3,940 research outputs found
Generalizing the Network Scale-Up Method: A New Estimator for the Size of Hidden Populations
The network scale-up method enables researchers to estimate the size of
hidden populations, such as drug injectors and sex workers, using sampled
social network data. The basic scale-up estimator offers advantages over other
size estimation techniques, but it depends on problematic modeling assumptions.
We propose a new generalized scale-up estimator that can be used in settings
with non-random social mixing and imperfect awareness about membership in the
hidden population. Further, the new estimator can be used when data are
collected via complex sample designs and from incomplete sampling frames.
However, the generalized scale-up estimator also requires data from two
samples: one from the frame population and one from the hidden population. In
some situations these data from the hidden population can be collected by
adding a small number of questions to already planned studies. For other
situations, we develop interpretable adjustment factors that can be applied to
the basic scale-up estimator. We conclude with practical recommendations for
the design and analysis of future studies
The Network Survival Method for Estimating Adult Mortality: Evidence From a Survey Experiment in Rwanda.
Adult death rates are a critical indicator of population health and well-being. Wealthy countries have high-quality vital registration systems, but poor countries lack this infrastructure and must rely on estimates that are often problematic. In this article, we introduce the network survival method, a new approach for estimating adult death rates. We derive the precise conditions under which it produces consistent and unbiased estimates. Further, we develop an analytical framework for sensitivity analysis. To assess the performance of the network survival method in a realistic setting, we conducted a nationally representative survey experiment in Rwanda (n = 4,669). Network survival estimates were similar to estimates from other methods, even though the network survival estimates were made with substantially smaller samples and are based entirely on data from Rwanda, with no need for model life tables or pooling of data from other countries. Our analytic results demonstrate that the network survival method has attractive properties, and our empirical results show that this method can be used in countries where reliable estimates of adult death rates are sorely needed
Learning Policies from Self-Play with Policy Gradients and MCTS Value Estimates
In recent years, state-of-the-art game-playing agents often involve policies
that are trained in self-playing processes where Monte Carlo tree search (MCTS)
algorithms and trained policies iteratively improve each other. The strongest
results have been obtained when policies are trained to mimic the search
behaviour of MCTS by minimising a cross-entropy loss. Because MCTS, by design,
includes an element of exploration, policies trained in this manner are also
likely to exhibit a similar extent of exploration. In this paper, we are
interested in learning policies for a project with future goals including the
extraction of interpretable strategies, rather than state-of-the-art
game-playing performance. For these goals, we argue that such an extent of
exploration is undesirable, and we propose a novel objective function for
training policies that are not exploratory. We derive a policy gradient
expression for maximising this objective function, which can be estimated using
MCTS value estimates, rather than MCTS visit counts. We empirically evaluate
various properties of resulting policies, in a variety of board games.Comment: Accepted at the IEEE Conference on Games (CoG) 201
Multi-region relaxed magnetohydrodynamics with anisotropy and flow
We present an extension of the multi-region relaxed magnetohydrodynamics
(MRxMHD) equilibrium model that includes pressure anisotropy and general plasma
flows. This anisotropic extension to our previous isotropic model is motivated
by Sun and Finn's model of relaxed anisotropic magnetohydrodynamic equilibria.
We prove that as the number of plasma regions becomes infinite, our anisotropic
extension of MRxMHD reduces to anisotropic ideal MHD with flow. The
continuously nested flux surface limit of our MRxMHD model is the first
variational principle for anisotropic plasma equilibria with general flow
fields.Comment: 11 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1401.307
Longitudinal assessment of reflexive and volitional saccades in Niemann-Pick Type C disease during treatment with miglustat
Peer reviewedPublisher PD
Framework for Electroencephalography-based Evaluation of User Experience
Measuring brain activity with electroencephalography (EEG) is mature enough
to assess mental states. Combined with existing methods, such tool can be used
to strengthen the understanding of user experience. We contribute a set of
methods to estimate continuously the user's mental workload, attention and
recognition of interaction errors during different interaction tasks. We
validate these measures on a controlled virtual environment and show how they
can be used to compare different interaction techniques or devices, by
comparing here a keyboard and a touch-based interface. Thanks to such a
framework, EEG becomes a promising method to improve the overall usability of
complex computer systems.Comment: in ACM. CHI '16 - SIGCHI Conference on Human Factors in Computing
System, May 2016, San Jose, United State
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Open Letter In Support of the Digital Humanities Studio Space at Butler Library
The Studio at Butler Library, as we imagine it, will host mix of scheduled events loosely related to digital humanities, along with providing an unstructured, community-driven workspace for all those interested in the applied aspects of book culture, data curation, knowledge design, big history, complex social systems, experimental philosophy and criticism, cultural analytics, network analysis, computational modeling, text mining, data visualization, and critical making
Quantum kinetic theory model of a continuous atom laser
We investigate the feasible limits for realising a continuously evaporated
atom laser with high-temperature sources. A plausible scheme for realising a
truly continuous atom laser is to outcouple atoms from a partially condensed
Bose gas, whilst continuously reloading the system with non-condensed thermal
atoms and performing evaporative cooling. Here we use quantum kinetic theory to
model this system and estimate feasible limits for the operation of such a
scheme. For sufficiently high temperatures, the figure of merit for the source
is shown to be the phase-space flux. The dominant process limiting the usage of
sources with low phase-space flux is the three-body loss of the condensed gas.
We conclude that certain double-magneto-optical trap (MOT) sources may produce
substantial mean condensate numbers through continuous evaporation, and provide
an atom laser source with a narrow linewidth and reasonable flux.Comment: 28 pages, 5 figure
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