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Sri Jayewardenepura Kotte, Sri Lanka

Hewawasam T.,Sabaragamuwa University of Sri Lanka | Hewawasam T.,University of Peradeniya | Fernando G.W.A.R.,Open University of Sri Lanka | Priyashantha D.,Sabaragamuwa University of Sri Lanka
Journal of Earth Science | Year: 2014

The serpentinite blocks of Indikolapelessa, located along an identified litho-tectonic boundary between the Highland Complex (HC) and the Vijayan Complex (VC) of Sri Lanka, have undergone extensive lateralization with metal enrichment. Characteristic serpentinite vegetation with some endemic species was recognized in the soils and supergene deposits develop on serpentinite lithology. This type of geological and ecological relationship forms vegetation covers on serpentinite lithologies which are sharply demarcated from the surrounding metamorphic terrains. The aforesaid "geo-ecological phenomenon" can be used as a tool for geo-vegetation mapping in ultramafic terrains to trace the geological boundaries in landscapes where rock outcrops are virtually absent. We successfully applied the concept of geo-vegetation mapping in order to demarcate the boundary of underlain serpentinite rocks from surrounding non-serpentinite metamorphic rocks (e.g. granitic gneiss). The hypothesis was supported by the geochemical variations of soils/supergene deposits found at serpentinite and non-serpentinite sites, especially immobile elements and some trace elements. Based on whole rock chemistry and soil chemical data obtained, we suggest that the Indikolapelessa serpentinite outcrop, together with the other four serpentinite outcrops, is more likely to represent the Mg-rich mantle fragments at the time of overthrusting of the two crustal blocks of HC and VC during the Pan-African event. © 2014 China University of Geosciences and Springer-Verlag Berlin Heidelberg.

Aponsu G.M.L.P.,Sabaragamuwa University of Sri Lanka | Wijayarathna T.R.C.K.,Sri Lanka Institute of Fundamental Studies | Perera I.K.,Sabaragamuwa University of Sri Lanka | Perera V.P.S.,Open University of Sri Lanka | Siriwardhana A.C.P.K.,Sabaragamuwa University of Sri Lanka
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

In this paper, the performance of nano-porous electrodes made of a composite material of SrTiO3 and SnO2 are compared with those made of bare SnO2. When these particular devices are analyzed in a comparative mode the results confirmed the enhancement of photovoltaic parameters in the former device. The performance of respective cells were examined by several methods including I-V characteristic measurements, photocurrent action spectra, dark I-V measurements, Mott-Schottky measurements and X-ray diffraction measurements. Even though such improvements in this particular cell could be explicated by the formation of a potential energy barrier of SrTiO3 particles of comparably large width at the SrTiO3/SnO2 interface, the passivation of voids in the SnO2 film by SrTiO3 particles to a certain extent could not be totally ruled out. Besides, high energetic electrons injected by dye molecules move more credibly through mini-bands formed in the chain of nano-crystalline SnO2 particles to the back contact. The blocking of the recombination path and the shifting up of the uppermost electron occupied level of SnO2 accompanying the conduction band edge in the SrTiO 3/SnO2 composite film, may have lead to the observed enhancement of the fill factor and photovoltage, respectively. © 2013 Elsevier B.V. All rights reserved.

Herath C.N.,Open University of Sri Lanka
Fibers and Polymers | Year: 2013

In this research work, air permeability variations of core spun cotton/spandex single jersey and 1×1 rib knitted structures were studied under relaxation treatments. Results are compared with similar fabrics made from 100 % cotton material. Even though cotton/spandex fabrics knitted with same stitch lengths, their structural spacing and stitch densities vary with the progression of treatments. Similar behavior was also observed with 100 % cotton knitted structures. Under higher machine set stitch lengths (i.e., lower fabric tightness factor), higher structural spacing and lower stitch densities were resulted and those variations significantly affected on the air permeability variations of knitted structures. 1×1 rib knitted structures showed significantly higher air permeability than single jersey structures and it is more prominent with cotton rib structures. However, cotton/spandex 1×1 rib and single jersey structures have not showed such significant deviations. Air permeability of cotton/spandex and 100 % cotton rib and single jersey knitted structures decreased with lower machine set stitch lengths (i.e., at higher fabric tightness factors). There was a correlation with fabric tightness, air permeability, areal density and fabric thickness such as knitted fabrics became tighter, their weight and thickness were higher, while their air permeability was lower. Thus, fabric areal density and fabric thickness are positively correlates to machine set stitch length-1 (fabric tightness factor). Air permeability of a knitted structure depends on material type, knitted structure, stitch length, relaxation treatment, structural spacing and stitch density. © 2013 The Korean Fiber Society and Springer Science+Business Media Dordrecht.

