[en] The paper describes the post dryout heat transfer in fuel rod clusters, which is obtained in an experiment performed in 28 rod clusters under the following conditions: pressure 30 and 70kg/cm², mass velocity from 400 to 1800kg/m²s, heat flux from 0.6 x 10⁶ to 1.4 x 10⁶kcal/m²hr. The results show that post dryout heat transfer can be expressed as the sum of single phase turbulent heat transfer and heat transfer induced by impinging and evaporation of droplets. (author)

[en] Precursory changes in the radon concentration of groundwater were observed prior to the Iau-Oshima-kinkai earthquake (magnitude 7.0) 14 January 1978. The distance from the epicenter to a continuous radon-monitoring station at Nakaizu was about 25 kilometers. A sudden drop and a subsequent increase in the radon concentration recorded on 9 January 1978 were significant. The size of the spike-like change was about 15%. After the earthquake, a remarkable increase in the radon concentration occurred

[en] The crystallographic features of the simple perovskite oxides La_1-xSr_xMnO₃ with 0≤x≤0.08, which are known to be correlated-electron insulators, have been examined by X-ray powder diffraction and transmission electron microscopy. It was confirmed on the basis of the powder diffraction profiles obtained that the orthorhombic-to-monoclinic structural phase transition took place; for instance, at 500 K in the x=0.08 sample. The profiles also indicated that the structural transition accompanied the introduction of the Jahn-Teller distortion and the increase in both the orthorhombic distortion and the A-site-ion displacement. Based on the reciprocal lattices determined from electron diffraction patterns, further, it was found that these distortions and displacement never resulted in the change in the extinction rule of diffraction spots, and that the monoclinic distortion was actually involved in the low-temperature phase. That is, the structural phase transition can basically be regarded as a ferroelastic transition in terms of the lowering of the symmetry

[en] A V-shaped Si target which consists of two Si planes is designed for an Ion beam sputter deposition (IBSD) system where Ar⁺ is generated in a Kaufman type ion source. The deposition rate of Si increases from 7.63 A/min to 10.23 A/min with the V-shaped target. Using this system, two types of structures with 5 and 20 Si and Ge layers are formed. High energy (1.0 MeV) Ge⁺ are irradiated on these films to doses of 1.0x10¹⁶ ions/cm² and 2.0x10¹⁶ ions/cm² at a substrate temperature of 350degC. Rutherford Backscattering Spectroscopy (RBS) reveals that a 20-layered Si and Ge film changes into a graded SiGe mixture film by the ion mixing, but the crystallization does not occur. (author)

[en] Characteristics of the electronic structure of anomalous muonium in diamond are investigated based on the relaxed-bond-centered (RBC) model by use of a self-consistent Green's-function method within the local-spin-density-functional formalism. A minimal basis set of well-contracted localized orbitals determined from first principles is used. For the case of 42% stretched C-C bond length, calculated values of -137 and 400 MHz for the Fermi-contact and dipolar hyperfine parameters, respectively, give good agreement with the experimental values of -206 and 374 MHz, strongly supporting the RBC model. A simple interpretation is also given of the mechanism for the negative Fermi-contact hyperfine parameter

[en] The electronic structure of the intermetallic compound LiAl, which has a B32 structure, has been studied by a self-consistent linear-muffin-tin-orbital method within the atomic-sphere approximation and in the local-density formalism. The overall band structure and density of states have a reasonable resemblance with those obtained previously by Zunger, except for several important differences near the Fermi energy. Whereas our results for ideal LiAl give poor agreement with experiments on real (''vacancy-defect'') LiAl, we obtain much better agreement after accounting for the presence of vacancies by shifting the Fermi level in a crude rigid-band manner corresponding to the vacancy concentration of roughly two percent estimated experimentally: The shifted results give satisfactory agreement with magnetic-susceptibility and Knight-shift experiments and predict p-type conduction for the real ''defect-phase'' LiAl, in agreement with recent experimental findings

[en] The most convincing candidate as main constituent of the dark matter in the Universe consists of Weakly Interacting Massive Particles (WIMPs). WIMPs must be electrically neutral and interact with a very low cross-section (σ < 10"−"4"0 cm"2) which makes them detectable in direct searches only through the observation of nuclear recoils induced by the WIMP rare scatterings. In the experiments carried out so far, recoiled nuclei are searched for as a signal over a background produced by Compton electrons and neutron scatterings. Signal found by some experiments have not been confirmed by other techniques. We propose an RandD program for a new experimental method able to observe the track of the scattered nucleus based on new developments in the nuclear emulsion technique. Nuclear emulsions would act both as the WIMP target and as the tracking detector able to reconstruct the direction of the recoiled nucleus. This unique characteristic would provide a new and unambiguous signature of the presence of the dark matter in our galaxy.

[en] The spin-lattice relaxation rates of HCP transition metals (Sc, Ti, Y, Zr and Tc) are calculated based on the ab initio semi-relativistic ASA-SCF-LMTO linear tetrahedron scheme. A thorough investigation of the off-diagonal contributions is presented. The off-diagonal contribution amounts to some 20% of the total relaxation rate and plays an important role in the anisotropy of the relaxation rate. The theoretical relaxation rates reproduce the experiments very well for Ti, Y and Tc, but some discrepancies do exist for Sc. It is suggested that the relativistic and exchange enhancements of the core polarisation would reduce the discrepancy in Sc significantly but make the agreement slightly worse for Y. As for Zr, the theoretical relaxation rate is about twice the experimental one. The reason for the discrepancy is not clear at present. It will be shown that the p contribution is very important for all the HCP transition elements studied here and that the contribution of the quadrupolar interaction is not negligibly small for ⁴⁷Ti. (author)

[en] We have been doing research and development for direct dark matter search by nuclear emulsion which is a solid state detector. This experiment enable directional detection of dark matter with the large mass target and model independent. Until now, we constructed a base of fully automatic analysis system and nuclear emulsion which can detect sub-micron tracks. We have demonstrated that it is possible to detect recoiled tracks of 100 nm or more by neutron irradiation. This track length is correspond to 37 keV in C(N,O) target. Additionally, we evaluated the angular resolution of the energy basis by using an ion implant system, and obtained 25 degrees or better resolution in 80 keV carbon ions. The fully automatic analysis system which can analyze very short tracks lead the experiment to next phase, we will do a quantitative study of the background toward gram scale test experiment at the Gran Sasso underground laboratory

[en] The spin-lattice relaxation rates of cubic transition metals (V, Cu, Nb, Mo, Rh, Pd and Ag) are calculated using the ab initio LMTO self-consistent band structure calculation. It is found that the p symmetry contribution is fairly large for BCC metals and that the core polarisation without exchange enhancement gives a minor contribution. The theoretical relaxation rates reproduce experiment reasonably well for V, Nb and Mo, but some noticeable discrepancies exist for other metals, especially for Pd. It is pointed out that the inclusion of the relativistic enhancement of the electron density at the nucleus may reduce the discrepancy and that the exchange enhancement of the core polarisation contribution should be taken into account for Pd. (author)