Viser treff 3241-3260 av 5336

    • The asymmetric geospace as displayed during the geomagnetic storm on 17 August 2001 

      Østgaard, Nikolai; Reistad, Jone Peter; Tenfjord, Paul; Laundal, Karl Magnus; Rexer, Theresa; Haaland, Stein; Snekvik, Kristian; Hesse, Michael; Milan, Stephen Eric; Ohma, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-29)
      Previous studies have shown that conjugate auroral features are displaced in the two hemispheres when the interplanetary magnetic field (IMF) has a transverse (<i><sub>Y</sub></i>) component. It has also been shown that a <i>B<sub>Y</sub></i> component is induced in the closed magnetosphere due to the asymmetric loading of magnetic flux in the lobes following asymmetric dayside reconnection when the ...
    • Electron Energy Spectrum and Auroral Power Estimation From Incoherent Scatter Radar Measurements 

      Virtanen, Ilkka I.; Gustavsson, Björn Johan; Aikio, Anita; Kero, Antti; Asamura, Kazushi; Ogawa, Yasunobu (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-23)
      Differential energy flux of electrons precipitating into the high‐latitude ionosphere can be estimated from incoherent scatter radar observations of the ionospheric electron density profile. We present a method called ELSPEC for electron spectrum estimation from incoherent scatter radar measurements, which is based on integration of the electron continuity equation and spectrum model selection by ...
    • Atypical biological features of a new cold seep site on the LofotenVesterålen continental margin (northern Norway) 

      Sen, Arunima; Himmler, Tobias; Hong, Wei-Li; Chitkara, Cheshtaa; Lee, Raymond W.; Ferré, Benedicte; Lepland, Aivo; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-11)
      A newly discovered cold seep from the Lofoten-Vesterålen margin (Norwegian Sea) is dominated by the chemosymbiotrophic siboglinid <i>Oligobrachia haakonmosbiensis</i> like other high latitude seeps, but additionally displays uncharacteristic features. Sulphidic bottom water likely prevents colonization by cnidarians and sponges, resulting in fewer taxa than deeper seeps in the region, representing ...
    • Monitoring Of CO2 Leakage Using High-Resolution 3D Seismic Data – Examples From Snøhvit, Vestnesa Ridge And The Western Barents Sea 

      Bellwald, Benjamin; Waage, Malin; Planke, S; Lebedeva-Ivanova, Nina; Polteau, S; Tasianas, Alexandros; Bünz, Stefan; Plaza-Faverola, Andreia; Berndt, Christian; Stokke, H.H.; Millett, John; Myklebust, R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-21)
      Injection of CO2 in subsurface reservoirs may cause overburden deformation and CO2 leakage. The aim of this study is to apply technologies for detection and monitoring of CO2 leakage and deformation above the injection reservoirs. The examples of this study include data from the Vestnesa Ridge natural seep site, the Snøhvit gas field and CO2 storage site region, and the Gemini North gas reservoir. ...
    • Diagrammatic Coupled Cluster Monte Carlo 

      Scott, Charles J. C.; Di Remigio, Roberto; Crawford, T. Daniel; Thom, Alex J. W. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-09)
      We propose a modified coupled cluster Monte Carlo algorithm that stochastically samples connected terms within the truncated Baker–Campbell–Hausdorff expansion of the similarity-transformed Hamiltonian by construction of coupled cluster diagrams on the fly. Our new approach—diagCCMC—allows propagation to be performed using only the connected components of the similarity-transformed Hamiltonian, ...
    • Intermittent fluctuations due to uncorrelated Lorentzian pulses 

      Garcia, Odd Erik; Theodorsen, Audun (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-31)
      Fluctuations due to a super-position of uncorrelated Lorentzian pulses with a random distribution of amplitudes and duration times are considered. These are demonstrated to be strongly intermittent in the limit of weak pulse overlap, resulting in large skewness and flatness moments. The characteristic function and the lowest order moments are derived, revealing a parabolic relationship between the ...
    • Discovery and characterization of a thermostable two-domain GH6 endoglucanase from a compost metagenome 

