Spin-momentum locking is widely regarded as an inherent property of evanescent waves,where the transverse spin angular momentum is intrinsically tied to the wave's polarization.This principle is well established i...Spin-momentum locking is widely regarded as an inherent property of evanescent waves,where the transverse spin angular momentum is intrinsically tied to the wave's polarization.This principle is well established in systems such as surface plasmon polaritons,surface elastic waves,and other evanescent modes.Here,we theoretically unveil an anomalous breakdown of spin-momentum locking in evanescent electromagnetic waves at a metalgyromagnetic interface.We show that the hybrid polarization of the field induces two successive reversals of transverse spin near the interface—directly violating the conventional locking between spin and momentum.As a result,identical chiral sources placed at different heights above the interface excite evanescent waves propagating in opposite directions,defying standard expectations.This discovery challenges the presumed universality of spin-momentum locking and opens new degrees of freedom for controlling wave propagation in photonic and plasmonic systems.展开更多
Structural manipulation plays a crucial role in material design,exerting a significant influence on various aspects of material performance.However,the impact of material microstructure on electromagnetic waves absorp...Structural manipulation plays a crucial role in material design,exerting a significant influence on various aspects of material performance.However,the impact of material microstructure on electromagnetic waves absorption properties has not been thoroughly investigated.In this study,based on ferrites,we controlled the micros tructural morphology by doping with light rare earth element Nd,and then formed heterogeneous structures through composite polypyrrole to enhance its performance.The structural changes in neodymium-doped ferrites and their corresponding variations in performance were systematically analyzed.The results indicate that Nd^(3+)ions doping has a pronounced effect on the microstructure of ferrites,significantly improving their dielectric loss capability for electromagnetic waves.The sample with optimal performance,Sr_(0.75)Nd_(0.25)Co_(2)Fe_(16)O_(27)@PPy,has a value of minimum reflection loss that can reach-63.11 dB,and the effective absorption bandwidth achieves 6.40 GHz at2.27 mm.This study provides instructive thinking for the structural manipulation of MA materials.展开更多
We have studied the absorption, reflection, and transmission of electromagnetic waves in an unmagnetized uniform plasma layer covering a metal surface in atmosphere conditions. Instead of the absorption of the electro...We have studied the absorption, reflection, and transmission of electromagnetic waves in an unmagnetized uniform plasma layer covering a metal surface in atmosphere conditions. Instead of the absorption of the electromagnetic wave propagating only once in previous work on the plasma layer, a general formula of total power absorption by the plasma layer with an infinite time of reflections between the atmosphere-plasma interface and the metal surface has been derived for the first time. Effects of plasma parameters, especially the dependence of the fraction of positive ions, negative ions and electrons in plasmas on the power absorption processes are discussed. The results show that the existence of negative ions significantly reduces the power absorption of the electromagnetic wave. Absorptions of electromagnetic waves are calculated.展开更多
The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious i...The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious impact on the propagation of HF EM waves.In this study,the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation.First,a twodimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere.A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities.Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities.In addition,corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities.The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde.Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere.This result was consistent with the ionosonde observations.展开更多
Based on the electromagnetic theory and by using an analytical technique-the transfer matrix method, the obliquely incident electromagnetic waves propagating in one-dimension plasma photonic crystals is studied. The d...Based on the electromagnetic theory and by using an analytical technique-the transfer matrix method, the obliquely incident electromagnetic waves propagating in one-dimension plasma photonic crystals is studied. The dispersion relations for both the P-polarization waves and S-polarization waves, depending on the plasma density, plasma thickness and period, are discussed.展开更多
