手性等离激元纳米晶制备技术的研究进展

生命体中大部分生物分子都具有手性。生物分子的手性构象与等离激元纳米晶的局域表面等离激元共振(LSPR)通过偶极子-偶极子耦合作用,在其LSPR的位置会诱导出一个新的圆二色吸收光谱,具有这种光学活性的等离激元纳米晶称为手性等离激元纳米晶。手性等离激元纳米晶的光学响应信号的稳定性和可重复性都比较高,广泛应用在生物传感、化学传感、圆偏振器、光催化、癌症治疗等领域。手性等离激元纳米晶的制备技术一直是该领域的研究热点。然而,通过将手性分子直接吸附在等离激元纳米晶表面的方式所诱导的手性光学响应信号非常弱,故本综述聚焦于手性等离激元纳米晶的其他制备技术,包括通过手性分子或者软模板组装技术获得手性等离激元超结构;湿化学法将手性分子嵌入到单个纳米晶当中制备出核-壳型手性等离激元纳米晶,或者将手性分子的手性构象传递到无机纳米材料的结构当中制备出单个螺旋型手性等离激元纳米晶等。基于目前对手性等离激元纳米晶的最新研究进展,对其纳米制备技术作了进一步的总结和展望。     

Multi-scroll hidden attractors and multi-wing hidden attractors in a 5-dimensional memristive system

A novel 5-dimensional(5D) memristive chaotic system is proposed, in which multi-scroll hidden attractors and multiwing hidden attractors can be observed on different phase planes. The dynamical system has multiple lines of equilibria or no equilibrium when the system parameters are appropriately selected, and the multi-scroll hidden attractors and multi-wing hidden attractors have nothing to do with the system equilibria. Particularly, the numbers of multi-scroll hidden attractors and multi-wing hidden attractors are sensitive to the transient simulation time and the initial values. Dynamical properties of the system, such as phase plane, time series, frequency spectra, Lyapunov exponent, and Poincar′e map, are studied in detail. In addition, a state feedback controller is designed to select multiple hidden attractors within a long enough simulation time. Finally, an electronic circuit is realized in Pspice, and the experimental results are in agreement with the numerical ones.     

Fixed time integral sliding mode controller and its application to the suppression of chaotic oscillation in power system

Chattering phenomenon and singularity are still the main problems that hinder the practical application of sliding mode control. In this paper, a fixed time integral sliding mode controller is designed based on fixed time stability theory,which ensures precise convergence of the state variables of controlled system, and overcomes the drawback of convergence time growing unboundedly as the initial value increases in finite time controller. It makes the controlled system converge to the control objective within a fixed time bounded by a constant as the initial value grows, and convergence time can be changed by adjusting parameters of controllers properly. Compared with other fixed time controllers, the fixed time integral sliding mode controller proposed in this paper achieves chattering-free control, and integral expression is used to avoid singularity generated by derivation. Finally, the controller is used to stabilize four-order chaotic power system. The results demonstrate that the controller realizes the non-singular chattering-free control of chaotic oscillation in the power system and guarantees the fixed time convergence of state variables, which shows its higher superiority than other finite time controllers.     

一种具有隐藏吸引子的分数阶混沌系统的动力学分析及有限时间同步

对于具有隐藏吸引子的混沌系统,既有文献大多只针对整数阶系统进行分析与控制研究.基于Sprott E系统,构建了仅有一个稳定平衡点的分数阶混沌系统,通过相位图、Poincare映射和功率谱等,分析了该系统的基本动力学特征.结果显示,该系统展现出了丰富而复杂的动力学特性,且通过随阶次变化的分岔图可知,系统在不同阶次下呈现出周期运动、倍周期运动和混沌运动等状态,这些动力学特征对于保密通信等实际工程领域有重要的研究价值.针对该具有隐藏吸引子的分数阶系统,应用分数阶系统有限时间稳定性理论设计控制器,对系统进行有限时间同步控制,并通过数值仿真验证了其有效性.