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norskInstitutt for fysikk og teknologi: Recent submissions
Now showing items 1381-1400 of 1428
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Multifractals and their application to geospace data
(Master thesis; Mastergradsoppgave, 2008-06-02)In this thesis I first introduce multifractal theory and mathematical concepts for multifractal analysis. Different methods for different uses are described, with focus on a differentiating between coarse and fine theory approaches. Methods for analysing time series are also described, more specificly a direct method based on the coarse theory analysis, the wavelet transform modulus maxima ... -
Aktive antenner for ultrabredbånd-radar til deteksjon av brystkreft
(Master thesis; Mastergradsoppgave, 2008-10-01)Motivasjonen for denne oppgaven er en aktiv, smertefri og ufarlig metode for deteksjon av brystkreft ved bruk av ultrabredbånd mikrobølgeradar. Montering av lavstøyforsterker direkte etter mottakerantennen har en positiv effekt på signal-til-støyforholdet i radar-systemet, og en vesentlig del av oppgaven er å måle lavstøyforsterkeren gir. Grunnleggende teori om mikrobølger, antenner, forsterkere, ... -
Motion induced electromagnetic fields in the ocean: Exploratory data analysis and signal processing
(Master thesis; Mastergradsoppgave, 2007-12-17)We will in this thesis analyse data from antennas located at the seafloor measuring the vertical component of the natural electric field. The internal source to electromagnetic fields in the ocean is saltwater crossing the geomagnetic field, and the main contributor to the motion induced vertical electric field is the water velocity in the East-West direction weighted by the North component of the ... -
A numerical study of planar elliptical antennas applied to ultrawideband (UWB) imaging of breast tissue
(Master thesis; Mastergradsoppgave, 2008-08)The thesis discusses the possibility of using ultrawideband (UWB) radar to detect breast cancer. At the present time, X-ray mammography and ultrasound are the golden standard imaging techniques for detection and evaluation of breast cancer, but they both have their limitations. UWB radar utilizes the difference in dielectric properties between a tumor and the surrounding healthy tissue. By interpreting ... -
Characterization of a magnetized plasma in cylindrical geometry
(Master thesis; Mastergradsoppgave, 2007-06)Njord is a novel plasma device in which a low-temperature plasma is produced by RF waves inductively coupled into a cylindrical, magnetized vacuum. The main part of this project is to carry out an experimental characterization of the plasma in this device. The plasma expansion and acceleration of the source plasma into the main chamber will be of specific interest. The ultimate aim will then be to ... -
Spectral observations of Polar Mesospheric Summer Echoes (PMSE)
(Master thesis; Mastergradsoppgave, 2007-06-15)We present spectral measurements of PMSE under the influence of HF heating cycles. The data has been obtained with EISCAT VHF radar, during the EISCAT campaign 2004 in Tromsø. Examples where the PMSE overshoot appears when the electrons are heated with a specific cycle are shown. A detailed analysis of PMSE spectral width during the heating cycles concluded that there is no evidence of a possible ... -
Analysis of the dynamical behavior of the Minidusty rocket payloads, and its influence on the plasma probe measurements
(Master thesis; Mastergradsoppgave, 2007-06-25)In the present master thesis the dynamical behavior of the Mini-Dusty rockets will be analyzed with the aim to obtain accurate information on the absolute coning and orientation history during the flight, and in particular around all the critical phases. -
Optiske bølgeledere av silisium-rik nitrid for manipulering av mikro- og nanopartikler
(Master thesis; Mastergradsoppgave, 2007-06-01)Målet med denne oppgaven er å karakterisere bølgeledere av silisium-rik nitrid, SiRN, med hensyn på koblingstap, propagasjonstap, tall på modi og feltfordeling. Det skal gjøres forsøk på å redusere tapet mest mulig ved å prøve ut forskjellige måter å koble inn lys og forbedre kuttingen av bølgelederene. Det skal også gjøres forsøk på å finne tykkelse og brytningsindeks på bølgelederene ved hjelp av ... -
Temperaturmåling på optiske bølgeledere
(Master thesis; Mastergradsoppgave, 2007-06)Oppgaven omhandler målemetoder og problemstillinger i forhold til temperaturmåling på optiske bølgeledere -
Måling av plasmadrift i den øvre atmosfære over Ny-Ålesund, Svalbard.
