Određivanje preostalog životnog veka i strategije zamene malouljnih prekidača na osnovu dinamičke analize rizika: doktorske disertacije

The main goal of this dissertation is to estimate the remaining useful life of minimum oil circuit breakers (CB) based on data collected during their regular inspection. Using the proposed approach, CB’s with the highest risk can be identified, whose failure can cause the greatest economic consequences, but also consequences for the stability of the power system. By determining the reliability and risk of minimum oil CB’s, it is possible to see what influence has the place of installation on the aging process. In this way, a correlation is established between the values of voltage drops and other categories such as: feeder type, voltage level, year of production, number of disconnected short-circuit currents. The end result of the CB’s analysis is the possibility of knowing its aging process, classification of the state of all CB’s based on the risk of failure, knowledge of the impact of CB’s replacement on the availability of the power station, without additional investment in new equipment or labor

PREDICTION OF TRAFFIC INTENSITY AT PAY TOLL STATIONS

U radu je predstavljen metod za predviđanje intenziteta saobraćaja na sistemu za naplatu putarine za različit broj unapred određnih naplatnih rampi koje će biti otvorene. Sistem za naplatu putarine je predstavljen kao više jednokanalnih sistema ospluživanja, gde jedan kanal predstavlja jednu naplatnu rampu. Razvijanjem metodologije zasnovane na predviđanju parametra opsluživanja za unapred zadati broj otvorenih kanala, kombinacijom neuronskih mreža i modela masovnog opsluživanja evaluirane su verovatnoće stanja sistema za naplatu putarine i ukupni troškovi istog . LSTM neuronska mreža (eng. Long short term memory) sa unutrašnjom standardizacijom korišćena je za predviđanje parametra opsluživanja. Analizirane su 24 arhitekture mreža, model sa najboljim prediktivnim performansama je izabran i korišćen u cilji predviđanja parametra opsluživanja.In this paper method for predicting states of toll station system for different number of open toll ramps is developed. The system for toll payment is modeled as single channel queuing model, where one channel presents toll ramp. The novel methodology based on combination of reccurent neural networks and queuing theory is presented. The goal of the methodlogy is to evaluate total costs and probability of traffic intensity at the pay toll stations.. Long short term memory neural network (LSTM) with layer normalization is used as a model for prediction intensity. The 24 different architectures of network are analyzed, and the best one is used as the predictor for intensity of vehicles arrivng time

Mogućnost predviđanja optimalnog perioda eksploatacije motornih vozila

By systematic observing the systems of armament and motor vehicle in their exploitation, and by analyzing the observed malfunctions and factors that influence their occurrence can be created a substantial data basis. By processing these data, with the application of the theory of reliability, can be obtained parameters necessary for designing the new and maintenance of existing motor vehicles.Sistemskim praćenjem motornog vozila u eksploataciji, analiziranjem uticaja svih faktora koji utiču na pojavu neispravnosti, može se stvoriti neophodna baza podataka. Obradom tih podataka, uz primenu teorije pouzdanosti, dobijaju se neophodni parametri za projektovanje novih i održavanje postojećih motornih vozila

Probabilistička analiza i optimizacija spregnutih konstrukcija tipa drvo-beton

Timber-concrete composite structures represent a composite system that is formed by coupling of timber and concrete elements using different types of connectors. They are applied in the rehabilitation and construction of new facilities. In order to enable their wider application, it is necessary to ensure the general availability of relevant technical regulations in relation to their design and construction. The main goal of the doctoral dissertation is to contribute to the improvement of the design process of timber-concrete composite structures and their maintenance during the service life. Thus, certain multi-parametric probabilistic analyzes and optimizations should be carried out which would result in certain recommendations that would have practical application in the certain conditions of design, construction and maintenance of these composite systems. In order to determine the most important design parameters, a stochastic sensitivity analysis of the maximum equivalent stress and maximum deflection of the timber-concrete composite beam was performed. A multiobjective optimization was also conducted in order to choose an optimal solution for the dimensions of the observed composite beam. A new probabilistic deterioration model has been developed that describes the true nature of the behavior of the timber-concrete composite system due to the long-term load

Performanse kooperativnih bežičnih telekomunikacionih sistema i mogućnosti povećanja kapaciteta kanala u prisustvu fedinga i međukanalne interferencije

