A Comparative Analysis of Optimal and Sub-Optimal Rules in Full-Information Duration Problem

The 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

Study on Advancement of PSI Management in Japan With S&OP

長崎総合科学大学博士（学術）2024doctoral thesi

A Study on Structural Optimization by Adjusting Plate Thickness under Displacement Excitation using FEM

In 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

ケミカルタンカー建造品質管理における検査手法のデジタル化に関する研究 : 造船工場の生産性向上を目指して

長崎総合科学大学博士（工学）2024doctoral thesi

CFRP積層板およびそのスカーフ修理部の静的強度・疲労強度に関する研究

長崎総合科学大学博士（工学）2025doctoral thesi

Research on practical experiments with logistics drones in the ceramic industry

The 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 Fracture Toughness at Bonded Interface of Stainless-clad Steel Plates for Chemical Takers

A few years ago, duplex stainless clad steel plates have been developed and released. They have recently been applied to the cargo tank of chemical tanker, in combination with the duplex stainless clad steel plate (SUS329J3L-clad) and the duplex stainless steel plate (SUS329J3L). For chemical tanker, the cruciform welded joints between the transverse bulkhead and the double bottom in the cargo tank require utmost attention to prevent fatigue crack formation. Therefore, we have conducted various kinds of fracture toughness tests on these duplex stainless clad steel plates (SUS329J3L-clad) as well as the austenitic stainless clad steel plates (SUS316L-clad and SUS317L-clad) to evaluate their fracture toughness at the bonded interface in terms of the safety and reliability. 　In this study, we comprehensively organized and evaluated these fracture toughness test results. For the valid Kc value at bonded interface of each stainless clad steel plate, we have obtained the following knowledge points ; it is considered that the valid Kc value is 1.25×103 N/mm3/2 for the austenitic stainless clad steel plates (SUS316L-clad) and it is 1.37×103 N/mm3/2 for the duplex stainless clad steel plates (SUS329J3L-clad), and the duplex stainless clad steel plates (SUS329J3L-clad) showed better fracture toughness than the austenitic stainless clad steel plates (SUS316L-clad and SUS317L-clad).departmental bulletin pape

都市の記憶ⅩⅣ 731部隊？なぜ今？

departmental bulletin pape

Study on the Influence of Amplitude Dependence of SEA parameters for a Single Flat Plate

In this paper, in order to assist in quantitative evaluation when constructing an experimental SEA model, we first conduct the FEM calculations in numerical experiments to determine the large and small damping characteristics of a single flat steel plate structure. Then, using FEM and real experiments, we show the degree of variation in the FRF results and the SEA parameter results at five levels of input force from 1 N to 5 N. As a result, in the case of structure with large damping, it cannot be seen the influence of amplitude dependence of the FRF results. However, the results of the subsystem vibration energy normalized by the input power, which is a SEA parameter, showed the influence of amplitude dependence at relatively small input force. In the case of structures with small damping, the influence of amplitude dependence can be seen in the FRF results. The results of the subsystem vibration energy normalized by the input power showed that the results were more likely to vary due to the spatial averaging process of the number of input and response.departmental bulletin pape

Study of modal energy propagation method

長崎総合科学大学博士（工学）2024doctoral thesi