Spectral Method for Thermal Conductivity Calculations

We discuss several post-processing issues in molecular dynamics (MD) calculation of lattice thermal conductivity using the Green–Kubo formula. For crystals with high thermal conductivity such as SiC, converting the MD raw data on heat current fluctuations into thermal conductivity result is non-trivial. One can accelerate the process using Fast Fourier Transform and the spectral method. A few mathematical subtleties are cleared up. Due to finite data length, integration of the correlation function must be terminated before noise takes over; two termination criteria are proposed which give reasonable results for crystalline β-SiC. A simple solvable model that illustrates the above points and can be used for code-checking is presented.     

基于光谱分析的主动式距离图像获取方法

Rainbow三维摄像机是一种基于光谱分析的快速在维信息获取方法,该方法利用连续变化的彩色光谱照射景物,彩色CCD摄像机摄取的景物图像将呈现有规律的颜色变化,而且不同的颜色（波长）构成了不同的空间颜色面,通过标定这些颜色面和摄像机成象模型,即可计算同图像中各点的三维坐标。     

Binary Star Reconstruction with Use of the Blind Deconvolution Method

Abstract

The iterative blind deconvolution method and a modified auto-correlation method are applied to reconstruct a binary star from a speckle interferogram. The results of two methods are compared to evaluate reconstructed images. For successful reconstruction, a method of frame selection of speckle interferograms is also proposed. A suitable frame selection improves the efficiency of the reconstruction. Some results of the binary star reconstruction are demonstrated to show the usefulness of our method.     

确定缓冲曲线的应力-能量法研究

应力-能量法是确定缓冲材料缓冲曲线的主要方法,其能预测任意高度的缓冲曲线,操作简便,且基于试验所得数据进行推算,可以得到较为精确完整的缓冲曲线,但由于应力-能量法是以假定缓冲材料在受到冲击过程中没有能量损失为前提,且该法较易受人为因素的影响,故利用应力-能量法的动能量公式计算得到的能量不够精确.现有对应力-能量法的应用研究可分为直接应用和改进应用两个方面,今后的研究可适当减少能量水平和跌落次数,进一步优化数据拟合函数的选取以及试验数据,从而更大程度地节省材料及试验时间,以获得更准确的缓冲曲线.     

光谱重建训练样本选择方法研究

目的研究光谱重建训练样本选择方法及训练样本集样本数量对光谱重建精度的影响。方法以光谱反射率已知的1687个矿物颜料样本为研究对象,搭建真实六通道宽带光谱成像系统并进行标定,利用宽带光谱成像系统对样本进行六通道数字响应值采集并进行校正,通过R-matrix光谱重建方法,对现有以及文中引入和提出的训练样本选择方法的光谱重建精度和计算效率进行比较。结果实验结果表明,分区最大化色域边界描述方法可以较好地应用于光谱成像过程中训练样本选择,其在保证光谱重建精度的同时大大提高了训练样本选择的效率,实验证明文中提出的基于色域最大化思想的训练样本方法,在面向复制的光谱成像流程中也具有一定的实用性。结论研究结果对于光谱成像过程中训练样本选择方法的选择具有一定指导作用。     

一种计算料斗曲线方程的新方法

根据圆锥料仓内的受力分析,得到一种计算曲线料仓的新方法。结果表明,在仓壁母线的切线倾角沿着水平方向均匀变化的假设下,可以计算出对数型曲线料仓形如y=Alnx+B的方程;在料仓的同一高度部位,对数型曲线料仓的垂直压力比圆锥料仓的小,因此不会产生堵料结拱的现象;在确定入料口尺寸后,可得卸料口处切线倾角与卸料口尺寸的函数关系,以避免堵料结拱,保证下料的均匀性和稳定性。     

一类具有时滞的非线性微分代数系统的谱方法

首先给出了一类带有时滞的非线性微分代数系统(DDAE)存在惟一解的充分条件:然后将原问题变形为无时滞的带有非局部边值条件的偏微分系统;接下来运用Chebyshev谱方法求得原问题的近似解。所用方法的优点在于避免了许多在处理时滞项时所遇到的数值困难,而且谱方法具有高精度;最后,给出了实例来说明所提出的方法的可行性。     

An Estimation Method for the Total Quantity of Goods in Distribution by the Use of a Regression Curve

A method for estimating the total quantity of goods distributed in a market is presented by the use of a polynomial regression curve on the plane where the y-coordinate consists of the rates of goods for their product numbers.

Two kinds of estimators for the above-mentioned total quantity are proposed with investigating their asymptotic properties.

As a practical example, estimating the total quantity of beer cases in a market is considered.

     

一种宽带光谱响应特性的测量方法

介绍了一种基于分束一步测量宽带（200nm-1750nm)光谱响应的方法。对该测量方法的基本构成、系统定标与校准、基本测量原理等问题均进行了详细分析。给出了实验测量结果，并与日本滨松公司的标准数据进行了对比，测量的平均绝对误差和平均相对误差分别为ε=1.37mA/W和εr=0.89%。理论分析与实验结果十分吻合。     

三维轮廓曲线的快速匹配方法

在许许多多出土文物碎片中借助计算机辅助文物碎片复原，迄今是一个没有被完全解决的问题。笔者给出从提取文物碎片轮廓线出发，解决空间曲线匹配来达到文物碎片复原的方法。同时给出了用于查找三维轮廓线匹配的哈希矢量，以及计算轮廓线子段曲率挠率匹配算法。通过比较两条轮廓线的哈希矢量来分析曲线段的相似度，从理论上给出了判断曲线匹配的性质，如果曲线段之间的距离越小则哈希矢量之间的距离也越小。     

