温敏型Keratin/PNIPAM水凝胶的制备及其对重金属离子的吸附性能和机理研究

以羽毛中提取的角蛋白为原料,N-异丙基丙烯酰胺（NIPAM）为温敏性单体,采用一锅法制备了对温度敏感的双网络型角蛋白/PNIPAM水凝胶,并对其结构、膨胀性能、吸附特性、吸附选择性及吸附机理进行了研究。结果表明,温敏型角蛋白/PNIPAM水凝胶符合负向温敏凝胶的特征,在高于低临界转变温度时凝胶排水收缩,在低于低临界转变温度时凝胶迅速吸水膨胀;温敏型角蛋白/PNIPAM水凝胶随着pH的增大对重金属Pb（Ⅱ）的吸附容量逐渐增大,在pH 5时达到最大吸附容量78.63 mg/g。温敏型角蛋白/PNIPAM水凝胶在吸附重金属Pb（Ⅱ）的过程中仅用30 min即可达到吸附平衡,对Pb（Ⅱ）的最大吸附容量为415.73 mg/g。吸附模型拟合和吸附动力学分析结果表明温敏型角蛋白/PNIPAM水凝胶符合Langmuir吸附模型（R²=0.992）,属于单层吸附。吸附动力学模型分析显示该凝胶符合准二级动力学模型,以化学吸附为主,物理吸附为辅。     

High-efficiency unidirectional wavefront manipulation for broadband airborne sound with a planar device

In the past decade, one-way manipulation of sound has attracted rapidly growing attention with application potentials in a plethora of scenarios ranging from ultrasound imaging to noise control. Here we propose a design of a planar device capable of unidirectionally harnessing the transmitted wavefront for broadband airborne sound. Our mechanism is to use the broken spatial symmetry to give rise to different critical angles for plane waves incident along opposite directions. Along the positive direction, the incoming sound is allowed to pass with high efficiency and be arbitrarily molded into the desired shape while any reversed wave undergoes a total reflection. We analytically derive the working bandwidth and incident angle range, and present a practical implementation of our strategy. The performance of our proposed device is demonstrated both theoretically and numerically via distinct examples of production of broadband anomalous refraction, acoustic focusing and non-diffractive beams for forward transmitted wave while virtually blocking the reversed waves. Bearing advantages of simple design, planar profile, broad bandwidth and high efficiency, our design opens the possibility for novel one-way acoustic device and may have important impact on diverse applications in need of special control of airborne sound.     

Lp混合均值积分的log-Minkowski不等式的简化证明

研究了关于Lp混合均值积分的log-Minkowski不等式,应用Jensen不等式给出Lp混合均值积分的log-Minkowski不等式的简化证明,同时应用加强的Jensen不等式给出一加强不等式.     

一类带Lévy跳的随机SIRS传染病模型的渐近性分析北大核心CSCD

研究了一类带有随机白噪声干扰及Lévy跳的SIRS型传染病模型.首先利用停时等方法证明了模型全局解的存在性和唯一性,然后得到了染病种群趋于灭绝及依平均持久的充分条件,最后对结果进行了数值模拟.