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Kocifaj, M. |
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Title |
Two-stream approximation for rapid modeling the light pollution levels in local atmosphere |
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Journal Article |
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2012 |
Publication |
Astrophysics and Space Science |
Abbreviated Journal |
Astrophys Space Sci |
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Volume |
341 |
Issue |
2 |
Pages |
301-307 |
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Keywords |
Light pollution; Atmospheric effects; Methods: numerical; Radiative transfer; Scattering; modeling; two-stream approximation |
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Abstract |
The two-stream concept is used for modeling the radiative transfer in Earth's atmosphere illuminated by ground-based light sources. The light pollution levels (illuminance and irradiance) are computed for various aerosol microphysical parameters, specifically the asymmetry parameter g A , single scattering albedo ω A , and optical thickness τ A . Two distinct size distributions of Junge's and gamma-type are employed. Rather then being a monotonic function of τ A , the diffuse illuminance/irradiance shows a local minimum at specific τ A, lim independent of size distribution taken into consideration. The existence of local minima has relation to the scattering and attenuation efficiencies both of which have opposite effects. The computational scheme introduced in this paper is advantageous especially if the entire set of calculations needs to be repeated with an aim to simulate diffuse light in various situations and when altering optical states of the atmospheric environment. |
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0004-640X |
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IDA @ john @ |
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273 |
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Author |
Kocifaj, M. |
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Title |
Light-pollution model for cloudy and cloudless night skies with ground-based light sources |
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Journal Article |
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Year |
2007 |
Publication |
Applied Optics |
Abbreviated Journal |
Appl. Opt. |
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46 |
Issue |
15 |
Pages |
3013 |
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Keywords |
light pollution; modeling |
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The scalable theoretical model of light pollution for ground sources is presented. The model is successfully employed for simulation of angular behavior of the spectral and integral sky radiance and∕or luminance during nighttime. There is no restriction on the number of ground-based light sources or on the spatial distribution of these sources in the vicinity of the measuring point (i.e., both distances and azimuth angles of the light sources are configurable). The model is applicable for real finite-dimensional surface sources with defined spectral and angular radiating properties contrary to frequently used point-source approximations. The influence of the atmosphere on the transmitted radiation is formulated in terms of aerosol and molecular optical properties. Altitude and spectral reflectance of a cloud layer are the main factors introduced for simulation of cloudy and∕or overcast conditions. The derived equations are translated into numerically fast code, and it is possible to repeat the entire set of calculations in real time. The parametric character of the model enables its efficient usage by illuminating engineers and∕or astronomers in the study of various light-pollution situations. Some examples of numerical runs in the form of graphical results are presented. |
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0003-6935 |
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IDA @ john @ |
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277 |
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Author |
Xavier Kerola, D. |
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Title |
Modelling artificial night-sky brightness with a polarized multiple scattering radiative transfer computer code: Modelling artificial night-sky brightness |
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Journal Article |
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2006 |
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Monthly Notices of the Royal Astronomical Society |
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365 |
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4 |
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1295-1299 |
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Skyglow; modeling; radiative transfer; Gauss-Seidel; light pollution; Garstang model |
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As part of an ongoing investigation of radiative effects produced by hazy atmospheres, computational procedures have been developed for use in determining the brightening of the night sky as a result of urban illumination. The downwardly and upwardly directed radiances of multiply scattered light from an offending metropolitan source are computed by a straightforward Gauss-Seidel (G-S) iterative technique applied directly to the integrated form of Chandrasekhar's vectorized radiative transfer equation. Initial benchmark night-sky brightness tests of the present G-S model using fully consistent optical emission and extinction input parameters yield very encouraging results when compared with the double scattering treatment of Garstang, the only full-fledged previously available model. |
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0035-8711 |
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IDA @ john @ |
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278 |
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Author |
Bará, S.; Nievas, M.; Sanchez de Miguel, A.; Zamorano, J. |
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Title |
Zernike analysis of all-sky night brightness maps |
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Journal Article |
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Year |
2014 |
Publication |
Applied Optics |
Abbreviated Journal |
Appl Opt |
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Volume |
53 |
Issue |
12 |
Pages |
2677-2686 |
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Keywords |
modeling; light at night; light pollution; all-sky; Zernike polynomials; image decomposition; sky brightness |
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All-sky night brightness maps (calibrated images of the night sky with hemispherical field-of-view (FOV) taken at standard photometric bands) provide useful data to assess the light pollution levels at any ground site. We show that these maps can be efficiently described and analyzed using Zernike circle polynomials. The relevant image information can be compressed into a low-dimensional coefficients vector, giving an analytical expression for the sky brightness and alleviating the effects of noise. Moreover, the Zernike expansions allow us to quantify in a straightforward way the average and zenithal sky brightness and its variation across the FOV, providing a convenient framework to study the time course of these magnitudes. We apply this framework to analyze the results of a one-year campaign of night sky brightness measurements made at the UCM observatory in Madrid. |
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Ãrea de Óptica, Dept. de FÃsica Aplicada, Fac. de FÃsica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain |
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Optical Society of America |
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English |
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0003-6935 |
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PMID:24787595 |
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Call Number |
IDA @ john @ |
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318 |
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Author |
Sweater-Hickcox, K.; Narendran, N.; Bullough, J.; Freyssinier, J. |
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Title |
Effect of different coloured luminous surrounds on LED discomfort glare perception |
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Journal Article |
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Year |
2013 |
Publication |
Lighting Research and Technology |
Abbreviated Journal |
Lighting Research and Technology |
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Volume |
45 |
Issue |
4 |
Pages |
464-475 |
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Keywords |
perception; subjective; LED; LED lighting; spectral power distribution; SPD |
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Abstract |
Recently, there has been increased interest in energy-efficient lighting as energy resources become higher in demand. Anecdotal evidence suggests that certain populations believe light-emitting diodes (LED) produce more glare than traditional technologies. This may be due to a number of factors such as spectral power distribution (SPD), source luminance, or beam intensity distribution. A study was conducted to assess the effect of different SPDs on the perception of discomfort glare from an LED source. For the range of conditions evaluated, the presence of any luminous surround significantly reduced the perception of discomfort glare from the LED array. The blue luminous surround reduced discomfort glare perception significantly less than the white or the yellow luminous surrounds. The implications for solid-state lighting systems are discussed. |
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Lighting Research Center, Rensselaer Polytechnic Institute, Troy, NY, USA |
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1477-1535 |
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IDA @ john @ |
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338 |
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