948 research outputs found
Improved content based watermarking for images
Due to improvements in imaging technologies and the ease with which digital content can be created and manipulated, there is need for the copyright protection of digital content. It is also essential to have techniques for authentication of the content as well as the owner. To this end, this thesis proposes a robust and transparent scheme of watermarking that exploits the human visual systems’ sensitivity to frequency, along with local image characteristics obtained from the spatial domain, improving upon the content based image watermarking scheme of Kay and Izquierdo. We implement changes in this algorithm without much distortion to the image, while making it possible to extract the watermark by use of correlation. The underlying idea is generating a visual mask based on the human visual systems’ perception of image content. This mask is used to embed a decimal sequence, while keeping its amplitude below the distortion sensitivity of the image pixel. We consider texture, luminance, corner and the edge information in the image to generate a mask that makes the addition of the watermark less perceptible to the human eye. The operation of embedding and extraction of the watermark is done in the frequency domain thereby providing robustness against common frequency-based attacks including image compression and filtering. We use decimal sequences for watermarking instead of pseudo random sequences, providing us with a greater flexibility in the choice of sequence. Weighted Peak Signal to Noise Ratio is used to evaluate the perceptual change between the original and the watermarked image
Chiral Symmetry Breaking and Dual Gluon Mass in the Confining Region of QCD
The Dual Meissner Effect description of QCD in the confining region provides
behaviour for the gluon propagator and involves the dual gluon
mass as a parameter. This is used in the Schwinger-Dyson equation for the
quarks in the infrared region to exhibit chiral symmetry breaking for light
quarks. Using the light quark condensate as input, the dual gluon mass is
determined and its importance in showing the asymptotic free behaviour of the
extrinsic curvature coupling in the rigid QCD string is discussed.Comment: 11 pages, Accepted for Publication in Phys.Lett.
Photometry and low resolution spectroscopy of hot post-AGB candidates
We have obtained Johnson U, B, V and Cousins R, I photometry and low
resolution spectra of a small sample of hot post-AGB candidates. Using the
present data in combination with JHK data from 2MASS, infrared data from the
MSX catalog and the IRAS fluxes, we have studied the spectral energy
distribution (SED) of these stars. Using the DUSTY code we have estimated the
dust temperatures, the distances to the stars, the mass-loss rates, angular
radii of the inner boundary of the dust envelopes and dynamical ages from the
tip of the AGB. These candidates have also been imaged through a narrow band
H-alpha filter, to search for nebulosity around the central stars. Our H-alpha
images revealed the bipolar morphology of the low excitation PN IRAS 17395-0841
with an angular extent of 2.8arcsec. The bipolar lobes of IRAS 17423-1755 in
H-alpha were found to have an angular extent of 3.5arcsec (south-east lobe) and
2.2arcsec (north-west lobe). The dust envelope characteristics, low resolution
spectrum and IRAS colors suggest that IRAS 18313-1738 is similar to the
proto-planetary nebula (PPN) HD 51585. The SED of IRAS 17423-1755, IRAS
18313-1738 and IRAS 19127+1717 show a warm dust component (in addition to the
cold dust) which may be due to recent and ongoing mass-loss.Comment: 20 pages, 6 figures, h-alpha figure compressed with XV, paper
accepted for publication in Astronomy & Astrophysic
Comparative effectiveness of inter-simple sequence repeat and randomly amplified polymorphic DNA markers to study genetic diversity of Indian Garcinia
A study to compare the effectiveness of inter-simple sequence repeats (ISSR) and randomly amplified polymorphic DNA (RAPD) profiling was carried out with a total of 65 DNA samples using 12 species of Indian Garcinia. ISSR and RAPD profiling were performed with 19 and 12 primers, respectively. ISSR markers generated a total number of 156 bands with 92 polymorphic bands, while RAPD markers produced a total of 134 bands with 80 polymorphic bands. Percentage of polymorphic loci in RAPD profiling was 60.4% while in ISSR profiling, it was 59.3%. Heterogeneity index was similar for the markers, 0.86 for ISSR and 0.89 for RAPD, indicating that both the marker systems are effective in determining polymorphism in Garcinia. ISSR markers showed clear distinction among the species whereas RAPD markers showed segregation based on geographical location as well as species based.Key words: Garcinia, genetic diversity, inter-simple sequence repeats, randomly amplified polymorphic DNA, principal component analysis
Weak G-band stars on the H-R Diagram: Clues to the origin of Li anomaly
Weak G-band (WGB) stars are a rare class of cool luminous stars that present
a strong depletion in carbon, but also lithium abundance anomalies that have
been little explored in the literature since the first discovery of these
peculiar objects in the early 50's. Here we focus on the Li-rich WGB stars and
report on their evolutionary status. We explore different paths to propose a
tentative explanation for the lithium anomaly. Using archive data, we derive
the fundamental parameters of WGB (Teff, log g, log(L/Lsun)) using Hipparcos
parallaxes and recent temperature scales. From the equivalent widths of Li
resonance line at 6707 {\AA}, we uniformly derive the lithium abundances and
apply when possible NLTE corrections following the procedure described by Lind
et al. (2009). We also compute dedicated stellar evolution models in the mass
range 3.0 to 4.5 Msun, exploring the effects of rotation-induced and
thermohaline mixing. These models are used to locate the WGB stars in the H-R
diagram and to explore the origin of the abundance anomalies. The location of
WGB stars in the H-R diagram shows that these are intermediate mass stars of
masses ranging from 3.0 to 4.5 Msun located at the clump, which implies a
degeneracy of their evolutionary status between subgiant/red giant branch and
core helium burning phases. The atmospheres of a large proportion of WGB stars
(more than 50%) exhibit lithium abundances A(Li) \geq 1.4 dex similar to
Li-rich K giants. The position of WGB stars along with the Li-rich K giants in
the H-R diagram however indicates that both are well separated groups. The
combined and tentatively consistent analysis of the abundance pattern for
lithium, carbon and nitrogen of WGB stars seems to indicate that carbon
underabundance could be decorrelated from the lithium and nitrogen
overabundances.Comment: 13 pages, 3 figures, Accepted for publication in Astronomy and
Astrophysic
A hybrid approach for text summarization using semantic latent Dirichlet allocation and sentence concept mapping with transformer
Automatic text summarization generates a summary that contains sentences reflecting the essential and relevant information of the original documents. Extractive summarization requires semantic understanding, while abstractive summarization requires a better intermediate text representation. This paper proposes a hybrid approach for generating text summaries that combine extractive and abstractive methods. To improve the semantic understanding of the model, we propose two novel extractive methods: semantic latent Dirichlet allocation (semantic LDA) and sentence concept mapping. We then generate an intermediate summary by applying our proposed sentence ranking algorithm over the sentence concept mapping. This intermediate summary is input to a transformer-based abstractive model fine-tuned with a multi-head attention mechanism. Our experimental results demonstrate that the proposed hybrid model generates coherent summaries using the intermediate extractive summary covering semantics. As we increase the concepts and number of words in the summary the rouge scores are improved for precision and F1 scores in our proposed model
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