2,061 research outputs found
Advancement of the Wide-angle JEM-EUSO Optical System with Holographic and Fresnel Lenses
JEM-EUSO is a space mission to observe extremely high-energy cosmic rays, evolved from the previous design studies of EUSO. It is adjusted for the Japan Experiment Module (JEM) of the International Space Station (ISS). JEM-EUSO uses a wide-angle refractive telescope in near-ultraviolet wavelength region to observe from ISS the time-and-space-resolved atmospheric fluorescence images of the extensive air showers. The JEM-EUSO optics is re-designed after the ESA-Phase A studies to upgrade the light-collecting-power by using a new material CYTOP, and its overall light-collecting power is about 1.5 times higher than the ESA-Phase A baseline optics. We describe in this paper an optimized optics design that maximizes the sensitivity of JEM-EUSO, and the results of the optics manufacturing tests
The JEM-EUSO Mission
JEM-EUSO is a science mission to explore extremes of the Universe. It observes the dark-side of the Earth and detects UV photons emitted from the extensive air shower caused by an extreme energy particle (about 10(exp 20) eV). Such a particle arrives almost straightly through our Milky Way Galaxy and is expected to allow us to trace the source location by its arrival direction. This will open the door to the new astronomy with charged particles. In its five years operation including the tilted mode, JEM-EUSO will detect at least 1,000 events with E>7 X 10(exp 19) eV and determine the energy spectrum of trans-GZK region with a statistical accuracy of several percent. JEM-EUSO is planned to be transported with HTV (H2 Transfer Vehicle) and attached to the Japanese Experiment Module/ Exposure Facility (JEM/EF) of International Space Station. JAXA has selected JEM-EUSO for one of the mission candidates of the second phase utilization of JEM/EF for the launch of early 2010s. One year-long phase-A study will be carried out under JAXA
The Impact of E-Mentoring on Information Technology Professionals
Our research examines the impact of virtual mentoring, or E-mentoring. We surveyed 133 IT professionals as to their experiences as protégés. We asked them about their mentoring relationships, as well as job and career outcomes, and the extent to which they interacted with the mentor virtually. We predicted that E-mentoring would lead to less effective mentoring relationships, less mentoring satisfaction, and lower career outcomes, and that these effects would be moderated by age (millennial protégés versus older protégés). We found few effects, other than lower satisfaction with E-mentoring relationships. The results suggest that E-mentoring can be as effective as face-to-face mentoring. However, few in our sample had completely virtual mentoring relationships, so it may still be possible that E-mentoring with almost no face-to-face interaction may be less effective
Di-hadron azimuthal correlation and Mach-like cone structure in parton/hadron transport model
In the framework of a multi-phase transport model (AMPT) with both partonic
and hadronic interactions, azimuthal correlations between trigger particles and
associated scattering particles have been studied by the mixing-event
technique. The momentum ranges of these particles are
GeV/ and GeV/ (soft), or 4
GeV/ and GeV/ (hard) in Au + Au collisions at
= 200 GeV. A Mach-like structure has been observed in
correlation functions for central collisions. By comparing scenarios with and
without parton cascade and hadronic rescattering, we show that both partonic
and hadronic dynamical mechanisms contribute to the Mach-like structure of the
associated particle azimuthal correlations. The contribution of hadronic
dynamical process can not be ignored in the emergence of Mach-like correlations
of the soft scattered associated hadrons. However, hadronic rescattering alone
cannot reproduce experimental amplitude of Mach-like cone on away-side, and the
parton cascade process is essential to describe experimental amplitude of
Mach-like cone on away-side. In addition, both the associated multiplicity and
the sum of decrease, whileas the increases, with the impact
parameter in the AMPT model including partonic dynamics from string melting
scenario.Comment: 9 pages, 5 figures; Physics Letters B 641, 362-367 (2006
System-size scan of dihadron azimuthal correlations in ultra-relativistic heavy ion collisions
System-size dependence of dihadron azimuthal correlations in
ultra-relativistic heavy ion collision is simulated by a multi-phase transport
model. The structure of correlation functions and yields of associated
particles show clear participant path-length dependences in collision systems
with a partonic phase. The splitting parameter and root-mean-square width of
away-side correlation functions increase with collision system size from
N+N to Au+Au collisions. The double-peak
structure of away-side correlation functions can only be formed in sufficient
"large" collision systems under partonic phase. The contrast between the
