2025-01-19
00:08 |
Portable emissions toxicity system: compact air-liquid interface system for exposure of cell cultures to diluted emissions and polluted air
Vojtíšek, M. ; Dittrich, L. ; Pechout, M. ; Červená, Tereza ; Vimrová, Anežka ; Sikorová, Jitka ; Závodná, Táňa ; Ondráček, Jakub ; Topinka, Jan ; Rössner ml., Pavel
Exposure of living cell cultures at air-liquid interface (ALI), mimicking i.e. human lung surface, is believed to be one of the most realistic means to model toxicity of complex mixtures of pollutants on human health. The complexity of the close cooperation of “emissions source” and toxicology groups and of the instrumentation are among the limiting factors of ALI.\nHere, the concepts of ALI exposure and real-world emissions monitoring using portable emissions monitoring systems (PEMS) are combined into a portable emissions toxicity systems (PETS), along with a mobile toxicological laboratory base, for field deployment, including operation in moving vehicles.
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2025-01-19
00:08 |
PHYSICAL STABILIZATION OF WATER-SOLUBLE PVA NANOFIBROUS MATERIALS FUNCTIONALIZED WITH BIOLOGICALLY ACTIVE SUBSTANCES
Lisnenko, M. ; Holeček, M. ; Kuželová Košťáková, E. ; Valtera, J. ; Rejman, Dominik ; Müllerová, J. ; Běhálek, L. ; Jenčová, V.
Tissue engineering aims to develop materials that enhance biological activity and promote tissue healing and regeneration. One promising approach is to functionalize nanofibrous materials with antimicrobial substances, such as lipophosphonoxin (LPPO), and use water-soluble polymers like polyvinyl alcohol (PVA) to incorporate bioactive molecules into fibers. However, water-soluble materials often face the issue of burst release, releasing over 90% of the active substances within the initial 24 hours. This research focuses on preparing functionalized nanofibrous materials based on PVA containing the experimental antimicrobial compound LPPO and subsequent physical stabilization of the materials using the Heat treatment method. The applied stabilization successfully reduced the incorporated substance's release rate by up to 50%. The resulting materials have the potential to provide functional cross-linked PVA nanofiber scaffolds for regenerative medicine applications in large and chronic skin injuries.
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2025-01-19
00:08 |
Cesta galeristy a jednoho obrazu. Mikoláš Lehmann a evropské výstavní turné s obrazem Veraikon Gabriela Maxe.
Česká, Lucie
Cesty s tzv. senzačními obrazy po nejrůznějších městech Evropy se staly pro mnohé galeristy nedílnou součástí jejich podnikatelských aktivit. Díla, se kterými byla taková mezinárodní turné podnikána, předcházela pověst a ať už se jednalo o jejich prezentaci v rámci pravidelných přehlídek umění nebo o výstavu samostatnou, vždy se těšily hojnému zájmu publika. Pro mezinárodní cesty s dílem, které budilo skutečnou senzaci, se v sedmdesátých letech 19. století rozhodl i pražský galerista Mikoláš Lehmann. Mikoláš Lehmann patřil mezi galeristy, jejichž podniky se v Praze etablovaly v poslední třetině 19. století, a které díky svým stálým výstavám rozšířily nabídku soudobé umělecké produkce pro zdejší publikum. Lehmannovým salonem prošla za více než třicet let jeho fungování díla českých i zahraničních umělců, mezi nimiž lze zmínit nejvýraznější spolupráci s malířem Gabrielem Maxem. Ten vytvořil dílo, se kterým se Mikoláš Lehmann rozhodl absolvovat svou první zahraniční cestu. Gabriel Max namaloval obraz „Kristova hlava na roušce svaté Veroniky“ roku 1874. Po uvedení v Lehmannově salonu vzbudila malba mezi návštěvníky skutečnou senzaci a mezi odborným publikem a uměleckými kritiky mnohé diskuse. Lehmann se odezvu rozhodl využít a s obrazem absolvoval zahraniční turné, jehož první zastávkou se roku 1875 stal Londýn, kde byl představen veřejnosti v rámci pravidelné jarní výstavy ve French Gallery. V kontextu Lehmannových obchodních strategií se jeho první zahraniční cesta stala velmi důležitou – pomohla galeristovi seznámit se se zahraničním prostředím, vybudovat důležité kontakty a poznat postupy, které využívali podnikatelé, jejichž galerie měly již zavedenou tradici.
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2025-01-19
00:08 |
Dynamic mode decompositions of phonation onset – Comparison of different methods
Valášek, Jan ; Sváček, P.
Four dynamic mode decomposition (DMD) methods are used to analyze a simulation of the phonation onset carried out by in-house solver based on the nite element method. The dataset consists of several last periods of the flow-induced vibrations of vocal folds (VFs). The DMD is a data-driven and model-free method typically used for finding a low-rank representation of a high-dimensional system. In general, the DMD decomposes a given dataset to modes with mono-frequency content and associated complex eigenvalues providing the growth/decay rate that allows a favourable physical interpretation and in some cases also a short-term prediction of system behaviour. The disadvantages of the standard DMD are non-orthogonal modes and sensitivity to an increased noise level which are addressed by following DMD variants. The recursive DMD (rDMD) is an iterative DMD decomposition producing orthogonal modes. The total least-square DMD and the higher order DMD (hoDMD) are methods substantially reducing a high DMD sensitivity to noise. All methods identi ed very similar DMD modes as well as frequency spectra. Substantial difference was found in the real part of the spectra. The nal dataset reconstruction is the most accurate in the case of the recursive variant. The higher order DMD method also outperforms the standard DMD. Thus the rDMD and the hoDMD decompositions are promising to be used further for the parametrization of a VF motion.
