Preliminary study of a wing-tip vortex using laser velocimetry

Measurements have been made in the wake of a semi-span NACA 0015 airfoil with emphasis on the region of the wing tip vortex. The spanwise and streamwise velocity components were measured using a two-component laser Doppler velocimeter. The purpose of the study was to initiate the operation of a laser velocimeter system and to perform preliminary wake measurements in preparation for a more extensive study of the structure and near field development of a tip vortex

Ferromagnetic behaviour in the strongly interacting two-component Bose gas

We investigate the low temperature behaviour of the integrable 1D two-component spinor Bose gas using the thermodynamic Bethe ansatz. We find that for strong coupling the characteristics of the thermodynamics at low temperatures are quantitatively affected by the spin ferromagnetic states, which are described by an effective ferromagnetic Heisenberg chain. The free energy, specific heat, susceptibility and local pair correlation function are calculated for various physical regimes in terms of temperature and interaction strength. These thermodynamic properties reveal spin effects which are significantly different than those of the spinless Bose gas. The zero-field susceptibility for finite strong repulsion exceeds that of a free spin paramagnet. The critical exponents of the specific heat $c_v \sim T^{1/2}$ and the susceptibility $\chi \sim T^{-2}$ are indicative of the ferromagnetic signature of the two-component spinor Bose gas. Our analytic results are consistent with general arguments by Eisenberg and Lieb for polarized spinor bosons.Comment: 15 pages, 6 figures, revised version, references added, minor correction

NACA 0015 wing pressure and trailing vortex measurements

A NACA 0015 semispan wing was placed in a low-speed wind tunnel, and measurements were made of the pressure on the upper and lower surface of the wing and of velocity across the vortex trailing downstream from the tip of the wing. Pressure data were obtained for both 2-D and 3-D configurations. These data feature a detailed comparison between wing tips with square and round lateral edges. A two-component laser velocimeter was used to measure velocity profiles across the vortex at numerous stations behind the wing and for various combinations of conditions. These conditions include three aspect ratios, three chord lengths, a square- and a round lateral-tip, presence or absence of a boundary-layer trip, and three image plane positions located opposite the wing tip. Both pressure and velocity measurements were made for the angles of attack 4 deg less than or equal to alpha less than or equal to 12 deg and for Reynolds numbers 1 x 10(exp 6) less than or equal to Re less than or equal to 3 x 10(exp 6)

Double-layer ion acceleration triggered by ion magnetization in expanding radiofrequency plasma sources

Ion energy distribution functions downstream of the source exit in magnetically expanding low-pressure plasmas are experimentally investigated for four source tube diameters ranging from about 5 to 15 cm. The magnetic-field threshold corresponding to a transition from a simple expanding plasma to a double layer-containing plasma is observed to increase with a decrease in the source tube diameter. The results demonstrate that for the four geometries, the double layer and the accelerated ion beam form when the ion Larmour radius in the source becomes smaller than the source tube radius, i.e., when the ions become magnetized in the source tube.This work is partially supported by a Grant-in-Aid for Young Scientists A, Grant No. 22684031, Japan. Part of this work is also supported by TEPCO Research Foundation

Current-induced spin torque resonance of magnetic insulators affected by field-like spin-orbit torques and out-of-plane magnetizations

The spin-torque ferromagnetic resonance (ST-FMR) in a bilayer system consisting of a magnetic insulator such as Y3Fe5O12 and a normal metal with spin-orbit interaction such as Pt is addressed theoretically. We model the ST-FMR for all magnetization directions and in the presence of field-like spin-orbit torques based on the drift-diffusion spin model and quantum mechanical boundary conditions. ST-FMR experiments may expose crucial information about the spin-orbit coupling between currents and magnetization in the bilayers.Comment: 4 pages, 2 figure

Properties of Scalar-Quark Systems in SU(3)c Lattice QCD

We perform the first study for the bound states of colored scalar particles $\phi$ ("scalar quarks") in terms of mass generation with quenched SU(3)$_c$ lattice QCD. We investigate the bound states of $\phi$, $\phi^\dagger\phi$ and $\phi\phi\phi$ ("scalar-quark hadrons"), as well as the bound states of $\phi$ and quarks $\psi$, i.e., $\phi^\dagger\psi$, $\psi\psi\phi$ and $\phi\phi\psi$ ("chimera hadrons"). All these new-type hadrons including $\phi$ have a large mass of several GeV due to large quantum corrections by gluons, even for zero bare scalar-quark mass $m_\phi=0$ at $a^{-1}\sim 1{\rm GeV}$. We find a similar $m_\psi$-dependence between $\phi^\dagger\psi$ and $\phi\phi\psi$, which indicates their similar structure due to the large mass of $\phi$. From this study, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluons

Revisiting the Constraint on the Helium Abundance from CMB

We revisit the constraint on the primordial helium mass fraction Yp from observations of cosmic microwave background (CMB) alone. By minimizing chi square of recent CMB experiments over 6 other cosmological parameters, we obtained rather weak constraints as 0.17 < Yp < 0.52 at 1 sigma C.L. for a particular data set. We also study the future constraint on cosmological parameters when we take account of the prediction of the standard big bang nucleosynthesis (BBN) theory as a prior on the helium mass fraction where Yp can be fixed for a given energy density of baryon. We discuss the implications of the prediction of the standard BBN on the analysis of CMB.Comment: 15 pages, 5 figures, published versio