. Phasor measurement units(PMUs) can realize the dynamic real-time monitoring of power systems. Based on PMU phasor measurements, this study proposes a method for SSO online monitoring and alarm implementation for the main station of a PMU. First, fast Fourier transform frequency spectrum analysis is performed on PMU current phasor amplitude data to obtain subsynchronous frequency components. Second, the support vector machine learning algorithm is trained to obtain the amplitude threshold and subsequently filter out safe components and retain harmful ones. Finally, the adaptive duration threshold is determined according to frequency susceptibility, amplitude attenuation, and energy accumulation to decide whether to transmit an alarm signal. Experiments based on field data verify the effectiveness of the proposed method.展开更多
Multiple broadband Alfvenic chirping modes(CMs),with frequencies in the wide range of f-35-150 kHz and chirping down rapidly,are found in HL-2A neutral beam injection plasmas,and the CMs can even coexist.The frequency...Multiple broadband Alfvenic chirping modes(CMs),with frequencies in the wide range of f-35-150 kHz and chirping down rapidly,are found in HL-2A neutral beam injection plasmas,and the CMs can even coexist.The frequency chirping down process can be completed within-1 ms,and the frequency shift can reach 30-50 kHz.The CMs propagate in ion diamagnetic drift directions poloidally.The toroidal mode number is confirmed to be n=1,2,3 and 4 for the f-35-65,55-90,70-120 and 100-150 kHz CMs,respectively.The CMs are more like to be energetic-particle continuum modes(EPMs),since the modes almost locate on the Alfven continuum.展开更多
We investigate the influence of an external electric field on the dewetting behavior of nitrogen-water systems between two hydrophobic plates using molecular dynamics simulations. It is found that the critical distanc...We investigate the influence of an external electric field on the dewetting behavior of nitrogen-water systems between two hydrophobic plates using molecular dynamics simulations. It is found that the critical distance of dewetting increases obviously with the electric field strength, indicating that the effective range of hydrophobic attraction is extended. The mechanism behind this interesting phenomenon is related to the rearrangement of hydrogen bond networks between water molecules induced by the external electric field. Changes in the hydrogen bond networks and in the dipole orientation of the water molecules result in the redistribution of the neutral nitrogen molecules, especially in the region close to the hydrophobic plates. Our findings may be helpful for understanding the effects of the electric field on the long-range hydrophobic interactions.展开更多
Camellia ptilophylla Chang is a wild tea tree containing theobromine and is caffeine-free.Lots of researches have been conducted for its domestication since it was discovered to contain theobromine in its shoots.First...Camellia ptilophylla Chang is a wild tea tree containing theobromine and is caffeine-free.Lots of researches have been conducted for its domestication since it was discovered to contain theobromine in its shoots.First,its pharmacological and physiological effects have been studied,demonstrating that it can be used as a new resource of tea as daily and healthy beverage.Cocoa tea differs from traditional tea in that it does not excite the nervous system.Second,various ways of propagation have been investigated,and sexless cutting has been the method adopted currently.Third,through selection and breeding,plantation of cocoa tea can be set up to cultivate new varieties,and cocoa tea of different flavors such as green cocoa tea,oolong cocoa tea,and black cocoa tea can be processed.Thus,cocoa tea will become a choice in the tea market.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11875237).
文摘The effects of an external electric field on the structure and stability of the nitrogen hydrate confined in a single-walled carbon nanotube(CNT)were studied by using molecular dynamics(MD)simulations.It was found that the structure of the nitrogen hydrate,the occupancy and distribution of the nitrogen molecules inside the nanotube depend sensitively on the direction of the external electric field.A parallel electric field can destabilize the nitrogen hydrate and cause the release of nitrogen molecules from the ice nanotube of the hydrate.While a vertical electric field can redistribute the nitrogen molecules from the core to the shell of the hydrate.The occupancy of the nitrogen molecules of the hydrate follows a sigmoid-like function as the direction of the electric field changes.Our findings may aid in the development of methods to control gas release and encapsulation by using electric fields.
