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Articles 211 - 233 of 233
Full-Text Articles in Engineering
Thermoluminescence Response Of Flat Optical Fiber Subjected To 9 Mev Electron Irradiations
Thermoluminescence Response Of Flat Optical Fiber Subjected To 9 Mev Electron Irradiations
Faculty of Engineering University of Malaya
We describe the efforts of finding a new thermoluminescent (TL) media using pure silica flat optical fiber (FF). The present study investigates the dose response, sensitivity, minimum detectable dose and glow curve of FF subjected to 9 MeV electron irradiations with various dose ranges from 0 Gy to 2.5 Gy. The above-mentioned TL properties of the FF are compared with commercially available TLD-100 rods. The TL measurements of the TL media exhibit a linear dose response over the delivered dose using a linear accelerator. We found that the sensitivity of TLD-100 is markedly 6 times greater than that of FF …
Thermal Characteristic Of Sintered Ag-Cu Nanopaste For High-Temperature Die-Attach Application
Thermal Characteristic Of Sintered Ag-Cu Nanopaste For High-Temperature Die-Attach Application
Faculty of Engineering University of Malaya
In this work, thermal characteristic of silver-copper (Ag-Cu) nanopaste that consists of a mixture of nano-sized Ag and Cu particles and organic compounds meant for high-temperature die-attach application is reported. The Ag-Cu nanopaste was sintered at 380 degrees C for 30 min without the need of applying external pressure and the effect of Cu loading (20-80 wt%) on the thermal properties was investigated in against of pure Ag nanopaste and pure Cu nanopaste. The results showed the specific heat of sintered Ag-Cu nanopaste was increased as the loading of Cu increased. For thermal conductivity and coefficient of thermal expansion (CTE) …
An Accelerated And Accurate Three-Dimensional Ray Tracing Using Red-Black Tree With Facet Mining And Object Bouncing Techniques
Faculty of Engineering University of Malaya
Recent trends show that it is a major challenge to predict the exact propagation path accurately and efficiently for three-dimensional (3D) indoor environments. Therefore, this study introduces a new 3D ray tracing algorithm based on a red-black tree with facet mining and object bouncing techniques. The red-black tree data structure offers a faster object searching operation while repeatedly performing intersection tests. On the other hand, extensive ray-facet intersection tests can be eliminated by using object and facet bouncing techniques, whereas the facet mining makes it easier to trace the transmitted ray paths accurately. The proposed method is compared with ray …
Thermal And Dynamic Mechanical Properties Of Grafted Kenaf Filled Poly (Vinyl Chloride)/Ethylene Vinyl Acetate Composites
Faculty of Engineering University of Malaya
The effects of kenaf and poly (methyl methacrylate grafted kenaf on the thermal and dynamic mechanical properties of poly (vinyl chloride), PVC and ethylene vinyl acetate, EVA blends were investigated. The PVC/EVA/kenaf composites were prepared by mixing the grafted and ungrafted kenaf fiber and PVC/ EVA blend using HAAKE Rheomixer at a temperature of 150 degrees C and the rotor speed at 50 rpm for 20 min. The composites were subjected to Differential Scanning Calorimetric (DSC), Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) and Scanning Electron Microscopy (SEM) studies. The DSC data revealed that the crystallinity …
Airborne Hyperspectral Discrimination Of Tree Species With Different Ages Using Discrete Wavelet Transform
Faculty of Engineering University of Malaya
In this article, the capability of discrete wavelet transform (DWT) to discriminate tree species with different ages using airborne hyperspectral remote sensing is investigated. The performance of DWT is compared against commonly used traditional methods, i.e. original reflectance and first and second derivatives. The hyperspectral data are obtained from Thetford forest of the UK, which contains Corsican and Scots pines with different ages and broadleaved tree species. The discrimination is performed by employing three different spectral measurement techniques (SMTs) including Spectral Angle Mapper (SAM), Spectral Information Divergence (SID), and a combination of SAM and SID. Five different mother wavelets with …
Effective Use Of An Edfa And Raman Pump Residual Powers Via A Bi-Edf In L-Band Multi-Wavelength Fiber Laser Generation
Faculty of Engineering University of Malaya
Residual powers of an erbium-doped fiber amplifier (EDFA) and a Raman pump are utilized effectively for pumping a 0.45 m long bismuth-based EDF (Bi-EDF) in linear-cavity L-band multi-wavelength fiber laser generation. A 7.7 km dispersion compensating fiber (DCF) operates as both Brillouin and Raman gain media and a 6.5 dBm fixed-power tunable laser source (TLS) amplified by an EDFA works as a Brillouin pump (BP). By inserting the Bi-EDF in the linear cavity and using the EDFA and the fixed Raman pump residual powers 13.6 mW and 64 mW, at wavelengths 978.8 nm and 1490.6 nm respectively, the gain spectrum …
