查看更多>>摘要：By considering the joint effects of the Kelvin-Helmholtz(KH)and Rayleigh-Taylor(RT)instabilities,this paper presents an interpretation of the wavy patterns that occur in explosive welding.It is assumed that the elasticity of the material at the interface effectively determines the wavelength,because explosive welding is basically a solid-state welding process.To this end,an analytical model of elastic hydrody-namic instabilities is proposed,and the most unstable mode is selected in the solid phase.Similar ap-proaches have been widely used to study the interfacial behavior of solid metals in high-energy-density physics.By comparing the experimental and theoretical results,it is concluded that thermal softening,which significantly reduces the shear modulus,is necessary and sufficient for successful welding.The thermal softening is verified by theoretical analysis of the increase in temperature due to the impacting and sliding of the flyer and base plates,and some experimental observations are qualitatively validated.In summary,the combined effect of the KH and RT instabilities in solids determines the wavy morphology,and our theoretical results are in good qualitative agreement with experimental and nu-merical observations.
查看更多>>摘要：Offboard active decoys(OADs)can effectively jam monopulse radars.However,for missiles approaching from a particular direction and distance,the OAD should be placed at a specific location,posing high requirements for timing and deployment.To improve the response speed and jamming effect,a cluster of OADs based on an unmanned surface vehicle(USV)is proposed.The formation of the cluster determines the effectiveness of jamming.First,based on the mechanism of OAD jamming,critical conditions are identified,and a method for assessing the jamming effect is proposed.Then,for the optimization of the cluster formation,a mathematical model is built,and a multi-tribe adaptive particle swarm optimization algorithm based on mutation strategy and Metropolis criterion(3M-APSO)is designed.Finally,the for-mation optimization problem is solved and analyzed using the 3M-APSO algorithm under specific sce-narios.The results show that the improved algorithm has a faster convergence rate and superior performance as compared to the standard Adaptive-PSO algorithm.Compared with a single OAD,the optimal formation of USV-OAD cluster effectively fills the blind area and maximizes the use of jamming resources.
查看更多>>摘要：Aiming at the practical application of Unmanned Underwater Vehicle(UUV)in underwater combat,this paper proposes a battlefield ambush scene with UUV considering ocean current.Firstly,by establishing these mathematical models of ocean current environment,target movement,and sonar detection,the probability calculation methods of single UUV searching target and multiple UUV cooperatively searching target are given respectively.Then,based on the Hybrid Quantum-behaved Particle Swarm Optimization(HQPSO)algorithm,the path with the highest target search probability is found.Finally,through simulation calculations,the influence of different UUV parameters and target parameters on the target search probability is analyzed,and the minimum number of UUVs that need to be deployed to complete the ambush task is demonstrated,and the optimal search path scheme is obtained.The method proposed in this paper provides a theoretical basis for the practical application of UUV in the future combat.
查看更多>>摘要：The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 mm.This study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic penetration.In the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/s.Severe erosion of the projectiles was observed during high-speed penetration of heteroge-neous targets,and apparent localized mushrooming occurred in the front nose of recovered projectiles.By examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration tests.Furthermore,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation mechanism.Finally,a model of high-speed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present study.Depending upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or hemispherical.Due to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.
查看更多>>摘要：This paper realizes the full-domain collaborative deployment of multiple interference sources of the global satellite navigation system(GNSS)and evaluates the deployment effect to enhance the ability to disturb the attacker and the capability to defend the GNSS during navigation countermeasures.Key evaluation indicators for the jamming effect of GNSS suppressive and deceptive jamming sources are first created,their evaluation models are built,and their detection procedures are sorted out,as the basis for determining the deployment principles.The principles for collaboratively deploying multi-jamming sources are developed to obtain the deployment structures(including the required number,structures in demand,and corresponding positions)of three single interference sources required by collaboratively deploying.Accordingly,simulation and hardware-in-loop testing results are presented to determine a rational configuration of the collaborative deployment of multi-jamming sources in the set situation and further realize the full-domain deployment of an interference network from ground,air to space.Varied evaluation indices for the deployment effect are finally developed to evaluate the deployment effect of the proposed configuration and further verify its reliability and rationality.
查看更多>>摘要：Taking CL-20(Hexanitrohexaazaisowurtzitane)-based aluminized explosives with high gurney energy as the research object,this research experimentally investigates the work capability of different aluminized explosive formulations when driving metal flyer plates in the denotation wave propagation direction.The research results showed that the formulations with 43 μm aluminum(Al)powder particles(The particle sizes of Al powder were in the range of 2～43 μm)exhibited the optimal performance in driving flyer plates along the denotation wave propagation direction.Compared to the formulations with Al powder 13 μm,the formulations with Al powder 2 μm delivered better performance in accelerating metal flyer plates in the early stage,which,however,turned to be poor in the later stage.The CL-20-based explosives containing 25％Al far under-performed those containing 15％Al.Based on the pro-posed quasi-isentropic hypothesis,relevant isentropy theories,and the functional relationship between detonation parameters and entropy as well as Al reaction degree,the characteristic lines of aluminized explosives in accelerating flyer plates were theoretically studied,a quasi-isentropic theoretical model for the aluminized explosive driving the flyer plate was built and the calculation methods for the variations of flyer plate velocity,Al reaction degree,and detonation product parameters with time and axial po-sitions were developed.The theoretical model built is verified by the experimental results of the CL-20-based aluminized explosive driving flyer plate.It was found that the model built could accurately calculate the variations of flyer plate velocity and Al reaction degree over time.In addition,how physical parameters including detonation product pressure and temperature varied with time and axial positions was identified.The action time of the positive pressure after the detonation of aluminized explosives was found prolonged and the downtrend of the temperature was slowed down and even reversed to a slight rise due to the aftereffect reaction between the Al powder and the detonation products.
