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Comparison of mechanical properties of wood determined by local gently destructive tests and fully destructive tests on building elements
Drdácký, Miloš; Kloiber, Michal; Valluzzi, M. R.; Casarin, F.
2022 - anglický
Demolition or repair of historic buildings is a valuable source of test materials for testing nondestructive and gently destructive methods for estimating the mechanical properties of built-in wood. The article uses the results of one such opportunity, when it was possible to study the mechanical properties of wood obtained by local measurements on a larger sample of historic and new wooden beams and compare them with the properties calculated from destructive tests of structural elements. Thirty-one wood elements (nineteen recovered from disassembled buildings and twelve new) were subjected to considerately destructive local tests using a loading mini-jack method. In this method, a small loading jack is inserted into a precisely drilled hole and a load test of the wood in compression along the fibers is performed on a part of the hole wall while measuring the achieved deformation under load. Red and white firs, and pine species constituted the recovered elements - red fir and larch the new ones. Destructive tests (in bending and compression) were also carried out on ten recovered and six new elements, and results were correlated with those of considerately destructive tests. Comparison of the assessed mechanical properties shows reasonably good correlation and promising conclusions for practical applications.
Klíčová slova:
considerately destructive tests; mini-jack method; destructive tests; assessment of mechanical characteristics of wood; historic timber
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Comparison of mechanical properties of wood determined by local gently destructive tests and fully destructive tests on building elements
Demolition or repair of historic buildings is a valuable source of test materials for testing nondestructive and gently destructive methods for estimating the mechanical properties of built-in wood. ...
Effect of molecular structure on liquid crystalline behaviour for chiral lactic acid derivatives
Mironov, Sergei; Bubnov, Alexej
2022 - anglický
Liquid crystals are self-organizing materials that have great potential for practical applications. The relationship has not been fully established and understood despite numerous studies. We discuss a relatively broad subclass of calamitic chiral lactic acid derivatives and provide specific examples of effective tuning of their mesomorphic and electro-optical behaviour using various types of lateral substitution placed on the molecular core.
Klíčová slova:
chiral liquid crystals; lateral substitution; ferroelectric smectic phase; spontaneous polarization; lactic acid
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Effect of molecular structure on liquid crystalline behaviour for chiral lactic acid derivatives
Liquid crystals are self-organizing materials that have great potential for practical applications. The relationship ...
A New Look to Information and Uncertainty of Continuous Distributions
Fabián, Zdeněk
2022 - anglický
We define information and uncertainty function of a family of continuous distributions. Their values are relative information and uncertainty of an observation from the given parametric family, their mean values are the generalized Fisher information and a new measure of variability, the score variance. In a series of examples we show why to use new concepts instead of the differential entropy.
Klíčová slova:
Differential entropy; information function; uncertainty function; mean information of distribution
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
A New Look to Information and Uncertainty of Continuous Distributions
We define information and uncertainty function of a family of continuous distributions. Their values are relative information and uncertainty of an observation from the given parametric family, their ...
Two-way fluid structure interaction study of aero-engine compressor blade vibration under air excitation
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Maturkanič, Dušan; Hodboď, Robert
2022 - anglický
In this paper, we provide a numerical method via FEM software (ANSYS) using two-way Fluid-Structure Interaction (FSI) solver to estimate the blade’s vibration where the force used to excitation is a continuous air jet. This will help to provide data to diagnostic blade condition and health monitoring and a bridge toward a precise study of the blade’s dynamic under rotation and the estimation of blade’s displacement to define the amplitude and the frequency that occurs under different types of excitation which is a pillar for the process of machine condition and health monitoring.
Klíčová slova:
two-way fluid structure interaction (FSI); air excitation; blade tip displacement
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Two-way fluid structure interaction study of aero-engine compressor blade vibration under air excitation
In this paper, we provide a numerical method via FEM software (ANSYS) using two-way Fluid-Structure Interaction (FSI) solver to estimate the blade’s vibration where the force used to excitation is a ...
The International Colloquium Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2022
Zolotarev, Igor; Pešek, Luděk; Kozień, M. S.
2022 - anglický
The papers of the DYMAMESI are divided into the three sections and focused on the Dynamics of Machines, Interactions and Power Engineering.
Klíčová slova:
dynamics; vibrations of mechanical systems; vibrodiagnostics; energy transformations
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The International Colloquium Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2022
The papers of the DYMAMESI are divided into the three sections and focused on the Dynamics of Machines, Interactions and Power Engineering.
Experimental and numerical evaluation of blade cascade instability using travelling wave mode approach
Chindada, Sony; Šnábl, Pavel; Pešek, Luděk
2022 - anglický
The stability of experimental blade cascade with five NACA 0010 profiles was measured and evaluated with travelling wave mode approach with three inner blades oscilating. The measured moment of the middle blade consist of not only the aerodynamic moment from the flow but also structural moment from the blade dynamics. Two days of obtaining the aerodynamic moment from the measured data are herein presented and the results compared. In addition, numercial simulations were done and the results from 2D CFD analysis in ANSYS are compared with the experimental data.
Klíčová slova:
blade cascade instability; travelling wave mode approach; flutter
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Experimental and numerical evaluation of blade cascade instability using travelling wave mode approach
The stability of experimental blade cascade with five NACA 0010 profiles was measured and evaluated with travelling wave mode approach with three inner blades oscilating. The measured moment of the ...
