Metal-organic frameworks(MOFs)derived composites are extremely potential electromagnetic wave(EMW)absorbers.However,the permittivity of absorbers directly derived from MOFs with solid structure is usually relatively l...Metal-organic frameworks(MOFs)derived composites are extremely potential electromagnetic wave(EMW)absorbers.However,the permittivity of absorbers directly derived from MOFs with solid structure is usually relatively low,inevitably limiting their further applications.Cation substitution can primely overcome the problem by regulating the morphology and atomic space occupation to enhance multiple loss mechanisms and impedance matching characteristics.However,universal mechanisms of the effect on EMW absorption performance influenced by cation substitution are still comparatively inadequate,which prospectively requires further exploration.Herein,a series of imidazolic MOFs were fabricated by ultrasonic symbiosis method and tailored by subsequent cation substitution strategy to prepare target porous composites.At a low filling rate and thin thickness,the as-obtained samples reach the optimal reflection loss and effective absorption bandwidth values of–49.81 dB and 7.63 GHz,respectively.The intercoupling between multiple atoms lays a significant foundation for abundant heterogeneous interfaces and defect vacancies,which effectively ameliorate the attenuation mechanisms.Meanwhile,the porous structure introduced by cation substitution reduces the bulk density to enhance the impedance matching and multiple reflections simultaneously.This study provides a helpful idea to exceedingly improve the EMW absorbing performance of imidazolic MOFs-derived composites by cation substitution.展开更多
In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of th...In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of the 21221 mining face at Qianqiu coal mine in Henan Province, China. This study established, a comprehensive monitoring system to investigate the interrelations and evolutionary characteristics among multiple mechanical parameters, including mining-induced stress, displacement, temperature, and acoustic emission events during overburden rock caving. It is suggested that, despite the uniformity of the overburden rock caving interval, the main characteristic of overburden rock lies in its uneven caving strength. The mining-induced stress exhibits a reasonable interrelation with the displacement, temperature, and acoustic emission events of the rock strata. With the advancement of the coal seam, the mining-induced stress undergoes four successive stages: gentle stability, gradual accumulation, high-level mutation, and a return to stability. The variations in other mechanical parameters does not synchronize with the signifcant changes in mining-induced stress. Before the collapse of overburden rock occurs, rock strata temperature increment decreases and the acoustic emission ringing counts surges with the increase of rock strata displacement and mining-induced stress. Therefore, the collaborative characteristics of mining-induced stress, displacement, temperature, and acoustic emission ringing counts can be identifed as the precursor information or overburden rock caving. These results are in good consistent with on-site situation in the coal mine.展开更多
The rate of hydrothermal reaction of SiO_2 and/or A1_2O_3 in the system of CaO-Al_2O_3-SiO_2-H_2O at 200℃ and the factors which influence the reactions are investigated by determining the reaction ratio.The rate of r...The rate of hydrothermal reaction of SiO_2 and/or A1_2O_3 in the system of CaO-Al_2O_3-SiO_2-H_2O at 200℃ and the factors which influence the reactions are investigated by determining the reaction ratio.The rate of reactions depends on the reactive activities of raw materials, initial composition of mixture and relative activity of SiO_2 and A12O3. The hydrothermal reaction can be accelerated by sodium hydroxide,in the case of silica,which has low activity, this is quite obvious.展开更多
In the new era,China’s education industry was ushered in a high-quality development stage.On the one hand,it is necessary to set a goal of education management on the all-round development of students.On the other ha...In the new era,China’s education industry was ushered in a high-quality development stage.On the one hand,it is necessary to set a goal of education management on the all-round development of students.On the other hand,we should innovate some practical application schemes of diversified incentive mechanism consistent with the needs of educational management.Taking this as the starting point,this paper summarizes the connotation of incentive mechanism and diversified incentive mechanism,and analyzes the practical problems of single incentive standard,issues on incentive timeliness,and reduced participation of incentive objects at the current stage.On this basis,this paper puts forward some corresponding measures from three angles:opening up thinking,updating in time and emphasizing the target.展开更多
Bone defects represent a significant clinical challenge with diverse etiologies,including but not limited to tumors,trauma,necrosis,and congenital deformities,imposing substantial patient suffering and socioeconomic b...Bone defects represent a significant clinical challenge with diverse etiologies,including but not limited to tumors,trauma,necrosis,and congenital deformities,imposing substantial patient suffering and socioeconomic burdens.In recent years,novel approaches for bone defect repair have been continuously explored.Biodegradable synthetic materials,particularly those capable of gradual decomposition during tissue regeneration processes,are recognized as ideal candidates for bone repair implants.Natural or synthetic polymer-based materials have been extensively employed in osteochondral repair due to their favorable biocompatibility.Furthermore,biodegradable magnesium(Mg)-based metals constitute another crucial category of bone substitutes.Mg alloys demonstrate unique advantages,including tunable degradation rates,excellent biocompatibility,appropriate mechanical strength,and remarkable osteogenic potential,positioning Mgcontaining implants as a pivotal direction in bone regenerative medicine.However,clinical applications of Mg alloys still face challenges such as rapid degradation kinetics and insufficient osteogenic performance.Further investigation into advanced application strategies for Mg alloys holds significant clinical implications for bone defect therapeutics.展开更多
There is limited research reported on the multiple loss mechanism of electromagnetic waves(EMW)and the development of interface models.Dielectric loss and magnetic loss,as the two primary attenuation mechanisms in EMW...There is limited research reported on the multiple loss mechanism of electromagnetic waves(EMW)and the development of interface models.Dielectric loss and magnetic loss,as the two primary attenuation mechanisms in EMW absorbers,still pose challenges,especially in elucidating the correlation between composition,morphology,interface,and performance.Here,we construct 3D hierarchical porous conducting network structures and Schottky heterojunctions(MoNi_(4)@NC-NiFe_(2)O_(4)@NC)with a high density of defects,using trimetallic NiMoFe-MOFs.Synergistic enhancement of the dielectric and magnetic losses is realized through manipulation of the defects,interfaces,phase engineering,and magnetic resonance.In particular,the even dispersion of magnetic MoNi_(4) and NiFe_(2)O_(4)nanoparticles(NPs)within the carbon matrix triggers the creation of multiple heterogeneous interfaces.These inseparable interfaces,along with oxygen vacancies,play a role in enhancing dielectric polarization,while the closely spaced interactions among magnetic units contribute to magnetic loss.After optimizing the interfacial structure,NiFe_(2)O_(4)/MoNi_(4)-NC exhibits remarkable EMW absorption properties.A reflection loss(RL)value of-67.91 dB can be achieved at an ultra-thin thickness of 1.95 mm,and the effective absorption bandwidth(EAB,RL≤-10 dB)is as high as 5.76 GHz.Furthermore,we conducted radar scattering cross-section(RCS)simulations using computer simulation technology(CST)software,which revealed that NiFe_(2)O_(4)/MoNi_(4)-NC exhibits an RCS reduction value of 39.1 dB m^(2).Hence,this work provides comprehensive guidance for the construction of Schottky heterojunctions for lightweight EMW absorbers from a mechanistic point of view.展开更多
