The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In th...The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.展开更多
Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(...Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.展开更多
A high-power laser ablating solid targets induces giant electromagnetic pulses(EMPs),which are intimately pertinent to laser parameters,such as energy and pulse width.In this study,we reveal the features of EMPs gener...A high-power laser ablating solid targets induces giant electromagnetic pulses(EMPs),which are intimately pertinent to laser parameters,such as energy and pulse width.In this study,we reveal the features of EMPs generated from a picosecond(ps)laser irradiating solid targets at the SG-Ⅱpicosecond petawatt(PSPW)laser facility.The laser energy and pulse,as well as target material and thickness,show determinative effects on the EMPs’amplitude.More intense EMPs are detected behind targets compared to those at the other three positions,and the EMP amplitude decreases from 90.09 kV/m to 17.8 kV/m with the gold target thickness increasing from 10μm to 20μm,which is suppressed when the laser pulse width is enlarged.The results are expected to provide more insight into EMPs produced by ps lasers coupling with targets and lay the foundation for an effective EMP shielding design in high-power laser infrastructures.展开更多
Giant electromagnetic pulses(EMPs) induced by high-power laser irradiating solid targets interfere with various experimental diagnoses and even damage equipment,so unveiling the evolution of EMPs inside the laser cham...Giant electromagnetic pulses(EMPs) induced by high-power laser irradiating solid targets interfere with various experimental diagnoses and even damage equipment,so unveiling the evolution of EMPs inside the laser chamber is crucial for designing effective EMP shielding.In this work,the transmission characteristics of EMPs as a function of distances from the target chamber center(TCC) are studied using B-dot probes.The mean EMP amplitude generated by picosecond laser-target interaction reaches 561 kV m^(-1),357 kV m^(-1),395 kV m^(-1),and 341 kV m^(-1)at 0.32 m,0.53 m,0.76 m,and 1 m from TCC,which decreases dramatically from 0.32 m to 0.53 m.However,it shows a fluctuation from 0.53 m to 1 m.The temporal features of EMPs indicate that time-domain EMP signals near the target chamber wall have a wider full width at half maximum compared to that close to TCC,mainly due to the echo oscillation of electromagnetic waves inside the target chamber based on simulation and experimentation.The conclusions of this study will provide a new approach to mitigate strong electromagnetic pulses by decreasing the echo oscillation of electromagnetic waves inside the target chamber during laser coupling with targets.展开更多
With the continuous advancement of communication technology,the escalating demand for electromagnetic shielding interference(EMI)materials with multifunctional and wideband EMI performance has become urgent.Controllin...With the continuous advancement of communication technology,the escalating demand for electromagnetic shielding interference(EMI)materials with multifunctional and wideband EMI performance has become urgent.Controlling the electrical and magnetic components and designing the EMI material structure have attracted extensive interest,but remain a huge challenge.Herein,we reported the alternating electromagnetic structure composite films composed of hollow metal-organic frameworks/layered MXene/nanocellulose(HMN)by alternating vacuum-assisted filtration process.The HMN composite films exhibit excellent EMI shielding effectiveness performance in the GHz frequency(66.8 dB at Kaband)and THz frequency(114.6 dB at 0.1-4.0 THz).Besides,the HMN composite films also exhibit a high reflection loss of 39.7 dB at 0.7 THz with an effective absorption bandwidth up to 2.1 THz.Moreover,HMN composite films show remarkable photothermal conversion performance,which can reach 104.6℃under 2.0 Sun and 235.4℃under 0.8 W cm^(−2),respectively.The unique micro-and macrostructural design structures will absorb more incident electromagnetic waves via interfacial polarization/multiple scattering and produce more heat energy via the local surface plasmon resonance effect.These features make the HMN composite film a promising candidate for advanced EMI devices for future 6G communication and the protection of electronic equipment in cold environments.展开更多
Carbonbased aerogels derived from biomass chitosan are encountering a flourishing moment in electromagnetic protection on account of lightweight,controllable fabrication and versatility.Nevertheless,developing a facil...Carbonbased aerogels derived from biomass chitosan are encountering a flourishing moment in electromagnetic protection on account of lightweight,controllable fabrication and versatility.Nevertheless,developing a facile construction method of component design with carbon-based aerogels for high-efficiency electromagnetic wave absorption(EWA)materials with a broad effective absorption bandwidth(EAB)and strong absorption yet hits some snags.Herein,the nitrogen-doped magnetic-dielectric-carbon aerogel was obtained via ice template method followed by carbonization treatment,homogeneous and abundant nickel(Ni)and manganese oxide(MnO)particles in situ grew on the carbon aerogels.Thanks to the optimization of impedance matching of dielectric/magnetic components to carbon aerogels,the nitrogen-doped magnetic-dielectric-carbon aerogel(Ni/MnO-CA)suggests a praiseworthy EWA performance,with an ultra-wide EAB of 7.36 GHz and a minimum reflection loss(RLmin)of−64.09 dB,while achieving a specific reflection loss of−253.32 dB mm−1.Furthermore,the aerogel reveals excellent radar stealth,infrared stealth,and thermal management capabilities.Hence,the high-performance,easy fabricated and multifunctional nickel/manganese oxide/carbon aerogels have broad application aspects for electromagnetic protection,electronic devices and aerospace.展开更多
Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimens...Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow of molten metal and eliminating solidification defects.In this study,the single-winding helical stirring(SWHS)was introduced,offering advantages such as smaller volume and lower electromagnetic shielding compared to traditional helical stirring methods.Following a comprehensive numerical simulation,the stirring parameters of SWHS were adjusted to yoke inclination angle of 43°and frequency of 12 Hz.The higher electromagnetic force and flow velocity in drawing direction,as well as the lower temperature gradient induced by the SWHS,are positive factors for homogeneous solidification of billet.The experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the SWHS process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element segregation.The SWHS process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,SWHS holds great promise as a potential approach for improving the quality of continuous casting billets.展开更多
The supercritical CO_(2)cOoled Lithium-Lead(COOL)blanket has been designed as one advanced blanket candidate for the Chinese Fusion Engineering Test Reactor(CFETR).This work focuses on the electromagnetic(EM)loads(Max...The supercritical CO_(2)cOoled Lithium-Lead(COOL)blanket has been designed as one advanced blanket candidate for the Chinese Fusion Engineering Test Reactor(CFETR).This work focuses on the electromagnetic(EM)loads(Maxwell force and Lorentz force)acting on the COOL blanket,which are important mechanical loads in further structural analysis of the COOL blanket.A 3D electromagnetic analysis is performed using the ANSYS finite element method to obtain EM loads on the COOL blanket in this study.At first,the magnetic scalar potential(MSP)method is used to obtain the magnetic field and the Maxwell force on the COOL blanket.Then,the magnetic vector potential(MVP)method is performed during a plasma disruption event to get the eddy current distribution.At last,a multi-step method is adopted for the calculation of the Lorentz force and the torque.The maximum Lorentz forces of inboard and outboard blanket structural components are 5624 kN and 2360 kN respectively.展开更多
Microseism,acoustic emission and electromagnetic radiation(M-A-E)data are usually used for predicting rockburst hazards.However,it is a great challenge to realize the prediction of M-A-E data.In this study,with the ai...Microseism,acoustic emission and electromagnetic radiation(M-A-E)data are usually used for predicting rockburst hazards.However,it is a great challenge to realize the prediction of M-A-E data.In this study,with the aid of a deep learning algorithm,a new method for the prediction of M-A-E data is proposed.In this method,an M-A-E data prediction model is built based on a variety of neural networks after analyzing numerous M-A-E data,and then the M-A-E data can be predicted.The predicted results are highly correlated with the real data collected in the field.Through field verification,the deep learning-based prediction method of M-A-E data provides quantitative prediction data for rockburst monitoring.展开更多
The signs of the electric field markers in Figs.2 and 4 of the paper[Chin.Phys.B 32104211(2023)]have been corrected.These modifications do not affect the results derived in the paper.
The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed.The spectrum spreads of different orbital angular mom...The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed.The spectrum spreads of different orbital angular momentum(OAM)modes in different non-line-of-sight situations are simulated.The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space.According to the research,the effects about spectrum spreads of higher OAM modes are more obvious.The error in detection is mainly affected by OAM spectrum spreading,which can be reduced by reasonably using different combinations of OAM modes in different practical situations.The above results provide a reference idea for investigating keyhole effect when vortex electromagnetic wave is used to detect accelerations.展开更多
Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention,yet encounter significant challenges.Developing new materials and innovative stru...Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention,yet encounter significant challenges.Developing new materials and innovative structural design concepts is crucial for expanding the application field of electromagnetic wave absorption.Particularly,hierarchical structure engineering has emerged as a promising approach to enhance the physical and chemical properties of materials,providing immense potential for creating versatile electromagnetic wave absorption materials.Herein,an exceptional multi-dimensional hierarchical structure was meticulously devised,unleashing the full microwave attenuation capabilities through in situ growth,selfreduction,and multi-heterogeneous interface integration.The hierarchical structure features a three-dimensional carbon framework,where magnetic nanoparticles grow in situ on the carbon skeleton,creating a necklace-like structure.Furthermore,magnetic nanosheets assemble within this framework.Enhanced impedance matching was achieved by precisely adjusting component proportions,and intelligent integration of diverse interfaces bolstered dielectric polarization.The obtain Fe_(3)O_(4)-Fe nanoparticles/carbon nanofibers/Al-Fe_(3)O_(4)-Fe nanosheets composites demonstrated outstanding performance with a minimum reflection loss(RLmin)value of−59.3 dB and an effective absorption bandwidth(RL≤−10 dB)extending up to 5.6 GHz at 2.2 mm.These notable accomplishments offer fresh insights into the precision design of high-efficient electromagnetic wave absorption materials.展开更多
Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness.In this study,KOH was evenly distributed ...Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness.In this study,KOH was evenly distributed on biomass Tremella using the swelling induction method,leading to the preparation of a three-dimensional network-structured hierarchical porous carbon(HPC)through carbonization.The achieved microwave absorption intensity is robust at-47.34 dB with a thin thickness of 2.1 mm.Notably,the widest effective absorption bandwidth,reaching 7.0 GHz(11–18 GHz),is attained at a matching thickness of 2.2 mm.The exceptional broadband and reflection loss performance are attributed to the 3D porous networks,interface effects,carbon network defects,and dipole relaxation.HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant.The uniform pore structures considerably optimize the impedance-matching performance of the material,while the abundance of interfaces and defects enhances the dielectric loss,thereby improving the attenuation constant.Furthermore,the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated.This research presents a strategy for preparing absorbing materials using biomass-derived HPC,showcasing considerable potential in the field of electromagnetic wave absorption.展开更多
Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the...Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the first time, the reduced graphene oxide(RGO) based absorbers are developed with regulatory absorption properties and the absorption mechanism of RGO is mainly originated from the carrier injection behavior of trace metal Fe nanosheets on graphene. Accordingly, the minimum reflection loss(RLmin) of Fe/RGO-2composite reaches-53.38 dB(2.45 mm), and the effective absorption bandwidth achieves 7.52 GHz(2.62 mm) with lower filling loading of 2 wt%. Using off-axis electron hologram testing combined with simulation calculation and carrier transport property experiments, we demonstrate here the carrier injection behavior from Fe to graphene at the interface and the induced charge accumulation and rearrangement, resulting in the increased interfacial and dipole polarization and the conductance loss. This work has confirmed that regulating the dielectric property of graphene itself by adding trace metals can not only ensure good impedance matching, but also fully exploit the dielectric loss ability of graphene at low filler content,which opens up an efficient way for designing lightweight absorbers and may be extended to other types materials.展开更多
The severe dependence of traditional phase change materials(PCMs)on the temperature-response and lattice deficiencies in versatility cannot satisfy demand for using such materials in complex application scenarios.Here...The severe dependence of traditional phase change materials(PCMs)on the temperature-response and lattice deficiencies in versatility cannot satisfy demand for using such materials in complex application scenarios.Here,we introduced metal ions to induce the self-assembly of MXene nanosheets and achieve their ordered arrangement by combining suction filtration and rapid freezing.Subsequently,a series of MXene/K^(+)/paraffin wax(PW)phase change composites(PCCs)were obtained via vacuum impregnation in molten PW.The prepared MXene-based PCCs showed versatile applications from macroscale technologies,successfully transforming solar,electric,and magnetic energy into thermal energy stored as latent heat in the PCCs.Moreover,due to the absence of binder in the MXene-based aerogel,MK3@PW exhibits a prime solar-thermal conversion efficiency(98.4%).Notably,MK3@PW can further convert the collected heat energy into electric energy through thermoelectric equipment and realize favorable solar-thermal-electric conversion(producing 206 mV of voltage with light radiation intensity of 200 mw cm^(−2)).An excellent Joule heat performance(reaching 105℃with an input voltage of 2.5 V)and responsive magnetic-thermal conversion behavior(a charging time of 11.8 s can achieve a thermal insulation effect of 285 s)for contactless thermotherapy were also demonstrated by the MK3@PW.Specifically,as a result of the ordered arrangement of MXene nanosheet self-assembly induced by potassium ions,MK3@PW PCC exhibits a higher electromagnetic shielding efficiency value(57.7 dB)than pure MXene aerogel/PW PCC(29.8 dB)with the same MXene mass.This work presents an opportunity for the multi-scene response and practical application of PCMs that satisfy demand of next-generation multifunctional PCCs.展开更多
Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference(EMI)shielding,achieving a flexible EMI shielding film,while maintaining a high transmittan...Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference(EMI)shielding,achieving a flexible EMI shielding film,while maintaining a high transmittance remains a significant challenge.Herein,a flexible,transparent,and conductive copper(Cu)metal mesh film for EMI shielding is fabricated by self-forming crackle template method and electroplating technique.The Cu mesh film shows an ultra-low sheet resistance(0.18Ω□^(-1)),high transmittance(85.8%@550 nm),and ultra-high figure of merit(>13,000).It also has satisfactory stretchability and mechanical stability,with a resistance increases of only 1.3%after 1,000 bending cycles.As a stretchable heater(ε>30%),the saturation temperature of the film can reach over 110°C within 60 s at 1.00 V applied voltage.Moreover,the metal mesh film exhibits outstanding average EMI shielding effectiveness of 40.4 dB in the X-band at the thickness of 2.5μm.As a demonstration,it is used as a transparent window for shielding the wireless communication electromagnetic waves.Therefore,the flexible and transparent conductive Cu mesh film proposed in this work provides a promising candidate for the next-generation EMI shielding applications.展开更多
Ultra-peripheral heavy-ion collisions(UPCs)offer unique opportunities to study processes under strong electromagnetic fields.In these collisions,highly charged fast-moving ions carry strong electromagnetic fields that...Ultra-peripheral heavy-ion collisions(UPCs)offer unique opportunities to study processes under strong electromagnetic fields.In these collisions,highly charged fast-moving ions carry strong electromagnetic fields that can be effectively treated as photon fluxes.The exchange of photons can induce photonuclear and two-photon interactions and excite ions.This excitation of the ions results in Coulomb dissociation with the emission of photons,neutrons,and other particles.Additionally,the electromagnetic fields generated by the ions can be sufficiently strong to enforce mutual interactions between the two colliding ions.Consequently,the two colliding ions experience an electromagnetic force that pushes them in opposite directions,causing a back-to-back correlation in the emitted neutrons.Using a Monte Carlo simulation,we qualitatively demonstrate that the above electromagnetic effect is large enough to be observed in UPCs,which would provide a clear means to study strong electromagnetic fields and their effects.展开更多
