Showing papers in "Indian Journal of Physics in 2021"

MHD Casson nanofluid flow over nonlinearly heated porous medium in presence of extending surface effect with suction/injection

Abstract: An exertion is executed to explicate thermophysical aspects of viscoelastic fluid flow produced by a nonlinearized stretched surface. Here, viscoelasticity is characterized by Casson fluid model and expressed rheologically in momentum equation. Flow attributes of Casson fluid are thoroughly investigated under transversal magnetized field and along with provision of suction/injection to surface. Flow medium is also considered to be porous. Convective heating is supplied to the surface to depict heat transfer change within the flow domain. Nanosized particles are hanged into the Casson fluid to understand the effectiveness of Brownian motion and thermophoretic forces on the diffusion of particles. Generative chemical reactions are also considered to measure mass transport. Initially, flow narrating differential equations for concerning a problem are attained in differential equations and later on transforming into ordinary differential coupled system via similarity approach. Variations in flow associated distributions against involved parameters are divulged through graphical structures. Wall drag, thermal and mass fluxes are also calculated. Credibility of computing results is tested with the aid of comparison with previously published data in limiting sense.

Slip flow of Casson–Maxwell nanofluid confined through stretchable disks

Abstract: This study reports an incompressible electrically conducting Casson–Maxwell fluid flow confined across two uniformly stretchable disks. Buongiorno nanofluid model is implemented in the fluid flow. Cattaneo–Christov theory of double-diffusion is characterized through the heat and mass equations. Velocity, thermal and concentration slip conditions are executed at the lower stretchable disk. The flow model is dimensionalized through the similarity functions and then numerical solution is attained by RKF-45 scheme combined with shooting technique. The results of physical parameters are discussed by plotting the effects of such parameters on velocity, thermal and concentration fields. The results revealed that the Maxwell liquid is highly effected by Lorentz force than the Casson liquid. Thermal gradient of Maxwell liquid is highly influenced by stretching ratio parameter when compared to Casson fluid. Increase in Casson parameter and Deborah number declines the velocity gradient. Rise in the values of Brownian motion parameter declines the concentration gradient. Finally, the upsurge in thermal relaxation time parameter enhances the thermal gradient quickly in absence of thermal slip parameter.

Studying the progress of COVID-19 outbreak in India using SIRD model.

Abstract: We explore a standard epidemiological model, known as the SIRD model, to study the COVID-19 infection in India, and a few other countries around the world We use (a) the stable cumulative infection of various countries and (b) the number of infection versus the tests carried out to evaluate the model The time-dependent infection rate is set in the model to obtain the best fit with the available data The model is simulated aiming to project the probable features of the infection in India, various Indian states, and other countries India imposed an early lockdown to contain the infection that can be treated by its healthcare system We find that with the current infection rate and containment measures, the total active infection in India would be maximum at the end of June or beginning of July 2020 With proper containment measures in the infected zones and social distancing, the infection is expected to fall considerably from August If the containment measures are relaxed before the arrival of the peak infection, more people from the susceptible population will fall sick as the infection is expected to see a threefold rise at the peak If the relaxation is given a month after the peak infection, a second peak with a moderate infection will follow However, a gradual relaxation of the lockdown started well ahead of the peak infection, leads to a nearly twofold increase of the peak infection with no second peak The model is further extended to incorporate the infection arising from the population showing no symptoms The preliminary finding suggests that random testing needs to be carried out within the asymptomatic population to contain the spread of the disease Our model provides a semi-quantitative overview of the progression of COVID-19 in India, with model projections reasonably replicating the current progress The projection of the model is highly sensitive to the choice of the parameters and the available data

Numerical study of electroosmosis-induced alterations in peristaltic pumping of couple stress hybrid nanofluids through microchannel

