bob手机在线登陆学报自然版

2019, 39(2): .

Abstract(718) PDF(304)

Abstract:

2019, 39(2): .

Abstract(645) PDF(263)

Abstract:

Investigation of the Effect of Montmorillonite Powders on Gas Explosion Parameters

WANG Yan, YI Hong-wei, MENG Xiang-qing, ZHENG Li-gang, YU Ming-gao

2019, 39(2): 111-117. doi:10.15918/j.tbit1001-0645.2019.02.001

Abstract(1031) PDF(464)

Abstract:
With natural mineral montmorillonite powder as gas explosion inhibitor, the effect of the concentration of montmorillonite powder on the characteristic parameters of explosion pressure and the average velocity of flame propagation at 9.5% methane-air premixed gas were tested using the 20 L spherical explosion device and the 5 L pipeline experimental system. The results showed that montmorillonite powder displayed a good suppression effect on methane explosion, the max-pressure of methane explosion and the average velocity of flame propagation of 9.5% methane-air premixed gas decreased firstly and then increased with the increased concentration of montmorillonite powder. The max-pressure of methane explosion, decreasing by 29.2%, was the lowest when the mass concentration of montmorillonite powder was 0.16 g/L in the 20 L spherical explosive device; in the pipeline explosion suppression test system, when the mass concentration of montmorillonite powder was 0.20 g/L, the flame propagation velocity was the lowest. In addition, the mechanism of the inhibition methane explosion by montmorillonite powder was also discussed.

Dynamic Failure Mechanisms and Anti-Penetration Performance of Graphene Reinforced Al/SiC Composite

XU Yu-xin, SUI Ming-bin, REN Jie, XIE Shi-yu, WU Yue

2019, 39(2): 118-124. doi:10.15918/j.tbit1001-0645.2019.02.002

Abstract(1866) PDF(498)

Abstract:
The dynamic mechanical behaviors, failure mechanisms and anti-penetration performance of graphene reinforced Al/SiC composite were investigated in this paper. The mechanical behaviors of the material under strain rate 0.001~5 200 s^-1were obtained by static and dynamic compression tests and its strain rate effect was revealed. Furthermore, the fracture mechanisms of graphene reinforced Al/SiC composite under static and dynamic compressive loading were analyzed by optical and scanning electronic microscopy (SEM) observations. In addition, ballistic impact experiments were conducted to acquire the ballistic limit velocity and specific energy absorption of Q235A/graphene reinforced Al/SiC composite structure and Q235A steel plates with thicknesses ranging from 12 mm to 18 mm. The results indicated that the specific energy absorption of Q235A/graphene reinforced Al/SiC composite structure is 1.79 times that of Q235A steel plates with thicknesses ranging from 12 mm to 14 mm, and the specific energy absorption of graphene reinforced Al/SiC composite with the thickness of 34.10 mm is the same as the value of Q235A steel plate with the thickness of 16.70 mm.

Research on Frequency Distribution of Peak Area of Blast Shock Wave

LI Xiang-rong, MA Yi-wen, LI Shuai, WANG Guo-hui, YANG Jian-bing

2019, 39(2): 125-130. doi:10.15918/j.tbit1001-0645.2019.02.003

Abstract(1097) PDF(514)

Abstract:
To solve the problem that armored vehicles' anti-blast shock performance is not strong, wavelet analysis was used together with time domain analysis to study the frequency distribution characteristics of the peak area of blast shock wave, and analyze the frequency of measured signal. The results show that the shock wave contains a wide frequency range; the noise frequency is mainly concentrated in the high frequency part; the peak frequency of the shock wave is mainly concentrated in the low frequency part, and reveals a exponential growth trend with the peak overpressure.

Numerical Simulation on the Impact of Explosion Shock Wave on Bullet-Proof Vest

XU Bin, WANG Cheng, ZANG Li-wei, GAO Tong, LIU Ya-jun

2019, 39(2): 131-134. doi:10.15918/j.tbit1001-0645.2019.02.004

Abstract(1075) PDF(497)

Abstract:
In order to study the impact of explosive shock wave on human body wearing a bullet-proof vest, the 2 and 3-dimensional numerical models of the blast wave impact on the bullet-proof vest were established. With the coupling of the Eulerian and Lagrangian grids, the forming explosion field due to the interaction between the shock wave and the bullet-proof vest was simulated. This research presented an analysis of the shock wave propagation process, including the reflection on the surface of the vest, the diffraction on the edge of the vest and the propagation process between the body and the bullet-proof vest. The simulation result indicates that the damage of shock wave on the human body is increased because of the interaction between the shock wave and the bullet-proof vest.

