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Studies on sulfur doping and figure of merit in vapor grown Sb2Te3 platelet crystals /
Journal Of Crystal Growth, Vol.412, pp.65-71, ISSN No: 0022-0248. -
Studies on sulfur doping and figure of merit in vapor grown Sb2Te3 platelet crystals
A series of p-type Sb2Te3-xSx(x=0, 0.1, 0.2, 0.3 and 0.4) samples for each sulfur composition was vapor deposited to explore the crystal growth mechanism of platelet morphology and to understand their potential use for thermoelectric devices. Structural characterization performed by X-ray diffraction exhibited consistent rhombohedral unit cell parameters for all the antimony telluride crystals with D3d5 space group symmetry. Scanning electron microscopy (SEM) and energy dispersive analysis by X-rays (EDAX) were employed for morphological and compositional studies. The Seebeck coefficient S (?c) of Sb2Te3-xSx crystals for sulfur composition, x=0.3 was remarkably improved, yielding a figure of merit (ZT)=0.54, which is ?2.5 fold rise compared to the melt grown Sb2Te3 crystals. The atomic force microscopic (AFM) imprints revealed that, with increasing content of dopant, distribution of etch pits and microhardness increased in sulfur doped crystals. By optimizing sulfur doping, the antisite (AS) defect formation can be suppressed for enhancing ZT and the results obtained enable to design novel thermoelectric materials for application in power generation and refrigeration. 2015 Elsevier B.V. All rights reserved. -
Studies on single crystals and thin films on tin sulfide (SnS) for photovoltaic applications
There is an increasing demand for renewable energy sources due to the limited availability of fossil, risk factor associated with nuclear fuel and due to growing environmental concern. Photovoltaic (PV) energy conversion has the potential to contribute significantly to the electrical energy of the main obstacles preventing production and application on a large scale. Availability of the materials and their processing cost are the two major constraints associated with the presently leading PV technologies. Hence, cost of the electricity produced by these technologies are not yet competitive compared to the electricity produced by conventional sources. -
Studies On Single Crystals and Thin Films of Tin Sulfide(SnS) For Photovoltaic Applications
The thesis is concerned with linear and nonlinear Rayleigh-Bard electroconvection in a horizontal porous layer. Modified Darcy law is employed to describe the fluid motion. The effect of non-classical heat conduction, chemical reaction, thermal radiation and finite amplitudes on the onset of Darcy electroconvection is considered. The findings of the problems investigated in the thesis may prove useful in heat transfer application situations with dielectric fluids as working medium. The summary of the problems addressed in the thesis is given below.Effect of non-classical heat conduction on Rayleigh-Bard newlineconvection in a horizontal layer of porous medium saturated with a dielectric fluid The method of small perturbations is used to examine the effect of non-classical heat conduction on the onset of Darcy electroconvection. Exact solutions for both stationary and oscillatory instability are obtained and known results have been deduced as limiting cases of the present study. It is shown that electroconvective instability in a Darcy porous layer is hastened by increasing the strengths of second sound and electric newlineforces and that the presence of second sound and dielectrophoretic force leads to shorter wavelength electroconvection. Further, it is found that the effect of Vadasz number is to advance the onset of oscillatory Darcy newlineelectroconvection and oscillatory instability sets in before stationary convection provided that the Vadasz number and the Cattaneo number are sufficiently large. Rayleigh-Bard convection in a horizontal layer of porous medium saturated with a chemically reacting dielectric fluid The problem of the effect of chemical reaction on the onset of Darcy electroconvection in a horizontal porous layer heated from below is newlineinvestigated. It is assumed that the fluid experiences a zero-order exothermic chemical reaction and that there exists a local thermal equilibrium between the fluid and the solid phases. -
Studies on photophysical properties of mono-carbonyl curcumin analogues: Experimental andtheoretical approach
The solvatochromic fluorescence behaviour of mono-carbonyl curcumin analogues has been studied in ten different solvents ranging from non-polar to polar. The solvent effect on the spectral properties of analogues has been discussed. The ground state dipole moments were estimated experimentally by Bilot-Kawski equation which is a function of Stokes shift with the solvent polarity parameters and Guggenheim method and theoretically by TD-DFT studies. The excited state dipole moment was determined using Bilot-Kawski equations. The excited state dipole moments for the two molecules were found to be higher than their corresponding ground state dipole moments. Theoretically Frontier molecular orbital (HOMO/ LUMO) energies were determined by Gaussian 09 W software using TD-DFT. 2018 Oriental Scientific Publishing Company. All rights reserved. -
Studies on Photophysical and Biological Activity of Newly Synthesized of 4-Methylpiperidin-4-ol Substituted Pyrazole Derivatives