Abstract: This paper presents a computational modeling approach to analyze the peristaltic pumping of couple stress hybrid nanofluids regulated by the electroosmosis mechanism through a microchannel. The effects of applied magnetic field, Joule heating and buoyancy have also been computed. In this analytical model, water-based titanium dioxide (TiO2) and silver (Ag) hybrid nanofluids have been considered. For more relevant physical problem, the axial velocity slip and thermal slip conditions have also been introduced. The nonlinear differential equations are simplified by considering the Huckel–Debye approximations as well as lubrication theory, and then the equations have been solved numerically by Mathematica 10 software via the NDsolve commands. The pertinent influences of key parameters on the axial velocity, nanoparticle temperature, Nusselt number and streamlines in the microchannel have been visualized graphically. It is observed that an increase in the thermal Grashof number produces a maximum axial velocity, and temperature of nanoparticles for both water–titanium dioxide and water–silver nanofluids. The maximum axial velocity and nanoparticle temperature occur in water–titanium dioxide as compared with water–silver. The outcomes of this model shall be very useful in the designs of smart electro-peristaltic pumps for thermal systems and drug delivery systems.

Thermodynamic functions for diatomic molecules with modified Kratzer plus screened Coulomb potential

Abstract: We have solved the Schrodinger equation with the modified Kratzer plus screened Coulomb potential using the modified factorization method. We have also employed both the Greene–Aldrich approximation scheme and a suitable transformation scheme to obtain the energy eigenvalues equation and its corresponding energy eigenfunctions for CO, NO, and N2 diatomic molecules. Numerical results of the energy eigenvalues for the selected diatomic molecules have been computed and discussed. The effects of the combined potential parameters on the energy eigenvalues have been evaluated. We have used the energy eigenvalues of the modified Kratzer plus screened Coulomb potential to obtain the vibrational partition functions and other thermodynamic functions for the selected diatomic molecules. Our results are relevant in other areas of theoretical physics and chemistry, and they agree perfectly with the results obtained in the literature.

Capturing the features of peristaltic transport of a chemically reacting couple stress fluid through an inclined asymmetric channel with Dufour and Soret effects in presence of inclined magnetic field

Abstract: The primary focus behind this research work is to unfold the heat and mass transfer characteristics of peristaltic transport of hydromagnetic couple stress fluid through a porous medium in an inclined channel of asymmetric kind. Consideration of both Dufour and Soret effects is one of the key factors of this investigation. Simultaneous convective conditions of mass and heat transfer are satisfied by the channel walls. Beneath the presumptions of small Reynolds number along with long wavelength, the governing two-dimensional coupled differential equations are simplified after incorporating dimensionless variables. To calculate the pressure difference, the technique of numerical integration has been employed. Graphical demonstrations for velocity, temperature, concentration profiles have been sketched out under the influence of pertinent flow parameters. Pumping characteristics and trapping phenomenon for some particular kind of waveshapes are also highlighted through contour plots. Noteworthy findings are that near the center of the channel the maximum value of the temperature is attained due to the intensification of heat generation parameter. Also, Dufour number tends to enhance the temperature of the fluid, whereas Soret effect results in a downfall in the concentration field. Heat and mass transfer Biot numbers lead to an elevation in the concentration and temperature profiles, respectively. It is also perceived that a reduction in concentration takes place due to the presence of destructive kind of chemical reaction while a reverse trend is being followed during a chemical reaction of constructive kind. Moreover, both the pressure gradient as well as pressure difference act as increasing functions of the angle of inclination of the channel. Additionally, the general propensity of couple stress fluid parameter is to diminish the volume of the trapped bolus.

Numerical treatment for MHD viscoelastic fluid flow with variable fluid properties and viscous dissipation

Abstract: Numerical and theoretical examinations of the viscous dissipation phenomenon on the viscoelastic fluid flow of type Walters’ liquid B model which is passing over a stretching sheet are described. The significance of both slip phenomenon and magnetic field in stimulating the heat transfer process is the main cause for considering them in this study. On the other hand, to gain high precision in our numerical study, some of fluid properties are assumed to depend on the fluid temperature. Since, both the viscosity and the conductivity of the fluid which are changing with temperature are taken into consideration, therefore, our obtained results are much more reliable than those the similar previous researches. In addition, this described physical problem is governed by three partial differential equations. After introducing suitable dimensionless variables, two differential equations are created: the first is of fourth order, whereas the second one is of second order. These two equations along with appropriate boundary conditions are then numerically solved via the shooting technique. Finally, in the light of the prominent outcomes, for both the viscoelastic and viscosity parameters growth, the enhancement of the sheet velocity is remarkable, whereas the drastically drop for the sheet velocity was observed for the magnetic parameter.

