Measurements of ortho-positronium gamma ray energies

Elektron i pozitron mogu tvoriti nestabilno vezano stanje zvano pozitronij (Ps). Pozitronij je egzotičan atom analogan vodiku, pa su im tako energijski nivoi slični. Spinovi elektrona i pozitrona mogu biti orijentirani u istom smjeru (singlet stanja) i suprotnom smjeru (triplet stanja). Singlet stanje (para-pozitronij) raspada se na dvije gama zrake, dok se triplet stanje (ortopozitronij) raspada na tri gama zrake. Dva različita stanja također imaju različito vrijeme života i vjerojatnost raspada. U ovom diplomskom radu mjerene su energije gama zraka za određene kutove emisije kod raspada orto-pozitronija. Za detekciju istih, korišten je sustav BaF2 detektora te brzi digitalizator signala za sakupljanje podataka. Za analizu podataka korištena je ROOT platforma.Electron and positron can be in an unstable bound state called positronium (Ps). Positronium is an exotic atom analogus to hidrogen, therefore, they share similar energy levels. The electron and positron spins can be aligned in the same direction (singlet states) or in the opposite directions (triplet states). Singlet state (para-positronium) and triple state (ortho-positronium) decay in two and three gamma rays respectively. Two different states also have different life time and decay probability. In this thesis, gamma rays energies were measured for certain emission angles of ortho-positronium decay. For detection of these photons, system of three BaF2 detectors and fast signal digitizer was used. Data analysis was made with ROOT platform

Radiološka procjena rizika: pregled uporabe ERICA integriranog pristupa i ERICA alata

The ERICA project (Environmental Risk from Ionising Contaminants: Assessment and Management) was co-funded by the European Union as part of the 6th Framework Programme (FP EURATOM). The project was carried out between 2004 and 2007 as the collective work of 15 organisations in seven European countries. Two significant outputs of the project are the ERICA Integrated Approach and the ERICA Tool. The ERICA Integrated Approach consists of three elements: assessment, risk characterisation and management. The ERICA Tool is a practical implementation of the assessment component of the ERICA Integrated Approach and has a three-tier structure. The aim of this review paper is to give a concise overview of ERICA project outputs and their structure, updates done since their first release in 2007, as well as to provide a context for their practical application in environmental radiation protection and radiological risk assessments for various engineering scenarios.Projekt ERICA (ekološki rizik od ionizirajućih onečišćivača: procjena i upravljanje) sufinanciran je od Europske unije u sklopu Šestog okvirnog programa (FP Euroatom). Projekt je proveden između 2004. i 2007. godine kao kolektivni rad 15 organizacija u sedam europskih zemalja. Dva su značajna rezultata projekta: ERICA integrirani pristup i ERICA alat. ERICA integrirani pristup sastoji se od triju elemenata: procjene, karakterizacije rizika i upravljanja. ERICA alat je praktična primjena komponente procjene unutar ERICA integriranoga pristupa te ima trorazinsku strukturu. Cilj je ovoga rada dati ne samo kratak pregled rezultata projekta ERICA i njihove strukture nego i ažuriranja rezultata od njihova prvog objavljivanja 2007. godine, te pružiti kontekst za njihovu praktičnu primjenu u zaštiti okoliša od zračenja i procjeni radiološkoga rizika za razne inženjerske primjene

Humidity sensing ceria thin-films

Lowering the constitutive domains of semiconducting oxides to the nano-range has recently opened up the possibility of added benefit in the research area of sensing materials, in terms both of greater specific surface area and pore volume. Among such nanomaterials, ceria has attracted much attention ; therefore, we chemically derived homogeneous ceria nanoparticle slurries. One set of samples was tape-casted onto a conducting glass substrate to form thin-films of various thicknesses, thereby avoiding demanding reaction conditions typical of physical depositions, while the other was pressed into pellets. Structural and microstructural features, along with electrical properties and derivative humidity-sensing performance of ceria thin-films and powders pressed into pellets, were studied in detail. Particular attention was given to solid- state impedance spectroscopy (SS-IS), under controlled relative humidity (RH) from 30%– 85%, in a wide temperature and frequency range. Moreover, for the thin-film setup, measurements were performed in surface-mode and cross-section- mode. From the results, we extrapolated the influence of composition on relative humidity, the role of configuration and thin-film thickness on electrical properties, and derivative humidity- sensing performance. The structural analysis and depth profiling both point to monophasic crystalline ceria. Microstructure analysis reveals slightly agglomerated spherical particles and thin-films with low surface roughness. Under controlled humidity, the shape of the conductivity spectrum stays the same along with an increase in RH, and a notable shift to higher conductivity values. The relaxation is slow, as the thickness of the pellet slows the return of conductivity values. The increase in humidity has a positive effect on the overall DC conductivity, similar to the temperature effect for semiconducting behavior. As for the surface measurement setup, the thin-film thickness impacts the shape of the spectra and electrical processes. The surface measurement setup turns out to be more sensitive to relative humidity changes, emphasized with higher RH, along with an increase in thin-film thickness. The moisture directly affects the conductivity spectra in the dispersion part, i.e., on the localized short-range charge carriers. Moisture sensitivity is a reversible process for thin-film samples, in contrast to pellet form samples

