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    30 May 2022, Volume 43 Issue 5
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    Contents
    2022, 43(5):  0. 
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    Paper
    Intelligent Control Strategy of Electromechanical Braking for Hybrid Tracked Vehicle
    ZHANG Wei, LIU Hui, HAN Lijin, LIU Baoshuai, ZHANG Xun, ZHANG Wannian
    2022, 43(5):  969-981.  doi:10.12382/bgxb.2021.0256
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    For the better stability of electromechanical braking of tracked vehicles equipped with hybrid electromechanical transmission(EMT) under all road conditions, a parallel electromechanical braking force distribution strategy with variable proportion coefficient based on motor saturation was proposed. This strategy effectively deals with the constraints of road adhesion conditions, driver intention, slip rate, and battery state of charge, and significantly reduces track slip and motor braking force saturation. Firstly, the dynamic model of the EMT was established, and the electromechanical braking characteristics and dynamic constraint boundary were analyzed. Secondly, the expected dynamic braking force distribution based on motor braking saturation was proposed. In addition, the slip rate controller was designed to calculate the total braking force and coordinate electromechanical braking force distribution to meet the braking stability target in all working conditions. Then, the extended state observer was applied to accurately estimate the time-varying road adhesion coefficient, and the control parameters were optimized based on genetic algorithm. Finally, hardware-in-the-loop simulation was applied to simulate the high-speed emergency braking. The results showed that the electromechanical braking control strategy for all road conditions considers the braking energy recovery efficiency and the safe operation of the motor, and effectively reduces the pressure of the hydraulic brake and improves the brake life and safety in the braking process.
    The Prediction Method Based on Neural Network Algorithm for the Bearing Capacity of Launching Site
    LI Mingjun, JIANG Yi, MA Liqi, PAN Xiao
    2022, 43(5):  982-991.  doi:10.12382/bgxb.2021.0245
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    A rapid prediction method of the bearing capacity of launching site is proposed to improve the quick response ability of the missile launching,which is based on linear multiple regression algorithm,back propagation(BP) algorithm and radial basis function (RBF) algorithm. An optimized Latin hypercube sampling method with parameter sensitivity is applied to construct the sample space. The approximate models evaluated by different algorithms under different loads are established and proved to be effective. Evaluation algorithm of the bearing capacity of unknown launching site is established to predict the probable maximum deflection under launch load using dynamical response of the launching site under erection load. The results show that the RBF algorithm has the best prediction performance and the regression coefficients under erection and launch loads are 0.941 and 0.983.The average error between predicted and simulated results is 10.46%. For the launching site with higher bearing capacity,the residual error of the evaluation algorithm ranges in ±2 mm.
    Fault Diagnosis Method of High-pressure Common Rail System Based on EEMD-SVM
    LI Liangyu, SU Tiexiong, MA Fukang, WU Xiaojun, XU Chunlong
    2022, 43(5):  992-1001.  doi:10.12382/bgxb.2021.0155
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    When the high-pressure common rail system for diesel engine is running, the rail pressure fluctuation signal fluctuates greatly and has obvious nonlinear characteristics, which makes the fault diagnosis more difficult. For the problem that the state parameters of rail pressure signal in high-pressure common rail system are difficult to extract and identify, a fault diagnosis method based on ensemble empirical mode decomposition (EEMD)-support vector machine (SVM) is proposed. The rail pressure signal is decomposed into a series of eigenmode functions by EEMD, and the eigenvalues in the eigenmode functions are extracted using the feature extraction criterion determined by the zero-crossing rate curve. The extracted eigenvalues are input into SVM for fault type diagnosis. The rail pressure signal is obtained through AMESim software simulation experiment, and seven different eigenvalue selection methods are compared. Finally, the energy eigenvalue is selected to construct the eigenvalue vector for identification, and the diagnosis results are analyzed to verify the correctness and accuracy of the proposed method. The results show that the proposed EEMD-SVM-based fault diagnosis method for high-pressure common rail system can be used to identify six different operating states, with the average fault diagnostic accuracy rate of 96.11%.
