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Programs and Algorithms of Numerical Mathematics 21 : Jablonec nad Nisou, June 19-24, 2022 : Proceedings of Seminar
Chleboun, J.; Kůs, Pavel; Papež, Jan; Rozložník, Miroslav; Segeth, Karel; Šístek, Jakub
2023 - English
These proceedings contain peer-reviewed papers that are based on the invited lectures, short communications, and posters presented at the 21st seminar Programs and Algorithms of Numerical Mathematics (PANM) held in Merkur Hotel, Jablonec nad Nisou, Czech Republic, June 19-24, 2022.\nThe seminar was organized by the Institute of Mathematics of the Czech Academy of Sciences under the auspices of EU-MATHS-IN.CZ, Czech Network for Mathematics in Industry, and with the nancial support provided by the RSJ Foundation. It continued the previous seminars on mathematical software and numerical methods held (biennially, with only one exception) in Alšovice, Bratříkov, Janov nad Nisou, Kořenov, Lázně Libverda, Dolní Maxov, Prague, and Hejnice in the period 1983-2020. The objective of this series of seminars is to provide a forum for presenting and discussing advanced topics in numerical analysis, computer implementation of numerical algorithms, new approaches to mathematical modeling, and single- or multi-processor applications of computational methods.
Keywords:
numerical mathematics
Available in digital repository of the ASCR
Programs and Algorithms of Numerical Mathematics 21 : Jablonec nad Nisou, June 19-24, 2022 : Proceedings of Seminar
These proceedings contain peer-reviewed papers that are based on the invited lectures, short communications, and posters presented at the 21st seminar Programs and Algorithms of Numerical Mathematics ...
Statistical Method Selection Matters: Vanilla Methods in Regression May Yield Misleading Results
Kalina, Jan
2023 - English
The primary aim of this work is to illustrate the importance of the choice of the appropriate methods for the statistical analysis of economic data. Typically, there exist several alternative versions of common statistical methods for every statistical modeling task\nand the most habitually used (“vanilla”) versions may yield rather misleading results in nonstandard situations. Linear regression is considered here as the most fundamental econometric model. First, the analysis of a world tourism dataset is presented, where the number of international arrivals is modeled for 140 countries of the world as a response of 14 pillars (indicators) of the Travel and Tourism Competitiveness Index. Heteroscedasticity is clearly recognized in the dataset. However, the Aitken estimator, which would be the standard remedy in such a situation, is revealed here to be very inappropriate. Regression quantiles represent a much more suitable solution here. The second illustration with artificial data reveals standard regression quantiles to be unsuitable for data contaminated by outlying values. Their recently proposed robust version turns out to be much more appropriate. Both\nillustrations reveal that choosing suitable methods represent an important (and often difficult) part of the analysis of economic data.
Keywords:
linear regression; assumptions; non-standard situations; robustness; diagnostics
Fulltext is available at external website.
Statistical Method Selection Matters: Vanilla Methods in Regression May Yield Misleading Results
The primary aim of this work is to illustrate the importance of the choice of the appropriate methods for the statistical analysis of economic data. Typically, there exist several alternative versions ...
Summary of the Liquid-Gas Ejector Hydraulic Behavior - Theory and Practice
Gebouský, Ondřej; Haidl, Jan
2023 - English
Liquid-gas ejectors (LGEs) are fascinating devices that use the kinetic energy of the liquid jet to entrain and eventually compress the gas. LGEs find applications in both industry and everyday life, e.g., as sprayers. However, a complex and reliable method for LGE design was not available in the open literature until recently. This contribution follows up on our recent works about the hydraulic behavior of LGE with undisturbed and destabilized liquid jets. This paper aims to summarize the device’s complicated hydraulics and characterize its optimal design for three industrially relevant applications - (a) LGE as the vacuum pump, (b) LGE as the gas purification equipment, and (c) LGE as the gas distributor for bioreactors.
