Now showing items 381-400 of 1057

    • Segmentation of PMSE data using random forests 

      Jozwicki, Dorota; Sharma, Puneet; Mann, Ingrid; Hoppe, Ulf-Peter Jürgen (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-22)
      EISCAT VHF radar data are used for observing, monitoring, and understanding Earth’s upper atmosphere. This paper presents an approach to segment Polar Mesospheric Summer Echoes (PMSE) from datasets obtained from EISCAT VHF radar data. The data consist of 30 observations days, corresponding to 56,250 data samples. We manually labeled the data into three different categories: PMSE, Ionospheric ...
    • Trans-polar drift-pathways of riverine European microplastic 

      Huserbråten, Mats Brockstedt Olsen; Hattermann, Tore; Broms, Cecilie; Albretsen, Jon (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-17)
      High concentrations of microplastic particles are reported across the Arctic Ocean–yet no meaningful point sources, suspension timelines, or accumulation areas have been identified. Here we use Lagrangian particle advection simulations to model the transport of buoyant microplastic from northern European rivers to the high Arctic, and compare model results to the flux of sampled synthetic particles ...
    • Quantitative assessment of two oil-in-ice surface drift algorithms 

      Martins de Aguiar, Victor Cesar; Dagestad, Knut-Frode; Hole, Lars Robert; Barthel, Knut Sven (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-04)
      The ongoing reduction in extent and thickness of sea ice in the Arctic might result in an increase of oil spill risk due to the expansion of shipping activity and oil exploration shift towards higher latitudes. This work assessed the response of two oil-in-ice surface drift models implemented in an open-source Lagrangian framework. By considering two numerical modeling experiments, our main finding ...
    • Impacts of a sudden stratospheric warming on the mesospheric metal layers 

      Feng, Wuhu; Kaifler, Bernd; Marsh, Daniel R.; Höffner, Josef; Hoppe, Ulf-Peter; Williams, Bifford P.; Plane, John M.C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-11)
      We report measurements of atomic sodium, iron and temperature in the mesosphere and lower thermosphere (MLT) made by ground-based lidars at the ALOMAR observatory (69°N, 16°E) during a major sudden stratospheric warming (SSW) event that occurred in January 2009. The high resolution temporal observations allow the responses of the Na and Fe layers to the SSW at high northern latitudes to be ...
    • A nested high-resolution unstructured grid 3-D ocean-sea ice-ice shelf setup for numerical investigations of the Petermann ice shelf and fjord 

      Prakash, Abhay; Zhou, Qin; Hattermann, Tore; Bao, Weiyang; Graversen, Rune Grand; Kirchner, Nina (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-18)
      Three-dimensional numerical simulation of circulation in fjords hosting marine-terminating ice shelves is challenging because of the complexity of processes involved in such environments. This often requires a comprehensive model setup. The following elements are needed: bathymetry (usually unknown beneath the glacier tongue), ice shelf draft (impacting water column thickness), oceanographic state ...
    • Multiplexed Mach-Zehnder interferometer assisted ring resonator sensor 

      Yadav, Mukesh; Aksnes, Astrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-04)
      A Mach-Zehnder interferometer assisted ring resonator configuration (MARC)-based multiplexed photonic sensor with a large measurement range is experimentally demonstrated. The presented MARC sensor consists of a balanced Mach-Zehnder interferometer and a ring resonator acting as a sensing component. It produces transmission responses with unique spectral signatures, which depend on the physical ...
    • Uncovering Contributing Factors to Interruptions in the Power Grid: An Arctic Case 

      Chiesa, Matteo; Bianchi, Filippo Maria; Eikeland, Odin Foldvik; Holmstrand, Inga Setså; Bakkejord, Sigurd; Santos, Sergio (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-03)
      Electric failures are a problem for customers and grid operators. Identifying causes and localizing the source of failures in the grid is critical. Here, we focus on a specific power grid in the Arctic region of Northern Norway. First, we collected data pertaining to the grid topology, the topography of the area, the historical meteorological data, and the historical energy consumption/production data. ...
    • The long sunspot cycle 23 predicts a significant temperature decrease in cycle 24 

