A Note on Stress Function Discontinuities in Plane Plastic Bending and Torsion

The variational and differential equation formulations of the stress function problem for combined plane bending and torsion of a fully plastic material are discussed. The nature of discontinuities to be expected as well as the actual degree of correspondence between the two formulations is determined. A modification of the variational integrand reveals the pattern of discontinuity which is then completely determined. This disposes of some mathematical issues raised by Steele and Imegwu in their relaxation numerical analysis of the problem

Flow field and Reynolds stress distribution in low turbulance natural convection in a triangular cavity

Triangular enclosures are typical configurations found in attic spaces of residential as well as industrial pitched-roof buildings. Previous studies on airflow within such spaces have focused on the laminar range. A numerical study has been carried out for time-dependent, two-dimensional low turbulence natural convection of air contained in the attic of a pitched roof of triangular cross-section. Two sets of boundary conditions have been considered: enclosure heated from the inclined walls and from the horizontal base wall, for aspect ratios (AR) of 0.33 ≤ AR ≤ 1.73 for Rayleigh number (Ra), 109 ≤ Ra ≤ 1011. In this paper, the flow field and Reynolds stress distribution are presented for the isothermal and isoflux cases

Comparison of bagged tomato storage characteristics under two different evaporative pad materials

Tomatoes are important in the agricultural sector as they serve as raw materials for the production of value added products. The aim of this study was to compare bagged tomato (tomato in sealed Ziploc bags storage characteristics using two evaporative pad materials (charcoal and river sand). River sand and charcoal were used as cooling pads with storage under ambient conditions being the third treatment (control). Each treatment had two replicates. Temperature, Relative humidity, Cooling efficiency, Weight, Firmness and Colour assessment were determined throughout the test period and the results were subjected to Analysis of Variance [ANOVA]. Means were separated using DMRT at 5 percent level of significance. Result from storing bagged fresh tomatoes under both media showed that a cooling chamber filled with charcoal as absorbent material with uninterrupted water supply performed best in the storing of tomato fruit when compared to tomatoes stored under ambient conditions or with river sand as evaporative media. It is therefore recommended that further studies should vary the use of different absorbent materials with respect to availability, cost, and durability among others. Comparison can also be further made between tomato storage under bagged and unbagged condition

Design and fabrication of a double- chamber solar dryer

Object of research: This paper discusses the design and construction of a modified, cost effective solar dryer for use by the average Nigerian farmer or agri-business entrepreneur. Investigated problem: Local farmers often have a lot of difficulties in properly drying harvested agricultural produce for storage and processing purposes, safely and efficiently due to capital constraints. There was therefore a need for an efficient, low cost solar dryer design to aid in this pursuit. Methodology: The designed dryer is a passive dryer that makes use of heat energy tapped through glass collectors placed over the drying and air inlet chambers respectively. The dryer was designed and constructed with carefully selected, inexpensive materials with dimensions of 40cm x 40cm x 60cm for the drying chamber and dimensions of 10cm x 80cm x 40cm for the heating chamber. The glass collectors (4mm thick) were inclined at an angle of incidence of 17.26°. Okra slices were used to test the performance of the dryer. Results / Area of practical use: The study yielded a low cost (€145.60) modified solar dryer capable of drying agricultural produce in a safe and clean way. During eight (8) hours of drying under a temperature range of 39 °C – 45 °C, the initial weight of the okra slices reduced from 150g to 9g, 9g, 10g and 9g on each of the four trays of the drying chamber respectively. Local farmers and agripreneurs will be encouraged to make use of this clean alternative of drying food produce without the drawbacks from regular sun drying. Conclusion: There is need for more work to be done in terms of installation of solar panels to enhance dryer performance. More work should also be carried out on tests during the dry season for increased dryer efficiency

Effect of coconut coir and poultry manure on the growth and yield of Amaranthus hybridus L.

