Number of found documents: 10827
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Post-processing the results of the topology optimization with the level set technique
Ježek, Ondřej; Kopačka, Ján; Gabriel, Dušan
2023 - English
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. Keywords: topology optimization; post-processing; level-set; signed distance function Available at various institutes of the ASCR
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 ...

Ježek, Ondřej; Kopačka, Ján; Gabriel, Dušan
Ústav termomechaniky, 2023

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 - English
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. Keywords: photosensitive chiral liquid crystal; lateral substitution; azobenzene; E-Z isomerization Available at various institutes of the ASCR
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 ...

Mironov, Sergei; Suchánek, T.; Marhoul, J.; Cigl, Martin; Hamplová, Věra; Bubnov, Alexej
Fyzikální ústav, 2023

Optical frequency distribution with full compensation of induced phase noise
Pravdová, Lenka; Čížek, Martin; Hrabina, Jan
2023 - Czech
In applications demanding high optical frequency stability, two or more reference stages are usually necessary to ensure the laser source's short-term and long-term stability. The short-term stability can be obtained by locking the laser to a high-finesse optical cavity, while the long-term stability can be formed by, for example, a hydrogen maser referenced by a synchronisation signal from a GPS receiver. During the distribution of stable optical frequencies to the target applications, the transmitted signal is affected by the interfering effects of the surrounding environment. This is especially evident in optical fibre transfers, where acoustic interference, vibrations and environmental temperature changes cause induced phase noise. This work describes the distribution network of stable optical frequencies between individual frequency references within the ISI CAS laboratories. The key parts of the setup are realised by free-space optics, and all of the optical links are fully compensated to induced phase noise effects. V aplikacích náročných na stabilitu optické frekvence je obvykle potřeba kombinovat dva nebo více referenčních stupňů tak, aby byla zajištěna krátkodobá i dlouhodobá stabilita laserového zdroje. Krátkodobou frekvenční stabilitu mohou zajistit například vysokojakostní optické rezonátory, druhý stupeň pro dlouhodobou stabilitu pak může tvořit např. vodíkový maser referencovaný synchronizačním signálem z GPS přijímače. Při distribuci stabilních optických kmitočtů k cílové aplikaci působí na přenášený signál rušivé vlivy okolního prostředí. Tyto efekty jsou zvláště patrné při přenosech optickými vlákny, kde akustické rušení, vibrace a změny teploty prostředí způsobují indukovaný fázový šum. Naše práce pojednává o řešení distribuční sítě stabilních optických kmitočtů pomocí volné optiky a popisuje vzájemnou návaznost jednotlivých referencí v rámci laboratoří ÚPT. Keywords: optical frequency distribution; time-frequency metrology Available at various institutes of the ASCR
Optical frequency distribution with full compensation of induced phase noise

In applications demanding high optical frequency stability, two or more reference stages are usually necessary to ensure the laser source's short-term and long-term stability. The short-term stability ...

Pravdová, Lenka; Čížek, Martin; Hrabina, Jan
Ústav přístrojové techniky, 2023

Surface acoustic wave microfluidic chip for rapid cell sorting
Vejrosta, Jakub; Maňka, Tadeáš; Plichta, Tomáš; Šerý, Mojmír
2023 - English
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. Keywords: microfluidics; surface acoustic wave; light microscopy Available at various institutes of the ASCR
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 ...

Vejrosta, Jakub; Maňka, Tadeáš; Plichta, Tomáš; Šerý, Mojmír
Ústav přístrojové techniky, 2023

