最大重迭分子轨道和核自旋偶合常数的计算

利用前文中建立的AM1级别上最大重迭对称性分子轨道计算方案,并结合最大键级杂化轨道方法,在对分子几何优化的基础上,计算系列化合物分子中各原子的电荷分布和杂化轨道组成系数,拟合出计算C-H及C-C偶合常数的简单关系式,计算各种分子中不同C-H键和C-C键偶合常数,所得计算值和实验数据较为吻合,两者相关系数和标准偏差:.1JCH为0.982 0和6.020 5,1JCC为0.988 8和7.346 2,为计算1JCH和1JCC提供简便而直观的方法.建立的公式可预测新化合物中的C-H及C-C偶合常数,对新化合物的性质和结构及成键情况也能起到辅助推断作用,且在大分子体系的研究中极易推广.计算结果进一步表明所建AM1级别上最大重迭对称性分子轨道计算方法是可行的.     

CNDO／E—改进的CNDO分子轨道方法

本文提出一个适用于计算分子生成热的CNDO改进方法,该方法在计算核实Hamilton矩阵元中明确考虑了轨道基的正交化。在计算中将 s,p 轨道分开处理。同时,重新进行了参数化,并将计算的分子生成热与实验结果作了比较。     

桂皮酰哌啶类化合物结构与抗惊活性关系的量子化学研究

利用量子化学从头算方法，对13种桂皮酰哌啶类化合物的结构与抗惊生物活性关系进行了研究。采用限制性Hartree-Fock(RHF)方法和6-31G基组，对13种化合物进行全参数优化，得到了它们的稳定构型。并对前线分子轨道能级、轨道组成等性质进行了分析，把它们与实验得到的生物活性参数进行了相关分析，并对某些参量进行了线性回归，得到了回归方程。通过研究发现，桂皮酰哌啶类化合物的抗惊生物活性与分子的前线轨道(HOMO、LUMO)能级和轨道组成存在一定的相关性。通过轨道组成分析发现，具有较高生物活性的分子，其HOMO、LUMO轨道中羰基和烯键所占的比重较大，说明羰基和烯键部位应为此类化合物的活性部位。     

多面体分子轨道的程序设计

基于多面体分子轨道的群论方法和等性杂化轨道的构造法,应用Ｃ语言编制了多面体分子轨道微机程序,该程序呆方便地计算出多面体分子轨道的轨道性格,群轨道和杂化轨道等。     

量化参数对脂肪醇的-lgSw、lgKow的QSPR研究

基于多元线性回归技术发展了对脂肪醇在298K下的水溶性作出精确估计的定量结构-性质关系。通过从头算分子轨道理论得到描述脂肪醇分子的结构描述符，如Ehomo,Elumot C-O键上碳原子电荷Qc。在HF／6-31g(d)水平下对脂肪醇分子进行全几何参数优化从头算。Qc容易获取，表征了醇分子同分异构体之间的结构差异。多元回归分析结果表明醇分子的-lgSw、lgKow都随分子所含碳原子数N的增加而增加，随着C-O键上碳原子电荷Qc的增大而减小，复相关系数均在0．99以上。从头算所得的量化参数Qc用于与脂肪醇的水溶解性关联优于分子连接性指数。     

变尺度法在分子几何构型优化中的应用

本文报告了变尺度法(BFS)在分子几何构型优化中的应用。该法数值稳定性好,收敛速度快,能量梯度以差分法计算,因此容易应用到各种半经验的和从头计算量子化学方法中去。文中给出将该法用于从头计算 MQ AB-80计算程序的一些算例。     

铁卟啉化合物与氧气分子形成的体系的密度泛函理论研究(英文)

