The estimation of evapotranspiration(ET) over heterogeneous land surface over arid and semi-arid region is quite complicated and significant. In this paper, NOAA/AVHRR remote sensing data, NCEP grid data and the meteorological stations data are used to estimate daily ET over the Heihe river basin by integrating Surface Energy Algorithm for Land model [1,2] and the Penman method[3]. As for clear days, Remote sensing model is used to retrieval the instantaneous ET to daily ET [4]. FAO-17 Penman method is also used to estimate the same day's reference crop ET by NCEP grid data and the meteorological stations data. The relationship between actual ET and the reference crop ET can be used to calculate the actual ET based on the results from FAO-17 Penman method on the cloudy days. These results are validated by observation data and other study in Heihe River Basin.

The corpus analysis methods in Chinese keyword extraction look on the corpus as a single sample of language stochastic process. But the distributions of keywords in the whole corpus and in each document are very different from each other. The extraction based on global statistical information only can get significant keywords in the whole corpus. Max-duplicated strings contain the local significant keywords in each document. In this paper, we designed an efficient algorithm to extract the max-duplicated strings by building PAT-tree for the document, so that the keywords can be picked out from the max-duplicated strings by their SIG values in the corpus.