Browsing by Author "Dissanayake, K"

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item: Conference-Full-text
Ecological evaluation of urban heat island effect in Colombo city, Sri Lanka based on landsat 8 satellite data
(IEEE, 2020-07) Dissanayake, K; Kurugama, K; Ruwanthi, C; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
The Colombo is the main commercial metropolitan city in Sri Lanka with having highest population and building density, making the city is more ideal place to form Urban Heat Islands. This study was conducted to ecologically evaluate the Urban Heat Island effect in Colombo city using Landsat 8 satellite data. The temperature variation of the city was acquired by Land Surface Temperature, a parameter derived from Landsat 8, band10 (Thermal Infrared band), band4 (Red band) and band5 (Near Infrared) using Radiative Transfer Method. Evaluation of ecological condition was assessed using Urban Thermal Field Variance Index, a quantitative measurement of the urban ecological quality of life with respect to Urban Heat Island effect. The model verification was obtained by theoretical relationships between Surface Temperature, Normalized Difference Built-up Index and Normalized Difference Vegetation Index. Temperature distribution in Colombo city revealed that, majority of the environmentally critical areas were located near the harbor, central business area along the main transport system and coastal belt. According to above index, the city experiences two extremes as areas of optimal micro-climate and areas with heat stresses indicating the requirement of strong Urban Heat Island mitigation measures in future landscape development and urban planning of the city.
item: Thesis-Abstract
An Evaluation of the million houses programme in regional planning perspective
(2015-08-26) Dissanayake, K
In addition to the major economic problems such as unemployment, 1ow productivity, balance of payment problems etc; housing has also become one of the major problems in almost all the developing countries. In the year 2000, there will be two billion people crowded in the cities of developing countries. More than half of them carp rise the absolutely poor people living in cities.1 Slum and squatter living in urban areas in developing countries are increasing at a rate that is almost four times faster than overall world 2 population growth population During every 24 hours approximately 50,000 such poverty stricken children die p re-maturely due to lack of adequate shelter ^adequacy of food, water and proper sanitation 3 .
item: Article-Full-text
Exploration for rare earth elements (REES) in different geological formations of Sri Lanka and their recovery potential
(2022-09) Batapola, N; Ratnayake, N; Abeysinghe, B; Premasiri, R; Rohitha, S; Dushyantha, N; Ilankoon, S; Dissanayake, K; Dharmaratne, P
Rare earth elements (REEs) are widely attracting global attention due to their crucial role in the modern lifestyle, especially in the industrial advancement towards a green economy through renewable technologies. This particular group of metals consists of the 15 lanthanides, yttrium (Y), and scandium (Sc). There are two subgroups, namely light rare earth elements (LREEs) from lanthanum (La) to europium (Eu) and heavy rare earth elements (HREEs) from gadolinium (Gd) to lutetium (Lu) and Y (Fig. 1a). Generally, LREEs are more abundant in the mineral deposits when compared to more priced HREEs [1].
item: Conference-Full-text
Extraction of copper from Seruwila copper magnetite deposit
(IEEE, 2020-07) Jayathilake, C; Rohitha, S; Dissanayake, K; Rushan, I; Dilshan, K; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Seruwila Copper Magnetite deposit remains unextracted, although proper exploration work have been carried out. A XRF characterization was conducted in the laboratory for the systematically collected field ore sample. It was confirmed that 0.6% Cu and 20-50% Fe are available in the sample on average. Raw ore samples followed a comminution process where the particle size was reduced up to 75μm. Sulfuric acid was used as the leaching medium. Particles below the size of 75μm gave optimum leaching efficiency. Leaching efficiency could be improved with increasing temperatures and acid concentrations. Optimum solid/liquid ratio was determined to be in the range 20/125 – 20/150 (g/ml) for leaching. Selective extraction of Cu cations from the leachate solution was successfully conducted using an Ammonia solution. Formed complex solution was filtered and treated with concentrated Sulfuric acid to prepare an electrolyte solution. Elemental analysis of the deposited layer from electrowinning the above solution gave 76.62% Cu along with current efficiency of 72% and power consumption of 1023.5 kWh/t. It was concluded that this methodology is economically feasible when compared with electrowinning the leachate directly, which resulted only 62.88% Cu with comparatively lower current efficiency of 50.95% and higher power consumption of 3097 kWh/t.
