Now showing items 312-331 of 414

    • Satellittovervåking av isdrift i Arktis 

      Kræmer, Thomas (Conference object; Konferansebidrag, 2013)
    • Scale-free vortex cascade emerging from random forcing in a strongly coupled system 

      Rypdal, Kristoffer; Ratynskaia, Svetlana; Klumov, Boris; Kozelov, Boris; Knapek, Christina (Working paper; Arbeidsnotat, 2008-03-04)
      The notions of self-organised criticality (SOC) and turbulence are traditionally considered to be applicable to disjoint classes of phenomena. Nevertheless, scale-free burst statistics is a feature shared by turbulent as well as self-organised critical dynamics. It has also been suggested that another shared feature is universal non-gaussian probability density functions (PDFs) of global fluctuations. ...
    • Scanning acoustic microscopy—A novel noninvasive method to determine tumor interstitial fluid pressure in a xenograft tumor model 

      Hofmann, Matthias; Pflanzer, Ralph; Habib, Anowarul; Shelke, Amit; Bereiter-Hahn, Jürgen; Bernd, August; Kaufmann, Roland; Sader, Robert; Kippenberger, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-22)
      Elevated tumor interstitial fluid pressure (TIFP) is a prominent feature of solid tumors and hampers the transmigration of therapeutic macromolecules, for example, large monoclonal antibodies, from tumor-supplying vessels into the tumor interstitium. TIFP values of up to 40 mm Hg have been measured in experimental solid tumors using two conventional invasive techniques: the wick-in-needle and the ...
    • A Scatter-Based Prototype Framework and Multi-Class Extension of Support Vector Machines 

      Jenssen, Robert; Kloft, Marius; Zien, Alexander; Sonnenburg, Soeren; Müller, Klaus R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      We provide a novel interpretation of the dual of support vector machines (SVMs) in terms of scatter with respect to class prototypes and their mean. As a key contribution, we extend this framework to multiple classes, providing a new joint Scatter SVM algorithm, at the level of its binary counterpart in the number of optimization variables. This enables us to implement computationally efficient ...
    • Scenario-based modelling of the potential for solar energy charging of electric vehicles in two Scandinavian cities 

      Good, Clara; Shepero, Mahmoud; Munkhammar, Joakim; Boström, Tobias (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-19)
      In order to contribute to the reduction of greenhouse gas emissions, electric vehicles (EVs) should be charged using electricity from renewable energy sources. This paper describes a study of photovoltaics (PV) utilization for EV charging in two Scandinavian cities: Tromsø in Norway and Uppsala in Sweden, with the objective to evaluate self-sufficiency and self-consumption. The suitable areas ...
    • The science case for the EISCAT_3D radar 

      McCrea, Ian W.; Aikio, Anita; Alfonsi, Lucilla; Belova, Evgenia; Buchert, Stephan C.; Clilverd, Mark; Engler, Norbert; Gustavsson, Björn Johan; Heinselman, C.; Kero, Johan; Kosch, Mike; Lamy, Herve; Leyser, Thomas; Ogawa, Yasunobu; Oksavik, Kjellmar; Pellinen-Wannberg, Asta; Pitout, Frederic; Rapp, Markus; Stanislawska, Iwona; Vierinen, Juha (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-29)
      The EISCAT (European Incoherent SCATer) Scientific Association has provided versatile incoherent scatter (IS) radar facilities on the mainland of northern Scandinavia (the EISCAT UHF and VHF radar systems) and on Svalbard (the electronically scanning radar ESR (EISCAT Svalbard Radar) for studies of the high-latitude ionised upper atmosphere (the ionosphere). The mainland radars were constructed ...
    • The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets 

      Jones, Geraint; Knight, Matthew; Battams, Karl; Boice, Daniel; Brown, John; Giordano, Silvio; Raymond, John; Snodgrass, Colin; Steckloff, Jordan; Weissman, Paul; Fitzsimmons, Alan; Lisse, Carey M; Opitom, Cyrielle; Birkett, Kimberley; Bzowski, Maciej; Decock, Alice; Mann, Ingrid; Ramanjooloo, Yudish; McCauley, Patrick (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-18)
      This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other ...
    • Scrape-off layer turbulence in TCV: Evidence in support of stochastic modelling. 

