Sökning: "head echoes"

Hittade 3 avhandlingar innehållade orden head echoes.

  1. 1. High-resolution meteor exploration with tristatic radar methods

    Författare :Johan Kero; Asta Pellinen-Wannberg; Sigrid Close; Umeå universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; meteors; meteoroids; interplanetary dust; radar; head echoes; ablation; meteoroid fragmentation; radar; huvudekon; ablation; meteorisk fragmentation; meteorer; meteoroider; interplanetärt stoft; Space engineering; Rymdteknik;

    Sammanfattning : A meteor observed with the naked eye is colloquially called a shooting star. The streak of light is generated by an extra-terrestrial particle, a meteoroid, entering the Earth’s atmosphere. The term meteor includes both luminosity detectable by optical means and ionization detectable by radar. LÄS MER

  3. 2. Radio meteors above the Arctic Circle : radiants, orbits and estimated magnitudes

    Författare :Csilla Szasz; Asta Pellinen-Wannberg; Noah Brosch; Umeå universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; meteors; meteoroids; dust; meteor radiants; meteoroid orbits; sporadic sources; radar; meteorradianter; meteoroidbanor; sporadiska källområden; radar; meteorer; meteoroider; interplanetärs stoft; Space engineering; Rymdteknik;

    Sammanfattning : This thesis presents results based on data collected with the 930 MHz EISCAT UHF radar system and three SKiYMet specular meteor radars. It describes in detail a method for meteoroid orbit calculation. The EISCAT UHF system comprises three identical 32 m parabolic antennae: one high-power transmitter/receiver and two remote receivers. LÄS MER

  4. 3. Characterization of the BOLD signal in functional MRI

    Författare :Tomas Jonsson; Karolinska Institutet; Karolinska Institutet; []
    Nyckelord :;

    Sammanfattning : In the last two decades, functional magnetic resonance imaging (fMRI) has become an important and widely used imaging technique for functional brain mapping. However, blood oxygen level dependent (BOLD) technique is quite insensitive and task invoked BOLD signal change at 3T is typically in the order of a few percent. LÄS MER