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Takahiro Ishida,Keisuke Ohira,Rio Hosoi,Naoko Tokugawa,Takahiro Tsukahara 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.4
Extensive research to establish an index of roughness that causes abrupt turbulent transition downstream of the roughness and affect natural laminar flow is performed. This study investigates turbulent transitions dominated by the roughness-induced crossflow instability on a swept wing and a swept flat plate. Direct numerical simulations (DNS) are performed considering the swept wing to determine the critical roughness height that induces abrupt turbulent transition. Compared to its no-roughness counterpart, the roughness increases both the pressure drag and skin-friction drag and decreases the lift owing to the onset of upstream turbulence. The wind tunnel tests are performed considering a swept flat-plate boundary-layer model. The development of turbulent regions due to the roughness is investigated. The results reveal the occurrence of a laminar-to-turbulent transition and relaminarization, along the boundary between laminar and localized turbulent regions. Moreover, the DNS results reveal the generation of traveling crossflow vortices from the localized turbulent region.
Takahiro Yonekawa,Shigekazu Kanehira,HIroshi Noda,Fumika Oi,Hiromu Satake,Teruaki Ito (사)한국CDE학회 2010 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
Industry-academia-government collaboration activities of the University of Tokushima started in 1991 when its Regional Joint Research Center was set up. Since then, the university developed the organization and activities concerning industry-academia-government collaboration. Number of the staff member has been increased since then from one person at first to 33 at present and the activities were strengthened remarkably and became extensive. This paper describes our basic policies, outline of major activities; Technology Licensing, Research Promotion, Intellectual Property Management, and Information Management and Utilization, and outline of a technology matching system called TPAS-Net that helps and facilitates industry-academia-government collaboration activities. Then it shows our human resources development program that was introduced in 2005 to secure leading engineers for local companies. The program consists of three courses: Production Management Course, Advanced Technology Course and Internship Course. The outline of these courses and the result of the training are explained. Finally the content of a subject on simulation and modeling is presented briefly as an example of the development program.
Study on Failure Diagnosis of Power Transformer using FRA
Takahiro Sano,Katsunori Miyagi 한국전기전자재료학회 2006 Transactions on Electrical and Electronic Material Vol.7 No.6
As the average usage period of transformers increases, it is becoming increasingly necessary to know the internal condition of transformers. It is therefore critically important to establish monitoring and diagnostic techniques that can perform transformer condition assessment. Frequency response analysis, generally known as FRA, is one of the technologies to diagnose transformers. Using case studies, this paper presents the effectiveness of FRA as measurements for detecting transformer failures. This paper introduces the fact that FRA waveforms have useful information about diagnosis of failure on core earths and winding shield, and that the condition outside transformers can affect frequency response characteristics.
Increase in Current Density at Metal/GeO2/n‑Ge Structure by Using Laminated Electrode
Takahiro Tsukamoto,Shota Kurihara,Nobumitsu Hirose,Akifumi Kasamatsu,Toshiaki Matsui,Yoshiyuki Suda 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.1
In a metal/n-Ge structure, Fermi level pinning tends to occur. The insertion of an oxide layer at the interface between electrodes and n-Ge can efectively reduce the Schottky barrier height. However, the attachment of metal and oxide can cause difusion of oxygen to the metal due to Gibbs free energy, which degrades the contact characteristics. In this study, we investigated the efects of a laminated electrode on the current density at a metal/GeO2/n-Ge structure. Ni, Pt, Al, or Ti layers with thicknesses of 0.5–20 nm were formed, followed by a deposition of 200-nm-thick Al. The J–V curves of these samples showed that the current density of the Al/Ti/GeO2/n-Ge structure was the largest among them and was about 126 times larger than that of the Al/GeO2/n-Ge structure. We also found that the current density depended on the flm thickness of Ti and was the highest at the flm thickness of about 2.5 nm or less. To investigate the efect of the Ti interlayer on the current density, we obtained the depth profles of X-ray photoelectron spectroscope spectra of the Al/Ti/GeO2/n-Ge and Al/ GeO2/n-Ge structures. Analysis showed that the difusion of the oxygen to Al was limited by the 20-nm-thick Ti, and the oxygen was difused to Al when the flm thickness of Ti was about 1 nm. These results demonstrate that laminated oxide structures such as AlOx/TiOx and TiOx/GeO2 can form on the sample with 1-nm-thick Ti, which increases the current density.
K-theory of Crossed Products of $C^*$-algebras Two Metric Spaces
Takahiro SUDO 한국수학교육학회 2005 純粹 및 應用數學 Vol.12 No.1
We study continuous ¯elds and K-groups of crossed products of C¤- algebras. It is shown under a reasonable assumption that there exist continuous ¯elds of C¤-algebras between crossed products of C¤-algebras by amenable locally compact groups and tensor products of C¤-algebras with their group C¤-algebras, and their K-groups are the same under the additional assumptions.