High thermal stability of diamond-cBN-B_4C-Si composites

Improving the thermal stability of diamond and other superhard materials has great significance in various applications. Here, we report the synthesis and characterization of bulk diamond–cBN–B_4C–Si composites sintered at high pressure and high temperature(HPHT, 5.2 GPa, 1620–1680 K for 3–5 min). The results show that the diamond, cBN, B_4C,B_xSiC, SiO_2 and amorphous carbon or a little surplus Si are present in the sintered samples. The onset oxidation temperature of 1673 K in the as-synthesized sample is much higher than that of diamond, cBN, and B_4C. The high thermal stability is ascribed to the covalent bonds of B–C, C–N, and the solid-solution of B_xSiC formed during the sintering process. The results obtained in this work may be useful in preparing superhard materials with high thermal stability.     

基于全局自适应处理的分块影像增强方法

针对现有全色遥感影像增强算法在增强影像中目标地物时对背景噪声过度增强的问题，提出一种基于全局自适应处理的分块影像增强方法。首先，进行分块处理并分别计算图像中每个影像块的影像增强参数；然后，构建块差异因子对相邻影像块进行合并，将影像块归类为细节块与噪声块，并进行全局自适应处理——计算全局自适应增强参数并用其修正噪声块的增强参数；最后，基于影像块的增强参数内插得到每个像元处的参数，根据这些参数对全色遥感影像进行增强。用该方法对多组不同场景的全色遥感影像进行仿真实验，并基于客观指标对增强方法的效果进行评估，结果表明该增强方法拥有较好的性能。