Faculty Publications

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Author: search.filters.author.D'Souza, A.

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    A parallel fuzzy C means algorithm for brain tumor segmentation on multiple MRI images
    (Springer Verlag service@springer.de, 2013) Ravi, A.; Suvarna, A.; D'Souza, A.; Guddeti, G.; Megha
    The Fuzzy C Means (FCM) algorithm has been extensively used in medical image segmentation. But for large data sets the convergence of the FCM algorithm is time consuming and also requires considerable amount of memory. In some real time applications, like Content Based Medical Image Retrieval (CBIR) systems, there is a need to segment a large volume of brain MRI images offline. In this paper, we present an efficient method to cluster data points of all the images at once. The gray level histogram is used in the FCM algorithm to minimize the time for segmentation and the space required. A parallel approach is then applied to further reduce the computation time. The proposed method is found to be almost twice as fast as conventional FCM. © 2013 Springer.
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    Synthesis and Optical Characterization of Amaranth Dye Doped Thiourea Barium Chloride (TBC) Single Crystals
    (Elsevier Ltd, 2018) Mahendra, K.; D'Souza, A.; Ifthekarahmed; Udayashankar, N.K.
    Thiourea barium chloride (TBC), Amaranth doped (0.05, 0.1 mM) TBC(ADTBC) crystals were synthesized at room temperature by solvent evaporation process. Structural analysis of TBC and ADTBC were studied using powder XRD, results confirmed that dye got incorporated into the host lattice. Optical analysis of the TBC and ADTBC crystals were carried using UV-Visible and photoluminescence spectrophotometer. Results showed that both pure and dye doped crystals had an absorption peak at around 264 nm. Optical bandgap of the crystal was found to be decreasing as the doping percentage of the crystal increased. Pure and doped crystals exhibit a strong emission peak in the blue region. © 2017 Elsevier Ltd.
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    Synthesis, structural, optical and electrical (DC) properties of a semiorganic Thiourea Barium Chloride (TBC) single crystal
    (Elsevier GmbH journals@elsevier.com, 2017) Mahendra, K.; D'Souza, A.; Udayashankar, N.K.
    In the present study, TBC single crystals were synthesized using solution evaporation method. The structural analysis of TBC crystal was studied using Powder X-ray diffraction. Optical properties of TBC crystals were carried out using UV–vis, FTIR, Raman and photoluminescence (PL) spectra. The crystal shows absorbance maxima at 209 nm and transparent in the visible region 300–900 nm. The various optical constants such as refractive index, reflectance, speed of light, extinction coefficient, electrical susceptibility, dielectric constant, optical and electrical conductivity were evaluated. Thus results revealed that all these optical constants shows a strong dependence on optical absorption coefficient. Using single oscillator model (Wemple ?Didomenico), lattice dielectric constant and the ratio of free charge carrier to their effective mass were evaluated. The PL study of TBC crystals shows two emission peaks (419 nm ?S, 441 nm- Ba) in blue region. The DC resistivity and conductivity of the crystal was investigated in the temperature range 26 °C–115 °C. © 2017 Elsevier GmbH
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    Effect of Zn doping on the structural, optical, photoluminescence and mechanical properties of thiourea barium chloride (TBC) crystal
    (Elsevier Ltd, 2017) Mahendra, K.; D'Souza, A.; Udayashankar, N.K.
    In the present work, a synthesis and comparative study on the effect of Zinc (Zn) on thiourea barium chloride (TBC) single crystals has been reported. Crystals of thiourea barium chloride and Zn-doped thiourea barium chloride crystals are prepared using slow evaporation from the saturated solution. The samples were subjected to single crystal and powder X-ray diffraction to study the unitcell parameters and structural variations. The functional groups present in the crystals are derived using FTIR and Raman analysis. The enhancement of transmittance with the addition of Zn and the variations in the parameters such as bandgap, extinction coefficient, reflectance, refractive index, optical and electrical conductivity, real and imaginary part of dielectric constant are studied from UV–vis spectrum analysis. Vickers hardness measurements are conducted for pure and Zinc-doped TBC single crystals. The emission spectrum of pure and Zn doped single crystals are studied using photoluminescence analysis. © 2017 Elsevier Ltd