Advanced Materials Research Vols. 538-541

Abstract: In this paper, on the basis of the theories and methods of ecology and ordinary differential equations, an ecological Gompertz model with Holling III functional response and stage structure for predator is established. By use of the stroboscopic map, a predator extinction periodic solution is obtained, and the global attractivity of the predator extinction periodic solution is analyzed. By using comparison theorem of impulsive differential equation and small amplitude perturbation skills, we get the sufficient condition for permanence of the system under impulsive harvest strategy for the prey and maturation time delay of predator.

Abstract: A shape optimization method for solving elastic contact problems is proposed based on gradient-less idea(a zero order optimization method). It is found that the contact stress on the elastic contact surface can be smoothed and reduced effectively by both changing the contact surface shape and changing the shape of non-contact surface. To avoid mesh distortion that results in undesirable shape, a move stratrgy for nodal movement has been used in the finite element model. Two examples are presented to show the effectiveness of the proposed method in dealing with elastic contact problems.

Abstract: The fluctuating wind field is simulated for digital by using the stationary Gauss processes, which Kaimal spectrum and Panofsky spectrum is used to the simulation of wind target spectrum with different direction and speed. According to Davenport quasi-steady buffeting force model formula, the time-history of wind velocity is converted to Buffeting force time history, which are applied to the Structure model node, combined with ANSYS for long-span continuous rigid frame bridge buffeting response analysis dynamic simulation.Taking a high pier and long span continuous rigid frame bridge as an example, analyzes dynamic buffeting response of the bridge under the action of the stochastic wind field, which as the guidance of high pier and long span continuous rigid frame bridge design work, practice has proved that the method is simple, reliable, also can be a way that dynamic analysis of buffeting response of large span bridge or tower structure under the action of stochastic wind field.

Abstract: A hydraulic excavator is taken as the object to study. Considering the characteristics of slewing transmission mechanism of hydraulic excavator, the torsional vibration equation is established by the finite element method. According to the torsional vibration equation, the effects of the equivalent moment of inertia of working device on the torsional dynamic properties of slewing transmission mechanism are analyzed. Using the optimization theory, the mathematical model is built, which is by means of the equivalent moment of inertia of working device as objective function and by means of the position parameters of the working device as design variables. Based on the mathematical model, the optimization of torsional dynamic properties of slewing transmission mechanism is studied. Finally, a numerical example is presented.

Abstract: On the base of the basic differential equation, a new GM (1,1) model applying to non-homogenous index series was established by optimizing the background of original differential equation. Meanwhile, solution algorithm and efficiency of the optimization model was presented and verified in the paper respectively. The results showed that this nonlinear discrete gray prediction model significantly improves the simulation accuracy and is suitable for the non-homogeneous high-growth series. Therefore, our research has certain theory significance and the practical application value for simulation of grey model.

Abstract: A hybrid method for identifying structural parameters is presented in this paper. All the measured and integrated responses are analysed using the identification method with a shift-average procedure to identify the stiffness and damping parameters as well as to reconstruct the unknown seismic input. To evaluate the reliability of the method, the identified structural stiffness is compared with the theoretical value computed from given material and geometric properties.

Abstract: A large amount of drilling pump vibration signals are acquired and decomposed optimally into time-frequency atoms by the Pattern Filter Method. All of these time-frequency atoms are falling into the multidimensional statistical cube which is formed by the time-frequency atomic parameter (α,f,φ,A) space with certain interval length. The atoms in every cube are counted and the results are stored in a database. When keeping any two parameters in a certain range, the quantitative distribution contour maps in the plane of other two parameters are demonstrated by the Graf software tool, then all sub-space results were aggregated to construct the macro-views of the BOU quantity distribution in the four-dimensional space ,meanwhile the quantitative distribution of these atoms are investigated, the distribution characteristics for various vibration signals of drilling pump are obtained and all atoms are classified according to their clustering state in this parametric space. Furthermore, every special signal corresponding to the parametric feature clustering of atoms in this multidimensional space have been identified. The desired results have been achieved in signal identification and drilling pump fault diagnosis by use of these consequences.

Abstract: In order to test the performance of Dongfeng 8B locomotive, a series of identification tests on prototype were carried out, which included the cab noise test, emergency braking distance test for single vehicle, weighing of locomotives traction performance test and dynamic performance test. A series of problems were discovered after a comprehensive operation test on the Southern Xinjiang Railway, relevant causes are identified after analysis and investigation, and appropriate corrective measures are proposed.

Abstract: The stochastic resonance (SR) for a time-delayed mono-stable system, driven by periodic square-wave signal, a dichotomous noise and a static force as well as multiplicative and additive noise is considered. It is found that the output signal-to-noise ratio (SNR) increases monotonically with the increase of the delayed time. The SNR varies non-monotonically with the intensities of the dichotomous noise and multiplicative and additive noise as well as the system parameter and the amplitude of the input square-wave signal.

Abstract: The signals of convoluted mixtures have a stated of non-stationary identity, and the change of their spectrum with time-varying usually could not be observed from the frequency domain, but they can be observed by the time-frequency method. Therefore, the blind separation of non-stationary convoluted mixtures based on time-frequency analysis is proposed in this paper. For the non-stationary identity, the space-albinism of the mixed matrices and the joint diagonalization of the time-frequency matrices are simulated to separate the convoluted mixtures. Two kinds of time-frequency analysis methods, Wigner-Ville distribution and improved Wigner-Ville distribution, are introduced, which are calculated with MATLAB 7.0 software. The simulated results show the improved Wigner-Ville distribution method has a better performance for blind separating of non-stationary convoluted and mixed signals.