3,150 research outputs found
Writing Reusable Digital Geometry Algorithms in a Generic Image Processing Framework
Digital Geometry software should reflect the generality of the underlying
mathe- matics: mapping the latter to the former requires genericity. By
designing generic solutions, one can effectively reuse digital geometry data
structures and algorithms. We propose an image processing framework focused on
the Generic Programming paradigm in which an algorithm on the paper can be
turned into a single code, written once and usable with various input types.
This approach enables users to design and implement new methods at a lower
cost, try cross-domain experiments and help generalize resultsComment: Workshop on Applications of Discrete Geometry and Mathematical
Morphology, Istanb : France (2010
Sources, Dangers and Treatments of Oily Soil Pollutants in Iraq
Oil pollution presents significant risks to living organism and human health because it can alter the ecosystem in rivers, seas, oceans, and pollutes air and soil. Oil, for example, can even reduce the efficiency of drinking water plants. Iraq suffers a lot from oil pollution as a result of wars that not only damage the oil infrastructures but also cause loss of thousand hectare of agriculture lands. In addition, oil pollution become primary factor that contribute to the electricity, fuel shortage and traffic jam problems. Oil pollution can be easily found in many parts of Iraq, even in main streets, houses and gardens due to the residents mismanagement and misuse of oily products. Therefore, the aim of this paper is to focus in detail about the sources and dangers of oil pollution on the environment and soil, as well as to provide some suggestions and measurements that can help in limiting the impact of oil pollution in Iraq
Evolution of the Dust Coma in Comet 67P/Churyumov-Gerasimenko Before 2009 Perihelion
Comet 67P/Churyumov-Gerasimenko is the main target of ESA's Rosetta mission
and will be encountered in May 2014. As the spacecraft shall be in orbit the
comet nucleus before and after release of the lander {\it Philae}, it is
necessary necessary to know the conditions in the coma. Study the dust
environment, including the dust production rate and its variations along its
preperihelion orbit. The comet was observed during its approach to the Sun on
four epochs between early-June 2008 and mid-January 2009, over a large range of
heliocentric distances that will be covered by the mission in 2014. An
anomalous enhancement of the coma dust density was measured towards the comet
nucleus. The scalelength of this enhancement increased with decreasing
heliocentric distance of the comet. This is interpreted as a result of an
unusually slow expansion of the dust coma. Assuming a spherical symmetric coma,
the average amount of dust as well as its ejection velocity have been derived.
The latter increases exponentially with decreasing heliocentric distance (\rh),
ranging from about 1 m/s at 3 AU to about 25-35 m/s at 1.4 AU. Based on these
results we describe the dust environment at those nucleocentric distances at
which the spacecraft will presumably be in orbit.
Astronomy and Astrophysics, in pressComment: 5 pages, 4 figure
Hubble Space Telescope Observations of Comet 9P/Tempel 1 during the Deep Impact Encounter
We report on the Hubble Space Telescope program to observe periodic comet
9P/Tempel 1 in conjunction with NASA's Deep Impact mission. Our objectives were
to study the generation and evolution of the coma resulting from the impact and
to obtain wide-band images of the visual outburst generated by the impact. Two
observing campaigns utilizing a total of 17 HST orbits were carried out: the
first occurred on 2005 June 13-14 and fortuitously recorded the appearance of a
new, short-lived fan in the sunward direction on June 14. The principal
campaign began two days before impact and was followed by contiguous orbits
through impact plus several hours and then snapshots one, seven, and twelve
days later. All of the observations were made using the Advanced Camera for
Surveys (ACS). For imaging, the ACS High Resolution Channel (HRC) provides a
spatial resolution of 36 km (16 km/pixel) at the comet at the time of impact.
Baseline images of the comet, made prior to impact, photometrically resolved
the comet's nucleus. The derived diameter, 6.1 km, is in excellent agreement
with the 6.0 +/- 0.2 km diameter derived from the spacecraft imagers. Following
the impact, the HRC images illustrate the temporal and spatial evolution of the
ejecta cloud and allow for a determination of its expansion velocity
distribution. One day after impact the ejecta cloud had passed out of the
field-of-view of the HRC.Comment: 15 pages, 14 postscript figures. Accepted for publication in Icarus
special issue on Deep Impac
Refurbishing Voyager 1 & 2 Planetary Radio Astronomy (PRA) Data
Voyager/PRA (Planetary Radio Astronomy) data from digitized tapes archived at
CNES have been reprocessed and recalibrated. The data cover the Jupiter and
Saturn flybys of both Voyager probes. We have also reconstructed
goniopolarimetric datasets (flux and polarization) at full resolution. These
datasets are currently not available to the scientific community, but they are
of primary interest for the analysis of the Cassini data at Saturn, and the
Juno data at Jupiter, as well as for the preparation of the JUICE mission. We
present the first results derived from the re-analysis of this dataset.Comment: Accepted manuscript for PRE8 (Planetary Radio Emission VIII
conference) proceeding
Two Gap State Density in MgB: A True Bulk Property or A Proximity Effect?
We report on the temperature dependence of the quasiparticle density of
states (DOS) in the simple binary compound MgB2 directly measured using
scanning tunneling microscope (STM). To achieve high quality tunneling
conditions, a small crystal of MgB2 is used as a tip in the STM experiment. The
``sample'' is chosen to be a 2H-NbSe2 single crystal presenting an atomically
flat surface. At low temperature the tunneling conductance spectra show a gap
at the Fermi energy followed by two well-pronounced conductance peaks on each
side. They appear at voltages V mV and V mV. With rising temperature both peaks disappear at the Tc of the bulk
MgB2, a behavior consistent with the model of two-gap superconductivity. The
explanation of the double-peak structure in terms of a particular proximity
effect is also discussed.Comment: 4 pages, 3 figure
Millimetre continuum observations of comet C/2009 P1 (Garradd)
Little is known about the physical properties of the nuclei of Oort cloud
comets. Measuring the thermal emission of a nucleus is one of the few means for
deriving its size and constraining some of its thermal properties. We attempted
to measure the nucleus size of the Oort cloud comet C/2009 P1 (Garradd). We
used the Plateau de Bure Interferometer to measure the millimetric thermal
emission of this comet at 157 GHz (1.9 mm) and 266 GHz (1.1 mm). Whereas the
observations at 266 GHz were not usable due to bad atmospheric conditions, we
derived a 3-sigma upper limit on the comet continuum emission of 0.41 mJy at
157 GHz. Using a thermal model for a spherical nucleus with standard thermal
parameters, we found an upper limit of 5.6 km for the radius. The dust
contribution to our signal is estimated to be negligible. Given the water
production rates measured for this comet and our upper limit, we estimated that
Garradd was very active, with an active fraction of its nucleus larger than
50%.Comment: Accepted for publication in Astronomy & Astrophysics. 5 pages, 2
figure
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