为研究飞秒脉冲激光冲击强化中等离子体压力时空演化规律,利用考虑电子态密度(DOS)效应的模型计算了电子热容和电声耦合系数随电子温度的演化规律,并与采用QEOS(quotidian equation of state)模型计算结果进行了对比;提出DOS飞秒脉冲激...为研究飞秒脉冲激光冲击强化中等离子体压力时空演化规律,利用考虑电子态密度(DOS)效应的模型计算了电子热容和电声耦合系数随电子温度的演化规律,并与采用QEOS(quotidian equation of state)模型计算结果进行了对比;提出DOS飞秒脉冲激光冲击强化模型,计算得到电子温度、晶格温度、等离子体羽位置时间演化规律和等离子体压力时空演化规律,并与QEOS飞秒脉冲激光冲击强化模型结果进行了对比。结果表明:DOS飞秒脉冲激光冲击强化模型计算得到的等离子体羽位置随时间的演化规律与实验结果吻合程度更好;增加激光能量或功率密度、考虑电子DOS效应会增加电子、晶格温度和等离子体压力。展开更多
The emission of CuInSe2-based spark discharge plasma at atmospheric pressure in air has been investigated by optical emission spectroscopy method. The plasma was formed by action of the high voltage pulse generator （...The emission of CuInSe2-based spark discharge plasma at atmospheric pressure in air has been investigated by optical emission spectroscopy method. The plasma was formed by action of the high voltage pulse generator （with nanosecond pulse） on the corresponding electrodes （CulnSe2 compound）. The emission characteristics have been obtained for the spark discharge plasma at 3 mm interelectrode distance. It was established that the spark discharge plasma radiation was determined by decay products of the compound from which electrodes were made. The most suitable spectral lines for plasma diagnostics is atomic copper lines in the visible spectrum and atomic indium lines in UV （ultraviolet） and visible spectrum.展开更多
Magnetic confinement of fusion plasma has a wide range of issues to be addressed. Convective transport of plasma in the scrape-off layer of magnetic confinement devices is an interesting research topic for scientists ...Magnetic confinement of fusion plasma has a wide range of issues to be addressed. Convective transport of plasma in the scrape-off layer of magnetic confinement devices is an interesting research topic for scientists and engineers. The interest in scrape-off layer convective transport has grown in last two decades because of its effect on plasma interaction with the first wall and divertor. By increasing the particle flux into the far scrape-off layer, blobs negatively affect limiters, radio frequency antennas and the first wall. Increased convective heat transport influences core plasma confinement, at least in L-mode plasmas. Here we have reported blob formation in the absent of external magnetic field. It is observed that at low pressure -0.01 rob, transport seems to be dominated by diffusive process. At pressure 〉 1 mb, we observe convective transport in high speed imaging experiments. The role of background neutrals outside plasma boundary has the befitting answer for this phenomenon. Plasma temperature is the other key player. Another interesting observation is that at diffusive transport regime plasma life time is of the order of voltage pulse duration fed to plasma source, where as at convective transport regime plasma life time is increased appreciably.展开更多
In this paper, an improved quasi-stable atmospheric pressure dielectric barrier discharge （DBD） plasma source is achieved after carefully controlled discharge voltage and current, discharge power, working gas, treat...In this paper, an improved quasi-stable atmospheric pressure dielectric barrier discharge （DBD） plasma source is achieved after carefully controlled discharge voltage and current, discharge power, working gas, treatment period, and gap between the electrodes. This plasma source has been used to modify the surface of Polybutylene Terephthalate （PBT） melt-blown nonwovens and Polyester （PET） fabrics, and the various influences on surface modification and the aging effect of treated polymeric materials have been systematically investigated. In addition, the method of spectrum analysis is also used for diagnosing plasma paramneters such as electron temperature. Experimental results indicate that both the wettablity and permeation of treated PBT melt-blown nonwovens and dyeing ability of treated PET fabrics are certainly improved.展开更多
A three-dimensional mathematical model for the transferred-type argon arc was developed to describe arc force on the anode surface. The software ANSYS was employed to solve the model. The model includes a part of torc...A three-dimensional mathematical model for the transferred-type argon arc was developed to describe arc force on the anode surface. The software ANSYS was employed to solve the model. The model includes a part of torch and tungsten electrode to achieve more reasonable resuits. The arc temperature and flow fields were derived. And the influences of welding parameters on arc force were also studied. The simulated results show that arc pressure at the anode are dependent on the welding current, plasma gas flow rate and electrode neck-in, while not sensitive to arc length.展开更多