Wi-Fi i ljudsko zdravlje

An enormous increase in the application of wireless communication in recent decades has intensified research into consequent increase in human exposure to electromagnetic (EM) radiofrequency (RF) radiation fields and potential health effects, especially in school children and teenagers, and this paper gives a snap overview of current findings and recommendations of international expert bodies, with the emphasis on exposure from Wi-Fi technology indoor devices. Our analysis includes over 100 in vitro, animal, epidemiological, and exposure assessment studies (of which 37 in vivo and 30 covering Wi-Fi technologies). Only a small portion of published research papers refers to the “real” health impact of Wi-Fi technologies on children, because they are simply not available. Results from animal studies are rarely fully transferable to humans. As highly controlled laboratory exposure experiments do not reflect real physical interaction between RF radiation fields with biological tissue, dosimetry methods, protocols, and instrumentation need constant improvement. Several studies repeatedly confirmed thermal effect of RF field interaction with human tissue, but non-thermal effects remain dubious and unconfirmed.Značajan porast uporabe bežične RF komunikacije u posljednjim desetljećima te s tim povezane izloženosti ljudi umjetno stvorenom neionizirajućem zračenju (RF polja), koje prije nije postojalo na Zemlji, tema su velikog broja istraživanja mogućih utjecaja tih zračenja na okoliš i zdravlje ljudi, osobito djece i mladih, kako bi se utvrdile činjenice o međudjelovanju RF polja s genskim materijalom živih bića. U ovom radu dan je pregled aktualnih istraživanja i preporuka međunarodnih stručnih tijela. Poseban naglasak dan je na mogući utjecaj radiofrekvencijskoga zračenja na mlade odnosno na školsku djecu koja su mu tijekom školovanja svakodnevno dodatno izložena tijekom e-škole korištenjem najmodernijih Wi-Fi tehnologijskih rješenja za komunikaciju u obrazovanju

Future and development potential of Croatian shipbuilding industry

Brod je jedan od najsloženijih i najkompleksnijih proizvod za izradu s visokom dodanom vrijednošću i najsloženiji proizvod koji se proizvodi u Hrvatskoj. Industrija i povezane tvrtke zapošljavaju velik broja radnika raznih djelatnosti te zbog složenosti i uvezanosti brodogradnje s ostalim industrijama njen utjecaj je od velikog značaja za Hrvatsku. Također brodogradnja je tijekom godina generirala značajne prihode te svojom izvoznom orijentiranošću utjecala na platnu bilancu. Brodograđevna industrija stoga predstavlja strateški vrlo važnu industriju za gospodarstvo Republike Hrvatske. Republika Hrvatska je zbog snažne izvozne orijentacije domaće brodogradnje, koja gotovo cjelokupnu proizvodnju plasira na inozemna tržišta, te njenoga učešća u ukupnoj zaposlenosti i bruto domaćem proizvodu, često bila potpomagana raznim subvencijama i jamstvima. Nadalje, brodogradnja pomaže u neutraliziranju velike sezonalnosti u primorskim krajevima koji uvelike ovise o turističkoj sezoni čime brodogradnja donosi uravnoteženje gospodarskih djelatnosti i zadržavanje radnika. Međutim održivost brodogradnje je dovedena u pitanje zbog velikog iznosa jamstava i subvencija iz državnoga proračuna. No ovaj rad pokazuje da je svaka proračunska kuna uložena u brodogradnju vratila 5,77 kn u državni proračun

