Highly efficient electron stimulated desorption of O+ from gadolinia-doped ceria surfaces

Highly efficient electron stimulated desorption of O+ from gadolinia-doped ceria (GDC) surfaces annealed at 850 K in ultrahigh vacuum is observed and investigated. O+ desorption has a major threshold of approximately 40 eV and an intrinsic kinetic energy of approximately 5.6 eV. Since the threshold energy is close to Ce 5s and Gd 5s core levels, Auger decay of core holes is likely associated with O+ desorption from sites related to oxygen vacancies. The interactions of water and molecular oxygen with GDC surfaces result in a decrease in O+ desorption, suggesting that water and oxygen molecules adsorb mainly to oxygen vacancies. The dependence of O+ kinetic energies on the incident electron energy and temperature reveals surface charging as a result of electron trapping, hole trapping, and electron-hole recombination. The activation energy for surface charge dissipation is found to be 0.43 eV, close to the activation energy for ionic conduction (0.47 to 0.6 eV) in the same material.     

利用可见轫致辐射计算EAST有效电荷数

利用弦积分的可见轫致辐射计算了先进实验超导托卡马克(EAST)的有效电荷数。对比分析EAST硼化前后的杂质含量,硼化后有效电荷数减小约40%,碳杂质含量减小约50%。统计分析了2009年EAST春季实验的有效放电,显示有效电荷数与碳杂质线辐射量存在很强的线性关系,得到的拟合系数是3.4~5.8,与等离子体电流和低杂波辅助加热功率都有明确的依赖关系。利用近紫外可见波段全谱对主要杂质的含量进行比较后显示,碳是最主要的杂质,大于其它轻杂质含量。同时,还介绍了新建成的多道轫致辐射诊断系统。     

一种改进型Stoilov算法相位测量轮廓术

提出了一种采用主动控制相移量的改进型Stoilov算法,按主动设定的相移量事先设计好五幅完全等相移正弦光栅图,由计算机编程控制数字投影仪依次投影该五幅光栅至待测物体表面,并对应采集五帧变形条纹,用所设定的相移量直接替代Stoilov算法中由变形条纹图解算的相移量,提高了相位提取和三维重构准确度.实验结果表明,平均绝对误差优于0.07,均方差优于0.07.     

Large eddy simulation using a new set of sixth order schemes for compressible viscous terms

A set of conservative sixth order central differencing schemes is suggested for compressible flows with variable viscosity coefficient. This new set of central differencing schemes has the stencil width matching that of the seventh order weighted essentially non-oscillatory scheme (WENO). This feature is important to maintain the compactness of the seventh order WENO scheme and facilitate boundary condition treatment. As an application example, a large eddy simulation (LES) is conducted for a cylinder flow using the seventh order WENO scheme for the convective terms and the new set of sixth order central differencing scheme for the viscous terms. The results are compared with those from other research groups and those obtained using the fifth order WENO scheme and fourth order central differencing.     

Adaptive Wavelet Solution to the Stokes Problem

This paper deals with the design and analysis of adaptive wavelet method for the Stokes problem. First, the limitation of Richardson iteration is explained and the multiplied matrix M0 in the paper of Bramble and Pasciak is proved to be the simplest possible in an appropiate sense. Similar to the divergence operator, an exact application of its dual is shown; Second, based on these above observations, an adaptive wavelet algorithm for the Stokes problem is designed. Error analysis and computational complexity are given; Finally, since our algorithm is mainly to deal with an elliptic and positive definite operator equation, the last section is devoted to the Galerkin solution of an elliptic and positive definite equation. It turns out that the upper bound for error estimation may be improved.     

氧分子离子第一负带系(b4∑g--a4∏u)(2,6)带的光谱测量与分析

采用光外差-速度调制分子离子吸收光谱技术,在近红外波段13170~13500 cm-1范围内,对氧分子离子第一负带(b4∑g--a4∏u)(2,6)带进行测量和分析,有关第一负带(2,6)带光谱测量尚未见文献报道.本文简述了光外差-速度调制光谱技术的特点,同时给出了对复杂四重态跃迁谱带的分析,运用非线性最小二乘拟合获得了该跃迁上下态精确的分子常数.     

The study on the surface state of CdZnTe (1 1 0) surface

Angle-resolved photoemission spectroscopy (ARPES) was used to characterize the surface state of clean CdZnTe (1 1 0) surface. The surface state of CdZnTe with the peak at 0.9 eV below the Fermi level is identified. Meanwhile, Photoluminescence (PL) spectrum confirmed that there existed a surface trap state which introduced a deep-level peak at 1.510 eV. The surface trap states can be decreased by aging in dry-air. The surface leakage current was measured also by I-V measurements. After aging, the leakage current was decreased remarkably, which suggested that the aging treatment is an effective method to decrease the surface trap state.     

The study on Schottky contact between Au and clean CdZnTe

Au Schottky contact was deposited on the clean CZT (1 1 0) and (1 1 1) A surface by molecular beam epitaxy (MBE). The real Schottky barrier heights were measured to be 0.738 eV and 0.566 eV by Synchrotron radiation photoemission spectroscopy (SRPES) respectively. The constituents of (1 1 0) and (1 1 1) A surfaces were measured by XPS. The Te concentration on (1 1 1) A surface is higher than that of (1 1 0) surface. And the difference of chemical reactivity and charge transfer were identified by Au 4f_7/2, Cd 4d, Te 4d_5/2 core level shifts using SRPES. Using metal-induced gap states model, the results of experiment were explained.     

考虑需求率变化与延期支付的临时订货模型

供应商给予临时价格折扣、并针对采购商的临时订货给予优惠的延期支付条件;同时考虑到采购商的自身需求即为终端需求并对价格敏感,由于考虑需求量变化的同时考虑到时间因素,因此需求率实际上发生了改变。在这样的背景下,采购商在价格变化时刻面临两种选择:以低价购进大量货物或者放弃这个机会。本文以EOQ模型单位产品成本为参考,从成本节约最大的角度出发,分析了采购商临时订货量的确定过程,并用数例分析了参数变化对最优订货以及成本节约情况的影响。     

基于最小凸输入需求集方法的基金业绩评价

本文首先回顾了传统基金业绩评价方法，然后运用Chang（1999）的最小凸输入需求集（MCIRS）方法对我国2000年前上市的20只封闭式证券投资基金在2000年的业绩进行综合评价。实证研究表明：同益、景博、汉盛、金鑫、兴和、泰和、天元、普丰共8只基金相对有效，而其余12只基金则相对无效。并将结果与数据包络分析（DEA）的结果进行了比较。