Now showing items 950-969 of 1261

    • Reservoir structure and geological setting of the shallow PEON gas reservoir 

      Mikalsen, Håkon (Master thesis; Mastergradsoppgave, 2015-06-01)
      In recent years, the petroleum industry started to look for new, unconventional energy resources. Peon, a shallow gas discovery in the northern North Sea, are being assessed as a possible energy resource. However, there are challenges related to reservoir pressure, sealing mechanism, and fluid migration. In this regard, geophysical and well log analyses is figured out to get a better understanding ...
    • Results from the intercalibration of optical low-light calibration sources 2011 

      Brändström, B. Urban E.; Enell, Carl-Fredrik; Widell, Ola; Hansson, Thord; Whiter, Daniel; Mäkinen, Sanna; Mikhaylova, Daria; Axelsson, Katarina; Sigernes, Fred; Gulbrandsen, Njål; Schlatter, Nicola M.; Gjendem, Amund Gjerde; Cai, L.; Reistad, Jone Peter; Daae, Marianne; Demissie, Teferi Dejene; Andalsvik, Yngvild Linnea; Roberts, Owen; Poluyanov, Stepan Viktorovich; Chernouss, Sergey (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-05-03)
      Following the 38th Annual European Meeting on Atmospheric Studies by Optical Methods in Siuntio in Finland, an intercalibration workshop for optical low light calibration sources was held in Sodankylä, Finland. The main purpose of this workshop was to provide a comparable scale for absolute measurements of aurora and airglow. All sources brought to the intercalibration workshop were compared to the ...
    • Results of the Dragon 4 Project on New Ocean Remote Sensing Data for Operational Applications 

      Gibert, Ferran; Boutin, Jacqueline; Dierking, Wolfgang Fritz Otto; Granados, Alba; Li, Yan; Makhoul, Eduard; Meng, Junmin; Supply, Alexandre; Vendrell, Ester; Vergely, Jean-Luc; Wang, Jin; Yang, Jungang; Xiang, Kunsheng; Yin, Xiaobin; Zhang, Xi (Journal article; Tidsskriftsartikkel, 2021-07-20)
      This paper provides an overview of the Dragon 4 project dealing with operational monitoring of sea ice and sea surface salinity (SSS) and new product developments for altimetry data. To improve sea ice thickness retrieval, a new method was developed to match the Cryosat-2 radar waveform. Additionally, an automated sea ice drift detection scheme was developed and tested on Sentinel-1 data, and the ...
    • Rethinking knowledge graph propagation for zero-shot learning 

      Kampffmeyer, Michael C.; Chen, Yinbo; Liang, Xiaodan; Wang, Hao; Zhang, Yujia; Xing, Eric P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019)
      Graph convolutional neural networks have recently shown great potential for the task of zero-shot learning. These models are highly sample efficient as related concepts in the graph structure share statistical strength allowing generalization to new classes when faced with a lack of data. However, multi-layer architectures, which are required to propagate knowledge to distant nodes in the graph, ...
    • Rethinking the role of solar energy under location specific constraints 

      Eikeland, Odin Foldvik; Apostoleris, Harry; Santos, Sergio; Ingebrigtsen, Karoline; Boström, Tobias; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-22)
      In this manuscript we evaluate the potential of photovoltaic systems to meet some dedicated energy demand in specific geographic locations. Our approach is based on location-specific constraints rather than on pre-established, location-independent methodologies or assumptions. First, we propose that a thorough analysis of the socio-economic and technical possibilities of a location must act as the ...
    • Retrieval of Marine Surface Slick Dielectic Properties From Radarsat-2 Data via a Polarimetric Two-Scale Model 

      Quigley, Cornelius; Brekke, Camilla; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-27)
      We propose the use of a polarimetric two-scale surface scattering model to retrieve the dielectric parameters of oil slick from the polarimetric synthetic aperture radar. The ocean surface is modeled as an ensemble of randomly orientated, slightly roughened, tilted facets, for which the small perturbation model is assumed to be valid under the condition of no tilt. The orientation of the random ...
    • Retrieval of Snow Depth on Arctic Sea Ice From Surface-Based, Polarimetric, Dual-Frequency Radar Altimetry 

