Temperature and stress state of the block-braked solid wheel in operation on Yugoslav railways

Termičko opterećenje monoblok točka železničkog vozila kočenog papučama je dominantno u odnosu na ostale vrste opterećenja. To opterećenje, koje je uglavnom posledica dugotrajnog kočenja na padovima u cilju održavanja brzine je osnovni uzrok pojave pukotina na površini kotrljanja točka i, kao krajnja posledica, loma točka. U radu su dati rezultati proračunske analize termičkog opterećenja monoblok točka na odabranoj karakterističnoj deonici pruge Jugoslovenskih železnica. Proračuni temperaturnih i naponskih stanja točka rađeni su pomoću metode konačnih elemenata.Thermal load of the block-braked solid wheel railway vehicles is dominant on the other types of loads. This load, which is mainly consequence of long-term braking on downgrades for maintaining the defined constant speed purpose, is the main cause of occurrence of cracks on treads of wheel and finally fractures of wheel. The paper gives the analysis calculation results of the thermal load of the railway vehicle block-braked solid wheel on characteristic selected line on Yugoslav Railways network. Thermal analysis was done using the finite elements method, which was also used for obtaining wheel temperature and stress states in the simulated operation conditions

Temperature and stress state of the block-braked solid wheel in operation on Yugoslav railways

Termičko opterećenje monoblok točka železničkog vozila kočenog papučama je dominantno u odnosu na ostale vrste opterećenja. To opterećenje, koje je uglavnom posledica dugotrajnog kočenja na padovima u cilju održavanja brzine je osnovni uzrok pojave pukotina na površini kotrljanja točka i, kao krajnja posledica, loma točka. U radu su dati rezultati proračunske analize termičkog opterećenja monoblok točka na odabranoj karakterističnoj deonici pruge Jugoslovenskih železnica. Proračuni temperaturnih i naponskih stanja točka rađeni su pomoću metode konačnih elemenata.Thermal load of the block-braked solid wheel railway vehicles is dominant on the other types of loads. This load, which is mainly consequence of long-term braking on downgrades for maintaining the defined constant speed purpose, is the main cause of occurrence of cracks on treads of wheel and finally fractures of wheel. The paper gives the analysis calculation results of the thermal load of the railway vehicle block-braked solid wheel on characteristic selected line on Yugoslav Railways network. Thermal analysis was done using the finite elements method, which was also used for obtaining wheel temperature and stress states in the simulated operation conditions

TIME SERIES ANALYSIS: FORECASTING SALES PERIODS IN WHOLESALE SYSTEMS

The main goal of time series analysis is explaining the correlation and the main features of the data in chronological order by using appropriate statistical models. It is being used in various aspects of life and work, as well as in forecasting future product demands, service demands, etc. The most common type of time series data is the one whose observations are taken in equally distributed time intervals (daily, weekly, monthly, etc.). However, in this paper, we analyze a different kind of time series which represents product purchase moments. Thus, since there are not any regular observation periods, this irregular time series must be transformed in some way before traditional methods of analysis can be applied.  After the data transformation is complete, the next step is modeling the nonstationary time series using commonly known models such as ARIMA and PNBD, which have been chosen for their fairly easy and successful forecasting processes. The goal of this analysis is timely product advertising to a customer in order to increase sales.Unlike some other models that consider the relationship between two or more different phenomena, time series models, including ARIMA, Pareto/NBD and Poisson models, examine the impact of historical values of a single phenomenon on its present and future value. This approach enables the study of the behavior of a given phenomenon over time and produces good results, especially if a large amount of historical data is available

Rolling stock doorways compatibility with platforms at Serbian Railways

Rad prikazuje neke poteškoće koje imaju putnici pri ulasku u voz. Prikazane su i razmotrene visine perona prema međunarodnim železničkim propisima. Dat je pregled visine perona na srpskim prugama i visine poda putničkih kola, dizel i električnih višedelnih jedinica za prigradski i regionalni saobraćaj. Rad se fokusira na razlikama između politike nabavke, u odnosu na kompatibilnost ulazišta sa peronima, dizel i električnih višedelnih jedinica Železnice Srbije i posledicama ovih nabavki.This paper shows some of the passenger difficulties when boarding trains. Overview of platform heights is discussed in accordance with international railway regulation. An overview of platform heights at Serbian railway lines and floor heights of passenger coaches, diesel units and electric multiple units for suburban and regional railway transport are shown. This paper is focused on the differences between procurement policy, regarding doorway compatibility with platforms, of diesel and electric multiple units for Serbian Railways and consequences of these acquisitions

