摘要 :
We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in contour integration. The preference for binding of oriented contours having same contrast polarity, over binding of opposite polarity...
展开
We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in contour integration. The preference for binding of oriented contours having same contrast polarity, over binding of opposite polarity ones (CP rule), has been used to explain several visual illusions. In three experiments we investigated how the binding effect is influenced by luminance contrast value, relatability of contour elements, and distance among them. Experiment 1 showed that the effect was indeed present only when the CP rule was satisfied, and found it to be stronger when the luminance contrast values of the elements are more similar. In experiment 2 the illusion was reported only with relatable edges, and its strength was modulated by the degree of relatability. The CP-rule effectiveness, thus, seems to depend on good continuation. The intensity of contrast polarity signals propagating from an oriented contour might be the less intense, the more its direction deviates from linearity. In experiment 3 we estimated the distance threshold and found it to be smaller than the one found for other illusions, arising with collinear fragments. This seems to show that the reach of the contrast polarity signal inside the association field of a contour unit is shorter along non-collinear orientations than along collinear ones.
收起
摘要 :
In his monograph Modularity of Mind (1983), philosopher Jerry Fodor argued that mental architecture can be partly decomposed into computational organs termed modules, which were characterized as having nine co-occurring features s...
展开
In his monograph Modularity of Mind (1983), philosopher Jerry Fodor argued that mental architecture can be partly decomposed into computational organs termed modules, which were characterized as having nine co-occurring features such as automaticity, domain specificity, and informational encapsulation. Do modules exist? Debates thus far have been framed very generally with few, if any, detailed case studies. The topic is important because it has direct implications on current debates in cognitive science and because it potentially provides a viable framework from which to further understand and make hypotheses about the mind's structure and function. Here, the case is made for the modularity of contour interpolation, which is a perceptual process that represents non-visible edges on the basis of how surrounding visible edges are spatiotemporally configured. There is substantial evidence that interpolation is domain specific, mandatory, fast, and developmentally well-sequenced; that it produces representationally impoverished outputs; that it relies upon a relatively fixed neural architecture that can be selectively impaired; that it is encapsulated from belief and expectation; and that its inner workings cannot be fathomed through conscious introspection. Upon differentiating contour interpolation from a higher-order contour representational ability ("contour abstraction") and upon accommodating seemingly inconsistent experimental results, it is argued that interpolation is modular to the extent that the initiating conditions for interpolation are strong. As interpolated contours become more salient, the modularity features emerge. The empirical data, taken as a whole, show that at least certain parts of the mind are modularly organized.
收起
摘要 :
The problem of computing overlap integrals of Slater-type orbitals on different centers for relativistic orbitals with a behavior of r~s at the nuclei is considered.The integrals can be expressed as integrals in momentum space inv...
展开
The problem of computing overlap integrals of Slater-type orbitals on different centers for relativistic orbitals with a behavior of r~s at the nuclei is considered.The integrals can be expressed as integrals in momentum space involving a spherical Bessel function j_L(kR).The problem of the oscillatory behavior of j_L(kR) at large kR can be eliminated by transforming the integral to a contour integral in the upper half-plane.A method of carrying out the numerical integration is described and the number of integration points required for a large number of cases are given.
收起
摘要 :
A rotation of an integration contour is shown to lead, in some cases, to interesting integral identities. Elementary and non-elementary examples are provided.
摘要 :
In this work, a new class of inverse Laplace transforms of exponential functions involving nested square roots are determined. Using these new inverses and other techniques from Laplace transform theory, a new class of three-param...
展开
In this work, a new class of inverse Laplace transforms of exponential functions involving nested square roots are determined. Using these new inverses and other techniques from Laplace transform theory, a new class of three-parameter definite integrals, that yield to exact evaluation, is generated. It is shown that these integrals evaluate to simple closed-form expressions. These results are then verified using independent analytical techniques. Special and limiting cases of the parameters are investigated, some of which yield well-known expressions from classical analysis. Asymptotic results for these integrals and inverses are also given. In addition, a representation of the complementary error function as a limit is presented. Last, some aspects concerning the numerical implementation of these inverses are discussed and several applications in continuum mechanics are noted. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 12]
收起
摘要 :
Rigorous nonequilibrium actions for the many-body problem are usually derived by means of path integrals combined with a discrete temporal mesh on the Schwinger-Keldysh time contour. The latter suffers from a fundamental limitatio...