This work detects multi-scale, from hour to seconds, pressure-balanced structures (PBSs) in the solar wind based on the anti- correlation between the plasma thermal pressure and the magnetic pressure measured by WIND ...This work detects multi-scale, from hour to seconds, pressure-balanced structures (PBSs) in the solar wind based on the anti- correlation between the plasma thermal pressure and the magnetic pressure measured by WIND at 1 AU on April 5th, 2001. In our former research based on Cluster measurements, we showed the anti-correlation between the electron density and the magnetic field strength in multi-scales, and we supposed these structures may be pressure-balanced structures. Thus, in this work we aim to prove our speculation by the direct evidence on pressure measurements. Different from our previous work, we apply the WIND measurements this time, for they have both the magnetic pressure and the plasma pressure which Cluster could not offer. We use the wavelet cross-coherence method to analyze the correlation between the plasma pressure (P th ) and the magnetic pressure (P B ), and also the electron density (N e ) and the magnetic field strength (B) on various scales. We observe the anti-correlation between P th and P B distributed at different temporal scales ranging from 1000 s down to 10 s. This result directly indicates the existence of pressure- balanced structures (PBSs) with different sizes in the solar wind. Further, We compare the wavelet cross correlation spectrum of P th -P B and N e -B. We notice that the two spectra are similar in general. Thus this result confirms that the relation between P th -P B and N e -B are consistent with each other in the PBSs we study. Moreover, we compare the power spectrum density (PSD) of relative N e fluctuation with our previous work based on Cluster measurements. The two spectra show similar trend with Komolgorov's -5/3 as their slopes. This may imply the similarity of the structures observed by both WIND and Cluster spacecrafts. Finally, we discuss the possible formation mechanisms for these multi-scale pressure-balanced structures. Our result is important to support the existence of multi-scale PBSs from one-hour scale down to one-minute, and is helpful to understand the role of compressive fluctuation in the solar wind turbulence dominated by Alfvénic cascading.展开更多
The effects of the ambient air pressure level on the performance of plasma synthetic jet actuator have been investigated through electrical and optical diagnostics.Pressures from 1 atm down to 0.1 atm were tested with...The effects of the ambient air pressure level on the performance of plasma synthetic jet actuator have been investigated through electrical and optical diagnostics.Pressures from 1 atm down to 0.1 atm were tested with a 10 Hz excitation.The discharge measurement demonstrates that there is a voltage range to make the actuator work reliably.Higher pressure level needs a higher breakdown voltage,and a higher discharge current and energy deposition are produced.But when the actuator works with the maximum breakdown voltage,the fraction of the initial capacitor energy delivered to the arc is almost invariable.This preliminary study also confirms the effectiveness of the plasma synthetic jet at low pressure.Indeed,the maximum velocities of the precursor shock and the plasma jet induced by the actuator with maximum breakdown voltage are independent of the ambient pressure level;reach about 530 and 460 m/s respectively.The mass flux of the plasma jet increases with ambient pressure increasing,but the strength of the precursor shock presents a local maximum at 0.6 atm.展开更多
