Institutt for fysikk og teknologi: Nye registreringer

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    • Dataverktøy til regning, skriving og tegning i naturfag 

      Haugland, Ole Anton (Book; Bok, 2007)

    • Fysikk i den polare atmosfæren og nordlyset 

      Brekke, Asgeir (Research report; Forskningsrapport, 2008)
      Den polare atmosfæren har fått mer oppmerksomhet i den senere tid enn den vanligvis har vært forunt. Dette henger sammen med tanken om at den er så ren og upåvirket av eventuelle forurensninger som vi pumper ut i atmosfæren i de mer urbane strøk. Dersom atmosfæren tar skade av denne aktiviteten, forventer en å se skadevirkningene først og klarest i den polare atmosfæren. Svekkelsen av ozonlaget ...

    • Three photometric methods tested on ground-based data of Q 2237+0305 

      Burud, I.; Østensen, R.; Stabell, R.; Magain, P.; Courbin, F.; Refsda, S.; Remy, M.; Teuber, J. (Journal article; Tidsskriftartikkel; Peer reviewed, 1998-09-09)
      The Einstein Cross, Q 2237+0305, has been photometrically observed in four bands on two successive nights at NOT (La Palma, Spain) in October 1995. Three independent algorithms have been used to analyse the data: an automatic image decomposition technique, a CLEAN algorithm and the new MCS deconvolution code. The photometric and astrometric results obtained with the three methods are presented. ...

    • Burst statistics of fluctuations in a simple magnetized torus configuration 

      Rypdal, Kristoffer; Živkovic, Tatjana; Østvand, Lene (Working paper; Arbeidsnotat, 2009-04-19)
      In a toroidal plasma confined by a purely toroidal magnetic field the plasma transport is governed by electrostatic turbulence driven by the flute interchange instability on the low-field side of the torus cross section. In this paper we revisit experimental data obtained from the Blaamann torus at the University of Tromso. On time-scales shorter than the poloidal rotation time, the time series of ...

    • Design, implementering og evaluering av et trådløst medisinsk radiometer basert på IEEE 802.15.4-standarden og Zigbee. 

      Johansen, Amund Kronen (Master thesis; Mastergradsoppgave, 2009-06-01)
      Brystkreft er den vanligste kreftformen for kvinner og overlevelsesraten er betydelig høyere ved tidlig deteksjon. De vanligste undersøkelsesmetodene (mammografi, ultralyd, MRI) er basert på aktive metoder som medfører en viss strålingsfare. Et enkelt, ikke-invasivt instrument som baserer seg på passive metoder er derfor motivasjonen for denne masteroppgaven. Oppgaven beskriver en konseptuell ...

    • Optisk resonans i mikrokuler av glass med høy brytningsindeks 

      Husabø, Bjarne Janson (Master thesis; Mastergradsoppgave, 2009-06-15)
      I denne oppgaven har vi sett på effekten av lys som kobles fra en bølgeleder inn i optiske mikrokuler av høyindeksglass. Vi har studert Q-faktorer, og funnet at disse er lavere for kuler omgitt av vann enn tørre kuler, men at forskjellen er mindre enn mellom individuelle kuler. Vi har observert høyere ordens resonanser i kuler med større diameter. Vi har også forsøkt å utnytte resonans til å flytte ...

    • Monostatisk antennearray for UWB radar 

      Andersen, Rolf (Master thesis; Mastergradsoppgave, 2009-06)
      Ultrabredbåndet (ultrawideband - UWB) radar brukt til deteksjon av bryst-kreft viser oppløftende resultater på grunn av dens gode romlige oppløsning og dype penetreringsdybde. Bakgrunnen for å bruke UWB-radar til dette formålet er kontrasten mellom de dielektriske egenskapene til friskt brystvev og en kreftsvulst. Noe som vil føre til relativt mye reflektert energi fra kreftsvulsten. En av utfordringene ...

    • Estimering av dempingskoeffisienter i elastiske materialer ved hjelp av bredbåndet ultralyd 

      Ali, Josoph Abuker (Master thesis; Mastergradsoppgave, 2009-07-01)
      Dette er en eksperimentell oppgave der et bredbåndet ultralydsystem er brukt til å undersøke hvordan dempingen av ultralydbølger i elastiske materialer, avhenger av frekvensen. For å gjøre denne undersøkelsen ble det utviklet en holder i pleksiglass med en ultralydtransduser på hver side. I denne holderen kan prøver av ulike materialer lett festes og undersøkes ved at holderen plasseres i et vannbad. ...