In order to improve the performance of the wireless signal transmission system in the presence of various types of interference, new methods of combining diversion techniques in the relay and on the receiving side have been proposed. When using diversi, the combining technique has shown a significant improvement in the performance of wireless relay signal transmission, and thus a lower probability of system failure. Increasing the capacity of wireless telecommunications systems is feasible in terms of fixed bandwidth and specified modulation format by using the cooperative concept to increase the signal strength to noise and interference ratio. By using mobile stations as a relay, performance improvement can be achieved in M2M communication, which can be rationally used to increase channel information capacity and transmission reliability. A more detailed analysis has been conducted and can answer questions about quantitative measures of improvement in the conditions of fading and inter-channel interference. The cases of relay transmission are discussed, as well as the possibility of applying a diversion technique to improve performance in conditions of simultaneous reception of a signal through a direct connection and through a relay. For the above cases, standard performance measures will be determined using statistical telecommunications theory

Quality control by monitoring central tendency of nongaussian random variables

Razmatran je dizajn kontrolnih grafika za pracenje centralne tendencije negausovih slucajnih velicina sa simetricnim ili pozitivno asimetricnim raspodelama. U slucaju negausovih simetricnih raspodela, u ovoj disertaciji je predložen modifikovani kontrolni grafik uzoracke sredine. Za odabranu Studentovu, Laplasovu, logisticku i uniformnu raspodelu izracunata je teorijska raspodela standardizovane uzoracke sredine i aproksimirana je Pirsonovom raspodelom II tipa ili Pirsonovom raspodelom VII tipa. Izracunate su širina kontrolnih granica i moc kontrolnog grafika uzoracke sredine, za datu verovatnocu greške prve vrste. Dobijeni rezultati ukazuju da odgovarajuca Pirsonova raspodela može poslužiti kao veoma dobra aproksimacija raspodele standardizovane uzoracke sredine. Za primenu kontrolnog grafika uzoracke sredine u praksi, pore ene su mere koeficijenta spljoštenosti i upotreba predloženog grafika ilustrovana je na podacima. U slucaju pozitivno asimetricnih raspodela, u ovoj disertaciji je predložen jednostrani kontrolni grafik medijane za pracenje centralne tendencije karakteristike kvaliteta. Za odabranu eksponencijalnu, gama i Vejbulovu raspodelu izvedena je teorijska raspodela uzoracke medijane i aproksimirana je Pirsonovom raspodelom I tipa ili Pirsonovom raspodelom VI tipa. Dobijene vrednosti za gornju kontrolnu granicu i moc kontrolnog grafika medijane za teorijsku raspodelu medijane i odgovarajucu Pirsonovu raspodelu su vrlo bliske. Za primenu predloženog kontrolnog grafika medijane, upore ene su mere koeficijenata asimetrije i spljoštenosti i zatim je konstruisan kontrolni grafik medijane za date podatke. Pored statistickog dizajna kontrolnih grafika za pracenje centralne tendencije negausovih slucajnih velicina, razmatran je i njihov optimalni ekonomsko-statisticki dizajn. U ovoj disertaciji je predložena upotreba genetskog algoritma za minimizaciju funkcije ocekivanog gubitka pod ogranicenjima. Odabrane su iste simetricne raspodele kao u slucaju statistickog dizajna kontrolnog grafika uzoracke sredine, odnosno iste pozitivno asimetricne raspodele kao u slucaju statistickog dizajna kontrolnog grafika medijane. Za sve odabrane raspodele karakteristike kvaliteta, odgovarajuca Pirsonova raspodela daje rezultate vrlo bliske rezultatima za teorijsku raspodelu standardizovane uzoracke sredine (uzoracke medijane).Design of control chart for monitoring central tendency of nongaussian random variables with symmetric or positively skewed distributions is considered. In the case of nongaussian symmetric distributions, modified X bar control chart is proposed in this dissertation. For chosen Student, Laplace, logistic and uniform distributions, theoretical distribution of the standardized sample mean is calculated and approximated with Pearson type II or Pearson type VII distributions. Width of control limits and power of X bar control chart are established, for a given probability of type I error. The results imply that the corresponding Pearson distribution represents very good approximation of the distribution of the standardized sample mean. For implementation of X bar control chart in practice, measures of sample kurtosis are compared and the usage of proposed chart is illustrated on given data. In the case of positively skewed distributions, one sided median control chart for monitoring central tendency of quality characteristics is proposed in this dissertation. For chosen exponential, gamma and Weibull distributions, theoretical distribution of sample median is calculated and approximated with Pearson type I or Pearson type VI distributions. Calculated values of upper control limits and power of median control chart for theoretical distribution of sample median and corresponding Pearson distribution are very close. For implementation of median control chart in practice, measures of sample skewness and sample kurtosis are compared and then proposed median chart is constructed for given data. Besides the statistical design of control charts for monitoring central tendency of nongaussian random variables, their optimal economic statistical design is also considered. Use of genetic algorithms for constrained minimization of expected loss function is proposed in this dissertation. Same symmetric distributions as in the case of statistical design of the X bar control chart and positively skewed distributions as in the case of statistical design of median control chart are chosen. For all chosen distributions of quality characteristic, a corresponding Pearson distribution gives results very close to results based on the theoretical distribution of the standardized sample mean (sample median)

