Journal of Advances in Engineering and Technology [JAET] Volume 03 Issue ii

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Open Access
Correlation of tensile strength of blended cement concrete with specimen dimensions and aggregate size: A practical test review
(SLIIT, Faculty of Engineering, 2025-02) Amarasinghe, N; Somaratna, N
Test specimen dimensions affect most strength properties of concrete. The existing empirical relationships in this regard are predominantly based on concrete samples made by using Ordinary Portland cement (OPC). An important recent trend in Sri Lanka has been the increasing use of blended cements. This makes it necessary to examine whether the relationships hold for blended cements as well. In this study, split cylinder tensile strength tests were conducted to determine whether the specimen size and the tensile strength of concrete prepared using a blended cement (Portland Composite Cement (PCC)) display relationships similar to OPC. Tests were conducted on specimens using two cement types – OPC and PCC - and three concrete mix ratios and a range of specimen dimensions to study the effect of the specimen length (L), diameter (D), and aggregate size (a) on the split cylinder tensile strength (T). The data was examined using dimensional analysis based on Buckingham's π theorem. A slight increasing trend was observed in the ratio of split cylinder tensile strength to mean a compressive strength (T/fc,mean) with an increasing L/D ratio. As for the ratio of the aggregate size to the specimen diameter (a/D), the analysis showed an increasing trend in T/fc,mean values with an increasing a/D ratio, indicating a significant correlation between T/fc,mean and a/D. A nonlinear regression analysis was used in an attempt to determine a functional relationship among the non-dimensional parameters T/fc,mean, L/D, and a/D. But the differences in the derived relationships for different concrete mixes were too large for reaching a common relationship. Perhaps this was due to the small number of data points available. It was seen that relationships established for OPC may hold true for PCC too. However, the data used was limited in range and more comprehensive further tests should be conducted to confirm these findings.
Open Access
Enhancing Load Frequency Control in Interconnected Power Systems with Zone-Specific Fuzzy Controllers: Principles and Methods
(SLIIT Faculty of Engineering, 2025-02) Jahangiri, S; Jones, K.O
This work focuses on load frequency control in interconnected power systems, a critical aspect of modern power grid operations. However, sudden load disturbances and generator outages can lead to transient oscillations between control areas, posing challenges to frequency control. The aim of the work was to investigate and enhance load frequency control behaviour, considering dynamic load changes and uncertainties. Fuzzy Logic Controllers optimized with Particle Swarm Optimization were applied to improve control robustness. The Particle Swarm Optimisation algorithm was used to tune the scaling factors and parameters of the fuzzy controllers to optimize their performance. The methods were tested on a standard four-area interconnected power system model equipped with load frequency control blocks, reheaters, governors, rate constraints, and thermal components. Different disturbance scenarios including parameter fluctuations and load changes were evaluated. The Fuzzy Logic Controllers demonstrate resilient response across scenarios without needing extensive tuning. Particle Swarm Optimization improves robustness through systematic exploration for constraint-based nonlinear optimization. Tuning fuzzy controllers with bio-inspired algorithms enhances efficiency in addressing complex grid conditions. The results provide insights into designing more secure and resilient grid controls, contributing to power system stability research.
Open Access
Intelligent Reflecting Surface for 6G Wireless Communication
(SLIIT, Faculty of Engineering, 2025-02) Malshan, K. A. T. I.; Iddamalgoda, G. D. D.; Rajendran, H.; Aashiq, M. N. A.; Haleem, M. A. L. A.
In the context of future 6G wireless communication, addressing challenges related to non-line-ofsight communication is paramount. This paper presents the design and prototyping of Intelligent Reflecting Surfaces (IRS) as a solution to provide wireless connectivity in the absence of Line-of-Sight (LoS) propagation paths for effective wireless communication. We simulated phase-shifter unit cell structures of IRS utilizing CST Studio software suite. A prototype IRS consisting of a two-dimensional array of unit cells was designed and built. Our tests on the prototype revealed the effectiveness of the design exhibiting a remarkable 315o of dynamic range in phase shift performance at 2.4 GHz. The losses introduced by the IRS in reflecting an incident signal were brought down to an acceptable limit via an iterative design and simulation process. Measurements on phase shifting properties were performed using a low-cost Vector Network Analyzer (VNA). A comparative study was carried out on the simulation and experimental outcomes and good agreement was found confirming the effectiveness of the prototype IRS.
Open Access
Linearization of Nonlinear Components in Instruments
(SLIIT, Faculty of Engineering, 2025-02) de Silva, Clarence W.
Real instruments, devices, and components are found to be nonlinear and are represented by nonlinear analytical models. Accordingly, linear systems (or models) have idealized representations. However, it is realized far more convenient to analyze, simulate, design, and implement nonlinear devices through the use of linear models. Also, regarding some devices, the degree of nonlinearity may not be significant. In such cases, nonlinear devices are often “approximated” by linear models. Against that background, this paper explores several important methods of linearization of nonlinear physical devices with practical examples.
Open Access
Material Wastage on Cost Overrun in Construction Projects: An Impact Study Carried Out in Sri Lanka
(SLIIT, Faculty of Engineering, 2025-02) Kothalawala, N.T.B.; Malkanthi, S.N.; Dharmaratne, P.D.
