48 research outputs found
Grooming of Dynamic Traffic in WDM Star and Tree Networks Using Genetic Algorithm
The advances in WDM technology lead to the great interest in traffic grooming
problems. As traffic often changes from time to time, the problem of grooming
dynamic traffic is of great practical value. In this paper, we discuss dynamic
grooming of traffic in star and tree networks. A genetic algorithm (GA) based
approach is proposed to support arbitrary dynamic traffic patterns, which
minimizes the number of ADM's and wavelengths. To evaluate the algorithm,
tighter bounds are derived. Computer simulation results show that our algorithm
is efficient in reducing both the numbers of ADM's and wavelengths in tree and
star networks.Comment: 15 page
Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive production
We present studies of single-spin asymmetries for neutral pion
electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV
polarized electrons from an unpolarized hydrogen target, using the CEBAF Large
Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator
Facility. A substantial amplitude has been measured in the
distribution of the cross section asymmetry as a function of the azimuthal
angle of the produced neutral pion. The dependence of this amplitude
on Bjorken and on the pion transverse momentum is extracted with
significantly higher precision than previous data and is compared to model
calculations.Comment: to be submitted PL
Proximity effect at superconducting Sn-Bi2Se3 interface
We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions
down to 250 mK and in different magnetic fields. A number of conductance
anomalies were observed below the superconducting transition temperature of Sn,
including a small gap different from that of Sn, and a zero-bias conductance
peak growing up at lower temperatures. We discussed the possible origins of the
smaller gap and the zero-bias conductance peak. These phenomena support that a
proximity-effect-induced chiral superconducting phase is formed at the
interface between the superconducting Sn and the strong spin-orbit coupling
material Bi2Se3.Comment: 7 pages, 8 figure
Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV
PHENIX has measured the centrality dependence of charged hadron p_T spectra
from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T
decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction
of the contribution from hard scattering to high p_T hadron production. For
central collisions the yield at high p_T is shown to be suppressed compared to
binary nucleon-nucleon collision scaling of p+p data. This suppression is
monotonically increasing with centrality, but most of the change occurs below
30% centrality, i.e. for collisions with less than about 140 participating
nucleons. The observed p_T and centrality dependence is consistent with the
particle production predicted by models including hard scattering and
subsequent energy loss of the scattered partons in the dense matter created in
the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to
Phys. Lett. B. Revised to address referee concerns. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
Evolution of the differential transverse momentum correlation function with centrality in Au+Au collisions at GeV
We present first measurements of the evolution of the differential transverse
momentum correlation function, {\it C}, with collision centrality in Au+Au
interactions at GeV. {\it C} exhibits a strong dependence
on collision centrality that is qualitatively similar to that of number
correlations previously reported. We use the observed longitudinal broadening
of the near-side peak of {\it C} with increasing centrality to estimate the
ratio of the shear viscosity to entropy density, , of the matter formed
in central Au+Au interactions. We obtain an upper limit estimate of
that suggests that the produced medium has a small viscosity per unit entropy.Comment: 7 pages, 4 figures, STAR paper published in Phys. Lett.
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
Building upon what is already there: The role of prior knowledge, background information, and scaffolding in inquiry learning
Prior knowledge is one of the most important factors for learning. During the iterative cycles of inquiry learning, learners' prior domain knowledge is modified, refined, and further developed, provided that learners act upon self-assessments of their understanding and that they can actually think of appropriate hypotheses. Furthermore, knowledge about inquiry strategies influences the quality of the learners' inquiry activities, and the lack there of requires compensatory support. This symposium brings together recent work about the role of prior knowledge for inquiry learning and ways to compensate for the lack of it. The four papers focus on the role of learners' self-assessment of their current understanding for their subsequent inquiry activities, on the gradual refinement of their knowledge on the basis of reflection, and on prior presentation of theoretical background information and concurrent presentation of inquiry strategies as ways to compensate for lack of prior theoretical knowledge and strategy knowledge, respectivel
Effects of boron doping on the grain-growth kinetics and mechanical properties of γ/γ′ nickel-aluminum alloys
The effects of 0.5 at. pct of boron doping on the microstructures and mechanical properties of γ/γ′ nickel-aluminum alloys have been investigated in the present study. A nickel-rich grain-boundary zone was observed in the boron-doped alloy after homogenization at 1100 °C and prolonged annealing at 1200 °C. Boron doping also caused remarkable improvements in toughness and tensile elongation and caused the fracture mode to change from completely intergranular to completely transgranular. The grain growth following recrystallization at 1200 °C was found to be retarded upon boron doping. A sudden increase in tensile elongation and a sudden drop in hardness were also observed upon prolonged heating during isothermal annealing at 1200 °C. The results are interpreted with reference to boron-nickel cosegregation at the grain boundaries.link_to_subscribed_fulltex