The in vitro antifungal, antibacterial, and antioxidant activities of a substituted pyrazole derivative (FHM) have been evaluated in the current work. The addition of 4-methylpiperidin-4-ol, which increases the molecules lipid solubility and speeds up absorption by increasing its rate of absorption, gives the molecule strong in vitro antifungal and antibacterial properties. Additionally, it is clear from the findings of structure-activity relationship (SAR) investigations. Additionally, the ab-intio technique was used to theoretically evaluate the photophysical characteristics of produced substances. Using the DFT-B3LYP-6-31G(d) basis set, the ground state optimization and HOMO-LUMO energy levels are computed. Global chemical reactivity and descriptive characteristics are evaluated using theoretically estimated HOMO-LUMO values, and the results demonstrate that the synthesized molecule possesses a high electrophilicity and electronegative index. Overall findings indicate that substituting a 4-methylpiperidin-4-ol substituted pyrazole derivative shows good photophysical and in vitro biological applications. 2024, HARD Publishing Company. All rights reserved. -
Studies on phase transitions and dielectric properties of biowaste synthesized porous carbon nanoparticlesferroelectric liquid crystal mixture
Ferroelectric liquid crystals(FLCs), an exciting class of liquid crystals(LCs), found potential applications in the display as well as non-display regimes due to their fast response, low driving voltage and nonvolatile memory. The amalgamation of nanoparticles into FLCs has opened up new avenues in the LCs research field by alterations/modification of the existing properties of LCs. In this work, porous carbon nanoparticles (PCNPs) were dispersed into FLC mixture (W206E) and investigated their doping effect on FLCs textural, phase transition temperatures and dielectric studies in planar-aligned cells. Dielectric spectroscopy was carried out in the frequency range of 20 Hz to 10 MHz to explore the frequency as well as the temperature dependent of FLC in the entire SmC* region. The transition temperature of FLC mixture is increased by 4 C in PCNPs doped FLC sample then undoped FLC sample. Nearly 8.42% increase in permittivity is observed. A Gold stone relaxation mode at ?627 Hz was observed at lower frequency. 2024 Taylor & Francis Group, LLC. -
Studies on Parametric Optimization of HVOF-Sprayed Cr2O3 Coatings on Al6061 Alloy
High-velocity oxy-fuel (HVOF) is a widely used thermal spray technique to obtain high density, high bond strength, and improved hardness coatings. In the present work, optimization of HVOF process parameters was carried out using the Taguchi method to minimize porosity and improve microhardness, and bond strength of Cr2O3 coatings. Based on the signal-to-noise ratio and analysis of variance, the significance of each process parameter and optimum parameter combination is obtained. Based on the signal-to-noise ratio, the most significant process parameter affecting porosity and microhardness was standoff distance, while for bond strength, it was powder feed rate. An optimal combination of process parameters for porosity, microhardness, and bond strength was obtained from S/N ratio analysis. For porosity, optimal parameters were standoff distance of 100rpm, powder feed rate of 30g/min, and gun speed of 250mm/s. The optimal process parameters for microhardness were standoff distance of 300rpm, powder feed rate of 50g/min, and gun speed of 200mm/s. Finally, for bond strength, the optimal process parameters were standoff distance of 300rpm, powder feed rate of 50g/min, and gun speed of 250mm/s. Statistical results for porosity, microhardness, and bond strength showed that the difference between the predicted R2 and adjusted R2 values were relatively minimal and close to the one highlighting the fitness of the regression model employed for analysis. Fracture analysis after bond strength test showed combined adhesion/cohesion type failure for the Cr2O3 coatings. 2021, The Indian Institute of Metals - IIM. -
Studies on K X Ray fluorescence parameters of low and medium Z elements
K X-ray fluorescence parameters for pure elements have been determined using different single and double reflection geometry by several researchers over the years. Horakeri et al.have shown that the K X-ray fluorescence parameters can also be determined by a simple 2and#960;-geometrical configuration method and a NaI(Tl) detector spectrometer for high Z elements. newlineHowever, in order to study the K XRF parameters for low Z elements, high resolution detector spectrometers are required.But in high resolution detectors like HPGe and Si(Li), due to the gap between window and the active area of the detector, the solid angle subtended by the detector at the target is not 2and#960;. Hence a suitable geometry correction is required for accurate newlinemeasurement of incident photons and the emitted K X-ray photons in order to determine the K XRF parameters in low Z elements. In the present study, employing a nearly 2and#960;-geometrical configuration and applying suitable geometry correction, we have determined the K X-ray fluorescence parameters of a few low and medium Z elements in the range of 27 and#8804; Z and#8804; 30 and 42 and#8804; Z and#8804; 47 respectively. The elements were procured in the form of thin foils and were irradiated by a weak radioactive source. The emitted K X-ray photons were detected using a low energy high resolution HPGe detector spectrometer. The incident photons, emitted K X-ray photons and the transmitted photons at newlinethe incident energy is measured and were corrected for window attenuation, efficiency, self-attenuation and geometry correction newlineto obtain the true intensities of incident photons, emitted K Xray photons and the transmitted photons at the incident energy. -