Radiation compatibility of thin layer resistors in integrated technology

U radu se razmatra dejstvo nuklearnog i elektromagnetnog zračenja na tanke izolacione slojeve koji su presudni u odvajanju elektronskih komponenti i struktura u višeslojnim gusto pakovanim integrisanim kolima. Naime, smanjenje debljine aktivnih i pasivnih slojeva integrisanih kola čini iste veoma osetljivim na dejstvo jonizujućeg zračenja i pojave prenapona atmosferskog i komutacionog porekla. Paralelno sa proizvodnjom takvih elektronskih kola razvoj tehnologije je doveo do povećanja nuklearne i elektromagnetne kontaminacije životne sredine. Istovremena pojava tankih višeslojnih elektronskih kola i nuklearne kontaminacije rezultirala je sinergijom koja je ograničila dalju minimizaciju elektronskih komponenti i sklopova postavivši jasnu granicu do koje ona može da ide. U pogledu dejstva nuklearnog zračenja i prenapona posebno je nepoželjan efekat koji može da dovede do proboja tankih izolacionih struktura. Takav efekat dovodi do kratkog spajanja elektronskih sklopova i komponenata čime se u potpunosti uništava višeslojno gusto pakovano integrisano kolo kao i ukupan sistem u koji je to kolo ugrađeno. Posebno nepovoljna situacija je kada se dejstvom jonskog zračenja stvori veće oštećenje u izolacionom sloju koje onda probiju i prenaponi submilivoltnog intenziteta, tj. kada dođe do sinergije između mehanički razarajućeg dejstva jonskog zračenja i električnog razaranja brzih prenaponskih pojava. Da bi se dobila slika o pouzdanosti komercijalnih električnih višeslojno integrisanih elektronskih komponenti u polju jonskog zračenja u ovom radu se opredelilo za numericki eksperiment primenom metode Monte Karlo. Pri tome je izabran optimalan generator slučajnih brojeva i napravljen je model ispitujućeg višeslojnog integrisanog kola pogodan za primenu postavljenog numeričkog eksperimenta. Realni eksperiment, koji je lakše izvodljiv, je izbegnut pošto se njime dobija integralna radijaciona kompatibilnost, a ne i diferencijalna, kao u slučaju numeričkog eksperimenta. Monte Karlo simulacije transporta protona kroz tanke slojeve SiO2, AlN, Al2O3 i polikarbonata su pokazali da su navedeni slojevi imuni na prolazak protona sa energijama većim od ∼10 MeV. Nejonizujući gubici energije ovih visokoenergetskih protona su mali i oni prolaze kroz slojeve bez mnogo atomskog rasejavanja. U donjem delu istraženog opsega protonske energije (od 10 keV do 1 MeV), treba očekivati značajne gubitke jonizacije. Jonizacija i oštećenja uzrokovana pomeranjima usled prolaska protona mogu uticati na svojstva pomenutih izolatora i ugroziti njihovu pouzdanost u složenim sklopovima i uređajima. Tačkasti defekti, od kojih su neki donori nosača naelektrisanja, nastaju u ozračenim izolatorima kao rezultat pomeranja (dislokacije) atoma. Visoko reaktivni slobodni radikali koji se mogu pojaviti u ozračenom leksanu izazivaju cepanje lanca i/ili umrežavanje, što utiče na izolaciona svojstva polikarbonatnih slojeva.The doctoral dissertation discusses the effect of nuclear and electromagnetic radiation on thin insulating layers that are crucial in the separation of electronic components and structures in multilayer densely packed integrated circuits. The thickness reducing of the active and passive layers of integrated circuits makes them very sensitive to the effects of ionizing radiation and the occurrence of overvoltages of atmospheric and commutation origin. In parallel with the production of such electronic circuits, the development of technology has led to an increase in nuclear and electromagnetic environmental contamination. The simultaneous emergence of thin multilayer electronic circuits and nuclear contamination has resulted in synergies that have limited further minimization of electronic components and assemblies by setting a clear limit to which it can go. With regard to the effects of nuclear radiation and overvoltage, the effect that can lead to the breakthrough of thin insulating structures is particularly undesirable. Such an effect leads to a short circuit of electronic assemblies and components, which completely destroys the multilayer densely packed integrated circuit as well as the overall system in which the circuit is installed. A particularly unfavorable situation is when the action of ion radiation creates greater damage in the insulating layer, which then breakthrough even overvoltages of submilivolt intensity, ie. when there is a synergy between the mechanically destructive effect of ion radiation and the electrical destruction of rapid surges. In order to obtain a picture of the reliability of commercial electrical multilayer integrated electronic components in the field of ion radiation, in this doctoral dissertation we decided on a numerical experiment using the Monte Carlo method. In doing so, the optimal random number generator was chosen and a model of the test multilayer integrated circuit suitable for the application of the set numerical experiment was made. A real experiment, which is easier to perform, is avoided because it gives integral radiation compatibility, and not differential, as in the case of a numerical experiment. Monte Carlo simulations of proton transport through thin layers of SiO2, AlN, Al2O3 and polycarbonate have shown that the investigated layers are immune to the passage of protons with energies higher than ∼10 MeV. Nonionizing energy loss of these high energy protons is low, and they traverse the layers without much atomic displacement. In the lower part of the investigated proton energy range (from 10 keV to 1 MeV), however, substantial ionization losses are to be expected. Ionization and displacement damage produced by protons could influence the properties of these insulators and compromise their reliability within complex structures and devices. Point defects, some of which are charge-carrier donors, arise in irradiated insulators as a result of atomic displacements. Highly reactive free radicals that can appear in irradiated lexan cause chain scission and/or cross-linking, which then affects the insulating properties of polycarbonate layers