results with partonic phase and with hadron gas could suggest some hints to
study onset of deconfinment.Comment: 8 pages, 4 figures, 1 table; Nucl. Phys. A (accepted
Effects of Temperature and Moisture on Sheet Molding Compounds
A summary is given on the effects of moisture and temperature on the properties of chopped fiber reinforced sheet molding compounds. The properties surveyed include tensile strength and modulus, compression strength and modulus, shear strength and modulus, flexural strength and modulus, fatigue, creep, vibration damping, moisture absorption characteristics, and thermal expansion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68648/2/10.1177_073168448300200201.pd
The triangular Ising antiferromagnet in a staggered field
We study the equilibrium properties of the nearest-neighbor Ising
antiferromagnet on a triangular lattice in the presence of a staggered field
conjugate to one of the degenerate ground states. Using a mapping of the ground
states of the model without the staggered field to dimer coverings on the dual
lattice, we classify the ground states into sectors specified by the number of
``strings''. We show that the effect of the staggered field is to generate
long-range interactions between strings. In the limiting case of the
antiferromagnetic coupling constant J becoming infinitely large, we prove the
existence of a phase transition in this system and obtain a finite lower bound
for the transition temperature. For finite J, we study the equilibrium
properties of the system using Monte Carlo simulations with three different
dynamics. We find that in all the three cases, equilibration times for low
field values increase rapidly with system size at low temperatures. Due to this
difficulty in equilibrating sufficiently large systems at low temperatures, our
finite-size scaling analysis of the numerical results does not permit a
definite conclusion about the existence of a phase transition for finite values
of J. A surprising feature in the system is the fact that unlike usual glassy
systems, a zero-temperature quench almost always leads to the ground state,
while a slow cooling does not.Comment: 12 pages, 18 figures: To appear in Phys. Rev.
Three-Particle Correlations from Parton Cascades in Au+Au Collisions
We present a study of three-particle correlations among a trigger particle
and two associated particles in Au + Au collisions at = 200 GeV
using a multi-phase transport model (AMPT) with both partonic and hadronic
interactions. We found that three-particle correlation densities in different
angular directions with respect to the triggered particle (`center', `cone',
`deflected', `near' and `near-away') increase with the number of participants.
The ratio of `deflected' to `cone' density approaches to 1.0 with the
increasing of number of participants, which indicates that partonic Mach-like
shock waves can be produced by strong parton cascades in central Au+Au
collisions.Comment: 9 pages, 6 figures; Final version to appear in Physics Letters
Longitudinal broadening of near side jets due to parton cascade
Longitudinal broadening along direction on near side in
two-dimensional () di-hadron correlation
distribution has been studied for central Au+Au collisions at =
200 GeV, within a dynamical multi-phase transport model. It was found that the
longitudinal broadening is generated by a longitudinal flow induced by strong
parton cascade in central Au+Au collisions, in comparison with p+p collisions
at = 200 GeV. The longitudinal broadening may shed light on the
information about strongly interacting partonic matter at RHIC.Comment: 5 pages, 4 figures; accepted by Eur. Phys. J.
Anomalous acoustic reflection on a sliding interface or a shear band
We study the reflection of an acoustic plane wave from a steadily sliding
planar interface with velocity strengthening friction or a shear band in a
confined granular medium. The corresponding acoustic impedance is utterly
different from that of the static interface. In particular, the system being
open, the energy of an in-plane polarized wave is no longer conserved, the work
of the external pulling force being partitioned between frictional dissipation
and gain (of either sign) of coherent acoustic energy. Large values of the
friction coefficient favor energy gain, while velocity strengthening tends to
suppress it. An interface with infinite elastic contrast (one rigid medium) and
V-independent (Coulomb) friction exhibits spontaneous acoustic emission, as
already shown by M. Nosonovsky and G.G. Adams (Int. J. Ing. Sci., {\bf 39},
1257 (2001)). But this pathology is cured by any finite elastic contrast, or by
a moderately large V-strengthening of friction.
We show that (i) positive gain should be observable for rough-on-flat
multicontact interfaces (ii) a sliding shear band in a granular medium should
give rise to sizeable reflection, which opens a promising possibility for the
detection of shear localization.Comment: 13 pages, 10 figure
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