Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 100 )

2018 ( 577 )

2017 ( 582 )

2016 ( 925 )

Custom range...

Search Results: 1 - 10 of 458883 matches for " Ján Vl?ko "
All listed articles are free for downloading (OA Articles)
Page 1 /458883
Display every page Item
Pou ití logistické regrese pro hodnocení náchylnosti k sesouvání ve st ední ásti Ch ib ( eská republika)
Ale? Havlín,Martin Bednarik,Barbora Magulová,Ján Vlko
Acta Geologica Slovaca , 2011,
Abstract: The paper presents use of logistic regression and analysis tools implemented in the Geographic Information System (GIS) environment for landslide susceptibility assessment. As a case study, the middle part of the Chriby Mountains (Czech Republic) widely affected by landslides was selected, with a total area of 147 km2. The landslide susceptibility assessment is based on the comparison and statistical elaboration of territorial dependence on input factors influencing the instability of the slopes. In this study, the lithology, slope angle, distance to stream, hypsographic level, and the current land cover were evaluated as the factors influencing slope stability and their susceptibility to sliding. The comparison shows that the high susceptibility to sliding is primarily in the areas of potential landslides and active, while 62 % of existing slope failures are created in areas highly susceptible to sliding, 32 % are in areas susceptible to moderate sliding. The remaining 6 % of the landslides are located in low areas prone to sliding. This may be the accumulation parts of landslide bodies. An overall assessment of the 33 % of the area can be classified as having a high degree of susceptibility to the sliding surface and 35 % as moderately susceptible to landsliding. Low degree of susceptibility to sliding represents the remaining 32 % area of the territory.
Distribúcia teploty, jej re im a h bkovy dosah v travertínovom masíve podlo ia Spi ského hradu
Martin Br?ek,Ján Vlko,Zuzana Kompaníková,Vladimír Greif
Acta Geologica Slovaca , 2011,
Abstract: The main goal of this paper is to illustrate some causal phenomena acting in nearby surface of the rock mass from the viewpoint of permanent factor temperature, or more precisely temperature change. Authors submit long-time research information about temperature regime in the travertine rock mass forming the subgrade of the Spi Castle. The research has shown that diurnal temperature changes influence mainly superficial parts of rock mass (to the depth of 1.5 m), deeper parts of rock mass are influenced by temperature change with longer time period, e.g. annual time period. Simultaneously,relation between moisture or saturation of the rock mass and temperature change with the depth within rock mass was determined. From these relations it was found out, that the precipitation rate higher than 1.5 mm.day-1 increased the depth of diurnal temperature changes by 0.3 m as compared to the period without precipitation.
Laboratory simulation of temperature changes by insolation and fire and their influence on physical properties of travertines
Zuzana Kompaníková,Ján Vlko,Martin Br?ek,Jana Michňová
Acta Geologica Slovaca , 2012,
Abstract: The influence of insolation and fire represents important factor for study of historical object destruction. The results have shown that temperature changes by insolation (60°C) and fire (200, 400, 600, and 800°C) significantly contributed to the change of physical properties of Slovak travertine from Spi ské Podhradie and Ludrová. Research was oriented not only on a visual change of rocks (colour change, brightness and surface roughness), but also on the quantitative and qualitative analyses of mineral composition, connected with structural changes as well as study of selected physical properties. The micropetrographic study indicated that increasing of temperature was followed by expand of fractures as reflected even change of true and specific bulk density. Significant increase of microcracks was determined at 600°C by optical microscopy. The macroscopic observation of microcracks was visible at 800°C subsequently followed by destruction of samples. By spectrophotometry was visible colour change by increasing of temperature. The brightness of travertine samples was decreasing till 600°C, but after 600°C it became markedly increasing. With increasing of temperature travertine surface samples had also change from a few hundred nanometres to several microns. The investigation of thermal decay by insolation and fire may lead to an improved assessment of natural building stones that have been used as building and decorative stone on ancient monument.
