Table of Content

28 June 2019, Volume 40 Issue 6

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Contents

2019, 40(6):  0. 

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Paper

Research on Adaptive High Resolution Forward-looking Imaging Strategy for Missile-borne Detector

CHENG Cheng, GAO Min, ZHOU Xiaodong, LI Chaowang, YU Bo, LIU Yongpeng

2019, 40(6):  1121-1129.  doi:10.3969/j.issn.1000-1093.2019.06.001

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An adaptive high resolution forward-looking imaging strategy for missile-borne millimeter detector is proposed for satisfying the combat mission of new generation optional burst height proximity fuze. The accuracy of azimuth angle estimation can be dynamically improved by processing the intercepted echo signal data in a distance zone, thus obtaining the more accurate azimuth information of targets, and generating the azimuth-range image of target. The proposed imaging strategy has broken through the traditional monopulse angle estimation method which uses the ideal azimuth curve to estimate the actual angles of different targets. The algorithm uses the actual echo signal data to modify the error generated by angle curve in real time to ensure the high estimation accuracy in azimuth direction. The experimental results show that the proposed imaging algorithm is used to obtain the optimal resolution angle curve in thesame range after 8 times iterative calculation, and achieve adaptive focusing in azimuth direction. Compared to traditional imaging strategy based on real beam scanning technology, the proposed imaging strategy based on monopulse imaging improves the azimuth resolution about 10 times. And the complexity of the algorithm also meets the requirement of missile platform. Key

Research on Wire-controlled Electro-mechanical Combined Braking Technology for Electric Drive Unmanned Tracked Vehicles

GUO Hongming， XI Junqiang， CHEN Huiyan， ZHANG Zihao

2019, 40(6):  1130-1136.  doi:10.3969/j.issn.1000-1093.2019.06.002

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The electric drive tracked vehicle has good motion controllability, and the problems of heavy load and short life of brake system for the traditional tracked vehicle can be relieved by means of electric brake, which is an ideal driving method for realizing the unmanned driving of tracked vehicle. Through the design of braking system for an electric drive unmanned tracked vehicle, a complete technical solution for the electro-mechanical combined braking system is proposed, which is totally controlled by wire. An improved three-stage mechanical-electric brake combination method is adopted, and according to the principle of maximizing braking energy recovery under the premise of ensuring the custom dynamic performance, a corresponding mechanical-electrical braking force distribution strategy is given. After the platform was built according to the scheme, the brake performance test was carried out. The test results show that the system has good braking performance and stability, and can fully meet the requirements of the national military standard for the braking performance of military tracked vehicles while ensuring the kinetic energy conversion efficiency being around 25%. Key

Analysis of Vibration Characteristics of Planetary Transmission Mechanism for Tracked Vehicle Based on Experimental Test

ZHANG Qiang， LI Hongwu， CHENG Yan， ZHANG Yudong

2019, 40(6):  1137-1145.  doi:10.3969/j.issn.1000-1093.2019.06.003

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In order to reveal the mapping relationship between internal excitation and vibration characteristics of planetary transmission mechanism, a vibration acceleration measurement system of planetary transmission mechanism was established by designing a vibration test scheme, and the vibration characteristics of typical gearshift 2 500 r/min planetary transmission mechanism were measured and analyzed. The results show that the vibration root mean square (RMS) value of planetary transmission mechanism is correlated with the position of measuring point. The measuring point is in the meshing position of planetary gear, and its vibration amplitude is larger. The vibration RMS value increases with the increase in the torque. The frequency spectrum analysis results show that the vibration energy mainly concentrates on the meshing frequency and multiple frequencies of planetary gears, and the axial frequency spectrum is similar to the radial frequency spectrum. The maximum amplitude of meshing vibration is obtained by measuring the vibration of planetary transmission mechanism and analyzing its frequency spectrum. Key