Cost overruns are a prevalent issue in construction industry, and material wastage is recognized as one of the key contributory factors of it. Against that background, this research investigates the impact of material wastage on cost overruns in construction projects experienced in Sri Lanka. It strives to achieve the objective of providing insights into the relationship between material wastage and cost overruns and identifying potential strategies to mitigate its impact. The research methodology developed in this concern involves a comprehensive literature review to establish a theoretical premise of material wastage and cost overruns in construction projects. The data about the issue was collected through surveys, interviews, and site inspections of a series of ongoing and completed construction projects in Sri Lanka. Later, the data was analyzed statistically to determine the extent of material wastage and its impact on cost overruns. The findings achieved thereby reveal a significant correlation between material wastage and cost overruns in construction projects in Sri Lanka, highlighting that inefficient project planning, inadequate supervision, lack of skilled labour, and ineffective procurement practices contribute to material wastage, which ultimately leads to cost overruns. The financial implications of this situation are substantial and affect project budgets and profitability. Based on the research findings, the paper strives to make recommendations for strategies to mitigate material wastage and reduce cost overruns in construction projects. These include improved project planning and scheduling, enhanced supervision and training, effective procurement and inventory management, and adoption of sustainable construction practices.
Open Access
Rice Husk Derived Biomass Briquettes for Boilers: Ingredient-Based Product Quality Study
(SLIIT, Faculty of Engineering, 2025-02) Lakshika, H.N.M.; Arachchige, U. S.P.R; Koliyabandara, P.A
This research investigates the feasibility of repurposing rice husk waste into sustainable biomass briquettes, addressing environmental and economic challenges associated with conventional biomass sources in Sri Lanka. The study involves a comprehensive analysis of rice husk utilization, focusing on three size fractions: original size, particles less than 5mm, and powder form. Rice husks less than 5mm was observed to have a composition of optimal fixed carbon content (11.63% ± 0.215), moisture content (10.53% ± 0.013), volatile matter (80.72% ± 0.005), and ash content (7.65% ± 0.004). The binding agents, namely starch, dummala tree resin, and wastepaper pulp, were used for briquette production. The optimal compositions for briquettes made with rice husk particles less than 5mm were determined as follows: rice husk with starch (1:6), rice husk with tree resin (1:7), and rice husk with wastepaper pulp (1:5). The calorific values of these optimum briquettes were found to be 15.446 MJ/kg for starch-based briquettes, 15.278 MJ/kg for paper pulp-based briquettes, and 15.323 MJ/kg for tree resin-based briquettes. In addition, briquettes made with an equal ratio (1:1) of binders showed calorific values of 14.175 MJ/kg for starch, 14.227 MJ/kg for paper pulp, and 15.275 MJ/kg for tree resin, with tree resinbased briquettes exhibiting the highest calorific value. In the product quality evaluation study carried out with these results, the proximate and ultimate analyses were conducted to characterize the briquettes and the thermogravimetric analysis (TGA) was conducted to characterize the rice husk and to examine the physical properties of the produced briquettes. The findings indicate that repurposing rice husk waste with various binding agents offers a sustainable solution for biomass fuel production. Accordingly, natural tree resin briquettes exhibited the highest density, compression ratio, and shatter resistance. These results suggest that utilizing natural tree resin can effectively address waste management challenges and create an environmentally friendly and economically viable industrial sector in Sri Lanka.
Open Access
Use of pine needles for producing high-calorific value bio-briquettes and pine resin for biomass boiler
(SLIIT, Faculty of Engineering, 2025-02) Tharukarathne, P.W.T.M.C; Arachchige, U. S.P.R.; Koliyabandara, P. A
Biomass, ranked as the fourth-largest energy source globally, presents a viable renewable energy option. However, inherent limitations such as low density and calorific value necessitate the development of quality-enhanced biomass, like biomass briquettes, for more efficient energy production. This study focuses on biomass briquette production using pine needles, abundant in the hilly regions of Sri Lanka, as a forestry waste-to-energy concept. The research aims to investigate the physicochemical properties of pine needles char for biomass briquette preparation and utilizing pine resin as a binding agent. Thermal degradation analysis, XRD tests, and physical property assessments were performed on raw materials and briquettes. The objectives include pine resin extraction and analysis of pine needles' properties, optimization of briquette composition to ensure high combustion efficiency and comparison of briquette properties with standards relevant to biomass. Results revealed that pine needle char possesses favorable characteristics for briquetting, with a moisture content of 6.105% and ash content of 4.233%. The 5:1 ratio briquette showed the best performance with a calorific value of 22.19 MJ/kg, a high density of 917.272 kg/m³, and a compression ratio of 3.507. Pine needle briquettes (PNB) were made with different ratio pine needles char and binder using a small-scale hydraulic press (2 tons; 5.5 MPa) with a honeycomb-type mold. The machine's estimated production capacity is 192 briquettes per day. The research results help to create inventive waste management solutions by transforming pine needles into valuable energy sources, benefiting the environment, industries, and self-employed individuals equally.