Viser treff 903-922 av 1261

    • QRA techniques on dynamic positioning systems during drilling operations in the Arctic: With emphasis on the dynamic positioning operator 

      Pedersen, Runar Nikolai (Master thesis; Mastergradsoppgave, 2015-06-01)
      With the Norwegian government moving the ice edge farther north than ever before, opening for new areas for petroleum exploration, it will need research on how these areas can affect oil and gas operations. A sensitive environment along with the harsh Arctic climate and remote distances means that severe accidents, like blowouts, will have serious impacts and make cleanup and rescue actions to ...
    • Quad-Polarimetric SAR for Detection and Characterization of Icebergs 

      Akbari, Vahid; Brekke, Camilla; Doulgeris, Anthony Paul; Storvold, Rune; Sivertsen, Agnar H. (Conference object; Konferansebidrag, 2016)
      This paper evaluates the performance of fully polarimetric SAR data in iceberg detection and characterization. The study aims to explore the potential of RADARSAT-2 SAR data to detect icebergs and growlers in Svalbard that have broken off from the glaciers nearby. To be able to detect iceberg/growlers in a SAR image, a significant contrast between iceberg and background clutter is required. The ...
    • Quantification of the NA dependent change of shape in the image formation of a z-polarised fluorescent molecule using vectorial diffraction simulations 

      Ströhl, Florian; Bruggeman, Ezra; Rowlands, Christopher; Wolfson, Deanna; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-19)
      The point spread function of a fixed fluorophore with its dipole axis colinear to the optical axis appears donut-shaped when seen through a microscope, and its light distribution in the pupil plane is radially polarized. Yet other techniques, such as photolithography, report that this same light distribution in the pupil plane appears as a solid spot. How can this same distribution lead to a spot ...
    • Quantification of van der Waals forces in bimodal and trimodal AFM 

      Santos Hernandez, Sergio; Gadelrab, Karim; Elsherbiny, Lamiaa; Drexler, Xaver; Olukan, Tuza Adeyemi; Font, Josep; Barcons, Victor; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-22)
      The multifrequency formalism is generalized and exploited to quantify attractive forces, i.e., van der Waals interactions, with small amplitudes or gentle forces in bimodal and trimodal atomic force microscopy (AFM). The multifrequency force spectroscopy formalism with higher modes, including trimodal AFM, can outperform bimodal AFM for material property quantification. Bimodal AFM with the second ...
    • Quantifying influence of local air pollution on measurements in Ny-Ålesund and at the Zeppelin station 

      Dekhtyareva, Alena (Master thesis; Mastergradsoppgave, 2014-06-02)
      In order to keep the scientific significance of the Ny-Ålesund station on Svalbard as the key place for the monitoring of background air it is needed to assess the influence from local human activities on the air quality. Whether research and tourist activity continues to grow or restrictions to be implied the change of impact may affect air chemistry data quality. Therefore the identification of ...
    • Quantitative assessment of morphology and sub-cellular changes in macrophages and trophoblasts during inflammation 

      Singh, Rajwinder; Dubey, Vishesh; Wolfson, Deanna; Ahmad, Azeem; Butola, Ankit; Acharya, Ganesh; Singh Mehta, Dalip; Basnet, Purusotam; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-12)
      In pregnancy during an inflammatory condition, macrophages present at the feto-maternal junction release an increased amount of nitric oxide (NO) and pro-inflammatory cytokines such as TNF-α and INF-γ, which can disturb the trophoblast functions and pregnancy outcome. Measurement of the cellular and sub-cellular morphological modifications associated with inflammatory responses are important in order ...
    • Quantitative assessment of two oil-in-ice surface drift algorithms 

      Martins de Aguiar, Victor Cesar; Dagestad, Knut-Frode; Hole, Lars Robert; Barthel, Knut Sven (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-04)
      The ongoing reduction in extent and thickness of sea ice in the Arctic might result in an increase of oil spill risk due to the expansion of shipping activity and oil exploration shift towards higher latitudes. This work assessed the response of two oil-in-ice surface drift models implemented in an open-source Lagrangian framework. By considering two numerical modeling experiments, our main finding ...
    • Quantitative phase microscopy of red blood cells during planar trapping and propulsion 

      Ahmad, Azeem; Dubey, Vishesh; Singh, Vijay; Tinguely, Jean-Claude; Øie, Cristina Ionica; Wolfson, Deanna; Mehta, Dalip Singh; So, Peter T. C.; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-22)
      Red blood cells (RBCs) have the ability to undergo morphological deformations during microcirculation, such as changes in surface area, volume and sphericity. Optical waveguide trapping is suitable for trapping, propelling and deforming large cell populations along the length of the waveguide. Bright field microscopy employed with waveguide trapping does not provide quantitative information about ...
    • Quasi Monte Carlo time-frequency analysis 

      Levie, Ron; Avron, Haim; Kutyniok, Gitta Astrid Hildegard (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-30)
      We study signal processing tasks in which the signal is mapped via some generalized time-frequency transform to a higher dimensional time-frequency space, processed there, and synthesized to an output signal. We show how to approximate such methods using a quasi-Monte Carlo (QMC) approach. We consider cases where the time-frequency representation is redundant, having feature axes in addition to the ...
    • Radar imaging with EISCAT 3D 

      Stamm, Johann; Vierinen, Juha; Urco, Juan M.; Gustavsson, Björn; Chau, Jorge L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-04)
      A new incoherent scatter radar called EISCAT 3D is being constructed in northern Scandinavia. It will have the capability to produce volumetric images of ionospheric plasma parameters using aperture synthesis radar imaging. This study uses the current design of EISCAT 3D to explore the theoretical radar imaging performance when imaging electron density in the E region and compares numerical techniques ...
    • Radar observations of space debris in polar orbits 2018–2021. A study on the evolution of the Microsat-R fragments 

