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81.
Tunable fluorescence from natural carbon source- Pandanus
Mohanachandran Nair Sindhu Swapna, SARITHA DEVI H V, AMBADAS G, Sankararaman S, 2019, original scientific article

Abstract: Carbon materials possessing photoluminescence properties are considered as potential candidates in a wide range of photonic and optoelectronic applications. In this work, the cellulose derived from the natural source, Pandanus, is autoclave-treated for the synthesis of fluorescent carbon. The natural fibres are greatly preferred over synthetic ones due to their cost-effectiveness, easy processability, non-abrasivity, non-toxic and environment-friendly characteristics along with high mechanical strength and damage tolerance. These properties enable them to be used as templates for synthesis, as important reinforcement materials for commercial thermoplastics and for making value-added products. In this study, the synthesised sample is subjected to structural, morphological, elemental and optical characterisations. These studies reveal that the sample can be used as a low-cost tunable light-emitting source for photonic, biomedical and biosensing applications.
Keywords: Fluorescence, Pandanus, natural carbon, cellulose
Published in RUNG: 04.07.2022; Views: 1165; Downloads: 0
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82.
Allotropic transformation instigated thermal diffusivity of soot nanofluid: Thermal lens study
Mohanachandran Nair Sindhu Swapna, RAJ VIMAL, Sankararaman S, 2019, original scientific article

Abstract: This paper employs the sensitive single-beam thermal lens technique for analyzing the thermal behavior of gasoline soot containing allotropes of carbon by preparing its nanofluid (NF). The soot, annealed at different temperatures up to 400 ○C (the samples), used for preparing the NF, is found to enhance the thermal diffusivity (α) up to 95% without changing the solid volume fraction, suggesting its possible use in coolants. The thermal induced modifications are understood from the field emission scanning electron microscopic, X-ray diffraction (XRD),thermogravimetric, and Raman spectroscopic analyses. The variation of α of the sample is found to exhibit similar variations observed in XRD and Raman spectroscopic analyses. The study stresses the significance of the optimum temperature (300 ○C) for the soot NF above which morphological and structural modifications may lead to thermal energy trapping rather than dissipation or cooling.
Keywords: petrol soot, thermal lens, thermal diffusivity
Published in RUNG: 04.07.2022; Views: 1271; Downloads: 0
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83.
Investigation of Fractality and variation of fractal dimension in germinating seed
Mohanachandran Nair Sindhu Swapna, SREEJYOTHI S, Sankararaman S, 2020, original scientific article

Abstract: The fractal analysis has now been recognized as a potential mathematical tool in analyzing complex structures. The present work reports not only the fractal nature of Vigna radiata seed analyzed with the help of Field Emission Scanning Electron Microscopic images but also the variation of fractal dimension (FD) in a germinating seed. The variation of FD during germination in different media—water, salt, and diesel soot with carbon nanoparticles (CNPs)—is studied using the box-counting technique. The study is the first report of the fractality of seed. Irrespective of the media, the FD attains a maximum value on the day of germination and decreases after that. The time (T) for achieving maximum FD varies with the nature of stress. In the study, when the CNPs of diesel soot lower the T value, the salt raises the T value with respect to the control set. The Fourier Transform Infrared analysis of the seeds germinating in different media shows an increased rate of protein formation during the initial stage of germination and a steady state after that. In conjunction with the literature, the variation in the amino nitrogen, soluble nucleotide—RNA, and protein content of the seed during the initial days of germination gets reflected in its FD.
Keywords: fractal analysis, seed germination, Vigna radiata
Published in RUNG: 04.07.2022; Views: 1296; Downloads: 0
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84.
Tuning the thermal diffusivity of the seed matter for enhanced biosynthesis: A thermal lens study
Mohanachandran Nair Sindhu Swapna, Sankararaman S, 2020, original scientific article

