化合物分子表面积计算方法的研究

化合物的分子表面积是重要的物理化学性质参数．根据不同的应用领域及数学方法,提出了多种分子表面积算法[1-10],由此产生了“分子表面积法”,各方法的有效性在各具体应用领域都已被验证．本文将统计方法中的随机变量引入计算化合物分子表面积体系,由分子模型化技术得到化合物分子的原子坐标,不考虑化合物分子中原子的相互作用及分子间近似,直接计算分子表面积．使用该方法可以计算“净”分子表面积、“溶剂可及表面积”、甚至分子结构片段,分子结构中有交叉重叠片段及存在“空洞”的各种分子表面积,该算法及程序较简捷,适应范围广,计算结果较为满意．     

Combinatorial-Multiplicative Method of Calculating the Limiting Filling of Composites with Solid Dispersed Components

A new method for engineering calculation of the limiting volume filling of various composites with particles of solid components with arbitrary granulometric composition is presented. A calculation of the density of random packing of dispersed fillers is described, including an algorithm for calculating the porosity of two fractions. The precision of the method is evaluated.     

A Computational Algorithm for the Polynomial Approximation Method of Sensitivity Analysis in Chemical Kinetics

This paper describes the logic for a program developed by the author to implement the polynomial approximation method (PAM) of sensitivity analysis for general kinetic purposes. The relevant equations and numerical details of the algorithm are outlined, a flow chart is provided, and some programming considerations are discussed in detail. A listing of the PAM code is given in the appendix. The paper also gives a few suggestions for possible improvements and extensions of the present algorithm.     

完全重叠色波二维谱的解析新方法

提出一种新的完全重叠色波二维谱解析方法。对于两组分色谱－光谱数据阵，只要在重叠区中存在单组分区，就能解得各组分的纯色谱和纯光谱，这种方法将求解纯谱问题转化为优化问题，再用数值遗传算法寻找最优解．本法用于２，４－二硝基苯酚和３，５－二硝基苯甲酸的合成实验以及四环素的杂质分析都得到满意的结果．     

A Simple Method of the Determination of the Structural Heterogeneity of Microporous Solids

A new procedure for determining the structural heterogeneity of microporous solids is presented. Applying the concept of a general adsorption isotherm equation, a method for solving this equation for adsorption in micropores is developed, and the applicability of a new simple algorithm for determining the parameters of microporous structure of two commercial carbons is shown. Copyright 2001 Academic Press.     

电位滴定法测定弱酸电离常数与混合酸组分浓度的一种通用处理方法

本文导出了由电位滴定数据求算弱酸电离常数与混合酸组分浓度的通用算式,按Rosenbrock算法设计程序并处理了某些实验数据,得到良好的结果。与处理同类问题的其它方法相比,本法是方便并可靠的。     

Method for reducing the ambiguity of comprehensive two-dimensional chromatography retention times

Comprehensive two-dimensional chromatography generates a two-dimensional chromatogram from a one-dimensional signal array. This process can only be done unambiguously when the range of secondary retention times is less than the modulation period. However, complex samples often produce wider ranges of secondary retention times. Peaks with retention times that exceed the modulation period are said to be "wrapped-around". A simple algorithm has been developed that determines absolute retention times when wrap-around occurs. A sample is first analyzed under standard modulation conditions and then re-analyzed with a modulation period that is increased by an integer fraction of the original modulation period. Retention shifts along the secondary axis are used to determine absolute retention times. A theoretical analysis has been performed to optimize the implementation conditions and characterize the technique limitations. The efficacy of this algorithm has been tested through a series of isothermal GC x GC separations. This method has been found to be particularly useful during the initial stages of method development.     

计算有机化合物脂水分配系数的新方法

A new method is presented for the calculation of octanol/water partition coefficients. On the basis of summation of atomic contributions, our algorithm, namely; XLOGP, also incorporate correction factors into the calculation. Multivariate regression analysis was performed on a training database of 1831 organic compounds with diverse structures to give the final model. The correlation coefficients for the whole set fitting is 0.968 and the standard deviation is 0.37. The result shows that our model is accurate enough for logP estimation in QSAR studies. Compared to other similar approaches, our method gives better results and is more convenient to use.     

