基于非正交坐标系下的SVPWM改进算法研究

分析传统的基于直角坐标系的空间矢量脉宽调制技术(SVPWM)的基本原理及缺点,提出一种基于非正交的斜角坐标系的SVPWM改进算法。该改进算法是将αβ直角坐标系转换为pq斜角坐标系,这样使得电压参考矢量在进行扇区判断和开关矢量作用时间的计算上都减少或避免了三角函数计算,降低了运算量,节约了运算时间,更容易数字实现。仿真结果验证了该算法的可行性。     

圆柱坐标系下非稳态导热问题改进数值求解方法

针对圆柱坐标系下的非稳态导热问题,通常采用集总参数法和格林函数法,但其具有一定的局限性。为提高求解精度和广度,将圆柱坐标系下的导热方程转化为类直角坐标系下的导热方程,采用有限容积法(FVM)求解计算区域内的温度场,通过加密网格确定网格无关解,并与两种坐标系下求出的温度对比。计算结果表明,类直角坐标系下得出的温度分布更符合实际情况。     

GAMIT/GLOBK软件中的坐标参考系及其相互转换

系统介绍了GAMIT/GLOBK软件中使用的协议天球与协议地球参考系、ITRF参考框架、WGS84坐标系、IGS精密星历参考框架、球面坐标系、站心地平坐标系、大地坐标系、空间直角坐标系以及NEU坐标系及其相互转换关系。     

双相材料模拟的区域分解重心插值配点法

针对双相材料力学性能分析,提出一种极坐标系下的区域分解重心插值配点法。根据材料界面将分析区域划分为两个计算区域,在每一个计算区域上建立极坐标系下重心插值配点法计算公式。组合两个区域上的计算公式,施加材料界面条件和边界条件,求解得到双相材料的位移场和应力场。双材料计算模型的数值算例表明了所提方法的计算精度。     

北京54坐标系坐标转换的探讨

坐标系之间的相互转换常用相似变换法,但如果公共点存在较大的误差,计算结果会使转换模型存在较大的差异.结合原有北京54坐标系和由GPS成果换算得的54坐标系之间进行相互转换的实例,探讨了公共点的误差对转换模型的影响,提出了转换计算前应对公共点进行筛选的设想,并利用Baarda数据探测法原理,对公共点进行筛选,剔除偏差较大的公共点,有效消除了公共点间隙较大的缺陷,使转换后的坐标更加符合相似变换的特征.     

高斯——牛顿法与梯度法波形反演比较研究

经典的地震波形反演采用梯度算法,该方法计算量小,但收敛速度慢,不容易重建速度场的低波数成分。我们在文中讨论了雅可比矩阵的计算,实现了高斯—牛顿法反演。数值例子表明,与梯度法相比,高斯—牛顿法收敛迅速,反演精度高,是一种更加有效可行的物性反演策略。     

各向同性颗粒系统数量平衡方程直接矩积分求解法的研究

随着颗粒系统微观行为研究的深入,数量平衡方程越来越受到重视。一般数量平衡方程由于复杂难以得到解析解。比较数量平衡方程的求解方法—分组方法(CM)、矩方法(MOM)和在矩方法基础上发展起来的直接矩积分方法(DQMOM),发现DQMOM具有计算量小,容易和计算流体力学(CFD)耦合等优点。运用直接矩积分方法对各向同性系统的颗粒长大、聚并和破碎等微观行为进行模拟,对各向同性液固系统的颗粒长大行为模拟的结果与文献的解析解吻合较好,误差小于10-5,对于各向同性液固系统的颗粒聚并和破碎行为模拟的结果与CM方法的精确解相比误差在2%以内。可见直接矩积分求解法在液固多相系统是有效的,具有良好的应用前景。     

基于切比雪夫矩的抗几何攻击图像水印

旋转、缩放和平移(RST)等几何攻击能够破坏水印检测的同步性,而使水印检测失败。本文提出了基于切比雪夫矩的抗几何攻击图像水印算法.首先计算原始图像的切比雪夫矩,并将其作为原始矩,然后将水印图像在空域直接嵌入到原始图像中,并提取嵌入区域的切比雪夫矩。当图像未受攻击时,利用嵌入区域的矩与原始矩之差便可以提取出水印图像。当图像受到攻击后,利用上述方法同样可以提取出水印图像,但是我们需要将原始图像做相应的变换。与使用Zernike矩相比,切比雪夫矩具有更好的图像描述能力。当水印图像的目标物体较小时,切比雪夫矩可以较好的提取出水印图像,而Zernike矩则无法做到,同时该算法对于旋转、缩放、噪声攻击也具有较好的鲁棒性。     