This study was carried out to determine the effect of coconut coir and poultry manure on the growth and yield of amaranthus hybridus L.  The parameters accessed are germination percentage, growth performance and yield of Amaranthus hybridus L. The experiment was laid out in Completely Randomized Design consisting of two (2) treatments and control, each with fifteen (15) replicates. The data collected were subjected to Analysis of Variance (ANOVA). The means were further separated using Least Significant Difference (L.S.D) where significant differences were observed. The data collection from the experiment was taken for seven (7) weeks. The results showed that coconut coir had the highest mean value of 14.71 mm, 10, 0.4290mm and 3.600mm for the plant height, for number of leaves, stem girth, and for weight of yield (harvested Amaranthus hybridus L.) respectively at seventh (7th) week. The results of analysis of variance indicated significant differences in plant height, number of leaves, and stem girth in coconut husk among treatments applied at 0.05 level of  probability. The results obtained for analysis of variance for (yield) weights of harvested Amaranthus hybridus L (yield) revealed significant difference in different media with the value of (2.000g of for top soil, 3.600g for coconut coir and 2.267g for poultry manure) among  treatments applied at 0.05 level of probability

Comparision of cowpea (Vigna unguiculata) storage characteristics under different storage media and conditions

This research was carried out to compare cowpea storage characteristics using different storage medium, under different weather conditions. Several technologies reputedly attribute losses of stored cowpea grain to bruchid beetles. Comparison of these different postharvest storage methods can provide the basis for deciding which performs best in terms of weight loss, pest infestation and nutritive losses. Proximate analysis was carried out before, during and after storage with two month intervals, over four months of storage in three storage media: a seed gene bank, modified anthill rhombus, and a covered container (the control). Temperature, humidity, and weight values (for moisture content analysis) were taken during the storage period. Results showed that the cowpea seed sample, stored in the AC section of the seed gene bank, proved to be more tolerant to pest infestation compared to seed samples, stored in the Modified anthill rhombus, and seed samples, stored under ambient conditions. The cowpea seeds weight recorded reduction after infestation, which also was significant when compared to the non-infested seeds in the seed gene bank. Proximate analysis of cowpea seeds after infestation showed a decrease in the value of carbohydrate content and protein, while crude fibre, moisture, fat and total ash recorded increased. Further research should be carried out on cowpea storage under different weather conditions, with and without insecticide, and using more media such as jute bags, etc. There should also be an extension of the storage period more than the four month

Neural network-based electronic nose for cocoa beans quality assessment

In this study, a prototype electronic nose was developed for monitoring the quality of cocoa beans.  The system comprises an array of metal-oxide semiconductor sensors and an artificial neural network pattern recognition unit.  The results obtained from assessment experiments on cocoa beans show good agreement with those obtained from the traditional ‘cut test', recording up to 95% accuracy.  This investigation demonstrates that the electronic nose technique holds promise as a successful technique in evaluating the quality of cocoa beans for industrial processing

Estimating Tree Height and Volume of Gmelina arborea and Three other Tree Species in Plantations of South-West, Nigeria

This study explores the estimation of stand structure of Gmelina arborea and three other tree species in two plantations, in Ibadan, South West Nigeria, with the primary objective of estimating plot – level mean tree height, merchantable tree height, and volume of Gmelina arborea, Terminalia montalis, Tectona grandis, and Triplochiton scleroxylon. The number of tree species and the volume of wood in the two selected plantations were determined. Random sampling method was adopted in carrying out the assessment of the stand structure. Each plantation was divided into three plots of dimension 32mx32m. Twenty (20) stands were selected randomly in each plot, hence sixty (60) stands in each plantation. Quantitative data were taken on: Diameter at breast height (DBH), Total tree height (TTH), Basal area (BA) and Total volume (of wood) (TVOL). A total of three species were encountered in the two study area; the family Verbenaceae has the highest tree species (75%) in the two plantations. During the assessment of the tree species in both plantations, the results revealed that majority of the trees’ (68%) diameter were within 10-20cm, and the number of tree species in the upper diameter class (>60cm) (20%) were considerably small. Trees in the Gmelina plantation had on average, lower merchantable heights than those in the College Arboretum, despite having higher total tree height, diameter at breast height, basal area, and area volume. Inventory analysis of these plantations will establish a base-line information about the stand, point out possible improvements to the management plan and provide information on the volume of merchantable logs that can be extracted from the stand