Natural fibres such as coir, jute, flax, and hemp have been considered for technical applications. These fibres, though with some desirable qualities such as low density and environmental compatibility, possess the common property of non-uniformity along their length and, as a result, variable diameter and variable cross-sectional area. Several other factors, such as gauge length, fibre species and origin, strain rate, method of extraction of the fibres, porosity and pore size distribution, have been identified to influence the tensile strength of natural fibres and limit their applications in composites. Besides, several authors have used different diameters for the same type of natural fibre, such as coir, resulting in significant inconsistency in the tensile properties. For the same type of coir fibre, and from tensile strength reports from ten authors, an average tensile strength of 120.97 ± 42.30 MPa was obtained. The average number of fibres used in most cases for the tensile test was less than the requirement for natural fibres. All these factors were addressed with the aim of improving the overall properties of natural fibres and their composites.
The effect of using mixtures of palm kernel shell and coconut shell as carburizers for low carbon steel at 950oC on the tensile properties and case hardness was studied. The carburizers were washed, dried, milled and sieved to 150µm particle size. They were mixed in various compositions to serve as carburizers. In each composition, 20wt% of calcium carbonate (CaCO3) was added as energizer. Tensile and hardness specimens were machined from low carbon steel. Seven tensile and seven hardness specimens were subjected to pack carburization process with different compositions of the carburizers, and thereafter quenched and tempered at 450oC for forty five minutes in a heat treatment furnace. The tensile and hardness properties show that better properties were obtained with mixtures of the carburizers compared to the use of single carburizing agent.
In this study, two supervised machine learning models (Extreme Gradient Boosting and K-nearest Neighbour) and four isotropic sky models (Liu and Jordan, Badescu, Koronakis, and Tian) were employed to estimate global solar radiation on daily data measured for one year period at the National Center for Energy, Research and Development (NCERD) at the University of Nigeria, Nsukka. Two solarimeters were employed to measure solar radiation: one measured solar radiation on a tilted surface at a 15° angle of tilt, facing south, and the other measured global horizontal solar radiation. The measured global horizontal solar radiation and the time and day number were used as input for the prediction process. Python computational software was used for model prediction, and the performance of each model was assessed using statistical methods such as mean bias error (MBE), mean absolute error (MAE), and root mean square error (RMSE) (RMSE). Compared to the measured data, it was discovered that the Extreme Gradient Boosting (XGBoost) algorithm offered the best performance with the least inaccuracy to sky models.
Barite is a very important industrial minerals used as weighting material in the petroleum industry. The nature of barite ores, geology of barite ores based on location were discussed. This paper presents top barite producing countries in the world, their production and consumption of barite, as well as their reserve. Despite all the barite deposits in Nigeria, which is approximately 15 million tonnes, it still imports barite from other countries for use in the drilling of oil and gas in Nigeria. This of course brings about unnecessary expenses been incurred by the government of Nigeria. Some of the challenges faced with the mining and processing of the Nigerian Barite were discussed. Proposed solutions to the mentioned challenges were also stated. The main challenge of the Nigerian barite is not with the American Petroleum Institute (API) standard, but the policies which do not favour investors. Investment by private companies into the mineral sector of Nigeria will bring about a lot of revenue to the government, if the right things are set in place. Keywords— Barite, producing countries, low-grade
The authors have retracted this article. After publication, the authors found that they did not have permission to publish the data used in the article.
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