Applied Mechanics and Materials Vols. 195-196

Abstract: Many dependence structures can consist of mixed copulas. In order to analyze the dependence of stock, we present the method of estimation for mixed copula models. Via generating random samples and using maximum likelihood estimation, the parameters of mixture of Archimedean copulas are estimated. Numerical results show that this method estimates effectively the parameters and tail dependence coefficients. Therefore we can use the method to analyze dependence structure for stocks.

Abstract: In this paper, a model of FH spread spectrum communication system has been built in Matlab/Simulink platform. Theoretical analysis of repeater jamming are derived. These limitations arise because of the geometry and so on. Then, we analyze the bit error rate performance in FH communication system under repeater jamming. The benefits of frequency hopping are potentially neutralized by a repeater jammer.

Abstract: A new topology of shunt active power filter with two-leg three-level clamped capacitor in the main circuit is presented, and the operation principle and control scheme are introduced. The adopted device is operated as a controllable current source to eliminate current harmonics. The new hysteretic current comparison control scheme is used to track the command current and to balance the neutral-point voltage. Meanwhile the redundant operating states in the adopted inverter can be selected to compensate the clamped capacitor voltage to achieve the dynamic balance of the capacity voltage. Simulation results show that the shunt active power filter can effectively eliminate harmonics of the nonlinear loads.

Abstract: In order to study the dynamic characteristics of dump truck with a T-type lifting mechanism, a detailed multi-body dynamic model of a dump truck was established by using SIMPACK software. With this model, which includes front suspension, balanced rear suspension, carriage, lifting mechanism, tyre model and so on, the kinematics and dynamics of the dump truck were studied by simulation. The variation of angular velocity, angular acceleration and applied force of carriage, tension rod and cylinder with lifting angle were obtained. This study will provide scientific reference for the structural design and strength analysis of lifting mechanism.

Abstract: The finite element analysis in theory of elasticity is corresponded to the quadratic programming with equality constraint, which can be further transformed into the unconstrained optimization. In the paper, the question is solved by modified Hopfield neural network based on the energy function of the neural network equals to the objective function of the finite element method and the minimum point, which is the stable equilibrium point of the network system, is the solution. In addition the authors present the computer simulation and analogue circuit experiment to verify this method. The results are revealed that: 1) The results of improved Hopfield neural network are reliable and accuracy; 2) The improved Hopfield neural network model has an advantage on circuit realization and the computing time, which is unrelated with complexity of the structure, is constant. It is practical significance for the research and calculation.

Abstract: In view of the uncertainty of evaluation indicators for water resources carrying capacity the theory of set pair analysis is adopted. The samples are preliminarily classified by calculating the connection degree between the samples and evaluation indicators. Then the samples are further ranked through the identity, difference and antagonism set pair analysis. The weights of evaluation factors in the model are obtained from the avail value of data reflecting the information entropy, by which the weight allocation is more reasonable. The application result of this model to an example is compared with those obtained from integrated evaluating methods and the attribute recognition method. It shows that the proposed method is practical and reasonable.

Abstract: The issue of CNC machine tool energy consumption and environmental protection plays an important role on manufacturing technology research since CNC machine tool energy is consumed during motor racing or cutting process. The paper analyzes CNC machine tool energy consumption influence by cutting parameters of cutting speed, feed speed, cutting depth. Based on nonlinear mapping ability of neural network, the model of CNC machine tool energy consumption related to cutting parameters is established by using experimental data, and then the optimal combination of cutting parameters are searched by using global optimization of genetic algorithm, and verified in CNC machine tool cutting experiment. The proposed method provides a good energy control proposal for CNC machine tool roughing process. The experimental results show that the energy consumption is optimal.

Abstract: In view of the problem that harmonics analysis by fast Fourier Transform can appear a higher error and the serious phenomenon of harmonics leakage and fence, it is put forward that a improved arithmetic that FFT of special Hanning interpolation combined with wavelet transform. It is proved by theory analysis and simulation calculation that: FFT arithmetic of special Hanning interpolation can raise the precision of steady-state harmonics analysis validly. And wavelet transform arithmetic can analyze time-varying harmonics and sudden-changing harmonics precisely. The arithmetic of wavelet transform combined with FFT can remedy the defects of harmonics analysis by FFT and analyze harmonics precisely, timely and validly.

Abstract: Evaluation for urban sustainable development is very significant to improve the future development of urban. The analytic hierarchy process (AHP) is very popular used to evaluate the urban sustainable development, but limited to forecasting the future development. In the study, a model designed based on SD and AHP is expected to resolve this problem. And we take Zhangye city in Gansu province as an example to study the evaluation performance of the model. The result of the urban sustainable development is getting better and better towards 2020. The result shows that the development of Zhangye city is going to be good in future 10 years. The experimental results indicate the effectiveness and correctness of the proposed method.

Abstract: In this paper, the fracture problem of functionally graded material (FGM) was studied, and the shear modulus was assumed to be an exponential function. The influences of inhomogeneous parameter, crack size and crack angle on the stress intensity factors have been analyzed by the finite element method. The results indicated that the stress intensity factors of mode I decreased with the increasing of the crack angle, the stress intensity factors of mode II increased with the increasing of the crack angle, and the crack stress intensity factor of mode I and mode II decreased with the increasing of the inhomogeneous parameters at crack tips, which was of certain directive significance for the FGM design and manufacture in the actual engineering.