Analysis of stress-strain state of bucket wheel excavator revolving platform structure: Fundament of efficient reconstruction

Rotorni bageri čine okosnicu sistema mehanizacije površinskih kopova Njihova eksploatacija u ekstremno teškim uslovima prouzrokuje otkaze delova noseće konstrukcije (plastične deformacije, prsline, pukotine, lomovi). Kao konkretni primeri, u radu su najpre prikazani izgledi tipičnih oštećenja konstrukcija obrtnih platformi bagera TAKRAF SRs 1200×24/4 (400 kW) + VR. Potom su izloženi postupci proračuna njihove konstrukcije čiju osnovu čine dve etape: formiranje konačno elementnih mreža i analiza opterećenja. Sprovođenjem izložene procedure proračuna, oblikovano je konstrukciono rešenje primenjeno prilikom rekonstrukcije obrtnih platformi dva bagera pomenutog tipa tokom 2005. godine. O valjanosti pristupa problemu i uspešnosti rešenja rekonstrukcije uverljivo govori podatak da su, nakon sanacije i rekonstrukcije, bageri otkopali više od 5 000 000 m3 otkrivke, a da pri tome, u zonama rekonstrukcije, nisu konstatovani bilo kakvi defekti konstrukcija obrtnih platformi.Bucket wheel excavators (BWE) are a part and parcel of the mechanization system in open pits. Their exploitation in heavy duty conditions causes failures of supporting structural parts (plastic deformations, cracks fractures, break-ages). As a real example, the paper first presents appearance of typical damages of revolving platform structures for BWE TAKRAF SRs 1200×24/4 (400 kW) + VR. Subsequently, techniques for calculating their structure are presented, whose basis is made in two stages: set up of finite element mesh and analysis of loads. The structural solution is developed by conducting the presented calculation procedure, and is applied during reconstruction of revolving platforms (2005) on two BWEs mentioned before. Validity of problem approach and efficiency of reconstruction solution is found in the fact that after reconstruction and repair BWE have excavated more than 5 000 000 m3 of barren soil, while at reconstruction zones no defects of revolving platform structures have been detected

Analysis of stress-strain state of bucket wheel excavator revolving platform structure: Fundament of efficient reconstruction

Rotorni bageri čine okosnicu sistema mehanizacije površinskih kopova Njihova eksploatacija u ekstremno teškim uslovima prouzrokuje otkaze delova noseće konstrukcije (plastične deformacije, prsline, pukotine, lomovi). Kao konkretni primeri, u radu su najpre prikazani izgledi tipičnih oštećenja konstrukcija obrtnih platformi bagera TAKRAF SRs 1200×24/4 (400 kW) + VR. Potom su izloženi postupci proračuna njihove konstrukcije čiju osnovu čine dve etape: formiranje konačno elementnih mreža i analiza opterećenja. Sprovođenjem izložene procedure proračuna, oblikovano je konstrukciono rešenje primenjeno prilikom rekonstrukcije obrtnih platformi dva bagera pomenutog tipa tokom 2005. godine. O valjanosti pristupa problemu i uspešnosti rešenja rekonstrukcije uverljivo govori podatak da su, nakon sanacije i rekonstrukcije, bageri otkopali više od 5 000 000 m3 otkrivke, a da pri tome, u zonama rekonstrukcije, nisu konstatovani bilo kakvi defekti konstrukcija obrtnih platformi.Bucket wheel excavators (BWE) are a part and parcel of the mechanization system in open pits. Their exploitation in heavy duty conditions causes failures of supporting structural parts (plastic deformations, cracks fractures, break-ages). As a real example, the paper first presents appearance of typical damages of revolving platform structures for BWE TAKRAF SRs 1200×24/4 (400 kW) + VR. Subsequently, techniques for calculating their structure are presented, whose basis is made in two stages: set up of finite element mesh and analysis of loads. The structural solution is developed by conducting the presented calculation procedure, and is applied during reconstruction of revolving platforms (2005) on two BWEs mentioned before. Validity of problem approach and efficiency of reconstruction solution is found in the fact that after reconstruction and repair BWE have excavated more than 5 000 000 m3 of barren soil, while at reconstruction zones no defects of revolving platform structures have been detected

Different aspect of sustainable use of fish resources in Serbia for the period 2006-2017

