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norskArtikler, rapporter og annet (fysikk og teknologi): Recent submissions
Now showing items 881-900 of 1057
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Oil spill characterization in the hybrid-polarity SAR domain using log-cumulants
(Peer reviewed; Journal article; Tidsskriftsartikkel, 2016-10-18)Log-cumulants have proven to be an interesting tool for evaluating the statistical properties of potential oil spills in polarimetric Synthetic Aperture Radar (SAR) data within the common horizontal (H) and vertical (V) polarization basis. The use of first, second, and third order sample log-cumulants has shown potential for evaluating the texture and the statistical distributions, as well as ... -
A Segmentation based CFAR detection algorithm using truncated statistics
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-18)Target detection in nonhomogeneous sea clutter environments is a complex and challenging task due to the capture effect from interfering outliers and the clutter edge effect from background intensity transitions. For synthetic aperture radar (SAR) measurements, those issues are commonly caused by multiple targets and meteorological and oceanographic phenomena, respectively. This paper proposes a ... -
A Multisensor Comparison of Experimental Oil Spills in Polarimetric SAR for High Wind Conditions
(Peer reviewed; Journal article; Tidsskriftsartikkel, 2016-06-23)In this paper, we present the experimental setup and data collection during the Norwegian Radar oil Spill Experiment 2015, followed by a comparison of a subset of the multisensory synthetic aperture radar (SAR) imagery collected during the experiment. Multipolarization SAR data acquired by Radarsat-2, TerraSAR-X, and the uninhabited aerial vehicle synthetic aperture radar (UAVSAR) less than 6 min ... -
Characterization and discrimination of evolving mineral and plant oil slicks based on L-band synthetic aperture radar (SAR)
(Peer reviewed; Journal article; Tidsskriftsartikkel, 2016-10-18)Evolution of the damping ratio for Bragg wavenumbers in the range 32-43 rad/m is evaluated for oil slicks of different composition released in the open ocean and allowed to develop naturally. The study uses quad-polarimetric L-band airborne synthetic aperture radar data acquired over three mineral oil emulsion releases of different, known oil-to-water ratio, and a near-coincident release of 2-ethylhexyl ... -
Level crossings, excess times, and transient plasma-wall interactions in fusion plasmas
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-19)Based on a stochastic model for intermittent fluctuations in the boundary region of magnetically confined plasmas, an expression for the level crossing rate is derived from the joint distribution of the process and its derivative. From this the average time spent by the process above a certain threshold level is obtained. This provides novel predictions of plasma–wall interactions due to transient ... -
Dynamics of the Terra Nova Bay Polynya: The potential of multi-sensor satellite observations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-10)Research on processes leading to formation, maintenance, and disappearance of polynyas in the Polar Regions benefits significantly from the use of different types of remote sensing data. The Sentinels of the European Space Agency (ESA), together with other satellite missions, provide a variety of data from different parts of the electromagnetic spectrum, at different spatial scales, and with ... -
Scrape-off layer turbulence in TCV: Evidence in support of stochastic modelling.
