Viser treff 839-858 av 942

    • Subaperture analysis of polarimetric SAR data for iceberg detection 

      Akbari, Vahid; Doulgeris, Anthony Paul; Brekke, Camilla (Konferansebidrag; Conference object, 2016-11-03)
      This paper is focused on investigations of the improved detection of icebergs in open water using spectral analysis of polarimetric SAR data. The objectives of this study are to analyze the behavior of ice objects in open water using the sublook cross-correlation magnitude (SCM). It is shown that there is an improvement of iceberg-sea contrast when the SCM is used instead of multilook intensities ...
    • Subauroral and polar traveling ionospheric disturbances during 7-9 September 2017 storms 

      Zhang, Shunrong; Erickson, Philip j.; Coster, Anthea; Rideout, William; Vierinen, Juha; Jonah, Olusegun; Goncharenko, Larisa (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-25)
      This study provides new scenarios for storm time traveling ionospheric disturbance excitation and subsequent propagation at subauroral and polar latitudes. We used ground‐based total electron content observations from Global Navigation Satellite System receivers combined with wide field, subauroral ionospheric plasma parameters measured with the Millstone Hill Incoherent Scatter Radar during strong ...
    • Subband Extraction Strategies in Ship Detection With the Subaperture Cross-Correlation Magnitude 

      Brekke, Camilla; Anfinsen, Stian Normann; Larsen, Yngvar (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-01-27)
      The subaperture cross-correlation magnitude (SCM) has previously been proposed as a statistic that improves the contrast between small ship targets and the surrounding sea in synthetic-aperture-radar images. This preprocessing technique utilizes the fast decorrelation of open-water surface ripples on the scale of the SAR wavelength relative to coherent targets such as a ship. However, optimization ...
    • Subseasonal Predictions of Polar Low Activity Using a Hybrid Statistical-Dynamical Approach 

      Boyd, Kevin; Wang, Zhuo; Walsh, John; Stoll, Johannes Patrick (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-21)
      The subseasonal prediction of polar low (PL) activity is explored using a hybrid statistical-dynamical approach. A previously developed PL genesis potential index is paired with ECMWF reforecasts and forecasts to predict regional statistics of PL activity across the sub-Arctic. Regional PL activity is skillfully predicted in all regions at forecast ranges of up to a month. Additionally, the ...
    • Summers with low Arctic sea ice linked to persistence of spring atmospheric circulation patterns 

      Kapsch, Marie-Luise; Skific, Natasa; Graversen, Rune; Tjernström, Michael; Francis, Jennifer A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-30)
      The declining trend of Arctic September sea ice constitutes a significant change in the Arctic climate system. Large yearto-year variations are superimposed on this sea–ice trend, with the largest variability observed in the eastern Arctic Ocean. Knowledge of the processes important for this variability may lead to an improved understanding of seasonal and long-term changes. Previous studies suggest ...
    • 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 ...
    • 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 ...
    • Supercm: Revisiting Clustering for Semi-Supervised Learning 

      Singh, Durgesh Kumar; Boubekki, Ahcene; Jenssen, Robert; Kampffmeyer, Michael (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-05)
      The development of semi-supervised learning (SSL) has in recent years largely focused on the development of new consistency regularization or entropy minimization approaches, often resulting in models with complex training strategies to obtain the desired results. In this work, we instead propose a novel approach that explicitly incorporates the underlying clustering assumption in SSL through extending ...
    • SuperDARN radar-derived HF radio attenuation during the September 2017 solar proton events 

      Bland, Emma; Heino, Erkka Petteri; Kosch, Michael J.; Partamies, Noora (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-10)
      Two solar proton events in September 2017 had a significant impact on the operation of the Super Dual Auroral Radar Network (SuperDARN), a global network of high‐frequency (HF) radars designed for observing F region ionospheric plasma convection. Strong polar cap absorption caused near‐total loss of radar backscatter, which prevented the primary SuperDARN data products from being determined for a ...
    • Superposed epoch analysis applied to large-amplitude travelling convection vortices. 

      Hansen, T.L.; Lühr, H.; Rother, M.; Iyemori, T.; Lepping, R.P. (Journal article; Tidsskriftartikkel, 1998)
      For the six months from 1 October 1993 to 1 April 1994 the recordings of the IMAGE magnetometer network have been surveyed in a search for large- amplitude travelling convection vortices (TCVs). The restriction to large amplitudes (>100 nT) was chosen to ensure a proper detection of evens also during times of high activity. Readings of all stations of the northern half of the IMAGE network ...
    • Superposition of semiconductor and semi-metal properties of self-assembled 2D SnTiS3 heterostructures 

      Tamalampudi, Srinivasa Reddy; Lu, Jin-You; Rajput, Nitul; Alfakes, Boulos; Sankar, Raman; Apostoleris, Harry; Patole, Shashikant; Almansouri, Ibraheem; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-15)
      Two-dimensional metal dichalcogenide/monochalcogenide thin flakes have attracted much attention owing to their remarkable electronic and electrochemical properties; however, chemical instability limits their applications. Chemical vapor transport (CVT)- synthesized SnTiS<sub>3</sub> thin flakes exhibit misfit heterojunction structure and are highly stable in ambient conditions, offering a ...
    • Superresolving the kidney – a practical comparison of fluorescence nanoscopy of the glomerular filtration barrier 

