bob手机在线登陆学报自然版

2020, 40(8): .

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2020, 40(8): .

Abstract(1827) PDF(2410)

Abstract:

Numerical Simulation of Wedge Induced Oblique Detonation at Near Critical Mach Number

WANG Cheng, WU Jing-chang, HAN Wen-hu, YANG Tong-hui

2020, 40(8): 803-809. doi:10.15918/j.tbit1001-0645.2019.143

Abstract(2086) PDF(2585)

Abstract:
In the study of detonation propulsion technology, it is very important to form stable detonation waves for the detonation engine to produce stable thrust. The curvilinear relationship between the angle of oblique detonation and the incoming flow Mach number was determined and the critical Mach number was obtained. The one-step reaction model was used to simulate the oblique detonation with and without viscous diffusion at the near critical Mach number on a large scale. For oblique detonation with a critical Mach number close to C-J characteristics, the simulation results under both viscid and inviscid conditions show that the C-J detonation translates upward in the oblique detonation at critical Mach number.As the oblique detonation stands,its propagation behaves globally oscialltions.

Construction and Validation for the Model of Bulging Movement in Explosion

ZHANG Zhi-yu, CHEN Chun-chao, HUANG Yong-hui, LI Hong-chao, LEI Zhen, WANG Jian-guo

2020, 40(8): 810-817. doi:10.15918/j.tbit1001-0645.2019.219

Abstract(2263) PDF(2501)

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In order to study the law of bulging movement of the blasting crater, the momentum conservation law was used to theoretically analyze the bulging movement speed, and experimental research was carried out by blasting funnel model test, high speed photography system and numerical analysis. The results show that the bulging movement rock mass was divided into numberless units, and the momentum conservation theory was used to obtain the blasting blaster bulging speed obeying exponential model. Through high-speed photography, the blasting drum bulging movement was recorded and analyzed. During the bulging movement, the free surface crack spread to the surrounding, so that the broken rock body presented a regular fan shape. With the uplift and rupture of the rock mass, the central point of the blasthole underwent variable acceleration. At different moments, the speed of movement decreased exponentially with the increase of the distance from the center of the blasthole. The speed of the bulge movement obeys the exponential model, and the center of the blasthole is the dominant variable acceleration motion, which decreases exponentially with the increase of the center distance of the blasthole. When the free surface bulge was completely broken, the broken rock mass was thrown at the maximum speed. When the angle of the projection was 45° with the horizontal, the farthest throw distance was reached.

Numerical Study on Ignition Transient Process of Solid Rocket Motor Based on Ignition Particle

DING Hong-ming, ZHUO Chang-fei, CHEN Hao-tian, TAI Jing-hua

2020, 40(8): 818-825. doi:10.15918/j.tbit1001-0645.2019.216

Abstract(2295) PDF(2557)

Abstract:
In order to study the flow and combustion characteristics of ignition particles in the combustion chamber during SRM ignition, based on the N-S equation and thek-εturbulence model, and using the discrete phase model + UDF interface program, numerical simulation analysis of the ignition transient process of a SRM was made. The calculation results show that during the ignition process of the SRM, the ignition powder particles reacted in a chain. The ignition powder particles reacted violently after being injected into the combustion chamber, which was beneficial to the ignition of the propellant and shortened the ignition delay time. The movement of ignition particles in the combustion chamber was complex. Pressure oscillation, local high temperature region and difference between internal and external pressures occurred in the flow field of the SRM. These phenomena varied with the amount of ignition and had a great influence on the propellant ignition and the structural integrity of the propellant. The research results can provide reference for the ignition design of SRM.

Numerical Study of Free Jet Noise Considering Solid Particles

RONG Ji-li, A Ni-su, CHENG Xiu-yan, FAN Bo-chao

2020, 40(8): 826-834. doi:10.15918/j.tbit1001-0645.2019.181

Abstract(2198) PDF(2544)

Abstract:
The effect of solid particles on the jet flow field and sound field was investigated. Six different turbulence models were to analyze the steady-state calculation of free jets. It s found that the RNGk-εmodel was most suitable for numerical simulation of steady-state jets. The LES model was used to calculate the unsteady results of the jet flow, and the FW-H equation was used to analyze the jet sound field. The comparison with the experimental data verified the correctness of the numerical model. Based on this model, the effect of solid particles on the free jet flow field and sound field was studied. The simulation results show that the presence of solid particles reduces the supersonic length of the jet flow field and significantly increases jet temperature. And it increases the noise in the downstream region of the jet and reduces the noise in the mid-upstream region.

