Strategic Defense and Attack for Series and Parallel Reliability Systems: Comment

The contest-theoretic literature on the attack and defense of networks of targets focuses primarily on pure-strategy Nash equilibria. Hausken\u27s 2008 European Journal of Operational Research article typifies this approach, and many of the models in this literature either build upon this model or utilize similar techniques. We show that Hausken\u27s characterization of Nash equilibrium is invalid for much of the parameter space examined and provides necessary conditions for his solution to hold. The complete characterization of mixed-strategy equilibria remains an open problem, although there exist solutions in the literature for special prominent cases

Redundancy effects in the processing of emotional faces

AbstractHow does the visual system represent the ensemble statistics of visual objects? This question has received intense interest in vision research, yet most studies have focused on the extraction of mean statistics rather than its dispersion. This study focuses on another aspect of ensemble statistics: the redundancy of the sample. In two experiments, participants were faster judging the facial expression and gender of multiple faces than a single face. The redundancy gain was equivalent for multiple identical faces and for multiple faces of different identities. To test whether the redundancy gain was due to increased strength in perceptual representation, we measured the magnitude of facial expression aftereffects. The aftereffects were equivalent when induced by a single face and by four identical faces, ruling out increased perceptual strength as an explanation for the redundancy gain. We conclude that redundant faces facilitate perception by enhancing the robustness of representation of each face

Some extensions to reliability modeling and optimization of networked systems

Ph.DDOCTOR OF PHILOSOPH

An Integrity Framework for Image-Based Navigation Systems

This work first examines fundamental differences between measurement models established for GPS and those of proposed image-based navigation systems. In contrast to single value per satellite GPS pseudorange measurements, image measurements are inherently angle-based and represent pixel coordinate pairs for each mapped target. Thus, in the image-based case, special consideration must be given to the units of the transformations between the states and measurements, and also to the fact that multiple rows of the observation matrix relate to particular error states. An algorithm is developed to instantiate a framework for image-based integrity analogous to that of GPS RAIM. The algorithm is applied cases where the navigation system is estimating position only and then extended to cases where both position and attitude estimation is required. Detailed analysis demonstrates the impact of angular error on a single pixel pair measurement and comparisons from both estimation scenario results show that, from an integrity perspective, there is significant benefit in having known attitude information. Additional work demonstrates the impact of pixel pair measurement relative geometries on system integrity, showing potential improvement in image-based integrity through screening and adding measurements, when available, to the navigation system solution

Detection of multidimensional targets in visual search

AbstractSearch performance for targets defined along multiple dimensions was investigated with an accuracy visual search task. Initially, threshold was measured for targets that differed from homogeneous distractors along a single dimension (e.g., a reddish target among achromatic distractors, or a right-tilted target among vertically oriented distractors). Threshold was then measured for a multidimensional target (a redundant target) that differed from homogeneous distractors along two dimensions (e.g., a reddish AND right-tilted target among achromatic, vertically oriented distractors). Search performance for multidimensional target combinations of chromaticity and luminance, chromaticity and orientation, and chromaticity and spatial frequency was tested. Measurements were evaluated within several summation models, allowing for a test of the mechanisms mediating the detection of multidimensional targets in search. Measurements were generally consistent with probability summation suggesting the particular combinations of stimulus dimensions tested were coded along independent, noisy, neural mechanisms