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Articles 31 - 60 of 233
Full-Text Articles in Engineering
H6-Type Transformerless Single-Phase Inverter For Grid-Tied Photovoltaic System
H6-Type Transformerless Single-Phase Inverter For Grid-Tied Photovoltaic System
Faculty of Engineering University of Malaya
There has been an increasing interest in transformerless inverter for grid-tied photovoltaic (PV) system because of the benefits of lower cost, smaller volume as well as higher efficiency compared with the ones with transformer. However, one of the technical challenges of the transformerless inverter is the safety issue of leakage current which needs to be addressed carefully. In addition, according to the international regulations, transformerless inverter should be capable of handling a certain amount of reactive power. In this study, a new H6-type transformerless inverter for grid-tied PV system is proposed that can eliminate the threat of leakage current. The …
Q-Switched Brillouin Fibre Laser With Multi-Wall Carbon Nanotube Saturable Absorber
Q-Switched Brillouin Fibre Laser With Multi-Wall Carbon Nanotube Saturable Absorber
Faculty of Engineering University of Malaya
A Q-switched Brillouin fibre laser (BFL) is successfully demonstrated using multi-walled carbon nanotubes (MWCNTs) embedded in polyvinyl alcohol (PVA) film as a passive saturable absorber (SA) for the first time. The SA is obtained by sandwiching the developed MWCNTs-PVA film between two FC/PC fibre connectors after depositing index-matching gel onto the fibre ends. The proposed Q-switched BFL incorporates a 5 km long dispersion shifted fibre in a ring cavity structure to generate Stokes shifted by 0.08 nm from the Brillouin pump wavelength. The BFL starts to generate a Q-switching pulse train at threshold pump power of 5 dBm. As the …
Tribological Investigation Of Ultra-High Molecular Weight Polyethylene Against Advanced Ceramic Surfaces In Total Hip Joint Replacement
Faculty of Engineering University of Malaya
The aim of the study was to investigate whether a modified ceramic head surface could reduce the friction and wear rate of simulated ceramic-on-polyethylene hip joints. To address this aim, ultra-high molecular weight polyethylene (UHMWPE) was made to slide on aluminium oxide (Al2O3), dimpled Al2O3, diamond-like carbon (DLC) coated and DLC-coated dimpled substrates. The experiment condition was replicated to simulate artificial hip joints in terms of contact pressure, speed and temperature. UHMWPE on non-dimpled Al2O3 showed lower friction coefficient and wear rate compared to other advanced surfaces. Lower wettability, and higher hardness and surface adhesion of DLC resulted in increased …
A Combination Of Computational Fluid Dynamics (Cfd) And Adaptive Neuro-Fuzzy System (Anfis) For Prediction Of The Bubble Column Hydrodynamics
Faculty of Engineering University of Malaya
This paper shows a combination of computational fluid dynamics (CFD) and adaptive neuro-fuzzy inference system (ANFIS) to propose a new viewpoint for multiphase flow modeling, including the accuracy of soft computing techniques in the prediction of a three dimensional (3D) bubble column reactor. Since there are some difficulties (i.e., high computational time in numerical methods and expensive equipment in experimental techniques) in predicting bubble column reactors, particularly at different column locations and various operation conditions, soft computing methods can be developed as a favorable replacement for conventional measurement and prediction techniques. This study employs CFD beside the ANFIS method to …
Multiple-Objective Optimization In Precision Laser Cutting Of Different Thermoplastics
Multiple-Objective Optimization In Precision Laser Cutting Of Different Thermoplastics
Faculty of Engineering University of Malaya
Thermoplastics are increasingly being used in biomedical, automotive and electronics industries due to their excellent physical and chemical properties. Due to the localized and non-contact process, use of lasers for cutting could result in precise cut with small heat-affected zone (HAZ). Precision laser cutting involving various materials is important in high-volume manufacturing processes to minimize operational cost, error reduction and improve product quality. This study uses grey relational analysis to determine a single optimized set of cutting parameters for three different thermoplastics. The set of the optimized processing parameters is determined based on the highest relational grade and was found …
Characterization Of Nickel-Doped Biphasic Calcium Phosphate/Graphene Nanoplatelet Composites For Biomedical Application
Faculty of Engineering University of Malaya
The effect of the addition of an ionic dopant to calcium phosphates for biomedical applications requires specific research due to the essential roles played in such processes. In the present study, the mechanical and biological properties of Ni-doped hydroxyapatite (HA) and Ni-doped HA mixed with graphene nanoplatelets (GNPs) were evaluated. Ni (3 wt.% and 6 wt.%)-doped HA was synthesized using a continuous precipitation method and calcined at 900 degrees C for 1 h. The GNP (0.5-2 wt.%)-reinforced 6% Ni-doped HA (Ni6) composite was prepared using rotary ball milling for 15 h. The sintering process was performed using hot isostatic pressing …
