Kuala Selangor, Malaysia
Kuala Selangor, Malaysia

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Begum M.,Multimedia University | Begum M.,Bangladesh Atomic Energy Commission | Rahman A.K.M.M.,Multimedia University | Rahman A.K.M.M.,Bangladesh Atomic Energy Commission | And 5 more authors.
Applied Radiation and Isotopes | Year: 2015

Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples ~0.5cm length are annealed at temperature of 400°C for 1h period to standardize their sensitivities and background. Standard TLD-100 chips are also annealed for 1h at 400°C and subsequently 2h at 100°C to yield the highest sensitivity. TL responses of these fibers show linearity over a wide gamma radiation dose that is an important property for radiation dosimetry. Among all fibers used in this study, 100μm core diameter fiber provides highest response that is 2.6 times than that of smallest core (20μm core) optical fiber. These fiber-samples demonstrate better response than commercial multi-mode optical fiber and also provide low degree of fading about 20% over a period of fifteen days for gamma radiation. Effective atomic number (Zeff) is found in the range (13.25-13.69) which is higher than soft tissue (7.5) however within the range of human-bone (11.6-13.8). All the fibers can also be re-used several times as a detector after annealing. TL properties of the Ge-doped optical fibers indicate promising applications in ionizing radiation dosimetry. © 2014 Elsevier Ltd.

Begum M.,Multimedia University | Rahman A.K.M.M.,Multimedia University | Abdul-Rashid H.A.,Multimedia University | Abdullah W.S.W.,Malaysian Nuclear Agency | And 9 more authors.
4th International Conference on Photonics, ICP 2013 - Conference Proceeding | Year: 2013

Thermoluminescence (TL) properties of five different core diameter of 6 mol% germanium (Ge) doped optical fibers have been investigated for the purpose of TL dosimetry. The optical fiber dosimeter TL properties is compared with commercially available TLD-100 chips (LiF:Mg,Ti). Samples were irradiated using Cobalt-60 standard radiation source ranging from 1Gy to 10 Gy. These fibers show good linear dose response up to 10 Gy. Highest core diameter of Ge doped optical fiber (core 100 μm) provides the best response among all fibers. We observe the larger core fiber show better response than smaller core fiber. The relative sensitivity of 100 μm core optical fiber is 0.26 ± 0.04 with respect to TLD-100 chip. © 2013 IEEE.

Wong S.-K.,Multimedia University | Kung F.,Multimedia University | Maisurah S.,Telekom Research and Development | Osman M.N.B.,Telekom Research and Development
Progress in Electromagnetics Research | Year: 2011

A WiMedia compliant CMOS RF power amplifier (PA) for ultra-wideband (UWB) transmitter in the 3.1 to 4.8 GHz band is presented in this paper. The proposed two-stage PA employs a cascade topology on the first stage as driver while the second stage is a simple common source (CS) amplifier. In order to improve the efficiency and output power, the output impedance of the driver amplifier (first stage) is optimized so that it falls on the source-pull contours of the second stage amplifier. On-wafer measurement on the fabricated prototype showed a maximum power gain of +15:8 dB, 0.6 dB gainatness, +11:3dBm of output 1 dB gain compression and up to a maximum of 17.3% power added effciency (PAE) at 4 GHz using a 50 load termination, while consuming only 25.7mW from a 1.8V supply voltage. Measurement results obtained are used to create a non-linear power-dependent S-parameter (P2D) model for wideband input and output matching optimizations and co-simulations with the UWB modulated test signals. Using the created P2D model, the PA achieved a maximum output channel power of +3:48dBm with an error vector magnitude (EVM) of -23.1 dB and complied with the WiMedia mask specifications.

