Now showing items 641-660 of 1407

    • 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 ...
    • A Lagrangian Snow Evolution System for Sea Ice Applications (SnowModel‐LG): Part II - Analyses 

      Stroeve, Julienne C.; Liston, Glen E.; Buzzard, Samantha; Zhou, Lu; Mallett, Robbie; Barrett, Andrew; Tschudi, Mark; Tsamados, Michel; Itkin, Polona; Stewart, Scott (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-02)
      Sea ice thickness is a critical variable, both as a climate indicator and for forecasting sea ice conditions on seasonal and longer time scales. The lack of snow depth and density information is a major source of uncertainty in current thickness retrievals from laser and radar altimetry. In response to this data gap, a new Lagrangian snow evolution model (SnowModel‐LG) was developed to simulate snow ...
    • Magnetopause Compressibility at Saturn with Internal Drivers 

      Hardy, Flavien; Achilleos, Nicholas; Guio, Patrick (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-07)
      We use magnetopause crossings of the Cassini spacecraft to study the response of Saturn's magnetosphere to changes in external and internal drivers. We explain how solar wind pressure can be corrected to account for the local variability in internal plasma particle pressure. The physics‐based method is applied to perform the most robust estimation of magnetopause compressibility at Saturn to date, ...
    • Comparison Between Dielectric Inversion Results From Synthetic Aperture Radar Co- and Quad-Polarimetric Data via a Polarimetric Two-Scale Model 

      Quigley, Cornelius; Brekke, Camilla; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-03)
      In this study, we compare the retrieval results for the dielectric properties of verified oil slick, acquired using airborne multifrequency synthetic aperture radar. A polarimetric two-scale model was used to invert the radar imagery by first employing solely the co-polarization channels, and then by employing the co-polarization channels in conjunction with the cross-polarization channels, and ...
    • Platelet ice under Arctic pack ice in winter 

      Katlein, Christian; Mohrholz, Volker; Sheikin, Igor; Itkin, Polona; Divine, Dmitry; Stroeve, Julienne C.; Jutila, Arttu; Krampe, Daniela; Shimanchuk, Egor; Raphael, Ian; Rabe, Benjamin; Kuznetsov, Ivan; Mallet, Maria; Liu, Hailong; Hoppmann, Mario; Fang, Ying‐Chih; Dumitrascu, Adela; Arndt, Stefanie; Anhaus, Philipp; Nicolaus, Marcel; Matero, Ilkka; Oggier, Marc; Eicken, Hajo; Haas, Christian (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-17)
      The formation of platelet ice is well known to occur under Antarctic sea ice, where subice platelet layers form from supercooled ice shelf water. In the Arctic, however, platelet ice formation has not been extensively observed, and its formation and morphology currently remain enigmatic. Here, we present the first comprehensive, long‐term in situ observations of a decimeter thick subice platelet ...
    • ELM-HTM guided bio-inspired unsupervised learning for anomalous trajectory classification 

      Sekh, Arif Ahmed; Dogra, Debi Prosad; Kar, Samarjit; Roy, Partha Pratim; Prasad, Dilip K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-23)
      Artificial intelligent systems often model the solutions of typical machine learning problems, inspired by biological processes, because of the biological system is faster and much adaptive than deep learning. The utility of bio-inspired learning methods lie in its ability to discover unknown patterns, and its less dependence on mathematical modeling or exhaustive training. In this paper, we propose ...
    • How Does El Niño–Southern Oscillation Change Under Global Warming—A First Look at CMIP6 

      Fredriksen, Hege-Beate; Berner, Judith; Subramanian, Aneesh C.; Capotondi, Antonietta (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-22)
      The latest generation of coupled models, the sixth Coupled Models Intercomparison Project (CMIP6), is used to study the changes in the El Niño–Southern Oscillation (ENSO) in a warming climate. For the four future scenarios studied, the sea surface temperature variability increases in most CMIP6 models, but to varying degrees. This increase is linked to a weakening of the east‐west temperature gradient ...
    • Trapped Particle Motion In Magnetodisc Fields 

      Guio, Patrick; Staniland, Ned; Achilleos, Nicholas; Arridge, Christopher (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-13)
      The spatial and temporal characterization of trapped charged particle trajectories in magnetospheres has been extensively studied in dipole magnetic field structures. Such studies have allowed the calculation of spatial quantities, such as equatorial loss cone size as a function of radial distance, the location of the mirror points along particular field lines (<i>L</i>‐shells) as a function of the ...
    • Photonic-chip assisted correlative light and electron microscopy 

      Tinguely, Jean-Claude; Steyer, Anna Maria; Øie, Cristina Ionica; Helle, Øystein Ivar; Dullo, Firehun Tsige; Olsen, Randi; McCourt, Peter; Schwab, Yannick; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)
      Correlative light and electron microscopy (CLEM) unifies the versatility of light microscopy (LM) with the high resolution of electron microscopy (EM), allowing one to zoom into the complex organization of cells. Here, we introduce photonic chip assisted CLEM, enabling multi-modal total internal reflection fluorescence (TIRF) microscopy over large field of view and high precision localization of the ...
    • In-Silico Evaluation of Glucose Regulation Using Policy Gradient Reinforcement Learning for Patients with Type 1 Diabetes Mellitus 

      Myhre, Jonas Nordhaug; Tejedor Hernandez, Miguel Angel; Launonen, Ilkka Kalervo; El Fathi, Anas; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-11)
      In this paper, we test and evaluate policy gradient reinforcement learning for automated blood glucose control in patients with Type 1 Diabetes Mellitus. Recent research has shown that reinforcement learning is a promising approach to accommodate the need for individualized blood glucose level control algorithms. The motivation for using policy gradient algorithms comes from the fact that adaptively ...
    • Extraordinary evanescent field confinement waveguide sensor for mid-infrared trace gas spectroscopy 