Development Of A Control System For Artificially Rehabilitated Limbs: A Review
Development Of A Control System For Artificially Rehabilitated Limbs: A Review
Faculty of Engineering University of Malaya
Development of an advanced control system for prostheses (artificial limbs) is necessary to provide functionality, effectiveness, and preferably the feeling of a sound living limb. The development of the control system has introduced varieties of control strategies depending on the application. This paper reviews some control systems used for prosthetics, orthotics, and exoskeletons. The advantages and limitations of different control systems for particular applications have been discussed and presented in a comparative manner to help in deciding the appropriate method for pertinent application. Link to Full-Text Articles : http://link.springer.com/article/10.1007/s00422-014-0635-1
Eggshells: A Novel Bio-Filler For Intumescent Flame-Retardant Coatings
Eggshells: A Novel Bio-Filler For Intumescent Flame-Retardant Coatings
Faculty of Engineering University of Malaya
The aim of this study was to develop intumescent flame-retardant coatings that incorporate chicken eggshell (CES) waste as a novel eco-friendly bio-filler. Three flame-retardant additives, namely, ammonium polyphosphate phase II, pentaerythritol and melamine were mixed with flame-retardant fillers and acrylic binder to synthesize the intumescent coatings. The fire performance of the coatings was evaluated in accordance with 'BS 476: Part 6-Fire Propagation' and 'BS 476: Part 7-Surface Spread of Flame' test standards. It was found that 4 out of 5 of the coated specimens (B, C, D and E) neither showed surface spread of flame nor any afterglow combustion upon …
Effects Of Engine Variables And Heat Transfer On The Performance Of Biodiesel Fueled Ic Engines
Effects Of Engine Variables And Heat Transfer On The Performance Of Biodiesel Fueled Ic Engines
Faculty of Engineering University of Malaya
These days internal combustion engines are the major source of transportation. They run mainly on fossil fuels which are depleting day by day not only that they cause pollution which endangers human life and creates environmental problems. Of late biodiesel has emerged as a better alternative fuel for internal combustion engines due to its comparable properties with that of fossil fuels. Today's automobiles require economy of operation, high power output and last but not the least, reduction in greenhouse gases emitted by the vehicles. Such specific demands have compelled the researchers not only to focus on the parameters affecting the …
Growth And Characterization Of The Oxide Scales And Core/Shell Nanowires On Ti-6al-4 V Particles During Thermal Oxidation
Faculty of Engineering University of Malaya
Nanowires were grown on as-received and milled particles of Ti-6Al-4 V (Ti64) alloy under an optimum condition of 750 degrees C in an Ar atmosphere containing 15 ppm of oxygen. The as-grown nanowires and the underneath oxide scales developed on Ti64 particles were characterized by X-ray diffiactometry (XRD), field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) equipped with energy dispersive X-ray spectroscope (EDS). Results revealed the formation of oxide scales consisting of double layers on the surface of Ti64 particles. The outer oxide scale was a mixture of Al2O3 …
Kinetic And Stoichiometric Characterization For Efficient Enhanced Biological Phosphorus Removal (Ebpr) Process At High Temperatures
Faculty of Engineering University of Malaya
A recently reported stable and efficient EBPR system at high temperatures around 30 degrees C has led to characterization of kinetic and stoichiometric parameters of the Activated Sludge Model no. 2d (ASM2d). Firstly, suitable model parameters were selected by identifiability analysis. Next, the model was calibrated and validated. ASM2d was found to represent the processes well at 28 and 32 degrees C except in polyhyroxyalkanoate (PHA) accumulation of the latter. The values of the kinetic parameters for PHA storage (q(PHA)), polyphosphate storage (q(PP)) and growth (mu(PAO)) of polyphosphate-accumulating organisms (PAOs) at 28 and 32 degrees C were found to be …
Rotation Invariant Bin Detection And Solid Waste Level Classification
Rotation Invariant Bin Detection And Solid Waste Level Classification
Faculty of Engineering University of Malaya
In this paper, a solid waste bin detection and waste level classification system that is rotation invariant is presented. First, possible locations and orientations of the bin are detected using Hough line detection. Then cross correlation is calculated to differentiate the true bin position and orientation from those of other similar objects. Next, features are extracted from the inside of the bin area and together with detected bin corners they are used to determine the bin's waste level. A few features are also obtained from the outside of the bin area to check whether there is rubbish littered outside the …
