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Reflectance spectroscopy reveals mineralogy and preservation of ceramics from the Bidong Shipwreck

Wed, 01 Jan 2025 00:00:00 GMT

標題: Reflectance spectroscopy reveals mineralogy and preservation of ceramics from the Bidong Shipwreck 作者: Yunos, Nur Khatibah Md; Pan, Hui-Juan; Yang, Shouye; Ifandi, Elena; Rahman, Muhd Nur Ismail Abdul; Ariffin, Effi Helmy; Shaari, Hasrizal 摘要: Shipwreck ceramics are rarely analysed in situ since conventional mineral tests require sampling and jeopardise conservation. This study present the first application of full-range visible-near-infrared (VIS-NIR, 350-2500 nm) reflectance spectroscopy to shipwreck ceramics, analysing 30 sherds from the 16th-century Bidong wreck off Peninsular Malaysia. CIELAB colour space reveals the a*-b* linearity improves markedly from R-2 <= 0.50 on uncleaned surfaces to 0.80 in clean-powder subsamples, providing an objective metric for de-encrustation. High chromaticity and pervasive hematite document dominantly oxidising, whereas a minority of grey fabrics signal reduction firing conditions. Varimax-rotated PCA (VPCA) resolves 18 spectral components in intact sherds but only 11 after cleaning, demonstrating how surface alteration inflates apparent mineral diversity. Diagnostic loadings for illite and Fe-rich pyroxene (hedenbergite) tie the ceramic body to Sukhothai red clays, while copper sulphides and marine carbonates fingerprint post-burial interaction with Cu fittings and seawater. A weak 600-620 nm shoulder tentatively matches lazurite, a blue pigment rarely reported in Southeast Asian wares thus requires micro-analytical confirmation. This rapid, micro-destructive VIS-NIR method provides preliminary information about the salvaged artifacts which can be further correlated with another scientific study for provenance and production techniques interpretation.

Wave Dynamics Around a Floating Circular Flexible Plate Over a Permeable Bed

Mon, 01 Jan 2024 00:00:00 GMT

標題: Wave Dynamics Around a Floating Circular Flexible Plate Over a Permeable Bed 作者: Gayathri, R.; Tsai, Chia-Cheng; Behera, Harekrushna 摘要: In this paper, to determine the efficacy of the porous bed on damping far-field wave energy, the wave dynamics around a circular plate is studied. By combining the appropriate boundary conditions, the unknown potential is attained for the free surface and the plate-covered region. The Bessel series solution is attained further, by employing the matched eigenfunction expansion technique. Wave force excitation on the circular plate, deflection of the plate, and flow distribution is calculated and examined to comprehend the efficacy of the current investigation. Moreover, the motion of the plate is assessed in the time domain. The study reveals a substantial reduction in wave amplitude on the plate's leeward side because of the energy dissipation by the porous bed. Also the study concludes that for intermediate values of porosity with larger wavenumbers, approximately 50% of wave power is dissipated with respect to incident wave power.

Wave Energy Conversion through Oscillating Water Columns: A Review

Mon, 01 Jan 2024 00:00:00 GMT

標題: Wave Energy Conversion through Oscillating Water Columns: A Review 作者: Gayathri, R.; Chang, Jen-Yi; Tsai, Chia-Cheng; Hsu, Tai-Wen 摘要: An oscillating water column (OWC) is designed for the extraction and conversion of wave energy into usable electrical power, rather than being a standalone renewable energy source. This review paper presents a comprehensive analysis of the mathematical modeling approaches employed in OWC systems, aiming to provide an in-depth understanding of the underlying principles and challenges associated with this innovative technology. A prominent classification within the realm of wave energy devices comprises OWC systems, which exhibit either fixed or floating configurations. OWC devices constitute a significant proportion of the wave energy converter prototypes currently operational offshore. Within an OWC system, a hollow structure, either permanently fixed or floating, extends below the water's surface, creating an enclosed chamber where air is captured over the submerged inner free surface. This comprehensive study offers a thorough assessment of OWC technology in conjunction with air turbines. Additionally, the investigation delves into theoretical, computational, and experimental modeling techniques employed for analyzing OWC converters. Moreover, this review scrutinizes theoretical, computational, and experimental modeling methodologies, providing a holistic understanding of OWC converters. Ultimately, this work contributes a thorough assessment of OWC technology's current state, accentuating its potential for efficient wave energy extraction and suggesting future research avenues.

Wave power extraction from slanted oscillating water columns in the presence of an array of arbitrary trenches

Sun, 01 Jan 2023 00:00:00 GMT

標題: Wave power extraction from slanted oscillating water columns in the presence of an array of arbitrary trenches 作者: Gayathri, R.; Chang, Jen-Yi; Tsai, Chia-Cheng 摘要: This paper investigates the impact of arbitrary bottom topography on the efficiency of a slanted oscillating water column device located in near-shore areas. The device incorporates a turbine positioned at its opening, which harnesses the oscillation of the fluid at the free surface, created by recurrent incident waves, to propel an air volume in a uni-direction. To analyze the wave power absorption capability of the system, an eigenfunction expansion and a boundary element model based on linear water wave theory are employed. The notion is to use the anticipated amplification of scattered and reflected wave fields resulting from the existence of a sloping wall to improve the wave power absorption caused by the walls' wave reflections. The accuracy of the current study's numerical results is ratified by conducting a comparative study using the available data given by other researchers. The study demonstrates that multiple efficiencies occur in the case of the long-wave region as compared to the short-wave region. Additionally, both the shape and magnitude of the efficiency curves are influenced by the slanted design of the device's front wall and the number of trenches.