Compressible vortex loops: effect of nozzle geometry

Vortex loops are fundamental building blocks of supersonic free jets. Isolating them allows for an easier study and better understanding of such flows. The present study looks at the behaviour of compressible vortex loops of different shapes, generated due to the diffraction of a shock wave from a shock tube with different exit nozzle geometries. These include a 15 mm diameter circular nozzle, two elliptical nozzles with minor to major axis ratios of 0.4 and 0.6, a 30 × 30 mm square nozzle, and finally two exotic nozzles resembling a pair of lips with minor to major axis ratios of 0.2 and 0.5. The experiments were performed for diaphragm pressure ratios of P4/P1=4, 8, and 12, with P4 and P1 being the pressures within the high pressure and low pressure compartments of the shock tube, respectively. High-speed schlieren photography as well as PIV measurements of both stream-wise and head-on flows have been conducted

Magnetic studies of the lightly Ru doped perovskite rhodates Sr(Ru,Rh)O3_3

The solid solution between the ferromagnetic metal SrRuO$_3$ and the enhanced paramagnetic metal SrRhO$_3$ was recently reported [K. Yamaura et al., Phys. Rev. B 69 (2004) 024410], and an unexpected feature was found in the specific heat data at $x$=0.9 of SrRu$_{1-x}$Rh$_x$O$_3$. The feature was reinvestigated further by characterizing additional samples with various Ru concentrations in the vicinity of $x$=0.9. Specific heat and magnetic susceptibility data indicate that the feature reflects a peculiar magnetism of the doped perovskite, which appears only in the very narrow composition range 0.85$<$$x$$\le$0.95.Comment: Accepted for publication in a special issue of Physica B (the proceedings of SCES04

Spin melting and refreezing driven by uniaxial compression on a dipolar hexagonal plate

We investigate freezing characteristics of a finite dipolar hexagonal plate by the Monte Carlo simulation. The hexagonal plate is cut out from a piled triangular lattice of three layers with FCC-like (ABCABC) stacking structure. In the present study an annealing simulation is performed for the dipolar plate uniaxially compressed in the direction of layer-piling. We find spin melting and refreezing driven by the uniaxial compression. Each of the melting and refreezing corresponds one-to-one with a change of the ground states induced by compression. The freezing temperatures of the ground-state orders differ significantly from each other, which gives rise to the spin melting and refreezing of the present interest. We argue that these phenomena are originated by a finite size effect combined with peculiar anisotropic nature of the dipole-dipole interaction.Comment: Proceedings of the Highly Frustrated Magnetism (HFM2006) conference. To appear in a special issue of J. Phys. Condens. Matte

Temperature Chaos and Bond Chaos in the Edwards-Anderson Ising Spin Glass : Domain-Wall Free-Energy Measurements

Domain-wall free-energy $\delta F$, entropy $\delta S$, and the correlation function, $C_{\rm temp}$, of $\delta F$ are measured independently in the four-dimensional $\pm J$ Edwards-Anderson (EA) Ising spin glass. The stiffness exponent $\theta$, the fractal dimension of domain walls $d_{\rm s}$ and the chaos exponent $\zeta$ are extracted from the finite-size scaling analysis of $\delta F$, $\delta S$ and $C_{\rm temp}$ respectively well inside the spin-glass phase. The three exponents are confirmed to satisfy the scaling relation $\zeta=d_{\rm s}/2-\theta$ derived by the droplet theory within our numerical accuracy. We also study bond chaos induced by random variation of bonds, and find that the bond and temperature perturbations yield the universal chaos effects described by a common scaling function and the chaos exponent. These results strongly support the appropriateness of the droplet theory for the description of chaos effect in the EA Ising spin glasses.Comment: 4 pages, 6 figures; The title, the abstract and the text are changed slightl

Scaling Analysis of Domain-Wall Free-Energy in the Edwards-Anderson Ising Spin Glass in a Magnetic Field

The stability of the spin-glass phase against a magnetic field is studied in the three and four dimensional Edwards-Anderson Ising spin glasses. Effective couplings and effective fields associated with length scale L are measured by a numerical domain-wall renormalization group method. The results obtained by scaling analysis of the data strongly indicate the existence of a crossover length beyond which the spin-glass order is destroyed by field H. The crossover length well obeys a power law of H which diverges as H goes to zero but remains finite for any non-zero H, implying that the spin-glass phase is absent even in an infinitesimal field. These results are well consistent with the droplet theory for short-range spin glasses.Comment: 4 pages, 5 figures; The text is slightly changed, the figures 3, 4 and 5 are changed, and a few references are adde

Reply to Comment on "Quantum Phase Transition of Randomly-Diluted Heisenberg Antiferromagnet on a Square Lattice"

This is a reply to the comment by A. W. Sandvik (cond-mat/0010433) on our paper Phys. Rev. Lett. 84, 4204 (2000). We show that his data do not conflict with our data nor with our conclusions.Comment: RevTeX, 1 page; Revised versio

Fine-grained rims surrounding chondrules in the carbonate-poor lithology of the Tagish Lake carbonaceous chondrite

第3回極域科学シンポジウム/第35回南極隕石シンポジウム 11月30日（金） 国立国語研究所 2階講