Intelligent Reflecting Surface-Aided Secure and Covert Communications

This work employs intelligent reflecting surface(IRS)to enhance secure and covert communication performance.We formulate an optimization problem to jointly design both the reflection beamformer at IRS and transmit power at transmitter Alice in order to optimize the achievable secrecy rate at Bob subject to a covertness constraint.We first develop a Dinkelbach-based algorithm to achieve an upper bound performance and a high-quality solution.For reducing the overhead and computational complexity of the Dinkelbach-based scheme,we further conceive a low-complexity algorithm in which analytical expression for the IRS reflection beamforming is derived at each iteration.Examination result shows that the devised low-complexity algorithm is able to achieve similar secrecy rate performance as the Dinkelbach-based algorithm.Our examination also shows that introducing an IRS into the considered system can significantly improve the secure and covert communication performance relative to the scheme without IRS.

白芍方药以及白芍总苷镇痛功效及其机理研究进展

目的综述古籍中对白芍镇痛功效的记载,以及近年来阐述白芍镇痛功效与机理的研究,为其临床应用和效应机制的深入研究提供参考依据。方法查阅古籍和近年有关白芍镇痛功效的文献报道,并进行归纳、分析和总结。结果历代诸多医家及著作均有对白芍镇痛功效与主治的详细描述。临床研究证实白芍方药及其提取物白芍总苷对于腰腿痛、内脏痛、头痛、癌性疼痛等痛证疗效确切,副作用少。基础实验表明,白芍及其提取物可通过调节前列腺素、相关受体和信号转导通路等多种途径发挥镇痛作用,还可拮抗吗啡等西药镇痛耐受,与甘草、川乌、马钱子等中药配伍后,还具有一定的增效减毒作用。结论白芍在治疗多种痛证方面疗效显著,机制复杂,具有很好的发展潜力和很高的研究价值,有待进一步探索发掘。