3,978 research outputs found
Eclipse maps of spiral shocks in the accretion disc of IP Pegasi in outburst
Eclipse lightcurves of the dwarf nova IP Peg during the November 1996
outburst are analysed with eclipse mapping techniques to constrain the location
and investigate the spatial structure of the spiral shocks observed in the
Doppler tomograms (Harlaftis et al. 1999). Eclipse maps in the blue continuum
and in the CIII+NIII 4650 emission line show two asymmetric arcs of \sim 90
degrees in azimuth and extending from intermediate to the outer disc regions (R
\simeq 0.2 - 0.6 R_{L1}, where R_{L1} is the distance from disc centre to the
inner Lagrangian point) which are interpreted as being the spiral shocks seen
in the Doppler tomograms. The HeII 4686 eclipse map also shows two asymmetric
arcs diluted by a central brightness source. The central source probably
corresponds to the low-velocity component seen in the Doppler tomogram and is
understood in terms of gas outflow in a wind emanating from the inner parts of
the disc. We estimate that the spirals contribute about 16 and 30 per cent of
the total line flux, respectively, for the HeII and CIII+NIII lines. Comparison
between the Doppler and eclipse maps reveal that the Keplerian velocities
derived from the radial position of the shocks are systematically larger than
those inferred from the Doppler tomography indicating that the gas in the
spiral shocks has sub-Keplerian velocities. We undertake simulations with the
aim to investigate the effect of artifacts on the image reconstruction of the
spiral structures.Comment: MNRAS, in press. 6 pages, 1 embedded PS and 3 JPEG figures; typed
with MNRAS latex styl
Observations of Faint Eclipsing Cataclysmic Variables
We present time-resolved photometry of six faint (V>17mag) cataclysmic
variables (CVs); one of them is V849 Oph and the others are identified from the
Sloan Digital Sky Survey (SDSS J0920+0042, SDSS J1327+6528, SDSS J1227+5139,
SDSS J1607.02+3623, SDSS J1457+5148). The optical CCD photometric observations
of these objects were performed at the T\"UB\.ITAK National Observatory
(Turkey) between February 2006 and March 2009. We aimed to detect short time
scale orbital variability arisen from hot-spot modulation, flickering
structures which occur from rapid fluctuations of material transferring from
red star to white dwarf and orbital period changes for selected short-period
(P<4h) CVs at quiescence. Results obtained from eclipse timings and light
curves morphology related to white dwarf stars, accretion disks and hot-spots
are discussed for each system. Analysis of the short time coverage of data,
obtained for SDSS J1227+5139 indicates a cyclical period change arisen from
magnetic activity on the secondary star. Photometric period of SDSS J1607+3623
is derived firstly in this study, while for the other five systems light
elements are corrected using the previous and new photometric observations. The
nature of SDSS J1457+5148 is not precisely revealed that its light curve shows
any periodicity that could be related to the orbital period
A spiral structure in the disk of EX Draconis on the rise to outburst maximum
We report on the R-band eclipse mapping analysis of high-speed photometry of
the dwarf nova EX Dra on the rise to the maximum of the November 1995 outburst.
The eclipse map shows a one-armed spiral structure of ~180 degrees in azimuth,
extending in radius from R ~0.2 to 0.43 R_{L1} (where R_{L1} is the distance
from the disk center to the inner Lagrangian point), that contributes about 22
per cent of the total flux of the eclipse map. The spiral structure is
stationary in a reference frame co-rotating with the binary and is stable for a
timescale of at least 5 binary orbits. The comparison of the eclipse maps on
the rise and in quiescence suggests that the outbursts of EX Dra may be driven
by episodes of enhanced mass-transfer from the secondary star. Possible
explanations for the nature of the spiral structure are discussed.Comment: To appear in the Astrophysical Journal Letters; 8 pages, 2 figures;
coded with AAS latex styl
Experimental observation of a complex periodic window
The existence of a special periodic window in the two-dimensional parameter
space of an experimental Chua's circuit is reported. One of the main reasons
that makes such a window special is that the observation of one implies that
other similar periodic windows must exist for other parameter values. However,
such a window has never been experimentally observed, since its size in
parameter space decreases exponentially with the period of the periodic
attractor. This property imposes clear limitations for its experimental
detection.Comment: 4.2 pages, 4 figure
V2051 Ophiuchi after superoutburst : out-of-plane material and the superhump light source
Aims. We performed a detailed spectroscopic analysis of the dwarf nova V2051 Oph at the end of its 1999 superoutburst. We studied and interpreted the simultaneous behaviour of various emission lines.
