• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Investigation into wideband electromagnetic stealth device based on plasma array and radar-absorbing materials

    2022-11-17 02:59:32XuesongDENG鄧學(xué)松ChenglongDING丁成龍YahuiWANG王亞輝ZhigangLI李志剛LiCHENG程立ZongshengCHEN陳宗勝XiangyinLV呂相銀andJiamingSHI時(shí)家明
    Plasma Science and Technology 2022年11期
    關(guān)鍵詞:李志剛成龍

    Xuesong DENG(鄧學(xué)松),Chenglong DING(丁成龍),Yahui WANG(王亞輝),*,Zhigang LI(李志剛),Li CHENG(程立),Zongsheng CHEN(陳宗勝),Xiangyin LV(呂相銀) and Jiaming SHI(時(shí)家明),*

    1 State Key Laboratory of Pulsed Power Laser Technology,National University of Defense Technology,Hefei 230037,People’s Republic of China

    2 Anhui Provincial Laboratory of Advanced Laser Technology,National University of Defense Technology,Hefei 230037,People’s Republic of China

    3 Key Laboratory of Infrared and Low Temperature Plasma of Anhui Province,National University of Defense Technology,Hefei 230037,People’s Republic of China

    Abstract Manipulation of electromagnetic waves is essential to various microwave applications,and absorbing devices composed of low-pressure gas discharge tubes and radar-absorbing materials(RAM)can bring new solutions to broadband electromagnetic stealth.The microwave transmission method is used to measure the physical parameters of the plasma unit.The designed structure exhibits superior absorption performance and radar cross-section(RCS)reduction capability in the 2-18 GHz band,with unique absorption advantage in the S and C frequency bands.It is found that the combination of the plasma and the RAM can significantly broaden the absorption frequency band and improve the absorption performance with excellent synergistic stealth capability.Experimental and simulation results present that broadband,wide-angle,tunable electromagnetic wave absorption and RCS reduction can be achieved by adjusting the spatial layout of the combined plasma layer and the type of RAMs,which creates opportunities for microwave transmission and selective stealth of equipment.Therefore,the wave manipulation by combined plasma array and RAM provides a valuable reference for developing numerous applications,including radar antenna stealth,spatial filter,and high power microwave shielding.

    Keywords:radar stealth,plasma stealth,radar cross-section,absorber

    1.Introduction

    Radar stealth technology has always been a research hotspot in the field of anti-detection.The key to radar stealth is primarily to reduce the target’s radar cross-section(RCS)to a level that is undetectable by the radar[1,2].Generally,the RCS reduction methods rely on modifying the target’s geometry and loading the target with the radar-absorbing material(RAM)[3].Target shaping is not perfect due to its complexity of design and its low efficiency at lower frequencies[1].Comparatively,loading RAMs on the target’s surface is a common method to reduce the RCS.Nevertheless,it is commonly known that traditional RAMs,such as ferrites and carbon-based materials,can only effectively absorb electromagnetic(EM)waves in relatively high-frequency bands[4-7].

    To overcome the above shortcomings of the stealth technology,researchers have introduced plasma stealth technology based on the plasma’s absorbing capability[8-11].The collisional plasma can effectively absorb EM waves in a wide frequency band,especially in the low-frequency range.Laroussi[12]studied the interaction of microwaves with atmospheric plasma gas.Vidmar[13]found that plasma generated in air or helium at atmospheric pressure could be an excellent broadband absorber from high frequency to S-band.Koretzky and Kuo[14]demonstrated that plasma torches can effectively attenuate EM waves.However,it is difficult to maintain high electron density in atmospheric pressure plasma owing to the extremely frequent collision between electrons and other heavy particles.Besides,the atmospheric plasma has obvious visible and infrared characteristics and is easily detected by photoelectric equipment.Thus,this atmospheric pressure plasma is not suitable for practical stealth applications.

    In contrast,plasma can be easily maintained in a confined cavity with low gas pressure[8,15].Yuanet al[2]proposed an enclosed plasma stealth structure,which is a three-layer configuration consisting of a RAM layer,a plasma slab,and a glass slab.Baiet al[3]analyzed the refraction and reflection of the EM waves obliquely incident on the plasma-RAM structure.Changet al[16,17]studied EM scattering characteristics of inductively coupled plasma superimposed on a honeycomb absorbing structure.Rahmanzadehet al[9]analyzed the absorbing properties of broadband absorbers of plasma-graphene structure.Ghayekhlooet al[11]analyzed the absorbing properties of the low-pressure plasma array formed of discharge tubes.It can be found that the flat plasma plate mostly consisted of gas discharge tubes,which are convenient to be deployed on the target.Several studies have revealed that the combination of plasma and RAM has excellent absorbing capability over a wide frequency band.Although many studies have focused on the EM wave absorption by plasma-RAM structure,little has been done concerning the experimental investigation into the effect of the plasma parameters on the EM absorption characteristics.While evaluating the plasma’s absorption characteristic,two parameters are indispensable,namely,electron density and collision frequency,which is challenging to select accurate plasma parameters to obtain ideal attenuation[18].Furthermore,not only their values but also their layouts affect the EM attenuation[19].

    In this work,a combined plasma-RAM unit is studied concerning the EM absorption.By adjusting the spatial distribution of plasma,the absorption rate of the plasma-RAM absorber is investigated over the 2-7 GHz microwave band.Two levels of the parameters are involved in this research.In addition,the RCS of the plasma-RAM structure is simulated.This study is valuable to the design of tunable broadband microwave absorbers.

    2.Plasma diagnostics

    While studying the interaction of the plasma with the EM wave,one has to mention two fundamental parameters,namely,the electron frequency and the electron neutral collision frequency.These two parameters are indispensable to the design of plasma absorbers[1].When EM waves interact with the plasma,the plasma parameters are diagnosed by analyzing the results from the microwave transmission experiment and numerical simulation.

