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  • 101.
    Ahlén, A
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Lindbom, L
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Sternad, M
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Analysis of stability and performance of adaptation algorithms with time-invariant gains2004Inngår i: IEEE Transactions on Signal Processing, Vol. 52, s. 103-116Artikkel i tidsskrift (Fagfellevurdert)
  • 102.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    An input estimation approach to differentiation of noisy data1984Rapport (Annet vitenskapelig)
  • 103.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Identifiability of an input estimation problem1986Rapport (Annet vitenskapelig)
  • 104.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Reglerteknik / Control theory: Inledande kurs / An introduction1985Rapport (Annet vitenskapelig)
  • 105.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlgren, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Grönroos, Roland
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Hjort, Klas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrostrukturteknik.
    Katardjiev, Ilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Presentation of the VINN Excellence Center for Wireless Sensor Networks (WISENET)2008Inngår i: Conference on Radio Science (RVK08), Växjö, 2008Konferansepaper (Fagfellevurdert)
  • 106.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Solbrand, Göte
    Repeated recursive identification for off line estimation1983Inngår i: ACI 83, 1983Konferansepaper (Fagfellevurdert)
  • 107.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Solbrand, Göte
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Numerisk lösning av ett optimalstyrproblem med evolutionsmetoden1982Rapport (Annet vitenskapelig)
  • 108.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Adaptive deconvolution based on spectral decomposition1991Rapport (Annet vitenskapelig)
  • 109.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Derivation and design of Wiener filters using polynomial equations1994Inngår i: Control and Dynamic Systems: Digital Signal Processing Techniques and Applications, Adacemic Press, New York , 1994Kapittel i bok, del av antologi (Fagfellevurdert)
  • 110.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Filter design via inner-outer factorization: Comments on "Optimal deconvolution filter design based on orthogonal principle"1992Inngår i: Signal ProcessingArtikkel i tidsskrift (Annet vitenskapelig)
  • 111.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Optimal filtering problems1992Inngår i: Polynomial methods in optimal control and filtering, Peter Peregrinus, London , 1992Kapittel i bok, del av antologi (Fagfellevurdert)
  • 112.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling. Signals and systems.
    Optimal input estimation: A polynomial approach1985Rapport (Annet vitenskapelig)
  • 113.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Åkerberg, J
    Eriksson, M
    Isaksson, A J
    Iwaki, T
    Johansson, K H
    Knorn, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Towards wireless control in industrial process automation2019Inngår i: IEEE Control Systems MagazineArtikkel i tidsskrift (Fagfellevurdert)
  • 114.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System. Univ Newcastle, Dept Elect & Comp Engn, Callaghan, NSW, Australia.
    Åkerberg, Johan
    ABB Corp, Vasteras, Sweden.
    Eriksson, Markus
    Scania CV, Sodertalje, Sweden.
    Isaksson, Alf J.
    Linkoping Univ, Linkoping, Sweden;Univ Newcastle, Callaghan, NSW, Australia;Royal Inst Technol, Stockholm, Sweden;ABB Corp Res, Vasteras, Sweden.
    Iwaki, Takuya
    JGC Corp, Yokohama, Kanagawa, Japan;KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Stockholm, Sweden.
    Johansson, Karl Henrik
    KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Stockholm, Sweden.
    Knorn, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System. Univ Newcastle, Ctr Complex Dynam Syst & Control, Callaghan, NSW, Australia.
    Lindh, Thomas
    Iggesund Mill, Maintenance Technol Dev, Iggesund Paperboard, Sweden.
    Sandberg, Henrik
    KTH Royal Inst Technol, Div Decis & Control Syst, Stockholm, Sweden;CALTECH, Pasadena, CA 91125 USA;MIT, Lab Informat & Decis Syst, 77 Massachusetts Ave, Cambridge, MA 02139 USA.
    Toward Wireless Control in Industrial Process Automation: A Case Study at a Paper Mill2019Inngår i: IEEE CONTROL SYSTEMS MAGAZINE, ISSN 1066-033X, Vol. 39, nr 5, s. 36-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wireless sensors and networks are used only occasionally in current control loops in the process industry. With rapid developments in embedded and highperformance computing, wireless communication, and cloud technology, drastic changes in the architecture and operation of industrial automation systems seem more likely than ever. These changes are driven by ever-growing demands on production quality and flexibility. However, as discussed in "Summary," there are several research obstacles to overcome. The radio communication environment in the process industry is often troublesome, as the environment is frequently cluttered with large metal objects, moving machines and vehicles, and processes emitting radio disturbances [1], [2]. The successful deployment of a wireless control system in such an environment requires careful design of communication links and network protocols as well as robust and reconfigurable control algorithms.

