Now showing items 581-600 of 1276

    • Getting adhesion force maps with an amplitude-modulation AFM in tapping mode 

      Chiesa, Matteo; Santos, Sergio; Lai, Chia-Yun; Olukan, Tuza Adeyemi (Research report; Forskningsrapport, 2020-07)
      Here we demonstrate how to get adhesion force maps with an amplitude-modulation AFM in tapping mode. Our method is tapping mode but it is carried out at ultra-small amplitudes in the presence of surface water layers. The tip is made to vibrated under the water layer in what we call Small Amplitude Small Set-point AM AFM. We show how this is done with an example based on the Cypher scanning probe ...
    • CMIP5 model selection for ISMIP6 ice sheet model forcing: Greenland and Antarctica 

      Barthel, Alice; Agosta, Cécile; Little, Christopher M.; Hattermann, Tore; Jourdain, Nicolas; Goelzer, Heiko; Nowicki, Sophie; Seroussi, Helene; Straneo, Fiammetta; Bracegirdle, Thomas J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-06)
      The ice sheet model intercomparison project for CMIP6 (ISMIP6) effort brings together the ice sheet and climate modeling communities to gain understanding of the ice sheet contribution to sea level rise. ISMIP6 conducts stand-alone ice sheet experiments that use space- and time-varying forcing derived from atmosphere–ocean coupled global climate models (AOGCMs) to reflect plausible trajectories for ...
    • Reconstructing force profiles with an amplitude-modulation AFM in tapping mode 

      Olukan, Tuza Adeyemi; Lai, Chia-Yun; Santos, Sergio; Amadei, Carlo Alberto; Chiesa, Matteo (Research report; Forskningsrapport, 2020-07)
      Here we demonstrate how to reconstruct force profiles with an amplitude-modulation AFM operated in in standard tapping mode. Our example is based on the Cypher scanning probe microscope from Asylum Research. The method is based on Sader and Katan’s algorithm, but we have implemented an experimental set-up that allows for robust reconstruction. We discuss the details here.
    • Automatic validation of Sentinel-1 borne snow avalanche detections 

      Pedersen, Jarle Langseth (Master thesis; Mastergradsoppgave, 2020-05-30)
      Snow avalanches threaten human lives, settlements and roads in snow covered mountainous areas. For avalanche forecasting, knowledge of the spatio-temporal occurrence of avalanche activity is critical. Automatic avalanche detection algorithms have been developed to enable consistent avalanche activity monitoring for large regions. The Satskred avalanche detection algorithm developed by NORCE applies ...
    • Explaining decisions of deep neural networks used for fish age prediction 

      Ordonez, Alba; Eikvil, Line; Salberg, Arnt-Børre; Harbitz, Alf; Murray, Sean Meling; Kampffmeyer, Michael (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-19)
      Age-reading of fish otoliths (ear stones) is important for the sustainable management of fish resources. However, the procedure is challenging and requires experienced readers to carefully examine annual growth zones. In a recent study, convolutional neural networks (CNNs) have been demonstrated to perform reasonably well on automatically predicting fish age from otolith images. In the present study, ...
    • Large-Scale Detection and Categorization of Oil Spills from SAR Images with Deep Learning 

      Bianchi, Filippo Maria; Espeseth, Martine; Borch, Njål Trygve (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-14)
      We propose a deep-learning framework to detect and categorize oil spills in synthetic aperture radar (SAR) images at a large scale. Through a carefully designed neural network model for image segmentation trained on an extensive dataset, we obtain state-of-the-art performance in oil spill detection, achieving results that are comparable to results produced by human operators. We also introduce a ...
    • First observations of the McMurdo-South Pole oblique ionospheric HF channel 

      Chartier, Alex T.; Vierinen, Juha; Jee, Geonhwa (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-09)
      We present the first observations from a new low-cost oblique ionosonde located in Antarctica. The transmitter is located at McMurdo Station, Ross Island, and the receiver at Amundsen–Scott Station, South Pole. The system was demonstrated successfully in March 2019, with the experiment yielding over 30 000 ionospheric echoes over a 2-week period. These data indicate the presence of a stable E layer ...
    • On the relation between polarimetric synthetic aperture radar (SAR) features and sea ice melt pond fraction 

      Fors, Ane Schwenke; Doulgeris, Anthony Paul; Renner, Angelika; Brekke, Camilla; Gerland, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-12)
      In this study we examine the relationship between sea ice melt pond fraction and two polarimetric C-band synthetic aperture radar (SAR) features. Three high-resolution SAR scenes were recorded in the Fram Strait in late summer 2011, covering iceberg-fast first-year and old sea ice. In addition, melt pond fraction was retrieved from photographs recorded during a helicopter flight at the study area. ...
    • Mapping sea-ice types from Sentinel-1 considering the surface-type dependent effect of incidence angle 

      Lohse, Johannes; Doulgeris, Anthony Paul; Dierking, Wolfgang (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-23)
      Automated classification of sea-ice types in Synthetic Aperture Radar (SAR) imagery is complicated by the class-dependent decrease of backscatter intensity with Incidence Angle (IA). In the log-domain, this decrease is approximately linear over the typical range of space-borne SAR instruments. A global correction does not consider that different surface types show different rates of decrease in ...
    • Ice extent in sub-arctic fjords and coastal areas from 2001 to 2019 analyzed from MODIS imagery 

      O'Sadnick, Megan Eileen; Petrich, Chris; Brekke, Camilla; Skardhamar, Jofrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-03)
      Results examining variations in the ice extent along the Norwegian coastline based on the analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) images from 2001 to 2019, February through May, are presented. A total of 386 fjords and coastal areas were outlined and grouped into ten regions to assess seasonal and long-term trends in ice extent. In addition, three fjords were examined to ...
    • Added value of multitemporal polarimetric UAVSAR data for permanent scatterers detection 