With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for th...With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for the shale oil industry.The process of energy storage fracturing induces significant changes in the pressure and saturation of the medium.However,conventional simulations often overlook the effects of fracturing and shut-in operations on the seepage field and production performance.Furthermore,fractured shale reservoirs exhibit complex non-Darcy flow characteristics due to intricate pore structures and multi-scale porous media.A comprehensive understanding of flow mechanisms is essential for effective reservoir development and CO_(2) storage.This study establishes a multi-component simulation model that encompasses the life-cycle of fracturing,shut-in,production,and CO_(2) huff-n-puff processes,thereby ensuring the continuity of the seepage field.The model accounts for the effect of nano-confinement on phase behavior by modifying the equation of state.Furthermore,the flux term is adjusted to incorporate Maxwell–Stefan diffusion,pre-/post-Darcy flow,and stress sensitivity.The embedded discrete fracture model(EDFM)is employed to simulate multiphase flow within multi-scale media,and the results from the validation model align satisfactorily with those derived from ECLIPSE.Mechanism analysis indicates that the interaction of multiple mechanisms significantly influences both production and storage performance.Under the multi-mechanism coupling,the cumulative oil production increased by 12.01%,while the utilization and storage factors increased by 62.93%and 8.93%,respectively.The role of molecular diffusion in shale oil reservoirs may be overstated,contributing only a 0.26% enhancement in oil production.Simulation results show that the energy storage fracturing strategy can increase oil production and net present value by 12.47%and 15.07%,respectively.Sensitivity analysis indicates that the CO_(2) injection rate is the main factor affecting the recovery factor,followed by CO_(2) injection time and the number of cycles,with fracturing fluid volume having the least impact.This study develops a multi-process,multi-mechanism simulation framework for multi-scale shale oil reservoirs.This framework provides a robust evaluation system for CCUS-EOR,facilitating informed decision-making in fracturing stimulation,development planning,and parameter optimization.展开更多
Carbon fiber(CF)has shown excellent performance in the application of absorbing materials,with characteristics such as high dielectric loss,strong flexibility,and lightweight are considered to be the support for furth...Carbon fiber(CF)has shown excellent performance in the application of absorbing materials,with characteristics such as high dielectric loss,strong flexibility,and lightweight are considered to be the support for further development of CF based microwave absorbing materials.However,its single component,unstable structure,monotonous absorption mechanism,and impedance mismatch limit its ability to become a thin,light,wide,and strong absorbing material.In this study,we first proposed porous carbon fiber(PC)composite magnetic nanoparticles and a multi-layer core-shell fiber membrane coated with transition metal sulfides,demonstrating outstanding microwave absorption performance with a remarkable reflection loss of-65 dB.The excellent electromagnetic wave absorption performance mainly comes from the processes of electrical relaxation and magnetic relaxation.The electrical relaxation is attributed to the high graphitization of N-doped carbon fibers,while the magnetic relaxation is attributed to the hysteresis loss caused by the Fe_(3)O_(4)core.Considering the influence of the structure of the absorbent on absorption performance,we also constructed porous and heterogeneous layer coating structures to increase multiple reflections.Provided valuable solutions for addressing issues such as electromagnetic interference,electromagnetic radiation protection,signal isolation,and improving equipment electromagnetic compatibility.展开更多
Here,the effect of cerium and terbium ions substitution on structural,optical,dielectric,and electrical properties of Ca_(0.95)Y_(0.05)Fe_(12)O_(19)M-type hexaferrite prepared by solvent free method i.e.,auto co mbust...Here,the effect of cerium and terbium ions substitution on structural,optical,dielectric,and electrical properties of Ca_(0.95)Y_(0.05)Fe_(12)O_(19)M-type hexaferrite prepared by solvent free method i.e.,auto co mbustion method was reported.The X-ray diffraction technique was used for the structural examination.The hexagonal structure of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples is confirmed by X-ray diffraction(XRD)pattern analysis.The crystallite size of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)(x=0.0,0.5,1.0,1.5,and 2.0)samples ranges from 28.37 to 39.12 nm.The Fourier transform infrared spectroscopy(FTIR)spectra confirm the lattice vibration at the octahedral and tetrahedral sites.The strong emission peaks of 3.40 eV are seen at 364 nm.It is found that photoluminescence intensity reduces with Ce-Tb substitution,which is associated with a reduction in electron-hole recombination.In the temperature range of room temperature(23℃)to 200℃,the dielectric constant,dielectric loss,and AC conductivity were computed over a broad frequency range of 10^(2)-10^(5) Hz.Maxwell-Wagner's two-laye r model explains the frequency dependent dielectric behaviour of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples.The dielectric constant increases for the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples as the Ce-Tb concentration increases up to x=1.0,and with further increasing the Ce^(3+)and Tb^(3+)ions up to x=2.0 the dielectric constant decreases.All of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples exhibit non-Debye type relaxation behaviour,according to the impedance measurement.The substitution of Ce^(3+)and Tb^(3+)ions reduces the grain boundary density,resulting in the low values of the impedance at the grain boundaries.It is found that the multiple hopping conduction process is the main mechanism in the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)compounds.展开更多
