EVALUATION OF INTERNAL COHESION OF MULTIPHASE PLASMA-SPRAYED COATINGS BY CAVITATION TEST: FEASIBILITY STUDY

Mechanical characterization of plasma-sprayed coatings at microscopic level represents a major challenge due to the presence of numerous inherent microstructural features such as cracks, pores, or splat boundaries, which complicate coatings characterization by conventional testing methods. Need for reliable testing of structural integrity of newly developed multiphase plasma-sprayed coatings introduced even more complexity to the testing. In this study, applicability of indirect vibratory cavitation test (adapted from ASTM G32 standard) for such testing was evaluated. Three plasmasprayed coatings having distinctive microstructures were tested: i) conventional alumina coating deposited from coarse powder, ii) hybrid coating deposited by co-spraying of coarse alumina powder and fine yttria-stabilized zirconia (YSZ) suspension, and iii) compact alumina coating deposited from fine ethanol-based suspension. Differences in the coatings internal cohesion were reflected in different failure mechanisms observed within the cavitation crater by scanning electron microscopy and mean erosion rates being i) 280 μm/hour, ii) 97 μm/hour and iii) 14 μm/hour, respectively

Multi-parameter approximation of stress field in a cracked specimen using purpose-built Java applications

A quality of multi-parameter approximation of the stress and displacement fields around a crack tip in a non-brittle material test specimen is studied in the paper. The stress field approximation using Williams power series is intended to be utilized for estimation of the nonlinear zone extent which potentially plays a role within methods for determination of true values of fracture parameters of materials exhibiting nonlinear failure. Considering the fact that in the case of elastic-plastic and especially quasi-brittle materials the size of this zone is substantial in comparison to the specimen dimensions, it is necessary to take a large region around the crack tip into account for this task. An automatic utility created to determine the values of coefficients of the higher order terms of Williams power series by usage of over-deterministic method applied on results of finite element analysis of arbitrary mode I test geometry is one of the tested procedures. The second one provides a backward reconstruction of the crack-tip stress field analytically by means of truncated Williams expansion. The developed procedures are based on the support of Java programming language and considerably simplify analyses of the mechanical fields’ description in a farther distance from the crack-tip. The presented research is focused on optimization of selection of FE nodal results for improvement of accuracy of the approximation

Dissolved and gaseous nitrogen losses in forests controlled by soil nutrient stoichiometry

Global chronic nitrogen (N) deposition to forests can alleviate ecosystem N limitation, with potentially wide ranging consequences for biodiversity, carbon sequestration, soil and surface water quality, and greenhouse gas emissions. However, the ability to predict these consequences requires improved quantification of hard-to-measure N fluxes, particularly N gas loss and soil N retention. Here we combine a unique set of long-term catchment N budgets in the central Europe with ecosystem 15N data to reveal fundamental controls over dissolved and gaseous N fluxes in temperate forests. Stream leaching losses of dissolved N corresponded with nutrient stoichiometry of the forest floor, with stream N losses increasing as ecosystems progress towards phosphorus limitation, while soil N storage increased with oxalate extractable iron and aluminium content. Our estimates of soil gaseous losses based on 15N stocks averaged 2.5 ± 2.2 kg N ha−1 yr−1 and comprised 20% ± 14% of total N deposition. Gaseous N losses increased with forest floor N:P ratio and with dissolved N losses. Our relationship between gaseous and dissolved N losses was also able to explain previous 15N-based N loss rates measured in tropical and subtropical catchments, suggesting a generalisable response driven by nitrate (NO3−) abundance and in which the relative importance of dissolved N over gaseous N losses tended to increase with increasing NO3− export. Applying this relationship globally, we extrapolated current gaseous N loss flux from forests to be 8.9 Tg N yr−1, which represent 39% of current N deposition to forests worldwide

Predicting sulphur and nitrogen deposition using a simple statistical method

Data from 32 long-term (1994–2012) monitoring sites were used to assess temporal development and spatial variability of sulphur (S) and inorganic nitrogen (N) concentrations in bulk precipitation, and S in throughfall, for the Czech Republic. Despite large variance in absolute S and N concentration/deposition among sites, temporal coherence using standardised data (Z score) was demonstrated. Overall significant declines of SO4 concentration in bulk and throughfall precipitation, as well as NO3 and NH4 concentration in bulk precipitation, were observed. Median Z score values of bulk SO4, NO3 and NH4 and throughfall SO4 derived from observations and the respective emission rates of SO2, NOx and NH3 in the Czech Republic and Slovakia showed highly significant (p < 0.001) relationships. Using linear regression models, Z score values were calculated for the whole period 1900–2012 and then back-transformed to give estimates of concentration for the individual sites. Uncertainty associated with the concentration calculations was estimated as 20% for SO4 bulk precipitation, 22% for throughfall SO4, 18% for bulk NO3 and 28% for bulk NH4. The application of the method suggested that it is effective in the long-term reconstruction and prediction of S and N deposition at a variety of sites. Multiple regression modelling was used to extrapolate site characteristics (mean precipitation chemistry and its standard deviation) from monitored to unmonitored sites. Spatially distributed temporal development of S and N depositions were calculated since 1900. The method allows spatio-temporal estimation of the acid deposition in regions with extensive monitoring of precipitation chemistry

