University of Ilorin

Residual stresses formed during quenching can significantly impact the integrity of engineering components. This study examined how varying immersion speeds in water affected both mechanical behavior and residual stress distribution in SAE 1025 steel. To achieve this, a hybrid approach combining finite element simulations (using ANSYS 2020 R1 and JMatPro) with controlled laboratory experiments was employed. The immersion speed control mechanism was developed and calibrated. Steel samples were quenched at five immersion speeds, ranging from 0.05 to 0.8 m/s. Metallographic analysis, Vickers microhardness testing and tensile testing were assessed and then compared to simulation predictions. A significant finding was the 83% reduction in maximum residual stress as immersion speed increased from 0.2 to 0.8 m/s. Furthermore, residual stress was significantly lower at the leading (first-contact) end of each sample and higher at the trailing end. Simulation results showed strong agreement with experimental findings, achieving an average error of 7.5% across the temperature range and a correlation coefficient (R2) of 0.97. Ultimately, the prediction of residual stress distributions achieved in this study will enable the production of safer and more durable components, critical for demanding engineering applications where performance and integrity are non-negotiable.

The chlorinated phenoxy herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most widely applied agricultural herbicides globally and is frequently detected in surface and groundwater at concentrations that pose ecological and public-health concerns, which motivates the development of low-cost, locally produced adsorbents for its sequestration. This study aimed to synthesize biochar from sugarcane leaves using a non-electrical top-lit updraft gasifier followed by ultrasonication, to characterize its physicochemical properties, and to evaluate its performance for the sequestration of 2,4-D from aqueous solution using a Box-Behnken response surface design. Proximate analysis of the feedstock showed 70.69% volatile matter and 23.46% fixed carbon. XRD revealed a turbostratic carbon structure with a (002) peak at 22.985° and crystallite size of 8.44 Å. Elemental composition showed carbon (67.45%), oxygen (17.31%) and silicon (5.06%). SEM micrographs revealed vesicular surfaces with bubble-like cavities. FTIR confirmed hydroxyl, aromatic CC and C-O functional groups. BET specific surface area was 409.934 m²/g with a BJH pore diameter of 2.136 nm. The point of zero charge of the biochar was 7.53, consistent with a weakly basic surface. Numerical optimization predicted a maximum removal efficiency of 91.81% and an equilibrium adsorption capacity of 163.97 mg/g at pH 9.07, adsorbent dosage 0.78 g/L, initial 2,4-D concentration 86.14 mg/L and contact time 758 min. The study concludes that sugarcane leaf biochar is an effective, low-cost adsorbent for 2,4-D sequestration.

Brake pads in automobiles are crucial, since their effectiveness determines the safety of vehicles in operation. Alternatives for brake pad liners are continuously being researched as a way of replacing detrimental materials such as asbestos and graphite. This research was aimed at developing some eco-friendly brake pad liners with agro-residue materials. The brake pad liners were produced using compression moulding employing particle sizes of three different sieve ranges of 400-300, 300-250 and 400-00 & micro;m. The composite materials for brake pad liners production included seashell, sawdust, palm kernel shell (PKS) and charcoal, serving the functions of structural, filler, abrasive and lubricant, respectively, while the binder used to hold the composite together was epoxy resin (polyepoxide) mixed with hardener (diethylenediamine) in 2:1 ratio. Microstructural analysis conducted on three samples, formulated based on selected sieve ranges, displayed the composite arrangement in the formulation, and the effect of particle sizes. Sample C (400-00 & micro;m) displayed an evenly distributed and closely packed particle sample. Results revealed that hardness of the composite material decreased with smaller sieve ranges. Sample C, with the compressive strength of 4.0839 MPa, had lowest hardness value and highest thermal stability of 394 degrees C, with corrosion rate of 0.0056 mm/yr.

Perfluorooctanesulfonic acid (PFOS), a persistent and bioaccumulative substance, has emerged as a major environmental contaminant of global concern. PFOS, widely used in industry and consumer products, is common in aquatic ecosystems and may harm primary producers like phytoplankton, though its effects on their community structure and physiology remain unclear. Here, we investigated the impact of PFOS on freshwater physicochemical parameters, phytoplankton community dynamics, biochemical composition, and oxidative stress responses in a mesocosm experiment over a 28-day period. The water quality indicators generally were unaltered by PFOS exposure, but phosphate levels decreased initially in the control. Phytoplankton biomass (cell density) decreased at 10 µg L−1 and 10 mg L−1 PFOS exposures. Phytoplankton species richness, Shannon, and Simpson diversity indices declined at 10 mg L−1, with communities at this concentration becoming distinctly different from the control and lower PFOS treatments by day 28. This shift in community structure was primarily driven by taxa such as Chlorogonium sp. and Microcystis aeruginosa, which contributed strongly to the observed compositional dissimilarity. Proteins content in the phytoplankton increased under PFOS exposure, peaking on day 21. In contrast, carbohydrate and lipid contents were reduced under PFOS relative to the control. PFOS exposure elevated glutathione-S-transferase activity, malondialdehyde, and hydrogen peroxide levels, whereas peroxidase activity was reduced. The phytoplankton biomass and lipids were positively associated, while oxidative stress markers were closely linked with high PFOS concentrations. Overall, these results highlight that PFOS exposure suppressed phytoplankton biomass, altered their community composition, and induced oxidative stress and metabolic shift at higher concentrations, highlighting its potential ecological risk in freshwater systems.

The dimensional analysis of the position and momentum variances-based quantum mechanical Heisenberg uncertainty measures was carried out for generalized Yukawa-type potential. The entropic information measures given by Shannon entropy sums and Fisher information products were obtained out for generalized Yukawa-type potential. It is interesting to observe that the Shannon entropy in position space, , increases and then decreases with the quantum number , suggesting a growth in delocalization due to a rapid increase in fluctuations. Likewise, the Shannon entropy in momentum space, , decreases and then increases with the quantum number , and vice versa. This unusual phenomenon may be explained by the parity restrictions inherent in the system. The Bialynicki-Birula and Mycielski (BBM) entropic uncertainty relation was verified to be saturated; however, the sum of the entropies increases with the quantum number up to a certain point and then decreases as continues to increase. We also found that the Fisher information accurately increases with the quantum number . The numerical results that support the validity of the scaling properties for Shannon entropy sum and Fisher information product were presented. The existence of a squeezed phenomenon in the ground and first excited state for some values of the potential screening parameter in momentum space was found. The Heisenberg uncertainty relation is met when the squeeze in one coordinate is compensated by an increase in the other coordinate. The results obtained exceed the theoretical lower bounds for all the information-theoretic measures considered, confirming their physical validity and accuracy.