This study aims to develop a damage-detection algorithm based on the electromagnetic wave properties inside a reinforced concrete structure.The proposed method involves employing two algorithms based on data measured ...This study aims to develop a damage-detection algorithm based on the electromagnetic wave properties inside a reinforced concrete structure.The proposed method involves employing two algorithms based on data measured using ground-penetrating radar—a common electromagnetic wave method in civil engineering.The possible defect area was identified based on the energy dissipated by the damage in the frequency-wavenumber domain,with the damage localized using the calculated relative permittivity of the measurements.The proposed method was verified through a finite difference time-domain-based numerical analysis and a testing slab with artificial damage.As a result of verification,the proposed method quickly identified the presence of damage inside the concrete,especially for honeycomb-like defects located at the top of the rebar.This study has practical significance in scanning structures over a large area more quickly than other non-destructive testing methods,such as ultrasonic methods.展开更多
Phase change materials(PCMs)offer a promising solution to address the challenges posed by intermittency and fluctuations in solar thermal utilization.However,for organic solid-liquid PCMs,issues such as leakage,low th...Phase change materials(PCMs)offer a promising solution to address the challenges posed by intermittency and fluctuations in solar thermal utilization.However,for organic solid-liquid PCMs,issues such as leakage,low thermal conductivity,lack of efficient solar-thermal media,and flamma-bility have constrained their broad applications.Herein,we present an innova-tive class of versatile composite phase change materials(CPCMs)developed through a facile and environmentally friendly synthesis approach,leveraging the inherent anisotropy and unidirectional porosity of wood aerogel(nanowood)to support polyethylene glycol(PEG).The wood modification process involves the incorporation of phytic acid(PA)and MXene hybrid structure through an evaporation-induced assembly method,which could impart non-leaking PEG filling while concurrently facilitating thermal conduction,light absorption,and flame-retardant.Consequently,the as-prepared wood-based CPCMs showcase enhanced thermal conductivity(0.82 W m^(-1)K^(-1),about 4.6 times than PEG)as well as high latent heat of 135.5 kJ kg^(-1)(91.5%encapsula-tion)with thermal durability and stability throughout at least 200 heating and cooling cycles,featuring dramatic solar-thermal conversion efficiency up to 98.58%.In addition,with the synergistic effect of phytic acid and MXene,the flame-retardant performance of the CPCMs has been significantly enhanced,showing a self-extinguishing behavior.Moreover,the excellent electromagnetic shielding of 44.45 dB was endowed to the CPCMs,relieving contemporary health hazards associated with electromagnetic waves.Overall,we capitalize on the exquisite wood cell structure with unidirectional transport inherent in the development of multifunctional CPCMs,showcasing the operational principle through a proof-of-concept prototype system.展开更多
This paper proposes a novel open set recognition method,the Spatial Distribution Feature Extraction Network(SDFEN),to address the problem of electromagnetic signal recognition in an open environment.The spatial distri...This paper proposes a novel open set recognition method,the Spatial Distribution Feature Extraction Network(SDFEN),to address the problem of electromagnetic signal recognition in an open environment.The spatial distribution feature extraction layer in SDFEN replaces convolutional output neural networks with the spatial distribution features that focus more on inter-sample information by incorporating class center vectors.The designed hybrid loss function considers both intra-class distance and inter-class distance,thereby enhancing the similarity among samples of the same class and increasing the dissimilarity between samples of different classes during training.Consequently,this method allows unknown classes to occupy a larger space in the feature space.This reduces the possibility of overlap with known class samples and makes the boundaries between known and unknown samples more distinct.Additionally,the feature comparator threshold can be used to reject unknown samples.For signal open set recognition,seven methods,including the proposed method,are applied to two kinds of electromagnetic signal data:modulation signal and real-world emitter.The experimental results demonstrate that the proposed method outperforms the other six methods overall in a simulated open environment.Specifically,compared to the state-of-the-art Openmax method,the novel method achieves up to 8.87%and 5.25%higher micro-F-measures,respectively.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.U21A2093)the Anhui Provincial Natural Science Foundation(No.2308085QE146)the National Natural Science Foundation of Jiangsu Province(No.BK20210894).
文摘The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.
基金This work was supported by the National Natural Science Foundation of China(Nos.12122501,11975037,61631001,and 11921006)the National Grand Instrument Project(Nos.2019YFF01014400,2019YFF01014404)the Foundation of Science and Technology on Plasma Physics Laboratory(No.6142A04220108).
文摘Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.
基金Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25020205)the program of Science and Technology on Plasma Physics Laboratory,China Academy of Engineering Physics(Grant No.6142A04220108)。
文摘A high-power laser ablating solid targets induces giant electromagnetic pulses(EMPs),which are intimately pertinent to laser parameters,such as energy and pulse width.In this study,we reveal the features of EMPs generated from a picosecond(ps)laser irradiating solid targets at the SG-Ⅱpicosecond petawatt(PSPW)laser facility.The laser energy and pulse,as well as target material and thickness,show determinative effects on the EMPs’amplitude.More intense EMPs are detected behind targets compared to those at the other three positions,and the EMP amplitude decreases from 90.09 kV/m to 17.8 kV/m with the gold target thickness increasing from 10μm to 20μm,which is suppressed when the laser pulse width is enlarged.The results are expected to provide more insight into EMPs produced by ps lasers coupling with targets and lay the foundation for an effective EMP shielding design in high-power laser infrastructures.
