Permutation Flip Processes
Hladký, Jan; Řada, Hanka
2023 - anglický We introduce a broad class of stochastic processes on permutations which we call flip processes. A single step in these processes is given by a local change on a randomly chosen fixed-sized tuple of the domain. We use the theory of permutons to describe the typical evolution of any such flip process started from any initial permutation. More specifically, we construct trajectories in the space of permutons with the property that if a finite permutation is close to a permuton then for any time it stays with high probability is close to this predicted trajectory. This view allows to study various questions inspired by dynamical systems. Klíčová slova: permutation; permuton; sorting dynamics; flip process Plné texty jsou dostupné v digitálním repozitáři Akademie Věd. Permutation Flip Processes

We introduce a broad class of stochastic processes on permutations which we call flip processes. A single step in these processes is given by a local change on a randomly chosen fixed-sized tuple of ...

Hladký, Jan; Řada, Hanka
Ústav informatiky, 2023

Zpřesnění distribuce sněhové pokrývky na vybraných povodích s využitím dat automatických sněhoměrných stanic
Procházka, J.; Šustková, V.; Tesař, Miroslav
2023 - český Studie hodnotí význam automatických sněhoměrných stanic (ASNS) provozovaných různými subjekty v oblasti vybraných subpovodí Šumavy spadajících do povodí přehradní nádrže Orlík. Je zde zdůrazněna potřeba monitoringu sněhové pokrývky jako významné složky hydrologické bilance povodí zejména v horských oblastech. Subpovodí Vltavy a Otavy reprezentují území pramenných oblastí v srážkově návětrné příhraniční části pohoří, kdežto subpovodí Volyňky a Blanice pramennou oblast závětrné vnitrozemské části pohoří. Význam ASNS je prokázán především v nejvyšších a odlehlých polohách Šumavy, kde chybí základní meteorologické stanice používané do běžných klimatologických a hydrologických hodnocení. Díky moderním podkladům a metodám je možné významně zpřesnit distribuci sněhové pokrývky a jejích vlastností. Kontinuální záznam výšky sněhu prostřednictvím ASNS takto poskytuje pro území vyšších poloh Šumavy nové poznatky a operativní údaje pro standardní klimatologická hodnocení i pro další aplikace využívané v rámci činnosti ČHMÚ, Povodí Vltavy, s. p. a dalšími institucemi např. pro správní a vědeckovýzkumné potřeby. The study evaluates the importance of automatic snow monitoring stations (ASMS) operated by different subjects in the chosen sub-catchments in the Šumava Mts. in the framework of water reservoir Orlík basin. The attention is paid to the snow cover monitoring as an important water balance component of a basin especially in the mountainous regions. Sub-catchments of the Vltava and Otava rivers represent head water regions of the rainfall windward part of the boarder mountains while Volyňka and Blanice sub-catchments represent leeward inland part of mountains. The importance of ASMS was proved especially in the highest and remote localities of the Šumava Mts. where the basic meteorological stations used for common climatological and hydrological evaluations are missing. The description of the snow cover and its characteristics is possible to improve significantly owing to recent sources and methods. The continual record of the snow cover depth gives for the higher regions of the Šumava Mts. new findings and operational data both for standard climatological evaluations and for further applications used in the framework various institutions, e.g. Czech Hydrometeorological Institute, State Enterprises, etc. Klíčová slova: Upper Vltava catchment; CHMI; climate map; snow data interpolation; amount of precipitation Dokument je dostupný na externích webových stránkách. Zpřesnění distribuce sněhové pokrývky na vybraných povodích s využitím dat automatických sněhoměrných stanic

Studie hodnotí význam automatických sněhoměrných stanic (ASNS) provozovaných různými subjekty v oblasti vybraných subpovodí Šumavy spadajících do povodí přehradní nádrže Orlík. Je zde zdůrazněna ...

