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norskInstitutt for fysikk og teknologi: Recent submissions
Now showing items 981-1000 of 1400
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Classification of Marine Oil Spills and Look-alikes in Sentinel-1 TOPSAR and Radarsat-2 ScanSAR Images
(Master thesis; Mastergradsoppgave, 2018-06-01)The main focus of this thesis is to investigate the potential for discrimination between marine oil spills and look-alikes in Synthetic Aperture Radar (SAR) imagery, using log-cumulants and other parameters describing the characteristics of a dark feature. Look-alikes denotes other phenomena known to cause similar SAR signatures as mineral oil. It is vital for the companies managing oil detection ... -
Analyzing Behavioral Biometrics of Handwriting Using Myo Gesture Control Armband
(Master thesis; Mastergradsoppgave, 2018-06-05)Through the last few decades, computer technology has gradually merged into our everyday lives. Computers and sensors are embedded in an increasing amount of household items, enabling us to monitor and remotely control our connected devices from apps on our smartphones. The technology interfaces are also evolving along with new technologies. Among the up and coming digital interfaces are wearable ... -
An evaluation of the reanalyses ERA-Interim and ERA5 in the Arctic using N-ICE2015 data
(Master thesis; Mastergradsoppgave, 2018-06-15)The Arctic climate has changed considerably in the last few decades. Hence, a large fraction of the current studies of the Arctic climate relies on global atmospheric reanalyses, due to the shortage of meteorological observations in the Arctic. However, global climate models have shown to struggle with simulating the current conditions in the Arctic region. Thus, the objective of this thesis is to ... -
Seasonal energy storage for district heating applications, including simulation and analysis of Borehole Thermal Energy Storage systems
(Master thesis; Mastergradsoppgave, 2018-06-18)The objective of this thesis is to analyse different energy storage technologies for seasonal energy storage in combination with district heating. Tromsø receives district heating (Kvitebjørn Varme). Their new heating central at Skattøra burn waste from industry and households in Tromsø and this heat is used to heat water. A part of this excess heat is lost to air during summer because of a lower ... -
Can we extend local sea-ice measurements to satellite scale? An example from the N-ICE2015 expedition
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-17)Knowledge of Arctic sea-ice conditions is of great interest for Arctic residents, as well as for commercial usage, and to study the effects of climate change. Information gained from analysis of satellite data contributes to this understanding. In the course of using in situ data in combination with remotely sensed data, the question of how representative local scale measurements are of a wider ... -
An objective global climatology of polar lows based on reanalysis data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-16)Here we present an objective global climatology of polar lows. In order to obtain objective detection criteria, the efficacy of several parameters for separating polar lows from other cyclones has been compared. The comparison and the climatology are based on the ERA‐Interim reanalysis from 1979 ‐ 2016 and the high‐resolution Arctic System Reanalysis from 2000 ‐ 2012. The most effective parameters ... -
Emulating sentinel-1 Doppler radial ice drift measurements using envisat ASAR data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-05)Using data from the Envisat Advanced Synthetic Aperture Radar (ASAR) instrument, this paper demonstrates how the high-precision radial surface velocity product, which will become available with the European Space Agency's Sentinel-1 satellite, can complement the analysis of sea ice motion. High-resolution Doppler frequency measurements are used to estimate the subsecond line-of-sight motion of ... -
High frequency copolymer ultrasonic transducer array of size-effective elements
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-05)A layer-by-layer deposition method for producing dual-layer ultrasonic transducers from piezoelectric copolymers has been developed. The method uses a combination of customized and standard processing to obtain 2D array transducers with electrical connection of the individual elements routed directly to the rear of the substrate. A numerical model was implemented to study basic parameters effecting ... -
Poleward energy transport: is the standard definition physically relevant at all time scales?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-17)Poleward energy transport in the atmosphere and oceans constitutes an important branch of the global energy budget, and its role in the climate system has been the subject of many studies. In the atmosphere, the transport is affected by “eddies” and large scale meridional cells, both with zero net mass transport across latitude circles, but also partly by processes associated with a net transport ... -
Accurate estimation of the illumination pattern’s orientation and wavelength in sinusoidal structured illumination microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-05)Structured illumination microscopy is able to improve the spatial resolution of wide-field fluorescence imaging by applying sinusoidal stripe pattern illumination to the sample. The corresponding computational image reconstruction requires precise knowledge of the pattern’s parameters, which are its phase (φ) and wave vector (<b>p</b>). Here, a computationally inexpensive method for estimation of ... -
