No abstract

Image reversible data hiding (RDH) using interpolation technology (IT) provides high singlelayer embedding capacity and has become a research hotspot. To solve serious image distortion in existing methods caused by secondary embedding based on interpolated pixels, we propose an RDH method for interpolated images based on modulo operation and prediction-error expansion (PEE). Our method differs from existing RDH methods that only consider embedding data into interpolated pixels. First, an image interpolation method is used to generate an interpolated image, which is partitioned into overlapping 3 × 3 blocks. For each block, secret data are embedded into interpolated pixels using the modulo operation and into reference pixel using the PEE. Standard grayscale images of size 512 × 512 were selected from the popular BossBase and BOWS-2 image databases as input images for experiments. Extensive experimental results show that the proposed method avoids pixel values underflow/overflow caused by embedding data and reduces image distortion effectively. For each standard test image, the maximum bits per pixel (BPP) is higher than 1.5, and the corresponding peak signal to noise ratio (PSNR) is higher than 45.0 dB. At the given embedding capacity, the proposed method outperforms recent similar methods regarding the watermarked image quality. Moreover, the proposed method can resist histogram analysis, and the subjective evaluation proves that the proposed method has good imperceptibility.INDEX TERMS Reversible data hiding, interpolated image, modulo operation, prediction-error expansion.

The coupling of the short wavelength ion temperature gradient mode (SWITG) and trapped electron mode (SWTEM) in the presence of impurity ions is numerically studied in tokamak plasmas. It is found that the coupling of SWITG and SWTEM modes is divided into hybrid and coexistent cases. The impurity ions always have stabilizing effects on the hybrid mode (namely, SWTE-ITG) with small ηi (ηi < 0.5), which is different from the conventional TE-ITG mode. In the lager ηi (ηi > 0.5) regime, the impurity ions with the density profiles peaked inwardly (outwardly) stabilize (destabilize) the SWTE-ITG mode. Another new finding in this paper is that the impurity ions stabilize the SWTEM mode independent of whether their density profile is peaked inwardly or outwardly. The result for the SWITG mode is similar to the SWTE-ITG mode in the lager ηi regime, except that the excitation of the SWTEM mode requires ηi higher than a certain threshold. In addition, the kθρs spectra, eigenmode structures, and the effects of different impurity ion species on the modes are discussed.