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Degassing of Aluminum and Aluminum Alloy Powders as Studied by Gas Chromatography
Watanabe Ryuzo,Choi Duk-Sun,Kawasaki Akira 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Gas release behavior from aluminum and Al 7075 alloy powders during heating in argon was investigated by in-situ gas chromatography. Water vapor, hydrogen, carbon mono-oxide were detected as individual evolution spectra against heating temperature and time. The mechanisms of water and hydrogen evolutions were studied in detail for the determination of effective degassing condition. Magnesium in the alloy powder was found to lower the hydrogen evolution temperature to enhance overall hydrogen release.
Thermomechanical Properties of Thermal-Stress Relief Type of Functionally Gradient Materials
Watanabe Ryuzo 한국분말야금학회 1993 한국분말야금학회 학술대회논문집 Vol.1993 No.1
The present status of the thennomechanica1 evaluation of functionally gradient materials(FGMs) for space plane application was reviewed, in which research activities and the cooperation of the national project team organized to study FGM science were demonstrated. The project team was divided into three working groups; de singing, processing and evaluation, each of which had their own tasks in the project cooperation. The testings details of the various thennomechanical tests for the FGM samples fabricated by the processing groups were described, along with their corresponding heating conditions of the real environments in the space plane application. For small-sized samples, laser beam heating test and burner heating test were well applied to study the heat shielding and heat resisting properties. Arc-heated wind tunnel test and high temperature!high velocity gas flow test were used for large-sized panel assemblies having cooling structures. The criteria for the evaluation of the heat shielding and heat resisting properties of the FGMs, as well as a crack activation mechanism in their differential temperature heating, were proposed on the basis of the observation in the burner heating test.
Present Status of Research on Design and Processing of Functionally Graded Materials
Watanabe, Ryuzo,Nishida, Toshihiko,Hirai, Toshio 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.6
Recent activities in the research of functionally graded materials (FGMs) are reviewed with an emphasis on the fabrication techniques for graded microstructure and functions. The research activities have focused on the processing of graded structures that satisfy the designed functions. Several examples of practical applications of FGMs are described in the present paper to demonstrate the fabrication approaches typical to this kind of material. The remainder of the paper is devoted to summarizing a recently finished national project supported by the Ministry of Education of Japan. Research and developments with respect to FGMs in various fields including physics, chemistry, medical science, and biology are briefly reviewed.
Fabrication of Artificial Crystal Architectures by Micro-manipulation of Spherical Particles
Takagi Kenta,Kawasaki Akira,Watanabe Ryuzo 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
We newly designed and manufactured a new arranging system for a three-dimensional artificial crystal of monosized micro particles. In this system, a robotic micro-manipulator accurately locates the spherical particle onto the lattice point, and subsequently fiber lasers micro-weld the contact points between the neighboring particles. Actually, one- and two-dimensional arrays were constructed using monosized tin particles with the diameter of 400 m. Moreover, due to optimization of the process parameters, we successfully constructed the artificial crystals of simple cubic and diamond structures. In particular, the diamond structure which can represent a large photonic band gap is expected to progress toward a practical photonic crystal device.
Yoko Kato,Kuriko Kagitani-Shimono,Junko Matsuzaki,Ryuzo Hanaie,Tomoka Yamamoto,Koji Tominaga,Yoshiyuki Watanabe,Ikuko Mohri,Masako Taniike 대한신경정신의학회 2019 PSYCHIATRY INVESTIGATION Vol.16 No.3
Objective: The purpose of the present study was to clarify the relationship between white matter tracts and cognitive symptoms in children with high-functioning autism spectrum disorder (ASD). Methods: We examined the cognitive functions of 17 children with high-functioning ASD and 18 typically developing (TD) controls and performed diffusion tensor imaging (DTI) tractography. We compared the results between the groups and investigated the correlations between the cognitive scores and DTI parameters within each group. Results: The Comprehension scores in the ASD group exhibited a positive correlation with mean diffusivity (MD) in the forceps minor (F minor). In the TD group, the Comprehension scores were positively correlated with fractional anisotropy (FA) in the right inferior fronto-occipital fasciculus (IFO) and left anterior thalamic radiation (ATR), and negatively correlated with MD in the left ATR, radial diffusivity (RD) in the right IFO, and RD in the left ATR. Additionally, a positive correlation was observed between the Matching Numbers scores and MD in the left uncinate fasciculus and F minor, and RD in the F minor. Furthermore, the Sentence Questions scores exhibited a positive correlation with RD in the right inferior longitudinal fasciculus. Relative to TD controls, the specific tract showing a strong correlation with the cognitive scores was reduced in the ASD group. Conclusion: Our findings indicate that white matter tracts connecting specific brain areas may exhibit a weaker relationship with cognitive functions in children with ASD, resulting in less efficient cognitive pathways than those observed in TD children.
연성금속분말의 기계적합금화에 있어서 분말입자의 응집과 코팅현상
이동원,이길근,박익민,하국현,도변용삼,김병기 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.10
Using Cu, Al and Ti powder as model materials, milling experiments were carried out to investigate the particle coagulation and coating on balls surface and or mill container wall during mechanical alloying of ductile metal powders. The change in particle number per unit weight during milling was analyzed as a function of particle coagulation and coating by Gillespie-Langstroth coagulation ratio equation which is based on probability theory. In the initial milling stage, the decrease in particle number was found to be due mainly to the particle coagulation. As the milling time increase, however, the contribution of the particle crating dominated the particle number decrease. It has been demonstrated that the particle coagulation and coating during milling occurred easily with increasing the ductility of metal power.