Investigating The Electrical Discharge Machining (Edm) Parameter Effects On Al-Mg2si Metal Matrix Composite (Mmc) For High Material Removal Rate (Mrr) And Less Ewr-Rsm Approach
Faculty of Engineering University of Malaya
Al-Mg2Si composite is a new group of metalmatrix composites (MMCs). Electrical discharge machining (EDM) is a nonconventional machining process for machining electrically conductive materials regardless of hardness, strength and temperature resistance, complex shapes, fine surface finish/textures and accurate dimensions. A copper electrode and oil-based dielectric fluid mixed with aluminum powder were used. The polarity of electrode was positive. Response surface methodology (RSM) was used to analyze EDM of this composite material. This research illustrates the effect of input variables (voltage, current, pulse ON time, and duty factor) on material removal rate (MRR), electrode wear ratio (EWR), and microstructure changes. The …
A New Hybrid Support Vector Machine–Wavelet Transform Approach For Estimation Of Horizontal Global Solar Radiation
Faculty of Engineering University of Malaya
In this paper, a new hybrid approach by combining the Support Vector Machine (SVM) with Wavelet Transform (WT) algorithm is developed to predict horizontal global solar radiation. The predictions are conducted on both daily and monthly mean scales for an Iranian coastal city. The proposed SVM-WT method is compared against other existing techniques to demonstrate its efficiency and viability. Three different sets of parameters are served as inputs to establish three models. The results indicate that the model using relative sunshine duration, difference between air temperatures, relative humidity, average temperature and extraterrestrial solar radiation as inputs shows higher performance than …
Analytical Wake Model Of Tidal Current Turbine
Analytical Wake Model Of Tidal Current Turbine
Faculty of Engineering University of Malaya
Prediction of the wake structure is important to understand the lee flow of a tidal current turbine. The proposed analytical wake model consists of several equations derived from the theoretical works of a ship propeller jet. Axial momentum theory was used to predict the minimum velocity at the immediate plane of the lee wake and followed by the proposed recovery equation to determine the minimum velocity at various lateral sections along the rotation axis. Gaussian probability distribution was used to predict the velocity distribution of lateral sections in a wake. Entire wake is able to be illustrated through the calculation …
The Effects Of Calcium-To-Phosphorus Ratio On The Densification And Mechanical Properties Of Hydroxyapatite Ceramic
Faculty of Engineering University of Malaya
In this work, hydroxyapatite (HA) powders were synthesized using calcium hydroxide Ca(OH)(2) and orthophosphoric acid H3PO4 via wet chemical precipitation method in aqueous medium. Calcium-to-phosphorus (Ca/P) ratio was set to 1.57, 1.67, 1.87 that yield calcium-deficient HA, stoichiometric HA, and calcium-rich HA, respectively. These synthesized HA powders (having different Ca/P ratio) were characterized in terms of particle size and microstructural examination. Then, the densification and mechanical properties of the calcium-deficient HA, stoichiometric HA, and calcium-rich HA were evaluated from 1000 to 1350 degrees C. Experimental results have shown that no decomposition of hydroxyapatite phase was observed for stoichiometric HA (Ca/P …
The Effects Of Calcium-To-Phosphorus Ratio On The Densification And Mechanical Properties Of Hydroxyapatite Ceramic
Faculty of Engineering University of Malaya
In this work, hydroxyapatite (HA) powders were synthesized using calcium hydroxide Ca(OH)(2) and orthophosphoric acid H3PO4 via wet chemical precipitation method in aqueous medium. Calcium-to-phosphorus (Ca/P) ratio was set to 1.57, 1.67, 1.87 that yield calcium-deficient HA, stoichiometric HA, and calcium-rich HA, respectively. These synthesized HA powders (having different Ca/P ratio) were characterized in terms of particle size and microstructural examination. Then, the densification and mechanical properties of the calcium-deficient HA, stoichiometric HA, and calcium-rich HA were evaluated from 1000 to 1350 degrees C. Experimental results have shown that no decomposition of hydroxyapatite phase was observed for stoichiometric HA (Ca/P …
Modeling And Simulation Of Metal Organic Halide Vapor Phase Epitaxy (Mohvpe) Growth Chambe
Modeling And Simulation Of Metal Organic Halide Vapor Phase Epitaxy (Mohvpe) Growth Chambe
Faculty of Engineering University of Malaya
