Miskolc, Hungary

University of Miskolc

Miskolc, Hungary

The University of Miskolc is the largest university of Northern Hungary. Wikipedia.

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Kaptay G.,Bay Zoltan Applied Research Nonprofit Ltd. | Kaptay G.,University of Miskolc
Acta Materialia | Year: 2012

A thermodynamic model has been developed for interfacial energies of coherent interfaces using only the molar Gibbs energy and the molar volume of the two phases surrounding the interface as the initial data. The analysis is started from the simplest case of the interface formed by two solutions on the two sides of a miscibility gap, when both phases are described by the same Gibbs energy and molar volume functions. This method is applied to the fcc Au-Ni, liquid Ga-Pb and liquid Al-Bi systems. Reasonable agreement was found with the measured values in liquid Ga-Pb and Al-Bi systems. It was shown that the calculated results are sensitive to the choice of the Calphad-estimated thermodynamic data. The method is extended to the case where the two phases are described by different Gibbs energy and molar volume functions. The extended model is applied to the interface present in an Ni-based superalloy between the AlNi 3 face-centered cubic (fcc) compound and the Ni-Al fcc disordered solid solution. The calculated results are found to be similar to other values recently obtained from the combination of kinetic and thermodynamic data. The method is extended to ternary and higher order systems. It is predicted that the interfacial energy will gradually decrease with the increase in number of components in the system. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Varga G.,University of Miskolc
Key Engineering Materials | Year: 2014

In this study we analysed the process of diamond burnishing. We examined the effect of burnishing technological parameters on the surface roughness of the burnished surface, and on the improvement ratio of surface roughness. Parameters taken into consideration during examinations are burnishing speed, burnishing feed, and burnishing force. We determined a formula suitable for determination of the improvement ratio of surface roughness by the factorial experimental design which is valid in the examined parameter range. © (2014) Trans Tech Publications, Switzerland.

The end-Triassic extinction (ETE), one of the five largest Phanerozoic mass extinctions, is associated with rapid and severe environmental change, but existing data permit alternative models of causation. Volcanism in the Central Atlantic Magmatic Province (CAMP) has been proposed as the main trigger, but direct evidence for this linkage is scarce. To help constrain scenarios for the ETE and other Triassic-Jurassic boundary (TJB) events, we obtained a temporally highly resolved, multidisciplinary dataset from the Kendlbachgraben section in the Northern Calcareous Alps in Austria. The section belongs to the same paleogeographic unit (Eiberg Basin) and share similar stratigraphy with the recently selected base Jurassic Global Stratotype Section and Point at Kuhjoch. Micromineralogic study of the topmost bed of the Rhaetian Kössen Formation revealed pseudomorphs of altered, euhedral pyroxene and amphibole crystals. Their well-faceted morphology is consistent with their origin from distal mafic volcanic ash fallout. Spherical grains were also observed in the same bed, likely representing clay-altered volcanic glass. Clay minerals of this bed include low- to medium-charged smectite and Mg-vermiculite, both typical alteration products of mafic rocks. The same bed yielded a rare earth element pattern that differs from all other levels in an enrichment of heavy REEs, hinting at some minor contribution from mafic magmatic material. These features from a layer that was deposited very near to the TJB are interpreted as direct evidence of CAMP volcanism, coeval or immediately preceding the ETE and the initial negative carbon isotope anomaly. The kaolinite-dominated clay mineral spectrum of the overlying boundary mudstone records intensive weathering under hot and humid greenhouse conditions. Redox-sensitive minor and trace elements do not support the development of widespread anoxia in the studied section. Although pyrite is common in several layers, framboid size indicates formation within a reductive zone, below the sediment/water interface, rather than in an anoxic water column. Our data provide a direct link between uppermost Triassic marine strata and CAMP-derived material. They support scenarios where CAMP volcanism induced climate and other environmental change, which in turn triggered the ETE and that is also reflected in the carbon isotope anomalies. © 2012 Elsevier B.V.

