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Experimental and numerical investigation of the frequency-modal properties of the switch box
Zolotarev, Igor; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Gabriel, Dušan; Mračko, Michal; Masák, Jan
2023 - anglický
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate modifications. This paper deals with numerical and experimental frequency-modal properties of the switch box and mutual comparison for numerical model validation.
Klíčová slova:
modal analysis; natural frequencies; eigen-modes of vibration
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Experimental and numerical investigation of the frequency-modal properties of the switch box
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate ...
Engineering Mechanics 2023
Radolf, Vojtěch; Zolotarev, Igor
2023 - anglický
The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech Society of Mechanics and being a part of IFTOMM (The International Federation for the Promotion of Mechanism and Machine Science) activities. As it corresponds with character of the conference, this proceedings consists of several topic oriented parts: Biomechanics, Fluid mechanics, Dynamics, Fracture mechanics, Mechatronics, Reliability of structures, Mechanics of solids, Technological processes, Thermodynamics. The volume represents a well-balanced overview of theoretical, numerical and experimental work on fundamental and applied studies.
Klíčová slova:
biomechanics; dynamics; mechatronics; fluid mechanics; mechanics of solids; fracture mechanics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Engineering Mechanics 2023
The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech ...
Conductive open-cell silicone foam for modulatable damping and impact sensing applications
Preuer, R.; Šleichrt, Jan; Kytýř, Daniel; Graz, I.
2023 - anglický
Nature has long served as a source of inspiration for the development of new materials, with foam-like structures in fruits such as oranges and pamelos serving as examples of efficient energy dissipation. In this study, we present the synthesis and characterization of a conductive silicone foam for potential impact sensing applications. By blending Sylgard 184 and Carbon Black, we create a highly porous structure capable of dissipating energy and modulating its resistance. To investigate the properties of the foam, we utilized both micro-computer tomography (μCT) and scanning electron microscopy (SEM) imaging techniques. The μCT imaging revealed the intricate pore network of the foam, reminiscent of the complex structure found in natural sponges. SEM imaging allowed for observation of the uniform distribution of Carbon Black particles within the foam, enabling the conductive properties of the foam. The foam’s mechanical behavior was characterized by a compression test under μCT imaging to measure the deformation behavior and changes in the foam’s resistance. Additionally, a ball drop test was conducted to investigate the foam’s damping behavior while simultaneously measuring the impact location by the local change in resistance. Remarkably, our results demonstrate the exceptional damping capabilities of the conductive silicone foam, with the damping ratio modulated by adjusting the degree of compression-induced deformation. This is attributed to the collapse of the foam’s porous structure, resulting in a significant increase in the foam’s contact area. Overall, our study provides valuable insights into the behavior of conductive silicone foams and their potential as an impact sensing material. The use of both CT and SEM imaging techniques allows for a comprehensive understanding of the foam’s properties, which can be optimized for a variety of applications. The foam’s ability to modulate its damping properties by adjusting the degree of deformation provides a promising avenue for future research in the field of materials science and engineering.
Klíčová slova:
silicone foam; conductive properties; deformation behaviour; damping
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Conductive open-cell silicone foam for modulatable damping and impact sensing applications
Nature has long served as a source of inspiration for the development of new materials, with foam-like structures in fruits such as oranges and pamelos serving as examples of efficient energy ...
Characterization of five mosaic mortar beds from Austria produced by A. Neuhauser/Tiroler Glasmalerei and J. Pfefferle
Bauerová, Pavla; Frankeová, Dita; Slížková, Zuzana
2023 - anglický
The report contains the results of material analyses of five mortar beds of mosaics produced by the Austrian studios Neuhauser/Tiroler Glasmalerei and Josef Pfefferle. The analysed samples come from mosaics made at the turn of the 19th and 20th centuries and located in various places in Tyrol. The mortars were analysed by SEM-EDS and thermal analysis. The results showed that, in addition to traditional materials such as marble dust, they also contain atypical or innovative components such as waste ceramic and glass shards or early Portland cement.
Klíčová slova:
SEM-EDS analysis; historic mortar; mosaic; thermal analysis
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Characterization of five mosaic mortar beds from Austria produced by A. Neuhauser/Tiroler Glasmalerei and J. Pfefferle
The report contains the results of material analyses of five mortar beds of mosaics produced by the Austrian studios Neuhauser/Tiroler Glasmalerei and Josef Pfefferle. The analysed samples come from ...
Measurements on Turbine Cascade KOBRA
Luxa, Martin; Hála, Jindřich; Šimurda, David
2023 - anglický
The report contains results and evaluation of aerodynamic measurement on a blade cascade representing the section imitating the conical stream line in the last rotor row of a gas trubine under considerable off-design condition. The research report contains detailed specifications of the measured model, overview of the results of the optical measurements (interferometry, schlieren method in Toepler configuration) and pneumatic measurements (traversing with five hole conical probe downstream the cascade).