Studies on design and simulation of di-methyl ether plant of 160 TPD capacity
Energy is needed to run almost everything we see around us, from cars to the electricity power generation plants and everything else. Fossil fuels produce harmful products on combustion. One such eco-friendly alternative is Di-Methyl Ether also known as DME. In this study, a DME plant of capacity 160 tons per day was designed. Methanol dehydration process has been adapted as the process of production. The purity of DME from this plant is 99.5% by weight. Distillation column T-202 and heat exchanger E-208 were designed in detail. The detail design results showed that T-202 needed 6 stages for separation and a column diameter of 1.28m, while the simulation results showed 7 stages and column diameter as 1.285m for the same separation process. Furthermore, E-208 is of type 1-2 shell & tube heat exchanger with 307 tubes and tube length of 5.5m, however the Aspen EDR simulation results were also in close agreement with 304 tubes and 5m length for the same heat exchanger. This paper presents the results of simulation results of the simulation of these equipment's and full plant done using Aspen plus V8.8 software and Aspen EDR. 2023 Author(s). -
Studies on dark matter dark energy and possible alternate models
The nature of dark matter (DM) and dark energy (DE) which is supposed to constitute about 95% of the energy density of the universe is still a mystery. There is no shortage of ideas regarding the nature of both. While some candidates for DM are clearly ruled out, there is still a plethora of viable particles that fit the bill. In the context of DE, while current observations favour a cosmological constant picture, there are other competing models which may be equally likely. The standard model for the formation of structure assumes that there newlineexisted small fluctuations in the early universe that grew due to gravitational instability. The origin of these fluctuations are still unclear. In this study, we proposed the role of dark matter in providing the seed for star formation in the early universe, which is supported by very recent observations. With this we set observable constraints on luminosities, temperatures, and lifetimes of the early stars with an admixture of dark matter. We also studied the effects of the background repulsive dark energy density for large scale cosmic structures. The relation, and#119872;and#8260;and#119877;2 and#8776; 1and#119892;/and#119888;and#119898;2, seems to hold true for primeval galaxies as well as those at present epoch. From this, we set constraints on the nature and evolution of dark energy. Besides, we also set constraints on the size of galaxy clusters and superclusters due to the repulsive cosmological dark energy. This could indicate as to why large scale cosmic structures much larger than and#8764;200 Mpc are not seen.This study also looked at the evolution of the concept of the cosmological constant from its inception a little over a hundred years ago when Einstein introduced the cosmological constant in his General Theory of Relativity newlinein order to obtain a static universe to conform to the philosophical view of newlinethe universe at that time to it possibly making up close to about 70% of the energy density of the universe. -
Studies on color energy and its variations in graphs
This thesis consists of studies on color energy and its variations in graphs. Apart from the exploration of color energy corresponding to various coloring schemes, the notion of P-energy as a generalization of color energy has been introduced. The computation of color energy and P-energy of graphs has been carried out using Python programs, while the general results are derived using research methods and proof techniques in linear algebra. The bounds of color energy for a graph G have been established in terms of several graph parameters such as chromatic number and#967;(G), domination number and#947;(G), maximum degree and#8710;(G) etc. It has been found out that the color energy of a graph G is greater than or equal to 1 n and#947;(G) q 2(m + mand#8242;c). Further, the bounds of color energy of a graph G in terms of extreme eigenvalues of color matrix of G have been obtained. The study on color energy with respect to the minimum number of colors and L(h, k)-coloring has been examined in detail for some families of graphs such as star graph, double star, crown graph and their color complements. We have also examined the variation of color energy in the specific cases of T-coloring and radio coloring for some families of graphs. The examination of color energy corresponding to some improper colorings such as Hamiltonian coloring, open neighborhood coloring and improper C-coloring has also been done. Moreover, the color equi-energetic families of graphs with respect to various coloring schemes have been investigated. The concept of P-energy has been introduced as a generalization of the concept of color energy. This stems from the fact that coloring problems in essence are vertex partition problems. For any vertex partition P having k elements, we define the P-matrix AP(G) having and#8722;1, 0, 1, 2 as off diagonal entries and diagonal entries represent the cardinality of the elements in partition P. Then, the P-energy EP(G) is defined as the sum of the absolute values of eigenvalues of P-matrix of G. -
