Browsing by Author "Bolaji BO"

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    An Improved multi-objective a-star algorithm for path planning in a large workspace: Design, Implementation, and Evaluation
    (2022) Martins OO; Adekunle AA; Olaniyan OM; Bolaji BO
    Improved path planning algorithms should minimize algorithm processing time, increase path smoothness, and shorten path length, all of which will be extremely beneficial for mobile robot traversal in large workspaces. As a result, an improved multi-objective A-star (IMOA-star) algorithm for mobile robot path planning in a large workspace was designed and implemented in Python 3.8.3 in this study. In four test cases, the proposed IMOA-star is evaluated in a large workspace with dimensions of 7120 cm × 9490 cm, and its performance is compared to the traditional A-star. When compared to the traditional A-star, the results showed that IMOA-star reduced the algorithm process time by 99.98%, improved path smoothness by 45%, reduced path length by 1.58%, and reduced the number of random points by 83.45%. Finally, the IMOA-star outperforms the traditional A-star in terms of algorithm processing time, path smoothness, path length, and the number of random points. As a result, it should be considered a viable alternative to the traditional A-star for mobile robot path planning in a large workspace.
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    Theoretical assessment of new low global warming potential refrigerant mixtures as eco-friendly alternatives in domestic refrigeration systems
    (2020) Bolaji BO
    Refrigerants of low global warming potentials (GWPs) of ≤ 150 are required by regulations as working fluids in domestic refrigeration systems. Therefore, this study theoretically investigated the performance of five new refrigerant mixtures (R440A, R441A, R444A, R445A and R451A) with zero ODP and GWPs of less than 150. The results showed that all the investigated refrigerants exhibited very low pressure ratios and discharge temperatures in comparison with R134a with average discharge temperatures of R451A and R440A lower by 8 and 7% respectively, than that of R134a. R451A and R440A have similar vapour specific volume and pressure-temperature characteristics with those of R134a which confirmed that they could be used as replacement for R134a. R440A and R451A have advantages of better COPs and volumetric cooling capacity (VCC) in comparison with R134a. Their average COPs are higher by 14 and 5% respectively, than that of R134a. The specific power consumptions (SPCs) of R441A and R445A are significantly higher by average of 57 and 44% respectively; while those of R440A and R451A are lower by average of 8 and 4% respectively, in comparison with R134a. In general, in terms of all the performance parameters considered, R441A and R445A consistently performed poorly, while R440A and R451A achieved better performance than R134a in all aspects. Beside the flammability of these two refrigerants, in which their use require following the established rules and regulations for the safety precautions, they can serve as long term eco-friendly substitute refrigerants for R134a in domestic refrigerators.