The streamer that is driven by the specific pulse DC discharge parameters can stably form a three-dimensional helical plasma channel in a long dielectric tube in the low-temperature plasma experiment,in cases when the...The streamer that is driven by the specific pulse DC discharge parameters can stably form a three-dimensional helical plasma channel in a long dielectric tube in the low-temperature plasma experiment,in cases when there were neither external background magnetic field or other factors that destroyed the poloidal symmetry of the tube.The formation mechanism and chirality of helical streamers are discussed according to the surface electromagnetic standing wave theory.The shape of the helical streamers and the characteristics of helical branches are quantitatively analyzed to further expand the application of plasma and streamer theory in the helix problem and chiral catalytic synthesis.展开更多
The electromagnetic surface antenna array(EMSAA)has been proposed for obtaining reflection suppression and excellent radiation simultaneously.The antenna with rectangular radiation patch is used to design anisotropic ...The electromagnetic surface antenna array(EMSAA)has been proposed for obtaining reflection suppression and excellent radiation simultaneously.The antenna with rectangular radiation patch is used to design anisotropic electromagnetic surface.Preternatural reflection characteristics of the element antenna can be tailored depending on the incident polarizations.EMSAA can be constructed by using single structured element antenna with 90° rotation and orthometric arrangement.This orthometric arrangement of EMSAA is helpful to achieve reflection suppression and excellent radiation.The simulated results show that the reflection of EMSAA is suppressed from 5.0 GHz to 8.0 GHz with peak reduction of 12.3 dB.The linear-and circular-polarized radiation properties of EMSAA are obtained and the maximum gain is 14.3 dBi.The measured results are consistent with the simulation results.The results demonstrate that the reflection suppression and excellent radiation are achieved simultaneously.Such design of EMSAA will open the path for integrating antenna fields and electromagnetic surface(EMS)fields.展开更多
In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularl...In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularly at high sea states. We present a nonlinear fractal sea surface model and derive an electromagnetic backscattering model. Using this model, we numerically calculate the normalized radar cross section (NRCS) of a nonlinear sea surface. Comparing the averaged NRCS between linear and nonlinear fractal models, we show that the NRCS of a linear fractal sea surface underestimates the NRCS of the real sea surface, especially for sea states with high fractal dimensions, and for dominant ocean surface gravity waves that are either very short or extremely long.展开更多
In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers (EMATs). With the modal expansion approach for wave...In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers (EMATs). With the modal expansion approach for waveguide excitation, an analytical expression of the Lamb wave's mode expansion coefficient is deduced, which is related to the driving frequency and the geometrical parameters of the EMAT's meander coil, and lays a theoretical foundation for exactly analyzing the selective generation of Larnb waves with EMATs. The influences of the driving frequency on the mode expansion coefficient of ultrasonic Lamb waves are analyzed when the EMAT's geometrical parameters are given. The numerical simulations and experimental examinations show that the ultrasonic Lamb wave modes can be effectively regulated (strengthened or restrained) by choosing an appropriate driving frequency of EMAT, with the geometrical parameters given. This result provides a theoretical and experimental basis for selectively generating a single and pure Lamb wave mode with EMATs.展开更多
Considering the rapid progress of theory,design,fabrication and applications,metasurfaces(MTSs)have become a new research frontier in microwave,terahertz and optical bands.Reconfigurable metasurfaces(R-MTSs)can dynami...Considering the rapid progress of theory,design,fabrication and applications,metasurfaces(MTSs)have become a new research frontier in microwave,terahertz and optical bands.Reconfigurable metasurfaces(R-MTSs)can dynamically modulate electromagnetic(EM)waves with unparalleled flexibility,which has led to a great surge of research in recent years.Numerous R-MTSs with powerful capabilities and various functions are being proposed explosively.Based on the five dimensions of EM waves,this review proposes a unified model to describe the interactions among R-MTSs,EM waves and EM information and suggests an information bit allocation strategy to categorize different types of R-MTSs systematically.Recent advances in R-MTSs and 1-bit and 2-bit elements manipulating different wave dimensions are reviewed in detail.Finally,this review discusses the future research trends of R-MTSs.R-MTSs with diverse dimensions and functions may propel the next generation of communication,detection,sensing,imaging and computing applications.展开更多
