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Study of substitution effects on structure and properties of high temperature superconductors and isostructure compounds
The branch of physics which deals with the properties of solid materials and their constituent particles such as protons, neutrons and electrons is known as solid state physics. There are wide ranges of physical properties of solids. Some of the materials are very good conductors of heat and electricity whereas others are bad conductors. -
Study of substituion effectson structure and properties of high temperature superconductors and isostructure compounds
The thesis mainly describes the investigation of the structural formation of higher order members of bismuth system of superconductors Bi1.6sPb0.35Sr2CazCu4Oy (n = 4, 2234 phase), Bi1.6sPb0.35Sr2Ca4CusOy (n = 5, 2245 phase) and Bi1.65Pb0.35Sr2CasCu,Oy (n = 9, 2289 phase). The samples were synthesized by solid state reaction technique. Micro-structural and morphological features of the synthesized samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The XRD pattern of all the samples revealed the presence of Bismuth 2212 and 2223 phases of which 2223 phase was found to be the predominant. Superconducting transition temperature (Tc) of the samples measured by self-inductance method and dc four probe method showed Tc value around 110 K. There was no signature of the formation of 2234, 2245 or 2289 phases in this investigation. newlineFormation of Bi-2245 compound was further investigated by preparing the sample in a new matrix route. The Tc on set of this sample was found to be 127 K which was the highest reported ever in bismuth system superconductors. The complete replacement of copper by nickel in bismuth system superconductor Bi2SraCu06 (2201) was ttempted by preparing the sample in air by solid state reaction method under open and closed environment. Morphological and microstructural features of the synthesized sample Bi2Sr2Ni0g was investigated by X-ray diffraction, SEM and EDAX. The analysis of X-ray diffraction pattern revealed that nickel can replace copper completely and form a single phase Bi2Sr2Ni06 only when prepared in a closed environment in air. This phase formation of BizSr2NiOo was reported first time. -
Study of stacking structure of amorphous carbon by X-ray diffraction technique
Random layered (graphene) structural parameters of the coals such as aromaticity fa, coal rank, number of carbon atoms per aromatic lamellae (n), lateral size La and stacking height Lc are determined using X-ray diffraction technique (XRD). It is found that the structural parameters like fa & Lc increases, where as interlayer spacing d002 decreases with increase in carbon content, aromaticity and coal rank. The number of layers and average number of carbon atoms per aromatic graphene are found to be varying from 7 to 8 and 16-21 for the coal samples with carbon content of 72- 77.4%. A good linear relationship exists between number of layers and stacking height of the aromatic lamellae in coal. 2012 by ESG. -
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Study of single and two component convection in micropolar liquid /
In this thesis, we study linear and non-linear analysis of RayleighBénard and double diffusive convection in a micropolar liquid. The effect of non-uniform basic temperature gradient, non-uniform basic concentration gradient, temperature modulation at the boundary and gravity modulation are studied.
The problem investigated in this thesis through a light on externally controlled internal convection in a micropolar liquid. The problems investigated in this thesis have possible application in geophysics, astrophysics, oceanography engineering and in space situations with gjitter connected with gravity stimulation study. With this motivation, we investigate in this thesis four problems and their summary is given below one by one.
(i) EFFECT OF GRAVITY MODULATION ON HEAT
TRANSFER BY RAYLEIGH-BÉNARD CONVECTION IN A
MICROPOLAR LIQUID The vertical oscillation, or g-jitter or gravity modulation, is known to appear in the situation of the satellite. In the laboratory, Rayleigh-Bénard system subjected to time-periodic vertical oscillations may be useful in regulating the onset of convection and heat transfer. This aspect is also in
focus in the thesis. In this problem the effect of time-periodic body force or grtavity modulation on the onset of Rayleigh-Bénard convection in a micropolar liquid is investigated. The linear and non-linear analyses are performed. The linear theory is based on normal mode analysis and perturbation method. The expression for correction Rayleigh number is obtained as a function of frequency of modulation and other micropolar
liquid parameters. The non-linear analysis is based on the truncated Fourier series representation. The resulting non-autonomous Lorenzvii model is solved numerically to quantify the heat transport. It is observed that the gravity modulation leads to delayed convection and reduced heat transfer.
