45,431 research outputs found
Vibrations and stresses in layered anisotropic cylinders
An equation describing the radial displacement in a k layered anisotropic cylinder was obtained. The cylinders are initially unstressed but are subjected to either a time dependent normal stress or a displacement at the external boundaries of the laminate. The solution is obtained by utilizing the Vodicka orthogonalization technique. Numerical examples are given to illustrate the procedure
Implications of binary black hole detections on the merger rates of double neutron stars and neutron star-black holes
We show that the inferred merger rate and chirp masses of binary black holes
(BBHs) detected by advanced LIGO (aLIGO) can be used to constrain the rate of
double neutron star (DNS) and neutron star - black hole (NSBH) mergers in the
universe. We explicitly demonstrate this by considering a set of publicly
available population synthesis models of \citet{Dominik:2012kk} and show that
if all the BBH mergers, GW150914, LVT151012, GW151226, and GW170104, observed
by aLIGO arise from isolated binary evolution, the predicted DNS merger rate
may be constrained to be ~\rate~ and that of NSBH mergers will be
constrained to ~\rate. The DNS merger rates are not constrained much
but the NSBH rates are tightened by a factor of as compared to their
previous rates. Note that these constrained DNS and NSBH rates are extremely
model dependent and are compared to the unconstrained values \rate~
and \rate, respectively, using the same models of
\citet{Dominik:2012kk}. These rate estimates may have implications for short
Gamma Ray Burst progenitor models assuming they are powered (solely) by DNS or
NSBH mergers. While these results are based on a set of open access population
synthesis models which may not necessarily be the representative ones, the
proposed method is very general and can be applied to any number of models
thereby yielding more realistic constraints on the DNS and NSBH merger rates
from the inferred BBH merger rate and chirp mass.Comment: 5 pages, no figures, 4 tables, v2: matches published versio
Renormalized Polyakov loops in many representations
We present a renormalization procedure for Polyakov loops which explicitly
implements the fact that the renormalization constant depends only on the
ultraviolet cutoff. Using this we study the renormalized Polyakov loops in all
representations upto the {\bf 27} of the gauge group SU(3). We find good
evidence for Casimir scaling of the Polyakov loops and for approximate large-N
factorization. By studying many loops together, we are able to show that there
is a matrix model with a single coupling which can describe the high
temperature phase of QCD, although it is hard to construct explicitly. We
present the first results for the non-vanishing renormalized octet loop in the
thermodynamic limit below the SU(3) phase transition, and estimate the
associated string breaking distance and the gluelump binding energy. By
studying the connection of the direct renormalization procedure with a
generalization of an earlier suggestion which goes by the name of the
renormalization procedure, we find that they are functionally equivalent.Comment: 17 pages, 24 figures, revtex
A Large-Diameter Hollow-Shaft Cryogenic Motor Based on a Superconducting Magnetic Bearing for Millimeter-Wave Polarimetry
In this paper we present the design and measured performance of a novel
cryogenic motor based on a superconducting magnetic bearing (SMB). The motor is
tailored for use in millimeter-wave half-wave plate (HWP) polarimeters, where a
HWP is rapidly rotated in front of a polarization analyzer or
polarization-sensitive detector. This polarimetry technique is commonly used in
cosmic microwave background (CMB) polarization studies. The SMB we use is
composed of fourteen yttrium barium copper oxide (YBCO) disks and a contiguous
neodymium iron boron (NdFeB) ring magnet. The motor is a hollow-shaft motor
because the HWP is ultimately installed in the rotor. The motor presented here
has a 100 mm diameter rotor aperture. However, the design can be scaled up to
rotor aperture diameters of approximately 500 mm. Our motor system is composed
of four primary subsystems: (i) the rotor assembly, which includes the NdFeB
ring magnet, (ii) the stator assembly, which includes the YBCO disks, (iii) an
incremental encoder, and (iv) the drive electronics. While the YBCO is cooling
through its superconducting transition, the rotor is held above the stator by a
novel hold and release mechanism (HRM). The encoder subsystem consists of a
custom-built encoder disk read out by two fiber optic readout sensors. For the
demonstration described in this paper, we ran the motor at 50 K and tested
rotation frequencies up to approximately 10 Hz. The feedback system was able to
stabilize the the rotation speed to approximately 0.4%, and the measured rotor
orientation angle uncertainty is less than 0.15 deg. Lower temperature
operation will require additional development activities, which we will
discuss
Research Notes : United States : Evaluation of soybean germplasm for stress tolerance and biological efficiency towards ; Air Pollution
Relationships between the three major ambient air pollutants -ozone (03), sulphur dioxide (S02) and nitrogen dioxide (N02) -have been explored experimentally using linear regression analysis. It has been shown that the amount of 03 in ambient air is based on the total amount of S02 + N02 and that the concentration of 03 can be predicted from the concentration of S02 + N02. On the basis of the data collected, a modified N02 -03 photolytic cycle has been proposed taking into account dry precipitation of S02 and N02
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