Methods. We obtained high-resolution echelle spectroscopic data at ESOâs NTT with EMMI, covering the spectral range of 4000â7500 Ă
. The analysis was performed using standard IRAF tools. The indirect imaging technique of Doppler tomography was applied, in order to map the accretion disc and distinguish between the different emission sources.
Results. The spectra are characterised by strong Balmer emission, together with lines of He i and the iron triplet Fe ii 42. All lines are double-peaked, but the blue-to-red peak strength and central absorption depth vary. The primaryâs velocity was found to be 84.9 kmsâ1. The spectrograms of the emission lines reveal the prograde rotation of a disc-like emitting region and, for the Balmer and He i lines, an enhancement of the red-wing during eclipse indicates a bright spot origin. The modulation of the double-peak separation shows a highly asymmetric disc with non-uniform emissivity. This is confirmed by the Doppler maps, which apart from the disc and bright spot emission also indicate an additional region of enhanced emission in the 4th quadrant (+Vx, âVy), which we associate with the superhump light source. Given the behaviour of the iron triplet and its distinct differences from the rest of the lines, we attribute its existence to an extended gas region above the disc. Its origin can be explained through the fluorescence mechanism
Structured and unstructured data integration with electronic medical records
Medicine is a field with high volatility of changes. Everyday new discoveries and procedures are tested with the sole goal of providing a better-quality life to patients. With the evolution of computer science, multiple fields saw an increase of productivity and solutions that could be implemented. More specifically, in medicine new techniques started being tested in order to understand how the systems and practices used can reach higher performances, while maintaining the predefined high standards of quality. For many years data generated in hospital was collected and stored yet few tools were implemented to extract knowledge or any type of advantage. One of the areas that successfully implemented in medicine was the usage of data processing tools and techniques to further extract information regarding the high abundance of data generated in a daily basis, in this field of work. This data can be stored in different ways which leads to multiple approaches on how to deals with it. The sole purpose of this paper is to give an overview of some case studies where structured and unstructured data was used, joint and separately and the value of it.info:eu-repo/semantics/publishedVersio
Tracing the spiral arms in IP Pegasi
We report the analysis of time-resolved spectroscopy of IP Pegasi in outburst with eclipse mapping techniques to investigate the location and geometry of the observed spiral structures. We were able to obtain an improved view of the spiral structures with the aid of light curves extracted in velocity bins matching the observed range of velocities of the spiral arms combined with a double default map tailored for reconstruction of asymmetric structures. Two-armed spiral structures are clearly seen in all eclipse maps. The arms are located at diïŹerent distances from the disc centre. The âblueâ arm is farther out in the disc (R = 0.55 ± 0.05 R L1 ) than the âredâ arm (R = 0.30 ± 0.05 R L1 ). There is evidence that
the velocity of the emitting gas along the spiral pattern is lower than the Keplerian velocity for the same disc radius. The discrepancy is smaller in the outer arm (measured velocities 10â15 per cent lower than Keplerian) and is more significant in the inner arm (observed velocities up to 40 per cent lower than Keplerian). We measured the opening angle of the spirals from the azimuthal intensity distribution of the eclipse maps to
be Ï = 25⊠± 3⊠. A comparison with similar measurements on data at diïŹerent outburst stages reveals that the opening angle of the spiral arms in IP Peg decreases while the outbursting accretion disc cools and shrinks, in agreement with the expected evolution of a tidally driven spiral
wave. The sub-Keplerian velocities along the spiral pattern and the clear correlation between the opening angle of the spirals and the outburst stage favors the interpretation of these asymmetric structures as tidally-induced spiral shocks
HST and ground-based eclipse observations of V2051 Ophiuchi: Binary parameters
We report on high-speed eclipse photometry of the dwarf nova V2051 Oph while
it was in a low brightness state, at B ~ 16.2 mag. In comparison to the average