item: Article-Full-text
Geochemical exploration for prospecting new rare earth elements (REEs) sources
(2023) Dushyantha, N; Ratnayake, N; Premasiri, R; Batapola, N; Panagoda, H; Jayawardena, C; Chandrajith, R; Ilankoon, IMSK; Rohitha, S; Ratnayake, AS; Abeysinghe, B; Dissanayake, K; Dilshara, P
Rare earth elements (REEs) are globally considered as critical elements due to their indispensable applications in various high-tech industries. With the ever-increasing demand, identified primary REE resources will not be able to fulfil the global requirements and thus exploration and exploitation of secondary REE deposits are essential. This work is designed to prospect REE potential in lake sediments in the proximity of the Eppawala Phosphate Deposit (EPD) in Sri Lanka. In this context, surface and core sediment samples were collected from 2 upstream lakes and one downstream lake (connected to a man-made water canal, namely Jaya-Ganga) with respect to the EPD. In the downstream, the average total rare earth element (TREE), light REE (LREE) and heavy REE (HREE) concentrations of the surface sediments were 1011.3, 904.6 and 66.6 mg/kg, respectively. The corresponding average values in downstream core sediments were 858.7, 719.3 and 100.2 mg/kg, respectively. The results suggested that the downstream lake sediments contained a high TREE content with a significant LREE enrichment compared to the upstream lake sediments. The EPD was identified as the main REE source and Jaya-Ganga, which flows across the EPD, was the main transport medium in this study. Phosphate-bearing minerals, such as fluorapatite and hydroxylapatite, derived from the EPD act as the REE carriers where REEs substitute isomorphous in the mineral lattice. Since REE grade is relatively high compared to some of the reported secondary REE sources, the downstream lake sediments could be a potential secondary source for REEs for future exploitation.
item: Conference-Full-text
Natural and enhanced contaminated waters
(2005) Hettiarachchi, M; Karunarathne, S; Dissanayake, K
Chromium is a highly soluble transition metal of vital industrial importance. It occurs in both trivalent and hexavalent forms. Due to many well identified adverse impacts of chromium to human health and natural ecosystems, treatment of chromium contaminated waters and remediation of contaminated aquatic systems has become a major concern of environmental engineers. The currently practiced conventional mechano-chemical treatment systems for remediation of chromium contaminated waters have high operational costs, therefore alternative natural attenuation systems are becoming the focus of modern research. This paper presents an analytical review on application of natural attenuation methods in removal of chromium in Sri Lanka. Some results presented on phyto-remediation and sorption of chromium by gravels are original research findings of the authors. Some possibilities sited in-literature are also reviewed.
item: Conference-Abstract
Online classification of imagined hand movement using a consumer grade EEG device
(2014-06-20) Dharmasena, S; Lalitharathne, K; Dissanayake, K; Pasqual, AA; Sampath, A
Brain-Computer Interaction (BCI) is a technology developed with the purpose of building a pathway between the brain and computer which is independent of neuromuscular functions. Potential applications in rehabilitation of patients with motor disabilities and video gaming make BCI an important field of research. A task like controlling a prosthetic limb using BCI is challenging. Performing this with readily available consumer grade EEG devices complicates the matters further due to lower accuracies. This paper presents the work related to an online classifier for imagined hand movement implemented using Emotiv Epoc for EEG data capturing. The system attempts to discriminate between left and right hand movement imagination by analysing the recordings of two electrodes placed over the motor-cortex. Auto-Regression (AR) based signal processing techniques are employed to derive features that enable classification. Especially, a cumulative score based method is used for identification of user specific frequencies. The system is evaluated in an experiment involving 8 subjects where an average accuracy of 70.375% is achieved.
