61. Soot effected sample entropy minimization in nanofluid for thermal system design : a thermal lens studyMohanachandran Nair Sindhu Swapna, Vimal Raj, K. Satheesh Kumar, Sankaranarayana Iyer Sankararaman, 2020, original scientific article Abstract: The present work suggests a method of improving the thermal system efficiency, through entropy minimisation,
and unveils the mechanism involved by analysing the molecular/particle dynamics in soot nanofluids (SNFs)
using the time series, power spectrum, and wavelet analyses of the thermal lens signal (TLS). The photothermal
energy deposition in the SNF lowers the refractive index due to the temperature rise. It triggers the particle dynamics that are investigated by segmenting the TLS and analysing the refractive index, phase portrait, fractal dimension (D), Hurst exponent (H), and sample entropy (SampEn). The wavelet analysis gives information about
the relation between the entropy and the frequency components. When the phase portrait analysis reflects the
complex dynamics from region 1 to 2 for all the samples, the SampEn analysis supports it. The decreasing
value of D (from 1.59 of the base fluid to 1.55 and 1.52) and the SampEn (from 1.11 of the base fluid to 0.385
and 0.699) with the incorporation of diesel and camphor soot, indicate its ability to lower the complexity, randomness, and entropy. The increase of SampEn with photothermal energy deposition suggests its relation to
the thermodynamic entropy (S). The lowering of thermal diffusivity value of the base fluid from
1.4 × 10−7 m2/s to 1.1 × 10−7 and 0.5 × 10−7 m2
/s upon diesel and camphor soot incorporation suggests the
heat-trapping and reduced molecular dynamics in heat dissipation.
Keywords: soot, entropy, thermal system, photothermal, time series, nanofluid, fractal
Published in RUNG: 30.06.2022; Views: 2247; Downloads: 0
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62. Unravelling the potential of phase portrait in the auscultation of mitral valve dysfunctionMohanachandran Nair Sindhu Swapna, SREEJYOTHI S, RENJINI A, RAJ VIMAL, SANKARARAMAN SANKARANARAYANA IYER, 2021, original scientific article Abstract: The manuscript elucidates the potential of phase portrait, fast Fourier transform, wavelet, and time-series analyses of the heart murmur (HM) of normal (healthy) and mitral regurgitation (MR) in the diagnosis of valve-related cardiovascular diseases. The temporal evolution study of phase portrait and the entropy analyses of HM unveil the valve dysfunctioninduced haemodynamics. A tenfold increase in sample entropy in MR from that of normal indicates the valve dysfunction. The occurrence of a large number of frequency components between lub and dub in MR, compared to the normal, is substantiated through the spectral analyses. The machine learning techniques, K-nearest neighbour, support vector machine, and principal component analyses give 100% predictive accuracy. Thus, the study suggests a surrogate method of auscultation of HM that can be employed cost-effectively in rural health centres.
Keywords: phase portrait, auscultation, mitral valve dysfunction, heart murmur, nonlinear time series analysis
Published in RUNG: 28.06.2022; Views: 2287; Downloads: 0
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63. Development of prototype of electronic speckle interferometry based spirometerMohanachandran Nair Sindhu Swapna, KUMAR ARUN, KUMAR SUNIL, SREEJYOTHI S, RAJ VIMAL, SANKARARAMAN SANKARANARAYANA IYER, 2021, original scientific article Abstract: The paper reports the design, construction, and calibration of the prototype of a spirometer based on electronic
speckle interferometry (ESPI). The conventional ESPI setup is modified by incorporating a DNM (Diaphragm-Nozzle-Mouthpiece) module comprising a metallic diaphragm, regulated airflow channel, and a mouthpiece. The
exhaled air after a deep breathe is channelled to the DNM module where the diaphragm gets deformed. From the
circular fringe pattern obtained by subtracting the speckled images before and after deformation of the metallic
diaphragm, the radius of curvature (R) due to deformation is calculated using the principle of Newton’s rings.
The value of R and peak expiratory flow rate (PEFR) from the standard spirometer reading are correlated. From
the 640 observations spread over the range 100 - 500 L/min in the standard spirometer, an empirical relation
is set in terms of R from the scatter plot. The ESPI spirometer (ESPIS) is validated by determining the value of
R corresponding to a particular PEFR from the empirical relation and also from the standard spirometer. The
PEFR calculated from ESPIS matches well with the standard spirometer reading, which suggests that the system
designed and constructed can be used for biomedical applications for assessing lungs’ efficiency.
Keywords: Speckle, Spirometer, DNM module, ESPIS, Peak expiratory flow rate
Published in RUNG: 28.06.2022; Views: 2155; Downloads: 0
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64. Thermal Lensing of Multi-Walled Carbon Nanotube Solutions as Heat-Transfer NanofluidsMohanachandran Nair Sindhu Swapna, RAJ VIMAL, CABRERA HUMBERTO, SANKARARAMAN SANKARANARAYANA IYER, 2021, original scientific article Abstract: This paper unwraps nanofluids’ particle dynamics with
multi-walled carbon nanotubes (MWCNTs) in base fluids such as
acetone, water, and ethylene glycol. Having confirmed the
morphology and structure of the MWCNTs by field emission
scanning electron microscopy, X-ray diffraction, and Raman
spectroscopic analyses, the nanofluids are prepared in three different concentrations. The nonzero absorbance at the laser wavelength, revealed through the UV−visible spectrum, makes the thermal diffusivity study of the sample by the sensitive nondestructive single beam thermal lens (TL) technique possible. The TL signal analysis by time series and fractal techniques divulges the complex particle dynamics, through phase portrait, sample entropy, fractal dimension, and Hurst exponent. The study unveils the effect of the amount of nanoparticles and the viscosity of the medium on thermal diffusivity and particle dynamics. The observed inverse relation between thermal diffusivity and viscosity is in good agreement with the
Sankar−Swapna model. The complexity of particle dynamics in MWCNT nanofluids reflected through sample entropy, and fractal
dimension shows an inverse relation to the base fluid’s viscosity. This paper investigates the role of viscosity of the base fluid on particle dynamics and thermal diffusivity of the nanofluid to explore its applicability in various thermal systems, thereby suggesting a method to tune the sample entropy through proper selection of base fluid.
Keywords: MWCNT, thermal lens, fractals, nonlinear time series, phase portrait, sample entropy
Published in RUNG: 28.06.2022; Views: 2477; Downloads: 0
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