1. No-hole λ-L (k, k – 1, …, 2,1)-labeling for square gridSoumen Atta, Stanisław Goldstein, Priya Ranjan Sinha Mahapatra, 2017, izvirni znanstveni članek Opis: Motivated by a frequency assignment problem, we demonstrate, for a fixed positive integer k, how to label an infinite square grid with a possibly small number of integer labels, ranging from 0 to λ −1, in such a way that labels of adjacent vertices differ by at least k, vertices connected by a path of length two receive values which differ by at least k − 1, and so on. The vertices which are at least k + 1 distance apart may receive the same label. By finding a lower bound for λ, we prove that the solution is close to optimal, with approximation ratio at most 9/8. The labeling presented is a no-hole one, i.e., it uses each of the allowed labels at least once.
Ključne besede: graph labeling, labeling number, no-hole labeling, square grid, frequency assignment problem, approximation ratio
Objavljeno v RUNG: 17.04.2023; Ogledov: 113; Prenosov: 0
Gradivo ima več datotek! Več... |
2. Atmospheric concentrations and emission ratios of black carbon and nitrogen oxides in the Arabian/Persian Gulf regionBálint Alföldy, Mohamed M. Mahfouz, Asta Gregorič, Matic Ivančič, Irena Ježek, Martin Rigler, 2021, izvirni znanstveni članek Ključne besede: black carbon, nitrogen oxides, emission ratio, Arabian Gulf region
Objavljeno v RUNG: 08.07.2021; Ogledov: 1472; Prenosov: 0
Gradivo ima več datotek! Več... |
3. Secondary organic aerosol formation from semi- and intermediate-volatility organic compounds and glyoxal : relevance of O/C as a tracer for aqueous multiphase chemistryEleanor M. Waxman, Katja Džepina, Barbara Ervens, Julia Lee-Taylor, Bernard Aumont, Jose L. Jimenez, Sasha Madronich, Rainer Volkamer, 2013, izvirni znanstveni članek Opis: The role of aqueous multiphase chemistry in the formation of secondary organic aerosol (SOA) remains difficult to quantify. We investigate it here by testing the rapid formation of moderate oxygen-to-carbon (O/C) SOA during a case study in Mexico City. A novel laboratory-based glyoxal-SOA mechanism is applied to the field data, and explains why less gas-phase glyoxal mass is observed than predicted. Furthermore, we compare an explicit gas-phase chemical mechanism for SOA formation from semi- and intermediate-volatility organic compounds (S/IVOCs) with empirical parameterizations of S/IVOC aging. The mechanism representing our current understanding of chemical kinetics of S/IVOC oxidation combined with traditional SOA sources and mixing of background SOA underestimates the observed O/C by a factor of two at noon. Inclusion of glyoxal-SOA with O/C of 1.5 brings O/C predictions within measurement uncertainty, suggesting that field observations can be reconciled on reasonable time scales using laboratory-based empirical relationships for aqueous chemistry.
Ključne besede: secondary organic aerosol, glyoxal, aqueous multiphase chemistry, oxygen-to-carbon ratio, single scattering albedo
Objavljeno v RUNG: 11.04.2021; Ogledov: 1310; Prenosov: 0
Gradivo ima več datotek! Več... |
4. Carcinogenic organic content of particulate matter at urban locations with different pollution sourcesGordana Pehnec, Ivana Jakovljević, Ranka Godec, Zdravka Sever Štrukil, Sabina Žero, Jasna Huremović, Katja Džepina, 2020, izvirni znanstveni članek Opis: Polycyclic aromatic hydrocarbons (PAHs) are compounds known for their adverse effects on human health. Many of them are proven carcinogens, especially those with 5 and 6 aromatic rings, which under normal tropospheric conditions are found in the particle-phase. Benzo(a)pyrene (BaP) is often measured as their general representative. Sarajevo, the capital of Bosnia and Herzegovina, is among the European cities with the poorest air quality. However, in Sarajevo PAHs are neither routinely measured within the air quality monitoring network nor have been a subject of extended, continuous field studies during the most polluted cold periods of the year. The capital of Croatia, Zagreb, is located approximately 300 km air distance north-west from Sarajevo.
