传统的电网可靠性评估采用固定不变的元件年均故障率模型,难以适应电力系统短期风险评估需求。电网故障与灾害性天气具有较强的时间相关性,气象灾害具有明显的季节性特征,因此电网风险也具有时间波动性。在描述电网元件故障参数时,需要...传统的电网可靠性评估采用固定不变的元件年均故障率模型,难以适应电力系统短期风险评估需求。电网故障与灾害性天气具有较强的时间相关性,气象灾害具有明显的季节性特征,因此电网风险也具有时间波动性。在描述电网元件故障参数时,需要从原来的一维横向连续时间下的年均值模型,拓展到考虑历史同期(纵向)时间和导致故障的因素,特别是外部气象环境因素,以便更准确地描述时间及环境相依的电网故障率。在传统年均值模型的基础上建立了不同时间尺度、不同气象灾害类型下的元件故障模型,并依据此模型进行电网可靠性评估。按照该方法对西南某省级电网近3年内500 k V输电线路的故障数据进行了分析,对该电网的可靠性进行了评估。计算结果表明,不同时间段电网的可靠性指标与年均值相比具有较大差异,验证了时空环境相依的可靠性评估的必要性。展开更多
Gelatin was covalently immobilized onto the polyurethane membrane surface grafted previously with poly(methacrylic acid) (PU g PMAA) using 1 [(3 dimethylamino)propyl] 3 ethyl carbodiimide as the condensing reagent. AT...Gelatin was covalently immobilized onto the polyurethane membrane surface grafted previously with poly(methacrylic acid) (PU g PMAA) using 1 [(3 dimethylamino)propyl] 3 ethyl carbodiimide as the condensing reagent. ATR FTIR and ESCA characterizations verify the occurrence of the grafting, and prove that the immobilized amount of gelatin is proportional to the number of active sites, i.e . carboxylic groups on PU surface. Endothelial cells culture reveals that the cell attachment and cell growth on PU g PMAA g Gelatin are both improved obviously, demonstrating that a cell compatible PU is obtained and the immobilizing method is quite effective to introduce cell growth factors onto polymer surface.展开更多
文摘传统的电网可靠性评估采用固定不变的元件年均故障率模型,难以适应电力系统短期风险评估需求。电网故障与灾害性天气具有较强的时间相关性,气象灾害具有明显的季节性特征,因此电网风险也具有时间波动性。在描述电网元件故障参数时,需要从原来的一维横向连续时间下的年均值模型,拓展到考虑历史同期(纵向)时间和导致故障的因素,特别是外部气象环境因素,以便更准确地描述时间及环境相依的电网故障率。在传统年均值模型的基础上建立了不同时间尺度、不同气象灾害类型下的元件故障模型,并依据此模型进行电网可靠性评估。按照该方法对西南某省级电网近3年内500 k V输电线路的故障数据进行了分析,对该电网的可靠性进行了评估。计算结果表明,不同时间段电网的可靠性指标与年均值相比具有较大差异,验证了时空环境相依的可靠性评估的必要性。
文摘Gelatin was covalently immobilized onto the polyurethane membrane surface grafted previously with poly(methacrylic acid) (PU g PMAA) using 1 [(3 dimethylamino)propyl] 3 ethyl carbodiimide as the condensing reagent. ATR FTIR and ESCA characterizations verify the occurrence of the grafting, and prove that the immobilized amount of gelatin is proportional to the number of active sites, i.e . carboxylic groups on PU surface. Endothelial cells culture reveals that the cell attachment and cell growth on PU g PMAA g Gelatin are both improved obviously, demonstrating that a cell compatible PU is obtained and the immobilizing method is quite effective to introduce cell growth factors onto polymer surface.
