bluuebunny/crossref_metadata_2025 huggingface dataset:
The fluid-based structure for human body impact protection
Authors: Pacek Dawid , Gieleta Roman
Published: July 2020

The article presents results of research and analysis of the currently conducted project aiming at the development of a flexible impact protector. The need to carry out the work results from the necessity of the ever-wider and more frequent use of body armours, including those resistant to blunt impacts, by the army, police and other public security services as well as a demand for impact protective elements in the civilian market. In the first part, the assumptions regarding the protective coverage under development and the origin of the topic with reference to earlier work on the use of non-Newtonian fluids in body armours are indicated. Next, the requirements for impact protectors and a review of the state of the art in the scope of this type of protective elements are presented. Finally, the results of the impact tests of armour samples are shown.
Experimental study on ignition reaction evolution of pressed PBX-B in long thick wall cylinder confinement
Authors: Qiu T , Wen S , Li T , Hu H , Fu H , Shang H
Published: July 2020

In order to explore the possibility of deflagration to detonation transition (DDT) of pressed HMX-based PBX inside long thick wall steel tube initiated by ignition composition, a new experiment apparatus was designed based on traditional DDT tube, in which strength at specific locations enhanced, and multichannel PDV probes and high speed photography were used to diagnose the expansion process and rupture characteristics of tube wall. Compared with the results initiated by detonator in the same explosives and confinement, the reaction durations of detonation and ignition differed by orders of magnitude; the pressure evolution measured by tube wall velocities, and the propagation process of tube wall movement were significantly different in two reaction. Analysis shows that the convective flow of reaction products along the seam between tube wall and explosives, high temperature and pressure, dominated the reaction evolution of PBX-B initiated by ignition composition under strong confinement, and appeared as laminar burning on explosive surface and structural response of confinement. There is no reaction activated in explosive bulk by the ramp wave caused by upper stream non shock initiation reaction, least of all DDT.
A study of the ballistic protection mechanism of two kinds of structure against 7.62×54 mm ball ammunition
Authors: Li G F , Yang L , Xu H , Guo Y Y , Wang Zh W , Wang L , Miao Ch , Wu Y Ch
Published: July 2020

In this work, the protection mechanism of two kinds of structure was studied using 7.62×54 mm ball ammunition, which still played an important role in the threat spectrum of military vehicles. The tested one structure is consisted with silicon carbide (SiC) ceramic and Ultra-High Molecular Weight Polyethylene (UHMWPE), and the other is UHMWPE only. Silicon carbide ceramic was chose as strike face material for the reason of its widely using in Light Weight Vehicle Armor. And the UHMWPE was widely used for personnel body armor, because of its high protection ability and low density. These two kinds of structure were tested with 7.62×54 mm ball ammunition using a 7.62 mm powder gun launching system. After the ballistic experiment, the target plate was evaluated, and the residual steel core was recovered and measured. It was found that the main effect of ceramic strike face was eroding the steel core, rather than breaking it in the scene of defeating AP round ammunition. Otherwise, there is a critical thickness with the ceramic strike face to erode the steel core in the ceramic/UHMWPE combination, for the reason of the presence of two intermediate parts, the jacket and lead filler, between the core and ceramic target. Furthermore, compared to the ceramic/UHMWPE structure, single UHMWPE laminate is more effective, because that is strong enough to mushroom the core and absorb the energy.
Simulation analysis of the effect of conical cap on the piercing performance of projectile
Authors: Niu G J , Shi X H , Li J C , Qian L X , Yu C X
Published: July 2020

To study on the effect of conical cap on the piercing performance of projectile( Φ 150mm) when penetrating three-interval-layer steel target ( target thickness: 20mm+20mm+20mm, the center of distance between adjacent targets is 1.5m ), the FEA model of penetrating performance of the projectile with conical cap was built by using Ls-dyna, and the attitude change law, velocity change law and impacting acceleration change law of projectile in the process of piercing the targets were analyzed under the different impact velocity(500m/s, 600m/s, 700m/s, 800m/s) and impact angle(0°, 25°, 50°) condition. The simulation results show that: with the increase of impact velocity and impact angle, the time of the conical cap separating from the head of projectile and breaking is earlier, and the breakage of the cap is also more severity. Under the same impact angle and different impact velocity condition, the maximum axial acceleration variation of projectile penetrating into each target is inconsistent, which is closely related to the separation of the cap from the projectile and the breaking of the cap. After the cap separating from the head of projectile, the cap will impact on the target firstly, which can reduce the axial acceleration when the projectile penetrates the target. Under the same impact velocity condition, the residual velocity of the projectile decreased with the increase of impact angle; and under the same impact angle condition, the velocity change after the projectile penetrates the target gradually decreases with the increase of the impact velocity of projectile. The amount of kinetic energy change of projectile increases with the increase of impact velocity of the projectile, that is to say, the higher of the impact velocity, the more of the kinetic energy loss in process of projectile penetrating target.
Dynamic mechanical response and weldability of high strength 7A62 aluminum alloy
Authors: Zhou G X , Lang Y J , Du X Zh , Mao H , Li J B , Wang Sh , Qiao L , Cai H
Published: July 2020

