Now showing items 143-162 of 414

    • High frequency copolymer ultrasonic transducer array of size-effective elements 

      Decharat, Adit; Wagle, Sanat; Habib, Anowarul; Jacobsen, Svein Ketil; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-05)
      A layer-by-layer deposition method for producing dual-layer ultrasonic transducers from piezoelectric copolymers has been developed. The method uses a combination of customized and standard processing to obtain 2D array transducers with electrical connection of the individual elements routed directly to the rear of the substrate. A numerical model was implemented to study basic parameters effecting ...
    • High-resolution optical nanoscopy of placental cells 

      Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2017)
      <i>Introduction</i>: The invention of fluorescence based super-resolution optical microscopy, commonly referred to as optical nanoscopy, has provided a glimpse of its future impacts on life science and medical care. Optical nanoscopy enables study of sub-cellular nanoscale biological systems in living cells, which in past was limited to electron microscopy (in fixed cells). Optical nanoscopy provide ...
    • Hon förebygger miljökatastrofer 

      Johansson, Malin; Avenius, Malin (Others; Andre, 2015)
      Det får inte hända. men om det ändå gör det behövs ny teknik för att mildra effekterna. Malin Johanssons forskning handlar om att förebygga miljökatastrofer, när oljebolagen söker sig allt längre in i Arktis.
    • The Hotelling-Lawley trace statistic for change detection in polarimetric SAR data under the complex Wishart distribution 

      Akbari, Vahid; Anfinsen, Stian Normann; Doulgeris, Anthony Paul; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-27)
      In this paper we propose a new test statistic for unsupervised changedetectioninpolarimetricsyntheticapertureradar(PolSAR) data. We work with multilook complex (MLC) covariance matrix data, whose underlying model is assumed to be the scaled complex Wishart distribution. We use the complex kind Hotelling-Lawley (HL) trace statistic for measuring the similarity of two covariance matrices. The sampling ...
    • HS 0705+6700: a new eclipsing sdB binary 

      Østensen, R.; Solheim, Jan Erik; Johannessen, F. (Journal article; Tidsskriftartikkel, 2001-10-09)
      We report the discovery of an eclipsing binary – HS 0705+6700 – being an sdB star with a faint companion. From its light curve the orbital period of 8263.87 s, the mass ratio of the system q = 0.28, the inclination of 84.◦4 and other system parameters are derived. The companion does not contribute to the optical light of the system except through a strong reflection effect. The semiamplitude of ...
    • Ice intelligence retrieval by remote sensing - Possibilities and challenges in an operational setting 

      Skarbø, Runa A.; Løset, Sveinung (Peer reviewed; Bokkapittel; Chapter, 2017)
      Detecting ice drift velocity when operating offshore in ice-covered waters is crucial during marine operations, as ice actions affect station keeping and ice management. Furthermore, other ice data/intelligence such as ice concentration and thickness are important parameters to determine ice resistance, evaluate performance of icebreakers and predict ice actions on structures. Different sensors are ...
    • ICEBEAR: An All‐Digital Bistatic Coded Continuous Wave Radar for Studies of the E Region of the Ionosphere 

      Huyghebaert, Devin; Hussey, Glenn; Vierinen, Juha; McWilliams, Kathryn; St‐Maurice, Jean-Pierre (Journal article; Peer reviewed, 2019-04-15)
      The Ionospheric Continuous-wave E region Bistatic Experimental Auroral Radar (ICEBEAR) is a coherent scatter ionospheric radar. It operates at a frequency of 49.5 MHz, which is ideal for observing E region coherent echoes. The radar is located in Saskatchewan, Canada, and is operated by the University of Saskatchewan. The ICEBEAR system uses a continuous-wave (CW) signal and requires isolation between ...
    • Iceberg detection in open water and sea ice using C-band radar polarimetry 

      Akbari, Vahid; Brekke, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)
      Icebergs can cause a significant danger for shipping, offshore oil exploration, and undersea or subsea pipelines and production facilities. Synthetic aperture radar (SAR) is very valuable tool of detecting and monitoring icebergs in the often dark and cloud-covered polar regions. Detection of small icebergs floating in nonhomegeous sea clutter environments is a challenging task in remote sensing. ...
    • An imaging interferometry capability for the EISCAT Svalbard Radar. 

      Chau, J.L.; Grydeland, Tom; La Hoz, C.; Brekke, Asgeir (Journal article; Peer reviewed; Tidsskriftartikkel, 2005-01-31)
      Interferometric imaging (aperture synthesis imaging) is a technique used by radio astronomers to achieve angular resolution that far surpasses what is possible with a single large aperture. A similar technique has been used for radar imaging studies of equatorial ionospheric phenomena at the Jicamarca Radio Observatory. We present plans for adding an interferometric imaging capability to the ...
    • Imaging Sea Ice Structure by Remote Sensing Sensors 

