MOLECULAR MODELS AND FLOW CALCULATIONS Ⅱ.SIMULATION OF STEADY PLANAR FLOW

A multibead-rod model is used to replace the constitutive equation of continuum me- chanics in solving flow problems of steady-state planar flows of rigid-rodlike molecular suspensions.The governing equations then constitute a set of differential equations of the elliptic type,which is more ame- nable to numerical treatment than those of the mixed type.The conservation equations of the flow fields are solved by the boundary element method with linear boundary elements in physical space and the diffusion equation of the distribution function is solved separately by the Galerkin method in phase space. The solution to the flow problem is obtained when the convergence of the iteration procedure between the two spaces has been reached.Several numerical examples are shown and the interesting features of the present method are discussed in this paper.

Digital image processing of saturation for two-phase flow in planar porous media model

In this paper, the accuracy of estimating stained non-wetting phase saturation using digital image processing is examined, and a novel post-processing approach for calculating threshold is presented. In order to remove the effect of the background noise of images and to enhance the high-frequency component of the original image, image smoothing and image sharpening methods are introduced. Depending on the correct threshold, the image binarization processing is particularly useful for estimating stained non-wetting phase saturation. Calculated saturation data are compared with the measured saturation data during the two-phase flow experiment in an artificial steel planar porous media model. The results show that the calculated saturation data agree with the measured ones. With the help of an artificial steel planar porous media model, digital image processing is an accurate and simple method for obtaining the stained non-wetting phase saturation.

Application of particle trajectory model in 1D planar ejection

A simple one-dimensional planar model for ejection was set up based on experiments.And numerical simulation was performed on this model with particle trajectory model method.An Eulerian finite volume method was conducted to resolve gas field.And Lagrangian method was imposed to track each particle.The interaction between gas and particles was responded as source terms in governing equations which were induced by forces.The effects of total spraying mass,particle size and other factors on the mixture of particles and gas were investigated.The spatial distributions of particle mass and velocity at different time were presented.The result shows that the numerical results are qualitatively consistent to those of experiments.

FURTHER RESEARCH ON THE SPLINE MODEL METHOD OF KED ANALYSIS IN A PLANAR FLEXIBLE LINKAGE

This paper relates to the deep research on the Splinc Model Method of KED analysis. With the use of cubic B-splinc function as a link’s transverse deflection interpolation function, the principle of virtual displacement is presented as a basic theory for the general formulation of the equations of motion, and thus abandoned the kinematic assumption and the instantaneous structure assumption which arc used in the Spline Model Method. In thc same time, the nonlinear terms sue as coupling terms between thc rigid body motion and elastic deformation arc included. New member’s spline models are established. Mass matrix, Coriolis mass matrix, normal and tangential mass matrix, linear stiffness matrix, nonlinear stiffness matrix and rotation matrix arc derived. The kinematic differential equations of a member and system are deduced in the end. The Newmark direct integration method is used as the solution scheme of the kinematic differential equations to get the periodic response.

A Method for Automatically Establishing a Mathematical Model of Kinematic Analysis to a Planar Mechanism with a Multiple Joint and Prismatic Pair

A method for automatically establishing a mathematical model of kinematic analysis to a planar mechanism with multiple joint and prismatic pair is presented. The breadth （ or depth ） first search spanning tree can be obtained based on an adjacency matrix of the mechanism. Then the kinematic chain （or mechanism）＇s basic loops can be obtained. On the basis of these basic loops, a mathematical model of kinematic analysis can be established and solved automatically. In the sense of a calculative mechanism, structural analysis of the kinematic chain relates to the kinematic analysis of a mechanism. Thus, an effective way is supplied to the given mechanism＇s kinematic analysis for automatic modeling and solving, and a method is supplied to the structural type to optimize kinematic synthesis.