The 7A62 as one kind of Al-Zn-Mg alloys is the highest strength weldable aluminum alloy currently. Plates and forgings of 7A62 alloy have been widely used in the defense system and main bearing parts of special vehicles. The microstructure, dynamic mechanical response and weldability of 7A62 aluminum alloy were investigated by OM, TEM, SHTB, DSC, microhardness and other tests. The morphology and mechanical test results showed that the 7A62 aluminum alloy strengthened by trans-scale precipitates had high strength, high hardness and good plastic toughness. The mechanical responses of the 7A62 aluminum alloy were found to be strain-rate sensitive and the dynamic response behavior was significantly higher than that of the 7A52 aluminum alloy through the SHTB test. In addition, for the as-welded 7A62 the tensile strength reached a scope of 260 MPa-305 MPa, which is considerably higher than the tensile properties reported when using ER5356. Because the weld of 7A62 alloy was free of macroscopic imperfections. The grains were highly equiaxed and homogeneous throughout the melting zone, showing smooth grain boundaries. Compared with 7A52, the lower melting point, low thermal enthalpy and low specific heat capacity of 7A62 alloy are more conducive to weld performed.
Investigation on formation process of a Ta-based dual phase alloy EFP liner
Authors: Hu X B , Wang C T , He Y , He Y , Guo Z P , Ma Y
Published: July 2020

Explosively formed projectile (EFP) has advantages of insensitive to the height of explosion, small interference from reactive armor and large penetration diameter. In this paper, a Ta based dual phase alloy was employed as the charge liner material. The software AUTODYN was used to simulate the formation of EFP under the conditions of different curvature, liner thickness and curvature radius. The following conclusions were obtained:(1), the ratio of length/diameter of EFP decreases with increase of liner thickness.(2) The liner with unequal thickness was proposed, the liner thickness is reduced from the top along the generatrix. The formed EFP from such liner has higher length/diameter ratio, compared to liner with the uniform thickness and the same internal curvature radius. (3) The formed EFP of Ta-based alloy liner could penetrate steel target, the chemical reaction caused by residual mass of EFP could release a large amount of chemical energy.
Study on the energy release rule of sniper projectile penetrating soft protective target
Authors: Li J M , Yan W M , Dong F D , Qu Y J
Published: July 2020

In order to investigate the penetrating mechanism of one sniper bullet against the gelatin target with soft armor under the condition of low speed, using gelatin as the imitation of biological targets, the energy release and transfer law were paid more attention. First of all the ultimate penetration velocity of the sniper projectile penetrating soft protection was carried out, with the ultimate penetration velocity was obtained, experiments and numerical simulation were carried out on the impact of the sniper projectile to soft protective gelatin below the velocity. The simulation results and test results were compared with the sniper projectile deformation and penetration of soft protective layer, gelatin bulging size, verified the accuracy of the numerical simulation. Thus further analysis with the result of numerical simulation, the stress, energy transfer and energy changes of soft protective gelatin penetrated by sniper projectile under non-penetrating conditions were analyzed, and the absorb energy law and the energy dissipation law of soft protective and gelatin in the process were obtained. The results showed that the main reason for the energy dissipation was bullet deformation. Under direct penetrating conditions, the energy of soft protective and gelatin increased with the increase of velocity, while the energy dissipation of sniper projectile also increased. The larger the penetration angle, the energy absorption of gelatin decreases with the increase of the penetration angle, energy dissipation of sniper projectile and energy absorption of soft protective were increased. The results can provide technical guidance for bullet design and individual soldier protection design.
The Research on Dilute Polymer Solutions Cavitating Flow through Venturi and Cavitation Induced Vibration Acceleration Characteristics
Authors: Yu L F , Zuo Zh G , Li L , Lu X X , Wang Zh X
Published: July 2020

The present work deals with an original study of vibration signals induced by unsteady cavitating flow of polymer solutions through a Venturi section. A blow-down Venturi experimental rig was utilized to generate cavitation in polymer solutions. The cavitating flows through the Venturi tunnel were captured by high-speed photography. The accelerometer was mounted on the upper wall of Venturi tunnel to gather the cavitation induced vibration accelerations. Results show that the morphologies of cavitation bubbles in polymer solutions are different from that of filtered water. Cavitation bubbles with bigger size and less number are observed in polymer solutions cavitating flow. It is observed that the peak value, kurtosis and the root-mean-square of vibration acceleration increase in polymer solutions. Meanwhile, a broader frequency band and a higher power spectral density level is observed in spectrogram of polymer solutions. It is inferred that the collapse of the vaporous cavity clouds with high void fraction developed in polymer solutions is responsible for this alteration.
Numerical simulation on continuous penetrating/blasting behavior of multi-projectiles against concrete target
Authors: Wang S P , Tan J Z , Su C H , Zheng Y F
Published: July 2020

