Absorption properties and mechanism of lightweight and broadband electromagnetic wave-absorbing porous carbon by the swelling treatment

Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness.In this study,KOH was evenly distributed on biomass Tremella using the swelling induction method,leading to the preparation of a three-dimensional network-structured hierarchical porous carbon(HPC)through carbonization.The achieved microwave absorption intensity is robust at-47.34 dB with a thin thickness of 2.1 mm.Notably,the widest effective absorption bandwidth,reaching 7.0 GHz(11–18 GHz),is attained at a matching thickness of 2.2 mm.The exceptional broadband and reflection loss performance are attributed to the 3D porous networks,interface effects,carbon network defects,and dipole relaxation.HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant.The uniform pore structures considerably optimize the impedance-matching performance of the material,while the abundance of interfaces and defects enhances the dielectric loss,thereby improving the attenuation constant.Furthermore,the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated.This research presents a strategy for preparing absorbing materials using biomass-derived HPC,showcasing considerable potential in the field of electromagnetic wave absorption.

Research progress of heterogeneous structure magnesium alloys:A review

In recent years,a new class of metallic materials featuring heterogeneous structures has emerged.These materials consist of distinct soft and hard domains with significant differences in mechanical properties,allowing them to maintain high strength while offering superior ductility.Magnesium(Mg)alloys,renowned for their low density,high specific strength,exceptional vibration damping,and electromagnetic shielding properties,exhibit tremendous potential as lightweight and functional materials.Despite their advantageous properties,high-strength Mg alloys often suffer from limited ductility.However,the emergence of heterogeneous materials provides a fresh perspective for the development of Mg alloys with both high strength and ductility.This article provided a fundamental overview of heterostructured materials and systematically reviewed the recent research progress in the design of Mg alloys with strength-ductility balance based on heterostructure principles.The review encompassed various aspects,including preparation methods,formation mechanisms of diverse heterostructures,and mechanical properties,both within domestic and international contexts.On this basis,the article discussed the challenges encountered in the design and fabrication of heterostructured Mg alloys,as well as the urgent issues that require attention and resolution in the future.

A Random Fusion of Mix 3D and Polar Mix to Improve Semantic Segmentation Performance in 3D Lidar Point Cloud

This paper focuses on the effective utilization of data augmentation techniques for 3Dlidar point clouds to enhance the performance of neural network models.These point clouds,which represent spatial information through a collection of 3D coordinates,have found wide-ranging applications.Data augmentation has emerged as a potent solution to the challenges posed by limited labeled data and the need to enhance model generalization capabilities.Much of the existing research is devoted to crafting novel data augmentation methods specifically for 3D lidar point clouds.However,there has been a lack of focus on making the most of the numerous existing augmentation techniques.Addressing this deficiency,this research investigates the possibility of combining two fundamental data augmentation strategies.The paper introduces PolarMix andMix3D,two commonly employed augmentation techniques,and presents a new approach,named RandomFusion.Instead of using a fixed or predetermined combination of augmentation methods,RandomFusion randomly chooses one method from a pool of options for each instance or sample.This innovative data augmentation technique randomly augments each point in the point cloud with either PolarMix or Mix3D.The crux of this strategy is the random choice between PolarMix and Mix3Dfor the augmentation of each point within the point cloud data set.The results of the experiments conducted validate the efficacy of the RandomFusion strategy in enhancing the performance of neural network models for 3D lidar point cloud semantic segmentation tasks.This is achieved without compromising computational efficiency.By examining the potential of merging different augmentation techniques,the research contributes significantly to a more comprehensive understanding of how to utilize existing augmentation methods for 3D lidar point clouds.RandomFusion data augmentation technique offers a simple yet effective method to leverage the diversity of augmentation techniques and boost the robustness of models.The insights gained from this research can pave the way for future work aimed at developing more advanced and efficient data augmentation strategies for 3D lidar point cloud analysis.

