University of MalayaKuala Lumpur


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Hindatu Y.,University of MalayaKuala Lumpur | Hindatu Y.,Bauchi State University | Annuar M.S.M.,University of MalayaKuala Lumpur | Gumel A.M.,University of Nigeria
Renewable and Sustainable Energy Reviews | Year: 2017

Microbial fuel cell (MFC) harnesses the metabolic activities of microorganism to generate electricity from substrate oxidation. However, the power generated from the MFC is relatively low for practical applications, thus the urgent need for its improvement. In MFC, anode is a crucial component of the setup, both structurally and functionally. It provides support for bacterial attachment and simultaneously acts as a sink for electrons from substrate metabolism. Poor performance of anode electrode in MFC is still a major setback for its practical applications. Successful anode electrode modification is expected to enhance the MFC electricity generation efficiency. Materials such as carbon nanotube, stainless steel, conducting polymers, metal oxides, and electrolytes have been employed as anode electrode modifiers with varying degree of success. Henceforth, this communication highlights and discusses the latest research advances made in MFC anode electrode modification using the aforementioned materials. The importance of the modification methods and their consequences towards anode architecture, biocompatibility, and longevity to improve the overall MFC performance are discussed. © 2017 Elsevier Ltd

Ashik U.P.M.,University of MalayaKuala Lumpur | Wan Daud W.M.A.,University of MalayaKuala Lumpur
RSC Advances | Year: 2015

n-Ni/SiO2, n-Fe/SiO2 and n-Co/SiO2 nano-catalysts were prepared by co-precipitation cum modified Stöber method and applied for thermocatalytic decomposition of methane in order to investigate their thermal stability and activity to produce greenhouse gas free hydrogen and nano-carbon. The mean particles sizes of the produced nano-catalysts obtained from BET analysis are 32.19 nm, 30.26 nm and 49.92 nm, respectively. Temperature programmed methane decomposition were conducted as a preliminary catalytic examination and further isothermal analyses were performed at 700 °C, 600 °C and 500 °C. Production of hydrogen at each experimental temperatures and corresponding carbon yield were measured. Among the three catalysts inspected, n-Ni/SiO2 was found to be the most efficient one for thermocatalytic methane decomposition. Furthermore, significant catalytic stability was observed with n-Ni/SiO2 at 500 °C and 600 °C. While, the rapid deactivation of the n-Fe/SiO2 and n-Co/SiO2 catalysts are attributed to particle agglomeration and the irregular formation of nano-carbon due to metal fragmentation. Physical and chemical characteristics of the produced nano-catalysts were investigated by N2 adsorption-desorption measurement (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM) and hydrogen-temperature programmed reduction (H2-TPR). Produced nano-carbon were inspected with TEM, FESEM and XRD. This journal is © The Royal Society of Chemistry.

Sudamalla P.,Indian National Institute of Engineering | Matheswaran M.,Indian National Institute of Engineering | Saravanan P.,University of MalayaKuala Lumpur
Sustainable Environment Research | Year: 2012

An adsorbent prepared from mango seed was used to study its sorption potential on removing Crystal Violet dye from aqueous solution. The influences of operating parameters like pH, temperature, initial concentration and adsorbent dosage on dye adsorption were studied. A maximum dye removal of 95% was achieved with an initial concentration of 10 mg L-1. The percentage removal was mathematically described as a function of experimental parameters and was modeled through response surface methodology. The results show that the responses of color removal in adsorption of dyes were significantly affected by the synergistic effect of linear term of time and dosage and the quadratic term of temperature and time. A 24 full factorial design of experiments was adopted and statistical analysis was performed in the form of the analysis of variance and Student's t-test, which gave good interpretation in terms of interaction of experimental parameters. The interaction of the parameters temperature, pH, dye concentration and adsorbent dosage on Crystal Violet removal is also highly significant with confidential level > 99%. © 2012, Chinese Institute of Environmental Engineering. All rights reserved.