一种基于傅立叶描述符的颗粒图像形状识别方法

颗粒图像形状的自动识别广泛应用于大气颗粒、细胞细菌采样分析等产品的研究开发.本文从应用的角度出发,提出了一种基于傅立叶描述符的颗粒形状自动识别方法.将采集的原始图像进行去噪、光照校正、边界提取等预处理以后,对获得的物体轮廓使用傅立叶描述符对颗粒图像进行形状识别.傅立叶描述符的优点在于它可以在一个统一的框架下描述相同形状的不同尺度、旋转和平移变化.实验结果表明使用傅立叶描述符方法对颗粒图像进行分析识别具有良好的效果,证明了本文方法的有效性和鲁棒性.     

非理想多元物系精馏塔动态数学模型

本文给出了一种新的精馏塔动态仿真模型,该模型除了气相上升量的计算是利用焓平衡关系导出的线性代数方程组进行外,其余变量均通过微分方程计算.这就可以避免以往的模型由于解非线性代数方程组不收敛而带来整个计算失败的问题.文中将一种计算病态常微分方程的积分方法——小参数法在IBM-PC/XT微机上算出一个有70层塔板、6个组分的脱乙烷塔模型(600多维的微分方程).小参数法的最大优点是无需矩阵求逆且不必计算雅可比矩阵.     

人机交互获取图像轮廓点位坐标的研究

产品设计过程中会遇到以图像形式给出的轮廓,在数控加工时也必须给出廓线的一系列坐标值。在此提出一种采用人机交互的方式,用若干段贝塞尔曲线逼近图像给出的廓线,实现从图像到CAD/CAM系统可以直接利用的坐标数据生成的方法。     

瓮福矿区控制网坐标系统的探讨

就瓮福磷矿是否需要建交独立坐标系,如需要,又采用怎样的方法建立等问题进行探讨。     

小炉斜坡碹的三维制图

在AutoCAD二维环境中精确绘制小炉斜坡碹比较困难,上下碹头的尺寸不好确定,加工砖材时要靠放线确定碹头砖尺寸,但在三维环境中,就可以比较准确地解决这个问题.本文介绍一种利用AutoCAD R14在三维坐标系中绘制小炉斜坡碹的方法.     

SmartPro系统多工程远程通讯的实现

从2套新的SmartPro系统投运后要实现其与调度室通讯的现实需要出发，简要介绍了和利时公司SmartPro系统的构成及实现远程调度和数据通讯的不同方法，重点介绍了建立以光缆为传输介质的以太网专用通讯网络实现2套装置的数据传输、远程通讯和调度的过程，并在调度室配置1台监控机对2套DCS系统的数据进行监控调度。整个调度系统能够满足通讯网络安全可靠、实时快捷的要求。     

Transition Pathway and Its Free-Energy Profile: A Protocol for Protein Folding Simulations

We propose a protocol that provides a systematic definition of reaction coordinate and related free-energy profile as the function of temperature for the protein-folding simulation. First, using action-derived molecular dynamics (ADMD), we investigate the dynamic folding pathway model of a protein between a fixed extended conformation and a compact conformation. We choose the pathway model to be the reaction coordinate, and the folding and unfolding processes are characterized by the ADMD step index, in contrast to the common a priori reaction coordinate as used in conventional studies. Second, we calculate free-energy profile as the function of temperature, by employing the replica-exchange molecular dynamics (REMD) method. The current method provides efficient exploration of conformational space and proper characterization of protein folding/unfolding dynamics from/to an arbitrary extended conformation. We demonstrate that combination of the two simulation methods, ADMD and REMD, provides understanding on molecular conformational changes in proteins. The protocol is tested on a small protein, penta-peptide of met-enkephalin. For the neuropeptide met-enkephalin system, folded, extended, and intermediate sates are well-defined through the free-energy profile over the reaction coordinate. Results are consistent with those in the literature.     