基金supported by the National Key R&D Pro gram (2017YFB0902901)National Nature Science Founda tion of China (51725702, 51627811, 51707064)。
文摘Owing to the large-scale grid connection of new energy sources, several installed power electronic devices introduce sub-/supersynchronous inter-harmonics into power signals, resulting in the frequent occurrence of subsynchronous oscillations(SSOs). The SSOs may cause significant harm to generator sets and power systems;thus, online monitoring and accurate alarms for power systems are crucial for their safe and stable operation. Phasor measurement units(PMUs) can realize the dynamic real-time monitoring of power systems. Based on PMU phasor measurements, this study proposes a method for SSO online monitoring and alarm implementation for the main station of a PMU. First, fast Fourier transform frequency spectrum analysis is performed on PMU current phasor amplitude data to obtain subsynchronous frequency components. Second, the support vector machine learning algorithm is trained to obtain the amplitude threshold and subsequently filter out safe components and retain harmful ones. Finally, the adaptive duration threshold is determined according to frequency susceptibility, amplitude attenuation, and energy accumulation to decide whether to transmit an alarm signal. Experiments based on field data verify the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China [grant numbers 4208810141901024+1 种基金42175168]the Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) [grant number 311021009]。
基金Supported by the National Key R&D Program of China (Grant Nos.2018YFE0304102,2019YFE03020000 and 2017YFE0301202)the National Natural Science Foundation of China (Grant Nos.11875024,11875021,11835010 and 12005054)the Sichuan Provincial Science and Technology Project (Grant Nos.2020YFSY0047 and 2020JDJQ0070)。
文摘Multiple broadband Alfvenic chirping modes(CMs),with frequencies in the wide range of f-35-150 kHz and chirping down rapidly,are found in HL-2A neutral beam injection plasmas,and the CMs can even coexist.The frequency chirping down process can be completed within-1 ms,and the frequency shift can reach 30-50 kHz.The CMs propagate in ion diamagnetic drift directions poloidally.The toroidal mode number is confirmed to be n=1,2,3 and 4 for the f-35-65,55-90,70-120 and 100-150 kHz CMs,respectively.The CMs are more like to be energetic-particle continuum modes(EPMs),since the modes almost locate on the Alfven continuum.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11875237)。
文摘We investigate the influence of an external electric field on the dewetting behavior of nitrogen-water systems between two hydrophobic plates using molecular dynamics simulations. It is found that the critical distance of dewetting increases obviously with the electric field strength, indicating that the effective range of hydrophobic attraction is extended. The mechanism behind this interesting phenomenon is related to the rearrangement of hydrogen bond networks between water molecules induced by the external electric field. Changes in the hydrogen bond networks and in the dipole orientation of the water molecules result in the redistribution of the neutral nitrogen molecules, especially in the region close to the hydrophobic plates. Our findings may be helpful for understanding the effects of the electric field on the long-range hydrophobic interactions.
基金This project was supported by the National Natural Science Foundation of China(Grant No.39570081)Natural Science Foundation of Guangdong Province(No.1987,1989,2005B2080100)+1 种基金Guangzhou Science&Technology Projects(No.956148-98-Z-702001-T-012-01).
文摘Camellia ptilophylla Chang is a wild tea tree containing theobromine and is caffeine-free.Lots of researches have been conducted for its domestication since it was discovered to contain theobromine in its shoots.First,its pharmacological and physiological effects have been studied,demonstrating that it can be used as a new resource of tea as daily and healthy beverage.Cocoa tea differs from traditional tea in that it does not excite the nervous system.Second,various ways of propagation have been investigated,and sexless cutting has been the method adopted currently.Third,through selection and breeding,plantation of cocoa tea can be set up to cultivate new varieties,and cocoa tea of different flavors such as green cocoa tea,oolong cocoa tea,and black cocoa tea can be processed.Thus,cocoa tea will become a choice in the tea market.
