短路电流计算在当前电力设计中采用的主要方法

短路电力计算是当前电力设计中必须进行的一项步骤,无论是选择载流导体还是应用电气设备,这都是必不可少的。而之前在短路电流的计算上大多使用手工方式进行,因而针对此提出了新的计算法,即应用计算机进行计算,这一段发采用了导纳矩阵法,经过推导和换算最终得到了相应的曲线模型,从而代替了人工方式,实现短路电流的自动求解,算法简便可靠性高。依照相关算法进行程序的编写可以对大规模的电力网络三相短路电流予以计算。并且在程序中采用插值法进行计算得出的结果同运算曲线基本一致。若是在小型电力网络系统的短路电流的计算中,使用手工方式需要两天,而计算机计算时间仅仅为10分钟。     

基于三相短路电流的计算机算法

根据三相短路网络计算模型,利用节点阻抗矩阵的计算原理,形成网络的节点阻抗矩阵,从而给出一种基于三相短路电流的节点阻抗矩阵计算短路电流的计算机流程图,并举例说明应用。     

双绕组电力变压器梯形网络频率响应的矩阵算法

针对双绕组电力变压器梯形网络的仿真软件建模的非完整性以及现存等效电路频率响应算法多变量求解的低效率,围绕一种电力变压器绕组高频等效模型频率响应的矩阵计算方法开展研究,基于等效电路的拓扑结构,给出了利用阻抗支路矩阵和导纳支路矩阵来完整表示该等效电路的方法。其次,通过矩阵运算,推导了阻抗支路电流、导纳支路电流以及节点电压列向量之间的关系,进而求解节点电压列向量,获得等效电路的频率响应。最后,将矩阵算法与基于电路仿真得到的频响曲线进行比较,结果表明,曲线相关系数较大,吻合程度很高,对于不含高幅值谐振峰(-500dB以上)的曲线,相关系数为10,即两者完全吻合,而矩阵算法的计算耗时少于电路仿真运算。上述分析表明,在保证仿真模型完整性和精确性的同时,提出的矩阵算法由于仅有两次矩阵取逆运算且求取的未知量较少,具有良好的计算效率及计算精度。     

矿山供用电系统短路电流实用计算机算法

本文提出的实用算法对复杂供用电网络自动形成节点导纳矩阵並通过消去运算求取短路点与电源之间的转移导纳;对开式网络简单地利用串联阻抗累加直接求出转移阻抗。並能自动查短路电流计算曲线,使短路计算全过程均由计算机完成。     

变结构网络故障分块算法中线路上短路的计算

将线路上短路点的电流向该线路端点等值转移，并综合应用线性网络特性、修正节点电流源与短路列阻抗元的方法，导出了大型电力系统短路故障分块算法中互感或无互感线路上任意点故障计算的通用模型和算法，适用于定结构及变结构系统。     

计及短路电流限额的网架优化模型及启发式算法

针对电网短路电流越限的问题,提出了计及短路电流限额约束的网架优化模型。采用0-1变量描述可变的网架拓扑,构建离散最优潮流模型。引入描述短路电流的非线性约束条件,将其考虑到离散最优潮流模型当中,使之计及短路电流限额约束。基于阻抗灵敏度和断线近似成本变化,提出求解所提模型的启发式算法,该算法以阻抗灵敏度最大的线路逐次替换断线近似成本增加最大的线路为思想,迭代求解所提模型。采用IEEE118系统作为算例对所提模型的实用性和有效性进行验证,结果表明:相比于商用优化求解器,所提算法在保证求解精度的同时具有较高的求解效率;网架优化能够在限制短路电流的同时降低电力系统运行成本。     

变结构电力系统短路故障分块计算的新方法

提出了用分块法仿真计算变结构大型电力系统短路故障的新模型和新算法，该法完全避免了对原网络节点阻抗（或导纳）矩阵的修正计算和各型故障计算中的重复计算。     

带负权最短路问题前趋法的改进

针对在带负权的有向网络中求最短路的前趋法的不足,结合动态规划思想从提高算法效率方面对其进行了改进,并提出了一种新算法.新算法通过引入变量记录当前节点到宿节点的最短路权,避免了前趋法中比较多条前趋路时反复计算最短路的冗余运算,同时弥补了动态规划不能直接求解带回路的有向网络最短路的缺陷,是一种计算带负权最短路问题的简便方法.该算法对非负权网络中的最短路问题同样有效.最后仿真结果和算例表明了新算法的有效性.     

电力系统任意复杂故障的计算方法研究

电力系统的发展对复杂故障的计算效率的要求越来越高.提出了一种基于多端口戴维南等值理论和叠加定理进行复杂故障计算的方法.将故障后的网络,划分成无故障部分和故障部分,分别对两部分网络进行补偿,并分别求出其对故障边界节点的多端口戴维南等值参数和诺顿等值参数,根据边界条件可求得两部分网络在边界处的端口电流.由端口电流则可将不对称的网络以电流源等值,根据叠加原理,可求得故障后网络各节点的电压.将上述算法思想编程计算得到的结果正确,且对各种复杂故障的求解,无需重新形成各序网节点阻抗阵.该处理方法同样适用于考虑网络操作对故障计算的影响.     

谈电厂并网变电所短路电流的计算

分析了电厂并网变电所短路电流的计算,介绍了用运算曲线法计算短路电流的方法。     

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.     

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.     

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.     

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.     

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.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

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。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.