The moisture – a negative deterioration factor of rock mass
Martin Br?ek,Ján Vlko,?udovít Kubi?ár,Vlastimil Bohá?
Acta Geologica Slovaca , 2009,
Abstract: The rock mass deterioration is caused by exogenous factors from which the main role play the temperature and moisture content. A monitoring system of the rock moisture content based on the transient Hot-ball method of measuring of the thermal conductivity of materials was installed on the Perún`s rock at the Spi Castle. So called, hot ball method was used for the estimation of the water content in various depths inside the rock mass in order to assess its effect on the temperature penetration depth beneath the surface, which might control the volumetric change (dilation) of the rock cliff and its stability. The preliminary results showed relation between q/Tm index and the precipitation registered by the nearby meteorological station. This dependence was manifested in the near subsurface parts of the rock face while the deeper sensors were not influenced. This suggests that the surface parts of the travertine rock body are more prone to the temperature dilation effects and therefore the thermal flux through the upper 40 cm of rock is faster than through the deeper parts.
Monitoring of travertine changes resulting from thermal load
Zuzana Kompaníková,Tatiana Durmeková,Ján Vlko,Martin Br?ek
Acta Geologica Slovaca , 2011,
Abstract: Travertines, despite of their unique noble appearance change their properties when affected by ageing like any other building and decorative stone. Some of the most noticeable changes are influenced by temperature fluctuations. From this point of view, the main purpose of presented research was to determine the influence of multiple temperature cycles for travertine from Spi ské Podhradie and Ludrová in temperature range of 25°C to 60°C corresponding to summer period temperature regimes. The weakening of the rock material by heating was determined by non-destructive techniques before and after thermal load. By ultrasound apparatus was observed by means of ultrasonic velocities change, when higher values of ultrasonic velocities were determined parallel to the bedding while the perpendicular direction had slower velocities. The change of colour was specified by spectrophotometer and no distinct visual colour change was determined with increasing temperature. By non-contact profilometer surface roughness data of samples profiles primarily indicate a decrease of roughness during heating. The coefficient of linear thermal expansion acquired by thermodilatometer varied from 4.6.10-3 to 7.8.10-3 mm.m-1.°C-1 for travertine from Spi ské Podhradie and 5.3.10-3 to 7.3.10-3 mm.m-1.°C-1 for travertine from Ludrová. This parameter characterizes the materials response to heating or cooling. The techniques mentioned above are non-destructive and some of them are innovative in laboratory testing.
Ko??álik Ján
Acta Montanistica Slovaca , 1997,
Abstract: Loesses in Western Carpathians cover the area of 7 000 square kilometres. The difference of paleographic relations between Eastern and Western Slovakia during the course of Pleistocen is reflected in their morphology, litotype, physical, chemical, and geocnemic properties, in the composition of extraction minerals, in the content of CaCO3, in the character of malacofauna, and the typology of fossile soils. To achieve the thickness of l-5-20 m, a maximum thickness being 35 to 40 m. Eolic sands can be found in the Záhorská ní ina lowlands, Podunajská rovina flatland, and East-Slovakian lowland. Morphologically, they form 5-20 m high piles of parabolic and longitudinal form. Winds from various directions were active in their formation. The association of extraction minerals proves that these had been blown out from neogene sediments of the nearby vicinity and from river sediments of the Morava, Danube, and Tisa rivers and their tributaries.
Ad Alta : Journal of Interdisciplinary Research , 2011,
Abstract: The paper introduces the basic calibration procedures of selected surveyinginstruments and ancillary equipment (digital levels and bar code levelling staffs, totalstations and electronic tacheometers, reflective systems). The results from testing ofthe light influence on work of digital level are presented. The testing procedure andresults of the calibration of horizontal circles of the surveying instruments on thecalibration device in the Slovak Institute of Metrology in Bratislava are introduced aswell.
Ovarian Follicular Atresia of Ewes during Spring Puerperium
Radoslava Vl?ková,Drahomíra Sopková,Ján Po?ivák,Igor Valocky
