Accurate and up-to-date global land cover data sets are necessary for various global change research studies including climate change, biodiversity conservation, ecosystem assessment, and environmental modeling. In recent years, substantial advancement has been achieved in generating such data products. Yet, we are far from producing geospatially consistent high-quality data at an operational l...

How can one find a subset, ideally as small as possible, that well represents a massive dataset? I.e., its corresponding utility, measured according to a suitable utility function, should be comparable to that of the whole dataset. In this paper, we formalize this challenge as a submodular cover problem. Here, the utility is assumed to exhibit submodularity, a natural diminishing returns condit...

large scale land use/cover changes and habitat fragmentation is a major factor in the distribution and functioning of ecosystems. for analysis the relationship between land use changes and their impacts on biodiversity, land cover and land use information is needed at different scales. the main goal of this study was to quantify the land use/ cover changes in arasbaran biosphere reserve, northw...

We introduce the successive Hitting Set model, where the set system is not given in advance but a set generator produces the sets that contain a specific element from the universe on demand. Despite incomplete knowledge about the set system, we show that several approximation algorithms for the conventional Hitting Set problem can be adopted to perform well in this model. We describe, and exper...

We study a geometric hitting set problem involving unirectional rays and curves in the plane. We show that this problem is hard to approximate within a logarithmic factor even when the curves are convex polygonal x-monotone chains. Additionally, it is hard to approximate within a factor of 76 even when the curves are line segments with bounded slopes. Lastly, we demonstrate that the problem is ...

in order to investigate genetic correlation and path analysis between grain yield and yield components, fifteen early maturing hybrids of grain corn (zea. mays) using a randomized complete block design with 4 replications were evaluated in khoramabad agricultural research center, iran. the data were collected and analyzed for ear emergence date, anthesis date, maturity date, plant height, ear h...

We consider the problem of hitting sets online. The hypergraph (i.e., rangespace consisting of points and ranges) is known in advance, and the ranges to be stabbed are input one-by-one in an online fashion. The online algorithm must stab each range upon arrival. An online algorithm may add points to the hitting set but may not remove already chosen points. The goal is to use the smallest number...