检索结果-南通市图书馆

Analysis of inverse synthetic aperture radar imaging in the presence of time-varying plasma sheath

在线全文

学校读者我要写书评

暂无评论

plasma Science and Technology 2022年第3期24卷 19-32页

作者： Yaocong XIE Xiaoping LI Fangfang SHEN Bowen BAI Yanming LIU Xuyang CHEN Lei SHI School of Aerospace Science and Technology Xidian UniversityXi'an 710071People's Republic of China

The plasma sheath can induce radar signal modulation,causing not only ineffective target detection,but also defocusing in inverse synthetic aperture radar(ISAR)*** this paper,through establishing radar echo models of the reentry object enveloped with time-varying plasma sheath,we simulated the defocusing of ISAR images in typical *** results suggested that the ISAR defocusing is caused by false scatterings,upon which the false scatterings’formation mechanism and distribution property are analyzed and *** range of false scattering correlates with the electron density fluctuation *** combined value of the electron density fluctuation and the pulse repetition frequency jointly determines the Doppler of false *** measurement metrics including peak signal-to-noise ratio and structural similarity are used to evaluate the influence of ISAR imaging.

关键词： ISAR imaging plasma sheath time-varying transmission line matrix defocusing

Analysis of the influence of sheath positions,flight parameters and incident wave parameters on the wave propagation in plasma sheath

在线全文

学校读者我要写书评

暂无评论

plasma Science and Technology 2022年第3期24卷 33-40页

作者： Qifan ZHANG Yiping HAN Qinlu DONG Chang DONG School of Physics and Optoelectronic Engineering Xidian UniversityXi'an 710071People's Republic of China

The plasma sheath covering hypersonic vehicles has a significant effect on the propagation of electromagnetic *** on the calculation of the flow field of a conical cylindrical,this work studies the propagation of electromagnetic waves in plasma sheath at L-band and Ku-band,and discusses the propagation characteristics in the head,side and tail of the *** dielectric properties of plasma sheath are related to flight speed and altitude.A flight condition corresponds to a unique distribution of dielectric *** the conical cylindrical,the results show that flight speed is generally negatively correlated with the transmissivity of the plasma *** reflection characteristics of electromagnetic waves at the L-band and Kuband when obliquely incident to the plasma sheath show a downward *** the frequency is increased to Ku-band,the propagation characteristics of electromagnetic waves in the plasma sheath are related to the position of the sheath.

关键词： plasma sheath reflection and transmission flow field

Sub-THz signals' propagation model in hypersonic plasma sheath under different atmospheric conditions

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2017年第11期60卷 242-252页

作者： Kai YUAN Yuhao WANG Linfang SHEN Ming YAO Xiaohua DENG Fuhui ZHOU Zhou CHEN Institute of Space Science and Technology Nanchang University Information Engineering School Nanchang University

One of the aims for modern hypersonic cruise flight is hypersonic global reach. The length of route for such flights could be up to thousands of kilometers. The atmospheric conditions on the route are complicated. On the other hand, hypersonic flights used to suffer from communication blackout. The sub-THz communication is considered as a potential solution to the ‘blackout’. In the present study the propagation for sub-THz signals in hypersonic plasma sheaths was modeled under different atmospheric conditions. According to the study, the electron density and the electron collision frequency near the onboard antenna linearly increase with the atmospheric mass density around the vehicle, hence the attenuation of sub-THz signals in hypersonic plasma sheaths increases with the atmospheric mass density. The impact led by the atmospheric temperature is ignorable. Based on the study a new sub-THz signals’ propagation model was developed, which could be utilized for quick estimation for signal propagation under different atmospheric conditions. The geographical difference of signal propagation over the whole globe was obtained with the new model. The results showed that the signal attenuation in plasma sheaths varies with latitude and longitude. The maximum signal attenuation occurs in Alaska, Canada and Russia.

关键词： sub-THz communication hypersonic cruise flight communication blackout plasma sheath signal propagation model signal attenuation

Effects of some parameters on the divertor plasma sheath characteristics and fuel retention in castellated tungsten tile gaps

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第11期23卷 403-409页

作者：桑超峰戴舒宇孙继忠 Bonnin Xavier 徐倩丁芳王德真 Key Laboratory of Materials Modification by Laser Ion and Electron Beams (Ministry of Education)School of Physics and Optoelectronic Engineering Dalian University of Technology LSPM-CNRS Universit Paris 13 Sorbonne Paris Cit Villetaneuse 93430 France Institute of plasma Physics Chinese Academy of Sciences

Castellation of plasma facing components is foreseen as the best solution for ensuring the lifetime of future fusion devices. However, the gaps between the resulting surface elements can increase fuel retention and complicate fuel removal issues. To know how the fuel is retained inside the gaps, the plasma sheath around the gaps needs to be understood first. In this work, a kinetic model is used to study plasma characteristics around the divertor gaps with the focus on the H＋ penetration depth inside the poloidal gaps, and a rate-theory model is coupled to simulate the hydrogen retention inside the tungsten gaps. By varying the magnetic field strength and plasma temperature, we find that the H＋ cyclotron radius has a significant effect on the penetration depth. Besides, the increase of magnetic field inclination angle can also increase the penetration depth. It is found in this work that parameters as well as the penetration depth strongly affect fuel retention in tungsten gaps.

