Now showing items 1-20 of 414

    • Noisy multi-label semi-supervised dimensionality reduction 

      Mikalsen, Karl Øyvind; Soguero-Ruiz, Cristina; Bianchi, Filippo Maria; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-29)
      Noisy labeled data represent a rich source of information that often are easily accessible and cheap to obtain, but label noise might also have many negative consequences if not accounted for. How to fully utilize noisy labels has been studied extensively within the framework of standard supervised machine learning over a period of several decades. However, very little research has been conducted ...
    • Consistent ice and open water classification combining historical synthetic aperture radar satellite images from ERS-1/2, Envisat ASAR, RADARSAT-2, and Sentinel-1A/B 

      Johansson, Malin; Malnes, Eirik; Gerland, Sebastian; Cristea, Anca; Doulgeris, Anthony Paul; Divine, Dmitry V; Pavlova, Olga; Lauknes, Tom Rune (Journal article; Tidsskriftartikkel, 2020)
    • Uncertainty and interpretability in convolutional neural networks for semantic segmentation of colorectal polyps 

      Jenssen, Robert; Kampffmeyer, Michael C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-20)
      Colorectal polyps are known to be potential precursors to colorectal cancer, which is one of the leading causes of cancer-related deaths on a global scale. Early detection and prevention of colorectal cancer is primarily enabled through manual screenings, where the intestines of a patient is visually examined. Such a procedure can be challenging and exhausting for the person performing the screening. ...
    • Plasma fluctuations in the scrape-off layer and at the divertor target in Alcator C-Mod and their relationship to divertor collisionality and density shoulder formation 

      Kuang, AQ; LaBombard, Brian; Brunner, D; Garcia, Odd Erik; Kube, Ralph; Theodorsen, Audun (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-15)
      Experiments indicate that the formation of density shoulders in the far scrape-off layer (SOL) is associated with an increase in cross-field transport and the propagation of coherent structures of high density known as blobs. It has been suggested that far SOL divertor collisionality (Λ<sub>div</sub>) may be a controlling parameter in this physics, which could be challenging for heat flux mitigation ...
    • Super-condenser enables labelfree nanoscopy 

      Ströhl, Florian; Opstad, Ida Sundvor; Tinguely, Jean-Claude; Dullo, Firehun Tsige; Mela, Ioanna; Osterrieth, Johannes W.M; Ahluwalia, Balpreet Singh; Kaminski, Clemens F. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-22)
      Labelfree nanoscopy encompasses optical imaging with resolution in the 100 nm range using visible wavelengths. Here, we present a labelfree nanoscopy method that combines coherent imaging techniques with waveguide microscopy to realize a <i>super-condenser</i> featuring maximally inclined coherent darkfield illumination with artificially stretched wave vectors due to large refractive indices of the ...
    • An Optimal Decision-Tree Design Strategy and Its Application to Sea Ice Classification from SAR Imagery 

      Lohse, Johannes; Doulgeris, Anthony Paul; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-03)
      We introduce the fully automatic design of a numerically optimized decision-tree algorithm and demonstrate its application to sea ice classification from SAR data. In the decision tree, an initial multi-class classification problem is split up into a sequence of binary problems. Each branch of the tree separates one single class from all other remaining classes, using a class-specific selected feature ...
    • OptiJ: Open-source optical projection tomography of large organ samples 

      Vallejo Ramirez, Pedro P.; Zammit, Joseph; Vanderpoorten, Oliver; Fergus, Riche; Blé, Francois-Xavier; Zhou, Xiao-Hong; Spiridon, Bogdan; Valentine, Christopher; Spasov, Simeon E.; Oluwasanya, Pelumi W.; Goodfellow, Gemma; Fantham, Marcus J.; Siddiqui, Omid; Alimagham, Farah; Robbins, Miranda; Stretton, Andrew; Simatos, Dimitrios; Hadeler, Oliver; Rees, Eric J.; Ströhl, Florian; Laine, Romain F.; Kaminski, Clemens F. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-30)
      The three-dimensional imaging of mesoscopic samples with Optical Projection Tomography (OPT) has become a powerful tool for biomedical phenotyping studies. OPT uses visible light to visualize the 3D morphology of large transparent samples. To enable a wider application of OPT, we present OptiJ, a low-cost, fully open-source OPT system capable of imaging large transparent specimens up to 13 mm tall ...
    • Developing a New Machine-Learning Algorithm for Estimating Chlorophyll-a Concentration in Optically Complex Waters: A Case Study for High Northern Latitude Waters by Using Sentinel 3 OLCI 

      Blix, Katalin; Li, Juan; Massicotte, Philippe; Matsuoka, Atsushi (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-04)
      The monitoring of Chlorophyll-a (Chl-a) concentration in high northern latitude waters has been receiving increased focus due to the rapid environmental changes in the sub-Arctic, Arctic. Spaceborne optical instruments allow the continuous monitoring of the occurrence, distribution, and amount of Chl-a. In recent years, the Ocean and Land Color Instruments (OLCI) onboard the Sentinel 3 (S3) A and B ...
    • Assessment of the RISAT-1 FRS-2 Mode for Oil Spill Observation 

      Skrunes, Stine; Brekke, Camilla; Espeseth, Martine M. (Peer reviewed; Chapter, 2017-12-04)
      Synthetic aperture radar data acquired by the Radar Imaging Satellite (RISAT-1) over experimental oil spills is here investigated. One quad-polarization scene in the Fine Resolution Alternate Polarization Stripmap (FRS-2) mode is analyzed to evaluate the potential of using this mode for oil spill observation.<br> Oil slicks of varying type and age are clearly detected in the HH and VV channels, with ...
    • Dust observations with antenna measurements and its prospects for observations with Parker Solar Probe and Solar Orbiter 

