查看更多>>摘要：Explosion-electricity coupling(EEC)is a technical method to induce electric energy into the plasma material produced by explosion to improve the output of explosion.Exploding foil initiator(EFI)which could produce plasma during electric explosion can serve as a good carrier for studying the EEC.To investigate the enhancement ability and mechanism of EEC in EFI ignition performance,a kind of EFI chips which could realize the EEC effect was designed and fabricated to observe the characteristics of current and voltage,flyer and plasma temperature during Boron Potassium Nitrate(BPN)ignition of the EFI.It was found that the EEC could enhance EFI ignition in terms of energy utilization,ignition contact surface,and high-temperature sustainability of plasma:firstly,the EEC prolonged the late time discharge(LTD)phase of the electric explosion,making the energy of capacitor effectively utilized;secondly,the EEC could create a larger area of ignition contact surface;last of all,the EEC effect enhanced its high-temperature sustainability by sustaining continuous energy input to plasma.It also was found that the ignition voltage of BPN could be reduced by nearly 600 V under the condition of 0.4 μF capacitance.The research has successfully combined EEC with EFI,revealing the behavioral characteristics of EEC and demonstrating its effective enhancement of EFI ignition.It introduces a new approach to improving EFI output,which is conducive to low-energy ignition of EFI,and expected to take the ignition technology of EFI to a new level.
查看更多>>摘要：Compared with PELE with inert fillings such as polyethylene and nylon,reactive PELE(RPELE)shows excellent damage effects when impacting concrete targets due to the filling deflagration reaction.In present work,an analytical model describing the jacket deformation and concrete target damage impacted by RPELE was presented,in which the radial rarefaction and filling deflagration reaction were considered.The impact tests of RPELE on concrete target in the 592-1012 m/s were carried out to verify the analytical model.Based on the analytical model,the angle-length evolution mechanism of the jacket bending-curling deformation was revealed,and the concrete target damage was further analyzed.One can find out that the average prediction errors of the front crater,opening and back crater are 6.8％,8.5％and 7.1％,respectively.Moreover,the effects of radial rarefaction and deflagration were discussed.It was found that the neglect of radial rarefaction overestimates the jacket deformation and concrete target damage,while the deflagration reaction of filling increases the diameter of the front crater,opening and back crater by 25.4％,24.3％and 31.1％,respectively.The research provides a valuable reference for un-derstanding and predicting the jacket deformation and concrete target damage impacted by RPELE.
查看更多>>摘要：With the continuous development of transportation electrification,the cybersecurity of energy infra-structure has become increasingly prominent.Explicitly,EVs resemble a significant tool to carryout cyberattacks since EVs are not only seen as dynamic loads but also as mobile energy sources that establish two-way communications with several players in the grid.This taxonomy aims to provide a comprehensive overview of cyberattacks against EVs from four distinct perspectives.The first is the research domains of EVs application,which investigates the different fields of research related to the development and application of EVs and how they are susceptible to cyber threats.The second is the CIA-based attacks,which examines the threats to the confidentiality,integrity,and availability of EVs'sen-sitive information and critical systems.The third taxonomy discusses the countermeasures and defensive mechanisms to secure the EVs against cyberattacks,including preventive measures,detection algo-rithms,response strategy,and recovery techniques.The fourth taxonomy is the verification and vali-dation methodologies,which explores the software tools and hardware testbeds used to test and evaluate the security of EVs against cyber threats.Finally,this taxonomy presents an understanding of the current state of cyberattacks against EVs and serves as a valuable resource for researchers and practitioners in the fields of cybersecurity and electric mobility.
查看更多>>摘要：The interfacial structure has an important effect on the mechanical properties and safety of the energetic material.In this work,a mesostructure model reflecting the real internal structure of PBX is established through image digital modeling and vectorization processing technology.The microscopic molecular structure model of PBX is constructed by molecular dynamics,and the interface bonding energy is calculated and transferred to the mesostructure model.Numerical simulations are used to study the influence of the interface roughness on the dynamic compression and impact ignition response of PBX,and to regulate and optimize the mechanical properties and safety of the explosive to obtain the optimal design of the surface roughness of the explosive crystal.The results show that the critical hot spot density of PBX ignition under impact loading is 0.68 mm-2.The improvement of crystal surface roughness can improve the mechanical properties of materials,but at the same time it can improve the impact ignition sensitivity and reduce the safety of materials.The optimal friction coefficient range for the crystal surface that satisfies both the mechanical properties and safety of PBX is 0.06-0.12.This work can provide a reference basis for the formulation design and production processing of energetic materials.
查看更多>>摘要：SiC aerogel presents several advantageous features like lightweight and high temperature resistance when applied as microwave absorbing material.In this paper,SiC aerogel was prepared eventually fol-lowed by the sol-gel and carbonization reduction process.The results showed that the effective elec-tromagnetic microwave absorption capacity of SiC aerogel was highly increased after being pyrolyzed at 1500 ℃,which presented a minimum reflection loss value of-57.80 dB at 3.10 mm and 9.86 GHz.Be-sides,the electromagnetic parameters of SiC aerogel with different paraffin ratios were discussed as well as the varying electromagnetic microwave absorption performances.The minimum reflection loss value first rose then fell as the SiC/paraffin ratio increased,which demonstrated the importance of SiC content.This study establishes the theoretical foundation for the subsequent functional application of SiC aerogel.