Study on the Resistance Characteristics of Elliptical Cross-Section Projectile Penetrating Concrete

LIU Zi-hao, WU Hai-jun, GAO Xu-dong, PI Ai-guo, HUANG Feng-lei

2019, 39(2): 135-141,146. doi:10.15918/j.tbit1001-0645.2019.02.005

Abstract(864) PDF(340)

Abstract:
In order to study the stress characteristics of projectile head during the process of penetrating concrete with elliptical cross-section heterogeneous projectile, numerical simulation of circular and equal cross-sectional area of the elliptical cross-section projectile penetrating concrete process was carried out, and the relationship between the normal stress and the normal velocity on the head surface during the penetration of different projectiles was analyzed. The relationship between the normal stress and the normal penetration velocity of the elliptical cross-section projectile's head surface at different ratios of the major axis to the minor axis and the position of the element was obtained, and the elliptic cross-section body penetration calculation formula was also obtained. The results show that compared with the same cross-sectional area of the circular cross-section projectile, and at the same normal velocity, the normal stress of elliptical cross-section projectile surface increases with the distance from the element of the head to the center of the ellipse. At the same penetration velocity, the penetration depth of the projectile increases with the ratio of the major axis to the minor axis of the cross section.

Effect of Cost Parameters Adjustment on the Accuracy of Bayesian Anti-Spam Filtering System

CUI Chao, LÜ Dan, JIANG Shu-feng

2019, 39(2): 142-146. doi:10.15918/j.tbit1001-0645.2019.02.006

Abstract(777) PDF(293)

Abstract:
In order to reduce the error rate in classification calculation of anti-spam filtering system, the automatic testing process of target email in the Bayesian anti-spam filtering system was analyzed, the definition of system cost was researched from two aspects of system filtering quality and user fault tolerance. Cost parameters were analyzed in the collection of different sample sets and attribute spaces, with disabling and enabling lemmatizer and stop-list. By adjusting the cost parameters, the results of the Bayesian filtering system in various assumptions were analyzed, the standard of system modeling was optimized, and system filtering quality was upgraded. The results prove that the scheme is feasible.

Automatic Labeling Method for Human Motion Time Series Using Wavelet Energy Entropy

LIANG Guan-hao, LUO Qing-sheng

2019, 39(2): 147-154. doi:10.15918/j.tbit1001-0645.2019.02.007

Abstract(747) PDF(382)

Abstract:
To enhance labeling efficiency of human motion time series, a new technique of automatic labeling for human motion time series was proposed.9 inertial measurement units placed on each of 6 subjects were used to acquire motion data from 17 human activities in terms of acceleration and angular velocity. Sliding window technique was adopted to segment motion data from each subject while multiresolution analysis was applied to calculate the corresponding wavelet energy entropy. A segmenting threshold and time constraints were chosen to label each subject's motion data automatically. The results showed that the average labeling accuracy reached 95.82%. It took the proposed method approximately 18.6 minutes to label motion data of all 6 subjects, which was 75.76% shorter than the average labeling time by human, 76.75 minutes. The proposed method improved the labeling process significantly with relatively high average labeling accuracy.

Anti-Sea Combat Capability Requirement Generation of New Naval Gun with Adjustable Muzzle Velocity

XU Jun-fei, LU Fa-xing, WANG Hang-yu, WU Ling

2019, 39(2): 155-161. doi:10.15918/j.tbit1001-0645.2019.02.008

Abstract(866) PDF(319)

Abstract:
In order to realize the transformation of naval gun from task to capability in anti-sea combat, the framework model of capability requirement was established. The paper analyzed the mapping relationship between sea combat task and combat capability based on the naval gun combat process. According to the mapping relationship, the mathematical models of the detection probability, maximum detection distance, reaction time and single-shot probability were established. The simulation experiment analyzed the capability requirements of the new naval gun at different firing distances with the fire control system accuracy when shooting at 20 km as the standard under the variable initial velocity of new naval gun, and analyzed the change trend of the capability index at different initial speeds. The result shows the higher precision of fire control system, the greater single-shot probability. For targets within sight distance, the higher the initial velocity, the better the single-shot probability. But the advantage of initial velocity is not obvious for long distance targets. The method has important theoretical and practical significance for scientific development of naval gun weapon equipment.

A Lifting Wavelet and Hilbert Transform Fusion Method for Transient Power Quality Detection

ZHENG Shu-hua, ZHANG Ning-ning, WANG Xiang-zhou

2019, 39(2): 162-168. doi:10.15918/j.tbit1001-0645.2019.02.009

Abstract(984) PDF(362)

Abstract:
In oeder to improve the location accuracy and the type identification speed of disturbance in the transient power quality detection, a lifting wavelet and Hilbert transform fusion method was proposed in this paper. Firstly, the lifting wavelet was employed to get signal approximation componentsA₁and detail componentsD₁from the disturbed signals. And then, the Hilbert transform was used to calculate the instantaneous amplitude of the two components. According to the instantaneous amplitude, the disturbance time and type were identified accurately. Simulation and experiment results show that, the disturbance time location accuracy can reach 95.7% and the type identification accuracy can reach 91.8% based on the proposed method.