We propose a method of applying a static magnetic field to reduce the attenuation of the magnetic field component(SH) of low-frequency electromagnetic(LF EM) waves in dense plasma. The principle of this method is to a...We propose a method of applying a static magnetic field to reduce the attenuation of the magnetic field component(SH) of low-frequency electromagnetic(LF EM) waves in dense plasma. The principle of this method is to apply a static magnetic field to limit electron movement, thereby increasing the equivalent resistance and thus reducing the induced current and SH. We consider the static magnetic field acting on the plasma of the entire induced current loop rather than on the local plasma, where the induced current is excited by the magnetic field component of LF EM waves. Analytical expressions of SH suitable for magnetized cylindrical enveloping plasma are derived by adopting an equivalent circuit approach, by which SHis calculated with respect to various plasma parameter settings. The results show that SH can be reduced under a static magnetic field and the maximum magnetic field strength that mitigates blackout is less than 0.1 T. Experiments in which LF EM waves propagate in a shock-tubegenerated magnetized cylindrical enveloping plasma are also conducted. SH measured under the magnetic field(the magnetic field strength B0 acting on the magnetic field probe was about0.06 T) reduces at f=10 MHz and f=30 MHz when ne≈1.9×1013 cm-3, which is consistent with theoretical results. The verification of the theory thus suggests that applying a static magnetic field with a weak magnetic field has the potential to improve the transmission capacity of LF EM waves in dense plasma.展开更多
Stealth technology plays an important role in modern military conflicts, especially when used in fighter jets. Since airfoil structures have a leading edge, inlet, and surface bulge that are easily detected by radar, ...Stealth technology plays an important role in modern military conflicts, especially when used in fighter jets. Since airfoil structures have a leading edge, inlet, and surface bulge that are easily detected by radar, it is necessary to study the stealth of these structures. In this study,we investigate structures coated with radionuclides to generate plasma. Using simulation and calculation methods, the attenuation of 0.1–10 GHz electromagnetic waves propagating in plasma was studied. The results showed that the attenuation of low-frequency electromagnetic waves is greater than that of high-frequency electromagnetic waves.The attenuation of 0.1–1 GHz electromagnetic waves is found to be less than-2.7 d B,-3.0 d B, and-15.6 d B at the airfoil leading edge, inlet, and surface bulge structures, respectively. We also found that the attenuation of electromagnetic waves with 0°-incidence is greater than that of waves with 10°, 20°, and 30° incidence angles.Additionally, the attenuation of electromagnetic waves decreases gradually as the incident angle increases.展开更多
We demonstrate theoretically that the epsilon-near-zero materials can be utilized to control effectively the polarization conversion of an electromagnetic wave through reflection. The significant feature differing fro...We demonstrate theoretically that the epsilon-near-zero materials can be utilized to control effectively the polarization conversion of an electromagnetic wave through reflection. The significant feature differing from all other means based on whatever natural materials or metamaterials is that for TM incident wave, the reflected phase is a constant, while for TE wave, the reflected phase is a linear function of the incident angle. The phase difference between them covers the range from -180°to 0°, and the polarization conversions from linear states to elliptical or circular states can be obtained by only adjusting the incident angle. Because no complex structures are employed, our proposal promises a simple approach for manipulating polarization conversion at both terahertz and optical frequencies.展开更多
In a recent article the authors described a possible process of generating electromagnetic waves in the range of 1-12 Hz caused by diamagnetic currents originated by heat in ionosphere by high frequency waves （HF）. ...In a recent article the authors described a possible process of generating electromagnetic waves in the range of 1-12 Hz caused by diamagnetic currents originated by heat in ionosphere by high frequency waves （HF）. The origin of the HF waves that reach the ionosphere can be sent from the Earth＇s surface （HAARP- High Frequency Active Auroral Research Program） or even solar. Through a SpectranNF-5035 detector, developed by German Aaronia with high sensitivity （1 μV） in a range of 1-12 Hz and low sampling time （5 ms）, it was possible to measure these waves. During the months of July and August of 2016, very dry and away from electrical discharges in the region of S~ Jos~ dos Campos, SP, Brazil were made several series of measurements to detect these waves. The positive results of these experimental observations as well as discussions and suggestions are presented in this paper.展开更多
We present preliminary results from the experimental investigation of the response of the atmosphere due to the impact of powerful shock waves. The response is evidenced as ultra low frequency electromagnetic wave rad...We present preliminary results from the experimental investigation of the response of the atmosphere due to the impact of powerful shock waves. The response is evidenced as ultra low frequency electromagnetic wave radiation at frequency of 2-5 kHz and in duration of 3 7s. We hypothesize that this radiation appears due to the following process： the shock wave ionizes the neutral particles in the air and these charged and neutral particles continue their vertical motion, which forms in the trail of the shock wave. Such motion can cause the cyclotron-like radiation measured.展开更多
The interaction of two coherent counter propagating TE （transverse-electric） and TM （transverse-magnetic） electromagnetic waves with different initial phases in the absorbing plate placed in the regular ideal wave...The interaction of two coherent counter propagating TE （transverse-electric） and TM （transverse-magnetic） electromagnetic waves with different initial phases in the absorbing plate placed in the regular ideal waveguide is considered. The losses of energy of TE and TM waves in the absorbing plate are calculated. Some features of tunnel interference in the absorbing plate in the waveguide are revealed. It is shown that the losses of energy strongly depend on the various parameters describing the interaction of the counter propagating waves. Definitely choosing the parameters we can control the electromagnetic processes in this case.展开更多
