IRA Academico Research IRA Academico ResearchIRA International Journal of
The journal regularly reviews the works on basic sciences, applied sciences, agriculture science, and food & nutritional sciences.
ISSN 2455-4499 | DOI 10.21013/jas
CAS CODEN: IJASNG | OCLC No. 953515792 | ZDB No. 2861287-5
Publication Frequency: Quarterly
This work presents a study of the influence of temperature on the series and shunt resistance of a silicon solar cell under polychromatic illumination. First, a theoretical study allowed us to give the expression of the density of minority carriers. From this expression of the minority carrier density, we determined the expression of the current density and the photovoltage. The expressions of the short circuit current density and the open circuit voltage were also determined. Under polychromatic illumination and temperature, we find that the short circuit current Icc and the open circuit voltage Vco have quasi-linear behaviour. The results obtained show that the series resistance Rs is of the type with a positive temperature coefficient, while the shunt resistance Rsh is of the type with a negative temperature coefficient.
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The main aim of this study was to assess and mapping of land cover (LC) / land use (LU), using Remote Sensing (RS) and Geographical Information System (GIS) techniques in Elnor natural forest reserve, Blue Nile state, Sudan. The study also attempted to update some information in the study area such as LC and contour map by using different methods of data transformation and analysis such as Normalized Different Vegetation Index (NDVI), interpolation and supervised classification. Thematic Mapper (TM), Landsat Enhanced Thematic Mapper (ETM+) and Landsat8 images were used in LCLU changes and supported by field observation. The study area was affected by cutting the mother trees and overgrazing. Closed forests during 2000, 2010 and 2019 decreased from 36.9%, 28.5% and 18.7% respectively. Moreover, the total area of bare soil increased by about 14.4%, 47.2% and 39.7% in 2000, 2010 and 2019 respectively. The open forest (grassland) decreased from 48.7% in (2000) to 41.7% in (2019). A Digital land cover map was produced using LCCS software; depending on the fieldwork data, they were found in four Classes. Mixed Woodland Single Layer, Semi-Deciduous Shrub land with Open Herbaceous, Open Grassland, Single XII Layer and Hardpans. The study revealed that there are some indicators of land degradation during the last 20 years (2000, 2010 and 2019) and is expected to continue increasing unless serious measures are carried out to reduce it.
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Jatropha curcas seed oil can be used for numerous purposes including fuel, soap and cosmetics. Better quality oil is obtained by cold pressing, the effectiveness of which is unfortunately limited by a low extraction rate. The objective of this study was to optimize cold hydraulic extraction parameters of Jatropha curcas seed oil by increasing the oil recovery and characterising the extracted oil. The key extraction parameters (dwell time, pressure, compression speed, and press cage charge) were determined using a laboratory hydraulic press. The results show that the unhulled and dehulled seeds contained 5.1 and 2.9% moisture, as well as 33.6 and 51.7% fat, respectively. Under the optimal operating conditions and at ambient temperature (25 °C), the oil recovery from whole (crushed) material was 38.2 (42.5)% unhulled seeds and 71.3 (69.5)% dehulled seeds. The physicochemical characteristics of cold-extracted Jatropha oil were 10ppm phosphorus, 1.9 ppm iron, 0.0 ppm copper, 0.15% water-volatile matter, 0.918 (15 °C) density, and 37.72 cSt (37.8 °C) kinematic viscosity, respectively. In conclusion, the optimized cold hydraulic extraction of jatropha seed oil leads to high oil recovery and good oil quality suitable for industrial applications.
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We propose, in this article, the study of the phenomena of energy storage in a wall in frequency dynamic mode. The optimal heat exchange coefficient and the maximum pulsation were determined from the temperature and flux density curves, respectively. An electric-thermal analogy made it possible to determine the phenomena of energy storage from Bode diagrams of thermal capacity and thermal inductance.
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