Comparative Analysis of AC and DC Distribution System with Respect to Harmonic Distortion Considering Daily Load Profile

Electrical energy is the most efficient and the cleanest form of energy at the moment that is being transmitted and distributed amongst end-users. From its earlier days, the AC system was preferred as an economical solution for transmission and distribution. However, the development in the power electronics technology and the evolution of highly efficient power electronic converters have established the resurgence of DC power system. Furthermore, the trend is shifting towards DC loads as various energy efficient appliances, such as DC inverter air conditioners, operate on DC nowadays. This further advocates the shift towards the DC power system. This research works is an effort to perform the comparative analysis of AC Distribution System (ACDS) and DC Distribution System (DCDS), with regards to power quality and harmonic distortion in particular. The comparison is performed considering load profile and load variation on daily basis. Simulations are performed in MATLAB. It has been concluded at the end that ACDS is better than DCDS in terms of power quality as total harmonic distortion of the DCDS under the same loading and same load variation during the whole day was significantly higher than that of ACDS.

Dynamics of Stem End Rot Disease of Mango Fruit and its Mangement

Stem end rot (SER) is a fungal disease complex that poses a major threat to the delivery of quality mangoes from Pakistan to export markets. The dynamics of this disease remain unclear, but must be elucidated so that effectiveness of disease management can be improved. The present study sought to describe the infection process and delineate a disease cycle of SER under Pakistani growing conditions. Culturing of symptomatic samples from traditional and good practices blocks revealed colonization of mango fruit by Lasiodiplodia theobromae, Phomopsis mangiferae, Colletotrichum gloeosporioides, Alternaria alternata and Botrytis cinerea, of which L. theobromae was the most prevalent. Fully mature but unripe mango fruits were collected from major mango growing belt of Punjab Province. The fruits were stored in cold storage (12oC; 21 days) and ambient storage (33oC; 9 days). After ripening, fruit under ambient and cold storage revealed that SER was the most prevalent disease. Pathogenicity assay revealed that all the artificially inoculated fungal pathogens were pathogenic. L. theobromae produced larger lesion diameter (74.6 mm) in ambient storage followed by C. gloeosporioides (54.6 mm). In cold storage, maximum lesion diameter (54.6 mm) was observed when spore suspension of L. theobromae was inoculated followed by C. gloeosporioides (37.6 mm). In another study, the relationship between lengths of fruit pedicle with SER disease development was investigated. It was found that retaining a portion of the pedicel on harvested fruit reduced development of SER during the course of ripening, in comparison to fruit from which the pedicel was removed. Histopathology of pedicel attached with mango fruit indicated an extensive distribution of L. theobromae infecting xylem vessels and other tissues. In subsequent research, the efficacy of fungicides - Cabrio Top®, Nativo®, Scholar®, Tecto®, Amistar®, and Sportak®, and plant extracts - ( Peganum harmala, Syzygium aromaticum, Cichorium intybus, Moringa oleifera, Cinnamomum zeylanicum and Coriandrum sativum) at several concentrations was assessed against SER pathogens in vitro and in vivo. Results indicated that Nativo and Cabrio Top at the concentration of 200 and 250 μg/mL, and M. oliefera, S. aromaticum and C. zeylanicum at the concentration of 25 and 50 μg/mL, provided statistically significant suppression of mycelial growth of tested pathogens and SER development.