1,063 research outputs found
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
Analytical investigations of thermodynamic effect on cavitation characteristics of sheet and tip leakage vortex cavitation
Vapor production in cavitation extracts the latent heat of evaporation from the surrounding liquid, which decreases the local temperature, and hence the local vapor pressure in the vicinity of cavity. This is called thermodynamic/thermal effect of cavitation. In the present study, the thermodynamic effect on cavitation characteristics such as cavitation compliance and mass flow gain factor, which are known to be important parameters for cavitation instabilities appearing in turbopumps, were studied. Main cavitations in turbopumps, blade and tip leakage vortex cavitations were separately analyzed by simple analytical methods developed based on the potential flow theory, taking account of the latent heat extraction and heat transfer between the cavity and the surrounding fluid. The cavitation characteristics were estimated for the partial cavity and the tip leakage vortex cavity, and the thermodynamic effects on those characteristics were discussed.http://deepblue.lib.umich.edu/bitstream/2027.42/84240/1/CAV2009-final40.pd
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
NGC 7538 : Multiwavelength Study of Stellar Cluster Regions associated with IRS 1-3 and IRS 9 sources
We present deep and high-resolution (FWHM ~ 0.4 arcsec) near-infrared (NIR)
imaging observations of the NGC 7538 IRS 1-3 region (in JHK bands), and IRS 9
region (in HK bands) using the 8.2m Subaru telescope. The NIR analysis is
complemented with GMRT low-frequency observations at 325, 610, and 1280 MHz,
molecular line observations of H13CO+ (J=1-0), and archival Chandra X-ray
observations. Using the 'J-H/H-K' diagram, 144 Class II and 24 Class I young
stellar object (YSO) candidates are identified in the IRS 1-3 region. Further
analysis using 'K/H-K' diagram yields 145 and 96 red sources in the IRS 1-3 and
IRS 9 regions, respectively. A total of 27 sources are found to have X-ray
counterparts. The YSO mass function (MF), constructed using a theoretical
mass-luminosity relation, shows peaks at substellar (~0.08-0.18 Msolar) and
intermediate (~1-1.78 Msolar) mass ranges for the IRS 1-3 region. The MF can be
fitted by a power law in the low mass regime with a slope of Gamma ~ 0.54-0.75,
which is much shallower than the Salpeter value of 1.35. An upper limit of 10.2
is obtained for the star to brown dwarf ratio in the IRS 1-3 region. GMRT maps
show a compact HII region associated with the IRS 1-3 sources, whose spectral
index of 0.87+-0.11 suggests optical thickness. This compact region is resolved
into three separate peaks in higher resolution 1280 MHz map, and the 'East'
sub-peak coincides with the IRS 2 source. H13CO+ (J=1-0) emission reveals peaks
in both IRS 1-3 and IRS 9 regions, none of which are coincident with visible
nebular emission, suggesting the presence of dense cloud nearby. The virial
masses are approximately of the order of 1000 Msolar and 500 Msolar for the
clumps in IRS 1-3 and IRS 9 regions, respectively.Comment: 27 pages, 18 figures, 5 tables. Accepted for publication in MNRA
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