Miroslav Němec

Dr. Miroslav Němec

orcid

Research Focus & Metrics

Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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24 May 2019 in Sustainability
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ADAnna Danihelová
Anna Danihelová
Miroslav NěmecMiroslav Němec
Miroslav Němec
Tomáš GergeľTomáš Gergeľ
Tomáš Gergeľ
Miloš GejdošMiloš Gejdoš
Miloš Gejdoš
JGJanka Gordanová
Janka Gordanová
PSPatrik Sčensný
Patrik Sčensný
The sound absorption coefficient is a commonly used parameter to characterize the acoustic properties of materials. The fire performance of construction products has to be evaluated on the basis of their reaction to fire performance. The evaluation of the reaction to fire performance for the flammable construction materials which are in Class E reaction to fire is based on the ignitability test and the thermal test using the radiant heat source. For this study, nine types of STERED® products, which were made from the recycled automotive technical textiles, were chosen in order to evaluate their ability for sound absorption and the reaction to fire. The fire performance was evaluated on the basis of the relative mass loss in the radiant heat source test; the ignitability in accordance with ISO 11925-2, the possible appearance of flame, duration of flame, and the glowing during the single flame source test. The sound absorption of nine products was rated on the basis of the sound absorption coefficient and the noise reduction coefficient. The measurement was performed using the transfer function method in accordance with ISO 10534-2. From the nine tested types of STERED® products, the product Senizol AT XX2 TL 60 had the lowest mass loss at thermal loads up to 700 °C and it fulfilled the conditions for Class E reaction to fire. This product had the highest noise reduction coefficient of 0.81 and a high absorption coefficient for frequencies ranging between 500 Hz and 2000 Hz. The STERED® product Senizol AT XX2 TL 60, as well as Senizol AT 22 TL 50, Senizol AT 40 TL 25, Senizol AT XX4 TL 50 and Senizol AT XX4 TL 10 with a sound absorption coefficient α of between 0.80 to 0.95 and corresponding NRCs from 0.66 to 0.81, these STERED® products can be classified according to ISO 11654 into the sound absorption classes A and B.

24 December 2018 in Sustainability
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RIRastislav Igaz
Rastislav Igaz
Richard KminiakRichard Kminiak
Richard Kminiak
ĽKĽuboš Krišťák
Ľuboš Krišťák
Miroslav NěmecMiroslav Němec
Miroslav Němec
Tomáš GergeľTomáš Gergeľ
Tomáš Gergeľ
The issue of the change in tool temperature as a result of the machining process is presented in this paper. The aim of the paper is to put forward a proposal and subsequently to verify the methodology of temperature monitoring in the process of computer numerical control (CNC) machining in real time. Subsequently, the data can be used in the process of adaptive machine-tool control. Experiments were used to determine whether the research method is appropriate. Oak, beech and spruce wood turning blanks with the thickness of 20 mm were machined using a 5-axis CNC machining centre. A temperature change observation resulting from the changes in parameters of the removed layer was used to test whether the research method is relevant. Parameters of the removed layer were affected by the changes in feed rate in the range from 1 ÷ 5 m·min−1 in the removed layer (1–5 mm) or in wood species used in the experiment. As emerges from the proposed methodology, it is possible to monitor the changes in tool temperature responding to minimal changes in technological parameters on a relatively small size of a milled surface quite accurately. Sensitivity to given changes in technological parameters as well as the importance of the methodology was proven.

7 July 2021 in Forests
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ETEugenia-Mariana Tudor
Eugenia-Mariana Tudor
LKLubos Kristak
Lubos Kristak
MBMarius Catalin Barbu
Marius Catalin Barbu
Tomáš GergeľTomáš Gergeľ
Tomáš Gergeľ
Miroslav NěmecMiroslav Němec
Miroslav Němec
RRRoman Reh
Roman Reh
The potential of tree bark, a by-product of the woodworking industry, has been studied for more than seven decades. Bark, as a sustainable raw material, can replace wood or other resources in numerous applications in construction. In this study, the acoustic properties of bark-based panels were analyzed. The roles of the particle size (4–11 mm and 10–30 mm), particle orientation (parallel and perpendicular) and density (350–700 kg/m3) of samples with 30 mm and 60 mm thicknesses were studied at frequencies ranging from 50 to 6400 Hz. Bark-based boards with fine-grained particles have been shown to be better in terms of sound absorption coefficient values compared with coarse-grained particles. Bark composites mixed with popcorn bonded with UF did not return the expected results, and it is not possible to recommend this solution. The best density of bark boards to obtain the best sound absorption coefficients is about 350 kg/m3. These lightweight panels achieved better sound-absorbing properties (especially at lower frequencies) at higher thicknesses. The noise reduction coefficient of 0.5 obtained a sample with fine particles with a parallel orientation and a density of around 360 kg/m3.