Sociological approach in managing high school violence in Serbia in the COVID - 19 postpandemic period

It is evident that the world has been grappling with violence of various kinds and levels through history. Precise analyses indicate that contemporary society views this issue from the perspectives of security and rights, emphasizing preventive action and the sanctioning of perpetrators. There are few studies that delve into the sociological aspect of violence, despite sociology being a social science which examines human relationships and interactions. Given that sociology has developed specialized branches such as cultural sociology, rural sociology, sociology of religion, business sociology, sociology of labour, sociology of sport, etc., there is a need to consider introducing sociology of violence as a branch of study that comprehensively addresses the issue of violence. This is significant as the intensity of violence not directly related to war activities is drastically increasing, even with dramatic consequences. In the light of the above, it is essential to focus attention specifically on certain types of violence and their causes. This paper draws attention to the sociological managerial aspect of high school violence in the Republic of Serbia, encompassing not only violence among students, but also violence by teachers against students, students against teachers, and violence perpetrated by parents against teachers. The research focuses on the period following the conclusion of the Covid-19 pandemic crisis in the Republic of Serbia, aiming to determine whether and to what extent the pandemic has affected violence in Serbia high schools. The aim of this paper is to highlight specific sociological phenomena that influence violence in Serbian high schools, with the intention that the research findings could be used to formulate policies and strategies against all types of violence in high schools

Seroprevalencija infekcije izazvane uzročnikom Anaplasma phagocytophilum kod pasa u Autonomnoj Pokrajini Vojvodini, Srbija.

Granulocytic anaplasmosis in dogs is a disease that is distributed worldwide, caused by the pathogen Anaplasma phagocytophilum. This disease is transmitted by ticks of the Ixodes genus. So far, no data have been published about the presence and prevalence of dog infections with A. phagocytophilum in the Autonomous Province of Vojvodina and the Republic of Serbia proper. The aim of this seroepidemiological research was to determine the seroprevalence of IgG antibodies to the agent A. phagocytophilum in the population of dogs in Vojvodina, Serbia. This seroepidemiological research involved 84 randomly selected dogs from the area of the Autonomous Province of Vojvodina. Aiming to determine the presence of antibodies of class G to the agent Anaplasma phagocytophilum, we used the indirect immunofluorescence antibody test (IFAT). By applying IFAT, in the area of the Autonomous Province of Vojvodina, Serbia, specifi antibodies of class G to agent A. phagocytophilum were found in the serums of 13/84 dogs, which points to a seroprevalence of 15.5 %. The detection of antibodies to the agent A. phagocytophilum in the dog population in the area of the Autonomous Province Vojvodina is the basis for further epidemiological, clinical and diagnostic research of this infection.Granulocitna anaplazmoza pasa proširena je diljem svijeta, a prouzročena je vrstom Anaplasma phagocytophilum. Prenosi se krpeljima roda Ixodes. Do sada u Autonomnoj Pokrajini Vojvodini i Republici Srbiji nema objavljenih podataka o prisutnosti i raširenosti infekcije pasa uzročnikom A. phagocytophilum. Cilj je ovoga seroepidemiološkog istraživanja da se utvrdi seroprevalencija IgG protutijela za A. phagocytophilum u populaciji pasa u Vojvodini, Srbija. Ovim seroepidemiološkim istraživanjem, obuhvaćena su 84 nasumično izabrana psa s područja Autonomne Pokrajine Vojvodine. U cilju utvrđivanja prisutnosti protutijela razreda IgG za A. phagocytophilum rabljen je test indirektne imunofl uorescencije (IFAT). Primjenom IFATa, na području Autonomne Pokrajine Vojvodine, Srbija, utvrđena su specifična protutijela IgG na uzročnika A. phagocytophilum u serumu 13 pasa, što predstavlja seroprevalenciju od 15,5 %. Dokaz protutijela za A. phagocytophilum u populaciji pasa na području Autonomne Pokrajine Vojvodine osnova je za daljnja epidemiološka, klinička i dijagnostička istraživanja ove infekcije

Application of the unmanned aerophotogrammetry in monitoring conditions and changes at the open pit mines

