车载雨刮电机电磁辐射干扰仿真模型

提出了基于仿真软件HFSS的车载雨刮电机辐射干扰仿真模型。分析了雨刮电机产生电磁辐射的原理,进而建立了车载雨刮电机辐射模型。在HFSS中将车体结构分解成若干简单模块,各模块的关键点坐标从导入的汽车CAD模型中提取,并分别对其进行网格剖分,然后组合成车体的有限元网格模型;利用自适应网格剖技术,得到满足精度要求的仿真结果;仿真结果与实测值变化趋势一致,峰值频点吻合,表明仿真模型是正确的,可用于雨刮电机在整车上的辐射干扰预测。研究方法有较高的通用性,对汽车其它电器部件或子系统的整车辐射仿真分析具有很好的参考价值。     

FDTD结合XFDTD研究TEM喇叭天线

针对需要研究的超宽带TEM喇叭天线,先应用XFDTD软件进行建模和剖分,然后使用Fortran语言读取包含网格剖分信息的文件,完成计算模型的初始化,再采用Fortran语言实现时域有限差分法算法,对天线模型在时域进行迭代运算,完成天线的仿真,并给出天线指定点的电磁场信息.与XFDTD软件相比,编写的FDTD程序具有计算...     

参数曲面三角网格生成的改进波前法

为了消除基于波前法的有限元三角网格算法在参数曲面网格剖分过程中单元形状映射畸变的问题,结合直接法和映射法各自的优点,提出了一种新的三角网格生成算法,即:对当前节点进行剖分,并在三维空间直接产生新节点且进行节点的合法性判断,再将物理网格映射到参数空间形成参数域网格;对相邻波前段形成的角度进行剖分,依据角度大小生成个数不等的单元,通过优先剖分锐角节点使波前段始终构成钝角多边形。经剖分算例表明:所提算法减少了节点合法性判断内容和判断次数,避免了重复剖分,取消了剖分结束算法,提高了网格剖分效率,生成了高质量的三角网格;仅需对网格排列情况的直观分析,便可定性判断三维曲面的空间曲率变化。该算法对叶片加工中振动分析、精密加工研究等具有指导意义。     

基于超单元形函数坐标变换的有限元网格剖分和冷却水管网格二次剖分方法

当用Ansys的前处理模块进行网格剖分建模时,映射网格剖分受到许多条件限制而自由网格剖分不容易控制,往往不能按照自己的意愿进行网格剖分,并且剖分出来的网格不规则.针对这一问题,采用超单元网格剖分的建模思想,通过基于形函数的坐标变换,用Fortran语言编程实现网格剖分.用该方法进行网格剖分,不但易于控制网格单元形状大小,而且便于修改网格.并且,用超单元的高次形函数进行坐标变换,可以很好地对曲边曲面形状的结构模型进行网格剖分.大体积混凝土的温控防裂一直是人们非常关注的问题,而冷却水管技术是一种有效可行的温控防裂技术.在超单元的基础上实现了添加冷却水管的网格二次剖分方法,使大体积混凝土的水管冷却仿真计算得以实现.     

基于渐变网格剖分方法的再生混凝土细观数值试验

细观上,把混凝土看成是由骨料、砂浆以及它们之间的界面等组成的多相复合材料,对于光滑的球形骨料,预先进行镶边处理,并在此基础上首先对封闭域形成表面单元,然后采用拓扑映射的渐变网格剖分方法往里拓扑成四面体单元网格,按同样方法依次生成界面单元网格和砂浆单元网格,删除表面单元和多余节点后形成混凝土试件的三维细观有限元网格模型。采用该细观有限元模型进行再生混凝土的单轴压缩数值破坏试验,结果表明,该网格模型在单机环境下很快的就能完成数值试验,与以往的自由网格剖分法和映射网格剖分法生成的细观有限元模型相比不仅在计算规模上大大缩小了,而且模拟的破坏形态与实际非常吻合,精度也很高。     

