Land cover classification using fuzzy rules and aggregation of contextual information through evidence theory

Land cover classification using multispectral satellite image is a very challenging task with numerous practical applications. We propose a multi-stage classifier that involves fuzzy rule extraction from the training data and then generation of a possibilistic label vector for each pixel using the fuzzy rule base. To exploit the spatial correlation of land cover types we propose four different information aggregation methods which use the possibilistic class label of a pixel and those of its eight spatial neighbors for making the final classification decision. Three of the aggregation methods use Dempster-Shafer theory of evidence while the remaining one is modeled after the fuzzy k-NN rule. The proposed methods are tested with two benchmark seven channel satellite images and the results are found to be quite satisfactory. They are also compared with a Markov random field (MRF) model-based contextual classification method and found to perform consistently better.Comment: 14 pages, 2 figure

Detection of interstellar cyanamide (NH2_{2}CN) towards the hot molecular core G10.47+0.03

In the interstellar medium, the amide-type molecules play an important role in the formation of the prebiotic molecules in the hot molecular cores or high-mass star formation regions. The complex amide-related molecule cyanamide (NH$_{2}$CN) is known as one of the rare interstellar molecule which has played a major role in the formation of urea (NH$_{2}$CONH$_{2}$). In this article, we presented the detection of the emission lines of cyanamide (NH$_{2}$CN) towards the hot molecular core G10.47+0.03 between the frequency range 158.49$-$160.11 GHz using the Atacama Large Millimeter/submillimeter Array (ALMA) interferometric radio telescope. The estimated column density of the emission lines of NH$_{2}$CN using the rotational diagram model was $N$(NH$_{2}$CN) = (6.60$\pm$0.1)$\times$10$^{15}$ cm$^{-2}$ with rotational temperature ($T_{rot}$) = 201.2$\pm$3.3 K. The fractional abundance of NH$_{2}$CN with respect to H$_{2}$ towards G10.47+0.03 was $f$(NH$_{2}$CN) = 5.076$\times$10$^{-8}$. Additionally, we estimated the NH$_{2}$CN/NH$_{2}$CHO abundance ratio towards the G10.47+0.03 was 0.170, which was nearly similar with NH$_{2}$CN/NH$_{2}$CHO abundance ratio towards IRAS 16293$-$2422 B and Sgr B2 (M). We found that the observed abundance of NH$_{2}$CN with respect to H$_{2}$ towards G10.47+0.03 fairly agrees with the theoretical value predicted by Garrod (2013). We also discussed the possible formation and destruction pathways of NH$_{2}$CN.Comment: 10 pages, 4 figure

Discovery of hydrogen cyanide (HCN) in the atmosphere of Saturn

In the interstellar medium and planetary atmosphere, the hydrogen cyanide (HCN) molecule plays an important role in the synthesis of many major prebiotic molecules (i.e, CH$_{2}$NH, CH$_{3}$NH$_{2}$, etc.). In several years, scientists try to detect the emission lines of HCN from the atmosphere of Saturn using ground and space-based radio telescopes but they can not detect it. We presented the first successful detection of the rotational emission line of HCN from the atmosphere of Saturn using the Atacama Large Millimeter/sub-millimeter Array band 7. The emission line of HCN was detected from the limb of Saturn at frequency 354.505 GHz with 5$\sigma$ statistical significance. We estimated the column density of HCN in the western limb was $N$(HCN) = (7.02$\pm$0.3)$\times$10$^{12}$ cm$^{-2}$ with excitation temperature ($T_{ex}$) = 195.72$\pm$12.3 K. The column density of HCN in the eastern limb was $N$(HCN) = (3.50$\pm$0.9)$\times$10$^{12}$ cm$^{-2}$ with excitation temperature ($T_{ex}$) = 198.23$\pm$16.8 K. After the detection of HCN, we searched for the evidence of methylamine (CH$_{3}$NH$_{2}$) in the atmosphere of Saturn because CH$_{3}$NH$_{2}$ is known as a possible precursor of HCN in the atmosphere of Saturn. We estimated the upper-limit column density of CH$_{3}$NH$_{2}$ in the atmosphere of Saturn was $\leqslant$5.0$\times$10$^{12}$ cm$^{-2}$. We also discussed the possible formation mechanism of HCN in the atmosphere of Saturn.Comment: 13 pages, 3 figures, comments are welcom