In the area of monitoring the spatial conditions and changes at the open pit mines, introduction of aerophotogrammetry with unmanned aerial vehicles significantly improves the effectivity and efficiency of the mining system monitoring in real and extended time. Since this is a relatively new technology, the paper presents our first experiences in the application of unmanned aerophotogrammetry, interesting also from the point of view of implementation into GIS systems

The effect of the refractory material on the phase transformation parameteres during forming of the Al-8wt%Si-3wt%Cu structure

Očvršćavanje legura aluminijuma se najčešće odvija u termootpornim oblogama sačinjenim ili od metala ili od oksida koji su stabilni na visokim temperaturama. Značajno različita toplotna provodljivost između metala i termootpornih oksida prouzrokuje očvršćavanje sa različitim brzinama hlađenja. U ovom radu smo formirali sekundarnu leguru Al-8wt%Si-3wt%Cu u kalupu od nerđajućeg čelika, tankozidnoj čaši od nerđajućeg čelika i debelozidnoj čaši od cirkonijum oksida. Tok formiranja očvrsle strukture je praćen zaronjenim termoparovima koji su omogućili kompjutersku analizu krive hlađenja. Parametri na koje je brzina hlađenja imala najznačajniji uticaj su vrednosti pothlađenja formiranja primarnih kristala aluminijuma, vreme rasta primarnih kristala aluminijuma i ukupno vreme očvršćavanja od pojave prvih čvrstih kristala do formiranja potpuno očvrsle strukture. Al-8wt%Si-3wt%Cu legura aluminijuma formirana u metalnim kalupima ima manju veličinu zrna i posledočno veću zateznu čvrstoću, manju makroporoznost i manje hrapavu površinu od legure formirane u oblogama od termootpornih oksida. Ispitivane termootporne obloge su uticale na formiranje tri osnovna mikrokonstituenta u Al-8wt%Si-3wt%Cu leguri u različitim vremenskim intervalima, što je dovelo do formiranja različite mikrostrukture, gde odluka o izboru materijala termootporne obloge zavisi od isplativosti celokupnog procesa, zahtevanog kvaliteta spoljnih površina i zahtevane minimalne čvrstoće konačnog proizvoda.Solidification of the aluminum alloys takes place in heat-resistant refractory materials made of either metal or oxides that are stable at high temperatures. The significantly different thermal conductivities between metals and heat-resistant oxides cause solidification with significantly different cooling rates. In this work, we formed a secondary Al-8wt%Si-3wt%Cu alloy in a stainless steel mould, a thin-walled stainless steel cup, and a thick-walled zirconium oxide cup. The course of the formation of the solidified structure was monitored by immersed thermocouples, which enabled the computer analysis of the cooling curves. The parameters on which the cooling rate had the most significant influence are the undercooling values of the formation of primary aluminum crystals, the time of the growth of primary aluminum crystals and the total solidification time from the formation of the first solid crystals to the formation of a fully solidified structure. The Al-8wt%Si-3wt%Cu aluminum alloy formed in metal mould has a smaller grain size and consequently higher tensile strength, lower macro-porosity and less rough surface than the alloy formed in refractory oxide coatings. The examined heat-resistant refractory material influenced the formation of three basic micro-constituents in the Al-8wt%Si-3wt%Cu alloy in different time intervals, which led to the formation of a different microstructure, where the decision on the choice of material for the heat-resistant refractory material depends on the profitability of the entire process, the required quality of the external surfaces and required minimum strength of the final product

Modeling of Impurities Evaporation Reaction Order in Aluminum Alloys by the Parametric Fitting of the Logistic Function

Advancements in computer capabilities enable predicting process outcomes that earlier could only be assessed after post-process analyses. In aerospace and automotive industries it is important to predict parts properties before their formation from liquid alloys. In this work, the logistic function was used to predict the evaporation rates of the most detrimental impurities, if the temperature of the liquid aluminum alloy was known. Then, parameters of the logistic function were used to determine the transition points where the reaction order was changing. Samples were heated to 610 °C, 660 °C, 710 °C, and 760 °C for one hour, after which the chemical analyses were performed and evaporation rates were calculated for Cd, Hg, Pb and Zn elements. The pressure inside the encapsulated area was maintained at 0.97 kPa. Whereas parameters that define the evaporation rate increase with the temperature increase, the maximum evaporation rates were deduced from the experimental data and fitted into the logistic function. The elemental evaporation in liquid-aluminum alloys is the best defined by the logistic function, since transitions from the first to zero-order-governed evaporation reactions have nonsymmetrical evaporation rate slopes between the lowest and the highest evaporation rate point