Now showing items 501-520 of 1276

    • A Novel Rayleigh Dynamical Model for Remote Sensing Data Interpretation 

      Bayer, Fábio M.; Bayer, Débora M.; Marinoni, Andrea; Gamba, Paolo (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-19)
      This article introduces the Rayleigh autoregressive moving average (RARMA) model, which is useful to interpret multiple different sets of remotely sensed data, from wind measurements to multitemporal synthetic aperture radar (SAR) sequences. The RARMA model is indeed suitable for continuous, asymmetric, and nonnegative signals observed over time. It describes the mean of Rayleigh-distributed ...
    • Comparison of Machine Learning Methods for Predicting Quad-Polarimetric Parameters from Dual-Polarimetric SAR Data 

      Blix, Katalin; Espeseth, Martine; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-17)
      This paper addresses the problem of up-scaling full polarimetric (quad-pol) parameters from small quad-pol synthetic aperture radar (SAR) scenes to large dual-pol scenes, using a sophisticated Machine Learning (ML) method, namely the Gaussian Process Regression (GPR). The approach is to let the GPR model learn the relationships between the dual-pol input data and the quad-pol parameters on a quad-pol ...
    • 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 ...
    • A Possible Explanation of Interhemispheric Asymmetry of Equatorial Plasma Bubbles in Airglow Images 

      Hickey, Dustin A.; Sau, Sukanta; Narayanan, Viswanathan Lakshmi; Gurubaran, S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-28)
      Equatorial plasma bubbles resulting from equatorial spread urn:x-wiley:jgra:media:jgra55597:jgra55597-math-0002 are well known to be aligned along the Earth's geomagnetic fields. During the geomagnetic storm on 17 March 2015, all‐sky airglow observations from Tirunelveli (8.7°N, 77.8°E, 1.7°N dip latitude) showed an apparent interhemispheric asymmetry in the tilt of the equatorial plasma bubbles. ...
    • Integrating Incidence Angle Dependencies Into the Clustering-Based Segmentation of SAR Images 

      Cristea, Anca; Van Houtte, Jeroen; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-28)
      Synthetic aperture radar systems perform signal acquisition under varying incidence angles and register an implicit intensity decay from near to far range. Owing to the geometrical interaction between microwaves and the imaged targets, the rates at which intensities decay depend on the nature of the targets, thus rendering single-rate image correction approaches only partially successful. The decay, ...
    • Necessary Conditions for Warm Inflow Toward the Filchner Ice Shelf, Weddell Sea 

      Daae, Kjersti; Hattermann, Tore; Darelius, Elin Maria K.; Mueller, Rachael D.; Naughten, Kaitlin A; Timmermann, Ralph; Hellmer, Hartmut H. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-09)
      Understanding changes in Antarctic ice shelf basal melting is a major challenge for predicting future sea level. Currently, warm Circumpolar Deep Water surrounding Antarctica has limited access to the Weddell Sea continental shelf; consequently, melt rates at Filchner‐Ronne Ice Shelf are low. However, large‐scale model projections suggest that changes to the Antarctic Slope Front and the coastal ...
    • Visualizing ultrastructural details of placental tissue with super-resolution structured illumination microscopy 

      Villegas Hernandez, Luis Enrique; Nystad, Mona; Ströhl, Florian; Basnet, Purusotam; Acharya, Ganesh; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-14)
      Super-resolution fluorescence microscopy is a widely employed technique in cell biology research, yet remains relatively unexplored in the field of histopathology. Here, we describe the sample preparation steps and acquisition parameters necessary to obtain fluorescent multicolor super-resolution structured illumination microscopy (SIM) images of both formalin-fixed paraffin-embedded and cryo-preserved ...
    • Dense dilated convolutions merging network for land cover classification 

      Liu, Qinghui; Kampffmeyer, Michael; Jenssen, Robert; Salberg, Arnt Børre (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-06)
      Land cover classification of remote sensing images is a challenging task due to limited amounts of annotated data, highly imbalanced classes, frequent incorrect pixel-level annotations, and an inherent complexity in the semantic segmentation task. In this article, we propose a novel architecture called the dense dilated convolutions' merging network (DDCM-Net) to address this task. The proposed ...
    • Machine Learning for Arctic Sea Ice Physical Properties Estimation Using Dual-Polarimetric SAR Data 

      Blix, Katalin; Espeseth, Martine; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-22)
      This work introduces a novel method that combines machine learning (ML) techniques with dual-polarimetric (dual-pol) synthetic aperture radar (SAR) observations for estimating quad-polarimetric (quad-pol) parameters, which are presumed to contain geophysical sea ice information. In the training phase, the output parameters are generated from quad-pol observations obtained by Radarsat-2 (RS2), and ...
    • 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 ...