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Articles 1 - 30 of 59
Full-Text Articles in Engineering
Optical Frequency Comb Generation Based On Chirping Of Mach-Zehnder Modulators
Optical Frequency Comb Generation Based On Chirping Of Mach-Zehnder Modulators
Faculty of Engineering University of Malaya
A new approach for the generation of an optical frequency comb, based on chirping of modulators, is proposed and numerically demonstrated. The setup includes two cascaded Mach-Zehnder Modulators (MZMs), a sinusoidal wave oscillator, and an electrical time delay. The first MZM is driven directly by a sinusoidal wave, while the second MZM is driven by a delayed replica of the sinusoidal wave. A mathematical model of the proposed system is formulated and modeled using the Matlab software. It is shown that the number of the frequency lines is directly proportional to the chirp factor. In order to achieve the highest …
Biosensing Enhancement Of Dengue Virus Using Microballoon Mixers On Centrifugal Microfluidic Platforms
Faculty of Engineering University of Malaya
Dengue is the current leading cause of death among children in several Latin American and Asian countries. Due to poverty in areas where the disease is prevalent and the high cost of conventional diagnostic systems, low cost devices are needed to reduce the burden caused by dengue infection. Centrifugal microfluidic platforms are an alternative solution to reduce costs and increase the availability of a rapid diagnostic system. The rate of chemical reactions in such devices often depends on the efficiency of the mixing techniques employed in their microfluidic networks. This paper introduces a micromixer that operates by the expansion and …
Single Phase Transformerless Inverter Topologies For Grid-Tied Photovoltaic System: A Review
Single Phase Transformerless Inverter Topologies For Grid-Tied Photovoltaic System: A Review
Faculty of Engineering University of Malaya
Grid-tied inverters are the key components of distributed generation system because of their function as an effective interface between renewable energy sources and utility. Recently, there has been an increasing interest in the use of transformerless inverter for low-voltage single-phase grid-tied photovoltaic (PV) system due to higher efficiency, lower cost, smaller size and weight when compared to the ones with transformer. However, the leakage current issues of transformerless inverter, which depends on the topology structure and modulation scheme, have to be addressed very carefully. This review focuses on the transformerless topologies, which are classified into three basic groups based on …
An Islanding Detection Strategy For Distribution Network Connected With Hybrid Dg Resources
An Islanding Detection Strategy For Distribution Network Connected With Hybrid Dg Resources
Faculty of Engineering University of Malaya
The exponential growth in electricity demand has driven the Distributed Generation (DG) technology a boost in the power system. The use of DG is beneficial to power utilities, DG owners', and end-users in terms of reliability, power quality, and economics. However, to fully utilize the benefits of DGs, some technical issues need to be addressed. Islanding condition is one of the most important issue in this context. Until now, several islanding detection techniques have been proposed for detecting the islanding condition. This paper presents a brief overview of existing islanding detection techniques with their relative merits and demerits. Apart from …
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
Faculty of Engineering University of Malaya
Smart grid (SG) application is being used nowadays to meet the demand of increasing power consumption. SG application is considered as a perfect solution for combining renewable energy resources and electrical grid by means of creating a bidirectional communication channel between the two systems. In this paper, three SG applications applicable to renewable energy system, namely, distribution automation (DA), distributed energy system-storage (DER) and electrical vehicle (EV), are investigated in order to study their suitability in Long Term Evolution (LTE) network. To compensate the weakness in the existing scheduling algorithms, a novel bandwidth estimation and allocation technique and a new …
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
A Novel Lte Scheduling Algorithm For Green Technology In Smart Grid
Faculty of Engineering University of Malaya
