National Research Repository
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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Registry of Repositories in Kenya (RoRiK)
NRF is developing a Registry of Research Repositories in Kenya (RoRiK) in an effort to promote access to research data in the country.
Recent Submissions
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.
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.
Structured channel metamaterials for deep sub wavelength resolution in guided ultrasonics
(AIP Publishing, 2020-06-19) John K. Birir, Michael J. Gatari and Prabhu Rajagopa
Experimental results on deep subwavelength resolution of defects are presented for the first time in the context of guided ultrasonic wave
inspection of defects, using novel “structured channel” metamaterials. An Aluminum bar with side-drilled holes is used as a test sam
ple, interrogated by the fundamental bar-guided symmetric mode. Simulations were conducted to optimize dimensional parameters of the
metamaterial structure. Experiments using metamaterials fabricated accordingly demonstrate a resolution down to 1/72 of the operating
wavelength, potentially bringing the resolution of guided wave inspection to the same range as that of bulk ultrasonics. This work has much
promise for remote inspection in industry and biomedicine.
Effects of Fluid and Reservoir Characteristics on Dimensionless Pressure and Derivative of a Horizontal Well in a Bounded Oil Reservoir with Simultaneous Single Edge and Bottom Water Drive
(American Journal of Engineering Research (AJER), 2021) Mutili Peter Mutisya, Adewole Stephen Ezizanami, Awuor Kennedy Otieno and Oyoo Daniel Okang’a
This study investigates the effects of fluid, wellbore and reservoir characteristics on dimensionless pressure and
dimensionless pressure derivatives at late time flow of a horizontal well in a bounded oil reservoir subjected to
a single edge and bottom water drive mechanisms. The properties considered in this paper include the
dimensionless well length, dimensionless reservoir width and dimensionless pay thickness. The main objective is
achieved by using the source and Green’s functions together with Newman product method. Spline functions for
interpolation in curve fitting was used to plot the graphs aided by MATLAB program. Results show that the
dimensionless pressure increases with decrease in dimensionless reservoir width and pay thickness. The
dimensionless pressure derivative potentially collapses to zero when the dimensionless pressure becomes
constant. Higher oil production is indicated by larger magnitudes of dimensionless pressure derivatives.
Information in this study will assist in designing and completion of horizontal wells in a bounded reservoir for
prolonged enhanced oil production.
Derivation of Black-Scholes-Merton Logistic Brownian Motion Di erential Equation with Jump Di usion Process
(JS Publication., 2019) Andanje Mulambula, D. B. Oduor and B. Kwach
Black- Scholes formed the foundation of option pricing. However, some of the assumptions like constant volatility and
interest among others are practically impossible to implement hence other option pricing models have been explored to
help come up with a much reliable way of predicting the price trends of options. Black-scholes assumed that the daily
logarithmic returns of individual stocks are normally distributed. This is not true in practical sense especially in short
term intervals because stock prices are able to reproduce the leptokurtic feature and to some extent the volatility smile .
To address the above problem the Jump-Di usion Model and the Kou Double-Exponential Jump-Di usion Model were
presented. But still they have not fully addressed the issue of reliable prediction because the observed implied volatility
surface is skewed and tends to atten out for longer maturities; The two models abilities to produce accurate results
are reduced. This paper ventures into a research that will involve Black-Scholes-Merton logistic-type option pricing with
jump di usion. The knowledge of logistic Brownian motion will be used to develop a logistic Brownian motion with jump
di usion model for price process.
MSC:
91GXX, 91G50, 62P05, 97M30.