基于离散Kirchhoff理论的多边形样条薄板单元

在有限元方法中,采用多边形单元可以有效地模拟材料的力学性能,又使得网格剖分变得灵活方便.此外,允许退化情形的多边形单元可以处理出现悬节点的奇异网格.但目前对多边形薄板单元的研究却不多.多边形单元的研究难点在于插值基函数的构造.本文采用样条和基于三角形面积坐标的B网方法,将多边形进行三角剖分,通过适当选取连续性条件消去内部节点自由度,构造允许1-irregular退化的多边形样条插值基函数,再结合离散Kirchhoff理论得到多边形薄板弯曲单元,记为DKPS单元.该单元的插值自由度为各个顶点处的扰度和两个转角,并对直角坐标具有二次完备性,可以处理凸多边形、凹多边形和退化的网格.而且,采用多项式B网方法,可以方便地进行单元刚度矩阵的计算,无需使用数值积分公式.数值实验显示该单元对畸变网格仍然能保持很好的计算精度,是一种高效的单元.     

基于三角形剖分的复杂GPR模型有限元法正演模拟

针对基于矩形网格剖分的时域有限差分法(FDTD)和有限单元法(FEM),对于物性参数分布复杂或几何特征不规则的模型适应性差的问题,从雷达波所满足的Maxwell方程出发,推导探地雷达(GPR)有限元波动方程,通过采用三角形网格剖分和线性插值基函数,在满足时间步长与空间网格差分稳定性前提下,应用Galerkin有限单元法求解GPR波波动方程;同时为消除FEM进行GPR正演模拟时来自截断边界处的超强反射,采用透射边界条件把GPR波在截断边界处的反射波透射出去,进而压制来自截断边界处的反射波。然后,编制GPR有限元正演模拟的Matlab程序。应用该程序分别对起伏分界面、"V"字形2个复杂地电模型进行FEM正演模拟,得到基于三角形网格剖分的FEM正演模拟GPR剖面图,并把该正演模拟剖面图与常规的基于矩形剖分的FEM正演模拟剖面图进行对比,结果表明:基于三角形剖分的FEM对于复杂GPR模型的物性参数分界面拟合更好,其模拟所得的正演剖面与实际模型更相符,具有更高的模拟精度,更有利于指导雷达剖面的数据解译。     

半挂汽车列车行驶稳定性问题研究

为探究汽车列车行驶过程中牵引车单元和半挂车单元的相互影响机理,通过整车行驶稳定性动力学分析建立了半挂汽车列车11自由度动力学模型,并利用Matlab对建立的模型进行了仿真分析;采用汽车列车实车行驶稳定性检测试验验证了整车动力学模型和数值仿真的正确性. 研究结果表明:路况良好时,两车辆单元侧向加速度与横摆角速度大小接近,半挂车运动响应略有滞后;汽车列车发生侧翻的可能性较大,而不易发生侧滑和折叠事故;车辆侧翻时,半挂车车轴首先提升,其次是牵引车后轴,牵引车前轴最后提升.     

有限元网格自动剖分方法及其在工程中的应用

介绍了一些特殊曲面的网格自动生成方法,从有限元网格的生成规律出发给出了三次样条曲线在网格划分中具体形成的方法。利用该方法建立了汽车车身有限元模型并进行了有限元网格剖分,以该汽车车身有限元网格剖分数据为基础对汽车车身进行了动力计算,给出了前几阶振动频率和振型。     

三维人体的点云获取与点云重建

针对三维人体重建中人体曲面复杂,点云庞大的问题,提出一种基于三维Voronoi图,并利用Delaunay三角剖分性质的Crust算法进行人体三维重建.采用三角测量原理计算三维坐标,散乱的点云构成Voronoi图,Delaunay三角剖分Voronoi图得到原始模型.利用Xjtuom三维面扫描仪测量人体点云,进而采集到了49幅不同角度和高度的图片,并用自带软件完成了配准.通过Matlab平台完成点云读取,点云精简和基于Crust算法的三维重建.实验表明,该算法可以保证曲面重建的拓扑正确性和收敛性.该三维重建系统能够实现人体庞大点云的三角剖分与人体复杂自由曲面的重建,并得到了360°无缝隙的人体重建模型.     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

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