University of Tenaga Nasional
Saidur R.,University of Malaya |
Leong K.Y.,National University of Malaysia |
Mohammad H.A.,University of Tenaga Nasional
Renewable and Sustainable Energy Reviews | Year: 2011
Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat transfer performance can be applied in many devices for better performances (i.e. energy, heat transfer and other performances). In this paper, a comprehensive literature on the applications and challenges of nanofluids have been compiled and reviewed. Latest up to date literatures on the applications and challenges in terms of PhD and Master thesis, journal articles, conference proceedings, reports and web materials have been reviewed and reported. Recent researches have indicated that substitution of conventional coolants by nanofluids appears promising. Specific application of nanofluids in engine cooling, solar water heating, cooling of electronics, cooling of transformer oil, improving diesel generator efficiency, cooling of heat exchanging devices, improving heat transfer efficiency of chillers, domestic refrigerator-freezers, cooling in machining, in nuclear reactor and defense and space have been reviewed and presented. Authors also critically analyzed some of the applications and identified research gaps for further research. Moreover, challenges and future directions of applications of nanofluids have been reviewed and presented in this paper. Based on results available in the literatures, it has been found nanofluids have a much higher and strongly temperature-dependent thermal conductivity at very low particle concentrations than conventional fluids. This can be considered as one of the key parameters for enhanced performances for many of the applications of nanofluids. Because of its superior thermal performances, latest up to date literatures on this property have been summarized and presented in this paper as well. However, few barriers and challenges that have been identified in this review must be addressed carefully before it can be fully implemented in the industrial applications. © 2010 Elsevier Ltd.
Iqbal A.,University of Tenaga Nasional
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011
In this article, we demonstrate the use of composing 'experience' in the form of piece location probability values derived from a database of matein- 3 chess problems. This approach was compared against a 'random' one. Comparisons were made using 'experiences' derived from three different databases, i.e. problems by human composers (HC), computer-generated compositions that used the HC experience (CG), and mating 'combinations' taken from tournament games between humans (TG). Each showed a reasonable and statistically significant increase in efficiency compared to the random one but not each other. Aesthetically, the HC and CG were better than the others. The results suggest that composing efficiency and quality can be improved using simple probability information derived from human compositions, and unexpectedly even from the computer-generated compositions that result. Additionally, these improvements come at a very low computational cost. They can be used to further aid and entertain human players and composers. © 2011 Springer-Verlag.
Chen S.-D.,University of Tenaga Nasional
Digital Signal Processing: A Review Journal | Year: 2012
Absolute Mean Brightness Error (AMBE) and Entropy are among the two most popular IQMs used to assess Histogram Equalization (HE) based techniques. To the best of author's knowledge, there is no evaluation report on how well the two IQMs correlate to human opinion. This paper reviews and discusses the potential flaws in using AMBE and Entropy to assess HE-based techniques. This paper presents results of a subjective quality assessment in which image quality data obtained from 1935 human observer opinion scores were used to evaluate the IQMs. The statistical evaluation results show that the two IQMs have poor correlation with human mean opinion score (MOS); Pearson Correlation Coefficient (PCC)<0.4, Root Mean Square Error (RMSE)>0.75, Outlier Ratio (OR)>20%. A new IQM which takes into account important properties of human visual perception (HVP) is proposed. It is tested and found to have significantly better correlation (PCC>0.86, RMSE<0.39 and OR=0%). The proposed IQM also outperforms Multi-Scale Structural Similarity (MSSIM) and Information Fidelity Criterion-based (IFC) measure, which are two prominent fidelity-based IQMs. © 2012 Elsevier Inc. All rights reserved.