The composites prepared by combining lightweight carbon materials with magnetic metals have demonstrated excellent dielectric and magnetic properties,indicating potential applications in the field of electromagnetic w...The composites prepared by combining lightweight carbon materials with magnetic metals have demonstrated excellent dielectric and magnetic properties,indicating potential applications in the field of electromagnetic wave(EMW)absorption.However,the rational microstructure design and component optimization of these composites in regulating their magnetic-dielectric balance to achieve high-performance EMW absorption remains challenging.Herein,hierarchical yolk-shell Fe@SiO_(2)@NC composites with dual impedance matching layers and dual built-in electric fields were prepared by self-template aggregation and in situ reduction strategies.The introduction of a SiO_(2)wave-transparent layer into a conventional dielectric-magnetic system has resulted in the successful realization of nanoscale precise impedance matching regulation in absorbers,thereby enabling effective ultra-wideband EMW absorption.The dual impedance matching layers of the internal void layer and the SiO_(2)wave-transparent layer facilitate multiple scattering and reflection of EMWs within the absorbers,and the dual built-in electric fields of Fe/SiO_(2)and SiO_(2)/NC can effectively enhance interfacial polarization effect to attenuate EMWs.The predominantly optimized Fe@SiO_(2)@NC-2 exhibits an ultra-wide effective absorption bandwidth(EAB)of 7.10 GHz and an impressive minimum reflection loss(RL_(min))of−64.83 dB,indicating that optimizing the impedance matching via quantitative design can maximize the EMW absorption performance.This work provides a straightforward yet effective approach for constructing multi-component materials with hierarchical yolk-shell structure,which offers valuable insight into the microstructure design and component optimization of innovative EMW absorption materials.展开更多
Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and ...Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and fracture structure lead to complex multiphase flow,comprehensively considering multiple mechanisms is crucial for development and CO_(2) storage in fractured shale reservoirs.In this paper,a multi-mechanism coupled model is developed by MATLAB.Compared to the traditional Eclipse300 and MATLAB Reservoir Simulation Toolbox(MRST),this model considers the impact of pore structure on fluid phase behavior by the modified Peng—Robinson equation of state(PR-EOS),and the effect simultaneously radiate to Maxwell—Stefan(M—S)diffusion,stress sensitivity,the nano-confinement(NC)effect.Moreover,a modified embedded discrete fracture model(EDFM)is used to model the complex fractures,which optimizes connection types and half-transmissibility calculation approaches between non-neighboring connections(NNCs).The full implicit equation adopts the finite volume method(FVM)and Newton—Raphson iteration for discretization and solution.The model verification with the Eclipse300 and MRST is satisfactory.The results show that the interaction between the mechanisms significantly affects the production performance and storage characteristics.The effect of molecular diffusion may be overestimated in oil-dominated(liquid-dominated)shale reservoirs.The well spacing and injection gas rate are the most crucial factors affecting the production by sensitivity analysis.Moreover,the potential gas invasion risk is mentioned.This model provides a reliable theoretical basis for CO_(2)-EOR and sequestration in shale oil reservoirs.展开更多
To tackle the aggravating electromagnetic wave(EMW)pollution issues,high-efficiency EMW absorption materials are urgently explored.Metal-organic framework(MOF)derivatives have been intensively investigated for EMW abs...To tackle the aggravating electromagnetic wave(EMW)pollution issues,high-efficiency EMW absorption materials are urgently explored.Metal-organic framework(MOF)derivatives have been intensively investigated for EMW absorption due to the distinctive components and structures,which is expected to satisfy diverse application requirements.The extensive developments on MOF derivatives demonstrate its significantly important role in this research area.Particularly,MOF derivatives deliver huge performance superiorities in light weight,broad bandwidth,and robust loss capacity,which are attributed to the outstanding impedance matching,multiple attenuation mechanisms,and destructive interference effect.Herein,we summarized the relevant theories and evaluation methods,and categorized the state-of-the-art research progresses on MOF derivatives in EMW absorption field.In spite of lots of challenges to face,MOF derivatives have illuminated infinite potentials for further development as EMW absorption materials.展开更多
Ingenious microstructure design and rational composition collocation have been proved to be an effective strategy for developing efficient electromagnetic wave(EMW)absorbers.It would be promising to fabricate a hollow...Ingenious microstructure design and rational composition collocation have been proved to be an effective strategy for developing efficient electromagnetic wave(EMW)absorbers.It would be promising to fabricate a hollow structured composite integrating multiple loss mechanisms(conduction,magnetic,and polarization losses)for excellent EMW absorption.Herein,a novel dielectric-magnetic compound of ZnO/Ni@C hollow microsphere was prepared through hydrothermal reactions followed by an in-situ chemical vapor deposition(CVD).In this ternary composite,abundant ZnO/Ni heterostructures formed the hollow microsphere skeletons and provided unique Schottky junctions,which endowed the composite with improved impedance matching and strong polarization loss.Meanwhile,the amorphouspolycrystalline carbon layer deposited on the surface of each microsphere enhanced the conduction and interfacial polarization losses.In addition,the magnetic Ni nanoparticles induced magnetic loss.Benefiting from the synergistic effect of the hollow structure and multiple loss mechanisms,the ternary composite exhibits an effective absorption bandwidth as wide as 6.55 GHz at a thickness of only 1.85 mm,accompanied by a minimum reflection loss of–39.8 dB.Besides,the radar cross-section and the electromagnetic field simulation further verify the superior EMW absorption performance of the composites.Our work provides a new reference for the fabrication of dielectric-magnetic ternary hollow microspheres as EMW absorbers with thin thickness and broad bandwidth.展开更多
Lithium-ion batteries(LIBs)have been used to power various electric devices and store energy,but their toxic components by using inorganic materials generally cause serious environmental issues when disused.Recently,e...Lithium-ion batteries(LIBs)have been used to power various electric devices and store energy,but their toxic components by using inorganic materials generally cause serious environmental issues when disused.Recently,environmentally friendly and naturally abundant organic compounds have been adopted as promising electrode materials for next-generation LIBs.Herein,a new organic anode electrode based on sodium citrate is proposed,which shows gradually activated electrochemical behavior and delivers a high reversible capacity of 776.8 mAh·g^(-1)after 1770 cycles at a current density of 2 A·g^(-1).With the aid of the electrochemical characterization,Fourier-transform infrared(FTIR)and X-ray photoelectron spectroscopy(XPS)analysis,the lithium uptake mechanism of sodium citrate-based anodes is identified to be a combination of three-electron lithiation/delithiation and fast Li+intercalation/deintercalation processes,in which Faradaic reactions could offer a theoretical contribution of312 mAh·g^(-1)and intercalation pseudocapacitance would provide extra capacity.This work demonstrates the great potential for developing high-capacity organic electrodes for LIBs in future.展开更多
Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering m...Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering multiple flow mechanisms such as dynamic effects of gas flow and surface diffusion,apparent permeability models are obtained to investigate the characteristics of unconventional gas migration.Compared to the gas transfer in single-porosity reservoirs,the gas migration ability of cleats in dual-porosity stratums rarely changes while that of organic pores is greatly improved because cleats sustain major geomechanical shrinkage deformation when the pore pressure drops.Further,the mass flux of reservoirs is dominated by the mass flux of cleats,which has a lower peak value,but a much longer production term than those in single-porosity reservoirs due to the interaction between organic pores and cleats.Parametric analysis is conducted to identify key factors significantly impacting mass flux in unconventional reservoirs.Reasons for the mass flux variation are also explored in terms of gas migration ability and pore pressure distribution.展开更多
Advanced materials with superior comprehensive mechanical properties are strongly desired,but it has long been a challenge to achieve high ductility in high-strength materials.Here,we proposed a new V 0.5 Cr 0.5 CoNi ...Advanced materials with superior comprehensive mechanical properties are strongly desired,but it has long been a challenge to achieve high ductility in high-strength materials.Here,we proposed a new V 0.5 Cr 0.5 CoNi medium-entropy alloy(MEA)with a face-centered cubic/hexagonal close-packed(FCC/HCP)dual-phase ultrafine-grained(UFG)architecture containing stacking faults(SFs)and local chemical order(LCO)in HCP solid solution,to obtain an ultrahigh yield strength of 1476 MPa and uniform elongation of 13.2%at ambient temperature.The ultrahigh yield strength originates mainly from fine grain strength-ening of the UFG FCC matrix and HCP second-phase strengthening assisted by the SFs and LCO inside,whereas the large ductility correlates to the superior ability of the UFG FCC matrix to storage disloca-tions and the function of deformation-induced SFs in the vicinity of the FCC/HCP boundary to eliminate the stress concentration.This work provides new guidance by engineering novel composition and stable UFG structure for upgrading the mechanical properties of metallic materials.展开更多
Finding the common origin of non-Fermi liquids(NFLs) transport in high-temperature superconductors(HTSCs)has proven to be fundamentally challenging due to the prominence of various collective fluctuations.Here,we prop...Finding the common origin of non-Fermi liquids(NFLs) transport in high-temperature superconductors(HTSCs)has proven to be fundamentally challenging due to the prominence of various collective fluctuations.Here,we propose a comprehensive non-Hermitian Hamiltonian(NHH) for quantum coupling of multiple scattering mechanisms associated with four types of order fluctuations.It predicts that the anticommutation symmetry of the spinor fermions constrains the scattering rate to a unified quadrature scaling,i.e.,Γ=Γ_(1)+√Γ_(Q)^(2)+(μk_(B)T)^(2)+(vμ_(B)B)^(2)+(γ_(E)E)^(2).This scaling yields a comprehensive and accurate description of two widespread NFL behaviors in HTSCs,i.e.,a temperature-scaling crossover between quadratic and linear laws and the quadrature magnetoresistance,validated by several dozens of data sets for broad phase regimes.It reveals that the common origin of these behaviors is the spinor-symmetry-constrained quantum coupling of spin-wave and topological excitations of mesoscopic orders.Finally,we show that this NHH can be easily extended to other complex quantum fluids by specifying the corresponding symmetries.It is concluded that this work uncovers a critical organization principle(i.e.,the spinor symmetry) underlying the NFL transport,thus providing a novel theoretical framework to advance the transport theory of correlated electron systems.展开更多
A new type of composite filler was designed by a modified sol-gel method using fly ash(FA),Fe(NO_(3))_(3)·9H_(2)O,and Ni(NO_(3))_(2)·6H_(2)O as raw materials.The composite filler was a spherical core-shell s...A new type of composite filler was designed by a modified sol-gel method using fly ash(FA),Fe(NO_(3))_(3)·9H_(2)O,and Ni(NO_(3))_(2)·6H_(2)O as raw materials.The composite filler was a spherical core-shell structure composed of FA as the core and NiFe_(2)O_(4)as the shell.Further,the composite filler was added into the silicone rubber to fabricate the high temperature vulcanized microwave absorption materials;X-ray diffraction,fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,and scanning electron microscope confirmed that NiFe_(2)O_(4)was successfully coated on the surface of FA and formed a uniform and continuous coating layer.As expected,silicone rubber filled with the composite filler had a minimum reflection loss of-23.8 dB at 17.5 GHz with the thickness of 1.8 mm,while the effective absorption bandwidth was as high as 12 GHz.The addition of the composite filler greatly enhanced the microwave absorption properties of the system,which was resulted from multiple losses mechanism:interface polarization losses,magnetic losses,and multiple reflection losses.Also,silicone rubber filled with the composite filler exhibited excellent thermal stability,flexibility,environmental resistance,and hydrophobicity compared with traditional silicone rubber.Therefore,this work not only responds to the green chemistry to achieve efficient FA recovery,but also devises a new strategy to prepare microwave absorption materials with strong potential for civilian applications.展开更多
In this paper,we analyzed the One Foundations relief and reconstruction activities after the Yaan earthquake.The analysis shows that the participation of NGOs in disaster relief activities has undergone different stag...In this paper,we analyzed the One Foundations relief and reconstruction activities after the Yaan earthquake.The analysis shows that the participation of NGOs in disaster relief activities has undergone different stages.In the Jiujiang earthquake,NGOs participation was in the rudimentary stage.In the Wenchuan earthquake,they became one of the active participants.In the Yaan earthquake,they played an active role through a cooperation mechanism.That means NGOs have had the capability of resource mobilization and cooperation with them will improve disaster management capacities,especially in the national significant seismic monitoring and protection regions.展开更多
The dynamics of compact binaries is very complicated because of spin-orbit cou- pling and spin-spin coupling. With Laskar＇s frequency map analysis （FMA） and frequency diffusion as an indicator, we found that misali...The dynamics of compact binaries is very complicated because of spin-orbit cou- pling and spin-spin coupling. With Laskar＇s frequency map analysis （FMA） and frequency diffusion as an indicator, we found that misalignment of the spins and orbital angular momentum has a great effect on the dynamics, and for systems with different mass ratios β = m2/ml chaos occurs at different spin-orbit configurations. For equal-mass binaries （β = 1）, chaos occurs when the spins nearly cancel each other out. For some other systems （for exampleβ - 1/2）, the binaries are irregular, even chaotic, when the spins are perpendicular to the orbital angular momentum. For the case where gravitational radiation is taken into account, we give an analytic estimation for the frequency diffusion based on the decay of the orbit, which is roughly consistent with our simulations. This means the FMA is not suitable as a chaos indicator for weak chaotic cases with dissipative terms.展开更多
基金supported by the Natural Science Foundation of Sichuan Province(No.2023NSFSC0435)Sichuan Agricultural University College Student Innovation Training Program Project Funding(No.202210626019)Sichuan Agricultural University double support(035–2221993150).
