Comparative study of gamma and neutron irradiation effects on the silicon solar cells parameters

Zbog širokog područja primene, solarne ćelije su, u svom radnom okruženju, izložene različitim vrstama zračenja (kosmičko zračenje u gornjim slojevima atmosfere, vojna i civilna nuklearna postrojenja). Štaviše, korišćeno nuklearno gorivo u isto vreme emituje i u fotone i neutrone tako da se u solarnim ćelijama smeštenim u blizini ovih goriva javljaju različite vrste radijacionih oštećenja. Ova oštećenja su uzrokovana i gama i neutronskim zračenjem. Zbog toga su preduzimana vrlo opsežna istraživanja sa ciljem razvoja poluprovodničkih uređaja čiji rad će biti pouzdan i u uslovima povećanog nivoa zračenja. Sa tehnološkog aspekta, važno je utvrditi promene, uzrokovane zračenjem, u parametrima solarnih ćelija koje utiču na njihov rad. Cilj ovog rada je da se predstavi uporedna studija efekata gama i neutronskog ozračivanja na parametre solarnih ćelija.Due to its wide application areas, solar cells are exposed, in their work environment, to different types of radiation (cosmic radiation in the upper layers of the atmosphere, military and civilian nuclear facilities). Moreover, the used nuclear fuel emits y photons and neutrons at the same time, so different types of radiation damage appeared in solar cells located in the vicinity of these fuels. These damage have been caused by both gamma and neutron radiation. That's why very extensive researches have been undertaken with the aim of developing semiconductor devices whose work will be reliable in terms of increased levels of radiation. From the technological point of view, it is important to determine changes, caused by radiation, in the parameters of the silicon solar cells that affect their work. The aim of this paper is to present the comparative study of gamma and neutron irradiation effects on the solar cells parameters

The Impact of Successive Gamma and Neutron Irradiation on Characteristics of PIN Photodiodes and Phototransistors

The aim of this paper is to explore the impact of increased gamma and neutron radiation on the PIN photodiodes and phototransistors and their output characteristics. Special attention was paid to the successive impact of gamma and neutron radiation when the components were located in the field of gamma radiation and after that in the field of neutron radiation. The impact of successive irradiation was compared with the influence of gamma and neutron radiation when they appear individually. An important result of this research is the observation that neutron irradiation of photovoltaic detectors, applied after gamma irradiation, leading to partial reparations of distorted semiconductor structure and increasing disrupted output characteristics (photocurrent, spectral response). Monte Carlo simulation of gamma photons transfer through the crystal lattice of the semiconductor has been shown that the cause of such effect of neutron radiation is a large number of divacancies caused by successive operation of the previous gamma radiation and the neutron radiation itself. Divacancies have created the basis for increased generation of charge carriers by direct transfer (tunneling) of carriers through the traps (recombination centers). This is so called intercenter charge transfer

Finite element model for stress analysis and nonlinear contact analysis of helical gears

Određivanje naponskog i deformacionog stanja na bokovima i u podnožju zubaca jedan je od osnovnih zadataka u toku proračuna opterećenja i provere nosivosti zupčanika. U ovom radu opisan je postupak razvijanja modela konačnih elemenata za istovremeno praćenje naponskog i deformacionog stanja bokova zubaca, podnožja zubaca i segmanata zupčanika sa kosim zupcima u toku sprezanja jednog para zubaca. Takođe, opisano je i simuliranje kontaktnih uslova kod evolventnih zupčanika sa kosim zupcima metodom konačnih elemenata (MKE). Izvršena je odgovarajuća analiza za izbor modela spregnutih zupčanika koji je istovremeno dovoljno ekonomičan i dovoljno geometrijski precizan. Razvijen je poseban algoritam za crtanje evolventnog profila zubaca. Ovaj algoritam ugrađen je u postojeći MKE softver i na taj način je obezbeđeno crtanje realne geometrije bokova zubaca u kontaktu. Takođe, izvršen je i izbor optimalne gustine mreže konačnih elemenata. Opisani modeli konačnih elemenata razvijeni su za jedan konkretan par zupčanika sa kosim zupcima. Dobijeni numerički rezultati pogodni su za praćenje promene deformacionog i naponskog stanja u toku perioda sprezanja para zubaca. .One of the main goals during load calculations and load capacity check for gears is determination of deformation and stress state in teeth contact zones and teeth fillets. This paper describes development of the finite element model for simultaneously monitoring the deformation and stress state of teeth flanks, teeth fillets and parts of helical gears during the tooth pair meshing period. The paper also describes the Finite Element Method simulation of contact conditions for helical gears teeth with an involute profile. A suitable analysis is performed in order to select a meshed gears model which is sufficiently economic and in same tame sufficiently geometrically accurate. The special algorithm for the tooth involute profile drawing is developed and built in a currently available software for Finite Element Analysis to assure drawing of real flanks contact geometry. The optimal mesh size level is chosen, too. The described finite element models are made for the particular helical gear pair. The obtained numerical results are suitable for tracking deformation and stress variables during the tooth pair meshing period.

