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Research on a Fast-Closing Switch Based Fault Current Limiter with Series Compensation
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作者 陈金祥 邹积岩 +1 位作者 董恩源 石晶 《Journal of Donghua University(English Edition)》 EI CAS 2002年第3期23-27,共5页
A new type of fault current limiter (FCL) with series compensation based fast-closing switch is proposed. It is composed of a capacitor bank and a reactor in series. The main control component is a fast-closing switch... A new type of fault current limiter (FCL) with series compensation based fast-closing switch is proposed. It is composed of a capacitor bank and a reactor in series. The main control component is a fast-closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. When fault occurs, the switch closes and bypasses the capacitors, and the fault is limited by the reactor then. Simulated analysis and experiments show that it is feasible to develop the FCL with low cost and high reliability. The effectiveness of transient stability for power system is evaluated by digital simulation. 展开更多
关键词 FAULT CURRENT limiter(FCL) series compensation fast-closing switch system stability.
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Coherence Modified for Sensitivity to Relative Phase of Real Band-Limited Time Series
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作者 William Menke 《Applied Mathematics》 2014年第17期2739-2745,共7页
As is well known, coherence does not distinguish the relative phase of a pair of real, sinusoidal time series;the coherence between them is always unity. This behavior can limit the applicability of coherence analysis... As is well known, coherence does not distinguish the relative phase of a pair of real, sinusoidal time series;the coherence between them is always unity. This behavior can limit the applicability of coherence analysis in the special case where the time series are band-limited (nearly-monoch- romatic) and where sensitivity to phase differences is advantageous. We propose a simple mod-ification to the usual formula for coherence in which the cross-spectrum is replaced by its real part. The resulting quantity behaves similarly to coherence, except that it is sensitive to relative phase when the signals being compared are strongly band-limited. Furthermore, it has a useful interpretation in terms of the zero-lag cross-correlation of real band-passed versions of the time series. 展开更多
关键词 Time series COHERENCE CROSS CORRELATION Band-limited MONOCHROMATIC FILTER
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Estimating Sums of Convergent Series via Rational Polynomials
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作者 Serdar Beji 《Advances in Pure Mathematics》 2023年第4期187-197,共11页
Sums of convergent series for any desired number of terms, which may be infinite, are estimated very accurately by establishing definite rational polynomials. For infinite number of terms the sum infinite is obtained ... Sums of convergent series for any desired number of terms, which may be infinite, are estimated very accurately by establishing definite rational polynomials. For infinite number of terms the sum infinite is obtained by taking the asymptotic limit of the rational polynomial. A rational function with second-degree polynomials both in the numerator and denominator is found to produce excellent results. Sums of series with different characteristics such as alternating signs are considered for testing the performance of the proposed approach. 展开更多
关键词 Sums of series Rational Polynomials Extrapolation to limit Asymptotic Value
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Limit Cycle for the RC Circuit with Square-Wave-Type Voltage
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作者 Hugo Ramón Olmedo Mareco 《Journal of Applied Mathematics and Physics》 2023年第12期3854-3866,共13页
The goal of this paper is to prove, by means of calculations the existence of the ω-limit cycle of a simple circuit where a resistor, a capacitor and a square-wave-type voltage source are in series.
关键词 DC RC Circuit One-Sided limits Geometric series
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SYNTHESIS AND CHARACTERIZATION OF A SERIES OF NOVEL INORGANIC MICROPOROUS CRYSTALS,BePO_4-CIn(n=4-7).
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作者 Long YU Wenqin PANG (Department of Chemistry,Jilin University,Changchun,130021) 《Chinese Chemical Letters》 SCIE CAS CSCD 1991年第1期67-70,共4页
A series of novet beryllophosphate zeolites,named BePO_4-CIn(n=4-7), are synthesized hydrothermally and characterized with X-ray powder diffraction,IR spectra,SEM,thermat analysis and ion-exchange.
