Institutt for fysikk og teknologi: Recent submissions
Now showing items 141-160 of 1294
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Polarimetric Guided Nonlocal Means Covariance Matrix Estimation for Defoliation Mapping
(Conference object; Konferansebidrag, 2020)In this study we investigate the potential for using synthetic aperture radar (SAR) data to provide high resolution defoliation and regrowth mapping of trees in the tundra-forest ecotone. Using aerial photographs, four areas with live forest and four areas with dead trees were identified. Quad-polarimetric SAR data from RADARSAT-2 was collected from the same area, and the complex multilook polarimetric ... -
Generation of Lidar-Predicted Forest Biomass Maps from Radar Backscatter with Conditional Generative Adversarial Networks
(Conference object; Konferansebidrag, 2020) -
Heterogeneous Change Detection with Self-supervised Deep Canonically Correlated Autoencoders
(Conference object; Konferansebidrag, 2020) -
Change Detection with Heterogeneous Remote Sensing Data: From Semi-Parametric Regression to Deep Learning
(Conference object; Konferansebidrag, 2020) -
Image denoising in acoustic microscopy using block-matching and 4D filter
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-14)Scanning acoustic microscopy (SAM) is a label-free imaging technique used in biomedical imaging, non-destructive testing, and material research to visualize surface and sub-surface structures. In ultrasonic imaging, noises in images can reduce contrast, edge and texture details, and resolution, negatively impacting post-processing algorithms. To reduce the noises in the scanned image, we have employed ... -
Better synoptic and subseasonal sea ice thickness predictions are urgently required: a lesson learned from the YOPP data validation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-20)In the context of global warming, Arctic sea ice has declined substantially during the satellite era (Kwok 2018). The retreating and thinning of Arctic sea ice provide opportunities for human activities in the Arctic, such as tourism, fisheries, shipping, natural resource exploitation, and wildlife management; however, new risks emerge. To ensure the safety and emergency management of human activities ... -
Wind redistribution of snow impacts the Ka- and Ku-band radar signatures of Arctic sea ice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-02)Wind-driven redistribution of snow on sea ice alters its topography and microstructure, yet the impact of these processes on radar signatures is poorly understood. Here, we examine the effects of snow redistribution over Arctic sea ice on radar waveforms and backscatter signatures obtained from a surface-based, fully polarimetric Ka- and Ku-band radar at incidence angles between 0∘ (nadir) and 50∘. ... -
Attention-guided Temporal Convolutional Network for Non-intrusive Load Monitoring
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-01)With the prevalence of smart meter infrastructure, data analysis on consumer side becomes more and more important in smart grid systems. One of the fundamental tasks is to disaggregate users' total consumption into appliance-wise values. It has been well noted that encoding of temporal dependency is a key issue for successful modelling of the relations between the total consumption and its decomposed ... -
Universality of intermittent fluctuations in the Alcator C-Mod scrape-off layer
(Conference object; Konferansebidrag, 2017) -
Blob shapes in the scrape-off layer: Comparison of measurements to simulations
(Conference object; Konferansebidrag, 2017) -
Adhesive free PVDF copolymer focused transducers for high frequency acoustic imaging
(Conference object; Konferansebidrag, 2019)The present study has demonstrated to produce a reliable PVDF copolymer focused transducers from a layer-by-layer deposition method by engraving milled spherical cavies in a PEI polymer substrate. The proposed method which process P(VDF-TrFE) from the fluid phase, is adhesive-free in the sense that it does not require any additional adhesive layers for material binding. The transducer was acoustically ... -
Dust Trajectory Calculations in the Inner Heliosphere and Circumstellar Debris Disks
(Conference object; Konferansebidrag, 2018) -
Subseasonal Predictions of Polar Low Activity Using a Hybrid Statistical-Dynamical Approach
(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 ... -
21st Century Scenario Forcing Increases More for CMIP6 Than CMIP5 Models
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-16)Although the Coupled Model Intercomparison Project 6 (CMIP6) protocol provides an experiment to estimate effective radiative forcing (ERF), it is only quantified for few models. We present new estimates of ERF for models participating in CMIP6 by applying the method developed in Fredriksen et al. (2021, https://doi.org/10.1029/2020JD034145), and validate our approach with available fixed-SST forcing ... -
Improving sea surface temperature in a regional ocean model through refined sea surface temperature assimilation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-26)Infrared (IR) and passive microwave (PMW) satellite sea surface temperature (SST) retrievals are valuable to assimilate into high-resolution regional ocean forecast models. Still, there are issues related to these SSTs that need to be addressed to achieve improved ocean forecasts. Firstly, satellite SST products tend to be biased. Assimilating SSTs from different providers can thus cause the ocean ... -
3D full-wave multi-scattering forward solver for coherent microscopes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-21)A rigorous forward model solver for conventional coherent microscope is presented. The forward model is derived from Maxwell’s equations and models the wave behaviour of light matter interaction. Vectorial waves and multiple-scattering effect are considered in this model. Scattered field can be calculated with given distribution of the refractive index of the biological sample. Bright field images ... -
The altitude of green OI 557.7 nm and blue N2+ 427.8 nm aurora
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-06)We have performed a large statistical study of the peak emission altitude of green O(1D2–1S0) (557.7 nm) and blue 1 N (427.8 nm) aurora using observations from a network of all-sky cameras stationed across northern Finland and Sweden recorded during seven winter seasons from 2000 to 2007. Both emissions were found to typically peak at about 114 km. The distribution of blue peak altitudes is more ... -
Horizontal Correlation Functions of Wind Fluctuations in the Mesosphere and Lower Thermosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-01)Measurements of kinetic energy in vortical and divergent fluctuations in the mesosphere and lower thermosphere can be used to study stratified turbulence (ST) and gravity waves. This can be done using horizontal correlation functions of the fluctuating component of velocity. This study introduces a novel method for estimating these correlation functions using radars that observe Doppler shifts ... -
A Comparison of Arctic Ocean Sea Ice Export Between Nares Strait and the Canadian Arctic Archipelago
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-13)Nares Strait and the channels of the Canadian Arctic Archipelago (CAA) act as conduits for sea ice export from the Arctic Ocean but have never been directly compared. Here, we perform such a comparison for both the sea ice area and volume fluxes from October 2016 to December 2021. Nares Strait provided the largest average seasonal (October through September) ice area flux of 95 ± 8 × 10<sup>3</sup> ... -
Synoptic Variability in Satellite Altimeter-Derived Radar Freeboard of Arctic Sea Ice
(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 ...