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norskInstitutt for fysikk og teknologi: Recent submissions
Now showing items 581-600 of 1407
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Electron Bulk Heating at Saturn’s Magnetopause
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-25)Magnetic reconnection at the magnetopause (MP) energizes ambient plasma via the release of magnetic energy and produces an “open” magnetosphere allowing solar wind particles to directly enter the system. At Saturn, the nature of MP reconnection remains unclear. The current study examines electron bulk heating at MP crossings, in order to probe the relationship between observed and predicted reconnection ... -
Wind Power Prediction with Machine Learning Methods in Complex Terrain Areas
(Master thesis; Mastergradsoppgave, 2021-06-29)The increasing amount of intermittant wind energy sources connected to the power grid present several challenges in balancing the power network. Accurate prediction of wind power production is identified as one of the most important measures for balancing the power network while maintaining a sustainable integration of wind power in the power grid. However, the volatile nature of wind makes wind ... -
Detection and Delineation of Produced Water Slicks in Sentinel-1 Synthetic Aperture Radar Images
(Master thesis; Mastergradsoppgave, 2021-06-21)Near oil and gas platforms oil detection services regularly detect oil slicks that are a result of legal releases of produced water. These slicks are usually observed using SAR imagery and the important task of observing and monitoring these slicks is as of now carried out manually by human operators aggregated with reported release information. In this thesis we propose three separate approaches ... -
Detection of Marine Plastic Debris in the North Pacific Ocean using Optical Satellite Imagery
(Master thesis; Mastergradsoppgave, 2021-06-15)Plastic pollution is ubiquitous across marine environments, yet detection of anthropogenic debris in the global oceans is in its infancy. Here, we exploit high-resolution multispectral satellite imagery over the North Pacific Ocean and information from GPS-tracked floating plastic conglomerates to explore the potential for detecting marine plastic debris via spaceborne remote sensing platforms. ... -
Fluorescence fluctuation-based super-resolution microscopy using multimodal waveguided illumination
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-19)Photonic chip-based total internal reflection fluorescence microscopy (c-TIRFM) is an emerging technology enabling a large TIRF excitation area decoupled from the detection objective. Additionally, due to the inherent multimodal nature of wide waveguides, it is a convenient platform for introducing temporal fluctuations in the illumination pattern. The fluorescence fluctuation-based nanoscopy technique ... -
Imputation and classification of time series with missing data using machine learning
(Mastergradsoppgave; Master thesis, 2021-06-21)This work is about classifying time series with missing data with the help of imputation and selected machine learning algorithms and methods. The author has used imputation to replace missing values in two data sets, one containing surgical site infection (SSI) data of 11 types of blood samples of patients over 20 days, and another data set called uwave which contain 3D accelerometer data of several ... -
Complexity-Entropy Analysis of Chaotic and Intermittent Fluctuations in Physical Systems
(Master thesis; Mastergradsoppgave, 2021-06-01)Time series from chaotic and stochastic systems share properties which can make it hard to distinguish them from each other. The Complexity-Entropy analysis provides appropriate measures of entropy and complexity and representing the calculated values in the representation space, the Complexity-Entropy plane, have been shown to be able to distinguish between time series of stochastic and chaotic ... -
Probabilistic Load Forecasting with Deep Conformalized Quantile Regression
(Master thesis; Mastergradsoppgave, 2021-06-01)The establishment of smart grids and the introduction of distributed generation posed new challenges in energy analytics that can be tackled with machine learning algorithms. The latter, are able to handle a combination of weather and consumption data, grid measurements, and their historical records to compute inference and make predictions. An accurate energy load forecasting is essential to assure ... -
Investigating the Impact of Susceptibility Artifacts on Adjacent Tumors in PET/MRI through Simulated Tomography Experiments
(Mastergradsoppgave; Master thesis, 2021-06-01)For quantitative PET imaging, attenuation correction (AC) is mandatory. Currently, all main vendors of hybrid PET/MRI systems apply a segmentation-based approach to compute a Dixon AC-map based on fat and water images derived from in- and opposed-phase MR-images. Changes in magnetic susceptibility pose major problems for MRI, which may lead to artifacts resulting in tissue misclassification in the ... -
Extracting Information from Multimodal Remote Sensing Data for Sea Ice Characterization
