Artikler, rapporter og annet (fysikk og teknologi): Nye registreringer
Viser treff 321-340 av 947
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Physics-based machine learning for subcellular segmentation in living cells
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-15)Segmenting subcellular structures in living cells from fluorescence microscope images is a ground truth (GT)-deficient problem. The microscopes’ three-dimensional blurring function, finite optical resolution due to light diffraction, finite pixel resolution and the complex morphological manifestations of the structures all contribute to GT-hardness. Unsupervised segmentation approaches are quite ... -
Multiobjective optimization of a hybrid wind/solar battery energy system in the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-30)This paper presents an optimal design of a hybrid wind turbine/PV/battery energy system for a household application using a multiobjective optimization approach, namely, particle swarm optimization (PSO). The ultimately optimal component selection of the hybrid renewable energy system (HRES) is suggested by comprehensively investigating the effects of various factors on the cost-reliability relation, ... -
Multiresolution Dynamic Mode Decomposition (mrDMD) of Elastic Waves for Damage Localisation in Piezoelectric Ceramic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-27)The performance of piezoelectric sensors deteriorated due to the presence of defect, delamination, and corrosion that needed to be diagnosed for the effective implementation of the structural health monitoring (SHM) framework. A novel experimental approach based on Coulomb coupling is devised to visualise the interaction of ultrasonic waves with microscale defects in the Lead Zirconate Titanate ... -
Detecting and Interpreting Faults in Vulnerable Power Grids With Machine Learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-10)Unscheduled power disturbances cause severe consequences both for customers and grid operators. To defend against such events, it is necessary to identify the causes of interruptions in the power distribution network. In this work, we focus on the power grid of a Norwegian community in the Arctic that experiences several faults whose sources are unknown. First, we construct a data set consisting ... -
Electron Density Depletion Region Observed in the Polar Cap Ionosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-16)This paper presents and discusses electron density depletion regions observed with the incoherent scatter EISCAT Svalbard Radar (ESR) located at 75.43°N geomagnetic latitude. The data include several decades of measurements, which make them suitable for studying statistical features and characteristics of the ionospheric parameters. Here we focus on the electron density depletions and their dependence ... -
Deriving high contrast fluorescence microscopy images through low contrast noisy image stacks
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-11)Contrast in fluorescence microscopy images allows for the differentiation between different structures by their difference in intensities. However, factors such as point-spread function and noise may reduce it, affecting its interpretability. We identified that fluctuation of emitters in a stack of images can be exploited to achieve increased contrast when compared to the average and Richardson-Lucy ... -
Sol-Gel Thin Film Processing for Integrated Waveguide Sensors
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-05)Integrated opto-chemical sensors present great advantages in comparison to the current lab equipment. They bring portability, reduced costs, facilitate in-situ measurements, as well as largely reduced sample volumes. In this quest, standard processing protocols over established materials, such as silicon nitride, silicon, silicon dioxide, titanium oxide, and even a wide variety of polymers have so ... -
Modelling the influence of meteoric smoke particles on artificial heating in the D-region
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-17)We investigate if the presence of meteoric smoke particles (MSPs) influences the electron temperature during artificial heating in the D-region. By transferring the energy of powerful high-frequency radio waves into thermal energy of electrons, artificial heating increases the electron temperature. Artificial heating depends on the height variation of electron density. The presence of MSPs can ... -
Ocean Applications
(Chapter; Bokkapittel, 2021-05-11)In this chapter, the most promising techniques to observe oil slicks and to detect metallic targets at sea using polarimetric synthetic aperture radar (SAR) data are reviewed and critically analysed. The detection of oil slicks in SAR data is made difficult not only by the presence of speckle but also by the presence of, e.g. biogenic films, low-wind areas, rain cells, currents, etc., which increase ... -
Comparison between mirror Langmuir probe and gas-puff imaging measurements of intermittent fluctuations in the Alcator C-Mod scrape-off layer
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-30)Statistical properties of the scrape-off layer plasma fluctuations are studied in ohmically heated plasmas in the Alcator C-Mod tokamak. For the first time, plasma fluctuations as well as parameters that describe the fluctuations are compared across measurements from a mirror Langmuir probe (MLP) and from gas-puff imaging (GPI) that sample the same plasma discharge. This comparison is complemented ... -
