A methodology for the reduction of radar cross section(RCS)of cambered platforms within the target airspace is presented,which utilizes a dual-polarized ultra-wide-angle artificial electromagnetic absorbing surface.By...A methodology for the reduction of radar cross section(RCS)of cambered platforms within the target airspace is presented,which utilizes a dual-polarized ultra-wide-angle artificial electromagnetic absorbing surface.By applying the theory of generalized Brewster complex wave impedance matching,five distinct unit cell designs are developed to attain more than95%absorption rate for dual-polarized incident waves within five angular ranges:0°-30°,30°-50°,50°-60°,60°-70°,and 70°-80°.To optimally reduce the RCS of a cambered platform,the five types of units can be evenly distributed on the surface based on the local incident angles of plane waves originating from the target airspace.As an illustrative example,the leading edge of an airfoil is taken into account,and experimental measurements validate the efficiency of the proposed structure.Specifically,the absorbing surface achieves more than 10 dB of RCS reduction in the frequency ranges from 5-10 GHz(about66.7%relative bandwidth)for dual polarizations.展开更多
Though the formation of polysulfide is desirable,as it contributes to the capacity build-up,it must not leak into the electrolyte.The loss of polysulfide causes capacity fade,a change in the local chemistry of the ele...Though the formation of polysulfide is desirable,as it contributes to the capacity build-up,it must not leak into the electrolyte.The loss of polysulfide causes capacity fade,a change in the local chemistry of the electrolyte,and anode poisoning.Constant efforts are in progress to find suitable polysulfide-absorbing materials;however,the magical polysulfide absorber is yet to be discovered or developed.Experimental methods alone often fall short in accelerating the investigations may be due to the complex Nature of the testing.This review focuses on the importance of computational methods,particularly density functional theory(DFT),in screening suitable polysulfide absorbers.It highlights the critical role of anchoring materials in improving Na-S battery performance,including pristine and doped graphene,metal–organic frameworks,carbon Nanofibers,vanadium disulfide,MXenes,and metal sulfides.By examining adsorption energies,charge transfer mechanisms,and catalytic properties,this review provides insights into the design of advanced materials that can effectively immobilize polysulfides and enhance battery stability.The review aims to guide future research efforts toward the development of high-performance RT Na-S batteries through a comprehensive understanding of the polysulfide-absorbing materials.展开更多
Since the view that the localized rail third-order bending mode can cause high-order polygonization(mainly 18-23)of high-speed train wheels was put forward in 2017,many scholars have attempted to link a connection bet...Since the view that the localized rail third-order bending mode can cause high-order polygonization(mainly 18-23)of high-speed train wheels was put forward in 2017,many scholars have attempted to link a connection between the localized rail bending modes and wheel polygonization phenomenon and polygonal wheel passing frequency.This paper first establishes a flexible track model considering the structural and parametric characteristics of fasteners,verifies the model by using vehicle tracking test data,then investigates the influence of fastener parameter matching on the localized rail bending modes,and obtains the following conclusions:(1)There is nearly a 1:1 mapping relationship between the localized rail bending modal frequency and polygonal wheel passing(PWP)frequency,which supports that the localized rail bending mode is one of the causes of wheel polygonization.(2)The iron plate of the fastener system plays a role of dynamic vibration absorber in the vehicle-rail coupled system,and the fastener parameters significantly influence the localized rail bending modal vibration.Finally,this paper proposes a design principle of a high-frequency vibration-absorbing fastener,which provides a feasible solution to mitigate the localized rail bending modal vibration and high-order wheel polygonization.Meanwhile,it points out that this measure may induce other high-frequency vibration problems,e.g.,aggravating modal vibration above 800 Hz.Further,this paper proposes a concept of differentiated arrangement of fasteners,suggesting that different high-frequency vibration-absorbing fasteners be installed in different sections of the whole line to make the localized rail bending modal frequency of the whole line disordered,thus disrupting and further mitigating the development of the wheel polygonization.展开更多
The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enh...The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enhancing absorption properties.In this work,a porous elastic Co@CNF-PDMS composite was prepared by freeze-drying and confined catalysis.The graphitization degree and conductivity loss of carbon nanofibers(CNFs)were regulated by heat treatment temperature and Co catalyst content.The construction of a heterointerface between Co and C enhances the interfacial polarization loss.The Co@CNF-PDMS composite with 4.5 mm achieves the minimum reflection loss(RLmin)of-81.0 dB at 9.9 GHz and RL no higher than-12.1 dB in the whole of the X-band.After applying a load of up to 40% strain and 100 cycles to Co@CNF-PDMS,the dielectric properties of the composite remain stable.With the increase of compression strain,the distribution density of the absorbent increases,and the CNF sheet layer extrusion contact forms a conductive path,which leads to the conductive loss increase,finally,the absorption band moves to a high frequency.The absorption band can be bi-directionally regulated by loading and strain with good stability,which provides a new strategy for the development of intelligent electromagnetic wave absorbing materials.展开更多
Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms ...Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms of scalability and mass production for practical application.In this work,we reported a successful attempt in modifying the 3D structure of mesoporous lanthanum oxide(La_(2)O_(3))for effective broadband MAMs candidate via simple co-precipitation process.The inclusion of cetyltrimethylammonium bromide(CTAB)and hydrothermal aging treatment result in a significant transformation of La_(2)O_(3)particles from their original polygonal form to a 3D coral-like and nano needle-like structure.The utilization of CTAB and hydrothermal aging results in the increase of surface area and a two-fold increase in pore volume of the resulting La_(2)O_(3).Due to its unique 3D structure,the 3D coral-like and nano needle-like La_(2)O_(3)materials possess a broadband electromagnetic(EM)wave absorption characteristic with the effective absorption bandwidth(EAB)covering the C-band frequency range.Specifically,in the La_(2)O_(3)C-H sample(with CTAB-with hydrothermal),it exhibits strong EM wave absorption with a reflection loss(RL)value of-33.07 dB which equals to 99.95%EM wave absorption at a thickness of only 1.50 mm.The detailed analysis of EM wave absorption properties reveals that the improvement of La_(2)O_(3)materials to attenuate EM wave energy arises from the dielectric loss phenomenon,the enhanced interfacial polarization,multiple reflections mechanism,and conduction loss mechanism induced by the 3D structural formation of the La_(2)O_(3)structure.This work proposes a novel and efficient approach in synthesizing and modifying 3D materials for effective broadband EM wave absorption.展开更多
In geotechnical engineering,rock bolts are commonly used for reinforcement,while the surrounding rock mass bears varying degrees of shear loads.The shear rate affects the stability of bolted rock joints,especially in ...In geotechnical engineering,rock bolts are commonly used for reinforcement,while the surrounding rock mass bears varying degrees of shear loads.The shear rate affects the stability of bolted rock joints,especially in projects susceptible to dynamic shear loads.In laboratory experiments,fully-grouted bolts and energy-absorbing bolts were used as research objects,and artificial rock specimens with rough joints were fabricated to analyze the shear characteristics and damage mechanisms of bolted rock joints under cyclic shear conditions and different shear velocities.The results showed that as the shear rate increased,the shear strength of bolted rock joint specimens decreased.Degradation of asperities resulted in no obvious peak shear stress in the specimens.Energy-absorbing bolts exhibited greater deformation capacity,with significant necking phenomena and the ability to withstand larger shear displacements.In contrast,fully-grouted bolts,which have threaded surfaces that provide higher bonding performance,exhibited a reduced capacity for plastic deformation and were prone to breaking under smaller shear displacements.Although the shear stiffness of specimens reinforced by energy-absorbing bolts was slightly lower than that of fully-grouted bolt specimens,they demonstrated greater stability under various shear rates.The absorbed shear energy showed that energy-absorbing bolts had superior coordinated deformation capabilities,thus exhibiting greater absorbed shear energy than fully-grouted bolts.Overall,fully-grouted bolts are more suitable for projects requiring higher rock shear strength and overall stiffness.In contrast,energy-absorbing bolts are more suitable for coping with dynamic or fluctuating load conditions to maintain the relative stability of jointed rock masses.展开更多
In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial w...In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial weight percent of Sr_(2)TiMoO_(6),were synthesized using the solid-state reaction method.Compared with STM100,some equilibrium phases,including SrTiO_(3),Mo,Sr_(8)(Al1_(2)O_(24))(MoO_(4))_(2)and a few undefined ones,are presented in the composites as evidenced by X-ray diffraction results and scanning electron microscopy due to the chemical reaction between Sr_(2)TiMoO_(6)and Al_(2)O_(3)component.Besides conductance loss,heterogeneous interfaces between various equilibrium phases introduce interfacial polarization,which causes an enhancement of dissipation for the incident electromagnetic wave.Among the synthesized samples,STM80 presents the best microwave absorbing properties.It has a minimum reflection loss(RLmin)of-26 dB and an effective absorbing bandwidth up to 2.7 GHz when the thickness is only 1 mm.This indicates that STM80 is a new type of microwave absorbing material with strong absorption and ultrathin thickness.展开更多
Electromagnetic(EM)metamaterial absorbers(MMAs)with broadband absorption are of growing interest for applications such as stealth and EM interference mitigation.In this work,we present a novel 3D-printed MMA based on ...Electromagnetic(EM)metamaterial absorbers(MMAs)with broadband absorption are of growing interest for applications such as stealth and EM interference mitigation.In this work,we present a novel 3D-printed MMA based on a fused annular microfluidic metaatom(FAMMA)architecture,designed for W-band absorption.The FAMMA structure features three kinds of orthogonally fused annual meta-atoms,forming a complex 3D microfluidic meta-atom with intricate architecture.Fabricated via high-precision micro 3D printing technology,the FAMMA-based MMA exploits the synergistic solid-liquid coupling effect of the unique three-dimensional orthogonal structure to achieve strong broadband absorption.Three representative FAMMAs with different geometric dimensions have achieved ultra-low reflection loss(RL of-42.1 dB),ultra-broadband effective absorption bandwidth(EAB of 31.3 GHz),and dual-band absorption(in 76.0-85.3 and 99.1-105.6 GHz),respectively.The underlying absorption mechanisms are elucidated by impedance matching theory and electromagnetic field distribution analyses.Application demonstrations show that the FAMMA-based MMA significantly suppresses radar echo power and renders metallic targets undetectable to both radar detector and radar imaging systems,highlighting its potential in stealth technology.Overall,this work establishes a new design concept for high-performance broadband millimeter wave MMAs,opening new avenue for future applications such as high-speed communication,through-wall sensing,and drone detection.展开更多
The emergence of precision electronic devices and wearable electronic products urgently requires high-performance multifunctional electromagnetic wave(EMW)absorbers to meet the applicability and versatility in various...The emergence of precision electronic devices and wearable electronic products urgently requires high-performance multifunctional electromagnetic wave(EMW)absorbers to meet the applicability and versatility in various applications.Herein,a dual-network(DN)gel was successfully prepared using acrylamide and sodium lignosulphonate as the basic units by simple chemical cross-linking and physical cross-linking methods.Specifically,the hydrogel forms two types of cross-linking networks through metal coordination and hydrogen bonding.Benefiting from the combined effects of dipole polarization and conductivity loss,the gel achieves an effective absorption bandwidth(EAB)of 6.74 GHz at a thickness of only 1.89 mm,demonstrating excellent EMW absorption performance.In addition,this unique structural configuration endows the EMW absorber with multifunctional features,such as remarkable tensile strength,good environmental compatibility,ultraviolet(UV)resistance,and excellent adhesion.Integrating multiple functional features into the EMW gels displays a broad application prospect in a variety of application scenarios.This research reveals the significance of DN structure design in the electromagnetic wave absorption(EWA)performance of gel-based materials,providing a substantial foundation for the multifunctional design of gel-based absorbers.展开更多