基金supported by National Grand Instrument Project (No.2019YFF01014404)the National Key Program for S & T Research and Development (No. 2022YFA1603202)+1 种基金National Natural Science Foundation of China (Nos.U2241281 and 11975037)the Foundation of Science and Technology on Plasma Physics Laboratory (No.6142A04220108)。
文摘Giant electromagnetic pulses(EMPs) induced by high-power laser irradiating solid targets interfere with various experimental diagnoses and even damage equipment,so unveiling the evolution of EMPs inside the laser chamber is crucial for designing effective EMP shielding.In this work,the transmission characteristics of EMPs as a function of distances from the target chamber center(TCC) are studied using B-dot probes.The mean EMP amplitude generated by picosecond laser-target interaction reaches 561 kV m^(-1),357 kV m^(-1),395 kV m^(-1),and 341 kV m^(-1)at 0.32 m,0.53 m,0.76 m,and 1 m from TCC,which decreases dramatically from 0.32 m to 0.53 m.However,it shows a fluctuation from 0.53 m to 1 m.The temporal features of EMPs indicate that time-domain EMP signals near the target chamber wall have a wider full width at half maximum compared to that close to TCC,mainly due to the echo oscillation of electromagnetic waves inside the target chamber based on simulation and experimentation.The conclusions of this study will provide a new approach to mitigate strong electromagnetic pulses by decreasing the echo oscillation of electromagnetic waves inside the target chamber during laser coupling with targets.
基金the Beijing Nova Program(20230484431)Opening Project of State Silica-Based Materials Laboratory of Anhui Province(2022KF12)is gratefully acknowledged.
文摘With the continuous advancement of communication technology,the escalating demand for electromagnetic shielding interference(EMI)materials with multifunctional and wideband EMI performance has become urgent.Controlling the electrical and magnetic components and designing the EMI material structure have attracted extensive interest,but remain a huge challenge.Herein,we reported the alternating electromagnetic structure composite films composed of hollow metal-organic frameworks/layered MXene/nanocellulose(HMN)by alternating vacuum-assisted filtration process.The HMN composite films exhibit excellent EMI shielding effectiveness performance in the GHz frequency(66.8 dB at Kaband)and THz frequency(114.6 dB at 0.1-4.0 THz).Besides,the HMN composite films also exhibit a high reflection loss of 39.7 dB at 0.7 THz with an effective absorption bandwidth up to 2.1 THz.Moreover,HMN composite films show remarkable photothermal conversion performance,which can reach 104.6℃under 2.0 Sun and 235.4℃under 0.8 W cm^(−2),respectively.The unique micro-and macrostructural design structures will absorb more incident electromagnetic waves via interfacial polarization/multiple scattering and produce more heat energy via the local surface plasmon resonance effect.These features make the HMN composite film a promising candidate for advanced EMI devices for future 6G communication and the protection of electronic equipment in cold environments.
基金the National Natural Science Foundation of China(No.21902085 and 52172213)Natural Science and Development Foundation of Shenzhen(JCYJ20190807093205660)Postdoctoral Innovation Project of Shandong Province(SDCX-ZG-202202015).
文摘Carbonbased aerogels derived from biomass chitosan are encountering a flourishing moment in electromagnetic protection on account of lightweight,controllable fabrication and versatility.Nevertheless,developing a facile construction method of component design with carbon-based aerogels for high-efficiency electromagnetic wave absorption(EWA)materials with a broad effective absorption bandwidth(EAB)and strong absorption yet hits some snags.Herein,the nitrogen-doped magnetic-dielectric-carbon aerogel was obtained via ice template method followed by carbonization treatment,homogeneous and abundant nickel(Ni)and manganese oxide(MnO)particles in situ grew on the carbon aerogels.Thanks to the optimization of impedance matching of dielectric/magnetic components to carbon aerogels,the nitrogen-doped magnetic-dielectric-carbon aerogel(Ni/MnO-CA)suggests a praiseworthy EWA performance,with an ultra-wide EAB of 7.36 GHz and a minimum reflection loss(RLmin)of−64.09 dB,while achieving a specific reflection loss of−253.32 dB mm−1.Furthermore,the aerogel reveals excellent radar stealth,infrared stealth,and thermal management capabilities.Hence,the high-performance,easy fabricated and multifunctional nickel/manganese oxide/carbon aerogels have broad application aspects for electromagnetic protection,electronic devices and aerospace.
基金financially supported by the National Key R&D Projects(No.2021YFB3702000)the Regional Company Projects in Ansteel Beijing Research Institute(No.2022BJB07GF&No.2022BJB-13GF)。
文摘Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow of molten metal and eliminating solidification defects.In this study,the single-winding helical stirring(SWHS)was introduced,offering advantages such as smaller volume and lower electromagnetic shielding compared to traditional helical stirring methods.Following a comprehensive numerical simulation,the stirring parameters of SWHS were adjusted to yoke inclination angle of 43°and frequency of 12 Hz.The higher electromagnetic force and flow velocity in drawing direction,as well as the lower temperature gradient induced by the SWHS,are positive factors for homogeneous solidification of billet.The experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the SWHS process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element segregation.The SWHS process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,SWHS holds great promise as a potential approach for improving the quality of continuous casting billets.
