Institutional Repositories DataBase (IRDB)
Not a member yet
4321294 research outputs found
Sort by
Role of retrogression and reaging in suppressing hydrogen-induced transgranular cracking in 7xxx Al alloys
No full textRetrogression and reaging (RRA) treatment is a distinctive approach to counteract hydrogen embrittlement in 7xxx Al alloys without compromising strength. However, the mechanistic understanding of RRA has long centered around grain-boundary-related phenomena, while the roles of grain-interior microstructures in hydrogen embrittlement have remained unclear. Here, we demonstrate the beneficial effect of RRA in reducing transgranular cracks in a specially selected high-Zn alloy that exhibits fully quasi-cleavage cracking, thereby enabling the precise decoupling of grain-interior and grain-boundary mechanisms. Using synchrotron radiation 3D observations, we identify a significant delay in the initiation of transgranular cracks in RRA-treated specimens as compared to those in the peak-aged condition. Atomic-resolution electron microscopy observations confirm the grain-interior partial transformation from the coherent η’ phase to the semi-coherent η phase. It is proposed that the increased fraction of semi-coherent η/Al interfaces reduces hydrogen coverage at coherent interfaces, thereby suppressing transgranular hydrogen-induced debonding on the slip planes
Infrared camera-based analysis of heat flux distribution in film boiling of water flow over a moving steel sheet
No full textThe film boiling of free-surface water flow over a moving hot steel sheet is a common occurrence in the run-out table (ROT) cooling process used in hot rolling mills in the steel industry. Engineers seek to optimize cooling operations, necessitating the comprehension of forced convective heat transfer characteristics between cooling water and hot steel sheets in the film-boiling regime. In this study, we developed an experimental methodology using an infrared camera to evaluate the heat flux distribution along a moving solid with a high spatial resolution. Specifically, a 0.5-mm-thick test sheet made of stainless steel was subjected to cooling by a water film flowing at 0.72 m/s. The surface heat flux was measured while varying the velocity of the test sheet (0.5, 1.0, and 1.5 m/s), temperature of the test sheet (450-590℃), and water temperature (30-60℃). The study revealed that the heat flux was highest in the region where the water first contacted with the moving solid and then decreased downstream. The peak values of the surface heat flux depended on the water temperature, but were almost independent of the moving velocity. We compared the results with the similarity solutions for single- and two-phase boundary layer theories to gain insights into the heat transfer mechanism and to discuss the effects of varying the examined parameters. In addition, we developed a correlation formula to predict the heat flux profile in the first contact region
Development of a sensitivity-enhanced fluorescence lifetime spectroscopic method for nondestructive quality monitoring of mature tomatoes during storage
No full textThe decay of fluorescence lifetime (FLT) is an absolute indication for observing the environment surrounding the fluorescent molecules. This study presents the characterization of fluorescence intensity and the FLT in tomatoes, spanning from the green to the red stage, using a novel time-resolved and laser-induced fluorescence (TRLIF) spectroscopic system. Furthermore, the applicability of this method was assessed for evaluating the postharvest quality of commercially acquired red tomatoes. The results collectively indicate a progressive decrease in the FLT of the red tomatoes throughout shelf-life storage. The average FLT loss decreased by approximately 17, 26, 32, and 38% after 1, 2, 3, and 4 d, respectively. Furthermore, the first principal component scores of the time-resolved spectra were confirmed to be stable for early quality degradation monitoring purposes. This investigation highlights that the devised TRLIF spectroscopic technique is a non-destructive and robust method for studying the degradation of fluorescent compounds. It facilitates an in-depth exploration of the underlying mechanisms behind the fluorescent phenomena in postharvest research
北アフリカにおける豪雨・林野火災を考慮した流域土砂管理に向けたハイブリッドモデルに関する国際研究拠点形成
No full text研究代表者: 田中賢治(京都大学防災研究所水資源環境研究センター 教授)本拠点研究は, 2015年10月にGADRIの課題別ワークショップとして防災研究所にて開催した「第1回国際シンポジウム」を受けたものであり, 以下に研究集会を実施した.Coordinator: Kenji Tanak
Does accrual information impact municipal bond prices? Evidence from Japan using AI
No full textThis study aims to empirically determine the extent to which accrual-based information disclosed by local governments contributes to the pricing of municipal bonds using eXplainable artificial intelligence, which provides better regression accuracy than multiple regression analysis. The analysis is particularly crucial in the world’s many non-bankruptcy law countries: those without legislation for local government failure. Very little research has been conducted to date on their municipal bond markets. This study focuses on the Japanese market as a representative non-bankruptcy law country. The results demonstrate that accrual-based information disclosed by local governments contributes as much to determining municipal bond prices as traditional disclosure information other than accrual-based information, even in a non-bankruptcy law country, such as Japan
Hysteretic magnetic field analysis with Second-Order homogenization
No full textA dynamic hysteresis model represented by the Cauer circuit was combined with the finite element analysis to efficiently compute magnetic field in micro-structured iron-cores. A finite element eddy-current analysis with higher order homogenization method is reformulated to implement the Cauer circuit representation. Three types of hysteretic Cauer circuits for the 2nd-order homogenization were examined. The analysis of wounded core under sinusoidal excitation showed that the 2nd order homogenization scheme with finite difference approximation improved the accuracy of representation of iron loss and current-flux loops. The 2nd-order scheme also improved the accuracy of homogenized representation under pulse-width-modulation excitation. The computation time was greatly reduced by the homogenization schemes
