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Primena diverziti tehnike i majoritetnog kombinovanja paketa predstavlja jednostavno i atraktivno rešenje za kontrolu grešaka u bežičnim telekomunikacionim sistemima. Ove tehnike su posebno interesantne u paketski orijentisanim mrežama sa višestrukim putanjama i kooperativnim mrežama sa jednom ili više predajnih i prijemnih antena. Tipičan primer su bežične senzorske mreže koje često rade u ekstremno otežanim uslovima prenosa, pri čemu zahtevi za pouzdanim prenosom imaju veći prioritet od zahteva za racionalnim korišćenjem komunikacionih kapaciteta. Teorijski i aproksimativni izrazi za verovatnoću pogrešnog prenosa paketa u slučaju proizvoljnog broja kanala sa različitim verovatnoćama grešaka predstavljaju ključne parametre za procenu energetske efikasnosti senzorskih čvorova. Cilj rada: U okviru ove problematike, u tezi su postavljeni sledeći ciljevi: (i) da se dobiju teorijski izrazi za verovatnoću pogrešnog prenosa paketa u slučaju primene selektivnog i majoritetnog odlučivanja, u uslovima kada su verovatnoće grešaka različite na različitim putanjama i kada je broj mogućih paralelnih putanja proizvoljan; analitički izrazi su veoma bitni prilikom odreĎivanja optimalnog broja putanja u senzorskoj mreži sa ciljem maksimalne uštede potrošnje energije u senzorskim čvorovima, (ii) da se analizira efikasnost hibridne ARQ šeme imajući u vidu različita scenarija pristizanja paketa u odredišni čvor; naime, prisustvo prostornih putanja pri kojima su na pojedim putanjama uslovi prenosa loši, ne obezbeĎuje garantovano prepoznavanje paketa i prenos po svim putanjama, tako da se uslovi za majoritetno odlučivanje mogu obezbediti posle jedne ili više retransmisija; zbog toga, realni scenario je kombinacija prostornog i vremenskog diverzitija u korist jednog ili drugog scenarija, (iii) da se sagleda mogućnost implementacije imajući u vidu korišćenje poznatih standarda i postojećih hardverskih i softverskih rešenja koja se koriste u senzorskim mrežama; posebno težište je bilo dato modifikaciji rešenja neohodnih za implementaciju korekcije grešaka na bazi majoritetnog kombinovanja paketa... The application of diversity technique and majority packet combining is a simple and attractive solution for error control in wireless telecommunication systems. These techniques are especially interesting in packet-oriented multipath and cooperative networks with one or more transmitting and receiving antennas. A typical example is wireless sensor network which often operates in extremely harsh conditions, where requirements for reliable packet transmission have a higher priority than requirements for efficient usage of communication capacities. Theoretical and approximate expressions of packet error probabilities in the case of an arbitrary number of channels with distinct channel error probabilities are key parameters for estimation of the energy efficiency of sensor nodes. Goal of research: As part of this problem, the thesis sets the following objectives: (i) to obtain theoretical expressions for packet error probability in the case of application of selective and majority decision when the number of parallel channels is arbitrary and channel error probabilities are distinct; analitical expressions are very important in determining the optimal number of paths in a sensor network in order to achieve maximum saving of energy in sensor nodes, (ii) to analyze the throughput efficiency of a hybrid ARQ scheme, considering various scenarios of packet receiving in the destination node; namely, the presence of spatial paths, with poor transmission conditions in certain paths, does not provide guaranteed detection and transmission of frame copies via all paths, so that the conditions for majority combining may be provided after one or more retransmissions; therefore, the real scenario is a combination of space and time diversity in favor of one or the other scenario, (iii) to examine the possibility of implementation of majority combining, having in mind the known standards and the usage of existing hardware and software solutions in sensor networks; the particular focus was given to the modification of solutions required for the implementation of error correction, based on majority packet combining...

