解双曲方程的一种高精度加权差分格式

利用一阶微商的四阶精度紧致差分逼近公式,给出了解双曲方程精度为o[(1-2θ△t,△t2+△x4)]的一种新的加权差分格式,并通过Fourier方法讨论格式的稳定性,证明了当0≤θ≤1/2时,格式是无条件稳定的;当1/2≤θ≤1时,格式是不稳定的,最后通过数值试验说明了这种方法的有效性.     

二维扩散反应方程的三次样条高精度加权隐式差分格式及其多重网格方法

利用二阶微商的三次样条四阶紧致差分逼近公式,推导出两种数值求解二维扩散反应方程的两层9点加权隐式紧致差分格式.当θ=1/2时,该格式在时间和空间方向上分别达到二阶和四阶精度.通过Fourier方法讨论知,当1/2≤θ≤1时,格式是无条件稳定的;当0≤θ<1/2时,格式是条件稳定的.为了克服传统迭代法在求解隐格式方面的困难,差分方程采用多重网格方法进行求解并将本文格式的结果与P-R格式及C-N格式下的结果进行比较.数值实验结果验证本文方法的精确性和可靠性及多重网格方法的效率.     

扩散方程的高精度加权差分格式

基于已发展的二阶微商三次样条四阶逼近公式,提出了数值求解含源汇项扩散方程的二层三点且在空间方向上达到四阶精度的加权差分格式．通过Ｆｏｕｒｉｅｒ方法讨论了文中格式的稳定性．证明了当１／２θ１时,格式是无条件稳定的,而当０θ＜１／２时,只有０＜ｒ１／［３（１－２θ）］,格式是稳定的．其中θ是权参量,ｒ＝Ｄτ／ｈ２为Ｆｏｕｒｉｅｒ数,Ｄ为扩散系数,而τ,ｈ分别为时间和空间网格长度     

解二维抛物型方程的恒稳高精度格式

建立了解二维抛物型方程的一族含参数的绝对稳定的高精度的差分格式,进而,在特殊情况（θ＝０,ｒ＝１／６）下,得到显式差分格式ω＾ｎ＋１＝（１＋１／３６□＋１／９◇）ω＾ｎ,这些格式对任意选取的参数θ≤１／６都是绝对稳定的。且当０≤θ≤ｍｉｎ（１／６,１／２－１／１２ｒ）时,其收敛阶为Ｏ（（Δｔ）＾２）。     

二维抛物型方程的高精度显式差分格式

用待定系数法构造了求解二维抛物型方程的高精度分支稳定的显式差分格式,格式的截断误差达到O(Δt2+Δx4).证明了当1/12≤r≤1/6时,差分格式是稳定的.通过数值试验比较了差分格式的解和精确解,说明了差分格式的有效性.     

二维抛物型方程的一个新的高精度显式差分格式

用待定系数法构造了求解二维抛物型方程的高精度分支稳定的显式差分格式.格式的截断误差达到O(Δt2+Δx4).证明了当1/15≤r≤1/9时,差分格式是稳定的.通过数值试验,比较了差分格式的解和精确解的区别,说明了差分格式的有效性.     

解抛物型方程的一族六点隐式差分格式

提出了求解一维抛物型方程的一族两层六点隐式格式.格式的截断误差为O(τ2+h4).利用Fourier方法证明了差分格式当1/2≤θ≤1时,格式绝对稳定;当0≤θ1/2时,只有r≤1/6(1-2θ),格式才是稳定的.数值试验表明,该族格式是有效的,且理论分析与实际计算相吻合.     

解抛物型方程的一个高精度显式差分格式

引入耗散项的方法,构造一个条件稳定的显格式,其稳定性条件为r≤1/2, 截断误差可达到O(τ2+h4+τ2/h2).当τ=O(h)时,此格式可逼近精度,特别当τ=O(h2)时,格式达到二阶精度.数值例子表明,所建立的差分格式是有效的.     

一族绝对稳定的高精度差分格式

建立了解三维抛物型方程的一族含参数的绝对稳定的高精度差分格式．李荣华等的结果可以看作两层差分格式的特例．进而，在特殊情况（θ＝０，ｒ＝１／６）下，我们得到显式差分格式．我们证明了这些格式对任意选取的参数θ≤１／３都是绝对稳定的且其截断误差阶为０（Δｔ）２＋Δｔ（Δｘ）２＋（Δｘ）４）＝０（（Δｔ）２）．     

一类二阶中立型时滞微分方程的振动准则

本文主要利用H（ t,s）型函数和广义Riccati变换技巧,建立二阶中立型时滞拟线性微分方程[r（t）｜x′（t）｜γ－1x′（t）]′＋q0（t）｜y（t －σ）｜γ－1y（t －σ）＋q1（t）｜y（t －σ1）｜α－1y（t －σ1）＋q2（t）｜y（t －σ2）｜β－1y（t －σ2）＝0．其中x（t）＝y（t）＋p（t）y（t－τ）,在0≤p（t）≤1的新的振动准则．     

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