      Jensen, Marianne Slang; Fredriksen, Lasse; Mackenzie, Alasdair; Pope, Phillip; Leiros, Ingar; Chylenski, Piotr; Williamson, Adele Kim; Christopeit, Tony; Østby, Heidi; Vaaje-Kolstad, Gustav; Eijsink, Vincent (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-24)
      Enzymatic depolymerization of recalcitrant polysaccharides plays a key role in accessing the renewable energy stored within lignocellulosic biomass, and natural biodiversities may be explored to discover microbial enzymes that have evolved to conquer this task in various environments. Here, a metagenome from a thermophilic microbial community was mined to yield a novel, thermostable cellulase, named ...
    • Evaluation of Speckle Variance, Higher Moments and Their Dependence on Incidence Angle. 

      Hallaråker, Jon Anders Vethe (Master thesis; Mastergradsoppgave, 2018-12-14)
      This thesis investigates speckle properties from Sentinel-1 GRDM data to explore its dependency of incidence angle. The data is processed using the SNAP-tool such that a uniform region can be selected and estimation of speckle variance, skewness and kurtosis can be carried out. These speckle properties are calculated over ocean and sea ice for comparison and modeled to fit a regression line. Hypothesis ...
    • Time Series Forecasting with Recurrent Neural Networks in Presence of Missing Data 

      Choi, Changkyu (Master thesis; Mastergradsoppgave, 2018-11-24)
      In many applications, time series forecasting plays an irreplaceable role in time-varying systems such as energy markets, financial markets, and so on. Predicting the dynamic of time-varying systems is essential but is a difficult task because it depends on not only the nature of the system but also on external influences, such as environmental conditions and social and economic status. Recurrent ...
    • Retrieving horizontally resolved wind fields using multi-static meteor radar observations 

      Stober, Gunter; Chau, Jorge L.; Vierinen, Juha; Jacobi, Christoph; Wilhelm, Sven (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-27)
      Recently, the MMARIA (Multi-static, Multi-frequency Agile Radar for Investigations of the Atmosphere) concept of a multi-static VHF meteor radar network to derive horizontally resolved wind fields in the mesosphere–lower thermosphere was introduced. Here we present preliminary results of the MMARIA network above Eastern Germany using two transmitters located at Juliusruh and Collm, and five receiving ...
    • Syn-kinematic hydration reactions, grain size reduction, and dissolution-precipitation creep in experimentally deformed plagioclase-pyroxene mixtures 

      Marti, Sina; Stunitz, Holger; Heilbronner, Renée; Plümper, Oliver; Kilian, Rüdiger (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-09)
      It is widely observed that mafic rocks are able to accommodate high strains by viscous flow. Yet, a number of questions concerning the exact nature of the involved deformation mechanisms continue to be debated. In this contribution, rock deformation experiments on four different water-added plagioclase–pyroxene mixtures are presented:(i) plagioclase(An60–70)–clinopyroxene–orthopyroxene,(ii) ...
    • Survey of conditions for artificial aurora experiments by the second electron gyro-harmonic at EISCAT Troms? using dynasonde data 

      Tsuda, T. T.; Rietveld, Michael T; Kosch, M.J; Oyama, S; Ogawa, Y; Hosokawa, K.; Nozawa, S; Kawabata, T; Mizuno, A (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-06)
      We report a brief survey of matching conditions for artificial aurora optical experiments utilizing the second electron gyro-harmonic (2.7-MHz frequency) in F region heating with O-mode at the EISCAT Tromsø site using dynasonde data from 2000 to 2017. Our survey indicates the following: The possible conditions for successful artificial aurora experiments are concentrated on twilight hours in both ...
    • Column leaching test on oxidized and non-oxidized tailings in northern Norway 

      Fu, Shuai; Lu, Jinmei (Journal article; Peer reviewed, 2018)
      Column leaching test was applied for oxide and non-oxide tailings in the Arctic area. Physico-chemical parameters (pH, pe: potential ecolotric, conductivity, TDS: Total dissolved solids, SO4 2−, salinity, Ni, Co, Zn and Mn) were measured to identified the effect of oxidized degree on heavy metals leaching from tailings. Results showed that oxidized tailings contained higher levels of Co and Ni, and ...
    • Anomaly Detection for Environmental Data Using Machine Learning Regression 

