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Evaluation of sample geometry effect on creep deformation progress using acoustic emission method
Dvořák, Jiří ; Sklenička, Václav ; Král, Petr ; Kvapilová, Marie ; Svobodová, M. ; Šifner, J. ; Koula, V.
This work deals with the determination of the influence of the sample geometry on the development of failure during creep exposure. Creep tests were carried out at temperature of 600 °C and a stress of 180 MPa in the protective atmosphere of argon. P92 steel samples with a conventional smooth surface and samples with a V-groove notch were chosen for the test tests. The results of creep resistance and fracture behaviour were complemented by detailed microstructural characterization to assess damage initiation and development. Based on the measured results, the creep data was evaluated using neural networks that systematically search for and process the signal from the acoustic emission (AE). Acoustic emission serves here as an effective non-destructive method for early prediction of the beginning of a possible accident of components of power and chemical plants.
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Kosher in lexicography. Problems of one religion term
Dvořáková, Žaneta
The Hebrew term košer (‘kosher’) came into Czech through Jewish sociolect / ethnolect. It was originally a religious term for what is ritually pure and appropriate. In addition to the adjective and adverb košer, Czech dictionaries also contain a number of other forms and derivatives, but some of them are no longer used at the moment (e.g. košerný, košerně). Our evaluation is based on an analysis of material base from the Syn2015 Corpus and from a probe into contemporary texts in Jewish magazines or on the websites of Jewish communities and organizations. In Czech dictionaries, we may see a reduction of the meaning compared to how the term is traditionally used in the Jewish community, e.g. the adjective košer is limited to meat, the verb košerovat is associated only with the ritual slaughter. The nouns mentioned in the dictionaries are also very debatable: masculine košer in the sense of ‘butcher’ and masculine košer with the meanings of ‘cut’ and ‘food appropriate for Jews to eat’, these are based on isolated documents from the works of authors apparently unfamiliar with the Jewish community. The question then is whether (and according to what criteria) such words should be included in the dictionaries.
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Digital twin skin of the drinking water treatment plant - development and use in practice
Sochorová, Helena ; Andreides, D. ; Hložanka, F. ; Prokopová, Michaela ; Stejskal, O. ; Chalupa, L. ; Šmejkalová, P. ; Dolejš, P.
The contribution presents experiences with the development of a digital twin for optimizing the control of the DWTP within the pilot project in the Železná Ruda locality. The digital twin consists of two components, i.e. digital documentation in the object architecture processed by the reverse engineering process, which is data-connected with the real physical infrastructure (virtual replica of the infrastructure) and a simulation tool based on a mathematical model or a neural network (simulation of the water treatment process). Both components are accessible to the user via a web application, in which one can choose from three operating states (monitoring of the real state - default, simulation of scenarios of operating settings and prediction of pressure loss).
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Tombstones of the Švamberks of the 15th – early 17th Century from an Art Historical Perspective
Chlíbec, Jan
Only a fragment has remained from the original collection of the Švamberk family tombstones that was still quite large at the beginning of the 18th century. Surprisingly,\neven though the Švamberks were a prominent noble family, the surviving works usually show average or below-average quality which, as far as the 15th century works are concerned, reflect the prevailing condition of sepulchral sculpture in Bohemia of the time. More factors could have been behind opting for an austere form of the tombstone. In addition to the Utraquist criticism of majestic funeral works and the lack of high-quality stonemasons after the Hussite Wars, it could be the general idea of resistance to pride and accentuation of the confirmation of Christian modesty regardless of the buried person’s confession.\n
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Non-linear Vibration of Planar Case of Three-blade Bundle with Dry Friction Contacts
Šnábl, Pavel ; Pešek, Luděk ; Půst, Ladislav
Using dry friction couplings (so called tie-bosses) between the blades in turbine rotors can be used to suppress dangerous resonant vibrations of turbine blades and it has been studied on our institute on various models. Experimental setup of three-blade bundle was built along with bladed wheel. The first set-up of the bundle was with blades turned 45 degrees to the disc plane. In that case the deformation of the blades causes turning of the ends of tie-bosses and edge contact together with multi-directional slip occurs. The experimental set-up was simplified herein so that the blades are parallel to the disc plane and in-line slip occurs. Although single electromagnet was used to excite the system, the first mode of vibration with no slip in tie-bosses just occurred. In case of bladed wheel, all blades have coupling through tie-bosses with neighbouring blades which stiffen them and raise their eigenfrequency. In our case, a mistuning by reducing mass of side blades caused similar behaviour. Steel to steel contact pair was used for the first tests.
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Numerical and Experimental Investigation of the Flow Field in Five Blade Linear Cascade in Subsonic Flow
Šnábl, Pavel ; Chindada, Sony ; Bublík, O. ; Procházka, Pavel P. ; Prasad, Chandra Shekhar
In large steam turbines, last stage blades are very long and must be designed very thin and with no shroud to minimize the centrifugal force which leads to low eigenfrequencies and low structural damping. In this case, aero-elastic damping plays important role on last stage bladed disc’s dynamics. Three major aero-elastic issues found in turbomachinery are forced response, non-synchronous vibrations, and flutter. Flutter is an unstable, self-excited vibration resulting from coupling between the structural vibrations and unsteady aerodynamic forces. It is clear that this unstable behaviour must be avoided and predictions of flutter behaviour need to be performed during design stage of the turbine.\n
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Modelling of pulse-triggered running waves on a blade cascade
Šnábl, Pavel ; Pešek, Luděk
An experimental cascade of five NACA 0010 blades with pitch degrees of freedom is excited by a moment pulse to one of the blades. Depending on the flow conditions, such as wind speed and the angle of attack of the wind on the blades, the vibration of the excited blade is transmitted by the wind to the other blades. This can result in a running wave that diminishes over time or in a flutter running wave. A simplified spring-mass-damper model with inter-blade connections and non-linear van der Pol dampers is tuned to match experimentally obtained stability curves and tested to see if it can qualitatively model the response of the cascade to the pulse excitation.\n
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Structural analysis of polysaccharides from mushroom hericium Erinaceus mftccb 134
Bleha, R. ; Čopíková, J. ; Sushytskyi, Leonid ; Vannucci, Luca ; Sinica, A. ; Jozífek, M. ; Jablonský, I. ; Klouček, P.
The aim of this research was the structural characterisation of polysaccharides isolated from fruiting bodies of the cultivating medicinal mushroom Hericium erinaceus MFTCCB 134. Cold and hot water extracts (CWE, HWE) were obtained and purified, and followed by alkali extraction from the reminder solids. The composition and structure of the fractions were analysed by FTIR spectroscopy, and neutral sugars/linkage analyses were determined by GC/FID and GC/MS, respectively. Galactose, fucose and glucose were found in purified CWE,\nwhile glucose predominated in purified HWE.
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