Conditions for dynamic balance of a rigid body with heavy foot

Opisan je model krutog tela i teškog stopala spojenih obrtnim zglobom u konstantnom gravitacionom polju. Kruto telo se kreće u vertikalnoj ravni, dok teško stopalo leži na ravnoj, vrlo hrapavoj horizontalnoj podlozi. Uslovi za dinamički balans ovog sistema matematički su izraženi koristeći metodu tačke nula momenta. Pokazuje se da oni određuju oblast u faznom prostoru u kojoj stanje sistema treba da bude da bi se dinamički balans sistema održao. Takođe se pogodnom simulacijom kretanja sistema u dinamičkom balansu pokazuje da ovi uslovi nisu dovoljni da sistem održi uspravan stav, već da su u vezi s njegovom upravljivošću. Ukratko se razmatra koji su neophodni uslovi da bi ovaj sistem u dinamičkom balansu zadržao uspravan stav.The model of a rigid body and heavy foot joined by the revolute joint in the constant gravitational field is described. The rigid body moves in the vertical plane, whereas the heavy foot lies on the flat, very rough horizontal support. Conditions for the dynamic balance of this system are mathematically expressed by using the ZMP method. It is shown that they determine an area in the phase space in which the state of the system should be in order that its dynamic balance is kept. It is also shown by appropriate simulations of motion of the system in the dynamic balance that these conditions are not sufficient for the system to keep its upright posture, but are in connection with its controllability. It is briefly discussed what are the necessary conditions for this system in dynamic balance to keep its upright posture

Conditions for dynamic balance of a rigid body with heavy foot

Opisan je model krutog tela i teškog stopala spojenih obrtnim zglobom u konstantnom gravitacionom polju. Kruto telo se kreće u vertikalnoj ravni, dok teško stopalo leži na ravnoj, vrlo hrapavoj horizontalnoj podlozi. Uslovi za dinamički balans ovog sistema matematički su izraženi koristeći metodu tačke nula momenta. Pokazuje se da oni određuju oblast u faznom prostoru u kojoj stanje sistema treba da bude da bi se dinamički balans sistema održao. Takođe se pogodnom simulacijom kretanja sistema u dinamičkom balansu pokazuje da ovi uslovi nisu dovoljni da sistem održi uspravan stav, već da su u vezi s njegovom upravljivošću. Ukratko se razmatra koji su neophodni uslovi da bi ovaj sistem u dinamičkom balansu zadržao uspravan stav.The model of a rigid body and heavy foot joined by the revolute joint in the constant gravitational field is described. The rigid body moves in the vertical plane, whereas the heavy foot lies on the flat, very rough horizontal support. Conditions for the dynamic balance of this system are mathematically expressed by using the ZMP method. It is shown that they determine an area in the phase space in which the state of the system should be in order that its dynamic balance is kept. It is also shown by appropriate simulations of motion of the system in the dynamic balance that these conditions are not sufficient for the system to keep its upright posture, but are in connection with its controllability. It is briefly discussed what are the necessary conditions for this system in dynamic balance to keep its upright posture

Foodways architecture: storing, processing and dining structures at the Late Neolithic Vinča culture site at Stubline

The paper presents an analysis of storing, processing and dining structures from the Vinča culture site at Stubline. Numerous clay structures found in houses were associated with everyday activities related to food. We argue that these structures were not only important in subsistence strategies, but were also profound symbolic agents involved in complex symbolic practices related to the conceptualisation of social spaces in Vinča culture houses.V članku predstavljamo analize struktur, povezanih s shranjevanjem, pripravo in uživanjem hrane v kulturi Vinča na najdišču Stubline. V hišah so bile najdene strukture, ki jih lahko povežemo s hrano in vsakodnevnimi aktivnostmi. Trdimo, da so strukture enako pomembne v subsistenčnih strategijah in kompleksnem simbolnem delovanju pri oblikovanju socialnega prostora v hišah kulture Vinča