      Yuan, Fuqing; Lu, Jinmei (Journal article; Peer reviewed, 2018)
      Environmental data exhibits as huge amount and complex dependency. Utilizing these data to detect anomaly is beneficial to the disaster prevention. Big data approach using the machine learning method has the advantage not requiring the geophysical and geochemical knowledge to detect anomaly. This paper using the popular support vector regression (SVR ) to model the correlation between factors. ...
    • Skewed Lorentzian pulses and exponential frequency power spectra 

      Garcia, Odd Erik; Theodorsen, Audun (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-18)
      Frequency power spectra due to a super-position of uncorrelated Lorentzian pulses with a random distribution of amplitudes are considered. For pulses with a constant duration, there is an exponential frequency spectrum which is independent of the degree of pulse overlap and the pulse amplitude distribution. The spectrum is furthermore shown to be unaffected by skewness of the Lorentzian pulses and ...
    • Rockfall hazard assessment based on semi-automatic point cloud analysis from UAV data 

      Bergbjørn, Anna Karin (Master thesis; Mastergradsoppgave, 2018-12-29)
      Slettind in Flaktstad municipality, Lofoten in Nordland, has numerous rockfalls throughout the year. Rockfalls hit Fv 805 on a weekly basis, and it is estimated the most dangerous road in Nordland county. A rock avalanche hit the road winter 2017 closing it for 2 weeks, and isolating the small village Myrland. Statens Vegvesen consider to build a tunnel to protect the road but the failure mechanisms ...
    • Endurance Test on Carbon Film Fixed Resistor under Escalated Voltage Stress 

      Yuan, Fuqing; Lu, Jinmei (Journal article; Peer reviewed; Tidsskriftartikkel, 2018)
      Film fixed resistor is a basic unit in the electronic devices. As it is less frequently failed than other units such as capacitor, the reliability and robustness of it are less concerned both in the academics and in the industries. This paper investigates the endurance of the carbon film fixed resistor. The resistance shift and life of it under the escalated voltage stress level are the aim. A PCB ...
    • Intermittent fluctuations in the Alcator C-Mod scrape-off layer for ohmic and high confinement mode plasmas 

      Garcia, Odd Erik; Kube, Ralph; Theodorsen, Audun; Labombard, B; Terry, J.L (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-20)
      Plasma fluctuations in the scrape-off layer of the Alcator C-Mod tokamak in ohmic and high confinement modes have been analyzed using gas puff imaging data. In all cases investigated, the time series of emission from a single spatially resolved view into the gas puff are dominated by large-amplitude bursts, attributed to blob-like filament structures moving radially outwards and poloidally. There ...
    • Clustering and climate associations of Kawasaki Disease in San Diego County suggest environmental triggers 

      Rypdal, Martin wibe; Rypdal, Veronika Gjertsen; Burney, Jennifer A.; Cayan, Daniel; Bainto, Emelia; Skochko, Shannon; Tremoulet, Adriana H.; Creamean, Jessie; Shimizu, Chisato; Kim, Ji-Hoon; Burns, Jane C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-12)
      Kawasaki Disease (KD) is the most common cause of pediatric acquired heart disease, but its etiology remains unknown. We examined 1164 cases of KD treated at a regional children’s hospital in San Diego over a period of 15 years and uncovered novel structure to disease incidence. KD cases showed a well-defined seasonal variability, but also clustered temporally at much shorter time scales (days to ...
    • On Atmospheric Energy Transport by Waves 

      Heiskanen, Tuomas Ilkka Henrikki (Master thesis; Mastergradsoppgave, 2018-12-14)
      Recently a new method, based on a Fourier decomposition in the zonal direction, for studying the atmospheric energy transport contribution by planetary and cyclone scale waves has been proposed. Recent studies based on this show that planetary waves contribute more than cyclone scale waves to the atmospheric energy transport into the Arctic. The planetary waves contribute to the Arctic amplification ...