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91.
Coupled irradiation-temperature effects on induced point defects in germanosilicate optical fibers
Layla Martin-Samos, 2017, original scientific article

Keywords: optična vlakna, strukturni defekti, obsevanje
Published in RUNG: 26.01.2018; Views: 3872; Downloads: 0
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92.
93.
94.
Evidence of enhanced photocurrent response in corannulene films
Nadya Patukhova, Layla Martin Samos, Egon Pavlica, Gvido Bratina, 2017, original scientific article

Abstract: Photoconductivity spectra measured in non-crystalline corannulene thin layers are compared to optical absorption in solution phase and thin films. The unexpected enhanced photoconductivity is correlated with GW–BSE theoretical predictions of corannulene gas-phase excitonic spectra. Theoretical analysis reveals a consistent contribution involving transitions to Super Atomic Molecular Orbitals (SAMOs), a unique set of diffuse orbitals typical of curved conjugated constructs. Results suggest SAMO population via direct photoexcitation as a potential mechanism towards exploiting these diffuse orbitals as conducting channels in suitably assembled quantum nanostructures or solids.
Keywords: Coranulene, photoconductivity, thin layers, photoexcitation
Published in RUNG: 26.09.2017; Views: 3800; Downloads: 204
.pdf Full text (644,91 KB)

95.
Electrochemical dissolution of iridium and iridium oxide particles in acidic media : transmission electron microscopy, electrochemical flow cell coupled to inductively coupled plasma mass spectrometry and X-ray absorption spectroscopy study
Primož Jovanovič, Nejc Hodnik, Francisco Ruiz-Zepeda, Iztok Arčon, Barbara Jozinović, Milena Zorko, Marjan Bele, Martin Šala, Vid Simon Šelih, Samo B. Hočevar, Miran Gaberšček, 2017, original scientific article

Abstract: Iridium based particles as the most promising proton exchange membrane electrolyser electrocatalysts were investigated by transmission electron microscopy (TEM), and by coupling of electrochemical flow cell (EFC) with online inductively coupled plasma mass spectrometer (ICP-MS). Additionally, a thin-film rotating disc electrode (RDE), an identical location transmission and scanning electron microscopy (IL-TEM and IL-SEM) as well as an X-ray absorption spectroscopy (XAS) studies have been performed. Extremely sensitive online time-and potential-resolved electrochemical dissolution profiles revealed that iridium particles dissolved already well below oxygen evolution reaction (OER) potentials, presumably induced by iridium surface oxidation and reduction processes, also referred to as transient dissolution. Overall, thermally prepared rutile type IrO2 particles (T-IrO2) are substantially more stable and less active in comparison to as prepared metallic (A-Ir) and electrochemically pretreated (E-Ir) analogues. Interestingly, under OER relevant conditions E-Ir particles exhibit superior stability and activity owing to the altered corrosion mechanism where the formation of unstable Ir(>IV) species is hindered. Due to the enhanced and lasting OER performance, electrochemically pre-oxidized E-Ir particles may be considered as the electrocatalyst of choice for an improved low temperature electrochemical hydrogen production device, namely a proton exchange membrane electrolyser.
Keywords: Iridium Oxide Par-ticles, Electrochemical Dissolution of Iridium, Ir L3-edge XANES
Published in RUNG: 23.08.2017; Views: 3786; Downloads: 0
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96.
KARREN OF THE KAMENJAK HUM (DALMATIAN KARST, CROATIA); FROM THE INITIAL DISSECTION OF FLAT SURFACES
Ela Šegina, 2015, original scientific article

Abstract: Rock relief is an important trace of the formation and development of karst phenomena on various carbonate rock. The existing current state is usually in a rich and diverse stage of homogeneous or heterogeneous development. The various forms of rock relief represent different ways and conditions a karst phenomenon formed and the developmental levels under the same conditions and with the same factors. Research into the connections between different developmental models is therefore necessary. Over time, not only rock relief but also rock forms begin to merge with one another. We are looking at the initial period of the development of a thick rock strata due to rain. On gently sloping rock strata, which tend to disintegrate at the edges, especially when they are inclined downwards, characteristic rock relief forms on the flat surfaces of larger planes, initially due to rainwater and sheets of creeping water and later through three-dimensional dissection and primarily the direct action of rainwater.
Keywords: karren, lithology, complexometry, rock relief, Lake Vrana, Croatia
Published in RUNG: 07.07.2017; Views: 3937; Downloads: 0
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97.
Characterization of Mg low-index surfaces by first-principles
Miha Gunde, 2017, master's thesis