Effect Of High-Energy Ball Milling On The Formation And Micro Structural Features Of Carbonated Chlorapatite Nanopowders
Faculty of Engineering University of Malaya
Carbonated chlorapatite nanopowders (n-CCAp) were synthesized by mechanochemical process from calcite (CaCO3), phosphorus pentoxide (P2O5), and calcium chloride (CaCl2) as raw materials. Results demonstrated that the formation of n-CCAp was influenced strongly by the milling time. At the beginning of milling (up to 15 min), CaCO3 and CaCl2 were the dominant phases, while P2O5 disappeared entirely due to its very high deliquescent nature. With increasing the milling time to 600 min, the progressive mechanochemical reaction was completed which resulted in the formation of nanostructured carbonated chlorapatite. According to the X-ray diffraction data, crystallite size of the product decreased from 24 …
Tailoring Zno Nanostructures By Spray Pyrolysis And Thermal Annealing
Tailoring Zno Nanostructures By Spray Pyrolysis And Thermal Annealing
Faculty of Engineering University of Malaya
We report a novel synthesis of ZnO nanorods with hexagonal pyramid-like heads by a simple and low cost technique of spray pyrolysis with the help of zinc acetate and tin (IV) chloride pentahydrate precursors. In the present study, the growth of ZnO nanorods is optimized by varying a number of sprays and annealing temperatures in the synthesis process. FESEM analysis reveals that ZnO nanorods are observed when the number of sprays exceeds 150 and film-like structure is observed below 150 sprays. Nanorods are formed when the molar ratio of zinc acetate to tin (IV) chloride pentahydrate in the solution mixture …
The Synthesis Of Bio-Lubricant Based Oil By Hydrolysis And Non-Catalytic Of Palm Oil Mill Effluent (Pome) Using Lipase
Faculty of Engineering University of Malaya
Synthesis of bio-lubricant from palm oil mill effluent (POME) using enzymatic hydrolysis and noncatalytic esterification has been investigated in this article. The effects of essential parameters, which are temperature, pH, agitation speed, enzyme loading, ratio of oil to fatty acid and alcohol to fatty acid, on the reaction rate were examined. The optimum hydrolysis rate (0.1639 mg/sec.L) was achieved at 40 degrees C, pH 7.0, 650 rpm, 20 U/mL of enzyme loading and 50% (v/v) of POME. As for non-catalytic esterification, the highest reaction rate attained was 0.0018 mg/sec.L at the operating conditions of 75 degrees C, 950 rpm, and …
Temperature Dependence Of Raman Scattering In 4h-Sic Films Under Different Growth Conditions
Temperature Dependence Of Raman Scattering In 4h-Sic Films Under Different Growth Conditions
Faculty of Engineering University of Malaya
The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80K to 550 K. The effects of growth conditions on E-2(TO), E-1(TO) and A(1)(LO) phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2(TO) modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E-2(TO) mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A(1) (longitudinal optical plasma coupling (LOPC)) mode does …
Influence Of Biodiesel Blending On Physicochemical Properties And Importance Of Mathematical Model For Predicting The Properties Of Biodiesel Blend
Faculty of Engineering University of Malaya
The growing demand for green world serves as one of the most significant challenges of modernization. Requirements like largest usage of energy for modern society as well as demand for friendly milieu create a deep concern in field of research. Biofuels are placed at the peak of the research arena for their underlying benefits as mentioned by multiple researches. Out of a number of vegetable oils, only a few are used commercially for biodiesel production. Due to various limitations of edible oil, non-edible oils are becoming a profitable choice. Till today, very little percentage of biodiesel is used successfully in …
Field Analysis Of Indoor Air Quality In High Rise And Low Rise Green Offices With Radiant Slab Cooling Systems In Malaysia
Faculty of Engineering University of Malaya
Even though the green building concept is fairly new in Malaysia, the development of this industry has been growing in recent years prior to the launch of Malaysia's own standard, namely the Green Building Index (GBI). One of the criteria assessed in the GBI is the energy efficiency, which takes about 21% of the overall assessment. Considering this, the passive design has been included in the green building concept to reduce the energy usage without compromising occupant thermal comfort. This study attempts to assess the passive design effectiveness in terms of indoor air quality in green office buildings in the …
An Experimental Investigation On A Single Tubular Sofc For Renewable Energy Based Cogeneration System