  • 115. Ahlén, I
    et al.
    Pettersson, L
    Svärdström, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    An instrument for detecting bat and insect sounds1983Inngår i: Myotis, Vol. 21-22, s. 82-88Artikkel i tidsskrift (Fagfellevurdert)
  • 116. Ahmad, H.
    et al.
    Coppens, S.
    Uzunoglu, Bahri
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Connection of an Offshore Wind Park to HVDC Converter Platform without Using Offshore AC Collector Platforms2013Inngår i: Green Technologies Conference, 2013 IEEE, 2013, s. 400-406Konferansepaper (Fagfellevurdert)
  • 117. Ahmad, M R
    et al.
    Esa, M R M
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Measurement of bit error rate at 2,4 GHz due to lightning interference2012Inngår i: Proceeding of the 31st International Conference on Lightning Protection ICLP 2012, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper analyzes the interference of lightning flashes with wireless communication systems operating in the microwave band at 2.4 GHz. A bit error rate (BER) measurement method was used to evaluate BER during 3 heavy thunderstorms on January 25, March 17 and March 20, all in year 2011. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW) conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-of-sight (LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higher recorded BER. The maximum recorded BER was 9.9·101 and the average recorded BER was 9.95·10 -3 during the thunderstorms with the average fair weather BER values under the influence of adjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10 -6 respectively. We conclude that wireless communication systems operating at 2.4 GHz microwave frequency can be significantly interfered by lightning.

  • 118.
    Ahmad, Mohd Riduan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Universiti Teknikal Malaysia Melaka.
    Interaction of Lightning Flashes with Wireless Communication Networks: Special Attention to Narrow Bipolar Pulses2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this thesis, the features of electric field signatures of narrow bipolar pulses (NBPs) generated by cloud flashes are investigated and their effects on wireless communication systems are studied. A handful amount of NBPs (14.5%) have been observed to occur as part of cloud-to-ground flashes in South Malaysia. Occurrence of NBPs in Sweden has been reported for the first time in this thesis. The electric field waveform characteristics of NBPs as part of cloud-to-ground flashes were similar to isolated NBPs found in Sweden and South Malaysia and also to those isolated NBPs reported by previous studies from various geographical areas. This is a strong indication that their breakdown mechanisms are similar at any latitudes regardless of geographical areas.

    A comparative study on the occurrence of NBPs and other forms of lightning flashes across various geographical areas ranging from northern regions to the tropics is presented. As the latitude decreased from Uppsala, Sweden (59.8°N) to South Malaysia (1.5°N), the percentage of NBP emissions relative to the total number of lightning flashes increased significantly from 0.13% to 12%. Occurrences of positive NBPs were more common than negative NBPs at all observed latitudes. However, as latitudes decreased, the negative NBP emissions increased significantly from 20% (Sweden) to 45% (South Malaysia). Factors involving mixed-phase region elevations and vertical extents of thundercloud tops are invoked to explain the observed results. These factors are fundamentally latitude dependent.

    In this thesis, the interaction between microwave radiations emitted by cloud-to-ground and cloud flashes events and bits transmission in wireless communication networks are also presented. To the best of our knowledge, this is the first time such effects are investigated in the literature. Narrow bipolar pulses were found to be the strongest source of interference that interfered with the bits transmission.

    Delarbeid
    1. Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    Åpne denne publikasjonen i ny fane eller vindu >>Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    2014 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Emneord
    Narrow bipolar pulse; Return stroke; Tropical thunderstorm.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233624 (URN)
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2017-12-05
    2. Narrow bipolar pulses and associated microwave radiation
    Åpne denne publikasjonen i ny fane eller vindu >>Narrow bipolar pulses and associated microwave radiation
    2013 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Stockholm: , 2013
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212898 (URN)
    Konferanse
    Progress in Electromagnetics Research Symposium
    Tilgjengelig fra: 2013-12-16 Laget: 2013-12-16 Sist oppdatert: 2015-01-23
    3. Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Åpne denne publikasjonen i ny fane eller vindu >>Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Vise andre…
    2014 (engelsk)Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Emneord
    Electric field; Narrow bipolar pulse; Sweden.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233636 (URN)
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2017-12-05
    4. Latitude Dependence of Narrow Bipolar Pulse Emissions
    Åpne denne publikasjonen i ny fane eller vindu >>Latitude Dependence of Narrow Bipolar Pulse Emissions
    Vise andre…
    2015 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 128, s. 40-45Artikkel i tidsskrift (Fagfellevurdert) Published
    Emneord
    Latitude; Narrow bipolar pulse; Thunderstorm.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233638 (URN)10.1016/j.jastp.2015.03.005 (DOI)000355717500005 ()
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2017-12-05bibliografisk kontrollert
    5. Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    Åpne denne publikasjonen i ny fane eller vindu >>Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    2014 (engelsk)Inngår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, s. 810-813Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    In this paper, temporal characteristics of several initial electric field pulses of preliminary breakdown process (PBP) from very close negative cloud-to-ground (CG) flashes are compared to close narrow bipolar pulses (NBPs) to observe any similarity that may exists. Interestingly, we found that the initial PBP pulses are similar to close NBP with zero crossing time less than 5 mu s, do not preceded by any slow field change and followed by pronounce static component. As NBPs are believed to be a result of relativistic runaway electron avalanches discharge, this finding is an indication that the initial electric field pulses of PBP are perhaps the result of the same discharge mechanism.