On the theory of the incoherent scatter gyrolines
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-20)The incoherent scatter spectrum feature referred to as the “gyroline” is investigated theoretically and experimentally. The gyroline is associated with the dispersion relation for electrostatic whistler waves. Earlier treatments by Trulsen and Bj⊘rna (1978, and references therein) derive the frequency and growth rate for these waves, but their derivation is only accurate for very small magnetic ... -
GNSS Observations of Ionospheric Variations During the 21 August 2017 Solar Eclipse
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-20)On 21 August 2017, during daytime hours, a total solar eclipse with a narrow ∼160 km wide umbral shadow occurred across the continental United States. Totality was observed from the Oregon coast at ∼9:15 local standard time (LST) (17:20 UT) to the South Carolina coast at ∼13:27 LST (18:47 UT). A dense network of Global Navigation Satellite Systems (GNSS) receivers was utilized to produce total ... -
Determination of the Edge of Criticality in Echo State Networks Through Fisher Information Maximization
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03)It is a widely accepted fact that the computational capability of recurrent neural networks (RNNs) is maximized on the so-called “edge of criticality.” Once the network operates in this configuration, it performs efficiently on a specific application both in terms of: 1) low prediction error and 2) high shortterm memory capacity. Since the behavior of recurrent networks is strongly influenced by the ... -
Ionospheric bow waves and perturbations induced by the 21 August 2017 solar eclipse
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)During solar eclipses, the Moon's shadow causes a large reduction in atmospheric energy input, including not only the stratosphere but also the thermosphere and ionosphere. The eclipse shadow has a supersonic motion which is theoretically expected to generate atmospheric bow waves, similar to a fast‐moving river boat, with waves starting in the lower atmosphere and propagating into the ionosphere. ... -
Training Echo State Networks with Regularization Through Dimensionality Reduction
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017)In this paper, we introduce a new framework to train a class of recurrent neural network, called Echo State Network, to predict real valued time-series and to provide a visualization of the modeled system dynamics. The method consists in projecting the output of the internal layer of the network on a lower dimensional space, before training the output layer to learn the target task. Notably, we ... -
Estimates of the size distribution of meteoric smoke particles from rocket-borne impact probes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-26)Ice particles populating noctilucent clouds and being responsible for polar mesosphericsummer echoes exist around the mesopause in the altitude range from 80 to 90 km during polar summer.The particles are observed when temperatures around the mesopause reach a minimum, and it is presumedthat they consist of water ice with inclusions of smaller mesospheric smoke particles (MSPs). This workprovides ... -
Inflammatory response of macrophages and trophoblasts investigated using structured illumination microscopy and quantitative phase microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09)<i>Introduction</i>: The super-resolution capability of structured illumination microscopy (SIM) (100 nm) enables 3D imaging of mitochondria, and label-free quantitative phase microscopy (QPM) provides nanoscale quantitative phase values relating to cellular thickness and the refractive index of cellular content. -
Radar observations of thermal plasma oscillations in the ionosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-02)Incoherent scatter radar observations of ionospheric plasmas rely on echoes from electron density fluctuations with properties governed by the dispersion relations for ion acoustic and Langmuir waves. Radar observations of echoes associated with Langmuir waves (plasma lines) from thermal plasma are weak, and only a few near‐thermal level measurements have been reported. Plasma line echoes are typically ... -
Localized mesosphere-stratosphere-troposphere radar echoes from the E region at 69 degrees N: Properties and physical mechanisms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2011-02-25)We present the first observations, to our knowledge, of a new class of high‐latitude mesosphere‐stratosphere‐troposphere radar echoes from the E region as observed with the Arctic Lidar Observatory for Middle Atmosphere Research wind radar during the period 2004–2008. These echoes occur primarily during the summer months and in the altitude range from 93 to 114 km, with a pronounced peak of maximum ... -
Agreement and Complementarity of Sea Ice Drift Products
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-08)Changes in Arctic sea ice have raised questions about changes in sea ice drift patterns. Reduced sea ice coverage may open up the Arctic to further exploration of maritime activities, particularly during the summer months. Given such changes, it is important to investigate differences between available sea ice drift products. Products based on synthetic aperture radar (SAR), radar scatterometer, and ...
