In this paper, we present a numerical approach to solving singularly perturbed semilinear convection-diffusion problems. The nonlinear part of the problem is linearized via the quasilinearization technique. We then design and implement a fitted operator finite difference method to solve the sequence of linear singularly perturbed problems that emerges from the quasilinearization process. We carry out a rigorous analysis to attest to the convergence of the proposed procedure and notice that the method is first-order uniformly convergent. Some numerical evaluations are implemented on model examples to confirm the proposed theoretical results and to show the efficiency of the method.

The transmission dynamics of Hepatitis B Virus in a population with infective immigrant is presented with the inclusion of an optimal control strategy to curtail the spread of the virus. To understand the spread of this infection, we develop a mathematical model with control variables of migrant screening and public sensitization. The optimality system is characterized using Pontryagin’s maximum principle and solve numerically with an implicit finite difference method.  Result of the numerical simulation is presented to illustrate the feasibility of this control strategy. The analysis reveals that combination of both control variables could be the most fruitful way to reduce the incidence of Hepatitis B virus.

In this paper, effect of radiation and heat source parameters on temperature, concentration and velocity profile of an electrically conducting fluid passing through an infinite permeable plate is investigated. The governing equation, which was based on the balanced mass, linear momentum, energy and species concentration, were non-dimensionalized to reduce the equations to system of ordinary differential equations. This was then solved by perturbation technique. Effects of radiation parameter, heat source parameter, and Schmidt parameter are analyzed. We observed that the velocity and concentration profiles increase with increase in radiation parameter and heat source parameter. The temperature profile increases with decrease in radiation parameter with increases boundary layer thickness.

Despite the availability of an abundant literature on singularly perturbed problems, interest toward non-linear problems has been limited. In particular, parameter-uniform methods for singularly perturbed semilinear problems are quasi-non-existent. In this article, we study a two-dimensional semilinear singularly perturbed convection-diffusion problems. Our approach requires linearization of the continuous semilinear problem using the quasilinearization technique. We then discretize the resulting linear problems in the framework of non-standard finite difference methods. A rigorous convergence analysis is conducted showing that the proposed method is first-order parameter-uniform convergent. Finally, two test examples are used to validate the theoretical findings.

The aim of this work is to carry out detailed sensitivity analysis of each parameter in order to know their relative importance in the epidemiological model. This mathematical model for hepatitis B virus is a system of non-linear differential equations which represents the interaction between diseases classes and other epidemiological parameters. The disease free equilibrium points and basic reproduction number of the cases were analyzed using the next generation matrix method.  Sensitivity analysis of with respect to the model parameters was carried out using normalized forward sensitivity index with graphical illustrations for clarity on the effects of these parameters. This analysis showed transmission rate  as the most sensitive parameter which means a reduction to zero of the transmission rate could lead to eradicating HBV infection. It was deduced that sensitivity analysis of these model parameters gives an insight into how best the spread of Hepatitis B Virus could be curtailed.