Objective] This study almed to compare the effects of three absorbing medium on microwave degradation of chIordane in contaminated soiI under alkaline condition. [Method] SoiI sampIes were coI ected from the original ...Objective] This study almed to compare the effects of three absorbing medium on microwave degradation of chIordane in contaminated soiI under alkaline condition. [Method] SoiI sampIes were coI ected from the original site of a reIocated pesticide production enterprise as experimental materials, to investigate the effects of Cu2O, MnO2 and activated carbon powder as absorbing medium on soiI warming and removal rate of chIordane under alkaline condition with 20% moisture content. In addition, the effects of activated carbon as the optimal absorbing media on the removal rate of chIordane in contaminated soiI were analyzed, and the effects on the removal rate of chIordane in different weights of soiI sampIes were investigated. [Result] The effects of three different absorbing medium on the removal rates of chIordane demonstrated a descending order of activated carbon ＆gt; MnO2 ＆gt; CuO2. Under the same microwave condition, the removal rate of chIordane decreased with the increase of soiI weights, but the utiIization efficiency of microwave was improved continuousIy and tended to be stabiIized with the increase of soiI weights. [Conclu-sion] This study provided a theoretical basis for further Iarge-scale appIication in soiI remediation.展开更多
In order to improve the absorbing properties of M- type barium ferrite absorbing materials, M-type barium ferrite/graphene oxide composites with different graphene oxide contents were synthesized by the sol-gel autoco...In order to improve the absorbing properties of M- type barium ferrite absorbing materials, M-type barium ferrite/graphene oxide composites with different graphene oxide contents were synthesized by the sol-gel autocombustion method. X-ray diffraction （XRD）, a scanning electronic microscopy （ SEM ）, a physical properties measurement system （PPMS-9）, and a vector network analyzer were used to analyze their structure, surface morphology, magnetic and absorbing properties, respectively. The results show that the absorbing band of the composite absorbing material is widened and the absorbing strength is increased compared with the pure M-type barium ferrite. The sample with the content of doped graphene oxide of 3% has the minimum reflectivity at 10 to 18 GHz frequencies. Hence, the doped graphene oxide effectively improves the absorbing properties of M-type barium ferrite.展开更多
The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C...The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.展开更多
The perfectly matched layer （PML） is a highly efficient absorbing boundary condition used for the numerical modeling of seismic wave equation. The article focuses on the application of this technique to finite-eleme...The perfectly matched layer （PML） is a highly efficient absorbing boundary condition used for the numerical modeling of seismic wave equation. The article focuses on the application of this technique to finite-element time-domain numerical modeling of elastic wave equation. However, the finite-element time-domain scheme is based on the second- order wave equation in displacement formulation. Thus, the first-order PML in velocity-stress formulation cannot be directly applied to this scheme. In this article, we derive the finite- element matrix equations of second-order PML in displacement formulation, and accomplish the implementation of PML in finite-element time-domain modeling of elastic wave equation. The PML has an approximate zero reflection coefficients for bulk and surface waves in the finite-element modeling of P-SV and SH wave propagation in the 2D homogeneous elastic media. The numerical experiments using a two-layer model with irregular topography validate the efficiency of PML in the modeling of seismic wave propagation in geological models with complex structures and heterogeneous media.展开更多
We apply the newly proposed double absorbing boundary condition（DABC）（Hagstrom et al., 2014） to solve the boundary reflection problem in seismic finite-difference（FD） modeling. In the DABC scheme, the local high...We apply the newly proposed double absorbing boundary condition（DABC）（Hagstrom et al., 2014） to solve the boundary reflection problem in seismic finite-difference（FD） modeling. In the DABC scheme, the local high-order absorbing boundary condition is used on two parallel artificial boundaries, and thus double absorption is achieved. Using the general 2D acoustic wave propagation equations as an example, we use the DABC in seismic FD modeling, and discuss the derivation and implementation steps in detail. Compared with the perfectly matched layer（PML）, the complexity decreases, and the stability and fl exibility improve. A homogeneous model and the SEG salt model are selected for numerical experiments. The results show that absorption using the DABC is considerably improved relative to the Clayton–Engquist boundary condition and nearly the same as that in the PML.展开更多
With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） meth...With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） method. The reflection of the ABC caused by both the truncated error and the phase velocity error is analyzed. Based on the phase velocity estimation and the nonuniform cell, two methods are studied and then adopted to improve the performance of the ABC. A calculation case of a rectangular waveguide which is a typical dispersive transmission line is carried out using the ADI-FDTD method with the improved ABC for evaluation. According to the calculated case, the comparison is given between the reflection coefficients of the ABC with and without the velocity estimation and also the comparison between the reflection coefficients of the ABC with and without the nonuniform processing. The reflection variation of the ABC under different time steps is also analyzed and the acceptable worsening will not obscure the improvement on the absorption. Numerical results obviously show that efficient improvement on the absorbing performance of the ABC is achieved based on these methods for the ADI-FDTD.展开更多
