Institutt for fysikk og teknologi: Recent submissions
Now showing items 721-740 of 1276
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Correction Strategies for Breathing Induced Motion in PET Images
(Master thesis; Mastergradsoppgave, 2019-06-03)Breathing induced motion highly impacts the quality of PET images. Motion blur impacts important parameters such as standardised uptake value (SUV) and lesion volume. To be able to stage lung cancer correctly, and provide correct treatment, the impact of motion needs to be reduced. There exists techniques to combat the breathing motion, such as elastic motion correction and gating strategies. ... -
Charging Effects and Detection of Mesospheric Dust with the Instrument SPID on the G-Chaser Rocket
(Master thesis; Mastergradsoppgave, 2019-06-01)Smoke Particle Impact Detector (SPID) is a faraday cup impact probe designed and built by the University of Tromso (UIT). Its main purpose is to measure nanometer sized smoke particles (in-situ) in the atmosphere, and to do that it needs to be launched on a sounding rocket. Its design is an open faraday cup with grids to shield out ambient plasma and a larger slanted impact grid to measure the ... -
On the Meteoric Smoke Particle Detector SPID: Measurements and analysis from the G-chaser rocket campaign
(Master thesis; Mastergradsoppgave, 2019-06-01)The Smoke Particle Impact Detector (SPID), newly designed at the University of Tromsø, was launched from Andøya 09:13 UTC the 13. January 2019. SPID is designed to detect meteoric smoke particles (MSPs) in winter mesospheric conditions. The rocket had a velocity of 1600 ms-1 at ~55 km where the nosecone was separated. At ~ 60km, SPID detected a signal of 17nA on the middle plate. The dynamics of the ... -
Angular dependence of wide altitude ion line enhancements (WAILEs) during ionospheric heating at the EISCAT Tromsø Facility
(Master thesis; Mastergradsoppgave, 2019-06-01)This thesis presents the first sub-radar beam resolution determination of the angular width of wide altitude ion line enhancements (WAILEs), found to be 0.5 degrees around magnetic zenith, observed during a HF radio wave heating experiment at the EISCAT Tromsø Heating facility on 27 November 2014. The results of ray tracing simulations are detailed. The simulations are based on the hypothesis that ... -
Forbedret tilstandsovervåkning av bærelager i Sjona kraftverk ved digitalisering
(Master thesis; Mastergradsoppgave, 2019-06-01)Økt konkurranse fra andre fornybare energikilder, økt energibehov og økt behov for reguleringsevne stiller stadig større krav til eksisterende og nye vannkraftverk. Vannkraftsektoren har de siste hundre årene ikke opplevd reell konkurranse fra andre teknologier her til lands, og har derfor ikke blitt tvunget til innovasjon og nytenking i samme grad som andre deler av kraftnæringen. De siste årene ... -
Deep Image Clustering with Tensor Kernels and Unsupervised Companion Objectives
(Master thesis; Mastergradsoppgave, 2019-05-31)Deep image clustering is a rapidly growing branch of machine learning and computer vision, in which deep neural networks are trained to discover groups within a set of images, in an unsupervised manner. Deep neural networks have proven to be immensely successful in several machine learning tasks, but the majority of these advances have been in supervised settings. The process of labeling data for ... -
ICEBEAR: An All‐Digital Bistatic Coded Continuous Wave Radar for Studies of the E Region of the Ionosphere
(Journal article; Peer reviewed, 2019-04-15)The Ionospheric Continuous-wave E region Bistatic Experimental Auroral Radar (ICEBEAR) is a coherent scatter ionospheric radar. It operates at a frequency of 49.5 MHz, which is ideal for observing E region coherent echoes. The radar is located in Saskatchewan, Canada, and is operated by the University of Saskatchewan. The ICEBEAR system uses a continuous-wave (CW) signal and requires isolation between ... -
Improved LLM Methods Using Linear Regression
(Journal article; Peer reviewed, 2017-12-04)This paper is focused on investigations of the improved correction of the effect of variation in incidence angle on ScanSAR data. Conventional correction methods (such as LLM, locally linear mapping) typically assume that each target class has a similarity distribution in the middle of the image. The objectives of this study are to extend the correction algorithm to full swath width without any ... -
Speeding Up Non-Gaussian POLSAR Image Analysis
(Journal article; Peer reviewed, 2017-12-04)Non-Gaussian statistical models fit SAR data better than Gaussian-based statistics, in most cases, but are complicated and time-consuming to use for unsupervised image segmentation via probabilistic clustering. The more advanced the model, the more complicated and slow the clustering. The U-distribution has been demonstrated to be one of the most flexible models, capturing the Gaussian/Wishart, the ... -
Evidence of L-mode electromagnetic wave pumping of ionospheric plasma near geomagnetic zenith