Faculty of Engineering University of Malaya
Having negative impacts on environment and the scarcity of resources of conventional fossil fuels, fuel cell technology draws more attention as an alternative for providing the electrical energy in parallel with thermal energy. In this study, a single tubular solid oxide fuel cell (SOFC) with an electrolyte of Yttria-Stabilized Zirconia 8 mol% ceramic powder was experimentally investigated. The investigation illustrated the effects of three different fuel flow-rates (175 ml/min, 250 ml/min and 325 ml/min) and two operating temperatures (650 degrees C and 750 degrees C) on the output electrical and thermal powers. The highest electrical voltage (open circuit) and overall …
Multi-Response Analysis In The Processing Of Poly (Methyl Methacrylate) Nano-Fibres Membrane By Electrospinning Based On Response Surface Methodology: Fibre Diameter And Bead Formation
Faculty of Engineering University of Malaya
The fabrication of the nano-scale fine fibres from poly (methyl methacrylate) (PMMA)-DMF solution was completed using the electrospinning process. Significantly, fibre membranes with an average diameter of 95 (+/- 32) nm and bead number 11 (+/- 2) were successfully achieved. The extensive analysis of the distribution of fibre diameters and bead formation was performed using different needle gauge, collector distance, voltage, concentration, feed rate and molecular weight by observing images in FESEM after explanation of regression. A regression model was applied to realize the dominant factors on the responses, from this model, the molecular weight was excluded to successfully obtain …
Performance Enhancement Of A Flat Plate Solar Collector Using Titanium Dioxide Nanofluid And Polyethylene Glycol Dispersant
Faculty of Engineering University of Malaya
The use of TiO2 water nanofluid as a working fluid for enhancing the performance of a flat plate solar collector has been studied. The volume fraction of the nanoparticles was 0.1% and 0.3% respectively, while the mass flow rates of the nanofluid varied from 0.5 to 1.5 kg/min, respectively. Thermo-physical properties and reduced sedimentation for TiO2-nanofluid was obtained using PEG 400 dispersant. The results reveal the impact and importance of each of these parameters. Energy efficiency increased by 76.6% for 0.1% volume fraction and 0.5 kg/min flow rate, whereas the highest exergy efficiency achieved was 16.9% for 0.1% volume fraction …
Production Of Greenhouse Gas Free Hydrogen By Thermocatalytic Decomposition Of Methane – A Review
Production Of Greenhouse Gas Free Hydrogen By Thermocatalytic Decomposition Of Methane – A Review
Faculty of Engineering University of Malaya
Thermocatalytic decomposition of methane (TCD) is a fully green single step technology for producing hydrogen and nano-carbon. This review studying all development in laboratory-scale research on TCD, especially the recent advances like co-feeding effect and catalyst regeneration for augmenting the productivity of the whole process. Although a great success on the laboratory-scale has been fulfilled, TCD for greenhouse gas (GHG) free hydrogen production is still in its infancy. The need for commercialization of TCD is greater than ever in the present situation of huge GHG emission. TCD usually examined over various kind of catalysts, such as monometallic, bimetallic, trimetallic, combination …
Using Finite State Machine And A Hybrid Of Eeg Signal And Eog Artifacts For An Asynchronous Wheelchair Navigation
Faculty of Engineering University of Malaya
In this study, an asynchronous wheelchair navigation system using a hybrid of EEG signal and EOG artifacts embedded in EEG signals is demonstrated. The EEG signals are recorded at three different locations on the scalp in the occipital and motor cortex regions. First, an EEG signal related to eyelid position is analyzed and used to determine whether the eyes are closed or open. If the eyes are closed, no wheelchair movement is allowed. If the eyes are open, EOG traces (artifacts) from two other EEG signals are examined to infer the gaze direction of the eyes. A sliding window is …
The Thermoluminescence Characteristics And The Glow Curves Of Thulium Doped Silica Fiber Exposed To 10 Mv Photon And 21 Mev Electron Radiation
Faculty of Engineering University of Malaya
The thermoluminescence (TL) glow curves and kinetics parameters of Thulium (Tm) doped silica cylindrical fibers (CF) are presented. A linear accelerator (LINAC) was used to deliver high-energy radiation of 21 MeV electrons and 10 MV photons. The CFs were irradiated in the dose range of 0.2-10 Gy. The experimental glow curve data was reconstructed by using WinREMS. The WinGCF software was used for the kinetic parameters evaluation. The TL sensitivity of Tm-doped silica CF is about 2 times higher as compared to pure silica CF. Tm-doped silica CF seems to be more sensitive to 21 MeV electrons than to 10 …
A Generalized Energy-Based Kinetic Model For Microwave-Assisted Extraction Of Bioactive Compounds From Plants