    Performance Prediction of Hydrogen-enriched Compressed Natural Gas Engine Based on Support Vector Machine
    DUAN Hao, CHEN Hui, ZHAI Zhaoyang, HAN Yu, MA Fanhua, CUI Yahui
    2022, 43(5):  1002-1011.  doi:10.12382/bgxb.2021.0199
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    A hydrogen-enriched compressed natural gas (HCNG) fuel engine with hydrogen volume fraction of 20% is experimentally studied and its performance is analyzed to improve the calibration efficiency of HCNG fuel engine and accurately predict the engine parameters. An engine parameter association model is established by using support vector machine (SVM) based on the steady-state experimental calibration data under high speed and low load conditions,and the different optimization algorithms are used to improve the prediction accuracy of engine parameters. Results show that the engine has the minimum brake specific fuel consumption (BSFC) and ideal brake specific NOx consumption level (BSNOx) at the minimum advance for best torque.The external characteristics is obviously improved when increasing the hydrogen ratio especially. The SVM model can describe the nonlinear relationship between the input and output parameters of the engine,and has high prediction accuracy and strong correlation between independent variables and dependent variables (all coefficients of determination R2 are all greater than 0.97). The optimal prediction model derived using the genetic algorithm has a high generalization capability,with mean absolute percentage errors of only 1.23%,1.98%,and 5.43% for torque,BSFC,and BSNOx, respectively.
    An Ammunition Quality Evaluation Method Based on Least Squares Support Vector Machine
    YANG Jianxin, LAN Xiaoping, FENG Yadong, YANG Yiming, GUO Zhiming
    2022, 43(5):  1012-1022.  doi:10.12382/bgxb.2021.0240
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    For the problems about the less sample data,large test consumption and ineffective use of manufacturing process quality data, in order to solve these problems,an ammunition quality evaluation method is proposed based on least squares support vector machine(LSSVM)optimized by improved salp swarm algorithm.The firing success rate of batches of new ammunition is estimated based on Bayesian by using target test data as input.On this basis,an evaluation model of the relationship between ammunition batch manufacturing quality data and ammunition firing success rate is developed using LSSVM.The LSSVM is optimized with an elite center of mass and a salp swarm algorithm improved by backward learning strategy,which effectively improves the accuracy of the evaluation model.And the validity of the evaluation model was verified by using a new type of ammunition as an example.The validated results show that the model has higher accuracy and stronger robustnesscompared with the traditional LSSVM,LSSVM improved by particle swarm algorithm and LSSVM improved bysalp swarm algorithm.
    Energy Output Characteristics of CL-20-based Aluminized Explosives with Different Al/O Ratios during Deep-water Explosion
    KAN Runzhe, NIE Jianxin, GUO Xueyong, YAN Shi, JIAO Qingjie, ZHANG Tao
    2022, 43(5):  1023-1031.  doi:10.12382/bgxb.2021.0227
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    In order to study the energy output characteristics of CL-20-based aluminized explosives in the high hydrostatic environment unique to deep-water explosion. A deep-water explosion pressure tank is used to simulate a 500-meter deep-water environment,and six groups of CL-20-based aluminized explosives with different Al/O ratios are used for deep-water explosion experiments.The energy output law and energy output structure of explosiveduring deep-water explosion under high hydrostatic pressure are analyzed through the experimental data. The experimental results show that the peak pressure of shock wave,specific shock wave energy,specific bubble energy and mechanical energy of deep-water explosion climb up and then decline with the increase in Al/O ratio,and the peak pressure of shock wave conforms to the similarity relationship. When the Al/O ratio is between 0.24 and 0.88,both the lost energy and its rate of increase with the test distance increase first and then decrease,reaching the peak value at 0.67 and 0.46,respectively. Therefore,the utilization efficiency of far-field energy of deep-water explosion can be measured by changing the Al/O ratio. In addition,the energy utilization rate of deep-water explosion continues to decrease with the increase in Al/O ratio,and the mechanical energy remains high between 0.46-0.67. By adjusting the Al/O ratio,the energy output ratio of specific shock wave energy and specific bubble energy can be changed on the premise of maintaining high mechanical energy of deep water explosion.