Two IFFT-Based Construction Models of 2D Road Roughness Considering the Coherence Function of Different Wheel Tracks

WANG Han-ping, ZHANG Zhe, LIAO Xiao-hua

2020, 40(8): 835-840. doi:10.15918/j.tbit1001-0645.2019.155

Abstract(2890) PDF(2576)

Abstract:
Based on the relationship between auto-power spectrum density (PSD), cross-PSD and Fourier transform of road roughness of different wheel tracks, the analytic coherence relation of the phase angle corresponding to inverse Fourier transform(IFT) of road roughness for left and right wheel track in IFFT method. Through LU decomposition of the PSD matrix of road roughness of different wheel tracks, the white noise filter transfer function of the road roughness of left and right wheel track, and then two IFFT models of random road simulation considering the coherence of different wheel tracks. The simulation results show that the auto-PSD and the coherence function of different wheel tracks had high reliability in the simulation of 2D road roughness.

Experimental Comparison of Indirect Digital Impression and 3D Data Deviation

JIANG Shu-feng, LIU Hong-fa, ZHOU Zi-ye, CUI Chao

2020, 40(8): 841-848. doi:10.15918/j.tbit1001-0645.2019.289

Abstract(2009) PDF(2495)

Abstract:
In the process of dental implant reverse modeling in digital dental diagnosis and treatment, the surface fitting error of three-dimensional raster scanning was used to influence modeling accuracy, and the point cloud data of traditional hole repair and reconstruction was distorted. Through the reverse modeling of indirect dental model and the comparison experiment of splicing error, a method to make up for the smoothness of digital impression reconstruction characteristic surface and effective noise reduction surface reconstruction was obtained, the optimized experimental process was obtained, and the 3D analysis results of different scanning methods were verified by 3D data comparison. The research results show that the improved experimental comparison method effectively finds out the causes of errors in clinical application of 3DP implants with indirect digital impression, and verifies the method for effectively improving 3D scanning accuracy, reducing the distortion rate of point cloud data vulnerability repair in reverse modeling.

Design of the Remote-Control System for Intelligent Wireless Nodes

LI Ming, LIU Ruo-yu, JIANG Chun-lan, KOU Jia-xun

2020, 40(8): 849-855. doi:10.15918/j.tbit1001-0645.2019.199

Abstract(2075) PDF(2626)

Abstract:
To solve the problems of networked ammunition's inability to return the battlefield status and the difficulty in "man-in-loop" active control in the battleground, an overall framework was proposed in accordance with the operation process. The remote-control system including software and hardware was designed, and multiple kinds of nodes were carried out. Based on the C# language, the simulation platform software and terminal command software including multiple modules were developed, which realized the key functions of multi-node networking, displaying the state and multi-class data transmission. An attack decision algorithm was written to make on-chip attack decisions, PC-assisted attack decisions and manual decisions. Simulation tests and comprehensive experiments show that the system can return and display nodes and targets information, remotely control nodes, make on-chip decisions and PC decisions, meeting the requirements for outdoor use.

A Fault Diagnosis Method of Vehicle Transmission System Based on Improved SVM

MA Li-ling, GUO Kai-jie, WANG Jun-zheng

2020, 40(8): 856-860. doi:10.15918/j.tbit1001-0645.2019.110

Abstract(2088) PDF(2399)

Abstract:
Fault diagnosis and performance evaluation with vehicle transmission system test data can play a role in fault warning, improving reliability, and further improving vehicle performance.However, the test data are very large and unbalanced, possess high dimensionality and noise, which make the traditional data analysis algorithm produce sub-optimal classification model. In order to solve the above problems, a new improved support vector machine (SVM) algorithm was proposed for imbalanced data classification. The algorithm was arranged to present different weights for each sample, improve the design of fuzzy membership degree with Mahalanobis distance to eliminate the interference of variable correlation, and to output the failure probability under normal state at the same time. The experimental results show that the algorithm can effectively improve the accuracy of fault diagnosis, and at the same time can use the probability output model to carry out fault warning and performance analysis.