Clinical Features, Outcomes, and Response to Corticosteroid Treatment of Acute Tubulointerstitial Nephritis: A Single-Centre Retrospective Cohort Study in the Czech Republic

Introduction: Acute tubulointerstitial nephritis (ATIN) is a well-recognized cause of acute kidney injury (AKI) due to the tubulointerstitial inflammation. The aim of this study was to explore the clinical features, outcomes, and responses to corticosteroid treatment in patients with ATIN. Methods: Patients with biopsy-proven ATIN, who were diagnosed between 1994 and 2016 at the Department of Nephrology, Charles University, First Faculty of Medicine, and General University Hospital in Prague, were included in the study. Patient demographics, the aetiological and clinical features, the treatment given, and the outcome at 1 year of follow-up were extracted from patient records. Results: A total of 103 ATIN patients were analysed, of which 68 had been treated with corticosteroids. There was no significant difference in the median serum creatinine 280 (169–569) µmol/L in the conservatively managed group versus 374 (249–558) µmol/L in the corticosteroid-treated group, p = 0.18, and dependence on dialysis treatment at baseline at the time of biopsy (10.3 vs. 8.6%). During the 1 year of follow-up, those ATIN patients who had been treated with corticosteroids did better and showed greater improvement in kidney function, determined as serum creatinine difference from baseline and from 1 month over 1-year period (p = 0.001). Conclusions: This single-centre retrospective cohort study supports the beneficial role of the administration of corticosteroid therapy in the management of ATIN

Pastoral Care by Jan Patočka

This thesis focuses on the key question of Patocka"s thinking - care of the soul. In Patocka"s texts it represents the difference between life based on opinions accepted without critical thinking or practical decisions, called naive life, and life based on critical examining. In my opinion, this dichotomy between the two "ways of life" makes some kind of backbone of Patocka"s Plato and Socrates interpretations in his postwar lectures. The philosopher in Patocka"s texts is Socrates. He first reveals the soul as "the most inherent nature of man", that needs to be taken care of. Aware of this Patocka approaches two other great Greek philosophers - Plato and Aristotle as well as the periods of Christianity, Renaissance and Enlightenment. This on the one hand means certain degree of adoption of Socrates" "care of the soul" but on the other hand falling away from it. In the time of Renaissance and especially during Enlightenment a new spiritual style "care of the world" is being born. This leads, according to Patocka, to such kind of understanding the being, that definite abandonment of Socrates" "care of the soul" follows, and the fixed essence of man is in jeopardy. The final part of our thesis introduces Patocka"s noteworthy idea of a victim. Only being a victim brings the genuine freedom of man, who is then..

The description and evaluation of the automation of selected technologies used for milking cattle

This Bachelor thesis is focused on automatic and conventional systems of milking cattle and further to compare fully automatic and less automatic milking systems for the cattle. In first chapter are listed basic legal standards, characteristic of milk and description of the basic elements of the milking equipment. In second chapter is described milking equipment, which are used for milking cattle. In third chapter is described milking using technology of milking robot and milking with operator. In last chapter is listed its own evaluation of individual used technologies and technological equipment with respect to the automation of selected activities

1D model of laser-assisted potential scattering

The aim of this thesis is to investigate the effect of strong ultrashort electric fields on scattering of a particle by a short range potential, using a simple one-dimensional model. The interaction potential has the form of a simple potential step. The transmission amplitude is calculated using Fourier analysis of the scattered wavefunction. The scat- tered wavefunction is obtained by solving numerically the time-dependent Schrödinger equation combining the finite difference spatial representation with the Crank Nicholson method to approximate the evolution operator. We validate and test the method on the analytically solvable problem of scattering by a potential barrier without the presence of the external field. Finally, we apply the method to calculation of laser assisted trans- mission through the potential barrier and find that transmission through the barrier can be strongly enhanced or suppressed depending on the choice of the field parameters. We provide elementary clues on interpretation of our findings.

Comparative analysis of factors influencing children's smoking

Smoking of children definitely is a huge social problem, which many governments around the world try to solve. Some of them are successful, other less. This paper focuses on the USA with the very good situation and, on the other hand, on the Czech Republic, where the situation is not so satisfactory. There are many factors that influence if a child smokes or not. And the main aim of this paper is to find the important factors in the both countries. Other aim is to compare significance of the factors' influence in the USA with the ones in the Czech Republic. Statistical description of datasets from NYTS survey in the USA in 2009 and from GYTS surveys in the Czech Republic in 2002 and 2007 show that there are less than 10% of child smokers in the age of 14 in the USA and the situation in the Czech Republic is getting better, although the amount of children who smoke is still three times higher. The influences of the factors are estimated by LPM methods, probit and logit models. American children are more affected by school class explaining danger and by other people who smoke in their presence, while the Czech children are mostly influenced by smokers among their closest friends and their parents