Comparative study of gamma and neutron irradiation effects on the silicon solar cells parameters

Zbog širokog područja primene, solarne ćelije su, u svom radnom okruženju, izložene različitim vrstama zračenja (kosmičko zračenje u gornjim slojevima atmosfere, vojna i civilna nuklearna postrojenja). Štaviše, korišćeno nuklearno gorivo u isto vreme emituje i u fotone i neutrone tako da se u solarnim ćelijama smeštenim u blizini ovih goriva javljaju različite vrste radijacionih oštećenja. Ova oštećenja su uzrokovana i gama i neutronskim zračenjem. Zbog toga su preduzimana vrlo opsežna istraživanja sa ciljem razvoja poluprovodničkih uređaja čiji rad će biti pouzdan i u uslovima povećanog nivoa zračenja. Sa tehnološkog aspekta, važno je utvrditi promene, uzrokovane zračenjem, u parametrima solarnih ćelija koje utiču na njihov rad. Cilj ovog rada je da se predstavi uporedna studija efekata gama i neutronskog ozračivanja na parametre solarnih ćelija.Due to its wide application areas, solar cells are exposed, in their work environment, to different types of radiation (cosmic radiation in the upper layers of the atmosphere, military and civilian nuclear facilities). Moreover, the used nuclear fuel emits y photons and neutrons at the same time, so different types of radiation damage appeared in solar cells located in the vicinity of these fuels. These damage have been caused by both gamma and neutron radiation. That's why very extensive researches have been undertaken with the aim of developing semiconductor devices whose work will be reliable in terms of increased levels of radiation. From the technological point of view, it is important to determine changes, caused by radiation, in the parameters of the silicon solar cells that affect their work. The aim of this paper is to present the comparative study of gamma and neutron irradiation effects on the solar cells parameters

Influence of world crisis on Western Balkans countries: undertaken measures and expected effects

This paper has attempted to analyse certain influence aspects the global crisis has had on the Western Balkans countries, above all on Serbia, Croatia, Bosnia and Herzegovina, Macedonia and Montenegro. Our analysis focuses on events on stock exchanges, for which we have applied comparative analysis method and noticed that indexes at Western Balkans countries stock exchanges have significantly more fallen (from -46,09% to -73,86%) for the same period of time from 1 January 2008 until 20 August 2009 than indexes at leading world stock exchanges, which have fallen in the ratio of -25,00% to -35,59%. In addition, we have discovered that reinforcement of the global crisis has led to a notable capital withdraw in Western Balkans countries; investors have lost trust in banking and financial system, as well as to a number of other negative occurrences. The world crisis has proven to have had a rather strong influence on countries in this part of Europe, which is an additional issue for governments of certain countries in finalising transition process and quicker accession to the European Union (EU). Different countries have reacted in different ways and this paper aims at underlining some of the most important undertaken measures, as well as at assessing their potential effects. The paper consists of five parts. The introduction reviews global crisis phenomenon, emphasizing a great number of issues open to debate and dilemmas it has brought about, trying to discover answers to some of them within this paper. The second part has been devoted to the crisis cause influence and its development phases, not only in developed countries, but in Western Balkans countries as well. The third part analyses empiric data on indexes fluctuation at stock exchanges of developed and Western Balkans countries. Following the review of negative effects of the global crisis, the forth part deals with a short analysis of measures that governments of the respective Western Balkans countries have undertaken in fighting the crisis, so that we are able to sum up in the fifth part and try to draw the most important conclusions

Variability of in vitro culture response in wheat genotypes, genotype and environmental effects

