Institutt for fysikk og teknologi: Nye registreringer
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Defending Against Poisoning Attacks in Federated Learning with Blockchain
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-18)In the era of deep learning, federated learning (FL) presents a promising approach that allows multiinstitutional data owners, or clients, to collaboratively train machine learning models without compromising data privacy. However, most existing FL approaches rely on a centralized server for global model aggregation, leading to a single point of failure. This makes the system vulnerable to ... -
Machine learning for gap-filling in greenhouse gas emissions databases
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-07-10)Greenhouse gas (GHG) emissions datasets are often incomplete due to inconsistent reporting and poor transparency. Filling the gaps in these datasets allows for more accurate targeting of strategies aiming to accelerate the reduction of GHG emissions. This study evaluates the potential of machine learning methods to automate the completion of GHG datasets. We use three datasets of increasing complexity ... -
Turbulence Around Auroral Arcs
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-08-18)The spectacular visual displays from the aurora come from curtains of excited atoms and molecules, impacted by energetic charged particles. These particles are accelerated from great distances in Earth's magnetotail, causing them to precipitate into the ionosphere. Energetic particle precipitation is associated with currents that generate electric fields, and the end result is a dissipation of the ... -
Turbulence Embedded Into the Ionosphere by Electromagnetic Waves
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-08-19)When charged particles are accelerated from Earth's magnetosphere and precipitate into the atmosphere, their impact with neutral gas creates the aurora. Structured electric fields drive the acceleration processes but they are also passed down to the ionosphere, meaning that turbulence can in part be embedded into the ionosphere rather than emerge through instability processes locally. Applying a ... -
Incipient fault detection and isolation with Cauchy–Schwarz divergence: A probabilistic approach
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-08-02)To monitor the dynamics and non-stationarity inherent in industrial processes, we propose a novel incipient fault detection and isolation scheme grounded in a probabilistic perspective, using the Cauchy–Schwarz (CS) divergence. Our innovation lies in the utilization of marginal CS divergence for incipient fault detection and the conditional CS divergence for fault isolation. This approach neither ... -
Roadmap on computational methods in optical imaging and holography [invited]
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-08-29)Computational methods have been established as cornerstones in optical imaging and holography in recent years. Every year, the dependence of optical imaging and holography on computational methods is increasing significantly to the extent that optical methods and components are being completely and efficiently replaced with computational methods at low cost. This roadmap reviews the current scenario ... -
Characterizing the consistency of motion of spermatozoa through nanoscale motion tracing
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-07-06)Objective: To demonstrate nanoscale motion tracing of spermatozoa and present analysis of the motion traces to characterize the consistency of motion of spermatozoa as a complement to progressive motility analysis.<p> <p>Design: Anonymized sperm samples were videographed under a quantitative phase microscope, followed by generating and analyzing superresolution motion traces of individual ... -
Skibotn Astrofysiske Observatorium. Et forsøk på å innføre observasjonsastrofysikk i Norge 1971 - 2002 - Og hvordan det gikk etterpå.
(Book; Bok, 2024)I forbindelse med etableringen av Universitetet i Tromsø ble det undersøkt om det var gode nok forhold for infrarøde astrofysiske observasjoner i lange, kalde vinternetter i Indre Troms. Mest klarvær om vinteren fant vi i ytre del av Skibotndalen. Fjellet Addjet (1405 m.o.h) ble i 1974 foreslått som sted for observatorium. Dette ble imidlertid vurdert for krevende og kostbart. Det ble i stedet vedtatt ... -
The effect of spatial resolution on the in-cloud atmospheric icing conditions in numerical weather model at the Fargernes mountain, Norway
(Chapter; Bokkapittel, 2024-06)Atmospheric icing poses significant risks to infrastructure, aviation, and the energy section. Numerical weather models, as the Weather Research and Forecasting model (WRF), can be used to describe the atmospheric conditions relevant for atmospheric icing. In this study, we will focus on the Fagernes mountain meteorological icing measurement site where the WRF model is set up using ERA5 input data, ... -
Atmospheric In-cloud Icing Using WRF for an Alpine Wind Power Plant in Norway
(Chapter; Bokkapittel, 2024-06)Troms Kraft have identified a location in Kvænangen, Norway, for a new wind power plant with promising wind resources. However, the site is in an arctic climate with mountainous terrain exposed to severe icing conditions. Assessments of icing conditions at proposed locations for new wind power plants in areas exposed to icing is crucial to identifying icing related challenges. This paper investigates ... -
