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31072. Testing mechanical properties of natural stones used as a building material
- Creator:
- Hasníková, Hana
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- mechanical properties, non-destructive testing, natural stone, historical buildings, and ultrasound
- Language:
- English
- Description:
- The aim of the paper is further presentation of some destructive and non-destructive methods for investigation of mechanical properties of natural stone quarried and used as a building material in Bohemia in the past. Tested samples were made both from virgin material from existing quarries (e.g. sandstone from Hořice) and from material acquired from historical constructions (various sandstones from the Charles Bridge in Prague), which was built-in for a long time. The flexural strength, the compressive strength and Young modulus were obtained from basic destructive tests. Before performing these tests the identical samples were investigated non-destructively by ultrasound and so called peeling test so that the two ways of testing could be compared in the end. and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
31073. Testing multi-factor asset pricing models in the Visegrad countries
- Creator:
- Morgese Borys, Magdalena, Univerzita Karlova. Centrum pro ekonomický výzkum a doktorské studium, and Národohospodářský ústav (Akademie věd ČR)
- Publisher:
- CERGE-EI
- Format:
- electronic and 40 s.
- Type:
- model:monograph and TEXT
- Subject:
- Finance, cenné papíry, kapitálové trhy, makroekonomické modely, země Visegrádské skupiny, 519.862, 336.763, 336.76, (4-191.2), (048.8), 4, and 336.7
- Language:
- English
- Description:
- Magdalena Morgese Borys. and born digital
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
31074. Testing of dynamics of blade wheel with double periodicity
- Creator:
- Pešek, Luděk, Vaněk, František, Půst, Ladislav, Bula, Vítězslav, and Cibulka, Jan
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- dynamics, bladed wheel, rotation, and mistuning
- Language:
- English
- Description:
- The dynamics of the mistuned model of the tests bladed disc with double perodicity was experimentally investigated. The mistuning arised due to the implemantation of two bunches of blades with damping heads fixed on opposite ends of the diameter. The dry friction effect in the heads was treated. The scale for measurement of the electromagnetic force acting on the disc was designed. It enables to analyse the real electromagnetic excitation of the disc under rotation and evaluation of the FRF characteristics from measured blade responses under rotation. The identified eigenfrequencies and damping constan ts served as indicators for assessment of stiffening and damping effects of the friction couplings in the heads. and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
31075. Testing predictions of stream landscape theory for fish assemblages in highly fragmented watersheds
- Creator:
- Bain, Mark B. and Wine, Michael L.
- Type:
- article and TEXT
- Subject:
- stream connections, fish communities, Salmonidae, fish barriers, aquatic landscapes, and fragmentation
- Language:
- English
- Description:
- Predictions of stream landscape theory were tested with common agency fishery data in watersheds heavily fragmented by dams and barriers; large stream fragments support higher species diversity, more abundant populations, and a greater range of fish sizes. Study watersheds discharge to the Hudson River in New York USA, drain rocky and high relief landscapes, and have numerous mill dams and stream barriers. Stream fragments with fish collections ranged from 0.3 km to 119 km in contiguous length. Larger stream fragments had more diverse fish communities but not higher fish densities nor a wider range of fish sizes. However, almost all large stream fragments were supporting reproduction and rearing of the dominant stream species (brown trout Salmo trutta, brook trout Salvelinus fontinalis) while small fragments had no evidence of providing this fish community support. Therefore, consistent with the fundamental basis of stream landscape theory, large stream networks provide support for more species and more secure populations. The study supports the concept that diverse fish communities and secure populations benefit from access to a wide range of stream habitats.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/
31076. Testosterone modulates cardiomyocyte Ca2+ handling and contractile function
- Creator:
- Curl, C. L., Delbridge, L. M. D., Canny, B. J., and Wendt, I. R.