关键词 n=4-7 CJ SYNTHESIS AND CHARACTERIZATION OF A series OF NOVEL INORGANIC MICROPOROUS CRYSTALS BePO4-CIn N
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Reliability of a Large Series-parallel System in Variable Operating Conditions
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作者 Joanna Soszynska 《International Journal of Automation and computing》 EI 2006年第2期199-206,共8页
In this paper, a semi-Markov model of system operation processes is proposed and its selected parameters are determined. A series-parallel multi-state system is considered, and its reliability and risk characteristics... In this paper, a semi-Markov model of system operation processes is proposed and its selected parameters are determined. A series-parallel multi-state system is considered, and its reliability and risk characteristics found. Subsequently, a joint model of system operation process and system multi-state reliability and risk is constructed. Moreover, the asymptotic approach to reliability and risk evaluation of a multi-state series-parallel system in its operation process is applied to a port grain transportation system. 展开更多
关键词 series-parallel system limit reliability function semi-Markov processes.
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Study of a Single-Phase Series Active Power Filter with Hysteresis Control
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作者 Mihail Antchev Mariya Petkova +2 位作者 Hristo Antchev Vanjo Gourgoulitsov Stanimir Valchev 《Journal of Energy and Power Engineering》 2012年第10期1635-1642,共8页
The paper presents results from a study of a series-connected single-phase APF (active power filter) with a control system based on hysteresis control, both with and without limitation of the maximum switching frequ... The paper presents results from a study of a series-connected single-phase APF (active power filter) with a control system based on hysteresis control, both with and without limitation of the maximum switching frequency. The general purpose of the series APF is to eliminate the low order harmonics of the source (grid) voltage. The filter operation at limited and unlimited maximum switching frequency is explained and it is described using building blocks and time diagrams illustrating the tracking down of the reference curve. Waveforms from the computer simulation and waveforms from the experimental tests of the filter are presented also for the two situations. Operations at limited and unlimited maximum switching frequency are compared regarding the quality of the voltage across the load, the complexity of the implementation of the control system, and the electromagnetic compatibility. The investigation proved capability of the series APF to achieve its general purpose using the hysteresis control methods studied (limited and unlimited switching frequency). 展开更多
关键词 series active power filter APF hysteresis control frequency limitation.
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Effect of calibration data series length on performance and optimal parameters of hydrological model 被引量:3
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作者 Chuan-zhe LI Hao WANG +3 位作者 Jia LIU Deng-hua YAN Fu-liang YU Lu ZHANG 《Water Science and Engineering》 EI CAS 2010年第4期378-393,共16页