Over the last few decades, there was a substantial appeal on the growth of gallium-nitride (Ga-N) based alloy for high performance optoelectronic devices such as blue/violet laser diode, blue/white light emitting diode etc. In the recent years, there have been revolutionary changes in semiconductor field. Growth method for GaN-based film has been extensively explored, with success of thick film growth using halide vapor-phase epitaxy technique. The theoretical changes were attributed from the experimental results where modeling was vastly used for the purpose of design of equipment. This is because of the cost of the equipment and it is one of …
Signal Quality Measures On Pulse Oximetry And Blood Pressure Signals Acquired From Self-Measurement In A Home Environment
Faculty of Engineering University of Malaya
Recently, decision support system (DSSs) have become more widely accepted as a support tool for use with telehealth systems, helping clinicians to summarize and digest what would otherwise be an unmanageable volume of data. One of the pillars of a home telehealth system is the performance of unsupervised physiological self-measurement by patients in their own homes. Such measurements are prone to error and noise artifact, often due to poor measurement technique and ignorance of the measurement and transduction principles at work. These errors can degrade the quality of the recorded signals and ultimately degrade the performance of the DSS system, …
A Pair Of Bubbles' Rising Dynamics In A Xanthan Gum Solution: A Cfd Study
A Pair Of Bubbles' Rising Dynamics In A Xanthan Gum Solution: A Cfd Study
Faculty of Engineering University of Malaya
The motion and interaction of a bubble pair in a non-Newtonian fluid (xanthan gum solution) were numerically simulated using a volume of fluid (VOF) method, in which the continuous surface tension model and the power-law model were adopted to represent the surface tension and rheological properties of non-Newtonian fluids, respectively. The effects of the initial horizontal bubble interval, oblique alignment and rheological properties of non-Newtonian fluids on a pair of bubbles rising side-by-side are evaluated in this study. The results indicate that for the case with a non-dimensional initial horizontal bubble interval h* = 4.0, the interaction between the bubbles …
Integration Of Biosensors Based On Microfluidic: A Review
Integration Of Biosensors Based On Microfluidic: A Review
Faculty of Engineering University of Malaya
Purpose - Biotechnology is closely associated to microfluidics. During the last decade, designs of microfluidic devices such as geometries and scales have been modified and improved according to the applications for better performance. Numerous sensor technologies existing in the industry has potential use for clinical applications. Fabrication techniques of microfluidics initially rooted from the electromechanical systems (EMS) technology. Design/methodology/approach - In this review, we emphasized on the most available manufacture approaches to fabricate microchannels, their applications and the properties which make them unique components in biological studies. Findings - Major fundamental and technological advances demonstrate the enhancing of capabilities and …
Classification Of Eyelid Position And Eyeball Movement Using Eeg Signals
Classification Of Eyelid Position And Eyeball Movement Using Eeg Signals
Faculty of Engineering University of Malaya
Contamination of EOG activities in EEG signals remains a significant problem in designing the hybrid BCI system. Since EEG signals have always been contaminated by EOG artifacts, we employ these artifacts as inputs into our system. Therefore, in this study we utilized theEEG and its EOG artifacts as inputs to the hybrid BCI and evaluated the classification performance between thresholding and classifier techniques to determine the eyelid position and eyeball movement from EEG signals and its EOG artifacts in real-time. The EEG signals are recorded from the occipital (channel O2) and motor cortex (channel C3 and C4) on the scalp …
Dry Reforming Of Methane: Influence Of Process Parameters-A Review
Dry Reforming Of Methane: Influence Of Process Parameters-A Review
Faculty of Engineering University of Malaya
This review will explore the influences of the active metal, support, promoter, preparation methods, calcination temperature, reducing environment, particle size and reactor choice on catalytic activity and carbon deposition for the dry reforming of methane. Bimetallic (Ni-Pt, Ni-Rh, Ni-Ce, Ni-Mo, Ni-Co) and monometallic (Ni) catalysts are preferred for dry reforming compared to noble metals (Rh, Ru and Pt) due to their low-cost Investigation of support materials indicated that ceria zirconia mixtures, ZrO2 with alkali metals (Mg2+, Ca2+, Y2+) addition, MgO, SBA-15, ZSM-5, CeO2, BaTiO3 and Ca0.8Sr0.2TiO3 showed improved catalytic activities and decreased carbon deposition. The modifying effects of cerium (Ce), …
Estimation Of The Effect Of Catalyst Physical Characteristics On Fenton-Like Oxidation Efficiency Using Adaptive Neuro-Fuzzy Computing Technique
Faculty of Engineering University of Malaya