      Willatt, Rosemary; Stroeve, Julienne; Nandan, Vishnu; Newman, Thomas; Mallett, Robbie; Hendricks, Stefan; Ricker, Robert; Mead, James; Itkin, Polona; Tonboe, Rasmus; Wagner, David N.; Spreen, Gunnar; Liston, Glen; Schneebeli, Martin; Krampe, Daniela; Tsamados, Michel; Demir, Oguz; Wilkinson, Jeremy; Jaggi, Matthias; Zhou, Lu; Huntemann, Marcus; Raphael, Ian A.; Jutila, Arttu; Oggier, Marc (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-18)
      Snow depth on sea ice is an Essential Climate Variable and a major source of uncertainty in satellite altimetry-derived sea ice thickness. During winter of the MOSAiC Expedition, the “KuKa” dual-frequency, fully polarized Ku- and Ka-band radar was deployed in “stare” nadir-looking mode to investigate the possibility of combining these two frequencies to retrieve snow depth. Three approaches ...
    • Retrieval of sodium number density profiles in the mesosphere and lower thermosphere from SCIAMACHY limb emission measurements 

      Langowski, M.P.; von Savigny, C.; Burrows, J.P.; Rozanov, V.V.; Dunker, Tim; Hoppe, Ulf-Peter; Sinnhuber, M; Aikin, A.C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-28)
      An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) limb measurements of the Na resonance fluorescence. The results are obtained between 50 and 150 km altitude and the resulting global seasonal variations of Na are analyzed. The retrieval approach ...
    • Retrieving horizontally resolved wind fields using multi-static meteor radar observations 

      Stober, Gunter; Chau, Jorge L.; Vierinen, Juha; Jacobi, Christoph; Wilhelm, Sven (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-27)
      Recently, the MMARIA (Multi-static, Multi-frequency Agile Radar for Investigations of the Atmosphere) concept of a multi-static VHF meteor radar network to derive horizontally resolved wind fields in the mesosphere–lower thermosphere was introduced. Here we present preliminary results of the MMARIA network above Eastern Germany using two transmitters located at Juliusruh and Collm, and five receiving ...
    • Revealing the Quasi-Periodic Crystallographic Structure of Self-Assembled SnTiS3 Misfit Compound 

      Rajput, Nitul S.; Baik, Hionsuck; Lu, Jin-You; Tamalampudi, Srinivasa Reddy; Sankar, Raman; Al Ghaferi, Amal; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-28)
      Chemical vapor transport synthesis of SnTiS3 yields a self-assembled heterostructure of two distinct constituent materials, the semiconductor SnS and the semimetal TiS2. The misfit layer compound, although thermodynamically stable, is structurally complex, and precise understanding of the structure is necessary for designing nanoengineered heterojunction compound devices or for theoretical studies. ...
    • Review and test of funnel shape geometries in solar wind acceleration 

      Trollebø, Robert (Master thesis; Mastergradsoppgave, 2009-12-15)
      The origin and heating of the solar wind is still a puzzle. We review in this study the idea that the solar wind originates in coronal funnels. We place emphasis on the fast solar wind. This study provides primarily a historic overview over the development of the idea of funnel expansion. We present examples of recent solar wind studies that investigate the funnel geometry. These studies include ...
    • A revisit of the Gram-Charlier and Edgeworth series expansions 

      Brenn, Torgeir; Anfinsen, Stian Normann (Journal article; Tidsskriftartikkel, 2017-07-31)
      In this paper we make several observations on the Gram- Charlier and Edgeworth series, which are methods for modeling and approximating probability density functions.We present a simplified derivation which highlights both the similarity and the differences of the series expansions, that are often obscured by alternative derivations. We also introduce a reformulation of the Edgeworth series ...
    • Revisiting Trans-Arctic Maritime Navigability in 2011–2016 from the Perspective of Sea Ice Thickness 

