241. Aerosol complex refractive index retrieval in the Paris urban area and its forested surroundings during the ACROSS field campaign : variability and constraint for direct radiative effect estimation in regional modelsLudovico Di Antonio, Griša Močnik, 2023, objavljeni povzetek znanstvenega prispevka na konferenci Opis: The complex refractive index (CRI) is one of the key parameter driving aerosol spectral optical properties and direct radiative effects (DRE). Its value and spectral variation under different conditions, such as anthropogenic− and biogenic−dominated environments and anthropogenic−biogenic mixing situations, remains not fully understood. As a consequence, oversimplified representations of aerosol optical properties are generally used in climate models. Therefore, measurements of aerosol CRI in different environments and their inclusion in models are needed. The field observations from the ACROSS campaign, performed in June-July 2022 in the Ile de France region, are used in this study to deepen the knowledge of aerosol optical properties, aiming to improve the aerosol representation in the CHIMERE model and provide the best constraint for DRE simulations. Measurements obtained both at the Paris city center and the Rambouilllet rural forest sites during ACROSS are considered, in order to explore the CRI variability from anthropogenic−dominated to biogenic−dominated environments, including anthropogenic−biogenic mixing situations. The CRI retrievals at seven different wavelengths, performed by combining the Mie theory with optical and size distribution measurements, are representative of different atmospheric conditions, aerosol loadings as well as type and chemical compositions. In fact, the June-July 2022 period was characterized by highly diversified weather conditions: 1) two strong heatwaves, promoting SOA build-up and favoring the export of the Paris pollution plume towards the forest site; 2) Saharan dust events transported from the upper atmosphere to the ground; 3) biomass burning episode; 4) periods with reduced anthropogenic influence. The CRI retrievals under these different conditions and their link to particulate chemical composition is investigated. Hence, the CRI dataset presented here constitutes a unique dataset from which models can benefit to validate and constrain simulations and DRE estimations, under both urban and biogenic emissions influence. These data, in conjunction with those from the aircraft observations during ACROSS, are used to initialize and perform sensitivity studies on the aerosol DRE, using the CHIMERE−WRF coupled model, the OPTSIM model for the aerosol optical properties and the Rapid Radiative Transfer Model for GCMs (RRTMG).Keywords: Complex refractive index, direct radiative effect, aerosol mixing, urban, forest Ključne besede: aerosol optical properties, refractive index Objavljeno v RUNG: 21.12.2023; Ogledov: 646; Prenosov: 2 Celotno besedilo (293,28 KB) |
242. Profiling Saharan airborne dust with UAV-based in-situ instrumentation during the ASKOS experiment in Cape VerdeMaria Kezoudi, Griša Močnik, 2023, objavljeni povzetek znanstvenega prispevka na konferenci Opis: The ASKOS experimental campaign of European Space Agency (ESA) was organised by the National Observatory of Athens, and aimed at the calibration and validation of the Aeolus satellite aerosol/cloud product. Airborne observations were performed by the Climate and Atmosphere Research Centre (CARE-C) team of the Cyprus Institute at the Cesaria Evora International Airport of the island of São Vicente in Cape Verde between 10 and 30 June 2022. These in-situ aerosol measurements were conducted using the advanced Unmanned Aerial Vehicles (UAVs) of the Unmanned System Research Laboratory (USRL), equipped with specialised aerosol in-situ sensors, capturing the Saharan Air Layer (SAL) from ground up to 5.3 km Above Sea Level (ASL). The new custom-designed Composite Bird (CoBi) USRL and Skywalker UAVs (Kezoudi et al., 2021), were equipped with Optical Particle Counters (OPCs), samplers and backscatter sondes.25 UAV vertical flights were performed in total, with 11 of them during night. The altitude of the Marine Boundary Layer (MBL) was mainly observed from ground up to about 1.0 km ASL, whereas during most of the flights, high concentrations of dust particles were found between 1.5 and 5.0 km ASL. Results obtained from OPCs show the presence of particles sizing up to 20 um within MBL and up to 40 um within SAL. Further information on morphology and mineralogy of observed particles will be given by the offline analysis of collected samples under Scanning Electron Microscope (SEM). COBALD observations alongside ground-based lidar measurements agree on the presence of non-spherical particles within dust layers. Ongoing exploitation of airborne observations along with coincident and collocated ground-based measurements will provide a complete picture for comparison with Aeolus data, particularly in relation to aerosols, where we have the most to learn. Ključne besede: mineral dust, UAV, airborne measurements, climate change, Aeolus satellite Objavljeno v RUNG: 21.12.2023; Ogledov: 658; Prenosov: 4 Celotno besedilo (290,96 KB) Gradivo ima več datotek! Več... |
