EFFECTS OF EXPERIMENTAL MODEL OF EXPLOSIVE STRENGTH IN REGULAR PHYSICAL EDUCATION CLASSES

.The study was conducted with the goal to determine the effects of explosive strength training on the transformation of motor skills and functional abilities during regular physical education classes, among students of primary schools. The sample of examinees consisted of 64 pupils from Niš, 14 years old. Experimental group comprised of 32 examinees, selected for the training of experimental model of explosive strength in the main part of regular physical education classes, three times per week, in duration of 45 minutes, for the period of eight weeks. One half of these classes was dedicated to regular PE curriculum, while the other half to an experimental program of explosive strength, in duration of eight weeks. Control group also comprised of 32 examinees, who attended regular physical education classes, three times per week in duration of 45 minutes, for the period of eight weeks. Following motor skill were assessed: coordination (two tests), sprint speed (two tests), repetitive strength (two tests), and explosive strength (two tests). Following functional abilities were assessed: pulse frequency after physical activity, Margaria test, and vital lung capacity. For processing of data, variance and covariance analysis were applied. Study results showed that experimental group of examinees achieved better results in motor skills and functional abilities, as well as that there were statistically significant effects at the final testin

MOTOR SKILLS IN FOURTH GRADE PRIMARY SCHOOL STUDENTS

The authors of this paper, which is a part of a more extensive research, provide an overview of anthropometric characteristics and motor skills in fourth-grade primary school students in Vranje and differences in these between boys and girls. The anthropometric characteristics included in the measurements were body height (Tv) and body weight (Tt), while the motor skills measured were the explosive leg power, explosive torso and shoulder power, speed, static (isometric) arm and shoulder strength, and flexibility (mobility).Body height was measured by a height meter, body weight by a weight scale, explosive leg power by a standing long jump (Sudm), explosive torso and shoulder power was measured by throwing a 2 kg medicine ball (Bm), speed was measured by a 30 m run from a high start (Tvs), static (isometric) arm and shoulder strength with pull-up endurance up to 120 seconds (Iuz) and flexibility (mobility) with standing hamstring stretch (Dpk). This research included 500 participants, fourth-grade primary school students in Vranje, both boys and girls. Statistical analysis provided us with descriptive data as well as with the differences between boys and girls in anthropometric and motor skill variables which were calculated using the t-test. The research results tell us that all the statistically significant differences are in favour of the boys. The same results that this research has provided can serve as a basis for further diagnostics efforts and  planning of physical education lessons. These findings have also shown us that it is necessary to identify reliable measuring instruments for monitoring and tracking the state and changes in the anthropometric characteristics of younger school age children.

Feasibility Analysis for Repair of Large Diameter Hydro Turbine Shaft Based on Weldability Test and Welding Cycle Simulation

Turbine and generator rotors and shafts undergo high stresses during regular working life and, from a safety and operational aspect, are the most significant components of a power generation system. Depending on the appropriate operating conditions, like temperature and/or corrosion the, shafts can be fabricated out of low/high alloy heat resistance material or of low alloyed, highly toughened material for different application. Despite known good practice and developed operation procedures, the failures of shafts sometimes occur. The right and well-defined failure analysis is the basis for feasibility analysis of repair method in the power generating industry. The analysis of direct and indirect costs of repair after the failure analysis as well as the analysis of the repair and post-repair conditions of the repaired element is the vital for decision on the key question. Is it possible to repair this element and what is the optimal repair strategy? This paper compares and analyses two approaches, by weldability analysis and weld cycle simulation, in order to determine welding feasibility analysis of cracked hydro turbine shafts

Assessment of Grain Size and Grain Refinement Efficiency by Calculation of Released Heat Attributed to Formation of Primary Aluminum Crystals During Solidification of Al7Si4Cu Alloy