    A Target Detecting Algorithm for Spinning Projectile Based on Improved YOLOv3 and KCF
    WANG Shaobo, ZHANG Cheng, SU Di, JI Ruijing
    2022, 43(5):  1032-1045.  doi:10.12382/bgxb.2021.0283
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    The image captured by the spinning projectile-borne TV camerawill rotate and jitter to become blurry. It is difficult to detect a target accurately when the target data is less in advance detection and the field of view in the terminal guidance phase is small. A target detection and tracking algorithm based on improved YOLOv3 and kernelized correlation filter (KCF) is proposed.On the premise of a small number of data samples,the complex environments such as different weather,illumination,motion,and rotation blur are simulated to complete the data enhancement and expansion in network learning; By adding the multi-scale branch structure of Induction based on YOLOv3 network,the adaptability of the network to different sizes of targets is increased and the number of network layers is reduced for small target detection. In the realization of target location method, the target detection is combined with tracking algorithm,a target loss discrimination mechanism based on Gaussian threshold is proposed ,and the target frame scale is updated by using the velocity-time information of trajectory. Simulated results show that the improved algorithm can achieve the target detection and tracking in the complex environment more effectively.
    Operating Characteristics of Aluminum Powder Rotating Detonation Engine
    XU Han, LUO Yongchen, NI Xiaodong, XIAO Bowen, ZHANG Feng, SU Xiaojie, ZHENG Quan, WENG Chunsheng
    2022, 43(5):  1046-1053.  doi:10.12382/bgxb.2022.0002
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    The aluminum/air and hydrogen/air rotating detonation engines (RDEs) are experimentally studied and compared to reveal the specific detonation characteristics and propulsion performance of aluminum powder RDE.The RDE engines work at the equivalence ratio of 1 and the air mass flow rate of 260 g/s. It's found that the thrust of aluminum/air RDE is 35% higher than that of hydrogen/air RDE; the pressure peak of aluminum/air is 11% higher than that of hydrogen/air; the detonation velocity of aluminum/air is 11% lower than that of hydrogen/air; and the detonation propagation mode of auminum/air is the same as that of hydrogen/air, which are single wave mode. The above differences are not only caused by the different properties of fuel,but also caused by the difference between the gas-solid two-phase detonation and the gaseous detonation. The experimental results could provide a feasible solution for the air breathing aluminum powder RDE and establish a foundation for the solid powder RDEs.
    Effect of Cavity on Scramjet Combustion Characteristics of Boron-containing Solid Rocket
    LING Jiang, XU Yihua, SUN Haijun, LIU Weigen, FENG Xiping
    2022, 43(5):  1054-1062.  doi:10.12382/bgxb.2021.0280
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    Cavity is often used to enhance the mixing of air and gas in scramjet,and improve the flame stability and combustion efficiency. The characteristics of flow field in supersonic combustor depend on the structure and distribution of cavity. In order to optimize the cavity structure and its distribution,and improve the combustion performance of secondary combustion chamber in solid rocket scramjet,the effects of cavity length-to-depth ratio and rear tilt angle on the combustion characteristics of boron-containing solid rocket scramjet were studied by numerical method. The calculation results show that, when the cavity length is constant and the length-to-depth ratios of cavity are 5,3.75,3,2.5,2.14,1.85,1.67,respectively, the length-to-depth ratio of cavity is 1.85,and the combustion efficiency and specific impulse of boron particles are the highest. When the length-to-depth ratio of cavity is 1.85,and the rear tilt angle of cavity is changed from 90° to 175°, the combustion efficiency of boron particles increases with the increase in the tilt angle. When the rear tilt angle is 175°,the combustion efficiency of boron particles is the highest,but the total pressure recovery coefficient and specific impulse are the smallest. And the specific impulse is the highest when the rear tilt angle is 165°.
