转轮内全三维不可压缩流动问题有限元统一解法研究

引入非正交曲线坐标系，克服反问题或混合问题所特有的求解域内边界未定的难点，本文建立转轮内部完全三维不可压缩流动问题（正问题、反问题以及混合问题）的通用数学模型．来用有限元技术并结合有限体积法，建立该三类流动问题的有限元统一解法，将三维正问题分析、叶片的完全三维设计以及三维叶片局部改型融合于同一种计算方法．     

多相泵导轮的准三维正反问题研究

以速度矩作为控制参数,推导出多相泵导轮中均匀流模型的准三维反问题计算公式;基于两类相对流面理论及气泡的受力分析,推导出气、液两相在多相泵导轮中运动的准三维正问题的计算公式,提出一种对多相泵导轮内流场进行准三维数值计算的方法.通过计算导轮的准三维反问题,对其叶片形状进行了初步设计,并根据计算结果分析了导轮中的流动状况.对计算结果的分析表明,利用准三维方法进行多相泵导轮的正反问题计算是经济且有效的.     

大型空腔定子叶片热处理变形的数字化测量及评定

针对大型空腔定子叶片在进行热处理工艺时易发生翘曲变形的问题,采用三维激光扫描测量设备对热处理前后的叶片进行数字化测量,并把测量得到的点云数据进行去噪、精简处理。将热处理后的叶片点云数据重构为三维数字化曲面模型,将热处理前的点云数据与热处理后三维曲面模型进行匹配,计算出大型空腔定子叶片热处理变形量的分布情况。研究结果表明:经过热处理工艺的叶片,变形较大的部位主要分布在空腔及其与实体连接部位,变形极大值为4.76 mm,极小值为-5.13 mm。     

基于PRO/E的混流式水轮机叶片的三维造型

针对混流式水轮机叶片形状的复杂性给其三维实体造型带来的困难,以混流式转轮叶片二维木模图为基础,基于PRO/E软件的三维建模功能,采用从点到线、线到面、面再到体的方法,对混流式水轮机叶片进行三维造型.为了提高造型的准确性,用切割的方法对叶片进水边、上冠及下环进行修型,从而可真实准确地得到木模图所表示的混流式水轮机叶片的三维实体造型.     

叶片弯曲程度对离心压气机性能的影响

采用离心压气机计算机辅助集成设计系统设计直叶片、正弯叶片和反弯叶片3种离心压气机叶轮.对具有不同弯曲程度的叶轮内部流场进行三维粘性计算,给出了不同弯曲程度的计算结果,比较了进口中间叶高处具有1.5 mm正弯和反弯叶形叶片压力面和吸力面上的熵分布.计算结果表明,进口正弯叶轮绝热效率略高于进口反弯叶轮的绝热效率;出口正弯和出口反弯叶轮绝热效率基本相同;叶形弯曲对小型离心压气机叶轮效率影响很小.     

多相泵叶轮准三维可控速度矩设计

以速度矩作为控制参数,推导多相泵叶轮中均匀流模型的准三维反问题计算公式,并给出叶轮叶片形状的反问题设计方法.通过选择合适的速度矩分布,进行叶轮的子午面反问题计算,对多相泵叶轮的叶片形状进行初步没计.对计算结果的分析表明,利用准三维方法进行多相泵叶轮的可控速度矩设计是经济且有效的.     

基于物理约束的玉米叶片建模方法

植物真实感建模与仿真不仅是现代农业科学与植物学领域面临的难点问题之一,也是计算机应用与虚拟现实技术领域的研究热点.而玉米是我国乃至世界范围内重要粮食作物,玉米叶片建模是现代农业虚拟植物领域中面临的重要问题.本文提出一种基于物理约束的玉米叶片三维建模方法,主要针对玉米叶片褶皱特征,建立基于质点弹簧系统的物理约束模型,并提取特征参数建立一种自适应物理约束机制,生成具有复杂形态的玉米叶片模型,并且通过一系列特征参数调控和特征点约束实现一种交互式玉米叶片建模机制,最后基于偏微分方程曲面建模方法构建真实感玉米叶片三维模型,并集成开发相应软件原型系统.结果表明,本文方法以一种自适应机制有效、高效生成具有一定真实感效果的玉米叶片模型,少量参数控制的建模方式使自动化生成大规模玉米三维群体模型成为可能,为虚拟植物领域建模应用提供可用的技术参考和方法工具.     

基于八叉树三维农作物叶片的体建模算法

为了实现在三维虚拟环境中对农作物叶片的形态建模与精确控制,根据体图形学理论与八叉树的特点,提出了一种针对三维农作物叶片的八叉树体建模算法,由于叶片模型内部实体属性变化的不均匀性,并且三维叶片纹理、叶片旋转角度、颜色密度分布等复杂属性的变化不规则性,算法选取不规则的八叉树体元作为形态建模的主元素,进而更加充分的表示叶片内部的细节,整体形态建模效果表明,文中算法能够充分表达农作物叶片的内部属性,建模效果真实感强,并且易于控制。     

低比转速离心叶轮圆柱形叶片的三维建模方法

针对离心叶轮圆柱形叶片几何形状一般比较复杂,三维建模具有一定难度的情况,基于离心叶轮圆柱形叶片结构的特点,采用数学分析法求解三维圆柱形叶片表面控制节点的位置,为快速准确地建立叶片三维模型提供理论依据.通过实例详细介绍圆柱形叶片三维建模的过程和方法,针对传统水力设计中无法考察叶片进口边安放角的分布规律及光滑性,提出叶片进口边建模及修正其形态的方法.依据该方法可以直观考察和修正叶片进口形态,改进和提升叶轮水力和空化性能,也为叶轮流场的CFD模拟和数控加工奠定理论基础.     

超低比转速高速离心泵复合叶轮短叶片的几何造型方法

离心泵叶片三维造型常用的平面翼型修型法计算工作量大,操作复杂.为此针对超低比转速高速离心泵复合叶轮短叶片的三维造型,提出一种基于Pro/E软件采用空间圆柱坐标系进行叶片三维实体造型,综合考虑短叶片进口位置、周向偏置度、偏转角等影响短叶片翼型设计的主要因素,在长叶片翼型基础上,进行适当修型,从而得到短叶片翼型.该方法操作简单,造型准确,便于叶片修型;生成的短叶片平顺光滑,可更准确地实现设计意图,为提高离心泵复合叶轮内部流动CFD数值模拟精度及其性能预测奠定可靠的基础.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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