      Eltoft, Torbjørn; Doulgeris, Anthony Paul; Brekke, Camilla; Solbø, Stian; Gerland, Sebastian; Hanssen, Alfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-14)
      This paper will investigate how new developments in remote sensing and sensor technologies can be applied to image the structure of the sea ice surface. Both segmentation of multipolarimetric synthetic aperture radar images and strategies for the analyses of polarimetric SAR data of sea ice are addressed. The analysis is based on a Radarsat 2 PolSAR scene of from the Fram Strait in September ...
    • The Impact of Additive Noise on Polarimetric RADARSAT-2 Data Covering Oil Slicks 

      Espeseth, Martine; Skrunes, Stine; Brekke, Camilla; Johansson, Malin (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-14)
      We attempt to understand how a set of well known polari-metric Synthetic Aperture Radar (SAR) features are impacted by the additive system noise for mineral oil and produced water slicks. For this, we use quad-polarimetric SAR scenes from Radarsat-2. Oil slicks at sea can be detected using SAR instruments, and the dual- (HH-VV) and quad-polarimetric modes can provide additional information about the ...
    • Impact of assimilating sea ice concentration, sea ice thickness and snow depth in a coupled ocean-sea ice modelling system 

      Fritzner, Sindre Markus; Graversen, Rune; Christensen, Kai Håkon; Rostosky, Philip; Wang, Keguang (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-08)
      The accuracy of the initial state is very important for the quality of a forecast, and data assimilation is crucial for obtaining the best-possible initial state. For many years, sea-ice concentration was the only parameter used for assimilation into numerical sea-ice models. Sea-ice concentration can easily be observed by satellites, and satellite observations provide a full Arctic coverage. During ...
    • Impact of sea ice drift retrieval errors, discretization and grid type on calculations of ice deformation 

      Griebel, Jakob; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-03)
      We studied two issues to be considered in the calculation of parameters characterizing sea ice deformation: the effect of uncertainties in an automatically retrieved sea ice drift field, and the influence of the type of drift vector grid. Sea ice deformation changes the local ice mass balance and the interaction between atmosphere, ice, and ocean, and constitutes a hazard to marine traffic and ...
    • Improved LLM Methods Using Linear Regression 

      Zhao, Zihang; Lang, Wenhui; Doulgeris, Anthony Paul; Chen, Lu (Journal article; Peer reviewed, 2017-12-04)
      This paper is focused on investigations of the improved correction of the effect of variation in incidence angle on ScanSAR data. Conventional correction methods (such as LLM, locally linear mapping) typically assume that each target class has a similarity distribution in the middle of the image. The objectives of this study are to extend the correction algorithm to full swath width without any ...
    • An improved spatial and temporal reflectance unmixing model to synthesize time series of landsat-like images 

      Ma, Jianhang; Zhang, Wenjuan; Marinoni, Andrea; Gao, Lianru; Zhang, Bing (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-31)
      The trade-off between spatial and temporal resolution limits the acquisition of dense time series of Landsat images, and limits the ability to properly monitor land surface dynamics in time. Spatiotemporal image fusion methods provide a cost-efficient alternative to generate dense time series of Landsat-like images for applications that require both high spatial and temporal resolution images. The ...
    • An Improved Spatial and Temporal Reflectance Unmixing Model to Synthesize Time Series of Landsat-Like Images 

      Ma, Jianhang; Wenjuan, Zhang; Marinoni, Andrea; Lianru, Gao; Bing, Zhang (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-31)
      The trade-off between spatial and temporal resolution limits the acquisition of dense time series of Landsat images, and limits the ability to properly monitor land surface dynamics in time. Spatiotemporal image fusion methods provide a cost-efficient alternative to generate dense time series of Landsat-like images for applications that require both high spatial and temporal resolution images. The ...
    • Improving Doppler frequency estimation from Envisat data 

      Kræmer, Thomas; Johnsen, Harald; Brekke, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-11-06)
      This paper shows that Envisat ASAR data are degraded by a small periodic variation in gain between internal calibration cycles of the antenna, which introduces a significant bias when we try to estimate line-of-sight surface velocities from the estimated Doppler frequency shifts. We investigate the impact of the gain problems on the derived surface velocity product and propose a simple correction ...
    • Improving Doppler frequency estimation from Envisat data 

      Kræmer, Thomas; Johnsen, Harald; Brekke, Camilla (Conference object; Konferansebidrag, 2014)
    • Incorporating Incidence Angle Variation into Sar Image Segmentation 

      Doulgeris, Anthony Paul; Cristea, Anca (Journal article; Tidsskriftartikkel; Peer reviewed, 2018)
      We present a new approach for incorporating incidence angle derived synthetic aperture radar (SAR) brightness variation directly into SAR image analysis. This approach is unique in that the incidence angle dependency is modeled explicitly into the probability density function rather than an image-wide pre-processing ‘correction’. It can then be used for supervised and unsupervised image analysis, ...
    • Incorporating Incidence Angle Variation into Sar Image Segmentation 

      Doulgeris, Anthony Paul; Cristea, Anca (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-05)
      We present a new approach for incorporating incidence angle derived synthetic aperture radar (SAR) brightness variation directly into SAR image analysis. This approach is unique in that the incidence angle dependency is modeled explicitly into the probability density function rather than an image-wide pre-processing `correction'. It can then be used for supervised and unsupervised image analysis, ...