Keywords:
liquid-gas ejector; jet pump; design method
Available in digital repository of the ASCR
Summary of the Liquid-Gas Ejector Hydraulic Behavior - Theory and Practice
Liquid-gas ejectors (LGEs) are fascinating devices that use the kinetic energy of the liquid jet to entrain and eventually compress the gas. LGEs find applications in both industry and everyday life, ...
Instruments for precipitation measurement from history to the present
Lipina, P.; Procházka, J.; Tesař, Miroslav
2023 - Czech
The precipitation amount is one of the most important meteorological elements. It is of fundamental importance for the creation of climatological characteristics, it is the basis of the water balance and the primarily monitored element in the forecasting and warning service. Precipitation measurement has been burdened with many uncertainties for a long time and is therefore consistently given due attention.\nThe first measurement of precipitation in Europe dates back to the 17th century. Regular but not complete measurements of precipitation at Prague's Klementine observatory began in 1752 (continuous series since 1804), in Brno in 1803. In 1817, M.A. David wrote the first guide for observing the weather in Bohemia, published in German, intended for volunteer observers. The activities of institutions and various associations, such as the Prague Klementinum, the Natural Research Society in Brno, the Central Institute for Meteorology and Earth Magnetism and others, had a fundamental influence on the establishment of meteorological stations and precipitation measurements. The Hydrographic Commission for the Kingdom of the Czech Republic and its hydrometric section were founded in 1875 under the leadership of F. J. Studnička E. Purkyně was responsible for the significant expansion of precipitation measurement at that time as part of the construction of a network of forest precipitation measuring stations. \nFor more than 200 years, rain gauges and precipitation measurements have been developed. The Metra 886 manual rain gauge, which has been used for a long time in the Czech lands, was developed according to the Austrian model of prof. Kostlivý. Since 1995, the automation of rainfall measurement was started, first with tipping bucket raingauges, which are gradually being replaced by weighing raingauges. Alternative methods of measuring precipitation are being tested in\nremote and forested areas. This post tries to bring the history, standards and development of precipitation measurement in our country at least as a guide. Úhrn srážek patří mezi nejdůležitější meteorologické prvky. Má zásadní význam pro tvorbu klimatologických charakteristik, je základem vodní bilance a primárně sledovaným prvkem v předpovědní a výstražné službě. Měření srážek je dlouhodobě zatíženo mnoha nejistotami a je mu proto věnována soustavně náležitá pozornost. \nPrvní měření srážek v Evropě se datuje k 17. století. Pravidelná, ale neúplná, měření srážek na pražské klementinské hvězdárně byla zahájena v roce 1752 (nepřetržitá řada od roku 1804), v Brně to bylo v roce 1803. V roce 1817 M. A. David publikoval první německy psaný návod pro pozorování počasí v Čechách určený dobrovolným pozorovatelům. Zásadní vliv pro vznik meteorologických stanic a měření srážek měly aktivity institucí a různých spolků, například pražské Klementinum, Přírodozpytný spolek v Brně, Ústřední ústav pro meteorologii a zemský magnetismus a jiné. Hydrografická komise pro království české a její hydrometrická sekce byla pod vedením F. J. Studničky založena roku 1875, o významné rozšíření měření srážek se v té době zasloužil v rámci budování sítě lesnických srážkoměrných stanic E. Purkyně.\nJiž více než 200 let dochází k vývoji srážkoměrů a metodik měření srážek. V českých zemích dlouhodobě využívaný manuální srážkoměr Metra 886 byl vyvinut podle rakouského vzoru prof. Kostlivého. Od roku 1995 byla zahájena automatizace měření srážek nejprve klopnými srážkoměry, které jsou postupně nahrazovány srážkoměry váhovými. V odlehlých a lesnatých oblastech jsou testovány alternativní způsoby měření srážek. Tento příspěvek se snaží historii, standardy a vývoj v měření srážek u nás alespoň orientačně přiblížit.