Rational construction of heterointerfaces in biomass sugarcane-derived carbon for superior electromagnetic wave absorption

The pervasive adoption of 5th generation mobile communication technology propels electromagnetic wave(EW)absorbents to achieve high-level performance.The heterointerface construction is crucial to the improvement of absorption ability.Herein,a series of ultralight composites with rational heterointerfaces(Co/ZnO@N-doped C/layer-stacked C,MSC)is fabricated by calcination with ration-al construction of sugarcane and CoZn-zeolitic imidazolate framework(ZIF).The components and structures of as-prepared composites were investigated,and their electromagnetic parameters could be adjusted by the content of CoZn-ZIFs.All composites possess excellent EW absorption performance,especially MSC-3.The optimal minimum reflection loss and effective absorption band of MSC-3 can reach−42 dB and 7.28 GHz at the thickness of only 1.6 mm with 20wt%filler loading.This excellent performance is attributed to the syner-gistic effect of dielectric loss stemming from the multiple heterointerfaces and magnetic loss induced by magnetic single Co.The sugar-cane-derived layer-stacked carbon has formed consecutive conductive networks and has further dissipated the electromagnetic energy through multiple reflection and conduction losses.Moreover,the simulated radar cross section(RCS)technology manifests that MSC-3 possesses outstanding EW attenuation capacity under realistic far-field conditions.This study provides a strategy for building efficient ab-sorbents based on biomass.

The effects of inner electrode shape on the performance of dielectric barrier discharge reactor for oxidative removal of NO and SO_(2)

Seagoing vessels are responsible for more than 90%of global freight traffic,but meanwhile,emission pollutants(NO_(x)and SO_(x))of seagoing vessels also cause serious air pollution.Nonthermal plasma(NTP)combined with wet scrubbing technology is considered to be a promising technology.In order to improve the oxidation efficiency and energy efficiency of the NTP reactor,the screw and rod inner electrodes of dielectric barrier discharge(DBD)reactor were investigated.To analyze the mechanism,the optical emission spectra(OES)of NTP were measured and numerical calculation was applied.The experiment results show that the NO oxidation removal efficiency of screw electrode is lower than that of rod electrode.However,the SO_(2)removal efficiency of screw electrode is higher.According to the OES experiment and numerical calculation,the electric field intensity of the screw electrode surface is much higher than that of the rod electrode surface,and it is easier to generate N radicals to form NO.For the same energy density condition,the OH radical generation efficiency of the screw electrode reactor is similar to that of the rod electrode,but the gas temperature in the discharge gap is higher.Therefore,the SO2 oxidation efficiency of the thread electrode is higher.This study provides guidance for the optimization of oxidation efficiency and energy consumption of DBD reactor.

Flexible Fixture Design for the Top and End Surface Processing of NP2_NP4 Cylinder Heads

This paper focuses on the design of fixtures for NP2 and NP4 cylinder heads on a horizontal machining center of flexible machining automatic lines.It began with an analysis of the diagrams of part processing and working procedure which formed the basis for the design of the processing technology scheme,a selection of suitable machine tools,and the setting of processing parameters.Fixtures tailored to the chosen machine tools were then designed to meet the processing requirements.Additional aspects of the project included the design of part drawings,calculation of working time quota,design of auxiliary guides,support clamping,and hydraulic circuits,all aimed at fulfilling practical production requirements.

Generation of microwave photon perfect W states of three coupled superconducting resonators

We propose an efficient method for the generation of perfect W states on three microwave superconducting resonators,of which the two nearest neighbors are coupled by a symmetric direct current superconducting quantum interference device(dc-SQUID).With suitable external magnetic fluxes applied to the dc-SQUID symmetry loops,on-chip tunable interactions between neighboring resonators can be realized,and different perfect W states can be deterministically created on-demand in one step.Numerical simulations show that high-fidelity target states can be generated and our scheme is robust against imperfect parameter tuning and environment-induced decoherence.The present work may have potential applications for implementing quantum computation and quantum information processing based on microwave photons.

Measurement of remanent magnetic moment using a torsion pendulum with single frequency modulation method

In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment mr of 1.1 kg dummy copper test mass, and the measurement result is(6.45 ± 0.04(stat) ± 0.07(syst)) × 10^(-8)A · m^(2). The measurement precision of the mr is about 0.9 n A · m^(2), well below the present measurement requirement of Tian Qin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.