Oil and organic solvent contamination, derived from oil spills and organic solvent leakage, has been recognized as one of the major environmental issues imposing a serious threat to both human and ecosystem health. Am...Oil and organic solvent contamination, derived from oil spills and organic solvent leakage, has been recognized as one of the major environmental issues imposing a serious threat to both human and ecosystem health. Among the various presented technologies applied for oil/water separation, oil absorption process has been explored widely and offers satisfactory results especially with surface modified oil-absorbing material and/or hybrid absorbents. In this review, we summarize the recent research activities involved in the designing strategies of oil-absorbing absorbents and their application in oil absorption. Then, an extensive list of various oil-absorbing materials from literature, including polymer materials, porous inorganic materials and biomass materials, has been compiled and the oil adsorption capacities toward various types of oils and organic solvents as available in the literature are presented along with highlighting and discussing the various factors involved in the designing of oil-absorbing absorbents tested so far for oil/water separation. Finally, some future trends and perspectives in oil-absorbing material are outlined.展开更多
La-doped Sr-hexaferrite（Sr（1-x）LaxFe（12）O（19））（x=0.05,0.10,0.15,0.20） nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel auto-combustion. The phase formation te...La-doped Sr-hexaferrite（Sr（1-x）LaxFe（12）O（19））（x=0.05,0.10,0.15,0.20） nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel auto-combustion. The phase formation temperature increases, while the particle size decreases as the Ladoping content goes up. The partial substitution of Sr^（2＋） by La^（3＋） results in the suppression effects on the growth-up of the crystallites and the enhancement of the electron hopping between Fe^（3＋） with different valences, which leads to the improvement in the dielectric loss and magnetic loss.Therefore, both the microwave absorbing abilities and absorbing frequency ranges are tuned by La-doping. The synthesized Sr-hexaferrite nanopowders with doping element content of 0.10 demonstrate the fine broad microwave absorbing properties.展开更多
The numerical wave channel has been developed based on the volume of fluid method (VOF) in conjunction with the Navier-Stokes equations. The absorbing wave-maker boundary on the left side of the channel is presented b...The numerical wave channel has been developed based on the volume of fluid method (VOF) in conjunction with the Navier-Stokes equations. The absorbing wave-maker boundary on the left side of the channel is presented by prescribing velocity reference to linear wave-maker theory. The principle of which is that the numerical wave-maker is designed to move in a way that generates the required incident wave and cancels out any reflected wave that reach it at the same time. On the right side of the channel, the open boundary is set to permit incident waves to be transmitted freely. The parametric studies have been carried out at a range of ratios of water depth to wave length d/ L from 0.124 to 0.219, with wave height in the front of paddle/water depth ratio (H0 / d) from 0.1 to 0.3. Wave height, wave pressure distribution along the channel and velocity field are obtained for both open boundary condition and reflective boundary condition at the other end of the channel. For a reflective case, it is shown that the absorbing wave-maker is very effective in canceling out the reflected wave that reaches the numerical paddle and highly repeatable waves can be generated.展开更多
Dy3+ doped Mn-Zn ferrites Mn0.3Zn0.7Fe2-xDyxO4(x=0,0.01,0.02,0.03,0.04)were prepared by the conventional solid-state reaction.The crystal structure,surface morphology and electromagnetic properties of the calcined sam...Dy3+ doped Mn-Zn ferrites Mn0.3Zn0.7Fe2-xDyxO4(x=0,0.01,0.02,0.03,0.04)were prepared by the conventional solid-state reaction.The crystal structure,surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction analysis(XRD),scanning electron microscopy(SEM) and network analyzer(Agilent 8722ET).All the XRD patterns showed the single phase of the spinel-type ferrite without other intermediate when x≤0.03.The average crystallite size was about 44?56 nm.The mi...展开更多
Soft magnetic metallic materials have been widely used for absorbing electromagnetic wave.Flaky Fe 86 t Si t Al 14（t=9,11,14 and 16） alloys powders were prepared from melt-quenched ribbons by annealing and milling.I...Soft magnetic metallic materials have been widely used for absorbing electromagnetic wave.Flaky Fe 86 t Si t Al 14（t=9,11,14 and 16） alloys powders were prepared from melt-quenched ribbons by annealing and milling.In a previous report we discussed the order-disordered structure of this alloys.In this article,we studied their electron structure.Covalence electron numbers of（111） and（100） plane increase with increasing Si content but Bohr magneton decreases.Complex permittivity and complex permeability are both decreased with increasing Si content t.The lowest value of reflectivity among the four alloys is originated from Fe 70 Si 14 Al 14.The peak values of reflectivity are all lower than 10 dB,and the absorbing frequency range（R 10 dB） increases from 1 to 2 GHz when t reaches 16.展开更多
基金supported by the National Key Research and Development Program of China(2023YFB3907304-3)the National Natural Science Foundation of China(NSFC)(62271050)。
文摘A methodology for the reduction of radar cross section(RCS)of cambered platforms within the target airspace is presented,which utilizes a dual-polarized ultra-wide-angle artificial electromagnetic absorbing surface.By applying the theory of generalized Brewster complex wave impedance matching,five distinct unit cell designs are developed to attain more than95%absorption rate for dual-polarized incident waves within five angular ranges:0°-30°,30°-50°,50°-60°,60°-70°,and 70°-80°.To optimally reduce the RCS of a cambered platform,the five types of units can be evenly distributed on the surface based on the local incident angles of plane waves originating from the target airspace.As an illustrative example,the leading edge of an airfoil is taken into account,and experimental measurements validate the efficiency of the proposed structure.Specifically,the absorbing surface achieves more than 10 dB of RCS reduction in the frequency ranges from 5-10 GHz(about66.7%relative bandwidth)for dual polarizations.