A finite difference time domain （FDTD） method is used to numerically study the power absorption of broadband terahertz （0.1 - 1.5 THz） electromagnetic waves in a partially ionized uniform plasma layer under low pr...A finite difference time domain （FDTD） method is used to numerically study the power absorption of broadband terahertz （0.1 - 1.5 THz） electromagnetic waves in a partially ionized uniform plasma layer under low pressure and atmosphere discharge conditions. The power absorption spectra are calculated numerically and the numerical results are in accordance with the analytic results. Meanwhile, the effects on the power absorption are calculated with different applied magnetic fields, collision frequencies and electron number densities, which depend strongly on those parameters. Under the dense strongly magnetized plasma conditions, the absorption gaps appear in the range of 0.3 - 0.36 THz, and are enlarged with the increasing electron number density.展开更多
In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infi...In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infiltration(CVI)process.The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network,which extends the transmission path of incident microwaves.The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase,and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves.As expected,the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of–37.8 dB,and the widest effective absorbing bandwidth(RL<–10 dB)of 5.90 GHz is obtained.The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.展开更多
The attenuation of electromagnetic （EM） waves in unmagnetized plasma generated by an inductively coupled plasma （ICP） actuator has been investigated both theoretically and experimentally. A numerical study is cond...The attenuation of electromagnetic （EM） waves in unmagnetized plasma generated by an inductively coupled plasma （ICP） actuator has been investigated both theoretically and experimentally. A numerical study is conducted to investigate the propagation of EM waves in multilayer plasma structures which cover a square fiat plate. Experimentally, an ICP actuator with dimensions of 20 cm×20 cm×4 cm is designed to produce a steady plasma slab. The attenuation of EM waves in the plasma generated by the ICP actuator is measured by a reflectivity arch test method at incident waves of 2.3 GHz and 10.1 GHz, respectively. A contrastive analysis of calculated and measured results of these incident wave frequencies is presented, which suggests that the experiment accords well with our theory. As expected, the plasma slab generated by the ICP actuator can effectively attenuate the EM waves, which may have great potential application prospects in aircraft stealth.展开更多
The relativistic interaction of charged particle beams with a circularly polarized electromagnetic wave propagating along a uniform guiding magnetic field in the tunneling of a dielectric medium is analyzed. The accel...The relativistic interaction of charged particle beams with a circularly polarized electromagnetic wave propagating along a uniform guiding magnetic field in the tunneling of a dielectric medium is analyzed. The acceleration mechanism and a self-consistent nonlinear theory are presented for the interaction of relativistic charged particle beams with electromagnetic waves. Numerical results show that the beam particle can be efficiently accelerated in the interaction process.展开更多
The main objective of this proposed article is to provide explanations to justify the validity of the results of the studies of the interaction between the electromagnetic fields and the human body. It can also find d...The main objective of this proposed article is to provide explanations to justify the validity of the results of the studies of the interaction between the electromagnetic fields and the human body. It can also find direct applications in the characterization and modeling of the macroscopic electrical properties of the biological media for assessing the effects of fields induced by electromagnetic radiation sources in the human body to set up new standards <span>on the Human exposure to electromagnetic fields. To do this, we have taken into account the different physical phenomena of propagation of a hyper-frequency electromagnetic plane wave and on the other hand, the expe</span>rimental values <span></span><span><span><span style="font-family:;" "="">in order to model the electrical behavior of human biological tissues based on an equivalent electronic circuit model composed of capacities, resistance and reel, which assimilates the biological tissues of the skin, grease, blood. This model using the characteristic impedance of the dielectric support makes it possible to evaluate the voltage induced by the electromagnetic waves of the hyper-frequencies in the studied biological system. The results of the simulations obtained from computer tools demonstrate that the hyper-frequency electromagnetic waves can result in an elevation of the electrical potential of the biological tissues. Despite this potential is a decreasing function of the penetration depth.</span></span></span>展开更多