Gregory J.,University College London | Barany S.,University of Miskolc
Advances in Colloid and Interface Science | Year: 2011

Polymers of various types are in widespread use as flocculants in several industries. In most cases, polymer adsorption is an essential prerequisite for flocculation and kinetic aspects are very important. The rates of polymer adsorption and of re-conformation (relaxation) of adsorbed chains are key factors that influence the performance of flocculants and their mode of action. Polyelectrolytes often tend to adopt a rather flat adsorbed configuration and in this state their action is mainly through charge effects, including 'electrostatic patch' attraction. When the relaxation rate is quite low, particle collisions may occur while the adsorbed chains are still in an extended state and flocculation by polymer bridging may occur. These effects are now well understood and supported by much experimental evidence. In recent years there has been considerable interest in the use of multi-component flocculants, especially dual-polymer systems. In the latter case, there can be significant advantages over the use of single polymers. Despite some complications, there is a broad understanding of the action of dual polymer systems. In many cases the sequence of addition of the polymers is important and the pre-adsorbed polymer can have two important effects: providing adsorption sites for the second polymer or causing a more extended adsorbed conformation as a result of 'site blocking'. © 2011 Elsevier B.V. All rights reserved.

Kaptay G.,University of Miskolc
Journal of Nanoscience and Nanotechnology | Year: 2012

The Kelvin equation, the Gibbs equation and the Gibbs-Thomson equation are compared. It is shown that the Kelvin equation (on equilibrium vapor pressure above nano-droplets) can be derived if the inner pressure due to the curvature (from the Laplace equation) is substituted incorrectly into the external pressure term of the Gibbs equation. Thus, the Kelvin equation is excluded in its present form. The Gibbs-Thomson equation (on so-called equilibrium melting point of a nano-crystal) is an analog of the Kelvin equation, and thus it is also excluded in its present form. The contradiction between the critical nucleus size (from the Gibbs equation) and the so-called equilibrium melting point of nano-crystals (from the Gibbs-Thomson equation) is explained. The contradiction is resolved if the Gibbs equation is applied to study both nucleation and equilibrium of nano-crystals. Thus, the difference in the behavior of nano-systems compared to macro-systems is due to their high specific surface area (Gibbs) and not to the high curvature of their interface (Kelvin). Modified versions of the Kelvin equation and the Gibbs-Thomson equation are derived from the Gibbs equation for phases with a general shape and for a spherical phase. Copyright © 2012 American Scientific Publishers.

Lukacs A.,University of Miskolc
Pediatric diabetes | Year: 2012

To evaluate motor performance and cardiorespiratory function in youths with type 1 diabetes in comparison with age-matched control groups and to analyze the influence of physical activity level, anthropometric and physical fitness parameters on long-term metabolic control. 106 youths with diabetes and 130 healthy youths aged 8-18 were assessed by the Eurofit test regarding motor performances, cardiorespiratory fitness (VO2max), skinfold thickness, and body mass index. Physical activity level was assessed through the use of questionnaires. Predictors of physical fitness and metabolic control were determined with regression analysis. There were no differences either in body composition or in physical activity level, but younger girls with diabetes had impaired results in speed of upper limb movement, abdominal muscle strength, upper body strength, running speed, and VO2max ; older girls with diabetes had poor results in speed of upper limb movement, abdominal muscle strength, upper body strength and VO2max . Younger boys with diabetes had impaired results in speed of upper limb movement, flexibility, static strength of hand, and abdominal muscle strength; and older boys with diabetes had poor results in speed of upper limb movement, flexibility, abdominal muscle strength, upper body strength, and VO2max compared with control groups. Older age, female gender, lower physical activity level, and higher HbA1c were significant independent predictors of poorer VO2max. Better VO2max proved to be the single predictor of favorable HbA1c . Youths with diabetes have reduced fitness parameters. Efforts should be carried out to improve physical fitness as part of treatment and care of children and adolescents with type 1 diabetes. © 2012 John Wiley & Sons A/S.

