Kvazistacionarni pristup za analizu mikrotalasnih vodova

Analysis of microwave transmission lines is the main subject of research in the world for more than six decades. Since the day of stripline invention, back in 1949, and its modifications that followed in the forthcoming years, an "army" of scientists was trying to analyze it, simplify it and design new structures. These structures, due to their characteristics, have found wide application in microwave integrated circuits, for microwave filters and antennas design, delay lines, directional couplers, etc. Various numerical and analytical methods such as: the variational method, the method of moments, the boundary element method, the conformal mapping, the moving perfect electric wall method, the equivalent electrodes method etc. can be applied with more or less accuracy to the microwave transmission lines analysis. The aim of this doctoral dissertation is quasi TEM analysis of microwave transmission lines using the hybrid boundary method (HBEM). This method, developed at the Department of Theoretical Electrical Engineering in the Faculty of Electronic Engineering of Niš, is based on the equivalent electrodes methods and the point-matching method for the potential of the perfect electric conductor electrodes and for normal component of the electric field at the boundary surface between any two dielectric layers. Until now, it was applied to multilayered electromagnetic problems, grounding systems, electromagnetic field determination in the vicinity of cable terminations as well as magnetic field and force calculations of permanent magnets. In order to expand the field of method’s application, it is, for the first time, applied for the microwave transmission lines analysis. Single and coupled, shielded and open microwave transmission lines with homogeneous, isotropic single-layer and multilayer dielectrics were analysed in the examples presented. Structures with the ground planes of infinite width, but also the real cases – geometry with ground planes of finite width, the finite metallization thickness and substrate width, are also shown in this dissertation. The hybrid boundary element method has been proved to be a very simple, powerful and accurate procedure for microwave transmission lines analysis. The obtained system of linear equations is always well-conditioned, as the system matrix always has the greatest elements on the main diagonal. Quite good convergence for the desired parameters is achieved for only 700-1500 unknowns (equivalent electrodes). For the most examples, the convergence of results, calculation time, equipotential contours and distribution of polarized charges per unit length along boundary surfaces are shown in the tables and graphically. In order to validate the characteristic parameters results, obtained by the hybrid boundary element method, all the results will be compared to those obtained by software FEMM and FlexPDE as well as the results already reported in the literature. These results were shown in tables and graphically. The relative error for the characteristic impedance is less than 0.5 % in regards to the results obtained using the FEMM with few thousands elements and the uniform meshing technique. The computation time is even several times shorter than in the case of the analysis using the FEMM and FlexPDE. The real challenge for the author was to apply the hybrid boundary element method for analysis of microstrip transmission lines with Tellegen material (non-reciprocal bi-isotropic media). Unlike a wide range of literature that deals with the analysis of microwave transmission lines with isotropic dielectric, bi-isotropic media, due to their complexity, are not so common subject of research. The hybrid boundary element method was successfully applied for the analysis of such structures. Applying the hybrid boundary element method it is possible to analyze quickly, easily and sufficiently accurate the complex configuration of microwave transmission lines with isotropic and bi-isotropic substrate. In that way this dissertation represents a small contribution to the history of the development of methods for the analysis of microwave lines long more than 60 years

INFLUENCE OF SKIN EFFECT ON THE CALCULATION OF BUSBAR SYSTEMS HAVING RECTANGULAR CROSS SECTION

One method for the calculation of current density distribution in a finite number of long parallel conductors, having rectangular cross section, is proposed in this paper. Numerical results aim to highlight the importance of the skin effect, which can be combined with the proximity effect. The method of superposition of these two effects was applied to the calculation of the electromagnetic field in electric power busbars systems. It has been shown that the skin effect has a much greater impact, especially when the conductors are thin and strong electric currents flow through them, so special attention is paid to its calculation. For numerical solution the integral equations are used. The function of current density is approximated by the finite functional series. This way leads to a very accurate solution with only two terms. Differential evolution method is applied for minimization of error function. To demonstrate the application of the proposed approach, numerical values for busbars are presented and compared with values obtained by using the finite elements method

Promene komponenti prinosa zrna sestrinskih linija soje u uslovima suše

Objective of this study was to investigate changes in soybean grain yield and its components as affected by drought conditions. During two year trial, 26 soybean lines from the same cross combination were tested. Average temperatures and total rainfall during the growing season were approximate in both years. The differences in the average monthly temperature and distribution of precipitation between years were of crucial importance, since they brought about changes in major yield components and grain yield per plant. In less favorable year 2012, drought period during seed filling was observed. The decrease in number of pods and number of seeds per plant, as well as in 1000 seeds weight was noted. In all sister lines included in trial, grain yield per plant was very significantly reduced in the year 2012, as compared to the year 2011.Proučavane su promene prinosa zrna po biljci i njegovih komponenti pod uticajem suše. U toku dve godine u Zemun Polju je testirano 26 linija iz iste kombinacije ukrštanja. Prosečne temperature u toku vegetacije i ukupne količine padavina su bile približne u obe godine. Od presudnog značaja su bile razlike srednjih mesečnih temperatura i rasporeda padavina između godina, koje su uticale na promene vrednosti glavnih komponenti prinosa zrna i prinosa zrna po biljci. Uočen je sušni period u toku nalivanja zrna u manje povoljnoj 2012. godini, pri čemu je došlo do smanjenja broja mahuna i broja zrna po biljci kao i mase 1000 zrna. Prinos zrna po biljci, kao kompleksna osobina, se takođe značajno smanjio kod svih sestrinskih linija obuhvaćenih istraživanjem

