Correlation between Surface Roughness Characteristics in CO2 Laser Cutting of Mild Steel

CO2 laser oxygen cutting of mild steel is widely used industrial application. Cut surface quality is a very important characteristic of laser cutting that ensures an advantage over other contour cutting processes. In this paper mathematical models for estimating characteristics of surface quality such as average surface roughness and ten-point mean roughness in CO2 laser cutting of mild steel based on laser cutting parameters were developed. Empirical models were developed using artificial neural networks and experimental data collected. Taguchi’s orthogonal array was implemented for experimental plan. From the analysis of the developed mathematical models it was observed that functional dependence between laser cutting parameters, their interactions and surface roughness characteristics is complex and non-linear. It was also observed that there exist region of minimal average surface roughness to ten-point mean roughness ratio. The relationship between average surface roughness and ten-point mean roughness was found to be nonlinear and can be expressed with a second degree polynomial

Abrasive Wear Resistance of the Iron- and WC-based Hardfaced Coatings Evaluated with Scratch Test Method

Abrasive wear is one of the most common types of wear, which makesabrasive wear resistance very important in many industries. Thehard facing is considered as useful and economical way to improve theperformance of components submitted to severe abrasive wear conditions, with wide range of applicable filler materials. The abrasive wear resistance of the three different hardfaced coatings (two iron‐based and one WC‐based), which were intended to be used for reparation of the impact plates of the ventilation mill, was investigated and compared. Abrasive wear tests were carried‐out by using the scratch tester under the dry conditions. Three normal loads of 10, 50 and 100 N and the constant sliding speed of 4 mm/s were used. Scratch test was chosen as a relatively easy and quick test method. Wear mechanism analysis showed significant influence of the hardfaced coatings structure, which, along with hardness, has determined coatings abrasive wear resistance

Optimization of construction design parameters of low-frequency reactors

Predmet istraživanja ove doktorske disertacije je optimizacija konstruktivnih parametara energetskih niskofrekventnih prigušnica. Predložen je novi metod proračuna veličine i broja vazdušnih procepa, dat je novi algoritam toka proračuna optimizovanih konstruktivnih parametara prigušnica sa jezgrom. Ova tematika svakako pripada aktuelnoj i značajnoj oblasti elektroenergetike, o čemu svedoče brojne međunarodne publikacije. Poslednjih godina, ova problematika dobija novi zamah usled sve većih zahteva za minijaturizacijom elemenata i sklopova koji predstavljaju sastavni deo elektromotornih pogona i postrojenja. Prigušnice u elektrotehnici imaju veliku primenu u svim sistemima gde su potrebne velike snage i mali gubici. Cilj ove disertacije je konstrukcija prigušnica sa jezgrom, koja u mnogome ima dosta zajedničkog sa transformatorima, tako da se sve optimizacione metode razvijenih za transformatore mogu primeniti u oba slučaja. Optimizacija parametara prigušnica sa jezgrom podrazumeva pronalaženje optimalnih konstruktivnih parametara za poznate vrednosti parametara induktivnosti, struje, radne frekvencije i porasta temperature. U prilog ovome, mnoge primene zahtevaju striktna ograničenja u radnoj frekvenciji i snazi pretvarača, čineći dizajn i konstrukciju prigušnica teškim zadatkom. U prvobitnom razvijenim tehnikama proračuna parametara prigušnice koristio se pristup „proizvoda površina“, čiji glavni nedostatak leži u činjenici da je zanemarena funkcionalna zavisnost gustina fluksa i struje od veličine magnetnog kola. Kasnije je ova metoda korigovana i unapređena uvođenjem zavisnosti između snage i gustine fluksa prema dimenzijama jezgra. Druge metode koriste iterativne postupke koji zahtevaju kombinovanje gustina fluksa i struje, i čineći time model najmanjih gubitaka. Neka istraživanja u tu svrhu koriste metode optimizacije putem „veštačke“ inteligencije...The scope of the research presented in this doctoral dissertation is optimization of construction parameters of low frequency reactors. A new method for calculation of number of air-gaps and number of gaps is proposed, also with new algorithm for construction parameters optimization of power reactors. This t o p i c cert ai n l y belongs t o t h e p o p u l a r and significant field of power engineering, as confirmed by numerous publications. In recent years, this topic has gained attention due to more demanding requirements regarding miniaturization of components and assemblies which are an integral part of electric drives and systems. Reactors in electrical engineering have been used in all systems where needed high power and small losses. Construction of iron-core inductor has a lot of common with transformer construction, so all optimization methods developed for transformers, could be used in both cases. Iron-core inductor design optimization implies that optimal construction parameters should be found for the known values of induction, current, working frequency and temperature increase. In addition to this, many applications require strict limitations and together with requirements in working frequency and converters’ power increasing, make inductors’ design a considerably difficult task. In early designs, the “area product” method had been utilized, wherein the main disadvantage of this method is in the fact that dependence of current and flux densities on the core size are ignored. Later, this method’s was corrected by relating quantitatively the power and flux densities to the core size. Other methods use the iterative procedure that requires the combination o f current and flux densities, which create the smallest losses in the inductor, and certain researchers use the artificial intelligence techniques..