Deep digger weapon system uses continuous kinetic energy and chemical energy of the penetrating/blasting projectiles to dig the concrete target. In the present paper, numerical simulations are conducted to study the continuous penetrating/blasting effects of multi-projectiles against concrete target. The simulation results show the KE penetration produces the crushing and rupturing zone, providing conditions for subsequent damage due to explosions. Then, the explosion further increases the diameters of the crushing and rupture area, and the cracks propagate inside the concrete target. The second penetration and blast further increase the depth and the damage area, achieving deep digger behavior to the concrete target. However, the throwing effect of secondary penetration/blast is slightly weaker than that of first one. Moreover, the simulation also shows the continuous penetrating/blasting behavior is influenced markedly by impact velocity.
Study on the air shock wave effect and engineering algorithm in the tunnel after the damage of protective door under different explosion conditions
Authors: Liu F , He X , Sun G J , Ren X J , Wang X , Chen L
Published: July 2020

In this study, the effect of an air shock wave discharged into a tunnel when an explosion occurs in front of a protective door was experimentally examined and the actual air shock waveforms in the tunnels with and without a protective door were analyzed and compared. It was found that both the waveform structure and the characteristic parameters of the air shock wave, such as the peak and the action time, were significantly changed after a protective door was installed. Moreover, by combing with dimensional analysis results, some detailed engineering algorithms of the residual shock wave effect, namely, the engineering algorithm of the overpressure peak of the residual shock wave in the tunnel, the equivalent explosive coefficient in the case without protective door, and the shock wave reduction coefficient with and without a protective door, were derived.
Numerical study on anti-penetration performance of metal packaged ceramic structure
Authors: Sun X , Tian Ch , Sun Q T , An X Y , Dong Y X
Published: July 2020

The anti-penetration performance of traditional layered ceramic composite structure is limited by the properties of the materials and the layered structure is difficult to resist the multi-hitting. Considering these two characteristics of the layered structure, the lightweight metal packaged ceramic composite structure is investigated to improve the anti-penetration performance by experiments and simulation. The finite element model was verified by ballistic range test, so it can well simulate the process of the penetrating and the result has high reliability. The metal packaged ceramic composite structure exhibits 50% higher anti-penetration performance than that of the equivalent titanium alloy plate and 20% higher than the layered ceramic composite structure. In metal packaged ceramic composite structure, the metal packaging interlayer can reduce the projectile energy by 55% and plays the most important role in the anti-penetration process. It is also found that the metal packaging increases the erosion of the projectile by confining the ceramic material and restricting the broken ceramic debris flying out. Thus, it can improve the anti-penetration performance of the composite structure. Moreover, metal packaging can also limit the propagation of cracks in the ceramics, thereby improving the ability of the composite structure to resist the multi-hitting. The metal packaged ceramic composite structure is less affected by the projectile penetration position.
Time-frequency characteristics of the strain signal of the metal shell under internal explosion
Authors: Wei D , Gan YD , Zhang Q M , Su J J , Long R R , Chen P W , Liang H Z
Published: July 2020

In this paper, the empirical mode decomposition-Hilbert Huang transform (EMD-HHT) was used to characterize the strain signal within metal cylindrical shell structure under internal blast loading. The received vibration frequencies of signal were closely consistent with FT characterization results. Through the EMD-HHT, instantaneous energy spectrum, marginal energy spectrum and Hilbert energy spectrum were determined, and these reflected the change in trend of signal energy in time domain, frequency domain, and time-frequency domain, showing the instantaneity and locality of explosion signal. The frequency components of the signal at any time were also determined, which proved that signals generated by the metal shell were the result of the superposition of different frequency signals under internal blast loading. This paper explains more clearly the time and frequency characteristics of blast signal, providing the theoretical basis for the study of antiknock in structures.
Study on jet forming characteristics of shaped charge with truncated-liner structure
Authors: Ji L , Zu X D , Xu M W , Wang P , Wang G C
Published: July 2020

In order to verify the jet forming characteristics of the shaped charge with a truncated-liner, numerical simulation and X-ray experimental research were carried out. The behavior of the truncated-liner and the top velocity, diameter and morphology of the jet were obtained, and the outcomes were compared with the characteristics of the jet formed by the traditional shaped charge. The results show that the numerical simulations are almost consistent with the results obtained by the X-ray test. The morphology of the two is nearly the same, and the data deviation is less than 6%. The truncated-liner can effectively improve the velocity of the jet head, which can reach more than 10km/s by structural optimization. In addition, the truncated-liner can decrease the diameter of the slug, meanwhile, increase the length of the jet and the quality utilization of the liner.
Effect of ultrasonic-electric surface modification on metal material
Authors: Liu D , Zhao J Z , Gao Y , Liu J B , Shen Y L , Meng C
Published: July 2020

