Displaying publications 1 - 20 of 341 in total

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  1. Alavi SE, Soltanian MR, Amiri IS, Khalily M, Supa'at AS, Ahmad H
    Sci Rep, 2016 Jan 27;6:19891.
    PMID: 26814621 DOI: 10.1038/srep19891
    5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated.
    Matched MeSH terms: Electricity
  2. Aimi Iznina Ahameed Tarmizi, Roslina Mohamad, Saiful Izwan Suliman, Murizah Kassim
    MyJurnal
    Distributed generator is one of the most common sources of electric power as it has many advantages. However, it might cause negative effects to the distribution system if appropriate conditions are undermined. Thus, this paper describes ways to optimise the use of distributed generator in a distribution system in order to reduce total power losses and to improve system performance by increasing stability of the voltage profile. This study focuses on the installation of distributed generator that is installed on 69-bus radial distribution system. Optimisation are done through Particle Swarm Optimization and Voltage Stability Indicator. The findings show that total power loss was reduced by 44.6%, and there was improvement in voltage profile stability.
    Matched MeSH terms: Electricity
  3. Soon, C.K., Zaini, Z., Mohd Ujang, A., Nagapan, S., Abdullah, A.H., Hasmori, M.F., et al.
    MyJurnal
    The building sector consumes about forty percent of world energy, making energy efficiency in existing buildings an important issue. This study has been undertaken to investigate energy consumption of a building that has been redesigned to incorporate energy efficient features. It was found that the introduction of energy efficient features has helped to achieve savings up to 46% of the total spent on energy particularly based on electricity bills.
    Matched MeSH terms: Electricity
  4. Alwi HA, Carey JR, Smith BV
    J Acoust Soc Am, 2000 Mar;107(3):1363-73.
    PMID: 10738791
    The chirp response of a thickness-drive tunable transducer for wide range time-bandwidth and sweep rates chirp signals is demonstrated experimentally and computationally. The computational evaluation uses recursive digital-filter model based on the z-transform method. The model is limited to simple lossless structure with no front and backing layers. The model and experimental results show that there is no limit on the maximum sweep rate of the chirp signal but practically the limit is determined by the limitation of the circuit that generates the control voltage that simulates a variable electric load.
    Matched MeSH terms: Electricity
  5. Wong LA, Shareef H, Mohamed A, Ibrahim AA
    ScientificWorldJournal, 2014;2014:752096.
    PMID: 25054184 DOI: 10.1155/2014/752096
    This paper presents the application of enhanced opposition-based firefly algorithm in obtaining the optimal battery energy storage systems (BESS) sizing in photovoltaic generation integrated radial distribution network in order to mitigate the voltage rise problem. Initially, the performance of the original firefly algorithm is enhanced by utilizing the opposition-based learning and introducing inertia weight. After evaluating the performance of the enhanced opposition-based firefly algorithm (EOFA) with fifteen benchmark functions, it is then adopted to determine the optimal size for BESS. Two optimization processes are conducted where the first optimization aims to obtain the optimal battery output power on hourly basis and the second optimization aims to obtain the optimal BESS capacity by considering the state of charge constraint of BESS. The effectiveness of the proposed method is validated by applying the algorithm to the 69-bus distribution system and by comparing the performance of EOFA with conventional firefly algorithm and gravitational search algorithm. Results show that EOFA has the best performance comparatively in terms of mitigating the voltage rise problem.
    Matched MeSH terms: Electricity*
  6. Islam MM, Shareef H, Mohamed A
    PLoS One, 2017;12(12):e0189170.
    PMID: 29220396 DOI: 10.1371/journal.pone.0189170
    The electric vehicle (EV) is considered a premium solution to global warming and various types of pollution. Nonetheless, a key concern is the recharging of EV batteries. Therefore, this study proposes a novel approach that considers the costs of transportation loss, buildup, and substation energy loss and that incorporates harmonic power loss into optimal rapid charging station (RCS) planning. A novel optimization technique, called binary lightning search algorithm (BLSA), is proposed to solve the optimization problem. BLSA is also applied to a conventional RCS planning method. A comprehensive analysis is conducted to assess the performance of the two RCS planning methods by using the IEEE 34-bus test system as the power grid. The comparative studies show that the proposed BLSA is better than other optimization techniques. The daily total cost in RCS planning of the proposed method, including harmonic power loss, decreases by 10% compared with that of the conventional method.
    Matched MeSH terms: Electricity*
  7. Solarin SA
    Environ Sci Pollut Res Int, 2019 Mar;26(9):8552-8574.