    sted, utgiver, år, opplag, sider
    IEEE conference proceedings, 2014
    Emneord
    Narrow bipolar pulse; Preliminary breakdown pulse; Relativistic runaway electron avalanches.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233639 (URN)000358572100153 ()978-1-4799-3544-4 (ISBN)
    Konferanse
    International Conference on Lightning Protection (ICLP), OCT 11-18, 2014, Tsinghua Univ, Shanghai, PEOPLES R CHINA
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2015-09-03bibliografisk kontrollert
    6. Lightning interference in multiple antennas wireless communication systems
    Åpne denne publikasjonen i ny fane eller vindu >>Lightning interference in multiple antennas wireless communication systems
    Vise andre…
    2012 (engelsk)Inngår i: Journal of Lightning Research, ISSN 1652-8034, Vol. 4, s. 155-165Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    This paper analyzes the interference of lightning flashes with multiple antennas wireless communicationsystems operating in the microwave band at 2.4 GHz and 5.2 GHz. A bit error rate (BER) measurement method was usedto evaluate BER and packet error rate (PER) during 5 heavy thunderstorms on January 25 and March 17 to 20, 2011,respectively. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW)conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-ofsight(LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higherrecorded BER. The maximum recorded BER was 9.9·10-1 and the average recorded BER and PER were 2.07·10-2 and2.44·10-2 respectively during the thunderstorms with the average fair weather BER and PER values under the influence ofadjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10-6 respectively. Weconclude that multiple antennas wireless communication systems operating at the microwave frequency can besignificantly interfered by lightning.

    sted, utgiver, år, opplag, sider
    Bentham open, 2012
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-190902 (URN)
    Tilgjengelig fra: 2013-01-09 Laget: 2013-01-09 Sist oppdatert: 2016-02-03
    7. Interference from cloud-to-ground and cloud flashes in wireless communication system
    Åpne denne publikasjonen i ny fane eller vindu >>Interference from cloud-to-ground and cloud flashes in wireless communication system
    2014 (engelsk)Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 113, s. 237-246Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this study, cloud-to-ground (CG) flash and intra-cloud (IC) flash events that interfere with the transmission of bits in wireless communication system operating at 2.4 GHz were analyzed. Bit error rate (BER) and consecutive lost datagram (CLD) measurement methods were used to evaluate BER and burst error from 3 tropical thunderstorms on November 27, 28, and 29 during 2012 northeastern monsoon in Malaysia. A total of 850 waveforms from the electric field change recording system were recorded and examined. Out of these, 94 waveforms of very fine structure were selected which matched perfectly with the timing information of the recorded BER. We found that both CG and IC flashes interfered significantly with the transmission of bits in wireless communication system. The severity of the interference depends mainly on two factors namely the number of pulses and the amplitude intensity of the flash. The interference level becomes worst when the number of pulses in a flash increases and the amplitude intensity of pulses in a flash intensifies. During thunderstorms, wireless communication system has experienced mostly intermittent interference due to burst error. Occasionally, in the presence of very intense NBP event, wireless communication system could experience total communication lost. In CG flash, it can be concluded that PBP is the major. source of interference that interfered with the bits transmission and caused the largest burst error. In IC flash, we found that the typical IC pulses interfered the bits transmission in the same way as PBP and mixed events in CG flash and produced comparable and in some cases higher amount of burst error. NBP has been observed to interfere the bits transmission more severely than typical IC and CG flashes and caused the most severe burst error to wireless communication system.

    Emneord
    Bit error rate, Cloud flash, Cloud-to-ground flash, Interference, Microwave radiation, Wireless system
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-228679 (URN)10.1016/j.epsr.2014.03.022 (DOI)000337554200032 ()
    Tilgjengelig fra: 2014-07-22 Laget: 2014-07-21 Sist oppdatert: 2017-12-05bibliografisk kontrollert
  • 119.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Narrow bipolar pulses and associated microwave radiation2013Konferansepaper (Fagfellevurdert)
  • 120.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, Eryk
    Interference from cloud-to-ground and cloud flashes in wireless communication system2014Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 113, s. 237-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, cloud-to-ground (CG) flash and intra-cloud (IC) flash events that interfere with the transmission of bits in wireless communication system operating at 2.4 GHz were analyzed. Bit error rate (BER) and consecutive lost datagram (CLD) measurement methods were used to evaluate BER and burst error from 3 tropical thunderstorms on November 27, 28, and 29 during 2012 northeastern monsoon in Malaysia. A total of 850 waveforms from the electric field change recording system were recorded and examined. Out of these, 94 waveforms of very fine structure were selected which matched perfectly with the timing information of the recorded BER. We found that both CG and IC flashes interfered significantly with the transmission of bits in wireless communication system. The severity of the interference depends mainly on two factors namely the number of pulses and the amplitude intensity of the flash. The interference level becomes worst when the number of pulses in a flash increases and the amplitude intensity of pulses in a flash intensifies. During thunderstorms, wireless communication system has experienced mostly intermittent interference due to burst error. Occasionally, in the presence of very intense NBP event, wireless communication system could experience total communication lost. In CG flash, it can be concluded that PBP is the major. source of interference that interfered with the bits transmission and caused the largest burst error. In IC flash, we found that the typical IC pulses interfered the bits transmission in the same way as PBP and mixed events in CG flash and produced comparable and in some cases higher amount of burst error. NBP has been observed to interfere the bits transmission more severely than typical IC and CG flashes and caused the most severe burst error to wireless communication system.