Abstract: The thermodynamics of the seed matter after imbibition is highly significant as the growth and germination involve complex biochemical exergonic process. The germination of seed and compositional variation of the seed matter has always been a fascinating field of research. The present work unveils the thermodynamics associated with the changing thermal diffusivity of the seed matter through the green technology-based single-beam thermal lens technique. Investigations are carried out in Vigna radiata seeds, germinating in media with and without carbon allotropes, through various spectroscopic techniques. The morphology of the soot and carbon allotropes is understood from the field emission scanning electron microscope images. The thermal lens study throws light into the energy trapping nature of the seed matter of the seed growing in carbon allotropic media which facilitates biosynthesis. The observed increased rate of growth of the seed is substantiated through the ultraviolet–visible–near-infrared (NIR), Fourier transform infrared, and photoluminescence (PL) spectroscopic analyses. The NIR and PL studies also reveal the formation of chlorophyll molecule during germination. Thus, the study suggests a mechanism for tuning the thermal diffusivity of the seed matter as to trap the biochemical energy to facilitate the further biosynthesis and thereby to enhance the growth rate.
Keywords: seed matter, thermal diffusivity, thermal lens, carbon nanoparticle, soot
Published in RUNG: 04.07.2022; Views: 1291; Downloads: 0
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85.
Absolute Porosity Analysis in Carbon Allotropic Nanofluids: A Sankar–Swapna Model Approach
Mohanachandran Nair Sindhu Swapna, SREEJYOTHI S, Sankararaman S, 2020, original scientific article

Abstract: Porous materials have gained significant attention in recent years as a class of material exhibiting interesting chemical and physical properties. The existing methods of porosity analysis have limitations that prevent absolute porosity measurement. Hence, a technique independent of surface physical properties alone can give the absolute porosity of the material. The porosity greatly influences the thermal diffusivity of a material. The manuscript is the first report of employing the Sankar–Swapna model for analyzing the porosity variations in carbon allotropic nanofluids. The model helps not only in getting information about the absolute porosity variations among samples, but also suggests morphological modifications through the thermal diffusivity study using the sensitive single-beam thermal lens technique. The variations in thermal diffusivity and absolute porosity values are also correlated to morphological modifications based on the theoretical model and thereby proposing this as a surrogate method for absolute porosity analysis.
Keywords: absolute porosity, Sankar–Swapna model, thermal diffusivity, thermal lens, thermal conductivity
Published in RUNG: 04.07.2022; Views: 1330; Downloads: 0
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86.
Organometallic sodium carbide for heat transfer applications: A thermal lens study
Mohanachandran Nair Sindhu Swapna, Sankararaman S, 2020, original scientific article

Abstract: The search for excellent heat transfer fuids necessitates the development of novel nanofuids. The paper is the frst report revealing the potential of sodium carbide (Na2C2) nanoparticle for heat transfer and thermal shielding applications. For this, Na2C2 is prepared from the porous carbon matrix of Aloe vera leaves by hydrothermal method. The morphological changes on hydrothermal treatment and the thermal stability are analyzed by Field Emission Scanning Electron Microscopy and Thermogravimetry. The X-ray difraction analysis reveals the formation of sodium carbide, which is confrmed by Fourier transform infrared, Ultraviolet–Visible–Near Infrared, and Raman spectroscopic analyses. The spectroscopic study of the sample synthesized shows indirect bandgap energy of 1.58 eV. The thermal difusivity of Na2C2 nanofuid, determined by the single-beam thermal lens technique, exhibited 87 % enhancement for the base fuid, suggesting its potential in heat transfer applications.
Keywords: Aloe vera, Heat transfer, Organometallic, Sodium carbide, Thermal lens
Published in RUNG: 04.07.2022; Views: 1186; Downloads: 0
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87.
The efflorescent carbon allotropes: Fractality preserved blooming through alkali treatment and exfoliation
Mohanachandran Nair Sindhu Swapna, Sankararaman S, 2020, original scientific article

