Browsing by Author "Tessema, Kassahun Mengist."

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Epidemiological modelling of foot and mouth disease control in cattle: incorporating time and spatial spread of disease dynamics.
(2019) Tessema, Kassahun Mengist.; Chirove, Faraimunashe.; Sibanda, Precious.
Foot and mouth disease (FMD) is a contagious animal viral infection that can spread rapidly if the disease is not monitored and controlled. Therefore, protecting livestock and controlling foot and mouth disease is important for preventing economic losses. Much of the global burden of economic losses due to foot and mouth disease falls on the worlds poorest countries that mostly depend upon the health of their livestock. In these countries, the availability of FMD also has an impact on the overall herd fertility, modifying the herd structure and affecting the selection of breeds. Modelling the dynamics of FMD using mathematical analysis and simulations can assist to monitor and control the spread of the disease. In this thesis, we develop, study, and analyse models of foot and mouth disease in cattle by incorporate vaccination that does not induce rapid protection, time delays, both time and spatial spread with different control strategies. The results show that even though vaccines may not induce rapid protection the combining of a high rate of vaccination and low loss of vaccine protection rate may be successful in reducing the foot and mouth burden provided critical vaccination thresholds are taken into consideration. The results also show that control strategies play a significant role in moving the animals into protected routes of infection than leaving more animals into the unprotected route of infection. We also capture the effects of prophylactic vaccination, reactive vaccination, prophylactic treatment, reactive culling and the effects of time delay. The results of foot and mouth disease with two-time delays show that the burden of infection decreases significantly when unprotected animals delay maximally their time to show clinical symptoms, and at the same time by increasing the effectiveness of the control strategies. The study also explores the effects of spatial diffusion, quarantine of clinically infected animals and shedding of foot and mouth disease virus into the environment. Analysis of foot and mouth disease control models suggests that implementing of an effective combination of control strategies, limiting the movement of susceptible animals and the shedding of FMDV protects animals from foot and mouth disease burden.
On free convection and heat transfer in a micropolar fluid flow past a moving semi-infinite plate.
(2012) Tessema, Kassahun Mengist.; Sibanda, Precious.
In this dissertation we investigate free convective heat and mass transfer in micropolar fluid flow past a moving semi-infinite vertical porous plate in the presence of a magnetic field. The aim of this study was to use recent semi-numerical methods such as the successive linearisation method and the spectral-homotopy analysis method to study the effects of viscous heating and the effects of different fluid parameters. The governing boundary layer equations for linear momentum, angular momentum (microrotation), temperature and concentration profiles are transformed to a system of ordinary differential equations and solved using the successive linearisation method and the spectral-homotopy analysis method. The accuracy of the solutions was determined by comparison with numerical approximations obtained using the Matlab bvp4c solver. The influences of the micropolar parameter, Darcy number, Prandtl number, Schmidt number, magnetic parameter, heat absorption parameter, Soret and Dufour numbers, local Reynolds number and Grashof number on velocity, microrotation, temperature and concentration profiles were determined. The results obtained are presented graphically and in tabular form.