TY - JOUR AU - Fehér, Anna Éva AU - Cseh, Dániel AU - Kovács, Róbert Sándor TI - Identifying correlations between metal foam thermal characteristics and non-Fourier behavior JF - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER J2 - INT COMMUN HEAT MASS VL - 170 PY - 2026 PG - 9 SN - 0735-1933 DO - 10.1016/j.icheatmasstransfer.2025.110008 UR - https://m2.mtmt.hu/api/publication/36416899 ID - 36416899 N1 - The research reported in this paper and carried out at BME has been supported by the grants of the Ministry for Innovation and Technology project EKÖP-24-3-BME-67 and NKFIH STARTING149487. The research was funded by the Sustainable Development and Technologies National Programme of the Hungarian Academy of Sciences (FFT NP FTA) . AB - Due to their low density and large specific surface area, metal foams are increasingly used as cellular materials that combine excellent structural and thermal properties. Their cellular structure makes them particularly suitable for use in heat exchangers, insulation, and fire protection layers. The heat transport that takes place within them is a complex phenomenon characterized by the simultaneous presence of heat conduction, heat transfer, and heat radiation, making their modeling a significant challenge. The aim of the research is to develop a one-dimensional, time-dependent, discrete numerical model capable of describing the effective thermal behavior of metal foams. The model takes into account heat conduction through the solid phase, conductive heat transfer in the closed cavities, thermal radiation between the pore walls, and by-passing heat conduction around the cavity. The results highlight that geometric features such as cavity size and arrangement have a significant impact on temperature distribution and confirm that classical Fourier-based models are not accurately applicable to porous materials. We found that the proposed one-dimensional approach is eligible to reproduce the experimentally observed non-Fourier effects for which modeling the Guyer–Krumhansl equations is a proper candidate. Identifying correlations between the thermal diffusivity and metal foam parameters, we showed that the emerging effective non-Fourier behavior is not purely a material property but depends on the geometrical structure as well. LA - English DB - MTMT ER - TY - GEN AU - Abac, Adrian AU - Abramo, Raul AU - Albanesi, Simone AU - Albertini, Angelica AU - Agapito, Alessandro AU - Agathos, Michalis AU - Albertus, Conrado AU - Andersson, Nils AU - Andrade, Tomas AU - Andreoni, Igor AU - Federico, Angeloni AU - Marco, Antonelli AU - John, Antoniadis AU - Fabio, Antonini AU - Manuel, Arca Sedda AU - M., Celeste Artale AU - Stefano, Ascenzi AU - Pierre, Auclair AU - Matteo, Bachetti AU - Charles, Badger AU - Biswajit, Banerjee AU - David, Barba-Gonzalez AU - Barta, Dániel AU - Nicola, Bartolo AU - Andreas, Bauswein AU - Andrea, Begnoni AU - Freija, Beirnaert AU - Michal, Bejger AU - Enis, Belgacem AU - Nicola, Bellomo AU - Laura, Bernard AU - Maria, Grazia Bernardini AU - Sebastiano, Bernuzzi AU - Christopher, P. L. Berry AU - Emanuele, Berti AU - Gianfranco, Bertone AU - Dario, Bettoni AU - Miguel, Bezares AU - Swetha, Bhagwat AU - Sofia, Bisero AU - Marie, Anne Bizouard AU - Jose, J. Blanco-Pillado AU - Simone, Blasi AU - Alice, Bonino AU - Alice, Borghese AU - Ssohrab, Borhanian AU - Elisa, Bortolas AU - Maria, Teresa Botticella AU - Marica, Branchesi AU - Matteo, Breschi AU - Richard, Brito AU - Enzo, Brocato AU - Floor, S. Broekgaarden AU - Tomasz, Bulik AU - Alessandra, Buonanno AU - Fiorella, Burgio AU - Adam, Burrows AU - Gianluca, Calcagni AU - Sofia, Canevarolo AU - Enrico, Cappellaro AU - Giulia, Capurri AU - Carmelita, Carbone AU - Roberto, Casadio AU - Ramiro, Cayuso AU - Pablo, Cerda-Duran AU - Prasanta, Char AU - Sylvain, Chaty AU - Tommaso, Chiarusi AU - Martyna, Chruslinska AU - Francesco, Cireddu AU - Philippa, Cole AU - Alberto, Colombo AU - Monica, Colpi AU - Geoffrey, Compere AU - Carlo, Contaldi AU - Maxence, Corman AU - Francesco, Crescimbeni AU - Sergio, Cristallo AU - Elena, Cuoco AU - Giulia, Cusin AU - Tito, Dal Canton AU - Gergely, Dalya AU - Paolo, D'Avanzo AU - Nazanin, Davari AU - Valerio, De Luca AU - Viola, De Renzis AU - Massimo, Della Valle AU - Walter, Del Pozzo AU - Federico, De Santi AU - Alessio, Ludovico De Santis AU - Tim, Dietrich AU - Ema, Dimastrogiovanni AU - Guillem, Domenech AU - Daniela, Doneva AU - Marco, Drago AU - Ulyana, Dupletsa AU - Hannah, Duval AU - Irina, Dvorkin AU - Nancy, Elias-Rosa AU - Stephen, Fairhurst AU - Anthea, F. Fantina AU - Matteo, Fasiello AU - Maxime, Fays AU - Rob, Fender AU - Tobias, Fischer AU - Francois, Foucart AU - Tassos, Fragos AU - Stefano, Foffa AU - Gabriele, Franciolini AU - Jacopo, Fumagalli AU - Jonathan, Gair AU - Rossella, Gamba AU - Juan, Garcia-Bellido AU - Cecilio, Garcia-Quiros AU - Gergely, Árpád László AU - Giancarlo, Ghirlanda AU - Archisman, Ghosh AU - Bruno, Giacomazzo AU - Fabian, Gittins AU - Ines, Francesca Giudice AU - Boris, Goncharov AU - Alejandra, Gonzalez AU - Stephane, Goriely AU - Luca, Graziani AU - Giuseppe, Greco AU - Leonardo, Gualtieri AU - Gianluca, Maria Guidi AU - Ish, Gupta AU - Maria, Haney AU - Mark, Hannam AU - Jan, Harms AU - Arus, Harutyunyan AU - Brynmor, Haskell AU - Andreas, Haungs AU - Nandini, Hazra AU - Gary, Hemming AU - Ik, Siong Heng AU - Tanja, Hinderer AU - Alexander, van der Horst AU - Qian, Hu AU - Sascha, Husa AU - Francesco, Iacovelli AU - Giulia, Illuminati AU - Gianluca, Inguglia AU - David, Izquierdo Villalba AU - Justin, Janquart AU - Kamiel, Janssens AU - Alexander, C. Jenkins AU - Ian, Jones AU - Kacskovics, Balázs AU - Ralf, S. Klessen AU - Kostas, Kokkotas AU - Hao-Jui, Kuan AU - Sumit, Kumar AU - Sachiko, Kuroyanagi AU - Danny, Laghi AU - Astrid, Lamberts AU - Gaetano, Lambiase AU - Francois, Larrouturou AU - Paola, Leaci AU - Michele, Lenzi AU - Andrew, Levan AU - T. G., F. Li AU - Yufeng, Li AU - Dicong, Liang AU - Marco, Limongi AU - Boyuan, Liu AU - Felipe, J. Llanes-Estrada AU - Eleonora, Loffredo AU - Oliver, Long AU - Eva, Lope-Oter AU - Georgios, Lukes-Gerakopoulos AU - Elisa, Maggio AU - Michele, Maggiore AU - Michele, Mancarella AU - Michela, Mapelli AU - Pablo, Marchant AU - Annarita, Margiotta AU - Alberto, Mariotti AU - Alisha, Marriott-Best AU - Sylvain, Marsat AU - Gabriel, Martinez-Pinedo AU - Andrea, Maselli AU - Simone, Mastrogiovanni AU - Isabela, Matos AU - Andrea, Melandri AU - Raissa, F. P. Mendes AU - Josiel, Mendonca Soares de Souza AU - Giorgio, Mentasti AU - Mar, Mezcua AU - Philipp, Mosta AU - Chiranjib, Mondal AU - Michele, Moresco AU - Tista, Mukherjee AU - Niccolo, Muttoni AU - Alessandro, Nagar AU - Harsh, Narola AU - Lara, Nava AU - Pablo, Navarro Moreno AU - Gijs, Nelemans AU - Alex, B. Nielsen AU - Samaya, Nissanke AU - Martin, Obergaulinger AU - Micaela, Oertel AU - Gor, Oganesyan AU - Francesca, Onori AU - Costantino, Pacilio AU - Giulia, Pagliaroli AU - Cristiano, Palomba AU - Peter, T. H. Pang AU - Paolo, Pani AU - Lucia, Papalini AU - Barbara, Patricelli AU - Alessandro, Patruno AU - Alessandro, Pedrotti AU - Albino, Perego AU - Maria, Angeles Perez-Garcia AU - Carole, Perigois AU - Gabriele, Perna AU - Celine, Peroux AU - J., Perret AU - Delphine, Perrodin AU - Alessandro, Pesci AU - Harald, P. Pfeiffer AU - Ornella, Juliana Piccinni AU - Mauro, Pieroni AU - Silvia, Piranomonte AU - Lorenzo, Pompili AU - E. K., Porter AU - Rafael, A. Porto AU - Adam, Pound AU - Jade, Powell AU - Mathieu, Puech AU - Geraint, Pratten AU - Anna, Puecher AU - Oriol, Pujolas AU - Miguel, Quartin AU - Adriana, R. Raduta AU - Antoni, Ramos-Buades AU - Aaron, Rase AU - Massimiliano, Razzano AU - Nanda, Rea AU - Tania, Regimbau AU - Arianna, Renzini AU - Piero, Rettegno AU - Angelo, Ricciardone AU - Antonio, Riotto AU - Alba, Romero-Rodriguez AU - Samuele, Ronchini AU - Dorota, Rosinska AU - Andrea, Rossi AU - Soumen, Roy AU - Diego, Rubiera-Garcia AU - J., Rubio AU - Pilar, Ruiz-Lapuente AU - Violetta, Sagun AU - Mairi, Sakellariadou AU - Om, Sharan Salafia AU - Anuradha, Samajdar AU - Nicolas, Sanchis-Gual AU - Andrea, Sanna AU - Filippo, Santoliquido AU - Bangalore, Sathyaprakash AU - Patricia, Schmidt AU - Stefano, Schmidt AU - Fabian, R. N. Schneider AU - Raffaella, Schneider AU - Armen, Sedrakian AU - Geraldine, Servant AU - Alexander, Sevrin AU - Lijing, Shao AU - Hector, O. Silva AU - Peera, Simakachorn AU - Stephen, Smartt AU - Thomas, P. Sotiriou AU - Mario, Spera AU - Antonio, Stamerra AU - Daniele, A. Steer AU - Jan, Steinhoff AU - Nikolaos, Stergioulas AU - Riccardo, Sturani AU - Duvier, Suarez AU - Jishnu, Suresh AU - Shaun, Swain AU - Matteo, Tagliazucchi AU - Nicola, Tamanini AU - Gianmassimo, Tasinato AU - Thomas, M. Tauris AU - Jacopo, Tissino AU - Giovanni, Maria Tomaselli AU - Silvia, Toonen AU - Alejandro, Torres-Forne AU - Cezary, Turski AU - Cristiano, Ugolini AU - Elias, C. Vagenas AU - Lorenzo, Valbusa Dall'Armi AU - Elena, Valenti AU - Rosa, Valiante AU - Chris, Van Den Broeck AU - Maarten, van de Meent AU - Lieke, A. C. van Son AU - Miguel, Vanvlasselaer AU - Massimo, Vaglio AU - Vijay, Varma AU - John, Veitch AU - Ville, Vaskonen AU - Susanna, D. Vergani AU - Milan, Wils AU - Helvi, Witek AU - Isaac, C. F. Wong AU - Stoytcho, Yazadjiev AU - Garvin, Yim AU - Fausto, Acernese AU - Hojae, Ahn AU - Annalisa, Allocca AU - Alex, Amato AU - Marc, Andres-Carcasona AU - Guerino, Avallone AU - Markus, Bachlechner AU - Patrick, Baer AU - Stefano, Bagnasco AU - Gabriele, Balbi AU - Fabrizio, Barone AU - Eugenio, Benedetti AU - Charlotte, Benning AU - Simone, Bini AU - Jose, Luis Blazquez Salcedo AU - Valerio, Bozza AU - Matteo, Bruno AU - Timo, Butz AU - Matteo, Califano AU - Enrico, Calloni AU - Giovanni, Carapella AU - Alessandro, Cardini AU - Shreevathsa, Chalathadka Subrahmanya AU - Francesco, Chiadini AU - Antonino, Chiummo AU - Spina, Cianetti AU - Giacomo, Ciani AU - Eugenio, Coccia AU - Andrea, Contu AU - Robin, Cornelissen AU - Andrea, Cozzumbo AU - Lewis, Croney AU - Mariateresa, Crosta AU - Rocco, D'Agostino AU - Stefan, Danilishin AU - Sabrina, D'Antonio AU - Jorden, De Bolle AU - Jerome, Degallaix AU - Mariafelicia, De Laurentis AU - Riccardo, della Monica AU - Francesco, De Marco AU - Ivan, de Martino AU - Rosario, De Rosa AU - Riccardo, De Salvo AU - Roberta, De Simone AU - Christophe, Detavernier AU - Giovanni, Diaferia AU - Martina, Di Cesare AU - Luciano, Di Fiore AU - Matteo, Di Giovanni AU - Sibilla, Di Pace AU - Jennifer, Docherty AU - Domenico, D'Urso AU - Oussama, El Mecherfi AU - Luciano, Errico AU - Federica, Fabrizi AU - Viviana, Fafone AU - Viviana, Fanti AU - Rosalba, Fittipaldi AU - Vincenzo, Fiumara AU - Andreas, Freise AU - Stefan, Funk AU - Mika, Gaedtke AU - Fabio, Garufi AU - Oliver, Gerberding AU - Edoardo, Giangrandi AU - Carlo, Giunchi AU - Victoria, Graham AU - Massimo, Granata AU - Veronica, Granata AU - Anna, Green AU - Karen, Haughian AU - Lavinia, Heisenberg AU - Margot, Hennig AU - Stefan, Hild AU - Van, Long Hoang AU - Nathan, Holland AU - Gerardo, Iannone