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Linear and nonlinear convection in dielectric fluids
The thesis is concerned with linear and nonlinear Rayleigh-Benard electroconvection in a horizontal porous layer. Modified Darcy law is employed to describe the fluid motion. The effect of non-0classical 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. -
Linear and non-linear stability analyses of Rayleigh-Bard convection in watercopper and wateralloy nanoliquids
In this paper, we perform linear and non-linear stability analyses of Rayleigh-Bard convection in a horizontal layer of watercopper and wateralloy nanoliquids. The corresponding eigen values for the problems involving the two nanoliquids are obtained and compared. The thermophysical properties of nanoliquids have been modelled as a function of the properties of water as base liquid, copper and alloy as nanoparticles. A non-linear analysis is performed using the energy method. The subcritical instability does not exist. As a limiting case the results of water are discussed with results of previous investigations, and a good agreement is found. The effect of nanoparticles is to destabilise the system. The results are depicted graphically. 2022 Informa UK Limited, trading as Taylor & Francis Group. -
Linear and non-linear magneto-convection in couple stress fluid with non-classical heat conduction law
A theoretical examination of the thermal convection for a couple stress fluid which is electrically conductive and possessing significant thermal relaxation time with an externally applied magnetic field is carried out. Fourier's law fails when fluids are subjected to rapid heating or when it is confined and in the case of nano-devices. A frame invariant constitutive equation for heat flux is considered. The linear analysis is carried out implementing a normal mode solution and the non-linear stability of the system is analyzed using a double Fourier series. The analysis of the transfer of heat is determined in terms of the Nusselt number. Published under licence by IOP Publishing Ltd. -
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Linear and non-linear analysis of solute-magneto convection in a couple stress fluid with porous medium under concentration modulation
The effect of concentration modulation and magnetic field in a couple stress fluid with porous medium and salted from above is studied using linear and non-linear analysis. Venezian approach based on perturbation method is used to obtain the expression for solute Rayleigh number and correction solute Rayleigh number. The expression for correction solute Rayleigh number is obtained as a function of couple stress parameter, Chandrashekar number, Darcy number and Schmidt number. The effect of parameters on symmetric and asymmetric concentration modulation are discussed in the paper. A non-autonomous Ginzburg-Landau equation with time periodic co-efficient is obtained to study the effect of parameters on mass transfer. It is found that onset of convection and mass transfer can be delayed or advanced by varying the parameters of the problem. Asymmetric modulation is found to be more stable than the symmetric modulation. 2019 Author(s). -
Linear and non-linear analyses of electrothermo convection in a micropolar fluid
The linear and weakly non-linear stability analyses of electrothermo convention in a micropolar fluid layer heated from below are studied. The linear and non-linear analyses are, respectively, based on normal mode technique and truncated representation of Fourier series. The influence of various parameters on the onset of convection has been analyzed in the linear case. The resulting autonomous Lorenz model obtained in non-linear analysis is solved numerically to quantify the heat transfer through Nusselt number. It is observed that the increase in concentration of suspended particles stabilizes the system and decreases the heat transfer and increase in electric Rayleigh number destabilizes the system and increases the heat transfer. 2017 Pushpa Publishing House, Allahabad, India. -
Linear and non-linear analyses of double-diffusive-Chandrasekhar convection coupled with cross-diffusion in micropolar fluid over saturated porous medium
Purpose: The problem aims to find the effects of coupled cross-diffusion in micropolar fluid oversaturated porous medium, subjected to Double-Diffusive Chandrasekhar convection. Design/methodology/approach: Normal mode and perturbation technique have been employed to determine the critical Rayleigh number. Non-linear analysis is carried out by deriving the Lorenz equations using truncated Fourier series representation. Heat and Mass transport are quantified by Nusselt and Sherwood numbers, respectively. Findings: Analysis related to the effects of various parameters is plotted, and the results for the same are interpreted. It is observed from the results that the Dufour parameter and Soret parameter have an opposite influence on the system of cross-diffusion. Originality/value: The effect of the magnetic field on the onset of double-diffusive convection in a porous medium coupled with cross-diffusion in a micropolar fluid is studied for the first time. 2020, Emerald Publishing Limited. -