A Ground Parameter Estimation Method for Independent Electric Tracked Vehicle

LIANG Wenli，CHEN Huiyan，WANG Boyang

2019, 40(6):  1146-1153.  doi:10.3969/j.issn.1000-1093.2019.06.004

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An algorithm combining the driving force statistical prediction model and the vehicle dynamics model is established to estimate the ground parameters based on the experimental data of independent electric tracked vehicles. The path is segmented according to the deviation point of zero course angle, and the Gaussian mixture model (GMM) is used for the multivariate clustering of path segments. The clustering tags of three consecutive path segments are used to represent the types of motion primitive; the data is grouped based on the types of motion primitive, and then GMM is used to build a statistical prediction model. When the ground parameters are estimated, the driving wheel torques are predicted by calling the driving force statistical prediction model and using the Gaussian mixture regression (GMR) after the primitive type is determined. The nonlinear least squares method is used to minimize the errors of the predicted torque values from the statistical prediction model and the theoretical torque values characterized by a kinetic equation, thereby gaining the estimated values of ground parameters. The test values of ground parameters are obtained by processing the data collected from real vehicles compared with the estimated values. The results show that the proposed method can be used to guarantee the precision of predicted results and the overall efficiency of the algorithm on the premise that fewer sensors are used. Key

Analysis of the Heat Transfer Characteristics of DNAN-based Melt-cast Explosive in Slow Cook-off Test

ZHOU Jie， ZHI Xiaoqi， LIU Zide， WANG Xue， WANG Shuai

2019, 40(6):  1154-1160.  doi:10.3969/j.issn.1000-1093.2019.06.005

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3 experimental devices were designed to investigate the internal heat transfer characteristics of 2,4-dinitroanisole(DNAN)-based melt-cast explosive in slow cook-off test, and tested by scaled thermal explosion experiment. The temperature curves of internal monitoring points in the explosive under a thermal stimulus with the rate of 1 K/min were obtained. It is found that the phase-transition temperature is 73 ℃, the ignition temperature is 205 ℃, and the incomplete combustion reaction occurs after ignition. The ignition location is estimated to be on the upper half of bomb body. The changing process of internal temperature of DNAN-based melt-cast explosive is described. The internal temperature field was analyzed by numerical simulation, and the whole process of phase transition was observed. The results show that the internal temperature field of explosive in solid phase is elliptical, and its internal temperature field in liquid phase is layered. A natural convection arises inside the explosive after phase transition, which is a major factor to affect the ignition location distribution of the explosive. Key

Numerical Study of Underwater Supersonic Gas Jets for Solid Rocket Engine

WANG Lili，LIU Ying，LI Daqin，WU Qin，WANG Guoyu

2019, 40(6):  1161-1170.  doi:10.3969/j.issn.1000-1093.2019.06.006

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The ignition process of gas jets under water is essentially complex, including multiphase flow and complicated flow structures. The Laval nozzle models with expansion ratios of 3.4 and 14.0 are numerically simulated. The CFD method is applied to study the flow structures and corresponding thrust characteristics of rocket engine and analyze the interaction between the high-speed gas jets and water environment. The results show that the flow structures and thrust characteristics of engine change periodically, and the process can be divided into three stages: necking, bulge and return stroke. The interaction between the water environment and the gas jet is the immediate cause leading to the back pressure oscillation, which also induces the fluctuation of shock waves, momentum thrust and pressure differential thrust. For the nozzles with different expansion ratios, the periodic variation of jets pattern and flow structures for the nozzle with expansion ratio of 14 can be more obviously observed, and the oscillation frequency of back pressure for the nozzle with expansion ratio of 3.4 is higher, accompanied with weak periodic characteristics and more stable thrust characteristics. Key

Research on General Detection Method of Coastline and Sea-sky Line in FLIR Image

QIU Rongchao, L Junwei, GONG Jian, XIU Bingnan, MA Xinxing, LIU Sitong

2019, 40(6):  1171-1178.  doi:10.3969/j.issn.1000-1093.2019.06.007

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The coastline and sea-sky line detection is a key technology in the forward looking infrared (FLIR) terminal guidance technology of anti-ship missile, which is always interfered by island, cloud, bright band, strip wave and so on. A general detection method for coastline and sea-sky line is proposed. An integral image is constructed for the original image, and the box filter is used to enhance the edge features of coastline and sea-sky line. The gradient saliency of the pixels in the rectangular region is counted to determine the potential area of the coastline and sea-sky line. The points with maximum saliency are extracted in each column of the potential area and are used to obtain the locations of coastline and sea-sky line by polynomial iterative fitting. The proposed method is verified and analyzed based on the actual FLIR images of sea scene. The results show that the proposed method can overcome the interference of island, cloud, bright band, and strip wave to detect the coastline and sea-sky line. The proposed method has good scene adaptability and real-time performance. Key