Bound state solutions of the generalized shifted Hulthén potential

Abstract: In this study, we obtain an approximate solution of the Schrodinger equation in arbitrary dimensions for the generalized shifted Hulthen potential model within the framework of the Nikiforov–Uvarov method. The bound state energy eigenvalues were computed, and the corresponding eigenfunction was also obtained. It is found that the numerical eigenvalues were in good agreement for all three approximations scheme used. Special cases were considered when the potential parameters were altered, resulting in Hulthen potential and Woods–Saxon Potential, respectively. Their energy eigenvalues expressions agreed with the already existing literature. A straightforward extension to the s-wave case for Hulthen potential and Woods–Saxon potential cases is also presented.

Strain effect on the electronic and optical properties of 2D Tetrahexcarbon: a DFT-based study

Abstract: A new two-dimensional (2D) carbon allotrope, namely Tetrahexcarbon (TH-carbon) semiconductor monolayer with a direct band gap resides in the visible region of the electromagnetic spectra, has been recently proposed theoretically. Herein, the influences of biaxial strains on the electrical and optical aspects of 2D TH-carbon are computationally investigated. To this end, first-principles calculations based on the properties of the density functional theory were employed. According to our simulations, the electronic and optical properties of 2D TH-carbon are effectively sensitive to the external strain effects. This obtained strain sensitivity suggests that this 2D material could be a promising material for usage in new electronic technologies.

New solitons and other solutions in saturated ferromagnetic materials modeled by Kraenkel–Manna–Merle system

Abstract: This study reveals some new solitons solutions to the Kraenkel–Manna–Merle (KMM) system which describes the nonlinear ultra-short wave pulse motions in saturated ferromagnetic materials having external field with zero-conductivity. Various kinds of soliton solutions such as dark, bright, singular, combined dark bright, combined dark-singular solitons, periodic and singular periodic waves are successfully constructed by applying two integration schemes, namely the extended sinh-Gordon equation expansion and the ( $$\frac{G^{\prime }}{G^2}$$ ) expansion function methods. Thus, this study shows the effectiveness and simplicity of the proposed methods. The physical features of some reported solutions are portrayed via the 3D, 2D, and contour graphs under the choice of the suitable values of the parameters. The results reveal the system theoretically possesses extremely rich soliton structures.

New exact solutions for the doubly dispersive equation using the improved Bernoulli sub-equation function method

Abstract: In this study, the doubly dispersive equation is presented by the application of the improved Bernoulli sub-equation function method (IBSEFM). The doubly dispersive equation which is a nonlinear partial differential equation is transformed into nonlinear ordinary differential equation using a wave transformation and then is solved by IBSEFM. Some new solutions are successfully constructed. All the obtained solutions in this study have been satisfied the doubly dispersive equation. In the present study, we have used Wolfram Mathematica 9 software for all of the computations and graphic plottings.

Entropy generation on double diffusive MHD Casson nanofluid flow with convective heat transfer and activation energy

Abstract: The viscous and Joule dissipation effects on stagnation point flow of thermally radiating Casson nanoliquid over a convectively heated stretching sheet under hydromagnetic assumptions are discussed. The influence of heat absorption on heat transfer and chemical reaction prompted by activation energy on mass transfer is also considered. The appropriate transformations are implemented for converting the governing partial differential equations into a set of coupled ordinary differential equations. BVP4C routine of MATLAB has been used to solve the coupled nonlinear ODEs. The way fluid velocity, concentration, temperature, Bejan number and entropy generation behave subject to change in the flow parameters, has been discussed through graphs, whereas the important physical quantities such as skin friction coefficient, Nusselt number and Sherwood number are analyzed on the basis of numerical values presented in tables. On the obtained numerical data of Nusselt number, linear and quadratic regression analyses have been performed. It is concluded that for larger values of thermal and concentration buoyancy parameters, fluid velocity tends to decrease inside the boundary layer region. It is also found that plastic dynamic viscosity of Casson nanoliquid tends to reduce the rate of entropy generation.

