Viser treff 488-507 av 942

    • Measurements of ionic liquids thermal conductivity and thermal diffusivity 

      Zhao, Yansong; Zhen, Yingpeng; Jelle, Bjørn Petter; Boström, Tobias (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-02)
      Thermal conductivity and thermal diffusivity of ionic liquids (ILs) are investigated in this work. A hot disk method for ILs thermal conductivity and thermal diffusivity measurement is utilized. Firstly, the thermal conductivity of water is measured to check the reliability of the hot disk method. In addition, the thermal conductivity of pure ILs, including BmimBF<sub>4</sub>, BmimPF<sub>6</sub>, ...
    • Measuring Wind Speed Using the Internal Stabilization System of a Quadrotor Drone 

      Simma, Magdalena; Mjøen, Håvard; Boström, Tobias (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-16)
      This article proposes a method of measuring wind speed using the data logged by the autopilot of a quadrotor drone. Theoretical equations from works on quadrotor control are utilized and supplemented to form the theoretical framework. Static thrust tests provide the necessary parameters for calculating wind estimates. Flight tests were conducted at a test site with laminar wind conditions with the ...
    • Mesopause dynamics from the scandinavian triangle of radars within the PSMOS-DATAR Project. 

      Hall, Chris; Manson, A.H.; Meek, C.E.; Nozawa, S.; Mitchell, N.J.; Pancheva, D.; Singer, W.; Hoffmann, P. (Journal article; Peer reviewed; Tidsskriftartikkel, 2004-01-01)
      The "Scandinavian Triangle" is a unique trio of radars within the DATAR Project (Dynamics and Temperatures from the Arctic MLT (60–97km) region): Andenes MF radar (69°N, 16°E); Tromsø MF radar (70°N, 19°E) and Esrange "Meteor" radar (68°N, 21°E). The radar-spacings range from 125-270km, making it unique for studies of wind variability associated with small-scale waves, comparisons of large-scale ...
    • Mesospheric dust and its secondary effects as observed by the ESPRIT payload 

      Havnes, Ove; Surdal, L. H.; Philbrick, C. R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)
    • Mesospheric temperatures and sodium properties measured with the ALOMAR Na lidar compared with WACCM 

      Dunker, Tim; Hoppe, Ulf-Peter; Feng, Wuhu; Plane, John M.C.; Marsh, Daniel R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-01-16)
      We present a comparison of the temperature and sodium layer properties observed by the ALOMAR Na lidar (69.3°N, 16.0°E) and simulated by the Whole Atmosphere Community Climate Model with specified dynamics and implemented sodium chemistry (WACCM-Na). To constrain the meteorological fields below 60 km, we use MERRA and GEOS-5. For the years 2008 to 2012, we analyse daily averages of temperature ...
    • The Meta-Evaluation Problem in Explainable AI: Identifying Reliable Estimators with MetaQuantus 

      Wickstrøm, Kristoffer Knutsen; Höhne, Marina Marie-Claire (Journal article; Tidsskriftartikkel, 2023)
      Explainable AI (XAI) is a rapidly evolving field that aims to improve transparency and trustworthiness of AI systems to humans. One of the unsolved challenges in XAI is estimating the performance of these explanation methods for neural networks, which has resulted in numerous competing metrics with little to no indication of which one is to be preferred. In this paper, to identify the most reliable ...
    • Metasurface supporting quasi-BIC for optical trapping and Raman-spectroscopy of biological nanoparticles 

      Hasan, Md Rabiul; Hellesø, Olav Gaute (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 ...
    • Method for detection of leads from Sentinel-1 SAR images 

      Murashkin, Dmitrii; Spreen, Gunnar; Huntemann, Marcus; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-05)
      The presence of leads with open water or thin ice is an important feature of the Arctic sea ice cover. Leads regulate the heat, gas and moisture fluxes between the ocean and atmosphere and are areas of high ice growth rates during periods of freezing conditions. Here, an algorithm providing an automatic lead detection based on synthetic aperture radar images is described that can be applied to a ...
    • A method to improve high-resolution sea ice drift retrievals in the presence of deformation zones 

      Griebel, Jakob; Dierking, Wolfgang Fritz Otto (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-12)
      Retrievals of sea ice drift from synthetic aperture radar (SAR) images at high spatial resolution are valuable for understanding kinematic behavior and deformation processes of the ice at different spatial scales. Ice deformation causes temporal changes in patterns observed in sequences of SAR images; which makes it difficult to retrieve ice displacement with algorithms based on correlation and ...
    • MIDAS-W: a workstation-based incoherent scatter radar data aquisition system. 

