Yes (2104)
Number of found documents:
2104
Published from
to
Calibrated finite volume method-based simulation framework for laser shock peening
Isoz, Martin; Gruber, Pavel; Schmidt, Jaroslav; Kubíčková, Lucie; Štefan, Jan; Kaufman, Jan; Brajer, Jan; Gabriel, Dušan
2023 - English
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening processes, such as the shot peening, are widely used in both automotive and aerospace industries. The laser shock\npeening (LSP), i.e. hardening of the material surface by a laser-induced shock wave, is a modern alternative to the standard peening. Concurrently, the industrial applications of LSP are promoted by recently emerged affordable high power-density lasers. However, the nascent LSP applications are still mostly a trial-and-error\nprocesses based on an extensive experimental testing. Consequently, we focused on a highly application-driven development of a framework for LSP modeling, and the internal workings and results of which are the focus of the present contribution.
Keywords:
laser shock peening; modeling; finite volume method; OpenFOAM
Fulltext is available at external website.
Calibrated finite volume method-based simulation framework for laser shock peening
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening ...
Average Reward Optimality in Semi-Markov Decision Processes with Costly Interventions
Sladký, Karel
2023 - English
In this note we consider semi-Markov reward decision processes evolving on finite state spaces. We focus attention on average reward models, i.e. we establish explicit formulas for the growth rate of the total expected reward. In contrast to the standard models we assume that the decision maker can also change the running process by some (costly) intervention. Recall that the result for optimality criteria for the classical Markov decision chains in discrete and continuous time setting turn out to be a very specific case of the considered model. The aim is to formulate optimality conditions for semi-Markov models with interventions and present algorithmical procedures for finding optimal solutions.
Keywords:
controlled semi-Markov reward processes; long-run optimality; intervention of the decision maker
Fulltext is available at external website.
Average Reward Optimality in Semi-Markov Decision Processes with Costly Interventions
In this note we consider semi-Markov reward decision processes evolving on finite state spaces. We focus attention on average reward models, i.e. we establish explicit formulas for the growth rate of ...
Permutation Flip Processes
Hladký, Jan; Řada, Hanka
2023 - English
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.
Keywords:
permutation; permuton; sorting dynamics; flip process
Available in digital repository of the ASCR
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 ...
Zpřesnění distribuce sněhové pokrývky na vybraných povodích s využitím dat automatických sněhoměrných stanic
Procházka, J.; Šustková, V.; Tesař, Miroslav
2023 - Czech
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.
Keywords:
Upper Vltava catchment; CHMI; climate map; snow data interpolation; amount of precipitation
Fulltext is available at external website.
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 ...
Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor
Idžakovičová, Kristýna; Haidl, J.; Gebouský, O.; Isoz, Martin
2023 - English
The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the central vortex creation. However, particular industries, such as biotechnology, have an increased need for a sterile environment that often results in the usage of atypical stirred vessel configurations. An example of a commonly equipped atypical stirred vessel is an unbaffled stirred tank with an eccentric magnetically driven impeller. However, there is only a little knowledge about the mixing characteristics of such designs. In this work, we list experimental results for both the standard and atypical stirred vessel configurations. Furthermore, we present a CFD model of the atypical configuration. The model is used to calculate its mixing characteristics that are subsequently compared against our experimental results. It is shown that for the liquid height (H) to the vessel diameter (T) ratio H/T ≲ 1.2, the characteristics of both the standard and atypical designs coincide. For higher liquid heights (i) the characteristics of the atypical design decrease dramatically, and (ii) the characteristics estimates based on approaches developed for the standard configuration become unreliable.
Keywords:
stirred vessel; eccentric impeller; unbaffled tank; CFD; OpenFOAM; experiment
Fulltext is available at external website.
Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor
The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the ...
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 - English
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.
Keywords:
loanwords; Bayesian methods; probabilistic graphical model
Fulltext is available at external website.
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 ...
Nová regionální reanalýza pro střední Evropu PERUN/Reanalysis
Pokorná, Lucie; Belda, M.; Beranová, Romana
2022 - Czech
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.
Keywords:
assimilation; model
Fulltext is available at external website.
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 ...
LA62. Elektronický sborník příspěvků multioborové konference LASER62
Růžička, Bohdan
2022 - Czech
Keywords:
laser; laser technology; optics; optical fiber
Fulltext is available at external website.
LA62. Elektronický sborník příspěvků multioborové konference LASER62
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 - English
Fulltext is available at external website.
16th Multinational Congress on Microscopy, 16MCM, 04-09 September 2022, Brno, Czech Republic. Book of abstracts
Innovative device for the simulation of environmental conditions and testing of building materials
Cacciotti, Riccardo; Wolf, Benjamin; Macháček, Michael; Frankl, Jiří
2022 - English
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.
Keywords:
building envelope; moisture; building material; wind tunnel; performance
Available in digital repository of the ASCR
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 ...
NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web
Send your suggestions and comments to nusl@techlib.cz
Provider
Other bases