Institutt for fysikk og teknologi: Recent submissions
Now showing items 201-220 of 1294
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Sea ice classification of TerraSAR-X ScanSAR images for the MOSAiC expedition incorporating per-class incidence angle dependency of image texture
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-16)We provide sea ice classification maps of a subweekly time series of single (horizontal–horizontal, HH) polarization X-band TerraSAR-X scanning synthetic aperture radar (TSX SC) images from November 2019 to March 2020, covering the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This classified time series benefits from the wide spatial coverage ... -
Solved and unsolved riddles about low-latitude daytime valley region plasma waves and 150-km echoes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-27)The Earth’s atmosphere near both the geographic and magnetic equators and at altitudes between 120 and 200 km is called the low-latitude valley region (LLVR) and is among the least understood regions of the ionosphere/thermosphere due to its complex interplay of neutral dynamics, electrodynamics, and photochemistry. Radar studies of the region have revealed puzzling daytime echoes scattered from ... -
Observations of the urban boundary layer in a cold climate city
(Journal article; Tidsskriftartikkel, 2022-11-30)Cold environment supports a large diversity of local climates. Among them, urban climates in northern cities stand out for their pronounced warm temperature anomaly known as the Urban Heat Island (UHI). UHI in northern cities has been already studies through satellite images and in-situ observations in the urban canopy layer (UCL). Yet, the vertical structure of the urban atmospheric boundary layer ... -
Borealis: An Advanced Digital Hardware and Software Design for SuperDARN Radar Systems
(Journal article; Tidsskriftartikkel, 2023-02-17)The Borealis radar system is a hardware and software upgrade to the conventional Super Dual Auroral Radar Network radar system, which has been used since the early 1990s. The conventional system has hardware and software that is aging, and many components are no longer supported. Limitations of the conventional system limit radar and data techniques for scientific discovery. Using software defined ... -
Instant Volume Microscopy of Organoids with SOLIS
(Journal article; Tidsskriftartikkel, 2023)Advancements in microscopy techniques have revolutionized our ability to explore the intricacies of biological systems, with engineered human heart tissue (EHT) being a particularly challenging target. In this article, we will have an in-depth look at the award-winning SOLIS technique (scanned oblique light-sheet instant-volume sectioning), a new twist on multifocus fluorescence microscopy. Through ... -
Apparent universality of 1/f spectra as an artifact of finite-size effects
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-29)Power spectral density scaling with frequency f as 1/ f <sup>β</sup> and β ≈ 1 is widely found in natural and socioeconomic systems. Consequently, it has been suggested that such self-similar spectra reflect the universal dynamics of complex phenomena. Here, we show that for a superposition of uncorrelated pulses with a power-law distribution of duration times the estimated scaling exponents β¯ ... -
Metasurface supporting quasi-BIC for optical trapping and Raman-spectroscopy of biological nanoparticles
(Journal article; Tidsskriftartikkel, 2023-02-09)Optical trapping combined with Raman spectroscopy have opened new possibilities for analyzing biological nanoparticles. Conventional optical tweezers have proven successful for trapping of a single or a few particles. However, the method is slow and cannot be used for the smallest particles. Thus, it is not adapted to analyze a large number of nanoparticles, which is necessary to get statistically ... -
Reconstruction of intermittent time series as a superposition of pulses
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05)Fluctuations in a vast range of physical systems can be described as a superposition of uncorrelated pulses with a fixed shape, a process commonly referred to as a (generalized) shot noise or a filtered Poisson process. In this paper, we present a systematic study of a deconvolution method to estimate the arrival times and amplitudes of the pulses from realizations of such processes. The method shows ... -
On Importance of Off-Diagonal Elements in the Polarimetric Covariance Matrix: A Sea Ice Application Perspective
(Conference object; Konferansebidrag, 2023-06) -
Optical Remote Sensing of Oil Spills by using Machine Learning Methods in the Persian Gulf: A Multi-Class Approach
(Master thesis; Mastergradsoppgave, 2023-06-15)Marine oil spills are harmful for the environment and costly for society. Coastal areas are particularly vulnerable since they provide habitats for organisms, animals and marine ecosystems. This thesis studied machine learning methods to classify thick oil in a multi-class case, using remotely sensed multi-spectral data in the Persian Gulf. The study area covers a large area between United Arab ... -
Solenergi i mikronett ved gårdsbruk på Røros
(Master thesis; Mastergradsoppgave, 2023-06-01)I denne masteroppgaven har jeg undersøkt hvilket solenergisystem som vil være det mest hensiktsmessige for å minimere belastningen på det lokale strømnettet på Røros. Dette ble gjort ved å se på dimensjonering av solenergianlegg og batteripakker i et mikronett. Dette gjorde jeg ved å bruke solstrålingsdatabaser, og basert på dagens solcelle- og batteriteknologi, beregne hvor mye strøm som kan ... -
Natural occuring oil seepages as a consequence of bottom trawling?
