降低高光谱(Hyperspectral,HS)图像中的噪声以提高图像质量一直是遥感图像处理领域的研究热点,而HS图像带有的混合光电噪声却难于准确估计,为此提出一种基于同性质区域(Homogeneous Region,HR)分割的HS图像混合噪声估计方法。首先结合HS图像的空间和光谱特性进行HR分割,然后在HR内通过多元线性回归(Multiple Linear Regression,MLR)方法去除区域相关性从而得到混合噪声,最后引进比例因子对混合噪声的内部参数进行估计。通过在仿真HS数据和真实AVIRIS数据上进行实验表明,该方法能够有效地进行HR分割,且对混合噪声的估计结果要优于其它传统噪声估计方法。
A combined method is proposed to determine the water entry acceleration at a low impact velocity through image processing. The procedure includes: (1) a sequence of images for water impact are recorded by a high speed camera, (2) the sub-pixel image processing method is employed to calculate the displacement with an accuracy on the "sub-pixel" level, (3) the acceleration of the object is acquired by differentiating the displacement twice and with results being further filtered by a carefully designed low-pass Butterworth filter. A theoretically based analysis is conducted for designing the parameters of the low-pass filters. It is shown that the water entry can be regarded as a procedure with a slowly changing velocity. The method is validated with the standard sinusoidal motion and the water entry of a sphere. This approach could be considered as an auxiliary method during the early-stage study of the water entry, and it could be further applied to some complicated circumstances, like the water entry of spinning spheres.
Generating computer animated flames is a difficult and computationally expensive problem. Dynamic textures provide an effective means for extrapolating and synthesizing dynamic flames, but aggravates color distortion due to the high correlation of RGB components. A novel method for dynamic flame texture synthesis using color temperature is proposed in this paper. Firstly, the colortemperature mapping is calculated by using the Planck's law and two-color pyrometric technique to avoid color distortion. Secondly, a novel dynamic texture model is presented to transform the RGB space into temperature space. Finally,the dynamic flames editing is presented to support physical temperature adjustment. Experimental results illustrate that our approach is effective to synthesize visually plausible dynamic flames without color distortions and to edit dynamic flames with intuitive physical interpretation.
In this paper, a method that combines the characteristic-based split finite element method(CBS-FEM) and the direct forcing immersed boundary(IB) method is proposed for the simulation of incompressible viscous flows. The structured triangular meshes without regarding the location of the physical boundary of the body is adopted to solve the flow, and the no-slip boundary condition is imposed on the interface. In order to improve the computational efficiency, a grid stretching strategy for the background structured triangular meshes is adopted. The obtained results agree very well with the previous numerical and experimental data. The order of the numerical accuracy is shown to be between 1 and 2. Moreover, the accuracy control by adjusting the number density of the mark points purely at certain stages is explored, and a second power law is obtained. The numerical experiments for the flow around a cylinder behind a backward-facing step show that the location of the cylinder can affect the sizes and the shapes of the corner eddy and the main recirculation region. The proposed method can be applied further to the fluid dynamics with complex geometries, moving boundaries, fluid-structure interactions, etc..