    Eighteen gas discharge tubes were closely arranged on the metal plate,with high voltage ballasts ionizing these gas discharge tubes to generate plasma,as displayed in figure 1,to measure the backscattering attenuation of the plasma array under transverse magnetic(TM)mode.After 5 min of stable discharge of the plasma unit,the peak voltage and current value of each plasma element of the ionization source were measured to be 0.8 kV and 40 mA,respectively.The power supply is the alternating current,the ballast is connected to 220 V voltage,and the frequency of the current output by the ballast is 40 kHz.The gas discharge tube and the ballast are connected in series,one ballast can control two gas discharge tubes,and the specifications of the ballasts and the gas discharge tubes are the same.The ballasts are connected in parallel,so that the output current of each ballast is consistent,to ensure the consistent discharge state of each fluorescent lamp.

    The distanceLbetween the horn antenna and the sample is 5 m to meet the far-field condition ofL≥2×D2/λ,whereDis the vertical dimension of the object to be tested,which is 0.2 m.The actual plasma units are composed of airtight glass tubes with an outside diameter of 15 mm,and a length of 42 cm,and the thickness of the glass tube is 1 mm,with the dielectric constant of 3.8.The cavity is filled mainly with argon and mercury,and the gas pressure was typically 2-3 Torr.The model of the vector network analyzer(VNA)is ANRITSU 3734D,which can measure the frequency range from 40 MHz to 20 GHz[20].Setting the time domain threshold can avoid space clutter interference so that the experimental results are more accurate than not.The signal transmitter and receiver source are a pair of broadband horn antennas with an operating range of 2-18 GHz.

    The VNA measures the backscattering attenuation spectrum of the plasma array,and the results are exhibited in figure 2.The numerical scattering coefficient of the plasma array is calculated by COMSOL simulation software,and the plasma parameters are estimated for simulating after several analyses to be qualitatively consistent with experimental results.In simulating,the electromagnetic wave frequency domain interface of the COMSOL RF module is used,periodic boundary conditions are set to simulate an infinite plasma array,and user-defined ports are set in thez-direction to simulate plane wave incidence.Therefore,the precise range of the plasma parameters could be deduced.The electron in plasma oscillates harmonically vibration under the excitation of a high voltage power supply,which is called plasma oscillation[21].Therefore,the Drude model is adopted to approximately represent the EM characteristics of non-magnetized plasma during simulation calculation.The relative permittivity of plasma can be expressed as follows:

    The formula aboveωpis the plasma frequency,νeis the electron collision frequency,andωis the angular frequency of the incident wave.The plasma frequency can be expressed as follows:is the electron density in the plasma,meis the electron mass,andeis the charge of the electron.

    The experimental and simulation results of the plasma units’backscattering attenuation are indicated in figure 2,and the two results are distinguished by different colors and symbols.TheSparameter of the initial state is normalized to zero during simulation and experiment,and the variation tendency of the two curves is approximately consistent.It can be observed that the positions of the attenuation peaks of the two curves are similar,and the decay amplitude will fluctuate slowly with the increase of discharge time,which is caused by the discharge unit’s fluctuation of collision frequency and electron density.The corresponding collision frequency can be inferred from the gas pressure in the discharge tube.The air pressure of the low-pressure discharge tube used in this work is 2-3 Torr,due to the limitation of the ballast’s power and plasma tube’s pressure,and the approximate range of the collision frequency can be obtained by calculation of about 1-3 GHz.According to the simulation results,it can be inferred that the plasma electron density ranges from 1×1017to 9×1017m-3,and the corresponding plasma frequency varies from 1.7×1010to 5.3×1010rad s-1.The plasma frequency used in the simulation results is 5.18×1010rad s-1,and the collision frequency is 1.256×1010rad s-1.The diagnosis method of plasma parameters by using estimation analysis combined with the microwave transmission method has been fully validated in other literature[11].

    3.Plasma-RAM absorbing properties

    The plasma spatial distribution can be altered by manipulating each discharge unit’s On/Off state or changing its voltage.This work proposes a new EM wave absorbing component that combines the double-layer plasma unit and the RAM.The plasma cylinder array is assumed to be infinitely distributed on a perfect electrical conductor(PEC)which is covered with traditional RAM.A schematic diagram of its structure is displayed in figure 3(a).Plasma with different electron densities can be obtained by adjusting the voltage of the rectifier.The effect of spatial plasma distribution on radar absorption is analyzed by simulation.Figure 3(a)indicates that the different combined distributions of plasma units with the two plasma frequencies are arranged respectively.Ne1andNe2represent the corresponding electron density,where the electron collision frequency is fixed at 1.256×1010rad s-1for convenience of analysis.According to the simulation results in figure 2,the plasma frequency in the gas discharge tube is 1.8×1010rad s-1and 5.18×1010rad s-1when the rectifier is loaded voltage with 140 V and 220 V,respectively.Adjusting the voltage can change the electron density,thereby changing the plasma frequency.Several simulation results reveal that the designed plasma structure can effectively absorb low-frequency EM waves when the plasma frequency is distributed alternately high and low.Figure 3(a)lists five different plasma distribution situations,whereNe1(1.8×1010rad s-1)corresponds to a plasma with low electron density,andNe2(5.18×1010rad s-1)corresponds to a plasma with high electron density.The absorbance of the five different distribution patterns is shown in figure 3(b).

    Figure 1.Configuration for the measurement of plasma backscattering attenuation spectrum.(a)Experiment setup,(b)schematic diagram.

    Figure 2.Comparison of simulation and experiment for backscattering attenuation.

    Figure 3.Absorption of electromagnetic waves by different plasma distribution.(a)Five plasma distribution modes,(b)absorbance corresponding to five modes and only RAM.

    Figure 4.The electric field distributions at each frequency point.(a)2.6 GHz,(b)6.6 GHz,(c)10.5 GHz,(d)16.5 GHz.

