Automation a conveyor belt furnace for annealing metals in a protective atmosphere

Abstract The paper presents the revitalization of a conveyor belt furnace for annealing metal, which included the design and implementation of a control system based on a programmable logic controller. The goal of the revitalization of the furnace is its modernization through the digital transformation of technological process variables as a new form of data availability in the context of Industry 4.0. The application of a modern control system ensures optimal control of the technological process and thus significantly extends the useful life of the machine

Frequency combs and optical feedback in Quantum Cascade Lasers: a unifying theoretical framework

We propose a unified theoretical framework for the frequency comb formation and optical feedback effects in semiconductor lasers. We use the quantum cascade laser as a suitable device to develop the framework unifying these two research areas, so far treated distinctly. We generate a novel feedback regime diagram and we provide a proof of principle that feedback can be used to induce and manipulate frequency combs, selecting their harmonic order. These results open a pathway towards new methodologies for hyperspectral imaging, multimode coherent sensing, and multi-channel communication

Alijansa univerziteta centralne i istočne Evrope (ACEU) kao primer razvoja regionalne međuuniverzitetske saradnje

Međunarodna saradnja, u najširem smislu, predstavlja značajan faktor razvoja, a u današnje vreme i opstanka, svakog univerziteta. Obuhvatajući najrazličitije oblike, od realizacije zajedničkih projekata, naučnih skupova, preko mobilnosti nastavnog kadra i studenata, međunarodna saradnja je neizostavni deo funkcionisanja svakog univerziteta, i njegov osnovni izvor konkurentnosti. Regionalno povezivanje, pre svega, razvijalo se kroz sam proces evolucije univerziteta tokom proteklih pedeset godina. Sve je uticajniji trend preorijentacije sa tradicionalne funkcije univerziteta, fokusirane prvenstveno na predavanje i prenošenje znanja, i u ograničenom smislu, na istraživanje, na regionalno povezivanje. Sama suština univerziteta prelazi sa želje da se poveća opšti nivo visokoobrazovanog stanovništva na rastuću potrebu da se celokupno obrazovanje i naučno – istraživački rad usmeri na ekonomske i socijalne ciljeve, specifične za određeni region. U stručnoj javnosti zastupljeno je mišljenje da je regionalno povezivanje univerziteta, praćeno razvojem ekonomije znanja, jedan od direktnih generatora regionalnog ekonomskog i društvenog razvoja. “Postepeni razvoj sektora visokog obrazovanja u pravcu regionalnog povezivanja, praćenog pojavom masovnog školovanja i celoživotnog učenja, uz opadanje broja i visine državnih stipendija, dovodi do razvitka sve oštrije konkurencije među univerzitetima, zbog koje su prinuđeni da se vode samostalnim stvaranjem profita.”[1] Samim tim okreću se sve bližem povezivanju sa preduzećima, industrijom, lokalnim i regionalnim vlastima i nevladinim sektorom, ali i sa drugim univerzitetima, sa kojima traže najraznovrsnije tačke saradnje, sa ciljem poboljšanja celokupnih performansi

Extracting complexity waveforms from one-dimensional signals

Background: Nonlinear methods provide a direct way of estimating complexity of one-dimensional sampled signals through calculation of Higuchi's fractal dimension (1<FD<2). In most cases the signal is treated as being characterized by one value of FD and consequently analyzed as one epoch or, if divided into more epochs, often only mean and standard deviation of epoch FD are calculated. If its complexity variation (or running fractal dimension), FD(t), is to be extracted, a moving window (epoch) approach is needed. However, due to low-pass filtering properties of moving windows, short epochs are preferred. Since Higuchi's method is based on consecutive reduction of signal sampling frequency, it is not suitable for estimating FD of very short epochs (N < 100 samples).Results: In this work we propose a new and simple way to estimate FD for N < 100 by introducing 'normalized length density' of a signal epoch,.where yn(i) represents the ith signal sample after amplitude normalization. The actual calculation of signal FD is based on construction of a monotonic calibration curve, FD = f(NLD), on a set of Weierstrass functions, for which FD values are given theoretically. The two existing methods, Higuchi's and consecutive differences, applied simultaneously on signals with constant FD (white noise and Brownian motion), showed that standard deviation of calculated window FD (FDw) increased sharply as the epoch became shorter. However, in case of the new NLD method a considerably lower scattering was obtained, especially for N < 30, at the expense of some lower accuracy in calculating average FDw. Consequently, more accurate reconstruction of FD waveforms was obtained when synthetic signals were analyzed, containig short alternating epochs of two or three different FD values. Additionally, scatter plots of FDwof an occipital human EEG signal for 10 sample epochs demontrated that Higuchi's estimations for some epochs exceeded the theoretical FD limits, while NLD-derived values did not.Conclusion: The presented approach was more accurate than the existing two methods in FD(t) extraction for very short epochs and could be used in physiological signals when FD is expected to change abruptly, such as short phasic phenomena or transient artefacts, as well as in other fields of science. © 2009 Kalauzi et al; licensee BioMed Central Ltd