      Holt, J.M.; Grydeland, Tom; Erickson, P.J.; Gorczyca, A.M. (Journal article; Tidsskriftartikkel, 2000)
      The Millstone Hill Incoherent Scatter Data Acquisition System (MIDAS) is based on an abstract model of an incoherent scatter radar. This model is implemented in a hierarchical software system, which serves to isolate hardware and low-level software implementation details from higher levels of the system. Inherent in this is the idea that implementation details can easily be changed in response to ...
    • Millstone Hill ISR Measurements of Small Aspect Angle Spectra 

      Longley, William; Erickson, Philip J.; Vierinen, Juha; Oppenheim, Meers; Lind, Frank David; Dimant, Yakov (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-04)
      The Millstone Hill incoherent scatter (IS) radar is used to measure spectra close to perpendicular to the Earth's magnetic field, and the data are fit to three different forward models to estimate ionospheric temperatures. IS spectra measured close to perpendicular to the magnetic field are heavily influenced by Coulomb collisions, and the temperature estimates are sensitive to the collision operator ...
    • Mission Performance Trade-offs of Battery-powered sUAS 

      Hovenburg, Anthony Reinier; Johansen, Tor Arne; Storvold, Rune (Chapter; Bokkapittel, 2017-07-27)
      A sensitivity analysis is presented on the influence of the weight, altitude and speed of battery-powered sUAS on the resulting stall speed, endurance and range. To aid in the determination of the aircraft performance prior to flight, a method is being brought forth that quantifies the impact of these mission parameters. As a case study the P31015 sUAS is used. The P31015 is a concept model of a ...
    • Mixing up contrastive learning: Self-supervised representation learning for time series 

      Wickstrøm, Kristoffer; Kampffmeyer, Michael; Mikalsen, Karl Øyvind; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-14)
      The lack of labeled data is a key challenge for learning useful representation from time series data. However, an unsupervised representation framework that is capable of producing high quality representations could be of great value. It is key to enabling transfer learning, which is especially beneficial for medical applications, where there is an abundance of data but labeling is costly and time ...
    • Model-Based Polarimetric Decomposition With Higher Order Statistics 

      Eltoft, Torbjørn; Doulgeris, Anthony Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-11)
      This letter presents a new general framework for solving polarimetric target decompositions that extends them to use more statistical information and include radar texture models. Polarimetric target decomposition methods generally have more physical parameters than equations and are, thus, underdetermined and have no unique solution. The common approach to solve them is to make certain assumptions, ...
    • Modeling iron abundance anhancements in the slow solar wind. 

      Byhring, Hanne Sigrun; Cranmer, S.R.; Lie-Svendsen, Øystein; Habbal, S. Rifai; Esser, Ruth (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      We have studied the behavior of Fe ions in the slow solar wind, using a fluid model extending from the chromosphere to 1 AU. Emphasis is on elemental "pileup" in the corona, i.e., a region where the Fe density increases and has a local maximum. We study the behavior of individual Fe ions relative to each other in the pileup region, where Fe(+10) and Fe(+12) have been used as examples. We find that ...
    • Modeling Microwave Scattering From Rough Sea Ice Surfaces 

      Xu, Xu; Doulgeris, Anthony Paul; Melandsø, Frank; Brekke, Camilla (Conference object; Konferansebidrag, 2017)
      In this paper, COMSOL Multiphysics® was used to simulate the microwave scattering from the rough sea ice surface. A nonperiodic model and a periodic model were built. The nonperiodic model considers the rough surface of finite length and introduces a tapered incident wave. In this model, the strategy of total and scattered-field decomposition (TSFD) was used to formulate the finite-element method ...
    • Modeling of photovoltaic power generation and electric vehicles charging on city-scale: A review 

      Shepero, Mahmoud; Munkhammar, Joakim; Widén, Joakim; DK Bishop, Justin; Boström, Tobias (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-19)
      <p>Photovoltaics (PV) and electric vehicles (EVs) are promising technologies for increasing energy efficiency and the share of renewable energy sources in power and transport systems. As regards the deployment, use and system integration of these technologies, spatio-temporal modeling of PV power production and EV charging is of importance for several purposes such as urban planning and power grid ...
    • Modeling Solar Orbiter dust detection rates in the inner heliosphere as a Poisson process 

      Kociscak, Samuel; Kvammen, Andreas; Mann, Ingrid; Sørbye, Sigrunn Holbek; Theodorsen, Audun; Zaslavsky, Arnaud (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-20)
      Context. Solar Orbiter provides dust detection capability in the inner heliosphere, but estimating physical properties of detected dust from the collected data is far from straightforward.<p> <p>Aims. First, a physical model for dust collection considering a Poisson process is formulated. Second, it is shown that dust on hyperbolic orbits is responsible for the majority of dust detections with ...
    • Modeling temporal fluctuations in avalanching system 

      Rypdal, Martin; Rypdal, Kristoffer (Working paper; Arbeidsnotat, 2008-07-22)
      We demonstrate how to model the toppling activity in avalanching systems by stochastic differential equations (SDEs). The theory is developed as a generalization of the classical mean field approach to sandpile dynamics by formulating it as a generalization of Itoh’s SDE. This equation contains a fractional Gaussian noise term representing the branching of an avalanche into small active clusters, ...
    • Modelling the influence of meteoric smoke particles on artificial heating in the D-region 

      Myrvang, Margaretha; Baumann, Carsten; Mann, Ingrid (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 ...