窄基角钢输电塔风载体型系数数值模拟

为研究基于计算流体动力学(computational fluid dynamics,CFD)数值模拟技术的窄基角钢输电塔整体建模及风载体型系数的合理取值问题,文章利用UG和GAMBIT软件建立了输电塔模型,利用Fluent软件进行了不同风向角下输电塔风载体型系数的计算,讨论了风速、风向对风载体型系数的影响,并与规范值进行了比较。研究发现,参考风速对风载体型系数影响很小;纵向及横向风载体型系数随风向角的变化均先增大后减小,分别在22.5°、67.5°达到最大值;模拟得到的输电塔各段风载体型系数比规范计算结果大20%以上,特别是塔腿和横担部分与规范相差更大。     

特高压长悬臂输电塔结构风振扭转响应

在分析±1 100 kV特高压长悬臂输电塔的风振扭转响应机制的基础上,通过有限元动力时程计算考察扭转效应对结构内力的影响。首先,计算特高压长悬臂输电塔结构横担部位的风振系数;其次,根据横担的位移时程结果明确输电塔结构的风振扭转效应;最后,定义等效扭转风振系数,计算脉动风作用下的附加扭转荷载,分析风向角和长悬臂输电塔横担总长度对结构扭转效应的影响。研究结果表明:在风荷载动力时程的作用下,长悬臂输电塔结构会产生约0.01 rad整体扭转,考虑附加扭转工况可以提高输电塔主材和斜材的设计可靠度,提高程度从高到低依次为塔身斜材、横担斜材、横担主材和塔身主材;应力包络程度从74.4%提升到93.6%,且对所有主材和斜材,考虑扭转荷载的静力计算结果对动力时程计算结果的包络程度均在90%以上;不同风向角时,输电塔结构的扭转效应和横担风荷载Y方向的分配系数呈正线性关系,其中0°风对应的等效扭转风振系数最大,达到0.75,而90°风对应的等效扭转风振系数为0。随着输电塔结构的横担总长度减小,结构的扭转效应也减小,0°风对应等效扭转风振系数先减小后稳定在0.55附近,且拐点与结构的扭转振型的阶次有关。当扭转阵型为低阶阵型时,长悬臂输电塔结构的风振扭转效应明显。     

特高压输电塔气弹模型风洞试验研究

为进一步了解特高压输电塔风振响应的特点,以正在建设的淮南-上海1000kV特高压线路中的一基双回路直线塔为原型,采用离散刚度法制作了输电塔气弹模型,进行了输电塔在紊流场中不同风速、不同风攻角下的气弹模型风洞试验.试验结果表明:输电塔模型的响应随风速的增大而增大;位移响应受风攻角的影响比较明显,在15°风时位移响应最大;各试验工况下,输电塔模型横风向的振动比较显著,X向和Y向的加速度响应处于同一量级且数值比较接近;Y向的加速度响应在0°风时最大,X向的加速度响应在90°风时最大,但任何工况下,输电塔X向的加速度响应均大于Y向的加速度响应.     

输电塔线体系动力特性及风振响应分析

基于110 kV高压输电塔项目,建立了输电塔线体系有限元模型,并验证了输电线有限元模型的准确性.对单塔及塔线体系的动力特性进行分析,分析表明,塔线体系平面外振动耦合效应大于平面内.以谐波叠加法对输电塔线体系风载荷时程进行了数值模拟,对单塔和塔线体系的风振响应进行了时域分析.结果表明,输电塔和输电线风振响应均以一阶振型为主.塔线体系塔顶位移响应均方根值在0°风向角下是单塔的1. 73倍,而90°风向角情况下是单塔的4. 95倍.90°风向角情况下塔线体系塔顶位移背景响应分量增加较大,塔线耦合效应大于0°风向角情况.输电塔和输电线的平面内耦合效应通过输电线端部动张力差实现.输电塔塔身第2层主材所受应力大于其他各层,是倒塌破坏的危险位置.     