文摘Metal-organic frameworks(MOFs)derived composites are extremely potential electromagnetic wave(EMW)absorbers.However,the permittivity of absorbers directly derived from MOFs with solid structure is usually relatively low,inevitably limiting their further applications.Cation substitution can primely overcome the problem by regulating the morphology and atomic space occupation to enhance multiple loss mechanisms and impedance matching characteristics.However,universal mechanisms of the effect on EMW absorption performance influenced by cation substitution are still comparatively inadequate,which prospectively requires further exploration.Herein,a series of imidazolic MOFs were fabricated by ultrasonic symbiosis method and tailored by subsequent cation substitution strategy to prepare target porous composites.At a low filling rate and thin thickness,the as-obtained samples reach the optimal reflection loss and effective absorption bandwidth values of–49.81 dB and 7.63 GHz,respectively.The intercoupling between multiple atoms lays a significant foundation for abundant heterogeneous interfaces and defect vacancies,which effectively ameliorate the attenuation mechanisms.Meanwhile,the porous structure introduced by cation substitution reduces the bulk density to enhance the impedance matching and multiple reflections simultaneously.This study provides a helpful idea to exceedingly improve the EMW absorbing performance of imidazolic MOFs-derived composites by cation substitution.
基金supported by the State Key Research Development Program of China(2022YFC3004602)Independent Research fund of Joint NationalLocal Engineering Research Centre for Safe and Precise Coal Mining(Anhui University of Science and Technology)(EC2022001)+2 种基金the National Natural Science Foundation of China(41872205)Beijing Natural Science Foundation(8202041)the Fundamental Research Funds for the Central Universities(2022YJSLJ08,2022JCCXNY03).
文摘In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of the 21221 mining face at Qianqiu coal mine in Henan Province, China. This study established, a comprehensive monitoring system to investigate the interrelations and evolutionary characteristics among multiple mechanical parameters, including mining-induced stress, displacement, temperature, and acoustic emission events during overburden rock caving. It is suggested that, despite the uniformity of the overburden rock caving interval, the main characteristic of overburden rock lies in its uneven caving strength. The mining-induced stress exhibits a reasonable interrelation with the displacement, temperature, and acoustic emission events of the rock strata. With the advancement of the coal seam, the mining-induced stress undergoes four successive stages: gentle stability, gradual accumulation, high-level mutation, and a return to stability. The variations in other mechanical parameters does not synchronize with the signifcant changes in mining-induced stress. Before the collapse of overburden rock occurs, rock strata temperature increment decreases and the acoustic emission ringing counts surges with the increase of rock strata displacement and mining-induced stress. Therefore, the collaborative characteristics of mining-induced stress, displacement, temperature, and acoustic emission ringing counts can be identifed as the precursor information or overburden rock caving. These results are in good consistent with on-site situation in the coal mine.
基金National H-Tech Program under contract 863-7152101
文摘The rate of hydrothermal reaction of SiO_2 and/or A1_2O_3 in the system of CaO-Al_2O_3-SiO_2-H_2O at 200℃ and the factors which influence the reactions are investigated by determining the reaction ratio.The rate of reactions depends on the reactive activities of raw materials, initial composition of mixture and relative activity of SiO_2 and A12O3. The hydrothermal reaction can be accelerated by sodium hydroxide,in the case of silica,which has low activity, this is quite obvious.
文摘In the new era,China’s education industry was ushered in a high-quality development stage.On the one hand,it is necessary to set a goal of education management on the all-round development of students.On the other hand,we should innovate some practical application schemes of diversified incentive mechanism consistent with the needs of educational management.Taking this as the starting point,this paper summarizes the connotation of incentive mechanism and diversified incentive mechanism,and analyzes the practical problems of single incentive standard,issues on incentive timeliness,and reduced participation of incentive objects at the current stage.On this basis,this paper puts forward some corresponding measures from three angles:opening up thinking,updating in time and emphasizing the target.
文摘Bone defects represent a significant clinical challenge with diverse etiologies,including but not limited to tumors,trauma,necrosis,and congenital deformities,imposing substantial patient suffering and socioeconomic burdens.In recent years,novel approaches for bone defect repair have been continuously explored.Biodegradable synthetic materials,particularly those capable of gradual decomposition during tissue regeneration processes,are recognized as ideal candidates for bone repair implants.Natural or synthetic polymer-based materials have been extensively employed in osteochondral repair due to their favorable biocompatibility.Furthermore,biodegradable magnesium(Mg)-based metals constitute another crucial category of bone substitutes.Mg alloys demonstrate unique advantages,including tunable degradation rates,excellent biocompatibility,appropriate mechanical strength,and remarkable osteogenic potential,positioning Mgcontaining implants as a pivotal direction in bone regenerative medicine.However,clinical applications of Mg alloys still face challenges such as rapid degradation kinetics and insufficient osteogenic performance.Further investigation into advanced application strategies for Mg alloys holds significant clinical implications for bone defect therapeutics.
基金supported by the National Natural Science Foundation of China(No.22269010)the Jiangxi Provincial Natural Science Foundation(No.20224BAB214021).
文摘There is limited research reported on the multiple loss mechanism of electromagnetic waves(EMW)and the development of interface models.Dielectric loss and magnetic loss,as the two primary attenuation mechanisms in EMW absorbers,still pose challenges,especially in elucidating the correlation between composition,morphology,interface,and performance.Here,we construct 3D hierarchical porous conducting network structures and Schottky heterojunctions(MoNi_(4)@NC-NiFe_(2)O_(4)@NC)with a high density of defects,using trimetallic NiMoFe-MOFs.Synergistic enhancement of the dielectric and magnetic losses is realized through manipulation of the defects,interfaces,phase engineering,and magnetic resonance.In particular,the even dispersion of magnetic MoNi_(4) and NiFe_(2)O_(4)nanoparticles(NPs)within the carbon matrix triggers the creation of multiple heterogeneous interfaces.These inseparable interfaces,along with oxygen vacancies,play a role in enhancing dielectric polarization,while the closely spaced interactions among magnetic units contribute to magnetic loss.After optimizing the interfacial structure,NiFe_(2)O_(4)/MoNi_(4)-NC exhibits remarkable EMW absorption properties.A reflection loss(RL)value of-67.91 dB can be achieved at an ultra-thin thickness of 1.95 mm,and the effective absorption bandwidth(EAB,RL≤-10 dB)is as high as 5.76 GHz.Furthermore,we conducted radar scattering cross-section(RCS)simulations using computer simulation technology(CST)software,which revealed that NiFe_(2)O_(4)/MoNi_(4)-NC exhibits an RCS reduction value of 39.1 dB m^(2).Hence,this work provides comprehensive guidance for the construction of Schottky heterojunctions for lightweight EMW absorbers from a mechanistic point of view.
