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X-Ray CT inspection of subsurface areas of concretes exposed to fast flowing liquids
Sitek, Libor; Hlaváček, Petr; Souček, Kamil; Bodnárová, L.; Foldyna, Josef; Zajícová, Vendula; Berčáková, Andrea; Foldyna, Vladimír
2019 - anglický
Concrete structures affected for a long time by flowing liquids are exposed to gradual erosion in surface layers caused by a combination of several degradation processes: abrasion, cavitation and chemical or bacterial impacts. Due to the complex phenomena and difficult-to-define initial and boundary conditions, the whole process cannot be easily simulated using the conventional computing tools. Laboratory experimental research is thus the most appropriate approach for the investigation of a suitable composition of concrete resistant to the flowing liquids. However, the methods used are often very time consuming and last even several years. High-speed water flows can be elegantly used for the acceleration of the mechanical simulation of a real situation. Several experiments on the effects of the high-speed water flows on concrete surfaces have been carried out. Using the X-Ray CT methods, subsurface structures of concretes exposed to the accelerated mechanical simulation of the erosion wear caused by fast flowing liquids were investigated and presented in the article. It has been shown that the simulation does not cause initiation of new fractures or cracks in the original concrete structure. The pure water flow mainly removes the hardened cement paste and reveals the aggregate grains. The water flow with abrasive particles disintegrates in greater depths and washes out entire aggregate grains, eventually amputates them and finally smoothens entire surface.
Klíčová slova:
erosion; concrete; fast flowing liquid; high-speed water jets; X-Ray CT
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
X-Ray CT inspection of subsurface areas of concretes exposed to fast flowing liquids
Concrete structures affected for a long time by flowing liquids are exposed to gradual erosion in surface layers caused by a combination of several degradation processes: abrasion, ...
Reliable computation and local mesh adaptivity in limit analysis
Sysala, Stanislav; Haslinger, Jaroslav; Repin, S.
2019 - anglický
The contribution is devoted to computations of the limit load for a perfectly plastic model with the von Mises yield criterion. The limit factor of a prescribed load is defined by a specific variational problem, the so-called limit analysis problem. This problem is solved in terms of deformation fields by a penalization, the finite element and the semismooth Newton methods. From the numerical solution, we derive a guaranteed upper bound of the limit factor. To achieve more accurate results, a local mesh adaptivity is used.
Klíčová slova:
limit analysis; von Mises yield criterion; penalization; finite element method; Newton-like method; local mesh adaptivity
Dokument je dostupný na externích webových stránkách.
Reliable computation and local mesh adaptivity in limit analysis
The contribution is devoted to computations of the limit load for a perfectly plastic model with the von Mises yield criterion. The limit factor of a prescribed load is defined by a specific ...
Application of bentonite-manganese oxide composites in removal of heavy metals
Dolinská, S.; Znamenáčková, I.; Tomčová, J.; Valovičová, Věra; Vaculíková, Lenka; Plevová, Eva
2019 - anglický
The paper is aimed on the using of non-homogeneous bentonites coated by manganese oxides for the removal of heavy metal cations from the water solutions. In the first stage Slovak natural bentonite was converted to sodium form using by Na2CO3 as the activating agent. After that the manganese oxides were precipitated on the surface of natural and sodium activated bentonite, respectively. The structural changes before and after the modifications of bentonites were characterized by X-ray diffraction analyses and X-ray photoelectron spectroscopy. To compare the sorption properties of the natural bentonite and modified bentonites, sorption experiments of Cd2+ from aqueous solutions were done.
Klíčová slova:
bentonite; composites; adsorption
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Application of bentonite-manganese oxide composites in removal of heavy metals
The paper is aimed on the using of non-homogeneous bentonites coated by manganese oxides for the removal of heavy metal cations from the water solutions. In the first stage Slovak natural bentonite ...
Thermal behaviour of organically modified smectites
Plevová, Eva; Vaculíková, Lenka; Valovičová, Věra; Simha Martynková, G.