A New Method for Molecular Mechanics

A promising new method for optimizing molecular structures is described. In place of the terms involving bond angles and torsion angles, used in the force fields of conventional molecular mechanics, two-body central forces between atoms are used exclusively, resulting in a considerable computational advantage. The program STRFIT, using this method has been tested by comparing geometries obtained with those found using the popular molecular mechanics program MM2 (Allinger) for a variety of cyclic and acyclic molecules. For unstrained molecules, the difference in steric energy between geometries refined by STRFIT and MM2 is only a few tenths of a kilocalorie and up to about a kilocalorie for strained molecules. Geometry optimization with STRFIT, to a structure that is slightly higher in energy than the structure arrived at by MM2 starting from the same initial starting geometry, is three to eight times faster. A complete new package of programs for conveniently and rapidly doing molecular mechanics calculations is described. It includes a convenient algorithm for the input of approximate molecular structures, a rapid structure-optimizing module using a pure Central force-field approach, and a drawing program designed for use with a dot-matrix printer or a laser printer.     

求解弱相互作用分子A-BC的振转能级和波函数的SCF-CI方法

给出了一种计A－BC型弱相互作用分子体系的分子间振转激发态的自洽场-组态相互作用(SCF－CI)方法. 首先使用SCF方法代化径向伸缩振动和弯曲振动的基函数,再用CI方法确定精确的振转激发态能级. 在求解-维的伸缩振动SCF方程时,采用Numerov－Johnson算法在给定区间上求解获得振动波函数的数值解. 具体计算了Ar－HCI和Ar－N₂体系的振转激发态的能级以验证该方法. 结果表明,本方法可用较少的组态就能获得可与其它大计算量的方法具有相比拟的精度的结果.     

径向基-偏最小二乘-贝叶斯方法及其在化学模式分类中的应用

提出一种用于模式分类的RBF-PLS—Bayes方法。它集成地应用径向基(RBF)变换与偏最小二乘(PLS)方法，从原有模式中提取出分类能力甚强的成分，然后进行贝叶斯(Bayes)判别。这种集成方法尤其适用于复杂化学信息的模式分类，本文将其应用于两种类型的化学模式分类问题，均取得了令人满意的效果。与经典的判别分析方法和单纯的神经网络方法相比，具有明显的优越性。     

一种基于光谱信息计算解析的液相色谱滤噪新方法

提出一种基于光谱信息计算解析的高效液相色谱滤噪新方法.对于HPLC/DAD所获得的二维量测数据,取半峰高以上色谱数据点所对应的各列光谱数据进行计算处理,求得在检测波长下的单位标准光谱,并根据光谱维数据与单位标准光谱的关系,采用最小二乘法重构计算求出色谱维数据,从而去除色谱噪声.仿真实验和实测谱图的滤噪结果表明,该方法能有效滤除常见噪声,与中值滤波算法相比较,滤噪性能明显优于后者,是提高色谱定量分析准确度的有力工具.     

自优化扩散量子Monte Carlo差值法

提出了自优化扩散量子MonteCarlo差值法,这是一个集优化、扩散和相关取样三项技术于一身的MonteCarlo新算法.这个算法能够在扩散过程中直接计算两个体系之间的能量差,且使计算结果的统计误差达到10^-5hartree数量级,获得相关能达80%以上.应用该方法研究分子势能面,使用"刚性移动"模型,利用Jacobi变换使分子两个几何构型的能量计算具有很好的正相关性,因而能得到准确的能量差值和分子势能面.另外,我们还首创了"平衡后留样"技术,可节省50%以上的计算量.该算法还可应用于分子光谱、化学反应能量变化值等领域的研究.     

基于非接触式电导信号的土壤速效钾含量检测方法

该文针对土壤中速效钾含量采用传统测定法操作复杂、检测时效滞后的问题,建立了基于非接触式电导检测信号快速检测土壤速效钾含量的分析方法。采用高效毛细管电泳/非接触式电导检测仪获取河南潮土的非接触式电导检测信号,并使用导数法与高斯曲线拟合法相结合进行初步峰谱识别,按条件进行峰值过滤后,引入基于Levenberg-Marquardt(L-M)的高斯分峰拟合算法,实现了单峰和重叠峰的拟合计算,得到高斯峰和相应的特征参数,包括峰位、峰高、半峰宽和峰面积;最后将拟合得到的高斯峰及相应的特征参数表征原始非接触式电导检测信号离子峰谱信息结合偏最小二乘法(PLS),确定特征参数与土壤速效钾含量的关系,建立模型,实现了对土壤中速效钾含量的预测。结果表明,将基于L-M的高斯分峰拟合算法结合偏最小二乘法应用于非接触式电导检测信号测定土壤速效钾含量时具有较高精度,回归模型决定系数(R²)为0.856 4,相对分析误差(RPD)为2.639,适用于土壤速效钾的快速检测分析。     