Analytical expression of non steady-state concentration profiles at planar electrode for the CE mechanism

The analytical solutions of the non-steady-state concentrations of species at a planar microelectrode are presented. These simple new approximate expressions of concentrations are valid for all values of time and possible values of rate constants. Analytical equations are given to describe the current when the homogeneous equilibrium position lies heavily in favour of the electroinactive species. Working surfaces are presented for the variation of limiting current with a homogeneous kinetic parameter and equilibrium constant. Moreover, in this work we employ the Homotopy perturbation method to solve the boundary value problem.

PROGRESSIVE FRACTURE MODELING OF THE FAILURE WAVE IN IMPACTED GLASS

The failure wave has been observed propagating in glass under impact loading since 1991. It is a continuous fracture zone which may be associated with the damage accumulation process during the propagation of shock waves. A progressive fracture model was proposed to describe the failure wave formation and propagation in shocked glass considering its heterogeneous meso-structures. The original and. nucleated microcracks will expand along the pores and other defects with concomitant dilation when shock loading is below the Hugoniot Elastic Limit. The governing equation of the failure wave is characterized by inelastic bulk strain with material damage and fracture. And the inelastic bulk strain consists of dilatant strain from nucleation and expansion of microcracks and condensed strain from the collapse of the original pores. Numerical simulation of the free surface velocity was performed and found in good agreement with planar impact experiments on K9 glass at China Academy of Engineering Physics. And the longitudinal, lateral and shear stress histories upon the arrival of the failure wave were predicted, which present the diminished shear strength and lost spall strength in the failed layer.

Recovering the Shape of Planar Object Depicted by a Line Drawing under Axonometric Projection

A new approach is proposed for automatically creating B-rep models of a three-dimensional planar object from a line drawing depicting the object under orthographically axonometric projection. A new line parameterization that satisfies the uniqueness, boundedness and uniformness for representing lines in 2D and 3D space is given. According to the location relation between lines and planes of object depicted by the line drawing, some constraints about object’s 3D information are produced and a linear system based on those constraints is established. 3D information of a planar body can be obtained by solving the linear system. It is proved that, during the processing, there existed at least four degrees of freedom. It is more convenient to use information about lines and planes instead of points and planes for computer vision and intelligent CAD systems to interpret line drawings of planar objects.

基于CATIA的平面机构自顶向下参数化设计

文章以缝纫机下针机构为例,介绍了在CATIA软件中实现平面机构自顶向下的参数化设计方法,为平面机构创新设计快速建模提供了一种快捷、实用的新思路。

Ionospheric time delay corrections based on the extended single layer model over low latitude region

Ionospheric delay error is considered to be one of the most prominent factors impacting the Global Navigation Satellite Systems(GNSS) positioning and navigation accuracies. Due to dispersive nature and anisotropic of the ionosphere above certain regions, the positioning accuracy is seriously affected when using a precision-limited model. In this paper, an attempt has been taken to estimate ionosphere-delays based on Planar Fit(PF) and Spherical Harmonic Function(SHF) models by applying the commonly used single layer Model(SLM) and an extended single layer model(ESLM) which has been explored sparsely over the region. The results show that ESLM of PF and SHF techniques performed better in estimating ionospheric delay compared to the existing SLM model. Although the performance of the ESLM approach is almost comparable to the SLM results during the quiet ionospheric conditions, the ESLM-PF and ESLMSHF models led to respective improvements of 4.66% and 7.14% over the classically used SLM model under the disturbed ionospheric conditions. In view of the uneven variability of equatorial/low latitude ionosphere above the Indian subcontinental region, the suitability of ESLM-PF and ESLM-SHF models has been emphasized and suggested for assessing its completeness and reliableness across other parts of the globe. The output of this work may be useful for high precession GNSS positioning through mitigating the ionospheric delays under quiet as well as varied ionospheric conditions across the low/equatorial latitude regions.

