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The National Research Fund facilitates research for the advancement of Science, Technology and Innovation. One of our core functions is to compile and maintain a national database of research and innovation projects funded by the Fund and other agencies as per the STI Act of 2013.

 

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CHANNEL STRUCTURED METAMATERIALS FOR SUPER RESOLUTION IMAGING
(ASME, 2019-07-14) ohn Birir1, Michael J. Gatari and Prabhu Rajagopal
ABSTRACT When inspection is required to be conducted from a remote distance, due for example to safety concerns, guided ultrasonic wave testing technique is the preferred choice. Guided waves are usually low frequency hence are not subjected to much attenuation relative to the bulk waves. As a result, guided waves can travel a longer distance. One of the limitations of guided waves however, is that the low frequency (longer wavelength) used lead to lower resolution capabilities due to the inherent diffraction limits of λ/2 (where λ is wavelength). Guided waves are therefore generally used as screening tools to locate areas of interest. A higher resolution technique is then employed to further investigate and characterize the features of defects in the identified areas. To overcome this challenge of resolution, a technique is proposed that increases the resolution capability of guided waves beyond the diffraction limit. Simulation using commercial finite element software is used to optimize variables involved in the proposed method. The simulation is then validated with experiments. In the present work a resolution of λ/72 is demonstrated experimentally.
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Drivers of Organic Fertiliser Adoption and Use Intensity Among Smallholder Maize Farmers in Lake Victoria Region, Western Kenya
(2025) Rosebell Achieng Owuor, Alphonce Juma Odondo, Caleb Ollweny, Mathews Dida
Smallholder farmers account for about 75% of maize production in Kenya. The current average on farm productivity is 1.43 ton/ha against the potential of 6 ton/ha. In Western Kenya, low soil organic carbon is one of the contributors to the low maize productivity. Studies have shown that organic fertilizers contribute towards increase in soil productivity. However, there is paucity of information on the relationship between drivers of organic fertilizers adoption and use intensity among the farmers, which the study seeks to address. A total of 358 farmers were interviewed in the 2020/21 growing seasons. Heckman’s two-stage model was estimated. The results demonstrate that age, education, gender, soil quality perception and access to supportive resources are pivotal in shaping organic farming decisions. There is need for targeted extension services to less educated and older farmers. Off-farm income generation should be encouraged. Integrated soil fertility management approaches that address nutrient replenishment and soil erosion control is necessary, and there is need to promote mechanization or subsidization of organic fertilizer application on larger farms as this may help overcome labour constraints and improve organic fertilizer adoption on a broader scale. The results may be a source of literature for subsequent studies in related fields.
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Pressure Distribution of a Horizontal Well in an Oil Reservoir Subject to Simultaneous Single Edged and Bottom Water Drive Mechanisms
(IOSR Journal of Mathematics (IOSR-JM), 2023-08-10) Mutili Peter Mutisya, Awuor Kennedy Otieno, Oyoo Daniel Okang’a and Adewole Stephen Ezizanami
In this study the pressure distribution in an oil reservoir with a horizontal well is investigated. A horizontal well with single-edged and constant bottom pressure is outlined. A reservoir bounded with two constant pressure boundaries, like an edge and bottom water, requires that the production engineer should adhere diligently to a production schedule, developed by a reservoir engineer, for clean oil production to be possible. This means that arbitrary production practices through selection of production rates could lead to production of these external fluids. This can mar the economics of the project. Production schedules or plans show acceptable rates, well design and production time that can guarantee only clean oil production. In this study, pressure behaviour of a horizontal well drilled and completed in a reservoir subject to with simultaneous single-edged and bottom water drives is investigated in detail. All possible flow periods or patterns that can be exhibited by the well are determined. Fluid flow in oil reservoirs in real time is governed by a heterogenous diffusivity equation, which describes reservoir pressure as a function of reservoir, fluid and wellbore properties. To solve this unsteady state