查看更多>>摘要：At the first time,the finite element method was used to model and analyze the free vibration and transient response of non-uniform thickness bi-directional functionally graded sandwich porous(BFGSP)skew plates.The whole BFGSP skew-plates is placed on a variable visco-elastic foundation(VEF)in the hygro-thermal environment and subjected to the blast load.The BFGSP skew-plate thickness is permitted to vary non-linearly over both the length and width of the skew-plate,thereby faithfully representing the real behavior of the structure itself.The analysis is based on a four-node planar quadrilateral element with eight degrees of freedom per node,which is approximated using Lagrange Q4 shape function and C1 level non-conforming Hermite shape function based on refined higher-order shear deformation plate theory.The forced vibration parameters of the non-uniform thickness BFGSP skew-plate are fully determined using Hamilton's principle and the Newmark-β direct integration technique.Accuracy of the calculation program is validated by comparing its numerical results with those from reputable sources.Furthermore,a thorough assessment is conducted to determine the impact of various parameters on the free and forced vibration responses of the non-uniform thickness BFGSP skew-plate.The findings of the paper may be used in the development of civil and military structures in situations that are prone to exceptional forces,such as explosions and impacts load.
查看更多>>摘要：To explore the penetration resistance of calcareous sand media,penetration tests have been conducted in the velocity range of 200-1000 m/s using conical-nosed projectiles with a diameter of 14.5 mm.Further,a pseudo fluid penetration model applicable to the penetration of rigid projectiles in sand media is established according to the approximate flow of compacted sand in the adjacent zone of penetration.The correlation between the impedance function of projectile-target interaction and the internal friction features of pseudo fluid is clarified,and the effects of sand density,cone angle of nose-shaped projectile,and dynamic hardness on the penetration depth are investigated.The results verify the feasibility,wide applicability,and much lower error(with respect to the experimental data)of the proposed model as compared to the Slepyan hydrodynamic model.
查看更多>>摘要：Dynamic analysis of the tethered satellite system(TSS)can provide a fundamental guideline to the evaluation of performance and robust design of the system examined.Uncertainties inherited with the parameters would induce unexpected variation of the response and deteriorate the reliability of the system.In this work,the effect of uncertain mass of the satellites on the deployment and retrieval dy-namics of the TSS is investigated.First the interval mode is employed to take the variation of mass of satellite into account in the processes of deployment and retrieval.Then,the Chebyshev interval method is used to obtain the lower and upper response bounds of the TSS.To achieve a smooth and reliable implementation of deployment and retrieval,the nonlinear programming based on the Gauss pseudo-spectral method is adopted to obtain optimal trajectory of tether velocity.Numerical results show that the uncertainties of mass of the satellites have a distinct influence on the response of tether tension in the processes of deployment and retrieval.
查看更多>>摘要：The integration method of exploding foil initiator system(EFIs)used to be researched to broaden its application range in military and aerospace in the last few decades.In order to lower the firing voltage below 1 kV,an integrated EFIs with enhanced energy efficiency was designed.Corresponding exploding foil initiator chips were fabricated in batch via micro electromechanical systems technology by inte-grating a unified foil,a flyer layer and a barrel on a glass substrate successively,meanwhile its package of the whole system was proposed at a volume of 2.194 cm3.The structural parameters were determined by predicted performance including flyer velocity,impact behavior and conduction property via the pro-posed theoretical models and the static electric field simulation.As expect,this integrated EFIs exhibited excellent functions,which could accelerate the flyer to a terminal velocity over 4 km/s and preeminently initiate HNS-IV pellet at a circuit of 0.24 μF/0.9 kV.Furthermore,the theoretical design,fabrication and performance test have been all included to validate the feasibility of this integrated EFIs that was beneficial for its commercial development in the future.
查看更多>>摘要：A differential game guidance scheme with obstacle avoidance,based on the formulation of a combined linear quadratic and norm-bounded differential game,is designed for a three-player engagement sce-nario,which includes a pursuer,an interceptor,and an evader.The confrontation between the players is divided into four phases(P1-P4)by introducing the switching time,and proposing different guidance strategies according to the phase where the static obstacle is located:the linear quadratic game method is employed to devise the guidance scheme for the energy optimization when the obstacle is located in the P1 and P3 stages;the norm-bounded differential game guidance strategy is presented to satisfy the acceleration constraint under the circumstance that the obstacle is located in the P2 and P4 phases.Furthermore,the radii of the static obstacle and the interceptor are taken as the design parameters to derive the combined guidance strategy through the dead-zone function,which guarantees that the pursuer avoids the static obstacle,and the interceptor,and attacks the evader.Finally,the nonlinear numerical simulations verify the performance of the game guidance strategy.
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