Institutt for fysikk og teknologi: Recent submissions
Now showing items 381-400 of 1402
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History of the Tromsø ionosphere heating facility
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-22)We present the historical background of the construction of a major ionospheric heating facility, “Heating”, near Tromsø, Norway, in the 1970s by the Max Planck Institute for Aeronomy; we also detail the facility’s subsequent operational history to the present. Heating was built next to the European Incoherent Scatter Scientific Association (EISCAT) incoherent scatter (IS) radar facility and in a ... -
Demystifying speckle field interference microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-27)Dynamic speckle illumination (DSI) has recently attracted strong attention in the feld of biomedical imaging as it pushes the limits of interference microscopy (IM) in terms of phase sensitivity, and spatial and temporal resolution compared to conventional light source illumination. To date, despite conspicuous advantages, it has not been extensively implemented in the feld of phase imaging due ... -
Arecibo measurements of D-region electron densities during sunset and sunrise: implications for atmospheric composition
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-02)Earth’s lower ionosphere is the region where terrestrial weather and space weather come together. Here, between 60 and 100 km altitude, solar radiation governs the diurnal cycle of the ionized species. This altitude range is also the place where nanometre-sized dust particles, recondensed from ablated meteoric material, exist and interact with free electrons and ions of the ionosphere. This ... -
On the Potential of Sequential and Nonsequential Regression Models for Sentinel-1-Based Biomass Prediction in Tanzanian Miombo Forests
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-03)This study derives regression models for aboveground biomass (AGB) estimation in miombo woodlands of Tanzania that utilize the high availability and low cost of Sentinel-1 data. The limited forest canopy penetration of C-band SAR sensors along with the sparseness of available ground truth restricts their usefulness in traditional AGB regression models. Therefore, we propose to use AGB predictions ... -
Evaluation of an emergent feature of sub-shelf melt oscillations from an idealized coupled ice sheet-ocean model using FISOC (v1.1) - ROMSIceShelf (v1.0) - Elmer/Ice (v9.0)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-15)Changes in ocean-driven basal melting have a key influence on the stability of ice shelves, the mass loss from the ice sheet, ocean circulation, and global sea level rise. Coupled ice sheet–ocean models play a critical role in understanding future ice sheet evolution and examining the processes governing ice sheet responses to basal melting. However, as a new approach, coupled ice sheet–ocean systems ... -
Ensemble Conformalized Quantile Regression for Probabilistic Time Series Forecasting
(Journal article; Tidsskriftartikkel, 2022-11-04)This article presents a novel probabilistic forecasting method called ensemble conformalized quantile regression (EnCQR). EnCQR constructs distribution-free and approximately marginally valid prediction intervals (PIs), which are suitable for nonstationary and heteroscedastic time series data. EnCQR can be applied on top of a generic forecasting model, including deep learning architectures. EnCQR ... -
Remote sensing image regression for heterogeneous change detection
(Conference object; Konferansebidrag, 2018-11-01)Change detection in heterogeneous multitemporal satellite images is an emerging topic in remote sensing. In this paper we propose a framework, based on image regression, to perform change detection in heterogeneous multitemporal satellite images, which has become a main topic in remote sensing. Our method learns a transformation to map the first image to the domain of the other image, and vice versa. ... -
Automatic Detection of Low-Backscatter Targets in the Arctic Using Wide Swath Sentinel-1 Imagery
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-12)Low backscatter signatures in synthetic aperture radar (SAR) imagery are characteristic to surfaces that are highly smooth and specular reflective of microwave radiation. In the Arctic, these typically represent newly formed sea ice, oil spills, and localized weather phenomena such as low wind or rain cells. The operational monitoring of low backscatter targets can benefit from a stronger integration ... -
Mission Performance Trade-offs of Battery-powered sUAS
(Chapter; Bokkapittel, 2017-07-27)A sensitivity analysis is presented on the influence of the weight, altitude and speed of battery-powered sUAS on the resulting stall speed, endurance and range. To aid in the determination of the aircraft performance prior to flight, a method is being brought forth that quantifies the impact of these mission parameters. As a case study the P31015 sUAS is used. The P31015 is a concept model of a ... -
Uncertainty-Aware Deep Ensembles for Reliable and Explainable Predictions of Clinical Time Series
