National Repository of Grey Literature 17 records found  previous11 - 17  jump to record: Search took 0.01 seconds. 
Methodology for evaluation of the gear windage loss and thermal load of a tooth
Bauer, Petr ; Bartoš, Ondřej ; Hrubý, Jan ; Kordík, Jozef ; Krátký, Tomáš ; Sedlář, Milan
This report contains results of experiments identifying thermo-physical properties of a gearbox oil mist. The main part of the report studies a dependency of a gear wheel windage power loss on the radial and axial gap between the wheel and its enclosure. This parametric study relies primarily on the results coming from numerical simulations (CFD analysis). For the default enclosure configuration the evaluated power dissipation is compared with the values obtained using theoretical relationships. The theory is based on one-dimensional turbulent velocity profiles over smooth and rough surfaces. A summary of the theoretical analysis and the derivations are also included in the report.\nThe influence of a tooth shape on the windage power loss is also studied using the numerical simulations. A change of a tooth top surface angle is technologically easily realizable adjustment, and can have a positive effect on the power loss reduction. In the report there are performed simulations for varying angles of this surface and the expected improvements in aerodynamic properties are confirmed.\nThe last part of the report contains the formulation of boundary conditions for numerical evaluation of gear wheel heat balance. This information is documented more in detail in related research reports.\n
The currency derivatives and their use for hedging of currency rate risk
Bartoš, Ondřej ; Málek, Jiří (advisor) ; Staniek, Dušan (referee)
My Bachelor s thesis deals with the analysis of currency derivatives and their use for hedging of currency rate risk. In the first part (chapters 1 and 2) the thesis describes foreign exchange markets and currency rate risk. In the second part (chapters 3 to 7) the thesis describes derivative instruments, in particular currency forwards, foreign exchange swaps and currency swaps, currency futures and currency options. In my thesis I focused only on the potential of hedging currency rate risk. The bachelor s thesis is theoretical and drew from Czech book publications, foreign book publications, information sources of the financial institutions and real statistical data. Based on the combination of theoretical facts and exact data the thesis illustrates that financial derivatives offer effective solution for hedging of currency rate risk a their use prevents future financial losses of the negative development of currency rates.
Experimental research of heterogeneous nuclei in superheated steam
Bartoš, Ondřej ; Kolovratník, M. ; Šmíd, Bohuslav ; Hrubý, Jan
A mobile steam expansion chamber has been developed to investigate experimentally homogeneous and heterogeneous nucleation processes in steam, both in the laboratory and at power plants using the steam withdrawn from the steam turbine. The purpose of the device is to provide new insight into the physics of nonequilibrium wet steam formation, which is one of the factors limiting the efficiency and reliability of steam turbines. The expanded steam or a mixture of steam with a non-condensable gas rapidly expands in the expansion chamber. Due to adiabatic cooling, the temperature drops below the dew point of the steam at a given pressure. When reaching a sufficiently high supersaturation, droplets are nucleated. By tuning the supersaturation in the so-called nucleation pulse, particles of various size ranges can be activated. This fact is used in the present study to measure the aerosol particles present in the air. Homogeneous nucleation was negligible in this case. The experiment demonstrates the functionality of the device, data acquisition system and data evaluation methods.
The influence of way and intensity of grassland exploitation on sward composition and crop yield
BARTOŠ, Ondrej
The aim of this work is to assess the influences of various methods of cultivating and making use of permanent grasslands in respect of their surface structure and productivity. At the same time we have to take into account the production and extra-production importance of permanent grasslands. That is affected by exploiting different pratotechnic methods (mowing, grazing, alternate ways of cultivation, absence of cultivation) which have an effect on the formation of vegetation structure of the grass growth. One of the consequent aspects is also fytocenologic and production characteristics of the grass growth. In the work there are also methods of assessment and classification of space types and the summary of the most widespread ones mentioned. The earning capability of various growth types and proper methods of their exploiting is also an important part of the work. Permanent grasslands are main component of fodder for livestock, and throught them we can make livestock farming more effective. For the best quality and profit of grasslands is necessary proper preparing a land, mainly by manuring and mulching. Well manured grasslands give higher crop yield than unmanured. Crop yield also dependson climatic conditions and soil qualities. Plant and grass biomass presents materials of identical origin, which can be used in various branches of agriculture and industry.Using appropriate pratotechnic procedures, corresponding with ecological and economical conditions, we can expect high-quality yield. Combination of mowing and grazing appears as the most convenient utilization of grasslands. Mulching is alternative and the cheapest way of farming on not used (by mowing or grazing) grasslands, because it prevents overgrowningUtilization of grasslands a grazings must be conected with enviromental protection and should be sustainable.
Nonequilibrium condensation processes in steam turbines in the light of new measurements of heterogeneous particles
Hrubý, Jan ; Kolovratník, M. ; Ždímal, Vladimír ; Bartoš, Ondřej ; Moravec, Pavel ; Jiříček, I.
In a steam turbine, droplets are formed either homogeneously or via heterogeneous nucleation on pre-existing heterogeneous particles. In a pioneering work, the present team developed a system to measure the number and size of heterogeneous particles down to diameter of 3 nm. This work reports on measurements at Power Plant Prunéřov II. For the first time, the data is at higher parameters (0.27 MPa, 250°C), and the diffusion battery was used to determine the size distribuition of the particles, showing count-mean diameter of about 13 nm.

National Repository of Grey Literature : 17 records found   previous11 - 17  jump to record:
See also: similar author names
16 BARTOŠ, Ondrej
16 BARTOŠ, Ondřej
1 Bartoš, O.
1 Bartoš, Otakar
Interested in being notified about new results for this query?
Subscribe to the RSS feed.