基金the National Natural Science Foundation of China(No.52341401)the National Key Research and Development Program of China under grant(No.2022YFE0206700)+4 种基金the National Natural Science Foundation of China(No.42302272)the State-funded Postdoctoral Fellowship Program(No.GZB20230862)the Science Foundation of China University of Petroleum,Beijing(No.2462023XKBH006)the Science Foundation of China University of Petroleum,Beijing(No.2462021YJRC012)the Open Project Program of Key Laboratory of Groundwater Resources and Environment(Jilin University),Ministry of Education(No.202306ZDKF05).
文摘With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for the shale oil industry.The process of energy storage fracturing induces significant changes in the pressure and saturation of the medium.However,conventional simulations often overlook the effects of fracturing and shut-in operations on the seepage field and production performance.Furthermore,fractured shale reservoirs exhibit complex non-Darcy flow characteristics due to intricate pore structures and multi-scale porous media.A comprehensive understanding of flow mechanisms is essential for effective reservoir development and CO_(2) storage.This study establishes a multi-component simulation model that encompasses the life-cycle of fracturing,shut-in,production,and CO_(2) huff-n-puff processes,thereby ensuring the continuity of the seepage field.The model accounts for the effect of nano-confinement on phase behavior by modifying the equation of state.Furthermore,the flux term is adjusted to incorporate Maxwell–Stefan diffusion,pre-/post-Darcy flow,and stress sensitivity.The embedded discrete fracture model(EDFM)is employed to simulate multiphase flow within multi-scale media,and the results from the validation model align satisfactorily with those derived from ECLIPSE.Mechanism analysis indicates that the interaction of multiple mechanisms significantly influences both production and storage performance.Under the multi-mechanism coupling,the cumulative oil production increased by 12.01%,while the utilization and storage factors increased by 62.93%and 8.93%,respectively.The role of molecular diffusion in shale oil reservoirs may be overstated,contributing only a 0.26% enhancement in oil production.Simulation results show that the energy storage fracturing strategy can increase oil production and net present value by 12.47%and 15.07%,respectively.Sensitivity analysis indicates that the CO_(2) injection rate is the main factor affecting the recovery factor,followed by CO_(2) injection time and the number of cycles,with fracturing fluid volume having the least impact.This study develops a multi-process,multi-mechanism simulation framework for multi-scale shale oil reservoirs.This framework provides a robust evaluation system for CCUS-EOR,facilitating informed decision-making in fracturing stimulation,development planning,and parameter optimization.
基金supported by the Natural Science Foundation of Shaanxi(2024JC-YBQN-0442)the Scientific Research Program Funded by Education Department of Shaanxi Provincial Government(24JR117)。
文摘Carbon fiber(CF)has shown excellent performance in the application of absorbing materials,with characteristics such as high dielectric loss,strong flexibility,and lightweight are considered to be the support for further development of CF based microwave absorbing materials.However,its single component,unstable structure,monotonous absorption mechanism,and impedance mismatch limit its ability to become a thin,light,wide,and strong absorbing material.In this study,we first proposed porous carbon fiber(PC)composite magnetic nanoparticles and a multi-layer core-shell fiber membrane coated with transition metal sulfides,demonstrating outstanding microwave absorption performance with a remarkable reflection loss of-65 dB.The excellent electromagnetic wave absorption performance mainly comes from the processes of electrical relaxation and magnetic relaxation.The electrical relaxation is attributed to the high graphitization of N-doped carbon fibers,while the magnetic relaxation is attributed to the hysteresis loss caused by the Fe_(3)O_(4)core.Considering the influence of the structure of the absorbent on absorption performance,we also constructed porous and heterogeneous layer coating structures to increase multiple reflections.Provided valuable solutions for addressing issues such as electromagnetic interference,electromagnetic radiation protection,signal isolation,and improving equipment electromagnetic compatibility.
文摘Here,the effect of cerium and terbium ions substitution on structural,optical,dielectric,and electrical properties of Ca_(0.95)Y_(0.05)Fe_(12)O_(19)M-type hexaferrite prepared by solvent free method i.e.,auto co mbustion method was reported.The X-ray diffraction technique was used for the structural examination.The hexagonal structure of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples is confirmed by X-ray diffraction(XRD)pattern analysis.The crystallite size of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)(x=0.0,0.5,1.0,1.5,and 2.0)samples ranges from 28.37 to 39.12 nm.The Fourier transform infrared spectroscopy(FTIR)spectra confirm the lattice vibration at the octahedral and tetrahedral sites.The strong emission peaks of 3.40 eV are seen at 364 nm.It is found that photoluminescence intensity reduces with Ce-Tb substitution,which is associated with a reduction in electron-hole recombination.In the temperature range of room temperature(23℃)to 200℃,the dielectric constant,dielectric loss,and AC conductivity were computed over a broad frequency range of 10^(2)-10^(5) Hz.Maxwell-Wagner's two-laye r model explains the frequency dependent dielectric behaviour of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples.The dielectric constant increases for the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples as the Ce-Tb concentration increases up to x=1.0,and with further increasing the Ce^(3+)and Tb^(3+)ions up to x=2.0 the dielectric constant decreases.All of the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)samples exhibit non-Debye type relaxation behaviour,according to the impedance measurement.The substitution of Ce^(3+)and Tb^(3+)ions reduces the grain boundary density,resulting in the low values of the impedance at the grain boundaries.It is found that the multiple hopping conduction process is the main mechanism in the Ca_(0.95)Y_(0.05)Ce_(x)Tb_(x)Fe_(12-2x)O_(19)compounds.
基金financially supported by the National Natural Science Foundation of China(Nos.52172222 and 51972226)the National Natural Science Foundation of Tianjin City(No.20JCZDJC00570).
