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RayleighBard and BardMarangoni magnetoconvection in variable viscosity finitely conducting liquids
The thermorheological effect on magneto-Bard-convection is studied numerically in fluids with finite electrical conductivity. A nonlinear thermorheological equation is considered in the problem. The results are compared with the classical approach of constant viscosity, which depicts the fact that the effect of increasing the strength of the magnetic field is to delay the onset of convection. The magnetic field is shown to have a rheostatic influence on convective instabilities. The results obtained by the study have possible applications in the field of astrophysics, sunspots, and in space applications under microgravity. 2021 Wiley Periodicals LLC -
Rayleigh-Benard-Marangoni electro-convection in a dielectic micropolar fluid /
The linear analysis of Rayleigh-B??nard-Marangoni convection in dielectric micropolar fluid is studied using the Galerkin technique. In the case of Rayleigh ?? B??nard convection, the eigenvalue is obtained for free - free, rigid ?? free and rigid ?? rigid velocity boundary combinations with isothermal and adiabatic on the spin-vanishing boundaries. A linear stability analysis is performed. The influence of various parameters on the onset of convection has been analyzed. In the case of Marangoni and Rayleigh-B??nard-Marangoni convection the eigenvalues are obtained for an upper free / adiabatic and lower rigid / isothermal boundaries. The microrotation is assumed to vanish at the boundaries. The influence of various parameters on the onset of convection has been analyzed and their comparative influence on onset is discussed. -
Rayleigh-Benard convection in a horizontal layer of porous medium saturated with a thermally radiating dielectric fluid /
IOSR Journal Of Mathematics, Vol.11, Issue 3, pp.465-474, ISSN No: 2278-5728 (Online) 2319-765X (Print). -
Rayleigh-benard convection in a dusty newtonian nanofluid with and without coriolis force
Theoretical investigation of the Rayleigh-Bard convection (TRBC) in nanofluid (NF) submerged with dust particles is carried out. Convection in dusty nanofluid is considered between two horizontal free boundaries. Effect of nanoparticles shape is also accounted. The Saffmans dusty fluid model is used to simulate the influence of dust particles, whereas the KVL (Khanafer-Vafai-Lightstone) model is employed to estimate the effective nanofluid properties. The fluid, dust particles and nanoparticles are in the thermal equilibrium state and move with the same velocity. The exact solutions are obtained using Normal Mode Analysis (NMA) method for two different cases namely (1) TRBC in dusty nanofluid (DNF) without Coriolis force (2) TRBC in DNF with Coriolis force. It is established that for the stationary convection, the effect of suspended particles hasten the onset of convection whereas the Coriolis force postpones the onset of convection. 2018 by American Scientific Publishers All rights reserved. -
Rayleigh-benard and benard-marangoni convection in micropolar fluid
We study in this thesis, Rayleigh-Bard and Bard-Marangoni convection in a micropolar fluid. We study the effects of temperature modulation at the boundary and gravity modulation in the presence of porous medium. The effects of rotation and internal heat generation are also investigated and results are presented graphically and discussed qualitatively. The problem presented in this thesis throws light on externally controlled internal convection in a micropolar fluid. These problems have many possible applications in geophysics, astrophysics, oceanography engineering and in space situations with g-jitter connected with gravity stimulation study. With this motivation, we examine in this thesis five problems and their summary is given below one by one. (i) THE EFFECT OF IMPOSED TIME-PERIODIC BOUNDARY TEMPERATURE AND POROUS MEDIUM ON THE ONSET OF RAYLEIGH-BARD CONVECTION IN A MICROPOLAR FLUID The analysis of buoyancy driven convection in a micropolar fluid saturated porous layer heated from below and subject to temperature modulation is presented. In addition to a steady temperature difference between the walls of the porous layer, a time-dependent periodic perturbation is applied to the wall temperatures. The small amplitude of the modulation is used to compute the critical Rayleigh number and critical wave number. Three cases of the oscillating temperature field are examined: (a) symmetric, so that the wall temperatures are modulated in phase, (b) asymmetric, corresponding to out-of-phase modulation, and (c) only the bottom wall is modulated. Possibilities of the occurrence of subcritical instabilities are also discussed. The shift in the critical Rayleigh number is calculated as a function of frequency and it is found that it is possible to advance or delay the onset of convection by time modulation of the wall temperatures. (ii)LINEAR AND NON-LINEAR ANALYSES OF GRAVITY MODULATION ON THE ONSET OF RAYLEIGH-BARD CONVECTION IN A MICROPOLAR FLUID WITH POROUS MEDIUM. -