In order to assess the effects of calibration data series length on the performance and optimal parameter values of a hydrological model in ungauged or data-limited catchments (data are non-continuous and fragmental ... In order to assess the effects of calibration data series length on the performance and optimal parameter values of a hydrological model in ungauged or data-limited catchments (data are non-continuous and fragmental in some catchments), we used non-continuous calibration periods for more independent streamflow data for SIMHYD (simple hydrology) model calibration. Nash-Sutcliffe efficiency and percentage water balance error were used as performance measures. The particle swarm optimization (PSO) method was used to calibrate the rainfall-runoff models. Different lengths of data series ranging from one year to ten years, randomly sampled, were used to study the impact of calibration data series length. Fifty-five relatively unimpaired catchments located all over Australia with daily precipitation, potential evapotranspiration, and streamflow data were tested to obtain more general conclusions. The results show that longer calibration data series do not necessarily result in better model performance. In general, eight years of data are sufficient to obtain steady estimates of model performance and parameters for the SIMHYD model. It is also shown that most humid catchments require fewer calibration data to obtain a good performance and stable parameter values. The model performs better in humid and semi-humid catchments than in arid catchments. Our results may have useful and interesting implications for the efficiency of using limited observation data for hydrological model calibration in different climates. 展开更多
关键词 calibration data series length model performance optimal parameter hydrological model data-limited catchment
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Nonlinear Optical Properties and Optical Limiting Measurements of {(1Z)-[4-(Dimethylamino)Phenyl]Methylene} 4-Nitrobenzocarboxy Hydrazone Monohydrate under CW Laser Regime
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作者 Fryad Z. Henari P. S. Patil 《Optics and Photonics Journal》 2014年第7期182-188,共7页
We report results from the investigation of the nonlinear refractive index and nonlinear absorption coefficient of {(1Z)-[4-(Dimethylamino)phenyl]methylene} 4-nitrobenzocarboxy hydrazone mono-hydrate (DMPM4NBCHM) solu... We report results from the investigation of the nonlinear refractive index and nonlinear absorption coefficient of {(1Z)-[4-(Dimethylamino)phenyl]methylene} 4-nitrobenzocarboxy hydrazone mono-hydrate (DMPM4NBCHM) solution using Z-scan technique with a continuous wave (CW) Argon ion laser. The results show that this type of organic material has a large nonlinear absorption and nonlinear refractive index at 488 nm and 514 nm. The origin of the nonlinear effects was discussed. We demonstrate that the light induced nonlinear refractive index variation, leads to limiting effect. The results indicated that DMPM4NBCHM could be promising candidates for application on nonlinear photonic devices and optical limiters. 展开更多