Tarlochan F.,University of Tenaga Nasional |
Ramesh S.,University of Malaya
Composite Structures | Year: 2012
Polymer composite sandwich structures are promising candidate structures for reducing vehicle mass, thereby improving the fuel economics. Nonetheless, to fully explore this material as the primary structure and energy absorber in vehicles, it is important to understand the energy absorption capability of this material. Hence, in the present work, comprehensive experimental investigation on the response of composite sandwich structures to quasi-static compression has been carried out. The crashworthiness parameters, namely the peak force, absorbed crash energy, specific absorbed energy, average crushing force and crush force efficiency of various types of composite sandwich structures were investigated in a series of edgewise axial compression tests. The tested composite sandwich specimens were fabricated from glass and carbon fiber with epoxy resin. Four distinct modes of failure were observed and recorded. The primary mode of failure observed was progressive crushing with high energy absorption capability. The optimized design in this study had a specific energy absorption capability of 47.1. kJ/kg with a good crush force efficiency of 0.77, higher than conventional metals. © 2011 Elsevier Ltd.
Jamel M.S.,University of Tenaga Nasional |
Abd Rahman A.,University of Tenaga Nasional |
Shamsuddin A.H.,University of Tenaga Nasional
Renewable and Sustainable Energy Reviews | Year: 2013
Pollution and increasing fuel prices are the main focus for governments today. The main cause of pollution is existing electricity power plants that use huge quantities of fossil fuel. A new strategy should be applied in the coming decades based on the integration of existing power plants with renewable energy sources, such as solar and wind energy. Hybridization of existing power plants with solar energy is one proven option to overcome the problems of pollution and increasing fuel prices. In this paper, a review of the previous studies and papers for integrating solar thermal energy with conventional and non-conventional power plants was carried out. The focus on hybrid solar conventional power plants includes: the review of studies of hybrid solar-steam cycle power plants, integrated solar combined-cycle systems (ISCCS) and hybrid solar-gas turbine power plants, while for hybrid solar non-conventional power plants the focus of study is hybrid solar-geothermal power plants. The most successful option is ISCCS due to their advantages and the plans for implementation at various power plants in the world like in Tunisia, Egypt, Spain, and Iran. © 2012 Published by Elsevier B.V. All rights reserved.
Inayat-Hussain J.I.,University of Tenaga Nasional
Mechanism and Machine Theory | Year: 2010
The dynamics of a rigid rotor supported by load-sharing between magnetic and auxiliary bearings are investigated for a range of realistic design and operating parameters. Numerical results indicate that the system's response is mainly influenced by the magnitude of the rotor imbalance. For relatively large imbalance magnitudes, non-synchronous vibrations were found to dominate the system's response over a substantial range of the operating speed. The magnitudes of the stiffness ratio and Coulomb sliding friction coefficient were found to have almost negligible effect on the system's response for relatively large imbalance levels. For relatively small imbalance levels, however, the variation of these parameters' magnitudes were found to be effective in reducing the system's response amplitude and decreasing or totally eliminating the range of operating speed where non-synchronous vibrations occurred in the system's response. Non-synchronous vibrations of period-2, -3, -4, -5, -6, -11 and chaos, which were observed in the system's response, are not desirable as they cause fluctuating stresses in the main components of the system, which may eventually lead to their failure due to fatigue. © 2010 Elsevier Ltd. All rights reserved.
Shamsuddin A.H.,University of Tenaga Nasional
Procedia Engineering | Year: 2012
Malaysia introduced renewable energy as the 5th fuel strategy in the energy-mix under the National Energy Policy in 2001. A target was set at 500 MW grid-connected power generations by 2005 from renewable energy sources. The small renewable energy power program (SREP) was launched at the same time with fiscal incentives to support this initiative. Malaysia has huge potential renewable energy resources in the form of biomass, solar and hydro. However, the implementation of SREP was not up to expectation due to several barriers and challenges faced by the authorities and developers, and the target was revised in 2006 to 350 MW by 2010. At the COP15 in Copenhagen, Malaysia pledged a voluntary reduction of up to 40% in terms of emissions intensity of GDP by the year 2020 compared to 2005 levels. With this commitment the Renewable Energy Act (RE Act 2010) was enacted in 2011 with provision of Feed-in Tariff, providing more attractive incentives to spur the implementation of grid-connected power generation from renewable energy resources. With the new RE Act2010, the target is revised to 985 MW by 2015, 2,080 MW (2020) and to 21,000 MW in 2050. This paper describes the development of renewable energy policy framework, strategies and initiatives for renewable energy implementation in Malaysia, in an effort to reduce carbon emissions as pledged at the COP15. This paper also provides examples of renewable power generation currently implemented and the on-going research and development activities to enhance the exploitation of renewable energy resources in Malaysia. © 2012 The Authors.