AU - Katharina-Sophie, Isleif AU - Robert, Joppe AU - Chang-Hee, Kim AU - Chunglee, Kim AU - Kyungmin, Kim AU - Erika, Korb AU - Mikhail, Korobko AU - Luise, Kranzhoff AU - Tim, Kuhlbusch AU - Gregoire, Lacaille AU - Angelique, Lartaux-Vollard AU - Lia, Lavezzi AU - Paul, Laycock AU - Sumi, Lee AU - Sumin, Lee AU - Sungho, Lee AU - Giovanni, Losurdo AU - Leonardo, Lucchesi AU - Harald, Luck AU - Adrian, Macquet AU - Ettore, Majorana AU - Valentina, Mangano AU - Filippo, Martelli AU - Iain, Martin AU - Mario, Martinez AU - Alberto, Masoni AU - Luca, Massaro AU - Daniele, Melini AU - Amata, Mercurio AU - Lorenzo, Mereni AU - Andrew, L. Miller AU - Lorenzo, Mirasola AU - Alexandra, Mitchell AU - Irene, Molinari AU - Matteo, Montani AU - Conor, Mow-Lowry AU - Riccardo, Murgia AU - Peter, Gordon Murray AU - Giuseppe, Muscas AU - Luca, Naticchioni AU - Ardiana, Nela AU - Marina, Nery AU - Tom, Niggemann AU - Niklas, Nippe AU - Jerome, Novak AU - Armin, Numic AU - Marco, Olivieri AU - Marco, Orsini AU - June, Gyu Park AU - Daniela, Pascucci AU - Antonio, Perreca AU - Francesco, Piergiovanni AU - Vincenzo, Pierro AU - Laurent, Pinard AU - Innocenzo, Pinto AU - Michele, Punturo AU - Paola, Puppo AU - Francesco, Quochi AU - Reinhardt, Omondi Rading AU - Piero, Rapagnani AU - Marco, Ricci AU - Davi, Rodrigues AU - Rocco, Romano AU - Davide, Rozza AU - Pooya, Saffarieh AU - Federica, Santucci AU - Steven, Schramm AU - Benjamin, Schwab AU - Valeria, Sequino AU - Liam, Shelling Neto AU - Laura, Silenzi AU - Alicia, M. Sintes AU - Carlos, F. Sopuerta AU - Andrew, Spencer AU - Achim, Stahl AU - Jessica, Steinlechner AU - Sebastian, Steinlechner AU - Robert, Szabo AU - Thomas, Thummler AU - Emanuele, Tofani AU - Stefano, Torniamenti AU - Riccardo, Travaglini AU - Lucia, Trozzo AU - M., Paola Vaccaro AU - Michele, Valentini AU - Ván, Péter AU - Jesse, van Dongen AU - Joris, van Heijningen AU - Zeb, van Ranst AU - Marco, Vardaro AU - Patrice, Verdier AU - Daniele, Vernieri AU - Nico, Wagner AU - Janis, Woehler AU - Joachim, Wolf AU - Guido, Zavattini AU - Adrian, Zink AU - Andreas, Zmija TI - The science of the Einstein telescope PY - 2025 PG - 899 UR - https://m2.mtmt.hu/api/publication/36868559 ID - 36868559 LA - English DB - MTMT ER - TY - JOUR AU - Csemány, Dávid AU - Kovács, Róbert Sándor TI - Comparative analysis of lumped parameter and one-dimensional continuum models for droplet evaporation at elevated pressures and temperatures JF - INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER J2 - INT COMMUN HEAT MASS VL - 169 PY - 2025 PG - 12 SN - 0735-1933 DO - 10.1016/j.icheatmasstransfer.2025.109547 UR - https://m2.mtmt.hu/api/publication/36300608 ID - 36300608 N1 - The research reported in this paper is part of project no. TKP-6-6/PALY-2021, implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-NVA funding scheme. The research carried out at BME has been also supported by the grant National Research, Development and Innovation Office-NKFIH STARTING_24 149487 and by the Sustainable Development and Technologies National Programme of the Hungarian Academy of Sciences (FFT NP FTA). This paper was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, Hungary. AB - Droplet evaporation plays a critical role in a wide range of industrial and technological applications, from combustion engines to spray coating and refrigeration. While Eulerian-Lagrangian models are widely used for predicting droplet behavior, they often assume a uniform internal temperature, which may not be valid under high-temperature and high-pressure conditions. This study compares the traditional lumped parameter model (LPM) with a novel one-dimensional model employing a staggered grid (1D-SG) approach. Both models are applied to water droplets in air over a broad range of initial diameters, relative velocities, and ambient pressures and temperatures. The analysis evaluates deviations in droplet lifetime and evaporation rate between the two approaches, emphasizing the influence of Biot number, which is more sensitive to pressure than to temperature. Results show that LPM remains accurate for small droplets and low convection conditions, with deviations under 1 %. However, for larger droplets and enhanced convection, discrepancies in evaporation rate and lifetime reach up to 6 % and 8 %, respectively. The findings demonstrate that while LPM is computationally efficient, its applicability depends on droplet size and flow conditions. The proposed 1D-SG model offers a more physically consistent alternative when higher accuracy is required, providing guidance for model selection in spray-related simulations. LA - English DB - MTMT ER - TY - JOUR AU - Fülöp, Tamás AU - Szücs, Mátyás AU - Takács, Donát M. TI - GENERIC-motivated extended symplectic numerical methods for dissipative mechanical systems: A concrete example and general messages JF - JOURNAL OF COMPUTATIONAL AND APPLIED MECHANICS J2 - J COMPUT APPL MECH VL - 20 PY - 2025 IS - 1 SP - 3 EP - 33 PG - 31 SN - 1586-2070 DO - 10.32973/jcam.2025.001 UR - https://m2.mtmt.hu/api/publication/36074073 ID - 36074073 AB - The GENERIC (General Equation for the Non-Equilibrium Reversible-Irreversible Coupling) framework is used, first, to present the irreversible thermodynamical formulation of the Rayleigh potential, and, subsequently, to realize the dynamical equations of motion of a supercritical van der Waals fluid separated from the environment by a movable rigid piston. Motivated by the latter, a quasi-symplectic generalization of the