Browsing by Author "Wanninayake, A."

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Paths, Places and Voids: some thoughts on a prehistoric symbolic representation recovered from a cave in Sabaragamuva Province, Sri Lanka
(The International Conference on Land Transportation, Locomotive Heritage and Road Culture - 2017, 2017) Somadeva1, R.; Wanninayake, A.; Devage, D.; Ambalampitiya, J; Fernando, R.
Symbolism is one of the major cognitive advances that had been prominently developed by anatomically modern humans. It involved a complex web of biological, ecological and social qualifiers acquired through the evolutionary pathways. Dealing with isolated disembodied symbolic expressions created by the non-literate communities in an archaeological perspective, poses a number of theoretical and methodological problems at the interpretative level. This paper discusses about a symbolic manifestation registered on a natural rock boulder situated in a rock shelter occupied by the prehistoric communities during the mid/late-Holocene (5000-3500 BCE). This symbolic register contains 659 individual minuscule cupules hewn into the rock surface which are scattered in an irregular pattern. This register was reproduced on a 1:1 scale on a paper and carefully documented, each and every character traceable in its physical appearance, for analysis. The regional distribution pattern of the prehistoric sites and the archeological materials excavated from five prehistoric cave shelters in the area, situated in the proximity of the present location were taken as proxy data to contextualize the social and ecological fabric of this symbolic register. Excavated food residues including charred floral residues and faunal remains of the hunted animals were carefully sorted to search for any changes which may have occurred in the subsistence strategy which was structurally coupled with the idea of territoriality. It is hypothesized that the rugged terrain in the surrounding area was inadequate to maintain an increased population within a limited area, thus compelling the decision makers in the prehistoric groups to share their memories and experiences on the landscape they utilized in order to control the competition for food quest. The preliminary analysis allows to formulate a working hypothesis which proposes that this symbolic representation manifests the imaginary landscape of the immediate surroundings of prehistoric communities of the area. This essay attempts to devise a method and framework of inference which will, in practice, allow the archaeological evidence to be used to make a contribution to the debate which goes beyond the general speculations while working with such symbolic artifacts.
Plasmonic effects of gold nanoparticles on the performance of organic photovoltaic devices
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Wanninayake, A.
Extracting energy from sun light is one of the most promising ways to solve today’s energy crisis. Direct conversion of sun energy to electrical energy using nanostructured organic/inorganic hybrid structures has attracted much attention for many years. In particular, plasmonics researchers are turning their attention to incorporation of metal nanoparticles (NPs) into the active layer of polymer solar cells (PSCs), where design approaches based localized plasmonic resonance effect (LSPR) can be used to enhance the optical absorption in photovoltaic devices, enabling a considerable reduction in the physical thickness of solar photovoltaic absorber layers. The localized surface plasmon resonance (LSPR) occurs in illuminated metallic nanoparticles, like gold nanoparticles (Au-NPs), when oscillations of the incident electric field resonate with the surface electronic charges on those nanoparticles. The strong LSPR near field mainly distributes laterally along the active layer, therefore, the metallic NPs can experimentally and theoretically enhance the light absorption in the active layer of PSCs. In this study, to enhance the power conversion efficiency (PCE) of the polymer solar cells (PSCs), Gold (Au) nanoparticles are incorporated into P3HT/PCBM active layers. Addition of Au NPs increased the power conversion efficiency by up to 43.9% compared to a reference cell without Au-NPs. The short circuit current(Jsc) of the cells containing 0.05 mg of Au NPs was measured at 7.509 mA/cm2 compared to 5.558 mA/cm2 in the reference cells without nanoparticles; meanwhile, the external quantum efficiency(EQE) increased from 61% to 65.5%, showing an enhancement of 7.37%. Au-NPs improved the charge collection at the anode, which results in higher short circuit current and fill factor.