(Master thesis; Mastergradsoppgave, 1977-11)Oppgaven bygger på målinger av plasmadrift i den øvre atmosfære over Ny-Ålesund, Svalbard. Som målemetode er brukt "spaced receivers" metoden. I kap. 2 er satt opp modeller for solvind, magnetosfære og ionosfære og en ser på fenomen som forplanter seg fra solvinden til ionosfæren. Ved hjelp av disse modeller beregnes så drift av plasma i ionosfæren. I kap. 3 beskrives målemetoden. Diffraksjonsmekanismen ... -
A comparative study of algorithms for blind source separation in the instantaneous linear mixture model
(Master thesis; Mastergradsoppgave, 2007-06-22)This thesis discusses some of the many techniques for performing blind source separation. Its focus is on the theoretical concepts that allow for the problem to be solved. It starts with presenting the EM algorithm, which is the method underpinning many of the algorithms that are presented later in the thesis. Some of the established methods are presented, and we proceed to devolop source separation ... -
Fluid-Thermal properties of electromagnetic heated water boli used in thermal treatment of superficial cancer
(Master thesis; Mastergradsoppgave, 2007-06-15)Hyperthermia treatment (tissue heating up to 42-45 ºC) based on microwave applicators always uses a temperature controlled coupling medium consisting of deionized water. The bolus prevents blisters in the skin and acts as an impedance matching layer for the electromagnetic energy between the antenna and the treatment volume. Little is known whether practically realizable water flow-rates and other ... -
A theoretical study of the coupling between minor ions and protons in the solar transition region
(Master thesis; Mastergradsoppgave, 2007-06-01)We have used a numerical model to calculate the flow velocities of six minor ion species, using two different background models for the fast solar wind, one with a slow expansion, and one with a very rapidly expanding geometry. By comparing the flow velocity of the minor ions and the protons, we have investigated the degree of coupling between minor ions and the background solar wind in the solar ... -
The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes
(Journal article; Peer reviewed; Tidsskriftartikkel, 2006-11-21)Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF) transmitter located near Tromsø (Norway). Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers ... -
Directional features of the downshifted peak observed in HF-induced stimulated electromagnetic emission spectra obtained using an interferometer.
(Journal article; Peer reviewed; Tidsskriftartikkel, 2006-08-09)A high frequency (HF) ionospheric modification experiment was carried out between 25 September and 8 October 2004, using the EISCAT HF transmitter located near Tromsø, Norway. During this experiment the spectra of the stimulated HF sideband waves (stimulated electromagnetic emission or SEE) induced by the HF pump were observed using an interferometer consisting of three spaced receiving antennas ... -
Plasma density over Svalbard during the ISBJØRN campaign.
(Journal article; Peer reviewed; Tidsskriftartikkel, 2000)In 1997, reliable operation of the EISCAT Svalbard Radar (ESR) was achieved and a rocket launching facility at Ny Ålesund on Svalbard (79°N, 12°E) (SVALRAK) was established. On 20 November, 1977, the first instrumented payload was launched from SVALRAK. Although the payload configuration had been flown many times previously from Andøya Rocket Range on the Norwegian mainland, this presented an ... -
Winter warmings, tides and planetary waves. Comparisions between CMAM (with interactive chemistry) and MFR-MetO observations and data.
(Journal article; Peer reviewed; Tidsskriftartikkel, 2006-10-20)Following earlier comparisons using the Canadian Middle Atmosphere Model (CMAM, without interactive chemistry), the dynamical characteristics of the model are assessed with interactive chemistry activated. Time-sequences of temperatures and winds at Tromsø (70° N) show that the model has more frequent and earlier stratospheric winter warmings than typically observed. Wavelets at mesospheric heights ... -
The effect of electron bite-outs on artificial electron heating and the PMSE overshoot.
(Journal article; Peer reviewed; Tidsskriftartikkel, 2005-12-23)We have considered the effect that a local reduction in the electron density (an electron bite-out), caused by electron absorption on to dust particles, can have on the artificial electron heating in the height region between 80 to 90 km, where noctilucent clouds (NLC) and the radar phenomenon PMSE (Polar Mesospheric Summer Echoes) are observed. With an electron density profile without ... -
Relative drift between black aurora and the ionospheric plasma.
(Journal article; Tidsskriftartikkel, 2005-07-27)Black auroras are recognized as spatially well-defined regions within uniform diffuse aurora where the optical emission is significantly reduced. Although a well studied phenomenon, there is no generally accepted theory for black auroras. One theory suggests that black regions are formed when energetic magnetospheric electrons no longer have access to the loss cone. If this blocking mechanism drifts ... -
The red-sky enigma over Svalbard in December 2002
(Journal article; Peer reviewed; Tidsskriftartikkel, 2005-07-27)On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral ...
