161 research outputs found
Wastewater treatment using artificial wetlands
In the study described in this paper, pilot scale vertical
flow wetlands were evaluated as a potential wastewater
treatment system for agricultural wastewater exiting from
swine farm. The criteria used for evaluation were based on
water quality requirements for irrigation
Euclid space mission: a cosmological challenge for the next 15 years
Euclid is the next ESA mission devoted to cosmology. It aims at observing
most of the extragalactic sky, studying both gravitational lensing and
clustering over 15,000 square degrees. The mission is expected to be
launched in year 2020 and to last six years. The sheer amount of data of
different kinds, the variety of (un)known systematic effects and the complexity
of measures require efforts both in sophisticated simulations and techniques of
data analysis. We review the mission main characteristics, some aspects of the
the survey and highlight some of the areas of interest to this meetingComment: to appear in Proceedings IAU Symposium No. 306, 2014, "Statistical
Challenges in 21st Century Cosmology", A.F. Heavens, J.-L. Starck & A.
Krone-Martins, ed
A conceptual modeling methodology based on niches and granularity
This paper presents a methodology for conceptual modeling which is based on a new modeling primitive, the niche, and associated constructs granularity and reconciliation. A niche is an environment where entities interact for a specific purpose, playing specific roles, and according to the norms and constraints of that environment. Granularity refers to the relative level of power or influence of an entity within a niche. Reconciliation is a relationship from N entities onto one reconciled entity, and represents explicitly a situation where two or more different perspectives of the same entity have been reconciled, by negotiation, into a single consensus view. The methodology we propose provides a systematic method of designing conceptual models along with a process for normalising inappropriate relationships. Normalising is a prescriptive process for identifying and remedying inconsistencies within a model based on granularities. Drawing on a number of case studies, we show how niches and granularity make complexity easier to manage, highlight inaccuracies in a model, identify opportunities for achieving project goals, and reduce semantic heterogeneity
Planck early results: first assessment of the High Frequency Instrument in-flight performance
The Planck High Frequency Instrument (HFI) is designed to measure the
temperature and polarization anisotropies of the Cosmic Microwave Background
and galactic foregrounds in six wide bands centered at 100, 143, 217, 353, 545
and 857 GHz at an angular resolution of 10' (100 GHz), 7' (143 GHz), and 5'
(217 GHz and higher). HFI has been operating flawlessly since launch on 14 May
2009. The bolometers cooled to 100 mK as planned. The settings of the readout
electronics, such as the bolometer bias current, that optimize HFI's noise
performance on orbit are nearly the same as the ones chosen during ground
testing. Observations of Mars, Jupiter, and Saturn verified both the optical
system and the time response of the detection chains. The optical beams are
close to predictions from physical optics modeling. The time response of the
detection chains is close to pre-launch measurements. The detectors suffer from
an unexpected high flux of cosmic rays related to low solar activity. Due to
the redundancy of Planck's observations strategy, the removal of a few percent
of data contaminated by glitches does not affect significantly the sensitivity.