In a quasi-two-dimensional model, the scattering of incident ordinary electromag- netic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering c...In a quasi-two-dimensional model, the scattering of incident ordinary electromag- netic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering cross-section and total cross-section are evaluated analytically in different approximate conditions, and the physical interpretations are discussed. When the wavelength of incident wave is much longer than the vortex radius （kia〈〈1）, it is found that the angle at which the scattering cross-section reaches its maxim depends significantly on the approximation of the parameters of the vortex used. It is also found that the total scattering cross-section has an affinitive relation with the parameters of the plasma, while it is irrelevant to the frequency of the incident wave in a wide range of parameters of the vortex. In a totally different range of parameters when incident wave is in the radar-frequency range （then kia 〈〈 1, the wavelength of incident wave is much shorter than the vortex radius）, the numerical procedure is conducted with computer in order to obtain the distribution and the total expression of the scattering crosssection. Then it is found that the total scattering cross-section in the low frequency range is much larger than that in high frequency range, so the scattering is more effective in the low frequency range than in high frequency range.展开更多
Energy dissipation and power deposition of electromagnetic waves(EMW)in the reentry plasma sheath provide an opportunity to investigate‘communication blackout’phenomena.Based on afinite element method(FEM)simulation...Energy dissipation and power deposition of electromagnetic waves(EMW)in the reentry plasma sheath provide an opportunity to investigate‘communication blackout’phenomena.Based on afinite element method(FEM)simulation,we analyze variation of EMW energy dissipation and power deposition profiles dependent on the wave polarization,wave incident angle,plasma density profile and electron collision frequency.Cutoff and resonance of EMW in the plasma sheath are crucial in explaining the regulation of energy dissipation and power deposition.展开更多
Intensive collisions between electrons and neutral particles in partially ionized plasmas generated in atmospheric/sub-atmospheric pressure environments can sufficiently affect the propagation characteristics of elect...Intensive collisions between electrons and neutral particles in partially ionized plasmas generated in atmospheric/sub-atmospheric pressure environments can sufficiently affect the propagation characteristics of electromagnetic waves, particularly in the sub-wavelength regime. To investigate the collisional effect in such plasmas, we introduce a simplified plasma slab model with a thickness on the order of the wavelength of the incident electromagnetic wave. The scattering matrix method （SMM） is applied to solve the wave equation in the plasma slab with significant nonuniformity. Results show that the collisions between the electrons and the neutral particles, as well as the incident angle and the plasma thickness, can disturb the transmission and reduce reflection significantly.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12434016 and 12474380)Science and Technology Project of Guangdong Province(Grant No.2020B0101-90001)+1 种基金the National Key Research and Development Program of China(Grant No.2023YFA1406900)the Natural Science Foundation of Guangdong Province(Grant No.2025A1515010714)。
文摘Spin-momentum locking is widely regarded as an inherent property of evanescent waves,where the transverse spin angular momentum is intrinsically tied to the wave's polarization.This principle is well established in systems such as surface plasmon polaritons,surface elastic waves,and other evanescent modes.Here,we theoretically unveil an anomalous breakdown of spin-momentum locking in evanescent electromagnetic waves at a metalgyromagnetic interface.We show that the hybrid polarization of the field induces two successive reversals of transverse spin near the interface—directly violating the conventional locking between spin and momentum.As a result,identical chiral sources placed at different heights above the interface excite evanescent waves propagating in opposite directions,defying standard expectations.This discovery challenges the presumed universality of spin-momentum locking and opens new degrees of freedom for controlling wave propagation in photonic and plasmonic systems.
基金financially supported by the National Natural Science Foundation of China(Nos.52273267 and 22271155)
文摘Structural manipulation plays a crucial role in material design,exerting a significant influence on various aspects of material performance.However,the impact of material microstructure on electromagnetic waves absorption properties has not been thoroughly investigated.In this study,based on ferrites,we controlled the micros tructural morphology by doping with light rare earth element Nd,and then formed heterogeneous structures through composite polypyrrole to enhance its performance.The structural changes in neodymium-doped ferrites and their corresponding variations in performance were systematically analyzed.The results indicate that Nd^(3+)ions doping has a pronounced effect on the microstructure of ferrites,significantly improving their dielectric loss capability for electromagnetic waves.The sample with optimal performance,Sr_(0.75)Nd_(0.25)Co_(2)Fe_(16)O_(27)@PPy,has a value of minimum reflection loss that can reach-63.11 dB,and the effective absorption bandwidth achieves 6.40 GHz at2.27 mm.This study provides instructive thinking for the structural manipulation of MA materials.