基金supported by the Comprehensive Research Facility for Fusion Technology(CRAFT)Program of China(No.2018-000052-73-01-001228)National Natural Science Foundation of China(No.12205330)。
文摘The supercritical CO_(2)cOoled Lithium-Lead(COOL)blanket has been designed as one advanced blanket candidate for the Chinese Fusion Engineering Test Reactor(CFETR).This work focuses on the electromagnetic(EM)loads(Maxwell force and Lorentz force)acting on the COOL blanket,which are important mechanical loads in further structural analysis of the COOL blanket.A 3D electromagnetic analysis is performed using the ANSYS finite element method to obtain EM loads on the COOL blanket in this study.At first,the magnetic scalar potential(MSP)method is used to obtain the magnetic field and the Maxwell force on the COOL blanket.Then,the magnetic vector potential(MVP)method is performed during a plasma disruption event to get the eddy current distribution.At last,a multi-step method is adopted for the calculation of the Lorentz force and the torque.The maximum Lorentz forces of inboard and outboard blanket structural components are 5624 kN and 2360 kN respectively.
基金supported by the National Natural Science Foundation of China(Grant No.51934007)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20220691).
文摘Microseism,acoustic emission and electromagnetic radiation(M-A-E)data are usually used for predicting rockburst hazards.However,it is a great challenge to realize the prediction of M-A-E data.In this study,with the aid of a deep learning algorithm,a new method for the prediction of M-A-E data is proposed.In this method,an M-A-E data prediction model is built based on a variety of neural networks after analyzing numerous M-A-E data,and then the M-A-E data can be predicted.The predicted results are highly correlated with the real data collected in the field.Through field verification,the deep learning-based prediction method of M-A-E data provides quantitative prediction data for rockburst monitoring.
文摘The signs of the electric field markers in Figs.2 and 4 of the paper[Chin.Phys.B 32104211(2023)]have been corrected.These modifications do not affect the results derived in the paper.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11804073 and 61775050).
文摘The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed.The spectrum spreads of different orbital angular momentum(OAM)modes in different non-line-of-sight situations are simulated.The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space.According to the research,the effects about spectrum spreads of higher OAM modes are more obvious.The error in detection is mainly affected by OAM spectrum spreading,which can be reduced by reasonably using different combinations of OAM modes in different practical situations.The above results provide a reference idea for investigating keyhole effect when vortex electromagnetic wave is used to detect accelerations.
基金funded by the National Natural Science Foundation of China(No.51873004).
文摘Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention,yet encounter significant challenges.Developing new materials and innovative structural design concepts is crucial for expanding the application field of electromagnetic wave absorption.Particularly,hierarchical structure engineering has emerged as a promising approach to enhance the physical and chemical properties of materials,providing immense potential for creating versatile electromagnetic wave absorption materials.Herein,an exceptional multi-dimensional hierarchical structure was meticulously devised,unleashing the full microwave attenuation capabilities through in situ growth,selfreduction,and multi-heterogeneous interface integration.The hierarchical structure features a three-dimensional carbon framework,where magnetic nanoparticles grow in situ on the carbon skeleton,creating a necklace-like structure.Furthermore,magnetic nanosheets assemble within this framework.Enhanced impedance matching was achieved by precisely adjusting component proportions,and intelligent integration of diverse interfaces bolstered dielectric polarization.The obtain Fe_(3)O_(4)-Fe nanoparticles/carbon nanofibers/Al-Fe_(3)O_(4)-Fe nanosheets composites demonstrated outstanding performance with a minimum reflection loss(RLmin)value of−59.3 dB and an effective absorption bandwidth(RL≤−10 dB)extending up to 5.6 GHz at 2.2 mm.These notable accomplishments offer fresh insights into the precision design of high-efficient electromagnetic wave absorption materials.
基金the National Natural Science Foundation of China(Nos.52102036 and52301192)the Sichuan Science and Technology Program,China(No.2021JDRC0099)+3 种基金Taishan Scholars and Young Experts Program of Shandong Province,China(No.tsqn202103057)the Qingchuang Talents Induction Program of Shandong Higher Education Institution,China(Research and Innovation Team of Structural-Functional Polymer Composites)Special Financial of Shandong Province,China(Structural Design of High-efficiency Electromagnetic Wave-absorbing Composite Materials and Construction of Shandong Provincial Talent Teams)“Sanqin Scholars”Innovation Teams Project of Shaanxi Province,China(Clean Energy Materials and High-Performance Devices Innovation Team of Shaanxi Dongling Smelting Co.,Ltd.)。
文摘Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness.In this study,KOH was evenly distributed on biomass Tremella using the swelling induction method,leading to the preparation of a three-dimensional network-structured hierarchical porous carbon(HPC)through carbonization.The achieved microwave absorption intensity is robust at-47.34 dB with a thin thickness of 2.1 mm.Notably,the widest effective absorption bandwidth,reaching 7.0 GHz(11–18 GHz),is attained at a matching thickness of 2.2 mm.The exceptional broadband and reflection loss performance are attributed to the 3D porous networks,interface effects,carbon network defects,and dipole relaxation.HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant.The uniform pore structures considerably optimize the impedance-matching performance of the material,while the abundance of interfaces and defects enhances the dielectric loss,thereby improving the attenuation constant.Furthermore,the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated.This research presents a strategy for preparing absorbing materials using biomass-derived HPC,showcasing considerable potential in the field of electromagnetic wave absorption.
