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An integer programming approach for university timetabling: a case study in Wayamba University of Sri Lanka
(University of Peradeniya , Sri Lanka, 2014-07-04) Prabodanie, R. A. R.
A binary integer programming model is proposed in a case study of university timetabling in the Faculty of Applied Sciences, Wayamba University of Sri Lanka. Binary variables which are used as the building blocks of the model are defined with fewer dimensions to reduce the model size of a large problem. Some binary matrices are used to describe the relationships between the courses and students, and courses and teachers. Staff and student preferences and various types of relevant constraints such as completeness (required hours), uniqueness (absence of overlaps), consecutive sessions, and resource capacities are included in the model. The problem is formulated using MS Excel and solved using OpenSolver which is a free solver available as an Excel add-in. It was experienced that the modelling capabilities of Excel significantly contribute to the efficiency of the timetabling process. The model was applied to produce faculty timetables for level-II and level-III courses simultaneously. The produced timetables highlighted some inefficiencies in the manually prepared timetables that are currently used. The results clearly showed that a currently used 49-hour timetable can be reduced to a 42-hour timetable without violating any applicable constraints. The IP model and the solver program were extremely capable of finding non-overlapping course combinations which can be scheduled in parallel. Thus the proposed IP model can be used to generate reliable timetables avoiding several difficulties faced by the students and staff owing to inefficient timetables.
Investigating spatial characteristics of tree species in Sinharaja Forest dynamic plot using binomial mixture models
(University of Peradeniya , Sri Lanka, 2014-07-04) Petangoda, M. A.; Manoj, C.; Wijekoon, P.; Gunathilake, L. A. U. N.
Individual tree species often exhibit heterogeneous behaviour in forest communities. Ecological and environmental factors such as topography, climate, soil nutrients and seed dispersal directly influence the occurrence and growth of the tree species. In general, all these factors are continually varying or unevenly distributed throughout the forest land. Investigating spatial characteristics of individual tree species in forest community would be advantageous for ecologists to acquire a better understanding on species richness and diversity of the forest. However, direct investigation of spatial characteristics often tends to make disturbances to the species population. To study the spatial characteristics, the two measures; “Degree of Spatial Heterogeneity” and “Mean Species Occurrence” of individual tree species are used in literature. The degree of spatial heterogeneity measures the uneven distribution of each species within an area. The mean species occurrence is the mean number of each species in a given area. The objective of the present study was modelling spatial distributions of 239 individual tree species existing in 25 hectares Forest Dynamic Plot (FDP) in the Sinharaja World Heritage Site, using Beta-Binomial distributions as proposed in the literature. For the cases where the Beta-Binomial fails, a novel method is introduced based on Generalized Beta Binomial distribution. Further, the degree of spatial heterogeneity and mean species occurrence of 239 individual tree species are measured using the estimated parameters of the fitted models. By following the method given by Shiyomi 𝘦𝘵.𝘢𝘭. (2000) to identify “high”, “moderate” and “low” mean occurrences, it was noted that there were only 2.97% of the individual tree species with high mean occurrence, 77.23% of the individual tree species with low mean occurrence, and 19.80% of individual tree species having a moderate occurrence in Sinharaja FDP. Out of 239 individual tree species, 198 tree species were adequately modelled using the Beta-Binomial distribution. Of the rest, 15 tree species were recognized as rarely occurring species, and 18 species were best fitted with Gaussian Hypergeometric Generalized Beta-Binomial Distribution (GHGBB). Among the modelled tree species the percentage occurrence of AGROHO, MESUNA and PALATH is 8.42%, ABARBI, BOMBCE and EUONWA is 35.64%, and PRUNWA, SEMEWA and MEMERY is 55.94% which exhibit high spatial heterogeneity, moderate spatial heterogeneity, and low spatial heterogeneity respectively. It can be further noted that most of the species with low occurrence are spatially less heterogeneous, and there were only a very few number of species having a very high mean occurrence and are highly spatially heterogeneous.
Performance of different rainguard types on rubber [Hevea brasiliensis (A. Juss.) Muell. Arg.]
(University of Peradeniya , Sri Lanka, 2014-07-04) Navarathne, H. M. N. D.; Senevirathna, P.; Jayasinghe, H. A. S. L.
Rubber tree in general, is tapped for latex once it has reached a tappable girth. Tapping is a specialized method by which, controlled wounding of the bark is done to open the latex vessels to harvest latex from the rubber tree. Due to the rain effect, tapping panel remains wet for long periods even after rain has ceased. It prevents the tapping of rubber trees during the rainy season and also leads to the loss of normal tapping days and infections in the tapping panel. Wetting of tapping panels can be minimized with the use of rain guards. Though there are many new technologies available to increase the production, the only rapid way to increase the production by about 20-30 % within a couple of months is the use of rain guards. This study was focused to compare the performance of Apron type rainguards which were used in early 1970 with Kissan type and Belgium type rainguards. Randomized Complete Block Design was adopted as an experimental design. Thousand trees with four main blocks were selected for this study. Each tapping block consisted of 250 trees and every main tapping block was sub-divided into four plots. Each tapping block consisted of three rainguards types as well as control. All trees were tapped at the half spiral alternate daily (1/2 S d/2) system with no stimulation during the two months period. Mean numbers of tapping days were recorded for the four treatments. The analysis of variance on rubber yield measured over the experimental period indicated significant differences between the types of rainguard (P=0.05) when girth is considered as a covariate. The Kissan type (K) gave the highest yield followed by the Apron type (AP) though did not differ significantly. The yields of both K and AP differ significantly with Control (C). However, the yields observed for Belgium type (BC) and C were not statistically different. Sealant cost and the polythene cost were the major cost components of rainguards which is about 65 % of total cost of a rainguard. At the current price of semisolid sealant (Rs. 125.75 /kg), use of AP and K types is more profitable than Belgium type. At current price of polythene (Rs.310 /kg), K type is cheaper than the cost of the AP type. Labour wage for the rainguard per tree is Rs. 11.46 including fixing cost. However, most of the smallholders may not be affected by high labour cost as they could use family labour. A net profit increment of Rs. 23,628 / ha has resulted from the use of AP type rainguard for the two month period, whereas Rs. 24,618 and Rs. 10,550 were gained from K type and Belgium type, respectively. The return on investment is higher in AP and K type rainguards compared to that of Belgium. It is recommended to conduct the study for one year period to account the variability in rainfall and to consider the maintenance cost for rainguard and their shelf lives in estimating the profit.
