Number of found documents: 15155
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Moving dynamic test loads for road bridges - a case study
Bayer, Jan; Urushadze, Shota
2019 - English
Two types of dynamic testing load for bridges - driving sprung mass and driving impulse load - areexamined from the drive-by identification point of view. Numerical studies in ANSYS using contact elements and in MATLAB using a modal solution together with coupling force were performed. Equations for the estimation of the impulse load caused by a rolling cogwheel were suggested. The experiments confirmed that a driving impulse load is more efficient in exciting bridge vibrations. This, together with the fact that impulse loading is not sensitive to surface roughness, leads to the conclusion that, as a method for bridge health monitoring, impulse loading is more promising than using a driving sprung mass Keywords: drive-by identification; bridge testing; moving sprung mass; impulse loading; vibration measurements; laboratory experiments Available at various institutes of the ASCR
Moving dynamic test loads for road bridges - a case study

Two types of dynamic testing load for bridges - driving sprung mass and driving impulse load - areexamined from the drive-by identification point of view. Numerical studies in ANSYS using contact ...

Bayer, Jan; Urushadze, Shota
Ústav teoretické a aplikované mechaniky, 2019

Shaanxi 2018 - první velké objevy
Motyčka, Z.; Filippi, Michal
2019 - Czech
Keywords: Shaanxi 2018 expedition; speleology; caves Available at various institutes of the ASCR
Shaanxi 2018 - první velké objevy

Motyčka, Z.; Filippi, Michal
Geologický ústav, 2019

Deformation response of polydimethylsiloxane substrates subjected to uniaxial quasi-static loading
Martino, F.; Vinařský, V.; Šleichrt, Jan; Kytýř, Daniel
2019 - English
To investigate cellular response of cardiomyocytes to substrate mechanics, biocompatible material with stiffness in physiological range is needed. Polydimethylsiloxane (PDMS) based material Sylgard 184 is used for construction of microfluidic organ on chip devices for cell culture due to ease of device preparation, bonding, and possibility of surface functionalization. However it has stiffness orders of magnitude out of physiological range. Therefore we adapted recently published protocol [1] aiming to prepare substrates which offer stiffness in physiological range 5−100 kPa using various mixtures of Sylgard 527 and Sylagard 184. The inhouse developed loading device with the loading capacity of 3 kN with 1 μm position tracking accuracy and sub-micron position sensitivity was employed for this experimental campaign. The experiments were controlled by the proprietary LinuxCNC software running on the real-time kernel [2]. All batches of the samples were subjected to monotonic compression loading. During the displacement driven experiment with loading rate 10 μm · s−1 the samples with diameter 12.00 ± 0.05mm and height 14 − 16mm were compressed to minimally 50% deformation. Because of high differences in the samples stiffness various load cells with nominal capacity 50N, 10N, and 1N was used for the most reliable force logging. Material properties for all batches were derived from a set of tests under dry and simulated physiological conditions. The results are represented in the form of stress-strain curves calculated from the acquired force and displacement data and elastic moduli are estimated as secant up to 10% deformation. Keywords: compression loading; hyperelasticity; polydimethylsiloxane substrates Available at various institutes of the ASCR
Deformation response of polydimethylsiloxane substrates subjected to uniaxial quasi-static loading

To investigate cellular response of cardiomyocytes to substrate mechanics, biocompatible material with stiffness in physiological range is needed. Polydimethylsiloxane (PDMS) based material Sylgard ...

Martino, F.; Vinařský, V.; Šleichrt, Jan; Kytýř, Daniel
Ústav teoretické a aplikované mechaniky, 2019

