Current Issue : January-March Volume : 2025 Issue Number : 1 Articles : 5 Articles
In classical guitar acoustic spectra, the lowest frequency body mode’s amplitude often significantly surpasses that of the string overtones. However, the characteristics of the body mode have not been systematically utilized to quantitatively represent the timbre of classical guitars. In this study, we propose a quantitative method for describing the body mode, which can effectively differentiate the timbre of classical guitars. Our approach involves three key parameters presented in a three-dimensional space, as follows: the frequency and quality factors of the body mode, along with the amplitude ratio of the plucked string note to the body mode in the soundboard’s vibration spectrum. This representation allows for the visualization, quantitative comparison, and classification of the body mode note and damping properties across classical guitars. The differences in body mode among guitars can be analyzed quantitatively using Euclidean distance....
Seafloor topography prediction can fill in sea areas without ship sounding data. However, the dependence of various topographic prediction algorithms on ship soundings varies significantly. Hence, this study explores the impact of the number and distributions of ship soundings on topographic prediction using the gravity–geologic method (GGM) and an analytical algorithm. Firstly, this study investigates the influence of ship sounding coverage on the two algorithms. The simulation results demonstrate that increasing coverage from 5.40% to 31.80%, coupled with more uniform distributions across the study area, substantially reduces the RMS error of the GGM. Specifically, the RMS error decreases from 238.68 m to 42.90 m, an improvement of 82.03%. The analytical algorithm maintains a consistent RMS error of 40.39 m because it does not depend on ship soundings. Furthermore, we select a 1◦ × 1◦ sea area (134.8◦–135.8◦E, 30.0◦–31.0◦N), and the ship soundings are divided into two control groups, Part I and Part II, with coverages of 8.19% and 33.19%, respectively. When Part II is used for calculation, the RMS error of the GGM decreases from 204.17 m to 126.95 m compared to when Part I is used, while the analytical algorithm exhibits an RMS error of 167.94 m. The findings indicate that the prediction accuracy of the GGM is significantly affected by ship soundings, whereas the analytical algorithm is more stable and independent of ship soundings. Based on simulation experiments and realistic examples, when the effective ship soundings coverage exceeds 30%, the GGM may have more advantages. Conversely, the analytical algorithm may be better. This suggests that effectively combining and utilizing different algorithms based on the ship sounding coverage can improve the accuracy of topographic prediction. This will provide a basis for integrating multiple algorithms to construct a global seafloor topography model....
In this study high-resolution stereo images and Digital Terrain Models (DTMs) from MErcury Surface, Space ENvironment, Geochemistry and Ranging (MESSENGER) mission were utilized to detect impact structures in regions not covered by Mercury’s Laser Altimeter (MLA), while gravitational data was utilized as a supported data set. We have established an inventory of 314 impact structures ≥ 150 km, classified on their morphological and gravitational characteristics. 24 basins ≥ 300 km have been newly discovered. Additionally, we have identified significant surface modifications in impact structures of smooth material infill, which can be either impact-induced or volcanic in origin. The Bouguer anomaly and crustal thinning in the center are displaying an interplay of predominant change of crustal structure in impact basins. Further, this study reveals a common impact history of Mercury and the Moon. Nevertheless, cumulative density distributions suggest the possibility of either a divergence in impactor populations responsible for forming large basins on both celestial bodies or a significant shift in impactor rates. This work holds important implications not only for understanding impact structure formation and evolution processes but also for interpreting the crustal structure. It presents an updated and expanded catalog of impact structures on Mercury, encompassing buried basins, and identifies new areas of interest, potentially serving as target sites for the forthcoming BepiColombo mission....
The aim of the presented research is to evaluate the potential performance of a new bending magnet X-ray beamline—PolyX, designed for microimaging and microspectroscopy at the National Synchrotron Radiation Centre SOLARIS in Krakow. Due to the short beamline length (<15 m), PolyX uses compact polycapillary and single-bounce monocapillary optics for X-ray focusing in the 4–15 keV energy range. Polycapillary optics require a dedicated approach for an efficient simulation of X-ray propagation in multiple capillary channels. Therefore, the PolyX beamline was ray traced by combining XRT (XRayTracer) and polycap libraries. In addition, to estimate the X-ray fluorescence spectra excited by focused beams, Monte Carlo simulations were conducted using XMI-MSIM. All simulations were aimed to estimate the crucial X-ray beam properties, i.e., the flux, the spot size, and the energy spectrum, for monochromatic and polychromatic X-ray beams....
Oil extraction is shifting towards high-temperature and high-pressure environments, which leads to the deterioration of the rubber material used in packer rubber cylinders, ultimately resulting in sealing failure. Hence, we propose enhancing the configuration of the rubber cylinder by incorporating a composite material consisting of metal and rubber. Additionally, we suggest integrating springs at the shoulders to fabricate a spring-embedded shoulder protection packer rubber cylinder. ABAQUS 2023 software was employed to simulate the packer setting process, investigating the variations in compression distance between a conventional packer rubber cylinder and a spring-embedded shoulder protection packer rubber cylinder. The results showed that at 25 ◦C and 177 ◦C, the compression distance of the fully seated spring-embedded shoulder protection packer rubber cylinder was reduced by 3% compared to the traditional packer rubber, Mises stress was reduced by 14%, and the sealing performance evaluation coefficient K of the rubber cylinder was increased by 2% to 10%.The stress in the spring-embedded shoulder protection packer rubber cylinder is primarily concentrated between the spring and the wire mesh, effectively ensuring the performance of the rubber cylinder and mitigating any potential decrease in sealing performance caused by internal stress concentration. The spring-embedded protective rubber cylinder will not experience shoulder protrusion during the sealing process. The incorporation of a spring-embedded shoulder protection mechanism in the packer rubber cylinder enhances the contact stress between the rubber cylinder and casing tube, mitigates stress concentration within the rubber cylinder, resolves shoulder protrusion issues, and ultimately improves both sealing performance and service life....
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