全站仪测量导线中的错误分析和处理

分析了采用全站仪进行导线测量时不同作业状态下可能出错的情形,即定向点坐标输入错误、定向角设置错误、测站坐标输入错误,以方位角进行定向设置和坐标输入错误同时以坐标进行定向设置4种情况,分析了出现错误的原因及误差超限的特点,提出了相应的粗差判断方法,并给出了导线测量后坐标数据粗差修正处理公式.     

全自动汽车煤炭采制样机的研究

介绍了全自动煤炭汽车采制样机的构成模块;分析了车辆信息采集、三维坐标点选取、采样方式及采样点坐标的测量、采样系统编码模块、采样系统与其他系统的接口等功能;该系统的应用实现了煤炭采制样系统真正意义上的全自动控制,引领了采样机控制技术的发展方向。     

Hydrodynamics of gas-solid flow around immersed tubes in bubbling fluidized beds

A numerical study was conducted based on the gas-solid two-fluid model using the body-fitted coordinate system to analyze the behavior of particles and bubbles flow in bubbling fluidized beds without and with immersed tubes. The kinetic theory of granular flow was implemented in the model. The images of simulated instantaneous particle concentration and velocity gave the process of the formation, coalescence and eruption of bubbles. The effects of the tube pitch and superficial gas velocity on the fluidization in a bubbling fluidized bed were investigated. Calculated bubble frequencies without and with immersed tubes were in agreement with previous experimental and simulation findings. The wavelet multi-resolution analysis was used to analyze the simulated data of instantaneous particle concentration. From the random-like particle concentration fluctuations, the fluctuating components due to particle flow and bubble motion can be extracted based on the wavelet multi-resolution analysis over a time-frequency plane.     

Conformational Motions and Functionally Key Residues for Vitamin B12 Transporter BtuCD–BtuF Revealed by Elastic Network Model with a Function-Related Internal Coordinate

BtuCD–BtuF from Escherichia coli is a binding protein-dependent adenosine triphosphate (ATP)-binding cassette (ABC) transporter system that uses the energy of ATP hydrolysis to transmit vitamin B12 across cellular membranes. Experimental studies have showed that during the transport cycle, the transporter undergoes conformational transitions between the “inward-facing” and “outward-facing” states, which results in the open–closed motions of the cytoplasmic gate of the transport channel. The opening–closing of the channel gate play critical roles for the function of the transporter, which enables the substrate vitamin B12 to be translocated into the cell. In the present work, the extent of opening of the cytoplasmic gate was chosen as a function-related internal coordinate. Then the mean-square fluctuation of the internal coordinate, as well as the cross-correlation between the displacement of the internal coordinate and the movement of each residue in the protein, were calculated based on the normal mode analysis of the elastic network model to analyze the function-related motions encoded in the structure of the system. In addition, the key residues important for the functional motions of the transporter were predicted by using a perturbation method. In order to facilitate the calculations, the internal coordinate was introduced as one of the axes of the coordinate space and the conventional Cartesian coordinate space was transformed into the internal/Cartesian space with linear approximation. All the calculations were carried out in this internal/Cartesian space. Our method can successfully identify the functional motions and key residues for the transporter BtuCD–BtuF, which are well consistent with the experimental observations.     

Dipole moments of copolymers in relation to the distribution of polar monomer unit sequences

A method for evaluating the dipole moments of copolymers in relation to the distribution of polar unit sequences is proposed. Experimental data on the synthesis and dipole moments of styrene-p-chlorostyrene and styrene-p-methoxystyrene copolymers were used to calculate the effective dipole moment of a polar unit in a copolymer. For this purpose, we assumed the following effective moment values for the corresponding polar unit sequences along the copolymer chains: when both of the nearest neighbours are polar, μ_PP, when one of the nearest neighbours is polar and the other is non-polar, μ_PS, and when both of the nearest neighbours are non-polar, μ_SS. The relative magnitudes of μ_SS, μ_PS and μ_PP calculated for both copolymers reflect the influence of dipole-dipole interactions on the effective dipole moment of a polar unit in a copolymer molecule.