5,774 research outputs found
Closed circuit TV system automatically guides welding arc
Closed circuit television /CCTV/ system automatically guides a welding torch to position the welding arc accurately along weld seams. Digital counting and logic techniques incorporated in the control circuitry, ensure performance reliability
The Facilitation of Students with Learning Disabilities to Postsecondary Education by Secondary Special Educators
This descriptive research was conducted to collect data concerning the attitudes and policies about transition to postsecondary education by secondary special educators in the State of Illinois. A survey was sent to 208 secondary special educators representing the independent high school districts in the state. The survey measured three variables in relation to size of school: special educators\u27 awareness of postsecondary educational opportunities, special educators\u27 expectations for students labeled learning disabled to pursue postsecondary education, and current practices for serving high school students labeled learning disabled. The findings showed that there were more likenesses than differences in the transition attitudes and practices of secondary special educators in large and small schools in the State of Illinois. Out of sixteen items analyzed a priori, only one item showed a significant difference. That difference was that a higher percentage of special educators from large schools were aware of postsecondary programs for students labeled learning disabled. In only one out of three variables, level of awareness, was there a significant difference based upon school size. There is a need in future research to focus on establishing criteria as to what levels schools are functioning at on these variables, so that intervention and staff-training can more readily and profitably be developed
The Facilitation of Students with Learning Disabilities to Postsecondary Education by Secondary Special Educators
This descriptive research was conducted to collect data concerning the attitudes and policies about transition to postsecondary education by secondary special educators in the State of Illinois. A survey was sent to 208 secondary special educators representing the independent high school districts in the state. The survey measured three variables in relation to size of school: special educators\u27 awareness of postsecondary educational opportunities, special educators\u27 expectations for students labeled learning disabled to pursue postsecondary education, and current practices for serving high school students labeled learning disabled. The findings showed that there were more likenesses than differences in the transition attitudes and practices of secondary special educators in large and small schools in the State of Illinois. Out of sixteen items analyzed a priori, only one item showed a significant difference. That difference was that a higher percentage of special educators from large schools were aware of postsecondary programs for students labeled learning disabled. In only one out of three variables, level of awareness, was there a significant difference based upon school size. There is a need in future research to focus on establishing criteria as to what levels schools are functioning at on these variables, so that intervention and staff-training can more readily and profitably be developed
Balance functions in coalescence model
It is shown that the quark-antiquark coalescence mechanism for pion
production allows to explain the small width of the balance function observed
for central collisions of heavy ions, provided effects of the finite acceptance
region and of the transverse flow are taken into account. In contrast, the
standard hadronic cluster model is not compatible with this data.Comment: 12 pages, 1 figur
System-size dependence of the pion freeze-out volume as a potential signature for the phase transition to a Quark Gluon Plasma
Hanburry-Brown-Twiss (HBT) correlation functions and radii of negatively
charged pions from C+C, Si+Si, Cu+Cu, and In+In at lower RHIC/SPS energies are
calculated with the UrQMD transport model and the CRAB analyzing program. We
find a minimum in the excitation function of the pion freeze-out volume at low
transverse momenta and around GeV which can be related to
the transition from hadronic to string matter (which might be interpreted as a
pre-cursor of the QGP). The existence of the minimum is explained by the
competition of two mechanisms of the particle production, resonance decays and
string formation/fragmentation.Comment: 12 pages, 4 fig
Is Strangeness still interesting at RHIC ?
With the advent of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven
National Laboratory (BNL), Heavy Ion Physics will enter a new energy regime.
The question is whether the signatures proposed for the discovery of a phase
transition from hadronic matter to a Quark Gluon Plasma (QGP), that were
established on the basis of collisions at the BEVALAC, the AGS, and the SPS,
respectively, are still useful and detectable at these high incident energies.