关键词 NONLINEAR Absorption NONLINEAR Refractive Index Z Scan Optical limiting {(Z)-[4-(Dimethylamino)Phenyl]Methylene} 4-Nitrobenzocarboxy Hydrazone MONOHYDRATE
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新时代高等数学“金课”建设新思路设计与研究——以数列极限概念为例
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作者 杨娜娜 孟新友 马成业 《科技风》 2024年第12期118-120,共3页
随着科技的发展、时代的进步,偏向于理论推导的“高等数学”课程传统教学模式已无法满足这个时代社会对人才的需求,而“金课”是知识、能力和素养的融合,不仅让学生获得知识、掌握技能,更重要的是培养其创造性思维和解决复杂问题的综合... 随着科技的发展、时代的进步,偏向于理论推导的“高等数学”课程传统教学模式已无法满足这个时代社会对人才的需求,而“金课”是知识、能力和素养的融合,不仅让学生获得知识、掌握技能,更重要的是培养其创造性思维和解决复杂问题的综合能力。本文将开展基于“金课”的“高等数学”教学研究工作,为进一步构建本科数学类金课课程提供积极探索,并以数列极限概念为例阐释其在高等数学“金课”探索中的应用。 展开更多
关键词 金课建设 高等数学 数列极限
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基于B-ELM的通航事故预测
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作者 常健 《电子质量》 2023年第2期9-13,共5页
高水平的航空安全始终是航空业追求的目标。为了满足未来通航业风险分析和优化的需求,基于美国国家运输安全委员会(NTSB)航空事故数据库近11年的数据,建立了基于极限学习机的小样本事故数据预测模型,并通过实验对比了普通增量式极限学... 高水平的航空安全始终是航空业追求的目标。为了满足未来通航业风险分析和优化的需求,基于美国国家运输安全委员会(NTSB)航空事故数据库近11年的数据,建立了基于极限学习机的小样本事故数据预测模型,并通过实验对比了普通增量式极限学习机模型及传统的小样本数据预测GM(1,1)模型。实验结果证明提出的分析方法和模型在通航业小样本数据集的输入情况下有较高的准确率,能够为行业安全发展起到一定的指导意义。 展开更多
关键词 通航事故分析 航空事故预测 小样本预测 时间窗序列预测 极限学习机 双向增量极限学习机
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串联系统小样本可靠度直接评估方法
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作者 傅惠民 李子昂 郭建超 《机电产品开发与创新》 2024年第4期1-5,共5页
建立了一种串联系统小样本可靠度直接评估方法,能够根据子系统的可靠度置信限直接给出串联系统的可靠度置信限,解决了目前常用的LM法和MML法等传统方法需将信息量较大的连续型分布的子系统试验数据转换为信息量较小的成败型数据,造成试... 建立了一种串联系统小样本可靠度直接评估方法,能够根据子系统的可靠度置信限直接给出串联系统的可靠度置信限,解决了目前常用的LM法和MML法等传统方法需将信息量较大的连续型分布的子系统试验数据转换为信息量较小的成败型数据,造成试验信息大量丢失,导致可靠度评估精度不高或偏于危险的问题。在此基础上,针对工程上许多成败型试验转计量型试验的机构都是正态分布串联系统的情况,建立了正态分布串联系统小样本可靠度直接评估方法,该方法能够根据子系统的小样本计量型数据对串联系统可靠度进行高精度评估。大量的Monte Carlo模拟验证和实例计算结果表明,传统方法在小样本情况下误差较大,甚至无法满足置信度要求,本文方法则不仅能够满足置信度要求,而且评估精度更高。此外,本文方法对工程上常用的指数分布、 Weibull分布和正态分布等连续分布均适用。 展开更多
关键词 串联系统 小样本 可靠度评估 置信限 成败型试验 计量型试验
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基于电压补偿原理的超导储能-限流集成系统 被引量:7
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作者 赵彩宏 郭风 +5 位作者 郭文勇 黄晓华 刘昕 肖立业 林良真 余运佳 《电力系统自动化》 EI CSCD 北大核心 2006年第2期68-71,108,共5页
基于电压补偿原理,将串联式超导储能系统和限流电抗器集成起来,提出了一种超导储能- 限流集成系统(SMES-CL)。该系统不仅解决了限流电抗器带来的稳态无功压降问题,而且解决了串联式超导储能系统保护困难的问题。它既可以快速自动投入限... 基于电压补偿原理,将串联式超导储能系统和限流电抗器集成起来,提出了一种超导储能- 限流集成系统(SMES-CL)。该系统不仅解决了限流电抗器带来的稳态无功压降问题,而且解决了串联式超导储能系统保护困难的问题。它既可以快速自动投入限制故障电流以保护整个变电站和自身,还可以对系统进行功率补偿以提高电能质量。文中分析了SMES-CL的集成结构,对于它的工作原理,包括稳态补偿原理和故障限流原理进行了讨论。在一个SMES-CL模型样机上进行了试验,验证了它的有效性。 展开更多
关键词 超导储能-限流集成系统 电压补偿 串联式超导储能系统 限流电抗器 集成结构
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VSC-HVDC串并联型D-PMSG风电场机组功率—电压协调控制 被引量:3
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作者 张文娟 彭婧 荣飞 《电机与控制学报》 EI CSCD 北大核心 2017年第8期88-94,共7页
针对串并联型D-PMSG风电场中同一串联簇机组在不同风速下最大功率追踪控制存在过电压、过调制问题,分析基于柔性直流输电的串并联型D-PMSG风电场机组的运行特性,提出一种适用于该拓扑型风电场机组的功率—电压协调最大功率追踪控制方法... 针对串并联型D-PMSG风电场中同一串联簇机组在不同风速下最大功率追踪控制存在过电压、过调制问题,分析基于柔性直流输电的串并联型D-PMSG风电场机组的运行特性,提出一种适用于该拓扑型风电场机组的功率—电压协调最大功率追踪控制方法,并探讨直流母线电压上限值的设定原则。该方法不仅可以将同一串联簇中其他各机组直流母线电压都钳制在安全范围内,还减少限压期间下的机组的弃风。搭建相应的仿真模型,仿真结果表明所提出的方法可确保各机组在安全范围内寻找最佳功率点。 展开更多
关键词 柔性直流输电 串并联拓扑 功率-电压协调控制 直流母线电压上限值
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一类正项级数比较判别法的教学探讨
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作者 乐瑞君 周彩莲 解烈军 《高等数学研究》 2024年第3期9-10,17,共3页
本文探讨用比较判别法判断正项级数的敛散性时出错的典型问题,及我们该如何启发与引导学生,让学生真正理解比较判别法的本质内涵.
