过电流保护在变压器合闸过程中的自适应策略

变压器铁磁材料的激磁特性呈现非线性,这将导致在变压器合闸过程中产生励磁涌流现象。过电流保护往往反映单一的电流幅值特征而动作,当变压器合闸过程发生时,励磁涌流及邻近区域内的穿越电流均可能导致相关联的过电流保护误动。从序分量的角度出发,构建了一个可通过标志函数的大小和突变,区分故障与涌流的序分量标志函数。通过PSCAD/EMTDC仿真表明,该标志函数能够充分反映电网结构的变化,有效区分变压器励磁涌流和故障。将该标志函数应用于过电流保护上可以减小励磁涌流的影响。     

电力系统不对称短路电流计算程序研究

通过MATLAB编制了电力系统短路电流计算的程序,为了提高计算的精确度,涉及的系统元件不仅考虑了电抗,而且考虑了电阻。基于对称分量法,针对不同的短路故障类型,形成相应的复合序网,求出所需的短路电流。针对IEEE-5和IEEE-14节点的算例分析,分别使用人工手算法和计算机算法对于同一节点发生短路时求解不同情况下的短路电流,对比分析表明计算机算法得到的结果是有效的,准确的。     

后掠式水平轴潮流能水轮机的载荷与获能特性研究

针对双向潮流能有效利用问题,设计一种基于对称翼型的新型后掠式水平轴潮流能水轮机,并研究其水动力性能。根据对称翼型升阻力特性与叶片展向攻角变化,采用变截面设计优化后掠式对称翼型叶片,并基于Buhl修正模型分析不同后掠偏移叶片所受推力与获能特性。通过3D建模与水槽实验,研究不同后掠偏移叶片的载荷与获能情况。模型实验研究表明,同一尖速比下,后掠偏移量为10%和15%的水轮机相对于偏移量为5%的水轮机所受推力最大分别降低4%和13.3%,获能效率最多分别减小3.8%和11.1%,其中推力比获能效率减幅更大。实验结果与理论分析变化趋势吻合,但减幅比理论值偏高。此外,该水轮机3种后掠偏移量下对应获能效率随桨距角的增大分别降低18%、14%和6%,获能效率下降显著,与300 kW样机实海况运行情况变化趋势相同。     

浅谈冲压件对压合工艺的影响

介绍了4门两盖冲压件的质量状态与要求,阐述冲压件对压合工艺的影响,分析并解决4门两盖、翼子板等包边件的变形缺陷,从而提高整车美容质量。     

浅析儒家“中和美”对我国传统建筑设计的影响

"中和"作为中国传统美学的一个核心范畴,伴随着人类文明的不断进步而逐渐清晰与完善.儒家"中和美"对我国传统建筑设计具有重要的指导意义,其主要表现在对建筑整体的设计以及建筑空间布局的影响.由此可见,认知我国传统建筑设计理念是对儒家"中和美"的深刻解读.     

新时期建筑设计方针的再思考

通过分析不同时期的建筑设计方针，重点对新时期的建筑设计方针作了阐述，并针对“适用、经济、美观”的指导方针进行了探讨，对促进我国建筑设计事业的发展起到了积极推动作用。     

钢笔画在学习和工作中的重要性

在现在学习和工作中,钢笔画有助于提高我们的技法表现、形式处理、审美创造能力和艺术修养.     

A novel method for analyzing dominant oscillation mode based on improved EMD and signal energy algorithm

In this paper,a novel method that integrates the improved empirical mode decomposition(EMD)and signal energy algorithm is proposed to estimate the dominant oscillation parameters and corresponding mode shape.Firstly,the EMD with symmetrical extrema extension(SEE)is utilized to decompose the measured data from wide area measurement system(WAMS)into a finite set of intrinsic mode functions(IMFs).Then,the signal energy algorithm is used to calculate the approximate oscillation parameters of the IMFs.The nodes ...     

Comparing spiritual transformations and experiences of profound beauty.

Certain highly emotional experiences have the potential to produce long-lasting and meaningful changes in personality. Two such experiences are spiritual transformations and experiences of profound beauty. However, little is known about the cognitive appraisals or narrative elements involved in such experiences, how they are similar, and how they differ. In a study of emotion-related narratives, these experiences were found to share many features but also differ in their valence. Experiences of profound beauty are almost always positive, but spiritual transformations are both positive and negative. Moreover, spiritual transformations seem to produce long-lasting change, but experiences of profound beauty, although evocative, do not seem to produce long-lasting change. An emotion approach helps to elucidate two understudied but important emotional experiences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Formation of a Third Liquid Phase and Its Reuse for Dibenzyl Ether Synthesis in a Tetraalkylammonium Salt Phase Transfer Catalytic System

This paper describes the formation of a third liquid phase in a phase transfer catalytic system in the presence of benzyl alcohol and potassium hydroxide, where dodecane and tetraalkylammonium bromide serve as organic solvent and catalyst, respectively. In this kind of system, a symmetrical ether (dibenzyl ether) was synthesized from benzyl chloride and benzyl alcohol at 323 K. In particular, the investigation demonstrates that the observed reaction rate constant depends on the length of the alkyl group of the catalyst. Tetrabutylammonium bromide exhibits the highest catalytic activity among the catalysts explored. With respect to the reuse of the third liquid phase, the results confirm that there is no decrease in phase transfer catalytic activity in three consecutive runs.