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Efficient electrochemical nitrogen fixation at iron phosphide (Fe_2P) catalyst in alkaline medium
Beata Rytelewska, Anna Chmielnicka, Takwa Chouki, Magdalena Skunik-Nuckowka, Shaghayegh Naghdi, Dominik Eder, Aleksandra Michalowska, Tomasz Ratajczyk, Egon Pavlica, Saim Emin, 2023, original scientific article

Abstract: A catalytic system based on iron phosphide (Fe2P) has exhibited electrocatalytic activity toward N2-reduction reaction in alkaline medium (0.5 mol dm−3 NaOH). Based on voltammetric stripping-type electroanalytical measurements, Raman spectroscopic and spectrophotometric data, it can be stated that the Fe2P catalyst facilitates conversion of N2 to NH3, and the process is fairly selective with respect to the competing hydrogen evolution. A series of diagnostic electrocatalytic experiments (utilizing platinum nanoparticles and HKUST-1) have been proposed and performed to control purity of nitrogen gas and to probe presence of potential contaminants such as ammonia, nitrogen oxo-species and oxygen. On the whole, the results are consistent with the view that the interfacial reduced-iron (Fe0) centers, while existing within the network of P sites, induce activation and reduction of nitrogen, parallel to the water splitting (reduction) to hydrogen. It is apparent from Tafel plots and impedance measurements that mechanism and dynamics of nitrogen reduction depends on the applied electroreduction potential. The catalytic system exhibits certain tolerance with respect to the competitive hydrogen evolution and gives (during electrolysis at -0.4 V vs. RHE) the Faradaic efficiency, namely, the selectivity (molar) efficiency, toward production of NH3 on the level of 60%. Under such conditions, the NH3-yield rate has been found to be equal to 7.5 µmol cm−2 h−1 (21 µmol m−2 s−1). By referring to classic concepts of electrochemical kinetic analysis, the rate constant in heterogeneous units has been found to be on the moderate level of 1-2*10−4 cm s−1 (at -0.4 V). The above mentioned iron-phosphorous active sites, which are generated on surfaces of Fe2P particles, have also been demonstrated to exhibit strong catalytic properties during reductions of other electrochemically inert reactants, such as oxygen, nitrites and nitrates.
Keywords: nitrogen reduction, alkaline medium, iron phosphide catalyst, ammonia, electrochemical determinations
Published in RUNG: 30.11.2023; Views: 947; Downloads: 4
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Lens parameters for Gaia18cbf – a long gravitational microlensing event in the Galactic plane
K. Kruszyńska, Ł. Wyrzykowski, K. A. Rybicki, M. Maskoliūnas, E. Bachelet, N. Rattenbury, P. Mróz, P. Zieliński, K. Howil, Z. Kaczmarek, S. T. Hodgkin, N. Ihanec, I. Gezer, M. Gromadzki, P. Mikołajczyk, A. Stankevičiūtė, V. Čepas, E. Pakštienė, K. Šiškauskaitė, J. Zdanavičius, V. Bozza, M. Dominik, R. Figuera Jaimes, A. Fukui, M. Hundertmark, N. Narita, R. Street, Y. Tsapras, Mateusz Bronikowski, M. Jabłońska, A. Jabłonowska, O. Ziółkowska, 2022, original scientific article

Abstract: Context. The timescale of a microlensing event scales as a square root of a lens mass. Therefore, long-lasting events are important candidates for massive lenses, including black holes. Aims. Here, we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It exhibited a long timescale and features that are common for the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model. Methods. We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigated the range of microlensing models and used them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using a known mass-brightness relation, we determined how likely it is that the lens is a main-sequence (MS) star. Results. This event is one of the longest ever detected, with the Einstein timescale of tE = 491.41−84.94+128.31 days for the best solution and tE = 453.74−105.74+178.69 days for the second best. Assuming Galaxy priors, this translates to the most probable lens masses of ML = 2.65−1.48+5.09 M⊙ and ML = 1.71−1.06+3.78 M⊙, respectively. The limits on the blended light suggest that this event was most likely not caused by a MS star, but rather by a dark remnant of stellar evolution.
Keywords: gravitational lensing: micro, Galaxy: stellar content, stars: black holes, stars: neutron, Astrophysics - Solar and Stellar Astrophysics
Published in RUNG: 13.11.2023; Views: 923; Downloads: 4
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Interpolation of Instrument Response Functions for the Cherenkov Telescope Array in the context of pyirf
R. M. Dominik, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution

Abstract: The Cherenkov Telescope Array (CTA) will be the next generation ground-based very-high-energy gamma-ray observatory, constituted by tens of Imaging Atmospheric Cherenkov Telescopes at two sites once its construction and commissioning are finished. Like its predecessors, CTA relies on Instrument Response Functions (IRFs) to relate the observed and reconstructed properties to the true ones of the primary gamma-ray photons. IRFs are needed for the proper reconstruction of spectral and spatial information of the observed sources and are thus among the data products issued to the observatory users. They are derived from Monte Carlo simulations, depend on observation conditions like the telescope pointing direction or the atmospheric transparency and can evolve with time as hardware ages or is replaced. Producing a complete set of IRFs from simulations for every observation taken is a time-consuming task and not feasible when releasing data products on short timescales. Consequently, interpolation techniques on simulated IRFs are investigated to quickly estimate IRFs for specific observation conditions. However, as some of the IRFs constituents are given as probability distributions, specialized methods are needed. This contribution summarizes and compares the feasibility of multiple approaches to interpolate IRF components in the context of the pyirf python software package and IRFs simulated for the Large-Sized Telescope prototype (LST-1). We will also give an overview of the current functionalities implemented in pyirf.
Keywords: Cherenkov Telescope Array, CTA, ground-based very-high-energy gamma-ray observatory, pyirf
Published in RUNG: 26.09.2023; Views: 873; Downloads: 4
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Substantial brown carbon emissions from wintertime residential wood burning over France
Yunjiang Zhang, Alexandre Albinet, Jean-Eudes Petit, Véronique Jacob, Florie Chevrier, Gregory Gille, Sabrina Pontet, Eve Chrétien, Marta Dominik-Sègue, Gilles Levigoureux, Griša Močnik, Valérie Gros, Jean-Luc Jaffrezo, Olivier Favez, 2020, original scientific article