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Online classification of imagined hand movement using a consumer grade EEG device
(2015-07-06) Dharmasena, S; Lalitharathne, K; Dissanayake, K; Sampath, A; Pasqual, AA
Brain-Computer Interaction (BCI) is a technology developed with the purpose of building a pathway between the brain and computer which is independent of neuromuscular functions. Potential applications in rehabilitation of patients with motor disabilities and video gaming make BCI an important field of research. A task like controlling a prosthetic limb using BCI is challenging. Performing this with readily available consumer grade EEG devices complicates the matters further due to lower accuracies. This paper presents the work related to an online classifier for imagined hand movement implemented using Emotiv Epoc for EEG data capturing. The system attempts to discriminate between left and right hand movement imagination by analysing the recordings of two electrodes placed over the motor-cortex. Auto-Regression (AR) based signal processing techniques are employed to derive features that enable classification. Especially, a cumulative score based method is used for identification of user specific frequencies. The system is evaluated in an experiment involving 8 subjects where an average accuracy of 70.375% is achieved
item: Conference-Full-text
Recovery of copper from concentrated Seruwila copper magnetite ore from chloride electrolyte in the presence of hydrochloric acid
(IEEE, 2020-07) Dissanayake, K; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Extraction of copper from concentrated Seruwila Copper-Magnetite from chloride solution in the presence of Hydrochloric acid using Lead anode and Copper cathode was investigated. Surface and borehole samples were collected in Arippu area of the deposit. Average copper concentration of the surface samples was 0.14% and subsurface borehole samples was 1.12%. Crushed borehole samples passed through the 75micron solid particles mixed with 25mg/kg of Pine oil and 250mg/kg of Xanthate and preparation of 10% solid slurry for froth floatation. Accordingly, 9.2 g of copper concentrate was recovered from froth floatation of 1.0kg of Copper magnetite ore. Weighed quantity of dried copper concentrate was dissolved in concentrated Sulfuric, Hydrochloric and Nitric acids separately. However, optimum dissolution was recorded when using concentrated Hydrochloric acid. The effect of the operating variables on current density upon copper concentration, applied potential, electrode spacing, area of electrodes, pH, temperature and stirring velocity were studied. The optimum variables discovered for effective electrowinning were 20g/l, 4.6V, 2cm, 30cm2, 4.2, 55-60 0C and 300rpm respectively. Overall copper recovery was reached to 82.14% from ROM samples and average power consumption and efficiency for copper extraction by electrowinning process was 6.78 kwh/kg and 72.23% respectively.
item: Conference-Full-text
Remote sensing and gis approach to monitor the land-use and land-cover change in Kaduwela metropolitan area
(IEEE, 2022-07) Kanagasundaram, G; Dissanayake, K; Samarasuriya, C; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
This article depicts the impact of Land Use and Land Cover (LULC) change using multi-temporal remotely sensed data in the Kaduwela metropolitan area located in Colombo District for the period between 1997 and 2019. To obtain information from the satellite data, the Maximum likelihood supervised classification technique and post-classification change detection strategy were applied. Besides, Spectral indices were utilized to define the ground truth. Thus, the study area was divided into four main land use/cover classes, and hence five satellite images for the years; 1997, 2007, 2014, 2017, and 2019 with low cloud cover were identified. According to the study, urban development resulted in a significant conversion of vegetation cover to the urban development of around 36 km 2 during the past 22 years. The generated map showed that between 1997 and 2019, the built-up area increased by 43.62 percent whereas vegetation cover decreased by 41.72 percent. The overall precision of the data produced ranged from 72 to 81 percent. The dramatic growth of the urban population will boost the risk of natural environmental diminishing. This study assesses the change in the LULC pattern for the previous 22 years, providing useful information for the urban planners to make sustainable environmental decisions.
