6,031 research outputs found
A Continuation Method for Nash Equilibria in Structured Games
Structured game representations have recently attracted interest as models
for multi-agent artificial intelligence scenarios, with rational behavior most
commonly characterized by Nash equilibria. This paper presents efficient, exact
algorithms for computing Nash equilibria in structured game representations,
including both graphical games and multi-agent influence diagrams (MAIDs). The
algorithms are derived from a continuation method for normal-form and
extensive-form games due to Govindan and Wilson; they follow a trajectory
through a space of perturbed games and their equilibria, exploiting game
structure through fast computation of the Jacobian of the payoff function. They
are theoretically guaranteed to find at least one equilibrium of the game, and
may find more. Our approach provides the first efficient algorithm for
computing exact equilibria in graphical games with arbitrary topology, and the
first algorithm to exploit fine-grained structural properties of MAIDs.
Experimental results are presented demonstrating the effectiveness of the
algorithms and comparing them to predecessors. The running time of the
graphical game algorithm is similar to, and often better than, the running time
of previous approximate algorithms. The algorithm for MAIDs can effectively
solve games that are much larger than those solvable by previous methods
Bald Eagles at the Savanna Army Depot
Eagle Valley Environmentalists Technical Report #SADE-81, Research Report conducted
December 1980 - March 1981, under a contract with the United States Arm
Plasmonic crystal demultiplexer and multiports
Artificially built periodic optical structures in dielectric and metallic
media have generated considerable interest due to their potential for optical
device miniaturization. In this context plasmonics, i.e., optics based on
surface plasmon polaritons (SPPs) offers new exciting prospects. SPPs are
hybrid light/electron surface waves at the interface between a dielectric and a
metal and as such hold the potential for 2D optical functionality. Indeed, SPP
elements as mirrors, splitters and interferometers have been recently
demonstrated. However, for plasmonics to qualify at the information technology
level requires necessarily the realization of wavelength division
(demultiplexing) which constitutes a fundamental ingredient of optical
communication. In the following we experimentally demonstrate 2D SPP
demultiplexing in the visible spectral range by using photonic crystals for
SPPs (plasmonic crystals). In addition, we demonstrate that plasmonic crystal
are capable of realizing integrated linear multiports which could constitute
building blocks of analog or quantum optical computing.Comment: Nano Lett.7, 1697 (2007
Homography-based ground plane detection using a single on-board camera
This study presents a robust method for ground plane detection in vision-based systems with a non-stationary camera. The proposed method is based on the reliable estimation of the homography between ground planes in successive images. This homography is computed using a feature matching approach, which in contrast to classical approaches to on-board motion estimation does not require explicit ego-motion calculation. As opposed to it, a novel homography calculation method based on a linear estimation framework is presented. This framework provides predictions of the ground plane transformation matrix that are dynamically updated with new measurements. The method is specially suited for challenging environments, in particular traffic scenarios, in which the information is scarce and the homography computed from the images is usually inaccurate or erroneous. The proposed estimation framework is able to remove erroneous measurements and to correct those that are inaccurate, hence producing a reliable homography estimate at each instant. It is based on the evaluation of the difference between the predicted and the observed transformations, measured according to the spectral norm of the associated matrix of differences. Moreover, an example is provided on how to use the information extracted from ground plane estimation to achieve object detection and tracking. The method has been successfully demonstrated for the detection of moving vehicles in traffic environments
Effects of scopolamine on matching to sample paradigm and related tests in human subjects
This was a double-blind placebo-controlled study with a cross-over design to examine the effects of scopolamine on cognitive functions in young healthy subjects. Scopolamine hydrobromide was administered subcutaneously to 12 subjects (mean +/- SD age 23.8 +/- 2.2 years) at doses of 0.3 and 0.6 mg in comparison with two placebo conditions. Scopolamine at both doses produced marked sedation as rated by subjects and an observer. In the continuous performance test, vigilance was impaired by both doses of scopolamine. The span of apprehension test showed differing results (only the high dose of scopolamine showed a performance decrement only in the three-character version of the span of apprehension test). Significant impairment by both doses of scopolamine was seen in immediate and delayed free recall, continuous visual recognition, running word recognition and running picture recognition. While scopolamine caused a significant slowing in average reaction times for simultaneous matching as well as for delayed matching, subjects made more errors under scopolamine compared to placebo only in delayed matching, not in simultaneous matching. Also, the main outcome of matching to sample showed significant effects only in delayed matching, not in simultaneous matching. Notable in this study is the incongruity between the simultaneous matching test and the span of apprehension test on the one hand and the other cognitive tests used on the other. These results demonstrated that scopolamine has a greater effect on memory than on attention. Thus, the scopolamine-induced effects in the present study seem to be more relevant to Alzheimer's disease in an advanced phase than to normal aging. Copyright (C) 2003 S. Karger AG, Basel
Polaron cross-overs and d-wave superconductivity in Hubbard-Holstein model
We present a theoretical study of superconductivity of polarons in the
Hubbard-Holstein model. A residual kinematic interaction proportional to the
square of the polaron hopping energy between polarons and phonons provides a
pairing field for the polarons. We find that superconducting instability in the
d-wave channel is possible with small transition temperatures which is maximum
in the large to small polaron cross-over region. An s-wave instability is found
to be not possible when the effective on-site interaction between polarons is
repulsive
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