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Asynchronous time integration while achieving zero interface energy
Dvořák, Radim; Kolman, Radek; Falta, J.; Neühauserová, M.
2023 - English
This contribution deals with an asynchronous direct time integration of the finite-element model. The proposed method is applied to the phenomenon of wave propagation through an elastic linear continuum. The numerical model is partitioned into individual subdomains using the domain decomposition method by means of localized Lagrange multipliers. For each subdomain, different time discretizations are used. No restrictions for relation between subdomain’s time steps are imposed. The coupling of the subdomains is forced by an acceleration continuity condition. Additionally, we use the a posteriori technique to also provide the displacement and velocity continuity at the interfaces, and hence we obtain exact continuity of all three kinematic fields. The proposed method is experimentally validated using the modified SHPB (split Hopkinson pressure bar) setup.
Keywords:
finite element method; direct time integration; asynchronous integration; domain decomposition; localized lagrange multipliers
Available at various institutes of the ASCR
Asynchronous time integration while achieving zero interface energy
This contribution deals with an asynchronous direct time integration of the finite-element model. The proposed method is applied to the phenomenon of wave propagation through an elastic linear ...
Comparison of finite element simulation of tungsten nanoindentation with Berkovich and conical indenter
Fiala, L.; Ballo, I.; Kovář, J.; Fuis, Vladimír
2023 - English
Finite Element Method (FEM) was used to study the difference between using Berkovich and conical indenters in nanoindentation test of tungsten specimen. The study was aimed to determine the\nmodulus of elasticity of a tested specimen and how it changes with different indenter. The FEM analysis also revealed that the modulus of elasticity was sensitive to the dimensions of both specimen and the indenter for which were made several numerical calculations with different dimensions.
Keywords:
nanoindentation; FEM; Berkovich indenter; conical indenter; tungsten
Available at various institutes of the ASCR
Comparison of finite element simulation of tungsten nanoindentation with Berkovich and conical indenter
Finite Element Method (FEM) was used to study the difference between using Berkovich and conical indenters in nanoindentation test of tungsten specimen. The study was aimed to determine the\nmodulus ...
Ambiguity in Stochastic Optimization Problems with Nonlinear Dependence on a Probability Measure via Wasserstein Metric
Kaňková, Vlasta
2023 - English
Many economic and financial applications lead to deterministic optimization problems depending on a probability measure. It happens very often (in applications) that these problems have to be solved on the data base. Point estimates of an optimal value and estimates of an optimal solutionset can be obtained by this approach. A consistency, a rate of convergence and normal properties, of these estimates, have been discussed (many times) not only under assumptions of independent data corresponding to the distributions with light tails, but also for weak dependent data and the distributions with heavy tails. However, it is also possible to estimate (on the data base) a confidence intervals and bounds for the optimal value and the optimal solutions. To analyze this approach we focus on a special case of static problems depending nonlineary on the probability measure. Stability results based on the Wasserstein metric and the Valander approach will be employed for the above mentioned analysis.
Keywords:
Stochastic optimization problems; static problems; empirical measure; point estimates; interval estimates; nonlinear dependence
Fulltext is available at external website.
Ambiguity in Stochastic Optimization Problems with Nonlinear Dependence on a Probability Measure via Wasserstein Metric
Many economic and financial applications lead to deterministic optimization problems depending on a probability measure. It happens very often (in applications) that these problems have to be solved ...
Improving computational efficiency of contact solution in fully resolved CFD-DEM simulations with arbitrarily-shaped solids
Studeník, Ondřej; Kotouč Šourek, M.; Isoz, Martin
2023 - English
The abundance of industrial processes containing both solid and liquid phases generate demand for fully resolved models allowing for detailed analysis and optimization of these processes. An established approach providing such models is based using a variant of an immersed boundary method to couple the computational fluid dynamics (CFD) and discrete element method (DEM). In the talk, we will present our custom and monolithic implementation of a fully-resolved CFDDEM solver and concentrate on the intricacies of solving contact between two arbitrarily-shaped solids. We shall propose an efficient contact treatment based on the concept of a virtual mesh, which provides the mesh resolution required by DEM through dividing the space around the contact point in a finite volume fashion without any changes to the CFD mesh itself. A substantial part of the talk will devoted to the parallelization of the contact solution, especially in the context of the domain decomposition method imposed by the CFD solver.
Keywords:
CFD; DEM; virtual mesh
Fulltext is available at external website.
Improving computational efficiency of contact solution in fully resolved CFD-DEM simulations with arbitrarily-shaped solids
The abundance of industrial processes containing both solid and liquid phases generate demand for fully resolved models allowing for detailed analysis and optimization of these processes. An ...
Dissolved and gaseous nitrogen losses in forests controlled by soil nutrient stoichiometry
Oulehle, Filip; Chuman, T.; Hruška, Jakub; Krám, Pavel; Navrátil, Tomáš; Tesař, Miroslav; Ač, Alexander; Urban, Otmar
2023 - English
This study investigates the consequences of chronic nitrogen deposition in forests, including its effects on soil and surface water quality, and greenhouse gas emissions. To predict these effects, the authors explore the controls over dissolved and gaseous nitrogen fluxes in temperate forests. Their findings indicate that stream leaching losses of dissolved nitrogen correspond with the nutrient stoichiometry\nof the forest floor, with stream N losses increasing as ecosystems progress towards phosphorus limitation. Soil nitrogen storage increases with oxalate extractable iron and aluminium content. The authors estimate soil gaseous losses based on 15 N stocks, which averaged 2.5±2.2 kg N ha-1 year-1 , comprising 20±14% of total nitrogen deposition. They also extrapolate the current gaseous nitrogen loss flux from forests globally to be 8.9 Tg N year-1 , which represents 39% of current nitrogen deposition to forests worldwide.
