29,539 research outputs found
The CDF Data Handling System
The Collider Detector at Fermilab (CDF) records proton-antiproton collisions
at center of mass energy of 2.0 TeV at the Tevatron collider. A new collider
run, Run II, of the Tevatron started in April 2001. Increased luminosity will
result in about 1~PB of data recorded on tapes in the next two years. Currently
the CDF experiment has about 260 TB of data stored on tapes. This amount
includes raw and reconstructed data and their derivatives.
The data storage and retrieval are managed by the CDF Data Handling (DH)
system. This system has been designed to accommodate the increased demands of
the Run II environment and has proven robust and reliable in providing reliable
flow of data from the detector to the end user. This paper gives an overview of
the CDF Run II Data Handling system which has evolved significantly over the
course of this year. An outline of the future direction of the system is given.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 7 pages, LaTeX, 4 EPS figures, PSN
THKT00
Eccentricity Excitation and Apsidal Resonance Capture in the Planetary System Upsilon Andromedae
The orbits of the outer two known planets orbiting Upsilon Andromedae are
remarkably eccentric. Planet C possesses an orbital eccentricity of e1 = 0.253.
For the more distant planet D, e2 = 0.308. Previous dynamical analyses strongly
suggest that the two orbits are nearly co-planar and are trapped in an apsidal
resonance in which the difference between their longitudes of periastron
undergoes a bounded oscillation about 0 degrees. Here we elucidate the origin
of these large eccentricities and of the apsidal alignment. Resonant
interactions between a remnant circumstellar disk of gas lying exterior to the
orbits of both planets can smoothly grow e2. Secular interactions between
planets D and C can siphon off the eccentricity of the former to grow that of
the latter. Externally amplifying e2 during the phase of the apsidal
oscillation when e2/e1 is smallest drives the oscillation amplitude towards
zero. Thus, the substantial eccentricity of planet C and the locking of orbital
apsides are both consequences of externally pumping the eccentricity of planet
D over timescales exceeding apsidal precession periods of order 1e4 yr. We
explain why the recently detected stellar companion to Upsilon Andromedae is
largely dynamically decoupled from the planetary system.Comment: accepted to Ap
Traction calculations and design data for two traction fluids
The rheological properties of the fluid under these certain conditions which precludes the use of most of the conventional instruments for steady state measurement were studied. The only suitable type of instrument is a disk machine where most of the conditions are the same of similar to those in traction drives. From the resulting traction tests, certain models are inferred. To the designer of traction drives, the traction behavior of the fluid under the severe conditions is of utmost importance because of the direct influence that it has on the efficiency, size, and life of a given drive
Optimal project rejection and new firm start-ups
Entrants are typically found to be more innovative than incumbent firms. Furthermore, these innovative ideas often originate with established firms in the industry. Therefore, the established firm and the start-up firm seem to select different types of projects. We claim that this is the consequence of their optimal project allocation mechanism, which depends on their comparative advantage. The start-up firm may seem more "innovative" than the established firm because the comparative advantage of the start-up firm is to commercialize "innovative" projects, i.e. projects that do not fit with the established firms' existing assets. Our model integrates various facts found in the industrial organization literature about the entry rate, firm focus, firm growth, industry growth and innovation. We also obtain some counter-intuitive results, such as that a reduction in the cost of start-ups may actually slow down start-ups, or that the firm may voluntarily give away the property rights to the inventions discovered within the firmManagement; Innovation management;
Resolving Gas Flows in the Ultraluminous Starburst IRAS23365+3604 with Keck LGSAO/OSIRIS
Keck OSIRIS/LGSAO observations of the ultraluminous galaxy IRAS~23365+3604
resolve a circumnuclear bar (or irregular disk) of semimajor axis 0.42" (520
pc) in Paschen-alpha emission. The line-of-sight velocity of the ionized gas
increases from the northeast toward the southwest; this gradient is
perpendicular to the photometric major axis of the infrared emission. Two pairs
of bends in the zero-velocity line are detected. The inner bend provides
evidence for gas inflow onto the circumnuclear disk/bar structure. We interpret
the gas kinematics on kiloparsec scales in relation to the molecular gas disk
and multiphase outflow discovered previously. In particular, the fast component
of the outflow (detected previously in line wings) is not detected, adding
support to the conjecture that the fast wind originates well beyond the
nucleus. These data directly show the dynamics of gas inflow and outflow in the
central kiloparsec of a late-stage, gas-rich merger and demonstrate the
potential of integral field spectroscopy to improve our understanding of the
role of gas flows during the growth phase of bulges and supermassive black
holes.Comment: 14 pages with 7 figures accepted to the astrophysical journa
Dust-driven Dynamos in Accretion Disks
Magnetically driven astrophysical jets are related to accretion and involve
toroidal magnetic field pressure inflating poloidal magnetic field flux
surfaces. Examination of particle motion in combined gravitational and magnetic
fields shows that these astrophysical jet toroidal and poloidal magnetic fields
can be powered by the gravitational energy liberated by accreting dust grains
that have become positively charged by emitting photo-electrons. Because a dust
grain experiences magnetic forces after becoming charged, but not before,
charging can cause irreversible trapping of the grain so dust accretion is a
consequence of charging. Furthermore, charging causes canonical angular
momentum to replace mechanical angular momentum as the relevant constant of the
motion. The resulting effective potential has three distinct classes of
accreting particles distinguished by canonical angular momentum, namely (i)
"cyclotron-orbit", (ii) "Speiser-orbit", and (iii) "zero canonical angular
momentum" particles. Electrons and ions are of class (i) but depending on mass
and initial orbit inclination, dust grains can be of any class. Light-weight
dust grains develop class (i) orbits such that the grains are confined to
nested poloidal flux surfaces, whereas grains with a critical weight such that
they experience comparable gravitational and magnetic forces can develop class
(ii) or class (iii) orbits, respectively producing poloidal and toroidal field
dynamos.Comment: 70 pages, 16 figure
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