    Numerical Simulation of Cavity Influence on C2H4/Air Rotating Detonation Flow Field in Annular Combustor
    MENG Haolong, WENG Chunsheng, WU Yuwen, ZHENG Quan, XIAO Qiang, WANG Fang, BAI Qiaodong
    2022, 43(5):  1063-1074.  doi:10.12382/bgxb.2021.0249
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    The three-dimensional numerical simulation of C2H4/Air rotating detonation combustor (RDC) is carried out to study the influence of cavity on the rotating detonation flow field in annular combustor by solving Navier-Stokes equations in the framework of open source computational fluid dynamics software OpenFOAM. The main flow field features of annular and cavity-based annular RDCs are compared under the conditions of total inlet pressure of 0.6 MPa and total temperatures of 300 K, 600 K and 800 K, the influence of cavity on the propagation characteristics of rotating detonation wave is studied, and the proportions of fuel consumed at different heat release rates are quantitatively analyzed. The results show that, for the cavity-based annular RDC, a recirculation zone exists in the cavity, which leads to a slow flow velocity in the upstream of the cavity, but the flow rate significantly accelerates in the contraction section of the cavity. The surface average Mach number at the outlet of RDC is larger than that of the corresponding annular RDC. Due to the lateral expansion of fuel towards the outlet of RDC and the inner wall of cavity, the detonation wave propagating in the cavity-based annular RDC has a higher velocity deficit than that in the annular RDC. Part of the fresh fuel is mixed with the combustion products in the cavity, which increases the temperature of reactant in front of detonation wave. The ratio of fuel consumption under different heat release rates was compared, which shows that the annular RDC consumes more fuel in the form of detonation than the cavity-based annular RDC under the same injection conditions.
    Acoustic Characteristics of Pulse Detonation Engine with Annular Nozzle
    KANG Yang, LI Ning, HUANG Xiaolong, WENG Chunsheng
    2022, 43(5):  1075-1082.  doi:10.12382/bgxb.2021.0241
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    The nozzle has a significant influence on the performance of detonation engine and acoustic characteristics of detonation acoustic wave.An acoustic wave experimental system is constructed in free space to explore the detonation acoustic wave characteristics of pulse detonation engine with annular nozzle,and the acoustic characteristics of pulse detonation engine, such as time-frequency domain characteristics,sound field directivity and duration, are measured and analyzed.The experimental results show that the annular nozzle changes the energy distribution of detonation acoustic wave and has the significant influence on detonation acoustic characteristics. The rising duration of detonation acoustic wave in 0° direction is relatively longer. The peak sound pressure of pulse detonation engine in 90° direction is the highest,and its attenuation speed and amplitude are the largest.The detonation acoustic wave radiates the most energy in 90° direction.The a duration of detonation acoustic wave of pulse detonation engine decreases with the increase in propagation angle.
    Artificial Neural Network-based Prediction Model for the Air Drag Coefficient of Non-spherical Fragments
    XIN Dajun, XUE Kun
    2022, 43(5):  1083-1092.  doi:10.12382/bgxb.2021.0121
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    The trajectory of non-spherical fragments is closely related to the drag coefficient from supersonic to subsonic velocities. The non-spherical fragments tumble or rotate during ballistic flight,and the drag coefficient changes with the attitude of fragment. In order to obtain the average fragment drag coefficient under tumbling state from the drag coefficients corresponding to the finite fragment attitudes,a regular icosahedron-based averaging method is proposed. The average fragment drag coefficient under tumbling state is obtained by averaging the drag coefficients corresponding to 32 specific fragment attitudes. The error between the average drag coefficients of the cubic and cylindrical fragments obtained by the proposed method and those obtained by the ballistic gun test is within 10%. On this basis, the effect of fragment morphology,that is,sphericity,on the fragment drag coefficient in the full Mach number range is studied. The drag coefficients of a large number of non-spherical fragments are calculated by using the averaging method,with a sphericity of 0.35-1.00. A drag coefficient prediction model based on Mach number and fragment shape is established by artificial neural network. The test results show that the prediction model has high accuracy.It is found that the sphericity is the most important shape factor affecting the fragment drag coefficient,and its influence is most obvious at subsonic velocity.The dependence of fragment drag coefficient on the sphericity is significantly reduced at supersonic velocity.