(Mastergradsoppgave; Master thesis, 2021-06-01)Remote sensing is the discipline that studies acquisition, preparation and analysis of spectral, spatial and temporal properties of objects without direct touch or contact. It is a field of great importance to understanding the climate system and its changes, as well as for conducting operations in the Arctic. A current challenge however is that most sensory equipment can only capture one or fewer ... -
Cross-platform application of a sea ice classification method considering incident angle dependency of backscatter intensity and its use in separating level and deformed ice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021)Wide-swath C-band synthetic aperture radar (SAR) has been used for sea ice classification and estimates of sea ice drift and deformation since it first became widely available in the 1990s. Here, we examine the potential to distinguish surface features created by sea ice deformation using ice type classification of SAR data. To perform this task with extended spatial and temporal coverage, we ... -
Newly-formed sea ice distinction near the oil platform Prirazlomnaya in the Pechora Sea using polarimetric Radarsat-2 SAR observations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-01)A polarimetric approach developed to discriminate oil slicks and look-alikes was used to study the polarimetric properties of newly-formed ice (NFI) observed near the Prirazlomnaya oil platform. This approach is based on the multipolarization parameter called Resonant to Non-resonant signal Damping (RND), which is related to the ratio between the ice damping and the short wind waves and wave breakings. ... -
Multi-mission remote sensing of low concentration produced water slicks
(Journal article; Tidsskriftartikkel, 2021-04)Produced water is legally released from oil platforms and often detected by oil spill detection services despite their low oil concentrations. Using fully-polarimetric RADARSAT-2 and dual-polarimetric Sentinel-1 data we investigate their synthetic aperture radar (SAR) characteristics. Detectability ranges within the SAR and optical Sentinel-2 and PlanetScope images are assessed and compared to in-situ ... -
Improving Chlorophyll-a Estimation from Sentinel-2 (MSI) in the Barents Sea using Machine Learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-22)This article addresses methodologies for remote sensing of ocean Chlorophyll-a (Chl-a), with emphasis on the Barents Sea. We aim at improving the monitoring capacity by integrating in situ Chl-a observations and optical remote sensing to locally train machine learning (ML) models. For this purpose, in situ measurements of Chl-a ranging from 0.014–10.81 mg/m <sup>3</sup> , collected for the years ... -
Towards Unsupervised Domain Adaptation for Diabetic Retinopathy Detection in the Tromsø Eye Study
(Mastergradsoppgave; Master thesis, 2021-05-29)Diabetic retinopathy (DR) is an eye disease which affects a third of the diabetic population. It is a preventable disease, but requires early detection for efficient treatment. While there has been increasing interest in applying deep learning techniques for DR detection in order to aid practitioners make more accurate diagnosis, these efforts are mainly focused on datasets that have been collected ... -
Detecting Unhealthy Comments in Norwegian using BERT
(Mastergradsoppgave; Master thesis, 2021-05-28)In this work we present a new Norwegian labeled dataset of 7078 comments for unhealthy comment detection. The dataset is used to fine-tune a BERT model, and demonstrates that BERT has the ability to detect subtle forms of toxicity, also in Norwegian. We compare how the different newly released Norwegian BERT models perform when fine-tuned on our dataset, and we also experiment with how English data ... -
Spectral shaping of ring resonator transmission response
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021)We present a Mach-Zehnder interferometer assisted ring resonator configuration (MARC) to realize resonator transmission spectra with unique spectral signatures and significantly large effective free spectral ranges. Transmission spectra with unique spectral signatures are generated by changing the angular separation between the through port and the drop port waveguides of the ring resonator (RR). ... -
Radar imaging with EISCAT 3D
(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 ... -
Predicting Energy Demand in Semi-Remote Arctic Locations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-03)Forecasting energy demand within a distribution network is essential for developing strategies to manage and optimize available energy resources and the associated infrastructure. In this study, we consider remote communities in the Arctic located at the end of the radial distribution network without alternative energy supply. Therefore, it is crucial to develop an accurate forecasting model to ... -
A new auroral phenomenon, the anti-black aurora
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-19)Black auroras are small-scale features embedded in the diffuse background aurora, typically occurring post-substorm after magnetic midnight and with an eastward drift imposed. Black auroras show a significant reduction in optical brightness compared to the surrounding diffuse aurora, and can appear as slow-moving arcs or rapidly-moving patches and arc segments. We report, for the first time, an even ...