查看更多>>摘要：RFID-based human activity recognition(HAR)attracts attention due to its convenience,non-invasiveness,and privacy protection.Existing RFID-based HAR methods use modeling,CNN,or LSTM to extract features effectively.Still,they have shortcomings:1)requiring complex hand-crafted data cleaning processes and 2)only addressing single-person activity recognition based on specific RF signals.To solve these problems,this paper proposes a novel device-free method based on Time-streaming Multiscale Transformer called TransTM.This model leverages the Transformer's powerful data fitting capabilities to take raw RFID RSSI data as input without pre-processing.Concretely,we propose a multiscale convolutional hybrid Transformer to capture behavioral features that recognizes single-human activities and human-to-human interactions.Compared with existing CNN-and LSTM-based methods,the Transformer-based method has more data fitting power,generalization,and scalability.Furthermore,using RF signals,our method achieves an excellent classification effect on human behavior-based classification tasks.Experimental results on the actual RFID datasets show that this model achieves a high average recognition accuracy(99.1％).The dataset we collected for detecting RFID-based indoor human activities will be published.
查看更多>>摘要：In order to improve the energy output consistency of 3,3'-diamino-4,4'-azoxyfurazan(DAAF)in the new insensitive booster and the safety and efficiency in the preparation process,a continuous preparation system of DAAF from synthesis to spherical coating was designed and established in this paper,which combined ultrasonic micromixing reaction with microdroplet globular template.In the rapid micro-mixing stage,the microfluidic mixing technology with ultrasonic was used to synergistically strengthen the uniform and rapid mass transfer mixing reaction between raw materials to ensure the uniformity of DAAF particle nucleation-growth,and to prepare high-quality DAAF crystals with uniform structure and morphology and concentrated particle size distribution.In the microdroplet globular template stage,the microfluidic droplet technology was used to form a droplet globular template with uniform size under the shear action of the continuous phase of the dispersed phase solution containing DAAF particles and binder.The size of the droplet template was controlled by adjusting the flow rate ratio between the continuous phase and the dispersed phase.In the droplet globular template,with the diffusion of the solvent in the dispersed phase droplets,the binder precipitates to coat the DAAF into a ball,forming a DAAF microsphere with high sphericity,narrow particle size distribution and good monodispersity.The problem of discontinuity and DAAF particle suspension in the process was solved,and the coating theory under this process was studied.DAAF was coated with different binder formulations of fluororubber(F2604),nitrocellulose(NC)and NC/glycidyl azide polymer(GAP),and the process verification and eval-uation of the system were carried out.The balling effects of large,medium and small droplet templates under different binder formulations were studied.The scanning electron microscope(SEM)results show that the three droplet templates under the three binder formulations exhibit good balling effect and narrow particle size distribution.The DAAF microspheres were characterized by powder X-ray diffraction(XRD),differential scanning calorimetry(DSC),thermo-gravimetric(TG)and sensitivity analyzer.The results showed that the crystal structure of DAAF did not change during the process,and the prepared DAAF microspheres had lower decomposition temperature and lower mechanical sensitivity than raw DAAF.The results of detonation parameters show that the coating of DAAF by using the above three binder formulations will not greatly reduce the energy output of DAAF,and has comparable detonation performance to raw DAAF.This study proves an efficient and safe continuous system from synthesis to spherical coating modification of explosives,which provides a new way for the continuous,safe and efficient preparation of spherical explosives.
查看更多>>摘要：The coupling effect of heat absorption and release exists in the thermal decomposition of a few chemical materials.However,the impact of the above coupling on thermal hazard assessment is not considered in the literature studies.In this work,nitroguanidine(NQ)and 1,3,5-trinitro-1,3,5-triazine(RDX)are selected as representative materials to explore the influence of the coupling effect on the thermal hazard assessment of chemical materials.The linear heating experiments of NQ and RDX are carried out by a microcalorimeter and synchronous thermal analyser.The thermal decomposition curves are decoupled by advanced thermokinetics software.The thermal decomposition and kinetic parameters before and after decoupling are calculated.The results of TG experiment show that both NQ and RDX began to lose mass during the endothermic stage.The endothermic melting and exothermic decomposition of NQand RDX are coupled within this stage.The coupling effect has different degrees of influence on its initial decomposition temperature and safety parameters.Compared with the parameters in the coupling state,the initial decomposition temperature and adiabatic induction period after decoupling decrease.The self-accelerating decomposition temperature increases,and internal thermal runaway time decreases.In the thermal hazard assessment of chemical materials with coupling effects,the calculated parameters after decoupling should be taken as an important safety index.
查看更多>>摘要：2,4-dinitroanisole(DNAN)is a good replacement for 2,4,6-trinitrotoluene(TNT)in melt-cast explosives due to its superior insensitivity.With the increasing use of DNAN-based melt-cast explosives,the pre-diction of reaction violence and hazard assessment of the explosives subjected to shock is of great sig-nificance.This study investigated the shock initiation characteristics for a DNAN-based melt-cast explosive,DHFA,using the one-dimensional Lagrangian apparatus.The embedded manganin gauges in the apparatus record the pressure histories at four Lagrangian positions and show that shock-to-detonation transition in DHFA needs a high input shock pressure.The experimental data are analyzed to calibrate the Ignition and Growth model.The calibration is performed using an objective function based on both pressure history and the arrival time of shock.Good agreement between experimental and calculated pressure histories indicates the high accuracy of the calibrated parameters with the optimi-zation method.
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