    Figure 3(b)exhibits that the plasma layer has a unique advantage when distributed according to Mode 1.It has a significant absorption capability for the EM waves in the S and C frequency bands,with an absorption rate that can reach over 90%,which cannot be achieved by other distribution modes.In addition,the absorption efficiency at 9.5-11.5 GHz and 15-18 GHz also exceeds 90%,which can realize excellent absorption stealth for multi-bands.The different plasma distribution modes present various characteristics of absorption in the X and Ku frequency bands,which is due to the combined interaction of the plasma and the RAM.In order to further analyze the absorption performance of the plasma-RAM structure in different frequency bands,the structure’s distribution of electric field values and energy flow density at different frequency points are listed below.Figure 4 presents the distribution of electric field values at 2.6 GHz,6.7 GHz,10.5 GHz,and 16.5 GHz,and figure 5 gives the distribution of power flow density at the corresponding frequency points.

    Figure 5.Power flow density distribution at each frequency point.(a)2.6 GHz,(b)6.6 GHz,(c)10.5 GHz,(d)16.5 GHz.

    It is widely known that when the frequency of the EM wave is higher than that of plasma,the EM wave cannot propagate within the plasma in specific frequency bands,which are called photonic bandgaps.When the frequency of the EM wave is lower than that of plasma,the EM wave cannot transmit inside the plasma,which is called the plasma cut-off frequency[22].Generally,is regarded as the plasma cut-off frequency,and the EM wave below the plasma cut-off frequency will be reflected and cannot enter the plasma.When the EM wave coupling enters plasma arrays with a large area,the inhomogeneous plasma layer can increase the possibility of absorbing broadband EM waves.The distribution of the plasma units arranged as Modes 2-5 in figure 3 is relatively homogeneous and presents lower absorption efficiency within 2-8 GHz band compared with Mode 1.Hence,the uneven distribution of thin plasma units can enable more EM waves to be coupled into the plasma layer,which can increase the possibility of multiple scattering of EM waves,dissipate EM energy and improve the absorptivity to EM waves.

    When the EM wave is incident normally to the plasma-RAM absorber,the low-frequency EM wave propagates in the plasma with low electron density.As presented in figure 4(a),the plasma units with an electron density ofNe1generate an intense coupling effect with the EM wave at 2.6 GHz.With the increase of EM wave frequency,more EM energy can be coupled into the plasma with high electron density.As shown in figure 4(b),the coupling effect between a 6.6 GHz EM wave and plasma with an electron density ofNe2is more intense.In contrast,the EM waves in the X and Ku frequency bands can pass through the plasma layer and be absorbed by RAM.Figures 4(c)and(d)display the reaction of EM waves and RAM,as well as the induced electric field in RAM,which indicates that such RAM has good absorption performance for high-frequency EM waves.The distribution of power flow density is illustrated in figure 5.It can be noticed from figures 5(a)and(b)that the EM energy in the X and Ku frequency bands is mainly concentrated on the upper surface of the plasma units.With the increases in the incident EM waves frequency,the EM energy is mainly concentrated in the gap outside the plasma units.That means multiple scattering of the EM waves between the gas discharge tube and RAM,and the EM energy is gradually dissipated in this process.

    Figure 6.Electromagnetic characteristics of magnetic and non-magnetic RAM.(a)Electromagnetic parameters of RAM,(b)electromagnetic absorption characteristics of RAM.

    RAM has the advantages of simple manufacture,light in weight,and easy coating on the surface of objects.Therefore,RAM is convenient for large-scale applications in radar stealth.Generally speaking,the RAM can be divided into non-magnetic dielectric absorbing materials and magnetic ferrite absorbing materials according to the different loss mechanisms.There are significant differences in the EM parameters of the two kinds of RAMs,and the absorption bands are also quite different.The following figure 6 content describes the comparison of the EM properties of the magnetic RAM and the non-magnetic RAM[23-25].In this work,non-magnetic dielectric absorbing materials are selected as the research carrier,and the whole work is based on the non-magnetic RAM.

    A vector network analyzer(VNA)was applied to determine the relative permeability and permittivity in the frequency range of 2-18 GHz for the calculation of reflection loss.Figure 6(a)shows the electromagnetic parameters including permittivity and permeability of the RAM.The electromagnetic parameters are measured by the coaxial line method in the Nicolson-Ross-Weir(NRW)theory[23-25].A sample containing 40 wt%of the obtained composites was pressed into a ring with an outer diameter of 7 mm,an inner diameter of 3 mm,and a thickness of 2 mm for microwave measurement in which paraffin wax was used as the binder.The sample is placed in a coaxial fixture,and the coaxial fixture is connected to the vector grid.Based on the NRW theory[23-25],the precise electromagnetic parameters of the RAM can be obtained as shown in figure 6(a).The electromagnetic parameters are brought into COMSOL software,and the frequency domain solver of the RF module can be used to simulate the absorption properties of a 2 mm thickness absorbing material in the corresponding frequency band,as shown in figure 6(b).

    It is known that relative complex permittivity(εr=εr′-jεr″)and complex permeability(μr=μr′-jμr″)dominate the properties of EM absorption materials.According to the previous study[23,24],the real part of permittivity(εr′)values of magnetic RAM and non-magnetic RAM exhibit distinct frequency dispersion behaviors,where their εr′values gradually decrease from 13.3 and 8.9 at 2.0 GHz to 11.2 and 6.3 at 18.0 GHz,respectively(figure 6(a1)).The imaginary part of permittivity(εr″)of magnetic RAM declines from 6.0 to 3.2 and presents a more apparent concave profile with a minimum of 3.6 at 12.0 GHz.In contrast,the εr″of nonmagnetic RAM keeps approximately constant in the 2-18 GHz frequency range(figure 6(a2)).Figure 6(a3)displays the real part of permeability(μr′)and imaginary part of permeability(μr″)values of non-magnetic RAM at about 1 and 0,respectively.On the contrary,magnetic RAM benefits from the magnetic metal particle and exhibits variational μrvalues(figure 6(a4)).Corresponding studies have presented that non-magnetic RAM indicates superior EM absorption ability in the high-frequency range,and magnetic RAM possesses evident EM attenuation behavior at low frequency.