The tissue culture response (TCR) of immature embryos, evaluated according to callus formation, percentage of regenerative green-spotted calli and the number of plants per embryo, was investigated in 96 wheat genotypes of worldwide origins. Immature embryos were collected 12-15 DAP from field-grown plants during three successive years 2003, 2004 and 2005. Year 2003 was with high air temperatures and tropical days during a period of vegetation, while the environmental conditions were more favorable for plant growth in the next two years, 2004 and 2005. Embryos were cultured on standard MS medium containing 2 mg l-1 2, 4-D. In all genotypes calli were efficiently induced, ranging from 36.7 to 100% (2003), 68.4 to 100% (2004), and 94.3 to 100% (2005). The calli occasionally formed green spots, but frequencies markedly differed among genotypes that varied from 0 to 72.5% (2003), 0 to 97.9% (2004), and 0 to 94.0% (2005). Coefficient of variation was highest in term of percent of regenerative calli (66.7%) following by a number of plants per embryo (35.6%) and callus formation (5.1%). Components of phenotypic variance showed that factor year (71.4%) had the highest impact on expression of callus formation, genetic factor (47,1%) on percentage of regenerative green-spotted calli and interaction year/genotype (30.3%) on number of plants per embryo. The results indicated factor genotype as the most important for determining regeneration potential in wheat

Nadgledanje ciljeva iza linije horizonta integracijom podataka sa OTN radara i drugih mornaričkih senzora

The subject of this dissertation’s research is the integration of data obtained from sensors that monitor the sea surface beyond the line of horizon. The primary sensor network is composed of OTH (Over the Horizon) radars, while the secondary data source is the AIS system (Automated Information System), both satellite and terrestrial. With the integration of all collected data, a unique operational picture is formed in order to control maritime traffic on the high seas. The emphasis is on the control of the Exclusive Economic Zone in order to increase the safety of navigation, preserve natural resources and prevent illegal activities. In order to solve the integration problem in an efficient way, two new algorithms for data integration have been proposed and implemented. The dissertation first presents an algorithm for efficient data fusion within network consisting of 2 or more OTH radars. Then, an algorithm for efficient integration of OTH radar tracks and other naval sensors, primarily AIS systems, was presented. For both algorithms, the results obtained through exploitation in real working environment (the Gulf of Guinea) are presented. At the end of this dissertation, the architecture of a hybrid empirical-neural model is proposed to estimate the number of false targets caused by the strong atmospheric disturbances, including even meteo-tsunamis, and to reduce false alarms in the OTH sensor network. The architecture of this model is based on the PNN (Probabilistic Neural Network)

Variability, heritability and correlations of some factors affecting productivity in peach

Factors affecting productivity in peach, such as flower density, initial and final fruit set by open pollination, and yield per m length of shoot were studied in 40 cultivars during a three-year period. Significant differences among cultivars were found for all studied properties. The coefficients of variability were the lowest for initial fruit set and then for final fruit set and flower density; while they were the highest for yield. The relatively high values of heritability were found for flower density and yield. Significant correlation coefficients were found between initial and final fruit set, flower density and yield, as well as between final fruit set and yield. In areas with a higher risk of freeze damage the cultivars characterized by higher flower density and fruit set should be grown because they can provide more consistent yield potential. At the same time, these cultivars require more intensive pruning and fruit thinning to achieve quality fruit

The impact of successive gamma and neutron irradiation on characterisics of photovoltaic detectors

