13 research outputs found

    ROTSE All Sky Surveys for Variable Stars I: Test Fields

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    The ROTSE-I experiment has generated CCD photometry for the entire Northern sky in two epochs nightly since March 1998. These sky patrol data are a powerful resource for studies of astrophysical transients. As a demonstration project, we present first results of a search for periodic variable stars derived from ROTSE-I observations. Variable identification, period determination, and type classification are conducted via automatic algorithms. In a set of nine ROTSE-I sky patrol fields covering about 2000 square degrees we identify 1781 periodic variable stars with mean magnitudes between m_v=10.0 and m_v=15.5. About 90% of these objects are newly identified as variable. Examples of many familiar types are presented. All classifications for this study have been manually confirmed. The selection criteria for this analysis have been conservatively defined, and are known to be biased against some variable classes. This preliminary study includes only 5.6% of the total ROTSE-I sky coverage, suggesting that the full ROTSE-I variable catalog will include more than 32,000 periodic variable stars.Comment: Accepted for publication in AJ 4/00. LaTeX manuscript. (28 pages, 11 postscript figures and 1 gif

    EVALUATING THE POTENTIAL FOR LOW ENERGY EMITTERS TO FACILITATE SOLAR-POWERED DRIP IRRIGATION IN SUB-SAHARAN AFRICA

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    Abstract Introducing irrigation to smallholder farms in Sub-Saharan Africa (SSA) can increase food security, improve nutrition, and reduce poverty. To explore the possibility of using drip irrigation on smallholder farms in SSA, we introduce a feasibility study that views the design space from both a user-centered lens, explaining how drip might be successful in the future, and from an engineering lens. With a first-order model, we compare estimated capital costs of drip and sprinkler systems for various farm profiles and show that drip has the potential to be a viable technology for many farms in SSA
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