Klíčová slova:
turbine cascade; turbine off-design condition; tarnsonic flow
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements on Turbine Cascade KOBRA
The report contains results and evaluation of aerodynamic measurement on a blade cascade representing the section imitating the conical stream line in the last rotor row of a gas trubine under ...
The influence of first CNN layer initialization on training convergence
Krejsa, Jiří; Věchet, Stanislav; Chen, K.S.
2023 - anglický
During evaluation of convolution neural networks on the task of sign language single hand alphabet classification we have discovered that in small but not negligible number of cases the training of the network does not converge at all. This paper investigates the problem that we believe is independent of the application. While the true cause of training divergence was not discovered, we can offer the reader an easy solution from practical point of view – initialization of the first CNN layer using pretrained networks parameters.
Klíčová slova:
convolution neural networks; training; initialization
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The influence of first CNN layer initialization on training convergence
During evaluation of convolution neural networks on the task of sign language single hand alphabet classification we have discovered that in small but not negligible number of cases the training of ...
Post-processing the results of the topology optimization with the level set technique
Ježek, Ondřej; Kopačka, Ján; Gabriel, Dušan
2023 - anglický
Topology optimization (TO) has come to the fore with the development of 3D printing. The most commonly used method is SIMP, a density-based approach, which outputs a per-element constant density field and thus requires post-processing to obtain the shape. Conventional post-processing methods extract optimized topologies in the form of brep models. It yields only C0 continuous geometries, which are usually not suitable for downstream applications such as prototyping, design validation, and design exploration. In this paper, we present a new post-processing method based on the level set principle that overcomes common post-processing issues, such as the lack of smoothness.
Klíčová slova:
topology optimization; post-processing; level-set; signed distance function
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Post-processing the results of the topology optimization with the level set technique
Topology optimization (TO) has come to the fore with the development of 3D printing. The most commonly used method is SIMP, a density-based approach, which outputs a per-element constant density field ...
Photo-active liquid crystalline materials: effect of lateral substitution far from the chiral center
Mironov, Sergei; Suchánek, T.; Marhoul, J.; Cigl, Martin; Hamplová, Věra; Bubnov, Alexej
2023 - anglický
Photosensitive liquid crystalline (LC) materials give a fascinating possibility to tune and control the optical properties of soft systems distantly by illumination by UV-Vis light. Lateral substitution on the molecular core is an effective tool to tune the behaviour of chiral LCs. The effect of lateral substitution (by F, Cl, Br and methyl group) on the self-assembling behaviour, several new LCs with substituents placed on the benzene ring far from the chiral centre are and studied. All compounds, with exception of Br-substituted one, possess the cholesteric phase. The photosensitive behaviour, in particular the conversion of the E-Z isomers, was studied in toluene solution by HPLC. The kinetics of the photo-isomerization was identified under illumination by UV light. Due to presence of a photo-active azo group these materials can be used as functional dopants for design of smart photo-active liquid crystalline mixtures targeted for various applications in optoelectronics.
Klíčová slova:
photosensitive chiral liquid crystal; lateral substitution; azobenzene; E-Z isomerization
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Photo-active liquid crystalline materials: effect of lateral substitution far from the chiral center
Photosensitive liquid crystalline (LC) materials give a fascinating possibility to tune and control the optical properties of soft systems distantly by illumination by UV-Vis light. Lateral ...
Surface acoustic wave microfluidic chip for rapid cell sorting
Vejrosta, Jakub; Maňka, Tadeáš; Plichta, Tomáš; Šerý, Mojmír
2023 - anglický
This work revolves around microfluidics and micro-objects manipulation in general. In our device, we are producing surface acoustic wave (SAW). The SAW can be used to sort particles by their size or physical properties and separate them. In medical analysis SAW on microfluidic chip can be used to pre-sorting of body fluids or blood serum for further optical or chemical analysis. The wave is produced by pair of interdigital transducers (IDTs), which are situated on opposite sides of microfluidic channel. As our active material we have used lithium niobate crystalline material for its great piezoelectric properties. This work is also the precursor for measuring the rheological properties of a medium, such as micro-viscosity, via the measurement of the trajectory of a flow trace.
Klíčová slova:
microfluidics; surface acoustic wave; light microscopy
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Surface acoustic wave microfluidic chip for rapid cell sorting
This work revolves around microfluidics and micro-objects manipulation in general. In our device, we are producing surface acoustic wave (SAW). The SAW can be used to sort particles by their size or ...
Modelling of pulse-triggered running waves on a blade cascade
Šnábl, Pavel; Pešek, Luděk
2023 - anglický
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
Klíčová slova:
pulse-triggered running waves; blade cascade; NACA 0010
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modelling of pulse-triggered running waves on a blade cascade
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 ...
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