Nagasaki Institute of Applied Science Institutional Repository (NiAS)
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Possible enhancement of the efficiency of an oscillating water column wave energy converter with artificial intelligence
Get PDFThe possibility of the efficiency enhancement of an oscillating water column (OWC) wave energy converter with artificial intelligence (AI) is investigated using the experimental data obtained in a water tank while changing the aperture ratio of the air outlet installed at the upper end of the OWC to three ways. After making the AI to learn the relationships between the waves incident to the OWC and the resultant wave movements, pressure variations in the OWC or the energy conversion efficiencies, it is examined if the corresponding AI could predict the wave movements, pressure variations in the OWC or the energy conversion efficiencies before they really take place. If these predictions are possible, the energy conversion efficiencies of an OWC could be enhanced by changing the aperture ratio of the air outlet to an optimum one in advance.departmental bulletin pape
Analysis on Aerodynamic Characteristics of WIG : Proposal of New Green’s Function considering Water Wave Generation caused by Aerial Vortices
Get PDFIn this paper, a Green’s function considering water wave generation caused by aerial vortices is proposed. The new function is derived in the form that the influence of pressure fluctuations on the water surface is reflected by using the Fourier transform method.
By performing an asymptotic analysis for the Green’s function, it is shown that the high-speed flow field due to an aerial vortex can be represented by placing a slightly weaker vortex at the mirror image position under the water surface. As a result, asymptotic wave profiles at the high speed swells up in the neighborhood of WIG.
Furthermore, the lift force and wave-making resistance acting on the WIG are analyzed based on the momentum theorem, and thereby smart calculation formulae are presented for the two forces. Based on the developed theory, specific numerical calculations of aerodynamic forces and water wave profiles are performed for NACA airfoils as an example of thick wings. Thereby a certain amount of knowledge was obtained about the water surface effects of WIG.departmental bulletin pape
Research on practical experiments with logistics drones in the ceramic industry
Get PDFThe ceramic industry in Hasami, Nagasaki Prefecture, is notable for its specialized division of labor, with distinct companies managing individual production stages. This structure has given rise to a unique logistical process known as "Kiji-biki," involving the inter-company transport of semi-finished goods. However, contemporary challenges, including traffic congestion, escalating CO2 emissions, and increased labor expenses, have emerged. This research investigates the potential of drone-based transport as a solution to these challenges, presenting a demonstration experiment to evaluate its efficacy.departmental bulletin pape
A Study on Structural Optimization by Adjusting Plate Thickness under Displacement Excitation using FEM
Get PDFIn this paper, taking into consideration future manufacturing methods using one-piece molding by aluminum extrusion, the target structures are a thin plate structure that extends the suspension of a car or a battery box cover of an electric vehicle simulating multiple flat plate. Using a multi-point excitation input method for base excitation using FEM, the vibration response energy is used as the objective function, and a structural optimization method for the plate thickness cross-section of FE elements grouped as design variables is considered. As a result, a comparison of the vibration response energy showed that multi-point excitation excites vibration modes that are not excited by the one way excitation. Furthermore, by averaging frequencies over a one third octave band, we were able to propose a structural optimization method that makes it easier to select the objective function.departmental bulletin pape
A Comparative Analysis of Optimal and Sub-Optimal Rules in Full-Information Duration Problem
Get PDFThe full-information duration problem with a random number N of applicants is considered by Tamaki (2016). The objective of the problem is to find a stopping rule that maximizes the duration of holding a relative maximum. While Tamaki’s optimal rule leads to complex expressions for the expected payoff, it is known that a remarkably simple relationship between the expected payoffs of the two models, Model1 and Model2, can be considered according to whether the planning horizon is N or n, where N is a random variable with a known upper bound n. We propose a sub-optimal rule based on a constant threshold rule, where the relatively best applicant is selected as soon as her/his value that can be observed exceeds a fixed threshold a(0 ≤ a ≤ 1). We analytically derive the expected payoffs under this sub-optimal rule for both Model1 and Model2. Our numerical experiments show that the proposed rule not only simplifies computation but also achieves performance close to that of the optimal rule.departmental bulletin pape
