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Novi Sad, Serbia

The University of Novi Sad is a university located in Novi Sad, the capital of the Serbian province of Vojvodina and the second largest city in Serbia.The University of Novi Sad is the second largest among six state universities in Serbia, behind the University of Belgrade. Having invested considerable efforts in intensifying international cooperation and participating in the process of university reforms in Europe, the University of Novi Sad has come to be recognized as a reform-oriented university in the region and on the map of universities in Europe. Wikipedia.

Napijalo V.,University of Novi Sad
IEEE Transactions on Microwave Theory and Techniques | Year: 2012

This paper presents 180° coupled line hybrids with noninterspersed inputs/outputs, which utilize Lange couplers. It demonstrates that, due to the near-TEM properties of the couplers, the asymmetry in power division found in previous work can be removed. A novel hybrid topology with increased layout flexibility and reduced substrate area is proposed and theoretically analyzed. Test circuits for the novel hybrid were designed to operate at 8 GHz and fabricated using low-temperature co-fired ceramic technology. Imperfections of the fabrication process have affected the coupled conductors of Lange couplers. A suitable simple model to account for the differences from the properties assumed in the design has been found. Samples have been measured with one port terminated in a grounded resistor, and the influence of termination was de-embedded from measured results. The de-embedded results are in good agreement with simulations. © 2012 IEEE. Source

Kovacic I.,University of Novi Sad
Journal of Sound and Vibration | Year: 2011

Harmonically excited oscillators with non-negative real-power geometric nonlinearities and no linear term in the restoring force are considered. Perturbation approaches are developed for the cases of weak and strong nonlinearity. Frequencyamplitude equations are derived for an arbitrary value of the non-negative real power of the restoring force as well as analytical expressions for the steady-state response at the frequency of excitation. It is shown that the system response is of a softening type for the powers lower than unity and of a hardening type for the powers higher than unity. Frequency-response curves of the antisymmetric (constant force) oscillator, the restoring force of which has a zero power, are also discussed. Comparisons with numerical results are presented for confirmation of the analytical results obtained. © 2011 Elsevier Ltd. Source

Cveticanin L.,University of Novi Sad
Journal of Sound and Vibration | Year: 2011

In this paper the excited vibrations of a truly nonlinear oscillator are analyzed. The excitation is assumed to be constant and the nonlinearity is pure (without a linear term). The mathematical model is a second-order nonhomogeneous differential equation with strong nonlinear term. Using the first integral, the exact value of period of vibration i.e., angular frequency of oscillator described with a pure nonlinear differential equation with constant excitation is analytically obtained. The closed form solution has the form of gamma function. The period of vibration depends on the value of excitation and of the order and coefficient of the nonlinear term. For the case of pure odd-order-oscillators the approximate solution of differential equation is obtained in the form of trigonometric function. The solution is based on the exact value of period of vibration. For the case when additional small perturbation of the pure oscillator acts, the so called 'Cveticanin's averaging method' for a truly nonlinear oscillator is applied. Two special cases are considered: one, when the additional term is a function of distance, and the second, when damping acts. To prove the correctness of the method the obtained results are compared with those for the linear oscillator. Example of pure cubic oscillator with constant excitation and linear damping is widely discussed. Comparing the analytically obtained results with exact numerical ones it is concluded that they are in a good agreement. The investigations reported in the paper are of special interest for those who are dealing with the problem of vibration reduction in the oscillator with constant excitation and pure nonlinear restoring force the examples of which can be found in various scientific and engineering systems. For example, such mechanical systems are seats in vehicles, supports for machines, cutting machines with periodical motion of the cutting tools, presses, etc. The examples can be find in electronics (electromechanical devices like micro-actuators and micro oscillators), in music instruments (hammers in piano), in human voice producing folds (voice cords), etc. © 2010 Elsevier Ltd. All rights reserved. Source

Milasinovic D.D.,University of Novi Sad
Thin-Walled Structures | Year: 2011

The paper describes a modified finite strip method embracing the harmonic coupled Fourier series treatment. The well known uncoupled formulation, first developed in the context of thin plate bending analysis, represents a semi-analytical finite element process. As far as linear analysis is concerned, it takes advantage of the orthogonality properties of harmonic functions in the stiffness matrix formulation. However in the case of the geometric stiffness matrix calculation, the integral expressions contain the products of trigonometric functions with higher-order exponents, and here the orthogonality characteristics are no longer valid. All harmonics are coupled, and the stiffness matrix order and bandwidth are proportional to the number of harmonics used. © 2010 Elsevier Ltd. All rights reserved. Source

Nedeljkov M.,University of Novi Sad
Archive for Rational Mechanics and Analysis | Year: 2010

This paper deals with two key problems for delta (or singular) shock solutions to systems of conservation laws: that of their entropy admissibility conditions (which is connected to the notorious uniqueness problem) and that of their interaction. We choose to represent systems of conservation laws by nets of functions which are piecewise constant (or constant with respect only to the space variable), here called shadow waves. All the calculations can then be done on each element of such nets using only the usual Rankine-Hugoniot conditions. A 3 × 3 pressureless gas dynamics model is the main example in the paper. © 2009 Springer-Verlag. Source

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