Elements of Road Drainage

Prometnice se kao građevina mogu podijeliti na gornji i donji ustroj; donji ustroj se odnosi na zemljani trup i objekte poput mostova, vijadukta, obložnih zidova i sl., a cilj mu je da se preuzme prometno opterećenje i cijela konstrukcija gornjeg ustroja. Gornji ustroj je dio ceste koji je preuzeo cjelokupno opterećenje, a koje je nastalo pod utjecajem prometa vozila te ga dalje prenosi na donji ustroj. Najveću opasnost na građevine donjeg ustroja predstavlja raznoliko djelovanje voda, pa se prilikom projektiranja prometnica u obzir uzima geološka građa terena, hidrogeološko obilježje terena te načini na koje dolazi do pojavljivanja vode kako bi se neophodni zahvati i građevine napravili što učinkovitije. Voda na građevine donjeg ustroja utječe i tijekom građenja i tijekom uporabe. Štetne učinke vode izazivaju vode stajaćice, vode tekućice, oborinske te podzemne vode, dok se i smrzavanje izdvaja kao važniji faktor štetnih učinaka na donji ustroj zbog čega dolazi do smanjivanja nosivosti koje dalje ima izravan utjecaj na gornji ustroj u momentima odmrzavanja kada dolazi do deformacije poddjelovanjem prometa. Podzemne vode mogu izazivati klizanje pokosa usjeka i nasipa ili pojavu strujnih tlakova, s obzirom na vrstu materijala. Stoga je sustav odvodnje i drenaže važno projektirati tako da se podzemne i površinske vode odvedu s donjeg ustroja najkraćim putem do odredišta na kojem više neće biti opasnosti za promet. S obzirom na način pojave vode koja se mora odvesti, izražena su dva sustava odvodnje, odnosno skupljanje i odvodnja površinskih voda te skupljanje i odvodnja podzemnih voda.As a structure, roadways are divided into upper and lower structures, where the lower structure represents the earth body and objects such as bridges, viaducts, facing walls, etc., and its goal is to take over the traffic load and the entire structure of the upper structure. The upper structure is the part of the road that takes all the loads caused by vehicle traffic and transfers it to the lower structure. The greatest danger for buildings of the lower structure is the different effects of water, therefore, when designing roads, the geological structure of the terrain, the hydrogeological characteristics of the terrain, as well as the way water appears, should be taken into account in order to make the necessary works and buildings as high quality as possible. Water affects the lower structure of buildings both during construction and during use. The harmful action of water causes water liquids, stagnant water, precipitation and underground water, and freezing is also one of the most important factors of harmful influence on the lower structure, which results in a reduction of the load-bearing capacity, which in turn directly affects the upper structure at the time of thawing, which causes deformation under the action traffic. Groundwater causes the slope of cuts and embankments to slide or the occurrence of flow pressures, depending on the type of material. The drainage and drainage system must therefore be designed in such a way that underground and surface water is taken from the lower structure by the shortest route to a place where it will no longer pose a danger to traffic. Depending on the form of water that needs to be removed, there are two drainage systems, namely the collection and drainage of surface water and the collection and drainage of underground water

Electronic Dosimetric Detector System for Time-resolved Measurements of Pulsed Ionizing Radiation Fields

Većina modernih elektroničkih generatora ionizirajućeg zračenja radi u impulsnom načinu rada ili koristi kratke ekspozicije trajanja do deset sekundi što ih svrstava u impulsne izvore zračenja. Donedavno je većina elektroničkih dozimetara bila konstruirana isključivo za mjerenje kontinuiranih izvora zračenja. Istraživanja radnih značajki elektroničkih dozimetara u impulsnim poljima u posljednjih deset godina pokazala su ozbiljne nedostatke u smislu točnosti, vremenske rezolucije i energijskog odziva. U ovom radu predložena je arhitektura elektroničkog dozimetrijskog detektorskog sustava koja omogućuje vremenski razlučivo mjerenje ambijentalnog doznog ekvivalenta H*(10) i brzine ambijentalnog doznog ekvivalenta dH*(10)/dt u impulsnim poljima ionizirajućeg zračenja s naglaskom na izvore prisutne u medicini. U tu svrhu izrađen je scintilacijski detektor s kristalom natrijeva jodida dopiranog talijem i silicijskim fotomultiplikatorom. Monte Carlo simulacijom transporta čestica kroz tvari za detektor razvijena je inovativna metoda energijske kompenzacije uporabom energijskog kompenzacijskog filtra. Njegova uporaba omogućuje integraciju izlaznog signala detektora što je rezultiralo povećanjem dinamičkog raspona za faktor 70 u odnosu na slične mjerne instrumente. Detektorski je sustav karakteriziran i validiran eksperimentalno uz impulsnu pobudu rendgenske cijevi i u snopu i za raspršeno zračenje, pri čemu je prikazana visoka razlučivost mjerenja ambijentalnog doznog ekvivalenta i njezine brzine. Postignuta vremenska razlučivost predstavlja poboljšanje za tri reda veličine u odnosu na trenutno komercijalno dostupne dozimetre.Majority of modern electronic generators of ionizing radiation work in pulsed regime or use short exposures up to ten seconds in duration, which classifies them as pulsed sources of ionizing radiation. Up to recently, most of electronic dosimeters were designed only for measurement of continuous sources of ionizing radiation. Investigation of their performance in last ten years has revealed some serious limitations concerning measurement accuracy, time resolution and energy response. This doctoral thesis proposed the architecture of dosimetric detector system which would enable time-resolved measurements of ambient dose equivalent H*(10) and H*(10) rate whose main purpose is measurement of pulsed ionizing radiation fields with the accent on sources present in medicine. For that purposes, the scintillation detector was made with thallium doped sodium iodide crystal and silicon photomultiplier. By means of Monte Carlo simulations of particle transport trough matter, an innovative method for energy compensation of the detector was developed employing energy compensation filter. Use of such filter enabled integration of the signal at the detector output, which resulted with increasing the dynamic range for the factor 70 when compared with similar dosimeters. Detector system was characterized and validated wherein was demonstrated high resolution for measurements of ambient dose equivalent and its rate. Achieved time resolution demonstrates improvement over commercial dosimeters for three orders of magnitude