243. Anthropic settlementsʹ impact on the light-absorbing aerosol concentrations and heating rate in the arcticNiccolò Losi, Piotr Markuszewski, Martin Rigler, Asta Gregorič, Griša Močnik, Violetta Drozdowska, Przemek Makuch, Tymon Zielinski, Paulina Pakszys, Małgorzata Kitowska, 2023, izvirni znanstveni članek Opis: Light-absorbing aerosols (LAA) impact the atmosphere by heating it. Their effect in the Arctic was investigated during two summer Arctic oceanographic campaigns (2018 and 2019) around the Svalbard Archipelago in order to unravel the differences between the Arctic background and the local anthropic settlements. Therefore, the LAA heating rate (HR) was experimentally determined. Both the chemical composition and high-resolution measurements highlighted substantial differences between the Arctic Ocean background (average eBC concentration of 11.7 ± 0.1 ng/m3) and the human settlements, among which the most impacting appeared to be Tromsø and Isfjorden (mean eBC of 99.4 ± 3.1 ng/m3). Consequently, the HR in Isfjorden (8.2 × 10−3 ± 0.3 × 10−3 K/day) was one order of magnitude higher than in the pristine background conditions (0.8 × 10−3 ± 0.9 × 10−5 K/day). Therefore, we conclude that the direct climate impact of local LAA sources on the Arctic atmosphere is not negligible and may rise in the future due to ice retreat and enhanced marine traffic. Ključne besede: light-absorbing aerosols, black carbon, climate change, heating rate Objavljeno v RUNG: 21.12.2023; Ogledov: 670; Prenosov: 5 Celotno besedilo (3,57 MB) Gradivo ima več datotek! Več... |
244. Materials for sustainable electrochemical energy conversionSaim Emin, Takwa Chouki, Manel Machreki, 2023, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje) Opis: The process of hydrogen evolution reaction (HER) through water electrolysis is an important technology for
establishing the so called "hydrogen economy". Here we will cover different systems for electrocatalytic HER.
Transition metal carbides and metal phosphides are alternative to platinum (Pt) and offer excellent electrocatalytic
activity for HER. Pyrolysis of hexacarbonyl tungsten, W(CO)6, in 1-octadecene has been used to prepare colloidal
tungsten, W, nanoparticles (NPs) [1]. The obtained W NPs has been spin-coated on graphite (C) electrodes. Heat
treatment of the W/C electrodes at elevated temperatures (≥ 900°C) allows the preparation of metallic W and
tungsten carbide (W2C@WC) thin films. The obtained W2C@WC electrodes were used for hydrogen evolution
studies (HER) in 0.5M H2SO4. Cyclic voltammetry tests for 1000 cycles showed that W2C@WC exhibit long term
stability without significant drop in current density. The overpotential defined at 10 mA/cm2
is 310 mV vs. RHE
giving an excellent catalytic activity for HER. Iron phosphide electrocatalysts were synthesized using a
triphenylphosphine (TPP) precursor. Different iron phosphide phases were synthesized at 300°C (Fe2P) and at
350°C ( FeP ) [2]. To enhance the catalytic activities of obtained iron phosphide particles heat-treatments were
carried out at elevated temperatures. Annealing at 500°C under reductive atmosphere induced structural changes
in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron
phosphide phases (Fe2P/FeP−500°C). The lowest electrode potential of 110 mV vs. a reversible hydrogen electrode
(RHE) at 10 mA cm−2 was achieved with Fe2P/FeP−500°C catalyst Ključne besede: Fe2P, electrocatalysis, hydrogen, ammonia Objavljeno v RUNG: 13.12.2023; Ogledov: 648; Prenosov: 3 Povezava na datoteko Gradivo ima več datotek! Več... |
245. The role of lattice defects on the optical properties of TiO[sub]2 nanotube arrays for synergistic water splittingManel Machreki, Takwa Chouki, Georgi Tyuliev, Mattia Fanetti, Matjaž Valant, Denis Arčon, Matej Pregelj, Saim Emin, 2023, izvirni znanstveni članek Opis: In this study, we report a facile one-step chemical method to synthesize reduced titanium dioxide (TiO2) nanotube arrays (NTAs) with point defects. Treatment with NaBH4 introduces oxygen vacancies (OVs) in the TiO2 lattice. Chemical analysis and optical studies indicate that the OV density can be significantly increased by changing reduction time treatment, leading to higher optical transmission of the TiO2 NTAs and retarded carrier recombination in the photoelectrochemical process. A cathodoluminescence (CL) study of reduced TiO2 (TiO2–x) NTAs revealed that OVs contribute significantly to the emission bands in the visible range. It was found that the TiO2 NTAs reduced for a longer duration exhibited a higher concentration of OVs. A typical CL spectrum of TiO2 was deconvoluted to four Gaussian components, assigned to F, F+, and Ti3+ centers. Ključne besede: TiO2 nanotubes, defects, cathodoluminescence Objavljeno v RUNG: 13.12.2023; Ogledov: 444; Prenosov: 7 Celotno besedilo (5,75 MB) Gradivo ima več datotek! Več... |