With the demand for the materials are increasing in the field of military and civilian application with each passing day, an ultrasonic-electric surface modification treatment was employed to improve the surface properties of metal material with different heat-treated conditions. The surface properties of the specimens after conventional cutting and ultrasonic-electric surface modification treatment were characterized, respectively. A grain refinement layer was formed on the surface of different heat-treated specimens after ultrasonic-electric surface modification treatments. The average grain size on the top surface was refined into the submicrometer or nanometers scale. This is caused mainly by two aspects: one is the accumulation of initial tiny particles during deformation; the other is that the ferrite is smashed into pieces due to micro-fatigue damage. Moreover, it was found out the specimens after ultrasonic-electric surface modification treatment had shown the optimal surface properties and friction-wear properties.
Effect of interfacial microstructure and mechanical properties of steel/copper casting bimetal by active protective agent
Authors: Kang Y Y , Zhang G W , Xu H , Niu J W
Published: July 2020

This article study on the 45#steel/high-lead tin bronze bimetal that were prepared by solid-liquid casting. Effect of interfacial microstructure and mechanical properties by active protective agents were investigated including Na2B4O7, H3BO3, AlPO3 and NaF. The results show that the effect of the single component active protective agent on the binding interface is Na2B4O7>H3BO3>AlPO3>NaF. The multiple components optimal ratio of the active protective agent is Na2B4O7:H3BO3:AlPO3:NaF=60:25:10:5(wt.%)after mixing, which make the interfacial bonding strength reach 168.4 MPa and diffusion distance of the Fe/Cu interface attain 12.4μm. When the thickness of Na2B4O7 is lower than 60%, FeP transition layer is precipitated at the interface, which depress the interface shear strength.
Quantitative study on SLIP model parameters based on multi-rigid-body dynamics
Authors: Han D L , Zhang R , Wen L G , Dong W C , Li T , Jiang L , Li J Q
Published: July 2020

The spring-loaded inverted pendulum (SLIP) model is often used to describe the interaction between hindlimbs and the ground during the locomotion of animals or humans. This model is frequently adopted to qualitatively explain the flexible deformation of legs and feet and the trajectory change of center of mass (COM), caused by the impact between hindlimbs and the ground. However, such research cannot provide precise reference on the structural parameters, spring and damper selections and their collocations for the design of robotic legs and feet. In this study, an SLIP model was established on the multi-rigid-body dynamics software Adams. The main influence factors on the SLIP model were determined by targeting at the touchdown-phase duration of animal or human locomotion. Then the main factors were quantitatively studied by combining a multivariate orthogonal polynomial regression design. Simulation showed that spring stiffness coefficient (Z1), damping coefficient (Z2), swing angular velocity (Z3) and initial swing position (Z4) were the main factors affecting the trajectory of COM. Multivariate orthogonal polynomial regression analyses showed the relationship between the COM fluctuation (y) and the main factors satisfied the following equation: y = 217.33 - 16.25 Z1 + 0.3975 Z12 - 194.6 Z2 - 0.953 Z3 + 0.755 Z4 + 8.1 Z1 Z2 + 0.043 Z1 Z3 + 0.6 Z2 Z3 - 0.0055 Z3 Z4.
An improved algorithm for target trajectory prediction in the active protection system based on converted measurement Kalman filter
Authors: Wang J L , Song H P , Chen R M , Zhang Y N
Published: July 2020

Fast and accurate prediction of the trajectory is the prerequisite for the successful interception of the incoming target by the active protection system (APS) of armoured vehicles. The traditional least-squares algorithm is susceptible to large errors in the initial stage of the tracking process, and the prediction of interception points converges slowly. This paper proposes an interception point prediction algorithm that combines the Kalman filter and least-squares estimation. By dynamically determining the convergence of the least-squares prediction, a converted measurement Kalman filter is used in the initial tracking stage to obtain higher prediction accuracy of the interception point. Simulations are performed in the scenario of the interception process of the APS. The results prove that the algorithm can effectively accelerate the convergence of the interception point prediction process.
Millimeter-wave radar image analysis for the traffic sensing
Authors: Wu H M , Qi F , Wang J K , Wang Y
Published: July 2020

Millimeter-wave(MMW) radar sensing is one of the most promising technologies to provide safe navigation for autonomous vehicles due to its expected high-resolution imaging capability However, driverless cars have higher request for different environment and light conditions. Therefore, millimetre-wave imaging is of paramount importance for complex load scenario. In this paper, we have built models of pavement pits and bulges and analysed their with differences ways of antennas. A comparison of the imaging performance of experimental systems operating at a MMW radar and a Lidar is presented with the analysis of features for initial image interpretation Experimental images of the complex road surface are made by a 94GHz frequency-modulated continuous-wave (FMCW) radar technique with 3mm wavelength.
Dynamic Analysis and State Estimation of Wearable Extra Robotic Limbs for Physical Assistance and Load Reduction in Missile-mounting
Authors: Li H B , Guan X R , Li Zh , Zou K F , Shi Y F , Xia X H , Guan L Sh , Zhu M , Zhang L F
Published: July 2020

