Dang J.,Standard Process Material Research Institute |
Liu T.,PLA Second Artillery Engineering University
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2017
Functionalized SiC particle-SiC whisker (SiCP-SiCW) hybrid fillers by γ-glycidoxypropyltrimethoxysilane (KH-560) were performed to fabricate the functionalized SiCP-SiCW/bismaleimide (SiCP-SiCW/BMI) thermal conductivity composites, BMI as the polymeric matrix and diallylbisphenol A (DABA) as a toughening agent, respectively. Effects of the shape, content, compound and surface functionalization of SiC fillers on the thermal conductivities, dielectric & mechanical properties and thermal stabilities of the functionalized SiCP-SiCW/BMI thermal conductivity composites were investigated. The results show that the functionalized SiCP-SiCW/BMI thermal conductivity composite with 40wt% functionalized SiCP-SiCW (1:3, mass ratio) hybrid fillers exhibits the best comprehensive performance, the corresponding thermally conductive coefficient λ of 1.125 W(m·K)-1, dielectric constant ε of 4.12, and 5wt% thermal mass loss temperature of 427℃. © 2017, Chinese Society for Composite Materials. All right reserved.
Qi L.,PLA Second Artillery Engineering University
Applied Mechanics and Materials | Year: 2014
In the large-capacity, high-speed and real-time data acquisition and transmission, PXI bus have a widely application in the field of data acquisition and transmission. This paper introduces the design and implement of simplified state machine in the measurement and control system based on PXI bus. The results of test indicate that the technology is practical and valuable. © (2014) Trans Tech Publications, Switzerland.
Zhang X.,PLA Second Artillery Engineering University |
Wang H.,PLA Second Artillery Engineering University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2010
Threshold is the key factor in threshold-based wavelet denoising. Conventional threshold estimation methods fail to estimate the appropriate threshold for ball bearing fault signals denoising. To improve the denoising performance of threshold-based wavelet denoising with the conventional threshold estimation methods, an evolutionary wavelet denoising method is proposed. In the method, wavelet transform is used for the noise-contaminated signal decomposition and reconstruction, a function that approximates to the estimation error of hard thresholding is constructed and then the optimal threshold at each decomposition level is obtained by applying particle swarm optimization to the constructed function. Extensive numerical experiments on simulated signals and ball bearing fault signals are carried out to confirm the effectiveness of the method. The experimental results indicate that the method is highly effective in noise reduction and fault feature extraction. In comparison with the conventional threshold-based wavelet denoising methods, the method has better denoising performance in the sense of signal-to-noise ratio and mean square error. © 2010 Journal of Mechanical Engineering.
Zhang X.,PLA Second Artillery Engineering University |
Wang H.-L.,PLA Second Artillery Engineering University
Wuli Xuebao/Acta Physica Sinica | Year: 2011
To solve the problem of extreme learning machine (ELM) on-line training with sequential training samples, a new algorithm called selective forgetting extreme learning machine (SF-ELM) is proposed and applied to chaotic time series prediction. The SF-ELM adopts the latest training sample and weights the old training samples iteratively to insure that the influence of the old training samples is weakened. The output weight of the SF-ELM is determined recursively during on-line training procedure according to its generalization performance. Numerical experiments on chaotic time series on-line prediction indicate that the SF-ELM is an effective on-line training version of ELM. In comparison with on-line sequential extreme learning machine, the SF-ELM has better performance in the sense of computational cost and prediction accuracy. © Chinese Physical Society.
Wang H.X.,PLA Second Artillery Engineering University
Advanced Materials Research | Year: 2013
Carbon nanofibers is a new kind of electromagnetic wave absorbing materials and it is expected as a new kind of smoke interference agent. To study the scattering and extinction characteristics of carbon nanofibers,the electromagnetic scattering calculating model was established, and the induced current equation was solved by moment method, as well as the relationship between the infrared extinction cross section and the length of carbon nanofibers was analyzed and calculated based on MATLAB. The results show that when the conductivity of carbon nanofibers is large, the extinction cross section appears a series of resonant peaks along with the length change, and when the length of carbon nanofibers is equal to the first resonant length, the extinction cross section of unit volume will reach the maximum value, and a good extinction effect can be achieved at the same time. The contribution of scattering to extinction is enhanced with the increase of electrical conductivity. © (2013) Trans Tech Publications, Switzerland.
