The greedy algorithm is known to have a guaranteed approximation performance in many variations of the well-known minimum set cover problem. We analyze the number of elements covered by the greedy algorithm for the minimum set cover problem, when executed for k rounds. This analysis quite easily yields in the p-partial cover problem over a ground set of m elements the harmonic approximation gua...

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cover

Vegetation cover is the first barrier for the raindrops resulting to the interception and infiltration loss. Interception as one of the main components of ecohydrology equation plays a major role in the water balance of rangelands. However, few studies have been done on the interception of rangeland plants in Iran. This study was carried out to find the interception rate in Astragalus parrowian...

satellite imagery was used as a rapid and spatially explicit method to delineate crop residue cover and to estimate the use and intensity of conservation tillage. the potential of multispectral high-spatial resolution of worldview-2 local data was evaluated using 11 satellite spectral indices and linear spectral unmixing analysis (lsua). experimental plots were examined; residue cover was measu...

vegetation cover on a variety of different land uses in different parts of a city creates different forms of heat flow that this, in turn, generates the main framework of urban microclimate. the objective of this study is to survey the effect of land cover type on air temperature in the isfahan city. to do this, five regions in the isfahan city with different land cover type were selected. in e...

Ice-core records show that climate changes in the past have been large, rapid, and synchronous over broad areas extending into low latitudes, with less variability over historical times. These ice-core records come from high mountain glaciers and the polar regions, including small ice caps and the large ice sheets of Greenland and Antarctica.

[1] We use 22 monthly GRACE (Gravity Recovery and Climate Experiment) gravity fields to estimate the linear trend in Greenland ice mass during 2002–2004. We recover a decrease in total ice mass of 82 ± 28 km of ice per year, consistent with estimates from other techniques. Our uncertainty estimate is dominated by the effects of GRACE measurement errors and errors in our post glacial rebound (PG...

A number of national, regional and global land cover classification systems have been developed to meet specific user requirements for land cover mapping exercises, independent of scale, nomenclature and quality. However, this variety of land-cover classification systems limits the compatibility and comparability of land cover data. Furthermore, the current lack of interoperability between diff...