The human visual system is adept at detecting and encoding statistical regularities in its spatio-temporal environment. Here we report an unexpected failure of this ability in the context of perceiving inconsistencies in illumination distributions across a scene. Contrary to predictions from previous studies [Enns and Rensink, 1990; Sun and Perona, 1996a, 1996b, 1997], we find that the visual system displays a remarkable lack of sensitivity to illumination inconsistencies, both in experimental stimuli and in images of real scenes. Our results allow us to draw inferences regarding how the visual system encodes illumination distributions across scenes. Specifically, they suggest that the visual system does not verify the global consistency of locally derived estimates of illumination direction.

Different theoretical models have tried to investigate the feasibility of recurrent neural mechanisms for achieving direction selectivity in the visual cortex. The mathematical analysis of such models has been restricted so far to the case of purely linear networks. We present an exact analytical solution of the nonlinear dynamics of a class of direction selective recurrent neural models with threshold nonlinearity. Our mathematical analysis shows that such networks have form-stable stimulus-locked traveling pulse solutions that are appropriate for modeling the responses of direction selective cortical neurons. Our analysis shows also that the stability of such solutions can break down giving raise to a different class of solutions ("lurching activity waves") that are characterized by a specific spatio-temporal periodicity. These solutions cannot arise in models for direction selectivity with purely linear spatio-temporal filtering.

The capability of estimating the walking direction of people would be useful in many applications such as those involving autonomous cars and robots. We introduce an approach for estimating the walking direction of people from images, based on learning the correct classification of a still image by using SVMs. We find that the performance of the system can be improved by classifying each image of a walking sequence and combining the outputs of the classifier. Experiments were performed to evaluate our system and estimate the trade-off between number of images in walking sequences and performance.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 96-98).

Menée en milieu minoritaire francophone, cette recherche porte sur la prise de décision complexe liée à la supervision pédagogique chez les directions d’école élémentaire de l’Ontario. Sachant que les élèves de certaines écoles francophones réussissent moins bien que ceux des écoles anglophones, l’objectif est de décrire et de comprendre comment les directions d’école prennent des décisions pédagogiques complexes. Pour y parvenir, cette recherche se fonde sur un cadre de référence hybride traitant de la prise de décision complexe et du leadership éducationnel en milieux linguistiques minoritaires. Précisons que notre recherche ne tente pas de comparer les milieux linguistiques mais bien de relever les particularités du milieu francophone minoritaire quant à la prise de décision complexe liée à la supervision pédagogique chez les directions d’école. Épousant le paradigme interprétatif, cette recherche utilise l’étude multicas pour la collecte des données réalisée à l’aide d’entrevues semi-structurées individuelles auprès d’acteurs scolaires tels que les directions d’école, les directions de l’éducation et les enseignants. Les données ont été organisées selon quatre sections : le profil des répondants du cas, la fonction de la direction d’école, le processus de la prise de décision complexe et les éléments qui l'influencent. L'analyse des données a été réalisée à l'aide du logiciel NVivo et elle nous a permis de dresser le profil des répondants de chacun des quatre cas et de faire ressortir, par une analyse comparative, les convergences et les divergences entre ceux-ci.Les résultats de l'analyse mettent en évidence le fait que les directions d'école ne suivent pas nécessairement les mêmes étapes quant à la prise de décision pédagogique complexe. Si la majorité d'entre elles prend des décisions complexes selon la méthode rationnelle, les autres évoquent le recours à un processus décisionnel cyclique et itérative. Toutefois, ells croient toutes que l'expérience de vie personnelle et professionnnelle exerce la principale influence sur leur prise de décision complexe. L'analyse comparative des données a permis de proposer un modèle de prise de décision reflétant le milieu scolaire minoritaire francophone de l'Ontario où la consultation est considérée comme une valeur ajoutée dans le processus décisionnel. Finalement, s'insérant dans les rapports à l'identité et à la gestion scolaire, cette recherche pose un jalon pour l'étude de la prise de décision pédoagogique complexe et propose des pistes de recherches futures afin de poursuivre la réflexion.

Understanding human spatial cognition and behaviour is not something easily studied. Many factors are involved that contribute in different ways for different individuals. Navigation and wayfinding have been used as an approach, or starting point, for such studies. Spatial abilities tests have long been used as reference points to generalize to overt navigational behaviour. Care needs to be taken in generalizing from paper to behaviour to make certain that it is a valid relationship exists.<p>The purpose of this study was to examine the extent to which certain psychometric spatial abilities tests are indicators of actual navigational decision making. The study was conducted in two phases. The navigational decision tasks were made up of four paths with two variables: length and number of turns. The participants were required to make a decision on which direction to go after being lead part of the way around a hallway. The choices were to either go back the way they were led or take a novel route along a previously un-travelled path (shortcut). Spatial abilities tests (MRT, PFT, and OLMT), a self-rating of SOD, and learning preference for novel environments were administered in phase two. <p>While efficient navigation was not explicitly required in the navigation tasks those participants making the most efficient decisions shared similar characteristics. Efficient navigators have a higher aptitude for mental manipulation (as measured by the MRT), express a preference for a more exploratory environmental learning style, are disproportionately male, and have a slightly higher self-rating of SOD. In addition to the collective set of four navigation decisions (one for each experimental path), path 2 demonstrated the efficient vs. non-efficient distinction quite well: in order to make the most efficient decision the individual must maintain the correct metric distance from the origin point and not be deterred by the passage of only half of the turns in the rectangular experimental environment.