Keywords:
rain gauge; measurement date; measurement history; meteorological station; guide for observers
Fulltext is available at external website.
Instruments for precipitation measurement from history to the present
The precipitation amount is one of the most important meteorological elements. It is of fundamental importance for the creation of climatological characteristics, it is the basis of the water balance ...
Bohl-Marek decomposition applied to a class of biochemical networks with conservation properties
Papáček, Štěpán; Matonoha, Ctirad; Duintjer Tebbens, Jurjen
2023 - English
This study presents an application of one special technique, further called as Bohl-Marek decomposition, related to the mathematical modeling of biochemical networks with mass conservation properties. We continue in direction of papers devoted to inverse problems of parameter estimation for mathematical models describing the drug-induced enzyme production networks [3]. However, being aware of the complexity of general physiologically based pharmacokinetic (PBPK) models, here we focus on the case of enzyme-catalyzed reactions with a substrate transport chain [5]. Although our ultimate goal is to develop a reliable method for fitting the model parameters to given experimental data, here we study certain numerical issues within the framework of optimal experimental design [6]. Before starting an experiment on a real biochemical network, we formulate an optimization problem aiming to maximize the information content of the corresponding experiment. For the above-sketched optimization problem, the computational costs related to the two formulations of the same biochemical network, being (i) the classical formulation x˙(t) = Ax(t) + b(t) and (ii) the 'quasi-linear' Bohl-Marek formulation x˙M(t) = M(x(t)) xM(t), can be determined and compared.
Keywords:
Mathematical modeling; Biochemical network; Pharmacokinetic (PBPK) models
Fulltext is available at external website.
Bohl-Marek decomposition applied to a class of biochemical networks with conservation properties
This study presents an application of one special technique, further called as Bohl-Marek decomposition, related to the mathematical modeling of biochemical networks with mass conservation properties. ...
Validation of numerical simulations of a simple immersed boundary solver for fluid flow in branching channels
Keslerová, R.; Lancmanová, Anna; Bodnár, Tomáš
2023 - English
This work deals with the flow of incompressible viscous fluids in a two-dimensional branching channel. Using the immersed boundary method, a new finite difference solver was developed to interpret the channel geometry. The numerical results obtained by this new solver are compared with the numerical simulations of the older finite volume method code and with the results obtained with OpenFOAM. The aim of this work is to verify whether the immersed boundary method is suitable for fluid flow in channels with more complex geometries with difficult grid generation.
Keywords:
immersed boundary method; finite volume method; OpenFOAM
Available in digital repository of the ASCR
Validation of numerical simulations of a simple immersed boundary solver for fluid flow in branching channels
This work deals with the flow of incompressible viscous fluids in a two-dimensional branching channel. Using the immersed boundary method, a new finite difference solver was developed to interpret the ...
Rooting algebraic vertices of convergent sequences
Hartman, David; Hons, T.; Nešetřil, J.
2023 - English
Structural convergence is a framework for convergence of graphs by Nešetřil and Ossona de Mendez that unifies the dense (left) graph convergence and Benjamini-Schramm convergence. They posed a problem asking whether for a given sequence of graphs (Gn) converging to a limit L and a vertex r of L it is possible to find a sequence of vertices (rn) such that L rooted at r is the limit of the graphs Gn rooted at rn. A counterexample was found by Christofides and Král’, but they showed that the statement holds for almost all vertices r of L. We offer another perspective to the original problem by considering the size of definable sets to which the root r belongs. We prove that if r is an algebraic vertex (i.e. belongs to a finite definable set), the sequence of roots (rn) always exists.
Keywords:
rooting; algebraic vertices; convergent sequences
Available in digital repository of the ASCR
Rooting algebraic vertices of convergent sequences
Structural convergence is a framework for convergence of graphs by Nešetřil and Ossona de Mendez that unifies the dense (left) graph convergence and Benjamini-Schramm convergence. They posed a problem ...
