bob手机在线登陆学报自然版

2020, 40(12): .

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2020, 40(12): .

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Penetration Enhancement Behavior of Reactive Material Double-Layered Liner Shaped Charge

GUO Huan-guo, LU Guan-cheng, HE Suo, WANG Hai-fu, XIAO Yan-wen, ZHENG Yuan-feng

2020, 40(12): 1259-1266. doi:10.15918/j.tbit1001-0645.2019.247

Abstract(1277) PDF(449)

Abstract:
To solve the problem of insufficient penetration depth of traditional polymer-based reactive liner shaped charge,a novel reactive material-copper liner shaped charge was designed. The jet formation and penetration enhancement behavior of the reactive material-copper jet against steel target were studied through combining simulations and experiments. Numerical simulations indicate that the inner copper liner mainly forms a high-velocity precursor jet to firstly penetrate the steel target,and the outer reactive liner becomes a major part of the slug,which can follow the copper jet into the penetration hole. Experimental results show that,compared with the traditional single reactive jet,this reactive material-copper jet produces a deeper penetration depth,and its penetration performance and reactive material mass entering the penetration hole are strongly influenced by the standoff. Further comparison analysis demonstrates that the deflagration reaction of reactive materials will lead to an early termination of the penetration process,and the likely mechanism is that reactive materials' chemical reaction would cause the serious instability of copper jet,eventually resulting in the residual jet not being able to continue penetration.

Study on Blasting Vibration Characteristics of Up and Down Cross Tunnels

LIU Dian-zhu, GAO Quan-chen, WANG Xin-yao

2020, 40(12): 1267-1274. doi:10.15918/j.tbit1001-0645.2019.279

Abstract(789) PDF(317)

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During the blasting excavation process of the up and down cross tunnels, it is a key issue to ensure the safety of the excavated tunnel under blasting load. Based on the tunnel engineering of Badaling Great Wall station, the blasting vibration monitoring with the blasting excavation of the main tunnel in the entrance layer was carried out, and the vibration velocity distribution law of each monitoring point was obtained when the excavation section was close to or far from the monitoring point. The frequency spectrum analysis was performed to obtain the energy distribution in different frequency ranges and the instantaneous energy at different times. The LS-DYNA program was used to establish the finite element model of the up and down cross tunnels. The velocity time history curves and effective stress time history curves of each monitoring unit were extracted. The results show that the vibration velocity distribution law of each unit was consistent with the measured vibration velocity distribution law. The effective stress value of each unit was less than the tensile yield strength of the rock mass, and the tunnel rock mass was not damaged. Combined with the numerical calculation results, the critical vibration velocity of particles was determined to ensure the safety of the excavated tunnel according to the effective stress criterion, which provides a theoretical basis for the blasting disturbance control of the lower tunnel by the upper tunnel excavation.

Study on Finite Element Modeling Method of Bolted Joints

HE Li-ping, REN Xue-mei

2020, 40(12): 1275-1281. doi:10.15918/j.tbit1001-0645.2019.253

Abstract(893) PDF(330)

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A finite element modeling method was studied and investigated for bolted joints in this paper. Taking the bolted flange connection as example,three kinds of finite element models,including solid bolt model,beam bolt model and rigid bolt model,were introduced based on finite element software ANSYS. And modal test and stress analysis were carried out. The results show that the solid bolt model and beam bolt model can be used for accurate static and dynamic analysis for the bolted flange connection,and possess wide applicability. Compared with the solid bolt model,the beam bolt model can improve modeling and computational efficiency,keeping key details. The rigid bolt model can only suit for modal analysis,and can't simulate the bolt pretension and contacts. Both experiment and simulation indicate that the magnitude of bolt pretension has little influence on structural natural frequency and mode shape. The simulation results show that the bolted joints have complex nonlinear behavior,such as nonlinear variation of stress,contact status variation between flanges,nonlinear variation of bolt tension,et a l.