文摘We have studied the absorption, reflection, and transmission of electromagnetic waves in an unmagnetized uniform plasma layer covering a metal surface in atmosphere conditions. Instead of the absorption of the electromagnetic wave propagating only once in previous work on the plasma layer, a general formula of total power absorption by the plasma layer with an infinite time of reflections between the atmosphere-plasma interface and the metal surface has been derived for the first time. Effects of plasma parameters, especially the dependence of the fraction of positive ions, negative ions and electrons in plasmas on the power absorption processes are discussed. The results show that the existence of negative ions significantly reduces the power absorption of the electromagnetic wave. Absorptions of electromagnetic waves are calculated.
基金We acknowledge the Institute of Earthquake Forecasting for providing the ionosonde data.This work was supported by the National Natural Science Foundation of China(no.41604133).
文摘The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious impact on the propagation of HF EM waves.In this study,the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation.First,a twodimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere.A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities.Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities.In addition,corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities.The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde.Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere.This result was consistent with the ionosonde observations.
基金supported by National Natural Science Foundation of China(No.10747153)
文摘Based on the electromagnetic theory and by using an analytical technique-the transfer matrix method, the obliquely incident electromagnetic waves propagating in one-dimension plasma photonic crystals is studied. The dispersion relations for both the P-polarization waves and S-polarization waves, depending on the plasma density, plasma thickness and period, are discussed.
基金supported by National Natural Science Foundation of China (Nos. 61771370, and 11704296)
文摘We propose a method of applying a static magnetic field to reduce the attenuation of the magnetic field component(SH) of low-frequency electromagnetic(LF EM) waves in dense plasma. The principle of this method is to apply a static magnetic field to limit electron movement, thereby increasing the equivalent resistance and thus reducing the induced current and SH. We consider the static magnetic field acting on the plasma of the entire induced current loop rather than on the local plasma, where the induced current is excited by the magnetic field component of LF EM waves. Analytical expressions of SH suitable for magnetized cylindrical enveloping plasma are derived by adopting an equivalent circuit approach, by which SHis calculated with respect to various plasma parameter settings. The results show that SH can be reduced under a static magnetic field and the maximum magnetic field strength that mitigates blackout is less than 0.1 T. Experiments in which LF EM waves propagate in a shock-tubegenerated magnetized cylindrical enveloping plasma are also conducted. SH measured under the magnetic field(the magnetic field strength B0 acting on the magnetic field probe was about0.06 T) reduces at f=10 MHz and f=30 MHz when ne≈1.9×1013 cm-3, which is consistent with theoretical results. The verification of the theory thus suggests that applying a static magnetic field with a weak magnetic field has the potential to improve the transmission capacity of LF EM waves in dense plasma.
文摘Stealth technology plays an important role in modern military conflicts, especially when used in fighter jets. Since airfoil structures have a leading edge, inlet, and surface bulge that are easily detected by radar, it is necessary to study the stealth of these structures. In this study,we investigate structures coated with radionuclides to generate plasma. Using simulation and calculation methods, the attenuation of 0.1–10 GHz electromagnetic waves propagating in plasma was studied. The results showed that the attenuation of low-frequency electromagnetic waves is greater than that of high-frequency electromagnetic waves.The attenuation of 0.1–1 GHz electromagnetic waves is found to be less than-2.7 d B,-3.0 d B, and-15.6 d B at the airfoil leading edge, inlet, and surface bulge structures, respectively. We also found that the attenuation of electromagnetic waves with 0°-incidence is greater than that of waves with 10°, 20°, and 30° incidence angles.Additionally, the attenuation of electromagnetic waves decreases gradually as the incident angle increases.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51406126 and 11604229
文摘We demonstrate theoretically that the epsilon-near-zero materials can be utilized to control effectively the polarization conversion of an electromagnetic wave through reflection. The significant feature differing from all other means based on whatever natural materials or metamaterials is that for TM incident wave, the reflected phase is a constant, while for TE wave, the reflected phase is a linear function of the incident angle. The phase difference between them covers the range from -180°to 0°, and the polarization conversions from linear states to elliptical or circular states can be obtained by only adjusting the incident angle. Because no complex structures are employed, our proposal promises a simple approach for manipulating polarization conversion at both terahertz and optical frequencies.