    FGCM-based Modeling Method of Intelligent Situation Awareness in Complex Battlefield
    CHEN Jun, ZHANG Yue, CHEN Xiaowei, TONG Yan
    2022, 43(5):  1093-1106.  doi:10.12382/bgxb.2021.0259
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    An intelligent situation awareness modeling method based on fuzzy grey cognitive map (FGCM) is proposed the dynamic and uncertain characteristics of complex battlefield environment. Based on situation awareness theory,the situation elements are extracted by top-down task driven situation awareness method. The target threat assessment is taken as the modeling object of situation understanding, and the dynamic FGCM model of threat assessment is established by using the model characteristics of FGCM in uncertain data expression and reasoning,in which the external environment control node is introduced. The target intention prediction is taken as the modeling object of situation prediction on the basis of FGCM model structure established based on expert knowledge, and the particle swarm optimization is used to improve the parameter learning ability of intention prediction model for historical data samples. The simulated results show that the intelligent situation awareness modeling method based on FGCM can deal with the dynamic and uncertain battlefield environment better,and play a comprehensive role of knowledge and data in modeling.
    Dual Encoding Integrating Key Frame Extraction for Video-text Cross-modal Entity Resolution
    ZENG Zhixian, CAO Jianjun, WENG Nianfeng, JIANG Guoquan, FAN Qiang
    2022, 43(5):  1107-1116.  doi:10.12382/bgxb.2021.0262
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    Existing video-text cross-modal entity resolution methods all adopt a method of uniformly extracting frames in video processing,which inevitably leads to the loss of video information and increases the model complexity.A dual encoding integrating key frame extraction (DEIKFE) is proposed for video-text cross-modal entity resolution. On the premise of fully retaining the video information,a key frame extraction algorithm is designed to extract the key frames in the video,which makes up the video key frame set. For the video key frame set and the text,a multi-level encoding method is adopted to extract the global,local,and time-series features,which are spliced to form a multi-level encoding representation. And the encoding representation is mapped into a common embedding space,and the model parameters are optimized by cross-modal triplet ranking loss based on the hard negative sample to make the matched video-text similarity greater and the unmatched video-text similarity smaller. The experiments on MSR-VTT and VATEX datasets show that the overall performance of R@sum is increased by 9.22% and 2.86%,respectively,comparedwith the existing methods, which can fully demonstrate the superiority of the proposed method.
    N-χ Coefficient Capture Decision Method Based on TDDM Signal
    FENG Yongxin, HE Kuan, LIU Fang, LIANG Dong
    2022, 43(5):  1117-1128.  doi:10.12382/bgxb.2021.0263
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    The application of time division data modulation (TDDM) signal greatly improves the frequency band utilization rate and the ability to adapt to complex environments of spread spectrum communication system.For the ambiguity problem of the baseband data reverse position during TDDM signal capture, a N-χ coefficient capture decision method is proposed, in whichthe unique modulation characteristics of TDDM signals and the shortcomings of the existing capture decision methods are considered. The proposed method is to establish the χ coefficient decision formulabased on the linear relationship between the baseband data reverse position and the correlation result in parallel processing, and the accurate position of the baseband data reverse is obtained by dividing the current accumulation time into N segments and measuring the average value of χ coefficient in each segment.The accuracy of the N-χ coefficient capture decision method to determine the baseband data reverse position is more than 99% for the number of segments N≥4. The proposed method is compared with the ambiguity suppression capture decision method.The simulated results show that N-χ coefficient capture decision method is better than ambiguity suppression capture decision methodin term of capture accuracy or environmental adaptability,verifying the effectiveness of this method in eliminating the ambiguity problem of baseband data reverse position.
