Hiroyuki Shibata

Electrical and thermal conductivities in quenched and aged high-purity Cu-Ti alloys

Abstract Electrical resistivity and thermal diffusivity at room temperature have been measured in quenched and aged high-purity copper–titanium alloys. The results show that the electrical and thermal conductivities increase as aging time at 720 K increases, which indicates that precipitation takes place in these alloys.

On the Nuclear Interaction of Mu-Mesons

The penetrating showers observed with a large multiplate cloud chamber at 50 mwe and 250 mwe underground have been analyzed. The frequencies of the penetrating showers which are experimentally verified to be produced by mu-mesons have been interpreted with the Williams-Weiszacker method and the constant photonuclear cross section of 1.4×10 -28 cm 2 /nucleon. It has been also shown that the angular distribution of secondary penetrating particles in multiple productions produced by mu-mesons is nearly isotropic in the center-of-mass system of the target nucleon and photon which is virtually associated with the incoming mu-mesons.

Thermal and Optical Properties of Yb3+-Doped Y2O3 Single Crystal Grown by the Micro-Pulling-Down Method

Refractory rare-earth sesquioxides (RE2O3, RE = Y, Lu, Sc) are promising host materials for solid-state lasers due to low phonon energy and high thermal conductivity. In this work, we investigated thermodynamic properties of Yb3+-doped Y2O3 single crystals, doping level ≤15 mol % Yb3+ grown by the micro-pulling-down method (µ-PD). The thermal diffusivity lowers with increasing Yb3+ content from 7.2 to 2.37 ×10-6 m2 s-1, heat capacity from 0.44 to 0.403 J g-1 K-1, and thermal conductivity from 15.94 to 5.35 W m-1 K-1. Spectroscopic data are discussed.

Molecular Structures and Percolative Phase Transition in Vinylidene Fluoride-Trifluoroethylene Copolymer Crystals

Thermal and structural properties of vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymers with VDF molar contents between 57 and 77 mol% are examined by differential scanning calorimetry, X-ray analysis, IR and 19 F NMR. It is found from the experimental results that VDF sequences with three or more monomers play an important role in the phase transition and/or phase appearance. Computer simulation for the copolymerization suggests that the copolymer chain of 65–70% VDF contains ca. 50% VDF which is included in the long VDF sequences with three or more monomers. This fraction (50%) is the site-percolation threshold for the two-dimensional triangular lattice; the transformation from the continuous structural change to the first-order phase transition with the increasing VDF fraction is understood as the percolative phase transition in the two-dimensional crystal system.

Narrow Muon Bundles below Ground

The observation of muon bundles caused by cosmic rays was carried out for 17,000 hours by means of spark chamber at 30 m.w.e. below ground. The muon bundles in a narrow region of 20∼30 cm in diameter were observed over the expectation from the fluctuation of spatial distribution or muons by the Monte Carlo method. Their frequency was about 2×10 -4 m -2 h -1 . The frequency of these muon bundles cannot be explained as known interaction processes without extreme assumptions.

BaTiO3 Single Crystals Subjected to Mechanical Impulses

Etching with fusion of NaOH delineates dislocations in the BaTiO3 crystals and by this use, the behavior of mechanically-treated crystal is investigated. When the crystal is subjected to a pointed impulse, a characteristic a-domain pattern appears near the point of contact. Annealing the mechanically-shocked crystal above 1000°C removes the pattern, while two parallel columns or parallel crosses of dislocation etch pits appear. It is supposed that the elastic strain may be released by taking place of a plastic flow upon heating. The part surrounded by parallel columns exhibits an anomalous birefringence, almost unchanged across the Curie point.

Phase-Transitional Behavior in Vinylidene Fluoride-Trifluoroethylene Copolymer Crystals under Elevated Pressures

Temperature dependence of d200,110-spacing in vinylidene fluoride (VDF)-trifluoroethylene copolymer crystals with VDF molar contents of 65 and 57% is measured at 0.1, 100, 200 and 300 MPa. In the crystal with 65% of VDF, continuous structural change transforms into the first-order phase transition at 300 MPa, suggesting a critical point in the P–T phase diagram of the crystal. Such phenomena is attributed to a decrease in the intermolecular distance with pressure, affecting the intermolecular Lennard-Jones potential to a greater extent than the electrostatic interaction.

KNO Scaling in High Energy Proton-Nucleus Interactions

The distributions of n s and N g in proton-nucleus interactions were investigated in the regions of 4≥ N h ≥1 and N h ≥18 making use of the nuclear emulsion pellicles exposed to 205 and 405 GeV proton beams, respectively. / D (dispersion of n s ) of high N h is significantly large compared with that of low N h . It can be considered that / D increases as ν (the number of target nucleons encountered with incident proton). KNO distribution may scale to the center of mass energy at a definite value of ν.