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Search Results: 1 - 10 of 2941 matches for " Edson Sekiya "
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Difference in Structural Relaxation Times of Inner Surface and Inner Bulk Region of Silica Glass Arc Tube  [PDF]
Takuya Honma, Nobuhiro Tamura, Kazuya Saito, Edson Sekiya
New Journal of Glass and Ceramics (NJGC) , 2013, DOI: 10.4236/njgc.2013.31008
Abstract: The fictive temperature and structural relaxation of a silica glass arc tube were investigated to elucidate the origin of cracking in the arc tubes used in high-intensity discharge lamps for vacuum ultraviolet light sources. The structural relaxation time near the inner surface was decreased much more than that in the inner bulk region, resulting in a large difference in the fictive temperature between these two areas at high-intensity discharge lamp operating temperatures. This difference should induce strain in the silica glass network. On the basis of our results, we suggest ways to avoid cracking and extend the lifetime of high-intensity discharge lamps.
Responses of Root Hydraulic Properties and Transpirational Factors to a Top Soil Drying in Cajanus cajan and Sesbania sesban  [PDF]
Nobuhito Sekiya, Hideki Araki
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.412A3005

Responses of leaf area (LA), stomatal conductance (gs), root length (RL) and root hydraulic conductance per unit of root length (Lpunit) to top soil dryness were investigated. Pigeon pea (Cajanus cajan) and sesbania (Sesbania sesban) were grown in a vertical split-root system. From sixty-six days after sowing, the top soil was dried while the bottom soil was kept wet. Pigeon pea increased LA while maintaining leaf water potential (ΨL) by reducing gs. Increased transpirational demand through canopy development was compensated for by increasing water extraction in the bottom soil. This was achieved by increasing not only RL but also Lpunit. Sesbania kept constant levels of gs, causing a transient reduction of ΨL. Ψ

Low Energy Investigations at Kamioka Observatory
Hiroyuki Sekiya
Physics , 2013, DOI: 10.1088/1742-6596/460/1/012017
Abstract: At Kamioka Observatory many activities for low energy rare event search are ongoing. Super-Kamiokande(SK), the largest water Cherenkov neutrino detector, currently continues data taking as the fourth phase of the experiment (SK-IV). In SK-IV, we have upgraded the water purification system and tuned water flow in the SK tank. Consequently the background level was lowered significantly. This allowed SK-IV to derive solar neutrino results down to 3.5MeV energy region. With these data, neutrino oscillation parameters are updated from global fit; $\Delta m^2_{12}=7.44^{+0.2}_{-0.19}\times10^{-5} {\rm eV}^2$, $\sin^2\theta_{12}=0.304\pm0.013$, $\sin^2\theta_{13}=0.030^{+0.017}_{-0.015}$. NEWAGE, the directional sensitive dark matter search experiment, is currently operated as "NEWAGE-0.3a" which is a $0.20\times0.25\times0.31$ m$^3$ micro-TPC filled with CF4 gas at 152 Torr. Recently we have developed "NEWAGE-0.3b". It was succeeded to lower the operation pressure down to 76 Torr and the threshold down to 50 keV (F recoils). XMASS experiment is looking for scintillation signals from dark matter interaction in 1 ton of liquid xenon. It was designed utilizing its self-shielding capability with fiducial volume confinement. However, we could lower the analysis threshold down to 0.3 keVee using whole volume of the detector. In February 2012, low threshold and very large exposure data (5591 kg$\cdot$days) were collected. With these data, we have excluded some part of the parameter spaces claimed by DAMA/LIBRA and CoGeNT experiments.
Semiconductor Optical Amplifier (SOA)-Fiber Ring Laser and Its Application to Stress Sensing  [PDF]
Yoshitaka Takahashi, Shinji Sekiya, Tatsuro Suemune
Optics and Photonics Journal (OPJ) , 2011, DOI: 10.4236/opj.2011.14027
Abstract: We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The frequency difference of the bi-directional laser is controlled by birefringence which is introduced in the ring laser cavity. The beat frequency generated by combining two counter-propagating oscillations is proportional to the birefringence, the fiber ring laser of the present study is, therefore, applicable to the fiber sensor. The sensing signal is obtained in a frequency domain with the material which causes the retardation change by a physical phenomenon to be measured. For the application to stress sensing, the present laser was investigated with a photoelastic material.