Rayleigh-Benard and Benard-Marangoni convection in micropolar fluid
We study in this thesis, Rayleigh-Bernard and Bernard-Marangoni convection in a micropolar fluid. We study the effects of temperature modulation at the boundary and gravity modulation in the presence of porous medium. The effects of rotation and internal heat generation are also investigated and results are presented graphically and discussed qualitatively. -
Rayleigh-Bard Convection of Water-Copper and Water-Alumina Nanofluids Based on Minimal- and Higher-Mode Lorenz Models
Linear and nonlinear stability analyses of Rayleigh-Bard convection in water-copper and water-alumina nanofluids are studied in the paper by considering a minimal as well as an extended truncated Fourier representation. These representations respectively result in a third-order classical Lorenz model and a five-dimensional extended Lorenz model. The marginal stability plots reveal that the influence of added dilute concentration of nanoparticles in water is to destabilize the system. The rate of destabilization depends on the nanoparticles' thermophysical properties and their volume fraction. Influence of adding an additional mode in the horizontal direction is to modify the cell size. This can be observed through the marginal curves as well as the stream line plots. Further, from the Nusselt number plots it is evident that the presence of dilute concentration of nanoparticles in water is to enhance heat transport in the system significantly. The dynamical behavior of the minimal and the extended Lorenz models is investigated using the bifurcation diagram. From the study an important finding that emerges is that the Fourier truncated solution is predicted to have different effects in lower-order and higher-order models. The extended penta-modal Lorenz system predicts advanced onset of chaos compared to that predicted by the classical third-order Lorenz model. The individual influence of both nanoparticles in water is to advance the onset of convection as well as to advance the onset of chaos. 2023 World Scientific Publishing Company. -
Rayleigh-Bard convection in mono and hybrid nanoliquids in an inclined slot
Linear stability analysis is conducted to investigate the longitudinal and transverse rolls (TRs) generated in Rayleigh-Bard convection in mono and hybrid nanoliquids confined between two infinite inclined parallel slots. Thermophysical properties of six mono nanoliquids and fifteen hybrid nanoliquids are calculated for different volume fractions (0.5%, 1%, 2%) using phenomenological laws and mixture theory. The shooting method is used to solve boundary eigenvalue problems to obtain the eigenvalues for 16 different boundary conditions. It is observed that as the inclination angle is increased, it delays the onset of longitudinal rolls in the case of all boundary conditions. However, it advances the onset of TRs except when the lower plate is adiabatic. The addition of mono and hybrid nanoparticles results in the advancement of the onset of convection. The addition of SWCNT and SWCNT Al 2 O 3 accelerates the onset of convection the most while Cu and Cu-Ag accelerates the onset of convection the least amongst the mono and hybrid nanoparticles considered in the study. 2023 IOP Publishing Ltd. -
Rayleigh-B nard convection in Casson and hybrid nano uids: An analytical investigation