A Linear Array Camera Calibration Method Based on Improved Genetic Optimization Algorithm

WANG Xiang-zhou, CHEN Dong-qing, ZHENG Shu-hua, QIAO Ya-jun

2020, 40(8): 861-866. doi:10.15918/j.tbit1001-0645.2019.239

Abstract(2301) PDF(2508)

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In order to obtain high-precision image with obvious defect characteristics in defect detection of mobile phone glass cover, the linear array camera with high-quality image need to be calibrated precisely. A calibration method with improved genetic optimization algorithm of linear array camera was proposed. Based on the existing linear scan model, the image distortion of linear scan image was corrected and the new calibration parameters were derived. The solution of new calibration parameters was a non-linear problem. An improved genetic optimization algorithm was proposed to optimize the solution process. The experimental results show that the proposed method has higher calibration accuracy in the actual scanning detection environment than the general genetic algorithm and image distortion correction.

Road Detection and Location Based on Multi-Channel Fusion and Polar Constraint

LI Jing, SHI Xin-xin, CHENG Zhi-peng, WANG Jun-zheng

2020, 40(8): 867-872. doi:10.15918/j.tbit1001-0645.2019.151

Abstract(1950) PDF(2508)

Abstract:
The use of computer binocular vision to study road detection and location plays an important role in realizing autonomous navigation of unmanned motion platforms. According to the binocular camera system model, a lane-line detection method based on multi-channel threshold fusion was proposed. The lane threshold and color information were combined to perform image threshold segmentation. The perspective transform and adaptive dynamic sliding window method were used to extract lane line pixels. The least squares method was adopted to fit road model, position according to the polar constraint relationship and project the result into the SLAM map. The experimental results show that the algorithm can accurately detect the lane line in the scenes of illumination change and shadow occlusion. Projecting the lane line information to the three-dimensional map can effectively fuse the lane information with the map information and improve the road perception ability.

Gesture Recognition Based on YOLO Algorithm

WANG Fen-hua, HUANG Chao, ZHAO Bo, ZHANG Qiang

2020, 40(8): 873-879. doi:10.15918/j.tbit1001-0645.2019.030

Abstract(2491) PDF(2475)

Abstract:
The application of YOLO (you only look once) algorithm in gesture recognition was studied to improve the speed and accuracy of detection under the background near the skin color, light and shade. Based on the end-to-end detection function, the YOLO algorithm could be arranged to improve operation speed greatly by automatically extracting target feature from convolution neural networks. Considering the excellent performance in target detection process, YOLO algorithm was applied to gesture recognition. Comparing with other application results with YOLO series algorithm, this application result of YOLO algorithm shows better performance in gesture recognition. At the same time, based on a YOLOv3-tiny algorithm, the fast version of YOLOv3 algorithm, a YOLOv3-tiny-T algorithm was proposed. The YOLOv3-tiny-T algorithm can achieve a mean average precision of 92.24% on the UST dataset with five gestures, increasing about 5% combined with YOLOv3-tiny.

A New Method for UAV's Datalink Adaptive to EMI

ZHANG Dong-xiao, CHEN Ya-zhou, CHENG Er-wei, XU Tong

2020, 40(8): 880-887. doi:10.15918/j.tbit1001-0645.2019.131

Abstract(2243) PDF(2363)

Abstract:
Complex electromagnetic environment can easily interfere with unmanned aerial vehicle's (UAV's) datalink, which seriously threatens the flight safety of UAV. In this paper, a new method of UAV's datalink adaptive to electromagnetic interference (EMI) was proposed based on environmental perception. This method was arranged to improve the active anti-jamming ability of UAV. The corresponding EMI thresholds were made to change nonlinearly with the dynamic change of the UAV's operation signals. After selecting training sample variables and observation values, adopting a method of the relevance vector machine regression (RVR), a dynamic training model was established to reasonably predict the EMI thresholds under different operation signals. An expert system was established for UAV's datalink adapted for EMI. Then, the EMI characteristic parameters were determined by the airborne EMI environment monitoring platform. And the interfered levels of the datalink against EMI were distinguished based on the prediction of the target value by using the trained model. Combining the the technology schemes and the tactical schemes, the new method can be used to effectively eliminate the effect of the EMI on the UAV's datalink.