Keywords:
nitrogen; catchment; isotope; mass balance; denitrification; carbon; sequestration
Available in digital repository of the ASCR
Dissolved and gaseous nitrogen losses in forests controlled by soil nutrient stoichiometry
This study investigates the consequences of chronic nitrogen deposition in forests, including its effects on soil and surface water quality, and greenhouse gas emissions. To predict these effects, the ...
Hazardous components: A case study in textile waste management
Shtukaturova, Anastasia
2023 - English
Textile waste, a problem that has been somewhat overlooked for many years, is now coming to the fore.1 The textile value chain is long\nand complex, with over 8000 chemicals used in different manufacturing processes.2 A wide variety of chemicals are used in the manufacture of textile products for the improvement of essential properties and performance of textiles. Chemicals used in textiles significantly improve their quality and appearance. However, the harmful effects of these chemicals can occur at various stages of textile production and processing, such as dyeing, printing and finishing, as well as during use by consumers and at the end-of-life stage.3 There is a lack of safety information on the presence and use of all of these chemicals in consumer products.
Keywords:
textile waste; waste management; chemicals
Available in a digital repository NRGL
Hazardous components: A case study in textile waste management
Textile waste, a problem that has been somewhat overlooked for many years, is now coming to the fore.1 The textile value chain is long\nand complex, with over 8000 chemicals used in different ...
Properties and use of high-temperature biochar
Sedmihradská, Anežka
2023 - English
Despite being a hot topic in environmental research, biochar and its properties have been mainly investigated from the perspectives of feedstock type and pyrolysis temperature. Few studies have explored the effect of particle size on biochar properties.Even when the effect of particle size on crop efficiency is recognized, there is a lack of corresponding data and analysis.2–7 Therefore, we thoroughly analyzed (proximate and ultimate analysis, SEM, XRD, Raman spectroscopy) four particle size fractions (< 0.5, 0.5–2, 2–5, > 5 mm) of high-temperature biochar from a gasification power plant, the sizes reflecting those of biochar actually used in agriculture. The < 0.5 mm fraction was significantly different in terms of carbon structure, and carbon and ash content. Consequently, pH, electric conductivity and heavy metal content also differed greatly. The corresponding results for the other particle fractions were broadly similar to each other. Interestingly, for all fractions, the porosity and H/C ratio were independent of particle size, meaning that, regardless of size, the investigated biochar fractions are equally stable in soil. The 0.5–2 mm fraction was then selected to be used in different industrial or agricultural processes such as the anaerobic digestion of wastewater or livestock feeding. The effect of biochar on these processes is currently under investigation, providing only initial data so far.
Keywords:
biochar; particle size on biochar; high-temperature biochar
Available in a digital repository NRGL
Properties and use of high-temperature biochar
Despite being a hot topic in environmental research, biochar and its properties have been mainly investigated from the perspectives of feedstock type and pyrolysis temperature. Few studies have ...
Vertical gradients of atmospheric aerosols chemical composition
Kovářík, Jiří
2023 - English
The aim of this work is to obtain data on the chemical composition of aerosols at two heights (4–5 metres above ground and at 230 metres on the atmospheric tower’s measurement platform). The following and sampling techniques will be used: Aerosol Mass\nSpectrometry) – in combination with PMF (Positive Matrix Factorisation), Aerosol Chemical Speciation Monitor and Particle Into Liquid Sampler coupled with Ion Chromatography.
Keywords:
aerosols; analytical methods; chemical composition
Available in a digital repository NRGL
Vertical gradients of atmospheric aerosols chemical composition
The aim of this work is to obtain data on the chemical composition of aerosols at two heights (4–5 metres above ground and at 230 metres on the atmospheric tower’s measurement platform). The following ...
Liquid mixing time and gas holdup in a bubble column bioreactor
Terentyak, Mark
2023 - English
The aim of the research is the experimental study of homogenisation and saeration in a bubble column in dependence on operational conditions and aspect ratio.
Keywords:
bubble column bioreactor; gas holdup; experiments
Available in a digital repository NRGL
Liquid mixing time and gas holdup in a bubble column bioreactor
The aim of the research is the experimental study of homogenisation and saeration in a bubble column in dependence on operational conditions and aspect ratio.
A new blade cascade for flutter studies
Šnábl, Pavel; Pešek, Luděk; Procházka, Pavel P.; Skála, V.
2023 - English
In this paper, a new blade cascade, developed in the Institute of Thermomechanics, is presented. The geometry of the cascade was modified so now the stall flutter can occur. It has some major construction improvements over the original cascade which now allow more precise and reliable measurements. The stability of the new blade cascade with five NACA 0010 profiles with rotational degree of freedom is assessed by Travelling Wave Mode approach and Aerodynamic Influence Coefficient approach.
Keywords:
blade cascade; stability; travelling wave mode; aerodynamic influence coefficient
Available at various institutes of the ASCR
A new blade cascade for flutter studies
In this paper, a new blade cascade, developed in the Institute of Thermomechanics, is presented. The geometry of the cascade was modified so now the stall flutter can occur. It has some major ...
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