In order to fully exploit the potential in the field of human augmentation, to help the wearer fulfil the task of physical assistance and load reduction, a new type of wearable robot that can perform tasks in close coordination with the wearer and assist the wearer with extra arms and legs secured around the body is presented. The system, named extra auxiliary robotic upper limbs-lower extremity exoskeleton (EARUL-LEE), consists of two additional robotic arms worn through a backpack around the upper body and two exoskeleton legs attached to the lower body tightly. The EARUL-LEE can assist the wearer by holding objects, lifting weights and streamlining the execution of a task. If the EARUL-LEE performs movements closely coordinated with the wearer and exhibits human-like dynamics, it might be incorporated into the body representation and perceived as parts of the wearer’s body. The EARUL-LEE can work closely with the soldier by supporting and securing the human body when lifting a missile, and more. Although the EARUL-LEE control performance is hindered by unpredictable disturbances due to involuntary motions of the soldier, which include postural sway and physiological tremor, the dynamic analysis the human-EARUL-LEE hybrid system include the models of human-induced disturbance based on biomechanics literature, extra auxiliary robotic upper limbs and lower extremity exoskeleton and state estimation method based on an orthogonal least squares for the EARUL-LEE, aimed to perform the missile-mounting for aircrafts on the ground or decks in tight coordination with the soldier as a close co-worker are presented here. Via the current study, the orthogonal least squares (OLS) filter is constructed to estimate the state and its performance is evaluated in terms of error covariance. The simulation results show that the orthogonal least squares filter can tracking desired trajectory and its convergence is better than without any filters. The results can be used to control the EARUL-LEE accordingly with the used end effectors and provide a method for improving the accuracy and stabilizing the human body and the EARUL-LEE.
A study of blockchain technology development and military application prospects
Authors: Zhu Y , Zhang X , Ju Zh Y , Wang Ch Ch
Published: July 2020

Once blockchain technology is successfully applied, it will certainly trigger revolutionary changes in the military development and combat mode, which are beyond the traditional military command and management scope. In the future, blockchain technology, by combining with military artificial intelligence, Internet of things, cloud computing and big data, will have priority to be applied in military management, support, security and even command. It is of great significance to excavate the military application potential of blockchain technology and scientifically predict its impact and influence on the military field, so as to improve the combat effectiveness of the army and promote its transformation and development.
A method of simulated motion tracking control based on lyapunov vector field
Authors: Huang D G , Sun J , Liu D
Published: July 2020

For the problem of irregular formation in aircraft cluster planning, this paper proposes a simulated motion tracking control of cluster planning. The simulated motion is the expected motion trajectory for one aircraft provided by the planning system. Using Lyapunov vector field guidance and omnidirectional speed control method, this paper realizes the tracking control of the simulated motion for the aircraft. The simulation results demonstrate that the proposed method can realize the tracking control of the simulated motion and achieve the expected effect, which lays a foundation for the cluster planning.
Research on anti UAV swarm system in prevention of the important place
Authors: Hao Q , Li W Z , Qiu Z K , Zhang J L
Published: July 2020

With the rapid development of artificial intelligence (AI) technology, UAV swarm has become possible. It has become an urgent problem that how to realize the effective counteraction to the UAV swarm in the important target security defence, or in the important place prevention in the war. In this paper, by analysing the development status and combat characteristics of UAV swarm, as well as existing anti-UAV technology, the countermeasures and technologies applicable to UAV swarm is combed. Then the further construction of anti UAV swarm control system is built to realize the effective anti UAV swarm in the key prevention and control.
Research on 100kJ pulsed power module for electromagnetic launch
Authors: Zhang Y Z , Li Y M , Yang L , Zhao B
Published: July 2020

With the development of the electromagnetic launch (EML) technology, the requirement of the pulsed power supply is increasing. Capacitor-based pulsed power supply usually consists of several hundred kilojoule level pulsed power modules (PPM) in parallel. The PPM for EML system requires the capability of continuous working ability, high energy storage density and high peak current. A 100kJ compact PPM with rated operational voltage 10kV was designed, the output peak current was about 90kA, and the continuous working ability was 6 times per minute. The design and selection of main components in the module were simulated. At last, the PPM was used in the testing of the coil gun. It provides transient pulse current test platform and technical support for the subsequent construction of megajoule level pulsed power supply.
A Non-Lethal Electric Shock Generator with Wireless Control Function
Authors: Yang Chunxia , Wan Gang , Liu Jian , Zhang Wenxuan , Tian Hui , Li Zhenxiao , Jin Yong , Li Baoming
Published: July 2020

