A two-dimensional electromagnetic Particle-in-Cell （PIC） simulation model is proposed to study the propagation of intense, ion beams with beaIn width wb small compared to the electron skin depth c/wpe through backg...A two-dimensional electromagnetic Particle-in-Cell （PIC） simulation model is proposed to study the propagation of intense, ion beams with beaIn width wb small compared to the electron skin depth c/wpe through background plaslnas in tile presence of external applied magnetic fields. The effcctive eleetron gyrora,dius wge is found to be an important parameter for ion beam transport in the presence of magnetic fields,In the bealn regions, the background plasmas respond differently to the ion beanl of width wb〈wge and wb 〉 wge for the given magnetic field and beaan encrgy, For the case of beam width wb 〈 wge with relative weak external magnetic fiehts, the rotalion effects of plasma electrons a,re found to be signifieant and contributes to the signitica,nt enilaneeinent of the self electric and seif-magnetic fields. While for the ease of beam width wb 〉 wge with relative strong external magnetic fields, the rotation effects of plasma cleetrons are strongly inhibited and a, well neutraliza, tion of ion beam current can be found. Finally, the influences of diftiuent beam widths. beam energies and magnetic fields on the neutralization of ion bc, anl eurrellt are summarized for the eases of wb 〈 wge〈 c/wpe,wge 〈wb〈c/wbp and wb〈c/wpe〈wge.展开更多
Two interplanetary shocks are examined to determine the responses of the magnetic field and plasma in the plasma sheet upon the shock impacts by using TC-1 observational data.The two shocks are observed by WIND on Nov...Two interplanetary shocks are examined to determine the responses of the magnetic field and plasma in the plasma sheet upon the shock impacts by using TC-1 observational data.The two shocks are observed by WIND on November 7,2004.Prior to and after the shock,the IMF is either weakly southward or northward.The responses of the plasma sheet to the two shocks are intense and much similar.When the shock interacts with the magnetosphere,the magnetic field impulsively increases 1-2 min after the geomagnetic field sudden impulse (SI) judged from the Sym-H index change,and the magnetic field line is stretched.On the other hand,all of the ion density,the ion temperature,and the velocity of ion flow in the plasma sheet increase.Interestingly,quasi-periodical oscillations of the ion flow are suddenly enhanced,and the plasma flow is basically perpendicular to the local magnetic field.The responses of the magnetic field and the plasma are nearly simultaneous.The responses in the plasma sheet are probably caused by the lateral compression due to the dynamic pressure enhancement downstream the shock when the shock propagates antisunward in the magnetosheath.展开更多
The capacity of supercapacitor charge storage depends on the size of the electrode surface area and the active material on the electrodes.To enhance the charge storage capacity with a reduced volume,silicon is used as...The capacity of supercapacitor charge storage depends on the size of the electrode surface area and the active material on the electrodes.To enhance the charge storage capacity with a reduced volume,silicon is used as the electrode material,and three-dimensional electrode structure is prepared to increase the electrode surface area on the footprint area by inductively coupled plasma reactive etching(ICP) techniques.The anodic constant current deposition method is employed to deposit manganese oxide on the electrode surface as the electroactive material.For comparison,samples without slot are prepared with a two-dimensional electrode.Scanning Electron Microscopy(SEM) and Energy Dispersive Spectroscopy(EDS) are used to characterize the surface morphology of the electrode structure and the deposited electroactive material.Electrochemical properties of the electrode are characterized by the cyclic voltammetry(CV) and the constant current charge-discharge method.Experimental results show that our approach can effectively increase the electrode surface area with more electroactive substances,and hence can increase storage capacity of the micro-supercapacitor.展开更多
基金This work was supported by the National Basic Research Program of China （Grant No. 2010CB832901）, the National Natural Science Foundation of China （Grant No. 11305024）, China Postdoctoral Science Foundation （Grant No. 2013M540219）, and the Fundamental Research Funds for the Cen- tral Universities （Grant No. DUT13RC（3）25）.
文摘A two-dimensional electromagnetic Particle-in-Cell （PIC） simulation model is proposed to study the propagation of intense, ion beams with beaIn width wb small compared to the electron skin depth c/wpe through background plaslnas in tile presence of external applied magnetic fields. The effcctive eleetron gyrora,dius wge is found to be an important parameter for ion beam transport in the presence of magnetic fields,In the bealn regions, the background plasmas respond differently to the ion beanl of width wb〈wge and wb 〉 wge for the given magnetic field and beaan encrgy, For the case of beam width wb 〈 wge with relative weak external magnetic fiehts, the rotalion effects of plasma electrons a,re found to be signifieant and contributes to the signitica,nt enilaneeinent of the self electric and seif-magnetic fields. While for the ease of beam width wb 〉 wge with relative strong external magnetic fields, the rotation effects of plasma cleetrons are strongly inhibited and a, well neutraliza, tion of ion beam current can be found. Finally, the influences of diftiuent beam widths. beam energies and magnetic fields on the neutralization of ion bc, anl eurrellt are summarized for the eases of wb 〈 wge〈 c/wpe,wge 〈wb〈c/wbp and wb〈c/wpe〈wge.
基金supported by the National Natural Science Foundation of China (Grant Nos.40804046,40890160 and 40731054)National Basic Research Program of China (Grant No.2006CB806304)the Specialized Research Fund for State Key Laboratories
文摘Two interplanetary shocks are examined to determine the responses of the magnetic field and plasma in the plasma sheet upon the shock impacts by using TC-1 observational data.The two shocks are observed by WIND on November 7,2004.Prior to and after the shock,the IMF is either weakly southward or northward.The responses of the plasma sheet to the two shocks are intense and much similar.When the shock interacts with the magnetosphere,the magnetic field impulsively increases 1-2 min after the geomagnetic field sudden impulse (SI) judged from the Sym-H index change,and the magnetic field line is stretched.On the other hand,all of the ion density,the ion temperature,and the velocity of ion flow in the plasma sheet increase.Interestingly,quasi-periodical oscillations of the ion flow are suddenly enhanced,and the plasma flow is basically perpendicular to the local magnetic field.The responses of the magnetic field and the plasma are nearly simultaneous.The responses in the plasma sheet are probably caused by the lateral compression due to the dynamic pressure enhancement downstream the shock when the shock propagates antisunward in the magnetosheath.
文摘The capacity of supercapacitor charge storage depends on the size of the electrode surface area and the active material on the electrodes.To enhance the charge storage capacity with a reduced volume,silicon is used as the electrode material,and three-dimensional electrode structure is prepared to increase the electrode surface area on the footprint area by inductively coupled plasma reactive etching(ICP) techniques.The anodic constant current deposition method is employed to deposit manganese oxide on the electrode surface as the electroactive material.For comparison,samples without slot are prepared with a two-dimensional electrode.Scanning Electron Microscopy(SEM) and Energy Dispersive Spectroscopy(EDS) are used to characterize the surface morphology of the electrode structure and the deposited electroactive material.Electrochemical properties of the electrode are characterized by the cyclic voltammetry(CV) and the constant current charge-discharge method.Experimental results show that our approach can effectively increase the electrode surface area with more electroactive substances,and hence can increase storage capacity of the micro-supercapacitor.