Unaprijeđeno upravljanje momentom visokobrzinskog pogona s asinkronim motorom bez mjerenja brzine

This paper presents improved torque control scheme for a high speed sensorless induction motor drive. The proposed high speed torque control scheme substitutes the flux oriented control by the voltage angle control in the flux weakening regime. This scheme uses maximum of available inverter voltage, alleviates well known problems of current control schemes in conditions with insufficient voltage margin and avoids the influence of estimated speed error to the achieved flux level. The algorithm uses similar slip control as flux oriented control algorithm, but is applied without an outer flux trajectory reference which is typical for the flux weakening, providing a fast and well damped torque response even if error in estimated speed is present. Experiments confirm the effectiveness of proposed torque control algorithm, smooth transition from the flux oriented control in the base speed region to the voltage angle control in the flux weakening, superior dynamic performance of the voltage angle torque control, and its robustness to an estimated rotor speed error.U radu je predstavljena unaprijeđena shema upravljanja za pogon visokobrzinskog asinkronog motora bez mjerenja brzine. Predloženi postupak zamjenjuje vektorsko upravljanje upravljačkom strukturom s upravljanjem kutom napona u slabljenju polja. Predložena shema koristi maksimalni raspoloživi napon invertora, eliminira dobro poznate probleme strujno reguliranih pogona u uvjetima s nedovoljnom rezervom napona i eliminira utjecaj greške u estimaciji brzine na dostignutu razinu toka. Algoritam koristi sličnu kontrolu klizanja kao i vektorsko upravljanje, ali bez tipičnog vanjskog zadavanja toka u slabljenju polja, pružajući brz i dobro prigušen odziv momenta čak i u slučaju greške u estimaciji brzine. Eksperimenti izvedeni na velikoj brzini vrtnje potvrđuju učinkovitost predložene regulacije momenta, gladak prijelaz iz baznog područja brzine u slabljenje polja, vrhunske dinamičke performanse upravljanja kutom napona i robusnost na pogrešku u estimiranoj brzini vrtnje

Modeling of thermoelectric module operation in inhomogeneous transient temperature field using finite element method

This paper is the result of research and operation modeling of the new systems for cooling of cutting tools based on thermoelectric module. A copper inlay with thermoelectric module on the back side was added to a standard turning tool for metal processing. For modeling and simulating the operation of thermoelectric module, finite element method was used as a method for successful solving the problems of inhomogeneous transient temperature field on the cutting tip of lathe knives. Developed mathematical model is implemented in the software package PAK-T through which numerical results are obtained. Experimental research was done in different conditions of thermoelectric module operation. Cooling of the hot module side was done by a heat exchanger based on fluid using automatic temperature regulator. After the calculation is done, numerical results are in good agreement with experimental. It can be concluded that developed mathe-matical model can be used successfully for modeling of cooling of cutting tools

In situ XRPD and DSC study of order-disorder phase transition in nanosize Li-ferrite

An order-disorder phase transition of nanosize Li-ferrite (Li0.50Fe2.50O4) was studied by DSC measurements and in situ XRPD technique. The phase transition temperature is found to be 762 °C (DSC) and (745±5) °C (XRPD).Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Mobilnost studenata i nastavnog kadra na primeru međunarodnog programa master akademskih studija "Zelena ekonomija"

Volatilne promene i brz razvoj privrednih sistema generišu nastanak novih trendova u visokom obrazovanju, insistirajući na sticanju interdisciplinarnih znanja i veština. Cilj ovog rada je da se prikaže inovativni pristup u funkcionisanju regionalnog studijskog programa “Zelena ekonomija”, koji je nastao u okvirima saradnje Alijanse univerziteta centralne i istočne Evrope. Autori će prikazati strukturu studijskog programa koja omogućava veliku mobilnost studenata i nastavnog kadra angažovanog na realizaciji ovog studijskog programa

Genotoxicity markers in human peripheral blood lymphocytes in response to ionizing radiation