2019 - anglický
The smectites were modified with different types of alkylammonium cations. The X-ray powder diffraction was used to calculate the values of the basal space of the modified smectites to confirm the intercalation of cations into the structure. The montmorillonites were also characterized by means of FTIR spectroscopy, which proved sorption or intercalation of the alkylammonium cations too. Thermal behaviour of the smectites was investigated by simultaneous thermogravimetry and differential thermal analysis. The temperatures of dehydratation and dehydroxylation and the temperatures related to total melting and recrystallization generally changed. Study of temperatures changes together with determination of kinetic parameters helped to obtained a comprehensive assessment of smectite thermal stability.
Klíčová slova:
smectites; intercalation; thermal analysis
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Thermal behaviour of organically modified smectites
The smectites were modified with different types of alkylammonium cations. The X-ray powder diffraction was used to calculate the values of the basal space of the modified smectites to confirm the ...
Effects of abrasives during accelerated simulation of mechanical corrosion of cement composites using abrasive water flow
Hlaváček, Petr; Sitek, Libor; Klichová, Dagmar; Bodnárová, L.
2019 - anglický
The paper deals with the use of the abrasive water flow technology in an accelerated simulation of the process of mechanical degradation of surface layers of cement-based composites by flowing liquids. Effects of the abrasive particle size and the mass flow rate of abrasives in an abrasive water flow impacting on the surface of concrete samples have been studied. In addition, suitability of the application of the abrasive water flow for the simulation of real situation of the surface wear by flowing liquids has been evaluated.
Klíčová slova:
cement-based composite; erosion; abrasion; cavitation; high-speed water flow; abrasive material
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Effects of abrasives during accelerated simulation of mechanical corrosion of cement composites using abrasive water flow
The paper deals with the use of the abrasive water flow technology in an accelerated simulation of the process of mechanical degradation of surface layers of cement-based composites by flowing ...
Evaluation of fracture response of Silesian granite specimens via Effective Crack Model approach and finite element analysis
Malíková, L.; Vavro, Leona; Vavro, Martin; Keršner, Z.
2019 - anglický
The paper is focused on the advanced evaluation of fracture tests of selected rock specimens. Assessment of fracture response of chevron notch cylindrical specimens of Silesian granite subjected to three-point bending test was performed. The effective crack model is used and academic software chevroncylinder (author Petr Frantík) based on the finite element method is applied for the analyses. Based on the described procedures, estimation of maximum values of the effective fracture toughness are established and discussed.
Klíčová slova:
granite; fracture test; chevron notch; load–displacement diagram; effective crack model
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Evaluation of fracture response of Silesian granite specimens via Effective Crack Model approach and finite element analysis
The paper is focused on the advanced evaluation of fracture tests of selected rock specimens. Assessment of fracture response of chevron notch cylindrical specimens of Silesian granite subjected to ...
Structural mapping of exploration boreholes walls within first phase - Safety boreholes for Boxcut
Waclawik, Petr; Souček, Kamil; Vavro, Martin; Kukutsch, Radovan; Ram, S.
2018 - anglický
Structural-geological analysis, i.e. core fracturing assessment within the boxcut safety\nborehole was carried out on the basis of optical televiewer record evaluation. In general,\noptical televiewer (OPTV) probe provides a continuous, unwrapped, high-resolution digital\n360° image of the borehole-walls oriented towards the cardinal points. This technique\nprovides information about the strike, dip direction, dip angle and depth of foliation, bedding\nplanes and fractures, as well as the frequency, aperture and infillings of fractures. Information\nabout spatial characteristics of structural elements is one of its indisputable advantages and\nallows for subsequent statistical evaluations.\nThe structural mapping of boreholes of Boxcut safety boreholes were carried out within the\ncontract of IG CAS (Contract No. D/18/156/00) GEOMET, s.r.o. (as a customer, contract No.\n01/2018). The aim of the contractual research was the realisation and interpretation of the\nfractures by digital logging of boreholes walls.