Monitoramento de servi os de hemoterapia no Estado de S o Paulo, por meio de Unidades Desvio-Padr o e Medida-Síntese
Sekiya Eliseo J.
Revista Brasileira de Hematologia e Hemoterapia , 2001,
Hiroyuki Sekiya,for the XMASS collaboration
Physics , 2010, DOI: 10.1088/1742-6596/308/1/012011
Abstract: The XMASS detector is a large single phase liquid Xenon scintillator.After its feasibility had been studied using a 100 kg size prototype detector, an 800 kg size detector is being built for dark matter search with the sensitivity of $10^{-45} {\rm cm}^2$ region in spin-independent cross section. The results of R\&D study for 800 kg detector, especially ultra low background technologies, and the prospects of the experiment are described.
The effects of the Tidal Force on Shear Instabilities in the Dust Layer of the Solar Nebula
Naoki Ishitsu,Minoru Sekiya
Physics , 2003, DOI: 10.1016/S0019-1035(03)00151-9
Abstract: The linear analysis of the instability due to vertical shear in the dust layer of the solar nebula is performed. The following assumptions are adopted throughout this paper: (1) The self-gravity of the dust layer is neglected. (2) One fluid model is adopted, where the dust aggregates have the same velocity with the gas due to strong coupling by the drag force. (3) The gas is incompressible. The calculations with both the Coriolis and the tidal forces show that the tidal force has a stabilizing effect. The tidal force causes the radial shear in the disk. This radial shear changes the wave number of the mode which is at first unstable, and the mode is eventually stabilized. Thus the behavior of the mode is divided into two stages: (1) the first growth of the unstable mode which is similar to the results without the tidal force, and (2) the subsequent stabilization due to an increase of the wave number by the radial shear. If the midplane dust/gas density ratio is smaller than 2, the stabilization occurs before the unstable mode grows largely. On the other hand, the mode grows faster by one hundred orders of magnitude, if this ratio is larger than 20. Because the critical density of the gravitational instability is a few hundreds times as large as the gas density, the hydrodynamic instability investigated in this paper grows largely before the onset of the gravitational instability. It is expected that the hydrodynamic instability develops turbulence in the dust layer and the dust aggregates are stirred up to prevent from settling further. The formation of planetesimals through the gravitational instabilities is difficult to occur as long as the dust/gas surface density ratio is equal to that for the solar abundance.
On the uniqueness of Sasaki-Einstein metrics
Ken'ichi Sekiya
Mathematics , 2009,
Abstract: Let $S$ be a compact Sasakian manifold which does not admit non-trivial Hamiltonian holomorphic vector fields. If there exists an Einstein-Sasakian metric on $S$, then it is unique.
Generalized almost contact structures and generalized Sasakian structures
Ken'ichi Sekiya
Mathematics , 2012,
Abstract: We introduce generalized almost contact structures which admit the $B$-field transformations on odd dimensional manifolds. We provide definition of generalized Sasakain structures from the view point of the generalized almost contact structures. We obtain a generalized Sasakian structure on a non-compact manifold which does not arise as a pair of ordinary Sasakian structures. However we show that a generalized Sasakian structure on compact 3-dimensional manifold is equivalent to a pair of Sasakian structures with the same metric. Finally we extend a definition of a generalized almost contact structure.
Tilting theoretical approach to moduli spaces over preprojective algebras
Yuhi Sekiya,Kota Yamaura
Mathematics , 2010,
Abstract: We apply tilting theory over preprojective algebras $Lambda$ to a study of moduli space of $Lambda$-modules. We define the categories of semistable modules and give an equivalence, so-called reflection functors, between them by using tilting modules over $Lambda$. Moreover we prove that the equivalence induces an isomorphism of algebraic varieties between moduli spaces. In particular, we study in the case when the moduli spaces related to the Kleinian singularity. We generalize a result of Crawley-Boevey which is known another proof of the McKay correspondence of Ito-Nakamura type.
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