(ii) LINEAR AND WEAKLY NON- LINEAR STABILITY
ANALYSIS OF DOUBLE-DIFFUSIVE CONVECTION IN A
MICROPOLAR LIQUID The linear and non-linear stability analysis of double diffusive convection in a micropolar liquid layer heated and saluted below and cooled from above is 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 and mass transforms through Nusselt and Sherwood number. It is observed that the increase in coupling parameter, micropolar heat conduction parameter and solutal Rayleigh number
increases the heat and mass transfer. (iii) THE EFFECT OF NON - UNIFORM TEMPERATURE / CONCENTRTION DISTRIBUTION ON THE ONSET OF DOUBLE-DIFFUSIVE CONVECTION IN A MICROPOLAR LIQUID The effect of non-uniform temperature/concentration distribution on the onset of double diffusive convection in a micropolar liquid layer heated and soluted below and cooled from above between two parallel
plates of infinite extend separated by a thin layer is studied using linear stability analysis based on normal mode technique. The eigen value is obtained for free-free, rigid-free, rigid-rigid, velocity boundary conditions with isothermal temperature boundary conditions using Galerkian method. It is observed that by choosing the appropriate non-uniformviii temperature or concentration gradient it is possible to advance or delay
the onset of double diffusive convection. (iv) EFFECT OF TEMPERATURE MODULATION ON THE ONSET OF DOUBLE – DIFFUSIVE CONVECTION IN A MICROPOLAR LIQUID
The effect of temperature modulation on the onset of double-diffusive convection in a micropolar liquid is investigated by making a linear stability analysis. The stability of a horizontal layer of fluid heated from below is examined when, in addition to a steady temperature difference between the walls of the layer, a time-periodic sinusoidal perturbation is applied to the wall temperatures. The Venezian approach is adopted in arriving at the critical Rayleigh and wave numbers for small amplitude
temperature. -
Study of single and two component convection in micropolar liquid
In this thesis, we study linear and non-linear analysis of RayleighBard and double diffusive convection in a micropolar liquid. The effect of non-uniform basic temperature gradient, non-uniform basic concentration gradient, temperature modulation at the boundary and gravity modulation are studied. newlineThe problem investigated in this thesis through a light on externally controlled internal convection in a micropolar liquid. The problems investigated in this thesis have possible application in geophysics, newlineastrophysics, oceanography engineering and in space situations with gjitter connected with gravity stimulation study. With this motivation, we investigate in this thesis four problems and their summary is given below one by one. (i) EFFECT OF GRAVITY MODULATION ON HEAT TRANSFER BY RAYLEIGH-BARD CONVECTION IN A MICROPOLAR LIQUID newlineThe vertical oscillation, or g-jitter or gravity modulation, is known to appear in the situation of the satellite. In the laboratory, Rayleigh-Bard system subjected to time-periodic vertical oscillations may be useful in regulating the onset of convection and heat transfer. This aspect is also in newlinefocus in the thesis. In this problem the effect of time-periodic body force or grtavity modulation on the onset of Rayleigh-Bard convection in a micropolar liquid is investigated. The linear and non-linear analyses are performed. The linear theory is based on normal mode analysis and perturbation method. The expression for correction Rayleigh number is obtained as a function of frequency of modulation and other micropolar liquid parameters. The non-linear analysis is based on the truncated Fourier series representation. The resulting non-autonomous Lorenzvii model is solved numerically to quantify the heat transport. It is observed that the gravity modulation leads to delayed convection and reduced heat newlinetransfer. (ii) LINEAR AND WEAKLY NON- LINEAR STABILITY ANALYSIS OF DOUBLE-DIFFUSIVE CONVECTION IN A MICROPOLAR LIQUID. -
Study of rotating Bard-Brinkman convection of Newtonian liquids and nanoliquids in enclosures
Taylor-Bard convection of water and water-based nanoliquids confined in three different types of high porosity rectangular enclosures, viz., shallow, square and tall, is studied analytically using both infinitesimal and finite amplitude stability analyses. We make use of the modified-Buongiorno-Brinkman model(MBBM) for the governing equations concerning nanoliquid-saturated porous enclosures bounded by rigid-rigid boundaries and obtain analytical results. Among three types of enclosures, maximum and minimum heat transfers are observed in tall and shallow enclosures respectively. Water well dispersed with a dilute concentration of single-walled carbon nanotubes(SWCNTs) is considered as a working medium. The water-SWCNTs is able to flow in the porous medium because the medium is loosely-packed with porosity in the range 0.5 ? ? ? 