symplectic Euler finite-difference numerical scheme is introduced for this setup. A remarkable advantage over the explicit Euler scheme regarding artificial numerical antidissipation is illustrated. The possibility of controlled artificial numerical damping is addressed. The quasi-symplectic scheme is proven to enable efficient simulation of the considerably nonlinear and sensitive processes near the liquid-vapour critical point. A numerically feasible quantitative measure of nonlinearity of time-dependent processes is introduced and applied. LA - English DB - MTMT ER - TY - JOUR AU - Ván, Péter TI - SOME REMARKS ON THE OBJECTIVITY AND THERMODYNAMIC CONSISTENCY OF KORTEWEG-TYPE FLUID JF - Annals of the Academy of Romanian Scientists. Mathematics and its Applications J2 - Annals of the Academy of Romanian Scientists. Mathematics and its Applications VL - 17 PY - 2025 IS - 3 SP - 257 EP - 267 PG - 11 SN - 2066-5997 DO - 10.56082/annalsarscimath.2025.3.257 UR - https://m2.mtmt.hu/api/publication/36868541 ID - 36868541 LA - English DB - MTMT ER - TY - JOUR AU - Somogyfoki, Réka AU - Ván, Péter TI - Volume in the Extensive Thermodynamics of Black Holes: AdS and Kiselev Spacetimes JF - ACTA PHYSICA POLONICA B PROCEEDINGS SUPPLEMENT J2 - ACTA PHYS POL B PROC SUPPL VL - 18 PY - 2025 IS - 6 PG - 5 SN - 1899-2358 DO - 10.5506/APhysPolBSupp.18.6-A12 UR - https://m2.mtmt.hu/api/publication/36868366 ID - 36868366 AB - Since black holes lack a straightforward notion of geometrical volume due to their event horizon structure and coordinate dependence, various approaches have been proposed to introduce a meaningful geometric and thermodynamic volume. In this work, we investigate the stability conditions of AdS black holes with and without volume. LA - English DB - MTMT ER - TY - JOUR AU - Somogyfoki, Réka AU - Famá, Alessio AU - Restuccia, Liliana AU - Ván, Péter TI - Thermodynamics and dynamic stability: extended theories of heat conduction JF - JOURNAL OF NON-EQUILIBRIUM THERMODYNAMICS J2 - J NON-EQUIL THERMODY VL - 50 PY - 2025 IS - 1 SP - 59 EP - 76 PG - 18 SN - 0340-0204 DO - 10.1515/jnet-2024-0041 UR - https://m2.mtmt.hu/api/publication/35419433 ID - 35419433 N1 - Export Date: 04 August 2025; CODEN: JNETD AB - The stability of homogeneous thermodynamic equilibrium is analyzed in heat conduction theories in the framework of nonequilibrium thermodynamics, where the internal energy, the heat flux and a second order tensor are thermodynamic state variables. It is shown, that the thermodynamic conditions of concave entropy and nonnegative entropy production can ensure the linear stability. Various special heat conduction theories, including Extended Thermodynamics, are compared in the general framework. LA - English DB - MTMT ER - TY - JOUR AU - Takács, Donát M. AU - Fülöp, Tamás TI - Improving the accuracy of the Newmark method through backward error analysis JF - COMPUTATIONAL MECHANICS J2 - COMPUT MECH VL - 75 PY - 2025 IS - 5 SP - 1585 EP - 1606 PG - 22 SN - 0178-7675 DO - 10.1007/s00466-024-02580-3 UR - https://m2.mtmt.hu/api/publication/34726196 ID - 34726196 AB - We use backward error analysis for differential equations to obtain modified or distorted equations describing the behaviour of the Newmark scheme applied to the transient structural dynamics equation. Based on the newly derived distorted equations, we give expressions for the numerically or algorithmically distorted stiffness and damping matrices of a system simulated using the Newmark scheme. Using these results, we show how to construct compensation terms from the original parameters of the system, which improve the performance of Newmark simulations. The required compensation terms turn out to be slight modifications to the original system parameters (e.g. the damping or stiffness matrices), and can be applied without changing the time step or modifying the scheme itself. Two such compensations are given: one eliminates numerical damping, while the other achieves fourth-order accurate calculations using the traditionally second-order Newmark method. The performance of both compensation methods is evaluated numerically to demonstrate their validity, and they are compared to the uncompensated Newmark method, the generalized-α method and the 4th-order Runge–Kutta scheme. © The Author(s) 2024. LA - English DB - MTMT ER - TY - JOUR AU - Takács, Donát M. AU - Fülöp, Tamás AU - Kovács, Róbert Sándor AU - Szücs, Mátyás TI - The piston effect in supercritical fluids investigated via a reversible–irreversible vector field splitting-based explicit time integration scheme JF - PHYSICS OF FLUIDS J2 - PHYS FLUIDS VL - 37 PY - 2025 IS - 7 PG - 19 SN - 1070-6631 DO - 10.1063/5.0271333 UR - https://m2.mtmt.hu/api/publication/36161803 ID - 36161803 N1 - Funding Agency and Grant Number: Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund [TKP-6-6/PALY-2021]; Sustainable Development and Technologies National Programme of the Hungarian Academy of Sciences (FFT NP FTA); Hungarian Scientific Research Fund [NKKP-Advanced150038]; Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences; University Researcher Scholarship Program (EKOP) of the National Research, Development and Innovation Office - Ministry of Culture and Innovation Funding text: Project No. TKP-6-6/PALY-2021 has been implemented withthe support provided by the Ministry of Culture and Innovation ofHungary from the National Research, Development and InnovationFund, financed under the TKP2021-NVA funding scheme. Theresearch was partially supported by the