    The absorption properties of the two RAMs are shown in figure 6(b).The non-magnetic RAM shows excellent absorption behavior in the Ku frequency band,while the magnetic RAM presents more outstanding in the 10.5-13.25 GHz band.The absorption performance of both materials for low-frequency EM waves is significantly decreased since the plasma-RAM structure can absorb the EM energy in the low-frequency band,so it can be inferred that the plasma makes the major contribution to the absorption of this.Different kinds of RAMs combined with the plasma layer designed in this work will possess different absorption effects.Figure 7 depicts the absorbing characteristics of the plasma layer placed on different substrates.There are three different substrates:the PEC without coated RAM,the PEC coated with magnetic RAM,and the PEC coated with nonmagnetic RAM.Figure 7 reveals that the plasma layer intensely absorbs EM energy in the frequency band of 2-7 GHz,which is not related to whether the PEC is coated with RAM or not.The RAM plays a significant role in absorbing EM energy above 7 GHz,and the corresponding pure plasma layer displays the limited absorption ability to high-frequency EM waves.RAM not only exhibits good absorption characteristics in its intrinsic absorption band but also expands the absorption band and improves the absorption efficiency after coupling with plasma.Thus the multi-band EM absorption can be achieved by transforming the RAM or changing the spatial distribution of the plasma.

    Figure 7.Wave absorption properties of plasma combined with different absorbing materials.

    Figure 8.Absorbing properties of single-layer and double-layer plasma arrays.

    The spatial distribution of the plasma is further discussed based on the non-magnetic RAM already coated on the PEC surface.The microwave absorption characteristics of the singlelayer and double-layer plasma array are discussed.The distance between single-layer plasma and the substrate(the PEC coated with non-magnetic RAM)is divided into two situations,the plasma layer near the PEC and away from the PEC,as depicted in figure 8,with the distance from the substrate being 0 mm and 13 mm,respectively.The electron density in the plasma layer is still arranged in an alternating high and low distribution.The three plasma distribution situations have a pronounced resonance absorption peak near 10.25 GHz,as shown in figure 8.Through simulation calculation and the results in figure 3(b),it can be concluded that the unexcited gas discharge tube structure determines the resonance absorption near 10.25 GHz.The single-layer plasma array near the substrate has a wider absorbing band than that away from the substrate and exhibits a stronger absorbing performance in X-band,which is inconsistent with the conclusion in[11].The reason may be the uneven distribution of plasma and the introduction of RAM in the designed structure,which changes the scattering path of the EM waves and increases the pathway for EM energy loss.The monolayer plasma arrays near the substrate can achieve over 90% absorption of EM energy in the X and Ku frequency bands.In contrast,monolayer plasma that away from the substrate,which facilitates the effective transmission of EM waves in the 6-8 GHz band.On the other hand,the tunable band-pass frequency range can be realized by adjusting the spatial distribution of plasma on the equipment’s surface,and radar stealth can be achieved without affecting the regular operation of the equipment.

    In order to verify the actual backscattering attenuation of EM waves by the plasma distribution proposed in the article,a corresponding test setup was built in the laboratory,as displayed in figure 9(b).The plasma absorber is placed on the aluminum plate substrate coated with non-magnetic RAM using the experiment system displayed in figure 1(b).The size of the aluminum plate is 20 cm×20 cm.By varying the voltage of the ballast,the plasma element has the corresponding plasma frequency to satisfy the pattern of alternating electron density distribution.The backscattering attenuation spectrum of the plasma-RAM absorber is obtained by the vector network analyzer.

    As presented in figure 10,the variation trend of the simulated and experimental data is roughly similar,and the positions of the attenuation peaks are also approximately the same.It is noteworthy that the experimental data exhibit more fluctuations,which may be caused by the unstable discharge state in the plasma tube.In addition,the exposed wires and connectors will inevitably scatter EM waves,which increases the EM waves’resonance space and scattering paths.

    4.RCS of plasma-RAM structure

    In practical applications,the target’s characteristics are often detected by radar.The RCS is a physical quantity that measures the echo intensity generated by the target under the irradiation of radar waves.The RCS is the ratio of the scattered energy to the incident energy,which can be calculated aswhereris the distance from the target to the detection point,σ3Dandσ2Dcorrespond to the RCS of a three-dimensional and two-dimensional target scatterer,respectively.

    The RCS of the proposed plasma-RAM absorber is simulated by using the simulation software COMSOL.Firstly,the RCS of the EM wave vertically incident metal plate is simulated.The results are presented in figure 11,which indicates that the RCS of the metal plate increases with the increase of the incident wave frequency.After coating the plasma-RAM absorber on the metal plate,the RCS of the composite absorber exhibits oscillation,which is similar to the changing tendency of the backscattering attenuation in figure 10.Comparing the two results can reveal the difference in RCS reduction of the plasma-RAM absorber for different frequencies.The plasma-RAM absorber demonstrates superior RCS reduction capability,which can reduce the RCS by 20 dB around the frequency points of 7 GHz,10 GHz,14 GHz,and 17 GHz.

    In addition,the target’s RCS exhibits different degrees of attenuation with varying incident degrees of the detection wave.Figure 12 depicts the omnidirectional angle RCS of the 7 GHz incident EM wave,where the incident pitch angleθ=°90,and the azimuth angleφchange from-180° to 180°.φ=°0 indicates that the incident wave radiates vertically to the target.According to figure 12,when the 7 GHz detection wave changes from vertical incidence to±55°,the RCS decreases by more than 10 dB.The RCS attenuation capability of the absorber is decreased when the incident angle exceeds±55°.Here,the thickness of the metal plate is only 5 mm,but in practice,the thickness of the target is far more than 5 mm.In addition,how the plasma-RAM absorber maintains low RCS when exposed to wide azimuth angle incident waves will be another research focus.Therefore,it is undeniable that the designed structure has a robust EM absorption capacity at wide incident angles.