Highly dispersive optical solitons in the nonlinear Schrödinger’s equation having polynomial law of the refractive index change

Abstract: In this paper, we apply the unified Riccati equation expansion method, as well as two forms of auxiliary equation methodology, to find highly dispersive optical solitons in the nonlinear Schrodinger’s equation having a polynomial law of the refractive index change. Bright, dark and singular solitons as well as periodic and Jacobi elliptic solutions are obtained that are presented together with their existence criteria.

Directional magnetic and electric vortex lines and their geometries

Abstract: In this study, we introduce directional Fermi–Walker transportation along with the vortex lines of nonvanishing vector fields in the ordinary three-dimensional space. Moreover, we investigate the geometric phase and angular velocity vector (Darboux vector) of vortex lines. Then, we define directional magnetic and electric vortex lines by considering the Lorentz force law and electromagnetic force equation. Finally, we prove a significant relation between directional magnetic and electric vortex lines and angular velocity vector of vortex lines.

Effect of thermal annealing on the optical properties of Ge 20 Se 65 S 15 thin films

Abstract: The present work reports the effect of heat treatment under vacuum on the optical properties of Ge20Se65S15 thin films prepared by the thermal evaporation technique The structural units and the surface morphology of the films were characterized using Raman spectroscopy and scanning electron microscopy (SEM), respectively The optical parameters of as-deposited and annealed films were calculated using the Swanepoel's method from the optical transmission spectra $$ T\left( \lambda \right) $$ in the wavelength range of 300–2500 nm The variations of Urbach energy EU and optical energy gap $$ E_{\text{g}}^{\text{Opt}} $$ with the annealing temperature are discussed in terms of the density states model in amorphous solids The refractive index dispersion is analyzed and discussed in terms of Sellmeier and Wemple–DiDomenico models The nonlinear susceptibility $$ \chi^{\left( 3 \right)} $$ and nonlinear refractive index n(2) were evaluated based on the generalized Miller’s rule as a function of annealing temperature Lastly, the two-photon absorption coefficient (βc) was obtained theoretically via $$ E_{\text{g}}^{\text{Opt3}} $$ scaling law

Importance of heat generation in chemically reactive flow subjected to convectively heated surface

Abstract: Our main emphasis here is to scrutinize the Lorentz’s force aspects on the flow of cross-fluid in cylindrical surface. More specifically, heat transfer features are examined subject to heat sink–source and radiative flux. Furthermore, aspects of quartic autocatalysis analysis are considered. Non-dimensional variables are introducing to develop the physical model. The physical problem by employing Bvp4c scheme. Influences of rheological parameters for concentration, temperature and velocity are discussed. Additionally, computational analysis for Nusselt number and skin friction coefficient is presented through tables.

Nonlinear periodic structures in a magnetized plasma with Cairns distributed electrons

Abstract: The electrostatic ion acoustic (IA) nonlinear periodic (cnoidal) waves are studied in a magnetized plasma comprising of cold ions and Cairns distributed electrons. By employing reductive perturbation technique (RPT), the nonlinear Korteweg-de Vries (KdV) and modified KdV (mKdV) equations are derived, and their cnoidal wave (CW) solutions are obtained. For a given set of plasma parameters, the present model supports both compressive and rarefactive nonlinear periodic structures. In the present work, the effects of plasma parameters like nonthermality of electrons ( $$\beta $$ ) and obliqueness ( $$ l_{z} $$ ) are investigated. It is found that increasing values of $$\beta $$ and $$l_{z}$$ lead to enhancement (reduction) in amplitude of IA compressive (rarefactive) nonlinear periodic structures. Our present study has some relevance to the CW structures observed in magnetosphere via POLAR and FAST spacecrafts.