Sustainable Development and Technologies National Programme of the Hungarian Academy of Sciences (FFT NP FTA) and by the Hungarian Scientific Research Fund under Grant agreement No. NKKP-Advanced150038 (Sz.M.). The research was supported by the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences (K.R.).The work was supported by the University Researcher Scholarship Program (EKOP) of the National Research, Development and Innovation Office, which is also supported by the Ministry of Culture and Innovation (T.D.). We also acknowledge KIFU(Governmental Agency for IT Development, Hungary) for grantingus access to the Komondor HPC facility based in Hungary. AB - In the vicinity of the liquid–vapor critical point, supercritical fluids behave strongly compressible and, in parallel, thermophysical properties have strong state dependence. These lead to various peculiar phenomena, one of which is the piston effect where a sudden heating induces a mechanical pulse. The coupling between thermal and mechanical processes, in the linear approximation, yields a non-trivially rich thermoacoustics. The numerous applications of supercritical fluids raise the need for a reliable yet fast and efficient numerical solution for thermoacoustic time and space dependence in this sensitive domain. Here, we present a second-order accurate, fully explicit staggered space–time grid finite difference method for such coupled linear thermoacoustic problems. Time integration is based on the splitting of the state space vector field representing the interactions that affect the dynamics into reversible and irreversible parts, which splitting procedure leads to decoupled wave and heat equations. The former is a hyperbolic partial differential equation, while the latter is a parabolic one; therefore, different time integration algorithms must be amalgamated to obtain a reliable, dispersion error-free, and dissipation error-free numerical solution. Finally, the thermoacoustic approximation of the supercritical piston effect is investigated via the developed method. LA - English DB - MTMT ER - TY - JOUR AU - Takács, Donát M. AU - Fülöp, Tamás TI - Improving Discrete Numerical Methods for Dynamics Using Continuous Mathematical Tools JF - ADVANCES IN SCIENCE AND TECHNOLOGY J2 - ADV SCI TECHNOL VL - 165 PY - 2025 SP - 21 EP - 30 PG - 10 SN - 1662-8969 DO - 10.4028/p-11TtO6 UR - https://m2.mtmt.hu/api/publication/36178057 ID - 36178057 N1 - Utánközlése: 36227399. AB - We briefly review backward error analysis as a useful mathematical technique for improving numerical methods used for solving ordinary differential equations describing dynamical systems. Then, we show how backward error analysis-based compensation, an approach recently introduced by the authors, can be applied to the second-order Newmark method for eliminating numerical damping and achieving fourth-order convergence. The presented improvements only require modifying the physical parameters of the system and the excitation, while the Newmark method is left intact. We compare the performance of the resulting improvements with that of several other numerical methods, including a novel partitioned method based on local extrapolation. LA - English DB - MTMT ER - TY - JOUR AU - Takács, Donát M. AU - Fülöp, Tamás TI - On the coordinate system-dependence of the accuracy of symplectic numerical methods JF - JOURNAL OF NUMERICAL ANALYSIS AND APPROXIMATION THEORY J2 - J NUMER ANA. APPROX THEORY VL - 54 PY - 2025 IS - 2 SP - 315 EP - 344 PG - 30 SN - 2457-6794 DO - 10.33993/jnaat542-1577 UR - https://m2.mtmt.hu/api/publication/36214178 ID - 36214178 N1 - The work of this author has been supported by the EKÖP-24-3-BME-247 grant of the National Research, Development and Innovation Office under the University Researcher Scholarship Program (EKÖP) AB - Symplectic numerical methods have become a widely-used choice for the accurate simulation of Hamiltonian systems in various fields, including celestial mechanics, molecular dynamics and robotics. Even though their characteristics are well-understood mathematically, relatively little attention has been paid in general to the practical aspect of how the choice of coordinates affects the accuracy of the numerical results, even though the consequences can be computationally significant. The present article aims to fill this gap by giving a systematic overview of how coordinate transformations can influence the results of simulations performed using symplectic methods. We give a derivation for the non-invariance of the modified Hamiltonian of symplectic methods under coordinate transformations, as well as a sufficient condition for the non-preservation of a first integral corresponding to a cyclic coordinate for the symplectic Euler method. We also consider the possibility of finding order-compensating coordinate transformations that improve the order of accuracy of a numerical method. Various numerical examples are presented throughout. LA - English DB - MTMT ER - TY - CHAP AU - Takács, Donát M. AU - Fülöp, Tamás ED - Csüllög, Mihály ED - Mankovits, Tamás TI - Improving Discrete Numerical Methods for Dynamics Using Continuous Mathematical Tools T2 - The 10th International Scientific Conference on Advances in Mechanical Engineering (ISCAME) PB - Trans Tech Publications CY - Bäch SN - 9783036406107 PY - 2025 SP - 235 EP - 244 PG - 10 UR - https://m2.mtmt.hu/api/publication/36227399 ID - 36227399 N1 - 36178057 utánközlése. AB - We briefly review backward error analysis as a useful mathematical