    A Linear Array Extension Based on Sub-arrays Covariance Matrix
    MAO Weining, QIAN Jin
    2022, 43(5):  1129-1134.  doi:10.12382/bgxb.2021.0282
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    A novel linear array extension method is proposed to mitigate the effect of low signal-to-noise ratio on weak target detection. A linear array aperture is increased by reconstructing the array receiving data using the covariance matrix for the received signals of two sub-arrays composed of odd and even array elements and the rotational invariance of the linear array, and the additive noises is mitigated when reconstructing the receiving array data. The simulated results show that the proposed algorithm can significantly reduce the beam sidelobes, improve the detectability of weak targets and provide robustness at low signal-to-noise. It has better application prospects in the weak target detection and direction-of-arrival estimation.
    Drag Reduction Characteristics of Bionic Non-smooth Surface for Underwater Vehicle
    TANG Jun, LIU Yanyan, YAN Yitian
    2022, 43(5):  1135-1143.  doi:10.12382/bgxb.2021.0204
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    In order to save energy and build high-performance vehicles,a new bionic non-smooth surface that can significantly reduce the drag of underwater vehicle is proposed based on the skin structure of killer whale.The drag reduction characteristics of non-smooth surface with different parameters are obtained through numerical simulation,and the influence of bionic non-smooth surface on near-wall flowfield and turbulence intensity is discussed. The results show that the bionic non-smooth surface can increase the turbulent boundary layer thickness in a wide range of velocities,and reduce the turbulence intensity and skin friction. In the range from 0.5 m/s to 15 m/s,the skin friction of plate with the bionic non-smooth surface is reduced by more than 9%,with a maximum total drag reduction ratio of 7.57%. By applying the bionic non-smooth surface to the SUBOFF submarine model, the maximum total drag reduction ratio of submarine achieves 11.31%. The new bionic non-smooth surface has a wide range of application,which can effectively reduce the total drag of underwater vehicles and has good prospects for engineering applications.
    Influence of Dwell on Anti-penetration Characteristics of Ceramic Composite Structure
    TIAN Chao, LI Zhipeng, DONG Yongxiang
    2022, 43(5):  1144-1154.  doi:10.12382/bgxb.2021.0270
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    The dwell phenomenon is of great significance to the design of armor structure. In this work,the anti-penetration characteristics of ceramic composite structure were studied numerically and experimentally. The characteristic of the failure of projectile during penetration process,projectile dwell time and energy dissipation were analyzed. Moreover,the influence of projectile velocity,nose shape and backplane thickness on the dwell and anti-penetration characteristic was explored as well. The results showed that in the penetration process,the projectile nose was completely eroded on ceramic surface,and a large amount of energy was dissipated at the same time. And the results also indicated that with increase of projectile velocity,the dwell time and projectile kinetic energy dissipation percentage decreased. When the projectile velocity is 600 m/s,the energy reduction percentage during the dwell period is up to 90%. As the cone angle of the projectile nose increases,the dwell time and kinetic energy dissipated during dwell show a trend of first increasing and then decreasing. And the energy reduction percentage during dwell period is about 80% when the half cone angle is 45°. In addition,as the thickness of the backplane decreases,the dwell time of projectile and the reduction of kinetic energy dissipation during the dwell did not change significantly.
    Development and Verification of Chemical Hazard Diffusion Prediction Solver Based on OpenFOAM
    HAN Chaoshuai, ZHU Xuezheng, GU Jin, ZHANG Hongyuan, ZHANG He, ZUO Qinwen
    2022, 43(5):  1155-1166.  doi:10.12382/bgxb.2021.0261
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    The diffusion prediction of chemical hazards is the key foundation of accurate chemical defense support. The key to the diffusion prediction of chemical hazards is how to accurately express the influence mechanisms of underlying surface, buildings and turbulence on the diffusion of chemical hazards. Based on the actual needs of the diffusion prediction, the information fusion module, data assimilation module, source term inversion module and intelligent optimization algorithm are innovatively implanted into OpenFOAM, and a ChdpFOAM solver is designed and developed for the diffusion prediction of chemical hazards. Through the experimental analysis of ChdpFOAM solver, it is found that the solver has higher prediction accuracy in the area with relatively flat underlying surface and few buildings, and the prediction accuracy decreases in the area with dense buildings. Compared with PISOFOAM solver, the calculation accuracy of ChdpFOAM solver is improved by about 6%, and the calculation efficiency is reduced by about 32.57%. ChdpFOAM solver has good portability and expansibility.
