A robust digital watermarking algorithm is proposed based on quaternion wavelet transform(QWT) and discrete cosine transform(DCT) for copyright protection of color images. The luminance component Y of a host color ima...A robust digital watermarking algorithm is proposed based on quaternion wavelet transform(QWT) and discrete cosine transform(DCT) for copyright protection of color images. The luminance component Y of a host color image in YIQ space is decomposed by QWT, and then the coefficients of four low-frequency subbands are transformed by DCT. An original binary watermark scrambled by Arnold map and iterated sine chaotic system is embedded into the mid-frequency DCT coefficients of the subbands. In order to improve the performance of the proposed algorithm against rotation attacks, a rotation detection scheme is implemented before watermark extracting. The experimental results demonstrate that the proposed watermarking scheme shows strong robustness not only against common image processing attacks but also against arbitrary rotation attacks.展开更多
Transient ischemic attack （TIA） is a temporary event, which portends a higher risk of a disabling stroke following the TIA. However, the evaluation and management of TIA vary worldwide and is debated and controversi...Transient ischemic attack （TIA） is a temporary event, which portends a higher risk of a disabling stroke following the TIA. However, the evaluation and management of TIA vary worldwide and is debated and controversial. With the development of brain imaging, particularly diffusion weighted imaging-magnetic resonance imaging （DWI-MRI）, the diagnosis of TIA changed from time-based definition to a tissue-based one. DWI-MRI be-came a mandatory tool in the TIA workup. The DWI-MRI provides not only the evidence to distinguish between TIA and acute ischemic stroke, fur-thermore it predicts TIA patients who are at higher risk of disabling stroke, which can be prevented by an immediate evaluation and treatment of TLA.展开更多
基金supported by the National Natural Science Foundation of China(Nos.61601467,61379102,61502498,U1433105 and U1433120)the Fundamental Research Funds for the Central Universities(3122017044)
文摘A robust digital watermarking algorithm is proposed based on quaternion wavelet transform(QWT) and discrete cosine transform(DCT) for copyright protection of color images. The luminance component Y of a host color image in YIQ space is decomposed by QWT, and then the coefficients of four low-frequency subbands are transformed by DCT. An original binary watermark scrambled by Arnold map and iterated sine chaotic system is embedded into the mid-frequency DCT coefficients of the subbands. In order to improve the performance of the proposed algorithm against rotation attacks, a rotation detection scheme is implemented before watermark extracting. The experimental results demonstrate that the proposed watermarking scheme shows strong robustness not only against common image processing attacks but also against arbitrary rotation attacks.
文摘Transient ischemic attack （TIA） is a temporary event, which portends a higher risk of a disabling stroke following the TIA. However, the evaluation and management of TIA vary worldwide and is debated and controversial. With the development of brain imaging, particularly diffusion weighted imaging-magnetic resonance imaging （DWI-MRI）, the diagnosis of TIA changed from time-based definition to a tissue-based one. DWI-MRI be-came a mandatory tool in the TIA workup. The DWI-MRI provides not only the evidence to distinguish between TIA and acute ischemic stroke, fur-thermore it predicts TIA patients who are at higher risk of disabling stroke, which can be prevented by an immediate evaluation and treatment of TLA.
