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Visar resultat 1 - 5 av 14 uppsatser som matchar ovanstående sökkriterier.

1. 1. Effects of reconstruction parameters on the image quality and quantification of PET images from PET/MRI and PET/CT systems

   Master-uppsats,

   Författare :Ali Amena Hussain; [2022-03-09]
   Nyckelord :Medical physics; PET CT; PET MRI; OSEM; BPL; NEMA IQ; positron emission tomography; magnetic resonance imaging; computed tomography; ordered Subset Expectation Maximization; The Bayesian Penalized Likelihood;

   Sammanfattning : Aim: To study how reconstruction parameters affect the positron emission tomography (PET) image quality and quantitative results for the different lesion to background radioactivity ratios in three different PET systems. Introduction: Multimodality imaging that combines magnetic resonance imaging (MRI) or computed tomography (CT) with a PET system can produce medical images containing both functional and anatomical information. LÄS MER

3. 2. Spectroscopic model characterisation of hot exoplanet atmospheres

   Master-uppsats, Lunds universitet/Astronomi - Genomgår omorganisation; Lunds universitet/Fysiska institutionen

   Författare :Elin Sandvik; [2022]
   Nyckelord :Transit method; Transmission spectroscopy; Exoplanets; Hot Jupiter; Modelling; Physics and Astronomy;

   Sammanfattning : Hot Jupiters are gas giants under intense stellar radiation with short orbital periods of only a few days. Due to their large radii, hot temperatures, and large scale heights, hot Jupiters can be observationally characterised in detail through spectroscopy over an entire orbital phase. LÄS MER

4. 3. Have Radial Velocity Surveys Missed Any Planets?

   Kandidat-uppsats, Lunds universitet/Astronomi - Genomgår omorganisation; Lunds universitet/Fysiska institutionen

   Författare :Shah Raj; [2021]
   Nyckelord :radial velocity survey; transit method; exoplanet; habitable zone; habitable zone boundaries; HZ; early Mars; recent Venus; stability; instability; chaos; REBOUND; MEGNO; MEGNO maps; Hill sphere; stable systems; unstable systems; Physics and Astronomy;

   Sammanfattning : The project was aimed at numerically assessing exoplanetary systems to distinguish their capabilities of hosting additional planets. The shortcomings of the radial velocity method sometimes causes hindrance in the detection of terrestrial planets. LÄS MER

5. 4. Magnificent beasts of the Milky Way: Hunting down stars with unusual infrared properties using supervised machine learning

   Master-uppsats, Uppsala universitet/Observationell astrofysik

   Författare :Julia Ahlvind; [2021]
   Nyckelord :machine learning; supervised machine learning; support vector machine; photometry; stars; stellar physics; astronomical archives;

   Sammanfattning : The significant increase of astronomical data necessitates new strategies and developments to analyse a large amount of information, which no longer is efficient if done by hand. Supervised machine learning is an example of one such modern strategy. LÄS MER

7. 5. Cosmological implications of a QCD-like composite Higgs model

   Master-uppsats, Lunds universitet/Teoretisk partikelfysik - Geonomgår omorganisation; Lunds universitet/Institutionen för astronomi och teoretisk fysik - Genomgår omorganisation

   Författare :Hristina Georgieva Hristova; [2021]
   Nyckelord :composite Higgs; technicolor; gravitational waves; LISA; phase transition; Physics and Astronomy;

   Sammanfattning : Some of the shortcomings of the Standard Model of particle physics are the 'unnatural' value of the mass of the Higgs boson and the fact that the model cannot account for the process of baryogenesis - a mechanism which generates the observed asymmetry between matter and anti-matter in the Universe. The former is related to the fundamental scalar nature of the Higgs boson, connected to quadratic divergences in the mass corrections. LÄS MER