technique for improving numerical methods used for solving ordinary differential equations describing dynamical systems. Then, we show how backward error analysis-based compensation, an approach recently introduced by the authors, can be applied to the second-order Newmark method for eliminating numerical damping and achieving fourth-order convergence. The presented improvements only require modifying the physical parameters of the system and the excitation, while the Newmark method is left intact. We compare the performance of the resulting improvements with that of several other numerical methods, including a novel partitioned method based on local extrapolation. LA - English DB - MTMT ER - TY - JOUR AU - Ván, Péter TI - Biró Tamás Sándor: Gintropy (A fiction on inequality) JF - FIZIKAI SZEMLE J2 - FIZIKAI SZEMLE VL - 75 PY - 2025 IS - 1 SP - 36 EP - 36 PG - 1 SN - 0015-3257 UR - https://m2.mtmt.hu/api/publication/35683742 ID - 35683742 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Ván, Péter TI - Ropolyi László – Szegedi Péter szerkesztők Fényes Imre válogatott írásai JF - MAGYAR TUDOMÁNY J2 - MAGYAR TUDOMÁNY VL - 186 PY - 2025 IS - 12 SP - 2535 EP - 2539 PG - 5 SN - 0025-0325 DO - 10.1556/2065.186.2025.12.24 UR - https://m2.mtmt.hu/api/publication/36492878 ID - 36492878 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Farkas, Csaba AU - Gál, László AU - Csiszár, András AU - Grennerat, Vincent AU - Jeannin, Pierre-Olivier AU - Xavier, Pascal AU - Rigler, Dániel AU - Krammer, Olivér AU - Plachy, Zbynek AU - Dusek, Karel AU - Kovács, Róbert Sándor AU - Fehér, Anna Éva AU - Géczy, Attila TI - Sustainable printed circuit board substrates based on flame-retarded PLA/flax composites to reduce environmental load of electronics: Quality, reliability, degradation and application tests JF - SUSTAINABLE MATERIALS AND TECHNOLOGIES J2 - SUSTAINABLE MATERIALS TECHNOLOGIES VL - 40 PY - 2024 PG - 15 SN - 2214-9929 DO - 10.1016/j.susmat.2024.e00902 UR - https://m2.mtmt.hu/api/publication/34746761 ID - 34746761 N1 - Funding Agency and Grant Number: National Research, Development and Innovation Office - NKFIH; Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund [242519/0579]; Interdisciplinary mission of the French CNRS [FK 132186]; [TKP2021-EGA] Funding text: The authors would like to acknowledge the support of: Fedrigoni (htt ps://paper.fedrigoni.com /fra/) , Cisteme (https://cisteme.net/) and the help of UniPCB Kft. colleagues and Istvan Hajdu. The support of the National Research, Development and Innovation Office - NKFIH, FK 132186 project, related to vapour phase soldering studies was necessary to conduct the reported soldering studies. Project no. TKP2021-EGA-02 has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-EGA funding scheme. The project received some funding from the Interdisciplinary mission of the French CNRS with the acronym CIRCABIO (number 242519/0579) under the call "Frugality-Sobriety 2023". AB - The present paper introduces a novel, sustainable approach to produce an eco-friendly Printed Circuit Board (PCB) substrate; a substitute for traditional substrates, to significantly reduce e-waste. We present the prepreg technology, the road to actual circuit assembly with application studies, life cycle analysis (LCA), and sustainability analysis. The flame-retarded prepregs and resulting PCB assemblies were based on polylactic acid (PLA), the structure is reinforced with flax textiles. After copper lamination, subtractive PCB production was performed, and thermal and mechanical reliability was investigated in the case of both laminated and bare substrates. Steps of surface roughness, peel and thermal analysis followed. After a new set of assemblies, the post-assembly analysis was extended with further shear strength analysis on the soldered components and mass analysis regarding thermal processes. The evaluation showed that PLA/Flax substrates provide reliable structural performance up to 200 °C in the reflow soldering process; this allows limited but stabilized application possibilities with specific eco-friendly lead-free solders. A basic blinker circuit and a field programmable gate array (FPGA)–based design was produced and tested; the latter has the general complexity of a commercial circuit. A vol% and wt% analysis extended our discussion with a reduction of harmful components in waste in the range of 90%, which is a disruptive and significant result. Life cycle analysis (LCA) quantified the ecological impact of the assembly, highlighting a significant ease on environmental load (∼10%) for the total assembly. Finally, a qualitative degradation study was introduced to the prepared samples to investigate short-term stability with mechanical-, colour-, mass- and scanning electron microscopy (structure) analysis. Early results show that the boards can withstand the harsh environment of a composting bin for a few days, but in the time of a few weeks, degradation starts, pointing to eventual decomposition. The work directly connects with multiple sustainability development goals. © 2024 The Authors LA - English DB - MTMT ER - TY - JOUR AU - Fehér, Anna Éva AU - Kovács, Róbert Sándor AU - Sudár, Ákos AU - Barnaföldi, Gergely Gábor TI - Challenges in the thermal modeling of highly porous carbon foams JF - JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY J2 - J THERM ANAL CALORIM VL - 149 PY - 2024 IS - 8 SP - 3605 EP - 3616 PG - 12 SN - 1388-6150 DO - 10.1007/s10973-024-12927-w UR - https://m2.mtmt.hu/api/publication/34691294 