  • 121.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, Eryk
    Performance analysis of audio streaming over lightning-interfered MIMO channels2012Konferansepaper (Fagfellevurdert)
  • 122.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, E.
    Wireless Communications and Networking Lab, Macquarie University, Sydney, Australien.
    Lightning interference in multiple antennas wireless communication systems2012Inngår i: Journal of Lightning Research, ISSN 1652-8034, Vol. 4, s. 155-165Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper analyzes the interference of lightning flashes with multiple antennas wireless communicationsystems operating in the microwave band at 2.4 GHz and 5.2 GHz. A bit error rate (BER) measurement method was usedto evaluate BER and packet error rate (PER) during 5 heavy thunderstorms on January 25 and March 17 to 20, 2011,respectively. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW)conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-ofsight(LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higherrecorded BER. The maximum recorded BER was 9.9·10-1 and the average recorded BER and PER were 2.07·10-2 and2.44·10-2 respectively during the thunderstorms with the average fair weather BER and PER values under the influence ofadjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10-6 respectively. Weconclude that multiple antennas wireless communication systems operating at the microwave frequency can besignificantly interfered by lightning.

  • 123.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza Binti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hettiarachchi, Pasan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Preliminary Observations of Lightning Signature At 2400 MHz in Sweden Thunderstorm2012Inngår i: / [ed] BinSulaiman, HA; Jaafar, A, NEW YORK: IEEE , 2012, s. 88-91Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a preliminary observation of lightning signature at 2400 MHz. We believe this is the first time such observation was made in such frequency band. One positive ground discharge and one cloud discharge waveforms have been selected from a collection of waveforms recorded using fast and slow broadband antenna systems. In addition, waveforms recorded directly from 2400 MHz whip antenna associated with the selected ground and cloud discharges waveforms were observed. The measurements were carried out in Uppsala, Sweden in July 2012. We discovered a possible lightning signature at 2400 MHz with the existence of bursts of pulses happened to occur simultaneously with preliminary breakdown, negative return stroke and cloud pulses. These bursts of pulses possibly interfered in some ways with the transmitted bits leading to higher recorded error bits during the thunderstorm.

  • 124.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Occurrence of Narrow Bipolar Event as Part of Cloud-to-Ground Flash in Tropical Thunderstorms2014Konferansepaper (Fagfellevurdert)
  • 125.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses2014Inngår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, s. 810-813Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, temporal characteristics of several initial electric field pulses of preliminary breakdown process (PBP) from very close negative cloud-to-ground (CG) flashes are compared to close narrow bipolar pulses (NBPs) to observe any similarity that may exists. Interestingly, we found that the initial PBP pulses are similar to close NBP with zero crossing time less than 5 mu s, do not preceded by any slow field change and followed by pronounce static component. As NBPs are believed to be a result of relativistic runaway electron avalanches discharge, this finding is an indication that the initial electric field pulses of PBP are perhaps the result of the same discharge mechanism.

  • 126.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Baharudin, Zikri Abadi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Universiti Teknikal Malaysia Melaka.
    Hettiarachchi, Pasan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Latitude Dependence of Narrow Bipolar Pulse Emissions2015Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 128, s. 40-45Artikkel i tidsskrift (Fagfellevurdert)
  • 127.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hettiarachchi, Pasan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Baharudin, Zikri Abadi
    Universiti Teknikal Malaysia Melaka.
    Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden2014Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikkel i tidsskrift (Fagfellevurdert)
  • 128.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Johari, Dalina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ismail, Mohd Muzafar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Chaotic Pulse Train in Cloud-to-Ground and Cloud Flashes of Tropical Thunderstorms2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we report for the first time the observation of chaotic pulse train (CPT) preceding natural subsequent negative return strokes and also CPT occurrence in IC flashes from tropical thunderstorms in South Malaysia. In CG flashes, all CPTs were occurred in between return strokes with 41.1% have occurred between the first and second return strokes. The maximum number of CPT in one sequence is 3, which can be observed between the first and third return strokes only. In IC flashes, all CPTs were observed to occur in between IC flash pulses.