Zatížení svorníků v silně namáhavém masivu
Waclawik, Petr; Sahendra, Ram; Šňupárek, Richard
2019 - Czech
Při zkušebním provozu modifikované metody komora-pilíř s ponechanými stabilními pilíři, nazvané chodba-pilíř byla na Dole ČSM použita svorníková výztuž stropu a boků chodeb (stěn ponechaných pilířů). Zatížení a deformace svorníků byly měřeny v rámci rozsáhlého geotechnického monitoringu [1,2]. Následně bylo použito matematického modelování v softwaru Itasca FLAC3D [3] pro lepší objasnění zatěžovacích charakteristik svorníkové výztuže. The trial test of new mining method “Roadway-Pillar” was finished at the underground coal mine – ČSM Mine. The wide ranging monitoring was focused on the load bearing capacity of coal pillars and strata deformation changes induced by the roadway-pillar mining method. The results of monitoring allowed bolts loading and loading characteristics to be described. Further, an attempt is made to understand the rock bolt loading characteristics at different stages of rib dilation using numerical modelling with the available properties of rock mass and reinforcement for the studied site. Elastic and Mohr Coulomb strain-softening constitutive models are considered in FLAC3D to evaluate the performance of the rock bolts. Keywords: Roadway-Pillar mining method; ČSM Mine; coal pillars Available in a digital repository NRGL
Zatížení svorníků v silně namáhavém masivu

Při zkušebním provozu modifikované metody komora-pilíř s ponechanými stabilními pilíři, nazvané chodba-pilíř byla na Dole ČSM použita svorníková výztuž stropu a boků chodeb (stěn ponechaných pilířů). ...

Waclawik, Petr; Sahendra, Ram; Šňupárek, Richard
Ústav geoniky, 2019

The scalar-valued score functions of continuous probability distribution
Fabián, Zdeněk
2019 - English
In this report we give theoretical basis of probability theory of continuous random variables based on scalar valued score functions. We maintain consistently the following point of view: It is not the observed value, which is to be used in probabilistic and statistical considerations, but its 'treated form', the value of the scalar-valued score function of distribution of the assumed model. Actually, the opinion that an observed value of random variable should be 'treated' with respect to underlying model is one of main ideas of the inference based on likelihood in classical statistics. However, a vector nature of Fisher score functions of classical statistics does not enable a consistent use of this point of view. Instead, various inference functions are suggested and used in solutions of various statistical problems. Inference function of this report is the scalar-valued score function of distribution. Keywords: Shortcomings of probability theory; Scalar-valued score functions; Characteristics of continous random variables; Parametric estimation; Transformed distributions; Skew-symmetric distributions Available at various institutes of the ASCR
The scalar-valued score functions of continuous probability distribution

In this report we give theoretical basis of probability theory of continuous random variables based on scalar valued score functions. We maintain consistently the following point of view: It is not ...

Fabián, Zdeněk
Ústav informatiky, 2019

Probability density determination by means of Gibbs entropy probability density
Náprstek, Jiří; Fischer, Cyril
2019 - English
A method of random response investigation of a nonlinear dynam-ical system is discussed. In particular, the solution of the probability density of a single/multi-degree of freedom (SDOF/MDOF) system response is investigated. Multiple stable equilibrium states with possible jumps of the snap-through type among them are considered. The system is Hamiltonian with weak damping excited by a set of non-stationary Gaussian white noises. The solution, which is based on the Gibbs principle of the maximum entropy of probability, can be employed in various branches of engineering. The search for the extreme of the Gibbs entropy functional is formulated as a constrained optimization problem. The secondary constraints follow from the Fokker-Planck equation (FPE) for the system considered or from the system of ordinary di_erential equations for the stochastic moments of the response derived from the relevant FPE Keywords: Fokker-Planck equation; Gibbs entropy functional; maximum entropy; probability density principle Available at various institutes of the ASCR
Probability density determination by means of Gibbs entropy probability density

A method of random response investigation of a nonlinear dynam-ical system is discussed. In particular, the solution of the probability density of a single/multi-degree of freedom (SDOF/MDOF) system ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2019

Laser-generated nanoparticles to change physical properties of solids, liquids and gases
Torrisi, Alfio; Cutroneo, Mariapompea; Ceccio, Giovanni; Cannavó, Antonino; Horák, Pavel; Torrisi, L.; Vacík, Jiří
2019 - English
Synthesis of nanoparticles was possible employing a Nd: YAG pulsed laser at fundamental harmonic. The production of nanoparticles in water depends mainly on the laser parameters (pulse duration, energy, wavelength), the irradiation conditions (focal spot, repetition rate, irradiation time) and the medium where the ablation occurs (solid target, water, solution concentration). The nanoparticles can be introduced in solids, liquids or gases to change many physical characteristics. The optical properties of polymers and solutions, the wetting ability of liquids, the electron density of laser-generated plasma, represent some examples that can be controlled by the concentration of metallic nanoparticles (Au, Ag, Ti, Cu). Some bio-medical applications will be presented and discussed. Keywords: bio-medical applications; laser; nanoparticles Available at various institutes of the ASCR
Laser-generated nanoparticles to change physical properties of solids, liquids and gases

Synthesis of nanoparticles was possible employing a Nd: YAG pulsed laser at fundamental harmonic. The production of nanoparticles in water depends mainly on the laser parameters (pulse duration, ...