1. In addition to this, the maximum volume fraction of nanoparticles considered in the system is 6% and thus this does not alter the fluidity of the system. We found from the study that the presence of low concentration(volume fraction-0.06) of SWCNTs in a water-saturated porous medium effectively improves the heat transport of the system due to its high thermal conductivity and large surface area. Due to the presence of a porous medium, however, the onset of convection gets delayed and heat transport in nanoliquids gets substantially reduced in a Bard-Brinkman configuration resulting from the weak thermal conductivity of the porous medium. Thus the porous medium acts as the heat storage system. Also, in a rotating frame of reference the heat transport gets reduced and rotation serves as an external mechanism of regulating heat transport in the system. The nonlinear dynamics of the system is studied using the 6-mode Lorenz model. Chaotic motion in the system is studied using the maximum Lyapunov exponent(MLE). The Hofp-bifurcation point of the system along with the MLE is used to investigate periodic, nearly periodic and mildly chaotic behaviors of the system. 2020 -
Study of Rayleigh-Benard Dynamical System Involving Newtonian and Nanofluids in Rectangular and Cylindrical Enclosures
Analyzing and#64258;uid and#64258;ow behavior in the presence of temperature gradients subjected to internal and external forces in diand#64256;erent geometries is essential for optimization newlineprocesses for various engineering applications, guiding the design of more efcient thermal systems. This thesis focuses on investigating the Rayleigh-Bard convection problems occupying rectangular and cylindrical enclosures. The linear and newlineweakly nonlinear analyses are carried out that reveal the results on regular convection, heat transport and chaotic motion for each of the problems. Steady and newlineunsteady states of the Rayleigh-Bard system are studied using the Lorenz model. The dynamical system is investigated to look for possible chaotic motion. Fluid systems can exhibit chaotic behavior, and understanding the chaotic nature of these and#64258;ows is essential for accurate predictions of their evolution over time. In view of this, the regular, chaotic, and periodic natures of the dynamical system is thoroughly analyzed. Further, the inand#64258;uence of various parameters on the indicators of chaos is explored. Additionally, the thermal performance of the system is looked into by introducing nanoparticles/nanotubes into the base and#64258;uid. newlineWith the aformentioned motivation, we now present the abstract of each of the problems considered in this thesis one-by-one. 1. Impact of boundary conditions on Rayleigh-Bard convection: stability, heat transfer and chaos In the frst problem of the thesis, discussed in Chapter 3, a comparison is made newlinebetween the results of Rayleigh-Bard convection problem for diand#64256;erent boundary combinations, namely, rigid-rigid-isothermal, rigid-free-isothermal and free-free isothermal boundaries for a Newtonian and#64258;uid. The linear and weakly-nonlinear analyses reveal that the onset of regular and chaotic motions in the case of rigid-freeisothermal boundaries happens later than that of free-free isothermal boundaries but earlier than rigid-rigid-isothermal boundaries.+ -
Study of Natural Convection with Local Thermal Non Equilibrium Effects in Nanoliquid-Saturated Low Porosity Enclosures
Natural convection of nanoliquid in densely packed vertical porous enclosure is studied by subjecting the vertical walls to constant heat flux under local thermal non-equilibrium (LTNE) assumptions. Water, copper nanoparticles and porous material made of aluminum foam, glass balls and sand are considered for the study. The governing equations are modelled using single-phase model. Thermophysical properties of nanoliquid and nanoliquid-saturated porous medium are calculated using phenomenological laws and mixture theory. An analytical expression for velocity and temperature profiles of nanoliquid (base liquid+nanoparticles) and solid (porous medium) phases has been obtained. Weighted average Nusselt number is expressed as a function of aspect ratio, volume fraction, and properties concerning LTNE effects. LTNE effect is shown to be a heat transfer enhancing mechanism. The presence of nanoparticles is to enhance the heat transfer in water. Local thermal equilibrium results are obtained as a limiting case of the present study and so obtained results are compared with previously published paper in the literature. 2022, The Author(s), under exclusive licence to Springer Nature India Private Limited. -
Study of Nanolayered Structure of Commercially Available Carbon Materials and Soot
