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Time delays shape the eco‑evolutionary dynamics of cooperation
Sourav Roy, Sayantan Nag Chowdhury, Srilena Kundu, Gourab Kumar Sar, Jeet Banerjee, Biswambhar Rakshit, Prakash Chandra Mali, Matjaž Perc, Dibakar Ghosh, 2023, original scientific article

Abstract: We study the intricate interplay between ecological and evolutionary processes through the lens of the prisoner’s dilemma game. But while previous studies on cooperation amongst selfsh individuals often assume instantaneous interactions, we take into consideration delays to investigate how these might afect the causes underlying prosocial behavior. Through analytical calculations and numerical simulations, we demonstrate that delays can lead to oscillations, and by incorporating also the ecological variable of altruistic free space and the evolutionary strategy of punishment, we explore how these factors impact population and community dynamics. Depending on the parameter values and the initial fraction of each strategy, the studied eco-evolutionary model can mimic a cyclic dominance system and even exhibit chaotic behavior, thereby highlighting the importance of complex dynamics for the efective management and conservation of ecological communities. Our research thus contributes to the broader understanding of group decision-making and the emergence of moral behavior in multidimensional social systems.
Keywords: cooperation, time delay, evolutionary dynamics, social dilemma, social physics
Published in DKUM: 04.04.2024; Views: 89; Downloads: 6
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Numerical simulations of the flow and aerosol dispersion in a violent expiratory event : Outcomes of the “2022 International Computational Fluid Dynamics Challenge on violent expiratory events
Jordi Pallares, Alexandre Fabregat Tomas, Akim Lavrinenko, Hadifathul Akmal bin Norshamsudin, Gabor Janiga, David Frederick Fletcher, Kiao Inthavong, Marina Zasimova, Vladimir Ris, Nikolay Ivanov, Robert Castilla, Pedro Javier Gamez-Montero, Gustavo Raush, Hadrien Calmet, Daniel Mira, Jana Wedel, Mitja Štrakl, Jure Ravnik, Douglas Hector Fontes, Francisco José De Souza, Cristian Marchioli, Salvatore Cito, 2023, original scientific article

Abstract: This paper presents and discusses the results of the “2022 International Computational Fluid Dynamics Challenge on violent expiratory events” aimed at assessing the ability of different computational codes and turbulence models to reproduce the flow generated by a rapid prototypical exhalation and the dispersion of the aerosol cloud it produces. Given a common flow configuration, a total of 7 research teams from different countries have performed a total of 11 numerical simulations of the flow dispersion by solving the Unsteady Reynolds Averaged Navier–Stokes (URANS) or using the Large-Eddy Simulations (LES) or hybrid (URANS-LES) techniques. The results of each team have been compared with each other and assessed against a Direct Numerical Simulation (DNS) of the exact same flow. The DNS results are used as reference solution to determine the deviation of each modeling approach. The dispersion of both evaporative and non-evaporative particle clouds has been considered in 12 simulations using URANS and LES. Most of the models predict reasonably well the shape and the horizontal and vertical ranges of the buoyant thermal cloud generated by the warm exhalation into an initially quiescent colder ambient. However, the vertical turbulent mixing is generally underpredicted, especially by the URANS-based simulations, independently of the specific turbulence model used (and only to a lesser extent by LES). In comparison to DNS, both approaches are found to overpredict the horizontal range covered by the small particle cloud that tends to remain afloat within the thermal cloud well after the flow injection has ceased.
Keywords: numerical simulations, computational fluid dynamics
Published in DKUM: 28.03.2024; Views: 332; Downloads: 449
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Numerical analysis of a wind turbine blade with different software
Gorazd Hren, 2019, original scientific article

Abstract: The development of wind power generation technology recognises the wind turbine blade design and manufacturing as crucial for its performance. The laboratory size wind turbine blade was analysed, considering the 3D printing plastic material for blades. Applying the structural dynamic equations of blades, the aero-elastic model of the rotating rotor and the numerical simulation method of the deflections are presented under the aerodynamic loads and centrifugal forces. Based on the parameters of aerofoil and the geometrical parameters of blade, 3D model of the blade was established with the modelling software. Then the model was introduced into computational flow dynamics software to carry out the loads on the blade and further into numerical structural analysis. The analysis was performed in two different software packages. Design of wind turbine blades depends on high precision, reliable and robust numerical predictions of performance where the plug-in software is found to be inadequate for nontrivial problems.
Keywords: computational fluid dynamics, numerical analysis, structural analysis, wind turbine blade
Published in DKUM: 22.02.2024; Views: 205; Downloads: 16
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Reconstruction of a fluid bed device for separating granular material from the grinding process of rapid antigen tests
Miha Jordan, Tilen Švarc, Peter Majerič, Rebeka Rudolf, Matej Zadravec, 2023, original scientific article

