Number of found documents: 2104
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Beyond the Erdős–Sós conjecture
Davoodi, Akbar; Piguet, Diana; Řada, Hanka; Sanhueza-Matamala, N.
2023 - English
We prove an asymptotic version of a tree-containment conjecture of Klimošová, Piguet and Rozhoň [European J. Combin. 88 (2020), 103106] for graphs with quadratically many edges. The result implies that the asymptotic version of the Erdős-Sós conjecture in the setting of dense graphs is correct. Keywords: conjecture; Erdős-Sós conjecture Available in digital repository of the ASCR
Beyond the Erdős–Sós conjecture

We prove an asymptotic version of a tree-containment conjecture of Klimošová, Piguet and Rozhoň [European J. Combin. 88 (2020), 103106] for graphs with quadratically many edges. The result implies ...

Davoodi, Akbar; Piguet, Diana; Řada, Hanka; Sanhueza-Matamala, N.
Ústav informatiky, 2023

Dynamics of surface water quality changes in model headwater areas of the Czech Republic
Fraindová, K.; Matoušková, M.; Kliment, Z.; Vlček, Lukáš; Vlach, V.; Šajnarová, L.
2023 - English
River headwaters have a high environmental value. Unfortunately, the biogeochemical processes in headwaters in context of different rainfall-runoff conditions and specific land cover have not been fully examined. This study focuses on changes in correlations of 16 biogeochemical parameters related to different types of rainfall-runoff events and land cover condition for eight headwater catchments in Central Europe. Multiple methods as linear regression, Spearman rank correlation, Principal Components Analysis and C/Q hysteresis loops revealed main relationships. Presence of peatlands and waterlogged spruce forests had decisive influence on the biogeochemistry (mainly for CODMn, humins, Fe, P-PO43− TP, and N-NO3−). The strongest positive correlation of organic matter (CODMn) and Fe is represented in a catchment with the largest area of damaged forest (70%), but with a smaller proportion of wetlands (8%). High flow rates influence the release of greater amounts of organic matter and N-NO3−. Keywords: headwater areas; organic matter; waterlogged areas; peatbogs; raifall-runoff events; water quality; electric conductivity Fulltext is available at external website.
Dynamics of surface water quality changes in model headwater areas of the Czech Republic

River headwaters have a high environmental value. Unfortunately, the biogeochemical processes in headwaters in context of different rainfall-runoff conditions and specific land cover have not been ...

Fraindová, K.; Matoušková, M.; Kliment, Z.; Vlček, Lukáš; Vlach, V.; Šajnarová, L.
Ústav pro hydrodynamiku, 2023

Spherical basis function approximation with particular trend functions
Segeth, Karel
2023 - English
The paper is concerned with the measurement of scalar physical quantities at nodes on the $(d-1)$-dimensional unit sphere surface in the hbox{$d$-dimensional} Euclidean space and the spherical RBF interpolation of the data obtained. In particular, we consider $d=3$. We employ an inverse multiquadric as the radial basis function and the corresponding trend is a polynomial of degree 2 defined in Cartesian coordinates. We prove the existence of the interpolation formula of the type considered. The formula can be useful in the interpretation of many physical measurements. We show an example concerned with the measurement of anisotropy of magnetic susceptibility having extensive applications in geosciences and present numerical difficulties connected with the high condition number of the matrix of the system defining the interpolation. Keywords: spherical interpolation; spherical radial basis function; inverse multiquadric Available in digital repository of the ASCR
Spherical basis function approximation with particular trend functions

The paper is concerned with the measurement of scalar physical quantities at nodes on the $(d-1)$-dimensional unit sphere surface in the hbox{$d$-dimensional} Euclidean space and the spherical RBF ...

Segeth, Karel
Matematický ústav, 2023

Semantic segmentation using support vector machine classifier
Pecha, Marek; Langford, Z.; Horák, David; Tran Mills, R.
2023 - English
This paper deals with wildfire identification in the Alaska regions as a semantic segmentation task using support vector machine classifiers. Instead of colour information represented by means of BGR channels, we proceed with a normalized reflectance over 152 days so that such time series is assigned to each pixel. We compare models associated with $\mathcal{l}1$-loss and $\mathcal{l}2$-loss functions and stopping criteria based on a projected gradient and duality gap in the presented benchmarks. Keywords: wildfire identification; semantic segmentation; support vector machines; distributed training Fulltext is available at external website.
Semantic segmentation using support vector machine classifier

This paper deals with wildfire identification in the Alaska regions as a semantic segmentation task using support vector machine classifiers. Instead of colour information represented by means of BGR ...

Pecha, Marek; Langford, Z.; Horák, David; Tran Mills, R.
Ústav geoniky, 2023

Estimation of EDZ zones in great depths by elastic-plastic models
Sysala, Stanislav
2023 - English
This contribution is devoted to modeling damage zones caused by the excavation of tunnels and boreholes (EDZ zones) in connection with the issue of deep storage of spent nuclear fuel in crystalline rocks. In particular, elastic-plastic models with Mohr-Coulomb or Hoek-Brown yield criteria are considered. Selected details of the numerical solution to the corresponding problems are mentioned. Possibilities of elastic and elastic-plastic approaches are illustrated by a numerical example. Keywords: tunnel stability; EDZ zones; elasto-plasticity; finite element method Fulltext is available at external website.
Estimation of EDZ zones in great depths by elastic-plastic models

This contribution is devoted to modeling damage zones caused by the excavation of tunnels and boreholes (EDZ zones) in connection with the issue of deep storage of spent nuclear fuel in crystalline ...

