Thermal and induced flow velocity characteristics of radio frequency（RF） surface dielectric barrier discharge（SDBD）plasma actuation are experimentally investigated in this paper. The spatial and temporal distribut...Thermal and induced flow velocity characteristics of radio frequency（RF） surface dielectric barrier discharge（SDBD）plasma actuation are experimentally investigated in this paper. The spatial and temporal distributions of the dielectric surface temperature are measured with the infrared thermography at atmospheric pressure. In the spanwise direction, the highest dielectric surface temperature is acquired at the center of the high voltage electrode, while it reduces gradually along the chordwise direction. The maximum temperature of the dielectric surface raises rapidly once discharge begins.After several seconds（typically 100 s）, the temperature reaches equilibrium among the actuator＇s surface, plasma, and surrounding air. The maximum dielectric surface temperature is higher than that powered by an AC power supply in dozens of k Hz. Influences of the duty cycle and the input frequency on the thermal characteristics are analyzed. When the duty cycle increases, the maximum dielectric surface temperature increases linearly. However, the maximum dielectric surface temperature increases nonlinearly when the input frequency varies from 0.47 MHz to 1.61 MHz. The induced flow velocity of the RF SDBD actuator is 0.25 m/s.展开更多
In this paper, aerodynamic actuation characteristics of radio-frequency(RF) discharge plasma are studied and a method is proposed for shock wave control based on RF discharge. Under the static condition, a RF diffuse ...In this paper, aerodynamic actuation characteristics of radio-frequency(RF) discharge plasma are studied and a method is proposed for shock wave control based on RF discharge. Under the static condition, a RF diffuse glow discharge can be observed; under the supersonic inflow, the plasma is blown downstream but remains continuous and stable.Time-resolved schlieren is used for flow field visualization. It is found that RF discharge not only leads to continuous energy deposition on the electrode surface but also induces a compression wave. Under the supersonic inflow condition, a weak oblique shock wave is induced by discharge. Experimental results of the shock wave control indicate that the applied actuation can disperse the bottom structure of the ramp-induced oblique shock wave, which is also observed in the extracted shock wave structure after image processing. More importantly, this control effect can be maintained steadily due to the continuous high-frequency(MHz) discharge. Finally, correlations for schlieren images and numerical simulations are employed to further explore the flow control mechanism. It is observed that the vortex in the boundary layer increases after the application of actuation, meaning that the boundary layer in the downstream of the actuation position is thickened. This is equivalent to covering a layer of low-density smooth wall around the compression corner and on the ramp surface, thereby weakening the compressibility at the compression corner. Our results demonstrate the ability of RF plasma aerodynamic actuation to control the supersonic airflow.展开更多
In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is...In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is derived in a probabilistic manner.The basic idea can be understood via treating the integrated heterogeneous wireless networks as different coupled and parallel queuing systems.The integrated network performance can approach that of one queue with maximal the multiplexing gain.For the purpose of illustrating the effectively of our proposed model,the Cellular/WLAN interworking is exploited.To minimize the average delay,a heuristic search algorithm is used to get the optimal probability of splitting traffic flow.Further,a Markov process is applied to evaluate the performance of the proposed scheme and compare with that of selecting the best network to access in terms of packet mean delay and blocking probability.Numerical results illustrate our proposed framework is effective and the flow splitting transmission can obtain more performance gain in heterogeneous wireless networks.展开更多
Resonance exhibits a dynamo mechanism of the Sun with an exotic behavior of a controlled thermonuclear fusion reaction in the presence of a magnetic mirror. A charged oscillator takes place of a periodic driving force...Resonance exhibits a dynamo mechanism of the Sun with an exotic behavior of a controlled thermonuclear fusion reaction in the presence of a magnetic mirror. A charged oscillator takes place of a periodic driving force so that the laser radiation is so intense with the growing of a magnetic field towards the resonant level. Following the representation of a new era of a magnetic field, it has many practical applications of magnetohydrodynamics. In response to the practical situation of interest, a mechanism has been developed with reference to a dynamo mechanism of the system.展开更多
