| 1. |
- Baharin, S. A. S., et al.
(författare)
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Wavelet Analysis of the Onset of VHF and Microwave Radiation Emitted by Lightning
- 2018
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Ingår i: 2018 INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND COMPUTER SCIENCE (ICECOS). - : IEEE. - 9781538657218 ; , s. 297-300
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Konferensbidrag (refereegranskat)abstract
- Lightning flash is an electrical discharge in air (dielectric breakdown) which emits electromagnetic (FM) fields across very wide spectra from a few Hertz up to visible wavelength. Electrical breakdown process is an important event that initiates lightning. For electrical breakdown process to occur, it must fulfill two conditions which are at least has one free electron and the electric field region is more than 3 MV/m. This process starts with electron avalanche in millimeter scale then grows into streamer in centimeter scale. Lastly, from streamer it will grow into leader in meter scale. It has already established that streamer emits intensely at Very High Frequency (VHF) band as it's already proven both theoretically and experimentally. A study by Cooray, theoretically proved that emission of electron avalanche peaks at microwave band. Air-gap parallel plate antenna which could operate at 1 GHz with remote sensing is designed and simulated to measure the microwave radiation emitted by lightning. Both temporal and wavelet analyses are used to compare the onset of microwave radiation and VHF radiation in both time and frequency domains to determine electron avalanche appears at which electromagnetic band.
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| 2. |
- Mohammad, S. A., et al.
(författare)
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Azimuth and elevation factors correction for single station lightning electromagnetic field sensor
- 2021
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Ingår i: Geografia. - : Penerbit Universiti Kebangsaan Malaysia (UKM Press). - 2180-2491. ; 17:4, s. 378-392
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to find the location of lightning return strokes using a single station electromagnetic field sensor with the implementation of magnetic field Factor B correction to best match with a reliable lightning strike location reference from TNB Research (TNBR) that uses Vaisala lightning detector with +/- 500m tolerance. A parallel plate antenna was used to measure the electric fields while two orthogonal loop antennas were used to measure the magnetic fields from thunderstorms in Melaka. Based on the type of Cloud-to-Ground flash and its recorded magnetic field peak amplitude polarities, the general direction of the lightning source could be determined in four quadrants divided equally between the cardinal directions. Measurement of return stroke peak amplitudes from electromagnetic field waveforms, distance between lightning measurement station and lightning strike was determined. Factor B corrections varied between 53M to 69M where the separation distance between compared strikes averaged 3.22 km. From the varied Factor B, it was averaged to 60.1M that yield a separation distance between the same compared strikes between 0.75 to 15.02 km. From all the strikes compared, the average separation distance between compared strikes was 7.64 km. It was determined that the accuracy of our lightning measurement system lightning location were between 7.14 and 8.14 km.
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| 3. |
- Seah, B. Y., et al.
(författare)
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Narrow Bipolar Events within Reversal Distance and Associated UHF-VHF Emissions
- 2019
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Ingår i: 2019 3RD INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND COMPUTER SCIENCE (ICECOS 2019). - : IEEE. - 9781728147147 ; , s. 132-136
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the characteristics of the ultra-high frequency (UHF) and Very High Frequency (VHF) emissions that associate with negative narrow bipolar events (NBEs) which occurred within reversal distance, drev of the base station. The UHF emissions were captured by using a parallel plates antenna with its center frequency at 0.97 GHz and 20 MHz bandwidth. There are thirteen samples whereby their VHF and FF signals were leaded by their corresponding UHF about (102.25 +/- 125.48) ns and (692.13 +/- 382.36) ns respectively. All the UHF were found to behave like continuous bursting while some of the VHF consisted of certain periods within its burst train whereby there was no any sign of pulse during that period.
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