Viser treff 4357-4376 av 4765

    • Temporal dynamics of intra-and extra-cellular microcystins concentrations in Koka reservoir (Ethiopia): Implications for public health risk 

      Tilahun, Samson; Kifle, Demeke; Zewde, Tigist W; Johansen, Jostein a; Demissie, Taye Beyene; Hansen, Jørn H (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-20)
      This study was carried out with a view of understanding the temporal dynamics of microcystin concentrations in both algal seston and water samples and the associated public health risk. All the major MC variants, namely MC-LR, MC-YR, and MC-RR, were detected in both the algal seston and water samples. In the majority of the samples, the most potent variant, MC-LR, constituted the greatest proportion ...
    • Temporal evolution of under-ice meltwater layers and false bottoms and their impact on summer Arctic sea ice mass balance 

      Salganik, Evgenii; Katlein, Christian; Lange, Benjamin; Matero, Ilkka; Lei, Ruibo; Fong, Allison A.; Fons, Steven; Divine, Dmitry; Oggier, Marc; Castellani, Giulia; Bozzato, Deborah; Chamberlain, Emelia; Hoppe, Clara J. M.; Müller, Oliver; Gardner, Jessie; Rinke, Annette; Simoes Pereira, Patric; Ulfsbo, Adam; Marsay, Christopher; Webster, Melinda; Maus, Sønke; Høyland, Knut Vilhelm; Granskog, Mats (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-31)
      Low-salinity meltwater from Arctic sea ice and its snow cover accumulates and creates under-ice meltwater layers below sea ice.These meltwater layers can result in the formation of new ice layers, or false bottoms, at the interface of this low-salinity meltwater and colder seawater. As part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), we used a ...
    • Temporal overdrive recurrent neural network 

      Bianchi, Filippo Maria; Kampffmeyer, Michael C.; Maiorino, Enrico; Jenssen, Robert (Chapter; Bokkapittel, 2017-07-03)
      In this work we present a novel recurrent neural network architecture designed to model systems characterized by multiple characteristic timescales in their dynamics. The proposed network is composed by several recurrent groups of neurons that are trained to separately adapt to each timescale, in order to improve the system identification process. We test our framework on time series prediction tasks ...
    • Temporal Variability of Surface Reflectance Supersedes Spatial Resolution in Defining Greenland’s Bare-Ice Albedo 

      Irvine-Fynn, Tristram D. L.; Bunting, Peter S.; Cook, Joseph M.; Hubbard, Alun; Barrand, Nicholas E.; Hanna, Edward; Hardy, Andy J.; Hodson, Andrew J.; Holt, Tom O.; Huss, Matthias; McQuaid, James B.; Nilsson, Johan; Naegeli, Kathrin; Roberts, Osian; Ryan, Jonathan C.; Tedstone, Andrew J.; Tranter, Martyn; Williamson, Christopher J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-23)
      Ice surface albedo is a primary modulator of melt and runoff, yet our understanding of how reflectance varies over time across the Greenland Ice Sheet remains poor. This is due to a disconnect between point or transect scale albedo sampling and the coarser spatial, spectral and/or temporal resolutions of available satellite products. Here, we present time-series of bare-ice surface reflectance data ...
    • Terrenganalyse og 3D snøskredsimuleringer for plassering av radar for snøskredvarsling 

      Christiansen, Lars Tveit (Master thesis; Mastergradsoppgave, 2018-10-09)
      Etter flere ulykker knyttet til snøskred på Europavei 8 i Lavangsdalen i Troms de siste årene, har Statens vegvesen gått inn for å bedre skredsikringen langs den 18 km lange dalen. Hovedformålet med denne masteroppgaven er å komme med innspill til hensiktsmessig plassering av automatiske overvåkningsanlegg for snøskred ved fire avgrensede strekninger langs vegen: Hestvollan, Sarasteinen, Stortinden ...
    • Testing miniaturized extraction chromatography protocols for combined 87Sr/86Sr and δ88/86Sr analyses of pore water by MC‐ICP‐MS 