    • Self-similar transport processes in a two-dimensional realization of multiscale magnetic field turbulence 

      Chiaravalloti, Francesco; Milovanov, Alexander V.; Zimbardo, Gaetano (Journal article; Tidsskriftartikkel; Peer reviewed, 2004-12-14)
      We present the results of a numerical investigation of charged-particle transport across a synthesized magnetic configuration composed of a constant homogeneous background field and a multiscale perturbation component simulating an effect of turbulence on the microscopic particle dynamics. Our main goal is to analyze the dispersion of ideal test particles faced to diverse conditions in the turbulent ...

    • Electron fishbones: theory and experimental evidence 

      Milovanov, Alexander V.; Zonca, F.; Buratti, P.; Cardinali, A.; Chen, L.; Dong, J.-Q.; Long, Y.-X.; Romanelli, F.; Smeulders, P.; Wang, L.; Wang, Z.-T.; Castaldo, C.; Cesario, R.; Giovannozzi, E.; Marinucci, M.; Ridolfini, V. Pericoli (Journal article; Tidsskriftartikkel; Peer reviewed, 2007-07-19)
      We discuss the processes underlying the excitation of fishbone-like internal kink instabilities driven by supra-thermal electrons generated experimentally by different means: Electron Cyclotron Resonance Heating (ECRH) and by Lower Hybrid (LH) power injection. The peculiarity and interest of exciting these electron fishbones by ECRH only or by LH only is also analyzed. Not only the mode stability ...

    • The WSO, a world-class observatory for the ultraviolet 

      Solheim, Jan Erik; Barstow, M.A.; Binette, L.; Brosch, N.; Cheng, F-Z.; Dennefeld, M.; Gomez de Castro, A.I.; Haubold, H.; van der Hucht, K.A.; Kappelmann, N.; Martinez, P.; Ribak, E.N.; Moisheev, A.; Pagano, I.; Sahade, J.; Wamsteker, W.; Werner, K.; Becker-Ross, H.; Florek, S.; Shustov, B. (Conference object; Konferansebidrag, 2002-09-17)
      The World Space Observatory is an unconventional space project proceeding via distributed studies. The present design, verified for feasibilty, consists of a 1.7-meter telescope operating at the second Largangian point of the Earth-Sun system. The focal plane instruments consist of three UV spectrometers covering the spectral band from Lyman alpha to the atmospheric cutoff with R~55,000 and offering ...

    • HS 0705+6700: a new eclipsing sdB binary 

      Østensen, R.; Solheim, Jan Erik; Johannessen, F. (Journal article; Tidsskriftartikkel, 2001-10-09)
      We report the discovery of an eclipsing binary – HS 0705+6700 – being an sdB star with a faint companion. From its light curve the orbital period of 8263.87 s, the mass ratio of the system q = 0.28, the inclination of 84.◦4 and other system parameters are derived. The companion does not contribute to the optical light of the system except through a strong reflection effect. The semiamplitude of ...

    • The optical afterglow and host galaxy of GRB 000926 

      Østensen, R.; Fynbo, J.U.; Solheim, Jan Erik; Gorosabe, J.; Dall, T.H.; Hjorth, J.; Pedersen, H.; Andersen, M.I.; Møller, P.; Holland, S.; Smail, I.; Kobayashi, N.; Rol, E.; Vreeswijk, P.; Vrba, F.; Burud, I.; Jensen, B.L.; Henden, A.; Thomsen, B.; Canzian, B.; Castro Cer´on, J.M.; Castro-Tirado, A.J.; Cline, T.; Goto, M.; Greiner, J.; Hanski, M.T.; Hurley, K.; Pursimo, T.; Lund, N.; Tanvir, N.; Terada, H. (Journal article; Tidsskriftartikkel, 2001-04-11)
      We present the discovery of the Optical Transient (OT) of the long–duration gamma-ray burst GRB 000926. The optical transient was detected independently with the Nordic Optical Telescope and at Calar Alto 22.2 hours after the burst. At this time the magnitude of the transient was R = 19.36. The transient faded with a decay slope of about 1.7 during the first two days after which the slope increased ...

    • Understanding the Cool DA White Dwarf Pulsator, G29–38 

      Solheim, Jan Erik; Kleinman, S. J.; Bruvold, A.; Nather, R. E.; Winget, D. E.; Clemens, J. C.; Bradley, A.; Kanaan, A.; Claver, C. F.; Watson, T. K.; Yanagida, K.; Nitta, A.; Dixson, J. S.; Grauer, A. D.; Hine, B. P.; Fontaine, G.; Liebert, James; Sullivan, D. J.; Wickramasinghe, D. T.; Achilleos, N.; Mara, T. M. K.; Seetha, S.; Ashoka, B. N.; Leibowitz, E. M.; Moskalik, P.; Krzesi´nski, J.; O’Donoghue, D.; Kurtz, D. W.; Warner, B.; Martinez, Peter; Dolez, N.; Chevreton, M.; Barstow, M. A.; Kepler, S. O.; Giovannini, O.; Hansen, C. J.; Augusteijn, T. (Journal article; Tidsskriftartikkel; Peer reviewed, 1997-10-10)
      The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post main sequence evolution, along with their cooling rates, allowing us to calibrate their ages directly. The most important set of white dwarf variables to ...