基于深度相机和二维码的室内移动机器人定位技术

提出一种以ORB_SLAM2为基本框架、使用二维码辅助深度相机的室内移动机器人定位方法。针对现有的视觉SLAM在定位过程中出现的Z轴漂移现象,提出平面运动模型约束,以降低机器人定位结果中的Z轴累计误差;针对视觉SLAM在弱纹理环境中算法退化、容易跟踪失败等问题,在室内环境中张贴二维码并将其数学模型作为定位约束,以提高系统的准确性与鲁棒性。真实环境下的实验结果表明:相比原始算法,所提算法在Z轴精度上提高了42.95%;以ORB_SLAM3的定位结果为真值,所提算法的定位精度提高了4.11%,该算法在室内环境下具有定位优势。

裂隙水作用下岩质边坡平面滑动力学模型

在降雨等水力条件作用下沿岩层层面的平面滑动是顺层岩质边坡最常见的一种破坏模式,而目前关于该类边坡的稳定性计算方法几乎很少考虑裂隙面粗糙度对地下水渗流力及滑面抗剪强度的影响,进而导致其稳定性计算结果误差较大。为此,首先对地下水作用下的顺层岩质边坡受力特征进行分析,认为地下水将对滑动岩体产生3个方面的力学作用:张裂隙中的静水压力、滑面上的扬压力和渗流力,由此建立了相应的边坡稳定性计算模型。其次,通过引入裂隙面粗糙度对裂隙抗剪强度及地下水渗流力的影响,提出了考虑裂隙粗糙及地下水渗流力的顺层岩质边坡稳定性计算模型。而后,通过对含一条贯通粗糙裂隙的岩质边坡稳定性为例,验证了该模型计算结果的合理性,同时计算结果表明裂隙面粗糙度系数JRC对边坡稳定性有重要影响,必须予以考虑。最后,基于参数敏感性分析研究了主要参数如裂隙面粗糙度系数、裂隙基本摩擦角、裂隙宽度、裂隙壁面岩石抗压强度及地下水位高度等对边坡稳定性的影响,结果表明:仅裂隙宽度对边坡稳定性影响很小,而其他参数对边坡稳定性影响则相对较大,不容忽视。且裂隙面粗糙度对边坡稳定性的影响与裂隙壁面岩石抗压强度密切相关,随着其增加,裂隙面粗糙度对边坡稳定性的影响程度逐渐变大。

基于二维云模型和ALARP准则的风险评价法

风险具有广泛性和显著的不确定性,合理地评价风险可以有效规避事故损失。基于传统ALARP风险矩阵和二维云理论,提出一种风险量化评价方法。参考以“发生概率”和“危害性”为风险指标的五阶ALARP风险矩阵,统计四类风险等级对应的风险指标组合情况,分别建立风险等级的二维云模型。对某风险因素评级时,令专家参照评估标准,对风险指标进行多次独立评级,建立风险评估样本的云模型。利用Matlab基于评估样本云参数生成大量样本点,带入风险等级的正向云发生器中计算平均确定度,作为确定最终风险评级的依据。最后以斜拉索耐久性风险评价为例,结合工程实际病害情况,验证了方法的有效性和可操作性。

LiDAR点云数据坐标转换关键技术研究

LiDAR技术近年来日趋成熟,在各行业得到了广泛应用。LAS文件格式标准,为LiDAR点云数据交换提供了便利。为实现点云数据的坐标转换,本文基于LASlib库和坐标转换模型,实现了LAS文件的坐标转换,并利用工程项目验证了其正确性。同时,针对不同坐标转换模型的坐标转换效率进行了分析,对LAS文件的坐标转换具有指导意义。

多裂缝形式下沥青混合料梁裂缝扩展研究

采用接近实际路面受力形式的平面支撑方式,对从参考标准高速公路搅拌、摊铺、碾压方式形成的沥青混凝土路面切割下的沥青混合料梁试件,开展表面、底部裂缝共存形式下路面面层裂缝扩展模拟,以期研究沥青路面面层顶部、底部裂缝共存形式下的裂缝扩展行为;针对沥青混凝土路面为包含沥青基质、骨料、空隙等的多相复合材料特点,基于ABAQUS平台建立沥青混合料梁细观异质模型,探讨了该模型下裂缝偏离跨中不同距离下裂缝扩展行为。在此基础上,进一步对复合小梁均质、细观异质模型偏裂缝形式下裂缝扩展过程中应力分布进行了对比分析,得出两者应力状态存在明显的不同,均质模型应力分布总体较均匀、突变不明显;细观异质模型则刚好相反,应力分布极不均匀,骨料周边应力突变较明显。两种模型对比而言,细观异质模型能够更好地解释试验过程中梁裂缝扩展沿着骨料周边进行,并且试验过程中骨料周边出现多裂纹的现象。梁细观异质模型数值模拟为建立更准确的路面裂缝扩展模型提供了参考。

