激波在air/SF_6气体界面上非定常折射的数值研究

本文数值研究了平面激波在air/SF_6凹形(凸形)界面上的非定常折射,着重关注入射角变化带来的波系结构变化.数值程序利用有限差分法离散可压缩多组分欧拉方程,采用双通量算法成功克服了物质界面附近由于比热比不同导致的数值振荡问题,并将该算法与高阶WENO以及三阶Runge-Kutta耦合,使得程序具有较高的时空分辨率.结果表明,相比于准定常折射,平面激波在凹形(凸形)界面上传播时由于入射角的连续变化会出现波系结构的转变现象.随着入射角由大变小,平面激波在凹形界面上依次出现了前曲折射、规则反射折射以及过渡规则折射.相比准定常折射,没有出现Mach反射折射,但出现新的折射波系——过渡规则折射,由流场的迟滞效应导致.随着入射角由小变大,平面激波在凸形界面上依次出现规则反射折射以及Mach反射折射.相比准定常折射,没有出现前曲折射,但Mach折射出现的角度区域推迟且范围变大.研究表明,流场的非定常性对激波折射波系具有重要影响.     

景物空间的镜面反射(折射)现象绘制方法

为了提高视点相关的镜面反射(折射)现象的绘制速度和绘制质量,提出了计算任意曲面反射(折射)光学映射虚物体的方法。该方法根据实际物体在反射/折射体中所成的像创建虚物体,利用图形加速硬件像处理实际三维物体一样绘制这些虚物体,将得到的关于虚物体的图像与实际反射/折射体的图像相混合,就可以得到有反射/折射效果的最终图像。实验结果表明:该方法可以克服光线跟踪方法当空间点采样不足时所带来的走样问题。该方法利用图形硬件加速,提高了绘制的速度。     

单球面反射和折射成像规律的分析

单球面成像是光学成像系统的基础,文章依据单球面成像的基本公式,对处于不同位置的物体经单球面折射和反射后所成像的性质进行了分析,对其规律进行了总结。     

光在扁旋转椭球面上的成像研究

通过研究光在扁旋转椭球面上的折射和反射,推导出近轴条件下的成像公式,完善了旋转二次曲面的成像化式。     

粗糙锐反射面水平运动时产生的多普勒频移

<正> 用火箭探测到E_s的资料如图1所示:从图中可以看出E_s层有很大的dN/dh,E_s层的厚度在0.5—2K_M之间,而电子密度的最大值往往很高.所以从E_s层的反射可能主要是由于折射指数梯度大造成的而不象缓变电离层中μ=0处反射回来(垂直入射).我们近似地认为E_s是粗糙锐边界的反射面.反射面处折射指数为1.当电波频率比较高时,D层对电波的折射指数可认为是1.由于电波反射处折射指数不为零,所以,反射面在传播方向发生运动时将会产生多普勒频移效应,有可能利用多普勒测量来研究E_s层反射面的扰     

浅析光程的等价替换方式

利用费马原理,以凹透镜为例推导薄透镜的成像公式,发现在成虚像的情况下,光程可以用一种较简单的等价方式替代.球面反射、球面折射成像都可以看作是薄透镜成像的特例,因此本文对薄透镜成像公式的推导和分析具有一定的实用性和通用性.     

旋转曲面的成像公式

根据费马原理,研究了光在旋转曲面上的折射和反射成像,给出了光焦度和焦距的定义以及物像公式．     

MOCVD法制备云母珠光颜料光学性能及微结构研究

在流化床反应器中以碳基铁为物源，用金属有机化学气相沉积(MOCVD)法制备了云母珠光颜料．由颜料的SEM和EPMA图分析表明：云母微粒为片状结构，平均粒径为50μm；沉积在云母表面上的是均匀分布的30-nm的透明氧化铁微粒，这种结构对光能产生多重散射、折射、反射，从而呈现出绚丽的珠光光泽．     

《墨经》中的光学思想

《墨经》中有八条关于光学的命题,这八条中的前五条记述了影的生成及有关规律.特别是其中的第三条描述了针孔成像实验,并用射箭的飞行来比喻光的直线传播.这是世界上最早的针孔成像实验,也是对光的直线传播特性的最早认识.八条中的后三条叙述了反射(平面、凹面、凸面)镜成像现象.其思想非常丰富与深刻.     

秘境寻踪

中秋节早晨,爸爸兴冲冲地对我说：＂咱们今天去一个神秘的地方,怎么样？＂我虽然有点丈二和尚摸不着头脑,但还是高兴地接受了爸爸的提议。来到目的地,我们经过层层安检,走进了一个科学秘境。最先映入我眼帘的是由很多平面镜组成的＂镜子迷宫＂。走进＂镜子迷宫＂,我在镜子里看到许多一模一样的影像,找不到出口,甚至不知道如何前进或后退,稍不留神,还会撞到镜子。解说员说：＂‘镜子迷宫’巧妙利用了光的直线传播原理和平面镜成像原理。由于光的反射,走进这里的人容易产生视错觉,仿佛进了迷宫。＂     

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