Abstract: Brown carbon (BrC) is known to absorb light at subvisible wavelengths but its optical properties and sources are still poorly documented, leading to large uncertainties in climate studies. Here, we show its major wintertime contribution to total aerosol absorption at 370 nm (18–42%) at 9 different French sites. Moreover, an excellent correlation with levoglucosan (r2 = 0.9 and slope = 22.2 at 370 nm), suggesting important contribution of wood burning emissions to ambient BrC aerosols in France. At all sites, BrC peaks were mainly observed during late evening, linking to local intense residential wood burning during this time period. Furthermore, the geographic origin analysis also highlighted the high potential contribution of local and/or small-regional emissions to BrC. Focusing on the Paris region, twice higher BrC mass absorption efficiency value was obtained for less oxidized biomass burning organic aerosols (BBOA) compared to more oxidized BBOA (e.g., about 4.9 ± 0.2 vs. 2.0 ± 0.1 m2 g−1, respectively, at 370 nm). Finally, the BBOA direct radiative effect was found to be 40% higher when these two BBOA fractions are treated as light-absorbing species, compared to the non-absorbing BBOA scenario.
Keywords: Brown carbon, Multi sites, Residential wood burning, Mass absorption efficiency, France
Published in RUNG: 20.07.2020; Views: 3284; Downloads: 0
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Dominik Nemec, Franci Novak, 2018, other monographs and other completed works

Keywords: air pollution, fireworks, airborne particles
Published in RUNG: 09.01.2019; Views: 3919; Downloads: 163
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International Conference on Functional Nanomaterials and Nanodevices
Saim Emin, Dominik Eder, Polina Mladenova, 2018, other monographs and other completed works

Keywords: energy conversion, catalysis, nanomaterials, nanobiotechnologies
Published in RUNG: 17.09.2018; Views: 4721; Downloads: 0
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Primerjalna analiza projekta poslovnih prostorov s stališča varčne rabe energije
Dominik Rijavec, 2006, undergraduate thesis

Abstract: V diplomskem delu obravnavamo problematiko ogrevanja poslovnih prostorov. Vpra.ali smo se, na kaj moramo biti pozorni pri določitvi sistema ogrevanja in kaj vpliva na ekonomičnost le tega? Najprej smo definirali parametre ugodja, ki vplivajo na počutje v prostoru. To so: temperatura zraka, temperatura obodnih sten, relativna vla.nost zraka, gibanje zraka in kvaliteta zraka. To so parametri, katere moramo upo.tevati pri določitvi ogrevalnega sistema. V nadaljevanju smo predstavili elemente,ki so ključnega pomena pri centralnem ogrevanju; kotel, dimnik, cevno, regulacija, ekspanzijska posoda, črpalke in ogrevala. Pri tehničnem izračunu smo najprej definirali generični poslovni prostor velikosti 100 m2. Izračunali smo toplotne prehodnosti obodnih sten, definirali projektne temperature in na podlagi tega izračunali toplotne izgube za dva različna načina gradnje (manj in bolj izoliranega). Nato smo izračunali .tevilo radiatorskih ogreval pri radiatorskem sistemu ogrevanja in dol.ino cevi pri talnem sistemu ogrevanja. Na podlagi tega smo določili moč kotla in temperaturni ogrevanja. Nato smo se osredotočili na ekonomski vidik diplomske naloge. Najprej smo ovrednotili posameznih sistemov ogrevanja in vrednost izolacije pri dodatno izolirani izvedbi stavbe. Izračunali smo porabo goriva in stro.ek ogrevanja na kurilno sezono za dva različna energenta (ekstra lahko kurilno olje in drva) in dve izvedbi gradnje. Glede na manj.e ogrevanja pri izvedbi gradnje z bolj.o izolacijo, smo izračunali prihranek energije. Ali je smiselno investirati v dodatno izolacijo ali ne, smo se odločili po metodi interne stopnje prihranka. Na koncu smo analizirali vseh deset variant in določili najprimernej.o varianto ogrevanja za poslovni prostor. Glede na vrednost in ogrevanja je najbolj.a varianta tista, kjer imamo radiatorski visoko temperaturni ogrevalni sistem na trdno gorivo. Glede na funkcionalnost sistema, ugodje v prostoru in prihranek energije pa varianta, pri kateri imamo poslovni prostor dodatno izoliran in imamo nizko temperaturni ogrevalnisistem talnega ogrevanja z ekstra lahkim kurilnim oljem. S tem dose.emo najbolj.e ugodje v sistemu.
Keywords: diplomske naloge, poslovni prostori, ogrevanje, izolacija, centralno ogrevanje, talno ogrevanje, goriva, prihranek
Published in RUNG: 15.10.2013; Views: 5585; Downloads: 428
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