The sole purpose of every form of visual representation is to make something look believable. Even among abstract or conceptual representation, the purpose is to create something that within the defined visual language the audience will consider believable and accepted. In the field of computer generated representation there are numerous visual languages that have been developed throughout the years, attempting to solve different visualization or artistic problems. This thesis presents an alternative light transfer model for participating media focused on the intuitive control of the illumination data and the artistic value of the resulting image. The purpose is not focused on accurately modeling lights physical behavior and its interaction with the surfaces and elements. My thesis describes an artistic approach which aims to offer an organic and intuitive control of the glow and temperature of the effects of participating media and direct the value and hues through the surfaces. The system described in the thesis approximates light transfer through a given volume by calculating light contribution in the volume with discreet sampling and subsequently gathering these values to determine the diffuse scattering contribution for the volume. I will also discuss the assumptions made to allow such approximations, as well as how the intuitive control offered by the approach and these approximations allow new forms or representation and artistic direction.

Understanding human spatial cognition and behaviour is not something easily studied. Many factors are involved that contribute in different ways for different individuals. Navigation and wayfinding have been used as an approach, or starting point, for such studies. Spatial abilities tests have long been used as reference points to generalize to overt navigational behaviour. Care needs to be taken in generalizing from paper to behaviour to make certain that it is a valid relationship exists.<p>The purpose of this study was to examine the extent to which certain psychometric spatial abilities tests are indicators of actual navigational decision making. The study was conducted in two phases. The navigational decision tasks were made up of four paths with two variables: length and number of turns. The participants were required to make a decision on which direction to go after being lead part of the way around a hallway. The choices were to either go back the way they were led or take a novel route along a previously un-travelled path (shortcut). Spatial abilities tests (MRT, PFT, and OLMT), a self-rating of SOD, and learning preference for novel environments were administered in phase two. <p>While efficient navigation was not explicitly required in the navigation tasks those participants making the most efficient decisions shared similar characteristics. Efficient navigators have a higher aptitude for mental manipulation (as measured by the MRT), express a preference for a more exploratory environmental learning style, are disproportionately male, and have a slightly higher self-rating of SOD. In addition to the collective set of four navigation decisions (one for each experimental path), path 2 demonstrated the efficient vs. non-efficient distinction quite well: in order to make the most efficient decision the individual must maintain the correct metric distance from the origin point and not be deterred by the passage of only half of the turns in the rectangular experimental environment.

No description available.

Pulp from recycled paper products contains various waxes, glues, adhesives, filler, and inorganics that are collectively referred to as contaminants. Contaminants that are not drained out during the forming process are trapped in the sheet and carried down the paper machine. These contaminant particles and contaminants in solution can become deposited on the dryer cylinders. The contaminants which deposit on the dryer cylinders lead to reduced quality and production of paper on the machine. The process by which contaminants are deposited on a dryer cylinder has not been explored at a fundamental level. Rather, quick industrial fixes have been tested to try and eliminate the contaminant deposition and only reductions in deposition have been achieved. The literature reviewed does not relate the flow of particle suspensions through porous media to the heat transfer and fluid dynamics processes associated with drying paper. The experiments in the literature showed the general trends of particle and dye distributions across the thicknesses of different porous media during forming or filtration processes. Filler and fines distribution were not able to be changed by flows induced by pressing a sheet. The mechanisms for how particles move through porous media found in the literature were a basis for what kind of phenomena would be expected in the particle flow experiments. A means of completely eliminating sticky deposits could be found by examining the parameters which contribute to the deposition process. The hypothesis proposed in this thesis is that contaminant particles and liquid containing contaminants are transported to the dryer can surface by liquid flows induced by the drying process. By performing particle flow experiments during drying, bounds for the particle size, initial drying surface temperature, drying time, and initial solids content will be determined for which the hypothesis is true. The particle and dye transport studies performed showed an array of processes at work simultaneously. The results from the particle and dye transport studies show that a particle diameter of ~1.0 and #956;m or less, handsheet solids content of less than 30%, open sheet structure and a high surface drying temperature (200C) were needed to create a significant change in filler and dye distribution across the thickness of a handsheet.