In the development of a multifunctional and multi-standard analog frontend module in emerging and future wireless systems,multifunction antenna array is an indispensable component.To this end,the aperture-shared techn...In the development of a multifunctional and multi-standard analog frontend module in emerging and future wireless systems,multifunction antenna array is an indispensable component.To this end,the aperture-shared technique has come of age,and demonstrated significant advantages in the cost-effective design of efficient,compact,multiband,multibeam,and polarization-diversified antenna arrays,particularly with high frequency ratios.In this paper,various antenna topologies and surface architectures based on this technique,which have been proposed and developed thus far for a wide variety of applications,are reviewed,examined,and categorized to highlight the nature of electromagnetic aperture-shared schemes and merits.Finally,we briefly discuss future research directions in this context for multifunction millimeter-wave and terahertz wireless systems development.展开更多
Geophysics offers an important means to investigate the physical processes occurring inside the earth.In particular,since the 1960s,electromagnetic(EM)methods have played important roles in mineral exploration and eng...Geophysics offers an important means to investigate the physical processes occurring inside the earth.In particular,since the 1960s,electromagnetic(EM)methods have played important roles in mineral exploration and engineering investigation.Such investigation requires extensive data acquisition and experimental analysis based on geophysical techniques.However,high-performance geophysical equipment,particularly EM exploration equipment,has been dominated by large geophysical companies from the United States,Canada,Germany,and other European countries for decades.This has limited the development of deep exploration technology in China.Recently,we have developed a high-resolution acquisition system with a wireless control unit and a high-power transmitting system for surface EM prospecting(SEP).The new system has been tested in the high-intensity,noisy environment in Jian-sanjiang area,Heilongjiang Province.We then conducted a field survey on the western edge of Qaidam Basin,Qinghai Province.A highly conductive anomaly was found in the upper mantle below the Qinmantage Mountains,which indicates a possible northward fluid channel that runs from below the Qinmantage Mountains to the bottom of the western crust of the Qaidam Basin.Identification of this significant feature was made possible by the new SEP for its better resolution than the previous systems.Also,geophysical analysis confirmed that the thick Cenozoic sediments of the Qaidam Basin are underlain by rigid Precambrian basement rocks and are characterized by a series of folds.The resistivity profile indicates that the Qaidam Basin was formed due to the folding structures in the northern part of the Qinghai-Tibet Plateau which provided an additional evidence for the uplifting of the Qinghai-Tibet Plateau.展开更多
基金This work was supported by National Natural Science Foundation of China(Nos.12005061,12065019)the Natural Science Foundation of Jiangxi Province(No.20202 BABL214036).
文摘The streamer that is driven by the specific pulse DC discharge parameters can stably form a three-dimensional helical plasma channel in a long dielectric tube in the low-temperature plasma experiment,in cases when there were neither external background magnetic field or other factors that destroyed the poloidal symmetry of the tube.The formation mechanism and chirality of helical streamers are discussed according to the surface electromagnetic standing wave theory.The shape of the helical streamers and the characteristics of helical branches are quantitatively analyzed to further expand the application of plasma and streamer theory in the helix problem and chiral catalytic synthesis.
基金supported by the National Natural Science Foundation of China(61901493,61901492)the Natural Science Foundation of Hunan Province(2020JJ5676)the Science and Technology Innovation Program of Hunan Province(2020RC2048).
文摘The electromagnetic surface antenna array(EMSAA)has been proposed for obtaining reflection suppression and excellent radiation simultaneously.The antenna with rectangular radiation patch is used to design anisotropic electromagnetic surface.Preternatural reflection characteristics of the element antenna can be tailored depending on the incident polarizations.EMSAA can be constructed by using single structured element antenna with 90° rotation and orthometric arrangement.This orthometric arrangement of EMSAA is helpful to achieve reflection suppression and excellent radiation.The simulated results show that the reflection of EMSAA is suppressed from 5.0 GHz to 8.0 GHz with peak reduction of 12.3 dB.The linear-and circular-polarized radiation properties of EMSAA are obtained and the maximum gain is 14.3 dBi.The measured results are consistent with the simulation results.The results demonstrate that the reflection suppression and excellent radiation are achieved simultaneously.Such design of EMSAA will open the path for integrating antenna fields and electromagnetic surface(EMS)fields.