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2025-01-19
00:08 |
Parallelization of DEM solver for non-spherical solids: A pathway to scalable CFD-DEM simulations
Studeník, Ondřej ; Kotouč Šourek, M. ; Isoz, Martin ; Kočí, P.
Granular matter formed from non-spherical solids appears in both natural and industrial settings. These include, among others, landslides, mixing, and fluidization. The commonly used predictive method for granular matter is the discrete element method (DEM). However, DEM was initially designed for spherical particles and faces many challenges in modeling the non-spherical ones , which are prevalent. Therefore, various approaches, including multi-sphere clusters, super-quadrics and polyhedral models, were developed to approximate the irregular shapes. The polyhedral approach offers the highest level of fidelity, but comes with the biggest computational costs, particularly for non-convex particles. Hence, optimization and parallelization of codes with polyhedron-based DEM solvers are of great interest. In this work, we present recent advances in the development of our custom polyhedron-based DEM solver, focusing on parallel computing. With improvements in the solver architecture and boosted computational efficiency, the DEM code scales well at least up to 32 cores and allows for efficient coupling with computational fluid dynamics (CFD) to simulate complex\nparticle-laden flows.
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2025-01-19
00:08 |
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2025-01-19
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Reynolds-averaged simulation of turbulent flows with immersed boundaries
Kubíčková, Lucie ; Isoz, Martin
Simulating turbulent flows in complex real-life geometries faces two major problems. First, direct simulation of turbulent flow is extremely costly. Second, a complex geometry-conforming mesh is required, and such mesh presumably suffers from several mesh-quality related problems lowering the solution accuracy and prolonging the simulation time. To solve the first problem, phenomenological turbulence models based on, e.g. Reynolds-averaging, are commonly utilized. To address the second one, a variant of an immersed boundary (IB) method can be used where the complex geometry is projected onto a simple mesh by an indi-cator field and adjustment of governing equations. Consequently, a connection of Reynolds-averaging and an immersed boundary method shall resolve both the problems and provide a simulation approach favorable for e.g. optimizations. However, such a connection is not common. In this contribution, we utilize our custom IB variant, the hybrid fictitious domain-immersed boundary method (HFDIB) and aim on extending the HFDIB by tools of the Reynolds-averaged simulation (RAS). In comparison with standard simulation approaches, the new HFDIB-RAS approach shows acceptable results in wide range of flow Reynolds numbers and in several testing geometries.
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2025-01-19
00:08 |
Data-driven approach to estimating soot distribution inside catalytic filters in utomotive exhaust gas aftertreatment
Khýr, Matyáš ; Plachá, M. ; Hlavatý, Tomáš ; Isoz, Martin
The performance and the necessary regeneration frequency of catalytic filters (CFs) used in the treatment of automotive exhaust gases depend strongly on the solid matter accumulated within their porous walls. Reliable predictions of solid matter (soot) accumulation are crucial in the development and optimisation of CFs. In this contribution, we exploit the tools of artificial intelligence (AI) to estimate the distribution of soot directly in the porous microstructure of CFs. Specifically, our AI model uses deep neural networks (DNNs) and convolutional autoencoders (CAEs) to predict the soot distribution from information about the microstructure and the initial velocity field. To provide the model with training and validation data, we used our previously developed transient numerical model of particle deposition in the CF walls to calculate soot distribution in a dataset of artificial 2D geometries. The results of the developed AI model are in good agreement with simulation regarding the total amount of accumulated soot. However, the accuracy in the spatial distribution of the soot is not optimal, and consequently, using estimated particle deposits to simulate the pressure drop in\nthe artificial microstructure results in 35 % accuracy.
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2025-01-19
00:08 |
Using finite volume method to simulate laser shock peening of 7050 Al alloy
Isoz, Martin ; Gruber, Pavel ; Ježek, Ondřej ; Kubíčková, Lucie ; Gabriel, Dušan ; Kaufman, Jan ; Brajer, Jan
Laser shock peening (LSP) is a modern alternative to standard peening processes such as shot peening. In general, peening is used to improve the strength and fatigue resistance of components by hardening their surface. In LSP, a laser-induced shockwave is used to harden the material to a depth of the order of 1 mm, that is, roughly twice as deep as can be achieved with shot peening. Frameworks for LSP simulation have been developed since the end of the 1990s and are exclusively based on the finite element method (FEM). The critical component of the framework is the dynamic simulation of the elastoplastic shockwave that subjects the component material to a strain rate of the order 10−7 s−1. In this contribution, we present a simulation framework for LSP based on the finite volume method (FVM) that allows for modeling the strain-rate hardening of the material. The framework is used to simulate the LSP of the 7050 aluminum alloy. Using a comparison\nof our FVM results with the FEM data available in the literature, we found that FVM can be applied to LSP simulation with the same success as the more traditional FEM.
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2025-01-19
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On diffusion, reaction, and flow of high-concentration multicomponent gas mixtures
Hlavatý, Tomáš ; Isoz, Martin
Heterogeneous catalysis contributes to producing more than 80% of all chemical products in the world. Industrial heterogeneous catalysis is a complex process that combines fully three-dimensional mass,momentum, and energy transport on several scales. In the present work, we leverage our previously developed CFD solver for non-isothermal heterogeneously catalyzed reactive flow based on the finite-volume method and extend it with multicomponent Stefan-Maxwell diffusion description to handle high-concetration multicomponent mixtures. The resulting framework is verified and validated on the simple Stefan tube experiment, for which an analytical solution is available.
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