Jedan od uzročnika oštećenja molekula DNK dejstvom jonizujućeg zračenja je i nastanak slobodnih radikala. Cilj istraživanja bio je utvrđivanje uticaja parametara oksidativnog statusa na učestalost citogenetičkih biomarkera delovanja zračenja. Istraživanje je obuhvatilo analizu uzoraka humane krvi na postojanje promena genetičkog materijala i promena u vrednostima parametara oksidativnog statusa, u odgovoru na delovanje tri aplikovane doze zračenja u odnosu na neozračene uzorke. Rezultati su pokazali postojanje inter-individualne varijabilnosti u svim analiziranim parametrima i njihovo dozno-zavisno formiranje, na svim dozama. Korelacionom analizom parametara koji govore o sveukupnom odgovoru donora ustanovljeno je da donori lošijeg antioksidativnog statusa pokazuju veći stepen citogenetičkih oštećenja. Nasuprot njima, grupa donora sa boljom antioksidativnom zaštitom, pokazala je niži odgovor na zračenje od očekivanog pri datoj dozi. Pored brojnim istraživanjima validovanih dicentrika i mikronukleusa, i parametri oksidativnog statusa mogu, u rutinskoj praksi radiološke zdravstvene zaštite, upotpuniti profil odgovora na kontinuiranu ekspoziciju malim dozama, ali i reakciju na incidentalna ozračivanja.Ionizing radiation in living cells can directly act on atomic structures, producing damage to biomolecules (DNA). Since ionizing radiation can cause oxidative damage and produce reactive oxygen species, the main goal of this investigation was to establish the influence of parameters of oxidative status and oxidative damage on chromosomal aberrations and micronuclei frequency in peripheral blood lymphocytes from donors and to examine possible correlations. The results showed significant inter-individual variability in all analyzed parameters, as well as dose-dependent increases. Correlation analysis for overall response („HRR“ parameters) confirmed the t-test analysis, i.e. donors with lower values for antioxidant status parameters had increased levels of cytogenetic damage and higher responses to irradiation. Unlike them, the group of donors with better antioxidative protection showed a lower response than expected. Besides well established cytogenetic biomarkers of radiation exposure, our results indicated a promising future use for biochemical oxidative status parameters in routine radiation protection practice, since together they can provide a complete radiation response profile in cases of continuous low dose exposure, as well as in a radiation emergency.Зборник радова : XXIX симпозијум ДЗЗСЦГ : Сребрно језеро, 27-29. септембар 2017. годин

Genotoxicity markers in human peripheral blood lymphocytes in response to ionizing radiation

Jedan od uzročnika oštećenja molekula DNK dejstvom jonizujućeg zračenja je i nastanak slobodnih radikala. Cilj istraživanja bio je utvrđivanje uticaja parametara oksidativnog statusa na učestalost citogenetičkih biomarkera delovanja zračenja. Istraživanje je obuhvatilo analizu uzoraka humane krvi na postojanje promena genetičkog materijala i promena u vrednostima parametara oksidativnog statusa, u odgovoru na delovanje tri aplikovane doze zračenja u odnosu na neozračene uzorke. Rezultati su pokazali postojanje inter-individualne varijabilnosti u svim analiziranim parametrima i njihovo dozno-zavisno formiranje, na svim dozama. Korelacionom analizom parametara koji govore o sveukupnom odgovoru donora ustanovljeno je da donori lošijeg antioksidativnog statusa pokazuju veći stepen citogenetičkih oštećenja. Nasuprot njima, grupa donora sa boljom antioksidativnom zaštitom, pokazala je niži odgovor na zračenje od očekivanog pri datoj dozi. Pored brojnim istraživanjima validovanih dicentrika i mikronukleusa, i parametri oksidativnog statusa mogu, u rutinskoj praksi radiološke zdravstvene zaštite, upotpuniti profil odgovora na kontinuiranu ekspoziciju malim dozama, ali i reakciju na incidentalna ozračivanja.Ionizing radiation in living cells can directly act on atomic structures, producing damage to biomolecules (DNA). Since ionizing radiation can cause oxidative damage and produce reactive oxygen species, the main goal of this investigation was to establish the influence of parameters of oxidative status and oxidative damage on chromosomal aberrations and micronuclei frequency in peripheral blood lymphocytes from donors and to examine possible correlations. The results showed significant inter-individual variability in all analyzed parameters, as well as dose-dependent increases. Correlation analysis for overall response („HRR“ parameters) confirmed the t-test analysis, i.e. donors with lower values for antioxidant status parameters had increased levels of cytogenetic damage and higher responses to irradiation. Unlike them, the group of donors with better antioxidative protection showed a lower response than expected. Besides well established cytogenetic biomarkers of radiation exposure, our results indicated a promising future use for biochemical oxidative status parameters in routine radiation protection practice, since together they can provide a complete radiation response profile in cases of continuous low dose exposure, as well as in a radiation emergency.Зборник радова : XXIX симпозијум ДЗЗСЦГ : Сребрно језеро, 27-29. септембар 2017. годин