Blar i utgivelsesdato Mastergradsoppgaver i fysikk
Viser treff 120 av 54

Måling av plasmadrift i den øvre atmosfære over NyÅlesund, Svalbard.
(Master thesis; Mastergradsoppgave, 197711)Oppgaven bygger på målinger av plasmadrift i den øvre atmosfære over NyÅlesund, Svalbard. Som målemetode er brukt "spaced receivers" metoden. I kap. 2 er satt opp modeller for solvind, magnetosfære og ionosfære og en ser på fenomen som forplanter seg fra solvinden til ionosfæren. Ved hjelp av disse modeller beregnes så drift av plasma i ionosfæren. I kap. 3 beskrives målemetoden. Diffraksjonsmekanismen ... 
Fotoelektriske observasjonar av stjerneokkultasjonar ved måneranda
(Master thesis; Mastergradsoppgave, 198001)Analyser av okkultasjonskurvene frå fotoelektriske observasjonar viser at ein stor del av dei observerte stjernene er dobbelstjerner. Okkultasjonsteknikken kan lett åtskilje stjerner som har ein vinkelavstand større enn 0",01 og under gunstige tilhøve kan oppløysinga vere 0",001. I tillegg kan analysen av observasjonen gje vinkeldiameteren til stjerna dersom han er større enn 0",001. Utfrå ... 
Observations of auroral plasma lines
(Master thesis; Mastergradsoppgave, 19980301)The thesis describes observations of strongly enhanced incoherent scatter plasma lines in the auroral ionosphere which were made with the EISCAT UHF radar in 1985. The linear theory of plasma instabilities is reviewed, and several possible explanations are discussed. The observations were found to be of insufficient resolution to unambiguously resolve which one would be the correct explanation. ... 
A detection theoretical approach to digital communications using autoregressive process shift keying
(Master thesis; Mastergradsoppgave, 20010310)I klassisk digital kommunikasjon overføres en bitstrøm gjennom en kanal ved å modulere parametrene til en deterministisk bærebølge. Noen kjente eksempler er amplitudemodulasjon (AM), frekvensmodulasjon (FM) og fasemodulasjon (PM). Mottakeren estimerer parametrene til det informasjonsbærende signalet og bruker en deteksjonsregel til å klassifisere den mottatte bølgeformen som en av flere mulige ... 
The harmonizable representation of complexvalued nonstationary random processes
(Master thesis; Mastergradsoppgave, 20050614)In this thesis we study the secondorder statistical moment functions that characterizes complexvalued harmonizable processes. A realvalued harmonizable process has four Hermitian secondorder functions. These functions are equivalent representations of the secondorder statistical quantities of the process. For a complexvalued harmonizable process, however, we need the complementary functions ... 
Statistical modelling of polarimetric SAR data
(Master thesis; Mastergradsoppgave, 20060602)A statistical modelling technique is developed to analyse polarimetric synthetic aperture radar (PolSAR) images. Polarimetric SAR data consists of four complex scattering coefficients at each image location, requiring multivariate modelling techniques, and this work focuses on a simple class of multivariate distributions, the scale mixture of Gaussians. Three parametric model families of that ... 
Lowfrequency noise power spectrum density characterizing of SiGe HBTs
(Master thesis; Mastergradsoppgave, 20060606)The main purposes of this thesis are the LowFrequency Noise measurement of SiliconGermanium Heterojunction Bipolar Transistors and its Power Spectrum Density Characterizing. The new generation 375 GHZ SiGe HBTs were measured in this work. We show that most of PSDs of the new generation SiGe HBTs have very ”bumpy” spectra which is contributed by GR noise sources. We investigated their basic ... 
A comparative study of algorithms for blind source separation in the instantaneous linear mixture model
(Master thesis; Mastergradsoppgave, 20070622)This thesis discusses some of the many techniques for performing blind source separation. Its focus is on the theoretical concepts that allow for the problem to be solved. It starts with presenting the EM algorithm, which is the method underpinning many of the algorithms that are presented later in the thesis. Some of the established methods are presented, and we proceed to devolop source separation ... 
A numerical study of planar elliptical antennas applied to ultrawideband (UWB) imaging of breast tissue
(Master thesis; Mastergradsoppgave, 200808)The thesis discusses the possibility of using ultrawideband (UWB) radar to detect breast cancer. At the present time, Xray mammography and ultrasound are the golden standard imaging techniques for detection and evaluation of breast cancer, but they both have their limitations. UWB radar utilizes the difference in dielectric properties between a tumor and the surrounding healthy tissue. By interpreting ... 