Determination of uniformity and field size of reference X-ray beams

Cilj ovog rada je da se ispita uniformnost i veličina referentnog polja generisanog pomoću generatora X-zračenja. U tu svrhu je koriššena jonizaciona komora male zapremine tako što su mapirane jačine doze. Na osnovu merenja, određen je korekcioni faktor za neuniformnost polja zračenja. Rezultati prikazani u ovom radu se odnose na polje kolimisano pomoću aperture prečnika 4,2 cm i generisano pomoću generatora X-zračenja konstantnog napona i struje. Ispitivanje je izvršeno u kvalitetu zračenja koji se koristi u dijagnostičkoj radiologiji, ali je ova procedura takođe primenjiva i na kvalitete koji se koriste za etaloniranje uređaja za zaštitu od zračenja definisane u novoj verziji ISO 4037 iz 2019. godine.The aim of this paper is to study the uniformity and the size of a reference radiation field produced by an x-ray generator. This work uses a technique to map dose distribution and measure dose rates with a small-volume spherical ionization chamber in order to determine the correction factor for non uniformity of the radiation field. Results shown in this paper are profile measurementsperformed in radiation beam collimated by a 4.2 cm diameter aperture, generated by calibration x-ray equipment of constant voltage and current. Thestudy was conducted in a diagnostic radiology radiation quality, but this procedure is also applicable to the new revised version of ISO 4037 standard from 2019 which specifies protection level reference radiation qualities.Proceedings: [http://vinar.vin.bg.ac.rs/handle/123456789/8681]XXX симпозијум ДЗЗСЦГ (Друштва за заштиту од зрачења Србије и Црне Горе), 2- 4. октобар 2019. године, Дивчибаре, Србиј

Configuring A Mini-Laboratory and Desktop 3-Axis Parallel Kinematic Milling Machine

Configuring new machine tools is a complex task that involves the use of a large range of conceptions, methods, models, virtual prototypes and simulations. This paper presents a methodology for configuring a new machine tool to the level of a virtual prototype by using CAD configurator Pro/WEB.Link and a top-down approach. This methodology is explained via an example of the development of a mini-laboratory and desktop 3-axis parallel kinematic milling machine (PKMM). The results are two variants of the virtual prototype and one real world prototype. The configured virtual prototypes are used for the verification of the machining program and programming system using machining simulation in the CAD/CAM environment. The mini-laboratory and desktop 3-axis PKMM has been verified by the successful machining of test workpieces

Configuring A Mini-Laboratory and Desktop 3-Axis Parallel Kinematic Milling Machine

Configuring new machine tools is a complex task that involves the use of a large range of conceptions, methods, models, virtual prototypes and simulations. This paper presents a methodology for configuring a new machine tool to the level of a virtual prototype by using CAD configurator Pro/WEB.Link and a top-down approach. This methodology is explained via an example of the development of a mini-laboratory and desktop 3-axis parallel kinematic milling machine (PKMM). The results are two variants of the virtual prototype and one real world prototype. The configured virtual prototypes are used for the verification of the machining program and programming system using machining simulation in the CAD/CAM environment. The mini-laboratory and desktop 3-axis PKMM has been verified by the successful machining of test workpieces

Methodology for configuring desktop 3-axis parallel kinematic machine

Konfigurisanje novih mašina alatki je kompleksan zadatak koji uključuje korišćenje širokog spektra koncepcija, metoda, modela, proračuna, tehnologija, simulacija, upravljanja, programiranja i tehnoekonomije. U radu se predstavlja metodologija funkcionalnog konfigurisanja novih mašina alatki, sa primerom primene ove metodologije na konkretan primer stone troosne mašine sa paralelnom kinematikom. Ovaj rad opisuje strukturu mašine, pristup modeliranju i konfigurisanje sistema upravljanja i programiranja baziranog na EMC sistemskom softveru, koji radi pod Linux operativnim sistemom u realnom vremenu. Stona glodalica je verifikovana uspešnom izgradnjom prvog prototipa.Configuring machine tools is a complex task which involves the use of huge spectra of conceptions, methods, models, calculations, technologies, simulations, control, programming, techno-economy. The paper presents the IDEF methodology for functional configuring of new machine tools, with an example of this methodology application for desktop 3-axis parallel kinematic machine. The paper describes the structure of the machine, modeling approach, and control and programming system based on PC Linux platform with real-time extension and EMC2 (the Enhanced Machine Controller) software system. Desktop3-axis parallel kinematic machine (PKM) has been verified by successful making of the first prototype

