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1.
Particle number size distribution statistics at City-Centre Urban Background, urban background, and remote stations in Greece during summer
S. Vratolis, Maria I. Gini, Spiros Bezantakos, Iasonas Stavroulas, Nikos Kalivitis, E. Kostenidou, E. Louvaris, D. Siakavaras, George Biskos, Nikolaos Mihalopoulos, 2019, original scientific article

Abstract: Particle number size distribution measurements were conducted during the summer of 2012 at City-Centre Urban Background (Patras-C), Urban Background (ICE-HT in Patras, DEM in Athens, EPT in Thessaloniki), and Regional Background stations (FIN in Crete). At the City-Centre Urban Background station, the average number distribution had a geometric mean diameter peak approximately at 60 nm and the highest number concentration, whereas at the Regional Background station and the Urban Background stations it displayed a major peak approximately at 100 nm, with the Regional Background station exhibiting the lowest number concentration. The particle number size distribution at each site was divided into size fractions and, based on their diurnal variation and previous studies, we concluded that the main sources for the City-Centre Urban Background station are traffic and the regional background concentration, for the Urban Background stations fresh traffic, aged traffic, cooking and the regional background concentration, and for the Regional Background station local activities (tourism, cooking) and regional background concentration. The median number concentration that is attributed to regional background concentration for the City-Centre Urban Background, the Urban Background and the Regional Background stations are respectively 13, 29 and 45% of the total number concentration. Nucleation events were identified at DEM station, where the newly formed particles accounted for 4% of the total particle concentration for the measurement period in the size range 10–20 nm, EPT, where they accounted for 12%, and FIN, where they accounted for 1%, respectively. New Particle Formation events contribution during summer to Condensation Cloud Nuclei were therefore insignificant in the Eastern Mediterranean. Modal analysis was performed on the number distributions and the results were classified in clusters. At the City-Centre Urban Background station, the cluster-source that dominated number concentration and frequency is related to fresh and aged traffic emissions, at the Urban Background stations aged traffic emissions, while at the Regional Background station number and frequency were dominated by the regional background concentration. Based on cluster analysis, 18% of the median number distribution was due to long range transport at the City-Centre Urban Background site, 37% at the Urban Background sites, and 59% at the Regional Background site. The Flexible Particle Dispersion Model (FLEXPART) was used in order to acquire geographic origin clusters and we concluded that the Etesian flow increases the median regional background number concentration in the Mediterranean basin by a factor of 2.5–4.
Keywords: Mediterranean aerosol, particle number size distribution clustering, FLEXPART clustering
Published in RUNG: 13.05.2024; Views: 132; Downloads: 0
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2.
Formation and growth of atmospheric nanoparticles in the eastern Mediterranean : results from long-term measurements and process simulations
Nikos Kalivitis, Veli-Matti Kerminen, Giorgos Kouvarakis, Iasonas Stavroulas, Evaggelia Tzitzikalaki, Panayiotis Kalkavouras, Nikos Daskalakis, Stelios Myriokefalitakis, Aikaterini Bougiatioti, Hanna E. Manninen, 2019, original scientific article

Abstract: Atmospheric new particle formation (NPF) is a common phenomenon all over the world. In this study we present the longest time series of NPF records in the eastern Mediterranean region by analyzing 10 years of aerosol number size distribution data obtained with a mobility particle sizer. The measurements were performed at the Finokalia environmental research station on Crete, Greece, during the period June 2008–June 2018. We found that NPF took place on 27 % of the available days, undefined days were 23 % and non-event days 50 %. NPF is more frequent in April and May probably due to the terrestrial biogenic activity and is less frequent in August. Throughout the period under study, nucleation was observed also during the night. Nucleation mode particles had the highest concentration in winter and early spring, mainly because of the minimum sinks, and their average contribution to the total particle number concentration was 8 %. Nucleation mode particle concentrations were low outside periods of active NPF and growth, so there are hardly any other local sources of sub-25 nm particles. Additional atmospheric ion size distribution data simultaneously collected for more than 2 years were also analyzed. Classification of NPF events based on ion spectrometer measurements differed from the corresponding classification based on a mobility spectrometer, possibly indicating a different representation of local and regional NPF events between these two measurement data sets. We used the MALTE-Box model for simulating a case study of NPF in the eastern Mediterranean region. Monoterpenes contributing to NPF can explain a large fraction of the observed NPF events according to our model simulations. However the adjusted parameterization resulting from our sensitivity tests was significantly different from the initial one that had been determined for the boreal environment.
Keywords: particles, number size distributions, new particle formation, regional background, SMPS, Eastern Mediterannean
Published in RUNG: 10.05.2024; Views: 145; Downloads: 2
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3.
On the regional aspects of new particle formation in the Eastern Mediterranean : a comparative study between a background and an urban site based on long term observations
Panayiotis Kalkavouras, Aikaterini Bougiatioti, Georgios Grivas, Iasonas Stavroulas, Nikos Kalivitis, Eleni Liakakou, Evangelos Gerasopoulos, Christodoulos Pilinis, Nikolaos Mihalopoulos, 2020, original scientific article

