三角网格模型多轴数控雕刻刀轨生成算法

提出一种基于三角网格模型的多轴数控雕刻刀轨生成算法,用于解决三角网格模型的多轴数控雕刻刀轨的生成效率低、存在刀轨干涉等问题.该算法采用R*S树动态空间索引结构组织三角面片的拓扑近邻关系,并依据三角网格模型的型面特征规划刀位驱动点,获取各驱动点的瞬时加工区域;根据刀具与瞬时加工区域中各三角面片的相切关系采用面相切、边相切...     

自由曲面自适应投影法精加工刀轨生成

提出并实现了适合于组合自由曲面整体加工的一种刀轨生成算法,该处蒙混过关针加工曲面离散成三角化模型,在三角化模型中直接生成无干涉刀位轨迹,刀轨生成与刀轨干涉处理统一在一个算法中,根据曲面的形状规划刀轨,使刀轨的行距能够随曲面的倾斜程度而调整,有效地解决了组曲面加工编程中曲面之间存在断开,裂缝,局部搭接现象,提高了加工效率和精度。     

整体叶轮五轴数控粗加工刀位轨迹规划

针对具有分流叶片的整体叶轮五轴数控粗加工,提出了一种刀位轨迹规划方法.采用偏置轮毂面分层加工方法对整体叶轮进行粗加工刀位轨迹规划,根据叶轮流道的几何特征,将叶轮的1个粗加工区域分成5个加工单元.在每个加工区域内,选用直径最大的刀具,计算边界面的刀位轨迹,再由边界面的刀位轨迹插值计算得到整个加工区域的刀位轨迹.利用VERICUT软件进行加工仿真,结果表明所提出的刀位轨迹生成算法可行.     

精密五轴联动机床非线性误差分析与后置处理

五轴联动机床的非线性误差和后置处理算法影响着机床的加工精度。本文针对自主研发的小型立式五轴联动机床进行了非线性误差分析,给出了误差补偿算法;对机床刀轴矢量和机床坐标变换进行了推理,分析UG生成的标准刀位文件和数控G代码之间的关系,利用MATLAB的GUI功能开发了后置处理器。以某眼镜片的修缘加工为例,验证了非线性误差分析和补偿方法的正确性及后处理的有效性。     

一种新的四轴加工刀轴矢量算法

根据回转型自由曲面四轴加工的特点，对刀轴矢量的形成进行了分析研究，提出了一种新的计算刀轴矢量算法，用垂直于回转轴的平面与刀具运动方向和前导角形成的圆锥面求交，生成刀轴矢量，该算法很好地解决了当曲面法矢在回转平面内投影为零时，刀轴矢量难以的问题，加工实例表明，该算法稳定，可靠，具有实用价值。     

基于偏置点寻优的弧面凸轮侧铣加工刀轨算法

针对弧面凸轮的非等径侧铣加工存在法矢异向误差的问题,为寻求加工误差最小的刀具位置,分析了理论非等径刀轴曲线的性质,根据等距曲面的误差传递关系,结合偏置点寻优算法进行刀位优化,提出了一种以非等径刀轨曲面与拟合直纹面误差最小为目标的双向搜索刀轴优化算法.在此基础上,通过遗传算法得到较高精度的优化数值解,并将解算出的刀轴端点作为初始数据,利用NURBS(非均匀有理B样条)插值反算重构侧铣加工刀轨直纹面.数值计算和仿真结果验证了该算法的有效性.     

圆环面刀具数控加工刀具路径规划

研究了数控加工中圆环面刀具路径规划,建立圆环面刀具数学模型,从刀位点计算、曲面边界离散、相邻刀轨计算等方面确定刀具路径规划算法.最后,利用Matlab工具编程对路径规划算法进行了具体实现,通过计算基于圆环面刀具的刀位点数据,拟合生成刀具轨迹,同时利用UG软件采用球头刀对相同曲面进行加工路径仿真,通过两者比较,可以得出圆环面刀具加工效率更高的结论.     

并联机床后置处理器的开发及实验研究

以六自由度6-TPS型并联机床为模型，阐述了机床控制数据的生成原理和流程；以此为基础，规划了后置处理器的功能和整体结构。对若干关键技术进行了研究和探讨，包括基于参数化二进制格式的内部数据传输，基于刀轴矢量的笛卡儿空间粗插补算法，三维和二维刀具半径补偿，刀位文件的预处理以及加工代码的词法和语法检查等。最后介绍了利用本系统进行的切削实验，验证了系统的工程实用性。     

三角Bézier曲面粗加工刀轨生成算法

为了解决三角Bézier曲面粗加工刀轨生成效率低以及存在的刀轨干涉等问题,提出了一种基于三角Bézier曲面粗加工刀轨生成算法.该算法采用R*S树建立三角Bézier曲面模型的动态索引,可快速获取瞬时加工区域三角Bézier曲面片,进而迭代计算无干涉刀位点.建立了三角Bézier曲面的z向包络线,根据z向包络线与切削平...     

基于包络面的网格曲面等残留高度路径规划

研究面向三角网格曲面数控加工的刀具路径设计，提出了一种基于刀具包络面的等残留高度刀具路径生成算法.该算法首先建立刀具运动刃口回转面的包络面方程，然后通过相邻轨迹刀具包络面求交得到残留曲线，并利用全局搜索和局部搜索两个步骤精确地计算残留高度值，据此判断当前刀位点是否满足等残留条件，若不满足则沿行距方向搜索等残留刀位点，最后进行加工干涉检查和处理.算例分析的结果表明，由本文的算法生成的刀具路径残留高度均匀，刀轨长度较短，无加工干涉，在保证加工精度的前提下，能够有效地提高加工效率.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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