A Vibration Isolation Control Based on Adaptive Impedance Control for Wheel-Legged Robot

WANG Shou-kun, SHI Ming-xin, YUE Bin-kai, XU Kang, WANG Jun-zheng

2020, 40(8): 888-893. doi:10.15918/j.tbit1001-0645.2019.133

Abstract(2161) PDF(2396)

Abstract:
Wheel-legged robots are inevitably in contact with the environment during movement. Due to the fixed parameters of the target impedance model, the traditional method of impedance isolation force control often puts up a poor robustness under an unknown information environment (stiffness and position) or time-varying. Considering traditional impedance control, an adaptive impedance controller was designed based on Lyapunov stability theorem. The method was arranged to indirectly adjust the impedance parameters with position compensation, make the steady-state error of the system to be zero and improve the adaptability to the unknown and changeable environment. Vibration isolation force control experiments were carried out for the robot under the condition of moving on different deceleration belts. Results show the superiority of the adaptive impedance control.

Modeling and Simulation of Piezoelectric Energy Harvesting System

WU Zhi-dong, FANG Jun-long, HE Yi-bo, PAN Di, LI Qiang

2020, 40(8): 894-900. doi:10.15918/j.tbit1001-0645.2019.194

Abstract(2152) PDF(2352)

Abstract:
The energy harvesting system for piezoelectric cantilever beam structure was modeled, the piezoelectric energy harvesting structure model was equated with the circuit system model by using the similar relationship between circuit system and mechanical system. To establish a complete model of piezoelectric energy harvesting system, the energy conversion circuit based on LTC3588-1 was equated with buck and rectifier circuit, the correctness of the equivalent circuit was verified by LTspice simulation. The whole model of piezoelectric energy harvesting system was built and simulated in Matlab/Simulink system, model parameters were optimized according to simulation results. Through the comparison and analysis of experimental data, the rationality of the system model was verified. The system can output 3.3 V DC voltage stably, and the output power is 2.6 mW under the optimal impedance matching condition.

Expression and Purification of holo-ACP Mutant and Property Study on the Corresponding acyl-ACP fromE`scherichia Coli

WANG Wen-qing, YANG Miao, FENG Yan-bin, JI Fang-ling, XUE Song

2020, 40(8): 901-907. doi:10.15918/j.tbit1001-0645.2019.123

Abstract(1983) PDF(2261)

Abstract:
As an acyl donor, the acyl-acyl carrier protein (acyl-ACP) plays pivotal roles in biosynthesis of various natural products, including fatty acids, polyketones and so on. At present the acyl-CoA has been used as a substitute for uncommercialized acyl-ACP to perform in vitro study of the relevant enzyme activity. By using acyl-CoA, the catalytic specificity of the enzymes can't be revealed correctly because the substrate protein acyl-ACP could interact with the relevant enzymes through the ACP. Based on the plasmid pET-28a(+) -ACP derived fromEscherichia coli, 12 single-site ACP mutants were designed, and the corresponding holo-ACPs were expressed and purified. These holo-ACPs were subsequently used as substrates to synthesize C16:0-ACP and C18:1-ACP. The HPLC results show that, ACP mutant with change in a single amino acid can effect on the acyl-ACP feature. In particular, the ACP mutant with change in T40 residue has notable impacts on hydrophobicity, ultraviolet absorption response and stability of acyl-ACP as well.

Study on the Sterilization Mechanism of Negative Corona Discharge

OUYANG Ji-ting, ZHANG Chen-yang, ZHANG Yu, LIU Si-han, MIAO Jin-song

2020, 40(8): 908-914. doi:10.15918/j.tbit1001-0645.2019.212

Abstract(2197) PDF(2340)

Abstract:
To investigate the sterilization mechanism of corona discharge in air, a needle-to-ring configuration was employed to produce atmospheric pressure negative corona plasma. The active species from the corona discharge were obtained. The sterilization efficiency of different active substances (i.e., UV, charged particles and neutral active species) were tested experimentally. The results show that, UV and ozone can alone achieve sterilization with high bactericidal efficiency, but they can not complete a simple synergy. In negative corona discharge, neutral active substances act as the key bactericidal agents and the charged particles also play an auxiliary role in sterilization. But individual charged particles have little or no bactericidal effect. It is suggested that improving the neutral active species of corona discharge is beneficial to the plasma sterilization.

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