基于铁塔等效的交叉跨越架空线安全距离分析

精细化塔线体系有限元模型动态响应计算需要耗费大量计算成本,不适应于重要交叉跨越线路动态安全距离的实时计算.给出了一种输电铁塔等效刚度的计算方法,并使用等效铁塔模型建立了交叉跨越塔线体系模型.针对一220 kV交叉跨越线路架空线动态安全距离实例分析,发现等效模型在静力特性、振型和固有频率方面与桁梁模型具有良好的一致性.在...     

特高压格构式输电塔线体系振动台试验设计

特高压输电塔线体系具有跨越档距大、塔体高的特点,进行地震模拟振动台试验测试时,现有结构试验方法难以完成.本文以特高压交流单回路输电线路工程为背景,设计制作了三塔两线体系缩尺模型,文中详细阐述了振动台试验的模型设计工作,其中包括试验材料的选取、动力相似关系的确定、模型的制作以及试验方案设计等方面.针对由强几何非线性的导、地线与弹性输电铁塔这两种不同形式的结构所组成的耦联体系提出了动力参数分离式模型设计方法,解决了塔线体系按统一比例无法满足振动台台面尺寸要求的问题.理论分析和实测对比验证了该模型较好地满足了振动台试验要求,该方法使得通过振动台试验研究特高压输电塔线体系的地震反应得以实现.     

大跨越输电塔线体系气弹模型风洞试验

以建设中世界最高输电铁塔——— 346 .5m高、5 0 0kV江阴大跨越塔为工程背景 ,通过气弹模型风洞试验 ,对大跨越输电塔线体系动力特性和风振响应进行了研究 .采用外形、质量、刚度分离的处理方法设计了大跨越塔模型 ,塔线体系为两塔三段线模型 .用自由振动法测得单塔和塔线体系的自振频率和阻尼比 ,进行了多个风速下单塔、塔线体系在均匀流场和紊流场中的风洞试验 .通过对试验结果的分析 ,揭示了大跨越输电塔线体系动力特性和风振响应特点 ,为实际工程抗风设计提供了依据     

输电塔线体系多因素风致动力响应分析

目的研究塔线耦联效应、几何非线性和线路初始张力对塔线体系动力响应的影响,并揭示各因素作用下塔线体系动力效应演化机制.方法运用ANSYS软件建立精细化仿真模型,对比简化模型和三塔四线模型在风荷载作用下的动力响应;对不同呼高的铁塔进行静力pushover分析,研究几何非线性对铁塔抗风承载力的影响以及线路初始张力的变化对塔线体系动力响应的影响.结果塔线耦联效应对塔顶位移和杆件应力的均值响应影响很小,对其均方根影响很大;当铁塔高度大于40 m时,是否考虑几何非线性所得结果相差达到25%以上.结论简化模型只能反应输电塔位移和应力的均值响应,利用塔线耦联模型才能得到真实的动力响应;几何非线性对铁塔抗风承载力的影响随塔身高度的增加而增大;导地线初始张力的变化对其动力响应影响很小,可忽略不计.     

面向跨音速气动弹性剪裁的颤振时域自动化预估方法

随着对燃油效率和先进气动、结构的关注,复合材料在飞行器结构设计中得到越来越多的应用.在复合材料气动弹性剪裁设计过程中,为了满足气动弹性要求,需要反复对复合材料结构参数进行修改,不可避免地需要重新构建气动弹性剪裁模型,气动弹性剪裁模型重建和气动弹性性能评估过程会耗费大量时间和人力,尤其在跨音速区域,这些都大大增加了飞行器设计的时间和人工成本.为了发展更高效复合材料机翼气动弹性剪裁方法,本文从提高气动弹性性能评估过程效率入手,基于结构动力重分析法提出了一种面向跨音速气动弹性剪裁的颤振时域自动化预估方法.采用改进Agard 445.6复合材料机翼为模型对本文所提出方法的有效性和精度进行了验证.仿真结果表明本文所提出的自动化气动弹性性能预估方法可以以较高的精度对气动弹性剪裁过程所必须的结构气动弹性响应进行预估,尤其可以避免大量的人工手动修改气动弹性模型的过程,这大大提高了跨音速复合材料机翼气动弹性剪裁自动化程度和设计效率.     

超音速二元翼极限环颤振的高次线化分析

以一个在俯仰方向带有初偏间隙非线性刚度的超音速二元机翼为模型,研究非线性气动弹性系统的双稳定极限环颤振问题.在利用二阶活塞理论计算非定常气动力和力矩的基础上,采用KBM法一次渐近解的等效线化分析方法对系统的颤振进行了定性分析,最后通过数值模拟验证了理论分析的正确性.     

输电塔线体系风洞试验模型的变比例问题分析

塔线体系的气弹模型风洞试验时,由于模型制作和现有风洞尺寸条件的限制,输电塔线体系中塔与线保持相同比例的气弹模型制作难度很大,往往需要将导线跨度的比例缩小.从数值分析的角度出发,以某1000 kV双回路线路的一段塔线体系为例,铁塔保持不变,导线的缩聚比例分别为1.00、0.50、0.25的情况进行顺风向的风振响应时程分析.结果显示,导线比例缩聚后,塔线体系的风振响应基本保持一致,缩聚模型的风洞试验结果可以比较准确的反映原型的风振响应.     

台风作用下输电线路风振系数及抗风性能研究

为研究良态风与台风作用下的输电线路风振系数,以广东省国古线一铁塔为原型建立了有限元模型,采用谐波叠加法模拟了台风风场,并开展了动力分析.首先,对比了5种国内外设计规范的风振系数计算方法,发现各规范均未单独考虑台风的强脉动特性;然后,基于惯性力法获取了铁塔风振系数并揭示了塔线耦联效应的影响.最后,利用生死单元法定量评估了两种风场下输电线路的抗风性能.结果表明:台风的高湍流特性导致顺风向风振系数大于良态风对应值;导线可增大铁塔横风向基频,并使铁塔振型由单塔的弯曲型变为塔线体系的弯剪型,塔线体系横担处风振系数大于单塔;湍流度从0.14提高至0.20,临界倒塌风荷载降低约11%.因此,台风多发地区的输电塔设计应适当提高湍流度取值,必要时还应考虑塔线耦联效应.     

大跨度拱桥气动弹性模型设计

气动弹性模型设计是桥梁模型风洞试验的先决条件．主要讨论了大跨度中承式拱桥的气动弹性模型设计问题,分析了不同横撑布置和抗弯刚度对模型设计的影响,指出不同的横撑刚度需要采用完全不同的方案设计．针对变截面空间拱,提出了利用将变截面空间投影变换到平面设计,然后将设计好的拱反投影到空间的方法,较好地实现模型设计．实例表明,该方法是有效的．     

钻石背弹翼的静气动弹性研究

使用动网格技术耦合结构模型和气动模型,利用逐次迭代法计算钻石背弹翼的气动弹性变形.使用模态法构造结构模型,求解N-S方程计算气动力.计算了不同刚度弹翼的气动弹性变形以及变形对气动特性的影响并与实验结果对比.结果表明:钻石背弹翼的气动弹性变形量越大,其法向力越小;柔性钻石背弹翼小直径炸弹的法向力大小以及随攻角变化趋势与计算风洞实验结果接近;钻石背弹翼两侧非对称变形会引起滚转力矩,并且滚转力矩随攻角增大而增大.     

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.     

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.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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