Linear and non-linear analyses of double diffusive chandrasekhar convection with heat and concentration source in micropolar fluid with saturated porous media under gravity modulation
In this paper, linear and non-linear analysis of Double-Diffusive convection in the presence of magnetic field and gravity modulation with heat and concentration source in a micropolar fluid is studied by assuming the strength of heat and concentration source same. The expression for Rayleigh number and correction Rayleigh number are obtained using regular perturbation method. The effects of parameters on heat and mass transport is investigated using non-linear analysis by deriving eighth order Lorenz equation. It is found that coupling parameter and Chandrasekhar number stabilizes the system. Whereas internal Rayleigh number and Darcy number destabilizes the system. 2020 International Association of Engineers. -
Linear and non linear electroconvection in a micropolar fluid /
This thesis presents a theoretical study of linear and non-linear analyses of Rayleigh–Bénard–Marangoni/Rayleigh–Bénard electro convection in a micropolar fluid. The effects of non-uniform basic temperature gradient, suction–injection combination and gravity modulation have been studied in the presence of electric field. The effect of heat transfer in a micropolar fluid in the presence of electric field is also studied and results are presented graphically and discussed qualitatively. These problems assume greater importance in geophysics, astrophysics, oceanography, and engineering and in space situations with g-jitter connected with gravity stimulation study. Keeping in mind the importance and relevance of externally controlled internal convection in a micropolar liquid. -
Linear and non linear electroconvection in a micropolar fluid
This thesis presents a theoretical study of linear and non-linear analyses of Rayleigh Bard Marangoni/Rayleigh Bard electro newlineconvection in a micropolar fluid. The effects of non-uniform basic temperature gradient, suction injection combination and gravity newlinemodulation have been studied in the presence of electric field. The effect of heat transfer in a micropolar fluid in the presence of electric field is also studied and results are presented graphically and discussed qualitatively. These problems assume greater importance in geophysics, newlineastrophysics, oceanography, and engineering and in space situations with g-jitter connected with gravity stimulation study. newlineKeeping in mind the importance and relevance of externally controlled internal convection in a micropolar liquid. We deal with four newlineproblems, details of which are given below. newline(i) Effect of non uniform basic temperature gradient on the onset of Rayleigh Bard Marangoni electro convection in a micropolar fluid. The non-uniform temperature gradient finds its origin in the transient heating or cooling at the boundaries and as a result the basic temperature profile depends explicitly on position and time. This has to be determined by solving the coupled momentum and energy equations. This coupling also makes the problem very complicated. In the present study, therefore, we adopt a series of temperature profiles based on a newlinesimplification in the form of a quasi-static approximation that consists of freezing the temperature distribution at a given instant of time. In this method, we assume that the perturbation grows much faster than the newlineinitial state and hence freeze the initial state into some spatial distribution. newlineTherefore the effects of these non-uniform basic temperature gradient and electric field are studied on the onset of Rayleigh Bard Marangoni convection in micropolar fluid. -
Linear and Global Stability Analyses on the Influences of Thermal Non-Equilibrium and Non-uniform Gravity Field on DarcyBrinkmanBard Convection
Global and linear stability analyses of DarcyBrinkmanBard convection in a liquid-saturated porous medium with a non-uniform gravity field using the local thermal non-equilibrium (LTNE) model are investigated. Linear and quadratic (parabolic) gravity field profiles are considered in the analysis. The OberbeckBoussinesq approximation is assumed to be a valid and the stationary mode of onset of convection is shown to be the preferred mode due to the validity of the principle of exchange of stabilities. Critical values of wavenumber and thermal Rayleigh number are obtained numerically using the higher-order Galerkin technique. The effect of an increase in the gravity fields strength is to delay the onset of convection, and to a growth in convective cell size. Further, linear convective profile is found to postpone convection compared to the quadratic one. Global stability ensures the existence of subcritical motions in the case of a non-uniform gravity field. In contrast, subcritical motions do not exist in constant gravity in LTE and LTNE situations. A non-uniform gravity field has a significant influence on the convective instability in a liquid-saturated high-porosity medium, lesser influence in the case of a low porosity medium and least in the case of a clear fluid layer. 2021, The Author(s), under exclusive licence to Springer Nature India Private Limited. -
