http://scholars.ntou.edu.tw/handle/123456789/163 Tue, 28 Apr 2026 10:17:23 GMT 2026-04-28T10:17:23Z https://scholars.ntou.edu.tw:443/retrieve/72/河海工程學系.jpg http://scholars.ntou.edu.tw/handle/123456789/163 http://scholars.ntou.edu.tw/handle/123456789/26540 標題: Modeling an array of surface-piercing piezoelectric plate wave energy converters for wave power absorption 作者: Sarkar, Biman; De, Soumen; Tsai, Chia-Cheng; Hsu, Tai-Wen 摘要: In recent years, the pursuit of sustainable ocean energy has accelerated, with wave energy conversion technologies emerging as a promising avenue for low-power electricity generation. Among various approaches, extracting electrical energy from ocean waves through piezoelectric mechanisms offers an innovative and eco-friendly solution. Acting as flexible plate-type wave energy converters, these structures are designed to efficiently capture the hydrodynamic energy of surface waves. The primary motivation behind this work arises from the observation that surface-piercing, vertically oriented piezoelectric plate-type wave energy converters have not been reported in the existing literature, to the best of the authors' knowledge. Despite their significant potential for practical marine energy applications, vertical piezoelectric configurations can provide advantages in achieving the optimum electrical load resistance, thereby maximizing harvested power, compared to horizontally oriented configurations (Kazemi et al., 2021). To overcome the mathematical complexities associated with the coupling between structural flexibility and piezoelectric interactions, a rigorous semi-analytical framework is developed. These complexities arise due to boundary conditions that involve higher-order derivatives with complex-valued coefficients. The governing problem is reformulated into a set of coupled integral equations by employing Green's function solutions along with mixed Fourier transform techniques. These equations are subsequently solved through a Singularity-Respecting Galerkin approximation, yielding accurate evaluations of the hydrodynamic response, including the reflection characteristics, wave power absorption efficiency and hydrodynamic wave forces. Furthermore, a comprehensive parametric investigation is undertaken to elucidate the influences of wave and structural parameters on plate deflection, bending moments and shear forces. Deploying multiple piezoelectric plates in an array has been found to be a more promising approach for wave power absorption. Widening the spacing between adjacent plates greatly influences the deflection of the leeward plate, regardless of whether the edges are clamped-clamped or clamped-free. The outcomes offer valuable physical insights into the energy extraction capability and dynamic behavior of the proposed array of surface-piercing piezoelectric plate-type wave energy converters. Thu, 01 Jan 2026 00:00:00 GMT http://scholars.ntou.edu.tw/handle/123456789/26540 2026-01-01T00:00:00Z http://scholars.ntou.edu.tw/handle/123456789/26537 標題: Scattering of capillary-gravity waves by surface-piercing porous barriers in the presence of uniform current over a porous sea bed 作者: Sahoo, Gagan; Behera, Harekrushna; Hsu, Tai-Wen 摘要: Capillary-gravity waves, influenced by both surface tension and gravity, interact strongly with marine structures, especially in the presence of uniform currents. Despite extensive studies on wave scattering by porous structures, the combined effects of surface tension, current, and porous barriers over a porous bottom remain insufficiently explored. This study examines the scattering of such waves by two thin surface-piercing porous barriers in the presence of a uniform current over a porous sea bed. A linear wave-structure interaction model is solved numerically through a hybrid Boundary Element-Finite Difference Method (BEM-FDM) and analytically through an eigenfunction expansion combined with a least-squares approach. The hybrid BEM-FDM efficiently handles higher-order boundary conditions that cannot be directly addressed by conventional BEM, while the analytical method eliminates the need for eigenfunction orthogonality and explicit mode coupling. The effects of surface tension, current velocity and direction, porous effect parameters of barriers as well as bottom, barrier length and spacing between them on reflection, transmission, and energy dissipation are analyzed. Results show that surface tension enhances reflection and dissipation while reducing transmission. Current direction strongly affects scattering: following currents enhance transmission, whereas opposing currents increase reflection and dissipation. Longer barriers and larger porous-effect parameters of both porous barriers and porous bottom enhance energy dissipation, while spacing between porous barriers induce interference driven oscillations. Thu, 01 Jan 2026 00:00:00 GMT http://scholars.ntou.edu.tw/handle/123456789/26537 2026-01-01T00:00:00Z http://scholars.ntou.edu.tw/handle/123456789/26514 標題: Dual boundary element method for solving the two-dimensional Helmholtz equation for the damped wave equation 作者: Chen, Kue-Hong; Liu, Yi-Kui; Chen, Jeng-Tzong 摘要: In this paper, the dual boundary integral formulation of the two-dimensional Helmholtz equation with complex wave number is derived. The presence of damping in the medium results in the Helmholtz equation incorporating complex wave numbers in mathematical models. To address the singular and hypersingular integrals, the addition theorem is used to expand the four kernel functions, originally expressed with complex variables in the dual formulation, into purely real-variable functions in a series form. Consequently, the singular and hypersingular integrals are successfully transformed into the summation of regular integrals in an infinite series through the proposed regularization technique. The regular integrals are then computed using the Gaussian quadrature rule. This paper examines the occurrence of eigenvalues in both interior and exterior Helmholtz problems to understand how damping influences resonances. To validate the proposed formulation, three cases with exact solutions are used as standard benchmarks to evaluate the convergence and accuracy of the developed dual boundary element method program. Finally, two more general cases with amoeba-shaped geometry, which lack an exact solution and pose challenges in obtaining a convergent solution due to their irregular shape, are considered to evaluate the applicability and effectiveness of the proposed formulation. (c) 2025 Acoustical Society of America. Wed, 01 Jan 2025 00:00:00 GMT http://scholars.ntou.edu.tw/handle/123456789/26514 2025-01-01T00:00:00Z http://scholars.ntou.edu.tw/handle/123456789/26502 標題: AI-Driven GIS Modeling of Future Flood Risk and Susceptibility for Typhoon Krathon under Climate Change 作者: Liu, Chih-Yu; Ku, Cheng-Yu; Tsai, Ming-Han; You, Jia-Yi 摘要: Amid growing typhoon risks driven by climate change with projected shifts in precipitation intensity and temperature patterns, Taiwan faces increasing challenges in flood risk. In response, this study proposes a geographic information system (GIS)-based artificial intelligence (AI) model to assess flood susceptibility in Keelung City, integrating geospatial and hydrometeorological data collected during Typhoon Krathon (2024). The model employs the random forest (RF) algorithm, using seven environmental variables excluding average elevation, slope, topographic wetness index (TWI), frequency of cumulative rainfall threshold exceedance, normalized difference vegetation index (NDVI), flow accumulation, and drainage density, with the number of flood events per unit area as the output. The RF model demonstrates high accuracy, achieving the accuracy of 97.45%. Feature importance indicates that NDVI is the most critical predictor, followed by flow accumulation, TWI, and rainfall frequency. Furthermore, under the IPCC AR5 RCP8.5 scenarios, projected 50-year return period rainfall in Keelung City increases by 42.40%-64.95% under +2 degrees C to +4 degrees C warming. These projections were integrated into the RF model to simulate future flood susceptibility. Results indicate two districts in the study area face the greatest increase in flood risk, emphasizing the need for targeted climate adaptation in vulnerable urban areas. Wed, 01 Jan 2025 00:00:00 GMT http://scholars.ntou.edu.tw/handle/123456789/26502 2025-01-01T00:00:00Z