一种求解一维对流扩散方程的高精度紧致隐式差分格式

提出了数值求解一维非定常对流扩散方程的一种两层四阶紧致隐式差分格式,其截断误差为O（τ^2＋h^4）.采用von Neumann方法证明了格式是无条件稳定的,并且由于每一时间层上只用到了3个网格点,所以可直接采用追赶法求解差分方程.数值实验结果验证了该方法的精确性和可靠性.     

三维波动方程的隐式多重网格方法

提出了数值求解三维波动方程的两种精度分别为O(τ^2 h^2)和O(τ h^4)的三层紧致隐格式,利用Fourier分析方法证明了格式均是无条件稳定的．并在此基础上提出了求解该问题的多重网格算法,从而克服了传统迭代法在求解隐格式时收敛速度慢的缺陷,大大加快了迭代收敛速度,提高了求解效率．数值实验结果验证了方法的精确性和可靠性．     

求解一维抛物型方程的一种高精度半显式差分方法

利用加权平均思想和二阶微商的四阶紧致差分逼近公式,构造了一种求解一维抛物型方程的高精度半显式差分格式,其截断误差为O(τ2 h4).通过Fourier分析方法证明了该格式是无条件稳定的.通过数值算例验证了本文方法的精确性和可靠性.     

求解二维扩散方程的加权平均隐式多重网格方法

提出了数值求解二维扩散方程两种精度分别为O(τ^2 h^2)和O(τ^2 h^4)的无条件稳定的加权平均隐格式，并采用多重网格方法进行求解，从而克服了传统迭代法在求解隐格式时收敛速度慢的缺陷，提高了求解效率．数值实验验证了该方法的精确性和可靠性．     

求解波动方程的高精度紧致隐式差分方法

基于二阶微商的二阶中心差商和四阶紧致差商逼近公式及其加权平均思想,推导出了数值求解一维波动方程的2种精度分别为O（x^2＋h^4）和O（x^4＋h^4）的三层隐式紧致差分格式,以夏与之相匹配的第一个时间步的同阶离散格式,并采用Fourier方法分析了格式的稳定性．由于每一时间层上最多只用到了3个网格点,所以可采用追赶法直接求解差分方程．数值实验结果验证了所得方法的精确性和可靠性．     

四阶抛物型方程的三层恒稳差分格式

为了解四阶抛物型方程эu/эt э^4u/эχ^4=0,建立两类新的、具三对角线型系数矩阵的三层隐式差分格式．其局部截断误差阶均为O(τ^2 h^2 (τ/h)^2),且都是绝对稳定的,并可用追赶法容易地求解．数值例子表明这些格式是有效的．     

解双抛物型方程的两类恒稳差分格式

提出解双抛物型方程的两类新的具三对角线型系数矩阵的三层隐式差分格式，其局部截断误差阶分别为O（r^2 h^2 τ/h)及O（τ^2 h^2 (τ/h)^2)．它们都是绝对稳定的且可用追赶法求解，数值例子表明这些格式是有效的，理论分析是正确的。     

解Schroedinger方程的一个新的高精度差分格式

本文对解Schroedinger方程δu/δt=iδ^2u/δx^2．构造了—个绝对稳定的三层隐式差分格式，格式的截断误差阶为O(τ^3 τ^2h^2 h^4).     

求解扩散方程的二级四阶隐式Runge-Kutta方法

对空间变量应用中心差分格式和紧致差分格式离散,时间变量采用二级四阶Runge-Kutta方法,构造求解扩散方程的精度为O(τ4+h2)和O(τ4+h4)的两种绝对稳定的隐式差分格式,讨论稳定性,并将数值试验结果与CrankNicholson格式进行比较,数值结果表明该方法是求解扩散方程的有效数值计算方法之一.     

求解一类非线性偏微分方程的高精度紧致差分方法

针对一类非线性偏微分方程,提出了一种新的高精度紧致差分方法.首先对内部网格节点处的空间一阶和二阶导数项采用四阶精度的Padé紧致差分格式进行离散,然后对时间导数项采用泰勒级数展开并使用截断误差余项修正法进行离散,最终得到了求解该非线性方程的一种三层隐式高精度紧致差分格式,其截断误差为O(τ2+τh2+h4),即当τ=O(h2)时,该格式在空间上具有四阶精度.最后通过对广义Burgers-Fisher方程和广义Burgers-Huxley方程的数值求解,验证了本文方法的精确性和可靠性.     

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