In the past two decades, measurements related to strangeness formation in the
collision were advocated as potential signatures and were tested in numerous
fixed target experiments at the AGS and the SPS. In this article I will review
the capabilities of the RHIC detectors to measure various aspects of
strangeness, and I will try to answer the question whether the information
content of those measurements is comparable to the one at lower energies.Comment: 12 pages, 7 figures, Invited Talk at the IV International Conference
on Strangeness in Quark Matter, Padova (Italy), July 20-24, 199
Applicability of Monte Carlo Glauber models to relativistic heavy ion collision data
The accuracy of Monte Carlo Glauber model descriptions of minimum-bias
multiplicity frequency distributions is evaluated using data from the
Relativistic Heavy Ion Collider (RHIC) within the context of a sensitive,
power-law representation introduced previously by Trainor and Prindle (TP).
Uncertainties in the Glauber model input and in the mid-rapidity multiplicity
frequency distribution data are reviewed and estimated using the TP centrality
methodology. The resulting errors in model-dependent geometrical quantities
used to characterize heavy ion collisions ({\em i.e.} impact parameter, number
of nucleon participants , number of binary interactions ,
and average number of binary collisions per incident participant nucleon )
are presented for minimum-bias Au-Au collisions at = 20, 62,
130 and 200 GeV and Cu-Cu collisions at = 62 and 200 GeV.
Considerable improvement in the accuracy of collision geometry quantities is
obtained compared to previous Monte Carlo Glauber model studies, confirming the
TP conclusions. The present analysis provides a comprehensive list of the
sources of uncertainty and the resulting errors in the above geometrical
collision quantities as functions of centrality. The capability of energy
deposition data from trigger detectors to enable further improvements in the
accuracy of collision geometry quantities is also discussed.Comment: 27 pages, 4 figures, 11 table
The Importance of Correlations and Fluctuations on the Initial Source Eccentricity in High-Energy Nucleus-Nucleus Collisions
In this paper, we investigate various ways of defining the initial source
eccentricity using the Monte Carlo Glauber (MCG) approach. In particular, we
examine the participant eccentricity, which quantifies the eccentricity of the
initial source shape by the major axes of the ellipse formed by the interaction
points of the participating nucleons. We show that reasonable variation of the
density parameters in the Glauber calculation, as well as variations in how
matter production is modeled, do not significantly modify the already
established behavior of the participant eccentricity as a function of collision
centrality. Focusing on event-by-event fluctuations and correlations of the
distributions of participating nucleons we demonstrate that, depending on the
achieved event-plane resolution, fluctuations in the elliptic flow magnitude
lead to most measurements being sensitive to the root-mean-square, rather
than the mean of the distribution. Neglecting correlations among
participants, we derive analytical expressions for the participant eccentricity
cumulants as a function of the number of participating nucleons,
\Npart,keeping non-negligible contributions up to \ordof{1/\Npart^3}. We
find that the derived expressions yield the same results as obtained from
mixed-event MCG calculations which remove the correlations stemming from the
nuclear collision process. Most importantly, we conclude from the comparison
with MCG calculations that the fourth order participant eccentricity cumulant
does not approach the spatial anisotropy obtained assuming a smooth nuclear
matter distribution. In particular, for the Cu+Cu system, these quantities
deviate from each other by almost a factor of two over a wide range in
centrality.Comment: 18 pages, 10 figures, submitted to PR
Centrality dependence of charged antiparticle to particle ratios near mid-rapidity in d+Au collisions at sqrt(s_NN)=200 GeV
The ratios of the yields of charged antiparticles to particles have been
obtained for pions, kaons, and protons near mid-rapidity for d+Au collisions at
sqrt(s_NN) = 200 GeV as a function of centrality. The reported values represent
the ratio of the yields averaged over the rapidity range of 0.1<y_pi<1.3 and
0<y_(K,p)<0.8, where positive rapidity is in the deuteron direction, and for
transverse momenta 0.1<p_(T)^(pi,K)<1.0 GeV/c and 0.3<p_(T)^(p)<1.0 GeV/c.
Within the uncertainties, a lack of centrality dependence is observed in all
three ratios. The data are compared to results from other systems and model
calculations.Comment: 6 pages, 4 figures, submitted to PR
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