1. Proučevanje eno in večkovinskih katalizatorjev na silikatnem nosilcu v naprednem oksidacijskem procesu za čiščenje odpadnih voda : magistrsko deloSara Kozjan, 2024, master's thesis Abstract: Ena izmed glavnih onesnaževal v odpadnih vodah so strupene organske spojine, katerih količina se z industrijskim razvojem nenehno povečuje. Najbolj nevarna so tako imenovana zaskrbljujoča onesnaževala (CEC – Contaminants of Emerging Concern), med katerimi so najpogostejših farmacevtski izdelki in izdelki za osebno nego. Za učinkovito odstranjevanje le-teh se raziskave osredotočajo na napredne oksidacijske procese (Advanced Oxidation Processes – AOP), ki s pomočjo katalizatorjev in oksidantov organska onesnaževala oksidirajo v ogljikov dioksid, vodo in mineralne kisline. Magistrska naloga se nanaša na proučevanje eno, dvo in trikovinskih katalizatorjev na silikatnem nosilcu. Kovine, ki smo jih proučevali, so bile baker, mangan in železo.
Katalizatorji so bili sintetizirani na Odseku za anorgansko kemijo in tehnologijo na Kemijskem inštitutu. Katalizatorje smo najprej ovrednotili z osnovnimi karakterizacijskimi metodami, kot so rentgenska difrakcija (XRD – X-Ray Diffraction), dušikova fizisorpcija in vrstična elektronska mikroskopija (SEM – Scanning Electron Microscopy). Ugotovili smo, da imajo višjo vsebnost kovin skoraj vsi kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji, kar lahko pripišemo ekstrakcijskemu postopku, med katerim se najverjetneje odstrani določeno množino kovin iz katalizatorjev. Postopek priprave bistveno ne vpliva na specifično površino, velikost por in volumen por katalizatorjev. Pri kalciniranih katalizatorjih, ki vsebujejo Cu, je le-ta prisoten v obliki CuO.
Katalitske teste sem izvedla na dveh modelnih onesnaževalih iz skupine CEC in sicer na kumarinu (Fenton in foto-Fenton AOP) in glifosatu (Fenton AOP). Ugotovila sem, da so v primeru obeh uporabljenih modelnih onesnaževal najbolj učinkoviti dvokovinski katalizatorji in sicer pri kumarinu katalizator s Cu in Mn ter pri glifosatu katalizator s Cu in Fe. Pri kumarinu katalizator s Cu in Mn kaže tudi na fotokatalitsko aktivnost pri obsevanju z vidno svetlobo. Prav tako sem ugotovila, da so tako kot pri kumarinu tudi pri glifosatu bolj učinkoviti kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji. To lahko pripišemo višji vsebnosti kovin ali/in prisotnosti Cu specij v obliki CuO v kalciniranih katalizatorjih. To ugotovitev bi bilo potrebno v nadaljevanju podrobneje raziskati.
Keywords: čiščenje odpadnih voda, napredni oksidacijski procesi, heterogena kataliza, katalizatorji na silikatnem nosilcu, glifosat, kumarin
Published in RUNG: 11.09.2024; Views: 904; Downloads: 13
 Full text (2,43 MB) |
2. Search for a signal from dark matter sub-halos with the galactic plane survey of CTA Observatory : master's thesisZoja Rokavec, 2024, master's thesis Abstract: Dark matter (DM), known to be a dominant matter component in the Universe,
has been searched for extensively, yet remains undetected. One of the promising
avenues of detecting a DM signal is to observe the so called ’DM sub-halos’ within
our galaxy. These sub-halos, which are numerous within the Milky Way, are formed
by the clustering of DM, as predicted by cosmological simulations, and most of
them lack baryonic matter counterparts, making them challenging to detect. How-
ever, the annihilation or decay of Weakly Interacting Massive Particles (WIMPs),
a leading candidate for DM, within these sub-halos is expected to produce very
high-energy (VHE) photons (called gamma-rays) at TeV energies, offering possible
indirect DM detection.
In this thesis, we focus on the Galactic Plane Survey (GPS) of the Cherenkov Tele-
scope Array Observatory (CTAO), an upcoming ground-based gamma-ray obser-
vatory, which promises unprecedented sensitivity and resolution in the detection
of cosmic gamma-ray sources in the ∼ 30 GeV to ∼ 100 TeV energy range. As
dark sub-halos are expected to appear as unidentified (point) sources in the CTAO
GPS data, we employ a machine learning (ML)-based approach, the AutoSour-
ceID framework, leveraging U-shaped networks (U-Nets) and Laplacian of Gaus-
sian (LoG) filter, for automatic source detection and localization, and apply it to
simulated GPS data. We establish detection thresholds for U-Nets trained on dif-
ferently scaled counts (counts, square root or log of counts) and identify which
approach offers best results (in terms of flux sensitivity and location accuracy).