Studies on color energy and its variations in graphs
This thesis consists of studies on color energy and its variations in graphs. Apart from the exploration of color energy corresponding to various coloring schemes, the notion of P-energy as a generalization of color energy has been introduced. The computation of color energy and P-energy of graphs has been carried out using Python programs, while the general results are derived using research methods and proof techniques in linear algebra. The bounds of color energy for a graph G have been established in terms of several graph parameters such as chromatic number χ(G), domination number γ(G), maximum degree ∆(G) etc. It has been found out that the color energy of a graph G is greater than or equal to 1 n γ(G) p 2(m+m′ c ). Further, the bounds of color energy of a graph G in terms of extreme eigenvalues of color matrix of G have been obtained. -
Studies on anti-microbial potential of withania somnifera (l.) dunal and future perspectives: An overview
Withania somnifera is a herb of immense ethnopharmacological importance in Ayurvedic, Siddha and Unani systems of medicine. Due to its immense therapeutic potential and being an important source of novel withanolides, it has been a subject of immense intrigue among researchers. Apart from its anti-inflammatory, antitumor, anti-stress, antioxidant, immunomodulatory, antidiabetic, sedative and hemopoetic properties, there is mounting evidence for its antimicrobial and antiviral properties too. Various withanolides and steroidal lactones isolated so far are known to have high therapeutic value, but works pertaining to their antimicrobial potential have largely been at the synergistic level. No single withanolide has been characterized as a sole antimicrobial and thus, work in this regard is still in the stage of infancy, except for withanone which has recently shown in silico activity against SARS-COV-2. This review summarizes the elaborate antibacterial, antifungal, antiprotozoal and anti-viral work that has been done so far and casts focus on the limitations, in terms of mechanistic aspects of each. 2021 Society for Biology and Biotechnology. All rights reserved. -
Studies on air jet erosion behavior of plasma-sprayed Cr2C3 coatings on Al6061 alloy
This study assesses the efficacy of plasma-sprayed Cr2C3 coatings on AA6061 aluminum alloy in reducing erosion at different angles (30, 60, and 90). The experimental setup involved maintaining a distance of 80 mm between the components, feeding the powder at a rate of 55 g/min, and applying a current density of 460 amps. Weight loss measurements and surface morphology analyses were performed using scanning electron and confocal microscopy. The findings suggest that the Cr2C3 coating significantly improves erosion resistance when compared to specimens without any coating. The erosion angle had a significant impact on the performance of the coating. The coating experienced the least weight loss at an angle of 30 (28.45 g), followed by increased losses at angles of 60 (30.34 g) and 90 (34.2 g). These findings emphasize the significance of the impact angle in determining the severity of material removal. 2024 The Authors -
Studey of different types of modulations on double diffusive convection in lodroyd-b liquids
The problem aims to find the effects of temperature modulation in viscoelastic newlinefluids namely Oldroyd B liquids subjected to double diffusive convection. Both linear as well as a non-linear study has been carried out. A regular perturbation technique has been employed to determine the correction Rayleigh number. The results show that the Lewis number and strain retardation parameter induces stability to the system whereas stress relaxation parameter destabilizes the system for synchronous modulation. Truncated Fourier series represents the non-linear newlineanalysis. Mean Nusselt number and mean Sherwood number are used to quantify the newlineheat and mass transfer respectively. Strain retardation parameter and the Lewis number decrease the heat and mass transfer for synchronous modulation while stress relaxation parameter increases them. The opposite results are obtained for newlineasynchronous and lower wall modulations. Modulation is shown mostly to give rise newlineto super critical motion. -
Students Satisfaction with Remote Learning During the COVID-19 Pandemic: Insights for Policymakers
