考虑设备状态和系统风险的设备重要度评估模型

为了给状态检修决策过程提供有用的设备重要度信息,基于缺电损失描述系统风险指标,首先研究了系统风险灵敏度指标和元件停运前后系统风险差值指标在状态检修体制下的适用性,接着提出了反映设备当前状态引起系统风险增量的输电设备重要度评估模型.理论推导和算例分析表明,灵敏度指标和设备停运前后系统风险差值指标不能正确反映设备当前状态对系统风险的影响,因而不适用于状态检修体制,文中提出的评估模型避免了上述两种指标的不足,在状态检修体制中有很好的适用性.     

基于典型运行场景聚类的电力系统灵活性评估方法

以风光水为代表的可再生能源电源会增加电力系统的不确定性.为了保证高比例可再生能源电力系统的灵活运行,提出一种典型运行场景电力系统灵活性评估方法.利用改进的K-means算法,将新能源和负荷的运行场景进行聚类组合得到典型运行场景.从区域内供需平衡、区域内潮流分布和区域间输电能力3个角度提出灵活性评估指标;计算每种典型场景的灵活性评估指标,并根据每种场景的出现概率计算得到综合评估指标以评估系统的整体灵活性.最后,基于南方某地区实际新能源和负荷历史数据在改进的IEEE 39节点系统上进行电力系统灵活性评估.结果表明,该聚类方法和灵活性指标可以有效反映电力系统的灵活性.     

计及输电线路相关停运的大电网可靠性评估

为了计算和分析输电线路对大电网可靠性评估的影响,提出一种计及双回平行输电线路独立停运、共同模式停运和相关停运的大电网可靠性评估模型和算法.计及共同模式停运和相关停运时,双回平行输电线路的两回线实际上是一个具有多个状态的元件.提出的算法可以在形成可靠性指标时,同时计算这种多状态元件造成系统失效状态下独立停运、共同模式停运和相关停运的概率和频率,减少了计算复杂性.通过对RBTS系统、IEEE-RTS96区域A系统和一个实际电力系统进行的可靠性计算分析,验证了提出的算法的正确性和有效性.     

输电网规划全寿命周期综合成本计算研究

为比较输电网规划方案的经济性,提出了一种基于全寿命周期成本,在规划期内逐年计算各项成本的线路综合成本计算方法.在计算线路故障率时,根据故障后果明确划分故障类型,并采用改进的灰色GM(1,1)模型对线路故障率进行中长期预测,使线路运维成本计算更准确.在进行经济方案优选时,利用区间分析法计算输电线路综合成本,消除单一定值引起的计算误差,能够更好地比较各方案的优劣性.根据实际工程算例验证文中综合成本模型在新旧混合线路规划中的通用性和有效性.     

基于随机模糊理论的交直流混联系统风险评估模型

对交直流混联输电系统的运行风险评估中,由于历史数据的缺失及气候等因素对数据测量精度的影响,输电线路的强迫停运率往往具有随机模糊的特性.文中提出了统一的交直流系统的随机模糊不确定性模型,并将随机模糊理论运用于交直流系统的运行风险评估中.该模型考虑了随机和模糊的特性,然后根据运行风险评估的定义给出了随机模糊不确定性运行风险评估指标,最后结合交直流系统的预想事故集用随机模糊模拟技术得到系统的运行风险指标期望值.文中还将该模型应用在改进的IEEE-30节点交直流系统中,算例结果证明了该模型的可行性.     

含分布式发电的输电扩展规划

分布式发电是增加输电扩展规划灵活性的有效措施。提出了一种新的输电扩展规划方法,考虑了分布式发电带来的这种投资灵活性,评估了输电扩展投资过程的实物期权价值。对于不可逆的大型输电投资项目,通过算例说明了不同的投资选择所带来的灵活性而产生的这种实物期权经济价值。     

基于PQ曲线的风电并网系统电压稳定性评估

提出一种基于负荷节点PQ曲线的风电并网系统电压稳定性能的评估方法,并且考虑不同负荷特性及风力发电机输出功率特性对电压稳定性的影响.首先,用电力系统仿真软件得到各节点的功率信息,然后依照节点的特性构造出风力发电机不同运行状态下的节点PQ曲线图.计算出节点功率运行点到PQ边界曲线的几何距离及其相对应的概率,由此构造出一种基于PQ曲线的风电并网系统电压稳定性评估指标,并将该指标用于确定系统中的薄弱节点.最后以IEEE30系统数据为算例,应用基于PV曲线的裕度灵敏度法验证本文中所提方法的有效性.为电网的规划和运行部门在进行电力系统电压稳定性评估时提供一种新的途径.     

如何提高输电线路故障查找的成功率

输电线路发生故障后,尽快查出故障点是降低故障损失、缩短线路故障停运时间的关键。根据多年从事输电线路故障巡视组织工作经验的积累,结合故障特征的分析,总结了一些实用的输电线路故障查找工作的组织程序和方法,对提高输电线路故障查找的成功率起到了积极的作用。     

计及电网停电风险的输电线路动态融冰决策方法

电网发生大面积冰灾情况时,多条输电线路存在覆冰故障隐患,电网稳定运行受到严重威胁,需要提前制定输电线路融冰方案,合理安排融冰顺序。针对此问题,分析输电线路覆冰继续运行给电网带来的停电风险,将与待融冰输电线路相关联的变电站的电气主接线展开,将传统削负荷模型改进后应用于输电网与变电站主接线的组合网络,建立断路器可靠性模型,计算靠后融冰线路因继续运行的电网停电风险;利用计及风速及降雨影响的输电线路覆冰增长预测模型,计算输电线路的覆冰率,根据覆冰率门槛值确定待融冰线路集,基于覆冰严重度模型构建系统全局的覆冰指数指标;综合考虑电网停电风险及系统全局覆冰指数建立输电线路融冰紧迫度指标,动态更新待融冰线路并决策融冰顺序。最后,以IEEE RBTS系统进行算例分析,验证了所提方法的可行性与合理性。     

含分布式电源配电系统的电压质量概率评估

针对含分布式电源配电系统概率潮流计算中随机变量多元化的特点,提出了基于组合抽样的蒙特卡罗(Monte Carlo,MC)方法,基于此方法对含分布式电源配电系统的电压质量进行概率评估分析.该方法不仅考虑了风速、光照强度的随机性以及基础负荷和电动汽车充电负荷(electric vehicle charging load,EVCL)的不确定性,而且计及了输电线路的故障率等随机因素.通过对IEEE9和IEEE34节点系统的算例分析,验证了所提方法的有效性、准确性、快速性和实用性.     

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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