Abstract: Atmospheric new particle formation (NPF) is an important source of submicron particles. In remote background environments where local sources are scarce such processes may impact significantly on climate-relevant parameters. On the other hand, in urban environments, newly-formed particles are adding up to submicron particles emitted from primary sources. As the exact mechanism which triggers NPF still remains elusive, so are the circumstances for simultaneous occurrence of such events in two different environments (urban vs. regional background). In this study, concurrent number size distribution measurements were conducted in the urban environment of Athens and at the regional background site of Finokalia, Crete, located 340 km away and spanning a 2-year period. It occurred that the relative frequency of NPF was similar at both sites (around 20%), with a higher frequency during spring and autumn at the urban site, while at the background site most events took place in August and December, during the studied period. There were 35 event days when NPF took place at both sites simultaneously, all associated with air masses originating from the Northern sector, indicating the presence of regional events in the extended geographical area and characterized by low condensation sink (CS). By comparing the common with the non-common class I NPF episodes, we conclude that the conditions applying when regional NPF events with growth are observed in the same day at the surface level of both areas, are: (i) lower CS, (ii) higher SO2 concentrations, (iii) lower RH, and finally (iv) lower formation and growth rates than those observed during the site-specific and more rapidly evolving NPF events.
Keywords: NPF, Athens, Eastern Mediterranean, particle number concentrations, size distributions, concurrent regional events
Published in RUNG: 10.05.2024; Views: 147; Downloads: 0
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4.
Regional new particle formation over the Eastern Mediterranean and Middle East
Panayiotis Kalkavouras, Aikaterini Bougiatioti, Tareq Hussein, Nikos Kalivitis, Iasonas Stavroulas, Panagiotis Michalopoulos, Nikolaos Mihalopoulos, 2021, original scientific article

Abstract: Atmospheric new particle formation (NPF) events taking place over large distances between locations, featuring similar characteristics, have been the focus of studies during the last decade. The exact mechanism which triggers NPF still remains indefinable, so are the circumstances under which simultaneous occurrence of such events take place in different environments, let alone in environments which are parted by over 1200 km. In this study, concurrent number size distribution measurements were conducted in the urban environments of Athens (Greece) and Amman (Jordan) as well as the regional background site of Finokalia, Crete, all located within a distance of almost 1300 km for a 6-month period (February–July 2017). During the study period Athens and Finokalia had similar occurrence of NPF (around 20%), while the occurrence in Amman was double. When focusing on the dynamic characteristics at each site, it occurs that formation and growth rates at Amman are similar to those at Finokalia, while lower values in Athens can be ascribed to a higher pre-existing particle number at this urban site. By comparing common NPF events there are 5 concomitant days between all three sites, highly related to air masses origin. Additionally, for another 19 days NPF takes place simultaneously between Finokalia and Amman, which also share common meteorological characteristics, adding to a total of 60% out of 41 NPF events observed at Finokalia, also simultaneously occurring in Amman.
Keywords: NPF, Eastern Mediterranean, particle number size distributions, concurrent regional events
Published in RUNG: 10.05.2024; Views: 127; Downloads: 3
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5.
An improved harmony search algorithm using opposition-based learning and local search for solving the maximal covering location problem
Soumen Atta, 2023, original scientific article

