The sequential cropping index of arable land is important agricultural information. The aim of this article is to monitor and analyze the parameter, and offer reference for agricultural production. The cropping index ...The sequential cropping index of arable land is important agricultural information. The aim of this article is to monitor and analyze the parameter, and offer reference for agricultural production. The cropping index of arable land in Zhejiang Province, China from 2001 to 2004 was calculated using the second order difference based MODIS （moderate resolution imagine spectroradimeter） vegetation data from NASA （National Aeronautic and Space Administration） in America and the land use map with a scale of 1：25 000. It was found that the peak of the time series of the NDVI curve indicated that the ground biomass of crops reached the maximum, and fluctuated with the crops growing processes such as sowing, seeding, heading, ripeness, and harvesting within one year. Thus, the sequential cropping index was defined as the number of peaks of the time series of the NDVI curve. The sequential cropping index of all cities in Zhejiang Province, China was worked out. It is seen from the spatial distribution that the cropping index in the southwest Zhejiang Province is larger than that in the northeast. As for the temporal distribution, the sequential cropping index decreased from 2001 to 2003, whereas it increased slightly from 2003 to 2004. However, the index of arable land was relatively low, as far as the geographic position and climatic resource were concerned, and the potential of the sequential cropping index was great.展开更多
电力市场环境下,频繁的电能交易使系统运行的不确定性急剧增加。为保证系统的安全、可靠和经济运行,必须合理考虑不确定性因素的影响后,再对电网输电能力进行评估。该文提出了一种基于序贯蒙特卡罗仿真的可用输电能力(available transfe...电力市场环境下,频繁的电能交易使系统运行的不确定性急剧增加。为保证系统的安全、可靠和经济运行,必须合理考虑不确定性因素的影响后,再对电网输电能力进行评估。该文提出了一种基于序贯蒙特卡罗仿真的可用输电能力(available transfer capability,ATC)计算方法,能综合考虑动态时变性和不确定性的影响,根据元件的运行特性及状态转移特性按时间顺序来仿真系统状态,并定义一系列的概率指标进行ATC评估。采用Matlab6.5编写相关的计算程序,通过IEEE39节点系统的算例分析,证明在ATC计算中,考虑不确定性和时变性因素的必要性。计算结果表明,该文提出的方法新颖实用,具有一定的工程应用价值。展开更多
文摘The sequential cropping index of arable land is important agricultural information. The aim of this article is to monitor and analyze the parameter, and offer reference for agricultural production. The cropping index of arable land in Zhejiang Province, China from 2001 to 2004 was calculated using the second order difference based MODIS （moderate resolution imagine spectroradimeter） vegetation data from NASA （National Aeronautic and Space Administration） in America and the land use map with a scale of 1：25 000. It was found that the peak of the time series of the NDVI curve indicated that the ground biomass of crops reached the maximum, and fluctuated with the crops growing processes such as sowing, seeding, heading, ripeness, and harvesting within one year. Thus, the sequential cropping index was defined as the number of peaks of the time series of the NDVI curve. The sequential cropping index of all cities in Zhejiang Province, China was worked out. It is seen from the spatial distribution that the cropping index in the southwest Zhejiang Province is larger than that in the northeast. As for the temporal distribution, the sequential cropping index decreased from 2001 to 2003, whereas it increased slightly from 2003 to 2004. However, the index of arable land was relatively low, as far as the geographic position and climatic resource were concerned, and the potential of the sequential cropping index was great.
文摘电力市场环境下,频繁的电能交易使系统运行的不确定性急剧增加。为保证系统的安全、可靠和经济运行,必须合理考虑不确定性因素的影响后,再对电网输电能力进行评估。该文提出了一种基于序贯蒙特卡罗仿真的可用输电能力(available transfer capability,ATC)计算方法,能综合考虑动态时变性和不确定性的影响,根据元件的运行特性及状态转移特性按时间顺序来仿真系统状态,并定义一系列的概率指标进行ATC评估。采用Matlab6.5编写相关的计算程序,通过IEEE39节点系统的算例分析,证明在ATC计算中,考虑不确定性和时变性因素的必要性。计算结果表明,该文提出的方法新颖实用,具有一定的工程应用价值。
