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Počet nalezených dokumentů:
344
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Stress state rock mass monitoring ahead of longwall No. 371 202 at 2ndA block, Mine Plant 2, OKD, a.s
Waclawik, Petr; Ptáček, Jiří; Koníček, Petr; Vavro, Martin; Staš, Lubomír; Souček, Kamil; Kukutsch, Radovan; Kajzar, Vlastimil
2015 - anglický
Generally, the accurate knowledge of the stress strain state of the rock mass in the neighbourhood of the mining galleries and underground openings is absolutely critical for their precise support designing, not only in the vicinity of them, but also at a greater distance from them if the phenomenon affecting the rock mass stress fields occurs. Measurement (investigation) of the rock stress is usually carried out by interpretation of the rock mass deformation processes, which can be relatively precisely observed and measured. The roadways are loaded not only by rock pressures in the front of the coalfaces but also by destress blasting realised in the overburden rock seam in the scope of the rockburst prevention. In addition, the rock stress distribution is influenced by old mining activities too, for example by abandoned coal pillars in the seams in overburden, respectively by goaf in the excavated seam. All of these factors can significantly affect the stress-strain behaviour of the rock mass around the mining works.
Klíčová slova:
stress state; monitoring; rock mass
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Stress state rock mass monitoring ahead of longwall No. 371 202 at 2ndA block, Mine Plant 2, OKD, a.s
Generally, the accurate knowledge of the stress strain state of the rock mass in the neighbourhood of the mining galleries and underground openings is absolutely critical for their precise support ...
Preliminary study using pulsating water jet for bone cement demolition
Hloch, Sergej; Kloc, J.; Foldyna, Josef; Pude, F.; Smolko, I.; Zeleňák, Michal; Sitek, Libor; Hvizdoš, P.; Monka, P.; Monková, K.; Kozak, D.; Stoić, A.; Sedmak, A.; Milosevic, M.; Lehocká, D.; Mihalčinová, E.
2015 - anglický
The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of bone cement which creates the interface between femoral stem and trabecular bone tissue. For investigation, commercial bone cements were used. Bone cements were tested by nanoindentation in order to review their mechanical properties. A representative sample Palacos R+G was selected for disintegration of bone cement. Bone cements samples fixed between two plexiglasses were disintegrated using ultrasonic water jet and water jet generated by self-resonating nozzle at the pressure level of 20 MPa. Visualisation of bone cement demolition was provided with high speed 1 kHz cameras with two led pulsed sources. Potential were observed for using of pulsating water jet for bone cement demoliton during femoral stem extraction.
Klíčová slova:
bone cement; ultrasonic pulsating water jet; revision arthroplasty
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Preliminary study using pulsating water jet for bone cement demolition
The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of bone cement which creates the interface between femoral stem and trabecular ...
Study of surface topography of material eroded by pulsating water jet
Klich, Jiří; Klichová, Dagmar
2015 - anglický
The paper focuses on the study of the effect of technological parameters on the topography of a surface eroded by a pulsating water jet. Parameters of the water pressure and the traversing velocity of the nozzle over the surface were observed. Effects of technological parameters were compared to the surface roughness parameters Ra, Rz, Rv, Rp, Rsk and Rku. The material tested was the aluminium alloy EN AW6060 T66. The surface was measured using an optical profilometer and further assessed using the confocal microscope based on a metallographic section.
Klíčová slova:
pulsating water jet (PWJ); surface roughness; erosion
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Study of surface topography of material eroded by pulsating water jet
The paper focuses on the study of the effect of technological parameters on the topography of a surface eroded by a pulsating water jet. Parameters of the water pressure and the traversing velocity ...
Abrasives and possibilities of increase in efficiency of abrasive waterjets
Martinec, Petr; Sitek, Libor
2015 - anglický
The contribution focuses on the research into abrasive materials and possibilities of adjustment of their properties in order to increase the efficiency of the processes of machining and cutting with abrasive waterjets. Cutting ability of commonly available garnet concentrates and nontraditional products which are starting to access to the Czech market were tested and compared. In addition, entirely new garnet products which are not commercially available yet, recycled abrasives, abrasives with various sizes of grains and heat-affected abrasives or abrasives coated with a thin plastic layer were studied.
Klíčová slova:
abrasive waterjets; abrasives; garnet; zirconia
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Abrasives and possibilities of increase in efficiency of abrasive waterjets
The contribution focuses on the research into abrasive materials and possibilities of adjustment of their properties in order to increase the efficiency of the processes of machining and cutting ...
Use of micro X-ray computed tomography for development and research into waterjets
Souček, Kamil; Sitek, Libor; Gurková, Lucie; Georgiovská, Lucie
2015 - anglický
Non-destructive methods for analysis of various types of materials have been increasingly applied recently. One of these methods is the industrial micro X-ray computed tomography (CT). This paper presents an overview of experience in using the industrial micro X-ray computed tomography during research activities at the Institute of Geonics of the CAS. It discusses possibilities of the nondestructive visualization of the inner structures of a wide range of materials and objects, including examples of its use in research and development activities related to high speed waterjets.