SERS-TAGS: Selective immobilization and detection of bacteria using specific antibodies and surface-enhanced Raman scattering
Benešová, Markéta; Bernatová, Silvie; Samek, Ota; Pokorná, Zuzana; Mika, Filip; Kizovský, Martin; Pilát, Zdeněk
2023 - Czech
Raman spectroscopy is a non-destructive instrumental analytical technique based on Raman scattering, which is the inelastic scattering of photons that occurs when interacting with electrons in chemical bonds. With the help of Raman spectroscopy, chemical compounds, their mixtures and biological samples, including living organisms, can be analyzed very quickly, non-contactly and non-destructively. The performed measurements can be compared with spectra databases. A problem with Raman spectroscopy is that samples sometimes give a weak signal that is often overlaid by intense fluorescence. SERS (surface-enhanced Raman spectroscopy) is used to amplify Raman scattering. Ramanova spektroskopie je nedestruktivní instrumentální analytická technika založená na Ramanově rozptylu, což je nepružný rozptyl fotonů, který vzniká při interakci s elektrony v chemických vazbách. S pomocí Ramanovy spektroskopie lze velmi rychle, bezkontaktně a nedestruktivně zanalyzovat chemické sloučeniny, jejich směsi a biologické vzorky, včetně živých organismů. Provedená měření lze srovnávat s databázemi spekter. Problémem Ramanovy spektroskopie je, že vzorky někdy poskytují slabý signál, který je často překryt intenzivní fluorescencí. K zesílení Ramanova rozptylu slouží SERS (povrchem zesílená Ramanova spektroskopie). Keywords: Raman spectroscopy; SERS; diagnostcs; SERS-labels Available at various institutes of the ASCR
SERS-TAGS: Selective immobilization and detection of bacteria using specific antibodies and surface-enhanced Raman scattering

Raman spectroscopy is a non-destructive instrumental analytical technique based on Raman scattering, which is the inelastic scattering of photons that occurs when interacting with electrons in ...

Benešová, Markéta; Bernatová, Silvie; Samek, Ota; Pokorná, Zuzana; Mika, Filip; Kizovský, Martin; Pilát, Zdeněk
Ústav přístrojové techniky, 2023

Modelling of pulse-triggered running waves on a blade cascade
Šnábl, Pavel; Pešek, Luděk
2023 - English
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 Keywords: pulse-triggered running waves; blade cascade; NACA 0010 Available at various institutes of the ASCR
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 ...

Šnábl, Pavel; Pešek, Luděk
Ústav termomechaniky, 2023

Measurement of ionising radiation using optical fibres
Zbožínek, Tadeáš; Jelínek, Michal; Mikel, Břetislav
2023 - Czech
The paper focuses on the method of measuring ionizing radiation using optical fibers. It focuses on the description and characterization of the method where optical fibers are used to transmit scintillation radiation. Different types of optical fibres are compared together with different types of scintillation sensors. Příspěvek se zaměřuje na metodu měření ionizujícího záření s využitím optických vláken. Zaměřuje se na popsání a charakterizaci metody, kdy dochází k využití optických vláken k přenosu scintilačního záření. Porovnány jsou jednotlivé druhy optických vláken společně s různými druhy scintilačních senzorů. Keywords: fibre sensors; silica optical fibres; ionising radiation detection Available at various institutes of the ASCR
Measurement of ionising radiation using optical fibres

The paper focuses on the method of measuring ionizing radiation using optical fibers. It focuses on the description and characterization of the method where optical fibers are used to transmit ...

Zbožínek, Tadeáš; Jelínek, Michal; Mikel, Břetislav
Ústav přístrojové techniky, 2023

Technology of laser welding with beam oscillation - principles and applications
Mrňa, Libor; Horník, Petr; Novotný, Jan; Šebestová, Hana
2022 - Czech
Laser welding with beam oscillation (wobbling) extends the possibilities of custom laser welding. Two examples of its industrial applications are shown. Further, the effect of oscillation mode and its characteristics on distribution of laser power density was simulated and compared with experimental weld cross-sections. Technologie laserového svařování s dynamickým vychylováním svazku - tzv. wobbling, rozšiřuje možnosti vlastního laserového svařování. Wobbling v principu znamená, že pomocí rozmítací jednotky obsažené v laserové svařovací hlavě se k základní svařovací trajektorii přičítá rozmítací křivka (kružnice, úsečka a další). Změnou rozmítacích parametrů lze měnit nejenom šířku svarové housenky, ale i distribuci dopadajícího laserového záření, potažmo tepla, v rámci příčného rozměru svarové housenky. Článek pojednává o simulaci vlivu rozmítacích parametrů (pro různé tvary rozmítacích křivek) na rozdělení intenzity laserového záření a porovnání výstupů těchto simulací s geometrií reálně vytvořených svarů. Na závěr jsou uvedeny dva praktické příklady využití této svařovací technologie v průmyslové praxi. Keywords: laser welding with beam oscillation; wobbling; simulation; process parameters; power density distribution; weld shape Available at various institutes of the ASCR
Technology of laser welding with beam oscillation - principles and applications

Laser welding with beam oscillation (wobbling) extends the possibilities of custom laser welding. Two examples of its industrial applications are shown. Further, the effect of oscillation mode and its ...