Developments in the modern world periodically call for the discovery or invention of new and exotic materials. In the present situation, to develop unique and novel materials, which move beyond the barriers of the physical limits of the amount of micro- miniaturization possible as well as the current technology and take advantage of the opportunities not yet imagined, is not at all a need but a necessity. The advent of Nano technology of carbon allotropes is a giant leap towards this goal. The starting of the era of carbon nanomaterials traces back to 1985 when the fullerenes with a foot ball structure were accidently discovered. From then on, the field of carbon nanotechnology was in the constant limelight on account of the amazing properties displayed by the various allotropes of carbon. These properties are dependent mainly on the type of hybridization present in the nanostructures, which categorizes them to amorphous or crystalline. Also, there exist some structures which are the combination of these two and are termed as nanocrystalline or turbostratic structures. The discovery of graphene, which has a turbostratic structure and is the thinnest material known and the strongest ever measured, with outstanding properties such as highest room temperature electrical conductivity; high mechanical robustness etc was a ground breaking one. These remarkable properties open up a wide range of potential applications ranging from clean energy to nano-electronics to bio-medical devices. Thus, it is a necessity to explore and characterize various effective sources of these nanomaterials. The present study is an attempt to investigate such efficient, easily available and cost-effective precursors. Soot, also known as black carbon, is a fine-grained solid residue that results from incomplete combustion of hydrocarbons and is a widely used precursor for the production of carbon nanomaterials. Carbon soot is a major component of smoke from the combustion of carbon-rich organic fuels and hydrocarbons and hence has a vast number of sources. In the study presented here soot obtained from the thermal decomposition of commercially available kerosene, diesel oil, paraffin wax and lubricant oil is investigated. Nanostructure of the commercially available carbon black is also studied. Various techniques such as Micro Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), High Resolution Scanning Electron Microscopy (HR-SEM), Electron dispersive spectroscopy (EDS) and elemental analysis are employed for the structural and morphological characterization of the samples. Raman scattering is used as a probe to study the disorder in the carbon skeleton materials. The intensity ratio of the D and G modes occurring in the spectra is proportional to the number of rings at the edge of the grain and also indicates the quality of the sample. FT-IR spectroscopy is used to characterize qualitatively the functional groups of carbon materials. XRD is the most common analytical technique used for determining the structure of ordered and disordered carbons from the positions of the diffraction peaks at 2?? angle. The structural parameters like the size of the ordered grains along c and a axis (Lc and La), the average spacing of the crystallographic (002) planes (d002) can be determined through Scherrer equations. SEM micrographs give the surface morphology of the nanomaterials present and the EDS analysis gives the abundance of the microscopic constituents. Elemental composition of the samples can be derived from the elemental analysis using CHNS (Carbon Hydrogen Nitrogen Sulphur) analyser. The present study shows that all the samples investigated obeys the Tuinstra-Koening relation and posses a nanocrystalline structure. The ratio of the defect and graphite bands is found to be very low, especially in the case of diesel soot which has a value very much lower than those reported in the earlier studies, indicating high quality and a low amount of disorder in the samples. HR-SEM micrographs clearly indicate that the carbon nanostructured present in the samples are in the form of non-uniform nanospheres with diameter varying between 26-100 nm. The characteristic diffraction peak of graphene corresponding to (100) diffraction is observed in the x-ray diffraction profiles of all the samples. The interlayer spacing determined in all the samples lies very close to that of graphite. The H/C atomic ratio from the CHNS analysis is found to be very low and confirms the nanocrystalline structure of the materials. The graphite band position in the IR spectra indicates that the nanospheres formed are to be composed more of crystalline graphitic carbon. From the EDS analysis it is evident that all the samples have very high carbon content and are free from impurities and thus concludes that the materials and methods used in the present study for the synthesis of carbon nanospheres possessing a nanocrystalline structure are efficient and cost effective and are good precursors for graphene. -
Study of nanofluid flow in a stationary cone-disk system with temperature-dependent viscosity and thermal conductivity
