Cracks are surface or subsurface fissures that develop in a material. Propagation energy derived from mechanical, thermal, chemical, and metallurgical effects, or a combination of these may influence crack initiation and growth. Various types of cracks exist in metals and can be categorised as cooling, solidification, centreline, crater, grinding, pickling, heat treatment, machining tears, plating, fatigue, creep, stress corrosion and hydrogen cracks. Cracks can grow and lead to complete fracture of the component posing significant threats to component life and may lead to serious injuries or loss of life. Brittle fracture in metals occurs with little or no visible warning. Discovery of any cracks warrants immediate interventions to arrest the cracks before they propagate to the point of fracture. Several crack detection and repair methods in metals have been developed, characterised and validated through research. This paper reviews the repair techniques of cracks in metals

Enzymatic hydrolysis of lignocellulose materials has been identified as the rate-limiting step during anaerobic digestion. The application of pretreatment techniques can influence the biodegradability of lignocellulose substrate. This study combined Fe₃O₄ nanoparticles, which serve as a heterogeneous catalyst during anaerobic digestion, with different particle sizes of Arachis hypogea shells. Batch anaerobic digestion was set up at mesophilic temperature for 35 days. The results showed that 20 mg/L Fe₃O₄ additives, as a single pretreatment, significantly influence biogas and methane yields with an 80.59 and 106.66% increase, respectively. The combination of 20 mg/L Fe₃O₄ with a 6 mm particle size of Arachis hypogea shells produced the highest cumulative biogas yield of 130.85 mL/gVS_added and a cumulative methane yield of 100.86 mL/gVS_added. This study shows that 20 mg/L of Fe₃O₄ additive, combined with the particle size pretreatment, improved the biogas and methane yields of Arachis hypogea shells. This result can be replicated on the industrial scale to improve the energy recovery from Arachis hypogea shells.

Jet Impingement Technology (JIT) is a heat transfer enhancement technique. Available literature soundly confirm its wide applications in the cooling of combustion chambers, critical parts of turbines, glass technology, electronic components, drying of paper and textile materials, drying of biomaterials and food preservation. The technology has interesting fluid dynamics and heat transfer properties. Its relative simplicity and low cost, abundance of air, generation of high heat transfer and faster freezing rates have made it a subject of extensive investigations. Several investigations on jet impingement quick food freezing and cooling systems which range from visualization, experimental, computational simulations and or numerical analysis, factorial and mathematical models have been studied. This paper reviews the governing parameters of the jet impingement quick food freezing and cooling systems