Flight Control Strategy for Distributed UAV Formation under the Conditions of Bounded Time-varying Delay andJointly-connected Topology

LI Xiaomin， MAO Qiong， GAN Qintao， DU Zhanlong

2019, 40(6):  1179-1189.  doi:10.3969/j.issn.1000-1093.2019.06.008

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A consistency theory-based distributed formation control strategy is proposed for the multi-UAVs with nonlinear dynamic characteristics, in which the communication delay is changed in bounded interval and the network topology is jointly-connected. The Lyapunov-Krasovskii function is used to analyze the formation stability and deduce its sufficient conditions. The derivative characteristic of time-delay is not considered, and the high dimensional matrix solution of communication topology is transformed into low dimensional matrix solution with several connected parts. The proposed strategy has the advantages of wide applicability, low computational cost and excellent real-time performance. The effectivity of the proposed method in the cases of nonlinear fast-varying and random hopping delays was verified through simulation experiment. Experimental results show that the proposed strategy can be used to direct the multi-UAVs to assemble and converge to any symmetric or asymmetric target formation with scheduled speed. Key

Influence of Aluminum Powder on Energy Release of HMX-based Air-blast Thermobaric Explosives

PIAO Zhongjie, ZHANG Ai'e, LUO Yu, OU Yapeng, JIAO Qingjie

2019, 40(6):  1190-1197.  doi:10.3969/j.issn.1000-1093.2019.06.009

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The shock wave overpressure field was measured through air-blast explosion experiment and calculated by using Autodyn to obtain the energy release law of the aluminized thermobaric explosive (TBX) and the influence of aluminum (Al) powder particle size. The overpressure field of TNT under air-blast loading was measured. The energy level of TBXs was evaluated based on TNT, and the after-burn effect of Al and its contribution to detonation heat were analyzed. The results show that the detonation heats of HMX and AP are due to the overpressure at 3 m. The energy release rate of aluminized TBX decreases due to the decalescence of Al, and increases after Al participating in the reaction. The after-burn effect of Al results in the high energy release rate in far-field, and the overpressure at 13 m approaches to 1.93 TNT equivalent. The two major influences of Al particle size on TBX mainly show in Al₂O₃ impairing the whole energy of TBX and the contribution of fine Al powder to the far-field overpressure of TBX being relatively lower. The results simulated by Autodyn was adjusted according to the measured data of 5 kg TBX, and the overpressure of 1 000 kg TBX was calculated using the adjusted constraint. The results show that the effective radius of damage of TBX approaches to 72 m, and is increased by about 50% compared with that of TNT. Key

Analysis of Similarity Law of Explosion in Multi-layer Concrete Medium

XIE Shuchun， JIANG Chunlan， WANG Zaicheng， LU Guangzhao

2019, 40(6):  1198-1206.  doi:10.3969/j.issn.1000-1093.2019.06.010

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A similarity model of internal explosion in multilayer concrete is established based on dimensional analysis for researching the similarity law of explosion in multilayer concrete. The influences of charge depth and scale ratio on the similarity of damage pattern and damage parameters of prototype and scale model were analyzed by LS-DYNA code. The similarity tests of internal explosion damages of TNT and aluminized explosive were carried out in the prototype and the scale model with scale ratio of 1/2. The results show that the damage patterns of prototype and scale model are the same at different charge depths. When the boundary constraint of a target is the same, the damage of aluminized explosive is similar in the prototype and the 1/2 reduced-scale model. After the normalization of scaled damage parameters, the deviation of the prototype is less than 8%. The deviation degree between the damage parameters of reduced-scale model and prototype is increased with the decrease in scale ratio. The damage effect of internal explosion of the prototype can be predicted by using the test results of appropriate scale ratio model. Key

Two-dimensional Direction-of-arrival Estimation for L-shaped Nested Array Based on Cross-covariance Matrix