基金supported by the Indian Institute of Technology Delhi (IIT Delhi)
文摘Though the formation of polysulfide is desirable,as it contributes to the capacity build-up,it must not leak into the electrolyte.The loss of polysulfide causes capacity fade,a change in the local chemistry of the electrolyte,and anode poisoning.Constant efforts are in progress to find suitable polysulfide-absorbing materials;however,the magical polysulfide absorber is yet to be discovered or developed.Experimental methods alone often fall short in accelerating the investigations may be due to the complex Nature of the testing.This review focuses on the importance of computational methods,particularly density functional theory(DFT),in screening suitable polysulfide absorbers.It highlights the critical role of anchoring materials in improving Na-S battery performance,including pristine and doped graphene,metal–organic frameworks,carbon Nanofibers,vanadium disulfide,MXenes,and metal sulfides.By examining adsorption energies,charge transfer mechanisms,and catalytic properties,this review provides insights into the design of advanced materials that can effectively immobilize polysulfides and enhance battery stability.The review aims to guide future research efforts toward the development of high-performance RT Na-S batteries through a comprehensive understanding of the polysulfide-absorbing materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.:52202423,U2268211,and 52475136)the China Postdoctoral Science Foundation(Grant Nos.:2022M712636 and 2023T160546)+1 种基金the Natural Science Foundation of Sichuan Province(Grant No.:2025ZNSFSC0398)the Independent R&D Project of the State Key Laboratory of Traction Power(Grant No.:2023TPL-T14).
文摘Since the view that the localized rail third-order bending mode can cause high-order polygonization(mainly 18-23)of high-speed train wheels was put forward in 2017,many scholars have attempted to link a connection between the localized rail bending modes and wheel polygonization phenomenon and polygonal wheel passing frequency.This paper first establishes a flexible track model considering the structural and parametric characteristics of fasteners,verifies the model by using vehicle tracking test data,then investigates the influence of fastener parameter matching on the localized rail bending modes,and obtains the following conclusions:(1)There is nearly a 1:1 mapping relationship between the localized rail bending modal frequency and polygonal wheel passing(PWP)frequency,which supports that the localized rail bending mode is one of the causes of wheel polygonization.(2)The iron plate of the fastener system plays a role of dynamic vibration absorber in the vehicle-rail coupled system,and the fastener parameters significantly influence the localized rail bending modal vibration.Finally,this paper proposes a design principle of a high-frequency vibration-absorbing fastener,which provides a feasible solution to mitigate the localized rail bending modal vibration and high-order wheel polygonization.Meanwhile,it points out that this measure may induce other high-frequency vibration problems,e.g.,aggravating modal vibration above 800 Hz.Further,this paper proposes a concept of differentiated arrangement of fasteners,suggesting that different high-frequency vibration-absorbing fasteners be installed in different sections of the whole line to make the localized rail bending modal frequency of the whole line disordered,thus disrupting and further mitigating the development of the wheel polygonization.
基金financially supported by the National Natural Science Foundation of China(No.52231007)the Natural Science Foundation of Shaanxi Province(No.2022JM-248)+1 种基金the Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials Laboratorythe Doctoral Scientific Research Foundation of Shaanxi University of Science&Technology(No.BJ16-06).
文摘The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enhancing absorption properties.In this work,a porous elastic Co@CNF-PDMS composite was prepared by freeze-drying and confined catalysis.The graphitization degree and conductivity loss of carbon nanofibers(CNFs)were regulated by heat treatment temperature and Co catalyst content.The construction of a heterointerface between Co and C enhances the interfacial polarization loss.The Co@CNF-PDMS composite with 4.5 mm achieves the minimum reflection loss(RLmin)of-81.0 dB at 9.9 GHz and RL no higher than-12.1 dB in the whole of the X-band.After applying a load of up to 40% strain and 100 cycles to Co@CNF-PDMS,the dielectric properties of the composite remain stable.With the increase of compression strain,the distribution density of the absorbent increases,and the CNF sheet layer extrusion contact forms a conductive path,which leads to the conductive loss increase,finally,the absorption band moves to a high frequency.The absorption band can be bi-directionally regulated by loading and strain with good stability,which provides a new strategy for the development of intelligent electromagnetic wave absorbing materials.
基金Project supported by National Research and Innovation Agency through Rumah Program Organisasi Riset Nanoteknologi dan Material Maj u(ORNM)2024Indonesia Ministry of Finance through the competitive research program of RISPRO Kompetisi(PRJ-68/LPDP/2023)。
文摘Structural modification of three dimensional(3D)materials for the application of dielectric loss-based microwave absorbing materials(MAMs)usually relies on intricate synthesis process and can pose challenges in terms of scalability and mass production for practical application.In this work,we reported a successful attempt in modifying the 3D structure of mesoporous lanthanum oxide(La_(2)O_(3))for effective broadband MAMs candidate via simple co-precipitation process.The inclusion of cetyltrimethylammonium bromide(CTAB)and hydrothermal aging treatment result in a significant transformation of La_(2)O_(3)particles from their original polygonal form to a 3D coral-like and nano needle-like structure.The utilization of CTAB and hydrothermal aging results in the increase of surface area and a two-fold increase in pore volume of the resulting La_(2)O_(3).Due to its unique 3D structure,the 3D coral-like and nano needle-like La_(2)O_(3)materials possess a broadband electromagnetic(EM)wave absorption characteristic with the effective absorption bandwidth(EAB)covering the C-band frequency range.Specifically,in the La_(2)O_(3)C-H sample(with CTAB-with hydrothermal),it exhibits strong EM wave absorption with a reflection loss(RL)value of-33.07 dB which equals to 99.95%EM wave absorption at a thickness of only 1.50 mm.The detailed analysis of EM wave absorption properties reveals that the improvement of La_(2)O_(3)materials to attenuate EM wave energy arises from the dielectric loss phenomenon,the enhanced interfacial polarization,multiple reflections mechanism,and conduction loss mechanism induced by the 3D structural formation of the La_(2)O_(3)structure.This work proposes a novel and efficient approach in synthesizing and modifying 3D materials for effective broadband EM wave absorption.