基金supported by the National Natural Science Foundation of China (Grant No. 40706058)the National High Technology Research and Development Program of China (Grant No. 2007AA12Z170)+1 种基金the Science-Technology Chenguang Foundation for Young Scientist of Wuhan, China (Grant No. 200850731388)the wind and waves component of the Canadian Space Agency GRIP Project entitled Building Satellite Data into Fisheries and Oceans Operational Systems
文摘In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularly at high sea states. We present a nonlinear fractal sea surface model and derive an electromagnetic backscattering model. Using this model, we numerically calculate the normalized radar cross section (NRCS) of a nonlinear sea surface. Comparing the averaged NRCS between linear and nonlinear fractal models, we show that the NRCS of a linear fractal sea surface underestimates the NRCS of the real sea surface, especially for sea states with high fractal dimensions, and for dominant ocean surface gravity waves that are either very short or extremely long.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474361 and 11274388)
文摘In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers (EMATs). With the modal expansion approach for waveguide excitation, an analytical expression of the Lamb wave's mode expansion coefficient is deduced, which is related to the driving frequency and the geometrical parameters of the EMAT's meander coil, and lays a theoretical foundation for exactly analyzing the selective generation of Larnb waves with EMATs. The influences of the driving frequency on the mode expansion coefficient of ultrasonic Lamb waves are analyzed when the EMAT's geometrical parameters are given. The numerical simulations and experimental examinations show that the ultrasonic Lamb wave modes can be effectively regulated (strengthened or restrained) by choosing an appropriate driving frequency of EMAT, with the geometrical parameters given. This result provides a theoretical and experimental basis for selectively generating a single and pure Lamb wave mode with EMATs.
基金supported in part by the National Natural Science Foundation of China(Grant No.U2141233)the ZTE Industry-Academia-Research Cooperation Funds,and the New Cornerstone Science Foundation through THE XPLORER PRIZE.
文摘Considering the rapid progress of theory,design,fabrication and applications,metasurfaces(MTSs)have become a new research frontier in microwave,terahertz and optical bands.Reconfigurable metasurfaces(R-MTSs)can dynamically modulate electromagnetic(EM)waves with unparalleled flexibility,which has led to a great surge of research in recent years.Numerous R-MTSs with powerful capabilities and various functions are being proposed explosively.Based on the five dimensions of EM waves,this review proposes a unified model to describe the interactions among R-MTSs,EM waves and EM information and suggests an information bit allocation strategy to categorize different types of R-MTSs systematically.Recent advances in R-MTSs and 1-bit and 2-bit elements manipulating different wave dimensions are reviewed in detail.Finally,this review discusses the future research trends of R-MTSs.R-MTSs with diverse dimensions and functions may propel the next generation of communication,detection,sensing,imaging and computing applications.
文摘In the development of a multifunctional and multi-standard analog frontend module in emerging and future wireless systems,multifunction antenna array is an indispensable component.To this end,the aperture-shared technique has come of age,and demonstrated significant advantages in the cost-effective design of efficient,compact,multiband,multibeam,and polarization-diversified antenna arrays,particularly with high frequency ratios.In this paper,various antenna topologies and surface architectures based on this technique,which have been proposed and developed thus far for a wide variety of applications,are reviewed,examined,and categorized to highlight the nature of electromagnetic aperture-shared schemes and merits.Finally,we briefly discuss future research directions in this context for multifunction millimeter-wave and terahertz wireless systems development.
基金supported by the National Key Research and Development Program(Grant No.2018YFC0603200)the Research and Development Program of Scientific Research Instruments and Equipment of the Chinese Academy of Sciences(Grant No.ZDZBGCH2018006)+1 种基金the Key Program of National Natural Science Foundation of China(Grant No.42030106)the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0804).
文摘Geophysics offers an important means to investigate the physical processes occurring inside the earth.In particular,since the 1960s,electromagnetic(EM)methods have played important roles in mineral exploration and engineering investigation.Such investigation requires extensive data acquisition and experimental analysis based on geophysical techniques.However,high-performance geophysical equipment,particularly EM exploration equipment,has been dominated by large geophysical companies from the United States,Canada,Germany,and other European countries for decades.This has limited the development of deep exploration technology in China.Recently,we have developed a high-resolution acquisition system with a wireless control unit and a high-power transmitting system for surface EM prospecting(SEP).The new system has been tested in the high-intensity,noisy environment in Jian-sanjiang area,Heilongjiang Province.We then conducted a field survey on the western edge of Qaidam Basin,Qinghai Province.A highly conductive anomaly was found in the upper mantle below the Qinmantage Mountains,which indicates a possible northward fluid channel that runs from below the Qinmantage Mountains to the bottom of the western crust of the Qaidam Basin.Identification of this significant feature was made possible by the new SEP for its better resolution than the previous systems.Also,geophysical analysis confirmed that the thick Cenozoic sediments of the Qaidam Basin are underlain by rigid Precambrian basement rocks and are characterized by a series of folds.The resistivity profile indicates that the Qaidam Basin was formed due to the folding structures in the northern part of the Qinghai-Tibet Plateau which provided an additional evidence for the uplifting of the Qinghai-Tibet Plateau.