凝点附近含蜡原油的粘弹性研究

使用控制应力流变仪,在原油凝点附近温度区域对大庆原油和胜利原油进行了线性粘弹性应力范围内的小振幅振荡剪切实验.以原油开始出现线性粘弹性应力区间的最高温度作为基准温度定义了相对温度,对粘弹性参数进行了分析对比.研究表明,大庆原油及胜利原油在各自凝点以上4 ℃时,均表现出明显的粘弹性特征,其损耗角分别为37.66°和76.55°.在相同的相对温度下,大庆原油的弹性特征明显好于胜利原油,大庆原油的粘弹性参数对温度的敏感性也明显好于胜利原油.两种原油粘弹性不同的主要原因是其胶质、沥青质含量和析蜡特性不同.凝点温度附近的原油流变性及其随温度的变化规律应该作为确定输油管道进站温度的重要依据,目前,仅以原油凝点作为确定进站温度的主要依据是不合理的.     

含蜡原油在凝点下的触变性研究

由于含蜡原油组分复杂、凝点高（20～30℃），其流变性质异常复杂．当原油温度逐渐降至凝点附近时，其流变性质表现出复杂的触变性．基于此对大庆原油在凝点下的触变性进行了实验研究．利用实验数据获得了不同温度下描述大庆原油初次裂降过程的R—G模型方程中的模型参数，对模型中的参数与温度的关系进行了曲线拟合，得到了各参数与温度的关系。计算结果与实验数据吻合良好．实验还发现原油降温速率对其触变性有着重要的影响，降温速率越大，屈服应力和平衡应力越高．     

含蜡原油低温粘弹性研究的现状与分析

我国盛产含蜡原油,在低温(凝点温度附近)条件下,含蜡原油具有一定的粘弹性。概述了国内外含蜡原油低温粘弹性研究的主要进展。含蜡原油粘弹性起因于其内部形成的蜡晶结构。振荡剪切实验方法最适合于含蜡原油的粘弹性测量。粘弹性与胶凝温度、胶凝强度、屈服应力和触变性等参数有关。含蜡原油经历的热历史、剪切历史以及析蜡特性是影响粘弹性的主要因素。分析了在含蜡原油低温粘弹性认识上和研究中存在的问题。建议进一步研究含蜡原油粘弹性与屈服应力、触变性的关系,在机理研究方面加大力度;通过研究粘弹性与热历史、剪切历史的关系,建立管道运行和停输期间含蜡原油胶凝特性的预测模型,以更加有效地指导管道的安全运行。     

含蜡原油低温粘弹性研究的现状与分析

我国盛产含蜡原油，在低温(凝点温度附近)条件下，含蜡原油具有一定的粘弹性。概述了国内外含蜡原油低温粘弹性研究的主要进展。含蜡原油粘弹性起因于其内部形成的蜡晶结构。振荡剪切实验方法最适合于含蜡原油的粘弹性测量。粘弹性与胶凝温度、胶凝强度、屈服应力和触变性等参数有关。含蜡原油经历的热历史、剪切历史以及析蜡特性是影响粘弹性的主要因素。分析了在含蜡原油低温粘弹性认识上和研究中存在的问题。建议进一步研究含蜡原油粘弹性与屈服应力、触变性的关系，在机理研究方面加大力度；通过研究粘弹性与热历史、剪切历史的关系。建立管道运行和停输期间含蜡原油胶凝特性的预测模型，以更加有效地指导管道的安全运行。     

大庆原油凝点温度附近屈服特性研究

为了研究停输后沿线管内原油的屈服应力分布,采用管输模拟的实验方法,研究了大庆原油在凝点温度附近的屈服特性.结果表明,大庆原油的屈服应力与动冷终温的关系曲线存在一拐点温度,此拐点温度为凝点以上2℃;当动冷终温一定时,原油的屈服应力与测量温度之间呈指数关系.通过对实验数据的综合分析,建立了屈服应力与动冷终温和测温的经验关系式,为铁大线管道停输后再启动过程的水力计算提供了基础数据.     

胶凝原油初始应力递增过程的力学模型

考虑胶凝原油具有蠕变与松弛特性,将Maxwell线性黏弹性体与幂律流体元件进行并联,得到机械比拟模型。在幂律流体元件应力项中引入与应变相关的损伤因子,Maxwell黏弹性体剪切应力项中引入完整性因子,得到胶凝原油初始应力递增阶段的描述公式。分别对大庆原油、南阳原油进行恒剪切速率试验测试,利用模型公式拟合初始应力递增阶段的试验数据,计算胶凝原油应力松弛过程。结果表明:拟合效果良好,模型参数不随剪切测试条件改变,能够反映胶凝原油的物性特征。该模型可以表述胶凝原油的松弛特性;应变幅值越大,结构损伤越明显,对应的剪切模量数值越小,符合胶凝原油的真实流变特性。     

胶凝原油的粘弹触变方程

粘弹性和触变性是胶凝原油重要的依时行为 ,能将胶凝原油的触变性和粘弹性统一起来的本构方程较为少见。利用机械比拟原理 ,建立了适用于胶凝原油的粘弹触变方程。分别对文献报道的以及旋转粘度计实验中获得的实验数据进行了拟合。结果表明 ,此方程能够较准确地描述恒剪切速率实验中胶凝原油的应力裂降过程 ,粘弹-触变方程中的参数可以反映出胶凝原油的相关特性     

胶凝原油的粘弹-触变方程

粘弹性和触变性是胶凝原油重要的依时行为,能将胶凝原油的触变性和粘弹性统一起来的本构方程较为少见。利用机械比拟原理,建立了适用于胶凝原油的粘弹-触变方程。分别对文献报道的以及旋转粘度计实验中获得的实验数据进行了拟合。结果表明,此方程能够较准确地描述恒剪切速率实验中胶凝原油的应力裂降过程,粘弹-触变方程中的参数可以反映出胶凝原油的相关特性。     

胶凝大庆原油不同加载时间下的屈服特性

为得到胶凝大庆原油的屈服过程与加载时间之问的关系,利用Haake RS-150控制应力流变仪通过恒剪切应力、剪切应力匀速增加和阶跃式增加3种不同的加载方式对其屈服过程进行了实验。研究发现：胶凝大庆原油的屈服过程与加载时间存在密切关系,屈服是变形随时间积累的结果;加载过程中各水平的应力作用时间延长,所得到的胶凝原油屈服应力下降,但屈服所需的时间延长,即应力值与作用时间相互弥补,在一定范围内小应力长加载时间和大应力短加载时间都能造成胶凝原油屈服;对剪切应力阶跃式加载而言,屈服应力随每阶段持续作用时间（单阶作用时间）的增加呈指数规律下降,屈服时间随单阶作用时间增加在双对数坐标中呈线性增加。     

移动荷载下钢桥面铺装表面拉应力粘弹性分析

正交异性钢桥面铺装体系的受力复杂,铺装表面承受较大的弯拉应力。沥青铺装层具有明显的粘弹性特征,其应力应变与时间、温度的关系密切。钢桥面铺装使用的荷载与温度条件相对恶劣,因此采用粘弹性材料模型,利用试验数据计算得到的材料计算参数,对钢桥面沥青铺装表面的拉应力进行了粘弹性有限元计算分析,相关结论供铺装设计进行参考。     

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