  • 129.
    Ahmad, Mohd Riduan
    et al.
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Periannan, Dinesh
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Sabri, Muhammad Haziq Mohammad
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Abd Aziz, Mohamad Zoinol Abidin
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Esa, Mona Riza Mohd
    UTM, Inst Voltan Tinggi & Arus Tinggi IVAT, Johor Bharu, Malaysia.
    Lu, Gaopeng
    Chinese Acad Sci, Beijing, Peoples R China.
    Zhang, Hongbo
    Chinese Acad Sci, Beijing, Peoples R China.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Emission Heights of Narrow Bipolar Events in a Tropical Storm over the Malacca Strait2017Inngår i: 2017 International Conference On Electrical Engineering And Computer Science (Icecos), IEEE , 2017, s. 305-309Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Emission heights for narrow bipolar events (NBEs) have been reported mostly from observations at mid latitudes but none have been reported from tropical regions. In this paper, we are reporting for the first time the heights of NBE emissions from a tropical storm over the Malacca Strait, a narrow water passage between the Malay Peninsula and Sumatra Island. A total of 49 positive NBEs (+NBEs) were detected from the storm. The NBE activity can be divided into two stages according to the emission heights and radar reflectivity data. The first stage (or S1) lasted for only 6 minutes, started with the first detected NBE, and produced 20 NBEs (41%). The emission heights ranged between 12.0 and 16.7 km. Radar reflectivity data showed that the storm reached maximum values at 55 dBZ within the period S1. In contrast, the second stage (S2) lasted longer (32 minutes) and produced 29 NBEs (59%). The emission heights were lower and ranged from 8.5 to 13.7 km. Radar reflectivity data showed that the storm reached maximum values at 50 dBZ within the period S2.

  • 130.
    Ahmad, M.R.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rashid, M.
    Aziz, M.H.A.
    Esa, M.R.M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, E.
    Analysis of Lightning-induced Transient in 2.4 GHz Wireless Communication System2011Inngår i: Proceeding of IEEE International Conference on Space Science and Communication (IconSpace), Penang, Malaysia, pp225-230, 2011Konferansepaper (Fagfellevurdert)
  • 131.
    Ahmad, Noor Azlinda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Broadband and HF Radiation from Cloud Flashes and Narrow Bipolar Pulses2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Remote measurement of electric field generated by lightning has played a major role in understanding the lightning phenomenon. Even though other measurements such as photographic and channel base current have contributed to this research field, due to practical reasons remote measurements of electric field is considered as the most useful tool in lightning research.

    This thesis discusses the remotely measured radiation field component of electric field generated by cloud flashes (ICs) and narrow bipolar pulses (NBPs). The associated HF radiation of these events at 3 MHz and 30 MHz are also discussed. To understand the initiation process of these discharges, a comparative study of the initial pulse of cloud flashes against the initial pulse of cloud to ground flashes was conducted. The result suggests that both discharges might have been initiated by similar physical processes inside the thunderclouds. Comparing the features of initial pulse of cloud and ground flashes with that of pulses that appeared in the later stages of cloud flashes suggests that the initiation process involved in both flashes are not very much different from the initiation of cloud flashes at the later stage. The average spectral amplitudes of electric field of full duration cloud flashes (180 ms) showed -1 frequency dependence within the interval of 10 kHz to approximately 10 MHz. This is in contrast to the standard -2 decrement (or even steeper ) at high frequency region for other lightning processes such as return strokes. It was suggested that small pulses which repeatedly appeared at the later stage of cloud flashes might have contributed to enhance the spectral amplitude at higher frequencies.

    Electric fields generated by Narrow Bipolar Pulses (NBPs), which are considered as one of the strongest sources of HF radiation, were measured in the tropics of Malaysia and Sri Lanka.  Their features were also studied and show a good agreement with previously published observations of NBPs from other geographical regions. Thorough analyses and observations of these pulses found previously unreported sharp, fine peaks embedded in the rising and decaying edge of the electric field change of NBPs. Therefore it was suggested that these fine peaks are mostly responsible for the intense HF radiation at 30 MHz.

    Delarbeid
    1. The first electric field pulse of cloud and cloud-to-ground lightning discharges
    Åpne denne publikasjonen i ny fane eller vindu >>The first electric field pulse of cloud and cloud-to-ground lightning discharges
    Vise andre…
    2010 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, nr 2-3, s. 143-150Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this study, the first electric field pulse of cloud and cloud-to-ground discharges were analyzed and compared with other pulses of cloud discharges. Thirty eight cloud discharges and 101 cloud-to-ground discharges have been studied in this analysis. Pulses in cloud discharges were classified as [`]small', [`]medium' and [`]large', depending upon the value of their relative amplitude with respect to that of the average amplitude of the five largest pulses in the flash. We found that parameters, such as pulse duration, rise time, zero crossing time and full-width at half-maximum (FWHMs) of the first pulse of cloud and cloud-to-ground discharges are similar to small pulses that appear in the later stage of cloud discharges. Hence, we suggest that the mechanism of the first pulse of cloud and cloud-to-ground discharges and the mechanism of pulses at the later stage of cloud discharges could be the same.