Faculty of Engineering University of Malaya
By considering the absorbed power and energy based on heating power profile during extraction, a generalized model with washing coefficient (b), diffusion coefficient (k) and predictive parameter namely absorbed power density (APD) was developed for microwave-assisted extraction (MAE) at any operational heating modes. To study the model, MAE of flavonoids from cocoa (Theobroma cacao L.) leaves was conducted using the heating modes (constant-power, two-steps-power, intermittent-power and constant-temperature) at various microwave power (100-300W) and extraction temperature (50 degrees C and 70 degrees C). The results shows that the model (b = 0.5595 and k' = 0.01279 mL/J) is able to predict …
Optimal Multiple Distributed Generation Output Through Rank Evolutionary Particle Swarm Optimization
Optimal Multiple Distributed Generation Output Through Rank Evolutionary Particle Swarm Optimization
Faculty of Engineering University of Malaya
The total power losses in a distribution network are usually minimized through the adjustment of the output of a distributed generator (DG). In line with this objective, most researchers concentrate on the optimization technique in order to regulate the DG's output and compute its optimal size. In this article, a novel Rank Evolutionary Particle Swarm Optimization (REPSO) method is introduced. By hybridizing the Evolutionary Programming (EP) in Particle Swarm Optimization (PSO) algorithm, it will allow the entire particles to move toward the optimal value faster than usual and reach the convergence value. Moreover, the local best (P-best) and global best …
Development Of Optimum Process Parameters And A Study Of The Effects Of Surface Roughness On Brazing Of Copper
Faculty of Engineering University of Malaya
Brazing experiments on commercially-pure copper plates, using brazing filler metal (MBF-2005), are conducted at temperatures in the range of 650-750 degrees C for time-durations in the range of 5-15 min. Shear tests for braze-joints involved use of a universal testing machine. Based on the shear-test results, a new brazing cycle has been developed that corresponds to the greatest shear strength of the braze-joint. The brazing cycle has been performed under a controlled dry-argon atmosphere in a tube furnace. Microscopic observations were made by use of both optical and electron microscopes; whereas surface roughness measurements were made by using a TRIO …
Flexural Behaviour Of Rc Beams Strengthened With Wire Mesh-Epoxy Composite
Flexural Behaviour Of Rc Beams Strengthened With Wire Mesh-Epoxy Composite
Faculty of Engineering University of Malaya
In this research work, the flexural behaviour of reinforced concrete (RC) beams strengthened with a new type of strengthening material, namely wire mesh-epoxy composite, was investigated. The flexural behaviour of RC beams strengthened using this new material was compared with RC beams strengthened with carbon fibre reinforced polymer (CFRP) sheet. In addition, the structural performance of a beam strengthened using a hybrid of wire mesh-epoxy and CFRP sheet was investigated. The results showed that the use of wire mesh-epoxy composite provides considerable enhancement in the performance of strengthened beams. Compared to CFRP, the wire mesh-epoxy strengthened beams showed more improvement …
Innovative Hybrid Bonding Method For Strengthening Reinforced Concrete Beam In Flexure
Innovative Hybrid Bonding Method For Strengthening Reinforced Concrete Beam In Flexure
Faculty of Engineering University of Malaya
This paper presents the test results of the experimental behavior of reinforced concrete (RC) beams strengthened with the newly proposed hybrid bonding technique, which is the wise combination of plate bonding and near surface mounting (NSM) technique. Many studies have focused on the experimental behavior of RC beams strengthened with externally bonded steel plates. However, the presence of high interfacial shear stresses at the end of the plate may reduce the resistance to failure of the strengthened structure. Recently, to a certain extent, the development of the near surface mounted strengthening technique can reduce the problem of this premature end …
Modified Two-Phase Model With Hybrid Control For Gas Phase Propylene Copolymerization In Fluidized Bed
Faculty of Engineering University of Malaya
In order to explore the dynamic behavior and process control of reactor temperature, a modified two-phase dynamic model for gas phase propylene copolymerization in a fluidized bed reactor is developed in which the entrainment of solid particles is considered. The modified model was compared with well-mixed and two-phase models in order to investigate the dynamic modeling response. The modified two-phase model shows close dynamic response to the well-mixed and two-phase models at the start of the polymerization, but begins to diverge with time. The proposed modified two-phase and two-phase models were validated with actual plant data. It was shown that …