基金supported by National Natural Science Foundation of China (NSFC 52372041, 52302087, 51772060, 51672059 and 51621091)Heilongjiang Touyan Team Program+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. HIT.OCEF.2021003)the Shanghai Aerospace Science and Technology Innovation Fund (SAST2022-60)。
文摘Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the first time, the reduced graphene oxide(RGO) based absorbers are developed with regulatory absorption properties and the absorption mechanism of RGO is mainly originated from the carrier injection behavior of trace metal Fe nanosheets on graphene. Accordingly, the minimum reflection loss(RLmin) of Fe/RGO-2composite reaches-53.38 dB(2.45 mm), and the effective absorption bandwidth achieves 7.52 GHz(2.62 mm) with lower filling loading of 2 wt%. Using off-axis electron hologram testing combined with simulation calculation and carrier transport property experiments, we demonstrate here the carrier injection behavior from Fe to graphene at the interface and the induced charge accumulation and rearrangement, resulting in the increased interfacial and dipole polarization and the conductance loss. This work has confirmed that regulating the dielectric property of graphene itself by adding trace metals can not only ensure good impedance matching, but also fully exploit the dielectric loss ability of graphene at low filler content,which opens up an efficient way for designing lightweight absorbers and may be extended to other types materials.
基金the National Natural Science Foundation of China[grant numbers 52203038,52173036 and 52073107]the National Key Technology R&D Program of China[grant number 2022YFC3901904,2022YFC3901903,and 2020YFB1709301]the Central University Basic Research Fund of China[grant number 2021XXJS035].
文摘The severe dependence of traditional phase change materials(PCMs)on the temperature-response and lattice deficiencies in versatility cannot satisfy demand for using such materials in complex application scenarios.Here,we introduced metal ions to induce the self-assembly of MXene nanosheets and achieve their ordered arrangement by combining suction filtration and rapid freezing.Subsequently,a series of MXene/K^(+)/paraffin wax(PW)phase change composites(PCCs)were obtained via vacuum impregnation in molten PW.The prepared MXene-based PCCs showed versatile applications from macroscale technologies,successfully transforming solar,electric,and magnetic energy into thermal energy stored as latent heat in the PCCs.Moreover,due to the absence of binder in the MXene-based aerogel,MK3@PW exhibits a prime solar-thermal conversion efficiency(98.4%).Notably,MK3@PW can further convert the collected heat energy into electric energy through thermoelectric equipment and realize favorable solar-thermal-electric conversion(producing 206 mV of voltage with light radiation intensity of 200 mw cm^(−2)).An excellent Joule heat performance(reaching 105℃with an input voltage of 2.5 V)and responsive magnetic-thermal conversion behavior(a charging time of 11.8 s can achieve a thermal insulation effect of 285 s)for contactless thermotherapy were also demonstrated by the MK3@PW.Specifically,as a result of the ordered arrangement of MXene nanosheet self-assembly induced by potassium ions,MK3@PW PCC exhibits a higher electromagnetic shielding efficiency value(57.7 dB)than pure MXene aerogel/PW PCC(29.8 dB)with the same MXene mass.This work presents an opportunity for the multi-scene response and practical application of PCMs that satisfy demand of next-generation multifunctional PCCs.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.523712475,2072415 and 62101352)Shenzhen Science and Technology Program(RCBS20210706092343016).
文摘Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference(EMI)shielding,achieving a flexible EMI shielding film,while maintaining a high transmittance remains a significant challenge.Herein,a flexible,transparent,and conductive copper(Cu)metal mesh film for EMI shielding is fabricated by self-forming crackle template method and electroplating technique.The Cu mesh film shows an ultra-low sheet resistance(0.18Ω□^(-1)),high transmittance(85.8%@550 nm),and ultra-high figure of merit(>13,000).It also has satisfactory stretchability and mechanical stability,with a resistance increases of only 1.3%after 1,000 bending cycles.As a stretchable heater(ε>30%),the saturation temperature of the film can reach over 110°C within 60 s at 1.00 V applied voltage.Moreover,the metal mesh film exhibits outstanding average EMI shielding effectiveness of 40.4 dB in the X-band at the thickness of 2.5μm.As a demonstration,it is used as a transparent window for shielding the wireless communication electromagnetic waves.Therefore,the flexible and transparent conductive Cu mesh film proposed in this work provides a promising candidate for the next-generation EMI shielding applications.
基金This work is supported in part by the National Key Research and Development Program of China(Nos.2022YFA1604900)the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008)+3 种基金the National Natural Science Foundation of China(Nos.12275053,12025501,11890710,11890714,12147101,12075061,and 12225502)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB34030000)Shanghai National Science Foundation(No.20ZR1404100)STCSM(No.23590780100).