Klíčová slova:
micro X-ray computed tomography; inner structure of materials; porosity; defectoscopy; waterjet
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Use of micro X-ray computed tomography for development and research into waterjets
Non-destructive methods for analysis of various types of materials have been increasingly applied recently. One of these methods is the industrial micro X-ray computed tomography (CT). This paper ...
Visualisation and quantitative analysis of flat continuous water jet structure
Ščučka, Jiří; Zeleňák, Michal; Foldyna, Josef; Lehocká, D.; Votavová, H.
2015 - anglický
The results of an experiment focused on the visualisation and structural analysis of flat continuous high-speed water jet used in descaling process are presented in this paper. The aim of the work was to test the applicability of the shadowgraph technique, combined with image processing and analysis methods, to visualise the water jet structure and analyse its main quantitative parameters. Volume percentage of water and air in the water jet structure, size of droplets and water bunches and other parameters were measured on digital images taken at various distances from the nozzle outlet. Knowledge of the water jet structure below the nozzle can facilitate an optimal setting of technological conditions of the water jetting with respect to the maximum disintegration effect on treated material. The described methods can also provide important information for development of new nozzles or entire water jetting tools for disintegration of materials.
Klíčová slova:
descaling; flat continuous water jet; visualisation; shadowgraph technique; image analysis
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Visualisation and quantitative analysis of flat continuous water jet structure
The results of an experiment focused on the visualisation and structural analysis of flat continuous high-speed water jet used in descaling process are presented in this paper. The aim of the work ...
CFD model of mixture gas flow in the vacuum column 12T-70102, existing state of internals
Říha, Zdeněk
2015 - anglický
The report contains description of fluid flow for case with existing state of the column 12T -70102. Vapor flow was mainly calculated in the above mentioned geometry. In last iteration the liquid droplet (diameter 0,3mm) were injected into the geometry through the nozzle 12, see enclosure in the report. Introductory section of the enclosuere contains pictures with geometry and boundary conditions description, See figure G1. Then, slice plan follows, see figure G2. Next pictures show distribution of pressure and velocity on given slices. Pictures at the end of the enclosure show path-lines distribution and droplets particle traces distribution in the solved geometry.
Klíčová slova:
CFD model; vacuum column; gas flow
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
CFD model of mixture gas flow in the vacuum column 12T-70102, existing state of internals
The report contains description of fluid flow for case with existing state of the column 12T -70102. Vapor flow was mainly calculated in the above mentioned geometry. In last iteration the liquid ...
CDF model of mixture gas flow in the vacuum column 12T-70102, revamp tower
Říha, Zdeněk
2015 - anglický
The report contains description of fluid flow for case with revamp tower of the column 12T -70102. Vapor flow was mainly calculated in the above mentioned geometry. In last iteration the liquid droplet (diameter 0,3mm) were injected into the geometry through the nozzle 12, see enclosure in the report. Introductory section of the enclosuere contains pictures with geometry and boundary conditions description, See figure G1. Then, slice plan follows, see figure G2. Next pictures show distribution of pressure and velocity on given slices. Pictures at the end of the enclosure show path-lines distribution and droplets particle traces distribution in the solved geometry.
Klíčová slova:
CDF model; vacuum column; gas flow
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
CDF model of mixture gas flow in the vacuum column 12T-70102, revamp tower
The report contains description of fluid flow for case with revamp tower of the column 12T -70102. Vapor flow was mainly calculated in the above mentioned geometry. In last iteration the liquid ...
Regional and flash flood as a limiting factor for development
Kolejka, Jaromír; Krejčí, Tomáš; Rapant, P.; Inspektor, T.
2015 - anglický
Locating and developing factors are generally well known, studied and taken into account in the accepting of the solution. In contrast, the limiting factors of development usually stands in the background. Current data sources, knowledge and modelling technologies allow greatly anticipate the extent of the flood situation. Evaluation of the risk of regional or flash floods is not discouraging information for investors, but rather to guide their activities to a safe area. Knowledge of risk locations in the Czech Republic in terms of these types of floods also help for the safety of visitors and the local population. Appropriately incorporated findings into the development plans of all dimensions support the initiatives of local and external investors. The paper illustrates the unconventional use of public available geodata in the form of an offer vital information into regional development plans.
Klíčová slova:
flood; regional development; limiting factors; natural hazard
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Regional and flash flood as a limiting factor for development
Locating and developing factors are generally well known, studied and taken into account in the accepting of the solution. In contrast, the limiting factors of development usually stands in the ...
Concrete damaged by high temperature – possibilities of treatment with high speed water jet
Bodnárová, L.; Válek, J.; Sitek, Libor; Foldyna, Josef; Klich, Jiří
2015 - anglický
The paper describes analysis of behavior of cement based composite materials (concrete) exposed to high temperature. Recommendations for minimization of damage of thermally loaded structures are proposed and possibilities of renovation of fire damaged concrete using the technology of high speed water jet to remove damaged layers are given.
Klíčová slova:
concrete; fire; high temperature; water jet
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Concrete damaged by high temperature – possibilities of treatment with high speed water jet
The paper describes analysis of behavior of cement based composite materials (concrete) exposed to high temperature. Recommendations for minimization of damage of thermally loaded structures are ...
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