    PMID: 30706273 DOI: 10.1007/s11356-019-04225-y
    This paper examines the pattern of convergence in electricity intensity in a sample of 79 countries. We apply the residual augmented least squares regression to the convergence of energy intensity. This method has been used in the convergence of per capita energy consumption but not convergence of energy intensity. Furthermore, in contrast to the previous studies which mainly used the conventional beta convergence approach to examine conditional convergence, we use a beta convergence method that is capable of identifying the actual number of countries that contribute to conditional convergence. The sigma and gamma convergences of electricity intensity are also examined. In addition to the full sample of countries, we also examine convergence in African countries, Asian and Oceanic countries, American countries and European countries, separately. Convergences in OECD and non-OECD countries are also examined, separately. In the full sample, the results show convergence exists in 54% of the countries in the total sample. There is convergence in 65% of the African countries, 61% of the American countries, 43% of the Asian and Oceanic countries and 33% of the European countries. In terms of the regional classification, it is also observed that convergence exists for 58% of the non-OECD countries and 31% of the OECD countries. There is evidence for sigma convergence in all the blocs with the exception of European and non-OECD countries. With the exception of African countries, there is evidence for gamma convergence in all the countries and the various blocs. The policy implications of the results are discussed.
    Matched MeSH terms: Electricity*
  8. Lum CY, Lim KG, Chew KH
    J Phys Condens Matter, 2020 Jun 16;32(42):425401.
    PMID: 32544898 DOI: 10.1088/1361-648X/ab9d4a
    We propose a thermodynamic model to the study the antiferroelectric (AFE) phase transitions in antiferroelectric-ferroelectric (AFE-FE) superlattices in which the coupling at the interface between two layers is mediated by local polarizations. Phase diagram of the AFE layer in term of the degree of interfacial effect λ and temperature T involving ferrielectric (FI) and ferroelectric (FE) phases is investigated. These two phases are stabilized by the interfacial effect and internal electric field. AFE thickness L AFE versus T phase diagram is also constructed. Intermediate regions of two-phase coexistence (IM) emerge in the λ-T and L AFE-T phase diagrams, if certain interface properties λ and layer thickness L AFE criteria are met. These IM regions are metastable states, which exist as a transition state between two phases. A tricritical point locates at the boundaries across the FI, IM and FE phases is found in the L AFE-T phase diagram. Competition among the internal electric field due to the electrostatic coupling, the FE ordering arises from the interfacial effect and the antiferroelectric ordering within the AFE layer giving rises to the rich AFE phase diagram.
    Matched MeSH terms: Electricity; Static Electricity
  9. Yusoff, M.H.M., Hassan, H.A., Hashim, M.R., Abd-Rahman, M.K.
    ASM Science Journal, 2008;2(2):139-148.
    MyJurnal
    The fabrication tolerance of a short and compact low refractive index grating waveguide polarisation splitter based on the principle of resonant tunnelling was analyzed in this study. The design utilised two grating waveguides with an intermediate conventional waveguide layer. The design and optimisation were conducted using the quasi 2-D effective index solver with global search algorithm. An optimum device operating at 1.55 μm wavelength was obtained at a length of 340 μm. The splitting ratios were calculated to be 36 dB and 15 dB, and the overall device transmission efficiencies, after considering the three-dimensional waveguide leakage loss, were estimated at 88% and 83% for tranverse magnetic and tranverse electric polarisation, respectively.
    Matched MeSH terms: Electricity
  10. Zurina Zainal Abidin, Zalini Yunus, Markx, Gerard H.
    MyJurnal
    The dielectrophoretic (DEP) separation of cell, using microelectrodes structure, has been limited to small scale due to size of the substrate. This work was carried out to extend the capability of microelectrodes system by orientating the microelectrodes in three dimensions (3-D) for larger scale dielectrophoretic separation of microorganism. The designed 3-D separation chamber consists of microelectrodes on two opposing walls. Based on the FEMLAB simulation, the electric field was seen to be generated across the chamber, rather than between adjacent electrodes in the same plane like in the small scale system. This configuration led to a stronger electric field in the bulk medium. The experimental results showed that the 3-D microelectrodes chamber behaved similar to the system with microelectrodes on one wall. The effects of the main parameters such as voltage, frequency and flow rates were similar to that of the systems with all the electrodes on one wall, but on the overall, capture more cells. A gap size between 250 – 500 μm resulted in an electric field which is strong enough to hold cells while giving a reasonable cross sectional area at the same time. Although there is some improvement achieved by 3-D system, it is still not very much, as compared to the small scale system.
