考虑输电线路阻抗频率特性的高精度行波定位方法

从理论上推导出了考虑集肤效应的三相输电线路的正序阻抗和零序阻抗随频率变化的公式,分析了输电线路的阻抗频率特性及输电线路阻抗的依频特性对行波定位和保护的影响,并提出了应用小波包分析对行波信号进行分解,分频段进行行波速度的计算并记录行波波头到达的时间来进行故障定位的方法.通过ATP仿真分析表明,该故障定位方法能有效消除行波色散特性的影响,提高故障定位的精度.     

输电线路阻抗测距法和单端行波测距法的对比仿真分析

简述了输电线路的故障测距算法,着重论述了阻抗法和单端行波法的测距原理．在ATPDraw环境下,建立了输电线路仿真模型,并在不同参数条件下和线路发生不同故障类型时,分别用阻抗法和单端行波法对线路故障距离进行仿真计算．仿真计算结果表明,单端行波法具有更高的测量精度和可靠性．     

一种不受波速影响的单端行波故障测距新算法

采用提升小波变换和奇异性检测原理对电流行波到达母线测量端的时刻进行检测.首先利用初始行波、故障点反射波及对端母线反射波计算出行波波速,然后在常规单端行波故障测距算法的基础上,通过消去行波波速参数,提出一种不受行波波速影响的单端行波故障测距新算法.PSCAD和MATLAB仿真验证结果证明该方法具有很高的测距精度和实用性.     

牵引网故障测距

牵引供电系统是电气化铁路的基础,但牵引供电系统由于受各种因素的影响,容易出现故障导致断电,所以牵引网的故障测距,有助于及时修复故障线路．减轻维护人员体力劳动．对铁路安全经济运营具有十分重要的意义。该文介绍分析牵引网故障测距中的主要方法及特点,为牵引网供电系统的安全运行和维护提供帮助。     

基于分布参数的直接供电铁道牵引网故障测距

电气化铁道牵引供电系统是电气化铁路的基础。由于电气化铁道牵引网中机车启动频繁,线路存在分布电容以及故障时过渡电阻等因素,因而传统的基于电抗法的测距算法精度不高。本文提出的基于分布参数的直接供电牵引网测距算法,受过渡电阻的影响小,具有较高的测距精度和较强的鲁棒性。     

基于DSP的输电线短路故障测距系统设计

考虑到目前电缆行波故障测距系统中存在精度低的问题,以提高故障定位的速度和精度为目标,设计了一种输电线缆短路故障测距系统。该测距系统以数字信号处理器(DSP)为核心控制器,能够准确地对故障行波信号进行实时采集和转换,进而实现线缆故障的准确定位和及时排除。仿真实验结果表明:所设计系统检测速度快、测距精度高。     

不受波速影响的输电线路双端行波故障测距算法

提出了一种双端行波故障测距新方法,该方法利用故障初始行波和两种反射行波到达线路两端的时刻来进行故障定位,有效降低了行波波速的不确定和输电线路长度差异对定位结果的不利影响,提高了定位精度.利用EMTP进行了仿真计算,仿真结果证明了其准确性.     

基于行波差动电流的输电线路接地故障测距

行波测距的准确性受多个因素影响.为此,分析了行波差动电流的不平衡输出,定义了经不平衡电流补偿的行波差流,推导了线路内部故障时该差流的表达式.由于行波在零模和线模上的传播速度不同,两种模量的行波差流也不相同,其幅值比和相角差与故障点位置相关,据此提出了基于行波差动电流的接地故障测距原理.该原理提取行波差动电流的工频分量进行测距,无需提取行波波头,不受线路对行波衰减及波速不确定等因素的影响,PSCAD仿真表明,测距误差很小,测距结果准确可靠.     

直供方式牵引网故障行波测距技术

目前应用于电气化铁道的故障测距以阻抗法为主,由于牵引网的复杂结构致使阻抗法的运用受到了诸多限制.利用双端行波法可以准确测量牵引网故障距离,避免了阻抗测距法的弊端.试运行结果表明,该方法测距误差缩小.     

基于小波分析的T型线路行波故障测距方法

在双端行波测距方法的基础上利用小波变换来提取到达T型线路各端母线侧电流行波的模极大值,并对电流故障行波在尺度1~3的小波模极大值的到达时间进行准确标定,获得故障电流初始行波到达的准确时间来进行测距.用PSCAD/EMTDC仿真软件对该方法进行了仿真分析.结果表明,该方法可准确判断T型线路的故障分支.     

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.     

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.     

A computer generator for randomly layered structures

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

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.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

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.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to