Intravenous injection of a variety of nanotechnology enhanced (liposomal, micellar, polymer-conjugated) and protein-based (antibodies, enzymes) drugs can lead to hypersensitivity reactions (HSRs), also known as infusion, or anaphylactoid reactions. The molecular mechanism of mild to severe allergy symptoms may differ from case to case and is mostly not known, however, in many cases a major cause, or contributing factor is activation of the complement (C) system. The clinical relevance of C activation-related HSRs, a non-IgE-mediated pseudoallergy (CARPA), lies in its unpredictability and occasional lethal outcome. Accordingly, there is an unmet medical need to develop laboratory assays and animal models that quantitate CARPA. This review provides basic information on CARPA; a short history, issues of nomenclature, incidence, classification of reactogenic drugs and symptoms, and the mechanisms of C activation via different pathways. It is pointed out that anaphylatoxin-induced mast cell release may not entirely explain the severe reactions; a "second hit" on allergy mediating cells may also contribute. In addressing the increasing requirements for CARPA testing, the review evaluates the available assays and animal models, and proposes a possible algorithm for the screening of reactogenic drugs and hypersensitive patients. Finally, an analogy is proposed between CARPA and the classic stress reaction, suggesting that CARPA represents a "blood stress" reaction, a systemic fight of the body against harmful biological and chemical agents via the anaphylatoxin/mast-cell/circulatory system axis, in analogy to the body's fight of physical and emotional stress via the hypothalamo/pituitary/adrenal axis. In both cases the response to a broad variety of noxious effects are funneled into a uniform pattern of physiological changes. © 2014 Elsevier Ltd.

Palmai Z.,University of Miskolc
Wear | Year: 2013

Based on studies of the physical characteristics of wear processes, the conclusion could be drawn that the cutting distance must be considered not only in abrasive and adhesive processes but also in thermally-activated diffusion and oxidation processes. Consequently, it can be proposed that a mathematical model of the rate of flank wear-an autonomous non-linear differential equation that takes into account the wear-accelerating effect of both the technological parameters of cutting and the temperature developing on the tool flank-can be applied. Furthermore, this model may be used to calculate the tool life and the Taylor formula related to any arbitrarily chosen failure criteria. Technological parameters may also change periodically or continuously depending on time. The constants of the wear equation and the apparent activation energy of the process can be determined by cutting experiments and also by measurements of wear performed during factory manufacturing under a variety of technological parameters. The complex wear equation was validated by the cutting tests performed with P20 carbide on AISI1045 carbon steel. The adverse effect of rapidly changing cutting speed on the wear of the tool during vibration could be modelled. A new theoretical model of the cutting tool's flank wear rate. The mathematical model is an autonomous non-linear differential equation. Technological parameters may also change depending on time. The measurement of wear performed during factory manufacturing. The wear equation was validated with P20 carbide on AISI1045 carbon steel. © 2013 Elsevier B.V.

Ecsedi I.,University of Miskolc
Mechanics Research Communications | Year: 2013

The Saint-Venant torsion of linearly elastic anisotropic cylindrical bars with solid and hollow cross-section is treated. The shear flexibility moduli of the non-homogeneous bar are given functions of the Prandtl's stress function of considered cylindrical bar when its material is homogeneous. The solution of the torsion problem of non-homogeneous anisotropic bar is expressed in terms of the torsion and Prandtl's stress functions of the corresponding homogeneous anisotropic bar having the same cross-section as the non-homogeneous bar. © 2013 Elsevier Ltd.

Kaptay G.,University of Miskolc
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2012

The rule of Lupis and Elliott (LE rule) proposed for the first time in 1966 is reformulated in this article as, "Real solid, liquid and gaseous solutions (and pure gases) gradually approach the state of an ideal solution (perfect gas) as temperature increases at any fixed pressure and composition." This rule is rationalized through the heat expansion of phases and loss of any interaction with increased separation between the atoms. It is shown that the rule is valid only if the standard state is selected properly, i.e., if mixing does not involve any hidden phase changes, such as melting. It is shown that the necessary and sufficient practical conditions to obey the LE rule is the equality of signs of the heat of mixing and excess entropy of mixing and the nonequality of signs of heat of mixing and excess heat capacity of mixing of the same solution. It is shown that these two conditions are fulfilled for most of the experimentally measured high-temperature solutions. The LE rule is compared with the existing laws of thermodynamics. It is shown that the LE rule can be considered as a potential fourth law of materials thermodynamics. © The Minerals, Metals & Materials Society and ASM International 2011.

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