Abstract: The work reported in the paper elucidates morphological modification induced nanoart and surface area enhancement of graphite, graphene, and soot containing carbon allotropes through ultrasonication and alkali-treatment. The field emission scanning electron microscopic (FESEM) analysis of the samples before and after exfoliation reveals the formation of brilliant flower-like structures from spindle-like basic units due to Ostwald ripening. The x-ray diffraction analysis of the samples gives information about structural composition. The fractal analysis of the FESEM images indicates a multifractal structure with the dimensions—box-counting dimension D0 (1.72), information dimension D1 (1.66), and correlation dimension D2 (1.63)—preserved upon exfoliation. The process of ultra-sonication assisted liquid phase exfoliation resembles blooming as if the carbon allotropes are efflorescent.
Keywords: carbon allotropes, fractal dimension, soot, fractality, alkali treatment, exfoliation
Published in RUNG: 04.07.2022; Views: 1328; Downloads: 0
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88.
Fractal Applications in Bio-Nanosystems
Mohanachandran Nair Sindhu Swapna, Sankararaman S, 2019, review article

Abstract: We live in a world of high complexity in all means. The present article is an attempt to elucidate the potential of fractal analysis in understanding and quantifying the complexity. Of several methods of fractal analysis, we have used only the box counting and power spectral methods for explaining the potential of the technique. The application of fractal analysis in bio-nanosystems, thin films, are forensic science are exemplified though our own work.
Keywords: fractal application, bionanosystem
Published in RUNG: 04.07.2022; Views: 1043; Downloads: 0
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89.
Unwrapping the phase portrait features of adventitious crackle for auscultation and classification: A machine learning approach
Mohanachandran Nair Sindhu Swapna, 2021, original scientific article

Abstract: The paper delves into the plausibility of applying fractal, spectral, and nonlinear time series analyses for lung auscultation. The thirty-five sound signals of bronchial (BB) and pulmonary crackle (PC) analysed by fast Fourier transform and wavelet not only give the details of number, nature, and time of occurrence of the frequency components but also throw light onto the embedded air flow during breathing. Fractal dimension, phase portrait, and sample entropy help in divulging the greater randomness, antipersistent nature, and complexity of airflow dynamics in BB than PC. The potential of principal component analysis through the spectral feature extraction categorises BB, fine crackles, and coarse crackles. The phase portrait feature-based supervised classification proves to be better compared to the unsupervised machine learning technique. The present work elucidates phase portrait features as a better choice of classification, as it takes into consideration the temporal correlation between the data points of the time series signal, and thereby suggesting a novel surrogate method for the diagnosis in pulmonology. The study suggests the possible application of the techniques in the auscultation of coronavirus disease 2019 seriously affecting the respiratory system.
Keywords: Auscultation, Biomedical signal processing, Fractals, Machine learning, Phase portrait, Pulmonary crackle.
Published in RUNG: 30.06.2022; Views: 1184; Downloads: 0
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90.
Development of Zinc Oxide-Multi-Walled Carbon Nanotube hybrid nanofluid for energy-efficient heat transfer application: A thermal lens study
Mohanachandran Nair Sindhu Swapna, 2021, original scientific article

Abstract: This paper addresses the need for developing an energy-efficient hybrid nanofluid with zinc oxide–multi-walled carbon nanotube (ZnO-MWCNT) for overcoming the bottleneck of efficient heat transfer in thermal systems. The concentration-dependent thermal diffusivity modifications are analyzed using the highly sensitive mode mismatched thermal lens technique. The hybrid composite is prepared by the solid-state mixing and annealing of a pure multi-walled carbon nanotube (MWCNT) and zinc oxide (ZnO), synthesized by the solution combustion method. The composite formation is studied by structural, morphological, and optical characterization techniques. Among the three nanofluids ZnO, MWCNT, and ZnO-MWCNT, the composite exhibits a drastic enhancement in thermal diffusivity at a lower solid volume fraction of 0.047 mg/ml containing 0.009 mg/ml of MWCNT. All the nanofluids show an optimum concentration beyond which the thermal diffusivity decreases with the nanoparticle concentration. Thus, this study suggests the potential application of ZnO-MWCNT hybrid nanofluids in thermal system design to enhance internal combustion engines' efficiency during cold-start.
Keywords: Zinc Oxide, MWCNT, hybrid nanofluid, thermal lens, diffusivity, engine efficiency
Published in RUNG: 30.06.2022; Views: 1457; Downloads: 0
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