文摘Ultra-peripheral heavy-ion collisions(UPCs)offer unique opportunities to study processes under strong electromagnetic fields.In these collisions,highly charged fast-moving ions carry strong electromagnetic fields that can be effectively treated as photon fluxes.The exchange of photons can induce photonuclear and two-photon interactions and excite ions.This excitation of the ions results in Coulomb dissociation with the emission of photons,neutrons,and other particles.Additionally,the electromagnetic fields generated by the ions can be sufficiently strong to enforce mutual interactions between the two colliding ions.Consequently,the two colliding ions experience an electromagnetic force that pushes them in opposite directions,causing a back-to-back correlation in the emitted neutrons.Using a Monte Carlo simulation,we qualitatively demonstrate that the above electromagnetic effect is large enough to be observed in UPCs,which would provide a clear means to study strong electromagnetic fields and their effects.
基金National Research Foundation of Korea(NRF)Funded by the Korean Government(MSIT)under Grant Nos.RS-2023-00210317 and 2021R1A4A3030117the Digital-Based Building Construction and Safety Supervision Technology Research Program Funded by the Ministry of Land,Infrastructure,and Transport of the Korean Government under Grant No.RS-2022-00143493the Korea Institute of Civil Engineering and Building Technology(KICT)of the Republic of Korea,Project under Grant No.2023-0097。
文摘This study aims to develop a damage-detection algorithm based on the electromagnetic wave properties inside a reinforced concrete structure.The proposed method involves employing two algorithms based on data measured using ground-penetrating radar—a common electromagnetic wave method in civil engineering.The possible defect area was identified based on the energy dissipated by the damage in the frequency-wavenumber domain,with the damage localized using the calculated relative permittivity of the measurements.The proposed method was verified through a finite difference time-domain-based numerical analysis and a testing slab with artificial damage.As a result of verification,the proposed method quickly identified the presence of damage inside the concrete,especially for honeycomb-like defects located at the top of the rebar.This study has practical significance in scanning structures over a large area more quickly than other non-destructive testing methods,such as ultrasonic methods.
基金funding from the National Natural Science Foundation of China(No.22268025)China Postdoctoral Science Foundation(NO.2022MD713757)+2 种基金Yunnan Provincial Postdoctoral Science Foundation(NO.34Y2022)Yunnan Province Joint Special Project for Enterprise Fundamental Research and Applied Basic Research(No.202101BC070001-016)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011985).
文摘Phase change materials(PCMs)offer a promising solution to address the challenges posed by intermittency and fluctuations in solar thermal utilization.However,for organic solid-liquid PCMs,issues such as leakage,low thermal conductivity,lack of efficient solar-thermal media,and flamma-bility have constrained their broad applications.Herein,we present an innova-tive class of versatile composite phase change materials(CPCMs)developed through a facile and environmentally friendly synthesis approach,leveraging the inherent anisotropy and unidirectional porosity of wood aerogel(nanowood)to support polyethylene glycol(PEG).The wood modification process involves the incorporation of phytic acid(PA)and MXene hybrid structure through an evaporation-induced assembly method,which could impart non-leaking PEG filling while concurrently facilitating thermal conduction,light absorption,and flame-retardant.Consequently,the as-prepared wood-based CPCMs showcase enhanced thermal conductivity(0.82 W m^(-1)K^(-1),about 4.6 times than PEG)as well as high latent heat of 135.5 kJ kg^(-1)(91.5%encapsula-tion)with thermal durability and stability throughout at least 200 heating and cooling cycles,featuring dramatic solar-thermal conversion efficiency up to 98.58%.In addition,with the synergistic effect of phytic acid and MXene,the flame-retardant performance of the CPCMs has been significantly enhanced,showing a self-extinguishing behavior.Moreover,the excellent electromagnetic shielding of 44.45 dB was endowed to the CPCMs,relieving contemporary health hazards associated with electromagnetic waves.Overall,we capitalize on the exquisite wood cell structure with unidirectional transport inherent in the development of multifunctional CPCMs,showcasing the operational principle through a proof-of-concept prototype system.
文摘This paper proposes a novel open set recognition method,the Spatial Distribution Feature Extraction Network(SDFEN),to address the problem of electromagnetic signal recognition in an open environment.The spatial distribution feature extraction layer in SDFEN replaces convolutional output neural networks with the spatial distribution features that focus more on inter-sample information by incorporating class center vectors.The designed hybrid loss function considers both intra-class distance and inter-class distance,thereby enhancing the similarity among samples of the same class and increasing the dissimilarity between samples of different classes during training.Consequently,this method allows unknown classes to occupy a larger space in the feature space.This reduces the possibility of overlap with known class samples and makes the boundaries between known and unknown samples more distinct.Additionally,the feature comparator threshold can be used to reject unknown samples.For signal open set recognition,seven methods,including the proposed method,are applied to two kinds of electromagnetic signal data:modulation signal and real-world emitter.The experimental results demonstrate that the proposed method outperforms the other six methods overall in a simulated open environment.Specifically,compared to the state-of-the-art Openmax method,the novel method achieves up to 8.87%and 5.25%higher micro-F-measures,respectively.