759 research outputs found
The role of the supply chain in the elimination and reduction of construction rework and defects: an action research approach
Since 2007, Ireland has suffered a circa 80% reduction in construction output. This has
resulted in bankruptcy, unemployment and bad debt. Contractors have attached greater
emphasis to production efficiency and cost reduction as a means of survival. An Action
Research (AR) strategy was used in this research to improve processes adopted by a SME
contractor for the control of defects in its supply chain. It is conservatively estimated that
rework, typically accounts for, circa 5% of total project costs. Rework is wasteful and
presents an obvious target for improvement. The research reported here concerns the (first)
diagnosing stage of the AR cycle only, involving: observation of fieldwork, analysis of
contract documents, and semi-structured interviews with supply chain members. The results
indicate potential for supply chain participants to identify root causes of defects and propose
solutions, having regard to best practice to avoid re-occurrence. A lack of collaborative
forums to contribute to production improvement was identified. Additionally the processes,
used to collect, manage and disseminate data were unstructured and uncoordinated, indicating
scope for developing more efficient methods. The research indicates good understanding of
the potential benefits for supply chain collaboration but suggests that the tools and knowledge
to collaborate are currently lacking in the SME sector
Dependence of Aspen Stands on a Subsurface Water Subsidy: Implications for Climate Change Impacts
The reliance of 10 Utah (USA) aspen forests on direct infiltration of growing season rain versus an additional subsurface water subsidy was determined from a trait‐ and process‐based model of stomatal control. The model simulated the relationship between water supply to the root zone versus canopy transpiration and assimilation over a growing season. Canopy flux thresholds were identified that distinguished nonstressed, stressed, and dying stands. We found growing season rain and local soil moisture were insufficient for the survival of 5 of 10 stands. Six stands required a substantial subsidy (31–80% of potential seasonal transpiration) to avoid water stress and maximize photosynthetic potential. Subsidy dependence increased with stand hydraulic conductance. Four of the six “subsidized” stands were predicted to be stressed during the survey year owing to a subsidy shortfall. Since winter snowpack is closely related to groundwater recharge in the region, we compared winter precipitation with tree‐ring chronologies. Consistent with model predictions, chronologies were more sensitive to snowpack in subsidized stands than in nonsubsidized ones. The results imply that aspen stand health in the region is more coupled to winter snowpack than to growing season water supply. Winters are predicted to have less precipitation as snow, indicating a stressful future for the region\u27s aspen forests
The velocity potential and the interacting force for two spheres moving perpendicularly to the line joining their centers
The velocity potential around two spheres moving perpendicularly to the line joining their centers is given by a series of spherical harmonics. The appropriateness of the truncation is evaluated by determining the residual normal surface velocity on the spheres. In evaluating the residual normal velocity, a recursive procedure is constructed to evaluate the spherical harmonics to reduce computational effort and truncation error as compared to direct transformation or numerical integration. We estimate the lift force coefficient for touching spheres to be 0.577771, compared to the most accurate earlier estimate of 0.51435 by Miloh (1977).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42701/1/10665_2004_Article_BF00127479.pd
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV
We present the first measurement of directed flow () at RHIC. is
found to be consistent with zero at pseudorapidities from -1.2 to 1.2,
then rises to the level of a couple of percent over the range . The latter observation is similar to data from NA49 if the SPS rapidities
are shifted by the difference in beam rapidity between RHIC and SPS.
Back-to-back jets emitted out-of-plane are found to be suppressed more if
compared to those emitted in-plane, which is consistent with {\it jet
quenching}. Using the scalar product method, we systematically compared
azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow
from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure
Azimuthal anisotropy: the higher harmonics
We report the first observations of the fourth harmonic (v_4) in the
azimuthal distribution of particles at RHIC. The measurement was done taking
advantage of the large elliptic flow generated at RHIC. The integrated v_4 is
about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8)
harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding
Kaon Production and Kaon to Pion Ratio in Au+Au Collisions at \snn=130 GeV
Mid-rapidity transverse mass spectra and multiplicity densities of charged
and neutral kaons are reported for Au+Au collisions at \snn=130 GeV at RHIC.
The spectra are exponential in transverse mass, with an inverse slope of about
280 MeV in central collisions. The multiplicity densities for these particles
scale with the negative hadron pseudo-rapidity density. The charged kaon to
pion ratios are and
for the most central collisions. The ratio is lower than the same
ratio observed at the SPS while the is higher than the SPS result.
Both ratios are enhanced by about 50% relative to p+p and +p
collision data at similar energies.Comment: 6 pages, 3 figures, 1 tabl
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
Plasma Wakefield Acceleration with a Modulated Proton Bunch
The plasma wakefield amplitudes which could be achieved via the modulation of
a long proton bunch are investigated. We find that in the limit of long bunches
compared to the plasma wavelength, the strength of the accelerating fields is
directly proportional to the number of particles in the drive bunch and
inversely proportional to the square of the transverse bunch size. The scaling
laws were tested and verified in detailed simulations using parameters of
existing proton accelerators, and large electric fields were achieved, reaching
1 GV/m for LHC bunches. Energy gains for test electrons beyond 6 TeV were found
in this case.Comment: 9 pages, 7 figure
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