      Theodorsen, Audun; Garcia, Odd Erik; Horacek, Jan; Kube, Ralph; Pitts, RA (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-28)
      Intermittent fluctuations in the TCV scrape-off layer have been investigated by analysing long Langmuir probe data time series under stationary conditions, allowing calculation of fluctuation statistics with high accuracy. The ion saturation current signal is dominated by the frequent occurrence of large-amplitude bursts attributed to filament structures moving through the scrape-off layer. The ...
    • Sea ice local surface topography from single-pass satellite InSAR measurements: A feasibility study 

      Dierking, Wolfgang Fritz Otto; Lang, Oliver; Busche, Thomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-29)
      Quantitative parameters characterizing the sea ice surface topography are needed in geophysical investigations such as studies on atmosphere–ice interactions or sea ice mechanics. Recently, the use of space-borne single-pass interferometric synthetic aperture radar (InSAR) for retrieving the ice surface topography has attracted notice among geophysicists. In this paper the potential of InSAR ...
    • Sea ice segmentation using Tandem-X pursuit mono static and alternative bistatic modes 

      Yitayew, Temesgen Gebrie; Doulgeris, Anthony Paul; Eltoft, Torbjørn; Dierking, Wolfgang Fritz Otto; Brekke, Camilla; Rösel, Anja (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)
      In this paper we investigate interferometric pairs of SAR images acquired by Tandem-X with the monostatic pursuit and the alternative bistatic modes for sea ice segmentation. The individual SAR images are modelled as non-Gaussian, and from the modelled data different features are extracted, stacked together and clustered. The interferometric coherence is regarded as an additional feature and utilized ...
    • Seasonal variations of the semi-diurnal and diurnal tides in the MLT: multi-year MF radar observations from 2–70 N, modelled tides (GSWM, CMAM) 

      Hall, Chris; Manson, A.H.; Meek, C.; Hagan, M.; Koshyk, J.; Franke, S.; Fritts, D.; Hocking, W.; Igarashi, K.; MacDougall, J.; Riggin, D.; Vincent, R. (Journal article; Peer reviewed; Tidsskriftartikkel, 2002)
      In an earlier paper (Manson et al., 1999a) tidal data (1990–1997) from six Medium Frequency Radars (MFR) were compared with the Global Scale Wave Model (GSWM, original 1995 version). The radars are located between the equator and high northern latitudes: Christmas Island (2° N), Hawaii (22° N), Urbana (40° N), London (43° N), Saskatoon (52° N) and Tromsø (70° N). Common harmonic analysis was applied, ...
    • Secondary charging effects due to icy dust particle impacts on rocket payloads 

      Bekele, Meseret Kassa; Rapp, M.; Hartquist, T W; Havnes, Ove (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      We report measurements of dust currents obtained with a small probe and a larger probe during the flight of the ECOMA-4 rocket through the summer polar mesosphere. The payload included two small dust probes behind a larger dust probe located centrally at the front. For certain phases of the payload rotation, the current registered by one of the small dust probes was up to 2 times the current measured ...
    • A Segmentation based CFAR detection algorithm using truncated statistics 

      Ding, Tao; Doulgeris, Anthony Paul; Brekke, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-18)
      Target detection in nonhomogeneous sea clutter environments is a complex and challenging task due to the capture effect from interfering outliers and the clutter edge effect from background intensity transitions. For synthetic aperture radar (SAR) measurements, those issues are commonly caused by multiple targets and meteorological and oceanographic phenomena, respectively. This paper proposes a ...
    • 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 ...
    • Sensitive on-chip methane detection with a cryptophane-A cladded Mach-Zehnder interferometer 

