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2021, 41(6): .

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2021, 41(6): .

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Current Research and Development of Ammunition Damage Effect Assessment Technology

XU Yuxin, CAI Zilei, WU Wei, ZHAO Pengduo, QIAO Zhijun

2021, 41(6): 569-578. doi:10.15918/j.tbit1001-0645.2020.194

Abstract(1107) PDF(425)

Abstract:
By summarizing the research status of ammunition damage effect assessment technology, the future development trend is prospected, which provides ideas for the development of ammunition damage effect assessment technology. According to the requirements of precise perception, precise command, precise attack, precise assessment and precise support in the new era, the difficulties and pain points in the acquisition and use of ammunition damage assessment data are analyzed, the research status of ammunition damage effect assessment technology is sorted out, the ammunition damage effect assessment technology system is constructed, and the future development trend of ammunition damage effect assessment technology is prospected.

Experiments and Three-Dimensional Finite Element Simulations on the Compressive Mechanical Properties of Closed-Cell Aluminum Foam

DAI Kaida, WU Dongxu, ZHANG Zhicheng, CHEN Pengwan

2021, 41(6): 579-587. doi:10.15918/j.tbit1001-0645.2020.075

Abstract(654) PDF(335)

Abstract:
Based onX-ray electronic computed tomography technology,a three-dimensional finite element model was established to reflect the true structure of closed-cell aluminum foam.Firstly,the quasi-static and dynamic compressive mechanical properties of closed-cell aluminum foam were analyzed based on experiments and numerical simulations.Then the deformation characteristics and mechanical properties of closed-cell aluminum foam were analyzed.Finally,the reliability of the model was verified.The results show that a long platform stage appears on the stress-strain curve of closed-cell aluminum foam under quasi-static and dynamic loading.Under quasi-static compression,the specimens exhibit local plastic deformation mainly along the loading axis at 45°.At low compression rate,the deformation mode is the same as under quasi-static compression,stress concentration occurs first in the structural weakness of the closed-cell aluminum foam specimen,until material plasticity bend.Under high-speed compression,the loading end of the specimen first reaches the yield stress.Comparing the yield strength at different strain rates,the yield strength of closed-cell aluminum foam under dynamic compression is higher than that of quasi-static compression.When the strain rate of closed-cell aluminum foam specimen is 280~700 s^-1,the change of yield strength is not obvious.The strain rate increases to 2 000 s^-1,and the yield strength increases slightly.

Influence of Radial Non-Uniform Pressure Distribution on Thermo Mechanical Coupling of Wet Friction Pairs

WANG Liyong, WU Jin, LI Le, ZHENG Changsong, ZHANG Jinle

2021, 41(6): 588-596. doi:10.15918/j.tbit1001-0645.2020.110

Abstract(614) PDF(264)

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Comparing five radial pressure distribution forms, the effect of radial non-uniform pressure distribution on thermo-mechanical coupling of wet friction pair was analyzed by means of finite element simulation and experiment. The results show that there is a strong coupling relationship among the temperature field, stress field and strain field of the dual steel sheet under the same radial pressure. At the end of the working state, the radial position of the temperature, stress and strain field and the maximum value of each physical quantity move to the center of the disk compared with the peak position of the original loading pressure, and the change rate of the radial position of the ring is 10%~40% of the disk width. The radial pressure distribution mode has a direct relationship with the temperature of the friction pair and the maximum value of stress and strain. When the pressure is distributed along the inner and outer radius wave crest, the value of temperature and strain is maximal. When the pressure is linearly reduced from the inner to the outer diameter, the value of stress gradually go to maximum. When the pressure changes along the inner diameter wave trough, the value of temperature, stress and strain is minimal.

Simulation Research on Air-Assisted Fuel Injection System for Keorsene Piston Engine

LIU Bolan, YAN Chao, YU Fei, WANG Wentai, HAN Yaohui, ZHAO Zhenfeng

2021, 41(6): 597-602. doi:10.15918/j.tbit1001-0645.2020.080

Abstract(538) PDF(247)

Abstract:
The simulation research on the air-assisted injection system of kerosene piston engine was carried out.Firstly,a mathematical model of air-assisted fuel injection system of an engine was established.Then a physical model of air-assisted fuel injection system was built and checked, and the effect of structure, operation and environmental parameters on the characteristics of the fuel system was analyzed.The results show that the smaller the volume of the pressure stabilizing chamber,the amplitude of pressure fluctuation is the larger.The greater of the pressure difference,the fuel flow is the greater under the same injection pulse width;Oil temperature has little effect on fuel flow.The higher the altitude,the slower the pressure build-up.As the altitude increases,so does the time it takes for the gas pressure to reach 600 kPa.The research provides a theoretical basis for the fuel system matching machine.