IUE spectra, the ultraviolet continuum and emission lines appear reduced by
factors of, respectively, ~4 and ~5. Flickering activity is mostly suppressed
and the lightcurve shows the eclipse of a compact white dwarf at disc centre
which contributes ~60 per cent of the total light at 3900--4300 A. We use
measurements of contact phases in the eclipse lightcurve to derive the binary
geometry and to estimate masses and relevant dimensions. We find a mass ratio
of q= 0.19+/-0.03 and an inclination of i= 83+/-2 degrees. The masses of the
component stars are M_1 = 0.78+/-0.06 M_dot and M_2 = 0.15+/-0.03 M_dot. Our
photometric model predicts K_1 = 83+/-12 km/s and K_2= 435+/-11 km/s. The
predicted value of K_1 is in accordance with the velocity amplitude obtained
from the emission lines after a correction for asymmetric line emission in the
disc is made (Watts et al. 1986). The secondary of V2051 Oph is significantly
more massive than the secondaries of the other ultra-short period dwarf novae.
V2051 Oph is probably a relatively young system, whose secondary star had not
enough time to evolve out of thermal equilibrium.Comment: 16 pages, 7 postscript figures, coded using MNRAS latex style. To
appear in Monthly Notices of the Royal Astronomical Society. Revised version
with changes in section 4.3. For related papers and files see
ftp://fsc01.fsc.ufsc.br/pub/bap and http://www.fsc.ufsc.br/~astr
ASSESSMENT OF ENERGY CONSUMPTION IN GREENHOUSE PRODUCTION IN THE WEST REGION OF PORTUGAL
Greenhouse production is a very important activity in the West region of Portugal, with an area of approximately 800 ha where the regular production consists in two crops per year, one in winter-spring and the other in summer-autumn. Many growers are now prepared to better exploit market opportunities, since they know that the big export window opportunity is from June to September, when the production is difficult in other regions of south due to high temperatures.
Growerâs use new and more productive varieties, either in soil or hydroponic systems, mostly in unheated greenhouses, naturally ventilated, and equipped with modern fertigation systems. Greenhouse production causes some environmental impacts due to the high use of inputs. Several improvements in technologies and crop practices may contribute to increase the use efficiency of resources, decreasing the negative environmental impacts.
Greenhouse vegetable production in Northern EU countries is based on the supply of heating and differs significantly from the production system in the Southern EU countries. In the Northern countries, direct energy inputs, mostly for heating, are predominant while in the South the indirect energy input is also important, mainly associated with fertilizers, plastic cover materials and other auxiliary materials.
The main objective of this work was to characterise the greenhouse production systems in the West region of Portugal, in order to evaluate the energetic consumptions (direct and indirect), the GHH emissions, the production costs and the farmerâs income. With this work the mostly important inputs were identified, allowing proposing alternative measures to improve efficiency and sustainability.
All the data was obtained by surveys performed directly with growers, previously selected to be representative of the crop practices and greenhouse type of the region. However, more research should be performed in order to develop and to test technologies capable to improve resources use efficiency in greenhouse production
Mutual information rate and bounds for it
The amount of information exchanged per unit of time between two nodes in a
dynamical network or between two data sets is a powerful concept for analysing
complex systems. This quantity, known as the mutual information rate (MIR), is
calculated from the mutual information, which is rigorously defined only for
random systems. Moreover, the definition of mutual information is based on
probabilities of significant events. This work offers a simple alternative way
to calculate the MIR in dynamical (deterministic) networks or between two data
sets (not fully deterministic), and to calculate its upper and lower bounds
without having to calculate probabilities, but rather in terms of well known
and well defined quantities in dynamical systems. As possible applications of
our bounds, we study the relationship between synchronisation and the exchange
of information in a system of two coupled maps and in experimental networks of
coupled oscillators
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