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norskBlar i tittel Artikler, rapporter og annet (fysikk og teknologi)
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Machine Learning Automatic Model Selection Algorithm for Oceanic Chlorophyll-a Content Retrieval
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-17)Ocean Color remote sensing has a great importance in monitoring of aquatic environments. The number of optical imaging sensors onboard satellites has been increasing in the past decades, allowing to retrieve information about various water quality parameters of the world’s oceans and inland waters. This is done by using various regression algorithms to retrieve water quality parameters from remotely ... -
Machine learning derived input-function in a dynamic 18F-FDG PET study of mice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-13)Tracer kinetic modelling, based on dynamic <sup>18</sup>F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is used to quantify glucose metabolism in humans and animals. Knowledge of the arterial input-function (AIF) is required for such measurements. Our aim was to explore two non-invasive machine learning-based models, for AIF prediction in a small-animal dynamic FDG PET study. 7 tissue ... -
Machine Learning Detection of Dust Impact Signals Observed by The Solar Orbiter
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-11)This article present results from automatic detection of dust impact signals observed by the Solar Orbiter – Radio and Plasma Waves instrument.<p> <p>A sharp and characteristic electric field signal is observed by the Radio and Plasma Waves instrument when a dust particle impact the spacecraft at high velocity. In this way, ∼5–20 dust impacts are daily detected as the Solar Orbiter travels through ... -
Machine Learning for Arctic Sea Ice Physical Properties Estimation Using Dual-Polarimetric SAR Data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-22)This work introduces a novel method that combines machine learning (ML) techniques with dual-polarimetric (dual-pol) synthetic aperture radar (SAR) observations for estimating quad-polarimetric (quad-pol) parameters, which are presumed to contain geophysical sea ice information. In the training phase, the output parameters are generated from quad-pol observations obtained by Radarsat-2 (RS2), and ... -
Machine Learning simulations of quad-polarimetric features from dual-polarimetric measurements over sea ice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06)In this paper, we investigated the capabilities of the Gaussian Process Regression (GPR) algorithm in predicting of two quad-polarimetric parameters (relevant for sea ice analysis) from 6-dimensional dual-polarimetric input vectors. The GRP is trained on few hundred samples selected randomly from an image subset, and tested on the entire image. The performance is assessed by visual comparisons, and ... -
Magnetic field-aligned plasma currents in gravitational fields
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-03-03)Analytical models are presented for currents along vertical magnetic field lines due to slow bulk electron motion in plasmas subject to a gravitational force. It is demonstrated that a general feature of this problem is a singularity in the plasma pressure force that develops at some finite altitude when a plasma that is initially in static equilibrium is set into slow motion. Classical fluid models ... -
Magnetopause Compressibility at Saturn with Internal Drivers
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-07)We use magnetopause crossings of the Cassini spacecraft to study the response of Saturn's magnetosphere to changes in external and internal drivers. We explain how solar wind pressure can be corrected to account for the local variability in internal plasma particle pressure. The physics‐based method is applied to perform the most robust estimation of magnetopause compressibility at Saturn to date, ... -
Magnetotelluric signatures of the complex tertiary fold–thrust belt and extensional fault architecture beneath Brøggerhalvøya, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-18)Magnetotelluric (MT) data were recently collected on Brøggerhalvøya, Svalbard, in a 0.003–1000 s period range along a curved WNW–ESE profile. The collected data manifested strong three-dimensional (3D) effects. We modelled the full impedance tensor with tipper and bathymetry included in 3D, and benchmarked the result with determinant data two-dimensional (2D) inversion. The final inversion results ... -
Magnitude of extreme heat waves in present climate and their projection in a warming world
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014)An extreme heat wave occurred in Russia in the summer of 2010. It had serious impacts on humans and natural ecosystems, it was the strongest recorded globally in recent decades and exceeded in amplitude and spatial extent the previous hottest European summer in 2003. Earlier studies have not succeeded in comparing the magnitude of heat waves across continents and in time. This study introduces a new ... -
Malin letar oljespill i ishavet
(Chronicle; Kronikk, 2020-03-13) -
Manx Arrays: Perfect Non-Redundant Interferometric Geometries