GAO Xiaofeng, LI Ping, LI Guolin, HAO Xinhong, JIA Ruili

2019, 40(6):  1207-1215.  doi:10.3969/j.issn.1000-1093.2019.06.011

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The direction of arrival （DOA）estimation for L-shaped uniform antenna array is limited by low resolution, number of incident signals and signal-to-noise ratio. A two-dimensional DOA estimation algorithm for L-shaped nested array based on cross-covariance matrix is proposed to solve this problem. In the proposed algorithm, the cross-covariance matrixes of different sub-arrays are used to generate longer virtual arrays without redundant elements, which eliminate the noise. To cope with the coherent signals of virtual arrays, several equivalent covariance matrixes are constructed by using the signal of virtual arrays and its conjugate signal. The rotational invariance technique is used to deal with the equivalent covariance matrixes to obtain the angle of incident signals, and the angles are matched by using the uniqueness of equivalent signal vectors of virtual arrays. The effectiveness of the proposed algorithm for DOA estimation was verified. The simulated results show that the proposed algorithm can achieve better DOA estimation performance in low SNR environment and identify more spatial sources compared to the L-shaped uniform array with the same number of array elements. Key

Experimental Study of Microbubble Flow and Drag Reduction Characteristics of Underwater Vehicle in Pitching Movement

SONG Wuchao, WANG Cong, WEI Yingjie, XIA Weixue

2019, 40(6):  1216-1225.  doi:10.3969/j.issn.1000-1093.2019.06.012

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To study the characteristics of the microbubble flow and the drag reduction characteristics of the underwater vehicle in the pitching movement, the water tunnel experiments were conducted with a self-designed driving equipment, a high speed camera and a six-component force balance. The driving equipment can rotate the underwater vehicle around its head at a sinusoidal regular angular velocity.The characteristics of microbubble flow are analyzed based on the high-speed camera system, and the hydrodynamic characteristics of underwater vehicle and the variation of microbubble drag reduction characteristics in maneuvering process are analyzed based on the six-component force balance. The results show that the discrete microbubbles are always evenly distributed on the surface of underwater vehicle when the air injection rate is low. As the air injection rate increases, the density of the microbubble flow gradually increases and the transparency gradually decreases. The discrete microbubbles are eventually coalesced into transparent cavities. During the pitching movement, the axial and lateral force coefficients of the underwater vehicle are basically sinusoidal, and the periods are basically synchronous with the changing period of attack angle. The variation of the axial force coefficients at various air injection rates is basically the same, which are all sinusoidal. With the increase in the air injection rate, the axial force coefficient of vehicle under the same posture decreases gradually and eventually becomes constant. Key

Experimental Research on Cavity Evolution Pattern and Trajectory Characteristics in the Water-exit Process of SalvoedRevolving Bodies

LU Jiaxing， WANG Cong， WEI Yingjie， XU Hao， SONG Wuchao

2019, 40(6):  1226-1234.  doi:10.3969/j.issn.1000-1093.2019.06.013

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In order to study the mutual interference between revolving bodies salvoed underwater in the water-exit process, the experimental research on the water-exit process of revolving bodies is carried out based on high-speed photography. The countors of cavity and revolving bodies are identified and extracted using image processing technology. The hydrodynamic disturbance between the revolving bodies in the water-exit process and the effect of frame velocity are analyzed by comparing the trajectory characteristics of single revolving body and two revolving bodies launched with and without submarine speed. The experimental results show that the low pressure zone formed by the first revolving body makes the cavity inside the second revolving body develops larger in the water-exit process without submarine speed, and the trajectory of the second revolving body deflects to the first revolving body. The cavity evolution rule and the trajectory characteristics of revolving body change in the presence of submarine speed under the action of high pressure at the up-flow side and current scour, the cavity develops towards the back-flow side, and the trajectory of the first revolving body deflects along the flow direction; and the second revolving body is in the wake field of the first revolving body, so the trajectory of the second revolving body still has the attitude and the track deflection to the first revolving body, but its deflection amplitude is relatively smaller than that of the revolving body launched without submarine speed. Key

Optimal Control of Supercavitating Vehicles Based on Unscented Kalman Filter

ZHANG Chengju，WANG Cong， CAO Wei， WANG Jinqiang

2019, 40(6):  1235-1243.  doi:10.3969/j.issn.1000-1093.2019.06.014

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An optimal control method based on unscented Kalman filter is proposed to solve the adverse effects due to environmental and measurement noises. Based on dynamic model of supercavitating vehicle, the environmental and measurement noises are added to the equation of state. An optimal controller without filter and with unscented Kalman filter was simulated and analyzed. Simulated results show that the tracking error of supercavitating vehicle is large，and its movement is extremely unstable under the disturbance of environmental and measurement noises. Under the action of the unscented Kalman filter, the tracking error of supercavitating vehicle is reduced significantly and the supercavitating vehicle reaches a full package state in a short period of time. It has better signal processing results. Key

