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Visar resultat 11 - 15 av 17 avhandlingar som matchar ovanstående sökkriterier.

1. 11. Measurements of X-Ray Emission from Laboratory Sparks and Upward Initiated Lightning

   Författare :Pasan Hettiarachchi; Vernon Cooray; Mats Leijon; Mahbubur Rahman; Marcos Rubinstein; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; X-ray; upward lighting; laboratory discharges; energy distribution;

   Sammanfattning : In 1925 Nobel laureate R. C. Wilson predicted that high electric fields of thunderstorms could accelerate electrons to relativistic energies which are capable of generating high energetic radiation. The first detection of X-rays from lightning was made in 2001 and from long sparks in 2005. LÄS MER

3. 12. Features and Origin of Electromagnetic Fields Generated by Lightning Flashes

   Författare :Mohd Muzafar Ismail; Vernon Cooray; Farhad Rachidi; Uppsala universitet; []
   Nyckelord :negative cloud-to-ground lightning flashes; HF and VHF radiation; chaotic pulse trains; lightning initiation; zero-crossing time; electromagnetic fields; Engineering Science with specialization in Atmospheric Discharges; Teknisk fysik med inriktning mot atmosfäriska urladdningar;

   Sammanfattning : Negative cloud-to-ground (CG) lightning flashes transport negative charge from cloud to ground. Negative ground flashes typically involve various processes identified as preliminary breakdown, stepped leader, return stroke, dart leader, dart-stepped leader, subsequent return stroke, and cloud activity between strokes, such as regular pulse trains and chaotic pulse trains. LÄS MER

4. 13. Features of the Electric Fields Generated by Lightning with Special Attention to Positive Ground Flashes

   Författare :Dalina Johari; Vernon Cooray; Mahbubur Rahman; Fridolin Heidler; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; positive ground flashes; preliminary breakdown pulses; multiple-trains PBPs; positive leader; bidirectional leader; negative leader branch; subsequent return strokes; distant lightning; Engineering Science with specialization in Atmospheric Discharges; Teknisk fysik med inriktning mot atmosfäriska urladdningar;

   Sammanfattning : This thesis focuses on the main processes in positive ground flashes and the distant lightning environment for both positive and negative ground flashes. It presents the characteristics of the preliminary breakdown pulses (PBPs), the characteristics of the electric field pulses observed during leader propagation, and the characteristics of the electric fields produced by the first and the subsequent return strokes. LÄS MER

5. 14. The Effects of Lightning on Low Voltage Power Networks

   Författare :Raul Montaño; Vernon Cooray; Marcos Rubinstein; Uppsala universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electrical engineering; Lightning induced effects; Lightning Electromagnetic fields; Electromagnetic Compatibility EMC ; Surge Protective Devices SPDs ; Low voltage power networks; Elektroteknik; elektronik och fotonik; Electrical engineering; electronics and photonics; Elektroteknik; elektronik och fotonik;

   Sammanfattning : The present society is highly dependant on complex electronics systems, which have a low damage threshold level. Therefore, there is a high risk of partial or total loss of the system’s electronics when they are exposed to a thunderstorm environment. LÄS MER

7. 15. NOx Production by Ionisation Processes in Air

   Författare :Mahbubur Rahman; Vernon Cooray; Pierre Laroche; Uppsala universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering physics; Nitrogen oxides; Lightning; Electrical Discharges; Cosmic Rays; Troposphere; Teknisk fysik; Engineering physics; Teknisk fysik;

   Sammanfattning : The study presented in this thesis was motivated by the large uncertainty on the concentration of atmospheric electrical discharges to the global nitrogen budget. This uncertainty is partly due to the fact that information concerning the NOx production efficiency of electrical discharges having current signatures similar to those of lightning flashes is not available in the literature. LÄS MER