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Boron Nitride Dispersed Nanocomposites with High Thermal Shock Resistance
Kusunose, T.,Sekino, T.,Choa, Y.H.,Nakayama, T.,Niihara, K. The Korean Powder Metallurgy Institute 2001 한국분말재료학회지 (KPMI) Vol.8 No.3
The microstructure and mechanical properties of $Si_3N_4/BN $nanocomposites synthesized by chemical processing were investigated. The nanocomposites containing 15 vol% hexagonal BN (h-BN) were fabricated by hot-pressing $\alpha-Si_3N_4$powders covered with turbostratic BN (t-BN). The t-BN coating on $\alpha-Si_3N_4$particles was prepared by heating $\alpha-Si_3N_4$ particles covered with a mixture of boric acid and urea in hydrogen gas. TEM observations of this nanocomposite revealed that nano-sized h-BN particles were homogeneously dispersed within $Si_3N_4$grains as well as at grain boundaries. The strength and thermal shock resistance were significantly improved in comparison with the $Si_3N_4/BN$ microcomposites.
Nakayama, S.,Mauger, C.,Ahn, M.H.,Aoki, S.,Ashie, Y.,Bhang, H.,Boyd, S.,Casper, D.,Choi, J.H.,Fukuda, S.,Fukuda, Y.,Gran, R.,Hara, T.,Hasegawa, M.,Hasegawa, T.,Hayashi, K.,Hayato, Y.,Hill, J.,Ichikawa Elsevier 2005 Physics letters: B Vol.619 No.3
<P><B>Abstract</B></P><P>Neutral current single <SUP>π0</SUP> production induced by neutrinos with a mean energy of 1.3 GeV is measured using a 1000 ton water Cherenkov detector in the K2K long baseline neutrino experiment. The cross section for this process relative to the total charged current cross section is measured to be 0.064±0.001(stat.)±0.007(sys.). The momentum distribution of neutral current <SUP>π0</SUP>s from a water target is measured with high statistics for the first time.</P>
″Drifting Cups on a Meandering Stream″ in Japan
Nakayama, Yasuki,Aoki, K.,Oki, M.,Kobayashi, T.,Saga, T.,Maruoka, H.,Kato, S. The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.12
Drifting Cups on a Meandering Stream (Kyokusui-no-En) is a Poetry Party that had its origin In ancient China, and was introduced to Japan passing through Korea. The flow of the meandering stream was made clear using the flow visualization techniques, surface floating method, PTV and the numerical simulation. At the same time, the motions of floating cup, the floating speed, relating speed and the trajectory of the cup were also analysed by using an originally developed image processing technique. Based on these researches, the model channel was considered. To make this party interesting the channel must has the characteristic that the drifting cups take the random pass and stagnant at the unexpected place. This model channel is satisfied with these conditions and the fluid mechanics consideration is performed on the both points of the experimental visualization and numerical simulation.
T. Ogawa,M. Nakayama,M. Haraguchi,M. Kuwahara,M. Fukui,S. Matsuo,T. Okamoto 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
We have macroscopically and microscopically investigated the localized surface plasmons (LSPs)on Ag anoparticles embedded in porous TiO2 glass. We have prepared TiO2 glass containing Ag nanoparticles (Ag/TiO2) by the sol-gel process and changed the porosity of the TiO2 glass by drying under a high vacuum condition. Using a spectrometer, we have macroscopically measured the absorption spectra (ABS) on all Ag nanoparticles and using near-field scanning optical microscopy (NSOM), we have microscopically measured the scattering spectra on a single Ag nanoparticle in the Ag/TiO2 after each drying process. Fitting the spectra derived from the numerical calculation based on the Mie theory to that evaluated from the ABS and the NSOM measurements, we have evaluated the deviation of the full width at half maximum evaluated by the experimental measurements from that derived from the theoretical calculation (FWHM) and the bound (Hashin-Shtrikman bounds) of the porosity of the TiO2 glass by the use of the Hashin Shtrikman limit, similar to the literature [1]. It has been found that the FWHM of the scattering spectra on the single Ag nanoparticle can be much smaller than one of the ABS on all Ag nanoparticles in the Ag/TiO2. This result is due to that the ABS is influenced by the aggregation and the size distribution of all Ag nanoparticles. Furthermore, on extrapolating from the plot of FWHM vs porosity, the FWHM is reduced to zero when the porosity is about 15 %.
Tanaka, T.,Abe, K.,Hayato, Y.,Iida, T.,Kameda, J.,Koshio, Y.,Kouzuma, Y.,Miura, M.,Moriyama, S.,Nakahata, M.,Nakayama, S.,Obayashi, Y.,Sekiya, H.,Shiozawa, M.,Suzuki, Y.,Takeda, A.,Takenaga, Y.,Ueno, IOP Publishing 2011 The Astrophysical journal Vol.742 No.2
<P>We present the result of an indirect search for high energy neutrinos from Weakly Interacting Massive Particle (WIMP) annihilation in the Sun using upward-going muon (upmu) events at Super-Kamiokande. Data sets from SKI-SKIII (3109.6 days) were used for the analysis. We looked for an excess of neutrino signal from the Sun as compared with the expected atmospheric neutrino background in three upmu categories: stopping, non-showering, and showering. No significant excess was observed. The 90% C. L. upper limits of upmu flux induced by WIMPs of 100 GeV c(-2) were 6.4 x 10(-15) cm(-2) s(-1) and 4.0 x 10(-15) cm(-2) s(-1) for the soft and hard annihilation channels, respectively. These limits correspond to upper limits of 4.5 x 10(-39) cm(-2) and 2.7 x 10(-40) cm(-2) for spin-dependent WIMP-nucleon scattering cross sections in the soft and hard annihilation channels, respectively.</P>