    Matched MeSH terms: Electricity
  11. A. Sahed, F. B. Ismail Alnaimi
    MyJurnal
    This paper presents the numerical modelling techniques for the simulation of the energy conversion chain from wave to electricity in an Oscillating Water Column (OWC) equipped with a full-scaled self rectifying turbine. The performance of the OWC device has been assessed for the stand-alone power system of a typical Irish climatic wave condition. The results showed that the overall performance of the complete device depends on the level of turbine damping, which in turn depends on the wave climate, especially the significant wave height. Furthermore, turbine efficiency predicted using quasi-steady showed qualitatively favourable agreement with the experimental results.
    Matched MeSH terms: Electricity
  12. Shaker M. Khudher, Ishak Aris, Nashiren F. Mailah, Sahbudin, R.K.Z.
    MyJurnal
    This paper discusses the harmonic analysis of the AC-to-DC uncontrolled converters commonly used in electric vehicles charging station. The aim of this paper is to model and simulate different rectifier models in addition to explaining the differences in input current harmonics, the total Harmonic Distortion (THD) as well as the power factor (pf). The converter configurations include single-phase bridge, 6-pulse and 12-pulse rectifier circuits. The single phase is normally used for electric scooter charging, while three-phase converters can be used for both electric bus and car charging. The circuit configurations of the rectifiers were modelled and simulated using Matlab R2014a to achieve the objective of the study. The results revealed that the THD levels were extremely high which is unacceptable if the system is connected to the utility grid.
    Matched MeSH terms: Electricity
  13. Rizwan K, Rasool N, Rehman R, Mahmood T, Ayub K, Rasheed T, et al.
    Chem Cent J, 2018 Jul 17;12(1):84.
    PMID: 30019193 DOI: 10.1186/s13065-018-0451-0
    A variety of imine derivatives have been synthesized via Suzuki cross coupling of N-(4-bromophenyl)-1-(3-bromothiophen-2-yl)methanimine with various arylboronic acids in moderate to good yields (58-72%). A wide range of electron donating and withdrawing functional groups were well tolerated in reaction conditions. To explore the structural properties, Density functional theory (DFT) investigations on all synthesized molecules (3a-3i) were performed. Conceptual DFT reactivity descriptors and molecular electrostatic potential analyses were performed by using B3LYP/6-31G(d,p) method to explore the reactivity and reacting sites of all derivatives (3a-3i).
    Matched MeSH terms: Static Electricity
  14. Islam MT, Ashraf FB, Alam T, Misran N, Mat KB
    Sensors (Basel), 2018 Sep 05;18(9).
    PMID: 30189669 DOI: 10.3390/s18092959
    A compact ultrawideband (UWB) antenna based on a hexagonal split-ring resonator (HSRR) is presented in this paper for sensing the pH factor. The modified HSRR is a new concept regarding the conventional square split-ring resonator (SSRR). Two HSRRs are interconnected with a strip line and a split in one HSRR is introduced to increase the electrical length and coupling effect. The presented UWB antenna consists of three unit cells on top of the radiating patch element. This combination of UWB antenna and HSRR gives double-negative characteristics which increase the sensitivity of the UWB antenna for the pH sensor. The proposed ultrawideband antenna metamaterial sensor was designed and fabricated on FR-4 substrate. The electrical length of the proposed metamaterial antenna sensor is 0.238 × 0.194 × 0.016 λ, where λ is the lowest frequency of 3 GHz. The fractional bandwidth and bandwidth dimension ratio were achieved with the metamaterial-inspired antenna as 146.91% and 3183.05, respectively. The operating frequency of this antenna sensor covers the bandwidth of 17 GHz, starting from 3 to 20 GHz with a realized gain of 3.88 dB. The proposed HSRR-based ultrawideband antenna sensor is found to reach high gain and bandwidth while maintaining the smallest electrical size, a highly desired property for pH-sensing applications.
    Matched MeSH terms: Electricity
  15. Nazriah Mahmud, Azli Yahya
    MyJurnal
    Electrical Discharge Machining, EDM is one of the technologies used for surface
    texturing such as the embedded micro-dimples on the metallic acetabular cup. During
    the machining process, changes in the gap distance may lead to load changes from
    open to short circuit. Limiting the load current under short circuit conditions and load
    voltage under open circuit conditions is the requirement in this system. Power supply
    is one of the elements that controls the process parameters which is related to improve
    the machining condition as well as Material Removal Rate (MRR). A considerable
    number of power supply design method were proposed for various EDM application.
    This research proposed a Switch Mode Power Supply method implementing new
    design of Flyback power supply which can stabilize the voltage during open circuit
    condition as well as during discharge condition. Experimental studies were conducted
    to verify the capability of Flyback power supply by machining eight micro-dimples in
    lower position and twelve micro-dimples in upper position, both in circular
    arrangement on metallic acetabular cup. Research conducted shows that the Flyback
    power supply improve the consistency of MRR when compared to Linear power supply.
