多元散射校正预处理波段对近红外光谱定标模型的影响

利用近红外光谱对非均匀样品进行分析时,所得样品光谱中包含由光散射导致的干扰信息,通常需要借助多元散射校正算法(multiple scattering correction, MSC)对光谱进行预处理。由于不同波段光谱中所包含的散射信息、噪声水平、基线漂移程度等存在差异,利用MSC方法对光谱进行预处理时,基于不同波段的光谱数据会得到不同的校正结果,进而影响所得定标模型的可靠性。以60个全麦粉样品为研究对象,确定定标区间后,对包含定标区间的不同波段的原始光谱分别进行MSC处理,并利用固定区间内的光谱数据结合偏最小二乘回归(partial least square regression, PLSR)方法建立分析样品中蛋白质含量的定标模型,研究了MSC光谱预处理波段对定标模型的影响,并对MSC光谱预处理波段进行了优化,使定标模型的相关系数由0.96提高到0.98,交互验证均方根误差(root mean squares error of cross validation, RMSECV)由0.37%降低到0.32%。结果表明：利用MSC方法对样品光谱预处理时,光谱预处理波段会影响多元散射校正对光谱中非化学吸收信息的校正能力,确定合适的预处理波段是获得可靠分析结果的一个前提条件。     

Negative capacitance in doped bi-layer organic light-emitting devices

This paper reports that the doped bi-layer organic light-emitting devices are fabricated by doping in different regions of the light-emitting layer,the admittance and luminance spectra to characterize the capacitance and luminance of the device are measured.Negative capacitance (NC) appeared at low frequencies when the doped devices are biased with high voltages.The measured phase difference between AC voltage applied across the device and AC current flowing through the device show that the device is inductive when NC appears.     

Qualitative analysis of the phase flow of an integrable approximation of a generalized roto-translatory problem

In this paper, we consider an integrable approximation of the planar motion of a gyrostat in Newtonian interaction with a spherical rigid body. We then describe the Hamiltonian dynamics, in the fibers of constant total angular momentum vector of an invariant manifold of motion. Finally, using the Liouville-Arnold theorem and a particular analysis of the momentum map in its critical points, we obtain a complete topological classification of the different invariant sets of the phase flow of this problem. The results can be applied to study two-body roto-translatory problems where the rotation of one of them has a strong influence on the orbital motion of the system.      

固体进样石墨炉原子吸收光谱技术在测定大鼠脑铁含量中的应用

石墨炉原子吸收光谱法是测定动物脑组织Fe含量的常用方法,然而由于传统的液体进样方法中,样品前处理阶段用硝酸消解周期长,成本高耗时长,限制了原子吸收光谱技术在测定动物组织中Fe含量的应用。文章以SD大鼠脑部海马、纹状体、皮层为实验材料,采用固体进样器进样,利用石墨炉原子吸收光谱技术对各组织中的Fe含量进行了测定,并与传统法方法——硝酸消解样品后,液体进样的石墨炉原子吸收光谱测定结果做了比较,结果表明这两种方法所测结果无显著性差异,但应用固体进样法,样品前处理阶段明显简单,显著节省了样品准备时间,降低了工作量,使测定时间明显缩短,成本明显降低,并且能够有效避免外界因素对测定结果的影响,为固体进样法的进一步应用奠定了基础。     

利用匹配区域的纹理特征改善重构三维图像的视觉质量

研究了计算机重构三维图像时分辨率低的问题,提出一种改善3D计算机全景重构图像的视觉质量的方法,该方法利用3D空间的物体部分在每个元素图像中形成的匹配区域的纹理特征,从两个相邻的元素图像中的匹配区域提取出多个像素,经过加权计算重构出相应的图像区域.该方法与传统的计算机重构方法相比,提高了图像分辨率,同时也消除了从每个元素图像中提取多个像素直接重构图像时存在的"像素块"效应,改善了重构图像的视觉质量.     