Oblast nauke i tehnike koja se bavi fotonaponskim poluprovodničkim detektorima je oblast koja je doživela izuzetno brz razvoj u poslednjih 20 godina. Razlog tome jesu, s jedne strane praktično neograničene mogućnosti primene ovih detektora (optički komunikacioni sistemi, medicinski uređaji, vojni uređaji, automatski upravljački sistemi, razni elektronski uređaji za široku upotrebu), a sa druge strane minijaturizacija elektronskih komponenti i usavršavanje serijske proizvodnje ovih uređaja što je omogućilo da im cena bude relativno niska i da budu dostupni širokoj populaciji. Posebno interesantne primene poluprovodničkih fotonaponskih detektora jesu u vojnim sistemima, u medicinskim aparatima i uređajima i kosmičkim sistemima. Ovo su oblasti primene gde je verovatnoća da se fotonaponski detektori nađu u polju povećane radijacije jako velika. Oblast fotonaponskih detektora i vrsta zračenja kojima oni mogu biti izloženi je jako velika. Ovaj rad se ograničio na posmatranje fotodioda, fototranzistora i solarnih ćelija i njihovo ponašanje u uslovima gama i neutronskog zračenja s obzirom da prilikom čestične emisije iz jezgra, po pravilu, dolazi i do istovremene deeksitacije jezgra potomka emisijom diskretnog gama zračenja. Poluprovodničke komponente, stoga, bivaju izložene superponirajućem dejstvu neutronskog i gama zračenja. Cilj rada jeste istraživanje uticaja pojačanog gama i neutronskog zračenja na PIN fotodiode, fototranzistore i solarne ćelije i na njihove izlazne karakteristike. Posebna pažnja je poklonjena sukcesivnom delovanju gama i neutronskog zračenja i to u dva slučaja. U prvom kada se komponente nalaze u polju gama zračenja a nakon toga u polju neutronskog zračenja, i u drugom kada je neutronsko ozračivanje prvo a gama drugo. Tokom posmatranja uticaja ove dve vrste zračenja na fotodetektore pre i nakon svakog pojedinačnog koraka ozračivanja, snimane su izlazne karakteristike, i to:...Science and technology that deals with photovoltaic semiconductor detectors is an area with an extremely rapid development in the last 20 years. The reason for this are, on the one hand, practically countless possibilities of application of these detectors(optical communication systems, medical devices, military equipment, automatic control systems, various electronic devices), and, on the other hand, miniaturization of electronic components and development of these devices mass production allowed them to have relatively low cost and to be accessible to the wide population. Particularly interesting applications of semiconductor photovoltaic detectors are in military systems, medical devices and equipment and cosmic systems. These are areas where the probability for photovoltaic detectors to be in increased radiation field is very large. The area of photovoltaic detectors and radiation type which they can be exposed is very large. This work is limited to the observation of the photodiodes, phototransistors and solar cells and their behavior in terms of gamma and neutron radiation considering that with particle emission from the core, as a rule, there have been a simultaneous deexcitations descendant core by a discrete gamma-ray emission. Semiconductor devices, therefore, are exposed to summary effect of neutron and gamma radiation. The aim of this paper is to explore the impact of increased gamma and neutron radiation on the PIN photodiodes, phototransistors and solar cells and their output characteristics. Special attention was paid to the successive impact of gamma and neutron radiation in two cases. One, when the components are in the field of gamma radiation and after that in the field of neutron radiation, and two, when neutron irradiation is the first and gamma is the second. During the observation of effects of these two types of radiation on the photodetectors, before and after each step of irradiation, output characteristics have been measured, namely: current-voltage characteristics and spectral response of PIN photodiodes and phototransistors and current-voltage characteristics, serial and parallel..

Acute kidney damage in pregnancy: Etiopathogenesis, diagnostics and basic principles of treatment

© 2020, University of Kragujevac, Faculty of Science. All rights reserved. Acute kidney damage associated with pregnancy occurs in 1/20.000 pregnancies. In developing countries, the main cause of the development of acute kidney damage is septic abortion, and preeclampsia in the developed countries of the world. Preeclamp-sia is defined as newly developed hypertension, proteinuria and swelling in pregnant women after the 20th week of gestation. It occurs due to disorders in the development of placenta and sys-temic disorders of the function of the endothelium of the mother. It is treated with methyldopa, magnesium sulfate and timely deliv-ery. Urgent delivery is indicated if the age of gestation is ≥ 34 weeks. HELLP syndrome is a difficult form of preeclampsia. Its main characteristics are decreased platelet count, microangio-pathic hemolysis anemia, increased concentration of aminotrans-ferase in the serum and acute kidney damage. Severe HELLP syndrome is treated with emergency delivery, antihypertensives, magnesium sulfate, and in some cases plasmapheresis and hemo-dialysis. Acute fatty liver in pregnancy occurs because of decreased activity of the LCHAD enzyme of the fetus. Due to the reduced beta oxidation of fatty acids in the hepatocytes of the fetus, long chain fatty acids that cause damage to the mother's hepato-cytes are released. Swansea criteria are used for diagnosis, and the difficult form of the disease is treated with plasmapheresis and extracorporeal liver support. Atypical HUS is due to a reduced protein activity that regulates the activity of the alternative pathway of the complement system. Its main features are thrombocy-topenia, microangiopathic hemolytic anemia and acute kidney damage. It is treated with plasmapheresis, and in case of resistance with eculizumab. Thrombotic thrombocytopenic purpura is due to decreased activity of the ADAMTS13 enzyme. It is char-acterized by thrombocytopenia, microangiopathic hemolytic ane-mia, high temperature, nervous system disorders and acute kidney damage. It is treated with plasmapheresis, and severe form of disease with corticosteroids and azathioprine. Early detection and timely treatment of acute kidney damage provides a good outcome for the mother and fetus