VALIDACE TERÉNNÍHO RENTGEN-FLUORESCENČNÍHO SPEKTROMETRU PRO POTŘEBY ANALÝZ PŮD, ŘÍČNÍCH SEDIMENTŮ A SUSPENDOVANÉ HMOTY

The portable X-ray-fluorescence analyser is being used for Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Ti, U, V, Zn a Zr. There is an Alpha model (Innov-X Systems, Inc) used at the Czech Geological Survey for geological mapping, contamination of the soil, stream sediment or vegetation and for geochemical purposes and environmental mapping. For the measurement the total amount of sample with 10–30 g of material was used, it means such amount of material which can cover in large measure the window of the instrument. The thickness of the measured layer varies from 3 to 20 mm. For the study purposes 100 samples was analyzed including 20 reference laboratory samples. Its specification is presented in Table 1. To compare both sets of samples the whole rock analysis of duplicate samples has to be mesasured and this kind of analysis was provided by Acme Analytical Laboratories (Vancouver) Ltd., Canada. The results shows that correlation between measurement based on XRF method and reference materials or classic laboratory measurements corresponds in a good way. The most of the evaluated components reaches acceptable relative errors by precision of the measurement. Using this instrument makes the process of samples selection for the regional environmental research or core samples measurement much easier. In a short period we can analyze the wide spectrum of components under the low cost budget

Comparison of the results of classical analytical methods with a portable X-ray fluorescence spectrometer in the map sheets 1 : 25 000 Brno-North and Mokrá-Horákov

New subchapter Geochemistry of soil cover in the chapter of the Geochemistry examines geochemical character of the forestry soils or soils that are not agriculturally used. For displaying of the results of the geochemical character of soils is best to use contour maps. For creating of contour maps is need for a large number of samples. The conventional laboratory methods of analysis are very expensive and consumed time. In addition to analysis performed conventionally laboratory methods FAAS, HGAAS and stationary XRF, these samples were analysed by the portable XRF spectrometer Alpha 4000 too. An accuracy of the portable XRF measurement was verified in five geo-referenced materials. Method of the portable XRF against to conventional laboratory methods is quick and cheap. Creating of the geochemical maps of soils 1 : 25,000 is needed to cover the whole map sheet regular grid sampling points. The results show that not all elements are measured with the same reliability. Therefore, it is appropriate to measure of the portable XRF to analyse by conventional laboratory methods about 10% of the total number of samples collected to evaluate the reliability the results.New subchapter Geochemistry of soil cover in the chapter of the Geochemistry examines geochemical character of the forestry soils or soils that are not agriculturally used. For displaying of the results of the geochemical character of soils is best to use contour maps. For creating of contour maps is need for a large number of samples. The conventional laboratory methods of analysis are very expensive and consumed time. In addition to analysis performed conventionally laboratory methods FAAS, HGAAS and stationary XRF, these samples were analysed by the portable XRF spectrometer Alpha 4000 too. An accuracy of the portable XRF measurement was verified in five geo-referenced materials. Method of the portable XRF against to conventional laboratory methods is quick and cheap. Creating of the geochemical maps of soils 1 : 25,000 is needed to cover the whole map sheet regular grid sampling points. The results show that not all elements are measured with the same reliability. Therefore, it is appropriate to measure of the portable XRF to analyse by conventional laboratory methods about 10% of the total number of samples collected to evaluate the reliability the results

On Dislocations in a Special Class of Generalized Elasticity

In this paper we consider and compare special classes of static theories of gradient elasticity, nonlocal elasticity, gradient micropolar elasticity and nonlocal micropolar elasticity with only one gradient coefficient. Equilibrium equations are discussed. The relationship between the gradient theory and the nonlocal theory is discussed for elasticity as well as for micropolar elasticity. Nonsingular solutions for the elastic fields of screw and edge dislocations are given. Both the elastic deformation (distortion, strain, bend-twist) and the force and couple stress tensors do not possess any singularity unlike `classical' theories.Comment: 28 pages, to appear in: physica status solid

Fracture mechanism simulation of inhomogeneous anisotropic rocks by extended finite element method

The vast majority of rock masses is anisotropic due to factors such as layering, unequal in-situ stresses, joint sets, and discontinuities. Meanwhile, given the frequently asymmetric distribution of pores, grain sizes or different mineralogical compounds in different locations, they are often classified as inhomogeneous materials. In such materials, stress intensity factors (SIFs) at the crack tip, which control the initiation of failure, strongly depend on mechanical properties of the material near that area. On the other hand, crack propagation trajectories highly depend on the orthotropic properties of the rock mass. In this study, the SIFs are calculated by means of anisotropic crack tip enrichments and an interaction integral are developed for inhomogeneous materials with the help of the extended finite element method (XFEM). We also use the T-stress within the crack tip fields to develop a new criterion to estimate the crack initiation angles and propagation in rock masses. To verify and validate the proposed approach, the results are compared with experimental test results and those reported in the literature. It is found that the ratio of elastic moduli, shear stiffnesses, and material orientation angles have a significant impact on the SIFs. However, the rate of change in material properties is found to have a moderate effect on these factors and a more pronounced effect on the failure force. The results highlight the potential of the proposed formulation in the estimation of SIFs and crack propagation paths in inhomogeneous anisotropic materials

Lomově-mechanické parametry obecných singulárních koncentrátorů napětí

A universal approach to assessment of general singular stress concentrtors in terms of linear elastic fracture mechanics is formulated. tentative criterion of stability suggested makes it possible to answer the question whether in the vicinity of the general singular stress concentrator the crack is initiated or not. The stability of a bi-material wedge is discussed

Zlatonosná struktura Pohronská Polhora-Krátke - nový typ Au mineralizace ve Veporidách

Import 21/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta hornicko-geologická. Institut geologického inženýrství (541