ID - 34691294 AB - The heat pulse (flash) experiment is a well-known, widely used method to determine thermal diffusivity. However, for heterogeneous, highly porous materials, neither the measurement nor the evaluation methodologies are straightforward. In the present paper, we focus on two open-cell carbon foam types, differing in their porosity but having the same sample size. Recent experiments showed that a non-Fourier behavior, called ’over-diffusive’ propagation, can be present for such a complex structure. The (continuum) Guyer–Krumhansl equation stands as a promising candidate to model such transient thermal behavior. In order to obtain a reliable evaluation and thus reliable thermal parameters, we utilize a novel, state-of-the-art evaluation procedure developed recently using an analytical solution of the Guyer–Krumhansl equation. Based on our observations, it turned out that the presence of high porosity alone is necessary but not satisfactory for non-Fourier behavior. Additionally, the mentioned non-Fourier effects are porosity-dependent; however, porous samples can also follow the Fourier law on a particular time scale. These data serve as a basis to properly identify the characteristic heat transfer mechanisms and their corresponding time scales, which altogether result in the present non-Fourier behavior. Based on these, we determined the validity region of Fourier’s law in respect of time scales. LA - English DB - MTMT ER - TY - JOUR AU - Fehér, Anna Éva AU - Maróti, János Endre AU - Takács, Donát M. AU - Orbulov, Imre Norbert AU - Kovács, Róbert Sándor TI - Thermal and mechanical properties of AlSi7Mg matrix syntactic foams reinforced by Al2O3 or SiC particles in matrix JF - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER J2 - INT J HEAT MASS TRANS VL - 226 PY - 2024 PG - 12 SN - 0017-9310 DO - 10.1016/j.ijheatmasstransfer.2024.125446 UR - https://m2.mtmt.hu/api/publication/34755651 ID - 34755651 LA - English DB - MTMT ER - TY - JOUR AU - Fehér, Anna Éva AU - Kovács, Róbert Sándor TI - On the dynamic thermal conductivity and diffusivity observed in heat pulse experiments JF - JOURNAL OF NON-EQUILIBRIUM THERMODYNAMICS J2 - J NON-EQUIL THERMODY VL - 49 PY - 2024 IS - 2 SP - 161 EP - 170 PG - 10 SN - 0340-0204 DO - 10.1515/jnet-2023-0119 UR - https://m2.mtmt.hu/api/publication/34733253 ID - 34733253 AB - Determining the thermal properties of materials with complex structures is still a major engineering challenge today. The well-known heat pulse experiment can be used to determine the thermal diffusivity by measuring the temperature history as a thermal response for a fast excitation. However, the evaluation of the measurements can be challenging, especially when dealing with non-homogeneous samples. The thermal behavior of such heterogeneous materials may exhibit a response including two-time scales. Therefore, the Fourier equation is not necessarily applicable. The simplest possible alternatives are the 2-temperature models the Guyer–Krumhansl and Jeffreys heat equations. In the present paper, we focus on the interpretation of the Jeffreys heat equation; studying its analytical solution, we present a fitting method for determining the unknown parameters. We also discuss its relation with the other two heat equations, and we offer an interpretation of how to characterize the transient response of heterogeneous materials. LA - English DB - MTMT ER - TY - JOUR AU - Fehér, Anna Éva TI - A hővezetés törvényének újragondolása - Mérnöki kihívások a mindennapokban JF - ÉLET ÉS TUDOMÁNY J2 - ÉLET ÉS TUDOMÁNY VL - 79 PY - 2024 IS - 29 SP - 915 EP - 917 PG - 3 SN - 0013-6077 UR - https://m2.mtmt.hu/api/publication/35149914 ID - 35149914 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Fehér, Anna Éva AU - Kovács, Róbert Sándor AU - Kun-Balog, Attila AU - Maróti, János Endre AU - Orbulov, Imre Norbert AU - Sztankó, Krisztián Endre AU - Szücs, Mátyás AU - Balog, Róbert AU - Takács, Donát M. TI - Szintaktikus fémhabok termikus és mechanikai tulajdonságai, valamint alkalmazhatóságuk fázisváltó hőtároló rendszerekben JF - ENERGIAGAZDÁLKODÁS J2 - ENGA VL - 65 PY - 2024 IS - Klsz. SP - 34 EP - 39 PG - 6 SN - 0021-0757 UR - https://m2.mtmt.hu/api/publication/35472736 ID - 35472736 N1 - További megjelenése In: ENERGIAGAZDÁLKODÁS (0021-0757 ): 65 5-6 pp 6-11 (2024) [35659955] LA - Hungarian DB - MTMT ER - TY - JOUR AU - Fehér, Anna Éva AU - Kovács, Róbert Sándor AU - Kun-Balog, Attila AU - Maróti, János Endre AU - Orbulov, Imre Norbert AU - Sztankó, Krisztián Endre AU - Szücs, Mátyás AU - Balog, Róbert AU - Takács, Donát M. TI - Szintaktikus fémhabok termikus és mechanikai tulajdonságai, valamint alkalmazhatóságuk fázisváltó hőtároló rendszerekben JF - ENERGIAGAZDÁLKODÁS J2 - ENGA VL - 65 PY - 2024 IS - 5-6 SP - 6 EP - 11 PG - 6 SN - 0021-0757 UR - https://m2.mtmt.hu/api/publication/35659955 ID - 35659955 N1 - Közlemény:35472736 utánközlése. LA - Hungarian DB - MTMT ER - TY - JOUR AU - Gál, Márton AU - Samaniego Andrade, Samantha Kathiuska AU - Fehér, Anna Éva AU - Farkas, Attila AU - Madarász, János AU - Horváth, Lili AU - Gordon, Péter AU - Kovács, Róbert Sándor AU - Nagyné László, Krisztina TI - Thermal diffusity in copper benzene-1,3,5-tricarboxylate–reduced graphite oxide mechanical composites JF - JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY J2 - J THERM ANAL CALORIM VL - 149 PY - 2024 IS - 12 SP - 5971 EP - 5983 PG - 13 SN - 1388-6150 DO - 10.1007/s10973-024-13021-x UR - https://m2.mtmt.hu/api/publication/34772009 ID - 