30,329 research outputs found
Automatic Clustering with Single Optimal Solution
Determining optimal number of clusters in a dataset is a challenging task.
Though some methods are available, there is no algorithm that produces unique
clustering solution. The paper proposes an Automatic Merging for Single Optimal
Solution (AMSOS) which aims to generate unique and nearly optimal clusters for
the given datasets automatically. The AMSOS is iteratively merges the closest
clusters automatically by validating with cluster validity measure to find
single and nearly optimal clusters for the given data set. Experiments on both
synthetic and real data have proved that the proposed algorithm finds single
and nearly optimal clustering structure in terms of number of clusters,
compactness and separation.Comment: 13 pages,4 Tables, 3 figure
GMRT observations of X-shaped radio sources
We present results from a study of X-shaped sources based on observations
using the Giant Metrewave Radio Telescope (GMRT). These observations were
motivated by our low frequency study of 3C 223.1 (Lal & Rao 2005), an X-shaped
radio source, which showed that the wings (or low-surface-brightness jets) have
flatter spectral indices than the active lobes (or high-surface-brightness
jets), a result not easily explained by most models. We have now obtained GMRT
data at 240 and 610 MHz for almost all the known X-shaped radio sources and
have studied the distribution of the spectral index across the sources. While
the radio morphologies of all the sources at 240 and 610 MHz show the
characteristic X-shape, the spectral characteristics of the X-shaped radio
sources, seem to fall into three categories, namely, sources in which (A) the
wings have flatter spectral indices than the active lobes, (B) the wings and
the active lobes have comparable spectral indices, and (C) the wings have
steeper spectral indices than the active lobes. We discuss the implications of
the new observational results on the various formation models that have been
proposed for X-shaped sources.Comment: The paper contains 12 figures and 3 tables, accepted for publication
in MNRAS Main Journal, please note, some figures are of lower qualit
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