采用密度泛函理论B3LYP方法在6-31G(d)基组水平下对氯化铁(+3)卟啉与氧气分子形成的体系进行了研究,得到了几何构型,电子性质及分子轨道结构等相关数据.对两个体系不同自旋状态下的几何构型参数和电子性质对比发现:受体系立体构型对称性的影响,在两个体系中凡是与卟啉环上N原子相关的几何参数及电子性质均呈现出相同规律性.又采用密度泛函理论UB3LYP/6-311G*//UB3LYP/6-31G*方法对这两个体系不同自旋状态下的能量进行了计算,分析表明自旋多重度越高体系越稳定.然后分别分析了两个体系在最稳定自旋状态下的分子轨道占据情况及中心Fe原子最外层3d轨道的电子分布情况,结果表明Fe原子的3d二和3dxz/3dyz与氧气分子的单占据反键轨道HOMO π*2px/π*2py之间存在相互作用,这种相互作用引起铁卟啉环与O2分子间的电子转移并使O2活化.然而,根据分析在通常状态下铁卟啉对O2分子的活化作用是微弱的.     

“虚拟反应”法处理H_2O分子的电子结构

为了弄清水分子几何构象的产生机制,构造了"2H+O=H_2O"的虚拟反应,利用前线轨道理论的化学反应三原则结合分子点群方法,得到了分子轨道轮廓图和能级图;并利用能级图解释了H_2O的结构。结果说明,虚拟反应方法结合点群理论在定性处理分子的电子结构方面具有较为直观的特点,所得结果能够为了解分子的电子结构特点和稳定性提供很有价值的信息。     

茂金属配合物[(eta5-C5H4Si2Me5)MoEt(CO)3]的电子结构研究

运用G98W，采用Lanl2dz基组，对茂金属配合物[(eta^5-C5H4Si2Me5)MoEt(CO)3]进行从头算研究，探讨配合物结构单元的稳定性、分子轨道能量、原子净电荷布居规律，以及一些前沿分子轨道的组成特征等，结果表明，标题配合物结构在能量上是较稳定的，作为结构单元而存在。为茂型金属配合物的合成、分子组装与结构研究提供理论基础。     

分子计算理论方法及在化工计算中的应用

论述了量子力学中从头计算、半经验和密度泛函方法及分子力学的基础理论，概述了常用的MD、MC分子模拟方法，总结了多种应用软件的主要功能，并结合实例对HyperChem．7软件的功能进行了具体的说明。     

改进临界多边形生成算法

在Burke等人提出的用于求解临界多边形的移动碰撞算法基础之上,提出了一种更加高效的求取NFP的改进算法。该算法大大降低了问题的几何复杂性,简化了计算最小移动距离的方法,使许多启发式策略可以更加容易地与该算法结合来求解二维排样问题。实例验证了改进算法是有效且可行的,已应用于皮革自动排样软件中。     

Near-optimum regulator design of singularly perturbed systems via Chandrasekhar equations

The singular perturbation theory provides a powerful design and analysis approach for model order reduction. Another method of simplifying the calculation of feedback gains in an LQG problem is the Chandrasekhar algorithm, which replaces the usual Riccati approach. The method presented in this paper combines the advantages inherent in the singular perturbation theory with those of the Chandrasekhar algorithm. This is accomplished by using lower dimensional Chandrasekhar equations for calculating the asymptotic expansion terms of the feedback gains. Two alternative design procedures are given. In one procedure the fast or boundary layer gains are calculated first followed by the slow or reduced gains. In the other procedure a more conventional design sequence is adopted. That is, first the reduced problem is solved and the boundary layer correction terms are added later on if needed.     

基于遗传算法的分子场分析方法研究

将遗传算法引入比较分子场分析方法中进行最佳构象的选择。通过遗传算法的优化,可以得到一组统计最优的三维构效关系模型。计算结果表明,通过遗传算法优化得到的最优模型要优于用传统比较分子场分析方法得到的模型;同时,从这个最优构象中我们可以确定这线化合物的活性构象。     

Finding the transfer function of time invariant linear system without computing (sI - A)−1

A method is presented for hand calculation of the one-sided inverse of the transfer function matrix for time invariant linear systems. Unlike conventional methods, this procedure does not require the inversion of the matrix (sI - A). For single input single output systems, the procedure leads to a direct calculation of the transfer function. In the third part of this paper, we show how to use block matrix operations to reduce the dimensions of the matrices involved in the method. An example is given to illustrate the method.     

