976 research outputs found
Dynamic Bayesian Combination of Multiple Imperfect Classifiers
Classifier combination methods need to make best use of the outputs of
multiple, imperfect classifiers to enable higher accuracy classifications. In
many situations, such as when human decisions need to be combined, the base
decisions can vary enormously in reliability. A Bayesian approach to such
uncertain combination allows us to infer the differences in performance between
individuals and to incorporate any available prior knowledge about their
abilities when training data is sparse. In this paper we explore Bayesian
classifier combination, using the computationally efficient framework of
variational Bayesian inference. We apply the approach to real data from a large
citizen science project, Galaxy Zoo Supernovae, and show that our method far
outperforms other established approaches to imperfect decision combination. We
go on to analyse the putative community structure of the decision makers, based
on their inferred decision making strategies, and show that natural groupings
are formed. Finally we present a dynamic Bayesian classifier combination
approach and investigate the changes in base classifier performance over time.Comment: 35 pages, 12 figure
Dynamical approach to spectator fragmentation in Au+Au reactions at 35 MeV/A
The characteristics of fragment emission in peripheral Au+Au
collisions 35 MeV/A are studied using the two clusterization approaches within
framework of \emph{quantum molecular dynamics} model. Our model calculations
using \emph{minimum spanning tree} (MST) algorithm and advanced clusterization
method namely \emph{simulated annealing clusterization algorithm} (SACA) showed
that fragment structure can be realized at an earlier time when spectators
contribute significantly toward the fragment production even at such a low
incident energy. Comparison of model predictions with experimental data reveals
that SACA method can nicely reproduce the fragment charge yields and mean
charge of the heaviest fragment. This reflects suitability of SACA method over
conventional clusterization techniques to investigate spectator matter
fragmentation in low energy domain.Comment: 6 pages, 5 figures, accepte
The C parameter distribution in e+e- annihilation
We study perturbative and non-perturbative aspects of the distribution of the
C parameter in e+e- annihilation using renormalon techniques. We perform an
exact calculation of the characteristic function, corresponding to the C
parameter differential cross section for a single off-shell gluon. We then
concentrate on the two-jet region, derive the Borel representation of the
Sudakov exponent in the large-beta_0 limit and compare the result to that of
the thrust T. Analysing the exponent, we distinguish two ingredients: the jet
function, depending on Q^2C, summarizing the effects of collinear radiation,
and a function describing soft emission at large angles, with momenta of order
QC. The former is the same as for the thrust upon scaling C by 1/6, whereas the
latter is different. We verify that the rescaled C distribution coincides with
that of 1-T to next-to-leading logarithmic accuracy, as predicted by Catani and
Webber, and demonstrate that this relation breaks down beyond this order owing
to soft radiation at large angles. The pattern of power corrections is also
similar to that of the thrust: corrections appear as odd powers of Lambda/(QC).
Based on the size of the renormalon ambiguity, however, the shape function is
different: subleading power corrections for the C distribution appear to be
significantly smaller than those for the thrust.Comment: 24 pages, Latex (using JHEP3.cls), 1 postscript figur
Взаємозв’язок великих кондратьєвських циклів розвитку економіки і системних світових конфліктів
Однією з найважливіших проблем, що постала перед сучасною наукою у зв’язку із стрімким розгортанням глобальної економічної кризи, загостренням світових конфліктів, є вироблення науково обґрунтованих «метричних» експрес прогнозів розвитку суспільства на ближчу і далеку перспективу
Event Shape/Energy Flow Correlations
We introduce a set of correlations between energy flow and event shapes that
are sensitive to the flow of color at short distances in jet events. These
correlations are formulated for a general set of event shapes, which includes
jet broadening and thrust as special cases. We illustrate the method for
electron-positron annihilation dijet events, and calculate the correlation at
leading logarithm in the energy flow and at next-to-leading-logarithm in the
event shape.Comment: 43 pages, eight eps figures; minor changes, references adde
‘Stepping away from the computer and into the sweats': The construction and negotiation of exercise identities in a Norwegian public company
While research has found that a developed exercise identity enables individuals to view exercise participation as self- reinforcing, the social barriers to such exercise identity development and participation have not been fully addressed. The subsequent aim of this study was to explore some of the social complexities at play in terms of how company employees construct and manage their exercise identities within a work place setting. A case-study method was used to address the research issue over a nine-month period. The case to be studied included a sample of 72 employees from a Norwegian public company who participated in an on-going work-based exercise programme called ‘Exercise for all’. The principal means of data collection comprised participant observation, individual interviews and exercise logbooks. The data were subject to inductive analysis. The primary barriers to exercise participation included high levels of social comparison in a competitive working context, particularly in relation to ‘competent colleagues’, and feelings of guilt associated with partaking in ‘recreational’ activities during work hours. Strategies engaged with to overcome and negotiate such obstacles included justifying participation through a health-related discourse, and constructing a more distinct ‘worker-exerciser’ identity
State of the field: What can political ethnography tell us about anti-politics and democratic disaffection?
This article adopts and reinvents the ethnographic approach to uncover what governing elites do, and how they respond to public disaffection. Although there is significant work on the citizens’ attitudes to the governing elite (the demand side) there is little work on how elites interpret and respond to public disaffection (the supply side). We argue that ethnography is the best available research method for collecting data on the supply side. In doing so, we tackle long-standing stereotypes in political science about the ethnographic method and what it is good for. We highlight how the innovative and varied practices of contemporary ethnography are ideally suited to shedding light into the ‘black box’ of elite politics. We demonstrate the potential pay-off with reference to important examples of elite ethnography from the margins of political science scholarship. The implications from these rich studies, we argue, suggest a reorientation of how we understand the drivers of public disaffection and the role that political elites play in exacerbating cynicism and disappointment. We conclude by pointing to the benefits to the discipline in embracing elite ethnography both to diversify the methodological toolkit in explaining the complex dynamics of disaffection,and to better enable engagement in renewed public debate about the political establishment
Determination of the Deep Inelastic Contribution to the Generalised Gerasimov-Drell-Hearn Integral for the Proton and Neutron
The virtual photon absorption cross section differences [sigma_1/2-sigma_3/2]
for the proton and neutron have been determined from measurements of polarised
cross section asymmetries in deep inelastic scattering of 27.5 GeV
longitudinally polarised positrons from polarised 1H and 3He internal gas
targets. The data were collected in the region above the nucleon resonances in
the kinematic range nu < 23.5 GeV and 0.8 GeV**2 < Q**2 < 12 GeV**2. For the
proton the contribution to the generalised Gerasimov-Drell-Hearn integral was
found to be substantial and must be included for an accurate determination of
the full integral. Furthermore the data are consistent with a QCD
next-to-leading order fit based on previous deep inelastic scattering data.
Therefore higher twist effects do not appear significant.Comment: 6 pages, 3 figures, 1 table, revte
Observation of a Coherence Length Effect in Exclusive Rho^0 Electroproduction
Exclusive incoherent electroproduction of the rho^0(770) meson from 1H, 2H,
3He, and 14N targets has been studied by the HERMES experiment at squared
four-momentum transfer Q**2>0.4 GeV**2 and positron energy loss nu from 9 to 20
GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the
nuclear transparency, was found to decrease with increasing coherence length of
quark-antiquark fluctuations of the virtual photon. The data provide clear
evidence of the interaction of the quark- antiquark fluctuations with the
nuclear medium.Comment: RevTeX, 5 pages, 3 figure
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
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