基于能量重分配的波长偏移校正方法

针对原子光谱分析中波长偏移问题,提出了一种基于能量重分配原理实现波长偏移校正的方法.用抛物线插值法对能量密度分布进行反演,以谱图相似度为判断指标,通过三分法确定最佳偏移量,并根据最佳偏移量与能量密度分布对光谱强度进行重新计算,实现了亚像素级别的波长校正.对微型光纤光谱仪与单道扫描光谱仪获得的谱图进行了算法验证,使Eu元素的背景噪音平均降低了48%,Mo元素的信号稳定度由20%改善至约5%.该方法对具有结构化特征的谱图具有较好的适用性,且无须寻峰算法配合使用,有助于提高光谱分析精确度.     

基于迭代小波变换的光谱信号本底扣除方法研究

本底会对光谱分析结果产生很大的干扰作用,为获取特征峰的有效信息,必须首先去除本底。该文提出了一种基于小波变换的本底扣除算法,通过对光谱及后续光谱迭代进行小波变换,利用逼近系数估计本底,直到本底收敛。提出了判断多次估计的本底最大误差是否足够小的收敛准则。利用该算法去除本底后,即可进行特征峰信息的提取。分别利用仿真光谱和实验能量色散X射线荧光光谱对算法进行了验证,并与传统小波变换和多项式拟合法进行了对比。结果表明,该算法能够更准确扣除光谱本底,对其他光谱的本底扣除也具有借鉴意义。     

基于加权相位分离的二维互相关弹性成像方法研究

弹性成像能够检测组织的弹性信息,进而描述组织生理、病理状态,对疾病的检测和诊断具有重要的应用价值。为了改善二维弹性算法的轴向分辨率,本文对一维和二维弹性成像算法进行了比较研究,提出一种基于加权相位分离和二维互相关的混合位移估计算法,首先利用二维时域互相关技术进行粗估计,然后再利用加权相位分离技术(WPS)对结果进行精估计。同时,通过仿真和仿体实验对算法的精确性和效率进行了验证。结果表明,算法具有较好的鲁棒性,能够有效地提高运行效率和图像信噪比,上述研究对高性能弹性成像系统的研究与设计具有重要的指导意义。     

一种用于二类样本判别分析的PLS方法

提出了一种新的用于两类样本判别分析问题的ＰＬＳ方法，该法对响应函数ｙ作了类似神经网络算法中用的Ｓｉｇｎｏｉｄ函数转换，可用一种新的优化目标判据来提取一组ＰＬＳ方法中两两正交的隐变量ｔ１，ｔ２．．．，用这些变量可构成判别分类图，并可得到比较理想的判别方向矢量。     

A New Method of Calculating Multicenter Matrix Elements in MO LCAO Theory Using an Exponential Type Basis

Using integral representation of the product of reduced Bessel functions (RBF) specified on different centers and a new generalized integral identity for RBF one can prove that the 4-center integral of Coulomb repulsion in an exponential type AO basis may be expressed as a three-dimensional integral over the volume of a cube with an edge 1. A new method of calculating the multicenter matrix elements of quantum chemistry in an exponential AO basis is suggested based on this representation. Numerical calculations of a number of multicenter integrals using this algorithm illustrate the efficiency of the method.     

基于局部加权偏最小二乘的近红外光谱分析方法研究

针对近红外光谱分析技术中分析对象非线性现象突出的情况,提出了一种新的模型计算方法——局部加权偏最小二乘法(LWPLS)。以安胎丸为研究对象,采用LWPLS算法进行其近红外定量模型的建立,并比较偏最小二乘法(PLS)与LWPLS两种算法建立定量模型的精度。结果测得两种算法建立的校正模型中,阿魏酸的模型相关系数(R²)分别为0.785 5、0.971 9,预测误差均方根(RMSEP)分别为0.126 6、0.043 8,相对预测误差(RE)分别为12.66%、9.18%;洋川芎内酯A的R²分别为0.886 4、0.964 9,RMSEP分别为0.114 8、0.077 1,RE分别为14.01%、7.81%,显示LWPLS算法建立的模型精度更高。研究表明,采用LWPLS算法可提高安胎丸定量模型的准确性,具有可推广性和广泛的应用性。