ERU - 2000http://dl.lib.uom.lk/handle/123/146732024-03-29T04:38:48Z2024-03-29T04:38:48ZProceedings of the 06th annual symposium 2000 (Pre Text)http://dl.lib.uom.lk/handle/123/214682023-10-13T02:30:18Z2000-12-01T00:00:00ZProceedings of the 06th annual symposium 2000 (Pre Text)
Hettiarachchi, P
2000-12-01T00:00:00ZPreparation and properties of starch xanthide encased powdered natural rubberAmarasinghe, ADUSSubramaniam, KMaduwage, Shttp://dl.lib.uom.lk/handle/123/94152019-11-28T08:45:13Z2000-01-01T00:00:00ZPreparation and properties of starch xanthide encased powdered natural rubber
Amarasinghe, ADUS; Subramaniam, K; Maduwage, S
Starch xanthide encased powdered natural rubber was produced by oxidatively co- precipitating the mixture of starch xanthate solution and natural rubber field latex under vigorous stirring. The resulting finely divided wet powdered rubber particles were separated by filtration and then converted to free-flowing powders by oven drying. The level of encapsulation as well as the properties of the resulting powder was highly dependent on the strength and the amount of the Starch Xanthate (SX) solution. The lower and the upper limits of Degree of Substitution (DS) of SX examined were 0.07 and 0.35 and the results suggested that the intermediate DS levels were more effective. The physical properties of the final vulcanizates were examined and found to be comparable with the rubbers available in the market.
2000-01-01T00:00:00ZPrediction of compressive strength of concreteNanayakkara, SMAhttp://dl.lib.uom.lk/handle/123/94142019-11-28T08:45:13Z2000-01-01T00:00:00ZPrediction of compressive strength of concrete
Nanayakkara, SMA
This report presents a method of predicting the compressive strength of concrete. The approach is based on experimental investigation of compressive strength development of four mix proportions with three different brands of cement. The criterion used for the prediction of strength involves the determination of equivalent age of concrete, which depends on curing temperature and age of concrete. It was found that the compressive strength of concrete varies linearly with respect to the logarithmic value of the equivalent age. Furthermore, it was observed that the rate of change of strength with respect to logarithmic value of equivalent age varies non-lincarly with respect to w/c ratio. This variation was not the same for all cement brands tested. Expressions were derived for compressive strength for each brand of cement with respect to w/c ratio, age and curing temperature. Based on these expressions, a chart was developed to establish the relationship between strength and w/c ratio for a range of strength grades. This chart can be used in mix design of concrete using local materials. Since it was not possible to develop a unique expression for the prediction of compressive strength of concrete in terms of mix design parameters such as w/c for any cement brand, the identified behavior of the strength development of concrete with respect to equivalent age was used in predicting strength of concrete. In the proposed method, the 28-day strength can be predicted with strength results at two ages such as 1-day and 3-day strengths. Good agreement with the predicted and experimental results have been obtained not only for test results obtained under this study but also for other published test data
2000-01-01T00:00:00ZPerformance analysis of pedestal fans an experimental investigationSugathapala, AGTSomarathne, PBIhttp://dl.lib.uom.lk/handle/123/94132022-10-26T03:54:09Z2000-01-01T00:00:00ZPerformance analysis of pedestal fans an experimental investigation
Sugathapala, AGT; Somarathne, PBI
Performances of pedestal fans were analysed through experimental measurements of the induced flow field (velocity distribution) and the power consumption by two different types of fans. A test rig was constructed to facilitate the measurement of axial flow velocities in the three dimensional space. In order to predict the jet pattern produced by the fan, axial velocity distributions on sufficient number of planes were measured. These data were used to calculate the jet diameter, flow rate, kinetic energy and the linear momentum of the flow at different planes from the rotor. The power consumption and the angular speed of the rotor for each regulator setting were also measured.
The velocity distributions measured on different planes from the rotor clearly illustrate the general characteristics of the flow generated by free flow fans, including the reverse flow near the rotor plane, jet entrainment and diffusion. The results show that the overall energy efficiency of a fan depends critically on its speed (i.e. regulator setting); efficiency increases with the speed. The results also indicate that the service factor defined by the flow rate at a specified section divided by the power consumption is not a suitable performance index for free-flow fans. Even with a similar axial velocity profile generated by two different fans could result in two different jet developments leading to completely different flow characteristics and performances. The results of the present study indicate the complexity of the jet development and the necessity for detailed experimental measurements of the flow velocity distribution including the swirl components in predicting performance of free-flow fans.
2000-01-01T00:00:00Z