Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 321-340 of 4870
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Numerical evaluation of line, surface and toroidal integrals on level sets of toroidally symmetric functions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-05)We investigate strategies to numerically integrate closed lines and surfaces that are implicitly defined by level sets (iso-contours) of continuously differentiable toroidally symmetric functions. The “grid-transform” approach transforms quantities given in non-surface-aligned coordinates onto a numerically constructed surface-aligned grid. Here, line and surface integrals, as well as so-called ... -
Numerical Investigation of Radiative Hybrid Nanofluid Flows over a Plumb Cone/Plate
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-18)Non-Newtonian fluids play a crucial role in applications involving heat transfer and mass transfer. The inclusion of nanoparticles in these fluids improves the efficiency of heat and mass transfer processes. This study employs a numerical solution approach to examine the flow of non-Newtonian hybrid nanofluids over a plumb cone/plate surface, considering the effects of magnetohydrodynamics (MHD) and ... -
Ionospheric Flow Vortex Induced by the Sudden Decrease in the Solar Wind Dynamic Pressure
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-30)Abrupt changes in the solar wind dynamic pressure can greatly affect the Earth's magnetosphere-ionosphere system. We present an ionospheric flow vortex in the morning sector during the sudden decrease in the solar wind dynamic pressure. The flow vortex was clearly observed by both the Hankasalmi radar and the azimuthal scan mode of the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR). The ... -
3D refractive index reconstruction from phaseless coherent optical microscopy data using multiple scattering-based inverse solvers - a study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-27)Reconstructing 3D refractive index profile of scatterers using optical microscopy measurements presents several challenges over the conventional microwave and RF domain measurement scenario. These include phaseless and polarization-insensitive measurements, small numerical aperture, as well as a Green's function where spatial frequencies are integrated in a weighted manner such that far-field angular ... -
Analysis of Deep Convolutional Neural Networks Using Tensor Kernels and Matrix-Based Entropy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-03)Analyzing deep neural networks (DNNs) via information plane (IP) theory has gained tremendous attention recently to gain insight into, among others, DNNs’ generalization ability. However, it is by no means obvious how to estimate the mutual information (MI) between each hidden layer and the input/desired output to construct the IP. For instance, hidden layers with many neurons require MI estimators ... -
Analyzing the Impact of Peak-Shaving on Load Reduction and on Battery Energy Storage System Degradation: A Simulation-Based Study in Husøy
(Mastergradsoppgave; Master thesis, 2023-11-14)The island of Husøy, in Northern Senja, Norway, faces numerous voltage quality difficulties, which arise from the consequent surge in electricity demand by the local growing fishing industry. Collaborating with the local distribution system operator (DSO), Arva, the current study explores the implementation of Battery Energy Storage Systems (BESS) using a peak-shaving strategy to alleviate high-demand ... -
Toward a Collaborative Platform for Hybrid Designs Sharing a Common Cohort
(Doctoral thesis; Doktorgradsavhandling, 2024-01-18)<p>This doctoral thesis binds together four included papers in a thematical whole and is simultaneously an independent work proposing a platform facilitating epidemiological research. <p><i>Population-based prospective cohort studies</i> typically recruit a relatively large group of participants representative of a studied population and follow them over years or decades. This group of participants ... -
Local Seismicity and Sediment Deformation in the West Svalbard Margin: Implications of Neotectonics for Seafloor Seepage
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-12)In the Fram Strait, mid-ocean ridge spreading is represented by the ultra-slow system of the Molloy Ridge, the Molloy Transform Fault and the Knipovich Ridge. Sediments on oceanic and continental crust are gas charged and there are several locations with documented seafloor seepage. Sedimentary faulting shows recent stress release in the sub-surface, but the drivers of stress change and its influence ... -
Towards high-throughput screening (HTS) of polyhydroxyalkanoate (PHA) production via Fourier transform infrared (FTIR) spectroscopy of Halomonas sp. R5-57 and Pseudomonas sp. MR4-99
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-08) -
Sea-spray measurement tools and technique employed in marine icing field expeditions: A critical literature review and assessment using CFD simulations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-24)Sea-spray icing resulting from sea spray droplets accreting on exposed surfaces poses a significant safety concern for vessels and marine structures operating in cold climate regions. One of the key parameters determining the amount of ice accretion is the quantity of incoming sea spray, which eventually comes in contact with the structure in the presence of brine film freezing temperature. Hence, ... -
