4,456 research outputs found
Neutron detector simultaneously measures fluence and dose equivalent
Neutron detector acts as both an area monitoring instrument and a criticality dosimeter by simultaneously measuring dose equivalent and fluence. The fluence is determined by activation of six foils one inch below the surface of the moderator. Dose equivalent is determined from activation of three interlocked foils at the center of the moderator
Long-Term Stability of Planets in Binary Systems
A simple question of celestial mechanics is investigated: in what regions of
phase space near a binary system can planets persist for long times? The
planets are taken to be test particles moving in the field of an eccentric
binary system. A range of values of the binary eccentricity and mass ratio is
studied, and both the case of planets orbiting close to one of the stars, and
that of planets outside the binary orbiting the system's center of mass, are
examined. From the results, empirical expressions are developed for both 1) the
largest orbit around each of the stars, and 2) the smallest orbit around the
binary system as a whole, in which test particles survive the length of the
integration (10^4 binary periods). The empirical expressions developed, which
are roughly linear in both the mass ratio mu and the binary eccentricity e, are
determined for the range 0.0 <= e <= 0.7-0.8 and 0.1 <= mu <= 0.9 in both
regions, and can be used to guide searches for planets in binary systems. After
considering the case of a single low-mass planet in binary systems, the
stability of a mutually-interacting system of planets orbiting one star of a
binary system is examined, though in less detail.Comment: 19 pages, 5 figures, 7 tables, accepted by the Astronomical Journa
Are the new and old EU countries financially integrated?
During the last four years, the eight Eastern European countries that joined the EU in 2004 have made significant strides toward financial integration with the EU. Several pieces of evidence support this finding. First, yields on long-term sovereign bonds in accession countries have converged towards EU levels. This is true for both bonds denominated in local currency and bonds denominated in euro. Second, while the issuance of euro-denominated corporate bonds from accession countries is limited, yields on existing corporate bonds are in line with those in the old EU countries. Third, margins in the banking sector have narrowed, which is consistent with the integration of banking markets. Finally, we note that the current stock market rally is consistent with equity market integration.financial integration, Eastern Europe, EU enlargement
Impact flux of asteroids and water transport to the habitable zone in binary star systems
By now, observations of exoplanets have found more than 50 binary star
systems hosting 71 planets. We expect these numbers to increase as more than
70% of the main sequence stars in the solar neighborhood are members of binary
or multiple systems. The planetary motion in such systems depends strongly on
both the parameters of the stellar system (stellar separation and eccentricity)
and the architecture of the planetary system (number of planets and their
orbital behaviour). In case a terrestrial planet moves in the so-called
habitable zone (HZ) of its host star, the habitability of this planet depends
on many parameters. A crucial factor is certainly the amount of water. We
investigate in this work the transport of water from beyond the snow-line to
the HZ in a binary star system and compare it to a single star system
Global dynamics and stability limits for planetary systems around HD 12661, HD 38529, HD 37124 and HD 160691
In order to distinguish between regular and chaotic planetary orbits we apply
a new technique called MEGNO in a wide neighbourhood of orbital parameters
determined using standard two-body Keplerian fits for HD 12661, HD 38529, HD
37124 and HD 160691 planetary systems. We show that the currently announced
orbital parameters place these systems in very different situations from the
point of view of dynamical stability. While HD 38529 and HD 37124 are located
within large stability zones in the phase space around their determined orbits,
the preliminary orbits in HD 160691 are highly unstable. The orbital parameters
of the HD 12661 planets are located in a border region between stable and
unstable dynamical regimes, so while its currently determined orbital
parameters produce stable regular orbits, a minor change within the margin of
error of just one parameter may result in a chaotic dynamical system.Comment: 12 pages, 3 figures, accepted ApJ, revised version following the
referee's repor
The pulsation spectrum of VX Hydrae
We present the results of a two-year, multisite observing campaign
investigating the high-amplitude delta Scuti star VX Hydrae during the 2006 and
2007 observing seasons. The final data set consists of nearly 8500 V-band
observations spanning HJD 2453763.6 to 2454212.7 (2006 January 28 to 2007 April
22). Separate analyses of the two individual seasons of data yield 25
confidently-detected frequencies common to both data sets, of which two are
pulsation modes, and the remaining 23 are Fourier harmonics or beat frequencies
of these two modes. The 2006 data set had five additional frequencies with
amplitudes less than 1.5 mmag, and the 2007 data had one additional frequency.
Analysis of the full 2006-2007 data set yields 22 of the 25 frequencies found
in the individual seasons of data. There are no significant peaks in the
spectrum other than these between 0 and 60 c/d. The frequencies of the two main
pulsation modes derived from the 2006 and 2007 observing seasons individually
do not differ at the level of 3-sigma, and thus we find no conclusive evidence
for period change over the span of these observations. However, the amplitude
of f(1) = 5.7898 c/d changed significantly between the two seasons, while the
amplitude of f(0) = 4.4765 c/d remained constant; amplitudes of the Fourier
harmonics and beat frequencies of f(1) also changed. Similar behavior was seen
in the 1950s, and it is clear that VX Hydrae undergoes significant amplitude
changes over time.Comment: 14 pages, 5 figures, published in Publications of the Astronomical
Society of the Pacific, v.121, p.1076 (October 2009
Data Processing in Multiport-Based Reflectometer System
The paper describes operations with DC output voltage of multiport based system. Proposed system is based on the same principle as common six ports systems, however the used coupler has more outputs. This allows extension of bandwidth and higher precision of the measurement. To process measured data standard six port system calculations are used. To get more accurate results than in the case of simple six port system additional statistical methods can be used. The higher number of outputs produces large amount of measurement and calibration data, however using described technique this amount of data were reduced
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