Anuar K.M.S.,Telekom Research and Development | Muhd-Yasin S.Z.,Telekom Research and Development | Zulkifli M.I.,Telekom Research and Development | Hanif S.,Telekom Research and Development | And 6 more authors.
Advanced Materials Research | Year: 2014

Development of rare earth doped silica fibre fabrication using MCVD furnace -chelate vapor phase delivery is presented. In this study, erbium and aluminum is used as the dopant with precursor erbium (III) tris (2,2,6,6-tetramethyl-3,5-heptanedionate) and aluminium chloride (AlCl3) respectively. The preform was designed for 10 layers of SiO2-P2O3 doped silica (clad structure) and 5 layers of SiO2-Al2O3-Er2O3 (core structure). Preform is analysed for the properties of layer structure i.e. refractive index profile using preform index profiler and EPMA (SEM-EDX) for dopant distribution. Results show good longitudinal uniformity despite condensation of metal organic precursor during the fabrication process. Maximum incorporation of Er2O3 is about 0.1 mole % with 1.2 mole% of Al2O3 in the core. © (2014) Trans Tech Publications, Switzerland.

Aljamimi S.M.,Multimedia University | Yusoff Z.,Multimedia University | Abdul-Rashid H.A.,Multimedia University | Anuar K.M.S.,Telekom Research and Development | And 4 more authors.
Advanced Materials Research | Year: 2014

This work is part of a study of solution doping in Modified Chemical Vapor Deposition (MCVD) used for silica optical fiber fabrication. This paper will concentrate on soot characterstics and the effect of different aluminum solution concentration. The effect of three different concentration of aluminum (0.3M,0.7M and 1.2M) with heat treatment are studied while the other parameters of MCVD and solution doping are fixed such as deposition temperature, SiCl4 flow, and soaking time. The porous core layer is deposited at 18000C and the porosity of the deposited porous layer is analyzed using gas adsorption method. Refractive index profile of the doped preform is measured using preform analyzer. The aluminum distribution across the sintered glass layer is also examined by EDX. © (2014) Trans Tech Publications, Switzerland.

Aljamimi S.M.,Multimedia University | Anuar M.S.K.,Telekom Research and Development | Muhamad-Yassin S.Z.,Telekom Research and Development | Zulkifli M.I.,Telekom Research and Development | And 4 more authors.
Fiber and Integrated Optics | Year: 2014

Incorporation of alumina (Al2O3) into a silica matrix by modified chemical vapor deposition and a solution doping technique is investigated in this study. Multiple soaking cycles were used to increase the aluminum content in the core layer. The effect of alumina retention in silica matrix soot is focused by multiple cycles of soaking with different solution concentrations, while the effect of the adsorption mechanism is fixed by maintaining the soot deposition process (such as temperature [1,800°C], precursor, total gas flow, and soaking time). The deposited soot is examined for porosity characteristics and effective surface area by a gas adsorption technique with Brunauer-Emett-Teller surface area analysis and the surface and cross-section morphology using scanning electron microscopy. Three different concentrations are used in this work (0.3, 0.7, and 1.2 M) with multiple cycles of soaking. Sintering and the collapsing process is controlled for each preform. The result shows that the alumina content is increased substantially as the number of soaking processes is increased, which may be due to the retention effect as only a small amount of adsorption process takes place as indicated by the slight decrease in the surface area of soot. The collapsed preforms are analyzed using a preform analyzer. Energy dispersive x-ray spectrometry is used to check aluminum content and distribution into the core layer. Copyright © Taylor & Francis Group, LLC.

Kanesan T.,Telekom Research and Development | Kanesan T.,Northumbria University | Rajbhandari S.,University of Oxford | Giacoumidis E.,Aston University | Aldaya I.,Monterrey Institute of Technology
Electronics Letters | Year: 2014

Owing to the limited cell size of eNodeB (eNB), the relay node has emerged as an attractive solution for the long-term evolution (LTE) system. The nonlinear limit of the alternative method to multipleinput and multiple-output (MIMO) based on frequency division multiplexing (FDM) for orthogonal FDM (OFDM) is analysed over varying transmission spans. In this reported work, it is shown that the degradation pattern over the linear, intermixing and nonlinear propagation regions is consistent for the 2 and the 2.6 GHz bands. The proposed bands experienced a linear increase in the error vector magnitude (EVM) for both the linear and the nonlinear regions proportional to the increasing transmission spans. In addition, an optical launch power between -2 and 2 dBm achieved a significantly lower EVM than the LTE limit of 8% for the 10-60 km spans. © The Institution of Engineering and Technology 2014.

