É V.P. Rácz

14050929000

Publications - 5

Integrated urban air pollution dispersion modelling framework and application in air quality prediction of the city of győr

É V.P. Rácz L. Környei Balázs Szintai István Harmati György Istenes Bence Liszkai Péter Zsebők Zoltán Horváth

Publication Name: Harmo 2016 17th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes Proceedings

Publication Date: 2016-01-01

Volume: 2016-May

Issue: Unknown

Page Range: 410-414

Description:

Model accuracy versus model running time - urban air pollution dispersion modellers have to balance between them when selecting models to be implemented. CFD based models seem to be the best candidates for an accurate model that can be validated at urban scale at highest level on the price of a longer running time. In this paper we shall introduce 3DAirQC software framework which addresses a portable and validated CFD model for air quality prediction and control.

Open Access: Yes

DOI: DOI not available

Small-scale differences of urban nox exposition in field measurement data

É V.P. Rácz Zoltán Horváth

Publication Name: Wit Transactions on Ecology and the Environment

Publication Date: 2014-09-23

Volume: 191

Issue: Unknown

Page Range: 1513-1522

Description:

Local differences in air pollution levels of different positions of even close points along a street can be dramatic due to mainly meteorological parameters and local geometry. Air pollution monitoring systems provide a huge amount of temporal data, but the number of monitoring sites is far from sufficient for fine spatial investigations. On the other hand, for reliable air pollution modelling and correct prediction of expositions, a more detailed spatial distribution of samples is needed. Small-scale differences and street canyons are often investigated by models. However, such small-scale real field data from direct measurements are rarely available. In this paper we provide evidence by measurements to the existence of significant small-scale differences in air pollution levels and provide data for model validation. Hence, we performed measurements inside a single crossing and along three main roads in the city of Győr. Air samples were sucked into Tedlar bags and NOx concentration was determined by a gas analyser using a chemiluminescent method. On the sampling days manual traffic counting and noise measurements were performed and meteorological data were also taken at the same time. Daily rhythm and spatiotemporal variation of NOx expositions were investigated and compared to traffic data and data from the two monitoring containers of Győr. We observed a similar daily profile as expected in an average workday out of heating season: a sharp peak in the morning and a wider rise of nitrogen oxide concentration in the afternoon. Canyon effects were detected inside the investigated crossing. It caused a difference in pollutant levels of the two sides of the street. Despite a relatively small number of sampling sites, significant differences were detected both inside the crossing level and between main streets at p = 0.055.

Open Access: Yes

DOI: 10.2495/SC141282

On the asymptotic behavior of spatially implicit models of competition of two species with overcolonization

É V.P. Rácz Irma Szimjanovszki János Karsai Szeged

Publication Name: Dynamic Systems and Applications

Publication Date: 2014-01-01

Volume: 23

Issue: 4

Page Range: 677-690

Description:

We consider patch-based population dynamics, called metapopulations, and investigate the spread of two species and their competition for habitat areas. Let 0 ≤ p1,p2 denote the proportion (density) of the areas occupied by the species 1 and 2, respectively. Obviously, 0 ≤ p1 + p2 ≤ 1. Both species can locally extinct and colonize empty patches or patches occupied by the other with different rates. Hence the model is P1′ = κ1P1 (1 - P1 - P2) - e1p1p2-C1P1P2 - C2P1P2 P2′ = κ1P1 (1 - P1 - P2) - e1p1p2-C1P1P2 - C2P1P2 where ej are the extinction rates, κ1 are the rates of colonization of empty patches, and species "i" overcolonize "j" with the rate c1(i,j=1,2; i≠j) We investigate the asymptotic stability properties of the equilibria of such systems and we give a complete characterization of the parameter space. We prove that there can appear a globally asymptotically stable coexisting equilibrium. On the other hand, this equilibrium can become unstable and then the exclusive equilibria are only locally asymptotically stable. We have also developed dynamic applications in Wolfram Mathematica to illustrate our results.

Open Access: Yes

DOI: DOI not available

The effect of initial pattern on competitive exclusion

É V.P. Rácz János Karsai Szeged

Publication Name: Community Ecology

Publication Date: 2006-08-01

Volume: 7

Issue: 1

Page Range: 23-33

Description:

We used cellular automata models to investigate the effect of initial pattern geometry on competition. We measured the average proportion of sites with foreign neighbours to track interspecific segregation during pattern development. Our simulation results show that intraspecific aggregation can considerably slow down the extinction of the weaker competitor. A series of experiments was performed to estimate the expected time to extinction for the weaker species. The perimeter-to-area ratio of the initial configuration proved to be an adequate determinant of expected time to-extinction. Furthermore, we demonstrated that the degree of aggregation is closely related to the local density dependence of the colonization functions.

Open Access: Yes

DOI: 10.1556/ComEc.7.2006.1.3

Local Scale Wind Regime Changes and their Consequences on Sustainability in the Carpathian Basin (Hungary)

É V.P. Rácz L. Környei

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 107

Issue: Unknown

Page Range: 475-480

Description:

The Carpathian basin is facing significant threats to its unique biogeography and the sustainability of its human society due to climate change. While studies have extensively analyzed temperature and precipitation changes, little attention has been given to the analysis of wind regime changes despite their potential correlation with diverse climatic effects. This paper presents a comprehensive analysis of long-term observational wind data at both local and regional scales of the basin. The study aims to identify trends in wind speed and direction and raises some implications for sustainability aspects such as forest health, agricultural potential, and availability of wind energy. To track the decadal trends in wind speed, two indexes were utilized: the number of calm days and the number of windy days. In addition to traditional wind roses, fine changes in wind direction distribution were visualized using heat maps. The dominance of local winds was also examined through aggregated wind roses. Our research findings reveal that contrary to predictions and reanalysis data, there has been a noteworthy rise in wind resources in the Hungarian Great Plain, accompanied by a decrease in the number of calm days. It is evident that there are variations among different geographical regions within Hungary regarding changes in wind regimes. These trends have the potential to impact current dominant climatic influences, leading to possible modifications in climate change patterns and necessitating a reassessment of main forest and agricultural species.

Open Access: Yes

DOI: 10.3303/CET23107080