文摘The composites prepared by combining lightweight carbon materials with magnetic metals have demonstrated excellent dielectric and magnetic properties,indicating potential applications in the field of electromagnetic wave(EMW)absorption.However,the rational microstructure design and component optimization of these composites in regulating their magnetic-dielectric balance to achieve high-performance EMW absorption remains challenging.Herein,hierarchical yolk-shell Fe@SiO_(2)@NC composites with dual impedance matching layers and dual built-in electric fields were prepared by self-template aggregation and in situ reduction strategies.The introduction of a SiO_(2)wave-transparent layer into a conventional dielectric-magnetic system has resulted in the successful realization of nanoscale precise impedance matching regulation in absorbers,thereby enabling effective ultra-wideband EMW absorption.The dual impedance matching layers of the internal void layer and the SiO_(2)wave-transparent layer facilitate multiple scattering and reflection of EMWs within the absorbers,and the dual built-in electric fields of Fe/SiO_(2)and SiO_(2)/NC can effectively enhance interfacial polarization effect to attenuate EMWs.The predominantly optimized Fe@SiO_(2)@NC-2 exhibits an ultra-wide effective absorption bandwidth(EAB)of 7.10 GHz and an impressive minimum reflection loss(RL_(min))of−64.83 dB,indicating that optimizing the impedance matching via quantitative design can maximize the EMW absorption performance.This work provides a straightforward yet effective approach for constructing multi-component materials with hierarchical yolk-shell structure,which offers valuable insight into the microstructure design and component optimization of innovative EMW absorption materials.
基金supported by the National Natural Science Foundation of China(No.52174038 and No.52004307)China Petroleum Science and Technology Project-Major Project-Research on Tight Oil-Shale Oil Reservoir Engineering Methods and Key Technologies in Ordos Basin(No.ZLZX2020-02-04)Science Foundation of China University of Petroleum,Beijing(No.2462018YJRC015)。
文摘Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and fracture structure lead to complex multiphase flow,comprehensively considering multiple mechanisms is crucial for development and CO_(2) storage in fractured shale reservoirs.In this paper,a multi-mechanism coupled model is developed by MATLAB.Compared to the traditional Eclipse300 and MATLAB Reservoir Simulation Toolbox(MRST),this model considers the impact of pore structure on fluid phase behavior by the modified Peng—Robinson equation of state(PR-EOS),and the effect simultaneously radiate to Maxwell—Stefan(M—S)diffusion,stress sensitivity,the nano-confinement(NC)effect.Moreover,a modified embedded discrete fracture model(EDFM)is used to model the complex fractures,which optimizes connection types and half-transmissibility calculation approaches between non-neighboring connections(NNCs).The full implicit equation adopts the finite volume method(FVM)and Newton—Raphson iteration for discretization and solution.The model verification with the Eclipse300 and MRST is satisfactory.The results show that the interaction between the mechanisms significantly affects the production performance and storage characteristics.The effect of molecular diffusion may be overestimated in oil-dominated(liquid-dominated)shale reservoirs.The well spacing and injection gas rate are the most crucial factors affecting the production by sensitivity analysis.Moreover,the potential gas invasion risk is mentioned.This model provides a reliable theoretical basis for CO_(2)-EOR and sequestration in shale oil reservoirs.
基金This work was supported by the National Natural Science Foundation of China(No.51572157,No.21902085,and No.51702188)the Natural Science Foundation of Shandong Province(No.ZR2019QF012,No.ZR2019BEM024,ZR2016BM16)+3 种基金the Fundamental Research Funds of Shandong University(2018JC036,2018JC046,2018JC047)Qilu Young Scholar Program of Shandong(No.31370088963043)the Young Scholars Program of Shandong University(2018WLJH25)Key Technology Research and Development Program of Shandong(2019JZZY010312).
文摘To tackle the aggravating electromagnetic wave(EMW)pollution issues,high-efficiency EMW absorption materials are urgently explored.Metal-organic framework(MOF)derivatives have been intensively investigated for EMW absorption due to the distinctive components and structures,which is expected to satisfy diverse application requirements.The extensive developments on MOF derivatives demonstrate its significantly important role in this research area.Particularly,MOF derivatives deliver huge performance superiorities in light weight,broad bandwidth,and robust loss capacity,which are attributed to the outstanding impedance matching,multiple attenuation mechanisms,and destructive interference effect.Herein,we summarized the relevant theories and evaluation methods,and categorized the state-of-the-art research progresses on MOF derivatives in EMW absorption field.In spite of lots of challenges to face,MOF derivatives have illuminated infinite potentials for further development as EMW absorption materials.
基金supported by the National Natural Science Foundation of China(Nos.52272288 and 51972039)the China Postdoctoral Science Foundation(No.2021M700658).
文摘Ingenious microstructure design and rational composition collocation have been proved to be an effective strategy for developing efficient electromagnetic wave(EMW)absorbers.It would be promising to fabricate a hollow structured composite integrating multiple loss mechanisms(conduction,magnetic,and polarization losses)for excellent EMW absorption.Herein,a novel dielectric-magnetic compound of ZnO/Ni@C hollow microsphere was prepared through hydrothermal reactions followed by an in-situ chemical vapor deposition(CVD).In this ternary composite,abundant ZnO/Ni heterostructures formed the hollow microsphere skeletons and provided unique Schottky junctions,which endowed the composite with improved impedance matching and strong polarization loss.Meanwhile,the amorphouspolycrystalline carbon layer deposited on the surface of each microsphere enhanced the conduction and interfacial polarization losses.In addition,the magnetic Ni nanoparticles induced magnetic loss.Benefiting from the synergistic effect of the hollow structure and multiple loss mechanisms,the ternary composite exhibits an effective absorption bandwidth as wide as 6.55 GHz at a thickness of only 1.85 mm,accompanied by a minimum reflection loss of–39.8 dB.Besides,the radar cross-section and the electromagnetic field simulation further verify the superior EMW absorption performance of the composites.Our work provides a new reference for the fabrication of dielectric-magnetic ternary hollow microspheres as EMW absorbers with thin thickness and broad bandwidth.
基金financially supported by the National Natural Science Foundation of China(Nos.21875155,51675275 and 21473119)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(No.KJQN201900527)the support from the Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province,Suzhou,China。
文摘Lithium-ion batteries(LIBs)have been used to power various electric devices and store energy,but their toxic components by using inorganic materials generally cause serious environmental issues when disused.Recently,environmentally friendly and naturally abundant organic compounds have been adopted as promising electrode materials for next-generation LIBs.Herein,a new organic anode electrode based on sodium citrate is proposed,which shows gradually activated electrochemical behavior and delivers a high reversible capacity of 776.8 mAh·g^(-1)after 1770 cycles at a current density of 2 A·g^(-1).With the aid of the electrochemical characterization,Fourier-transform infrared(FTIR)and X-ray photoelectron spectroscopy(XPS)analysis,the lithium uptake mechanism of sodium citrate-based anodes is identified to be a combination of three-electron lithiation/delithiation and fast Li+intercalation/deintercalation processes,in which Faradaic reactions could offer a theoretical contribution of312 mAh·g^(-1)and intercalation pseudocapacitance would provide extra capacity.This work demonstrates the great potential for developing high-capacity organic electrodes for LIBs in future.