    Figure 9.Plasma-RAM composite absorber model and experimental setup.(a)Schematic diagram,(b)experiment setup.

    Figure 10.Backscattering attenuation spectrum of a plasma-RAM composite absorber.

    Figure 11.Target RCS versus frequency.

    Figure 12.Omnidirectional RCS of the plasma-RAM absorber.

    5.Conclusion

    This study demonstrates a radar stealth structure composed of a plasma array and RAM.The absorption and RCS reduction performance of this stealth structure in the 2-18 GHz frequency band are analyzed.The plasma parameters are obtained by analyzing the results from the microwave transmission experiment and numerical simulation.The absorption efficiency of electromagnetic waves by plasmas of various spatial distributions is analyzed by simulation and experiment.The results show that the plasma array composed of tubes with alternating high and low electron density can absorb up to 90%of the EM energy in the S and C frequency bands.Based on this structure,the effect on the absorption performance of the type of RAMs and the distance from the plasma array to the substrate is further discussed.The plasma-RAM stealth structure can achieve an RCS reduction of more than 10 dB for broad frequency bands and wide incident angles.Meanwhile,this structure is easy to deploy on the surface of the equipment.Furthermore,the radar stealth ability of the structure is tunable by changing the plasma layout and the type of the RAM.This research provides a new approach to the synergistic stealth of targets and has a particular reference value for engineering applications.

    Acknowledgments

    This work was supported by National Natural Science Foundation of China(No.51907198),Natural Science ResearchFoundationofAnhuiProvince(No.1908085MF205),Director Fund of State Key Laboratory of Pulsed Power Laser Technology(Nos.SKL2021ZR07,SKL2021ZR06),China Postdoctoral Science Foundation(No.2021MD703944).