The thermal Rayleigh-Bard convection (TRBC) in two different fluids namely Casson fluid and hybrid nanofluid is investigated analytically. The stability analysis is performed in both linear and non-linear form. The nanofluid properties like thermal conductivity, viscosity, thermal expansion coefficient and density are considered to be functions of the volume fraction of nanoparticles whereas the same properties of Casson fluid are assumed to be constant. The amount of heat transfer is analyzed in the non-linear analysis using the generalized Lorenz model. The influence of Casson fluid parameter and nanoparticles (single and or binary) which affect the onset of convection is analyzed. It is found that hybrid nanofluid delays the convection and will further enhance the heat transfer rate. Also, the Casson parameter advances the convection while it reduces the heat transfer rate. 2019 by American Scientific Publishers. -
Rayleigh bernard convection in couple stress fluid with maxwell cattaneo law
The onset of thermal instability in horizontal layers of fluid heated from below illustrates many physical and mathematical features of the general theory of hydrodynamic stability. The effect of non-Fourier heat transfer in couple stress in a Rayleigh Benard configuration is analyzed theoretically in this thesis. Broad range of applications of couple stress fluid and the need for its characterization at a relatively small scale of time and length act as a motivation for the study of buoyancy driven convection in such fluids under the influence of magnetic field and under various modulations such as temperature, gravity, rotation and magnetic field by employing Maxwell Cattaneo law. newlineLinear and non linear magneto convection in couple stress fluid with Maxwell Cattaneo law newlineThe interesting facets brought about by the interactions between convection and magnetic fields in a Rayleigh Benard configuration for free free boundaries are analyzed in this chapter. Linear and weakly non linear stability analysis are carried out to study the system. It is proved that the oscillatory mode is not the preferred mode of instability. The couple stresses in the fluid and magnetic field are found to enhance the stability of the system whereas non-Fourier effects destabilized the system. newlineEffect of temperature modulation on the onset of Rayleigh Benard convection in a couple stress fluid with Maxwell Cattaneo law newlineThe effect of externally imposed time-periodic boundary temperature on the setting in of convection is examined using linear stability analysis. The Venezian approach is applied to deduce the critical Rayleigh number and critical wave number. The stability of the system is characterized by a correction Rayleigh number and is obtained as a function of the Cattaneo number couple stress parameter Prandtl number and the frequency of modulation. The study analyzes three types of temperature modulations viz. in phase, out of phase and only lower wall modulation. -
RAYLEIGH B??NARD - CONVECTION IN MICROPOLAR FLUID SATURATED POROUS MEDIA WITH MAXWELL - CATTANEO LAW
In this paper we find the effects of saturated porous media on the onset of Rayleigh-Benard convection in a micropolar fluid with Maxwell-Cattaneo law. We have done a linear study of the problem and the Rayleigh number has been arrived at using Galerkian method. The critical Rayleigh number has been found for different boundary conditions and graphs have been plotted for the same. -
Rationally designed CeO2 decorated Ti3C2 MXene interface for efficient water splitting and enhanced supercapacitor performance
MXenes serve as competent electrodes for applications such as energy storage and conversion owing to their unique characteristics, which include substantial surface area, excellent conductivity, abundant surface-terminating groups, and high hydrophilicity. However, MXene nanosheets exhibit a pronounced tendency to restack via Van der Waals force, hindering the active sites and resulting in sluggish electronic and ionic kinetics. This phenomenon limits the capabilities, processability, and overall performance of MXene. In this study, CeO2 is utilized as an interlayer spacer for the Ti3C2 MXene substrate, providing a promising noble metal-free multifunctional electrode. The Ti3C2/CeO2 composite, synthesized via the hydrothermal method, efficiently mitigates restacking while exhibiting excellent conductivity, substantial surface area, and enhanced kinetics. The as-synthesized catalysts undergo diverse physiochemical characterizations and electrochemical measurements to understand their properties and potential multiapplications. The fabricated electrode material, Ti3C2/CeO2, shows excellent specific capacitance of 1908.5 Fg?1 at 1 Ag?1 in a three-electrode setup using 3 M KOH as electrolyte. It has a capacitive retention of 91% even after 4000 cycles. Besides, Ti3C2/CeO2 also functions as a proficient electrode material for overall water splitting, having a lower overpotential of 178 mV and 350 mV for hydrogen and oxygen evolution reactions, respectively, at a current density of 10 mAcm?2. It also displays a lower cell voltage of 1.78 V to obtain a current density of 10 mAcm?2. This study introduces the multi applications of a well-designed interface between Ti3C2 layers and CeO2 within the realm of electrochemical energy storage and conversion. 2024 Elsevier B.V. -