Performanse bežičnog telekomunikacionog sistema u prisustvu n-m fedinga

In this thesis characteristics of wireless communication system operating over η-μ fading channel are considered together with diversity reception techniques which reduce the influence of η-μ fading on the system’s outage probability, average bit error rate, channel capacity, level crossing rate and average fade duration. Performance improvement is very significant within radio systems operating into cell network configuration. Cell network configuration realization could be used for increasing capacity of wireless communication system. With the increase of number of cells, i.e. with reducing the surface area of each cell, channel capacity increases. With the increase of number of cells, co-channel interference level increase, which degrades system performance values. In this work the compromise between the system capacity and reception quality is inquired. By applying diversity reception techniques, system performance values, degraded by the influences of slow fading, multipath fading and co-channel interference, are improved, so it is possible to reduce the cell area and to increase system capacity. In the second part of Phd thesis, various distributions for modeling the envelope variations in fading channels have been presented, cases in which these models are used have been pointed out, and advantages and imperfections of corresponding models for corresponding propagation scenarios have been presented. In third chapter, statistical characteristics of the first order of η-μ random variable, α-η-μ random variable and squared η-μ random variable are considered. For each mentioned variables, expressions for probability density function, cumulative distributive function, characteristic function and moments have been derived. Also for each observed case sum of two random variables, product of two random variables, ratio of two random variables, maximal value of two random variables and minimum value of two random variables have been determined. Obtained results are used for determining performances of wirelles reception with applied diversity technique for mitigation fading influence on system performances. Based on obtained expressions, graphs are depicted for probability density functions and cumulative distribution functions for the various values of propagation environment parameters. Probability density function and cumulative distribution function values are also graphically presented for α-η-μ random variable in the function of α and μ parameter change. For the purpose of performance analysis in η-μ fading environment, in the fourth chapter have been considered transformations of three η-μ random variables. Based on presented transformations of η-μ random variables, transmission performances estimation has been conducted, for the η-μ fading channel. Estimation of signal performances for the cases when diversity techniques are applied are carried out based on standard signal performance measures, i.e. outage probability (OP), average bit error probability (ABER), for observed modulation format and channel capacity. Graphically are presented ABER values for various values of system parameters when transmission is carried out with different modulation formats. By comparing obtained values it can be seen received signal performance improvement for the cases when diversity techniques are apliied over the reception case when there is no diversity technique applied. In the fifth chapter statistical characteristics of the second order of η-μ radnom proccess, and random proccesses which represent various variations of η-μ radnom proccess, are considered. Brand new random proccesses, for describing fading in special channel conditions are fromed. For all this cases level crossing rates are determined. In the sixth chapter of this Phd thesis are considered wireless communication systems with reception with applied diversity techniques for mitigating the influence of η-μ fading on system performances. Space diveristy technique has been used. Useful signals are accepted at the antennas, envelopes of these signals are combined and decision is made based on the signal values at the combiner outputs. System performances are determined for the cases of SC and MRC combining. For bouth cases probability density function and cumulative distribution function of the signal at the combiners outouts are derived, as well as the average bit error rate for the various used modualtion formats and level crossing rate. Results for ABER for various modulation formats are graphically presented as well as the improvement of the outage probability at the reception obtained by applying SC with two reception branches. In this part it has also been considered the case when bouth desired and interferring signal are described with η-μ distribution, as well as the case when desired signal has been described with η-μ distribution while interference has been described with κ-μ distribution. In the seventh chapter macrodiversity sistem with SC reception and two MRC microdiversity combiners has been considered. At the inputs at the microdiversity combiners η-μ fading is present, while at the inputs as macrodiversity combiners slow Gamma fading is present. For this model of system it has been calculated probability density function, cumulative distribution function, characteristic function, moments, variance, outage probability and level crossing rate for the signal at the macrodiversity combiner output. Results obtained for level croosing rate at the macrodiversity combiner output are graphically presented

