Colour Modification of Wood by Dry Thermal Treatment Between 90°C and 200°C = A faanyag színének változása száraz hőkezelés hatására 90°C és 200°C között

The colour modification effect of dry thermal treatment was studied in black locust (Robinia pseudoacacia L.), poplar (Populus x euramericana cv. Pannonia), Scots pine (Pinus sylvestris L.), spruce (Picea abies Mill.) and larch (Larix decidua L.) species in the temperature range 90-200 °C. Colour data were presented and evaluated in the CIE L*a*b* coordinate system. All thermal treatments applied altered the wood colour throughout the entire cross section regardless of the treatment temperature. At lower temperatures, wood extractives played a decisive role in colour change. The degradation products of hemicelluloses were the major determinant of the change in lightness at 200°C. Redness change in percentage showed much greater alteration than the yellowness and the lightness change. Spruce presented the greatest chromaticity coordinate (a* and b*) alteration among the investigated species. Changes in redness and yellowness followed the Arrhenius law during the investigated dry thermal treatments confirming that the temperature dependence of these colour parameters is exponential for wood material. Száraz körülmények között végrehajtott termikus kezelés színváltoztató hatását vizsgáltuk akác (Robinia pseudoacacia L.), nyár (Populus x euramericana cv. Pannonia), erdei fenyő (Pinus sylvestris L.), lucfenyő (Picea abies Mill) és vörösfenyő (Larix decidua L.) faanyag esetében 90 – 200 °C hőmérséklet tartományban. A szín adatokat a CIE L*a*b* koordináta rendszerben adtuk meg és értékeltük. Az alkalmazott hőkezelések a faanyag színét, függetlenül az alkalmazott hőmérséklettől, a próbatestek teljes keresztmetszetében megváltoztatták. Alacsony hőmérsékleten az extrakt anyagtartalom volt meghatározó a színváltozásban. A hemicellulózok degradációs termékei határozták meg döntő mértékben a világosság változását 200 °C-on. A százalékosan megadott vörös színezetváltozás sokkal nagyobb mértékű volt, mint a sárga színezet és a világosság változása. A luc faanyaga mutatta a legnagyobb színezeti koordináta-változást (a*és b*) a vizsgált faanyagok közül. A vörös és a sárga színezet változása követte az Arrhenius törvényt a száraz termikus kezelések során mutatva, hogy ezeknek a paramétereknek a hőmérséklet függése exponenciális faanyag esetében

Characteristics of Resonance Sound in a Circular Saw Enclosure

Several studies have been conducted to reduce the idling noise of circular saws because the sound level is extremely high and harms the environment. However, conventional noise suppression technology only controls the vibrations of the circular saw itself, whereas idling noise can be generated when the air inside the enclosure is resonant. In this study, the relationship between the rotational speeds of the circular saw blade and the frequencies of the resonance sound when the circular saw blade is running idle in an enclosure was examined. Additionally, the sound pressure modes and frequencies of the air in the enclosure were analyzed using the finite element method of acoustic analysis. The results showed that resonance sound was generated only when the circular saw blade was enclosed. The frequencies of the resonance sound generated by a circular saw blade made of acrylic plastic were the same as those generated by a steel saw blade. The resonance sound was generated regardless of the outer diameter of the circular saw blade. The peak resonant frequencies formed a step-like line during the analysis in which the rotational speed of the saw blade was steadily increased

Validation study on light scattering changes in kiwifruit during postharvest storage using time-resolved transmittance spectroscopy

Abstract Visible and near-infrared spectroscopy has been well studied for characterizing the organic compounds in fruit and vegetables from pre-harvest to late harvest. However, due to the challenge of decoupling of optical properties, the relationship between the collected samples’ spectral data and their properties, especially their mechanical properties (e.g., firmness, hardness, and resilience) is hard to understand. This study developed a time-resolved transmittance spectroscopic method to validate the light scattering changing characteristics in kiwifruit during shelf-life and in cold storage conditions. The experimental results demonstrated that the reduced scattering coefficient ( $${\mu }_{s}^{\prime}$$ μ s ′ ) of 846 nm inside kiwifruit decreased steadily during postharvest storage and is more evident under shelf-life than in cold storage conditions. Moreover, the correlation between the $${\mu }_{s}^{\prime}$$ μ s ′ and the storage time was confirmed to be much higher than that using the external color indexes measured using a conventional colorimeter. Furthermore, employing time-resolved profiles at this single wavelength, an efficacious mathematical model has been successfully formulated to classify the stages of kiwifruit softening, specifically early, mid-, and late stages. Notably, classification accuracies of 84% and 78% were achieved for the shelf-life and cold storage conditions, respectively