Approximate solutions of D-dimensional Klein–Gordon equation with Yukawa potential via Nikiforov–Uvarov method

Abstract: In this work, we obtain the Klein–Gordon equation solutions for the Yukawa potential using the Nikiforov–Uvarov method. The energy eigenvalues are obtained both in relativistic and non-relativistic regime. The corresponding eigenfunction are obtained in terms of Laguerre polynomial. We applied the present results to calculate heavy-meson masses of charmonium $$ c\bar{c} $$ and bottomonium $$ b\bar{b} $$ , and we got the numerical values for states 1S–1F. The results are in good agreement with experimental data and the work of other researchers.

Effect of Hall current in transversely isotropic magneto-thermoelastic rotating medium with fractional-order generalized heat transfer due to ramp-type heat

Abstract: This investigation is focused on the study of Hall current effect in homogeneous transversely isotropic magneto-thermoelastic (HTIMT) rotating medium with fractional-order heat transfer due to ramp-type heat. Investigation of interaction between the strain, thermal and electromagnetic fields becomes a new area of research, which is called magneto-thermoelasticity because of its effective aspects in various domains of science and technology. Laplace and Fourier transform is used for solving field equations. The expressions of temperature, stress components, displacement components, and current density components are computed in the transformed domain. The effects of Hall current, rotation and fractional-order parameter at different values in HTIMT solid are represented graphically.

Stefan blowing on chemically reactive nano-fluid flow containing gyrotactic microorganisms with leading edge accretion (or) ablation and thermal radiation

Abstract: The present study analyzes the forced convective boundary layer flow of viscous incompressible time-established fluid. The base fluid containing water-based nanoparticles and gyrotactic microbes. The flat surface is considered with leading-edge accretion (or) ablation. Characteristics of flow are explored by the impacts of thermal radiation and constructive/destructive chemical reaction. The present flow problem is formed with the partial differential equations, and transformed nonlinear boundary value problems are solved mathematically by the finite difference with the collocation method. There is a good correlation between present work and previous work. Results of selected parameters on velocity, temperature, nanoparticles volume fraction, and microbe density function are discovered. Skin friction, heat transport, mass transfer, and microbes transfer rates are tabular. Efforts of the current work rise in progressive microflow devices to bio-modified nanomaterial dispensation.

Hall current and thermo-diffusion effects on magnetohydrodynamic convective flow near an oscillatory plate with ramped type thermal and solutal boundary conditions

Abstract: The present discussion deals with the study of time-dependent hydromagnetic free convection fluid flow with heat and mass transfer over an oscillating vertical plate which is placed in a porous medium with ramped wall temperature and wall concentration in the presence of Hall current, rotation, chemical reaction, thermal radiation, thermo-diffusion (Soret effect). The governing system of equations is non-dimensionalized by using suitable dimensionless variables and parameters. The non-dimensional equations are solved analytically using the Laplace transform technique. The influence of various pertinent flow parameters on velocity, temperature and concentration fields are analyzed and portrayed through figures, whereas the skin friction, Nusselt number and Sherwood number are described and shown in tabular form.

Modeling of shallow extension engineered dual metal surrounding gate (SEE-DM-SG) MOSFET gate-induced drain leakage (GIDL)

Abstract: In this paper, an analytical paradigm for the gate-induced drain leakage (GIDL) for shallow extension engineered dual metal surrounding gate (SEE-DM-SG) MOSFET using superposition technique with appropriate boundary conditions is proposed. Electric field, Ez, gate-induced drain leakage current, IGIDL, and surface potential have been modeled. The analytical model has been critically examined for different channel lengths, silicon film radii and temperatures. The Arrhenius plot for the gate leakages has also been modeled. The analytical results obtained have been verified with the simulated data. In addition to the analytical results, the curtailment of the band-to-band tunneling (which further reduces the leakages, in particular GIDL) by SEE-DM-SG MOSFET is deeply studied and investigated by analyzing band energy across the valence and conduction bands.