The substantial temperature gradient experienced by systems operating at relatively high temperatures significantly impacts the transport characteristics of fluids. Hence, considering temperature-dependent fluid properties is critical for obtaining realistic prediction of fluid behavior and optimizing system performance. The current study focuses on the flow of nanofluids in a stationary cone-disk system (SCDS), taking into account temperature-dependent thermal conductivity and viscosity. The influence of Brownian motion, thermophoresis, and Rosseland radiative flux on the heat transport features are also examined. The Reynolds model for viscosity and Chiam's model for thermal conductivity are employed. The Navier-Stokes equation, the energy equation, the incompressibility condition, and the continuity equation for nanoparticles constitute the governing system. The Lie-group transformations lead the self-similar ordinary differential equations, which are then solved numerically. Multi-variate non-linear regression models for the rate of heat and mass transfers on the disk surface were developed. Our study reveals a notable decrease in the rate of heat and mass transfer when pre-swirl exists in the flow. The significant influence of nanofluid slip mechanisms on the effective temperature and nanofluid volume fraction (NVF) within the system is highlighted. Furthermore, the variable viscosity property enhances the temperature and NVF of the SCDS. 2024 Author(s). -
Study of nanofluid flow and heat transfer in a stationary cone-disk system
Rheometric, viscosimetric, bio-medical, and several other pharmaceutical machineries utilize the structural advantages provided by the geometry of a stationary conical diffuser. The problem of the Buongiorno nanofluid flow in the conical gap of a stationary cone-disk system for isothermal boundaries is studied. The governing system, comprising the incompressibility condition, NavierStokes equation, energy conservation equation, and conservation of Nanoparticle Volume Fraction (NVF) equation, is analyzed. The Lie-group theory has been used to derive a self-similar model. Solutions of the self-similar equations were computed numerically, and the expressions for the Nusselt number and Sherwood number are obtained. The parametric investigation reveals that the heat and mass transfer rate subside significantly when pre-swirl is introduced to the flow. Furthermore, the nanofluid slip mechanisms enhance the effective temperature of the system. 2023 Elsevier Ltd -
Study of multilayer flow of two immiscible nanofluids in a duct with viscous dissipation
Numerical simulations for the mixed convective multilayer flow of two different immiscible nanofluids in a duct with viscous heating effects were performed in this study. The left and right faces of the duct are maintained to be isothermal, while other side faces are insulated. The mathematical governing system for each layer consists of an incompressibility condition equation, the Navier-Stokes momentum equation, and the conservation of energy equation. At the interface of the immiscible layer, the continuity of velocity, shear stress, temperature, and heat flux are considered. The dimensionless equations governing each layer were numerically integrated using the finite difference method and the Southwell-over-relaxation method. A mesh independence test is conducted. Furthermore, a parametric study is performed to analyze how the different nanoparticle volume fractions and viscous heating affect the transport characteristics of engine oil-copper and mineral oil-silver nanofluids. The study also examined the effects of various types of nanoparticles and base fluids. The results demonstrated that heat transport could be efficiently controlled by considering the viscous heating aspect. Moreover, the effects of different nanoparticles on heat transport were found to be more significant than those of base fluids. Finally, a point-wise comparison of our numerical results demonstrates a good agreement with existing studies in the literature. 2023 Author(s). -
Study of multilayer flow of non-Newtonian fluid sandwiched between nanofluids
This theoretical investigation examines the nonlinear convective heat transport and multilayer flow of a non-Newtonian fluid within a vertical slab, incorporating viscous heating effects. The middle layer of the slab contains a third-grade fluid, while the outer layers are filled with a water-based Ag-MgO hybrid nanoliquid. Continuity in temperature, heat flux, velocity, and shear stress is maintained at the interfaces of the fluid layers. The thermal buoyancy force is modeled using the nonlinear Boussinesq approximation. The governing system comprises conservation equations for mass, momentum (Navier-Stokes), and energy for each of the three layers. These differential equations are non-dimensionalized, and the resulting dimensionless four-point nonlinear boundary value problem is transformed into a two-point boundary value problem before being solved numerically. For limiting cases, analytical and semi-analytical solutions are computed and used