Illias H.A.,University of Malaya | Mokhlis H.,University of Malaya | Ibrahim M.S.B.,Telekom Research and Development | Bakar A.H.A.,University of Malaya
Proceedings of the 2014 IEEE 8th International Power Engineering and Optimization Conference, PEOCO 2014 | Year: 2014

Temperature increment in high voltage copper conductors is one of the important parameters that needs to be monitored continuously. This is due to significant temperature rise in the conductor may lead to thermal breakdown, which consequently causing power outage. One of the factors affecting temperature rise in conductors is the applied voltage waveform. In this work, simulation of temperature increment in high voltage conductors under different applied voltage waveform was performed using finite element analysis (FEA) software. From the simulation results, applied voltage waveform which yields the highest temperature increment in high voltage conductors can be identified, which are DC and square waveforms. Triangular waveform yields the lowest temperature increment in the conductor. The results from this work may increase an understanding about heat transfer under different applied current or voltage waveform. © 2014 IEEE.

Aris T.N.M.,University Putra Malaysia | Nazeer S.A.,Telekom Research and Development
2011 5th Malaysian Conference in Software Engineering, MySEC 2011 | Year: 2011

Comprehending Object-Oriented Programming (OOP) concepts is a difficult task especially for novice students. This usually happens during the transition form learning fundamental concepts to object-oriented (OO) concepts. When given an OO problem to solve, novices find it hard to relate with objects. If novices can view the world based on real objects, this can help them solve their problem of comprehending the OO concepts. In this paper, we propose to design an agent model to understand the semantics of OO Java source codes. The agents are designed based on the Belief-Desire-Intention (BDI) architecture. Three agents namely GUI agent, semantic agent and novice agents are constructed. The GUI agent is controlled by the user to provide source codes examples. The semantic agent submits the source codes to the novice agent and explains the semantic or meaning of the source codes to the novice agent. The process involves source codes comparison technique. This model provides an OOP semantics knowledge representation based on intelligent agents. © 2011 IEEE.

Salleh S.,Telekom Research and Development | Hashim M.F.,Telekom Research and Development
Proceedings of the 2nd Asia Symposium on Quality Electronic Design, ASQED 2010 | Year: 2010

A low-noise amplifier (LNA) integrated circuit (IC) has been designed and implemented on a 0.13μm RF CMOS process technology. The performance of the LNA has been targeted to exceed WCDMA standard specification. This paper presents the design methodology and compares the simulated and measurement results of the cascode LNA with inductive degeneration. There were expected mismatch between simulation and measurement data, thus some of the matching elements were intentionally placed outside of the chip. Additionally, target frequency on simulation was designed at a general 850MHz frequency but later on measurement the target frequency was moved close to the center of receive frequency of Band V of WCDMA. On the simulation, at resonance frequency of 850MHz the NF is 0.54dB, 1dB input compression point is -26.67dBm and S21 is 27.86dB. On measurement where impedance matching were done exactly as in simulation with the exception in value of quality factor Q of the external passive devices, the NF about 2dB, 1dB input compression point is -25.3dB and S21 is 18dB at 875MHz. Value of LS and LG were adjusted to move peak of S21 to be at almost the new target frequency of 881.5MHz. Measurement result after impedance was matched to the band V receive center frequency, S21 has dropped to 13.37dB, NF has jumped to 2.65dB but linearity improved where 1dB input compression point has increased to -18.14dBm mainly because the drop in S21. © 2010 IEEE.

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