Viser treff 261-280 av 947

    • Plasma-neutral gas interactions in various space environments: Assessment beyond simplified approximations as a Voyage 2050 theme 

      Yamauchi, Masatoshi; De Keyser, Johan; Parks, George; Oyama, Shin-ichiro; Wurz, Peter; Abe, Takumi; Beth, Arnaud; Daglis, Ioannis A.; Dandouras, Iannis; Dunlop, Malcolm; Henri, Pierre; Ivchenko, Nickolay; Kallio, Esa; Kucharek, Harald; Liu, Yong C.-M.; Mann, Ingrid; Marghitu, Octav; Nicolaou, Georgios; Rong, Zhaojin; Sakanoi, Takeshi; Saur, Joachim; Shimoyama, Manabu; Taguchi, Satoshi; Tian, Feng; Tsuda, Takuo; Tsurutani, Bruce; Turner, Drew; Ulich, Thomas; Yau, Andrew; Yoshikawa, Ichiro (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-26)
      In the White Paper, submitted in response to the European Space Agency (ESA) Voyage 2050 Call, we present the importance of advancing our knowledge of plasma-neutral gas interactions, and of deepening our understanding of the partially ionized environments that are ubiquitous in the upper atmospheres of planets and moons, and elsewhere in space. In future space missions, the above task ...
    • Generating customer's credit behavior with deep generative models 

      Andrade Mancisidor, Rogelio; Kampffmeyer, Michael; Aas, Kjersti; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-17)
      Banks collect data x<sub>1</sub> in loan applications to decide whether to grant credit and accepted applications generate new data x<sub>2</sub> throughout the loan period. Hence, banks have two measurement-modalities, which provide a complete picture about customers. If we can generate x<sub>2</sub> conditioned on x<sub>1</sub> keeping the relationship between these two modalities, credit and ...
    • Anomaly detection-inspired few-shot medical image segmentation through self-supervision with supervoxels 

      Hansen, Stine; Gautam, Srishti; Jenssen, Robert; Kampffmeyer, Michael (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-11)
      Recent work has shown that label-efficient few-shot learning through self-supervision can achieve promising medical image segmentation results. However, few-shot segmentation models typically rely on prototype representations of the semantic classes, resulting in a loss of local information that can degrade performance. This is particularly problematic for the typically large and highly heterogeneous ...
    • Evaluation of crystalline structure quality of Czochralski-silicon using near-infrared tomography 

      Jensen, Mathias Novik; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-22)
      In this work, three silicon samples are subject to tomographic scans using a 1.6μm laser. The samples were prematurely terminated due to anomalies during the Czhochralski-process. They are taken as analogues of the in situ crystal, where one sample has known aberrant structure in its lowermost 45 mm. The results of the tomographic scans show a distinct difference in transmission profile between ...
    • Electron-neutral collisions effects on Langmuir probe in the lower E-region ionosphere 

      Brask, Steffen Mattias; Marholm, Sigvald; Di Mare, Francesca; Adhikari, Sayan; Spicher, Andres; Takahashi, T.; Miloch, Wojciech Jacek (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-21)
      We present the first set of particle-in-cell simulations including Monte Carlo collisions between charged and neutral particles used to simulate a cylindrical Langmuir probe in the electron saturation regime with a collisional electron sheath. We use a setup focused on the E-region ionosphere; however, the results of these simulations are analyzed in a general sense using dimensionless values. We ...
    • The impact of atmospheric Rossby waves and cyclones on the Arctic sea ice variability 

      Hofsteenge, Marte G.; Graversen, Rune Grand; Rydsaa, Johanne Hope; Rey, Zoé (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-17)
      The Arctic sea-ice extent has strongly declined over recent decades. A large inter-annual variability is superimposed on this negative trend. Previous studies have emphasised a significant warming effect associated with latent energy transport into the Arctic region, in particular due to an enhanced greenhouse effect associated with the convergence of the humidity transport over the Arctic. The ...
    • Multidisciplinary biophotonics, open science, and. . . plug & pray deep learning? 

      Opstad, Ida Sundvor (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-06)
      Due to its great creative potential for innovation and scientific discovery, inter- and multidisciplinary collaboration is being increasingly encouraged by institutions and funding agencies. The increased opportunities in the multidisciplinary arena also come with significant challenges like the added experimental, analytical and logistical complexity, blended with a high likelihood of miscommunications. ...
    • First observation of the anomalous electric field in the topside ionosphere by ionospheric modification over EISCAT 

      Kosch, Michael; Vickers, Hannah; Ogawa, Yasunobu; Senior, Andrew; Blagoveshchenskaya, Natalya (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-10-24)
      We have developed an active ground-based technique to estimate the steady state field-aligned anomalous electric field (E*) in the topside ionosphere, up to ~600 km, using the European Incoherent Scatter (EISCAT) ionospheric modification facility and UHF incoherent scatter radar. When pumping the ionosphere with high-power high-frequency radio waves, the F region electron temperature is significantly ...
    • First modulation of high-frequency polar mesospheric summer echoes by radio heating of the ionosphere 

      Senior, Andrew; Mahmoudian, Alireza; Pinedo Nava, Henry; La Hoz, Cesar; Rietveld, Michael T; Scales, Wayne A.; Kosch, M.J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-07-23)
      The first high-frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the European Incoherent Scatter facility in northern Norway. It is shown that model results are in qualitative and partial quantitative ...
    • Increasing Multiyear Sea Ice Loss in the Beaufort Sea: A New Export Pathway for the Diminishing Multiyear Ice Cover of the Arctic Ocean 

      Babb, David G; Galley, Ryan; Howell, Stephen; Landy, Jack Christopher; Barber, David G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-16)
      Historically, multiyear sea ice (MYI) covered a majority of the Arctic and circulated through the Beaufort Gyre for years. However, increased ice melt in the Beaufort Sea during the early 2000s was proposed to have severed this circulation. Constructing a regional MYI budget from 1997 to 2021 reveals that MYI import into the Beaufort Sea has increased year-round, yet less MYI now survives through ...
    • 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 ...