On Measures of Uncertainty in Classification
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-12)Uncertainty is unavoidable in classification tasks and might originate from data (e.g., due to noise or wrong labeling), or the model (e.g., due to erroneous assumptions, etc). Providing an assessment of uncertainty associated with each outcome is of paramount importance in assessing the reliability of classification algorithms, especially on unseen data. In this work, we propose two measures of ... -
Interplay between advective, diffusive and active barriers in (rotating) Rayleigh-Bénard flow
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-22)Our understanding of the material organization of complex fluid flows has benefited recently from mathematical developments in the theory of objective coherent structures. These methods have provided a wealth of approaches that identify transport barriers in three-dimensional (3-D) turbulent flows. Specifically, theoretical advances have been incorporated into numerical algorithms that extract ... -
Simultaneous Global Ionospheric Disturbances Associated With Penetration Electric Fields During Intense and Minor Solar and Geomagnetic Disturbances
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-29)A new observational phenomenon, named Simultaneous Global Ionospheric Density Disturbance (SGD), is identified in GNSS total electron content (TEC) data during periods of three typical geospace disturbances: a Coronal Mass Ejection-driven severe disturbance event, a high-speed stream event, and a minor disturbance day with a maximum Kp of 4. SGDs occur frequently on dayside and dawn sectors, with ... -
The effect of a water-ice mantle on dust trajectories in the Kuiper belt
(Mastergradsoppgave; Master thesis, 2023-07-12)The New Horizons spacecraft has travelled through the Solar System and has reached a distance of 55 AU as of 2023. For one of the first times, the dust flux in the outer Solar System has been measured, using the instrument Student Dust Counter (SDC) onboard New Horizons. Between 30 and 50 AU is the Kuiper belt, which is a disk consisting of icy objects. These objects can undergo collisions, causing ... -
Revisiting the ‘Whys’ and ‘Hows’ of the Warm-Up: Are We Asking the Right Questions?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-02)The warm-up is considered benefcial for increasing body temperature, stimulating the neuromuscular system and overall preparing the athletes for the demands of training sessions and competitions. Even when warm-up–derived benefts are slight and transient, they may still beneft preparedness for subsequent eforts. However, sports training and competition performance are highly afected by contextual ... -
A deep learning approach for anomaly identification in PZT sensors using point contact method
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-21)The implementation of piezoelectric sensors is degraded due to surface defects, delamination, and extreme weathering conditions, to mention a few. Hence, the sensor needs to be diagnosed before the efficacious implementation in the structural health monitoring (SHM) framework. To rescue the problem, a novel experimental method based on Coulomb coupling is utilised to visualise the evolution of ... -
Investigating Spatial and Temporal Structuring of E-Region Coherent Scattering Regions Over Northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-26)Recently, it has been shown that the Spread Spectrum Interferometric Multistatic meteor radar Observing Network radar system located in northern Norway is capable of measuring ionospheric E-region coherent scatter with spatial and temporal resolutions on the order of 1.5 km and 2 s, respectively. Four different events from June and July of 2022 are examined in the present study, where the coherent ... -
Elevated methane alters dissolved organic matter composition in the Arctic Ocean cold seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-15)Cold seeps release methane (CH<sub>4</sub>) from the seafloor to the water column, which fuels microbially mediated aerobic methane oxidation (MOx). Methane-oxidising bacteria (MOB) utilise excess methane, and the MOB biomass serves as a carbon source in the food web. Yet, it remains unclear if and how MOx modifies the composition of dissolved organic matter (DOM) in cold seeps. We investigated MOx ... -
Effects of subglacial meltwater runoff on the ocean circulation beneath the Filchner Ice Shelf
(Mastergradsoppgave; Master thesis, 2023-06-15)Antarctic ice shelves, by restraining ice streams and affecting the discharge of grounded ice, play a critical role in the mass balance of the Antarctic ice sheet. In this study, sub-ice shelf CTD measurements and time series data from an ice shelf cavity mooring were used to detect subglacial runoff beneath the Filchner Ice Shelf. CTD measurements from four boreholes across the southern Filchner ... -
On the Linkage Between Rossby Waves and Heatwaves
(Mastergradsoppgave; Master thesis, 2023-05-14)This thesis examines the relationship between upper-level atmospheric circulation and heatwaves. We studied the role of planetary Rossby waves in the observed increase in intensity, frequency, and duration of extreme temperature events in the mid-latitudes. Focusing on the summer season, we tested the proposed hypothesis that links recent changes in the Rossby wave amplitudes and propagation speed ...