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The measurement of the velocity of abrasive particles at the suction part of the cutting head
Foldyna, Josef; Zeleňák, Michal; Klich, Jiří; Hlaváček, Petr; Sitek, Libor
2013 - English
To be able to optimize the design of the abrasive cutting head using numerical simulation, it is necessary to gather as much information about processes occurring in the cutting head as possible. The development of the numerical model of processes occurring in the abrasive water jet cutting head during the process of creation and forming of abrasive water jet is currently in progress at the Institute of Geonics in Ostrava. The verification of the model requires, among others, to determine the behaviour of abrasive particles at the input of the cutting head. Therefore, the visualisation of abrasive particles at the input using various parameters of abrasive jet and its subsequent analysis was performed using shadowgraphy (backlighting) technique and the results are presented in the paper.
Keywords:
abrasive water jet; velocity of abrasive particles; shadowgraphy
Available in a digital repository NRGL
The measurement of the velocity of abrasive particles at the suction part of the cutting head
To be able to optimize the design of the abrasive cutting head using numerical simulation, it is necessary to gather as much information about processes occurring in the cutting head as possible. The ...
Effects of pulsating water jet on materials with variously modified surface
Klich, Jiří; Klichová, Dagmar; Hlaváček, Petr
2013 - English
The paper deals with determination of erosion effects of pulsating water jet impinging the surface of aluminium alloy samples treated by various techniques (rough and fine milling, planing and rolling). The influence of the initial surface topography on the final topography of the sample exposed to pulsating water jet was investigated. Erosion of surface layer was analysed and discussed with respect to the traversing velocity of the jet. It was found, that properties of the initial surface have a significant impact on the final topography. Degree of erosion of the surface was determined by the measurement of surface parameter Ra.
Keywords:
pulsating water jet; surface topography; material erosion
Available in a digital repository NRGL
Effects of pulsating water jet on materials with variously modified surface
The paper deals with determination of erosion effects of pulsating water jet impinging the surface of aluminium alloy samples treated by various techniques (rough and fine milling, planing and ...
Study of behavior of concrete and cement based composite materials exposed to high temperatures
Bodnárová, L.; Horák, D.; Válek, J.; Hela, R.; Sitek, Libor
2013 - English
The paper describes possibilities of observation of behaviour of concrete and cement based composite material exposed to high temperatures. Nowadays, for large-scale tests of behaviour of concrete exposed to high temperatures, testing devices of certified fire testing stations in the Czech Republic and surrounding states are used. These tests are quite expensive. For experimental verification of smaller test specimens, a testing device was built at the Technical University in Brno, where tests of thermal loading of concrete tests specimens of various sizes can be carried out (dimensions up to 800 x 800 x 800 mm or slabs up to 1100 mm of length). The testing device opens new ways of observation of behaviour of concrete and cement based composite materials exposed to high temperatures as well as preparation of specimens for observation of interaction of water jet and concrete degraded by action of high temperatures.
Keywords:
concrete; high temperature; water jet
Available in a digital repository NRGL
Study of behavior of concrete and cement based composite materials exposed to high temperatures
The paper describes possibilities of observation of behaviour of concrete and cement based composite material exposed to high temperatures. Nowadays, for large-scale tests of behaviour of concrete ...
Influence of the transition area on efficiency of the water jet cutting
Říha, Zdeněk; Foldyna, Josef; Hlaváček, Petr
2013 - English
The transition area between big and small pipe diameter in the tool for water jet cutting creates subject of researching. Three kinds of transition areas were tested such as conical change, radius change and step change. The efficiency of the water jet cutting was evaluated for above mentioned transition areas. This work brings new possibilities for design of the water jet cutting tool.
Keywords:
water jet cutting; cutting trace; transition area
Available in a digital repository NRGL
Influence of the transition area on efficiency of the water jet cutting
The transition area between big and small pipe diameter in the tool for water jet cutting creates subject of researching. Three kinds of transition areas were tested such as conical change, radius ...
Present situation and development trends in the area of underground nuclear waste storage sites
Šňupárek, Richard; Kukutsch, Radovan; Koníček, Petr
2013 - English
A secure solution of nuclear power plants fuel cycle end is undoubtedly a great technical challenge facing all developed countries, using nuclear energy. High demands on safety performance target solutions are enhanced primarily by the requirement to actually "geological" life of the project period, which represents a period of about 100,000 years. Although currently is not implemented yet neither persistent storage, it is interesting to compare the solutions prepared in different countries from different aspects of natural conditions, structures, volume and time schedules or ongoing research programs. The subject paper is based on publicly available information sources, especially from the pu-blications and presentations at scientific conferences in the last 2 years.
Keywords:
nuclear waste; high-level waste repository; underground storage
Available in a digital repository NRGL
Present situation and development trends in the area of underground nuclear waste storage sites
A secure solution of nuclear power plants fuel cycle end is undoubtedly a great technical challenge facing all developed countries, using nuclear energy. High demands on safety performance target ...
Iterative solution of singular systems with applications
Blaheta, Radim; Jakl, Ondřej; Starý, Jiří; Turan, E.
