Based on the experience of GIS equipment maintenance, the causes of air leakage defects of GIS equipment running in a 330 substation were analyzed. After the equipment was disassembled, the main causes of air leakage ...Based on the experience of GIS equipment maintenance, the causes of air leakage defects of GIS equipment running in a 330 substation were analyzed. After the equipment was disassembled, the main causes of air leakage were found, and a series of improvement measures were taken to eliminate the GIS equipment leakage defect. And the effective and feasible advice was put forward for this type of air leakage problem. The results lay a foundation for the safe and stable operation of GIS equipment.展开更多
Satellite and human visual observation are two of the most important observation approaches for cloud cover. In this study, the total cloud cover （TCC） observed by MODIS onboard the Terra and Aqua satellites was com...Satellite and human visual observation are two of the most important observation approaches for cloud cover. In this study, the total cloud cover （TCC） observed by MODIS onboard the Terra and Aqua satellites was compared with Synop meteorological station observations over the North China Plain and its surrounding regions for 11 years during daytime and 7 years during nighttime. The Synop data were recorded eight times a day at 3-h intervals. Linear interpolation was used to interpolate the Synop data to the MODIS overpass time in order to reduce the temporal deviation between the satellite and Synop observations. Results showed that MODIS-derived TCC had good consistency with the Synop observations; the correlation coefficients ranged from 0.56 in winter to 0.73 in summer for Terra MODIS, and from 0.55 in winter to 0.71 in summer for Aqua MODIS. However, they also had certain differences. On average, the MODIS-derived TCC was 15.16% higher than the Synop data, and this value was higher at nighttime （15.58%-16.64%） than daytime （12.74%-14.14%）. The deviation between the MODIS and Synop TCC had large seasonal variation, being largest in winter （29.53%-31.07%） and smallest in summer （4.46%-6.07%）. Analysis indicated that cloud with low cloud-top height and small cloud optical thickness was more likely to cause observation bias. Besides, an increase in the satellite view zenith angle, aerosol optical depth, or snow cover could lead to positively biased MODIS results, and this affect differed among different cloud types.展开更多
水轮机组联接螺栓的工作状态对水轮机组的稳定运行起重要作用。该文根据预紧力施加准则,在一定范围内选择多组工况,研究分析不同预紧力作用下,水轮机顶盖结构的变形规律和联接螺栓的应力特性。结果表明:施加335 k N预紧力时,顶盖最大变...水轮机组联接螺栓的工作状态对水轮机组的稳定运行起重要作用。该文根据预紧力施加准则,在一定范围内选择多组工况,研究分析不同预紧力作用下,水轮机顶盖结构的变形规律和联接螺栓的应力特性。结果表明:施加335 k N预紧力时,顶盖最大变形为2.53 mm、内顶盖联接螺栓最大应力为91 MPa,施加945 k N预紧力时,顶盖最大变形为2.31 mm、内顶盖联接螺栓最大应力为238.5 MPa,螺栓应力均小于其承载极限;预紧力越大,则顶盖变形越小、螺栓承受应力越大,且螺栓的最大应力集中分布在其与顶盖法兰把合面附近。展开更多
文摘Based on the experience of GIS equipment maintenance, the causes of air leakage defects of GIS equipment running in a 330 substation were analyzed. After the equipment was disassembled, the main causes of air leakage were found, and a series of improvement measures were taken to eliminate the GIS equipment leakage defect. And the effective and feasible advice was put forward for this type of air leakage problem. The results lay a foundation for the safe and stable operation of GIS equipment.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41590874 and 41590875)the Ministry of Science and Technology of China (Grant No. 2014CB953703)
文摘Satellite and human visual observation are two of the most important observation approaches for cloud cover. In this study, the total cloud cover （TCC） observed by MODIS onboard the Terra and Aqua satellites was compared with Synop meteorological station observations over the North China Plain and its surrounding regions for 11 years during daytime and 7 years during nighttime. The Synop data were recorded eight times a day at 3-h intervals. Linear interpolation was used to interpolate the Synop data to the MODIS overpass time in order to reduce the temporal deviation between the satellite and Synop observations. Results showed that MODIS-derived TCC had good consistency with the Synop observations; the correlation coefficients ranged from 0.56 in winter to 0.73 in summer for Terra MODIS, and from 0.55 in winter to 0.71 in summer for Aqua MODIS. However, they also had certain differences. On average, the MODIS-derived TCC was 15.16% higher than the Synop data, and this value was higher at nighttime （15.58%-16.64%） than daytime （12.74%-14.14%）. The deviation between the MODIS and Synop TCC had large seasonal variation, being largest in winter （29.53%-31.07%） and smallest in summer （4.46%-6.07%）. Analysis indicated that cloud with low cloud-top height and small cloud optical thickness was more likely to cause observation bias. Besides, an increase in the satellite view zenith angle, aerosol optical depth, or snow cover could lead to positively biased MODIS results, and this affect differed among different cloud types.
文摘水轮机组联接螺栓的工作状态对水轮机组的稳定运行起重要作用。该文根据预紧力施加准则,在一定范围内选择多组工况,研究分析不同预紧力作用下,水轮机顶盖结构的变形规律和联接螺栓的应力特性。结果表明:施加335 k N预紧力时,顶盖最大变形为2.53 mm、内顶盖联接螺栓最大应力为91 MPa,施加945 k N预紧力时,顶盖最大变形为2.31 mm、内顶盖联接螺栓最大应力为238.5 MPa,螺栓应力均小于其承载极限;预紧力越大,则顶盖变形越小、螺栓承受应力越大,且螺栓的最大应力集中分布在其与顶盖法兰把合面附近。