Ultrasonic Anti-Recording Shielding Scheme Based on Acoustic Parametric Array

SONG Yu-bo, MA Xiao-song, TAO Yi-hang, GAO Sheng-yi, SA Peng-cheng, LI Pei-xuan

2020, 40(12): 1282-1288. doi:10.15918/j.tbit1001-0645.2019.252

Abstract(1051) PDF(342)

Abstract:
With the rapid development of smart devices, some recording devices such as smart phones, recording pens and other means are more convenient and hidden to steal information, causing a great hidden trouble for individuals, enterprises and the government. The traditional countermeasures, background noise shielding and electromagnetic wave shielding, show their limitations. Playing loud noise to overwrite the conversation, the background noise shielding interferes with the normal progress of the conversation. Emitting high-power electromagnetic wave to shield the recording equipment, the electromagnetic wave shielding can only provide a limited shielding distance and effect. To solve the problems, a scheme of ultrasonic anti-recording screen was proposed based on acoustic parametric array theory to effectively shield the eavesdropping without the influence on the normal conversation. According to the acoustic parametric array theory, multiple high frequency ultrasonic waves were arranged to pass through a nonlinear system to produce low frequency acoustic signals under the nonlinear effect. According to this principle, the low-frequency wideband noise signal was generated at first, and then BASK modulation was carried out to modulate it to the high-frequency carrier. After power amplification, the noise signal was transmitted to the target recording device by transducer array. Experimental results show that recording functions of iPhone6s, Huawei p10, Huawei glory 9 and other smart phones can be effectively blocked with the maximum shielding distance ranging from 1~3 meter. Due to the universality of shielding principle, the proposed scheme can shield the terminals with recording function such as most models of smart phones and recording pens.

Phishing Mail Detection System Based on LSTM Neural Network

ZHANG Peng, SUN Bo-wen, LI Wei-shi, XU Jun-feng, SUN Yan-wei

2020, 40(12): 1289-1294. doi:10.15918/j.tbit1001-0645.2019.262

Abstract(1004) PDF(321)

Abstract:
A long short-term memory (LSTM)-based phishing email detection method was proposed.This method was arranged mainly with two parts:data expansion part and model training part.In the data extension part, KNN and K-means algorithms were used to extend the training data set to make the number of data sets capable support deep learning algorithms. In the model training part,the data were preprocessed and transformed into a word vector matrix.And then the word vector matrix was trained to form LSTM neural network model.Finally,the mail can be divided into normal mail and phishing mail according to the trained LSTM model.Experiments were carried out to evaluate the proposed algorithm.The experimental results show that the proposed algorithm can achieve the accuracy up to 95%.

Research and Implementation of Kernel Malicious Code Detection Based on Machine Learning

TIAN Dong-hai, WEI Hang, ZHANG Bo, YU Yu-lei, LI Jia-suo, MA Rui

2020, 40(12): 1295-1301. doi:10.15918/j.tbit1001-0645.2019.261

Abstract(984) PDF(308)

Abstract:
With the development of computer science, the world is becoming more and more dependent on computers, and computer security is becoming more and more important. Malicious code is the biggest enemy of computer security. In this paper, a new method was proposed based on machine learning and new classification features to identify malicious programs, make a preliminary family classification of them, point out some shortcomings of previous machine learning in malicious code detection and classification, and screen out better distinguishing features. Firstly,n-gram algorithm was used to optimize the opcode characteristics in the disassembly code of malicious code. And then a Bag of Words model and TF-IDF algorithm were used to optimize the API call characteristics. Finally, a model was programmed and the data set was used to train and test the model. In the experiment, the classification accuracy of the model with decision tree algorithm can reach 87.41%, and the classification accuracy of the model with random forest algorithm can reach 90.06%. The experimental results show that, compared with others presented in the detection and classification of malicious code, the features of proposed method can achieve a better effect.

A Novel Coverless Steganography Method Based on Image Hashing

HUANG Cheng, QIAN Zhen-xing, ZHANG Xin-peng

2020, 40(12): 1302-1306,1313. doi:10.15918/j.tbit1001-0645.2019.265

Abstract(787) PDF(300)

Abstract:
A novel coverless steganography method based on cover selection was proposed. The sender was arranged firstly to establish a connection between the secret information and the cover image based on the iterative quantization hashing, and then to select the appropriate cover from the image set to transmit the secret information according to the connection. According to the pre-agreed rules, the receiver was arranged to extract the secret information from the image based on the image hashing technique. Experiments show that this method is superior to the traditional information-embedded steganography method in terms of security, and is slightly better than other coverless steganography methods in terms of robustness and steganographic capacity.

