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This was reverted to desorption at 65% RH (air-conditioning stage 3), and the last phase was the reverse drying of the samples back to 0% moisture at 103 °C (air- conditioning stage 4). Weight with dimensions of test specimens at marked points was determined at each stage. Ⱦ ୶ ሺΨሻൌ ୪ ౮ ି ୪ బ ୪ బ ͳͲͲ (2) Measuring points were indicated to ensure repeatability by measuring (mm) in the same position for all air-conditioning stages (x = 0 to 4). Furthermore, the moisture content of samples Z x (%) according to Eq. 3 was determined, where P 0 is the dry sample weight (g) and mass P x is the weight of the samples at air-conditioning levels (g). The density of the samples ȡ x (kg/m 3 ) was again calculated from the mass P x and the sample volume 9 x according to Eq. 4: ୶ ሺΨሻൌ ୫ ౮ ି ୫ బ ୫ బ ͳͲͲ (3) ɏ ୶ ሺ כ ି ଷ ሻൌ ୫ ౮ ౮ (4) The vertical density profile of boards was measured on a Compact X-ray density profile Analyser DPX300-LTE (Imal, Modena, Italy). The test samples had dimensions of 50 mm × 50 mm and were air-conditioned at 20 °C and 65% RH. Scanning electron microscopy (SEM) of ruptured samples, after internal bonding tests were performed using a MIRA 3 electron microscope (Tescan Orsay Holding, Brno, Czech Republic) with a secondary electron detector, operated at 15 kV acceleration voltage. 6WDWLVWLFDOPHWKRGV Besides descriptive statistics, an analysis of variance was used to determine whether any of the pairwise differences from the number of means were significant. The Tukey SRVWKRF test was employed to determine the significant differences between group means. A significance level of α = 0.05 was selected and all computations were performed using Statistica12 software (StatSoft CR s.r.o., Prague, Czech Republic). A digital imaging analysis revealed a heterogeneous proportion of the used wheat straw particles from which the boards were made. As shown in Fig. 3, there are also a number of dust particles in addition to the wheat straw stalks. Nevertheless, it was found that from 100 g of the sample, 30.9% of the particle was from 1.657 mm to 2.696 mm wide. In terms of length (Feret diameter), 29.1% of particle sizes ranged from 8.393 mm to 13.656 mm. The projection of some deformed particles may result in inaccuracies in measurements, which may be due to the processing of, for example, broad and thin or narrow and long stalks. To avoid distortion of the results, a sufficiently large set of 100 g was chosen to cover these inaccuracies. RESULTS AND DISCUSSION 3DUWLFOHVL]HDQDO\VLV
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Hýsek et al . (2018). “Cold plasma & straw board,” B io R esources 13(3), 5065-5079.
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