Morphological and growth variations of 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 isolates associated with anthracnose disease of banana
(University of Peradeniya , Sri Lanka, 2014-07-04) Manahari, P. D. D. P.; Vengadaramana, A.; De Costa, D. M.
Anthracnose is a highly destructive post-harvest disease of banana caused by the fungal pathogen 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 𝘮𝘶𝘴𝘢𝘦. The present study was conducted to determine the growth and morphological variations among 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 spp. associated with anthracnose disease of banana. Sixteen 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 isolates, including 𝘊. 𝘮𝘶𝘴𝘢𝘦 which were isolated from a range of banana cultivars showing typical anthracnose symptoms and collected from different locations were used for the study. Colony characteristics, growth rate, spore dimensions and sensitivity to fungicides (𝘪𝘯 𝘷𝘪𝘵𝘳𝘰) were used to determine morphological variations of the fungal isolates. Out of the sixteen 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 isolates, four isolates were identified as 𝘊. 𝘨𝘭𝘦𝘰𝘴𝘱𝘰𝘳𝘪𝘰𝘪𝘥𝘦𝘴 and another four were identified as 𝘊. 𝘢𝘤𝘶𝘵𝘢𝘵𝘶𝘮 based on colony and spore morphology. Colony growth rate was highly variable among the tested isolates of 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 and the highest growth rate was shown by 𝘊. 𝘮𝘶𝘴𝘢𝘦. Recommended dosage of the fungicide Homai (Thiophanate-methyl 50% + Thiram 30% WP) completely inhibited the mycelial growth of all isolates tested 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰. However, the recommended dosage of Daconil (Chlorothalonic 500g/L) did not completely control any of the isolates of 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 tested under 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰 conditions. The findings revealed that morphological and growth variations exist among the 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 isolates recovered from anthracnose developed-banana fruits.
Performance of liquid stationary culture of banana under CSUP technique
(University of Peradeniya , Sri Lanka, 2014-07-04) Rajapaksha, A. P. B. S.; Peiris, S. E.; Peiris, B. C. N.
Production of planting material of horticultural crops through micropropagation is limited due to the high production cost. This study was conducted with the objective of investigating the cost reduction applications in micropropagation to facilitate production of horticultural crops at commercial scale. The sterilizing technique (CSUP), which replaces the autoclave and the laminar air flow cabinet with the use of NaOCl solution is a promising technique to reduce the cost of production. Agitated liquid cultures, which cuts down the cost for agar, allow rapid multiplication in micropropagation and thus, the time required for multiplication is reduced along with many other advantages. Maintaining a shaker is also an additional cost. Therefore, in this experiment liquid stationary cultures were used along with CSUP method for the micropropagation of an economically important crop, banana. Multiplication stage of banana was investigated with the use of six treatments to find the compatibility of CSUP method for liquid cultures within one sub culture period. The experimental design was a completely randomized design (CRD). Four treatments with the CSUP concentrations (5, 10, 15 and 20 %) as the sterilization method with liquid cultures and two conventional applications as autoclaved liquid cultures and 10 % CSUP with semi- solid (agar) cultures were used. Contamination percentage of each treatment, number of shoots and dry weight after multiplication were assessed. In liquid medium, a raft was used to anchor the plants, which made out of disposable plastics with no cost. Hundred percent contamination free cultures were obtained from CSUP treated liquid cultures. According to 𝘊𝘩𝘪- square frequency distribution test, higher shoot number was achieved in the liquid medium with 5 % CSUP treated cultures, while the lowest shoot number was reported for the semi-solid CSUP treated treatment (p = 0.0001). The highest dry matter accumulation was found in the treatment with liquid medium sterilized with 15 % CSUP and significantly lower dry matter was observed in semi-solid medium sterilized with 10 % CSUP (p<0.0001). The higher dry matter gave lower shoot number with comparatively larger shoot size, while the shoots with higher number were smaller in size. Further investigations are needed to measure the level of toxicity in the treatments, because there were different observations in some of the CSUP concentrations. Since the CSUP technique with liquid cultures gave a significantly higher shoot number and dry matter with no contaminations, CSUP method can be applied in liquid culturing of banana with modifications (rafting) during the multiplication stage. This method is a low cost alternative for the use of semi solid agar medium.