    • WSO/UV: World Space Observatory/Ultraviolet 

      Solheim, Jan Erik; Hernanza, M.; González-Riestra, R.; Wamsteker, W.; Shustov, B.; Barstow, M.; Brosch, N.; Fu-Zhen, C.; Dennefeld, M.; Dopita, M.; Gómez de Castro, A.I.; Kappelmannc, N.l.; Pagano, I.; Sahade, J.; Haubold, H.; Solheim, J.-E.; Martínezc, P. (Journal article; Tidsskriftartikkel, 2002-11-05)
      We summarize the capabilities of the World Space Observatory (UV) Project (WSO/UV). An example of the importance of this project (with a planned launch date of 2007/8) for the study of Novae is given.

    • The Everchanging Pulsating White Dwarf GD358 

      Kepler, S.O.; Solheim, Jan Erik; Nather, R. Edward; Gonzalez Perez, Jose M.; Johannessen, Frank; Winget, Don E.; Nitta, Atsuko; Kleinman, S. J.; Metcalfe, Travis; Sekiguchi, Kazuhiro; Xiaojun, Jiang; Sullivan, Denis; Sullivan, Tiri; Janulis, Rimvydas; Meistas, Edmund; Kalytis, Romualdas; Krzesinski, Jurek; Ogloza, Waldemar; O’Donoghue, Darragh; Romero-Colmenero, Encarni; Martinez, Peter; Dreizler, Stefan; Deetjen, Jochen; Nagel, Thorsten; Schuh, Sonja L.; Vauclair, Gerard; Ning, Fu Jian; Chevreton, Michel; Kanaan, Antonio; Costa, Jos´e Eduardo; Costa, Alex Fabiano Murillo; Wood, Matt A.; Silvestri, Nicole; Ahrens, T.J.; Jones, Aaron Kyle; Collins, Ansley E.; Boyer, Martha; Mukadam, Anjum; Klumpe, Eric W.; Larrison, Jesse; Kawaler, Steve; Riddle, Reed; Ulla, Ana; Bradley, Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2003-01-23)
      We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2000. We acquired more than 232 000 independent measurements. We also report on 48 hours of time-series photometric observations in Aug 1996. We detected the non-radial g-modes consistent with degree ℓ = 1 and radial ...

    • Multiwavelength observations revealing the outbursts of the two soft X-ray transients XTE J1859+226 and XTE J1118+480 

      Solheim, Jan Erik; Chaty, S.; Haswell, C.A.; Østensen, R.; Hynes, R.I.; Shrader, C.R.; Cui, W.; Mauche, C.W.; Norton, A.J.; Geballe, T.R.; Ioannou, Z.; King, A.R. (Conference object; Konferansebidrag, 2001-02-06)
      We report here on multiwavelength observations of the two new soft X-ray transients (SXTs) XTE J1859+226 and XTE J1118+480, which we observed with HST/RXTE/UKIRT. For XTE J1118+480 we also used EUVE since it is located at a very high galactic latitude and suffers from very low extinction. The two sources exhibited very different behaviour. XTE J1859+226 seems quite normal and therefore a good ...

    • Combining ENVISAT ASAR and MODIS data to enable improved snow cover maps 

      Mjøen, Håvard Uv (Master thesis; Mastergradsoppgave, 2008-06)
      Information about snow covered area is important for several purposes, and this information can be found by detecting reflection of optical waves using optical sensors or by using active radars such as SAR. This thesis is explaining how information from the measurements are used to make snow maps. Optival sensors cannot detect snow when the area is covered by clouds, and this is a problem in the ...

    • Evidence of low-dimensional chaos in magnetized plasma turbulence 

      Živkovic, Tatjana; Rypdal, Kristoffer (Working paper; Arbeidsnotat, 2008-03-10)
      We analyze probe data obtained from a toroidal magnetized plasma configuration suitable for studies of low-frequency gradient-driven instabilities. These instabilities give rise to field-aligned convection rolls analogous to Rayleigh-Benard cells in neutral fluids, and may theoretically develop similar routes to chaos. When using mean-field dimension analysis, we observe low dimensionality, but ...

    • Modeling temporal fluctuations in avalanching system 

      Rypdal, Martin; Rypdal, Kristoffer (Working paper; Arbeidsnotat, 2008-07-22)
      We demonstrate how to model the toppling activity in avalanching systems by stochastic differential equations (SDEs). The theory is developed as a generalization of the classical mean field approach to sandpile dynamics by formulating it as a generalization of Itoh’s SDE. This equation contains a fractional Gaussian noise term representing the branching of an avalanche into small active clusters, ...