关键词 正项级数 比较判别法 敛散性 极限形式
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多元秩-序模型中回归系数的估计
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作者 马建军 徐兴忠 《高校应用数学学报(A辑)》 CSCD 北大核心 2008年第3期287-294,共8页
通过对多元秩-序模型的研究得到了模型的逆回归性质,基于该性质提出了回归系数的估计方法.当自变量满足线性条件时,不用预先设定扰动项的具体分布便可以得到回归系数方向的估计,并且这个估计与回归系数只相差一个正常数因子.证明了估计... 通过对多元秩-序模型的研究得到了模型的逆回归性质,基于该性质提出了回归系数的估计方法.当自变量满足线性条件时,不用预先设定扰动项的具体分布便可以得到回归系数方向的估计,并且这个估计与回归系数只相差一个正常数因子.证明了估计是n^(1/2)相合的.模拟结果表明估计有良好的大样本性质. 展开更多
关键词 limitED DEPENDENT variable模型 多元秩-序模型 逆回归
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The Space Dilation: Analyzing Progressive Speed Reduction and Its Relativistic Parallels
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作者 Kreshnik Feka 《Journal of Applied Mathematics and Physics》 2024年第8期2990-3005,共16页
This paper presents a conceptual exploration that draws an intriguing parallelbetween a hypothetical travel scenario and the principles of special relativity. The scenario involves a traveler who reduces their speed b... This paper presents a conceptual exploration that draws an intriguing parallelbetween a hypothetical travel scenario and the principles of special relativity. The scenario involves a traveler who reduces their speed by an amount proportional to the distance traveled. Despite initially traveling at a high speed towards a given destination, the continual reduction in speed results in an asymptotic approach to the goal, analogous to the unattainable speed of light in relativity. Mathematically, the scenario is expressed through the Harmonic Series, demonstrating that the total travel time increases without bound, making the destination theoretically unreachable within a finite timeframe. This exploration mirrors the relativistic velocity addition and time dilation effects, providing a compelling analogy for understanding asymptotic limits. By highlighting the profound implications of diminishing returns and unattainable goals, this paper aims to stimulate further discussion and exploration of these fascinating parallels. 展开更多
关键词 Asymptotic limits Special Relativity Harmonic series Time Dilation Diminishing Returns
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数列极限ε-N定义的注记
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作者 师小侠 李琨 《咸阳师范学院学报》 2004年第4期59-60,84,共3页
从数列极限概念的定性描述出发,通过对"无限增大"、"无限接近"的精确数学表 述,引出了数列极限的定义,并对数列极限的定义作了几何上的分析。
关键词 数列 数列极限 定义
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幂级数的和函数及其应用
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作者 赵莉莉 王蕾 《河南财政金融学院学报(自然科学版)》 2024年第3期48-52,共5页
总结了幂级数的系数在关于n的假分式、关于n的真分式和含有n的阶乘等3种情形下,求幂级数和函数的方法。介绍了幂级数的和函数在求常数项级数的和、求数列极限,以及在近似计算中的应用。
关键词 幂级数 和函数 常数项级数 收敛域 近似计算 极限
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断路器后备保护和大短路电流下的上下级选择性研究
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作者 陈科 《建筑电气》 2024年第6期26-32,共7页
引入电流三区段概念,主要分析在选择性极限电流I_(s)超过上级断路器短路保护阈值时的上下级选择性问题,并就实际工程应用给出相关建议。
关键词 断路器串联回路 选择性 电流三区段 选择性极限电流 选择性配合表 断路器极限分断能力 后备保护 保护配合
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