基金partially funded by the National Natural Science Foundation of China(Grant Nos.52179098 and 41907251)the State Scholarship Fund of China(Grant No.202306650001).
文摘In geotechnical engineering,rock bolts are commonly used for reinforcement,while the surrounding rock mass bears varying degrees of shear loads.The shear rate affects the stability of bolted rock joints,especially in projects susceptible to dynamic shear loads.In laboratory experiments,fully-grouted bolts and energy-absorbing bolts were used as research objects,and artificial rock specimens with rough joints were fabricated to analyze the shear characteristics and damage mechanisms of bolted rock joints under cyclic shear conditions and different shear velocities.The results showed that as the shear rate increased,the shear strength of bolted rock joint specimens decreased.Degradation of asperities resulted in no obvious peak shear stress in the specimens.Energy-absorbing bolts exhibited greater deformation capacity,with significant necking phenomena and the ability to withstand larger shear displacements.In contrast,fully-grouted bolts,which have threaded surfaces that provide higher bonding performance,exhibited a reduced capacity for plastic deformation and were prone to breaking under smaller shear displacements.Although the shear stiffness of specimens reinforced by energy-absorbing bolts was slightly lower than that of fully-grouted bolt specimens,they demonstrated greater stability under various shear rates.The absorbed shear energy showed that energy-absorbing bolts had superior coordinated deformation capabilities,thus exhibiting greater absorbed shear energy than fully-grouted bolts.Overall,fully-grouted bolts are more suitable for projects requiring higher rock shear strength and overall stiffness.In contrast,energy-absorbing bolts are more suitable for coping with dynamic or fluctuating load conditions to maintain the relative stability of jointed rock masses.
基金supported by the National Natural Science Foundation of China(No.52402078)Yunnan Major Scientific and Technological Projects(No.202302AG050010)+1 种基金Yunnan Fundamental Research Projects(No.202201BE070001-008)the National Key Research and Development Program of China(No.2022YFB3708600)。
文摘In this work,a novel microwave absorbing material(MAM)made of a pseudo-binary of Sr_(2)TiMoO_(6)-Al_(2)O_(3)(STM)is proposed first.The MAMs labeled as STM X(X=60,70,80 and 100,respectively),in which X is the initial weight percent of Sr_(2)TiMoO_(6),were synthesized using the solid-state reaction method.Compared with STM100,some equilibrium phases,including SrTiO_(3),Mo,Sr_(8)(Al1_(2)O_(24))(MoO_(4))_(2)and a few undefined ones,are presented in the composites as evidenced by X-ray diffraction results and scanning electron microscopy due to the chemical reaction between Sr_(2)TiMoO_(6)and Al_(2)O_(3)component.Besides conductance loss,heterogeneous interfaces between various equilibrium phases introduce interfacial polarization,which causes an enhancement of dissipation for the incident electromagnetic wave.Among the synthesized samples,STM80 presents the best microwave absorbing properties.It has a minimum reflection loss(RLmin)of-26 dB and an effective absorbing bandwidth up to 2.7 GHz when the thickness is only 1 mm.This indicates that STM80 is a new type of microwave absorbing material with strong absorption and ultrathin thickness.
基金support by the National Key Research and Development Program of China(Xiaosheng Zhang:No.2022YFB3206100)the National Natural Science Foundation of China(Yi Zhang:No.62271107,Qiye Wen:No.62235004,62311530115,Shaomeng Wang:T2241002)+2 种基金the Natural Science Foundation of Sichuan Province(Yi Zhang:No.2025ZNSFSC0464)the Key R&D Program of Mianyang(Xiaosheng Zhang:No.2023ZYDF019)the Fundamental Research Funds for the Central Universities(Yi Zhang:No.ZYGX2022YGRH007).
文摘Electromagnetic(EM)metamaterial absorbers(MMAs)with broadband absorption are of growing interest for applications such as stealth and EM interference mitigation.In this work,we present a novel 3D-printed MMA based on a fused annular microfluidic metaatom(FAMMA)architecture,designed for W-band absorption.The FAMMA structure features three kinds of orthogonally fused annual meta-atoms,forming a complex 3D microfluidic meta-atom with intricate architecture.Fabricated via high-precision micro 3D printing technology,the FAMMA-based MMA exploits the synergistic solid-liquid coupling effect of the unique three-dimensional orthogonal structure to achieve strong broadband absorption.Three representative FAMMAs with different geometric dimensions have achieved ultra-low reflection loss(RL of-42.1 dB),ultra-broadband effective absorption bandwidth(EAB of 31.3 GHz),and dual-band absorption(in 76.0-85.3 and 99.1-105.6 GHz),respectively.The underlying absorption mechanisms are elucidated by impedance matching theory and electromagnetic field distribution analyses.Application demonstrations show that the FAMMA-based MMA significantly suppresses radar echo power and renders metallic targets undetectable to both radar detector and radar imaging systems,highlighting its potential in stealth technology.Overall,this work establishes a new design concept for high-performance broadband millimeter wave MMAs,opening new avenue for future applications such as high-speed communication,through-wall sensing,and drone detection.
基金supported by the National Natural Science Foundation of China(Nos.52231007,51872238,52074227,and 21806129)the Fundamental Research Funds for the Central Universities(Nos.3102018zy045,3102019AX11,and 5000220455)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2017JQ5116 and 2020JM-118).