High spatial and temporal resolution L- and C-band Synthetic Aperture Radar data analysis from the yearlong MOSAiC expedition
(Conference object; Konferansebidrag, 2021-04)In the yearlong MOSAIC expedition (2019-2020) R/V Polarstern drifted with sea ice through the Arctic Ocean, with the goal to continually monitor changes in the coupled ocean-ice-atmosphere system throughout the seasons. A substantial amount of synthetic aperture radar (SAR) satellite images overlapping the campaign was collected. Here, we investigate the change in polarimetric features over sea ice ... -
The Structure of Climate Variability Across Scales
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-05)One of the most intriguing facets of the climate system is that it exhibits variability across all temporal and spatial scales; pronounced examples are temperature and precipitation. The structure of this variability, however, is not arbitrary. Over certain spatial and temporal ranges, it can be described by scaling relationships in the form of power laws in probability density distributions and ... -
First dust measurements with the Solar Orbiter Radio and plasma wave instrument
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-14)Context - Impacts of dust grains on spacecraft are known to produce typical impulsive signals in the voltage waveform recorded at the terminals of electric antennas. Such signals (as may be expected) are routinely detected by the Time Domain Sampler (TDS) system of the Radio and Plasma Waves (RPW) instrument on board Solar Orbiter.<p> <p>Aims - We investigate the capabilities of RPW in terms of ... -
Dynamics of nanodust in the vicinity of a stellar corona: Effect of plasma corotation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-24)Context - In the vicinity of the Sun or other stars, the motion of the coronal and stellar wind plasma must include some amount of corotation, which could affect the dynamics of charged dust particles. In the case of the Sun, this region is now investigated in situ by the Parker Solar Probe. Charged dust particles coming from the vicinity of the Sun can also reach, and possibly be detected by, ... -
Endocytic motif on a biotin-tagged hiv-1 env modulates the co-transfer of env and gag during cell-to-cell transmission
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-31)During HIV-1 transmission through T cell virological synapses, the recruitment of the envelope (Env) glycoprotein to the site of cell–cell contact is important for adhesion and for packaging onto nascent virus particles which assemble at the site. Live imaging studies in CD4 T cells have captured the rapid recruitment of the viral structural protein Gag to VSs. We explored the role of endocytic ... -
Charged dust in the D-region incoherent scatter spectrum
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-14)We investigate the influence of charged dust on the incoherent scatter from the D-region ionosphere. Incoherent scatter is observed with high-power, large aperture radars and results from electromagnetic waves scattering at electrons that are coupled to other charged components through plasma oscillations. The influence of charged dust can hence be considered an effect of dusty plasma. The D-region ... -
Towards automatic detection of dark features in the Barents Sea using synthetic aperture radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-17)Increased human presence and commercial activities in the Barents Sea (fishing, offshore oil and gas exploration) are amplifying the need for large-scale operational ocean monitoring of the eventual oil spills in the region. The geographical location and climate impose additional constraints on satellite-based monitoring, making it necessary to use Synthetic Aperture Radar (SAR). Dark features or ... -
A comparison of contact charging and impact ionization in low-velocity impacts: implications for dust detection in space
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-15)We investigate the generation of charge due to collision between projectiles with sizes below ∼1 µm and metal surfaces at speeds ∼0.1 to 10 km s<sup>−1</sup>. This corresponds to speeds above the elastic limit and well below speeds where volume ionization can occur. Impact charge production at these low to intermediate speeds has traditionally been described by invoking the theory of shock wave ... -
Ion Cloud Expansion after Hypervelocity Dust Impacts Detected by the MMS Electric Probes in the Dipole Configuration
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-08)Dust impact detection by electric field instruments is a well-established technique. On the other hand, not all aspects of signal generation by dust impacts are completely understood. We present a study of events related to dust impacts on the spacecraft body detected by electric field probes operating simultaneously in the monopole (probe-to-spacecraft potential measurement) and dipole (probe-to-probe ... -
What is going on with Middle Eastern solar prices, and what does it mean for the rest of us?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-04)For the third time in a decade, solar energy pricing records are tumbling in the Persian Gulf. As each previous wave of new records was met with incredulity, only for these prices to become the new normal around the world within a few years, it would be unwise to once again dismiss low prices as unrepresentative outliers. In this study, we show how local conditions and global macroeconomic factors ...