Miroslav NěmecMiroslav Němec
Miroslav Němec
ADAnna Danihelová
Anna Danihelová
Tomáš GergeľTomáš Gergeľ
Tomáš Gergeľ
Miloš GejdošMiloš Gejdoš
Miloš Gejdoš
VOVojtěch Ondrejka
Vojtěch Ondrejka
ZDZuzana Danihelová
Zuzana Danihelová
The paper deals with comparing the measurement of noise from the railroads in the residential zone of the town of Zvolen with the results calculated using the prediction methods “Schall 03“ (Deutsche Bundesbahn, 1990) and “Methodical instructions for the calculation of sound pressure level from transport” (MPVHD). The first is used in the Slovakia and second in the Czech Republic. The measurement results and the results obtained from the prediction methods for both measurement locations were evaluated graphically and statistically. The evaluation of the conformity of the measurement with the prediction showed that the results obtained using the method “Schall 03” are in better agreement with the measurement.

3 January 2022 in Coatings
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JFJozef Fekiač
Jozef Fekiač
JSJán Svoreň
Ján Svoreň
JGJozef Gáborík
Jozef Gáborík
Miroslav NěmecMiroslav Němec
Miroslav Němec
Cutting, as the most widely used machining process, is applied in both primary and secondary wood processing. Optimum cutting conditions that result in the high quality of the machined surface and low energy consumption are crucial for wood processing. The effects of the feed speed, cutting speed and average chip thickness on the energy consumption and surface temperature of a circular saw blade during the cutting process of two types of plywood with a thickness of h = 14 mm is described in this paper. In experimental measurements, two circular saw blades with cutting tungsten carbide inserts for wood were used as tools. One circular saw blade was standard, and was not surface treated (CSB1), and second circular saw blade (CSB2) differed by the powder coating surface and the length of the cutting edge. In the experiment, the energy consumption and the surface temperature of the circular saw blade was measured in order to find the optimal cutting conditions for the most energy-efficient cutting process. The results show that the cutting power and the surface temperature of the circular saw blade increased when the feed speed increased. The investigated values of the surface-treated circular saw blade were lower compared to the values of the standard circular saw blade. When comparing the lightweight plywood with the classic plywood, experimentally obtained cutting power values of the circular saw were made 19% lower on average by using the circular saw blade CSB1. When using the CSB2 circular saw blade, these values of the cutting power of the circular saw were 22% lower on average. The surface temperature of the circular saw blade is the highest on the outer edge (tooth root area 31.7 °C) and decreases towards the center of the circular saw blade. There must be a reasonable compromise between machine productivity and energy consumption.

17 January 2023 in Forests
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Richard KminiakRichard Kminiak
Richard Kminiak
Miroslav NěmecMiroslav Němec
Miroslav Němec
RIRastislav Igaz
Rastislav Igaz
Miloš GejdošMiloš Gejdoš
Miloš Gejdoš
The operation of CNC machining centers, despite their technological progress, can still be affected by undesirable events associated with the technological parameters of their operation. The minimization of these risks can be achieved via their adaptive control in the process of operation. Several input parameters for adaptive control are still the subject of research. The work aimed to find out the influence of the change in feed speed, revolutions, and radial depth of cut on the noise and temperature of the tool during the milling of wood-based composite material particleboard. At the same time, it was evaluated whether it is possible to use the measured values of these parameters in the future in the process of an adaptive control of the CNC machine with the minimization of their negative influence. The methods of measuring these parameters were chosen based on valid legislation and previous research. The results of the research show that all parameters influence both the noise and temperature of the tool, while the rate of the radial depth of cut has the greatest influence on the increase in temperature, and the noise is most affected by the revolutions. The effect of temperature during woodworking can also be characterized in terms of the potential long-term wear of the cutting tool. The setting of optimization algorithms of monitored parameters in the adaptive control of the CNC machining center will be the subject of further research.