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191.
192.
采用循环伏安法和交流阻抗法系统研究了粉煤灰、矿渣粉和石灰石粉水泥浆体的电学特性,通过等效电路对电学测试结果进行拟合,并将拟合所得浆体电学参数与浆体化学结合水和压汞所测孔结构之间的相关性进行比较。结果表明:浆体的化学结合水与其电阻率具有较好的正相关性,即化学结合水越多,水化程度越大,浆体电阻率越高;粉煤灰和矿渣粉可以提高浆体电阻率,而石灰石粉在5%掺量下对浆体电阻率无影响;随着水化龄期的延长,浆体孔溶液电阻增大,其变化规律与浆体电阻率一致;浆体凝胶电容和凝胶电阻与C-S-H凝胶含量有关,二者有很好的负相关性;随着水化龄期的延长,浆体孔结构曲折程度提高,交流阻抗法所测得常相角指数减小,压汞测得的分形维数增大。 相似文献
193.
Diah Permata Naoto Nagaoka 《IEEJ Transactions on Electrical and Electronic Engineering》2015,10(Z1):S28-S33
Transient characteristic of power system apparatus in a high‐frequency region should be modeled with stray capacitors. Pi‐type circuit is commonly used to represent the stray capacitors between terminals and those to the ground. A modeling method for the pi‐type circuit with unsymmetrical stray capacitances to ground is proposed in this paper. To obtain the unsymmetrical stray capacitances to ground, a couple of differential‐mode measurements are interchangeably applied. The parameters of the pi‐type circuit can be determined by the measurements with a common‐mode measurement. A nonlinear least‐squares method is used to estimate the capacitances. The method is applied to compose an equivalent circuit of a miniature circuit breaker (MCB), which has unsymmetrical stray capacitances to ground. The application is not only for the MCB but also for a scaled model of a high‐voltage circuit breaker. A gas‐filled arrester is used as a voltage sensor for the test because the voltage across the stray capacitor cannot be directly measured due to the input capacitance of a voltage probe. A transient response of the MCB with the gas‐filled arresters is numerically simulated to show the usefulness of the equivalent circuit. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
194.
Ning Tong Shan He Xiangning Lin Rui Zhang Dexian Yang 《IEEJ Transactions on Electrical and Electronic Engineering》2015,10(5):539-546
While the high‐resistance earth fault frequently occurs on extra high voltage (EHV) transmission lines, existing protection schemes show great limitation for coping with this kind of fault scenario when the fault resistance is very high. In this paper, a novel protection methodology combining the measured impedance of the two ends is introduced, and a so‐called summation impedance protection, making use of this critical information, is thus put forward and assessed. Emphasis is placed on the principle of the summation impedance protection and its adaptive thresholds. A simulation model based on EMTDC/PSCAD, by which the performance of the summation impedance protection is evaluated, is then established. As confirmed by quantitative theoretical and experimental studies, the results indicate that the proposed protection scheme works well even when the fault resistance is extremely high under the internal fault condition, and it keeps itself from maloperation as an effect of its adaptive thresholds wherever an external fault occurs. These results highlight the necessity to work in conjunction with the existing main protections of transmission lines, by which means an enhanced ability to cope with the high‐resistance single‐phase earth fault can be achieved. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
195.
从三维轴对称的非饱和土波动方程出发,考虑土中基质吸力对剪切模量的影响,对端承桩在纵向简谐荷载作用下桩土耦合振动特性进行了研究。利用算子分解和分离变量法直接对耦合方程进行解耦,在求得非饱和土层振动模态形式和阻抗因子的基础上,结合桩土界面处的衔接条件以及桩端刚性支承形式,对桩的一维波动方程进行求解,得到了桩顶复刚度函数、土层阻抗因子的频域形式解答,并讨论了主要参数对桩基动力行为的影响。计算结果表明:随着饱和度的减小,桩顶动刚度因子和等效阻尼的振幅随之减小,但桩土体系的共振频率则基本不受其影响。在桩土模量比的分析中,应区别对待土和桩弹性模量引起的不同反应。模型揭示了土体动力响应从单相到饱和两相介质条件下的完整演化过程,为描述实际土体环境下桩基动力行为提供了较为完备的理论框架。 相似文献
196.
197.
根据高阻抗电弧炉电气设计原理及60 t电弧炉基础设计数据,对其供电模式进行重新计算与优化,使热效率提高,平均吨钢电耗降低约44 k Wh,经济效益显著。 相似文献
198.
Francesco Malara Alessandro Cannavale Giuseppe Gigli 《Progress in Photovoltaics: Research and Applications》2015,23(3):290-301
In the last few years, a new class of smart multifunctional photoelectrochemical devices has been attracting the interest of several academic institutions and industrial companies: photovoltachromic cells, combining the features of photoelectrochromic cells with those of dye‐sensitized solar cells. Here, we report the results of a detailed electrochemical analysis aiming at investigating the electrochemical behavior of these complex photoelectrochemical devices. In particular, we have been focused on the effect of Li+ ions displacement during the coloration of the electrochromic tungsten oxide on the performances of the photovoltaic unit. As we had previously observed striking differences between the performances of the barely photovoltaic mode (with the tungsten oxide in the bleached state) and the photovoltachromic mode (with the tungsten oxide in the colored state), we thus attempted to provide a reasonable physical interpretation to the observed phenomena. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
199.
Nano-hardness (Hnano) and nano-elastic modulus (Enano) of corroded coating surface layer were investigated using nano-indentation after epoxy coated specimens were immersed in 5% NaCl solution. The penetration depths (d) of corrosive media into epoxy coating were calculated fitting the curves of (H/E)nano vs. indentation depth (h). EIS spectra of epoxy coated specimens immersed in 5% NaCl solution for different time were measured. Finally the relationship of capacitance (Cf,T) of corroded epoxy coating with the penetration depth of corrosive media was studied. The experimental results showed that the transportation process of corrosive media into epoxy coating was studied through the profiles of (H/E)nano with indentation depth. The penetration depth of corrosive media into the epoxy coating increases rapidly with immersed time firstly, and then increases slowly. The capacitance of corroded epoxy coating has a linear function relationship with the penetration depth of corrosive media into epoxy coating. Nano-indentation can be used to study the transportation process of corrosive media into organic coating. 相似文献
200.
土地更新调查县(区、市)级行政界线及面积接边方法——以昆明市为例 总被引:1,自引:0,他引:1
民政勘界形成的行政界线和行政区面积成果是国家相关法律认定的法定成果,土地利用现状更新调查的土地权属界定和面积量算控制必须严格沿用民政勘界成果。针对1∶5万民政堪界成果转绘到1∶1万土地利用现状图上后,产生权属界线与实地微观地形、地貌不符、1∶1万图幅之间的权属、图斑界线产生接边误差、1∶5万图幅与其相应的1∶1万分幅面积之和存在误差等问题,提出了基于土地利用现状数据库、利用数字制图和数据库管理技术进行行政界线和面积接边的方法。 相似文献