Experimental Research Using of MQL in Metal Cutting

In this paper an effect of using of minimal quantity lubrication (MQL) technique in turning operations is presented. Experimental research was performed on carbon steel C45E. Technological parameters: depth of cut, feed rate and cutting speed were adjusted to semi-machining and roughing. Higher values ​​of feed and cutting speed were used, than recommended from literature and different types of cooling and lubrication in turning conditions were applied. As a conventional procedure and technology, lubrication with flooding was applied. As special lubrication the MQL technique was used. During research, monitoring of the cutting force, chip shape, tool wear and surface roughness was performed. Relations between parameters, material machinability and economy of process were analyzed

Sadržaj i distribucija žive (Hg) u kućnoj prašini i zemljištu grada Šida

Mercury (Hg) and potentially toxic elements (PTEs) are components of household dust and are a risk for human health. The aim of this study was to determine the concentrations of Hg and PTEs in household dust in individual housing facilities in the town of Šid, Serbia and their correlation to the content of the elements found in the surrounding garden soil. Total of 64 samples of household dust were collected from 16 locations of individual housing facilities on 4 occasions. Samples of surrounding yard and garden soil were simultaneously collected. None of the 64 analysed soil samples exceeded the threshold limit (TL) prescribed by law for non-agricultural soil, which is 0.3 mg kg-1 DM. Content of Hg in household dust was much higher than in the surrounding soil and ranged from 0.005 to 1.566 mg kg-1 DM. The resulting values of PTEs (As, B, Co, Cr, Cu, Ni, Pb, and Zn) in household dust had a significantly higher range than in the soil. Contents of Hg, B, Cu, and Zn were much higher in household dust than in the soil. According to the results of correlations of the analysed elements in household dust and surrounding soil, and according to the analysed locations, direct effect of Hg and PTEs contents on the content of the same elements in household dust was not confirmed.Živa i potencijalno toksični elementi (PTE) kao sastavni deo kućne prašine predstavljaju rizik za ljudsko zdravlje. Cilj ovog rada je utvrđivanje koncentracija Hg i PTE u kućnoj prašini, u objektima individualnog stanovanja, grada Šida i njihova veza sa sadržajem elemenata u okolnom zemljištu baštâ i okućnica. Uzeto je 64 uzorka kućne prašine na 16 lokacija individualnog stanovanja u četiri vremenska perioda. Istovremeno su uzeti uzorci okolnog zemljišta okućnicâ i baštâ. Nijedan od 64 ispitivana uzorka zemljišta ne prelazi zakonski propisanu graničnu vrednost (GV) za nepoljoprivredno zemljište od 0,3 mg kg-1 SM. Sadržaj Hg u kućnoj prašini je mnogo viši od okolnog zemljišta i kretao se u intervalu od 0,005 do 1,566 mg kg-1 SM. Dobijene vrednosti PTE (As, B, Co, Cr, Cu, Ni, Pb, Zn) u kućnoj prašini imaju statistički značajan veći raspon u odnosu na zemljište. Sadržaj Hg, B, Cu, Zn je mnogo veći u kućnoj prašini u odnosu na okolno zemljište. Prema dobijenim korelacijama posmatranih elemenata u prašini i zemljištu, kao i prema posmatranim lokacijama, generalno nije utvrđen direktni uticaj sadržaja Hg i PTE u zemljištu na sadržaj ovih elemenata u kućnoj prašini

Korelacija morfoloških i proizvodnih osobina društava medonosne pčele sa područja Srbije