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-28)Intermittent fluctuations in the TCV scrape-off layer have been investigated by analysing long Langmuir probe data time series under stationary conditions, allowing calculation of fluctuation statistics with high accuracy. The ion saturation current signal is dominated by the frequent occurrence of large-amplitude bursts attributed to filament structures moving through the scrape-off layer. The ... -
Stochastic modelling of intermittent fluctuations in the scrape-off layer: Correlations, distributions, level crossings, and moment estimation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05)A stochastic model is presented for intermittent fluctuations in the scrape-off layer of magnetically confined plasmas. The fluctuations in the plasma density are modeled by a super-position of uncorrelated pulses with fixed shape and duration, describing radial motion of blob-like structures. In the case of an exponential pulse shape and exponentially distributed pulse amplitudes, predictions are ... -
Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-02)The geomagnetic field often experiences large fluctuations, especially at high latitudes in the auroral zones. We have found, using simulations, that there are significant differences in the substorm signature, in certain coordinate systems, as a function of longitude. This is confirmed by the analysis of real, measured data from comparable locations. Large geomagnetic fluctuations pose ... -
Delt situasjonsforståelse under søk og redning i nordområdene
(Research report; Forskningsrapport, 2016-05-03)Prosjektets mål er å bidra til økt kunnskap om hvordan etablere delt situasjonsforståelse mellom sentrale aktører innen SAR i Nordområdet. Prosjektgruppa har arbeidet ut ifra en menneske-teknologi-organisasjon (MTO) tilnærming og hvor vi har sett på <br>1) menneskelige og organisatoriske faktorer og <br>2) tekniske faktorer som virker inn på etableringen av delt situasjonsforståelse mellom aktører.<br> ... -
Scanning acoustic microscopy—A novel noninvasive method to determine tumor interstitial fluid pressure in a xenograft tumor model
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-22)Elevated tumor interstitial fluid pressure (TIFP) is a prominent feature of solid tumors and hampers the transmigration of therapeutic macromolecules, for example, large monoclonal antibodies, from tumor-supplying vessels into the tumor interstitium. TIFP values of up to 40 mm Hg have been measured in experimental solid tumors using two conventional invasive techniques: the wick-in-needle and the ... -
Amplitude and size scaling for interchange motions of plasma filaments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-07)The interchange dynamics and velocity scaling of blob-like plasma filaments are investigated using a two-field reduced fluid model. For incompressible flows due to buoyancy, the maximum velocity is proportional to the square root of the relative amplitude and the square root of its cross-field size. For compressible flows in a non-uniform magnetic field, this square root scaling only holds ... -
Wind speed and direction predictions by WRF and WindSim coupling over Nygårdsfjell
(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 ... -
Interpreting sea surface slicks on the basis of the normalized radar cross-section model using RADARSAT-2 copolarization dual-channel SAR images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-03-24)A simple automatic multipolarization technique for discrimination of main types of thin oil films (of thickness less than the radio wave skin depth) from natural ones is proposed. It is based on a new multipolarization parameter related to the ratio between the damping in the slick of specially normalized resonant and nonresonant signals calculated using the normalized radar cross-section model ... -
Rib waveguides for trapping and transport of particles
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-23)Rib waveguides are investigated as an alternative to strip waveguides for planar trapping and transport of microparticles. Microparticles are successfully propelled along the surface of rib waveguides and trapped in the gap between opposing rib waveguides. The trapping capabilities of waveguide end facets formed by a single and opposing waveguide geometries are investigated. The slab beneath a rib ... -
An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-13)Incoherent scatter radar measurements are an important source for studies of ionospheric plasma parameters. In this paper the EISCAT Svalbard radar (ESR) long-term database is used to evaluate the International Reference Ionosphere (IRI) model. The ESR started operations in 1996, and the accumulated database up to 2012 thus covers 16 years, giving an overview of the ionosphere in the polar cap and ... -
Integrated Monitoring of Mola mola Behaviour in Space and Time
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-05)Over the last decade, ocean sunfish movements have been monitored worldwide using various satellite tracking methods. This study reports the near-real time monitoring of fine-scale (< 10 m) behaviour of sunfish. The study was conducted in southern Portugal in May 2014 and involved satellite tags and underwater and surface robotic vehicles to measure both the movements and the contextual environment ... -
Retrieval of sodium number density profiles in the mesosphere and lower thermosphere from SCIAMACHY limb emission measurements
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-28)An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) limb measurements of the Na resonance fluorescence. The results are obtained between 50 and 150 km altitude and the resulting global seasonal variations of Na are analyzed. The retrieval approach ... -
Late summer sea ice segmentation with multi-polarisation SAR features in C- and X-band
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-09-01)In this study we investigate the potential of sea ice segmentation by C- and X-band multi-polarisation synthetic aperture radar (SAR) features during late summer. Five high-resolution satellite SAR scenes were recorded in the Fram Strait covering iceberg- fast first-year and old sea ice during a week with air temperatures varying around zero degrees Celsius. In situ data consisting of sea ice ... -
Sensitive on-chip methane detection with a cryptophane-A cladded Mach-Zehnder interferometer
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-24)We report a methane sensor based on an integrated Mach-Zehnder interferometer, which is cladded by a styrene-acrylonitrile film incorporating cryptophane-A. Cryptophane-A is a supramolecular compound able to selectively trap methane, and its presence in the cladding leads to a 17-fold sensitivity enhancement. Our approach, based on 3 cm-long low-loss Si3N4 rib waveguides, results in a detection limit ...