Smart grid (SG) application is being used nowadays to meet the demand of increasing power consumption. SG application is considered as a perfect solution for combining renewable energy resources and electrical grid by means of creating a bidirectional communication channel between the two systems. In this paper, three SG applications applicable to renewable energy system, namely, distribution automation (DA), distributed energy system-storage (DER) and electrical vehicle (EV), are investigated in order to study their suitability in Long Term Evolution (LTE) network. To compensate the weakness in the existing scheduling algorithms, a novel bandwidth estimation and allocation technique and a new …
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 …
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 …
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 …
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 …
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 …
Recursive Construction Of Output-Context Fuzzy Systems For The Condition Monitoring Of Electrical Hotspots Based On Infrared Thermography
Faculty of Engineering University of Malaya
Infrared thermography technology is currently being used in various applications, including fault diagnosis in electrical equipment. Thermal abnormalities are diagnosed by identifying and classifying the hotspot conditions of electrical components. In this article, a new recursively constructed output-context fuzzy system is proposed to characterize the condition of electrical hotspots. An infrared camera is initially used to capture the thermal images of components with hotspots, and intensity features are extracted from each hotspot. The Recursively Constructed Fuzzy System (RCFS) is then applied to automatically realize and formulate the conditions of the thermal abnormalities. On the basis of the priority level, the …
Too Enthusiastic To Care For Safety: Present Status And Recent Developments Of Nanosafety In Asean Countries
Faculty of Engineering University of Malaya
Nanotechnology has the prospect to vibrate the imagination of human being and has the ability to be used in almost every sector of human need. With its limitless potentials, there are many environmental, health and safety related concerns due to extremely ambivalent effects of nanoparticles. Studies revealed that nanoparticles can enter the human body through the lungs, intestinal tract, and skin. Therefore, the researchers and workers who handle nanoparticles and nanomaterials can theoretically and primarily be affected, whereas on the consumers this will have secondary effects. This paper aims at sharing and evaluating the investment scenario, present status and recent …
Mode-Locked 2 Mu M Fiber Laser With A Multi-Walled Carbon Nanotube As A Saturable Absorber
Mode-Locked 2 Mu M Fiber Laser With A Multi-Walled Carbon Nanotube As A Saturable Absorber
Faculty of Engineering University of Malaya
We propose and demonstrate a passively mode-locked fiber laser operating at 1951.8 nm using a commercial thulium-doped fiber (TDF) laser, a homemade double-clad thulium-ytterbium co-doped fiber (TYDF) as the gain media, and a multi-walled carbon nanotube (MWCNT) based saturable absorber (SA). We prepare the MWCNT composite by mixing a homogeneous solution of MWCNTs with a diluted polyvinyl alcohol (PVA) polymer solution and then drying it at room temperature to form a film. The film is placed between two fiber connectors as a SA before it is integrated into a laser ring cavity. The cavity consists of a 2 m long …
Simulation Of Unsteady Heat And Mass Transport With Heatline And Massline In A Partially Heated Open Cavity
Faculty of Engineering University of Malaya
A computational work is performed to investigate the transient heat and mass transfer inside a ventilated enclosure. The enclosure has two ventilation ports as inlet and outlet. Three different configurations are tested according to location of outlet ports while location of inlet port is fixed. In case 1, the outlet port is located on the top of the left vertical wall, in case 2 at the right and case 3 at the middle of the ceiling. Finite element method is employed to solve the governing equations of flow, heat and mass transfer. Also, the heatline and massline techniques are used …
A Distributed Particle Filtering Approach For Multiple Acoustic Source Tracking Using An Acoustic Vector Sensor Network
Faculty of Engineering University of Malaya
Different centralized approaches such as least-squares (LS) and particle filtering (PF) algorithms have been developed to localize an acoustic source by using a distributed acoustic vector sensor (AVS) array. However, such algorithms are either not applicable for multiple sources or rely heavily on sensor-processor communication. In this paper, a distributed unscented PF (DUPF) approach is proposed for multiple acoustic source tracking. At each distributed AVS node, the first-order and the second-order statistics of the local state are estimated by using an unscented information filter (UIF) based PF. The UIF is employed to approximate the optimum importance function due to its …