Line completion number of grid graph Pn Pm
The concept of super line graph was introduced in the year 1995 by Bagga, Beineke and Varma. Given a graph with at least r edges, the super line graph of index r, Lr(G), has as its vertices the sets of r-edges of G, with two adjacent if there is an edge in one set adjacent to an edge in the other set. The line completion number lc(G) of a graph G is the least positive integer r for which Lr(G) is a complete graph. In this paper, we find the line completion number of grid graph Pn Pm for various cases of n and m. 2021 Azarbaijan Shahid Madani University. -
Limelight in Dark Times: Jyoti Kumari's 'Cyclothon'
[No abstract available] -
Limaco?n Inspired Particle Swarm Optimization forLarge-Scale Optimization Problem
Large-scale optimization problems are a complex problem in the class of NP-Hard. These problems are not solvable by traditional methods in a reasonable time. Single machine total weighted tardiness scheduling problem (SMTWTSP) is a complex problem in this category. It has a set of different events with varying criteria that need to be scheduled on one machine. The main aim of this problem is to find the minimum possible total weighted tardiness. Particle swarm optimization (PSO) algorithm has performed admirably in the field of optimization. To solve complex optimization problems, several new variants of this algorithm are being developed since its inception. This work proposed an influential local search (LS) technique inspired by limaco?n curve. The new local search is hybridized with PSO and named Limaco?n inspired PSO (LimPSO) algorithm. The efficiency and accuracy of the designed LimPSO strategy are tested over the large-scale SMTWTS problem, which shows that LimPSO can be considered an effective method for solving the combinatorial optimization problems. 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. -
Lilliputians' dilemma: Survival strategies of small states in South Asia
One of the most striking features of contemporary international politics is asymmetrical power relations among states. With the birth of the United Nations, the sovereign equality of the states began to be fully respected, at least in principle. During the Cold War, small states gained much importance when superpowers tried to co-opt them. Small states situated in specific geo-strategic areas were seen as 'assets' or 'trouble spots' depending on their ideological leaning. 1 Given the fact that small states constitute majority in terms of numbers in global politics, but at the same time facing numerous politico-security and economic issues, several interesting questions arise. Do small states feel secured in regional and international politics dominated by big and middle powers? What survival strategies do they adopt to secure themselves? How does this translate to South Asian region that is commonly viewed as 'India-dominant'? Do small states of South Asia follow similar or differing strategies to safeguard their security? South Asia offers a right case to look at the issue of survival strategies of small states in regional politics from both theoretical and empirical contexts. 2024 selection and editorial matter, Adluri Subramanyam Raju and R. Srinivasan. All rights reserved. -
Lignocellulosic biomass for biochar production: A green initiative on biowaste conversion for pharmaceutical and other emerging pollutant removal
Lignocellulosic waste generation and their improper disposal has accelerated the problems associated with increased greenhouse gas emissions and associated environmental pollution. Constructive ways to manage and mitigate the pollution associated with lignocellulosic waste has propelled the research on biochar production using lignocellulose-based substrates. The sustainability of various biochar production technologies in employing lignocellulosic biomass as feedstock for biochar production not only aids in the lignocellulosic biomass valorization but also helps in carbon neutralization and carbon utilization. Functionalization of biochar through various physicochemical methods helps in improving their functional properties majorly by reducing the size of the biochar particles to nanoscale and modifying their surface properties. The usage of engineered biochar as nano adsorbents for environmental applications like dye absorption, removal of organic pollutants and endocrine disrupting compounds from wastewater has been the thrust areas of research in the past few decades. This review presents a comprehensive outlook on the up-to-date research findings related to the production and engineering of biochar from lignocellulosic biomass and their applications in environmental remediation especially with respect to wastewater treatment. Further a detailed discussion on various biochar activation methods and the future scope of biochar research is presented in this review work. 2024 Elsevier Ltd -