      Nikaein, Tina; Akbari, Vahid; Arefi, Hossein (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-05)
      In the last decades, differential synthetic aperture radar (SAR) interferometric (InSAR) (DInSAR) techniques have been used to estimate the Earth's surface deformation with high resolution. In this paper, we present an approach for increasing the quantity of permanent scattered pixels. These pixels are selected for DInSAR processing based on polarimetric information prepared by new sensors. The ...
    • The impact of system noise in polarimetric SAR imagery on oil spill observations 

      Espeseth, Martine; Brekke, Camilla; Jones, Cathleen Elaine; Holt, Benjamin; Freeman, Anthony (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-16)
      The effects of both system additive and multiplicative noise on the X-, C-, and L-band synthetic aperture radar (SAR) data covering oil slicks are examined. Prior studies have attempted to characterize such oil slicks, primarily through analysis of polarimetric SAR data. In this article, we factor in system noise that is added to the backscattered signal, introducing artifacts that can easily be ...
    • Sampling moiré method: a tool for sensing quadratic phase distortion and its correction for accurate quantitative phase microscopy 

      Jayakumar, Nikhil; Ahmad, Azeem; Mehta, Dalip Singh; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-24)
      The advantages of quantitative phase microscopy (QPM) such as label-free imaging with high spatial sensitivity, live cell compatibility and high-speed imaging makes it viable for various biological applications. The measurement accuracy of QPM strongly relies on the shape of the recorded interferograms, whether straight or curved fringes are recorded during the data acquisition. Moreover, for a ...
    • Automatic fringe pattern enhancement using truly adaptive period-guided bidimensional empirical mode decomposition 

      Gocłowski, Paweł; Trusiak, Maciej; Ahmad, Azeem; Styk, Adam; Mico, Vicente; Ahluwalia, Balpreet Singh; Patorski, Krzysztof (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-19)
      Fringe patterns encode the information about the result of a measurement performed via widely used optical full-field testing methods, e.g., interferometry, digital holographic microscopy, moiré techniques, structured illumination etc. Affected by the optical setup, changing environment and the sample itself fringe patterns are often corrupted with substantial noise, strong and uneven background ...
    • Sub-nanometer height sensitivity by phase shifting interference microscopy under environmental fluctuations 

      Ahmad, Azeem; Dubey, Vishesh Kumar; Butola, Ankit; Tinguely, Jean-Claude; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-18)
      Phase shifting interferometric (PSI) techniques are among the most sensitive phase measurement methods. Owing to its high sensitivity, any minute phase change caused due to environmental instability results into, inaccurate phase measurement. Consequently, a well calibrated piezo electric transducer (PZT) and highly-stable environment is mandatory for measuring accurate phase map using PSI implementation. ...
    • Measuring Wind Speed Using the Internal Stabilization System of a Quadrotor Drone 

      Simma, Magdalena; Mjøen, Håvard; Boström, Tobias (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-16)
      This article proposes a method of measuring wind speed using the data logged by the autopilot of a quadrotor drone. Theoretical equations from works on quadrotor control are utilized and supplemented to form the theoretical framework. Static thrust tests provide the necessary parameters for calculating wind estimates. Flight tests were conducted at a test site with laminar wind conditions with the ...
    • Electron heating by HF pumping of high-latitude ionospheric F-region plasma near magnetic zenith 

      Leyser, Thomas B; Gustavsson, Björn Johan; Rexer, Theresa; Rietveld, Michael T (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-06)
      High-frequency electromagnetic pumping of ionospheric F-region plasma at high and mid latitudes gives the strongest plasma response in magnetic zenith, antiparallel to the geomagnetic field in the Northern Hemisphere. This has been observed in optical emissions from the pumped plasma turbulence, electron temperature enhancements, filamentary magnetic field-aligned plasma density irregularities, and ...
    • MusiJ: an ImageJ plugin for video nanoscopy 

      Acuña Maldonado, Sebastian Andres; Ströhl, Florian; Opstad, Ida Sundvor; Ahluwalia, Balpreet S.; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-14)
      We present an open-source implementation of the fluctuation-based nanoscopy method MUSICAL for ImageJ. This implementation improves the algorithm’s computational efficiency and takes advantage of multi-threading to provide orders of magnitude faster reconstructions than the original MATLAB implementation. In addition, the plugin is capable of generating super-resolution videos from large stacks of ...
    • Ice extent in sub-arctic fjords and coastal areas from 2001 to 2019 analyzed from MODIS imagery 

      O'Sadnick, Megan; Petrich, Christian; Brekke, Camilla; Skarðhamar, Jofrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-03)
      Results examining variations in the ice extent along the Norwegian coastline based on the analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) images from 2001 to 2019, February through May, are presented. A total of 386 fjords and coastal areas were outlined and grouped into ten regions to assess seasonal and long-term trends in ice extent. In addition, three fjords were examined to ...
    • Exploring the temporal variation of the solar quadrupole moment from relativistic gravitation contributions: A fortuitous circumstance? 

      Rozelot, JP; Eren, Saliha (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-08)
      Due to its oblateness, the Sun carries a solar quadrupole moment playing a key role at the crossroad of fundamental solar physics, astrometry and celestial mechanics. There is nowadays a general agreement on its order of magnitude ( ≈2×10-7 ), but its temporal dependence is still poorly known. Helioseismology led to a variation within the solar cycle by less than 0.04%, not yet ...