Assessing heat released only related to the formation of primary crystals provides results with a significantly higher sensitivity than a traditional assessment of undercooling value. In this work, two similar Ti5B1 master alloys (commercial and refined) are used for grain refinement of Al7Si4Cu aluminum alloy to assess narrow differences in heat release during primary crystallization. The heat released related to primary crystallization is 2.50 ± 0.03, 3.16 ± 0.12, and 7.92 kJ kg-1 for samples treated with the refined master alloys, commercial master alloys, and sample solidified without grain refinement, respectively. The acquired results showed that the suggested method is more efficient in comparison with traditional metallographic or undercooling methods for the assessment of grain refining efficiency with the potential to extend the suggested approach on a wide range of metallic structures where solidification occurs by eutectic-type primary crystallization characteristics

THE RELATIONSHIP BETWEEN TECHNICAL AND TACTICAL ELEMENTS OF DIRECT POINTS WITH REGARD TO THE QUALIFICATIONS FOR THE 2018 VOLLEYBALL WOMEN’S WORLD CHAMPIONSHIP

The goal of this paper is to analyse the relationships and differences among volleyball teams, participants of the 2018 World Cup in Japan, divided into three categories by their final standings (1st to 4th place, 5th to 8th place and others), based on the elements of situation-based efficiency. For the purposes of this paper, information from the official match reports (p 2 report) related to the way of winning points in the match was used, and these data were analysed using the program Volleyball Information System (VIS). The data obtained were analysed in relation to the team category and the outcome of the match. The data were obtained using descriptive and comparative statistical procedures. The survey sample includes all the women’s volleyball championship games played in Japan in 2018. Based on the final standings, the teams were divided into three groups: 1) the teams who reached the 3rd stage of the tournament (6 teams, from 1st to 6th place); 2) the teams that finished the competition in phase 2 (10 national teams, ranking 7th to 16th); 3) national teams that finished the competition in phase 1 (8 national teams, ranking 17th to 24th). The results obtained indicate that the teams had an equally good performance of the block and serve game elements; statistically these were not significant for the match outcome, but they rather serve as an aid for the overall game and for the final outcome of the match. The results of this research also highlight the spike as the key element affecting the positive end result of the match. It is important to emphasize that the opponent errors are a factor that depends exclusively on the opponent, but they also determine the overall score of the winning team

Role of dogs in contamination of urban environment with causes of parasitic zoonoses

Dogs belong to the group of animals that were the first to be domesticated. They live in cohabitation with humans and share their environment much more intimately than any other animal specie. The close contact between strays and pets, on the one side, and the pollution of urban areas with the feces of these animals, on the other, close the chain of infection with parasites, which jeopardizes also human health in the final link of that chain. Dogs are carriers and the true hosts to large numbers of species of zoonotic parasites - Cryptosporidium parvum, Giardia lamblia, Echinoccocus granulosus, Dipyllidium caninum, Toxocara canis, Ancylostomidae spp. and others, whose eggs or other developmental forms they eliminate into the environment through feces. The increase in the number of cases of toxocarosis in humans (syndrome of visceral larvae migrans), ancylostomosis (cutanea larvae migrans), hydatidosis, toxoplasmosis, or cryptosporidiosis are the best indicators of these relations. In order to resolve this problem, it is necessary to conduct systematic investigations of their parasitic fauna with the maximum cooperation of the animal owners, compulsory health education of the population in the area of the diseases that are transferred from animals to humans, and, certainly, carrying out the dehelminthization of dogs