State of mutual or reciprocal relationship between traits is determined by the correlation coefficients. Correlation of morphological and production traits was determined in two generations of honey bee colonies. In the first generation, mother queen bees were studied, and in the second generation, their offspring. The study of one generation lasted two years. Morphological traits were determined in the beginning of the study and production traits were determined in the spring and autumn inspections of every year. In the first generation, the positive and mostly high correlation between morphological traits, and honey yield and hygienic behavior was determined. Correlation of morphological traits, colony strength and food supplies per colony ranged from highly positive to slightly negative values. It was found that there was a high correlation between some production traits (colony strength in the spring and autumn inspections and honey yield per colony). In the analysis of offspring (second generation), most traits that were positively correlated in mother generation now, also, showed a similar relationship. The only difference, in contrast to mother generation, was that, for most traits, the intensity of interaction increased.Stanje uzajamne ili recipročne povezanosti jedne osobine od druge utvrđuje se na osnovu koeficijenta korelacije. Korelacija morfoloških i proizvodnih osobina utvrđivana je kroz dve generacije društava medonosne pčele. U prvoj generaciji praćene su majke matice, a u drugoj njihovo potomstvo. Ispitivanje po jednoj generaciji trajalo je dve godine. Morfološke osobine su utvrđene na početku praćenja generacija, a proizvodne na prolećnom i jesenjem pregledu svake godine. U prvoj generaciji utvrđena je pozitivna i mahom visoka korelacija između morfoloških osobina, prinosa meda i higijenskog ponašanja. Stepen korelacije morfoloških osobina, snage društva i zaliha hrane po društvu bio je od visoko pozitivne do slabo negativne vrednosti. Ustanovljeno je da postoji i visok stepen korelacije između pojedinih proizvodnih osobina (snaga društava na prolećnom i jesenjem pregledu i prinosa meda po društvu). Prilikom testiranja potomstva (II generacija) većina osobina koje su bile u pozitivnoj korelaciji kod roditelja i sada su pokazivala uzajamni odnos. Jedina razlika u odnosu na roditelje je u tome da se, za većinu osobina, intezitet međusobnog uticaja povećao

Diferencijacija prednjeg krila medonosne pčele iz Srbije

In this study, 12 morphological characteristics were measured on worker bee samples collected from seven different locations covering the territory of Republic Serbia. The measurement of 11 angles on the front wing and cubital index was done with stereo microscope Leica XTL-3400D, and software package IL 1009 in accordance with the standard method. The results showed significant differences between the groups of bees and investigation of angles on the forewing could be contributed to a clearer separation of groups of bees inside domestic population.U ovom istraživanju mereno je 12 morfoloških karakteristika prednjeg krila pčela radilica u skladu sa metodama Ruttner i sar. (1978). Uzorci pčela radilica su prikupljeni sa 7 različitih lokacija čime su pokriveni glavni pčelarski regioni na teritoriji Republike Srbije. Morfometrijska istraživanja pokazala su da pčele iz Zapadno Bačkog regiona u Vojvodini imaju najveću vrednost uglova B4 (113,17º), D7 (100,10º), E9 (24,28º), K19 (79,60º) i najveći kubitalni indeks (2,92). Iste pčele se na osnovu multivarijantne diskriminantne analize najviše razlikuju od grupe pčela sa Kosova. Na osnovu analize varijanse, utvrđeno je da postoji vrlo značajna razlika (P lt 0.01) u 7 morfoloških karakteristika između grupa pčela sa izabranih lokaliteta. Može se zaključiti da utvrđene vrednosti za ispitivane karaktere ukazuju na postojanje značajne varijabilnosti i impliciraju na postojanje subpopulacija uslovljenih delovanjem čoveka

MOGUĆNOSTI PRIMENE IOT TEHNOLOGIJE U STOČARSTVU I VETERINI

Internet stvari (eng. Internet of Things, IoT) je niz tehnologija za povezivanje nainternet uređaja kao što su senzori, laboratorijska i druga merna oprema koji prikupljajuinformacije od značaja i njihovo slanje prema serverima smeštenim u oblakuna kojima se vrši agregacija podataka i njihovo pretvaranje u informacije i izveštavanjenad njima prema potrebama različitih zainteresovanih strana. IoT tehnologijazasniva se na projektovanju i izradi vertikalnih rešenja za izveštavanje korisnika sistemao događajima i procesima od interesa. Poslednjih godina razvijeno je niz vertikalnihIoT rešenja u stočarstvu i veterini kojima se omogućavaju telemedicina,totalno praćenje lanaca snabdevanja prehrambenim proizvodima te informacije ozdravstvenom stanju stoke. Kao suštinski revolucionarna tehnologija, IoT bi mogaotransformisati način na koji posluje agrarni sektor, ali i način na koji se kontroliše ivrši upravljanje bezbednošću prehrambenih proizvoda

