549 research outputs found
Numerical simulation of interaction between two Savonius turbines aimed at practical application of ocean current power generation
One of the vertical axis wind turbines that utilize drag force is the Savonius wind turbine. Savonius wind turbines are characterized by low speed rotation and high torque, so they are rarely used for wind power generation but have possibility to apply to ocean current power generation, which has been attracting attention recently. In this report, we actually performed a numerical simulation of the flow using suitable grid, focusing mainly on the case where two wind turbines are rotating in reverse at a constant speed, and investigated the state of the flow field. Two-dimensional incompressible Navier-Stokes equations are adopted as the basic equation and solved numerically using the finite difference method. In addition, in order to enable calculation even in a high Reynolds number flow, the nonlinear term of the equations are approximated by using the third-order accuracy upstream difference method. The simulation is performed under the condition that the flow corresponds to three types of angles of 90 degrees, 45 degrees, and 0 degrees with respect to the line connecting the centers of the two wind turbines. The flow field differs greatly depending on each angle, and the interaction between the two wind turbines has been clarified
Molecular clouds towards RCW 49 and Westerlund 2; Evidence for cluster formation triggered by cloud-cloud collision
We have made CO(J=2-1) observations towards the HII region RCW 49 and its
ionizing source, the rich stellar cluster Westerlund 2 (hereafter Wd2), with
the NANTEN2 sub-mm telescope. These observations have revealed that two
molecular clouds in velocity ranges of -11 to +9 km/s and 11 to 21 km/s
respectively, show remarkably good spatial correlations with the Spitzer IRAC
mid-infrared image of RCW 49, as well a velocity structures indicative of
localized expansion around the bright central regions and stellar cluster. This
strongly argues that the two clouds are physically associated with RCW 49. We
obtain a new kinematic distance estimate to RCW 49 and Wd2 of 5.4^{+ 1.1}_{-
1.4} kpc, based on the mean velocity and velocity spread of the associated gas.
We argue that acceleration of the gas by stellar winds from Wd2 is insufficient
to explain the entire observed velocity dispersion of the molecular gas, and
suggest a scenario in which a collision between the two clouds ~4 Myrs ago may
have triggered the formation of the stellar cluster.Comment: A version with higher resolution figures is available from
http://www.a.phys.nagoya-u.ac.jp/~naoko/research/apjl2009/fur09_rev_highreso.pd
Possible Spin-Density Wave on Fermi Arc of Edge State in Single-Component Molecular Conductors [Pt(dmdt)] and [Ni(dmdt)]
We construct three-orbital tight-binding models describing single-component
molecular conductors [Pt(dmdt)] and [Ni(dmdt)] using first-principles
calculations. We show that [Ni(dmdt)] is a Dirac nodal line system with
highly one-dimensional edge states at the (001) edge, similar to
[Pt(dmdt)], as demonstrated in prior studies. To investigate possible edge
magnetism, we calculate longitudinal and transverse spin susceptibilities using
real-space-dependent random-phase approximation (RPA) in three-orbital Hubbard
models in the presence of spin--orbit coupling. We find that the edge
spin-density wave (SDW) is induced by the Coulomb repulsion and incommensurate
nestings of the Fermi arcs. We also find that the magnetic structure of the
edge SDW can be changed via extremely small carrier doping, which is
controllable in molecular conductors
Extinction map of the Small Magellanic Cloud based on SIRIUS and 6X 2MASS point source catalogs
In this paper, we present the first extinction map of the Small Magellanic Cloud (SMC) constructed using the color excess at near-infrared wavelengths. Using a new technique named "X percentile method", which we developed recently to measure the color excess of dark clouds embedded within a star distribution, we have derived an E(J β H) map based on the SIRIUS and 6X Two Micron All Sky Survey (2MASS) star catalogs. Several dark clouds are detected in the map derived from the SIRIUS star catalog, which is deeper than the 6X 2MASS catalog. We have compared the E(J β H) map with a model calculation in order to infer the locations of the clouds along the line of sight, and found that many of them are likely to be located in or elongated toward the far side of the SMC. Most of the dark clouds found in the E(J β H) map have counterparts in the CO clouds detected by Mizuno et al. with the NANTEN telescope. A comparison of the E(J β H) map with the virial mass derived from the CO data indicates that the dust-to-gas ratio in the SMC varies in the range A_V /N_H = 1-2 Γ 10^(β22) mag H^-1 cm^2 with a mean value of ~1.5 Γ 10^(β22) mag H^-1 cm^2. If the virial mass underestimates the true cloud mass by a factor of ~2, as recently suggested by Bot et al., the mean value would decrease to ~8Γ10^(β23) mag H^-1 cm^2, in good agreement with the value reported by Gordon et al., 7.59 Γ 10^(β23) mag H^-1 cm^2
Tbx-associated transcriptional corepressor, Ripply3, plays essential roles in pharyngeal development
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