    Fine Recognition of Human Gait with Vortex Electromagnetic Wave Radar
    YUAN Hang, LUO Ying, LI Kaiming, CHEN Yijun, ZHANG Qun
    2022, 43(5):  1167-1174.  doi:10.12382/bgxb.2021.0294
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    Radar-based human target recognition technology has important applications in many fields. The vortex electromagnetic (EM) wave carries orbital angular momentum,and the target motion may cause the linear and angular Doppler effects. Vortex EM wave contains more target information,which can provide more information for identification. But the angular Doppler effect is much smaller than the linear Doppler effect,so it is difficult to separate them.A multi-transmitter and multi-receiver model is used to generate linear frequency modulation vortex electromagnetic wave,and the linear Doppler is suppressed by dual-mode echo interference. Then,the linear and angular Doppler time-frequency images of the dual-mode echo are obtained by using the short-time Fourier transform. The amplitude values of the time-frequency images are input into the dual-channel convolutional neural network model to obtain the classification results.The simulated results show that the fine recognition ability of human gait is improved by separating the linear Doppler and angular Doppler.
    Analysis of Dynamic Characteristics of Four-rotor Aircraft Gearbox-arm Component
    ZHAO Wenhui, SUN Xiaoheng, ZHANG Weidong, ZHENG Peng, YANG Fan
    2022, 43(5):  1175-1184.  doi:10.12382/bgxb.2021.0001
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    The dynamic characteristics of gearbox-arm component are analyzed to improve the flight stability of a heavy-duty oil-powered four-rotor aircraft. The Lanczos eigenvalue solver is used to solve the modal of gearbox-arm component. The vibration acceleration value at the center of the component is collected through experiment,and the length-to-diameter ratio of mandrel is optimized. Runge-Kutta method is used to solve the dynamic equation of the component,and the law of vibration and influencing factors of the component are summarized. The results show that the mandrel's length-to-diameter ratio greater than 20 will produce larger bending vibration. The length-to-diameter ratio (<14) of the mandrel can be optimized to change the natural frequency of its vibration,and avoid the excitation frequency and frequency multiplication. The vibration acceleration increases first and then decreases with the increase in rotating speed,and reaches the maximum when the excitation frequency is equal to the natural frequency of the system. The stiffness of the system is improved to achieve vibration reduction by optimizing the angle of the inclined support.
    Quasi-static Compression Responseof Multicellular Structures with Carbon Fiber Reinforced Epoxy Composite Tubes
    ZHANG Zhendong, WANG Xueqin, REN Jie, LIU Zheng, GAO Yuan, WANG Xi
    2022, 43(5):  1185-1193.  doi:10.12382/bgxb.2021.0231
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    The multicellular structures made of fiber reinforced composites have excellent energy absorption characteristics,and have a broad application prospect in the field of energy dissipation and buffering. In order to simplify the manufacturing process,carbon fiber reinforced epoxy resin composite(CFRP) circular tubes are bonded together with epoxy resin adhesive to form multicellular structures with CFRP tubes (MSCT). The compression failure mode and energy dissipation characteristics of MSCT are analyzed through quasi-static compression test. The results show that MSCT present progressive compression failure,but the bonding surface will crack when the wall thickness of CFRP tube is greater than 0.5 mm;because the adjacent CFRP tubes hinder the expansion of the fiber bundle,the compression load increases,which makes the actual average load of MSCT higher than the theoretical average load,and causes the actual energy absorption higher than the theoretical energy absorption。Compared with a single CFRP tube,the performance of MSCT is better. The maximum specific energy absorption is 82 J/g,and the increment ratio of maximum specific energy absorption is 37.9%.