Purpose: This study aimed to learn more about the factors influencing student happiness and involvement in remote learning in Indian higher education institutions (HEIs). The study aims to assist administrators, strategists, and politicians in efficiently dealing with educations new normal. Methodology: The study used a quantitative research approach to fulfill the research aims. A sample of 546 students from various Indian HEIs was chosen, and data were gathered using standardized questionnaires. Structural equation modeling, confirmatory factor analysis, and importance-performance analysis (IPA) were used to calculate the student satisfaction index and examine the impact of various factors. Findings: The findings of this study revealed that institutional and faculty support emerged as the most influential factor impacting students satisfaction through remote learning. It also highlighted the need for HEIs to redesign the assessment process and evaluation techniques to adapt to the remote learning environment. Practical Implications: The findings of this study indicated the practical consequences for administrators, strategists, and policymakers at Indian HEIs. It was advised that improving institutional and teacher support should be a major concern in order to improve student happiness in remote learning situations. Furthermore, redesigning assessment procedures and evaluation processes may improve learning outcomes and student engagement. Originality: This study contributed to the existing body of knowledge by specifically investigating the factors influencing student satisfaction in remote learning within Indian HEIs. The findings shed light on the unique challenges and opportunities the shift to remote education presented. They offered valuable insights for managing and improving the quality of education during and beyond the pandemic. 2023, Associated Management Consultants Pvt. Ltd.. All rights reserved. -
Students Perception of Chat GPT
An artificial intelligence based Chatbot, ChatGPT was launched by Open AI in November 2022. In the field of education, ChatGPT has several benefits as well as challenges. Chat GPT can be considered as an advanced and a powerful tool to enhance the learning experience. It adds value to the education system only when it is used wisely. However, it is important to understand that the challenges must be addressed. It may act as a good source for collating the information, but it is always advised by the researchers that ones own perspective must be added to draw inferences from the output generated by ChatGPT. Our study supports the finding that ChatGPT can be used for the generation of ideas or to learn a new language. It also becomes imperative for the faculties to motivate students to use ChatGPT and add their inferences as well. AI models like ChatGPT can provide assistance, answer questions and provide explanations on various topics, making learning more accessible and tailored to individual needs. With this paper, we aim to provide a more informed discussion around the usage of ChatGPT in education. 2023 IEEE. -
Student's Performance Prediction Using Modified PSO
In the present-day education system, evaluating students' performance is very important. The prediction of student performance is helpful to students and instructors in maintaining a student's progress. Presently, institutions are implementing Continuous Evaluation Systems. This system is beneficial for improving the students' performance and helps increase their regularity in their studies. This work proposed a new version of the particle swarm optimization algorithm to classify students into different categories based on their performance with the help of various factors. The proposed model modified the strategy to increase the optimization algorithm's efficiency. This model deals with the bag of features with the modified optimization algorithm to recognize students' performance based on 33 features. These features are used for training, validation, and testing of the student's performance and generate a classification report which includes F-measure, recall, precision, and accuracy. Based on the classification report, the proposed model is compared with the existing methods, and the better performance of the proposed model is ascertained. 2023 IEEE. -
Student-Teacher Relationship Patterns in Undergraduate College
The student-teacher relationship has always been important at all levels of formal education, including undergraduate level. Positive student-teacher relationship plays direct role in facilitating students experience, and ultimately enhancing the academic outcomes. Furthermore, such relationship, especially at undergraduate level, becomes crucial since it also helps to facilitate the change and transformation process of adolescents who are stepping out from kindergraten-12th grade (K-12) system of education and venturing into college life. Given such importance and closeness in the relationship, this study attempted to examine the attachment patterns of the student-teacher relationship at undergraduate level. The research was guided by two broad questions. First, is student-teacher relationship at undergraduate level an attachment relationship? Second, if it is an attachment relationship, do distinct patterns exist? Drawing on two-dimensional internal working model of adult attachment postulated by Bartholomew (1980) as conceptual framework, the study explored the perception of 216 undergraduate students on student-teacher relationship from a university in Bangalore by using exploratory factor analysis (EFA). From the result two distinct dimensions, first related to students self and second associated to their view about availability of teachers and how they would reciprocate in the interactions, were observed which was later confirmed by CFA. The finding could help in future research to find the aspects of the relationship that promote the sense of security and supportiveness to enhance the academic outcomes of the students. Keywords: adult attachment patterns, student-teacher relationship