53 research outputs found
An automatic and efficient foreground object extraction scheme
This paper presents a method to differentiate the foreground objects from the
background of a color image. Firstly a color image of any size is input for
processing. The algorithm converts it to a grayscale image. Next we apply canny
edge detector to find the boundary of the foreground object. We concentrate to
find the maximum distance between each boundary pixel column wise and row wise
and we fill the region that is bound by the edges. Thus we are able to extract
the grayscale values of pixels that are in the bounded region and convert the
grayscale image back to original color image containing only the foreground
object
An inverse technique for reconstructing ocean’s density stratification from surface data
In this article, we propose an inverse technique that accurately reconstructs
the ocean's density stratification profile simply from free surface elevation
data. Satellite observations suggest that ocean surface contains the signature
of internal tides, which are internal gravity waves generated by the barotropic
tides. Since internal tides contain the information of ocean's density
stratification, the latter can in principle be reconstructed from the free
surface signature. We consider a simple theoretical model that approximates a
continuously stratified ocean as discrete layers of constant buoyancy
frequency; this facilitates the derivation of a closed-form dispersion
relation. First, we numerically simulate internal tide generation for toy ocean
scenarios and subsequently perform Space-Time Fourier Transform (STFT) of the
free surface, which yields internal tide spectra with wavenumbers corresponding
to the tidal frequency. The density profile is reconstructed by substituting
these wavenumbers into the dispersion relation. Finally, we consider a more
realistic situation with rotation, bottom topography, shear and density
profiles representative of the Strait of Gibraltar. Density reconstruction in
the presence and absence of shear are respectively found to be and
accurate
Morpho-kinematic and photoionization models of the multipolar structures in planetary nebula NGC 6572
We have studied the planetary nebula (PN) NGC 6572 through 3D
morpho-kinematic and photoionization modelling. The 3D morphology is
reconstructed from the Hubble Space Telescope images in different narrow band
filters and position-velocity spectra. The PN have a multipolar morphology
consisting of highly collimated outflows. The nebular image show signatures of
multiple lobes within a spiral-ring-like structure. The multipolar structure is
modelled with two bipolar shells (axes ratios 5.5:1 and 3:1), having closed and
opened lobes, respectively. A toroidal structure (radius:height = 1:3)
surrounds the shells at the waist. The toroidal axis aligns with the major axes
of the bipolar shells. Our study reveals the nebula to have a history of
collimated polar outflow perpendicular to a higher density equatorial wind with
the outflow seemingly have episodes of changing direction of ejection. We
construct a photoionization model of NGC 6572 using the deep optical spectra
obtained at the 2 m Himalayan Chandra Telescope. For the photoionization model,
we configure the input shell geometry in form of a highly bipolar nebular shell
with reference to the 3D morphology. Our photoionization model satisfactorily
reproduces the observables. We estimate the nebular elemental abundances, and
important characteristic parameters of the central star (e.g., effective
temperature, luminosity, gravity, mass, etc.) and the nebula (e.g., hydrogen
density profiles, radii, etc.). We compare the resolved H, [O III], and
[N II] profiles in the 4.2 m William Herschel Telescope with that from the
photoionization model and find a good characteristic match.Comment: 14 pages, 10 figures, 6 table
CURATION AND MANAGEMENT OF CULTURAL HERITAGE THROUGH LIBRARIES
Libraries, museums and archives hold valuable collections in a variety of media, presenting a vast
body of knowledge rooted in the history of human civilisation. These form the repository of the
wisdom of great works by thinkers of past and the present. The holdings of these institutions are
priceless heritage of the mankind as they preserve documents, ideas, and the oral and written
records. To value the cultural heritage and to care for it as a treasure bequeathed to us by our
ancestors is the major responsibility of libraries. The past records constitute a natural resource
and are indispensable to the present generation as well as to the generations to come. Libraries
preserve the documentary heritage resources for which they are primarily responsible. Any loss of
such materials is simply irreplaceable. Therefore, preserving this intellectual, cultural heritage
becomes not only the academic commitment but also the moral responsibility of the
librarians/information scientists, who are in charge of these repositories.
The high quality of the papers and the discussion represent the thinking and experience of experts
in their particular fields. The contributed papers also relate to the methodology used in libraries
in Asia to provide access to manuscripts and cultural heritage. The volume discusses best practices
in Knowledge preservation and how to collaborate and preserve the culture. The book also deals with
manuscript and archives issues in the digital era.
