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Traveling ionospheric disturbances and ionospheric perturbations associated with solar flares in September 2017
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-10)Solar flares provide strong impulsive radiation and energy injection to the sunlit upper atmosphere. The impact on the ionosphere is immense in spatial scale, and therefore, it is not immediately evident if dramatically elevated neutral heating can lead to excitation of acoustic gravity waves. Using primary observations from Global Navigation Satellite System differential TEC (total electron ... -
Assessment of Polarimetric Variability by Distance Geometry for Enhanced Classification of Oil Slicks Using SAR
(Peer reviewed; Chapter; Bokkapittel, 2019-11-14)In this paper, we introduce a new approach for investigation of polarimetric Synthetic Aperture Radar (PolSAR) images for oil slick analysis. Our method aims at enhancing discrimination of oil types by exploring the polarimetric features that can be produced by processing PolSAR scenes without dimensionality reduction. Taking advantage of a mixture description of the interactions among classes within ... -
Lumikot: Fast auroral transients during the growth phase of substorms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-25)The development of a magnetospheric substorm may be classified into three phases: growth, expansion, and recovery. The growth phase is important as it includes processes that lead to the expansion. In a recent growth-phase study, a type of fast discrete auroral transient phenomena -- referred to as Lumikot -- were observed. The Lumikot are several kilometers across and move in the high-energy ... -
Relationship between the source size at the diffuser plane and the longitudinal spatial coherence function of the optical coherence microscopy system
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-25)Coherence properties of light sources are indispensable for optical coherence microscopy/tomography as they greatly influence the signal-to-noise ratio, axial resolution, and penetration depth of the system. In the present paper, we report the investigation of longitudinal spatial coherence properties of a pseudothermal light source (PTS) as a function of the laser spot size at the rotating diffuser ... -
Thickness-Dependent Resonant Raman and E' Photoluminescence Spectra of Indium Selenide and Indium Selenide/Graphene Heterostructures
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-28)Atomically thin, two-dimensional (2D) indium selenide (InSe) has attracted considerable attention because of the dependence of its bandgap on sample thickness, making it suitable for small-scale optoelectronic device applications. In this work, by the use of Raman spectroscopy with three different laser wavelengths, including 488, 532, and 633 nm, representing resonant, near-resonant, and conventional ... -
Hybrid graphene metasurface for near-infrared absorbers
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-19)We experimentally demonstrated an amorphous graphene-based metasurface yielding near-infrared super absorber characteristic. The structure is obtained by alternatively combining magnetron-sputtering deposition and graphene transfer coating fabrication techniques. The thickness constraint of the physical vapor–deposited amorphous metallic layer is unlocked and as a result, the as-fabricated graphene-based ... -
Comparative net energy analysis of renewable electricity and carbon capture and storage
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-08)Carbon capture and storage (CCS) for fossil-fuel power plants is perceived as a critical technology for climate mitigation. Nevertheless, limited installed capacity to date raises concerns about the ability of CCS to scale sufficiently. Conversely, scalable renewable electricity installations—solar and wind—are already deployed at scale and have demonstrated a rapid expansion potential. Here we show ... -
Evaluation of Six Atmospheric Reanalyses over Arctic Sea Ice from Winter to Early Summer
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-19)This study evaluates the performance of six atmospheric reanalyses (ERA-Interim, ERA5, JRA-55, CFSv2, MERRA-2, and ASRv2) over Arctic sea ice from winter to early summer. The reanalyses are evaluated using observations from the Norwegian Young Sea Ice campaign (N-ICE2015), a 5-month ice drift in pack ice north of Svalbard. N-ICE2015 observations include surface meteorology, vertical profiles from ... -
High-Throughput Total Internal Reflection Fluorescence and Direct Stochastic Optical Reconstruction Microscopy Using a Photonic Chip
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-16)Total internal reflection fluorescence (TIRF) is commonly used in single molecule localization based super-resolution microscopy as it gives enhanced contrast due to optical sectioning. The conventional approach is to use high numerical aperture microscope TIRF objectives for both excitation and collection, severely limiting the field of view and throughput. We present a novel approach to generating ... -
On the Role of the Atmospheric Energy Transport in 2xCO2-Induced Polar Amplification in CESM1
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-12)A doubling of the atmospheric CO<sub>2</sub> content leads to global warming that is amplified in the polar regions. The CO<sub>2</sub> forcing also leads to a change of the atmospheric energy transport. This transport change affects the local warming induced by the CO<sub>2</sub> forcing. Using the Community Earth System Model (CESM), the direct response to the transport change is investigated. ... -