Electronic Dosimetric Detector System for Time-resolved Measurements of Pulsed Ionizing Radiation Fields

Većina modernih elektroničkih generatora ionizirajućeg zračenja radi u impulsnom načinu rada ili koristi kratke ekspozicije trajanja do deset sekundi što ih svrstava u impulsne izvore zračenja. Donedavno je većina elektroničkih dozimetara bila konstruirana isključivo za mjerenje kontinuiranih izvora zračenja. Istraživanja radnih značajki elektroničkih dozimetara u impulsnim poljima u posljednjih deset godina pokazala su ozbiljne nedostatke u smislu točnosti, vremenske rezolucije i energijskog odziva. U ovom radu predložena je arhitektura elektroničkog dozimetrijskog detektorskog sustava koja omogućuje vremenski razlučivo mjerenje ambijentalnog doznog ekvivalenta H*(10) i brzine ambijentalnog doznog ekvivalenta dH*(10)/dt u impulsnim poljima ionizirajućeg zračenja s naglaskom na izvore prisutne u medicini. U tu svrhu izrađen je scintilacijski detektor s kristalom natrijeva jodida dopiranog talijem i silicijskim fotomultiplikatorom. Monte Carlo simulacijom transporta čestica kroz tvari za detektor razvijena je inovativna metoda energijske kompenzacije uporabom energijskog kompenzacijskog filtra. Njegova uporaba omogućuje integraciju izlaznog signala detektora što je rezultiralo povećanjem dinamičkog raspona za faktor 70 u odnosu na slične mjerne instrumente. Detektorski je sustav karakteriziran i validiran eksperimentalno uz impulsnu pobudu rendgenske cijevi i u snopu i za raspršeno zračenje, pri čemu je prikazana visoka razlučivost mjerenja ambijentalnog doznog ekvivalenta i njezine brzine. Postignuta vremenska razlučivost predstavlja poboljšanje za tri reda veličine u odnosu na trenutno komercijalno dostupne dozimetre.Majority of modern electronic generators of ionizing radiation work in pulsed regime or use short exposures up to ten seconds in duration, which classifies them as pulsed sources of ionizing radiation. Up to recently, most of electronic dosimeters were designed only for measurement of continuous sources of ionizing radiation. Investigation of their performance in last ten years has revealed some serious limitations concerning measurement accuracy, time resolution and energy response. This doctoral thesis proposed the architecture of dosimetric detector system which would enable time-resolved measurements of ambient dose equivalent H*(10) and H*(10) rate whose main purpose is measurement of pulsed ionizing radiation fields with the accent on sources present in medicine. For that purposes, the scintillation detector was made with thallium doped sodium iodide crystal and silicon photomultiplier. By means of Monte Carlo simulations of particle transport trough matter, an innovative method for energy compensation of the detector was developed employing energy compensation filter. Use of such filter enabled integration of the signal at the detector output, which resulted with increasing the dynamic range for the factor 70 when compared with similar dosimeters. Detector system was characterized and validated wherein was demonstrated high resolution for measurements of ambient dose equivalent and its rate. Achieved time resolution demonstrates improvement over commercial dosimeters for three orders of magnitude