      Solheim, Jan Erik; Stordahl, Kjell; Humlum, Ole (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-02-16)
      Relations between the length of a sunspot cycle and the average temperature in the same and the next cycle are calculated for a number of meteorological stations in Norway and in the North Atlantic region. No significant trend is found between the length of a cycle and the average temperature in the same cycle, but a significant negative trend is found between the length of a cycle and the ...
    • Understanding Cassini RPWS Antenna Signals Triggered by Dust Impacts 

      Ye, Sheng - Yi; Vaverka, Jakub; Nouzak, Libor; Sternovsky, Zoltan; Zaslavsky, Arnaud; Pavlu, Jirka; Mann, Ingrid; Hsu, Sean; Averkamp, Terrance, F.; Sulaiman, Ali H.; Pisa, D.; Hospodarsky, George; Kurth, William, S.; Horanyi, Mihaly (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-04)
      Electric field antennas are capable of detecting dust impacts in different space environment. We analyze the dust impact signals detected by the Cassini Radio and Plasma Wave Science instrument at different locations around Saturn and compare them with dust impact signals simulated in laboratory conditions and numerically. The spacecraft potential, the size, and capacitance of the impacted element ...
    • Isotope effect on filament dynamics in fusion edge plasmas 

      Meyer, Ole; Kendl, Alexander (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-20)
      The influence of the ion mass on filament propagation in the scrape-off layer of toroidal magnetised plasmas is analysed for various fusion relevant majority species, like hydrogen isotopes and helium, on the basis of a computational isothermal gyrofluid model for the plasma edge. Heavy hydrogen isotope plasmas show slower outward filament propagation and thus improved confinement properties ...
    • Concepts for structured illumination microscopy with extended axial resolution through mirrored illumination 

      Manton, James D.; Ströhl, Florian; Fiolka, Reto; Kaminski, Clemens F.; Rees, Eric J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-20)
      Wide-field fluorescence microscopy, while much faster than confocal microscopy, suffers from a lack of optical sectioning and poor axial resolution. 3D structured illumination microscopy (SIM) has been demonstrated to provide optical sectioning and to double the resolution limit both laterally and axially, but even with this the axial resolution is still worse than the lateral resolution of ...
    • On the symmetry of ionospheric polar cap patch exits around magnetic midnight 

      Moen, Jøran Idar; Gulbrandsen, Njål; Clausen, Lasse Boy Novock (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-14)
      In this paper we examine how polar cap patches, which have been frozen into the antisolar flow over the polar cap, are transported into the nighttime auroral oval. First we present a detailed case study from 12 January 2002, with continuous observations of polar cap patches exiting into the nighttime auroral oval in the Scandinavian sector. Satellite images of the auroral oval and all-sky camera ...
    • Dust observations from Parker Solar Probe: Dust ejection from the inner Solar System 

      Mann, Ingrid; Czechowski, Andrzej (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-02)
      Context. The FIELDS instrument onboard Parker Solar Probe (PSP) observes dust impacts on the spacecraft. The derived dust flux rates suggest that the particles originate from the vicinities of the Sun and are ejected by radiation pressure. Radiation pressure typically ejects particles of several 100 nm and smaller, which are also affected by the electromagnetic force.<p> Aims. We aim to understand ...
    • Effects of the tropospheric large-scale circulation on European winter temperatures during the period of amplified Arctic warming 

      Vihma, Timo; Graversen, Rune; Chen, Linling; Handorf, Dörthe; Skific, Natasa; Francis, Jennifer A.; Tyrrell, Nicholas; Hall, Richard; Hanna, Edward; Uotila, Petteri; Dethloff, Klaus; Karpechko, Alexey Yu.; Björnsson, Halldór; Overland, James E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-08)
      We investigate factors influencing European winter (DJFM) air temperatures for the period 1979–2015 with the focus on changes during the recent period of rapid Arctic warming (1998–2015). We employ meteorological reanalyses analysed with a combination of correlation analysis, two pattern clustering techniques, and backtrajectory airmass identification. In all five selected European regions, severe ...
    • A Lagrangian Snow‐Evolution System for Sea‐Ice Applications (SnowModel‐LG): Part I – Model Description 

