2,838 research outputs found
Theoretical Study of Fluid Forces on a Centrifugal Impeller Rotating and Whirling in a Volute
Fluid forces on a rotating and whirling centrifugal impeller in a volute are analyzed with the assumption of a two-dimensional rotational, inviscid flow. For simplicity, the flow is assumed to be perfectly guided by the impeller vanes. The theory predicts the tangential and the radial force on the whirling impeller as functions of impeller geometry, volute spacing, and whirl ratio. A good qualitative agreement with experiment is found
Monolithic superconducting emitter of tunable circularly polarized terahertz radiation
We propose an approach to control the polarization of terahertz (THz)
radiation from intrinsic Josephson-junction stacks in single crystalline
high-temperature superconductor . By monolithically
controlling the surface current distributions in the truncated square mesa
structure, we can modulate the polarization of the emitted THz wave as a result
of two orthogonal fundamental modes excited inside the mesa. Highly polarized
circular terahertz waves with a degree of circular polarization of more than
99% can be generated using an electrically controlled method. The emitted
radiation has a high intensity and a low axial ratio (AR<1 dB). The intuitive
results obtained from the numerical simulation based on the conventional
antenna theory are consistent with the observed emission characteristics.Comment: Submitted to PRApplie
Contribution of Type Ia and Type II Supernovae for Intra-Cluster Medium Enrichment
The origin of the chemical composition of the intracluster medium (ICM) is
discussed in this paper. In particular, the contribution from Type Ia
supernovae (SNe Ia) to the ICM enrichment is shown to exist by adopting the
fitting formulas which have been used in the analysis of the solar system
abundances. Our analysis means that we can use the frequency of SNe Ia relative
to SNe II as the better measure than for
estimating the contribution of SNe Ia. Moreover, the chemical compositions of
ICMs are shown to be similar to that of the solar system abundances. We can
also reproduce the sulfur/iron abundance ratio within a factor of 2, which
means that the abundance problem of sulfur needs not to be emphasized too
strongly. We need more precise observations to conclude whether ICMs really
suffer the shortage problem of sulfur or not.Comment: 20 pages, LaTeX text and 15 postscript figures. Accepted for
publication in Astrophysical Journa
Two-dimensional unsteady analysis of fluid forces on a whirling centrifugal impeller in a volute
Destabilizing fluid forces on a whirling centrifugal impeller rotating in a volute were observed. A quasisteady analysis neglecting shed vorticity or an unsteady analysis without a volute does not predict the existence of such destabilizing fluid forces on a whirling impeller. The effects of a volute and the shed vorticity are considered. We treat cases when an impeller with an infinite number of vanes rotates with a constant velocity omega and its center whirls with a constant eccentric radius epsilon and a constant whirling velocity psi. It is assumed that: (1) the number of the vanes is so large that the impeller can be treated as an actuator impeller in which the flow is perfectly guided; (2) flow is inviscid, incompressible and two dimensional; (3) the eccentricity epsilon is so small that unsteady components can be linearized; (4) vorticity is transported on a prescribed mean flow, the operating point is near design flow rate; and (5) the volute can be represented by a curved plate
Polarization Enhancement of terahertz radiation generated by intrinsic Josephson junctions in a truncated edge square Bi_{2}Sr_{2}CaCu_{2}O_{8+{\delta}} mesa
In this study, we investigated the terahertz radiation from a truncated edge
square mesa structure made from a superconducting
Bi_{2}Sr_{2}CaCu_{2}O_{8+{\delta}} . Using a commercial software, the
polarization characteristics were determined, and introduced, while accounting
for the skin effect. The axial ratio was enhanced in the simulation by
performing a parametric study on the design.Comment: Proceedings of the 28th International Symposium on Superconductivity,
ISS 2015, November 16-18, 2015, Tokyo, Japa
An Algebraic Model for the Multiple Meixner Polynomials of the First Kind
An interpretation of the multiple Meixner polynomials of the first kind is
provided through an infinite Lie algebra realized in terms of the creation and
annihilation operators of a set of independent oscillators. The model is used
to derive properties of these orthogonal polynomials
Deep Near-Infrared Observations and Identifications of Chandra Sources in the Orion Molecular Cloud 2 and 3
We conducted deep NIR imaging observations of the Orion molecular cloud 2 and
3 using QUIRC on the 88-inch telescope of the University of Hawaii. Our
purposes are 1) to generate a comprehensive NIR source catalog of these star
forming clouds, and 2) to identify the NIR counterpart of the Chandra X-ray
sources that have no counterpart in the 2MASS catalog. Our J-, H-, and K-band
observations are about 2 mag deeper than those of 2MASS, and well match the
current Chandra observation. We detected 1448 NIR sources, for which we derived
the position, the J-, H-, and K-band magnitude, and the 2MASS counterpart.
Using this catalog, we identified the NIR counterpart for about 42% of the
2MASS-unIDed Chandra sources. The nature of these Chandra sources are discussed
using their NIR colors and spatial distributions, and a dozen protostar and
brown dwarf candidates are identified.Comment: 39 pages, 9 postscript figures, accepted for publication in A
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