      Mann, Ingrid; Nouzak, Libor; Vaverka, Jakub; Antonsen, Tarjei; Fredriksen, Åshild; Issautier, Karine; Malaspina, David; Meyer-Vernet, Nicole; Pavlu, Jiri; Sternovsky, Zoltan; Stude, Joan; Ye, Shengyi; Zaslavsky, Arnaud (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-10)
      The electric and magnetic field instrument suite FIELDS on board the NASA Parker Solar Probe and the radio and plasma waves instrument RPW on the ESA Solar Orbiter mission that explore the inner heliosphere are sensitive to signals generated by dust impacts. Dust impacts have been observed using electric field antennas on spacecraft since the 1980s and the method was recently used with a number of ...
    • Understanding Cassini RPWS Antenna Signals Triggered by Dust Impacts 

      Ye, Shengyi; Vaverka, Jakub; Nouzak, Libor; Sternovsky, Zoltan; Zaslavsky, Arnaud; Mann, Ingrid; Hsu, H-W.; Averkamp, Terrance, F.; Sulaiman, AH; Pisa, D.; Hospodarsky, G. B.; Kurth, W.S.; Horanyi, M. (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 ...
    • Four dimensional quantification of Kelvin-Helmholtz instabilities in the polar summer mesosphere using volumetric radar imaging 

      Chau, Jorge L.; Urco, Miguel; Avsarkisov, Victor; Vierinen, Juha; Latteck, Ralph; Hall, Chris; Tsutsumi, Masaki (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-13)
      We present and characterize in time and three spatial dimensions a Kelvin‐Helmholtz Instability (KHI) event from polar mesospheric summer echoes (PMSE) observed with the Middle Atmosphere Alomar Radar System. We use a newly developed radar imaging mode, which observed PMSE intensity and line of sight velocity with high temporal and angular resolution. The identified KHI event occurs in a narrow layer ...
    • Cosmic noise absorption during solar proton events in WACCM-D and riometer observations 

      Heino, Erkka Petteri; Verronen, Pekka T.; Kero, Antti; Kalakoski, Niilo; Partamies, Noora (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-18)
      Solar proton events (SPEs) cause large‐scale ionization in the middle atmosphere leading to ozone loss and changes in the energy budget of the middle atmosphere. The accurate implementation of SPEs and other particle ionization sources in climate models is necessary to understand the role of energetic particle precipitation in climate variability. We use riometer observations from 16 riometer stations ...
    • Power-law scaling of uncorrelated plasma bursts 

      Theodorsen, Audun; Garcia, Odd Erik; Rypdal, Martin wibe (Conference object; Konferansebidrag, 2019-07)
    • Synthetic Aperture Radar Remote Sensing of Operational Platform Produced Water Releases 

      Skrunes, Stine; Johansson, Malin; Brekke, Camilla (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-03)
      Oil spill detection services based on satellite synthetic aperture radar (SAR) frequently detect oil slicks close to platforms due to legal releases of produced water. Separating these slicks from larger releases, e.g., due to accidental leakage is challenging. The aim of this work is to investigate the SAR characteristics of produced water, including the typical appearance in HH/VV data, possible ...
    • Separation and characterisation of mineral oil slicks and newly formed sea ice in L-band synthetic aperture radar 

      Johansson, Malin; Espeseth, Martine; Brekke, Camilla; Skrunes, Stine (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-14)
      Maritime activities in the Arctic Ocean is increasing and consequently the risk for an oil spill there is rising. Synthetic Aperture Radar (SAR) is used operationally to detect and monitor oil slicks and for sea ice monitoring and observations. Leads are often used for ship routing and within the leads newly formed sea ice is often present. Separation between the low backscatter areas that constitutes ...
    • Towards operational sea ice type retrieval using L-band Synthetic aperture radar 

      Singha, Suman; Johansson, Malin; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-14)
      Operational ice services around the world have recognized the economic and environmental benefits that come from the increased capabilities and uses of space-borne Synthetic Aperture Radar (SAR) observation system. The two major objectives in SAR based remote sensing of sea ice is on the one hand to have a large areal coverage, and on the other hand to obtain a radar response that carries as much ...
    • 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 ...
    • Measurement of inner wall limiter SOL widths in KSTAR tokamak 

      Bak, J. G.; Pitts, RA; Kim, HS; Lee, H; Bin, C.; Juhn, JW; Hong, SH; Garcia, Odd Erik; Kube, Ralph Arthur; Seo, DC (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-27)
      Scrape-off layer (SOL) widths <i>λ<sub>q</sub></i> are presented from the KSTAR tokamak using fast reciprocating Langmuir probe assembly (FRLPA) measurements at the outboard mid-plane (OMP) and the infra-Red (IR) thermography at inboard limiter tiles in moderately elongated (<i>κ</i> = 1.45 – 1.55) L-mode inner wall-limited (IWL) plasmas under experimental conditions such as B<sub>T</sub> = 2.0 T, ...
    • SOL width and intermittent fluctuations in KSTAR 

      Garcia, Odd Erik; Kube, Ralph Arthur; Theodorsen, Audun; Bak, J. G.; Hong, SH; Kim, H.S.; KSTAR, project team; Pitts, RA (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-27)
      Radial profiles of the ion saturation current and its fluctuation statistics are presented from probe measurements in L-mode, neutral beam heated plasmas at the outboard mid-plane region of KSTAR. The results are consistent with the familiar two-layer structure, seen elsewhere in tokamak L-mode discharges, with a steep near-SOL profile and a broad far-SOL profile. The profile scale length in the ...