A multidisciplinary study on magnesium

During plasma electrolytic oxidation of a magnesium alloy (96% Mg, 3% Al, 1% Zn) we obtained a luminescence spectrum in the wave number range between 19 950 and 20 400 cm-1. The broad peak with clearly pronounced structure was assigned to the v’-v” = 0 sequence of the B 1Σ+ → X 1Σ+ electronic transition of MgO. Quantum-mechanical perturbative approach was applied to extract the form of the potential energy curves for the electronic states involved in the observed spectrum, from the positions of spectral bands. These potential curves, combined with the results of quantum-chemical calculations of the electric transition moment, were employed in subsequent variational calculations to obtain the Franck-Condon factors and transition moments for the vibrational transitions observed. Comparing the results of these calculations with the measured intensity distribution within the spectrum we derived relative population of the upper electronic state vibration levels. This enabled us to estimate the plasma temperature. Additionally, the temperature was determined by analysis of the recorded A 2Σ+ (v’ = 0) - X 2П (v” = 0) emission spectrum of OH. The composition of plasma containing magnesium, oxygen, and hydrogen under assumption of local thermal equilibrium was calculated in the temperature range up to 12 000 K and for pressures of 105, 106, 107, and 108 Pa, in order to explain the appearance of the observed spectral features and to contribute to elucidation of processes taking place during the electrolytic oxidation of Mg. [Projekat Ministarstva nauke Republike Srbije, br. 172040

Simulation of crack propagation in titanium mini dental implants (MDI)

Unapređenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka povećanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeće implantate. Međutim, tokom ugradnje MDI-a može doći do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo širenje prsline u titanijumskom MDI-u, korišćeni su softveri za primenu metode konačnih elemenata (MKE) ANSYS v13 i FRANC3D v5. Korišćenjem FRANC3D programa izmodelirane su prsline različitih veličina i oblika na 3D geometriji MDI-a i izvršeno je simuliranje njihovog širenja. Na osnovu rezultata simulacije izračunat je približan zamorni vek oštećenog MDI-a.Developments in mini dental implants (MDI) manufacturing are aimed at making them more biocompatible and, at the same time, lighter, more durable and simultaneously safer than the existing implants. But, occasionally, during installation the failure of MDI may occur or cracks may appear, which could lead to the later failure of MDI. In order to understand and assess crack growth in titanium MDI, Finite Element (FE) software packages ANSYS v13 and FRANC3D v5 have been used. Using FRANC3D software different crack sizes and shapes have been modeled and simulations of crack propagations in three-dimensional model of MDI have been performed. Based on simulation results, the approximate fatigue life of damaged MDI was calculated

The effects of nitrogen on protein, oil and trypsin inhibitor content of soybean

Nitrogen fertilization have influence on protein, oil and trypsin inhibitor content of different soybean genotypes. Seed protein content was increased over control by 60 kg ha-1 nitrogen while trypsin inhibitor was reduced by all treatmens (30, 60,90 N kg ha-1) as compared to controls. Significant genetic variation in TI was found both within the genotype class with the Kunitz inhibitor present as well as within the class lacking this inhibitor. Genotypes containing the Kunitz trypsin inhibitor protein (KTI) exhibit a higher TI than genotypes lacking this protein, however, in both groups of genotypes TI was similary affected by nitrogen application. Oil content was reduced following nitrogen fertilisation

Simulation of crack propagation in titanium mini dental implants (MDI)

Unapređenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka povećanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeće implantate. Međutim, tokom ugradnje MDI-a može doći do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo širenje prsline u titanijumskom MDI-u, korišćeni su softveri za primenu metode konačnih elemenata (MKE) ANSYS v13 i FRANC3D v5. Korišćenjem FRANC3D programa izmodelirane su prsline različitih veličina i oblika na 3D geometriji MDI-a i izvršeno je simuliranje njihovog širenja. Na osnovu rezultata simulacije izračunat je približan zamorni vek oštećenog MDI-a.Developments in mini dental implants (MDI) manufacturing are aimed at making them more biocompatible and, at the same time, lighter, more durable and simultaneously safer than the existing implants. But, occasionally, during installation the failure of MDI may occur or cracks may appear, which could lead to the later failure of MDI. In order to understand and assess crack growth in titanium MDI, Finite Element (FE) software packages ANSYS v13 and FRANC3D v5 have been used. Using FRANC3D software different crack sizes and shapes have been modeled and simulations of crack propagations in three-dimensional model of MDI have been performed. Based on simulation results, the approximate fatigue life of damaged MDI was calculated

