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发电厂直流系统接地故障分析与处理 总被引:1,自引:0,他引:1
分析发电厂直流系统接地故障的原因与危害,介绍了几种查找接地故障的方法,但因受直流系统分布电容的干扰,检测精度往往不够,需要进行改进,以提高直流系统的安全运行水平。 相似文献
223.
This study investigated the impact of weblog use on individual learning in the context of university senior-level business education. As an emergent form of personal communication, weblogs enable people to publish their thoughts as webpages, and to share information and knowledge. Recognizing the potential impact of weblogs on knowledge expression and sharing, this research sought to empirically examine whether the continuous use of weblogs as online learning logs would affect student learning performance. The assumption was that effective use of weblogs promoted the constructivist models of learning by supporting both cognitive and social knowledge construction, and by reinforcing individual accountability in learning. Results from an Information Systems undergraduate course with 31 participants indicated that the performance of students' weblogs was a significant predictor of the learning outcome (while traditional coursework was not). Moreover, individuals' cognitive construction effort to build their own mental models and social construction effort to further enrich/expand knowledge resources appeared to be two key aspects of the constructivist learning with weblogs. Our results imply the potential benefit of using weblogs as a knowledge construction tool and a social learning medium 相似文献
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关于移动平均过程两系数的推导 总被引:1,自引:0,他引:1
杜德文 《石油化工高等学校学报》1995,(2)
对经济预测方法中两公式给出了证明,两公式的系数被显式推导出来,这两个公式是时间序列模型公式,广泛用于经济预测之中,但文献上很难找到推导过程,本文的证明是基本的,无需高深数学知识即可理解. 相似文献
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较深入地研究了折反光学系统的红外像面,为确定实际的红外像面提出了一个新方法—计算从可见光边缘无色的弥散圆到红外最佳像面的距离。实践证明,这是确定这类光学系统最佳像面的一个方便、可靠的方法。 相似文献
228.
Hot-isostatically pressed silicon oxynitride (Si2N2O) ceramics free from sintering aids were oxidized in 1 atm dry oxygen at 1100 and 1300°C. The structural and chemical characteristics of the oxide and the nature of the oxide–Si2N2O interface were determined using cross-sectional transmission electron microscopy in conjunction with small-probe energy dispersive X-ray analysis and selected-area electron diffraction. Oxidation of Si2N2O resulted in the formation of amorphous SiO2. The oxide–Si2N2O interface was chemically abrupt. The interface was very flat when parallel to low-index, high atomic density Si2N2O crystal planes but became notably undulated if oriented to high index, low atomic density planes. About 6 vol% residual SiO2 phase was present in the bulk of the Si2N2O ceramics. Current results have provided an important baseline for the understanding of the oxidation behaviour of Si2N2O. © 1998 Kluwer Academic Publishers 相似文献
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Infiltration and localization of preferential infiltration zones at the dam abutment are measured using radioactive tracer tests of flow in boreholes,meanwhile interconnection between boreholes and the energing water points is analysed.The theory and practice of radioactive tracer synthetic detective method are described to give methods and calculation formulae used under the condition of stable flow in single well to measure permeability coefficient and hydrostatic heads.Major single hole techniques including measurement for seepage line,velocity,rate of seepage flow and relationship of recharge of groundwater in aquifers are introduced briefly.The possibilities offered by natureal tracers are analysed,uincluding electric-conduct,pH-value and temperature of water as well as stable isotopes(D,^18O) and tritium.Furthermore,the sensibilities of this theory and methods were confirmed by detecting seepage flow field of Xinanjiang Dam. 相似文献