Drivers of Private Equity Activity across Europe: An East-West Comparison
Kočenda, Evžen; Shivendra, R.
2023 - English
We investigate the key macroeconomic and institutional determinants of fundraising and investment activities and compare them across Europe, covering 13 Central and Eastern European (CEE) and 16 Western European (WE) countries. Five macroeconomic variables and nineteen institutional variables are selected. These variables are studied using panel data analysis with fixed effects and random effects models over an eleven-year observation period (2010–2020). Bayesian Model Averaging (BMA) is applied to select the key variables. Our results suggest that macroeconomic variables have no significant impact on fundraising and investment activity in either region. Investment activity is a significant driver of fundraising across Europe. Similarly, fundraising and divestment activity are significant drivers of investments across Europe. Institutional variables, however, affect fundraising and investment activity differently. While investment freedom has a significant effect on funds raised in the WE and CEE countries, government integrity and trade freedom are both significant determinants of investments in both European regions. In addition, the results demonstrate that, in contrast to the WE region, fundraising in the CEE region is not country specific. We investigate the key macroeconomic and institutional determinants of fundraising and investment activities and compare them across Europe, covering 13 Central and Eastern European (CEE) and 16 Western European (WE) countries. Five macroeconomic variables and nineteen institutional variables are selected. These variables are studied using panel data analysis with fixed effects and random effects models over an eleven-year observation period (2010–2020). Bayesian Model Averaging (BMA) is applied to select the key variables. Our results suggest that macroeconomic variables have no significant impact on fundraising and investment activity in either region. Investment activity is a significant driver of fundraising across Europe. Similarly, fundraising and divestment activity are significant drivers of investments across Europe. Institutional variables, however, affect fundraising and investment activity differently. While investment freedom has a significant effect on funds raised in the WE and CEE countries, government integrity and trade freedom are both significant determinants of investments in both European regions. In addition, the results demonstrate that, in contrast to the WE region, fundraising in the CEE region is not country specific.
Keywords:
Private equity; Fundraising; Investment
Fulltext is available at external website.
Drivers of Private Equity Activity across Europe: An East-West Comparison
We investigate the key macroeconomic and institutional determinants of fundraising and investment activities and compare them across Europe, covering 13 Central and Eastern European (CEE) and 16 ...
On the problem of singular limit
Caggio, Matteo; Ducomet, B.; Nečasová, Šárka; Tang, T.
2023 - English
We consider the problem of singular limit of the compressible Euler system confined to a straight layer Ωδ = (0, δ)×R², δ > 0. In the regime of low Mach number limit and reduction of dimension the convergence to the strong solution of the 2D incompressible Euler system is shown.
Keywords:
compressible Euler equations; dissipative measure-valued solutions; low Mach number; thin domain
Available in digital repository of the ASCR
On the problem of singular limit
We consider the problem of singular limit of the compressible Euler system confined to a straight layer Ωδ = (0, δ)×R², δ > 0. In the regime of low Mach number limit and reduction of dimension the ...
Deep learning methods for the acoustic emission methods to evaluate an onset of plastic straining
Parma, Slavomír; Kovanda, Martin; Chlada, Milan; Štefan, Jan; Kober, Jan; Feigenbaum, H. P.; Plešek, Jiří
2023 - English
Development of phenomenological plasticity models, hardening rules, and plasticity theories relies on experimental data of plastic straining. The experimental data are usually measured as the stress–strain response of the material being loaded and do not provide any clues or information about the local response of\nmaterial. In this paper, we analyze the plastic deformation of the material using the acoustic emission method and current state-of-the-art neural network models such as the InceptionTime architecture.
Keywords:
metal plasticity; strain hardening; acoustic emission; neural networks
Fulltext is available at external website.
Deep learning methods for the acoustic emission methods to evaluate an onset of plastic straining
Development of phenomenological plasticity models, hardening rules, and plasticity theories relies on experimental data of plastic straining. The experimental data are usually measured as the ...
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