A Non-lethal electric shock generator is presented and tested. This non-lethal electric shock generator without trail wires, is different from Taser series stun guns or Husha TX series electric shock guns which all have trail wires. And the intensity of electric shock can be adjusted by remote control device according to the status of the target. This no-lethal electric shock generator extends the range of application of electric shock from about 9 meters to 30 meters. The manner of using electric shocks of single intensity is also changed by telecontrol adjustment. It can provide electric shocks of different intensities for different conditions, such as different distances from special electrodes to targets, different targets with different clothes and different height or weight. Basic functions of the non-lethal electric shock generator are tested. Results show that the prototype projectile can be launched from a barrel stably, and the flight range is over 30 meters. When it captured the target, it can be triggered via the telecontrol adjustment. The prototype projectile can support a series of pulses at a rate of 20 r/s with the peak voltage of 30kV.
Numerical study on aerodynamic characteristics of rotating missile launched vertically under strong transverse wind
Authors: Xu Yihang , Chen Shaosong , Zhou Hang
Published: July 2020

Numerical simulation of low speed high Angle of attack rotating missile was carried out by using different turbulence models, and the numerical simulation results were compared with the experimental results. The results show that the SST-DDES model can well simulate the aerodynamic characteristics of the rotating missile at low speed and high Angle of attack. Under the condition of low speed and high Angle of attack, the difference of the lateral force produced by the missile’s tail fin is small, and the variation of the total missile lateral force mainly depends on the variation of the projectile body lateral force. When the Angle of attack increases from 40.1° to 60.1°, the direction of the missile’s lateral force changes. This is because with the increase of the Angle of attack, the fluid velocity perpendicular to the projectile increases, resulting in the interaction and fusion of asymmetric vortexes on the leeward side, resulting in the change of lateral force direction.
Fault diagnosis of missile refrigeration system based on the belief rule base
Authors: Liu Zh Zh , Xiao M Q , Zhu H Z , Li J F
Published: July 2020

In order to diagnose the fault of missile refrigeration system, aiming at the complex nonlinear relationship between the causes and symptoms of missile refrigeration system, we propose a method for fault diagnosis of refrigeration system based on the belief rule base (BRB). The method can use quantitative and qualitative information to establish a nonlinear model between input and output, and diagnose the system through optimization model. BRB can make comprehensive use of expert knowledge and historical data, which is more suitable for fault diagnosis. In order to address the problem of parameter inaccuracy in the initial BRB given by experts, combined with the information type of the failure of the refrigeration system, we use the chaotic particle swarm optimization learning model to train the initial BRB parameters given by experts to achieve the diagnosis of refrigeration faults in the refrigeration system. The experimental results show that the BRB after parameter optimization can better identify the state of the missile system and improve the accuracy of fault diagnosis.
Research on ignition process of micro solid rocket motor in vacuum
Authors: Wen J J , Deng H Y , Zheng K , Liao W H
Published: July 2020

Aiming at the ignition process of micro solid rocket motor in space, the effects of different structure on the ignition gas filling process were investigated by means of experiment and numerical simulation. By establishing numerical simulation model and the mass flow rate model of ignition chamber for black powder, pressure establishment process was researched under different parameters (the igniter quantity is 0.2g and 0.5g, outlet size of ignition chamber is Φ4mm and Φ7mm respectively). Meanwhile, the ignition experiment was conducted in vacuum (the ambient pressure is 16Pa) that pressure curve and vacuum plume phenomenon were obtained. The results indicate that simulation value of pressure establishing process relatively consistent with experimental one, so the mass flow rate model of ignition chamber for the black powder is evidently efficient. Therefore, the numerical method proposed in this paper can provide a theoretical basis for further research on the ignition process of micro solid rocket motor.
Solution of motion parameters of natural fragments based on monte carlo subdivision projection simulation
Authors: Liu X Y , Zhan R J , Li Y L
Published: July 2020

In order to get the average windward area of natural fragments of non-metallic materials more accurately and efficiently, and to further simulate the motion parameters, a simulation calculation model of the average windward area of natural fragments is established based on the Monte Carlo subdivision projection method. By the finite element modeling, coordinate translation, random rotation, plane projection and triangulation, the average windward area of natural fragments with arbitrary irregular shape is simulated. Then, based on aerodynamics, the dispersion model of natural fragments is established. The simulation results of the two-dimensional trajectory and the farthest distance of natural fragments are obtained by Runge-Kutta method and cubic spline interpolation, which are compared with the empirical formula of the average windward area of regular fragments. The results show that the value by the Monte Carlo split projection simulation are more consistent with the experimental value, compared with the empirical formula of the windward area of spherical fragment, cube fragment, short cylinder fragment, cylinder fragment, rhombus fragment and cuboid fragment. The error of the farthest distance is between 13% and 25%. It is proved that the result of the average windward area based on Monte Carlo Subdivision Projection Simulation is more suitable for solving the dispersion model of natural fragments of low-speed and non-metallic materials.
Numerical study on hydroballistic and flow field characteristics of projectiles ejected from a vertical launch system underwater
Authors: Xu H , Wei Y J
Published: July 2020