Lignite-derived nanocarbon as surface passivator and cosensitizer in dye-sensitized solar cell
Interfacial exciton recombination and narrow absorption region are two bottlenecks that limit the performance of a dye-sensitized solar cell (DSSC). The present study focuses on improving the solar cell's efficiency by utilizing a lignite-derived nanocarbon that behaves as a surface passivator and cosensitizer. Incorporating nanocarbon enhanced the spectral absorption region of the N719 dye with a bathochromic shift and played the role of a cosensitizer. In addition, the quenched photoluminescence spectra revealed that nanocarbon also aids in the swift transfer of electrons to the conduction band of TiO2 by reducing the exciton recombination and acting as a surface passivator. On measuring the fabricated DSSC under AM 1.5G irradiation with the intensity of 100 mW/cm2, the nanocarbon-based device exhibited an efficiency (?) of 9.02% with a photocurrent density of 20.45 mA/cm2, outperforming the pristine device (? = 6.21%). An enhancement of 45% in the power conversion efficiency was achieved. Thus, the results unveiled that nanocarbons derived from pollution-causing fuel synergistically aided in enhancing the performance of DSSC. 2024 Elsevier Ltd -
Lignin-based nanomaterials for food and pharmaceutical applications: Recent trends and future outlook
Small particles of size ranging from 1 to 100 nm are referred to as nanoparticles. Nanoparticles have tremendous applications in various sectors, including the areas of food and pharmaceutics. They are being prepared from multiple natural sources widely. Lignin is one such source that deserves special mention due to its ecological compatibility, accessibility, abundance, and low cost. This amorphous heterogeneous phenolic polymer is the second most abundant molecule in nature after cellulose. Apart from being used as a biofuel source, lignin is less explored for its potential at a nano-level. In plants, lignin exhibits cross-linking structures with cellulose and hemicellulose. Numerous advancements have taken place in synthesizing nanolignins for manufacturing lignin-based materials to benefit from the untapped potential of lignin in high-value-added applications. Lignin and lignin-based nanoparticles have numerous applications, but in this review, we are mainly focusing on the applications in the food and pharmaceutical sectors. The exercise we undertake has great relevance as it helps scientists and industries gain valuable insights into lignin's capabilities and exploit its physical and chemical properties to facilitate the development of future lignin-based materials. We have summarized the available lignin resources and their potential in the food and pharmaceutical industries at various levels. This review attempts to understand various methods adopted for the preparation of nanolignin. Furthermore, the unique properties of nano-lignin-based materials and their applications in fields including the packaging industry, emulsions, nutrient delivery, drug delivery hydrogels, tissue engineering, and biomedical applications were well-discussed. 2023 Elsevier B.V. -
Lignin nanoparticles from Ayurvedic industry spent materials: Applications in Pickering emulsions for curcumin and vitamin D3 encapsulation
Lignin nanoparticles (LNP), extracted from spent materials of Dashamoola Arishta (Ayurvedic formulation), shared a molecular weight of 14.42 kDa with commercial lignin. Processed into LNPs (496.43 0.54 nm) via planetary ball milling, they demonstrated stability at pH 8.0 with a zeta potential of ?32 0.27 mV. Operating as Pickering particles, LNP encapsulated curcumin and vitamin D3 in sunflower oil, forming LnE + Cu + vD3 nanoemulsions (particle size: 347.40 0.71 nm, zeta potential: ?42.27 0.72 mV) with high encapsulation efficiencies (curcumin: 87.95 0.21%, vitamin D3: 72.66 0.11%). The LnE + Cu + vD3 emulsion exhibited stability without phase separation over 90 days at room (27 2 C) and refrigeration (4 1 C) temperatures. Remarkably, LnE + Cu + vD3 exhibited reduced toxicity, causing 29.32% and 34.99% cell death in L6 and RAW264.7 cells respectively, at the highest concentration (50 ?g/mL). This underscores the potential valorization of Ayurvedic industry spent materials for diverse industrial applications. 2024 Elsevier Ltd