as benchmark results to validate the numerical method employed. Entropy generation analysis indicates that higher third-grade fluid parameters reduce the magnitude of velocity and temperature fields, as well as entropy production across all regions. The third-grade fluid parameter shows a decreasing influence on velocity and temperature fields throughout the system. The continuity of interfacial conditions induces a dragging effect; despite the absence of third-grade fluid parameters in regions I and III, their influence is apparent in these regions. The Bejan number slightly decreases at the walls with increasing third-grade fluid parameters, exhibiting a dual effect in the third-grade fluid layer. Near the walls, the Bejan number decreases as the nanoparticle volume fraction increases. Findings of this work may have applications in polymer industries and processes involving high temperatures. 2024 -
Study of multilayer flow of a bi-viscous Bingham fluid sandwiched between hybrid nanofluid in a vertical slab with nonlinear Boussinesq approximation
Bi-viscosity Bingham plastic fluids are used to understand the rheological characteristics of pigment-oil suspensions, polymeric gels, emulsions, heavy oil, etc. In many industrial and engineering problems involving high-temperature situation, a linear density-temperature variation is inadequate to describe the convective heat transport. Therefore, the characteristics of the nonlinear convective flow of a bi-viscous Bingham fluid (BVBF) through three layers in a vertical slab are studied. The two outer layers of the oil-based hybrid nanofluid and the intermediate layer of BVBF are considered. The thermal buoyancy force is governed by the nonlinear Boussinesq approximation. Continuity of heat flux, velocity, shear stress, and temperature are imposed on the interfaces. The governing equations are derived from the Navier-Stokes equation, conservation of energy, and conservation of mass for three layers. The nonlinear multi-point (four-point) boundary value problem is solved using the differential transform method (DTM). Converging DTM solutions are obtained, and they are validated. The entropy equation and Bejan number were also derived and analyzed. It is established that the nonlinear density-temperature variation leads to a significant improvement in the magnitude of the velocity and temperature profiles due to the increased buoyancy force, and as a result, the drag force on the walls gets reduced. The drag force on the slab gets reduced by decreasing the volume fraction of nanoparticles. Furthermore, nonlinear convection and mixed convection give rise to an advanced rate of heat transport on the walls and thereby to an enhanced heat transport situation. 2022 Author(s). -
Study of mineral and nutritional composition of some seaweeds found along the coast of Gulf of Mannar, India
The presence of Algae on the Earth is ubiquitous. The industry that widely uses algae is food industry, where the algae are used as a food supplement and also as an addition to the nutrient rich food. This study emphasizes on the mineral and nutritional composition of the selected fourteen algal species which are abundantly found along the coast of the Gulf of Mannar. The selected species of algae belong to different algal families such as Chlorophyta, Phaeophyta and Rhodophyta. The amount of minerals such as Ca, Zn, Fe, K, Mg, Mn, and Cu were estimated by employing the method of acid digestion followed by atomic absorption spectroscopy. We estimated the nutritional content based on the assessment of total protein, carbohydrate, phenol, ash and moisture contents of the algal species. The results based on the analysis of the mineral content in the algal seaweeds depicted that the seaweeds comprised of high amount of the macro minerals and trace minerals. Estimation of nutritional composition revealed that these algal species are rich in protein and carbohydrate. The ash contents were found to be very high in Jania rubens (86.66%), Padina boergesenii (85%) and Valoniopsis pachynema (84%). Based on the present study we infer that the algal seaweeds contained high amount of the nutritional compounds, which might pave the way for a higher standard of nutritional supply to the humans in the future. Jose & Xavier (2020). This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited (https://creativecommons.org/licenses/by/4.0/). -
Study of micro and small enterprises' readiness in implementing industry 4.0: A study in marathwada district of maharashtra, india
Industry 4.0 aims tp transform the development of global value chains and the development of a digital revolution, with intelligent machines capable of communicating via wireless connections and a connection thought system, resulting in autonomous decision-making. Although large sized firms are adopting Industry 4.0, the small and micro enterprises are facing great difficulties in adopting them. This study aims to identify the areas in which Enterprises need to focus for improving their level of readiness and develop strategies and plans to adopt Industry 4.0 technologies successfully. 219 samples were collected using snowball sampling from Marathwada District in Maharashtra, India. factor analysis was conducted using SPSS and different factors acting as barriers to implementation of Industry 4.0 technologies were identified. 2023 by IGI Global. All rights reserved. -
