333 research outputs found
Inflating hollow nanocrystals through a repeated Kirkendall cavitation process.
The Kirkendall effect has been recently used to produce hollow nanostructures by taking advantage of the different diffusion rates of species involved in the chemical transformations of nanoscale objects. Here we demonstrate a nanoscale Kirkendall cavitation process that can transform solid palladium nanocrystals into hollow palladium nanocrystals through insertion and extraction of phosphorus. The key to success in producing monometallic hollow nanocrystals is the effective extraction of phosphorus through an oxidation reaction, which promotes the outward diffusion of phosphorus from the compound nanocrystals of palladium phosphide and consequently the inward diffusion of vacancies and their coalescence into larger voids. We further demonstrate that this Kirkendall cavitation process can be repeated a number of times to gradually inflate the hollow metal nanocrystals, producing nanoshells of increased diameters and decreased thicknesses. The resulting thin palladium nanoshells exhibit enhanced catalytic activity and high durability toward formic acid oxidation
Clustering Instabilities in Gas-Solid Systems: Role of Dissipative Collisions vs. Viscous Losses
Clustering Instabilities in Gas-Solid Systems: Role of Dissipative Collisions vs. Viscous Losses
https://digitalrepository.unm.edu/abq_mj_news/4755/thumbnail.jp
Robust image steganography against lossy JPEG compression based on embedding domain selection and adaptive error correction
Transmitting images for communication on social networks has become routine,
which is helpful for covert communication. The traditional steganography
algorithm is unable to successfully convey secret information since the social
network channel will perform lossy operations on images, such as JPEG
compression. Previous studies tried to solve this problem by enhancing the
robustness or making the cover adapt to the channel processing. In this study,
we proposed a robust image steganography method against lossy JPEG compression
based on embedding domain selection and adaptive error correction. To improve
anti-steganalysis performance, the embedding domain is selected adaptively. To
increase robustness and lessen the impact on anti-steganalysis performance, the
error correction capacity of the error correction code is adaptively adjusted
to eliminate redundancy. The experimental results show that the proposed method
achieves better anti-steganalysis and robustness
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