Detection and chemical modelling of complex prebiotic molecule cyanamide in the hot molecular core G31.41+0.31

In the interstellar medium (ISM), the complex prebiotic molecule cyanamide (NH$_{2}$CN) plays a key role in producing adenine (C$_{5}$H$_{5}$N$_{5}$), purines (C$_{5}$H$_{4}$N$_{4}$), pyrimidines (C$_{4}$H$_{4}$N$_{2}$), and other biomolecules via a series of reactions. Therefore, studying the emission lines of NH$_{2}$CN is important for understanding the hypothesis of the pre-solar origin of life in the universe. We present the detection of the rotational emission lines of NH$_{2}$CN with vibrational states $v$ = 0 and 1 towards the hot molecular core G31.41+0.31 using the high-resolution twelve-meter array of Atacama Large Millimeter/Submillimeter Array (ALMA) band 3. The estimated column density of NH$_{2}$CN towards G31.41+0.31 using the local thermodynamic equilibrium (LTE) model is (7.21$\pm$0.25)$\times$10$^{15}$ cm$^{-2}$ with an excitation temperature of 250$\pm$25 K. The abundance of NH$_{2}$CN with respect to H$_{2}$ towards G31.41+0.31 is (7.21$\pm$1.46)$\times$10$^{-10}$. The NH$_{2}$CN and NH$_{2}$CHO column density ratio towards G31.41+0.31 is 0.13$\pm$0.02. We compare the estimated abundance of NH$_{2}$CN with that of other hot cores and corinos and observed that the abundance of NH$_{2}$CN towards G31.41+0.31 is nearly similar to that of the hot molecular core G358.93$-$0.03 MM1, the hot corinos IRAS 16293-2422 B, and NGC 1333 IRAS4A2. We compute the two-phase warm-up chemical model of NH$_{2}$CN using the gas-grain chemical code UCLCHEM, and after chemical modelling, we notice that the observed and modelled abundances are nearly similar. After chemical modelling, we conclude that the neutral-neutral reaction between NH$_{2}$ and CN is responsible for the production of NH$_{2}$CN on the grain surface of G31.41+0.31.Comment: Accepted for publication in ACS Earth and Space Chemistr

Detection of complex nitrogen-bearing molecule ethyl cyanide towards the hot molecular core G10.47+0.03

The studies of the complex molecular lines towards the hot molecular cores at millimeter and submillimeter wavelengths provide instructive knowledge about the chemical complexity in the interstellar medium (ISM). We presented the detection of the rotational emission lines of the complex nitrogen-bearing molecule ethyl cyanide (C$_{2}$H$_{5}$CN) towards the hot molecular core G10.47+0.03 using the Atacama Large Millimeter/Submillimeter Array (ALMA) band 4 observations. The estimated column density of C$_{2}$H$_{5}$CN towards G10.47+0.03 was (9.5$\pm$0.1)$\times$10$^{16}$ cm$^{-2}$ with the rotational temperature of 223.8$\pm$4.3 K. The estimated fractional abundance of C$_{2}$H$_{5}$CN with respect to H$_{2}$ towards G10.47+0.03 was 1.90$\times$10$^{-8}$. We observed that the estimated fractional abundance of C$_{2}$H$_{5}$CN is nearly similar to the simulated abundance of C$_{2}$H$_{5}$CN which was predicted by the three-phase warm-up model from Garrod (2013). We also discuss the possible formation mechanism of C$_{2}$H$_{5}$CN towards the hot molecular cores and we claimed the barrierless and exothermic radical-radical reaction between CH$_{2}$ and CH$_{2}$CN is responsible for the production of high abundant C$_{2}$H$_{5}$CN ($\sim$10$^{-8}$) towards G10.47+0.03 during the warm-up phases.Comment: 19 pages, 4 figure