      Argentino, Claudio; Lugli, Federico; Cipriani, Anna; Panieri, Giuliana (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-04)
      We tested two miniaturized extraction chromatography protocols for strontium isolation based on 300 μL (Protocol 1) and 30 μL (Protocol 2) column volumes of Sr‐Spec resin, for the simultaneous determination of 87Sr/86Sr and δ88/86Sr by MC‐ICP‐MS. The accuracy and precision of the Sr isotope ratios have been evaluated by analyzing JCt‐1 and SRM 1640a reference materials, resulting in a reproducibility ...
    • Testing the hypothesis of the influence of neutral turbulence on the deduction of ambipolar diffusivities from meteor trail expansion 

      Hall, Chris; Aso, T.; Tsutsumi, M.; Nozawa, S.; Manson, A.H.; Meek, C.E. (Journal article; Peer reviewed; Tidsskriftartikkel, 2005-03-30)
      Fading times of radar echoes from underdense meteor trails in the upper mesosphere/lower thermosphere are commonly used to determine ambipolar diffusivities and hence ambient temperature. Diffusivities are generally expected to increase exponentially with height through the region from which the meteor trail echoes are obtained, viz., typically 70-110km altitude for a ~30-MHz radar. In practice, ...
    • A Textural–Contextual Model for Unsupervised Segmentation of Multipolarization Synthetic Aperture Radar Images 

      Akbari, Vahid; Doulgeris, Anthony Paul; Gabriele, Moser; Eltoft, Torbjørn; Sebastiano, B. Serpico; Anfinsen, Stian Normann (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      This paper proposes a novel unsupervised, non-Gaussian, and contextual segmentation method that combines an advanced statistical distribution with spatial contextual informa-tion for multilook polarimetric synthetic aperture radar (PolSAR)data. This extends on previous studies that have shown the added value of both non-Gaussian modeling and contextual smoothing individually or for intensity channels ...
    • TFHE-rs: A library for safe and secure remote computing using fully homomorphic encryption and trusted execution environments 

      Brenna, Lars; Singh, Isak Sunde; Johansen, Håvard D.; Johansen, Dag (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-20)
      Fully Homomorphic Encryption (FHE) and Trusted Execution Environ-ments (TEEs) are complementing approaches that can both secure computa-tions running remotely on a public cloud. Existing FHE schemes are, however, malleable by design and lack integrity protection, making them susceptible to integrity breaches where an adversary could modify the data and corrupt the output. This paper describes how ...
    • A Theoretical Analysis of Deep Neural Networks and Parametric PDEs 

      Kutyniok, Gitta Astrid Hildegard; Petersen, Philipp; Raslan, Mones; Schneider, Reinhold (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-02)
      We derive upper bounds on the complexity of ReLU neural networks approximating the solution maps of parametric partial differential equations. In particular, without any knowledge of its concrete shape, we use the inherent low dimensionality of the solution manifold to obtain approximation rates which are significantly superior to those provided by classical neural network approximation results. ...
    • Theoretical Analysis of NMR Shieldings in XSe and XTe (X= Si, Ge, Sn and Pb): The Spin–Rotation Constant Saga 

      Demissie, Taye Beyene (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-21)
      The nuclear spin-rotation (NSR) and absolute nuclear magnetic resonance (NMR) shielding tensors of the nuclei in the series of X<sup>77</sup>Se and X<sup>125</sup>Te (X = <sup>29</sup>Si, <sup>73</sup>Ge, <sup>119</sup>Sn and <sup>207</sup>Pb) are calculated using fourcomponent relativistic density functional theory (DFT) and coupled-cluster singles-doubles with a perturbative triples correction ...
    • A Theoretical Model of Drumlin Formation Based on Observations at Múlajökull, Iceland 