A Comparative Study Of Multi-Objective Optimal Power Flow Based On Particle Swarm, Evolutionary Programming, And Genetic Algorithm
Faculty of Engineering University of Malaya
This paper compares the performance of three population-based algorithms including particle swarm optimization (PSO), evolutionary programming (EP), and genetic algorithm (GA) to solve the multi-objective optimal power flow (OPF) problem. The unattractive characteristics of the cost-based OPF including loss, voltage profile, and emission justifies the necessity of multi-objective OPF study. This study presents the programming results of the nine essential single-objective and multi-objective functions of OPF problem. The considered objective functions include cost, active power loss, voltage stability index, and emission. The multi-objective optimizations include cost and active power loss, cost and voltage stability index, active power loss and voltage …
Multilevel Voltage Source Inverter With Optimised Usage Of Bidirectional Switches
Multilevel Voltage Source Inverter With Optimised Usage Of Bidirectional Switches
Faculty of Engineering University of Malaya
This study presents a multilevel voltage source inverter that has been designed to reduce circuit complexity by optimising the use of bidirectional switches. The proposed inverter is built by adding an auxiliary circuit comprising an arrangement of bidirectional switches to the three-phase, six-switch, full-bridge configuration. Several bidirectional switches are made to function in the optimised mode in which their operations are divided among the three phases. The presence of the optimised mode considerably reduces the number of power switches as the number of levels in the line-to-line voltage waveform increases. A novel modulation scheme based on space vector concept with …
A Q-Switched Fibre Laser Operating In The 2 Mu M Region Based On Nonlinear Polarization Rotation Technique
Faculty of Engineering University of Malaya
We demonstrate a Q-switched fibre laser operating at 1949.0 nm, which is based on a nonlinear polarization rotation (NPR) technique. It uses a 2 m long commercial thulium-doped fibre and a 15 m long homemade thulium-ytterbium co-doped fibre as active media. They are pumped respectively by 800 nm single-mode and 905 nm multimode radiations. A stable Q-switched pulse train with the repetition rate 13.49 kHz and the pulse width 3.089 mu s is obtained when the 905 nm and 800 nm pump powers are fixed at 2.3 W and 110.4 mW, respectively. The maximum pulse energy, 11 nJ, is obtained …
Bit-Depth Scalable Lossless Coding For High Dynamic Range Images
Bit-Depth Scalable Lossless Coding For High Dynamic Range Images
Faculty of Engineering University of Malaya
In this paper, we propose a bit-depth scalable lossless coding method for high dynamic range (HDR) images based on a reversible logarithmic mapping. HDR images are generally expressed as floating-point data, such as in the OpenEXR or RGBE formats. Our bit-depth scalable coding approach outputs base layer data and enhancement layer data. It can reconstruct the low dynamic range (LDR) image from the base layer data and reconstructs the HDR image by adding the enhancement layer data. Most previous two-layer methods have focused on the lossy coding of HDR images. Unfortunately, the extension of previous lossy methods to lossless coding …
A New Low-Profile Inverted A-Shaped Patch Antenna For Multi-Band Operations
A New Low-Profile Inverted A-Shaped Patch Antenna For Multi-Band Operations
Faculty of Engineering University of Malaya
This paper presents the design and analysis of a compact modified inverted-A shape multi-band patch antenna for WiMAX and C-band telecommunication satellite applications. The proposed antenna has simple geometrical structure which consist of 20 mm x 20 mm radiating patch with slot loading and fed by 4 mm long microstrip line. The proposed antenna is designed and analyzed by using commercially available full-wave 3D high frequency electromagnetic simulator namely Ansys HFSS. The optimized design of the proposed multi-band patch antenna is fabricated on 1.6 mm thick fiberglass polymer resin dielectric material substrate with reduced ground plane by using in-house PCB …
Study On Coarsening Of Ag3sn Intermetallic Compound In The Fe-Modified Sn-1ag-0.5cu Solder Alloys
Study On Coarsening Of Ag3sn Intermetallic Compound In The Fe-Modified Sn-1ag-0.5cu Solder Alloys
Faculty of Engineering University of Malaya
