The incorporation of waste materials into cementitious binders serves as a strategy to diminish waste volume and lower carbon emissions. This study presents an in-depth evaluation of calcium carbide residue and coal fly ash as alternative binders. The assessment of raw materials emphasized their chemical composition and potential for pozzolanic reactions. Based on these factors, the optimal ratio of Ca/(SiO₂ + Al₂O₃) in the raw materials was determined to be 1.5. Therefore, this study was designed to vary the raw material composition with a CaO/(SiO₂ + Al₂O₃) ratio ranging from 1.7 to 0.9. Upon investigating the effect of the raw material proportion on the compressive strength of pastes and mortars, the composition yielding the highest compressive strength was selected for its potential application as a stabilizer for loess soil. A mixture of calcium carbide residue and coal fly ash with a Ca/(SiO₂ + Al₂O₃) ratio of 1.5 resulted in the highest compressive strength at long curing periods in both pastes and mortars. Mineralogical and microstructural analyses revealed several products, beyond those formed from the pozzolanic reactions, that occurred and enhanced the compressive strength of samples. The highest performing mixture of carbide residue and coal fly ash was then used to stabilize loess soil at 10–25 wt%. The unconfined compressive strength, along with mass and strength loss due to wetting and drying cycles, was also studied. It was observed that the unconfined compressive strength of the stabilized soils remained consistent after six wet-dry cycles but decreased after twelve cycles due to microcracks. The findings suggest that carefully designed mixtures based on the chemical interactions of calcium carbide residue and coal fly ash can offer a sustainable, efficient approach for soil stabilization, potentially revolutionizing construction practices.

This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm³, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm³, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm³. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz.

Low rural electrification rate is a major problem, and continue posing huge challenges especially in remote areas. It was found that Farafenni town is present in a region with the high solar radiation values (4.5–7 kWh/m2/day) in all year round, making it a suitable town for PV power plant investments. 1 MW PV power plant was studied to evaluate the feasibility between crystalline Si (c-Si) and thin film (CdTe) modules by varying the feed in tariffs (FIT). The present FIT of 0.24 US$/kWh showed that CdTe modules present not only higher NPV (2,053,869 US$), IRR (7%), BCR (1.60), but also shorter PBP (9.48 years) values than those values of the c-Si modules with NPV (1,189,576 US$), IRR (4%), BCR (1.30) and longer PBP (11.68 years). Based on technical and economic assessments of the c-Si and CdTe PV power plants, the CdTe PV power plant presented the reasonable technology for rural electrification in The Gambia