NS Ibar and NS Ulog - nove sorte ozimog stočnog ječma

At Institute of Field and Vegetable crops for decades, new varieties of winter six-row feed barley having high yield, good adaptability, stability and quality are produced. As a result of long process of breeding, two new varieties of winter six-row barley - NS Ibar and NS Ulog have been selected. The primary aim during creation of these varieties was selection for yield, and maintaining quality and other agronomic traits at least to the standard variety level. The two-year multilocation trial of Commission for the registration of varieties, showed that the NS Ibar and NS Ulog are distinct, uniform and stable varieties, and that on the base of average for all the test sites and years they achieved a significantly higher yield than the standard variety. New varieties of winter six-row feed barley are characterized by high genetic potential for yield, which is more than 10 t ha-1. NS Ibar i NS Ulog had a shorter plant, while the resistance to lodging was at the level of the standard variety.U Institutu za ratarstvo i povrtarstvo se decenijama stvaraju nove sorte ozimog višeredog stočnog ječma, koje imaju visok prinos, dobru adaptabilnost, stabilnost i kvalitet. Kao rezultat višegodišnjeg procesa oplemenjivanja, stvorene su dve nove sorte ozimog višeredog stočnog ječma - NS Ibar i NS Ulog. Primarni cilj prilikom stvaranje ovih sorti je bila selekcija na prinos, uz zadržavanje kvaliteta i drugih agronomskih osobina najmanje na nivou sorte standarda. U dvogodišnjim multilokacijskim ogledima Komisije za priznavanje sorti utvrđeno je da su NS Ibar i NS Ulog različite, uniformne i stabilne sorte i da su u proseku za sve lokalitete i godine ispitivanja ostvarile prinos značajno veći od prinosa sorte standarda Grand. Nove sorte ozimog višeredog stočnog ječma odlikuju se visokim genetičkim potencijalom za prinos koji iznosi preko 10 t ha-1. NS Ibar i NS Ulog su imale kraću stabljiku, dok je otpornost prema poleganju bila na nivou sorte standard

Comparison of Aeroponics and Conventional Production System of Virus-free Potato Mini Tubers in Serbia

Virus free mini tubers are starting materials for the production of seed potatoes without the diseases. Conventionally, mini-tubers are produced from in vitro plants in various solid media. The aeroponics system refers to the process of growing plants in the air or in the fog environment without the use of soil or any other substrate. The aim of this study is to assess the application of aeroponics and conventional production system of virus-free potato mini tubers in Serbia. The experiment included three varieties of potatoes: Cleopatra, Kennebec and Agria. All three varieties were cultivated within two systems: aeroponics and conventional rooting in the substrate. In the aeroponics system, with all three varieties, an average of 17.87 mini tubers was obtained, which is 5.39 times more than in the conventional substrate. This ratio was the highest in the variety Kenebec (6.46), followed by Agria (5.71) and the lowest in Cleopatra (4.01). The average weight of mini tubers produced in the conventional substrate was higher by 3.49 g compared to the aeroponics system. The aeroponics system offers a potential opportunity to improve the production of mini potato tubers in Serbia