problem, Green’s functions were deployed to represent the boundaries of the reservoir selected for study. The Green’s functions selected are for flow from start of transient to late time, when all the external boundaries are felt. Newman product rule was used to derive a dimensionless pressure expression for the reservoir system oil flow. The source of pressure transient was production throughout. All the resulting integrals were performed numerically. MATLAB programming was used to plot the curves by applying spline functions interpolation. Influence of reservoir, fluid and wellbore properties on reservoir pressure was investigated in real time. To assist interpretation, dimensionless pressure derivatives were also computed. Near wellbore problems, like skin and wellbore storage, which affect well performance only at very early time, were not considered in the study. From the results, 𝑃𝐷 and 𝑃𝐷 ′ vary directly with ℎ𝐷 and inversely as 𝐿𝐷. The 𝑃𝐷 ′ gradually reduces to zero when 𝑃𝐷 begins to exhibit a constant trend. 𝑃𝐷 ′ vary inversely with ℎ𝐷 and 𝑦𝑒𝐷 at all flow times. The number of flow periods varies with reservoir size, well length and production time. The time at which the 𝑃𝐷 ′ starts to exhibit a downward trend is the external fluid breakthrough time. The breakthrough time is affected by well design. Longer wells exhibit delayed breakthrough time because of lower pressure drawdown associated with increased well length. If production rate is sustained for any particular well design, the well will completely water-out. Finally, infinite conductivity 𝑥𝐷 = 0.732 and uniform flux condition do not really affect 𝑃𝐷 and 𝑃𝐷 ′ at early time.
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Assessing the impact of optimized prevention strategies for mother-to-child HIV transmission dynamics in Kenya: a mathematical modeling study
(medRxiv, 2025-04-19) Robert Mureithi Maina, Samuel Musili Mwalili, Duncan Kioi Gathungu
HIV can be transmitted from a HIV infected mother to her child during pregnancy, delivery, or breastfeeding. According to NSDCC 2023, Kenya has estimated PMTCT coverage of 89.56% and PMTCT transmission rate of 8.6%. Even though there has been strides to address PMTCT, there is need to gear up approaches in addressing MTCT in order to significantly advance elimination. This research formulates a mathematical model to represent the dynamics of MTCT. Equilibrium points of the model are computed and the stability of HIV-free point is investigated. The numerical results show that a 50% decrease in maternal HIV transmission lowers infant infection rates by about 17.7%, whereas the same reduction in infant transmission decreases infections by nearly 39%, highlighting the greater sensitivity of infant transmission rates to direct interventions. While combination of strategies achieves the highest HIV minimization rates of up to 99.89% on infants, ART adherence alone significantly reduces transmission, particularly on infants (91.42%) while use of post-exposure prophylaxis (PEP) shows limited effectiveness when used alone(39.65%), suggesting that it should be complemented with other strategies for optimal impact. These findings emphasize the critical need for integrated interventions, where combining multiple prevention methods yields the best outcomes in reducing HIV infections on infants and moving closer to the elimination of pediatric HIV. These findings align with global recommendations from World Health Organization (WHO). This research can be used by the ministry of health to inform policy as well as recreated for other maternal infections.
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Metamaterial enhanced subwavelength imaging of inaccessible defects in guided ultrasonic wave inspection
(ScienceDirect, 2024-04) John Kiprotich Birir, Michael James Gatari , Mohamed Subair Syed Akbar Ali and Prabhu Rajagopal
Detection of defects located close to design features such as welds and supports remains a challenge in guided ultrasonic wave inspection, primarily due to the diffraction limit. Although metamaterial based approaches hold promise, the best previous work in this regard required placing a sensor right above the defect location to achieve resolution. Here, a novel angled channel metamaterial concept is proposed to overcome this limitation, thus permitting placing of a sensor at an offset from the defect location. The concept is demonstrated and discussed using simulations validated by experiments. It is shown that sub-wavelength resolution of crack-like defects is possible using the angled channel metamaterial offset by a distance of up to half the wavelength. The operating physics of this problem is further discussed using simulations and analysis, bringing out the strengths and limitations of the proposed technique, highlighting the benefits for guided wave screening of hidden regions.