Research on Anti-aircraft Smoke Equipment Position Disposition Model Based on Infrared Shielding

ZENG Zhaokai, ZHU Dongsheng, GUO Xiaodi, WANG Ding, GAO Xiaohui

2019, 40(6):  1244-1251.  doi:10.3969/j.issn.1000-1093.2019.06.015

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In the modern air defense operation, the smoke equipment should be prepositioned timely and rapidly, and the shielding effectiveness of smokescreen should be maximized. The analytic geometry and numerical analysis methods are applied to the research on the position disposition. A calculation model of smoke scale and location is established by using the analytic geometry according to the three-dimensional battlefield space and smoke demand, and a calculation model of single point smoke laying is established by using the mathematical derivation and Newton down-hill method based on the smoke diffusion model—Gaussian plume mode. And finally, a calculation model of multi-point smoke laying, viz., the anti-aircraft smoke equipment position disposition model for IR guided weapons, is established by taking the single point smoke laying as constituent unit and the smoke demand as final standard. The comparison between the calculated and test results show that the calculated results are in good agreement with the test results. Key

Adsorption Kinetics of Benzene Vapor by a Double-layer Fixed Beds Packed with Microfibrous Entrapped Sorbent andActivated Carbon

WANG Lingyun， YE Pingwei， LI Kai， HUANGFU Xile， SI Fangfang

2019, 40(6):  1252-1257.  doi:10.3969/j.issn.1000-1093.2019.06.016

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Microfibrous entrapped sorbent（MFS）with nickel fibers was prepared by a traditional wet paper making/sintering process，and a double-layer bed is composed of MFS and conventional packed bed (PB) of granular activated carbon (GAC). The adsorption behaviors of benzene vapor in fixed bed at various challenge concentrations are studied. The unused layer depth and adsorption capacity of the bed are calculated using Shilov's equation. Yoon-Nelson equation is used to simulate the breakthrough behaviors of both single- and double-layer fixed beds. The results show that, for both GAC bed and double-layer fixed bed, the unused layer depth and adsorption capacity decrease with the decrease of the challenge concentration. The adsorption efficiency of double-layer fixed bed with benzene vapor is significantly improved compared with GAC bed at the same concentration ratio and flow rate, owing to that the mass transfer efficiency of double-layer bed is improved by MFS at the end of air flow. The results also show that the theoretical curves agreed with the experimental data very well. Key

Multi-field Coupling Simulation and Experiment of Laser Cladding under Thermal Dependent Physical Properties

LI Chang, YU Zhibin, GAO Jingxiang, LI Yunfei, HAN Xing

2019, 40(6):  1258-1270.  doi:10.3969/j.issn.1000-1093.2019.06.017

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The thermal-elastic-plastic-flow multi-field coupling changes exist in laser cladding, which affects convection, heat, mass transfer, and solidification process. The mechanism of multi-field coupling evolution is hard to be dynamically tracked and revealed because of the small volume of molten pool, large temperature gradient and very strong instantaneous characteristics. A multi-field coupled 3D mathematical model of disk laser in the process of cladding Fe60 powder on 45 steel was established.The interaction between the powder flow and the laser energy beam, the influences of surface tension and buoyancy on the fluid flow in the melt pool, and the instantaneous change of cladding layer shape are taken into account in the proposed model. The thermal dependent physical properties of substrate and powder were obtained by using the CALPHAD phase diagram calculation method. The model was solved to obtain the distribution state and evolution law of temperature field and velocity field in the process of laser cladding. The results show that the laser cladding morphology and solidification microstructure predicted by simulation agree well with the metallographic results obtained by using Zeiss-IGMA HD field emission scanning electron microscope. Key

Investigation into Residual Stress of Austenitic 304 Stainless Steel at Cryogenic Temperature