(Mastergradsoppgave; Master thesis, 2023-05-31)Bottom trawling is used to capture fish species that live in the seabed. The damage on the seabed trawling causes has been discussed for many years. This thesis aims to investigate whether bottom trawling for sand eels can be a cause for some of the detected oil seepages in the North Sea. We investigated this using manual delineation of oil seepages in Synthetic Aperture Radar (SAR) satellite ... -
Viewing life without labels under optical microscopes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-25)Optical microscopes today have pushed the limits of speed, quality, and observable space in biological specimens revolutionizing how we view life today. Further, specific labeling of samples for imaging has provided insight into how life functions. This enabled label-based microscopy to percolate and integrate into mainstream life science research. However, the use of labelfree microscopy has been ... -
Deep generative models for reject inference in credit scoring
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-21)Credit scoring models based on accepted applications may be biased and their consequences can have a statistical and economic impact. Reject inference is the process of attempting to infer the creditworthiness status of the rejected applications. Inspired by the promising results of semi-supervised deep generative models, this research develops two novel Bayesian models for reject inference in credit ... -
Learning latent representations of bank customers with the Variational Autoencoder
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-15)Learning data representations that reflect the customers’ creditworthiness can improve marketing campaigns, customer relationship management, data and process management or the credit risk assessment in retail banks. In this research, we show that it is possible to steer data representations in the latent space of the Variational Autoencoder (VAE) using a semi-supervised learning framework and a ... -
Oceanographic variability and change in two fjords in northern Norway
(Mastergradsoppgave; Master thesis, 2023-06-01)Long-term hydrographic time series data from two fixed stations in the northern Norwegian fjords Malangen and Balsfjorden from the period 1980 - 2022 have been examined. The data have been supplemented with model results from the ocean model NorFjords160 over the period April 1st 2017 to December 31st 2022. To gain a deeper understanding of the oceanographic variability and change, the environmental ... -
Conditional averaging of overlapping pulses
(Mastergradsoppgave; Master thesis, 2023-05-15)Conditional averaging is a signal processing method used to study turbulent fluctuations in a variety of fields. The method, in its simplest form, works by finding peaks in a signal that fulfill a certain size threshold. Equally sized excerpts of the signal around every peak are then cut out and averaged. This yields the average shape of the events that fulfill the condition. Based on the peak ... -
An investigation on the damping ratio of marine oil slicks in synthetic aperture radar imagery
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-12)The damping ratio has recently been used to indicate the relative internal oil thickness within oil slicks observed in synthetic aperture radar (SAR) imagery. However, there exists no well-defined and evaluated methodology for calculating the damping ratio. In this study, we review prior work regarding the damping ratio and outline its theoretical and practical aspects. We show that the most often ... -
Towards automation in the fish processing industry using machine learning
(Master thesis; Mastergradsoppgave, 2023-04-11)This master project was inspired by challenges faced by commercial fisheries in the north of Norway of controlling food quality and food safety. In this thesis, four different ML models’ ability to do object and keypoint detection on specific anatomy parts of fish, has been studied. With the aim of recommending a suitable model to be part of a CV system for an industrial fish gutting machine that ... -
A comparative study of lens-less and lens-based optical imaging using full electric field analysis
(Mastergradsoppgave; Master thesis, 2021-05-13)The focus of this thesis is to investigate the feasibility of a lens-less label-free microscope system, and compare this with a conventional lens-based microscope. The imaging performance of conventional microscopes are greatly dependent on the objective lens, due to their inherent physical space constraint and spherical aberrations. We, therefore, will investigate the conceptual feasibility of a ...