Now showing items 1141-1160 of 1407

    • Investigation of seafloor craters and mounds in the central Barents Sea 

      Sørbø, Magnus (Master thesis; Mastergradsoppgave, 2016-06-01)
      Recently acquired datasets of multibeam, echosounder and seismic data reveal the geomorphology and distribution of seafloor craters and mounds in central Barents Sea. The study found 288 craters, 227 pingos and 119 gas flares in the area, each with its own distinctive appearance. The majority of pingos lie inside or close to craters. This indicate a connection between the two features. Inspection ...
    • Shallow and Deep Seismic Amplitude Anomalies Indicate Times of Fluid Accumulation and Tectonic Activity in the Barents Sea 

      Pedersen, Magnus (Master thesis; Mastergradsoppgave, 2016-06-01)
      This master thesis studied the 3D-seismic dataset ST0825 located in the southwest Barents Sea. Aiming to map seismic anomalies and faults above and below the Upper Regional Unconformity (URU). The survey partly covers four different structural elements: Finnmark Platform, Tromsø Finnmark Fault Complex, Hammerfest Basin and Ringvassøy Loppa Fault Complex, south to north respectively. These areas ...
    • Possible gas hydrates on the Bjarmeland Platform; seismic expression and stability modelling 

      Løvaas, John Sverre (Master thesis; Mastergradsoppgave, 2016-05-24)
      Seismic evidence of shallow gas anomalies are prominent at Ververis Dome structure and Hoop Fault Complex in Bjarmeland Platform. Ubiquitous high amplitude anomalies at the same depth as these shallow gas anomalies infer a possible relation to gas hydrates. A wide range of fluid flow structures within the two study areas have previously been discovered and reported, and may possibly feed the base ...
    • Seafloor craters and mounds in the central Barents Sea 

      Isaksen, Nataliia (Master thesis; Mastergradsoppgave, 2016-05-31)
      Multiple giant craters and mounds have been identified in the area of the Upper Bjørnøyrenna in the central Barents Sea from the reflection seismic and echo sounder data. Analysis of seismic and echo sounder data revealed clear connection between these distinct seafloor features and seismic amplitude anomalies. Distribution pattern of the numerous water column anomalies registered in the area and ...
    • Fluid flow features and gas hydrates in the outer Vøring Basin 

      Varjola, Carita E. Eira (Master thesis; Mastergradsoppgave, 2015-12-15)
      The 3D seismic survey ST0827 in the outer Vøring Basin reveals a complex fluid flow system consisting of hydrothermal vents, polygonal faults and acoustic pipes. The polygonal faults are bound to the fine-grained Top Brygge Formation and ooze-dominated Kai Formation. The Kai Formation is overlain by the Naust Formation, in which glacigenic debris flow units are observed. As polygonal faults can be ...
    • Late summer sea ice segmentation with multi-polarisation SAR features in C- and X-band 

      Fors, Ane Schwenke; Brekke, Camilla; Doulgeris, Anthony Paul; Eltoft, Torbjørn; Renner, Angelika; Gerland, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-09-01)
      In this study we investigate the potential of sea ice segmentation by C- and X-band multi-polarisation synthetic aperture radar (SAR) features during late summer. Five high-resolution satellite SAR scenes were recorded in the Fram Strait covering iceberg- fast first-year and old sea ice during a week with air temperatures varying around zero degrees Celsius. In situ data consisting of sea ice ...
    • 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 ...
    • Optical transport, lifting and trapping of micro-particles by planar waveguides 

      Helle, Øystein Ivar; Ahluwalia, Balpreet Singh; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-03-03)
      Optical waveguides can be used to trap and transport micro-particles. The particles are held close to the waveguide surface by the evanescent field and propelled forward. We propose a new technique to lift and trap particles above the surface of the waveguides. This is made possible by a gap between two opposing, planar waveguides. The field emitted from each of the waveguide ends diverge fast, away ...
    • Eastward-expanding auroral surges observed in the post-midnight sector during a multiple-onset substorm 

      Tanaka, Yoshimasa; Ogawa, Yasunobu; Kadokura, Akira; Partamies, Noora; Whiter, Daniel; Enell, Carl-Fredrik; Brändström, Urban; Sergienko, Tima; Gustavsson, Björn Johan; Kozlovsky, Alexander; Miyaoka, Hiroshi; Yoshikawa, Akimasa (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-09)
      We present three eastward-expanding auroral surge (EEAS) events that were observed intermittently at intervals of about 15 min in the post-midnight sector (01:55–02:40 MLT) by all-sky imagers and magnetometers in northern Europe. It was deduced that each surge occurred just after each onset of a multiple-onset substorm, which was small-scale and did not clearly expand westward, because they were ...
    • 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 ...
    • Polarimetric SAR Change Detection with the Complex Hotelling-Lawley Trace Statistic 

      Akbari, Vahid; Anfinsen, Stian Normann; Doulgeris, Anthony Paul; Eltoft, Torbjørn; Moser, Gabriele; Serpico, Sebastian Bruno (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-03-15)
      In this paper, we propose a new test statistic for unsupervised change detection in polarimetric radar images. We work with multilook complex covariance matrix data, whose underlying model is assumed to be the scaled complex Wishart distribution. We use the complex-kind Hotelling-Lawley trace statistic for measuring the similarity of two covariance matrices. The distribution of the Hotelling-Lawley ...
    • The environment-induced cracking of as-annealed Ni3(Si,Ti) and Ni3(Si,Ti) with 2Mo in sodium chloride solutions 

