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

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

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

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

Primena inženjerskih softvera pri projektovanju kompozitnih komponenata vetroturbine

Zbog svojih višestrukih prednosti u odnosu na metale, primena kompozitnih materijala u proizvodnji lopatica vetroturbina je veoma rasprostranjena. Velika kompleksnost projektovanja, analize i izrade odgovornih delova od kompozitnih materijala rezultovala je pojavom brojnih softverskih alata koji se bave različitim fazama projektovanja i izrade kompozitnih delova. Korišćenjem posebnog modula za kompozitne konstrukcije u okviru programskog paketa CATIA V5 moguće je efikasno konstruisati kompozitne delove. U ovom radu prikazan je proces preliminarnog projektovanja kompozitne lopatice vetroturbine primenom paketa CATIA V5 i ukazano je na dalje mogućnosti korišćenja CATIA-e pri izradi glavnog projekta lopatice

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

High-yielding and chemically enriched maize hybrids bred in Serbia - the best basis for super quality feed and food

Introduction/purpose: This paper presents the results of several different research studies. The inbred lines ZPPL 146 and ZPPL 159 and the maize hybrids ZP 633, ZP 735, and ZP 737 are primarily intended for human and livestock nutrition. Their selection took about four decades. Methods: Spectral bands were registered using the method of resonant Raman spectroscopy of the leaves of inbred maize lines. These spectral bands indicate the conformational characteristics of not only carotenoid molecules but also other compounds (phosphate, gluten, and amide III) in the leaf. Results: A systematic examination of the inbred lines ZPPL 146 and ZPPL 159 and their maize hybrids ZP 633, ZP 735, and ZP 737 was performed in this paper. It was stated that the new inbred lines of corn, i.e. ZPPL 146 and ZPPL 159, are rich in carotenoids and yellow pigments. These lines also have significant quantities of other valuable bioactive compounds and good physical characteristics. The lines have an upright position of the top leaves and belong to the group of maize lines with significant characteristics of the photosynthetic model. They are resistant to high temperatures and are drought tolerant. Conclusion: This paper presents the relevant properties, characteristics and parameters of the new studied inbred maize lines that can be used in selection processes in the future. High-yielding and high-quality maize hybrids, i.e. ZP 633, ZP 735, and ZP 737, have been created from the mentioned inbred maize lines. They are recognizable by their qualities. The hybrid ZP633 is especially noteworthy for human consumption (children and the elderly). Further, from the agronomic-veterinary point of view, it is confirmed that the hybrids ZP 735 and ZP 737 are the most suitable for livestock feeding with the programmed use of corn silage. The relevant agronomic, morphological and nutritional properties of the maize hybrids ZP 633, ZP 735, and ZP 737 are also presented in this paper. The results regarding the grain structure and yield height for grain and silage for the hybrids ZP 677 and ZP 684, produced in Serbia and the countries of Southeastern Europe, are also given