Patch Size Evolution During Pulsating Aurora
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-30)We report both decreasing and increasing trends in the patch sizes during pulsating aurora events. About 150 pulsating auroral events over the Fennoscandian Lapland have been successfully analyzed for their average patch size, total patch area, and number of patches as a function of event time, typically 1–2 hr. An automatic routine has been developed to detect patches in the all‐sky camera images. ... -
Observation of mesospheric dust and ionospheric conditions during the G-chaser rocket campaign
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10)SPID, Smoke Particle Impact Detector, is a Faraday cup detector designed to measure nanometer-sized meteoric smoke particles during rocket flights. We report measurements made with SPID during the G-Chaser student rocket campaign 13 January 2019 and describe the design of the SPID instruments. Model calculations of dust trajectories within the detector result in an effective crosssection of 0.97 for ... -
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
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-17)Synthetic Aperture Radar (SAR) satellite images are used to monitor Arctic sea ice, with systematic data records dating back to 1991. We propose a semi-supervised classification method that separates open water from sea ice and can utilise ERS-1/2, Envisat ASAR, RADARSAT-2 and Sentinel-1 SAR images. The classification combines automatic segmentation with a manual segment selection stage. The ... -
Analyse av energibruk og teknisk drift ved Bryne videregående skole
(Master thesis; Mastergradsoppgave, 2019-12-15)Tidligere Bryne videregående skole (vgs.) og Time vgs. ble i 2015 slått sammen til nye Bryne vgs. I den anledning ble det bygget tre nye skolebygg med et moderne og komplekst energisystem. Skolen er et pilotprosjekt i tråd med Rogaland fylkeskommune sin miljøpolitikk og er bygget med fokus på bærekraftige prinsipper, lavt energiforbruk og bruk av energikilder med begrenset CO2 utslipp. Skolens varme ... -
Comparison of the Ice Watch Database and Sea Ice Classification from Sentinel-1 Imagery
(Master thesis; Mastergradsoppgave, 2019-12-13)In this thesis,we investigate the potential use of in-situ sea ice observations from the Ice Watch database as ground truth data for an automated classification algorithm of sea ice types from Sentinel-1 SAR data. The Ice Watch database and the Sentinel-1 data archive are searched for in-situ observations and satellite data acquisitions in Extra Wide swath mode overlapping in both space and time. ... -
Wind resource assessment using weather research and forecasting model. A case study of the wind resources at Havøygavlen wind farm
(Master thesis; Mastergradsoppgave, 2019-12-13)The need for energy increases globally due to rapid expansion of population and prosperity. To meet this demand while decreasing carbon emission and eventually transition out fossil fuel, efficient utilization of wind power is prominent. This study evaluates the performance of the Weather Research and Forecast model (WRF) with respect to wind speed and wind direction. The area of the study is ... -
Short-term wind power prediction models in complex terrain based on statistical time series analysis
(Master thesis; Mastergradsoppgave, 2019-12-13)One of the largest challenges with the utilization of wind as a renewable resource, is its natural variability and intermittent nature. To achieve a sustainable integration of wind power into the power grid, a precise and reliable prediction method is therefore required. In this study, several short-term wind power prediction models based on statistical time series analysis were developed and tested, ... -
Affinity-Guided Image-to-Image Translation for Unsupervised Heterogeneous Change Detection
(Master thesis; Mastergradsoppgave, 2019-12-16)Change detection in earth observation remote sensing images can be used to describe the extent of natural disasters, e.g., forest fires and floods. When time is of the essence, the ability to utilize heterogeneous images is fundamental, i.e., images that are not directly comparable due to the sensors used or the capturing conditions. The recent advances in machine learning have dispersed into the ... -
On-Site Ribosome Remodeling by Locally Synthesized Ribosomal Proteins in Axons
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-10)Ribosome assembly occurs mainly in the nucleolus, yet recent studies have revealed robust enrichment and translation of mRNAs encoding many ribosomal proteins (RPs) in axons, far away from neuronal cell bodies. Here, we report a physical and functional interaction between locally synthesized RPs and ribosomes in the axon. We show that axonal RP translation is regulated through a sequence motif, ... -
Partially spatially coherent digital holographic microscopy and machine learning for quantitative analysis of human spermatozoa under oxidative stress condition
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-05)Semen quality assessed by sperm count and sperm cell characteristics such as morphology and motility, is considered to be the main determinant of men’s reproductive health. Therefore, sperm cell selection is vital in assisted reproductive technology (ART) used for the treatment of infertility. Conventional bright field optical microscopy is widely utilized for the imaging and selection of sperm cells ...
