National Repository of Grey Literature 19 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Dynamic and heat transfer analysis of a container with measuring instruments for space probes
Zolotarev, Igor ; Bula, Vítězslav ; Šnábl, Pavel ; Gabriel, Dušan ; Dobiáš, Jiří ; Masák, Jan ; Snížek, Jan ; Souček, Jan
Rocket boosters and spacecraft are subject to intense acoustic environments during launch, which induce high levels of vibration in structural elements and equipment. In addition, elastic structural interactions with propulsion systems and flight control systems can produce low-frequency, high-deflection flight instabilities. Natural vibration of the container with measuring equipment were studied by numerical and experimental methods in the laboratory of Institute termomechanics CAS. Heat transfer analysis inside the container was made by FEM with respect to the conditions during start of the rocket and work in space.\n
Experimental evaluation of the gear windage loss and thermal load of a gear tooth
Kordík, Jozef ; Dobiáš, Jiří ; Hrubý, Jan
The report is written for the needs of the project no. TA04011656 (Research and development of new type of high-speed planetary gear unit with the flexible pin technology to support the planet wheels enabling the transmission of high outputs.). The first part of the report targets the topic of windage losses of a rotating toothed wheel, the experiments with testing gearbox Alfa II are introduced here, as well. The experiments included measurements of windage losses and temperature measurements along a wheel tooth width. Three geometrical configurations differing in wheel enclosure distance were tested, the case without the enclosure was tested too. The outcome of this part is an extension of the previous windage loss model for real geometry configuration: a wheel with an enclosure opened at place of oil outflow and at place of meshing with pinion.\nThe second part of the report targets the thermal load of a wheel tooth and presents experimental results of measurements of temperature distribution along the tooth. This part also contains the details concerning the numerical modeling of this problematic. The numerical analysis included (i) development of methodology for modeling of tooths meshing, (ii) development of the computational model, (iii) development of methodology for assessment of unknown values of some parameters of the model, (iv) development of algorithm. \n
The study of adhesion of glued balistic composites on the dependence of materials used.
Dobiáš, Jiří ; Másilko, Jiří (referee) ; Šiler, Pavel (advisor)
The aim of this work was to investigate the properties of bonded ballistic materialsBalistic composites are mainly glued to reduce weight while keeping their protective properties. On this basis, the materials used were ballistic steel, ceramics, rubber kevlar, non-gummed kevlar, Dyneema and fiberglass. For bonding used were a one-component adhesive Collano 36.104 and two-component adhesive Biresin U1305. The strength of the joint was measured in shear at tensile loads. From these results, deformation energy was further calculated.
Quantitation of agents in exhaled breath condensate.
Dobiáš, Jiří ; Jílek, Petr (advisor) ; Konečná, Klára (referee)
Measurement of parameters in exhaled breath condensate constitute (EBC) a rapidly progressing field of research. The collection procedure is simply and comletely noninvasive. EBC contains large number of biomarkers including hydrogen peroxide, nitrite, nitrate, 3-nitrotyrosine, nitrosothiols, adenosine, prostaglandines, thromboxanes, leukotrienes, isoprostanes, cytokines. Use of EBC is based on hypothesis that aerosol particules exhaled in human breath reflect the composition of the bronchoalveolar extracellular lining fluid. The term EBS stricly relates to exhaled samples collected by cooling the exhaled breath. Measurement very low concentrations of some biomarkers requires very senzitive analytical methods. The evaluation of the available studies revealed that asthma, COPD and ARDS compered with healthy control groups lead to a significant increase in hydrogen peroxide concentration. The result of the work indicate that the content of hydrogen peroxide in the breath condensate provides new information for diagnosis and therapy of inflammatory diseases of the respiratory tract when the collection of specimen and the measurement procedure are standardized.
The influence of zinc oxide on the cement composite with silica fume.
Dobiáš, Jiří ; Koutný, Ondřej (referee) ; Šiler, Pavel (advisor)
The aim of this work was to investigate the influence of zinc oxide on the properties of blended Portland cement mixed with silica fume. On the pastes were monitored flow properties and by using of isoperibolic calorimetry process of the hydration. On the prepared samples were studied mechanical properties of obtaining values of compressive and flexural strength after 1, 7 and 28 days. By using of XRD were measured phase composition and microstructure development war observed by SEM. The elemental composition of cement leaches was measured by using of ICP-OES.
Low potential heat for electrical power generation
Dobiáš, Jiří ; Radil, Lukáš (referee) ; Bartošík, Tomáš (advisor)
This bachelor’s thesis deals with low potential heat sources for electrical power generation. It mentions primarily low potential heat sources, their distribution by origin and where you can find such resources. Another part deals with the technology that uses low potential heat to heat production of higher temperature level and power generation. These are discussed here with a heat pump, regenerative heating, Stirling engine, solar collectors, Peltier cells, etc. In addition is to their use in practice. The last chapter deals with the replacement of the heater in the regeneration heating coil from the solar collectors. It is thus the use of renewable energy sources. Carry out technical and economic calculations for the real utility of such a plan.
Evaluation of optical components for LED
Dobiáš, Jiří ; Pavelka, Tomáš (referee) ; Škoda, Jan (advisor)
This thesis deals with an evaluation of optical components for LED, which is based on laboratory measurements of available LED samples and optical elements. The evaluation is done according to established standards and is focused on efficiency and adjustment of luminous flux (beam angle, luminous curve). Furthermore was made a study engaged in an optical element influence on LED color properties (color temperature, spectral characteristics). In conclusion there is an optical elements usage overview and recommended procedure for selecting appropriate combination of LED and optical element.
Scalable algorithm for non-linear problems of solid mechanics
Dobiáš, Jiří ; Pták, Svatopluk ; Dostál, Z. ; Kozubek, T. ; Markopoulos, A.
The paper is concerned with a novel algorithm for solution to contact problems stemming from the TFETI domain decomposition method.Our new algorithm exhibits both parallel and numerical scalabilities. Numerical experiments include solutions to steady-state problems with non-linear effects.
Škálovatelné algoritmy pro řešení kontaktních problémů s geometrickými a materiálovými nel
Dobiáš, Jiří ; Pták, Svatopluk ; Dostál, Z. ; Vondrák, V.
The paper describes a new version of FETI domain decomposition method and its application to contact problems.
Semikoercivní kontaktní problémy
Pták, Svatopluk ; Dobiáš, Jiří ; Dostál, Z. ; Vondrák, V.
This paper is concerned with application of the Finite Element Tearing and Interconnecting domain decomposition method to solution to contact problems. Then results of numerical experiments are show for some semi-coercive cases.

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3 Dobiáš, Jakub
6 Dobiáš, Jan
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