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An estimation of static aerodynamic forces of box girders using computational fluid dynamics
Watanabe, Shigeru,Inoue, Hiroo,Fumoto, Koichiro Techno-Press 2004 Wind and Structures, An International Journal (WAS Vol.7 No.1
This study has focused on aerodynamics for a wind-resistance design about the single and tandem box girder sections to realize a super-long span bridge in the near future. Three-dimensional static analysis of flows around the fundamental single and tandem box girder sections with fairing is carried out by means of the IBTD/FS finite element technique with LES turbulence model. As the results of the analysis, computations have verified aerodynamic characteristics of both sections by the histories of aerodynamic forces, the separation and reattachment flow patterns and the surface pressure distributions. The relationship between the section shapes and the aerodynamic characteristics is also investigated in both sections. And the mechanism about the generation of fluctuating aerodynamic forces is discussed.
Shigeru Kaku,Satoshi Miyauchi,Yukio Watanabe 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
We report the nanoscopic properties of the clean, free surface of a BaTiO3 single crystal in an ultra-high vacuum. Atomic force microscopy, piezoelectric force microscopy and Kelvin force microscopy measurements show that the potential difference between upward and downward 180˚ domain is approx 100 mV. This value is 100 times smaller than the value estimated by using the standard 180˚ domain theory. Furthermore, our experiments show that this result cannot be explained only by the conventional explanations (that is, a decrease in the depolarization field by closure domains, the compensation of polarization bound charge by contamination or by oxygen excess and deficiency or ion transport). The results suggest a possibility that an intrinsic electrostatic shielding mechanism exists in the ferroelectrics and is essential for 180˚ domains. We report the nanoscopic properties of the clean, free surface of a BaTiO3 single crystal in an ultra-high vacuum. Atomic force microscopy, piezoelectric force microscopy and Kelvin force microscopy measurements show that the potential difference between upward and downward 180˚ domain is approx 100 mV. This value is 100 times smaller than the value estimated by using the standard 180˚ domain theory. Furthermore, our experiments show that this result cannot be explained only by the conventional explanations (that is, a decrease in the depolarization field by closure domains, the compensation of polarization bound charge by contamination or by oxygen excess and deficiency or ion transport). The results suggest a possibility that an intrinsic electrostatic shielding mechanism exists in the ferroelectrics and is essential for 180˚ domains.
Novel Inversion Theory and Sensor Structure of Biomimicry Directional Microphone
Shigeru Ando,Toru Kurihara,Kentaro Watanabe,Yoshiki Yamanishi,Takahiko Ooasa 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
Micromachined directional microphones(sound source localization sensor) mimicking an auditory organ of Ormia Ochracea have been intensively studied based on center-supported, marginally free1-Dor2-D diaphragm struc-tures. This paper first describes an exact mathematical theory of sound source localization based on the partial differential equation(pde) for mulation of the problem and the weighted integral method to obtain an exact direct algebraic solution of the sound distance and direction. This theory shows a Gaussian weight function on the diaphragm is inevitable in thetransduction of 1st and 2nd moments. An analysis was performed to obtain the weight distribution assuming an arbitrary thickness distribution of a shell-structured diaphragm. The best result was amarginally-supported face-to-face cantilever structure. We fabricated this structure using SOI wafer and RIE. The experimental results show a strong dependence of the vibration pattern on both zenith and azimuth angles, and a greatly enhanced sensitivity to inclined sound pressure.
Resistance Switching in View of Electron Hole Dynamics in Ferroelectric Related Oxides
Yukio Watanabe,Daisuke Matusmoto,Mizuki Yamato,Shigeru Kaku 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
An examination of typical switching experiments shows that the performances of the resistance switching in transition-metal oxides vary widely and depend on the details of each experiment. Conventional defect mechanisms, such as oxygen vacancies, work in some experiments. However, by comparing the macroscopic and the nanometer-scale characteristics and switching, we show here that other experiments indicate the possible existence of a more intrinsic physically new mechanism.VISITOR=Gzm-G
A System Concept for EFD/CFD Integration
Shigeya Watanabe,Shigeru Kuchi-ishi,Hiroyuki Kato,Takeshi Aoyama,Keiichi Murakami,Atsushi Hashimoto,Naoyuki Fujita,Yuichi Matsuo 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
A trail towards integration of EFD (Experimental Fluid Dynamics) and CFD (Computational Fluid Dynamics), that is. the development of a system called Digital/Analog Hybrid Wind Tunnel, is introduced. The aim of the system is to improve efficiency, accuracy, and reliability of aerodynamic characteristics evaluation in aerospace vehicle developments through mutual support between EFD and CFD. The function of the system consists of optimization of test planning utilizing pretest CFD calculations, an accurate correction of the wind tunnel wall and support interaction effects through CFD, CFD data refinement based on EFD data, the most probable aerodynamic characteristics estimation based on both EFD and CFD data, database including EFD and CFD data at an identical condition, and so forth. Key technical challenges in the system development, such as an automatic grid generation and high-speed solver development for CFD, a highly efficient data reduction technique for image measurement data. and techniques integrating EFD and CFD. are addressed.