208 research outputs found
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 NiÅ”, 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 methodās 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 ā 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 suŔe
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.ProuÄavane su promene prinosa zrna po biljci i njegovih komponenti pod uticajem suÅ”e. U toku dve godine u Zemun Polju je testirano 26 linija iz iste kombinacije ukrÅ”tanja. ProseÄne temperature u toku vegetacije i ukupne koliÄine padavina su bile približne u obe godine. Od presudnog znaÄaja su bile razlike srednjih meseÄnih temperatura i rasporeda padavina izmeÄu godina, koje su uticale na promene vrednosti glavnih komponenti prinosa zrna i prinosa zrna po biljci. UoÄen je suÅ”ni period u toku nalivanja zrna u manje povoljnoj 2012. godini, pri Äemu je doÅ”lo do smanjenja broja mahuna i broja zrna po biljci kao i mase 1000 zrna. Prinos zrna po biljci, kao kompleksna osobina, se takoÄe znaÄajno smanjio kod svih sestrinskih linija obuhvaÄenih 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 vā-vā = 0 sequence of the B 1Ī£+ ā X 1Ī£+ 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 2Ī£+ (vā = 0) - X 2Š (vā = 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)
UnapreÄenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka poveÄanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeÄe implantate. MeÄutim, tokom ugradnje MDI-a može doÄi do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo Å”irenje prsline u titanijumskom MDI-u, koriÅ”Äeni su softveri za primenu metode konaÄnih elemenata (MKE) ANSYS v13 i FRANC3D v5. KoriÅ”Äenjem FRANC3D programa izmodelirane su prsline razliÄitih veliÄina i oblika na 3D geometriji MDI-a i izvrÅ”eno je simuliranje njihovog Å”irenja. Na osnovu rezultata simulacije izraÄunat je približan zamorni vek oÅ”teÄenog 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)
UnapreÄenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka poveÄanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeÄe implantate. MeÄutim, tokom ugradnje MDI-a može doÄi do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo Å”irenje prsline u titanijumskom MDI-u, koriÅ”Äeni su softveri za primenu metode konaÄnih elemenata (MKE) ANSYS v13 i FRANC3D v5. KoriÅ”Äenjem FRANC3D programa izmodelirane su prsline razliÄitih veliÄina i oblika na 3D geometriji MDI-a i izvrÅ”eno je simuliranje njihovog Å”irenja. Na osnovu rezultata simulacije izraÄunat je približan zamorni vek oÅ”teÄenog 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 Äinioci 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.), graÅ”ka (Pisum sativum L.), boba (Vicia faba L.), lupina (Lupinus spp.), obiÄne grahorice (Vicia sativa L.) i sastrice (Lathyrus sativus L.) predstavljaju jedno od najkvalitetnijih i najjevtinijih reÅ”enja za dugoroÄni nedostatak biljnih proteina u stoÄarstvu. Jedno od ograniÄenja poveÄanju koriÅ”Äenja zrnenih mahunarki u ishrani domaÄih životinja jeste prisustvo razliÄitih sastojaka u zrnu, tzv. antinutritivnih Äinilaca, koji umanjuju njihovu hranljivu vrednost i, u sluÄaju da se unesu u veÄoj koliÄini, mogu da dovedu do teÅ”kih posledica po ljude i životinje. Iz tog razloga, oplemenjivanje svih zrnenih mahunarki usmereno je i ka snižavanju sadržaja antinutritivnih Äinilaca na bezopasan nivo. Oplemenjivanje soje na smanjeni sadržaj antinutritivnih Äinilaca dovelo je do stvaranja Kunitz-free sorti soje, pogodnih za termiÄku obradu na nižim temperaturama i kraÄeg trajanja, Å”to je naÄin uÅ”tede energije i oÄuvanja vrednih hranljivih sastojaka sojinog zrna. Å to se tiÄe drugih zrnenih mahunarki, najveÄi napredak ostvaren je kod proteinskog graÅ”ka, kod kojeg sve savremene sorte imaju nizak ili vrlo nizak sadržaj antinutritivnih Äinilaca. MeÄu dostignuÄima su i zero-tannin sorte boba, sa Å”irokom upotrebom u stoÄarstvu i industriji hleba, sorte obiÄne grahorice sa niskim sadržajem toksina, tzv. slatke sorte lupina i sorte sastrice sa niskim sadržajem ODAP
Simulacija Ŕirenja 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.UnapreÄenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka poveÄanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeÄe implantate. MeÄutim, tokom ugradnje MDI-a može doÄi do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo Å”irenje prsline u titanijumskom MDI-u, koriÅ”Äeni su softveri za primenu metode konaÄnih elemenata (MKE) ANSYS v13 i FRANC3D v5. KoriÅ”Äenjem FRANC3D programa izmodelirane su prsline razliÄitih veliÄina i oblika na 3D geometriji MDI-a i izvrÅ”eno je simuliranje njihovog Å”irenja. Na osnovu rezultata simulacije izraÄunat je približan zamorni vek oÅ”teÄenog 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
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