文摘In a recent article the authors described a possible process of generating electromagnetic waves in the range of 1-12 Hz caused by diamagnetic currents originated by heat in ionosphere by high frequency waves （HF）. The origin of the HF waves that reach the ionosphere can be sent from the Earth＇s surface （HAARP- High Frequency Active Auroral Research Program） or even solar. Through a SpectranNF-5035 detector, developed by German Aaronia with high sensitivity （1 μV） in a range of 1-12 Hz and low sampling time （5 ms）, it was possible to measure these waves. During the months of July and August of 2016, very dry and away from electrical discharges in the region of S~ Jos~ dos Campos, SP, Brazil were made several series of measurements to detect these waves. The positive results of these experimental observations as well as discussions and suggestions are presented in this paper.
文摘We present preliminary results from the experimental investigation of the response of the atmosphere due to the impact of powerful shock waves. The response is evidenced as ultra low frequency electromagnetic wave radiation at frequency of 2-5 kHz and in duration of 3 7s. We hypothesize that this radiation appears due to the following process： the shock wave ionizes the neutral particles in the air and these charged and neutral particles continue their vertical motion, which forms in the trail of the shock wave. Such motion can cause the cyclotron-like radiation measured.
文摘The interaction of two coherent counter propagating TE （transverse-electric） and TM （transverse-magnetic） electromagnetic waves with different initial phases in the absorbing plate placed in the regular ideal waveguide is considered. The losses of energy of TE and TM waves in the absorbing plate are calculated. Some features of tunnel interference in the absorbing plate in the waveguide are revealed. It is shown that the losses of energy strongly depend on the various parameters describing the interaction of the counter propagating waves. Definitely choosing the parameters we can control the electromagnetic processes in this case.
基金supported by National Natural Science Foundation of China (Nos.10675029, 11075030)National Basic Research Program of China (Nos.2008CB717801, 2008CB787103, 2009GB105004,2010GB106002)Fundamental Research Funds for the Central Universities of China
文摘A finite difference time domain （FDTD） method is used to numerically study the power absorption of broadband terahertz （0.1 - 1.5 THz） electromagnetic waves in a partially ionized uniform plasma layer under low pressure and atmosphere discharge conditions. The power absorption spectra are calculated numerically and the numerical results are in accordance with the analytic results. Meanwhile, the effects on the power absorption are calculated with different applied magnetic fields, collision frequencies and electron number densities, which depend strongly on those parameters. Under the dense strongly magnetized plasma conditions, the absorption gaps appear in the range of 0.3 - 0.36 THz, and are enlarged with the increasing electron number density.
基金supported by the National Natural Science Foundation of China(No.51772310)National Natural Science Foundation of China(No.52222202)+3 种基金Chinese Academy of Sciences Key Research Program of Frontier Sciences(No.QYZDYSSWJSC031)Key Deployment Projects of the Chinese Academy of Sciences(No.ZDRW-CN2019-01)Shanghai Sailing Program(No.21YF1454600)Outstanding Chinese and Foreign Youth Exchange Program of China Association of Science and Technology.
文摘In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infiltration(CVI)process.The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network,which extends the transmission path of incident microwaves.The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase,and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves.As expected,the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of–37.8 dB,and the widest effective absorbing bandwidth(RL<–10 dB)of 5.90 GHz is obtained.The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.
基金supported by National Natural Science Foundation of China(Nos.51276197,11472306 and 11402301)
文摘The attenuation of electromagnetic （EM） waves in unmagnetized plasma generated by an inductively coupled plasma （ICP） actuator has been investigated both theoretically and experimentally. A numerical study is conducted to investigate the propagation of EM waves in multilayer plasma structures which cover a square fiat plate. Experimentally, an ICP actuator with dimensions of 20 cm×20 cm×4 cm is designed to produce a steady plasma slab. The attenuation of EM waves in the plasma generated by the ICP actuator is measured by a reflectivity arch test method at incident waves of 2.3 GHz and 10.1 GHz, respectively. A contrastive analysis of calculated and measured results of these incident wave frequencies is presented, which suggests that the experiment accords well with our theory. As expected, the plasma slab generated by the ICP actuator can effectively attenuate the EM waves, which may have great potential application prospects in aircraft stealth.
