694 research outputs found

    Reliable camera motion estimation from compressed MPEG videos using machine learning approach

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    As an important feature in characterizing video content, camera motion has been widely applied in various multimedia and computer vision applications. A novel method for fast and reliable estimation of camera motion from MPEG videos is proposed, using support vector machine for estimation in a regression model trained on a synthesized sequence. Experiments conducted on real sequences show that the proposed method yields much improved results in estimating camera motions while the difficulty in selecting valid macroblocks and motion vectors is skipped

    Embedded Sensor System for Five-degree-of-freedom Error Detection on Machine Tools

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    Any linear stage of machine tool has inherent six-degree-of-freedom (6-DOF) geometric errors. Its motion control system, however, has only the position feedback. Moreover, the feedback point is not the commanded cutting point. This is the main reason why the positioning error along each axis and the volumetric error in the working space are inevitable. This paper presents a compact 5-DOF sensor system that can be embedded in each axis of motion as additional feedback sensors of the machine tool for the detection of three angular errors and two straightness errors. Using the derived volumetric error model, the feedback point can be transferred to the cutting point. The design principle of the developed 5-DOF sensor system is described. An in-depth study of systematic error compensation due to crosstalk of straightness error and angular error is analyzed. A prototype has been built into a three-axis NC milling machine. The results of a series of the comparison experiments demonstrate the feasibility of the developed sensor system

    Error estimates of a high order numerical method for solving linear fractional differential equations

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    In this paper, we first introduce an alternative proof of the error estimates of the numerical methods for solving linear fractional differential equations proposed in Diethelm [6] where a first-degree compound quadrature formula was used to approximate the Hadamard finite-part integral and the convergence order of the proposed numerical method is O(∆t 2−α ), 0 < α < 1, where α is the order of the fractional derivative and ∆t is the step size. We then use the similar idea to prove the error estimates of a high order numerical method for solving linear fractional differential equations proposed in Yan et al. [37], where a second-degree compound quadrature formula was used to approximate the Hadamard finite-part integral and we show that the convergence order of the numerical method is O(∆t 3−α ), 0 < α < 1. The numerical examples are given to show that the numerical results are consistent with the theoretical results
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