Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


21 - 25 / 25
First pagePrevious page123Next pageLast page
21.
Analysis and characterization of thermal systematic effects on the PLANCK LFI data
Tanja Petrushevska, 2010, master's thesis

Abstract: The cosmic microwave background radiation discovered by Penzias and Wilson in 1965, is considered one of the most important experimental evidences in favour of the Hot Big Bang standard cosmological model. This radiation provides an image of the Universe when it was about 380,000 years old and has a blackbody spectral distribution at temperature T=2.725±0.002 K, index of thermodynamic equilibrium with the mater in epoch when it was released. The cosmic background radiation presents anisotropies at level of 10 5 which provide valuable information about the origin and the evolution of the Universe. After the discovery of background radiation, tens of experiments have been performed to measure this radiation and its anisotropies. In 1992 the COBE satellite revolutionized cosmology by detecting temperature anisotropies for the first time. Launched on May 14, 2009, Planck is a European Space Agency mission designed to measure the CMB anisotropies with an accuracy set by fundamental astrophysical limits. To do this, Planck is imaging the whole sky with an unprecedented combination of sensitivity ( ΔT/T~2*10^-6), angular resolution (to 5’), and 9 frequency coverage (30 857 GHz). To reach these ambitious requirements, Planck uses an active cryogenic thermal system which cools the instruments to 0.1 K. The high sensitivity of the instrument and the cryogenic system makes the thermal systematic effects study of crucial importance to the scientific success. The thesis is divided into six chapters: 1. Chapter 1 explains the properties of the cosmic background radiation and its anisotropies; 2. Chapter 2 presents a short overview of the various experiments dedicated to the study of cosmic background radiation; 3. Chapter 3 describes the Planck mission, its instruments and its goals, in particular the Low Frequency Instrument (LFI) and its thermal structure; Chapter 4 discusses the analysis of the LFI thermal stability. This work was carried out in the Physics department at the University of Trieste, at the LFI Data Processing Centre located at INAF (Instituto Nazionale di AstroFisica) - OATS (Astronomical Observatory of Trieste); Chapter 5 presents the results of this analysis; in Chapter 6 conclusions are drawn and proposals for future work are discussed.
Keywords: Cosmic background radiation, CMB, Planck, satellite mission
Published in RUNG: 24.01.2018; Views: 3063; Downloads: 108
.pdf Full text (23,33 MB)

22.
Atomic-level mechanisms of magnesium oxidation
Sandra Gardonio, Mattia Fanetti, Matjaž Valant, Dmytro Orlov, 2016, published scientific conference contribution

Abstract: Magnesium has been recently becoming an increasingly popular material for various applications. However, excessive chemical reactivity, and oxidation rate in particular, is a major obstruction on the way of Mg to become widely adopted. A significant problem causing the lack of Mg reactivity control is insufficient understanding of mechanisms involved in the oxidation of magnesium surface. Herewith we present the investigation of atomic-level mechanisms of oxidation initiation and propagation in pure Mg. Namely, X-ray photoelectron spectroscopy at synchrotron Elettra was used as a surface sensitive direct method to determine the valence of Mg and O and the valence band states at the early stage of oxide formation over a principal, most densely packed, crystallographic plane (0001) in pure Mg. The mechanisms of oxygen adsorption on magnesium free surface followed by oxidation (i.e. initiation and kinetics of MgO formation) are clarified. Copyright © 2016 by The Minerals, Metals & Materials Society. All rights reserved.
Keywords: Magnesium, Oxidation, Synchrotron radiation, X-ray photoelectron spectroscopy
Published in RUNG: 25.08.2017; Views: 5002; Downloads: 0
This document has many files! More...

23.
24.
FERMI-LAT OBSERVATIONS OF HIGH-ENERGY γ-RAY EMISSION TOWARD THE GALACTIC CENTER
Gabrijela Zaharijas, B. L. Winer, 2016, original scientific article

Abstract: The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy γ-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1–100 GeV from a 15° × 15° region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the γ-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner ∼1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15° × 15° region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point Source Catalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with γ-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.
Keywords: cosmic rays – Galaxy: center – gamma-rays: general – gamma-rays: ISM – radiation mechanisms: non-thermal
Published in RUNG: 02.03.2016; Views: 5123; Downloads: 289
.pdf Full text (6,36 MB)

25.
Chemical and structural investigation of the cobalt phthalocyanine
Matija Stupar, 2015, master's thesis

Abstract: In the last two decades, studies on organic molecules mimicking substances of fundamental importance in nature, like chlorophyll or hemoglobin, have attracted researchers’ attention. These molecules are building blocks for a family of materials also referred to as “organic semiconductors”. Such compounds can be implemented in numerous applications, ranging from data-storage to light harvesting. Some of their fundamental advantages include low cost, light weight, relatively easy engineering and mechanical flexibility, compatible with bending plastic substrates. In this thesis work we investigated the chemical, structural and electronic properties of cobalt phthalocyanines (CoPc). These molecules have promising applications in the field of magnetic data storage and spintronics in general, due to the ferromagnetic properties of the cobalt atom. Several techniques like photoemission core-level spectroscopy and valence band spectroscopy, together with X-ray absorption, have been used in order to determine the CoPc properties in gaseous phase, i.e. in the absence of interaction with the surrounding environment. Another set of experiments was devoted to the commissioning of the CITIUS time-resolved photoemission setup, that will be used in future studies of CoPc molecules on surfaces.
Keywords: Cobalt phthalocyanine (CoPc), photoemission spectroscopy (PES), X-ray absorption spectroscopy (XAS), synchrotron radiation, laser, high order harmonic generation (HHG), time resolved spectroscopy
Published in RUNG: 29.09.2015; Views: 8713; Downloads: 280
.pdf Full text (2,96 MB)

Search done in 0.03 sec.
Back to top