To improve the precision and reliability in predicting methane hazard in working face of coal mine, we have proposed a forecasting and forewarning model for methane hazard based on the least square support vector (LS-...
详细信息
To improve the precision and reliability in predicting methane hazard in working face of coal mine, we have proposed a forecasting and forewarning model for methane hazard based on the least square support vector (LS-SVM) multi-classifier and regression machine. For the forecasting model, the methane concentration can be considered as a nonlinear time series and the time series analysis method is adopted to predict the change in methane concentration using LS-SVM regression. For the forewarning model, which is based on the forecasting results, by the multi-classification method of LS-SVM, the methane hazard was identified to four grades: normal, attention, warning and danger. According to the forewarning results, corresponding measures are taken. The model was used to forecast and forewarn the K9 working face. The results obtained by LS-SVM regression show that the forecast- ing have a high precision and forewarning results based on a LS-SVM multi-classifier are credible. Therefore, it is an effective model building method for continuous prediction of methane concentration and hazard forewarning in working face.
Structural damage detection is a very important process for structural health monitoring. It is often converted into a constrained optimization problem in mathematics. In this paper, an improved Particle Swarm Optimiz...
详细信息
Structural damage detection is a very important process for structural health monitoring. It is often converted into a constrained optimization problem in mathematics. In this paper, an improved Particle Swarm Optimization (IPSO) algorithm is proposed for structural damage detection based on macro-economic control strategy, which aims to increase its convergence rate and thereby to obtain an acceptable solution of the premature convergence problem that is easy to occur in the later phase of the general PSO algorithm. The IPSO algorithm was empirically studied with a suite of four well-known benchmark functions, and further examined with both numerical simulations about single and multi-damage of a 2-story rigid frame and some experiments on a 3-story building model. The illustrated results show that the improved PSO algorithm is effective and applicable to the structural damage detection.
Based on dual path reaction mechanism, a nonlinear dynamics model reflecting the potential oscilla- tion in electrooxidation of methanol on Pt surface was established. The model involves three variables, the electrode...
详细信息
Based on dual path reaction mechanism, a nonlinear dynamics model reflecting the potential oscilla- tion in electrooxidation of methanol on Pt surface was established. The model involves three variables, the electrode potential (e), the surface coverage of carbon monoxide (x), and adsorbed water (y). The chemical reactions and electrode potential were coupled together through the rate constant ki = exp(ai(e ? ei)). The analysis to the established model discloses the following: there are different kinetics be- haviors in different ranges of current densities. The chemical oscillation in methanol electrooxidation is assigned to two aspects, one from poison mediate CO of methanol electrooxidation, which is the in- duced factor of the chemical oscillation, and the other from the oxygen-containing species, such as H2Oa. The formation and disappearance of H2Oa deeply depend on the electrode potential, and directly cause the chemical oscillation. The established model makes clear that the potential oscillation in methanol electrooxidation is the result of the feedback of electrode potential e on the reactions in- volving poison mediates CO and oxygen-containing species H2Oa. The numerical analysis of the estab- lished model successfully explains why the potential oscillation in methanol galvanostatic oxidation on a Pt electrode only happens in a certain range of current densities but not at any current density.
A new moving load identification method is presented based on function fitting technology and finite element method. According to the linear relation of the load and the structure response, the fitting coefficients ca...
详细信息
A new moving load identification method is presented based on function fitting technology and finite element method. According to the linear relation of the load and the structure response, the fitting coefficients can be identified, then by these coefficients, the moving load can also be *** method can be applied to all complex structure with various boundary conditions. And it can also identify the varying-speed moving load. How to equal discrete node load to continious moving load is discussed. Numerical simulations and experimental results demonstrate the briefness, effectiveness and anti-interfered capacity of the method. Thus the method can identify the moving load for complex engineering structure.
The impact trend of reck-coal system was studied by the method of accumulating and releasing of deformation energy and interaction of rock-coal system. The system model of roof-coal-floor was established. Based on the...
详细信息
The impact trend of reck-coal system was studied by the method of accumulating and releasing of deformation energy and interaction of rock-coal system. The system model of roof-coal-floor was established. Based on the RFPA software, rock fracture process analysis system, the numerical test of deformation, fracture and energy transmission of nonlinear and nonhomogeneous rock-coal system, and the numerical test and evaluating method of impact trend of reck-coal system were achieved. When the same coal seam was in different roof and floor conditions, the fracture process of reck-coal system can be classified as gradual, sudden and delayed fracture three kinds, and their impact trend can be classified as void, intense and medium correspondingly. The rock-coal system＇s impact trend is evaluated by the system impact index p and burst expanding forms. The criteria μ are μ〈1.0, 1.0≤μ〈l .5 and μ≥1.5 when the impact trend is void, intense or medium, which are tested and verified by the No.2 and No.4 coal seams in Sun- cun mine.
The performance of optical power transmission through a side polished fiber manufactured by wheel polishing method were investigated, in which materials of different refractive indices were overlaid on the polished su...
详细信息
The performance of optical power transmission through a side polished fiber manufactured by wheel polishing method were investigated, in which materials of different refractive indices were overlaid on the polished surface. The experiments showed that the transmitted optical power through the side-polished fiber varied with the refractive index of the overlaid material. The result of our experiments fitted well the theoretical calculation. Side-polished fiber manufactured by wheel polishing method can not only be used to control optical power transmission through the fiber core but also be used as a refractive index sensor.
On the basis of investigations on the composition and contents of heavy metals in the domestic refuse in the Three-Gorges region of the Yangtze River, in combination with the experimental results, this paper deals wit...
详细信息
On the basis of investigations on the composition and contents of heavy metals in the domestic refuse in the Three-Gorges region of the Yangtze River, in combination with the experimental results, this paper deals with the distribution rule of heavy metals in the various compartments of an incineration system:leachate pool, fly ash and residue. It is concluded that in the leachate pool heavy metals should not be neglectable since about 30% of Pb and 10% of Cr are leached here; in the incineration system, above 74% of Cr, As and Pb exists in residue; above 96% of Hg exists in fly ash and the contents of Cd in fly ash are close to those of residue. It is also concluded that the physical conditions of incineration have a significant influence on the distribution of heavy metals in the incineration system.
It is suggested in this paper to denoise the ultrasonic inspection signals using wavelet transform. The theoretic base is that wavelet transform is a band-pass filter. Firstly, the frequencies of the inspection signal...
详细信息
It is suggested in this paper to denoise the ultrasonic inspection signals using wavelet transform. The theoretic base is that wavelet transform is a band-pass filter. Firstly, the frequencies of the inspection signal are evaluated according to the excited signal. Secondly, an appropriate scale for wavelet transform is computed following the laws between the scale and the frequency. Thirdly, wavelet transform with the scale would be operated. As results, the echoes by the flaws could be discerned in the wavelet coefficients. Finally, the propagation of the guided wave in a damaged pipe is simulated by code ANSYS and the signal processing are operated by code MATLAB. The different wavelet functions are also discussed aiming at the denoised qualities. The signal-to-noise ratio (SNR) is used to evaluate the quality for different wavelet. It could be concluded that the Morlet wavelet is suitable to operate the ultrasonic inspection signal excited by a sinusoidal signal modulation by Hanning windows.
暂无评论