Now showing items 369-388 of 393

    • Ultrasonic imaging of pitting using multilayer synthetic aperture focusing 

      Skjelvareid, Martin Hansen; Olofsson, Tomas; Birkelund, Yngve (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      Synthetic aperture focusing is known to increase both the lateral resolution and signal-to-noise level of pulse-echo ultrasonic images. In this paper, the use of synthetic aperture imaging for detection and sizing of pitting in a plate is considered. It is assumed that a water layer is present between the transducer and the plate, and that the pitting is on the back side of the plate, seen from the ...
    • Ultrasonic measurements of surface defects on flexible circuits using high-frequency focused polymer transducers 

      Wagle, Sanat; Habib, Anowarul; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-12)
      High frequency transducers made from a layer-by-layer deposition method are investigated as transducers for ultrasonic imaging. Prototypes of adhesive-free transducers with four active elements were made on a high performance PEI (Polyetherimide) substrate with precision milled spherical cavities used to produce focused ultrasonic beams. The transducer prototypes ...
    • Ultrasonic properties of all-printed piezoelectric polymer transducers 

      Wagle, Sanat; Decharat, Adit; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      The ability of producing ultrasonic transducers from screen-printing has been explored experimentally, through printing and characterization of a large number of transducers. In an allprinted test design, 124 transducers with four different electrode sizes ranging from 1 to 4.9 mm2, were printed layer-by-layer on a high performance polyethyleneimine polymer. Inks from ferroelectric and conductive ...
    • Understanding the Cool DA White Dwarf Pulsator, G29–38 

      Solheim, Jan Erik; Kleinman, S. J.; Bruvold, A.; Nather, R. E.; Winget, D. E.; Clemens, J. C.; Bradley, A.; Kanaan, A.; Claver, C. F.; Watson, T. K.; Yanagida, K.; Nitta, A.; Dixson, J. S.; Grauer, A. D.; Hine, B. P.; Fontaine, G.; Liebert, James; Sullivan, D. J.; Wickramasinghe, D. T.; Achilleos, N.; Mara, T. M. K.; Seetha, S.; Ashoka, B. N.; Leibowitz, E. M.; Moskalik, P.; Krzesi´nski, J.; O’Donoghue, D.; Kurtz, D. W.; Warner, B.; Martinez, Peter; Dolez, N.; Chevreton, M.; Barstow, M. A.; Kepler, S. O.; Giovannini, O.; Hansen, C. J.; Augusteijn, T. (Journal article; Tidsskriftartikkel; Peer reviewed, 1997-10-10)
      The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post main sequence evolution, along with their cooling rates, allowing us to calibrate their ages directly. The most important set of white dwarf variables to ...
    • Unified transport scaling laws for plasma blobs and depletions 

      Wiesenberger, Matthias; Held, Markus; Kube, Ralph; Garcia, Odd Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-14)
      We study the dynamics of seeded plasma blobs and depletions in an (effective) gravitational field. For incompressible flows, the radial center of mass velocity of blobs and depletions is proportional to the square root of their initial cross-field size and amplitude. If the flows are compressible, this scaling holds only for ratios of amplitude to size larger than a critical value. Otherwise, the ...
    • Universality of Poisson-driven plasma fluctuations in the Alcator C-Mod scrape-off layer 

      Theodorsen, Audun; Garcia, Odd Erik; Kube, Ralph; LaBombard, Brian; Terry, James L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-18)
      Large-amplitude, intermittent fluctuations are ubiquitous in the boundary region of magnetically confined plasmas and lead to detrimental plasma-wall interactions in the nextgeneration, high duty cycle fusion power experiments. Using gas puff imaging data time series from the scrape-off layer in the Alcator C-Mod device, it is here demonstrated that the large-amplitude fluctuations can be described ...
    • Unsupervised domain adaptation for automatic estimation of cardiothoracic ratio 

      Dong, Nanqing; Kampffmeyer, Michael C.; Liang, Xiaodan; Wang, Zeya; Dai, Wei; Xing, Eric P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-26)
      The cardiothoracic ratio (CTR), a clinical metric of heart size in chest X-rays (CXRs), is a key indicator of cardiomegaly. Manual measurement of CTR is time-consuming and can be affected by human subjectivity, making it desirable to design computer-aided systems that assist clinicians in the diagnosis process. Automatic CTR estimation through chest organ segmentation, however, requires large amounts ...
    • Unsupervised Estimation of the Equivalent Number of Looks in PolSAR Image with High Heterogeneity 

      Hu, Dingsheng; Qiu, Xiaolan; Anfinsen, Stian Normann; Lei, Bin (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-01)
      Equivalent Number of Looks (ENL) is an important parameter in statistical modelling of multi-look Polarimetric SAR (PolSAR) data. In some automated applications of PolSAR images, it is necessary to estimate the ENL in an unsupervised way without any manual intervention. The existing unsupervised estimation of ENL can not obtain accurate estimates for the images with high heterogeneity. To address ...
    • An unsupervised method for equivalent number of looks estimation in complex SAR scenes 

