University of Maribor

About: University of Maribor is a education organization based out in Maribor, Slovenia. It is known for research contribution in the topics: Population & KEKB. The organization has 3987 authors who have published 13077 publications receiving 258339 citations. The organization is also known as: Univerza v Mariboru.

Integrated Genetic Programming and Genetic Algorithm Approach to Predict Surface Roughness

Abstract: In this article we propose a new integrated genetic programming and genetic algorithm approach to predict surface roughness in end-milling. Four independent variables, spindle speed, feed rate, depth of cut, and vibrations, were measured. Those variables influence the dependent variable (i.e., surface roughness). On the basis of training data set, different models for surface roughness were developed by genetic programming. The floating-point constants of the best model were additionally optimized by a genetic algorithm. Accuracy of the model was proved on the testing data set. By using the proposed approach, more accurate prediction of surface roughness was reached than if only modeling by genetic programming had been carried out. It was also established that the surface roughness is most influenced by the feed rate, whereas the vibrations increase the prediction accuracy.

In-line short cavity Fabry-Perot strain sensor for quasi distributed measurement utilizing standard OTDR.

Abstract: This paper presents an in-line, short cavity Fabry-Perot fiber optic strain sensor. A short air cavity inside a single-mode fiber is created by the fusion splicing of appropriately micro machined fiber tips. A precise tuning of the cavity length is introduced and used for the setting of the sensor static characteristics within the quasi-linear range around a quadrature point, which significantly simplifies signal processing. Sensor insertion losses achieved by short cavity design and optimized fusion splicing proved to be below 1 dB. Low insertion loss allows for effective cascading of the proposed strain sensors into a quasi-distributed sensor array. A practical 10-point quasi-distributed strain sensor array was demonstrated in practice, where each in-line sensor was tuned to the same operating point in the static characteristics, thus allowing for simple interrogation of the sensor array by using standard telecommunication OTDR. In addition, precise tuning of the short cavity Fabry Perot sensor was applied for an effective compensation of temperature-induced strain errors and for an increase in the unambiguous measuring range, while improving the overall linearity of the sensor system.

Effects of competition on pattern formation in the rock-paper-scissors game

Abstract: We investigate the impact of cyclic competition on pattern formation in the rock-paper-scissors game. By separately considering random and prepared initial conditions, we observe a critical influence of the competition rate $p$ on the stability of spiral waves and on the emergence of biodiversity. In particular, while increasing values of $p$ promote biodiversity, they may act detrimentally on spatial pattern formation. For random initial conditions, we observe a phase transition from biodiversity to an absorbing phase, whereby the critical value of mobility grows linearly with increasing values of $p$ on a log-log scale but then saturates as $p$ becomes large. For prepared initial conditions, we observe the formation of single-armed spirals, but only for values of $p$ that are below a critical value. Once above that value, the spirals break up and form disordered spatial structures, mainly because of the percolation of vacant sites. Thus there exists a critical value of the competition rates ${p}_{c}$ for stable single-armed spirals in finite populations. Importantly though, ${p}_{c}$ increases with increasing system size because noise reinforces the disintegration of ordered patterns. In addition, we also find that ${p}_{c}$ increases with the mobility. These phenomena are reproduced by a deterministic model that is based on nonlinear partial differential equations. Our findings indicate that competition is vital for the sustenance of biodiversity and the emergence of pattern formation in ecosystems governed by cyclical interactions.

Derivations on semiprime rings

Abstract: The main result: Let R be a 2-torson free semiprime ring and let D: R → R be a derivation. Suppose that [[D(x), x], x] = 0 holds for all x ∈ R. In this case [D(x), x] = 0 holds for all x ∈ R.