Rationality of the Terrorist Group and Governments Policy: A Game Theoretic Approach
The two ideas of the rationality of terrorist organisations and the costly leader game are used in this paper to construct a game theoretic model. It is an addition to the literature on terrorism and leader-follower games, in which the government and a terrorist organisation are the two players. Terrorist group can be rational or irrational. In case it is rational, it does the cost-benefit analysis and is open to negotiation. Only in this case, the government chooses to not spend on counter-terrorist measures. The irrational group has lexicographic preferences, which means that it prefers a successful attack to attract attention and recruits at the beginning or finish of its operation. Consequently, it is assumed that the irrational group will always attack. the irrational terrorist organisation has the option of either choosing not to mimic the rational group or choosing to do so at a psychological cost. Although the irrational group dislikes imitation. It seeks to duplicate the rational group so that the government withdraws and cuts back on spending on counter-terrorism. A costly leader model is set up in the paper, where the government can incur a cost to gather information about the type of terrorist group. In this framework, the paper provides policy prescriptions concerning counter-terrorist measures that the government should take in case the type of terrorist group being rational or irrational is unknown and it highlights the importance of intelligence. 2024 Walter de Gruyter GmbH. All rights reserved. -
Rational suitability of low cost activated carbon in removing hexavalent chromium ions from wastewater by uninterrupted mode of adsorption
Heavy metals such as chromium, lead, arsenic and others are dense metals whose contamination of water may exterminate life on earth at the niche in industrial activities, foodstuffs or medicines and so on. Activated carbons are very helpful in removing heavy metal ions from aqueous solutions by adsorption, and have been investigated by many researchers so far. The practical relevance of activated carbon made from de oiled soya in the removal of hexavalent chromium ions through continuous adsorption mode is reported in this paper. A breakthrough plot was plotted in finding the effect of initial concentration and adsorbent bed height in the adsorption of hexavalent chromium through activated carbon of de oiled soya. The breakthrough time and saturation time increased as the concentration of the initial solution shot up from 40 mg/L to 60 mg/L. The saturation time was in an incremental mode when the thickness of the adsorbent bed height in a fixed bed was increased from 5cm to 7cm for 40 mg/L initial concentration of hexavalent chromium. The Adams-Bohart's model was found to fit perfectly the fixed bed column in the removal of hexavalent chromium from aqueous solutions. The fabricated adsorbent worked well in detoxifying hexavalent chromium metal ion contaminated wastewater. 2020 Published under licence by IOP Publishing Ltd. -
Rational Designing of Ni-Ag/C Bimetallic Nanoparticles
Bimetallic nanoparticles have been found to show improved properties due to the synergistic effect between the incorporated metals as a result of electronic charge transfer between them. The importance of using bimetallic particles lies in the high selectivity that they offer. Ni being a reactive metal, was doped with Ag, a highly selective host. In this study, Ni-Ag bimetallic nanoparticles supported on carbon have been synthesized by co-impregnation by using nickel (II) nitrate and silver nitrate as precursors. The catalyst is characterized using XRD, FTIR, DLS, Zeta potential, EDX, SEM, and TEM. The scope of this synthesized catalyst can be extended to several reactions like CO2 reduction reaction, hydrogenation, and industrially important organic reactions. 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. -