Ovaj rad ima za cilj da ustanovi koja je uloga zakona u dobrom upravljanju ribolovnim resursima. Zaštita i održivo korišćenje ribljeg fonda u Srbiji regulisano je istoimenim zakonom, a odvija se na 17 ribarskih područja i 29 ribarskih područja u zaštićenim prirodnim dobrima. Na 17 osnovnih ribarskih područja upravljaju „javna preduzeća“ ili privatne firme u statusu „doo“. Kod većih područja, posebno u Vojvodini, postoji više upravljača za jedno ribarsko područje. U zaštićenim prirodnim dobrima upravljači su ujedno i korisnici ribljeg fonda. U periodu od 2006. do 2017. godine Zakon o zaštiti i održivom korišćenju ribljeg fonda menjan je u dva navrata: 2009. i 2014. godine. Podzakonska akta su takođe podložna vrlo čestim promenama. U radu se prate efekti promene zakonske regulative na broj rekre ativnih i profesionalnih ribolovaca, broj ribočuvara i trendove u ulovima. Osnovni trendovi su da broj rekreativnih ribolovaca u navedenom periodu opada, broj profesionalnih riba ra stagnira, dok broj ribočuvara raste. Ulov ima tendenciju opadanja za sve vrste koje se statististički prate (šaran, som, smuđ i deverika od autohtonih vrsta, i babuška i tolstolobik od alohtonih). Odnos ulova u rekreativnom i komercijalnom ribolovu pokazuje značajne promene u poslednjih desetak godina: osim za tolstolobika, kod koga dominira komer cijalni ulov, kod ostalih vrsta je došlo do zamene u smislu da rekreativni ulov preuzima dominaciju u poslednjih nekoliko godin

Genetic differentiation of European grayling (Thymallus thymallus) populations in Serbia, based on mitochondrial and nuclear DNA analyses

<p>Abstract</p> <p>Background</p> <p>The structure and diversity of grayling (<it>Thymallus thymallus</it>) populations have been well studied in most of its native habitat; however the southernmost populations of the Balkan Peninsula remain largely unexplored. The purpose of this study was to assess the genetic diversity of Serbian grayling populations, detect the impact of stocking and provide guidelines for conservation and management.</p> <p>Methods</p> <p>Eighty grayling individuals were collected from four rivers (Ibar, Lim, Drina and Rzav). The mitochondrial DNA control region (CR; 595 bp of the 3'end and 74 bp of flanking tRNA) and the ATP6 gene (630 bp fragment) were sequenced for 20 individuals (five from each locality). In addition, all individuals were genotyped with 12 microsatellite loci. The diversity and structure of the populations as well as the recent and ancient population declines were studied using specialized software.</p> <p>Results</p> <p>We detected three new haplotypes in the mtDNA CR and four haplotypes in the ATP6 gene of which three had not been described before. Previously, one CR haplotype and two ATP6 gene haplotypes had been identified as allochthonous, originating from Slovenia. Reconstruction of phylogenetic relations placed the remaining two CR haplotypes from the River Danube drainage of Serbia into a new clade, which is related to the previously described sister Slovenian clade. These two clades form a new Balkan clade. Microsatellite marker analysis showed that all four populations are genetically distinct from each other without any sign of intra-population structure, although stocking of the most diverse population (Drina River) was confirmed by mtDNA analysis. Recent and historical population declines of Serbian grayling do not differ from those of other European populations.</p> <p>Conclusions</p> <p>Our study shows that (1) the Ibar, Lim and Drina Rivers grayling populations are genetically distinct from populations outside of Serbia and thus should be managed as native populations in spite of some introgression in the Drina River population and (2) the Rzav River population is not appropriate for further stocking activities since it originates from stocked Slovenian grayling. However, the Rzav River population does not represent an immediate danger to other populations because it is physically isolated from these.</p

Parasitofauna of freshwater fishes in the Serbian open waters: a checklist of parasites of freshwater fishes in Serbian open waters

As a result of freshwater fish parasitofauna investigations, throughout the past 75 years, the number of parasitic species is presented. This paper reviews the history, current state, and tendencies of the fish parasitofauna studies in Serbian open waters. Up to now, in total 170 parasitic species have been reported. Systematic parasitofauna investigations have been carried out on 54 freshwater fish species in waters of the Danube River Basin in Serbia, also in hill-mountanious watercourses, lakes and salmonid fishpond of Sjenicko-Pesterska plateau (south-west region of Serbia), Homolje area (east Serbia), and in Vlasina lake (south-east Serbia). This data review pointed that it is necessary to continue the investigation on fish parasites in Serbia. The data on freshwater fish parasites are important for evaluation of general influence on the community structure.Ministry of Science and Technological Development of Republic of Serbia [173045, 173025

Speaking their language – development of a multilingual decision-support tool for communicating invasive species risks to decision makers and stakeholders

Environmental changes due to non-native species introductions and translocations are a global concern. Whilst understanding the causes of bioinvasions is important, there is need for decision-support tools that facilitate effective communication of the potential risks of invasive non-native species to stakeholders. Decision-support tools have been developed mostly in English language only, which increases linguistic uncertainty associated with risk assessments undertaken by assessors not of English mother tongue and who need to communicate outcomes to local stakeholders. To reduce language-based uncertainty, the ‘ecology-of-language’ paradigm was applied when developing the Aquatic Species Invasiveness Screening Kit (AS-ISK), a decision-support tool that offers 32 languages in which to carry out screenings and communicate outcomes to stakeholders. Topics discussed include uncertainty related to language-specific issues encountered during the AS-ISK translation and the potential benefits of a multilingual decision-support tool for reducing linguistic uncertainty and enhancing communication between scientists, environmental managers, policy and decision makers