展开
Rigorous nonequilibrium actions for the many-body problem are usually derived by means of path integrals combined with a discrete temporal mesh on the Schwinger-Keldysh time contour. The latter suffers from a fundamental limitation: the initial state on this contour cannot be arbitrary, but necessarily needs to be described by a non-interacting density matrix, while interactions are switched on adiabatically. The Kostantinov-Perel' contour overcomes these and other limitations, allowing generic initial-state preparations. In this article, we apply the technique of the discrete temporal mesh to rigorously build the nonequilibrium path integral on the Kostantinov-Perel' time contour.
收起
摘要 :
Resultants are important special functions used to describe nonlinear phenomena. The resultant R _(r1...rn) determines a consistency condition for a system of n homogeneous polynomials of degrees r _1, ..., r _n in n variables in ...
展开
Resultants are important special functions used to describe nonlinear phenomena. The resultant R _(r1...rn) determines a consistency condition for a system of n homogeneous polynomials of degrees r _1, ..., r _n in n variables in precisely the same way as the determinant does for a system of linear equations. Unfortunately, there is a lack of convenient formulas for resultants in the case of a large number of variables. In this paper we use Cauchy contour integrals to obtain a polynomial formula for resultants, which is expected to be useful in applications.
收起
摘要 :
Cast shadows have been shown to provide an effective ordinal cue to the depth position of objects. In the present study, two experiments investigated the effectiveness of cast shadows in facilitating the detection of spatial conto...
展开
Cast shadows have been shown to provide an effective ordinal cue to the depth position of objects. In the present study, two experiments investigated the effectiveness of cast shadows in facilitating the detection of spatial contours embedded in a field of randomly placed elements. In Experiment 1, the separation between the cast shadow and the contour was systematically increased to effectively signal different contour depth positions (relative to background elements), and this was repeated for patterns in which the lighting direction was above and from below. Increasing the shadow separation improved contour detection performance, but the degree to which sensitivity changed was dependent on the lighting direction. Patterns in which the light was from above were better detected than patterns in which the lighting direction was from below. This finding is consistent with the visual system assuming a light-from-above rule when processing cast shadows. In Experiment 2, we examined the degree to which changing the shape of the cast shadow (by randomly jittering the position of local cast shadow elements) affected the ability of the visual system to rely on the cast shadow to cue the depth position of the contour. Consistent with a coarse scale analysis, we find that cast shadows remained an effective depth cue even at large degrees of element jitter. Our findings demonstrate that cast shadows provide an effective means of signaling depth, which aids the process of contour integration, and this process is largely tolerant of local variations in lighting direction.
收起
摘要 :
In order to gain a better understanding of visual saliency, we have developed algorithm which simulates the phenomenon of contour integration for the purpose of visual saliency. The model developed consists of the classical butter...
展开
In order to gain a better understanding of visual saliency, we have developed algorithm which simulates the phenomenon of contour integration for the purpose of visual saliency. The model developed consists of the classical butterfly pattern of connection between orientation selective neurons in the primary visual cortex. In addition, we also add a local group suppression gain control to eliminate extraneous noise and a fast plasticity term which helps to account for closure effect often observed in humans exposed to closed contour maps. Results from real world images suggest that our algorithm is effective at picking out reasonable contours from a scene. The results improved with the introduction of both the fast plasticity and group suppression. An addition of multi-scale analysis has also increased the effectiveness as well.
收起
摘要 :
In this paper, a contour integral method (especially the block Sakurai-Sugiura method) is used to solve the eigenvalue problems governed by the Helmholtz equation, and formulated through two meshless methods. Singular value decomp...
展开
In this paper, a contour integral method (especially the block Sakurai-Sugiura method) is used to solve the eigenvalue problems governed by the Helmholtz equation, and formulated through two meshless methods. Singular value decomposition is employed to filter out the irrelevant eigenvalues. The accuracy and the ease of use of the proposed approach is illustrated with some numerical examples, and the choice of the contour integral method parameters is discussed. In particular, an application of the method on a sphere with realistic impedance boundary condition is performed and validated by comparison with results issued from a finite element method software.
收起
原文获取