Wong L.S.,University of Tenaga Nasional
Journal of Cleaner Production | Year: 2015
Abstract The world is facing sustainability crisis as the survivability of natural environments and biota life continues to be threatened due to extensive usage of non biodegradable and polluting substances for producing cement-based materials. One alarming situation is the acceleration of global warming and climate change as a result of carbon dioxide release from cement manufacturing to the atmosphere. In another negative scenario, the widespread application of conventional water repellents such as silane and siloxane on cement-based materials poses a serious environmental threat due to their non biodegradability in nature. A viable solution that can be strategized to tackle the environmental issues is to utilize calcite from Bacillus genus bacteria for microbial cementation with the aim to optimize the mechanical behavior of cement-based materials. Bacillus genus bacteria are largely found in natural environments. Their capability to cultivate easily, absorb heavy metals and biocrystallize to form calcite has made the bacteria the promising microbes for biomineralization purpose in construction industry. This article reviews the positive influence of the bacteria at inducing calcite precipitation on cement-based materials. The rates of urea hydrolysis, calcite saturation and calcite precipitation of the bacteria which largely depend on the conditions of growth such as pH, temperature, bacterial cell concentration, calcium concentration and urea concentration are elucidated. Subsequent discussion concentrates on the current trend of crack reparation and surface treatment of cement-based materials, the prospect of developing biomineralized materials using the bacteria, and heavy metal biosorption of the bacteria. © 2015 Elsevier Ltd. All rights reserved.
Mohammed B.S.,University of Tenaga Nasional
Construction and Building Materials | Year: 2010
Many research works have been conducted to study the fresh and hardened properties of concrete containing crumb rubber as replacement to fine aggregate. The outcome of these researches indicated that though the compressive and flexural strength of crumb rubber concrete (CRC) decreased as percentage of fine aggregate replacement increased; the CRC has lower unit weight, better slump values, better toughness and absorb more energy before failure. In view of the fact that the main strength of composite floor slab lies within the bond between the concrete and the profiled steel sheeting, therefore the using of more ductile concrete such as CRC to toping the profiled steel sheeting could produce a new composite slab system. Two sets of slabs; each set comprising three CRC composite slabs and one conventional concrete slab has been tested with two shear span (450 and 900 mm). The results showed that the CRC slabs behavior could be characterized as ductile, while the m-k value has been found to be 80.7 and 0.037, respectively. © 2009 Elsevier Ltd. All rights reserved.
Kyaw M.M.,University of Tenaga Nasional |
Ramachandaramurthy V.K.,University of Tenaga Nasional
Renewable Energy | Year: 2011
High penetration of wind generation challenges wind turbine operators to supply reliable power and extract optimum power from the wind. Hence, the fault ride through (FRT) capability of wind turbine together with the optimum power tracking and regulation of wind turbine output voltage due to fluctuating nature of the wind becomes essential. In this paper, a method is proposed to ensure that the double fed induction generator (DFIG) wind turbine continues to operate during severe grid faults and maintains a constant output voltage, irrespective of the fluctuating wind. The proposed controller also allows the DFIG wind turbine to track optimum power from the wind. Extensive simulation is performed using PSCAD/EMTDC software and results obtained show that the DFIG output voltage fulfills the grid code requirements. The results also show that the proposed method is able to track the optimum power, regulate the DFIG output voltage and perform fault ride through of wind turbine. © 2010 Elsevier Ltd.