文摘The emergence of precision electronic devices and wearable electronic products urgently requires high-performance multifunctional electromagnetic wave(EMW)absorbers to meet the applicability and versatility in various applications.Herein,a dual-network(DN)gel was successfully prepared using acrylamide and sodium lignosulphonate as the basic units by simple chemical cross-linking and physical cross-linking methods.Specifically,the hydrogel forms two types of cross-linking networks through metal coordination and hydrogen bonding.Benefiting from the combined effects of dipole polarization and conductivity loss,the gel achieves an effective absorption bandwidth(EAB)of 6.74 GHz at a thickness of only 1.89 mm,demonstrating excellent EMW absorption performance.In addition,this unique structural configuration endows the EMW absorber with multifunctional features,such as remarkable tensile strength,good environmental compatibility,ultraviolet(UV)resistance,and excellent adhesion.Integrating multiple functional features into the EMW gels displays a broad application prospect in a variety of application scenarios.This research reveals the significance of DN structure design in the electromagnetic wave absorption(EWA)performance of gel-based materials,providing a substantial foundation for the multifunctional design of gel-based absorbers.
基金Supported by Special Fund for the Transformation of Scientific and Technologica Achievements in Jiangsu Province(BA2013057)~~
文摘Objective] This study almed to compare the effects of three absorbing medium on microwave degradation of chIordane in contaminated soiI under alkaline condition. [Method] SoiI sampIes were coI ected from the original site of a reIocated pesticide production enterprise as experimental materials, to investigate the effects of Cu2O, MnO2 and activated carbon powder as absorbing medium on soiI warming and removal rate of chIordane under alkaline condition with 20% moisture content. In addition, the effects of activated carbon as the optimal absorbing media on the removal rate of chIordane in contaminated soiI were analyzed, and the effects on the removal rate of chIordane in different weights of soiI sampIes were investigated. [Result] The effects of three different absorbing medium on the removal rates of chIordane demonstrated a descending order of activated carbon ＆gt; MnO2 ＆gt; CuO2. Under the same microwave condition, the removal rate of chIordane decreased with the increase of soiI weights, but the utiIization efficiency of microwave was improved continuousIy and tended to be stabiIized with the increase of soiI weights. [Conclu-sion] This study provided a theoretical basis for further Iarge-scale appIication in soiI remediation.
基金The National Natural Science Foundation of China(No.51205282)
文摘In order to improve the absorbing properties of M- type barium ferrite absorbing materials, M-type barium ferrite/graphene oxide composites with different graphene oxide contents were synthesized by the sol-gel autocombustion method. X-ray diffraction （XRD）, a scanning electronic microscopy （ SEM ）, a physical properties measurement system （PPMS-9）, and a vector network analyzer were used to analyze their structure, surface morphology, magnetic and absorbing properties, respectively. The results show that the absorbing band of the composite absorbing material is widened and the absorbing strength is increased compared with the pure M-type barium ferrite. The sample with the content of doped graphene oxide of 3% has the minimum reflectivity at 10 to 18 GHz frequencies. Hence, the doped graphene oxide effectively improves the absorbing properties of M-type barium ferrite.
基金Project(51072165)supported by the National Natural Science Foundation of ChinaProject(201305)supported by the Fund of State Key Laboratory of Solidification Processing,ChinaProjects(2013JK0921,2013JK0922)supported by Shaanxi Provincial Education Department of China
文摘The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.
基金sponsored by the National Natural Science Foundation of China Research(Grant No.41274138)the Science Foundation of China University of Petroleum(Beijing)(No.KYJJ2012-05-02)
文摘The perfectly matched layer （PML） is a highly efficient absorbing boundary condition used for the numerical modeling of seismic wave equation. The article focuses on the application of this technique to finite-element time-domain numerical modeling of elastic wave equation. However, the finite-element time-domain scheme is based on the second- order wave equation in displacement formulation. Thus, the first-order PML in velocity-stress formulation cannot be directly applied to this scheme. In this article, we derive the finite- element matrix equations of second-order PML in displacement formulation, and accomplish the implementation of PML in finite-element time-domain modeling of elastic wave equation. The PML has an approximate zero reflection coefficients for bulk and surface waves in the finite-element modeling of P-SV and SH wave propagation in the 2D homogeneous elastic media. The numerical experiments using a two-layer model with irregular topography validate the efficiency of PML in the modeling of seismic wave propagation in geological models with complex structures and heterogeneous media.
基金supported by the National Nature Science Foundation of China(Grant No.U1262208)the Important National Science & Technology Specific Projects(Grant No.2011ZX05019-008)
文摘We apply the newly proposed double absorbing boundary condition（DABC）（Hagstrom et al., 2014） to solve the boundary reflection problem in seismic finite-difference（FD） modeling. In the DABC scheme, the local high-order absorbing boundary condition is used on two parallel artificial boundaries, and thus double absorption is achieved. Using the general 2D acoustic wave propagation equations as an example, we use the DABC in seismic FD modeling, and discuss the derivation and implementation steps in detail. Compared with the perfectly matched layer（PML）, the complexity decreases, and the stability and fl exibility improve. A homogeneous model and the SEG salt model are selected for numerical experiments. The results show that absorption using the DABC is considerably improved relative to the Clayton–Engquist boundary condition and nearly the same as that in the PML.
