National Repository of Grey Literature 18 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Relativistic effects in plasma produced with sub-nanosecond 3-TW laser
Krása, J. ; Klír, Daniel ; Řezáč, Karel ; Cikhardt, Jakub ; Krůs, Miroslav ; Velyhan, Andriy ; Pfeifer, Miroslav ; Dostál, Jan ; Dudžák, Roman ; Krupka, Michal ; Kaufman, J. ; Pisarczyk, T. ; Kalinowska, Z. ; Chodukowski, T.
This contribution deals with observations of relativistic electrons produced in a laser plasma interaction experiment at the PALS laser system operated at the Institute of Plasma Physics in Prague. The PALS laser is a near-infrared 3-TW iodine laser designed to deliver irradiance on target of 1016 Wcm2- in≈300 ps pulses at the wavelength of 1.315 μm. Various foils of 6 500 μm in thickness were irradiated with Iλ2 ≈5×1016 W cm-2 μm2 Under these conditions we have observed relativistic electrons expanding into the vacuum with maximum energy going beyond 4 MeV. The relativistically accelerated forward electrons escaping from the rear target surface were observed with the use of electron energy analysers. The observed electron energy spectra indicate that the applied laser intensity was increased by the thermal and relativistic self-focusing. The application of a unique femtosecond interferometry technique allowed us to observe bunches of thermal electrons occurring in the plasma expanding against the focused laser beam.
Generation of short-wavelength (<160 nm) radiation by conventional lasers
Chalupský, Jaromír ; Malý, Petr (advisor) ; Krása, Josef (referee)
The theoretical part of this diploma thesis seeks to explain the methods used for generation of coherent short-wavelength radiation. It describes the principles and the operation conditions of direct laser sources and indirect coherent radiation sources based on non-linear effects. Special attention is then paid to the short-wavelength free-electron lasers. This work summarizes properties of numerous sources of this kind. The introductory part of the thesis deals with the physical background of the generation and the manipulation of shortwavelength (VUV/XUV) radiation. The experimental part gives a summary of the results obtained at the FLASH facility (Free Electron LASer in Hamburg; earlier known as VUV FEL) operated at DESY. Methods and instrumentation used for investigating the materials damage due to laser ablation are described in this part of the thesis. UV-vis emission spectra of ablation plume were measured. Main goal is here to determine the ablation thresholds and the effective atenuation lengths in poly (methyl methacrylate) (PMMA), quartz (a-SiO2) and monocrystalline silicon irradiated with pulsed (~30fs) short-wavelength (32nm) intense laser radiation.
Bucket-wheel boom of stacker/reclaimer
Štursa, Martin ; Krása, Jakub (referee) ; Pokorný, Přemysl (advisor)
This master’s thesis deals with the construction of parts of a bucket-wheel stacker/reclaimer designed to operate lignite stockyard at coal power plant. First the basic parameters of machine and loads applied in service are defined. The work also includes the design of steel structure of bucket-wheel boom, bucket-wheel, buckets, bucket-wheel drive, shaft, bearings and other parts of bucket-wheel boom. These parts are verified by analytical or finite element analysis.
Rail undercarriage of stacker/reclaimer
Schűssel, Jiří ; Krása, Jakub (referee) ; Pokorný, Přemysl (advisor)
This diploma thesis deals with rail undercarriage of stacker/reclaimer used in thermal power plants. The paper focuses on a conceptual framework of two-track bogie rail undercarriage and on a calculation of maximal load of undercarriage wheels within operational processes. The results are used for a design of two-wheel driven bogie and its main parts. The next part of the thesis presents finite element method analysis of a designed bogie along with a projection drawing. The diploma thesis was elaborated in cooperation with a company NOEN a. s.
Drive of coal transport belt conveyor
Kliš, Kamil ; Krása, Jakub (referee) ; Pokorný, Přemysl (advisor)
This diploma thesis deals with designing a drivetrain for a coal belt conveyor. Thesis contains necessary calculations according to norms needed for determining suitable components of a belt conveyor. The goal of this diploma thesis was to design a drivetrain for a belt conveyor, all its components including a frame of the drivetrain and to create drawing documentation.
Erosion of agricultural land and its importance for siltation and eutrophication of reservoirs in the Czech Republic
Krása, J. ; Jáchymová, B. ; Bauer, M. ; Dostál, T. ; Rosendorf, P. ; Hejzlar, Josef ; Borovec, Jakub ; Bečička, M.
In 58 large catchments of the Czech Republic (covering ca 35000 km2) the sediment transport processes were assessed. Amount of sediment flux into the streams and reservoirs from agricultural land was estimated. Sediment retention in all reservoirs was considered based on reservoirs‘ outflow. For thousands of small ponds the volumes and outflow had to be estimated based on reservoir areas and specific flow rates in catchments. The distributed approach allowed considering importance of particular agricultural fields for stream silting. The maps of annual sediment flow in all streams were derived. The sediment fluxes cause serious problems not only concerning eutrophication. For example Vltava river watershed up to Slapy dam (12 965 km2) exports 2.34 million tons of sediment by water erosion annually. 626 thousand ton is exported into the streams, and 615 500 t is then deposited in the reservoirs.
Methodology for assessment of vulnerability of water reservoirs from eutrophication caused by supply of phosphorus from soil erosion
Krása, J. ; Dostál, T. ; Rosendorf, P. ; Hejzlar, Josef ; Borovec, Jakub
Vodní nádrže v ČR jsou dlouhodobě ohroženy eutrofizací (podmíněnou přebytkem dostupného fosforu), sedimentem a dále toxickými látkami (rozpuštěnými, ale často rovněž vázanými na sediment). S narůstající extrémností klimatu ve středoevropském regionu je v posledních letech zanášení nádrží ještě eskalováno. Za účelem celorepublikového posouzení rizika eutrofizace povrchových vod je řešen projekt QI102A265 „Určení podílu erozního fosforu na eutrofizaci ohrožených útvarů stojatých povrchových vod“. Metodika se skládá z několika částí: posouzení stavu trofie povrchových vod a ohroženosti nádrží; bilanční vyhodnocení jednotlivých zdrojů ve velkých povodích; kvantifikace erozního smyvu; kvantifikace transportu sedimentu do jednotlivých nádrží; určení celkového a rozpuštěného fosforu pocházejícího z eroze, resp. určení eutrofního potenciálu erozního smyvu. Stručně jsou zmíněna možná ochranná opatření proti vstupu erozního smyvu do nádrží.
Assessment of vulnerability of water reservoirs to sediment loads and eutrophication caused by soil erosion
Krása, J. ; Rosendorf, P. ; Hejzlar, Josef ; Borovec, Jakub ; Dostál, T. ; David, V. ; Ansorge, L. ; Duras, J. ; Janotová, B. ; Bauer, M. ; Devátý, J. ; Strouhal, L. ; Vrána, K. ; Fiala, D.
This methodology has the following aims: Allow any investigator to evaluate the erosion and transport of sediment phosphorus in large river basins. Allow investigators to estimate the importance of erosion for the eutrophication of the target reservoir. Allow investigators to estimate the importance of other sources of phosphorus in the watershed. Allow investigators to estimate the behavior of the other tanks in the current state of phosphorus loads from the watershed. The methodology is focused on solutions in large river basins.

National Repository of Grey Literature : 18 records found   1 - 10next  jump to record:
See also: similar author names
6 Krása, J.
1 Krása, Jakub
2 Krása, Josef
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