基金supported by National Natural Science Foundation of China(Nos.51275029,51102007 and 11275007)
文摘The relativistic interaction of charged particle beams with a circularly polarized electromagnetic wave propagating along a uniform guiding magnetic field in the tunneling of a dielectric medium is analyzed. The acceleration mechanism and a self-consistent nonlinear theory are presented for the interaction of relativistic charged particle beams with electromagnetic waves. Numerical results show that the beam particle can be efficiently accelerated in the interaction process.
文摘The main objective of this proposed article is to provide explanations to justify the validity of the results of the studies of the interaction between the electromagnetic fields and the human body. It can also find direct applications in the characterization and modeling of the macroscopic electrical properties of the biological media for assessing the effects of fields induced by electromagnetic radiation sources in the human body to set up new standards <span>on the Human exposure to electromagnetic fields. To do this, we have taken into account the different physical phenomena of propagation of a hyper-frequency electromagnetic plane wave and on the other hand, the expe</span>rimental values <span></span><span><span><span style="font-family:;" "="">in order to model the electrical behavior of human biological tissues based on an equivalent electronic circuit model composed of capacities, resistance and reel, which assimilates the biological tissues of the skin, grease, blood. This model using the characteristic impedance of the dielectric support makes it possible to evaluate the voltage induced by the electromagnetic waves of the hyper-frequencies in the studied biological system. The results of the simulations obtained from computer tools demonstrate that the hyper-frequency electromagnetic waves can result in an elevation of the electrical potential of the biological tissues. Despite this potential is a decreasing function of the penetration depth.</span></span></span>
基金National Natural Science Foundation of China(Nos,10375063.40336052)
文摘In a quasi-two-dimensional model, the scattering of incident ordinary electromag- netic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering cross-section and total cross-section are evaluated analytically in different approximate conditions, and the physical interpretations are discussed. When the wavelength of incident wave is much longer than the vortex radius （kia〈〈1）, it is found that the angle at which the scattering cross-section reaches its maxim depends significantly on the approximation of the parameters of the vortex used. It is also found that the total scattering cross-section has an affinitive relation with the parameters of the plasma, while it is irrelevant to the frequency of the incident wave in a wide range of parameters of the vortex. In a totally different range of parameters when incident wave is in the radar-frequency range （then kia 〈〈 1, the wavelength of incident wave is much shorter than the vortex radius）, the numerical procedure is conducted with computer in order to obtain the distribution and the total expression of the scattering crosssection. Then it is found that the total scattering cross-section in the low frequency range is much larger than that in high frequency range, so the scattering is more effective in the low frequency range than in high frequency range.
基金funded by National Natural Science Foundation of China(Nos.61627901 and 61871302)the Shaanxi National Natural Science Foundation under Grant No.2019JZ-15
文摘Energy dissipation and power deposition of electromagnetic waves(EMW)in the reentry plasma sheath provide an opportunity to investigate‘communication blackout’phenomena.Based on afinite element method(FEM)simulation,we analyze variation of EMW energy dissipation and power deposition profiles dependent on the wave polarization,wave incident angle,plasma density profile and electron collision frequency.Cutoff and resonance of EMW in the plasma sheath are crucial in explaining the regulation of energy dissipation and power deposition.
基金supported by National Natural Science Foundation of China (Nos. 41674165, 11405038)the China Postdoctoral Science Foundation (No. 2015M570283)
文摘Intensive collisions between electrons and neutral particles in partially ionized plasmas generated in atmospheric/sub-atmospheric pressure environments can sufficiently affect the propagation characteristics of electromagnetic waves, particularly in the sub-wavelength regime. To investigate the collisional effect in such plasmas, we introduce a simplified plasma slab model with a thickness on the order of the wavelength of the incident electromagnetic wave. The scattering matrix method （SMM） is applied to solve the wave equation in the plasma slab with significant nonuniformity. Results show that the collisions between the electrons and the neutral particles, as well as the incident angle and the plasma thickness, can disturb the transmission and reduce reflection significantly.