Veterinary Medicine International , 2012, DOI: 10.1155/2012/638928
Abstract: The distribution of healthy and atretic follicles on the ovarian surface of improved Valachian ewes 17, 24, and 32 days postpartum is reported in this study. The number of healthy follicles was higher on day 24 postpartum and their mean diameter tended to increase to day 32 ( ) with the greatest diameter of 5?mm. 78–81% of atretic follicles ≥3?mm in diameter was observed where apoptosis began in the follicular cells situated at the follicular cavity. The early atretic follicles are characterized by the presence of mitotic pictures. In one ewe 24 days postpartum, small regressive follicular cysts were observed. Contracting atresia is characterized by thickening of the theca interna even to 190?μm. Progesterone and oestradiol-17 concentrations were maintained at relatively low levels, but with no significant difference between the days postpartum. 1. Introduction Folliculogenesis progresses in the postpartum period of ewes similarly as in cows [1–3]. In our latitude (48° 40′ 0′′N), the first ovulation after parturition is determined by many factors and may occur 60–70 days at the earliest after lambing, but generally appears in the autumn mating season. Only a few hundred follicles mature throughout the life of an ewe and the others undergo atresia, which occurs in 99.9% of mammals [4–7]. Follicular atresia in themajority of mammals is primarily induced by programmed cell death or apoptosis of granulose and theca cells. Apoptosis is characterized by the fragmentation of internucleosomal DNA, reduction of cell mass, bubbling of the cytoplasmic membrane, and formation of apoptotic bodies [8]. Apoptosis of the granulose cells relates to imbalance between oestradiol and progesterone (E2↓, P4 ↑) in the follicular fluid [9–11], which stimulates the atresia formation [7, 12]. The concentration of IGF-I is the crucial factor deciding whether the follicle matures or undergoes atresia [9, 10, 13]. There are three basic types of atresia described in cattle—early, definite, and late [14–16]. Marion et al. [14] indicated some thickening of granulose and theca layers in various types of atresia in cattle, but there are no reports of this in ewes. The aim of this study was to observe the distribution of healthy and atretic follicles on the ovaries of ewes in the spring puerperal period, and to establish whether these parameters relate to thickening of the granulose and theca layers of healthy follicles and specific types of atresia, and with hormonal concentrations in the blood (progesterone, oestradiol- ). 2. Materials and Methods 2.1. Animals The experiments were
Synthesis and Molecular Structure of Methyl 4-O-methyl-α-D-glucopyranuronate
Ján Hirsch,Vratislav Langer,Miroslav Koó?
Molecules , 2005, DOI: 10.3390/10010251
Abstract: A method for the preparation of methyl 4-O-methyl-α-D-glucopyranuronate andits single crystal X-ray structure determination are reported. The molecule adopts an almostideal 4C1 (OC3) conformation.
Possibilities of eliminating the refraction influence on the trigonometric elevation measurement
?tefan Sokol,Ján Je?ko
Acta Montanistica Slovaca , 2005,
Abstract: The most of geodetic measurements are carried out in the lowest non-stable air levels over the terrain, which are very difficult and change in time with the optical environment. These air levels are approximately parallel with the earth surface, reaching the elevation of several metres, and about 99 % of all geodetic measurements are realized here. In the last years there was a great development in the area of constructional solution of measuring instruments. Modern electronic theodolites of the highest accuracy class reach the accuracy of direction (angle) measurement of 0,1 – 0,2 mgon and electronic rangefinders more than 0,5 mm for 1 – 2 km distances. That’s why the situation rise up where the important source of systematic errors in the measuring process are not instrumental errors but errors of the environment, in which is the measuring process realized. Because of this high accuracy of geodetic instruments, the refraction influence is a base limiting factor of increasing the measurement accuracy. In the past, the refraction influence was mostly neglected in the engineering geodesy but, in a present, requirements are given on a higher accuracy. That’s why various theoretical refraction models and practical inspecting processes are used, which enable us to decrease the refraction influence on the measured values.
Page 1 /458883
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.