    猜你喜歡
    李志剛成龍
    Un ser mítico que se globaliza
    物種緣何瀕危
    意林彩版(2022年1期)2022-05-03 10:25:07
    口頭戀人
    成龍:奧斯卡來(lái)找我,不是我找?jiàn)W斯卡
    海峽姐妹(2017年4期)2017-05-04 04:03:41
    A numerical model for pipelaying on nonlinear soil stiffness seabed*
    Beamforming of Whole Airspace Phased Array TT&C System Based on Linear Subarrays
    《過(guò)中國(guó)年》
    海峽影藝(2013年3期)2013-11-30 08:15:58
    Value of quantitative examination via contrast-enhanced ultrasonography in evaluating the activity of Crohn disease at endoscopy
    Development of an occupant restraint system model and parametric study on equivalent crash pulse in vehicle frontal offset crash
    尋找成龍等
    欧美少妇被猛烈插入视频| 22中文网久久字幕| 国产中年淑女户外野战色| 777米奇影视久久| 肉色欧美久久久久久久蜜桃| 九九爱精品视频在线观看| 性色avwww在线观看| av免费观看日本| 精品酒店卫生间| 国产精品伦人一区二区| 国产黄片视频在线免费观看| 国产亚洲最大av| av播播在线观看一区| 色综合色国产| 国产色婷婷99| 久久精品久久久久久久性| 精品久久久久久久末码| 一级a做视频免费观看| 3wmmmm亚洲av在线观看| 欧美xxⅹ黑人| 欧美日本视频| 99久久人妻综合| 国产 精品1| 啦啦啦视频在线资源免费观看| 国产欧美另类精品又又久久亚洲欧美| 久久久午夜欧美精品| 色综合色国产| 男女无遮挡免费网站观看| 亚洲欧美日韩另类电影网站 | 国产精品一区二区在线不卡| 蜜臀久久99精品久久宅男| 日韩,欧美,国产一区二区三区| 新久久久久国产一级毛片| 免费黄色在线免费观看| 久久 成人 亚洲| 精品一区在线观看国产| 大码成人一级视频| 国产精品一及| 亚洲精品久久久久久婷婷小说| 亚洲成色77777| 欧美日本视频| tube8黄色片| 天堂俺去俺来也www色官网| 日韩免费高清中文字幕av| 在线观看美女被高潮喷水网站| 国产精品国产三级国产av玫瑰| 自拍偷自拍亚洲精品老妇| 成年美女黄网站色视频大全免费 | 久久久久精品久久久久真实原创| 成人毛片60女人毛片免费| 十八禁网站网址无遮挡 | 亚洲精品456在线播放app| 老司机影院成人| 国产精品人妻久久久影院| 亚洲欧美日韩无卡精品| 亚洲成人av在线免费| 欧美变态另类bdsm刘玥| 日韩 亚洲 欧美在线| 美女内射精品一级片tv| 欧美另类一区| av免费在线看不卡| 欧美日韩在线观看h| 中文天堂在线官网| 大香蕉久久网| 91精品一卡2卡3卡4卡| 国产免费又黄又爽又色| 狠狠精品人妻久久久久久综合| 亚洲国产精品成人久久小说| 久久午夜福利片| 一级毛片久久久久久久久女| 又粗又硬又长又爽又黄的视频| 欧美日韩精品成人综合77777| 我的老师免费观看完整版| 成人免费观看视频高清| 成人午夜精彩视频在线观看| 亚洲av在线观看美女高潮| 天堂俺去俺来也www色官网| 下体分泌物呈黄色| av国产久精品久网站免费入址| 欧美性感艳星| 一边亲一边摸免费视频| 免费不卡的大黄色大毛片视频在线观看| 国产 一区精品| 日韩av在线免费看完整版不卡| 亚洲电影在线观看av| 久久久久国产网址| 午夜免费男女啪啪视频观看| 乱码一卡2卡4卡精品| 国产爽快片一区二区三区| 三级国产精品片| 中文乱码字字幕精品一区二区三区| 91精品国产国语对白视频| 一级毛片久久久久久久久女| 一级毛片电影观看| 中文精品一卡2卡3卡4更新| 国产精品国产三级国产av玫瑰| 久久99热这里只有精品18| 自拍偷自拍亚洲精品老妇| 中文天堂在线官网| 国产有黄有色有爽视频| 亚洲中文av在线| 午夜免费男女啪啪视频观看| 亚洲第一av免费看| 精品亚洲成国产av| 国产爽快片一区二区三区| 韩国高清视频一区二区三区| 国产精品一区www在线观看| 亚洲欧美清纯卡通| 亚洲成人手机| 久久午夜福利片| 嫩草影院新地址| 日本爱情动作片www.在线观看| 青春草亚洲视频在线观看| 国产国拍精品亚洲av在线观看| 亚洲怡红院男人天堂| av国产免费在线观看| 日韩一本色道免费dvd| 我的老师免费观看完整版| 欧美bdsm另类| 一区二区三区精品91| 午夜福利高清视频| 国产有黄有色有爽视频| 国产高清不卡午夜福利| 久久久久久久久久成人| 日韩成人伦理影院| 国产精品人妻久久久久久| 少妇高潮的动态图| 亚洲电影在线观看av| 3wmmmm亚洲av在线观看| 97在线视频观看| 久久久国产一区二区| 亚洲自偷自拍三级| 亚州av有码| 18禁裸乳无遮挡动漫免费视频| 精品久久久久久电影网| 成人国产麻豆网| 男女下面进入的视频免费午夜| 五月伊人婷婷丁香| freevideosex欧美| 在线观看免费日韩欧美大片 | 欧美日韩视频高清一区二区三区二| 久久影院123| 一级二级三级毛片免费看| av一本久久久久| 91久久精品国产一区二区三区| 精品一区在线观看国产| 久久久久人妻精品一区果冻| 国产高清国产精品国产三级 | 精品人妻一区二区三区麻豆| av线在线观看网站| 精品亚洲乱码少妇综合久久| 直男gayav资源| 亚洲精品一区蜜桃| 高清在线视频一区二区三区| 高清在线视频一区二区三区| 久久久久久久久久久丰满| 中文在线观看免费www的网站| 丝袜喷水一区| 97在线人人人人妻| 久久久久久久亚洲中文字幕| 国产又色又爽无遮挡免| 久久久欧美国产精品| 亚洲,欧美,日韩| 伊人久久精品亚洲午夜| www.av在线官网国产| 久久国产精品大桥未久av | 国产午夜精品一二区理论片| 日韩成人伦理影院| 