Izgradnja kružnih tokova intenzivirana je posljednjih 20 godina u svim europskim zemljama. U skladu s tim, ovakva raskrižja i u Hrvatskoj dobivaju sve značajniju primjenu. Razlog tomu su brojne prednosti koje kružna raskrižja imaju pred klasičnim raskrižjima. Osnovne karakteristike ovih raskrižja su kanalizirani promet koji se odvija u smjeru suprotnom od kazaljke na satu, mogućnost spajanja 4 i više priključaka te smanjenje broja konfliktnih točaka s obzirom na klasična raskrižja. To rezultira povećanjem sigurnosti i propusne moći, što se ističe i kao njihova najveća prednost. U gradu Osijeku je dosada izgrađeno pet kružnih raskrižja. Kako su se postojeća kružna raskrižja pokazala kao korisna i praktična rješenja, njihov broj bi se u skoroj budućnosti trebao povećati. U radu su opisane osnovne karakteristike kružnih raskrižja te specifičnosti onih izgrađenih na području grada Osijeka., Construction of roundabouts is intensified over the past 20 years in all European countries. Accordingly, those kinds of intersection are becoming more important in Croatia. The reasons for this are numerous advantages of a roundabout over the conventional intersections. Basic characteristics of roundabouts are traffic channelization, the possibility of connecting 4 or more junction roads and reduction of conflict points. This results in improved security and higher intersection capacity as their greatest advantage. There are five roundabouts built in the city of Osijek. As the existing roundabout proved to be useful and practical solutions, their number will increase in the near future. In this paper the basic characteristics of roundabouts and the specifics of roundabouts built in the city of Osijek are presented.

Designing and implementing new technologies in to the existing shipyard production process is common but complex task. In general, the basic parameters for designing such new technology are derived from benchmarking with shipyards that similar technology already have. Authors consider such approach unsuitable because it uses, as basic benchmarking value, capacity, expressed in average categories of production process over the certain time period. Such solution often does not provide a layout that optimally meets the specificities of the observed shipyard production process. In this paper authors suggest an approach using throughput which is based on fabrication sample of highest complexity. Such approach to shipyard process design is more appropriate and reliable in a way to obtain its optimal layout, enabling lover risk and involving less financial resources

Projektiranje novoga proizvodnog procesa zadatak je koji se izvodi temeljem raznih pretpostavki uz poznata ograničenja. Rješenje je nužno rezultat složene međuovisnosti elemenata u postupku odlučivanja. Autori su prethodno predložili nov pristup projektiranju proizvodnog procesa, temeljen na propusnosti proizvodne linije, kao osnovnoj pretpostavci uravnoteženog procesa. Propusnost se pri tome definira kao skupna tehničko-proizvodna jedinica mjere koja pokazuje vremensku zauzetost odabranoga proizvodnog procesa s točno određenom mjernom jediničnom količinom obrade. U ovom je radu za provjeru i potvrdu ovih teorijskih postavki primijenjena metoda simulacijskog modeliranja. Njome je potvrđeno da takav pristup omogućava pouzdanije uspoređivanje zamjenskih tehnologija i definiranje layouta proizvodnog procesa, u odnosu na konvencionalni pristup temeljen na proizvodnom kapacitetu kao prosječnoj veličini te na nizu nedovoljno točnih pretpostavki. Vrednovanjem je ujedno potvrđeno da pristup temeljen na propusnosti umanjuje financijski rizik i osigurava zadovoljavajuću razinu kvalitete definiranoga projektnog rješenja., Any improvement from an existing fabrication technology level to a higher one is a task performed upon different assumptions and within known limitations. The solution should be the result of the interaction of complex elements derived from the decision making process. The authors have previously suggested a new approach for the definition and verification of new production line parameters based on the production process throughput as one of the critical assumptions for defining continuous workflow in the production process. Throughput is a group unit based technical production measure for expressing processing time of a particularly complex production group along the analyzed line. In this paper, for testing and evaluation of such an approach, simulation modelling has been applied. Furthermore, the proposed approach was confirmed as more suitable for defining new technologies and optimal production line layout, compared to the conventional approach, which is based on production capacity as an average category, and on many uncertain assumptions. Furthermore, the authors emphasize that the proposed approach also enables lower risk in terms of financial investments and a higher quality solution for the shipyard.