既有350 km/h铁路运行更高速铁路线路平面参数适应性分析

通过采用车线动力学分析方法,基于建立的动力学仿真模型,对某既有设计速度目标值为350 km/h的铁路曲线段进行了400 km/h运行的线路平面参数适应性研究。结果表明:(1)当列车速度提升至400 km/h后,多项动力学指标较350 km/h时增加较为明显,安全性与舒适性均有所下降;(2)尽管列车的安全性可以得到保障,但乘坐舒适度下降,存在一定的舒适度隐患,适应性有待进一步提高;(3)建议在可能的情况下,适当增大曲线半径与夹直线的长度,以保证旅客乘坐的安全性与舒适度。

基于二维平面水流数学模型的平原河道上跨改建桥梁流场影响分析

模型基于全方位不可压缩与雷诺数均匀分布的纳维斯托克斯方程,并服从于非线性布西尼斯克方程假定和静水压强的假定,通过对皖北平原河流上跨桥梁的河道二维水流数学模型研究,分析了平原河流在上跨桥梁改建后的流场变化,对比流速、流向变化,分析认为工程实施后,河道流速较小,减轻了洪水期现状河道的岸坡及主河槽的冲刷,受桥墩阻水作用影响,桥墩局部流场发生细微变化,但对河道流场的影响程度和影响范围较小,在较短河段内便可消除,工程对整个河道的流场影响较小。

基于地质剖面构建三维地质模型的方法研究

地质剖面是三维地质建模的重要数据源,运用地质剖面构建三维地质模型的方法应用较为广泛。在模型构建之前,统一确定模数据的坐标系和比例足,建立原始资料数据库。构建三维地质模型的关键是不同地质界面。本文详细介绍了模型边界面、断层面、地层界面、岩体界面等4种主要地质界面的构建流程与方法,尤其对褶皱构造、地层界面的断层效应、复杂岩体界面等的构建进行了重点阐述按模型边界面(模型的底界面和四周边界面)、DEM面、断层面、其他地质界面的顺序依次构建地质界面,构建断层面和其他地质界面时严格按先新后老的顺序。运用已构建好的地质界面按先新后老的顺序逐个、依次建立单个地质体,再将所有地质体的面模型组合成整个模型的面模型。通过对面模型进行网格(实体)填充和对网格赋予相应的属性值,最终构建三维地质模型。

基于特征的城市交通网络非平面数据模型

本文通过分析交通网络特性 ,提出了一种适合城市交通网络数据表达与操作、基于完整交通特征的 GIS数据模型 ,以弥补传统基于弧段 -节点的 GIS数据模型在城市交通网络建模中的不足 ,并在此基础上将传统的交通网络平面图表达模式升华到非平面模式 ,设计了基于特征的交通网络非平面数据模型的概念建模与逻辑建模方法 ,为相应的数据结构与数据库实现奠定了基础。

基于特征线条的手势识别

单目视觉的手势识别系统,通常把人手建模成一个像素或者一块,从整体上分析手势的运动参数并提取表观特征.从细微之处着手,融合颜色、运动和边缘等多种信息以提取能够反应人手结构特性的特征线条,并将特征线条分割成小的曲线段,跟踪这些曲线段的运动.采用平面模型对手势图像表观的变化建模,根据各个曲线段的运动,融合成手的整体运动分量.同时分析了图像坐标系的选取和对运动参数的影响,提出了随手运动的坐标系,以抽取平移不变的平面模型参数,进行手势识别.