      Iverson, N. R.; McCracken, R. G.; Zoet, L. K.; Benediktsson, Í. Ö.; Schomacker, Anders; Johnson, M. D.; Woodard, J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-20)
      The drumlin field at the surge‐type glacier, Múlajökull, provides an unusual opportunity to build a model of drumlin formation based on field observations in a modern drumlin‐forming environment. These observations indicate that surges deposit till layers that drape the glacier forefield, conform to drumlin surfaces, and are deposited in shear. Observations also indicate that erosion helps create ...
    • Theoretical Photoelectron Spectroscopy of Low-Valent Carbon Species: A ∼6 eV Range of Ionization Potentials among Carbenes, Ylides, and Carbodiphosphoranes 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-02)
      High-quality density functional theory calculations underscore a nearly 6 eV range for the ionization potentials (IPs) of neutral, low-valent carbon compounds, including carbenes, ylides, and zero-valent carbon compounds (carbones) such as carbodiphosphoranes (CDPs) and carbodicarbenes. Thus, adiabatic IPs as low as 5.5 ± 0.1 eV are predicted for CDPs, which are about 0.7–1.2 eV lower than those of ...
    • A Theoretical Search for Stable Terminal Carbides 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-20)
      xploratory scalar-relativistic density functional theory (B3LYP*-D3/ZORA-STO-TZ2P) calculations have been used to examine the stability and bonding of pseudotetrahedral Group 8 (Fe, Ru, and Os) and Group 9 (Co, Rh, and Ir) terminal carbide complexes with dδ4 ground states and tripodal tris(N-heterocyclic-carbene) supporting ligands. The calculations predict relatively low adiabatic ionization ...
    • Theoretical studies of natural and electromagnetically induced birefringences 

      Shcherbin, Dmitry (Doctoral thesis; Doktorgradsavhandling, 2011-06-01)
    • Theoretical studies of natural and magnetic circular dichroism 

      Solheim, Harald (Doctoral thesis; Doktorgradsavhandling, 2011-06-23)
      This dissertation presents theoretical studies mainly of natural and magnetic circular dichroism spectra. For magnetic circular dichroism, the importance of electron correlation effects, here included at the density-functional functional level of theory, and solvent effects are discussed, both being shown to have significant impact on the final spectra. In addition, a unified approach for calculating ...
    • A theoretical study of the coupling between minor ions and protons in the solar transition region 

      Byhring, Hanne Sigrun (Master thesis; Mastergradsoppgave, 2007-06-01)
      We have used a numerical model to calculate the flow velocities of six minor ion species, using two different background models for the fast solar wind, one with a slow expansion, and one with a very rapidly expanding geometry. By comparing the flow velocity of the minor ions and the protons, we have investigated the degree of coupling between minor ions and the background solar wind in the solar ...
    • Theory of linear G-difference equations 

      Lychagin, Valentin V.; Jakobsen, Per K. (Journal article; Tidsskriftartikkel; Peer reviewed, 1997-12-17)
      We introduce the notion of difference equation defined on a structured set. The symmetry group of the structure determines the set of difference operators. All main notions in the theory of difference equations are introduced as invariants of the action of the symmetry group. Linear equations are modules over the skew group algebra, solutions are morphisms relating a given equation to other ...
    • Thermal analysis of PTC heaters. Thermography of PTC and Peltier heaters. Labview® based control and Matlab® Simulink simulations of PTC heaters. 

      Taimur, Madiha (Master thesis; Mastergradsoppgave, 2018-06-15)
      A large variety of heating devices are being used in the industry. Two widely used smart heating devices are discussed in this study. These heating devices are Peltier/thermoelectric (TE) and Positive Temperature Coefficient (PTC) resistive heater. This study provides detailed experimentation of PTC heater and Peltier device at room conditions and cold environment. The thermal response of both ...
    • Thermal and Mechanical Properties of SK One Component Polyurethane (SKOCP). Determining the Thermal and Mechanical properties of SKOCP in Colder Conditions 

      Eidesen, Hans-Kristian Norum (Master thesis; Mastergradsoppgave, 2017-05-30)
      Polymers have an extreme wide range of potential applications. From artificial heart valves, computer hardware, coating materials, noise damping materials and so on. Polyurethane is one of the such materials with a broad range of applications. A few such applications and properties are, but not limited to, treatment of leakage of an expansion joint, abrasion resistance, anti-freezing performance and ...