机械搅拌混响室独立样本数建模及实验

混响室测试技术的精确性取决于混响室能够产生大量的独立测试样本。通过理论分析得到混响室的体积、搅拌器的尺寸以及腔体的工作频率与独立样本数的关系,推导出独立样本数的近似模型,并将实验数据与模型计算结果进行比较,对模型进行了改进和验证。结果表明:独立样本数与混响室的体积、品质因数、搅拌器的尺寸正相关,在一定范围内与搅拌器的电学尺寸负相关。该模型可以用于计算具有不同配置的不同混响室的独立样本数,具有良好的准确性和一般性。     

Static and dynamic effects of confinement on self-diffusion

Expressions for second and fourth sum rules of velocity autocorrelation function have been derived for fluid confined to a rectangular nanotube. Expressions obtained for these sum rules involve density profiles which vary with distance from walls of the tube. These sum rules, incorporating the effect of static changes made due to confinement, and the model which involves dynamical effect have been coupled to study the self-diffusion coefficient. By considering model density profiles, it is found that the self-diffusion coefficient in a direction perpendicular to the wall behaves differently from that in a direction parallel to the wall. The perpendicular diffusion coefficient is found to be more strongly dependent on the width of the tube than the parallel diffusion. It is found that dynamical effects are more in the region that is near to the confining wall than the static effects which track density profile.     

Abelian difference sets of order n dividing λ

We show that difference sets satisfying the condition n|λ have a product property which can be exploited to construct more difference sets. Many of the newly discovered difference sets arise in precisely this way. Dedicated to Dan Hughes on the occasion of his 80th birthday.     

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.     

Ab Initio molecular dynamics study of ethylene adsorption onto Si(001) surface: Short‐time fourier transform analysis of structural coordinate autocorrelation function

The reaction dynamics of ethylene adsorption onto the Si(001) surface have been studied by combining density functional theory‐based molecular dynamics simulations with molecular adsorption sampling scheme for investigating all kinds of reaction pathways and corresponding populations. Based on the calculated results, three possible reaction pathways—the indirect adsorption, the direct adsorption, and the repelling reaction—have been found. First, the indirect adsorption, in which the ethylene (C₂H_4(ads)) forms the π‐bonded C₂H_4(ads) with the buckled‐down Si atom to adsorb on the Si(001) surface and then turns into the di‐σ‐bonded C₂H_4(ads), is the major reaction pathway. The short‐time Fourier transform analysis of structural coordinate autocorrelation function is performed to further investigate the evolution of different vibrational modes along this indirect reaction pathway. This analysis illustrates that the Infrared (IR) inactive peak of the C?C stretching mode of the π‐bonded C₂H_4(ads) shifts to the IR inactive peak of the C? C stretching mode of di‐σ‐bonded C₂H_4(ads), which is in a good agreement with the IR inactive peak of the C?C stretching mode vanished in the vibrational spectrum at 150 K (Nagao et al., J. Am. Chem. Soc. 2004 , 126, 9922). Second, the direct adsorption, in which the di‐σ‐bonded C₂H_4(ads) is formed directly with the Si intradimer or the Si interdimer on the Si(001) surface, is the less significant reaction pathway. This reaction pathway leads to the C? C stretching mode and the C? H stretching mode of the di‐σ‐bonded C₂H_4(ads) appeared in the vibrational spectra at 48 and 150 K, respectively (Nagao et al., J. Am. Chem. Soc. 2004 , 126, 9922). Finally, the repelling reaction, in which the C₂H_4(g) first interacts with the Si dimer and then is repelled by Si atoms, is the least important reaction pathway. Consequently, neither the π‐bonded C₂H_4(ads) nor the di‐σ‐bonded C₂H_4(ads) is formed on the Si(001) surface. © 2013 Wiley Periodicals, Inc.     

自相关过程的质量控制图

常规控制图应用的基本假设是从过程得到的测量值彼此独立,但许多连续型的制造业生产过程(例如化学和制药)往往存在自相关,此时常规控制图容易虚发警报。基于数据的样本自相关函数,本文改进了常规控制图的控制界限,使之适用于自相关过程,并运用常规X-s控制图和本文修正的X控制图对一个实际案例进行了比较分析,结果表明本文修正的X控制图可正确地判断过程是否处于受控状态。     

环烷烃及烷烃的折光指数与结构的关系研究

以分子拓扑学点价和自相关函数研究为基础,设计开发出一种新的以点价计算为基础的结构信息自相关拓扑指数tX.基于多元线性回归技术建立了对环烷烃及其烷烃的折光指数作出估算的定量结构性质关系.点价被定义为βi,由βi建构结构信息自相关拓扑指数tX.得到了它们与64种环烷烃的折光指数(nD)的二元回归方程和与27种烷烃的折光指数的二元回归方程.对环烷烃和烷烃折光指数的计算结果表明,计算值与实验值的一致性令人满意,平均误差为0. 25% .利用建立的模型,对另外5种烷烃的折光指数进行了预测.     

A bivariate uniform autoregressive process

We define the bivariate first order stationary autoregressive process {(X _n ,Y _n )} with uniform marginal distribution where {X _n } and {Y _n } are the two stationary sequences with uniformU(0, 1) marginal distributions. We also estimate the unknown parameters of the model.     

对DW检验法的补充和改进

自相关检验是回归分析的一项重要内容，ＤＷ检验法又是自相关检验的最常用方法。但是，我国现有教科书中所介绍的ＤＷ检验都存在两个不确定的区间。对于这两个区间内的自相关如何判定，一直为我国学者所忽视。本文则是针对这一问题，特介绍一种方法，以解决之。