Efficient Open World Reasoning for Planning

We consider the problem of reasoning and planning with incomplete knowledge and deterministic actions. We introduce a knowledge representation scheme called PSIPLAN that can effectively represent incompleteness of an agent's knowledge while allowing for sound, complete and tractable entailment in domains where the set of all objects is either unknown or infinite. We present a procedure for state update resulting from taking an action in PSIPLAN that is correct, complete and has only polynomial complexity. State update is performed without considering the set of all possible worlds corresponding to the knowledge state. As a result, planning with PSIPLAN is done without direct manipulation of possible worlds. PSIPLAN representation underlies the PSIPOP planning algorithm that handles quantified goals with or without exceptions that no other domain independent planner has been shown to achieve. PSIPLAN has been implemented in Common Lisp and used in an application on planning in a collaborative interface.Comment: 39 pages, 13 figures. to appear in Logical Methods in Computer Scienc

Local statistics for random domino tilings of the Aztec diamond

We prove an asymptotic formula for the probability that, if one chooses a domino tiling of a large Aztec diamond at random according to the uniform distribution on such tilings, the tiling will contain a domino covering a given pair of adjacent lattice squares. This formula quantifies the effect of the diamond's boundary conditions on the behavior of typical tilings; in addition, it yields a new proof of the arctic circle theorem of Jockusch, Propp, and Shor. Our approach is to use the saddle point method to estimate certain weighted sums of squares of Krawtchouk polynomials (whose relevance to domino tilings is demonstrated elsewhere), and to combine these estimates with some exponential sum bounds to deduce our final result. This approach generalizes straightforwardly to the case in which the probability distribution on the set of tilings incorporates bias favoring horizontal over vertical tiles or vice versa. We also prove a fairly general large deviation estimate for domino tilings of simply-connected planar regions that implies that some of our results on Aztec diamonds apply to many other similar regions as well.Comment: 42 pages, 7 figure

The effect of different module configurations on the radiation tolerance of multijunction solar cells

The effect of different module configurations on the performance of multijunction (MJ) solar cells in a radiation environment was investigated. Module configuration refers to the electrical circuit in which the subcells of the multijunction cell are wired. Experimental data for AlCaAs, GaAs, InGaAs, and silicon single-junction concentrator cells subjected to 1 MeV electron irradiation was used to calculate the expected performance of AlGaAs/InGaAs, AlGa/silicon, GaAs/InGaAs, and GaAs/silicon Mj concentrator cells. These calculations included independent, series, and voltage-matched configurations. The module configuration was found to have a significant impact on the radiation tolerance characteristic of the MJ cells

An update on the diagnosis and treatment of early Lyme Disease: Focusing on the bull\u27s eye, you may miss the mark

To confidently diagnose and treat Lyme disease, the clinician must first understand the natural history of this disease, especially its protean early manifestations. Emergency physicians, primary care physicians, and other providers need to be vigilant in terms of the timely recognition of erythema migrans (EM), the unique marker of early localized stage 1 disease. The classic EM, originally described as a slowly expanding bull\u27s eye lesion, is now recognized to be present in only the minority of cases (9%); the dominant morphologic lesion of EM is now recognized to be the diffusely homogenous red plaque or patch, which occurs in over 50% of cases. This update will define the current morphologic features of early Lyme disease, the indication for serologic studies, and the most recent treatment guidelines, including therapeutic pitfalls

A comparison of the radiation tolerance characteristics of multijunction solar cells with series and voltage-matched configurations

The effect of series and voltage-matched configurations on the performance of multijunction solar cells in a radiation environment was investigated. It was found that the configuration of the multijunction solar cell can have a significant impact on its radiation tolerance characteristics