The present study focuses on coarsening of Ag3Sn intermetallic compound in the Sn-1Ag-0.5Cu and Fe-modified Sn-1Ag-0.5Cu solder alloy. The investigations showed that the Ag3Sn intermetallics coarsened rapidly in the Sn-1Ag-0.5Cu solder alloy whereas the Ag3Sn intermetallics were found to be quite stable in the Fe-modified Sn-1Ag-0.5Cu solder alloy. The lattice strain in the Ag3Sn intermetallics and the blocking effect on Ag diffusivity in Sn matrix suggested the possible mechanisms for the coarsening suppression of the Ag3Sn intermetallics in the Fe-modified solder alloy. (C) 2014 Elsevier B.V. All rights reserved. Link to Full-Text Articles : http://www.sciencedirect.com/science/article/pii/S0925838814024621
Zigbee-Based Data Acquisition System For Online Monitoring Of Grid-Connected Photovoltaic System
Zigbee-Based Data Acquisition System For Online Monitoring Of Grid-Connected Photovoltaic System
Faculty of Engineering University of Malaya
For grid-connected photovoltaic (PV) system, monitoring is considered as a crucial aspect for observing the stability and performance of the system. The simplest method is to have the data collected and transmitted across data cables. Due to the cost and technical limitations of the data cable, the monitoring station needs to be located reasonably close to the monitored plant. Apart being inconvenient, the use of data cable often adds capital and maintenance cost to the system. In this research project, a Zigbee-based wireless monitoring system is developed for online monitoring of a grid-connected photovoltaic system. Parameters like temperature, irradiation, PV …
Development Of Novel Passive Check Valves For The Microfluidic Cd Platform
Development Of Novel Passive Check Valves For The Microfluidic Cd Platform
Faculty of Engineering University of Malaya
Microfluidic CD platforms are utilized to perform different biological processes and chemical analyses. In general, a microfluidic CD implements the centrifugal force that is created by the spinning of the platform to pump liquid through the microfluidic network of chambers and channels. Over the last few decades, a wide range of active and passive valving methods were proposed and tested on various microfluidic platforms. Most of the presented valves are too complex to design and involve lengthy fabrication processes. In this paper, easy to fabricate air and liquid check valves for centrifugal microfluidic platforms are presented: a Terminal Check Valve …
Development Of Nanoengineered Thulium-Doped Fiber Laser With Low Threshold Pump Power And Tunable Operating Wavelength
Faculty of Engineering University of Malaya
A tunable and low-threshold thulium (Tm)-doped fiber (TDF) laser is demonstrated using a new silica-based nanoengineered TDF in a linear configuration, in conjunction with 1552-nm pumping. The TDF used in these experiments had a Tm-doped nanoengineering yttrium-alumina-silica glass core with a diameter of 13.43 mu m and 0. 21 NA, which is surrounded by a pure silica inner cladding with normal acrylate polymer resin coating. The nanoengineered TDF was fabricated using a modified chemical vapor deposition (MCVD) process, in conjunction with a solution-doping technique. The fabricated fiber shows an absorption loss of 165 dB/m at 793 nm. A maximum lasing …
A Configurable Architecture For Fast Moments Computation
A Configurable Architecture For Fast Moments Computation
Faculty of Engineering University of Malaya
No abstract provided.
Enhancement Of Thulium-Ytterbium Doped Fiber Laser Efficiency Using Dual-Pumping Method
Enhancement Of Thulium-Ytterbium Doped Fiber Laser Efficiency Using Dual-Pumping Method
Faculty of Engineering University of Malaya
Performance enhancement of laser acquired from a newly developed double-clad Yb3+/Tm3+ codoped fiber (YTDF) is demonstrated using dual-pumping scheme. The laser uses a 2 m long YTDF fiber with a core dopant concentrations (in wt%) of 2.00 Yb2O3, 0.5 Tm2O3, 1.0 Al2O3, and 3.00 Y2O3 as a gain medium in conjunction with a pair of fiber Bragg grating in a linear cavity resonator to generate lasing at 1901.6 nm. The best efficiency of 2.9% and the highest output power of 27 mW are obtained by combining 927 nm pump with 905 nm pump. As compared to a single pumping scheme …
Effective Utilization Of Excess Energy In Standalone Hybrid Renewable Energy Systems For Improving Comfort Ability And Reducing Cost Of Energy: A Review And Analysis
Faculty of Engineering University of Malaya
One of the features that characterize renewable energy sources is their variability and intermittency. Intermittency covers both the predictable and unpredictable variations of their power outputs and uncertainty in the power availability. To overcome the drawback of intermittency, special design considerations should be taken into account. These additional design considerations increases the overall cost of the renewable energy systems. Adding storage system and/or backup source to the renewable sources is one of the measures used to guarantee the continuity of power supply to the loads, and therefore improve the reliability of the renewable energy systems. The operation of renewable energy …