Our findings suggest that using log-scaled counts yields a factor of 1.7 lower flux
threshold compared to counts alone. In addition, we compare our ML outcomes
with traditional methods; however, this comparison is not straightforward, as ML
and traditional approaches fundamentally differ in their methodologies and un-
derlying assumptions. Nevertheless, The flux threshold obtained using log-scaled
counts is comparable to that of the traditional likelihood-based detection method
implemented in the Gammapy library, although further study is needed to estab-
lish a more definitive comparison. These preliminary results also suggest that the
flux threshold for detecting 90% of true sources with the ML approach is approx-
imately two times lower than the sensitivity reported for the GPS in the CTAO
publication. Although these results are not directly comparable due to differences
in methodology, they hint that ML methods may offer superior performance in
certain scenarios. Furthermore, we discuss the implications of our results on the
sensitivity to DM sub-halos, improving it by a factor of 4, highlighting the possi-
bility of detecting at least one sub-halo with a cross section approximately ⟨σv⟩ =
2.4 × 10−23 cm3 /s.
Keywords: Cherenkov Telescope Array Observatory, dark matter, sub-halos, machine learning, gamma-rays, master's thesis
Published in RUNG: 06.09.2024; Views: 777; Downloads: 12
Full text (5,39 MB) |
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8. Charge transport characterization of P3HT thin-film organic semiconductor : Written report: in fulfilment of diploma seminar 1FAF29 requirementMatija Filipčič, 2021, research project (high school) Abstract: The focus of this diploma seminar is to describe different types of charge transport theory and
models used for finding mobility in semiconductors, more specifically focused on P3HT thin-film
organic semiconductor. It also describes the time-of-flight method, which was used to measure the
experimental data for P3HT with time dependent current I(t) curve. Another data set was obtained
by performing Kinetic Monte Carlo (KMC) simulations using Miller-Abrahams hopping formalism.
KMC was used to determine the material disorder, simulate I(t) curve and transit time for every
charge carrier. Simulated data, different transit times and mobilities were then finally compared
with experimental, in order to find agreements between the two.
Keywords: charge transport, P3HT, thin-film organic semiconductor
Published in RUNG: 15.09.2021; Views: 3512; Downloads: 0
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9. Vibrational spectra of am-Al 2 O 3 : tuning a parametric model. : Written report: in fulfillment of Diploma Seminar 1FAF29 requirementsKurtović Jasmin, 2021, research project (high school) Abstract: The present diploma seminar work has been dedicated first to the implementation of a procedure
to calculate the vibrational density of states of two structural models of vitreous SiO 2 (v-
SiO 2 ) and amorphous Al 2 O 3 (am-Al 2 O 3 ) models, and next to tune a parametric model for the
calculation of the infrared (IR) spectra of am-Al 2 O 3 , in particular of the imaginary part of
the dielectric function. The ground state of both structural models is obtained by relaxing
the atomic structure by using the conjugate gradient method as implemented in the LAMMPS
code. Vibrational frequencies and modes are obtained, in the harmonic approximation, by
diagonalizing the dynamical matrices calculated for the given v-SiO 2 and am-Al 2 O 3 structural
models. Dynamical matrices are obtained through a finite differences approach and vibrational
density of states are plotted by applying Gaussian broadening. The calculation of the dielectric
function requires the knowledge of the vibrational frequencies as well as the knowledge of the
dynamical (or Born) charge tensors related to the atoms of the am-Al 2 O 3 structural model.
For the latter model, a parametrization of the ab-initio Born charge tensors has been carried
out with the purpose to allow for the fast calculation of the IR spectrum of any other am-
Al 2 O 3 model without the need to calculate for it the Born charge tensors using expensive ab-
initio methods. The parametrization of Born charge tensors takes into account, for aluminium
atoms, only of the isotropic charge which depends on coordination number and average Al-
O bond length of aluminium atoms, while for oxygen atoms coordinated to three Al atoms
(75%), dynamical charges are parametrized also by the area bounded by aluminium atoms
nearest neighbours of the 3-coordinated oxygen atom. Moreover for analyzing the dynamical
charge tensors of 3-coordinated oxygen atoms a decomposition in terms of the representations
of the spatial rotations was used. The IR spectrum obtained by means of the above described
parametrization provides a good approximation to the IR spectrum obtained by using the ab-
initio calculated dynamical charges, as it differs from it, on average, by around 5.1% which
is much better (12%) than using a average isotropic charge model (i.e. diagonal Born charge
tensors where each diagonal element is one third of the average isotropic charge).
Keywords: Vibrational spectra, am-Al 2 O 3, parametric model
Published in RUNG: 15.09.2021; Views: 3119; Downloads: 0
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