Research on Obstacle Avoidance Method of Intelligent Car Based on Optimized Fuzzy Control Algorithm

In order to realize the accurate obstacle avoidance function of intelligent car, we propose an intelligent car obstacle avoidance system based on optimized fuzzy control algorithm. Firstly, the kinematics model of intelligent car obstacle avoidance is established, and an efficient environment information collection system composed of multiple sensors is designed to realize the comprehensive collection of obstacle information. Then, the optimized fuzzy control system is adopted to improve the position control accuracy and obstacle avoidance ability. Through the physical debugging and joint simulation of the intelligent car fuzzy controller in the MATLAB and Simulink environment, the simulation results show that the control method can make the collision-free path planned by the intelligent car from the initial state to the obstacle avoidance smoother, and at the same time, the obstacle avoidance of the intelligent car. The actual running distance is reduced by about 16%, which can ensure the practicability of the obstacle avoidance system, provide a new guarantee for the safe operation of the car, and also provide a new idea for the development of the unmanned car.

Microstructure and Wear Performance of High Volume Fraction Carbide M_7C_3 Reinforced Fe-based Composite Coating Fabricated by Plasma Transferred Arc Welding

The fabrication of high volume fraction （HVF） M7C3 （M=Cr, Fe） reinforced Fe-based composite coating on ASTM A36 steel plate using plasma transferred arc （PTA） welding was studied. The results showed that the volume fraction of carbide M7C3 was more than sixty percent, and the relative wear resistance of the coating tested on a block-on-ring dry sliding tester at constant load （100 N） and variable loads （from 100 to 300 N） respectively was about 9 and 14 times higher than that of non-reinforced a-Fe coating. In addition, under constant load condition the friction coefficients （FCs） of two coatings increased first and then decreased with increasing sliding distance. However, under variable loads condition the FCs of non-reinforced a-Fe based coating increased gradually, while that of HVF MTC3 reinforced coating decreased as the load exceeded 220 N. The worn surface of non-reinforced a-Fe based coating was easily deformed and grooved, while that of the HVF M7C3 reinforced coating was difficult to be deformed and grooved.

Electronic and mechanical properties of half-metallic half-Heusler compounds CoCrZ(Z=S, Se, and Te)

The electronic structures, magnetic properties, half-metallicity, and mechanical properties of half-Heulser compounds CoCrZ （Z = S, Se, and Te） were investigated using first-principles calculations within generalized gradient approximation based on the density function theory. The half-Heusler compounds show half-metallic properties with a half-metallic gap of 0.15 eV for CoCrS, 0.10 eV for CoCrSe, and 0.31 eV for CoCrTe at equilibrium lattice constant, respectively. The total magnetic moments are 3.00/-tB per formula unit, which agrees well with the Slater-Pauling rule. The half-metallicity, elastic constants, bulk modulus, shear modulus, Pough＇s ratio, Frantesvich ratio, Young＇s modulus, Poisson＇s ratio, and Debye temperature at equilibrium lattice constant and versus lattice constants are reported for the first time. The results indicate that the half-Heulser compounds CoCrZ （Z = S, Se, and Te） maintain the perfect half-metallic and mechanical stability within the lattice constants range of 5.18-5.43 A for CoCrS, 5.09-5.61 A for CoCrSe, and 5.17-6.42 A for CoCrTe, respectively.

Reconstructions of velocity distributions from fast-ion D-alpha(FIDA)measurements on EAST

2D fast-ion velocity-space distributions have been reconstructed from two-view fast-ion D-alpha(FIDA)measurements on experimental advanced superconducting tokamak(EAST).To make up for the sparse data and incomplete velocity-space coverage with the dual-view,we use nonnegativity and null-measurements as prior information to reconstruct the velocity distribution in experiments with co-and counter-current neutral beam injection.An improved reconstructed fast-ion distribution is achieved by combining the existing O-and B-port FIDA measurements with the proposed A-port FIDA view.To further improve the reliability of FIDA-based reconstructions on EAST,based on real multi-view FIDA measurements on EAST in the near future,various bases will be studied further.