      Dullo, Firehun Tsige; Lindecrantz, Susan; Jagerska, Jana; Hansen, Jørn H; Engqvist, Stig Olov Magnus; Solbø, Stian; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-24)
      We report a methane sensor based on an integrated Mach-Zehnder interferometer, which is cladded by a styrene-acrylonitrile film incorporating cryptophane-A. Cryptophane-A is a supramolecular compound able to selectively trap methane, and its presence in the cladding leads to a 17-fold sensitivity enhancement. Our approach, based on 3 cm-long low-loss Si3N4 rib waveguides, results in a detection limit ...
    • Separation and characterisation of mineral oil slicks and newly formed sea ice in L-band synthetic aperture radar 

      Johansson, Malin; Espeseth, Martine; Brekke, Camilla; Skrunes, Stine (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-14)
      Maritime activities in the Arctic Ocean is increasing and consequently the risk for an oil spill there is rising. Synthetic Aperture Radar (SAR) is used operationally to detect and monitor oil slicks and for sea ice monitoring and observations. Leads are often used for ship routing and within the leads newly formed sea ice is often present. Separation between the low backscatter areas that constitutes ...
    • Serial Raman spectroscopy of particles trapped on a waveguide 

      Løvhaugen, Pål; Ahluwalia, Balpreet Singh; Huser, Thomas Rolf; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      We demonstrate that Raman spectroscopy can be used to characterize and identify particles that are trapped and propelled along optical waveguides. To accomplish this, microscopic particles on a waveguide are moved along the waveguide and then individually addressed by a focused laser beam to obtain their characteristic Raman signature within 1 second acquisition time. The spectrum is used to distinguish ...
    • Shock location and CME 3D reconstruction of a solar type II radio burst with LOFAR 

      Zucca, P; Morosan, D; Rouillard, A; Fallows, Richard; Gallagher, P. T.; Magdalenic, J; Klein, K-L; Mann, G; Vocks, C; Carley, E. P.; Bisi, M. M.; Kontar, E. P.; Rothkaehl, Hanna; Dabrowski, B; Krankowski, A; Anderson, James; Asgekar, A; Bell, M. E.; Bentum, M. J.; Best, P; Blaauw, R; Breitling, F.; Broderick, J. W.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; de Geus, E.; Deller, A.; Duscha, S.; Eislöffel, J.; Garrett, M. A.; Grießmeier, J. M.; Gunst, A. W.; Heald, G.; Hoeft, M.; Hörandel, J.; Iacobelli, M.; Juette, E; Karastergiou, A.; van Leeuwen, J.; McKay, Derek; Mulder, H.A.; Munk, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey, V. N.; Pekal, R.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Rowlinson, A.; Schwarz, D. J.; Shulevski, A.; Sluman, J.; Smirnov, O.V.; Sobey, C.; Soida, M.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; van Weeran, R. J.; Wucknitz, O.; Zarka, P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-19)
      <p><i>Context - </i>Type II radio bursts are evidence of shocks in the solar atmosphere and inner heliosphere that emit radio waves ranging from sub-meter to kilometer lengths. These shocks may be associated with coronal mass ejections (CMEs) and reach speeds higher than the local magnetosonic speed. Radio imaging of decameter wavelengths (20–90 MHz) is now possible with the Low Frequency Array ...
    • Short-Time Ice Drift and Deformation Measurements Using Multi-Mission Synethetic Aperture Radar 

      Kræmer, Thomas; Brekke, Camilla (Journal article; Tidsskriftartikkel, 2015-06)
      Norway is in a good position regarding frequent access to synthetic aperture radar data. A Norwegian– Canadian agreement provides large quotas of RADARSAT-2 images used operationally by e.g. the Norwegian Ice Service. More recently, Norway’s participation in the Copernicus program also allows rapid access to SENTINEL-1A data. By combining these data sources we can get satellite time series ...
    • Signature of Arctic first-year ice melt pond fraction in X-band SAR imagery 

      Fors, Ane Schwenke; Divine, Dmitry V; Doulgeris, Anthony Paul; Renner, Angelika; Gerland, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-23)
      In this paper we investigate the potential of melt pond fraction retrieval from X-band polarimetric synthetic aperture radar (SAR) on drifting first-year sea ice. Melt pond fractions retrieved from a helicopter-borne camera system were compared to polarimetric features extracted from four dual-polarimetric X-band SAR scenes, revealing significant relationships. The correlations were strongly dependent ...