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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: 04.07.2022; Ogledov: 105; Prenosov: 0
.pdf Polno besedilo (2,26 MB)

Neural net pattern recognition based auscultation of croup cough and pertussis using phase portrait features
SWAPNA MOHANACHANDRAN NAIR SINDHU, 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: 04.07.2022; Ogledov: 82; Prenosov: 0
.pdf Polno besedilo (5,42 MB)

Evolution of fractal dimension in pulsed laser deposited MoO3 film with ablation time and annealing temperature
SWAPNA MOHANACHANDRAN NAIR SINDHU, 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: 04.07.2022; Ogledov: 88; Prenosov: 0
.pdf Polno besedilo (2,53 MB)

Acclimatisation through thermal diffusivity tuning of coconut oil – A mode mismatched dual-beam thermal lens study
SWAPNA MOHANACHANDRAN NAIR SINDHU, 2022, izvirni znanstveni članek

Opis: Background: Ayurvedic medicinal oils traditionally prepared by blending herbal extracts in different compositions are commonly used for treatment and improving health. The estimation of the thermal properties of medicinal oils is essential for practical applications. Objective: The present work aims to expound the ability of medicinal oils for the acclimatization of body temperature by determining its thermal diffusivity and thereby providing a validation to the traditional knowledge. Materials and methods: The medicinal oils are prepared by incorporating black pepper (Piper nigrum), aloe vera (Aloe barbadensis), hibiscus bud (Hibiscus rosa-sinensis) and Ocimum sanctum in coconut oil base. The samples are subjected to thermal diffusivity study using the mode-mismatched dual-beam thermal lens technique. Results: The study reveals that the incorporation of black pepper (Piper nigrum), having hot potency (Ushna veerya), to the base fluid lowers the thermal diffusivity value, suggesting its potential in heattrapping. The addition of aloe vera (Aloe barbadensis), hibiscus bud (Hibiscus rosa-sinensis), and O. sanctum dissipates heat energy quickly, thus increases the thermal diffusivity of coconut oil revealing a cold potency (Sheeta veerya). The study provides a validation for traditional knowledge and delineates the possiblity of thermal diffusivity tuning of the base fluids. Conclusion: The thermal diffusivity tuning through incorporation of herbal extracts can effectively be used to acclimatize the human body temperature with the surroundings. A higher thermal diffusivity value induces a cooling effect and the lower value causes heating effect. This, opens up the possibility of using thermally tuned oils depending on climate and geographical location.
Ključne besede: Ayurveda, Acclimatization, Medicinal oils, Thermal lens spectroscopy Thermal diffusivity
Objavljeno: 04.07.2022; Ogledov: 73; Prenosov: 0
.pdf Polno besedilo (998,33 KB)

Tunable fluorescence from natural carbon source- Pandanus

Opis: 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 environmentfriendly 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.
Ključne besede: Fluorescence, Pandanus, natural carbon, cellulose
Objavljeno: 04.07.2022; Ogledov: 81; Prenosov: 0
.pdf Polno besedilo (1,58 MB)

The coded literary discourse of the Senjam Song Festival of Benečija
Ana Toroš, 2022, izvirni znanstveni članek

Opis: The following article discusses the poetic output in Beneška Slovenia (Benečija) written for the Senjam Song Festival of Benečija. While considering the context of the region’s history and migrations, it focuses on the literary aspects of the festival, particularly on the analysis of the themes and the poetry writing technique. It builds on certain theoretical premises from literary imagology and psychoanalysis. The subject of the analysis are the lyrics from the period between 1971 and 2012, published in a three-volume collection featuring over 150 authors. The article notes the following most prevalent themes: issues of assimilation, migration, and the dying of villages in Benečija. Categorised by basic mood, they fall under one of two extremes: they are either cheerful and humorous in order to encourage and bring joy and hope to the Slovenes of Benečija; or they are pervaded with deep pain and concern over the situation in their region. The lyrics of the latter use a particular writing technique, which merely hints at the pressures of assimilation, conveying them through images and metaphors.
Ključne besede: Benečija, migration, poetry, minority, trauma
Objavljeno: 04.07.2022; Ogledov: 106; Prenosov: 0
.pdf Polno besedilo (265,77 KB)

Allotropic transformation instigated thermal diffusivity of soot nanofluid: Thermal lens study

Opis: 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.
Ključne besede: petrol soot, thermal lens, thermal diffusivity
Objavljeno: 04.07.2022; Ogledov: 119; Prenosov: 0
.pdf Polno besedilo (3,08 MB)

Investigation of Fractality and variation of fractal dimension in germinating seed

Opis: 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.
Ključne besede: fractal analysis, seed germination, Vigna radiata
Objavljeno: 04.07.2022; Ogledov: 119; Prenosov: 0
.pdf Polno besedilo (2,74 MB)

Tuning the thermal diffusivity of the seed matter for enhanced biosynthesis: A thermal lens study

Opis: 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.
Ključne besede: seed matter, thermal diffusivity, thermal lens, carbon nanoparticle, soot
Objavljeno: 04.07.2022; Ogledov: 87; Prenosov: 0
.pdf Polno besedilo (2,68 MB)

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