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Dust Properties (dust + property)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Baghouse system design based on economic optimization

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2000
Antonio C. Caputo
In this paper a method is described for using economic optimization in the design of baghouse systems. That is, for a given emission control problem, the total filtration surface area, the overall pressure drop, fabric material effects, and the cleaning cycle frequency, may all be evaluated simultaneously. In fact, as baghouse design parameters affect capital and operating expenses in interrelated and counteracting manners, a minimum total cost may be searched defining the best arrangement of dust collection devices. With this in mind, detailed cost functions have been developed with the aim of providing an overall economic model. As a result, a discounted total annual cost has been obtained that may be minimized by allowing for optimal baghouse characterization. Finally, in order to highlight the capabilities of the proposed methodology, some optimized solutions are also presented, which consider the economic impact of both bag materials and dust properties. [source]

A large-scale extinction map of the Galactic Anticentre from 2MASS

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007
D. Froebrich
ABSTRACT We present a 127 × 63 -deg2 extinction map of the Anticentre of the Galaxy, based on ,J,H, and ,H,K, colour excess maps from the Two-Micron All-Sky Survey. This 8001-deg2 map with a resolution of 4 arcmin is provided as online material. The colour excess ratio ,J,H,/,H,K, is used to determine the power-law index of the reddening law (,) for individual regions contained in the area (e.g. Orion, Perseus, Taurus, Auriga, Monoceros, Camelopardalis, Cassiopeia). On average we find a dominant value of ,= 1.8 ± 0.2 for the individual clouds, in agreement with the canonical value for the interstellar medium. We also show that there is an internal scatter of , values in these regions, and that in some areas more than one dominant , values are present. This indicates large-scale variations in the dust properties. The analysis of the AV values within individual regions shows a change in the slope of the column density distribution with distance. This can be attributed either to a change in the governing physical processes in molecular clouds on spatial scales of about 1 pc or to an AV dilution with distance in our map. [source]

Dust attenuation in starburst galaxies determined by measuring the dependence of the optical color indices on galaxy inclination

ASTRONOMISCHE NACHRICHTEN, Issue 7 2010
O. Vince
Abstract We use optical color indices (colors) from the SDSS database to study the effect of dust in starburst galaxies by mea-suring the dependence of colors on galaxy inclination. Starburst galaxies with ongoing star formation, are rich with metals/dust and are, therefore, an excellent objects for studying the effect of dust in galaxies. They are selected using the [O III], 5007/H, vs. [N II], 6584/H, diagram, that is, the BPT-diagram. We use Kauffmann's empirical demarcation line in the BPT-diagram to exclude galaxies with active galactic nuclei (AGN) from the sample because they have different physical and dust properties from normal galaxies. The sample is divided into bins according to galaxy stellar mass and 4000 Å break (which is a coarse measure of a galaxy star formation history; SFH) and the reddening with inclination is studied as a function of these two physical parameters. Assuming that the dust effect is negligible in the SDSS z -band, we derive the attenuation curves for these galaxies. We fit the attenuation curves with a simple power law and use power law index to interpret the relative distribution of dust and stars in the starburst galaxies (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Spectroscopy of Hydrocarbon Grains toward the Galactic Center and Quintuplet Cluster

ASTRONOMISCHE NACHRICHTEN, Issue S1 2003
J.E. Chiar
Abstract Our view of the Galactic center (GC) is affected by extinction from both diffuse interstellar medium (ISM) dust and dense molecular clouds along the line of sight. The enormous visual extinction present toward the center of our Galaxy (,31 magnitudes) necessitates a study of the interstellar dust properties as well as an investigation into the distribution of the different dust components. We have built upon the historic spectroscopy of Willner et al. (1979), Butchart et al. (1986), and McFadzean et al. (1989) in order to investigate the distribution of these dust components across the GC field. Specifically, we employ spectroscopy in the 3 ,m region to investigate absorption features at 3.0 ,m and 3.4 ,m in lines of sight toward the GC central cluster and the Quintuplet cluster to the northeast. The 3.4 ,m feature is one of the primary spectral signatures of the organic component of interstellar dust and is, to date, only observed in the cold diffuse interstellar medium. The 3.0 ,m ice feature is carried by dense molecular cloud material, and can therefore be used to loosely trace the distribution of such material across the GC field. By obtaining spectra for multiple sightlines we have been able to deconvolve the diffuse ISM and dense molecular cloud components. Our study shows that differences exist in the spectra of relatively nearby lines of sight in the Galactic center central cluster. The depth of the 3.0 ,m water-ice feature varies by a factor of almost 5 across a 2 parsec (in projection) region, perhaps re.ecting the clumpy nature of the dense clouds. In addition, we found that the 3.4 ,m hydrocarbon feature varies in depth across the areas studied toward the central cluster, whereas the depth is relatively constant toward the Quintuplet cluster. This is likely a reflection of the distribution of extinction from the foreground diffuse ISM. Our ground-based and space-based spectroscopy reveals differences in absorption features in the 3 and 6 ,m regions between sightlines toward the GC central cluster and those toward the Quintuplet cluster. While the 3 ,m spectra of both regions show a broad absorption feature blueward of the 3.4 ,m absorption, only the Quintuplet spectra show a distinct absorption feature at 3.28 ,m. This feature is indicative of the presence of polycyclic aromatic hydrocarbons (PAHs) along the line of sight. The Quintuplet-proper sources have 6 ,m spectra that are markedly different than that of GC IRS 7 in the central cluster, and instead strongly resemble the spectra seen toward dusty late-type carbon-class (WC)Wolf-Rayet stars. This is the first hint of some spectroscopic similarity between the Quintuplet sources and dusty WC stars. [source]