单负材料一维光子晶体的透射谱特性

利用传输矩阵法研究了单负材料一维光子晶体(AB)m(ADBDB)n(AB)mA的透射谱,发现:透射谱中出现2个共振隧穿模,其位置和间距可由周期数m或n,以及介质层厚度d调节控制。改变m,会出现2个恒定间距的共振隧穿模;改变dA,共振隧穿模间距增大,且当dA≥25mm时,间距增大加剧;改变n,共振隧穿模逐渐趋于简并,当n≥6时,两隧穿模合二为一;改变dD,两共振隧穿模亦逐渐趋于简并,当dD≥20mm时,两隧穿模亦合二为一。这些特性可为利用光子晶体设计可调性高品质单通道、双通道滤波器提供参考。     

膜系光谱系数对膜层参数的一阶和二阶偏导数的计算模型

为了寻找一种膜系深入分析与设计的有力辅助计算工具,从光学薄膜光谱系数的矩阵计算理论出发,基于对矩阵求迹运算的巧妙运用,从数学上建立了准确计算膜系光谱系数关于膜层几何厚度、实际折射率和消光系数等膜层参数的一阶和二阶偏导数的解析模型。这一偏导数计算模型物理上与矩阵理论具有一致的通用性和普适性,适用于任何各向同性的均匀膜系统。在数学上也严格成立,数值编程计算不存在差分近似,精度达到了计算机浮点运算的极限精度。而且算法运算费时少,计算速度快,取得了高度准确性和便于实时化的双重优越性能,非常有利于应用于膜系设计领域来提高膜层数较大时的设计速度和效率。同时,这一模型能非常便捷和准确地给出膜系许多实用的导数信息,对膜系分析、测量和膜厚监控等领域中的相关应用具有重要的参考意义。     

含有格点势的一维Fibonacci链热传导性质的研究

用传输矩阵的方法,研究了格点势(on-site势)对一维Fibonacci链的热传导性质(透射系数、Lyapunov指数及热导率κ)的影响.研究结果表明:当固定原子质量比和力作用常数比时,随着格点势的增大,低频区域的透射系数减小,对应的Lyapunov指数增大,透射谱向高频方向移动.同时,格点势越大,同样大小的体系对应的κ越小,当格点势足够大时,κ会趋近零.在热导率κ对振动频率ω²作图中,κ呈现台阶式缓慢上升的趋势,且在高频     

Chaos synchronization of unified chaotic systems via LMI

This Letter focuses on the master-slave synchronization problem of the unified chaotic systems. Based on Lyapunov stability theory and linear matrix inequality (LMI) formulation, a simple linear feedback control law is obtained to make the state of two identical unified chaotic systems asymptotically synchronized. Simulation results have illustrated the effectiveness of the proposed chaos synchronization solution.     

Wave properties of an annular periodic multilayer structure containing the single-negative materials

The optical properties of an annular periodic multilayer structure containing two kinds of single-negative materials are theoretically investigated based on the transfer matrix method of the cylindrical waves. At the azimuthal mode number m1 and near the magnetic plasma frequency and the electronic plasma frequency for the TE wave and TM wave, respectively, we find that there is an additional high-reflectance band and some reflection dips exist when the plasma frequency is located in the photonic band gap. These two special features arising from the higher order azimuthal mode of the cylindrical waves are not seen in the planar one-dimensional Bragg reflector consisting of the single-negative materials. Such filtering responses provide a feasible way of designing a narrowband resonator without physically introducing any defect layer in the structure.     

Electronic transport on graphene armchair-edge nanoribbons with Fermi velocity and potential barriers

The transport properties of Dirac fermions through armchair-edge graphene nanoribbons (AGNRs) with a single and double rectangular Fermi velocity $v_F$ and electrostatic potential U barriers is investigated. We employ a transfer matrix method (TMM) to compute the transmission coefficient of the full set of propagating mode which is used to obtain the conductance and Fano factor spectra for both metallic and semiconducting nanoribbons. We show that a reduced Fermi velocity within the barrier region can partially suppress the backscattering resulting from the electrostatic potential. In a double barrier structure, the emergence of high-order transmitting modes is shown to substantially reduce the Fano factor in the spectral region around U. These results indicate that the simultaneous tuning of $v_F$ and U in barrier regions can be explored to control the electronic transport in graphene-based nanoelectronics structures.     

Hidden Markov models revealing the stress field underlying the earthquake generation

The application of the hidden Markov models (HMMs) is attempted for revealing key features for the earthquake generation which are not accessible to direct observation. Considering that the states of the HMM correspond to levels of the stress field, our objective is to identify these states. The observations are considered after grouping earthquake magnitudes and the cases of different number of states are examined. The problems of HMMs theory are solved and the ensuing HMMs are compared on the basis of Akaike and Bayesian information criteria. A new insight on the evaluation of future seismic hazard is given by calculating the mean number of steps for the first visit to a particular state, along with the respective variance. We further calculate an estimator of the mean number of steps for the first visit to a particular state and we construct its confidence interval. Additionally, a second approach to the problem is followed by assuming a different determination of observations. The HMMs applied to both approaches, contribute significantly to seismic hazard assessment via revealing the number of the stress levels as well as the way in which these levels are associated with certain earthquake occurrence.     

反射式光学电压互感器光路建模及偏振误差分析

光路系统的偏振误差极大地制约着准互易反射式光学电压互感器的准确度.借助琼斯矩阵,建立了分立光学器件及光纤熔接点的传输模型,推导出完整的电压互感器光路系统的数学模型.以此模型为基础,对电压互感器中的偏振误差进行了仿真分析.结果表明：光源偏振度、起偏器消光比及起偏器与相位调制器的对轴角度主要影响系统的检测灵敏度|法拉第准直旋光器的旋光角度、法拉第准直旋光器与BGO晶体的对轴角度误差是主要的偏振误差源,影响系统的测量准确度及稳定性|根据电子式电压互感器IEC60044-7 0.2S级标准,法拉第旋光角度误差应该小于1.6°,旋光器与BGO晶体对轴角度误差小于1.85°.该研究对准互易反射式光学电压互感器光路设计和误差抑制具有一定的参考价值和指导意义.     

一维三元异质结构光子晶体反射特性

利用传输矩阵法对一维三元光子晶体异质结构的光学特性进行了研究,讨论了介质层厚无序度对三元结构光子禁带的影响.研究表明,将具有相互交叠光子禁带的一维光子晶体叠加构成异质结,可以有效地增大全角度反射的频率范围,当入射角从0°增大到89°,该结构均可实现从0.410 w/w0到0.654 w/w0宽频波段的全反射;相对于二元结构,三元结构可以减小在实际制作过程中随机误差引起的介质层厚无序对光子带隙的影响.该研究结果可为实现可见光及红外光波段大角度反射器的制备及应用提供理论支持.     

Analytical expressions for partial wave two-body Coulomb transition matrices at ground-state energy

Leaning upon the Fock method of the stereographic projection of the three-dimensional momentum space onto the four-dimensional unit sphere the possibility of the analytical solving of the Lippmann–Schwinger integral equation for the partial wave two-body Coulomb transition matrix at the ground bound state energy has been studied. In this case new expressions for the partial p$p$-, d$d$- and f$f$-wave two-body Coulomb transition matrices have been obtained in the simple analytical form. The developed approach can also be extended to determine analytically the partial wave Coulomb transition matrices at the energies of excited bound states.