The present investigation reveals to a magnetohydrodynamic (MHD) start up flow of a rotating environment permeated by a traveling magnetic field with reference to a periodic driving force to explore the behaviour of a...The present investigation reveals to a magnetohydrodynamic (MHD) start up flow of a rotating environment permeated by a traveling magnetic field with reference to a periodic driving force to explore the behaviour of a magnetic field at the resonant level. In a time varying electromagnetic field of sinusoidal in nature subject to ∇⋅J≠0, an oscillating current flow emerges the backbone of a radio emission in which the emission of hot electron gyrates in a magnetic field in the presence of a radiofrequency accelerator. The expedition of a radiofrequency field determines X-emission to expedite radiofrequency voltage under the influence of A.C circuit subject to ∇⋅J≠0. An oscillating current flow deals with an excitation frequency in such a way that phase angle rotates with angular frequency, the magnetic field grows towards the resonant level when the phase angle ωτ=π/2 is compatible with ω】0. In turn, plasma induced laser radiation is influenced by an oscillator with a decisive importance to an excitation frequency in the presence of a magnetic mirror so that maximum reflection occurs as the magnetic field increase in strength abruptly to exhibit resonance fluorescence. A synchronized laser photon light in transmitted from the Sun subject to ωτ=π/2.展开更多
优化台址风环境对提高大口径、高精度射电望远镜在中高频段的有效观测时长具有重要意义。通过风障调控风场可以有效减小风荷载对望远镜的影响。风障的布局设计除了与风障高度、孔隙率等参量有关外,还要综合考虑台址地形对挡风效率的影...优化台址风环境对提高大口径、高精度射电望远镜在中高频段的有效观测时长具有重要意义。通过风障调控风场可以有效减小风荷载对望远镜的影响。风障的布局设计除了与风障高度、孔隙率等参量有关外,还要综合考虑台址地形对挡风效率的影响。以奇台射电望远镜(QiTai radio Telescope,QTT)台址为研究对象,开展不同地形对风场调控影响的数值模拟研究。仿真结果表明,无风障时望远镜区的风速大小主要与上下游边界地形的最高海拔有关;布设风障时,若望远镜区域为水平地形,风障遮蔽区降低风速的大小与上游入流风攻角以及下游地形的海拔高度有关;台址实际斜坡地形增加了流场的复杂程度,在进行风障风场仿真时,上游边界要尽量延伸到相对较高山体的外围。不同边界地形的仿真结果表明,望远镜区风速折减效率差值最大达到6%。该研究可以为望远镜台址风场调控仿真中的地形建模提供可靠的参考。展开更多
The tokamak plasma flows induced by the local radio frequency （RF） forces in the core region are analyzed. The effective components of local RF forces are composed of the momentum absorption term and the resonant pa...The tokamak plasma flows induced by the local radio frequency （RF） forces in the core region are analyzed. The effective components of local RF forces are composed of the momentum absorption term and the resonant parallel momentum transport term （i.e. the parallel component of the resonant ponderomotive forces）. Different momentum balance relations are em- ployed to calculate the plasma flows depending on different assumptions of momentum transport. With the RF fields solved from RF simulation codes, the toroidal and poloidal flows by these forces under the lower hybrid current drive and the mode conversion ion cyclotron resonance heating on EAST-like plasmas are evaluated.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11472306,51407197,and 51507187)
文摘Thermal and induced flow velocity characteristics of radio frequency（RF） surface dielectric barrier discharge（SDBD）plasma actuation are experimentally investigated in this paper. The spatial and temporal distributions of the dielectric surface temperature are measured with the infrared thermography at atmospheric pressure. In the spanwise direction, the highest dielectric surface temperature is acquired at the center of the high voltage electrode, while it reduces gradually along the chordwise direction. The maximum temperature of the dielectric surface raises rapidly once discharge begins.After several seconds（typically 100 s）, the temperature reaches equilibrium among the actuator＇s surface, plasma, and surrounding air. The maximum dielectric surface temperature is higher than that powered by an AC power supply in dozens of k Hz. Influences of the duty cycle and the input frequency on the thermal characteristics are analyzed. When the duty cycle increases, the maximum dielectric surface temperature increases linearly. However, the maximum dielectric surface temperature increases nonlinearly when the input frequency varies from 0.47 MHz to 1.61 MHz. The induced flow velocity of the RF SDBD actuator is 0.25 m/s.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11472306,51407197,and 51507187)
文摘In this paper, aerodynamic actuation characteristics of radio-frequency(RF) discharge plasma are studied and a method is proposed for shock wave control based on RF discharge. Under the static condition, a RF diffuse glow discharge can be observed; under the supersonic inflow, the plasma is blown downstream but remains continuous and stable.Time-resolved schlieren is used for flow field visualization. It is found that RF discharge not only leads to continuous energy deposition on the electrode surface but also induces a compression wave. Under the supersonic inflow condition, a weak oblique shock wave is induced by discharge. Experimental results of the shock wave control indicate that the applied actuation can disperse the bottom structure of the ramp-induced oblique shock wave, which is also observed in the extracted shock wave structure after image processing. More importantly, this control effect can be maintained steadily due to the continuous high-frequency(MHz) discharge. Finally, correlations for schlieren images and numerical simulations are employed to further explore the flow control mechanism. It is observed that the vortex in the boundary layer increases after the application of actuation, meaning that the boundary layer in the downstream of the actuation position is thickened. This is equivalent to covering a layer of low-density smooth wall around the compression corner and on the ramp surface, thereby weakening the compressibility at the compression corner. Our results demonstrate the ability of RF plasma aerodynamic actuation to control the supersonic airflow.