Mutation Scheme for Fuzzing Based on Thompson Sampling

MA Rui, HE Jin-yuan, WANG Xue-fei, WANG Xia-jing, LI Bin-bin, HU Chang-zhen

2020, 40(12): 1307-1313. doi:10.15918/j.tbit1001-0645.2019.256

Abstract(1085) PDF(269)

Abstract:
Fuzzing is one of the representative vulnerability detection technologies,which generates a set of inputs to test program,so as to find errors and identify security vulnerabilities during execution. Analyzing AFL (American fuzzy lop),a mainstream open-source fuzzer,and improving the selection method of mutation operators in the process of input mutation,this paper proposed TPSFuzzer,an automatically mutation approach of fuzzing based on Thompson sampling to support the fuzzing for binary program. The approach was designed to transform the selection of mutation operators in fuzzing into the problem of multi-armed bandit,and employ Thompson sampling optimization method to adaptively learn the probability distribution of mutation operators. Meanwhile,the proposed approach was arranged to utilize Intel processor trace mechanism to accurately collect path information and assist the selection of mutation operation,so that AFL could effectively discover more hard-to-trigger vulnerabilities. Compared with PTFuzzer,the experimental results on the LAVA data set and two real-world binaries show that TPSFuzzer can produce higher code coverage and achieve better fuzzing efficiency.

Adaptive Guidance Method of Hypersonic Vehicles in High-Altitude Based on Linear Quadratic Regulator

ZHANG Yi-jie, JIANG Yun-tao, LIU Yong, WANG Liang

2020, 40(12): 1314-1320. doi:10.15918/j.tbit1001-0645.2019.202

Abstract(833) PDF(267)

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For the reentry of glide hypersonic vehicles with large maneuverability flying in complex high altitude environment, a multi-state adaptive guidance method was proposed based on linear quadratic regulator (LQR). On the basis of the dimensionless reentry movement model of the vehicle, taking the flight dynamic characteristics, path constraints and terminate constraints into account, a safe flight corridor was designed, and polynomial fitting method was used to convert the standard trajectory into a function with range, altitude, velocity and flight-path angle. Then, a multi-state adaptive guidance law was designed based on the LQR and polynomial fitting method was used to implement a gain scheduling function for trajectory guidance law. A complete guidance method design process for the reentry of the glide vehicle based on reference trajectory and multi-state LQR was formed. A simulation verified the guidance method and indicated that it is an effective and high-accuracy adaptive guidance method.

Boundary Establishment and Analysis of Influencing Factors in the Mid-End Guidance Transfer Space

SUN Xi-tong, LUO Xing-bai, GAO Min, LÜ Jing, CHEN Hao

2020, 40(12): 1321-1331,1355. doi:10.15918/j.tbit1001-0645.2020.111

Abstract(785) PDF(325)

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Reliable handover of intermediate terminal guidance handover section of laser terminal guided mortar is a prerequisite for successfully capturing the target. In view of the uncertainty of shift handover space, the scope of the shift handover space and the influence of related factors on the shift handover space were studied. Firstly, based on the constructed trajectory model and jamming model with six degree of freedom, the constraint conditions of handover space were presented from the aspects, including the perspectives of ballistic constraint, seeker operating distance, field of seeker view angle and correction ability. Then, based on Monte Carlo shooting simulation and linear interpolation fitting method, a handover space boundary under the condition of uncontrolled full interference was established as the reference handover space, providing the limits of time, pitch angle, yaw angle, range, ballistic height and lateral distance. And the wind, initial velocity deviation and shooting angle deviation were selected as the influencing factors of space boundary. Through the simulation, the space boundary of shift handover was established under the condition of uncontrollable and eliminating wind, initial velocity deviation and shooting angle deviation respectively. Finally, simulation analysis was carried out. The results show that, among the main factors, wind is the most important one among the factors to have the influence on the spatial boundary of shift handover. The muzzle velocity deviation has great influence on the shift time, range and ballistic height of mortar ammunition. The deviation of firing angle can increase the shift time and range. According to the results, the muzzle velocity deviation and firing angle deviation should be reduced as far as possible, especially when the wind speed is small. In this paper, the establishment of the handover space can also provide the judgment criteria for the time when the guided mortar starts the laser terminal guidance. Only the laser terminal guidance works under the condition that the missile body parameters meet the handover space, the projectile can hit the target accurately.

Coordinated Control of Hybrid Electric Vehicle Based on Stochastic Network Delay Compensation

WANG Jia-jia, CAI Ying-feng, CHEN Long, WANG Shao-hua, SHI De-hua, ZHU Zhen

2020, 40(12): 1332-1339. doi:10.15918/j.tbit1001-0645.2019.237

Abstract(749) PDF(285)

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In order to improve the mode switching quality of the power-split hybrid vehicle, a torque coordinated control strategy based on stochastic network delay compensation was proposed. On the basis of the general motor torque compensation control strategy, the influence law of different communication network time delay on the stability of motor compensation control was studied to improve the accuracy of vehicle distributed coordinated control system. The composite coordinated control strategy including the BP-Smith adaptive compensation module and motor torque change rate limiting module was then proposed and verified by simulation. The results show that the control strategy can improve the system stability and smoothness of mode switching under the interference of stochastic network delay.