Mrňa, Libor; Horník, Petr; Novotný, Jan; Šebestová, Hana
Ústav přístrojové techniky, 2022

Multiband fiber polygon for accurate time and coherent frequency transmission
Havliš, O.; Vojtěch, J.; Šlapák, M.; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Pravdová, Lenka; Slodička, L.
2022 - Czech
The CESNET association, in cooperation with the Institute of Scientific Instruments of the Academy of Sciences of the Czech Republic (Institute of Scientific Instruments of the CAS, abbreviated ISI CAS), ČD Telematika and University Palacký in Olomouc (UPOL) Department of Optics built a multiband polygon on real optical routes . The multiband polygon is designed for two-way transmission of ultra-stable quantities, i.e. transmission of acurrate time and coherent frequency (T/F). Sdružení CESNET ve spolupráci s Ústavem přístrojové techniky akademií věd České republiky (Institute of Scientific Instruments of the CAS, zkr. ISI CAS), ČD Telematika a Univerzitou Palackého v Olomouci (UPOL) katedry optiky v rámci výzkumných aktivit vybudovaly multipásmový polygon na reálných optických trasách. Multipásmový polygon je určen pro obousměrný přenos ultra-stabilních veličin, tedy přenos přesného času a koherentní frekvence (T/F). Keywords: multiband; T/F; CLA BiDi; SOA Available at various institutes of the ASCR
Multiband fiber polygon for accurate time and coherent frequency transmission

The CESNET association, in cooperation with the Institute of Scientific Instruments of the Academy of Sciences of the Czech Republic (Institute of Scientific Instruments of the CAS, abbreviated ISI ...

Havliš, O.; Vojtěch, J.; Šlapák, M.; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Pravdová, Lenka; Slodička, L.
Ústav přístrojové techniky, 2022

Optical cavity for ultra-narrow linewidth laser system
Pravdová, Lenka; Hrabina, Jan; Čížek, Martin; Číp, Ondřej; Procháska, František; Beneš, Jiří
2022 - Czech
We designed an optical resonator cavity for narrowing standard commercial laser to sub-Hz linewidth. The optical Fabry Perot resonator is designed hemispherical with all components from ULE material and zero crossing temperature at 33°C. The support Zerodur shelf is isolated from the resonator by two Viton O-rings. The resonator is located in an Aluminium chamber with direct temperature stabilization. 2nd temperature stabilisation is provided by 4 Peltier modules enabling heat exchange between the copper jacket and the assembly surroundings. The stainless-steel jacket has passive isolation and protective function. Navrhli jsme optický rezonátor pro zúžení šířky spektrální čáry standardního komerčního laseru. Optický Fabry-Perotův rezonátor je navržen jako polokulový se všemi součástmi z materiálu ULE teplotou nulové roztažnosti při 33°C. Nosná police z materiálu Zerodur je izolována od rezonátoru dvěma O-kroužky z Vitonu. Rezonátor je umístěn v hliníkové komoře s přímou stabilizací teploty. 2. teplotní stabilizaci zajišťují 4 Peltierovy moduly umožňující výměnu tepla mezi měděným pláštěm a okolím sestavy. Nerezový plášť funguje jako pasivní izolace a mechanická ochrana systému. Keywords: length metrology; construction; vacuum chambre Available at various institutes of the ASCR
Optical cavity for ultra-narrow linewidth laser system

We designed an optical resonator cavity for narrowing standard commercial laser to sub-Hz linewidth. The optical Fabry Perot resonator is designed hemispherical with all components from ULE material ...

Pravdová, Lenka; Hrabina, Jan; Čížek, Martin; Číp, Ondřej; Procháska, František; Beneš, Jiří
Ústav přístrojové techniky, 2022

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