Torrisi, Alfio; Cutroneo, Mariapompea; Ceccio, Giovanni; Cannavó, Antonino; Horák, Pavel; Torrisi, L.; Vacík, Jiří
Ústav jaderné fyziky, 2019

Experimentální vyšetřování vhodné poréznosti protiprašné stěny
Nosek, Štěpán
2019 - Czech
Článek seznamuje čtenáře se základními principy fyzikálního modelování atmosférické mezní vrstvy ve větrných tunelech a jejich aplikací na řešení prašnosti. Je uveden praktický příklad použití těchto metod v rámci řešení šíření prašnosti z pásových dopravníků do bezprostředního okolí protiprašnou stěnou. The paper introduces the reader to the basic principles of physical modelling of the atmospheric boundary layer in wind tunnels and their application to the solution of dustiness. A practical example elucidates the use of these methods in the solution of dustiness from conveying belts to immediate surroundings. Keywords: atmospheric boundary layer; physical modelling; porosity; dustiness; wind tunnel Available at various institutes of the ASCR
Experimentální vyšetřování vhodné poréznosti protiprašné stěny

Článek seznamuje čtenáře se základními principy fyzikálního modelování atmosférické mezní vrstvy ve větrných tunelech a jejich aplikací na řešení prašnosti. Je uveden praktický příklad použití těchto ...

Nosek, Štěpán
Ústav termomechaniky, 2019

Characterization of fine-grained montmorillonite fractions suitable for composite preparation
Valovičová, Věra; Vaculíková, Lenka; Plevová, Eva; Dolinská, S.; Znamenáčková, I.; Danková, Z.
2019 - English
The aim of this experimental study was to characterize a fine-grained fraction of montmorillonites (SAz-2, STx-1, SWy-2 and Kunipia-F). It was investigated in order to provide more precise information of used montmorillonites than could be obtained by analysis of the unfractioned montmorillonites. At first, the fine fraction of montmorillonites were prepared by sedimentation and activation by means of Na2CO3. The prepared clay materials were characterized by the X-ray diffraction analysis and FTIR spectroscopy. The thermal behaviour of the studied samples was determinated according to the characteristic temperatures obtained from TG/DTA curves. The temperatures of dehydratation and dehydroxylation were evaluated and kinetic parameters were also calculated. The porosity and surface properties of the studied samples were gained by the nitrogen adsorption measurements. The obtained results confirmed that the fine fraction of montmorillonites could be a suitable material for subsequent preparation of composites with enhanced sorption properties, especially montmorillonite/MnO2 composite. Keywords: montmorillonite; activation; characterization; composites Available in digital repository of the ASCR
Characterization of fine-grained montmorillonite fractions suitable for composite preparation

The aim of this experimental study was to characterize a fine-grained fraction of montmorillonites (SAz-2, STx-1, SWy-2 and Kunipia-F). It was investigated in order to provide more precise information ...

Valovičová, Věra; Vaculíková, Lenka; Plevová, Eva; Dolinská, S.; Znamenáčková, I.; Danková, Z.
Ústav geoniky, 2019

Note on the problem of compressible non-Newtonian fluids
Caggio, M.; Nečasová, Šárka
2019 - English
The aim of the paper is to consider the compressible non-Newtonian fluids of power law type when the viscosity coeffcients depend not only on invariants of velocity field but also on the density. We introduce approximation scheme using model of multipolar fluids. After then passing with higher viscosity to zero we get the measure valued solution of the problem. Keywords: non-Newtonian fluid; compressible fluid; multipolar fluid; measure-valued solution Available in digital repository of the ASCR
Note on the problem of compressible non-Newtonian fluids

The aim of the paper is to consider the compressible non-Newtonian fluids of power law type when the viscosity coeffcients depend not only on invariants of velocity field but also on the density. We ...

Caggio, M.; Nečasová, Šárka
Matematický ústav, 2019

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