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-09)Interferometry applications (e.g., radio astronomy) often wish to optimize the placement of the interferometric elements. One such optimal criterion is a uniform distribution of non-redundant element spacings (in both distance and position angle). While large systems, with many elements, can rely on saturating the sample space, and disregard “wasted” sampling, small arrays with only a few elements ... -
Mapping sea-ice types from Sentinel-1 considering the surface-type dependent effect of incidence angle
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-23)Automated classification of sea-ice types in Synthetic Aperture Radar (SAR) imagery is complicated by the class-dependent decrease of backscatter intensity with Incidence Angle (IA). In the log-domain, this decrease is approximately linear over the typical range of space-borne SAR instruments. A global correction does not consider that different surface types show different rates of decrease in ... -
Mapping the extent of giant Antarctic icebergs with deep learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-09)Icebergs release cold, fresh meltwater and terrigenous nutrients as they drift and melt, influencing the local ocean properties, encouraging sea ice formation and biological production. To locate and quantify the fresh water flux from Antarctic icebergs, changes in their area and thickness have to be monitored along their trajectories. While the locations of large icebergs are operationally tracked ... -
Maximizing Interpretability and Cost-Effectiveness of Surgical Site Infection (SSI) Predictive Models Using Feature-Specific Regularized Logistic Regression on Preoperative Temporal Data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-19)This study describes a novel approach to solve the surgical site infection (SSI) classification problem. Feature engineering has traditionally been one of the most important steps in solving complex classification problems, especially in cases with temporal data. The described novel approach is based on abstraction of temporal data recorded in three temporal windows. Maximum likelihood L1-norm ... -
Measurement of inner wall limiter SOL widths in KSTAR tokamak
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-27)Scrape-off layer (SOL) widths <i>λ<sub>q</sub></i> are presented from the KSTAR tokamak using fast reciprocating Langmuir probe assembly (FRLPA) measurements at the outboard mid-plane (OMP) and the infra-Red (IR) thermography at inboard limiter tiles in moderately elongated (<i>κ</i> = 1.45 – 1.55) L-mode inner wall-limited (IWL) plasmas under experimental conditions such as B<sub>T</sub> = 2.0 T, ... -
Measurement of Oil Slick Transport and Evolution in the Gulf of Mexico using L-band Synthetic Aperture Radar
(Journal article; Tidsskriftartikkel, 2018-06)The transport and evolution of a mineral oil slick originating at a seep in the Gulf of Mexico approximately 16 km offshore of the mouth of the Mississippi River is measured using a series of images acquired at 40 minute intervals with the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), an L-band, high resolution, high signal-to-noise instrument operated by the U.S. National Aeronautics ... -
Measurement of snow water equivalent using drone-mounted ultra-wide-band radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-02)The use of unmanned aerial vehicle (UAV)-mounted radar for obtaining snowpack parameters has seen considerable advances over recent years. However, a robust method of snow density estimation still needs further development. The objective of this work is to develop a method to reliably and remotely estimate snow water equivalent (SWE) using UAV-mounted radar and to perform initial field experiments. ... -
Measurements of ionic liquids thermal conductivity and thermal diffusivity
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-02)Thermal conductivity and thermal diffusivity of ionic liquids (ILs) are investigated in this work. A hot disk method for ILs thermal conductivity and thermal diffusivity measurement is utilized. Firstly, the thermal conductivity of water is measured to check the reliability of the hot disk method. In addition, the thermal conductivity of pure ILs, including BmimBF<sub>4</sub>, BmimPF<sub>6</sub>, ... -
Measuring Wind Speed Using the Internal Stabilization System of a Quadrotor Drone
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-16)This article proposes a method of measuring wind speed using the data logged by the autopilot of a quadrotor drone. Theoretical equations from works on quadrotor control are utilized and supplemented to form the theoretical framework. Static thrust tests provide the necessary parameters for calculating wind estimates. Flight tests were conducted at a test site with laminar wind conditions with the ... -
Mesopause dynamics from the scandinavian triangle of radars within the PSMOS-DATAR Project.
(Journal article; Peer reviewed; Tidsskriftartikkel, 2004-01-01)The "Scandinavian Triangle" is a unique trio of radars within the DATAR Project (Dynamics and Temperatures from the Arctic MLT (60–97km) region): Andenes MF radar (69°N, 16°E); Tromsø MF radar (70°N, 19°E) and Esrange "Meteor" radar (68°N, 21°E). The radar-spacings range from 125-270km, making it unique for studies of wind variability associated with small-scale waves, comparisons of large-scale ...