      Wunderlich, Lucia; Ströhl, Florian; Ströhl, Stefan; Vanderpoorten, Oliver; Mascheroni, Luca; Kaminski, Clemens F. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-05)
      Immunofluorescence microscopy is routinely used in the diagnosis of and research on renal impairments. However, this highly specific technique is restricted in its maximum resolution to about 250 nm in the lateral and 700 nm in the axial directions and thus not sufficient to investigate the fine subcellular structure of the kidney’s glomerular filtration barrier. In contrast, electron microscopy ...
    • Supervised Classifications of Optical Water Types in Spanish Inland Waters 

      Pereira-Sandoval, Marcela; Ruescas, Ana Belen; García-Jimenez, Jorge; Blix, Katalin; Delegido, Jesús; Moreno, José (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-04)
      Remote sensing of lake water quality assumes there is no universal method or algorithm that can be applied in a general way on all inland waters, which usually have different in-water components affecting their optical properties. Depending on the place and time of year, the lake dynamics, and the particular components of the water, non-tailor-designed algorithms can lead to large errors or lags in ...
    • Surface aging investigation by means of an AFM-based methodology and the evolution of conservative nanoscale interactions 

      Chiesa, Matteo; Lai, Chia-Yun (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-05)
      The divergence in physical properties of surfaces exposed to airborne contaminants in the atmosphere has been widely investigated in recent years, but agreement regarding the role that airborne hydrocarbons and water contamination have on surface property evolution remains elusive. Here we investigate the evolution of a freshly grown highly oriented pyrolytic graphite (HOPG) surface exposed to a ...
    • Surface-based Ku-and Ka-band polarimetric radar for sea ice studies 

      Stroeve, Julienne C.; Nandan, Vishnu; Willatt, Rosemary; Tonboe, Rasmus; Hendricks, Stefan; Ricker, Robert; Mead, James; Mallett, Robbie; Huntemann, Marcus; Itkin, Polona; Schneebeli, Martin; Krampe, Daniela; Spreen, Gunnar; Wilkinson, Jeremy; Matero, Ilkka; Hoppmann, Mario; Tsamados, Michel (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-04)
      To improve our understanding of how snow properties influence sea ice thickness retrievals from presently operational and upcoming satellite radar altimeter missions, as well as to investigate the potential for combining dual frequencies to simultaneously map snow depth and sea ice thickness, a new, surface-based, fully polarimetric Ku- and Ka-band radar (KuKa radar) was built and deployed ...
    • Survey of conditions for artificial aurora experiments at EISCAT Tromsø using dynasonde data 

      Tsuda, T. T.; Rietveld, Michael T; Kosch, Michael J.; Oyama, S; Hosokawa, K.; Nozawa, Satonori; Kawabata, T; Mizuno, A; Ogawa, Y (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-14)
      We report a brief survey on conditions for artificial aurora optical experiments in F region heating with O-mode at the EISCAT Tromsø site using dynasonde data from 2000 to 2017. The results obtained in our survey indicate the following: The possible conditions for conducting artificial aurora experiments are concentrated in twilight hours in both evening and morning, compared with late-night hours; ...
    • Survey of conditions for artificial aurora experiments by the second electron gyro-harmonic at EISCAT Troms? using dynasonde data 

      Tsuda, T. T.; Rietveld, Michael T; Kosch, M.J; Oyama, S; Ogawa, Y; Hosokawa, K.; Nozawa, S; Kawabata, T; Mizuno, A (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-06)
      We report a brief survey of matching conditions for artificial aurora optical experiments utilizing the second electron gyro-harmonic (2.7-MHz frequency) in F region heating with O-mode at the EISCAT Tromsø site using dynasonde data from 2000 to 2017. Our survey indicates the following: The possible conditions for successful artificial aurora experiments are concentrated on twilight hours in both ...
    • Synoptic Variability in Satellite Altimeter-Derived Radar Freeboard of Arctic Sea Ice 

      Nab, Carmen; Mallett, Robbie; Gregory, William; Landy, Jack Christopher; Lawrence, Isobel; Willatt, Rosemary; Stroeve, Julienne; Tsamados, Michel (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-09)
      Satellite observations of sea ice freeboard are integral to the estimation of sea ice thickness. It is commonly assumed that radar pulses from satellite-mounted Ku-band altimeters penetrate through the snow and reflect from the snow-ice interface. We would therefore expect a negative correlation between snow accumulation and radar freeboard measurements, as increased snow loading weighs the ice floe ...
    • 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 ...
    • Synthetic wavelength scanning interferometry for 3D surface profilometry with extended range of height measurement using multi-colour LED light sources 

      Mann, Priyanka; Dubey, Vishesh Kumar; Ahmad, Azeem; Butola, Ankit; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-05)
      We report three-dimensional surface profilometry with extended range of height measurements using synthetic wavelength scanning interferometry without tunable filters, wavelength-tuning lasers, grating elements. We have used inexpensive multiple colour light emitting diodes (LEDs) and operate them sequentially one by one or combination of two or more colours simultaneously to visualize synthetic ...