2013 - English
This contribution concerns the iterative solution of singular systems which arise in many applications. Let us mention the following: - solution of PDE problems with pure Neumann boundary conditions (which is our main aim), see [7], [8], [20]. Such problems have a specific role in numerical upscaling, see [6], - solution of Neumann type subproblems in domain decomposition techniques as FETI, Neumann-Neumann, BDDC methods, see [22], [16], - analysis of Markov chain problems, computation of stochastic vector, see e.g. [18], [19], - computer tomography [15], [14] and inverse problems [4], [21].
Keywords:
iterative solution; singular systems; Neumann boundary conditions
Available in a digital repository NRGL
Iterative solution of singular systems with applications
This contribution concerns the iterative solution of singular systems which arise in many applications. Let us mention the following: - solution of PDE problems with pure Neumann boundary conditions ...
Consequences of post-war ethnically based population exchange in the Czech borderland for the regional development
Vaishar, Antonín; Dvořák, Petr; Nosková, Helena; Zapletalová, Jana
2012 - English
About 3,1 millions of Germans lived in Czechoslovakia in 1930s forming the biggest ethnical minority. This minority almost completely disappeared as a consequence of the WWII. About 300-500 thousands of them were killed in the war as soldiers of German military forces. Some dozens of thousands were killed by the Nazi regime (anti-Nazi and German Jews), about 300 thousands fled on the base of Hitler´s command, about 20-30 thousands were killed or died within "wild displacement". The majority (2,1 million) were transferred into individual occupation zones in Germany. Only established anti-Nazis, people from mixed matrimonies and indispensable experts in economic branches were allowed to stay.Excluding big cities and some inner enclaves, the majority of German population was transferred from the borderland. Before the WWII, almost all the borderland of Bohenia and Moravia was formed by German speaking regions.
Keywords:
population exchange; Czech borderland; regional development
Available in a digital repository NRGL
Consequences of post-war ethnically based population exchange in the Czech borderland for the regional development
About 3,1 millions of Germans lived in Czechoslovakia in 1930s forming the biggest ethnical minority. This minority almost completely disappeared as a consequence of the WWII. About 300-500 thousands ...
Renewable energy sources as an alternative to the new usage of brownfields
Kunc, Josef; Klusáček, Petr; Martinát, Stanislav; Tonev, P.
2012 - English
The subject of brownfields has recently become a widely discussed issue. The number of abandoned and unused facilities in the Czech Republic is quite large, which results in a number of problems. Typical example of a revitalization is a complex demolition or renewable which would give the place in question a new function. (business, administrative, residential, free-time.). Another typical example is a revitalization of the object or the area while keeping some of its original construction and functional features. An example of an "alternative solution" is to make use of brownfields in a way that would support the development of renewable sources of energy, especially solar and wind power stations, an activity that can be observed in many countries of the world.
Keywords:
brownfields; renewable energy sources; alternative usage; world; the Czech Republic
Available in a digital repository NRGL
Renewable energy sources as an alternative to the new usage of brownfields
The subject of brownfields has recently become a widely discussed issue. The number of abandoned and unused facilities in the Czech Republic is quite large, which results in a number of problems. ...
Solving an elasto-plastic problems by Newton-like methods
Byczanski, Petr; Sysala, Stanislav
2010 - English
In this contribution, we will apply the semismooth Newton methods with and without damping to solving a one-time step problem in elesto-plasticity. First, we briefly describe the elasto-plastic model and formulate the corresponding one-time step problem in the form of the non-linear variational equation. Then we characterize the used numerical methods. Finally, we illustrate the methods on a 2D numerical example.
Keywords:
elasto-plasticity; semismooth Newton method; damping
Fulltext is available at external website.
Solving an elasto-plastic problems by Newton-like methods
In this contribution, we will apply the semismooth Newton methods with and without damping to solving a one-time step problem in elesto-plasticity. First, we briefly describe the elasto-plastic ...
Using DCT/DCE In Parallel Rotor Computations
Jakl, Ondřej; Musil, Tomáš
2008 - English
Four years ago, The MathWorks, the producer of Matlab, fulfilled the wishes of many users and released the first version of the DCT/DCE tools enhancing Matlab’s capabilities towards parallel processing, to take advantage of the modern multiprocessor/multicore computer architectures. We followed DCT/DCE’s development, investigated this computing environment from the point of view of the “classical” parallel programming and took advantage of it in a set of Matlab codes for modelling of nonlinear dynamics of rotors. This paper summarizes our (throughout positive) experience. Před čtyřmi lety The MathWorks, výrobce systému Matlab, splnil přání mnoha uživatelů a vydal první verzi nástrojů DCT/DCE, které rozšířily možnosti Matlabu směrem k paralelnímu zpracování, aby byl s to využít moderních multiprocesorových a multijádrových počítačových architektur. Sledovali jsme vývoj DCT/DCE, zkoumali toto výpočetní prostředí z pohledu “klasického” paralelního programování a využili ho v kolekci matlabovských kódů pro modelování nelineární dynamicky rotorů. Příspěvek shrnuje naše (vesměs pozitivní) zkušenosti.
Keywords:
Parallel Matlab; DCT/DCE; steady-state response of rotor systems
Fulltext is available at external website.
Using DCT/DCE In Parallel Rotor Computations
Four years ago, The MathWorks, the producer of Matlab, fulfilled the wishes of many users and released the first version of the DCT/DCE tools enhancing Matlab’s capabilities towards parallel ...
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