Klíčová slova:
boreholes; structural mapping; rock quality
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Structural mapping of exploration boreholes walls within first phase - Safety boreholes for Boxcut
Structural-geological analysis, i.e. core fracturing assessment within the boxcut safety\nborehole was carried out on the basis of optical televiewer record evaluation. In general,\noptical televiewer ...
Cultural heritage and geodiversity of landforms in the landscape of the Archdiocese of Olomouc
Kirchner, Karel; Kuda, František; Kubalíková, Lucie; Havlíček, M.; Machar, I.; Pechanec, V.
2018 - anglický
Within the framework of the NAKI II project – Cultural heritage of landscape of the Archdiocese of Olomouc - research, presentation and management (DGB 16P02B014), we focus on the results that will contribute to the sustainable development of regional cultural identity through applied cultural heritage research in the cultural landscape of the area of interest. As part of the material cultural heritage, we include the landforms that originated from the conscious activity of man - the anthropogenic relief forms. These landforms complement the geodiversity of the landscape and are referred to as secondary geodiversity. Therefore, their identification and interpretation will make it possible to complement and enhance the diversity of cultural heritage and to specify the development of the cultural landscape. The first results from the area of Central Moravia will be presented with the using of the historical maps, the digital model of the relief DMR5G and the field research.
Klíčová slova:
cultural heritage; secondary geodiversity; Archdiocese of Olomouc
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Cultural heritage and geodiversity of landforms in the landscape of the Archdiocese of Olomouc
Within the framework of the NAKI II project – Cultural heritage of landscape of the Archdiocese of Olomouc - research, presentation and management (DGB 16P02B014), we focus on the results that will ...
Tourist interest in illicit zone of ice caves
Nováková, Eva; Kuda, František; Kubalíková, Lucie
2018 - anglický
Ledové sluje (Ice Caves) in the Podyjí National Park represents one of the most spectacular sites within the area. It consists of the large boulder field and several pseudokarst caverns on the north-western slope of the ridge that are very important from the ecological and geomorphological point of view. The access to the site is restricted for the visitors of National Park as there exists a risk of damage and disturbance of these unique phenomena, tourist can use the marked paths leading around the site, they can reach the top part of the ridge. Currently, there are only several persons who have legal access to the site (employees of the National Park Administration and other researches with the permission issued by NP Administration). However, the installed sensor that counts the passages proved that the site is visited more frequently than it should be. The number of people who visit this site (situated within the first zone of National Park where there is no marked path and so the access is forbidden by decree) is quite alarming. Based on these findings, some proposals for the solution of this unfavourable situation are proposed and other possibilities how to avoid this undesirable phenomenon are discussed.\n
Klíčová slova:
Podyji National Park; restricted area; passages monitoring
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Tourist interest in illicit zone of ice caves
Ledové sluje (Ice Caves) in the Podyjí National Park represents one of the most spectacular sites within the area. It consists of the large boulder field and several pseudokarst caverns on the ...
European Countryside and its Perception. Book of Abstracts
Zapletalová, Jana; Vaishar, A.; Šťastná, M.
2018 - anglický
Rural area was traditionally connected with agriculture. To compare with urban, rural areas were considered to be backwarded, retarded, not worthy of an intensive research. But the situation has changed during the last years. Although cities are still centres of development within the globalization process, people in Europe abandon them as a result of the trends of suburbanization, counter-urbanization, naturbanization. We intend to pay our attention on transformation trends of the European countryside where focusing on more processes occurring there as: transformation from productive to non-productive function,from central planned to the market oriented countryside, from the mono-functional to the multifunctional one, from the national to European and globalized scale. Such a transformation generates many impacts on natural, economic and social processes occurring \nin present European countryside. Their combination creates a set of different countryside types.
Klíčová slova:
countryside; geography; Europe
Dokument je dostupný na externích webových stránkách.
European Countryside and its Perception. Book of Abstracts
Rural area was traditionally connected with agriculture. To compare with urban, rural areas were considered to be backwarded, retarded, not worthy of an intensive research. But the ...
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