Procházka, J.; Šustková, V.; Tesař, Miroslav
Ústav pro hydrodynamiku, 2023

Modeling the spread of loanwords in South-East Asia using sailing navigation software and Bayesian networks
Kratochvíl, F.; Kratochvíl, Václav; Saad, G.; Vomlel, Jiří
2022 - anglický A loanword is a word permanently adopted from one language and incorporated into another language without translation. In this paper, we study loanwords in the South-East Asia Archipelago, home to a large number of languages. Our paper is inspired by the works of Hoffmann et al. (2021) Bayesian methods are applied to probabilistic modeling of family trees representing the history of language families and by Haynie et al. (2014) modeling the diffusion of a special class of loanwords, so-called Wanderw ̈orter in languages of Australia, North America, and South America. We assume that in the South-East Asia Archipelago Wanderwörter spread along specific maritime trade routes whose geographical characteristics can help unravel the history of Wanderwörter diffusion in the area. For millennia trade was conducted using sailing ships which were constrained by the monsoon system and in certain areas also by strong sea currents. Therefore rather than the geographical distances, the travel times of sailing ships should be considered as a major factor determining the intensity of contact among cultures. We use sailing navigation software to estimate travel times between different ports and show that the estimated travel times correspond well to the travel times of a Chinese map of the sea trade routes from the early seventeenth century. We model the spread of loanwords using a probabilistic graphical model - a Bayesian network. We design a novel heuristic Bayesian network structure learning algorithm that learns the structure as a union of spanning trees for graphs of all loanwords in the training dataset. We compare this algorithm with BIC optimal Bayesian networks by measuring how well these models predict the true presence/absence of a loanword. Interestingly, Bayesian networks learned by our heuristic spanning tree-based algorithm provide better results than the BIC optimal Bayesian networks. Klíčová slova: loanwords; Bayesian methods; probabilistic graphical model Dokument je dostupný na externích webových stránkách. Modeling the spread of loanwords in South-East Asia using sailing navigation software and Bayesian networks

A loanword is a word permanently adopted from one language and incorporated into another language without translation. In this paper, we study loanwords in the South-East Asia Archipelago, home to a ...

Kratochvíl, F.; Kratochvíl, Václav; Saad, G.; Vomlel, Jiří
Ústav teorie informace a automatizace, 2022

Nová regionální reanalýza pro střední Evropu PERUN/Reanalysis
Pokorná, Lucie; Belda, M.; Beranová, Romana
2022 - český Tento příspěvek se věnuje obecnému popisu atmosférických reanalýz, jejich koncepci a roli při výzkumu atmosféry a klimatu. Představuje regionální reanalýzu PERUN/Reanalysis, která vznikla s využitím numerického modelu ALADIN v ČHMÚ v letech 2021-2022. The contribution describes atmospheric reanalyses in general, their concept and role in atmospheric and climate research. The novel PERUN/Reanalysis regional reanalysis based on the ALADIN numerical model opreating at the Czech National Institute of Hydrometeorology is presented. Klíčová slova: assimilation; model Dokument je dostupný na externích webových stránkách. Nová regionální reanalýza pro střední Evropu PERUN/Reanalysis

Tento příspěvek se věnuje obecnému popisu atmosférických reanalýz, jejich koncepci a roli při výzkumu atmosféry a klimatu. Představuje regionální reanalýzu PERUN/Reanalysis, která vznikla s využitím ...

Pokorná, Lucie; Belda, M.; Beranová, Romana
Ústav fyziky atmosféry, 2022

Automation of metallographic sample cleaning process
Čermák, Jan; Ambrož, Ondřej; Jozefovič, Patrik; Mikmeková, Šárka
2022 - anglický Specimen cleaning and drying are critical processes following any metallographic preparation steps. The paper focuses on automation by reason of absence of the process repeatability during manual sample handling. An etchant or electrolyte results in inhomogeneous surface quality because the solution runs off the specimen surface during its removal from the beaker. High-quality specimen cleaning is absolutely crucial for the acquisition of the specimen suitable for characterization by a scanning electron microscope operated at very low landing energies of the primary electrons (SLEEM). The SLEEM technique is a powerful tool for the characterization of advanced steels, as described by many scientific papers. The SLEEM requires the specimen absolutely free of water and any organic residues on the surface. This work presents a novel unique apparatus enabling automatic specimen cleaning and drying after the etching or electropolishing processes. Automation reduces the influence of dependent variables that would be introduced into the process by the metallographer. These variables include cleaning time, kinematics, and motion dynamics, but the process can also be affected by variables that are not obvious. Performed experiments clearly demonstrate our in-house designed apparatus as a useful tool improving efficiency and consistency of the sample cleaning process. The high quality of the specimen surface is verified using a light optical microscope, an electron scanning microscope, and above mentioned SLEEM technique. Klíčová slova: metallography; sample cleaning; process automation; repeatability Dokument je dostupný na externích webových stránkách. Automation of metallographic sample cleaning process

Specimen cleaning and drying are critical processes following any metallographic preparation steps. The paper focuses on automation by reason of absence of the process repeatability during manual ...