    Emneord
    Cloud discharges, Electromagnetic field, Lightning, Electric field pulses
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-140337 (URN)10.1016/j.jastp.2009.11.001 (DOI)
    Tilgjengelig fra: 2011-01-05 Laget: 2011-01-05 Sist oppdatert: 2017-12-11
    2. Radiation Field Spectra of Long-duration Cloud Flashes
    Åpne denne publikasjonen i ny fane eller vindu >>Radiation Field Spectra of Long-duration Cloud Flashes
    (engelsk)Inngår i: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187XArtikkel i tidsskrift (Fagfellevurdert) Submitted
    Abstract [en]

    The radiation electric fields produced by long-duration cloud flashes have been Fourier analyzed to determined the frequency spectrum in the range of 10 kHz to 10 MHz. The flashes were recorded within a distance of less than 20 km. The spectrum was normalized to 50 km distance and it shows a f-1 dependence within the entire frequency range.

    Identifikatorer
    urn:nbn:se:uu:diva-150952 (URN)
    Tilgjengelig fra: 2011-04-08 Laget: 2011-04-08 Sist oppdatert: 2017-12-11
    3. Characteristics of narrow bipolar pulses observed in Malaysia
    Åpne denne publikasjonen i ny fane eller vindu >>Characteristics of narrow bipolar pulses observed in Malaysia
    Vise andre…
    2010 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, nr 5-6, s. 534-540Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Narrow bipolar pulses (NBPs) are considered as isolated intracloud events with higher peak amplitude and strong high frequency emission compared to the first return strokes and other intracloud discharges. From 182 NBPs recorded in Malaysia in the tropic, 75 were narrow negative bipolar pulses (NNBPs) while 107 were narrow positive bipolar pulses (NPBPs). The mean duration of NNBPs was 24.6 +/- 17.1 mu s, while 30.2 +/- 12.3 mu s was observed for NPBPs. The mean full-width at half-maximum (FVVHM) was 2.2 +/- 0.7 and 2.4 +/- 1.4 mu s for NNBPs and NPBPs, respectively. The mean peak amplitude of NPBPs normalized to 100 km was 22.7 V/m, a factor of 1.3 higher than that of NNBPs which is 17.6 V/m. In contrast to the previous studies, it was observed that the electric field change was characterized by a bipolar pulse with a significant amount of fine structures separated by a few tens of nanoseconds intervals, embedded on it. (C) 2010 Elsevier Ltd. All rights reserved.

    Emneord
    Narrow bipolar pulses, Lightning, Cloud discharges, Electric field
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-137067 (URN)10.1016/j.jastp.2010.02.006 (DOI)000276428600020 ()
    Tilgjengelig fra: 2010-12-15 Laget: 2010-12-15 Sist oppdatert: 2017-12-11bibliografisk kontrollert
    4. Some features of electric field waveform of Narrow Bipolar Pulses
    Åpne denne publikasjonen i ny fane eller vindu >>Some features of electric field waveform of Narrow Bipolar Pulses
    (engelsk)Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Abstract [en]

    Narrow Bipolar Pulses (NBPs) are generated by intra-cloud discharge processes and they are of interest due to their strong broadband and high frequency (HF) emissions. In this study, we present some features of electric field waveform of NBPs which have not been reported in the literature.  The HF emission was observed to begin simultaneously with the onset of NBPs indicating no streamers or stepped-leader process was taking place before the initiation of NBPs. The electric field waveforms of NBPs were characterized by many fine peaks embedded intermittently on the rising and decaying edge of NBPs suggesting that some small scale electrical discharges were involved during the formation of NBPs.

     