Study of magnetoconvection with maxwell cattaneo law /
This thesis deals with the study of Rayleigh-Bénard-convection in a Newtonian fluid and micropolar fluid by replacing the classical Fourier law by non-classical Maxwell-Cattaneo heat flux law. The effects of second sound, non-uniform basic temperature gradients, suctioninjection-combination, temperature modulation and gravity modulation in
presence of external constraints like magnetic field and rotation are studied. The problems investigated in this thesis throw light on externally controlled convection in Newtonian and micropolar fluids in the presence of Maxwell-Cattaneo law. The problems investigated in this thesis deal with practical problems with very large heat fluxes and/or short time duration. With this motivation, we investigate in this thesis five problems and their summary is given below. (i) Effects of Coriolis force and non-uniform basic temperature gradients on the onset of Rayleigh-Bénard-Chandrasekhar convection with Maxwell-Cattaneo law The effect of non-uniform temperature gradient on RayleighBénard-Chandrasekhar convection in a rotating Newtonian fluid with
Maxwell-Cattaneo law is studied using the Galerkin technique. The eigenvalues is obtained for free-free, rigid-free and rigid-rigid velocity boundary combinations with isothermal and adiabatic boundaries. A linear stability analysis is performed. The influence of various parameters on the onset of convection has been analyzed. One linear and fiveix non-linear temperature profiles are considered and their comparative influence on onset is discussed. It is found that the results are noteworthy
at short times and the critical eigenvalues are less than the classical ones. It is shown that the system having magnetic field will delay in the onset of instability. In general, it is observed that step function and inverted parabolic temperature profile are the most destabilizing and stabilizing profiles. The range of values of the parameters of the problem for which oscillatory convection in the case of free-free isothermal boundary exists is also discussed. (ii) The effect of temperature modulation on the onset of RayleighBénard-Chandrasekhar convection using Maxwell-Cattaneo law The effect of imposed time-periodic boundary temperature (ITBT, also called temperature modulation) and magnetic field at the onset of Rayleigh-Bénard convection is investigated by making a linear analysis. The classical Fourier heat law is replaced by the non-classical MaxwellCattaneo law. The venezian approach is adopted in arriving at the critical Rayleigh number and wave number for small amplitude of ITBT. Three
cases of 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 lower wall is modulated. The temperature modulation is shown to give rise to sub-critical motion. 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. It is shown that the system is more stable when the boundary temperatures are modulated out of phase.x
(iii) The effect of gravity modulation on the onset of RayleighBénard-Chandrasekhar convection using Maxwell-Cattaneo law The effect of gravity modulation and magnetic field at the onset of Rayleigh-Bénard-Chandrasekhar convection is investigated by making a regular perturbation technique. The stability of the horizontal fluid layer heated from below is examined by assuming time-periodic body acceleration called g-jitter, which normally occurs in satellites and in vehicles connected with microgravity simulation studies. The venezian
approach is adopted in arriving at the critical Rayleigh number and wave number for small amplitude of gravity modulation. The shift in the critical Rayleigh number is calculated as a function of frequency of modulation. It is observed that gravity modulation leads to delayed convection. (iv) The effect of suction-injection-combination (SIC) on the onset of Rayleigh-Bénard-Chandrasekhar convection in a micropolar fluid with Maxwell-Cattaneo law The effect of suction-injection-combination (SIC) on the onset of Rayleigh-Bénard-Chandrasekhar convection in a micropolar fluid with Maxwell-Cattaneo law is studied using the Galerkin technique. The eigenvalue is obtained for free-free, rigid-free and rigid-rigid velocity boundary combinations with isothermal and adiabatic on the spinvanishing boundaries. A linear stability analysis is performed. The influence of various micropolar fluid parameters on the onset of convection has been analyzed. It is found that the effect of Prandtl number on the stability of the system is dependent on the SIC beingxi pro-gravity or anti-gravity. A similar Pe-sensitivity is found in respect of the critical wave number. The problem suggests an elegant method of external control of internal convection. (v) The effect of non-uniform temperature gradients on RayleighBénard-Chandrasekhar convection in a micropolar fluid with
