Selective LPE-growth of ln0.53Ga0.47As on semi-insulating InP

Selective liquid phase epitaxy (SLPE) of high purity(n = 2 × 10¹⁵ cm^-3) In_0.53Ga_0.47As on SiO₂-masked (100)-InP:Fe substrates has been performed and investigated using Normarski interference contrast microscopy and SEM. The infill growth was done at low temperatures (˜ 585° C) directly into chemically (HC1:CH₃COOH:H₂O₂) etched cavities without melt-etching. Square and circular recesses of 2–3 μm depth and varying size (100-500 μm) have been used in contrast to common reported regrowth experiments in long channels. Enormously enhanced growth rates have been found within the small structures. Orientation dependent growth effects are described. The realization of selectively grown areas with flat surface morphology has been achieved which is important for optoelectronic integration. Most information contained in this paper was presented at the 27th Electronic Materials Conference, Boulder, Co., June 20, 1985.     

全固态激光器抽运的PPLN光参变振荡

用全固态1064nm调Q激光输出，抽运多周期PPLN，实现了宽调谐的准相位匹配光参变振荡，振荡阈值10．3μJ（脉宽22ns)，信号光最高输出平均功率为42．5mW，斜率效率为12．5％。     

A Quasi Fixed-Point Theorem for a Product of u.s.c. or o.l.s. Correspondences with an Economic Application

In the first place, we present a quasi fixed-point theorem for a correspondence defined on some infinite-dimensional locally convex topological vector space such that some variables have open lower sections and the other ones are upper semicontinuous.In the second place, we propose a direct application of the quasi fixed-point result in an economic model. More precisely, we prove a nonemptiness result of the core of an exchange economy with asymmetric information, a continuum of states and a finite number of commodities.     

单晶SiNd：YAG激光连续退火的数值计算

应用固相外延模型来模拟单晶Si的连续Nd：YAG激光退火过程,在低功率密度连续激光退火下,用准静态模型模拟辐照区向非辐照区的径向传导散热。在数值计算中，应用部分线性法处理非线性非齐次热传导方程,得到相应的隐格式差分方程，再用追赶法求解隐格式差分方程,得出绝热边界条件下的温度的时间和空间分布，从而得出激光退火的再结晶厚度。当激光波长λ=1．06μm、功率密度io=700W／cm^2。预热温度T0=523K时，经过0．7秒，表面温度度升到1290K左右，再结晶厚度约为0．5μm。     

Fullerene[51] with Quasi-planar Tetracoordinate Carbons and Its Derivatives

我们设计了包含准平面四配位碳原子的Fullerene[51]及其八个包含准平面四配位碳原子的衍生物，而且采用B3LYP方法研究了它们的结构、稳定性和成键性质。结果表明：这九种新型化合物是稳定的，它们的垂直电离能很大，而垂直电子亲和势相对较小。这些结构都包含五员环和六员环、以及更大的十员环。     

High performance AlyGa1−yAs-GaAs-lrxGa1−xAs quantum well lasers defined by silicon-oxygen impurity-induced layer disordering

In these experiments impurity-induced layer disordering (IILD) utilizing chemical reduction of SiO₂ by Al (from Al_0.8Ga_0.2As) is employed to generate Si and O to effect layer disordering. The SiO₂-Al_0.8Ga_0.2As reaction is studied with respect to annealing ambient. By controlling the extent of disordering via As₄ overpressure, closely spaced (∼1μm) Si-O IILD buried heterostructure lasers can be optically coupled or uncoupled. Direct observation of O incorporation into the buried layers is shown using secondary ion mass spectroscopy (SIMS). The thermal stability of separate-confinement Al_yGa_1−yAs-GaAs-In_xGa_1−xAs quantum well heterostructure (QWH) laser crystals is investigated using SIMS, transmission electron microscopy (TEM), and photoluminescence (PL) measurements. The data show that the thermal stability of a strained-layer In_0.1Ga_0.9As quantum well (QW) is strongly dependent upon: (1) the layer thickness and heterointerfaces of the Al_yGa_1−yAs-GaAs waveguide layers located directly above and below the QW, (2) the type of surface encapsulant employed, and (3) the annealing ambient. Narrow single-stripe (<2μm) lasers fabricated via Si-O diffusion and layer disordering exhibit low threshold currents (I_th ∼ 4 mA) and differential quantum efficiencies,η, of 22% per facet under continuous (cw) room-temperature operation.     

Determination of Band Structure Parameters and the Quasi‐Particle Gap of CdSe Quantum Dots by Cyclic Voltammetry

Band structure parameters such as the conduction band edge, the valence band edge and the quasi‐particle gap of diffusing CdSe quantum dots (Q‐dots) of various sizes were determined using cyclic voltammetry. These parameters are strongly dependent on the size of the Q‐dots. The results obtained from voltammetric measurements are compared to spectroscopic and theoretical data. The fit obtained to the reported calculations based on the semi‐empirical pseudopotential method (SEPM)—especially in the strong size‐confinement region, is the best reported so far, according to our knowledge. For the smallest CdSe Q‐dots, the difference between the quasi‐particle gap and the optical band gap gives the electron–hole Coulombic interaction energy (J_e1,h1). Interband states seen in the photoluminescence spectra were verified with cyclic voltammetry measurements.     

Discontinuous boundary implementation for the shallow water equations

Quasi‐bubble finite element approximations to the shallow water equations are investigated focusing on implementations of the surface elevation boundary condition. We first demonstrate by numerical results that the conventional implementation of the boundary condition degrades the accuracy of the velocity solution. It is also shown that the degraded velocity leads to a critical instability if the advection term is present in the momentum equation. Then we propose an alternative implementation for the boundary condition. We refer to this alternative implementation as a discontinuous boundary (DB) implementation because it introduces at each boundary node two independent mass–flux values that result in a discontinuity at the boundary. Numerical results show that the proposed DB implementation is consistent, stabilizes the quasi‐bubble scheme, and leads to second‐order accuracy at the surface elevation specified boundary. Copyright © 2004 John Wiley & Sons, Ltd.     

多点光纤光栅测温系统在渗流监测中的应用研究

为了监测土石坝内的渗流水的情况,提出一种多点光纤Bragg 光栅传感器(FBG)的结构,采用InGaAs光电探测器阵列探测光强的光纤光栅传感阵列的波长解调方法。根据室内实验结果,对多点光纤光栅传感系统的可行性和监测数据的可靠性进行分析, 给出用于坝体温度场监测的光纤光栅传感器波长温度响应灵敏度可达到0.0091nm/℃。工程中采用电热脉冲方式对传感器附近小范围的土壤进行加热,使其与水的温度形成一定的温差,实测结果表明可以利用光纤光栅传感器监测温度异常的方法判断是否发生渗流, 从而实现对坝体内集中渗漏点的定位和自动监测。在系统防雷击、抗干扰性方面, 采用光纤光栅传感监测系统与传统仪器相比具有明显优势。     

空间域容量控制多分辨粒子滤波算法

 针对多分辨分析方法用于降低粒子滤波样本集容量时,因多次迭代引起的样本数急剧下降而导致滤波性能不稳定的问题,提出一种通过监测拟测量误差相关统计量来预警可能出现的误差扩大,当系统处于性能临界区时,在原样本空间上进行准蒙特卡罗增量采样或复制原样本集来控制样本集容量,规避滤波发散的风险.仿真实验表明该算法保持了粒子滤波算法的估计性能,同时有效降低了粒子滤波样本数目,提高了计算效率.