      Liston, Glen E.; Itkin, Polona; Stroeve, Julienne C.; Tschudi, Mark; Stewart, J. Scott; Pedersen, Stine Højlund; Reinking, A.K.; Elder, Kelly (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-06)
      A Lagrangian snow-evolution model (SnowModel-LG) was used to produce daily, pan-Arctic, snow-on-sea-ice, snow property distributions on a 25 × 25-km grid, from 1 August 1980 through 31 July 2018 (38 years). The model was forced with NASA's Modern Era Retrospective-Analysis for Research and Applications-Version 2 (MERRA-2) and European Centre for Medium-Range Weather Forecasts (ECMWF) ReAnalysis-5th ...
    • Sub-kilometre scale distribution of snow depth on Arctic sea ice from Soviet drifting stations 

      Mallett, Robbie; Stroeve, Julienne C.; Tsamados, Michel; Willatt, Rosemary; Newman, Thomas; Nandan, Vishnu; Landy, Jack Christopher; Itkin, Polona; Oggier, Marc; Jaggi, Matthias; Perovich, Don (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-04)
      The sub-kilometre scale distribution of snow depth on Arctic sea ice impacts atmosphere-ice fluxes of energy and mass, and is of importance for satellite estimates of sea-ice thickness from both radar and lidar altimeters. While information about the mean of this distribution is increasingly available from modelling and remote sensing, the full distribution cannot yet be resolved. We analyse 33 539 ...
    • Shearlets as feature extractor for semantic edge detection: The model-based and data-driven realm: Shearlets for Semantic Edge Detection 

      Andrade-Loarca, Héctor; Kutyniok, Gitta Astrid Hildegard; Öktem, Ozan (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-25)
      Semantic edge detection has recently gained a lot of attention as an image-processing task, mainly because of its wide range of real-world applications. This is based on the fact that edges in images contain most of the semantic information. Semantic edge detection involves two tasks, namely pure edge detection and edge classification. Those are in fact fundamentally distinct in terms of the level ...
    • Superposition of semiconductor and semi-metal properties of self-assembled 2D SnTiS3 heterostructures 

      Tamalampudi, Srinivasa Reddy; Lu, Jin-You; Rajput, Nitul; Alfakes, Boulos; Sankar, Raman; Apostoleris, Harry; Patole, Shashikant; Almansouri, Ibraheem; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-15)
      Two-dimensional metal dichalcogenide/monochalcogenide thin flakes have attracted much attention owing to their remarkable electronic and electrochemical properties; however, chemical instability limits their applications. Chemical vapor transport (CVT)- synthesized SnTiS<sub>3</sub> thin flakes exhibit misfit heterojunction structure and are highly stable in ambient conditions, offering a ...
    • Dielectric optical nanoantennas 

      Hasan, Md Rabiul; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-22)
      Nanophotonics allows the manipulation of light on the subwavelength scale. Optical nanoantennas are nanoscale elements that enable increased resolution in bioimaging, novel photon sources, solar cells with higher absorption, and the detection of fluorescence from a single molecule. While plasmonic nanoantennas have been extensively explored in the literature, dielectric nanoantennas have several ...
    • Towards Scalable Unpaired Virtual Try-On via Patch-Routed Spatially-Adaptive GAN 

      Xie, Zhenyu; Huang, Zaiyu; Zhao, Fuwei; Dong, Haoye; Kampffmeyer, Michael; Liang, Xiaodan (Journal article; Tidsskriftartikkel; Peer reviewed, 2021)
      Image-based virtual try-on is one of the most promising applications of human-centric image generation due to its tremendous real-world potential. Yet, as most try-on approaches fit in-shop garments onto a target person, they require the laborious and restrictive construction of a paired training dataset, severely limiting their scalability. While a few recent works attempt to transfer garments ...