New measuring method of fiber alignment in precision torsion pendulum experiments

Testing the extreme weak gravitational forces between torsion pendulum and surrounding objects will indicate new physics which attracts many interests.In these measurements,the fiber alignment plays a crucial role in fulfilling high precision placement measurement,especially in measuring the deviation between the fiber and source mass or other objects.The traditional way of the fiber alignment requires to measure the component of the pendulum body and then transfer to the torsion fiber by some complicated calculations.A new method is reported here by using a CCD camera to get the projection image of the torsion fiber,which is a direct and no-contact measurement.Furthermore,the relative position change of the torsion fiber can also be monitored during the experiment.In our experiment,the alignment between the fiber and the center of the turntable has been operated as an example.Our result reaches the accuracy of several micrometers which is higher than the previous method.

First-principles investigations on the mechanical, thermal,electronic, and optical properties of the defect perovskites Cs_2SnX_6(X= Cl, Br, I)

The mechanical properties, thermal properties, electronic structures, and optical properties of the defect perovskites Cs2SnX6（X = Cl, Br, I） were investigated by first-principles calculation using PBE and HSE06 hybrid functional. The optic band gaps based on HSE06 are 3.83 eV for Cs2SnCl6, 2.36 eV for Cs2SnBr6, and 0.92 eV for Cs2SnI6, which agree with the experimental results. The Cs2SnCl6, Cs2SnBr6, and Cs2SnI6 are mechanically stable and they are all anisotropic and ductile in nature. Electronic structures calculations show that the conduction band consists mainly of hybridization between the halogen p orbitals and Sn 5s orbitals, whereas the valence band is composed of the halogen p orbitals. Optic properties indicate that these three compounds exhibit good optical absorption in the ultraviolet region, and the absorption spectra red shift with the increase in the number of halogen atoms. The defect perovskites are good candidates for probing the lead-free and high power conversion efficiency of solar cells.

Preparation, Antibacterial and Antistatic Properties of PP/Ag-Ms/CB Composites

Polypropylene（PP） composites that contain silver micro-particles（MILLION KILLER, denoted as Ag-Ms） and conductive carbon black（CB） have both antibacterial and antistatic properties. In the present study, the antibacterial and antistatic PP/Ag-Ms/CB composites were prepared by melt blending. The results showed that when the content was 0.8 wt%, Ag-Ms could be uniformly dispersed in the PP matrix and the mechanical properties of the composites remained stable. And the reduction percentages of Staphylococcus aureus and Escherichia coli were more than 80% which showed the good antibacterial behavior. In addition, conductive carbon black had reinforcing and toughening effects on the mechanical properties of PP/Ag-Ms/CB composites. When the content of CB was beyond 30 wt%, the surface resistance of the composite was reduced to less than 108 Ω which showed a remarkable antistatic property. According to the different filling content of conductive carbon black, it can flexibly regulate the resistivity of PP, and the conductive effect is durable and stable. We thus can produce permanent antistatic materials.

Thickening and Rheological Properties of Crystalline Polyester Used in Low Pressure Sheet Molding Compounds

Low pressure sheet molding compound （LPMC,1.0-3.0 MPa,95-103 ℃） is a new kind of thermosetting material with crystalline polyester as a physical thickenner.LPMC is different from conventional SMC using an earth oxide thickening agent （e.g.MgO） as chemical thickenner,it relies on the physical thickening of crystalline polyester.Crystalline polyester resin is the key material to mold LPMC parts.Currently there was no report about the thickening mechanism of crystalline polyester in LPMC.In this article,crystalline polyester resins,whose melting points were between 45 ℃ and 89 ℃,were synthesized by a two-step esterification.The melt points of crystalline polyesters are controlled by regulating the mol ratio of the two glycols and the two acids.And by means of varying the content of crystalline polyester resin,the thickening effect on resin paste is investigated.In addition,the thickening mechanism of crystalline polyester in LPMC was investigated by FTIR and DSC analysis.The effects of the diameters and viscosity of crystalline polyester on the rheological property and fiber distribution of LPMC sheets were studied,too.Results show that the thickening effect is excellent when the weight content of crystalline polyester resin is 3%.And there exists three kinds of functions acting in the process of thickening：swelling,hydrogen bonds and induction crystallization.During the preparing process of resin paste in LPMC,the temperature of resin paste must be kept at 90 ℃.In addition,crystalline polyester make LPMC have a perfect fluid property.When the viscosity of LPMC sheet is beyond 1 kPa s,the fiber orientation is not obvious.But when the viscosity of LPMC sheet is about 500 Pa s,the fiber shows a certain degree of orientation.Moreover the study of physical and chemical thickening mechanism of crystalline polyester and the rheological discipline of LPMC sheets in the hot mould will provide the researchers and enterprises with theory guidance.

