Botswana International University of Science and Technology

Sclerocarya birrea (A. Rich.) Hochst. (marula), with its rich phytochemical content, is highly regarded in southern African communities. Characterisation studies on fruit, bark and other parts of the plant identified valuable phytochemicals like tannins, terpenes, flavonoids, alkaloids, oils, vitamins and many others which calls for unlimited research on marula applications. Though not usually very efficient, use of hand tools in the sampling of roots, bark, leaves and fruits is the most practised method of harvesting due to affordability in communities. Marula roots, leaves and barks are exploited mostly for their medicinal phytochemical content, fruits for their beverage and nutritional benefits while seeds are a source of food and oils used for skin care. Biodiesel, skin care products and alcoholic beverages production have been reported among commercial opportunities for S. birrea. Community based commercial activities involve vending wine, oils, jam and butter as a source of income. Other potential areas of application including paint additives, green corrosion inhibitors and surfactant manufacture among others, need research attention to scale up on S. birrea economic value and commercialisation. More sector specific organisations are required to coordinate knowledge and operations in the marula economy to widen the applications and adoption of marula products into the global markets. Future demand and interest on S. birrea-based products calls for sustainable exploitation and domestication of the plant as alternative conservation measures.

Abstract The paper proposes an adaptive current injection method for master-slave synchronization of two electronic circuits, applied to a modified Wien bridge oscillator. The dynamic study includes stability analysis of equilibrium points, bifurcation diagrams, Lyapunov exponents, and isospikes, revealing critical values of resistances for Hopf bifurcation and period doubling. The numerical simulations confirm the hysteresis and the bifurcations in “hubs” and validate the analytical results.The control of multistability leads to a monostable regime. A robust adaptive sliding mode con-troller whose stability is validated by Lyapunov’s theorem is proposed. Compared to conventional controllers such as sliding mode, single active, and time-delay feedback adaptive control, it improves synchronization by 37.98%, 45.41%, and 42.46% respectively. Finally, numerical simulations and PSpice validate the adaptive current injection synchronization, a method generalizable to other circuits.

In nature, bioconvection generated by motile microorganisms may offer great opportunities in various applications such as environmental engineering, renewable energy technologies, and biomedical applications. In this paper, for the enrichment of heat transport and the regulation of bioconvection, a trihybrid nanofluid composed of gold (Au), silver (Ag), and multi-walled carbon nanotube (MWCNT) nanoparticles are considered within an MHD flow over a stretching cylinder. Unlike common single-nanoparticle nanofluids, trihybrid nanofluids utilize the synergistic behavior of multiple nanoparticles to achieve superior thermal conductivity, improved energy transport, and increased stability of fluids. The various key physical mechanisms incorporated here are thermal radiation, internal heat generation or absorption, electroosmotic effects and electromagnetic forces, to evaluate their impacts on microbial motility and bio-convective flow behavior. Furthermore, an activation energy-based chemical reaction is considered to show the moderation in microbial activity and enhancement in system performance. This set of coupled nonlinear partial differential equations is reduced to a system of ODEs by invoking proper similarity transformations and solved numerically via the Galerkin finite element method (G-FEM). Both multiple linear and quadratic regression analyses have been performed to develop the predictive models. It has been observed that the quadratic model presents more reliable and accurate predictions compared to the linear one. In general, the results show that bioconvection can be effectively controlled through adjusting parameters of the bioconvective Schmidt number, Peclet number, and Biot number to enhance heat and mass transfer characteristics of the system.

In this study, we model a solution surface using an ensemble machine learning approach to simultaneously predict and optimise rock fragmentation and ground vibration during blasting operations at the Jwaneng Diamond Mine in Botswana. Using 120 production blasts and ten input parameters, we trained several models: ANN, RF, ANN-RF and other hybrid baselines PSO-ANN, PSO-ELM, ANN-SVR, PSO-XGBoost and GA-ANN . The ANN-RF ensemble achieved the best test performance (R2 = 0.956, RMSE = 0.315, MAE = 0.250, and VAF = 95.5 for fragmentation; R2 = 0.930, RMSE = 0.380, MAE = 0.302, VAF = 92.5 for PPV). Tree-SHAP analysis identified powder factor and burden as dominant fragmentation drivers, and burden, charge per delay, and distance as key vibration controls. A projected gradient-descent search on the learned solution surface produced feasible blast settings that increase fragmentation toward approximately 84% while reducing PPV to nearly 0.12 mm/s. This approach allows blasting engineers to interactively vary input parameters within defined constraints to obtain optimal environmental and operational outcomes. The input parameters include spacing, charge per delay, burden, stemming length, powder factor, hole depth, hole diameter, rock factor, distance from the blast point to the monitoring point and blastability index, offering a comprehensive AI-driven framework for precision blast design in open-pit mining.

Waste generated from agricultural activities is anticipated to increase in the future, especially in less developed countries, and this could cause environmental health risks if these wastes are not well managed. The anaerobic digestion (AD) by co-digesting organic waste is a technology used to produce biogas while utilizing biodigestate as a biofertilizer; however, AD requires a lot of water to be efficient, which could pose water challenges to arid areas. This study evaluated biogas production under semi-dry conditions by augmenting the process with a high-water content wild melon and determined the nutrient composition of the resultant biodigestate. Batch studies of AD were performed to evaluate methane potential of the different animal waste using an online and standardized Automatic Methane Potential Test System (AMPTS) II light for approximately 506 h (21 days) at 38 °C. The highest biomethane potential (BMP) determined for mono and co-substrate digestion was 29.5 NmL CH4/g VS (CD) and 63.3 NmL CH4/g VS (CMWM), respectively, which was calculated from AMPTS biomethane yield of 3166.2 NmL (CD) and 1480.6 NmL (CMWM). Water-displacement method was also used to compare biogas yield in wet and semi-dry AD. The results showed high biogas yield of 8480 mL for CM (mono-substrate) and 10,975 mL for CMCC in wet AD. Semi-dry AD was investigated by replacing water with a wild melon (WM), and the highest biogas production was 8000 mL from the CMCC combination augmented with WM. Generally, in wet AD, co-digestion was more effective in biogas production than mono-substrate AD. The biodigestate from different substrate combinations were also evaluated for nutrient composition using X-ray Fluorescence (XRF) analysis, and all the samples contained fair amount of essential nutrients such as calcium (Ca), phosphorus (P), potassium (K) and microelements such as chloride (Cl), magnesium (Mn), iron (Fe), zinc (Zn). This study successfully implemented semi-dry AD from co-digested animal wastes to produce biogas as an energy solution and biofertilizer for crop production, thereby creating a closed-loop system that supports a circular bioeconomy. In addition, the study confirmed that lowering the water content in the AD process is feasible without compromising substantial biogas production. This technology, when optimized and well implemented, could provide sustainable biogas production in areas with water scarcity, therefore making the biogas production process accessible to rural communities.