12,967 research outputs found
Analysis & design of data farming algorithm for cardiac patient data
Data farming is a process to grow data by applying various statistical, predictions, machine learning and data mining approach on the available data. As data collection cost is high so many times data mining projects use existing data collected for various other purposes, such as daily collected data to process and data required for monitoring & control. Sometimes, the dataset available might be large or wide data set and sufficient for extraction of knowledge but sometimes the data set might be narrow and insufficient to extract meaningful knowledge or the data may not even exist. Mining from wide datasets has received wide attention in the available literature. Many models and algorithms for data reduction & feature selection have been developed for wide datasets. Determining or extracting knowledge from a narrow data set (partial availability of data) or in the absence of an existing data set has not been sufficiently addressed in the literature. In this paper we propose an algorithm for data farming, which farm sufficient data from the available little seed data. Classification accuracy of J48 classification for farmed data is achieved better than classification results for the seed data, which proves that the proposed data farming algorithm is effective
Multiwavelength Study of NGC 281 Region
We present a multiwavelength study of the NGC 281 complex which contains the
young cluster IC 1590 at the center, using deep wide-field optical UBVI_c
photometry, slitless spectroscopy along with archival data sets in the
near-infrared (NIR) and X-ray. The extent of IC 1590 is estimated to be ~6.5
pc. The cluster region shows a relatively small amount of differential
reddening. The majority of the identified young stellar objects (YSOs) are low
mass PMS stars having age <1-2 Myr and mass 0.5-3.5 M_\odot. The slope (\Gamma)
of the mass function for IC 1590, in the mass range 2 < M/M_\odot \le 54, is
found to be -1.11+-0.15. The slope of the K-band luminosity function
(0.37+-0.07) is similar to the average value (~0.4) reported for young
clusters. The distribution of gas and dust obtained from the IRAS, CO and radio
maps indicates clumpy structures around the central cluster. The radial
distribution of the young stellar objects, their ages, \Delta(H-K) NIR-excess,
and the fraction of classical T Tauri stars suggest triggered star formation at
the periphery of the cluster region. However, deeper optical, NIR and MIR
observations are needed to have a conclusive view of star formation scenario in
the region. The properties of the Class 0/I and Class II sources detected by
using the Spitzer mid-infrared observations indicate that a majority of the
Class II sources are X-ray emitting stars, whereas X-ray emission is absent
from the Class 0/I sources. The spatial distribution of Class 0/I and Class II
sources reveals the presence of three sub-clusters in the NGC 281 West region.Comment: 29 pages, 21 figures and 11 tables, Accepted for the publication in
PAS
A Study of starless dark cloud LDN 1570: Distance, Dust properties and Magnetic field geometry
We wish to map the magnetic field geometry and to study the dust properties
of the starless cloud, L1570, using multi-wavelength optical polarimetry and
photometry of the stars projected on the cloud. We made R-band imaging
polarimetry of the stars projected on a cloud, L1570, to trace the magnetic
field orientation. We also made multi-wavelength polarimetric and photometric
observations to constrain the properties of dust in L1570. We estimated a
distance of 394 +/- 70 pc to the cloud using 2MASS JHKs colours. Using the
values of the Serkowski parameters namely , ,
{\lambda}max and the position of the stars on near infrared color-color
diagram, we identified 13 stars that could possibly have intrinsic polarization
and/or rotation in their polarization angles. One star, 2MASS
J06075075+1934177, which is a B4Ve spectral type, show the presence of diffuse
interstellar bands in the spectrum apart from showing H{\alpha} line in
emission. There is an indication for the presence of slightly bigger dust
grains towards L1570 on the basis of the dust grain size-indicators such as
{\lambda}max and Rv values. The magnetic field lines are found to be parallel
to the cloud structures seen in the 250{\mu}m images (also in 8{\mu}m and
12{\mu}m shadow images) of L1570. Based on the magnetic field geometry, the
cloud structure and the complex velocity structure, we believe that L1570 is in
the process of formation due to the converging flow material mediated by the
magnetic field lines. Structure function analysis showed that in the L1570
cloud region the large scale magnetic fields are stronger when compared with
the turbulent component of magnetic fields. The estimated magnetic field
strengths suggest that the L1570 cloud region is sub-critical and hence could
be strongly supported by the magnetic field lines.Comment: 26 pages, 22 figures, and 7 tables; Accepted for its publication in
A&
Electronic conduction in a three-terminal molecular transistor
The electronic conduction of a novel, three-terminal molecular architecture,
analogous to a heterojunction bipolar transistor is studied. In this
architecture, two diode arms consisting of donor-acceptor molecular wires fuse
through a ring, while a gate modulating wire is a \pi-conjugated wire. The
calculated results show the enhancement or depletion mode of a transistor by
applying a gate field along the positive or negative direction. A small gate
field is required to switch on the current in the proposed architecture. The
changes in the electronic conduction can be attributed to the intrinsic dipolar
molecular architecture in terms of the evolution of molecular wavefunctions,
specifically the one associated with the terphenyl group of the modulating wire
in the presence of the gate field.Comment: 13 pages, 5 figure
Low-mass young stellar population and star formation history of the cluster IC 1805 in the W4 H{\sc ii} region
W4 is a giant H{\sc ii} region ionized by the OB stars of the cluster
IC~1805. The H{\sc ii} region/cluster complex has been a subject of numerous
investigations as it is an excellent laboratory for studying the feedback
effect of massive stars on the surrounding region. However, the low-mass
stellar content of the cluster IC~1805 remains poorly studied till now. With
the aim to unravel the low-mass stellar population of the cluster, we present
the results of a multiwavelength study based on deep optical data obtained with
the Canada-France-Hawaii Telescope, infrared data from 2MASS, Space
Telescope and X-ray data from Space Telescope. The present optical
dataset is complete enough to detect stars down to 0.2~M, which is the
deepest optical observations so far for the cluster. We identified 384
candidate young stellar objects (YSOs; 101 Class I/II and 283 Class III) within
the cluster using various colour-colour and colour-magnitude diagrams. We
inferred the mean age of the identified YSOs to be 2.5 Myr and mass in
the range 0.3 - 2.5 M. The mass function of our YSO sample has a power
law index of -1.23 0.23, close to the Salpeter value (-1.35), and
consistent with those of other star-forming complexes. We explored the disk
evolution of the cluster members and found that the diskless sources are
relatively older compared to the disk bearing YSO candidates. We examined the
effect of high-mass stars on the circumstellar disks and found that within
uncertainties, the influence of massive stars on the disk fraction seems to be
insignificant. We also studied the spatial correlation of the YSOs with the
distribution of gas and dust of the complex to conclude that IC 1805 would have
formed in a large filamentary cloud.Comment: Accepted for publication in MNRAS; 34 pages, 10 figure
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