http://ir.lib.seu.ac.lk/handle/123456789/3237 Tue, 14 Apr 2026 21:24:58 GMT 2026-04-14T21:24:58Z http://ir.lib.seu.ac.lk/handle/123456789/3323 Title: A Study of sound absorption coefficient of natural fiber samples, coir fiber and rice dust at dry and wet conditions Authors: Weerasuriya, W.A.A.W.P.; Zainudeen, U.L.; Priyadharshana, P.A.N.S. Abstract: Noise control and its principles play an important role in creating an acoustically pleasing environment. This can be achieved when the intensity of sound is brought down to a level which is not harmful to human ears. Absorption, isolation, vibration isolation and vibration damping are four basic principles employed to reduce noise. The most recognized technique is sound absorption on the materials itself. The main aim of this work is to investigate the sound absorption coefficient in impedance tube standing wave ratio method using two natural fiber samples coir fiber and rice dust. The experimental setup was constructed newly to measure the sound absorption coefficient. Accuracy of the constructed experimental setup was examined by using a standard material called as glass wool sample. The experimental values of sound absorption coefficient of standard material agreed well with the values provided in the datasheets under ASTM C-423 standards, demonstrating the capability of the experimental setup to use for the measurements. The samples used for this study, coir fiber and rice dust are heavily wasted, and freely available as a natural materials in Sri Lanka. Absorption coefficients were measured in dry form and wet form separately. Both materials got wet till their maximum level. Results obtained show a significant variation in the absorption coefficient with sample condition. The sound absorption coefficient decreases when the relevant material got wet. Number, size and pore type are found to be important factors in determining the sound absorption mechanism in porous materials. Sound must enter the porous material, meaning that at the surface of the material there should be enough open pores to allow this to happen. As the materials used have porous surfaces, they exhibit a natural condition to retain water inside its cavities. In case of moisture conditions, the empty spaces will be filled with water. It alters the sound absorption characteristics, as the water entraps the air voids or, at least, reduces their volume. Tue, 28 Nov 2017 00:00:00 GMT http://ir.lib.seu.ac.lk/handle/123456789/3323 2017-11-28T00:00:00Z http://ir.lib.seu.ac.lk/handle/123456789/3311 Title: Leaf trait and growth parameter relationship of three greenhouse grown dry zone tree species at seedling stage Authors: Rizvi, E.M.J.M.; Mafaziya Nijamdeen, T.W.G.F.; Samsar, A. Abstract: Various plant traits are used to determine plant growth and development. Variation in plant traits and there associations within and among species, is associated with many important ecological processes at a range of scales. These traits could be used in restoration ecology to determine the competition and performance of introduced plant species. Leaf traits are among the widely used. This study was performed to compare the different leaf traits of three dry zone tree species i.e. Berrya cordifolia, Ficus racemosa and Terminalia arjuna to be used as performance indicators in restoration. Leaf parameters (leaf number, area and dry weight) and root and shoot dry weights were recorded of eight month old seedlings, in triplicates per species, grown under greenhouse conditions and required traits i.e. LMA (leaf mass per unit area), SLA (specific leaf area – leaf area per unit leaf mass) and LMF (Leaf Mass Fraction, fraction of plant biomass allocated to leaves) were derived. Data were analysed using one way ANOVA and Turkey’s pair wise comparison and regression analysis. No significant different was found among species in their growth status apparently due lack of competition among them. However, tested leaf traits, both raw and derived, showed significant differences among the species and a particular pattern were observed between leaf trait verses growth parameter relationships. The correlation shifts from raw leaf parameters to derived leaf parameters and from LMA and SLA of mature leaves to those of composite leaves with increase of LMA. Further studies using mature plants and plants from different environments are underway to test the behavior of these traits. Tue, 28 Nov 2017 00:00:00 GMT http://ir.lib.seu.ac.lk/handle/123456789/3311 2017-11-28T00:00:00Z http://ir.lib.seu.ac.lk/handle/123456789/3310 Title: A study of soluble phosphate content in animal wastes Authors: Nawas, M.F. Abstract: Fertilizers are an important factor in modern-day agriculture. Phosphorus (P) is one of the essential and un-sustainable nutrients for plants and animals; but the reserves of phosphate rock-the major source of P, are finite. P rich animal wastes, such as bone meal (BM) and cattle manures (CattleM) are potential P sources in plant production systems. However, the solubility of P and its availability to plants in these forms are in question. We characterized P solubility in BM, CattleM and dairy manure (DairyM) by Hedley fractionation method. Up to 81% of P was water-soluble in DairyM, but only about 3 and 15% was soluble in BM and CattleM products, respectively. Of the P in BM and CattleM, 90 and 75%, respectively, was soluble only in 1M HCl. Additions of the sparingly soluble P sources BM and CattleM increased the acid-soluble P concentrations in the experimental soil, with BM having the strongest effect. However, the acid-soluble P fraction decreased with time. Although the immediate bio availability of P in sparingly soluble P sources was lower than that in DairyM and super phosphate (SP), literature suggest that use of animal wastes as a long-term P supply for perennial plants could be encouraged. In order to ensure environmentally and economically sustainable methods of using these sparingly soluble P sources in plant production systems, the availability of P for plants in these products needs to be further clarified. Tue, 28 Nov 2017 00:00:00 GMT http://ir.lib.seu.ac.lk/handle/123456789/3310 2017-11-28T00:00:00Z http://ir.lib.seu.ac.lk/handle/123456789/3309 Title: A Pattern to draw lattice diagrams in a fixed field Authors: Fasmie, N.M. Abstract: A polynomial with order 𝑛 is isomorphic to symmetric group of order 𝑛 (𝑆𝑛). There are many ways to find the subgroup of a symmetric group. The fixed field for a given subgroup can be found using Galois Theory. Further, subgroups Are found using slow theorem, Van der Warden criterion, maximal ideal and group actions etc. In this work a method to draw lattice diagrams with the help of fixed field concept which intern found using subgroups is proposed. Drawing lattice diagram for polynomials is not an easy task. Complex polynomials face difficulties in drawing lattice diagram. In this proposed approach, a pattern which can be used to draw lattice diagram for complex polynomials is found in fixed field. Thus, the pattern helps to reach the fixed field in an easy and quick manner comparatively. Three types of patterns namely for polynomials which are isomorphic to ℤ2 × ℤ2 × … … × ℤ2, polynomials with unique field of order 𝑃𝑛 And polynomials of order 𝑛 are found using the proposed approach. Tue, 28 Nov 2017 00:00:00 GMT http://ir.lib.seu.ac.lk/handle/123456789/3309 2017-11-28T00:00:00Z