      Priyotomo, Gadang; Wagle, Sanat; Okitsu, Kenji; Iwase, Akihiro; Kaneno, Yasuyuki; Nishimura, Rokuro; Takasugi, Takayuki (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-01)
      Background The environment-induced cracking (EIC) of as-annealed Ni3(Si,Ti) and Ni3(Si,Ti) with 2Mo has been researched as functions of applied stress, chloride ion concentration, test temperature, and pH. Methods The investigation of EIC was carried out by applying a constant method in NaCl solutions. Results The EIC susceptibility of both intermetallic compounds increased with ...
    • Chip-based optical microscopy for imaging membrane sieve plates of liver scavenger cells 

      Helle, Øystein Ivar; Øie, Cristina Ionica; McCourt, Peter Anthony; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-26)
      The evanescent field on top of optical waveguides is used to image membrane network and sieve-plates of liver endothelial cells. In waveguide excitation, the evanescent field is dominant only near the surface (~100-150 nm) providing a default optical sectioning by illuminating fluorophores in close proximity to the surface and thus benefiting higher signal-to-noise ratio. The sieve plates of liver ...
    • Hon förebygger miljökatastrofer 

      Johansson, Malin; Avenius, Malin (Others; Andre, 2015)
      Det får inte hända. men om det ändå gör det behövs ny teknik för att mildra effekterna. Malin Johanssons forskning handlar om att förebygga miljökatastrofer, när oljebolagen söker sig allt längre in i Arktis.
    • Imaging Sea Ice Structure by Remote Sensing Sensors 

      Eltoft, Torbjørn; Doulgeris, Anthony Paul; Brekke, Camilla; Solbø, Stian; Gerland, Sebastian; Hanssen, Alfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-14)
      This paper will investigate how new developments in remote sensing and sensor technologies can be applied to image the structure of the sea ice surface. Both segmentation of multipolarimetric synthetic aperture radar images and strategies for the analyses of polarimetric SAR data of sea ice are addressed. The analysis is based on a Radarsat 2 PolSAR scene of from the Fram Strait in September ...
    • Characterization of a waveguide Mach-Zehnder interferometer using PDMS as a cover layer 

      Lindecrantz, Susan Mariah; Tinguely, Jean-Claude; Ahluwalia, Balpreet Singh; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2015)
      A Mach-Zehnder interferometer made with shallow rib waveguides is studied experimentally and using simulations. The rib-height giving single-mode guidance is found as function of core thickness and polarization. Devices have been made using shallow rib waveguides (5 nm rib height) in silicon nitride. The sensitivity and the limit of detection (LOD) is studied experimentally regarding the length of ...
    • Single-mode limit and bending losses for shallow Rib Si3N4 waveguides 

      Dullo, Firehun Tsige; Tinguely, Jean-Claude; Solbø, Stian; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-01-07)
      The single-mode limit and bending losses for shallow rib waveguides are studied using the full vectorial film mode matching method. The maximum rib height for single-mode waveguides is found to be on the order of 10 nm for a rib width of 2 m and a wavelength of 785 nm, with the exact value depending on the core thickness and the polarization. Bending losses are calculated as a function of several ...
    • Consensus Clustering Using kNN Mode Seeking 

      Myhre, Jonas Nordhaug; Mikalsen, Karl Øyvind; Løkse, Sigurd; Jenssen, Robert (Chapter; Bokkapittel, 2015-06-09)
      In this paper we present a novel clustering approach which combines two modern strategies, namely consensus clustering, and two stage clustering as represented by the mean shift spectral clustering algorithm. We introduce the recent kNN mode seeking algorithm in the consensus clustering framework, and the information theoretic kNN Cauchy Schwarz divergence as foundation for spectral clustering. In ...
    • The auroral red line polarisation: modelling and measurements 

      Lilensten, J.; Bommier, V.; Barthelemy, M; Lamy, Herve; Bernard, D; Moen, Jøran Idar; Johnsen, Magnar Gullikstad; Løvhaug, Unni Pia; Pitout, Frederic (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-12)
      In this work, we model the polarisation of the auroral red line using the electron impact theory developed by Bommier et al. (2011). This theory enables the computation of the distribution of the Degree of Linear Polarisation (DoLP) as a function of height if the flux of precipitated electrons is provided as input. An electron transport code is used to infer the stationary electron flux at each ...
    • A case study on generation mechanisms of a sporadic sodium layer above Tromsø (69.6° N) during a night of high auroral activity 

      Takahashi, Toru; Nozawa, Satonaori; Tsuda, Takuo T.; Ogawa, Yasunobu; Saito, Norihito; Hidemori, Takehiro; Kawahara, Takuya D.; Hall, Chris; Fujiwara, Hitoshi; Matuura, Nobuo; Brekke, Asgeir; Tsutsumi, Masaki; Wada, Satoshi; Kawabata, Tetsuya; Oyama, Shinichiro; Fujii, Ryoichi (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-05)
      We have quantitatively evaluated generation mechanisms of a sporadic sodium layer (SSL) based on observational data obtained by multiple instruments at a high-latitude station: Ramfjordmoen, Tromsø, Norway (69.6° N, 19.2° E). The sodium lidar observed an SSL at 21:18 UT on 22 January 2012. The SSL was observed for 18 min, with a maximum sodium density of about 1.9 × 1010 m−3 at 93 km with a 1.1 km ...