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33. The role of hydroxyl ions in the evolution of optical nonlinearity of CuO : a Z scan studyRiya Sebastian, Mohanachandran Nair Sindhu Swapna, H. V. Saritha Devi, Vimal Raj, Misha Hari, Sankaranarayana Iyer Sankararaman, 2019, original scientific article Keywords: hydroxyl ions, optical nonlinearity, Z scan, copper oxide
Published in RUNG: 05.07.2022; Views: 1084; Downloads: 58
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37. Speckle interferometric investigation of argon pressure-induced surface roughness modifications in RF-sputtered MoO[sub]3 filmS. Soumya, R. Arun Kumar, S. Sreejyothi, Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: Film quality analysis is of more considerable signifcance due to its diversifed applications in various felds of technology.
The present work reports the speckle interferometric analysis of the argon pressure-induced surface roughness modifcations
of RF sputtered MoO3 flms. The paper suggests a new method of surface quality analysis of thin flms through a parameter
δ, which is the diference between the initial and fnal inertia moment values in the study of the thermal-induced dynamic
speckle pattern. The limitations of root mean square surface roughness analysis of the atomic force microscopic image of the
flms is also exemplifed. The research suggests that argon pressure plays a vital role in the surface property of RF sputtered
flms and also that the dynamic speckle analysis can give precise information about the quality of flms. The contour plot of
particle displacement vector under thermal stress, suggests the degree of uniformity in the distribution of particles in the flm.
Keywords: speckle pattern interferometry, time history of speckle pattern, cross correlation, inertia moment
Published in RUNG: 04.07.2022; Views: 1180; Downloads: 0
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38. Hidden periodicity in Stripe 82 with Saraswati supercluster—a fractal analysisVimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: The manuscript attempts to explore the periodicity in the distribution of galaxies in the recently
reported Saraswati supercluster and the Stripe 82 region containing it as an example. The report
of 120 Mpc periodicity in the Abell galaxy clusters by power spectrum analysis is the motivation
behind the study. The power spectral analysis across the central part of the Stripe 82 region
shows a periodic variation of 3.09° or 71 Mpc in fractal dimension whereas an average angular
periodicity of 3.45° or 94 Mpc is observed across the Stripe 82 region. This refers to the
periodicity of complexity or cluster density of galaxy distribution. The texture of the distribution
pattern understood through lacunarity analysis indicates a near symmetric distribution. Fractal
dimensions like box-counting dimension, information dimension and correlation dimension are
also found through multifractal analysis. While the information dimension tells about the
distribution density of galactic points, the correlation dimension details the distribution of
galaxies in the neighbourhood
Keywords: galaxy distribution, fractal analysis, multifractals, lacunarity, Saraswati supercluster, Stripe 82
Published in RUNG: 04.07.2022; Views: 1143; Downloads: 0
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39. Thermal diffusivity downscaling of molybdenum oxide thin film through annealing temperature-induced nano-lamelle formation: a photothermal beam deflection studyS. Soumya, Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: The present work proposes a method of downscaling the thermal diffusivity (α)
of MoO3 thin films through annealing temperature-induced nano-lamelle formation. The
thermal diffusivity modification of the MoO3 films, prepared by the doctor blade method,
is investigated by the sensitive transverse photothermal beam deflection technique. The X-ray diffraction analysis confirms the structural phase transformation from monoclinic to
orthorhombic in the films annealed from 300 to 450 °C. The thermal induced anisotropy of
the film is evident from the variation of the morphology index and texture coefficient. The
field emission scanning electron microscopic analysis unveils the morphology modifications
from blocks to the nano-lamelle structure with layers of average thickness ~ 77 nm. The
thermal diffusivity measurement reveals a 53% reduction upon annealing the film to 450 °C.
The drastic reduction is achieved through the annealing temperature-induced nano-lamelle
formation and the phase transformation from monoclinic to orthorhombic in the MoO3 films.
Keywords: thermal diffusivity, molybdenum oxide, thin film, nano-lamelle, photothermal beam deflection
Published in RUNG: 04.07.2022; Views: 1130; Downloads: 26
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40. Concentration-dependent thermal duality of hafnium carbide nanofluid for heat transfer applications : a mode mismatched thermal lens studyVijayakumar Gokul, Mohanachandran Nair Sindhu Swapna, Vimal Raj, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: he mode mismatch dual-beam thermal lens technique is a sensitive tool for studying the nanofuids’ thermal difusivity in thermal engineering. The work reports
the low-temperature green synthesis of hafnium carbide (HfC) using rice four as a natural carbon precursor and its potential in heat transfer nanofuids by studying the concentration-dependent thermal difusivity. The structure characterisations confirm the formation of HfC, whose refractory nature is revealed through the high thermal stability observed in the thermogravimetric analysis. The Tauc plot analysis shows direct bandgap energy of 2.92 eV. The fuorescence study suggests bluish-pink emission with CIE coordinates (0.271, 0.263). The existence of the critical concentration of HfC in the nanofuid decides its suitability for heat transfer or heat trap applications indicating a concentration-dependent thermal duality. Thus, the study is signifcant as it overcomes the major drawbacks of the existing methods of the synthesis of refractory HfC, using toxic chemical and costly equipment for heat transfer applications.
Keywords: hafnium carbide, hydrothermal synthesis, rice flour, thermal lens spectroscopy
Published in RUNG: 04.07.2022; Views: 1166; Downloads: 0
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