基金ACKNOWLEDGEMENT This work was supported by National Natural Science Foundation of China （Grant No. 61231008）, National Basic Research Program of China （973 Program） （Grant No. 2009CB320404）, Program for Changjiang Scholars and Innovative Research Team in University （Grant No. IRT0852）, and the 111 Project （Grant No. B08038）.
文摘In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is derived in a probabilistic manner.The basic idea can be understood via treating the integrated heterogeneous wireless networks as different coupled and parallel queuing systems.The integrated network performance can approach that of one queue with maximal the multiplexing gain.For the purpose of illustrating the effectively of our proposed model,the Cellular/WLAN interworking is exploited.To minimize the average delay,a heuristic search algorithm is used to get the optimal probability of splitting traffic flow.Further,a Markov process is applied to evaluate the performance of the proposed scheme and compare with that of selecting the best network to access in terms of packet mean delay and blocking probability.Numerical results illustrate our proposed framework is effective and the flow splitting transmission can obtain more performance gain in heterogeneous wireless networks.
文摘Resonance exhibits a dynamo mechanism of the Sun with an exotic behavior of a controlled thermonuclear fusion reaction in the presence of a magnetic mirror. A charged oscillator takes place of a periodic driving force so that the laser radiation is so intense with the growing of a magnetic field towards the resonant level. Following the representation of a new era of a magnetic field, it has many practical applications of magnetohydrodynamics. In response to the practical situation of interest, a mechanism has been developed with reference to a dynamo mechanism of the system.
文摘The present investigation reveals to a magnetohydrodynamic (MHD) start up flow of a rotating environment permeated by a traveling magnetic field with reference to a periodic driving force to explore the behaviour of a magnetic field at the resonant level. In a time varying electromagnetic field of sinusoidal in nature subject to ∇⋅J≠0, an oscillating current flow emerges the backbone of a radio emission in which the emission of hot electron gyrates in a magnetic field in the presence of a radiofrequency accelerator. The expedition of a radiofrequency field determines X-emission to expedite radiofrequency voltage under the influence of A.C circuit subject to ∇⋅J≠0. An oscillating current flow deals with an excitation frequency in such a way that phase angle rotates with angular frequency, the magnetic field grows towards the resonant level when the phase angle ωτ=π/2 is compatible with ω】0. In turn, plasma induced laser radiation is influenced by an oscillator with a decisive importance to an excitation frequency in the presence of a magnetic mirror so that maximum reflection occurs as the magnetic field increase in strength abruptly to exhibit resonance fluorescence. A synchronized laser photon light in transmitted from the Sun subject to ωτ=π/2.
文摘优化台址风环境对提高大口径、高精度射电望远镜在中高频段的有效观测时长具有重要意义。通过风障调控风场可以有效减小风荷载对望远镜的影响。风障的布局设计除了与风障高度、孔隙率等参量有关外,还要综合考虑台址地形对挡风效率的影响。以奇台射电望远镜(QiTai radio Telescope,QTT)台址为研究对象,开展不同地形对风场调控影响的数值模拟研究。仿真结果表明,无风障时望远镜区的风速大小主要与上下游边界地形的最高海拔有关;布设风障时,若望远镜区域为水平地形,风障遮蔽区降低风速的大小与上游入流风攻角以及下游地形的海拔高度有关;台址实际斜坡地形增加了流场的复杂程度,在进行风障风场仿真时,上游边界要尽量延伸到相对较高山体的外围。不同边界地形的仿真结果表明,望远镜区风速折减效率差值最大达到6%。该研究可以为望远镜台址风场调控仿真中的地形建模提供可靠的参考。
基金supported by National Natural Science Foundation of China(Nos.11405218,11325524,11375235 and 11261140327)in part by the National Magnetic Confinement Fusion Science Program of China(Nos.2013GB111002,2013GB112001 and 2013GB112010)the Program of Fusion Reactor Physics and Digital Tokamak with the CAS"One-Three-Five"Strategic Planning
文摘The tokamak plasma flows induced by the local radio frequency （RF） forces in the core region are analyzed. The effective components of local RF forces are composed of the momentum absorption term and the resonant parallel momentum transport term （i.e. the parallel component of the resonant ponderomotive forces）. Different momentum balance relations are em- ployed to calculate the plasma flows depending on different assumptions of momentum transport. With the RF fields solved from RF simulation codes, the toroidal and poloidal flows by these forces under the lower hybrid current drive and the mode conversion ion cyclotron resonance heating on EAST-like plasmas are evaluated.