基金The National Natural Science Foundation of China(No.60702027)the Free Research Fund of the National Mobile Communications Research Laboratory of Southeast University (No.2008B07)the National Basic Research Program of China(973 Program)(No.2007CB310603)
文摘With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） method. The reflection of the ABC caused by both the truncated error and the phase velocity error is analyzed. Based on the phase velocity estimation and the nonuniform cell, two methods are studied and then adopted to improve the performance of the ABC. A calculation case of a rectangular waveguide which is a typical dispersive transmission line is carried out using the ADI-FDTD method with the improved ABC for evaluation. According to the calculated case, the comparison is given between the reflection coefficients of the ABC with and without the velocity estimation and also the comparison between the reflection coefficients of the ABC with and without the nonuniform processing. The reflection variation of the ABC under different time steps is also analyzed and the acceptable worsening will not obscure the improvement on the absorption. Numerical results obviously show that efficient improvement on the absorbing performance of the ABC is achieved based on these methods for the ADI-FDTD.
基金Supported by the National Natural Science Foundation of China(21706100 and U1507115)Natural Science Foundation of Jiangsu Province(BK20160500,BK20161362and BK20160491)+4 种基金the China Postdoctoral Science Foundation(2016M600373,2018T110452 and 2017M621649)China Postdoctoral Science Foundation of Jiangsu Province(1601016A,1701067C and 1701073C)Scientific Research Foundation for Advanced Talents,Jiangsu University(15JDG142)High-Level Personnel Training Project of Jiangsu Province(BRA2016142)Key Research and Development Program of Jiangxi Province(20171BBH80008)
文摘Oil and organic solvent contamination, derived from oil spills and organic solvent leakage, has been recognized as one of the major environmental issues imposing a serious threat to both human and ecosystem health. Among the various presented technologies applied for oil/water separation, oil absorption process has been explored widely and offers satisfactory results especially with surface modified oil-absorbing material and/or hybrid absorbents. In this review, we summarize the recent research activities involved in the designing strategies of oil-absorbing absorbents and their application in oil absorption. Then, an extensive list of various oil-absorbing materials from literature, including polymer materials, porous inorganic materials and biomass materials, has been compiled and the oil adsorption capacities toward various types of oils and organic solvents as available in the literature are presented along with highlighting and discussing the various factors involved in the designing of oil-absorbing absorbents tested so far for oil/water separation. Finally, some future trends and perspectives in oil-absorbing material are outlined.
基金financially supported by the National Natural Science Foundation of China(No.51103125)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(Chemistry)+2 种基金the Natural Science Foundation of Yangzhou(No.YZ2014043)the Science Innovative Foundation of Yangzhou University(No.2014CXJ017)the Graduate Student Innovation foundation of Yangzhou University(No.CXLX 1413)
文摘La-doped Sr-hexaferrite（Sr（1-x）LaxFe（12）O（19））（x=0.05,0.10,0.15,0.20） nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel auto-combustion. The phase formation temperature increases, while the particle size decreases as the Ladoping content goes up. The partial substitution of Sr^（2＋） by La^（3＋） results in the suppression effects on the growth-up of the crystallites and the enhancement of the electron hopping between Fe^（3＋） with different valences, which leads to the improvement in the dielectric loss and magnetic loss.Therefore, both the microwave absorbing abilities and absorbing frequency ranges are tuned by La-doping. The synthesized Sr-hexaferrite nanopowders with doping element content of 0.10 demonstrate the fine broad microwave absorbing properties.
文摘The numerical wave channel has been developed based on the volume of fluid method (VOF) in conjunction with the Navier-Stokes equations. The absorbing wave-maker boundary on the left side of the channel is presented by prescribing velocity reference to linear wave-maker theory. The principle of which is that the numerical wave-maker is designed to move in a way that generates the required incident wave and cancels out any reflected wave that reach it at the same time. On the right side of the channel, the open boundary is set to permit incident waves to be transmitted freely. The parametric studies have been carried out at a range of ratios of water depth to wave length d/ L from 0.124 to 0.219, with wave height in the front of paddle/water depth ratio (H0 / d) from 0.1 to 0.3. Wave height, wave pressure distribution along the channel and velocity field are obtained for both open boundary condition and reflective boundary condition at the other end of the channel. For a reflective case, it is shown that the absorbing wave-maker is very effective in canceling out the reflected wave that reaches the numerical paddle and highly repeatable waves can be generated.
基金supported by the National Defence Fundamental Research (MKPT-232)
文摘Dy3+ doped Mn-Zn ferrites Mn0.3Zn0.7Fe2-xDyxO4(x=0,0.01,0.02,0.03,0.04)were prepared by the conventional solid-state reaction.The crystal structure,surface morphology and electromagnetic properties of the calcined samples were characterized by X-ray diffraction analysis(XRD),scanning electron microscopy(SEM) and network analyzer(Agilent 8722ET).All the XRD patterns showed the single phase of the spinel-type ferrite without other intermediate when x≤0.03.The average crystallite size was about 44?56 nm.The mi...
基金State Key Laboratory of Electronic Thin Films and Integrated Devices for support of this work (KFJJ200815)supported by the Scientific Research Fund of Sichuan Provincial Education Department,China (08ZA026)Talents Project of Xihua University,China (R1020106)
文摘Soft magnetic metallic materials have been widely used for absorbing electromagnetic wave.Flaky Fe 86 t Si t Al 14（t=9,11,14 and 16） alloys powders were prepared from melt-quenched ribbons by annealing and milling.In a previous report we discussed the order-disordered structure of this alloys.In this article,we studied their electron structure.Covalence electron numbers of（111） and（100） plane increase with increasing Si content but Bohr magneton decreases.Complex permittivity and complex permeability are both decreased with increasing Si content t.The lowest value of reflectivity among the four alloys is originated from Fe 70 Si 14 Al 14.The peak values of reflectivity are all lower than 10 dB,and the absorbing frequency range（R 10 dB） increases from 1 to 2 GHz when t reaches 16.
