Browsing by Author "Zakariyya, O.S."
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Item Effects of Ionospheric Scintillation on Communication Systems: GPS and Satellite(Begell House incorporated, 2017) Ajiboye, A.; Abdulrahman, A.Y.; Falade, A.J.; Ajiboye, A.T.; Zakariyya, O.S.; Rahman, T.A.Item Parametric Modelling of Phase-Shifted Full-Bridge Zero Voltage Switching DC-DC Converter(Jordan Journal of Electrical Engineering. All rights reserved-Volume, 2021-03) Ibrahim, Oladimeji; Yahaya, N.Z.B.; Otuoze, Abdulrahaman; Saad, N; Hasan, K.N.B.M; Shannan, N.M.; Zakariyya, O.S.Modelling of switching pulse width modulated phase-shifted full-bridge zero voltage converter is highly challenging due to several transitional stages involved in a complete switching cycle. The circuit averaging technique has been favored in the past three decades considering phase-shifted full-bridge converter as a buckderived converter. This modelling approach requires several assumptions that include zero equivalent series resistance of output capacitor, zero leakage inductance and unity transformer turn ratio which results in a less accurate system dynamics. In this paper, a system identification approach is proposed for obtaining a more accurate model of phase-shifted full-bridge PWM switching converter using the input-output test data. The model parameter estimation is implemented in Simulink environment incorporating all circuit parasitic parameters and the resulting system’s frequency response shows a good agreement when compared with reported measured response.Item Replacement Model for Street Lighting Systems(Nigerian Journal of Technology, 2021) Otuoze, Abdulrahaman; Usman, A.M.; Adediran, Y.A.; Mohammed, OO; Zakariyya, O.S.Replacing failed bulbs of streetlights in a location can be very tasking and expensive if the optimal time for replacement is not determined. In this paper, a model has been developed that helps to establish the optimal time for the replacement of streetlight bulbs. Burnt-out bulbs are replaced individually when they fail, and group replacement is carried out on all bulbs after a specified time. The costs for both individual replacement and group replacement are determined. The developed model was applied to locally sourced data from a field survey of a streetlight installation at the University of Ilorin, Ilorin, North-central Nigeria. The model gave the optimum replacement time of burnt-out bulbs as the eighteenth week when applied to the data used in this work. The optimum replacement time will be dependent on the dataset used. This makes the developed model useful in establishing the optimal replacement time of any stochastically failing items that are in large quantities. The model will help to reduce maintenance costs for facility managers.