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Characterization of fine-grained montmorillonite fractions suitable for composite preparation
Valovičová, Věra; Vaculíková, Lenka; Plevová, Eva; Dolinská, S.; Znamenáčková, I.; Danková, Z.
2019 - English
The aim of this experimental study was to characterize a fine-grained fraction of montmorillonites (SAz-2, STx-1, SWy-2 and Kunipia-F). It was investigated in order to provide more precise information of used montmorillonites than could be obtained by analysis of the unfractioned montmorillonites. At first, the fine fraction of montmorillonites were prepared by sedimentation and activation by means of Na2CO3. The prepared clay materials were characterized by the X-ray diffraction analysis and FTIR spectroscopy. The thermal behaviour of the studied samples was determinated according to the characteristic temperatures obtained from TG/DTA curves. The temperatures of dehydratation and dehydroxylation were evaluated and kinetic parameters were also calculated. The porosity and surface properties of the studied samples were gained by the nitrogen adsorption measurements. The obtained results confirmed that the fine fraction of montmorillonites could be a suitable material for subsequent preparation of composites with enhanced sorption properties, especially montmorillonite/MnO2 composite.
Keywords:
montmorillonite; activation; characterization; composites
Available in digital repository of the ASCR
Characterization of fine-grained montmorillonite fractions suitable for composite preparation
The aim of this experimental study was to characterize a fine-grained fraction of montmorillonites (SAz-2, STx-1, SWy-2 and Kunipia-F). It was investigated in order to provide more precise information ...
Cultural functions and services of geodiversity within urban areas (with a special regard on tourism and recreation)
Kubalíková, Lucie; Bajer, A.; Drápela, E.; Zapletalová, D.; Kirchner, Karel; Balková, M.; Zágoršek, K.; Kuda, František; Roštínský, Pavel
2019 - English
Geodiversity (or abiotic nature) within urban areas has numerous functions and offers various benefits and services. In addition, it has strong links to cultural heritage and historical aspects and it influences and is influenced by urban development and planning. The geodiversity functions and services can be sorted according to the ecosystem services approach: regulating, supporting, provisioning and cultural services. The last mentioned includes a wide spectrum of aspects (spiritual, religious, historical, archaeological, social, artistic, sense of place etc.) and besides this, it encompasses also the tourist and recreational functions which are (in some cases) unexplored and underestimated in urban areas. The paper presents examples from two different Czech cities – Brno and Liberec. Selected geocultural sites are described and assessed and specific proposals for tourist, recreational and educational use are outlined. The results of evaluation show that they can represent an interesting alternative to the traditional tourist destinations within urban areas.
Keywords:
geotourism; geocultural site; assessment; Brno; Liberec
Available in digital repository of the ASCR
Cultural functions and services of geodiversity within urban areas (with a special regard on tourism and recreation)
Geodiversity (or abiotic nature) within urban areas has numerous functions and offers various benefits and services. In addition, it has strong links to cultural heritage and historical aspects and it ...
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 - English
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.
Keywords:
erosion; concrete; fast flowing liquid; high-speed water jets; X-Ray CT
Available in digital repository of the ASCR
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 - English
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.
Keywords:
limit analysis; von Mises yield criterion; penalization; finite element method; Newton-like method; local mesh adaptivity
Fulltext is available at external website.
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 - English
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.
Keywords:
bentonite; composites; adsorption
Available in digital repository of the ASCR
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 - English
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.
Keywords:
smectites; intercalation; thermal analysis
Available in digital repository of the ASCR
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 ...
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 - English
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.
Keywords:
granite; fracture test; chevron notch; load–displacement diagram; effective crack model
Available in digital repository of the ASCR
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 ...
Tourist interest in illicit zone of ice caves
Nováková, Eva; Kuda, František; Kubalíková, Lucie
2018 - English
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
Keywords:
Podyji National Park; restricted area; passages monitoring
Available in a digital repository NRGL
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 ...
Geotourism within urban areas: New ways of promotion of natural and cultural heritage (Case study from Brno City).
Kubalíková, Lucie; Bajer, A.
2018 - English
Geotourism is based especially on geodiversity, but it also uses the cultural-historical aspects of an area, it is linked to the education and counts with active engagement of local people. Currently, geotourism is developed mainly within rural areas, but there are activities that point on the geodiversity and its importance within urban areas. Rational and sustainable use of geodiversity within urban areas can represent an alternative to the traditional tourist destinations and contributes to the understanding of the importance and necessity of protection of geodiversity itself. Geodiversity, respectively geoheritage within urban areas does not include only issues of primary (natural) geodiversity (substrate, Iandforms, soils), but also anthropogenic landforms and processes (secondary geodiversity), hydrological features (wells, millraces) and geodiversity ex-situ (museum collections, building material). The paper presents this new form of tourism and gives examples of selected geodiversity/geoheritage features within the Brno city.
Keywords:
geodiversity; geoheritage; urban geotourism; Brno
Fulltext is available at external website.
Geotourism within urban areas: New ways of promotion of natural and cultural heritage (Case study from Brno City).
Geotourism is based especially on geodiversity, but it also uses the cultural-historical aspects of an area, it is linked to the education and counts with active engagement of local people. Currently, ...
Assessment of anthropogenic landforms for the geotourism purposes (case study: Velké Opatovice fortification site, Archdiocese of Olomouc, Czech Republic)
Kirchner, Karel; Kubalíková, Lucie; Machar, I.
2018 - English
The human impact on the relief is often very devastating: natural landforms are modified, damaged or destroyed and the intensity of human-induced processes even surpasses the natural ones. However, people also create new landforms which are interesting from geoconservation, educational, cultural and historical points of view. Thanks to these aspects, they also have a potential for geotourism, geoeducation and recreation. For the assessment of anthropogenic landforms (respectively anthropogenic geosites and geomorphosites), a method based on the concept of geomorphosties and taking into account the holistic approach to geotourism, is proposed. The article presents an example of anthropogenic landforms on geo-cultural site Velke Opatovice fortification site situated in the western part of the Archdiocese of Olomouc. Based on the detailed fieldwork, the inventory of landforms and other features, the assessment and some proposals for geotourist use of the site are presented.
Keywords:
geo(morpho)sites; cultural heritage; Archdiocese of Olomouc
Available in a digital repository NRGL
Assessment of anthropogenic landforms for the geotourism purposes (case study: Velké Opatovice fortification site, Archdiocese of Olomouc, Czech Republic)
The human impact on the relief is often very devastating: natural landforms are modified, damaged or destroyed and the intensity of human-induced processes even surpasses the natural ones. However, ...
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