    Thermal Characteristics of Thermal Batteries during Activation Based on Heat Transfer Simulation
    CHEN Hengshuai, ZHU Yanli, LI Wei, BAI Jie
    2022, 43(5):  1194-1200.  doi:10.12382/bgxb.2021.0271
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    The activation of a thermal battery (TB) depends on the internal heat source to melt insulating solid electrolyte to highly ionic conductive melten state. A 2D model of a thermal battery is developed to simulate the heat transfer during TB activation based on multiphysics coupling software COMSOL.The heat releasing process of a pyrotechnic system is simulated with the user-defined heat source function. The temperature probes are set in the seventh unit cell and adjacent components at the center of TB stack. Temperature distribution, temperature curves of unit cell, and melting phase change are calculated.The time when the solid electrolyte melts enough to connect the cathodes and anodes is taken as the symbol of TB's activation to predict the shortest activation time. Two TBs are tested to verify the predicted results. Furthermore, an igniting tape built-in TB model is developed to study the influence of igniting tape's position on the activation time. The results show that the temperatures at the ends of TB stack are higher to compensate for heat dissipation during discharge. The current collectors can withstand thermal impact. The probes maintain at 560 ℃ in a short time. The predicted activation time is about 45 ms, the test activation times are 42 ms and 47 ms,indicating the model and prediction method are of high accuracy. The activation time of the built-in TB reduces to 30 ms.
    Polarization Pattern of Skylight in Multi-layer Environment of Atmosphere and Sea Fog
    LIU Yang, FU Qiang, ZHANG Su, ZHAN Juntong, SHI Haodong, LI Yingchao, LIU Yi, LOU Yan, YU Yixin
    2022, 43(5):  1201-1207.  doi:10.12382/bgxb.2021.0143
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    The polarization distribution pattern of skylight in the atmosphere and sea fog multilayer medium in the vertical direction is researched.The simplified double layer structure of atmosphere and sea fog is applied to modulate the complicated marine environment,and the scattering coefficients of atmosphere and sea fog uniform medium are calculated with Rayleigh and Mie scattering methods,respectively.The transmission of radiation between the two layers of medium is computed to get the polarization distribution conditions of skylight by using the adding-doubling method(RT3) based on vector radiation transmission equation,and the variation tendency of the polarization characteristics observed from the ground is studied for the downwelling radiation of sea fog on the meridian of the sun.The results show that the minimum degree of polarization (DOP) can be obtained on the position of the sun. And when the angle between the solar altitude angle and the observed altitude angle is 90°,the maximum DOP can be obtained. With the decrease in the visibility,DOP gradually increases. When the observing altitude angle is larger than 90°,the increasing effect of DOP is obvious. For the typically visible wavelengths,DOP gradually reduces when the wavelength increases. The wavelength has less effect on the DOP with the smaller visibility.The research gives the theoretical guidance for polarization detection in the vertical sea fog environment with different visible wavelengths and different visibilities.
    Intercomparison-oriented Evaluation of Equipment's Contribution Rate to Armament System-of-Systems Construction
    CHEN Lixin, XU Zhongxiang, WANG Congrong, HUANG Desuo, CHEN Zhining
    2022, 43(5):  1208-1214.  doi:10.12382/bgxb.2021.0052
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    The evaluated results of equipment's contribution rate to armament system-of-systems construction(ECRASSC)are difficultly compared. In the armament system-of-systems construction and design,the completion rate of assigned tasks under the rated conditions of equipment is taken as the metrics for ECRASSC,and the evaluation of ECRASSC is translated into the optimal distribution of task completion rate in armament system-of-systems design. Lagrange multiplier method is used to solve the optimal model,the possible extreme point of the condition is obtained as the optimized result of completion rate of assigned tasks. In the light of the three type cooperative relationships of serial,parallel and hybrid configurations between armaments, the three type functions of task completion rate is established by using the probability theory and Lagrange multiplier method,and the three type ECRASSC evauation models are solved,realizing the unified metric and comparative analysis of ECRASSC between all armaments. The validity and feasibility of evaluation model is verified by a case study.