This study presents observation and detailed analysis on the double layers （DLs） in the ramp and the foreshock contacting with the foot of the terrestrial bow shock by THEMIS on September 14, 2008 under enhanced dyn...This study presents observation and detailed analysis on the double layers （DLs） in the ramp and the foreshock contacting with the foot of the terrestrial bow shock by THEMIS on September 14, 2008 under enhanced dynamic pressure in the solar wind. The results reveal that： （1） The time duration of the double layers is nus 10-40 mV/m. （2） On assuming a propagation speed at the ion mainly 3-8 ms, and their max parallel electric field is miacoustic speed （vs）, their spatial scale is estimated to be 0.3-1.15 km （about 75-200 2D）. （3） The net potential drop of DLs is estimated to be 5-32 V. （4） The DLs in the ramp and the foreshock contacting to the foot of the bow shock is current-carrying as a result of development and evolution of nonlinear phase of instability in the self-consistent current-carrying plasma. The DLs may play an important role in strong turbulence in the foreshock contacting with the foot of the bow shock.展开更多
文摘为研究飞秒脉冲激光冲击强化中等离子体压力时空演化规律,利用考虑电子态密度(DOS)效应的模型计算了电子热容和电声耦合系数随电子温度的演化规律,并与采用QEOS(quotidian equation of state)模型计算结果进行了对比;提出DOS飞秒脉冲激光冲击强化模型,计算得到电子温度、晶格温度、等离子体羽位置时间演化规律和等离子体压力时空演化规律,并与QEOS飞秒脉冲激光冲击强化模型结果进行了对比。结果表明:DOS飞秒脉冲激光冲击强化模型计算得到的等离子体羽位置随时间的演化规律与实验结果吻合程度更好;增加激光能量或功率密度、考虑电子DOS效应会增加电子、晶格温度和等离子体压力。
文摘The emission of CuInSe2-based spark discharge plasma at atmospheric pressure in air has been investigated by optical emission spectroscopy method. The plasma was formed by action of the high voltage pulse generator （with nanosecond pulse） on the corresponding electrodes （CulnSe2 compound）. The emission characteristics have been obtained for the spark discharge plasma at 3 mm interelectrode distance. It was established that the spark discharge plasma radiation was determined by decay products of the compound from which electrodes were made. The most suitable spectral lines for plasma diagnostics is atomic copper lines in the visible spectrum and atomic indium lines in UV （ultraviolet） and visible spectrum.
文摘Magnetic confinement of fusion plasma has a wide range of issues to be addressed. Convective transport of plasma in the scrape-off layer of magnetic confinement devices is an interesting research topic for scientists and engineers. The interest in scrape-off layer convective transport has grown in last two decades because of its effect on plasma interaction with the first wall and divertor. By increasing the particle flux into the far scrape-off layer, blobs negatively affect limiters, radio frequency antennas and the first wall. Increased convective heat transport influences core plasma confinement, at least in L-mode plasmas. Here we have reported blob formation in the absent of external magnetic field. It is observed that at low pressure -0.01 rob, transport seems to be dominated by diffusive process. At pressure 〉 1 mb, we observe convective transport in high speed imaging experiments. The role of background neutrals outside plasma boundary has the befitting answer for this phenomenon. Plasma temperature is the other key player. Another interesting observation is that at diffusive transport regime plasma life time is of the order of voltage pulse duration fed to plasma source, where as at convective transport regime plasma life time is increased appreciably.
文摘In this paper, an improved quasi-stable atmospheric pressure dielectric barrier discharge （DBD） plasma source is achieved after carefully controlled discharge voltage and current, discharge power, working gas, treatment period, and gap between the electrodes. This plasma source has been used to modify the surface of Polybutylene Terephthalate （PBT） melt-blown nonwovens and Polyester （PET） fabrics, and the various influences on surface modification and the aging effect of treated polymeric materials have been systematically investigated. In addition, the method of spectrum analysis is also used for diagnosing plasma paramneters such as electron temperature. Experimental results indicate that both the wettablity and permeation of treated PBT melt-blown nonwovens and dyeing ability of treated PET fabrics are certainly improved.
基金National Natural Science Foundation of China(No.50275106)
文摘A three-dimensional mathematical model for the transferred-type argon arc was developed to describe arc force on the anode surface. The software ANSYS was employed to solve the model. The model includes a part of torch and tungsten electrode to achieve more reasonable resuits. The arc temperature and flow fields were derived. And the influences of welding parameters on arc force were also studied. The simulated results show that arc pressure at the anode are dependent on the welding current, plasma gas flow rate and electrode neck-in, while not sensitive to arc length.
