19,612 research outputs found
Relaxing The Hamilton Jacobi Bellman Equation To Construct Inner And Outer Bounds On Reachable Sets
We consider the problem of overbounding and underbounding both the backward
and forward reachable set for a given polynomial vector field, nonlinear in
both state and input, with a given semialgebriac set of initial conditions and
with inputs constrained pointwise to lie in a semialgebraic set. Specifically,
we represent the forward reachable set using the value function which gives the
optimal cost to go of an optimal control problems and if smooth satisfies the
Hamilton-Jacobi- Bellman PDE. We then show that there exist polynomial upper
and lower bounds to this value function and furthermore, these polynomial
sub-value and super-value functions provide provable upper and lower bounds to
the forward reachable set. Finally, by minimizing the distance between these
sub-value and super-value functions in the L1-norm, we are able to construct
inner and outer bounds for the reachable set and show numerically on several
examples that for relatively small degree, the Hausdorff distance between these
bounds is negligible
Hidden-Markov Program Algebra with iteration
We use Hidden Markov Models to motivate a quantitative compositional
semantics for noninterference-based security with iteration, including a
refinement- or "implements" relation that compares two programs with respect to
their information leakage; and we propose a program algebra for source-level
reasoning about such programs, in particular as a means of establishing that an
"implementation" program leaks no more than its "specification" program.
This joins two themes: we extend our earlier work, having iteration but only
qualitative, by making it quantitative; and we extend our earlier quantitative
work by including iteration. We advocate stepwise refinement and
source-level program algebra, both as conceptual reasoning tools and as targets
for automated assistance. A selection of algebraic laws is given to support
this view in the case of quantitative noninterference; and it is demonstrated
on a simple iterated password-guessing attack
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The first signs of language: Phonological development in British sign language
A total of 1018 signs in one deaf child’s naturalistic interaction with her deaf mother, between the ages 19-24 months were analysed. This study summarises regular modification processes in the phonology of the child sign’s handshape, location, movement and prosody. Firstly changes to signs were explained by the notion of phonological markedness. Secondly, the child managed her production of first signs through two universal processes: structural change and substitution. Constraints unique to the visual modality also caused sign language specific acquisition patterns, namely: more errors for handshape articulation in locations in peripheral vision, a high frequency of whole sign repetitions and feature group rather than one-to-one phoneme substitutions as in spoken language development
Pennsylvania: Base Line Report - State Level Field Network Study of the Implementation of the Affordable Care Act
This report is part of a series of 21 state and regional studies examining the rollout of the ACA. The national network -- with 36 states and 61 researchers -- is led by the Rockefeller Institute of Government, the public policy research arm of the State University of New York, the Brookings Institution, and the Fels Institute of Government at the University of Pennsylvania.Although the ACA will no doubt have real financial consequences for insurers, hospitals, and health care providers, at this early stage in implementation, it is difficult to calculate precise gains and losses. For example, the Hospital Association of Pennsylvania supported the ACA, believing, in part, that reform was necessary to reduce current levels of uncompensated care and to reduce reliance on emergency care for patients who put off treatment for as long as possible to avoid out-of-pocket costs. The association agreed to significant cuts in Medicare and Medicaid to support the bill's passage. However, because cost savings from universal coverage have not yet been realized, hospitals reported cutting staff in April 2014 to offset the loss of Medicaid and Medicare funding. Safety net hospitals, which are required to serve all populations, seem especially affected, as many of their patients who fall into the Medicaid coverage gap are still showing up in emergency rooms without insurance
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