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)Deep learning-based support systems have demonstrated encouraging results in numerous clinical applications involving the processing of time series data. While such systems often are very accurate, they have no inherent mechanism for explaining what influenced the predictions, which is critical for clinical tasks. However, existing explainability techniques lack an important component for trustworthy ... -
Multifocus microscopy with optically sectioned axial superresolution
(Journal article; Tidsskriftartikkel, 2022)Multifocus microscopy enables recording of entire volumes in a single camera exposure. In dense samples, multifocus microscopy is severely hampered by background haze. Here, we introduce a scalable multifocus method that incorporates optical sectioning and offers axial superresolution capabilities. In our method, a dithered oblique light-sheet scans the sample volume during a single exposure, while ... -
A year-round satellite sea-ice thickness record from CryoSat-2
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-14)Arctic sea ice is diminishing with climate warming at a rate unmatched for at least 1,000 years. As the receding ice pack raises commercial interest in the Arctic, it has become more variable and mobile, which increases safety risks to maritime users. Satellite observations of sea-ice thickness are currently unavailable during the crucial melt period from May to September, when they would be most ... -
RS-HeRR: a rough set-based Hebbian rule reduction neuro-fuzzy system
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-01)Interpretabilty is one of the desired characteristics in various classification task. Rule-based system and fuzzy logic can be used for interpretation in classification. The main drawback of rule-based system is that it may contain large complex rules for classification and sometimes it becomes very difficult in interpretation. Rule reduction is also difficult for various reasons. Removing important ... -
Oscillations:Linear theory and applications in AFM
(Research report; Forskningsrapport, 2022)The theory of oscillations can be studied from a mathematical point of view in terms of differential equations. The differential equation is written and then the solution or solutions worked out and mathematically analysed. Provided physical, economic, social, or other phenomena can be modelled in terms of equivalent differential equations, the solutions and results are applicable to all phenomena ... -
Towards population counting of marine mammals based on drone images
(Mastergradsoppgave; Master thesis, 2022-07-11)In marine science, there is a need for tools for population counting of species. Through this thesis we aim to achieve the follow three objectives: first, briefly discuss the state-of-the-art object detectors that can be used for the detection of porpoises in drone images/videos. Second, test and compare a few stateof-the-art object detectors in both quantitative and qualitative manner. Third, based ... -
Multifocus microscopy with optical sectioning and high axial resolution
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022)Multifocus microscopy enables recording of entire volumes in a single camera 11 exposure. In dense samples, multifocus microscopy is severely hampered by background haze. 12 Here, we introduce a scalable multifocus method that incorporates optical sectioning and offers 13 improved axial resolution capabilities. In our method, a dithered oblique light-sheet scans the 14 sample volume during a ... -
Springtime nitrogen oxides and tropospheric ozone in Svalbard: results from the measurement station network
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-09)Svalbard is a remote and scarcely populated Arctic archipelago and is considered to be mostly influenced by long-range-transported air pollution. However, there are also local emission sources such as coal and diesel power plants, snowmobiles and ships, but their influence on the background concentrations of trace gases has not been thoroughly assessed. This study is based on data of tropospheric ... -
Rapid Colorimetric pH-Responsive Gold Nanocomposite Hydrogels for Sensing Applications
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-27)Surface functionalization of metallic nanoparticles (NPs) with external groups can be engineered to fabricate sensors that are responsive to various stimuli like temperature, pH, and numerous ions. Herein, we report the synthesis of gold nanoparticles (GNPs) functionalized with 3-mercaptopropionic acid (GNPs-MPA) and the doping of these nanoparticles into hydrogel materials using the ... -
Configuring electrochemical 3D printer for PCB production
(Master thesis; Mastergradsoppgave, 2022-08-02)In this document I look at an electrochemical 3D printer and compare it to a more established machine for the making of printing printed circuit board. -
A new Method for Estimating 3-Dimensional Ionospheric Currents from Ground-Based Magnetometers
(Mastergradsoppgave; Master thesis, 2022-07-17)The ionosphere is a region of the upper atmosphere where a significant rate of photo-ionisation from solar ultraviolet radiation cause an increased plasma density. In this region a system of electrical currents flow, driven by electric fields generated by fluctuating dynamics within the Earths magnetosphere. These fluctuating dynamics are caused by interactions between the magnetosphere and the solar ...