Temperature effects on the nuclear symmetry energy and symmetry free energy with an isospin and momentum dependent interaction

Within a self-consistent thermal model using an isospin and momentum dependent interaction (MDI) constrained by the isospin diffusion data in heavy-ion collisions, we investigate the temperature dependence of the symmetry energy $E_{sym}(\rho, T)$ and symmetry free energy $F_{sym}(\rho, T)$ for hot, isospin asymmetric nuclear matter. It is shown that the symmetry energy $E_{sym}(\rho, T)$ generally decreases with increasing temperature while the symmetry free energy $F_{sym}(\rho, T)$ exhibits opposite temperature dependence. The decrement of the symmetry energy with temperature is essentially due to the decrement of the potential energy part of the symmetry energy with temperature. The difference between the symmetry energy and symmetry free energy is found to be quite small around the saturation density of nuclear matter. While at very low densities, they differ significantly from each other. In comparison with the experimental data of temperature dependent symmetry energy extracted from the isotopic scaling analysis of intermediate mass fragments (IMF's) in heavy-ion collisions, the resulting density and temperature dependent symmetry energy $E_{sym}(\rho, T)$ is then used to estimate the average freeze-out density of the IMF's.used to estimate the average freeze-out density of the IMF's.Comment: 9 pages, 7 figures, 1 figure added to show the temperature dependence of the potential and kinetic parts of the symmetry energy. Revised version to appear in PR

Digital Image Watermarking Algorithm Using the Intermediate Frequency

Digital image watermarking is one of the proposed solutions for copyright protection of multimedia data. This technique is better than Digital Signatures and other methods because it does not increase overhead. Watermarking adds the additional requirement of robustness. To improve the robustness of digital image watermarking method based on the image frequency, this paper adopts the intermediate frequency to embed the watermarking and proposes an digital image watermarking algorithm based on robust principal component analysis (RPCA) and discrete cosine transform (DCT). Firstly, the high frequency part and the low frequency part of the image are extracted by the RPCA algorithm. Because the high frequency part has complex statistical characteristics, this paper processes the high frequency part with "8×8" DCT method to obtain intermediate frequency coefficients and then the watermarking information is embedded into the obtained intermediate frequency coefficients. The experimental results show that the proposed algorithm leads to satisfactory robustness to the attacks of impulse noise and cropping

Microcodium in Chinese loess as a recorder for the oxygen isotopic composition of monsoonal rainwater

Records of Asia Summer Monsoon (ASM) from the Chinese loess and the speleothem display distinct features. The very different proxies that were applied to the two archives may be responsible for this discrepancy. A direct comparison between the speleothem and the loess records under the same proxy system of rainwater delta O-18 may help to resolve this puzzle. Here we show that the calcified microcodium in the loess deposits may record the oxygen isotopic composition of the summer rainwater. A microcodium based delta O-18 record covering the past 140 kyrs was generated, which shows similar magnitude of the overall variation to that of the speleothem records. However, much weaker precession variability was registered in the microcodium record during the last interglacial period. Instead, the microcodium delta O-18 record is more consistent with the widely used summer monsoon proxy of magnetic susceptibility in the loess deposits with clear glacial-interglacial pattern. This similarity may originate from the low sedimentation rate of the interglacial paleosol layer that preferentially record the peak ASM signals on the precession band. It is also possible that the orbital variability of ASM between the North China and South China is inherently different with more ice-volume related influence in the north. A longer microcodium delta O-18 record in sequences of higher sedimentation rate and a reliable record of summer rainfall may help to resolve these possibilities. (C) 2017 Elsevier Ltd and INQUA. All rights reserved