      Hu, Dingsheng; Doulgeris, Anthony Paul; Qiu, Xiaolan (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-12)
      This paper introduces a novel unsupervised estimator of equivalent number of looks (ENL) that can be applied to an arbitrary image. It avoids the assumption that homogeneous speckle will dominate the investigated image that is followed by current unsupervised ENL estimators but not always valid, especially for the complex SAR scenes with high mixture and texture. Incorporating the statistical ...
    • Unsupervised Mixture-Eliminating Estimation of Equivalent Number of Looks for PolSAR Data 

      Hu, Dingsheng; Anfinsen, Stian Normann; Qiu, X; Doulgeris, Anthony Paul; Lei, Bin (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-22)
      This paper addresses the impact of mixtures between classes on equivalent number of looks (ENL) estimation. We propose an unsupervised ENL estimator for polarimetric synthetic aperture radar (PolSAR) data, which is based on small sample estimates but incorporates a mixture-eliminating (ME) procedure to automatically assess the uniformity of the estimation windows. A statistical feature derived from ...
    • Urban land cover classification with missing data modalities using deep convolutional neural networks 

      Kampffmeyer, Michael C.; Salberg, Arnt Børre; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-14)
      Automatic urban land cover classification is a fundamental problem in remote sensing, e.g., for environmental monitoring. The problem is highly challenging, as classes generally have high interclass and low intraclass variances. Techniques to improve urban land cover classification performance in remote sensing include fusion of data from different sensors with different data modalities. However, ...

      Vierinen, Juha; Markkanen, Jussi; Krag, Holger; Siminski, Jan; Mancas, Alexandru (Peer reviewed; Conference object; Konferansebidrag, 2017-06)
      We investigate the capabilities of the next generation ionospheric research radar EISCAT 3D (E3D) for observations of space objects. The radar is multi-static, and is therefore capable of observing instantaneous threedimensional vector velocity and position by observing round-trip delay and Doppler shift between the transmitter and three receiver sites. The radar is to be located in Northern ...
    • Using anchors from free text in electronic health records to diagnose postoperative delirium 

      Mikalsen, Karl Øyvind; Soguero-Ruiz, Cristina; Jensen, Kasper; Hindberg, Kristian; Gran, Mads; Revhaug, Arthur; Lindsetmo, Rolv-Ole; Skrøvseth, Stein Olav; Godtliebsen, Fred; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-19)
      Objectives:<br> Postoperative delirium is a common complication after major surgery among the elderly. Despite its potentially serious consequences, the complication often goes undetected and undiagnosed. In order to provide diagnosis support one could potentially exploit the information hidden in free text documents from electronic health records usin ...
    • Using Silver Nano-Particle Ink in Electrode Fabrication of High Frequency Copolymer Ultrasonic Transducers: Modeling and Experimental Investigation 

      Decharat, Adit; Wagle, Sanat; Jacobsen, Svein Ketil; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-04-20)
      High frequency polymer-based ultrasonic transducers are produced with electrodes thicknesses typical for printed electrodes obtained from silver (Ag) nano-particle inks. An analytical three-port network is used to study the acoustic effects imposed by a thick electrode in a typical layered transducer configuration. Results from the network model are compared to experimental findings for the implemented ...
    • Validation of SAR Iceberg Detection with Ground-Based Radar and GPS Measurements 

      Akbari, Vahid; Lauknes, Tom Rune; Rouyet, Line; Negrel, Jean; Eltoft, Torbjørn (Peer reviewed; Chapter; Bokkapittel, 2018-11-05)
      Calving of icebergs at the tidewater glacier fronts is a component of the mass loss in Polar regions. Studying the regional distribution of icebergs, their volume, motion, and interaction with the environment is of interest. Here, we present the results from a fieldwork campaign conducted in Kongsfjorden, Svalbard in April 2016, where both satellite and ground-based remote sensing instruments were ...
    • Velocity distribution of Gold nanoparticles trapped on an optical waveguide 

      Grujic, Katarina; Hole, JP; Wilkinson, JS; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2005)
    • Velocity scaling for filament motion in scrape-off layer plasmas 

      Kube, Ralph; Garcia, Odd Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
    • Weather situation during observed ship-icing events off the coast of Northern Norway and the Svalbard archipelago 

      Samuelsen, Eirik Mikal; Graversen, Rune (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-19)
      Ship icing may lead the ship and crew in great jeopardy. Usually, predictions of such ice build-up are based on the modelling of the heat fluxes capable of freezing sea water originated from wave-ship interactions. This study, on the other hand, follows a different and more general approach by investigating the relationship between the weather situation and icing both using observed parameters from ...
    • Wind power predictions in complex terrain using analog ensembles 

      Birkelund, Yngve; Alessandrini, Stefano; Byrkjedal, Øyvind; Monache, Luca Delle (Journal article; Tidsskriftartikkel, 2018)
    • Wind speed and direction predictions by WRF and WindSim coupling over Nygårdsfjell 

      Bilal, Muhammad; Birkelund, Yngve; Solbakken, Kine (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      In this study, the performance of the mesoscale meteorological Weather Research and Forecast (WRF) model coupled with the microscale computational fluid dynamics based model WindSim is investigated and compared to the performance of WRF alone. The two model set-ups, WRF and WRF-WindSim, have been tested on three high-wind events in February, June and October, over a complex terrain at the ...