This paper explores the dynamic behavior of different wood species in the form of violin boards, based on experimental modal analysis using a single-input, multiple-output configuration. Thus, two groups of species were studied: the first group for the violin top plates, being analyzed Picea abies (spruce), Taiwania cryptomerioides Hayata (Taiwania), and Cryptomeria japonica (Japanese cedar), and the second group, with species for the back plates, such as Acer pseudoplatanus (maple), Populus nigra (poplar), Salix alba (willow), and Firmiana simplex (Chinese parasol). The results highlighted the frequency spectrum and the dominant resonance frequency, as well as the frequency damping, the signal processing analysis being based on Fast Fourier Transform and Wigner–Ville distribution of signals. The results highlighted that the lowest values of acoustic radiation are recorded for maple wood (7.8 m⁴ kg⁻¹ s⁻¹) and Taiwania (10.08 m⁴ kg⁻¹ s⁻¹), and the highest values for spruce (14.7 m⁴ kg⁻¹ s⁻¹) and Chinese parasol (15.58 m⁴ kg⁻¹ s⁻¹). Regarding the resonance frequency, the Taiwania and Japanese cedar plates present the dominant frequency around 600–635 Hz in comparison with Norway spruce having 920 Hz. The ratios between dominant frequencies of the Chinese parasol, poplar, maple, and willow are 1:1.42:2.62:2.98. It can be concluded that spruce and maple wood present the best dynamic properties, but when using other species, Japanese cedar wood for the top plate and Chinese parasol wood for the back plate represent species with potential in the construction of stringed musical instruments. Either a mechano-thermal treatment or an appropriate finish can enhance the acoustic qualities of these wood species, research that can be undertaken in the future.

T he objective of this study was to investigate the chlorine-related challenges in Automotive Shredder Residue (ASR) by developing a de-chlorination strategy and formulating Solid Recovered Fuel (SRF) pellets with improved environmental and fuel quality. A ternary blending approach was employed using Fe–Ca-based inorganic dechlorinating agents and thorny bamboo biomass as co-materials with ASR. The de-chlorination efficiency, calorific value, and ash content of the resulting SRF were evaluated. Results indicated that the optimal dechlorinating formulation reduced the chlorine content of PVC from 43.26 wt% to 0.59 wt%, achieving a de-chlorination efficiency of 97.23%. A second-order polynomial regression model （ η_DeCl = –1.5277x² + 2.5519x – 0.0225 ， R² = 0.9347 ） was developed to predict the de-chlorination performance based on the blending ratio of dechlorinating agent to ASR, demonstrating behavior consistent with first-order reaction kinetics observed in pyrolytic de-chlorination. The final ternary formulation—comprising 55% thorny bamboo, 37.5% ASR, and 7.5% dechlorinating agent—produced SRF pellets with improved overall quality, demonstrating effective chlorine control, reasonable ash content, and enhanced thermal properties suitable for regulatory compliance and practical application. S uch findings meet the criteria set by EN ISO 21640:2021 (Class 2), JIS Z7311 (Grade A), and forthcoming Taiwanese SRF regulations. B ased on the findings in this work it can be stated that the high de-chlorination potential of Fe–Ca-based additives for chlorine-rich waste and introduces a predictive formulation model that supports both resource circularity and clean fuel production.

The aim of this research is to develop and validate an experimental model testing method in the erhu instrument. The model analysis is dependent on the dynamic behavior of materials which results the relationships to be naturally excited due to the structure. There are three major factors which would directly affect the performance of erhu vibroacoustic: (1) string, (2) vibrating skin, and (3) wooden soundbox. However, the transducer mass effect is the significant impact factor in the membrane vibration measurement. The attention is focused on the erhu skin vibration modes by using the scanning laser method. The method for experimental mode shapes of erhu skin was notable in that the equipment assembled a loudspeaker, a signal point laser, and a scanning laser vibrometer. The mode shapes can be excited depending on the white noise with plane acoustic wave to push on the skin surface. The scanning laser method is content two types of laser doppler vibrometer for various purpose. The single point laser measured the driving point vibration as the reference in the center of the skin surface. The responses were measured by the scanning laser vibrometer with 276 measuring points on the surface. The results showed the vibroacoustic of erhu skin which the various mode shapes are dependent on the frequency diversifications. The mode shapes of the erhu skin can be characteristic into five vibroacoustic patterns by the various frequency ranges (20 to 5,000 Hz). Obviously, the scanning laser method is a convenient and readily reproducible setup to evaluate in the erhu vibroacoustic properties. As an engineering application, the proposed method can be served as a fundamental tool when predicting or even suppressing the possible excitations associated with particular vibration modes in the mechanical designs of the instruments.