In this study, fluid flow around bluff bodies are studied to examine the vortex shedding phenomenon in conjuction with the geometrical shapes of these vortex shedders. These flow phenomena are numerically simulated. A finite volume method is employed to solve the incompressible two-dimensional Navier-Stokes equations. Thus, quantitative descriptions of the vortex shedding phenomenon in the near wake were made, which lead to a detailed description of the vortex shedding mechanism. Streamline contours, figures of lift coefficent, and figures of drag coefficent in various time, are presented, respectively, for a physical description.

The purpose of this research is to study the effect of motion curves on the curvature of variable pitch lead screw (hereinafter VPLS) transmission mechanisms with different meshing elements. The surfaces of VPLS are generated based on various meshing elements with different specified motion curves. There are three kinds of ruled- and one involute-revolution surface meshing elements, and four types of motion curves are studied, which including modified trapezoidal (MT) curve, modified sine (MS) curve, modified constant velocity (MCV) curve, and polynomial (PL) curve. The curvature analyses include the determination of direction of contact line, induced principal radii of curvature, and lubrication angles between the surfaces of VPLS and various meshing elements. The results of this work provide a comparison between the effect of motion curve on the curvature of VPLS transmission mechanisms with different meshing elements.

The dynamical system considered in this paper is an inelastic beam whose supports are subjected to a harmonic excitation. This paper first explores whether the system has chaotic motion. The appearance of the irregular time history, strange attractor on the Poincaré map as well as period-doubling bifurcation phenomenon strongly indicates that chaos indeed exist in this system. After finding the chaos phenomenon, this paper continues to investigate the relationship between the decay time of the autocorrelation function and the largest Lyapunov exponent. The Poincaré mapping points are chosen to be the sampled function of the discrete autocorrelation function. It's found that a power model of regression analysis can fit with good accuracy the data points, which are composed of the mapping times for the autocorrelation to decay into the square of the mean of the Poincaré points and the corresponding largest Lyapunov exponent.

We propose a new path following control algorithm. The algorithm decomposes the trajectory errors into tangential and normal components. The normal component minimizes the tracking error, while the tangential component maintains the desired speed. Experimental results using an X-Y table indicate that the proposed method possesses satisfactory tracking characteristics. It resolves certain previously difficult to control problems.