      Vlk, Marek; Datta, Anurup; Alberti, Sebastian; Yallew, Henock Demessie; Mittal, Vinita; Murugan, Ganapathy Senthil; Jágerská, Jana (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-29)
      Nanophotonic waveguides are at the core of a great variety of optical sensors. These structures confine light along defined paths on photonic chips and provide light–matter interaction via an evanescent field. However, waveguides still lag behind free-space optics for sensitivity-critical applications such as trace gas detection. Short optical pathlengths, low interaction strengths, and spurious ...
    • Incident Angle Dependence of Sentinel-1 Texture Features for Sea Ice Classification 

      Lohse, Johannes; Doulgeris, Anthony Paul; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-04)
      Robust and reliable classification of sea ice types in synthetic aperture radar (SAR) images is needed for various operational and environmental applications. Previous studies have investigated the class-dependent decrease in SAR backscatter intensity with incident angle (IA); others have shown the potential of textural information to improve automated image classification. In this work, we investigate ...
    • Wind at Northern Senja: Use of numerical weather prediction models for wind resource assessment 

      Hansen, Gjøran Emil (Master thesis; Mastergradsoppgave, 2020-12-15)
      Wind resource assessment for establishing decentralized power production in remote and complex areas, is challenging due to a lack of observational data. To overcome this problem, Numerical Weather Prediction (NWP) models can be used to provide data where no observations exist. This thesis uses NWP models to do a wind resource assessment at northern Senja. The power grid in the area is prone to ...
    • CO2 Increase Experiments Using the CESM: Relationship to Climate Sensitivity and Comparison of CESM1 to CESM2 

      Bacmeister, Julio T.; Hannay, Cecile; Medeiros, Brian; Gettelmann, Andrew; Neale, Richard; Fredriksen, Hege-Beate; Lipscomb, William H.; Simpson, Isla; Bailey, David Anthony; Holland, Marika M.; Lindsay, Keith; Otto-Bliesner, Bette L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-14)
      We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that ...
    • Klimanøytral miljøpark – en vurdering av kostnader og nytteverdi for klimagassreduserende tiltak 

      Strand, Petter Hofstad (Master thesis; Mastergradsoppgave, 2020-12-14)
      Remiks AS har gjennom flere år gjort en kartlegging av klimagassutslipp knyttet til egen virksomhet. På bakgrunn av dette er det iverksatt flere tiltak på aktuelle områder som har blitt identifisert. Det er i midlertidig ikke sikkert at investeringene som er gjort er de mest effektive tiltakene om man vurderer kostnadene mot klimanytten. Denne studien vil vurdere tiltakene solenergi, biodrivstoff, ...
    • Wideband Self-Interference Cancellation Using Multi-Tap Filter in Radar Front End 

      Heiskel, Bendik (Mastergradsoppgave; Master thesis, 2020-12-14)
      The largest hurdle in full duplex wireless systems is the self-interference introduced by the transmitted signal into the received signal. In multi antenna systems this interference is caused by the direct coupling between the transmitting and receiving antennas. In systems where the transmitter and receiver uses the same antenna the interference is caused by inadequate isolation between the ...
    • Performance and Future Potential of Solar Photovoltaics in Arctic Settlements 

      Mathiesen, Vemund Nygaard (Master thesis; Mastergradsoppgave, 2020-12-15)
      Data from a solar photovoltaic (PV) installation on Svalbard Airport Longyear has been analyzed to investigate performance of solar photovoltaics in the Arctic. Results show that the average capacity factor at the facility is 5.6 % after its first two full years of production. While the production in the winter is zero, monthly capacity factors are observed to be as high as 16 % in the summer. On ...
    • Silicon substrate significantly alters dipole-dipole resolution in coherent microscope 

      Liu, Zicheng; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-16)
      Considering a coherent microscopy setup, influences of the substrate below the sample in the imaging performances are studied, with a focus on high refractive index substrate such as silicon. Analytical expression of 3D full-wave vectorial point spread function, i.e. the dyadic Green's function is derived for the optical setup together with the substrate. Numerical analysis are performed in order ...
    • Deep learning architecture “LightOCT” for diagnostic decision support using optical coherence tomography images of biological samples 

      Butola, Ankit; Prasad, Dilip Kumar; Ahmad, Azeem; Dubey, Vishesh Kumar; Qaiser, Darakhshan; Srivastava, Anurag; Senthilkumaran, Paramasivam; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)
      Optical coherence tomography (OCT) is being increasingly adopted as a label-free and non-invasive technique for biomedical applications such as cancer and ocular disease diagnosis. Diagnostic information for these tissues is manifest in textural and geometric features of the OCT images, which are used by human expertise to interpret and triage. However, it suffers delays due to the long process of ...
    • Properties and dynamics of mesoscale eddies in Fram Strait from a comparison between two high-resolution ocean-sea ice models 

      Wekerle, Claudia; Hattermann, Tore; Wang, Qiang; Crews, Laura; von Appen, Wilken-Jon; Danilov, Sergey (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-23)
      Fram Strait, the deepest gateway to the Arctic Ocean, is strongly influenced by eddy dynamics. Here we analyse the output from two eddy-resolving models (ROMS – Regional Ocean Modeling System; FESOM – Finite-Element Sea-ice Ocean Model) with around 1 km mesh resolution in Fram Strait, with a focus on their representation of eddy properties and dynamics. A comparison with mooring observations shows ...