Sysala, Stanislav
Ústav geoniky, 2023

COMPUTER SIMULATION STUDY OF THE STABILITY OF UNDERACTUATED BIPEDAL ROBOT MODELS (motivated by Griffin and Grizzle, 2017)
Polach, P.; Anderle, Milan; Zezula, Pavel; Papáček, Štěpán
2023 - English
A key feature for bipedal walkers (robots and humans as well) is their stability or disturbance rejection defined as the ability to deal with unexpected disturbances. The paper by Griffin and Grizzle (2017) have significantly contributed to the shift from flat ground to slopes and steps when evaluating the walking efficiency of their robots. Similarly, in this contribution, based on the appropriate model of robot dynamics and control law, we examine the stability of walking-without-falling for different ground perturbations for a threelink compass gait walker. I.e., we perform the sensitivity analysis of the walking stability of underactuated bipedal walker with respect to certain disturbation using the alaska/MultibodyDynamics simulation tool. Keywords: Mechatronics; Bipedal robot; Multibody dynamics; Acrobot; Control applications Fulltext is available at external website.
COMPUTER SIMULATION STUDY OF THE STABILITY OF UNDERACTUATED BIPEDAL ROBOT MODELS (motivated by Griffin and Grizzle, 2017)

A key feature for bipedal walkers (robots and humans as well) is their stability or disturbance rejection defined as the ability to deal with unexpected disturbances. The paper by Griffin and Grizzle ...

Polach, P.; Anderle, Milan; Zezula, Pavel; Papáček, Štěpán
Ústav teorie informace a automatizace, 2023

Book of Abstracts. 18th Youth Symposium on Experimental Solid Mechanics
Kytýř, Daniel; Doktor, Tomáš; Zlámal, Petr
2023 - English
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all areas of experimental research and its application in solid and fluid mechanics. The topic will particularly concern to: Conventional and Advanced Experimental Methods in Solid and Fluid Mechanics; Non-Destructive Testing and Inspection, Measurements in Material Science, Computer Assisted Testing and Simulation, Engineering Design Simulation, Hybrid Methods, Experimental Techniques – Numerical Simulation, Optical Methods and Image Processing, Measurements in Biomechanics, Sensor Techniques for Micro- and Nano-Applications, Measurement Methods for Forensic Engineering. Keywords: experimental mechanics; fluid mechanics; mechanics of solids Fulltext is available at external website.
Book of Abstracts. 18th Youth Symposium on Experimental Solid Mechanics

The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all ...

Kytýř, Daniel; Doktor, Tomáš; Zlámal, Petr
Ústav teoretické a aplikované mechaniky, 2023

Souvislost mezi principem nejmenší akce a termodynamickou podmínkou stability
Maršík, František; Trávníček, Zdeněk; Antošová, Zuzana
2023 - English
The extended principle is formulated for a material point (M.P.) X, which has nonzero mass, temperature, and trajectory x(X,t). The Lagrangian of this variation principle is equal to the kinetic energy from which, the internal energy of the material point (which depends on the entropy) and the additional energy caused by the frictional force are subtracted. The relation between the inertial force and the entropy gradient is found and the gravitational force is completely replaced by the entropy gradient. Thanks to the mentioned properties of the total enthalpy, the Thermodynamic criterion of stability of the state of M.P., is formulated. Keywords: principle of the least action; thermodynamic stability condition; annular swirl flow Fulltext is available at external website.
Souvislost mezi principem nejmenší akce a termodynamickou podmínkou stability

The extended principle is formulated for a material point (M.P.) X, which has nonzero mass, temperature, and trajectory x(X,t). The Lagrangian of this variation principle is equal to the kinetic ...

Maršík, František; Trávníček, Zdeněk; Antošová, Zuzana
Ústav termomechaniky, 2023

Texture Spectral Similarity Criteria Comparison
Havlíček, Michal; Haindl, Michal
2023 - English
Criteria capable of texture spectral similarity evaluation are presented and compared. From the fifteen evaluated criteria, only four criteria guarantee zero or minimal spectral ranking errors. Such criteria can support texture modeling algorithms by comparing the modeled texture with corresponding synthetic simulations. Another possible application is the development of texture retrieval, classification, or texture acquisition system. These criteria thoroughly test monotonicity and mutual correlation on specifically designed extensive monotonously degrading experiments. Keywords: Texture Comparison; Texture Modeling; Texture Retrieval; Texture Classification; Texture Acquisition Fulltext is available at external website.
Texture Spectral Similarity Criteria Comparison

Criteria capable of texture spectral similarity evaluation are presented and compared. From the fifteen evaluated criteria, only four criteria guarantee zero or minimal spectral ranking errors. Such ...

Havlíček, Michal; Haindl, Michal
Ústav teorie informace a automatizace, 2023

Book of abstracts of the 1st outdoor seminar of the Department of Optical Materials: Advances in the new materials engineering and study
Buryi, Maksym; Král, Robert
2023 - English
The seminar is dedicated to the main activities of the department of Optical Materials, FZU - Institute of Physics of the Czech Academy of Sciences in the course of national and international collaborations. In particular, the advanced methods of the (nano)materials synthesis, fabrication, and characterization are presented and discussed in detail. The aim of the seminar is to establish more of the effective paths of communication and data exchange by creating and maintaining links among the teams of national and international experts in various fields of physical and chemical knowledge, both experimental and theoretical. Keywords: nanomaterials; synthesis; data exchange Fulltext is available at external website.
Book of abstracts of the 1st outdoor seminar of the Department of Optical Materials: Advances in the new materials engineering and study

The seminar is dedicated to the main activities of the department of Optical Materials, FZU - Institute of Physics of the Czech Academy of Sciences in the course of national and international ...

Buryi, Maksym; Král, Robert
Fyzikální ústav, 2023

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