item: Article-Full-text
Sustainability dichotomies of used clothes supply chains
(Emerald Publishing Limited, 2023-02) Dissanayake, K; Pal, R
Purpose Used clothes supply chains are becoming increasingly complex, fragmented and less transparent due to rising volumes of discarded clothes and its dispersed reverse logistics operations across the Global North (GN) and Global South (GS). While it has a promising impact on circular economy and international trade growth, increasing exports of used clothes and overflowing landfills raise some negative concerns on its overall sustainability. This paper addresses the dichotomy that exists in terms of interpreting the sustainability credentials of used clothes supply chains.
item: Conference-Full-text
Sword ferns for phytoremediation of chromium contaminated waters
(Department of Earth Resources Engineering, 2006-10) Hettiarachchi, M; Karunarathne, S; Dissanayake, K; Karunaratne, S
Chromium is a highly soluble transition metal of vital industrial importance. It occurs in both trivalent and hexavalent forms. Due to many well identified adverse impacts of chromium to human health and natural ecosystems, treatment of chromium contaminated waters has become a major concern and challenge for environmental engineers. The currently practiced conventional mechano-chemical treatment systems for remediation of chromium contaminated waters have high operational costs, especially when the concentrations are low. Therefore alternative natural attenuation systems are becoming the focus of modem research. This paper presents a research to asses the applicability of Common Sword Ferns in phytoremediation of water contaminated with low or medium concentration of bot trivalent and hexavalent chromium. Saword ferns (N. Exaltata) showed very high removal rates (about 99%) in a Hydroponic medium upto 50 ppmcontamination of T-Cr. The mass balance shows that most of the Cr taken up by the plant is retained in the roots (about 75 % or 3500 mg/kg). Little is translocated to above-ground tissues (4% or 120 mg/kg). Therefore the mechanism of removal is mainly Rizofiltration. The mechanism of uptake may be Biosorption or Active uptake by root cells. N. Exaltata hardly shows any symptoms ofPhyto-toxic affects upto 50 ppm of Cr +3, and 15 ppm ofCr+6• But in a Soil water system mass balances show that most of water soluble Cr+3 is sorbed to soil (about 90%). N. exaltata is poor in de-mineralizing, mobilizing and uptake of soil bound Cr +3. Sand has a remarkable capacity to immobilize Cr+3 in water.
item: Conference-Full-text
Upgrading low-grade graphite tailing into high-grade graphite using agglomeration
(IEEE, 2021-07) Patikiri Arachchige, M; Rohitha, S; Dissanayake, K; Lakshitha, P; Kusumsiri, R; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Low grade Graphite ore is mostly beneficiated by froth flotation. For the liberation of Graphite from the related gangue materials, flotation circuits depend heavily on wet grinding of the ore with grinding mills. This produces significant amounts of Graphite fines, which are eventually lost to the tailings and discarded as wastes without further Graphite recovery. Agglomeration of the Graphite fines has been proven to be a size enlargement technique by previous studies. The character of Graphite agglomeration for beneficiation of low-grade Graphite tailing samples containing 23.4% to 25.5% Fixed Carbon (FC) obtained from Ragedara Graphite mine, Sri Lanka was assessed by varying the bridging liquid to tailing ratio and increasing the sample size. Comparative surface changes of upgraded Graphite were observed using Hitachi SU6600 Analytical VP FE-SEM. With respect to the froth flotation process, this novel method will need low water requirement while reducing the time for the separation of Graphite. The beneficiation study was able to obtain a concentrate with 88% fixed carbon at 69.6% recovery for 25 kg sample with no major surface structural changes compared with Natural Vein Graphite, indicating that it could be applied on commercial scale with periodic iterations for upgrading over 99% fixed carbon.