7,040 research outputs found
The Use Of Prediction In Teaching The German Verb
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98320/1/j.1467-1770.1955.tb01420.x.pd
Origin of line tension for a Lennard-Jones nanodroplet
The existence and origin of line tension has remained controversial in
literature. To address this issue we compute the shape of Lennard-Jones
nanodrops using molecular dynamics and compare them to density functional
theory in the approximation of the sharp kink interface. We show that the
deviation from Young's law is very small and would correspond to a typical line
tension length scale (defined as line tension divided by surface tension)
similar to the molecular size and decreasing with Young's angle. We propose an
alternative interpretation based on the geometry of the interface at the
molecular scale
An Autonomous Onboard Targeting Algorithm Using Finite Thrust Maneuvers
In earlier investigations, the adaptation and implementation of a modified two-level corrections process as the onboard targeting algorithm for the Trans-Earth Injection phase of Orion is presented. The objective of that targeting algorithm is to generate the times of ignition and magnitudes of the required maneuvers such that the desired state at entry interface is achieved. In an actual onboard flight software implementation, these times of ignition and maneuvers are relayed onto Flight Control for command and execution. Although this process works well when the burn durations or burn arcs are small, this might not be the case during a contingency situation when lower thrust engines are employed to perform the maneuvers. Therefore, a new version of the modified two-level corrections process is formulated to handle the case of finite burn arcs. This paper presents the development and formulation of that finite burn modified two-level corrections process which can again be used as an onboard targeting algorithm for the Trans-Earth Injection phase of Orion. Additionally, performance results and a comparison between the two methods are presented. The finite burn two-level corrector formulation presented here ensures the entry constraints at entry interface are still met without violating the available fuel budget, while still accounting for much longer burn times in its design
IMLI: An Incremental Framework for MaxSAT-Based Learning of Interpretable Classification Rules
The wide adoption of machine learning in the critical domains such as medical
diagnosis, law, education had propelled the need for interpretable techniques
due to the need for end users to understand the reasoning behind decisions due
to learning systems. The computational intractability of interpretable learning
led practitioners to design heuristic techniques, which fail to provide sound
handles to tradeoff accuracy and interpretability.
Motivated by the success of MaxSAT solvers over the past decade, recently
MaxSAT-based approach, called MLIC, was proposed that seeks to reduce the
problem of learning interpretable rules expressed in Conjunctive Normal Form
(CNF) to a MaxSAT query. While MLIC was shown to achieve accuracy similar to
that of other state of the art black-box classifiers while generating small
interpretable CNF formulas, the runtime performance of MLIC is significantly
lagging and renders approach unusable in practice. In this context, authors
raised the question: Is it possible to achieve the best of both worlds, i.e., a
sound framework for interpretable learning that can take advantage of MaxSAT
solvers while scaling to real-world instances?
In this paper, we take a step towards answering the above question in
affirmation. We propose IMLI: an incremental approach to MaxSAT based framework
that achieves scalable runtime performance via partition-based training
methodology. Extensive experiments on benchmarks arising from UCI repository
demonstrate that IMLI achieves up to three orders of magnitude runtime
improvement without loss of accuracy and interpretability.Comment: 10 pages, published in the proceedings of AAAI/ACM Conference on AI,
Ethics, and Society (AIES 2019
Investigation of Alternative Return Strategies for Orion Trans-earth Injection Design Options
The purpose of this study is to investigate alternative return strategies for the Orion trans-Earth injection (TEI) phase. A dynamical systems analysis approach considers the structure of the stable and unstable Sun perturbed Earth-Moon manifolds near the Earth-Moon interface region. A hybrid approach, then, combines the results from this analysis with classical two-body methods in a targeting process that seeks to expand the window of return opportunities in a precision entry scenario. The resulting startup arcs can be used, for instance, to enhance the block set of solutions available onboard during an autonomous targeting process
Repetitive transcranial magnetic stimulation and transcranial direct current stimulation in motor rehabilitation after stroke: An update
AbstractStroke is a leading cause of adult motor disability. The number of stroke survivors is increasing in industrialized countries, and despite available treatments used in rehabilitation, the recovery of motor functions after stroke is often incomplete. Studies in the 1980s showed that non-invasive brain stimulation (mainly repetitive transcranial magnetic stimulation [rTMS] and transcranial direct current stimulation [tDCS]) could modulate cortical excitability and induce plasticity in healthy humans. These findings have opened the way to the therapeutic use of the 2 techniques for stroke. The mechanisms underlying the cortical effect of rTMS and tDCS differ. This paper summarizes data obtained in healthy subjects and gives a general review of the use of rTMS and tDCS in stroke patients with altered motor functions. From 1988 to 2012, approximately 1400 publications were devoted to the study of non-invasive brain stimulation in humans. However, for stroke patients with limb motor deficit, only 141 publications have been devoted to the effects of rTMS and 132 to those of tDCS. The Cochrane review devoted to the effects of rTMS found 19 randomized controlled trials involving 588 patients, and that devoted to tDCS found 18 randomized controlled trials involving 450 patients. Without doubt, rTMS and tDCS contribute to physiological and pathophysiological studies in motor control. However, despite the increasing number of studies devoted to the possible therapeutic use of non-invasive brain stimulation to improve motor recovery after stroke, further studies will be necessary to specify their use in rehabilitation
Migration, entrepreneurship and development : a critical review
We provide an assessment of the state of scholarly and policy debates on migrant entrepreneurs in development. They are often described as super-entrepreneurs who contribute to development through (i) being more entrepreneurial than natives; (ii) providing remittances that fund start-ups in their countries of origin and (iii) returning entrepreneurial skills to their home countries when they re-migrate. We evaluate these three views and conclude that the empirical evidence to support the notion of the migrant as a super-entrepreneur is weak. We further argue that the evidence is less ambiguous on the general development contribution of migration over and above its contribution through entrepreneurship. The implication is that removal of discriminatory barriers against migrants and against migrant entrepreneurs in labour, consumer and financial markets will promote development in both sending and receiving countries, not least through reducing the shares of migrants that are reluctant entrepreneurs
The Coulomb Sum and Proton-Proton Correlations in Few-Body Nuclei
In simple models of the nuclear charge operator, measurements of the Coulomb
sum and the charge form factor of a nucleus directly determine the
proton-proton correlations. We examine experimental results obtained for
few-body nuclei at Bates and Saclay using models of the charge operator that
include both one- and two-body terms. Previous analyses using one-body terms
only have failed to reproduce experimental results. However, we find that the
same operators which have been used to successfully describe the charge form
factors also produce substantial agreement with measurements of the Coulomb
sum.Comment: 11 pages, Revtex version 3.0 with 3 Postscript figures appended, ANL
preprint PHY-7473-TH-9
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