248,623 research outputs found
Searching for radiative pumping lines of OH masers: II. The 53.3um absorption line towards 1612MHz OH maser sources
This paper analyzes the 53.3um line in the ISO LWS spectra towards a similar
sample of OH/IR sources. We find 137 LWS spectra covering 53.3um and associated
with 47 galactic OH/IR sources. Ten of these galactic OH/IR sources are found
to show and another 5 ones tentatively show the 53.3um absorption while another
7 sources highly probably do not show this line. The source class is found to
be correlated with the type of spectral profile: red supergiants (RSGs) and AGB
stars tend to show strong blue-shifted filling emission in their 53.3um
absorption line profiles while HII regions tend to show a weak red-shifted
filling emission in the line profile. GC sources and megamasers do not show
filling emission feature. It is argued that the filling emission might be the
manifestation of an unresolved half emission half absorption profile of the
53.3um doublet. The 53.3 to 34.6um equivalent width (EW) ratio is close to
unity for RSGs but much larger than unity for GC sources and megamasers while H
II regions only show the 53.3um line. The pump rate defined as maser to IR
photon flux ratio is approximately 5% for RSGs. The pump rates of GC sources
are three order of magnitude smaller. Both the large 53.3 to 34.6um EW ratio
and the small pump rate of the GC OH masers reflect that the two detected
`pumping lines' in these sources are actually of interstellar origin. The pump
rate of Arp 220 is 32%--much larger than that of RSGs, which indicates that the
contribution of other pumping mechanisms to this megamaser is important.Comment: 34 pages, 12 figures, 4 table
Transonic Shocks In Multidimensional Divergent Nozzles
We establish existence, uniqueness and stability of transonic shocks for
steady compressible non-isentropic potential flow system in a multidimensional
divergent nozzle with an arbitrary smooth cross-section, for a prescribed exit
pressure. The proof is based on solving a free boundary problem for a system of
partial differential equations consisting of an elliptic equation and a
transport equation. In the process, we obtain unique solvability for a class of
transport equations with velocity fields of weak regularity(non-Lipschitz), an
infinite dimensional weak implicit mapping theorem which does not require
continuous Frechet differentiability, and regularity theory for a class of
elliptic partial differential equations with discontinuous oblique boundary
conditions.Comment: 54 page
Effects of noise suppression and envelope dynamic range compression on the intelligibility of vocoded sentences for a tonal language
Vocoder simulation studies have suggested that the carrier signal type employed affects the intelligibility of vocoded speech. The present work further assessed how carrier signal type interacts with additional signal processing, namely, single-channel noise suppression and envelope dynamic range compression, in determining the intelligibility of vocoder simulations. In Experiment 1, Mandarin sentences that had been corrupted by speech spectrum-shaped noise (SSN) or two-talker babble (2TB) were processed by one of four single-channel noise-suppression algorithms before undergoing tone-vocoded (TV) or noise-vocoded (NV) processing. In Experiment 2, dynamic ranges of multiband envelope waveforms were compressed by scaling of the mean-removed envelope waveforms with a compression factor before undergoing TV or NV processing. TV Mandarin sentences yielded higher intelligibility scores with normal-hearing (NH) listeners than did noise-vocoded sentences. The intelligibility advantage of noise-suppressed vocoded speech depended on the masker type (SSN vs 2TB). NV speech was more negatively influenced by envelope dynamic range compression than was TV speech. These findings suggest that an interactional effect exists between the carrier signal type employed in the vocoding process and envelope distortion caused by signal processing
Is the CMB asymmetry due to the kinematic dipole?
Parity violation found in the Cosmic Microwave Background (CMB) radiation is
a crucial clue for the non-standard cosmological model or the possible
contamination of various foreground residuals and/or calibration of the CMB
data sets. In this paper, we study the directional properties of the CMB parity
asymmetry by excluding the modes in the definition of parity parameters.
We find that the preferred directions of the parity parameters coincide with
the CMB kinematic dipole, which implies that the CMB parity asymmetry may be
connected with the possible contamination of the residual dipole component. We
also find that such tendency is not only localized at , but in the
extended multipole ranges up to .Comment: 17 pages, 5 figures, 2 tables, improved version, ApJ accepte
Stability Of contact discontinuity for steady Euler System in infinite duct
In this paper, we prove structural stability of contact discontinuities for
full Euler system
Analysis of elastically tailored viscoelastic damping member
For more than two decades, viscoelastic materials have been commonly used as a passive damping source in a variety of structures because of their high material loss factors. In most of the applications, viscoelastic materials are used either in series with or parallel to the structural load path. The latter is also known as the constrained-layer damping treatment. The advantage of the constrained-layer damping treatment is that it can be incorporated without loss in structural integrity, namely, stiffness and strength. However, the disadvantages are that: (1) it is not the most effective use of the viscoelastic material when compared with the series-type application, and (2) weight penalty from the stiff constraining layer requirement can be excessive. To overcome the disadvantages of the constrained-layer damping treatment, a new approach for using viscoelastic material in axial-type structural components, e.g., truss members, was studied in this investigation
Shifted one-parameter supersymmetric family of quartic asymmetric double-well potentials
Extending our previous work (Rosu, Mancas, Chen, Ann.Phys. 343 (2014)
87-102), we define supersymmetric partner potentials through a particular
Riccati solution of the form F(x)=(x-c)^2-1, where c is a real shift parameter,
and work out the quartic double-well family of one-parameter isospectral
potentials obtained by using the corresponding general Riccati solution. For
these parametric double well potentials, we study how the localization
properties of the two wells depend on the parameter of the potentials for
various values of the shifting parameter. We also consider the supersymmetric
parametric family of the first double-well potential in the Razavy chain of
double well potentials corresponding to F(x)=(1/2)sinh 2x-2(1+sqrt 2)sinh
2x/[(1+sqrt 2) cosh 2x+1], both unshifted and shifted, to test and compare the
localization propertiesComment: 11 pages, 4 figures, published versio
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