Wu W.,PLA Second Artillery Engineering University |
Chen X.,PLA Second Artillery Engineering University |
Su X.,PLA Second Artillery Engineering University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2011
Blind source separation (BSS) is an effective method to diagnose multi-fault of mechanical equipment. Empirical mode decomposition (EMD) is a potent tool to analyze non-stationary signals and it can decompose nonlinear and non-stationary signal into a set of linear and stationary intrinsic mode functions. In blind source separation of mechanical fault signals, single-channel mechanical signal separation is an ill-conditioned problem. Here, by combining the respective advantages of BSS and EMD, a blind source separation method based on empirical mode decomposition is proposed to solve the difficult problem of single-channel mechanical signal separation. This algorithm is composed of three steps. Step 1 is empirical mode decomposition of single-channel mechanical signal and its combining with intrinsic mode functions. Step 2 is to estimate mechanical sources number by singular value decomposition (SVD). Step3 is to recombine multi-channel mixed mechanical signals according to estimated sources number and separate mechanical sources with FastICA algorithm. This method is applied to the simulation research of bearing and gear in order to correctly separate their source signals. Simulation research indicates that it can well solve the difficult problem of source number estimation and blind source separation of single-channel mechanical signal. © 2011 Journal of Mechanical Engineering.
Yang Z.-Y.,PLA Second Artillery Engineering University |
Zhou Z.-F.,PLA Second Artillery Engineering University |
Zhang Z.-L.,PLA Second Artillery Engineering University
Guangxue Jingmi Gongcheng/Optics and Precision Engineering | Year: 2012
To enlarge the transmission scale and improve the transmission precision of an azimuth transmission system based on sine wave magneto-optic modulation, a new method of transmitting the azimuth in a large-scale and high-precision was established. The principle of the current azimuth transmission system was analyzed, and a double-angle formula was introduced to enlarge the transmission scale. A model to measure the azimuth was established according to analyzing the relationship between the azimuth and the extremum of the modulated light, and the measurement model was expatiated by comparing the extremums. A integrated method combined the approximation in little-scale with the looking-up table in large-scale was presented to calculate the arc tangent function in the model. Simulation results indicate that the theoretic transmission scale is widened obviously and the precision is improved. Experiment results show that the actual transmission scale is -64-64° and the transmission error is under 10″, which is better than those of the current methods. The method provides a new way to transmit the spatial azimuth in large-scales and high-precision.
Li B.-P.,PLA Second Artillery Engineering University
Baozha Yu Chongji/Explosion and Shock Waves | Year: 2010
Guided bombs were taken as the research objects to numerically simulate the penetration and explosion process of large-aperture-heavy weapons by using a three-dimensional arbitrary Lagrange-Eulerian (ALE) code and to explore damage effects of a roller compacted concrete gravity dam under continuous attacks of two precision-guided bombs. Results show that the vibration caused by penetration is weak, while the particle vibration is mainly caused by ammunition explosion. The intermission time of sequential attacks is far longer than the dynamic response stretch of the dam, and the dam vibration caused by sequential attacks scarcely takes on the superposition effect. But the damage effect of penetration and explosion for the former missile provides the freedom surface for the subsequent missile, and the penetration depth and explosion-damaged range of the subsequent missile increase. The explosion-damaged ranges basically connect with each other, which threat to the normal running and security of the dam.
Liu J.,PLA Second Artillery Engineering University |
Yu Z.,PLA Second Artillery Engineering University |
Ma X.,PLA Second Artillery Engineering University
Guangxue Xuebao/Acta Optica Sinica | Year: 2012
To solve the problem of the low accuracy of the fiber optic gyroscope (FOG), which is influenced by the bad temperature stability of FOG that the parameters are changed, a new static synthetically compensation method is proposed. Thinking of the property of the temperature, the scale factor nonlinearity and the null-bias drift of FOG, a novel model is researched, which is related to factors of operating time, temperature and input angular rate. The model orders are identified using the classification fitting method. Based on a great deal of tests of temperatures and input angular rates, error-compensation iterative algorithm is proposed. The test results show that the compensation algorithm is effective at full temperatures and full rotate rates, which eliminates the influence of temperature and nonlinearity of FOG.
Wang J.,PLA Second Artillery Engineering University
Advances in Intelligent Systems and Computing | Year: 2014
To get a better quality of defocused image restoration, the degradation function for the defocused image is studied first in this paper, second, various degradation functions were compared and analyzed, and last, a model that can represent its degradation accurately is proposed. © Springer India 2014.