183 research outputs found
Stability of Terrestrial Planets in the Habitable Zone of Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208
We have undertaken a thorough dynamical investigation of five extrasolar
planetary systems using extensive numerical experiments. The systems Gl 777 A,
HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of
whether they could host terrestrial like planets in their habitable zones
(=HZ). First we investigated the mean motion resonances between fictitious
terrestrial planets and the existing gas giants in these five extrasolar
systems. Then a fine grid of initial conditions for a potential terrestrial
planet within the HZ was chosen for each system, from which the stability of
orbits was then assessed by direct integrations over a time interval of 1
million years. The computations were carried out using a Lie-series integration
method with an adaptive step size control. This integration method achieves
machine precision accuracy in a highly efficient and robust way, requiring no
special adjustments when the orbits have large eccentricities. The stability of
orbits was examined with a determination of the Renyi entropy, estimated from
recurrence plots, and with a more straight forward method based on the maximum
eccentricity achieved by the planet over the 1 million year integration.
Additionally, the eccentricity is an indication of the habitability of a
terrestrial planet in the HZ; any value of e>0.2 produces a significant
temperature difference on a planet's surface between apoapse and periapse. The
results for possible stable orbits for terrestrial planets in habitable zones
for the five systems are summarized as follows: for Gl 777 A nearly the entire
HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive
for a sufficiently long time, while for Gl 614 our results exclude terrestrial
planets moving in stable orbits within the HZ.Comment: 14 pages, 18 figures submitted to A&
SPICES: Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems
SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary
Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its
purpose is to image and characterize long-period extrasolar planets and
circumstellar disks in the visible (450 - 900 nm) at a spectral resolution of
about 40 using both spectroscopy and polarimetry. By 2020/22, present and
near-term instruments will have found several tens of planets that SPICES will
be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES
can preferentially access exoplanets located at several AUs (0.5-10 AU) from
nearby stars (25 pc) with masses ranging from a few Jupiter masses to Super
Earths (2 Earth radii, 10 M) as well as circumstellar
disks as faint as a few times the zodiacal light in the Solar System
MEIC Design Progress
This paper will report the recent progress in the conceptual design of MEIC, a high luminosity medium energy polarized ring-ring electron-ion collider at Jefferson lab. The topics and achievements that will be covered are design of the ion large booster and the ERL-circulator-ring-based electron cooling facility, optimization of chromatic corrections and dynamic aperture studies, schemes and tracking simulations of lepton and ion polarization in the figure-8 collider ring, and the beam-beam and electron cooling simulations. A proposal of a test facility for the MEIC electron cooler will also be discussed
The deindustrialisation/tertiarisation hypothesis reconsidered: a subsystem application to the OECD7
The diffusion of outsourcing, both national and international, and
vertical FDIs among manufacturing firms, along with the higher integra-
tion of business services in manufacturing, has recently led to question
the empirical evidence supporting the Deindustrialisation/Tertiarisation
(DT) hypothesis. Rather than a \real" phenomenon, it has been argued,
DT would be an \apparent" one, mainly due to the reorganization of
production across national and sectoral boundaries.
The empirical studies that have dealt with the topic so far have
not been able to effectively rule out such possibility, because of two
main limitations: the sectoral level of the analysis and/or the national
focus. In order to overcome them, the paper carries out an appreciative
investigation of the actual extent of the DT occurred in the OECD
area over the '80s and the '90s by moving from a sector to a subsystem
perspective, thus retaining both direct and indirect relations, and by
referring to a \pseudo-World" of 7 OECD countries, thus taking into
account the \global" dimension of the phenomenon.
The results strongly support the DT hypothesis: although the weight
of business sector services in the manufacturing subsystem increased,
acting as a counterbalancing tendency to the manufacturing decline,
subsystem shares significantly decreased, thus confirming DT as a more
fundamental trend of modern economies
Physics of the AGS-to ?RHIC Transfer Line Commissioning
This paper presents beam physics results from the fall 1995 AGS-to- RHIC (ATR) transfer line commissioning run with fully ionized gold nuclei. We first describe beam position monitors and transverse video profile monitors, instrumentation relevant to measurements performed during this commissioning. Measured and corrected beam trajectories demonstrate agreement with design optics to a few percent, including optical transfer functions and beamline dispersion. Digitized 2- dimensional video profile monitors were used to measure beam emittance, and beamline optics and AGS gold ion beam parameters are shown to be comparable to RHIC design requirements
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Physics of the AGS-to-RHIC transfer line commissioning
This paper presents beam physics results from the fall 1995 AGS-to- RHIC (ATR) transfer line commissioning run with fully ionized gold nuclei. We first describe beam position monitors and transverse video profile monitors, instrumentation relevant to measurements performed during this commissioning. Measured and corrected beam trajectories demonstrate agreement with design optics to a few percent, including optical transfer functions and beamline dispersion. Digitized 2- dimensional video profile monitors were used to measure beam emittance, and beamline optics and AGS gold ion beam parameters are shown to be comparable to RHIC design requirements
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Experience with IBS-suppression lattice in RHIC
An intra-beam scattering (IBS) is the limiting factor of the luminosity lifetime for RHIC operating with heavy ions. In order to suppress the IBS we designed and implemented new lattice with higher betatron tunes. This lattice had been developed during last three years and had been used for gold ions in yellow ring of the RHIC during d-Au part of the RHIC Run-8. The use of this lattice allowed both significant increases in the luminosity lifetime and the luminosity levels via reduction of beta-stars in the IPS. In this paper we report on the development, the tests and the performance of IBS-suppression lattice in RHIC, including the resulting increases in the peak and the average luminosity. We also report on our plans for future steps with the IBS suppression
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Experience in Reducing Electron Cloud and Dynamic Pressure Rise in Warm and Cold Regions in Rhic.
The large scale application of non-evaporable getter coating in RHIC has been effective in reducing the electron cloud. Since beams with higher intensity and smaller bunch spacing became possible in operation, the emittance growth is of concern. Study results are reported together with experiences of machine improvements: saturated NEG coatings, anti-grazing ridges in warm sections, and the pre-pumping in cryogenic regions
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