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71.
Speckle interferometric investigation of argon pressure-induced surface roughness modifications in RF-sputtered MoO[sub]3 film
S. Soumya, R. Arun Kumar, S. Sreejyothi, Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek

Opis: 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.
Ključne besede: speckle pattern interferometry, time history of speckle pattern, cross correlation, inertia moment
Objavljeno v RUNG: 04.07.2022; Ogledov: 1463; Prenosov: 0
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72.
Hidden periodicity in Stripe 82 with Saraswati supercluster—a fractal analysis
Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek

Opis: 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
Ključne besede: galaxy distribution, fractal analysis, multifractals, lacunarity, Saraswati supercluster, Stripe 82
Objavljeno v RUNG: 04.07.2022; Ogledov: 1451; Prenosov: 0
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73.
Thermal diffusivity downscaling of molybdenum oxide thin film through annealing temperature-induced nano-lamelle formation: a photothermal beam deflection study
S. Soumya, Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek

Opis: 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.
Ključne besede: thermal diffusivity, molybdenum oxide, thin film, nano-lamelle, photothermal beam deflection
Objavljeno v RUNG: 04.07.2022; Ogledov: 1421; Prenosov: 26
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74.
Concentration-dependent thermal duality of hafnium carbide nanofluid for heat transfer applications : a mode mismatched thermal lens study
Vijayakumar Gokul, Mohanachandran Nair Sindhu Swapna, Vimal Raj, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek

Opis: 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.
Ključne besede: hafnium carbide, hydrothermal synthesis, rice flour, thermal lens spectroscopy
Objavljeno v RUNG: 04.07.2022; Ogledov: 1461; Prenosov: 0
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75.
Boron carbide Nanowires from castor oil for optronic applications: A low-temperature greener approach
Mohanachandran Nair Sindhu Swapna, 2021, izvirni znanstveni članek

Opis: The development of one-dimensional nanostructures has revolutionized electronic and photonic industries because of their unique properties. The present paper reports the low-temperature green synthesis of boron carbide nanowires, of diameter 14 nm and length 2 lm, by the condensation method using castor oil as the carbon precursor. The nanowires synthesized exhibit beaded chain morphology, and bandgap energy of 2.08 eV revealed through the Tauc plot analysis. The structure of boron carbide nanowires is revealed by micro-Raman, Fourier transform infrared spectroscopic, and X-ray diffraction analyses. The thermogravimetric analysis of the sample reveals the excellent thermal stability. The photoluminescence study reveals the nanowire’s blue light emission capability under ultraviolet excitation, which is substantiated by the CIE plot suggesting its potential in photonic applications.
Ključne besede: Boron carbide, Nanowires, castor oil, green synthesis
Objavljeno v RUNG: 04.07.2022; Ogledov: 1378; Prenosov: 0
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76.
Thermal diffusivity of molybdenum oxide nanowire film: a photothermal beam deflection study
Mohanachandran Nair Sindhu Swapna, 2021, izvirni znanstveni članek

Opis: The paper reports the preparation of thin film with MoO3 nanowires (NWs) by the doctor blade method and the study of its thermal diffusivity (α) by the sensitive photothermal beam deflection (PTD) method. When the Field Emission Scanning Electron Microscopic and Atomic Force Microscopic analysis unveil its morphology as NW bundles, the X-ray diffraction analysis reveals the structure to be orthorhombic. The NWs formed are of diameter ~ 20 nm and length up to 5 μm. The standardization of the transverse PTD setup is done by determining the value of α of iron, which agrees well with literature reports. The thermal diffusivity of MoO3 NW film is obtained as 0.0036 cm2 /s, which is 9.48% of its bulk counterpart. The reduction in the thermal diffusivity of NW makes it a suitable candidate for thermoelectric applications.
Ključne besede: Nanowires Molybdenum oxide Photothermal beam deflection Thermal diffusivity
Objavljeno v RUNG: 04.07.2022; Ogledov: 1501; Prenosov: 0
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77.
Laser-induced thermal lens study of the role of morphology and hydroxyl group in the evolution of thermal diffusivity of copper oxide
Riya Sebastian, Mohanachandran Nair Sindhu Swapna, Vimal Raj, Sankaranarayana Iyer Sankararaman, 2022, izvirni znanstveni članek

Opis: The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens (TL) technique. For this purpose, the decomposition of Cu(OH)2 into CuO is studied in a time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications, from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement of base fluid’s thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of CuO.
Ključne besede: thermal diffusivity, CuO, thermal lens, morphology, hydroxyl group
Objavljeno v RUNG: 04.07.2022; Ogledov: 1307; Prenosov: 0
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78.
79.
Neural net pattern recognition based auscultation of croup cough and pertussis using phase portrait features
Mohanachandran Nair Sindhu Swapna, 2021, izvirni znanstveni članek

Opis: Cough signal analysis for understanding the pathological condition has become important from the outset of the exigency posed by the epidemic COVID-19. The present work suggests a surrogate approach for the classification of cough signals - croup cough (CC) and pertussis (PT) – based on spectral, fractal, and nonlinear time-series techniques. The spectral analysis of CC reveals the presence of more frequency components in the short duration cough sound compared to PT. The musical nature of CC is unveiled not only through the spectral analysis but also through the phase portrait features – sample entropy (S), maximal Lyapunov exponent (L), and Hurst exponent (Hb). The modifications in the internal morphology of the respiratory tract, giving rise to more frequency components associated with the complex airflow dynamics, get staged through the higher fractal dimension of CC. Among the two supervised classification tools, cubic KNN (CKNN) and neural net pattern recognition (NNPR), used for classifying the CC and PT signals based on nonlinear time series parameters, NNPR is found better. Thus, the study opens the possibility of identification of pulmonary pathological conditions through cough sound signal analysis.
Ključne besede: Croup cough Pertussis Fractal dimension Phase portrait Sample entropy Machine learning techniques
Objavljeno v RUNG: 04.07.2022; Ogledov: 1314; Prenosov: 0
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80.
Evolution of fractal dimension in pulsed laser deposited MoO3 film with ablation time and annealing temperature
Mohanachandran Nair Sindhu Swapna, 2021, izvirni znanstveni članek

Opis: The multifractal analysis is a potential method for assessing thin flm surface morphology and its changes due to diferent deposition conditions and post-deposition treatments. In this work, the multifractal analysis is carried out to understand the surface morphology—root mean square (RMS) surface roughness—of nanostructured MoO3 flms prepared by pulsed laser deposition technique by varying the ablation time and post-deposition annealing. The XRD analysis shows the evolution of crystalline nature with annealing temperature. The XRD pattern of all the annealed flms shows the characteristic peak of the orthorhombic MoO3 phase. The FESEM and AFM analysis reveals the morphological modifcation with ablation time and annealing temperature. The multifractal analysis of the AFM images shows that the box—counting, information and correlation dimension varies with the annealing temperature. The study also reveals the inverse relation between the fractal dimension and the RMS surface roughness due to the annealing induced particle size variation and reorientation. The fractal dimension’s evolution in the pulsed laser deposited MoO3 flm with ablation time and annealing temperature is also investigated. Thus, the study reveals the potential of multifractal analysis in the thin flm surface characterizatio
Ključne besede: Multifractal analysis · Pulsed laser deposition · Molybdenum oxide · Atomic force microscopy · Fractal dimension
Objavljeno v RUNG: 04.07.2022; Ogledov: 1502; Prenosov: 0
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