      Paulsen, Martinius Ekeland (Master thesis; Mastergradsoppgave, 2021-07-02)
      Orbits are an invaluable resource for the global community. However, space pollution is becoming more pronounced as the accumulation of debris continues. Deliberate collisions are a relevant source contributing to this development. When Microsat-R was destroyed with a missile in 2019, it ejected numerous fragments into orbit. Based on observations made with EISCAT UHF, this thesis will investigate ...
    • Radar observations of thermal plasma oscillations in the ionosphere 

      Vierinen, Juha; Gustavsson, Björn Johan; Hysell, David; Sulzer, M.; Perillat, Phil; Kudeki, Erhan (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-02)
      Incoherent scatter radar observations of ionospheric plasmas rely on echoes from electron density fluctuations with properties governed by the dispersion relations for ion acoustic and Langmuir waves. Radar observations of echoes associated with Langmuir waves (plasma lines) from thermal plasma are weak, and only a few near‐thermal level measurements have been reported. Plasma line echoes are typically ...
    • Radar size inference from statistics of RCS samples 

      Anfinsen, Stian Normann; Grydeland, Tom; Vierinen, Juha; Kastinen, Daniel; Ricker, Robert; Arntzen, Ingar M; Kero, J.; Høgda, Kjell Arild (Journal article; Tidsskriftartikkel; Peer reviewed, 2023)
      Radar Beam-park experiments have been very successful in characterizing the distribution of space debris objects, both in terms of orbital parameters but also in terms of limiting the estimates of their radar cross section, or RCS. A recent paper \[0\] used observed range and range rates to refine orbit estimates by matching up the observed SNR curve to that predicted by simulations. This gives good ...
    • Radar studies of ionospheric dust - plasma phenomena 

      Mann, Ingrid (Conference object; Konferansebidrag, 2018)
      Dust plasma phenomena occur in the Earth ionosphere in particular in the meteor ablation zone at altitudes ~50-95 km and above where radar meteors form. Radar also detect coherent polar mesospheric radar echoes (PME), i.e. radar echoes that are caused by spatial variations in the plasma refractive index at around 80 to 90 km altitude in the Earth’s mesosphere. During summer, PM(S)E form in the ...
    • Radar studies of ionospheric dusty plasma phenomena 

      Mann, Ingrid; Gunnarsdottir, Tinna; Häggström, Ingemar; Eren, Saliha; Tjulin, Anders; Myrvang, Margaretha; Rietveld, Mike T; Dalin, Peter; Jozwicki, Dorota; Trollvik, Henriette Marie Tveitnes (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-17)
      We discuss the influence of charged dust on radar observations in the Earth ionosphere. This region in the upper Earth atmosphere can be described as a partially ionized, low‐temperature plasma. Plasma parameters vary by orders of magnitude spatially and in time. Dust particles influence the charge balance, in some cases dusty plasma condition is met. The polar mesospheric echoes are an example of ...
    • Radio occultation observations of the solar corona over 1.60-1.86R⊙: Faraday rotation and frequency-shift analysis 

      Wexler, David; Hollweg, Joseph V; Efimov, Anatoli I; Song, Paul; Jensen, Elizabeth T; Lionello, Roberto; Vierinen, Juha; Coster, Anthea (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-02)
      The study of coronal energy transport, central to the solar wind acceleration problem, relies upon accurate representation of magnetic fields and plasma electron densities. This information is difficult to obtain in middle‐to‐lower coronal regions that may contain complex magnetic structures. Faraday rotation (FR) solar radio occultation observations, which reveal line‐of‐sight (LOS) integrated ...
    • Radiometric temperature reading of a hot ellipsoidal object inside the oral cavity by a shielded microwave antenna put flush to the cheek 

      Klemetsen, Øystein; Jacobsen, Svein Ketil; Birkelund, Yngve (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      A new scheme for detection of vesicoureteral reflux (VUR) in children has recently been proposed in the literature. The idea is to warm bladder urine via microwave exposure to at least fever temperatures and observe potential urine reflux from the bladder back to the kidney(s) by medical radiometry. As a preliminary step toward realization of this detection device, we present non-invasive temperature ...
    • RAM analysis of mining equipment and framework for data collection 

      Sneve, Terje (Master thesis; Mastergradsoppgave, 2015-06-01)
      In the mining industry, equipment are continuously increasing in size and complexity. At the same time, the demand for available plants and continuous production has never been higher. The performance of equipment depends on the reliability and maintainability performance of the equipment along with the maintenance supportability, operational conditions, and environmental conditions. In order to ...
    • Raman-spectroscopy and of optically trapped nanoparticles 

      Mikheev, Ivan (Mastergradsoppgave; Master thesis, 2022-11-06)
      The present work begins a large layer of experiments on the study of Raman radiation from extracellular vesicles. It is a promising method that provides unique information about the global biomolecular composition of a single vesicle or a small number of vesicles. Two physical phenomena are present in this work, Raman scattering and optical trapping. In Raman scattering, the scattered radiation ...
    • Range-Doppler Mapping of Space-Based Targets Using the JRO 50 MHz Radar 

      Kesaraju, Saiveena; Mathews, J. D.; Milla, M.; Vierinen, Juha (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-02)
      The Jicamarca Radio Observatory (JRO) two-dimensional square array radar system operating at ~ 6-m wavelength was used to study the Moon and low Earth orbit satellites using the Range-Doppler inverse synthetic aperture radar technique also known as Delay-Doppler imaging. The radar data was collected on Oct 21, 2015. A circularly polarized coded pulse was transmitted from a quarter-array antenna ...