关键词： divertor gaps penetration depth plasma sheath fuel retention

Numerical investigation of dynamic properties of plasma sheath with pitching motion

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2020年第3期21卷 209-217页

作者： De-yang TIAN Guo-chao FAN Wei-fang CHEN School of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310027China

Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle *** paper investigates the dynamic properties of the plasma sheath by using the simplified conventional Burnett(SCB)equations and the Navier-Stokes(NS)equations with the thermochemical non-equilibrium *** eleven-species chemical kinetic models are applied to the comparison and there is verification of a dynamic plasma sheath simulation for the first *** the introduction of vehicle pitching motion,the dynamic results are more consistent with the experimental data than the simulated results when treating it as static *** plasma sheath characteristic parameters show periodic properties,whose changing period is the same as the pitching motion ***,because of different velocities of the pitching motion,phase shifts exist in different positions of the *** enhancement of the rarefied effect weakens the disturbance to the plasma *** research reveals the distribution and regularities of the dynamic plasma *** is significant in solving the ionization blackout problem and the design of the reentry vehicle,and provides reliable data for further research on the dynamic plasma sheath.

关键词： plasma sheath Dynamic Thermodynamic non-equilibrium Rarefied flow

Adaptive protograph-based BICM-ID relying on the RJ-MCMC algorithm:a reliable and efficient transmission solution for plasma sheath channels

在线全文

学校读者我要写书评

暂无评论

plasma Science and Technology 2022年第4期24卷 96-105页

作者： Yanming LIU Hailiang WEI Lei SHI Bo YAO Key Laboratory of Information and Structure Efficiency in Extreme Environment Ministry of Education of ChinaXi'an 710071People's Republic of China School of Aerospace Science and Technology Xidian UniversityXi'an 710071People's Republic of China

For reentry communication,owing to the influence of the highly dynamic plasma sheath(PS),the parasitic modulation effect can occur and the received phase shift keying(PSK)signal constellation can be severely rotated,leading to unacceptable demodulation performance *** this work,an adaptive non-coherent bit-interleaved coded modulation with iterative decoding(BICM-ID)system with binary PSK(BPSK)modulation and protograph lowdensity parity-check under the PS channel is *** proposed protograph-based BICMID(P-BICM-ID)system can achieve joint processing of demodulation and decoding,where the soft information is adaptively estimated by reversible-jump Markov chain Monte Carlo(RJMCMC)*** results indicate that compared to existing algorithms,the proposed system can adapt well to the dynamic characteristics of the PS channel and can obtain a 5dB performance improvement at a bit error rate of 10^(-6).

关键词： plasma sheath BICM-ID Markov model joint demodulation and decoding

Effects of pulsed magnetic field on density reduction of high flow velocity plasma sheath

在线全文

学校读者我要写书评

暂无评论

plasma Science and Technology 2021年第7期23卷 53-66页

作者： Jiahao XU Xiaoping LI Donglin LIU Yuan WANG School of Aerospace Science and Technology Xidian UniversityXi’an 710071People’s Republic of China

A three-dimensional model is proposed in this paper to study the effect of the pulsed magnetic field on the density distribution of high flow velocity plasma *** the typical parameters of plasma sheath at the height of 71 km as an example,the distribution characteristics and time evolution characteristics of plasma density in the flow field under the action of pulsed magnetic field,as well as the effect of self-electric field on the distribution of plasma density,are *** simulation results show that pulsed magnetic field can effectively reduce the density of plasma ***,the simulation results of three-dimensional plasma density distribution show that the size of the density reduction area is large enough to meet the communication requirements of the Global Position System(GPS)***,the location of density reduction area provides a reference for the appropriate location of *** time evolution of plasma density shows that the effective density reduction time can reach 62%of the pulse duration,and the maximum reduction of plasma density can reach 55%.Based on the simulation results,the mechanism of the interaction between pulsed magnetic field and plasma flow field is physically ***,the simulation results indicate that the density distributions of electrons and ions are consistent under the action of plasma self-electric ***,the quasi neutral assumption of plasma in the flow field is not appropriate,because the self-electric field of plasma will weaken the effect of the pulsed magnetic field on the reduction of electron density,which cannot be *** calculation results could provide useful information for the mitigation of communication blackout in hypersonic vehicles.

关键词： pulsed magnetic field plasma sheath communication blackout

Dynamics of Dust in a plasma sheath with Magnetic Field

在线全文

学校读者我要写书评

暂无评论

plasma Science and Technology 2007年第4期9卷 394-397页

作者：段萍刘金远宫野刘悦王晓钢 State Key Laboratory of Material Modification by Laser Electron and Ion BeamsDepartment of Physics and College of Advanced Science and TechnologyDalian University of TechnologyDalian 116024China College of Physics Science and TechnologyDalian UniversityDalian 116622China State Key Laboratory of Material Modification by Laser Electron and Ion BeamsDepartment of Physics and College of Advanced Science and TechnologyDalian University of TechnologyDalian 116024China

Dynamics of dust in a plasma sheath with a magnetic field was investigated using a single particle model. The result shows that the radius, initial position, initial velocity of the dust particles and the magnetic field do effect their movement and equilibrium position in the plasma sheath. Generally, the dust particles with the same size, whatever original velocity and position they have, will locate at the same position in the end under the net actions of electrostatic, gravitational, neutral collisional, and Lorentz forces. But the dust particles will not locate in the plasma sheath if their radius is beyond a certain value.

关键词： plasma sheath magnetic field dust particles

Bohm Criterion in a Magnetized plasma sheath

在线全文

学校读者我要写书评

暂无评论

plasma Science and Technology 2011年第5期13卷 519-522页

作者：籍延坤邹秀刘惠平邱明辉 School of Science Dalian Jiaotong University

Bohm criterion in a magnetized plasma sheath is investigated with a fluid model. The upper and lower limits for the sheath criterion in different states of applied magnetic field are studied. The results from numerical simulation reveal that the magnetic field affects significantly the ion Mach number. The variation of the ion Mach number with the incident angle of the ions is also presented.

关键词： plasma sheath magnetic field