Impact of general anesthesia on sleep in the experimental model of Parkison's disease neuropathology - possible risks of postoperative recovery

U ovoj doktorskoj disertaciji ispitivan je uticaj ketamin/diazepam i pentobarbital opšte anestezije na EEG mikrostrukturu i obrazac disanja tokom anestezije, kao i na arhitekturu spavanja i strukturu prelaznih stanja, EEG mikrostrukturu i dinamiku epizoda svih faza spavanja nakon anestezije, kako u fiziološkim kontrolama, tako i u eksperimentalnom modelu holinergičke neuropatologije Parkinsonove bolesti (bilateralna lezija PPT jedra). Rezultati ove doktorske disertacije pokazali su da je ketamin/diazepam anestezija operativnog nivoa izazvala ozbiljan poremećaj respiratornog obrasca i EEG mikrostrukture tokom anestezije. Međutim, jednako vreme potrebno za uspostavljanje stabilne anestezije u pacova sa bilateralnom lezijom PPT jedra kao i dugotrajni suprimirajući efekti na povećanu NREM beta i teta amplitudu (elektrofiziološki markeri deficita holinergičkih neurona PPT jedra) nakon anestezije, ukazuju da je ova anestezija potencijalno povoljnija, kako za ulazak u anesteziju, tako i za NREM fazu spavanja nakon operativnih zahvata kod gerijatrijskih pacijenata, kao i pacijenata obolelih od Parkinsonove i Alchajmerove bolesti. Nasuprot ketamin/diazepam anesteziji, pentobarbital anestezija ima povoljnije dejstvo na REM fazu spavanja nakon anestezije, kako kod fizioloških kontrola, tako i u eksperimentalnom modelu holinergičke neuropatologije Parkinsonove bolesti na osnovu: dugotrajnih poremećaja REM spavanja i strukture prelaznih stanja kod fizioloških kontrola koje izaziva ketamin/diazepam anestezija; suprimirajućih efekata obe anestezije operativnog nivoa na produženu REM/REM1 fazu spavanja i poremećaj njihove EEG mikrostrukture kod bilateralne lezije PPT jedra; suprimirajućeg efekta pentobarbital anestezije na povećani broj NREM/REM/NREM prelaza uzrokovanih lezijom PPT jedra; kao i na osnovu EEG mikrostrukture tokom stabilne pentobarbital anestezije, koja se ne razlikuje u poređenju PPT lezije i fiziološke kontrole