欧美激情国产日韩精品一区| 国产一区二区三区综合在线观看 | 97超碰精品成人国产| 内射极品少妇av片p| 女人久久www免费人成看片| 永久网站在线| 亚洲欧美日韩无卡精品| 亚洲美女视频黄频| 又粗又硬又长又爽又黄的视频| 精品久久久久久久久av| 亚洲av电影在线观看一区二区三区| 18禁在线播放成人免费| 亚洲色图综合在线观看| 久久午夜福利片| 亚洲四区av| 国产黄色视频一区二区在线观看| 久久精品国产亚洲网站| 晚上一个人看的免费电影| 中文字幕人妻熟人妻熟丝袜美| 国产成人精品一,二区| 赤兔流量卡办理| 岛国毛片在线播放| 亚洲成人av在线免费| 永久免费av网站大全| 日日啪夜夜撸| 亚洲天堂av无毛| 草草在线视频免费看| 亚洲av成人精品一二三区| 中文精品一卡2卡3卡4更新| 成人影院久久| 久久久久久久精品精品| 天天躁日日操中文字幕| 国产淫片久久久久久久久| 国产亚洲一区二区精品| 老熟女久久久| av专区在线播放| 精品少妇黑人巨大在线播放| 亚洲成色77777| 亚洲av欧美aⅴ国产| 街头女战士在线观看网站| 美女主播在线视频| 美女国产视频在线观看| 麻豆国产97在线/欧美| 亚洲,一卡二卡三卡| 亚洲精品国产av成人精品| 51国产日韩欧美| 蜜桃久久精品国产亚洲av| 青春草视频在线免费观看| 中文字幕av成人在线电影| 久久综合国产亚洲精品| 国产成人91sexporn| 美女xxoo啪啪120秒动态图| 国内精品宾馆在线| 成人二区视频| 亚洲三级黄色毛片| 在线精品无人区一区二区三 | 少妇人妻一区二区三区视频| www.色视频.com| 欧美少妇被猛烈插入视频| 免费观看无遮挡的男女| 精品一区二区三区视频在线| 久久精品国产a三级三级三级| 亚洲精华国产精华液的使用体验| 制服丝袜香蕉在线| 欧美精品一区二区免费开放| 七月丁香在线播放| 综合色丁香网| av不卡在线播放| 国产无遮挡羞羞视频在线观看| 99热这里只有是精品50| 色综合色国产| 亚洲精品亚洲一区二区| 九九久久精品国产亚洲av麻豆| 亚洲内射少妇av| 欧美xxxx黑人xx丫x性爽| 韩国av在线不卡| 极品少妇高潮喷水抽搐| 国产av一区二区精品久久 | 国产有黄有色有爽视频| 国产精品偷伦视频观看了| 99热网站在线观看| 狂野欧美激情性xxxx在线观看| 国产在视频线精品| 亚洲av综合色区一区| 久久国产精品男人的天堂亚洲 | 一个人免费看片子| 国产成人午夜福利电影在线观看| 精品酒店卫生间| 两个人的视频大全免费| 日本av免费视频播放| 亚洲精品色激情综合| 国精品久久久久久国模美| 国产黄色视频一区二区在线观看| av在线app专区| 人妻一区二区av| 午夜福利在线观看免费完整高清在| av国产免费在线观看| 激情五月婷婷亚洲| 日本欧美国产在线视频| 如何舔出高潮| 少妇的逼水好多| 久久久久久久久久久免费av| 成人毛片a级毛片在线播放| 观看av在线不卡| 黑人猛操日本美女一级片| 大香蕉97超碰在线| 欧美 日韩 精品 国产| 不卡视频在线观看欧美| 日韩一本色道免费dvd| 亚洲美女黄色视频免费看| 高清日韩中文字幕在线| 深爱激情五月婷婷| 最近2019中文字幕mv第一页| 99久久人妻综合| 人妻一区二区av| 国产女主播在线喷水免费视频网站| 3wmmmm亚洲av在线观看| av又黄又爽大尺度在线免费看| 免费观看无遮挡的男女| 久久精品久久久久久久性| 18+在线观看网站| 一级毛片黄色毛片免费观看视频| 九九久久精品国产亚洲av麻豆| 观看美女的网站| 久久人人爽人人片av| 亚洲人成网站高清观看| 国产黄片美女视频| 精华霜和精华液先用哪个| 国产免费视频播放在线视频| 九九爱精品视频在线观看| 日韩成人伦理影院| 全区人妻精品视频| 最黄视频免费看| 18禁在线播放成人免费| 乱系列少妇在线播放| 久久久久久久亚洲中文字幕| 国产男女超爽视频在线观看| 日韩伦理黄色片| 欧美性感艳星| 日韩 亚洲 欧美在线| 国产成人a区在线观看| 性高湖久久久久久久久免费观看| 久久99精品国语久久久| 高清av免费在线| 黑丝袜美女国产一区| 午夜日本视频在线| 免费大片18禁| 久久精品久久久久久久性| 97超碰精品成人国产| 1000部很黄的大片| 色婷婷av一区二区三区视频| 91精品伊人久久大香线蕉| 极品教师在线视频| 97超碰精品成人国产| 3wmmmm亚洲av在线观看| 一二三四中文在线观看免费高清| 美女视频免费永久观看网站| 亚洲欧美成人精品一区二区| 成人毛片60女人毛片免费| 久久久久久久久大av| 性色avwww在线观看| 亚洲图色成人| h日本视频在线播放| 搡女人真爽免费视频火全软件| 最近中文字幕高清免费大全6| 黄色视频在线播放观看不卡| 欧美变态另类bdsm刘玥| 中文字幕av成人在线电影| 91久久精品国产一区二区三区| 97精品久久久久久久久久精品| 大又大粗又爽又黄少妇毛片口| 国产有黄有色有爽视频| 亚洲精品乱久久久久久| 日本欧美国产在线视频| 日韩视频在线欧美| 精品熟女少妇av免费看| 高清日韩中文字幕在线| 国模一区二区三区四区视频| 亚洲图色成人| 性高湖久久久久久久久免费观看| 国产伦精品一区二区三区视频9| 国产免费视频播放在线视频| 亚洲人成网站在线播| 五月开心婷婷网| 日本午夜av视频| 日韩成人av中文字幕在线观看| 亚洲不卡免费看| 亚洲av二区三区四区| 日韩伦理黄色片| 欧美xxxx黑人xx丫x性爽| 丝瓜视频免费看黄片| 国产欧美亚洲国产| 日韩中字成人| 欧美zozozo另类| 精品99又大又爽又粗少妇毛片| 国产在线免费精品| 欧美日韩精品成人综合77777| 国产免费视频播放在线视频| 亚洲图色成人| 五月开心婷婷网| 日本wwww免费看| 最近手机中文字幕大全| av在线老鸭窝| 午夜福利网站1000一区二区三区| 国国产精品蜜臀av免费| 在线 av 中文字幕| 秋霞伦理黄片| 这个男人来自地球电影免费观看 | 国产精品成人在线| 舔av片在线| 久久99热6这里只有精品| 在线精品无人区一区二区三 | 简卡轻食公司| 色5月婷婷丁香| 久久久久精品久久久久真实原创| 午夜老司机福利剧场| 联通29元200g的流量卡| 精品人妻偷拍中文字幕| 精品久久国产蜜桃| 免费看av在线观看网站| 久久鲁丝午夜福利片| 观看av在线不卡| 亚洲色图综合在线观看| 精品久久久噜噜| 