Relativistic and nonrelativistic treatment of Hulthen-Kratzer potential model in D-dimensions

Abstract: We present approximate solutions of the Klein–Gordon equation containing an interaction of the Hulthen and modified Kratzer potential using the procedure of Nikiforov–Uvarov and the Greene–Aldrich approximation method of handling centrifugal barriers. In our results, we obtained the bound-state relativistic energy eigenvalues and their corresponding eigenfunctions in terms of the Jacobi polynomials. We then showed that in the nonrelativistic limit, the energy eigenvalues reduces to the one obtained using the Schrodinger equation. Furthermore, to get a better insight into the behaviour of diatomic molecular systems, we investigated the behaviour of some selected diatomic molecules, namely N2, I2, CO, NO and HCl, when subjected to the potentials under study. This was done by determining the shape of the potential of the molecules when the interatomic distance r equals the equilibrium bond length re. Also, the energy spectrum was computed for the selected diatomic molecules for various vibrational and rotational quantum numbers. Special cases of the potential and their corresponding energies were deduced and were found to be in agreement with the literature. Finally, we present the variations of the energy eigenvalues with the potential strength, equilibrium bond length, dissociation energy, screening parameter, dimensions, vibrational and rotational quantum numbers, respectively.

Design and synthesis of polyaniline/MWCNT composite hydrogel as a binder-free flexible supercapacitor electrode

Abstract: The novel polyaniline/MWCNT composite hydrogel has been successfully synthesized on carbon cloth using in situ oxidative polymerization of aniline in the presence of MWCNT and phytic acid which can further be used as a binder-free electrode for supercapacitor. The use of electrode without binder is an effective approach to get better electrochemical behavior, which makes the ions move quicker. The supercapacitor cell has been built in a Teflon Swagelok assembly by sandwiching a separator impregnated with 1 M H2SO4 electrolyte between two symmetrical hydrogel electrodes and used further for electrochemical characterization. The electrochemical behavior of supercapacitor electrodes has been explored in a two-electrode cell configuration using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements. The electrochemical results reveal that in 1 M H2SO4 aqueous solution, polyaniline/MWCNT composite hydrogel possesses a high specific capacitance (Cs) value of 277.59 F/g as compared to Cs value of 142.24 F/g for polyaniline hydrogel at 0.25 A/g. The polyaniline/MWCNT electrode shows superior rate capability and outstanding cyclic stability up to 5000 consecutive cycles. The electrochemical performance of composite hydrogel may be attributed to its well-designed nanostructure and the collective effect of both components. It may be concluded that as prepared composite hydrogel serves as a favorable electrode material for highly capable flexible energy storage system.

Cluster decay half-lives using modified generalized liquid drop model (MGLDM) with different pre-formation factors

Abstract: Cluster decay from 212–240Pa, 219–245Np, 228–246Pu, 230–249Am, and 232–252Cm has been studied by including three different pre-formation factors that depend on cluster size, atomic number of cluster and daughter nuclei, and Q value in MGLDM, an approach developed by modifying GLDM with proximity 77 potential. In MGLDM, where Q value-dependent pre-formation factor is added, the standard deviation of logarithmic half-lives was found to be 0.83, and the experimental half-lives were successfully reproduced using MGLDM with cluster size-dependent, and atomic number of cluster and daughter nuclei-dependent pre-formation factor with a standard deviation of 0.58 and 0.63, respectively. The half-lives of heavy elements in trans-lead region emitting 22Ne, 24Ne, 26Mg, 28Mg, 32Si and 33Si clusters, which have not been experimentally determined so far, have been predicted by incorporating three types of pre-formation factors to MGLDM. As all the predicted half-lives are below 1030s and are within the experimentally measurable range, we hope that our present predictions would be helpful for future studies in this field.

Investigation of optical solitons with Chen–Lee–Liu equation of monomode fibers by five free parameters

Abstract: The optical solitons are extracted with Chen–Lee–Liu (CLL) equation that is considered with group velocity dispersion. The CLL equation describes the propagation of optical pulses in monomode fibers. In this article, the variety of solitons like dark, singular, dark-singular, bright-dark and periodic solutions are obtained by the mean of Fan-extended sub equation method under different constraint conditions. Moreover, for showing the physical interpretation of some recovered solutions, we also plot 3D maps by using the suitable values of involved parameters in solutions. The performance of the used method shows the adequate, validity and ability for implementation to many other nonlinear models.

