Gaussian beam divergence using paraxial approximation

Gaussian beam intensity follows a normal distribution curve in free space. As it propagates, the divergence and the width increase with distance. Using paraxial approximation, the effect of the distance on the intensity, width, radius of curvature and divergence was investigated. Matlab software was used for characteristics parameters calculation. The divergence angle range (26.67o≤ θ ≤35.85o) was obtained at a distance between 3mm and 4mm, and compared with the divergence angle range (43o≤ θ ≤53o) obtained experimentally for the distance between 3mm and 4.5mm. The result obtained in this work indicates smaller angles of divergence that can produce a better beam quality and intensity. Finally, this will serve as a great importance for application such as pointing, free space optical communication etc.Keyword: Gaussian beam, Paraxial approximation, Beam divergence, Normal distribution curve

Effect of operating parameters on decortication of Jatropha curcas fruits

A Jatropha decorticator was designed, fabricated and its performance evaluation was carried out. Measured performance parameters included Decorticating efficiency, Cleaning efficiency, Percentage seed loss, Mechanical damaged index, and Decorticating performance index. A 5 × 2 × 2 factorial experiment in Completely Randomized Design was used to investigate the performance of the machine. The highest Decorticating efficiency, Cleaning efficiency and Decorticating performance index were 93.25%, 93% and 91.28% respectively. The lowest Percentage seed loss and Mechanical damage index were 1.49% and 1.19% respectively. More seed loss was experienced as the machine speed increased. Also, seed breakage was recorded at higher machine speed. Hence, biodiesel production from Jatropha would be highly productive and sustainable with this decorticating machine

Development and Preliminary testing of a Mixing and Pelletizing Machine for Livestock Feeds Production

Agro crop residues such as cereal, stovers and fodders do not individually contain all the nutrients required for the optimum growth of ruminant animals, hence, the need to bring them together to form a balanced diet. A mixing and pelletizing machine was designed and constructed to mix and pelletize pulverized feed materials (elephant grass, wheat bran, cassava peel, molasses, cassava starch, bone meal, maize stover and groundnut cake). The mixing unit consists of the mixing hopper and a mixing chamber that houses the mixer shaft and the mixing paddles while the pelletizingunit consists of the pelletizer hopper, pelletizing barrel, a shaft with worm thread and die perforation as outlet for the pellets. A preliminary performance test was carried out on the machine to determine the effects of binder condition and moisture content on the throughput capacity and pelletizing efficiency. Three levels of binder conditions (0 kg, 0.5kg and 0.9 kg of molasses) and five levels of moisture contents (20, 22, 24, 26 and 28% (dry basis)) were used. The results showed that the highest throughput capacity and pelletizing efficiency were 116.12 kg/h and 86.76 % at a moisture content of 26 % (db) respectively. From the proximate analysis done, samples with 0.9 kg molasses generally had the highest amount of ash content, crude fibre, crude protein and crude fat. This machine would enhance the availability of nutritious pelletized feedstock for ruminant animals all year round

Estimation of soil water evaporative loss after tillage operation using the stable isotope technique

Application of stable isotopes in soil studies has improved quantitative evaluation of evaporation and other hydrological processes in soil. This study was carried out to determine the effect of tillage on evaporative loss of water from the soil. Zero tillage and conventional tillage were compared. Suction tubes were installed for soil water collection at the depths 0.15, 0.50, and 1.0 m by pumping soil water with a peristaltic pump. Soil water evaporation was estimated using stable isotopes of water. The mean isotopic composition of the soil water at 0.15 m soil depth were -1.15 parts per thousand (delta O-18) and -0.75 parts per thousand (delta D) and were highly enriched compared with the isotopic compositions of the site precipitation. Soil water stable isotopes (delta O-18 and delta D) were more enriched near the surface under zero tillage while they were less negative down the profile under zero tillage. This suggests an occurrence of more evaporation and infiltration under conventional then zero tillage, respectively, because evaporative fractionation contributes to escape of lighter isotopes from liquid into the vapour phase leading to enrichment in heavy isotopes in the liquid phase. The annual evaporation estimated using the vapour diffusion equation ranges from 46-70 and 54-84 mm year(-1) under zero and conventional tillage, respectively, indicating more evaporation under conventional tillage compared with zero tillage. Therefore, to reduce soil water loss, adoption of conservation tillage practices such as zero tillage is encouraged