464 research outputs found
Pointwise consistency of the kriging predictor with known mean and covariance functions
This paper deals with several issues related to the pointwise consistency of
the kriging predictor when the mean and the covariance functions are known.
These questions are of general importance in the context of computer
experiments. The analysis is based on the properties of approximations in
reproducing kernel Hilbert spaces. We fix an erroneous claim of Yakowitz and
Szidarovszky (J. Multivariate Analysis, 1985) that the kriging predictor is
pointwise consistent for all continuous sample paths under some assumptions.Comment: Submitted to mODa9 (the Model-Oriented Data Analysis and Optimum
Design Conference), 14th-19th June 2010, Bertinoro, Ital
Cosmic Calibration: Constraints from the Matter Power Spectrum and the Cosmic Microwave Background
Several cosmological measurements have attained significant levels of
maturity and accuracy over the last decade. Continuing this trend, future
observations promise measurements of the statistics of the cosmic mass
distribution at an accuracy level of one percent out to spatial scales with
k~10 h/Mpc and even smaller, entering highly nonlinear regimes of gravitational
instability. In order to interpret these observations and extract useful
cosmological information from them, such as the equation of state of dark
energy, very costly high precision, multi-physics simulations must be
performed. We have recently implemented a new statistical framework with the
aim of obtaining accurate parameter constraints from combining observations
with a limited number of simulations. The key idea is the replacement of the
full simulator by a fast emulator with controlled error bounds. In this paper,
we provide a detailed description of the methodology and extend the framework
to include joint analysis of cosmic microwave background and large scale
structure measurements. Our framework is especially well-suited for upcoming
large scale structure probes of dark energy such as baryon acoustic
oscillations and, especially, weak lensing, where percent level accuracy on
nonlinear scales is needed.Comment: 15 pages, 14 figure
The Obliteration of Truth by Management: Badiou, St. Paul and the Question of Economic Managerialism in Education
This paper considers the questions that Badiou’s theory of the subject poses to cultures of economic managerialism within education. His argument that radical change is possible, for people and the situations they inhabit, provides a stark challenge to the stifling nature of much current educational climate. In 'Saint Paul: The Foundation of Universalism', Badiou describes the current universalism of capitalism, monetary homogeneity and the rule of the count. Badiou argues that the politics of identity are all too easily subsumed by the prerogatives of the marketplace and unable to present, therefore, a critique of the status quo. These processes are, he argues, without the potential for truth. What are the implications of Badiou’s claim that education is the arranging of ‘the forms of knowledge in such a way that truth may come to pierce a hole in them’ (Badiou, 2005, p. 9)? In this paper, I argue that Badiou’s theory opens up space for a kind of thinking about education that resists its colonisation by cultures of management and marketisation and leads educationalists to consider the emancipatory potential of education in a new light
A bounded confidence approach to understanding user participation in peer production systems
Commons-based peer production does seem to rest upon a paradox. Although
users produce all contents, at the same time participation is commonly on a
voluntary basis, and largely incentivized by achievement of project's goals.
This means that users have to coordinate their actions and goals, in order to
keep themselves from leaving. While this situation is easily explainable for
small groups of highly committed, like-minded individuals, little is known
about large-scale, heterogeneous projects, such as Wikipedia.
In this contribution we present a model of peer production in a large online
community. The model features a dynamic population of bounded confidence users,
and an endogenous process of user departure. Using global sensitivity analysis,
we identify the most important parameters affecting the lifespan of user
participation. We find that the model presents two distinct regimes, and that
the shift between them is governed by the bounded confidence parameter. For low
values of this parameter, users depart almost immediately. For high values,
however, the model produces a bimodal distribution of user lifespan. These
results suggest that user participation to online communities could be
explained in terms of group consensus, and provide a novel connection between
models of opinion dynamics and commons-based peer production.Comment: 17 pages, 5 figures, accepted to SocInfo201
Open TURNS: An industrial software for uncertainty quantification in simulation
The needs to assess robust performances for complex systems and to answer
tighter regulatory processes (security, safety, environmental control, and
health impacts, etc.) have led to the emergence of a new industrial simulation
challenge: to take uncertainties into account when dealing with complex
numerical simulation frameworks. Therefore, a generic methodology has emerged
from the joint effort of several industrial companies and academic
institutions. EDF R&D, Airbus Group and Phimeca Engineering started a
collaboration at the beginning of 2005, joined by IMACS in 2014, for the
development of an Open Source software platform dedicated to uncertainty
propagation by probabilistic methods, named OpenTURNS for Open source Treatment
of Uncertainty, Risk 'N Statistics. OpenTURNS addresses the specific industrial
challenges attached to uncertainties, which are transparency, genericity,
modularity and multi-accessibility. This paper focuses on OpenTURNS and
presents its main features: openTURNS is an open source software under the LGPL
license, that presents itself as a C++ library and a Python TUI, and which
works under Linux and Windows environment. All the methodological tools are
described in the different sections of this paper: uncertainty quantification,
uncertainty propagation, sensitivity analysis and metamodeling. A section also
explains the generic wrappers way to link openTURNS to any external code. The
paper illustrates as much as possible the methodological tools on an
educational example that simulates the height of a river and compares it to the
height of a dyke that protects industrial facilities. At last, it gives an
overview of the main developments planned for the next few years
Constraining the initial state granularity with bulk observables in Au+Au collisions at GeV
In this paper we conduct a systematic study of the granularity of the initial
state of hot and dense QCD matter produced in ultra-relativistic heavy-ion
collisions and its influence on bulk observables like particle yields,
spectra and elliptic flow. For our investigation we use a hybrid transport
model, based on (3+1)d hydrodynamics and a microscopic Boltzmann transport
approach. The initial conditions are generated by a non-equilibrium hadronic
transport approach and the size of their fluctuations can be adjusted by
defining a Gaussian smoothing parameter . The dependence of the
hydrodynamic evolution on the choices of
and is explored by means of a Gaussian emulator.
To generate particle yields and elliptic flow that are compatible with
experimental data the initial state parameters are constrained to be
fm and fm. In addition, the influence of changes in the
equation of state is studied and the results of our event-by-event calculations
are compared to a calculation with averaged initial conditions. We conclude
that even though the initial state parameters can be constrained by yields and
elliptic flow, the granularity needs to be constrained by other correlation and
fluctuation observables.Comment: 14 pages, 8 figures, updated references, version to appear in J.
Phys.
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