PENG Zeyu， YAN Pei

2019, 40(6):  1271-1276.  doi:10.3969/j.issn.1000-1093.2019.06.018

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In order to improve the workability of Austenitic 304 stainless steel, the residual stress of Austenitic 304 stainless steel was studied by cutting the austenitic stainless steel at cryogenic. The temperature field distribution of liquid nitrogen immersed workpiece is analyzed by the finite element software ANSYS, guiding the actual precooling workpiece test. The residual stress of metal cutting is qualitatively analyzed. The cryogenic cutting test under different precooling temperature is carried out, and the cutting force in cutting process is measured by force measuring instrument. DEFORM finite element software is used to simulate the process of cutting at different temperatures, and the temperature distribution in the cutting process is observed by the post processing function. The results show that the cutting force of the cutting process can be increased and the temperature defference of workpiece surface is decreased during the cryogenis cutting. This makes the residual tensile stress decrease or the residual compressive stress increase, and the lower the temperature is, the more obvious the effect is. Key

Effectiveness Evaluation of Equipment Maintenance Support System Based on Asymmetric Grey Cloud Model

WANG Shuangchuan, HU Qiwei, BAI Yongsheng, GUO Chiming, MA Yunfei

2019, 40(6):  1277-1286.  doi:10.3969/j.issn.1000-1093.2019.06.019

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For the fuzziness, randomness and incompleteness of decision information in the process of effectiveness evaluation of equipment maintenance support system, an asymmetric grey cloud model is established to evaluate the system effectiveness. On the basis of analyzing the limitations of normal grey cloud model, an asymmetric grey cloud model is established, in which the characteristic values become more flexible. A method of determining the index weight based on the subjective and objective integrated weights is proposed, so that the index weight can reflect both subjective and objective factors.The grey class of systems is determined by grey fixed weight clustering method. The application process of the proposed model is illustrated by an example, and the evaluated results are compared with those of fractal evaluation algorithm and set-pair analysis method. The research results show that the asymmetric grey cloud model is more practical than the original method. The proposed method is applicable to the effectiveness evaluation of equipment maintenance support system. Key

Joint Fire Attack Mission Planning Method Based on Intelligent Confrontation Evolution

LIU Hao，ZHANG Ce，DING Wentao

2019, 40(6):  1287-1296.  doi:10.3969/j.issn.1000-1093.2019.06.020

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In view of the fact that the conventional joint fire attack mission planning method rarely involves an issue of friend-foe confrontation leading to the change in evaluation environment, a smart confrontation evolution algorithm based on the evolution of friend-foe confrontation is proposed. The proposed algorithm is based on genetic algorithm, in which the simulation of biological competition mechanism is introduced into the two populations of friend and foe for implementing the confrontational evolution. An observe-orient-decide-act (OODA) super-network is constructed based on the battlefield situation map, and then the OODA cycle efficiency is calculated to determine the order of friend and foe attacks. The task-planning optimal individuals can adapt to the dynamic changes of the battlefield through the confrontation evolution of multiple generations. The simulated results show that the multi-generation evolutionary optimal individual has stronger dynamic adaptability, and the joint firepower strike rate is higher. The response mechanism to respond to the emergencies is more perfect, which can effectively solve the evaluation optimization issues of joint firepower mission planning. Key

Research Notes

Research on Recoil Law of Bolt-fastened Railgun

MA Xinke, QIU Qunxian, HE Hang, GAO Bo, GENG Hao, HE Xuguang

2019, 40(6):  1297-1303.  doi:10.3969/j.issn.1000-1093.2019.06.021

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The two parallel rails of railgun are subjected to lateral tension during launching. A bolt-fastened encapsulation structure was adopted to restrain the expansion of the rails. For the sake of research on recoil law of bolt-fastened railgun, a launch system model is established, the force acting on the recoils in launching process is analyzed, and a differential equation of recoil and counterrecoil motion is established. For two kinds of counterrecoil mechanison schemes, the recoil of bolt-fastened railgun was simulated and tested. The simulated and experimental results were compared and analyzed. It is concluded that, compared with the conventional gun, the bolt-fastened railgun has the characteristics of short recoil stroke and low recoil velocity, and because of the low recoil velocity, the throttling bar recoil brake used in bolt-fastened railgun needs a smaller flow hole area to improve the recoil force. Key

Research on Prediction Theoretical Model of Projectile Base Pressure during Aftereffect Period