The cosmic rays heat up significantly the bolometer plate and the modulation on
periods of days to months of the heat load creates a common drift of all
bolometer signals which do not affect the scientific capabilities. Only the
high energy cosmic rays showers induce inhomogeneous heating which is a
probable source of low frequency noise.Comment: Submitted to A&A. 22 pages, 6 tables, 21 figures. One of a set of
simultaneous papers for the Planck Missio
Euclid preparation XVIII. The NISP photometric system
Euclid will be the first space mission to survey most of the extragalactic sky in the 0.95â2.02 ”m range, to a 5 Ï point-source median depth of 24.4 AB mag. This unique photometric dataset will find wide use beyond Euclidâs core science. In this paper, we present accurate computations of the Euclid YE, JE, and HE passbands used by the Near-Infrared Spectrometer and Photometer (NISP), and the associated photometric system. We pay particular attention to passband variations in the field of view, accounting for, among other factors, spatially variable filter transmission and variations in the angle of incidence on the filter substrate using optical ray tracing. The response curvesâ cut-on and cut-off wavelengths â and their variation in the field of view â are determined with âŒ0.8 nm accuracy, essential for the photometric redshift accuracy required by Euclid. After computing the photometric zero points in the AB mag system, we present linear transformations from and to common ground-based near-infrared photometric systems, for normal stars, red and brown dwarfs, and galaxies separately. A Python tool to compute accurate magnitudes for arbitrary passbands and spectral energy distributions is provided. We discuss various factors, from space weathering to material outgassing, that may slowly alter Euclidâs spectral response. At the absolute flux scale, the Euclid in-flight calibration program connects the NISP photometric system to Hubble Space Telescope spectrophotometric white dwarf standards; at the relative flux scale, the chromatic evolution of the response is tracked at the milli-mag level. In this way, we establish an accurate photometric system that is fully controlled throughout Euclidâs lifetime
Euclid preparation. XVIII. The NISP photometric system
Euclid will be the first space mission to survey most of the extragalactic
sky in the 0.95-2.02 m range, to a 5 point-source median depth of
24.4 AB mag. This unique photometric data set will find wide use beyond
Euclid's core science. In this paper, we present accurate computations of the
Euclid Y_E, J_E and H_E passbands used by the Near-Infrared Spectrometer and
Photometer (NISP), and the associated photometric system. We pay particular
attention to passband variations in the field of view, accounting among others
for spatially variable filter transmission, and variations of the angle of
incidence on the filter substrate using optical ray tracing. The response
curves' cut-on and cut-off wavelengths - and their variation in the field of
view - are determined with 0.8 nm accuracy, essential for the photometric
redshift accuracy required by Euclid. After computing the photometric
zeropoints in the AB mag system, we present linear transformations from and to
common ground-based near-infrared photometric systems, for normal stars, red
and brown dwarfs, and galaxies separately. A Python tool to compute accurate
magnitudes for arbitrary passbands and spectral energy distributions is
provided. We discuss various factors from space weathering to material
outgassing that may slowly alter Euclid's spectral response. At the absolute
flux scale, the Euclid in-flight calibration program connects the NISP
photometric system to Hubble Space Telescope spectrophotometric white dwarf
standards; at the relative flux scale, the chromatic evolution of the response
is tracked at the milli-mag level. In this way, we establish an accurate
photometric system that is fully controlled throughout Euclid's lifetime.Comment: 33 pages, 25 figures, accepted for publication in A&
Euclid preparation: I. the Euclid Wide Survey
Euclid is a mission of the European Space Agency that is designed to constrain the properties of dark energy and gravity via weak gravitational lensing and galaxy clustering. It will carry out a wide area imaging and spectroscopy survey (the Euclid Wide Survey: EWS) in visible and near-infrared bands, covering approximately 15 000 deg2 of extragalactic sky in six years. The wide-field telescope and instruments are optimised for pristine point spread function and reduced stray light, producing very crisp images. This paper presents the building of the Euclid reference survey: The sequence of pointings of EWS, deep fields, and calibration fields, as well as spacecraft movements followed by Euclid as it operates in a step-And-stare mode from its orbit around the Lagrange point L2. Each EWS pointing has four dithered frames; we simulated the dither pattern at the pixel level to analyse the effective coverage. We used up-To-date models for the sky background to define the Euclid region-of-interest (RoI). The building of the reference survey is highly constrained from calibration cadences, spacecraft constraints, and background levels; synergies with ground-based coverage were also considered. Via purposely built software, we first generated a schedule for the calibrations and deep fields observations. On a second stage, the RoI was tiled and scheduled with EWS observations, using an algorithm optimised to prioritise the best sky areas, produce a compact coverage, and ensure thermal stability. The result is the optimised reference survey RSD-2021A, which fulfils all constraints and is a good proxy for the final solution. The current EWS covers âŒ14.500 deg2. The limiting AB magnitudes (5Ïpoint-like source) achieved in its footprint are estimated to be 26.2 (visible band IE) and 24.5 (for near infrared bands YE, JE, HE); for spectroscopy, the Hα line flux limit is 2.10-16 erg-1 cm-2 s-1 at 1600 nm; and for diffuse emission, the surface brightness limits are 29.8 (visible band) and 28.4 (near infrared bands) mag arcsec-2
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