171 research outputs found
On Partial Identification of the Pure Direct Effect
In causal mediation analysis, nonparametric identification of the pure
(natural) direct effect typically relies on, in addition to no unobserved
pre-exposure confounding, fundamental assumptions of (i) so-called
"cross-world-counterfactuals" independence and (ii) no exposure- induced
confounding. When the mediator is binary, bounds for partial identification
have been given when neither assumption is made, or alternatively when assuming
only (ii). We extend existing bounds to the case of a polytomous mediator, and
provide bounds for the case assuming only (i). We apply these bounds to data
from the Harvard PEPFAR program in Nigeria, where we evaluate the extent to
which the effects of antiretroviral therapy on virological failure are mediated
by a patient's adherence, and show that inference on this effect is somewhat
sensitive to model assumptions.Comment: 24 pages, 4 figure
Decentralized Output Sliding-Mode Fault-Tolerant Control for Heterogeneous Multiagent Systems
This paper proposes a novel decentralized output sliding-mode fault-tolerant control (FTC) design for heterogeneous multiagent systems (MASs) with matched disturbances, unmatched nonlinear interactions, and actuator faults. The respective iteration and iteration-free algorithms in the sliding-mode FTC scheme are designed with adaptive upper bounding laws to automatically compensate the matched and unmatched components. Then, a continuous fault-tolerant protocol in the observer-based integral sliding-mode design is developed to guarantee the asymptotic stability of MASs and the ultimate boundedness of the estimation errors. Simulation results validate the efficiency of the proposed FTC algorithm
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