34772009 AB - Metal organic frameworks (MOFs) and particularly copper benzene-1,3,5-tricarboxylate (HKUST-1) are excellent materials for gas storage (e.g., CH 4 , N 2 , H 2 adsorption) and gas separation. In this work, reduced graphene oxide (RGO)–HKUST-1 mechanical mixtures were studied in order to reveal the effect of RGO content on the pressure tolerance of the texture and heat conductivity. HKUST-1 was obtained by two different synthesis routes. Air-dried MOF and RGO were thoroughly mixed prior to the compression. Powder XRD and Raman spectroscopy were used to characterize the response of the crystal structure, while low-temperature nitrogen adsorption was used the follow the adsorption properties of the pellets. Finally, the "flash" heat pulse method was used to assess the thermal properties. The gas adsorption isotherms revealed that the adsorption capacity decreases when RGO is added. Based on Raman and XRD results, we found that the synthesis route has an effect on multiple scales. We experimentally confirmed that evaluation of the thermal diffusivity requires a model more complex than the simple Fourier equation, due to the inherent heterogeneous structure of the material. A good approximation of the Fourier coefficient of thermal diffusivity was obtained using the parameters of the Guyer–Krumhansl equation. The heat pulse experiments also revealed possible size-dependent behavior. LA - English DB - MTMT ER - TY - JOUR AU - Giordano, Domenico AU - Amodio, Pierluigi AU - Iavernaro, Felice AU - Mazzia, Francesca AU - Ván, Péter AU - Szücs, Mátyás TI - Fluid statics of a self-gravitating isothermal sphere of van der Waals' gas JF - PHYSICS OF FLUIDS J2 - PHYS FLUIDS VL - 36 PY - 2024 IS - 5 PG - 23 SN - 1070-6631 DO - 10.1063/5.0206334 UR - https://m2.mtmt.hu/api/publication/34893181 ID - 34893181 AB - We subject to scrutiny the physical consistency of adopting the perfect-gas thermodynamic model within self-gravitation circumstances by studying the fluid statics of a self-gravitating isothermal sphere with the van der Waals' thermodynamic model, whose equation of state features well-known terms that account for molecular attraction and size. The governing equations are formulated for any thermodynamic model with two intensive degrees of freedom, applied with the van der Waals' model and solved numerically in nondimensional form by finite-difference algorithms. After a brief summary of thermodynamic characteristics possessed by the van der Waals' model, and relevant to the present study, we proceed to the description of the results in terms of comparative graphs illustrating radial profiles of density, pressure, and gravitational field. We complement them with graphs that compare the dependence of central and wall densities on gravitational number for both perfect-gas and van der Waals' models and that attest dramatically and unequivocally how the presence of molecular-attraction and -size terms removes questionable fluid-statics results systematically found accompanying the perfect-gas model in standard treatments. We also describe, within a very brief and preliminary digression, how the sanitizing action of the mentioned terms affects the thermodynamics of the isothermal sphere by providing evidence of how the gravitational correction to entropy corresponding to the van der Waals' model makes sure that there is no risk of gravothermal catastrophes, negative specific heats, and thermal instabilities. Furthermore, we investigate the phenomenology related to self-gravitationally induced both liquid-gas phase equilibria and metastable-gas states and we describe how they arise naturally and self-consistently from the governing equations. We conclude with a summary of the main results and with a challenging proposal of future work meant to attempt a revalorization the perfect-gas model. © 2024 Author(s). LA - English DB - MTMT ER - TY - JOUR AU - Kovács, Róbert Sándor TI - Heat equations beyond Fourier: From heat waves to thermal metamaterials JF - PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS J2 - PHYS REP VL - 1048 PY - 2024 SP - 1 EP - 75 PG - 75 SN - 0370-1573 DO - 10.1016/j.physrep.2023.11.001 UR - https://m2.mtmt.hu/api/publication/34297744 ID - 34297744 LA - English DB - MTMT ER - TY - JOUR AU - Munafò, C.F. AU - Rogolino, P. AU - Kovács, Róbert Sándor TI - Nonlinear thermal analysis of two-dimensional materials with memory JF - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER J2 - INT J HEAT MASS TRANS VL - 219 PY - 2024 PG - 19 SN - 0017-9310 DO - 10.1016/j.ijheatmasstransfer.2023.124847 UR - https://m2.mtmt.hu/api/publication/34225898 ID - 34225898 AB - A nonlinear hyperbolic heat transport equation has been proposed based on the Cattaneo model without mechanical effects. We analyze the two-dimensional Maxwell-Cattaneo-Vernotte heat equation in a medium subjected to homogeneous and non-homogeneous boundary conditions and with thermal conductivity and relaxation time linearly dependent on temperature. Since these nonlinearities are essential from an experimental point of view, it is necessary to establish an effective and reliable way to solve the system of partial differential equations and study the behavior of temperature evolution. A numerical scheme of finite differences for the solution of the two-dimensional non-Fourier heat transfer equation is introduced and studied. We also investigate the attributes of the numerical method from the aspects of stability, dissipation and dispersive errors. LA - English DB - MTMT ER -