Investigation of bandgap properties in one-dimensional binary superconductor–dielectric photonic crystal: TE case

Abstract: A binary superconductor–dielectric photonic crystal (PC) is proposed. The PC has the structure (AB)N with layer A representing the superconducting layer and layer B the dielectric material. The transfer matrix technique is used to deduce the transmission coefficient through the PC. The properties of photonic bandgaps (PBGs) arising in the transmission spectra are studied with the angle of incidence and with all parameters of the superconductor such as thickness, London penetration length, and critical temperature. Many interesting findings were reached: The PBG width decreases with increasing the incidence angle until it disappears for high incidence angles. There is an optimum superconducting layer thickness at which the PBG shows a maximum. The critical temperature has the lowest effect on the PBG width among the superconductor parameters, whereas London penetration length has the topmost effect.

Investigation of gas sensing property of zinc oxide thin films deposited by Sol-Gel method: effects of molarity and annealing temperature

Abstract: Sol-Gel method has been used to deposit pure zinc oxide on glass substrates in two different conditions. The molarity was selected 0.2, 0.3 and 0.4 molar, and the annealing temperature was chosen 450 °C, 500 °C and 550 °C. The structural and morphological properties of the thin films have been investigated using X-ray diffraction and field emission scanning electron microscopy, and some important structural parameters of the optimized sample were determined. By using an electric circuit, their ethanol sensing features have been studied. Several related sensing parameters such as activation energy, optimal operating temperature, dynamic response, sensitivity and response/recovery times of the samples were determined and compared. An uncommon p-type sensing behavior is observed in all samples during the increase in operating temperature (at a temperature of about 370 °C). Considering all the sensing parameters, it seems that the sample Zn4 (0.4 molar zinc oxide with 450 °C annealing temperature) is optimized as a sensor.

Entropy generation on double-diffusive MHD slip flow of nanofluid over a rotating disk with nonlinear mixed convection and Arrhenius activation energy

Abstract: The present study deals with the swirling flow problem for the nanoliquid over a radially stretchable rotating disk with the consideration of nonlinear mixed convection and chemical reaction defined by Arrhenius model. The surface of the stretchable rotating disk concedes with the Navier’s velocity slip condition. The temperature jump condition due to imperfect liquid–solid energy interaction is also considered. The flow model is established by incorporating the well-known Buongiorno’s nanofluid model and therefore, Brownian motion and thermophoretic diffusion are incorporated in the mathematical modeling. Heat transport is performed taking into account the heat generation owing to viscous and Joule dissipations and internal energy generation/absorption of the fluid. The coupled nonlinear partial differential equations (PDEs) are converted to the non-dimensional ordinary differential equations (ODEs) through the similarity transformation. These ODEs together with the physical conditions are then solved by the “bvp4c” technique. The impact of present flow characteristics on the entropy generation and Bejan number, flow fields (axial and radial velocities), temperature and concentration profiles are presented graphically. Moreover, the surface drag force, strength of energy and mass transport are calculated and presented in tabular forms. The outcomes show that an increase in magnetic and slip parameter values decrease the fluid velocities (axial and radial). Entropy generation gets improved with the increase in either Brinkman number or magnetic parameter values.

The impacts of meteorological parameters on the seasonal, monthly, and annual variation of radio refractivity

Abstract: Results of the variations of radio refractivity, computed from the measurements of ambient temperature, atmospheric pressure, and relative humidity, were studied in Calabar for a period of 12 years (2005–2016) with the archived data provided by the Nigerian Meteorological Agency (NIMET). Correlation plots and modeling show that refractivity is mostly affected by the water vapor content of the atmosphere, and this means that relative humidity can be used to accurately develop models for the variations of refractivity as the refractivity variation within a year showed an almost uniform value which corresponded to the monthly relative humidity trend. The annual variation of refractivity also corresponded to the annual variation of relative humidity with its highest coming in 2012 with 391 N Units. Results also show that the ambient temperature and the atmospheric pressure in the region are not reducing annually and this has a very significant effect on climate change. On climate change, the obtained meteorological parameters have over the years affected the climate of the region as an increase in annual atmospheric pressure as well as the relative humidity has brought about a steady increase in amount of heat retained on the earth’s surface; this is due to the water vapor (a greenhouse gas) in the atmosphere of this region.