23 research outputs found
Constraining the structure of the non-spherical preprotostellar core L1544
A series of self-consistent, three-dimensional continuum radiative transfer
models are constructed of the pre-protostellar core L1544, with the results
compared with existing SCUBA and ISO data. The source is well-fit by a prolate
spheroid, having an ellipsoidal power-law density distribution of index m ~ 2
(1.75 < m < 2.25) in to at least r ~ 1600AU. For r<1600 AU, the data are
consistent with either an extension of the power law to smaller radii, or a
flattened (Bonner-Ebert like) density distribtion. We can further constrain the
optical depth along the short axis at 1300um to be ~ 5e-3, the central
luminosity to be L < 1e-3 solar luminosities, the long axis diameter D ~ 0.1
pc, the axis ratio to be q ~ 2, and the external ISRF to be similar to that
defined by Mathis, Mezger, & Panagia (1983) to within 50 per cent. The outer
diameter and axis ratio may each be somewhat larger due to potential on-source
chopping in the observations, and the projection of the long axis onto the
plane of the sky. While these results are similar to those inferred directly
from observations or spherical modeling due to the source transparency at
submillimeter wavelengths, we infer a smaller size, lower mass, and higher
optical depth / column density, exposed to a stronger external radiation field
than previously assumed. Finally, we find that both the spectral energy
distribution (SED) and surface brightness distribution are necessary to
constrain the source properties in this way.Comment: 9 pages; 8 figures; accepted for publication in MNRA
Interactions between magnetohydrodynamic shear instabilities and convective flows in the solar interior
Motivated by the interface model for the solar dynamo, this paper explores
the complex magnetohydrodynamic interactions between convective flows and
shear-driven instabilities. Initially, we consider the dynamics of a forced
shear flow across a convectively-stable polytropic layer, in the presence of a
vertical magnetic field. When the imposed magnetic field is weak, the dynamics
are dominated by a shear flow (Kelvin-Helmholtz type) instability. For stronger
fields, a magnetic buoyancy instability is preferred. If this stably stratified
shear layer lies below a convectively unstable region, these two regions can
interact. Once again, when the imposed field is very weak, the dynamical
effects of the magnetic field are negligible and the interactions between the
shear layer and the convective layer are relatively minor. However, if the
magnetic field is strong enough to favour magnetic buoyancy instabilities in
the shear layer, extended magnetic flux concentrations form and rise into the
convective layer. These magnetic structures have a highly disruptive effect
upon the convective motions in the upper layer.Comment: 11 pages, 10 figures, accepted for publication in MNRA
Balancing relevance criteria through multi-objective optimization
Offline evaluation of information retrieval systems typically focuses on a single effectiveness measure that models the utility for a typical user. Such a measure usually combines a behavior-based rank discount with a notion of document utility that captures the single relevance criterion of topicality. However, for individual users relevance criteria such as credibility, reputability or readability can strongly impact the utility. Also, for different information needs the utility can be a different mixture of these criteria. Because of the focus on single metrics, offline optimization of IR systems does not account for different preferences in balancing relevance criteria. We propose to mitigate this by viewing multiple relevance criteria as objectives and learning a set of rankers that provide different trade-offs w.r.t. these objectives. We model document utility within a gain-based evaluation framework as a weighted combination of relevance criteria. Using the learned set, we are able to make an informed decision based on the values of the rankers and a preference w.r.t. the relevance criteria. On a dataset annotated for readability and a web search dataset annotated for sub-topic relevance we demonstrate how trade-offs between can be made explicit. We show that there are different available trade-offs between relevance criteria
Ranking Health Web Pages with Relevance and Understandability
International audienc
ShARe/CLEF eHealth Evaluation Lab 2014, Task 3: User-centred health information retrieval
International audienceThis paper presents the results of task 3 of the ShARe/CLEF eHealth Evaluation Lab 2014. This evaluation lab focuses on improving access to medical information on the web. The task objective was to investigate the effect of using additional information such as a related discharge summary and external resources such as medical ontologies on the effectiveness of information retrieval systems, in a monolingual (Task 3a) and in a multilingual (Task 3b) context. The participants were al-lowed to submit up to seven runs for each language (English, Czech, French, German), one mandatory run using no additional information or external resources, and three each using or not using discharge sum-maries
LifeSnaps, a 4-month multi-modal dataset capturing unobtrusive snapshots of our lives in the wild
Ubiquitous self-tracking technologies have penetrated various aspects of our lives, from physical and mental health monitoring to fitness and entertainment. Yet, limited data exist on the association between in the wild large-scale physical activity patterns, sleep, stress, and overall health, and behavioral and psychological patterns due to challenges in collecting and releasing such datasets, including waning user engagement or privacy considerations. In this paper, we present the LifeSnaps dataset, a multi-modal, longitudinal, and geographically-distributed dataset containing a plethora of anthropological data, collected unobtrusively for the total course of more than 4 months by n = 71 participants. LifeSnaps contains more than 35 different data types from second to daily granularity, totaling more than 71 M rows of data. The participants contributed their data through validated surveys, ecological momentary assessments, and a Fitbit Sense smartwatch and consented to make these data available to empower future research. We envision that releasing this large-scale dataset of multi-modal real-world data will open novel research opportunities and potential applications in multiple disciplines
The Scholarly Impact and Strategic Intent of CLEF eHealth Labs from 2012 to 2017
International audienc