Rational design of PANI incorporated PEG capped CuO/TiO2 for electrocatalytic hydrogen evolution and supercapattery applications
Synthesis of efficient electrocatalysts for energy applications is a major area scientists are currently focusing on to address the twin challenges of energy shortfall and the production of clean energy. Herein, an efficient electrocatalyst, polyaniline incorporated with polyethylene glycol capped CuO/TiO2 is prepared, which is effective in hydrogen evolution reactions and energy storage applications. The characterizations like XPS, XRD, FT-IR, FE-SEM, HR-TEM, and BET have been carried out to confirm the successful formation of the synthesized PANI/CuO/TiO2 composite. At 10 mA/cm2 current density, the prepared composite exhibits a lesser overpotential of 536 mV and 1587.2 C/g at 1 A/g as the specific capacity. The electrode prepared using the PANI/CuO/TiO2 composite also shows cyclic stability up to 2000 cycles. The synthesized composite is an efficient electrocatalyst for energy related applications. 2023 Hydrogen Energy Publications LLC -
Rational design of bifunctional catalyst from KF and ZnO combination on alumina for cyclic urea synthesis from CO2 and diamine
This study is mainly focused on the design of stable, active and selective catalyst for direct synthesis of 2-imidazolidinone (cyclic urea) from ethylenediamine and CO2. Based on the rationale for the catalyst properties needed for this reaction, KF, ZnO and Al2O3 combination was selected to design the catalyst. ZnO/KF/Al2O3 catalyst was prepared by stepwise wet-impregnation followed by the removal of physisorbed KF from the surface. High product yield could be achieved by tuning acid-base sites by varying the composition and calcination temperature. The catalysts were characterized by various techniques like XRD, N2-sorption, NH3-TPD, CO2-TPD, TEM, XPS and FT-IR measurements. It is shown that acidic and basic properties of the solvent can influence the activity and product selectivity for this reaction. Under optimized condition; 180 C, 10 bar and 10 wt.% catalyst in batch mode, 96.3 % conversion and 89.6 % selectivity towards the 2-imidazolidinone were achieved. 2020 Elsevier B.V. -
Rational bubble testing: An in-depth study on CNX nifty /
Asian Journal of Research in Banking and Finance, Vol.6, Issue 6, pp.10-16, ISSN: 2249-7323. -
Rating-Based Cyberbullying Detection with Text, Emojis on Social Media
In the dynamic landscape of online interactions, cyberbullying has become pervasive, profoundly impacting user's digital well-being. Public figures, especially celebrities and influencers, face heightened vulnerability to online harassment, exacerbated by the post-pandemic surge in social media usage. To address this challenge, our research adopts a holistic approach to detect cyberbullying in text, considering both textual content and the nuanced expressions conveyed through emojis on social media platforms. We employed a diverse set of machine learning and deep learning models, including Support Vector Classifier, Logistic Regression, Random Forest, XGBoost, LSTM, Bi-LSTM, GRU, and Bi-GRU, to accurately classify non cyberbullying or cyberbullying text. Beyond classification, our study introduces an offensive rating system, assigning severity ratings on a 1-5 scale to identify cyberbullying instances. A critical aspect is the establishment of a threshold value which depends on user security and safety ethics of different social media platforms; texts surpassing this trigger an automatic recommendation to block the user, ensuring a proactive response to minimize harm. This recent contribution not only comprehensively addresses cyberbullying but also empowers society. 2024 IEEE. -
Rating of Online Courses: A Machine Learning Based Prediction Model
Online courses market has provided an economical and easy access to knowledge. When it comes to make a decision related to purchase of online course, little is known about what attributes can be depended upon to guess the quality of an online course. Ratings for online courses act as a reliable signal for assessing the quality of a course. The study discusses the prediction of ratings for online courses using Artificial Neural Network based on Particle Swarm Optimization (ANN-PSO). The experimental results suggests that ANN-PSO model has the capacity to predict the ratings for online courses on the basis of its attributes with accuracy. 2021 IEEE.