      Zhou, Xiangying; Min, Chao; Yang, Yijun; Landy, Jack Christopher; Mu, Longjiang; Yang, Qinghua (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-14)
      Arctic navigation has become operational in recent decades with the decline in summer sea ice. To assess the navigability of trans-Arctic passages, combined model and satellite sea ice thickness (CMST) data covering both freezing seasons and melting seasons are integrated with the Arctic Transportation Accessibility Model (ATAM). The trans-Arctic navigation window and transit time are thereby obtained ...
    • RFEA Measurements of High-Energy Electrons in a Helicon Plasma Device with Expanding Magnetic Field 

      Gulbrandsen, Njål; Fredriksen, Åshild (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-26)
      In the inductively coupled plasma of the Njord helicon device we have, for the same parameters as for which an ion beam exists, measured a downstream population of high-energy electrons emerging from the source. Separated measurements of energetic tail electrons was carried out by Retarding Field Energy Analyzer (RFEA) with a grounded entrance grid, operated in an electron collection mode. In a ...
    • Rib waveguides for trapping and transport of particles 

      Ahluwalia, Balpreet Singh; Helle, Øystein Ivar; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-23)
      Rib waveguides are investigated as an alternative to strip waveguides for planar trapping and transport of microparticles. Microparticles are successfully propelled along the surface of rib waveguides and trapped in the gap between opposing rib waveguides. The trapping capabilities of waveguide end facets formed by a single and opposing waveguide geometries are investigated. The slab beneath a rib ...
    • Risk analysis of well control operations considering Arctic environmental conditions 

      Bergan, Håvard Hegg (Master thesis; Mastergradsoppgave, 2015-06-01)
      Oil and gas development in the Arctic is becoming a major focus in the industry today. However, compared to other regions, there is less experience regarding drilling operations in the Arctic environment. This fact raises concerns about high-risk scenarios, which might take place because of the harsh environmental conditions and the effects they have on various phases of operations, equipment and ...
    • Robustness of SAR Sea Ice Type classification across incidence angles and seasons at L-band 

      Singha, Suman; Johansson, Malin; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel, 2020-11-16)
      In recent years, space-borne synthetic aperture radar (SAR) polarimetry has become a valuable tool for sea ice type retrieval. L-band SAR has proven to be sensitive toward deformed sea ice and is complementary compared with operationally used C-band SAR for sea ice type classification during the early and advanced melt seasons. Here, we employ an artificial neural network (ANN)-based sea ice type ...
    • Role of hafnium doping concentration on the structural and surface properties of ZnO surfaces 

      Moser, Toni (Master thesis; Mastergradsoppgave, 2019-05-31)
      The presented thesis deals with the characterisation of hafnium doped zinc oxides with focus on the application as transparent conducting film (TCF) or electron transport layer (ETL) in heterojunction solar cells. Atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrical and optical methods have been applied to characterise the examined ...
    • Rossby Wave Changes During the Recent Decades in Mid-Latitude Continents in the Northern Hemisphere 

      Juskenaite, Ieva (Master thesis; Mastergradsoppgave, 2022-06-22)
      Increasing frequency and severity of extreme weather events throughout the recent years is a highly concerning topic. Extreme and unusual weather conditions, such as heat waves, floods and cold spells are causing a major concern for humanity. Agricultural changes, damages in infrastructure and the loss of human lives are some of the extreme weather event consequences, with the most drastic consequences ...
    • RS-HeRR: a rough set-based Hebbian rule reduction neuro-fuzzy system 

      Liu, Feng; Sekh, Arif Ahmed; Quek, Chai; Ng, Geok See; Prasad, Dilip K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-01)
      Interpretabilty is one of the desired characteristics in various classification task. Rule-based system and fuzzy logic can be used for interpretation in classification. The main drawback of rule-based system is that it may contain large complex rules for classification and sometimes it becomes very difficult in interpretation. Rule reduction is also difficult for various reasons. Removing important ...