ZHOU Mengdi， CAO Congyong， QIAN Linfang

2019, 40(6):  1304-1309.  doi:10.3969/j.issn.1000-1093.2019.06.022

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The projectile is disturbed by high-pressure gas during aftereffect period, which affects its exterior ballistic characteristics. The change of pressure on the base of projectile during the aftereffect period is studied for improving the accuracy firing table and optimized design of projectile. As computational fluid dynamics (CFD) simulation takes a long time, a theoretical model based on Prandtl-Meyer wave and isentropic flow is established for predicting the pressure on the base of projectile, and a modified model of pressure boundary estimation is proposed. The muzzle dates measured in a firing practice test were analyzed. The results show that the simulated results of the proposed model and CFD 3D model have less difference, but the calculating time of the proposed model is shorter, which is decreased from about 1.5 h to less than 1 s. Key

Scheduling Optimization of Test Tasks Based on Ant Colony Algorithm

HU Tao, MA Chenhui, SHEN Liqun, LIANG Jie

2019, 40(6):  1310-1316.  doi:10.3969/j.issn.1000-1093.2019.06.023

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The problems of complex tasks, long test time, and wasting of resources exist in the test of complex system. The reasonable scheduling of the resources and tasks is of great importance in real application. An optimization method for parallel task scheduling of test process based on ant colony algorithm is proposed. Considering ant colony algorithm, the heuristic function and state transition rule are designed to describe test problem. The task scheduling sequence with the shortest test time can be obtained according to the algorithm flow. To solve the multi solution problem of task sequence, an evaluation criterion based on resource balance degree is proposed to get the optimal task scheduling sequence. The task scheduling problem of complex system is solved by using the ant colony algorithm. A real test task was scheduled and simulated. Effectiveness of the proposed method is verified by comparing with the random exhaustive method. Results show that the proposed method can save test time greatly and improve the test efficiency by 43.07% compared with the semi-serial test, and the balance degree of resources in the task scheduling sequence with the shortest test time is the highest. Key

Low Temperature Reaction of Portable Metal-free Solid Oxygen Candle

ZHANG Yanjun， MA Jun, TIAN Tao, SONG Zhenxing, SANG Wei, GONG Shihong, WANG Yuhang, HUANG Weidong, WU Hao, XIANG Xin, LI Renjie, LIU Jian

2019, 40(6):  1317-1322.  doi:10.3969/j.issn.1000-1093.2019.06.024

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A cobalt salt catalyst was synthesized with the aim of decreasing the decomposition temperature of sodium chlorate. The composition, assembly structure and decomposition behaviors of oxygen candle were investigated by consiclering the influences of catalyst, solvent, binder, chlorine suppression agent and pressing process. Portable metal-free oxygen candle was fabricated using a comprehensive manufacturing process. The oxygen candle can burn at the temperature lower than the melt temperature of sodium chlorate, of which the releasing rate of oxygen is 0-5 L oxygen per minute and the release amount of chlorine is less than 0.001 mg/L. Catalyst and pressing process are key factors for the manufacturing of low temperature combustible sodium chlorate oxygen candle. Key

Experimental Study on the Aerodynamic Arrangement of Small Multi-rotor Aircraft with High Capacity Payload

LEI Yao， LIN Rongzhao， WU Zhiquan

2019, 40(6):  1323-1328.  doi:10.3969/j.issn.1000-1093.2019.06.025

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The hover efficiency of multi-rotor aircraft is mainly determined by the configuration of rotor system. In order to obtain the hover efficiency of multi-rotor system with different aerodynamic parameters, the thrust and power consumption of multi-rotor system with different rotor position, the number of rotor blades, the shape and size of rotor arm, the spacing of coaxial rotors and the overlap area of non-coaxial rotors are measured experimentally. The variation of hover efficiency with the disk loading for rotor different configurations is also analyzed. The experimental results show that the 2-blade rotor with pusher configuration is characterized with better hovering efficiency; the size of rotor arm has a greater influence on the hovering efficiency compared with its shape; the hovering efficiency of coaxial rotor is close to that of interference-free single rotor under a higher rotor disk loading， and achieves better performance when the spacing ratio is 30.4%; and the energy loss can be effectively reduced by adjusting the vertical and horizontal spacing ratios of the non-coaxial overlap region, and the hovering efficiency is significantly improved when the horizontal spacing ratio is ranged from 10% to 15% with a smaller vertical spacing ratio. Key