Splitting the surface wave in metal/dielectric nanostructures

We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain (FDTD) simulation method. The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths, thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4～5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.     

基于群体共识的农村土地流转优化决策方法

农村土地流转涉及到政府部门的心理预期和承包企业的利益参照点。如果两者不能达成共识,很难达到农村土地流转帕累托改善。本文主要研究这两方流转主体在群体演化博弈中累积的共识达成过程,及其对现有土地效率的优化机制作用规律。在考虑双方异质性累积前景预期值的基础上,利用模拟仿真研究政府和企业之间的博弈演化过程,发现在双方心理预期均获得满足的条件下,群体能够达成共识,农村土地流转效率最高。     

基于两端自发荧光辐射的808nm半导体激光器增益偏振特性实验表征和能带分析

通过半导体激光器两端的放大自发荧光辐射可以获取器件的光学增益信息. 本文利用这一新的增益实验测量方法, 开展了对连续运行的808nm GaAs/AlGaAs量子阱激光器横向电场 (TE)与磁场(TM)偏振增益特性的实验研究. 通过将实验结果与理论增益曲线对比, 分析了非应变GaAs量子阱TE和TM极化偏振对应的空穴子能带随注入电流的变化规律, 以及激光器在连续运行状态下的实际增益状态和影响因素. 关键词： 半导体激光器 增益测量 偏振 量子阱和能带     

一种基于邻近点算法的变步长原始-对偶算法

本文考虑求解一种源于信号及图像处理问题的鞍点问题.基于邻近点算法的思想,我们对原始-对偶算法进行改进,构造一种对称正定且可变的邻近项矩阵,得到一种新的原始-对偶算法.新算法可以看成一种邻近点算法,因此它的收敛性易于分析,且无需较强的假设条件.初步实验结果表明,当新算法被应用于求解图像去模糊问题时,和其他几种主流的高效算法相比,新算法能得到较高质量的结果,且计算时间也是有竞争力的.     

液态电极等离子体发射光谱技术检测金属离子的研究应用

快速准确的金属离子检测是涉及多个学科领域及检测技术的研究课题,文章综述了液体电极等离子体发射光谱技术在金属离子检测领域的研究及应用。首先介绍了基于电化学原理的电极法,包括离子选择性电极及阳极溶出法,及基于原子吸收或发射光谱等检测金属离子常用方法技术的原理及优缺点;然后阐述了基于等离子体的液体电极光谱技术的原理及特点,包括等离子体的产生机理、光谱特点以及其检测技术的优势;并按照液态电极数目及放电系统结构分成单液态电极及双液态电极放电系统两类,重点介绍了液态电极发射光谱技术的发展历程及研究进展,其中详细说明了ELCAD、SCGD、LS-APGD及毛细管放电等电解质放电系统的结构及特点;利用液态电极等离子体发射光谱技术,对铜、汞、银等重金属以及钠、钾、镁等活泼金属离子的检测限可达μg·L-1。最后探讨了该技术应用于检测金属离子的优势及存在的问题,并展望了其应用前景。     

Modeling of resistance characteristics of a continuously-graded distributed Bragg reflector in a 980-nm vertical-cavity surface-emitting laser

The resistance characteristics of a continuously-graded distributed Bragg reflector(DBR) in a 980-nm verticalcavity surface-emitting laser(VCSEL) are modeled in detail.The junction resistances between the layers of both the p-and n-DBR mirrors are analysed by combining the thermionic emission model and the finite difference method.In the meantime,the intrinsic resistance of the DBR material system is calculated to make a comparison with the junction resistance.The minimal values of series resistances of the graded p-and n-type DBR mirrors and the lateral temperature-dependent resistance variation are calculated and discussed.The result indicates the potential to optimize the design of the DBR reflectors of the 980-nm VCSELs.     

Numerical simulation of the initial plasma formation and current transfer in single-wire electrical explosion in vacuum

In this paper, a computational model is constructed to investigate the phenomenon of the initial plasma formation and current transfer in the single-wire electrical explosion in a vacuum. The process of the single-wire electrical explosion is divided into four stages. Stage Ⅰ: the wire is in solid state. Stage Ⅱ: the melting stage. Stage Ⅲ: the wire melts completely and the initial plasma forms. Stage IV: the core and corona expand separately. The thermodynamic calculation is applied before the wire melts completely in stages Ⅰ and Ⅱ. In stage Ⅲ, a one-dimensional magnetohydrodynamics model comes into play until the instant when the voltage collapse occurs. The temperature, density, and velocity, which are derived from the magnetohydrodynamics calculation, are averaged over the distribution area. The averaged parameters are taken as the initial conditions for stage Ⅳ in which a simplified magnetohydrodynamics model is applied. A wide-range semi-empirical equation of state, which is established based on the Thomas-Fermi-Kirzhnits model, is constructed to describe the phase transition from solid state to plasma state. The initial plasma formation and the phenomenon of current transfer in the electrical explosion of aluminum wire are investigated using the computational model. Experiments of electrical explosion of aluminum wires are carried out to verify this model. Simulation results are also compared with experimental results of the electrical explosion of copper wire.     

双绞铝丝纳秒电爆炸实验研究

在快前沿放电装置(约2 k A,12 ns)上对四种绞合波长(λt=0.37,0.5,0.75,1.0 mm)的双绞铝丝开展了纳秒电爆炸实验研究.实验结果表明,特定绞合波长会对能量沉积、膨胀过程、光辐射产生显著影响,当绞合波长为0.5 mm时,能量沉积为原子化焓的3.2倍,而其他三种绞合波长能量沉积变化不大,约为原子化焓的1.8倍;绞合波长为0.5 mm时膨胀速度达3.8×103m/s,光辐射相对强度也最高,在膨胀过程中较好地保持了初始结构,在t=246ns时,形成了密度约为1019cm-3,直径约为1.6 mm的中性原子柱,并且在表面形成了波长约为0.5 mm,幅值约为0.3 mm的周期性结构.     

铝单丝Z箍缩形成无核冕结构的物理分析

针对铝单丝Z箍缩负载,计算其可形成金属蒸气而不形成核冕等离子体的电路和负载参数范围。提出了铝丝电爆炸形成金属蒸气的能量沉积判据和击穿电压判据;建立了热动力学模型,选取电路参数使得金属丝气化时放电回路电流恰好迅速下降,从而避免发生电压击穿。计算了典型电路下的负载电流、电压、电阻及沉积能量的变化曲线,并分析了回路总电感、充电电压以及负载丝长度、直径对其的影响规律。计算结果表明:当储能电容为150pF、充电电压为65kV、回路电感为300nH时,可驱动直径20μm、长2cm的铝丝电爆炸形成铝丝蒸气。快电流前沿、小丝直径和较短的丝长度有助于提高负载中的单位质量沉积能量,容易电爆炸形成金属蒸气负载。     

可延展柔性无机微纳电子器件原理与研究进展

为适应下一代电子产品便携性、形状可变性、人体适用性等方面的进一步需求,近年来基于无机电子材料的可延展柔性电子技术成为全球电子产业界与学术界关注的新焦点.与有机柔性电子学器件不同,可延展柔性无机电子器件指的是建立在柔性基底上的无机电子组件.这种具有柔性的集成电路利用力学设计提供大变形,在保持无机脆性电子器件高性能和高可靠性的同时,具备形状可弯曲、可伸缩等柔性性能.本文综述了近年来无机柔性电子器件的进展,包括力学设计原理、基于界面黏附的转印集成方法以及柔性大变形下的失效机理等,并展望了未来的应用和发展.