PAH mass concentrations in Zagreb have been measured continuously since 1994 within air quality monitoring networks. During winter 2017/2018, the SAFICA project (Sarajevo Canton Winter Field Campaign 2018) was carried out in order to characterize the chemical composition of organic and inorganic aerosol in the Sarajevo Canton. This paper presents the results of PAH measurements in the cities of Sarajevo and Zagreb at one urban
location per city. Daily (24 h), continuous samples of PM10 (particulate matter with aerodynamic diameters
≤10 μm) were collected during heating season, from December 27, 2017 to February 27, 2018. Mass concentrations of eleven particle-phase PAHs in Sarajevo and Zagreb from filter samples collected during the same period were compared. The average BaP ambient mass concentrations in Sarajevo and Zagreb were 6.93 ng m−3 and 3.11 ng m−3, respectively. The contribution of BaP to the total PAH mass concentration was similar at both locations (11%). However, much higher contributions of particle-phase fluoranthene and pyrene were found in Sarajevo. Contributions of individual PAH, diagnostic ratios and factor analysis indicate that combustion of gasoline and diesel from vehicle traffic are a potential source of PAHs at both locations, as well as combustion of other liquid fossil fuels (petroleum and fuel oil). Wood burning was occasionally indicated as a PAH emission source in
Zagreb, while in Sarajevo the contribution of PAHs from wood and coal combustion was more evident. Calculated value for total carcinogenic potency (TCP) of PAHs, which was estimated using toxic equivalence factors from the literature, in PM10 samples collected in Sarajevo was more than twice higher than in Zagreb (10.6 ng m−3 and 4.7 ng m−3, respectively). BaP had the highest contribution to the TCP at both locations (69 and 67%).
Ključne besede: carcinogenic potency, diagnostic ratio, factor analysis, PM10, polycyclic aromatic hydrocarbons
Objavljeno v RUNG: 09.04.2021; Ogledov: 1422; Prenosov: 0
Gradivo ima več datotek! Več... |
5. Stable carbon isotope analysis of selected halocarbons at parts per trillion concentration in an urban locationM Iqbal Mead, M Anwar H Khan, Ian D Bull, Iain R White, Graham Nickless, Dudley E Shallcross, 2008, izvirni znanstveni članek Opis: ∂13C values of a suite of halocarbons have been determined in an urban background site in Bristol, UK. A novel mobile preconcentration system, based on the use of multi-adsorbent sample tubes, has been developed for trapping relatively large-volume air samples in potentially remote areas. An Adsorption Desorption System-Gas Chromatography-Electron Capture Detector was used to measure the mixing ratios of the selected halocarbon species, while a Gas ChromatographyCombustionIsotope Ratio Mass Spectrometer was used to determine ∂13C values. For the species with strong local sources, the variation of isotope ratios has been observed over the experimental period. Some of the results reported in the present study differ from previously reported values and reasons for this are discussed. The reporting of different ∂13C values for selected halocarbons from different areas in the present study suggests that ∂13C values may be used to determine the relative magnitudes of anthropogenic and biogenic sources.
Ključne besede: Adsorption Desorption System (ADS), Automated Thermal Desorber (ATD), Electron Capture Detector (ECD), Gas Chromatography (GC), Isotope Ratio Mass Spectrometry (IRMS)
Objavljeno v RUNG: 18.07.2019; Ogledov: 2399; Prenosov: 0
Gradivo ima več datotek! Več... |
6. Biogas production from brewery spent grain as a mono-substrate in a two-stage process composed of solid-state anaerobic digestion and granular biomass reactorsMario Panjicko, Gregor Drago Zupančič, Romana Marinšek-Logar, Lijana Fanedl, Marina Tišma, Bruno Zelić, 2017, izvirni znanstveni članek Opis: Anaerobic digestion of brewery spent grain as a mono-substrate was studied. Brewery spent grain is a substrate consisting largely of cellulose, hemicellulose and lignin, which are difficult to degrade anaerobically, mostly due to the presence of degradation products, such as phenolic compounds, which cause process inhibition. Therefore, a two-stage system was used for anaerobic digestion. Anaerobic digestion was phase separated in a solid-state anaerobic digestion reactor, where microbiological hydrolysis and acidogenesis occurred and in a granular biomass reactor where mostly methanogenesis was performed. The overall process exhibited total solids degradation efficiency between 75.9 and 83.0 %. Average specific biogas production was 414±32 L/kg, whereas biomethane production was 224±34 L/kg of added total solids. Granular biomass after adaptation exhibited stable operation at substrate C/N ratios in range 0.16 – 4.68. p-cresol was present in concentrations up to 45 mg/L and during the process was successfully degraded by granular biomass. The excellent adaptability of granular biomass was confirmed by 68.2 % shift in bacterial and a 31.8 % shift in archaeal community structure in a granular biomass reactor. The structure of the bacterial community from granular biomass reactor and solid-state anaerobic digestion reactor remained 79.4 % similar at the end of the experiment, whereas archaeal community was only 31.6 % similar. The process exhibited stable operation for 198 days, which shows that brewery spent grain can be successfully anaerobically digested and used for biogas production.
Ključne besede: biogas production, brewery spent grain, C/N ratio, dry digestion, microbial biomass, solid-state anaerobic digestion
Objavljeno v RUNG: 18.08.2017; Ogledov: 3695; Prenosov: 0
Gradivo ima več datotek! Več... |