日韩av在线免费看完整版不卡| 亚洲av电影在线观看一区二区三区| 国产69精品久久久久777片| 欧美人与善性xxx| 亚洲欧洲国产日韩| 中文字幕精品免费在线观看视频 | 免费黄网站久久成人精品| 欧美区成人在线视频| 18禁裸乳无遮挡动漫免费视频| 久久99热6这里只有精品| 伦理电影大哥的女人| 成人国产av品久久久| 99久久人妻综合| 成人高潮视频无遮挡免费网站| av免费观看日本| 好男人视频免费观看在线| 最近最新中文字幕大全电影3| 边亲边吃奶的免费视频| 久久久国产一区二区| 99热全是精品| 人妻制服诱惑在线中文字幕| 亚洲av.av天堂| 美女cb高潮喷水在线观看| 在线观看免费视频网站a站| 蜜臀久久99精品久久宅男| 偷拍熟女少妇极品色| 国产欧美日韩一区二区三区在线 | 久久人人爽av亚洲精品天堂 | 久久久午夜欧美精品| 亚洲精品国产av成人精品| 少妇的逼水好多| 亚洲欧美成人综合另类久久久| 国产在视频线精品| 97超碰精品成人国产| 少妇丰满av| 在现免费观看毛片| 日韩,欧美,国产一区二区三区| 日本猛色少妇xxxxx猛交久久| 尾随美女入室| freevideosex欧美| 免费观看无遮挡的男女| 伊人久久国产一区二区| 国产成人精品久久久久久| 久久久精品94久久精品| 成人二区视频| 亚洲av二区三区四区| 一本—道久久a久久精品蜜桃钙片| 在线 av 中文字幕| 91精品一卡2卡3卡4卡| 国产一区二区在线观看日韩| 国产在视频线精品| 秋霞伦理黄片| 少妇人妻久久综合中文| 亚洲四区av| 色综合色国产| 一级毛片 在线播放| 久久久久网色| 中文资源天堂在线| 视频区图区小说| 在线 av 中文字幕| 中文资源天堂在线| 日本wwww免费看| 韩国av在线不卡| 欧美区成人在线视频| 美女xxoo啪啪120秒动态图| 在线观看人妻少妇| 蜜臀久久99精品久久宅男| 18禁裸乳无遮挡免费网站照片| 在线播放无遮挡| 99热网站在线观看| 观看av在线不卡| 欧美zozozo另类| 亚洲国产毛片av蜜桃av| 美女主播在线视频| 一本一本综合久久| 黄色配什么色好看| 噜噜噜噜噜久久久久久91| 观看免费一级毛片| 亚洲激情五月婷婷啪啪| 日本爱情动作片www.在线观看| 老师上课跳d突然被开到最大视频| 国产精品国产三级专区第一集| 国产黄片视频在线免费观看| 亚洲av中文av极速乱| 少妇人妻久久综合中文| 三级国产精品片| 国产精品一区二区三区四区免费观看| 国产精品人妻久久久影院| 久久精品久久久久久久性| 亚洲成色77777| 有码 亚洲区| 晚上一个人看的免费电影| 国产高潮美女av| 欧美zozozo另类| 中文字幕久久专区| 日韩av在线免费看完整版不卡| 免费观看无遮挡的男女| 国产欧美日韩精品一区二区| 日本色播在线视频| 亚洲欧美一区二区三区国产| 精品国产露脸久久av麻豆| 亚洲精品久久午夜乱码| 国产欧美日韩精品一区二区| 99久久精品热视频| 最近的中文字幕免费完整| 一个人看的www免费观看视频| 精品久久久久久久久av| 国产乱人偷精品视频| 亚洲欧洲国产日韩| 久热久热在线精品观看| 熟女电影av网| 亚洲国产欧美人成| 亚洲精品乱码久久久v下载方式| 久久久亚洲精品成人影院| 成人无遮挡网站| 精品一品国产午夜福利视频| 欧美亚洲 丝袜 人妻 在线| 性色avwww在线观看| 人人妻人人爽人人添夜夜欢视频 | 晚上一个人看的免费电影| 人妻夜夜爽99麻豆av| 午夜福利视频精品| 中国美白少妇内射xxxbb| 亚洲国产欧美在线一区| 欧美成人午夜免费资源| 91aial.com中文字幕在线观看| 97热精品久久久久久| 不卡视频在线观看欧美| 丰满人妻一区二区三区视频av| 丝袜脚勾引网站| 欧美xxⅹ黑人| 啦啦啦中文免费视频观看日本| 成年女人在线观看亚洲视频| 亚洲综合色惰| 欧美成人精品欧美一级黄| 久久久午夜欧美精品| 国内精品宾馆在线| 人人妻人人澡人人爽人人夜夜| 中国国产av一级| 成人美女网站在线观看视频| 亚洲天堂av无毛| 欧美xxxx性猛交bbbb| 人体艺术视频欧美日本| 青青草视频在线视频观看| 精品视频人人做人人爽| 亚洲综合色惰| 晚上一个人看的免费电影| 久久精品人妻少妇| 大香蕉97超碰在线| 三级经典国产精品| 久久综合国产亚洲精品| h视频一区二区三区| 爱豆传媒免费全集在线观看| 亚洲人成网站在线播| 自拍偷自拍亚洲精品老妇| 国产精品一区www在线观看| 肉色欧美久久久久久久蜜桃| 男男h啪啪无遮挡| 伊人久久精品亚洲午夜| 成人漫画全彩无遮挡| 大又大粗又爽又黄少妇毛片口| 18禁裸乳无遮挡动漫免费视频| av在线app专区| 日日撸夜夜添| 99久久人妻综合| 日韩不卡一区二区三区视频在线| 婷婷色av中文字幕| av在线观看视频网站免费| 丝袜脚勾引网站| 天堂中文最新版在线下载| 免费观看无遮挡的男女| 色综合色国产| 少妇的逼好多水| 久久久久久久大尺度免费视频| 久久久精品免费免费高清| 视频区图区小说| 亚洲精品日本国产第一区| 国产有黄有色有爽视频| 丰满人妻一区二区三区视频av| 久久久久久久国产电影| 22中文网久久字幕| 国产免费一区二区三区四区乱码| 日韩,欧美,国产一区二区三区| 少妇猛男粗大的猛烈进出视频| 免费黄频网站在线观看国产| 日韩制服骚丝袜av| 欧美丝袜亚洲另类| 少妇的逼水好多| 国产男女内射视频| 国产亚洲av片在线观看秒播厂| 99久久精品热视频| 国产精品一二三区在线看| 中文字幕av成人在线电影| 日韩 亚洲 欧美在线| 五月开心婷婷网| 少妇裸体淫交视频免费看高清| 日韩在线高清观看一区二区三区| 在线观看三级黄色| 九九爱精品视频在线观看| 久久精品久久久久久噜噜老黄| 成年免费大片在线观看| 午夜福利在线在线| 韩国高清视频一区二区三区| 国产精品一区二区性色av| 中文字幕精品免费在线观看视频 | 久热这里只有精品99| 久久99热这里只有精品18| 在现免费观看毛片| 身体一侧抽搐| 男人和女人高潮做爰伦理| 国产在线免费精品| 91在线精品国自产拍蜜月| 久久av网站| 久久人人爽av亚洲精品天堂 | 久久久午夜欧美精品| 91久久精品国产一区二区成人| 一个人看视频在线观看www免费| 青青草视频在线视频观看| 青春草视频在线免费观看| 日韩三级伦理在线观看| 精品亚洲成a人片在线观看 | av国产久精品久网站免费入址| 亚洲色图av天堂|