Menadžment i kontrola programa suzbijanja i eradikacije klasične kuge svinja u Srbiji

Classical swine fever (CSF) has been present in Serbia for a long period of time as an endemic disease, and it occurs with lesser or greater intensity from year to year. Since it is a highly contagious disease of domestic and wild pigs, the outbreaks of the disease causes severe consequences for animal welfare, livestock production and economic losses to the national economies in countries where it occurs. Therefore, CSF has a great epizootiological and economic importance to the swine production, primarily because of trade restrictions for live pigs and pork products. CSF eradication and control programmes are generally based on vaccination strategies in countries with endemic occurrence of CSF or non-vaccination policies in countries which successfully eradicated or are free of CSF. Whatever the general eradication strategy is in place, in the case of an outbreak of CSF the stamping-out method is used for suppression and eradication of the disease, with strict implementation of specific veterinary-sanitary measures in the infected and surveillance zones, clearly defined by legal provisions. In the period before 2006, there were certain regions in Serbia where CSF occurred almost every year, including regions where pig farming was not the primary branch of animal husbandry. Pig identification and implementation of vaccination, as well as the control of trade of pigs from infected areas to other parts of the country were not very successful. Due to the serious losses inflicted by the disease, a new Programme of CSF control was adopted in 2006, which inter alia included the obligatory identification of pigs, registration of pig holdings and free of charge vaccination of all susceptible animals in the country, as well as the implementation of other statutory measures, including obligatory evidence of veterinary activities in the national Veterinary information system. The results obtained in the period after the implementation of the Programme of CSF control (2007, 2008 and 2009) indicate a positive impact on the reduction of outbreaks of CSF, as well as on the reduction of prevalence (p lt 0.001). Also, the effectiveness of vaccination of pigs in 2007 compared to the period before and after the implementation of the Programme was the highest (97.78%), as well as the costs of its implementation.Klasična kuga svinja (KKS) je prisutna u Srbiji prisutna duži vremenski period i sa manjim ili većim intenzitetom javlja se iz godine u godinu. Kako je u pitanju infektivna bolest svinja, a polazeći od karaktera njenog širenja sama pojava bolesti nanosi velike ekonomske štete za privredu svake zemlje. Stoga KKS ima veliki epizootiološki i ekonomski značaj za svinjarsku proizvodnju, a pre svega za stvaranje nesmetane mogućnosti odvijanja prometa svinja i proizvoda od svinjskog mesa. Program kontrole KKS se može izvoditi vakcinacijom ili biti bez nje. Kod pojave bolesti se i u jednom i drugom slučaju za suzbijanje i iskorenjivanje primenjuje metod 'stamping-out', i sprovode se određene veterinarsko-sanitarne mere u zaraženom i ugroženom dvorištu koje su decidno definisane zakonskim propisima. U proteklom periodu u Srbiji su postojali određeni regioni gde se KKS javljala skoro svake godine, a naročito je bila zabrinjavajuća pojava širenja bolesti u regione gde svinjarstvo nije primarna grana stočarstva. Kontrola prometa svinja iz zaraženih područja u druge delove zemlje bila je na niskom nivou. Zbog ozbiljnih gubitaka koje je nanosila pojava bolesti, donet je novi Program kontrole KKS koji između ostalog podrazumeva obavezno obeležavanje svinja i besplatnu vakcinaciju svih prijemčivih životinja u zemlji, kao i sprovođenje drugih zakonom propisanih mera. Dobijeni rezultati u periodu posle sprovođenja Programa kontrole KKS (2008. i 2009. godine) ukazuju na pozitivan uticaj ovih mera na smanjenje pojave žarišta KKS, kao i na smanjenje prevalance (p lt 0,001). Takođe, efikasnost sprovođenja vakcinacije svinja bila je najveća (97,78%) u 2007. godini, u odnosu na period pre i posle sprovođenja Programa

Supplementary data for the article: Gligorijević, N.; Minić, S. L.; Robajac, D. B.; Nikolić, M.; Ćirković-Veličković, T.; Nedić, O. Characterisation and the Effects of Bilirubin Binding to Human Fibrinogen. International Journal of Biological Macromolecules 2019, 128, 74–79. https://doi.org/10.1016/j.ijbiomac.2019.01.124

Supplementary material for: [https://www.sciencedirect.com/science/article/pii/S014181301835880X?via%3Dihub]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2824]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/2825