The structural, electronic, and optical properties of rutile-type SnO2 are studied by plane-wave pseudopotential density functional theory (DFT) with GGA, LDA, B3LYP and PBE0 respectively. The computing results show that the band gap getting from PBE0 and B3LYP is much more consistent with the available experimental data than that from GGA and LDA, no matter what the latter use ultra-soft pseudopotential or norm conserving pseudopotential. However, the density of state, real part and imaginary part of dielectric function calculating from every type is basically similar in qualitative analysis.
According to the important position of DCT in image coding, the research of image retrieval performance based on DCT is advanced. In the paper, we take color descriptors of MPEG-7 as the color image feature, and acquire new image features through giving different weights to the different elected DCT coefficients, Using Euclidean distance as the similar distance measurement to retrieve color images in DCT. Then the relationship between the choice of weight and retrieval performance is studied by experiments, and moreover the retrieval conclusion is analyzed in detail. The result shows it can acquire relatively satisfactory outcome when selecting right weights of the elected DCT coefficients based on a concrete condition.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.