Catalyst size, which determines surface area, is one of the major factors in catalytic performance. In this study, response surface methodology (RSM) and an adaptive neuro-fuzzy inference system (ANFIS) were applied to quantify the effects of physical characteristics of magnetite on Fenton-like oxidation efficiency of methylene blue. For this purpose, two magnetite samples (M and N) were used and characterized by XRD, BET surface area, particle size analyzer and FE-SEM. Central composite design (CCD) was applied to design the experiments, develop regression models, optimize and evaluate the individual and interactive effects of five independent variables: H2O2 and catalyst concentrations, pH, …
Influences Of Flame-Retardant Fillers On Fire Protection And Mechanical Properties Of Intumescent Coatings
Faculty of Engineering University of Malaya
A combination of acrylic binder and flame-retardant ingredients was used to synthesize the solvent-borne intumescent coatings designed for steel substrates. The influences of individual and various combinations of flame-retardant fillers on the fire protection and mechanical properties of the coatings were characterized by using Bunsen burner, thermogravimetric analysis, limiting oxygen index, field emission scanning electron microscopy, freeze thaw cycles, static immersion and pull-off type equipment. It was found that the combination of aluminium hydroxide (Al(OH)(3)) and titanium dioxide (TiO2) has significantly improved the fire protection, thermal stability and water resistance of the coating. This formulation had an LOI value of …
A Dft Study On An Alkali Atom Doped Decahedral Silver Nanocluster For Potential Application In Opto-Electronics And Catalysis
Faculty of Engineering University of Malaya
A systematic study of the structural, electronic and optical properties of the decahedral bimetallic Ag12X cluster is presented in the framework of density functional theory (DFT), where one atom of an alkali metal (X = Li, Na, K, Rb, Cs, Fr) is added, replacing a Ag atom in the decahedral Ag-13 cluster in core (c-doped), vertex (v-doped) and surface (s-doped) positions. Geometrical optimization of the clusters indicated that Li and Na doped clusters exhibited the highest stability. The binding energy (BE), vertical ionization potential (VIP), vertical electron affinity (VEA) and HOMO-LUMO gaps were calculated to compare the electronic stability and …
Comparative Evaluation Of The Blends Of Gas-To-Liquid (Gtl) Fuels And Biodiesels With Diesel At High Idling Conditions: An In-Depth Analysis On Engine Performance And Environment Pollutants
Faculty of Engineering University of Malaya
This study focuses on the physicochemical fuel characteristics and engine performance-emission features of three prospective alternative transportation fuels: Alexandrian laurel biodiesel (ALBD), jatropha biodiesel (JBD) and GTL fuel at high idling conditions. The blends of GTL fuel (G10, G20), JBD (J10, J20) and ALBD (AL10, AL20) with diesel had been investigated in a multi-cylinder diesel engine at different load-speed conditions. Analysis of the fuel properties showed a linear variation of the major fuel properties with an increase of alternative fuel quantity in the blends. Engine performance test results revealed an average decrease of brake specific fuel consumption (BSFC) (ca. 8.65-12.26%) …
Application Of Colloidal Gas Aphron Suspensions Produced From Sapindus Mukorossi For Arsenic Removal From Contaminated Soil
Faculty of Engineering University of Malaya
Colloidal gas aphron dispersions (CGAs) can be described as a system of microbubbles suspended homogenously in a liquid matrix. This work examines the performance of CGAs in comparison to surfactant solutions for washing low levels of arsenic from an iron rich soil. Sodium Dodecyl Sulfate (SDS) and saponin, a biodegradable surfactant, obtained from Sapindus mukorossi or soapnut fruit were used for generating CGAs and solutions for soil washing. Column washing experiments were performed in down-flow and up flow modes at a soil pH of 5 and 6 using varying concentration of SDS and soapnut solutions as well as CGAs. Soapnut …
Intermixing Reactions In Electrodeposited Cu/Sn And Cu/Ni/Sn Multilayer Interconnects During Room Temperature And High Temperature Aging
Faculty of Engineering University of Malaya
Current push for miniaturization and 3D packaging makes it important to understand reactions in interconnects with ultra small volume. In order to reduce processing time and to have more homogeneous interconnects, solder can be designed in a multilayer form with components layer thickness in the sub-micron or even nanometer range. In this work, reaction kinetics in multilayer interconnects consisting stacks of Cu/Sn/Cu and Cu/Ni/Sn/Ni/Sn deposited by electrodeposition were investigated at room temperature and 150 A degrees C. The progress of the reaction in the multilayers was monitored by using XRD, SEM and EDX. Results show that by inserting a 70 …