246. AutoSourceID-Classifier : star-galaxy classification using a convolutional neural network with spatial informationF. Stoppa, Saptashwa Bhattacharyya, R. Ruiz de Austri, P. Vreeswijk, S. Caron, Gabrijela Zaharijas, S. Bloemen, G. Principe, D. Malyshev, Veronika Vodeb, 2023, izvirni znanstveni članek Opis: Aims: Traditional star-galaxy classification techniques often rely on feature estimation from catalogs, a process susceptible to introducing inaccuracies, thereby potentially jeopardizing the classification’s reliability. Certain galaxies, especially those not manifesting as extended sources, can be misclassified when their shape parameters and flux solely drive the inference. We aim to create a robust and accurate classification network for identifying stars and galaxies directly from astronomical images.
Methods: The AutoSourceID-Classifier (ASID-C) algorithm developed for this work uses 32x32 pixel single filter band source cutouts
generated by the previously developed AutoSourceID-Light (ASID-L) code. By leveraging convolutional neural networks (CNN) and
additional information about the source position within the full-field image, ASID-C aims to accurately classify all stars and galaxies within a survey. Subsequently, we employed a modified Platt scaling calibration for the output of the CNN, ensuring that the derived probabilities were effectively calibrated, delivering precise and reliable results.
Results: We show that ASID-C, trained on MeerLICHT telescope images and using the Dark Energy Camera Legacy Survey (DECaLS) morphological classification, is a robust classifier and outperforms similar codes such as SourceExtractor. To facilitate a rigorous comparison, we also trained an eXtreme Gradient Boosting (XGBoost) model on tabular features extracted by SourceExtractor.
While this XGBoost model approaches ASID-C in performance metrics, it does not offer the computational efficiency and reduced
error propagation inherent in ASID-C’s direct image-based classification approach. ASID-C excels in low signal-to-noise ratio and crowded scenarios, potentially aiding in transient host identification and advancing deep-sky astronomy. Ključne besede: astronomical databases, data analysis, statistics, image processing Objavljeno v RUNG: 12.12.2023; Ogledov: 611; Prenosov: 4 Celotno besedilo (10,31 MB) Gradivo ima več datotek! Več... |
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249. An in situ proton filter covalent organic framework catalyst for highly efficient aqueous electrochemical ammonia productionKayaramkodath C. Ranjeesh, Sukhjot Kaur, Abdul K. Mohammed, Safa Gaber, Divyani Gupta, Khaled Badawy, Mohamed Aslam, Nirpendra Singh, Tina Škorjanc, Matjaž Finšgar, 2023, izvirni znanstveni članek Opis: The electrocatalytic nitrogen reduction reaction (NRR) driven by renewable electricity provides a green synthesis route for ammonia (NH3) production under ambient conditions but suffers from a low conversion yield and poor Faradaic efficiency (F.E.) because of strong competition from hydrogen evolution reaction (HER) and the poor solubility of N2 in aqueous systems. Herein, an in situ proton filter covalent organic framework catalyst (Ru-Tta-Dfp) is reported with inherent Ruthenium (Ru) sites where the framework controls reactant diffusion by suppressing proton supply and enhancing N2 flux, causing highly selective and efficient catalysis. The smart catalyst design results in a remarkable ammonia production yield rate of 2.03 mg h−1 mgcat−1 with an excellent F.E. of ≈52.9%. The findings are further endorsed with the help of molecular dynamics simulations and control COF systems without in situ proton filter feasibility. The results point to a paradigm shift in engineering high-performance NRR electrocatalysts for more feasible green NH3 production. Ključne besede: covalent organic frameworks, ammonia, electrochemical synthesis, electrochemistry, nitrogen reduction reaction, ruthenium Objavljeno v RUNG: 11.12.2023; Ogledov: 591; Prenosov: 5 Celotno besedilo (2,77 MB) Gradivo ima več datotek! Več... |
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