Initial conditions of impact dynamics

The effects of the initial conditions of impact dynamics equations are investigated numerically and experimentally. The inadequacies of previous studies on initial conditions are pointed out. Then a coefficient of velocity jump at the moment of impact is introduced, and the experiments for the mental rods are implemented to validate the appending constraints modeling methods for impact process. The comparisons between the experimental and simulated results at different coefficients are used to study the effects of the velocity jump conditions to the numerical simulation. The results indicate that the physical velocity response of bodies during impact is smooth; the different values of velocity jump only have small effects on numerical oscillation of velocity response, and they have no effects on the time history of impact force.     

Dynamic investigation on composite flexible multi-body system considering thermal effect

The dynamic performance of composite flexible multi-body system under the simultaneous action of thermal fields and driving constraint is analyzed. Based on strain-displacement relation of the Mindlin plate theory which includes transverse shear deformation, and considering thermal effect, variation equations of laminated plate are derived by the principle of virtual work. The finite element method is used for discretization. According to kinematics constraint relation, dynamic equations for spatial slider-crank system are established. Simulation results show that spatial deformation (torsion deformation) appears in the multi-layered composite slider-crank mechanism which is simulated with planar motions. Furthermore, the influence of coupling between thermal expansion and flexible deformations of non-symmetrical composite plates on the large overall motion under the uniform temperature field is investigated. Finally, significant change in constraint force due to the spatial deformation is shown.     

Numerical implementation of meshless method for electromagnetic field governing equations

For electromagnetic governing equations formulated by magnetic vector potential and electric scalar potential, its detailed numerical implementation is achieved by using meshless method and Galerkin approach. And essential boundary and interface condition of electromagnetic field are imposed by means of Lagrange multiplier method. Furthermore, the influences of interpolation point number at essential boundary and interface on computational results are also discussed. Examples are given to validate the effects of meshless method and Lagrange multiplier approach for electromagnetic field.     

Numerical analysis and experimental study of the effect of workpiece thickness on flow field in laser cutting

Based on Navier-Stokes equation and renormalization group (RNG) onflow model, the 3D symmetrical impinging jet model of laser cutting is established by adopting a taper nozzle and a convergence nozzle. Numerical simulation of gas flow in laser cutting is used to investigate the effect of workpiece thickness on flow field of assist gas in cutting slot. The isolines of static pressure as well as the distributions of static pressure and velocity are analyzed in details with different workpiece thickness, and the trend of dynamics characteristics of gas jet is shown in the study. For taper nozzles and convergence nozzles, the dynamic structure of assist gas being close to the lower surface of workpiece is exacerbated while the cutting quality and cutting efficiency become worse with the increasing of workpiece thickness. The parallel degree between assist gas and the axis of convergence nozzle is better than that of taper nozzle after the gas goes out of the nozzles. Two typical subsonic nozzles are designed for the cutting experiment at the end of the paper.     

Novel mesh technique and its application in the wind field simulation for flexible spatial structure

In this paper, novel mesh techniques are proposed for wind field simulation of flexible spatial structure. For mesh generation, an interpolation strategy is presented to obtain a mesh system with variable density. Two spatial structure examples are used to examine the efficiency and applicability of this technique. Then based on the structured mesh system generated by the technique, the mesh nodal coordinates are updated to adapt the moving boundary conditions by means of the mapping interpolation functions and some examples are given to verify the effectiveness. Furthermore, the constrained counterforce distribution technique and projection interpolation strategy are developed to implement the data exchange on the interaction surface of wind and structure. Finally, the computational accuracy is numerically validated.     

Grafting watermelon seedling production management system based on process control strategy

Greenhouse environmental management, seedling bed scheduling, and fertilizer and water management are the core technologies of seedling nursery. Precision management and control of the whole production process guarantees high grated seedling quality. In order to improve management efficiency of grafted watermelon seedling production and seedling quality, this paper designs and develops a grafted watermelon seedling production management system based on process control methods by process control strategy, seedling bed planning design, and handheld device technology.     

Image fusion scheme based on nonsubsampled contourlet and block-based cosine transform

A kind of nonsubsampled contourlet and block-based cosine transform (NSCBCT) is developed, and its application in image fusion is studied in this paper. The construction of filtering banks is based on the nonsubsampled contourlet transform (NSCT) and block-based discrete cosine transform (B-DCT). We combine NSCT and B-DCT to design filters that lead to NSCBCT with better singularity representation than either of them in isolation. A design framework based on the hybrid approach is proposed, which allows for the fast implementation based on NSCT and B-DCT respectively. In addition, a new image fusion scheme based on NSCBCT for multispectral and panchromatic satellite images is proposed. Firstly, because it adopts NSCT, the fused satellite images have higher spatial resolution than those based on wavelets. Secondly, based on the localized high frequency information provided by B-DCT, the proposed fusion scheme can reduce the spectral distortion of the fused image further. Experimental results show that the proposed fusion method is able to increase the spatial resolution and reduce the spectral distortion of the fused image at the same time.     

Nonlinear analyses of exchange rates of six emerging markets

This paper presents some empirical evidences on the presence of nonlinearity of exchange rates of six emerging markets by using Brock-Dechert-Scheinkman (BDS) test and Volterra-Wiener-Korenberg (VWK) model, respectively. The nonlinear dependences are found in the exchange rates of six emerging markets. Furthermore, this paper applies the VWK model with surrogate data method to detect if their nonlinear dependences are deterministic or not. The results show that the above exchange rates are deterministic and nonlinear time series. These imply that the exchange rate markets do not conform to the requirements of the random walk hypothesis. Therefore, the nonlinear dynamic model should be used to analyze the exchange rates.     

TDOA Passive Location Based on Cuckoo Search Algorithm

This paper formulates a new framework to estimate the target position by adopting cuckoo search(CS)positioning algorithm. Addressing the nonlinear optimization problem is a crucial spot in the location system of time difference of arrival(TDOA). With the application of the Levy flight mechanism, the preferential selection mechanism and the elimination mechanism, the proposed approach prevents positioning results from falling into local optimum. These intelligent mechanisms are useful to ensure the population diversity and improve the convergence speed. Simulation results demonstrate that the cuckoo localization algorithm has higher locating precision and better performance than the conventional methods. Compared with particle swarm optimization(PSO) algorithm and Newton iteration algorithm, the proposed method can obtain the Cram′er-Rao lower bound(CRLB) and quickly achieve the global optimal solutions.     

Adaptive Sliding-Mode Tracking Control for an Uncertain Nonlinear SISO Servo System with a Disturbance Observer

An adaptive sliding mode controller with a disturbance observer (ASMC-DO) is proposed for the control of a single-input and single-output (SISO) servo system which has uncertain parameters, nonlinear friction, disturbance and input saturation. It is difficult to choose the suitable value of the parameters. The newly designed adaptive method is used to reduce the effects of system time-varying parameters, such as the moment of inertia and the damp coefficient. The robustness of object is improved. A DO is selected to approximate the compound disturbance and to render the estimate error convergent in finite time. The stability and the convergence of the closed-loop system are proved by using the Lyapunov theory. Experimental results show that the proposed ASMC-DO can better satisfy the influence of variable parameters and external disturbance to the control precision of the SISO servo system than other two controllers. The effectiveness of the proposed controller is showed. The control input stability and robust performances of the input saturation system are enhanced and the chattering is reduced.