A multiwavelet approach to the direct solution of the Poisson equation: implementation and optimization
(Master thesis; Mastergradsoppgave, 20091115)This work is presenting a fully numerical approach for the direct solution of the Poisson equation for the electrostatic potential given by an arbitrary charge density. Efficient solution of this equation is important in many fields of science, where the current work is dealing with nuclear and electronic potential calculations, used in the field of computational chemistry. The equation is solved ... 
Numerical studies of radial filament motion in toroidally confined plasmas
(Master thesis; Mastergradsoppgave, 201005)Numerical studies of radial filament motions in the SOL of toroidally confined plasmas are studies. We use a two dimensional twofield model to characterize bloblike structures in the radialpoloidal domain. These structures are observed to achieve velocities in the order of the ion acoustic velocity in the SOL of tokamaks and other toroidal confinement devices. By numerical means we find a ... 
Simulations of plasma filament dynamics in toroidal geometry
(Master thesis; Mastergradsoppgave, 20100518)Interchange driven propagation of socalled "blobs" arises in basic laboratory plasmas, in the scrapeoff layer of fusion plasmas and as Equatorial SpreadF (ESF) phenomena. The propagation of such blobs has been demonstrated in the VTF experiment at MIT and in earlier simulations. Experimental results show that the velocity of these blobs is inverse proportional to the neutral gas pressure. These ... 
Frequencydependent magnetizability
(Master thesis; Mastergradsoppgave, 20101115)This work discusses the theory of the magnetizability. The magnetizability is a molecular property defined as the secondorder perturbation of the energy in the presence of an external magnetic field. When the magnetic field is static, perturbation and multipole theories lead to an originindependent expression for the magnetizability, whereas for a frequencydependent magnetic field its expression ... 
Trapping of Nanoparticles with Optical Waveguides
(Master thesis; Mastergradsoppgave, 20110518)Over the last few years, the notion that links optical trapping with strong intensity of light (high energy photon) not only forced the modification of optical tweezer, but it also open up the door for evanescent wave field trapping. While optical tweezer is merely suitable for trapping microsized particles, trapping by evanescent field of a channel waveguide enables both micro and nanosized particles ... 
Multisensor data fusion and feature extraction for forest applications
(Mastergradsoppgave; Master thesis, 20120515)The purpose of this study was to extract, evaluate and select different multifrequency polarimetric SAR and multispectral optical features to demonstrate the benefit of multisensor data fusion for forest applications. Multifrequency fully Polarimetric SAR data at P, L and Cband and multispectral Landsat TM data acquired over the Nezer forest in France were used for demonstration. The scene ... 
Spectral analysis of radar coherent echoes and its relation to turbulence
(Master thesis; Mastergradsoppgave, 201211)The measurements of polar mesosphere summer echoes has been performed since a long time by the ground based techniques with EISCAT VHF and UHF radar system and recently with MORRO. Based on these observation, my thesis is focussed on the data obtained from manda program to get data from EISCAT 3D demonstrator antenna array in Kiruna that receives from EISCAT VHF transmitter here from Tromso in the ... 
Suppression of fingering instabilities in superconductors by magnetic braking
(Master thesis; Mastergradsoppgave, 201211)Superconductors are materials that can transport electric current without resistance and loss of energy at low temperature. This thesis is a theoretical investigation problem about the thermomagnetic instability in superconductor and its suppression by deposing a metallic layer. 
Studies of plasma potential with emissive probes in the low temperature plasma experiment NJORD
(Master thesis; Mastergradsoppgave, 20121102)In this thesis, the concept of an emissive probe has been used to obtain the plasma potential in the low temperature plasma experiment NJORD. An emissive probe is a probe concept in which a wire is heated strong enough to emit a Richardson current. The probe is then swept through several voltage biases and thus, an IV trace obtained. With the current from the emission and the collected current, ... 
Drift wave turbulence and zonal flows
(Master thesis; Mastergradsoppgave, 20121115)Anomalously large radial transport levels in fusion devices is commonly believed to be the cause of smallscale edge localized electrostatic drift wave turbulence. We review the basic drift wave instability mechanism and show how poloidally elongated structures can selfconsistently emerge from the smallscale turbulent motions through envelope modulation governed by the cubic nonlinear ... 
Longrange memory in Earth surface temperatures: spatial scale dependence and landsea differences
(Master thesis; Mastergradsoppgave, 20130515)The use of longrange memory models as a description of the noise in Earth surface temperatures has increased the recent years, and as a measure of the persistence for such time series we have the Hurst exponent. It is known that sea surface temperatures are more persistent than land temperatures, and that global temperatures are more persistent than local temperatures. We also know that the persistence ...