    Identifikatorer
    urn:nbn:se:uu:diva-150953 (URN)
    Tilgjengelig fra: 2011-04-08 Laget: 2011-04-08 Sist oppdatert: 2017-12-11
  • 132.
    Ahmad, Noor Azlinda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Broadband and HF radiation from cloud flashes and narrow bipolar pulses2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Remote measurement of electric field generated by lightning has played a major role in understanding the lightning phenomenon. Even though other measurements such as optical, photographic, channel base current and thunder signatures have contributed in this regards, due to practical reasons remote measurements of electric field is considered as the most useful tool in lightning research. This thesis discussed about the remotely measured radiation field component of electric field generated by cloud flashes (ICs) and narrow bipolar pulses (NBPs). The associated HF radiation of these events at 3 MHz and 30 MHz were also discussed. To understand the initiation process of these discharges, a comparative study of the initial pulse of cloud flashes with the initial pulse of cloud to ground flashes was conducted. The result suggests that both discharges might have been initiated by similar physical process inside the thunderclouds. Comparing the features of initial pulse of cloud and ground flashes with that of pulses appeared in the later stages of cloud flashes suggests that the initiation process involved in both flashes are not very much differ from the initiation of cloud flashes at the later stage. The average spectral amplitudes of electric field for first 120 ms of cloud flashes showed f-1 frequency dependence within the interval of 100 kHz to about 2 MHz and does not follow the standard f-2 decrease (or even more) at high frequency region. It was suggested that small pulses which repeatedly appeared at the later stage of cloud flashes might have contribute to enhance the spectral amplitude at higher frequencies. Electric fields generated by Narrow Bipolar Pulses (NBPs), which are considered as one of the strongest source of HF radiation were measured in Malaysia in the tropic and their features were also studied. Result shows a good agreement with previously published observations of NBPs in other geographical regions. The pulse duration of NBPs is varied within 20 – 30μs with the normalized peak amplitude is of the order of 10 V/m, averagely 2– 3 times larger than the peak amplitude of ordinary return strokes. They were observed to emit intense burst of HF radiation at 30 MHz. Thorough analyses and observation of these pulses found previously unreported sharp, fine peaks embedded at the rising and decaying edge of the electric field change of NBPs. Therefore it was suggested that these fine peaks were most probably to be responsible for the intense HF radiation at 30 MHz.

  • 133. Ahmad, Noor Azlinda
    et al.
    Baharudin, Zikri A
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fernando, M.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Radiation field spectra of long-duration cloud flashes2015Inngår i: Atmospheric Science Letters, ISSN 1530-261X, E-ISSN 1530-261X, Vol. 16, nr 2, s. 91-95Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The preliminary results of radiation electric fields produced by long-duration cloud flashes have been Fourier analyzed to determine the frequency spectrum in the range of 10kHz-10MHz. The flashes were recorded within a distance of less than 20km. The spectrum was normalized to 50km distance and it shows a f(-1) dependence within the entire frequency range.

  • 134.
    Ahmad, Noor Azlinda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fernando, Mahendra
    Baharudin, Z. A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Saleh, Ziad
    Dwyer, Joseph R.
    Rassoul, Hamid K.
    The first electric field pulse of cloud and cloud-to-ground lightning discharges2010Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, nr 2-3, s. 143-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the first electric field pulse of cloud and cloud-to-ground discharges were analyzed and compared with other pulses of cloud discharges. Thirty eight cloud discharges and 101 cloud-to-ground discharges have been studied in this analysis. Pulses in cloud discharges were classified as [`]small', [`]medium' and [`]large', depending upon the value of their relative amplitude with respect to that of the average amplitude of the five largest pulses in the flash. We found that parameters, such as pulse duration, rise time, zero crossing time and full-width at half-maximum (FWHMs) of the first pulse of cloud and cloud-to-ground discharges are similar to small pulses that appear in the later stage of cloud discharges. Hence, we suggest that the mechanism of the first pulse of cloud and cloud-to-ground discharges and the mechanism of pulses at the later stage of cloud discharges could be the same.

  • 135.
    Ahmad, Noor Azlinda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fernando, Mahendra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Baharudin, Zikri A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ahmad, H.
    Malek, Z. Abdul
    Characteristics of narrow bipolar pulses observed in Malaysia2010Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, nr 5-6, s. 534-540Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Narrow bipolar pulses (NBPs) are considered as isolated intracloud events with higher peak amplitude and strong high frequency emission compared to the first return strokes and other intracloud discharges. From 182 NBPs recorded in Malaysia in the tropic, 75 were narrow negative bipolar pulses (NNBPs) while 107 were narrow positive bipolar pulses (NPBPs). The mean duration of NNBPs was 24.6 +/- 17.1 mu s, while 30.2 +/- 12.3 mu s was observed for NPBPs. The mean full-width at half-maximum (FVVHM) was 2.2 +/- 0.7 and 2.4 +/- 1.4 mu s for NNBPs and NPBPs, respectively. The mean peak amplitude of NPBPs normalized to 100 km was 22.7 V/m, a factor of 1.3 higher than that of NNBPs which is 17.6 V/m. In contrast to the previous studies, it was observed that the electric field change was characterized by a bipolar pulse with a significant amount of fine structures separated by a few tens of nanoseconds intervals, embedded on it. (C) 2010 Elsevier Ltd. All rights reserved.

  • 136.
    Ahmad, Noor Azlinda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fernando, Mahendra
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    ON THE DERIVATIVES OF NARROW BIPOLAR PULSES2010Konferansepaper (Fagfellevurdert)
  • 137.
    Ahmadi, Mohammad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Wirell, Vilhelm
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Bullerskärmar i betong: En teknisk studie om gröna bullerskärmar i betong2019Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    As cities grow and densify, the amount of traffic in and through settlement also increases. Horizontal surfaces are increasingly disappearing in favor of housing and infrastructure. This leads to increased noise levels and increased emissions in both residential and green belts.