Proizvodnja mini krtola krompira u aeroponik sistemu gajenja

At the micropropagation laboratory of the Potato Research Centre in Gucha, the following five virus-free in vitro potato cultivars are produced: 'Desiree', 'Kennebec', 'Agria', 'Cleopatra' and 'Sinora'. Acclimatized and rooted plants were transplanted and grown in the three production systems: 1) the aeroponic system, 2) the substrate system, and 3) a combination of the substrate and aeroponic systems. The results obtained indicate that the cultivation system exerts a significant effect on the number and the total yield of potato mini-tubers. In the aeroponic production system, 4.08 times as many mini-tubers were produced compared to the number of mini-tubers produced in the substrate system, whereas 1.29 times as many mini-tubers were produced compared to the number of mini-tubers produced in the combined production system (substrate + aeroponics). The aeroponic mini-tuber production system offers an opportunity to improve the production of seed potatoes in Serbia..Proizvodnja bezvirusnog semenskog krompira danas se odvija preko metode poznate kao kultura tkiva (mikropropagacija in vitro), čija je suština da se za relativno kratko vreme, i u kontrolisanim uslovima, dobije veliki broj bezvirusnih mini ili mikro krtola. U laboratoriji za mikropropagaciju Centru za krompir u Guči proizvedene su bezvirusne biljke in vitro pet sorti krompira: Desiree, Kennebec, Agria, Cleopatra i Sinora. Aklimatizovane i ožiljene biljke presađene su i gajene u tri sistema proizvodnje: 1) aeroponik, 2) u supstratu i 3) kombinaciji dva sistema gajenja (supstrat+aeroponik). Cilj rada je bio da se izvrši poređenje aeroponik sistema gajenja sa druga dva sistema proizvodnje mini krtola. Mini krtole u aeroponik sistemu posle 40-45 dana gajenja sukcesivno su ubirane u četiri roka berbe u intervalima od 10-15 dana. U ostala dva sistemima gajenja mini krtole su vađene na kraju vegetacionog perioda. Analiziran je broj mini krtola po m2, prosečna masa krtola i ukupan prinos. Najveći prosečan broj mini krtola utvrđen je kod sorte Desiree, dok je najmanji broj mini krtola zabeležen kod sorte Sinora i Cleopatra. Kod sorte Agria konstatovan je najveći prosečnan prinos mini krtola, a zatim kod sorte Kennebec. Dobijeni rezultati ukazuju da sistem gajenja značajno utiče broj mini krtola i ukupan prinos. Kod aeroponik sistema proizvodnje postignut je 4,08 puta veći broj mini krtola, u odnosu na broj mini krtola dobijen u supstratu, odnosno 1,29 puta veći broj mini krtola, u odnosu na kobinovani način proizvodnje (supstrata+aeroponik). Aeroponik sistem proizvodnje mini krtola nudi potencijalnu mogućnost za poboljšanje proizvodnje semenskog krompira u Srbiji

Repair welding of the coal mill disk made of Cr-Mo steel

U ovom radu prikazano je istraživanje u cilju određivanja optimalnih parametara reparaturnog navarivanja diska radnog kola mlina za ugalj u termoelektrani, koji je oštećen abrazijom. Reparatura je izvedena na radnom kolu, bez njegove demontaže na sastavne delove kao što su disk, prsten i udarne ploče. Prečnik radnog kola je θ 4100 mm, a težina 23 tone. Odlivak diska radnog kola je izrađen od čelika GS17CrMo55, koji spada u grupu uslovno zavarljivih čelika, koji mogu uspešno da se zavaruju uz primenu posebnih dodatnih materijala, predgrevanja i drugih mera predostrožnosti. Iz tih razloga izvršena je anlitička procena zavarljivosti, ispitivanja na osnovu tehnoloških proba i izvedeno nekoliko serija probnih navarivanja CrMo čeličnog liva sa različitim uslovima navarivanja i termičke obrade. Na osnovu ovih ispitivanja izvedena je analiza uticaja primene različitih postupaka i uslova navarivanja, dodatnih materijala, kao i različitih uslova termičke obrade pre i posle zavarivanja na strukturno - mehaničke osobine CrMo liva. Rezultati analize omogućili su izbor optimalnih parametara navarivanja i izvođenje reparaturnog navarivanja diska radnog kola mlina za ugalj. Rezultati merenja tvrdoće i IBR-a potvrdila su zadovoljavajući kvalitet reparaturnog navarivanja diska.In the paper the details of the investigation of the optimal parameters for repair welding of abrasive damaged working wheel of the coal mill are presented. Repair was performed without disassemble of the wheel. Diameter of the wheel was θ 4100 mm, and a weight was approximately 23 tons. The wheel was made of the cast steel GS17CrMo55. As the weld ability of this steel is limited, weld ability analysis of the base material by the analytical equations was performed and a series of trial welds with different welding and thermal conditions were done. The effects of the different welding processes and parameters, different filler materials and different preheating and post weld heat treatment conditions on hardness and macro and micro structure were analyzed. The Y probe was used for sensitivity testing to crack forming. Based on obtained results, the optimal welding parameters were selected, and the repair welding of the wheel was performed. Hardness measurement and NDT testing were verified quality of the applied repair welding