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Flux and color variations of the doubly imaged quasar UM673
, Article Astronomy and Astrophysics ; Volume 551 , 2013 ; 00046361 (ISSN) ; Elyiv, A ; Finet, F ; Wertz, O ; Alsubai, K ; Anguita, T ; Bozza, V ; Browne, P ; Burgdorf, M ; Calchi Novati, S ; Dodds, P ; Dominik, M ; Dreizler, S ; Gerner, T ; Glitrup, M ; Grundahl, F ; Hardis, S ; Harpsøe, K ; Hinse, T. C ; Hornstrup, A ; Hundertmark, M ; Jørgensen, U. G ; Kains, N ; Kerins, E ; Liebig, C ; Maier, G ; Mancini, L ; Masi, G ; Mathiasen, M ; Penny, M ; Proft, S ; Rahvar, S ; Scarpetta, G ; Sahu, K ; Schäfer, S ; Schönebeck, F ; Schmidt, R ; Skottfelt, J ; Snodgrass, C ; Southworth, J ; Thöne, C. C ; Wambsganss, J ; Zimmer, F ; Zub, M ; Surdej, J ; Sharif University of Technology
2013
Abstract
Aims. With the aim of characterizing the flux and color variations of the multiple components of the gravitationally lensed quasar UM673 as a function of time, we have performed multiepoch and multiband photometric observations with the Danish telescope at the La Silla Observatory. Methods. The observations were carried out in the VRi spectral bands during four seasons (2008-2011). We reduced the data using the point spread function photometric technique as well as aperture photometry. Results. Our results show for the brightest lensed component some significant decrease in flux between the first two seasons (+ 0.09/+ 0.11/+ 0.05 mag) and a subsequent increase during the following ones (-...
Flux and color variations of the quadruply imaged quasar HE 0435-1223
, Article Astronomy and Astrophysics ; Volume 528 , April , 2011 ; 00046361 (ISSN) ; Poels, J ; Elyiv, A ; Finet, F ; Sprimont, P. G ; Anguita, T ; Bozza, V ; Browne, P ; Burgdorf, M ; Calchi Novati, S ; Dominik, M ; Dreizler, S ; Glitrup, M ; Grundahl, F ; Harpsøe, K ; Hessman, F ; Hinse, T. C ; Hornstrup, A ; Hundertmark, M ; Jørgensen, U. G ; Liebig, C ; Maier, G ; Mancini, L ; Masi, G ; Mathiasen, M ; Rahvar, S ; Scarpetta, G ; Skottfelt, J ; Snodgrass, C ; Southworth, J ; Teuber, J ; Thöne, C. C ; Wambsganß, J ; Zimmer, F ; Zub, M ; Surdej, J ; Sharif University of Technology
Abstract
Aims: We present VRi photometric observations of the quadruply imaged quasarHE0435-1223, carried out with the Danish 1.54 m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time. Methods. We monitored the object during two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data with two independent techniques: difference imaging and point spread function (PSF) fitting. Results. Between these two seasons, our results show an evident decrease in flux by ≈ 0.2-0.4 magnitudes of the four lensed components in the three filters. We also found a significant increase (≈ 0.05-0.015) in their V -...
Using metaheuristic algorithms to improve the estimation of acidity in Fuji apples using NIR spectroscopy
, Article Ain Shams Engineering Journal ; Volume 13, Issue 6 , 2022 ; 20904479 (ISSN) ; Sabzi, S ; Rohban, M. H ; García Mateos, G ; Paliwal, J ; Molina Martínez, J. M ; Sharif University of Technology
Ain Shams University
2022
Abstract
This study focuses on the spectrochemical estimation of pH and titratable acidity (TA) of apples of Fuji variety at different stages of ripening. A novel approach is proposed for near-infrared (NIR) spectral analysis using hybrid machine learning methods that combine artificial neural networks (ANN) and metaheuristic algorithms. One hundred twenty samples were collected at three ripening stages and spectral data within two bands of NIR were extracted from each sample to predict the acidity properties. Alternatively, the 4 most effective wavelengths were also selected using a hybrid of ANN and the cultural algorithm. The experimental results prove that the models using spectral bands and the...