    This may help to predict the machining time, thus improving the production of microdimples
    in required time.
    Matched MeSH terms: Electricity
  16. Yasir SF, Jani J, Mukri M
    Data Brief, 2018 Dec;21:907-910.
    PMID: 30426044 DOI: 10.1016/j.dib.2018.10.057
    In the study, a relationship was establishment between electrical resistivity by using electrical resistivity imaging (ERI) technique with hydraulic conductivity. By using Schlumberger array configuration, 2D electrical resistivity image was produced by using ABEM SAS 4000 with eighty-one (81) electrodes (Loke, 2004) [1]. By using regression equation, hydraulic conductivity was calculated from electrical resistivity and this result was compared with the hydraulic conductivity obtained from pumping tests (Butler, 2005). This data suggested that electrical resistivity survey can be used as preliminary tool to assess any subsurface zone with non- invasive nondestructive for soil, reducing time and cost.
    Matched MeSH terms: Electricity
  17. Makmud MZH, Illias HA, Chee CY, Dabbak SZA
    Materials (Basel), 2019 Mar 11;12(5).
    PMID: 30861988 DOI: 10.3390/ma12050816
    This study provides a thorough investigation of partial discharge (PD) activities in nanofluid insulation material consisting of different types of nanoparticles, which are conductive and semiconductive when subjected to high voltage stress is presented. Nanofluids have become a topic of interest because they can be an alternative to liquid insulation in electrical apparatus due to their promising dielectric strength and cooling ability. However, during in-service operation, PDs can occur between conductors in the insulation system. Therefore, this study presents the behavior of PDs within nanofluid dielectric materials consisting of conductive and semiconductive nanoparticles. The results show that there is an improvement in the PD resistance and a reduction in the tan delta of nanofluids at power frequency after the incorporation of conductive or semiconductive nanoparticles in the nanofluid oil. However, the most suitable concentration of conductive and semiconductive nanoparticles in the base fluid was found to be, respectively, 0.01 g/L and 1.0 g/L at PD inception and PD steady-state conditions. The clustering of nanoparticles in a nanofluid suspension due to PD activities is also discussed in this study.
    Matched MeSH terms: Electricity
  18. Benaissa M, Vennéguès P
    Sains Malaysiana, 2008;37:233-237.
    A complete nanoscale study on GaN thin films doped with Mg. This study was carried out using TEM and associated techniques such as HREM, CBED, EDX and EELS. It was found that the presence of triangular defects (of few nanometers in size) within GaN:Mg films were at the origin of unexpected electrical and optical behaviors, such as a decrease in the free hole density at high Mg doping. It is shown that these defects are inversion domains limited with inversion-domains boundaries.
    Matched MeSH terms: Electricity
  19. Ueng SK, Chan Yao-Hong, Lu WH, Chang HW
    Sains Malaysiana, 2015;44:1701-1706.
    Wind turbines are massive electrical structures. They produce large returns when illuminated by radar waves. These
    scatterings have a great impact on the operation of surveillance, air traffic control and weather radars. This paper presents
    two geometric modelling methods for reshaping wind turbine towers so that the Radar Cross Section (RCS) of wind turbines
    is reduced. In the proposed reshaping methods, bump structures are created on the surface of the conventional cylinder
    wind turbine tower. When a reshaped tower is illuminated by radar waves, the bump structures scatter incident radar
    waves into insignificant directions so that the strength of back-scattering is declined and the RCS of the wind turbine is
    decreased. The test results confirmed that the proposed methodssignificantly reduce bi-static RCS values of wind turbines.
    The proposed reshaping methods are practical, flexible and effective in alleviating the scatterings of wind turbines.
    Matched MeSH terms: Electricity
  20. Tay W, Yap S, Wong C
    Sains Malaysiana, 2014;43:583-594.
    The electrical characteristics of a filamentary dielectric barrier discharge (DBD) are studied experimentally and numerically. The DBD system which has parallel plate electrodes geometry is powered by a 50 Hz power supply and operated at atmospheric air. A dynamic electric circuit model considering the discharge region and the non-discharge region being connected by a surface resistance is proposed. Simulation using this model is shown to fit the experimentally measured QV diagram satisfactorily. The effects of the air gap distance and the dielectric surface on the discharge behavior are then investigated. It is found that the surface resistivity of the dielectric is one of the important parameters governing the discharge behavior.
    Matched MeSH terms: Electricity
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