The troposphere's internal processes are complex and exhibit nonlinear trends, which have a significant impact on the transmission and reception of high-quality signals worldwide. This study used measured monthly climatic data of temperature, relative humidity, and atmospheric pressure for Maiduguri and Sokoto from the National Aeronautic and Space Administration (NASA) over a forty-two-years period (1981 to 2022) to estimate the seasonal tropospheric radio refractivity and examine its variations with other meteorological parameters and refractive index. The refractivity gradiant, effective earth radius, and percentage contribution of the dry and wet term radio refractivity were also examined. According to the results, radio refractivity was found to be highest at the two locations during the rainy season and lowest during the dry season. In Maiduguri, during the rainy season and dry seasons are 361.4837 N-units in August, 272.4506 N-units in March while for Sokoto are 366.7093 N-units in August, 277.1162 N-units in February. For Maiduguri and Sokoto, the wet term (Nwet) contributes to the significant variation with 19.9753 % and 21.1831%, respectively, while the dry term (Ndry) contributes 80.0247 % and 78.8169 % to the total value of radio refractivity. The average refractivity gradients in the studied locations were found to be -42.3746 and -42.3928 N-units/km. Furthermore, it was discovered that Maiduguri and Sokoto had average effective earth radiuses (k-factors) of 1.3697 and 1.3698, respectively. These values implied super refraction propagation condition.

An electrochemical oxidation process with an aluminum-doped copper oxide (Al@CuO) anode was modeled and optimized for the degradation of methylene blue (MB). The Al@CuO anode material was prepared by the thermal decomposition method. X-ray fluorescence (XRF) analysis confirmed the successful deposition of CuO on the aluminum substrate. The influence of current density, electrolysis time, and MB concentration on the performance of the electrochemical degradation of MB was modeled using Box-Behnken design (BBD). The accuracy of the proposed quadratic model by BBD was confirmed with a p-value < 0.0001 and adj-R2 > 0.9. The optimum MB degradation efficiency of 53.23 % was obtained at 80 mg MB concentration, 40 min electrolysis time, and 3.75 V applied current. The kinetics on the MB electrochemical degradation process using Al@CuO followed pseudo first-order kinetics model. These studies revealed that the Al@CuO anode electrode is not a promising anode for the electrochemical degradation of methylene blue.

Hydrogen serves as an optimal fuel for engines. Pure hydrogen engines do not generate carbon monoxide and hydrocarbon emissions; instead, they encounter significant nitrogen oxide emissions. Inner-engine control and outer-engine control are two methods to reduce NOx emissions. Outer-engine control primarily mitigates NOx emissions by selective catalytic reduction (SCR), a process that has been extensively researched. Nevertheless, there is a paucity of research about NOx emission regulation in pure hydrogen engines via internal engine management. This work utilised the closed homogeneous reactor (CHR) in Chemkin Pro to model the primary NOx emission control within pure hydrogen engines. The findings indicate that single exhaust gas recirculation (EGR) reduces NOx emissions by 45.3% at an EGR ratio of 20%, suggesting that the reduction in NOx emissions is not substantial. Nonetheless, EGR combined with lean burn reduces NOx emissions by 96.31% at a λ of 1.4 and an EGR ratio of 20%, resulting in ultra-low NOx emissions from pure hydrogen engines. In comparison to single EGR and EGR combined with lean-burn, SNCR is more effective for NOx emission control. An NH3 ratio of merely 10% can reduce NOx emissions by 96.32% in pure hydrogen engines, whilst a 15% NH3 ratio can attain zero NOx emissions in pure hydrogen engines without necessitating a high λ value or EGR ratio. It is essential to precisely regulate the NH3 ratio in the cylinder; otherwise, residual NH3 may be generated, leading to environmental pollution.