Eswaran U.,University of MalayaKuala Lumpur | Ramiah H.,University of MalayaKuala Lumpur | Kanesan J.,University of MalayaKuala Lumpur | Reza A.W.,University of MalayaKuala Lumpur
Renewable and Sustainable Energy Reviews | Year: 2015

Abstract Energy saving power amplifier design methodologies are gaining increasing momentum in the exponential growth of wireless communications due to the demand of high data rates. The demand in high data rates bottlenecks linear transmission specifications for the power amplifier, thus mandates the device to drain more battery energy. In other words, the efficiency of the PA degrades significantly. The improvement in PA's overall efficiency is possible with the innovation of various circuit topology, which has paved the path to reduce the overall battery energy consumption. In this paper, these techniques are reviewed, explicitly. Also reviewed are recent reported works which attempts low voltage headroom implementation in complementing the reduction of battery energy consumption and design cost through the use of Complementary Metal Oxide Semiconductor (CMOS) process. © 2015 Elsevier Ltd.

Shafaghat H.,University of MalayaKuala Lumpur | Rezaei P.S.,University of MalayaKuala Lumpur | Ashri Wan Daud W.M.,University of MalayaKuala Lumpur
RSC Advances | Year: 2015

Pyrolysis bio-oil is recognized as a renewable and carbon-neutral fuel which could be a potential alternative for depleting fossil fuels. However, bio-oil is highly oxygenated and needs to be upgraded prior to be used as fuel additive. Catalytic hydrodeoxygenation (HDO) is an efficient technique for bio-oil upgrading. The reaction pathway for HDO of bio-oil is unknown since it is a mixture of hundreds of different compounds. The study on mechanism of transformation of these compounds could be helpful to propose an overall pathway for HDO of bio-oil. Phenols which are derived from pyrolysis of lignin fraction of biomass are considered as attractive model compounds for study of bio-oil HDO since they are highly stable in HDO reaction. Reaction pathway and product selectivity in HDO of phenols are highly affected by type of catalyst promoters and supports, catalyst preparation procedure, solvent type, chemicals used as co-feed and operating conditions (i.e., temperature and pressure). The effects of these factors on selective production of high-value hydrocarbons of aromatics and alicyclics from HDO of phenol, cresol, guaiacol and anisole are discussed in this review. © The Royal Society of Chemistry.

Aris M.H.,University of MalayaKuala Lumpur | Annuar M.S.M.,University of MalayaKuala Lumpur | Ling T.C.,University of MalayaKuala Lumpur
Polymer Degradation and Stability | Year: 2016

Lipase-catalyzed hydrolysis of poly(ɛ-caprolactone) (PCL) in toulene was investigated. PCL with number-average molecular weight (Mn) 10,000 g mol−1 was hydrolyzed using immobilized Candida antarctica lipase B (CALB). The increase in PCL concentration led to a decrease in degradation rate. Enhanced rate was observed when reaction temperature was increased from 30 to 50 °C. Enzymatic chain scission of PCL yielded cyclic dicaprolactone, tricaprolactone, tetracaprolactone and oligomers with Mn less than ∼1000 g mol−1. Catalytic formation of cyclic lactones via back-biting mechanism in low water content environment was attributed to CALB. Its hydrolysis of PCL displayed consecutive random- and chain-end scission with time from detailed thermal, molecular weight and structural analyses. Apparent activation energy, Ea for hydrolysis was 45 kJ mol−1 i.e. half of that reverse reaction. Dicaprolactone and oligomers from hydrolysis readily re-polymerized to produce mid-range polymer with Mn 1400 g mol−1 after 36 h in the same reaction medium. © 2016 Elsevier Ltd

Baghaee Moghaddam T.,University of MalayaKuala Lumpur | Baghaee Moghaddam T.,University of Waterloo | Soltani M.,University of MalayaKuala Lumpur | Karim M.R.,University of MalayaKuala Lumpur | Baaj H.,University of Waterloo
Measurement: Journal of the International Measurement Confederation | Year: 2015

Abstract Optimization of polymer and asphalt content in polymer modified asphalt mixture is the aim of road engineers and designers. The purpose of this study is to characterize Stone Mastic Asphalt (SMA) mixture's properties containing waste polyethylene terephthalate (PET) which is a type of polymer material. Response Surface Methodology (RSM) was designated as a new method to measure mixture properties at different PET content and asphalt binder value. To fabricate the mixture fresh 80/100 penetration grade asphalt binder with different percentages (5-7% by weight of aggregate particles) was utilized. Different amounts of PET were used from 0% to 1% by weight of aggregate particles. Marshall Stability and Flow test was performed on the mixtures. Specific gravity and volumetric properties of mixtures were obtained. RSM was used to analyze Marshall and volumetric properties of unmodified and PET modified asphalt mixtures. Models were produced to fit the experimental results. As shown in this study suggested models were successfully fitted to the experimental results. Based on the results achieved amounts of 5.88% of asphalt content and 0.18% of PET were found to be the optimal values. © 2015 Elsevier Ltd.