Overview of the existing UAV regulatory framework in European contries in the context of an emergency response and emergency response exercises

Bespilotne letelice, kolokvijalno poznatije kao dronovi, mogu biti od velike pomoći prilikom prikupljanja podataka visoke rezolucije, naročito u slučajevima kada direktno uključivanje obučenog osoblja na lokaciji od interesa ne bi bilo poželjno. Takav je slučaj sa reagovanjem u slučaju nuklearnog ili radiološkog akcidenta. Dron koji bi imao niz kompaktnih senzora, koji bi sadržali i specijalizovanu opremu koja nije deo standardnog tovara drona, kao što je npr. gama spektrometar, bi bio od velike pomoći, naravno pod pretpostavkom pouzdanog linka za prenos podataka u izazovnom okruženju kakvo je i očekivano u tom slučaju. Pitanje koje komplikuje upotrebu dronova u ovakvim situacijama, a možda i više u slučaju istraživanja i vežbi (koje moraju prethoditi bilo kakvoj realnoj upotrebi) je heterogeni regulatorni okvir koji postoji u evropskim zemljama. Ova fragmentacija je potekla od činjenice da je Evropska komisija ostavila regulisanje dronova mase ispod 150kg zemljama članicama. Iako je nova, harmonizujuća regulativa u procesu donošenja i primene, različiti nacionalni regulatorni okviri su još uvek na snazi, i oni imaju i slučnosti ali i kontrastirajuće elemente. U ovom radu je dat pregled odabranih nacionalnih regulativa u kontekstu reagovanja u vanrednim situacijama kao i uvid u neke buduće trendove.Unmanned aerial vehicles -UAVs, more colloquially known as drones, can be of great help in high resolution data acquisition, especially in situations where direct, on-the-ground involvement of trained personnel would be strongly undesirable. One such case is an emergency response following a nuclear or radiological event. Drone mounted with array of compact sensors, which may include specialized equipment not commonly found in the payload, such as gamma spectrometer, would be of great help to first responders, of course under assumption of a reliable data link in a complicated environment. Issue that complicates use of drones in emergency situations, and maybe even more so in research and exercises (that must precede any realistic use) is heterogeneous regulatory framework that currently exists in European countries. This fragmentation originated from the fact that European Commission left regulation of drones under 150kg to Member States. While new harmonizing legislation is under discussion, various national UAV regulations are still in place, with strong similarities but also with contrasting elements. This work summarizes current status of various national UAV regulations in the context of emergency response and also gives perspective into future trends.Proceedings: [http://vinar.vin.bg.ac.rs/handle/123456789/8681]XXX симпозијум ДЗЗСЦГ (Друштва за заштиту од зрачења Србије и Црне Горе), 2- 4. октобар 2019. године, Дивчибаре, Србиј

EXTRACURRICULAR ACTIVITIES IN THE FUNCTION OF IMPROVING PRACTICAL SKILLS OF FUTURE STUDENTS IN THE FIELD OF ЕLECTRICAL ENGINEERING AND COMPUTING

This paper is based on the authors’ many years of experience in teaching, organizing special courses and one-day workshops for different groups of students, as well as IEEESTEC students’ project conferences. The manuscript contains a brief description and results of the implementation and evaluation of the special course “Let’s put knowledge into practical work” for grammar school students. In order to continue their study and provide students with additional knowledge, the Arduino course was designed. Since 2018, by attending the course as an extracurricular activity, students gain new knowledge in the field of electronic components and microcontroller programming. Based on the conducted analyzes and evaluations, as well as current pedagogical trends, the authors give recommendations on how to overcome problems that may arise due to a lack of practical knowledge and increase students’ self-confidence and indicate the importance of a course designed in this way for those freshmen who want to acquire some new skills and knowledge

Optimisation of indoor radon concentration measurements by means of charcoal canisters