Synthesis of a ternary amide LixKy（NH2）x+y and a novel Li3K（NH2）4–xMgH2 combination system for hydrogen storage

The ternary amides LiK2(NH2)3, LiK(NH2)2, and Li3 K(NH2)4 are successfully synthesized by ball milling mixtures of LiNH2 and KNH2, and the hydrogen storage properties of Li3K(NH2)4–xMgH2(x = 1, 2, 3,4) are systematically investigated. The Li3K(NH2)4–2 Mg H2 sample displays optimized hydrogen storage properties, releasing 6.37 wt% of hydrogen in a two-stage reaction with an onset temperature of 60 °C.The first dehydrogenation stage exhibits good reaction kinetics and thermodynamic properties because of a lower activation energy and appropriate enthalpy change. After full dehydrogenation at 130 °C, the Li3K(NH2)4–2 MgH2 sample absorbs 3.80 wt% of H2 below 160 °C in a variable temperature hydrogenation mode. Mechanistic investigations indicate that Li3 K(NH2)4 reacts with Mg H2 to produce Mg(NH2)2, LiH,and KH during ball milling. In the heating process, Mg(NH2)2 first reacts with Li H to form Li2 Mg2 N3 H3 and Li NH2, while KH works as a catalyst, and then, KH reacts with Li2Mg2N3H3 and Li NH2 to generate a new K-containing compound.

Optimization of Supplier Switching with Asymmetric Information

The buyer-supplier relationship plays a great role in most economic systems. The buying firm usually tries to find a new supplier who provides products with satisfying quality and lower price. A broad branch of literature deals with the development of buyer-supplier relationships, but limited research is on the circumstances under which a buyer should terminate such a relationship and switch to a new supplier. In this paper, the incentive compatibility constraint (IC) which induces the entrant supplier to report his true cost is considered, and the participation constraint (PC) which ensures the entrant supplier to get at least reservation profit is taken into account. Then the supplier switching model is set up to minimize the buying firm's total procurement cost which includes the transfer payment to the incumbent supplier, the payment to the entrant supplier and the switching cost, and the buying firm's switching cost is considered as a function of the switching quantity. With the theoretical analysis of IC, PC and the proposed model, the optimal supplier switching strategy can be obtained. Finally, a numerical example is given to illustrate the effectiveness of the proposed model and the switching strategy.

Electronic Structure and Magnetic Properties of Cu[C(CN)_3]_2 and Mn[C(CN)_3]_2 Based on First Principles

The electronic structure and the magnetic properties of the molecule-based ferromagnets Cu[C（CN）3]2 and Mn[C（CN）3]2 are studied according to first principles within density-functional theory （DFT） and the full potential linearized augmented plane wave （FP-LAPW） method. The total energy, atomic spin magnetic moments, and density of states （DOS） of Cu[C（CN）3]2 and Mn[C（CN）3]2 are all calculated. The calculations reveal that the compounds have a stable ferromagnetic ground state and half-metallic properties. The total spin magnetic moment is 1.0μB for Cu[C（CN）3]2 and 5.0#B for Mn[C（CN）3]e per molecule, the magnetic moment mainly comes from metal atoms, although there is a slight contribution from N and C atoms.

Analysis on the Impacts of Precise Poverty Alleviation on Folk Customs and Control Measures

The promotion of precise poverty alleviation in poverty-stricken areas will inevitably lead to changes in local folk customs.The economic development may bring about greater development of folk customs,and may also lead to qualitative changes in folk customs.This paper mainly introduced the impact of the precise poverty alleviation on the folk customs.Based on the analysis,it came up with pertinent control measures,to better combine the folk customs with precise poverty alleviation measures,to promote common development of economy and culture in poverty stricken areas.