M'Ng J.C.P.,University of MalayaKuala Lumpur | Mehralizadeh M.,University of MalayaKuala Lumpur
PLoS ONE | Year: 2016

The motivation behind this research is to innovatively combine new methods like wavelet, principal component analysis (PCA), and artificial neural network (ANN) approaches to analyze trade in today's increasingly difficult and volatile financial futures markets. The main focus of this study is to facilitate forecasting by using an enhanced denoising process on market data, taken as a multivariate signal, in order to deduct the same noise from the open-high-low-close signal of a market. This research offers evidence on the predictive ability and the profitability of abnormal returns of a new hybrid forecasting model using Wavelet-PCA denoising and ANN (named WPCA-NN) on futures contracts of Hong Kong's Hang Seng futures, Japan's NIKKEI 225 futures, Singapore's MSCI futures, South Korea's KOSPI 200 futures, and Taiwan's TAIEX futures from 2005 to 2014. Using a host of technical analysis indicators consisting of RSI, MACD, MACD Signal, Stochastic Fast %K, Stochastic Slow %K, Stochastic %D, and Ultimate Oscillator, empirical results show that the annual mean returns of WPCA-NN are more than the threshold buy-and-hold for the validation, test, and evaluation periods; this is inconsistent with the traditional random walk hypothesis, which insists that mechanical rules cannot outperform the threshold buy-andhold. The findings, however, are consistent with literature that advocates technical analysis. © 2016 Chan Phooi M'ng, Mehralizadeh.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Shadman F.,University of MalayaKuala Lumpur | Sadeghipour S.,University of MalayaKuala Lumpur | Moghavvemi M.,University of Malaya | Moghavvemi M.,University of Science and CultureTehran | Saidur R.,University of MalayaKuala Lumpur
Renewable and Sustainable Energy Reviews | Year: 2016

The availability and reliability of renewable energy sources are highly dependent on climate conditions, which may vary due to possible global climatic changes. Long-term energy planning, however, does not normally take into account future threats of climate change on energy security. This paper shows the impacts of drought, as one of the main features of climate change, on the technology of electricity generation and on CO2 emissions in the Association of Southeast Asian Nations-6 (ASEAN-6). We provide insights into the extent of the vulnerability of electricity generation options to drought. The findings increase awareness for future planning of the energy generation mix and emphasizes on an integrated and collaborative management plan based on drought planning initiatives and measures. © 2015 Elsevier Ltd.

Vignesvaran K.,University of MalayaKuala Lumpur | Alias Z.,University of MalayaKuala Lumpur
Archives of Insect Biochemistry and Physiology | Year: 2016

Drosophila melanogaster glutathione S-transferase D3 (DmGSTD3) has a shorter amino acid sequence as compared to other GSTs known in the fruit flies. This is due to the 15 amino acid N-terminal truncation in which normally active amino acid residue is located. The work has made use of homology modeling to visualize the arrangement of amino acid side chains in the glutathione (GSH) substrate cavity. The identified amino acids were then replaced with amino acids without functional groups in the side chains and the mutants were analyzed kinetically. Homology modeling revealed that the side chains of Y89 and Y97 were shown facing toward the substrate cavity proposing their possible role in catalyzing the conjugation. Y97A and Y89A GSH gave large changes in Km (twofold increase), Vmax (fivefold reduction), and Kcat/Km values for GSH suggesting their significant role in the conjugation reaction. The replacement at either positions has not affected the affinity of the enzyme toward 1-chloro-2,4-dinitrobenzene as no significant change in values of Kmax was observed. The replacement, however, had significantly reduced the catalytic efficiency of both mutants with (Kcat/Km)GSH and (Kcat/Km)CDNB of eight- and twofold reduction. The recombinant DmGSTD3 has shown no activity toward 1,2-dichloro-4-nitrobenzene, 2,4-hexadienal, 2,4-heptadienal, p-nitrobenzyl chloride, ethacrynic acid, and sulfobromophthalein. Therefore, it was evident that DmGSTD3 has made use of distal amino acids Y97 and Y89 for GSH conjugation. © 2016 Wiley Periodicals, Inc.

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