802 research outputs found
Effect of blade planform variation on the forward-flight performance of small-scale rotors
An investigation was conducted in the Glenn L. Martin Wind Tunnel to determine the effect of blade planform variation on the forward-flight performance of four small-scale rotors. The rotors were 5.417 ft in diameter and differed only in blade planform geometry. The four planforms were: (1) rectangular; (2) 3:1 linear taper starting at 94 percent radius; (3) 3:1 linear taper starting at 75 percent radius; and (4) 3:1 linear taper starting at 50 percent radius. Each planform had a thrust-weighted solidity of 0.098. The investigation included forward-flight simulation at advance ratios from 0.14 to 0.43 for a range of rotor lift and drag coefficients. Among the four rotors, the rectangular rotor required the highest torque for the entire range of rotor drag coefficients attained at advanced ratios greater than 0.14 for rotor lift coefficients C sub L from 0.004 to 0.007. Among the rotors with tapered blades and for C sub L = 0.004 to 0.007, either the 75 percent tapered rotor or the 50 percent tapered rotor required the least amount of torque for the full range of rotor drag coefficients attained at each advance ratio. The performance of the 94 percent tapered rotor was generally between that of the rectangular rotor and the 75 and 50 percent tapered rotors at each advance ratio for this range of rotor lift coefficients
Leading particle effect, inelasticity and the connection between average multiplicities in {\bf } and {\bf } processes
The Regge-Mueller formalism is used to describe the inclusive spectrum of the
proton in collisions. From such a description the energy dependences of
both average inelasticity and leading proton multiplicity are calculated. These
quantities are then used to establish the connection between the average
charged particle multiplicities measured in {\bf } and {\bf } processes. The description obtained for the leading proton cross section
implies that Feynman scaling is strongly violated only at the extreme values of
, that is at the central region () and at the diffraction
region (), while it is approximately observed in the
intermediate region of the spectrum.Comment: 20 pages, 10 figures, to be published in Physical Review
An SU(3) model for octet baryon and meson fragmentation
The production of the octet of baryons and mesons in e^+ e^- collisions is
analysed, based on considerations of SU(3) symmetry and a simple model for
SU(3) symmetry breaking in fragmentation functions. All fragmentation
functions, D_q^h(x, Q^2), describing the fragmentation of quarks into a member
of the baryon octet (and similarly for fragmentation into members of the meson
octet) are expressed in terms of three SU(3) symmetric functions, \alpha(x,
Q^2), \beta(x, Q^2), and \gamma(x, Q^2). With the introduction of an SU(3)
breaking parameter, \lambda, the model is successful in describing
hadroproduction data at the Z pole. The fragmentation functions are then
evolved using leading order evolution equations and good fits to currently
available data at 34 GeV and at 161 GeV are obtained.Comment: 24 pages LaTeX file including 11 postscript figure file
Pion photoproduction on the nucleon in the quark model
We present a detailed quark-model study of pion photoproduction within the
effective Lagrangian approach. Cross sections and single-polarization
observables are investigated for the four charge channels, , , , and .
Leaving the coupling strength to be a free parameter, we obtain a
reasonably consistent description of these four channels from threshold to the
first resonance region. Within this effective Lagrangian approach, strongly
constrainted by the quark model, we consider the issue of double-counting which
may occur if additional {\it t}-channel contributions are included.Comment: Revtex, 35 pages, 16 eps figures; version to appear on PR
A New 5 Flavour NLO Analysis and Parametrizations of Parton Distributions of the Real Photon
New, radiatively generated, NLO quark (u,d,s,c,b) and gluon densities in a
real, unpolarized photon are presented. We perform three global fits, based on
the NLO DGLAP evolution equations for Q^2>1 GeV^2, to all the available
structure function F_2^gamma(x,Q^2) data. As in our previous LO analysis we
utilize two theoretical approaches. Two models, denoted as FFNS_{CJK}1 & 2 NLO,
adopt the so-called Fixed Flavour-Number Scheme for calculation of the
heavy-quark contributions to F_2^gamma(x,Q^2), the CJK NLO model applies the
ACOT(chi) scheme. We examine the results of our fits by a comparison with the
LEP data for the Q^2 dependence of the F_2^gamma, averaged over various
x-regions, and the F_2,c^gamma. Grid parametrizations of the parton densities
for all fits are provided.Comment: 49 pages, 27 postscript figures; FORTRAN programs available at
http://www.fuw.edu.pl/~pjank/param.htm
Systematic event generator tuning for the LHC
In this article we describe Professor, a new program for tuning model
parameters of Monte Carlo event generators to experimental data by
parameterising the per-bin generator response to parameter variations and
numerically optimising the parameterised behaviour. Simulated experimental
analysis data is obtained using the Rivet analysis toolkit. This paper presents
the Professor procedure and implementation, illustrated with the application of
the method to tunes of the Pythia 6 event generator to data from the LEP/SLD
and Tevatron experiments. These tunes are substantial improvements on existing
standard choices, and are recommended as base tunes for LHC experiments, to be
themselves systematically improved upon when early LHC data is available.Comment: 28 pages. Submitted to European Physical Journal C. Program sources
and extra information are available from
http://projects.hepforge.org/professor
Inducing safer oblique trees without costs
Decision tree induction has been widely studied and applied. In safety applications, such as determining whether a chemical process is safe or whether a person has a medical condition, the cost of misclassification in one of the classes is significantly higher than in the other class. Several authors have tackled this problem by developing cost-sensitive decision tree learning algorithms or have suggested ways of changing the
distribution of training examples to bias the decision tree learning process so as to take account of costs. A prerequisite for applying such algorithms is the availability of costs of misclassification.
Although this may be possible for some applications, obtaining reasonable estimates of costs of misclassification is not easy in the area of safety.
This paper presents a new algorithm for applications where the cost of misclassifications cannot be quantified, although the cost of misclassification in one class is known to be significantly higher than in another class. The algorithm utilizes linear discriminant analysis to identify oblique relationships between continuous attributes and then carries out an appropriate modification to ensure that the resulting tree errs on the side of safety. The algorithm is evaluated with respect to one of the best known cost-sensitive algorithms (ICET), a well-known oblique decision tree algorithm (OC1) and an algorithm that utilizes robust linear programming
Transverse polarization in inclusive quasi-real photoproduction at the current fragmentation
It is shown that the recent HERMES data on the transverse
polarization in the inclusive quasi-real photoproduction at can be
accommodated by the strange quark scattering model. Relations with the quark
recombination approach are discussed.Comment: 5 pages, 3 figures, accepted by Eur. Phys. J.
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