Spatial variability of 2H and 18O composition of meteoric freshwater lakes in Scotland

Coastal regions, and in particular islands where precipitation from clouds formed out at sea occurs for the first time, are prime candidates for regions where ²H and ¹⁸O composition of precipitation will deviate significantly from the global mean geographic and physiographic trends of vapour-transport patterns. The results reported here are the outcome of a study that aimed to test this hypothesis by ‘isotopographically’ mapping the characteristic δ²H and δ¹⁸O signatures of Scottish freshwaters. The resulting isotope abundance landscapes or ‘isoscapes’ will underpin studies aiming to authenticate origin of Scottish produce but may also offer a baseline against which environmental changes could be assessed. Between April 2011 and May 2012 freshwater samples were collected from 127 different freshwater lochs and reservoirs across Scotland, and analysis results were compared to precipitation data provided by the British Geological Survey. Here we present the results of the ²H and ¹⁸O analyses of these water samples as well as the first detailed Scotland freshwater isoscapes with a grid resolution of about 5 × 5 km (0.05 degrees).     

Caustics,pseudocaustics and the related illuminated and dark regions with the computational method of quantifier elimination

The method of caustics is a powerful experimental method in elasticity and particularly in fracture mechanics for crack problems. The related method of pseudocaustics is also of interest. Here we apply the computational method of quantifier elimination implemented in the computer algebra system Mathematica in order to determine (i) the non-parametric equation and two properties of the caustic at a crack tip and especially (ii) the illuminated and the dark regions related to caustics and pseudocaustics in plane elasticity and plate problems. The present computations concern: (i) The derivation of the non-parametric equation of the classical caustic about a crack tip through the elimination of the parameter involved (here the polar angle) as well as two geometrical properties of this caustic. (ii) The derivation of the inequalities defining the illuminated region on the screen in the problem of an elastic half-plane loaded normally by a concentrated load with the boundary of this illuminated region related to some extent to the caustic formed. (iii) Similarly for the problem of a clamped circular plate under a uniform loading with respect to the caustic and the pseudocaustic formed. (iv) Analogously for the problem of an equilateral triangular plate loaded by uniformly distributed moments along its whole boundary, which defines the related pseudocaustic. (v) The determination of quantities of interest in mechanics from the obtained caustics or pseudocaustics. The kind of computations in the applications (ii) to (iv), i.e. the derivation of inequalities defining the illuminated region on the screen, seems to be completely new independently of the use here of the method of quantifier elimination. Additional applications are also possible, but some of them require the expansion of the present somewhat limited power of the quantifier elimination algorithms in Mathematica. This is expected to take place in the future.     

Stress analysis of Si1−xGex embedded source/drain junctions

The purpose of this paper is to evaluate the impact of the geometry of embedded Si_1−xGe_x source/drain junctions on the stress field. Stress simulations were performed using TSUPREM4 2D software to further investigate the elastic strain relaxation as a function of Si_1−xGe_x alloy active size, in the regime where no plastic relaxation is present. Moreover, the role of the epilayer thickness and the Ge content on the stress levels is also discussed. The work is complemented with experimental Raman spectroscopy.     

以小区域内的离子数为控制信息实现束晕的有效控制

利用匹配半径外的某些固定区域内的离子数目提供控制信息,采用对数函数控制器对强流离子束进行束晕－混沌控制的数值模拟研究. 结果显示,该方法能够有效地抑制五种不同初始分布的离子束的束晕再生现象. 该方法由于控制信息的探测区域小且能固定,在实验上便于实施. 关键词： 束晕 控制 局部区域 信息     

采用重要抽样法的结构动力可靠度计算

首次对比分析了结构动力可靠度计算的三种重要抽样法,并对部分方法进行了补充修正.单元失效域法补充了依据随机教决定抽样区间的产生方法,根据单元失效域的条件概率和权重系数给出重要抽样密度函教.方差放大系数法直接通过激励过程的特性给出重要抽样密度函数的具体表达式.功率谱法的重要抽样密度函数仅为激励幅值的函数,根据结构反应的功率谱密度增大激励幅值的方差,建议幅值样本值的联合概率密度函数可表示为幅值样本值分量的概率密度函数的连乘形式.结果表明:对于线性体系三种方法的计算效率均比Monte-Carlo法有显著提高,而单元失效域法的计算效率又比另两种方法高.