Abstract: The article includes the study and reconstruction of a fluid bed device with the purpose of separating the granular material from the grinding process of rapid antigen tests. The following techniques were performed, with the purpose of characterisation of the ground particles: sieve analysis, X-ray fluorescence spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The paper includes experimental testing of a simplified separation process with zeolite spheres and paper strips, supported by a numerical model. The flow conditions’ impact on the behaviour and interactions of particles of the considered problem were simulated using coupled computational fluid dynamics (CFD) and the discrete element method (DEM) approach. The separation process of zeolite spheres and paper strips was found to be efficient. The simulation results showed the appropriate behaviour of the particles during the process. We explained the results’ deviations, and we also presented the shortcomings and possible improvements. Further research is required to define the adequacy of the process, while using actual ground material of rapid antigen tests.
Keywords: rapid antigen tests, nanomaterials, fluidised bed, computational fluid dynamics, discrete element method, characterisation
Published in DKUM: 05.01.2024; Views: 265; Downloads: 22
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Influence of Numerical Mesh Type on Airfoil Aerodynamic Characteristics
Marko Pezdevšek, Matej Fike, Andrej Predin, Gorazd Hren, 2019, published scientific conference contribution

Abstract: In this paper, we will examine how different mesh types affect the aerodynamic characteristic of an airfoil. The airfoil used for this paper was the NREL S809. Three different mesh types were created, a blocked structured mesh, an unstructured mesh and a hybrid mesh containing a blocked structured mesh near the surface of the airfoil and an unstructured mesh on the outside perimeter. Steady state simulations were performed for angles of attack between 0°and 22°. Lift and drag coefficient for all created meshes were compared to experimental results from literature. From angles of attack between 2° and 8° all three meshes predict similar lift and drag coefficients. We encountered problems with convergence for the unstructured mesh at angles of attack higher than 8°. Structured and hybrid mesh had similar lift and drag coefficients across all angles of attack.
Keywords: computational fluid dynamics, NREL S809, structured mesh, unstructured mesh, hybrid mesh
Published in DKUM: 04.12.2023; Views: 257; Downloads: 15
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Vpliv kritičnih dejavnikov uspeha na uvedbo ERP rešitve Microsoft Dynamics Business Central
Laura Jurgec, 2023, master's thesis

Abstract: Podjetja za uspešno poslovanje potrebujejo orodje, ki jim pomaga pri avtomatizaciji in upravljanju njihovih osnovnih poslovnih procesov. To orodje so celovite informacijske rešitve oziroma rešitve ERP. Rešitve ERP pomagajo pri pretoku podatkov med različnimi oddelki podjetja, kot so finance, nabava, prodaja, proizvodnja itd., in ker so podatki shranjeni v skupni bazi podatkov, vsi oddelki vidijo enake podatke, zaradi česar ne more priti do podvajanja podatkov. Rešitve ERP lahko korenito izboljšajo učinkovitost poslovanja podjetja, zato se vse več podjetij odloča za njihovo uvedbo, vendar pa se mnogokrat zgodi, da je uvedba neuspešna. Z namenom, da bi bilo čim manj neuspešnih uvedb rešitev ERP, so bili vpeljani t. i. kritični dejavniki uspeha, ki nam pomagajo oziroma nas vodijo do opredelitve tistega, kar nam največ pomeni. Na te izsledke se nato osredotočimo tudi pri sami uvedbi rešitve ERP. Na začetku magistrskega dela smo se osredotočili na rešitve ERP na splošno, torej opredelili njihove značilnosti in določili najpogostejše module, medsebojno primerjali rešitve ERP, nameščene na lokaciji in v oblaku, opisali arhitekturno rešitev, predstavili ponudnike, njihove prednosti in slabosti ter trende, ki jih lahko pričakujemo v prihodnje. V nadaljevanju smo podrobneje opisali proces uvedbe rešitve ERP, kjer smo predstavili faze in življenjski cikel uvedbe, korake do uspešne uvedbe, metodologije vodenja projektov in pristope pri uvedbi rešitev ERP. V nadaljevanju magistrskega dela smo se osredotočili na kritične dejavnike uspeha. Ker vemo, da so rešitve ERP lahko nameščene na lokaciji ali v oblaku, smo preučili članke z obeh področij. Ker je računalništvo v oblaku razmeroma nova tehnologija, obstaja manj člankov na to temo, zato smo se osredotočili na zgolj enega, medtem ko smo za rešitve ERP, nameščene na lokaciji, preučili sedem člankov. Ker je na trgu mnogo ponudnikov rešitev ERP, smo na koncu magistrskega dela osredotočili na rešitev Business Central. V tem delu smo podrobneje opisali značilnosti rešitve Business Central, njene module in arhitekturo ter proces uvedbe s pomočjo metodologije Sure Step, prav tako smo ugotovili, kateri so kritični dejavniki uspeha, ki pozitivno vplivajo na uspešnost uvedbe rešitev ERP na splošno kot tudi na uspešnost specifične rešitve ERP Business Central.
Keywords: rešitve ERP, Business Central, kritični dejavniki uspeha, KDU, Microsoft Dynamics, Dynamics 365
Published in DKUM: 25.10.2023; Views: 270; Downloads: 24
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Delovanje erp rešitev v računalniškem oblaku
Nina Margon, 2013, undergraduate thesis