Čermák, Jan; Ambrož, Ondřej; Jozefovič, Patrik; Mikmeková, Šárka
Ústav přístrojové techniky, 2022

LA62. Elektronický sborník příspěvků multioborové konference LASER62
Růžička, Bohdan
2022 - český Klíčová slova: laser; laser technology; optics; optical fiber Dokument je dostupný na externích webových stránkách. LA62. Elektronický sborník příspěvků multioborové konference LASER62

Růžička, Bohdan
Ústav přístrojové techniky, 2022

16th Multinational Congress on Microscopy, 16MCM, 04-09 September 2022, Brno, Czech Republic. Book of abstracts
Krzyžánek, Vladislav; Hrubanová, Kamila; Hozák, Pavel; Müllerová, Ilona; Šlouf, Miroslav
2022 - anglický Dokument je dostupný na externích webových stránkách. 16th Multinational Congress on Microscopy, 16MCM, 04-09 September 2022, Brno, Czech Republic. Book of abstracts

Krzyžánek, Vladislav; Hrubanová, Kamila; Hozák, Pavel; Müllerová, Ilona; Šlouf, Miroslav
Ústav přístrojové techniky, 2022

Innovative device for the simulation of environmental conditions and testing of building materials
Cacciotti, Riccardo; Wolf, Benjamin; Macháček, Michael; Frankl, Jiří
2022 - anglický Excessive humidity influences the performance of building envelopes and the safety of their occupants. Moisture related problems can indeed impose significant health risks for buildings’ users and even lead, under extreme scenarios, to structural failures. This paper investigates an innovative experimental setup for evaluating the influence of changing environmental conditions on the performance of building materials. It stems out from a broader ongoing research aimed at studying the trends of mould growth on wooden building components. The presented results include the design, construction and numerical validation of a small-scale climatic wind tunnel (2m x 1.8m ca.) to be used for the simulation of natural ventilation and daily humidity and temperature fluctuations. Key findings include the final design of a low cost, modular construction which allows gathering reliable data on the response of building materials exposed to changing boundary conditions, intended for improving current mould growth models. Future work is also suggested. Klíčová slova: building envelope; moisture; building material; wind tunnel; performance Plné texty jsou dostupné v digitálním repozitáři Akademie Věd. Innovative device for the simulation of environmental conditions and testing of building materials

Excessive humidity influences the performance of building envelopes and the safety of their occupants. Moisture related problems can indeed impose significant health risks for buildings’ users and ...

Cacciotti, Riccardo; Wolf, Benjamin; Macháček, Michael; Frankl, Jiří
Ústav teoretické a aplikované mechaniky, 2022

Application of first integrals in the construction of the Lyapunov function for the random response stability testing
Náprstek, Jiří; Fischer, Cyril
2022 - anglický The paper deals with a possibility of using the properties of first integrals for the construction of Lyapunov function for the analysis of a dynamic system stability in the stochastic domain. It points out certain characteristics of first integrals resulting in the necessity to introduce additional constraints to assure the principal properties of the Lyapunov function. A number of these constraints has their physical interpretation with reference to system stability. The advantage of this method constructing the Lyapunov function consists in the fact that the Lyapunov function itself contains information on the examined system and, consequently, it is not merely a positive definite function without any relation to the actual case concerned. The presented theory finds application in many dynamical systems. The procedure is illustrated by a nonlinear SDOF example. Klíčová slova: stochastic stability; Lyapunov function; first integrals; cyclic coordinates Plné texty jsou dostupné v digitálním repozitáři Akademie Věd. Application of first integrals in the construction of the Lyapunov function for the random response stability testing

The paper deals with a possibility of using the properties of first integrals for the construction of Lyapunov function for the analysis of a dynamic system stability in the stochastic domain. It ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2022

100 years of the Friedmann equation
Křížek, Michal
2022 - anglický In 1922, Alexander Friedmann applied Einstein’s equations to a three-dimensional sphere to describe the evolution of our universe. In this way he obtained a nonlinear ordinary differential equation (called after him) for the expansion function representing the radius of that sphere. At present, the standard cosmological ΛCDM model of the universe is based just on the Friedmann equation. It needs a significant amount of dark matter, about six times that of the usual baryonic matter, besides an even larger amount of dark energy to be consistent with the real universe. But to date, both dark matter and dark energy have remained without concrete evidence based on direct physical measurements. We present several arguments showing that such a claimed amount of dark matter and dark energy can only be the result of vast overestimation, incorrect extrapolations, and that it does not correspond to the real universe. The spatial part of our universe seems to be locally flat and thus it can be locally modeled by the Euclidean space. However, Friedmann did not consider the flat space with zero curvature. Therefore, in the second part of this paper we will derive a general form of the corresponding metric tensor satisfying Einstein’s equations with zero right-hand side. Klíčová slova: Einstein's equations; modeling error; incorrect extrapolations; dark matter Dokument je dostupný na externích webových stránkách. 100 years of the Friedmann equation

In 1922, Alexander Friedmann applied Einstein’s equations to a three-dimensional sphere to describe the evolution of our universe. In this way he obtained a nonlinear ordinary differential equation ...

Křížek, Michal
Matematický ústav, 2022