A numerical simulation was performed to study the hydroballistic and flow field characteristics of projectiles launched successively underwater through a vertical launch system. The evolution of the projectile turbulence wake flow and its influence on the trajectory of other projectiles were studied under various launcher transport speed and launch sequence. Two major vortex structures are discovered in the wake: the vortex ring and the counter-rotating vortex pair. The vortex rings are generated when the projectile angle of attack is relatively small, and the counter-rotating vortex pairs are generated when it becomes larger. These large scale vortices are highly directional before breaking up. The counter-rotating vortex pairs can impose significant influence on projectile attitude upon wake vortex encounter. The outcome of such an encounter is highly unpredictable due to the nonlinear nature of these vortices. Projectiles launched with a higher platform transport speed are more likely to be affected due to the strong counter-rotating vortex pairs generated by previous projectiles with a high angle of attack.
The combination of numerical simulation of strong dynamic loading effects and big data technologies
Authors: Deng G Q
Published: July 2020

Near the zones of impact, explosion and other strong dynamic loading, the stress peak is very high, action time is very short, and the medium distortion is very large. The involving scientific problems are strong nonlinearity, multi-physics coupling, and so on. Numerical simulation and experimental investigation are mainly research method for these effects. However, the difficulty of the numerical simulation is at the top of the pyramid of scientific computation, and the noise, simulation is not true, is the biggest trouble currently existed. The emergence of big data technologies provides a feasible way to solve the current dilemma and realize accurate numerical simulation. Combination the big data technologies, such as data acquisition, infrastructure, data mining, statistical analysis, model prediction and so on, the numerical simulation of strong dynamic load effects is possible to achieve precision by automation of solver, intelligence of material state description library, expertization of human-computer interaction interface, credibility of simulation result data, virtual reality of simulation image. The combination of big data technology and numerical simulation will be the key to research the strong dynamic load effects, which would realize the transformation from numerical simulation to digital experiment, and the noise, simulation is not true, would be disappear completely.
Modelling and Production of artillery firing-tables: case-study
Authors: Mady Mohamed , Khalil Mostafa , Yehia Mahmoud
Published: July 2020

Projectile firing accuracy is an important artillery issue to increase killing probability with minimum number of rounds per target. This can be achieved through constructing a firing-table (FT) with both standard and non-standard conditions. Therefore, lot of rounds need to be shoot for different target ranges as well as meteorological conditions to increase such firing accuracy. Developing an accurate computational FT prior to shoots has the advantages of minimizing the cost and providing preliminary prediction of dispersion. In this study, a computational FT algorithm has been proposed based on the modified-point-mass projectile trajectory model for solving the ballistics problem. A flow-chart is proposed to illustrate the FT production levels and the corresponding procedures. A case study for 155mm-M107-HE projectile is utilized. In order to validate the proposed algorithm, a comparison has been implemented with results obtained from the well-known commercial package PRODAS. Finally, based on real firing data available including the corresponding meteorological conditions, a provisional firing table has been developed.
Research on explosive dust space ventilation scheme based on CFD simulation
Authors: Wang D , Jing Q , Qian X M , Yuan M Q , Liu S Q
Published: July 2020

Aluminum powder with high explosive sensitivity, strong detonation performance and low price has become the first choice fuel for fuel air explosives. Design three types of exhaust schemes for specific powder operation spaces, and use CFD simulation technology to study the flow field and dust removal characteristics of the three schemes. The results show that the bottom ventilation scheme has the best dust removal effect, the characteristic time of dust removal is 9.4s, and the maximum dust concentration is 85g/m3. And the characteristic flow field range of the bottom exhaust scheme is the smallest (4.12m×3.05m), which indicates bottom scheme has the least disturbance to the spatial flow field, so this scheme should be selected for ventilation and dust removal design. In addition, the function relationship between the wind pressure and the characteristic dust removal time is obtained by setting different wind pressures, which provides a basis for the design of the graded ventilation dust removal side according to the design.
A target detection algorithm based on gray distribution characteristics
Authors: Sun G B , Fan Q , Zou E B
Published: July 2020

The two-dimensional distribution of gray scale is an important feature of image target, but there is no effective description method for the two-dimensional distribution of gray scale. To solve this problem, a GRD operator is proposed to describe the two-dimensional distribution of gray scale. The design model and calculation steps of GRD operator are discussed. The experimental results of image data show that GRD operator is very effective to describe the features of image target. GRD operator can effectively detect and extract the target, which has a wide range of application value in image target detection, tracking, recognition and so on.
A Human Target Infrared Image Segmentation Approach Based on Convolution Neural Network
Authors: Liu Chao , Hu Qingping , Yao Yuan
Published: July 2020