The approach of this book is concise, comprehensively, covering all major aspects of preservation
and conservation through libraries. The readership of the book is not just limited to library and
information science professionals, but also for those involved in conservation, preservation,
restoration or other related disciplines. The book will be useful for librarians, archivists and
conservators.
We thank the Sunan Kalijaga University, Special Libraries Association- Asian Chapter for their
trust and their constant support, all the contributors for their submissions, the members of the Local
and International Committee for their reviewing effort for making this publication possible
Radial magnetic field in a nonlinear dynamo model
Generation of magnetic field from seed magnetic field in a nonlinear rotating dynamo model. The initial magnetic field is axial-dipole. The important point is
change of magnetic field structure as the field grows. The field go
through a chaotic structure from initial axial-dipole structure and as
soon as magnetic field starts effecting the flow, the field emerges as a
large scale structure
Radial magnetic field in a kinematic dynamo model
Generation of magnetic field from seed magnetic field in a kinematic
dynamo model, where Lorentz force has been dropped from momentum
equation. The initial magnetic field is axial-dipole. After some time,
the radial magnetic field loose the large-scale structure and dominated by
small-components of the field
Energy exchanges between a two-dimensional front and internal wave modes
Fronts and near-inertial waves are energetic motions in the upper ocean that
can interact and provide a route for kinetic energy (KE) dissipation of
balanced oceanic flows. A quasilinear model is developed to study the KE
exchanges between a two-dimensional geostrophically-balanced front undergoing
strain-induced semigeostrophic frontogenesis and internal wave (IW) vertical
modes. The quasilinear model is solved numerically for variable imposed strain
magnitudes, initial IW vertical modes, and for both minimum frequency
(near-inertial, NI) and high-frequency IWs. The front-IW KE exchanges are
quantified separately during two frontogenetic stages -- an exponential
sharpening stage that is characterized by a low Rossby number and is driven by
the imposed geostrophic strain, followed by a superexponential sharpening stage
that is characterized by an order-one Rossby number and is driven by the
convergence of the ageostrophic secondary circulation. It is demonstrated that
high-frequency IWs quickly escape the frontal zone and are very efficient at
extracting KE from the imposed geostrophic strain field through the deformation
shear production (DSP) mechanism. Part of the extracted KE is then converted to
wave potential energy. Minimum frequency IWs remain locked to the frontal zone
and therefore exchange energy with the ageostrophic frontal circulation. During
the exponential stage, IWs extract KE from the geostrophic strain through DSP
and transfer it to the frontal secondary circulation via the ageostrophic shear
production (AGSP) mechanism. During the superexponential stage a newly
identified mechanism, convergence production (CP), which is directly linked to
the convergent secondary circulation, plays an important role in the NIW KE
budget
Letter:Ocean bathymetry reconstruction from surface data using hydraulics theory
Here we propose a technique that successfully reconstructs ocean bathymetry
from the free surface velocity and elevation data. This technique is based on
the principles of open-channel hydraulics, according to which a sub-critical
flow over a seamount creates a free surface dip. The proposed method recognizes
that such free surface dip contains the signature of the bottom topography,
hence inverts the free surface to reconstruct the topography accurately. We
applied our inversion technique on re-analysis data, and reconstructed the
Mediterranean and the Red sea bathymetries of resolution with
approximately \% accuracy.Comment: Accepted for publication in Physics of Fluids (Letters
White Light Emission From Surface-Oxidized Manganese-Doped Zns Nanorods
Mn-doped ZnS nanorods synthesized on zinc foils by a solvothermal approach exhibited white light emission upon excitation in the UV range (300-330 nm). X-ray diffraction studies coupled with energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy indicated the presence of a thin oxide layer on the Mn-doped ZnS nanorods. The diameters and lengths of the nanorods varied within the ranges 5-12 and 50-100 nm, respectively. The emitted white light was found to be the result of blue, green, and orange emission bands. The blue bands at ∼400 and 459 nm were attributed to sulfur vacancies and surface states, respectively. The green band at ∼511 nm was associated with the singly ionized oxygen vacancy of the ZnO shell layer. The orange emission originated from the 4T1-6A1 transition of the Mn2+ ions. Thus, the emissions from the Mn-doped ZnS core and the outer ZnO shell combine together to produce the white light. © 2008 American Chemical Society
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