Applied Mechanics and Materials Vols. 66-68

Abstract: A K-Means kernel density estimation was proposed and it was used in the pretreatment process of circuit fault diagnosis. The unequal division and losing division problem caused by the traditional method are solved by this method. It also avoid the singular problem which is usually caused by the high dimension of characteristic data. A kernel function is designed and it was integrated with fuzzy support vector machine method to solve the classification problem of multi-faults . At last, a solution of optimal bandwidth is given to improve the proposed method.

Abstract: A simple differential sliding mode control law was designed for the missile overload control system without considering the uncertainties of air-dynamic coefficients. The sliding mode was composed of overload error and the differential error of overload. Finally, a numerical simulation was down and it testified that it is unable to make the system stable with only pure overload control strategy. Although the sliding mode was arrived , Oscillation phenomenon was caused by the poles in imaginary axis.

Abstract: Considering the no uncertain air-dynamic coefficients situation, a kind of sliding mode control law, which was composed of the angle velocity and overload error, was designed for the overload control system of missile. And the accessibility of sliding mode was analyzed. What worthy pointing out is that a transfer- function-type backstepping algorithm was adopted to solve the derivative item of actuator and a novel type of control was proposed.

Abstract: Based on Lyapunov stability theorem, a common adaptive strategy was designed for a common class of chaotic systems with uncertain parameters. And the discuss on the sign of unknown parameters were avoided because of the adopting of a novel kind of adaptive weight turning law. At last, the convergence time was analyzed to provide a dynamic information for system users

Abstract: Considering the situation with both unknown multi-parameters and uncertain multi- functions, a robust adaptive controller was constructed to solve the tracking problem of a general class of chaotic systems. What is worthy pointing out is that the uncertainties are assumed to be bounded with triangular functions which is meaningful in engineering application.

Abstract: Dye-sensitized solar cells based on Zn-doped TiO₂ thin film prepared by the hydrothermal method show a photovoltaic efficiency of 7.68%, which is higher than that of the undoped TiO₂ thin film (6.16%). The Zn-doped films exhibit an elevated electron Fermi level,which may enhance band bending to lower the density of empty trap states.Because of this Zn-doping,the consequent Dsscs can alleviate the decay of light to electric energy conversion efficiency due to light intensity reduction. Intensity-modulated photocurrent spectroscopic analysis reveals that enhanced transport of photogenerated electrons as a result of the trap density minimization is responsible for the high photovoltaic performance.

Abstract: A three-degree-of-freedom vibro-impact system with symmetric two-sided constraints is considered. Existence conditions of the symmetric period -2 motion are given, and the symmetric period n-2 motion of the system is deduced analytically. The six dimensional Poincaré map is established, and the Jacobi matrix of the symmetrixc fixed point is obtained. By the numerical simulations, we show that symmetry breaking and symmetry increasing exists in the vibro-impact system with symmetric two-sided constraints.

Abstract: At present, on-machine measurement has received extensive attention due to high efficiency and automatic quality control. In this paper, two applications of on-machine vision measurement of metal parts were introduced. With regard to geometric measurement of small square part, four sides and angle were measured. The procedure of camera calibration, image processing and geometric representation was expounded. For medium square part, four overlapped images were captured by controlling the worktable movement. Size and shape measurement were achieved after image mosaicing. Two application results proved that this kind of on-machine visual measurement is efficient and practical.

Abstract: The amorphous alloy application is limited because of its brittleness property. Based on the grain structural characteristics of nanocrystal alloys, the mechanical behavior of the amorphous/nanocrystal Ni-Mo_23.56 alloy is investigated in this text. The microstructure of the deposit and the crack propagation were discussed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results show that amorphous/nanocrystal Ni-Mo_23.56 alloy has a higher microhardness, a strong binding force between a certain thickness coating with the substrate. The tensile stress-strain pattern shows a certain degree of plastic deformation behavior in the coating and tensile fracture surface of radial vein structure, in line with the free volume fracture model.

Abstract: The shock characteristics of a cubic nonlinear stacking packaging system were investigated under the action of half-sine acceleration pulse. The dynamical model of the system was developed, and the numerical results of the dynamical equations were obtained. Based on the results, a new concept of combined shock response spectrum was proposed to describe the shock characteristics of cubic stacking packaging system, focusing more on the maximum of the peak response acceleration of all products at all sensitive frequency since the damage of stacking packaging system occurs when any of the products was damaged. And it’s found that the combined shock spectrum is always made up of the shock spectrum of the bottom layer at lower dimensionless pulse duration and the shock spectrum of the top layer at higher dimensionless pulse duration. Then, the effect of the peak pulse acceleration, the defined system parameter, the damping ratio of cushioning pad in addition to the number of stacking layers on the combined shock spectrum of the system was discussed. It’s shown that all of their effect are noticeable. The results lead to some insights into the design of cushioning packaging.