Abstract: In this work, three surfaces, namely, Mg(0001), Mg(10 ̄1 0) and Mg(11 ̄2 0) are investigated by means of Density Functional Theory and Generalized Gradient Approximation first-principle calculations. The surfaces have been characterized in terms of their interlayer distances, surface energies, Projected Density of States and Surface Core Level Shifts. Contrary to what was found in previous studies based on Density Functional Theory-Local Density Approximation, the use of Generalized Gradient Approximation exchange correlation functional unravels the oscillatory behavior of both interlayer distances and Surface Core Level Shifts of Mg(10 ̄1 0). Moreover, the Projected Density Of States of un-reconstructed Mg(11 ̄2 0) exhibit the typical quantisation of electronic levels associated to a 2D-confinement of a 3D nearly-free electron gas, as observed in nano-wires, and a Peierls instability along the unconfined direction. Different possible reconstructions on Mg(11 ̄2 0) have then been investigated. In particular, it is found that the surface energy of (2X1) and (3X1) reconstructions is almost degenerate and lower than the surface energy of the unreconstructed Mg(11 ̄2 0) surface. Because of the quasi-degeneracy of surface energies, Mg(11 ̄2 0) surface should be composed by a combination of all the quasi degenerate phases.
Keywords: Density Functional Theory, first-principle calculations, Mg surface, Surface Core-Level Shift, surface relaxation, surface reconstruction
Published in RUNG: 04.07.2017; Views: 5984; Downloads: 2104
.pdf Full text (1,77 MB)

98.
99.
Detection of gravitational waves : Diploma thesis
Gregor Mrak, 2016, undergraduate thesis

Abstract: This report mainly focuses on the first two detections of gravitational waves (GW). At the beginning of the thesis the historical background of GW explorations is discussed by pointing out some arguments and researchers that were essential for the progress. Continuing with the derivation based on the theory of general relativity, in order to express where certain properties derive. In the main part of the report, the subject of interest becomes Laser interferometer gravitational-wave observatory (LIGO), beginning with the problems occurring on the way to detection, describing different noise sources one by one. After pointing out the problems, solutions are discussed, namely the technological advances made to lower the background noise as much as possible. The chapter (4) points out different parts of the detector which are implemented to produce a clearer signal. As only physical noise reduction methods are not enough, digital signal processing algorithms are mentioned as well which are used to analyze the data. Subsequently the required theoretical knowledge is given, so the main part ends with the analysis of actual data taken from LIGO’s public release for both GW150914 and GW151226 events (first and second official detections). In the conclusion of the report a brief descriptions of various detectors besides Ligo are given and some insight of the future detectors that are planned to be built.
Keywords: Gravitational waves, Ligo, Binary black hole merger, gravitational wave interferometry
Published in RUNG: 27.09.2016; Views: 6919; Downloads: 315
.pdf Full text (3,27 MB)

100.
Atomically resolved dealloying of structurally ordered Pt nanoalloy as an oxygen reduction reaction electrocatalyst
Andraž Pavlišič, Primož Jovanovič, Vid Simon Šelih, Martin Šala, Marjan Bele, Goran Dražić, Iztok Arčon, Samo B. Hočevar, Anton Kokalj, Nejc Hodnik, Miran Gaberšček, original scientific article

Abstract: The positive effect of intermetallic ordering of platinum alloy nanoparticles on oxygen reduction reaction (ORR) activity has been well established. What is still missing is an understanding of selective leaching of the less noble metal from the ordered structure and its correlation to longterm ORR performance. Using a combination of kinetic Monte Carlo simulations and advanced characterization techniques, we provide unprecedented insight into dealloying of intermetallic PtCu3 nanoparticles a well-known binary alloy. Comparison of ordered and disordered samples with identical initial compositions and particle size distributions reveals an unexpected correlation: whereas the copper dealloying rates in the ordered and disordered counterparts are almost the same, in the ordered structure Pt atoms are surrounded by 15−30% more Cu atoms throughout all the stages of acid leaching. This more convenient Pt−Cu coordination explains the statistically significant increase of 23−37% in ORR activity of the ordered structure at all stages of alloy degradation.
Keywords: ORR activity, fuel cells, platinum alloy, nanoparticle stability, intermetallic ordering, kinetic Monte Carlo, dealloying, in situ ICP-MS
Published in RUNG: 27.09.2016; Views: 5528; Downloads: 0
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