Analysis of periodic motions in relay feedback systems with saturation in plant dynamics

In this article a method of analysis of possible periodic motions in relay feedback systems that have saturation in plant dynamics is presented. Also, a methodology of analysis of local orbital stability of those periodic motions is proposed. The given analysis is based on the concept of the state locus of a relay feedback system. Techniques for computing the state locus are proposed. Also, a methodology of finding a periodic motion that involves the state locus is given. Finally, the proposed method is illustrated by an example.     

使用MATLAB绘制原子轨道和电子云图形

绘制原子轨道和电子云图形是量子化学、结构化学研究和教学的重要内容。以氢原子为例，以MATLAB为程序开发语言，设计了一种精确、快速、简便地绘制原子轨道和电子云图形的应用程序。介绍了该程序设计的过程，给出了源程序和运行结果示例，并讨论了MATLAB的三维球坐标图形、四维图形的绘制技术。研究结果表明MATLAB是解决结构化学数值计算和数据可视化问题的一种非常有效的工具。     

Neural networks to determine task oriented dexterity indices for an underwater vehicle-manipulator system

A method for the fast approximation of dexterity indices for given underwater vehicle-manipulator systems (UVMS) configurations is presented. Common underwater tasks are associated with two well-known dexterity indices and two types of neural networks are designed and trained to approximate each one of them. The method avoids the lengthy calculation of the Jacobian, its determinant and the computationally expensive procedure of singular value decomposition required to compute the dexterity indices. It provides directly and in a considerably reduced computational time the selected dexterity index value for the given configuration of the system. The full kinematic model of the UVMS is considered and the NN training dataset is formulated by the conventional calculation of the selected dexterity indices. A comparison between the computational cost of the analytical calculation of the indices and their approximation by the two NN is presented for the validation of the proposed approach. This paper contributes mainly on broadening the applications of NN to a problem of high complexity and of high importance for UVMS high performance intervention.     

A new class of Zernike moments for computer vision applications

A Modified Direct Method for the computation of the Zernike moments is presented in this paper. The presence of many factorial terms, in the direct method for computing the Zernike moments, makes their computation process a very time consuming task. Although the computational power of the modern computers is impressively increasing, the calculation of the factorial of a big number is still an inaccurate numerical procedure. The main concept of the present paper is that, by using Stirling’s Approximation formula for the factorial and by applying some suitable mathematical properties, a novel, factorial-free direct method can be developed. The resulted moments are not equal to those computed by the original direct method, but they are a sufficiently accurate approximation of them. Besides, their variability does not affect their ability to describe uniquely and distinguish the objects they represent. This is verified by pattern recognition simulation examples.     

Ray tracing objects defined by sweeping a sphere

The basic calculation underlying ray tracing is that of the intersection of a line with the surfaces of an object. A method is presented here for performing this calculation for a new and powerful class of objects, those defined by sweeping a sphere of varying radius along a 3D trajectory. When polynomials are used for the parametrization of the centre and radius of the sphere, the intersection problem reduces to the location of the roots of a polynomial. An implementation is presented, together with sample applications.     

Development of a regressive finite element model optimization technique making use of transmissibilities

Optimization of vibrating structures by means of finite element models usually requires a high number of optimization runs, where the finite element analysis time itself is often already a serious issue. The total optimization time consists of the finite element (FE) analysis calculation time multiplied by the number of optimization iterations. In this paper a computationally efficient strategy for optimization of structures is presented. Transmissibility functions are introduced to speed-up the FE analysis step, making use of the modal model. The method demonstrates it usefulness in the case of random response analysis where the external loading types are defined statistically by means of power spectral density functions. The relationship between random response displacement power spectral density and input base acceleration power spectral density is written in terms of a transmissibility function between response and excitation. An important feature of the presented method is its numerical efficiency with respect to calculation times. A comparison will be made with existing methods available in commercial FE software. The effectiveness of the proposed procedure is illustrated by means of a case study.