An IAE Filter with Dynamic Resizing Window for the Stereo Vision Measurement

WANG Xiang-zhou, SHI Xiao-min, ZHENG Shu-hua

2019, 39(2): 169-174. doi:10.15918/j.tbit1001-0645.2019.02.010

Abstract(775) PDF(348)

Abstract:
For measurement of moving objects in stereo vision, IAE filter was introduced and a method of the IAE filter window dynamic resizing (IAE-DW) was proposed. Firstly, the range of window size was constrained according to the relation between the window size and standard deviation estimation error of the IAE. Then the window size was adjusted dynamically based on the variance ratio of standard deviation calculated with the change rate of motion depth. Thus, the estimation accuracy of IAE to noise statistics can be improved. The experimental results demonstrate that the proposed algorithm can provide better filtering ability.

An Approach to Free-Hand Interaction for 3D Scene Modeling

WAN Hua-gen, LI Ting, FENG Li-wen, CHEN Ying-shu

2019, 39(2): 175-180. doi:10.15918/j.tbit1001-0645.2019.02.011

Abstract(1055) PDF(425)

Abstract:
To solve the problem of a free-hand interaction method in 3D scene modeling, some possible solutions were put forward from three levels for the key problems of scene modeling. On the macroscopic level, an interaction frame was established based on user activities and system tasks. On the middle level, a method was proposed to construct a complete and practical gesture set, and then a gesture set was designed for the system based on the proposed method. On the microcosmic level, to solve the "Midas touch" problem, an optimal method was put forward from the aspects of time, space, and gesture assistance to improve the recognition rate of gestures. Finally, experiment was carried out to verify the availability of proposed methods, providing a future research direction.

Designing for Tactile Braille Reading Methods on Smartphones

CHU Shao-wei, ZHU Ke-ying

2019, 39(2): 181-186. doi:10.15918/j.tbit1001-0645.2019.02.012

Abstract(887) PDF(513)

Abstract:
In this paper, three new methods were presented for tactile Braille reading on smart phones, including left and right sliding, sliding to the right, and sliding down. The three methods were designed based on vibrotactile feedback of mobile phone and the direction encoding of finger movements. A series of pilot studies were carried out to tune and optimize the tactile parameters. And then, twelve participants were invited to implement a formal user experiment, evaluating the usability of three methods. The experiment results show that the three methods can reach adequate speeds, in 3.62, 3.16 and 4.09 seconds for average every character. The accuracy of the gestures can reach 98.1%, 98.1% and 96.9% respectively. The method with sliding to the right gesture is the most efficient one and also the user's most satisfied one.

Research on Leg Impedance Control for Electronic Wheel-Legged Robot Based on Fractional Order

ZHAO Jiang-bo, CHEN Ying-hui, WANG Jun-zheng

2019, 39(2): 187-192. doi:10.15918/j.tbit1001-0645.2019.02.013

Abstract(1033) PDF(435)

Abstract:
In order to reduce the impacts and improve robot's adaptability to complex terrain, position-based impedance control was applied to the compliance control for legged locomotion of the electronic wheel-legged robot and a new impedance controller with fractional order was proposed to improve the contact performance. As the bandwidth of the position closed-loop could affect the realization of the target impedance, an inverse position-loop compensator was introduced to improve the system impedance tracking performance. Simulation and experiment results show that the fractional-order impedance control can not only realize stable contact between the foot and the ground, but also achieve superior contact transition performance in comparison to the conventional second-order mass-damping-spring impedance controller.

Adaptive Parameter Estimate and Control Based on Prescribed Performance for the Turntable Servo Mechanism

WANG Shu-bo, REN Xue-mei, LI Si-qi, SUN Zi-mei

2019, 39(2): 193-197. doi:10.15918/j.tbit1001-0645.2019.02.014

Abstract(1017) PDF(346)

Abstract:
In this paper, a parameter estimate and adaptive control method was proposed based on prescribed performance function(PPF) for the turntable servo mechanisms with unknown parameters and nonlinearity friction dynamics. A continuous friction model was employed to capture the friction dynamics of the turntable servo mechanism, and high-order neural network(HONN) was adopted to approximate the nonlinearity friction dynamics. An auxiliary filter variable was designed to drive the information of the parameter estimation, which was used as a new leakage term of parameter update law to make the estimation values achieve to true values. To improve the transient behavior and steady-state performance of the turntable servo mechanism, the PPF was adopted to translate the error system of the original system into a new error system. Simulation results validate the effectiveness of the proposed control scheme.

