4,006 research outputs found
Secure Metric-Based Index for Similarity Cloud
We propose a similarity index that ensures data privacy and thus is suitable for search systems outsourced in a cloud. The proposed solution can exploit existing efficient metric indexes based on a fixed set of reference points. The method has been fully implemented as a security extension of an existing established approach called M-Index. This Encrypted M-Index supports evaluation of standard range and nearest neighbors queries both in precise and approximate manner. In the first part of this work, we analyze various levels of privacy in existing or future similarity search systems; the proposed solution tries to keep a reasonable privacy level while relocating only the necessary amount of work from server to an authorized client. The Encrypted M-Index has been tested on three real data sets with focus on various cost components
The Environment of HII Galaxies revisited
We present a study of the close (< 200 kpc) environment of 110 relatively
local (z< 0.16) HII galaxies, selected from the Sloan Digital Sky Survey (SDSS;
DR7). We use available spectroscopic and photometric redshifts in order to
investigate the presence of a close and possibly interacting companion galaxy.
Our aim is to compare the physical properties of isolated and interacting HII
galaxies and investigate possible systematic effects in their use as
cosmological probes. We find that interacting HII galaxies tend to be more
compact, less luminous and have a lower velocity dispersion than isolated ones,
in agreement with previous studies on smaller samples. However, as we verified,
these environmental differences do not affect the cosmologically important
L_{H{\beta}}-{\sigma} correlation of the HII galaxies.Comment: 5 pages, accepted for publication in A&
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