Uporaba abrazivnog vodenog mlaza za mjerenje zaostalih naprezanja u željezničkim kotačima

The paper provides a general introduction to methods of measurement of residual stresses on railway wheels. Determination of residual stress distribution is necessary for the prediction of wheel service life and possible catastrophic failure. Therefore experimental section is devoted to residual stress measurement using strain gauges according to standard EN 13262 + A1. During measurement, several segments of tested wheel were cut by abrasive water jet to detect changes of residual stresses on specified places. It was found that abrasive water jet technology can cut wheel segments faster, more accurately and with negligible mechanical and thermal load compared to mechanical cutting by band saw. Therefore the use of abrasive water jet is recommended for the measurement of residual stresses in railway wheels.The paper provides a general introduction to methods of measurement of residual stresses on railway wheels. Determination of residual stress distribution is necessary for the prediction of wheel service life and possible catastrophic failure. Therefore experimental section is devoted to residual stress measurement using strain gauges according to standard EN 13262 + A1. During measurement, several segments of tested wheel were cut by abrasive water jet to detect changes of residual stresses on specified places. It was found that abrasive water jet technology can cut wheel segments faster, more accurately and with negligible mechanical and thermal load compared to mechanical cutting by band saw. Therefore the use of abrasive water jet is recommended for the measurement of residual stresses in railway wheels.Web of Science19239038

Lukashenka’s Belarus – the Case Study of Non-Democratic Regime

The article focuses on the characterization of the identity of non-democratic regime in Post-Soviet Belarus, namely regime of A. Lukashenka. The aim is to apply classical theory of non-democratic regimes of Juan Jose Linz to Belarusian situation in last decade of the 20th century and to evaluate the limits (and convenience) of that application in regards to searching for exact classification of this regime. In this sense, the text offers the empiric-analytical analysis of contemporary Belarusian political system with the help of standard theoretical approaches of theory of non-democratic regimes

Opposition in Non-Democratic Regimes. Limits and Potential of Current Theoretical Concepts

The topic of this paper is an analysis of the term opposition (its definition and role) as an important factor within the functioning of non-democratic regimes. The paper attempts to conceptualize the term opposition in a non-democratic regime, to compare it with the general definition of that term (using a consolidated democracy as the research framework), and to evaluate existing selected theories dealing with opposition in non-democratic regimes. The aim of the paper is to identify aspects which may be problematic, as well as to evaluate the possibilities and limits for an analysis of the function of non-democratic regimes offered by the term opposition and related theories

Mono-\u3cem\u3eN\u3c/em\u3e-acyl-2,6-diaminopimelic Acid Derivatives: Analysis by Electromigration and Spectroscopic Methods and Examination of Enzyme Inhibitory Activity

Thirteen mono-N-acyl derivatives of 2,6-diaminopimelic acid (DAP)—new potential inhibitors of the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE; EC 3.5.1.18)—were analyzed and characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies and two capillary electromigration methods: capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC). Structural features of DAP derivatives were characterized by IR and NMR spectroscopies, whereas CZE and MEKC were applied to evaluate their purity and to investigate their electromigration properties. Effective electrophoretic mobilities of these compounds were determined by CZE in acidic and alkaline background electrolytes (BGEs) and by MEKC in acidic and alkaline BGEs containing a pseudostationary phase of anionic detergent sodium dodecyl sulfate (SDS) or cationic detergent cetyltrimethylammonium bromide (CTAB). The best separation of DAP derivatives, including diastereomers of some of them, was achieved by MEKC in an acidic BGE (500 mM acetic acid [pH 2.54] and 60 mM SDS). All DAP derivatives were examined for their ability to inhibit catalytic activity of DapE from Haemophilus influenzae (HiDapE) and ArgE from Escherichia coli (EcArgE). None of these DAP derivatives worked as an effective inhibitor of HiDapE, but one derivative—N-fumaryl, Me-ester-DAP—was found to be a moderate inhibitor of EcArgE, thereby providing a promising lead structure for further studies on ArgE inhibitors

Spectral analysis of metallic surfaces topography generated by abrasive waterjet

Osnovna studija topografije površina nastalih rezanjem abrazivnim vodenim mlazom izrađena je uz pomoć spektralne analize tih površina. Početni podatci su prikupljeni primjenom optičkog profilometra MicroProf FRT u obliku 2D karata visina površina. U radu se predstavljeni osnovni pojmovi spektralne analize primijenjeni na topografiju površine. Razmotrena su ograničenja postupka mjerenja. Raspravljena su iskrivljavanja površinske gustoće spektra snage. Procjena površinske gustoće spektra snage je obavljena pomoću metode periodograma u kombinaciji s Welchovom metodom. Uspoređene su površine dobivene rezanjem pomoću abrazivnog vodenog mlaza uz različite vrijednosti tehnoloških parametara rezanja. Pokazano je da se spektralnom analizom navedenih površina nude nove mogućnosti karakterizacije njihove topografije.Abasic study of a surface topography generated by an abrasive waterjet cutting is performed by means of the spectral analysis of these surfaces. The initial data were acquired by using an optical profilometer MicroProf FRTin the form of 2D maps of the surfaces\u27 heights. The basic notions of the spectral analysis applied to the surface topography are presented. Limitations of the measurement procedure are considered. Distortions of the areal power spectral density are discussed. An estimation of the areal power spectral density is carried out using a periodogram method combined with the Welch´s method. A comparison of surfaces prepared by the abrasive waterjet cutting with different values of the cutting technological parameters is performed. It has been demonstrated that the areal spectral analysis of the aforementioned surfaces offers new possibilities of their topography characterization

Measurement of Fine Grain Copper Surface Texture Created by Abrasive Water Jet Cutting

The paper presents results of experiments performed on copper with commercial purity to determine the influence of material grain size on both mechanical properties and texture of surface machined by abrasive water jet. An Equal Channel Angular Extrusion technology was used for creation of fine-grain copper samples. Hardness and grain size of fine-grain copper were measured, and, subsequently, surface of prepared copper samples was machined by abrasive water jet technology. Surface irregularities produced by the abrasive water jet were evaluated by means of surface profile roughness parameter Ra. It was found that the grain size of the material represents important factor affecting the final shape of surface topography in case of abrasive water jet machining

Ekonomska usporedba rezanja materijala pomoću lasera, plazme i kisika

This paper compares three of the most common processes: laser, plasma and oxygen cutting in terms of economical point of view. It illustrates the introduction of thermal cutting methods into the manufacturing of the companies with an emphasis on their productivity. This comparison can be carried out only to a limited extent what is given by many factors.U članku se uspoređuju tri najčešća procesa: rezanje laserom, plazmom i kisikom s ekonomskog motrišta. Članak prikazuje uvođenje metoda toplinskog rezanja u proizvodnju poduzeća s naglaskom na njihovu produktivnost. Ova usporedba može se provoditi samo u ograničenom opsegu, što je dano pomoću mnogo faktora.Web of Science19481781

Techno-economical comparison of cutting material by laser, plasma and oxygen

U članku se uspoređuju tri najčešća procesa: rezanje laserom, plazmom i kisikom s ekonomskog motrišta. Članak prikazuje uvođenje metoda toplinskog rezanja u proizvodnju poduzeća s naglaskom na njihovu produktivnost. Ova usporedba može se provoditi samo u ograničenom opsegu, što je dano pomoću mnogo faktora.This paper compares three of the most common processes: laser, plasma and oxygen cutting in terms of economical point of view. It illustrates the introduction of thermal cutting methods into the manufacturing of the companies with an emphasis on their productivity. This comparison can be carried out only to a limited extent what is given by many factors