On transient flow of a reactive variable viscosity third-grade fluid through a cylindrical pipe with convective cooling

This paper studies the transient flow of a reactive variable viscosity third grade fluid in a cylindrical pipe with convective heat exchange at the pipe surface. It is assumed that exothermic chemical reactions take place in the flow system. The coupled nonlinear partial differential equations governing the problem are derived and solved numerically using an unconditionally stable and convergent semi-implicit finite difference scheme. Both numerical and graphical results are presented and physical aspects of the problem are discussed with respect to various parameters embedded in the system.     

Heat and mass transfer by MHD mixed convection stagnation point flow toward a vertical plate embedded in a highly porous medium with radiation and internal heat generation

This paper examined the hydromagnetic mixed convection stagnation point flow towards a vertical plate embedded in a highly porous medium with radiation and internal heat generation. The governing boundary layer equations are formulated and transformed into a set of ordinary differential equations using a local similarity approach and then solved numerically by shooting iteration technique together with Runge-Kutta sixth-order integration scheme. A representative set of numerical results are displayed graphically and discussed quantitatively to show some interesting aspects of the pertinent parameters on the dimensionless axial velocity, temperature and the concentration profiles, local skin friction, local Nusselt number and local Sherwood number, the rate of heat and mass transfer. Good agreement is found between the numerical results of the present paper with the earlier published works under some special cases.     

Design of a biaxial extensometer for measuring strains in cruciform specimens

A biaxial extensometer for measuring strains in flat cruciform specimens is presented. This extensometer allows for the use of two displacement or strain transducers to control and measure strains along mutually orthogonal directions in the plane of the specimen. The measurement and control of strains along each direction are completely independent of each other. The resolution and the measurable strain range of the biaxial extensometer depend on the particular displacement transducers employed. Independently adjustable gage lengths are incorporated along the two directions such that different strain ranges can be measured with the same transducer displacement range. The use of the biaxial extensometer with cruciform specimens and other applications, including the possibility for measuring triaxial strains in a plate specimen, are discussed.     

Computational analysis of CO2 emission,O2 depletion and thermal decomposition in a cylindrical pipe filled with reactive materials

In this paper we present a nonlinear mathematical model for estimating the CO₂ emission, O₂ depletion and thermal decomposition in a stockpile of a reactive material undergoing an exothermic chemical reaction inside a long cylindrical pipe with convective heat and mass transfer characteristics at its surface. By employing a semi-implicit finite difference scheme, the problem is solved numerically. The graphical results are discussed in terms of the relationships between the processes that affect the oxidation reactions on the one hand and oxygen depletion as well as carbon dioxide emission on the other hand. The relationships between thermal stability and the processes that influence the oxidation reactions are also explored and discussed.     

Band alignment and charge transport characteristics of TPP/ZnO hybrid for photovoltaic cell potential

Growth of ZnO nanocrystals has been carried out by a two-electrode electrochemical cell arrangement. The nanocrystals serve as substrates onto which tetraphenylporphyrin (TPP) is evaporated under integrated UHV conditions for the development of TPP/ZnO hybrid specimen. The quality of the hybrid specimen is investigated by XPS measurement. Direct interaction between the valence electrons of the adsorbed TPP molecules and ZnO electronic levels is revealed by Ultraviolet Photoemission Spectroscopy (UPS). Absorption spectroscopic studies are used to examine the ground state electronic structure and polarization dependence (excitation to π* and σ* vacant orbitals) of the hybrid specimen. The studies further show efficient charge transfer from donor (TPP) to proximate acceptor (ZnO). Thus, porphyrin molecules act as an active layer for generation of electron and as an enhancement for subsequent sudden transfer of the charge to the ZnO at a timescale faster than that of core hole.     

