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SUMMARYThis paper is concerned with the stability and L 2 -gain problems for a class of continuous-time linear switched systems with the existed asynchronous behaviors, where 'asynchronous' means that the switching of the controllers to be designed has a lag to the switching of the system modes. Firstly, a new sufficient condition on the asymptotic stability and weighted L 2 -gain analysis is obtained by using multiple Lyapunov functions combined with the average dwell time technique. Moreover, a result that is formulated in form of linear matrix inequalities is derived for the problem of asynchronous H 1 control. Based on the result, the mode-dependent controllers can be designed. Finally, an illustrative numerical example is presented to show the effectiveness of the obtained results.

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Removing rain streaks from a single image continues to draw attentions today in outdoor vision systems. In this paper, we present an efficient method to remove rain streaks. First, the location map of rain pixels needs to be known as precisely as possible, to which we implement a relatively accurate detection of rain streaks by utilizing two characteristics of rain streaks.The key component of our method is to represent the intensity of each detected rain pixel using a linear model: p = αs+β, where p is the observed intensity of a rain pixel and s represents the intensity of the background (i.e., before rain-affected). To solve α and β for each detected rain pixel, we concentrate on a window centered around it and form an L2-norm cost function by considering all detected rain pixels within the window, where the corresponding rain-removed intensity of each detected rain pixel is estimated by some neighboring non-rain pixels. By minimizing this cost function, we determine α and β so as to construct the final rainremoved pixel intensity. Compared with several state-of-the-art works, our proposed method can remove rain streaks from a single color image much more efficiently -it offers not only a better visual quality but also a speed-up of several times to one degree of magnitude.