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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 ... -
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 ... -
Statistical Studies of Plasma Structuring in the Auroral Ionosphere by the Swarm Satellites
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-02-11)This study uses over 2 years of 16 Hz density measurements, 50 Hz magnetic field data and ROTI data from the Swarm mission to perform long term statistics of plasma structuring in the polar ionosphere. The timeframe covers more than 2 years near the 24th solar cycle peak. We additionally use 3 years of data obtained from a timeframe close to solar minimum for discussion. We present power spectral ... -
On the impact of net-zero forcing Q-flux change
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-02-22)Numerical climate model simulations suggest that global warming is enhanced or hampered by the spatial pattern of the warming itself. This phenomenon is known as the “pattern effect” and has in recent years become the most promising explanation for the change over time of climate sensitivity in climate models. Under historical global warming, different patterns of surface-temperature change have ... -
Stochastic modeling of blob-like plasma filaments in the scrape-off layer: Correlated amplitudes and velocities
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-19)A stochastic model for a superposition of uncorrelated pulses with a random distribution of amplitudes, sizes, and velocities is analyzed. The pulses are assumed to move radially with fixed shape and amplitudes decreasing exponentially in time due to linear damping. The pulse velocities are taken to be time-independent but randomly distributed. The implications of a broad distribution of pulse ... -
Probabilistic impact localization in composites using wavelet scattering transform and multi-output Gaussian process regression
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-06-14)Data-driven machine-learning models offer considerable promise for acoustic source localization. However, many existing models rely on training data that correlates time-of-flight (TOF) measurements with source locations, yet they struggle to handle the complexities arising from nonlinear wave propagation in materials with varying properties. Furthermore, these models overlook the noise and ... -
Statistical Analysis of Off-Great Circle Radio Wave Propagation in the Polar Cap
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-08)High latitude ionospheric density structures such as polar cap patches and arcs are capable of deflecting high frequency (HF) radio waves to off‐great circle paths, and are likely detrimental to technologies dependent on HF radio propagation. In this study, nearly 2.5 years of 4.6–14.4 MHz data from a multi‐frequency HF radio link between Qaanaaq, Greenland and Alert, Canada are used to investigate ... -
A mesoscopic axially swept oblique plane microscope for imaging of freely moving organisms with near-isotropic resolution
(Journal article; Tidsskriftartikkel, 2024-08-09)Rapid three-dimensional imaging over extended fields of views (FOVs) is crucial to the study of organism-wide systems and biological processes in vivo. Selective-plane illumination microscopy (SPIM) is a powerful method for high spatio-temporal resolution in toto imaging of such biological specimens. However, typical SPIM implementations preclude conventional sample mounting and have anisotropic ... -
Arctic Freeboard and Snow Depth From Near-Coincident CryoSat-2 and ICESat-2 (CRYO2ICE) Observations: A First Examination of Winter Sea Ice During 2020–2022
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-18)In the summer of 2020, ESA changed the orbit of CryoSat-2 to align periodically with NASA's ICESat-2 mission, a campaign known as CRYO2ICE, which allows for near-coincident CryoSat-2 and ICESat-2 observations in space and time over the Arctic until summer 2022, where the CRYO2ICE Antarctic campaign was initiated. This study investigates the Arctic CRYO2ICE radar and laser freeboards acquired by ... -
Quantification of impedance and mechanical properties of Zeonor using scanning acoustic microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-27)This article explores the potential of Zeonor, a transparent cyclic olefin polymer, for applications in transparent acoustic/photo-acoustic transducers. Despite its widespread use in optics, microfluidics, medical devices, and electronics, Zeonor’s acoustic properties remain understudied. To extend this, the current work employs scanning acoustic microscopy (SAM) to obtain its mechanical properties. ... -
An exploratory study of self-supervised pre-training on partially supervised multi-label classification on chest X-ray images
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-06-14)This paper serves as the first empirical study on self-supervised pre-training on partially supervised learning, an emerging yet unexplored learning paradigm with missing annotations. This is particularly important in the medical imaging domain, where label scarcity is the main challenge of practical applications. To promote the awareness of partially supervised learning, we leverage partially ... -
Deep learning derived input function in dynamic [18F]FDG PET imaging of mice
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-11)Dynamic positron emission tomography and kinetic modeling play a critical role in tracer development research using small animals. Kinetic modeling from dynamic PET imaging requires accurate knowledge of an input function, ideally determined through arterial blood sampling. Arterial cannulation in mice, however, requires complex, time-consuming and terminal surgery, meaning that longitudinal ... -
Using clustering to understand intra-city warming in heatwaves: insights into Paris, Montreal, and Zurich
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-05-10)We introduce a novel methodological advancement by clustering paired near-surface air temperature with the planetary boundary layer height to characterize intra-city clusters for analytics. To illustrate this approach, we analyze three heatwaves (HWs): the 2019 HW in Paris, the 2018 HW in Montreal, and the 2017 HW in Zurich. We assess cluster-based characteristics before, during, and after ...
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