Abrupt Fault Diagnosis for Electro-Mechanical Actuator Based on IMM-UKF

WANG Jian, WANG Xin-ming, XIE Rong, LI Ting, CAO Yu-yan

2019, 39(2): 198-202,208. doi:10.15918/j.tbit1001-0645.2019.02.015

Abstract(1048) PDF(404)

Abstract:
The abrupt faults of electromechanical actuator (EMA) can cause the safety problem of plane flight control system, so as to the plane lose control. A diagnostic method for abrupt faults of electromechanical actuator (EMA) was proposed based on interactive multiple model (IMM) and unscented Kalman filter (UKF). The UKF was used to make the state equation be close to a nonlinear feature and make the filter represent a better stability and an acceptable computational complexity. And the IMM was used to solve the problem of the diagnosed model with a few measurable parameters, but also to improve the speediness and accuracy of the fault diagnosis in the case of large difference between the occurrence of the fault and the presupposed fault. The effectiveness of proposed IMM-UKF fault diagnosis method of EMA was verified by simulation. The results show that the proposed IMM-UKF method can obtain real-time and accurate diagnostic values of the abrupt faults of components and sensor in EMA.

A Multi-Neuron Neural Network Algorithm for DSP Servo Control System of Unmanned Reconnaissance Vehicle

YUE Guang, PAN Yu-tian, ZHANG Hua-jun, LIU Xue-jie, LI Yu-feng

2019, 39(2): 203-208. doi:10.15918/j.tbit1001-0645.2019.02.016

Abstract(960) PDF(422)

Abstract:
To solve the problem of slow data processing speed, inflexible design and application restriction of intelligent algorithm in domestic single-chip servo control system, a new method was proposed based on an improved multi-neuron neural network algorithm for DSP servo control system of the unmanned reconnaissance vehicle. The multi-neuron PID controller was constructed in a parallel connection and intercross form, and operated in DSP. Experiment and simulation results show that the method can converge quickly and can realize self-adjusting of the system controlled quantity without human intervention, validating the validity of the algorithm. The basic research provides a theoretical basis and a reference for further application of the unmanned reconnaissance vehicle in battlefield reconnaissance and emergency rescue of unexpected disasters.

Research on Technology of Non-Balanced Reactor 24-Pluse Auto-Transformer Rectifier

GE Hong-juan, YANG Guang, JIANG Fan, ZHANG Lu

2019, 39(2): 209-214,220. doi:10.15918/j.tbit1001-0645.2019.02.017

Abstract(873) PDF(332)

Abstract:
In this paper, a topology of non-balanced reactor 24-pluse auto-transformer rectifier was proposed based on the composition of voltage vector. Each phase of the auto-transformer was arranged with five windings, conducting two diodes of four rectifier bridges at synchronization according to the voltage vector superposition of different windings and outputting the line voltage with the maximum vector difference. Conducting the main rectifier bridge and the auxiliary bridge successively according to the time zone of the main and auxiliary vector composition, the rectifier bridges could parallelly output the 24-pluse DC voltage due to the composition form of the asymmetric output voltage. The turn ratio of the auto-transformer, the expression of input current and output voltage were derived, and the system performance was analyzed by calculating the input current harmonic content and the equivalent capacity of transformer. Finally, the rationality of the design was verified by simulation and experiment.

A Low-Power MEMS Piezoresistive Sensor Dynamic Test System

LIU Feng, JIN Lei, NIU Shao-hua, LIU Hai-peng, GUO Jian-chang

2019, 39(2): 215-220. doi:10.15918/j.tbit1001-0645.2019.02.018

Abstract(1231) PDF(400)

Abstract:
In order to accurately analyze the penetrating overload signal, a low-power, high-load dynamic test system was proposed. The system could withstand 2×10⁵goverload signals. In order to achieve the characteristics of high sampling rate, low power consumption, and shock resistance, the system adopted silicon crystal oscillator as the main oscillator, using low-power CMOS chips. When the system started to work, the processor entered the deep sleep mode and started to supply power to the peripheral circuit when entering the transmit mode. When the missile emitted a signal, a trigger signal from the hysteresis trigger circuit would be generated, so the acquisition system was started to collect data. Experiments have shown that with this scheme, the life cycle of the missile can be prolonged, and the overload signal of the air gun can be accurately collected.

Submission System

Author Related

Writing Norms

Links

2019 Vol. 39, No. 2

Archive