基金supported by the Fundamental Research Funds for the Central Universities(2011YYL127)supported by the National Natural Science Foundation of China(40874090,40931055 and 40890162)
文摘This work detects multi-scale, from hour to seconds, pressure-balanced structures (PBSs) in the solar wind based on the anti- correlation between the plasma thermal pressure and the magnetic pressure measured by WIND at 1 AU on April 5th, 2001. In our former research based on Cluster measurements, we showed the anti-correlation between the electron density and the magnetic field strength in multi-scales, and we supposed these structures may be pressure-balanced structures. Thus, in this work we aim to prove our speculation by the direct evidence on pressure measurements. Different from our previous work, we apply the WIND measurements this time, for they have both the magnetic pressure and the plasma pressure which Cluster could not offer. We use the wavelet cross-coherence method to analyze the correlation between the plasma pressure (P th ) and the magnetic pressure (P B ), and also the electron density (N e ) and the magnetic field strength (B) on various scales. We observe the anti-correlation between P th and P B distributed at different temporal scales ranging from 1000 s down to 10 s. This result directly indicates the existence of pressure- balanced structures (PBSs) with different sizes in the solar wind. Further, We compare the wavelet cross correlation spectrum of P th -P B and N e -B. We notice that the two spectra are similar in general. Thus this result confirms that the relation between P th -P B and N e -B are consistent with each other in the PBSs we study. Moreover, we compare the power spectrum density (PSD) of relative N e fluctuation with our previous work based on Cluster measurements. The two spectra show similar trend with Komolgorov's -5/3 as their slopes. This may imply the similarity of the structures observed by both WIND and Cluster spacecrafts. Finally, we discuss the possible formation mechanisms for these multi-scale pressure-balanced structures. Our result is important to support the existence of multi-scale PBSs from one-hour scale down to one-minute, and is helpful to understand the role of compressive fluctuation in the solar wind turbulence dominated by Alfvénic cascading.
基金supported by the National Natural Science Foundation of China(Grant No.11372349)the Foundation for the Author of National Excellent Doctor Dissertation of China(Grant No.201058)the Nature Science Fund for Distinguished Young Scholars of National University of Defense Technology,China(Grant No.CJ110101)
文摘The effects of the ambient air pressure level on the performance of plasma synthetic jet actuator have been investigated through electrical and optical diagnostics.Pressures from 1 atm down to 0.1 atm were tested with a 10 Hz excitation.The discharge measurement demonstrates that there is a voltage range to make the actuator work reliably.Higher pressure level needs a higher breakdown voltage,and a higher discharge current and energy deposition are produced.But when the actuator works with the maximum breakdown voltage,the fraction of the initial capacitor energy delivered to the arc is almost invariable.This preliminary study also confirms the effectiveness of the plasma synthetic jet at low pressure.Indeed,the maximum velocities of the precursor shock and the plasma jet induced by the actuator with maximum breakdown voltage are independent of the ambient pressure level;reach about 530 and 460 m/s respectively.The mass flux of the plasma jet increases with ambient pressure increasing,but the strength of the precursor shock presents a local maximum at 0.6 atm.
基金supported by the National Natural Science Foundation of China(Grant No.41304132)the 53-Class General Financial Grant from the China Postdoctoral Science Foundation(Grant No.2013M532115)
文摘This study presents observation and detailed analysis on the double layers （DLs） in the ramp and the foreshock contacting with the foot of the terrestrial bow shock by THEMIS on September 14, 2008 under enhanced dynamic pressure in the solar wind. The results reveal that： （1） The time duration of the double layers is nus 10-40 mV/m. （2） On assuming a propagation speed at the ion mainly 3-8 ms, and their max parallel electric field is miacoustic speed （vs）, their spatial scale is estimated to be 0.3-1.15 km （about 75-200 2D）. （3） The net potential drop of DLs is estimated to be 5-32 V. （4） The DLs in the ramp and the foreshock contacting to the foot of the bow shock is current-carrying as a result of development and evolution of nonlinear phase of instability in the self-consistent current-carrying plasma. The DLs may play an important role in strong turbulence in the foreshock contacting with the foot of the bow shock.