Antinutritivni činioci nekih zrnenih mahunarki

Grain legumes, such as soybean (Glycine max (L.) Merr.), pea (Pisum sativum L.), faba bean (Vicia faba L.), lupins (Lupinus spp.), common vetch (Vicia sativa L.) and grass pea (Lathyrus sativus L.), represent one of the most quality and least expensive solutions for a long-term demand for plant protein in animal husbandry. One of the limitations to an increased use of grain legumes as feed is the presence of diverse compounds in their grain, commonly referred to as anti-nutritional factors, that both decrease nutritive value of grain legumes and, if taken in larger amounts, cause health problems that may be fatal for both human and the animals. By this reason, breeding programmes of all grain legumes is aimed at decreasing the content of anti-nutritional factors to a safe extent. Breeding of soybean cultivars for reduced amount of antinutritive factors resulted in the development of Kunitz-free soybean cultivars, which are suitable for thermal processing at lower temperatures and during a shorter period of time. This is the way of saving energy and preserving valuable nutritional composition of soybean grain. As for other species, the most significant progress has been made in protein pea, where all modern cultivars have either low or very low content of various antinutritional factors. Among the improvements are also 'zero-tannin' cultivars in faba bean, with a wide utilization in both animal feeding and bread industry, lowtoxin common vetch cultivars, 'sweet' cultivars in lupins and low-ODAP cultivars in grass pea.Zrnene mahunarke, poput soje (Glycine max (L.) Merr.), graška (Pisum sativum L.), boba (Vicia faba L.), lupina (Lupinus spp.), obične grahorice (Vicia sativa L.) i sastrice (Lathyrus sativus L.) predstavljaju jedno od najkvalitetnijih i najjevtinijih rešenja za dugoročni nedostatak biljnih proteina u stočarstvu. Jedno od ograničenja povećanju korišćenja zrnenih mahunarki u ishrani domaćih životinja jeste prisustvo različitih sastojaka u zrnu, tzv. antinutritivnih činilaca, koji umanjuju njihovu hranljivu vrednost i, u slučaju da se unesu u većoj količini, mogu da dovedu do teških posledica po ljude i životinje. Iz tog razloga, oplemenjivanje svih zrnenih mahunarki usmereno je i ka snižavanju sadržaja antinutritivnih činilaca na bezopasan nivo. Oplemenjivanje soje na smanjeni sadržaj antinutritivnih činilaca dovelo je do stvaranja Kunitz-free sorti soje, pogodnih za termičku obradu na nižim temperaturama i kraćeg trajanja, što je način uštede energije i očuvanja vrednih hranljivih sastojaka sojinog zrna. Što se tiče drugih zrnenih mahunarki, najveći napredak ostvaren je kod proteinskog graška, kod kojeg sve savremene sorte imaju nizak ili vrlo nizak sadržaj antinutritivnih činilaca. Među dostignućima su i zero-tannin sorte boba, sa širokom upotrebom u stočarstvu i industriji hleba, sorte obične grahorice sa niskim sadržajem toksina, tzv. slatke sorte lupina i sorte sastrice sa niskim sadržajem ODAP

Simulacija širenja prsline u titanijumskim mini dentalnim implantima (MDI)

Developments in mini dental implants (MDI) manufacturing are aimed at making them more biocompatible and, at the same time, lighter, more durable and simultaneously safer than the existing implants. But, occasionally, during installation the failure of MDI may occur or cracks may appear, which could lead to the later failure of MDI. In order to understand and assess crack growth in titanium MDI, Finite Element (FE) software packages ANSYS v13 and FRANC3D v5 have been used. Using FRANC3D software different crack sizes and shapes have been modeled and simulations of crack propagations in three-dimensional model of MDI have been performed. Based on simulation results, the approximate fatigue life of damaged MDI was calculated.Unapređenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka povećanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeće implantate. Međutim, tokom ugradnje MDI-a može doći do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo širenje prsline u titanijumskom MDI-u, korišćeni su softveri za primenu metode konačnih elemenata (MKE) ANSYS v13 i FRANC3D v5. Korišćenjem FRANC3D programa izmodelirane su prsline različitih veličina i oblika na 3D geometriji MDI-a i izvršeno je simuliranje njihovog širenja. Na osnovu rezultata simulacije izračunat je približan zamorni vek oštećenog MDI-a

A model for cross-referencing and calculating similarity of metal alloys

This paper presents an innovative model for the comparison and crossreferencing of metal alloys, in order to determine their interchangeability in engineering, manufacturing and material sourcing. The model uses a large alloy database and statistical approach to estimate missing composition and mechanical properties parameters and to calculate property intervals. A classification of metals and fuzzy logic are then applied to compare metal alloys. The model and its algorithm have been implemented and tested in real-life applications. In this paper, an application of the model in finding unknown equivalent metals by comparing their compositions and mechanical properties in a very large metals database is described, and possibilities for further research and new applications are presented