Maxwell-Cattaneo law The effect of non-uniform temperature gradient on RayleighBénard-Chandrasekhar convection in a micropolar fluid with MaxwellCattaneo law is studied using the Galerkin technique. 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 micropolar fluid parameters on the onset of convection has been
analyzed. Six different non-uniform temperature profiles are considered their comparative influence on onset is discussed. It is observed that the micropolar fluid layer heated from below is more stable compared to the classical Newtonian fluid layer. -
Study of magnetoconvection with maxwell cattaneo law
This thesis deals with the study of Rayleigh-Bard-convection in a Newtonian fluid and micropolar fluid by replacing the classical Fourier law by non-classical Maxwell-Cattaneo heat flux law. The effects of second sound, non-uniform basic temperature gradients, suctioninjection-combination, temperature modulation and gravity modulation in newlinepresence of external constraints like magnetic field and rotation are studied. newlineThe problems investigated in this thesis throw light on externally controlled convection in Newtonian and micropolar fluids in the presence of Maxwell-Cattaneo law. The problems investigated in this thesis deal newlinewith practical problems with very large heat fluxes and/or short time duration. With this motivation, we investigate in this thesis five problems and their summary is given below. (i) Effects of Coriolis force and non-uniform basic temperature gradients on the onset of Rayleigh-Bard-Chandrasekhar newlineconvection with Maxwell-Cattaneo law The effect of non-uniform temperature gradient on RayleighBard-Chandrasekhar convection in a rotating Newtonian fluid with Maxwell-Cattaneo law is studied using the Galerkin technique. The eigenvalues is obtained for free-free, rigid-free and rigid-rigid velocity boundary combinations with isothermal and adiabatic boundaries. A linear stability analysis is performed. The influence of various parameters on the onset of convection has been analyzed. One linear and five non-linear temperature profiles are considered and their comparative influence on onset is discussed. It is found that the results are noteworthy at short times and the critical eigenvalues are less than the classical ones. It is shown that the system having magnetic field will delay in the onset newlineof instability. In general, it is observed that step function and inverted parabolic temperature profile are the most destabilizing and stabilizing profiles. -
Study of Low-Mass Stars and Brown Dwarfs In Star Forming Regions of Diverse Environments
The formation and evolution of low-mass stars and brown dwarfs is an intricate process orchestrated by the environmental conditions in which they form. As a natural byproduct of this process, circumstellar disks are formed, whose dynamic relationship with the environment plays a pivotal role in determining the fate of the star and the timescale for planet formation. While low-mass stars are a dominant product of the star formation process, brown dwarfs occupy a unique position, bridging the gap between newlinelow-mass stars and planets. In this thesis, we have examined the low-mass stars and brown dwarfs in young clusters located at different distances with diverse UV radiation felds and stellar densities to decode the role of environment in shaping the IMF, its inand#64258;uence on disk evolution and to understand the formation of brown dwarfs. We have targeted three young star forming regions for the newlinestudy namely and#963; Orionis, twin clusters IC 1848-East and West, and IC 1396 using deep multi-wavelength photometry as well as near-IR spectroscopy with 4m and 10m class facilities. For the and#963; Orionis cluster we used deep CFHT-WIRCAM near-IR data and the novel water-band photometry technique along with Gaia DR3 to identify the candidate low-mass members. Spectroscopic follow-up observations conducted with IRTF-SpeX validated the selection of the candidates by this technique with a 100% effcacy. We then compiled a comprehensive membership catalog for a mass range and#8764;19-0.004 Mand#8857;. The form of the stellar-substellar IMF was found to be consistent with other nearby star forming regions suggesting a lack of signifcant environmental inand#64258;uence. Further, we analysed the evolutionary class of the members based on the mid-IR slope of the SED to study their disk properties. We estimated the disk fraction of the low-mass sources to be consistent with other star form ing regions considering the age of the cluster. This showed that in this region, external photoevaporation does not play a major role in the inner disk evolution.