Entropy analysis of unsteady magneto-nanofluid flow past accelerating stretching sheet with convective boundary condition

The unsteady laminar magnetohydrodynamics(MHD) boundary layer flow and heat transfer of nanofluids over an accelerating convectively heated stretching sheet are numerically studied in the presence of a transverse magnetic field with heat source/sink. The unsteady governing equations are solved by a shooting method with the Runge-KuttaFehlberg scheme. Three different types of water based nanofluids, containing copper, aluminium oxide, and titanium dioxide, are taken into consideration. The effects of the pertinent parameters on the fluid velocity, the temperature, the entropy generation number, the Bejan number, the shear stress, and the heat transfer rate at the sheet surface are graphically and quantitatively discussed in detail. A comparison of the entropy generation due to the heat transfer and the fluid friction is made with the help of the Bejan number. It is observed that the presence of the metallic nanoparticles creates more entropy in the nanofluid flow than in the regular fluid flow.     

Magneto-Compound Reaction of Convective Flow via a Porous Inclined Plate with Heat Energy Absorption

The current study is concerned with the unsteady heat and mass transfer of MHD free convection flow via a porous inclined plate that accelerates exponentially with temperature and concentration. Heat emission, source/sink, radiation absorption, and reaction are taken into account in the energy and species equations. The innovative part of the work is the analysis of the flow phenomenon with a heat source or sink and radiation absorption along the chemical reaction. The governing PDEs are reduced into ODEs via the non-dimensional variables and afterward solved analytically utilizing the perturbation strategy. Graphical representations of liquid temperature, speed, and concentration as well as the Sherwood \& Nusselt quantities and the skin friction factor are displayed in tabular form for different combinations of appropriate stream quantities. The analysis of a resistance quantum grows with the size of the magnetic, whereas the rates of mass and heat transfer decline with increasing radiation, reaction, and Schmidt number. Thermal-velocity and concentration-velocity profiles interact reciprocally with the accelerating radiation, heat source, and compound reaction. The growth of speed and thermal profiles is clearly visible due to the absorption and Prandtl values. The present results are in strongly consistent with the earlier published results. There are numerous applications for this research in many sectors and material processing for understanding drag in seepage flows on heated/cooled and inclined surfaces.     

Entropy generation in a liquid film falling along an inclined porous heated plate

In this paper, the second law analysis of a laminar falling viscous incompressible liquid film along an inclined porous heated plate is investigated. The upper surface of the liquid film is considered free and adiabatic. Based on some simplifying assumptions, analytical solutions for the fluid velocity and temperature are constructed. The expressions for the entropy generation rate and irreversibility ratio are obtained and the results are presented graphically and discussed quantitatively for several values of suction Reynolds number (Re) and group parameter (BrΩ⁻¹).     

Impact of optimal control on the treatment of HIV/AIDS and screening of unaware infectives

In this paper, we study the impact of optimal control on the treatment of HIV/AIDS and screening of unaware infectives on the transmission dynamics of the disease in a homogeneous population with constant immigration of susceptibles incorporating use of condom, screening of unaware infectives and treatment of the infected. Initially we consider constant controls and thereafter treat control measures as time dependent control parameters. In the constant controls case, we calculate the basic reproduction number and investigate the existence and stability of equilibria. The model is found to exhibit transcritical bifurcation. For the time dependent controls, we formulate the appropriate optimal control problem and investigate the necessary conditions for the disease control in order to determine the role of unaware infectives in the spread of HIV/AIDS. We observed that unawareness by infectives has a great cost impact on the community. We further investigate the impact of combinations of the strategies in the control of HIV/AIDS. Carrying out cost-effectiveness analysis, we found that the most cost-effective strategy is the combination of all the control strategies.     

On thermal stability of a reactive third-grade fluid in a channel with convective cooling the walls

In this paper, the thermal stability of a reactive third-grade liquid flowing steadily between two parallel plates with symmetrical convective cooling at the walls is investigated. The system is assumed to exchange heat with the ambient following Newton’s cooling law and the reaction is exothermic under Arrhenius kinetics, neglecting the consumption of the material. Approximate solutions are constructed for the governing nonlinear boundary value problem using regular perturbation techniques together with a special type of Hermite-Padé approximants and important properties of the velocity and temperature fields including bifurcations and thermal criticality conditions are discussed. It is observed that a combined increase in non-Newtonian parameter and convective cooling enhances the thermal stability of the material.