Finite Element Analysis and Experimental Verification of Heat Insulation Performance of Piston

CHEN Guozheng, ZHANG Weizheng, YUAN Yanpeng, JI Yameng

2021, 41(6): 603-610. doi:10.15918/j.tbit1001-0645.2020.101

Abstract(532) PDF(234)

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The heat insulation performance of a new heat insulated piston was studied based on finite element analysis and experimental verification. Firstly, the heat exchange coefficient of the piston was determined by means of performance simulation calculation and empirical equations. Secondly, the temperature field and the heat flux distribution model were obtained using finite element thermal analysis. And the changes of heat flux distribution model were also discussed for the piston with compound heat insulation structure. Finally, the heat insulation performance of the piston was verified by the temperature field simulation test. The results show that the heat insulation structures, such as heat insulation pad and air gap, can greatly improve the heat and load carrying capacity of the piston. And the heat insulation degree of the piston can exceed 60%. The error between the simulation results and the finite element calculation results is within 5%, which indicates that the finite element calculation results have high engineering reference value.

Radar Range Profile Target Recognition Based on FLAKNN

HAN Lei, ZHOU Shuai

2021, 41(6): 611-618. doi:10.15918/j.tbit1001-0645.2020.181

Abstract(537) PDF(207)

Abstract:
Due to the deficiency of traditional KNN algorithm in target recognition of high range profile, such as using fixedkvalue globally and not considering the influence of each characteristic component on classification, the target recognition performance is poor. Therefore, an improved KNN algorithm-FLAKNN, was proposed. By extracting the stable characteristics such as the size, entropy, center distance, irregularity, scaling feature and symmetry of the high range profile of the target, Fisher discriminant analysis was used to project all feature components to the low-dimensional space, so as to achieve the maximum separability among different categories. Combined with the local distribution of adjacent samples and the adjustment ofkvalue, the principle of majority voting was finally used to determine the category of test samples. The results show that compared with the traditional KNN algorithm, this algorithm further improves the recognition performance.

Content Retrieval Protocol of Vehicular Network Based on NDN Architecture

LI Danxia, YANG Yating, HUANG Wanying

2021, 41(6): 619-628. doi:10.15918/j.tbit1001-0645.2020.227

Abstract(578) PDF(321)

Abstract:
In the existing content retrieval protocols of vehicular named data networking (VNDN), the content retrieval for location-independent applications is usually to obtain the location of the content provider based on flooding. This method not only costs much, but also is unable to adapt to the highly dynamic changes of the location of content providers. In this paper, a content retrieval protocol, CPCoR, was proposed based on clustering and prediction mechanism for VNDN. The CPCoR was arranged to establish a dynamic network content index table through the collaborative interaction between vehicles and roadside units. In the intra-street forwarding mechanism, the index was designed to forward according to the cluster head with stable link connection. In the inter-street forwarding mechanism, the index was designed to select the best forwarding street according to the routing performance of streets. Experimental results show that, compared with existing protocols, Navigo and CCVN, CPCoR protocol can not only improve the success rate of content acquisition by 21.5% and 51.3%, but also can effectively reduce the cost of content acquisition by 22.6% and 28.4%.

A Deep Learning Detection Method for Soldier Target Based on Few Samples

WANG Jianzhong, WANG Hongfeng, LIU Hongyang, LI Bo, SUN Yong, ZHANG Chiyi

2021, 41(6): 629-635. doi:10.15918/j.tbit1001-0645.2020.229

Abstract(778) PDF(271)

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A deep learning method detection for target with few samples based on YOLOv3 was proposed to solve the problem of small enemy soldiers’ datasets. Data augmentation was used to improve the robustness of the small-sample target detection model, and improve the network structure by connecting the shallow network feature map to the deep network across layers.k-means clustering was used to obtain anchor boxes suitable for soldier target characteristics, and pre-training was used to improve the convergence speed of model training. The results show that the method in this paper has a success rate (mAP) of 85.6% for target detection of enemy soldiers with small enemy soldiers’ datasets, a detection accuracy (IOU) of 82.18%, and a good detection effect for small and occluded targets. The detection speed deployed on NVIDIA TITAN V GPU computer and NVIDIA Xavier reaches 54.6 and 26.8 fps, which means a good real-time performance.

Trend Removing Method of Blasting Vibration Signals Based on MEEMD

LI Chen, LIANG Shufeng, LIU Chuanpeng, CHENG Jian, LIU Dianshu

2021, 41(6): 636-641. doi:10.15918/j.tbit1001-0645.2020.052

Abstract(551) PDF(176)

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A trend removing method based on modified ensemble empirical mode decomposition (MEEMD) was proposed,to solve the trend interference problem existing in blasting vibration tests,and the extensive simulations of analog signals and the case analysis of blasting vibration signal were carried out. The extensive simulations show that the results of the proposed method for sustained vibration signals are close to the results of the existing trend removing methods based on empirical mode decomposition (EMD) or ensemble empirical mode decomposition (EEMD). When the test signals are intermittent,the proposed method can extract the trend more fully,which embodies its superiority and applicability to remove the trend in blasting vibration signal. In the meantime,the reliability of the proposed method in practical application was proved by the case analysis.