(Journal article; Peer reviewed, 2018-02-21)The response of ionospheric plasma to pumping by powerful HF (high frequency) electromagnetic waves transmitted from the ground into the ionosphere is the strongest in the direction of geomagnetic zenith. We present experimental results from transmitting a left-handed circularly polarized HF beam from the EISCAT (European Incoherent SCATter association) Heating facility in magnetic zenith. The ... -
First Simultaneous Rocket and Radar Detections of Rare Low Summer Mesospheric Clouds
(Journal article; Peer reviewed, 2018-06-10)On 30 June 2016 a layer of dust, possibly meteoric smoke particles (MSPs), was observed with a rocket borne probe at 69.29°N, 16.02°E and altitudes of ~74 km where patchy thin cloud layers, detected with the Middle Atmosphere Alomar Radar System, were present. The rocket traversed a layer with a net positive dust charge density of ~107 unit charges per cubic meters and a number density of neutral ... -
Faraday rotation fluctuations of MESSENGER radio signals through the equatorial lower corona near solar minimum
(Journal article; Peer reviewed; Tidsskriftsartikkel, 2016-12-26)Faraday rotation (FR) of transcoronal radio transmissions from spacecraft near superior conjunction enables study of the temporal variations in coronal plasma density, velocity, and magnetic field. The MESSENGER spacecraft 8.4 GHz radio, transmitting through the corona with closest line-of-sight approach 1.63–1.89 solar radii and near-equatorial heliolatitudes, was recorded soon after the deep ... -
Thermal analysis of PTC heaters. Thermography of PTC and Peltier heaters. Labview® based control and Matlab® Simulink simulations of PTC heaters.
(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 ... -
First results from the Njord device for space related plasma experiments
(Conference object; Konferansebidrag, 2007-08-05)The Njord device at Aurolab, University of Tromsø, has been constructed to carry out experiments on instabilities and heating in plasma flows and beams, with relevance to near-Earth space plasmas. For plasma production, Njord combines a 13.56 MHz RF source with a Double Plasma chamber equipped with filaments along the walls. The source is equipped dwith two coils operated at 0-6A, providing magnetic ... -
Spacecraft Radio Frequency Fluctuations in the Solar Corona: A MESSENGER–HELIOS Composite Study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-31)Fluctuations in plasma electron density may play a role in solar coronal energy transport and the dissipation of wave energy. Transcoronal spacecraft radio sounding observations reveal frequency fluctuations (FFs) that encode the electron number density disturbances, allowing an exploration of the coronal compressive wave and advected inhomogeneity models. Primary FF observations from MESSENGER 2009 ... -
Remote Sensing of Coastal Waters
(Master thesis; Mastergradsoppgave, 2019-03-01)The coastal areas outside Lofoten, Vesterålen and Senja, in the northern Norwegian coast, are known for their incredible nature, majestic mountains and unique fishing communities. This coastal area is known for high marine productivity and an important marine environment, being the home for valuable fish stocks including pollock, haddock, herring and cod. To study the characteristics of coastal ... -
Modeling of photovoltaic power generation and electric vehicles charging on city-scale: A review
(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 ... -
Gaussian Markov random field priors in ionospheric 3D multi-instrument tomography
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-22)In ionospheric tomography, the atmospheric electron density is reconstructed from different electron density related measurements, most often from ground-based measurements of satellite signals. Typically, ionospheric tomography suffers from two major complications. First, the information provided by measurements is insufficient and additional information is required to obtain a unique solution. ... -
Bistatic Observations of the Ocean Surface with HF Radar, Satellite and Airborne Receivers
(Journal article; Peer reviewed, 2017-12-25)A new concept has been developed which can view vast regions of the Earth’s surface. Ground HF transmissions are reflected by the ionosphere to illuminate the ocean over a few thousand kilometers. HF receivers detect the radio waves scattered by the sea and land surface. Using the theory of radio wave scatter from ocean surfaces, the HF data is then processed to yield the directional wave-height ... -
EISCAT 3D: the next generation international atmosphere and geospace research radar
(Journal article; Tidsskriftartikkel, 2019)EISCAT_3D is the next generation international atmosphere- and geospace research radar under development in Arctic Europe. Construction have started in September 2017 and the radar system is expected to be operational in the end of 2021. The EISCAT_3D facility will be distributed across three sites in Northern Scandinavia - in Skibotn, Norway, near Kiruna in Sweden, and near Karesuvanto in Finland. ...