Gaze Estimation Based on Sample Expansion and Improved Lasso Regression

WANG Hong-feng, WANG Jian-zhong, BAI Ke-meng, ZHANG Sheng

2020, 40(12): 1340-1346. doi:10.15918/j.tbit1001-0645.2019.260

Abstract(728) PDF(294)

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In order to make use of eye features for accurate line-of-sight estimation, a method based on sample expansion and improved Lasso regression was proposed to establish the mapping relationship between eye features and line of sight. Quality samples were obtained by scoring all samples, and then sample expansion was completed. The improved Lasso regression was used to obtain an accurate line-of-sight estimation model. This method is robust for interference such as blinking in the calibration process, and can still maintain a relatively high accuracy of line-of-sight estimation with interference. The experimental results show that the accuracy of sight estimation of this method is 11.25% higher than that of the traditional method without interference; the accuracy of sight estimation of this method is 22.62% higher than that of the traditional method with 6.67% abnormal data in the calibration data.

Design Method of Sensor Self-Powered System Based on Piezoelectricity

WU Zhi-dong, FANG Jun-long, SUN Pei-dong, FENG Yu-chen, WANG Guang-ya, PAN Di

2020, 40(12): 1347-1355. doi:10.15918/j.tbit1001-0645.2019.264

Abstract(776) PDF(259)

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According to the requirements of ventilation condition monitoring for large-scale farms, a system of wind-induced vibration piezoelectric harvesting energy was designed to solve the self-powered problem of monitoring sensors. The self-powered system consists of piezoelectric energy harvesting structure and energy management circuit, and that can convert wind energy into electricity. The results of the analysis and testing indicate that the piezoelectric energy harvesting structure could output 10.88 V voltage and 6.975 mW power. The results of LTspice simulation show that the energy management circuit based on LTC3588-1 could realize the function of voltage conversion and output 3.3 V voltage stably. According to the similarity between mechanical system and electrical system, the overall model of the self-powered system was built, the simulation results of Matlab/Simulink show that the piezoelectric energy harvesting structure could output 10.87 V voltage and 6.989 mW power, and the end self-powered system could output 3.3 V voltage. All the above results are basically consistent with the simulation and test results of energy harvesting structure and energy management circuit, indicating that the overall modeling of the system is correct and the scheme is reasonable. Through the field test, when the wind speed was 2.6 m/s at the vent, the self-powered system could output 3.3 V voltage, and supply power to the sensor monitoring system stably. This study can be used in the ventilation monitoring sensor self-powered system widely.

A New Space-Time Compensation Method for STAP in Non-Stationary Clutter

ZHANG Wei, ZHENG Kun

2020, 40(12): 1356-1361. doi:10.15918/j.tbit1001-0645.2018.177

Abstract(660) PDF(273)

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A space-time compensation method, which mitigates the range dependence of ground clutter for the side-looking airborne radar was proposed. By using the specific structure of the space-time steering vector of the clutter, the proposed method was arranged to mitigate the range dependence of both the main-lobe and side-lobe clutter. The simulation results show that, the proposed method can compensate non-stationary distribution of ground clutter, improving the performance of the space-time adaptive processing (STAP).

Influence of Bulk Current Injection Probe on Electromagnetic Radiation Sensitivity Research

SUN Yong-wei, YANG Mao-song, PAN Xiao-dong, LU Xin-fu

2020, 40(12): 1362-1368. doi:10.15918/j.tbit1001-0645.2018.293

Abstract(958) PDF(239)

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With the increasingly harsh electromagnetic environment of the battlefield, the technical requirements for assessing the adaptability of weapons equipment to the conditions of strong electromagnetic fields have become higher and higher. In the study about taking bulk current injection to replace continuous-wave strong-field electromagnetic radiation, the effect of current injection probe is unavoidable. In this paper, an experimental method was analyzed to implement injection equivalent radiation replacement for nonlinear interconnected systems. The bulk current injection probes of key devices and their equivalent circuit models were introduced. Through theoretical analysis and experimental verification, it is found that the equivalent error is not negligible when the radiation experiment performs without bulk current injection probe, and the same equivalent circuit must be provided for both radiation and injection conditions. The test results on the probe performance show that, at 150 MHz frequency, the linear error of probe injection and output can be higher than 12% when the injection power reaches to 60 W, demonstrating the effect of performance of injected probe itself on the equivalent in the equivalent high field electromagnetic radiation experiment.

2020, 40(12): 1369-1386.

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