Research on Transmission Performance of Ground Antenna in Wireless Overpressure Test System

LÜ Zhongjie, LI Huiwu, GAO Chenyu, LIU Yan, HUANG Fenglei

2021, 41(6): 642-648. doi:10.15918/j.tbit1001-0645.2020.204

Abstract(527) PDF(203)

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In response to the requirements for efficiency, accuracy and safety of shock wave testing, a wireless shock wave overpressure test system was developed by using 4G wireless communication technology and storage testing methods. A study on the transmission performance of ground antennas was carried out, and a free-space modified model was established, which characterizes the relationship between the reference signal received powerP_RSRand any transmission distanceL. The experiment results show that the theoretical value is in good agreement with the experimental value, and theP_RSRdecreases with the increase ofL. Within a certain range, the ground influence factorωdecreases with the increase of the antenna height at the receiving end, the free space transmission path lossL_Fdecreases and theP_RSRincreases accordingly.

An Improved Neural Network Based Research on Generalization of an Optical Fiber Pre-Warning System

WANG Fang, XING Jichuan

2021, 41(6): 649-657. doi:10.15918/j.tbit1001-0645.2020.070

Abstract(511) PDF(245)

Abstract:
There is a high false alarm rate in identifying event process of traditional long-distance optical fiber pre-warning system. To solve the problem, an optical fiber pre-warning system was proposed based on an improved neural network and its adaptability to different environments was studied. Firstly, Phi-OTDR technology was applied to design the distributed sensing part of the system. And then, an improved neural network was used for the signal recognition part to identify and classify intrusion events. Finally, experiments were carried out in three cases to analyze the adaptability of the system. The results show that the system can provide an excellent classification effect in the recognition of optical fiber vibration signals, and it also has better adaptability under different environmental conditions.

Antenna Directivity Effect Analysis for Ground-Based GNSS-R Power Measurement Applications

HONG Xuebao, ZHANG Bo, YANG Dongkai, HAN Mutian

2021, 41(6): 658-664. doi:10.15918/j.tbit1001-0645.2020.062

Abstract(550) PDF(229)

Abstract:
In ground-based global navigation satellite system reflectometry (GNSS-R) power measurement applications, signal-receiving antennas could not perfectly suppress the co-polarized signal from backwards and the cross-polarized signal from both forwards and backwards.In order to analyze the influence of the antenna directivity on the correlation power of the target signals, a right hand circular polarized (RHCP) antenna and a left hand circular polarized (LHCP) antenna were used to receive the direct signal and reflected signal, respectively. The correlation power models of the signals received by the actual antennas were firstly established, and then the probability distribution and numerical characteristics of the actual signal correlation powers were determined successively. Based on simulating the numerical characteristics, the relative deviations and variation coefficients of the correlation powers were calculated and analyzed. Simulation results show that the actual antenna directivity can cause errors in the correlation power measurement of target signals. The RHCP antenna ’s directivity has a considerable impact on measuring the correlation power of direct target signal in the low elevation angle range, while the LHCP antenna ’s directivity significantly affects the measurement of reflected signal correlation power in entire elevation range.

Research and Application of Artifact Identification Method for Wearable ECG Devices

SHANGGUAN Weihua, LI Ye, WU Min

2021, 41(6): 665-670. doi:10.15918/j.tbit1001-0645.2020.083

Abstract(544) PDF(190)

Abstract:
The electrocardiogram(ECG) signals from wearable ECG monitoring equipment usually contain movement and device artifact.In this paper,a combined artifact recognition algorithm was developed based on the mutation degree of ECG amplitude and the connectivity of mutation distribution,the disorder degree of transformed ECG maximum and minimum values,and abnormal cardiac beat characteristics,etc.Embedding three key links in ECG automatic analysis,the combined artifact recognition algorithm was carried out,and selecting four kinds of data samples from three kinds of equipment,the algorithm was verified.Test results show that the combined artifact recognition algorithm can provide an artifact recognition sensitivity up to 98.35%,and improve QRS detection accuracy by 3.08%,at the same time,make the ECG automatic analysis operation time no increase and no rely on specific hardware equipment.The combined artifact recognition algorithm can be applied to ECG data analysis of various wearable devices universally and efficiently.

Design and Implementation of Integration Padding Reconfigurable Hash Algorithm Circuit

CHEN Tao, LIAN Yixin, LI Wei, NAN Longmei

2021, 41(6): 671-678. doi:10.15918/j.tbit1001-0645.2020.105

Abstract(574) PDF(200)

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In view of the lack of filling circuits in the implementation of existing domestic hash algorithms, and the existing designs do not support the SHA3 algorithm standard, a complete circuit was designed to support 11 common hash algorithms in 5 categories, including MD5, SHA1, SM3, SHA2 and SHA3 series. Firstly, analyzing 2 types of filling rules and 6 filling bit widths, the filling process was arranged with different states. Then, considering the characteristics of each arithmetic operation circuit and the reuse of operation unit resources, a reconfigurable operation circuit was designed. Finally, a complete circuit was integrated from algorithm filling to output. Compared with the software filling method under the synthesis of 55nm process library, the performance of SM3, SHA2 _ 384, and SHA2 _ 512 can be improved by 11%, 22% and 22% respectively.

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