Snow on sea ice
(Chapter; Bokkapittel, 2023-08-01)The overlying snow cover on sea ice has a profound influence on what lies below. Being both highly optically reflective and thermally insulating, the snow influences the rate and timing with which the sea ice grows and melts seasonally. The shade introduced by the snow radically reduces the light intensity in and under the ice, affecting which organisms can survive there and how active they can be. ... -
Assessing the Transferability of Neural Network-Based Sea Ice Classification between the Arctic and Antarctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-09-05)In this study, we trained a supervised neural network for sea ice classification using X-band SAR images obtained during an Antarctic fieldwork campaign and applied it to Arctic X-band data acquired during sea ice fieldwork campaigns. The results revealed a pronounced correlation between the predicted sea ice class and measured snow depth in the Arctic. This correlation is likely attributed to the ... -
On the use of the polarization difference to separate young from deformed sea ice in L- and C-band SAR
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-09-05)Separation between deformed sea ice and high-backscatter young ice (YI) areas is one of the remaining challenges for automatic classification of sea ice types in synthetic aperture radar (SAR) images. While high-backscatter areas are usually interpreted and classified as deformed sea ice or multi-year ice, they may at times be new ice or YI areas with a rough surface due to frost flowers, snow crusts, ... -
Block-matching and 3D filtering-based denoising of acoustic images obtained through point contact excitation and detection method
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-01-13)A novel experimental method based on the Coulomb coupling technique is used for visualizing the interaction of ultrasonic waves in PZT (Lead Zirconate Titanate - (Pb[ZrxTi1-x]O3 (0 ≤ x ≤ 1)) ceramic materials. The method of excitation and detection through a point contact produces representations of propagating wave vectors in the time domain as a series of images. In the acoustic image, several ... -
2-D Total Electron Content and 3-D Ionospheric Electron Density Variations During the 14 October 2023 Annular Solar Eclipse
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-18)This study investigates the ionospheric total electron content (TEC) responses in the 2‐D spatial domain and electron density variations in the 3‐D spatial domain during the annular solar eclipse on 14 October 2023, using ground‐based Global Navigation Satellite System (GNSS) observations, a novel TEC‐based ionospheric data assimilation system (TIDAS), ionosonde measurements, and satellite in ... -
The Value of Sentinel-1 Ocean Wind Fields Component for the Study of Polar Lows
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-10)Polar lows can pose serious threats to maritime operations and coastal communities in polar regions, especially due to their extreme wind speeds. The accurate and reliable representation of their wind field thus plays a crucial role in forecasting and mitigating the risks associated with this phenomenon. This study aims to evaluate the value of the SAR-based Sentinel-1 Ocean Wind Field product ... -
LSNetv2: Improving weakly supervised power line detection with bipartite matching
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-24)This paper addresses the crucial task of power line detection and localization in electrical infrastructure inspection using Unmanned Aerial Vehicles (UAVs) from weak supervision, polyline annotations. We first identify several limitations in the state-of-the-art approach LSNet. In particular, the inability of LSNet to detect line-crossings and lines in close proximity. To overcome these limitations, ... -
Long-term performance evaluation of VCRS-based atmospheric water generation in arid climates
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-07-14)The paper evaluates the EW-1000 Atmospheric Water Generation-Vapor Compression Refrigeration system (AWG-VCRS) as a sustainable alternative to seawater desalination in the GCC. Conducted in Masdar City, Abu Dhabi, from July 2023 to January 2024, the study measured temperature, humidity, energy consumption, and water production. Key findings include a peak water production of 1500 LPD in September ... -
Presisjons fotometri ved Skibotn observatorium
(Master thesis; Mastergradsoppgave, 1996-12-17)Denne oppgaven viser at det er mulig å gjøre differensiell fotometri av ∂-Scuti stjerner med rimelig god presisjon ved Skibotn observatorium. Den høyeste presisjonen som ble oppnådd i C1-C2 var 28 mmag. Sammenligningen av den beste natten fra Skibotn med en god natt fra FG Vir kampanjen (året før) viser at muligheten er til stede for å oppnå gode resultater. En bekreftelse på dette fikk vi da to av ... -
Uncertainty analysis of Altantic salmon fish scale's acoustic impedance using 30 MHz C-Scan measurements
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-06-06)Understanding the biomechanics of fish scales is crucial for their survival and adaptation. Ultrasonic Cscan measurements offer a promising tool for non-invasive characterization, however, existing literature lacks uncertainty analysis while evaluating acoustic impedance. This article presents an innovative integration of uncertainty into the analytical framework for estimating stochastic specific ...