In order to effectively segment the human target under complex background constraints, we present an infrared target segmentation method based on deep convolution neural network, and proposes the loss function based on the intersection-over-union for network optimization. Firstly, we design the network architecture which consists of a contracting path to capture the feature content and a symmetric expanding path that enables precise localization. And then rely on the powerful data amplification technology to effectively train the available sample data. The experimental results show that the network can make full use of the prior information of the data to study the characteristics of the human target, which can use less training data for end-to-end training in the human body target infrared image segmentation. And segmentation effect is superior to the traditional image segmentation algorithm. In addition, the network segmentation speed is very fast, 320 ×256 size image segmentation takes less than 0.2 seconds, to meet the human body target image segmentation of the effectiveness and real-time needs.
Modelling conditional probabilities with Riemann-Theta Boltzmann Machines
Authors: Carrazza Stefano , Krefl Daniel , Papaluca Andrea
Published: July 2020

The probability density function for the visible sector of a Riemann-Theta Boltzmann machine can be taken conditional on a subset of the visible units. We derive that the corresponding conditional density function is given by a reparameterization of the Riemann-Theta Boltzmann machine modelling the original probability density function. Therefore the conditional densities can be directly inferred from the Riemann-Theta Boltzmann machine.
reFORM: designing a new symbolic manipulation toolkit
Authors: Ruij Ben
Published: July 2020

Since modern-day multi-loop Feynman diagram computations often require manipulating billions of terms, taking up terabytes of memory, a powerful symbolic manipulation toolkit (SMT) is essential. The de facto solution is Form, but it has several shortcomings. In this work we present reForm, a new SMT in early development, that will handle the same workload as Form but does not have its shortcomings. We showcase some features of reForm, including Python and C APIs. Finally, we provide benchmarks for polynomial GCD computations, which show that reForm often outperforms its competitors. A link to the source code of the technical preview version is provided.
Numerical calculation of 5-loop QED contributions to the electron anomalous magnetic moment
Authors: Volkov Sergey
Published: July 2020

Preliminary numerical results of calculating the 5-loop QED contributions to the electron (and muon) anomalous magnetic moment are presented. The results include the total contribution of the 5-loop Feynman diagrams without lepton loops and the contributions of nine gauge-invariant classes that form that set. A discrepancy with known results is revealed. The contributions of the gauge-invariant classes are presented for the first time. The method of the computation is briefly described (with the corresponding references). The calculation is based on the following elements:

(i)a subtraction procedure for removing infrared (IR) and ultraviolet (UV) divergences point by point in Feynman parametric representation before integration;

(ii)a nonadaptive Monte Carlo integration method that is founded on probability density functions (PDF) that are constructed for each Feynman diagram individually using its combinatorial structure;

(iii)a GPU-based numerical integration with the help of the supercomputer “Govorun” (JINR, Dubna, Russia).
HepMC3 Event Record Library for Monte Carlo Event Generators
Authors: Verbytskyi Andrii , Buckley Andy , Grellscheid David , Konstantinov Dima , William Monk James , Lönnblad Leif , Przedzinski Tomasz , Pokorski Witold
Published: July 2020

We present the HepMC3 library designed to perform manipulations with event records of High Energy Physics Monte Carlo Event Generators (MCEGs). The library is a natural successor of HepMC and HepMC2 libraries used in the present and in the past. HepMC3 supports all functionality of previous versions and significantly extends them. In comparison to the previous versions, the default event record has been simplified, while an option to add arbitrary information to the event record has been implemented. Particles and vertices are stored separately in an ordered graph structure, reflecting the evolution of a physics event and enabling usage of sophisticated algorithms for event record analysis. The I/O functionality of the library has been extended to support common input and output formats of HEP MCEGs, including formats used in Fortran HEP MCEGs, formats used in HepMC2 library and ROOT. The functionality of the library allows the user to implement a customised input or output format. The library is already supported by popular modern MCEGs (e.g. Sherpa and Pythia8) and can replace the older HepMC versions in many others.
Computational challenges for MC event generation
Authors: Buckley Andy
Published: July 2020

The sophistication of fully exclusive MC event generation has grown at an extraordinary rate since the start of the LHC era, but has been mirrored by a similarly extraordinary rise in the CPU cost of state-of-the-art MC calculations. The reliance of experimental analyses on these calculations raises the disturbing spectre of MC computations being a leading limitation on the physics impact of the HL-LHC, with MC trends showing more signs of further cost-increases rather than the desired speed-ups. I review the methods and bottlenecks in MC computation, and areas where new computing architectures, machine-learning methods, and social structures may help to avert calamity.