半导体少长针消雷器风荷载数值研究

使用FLUENT软件求解定常不可压缩流动的RANS方程和标准k-ε湍流模型，数值模拟风场中绕半导体少长针消雷器圆柱杆件的复杂流动，研究风向角对杆件风荷载的影响．计算结果给出了不同风向角下消雷器各杆件的气动力系数，风向角β=0°时各杆件纵截面和横截面上的压力系数分布，不同风向角下流场截面内的截面流线分布和等压线分布．     

山区覆冰输电塔线体系风致不平衡张力的研究

针对5B-ZBC1输电塔,采用数值试验的方法研究了风速、初始风攻角、输电塔高差和导线覆冰厚度对输电塔纵向不平衡张力的影响.作用在输电塔线上的脉动风时程是利用谐波合成法生成,通过改变高差、覆冰厚度,获得了输电塔上纵向不平衡张力的变化规律.该规律表明,在一些情况下现行规范规定所计算的输电塔不平衡张力偏小.在此基础上提出了山区这类塔型在雪荷载和风荷载共同作用下的纵向不平衡张力的理论公式.该公式的结果与数值试验结果相比误差在±6%以内,具有较好的精度.     

500kV输电钢管塔局部模态分析及其影响因素

为了研究500 kV输电钢管塔的动力特性,比较了有预应力和无预应力下输电塔局部模态的异同,分析了调整隔面间距以及斜材长细比对输电塔动力特性的影响。结果表明:实际工程中,预应力对于输电塔局部模态的作用无显著效果;调整隔面间距以及斜材长细比对于输电塔的整体模态无显著影响,而对于输电塔局部模态有较大影响。     

山区输电塔滚石撞击响应分析及撞击力计算

为了掌握滚石撞击作用下山区输电塔受力特性,以某山区800kV特高压输电线路T型输电塔为对象,采用非线性显式动力学分析软件,建立了输电塔滚石撞击有限元模型,研究了输电塔撞击区域杆件变形、应力及其时程变化,分析了滚石撞击位置、角度、速度以及滚石直径对输电塔撞击响应的影响规律,给出了输电塔滚石撞击力峰值计算公式,并与其它算法对比验证。结果表明：输电塔滚石撞击力呈现三角脉冲形态,持续时间短、冲击力大;输电塔撞击区域塔杆变形和内力较大,撞击时塔杆应力水平瞬时达到峰值,随后迅速振荡衰减,并逐渐稳定;滚石撞击后塔杆发生塑性变形,出现残余应力,但残余剪应力水平小于残余轴向应力;滚石撞击位置处于1/6到1/8塔高时,滚石撞击力峰值和杆件的残余轴向应力相对较大,撞击角度为0°时,输电塔的撞击响应最为剧烈,撞击速度和滚石直径对输电塔撞击响应影响较大;④撞击力峰值拟合公式可用于输电塔滚石撞击力的估算。     

高压输电塔风振控制的能量特性

研究了输电塔线体系风振控制的能量评估问题.采用多自由度模型建立了输电塔线体系动力分析模型和磁流变(MR)阻尼器的力学模型,研究了安装有MR阻尼器的塔线耦联体系的动力分析模型和受控运动方程,并采用局域反馈的固定增量半主动控制策略来实现输电塔结构风振反应的半主动控制.提出了设置有MR阻尼器的输电塔结构风振反应的能量评价标准并将其应用于某大跨越输电塔线体系的风振控制.分析表明:MR阻尼器可以有效地抑制输电塔结构的风振反应,通过能量评定方法可以准确地考察不同控制方法的控制效果.     

特高压长悬臂输电塔与输电塔-线耦合体系的风振特性

对±1 100 kV特高压长悬臂输电塔进行了有限元动力时程分析,采用单塔模型和塔线体系研究了不同风向作用下塔身和横担的风振响应特性,分析了横担总宽度对输电塔风振响应的影响.结果表明:长悬臂输电塔的一阶振型为扭转振型;随着分析的横担部位不断远离塔身中心,位移响应均方根在X方向略有削弱而在Y方向逐渐增大; 0°风向下塔线体系模型和单塔模型的风振响应较为接近,而在45°风向和90°风向下塔线体系模型的风振响应较大;横担总宽度增大时塔身部位风振响应也相应增大,横担部位风振响应在Y方向增大而在X方向略有减小,且影响效果在不同风向时呈现出一定的规律性.分析结果为长悬臂输电塔的抗风设计提供参考.     

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.     

A computer generator for randomly layered structures

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

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。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

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     

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

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

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.     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.