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Taiki Takamine,Shotaro Nakano,Satoshi Watanabe,Hiroyoshi Watanabe 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.4
In this study, experimental/numerical investigations on the effect of axial offset of rotor offset in a final stage model of a three-stage centrifugal pump are carried out. The axial offset is intentionally given to the shaft system to both of discharge/suction side. As a result, the axial thrust is significantly affected by the axial offset in the flow rate range below 50% of the design flow rate. From the flow field computed in CFD analysis, the flow mechanism induced by the axial offset leading to the change in the axial thrust is elucidated; the interaction between the back flow form the diffuser and the impeller exiting flow is affected by the axial offset, which are responsible for the change in the angular momentum brought into side gaps and therefore in the pressure distribution inside the side gaps.
Sadaoki Matsui,Shotaro Uto,Yasuhira Yamada,Shinpei Watanabe 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.3
The present paper considers the contact between energy-saving device of ice-class vessel and ice block. The main objective of this study is to clarify the tendency of the ice impact force and the structural response as well as interaction effects of them. The contact analysis is performed by using LS-DYNA finite element code. The main collision scenario is based on Finnish-Swedish ice class rules and a stern duct model is used as an energy-saving device. For the contact force, two modelling approaches are adopted. One is dynamic indentation model of ice block based on the pressure-area curve. The other is numerical material modelling by LS-DYNA. The authors investigated the sensitivity of the structural response against the ice contact pressure, the interaction effect between structure and ice block, and the influence of eccentric collision. The results of these simulations are presented and discussed with respect to structural safety.
Matsui, Sadaoki,Uto, Shotaro,Yamada, Yasuhira,Watanabe, Shinpei The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.3
The present paper considers the contact between energy-saving device of ice-class vessel and ice block. The main objective of this study is to clarify the tendency of the ice impact force and the structural response as well as interaction effects of them. The contact analysis is performed by using LS-DYNA finite element code. The main collision scenario is based on Finnish-Swedish ice class rules and a stern duct model is used as an energy-saving device. For the contact force, two modelling approaches are adopted. One is dynamic indentation model of ice block based on the pressure-area curve. The other is numerical material modelling by LS-DYNA. The authors investigated the sensitivity of the structural response against the ice contact pressure, the interaction effect between structure and ice block, and the influence of eccentric collision. The results of these simulations are presented and discussed with respect to structural safety.
Selective Laser Ablation of Metal Thin Films Using Ultrashort Pulses
Byunggi Kim,Han Ku Nam,Shotaro Watanabe,Sanguk Park,Yunseok Kim,Young Jin Kim,Kazuyoshi Fushinobu,김승우 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.3
Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron–phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.