    Where exploitation cannot be adapted in any other way, or where natural shielding against noise cannot be achieved, noise screens are often erected to minimize noise propagation from roads and railways. The most commonly occurring noise screen today consists of wood, but given its prerequisites, the study intends to investigate whether noise screens in concrete can be a better alternative.

    The purpose is thus to design and dimension noise screens in concrete. The study is carried out in collaboration with Butong AB, which since 2009 has developed and constructed plant walls in concrete.

    The objective is to construct and dimension a self-supporting noise shield, with integrated substrate for plants to grow and germinate, based on Butong's existing plant walls. To achieve the report's objectives, different types of matrices and designs have been evaluated with respect to strength and mechanical properties. The calculations made are numerical and performed in SolidWorks.

    The results from the numerical tests have been used to produce a noise shield with intended dimensions and where loads have been applied according to current eurocodes and SIS standards.

    The conclusion indicates that green noise screens in concrete maintain a high competitiveness against noise screens in wood. The long span, good mechanical properties and aesthetically pleasing design are some of the factors that support the conclusion.

  • 138.
    Ahmadifakhr, Saman
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Backer-Meurke, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Caliskan, Emina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Johansson, Isabell
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Lundsten, Petter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Piitulainen, Timo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Rashid, Akar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Materialkarakterisering av AM-material: En undersökning av 3D-skrivet rostfritt stål2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Kärnkraftsverkens materialgrupp söker nya alternativa material som är nötnings- och korrosionsbeständiga samt koboltfria. Ett möjligt alternativ är ett koboltfritt, martensitiskt, rostfritt stål av vilket komponenter tillverkas genom 3D-skrivning. Dokumenteringen av egenskaperna hos detta material är ännu inte komplett. I detta arbete har en sådan legering, benämnd VRF, analyserats. Korrosionstester utförda på legeringen före och efter värmebehandling visar att materialets korrosionsmotstånd minskat signifikant efter värmebehandlingen, dock påverkar inte materialets uppbyggnadsriktning korrosionsegenskaperna hos materialet, då både kort- och långsidan ger liknande resultat på korrosionsmätningarna. Analys av mikrostrukturen visar att en betydande volym av materialet utgörs av sekundära faser, såsom nitrider och karbider. Ingen stor skillnad i sammansättningen av, eller mängden av, sekundära faser kunde ses före och efter värmebehandling av legeringen. Materialets hårdhet mättes i olika områden av både det värmebehandlade och ej värmebehandlade materialet. I det ej värmebehandlade provet var hårdheten förhållandevis låg, men homogen genom hela provet. Hårdheten i det värmebehandlade provet var högre, men var inte homogen, utan varierade mycket i provet. Orsaken till variationen i hårdhet och de oväntat låga värdena tros vara en ej optimerad värmebehandlingsprocess. Då materialet har en relativt låg hårdhet och lågt korrosionsmotstånd är slutsatsen från detta arbete att materialet behöver genomgå en mer optimerad värmebehandlingsprocess innan det kan vara ett lämpligt alternativ inom kärnkraftsindustrin.

  • 139.
    Ahmed, Besam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Industriell teknik.
    Design Automation of a Vacuum Chamber: Creating Rules for Configurator2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    The report is a degree project for the bachelor's level in Mechanical Engineering atUppsala University. The thesis was carried out at Scienta Omicron AB in Uppsala,Sweden and it is provided a basis determining rules for a vacuum chamberconfigurator that will be used by Scienta Omicron AB.Scienta Omicron AB wants to automate its vacuum chamber design to increasecompany productivity and profitability within this product line. This degree projectdescribes a basis for a configurator that will be used by the company later.This degree project begins by interviewing Scienta Omicron's R&D manager and theDesign Team to understand the company's needs and the reasons behind the desireto change the company's current process. After discussion with the company, aproject plan for the thesis is established to ensure that all parts of the thesis areperformed in time with good quality.The report presents briefly the theory of vacuum technology, especially regardingultra-high vacuum that is used by Scienta Omicron and several methods are used toachieve the project. The report ends with recommendations for Scienta Omicronwith the intention of continuously improving the result of this thesis i.e. implementingthe new process.An intensive study of vacuum chambers manufactured by the company is carried outby reviewing the company's email conversation between the design department andcustomers as well as chamber drawings in order to understand the design conceptand its limitations.As a part of the project, a requirement specification of the thesis has beendetermined and concept generating performed, resulting in two concepts," clashmodels" and" matrix". These enable the design and implementation of a vacuumchamber configurator by an external company specializing in customer productconfiguration.The chosen concept is clash models because it facilitates the implementation of theconfigurator later. A third-party company, Animech, which will implement the rulesdetermined in this thesis when constructing the configurator which will be used bySOAB. The configurator will be a tool that replaces the design team and gives themtime resources to develop new solutions and products.

  • 140.
    Ahmed, Elajez