Ariyasingha I.D.I.D.,Open University of Sri Lanka | Fernando T.G.I.,University of Sri Jayewardenepura
Swarm and Evolutionary Computation | Year: 2015

Most real world combinatorial optimization problems are difficult to solve with multiple objectives which have to be optimized simultaneously. Over the last few years, researches have been proposed several ant colony optimization algorithms to solve multiple objectives. The aim of this paper is to review the recently proposed multi-objective ant colony optimization (MOACO) algorithms and compare their performances on two, three and four objectives with different numbers of ants and numbers of iterations. Moreover, a detailed analysis is performed for these MOACO algorithms by applying them on several multi-objective benchmark instances of the traveling salesman problem. The results of the analysis have shown that most of the considered MOACO algorithms obtained better performances for more than two objectives and their performance depends slightly on the number of objectives, number of iterations and number of ants used. © 2015 Elsevier B.V.

Dissanayake M.A.K.L.,Sri Lanka Institute of Fundamental Studies | Dissanayake M.A.K.L.,University of Peradeniya | Thotawatthage C.A.,Sri Lanka Institute of Fundamental Studies | Senadeera G.K.R.,Sri Lanka Institute of Fundamental Studies | And 4 more authors.
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2012

Dye-sensitized solar cells based on nano-porous TiO 2 photo-anode and quasi-solid polymer (or gel) electrolytes are emerging as low cost alternatives to conventional inorganic photovoltaic devices. Although many attempts have been made in order to improve the relatively low power conversion efficiencies of these solar cells, to our knowledge there are very few reports aimed at using a binary system of two different iodide salts toward efficiency enhancement in these cells. In this paper we report for the first time in detail, the effect of using a binary iodide salt mixture with different size cations on the efficiency enhancement in dye sensitized solar cells with polyacrylonitrile (PAN) based gel polymer electrolyte and suggest a possible mechanism for this enhancement, based on short circuit photocurrent which is directly related to the iodide ion concentration [I -]. The gel electrolyte was made of PAN, ethelene carbonate (EC), Propylene carbonate (PC), salt mixture and I 2. The binary iodide salt mixture consists of potassium iodide (KI) and Tetra propyl ammonium iodide (Pr 4NI). Although the gel electrolyte with 100% (w/w) KI exhibited the highest overall ionic conductivity at room temperature, it showed the lowest iodide ion (I -) contribution to conductivity. On the other hand, the electrolyte with 100% (w/w) Pr 4NI exhibited the lowest overall ionic conductivity but had the highest iodide ion(I -) contribution. The dye-sensitized solar cells of configuration Glass/FTO/TiO 2/N-719 Dye/electrolyte/Pt/FTO/glass were fabricated using the gel electrolytes of different salt ratios and with nanoporous TiO 2 electrode sensitized with Ruthenium dye (N719). With identical electrolyte compositions, the solar cell with 100% (w/w) KI showed an efficiency of 4.98% and the cell with 100% (w/w) Pr 4NI showed an efficiency of 4.47%. However, the cell with the mixed iodide system, 16.6% (w/w) KI + 83.4%(w/w) Pr 4NI showed the highest efficiency of 5.36% with maximum short circuit current density (J sc) of 13.79 mA cm -2, open circuit voltage (V oc) of 679.10 mV and a fill factor of 57.25%. The variation of efficiency (η) with iodide ion concentration [I -] follows the same trend as the J SC which appears to be governed by the iodide ion conductivity of the gel electrolyte. The dependence of the short circuit photocurrent and the open circuit photovoltage on the cation type generally agrees with reported data for related systems. However, the occurrence of a maximum in the solar cell efficiency and short circuit photocurrent at 16.6% (w/w) KI + 83.4% (w/w) Pr 4NI salt composition is an important finding. The efficiency enhancement of about 8% achieved by employing the binary iodide mixture in the gel electrolyte instead of a single iodide salt, could be utilized for achieving efficiency enhancement in many dye sensitized solar cell systems based on polymeric, gel or solvent electrolytes. © 2012 Elsevier B.V. All rights reserved.

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