Abstract: V 21. stoletju je tehnološki napredek dosegel že zelo veliko. Pojavljati so se začeli vedno novi in novi trendi, ki silijo podjetja k spreminjanju in posodabljanju svojega poslovanja in k novim trendom, ki jih narekuje trg. Podjetja, ki se slabo prilagajajo razmeram na trgu, so običajno tista, ki ne preživijo in jih pokoplje konkurenca. Ravno iz tega razloga je potrebno, predvsem za podjetja, spremljati trg na katerem se nahajajo in se mu prilagajati, zaznati spremembe in jih čim prej odpraviti, da podjetje lahko nemoteno posluje naprej ter jih konkurenca ne prehiti.
Keywords: Računalništvo v oblaku, ERP rešitve, Cloud Computing, SAP, Microsoft Dynamics NAV
Published in DKUM: 18.10.2023; Views: 297; Downloads: 6
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Fluctuating number of energy levels in mixed-type lemon billiards
Črt Lozej, Dragan Lukman, Marko Robnik, 2021, original scientific article

Abstract: In this paper, the fluctuation properties of the number of energy levels (mode fluctuation) are studied in the mixed-type lemon billiards at high lying energies. The boundary of the lemon billiards is defined by the intersection of two circles of equal unit radius with the distance 2B between the centers, as introduced by Heller and Tomsovic. In this paper, the case of two billiards, defined by B = 0.1953, 0.083, is studied. It is shown that the fluctuation of the number of energy levels follows the Gaussian distribution quite accurately, even though the relative fraction of the chaotic part of the phase space is only 0.28 and 0.16, respectively. The theoretical description of spectral fluctuations in the Berry-Robnik picture is discussed. Also, the (golden mean) integrable rectangular billiard is studied and an almost Gaussian distribution is obtained, in contrast to theory expectations. However, the variance as a function of energy, E, behaves as - E, in agreement with the theoretical prediction by Steiner.
Keywords: nonlinear dynamics, quantum chaos, mixed-type systems, energy level statistics, lemon billiards, billiards
Published in DKUM: 13.10.2023; Views: 429; Downloads: 12
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Quantum chaos in triangular billiards
Črt Lozej, Giulio Casati, Tomaž Prosen, 2022, original scientific article

Abstract: We present an extensive numerical study of spectral statistics and eigenfunctions of quantized triangular billiards. We compute two million consecutive eigenvalues for six representative cases of triangular billiards, three with generic angles with irrational ratios with π, whose classical dynamics is presumably mixing, and three with exactly one angle rational with π, which are presumably only weakly mixing or even nonergodic in case of right triangles. We find excellent agreement of short- and long-range spectral statistics with the Gaussian orthogonal ensemble of random matrix theory for the most irrational generic triangle, while the other cases show small but significant deviations which are attributed either to a scarring or superscarring mechanism. This result, which extends the quantum chaos conjecture to systems with dynamical mixing in the absence of hard (Lyapunov) chaos, has been corroborated by analyzing distributions of phase-space localization measures of eigenstates and inspecting the structure of characteristic typical and atypical eigenfunctions.
Keywords: quantum physics, quantum chaos, quantum scars, wave chaos, billiards, chaos and nonlinear dynamics, ergodic theory
Published in DKUM: 12.10.2023; Views: 215; Downloads: 28
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