Browsing by Author "Opoku-Sarkodie, R."

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Bifurcation analysis of waning-boosting epidemiological models with repeat infections and varying immunity periods
(Elsevier, 2024-04) Opoku-Sarkodie, R.; Bartha, F.A; Polner, M.; Röst, G.
We consider the SIRWJS epidemiological model that includes the waning and boosting of immunity via secondary infections. We carry out combined analytical and numerical investigations of the dynamics. The formulae describing the existence and stability of equilibria are derived. Combining this analysis with numerical continuation techniques, we construct global bifurcation diagrams with respect to several epidemiological parameters. The bifurcation analysis reveals a very rich structure of possible global dynamics. We show that backward bifurcation is possible at the critical value of the basic reproduction number, 0 = 1. Furthermore, we find stability switches and Hopf bifurcations from steady states forming multiple endemic bubbles, and saddle–node bifurcations of periodic orbits. Regions of bistability are also found, where either two stable steady states, or a stable steady state and a stable periodic orbit coexist. This work provides an insight to the rich and complicated infectious disease dynamics that can emerge from the waning and boosting of immunity.
Modelling the Queue at the Scan Station of Tema Port: An Application of Queuing Theory
(Asia Pacific Journal of Education, Arts and Sciences, 2015-07-03) Acheampong, E.; Opoku-Sarkodie, R.
The long hours spent in queues by imported consignment of goods waiting to be scanned causes congestion at the Tema Port. This study was conducted to find ways of reducing the time spent in queues by imported consignment of goods at the Tema Port. The main objective of this study was to minimize the time spent in queues by imported consignment of goods designated for the two scanners (Scanco and Nick-TC) for examination at the Tema Port. The study employed the technique of queuing theory for the analysis. We found that, the Scanco scanner had a faster service rate than the Nick-TC scanner when both were considered under the M/M/1 model where the two scanners served two independent queues. However, under the M/M/2 model where the two independent parallel scanners served one queue of designated consignments, the number of consignments (mean system size) in the queuing system reduced to 8.3984 per hour with an average waiting time of 0.5339 hours. Based on the findings, the following policy recommendations were made: The Ghana Ports and Harbours Authority, and the Government of Ghana must formulate policies to permit the two current existing scanners to serve only one single queue in order to ease the congestion caused by long hours of waiting in a queue.
Optimum production scheduling for a beverage firm based in Accra
(Research Journal of Applied Sciences, Engineering and Technology, 2011-02-20) Amponsah, S.K; Ofosu, J.B.; Opoku-Sarkodie, R.
This study, which was conducted in Accra, Ghana, presents a production scheduling problem for a beverage firm based in Accra, all in an attempt to cut down manufacturing cost and increase efficiency. The creation of an optimum production schedule requires the modelling of the scheduling problem as a balanced transportation problem. An important result upon the implementation of the model is the allocation of the optimum level of production necessary to meet a given demand at a minimum cost.
A simple air deterministic mathematical model for determining oxygen and carbondioxide concentration in a sealed environment
(Research Journal of Mathematics and Statistics, 2014-08-25) Acheampong, E.; Gardiner, P.; Opoku-Sarkodie, R.; Manu, T.
This study presents a mathematical model that simulates oxygen and carbon-dioxide concentrations in a sealed environment without the actual measurement of the presence of these substances. Using Mathematical software for simulation, the model was tested using data (volume in cubic meters) of a sealed environment whiles varying the number of people in that environment. The results revealed that, the number of people in the sealed environment affected the concentrations of these substances in the air. Also the model revealed that there is a time (threshold) beyond which it will be unsafe to stay in such an environment.