卧式金属罐罐容曲线的图形监控方法

介绍了卧式金属罐罐容曲线的图形监控方法和实现过程,包括单独罐容曲线图形监控、两组罐容曲线的差异对比、罐容表数据自动提取技术等,并给出了VBA代码可供参考;有利于分析罐容曲线上存在的问题、找到不同罐容曲线间的显著差异,为后续的问题处理打下基础。     

一种将一般有理参数曲线转化为有理Bézier曲线的方法

讨论了一般有理参数曲线到有理Bézier曲线的转化问题。一个n次有理参数曲线一般不能转化为权值都不为0的n次有理Bézier曲线。作者对转化得到的n次有理Bézier曲线进行升阶。求出了n次一般有理参数曲线对应的有理Bézier曲线,保证了得到的有理Bézier曲线的权值非零,并且次数最低。该方法也可得到权值大于0的有理Bézier曲线,拓宽了适用范围。最后给出了n(n=2,3,4)次一般有理参数曲线到有理Bézier曲线的转化结果。更高次曲线的转化结果可依法得到。     

Sparse Deconvolution Methods for Ultrasonic NDT

In this work we present two sparse deconvolution methods for nondestructive testing. The first method is a special matching pursuit (MP) algorithm in order to deconvolve the mixed data (signal and noise), and thus to remove the unwanted noise. The second method is based on the approximate Prony method (APM). Both methods employ the sparsity assumption about the measured ultrasonic signal as prior knowledge. The MP algorithm is used to derive a sparse representation of the measured data by a deconvolution and subtraction scheme. An orthogonal variant of the algorithm (OMP) is presented as well. The APM technique also relies on the assumption that the desired signals are sparse linear combinations of (reflections of) the transmitted pulse. For blind deconvolution, where the transducer impulse response is unknown, we offer a general Gaussian echo model whose parameters can be iteratively adjusted to the real measurements. Several test results show that the methods work well even for high noise levels. Further, an outlook for possible applications of these deconvolution methods is given.     

近红外光谱测量中的多尺度建模新方法

近红外光谱学是近十年来发展最快、最引人注目的光谱分析技术之一,其高精度测量依赖于化学计量学方法以准确提取光谱信息.针对近红外光谱单尺度传统建模方法中存在的信息易丢失问题,发展了一种多尺度建模新方法.多尺度建模可有效协同利用信号的时/频多尺度特性,并将多尺度特性以加权形式统一映射到多元校正空间,有效避免了信息丢失.该算法成功地应用于面粉中掺杂有毒非法添加剂硼砂含量检测,经验证后模型的预测值与真实值的相关系数和预测均方根误差分别为0.974和0.0019,其预测相对误差为1.9%.研究结果表明,多尺度建模方法完全满足近红外光谱高精度测量的要求.     

Frequency Shift Curve Based Damage Detection Method for Beam Structures

Vibration based damage detection methods play an important role in the maintenance of beam structures such as bridges. However, most of them require the accurate measurement of structural mode shapes, which may not be easily satisfied in practice. Since the measurement of frequencies is more accurate than that of mode shapes, this paper proposes a frequency shift curve (FSC) method, based on the equivalence between the FSC due to auxiliary mass and the mode shape square, which has been demonstrated to be effective in structural damage detection. Two damage indices based on the FSC are developed, which are called the local outlier detection index and the global outlier detection index, respectively. The efficiency and reliability of the proposed method are demonstrated by numerical simulations and experimental results. Compared with traditional methods, this method can provide reliable results without the requirement of fixing many sensors on the structure.     

非线性振动分析的切比雪夫谱元法

为了进一步探索Chebyshev时间谱元法求解非线性的振动问题,从Bubnov-Galerkin方法出发,在第二类Chebyshev正交多项式极点处;用重心Lagrange插值来构造节点基函数及其特性,推导了非线性振动问题的伽辽金谱元离散方案,借助Newton-Raphson法求解非线性方程组。对于非线性单摆,还需要将二分法和重心Lagrange插值结合求解角频率。以Duffing型非线性振动和非线性单摆振动问题为例,验证了此方法具有现实可行和高精度的优点。     

颈动脉粥样硬化斑块模型的谱元法计算

本文考虑人体颈动脉粥样硬化斑块的力学建模及其数值计算.颈动脉粥样硬化斑块的动力学行为由控制血液流动的不可压缩Navier-Stokes方程和控制动脉形变的弹性方程耦合描述,因此完整的硬化斑块模型是一组三维流体/固体耦合方程,其数学理论和数值计算都面临极大的困难.但在一定的假设条件下,该问题可简化为一个弹性力学方程.本文考虑粥样硬化斑块简化模型的数值计算问题.我们构造了一个针对模型简化方程的有效算法,即基于空间方向上的谱元离散和时间方向的Newmark格式的计算方法.分析显示前者对光滑解具有指数收敛性,而后者具有二阶收敛精度并且在特定的参数条件下无条件稳定.论文不仅讨论了连续问题以及半离散问题的稳定性,而且给出了全离散格式的最优误差估计.最后通过数值模拟验证了所提算法的有效性和理论分析结果,并对一些具有实际背景参数的模型问题进行了模拟.     

一种高效的胞元光谱纽介堡模型胞元搜索算法

采用训练样本排序框定初始胞元、差异优先搜索最优胞元和初始胞元再扩大方法,建立了CYNSN 模型的胞元搜索算法。实验结果表明,CYNSN 模型胞元搜索算法能使CYNSN 反向模型在色度和光谱反射率上实现高精度复制,和已有的CYNSN 模型相比,胞元搜索算法不仅保持了CYNSN 模型的精度,而且效率提高了10倍。