Merenje koncentracija radona u zatvorenom prostoru metodom ugljenih filtera se sprovodi duže od 30 godina. Postoji više varijanti ove metode, a varijanta koja se zasniva na otvorenim kanisterima i gama-spektrometrijskim merenjima (EPA metoda) ima relativno nizak prag detekcije i koristi se za kraća merenja, ali je osetljiva na promenu uslova tokom izlaganja kanistera. U ovoj tezi su metoda i njena primena detaljno opisane i izvršen pregled dostupne literature, a posebna pažnja je posvećena određivanju krivih kalibracionog faktora i faktora podešavanja i diskutovani su alternativni načini kalibracije. U dostupnoj literaturi postoji vrlo malo podataka o određivanju merne nesigurnosti EPA metode. Na osnovu merenja u školama i stanovima, određen je jednostavan model merne nesigurnosti, koji je primenjiv za najveći broj izlaganja kanistera. Takođe su određena optimalna podešavanja za gama-spektrometrijska merenja, uzevši u obzir mernu nesigurnost, jednostavnost merenja i potrebno vreme. U laboratorijskoj zgradi u INN “Vinča” je sprovedena dugotrajna kampanja merenja koncentracije radona i pokazano je kako se ova metoda može koristiti za određivanje srednjih mesečnih i godišnjih koncentracija i sezonskih korekcionih faktora. Tokom izlaganja kanistera, kontinuirano su praćeni temperatura i relativna vlažnost vazduha, što je omogućilo da se proveri uticaj ovih parametara na masu adsorbovane vode u recikliranim kanisterima i uporedi sa rezultatima ostvarenim sa novim kanisterima tokom kalibracije. Pošto su primećene značajne razlike u ponašanju kanistera, predložena je korekcija. Poređenje rezultata ostvarenih EPA metodom sa drugim metodama, kao i sa drugim laboratorijama koje takođe koriste EPA metodu, pokazalo je da je podudaranje rezultata u većini okolnosti zadovoljavajuće, ali da to nije uvek slučaj. Takvi nalazi su zahtevali da se ponovo preispita budžet merne nesigurnosti, kao i zahtevi za način postavljanja kanistera. Dodatnim merenjima i detaljnom analizom postojećih rezultata, kao i analizom dostupnih literaturnih podataka, identifikovan je niz doprinosa mernoj nesigurnosti koji nisu razmatrani u literaturi niti u prethodnim merenjima u INN Vinča. Ovi doprinosi su kvantifikovani i određene su preporuke za postavljanje kanistera u cilju smanjenja merne nesigurnosti i optimizacije metode...Indoor radon concentrations have been measured by means of charcoal canisters for over 30 years. There are several variations of this method. Variant of the method with open-faced canisters and gamma spectrometric measurements (EPA method) is relatively sensitive and is used for short time measurements, but is susceptible to change in conditions during canister exposure. The method and its application are described in detail in this thesis and an overview of available literature is presented. Special attention is given to determination of calibration factors and adjustment factors. Alternative calibration procedures are also discussed. In the available literature, there is very little information about measurement uncertainty of EPA method. A simple measurement uncertainty budget is presented, based on the measurements performed in schools and dwellings. This budget is applicable for most of the canister exposures and is easy for application. Optimum settings of the range of interest in gamma spectrum are determined, having in mind measurement uncertainty, ease of application and needed time. Long term measurement campaign was conducted in a laboratory building in Vinča Institute. The results were used to show how EPA method can be used for determination of mean monthly and yearly concentrations and for calculation of seasonal correction factors. During the canister exposures, ambient temperature and relative air humidity were continuously monitored, which allowed the investigation of the influence of these parameters on the mass of adsorbed water in recycled canisters and comparison with the results for new canisters used for calibration. Significant differences were observed, and a correction was proposed. Comparison of results obtained by EPA method with other methods, as well as with other laboratories using the same method, has shown that there are no significant differences for most exposure conditions. However, in some cases, significant differences were observed. Such observations prompted reevaluation of uncertainty budget and the requirements for canister exposure. Additional measurements were conducted, the existing measurements analyzed and a detailed overview of available literature was conducted, which allowed to identify contributions to measurement uncertainty that are not discussed in available literature and not taken into account in previous measurements. These contributions were quantified and new recommendations for canister exposure are proposed, in order to optimize the method..