基金the National Natural Science Foundation of China(Grant Nos.12102372 and 11872324)the Open Research Fund of CNMGE Platform&NSCC-TJ(Grant No.CNMGE2023011).
文摘Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering multiple flow mechanisms such as dynamic effects of gas flow and surface diffusion,apparent permeability models are obtained to investigate the characteristics of unconventional gas migration.Compared to the gas transfer in single-porosity reservoirs,the gas migration ability of cleats in dual-porosity stratums rarely changes while that of organic pores is greatly improved because cleats sustain major geomechanical shrinkage deformation when the pore pressure drops.Further,the mass flux of reservoirs is dominated by the mass flux of cleats,which has a lower peak value,but a much longer production term than those in single-porosity reservoirs due to the interaction between organic pores and cleats.Parametric analysis is conducted to identify key factors significantly impacting mass flux in unconventional reservoirs.Reasons for the mass flux variation are also explored in terms of gas migration ability and pore pressure distribution.
基金supported by the National Natural Science Foundation of China(Nos.U1530401,52071038,51871194)the Fundamental Research Funds for the Central Universities(No.N2102008)the Innovation Research Group Project of Hebei Natural Science Foundation,China(No.E2021203011).
文摘Advanced materials with superior comprehensive mechanical properties are strongly desired,but it has long been a challenge to achieve high ductility in high-strength materials.Here,we proposed a new V 0.5 Cr 0.5 CoNi medium-entropy alloy(MEA)with a face-centered cubic/hexagonal close-packed(FCC/HCP)dual-phase ultrafine-grained(UFG)architecture containing stacking faults(SFs)and local chemical order(LCO)in HCP solid solution,to obtain an ultrahigh yield strength of 1476 MPa and uniform elongation of 13.2%at ambient temperature.The ultrahigh yield strength originates mainly from fine grain strength-ening of the UFG FCC matrix and HCP second-phase strengthening assisted by the SFs and LCO inside,whereas the large ductility correlates to the superior ability of the UFG FCC matrix to storage disloca-tions and the function of deformation-induced SFs in the vicinity of the FCC/HCP boundary to eliminate the stress concentration.This work provides new guidance by engineering novel composition and stable UFG structure for upgrading the mechanical properties of metallic materials.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 91952201 and 11452002)。
文摘Finding the common origin of non-Fermi liquids(NFLs) transport in high-temperature superconductors(HTSCs)has proven to be fundamentally challenging due to the prominence of various collective fluctuations.Here,we propose a comprehensive non-Hermitian Hamiltonian(NHH) for quantum coupling of multiple scattering mechanisms associated with four types of order fluctuations.It predicts that the anticommutation symmetry of the spinor fermions constrains the scattering rate to a unified quadrature scaling,i.e.,Γ=Γ_(1)+√Γ_(Q)^(2)+(μk_(B)T)^(2)+(vμ_(B)B)^(2)+(γ_(E)E)^(2).This scaling yields a comprehensive and accurate description of two widespread NFL behaviors in HTSCs,i.e.,a temperature-scaling crossover between quadratic and linear laws and the quadrature magnetoresistance,validated by several dozens of data sets for broad phase regimes.It reveals that the common origin of these behaviors is the spinor-symmetry-constrained quantum coupling of spin-wave and topological excitations of mesoscopic orders.Finally,we show that this NHH can be easily extended to other complex quantum fluids by specifying the corresponding symmetries.It is concluded that this work uncovers a critical organization principle(i.e.,the spinor symmetry) underlying the NFL transport,thus providing a novel theoretical framework to advance the transport theory of correlated electron systems.
文摘A new type of composite filler was designed by a modified sol-gel method using fly ash(FA),Fe(NO_(3))_(3)·9H_(2)O,and Ni(NO_(3))_(2)·6H_(2)O as raw materials.The composite filler was a spherical core-shell structure composed of FA as the core and NiFe_(2)O_(4)as the shell.Further,the composite filler was added into the silicone rubber to fabricate the high temperature vulcanized microwave absorption materials;X-ray diffraction,fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,and scanning electron microscope confirmed that NiFe_(2)O_(4)was successfully coated on the surface of FA and formed a uniform and continuous coating layer.As expected,silicone rubber filled with the composite filler had a minimum reflection loss of-23.8 dB at 17.5 GHz with the thickness of 1.8 mm,while the effective absorption bandwidth was as high as 12 GHz.The addition of the composite filler greatly enhanced the microwave absorption properties of the system,which was resulted from multiple losses mechanism:interface polarization losses,magnetic losses,and multiple reflection losses.Also,silicone rubber filled with the composite filler exhibited excellent thermal stability,flexibility,environmental resistance,and hydrophobicity compared with traditional silicone rubber.Therefore,this work not only responds to the green chemistry to achieve efficient FA recovery,but also devises a new strategy to prepare microwave absorption materials with strong potential for civilian applications.
基金sponsored by the National Social Science Fund of China "Research on the Status,Efficiencies and the Policy on the National Significant Seismic Monitoring and Protection Regions"(11&ZD054)Policy Research Projects of China Earthquake Administration in 2014 "The Role of NGOs in Earthquake Relief and the Meaning to Policy"
文摘In this paper,we analyzed the One Foundations relief and reconstruction activities after the Yaan earthquake.The analysis shows that the participation of NGOs in disaster relief activities has undergone different stages.In the Jiujiang earthquake,NGOs participation was in the rudimentary stage.In the Wenchuan earthquake,they became one of the active participants.In the Yaan earthquake,they played an active role through a cooperation mechanism.That means NGOs have had the capability of resource mobilization and cooperation with them will improve disaster management capacities,especially in the national significant seismic monitoring and protection regions.
基金Supported by the National Natural Science Foundation of China.
文摘The dynamics of compact binaries is very complicated because of spin-orbit cou- pling and spin-spin coupling. With Laskar＇s frequency map analysis （FMA） and frequency diffusion as an indicator, we found that misalignment of the spins and orbital angular momentum has a great effect on the dynamics, and for systems with different mass ratios β = m2/ml chaos occurs at different spin-orbit configurations. For equal-mass binaries （β = 1）, chaos occurs when the spins nearly cancel each other out. For some other systems （for exampleβ - 1/2）, the binaries are irregular, even chaotic, when the spins are perpendicular to the orbital angular momentum. For the case where gravitational radiation is taken into account, we give an analytic estimation for the frequency diffusion based on the decay of the orbit, which is roughly consistent with our simulations. This means the FMA is not suitable as a chaos indicator for weak chaotic cases with dissipative terms.