- Format:
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie, testosteron, physiology, testosterone, cardiac myocyte, cardiac contractility, gonadectomy, intracellular calcium, isotonic shortening, 14, and 612
- Language:
- English
- Description:
- The extent to which sex differences in cardiac function may be attributed to the direct myocardial influence of testosterone is unclear. In this study the effects of gonadal testosterone withdrawal (GDX) and replacement (GDX+T) in rats, on cardiomyocyte shortening and intracellular Ca2+ handling was investigated (0.5 Hz, 25 oC). At all extracellular [Ca2+] tested (0.5-2.0 mM), the Ca2+ transient amplitude was significantly reduced (by ~ 50 %) in myocytes of GDX rats two weeks post- gonadectomy. The time course of Ca2+ transient decay was significantly prolonged in GDX myocytes (tau, 455±80 ms) compared with intact (279±23 ms) and GDX+T (277±19 ms). Maximum shortening of GDX myocytes was markedly reduced (by more than 60 %) and relaxation significantly delayed (by more than 35 %) compared with intact and GDX+T groups. Thus testosterone replacement completely reversed the cardiomyocyte hypocontractility induced by gonadectomy. These results provide direct evidence for a role of testosterone in regulating functional Ca2+ handling and contractility in the heart., C. L. Curl ... [et al.]., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
31077. Testování a kalibrace RGB kolorimetrů
- Creator:
- Roik, Jan and Lemr, Karel
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- RGB colorimeters, calibration, monochromator, correction matrix, RGB kolorimetr, kalibrace, monochromátor, and kalibrační matice
- Language:
- Czech
- Description:
- The aim of this work was testing and subsequent calibration of RGB colorimeters. RGB colorimeters are cost-effective tools allowing to perform a number of colorimetric measurements. The aim of this work was to verify their accuracy and to develop methods for their calibration. We show how the calibration method proposed in this paper allows to work even with probes that provide inaccurate measurements due to faulty hardware. and Cílem této práce bylo testování a následná kalibrace RGB kolorimetrů. RGB kolorimetry představují cenově dostupné nástroje umožňující provádět celou řadu kolorimetrických měření. Cílem naší práce bylo ověření jejich přesnosti a vypracování metody jejich kalibrace. Ukazujeme, jak námi navržená metoda kalibrace umožňuje pracovat i se sondami, které již samy o sobě vlivem hardwarových chyb poskytují nepřesná data.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
31078. Testování experimentálních lešticích nástrojů pro potlačení mid-spatial frequency na asférické optice
- Creator:
- Beneš, Jiří, Procháska, František, and Matoušek, Ondřej
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- aspherical optics, mid-spatial frequency, CNC polishing, asférická optika, střední prostorové frekvence, and CNC leštění
- Language:
- Czech
- Description:
- One of the biggest problem in the production of very precise aspherical optics is the mid-spatial frequency. These frequencies are created during grinding and lapping of optical surfaces on CNC machines. Using today’s conventional sub-aperture CNC polishing techniques, we are able to correct these defects only to a very limited extent. With a thorough analysis of these defects, a polishing tool can be developed to successfully suppress these defects. The article deals with the test of experimental instruments developed for the purpose of suppression of mid-spatial frequencies to very precise aspherical optics. These tests were performed on a CNC Optotech MCP 250 polishing machine using conventional polishing processes. and Jednou z největších překážek při výrobě velmi přesné asférické optiky jsou dnes tzv. střední prostorové frekvence. Tyto frekvence vznikají převážně při broušení a lapování optických ploch na CNC strojích. Pomocí dnešních konvenčních technik subaperturního CNC leštění jsme schopni tyto vady korigovat jen ve velmi omezené míře. Za pomoci důkladného rozboru vzniku těchto vad bude možno vyvinout lešticí nástroj, pomocí kterého by bylo možno tyto vady úspěšně potlačovat. Článek řeší tématiku testů experimentálních nástrojů vyvíjených za účelem potlačování středních prostorových frekvencí na velmi přesné asférické optice. Tyto testy byly prováděny na CNC lešticím stroji Optotech MCP 250 s použitím konvenčních lešticích procesů.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
31079. Testování principu ekvivalence
- Creator:
- Wernerová, Markéta, Olivová, Jana, and Zlosnik, Thomas
- Type:
- article, model:article, and TEXT
- Language:
- Czech
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
31080. Testování solárních článků pro vesmírné aplikace
- Creator:
- Rabochová, Michaela, Mohyla, Roman, and Magyar, Martin
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- vesmír, fyzika, universe, physics, 6, and 53
- Language:
- Czech
- Description:
- Technologie v Centru výzkumu Řež byly primárně postaveny za účelem vývoje a testování materiálů pro jaderné elektrárny současné i budoucí generace, nicméně jejich využití je mnohem širší. Jednou z možností je vytváření ekvivalentních podmínek, jaké panují ve vesmíru. Proto vznikl projekt zaměřený na testování komponentů pro vesmírný průmysl. Na konci bylo představení výsledků v podobě radiačního testování elektrických vlastností solárních článků od společností Spectrolab, Inc., a Azur Space Power GmbH. Tedy těch, které jsou používány pro vesmírné aplikace a v případě Azur Space i typově stejné, jaké byly umístěny na první slovenské družici skCUBE, která úspěšně krouží na orbitě Země od června 2017., Michaela Rabochová, Roman Mohyla, Martin Magyar., and Obsahuje bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public