Experimental investigation of homogeneous nucleation of water in various gases using an expansion chamber
Lukianova, Tetiana; Lukianov, Mykola; Hrubý, Jan
2022 - anglický
Nucleation is an integral part of phase transitions and plays an important role in technology. The control of nucleation in devices such as turbines, rocket and jet engines, wind tunnels, and combustion processes is key to achieving efficient, ecologically sound operation. Our paper presents information about a modernized experimental setup used for homogeneous water nucleation research.\nThe main goal of the study is an analysis of the influence of carrier gas on homogeneous nucleation.The experimental setup based on an expansion chamber has been used for research of homogeneous nucleation over several decades and has undergone various technical improvements. In the Institute of Thermomechanics, the setup was been completely disassembled and cleaned. Pressure transducers, laser, and the data acquisition system have been replaced with modern parts. After that, the chamber was assembled, and thoroughly tested and calibrated.Our investigations were carried with argon and nitrogen as carrier gases in a range of nucleation temperatures 220 – 260 K, pressure range 80-150 kPa, at several concentrations of water vapour. The results thus obtained are consistent with literature data.The findings suggest that this experimental approach is useful for homogeneous water nucleation research.
Klíčová slova:
homogeneous nucleation; pulse chamber; nucleation rate
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Experimental investigation of homogeneous nucleation of water in various gases using an expansion chamber
Nucleation is an integral part of phase transitions and plays an important role in technology. The control of nucleation in devices such as turbines, rocket and jet engines, wind tunnels, and ...
Current status of natural refrigerants for heat pumps in an electric bus
Aminian, Ali; Vinš, Václav
2022 - anglický
The technical report provides a survey on the current status of hydrocarbons, with special focus on propane (R290), used as natural refrigerants in air‐conditioning units and heat pumps. Due to the\nexpected phase‐down of halogenated refrigerants planned in the regulation of the European Parliament no. 2022/0099/COD, alternatives such as hydrocarbons, carbon dioxide or ammonia are\nmost probably to be used in EU in the near future. A review of recent developments of HVAC units for residential use and for electric vehicles operated with natural refrigerants is presented.
Klíčová slova:
heat pump; electric bus; refrigeration
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Current status of natural refrigerants for heat pumps in an electric bus
The technical report provides a survey on the current status of hydrocarbons, with special focus on propane (R290), used as natural refrigerants in air‐conditioning units and heat pumps. Due to ...
Advanced statistical evaluation of fatigue data obtained during the measurement of concrete mixtures with various water-cement ratio
Seitl, Stanislav; Benešová, A.; Blasón, S.; Miarka, Petr; Klusák, Jan; Bílek, V.
2022 - anglický
The Basquin’s law is usually applied for the evaluation of fatigue properties of civil engineering \nmaterials. For materials like concrete, some researchers recommended applying the Weibull model. In this\ncontribution, Basquin’s law, Castillo-Canteli model and Kohout-Věchet model were applied for the advanced \nstatistical description of S−N curves (Wöhler curve). For the application of the models, the experimental data \nmeasured on reference concrete mixtures used for the development of self-healing concrete at the Faculty of \nCivil Engineering, TU Ostrava. Fitting data of applied models were compared and analyzed
Klíčová slova:
Concrete, fatigue; fatigue; S-N curve; Kohout-Věchet model; Castillo-Canteli model; Basquin model
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Advanced statistical evaluation of fatigue data obtained during the measurement of concrete mixtures with various water-cement ratio
The Basquin’s law is usually applied for the evaluation of fatigue properties of civil engineering \nmaterials. For materials like concrete, some researchers recommended applying the Weibull model. In ...
Plasma-synthesised zinc oxide nanoparticle behavior in liquids
Rutherford, D.; Jíra, J.; Kolářová, Kateřina; Matolínová, I.; Remeš, Zdeněk; Kuliček, J.; Padmanaban, D.; Maguire, P.; Mariotti, D.; Rezek, B.
2021 - anglický
ZnO nanoparticles have been synthesized using non-thermal atmospheric pressure plasma (ZnO-NTP). We investigated the behavior of these ligand-free as a colloid suspension using different solvents, from deionized water to physiological saline and microbial culture broth. We found that the zeta potential of ZnONTP became more negative after exposure to microbial culture broth relative to water, which suggests increased colloid stability. Photoluminescence spectra of ZnO-NTP were similar regardless of liquid type, yet optical and fluorescent images of samples showed different agglomeration behaviour depending on liquid type. Scanning electron microscopy images revealed large agglomerates of ZnO-NTP interacting with the surface of bacteria cells, ranging in size from 200 nm up to 2 µm. We also studied effect of sub-lethal concentrations of ZnO-NTP on bacteria under illumination. There was no significant difference in viable bacteria concentration after 24h exposure to 10 µg/mL ZnO-NTP.
Klíčová slova:
zinc oxide; nanotechnology; colloid suspension; bacteria
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Plasma-synthesised zinc oxide nanoparticle behavior in liquids
ZnO nanoparticles have been synthesized using non-thermal atmospheric pressure plasma (ZnO-NTP). We investigated the behavior of these ligand-free as a colloid suspension using different solvents, ...
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