No (14209)
Yes (2033)
Number of found documents:
16242
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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 ...
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 ...
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 ...
Stereolithography for manufacturing of advanced porous solids
Drechslerová, V.; Neuhäuserová, M.; Falta, J.; Šleichrt, J.; Kytýř, Daniel
2023 - English
The aim of this paper is focused on benefits of stereolithography (SLA) technology for the fabrication of the lightweight lattice structures with potential for load-bearing function and high absorption of impact energy. SLA is an additive manufacturing technology employing the principle of liquid resins curing moderated by radiation of a wavelength from ultra-violet band where resulting material parameters are tunable by setting of the curing process. The batches of samples manufactured using three different resins were subjected to quasi-static uni-axial tensile and compression tests. Acquired data were processed to derive deformation behaviour expressed as stress-strain diagrams and fundamental material properties. Based on the knowledge obtained from the mechanical tests, the setup of the fabrication parameters, the most suitable resin for manufacturing of the lattice structures and the overall suitability of SLA technology for the fabrication of advanced porous materials, were determined.
Keywords:
stereolithography; advanced porous materials; quasi-static testing; resin; mechanical characteristics
Available at various institutes of the ASCR
Stereolithography for manufacturing of advanced porous solids
The aim of this paper is focused on benefits of stereolithography (SLA) technology for the fabrication of the lightweight lattice structures with potential for load-bearing function and high ...
Vyšetření základních mechanických a lomově-mechanických vlastností vzorků odebraných z VTL plynovodu – lokalita L177/2 po 21 měsíční expozici ve vlhké a suché vodíkové atmosféře při tlaku 3 MPa
Gajdoš, Lubomír; Šperl, Martin; Šorm, Filip; Bejdl, Jan
2023 - Czech
Vyšetření vlivu vlhkého a suchého vodíku stlačeného na tlak 3 MPa na mechanické a lomové vlastnosti plynovodní oceli ČSN 13126, tahové vzorky, Charpy vzorky i CT vzorky byly během expozice ve vlhkém vodíku trvale zatíženy, po 21 měsících expozice byl zjištěn pokles tažnosti tahových vzorků, pokles lomových parametrů Jin a J0,2 a mírné zvýšení parametru Jm. Investigation of the effect of moist and dry hydrogen pressurized to 3 MPa on mechanical and fracture properties of gas pipeline steel ČSN 13126, tensile specimens, Charpy specimens and CT specimens were kept loaded during the exposition in moist hydrogen, after a 21th months exposition it was found that ductility of tensile specimens and fracture parameters Jin and J0,2 of CT specimens decreased whilst the parameter Jm was slightly increased.
Keywords:
stress-strain diagram; Ramberg-Osgood dependence; impact strength; fracture toughness
Available at various institutes of the ASCR
Vyšetření základních mechanických a lomově-mechanických vlastností vzorků odebraných z VTL plynovodu – lokalita L177/2 po 21 měsíční expozici ve vlhké a suché vodíkové atmosféře při tlaku 3 MPa
Vyšetření vlivu vlhkého a suchého vodíku stlačeného na tlak 3 MPa na mechanické a lomové vlastnosti plynovodní oceli ČSN 13126, tahové vzorky, Charpy vzorky i CT vzorky byly během expozice ve vlhkém ...
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 ...
Instrumentální neutronová aktivační analýza omamných a psychotropních látek, zejména heroinu, kokainu, metamfetaminu a možných adulterantů
Kameník, Jan; Kučera, Jan
2023 - Czech
Instrumentální neutronová aktivační analýza je založena na robustním teoretickém základu a umožňuje analýzu vzorků v pevném stavu bez nutnosti jejich převedení do roztoku. Text metodiky zahrnuje představení základů INAA a příklady postupů používaných pro kontrolu přesnosti výsledků. Uveden je popis postupu analýzy heroinu, kokainu a metamfetaminu. Aplikace pro využití INAA zahrnují odhad čistoty a použitých ředících látek a profilování vzorků drog. Metodika je založena na analýze laboratorních a reálných vzorků. Instrumental neutron activation analysis (INAA) is a robust analytical method theoretically well descibed and understood. INAA works with solid samples, dissolution is not required. The methodology introduces INAA background and lists procedures used for quality control. Protocols for INAA of heroin, cocaine and methamphetamine are described in details. Applications of INAA for psychoactive substances includes estimation of purity and adulterants used and drogs profiling. The metodology is based on measurement of laboratory and real samples.
Keywords:
NAA; psychotropic substances; methodology
Available at various institutes of the ASCR
Instrumentální neutronová aktivační analýza omamných a psychotropních látek, zejména heroinu, kokainu, metamfetaminu a možných adulterantů
Instrumentální neutronová aktivační analýza je založena na robustním teoretickém základu a umožňuje analýzu vzorků v pevném stavu bez nutnosti jejich převedení do roztoku. Text metodiky zahrnuje ...
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 ...
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 ...
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 ...
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