Jan Simon
@uniza.sk
Department of Applied Mathematics, Faculty of Mechanical Engineering
University of Zilina
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Branislav Ftorek, Ján Šimon, Michail Kiselev, Vladimír Vavrúš, and Ján Vittek
MDPI AG
The main contribution of this paper is the verification of a new train control system applied to the drive with a.c. motors that is energy near optimal with respect to electrical and mechanical energy minimization. All simulations are related to the one traction motor yielding its best exploitation. Load torque treated as a state variable consists of constant, linear, and quadratic components as a function of rotor speed. The required performance of the energy-saving control is rendered straightforward using precomputed energy optimal state variables or a prediction of losses for a symmetrical trapezoidal speed profile as the second alternative. An energy-saving reference position generator provides the state variables, which are faithfully followed by a feedback control based on field orientation, which is completed with a matched zero dynamic lag pre-compensator yielding prescribed closed-loop dynamics. Simulation results mutually compared confirm the capability of an overall drive control system to follow generated state variables for two different service conditions and the possibility of energy savings.
Ján Šimon and Branislav Ftorek
MDPI AG
A knot is the weakest point of every rope, and the knot efficiency measures the portion of original rope strength taken away by the knot. Despite possible safety implications, surprisingly little attention has been paid to this life-critical quantity in research papers. Knot efficiency is directly immeasurable and the only way to obtain it is by calculation from rope breaking strength. However, this complication makes room for a wide spectrum of misleading concepts. The vast majority of authors do not treat knot efficiency as a random variable, and published results mostly suffer from incorrect statistical processing. The main goal of the presented paper is to fix this issue by proposing correct statistical tools needed for knot efficiency assessment. The probability density function of knot efficiency ψ(η) has been derived in general, as well as for normally distributed breaking strength. Statistical properties of knot efficiency PDF have been discussed, and a less complex approximation of knot efficiency PDF has been proposed and investigated.
J. Šimon, V. Dekýš, and P. Palček
Institute of Physics, Polish Academy of Sciences
Department of Applied Mathematics, Faculty of Mechanical Engineering, University of Žilina, Univerzitná 8215/1, 010 26 Žilina, Slovakia Department of Applied Mechanics, Faculty of Mechanical Engineering, University of Žilina, Univerzitná 8215/1, 010 26 Žilina, Slovakia Department of Materials Engineering, Faculty of Mechanical Engineering, University of Žilina, Univerzitná 8215/1, 010 26 Žilina, Slovakia
I Pobočíková, Z Sedliačková, J Šimon, and D Jurášová
IOP Publishing
The 2-parameter Weibull distribution was used to analyse the wind speed at high-altitude mountain site Chopok, situated in the central part of Nízke Tatry mountains in Slovakia. Analysed wind speed data has been collected over 11 year period (2005–2015) and measured under standard conditions – in the height of 10 m over above ground using calibrated anemometers. Suitability of Weibull distribution was assessed using the coefficient of determination and root mean square error. From the results it is concluded that the 2-parameter Weibull distribution adequately describe the observed wind speed and can be used with acceptable statistical accuracy for prediction the wind speed data at this location.
Ondrej Stalmach, Vladimir Dekys, Frantisek Barnik, and Jan Simon
EDP Sciences
This paper deals with measurement of emissivity of the composite samples. Three composite samples with the different thickness are heated to the temperature sixty-five degrees Celsius. On each sample must be applied a known emissivity coating. Unknown emissivity is calculated using the information obtained during the measurement. The aim of this paper is to show one of the possible approaches to find out the emissivity of the composite material.
J. Šimon and M. Bulko
Hindawi Limited
This paper deals with the derivation of a simple mathematical model of cyclic learning with a period of 24 hours. Various requirements are met with an emphasis and approach which relies on simple mathematical operations, the prediction of measurable quantities, and the creation of uncomplicated processes of calibration. The presented model can be used to answer questions such as the following.Will I be able to memorize a given set of information? How long will it take to memorize information? How long will I remember the information that was memorized?The model is based on known memory retention functions that are in good agreement with experimental results. By the use of these functions and by formalism of differential equations, the concurrent processes of learning and forgetting are described mathematically. The usability of this model is limited to scenarios where logical bonds (connections to prior learning) are not created and mnemonic devices cannot be utilized during the learning process.
I Svetlik, P P Povinec, M Molnár, F Meinhardt, V Michálek, J Simon, and É Svingor
Cambridge University Press (CUP)
Fossil CO2 emissions have been diluting the global 14C/C ratio of atmospheric CO2 (Suess effect). We estimated the 14CO2 amount in the atmosphere (and its trend) utilizing the calculated 14CO2 activity concentration in the atmosphere (aacn, reported in mBq m–3). This parameter, calculated from Δ14CO2 and the CO2 mixing ratio (reported in micromoles of CO2 per mole of air), is connected with the 14CO2 quantity in the volume or mass unit of air, which is not influenced by the Suess effect. This parameter can only be influenced by processes linked to 14CO2 emissions/uptake, e.g. associated with atmosphere-biosphere or atmosphere-ocean CO2 exchange as well as by anthropogenic emissions of 14CO2. Results obtained from measurements at Schauinsland station, Germany, indicate a stable amount of 14CO2 in the atmosphere since the early 1990s.
Jan Simon, Jana Meresova, Ivan Sykora, Miroslav Jeskovsky, and Karol Holy
Elsevier BV
P.P. Povinec, M. Chudý, A. Šivo, J. Šimon, K. Holý, and M. Richtáriková
Elsevier BV
P.P. Povinec, A. Šivo, J. Šimon, K. Holý, M. Chudý, M. Richtáriková, and J. Morávek
Elsevier BV
J. Šimon, K. Holý, M. Bulko, Carlos Granja, Claude Leroy, and Ivan Stekl
AIP
This paper deals with the so‐called quantity “equivalent mixing height” (h), closely related to the dynamic state of the ground and boundary layer of the atmosphere, where convective flows of substances are present. Based on the theory of fluid mechanics, equations describing h are derived. Quantitative relations between 222Rn volume activity, h and eddy diffusion coefficient are described. A possibility of using h for assessing the atmospheric stability is explored.
M. Bulko, K. Holy, M. Mullerova, J. Simon, Carlos Granja, Claude Leroy, and Ivan Stekl
AIP
Various sources of atmospheric radon, as well as the results of radon monitoring at the Faculty of Mathematics, Physics and Informatics (FMFI CU) campus are discussed. The evaluation of the risk caused by radon and its decay products in the Bratislava atmosphere is given.