Abstract: In this article, an improved harmony search algorithm (IHSA) that utilizes opposition-based learning is presented for solving the maximal covering location problem (MCLP). The MCLP is a well-known facility location problem where a fixed number of facilities are opened at a given potential set of facility locations such that the sum of the demands of customers covered by the open facilities is maximized. Here, the performance of the harmony search algorithm (HSA) is improved by incorporating opposition-based learning that utilizes opposite, quasi-opposite and quasi-reflected numbers. Moreover, a local search heuristic is used to improve the performance of the HSA further. The proposed IHSA is employed to solve 83 real-world MCLP instances. The performance of the IHSA is compared with a Lagrangean/surrogate relaxation-based heuristic, a customized genetic algorithm with local refinement, and an improved chemical reaction optimization-based algorithm. The proposed IHSA is found to perform well in solving the MCLP instances.
Keywords: maximal covering location problem, harmony search algorithm, opposition-based learning, facility location problem, opposite number
Published in RUNG: 05.10.2023; Views: 923; Downloads: 7
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6.
Does grammatical number support the acquisition of number words?
Anna Shusterman, Abigail Seevak, Petra Mišmaš, Franc Marušič, Rok Žaucer, 2023, published scientific conference contribution

Keywords: Slovenian, grammatical number, acquisition, number words, dual
Published in RUNG: 21.07.2023; Views: 954; Downloads: 2
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7.
L(4, 3, 2, 1)-Labeling for Simple Graphs
Soumen Atta, Priya Ranjan Sinha Mahapatra, 2015, published scientific conference contribution

Abstract: An L(4, 3, 2, 1)-labeling of a graph is a function which assigns label to each vertex of the graph such that if two vertices are one, two, three and four distance apart then assigned labels must have a difference of at least 4, 3, 2 and 1 respectively between them. This paper presents L(4, 3, 2, 1)-labeling number for simple graphs such as complete graphs, complete bipartite graphs, stars, paths and cycles. This paper also presents an L(4, 3, 2, 1)-labeling algorithm for paths which is optimal for paths on n≥7 vertices.
Keywords: L(4, 3, 2, 1)-labeling, Labeling number, Graph labeling, Channel assignment problem
Published in RUNG: 05.06.2023; Views: 802; Downloads: 0
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8.
L (D, 2, 1)-labeling of Square Grid
Soumen Atta, Priya Ranjan Sinha Mahapatra, 2019, original scientific article

Abstract: For a fixed integer $D (\geq 3)$ and $\lambda$ $\in$ $\mathbb{Z}^+$, a $\lambda$-$L(D, 2, 1)$-$labeling$ of a graph $G = (V, E)$ is the problem of assigning non-negative integers (known as labels) from the set $\{0, \ldots, \lambda\}$ to the vertices of $G$ such that if any two vertices in $V$ are one, two and three distance apart from each other then the assigned labels to these vertices must have a difference of at least $D$, 2 and 1 respectively. The vertices which are at least $4$ distance apart can receive the same label. The minimum value among all the possible values of $\lambda$ for which there exists a $\lambda$-$L(D, 2, 1)$-$labeling$ is known as the labeling number. In this paper $\lambda$-$L(D, 2 ,1)$-$labeling$ of square grid is considered. The lower bound on the labeling number for square grid is presented and a formula for $\lambda$-$L(D, 2 ,1)$-$labeling$ of square grid is proposed. The correctness proof of the proposed formula is given here. The upper bound of the labeling number obtained from the proposed labeling formula for square grid matches exactly with the lower bound of the labeling number.
Keywords: Graph labeling, Square grid, Labeling number, Frequency assignment problem (FAP)
Published in RUNG: 17.04.2023; Views: 837; Downloads: 0
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9.
No-hole λ-L (k, k – 1, …, 2,1)-labeling for square grid
Soumen Atta, Stanisław Goldstein, Priya Ranjan Sinha Mahapatra, 2017, original scientific article

Abstract: 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.
Keywords: graph labeling, labeling number, no-hole labeling, square grid, frequency assignment problem, approximation ratio
Published in RUNG: 17.04.2023; Views: 823; Downloads: 0
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10.
Investigation of Slovenian copular agreement
Franc Marušič, Rok Žaucer, 2021, published scientific conference contribution

Abstract: This paper reports on a detailed investigation of agreement inside simple predicative sentences. In this type of sentence, both noun phrases are in the nominative, so in principle either one can trigger agreement on the copular verb. We examine various types of copular contructions and show that regardless of the type of predicative sentence, when a plural is combined with a singular, it is always the plural that agrees. Similarly, when a dual is combined with a singular, the dual wins out. But when we combine a dual and a plural, the copula can agree with either of the two noun phrases, with a preference for the noun phrase following the copula. We discuss the relevance of these findings for recent literature on predication.
Keywords: agreement, copula, number, singular, dual, plural, Slovenian
Published in RUNG: 31.01.2022; Views: 1791; Downloads: 0
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