Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry, and minimally distinct border: implications for the neural mechanisms underlying induction

Brightness induction refers to the finding that the apparent brightness of a stimulus changes when surrounded by a black versus a white stimulus. In the current study, we investigated the effects of black/white surrounding stimuli on settings made between red and green stimuli on three different tasks: heterochromatic brightness matching (HBM), heterochromatic flicker photometry (HFP), and minimally distinct border (MDB). For HBM, subjects varied the relative luminance between the red and green stimuli so that the brightness of the two colors appeared equal. For the two other tasks, matches were made based on minimizing red/green flicker (HFP) or the saliency of a red/green border (MDB). For all three tasks, the presence of black/white surrounding stimuli significantly altered red/green settings, demonstrating the existence of induction effects. These results are discussed in terms of which underlying color pathways (L+ M versus L-M) may contribute to induction effects for the different tasks.     

Recurrent networks in human visual cortex: psychophysical evidence

To study the neuronal circuitry underlying visual spatial-integration processes, we measured the effect of short and long chains of proximal Gabor-signal (GS) flankers (sigma = lambda = 0.15 degrees) on the contrast-discrimination function of a foveal GS target. We found that the same pattern of lateral masks enhanced target detection with low-contrast pedestals and strongly suppressed the discrimination of a range of intermediate pedestal contrasts (pedestal contrast <30%). Increasing the number of the flankers reversed the suppressive effect. The data suggest that the main influence of the proximal flankers is maintained by activity-dependent interactions and not by linear spatial summation. With an increased number of flankers, we found a nonmonotonic relationship between the discrimination thresholds and the number of flankers, supporting the notion that the discrimination thresholds are mediated by excitatory-inhibitory recurrent networks that manifest the dynamics of large neuronal populations in the neocortex [Proc. Natl. Acad. Sci. USA 94, 10426 (1997)].     

Palletisation efficiency as a criterion for product design

The paper is concerned with the question of how implications for palletisation efficiency may be taken into account in the product/packaging design process. The perspective from which this topic is approached is the reverse of that usually adopted: rather than dealing with an evaluation of pre-determined design alternatives, the paper considers the problem of identifying the options open to the designer if a given palletisation efficiency target is to be achieved. In addition to a number of algorithmic issues various practical aspects of the problem are also discussed. The results of two case studies provide a concrete frame of reference throughout the paper.     

The J-integral as a fracture criterion for polycarbonate thermoplastic

Fracture behaviour of a polycarbonate thermoplastic has been investigated. Fracture tests were conducted on single edge notched specimens and the J-integral evaluated using energy rate interpretation. Its value has been found to be independent of crack length when crack length to specimen width (a/w) is larger than 0.34. For smaller cracks general material damage away from the crack tip is also found to influence the energy absorbed. An extrapolation method has been used to separate the crack tip energy from the energy absorbed due to general material damage. The J-integral thus obtained is independent of crack length and specimen length and its critical value is the same as obtained fora/w > 0.34 without extrapolation. The critical stress intensity factor was also evaluated using the R-curve approach. It has been found that the J-integral agrees well with the criticial stress intensity factor obtained using the R-curve approach.     

Thinning as a failure criterion during sheet metal forming

Thinning during forming is often considered a failure criterion in the metal forming industry. It is believed that a critical amount of thinning takes place in a sheet metal before failure. In this study, varying widths of low-carbon steel sheets were punch stretched under laboratory conditions. Thinning during punch stretching was measured at various locations along the steel sheets. These measurements demonstrated that thinning during forming is not constant, but that it is a function of the strain path followed by the sheet. Hence, thinning should not be used as a failure criterion during forming of sheet metals.     

The cyclicJ-integral as a criterion for fatigue crack growth

The definition of the cyclic J-integral is offered and its physical significance for fatigue crack growth is discussed using the Dugdale model on the assumption that the crack closure, cycle dependent creep deformation, and crack extension under cycling can be neglected. It is shown that the cyclic J-integral for small scale yielding is equivalent to theJ-integral for linear elastic crack independent of loading processes, while the value for large scale yielding varies with the loading processes. However, in both cases, the cyclicJ-integral remains constant during the reversal of loading under a constant stress range, if the first monotonic loading stage is excluded. In this situation, the cyclicJ-integral can be applied as a criterion for fatigue crack growth, since it is evaluated as a generalized force on dislocations to be moved or the energy flow rate to be dissipated to heat by the dislocation movements in an element just attached to the fatigued crack tip during one cycle of loading. It is suggested that the available experimental data of different materials for fatigue crack growth can be generalized to a unified formulation on the basis of the energy criterion. It is also deduced that the threshold J corresponding to K _th should be larger than 4 where is the surface energy of the material. Finally the operational definition of the cyclicJ-integral on single loadversus displacement curves is given for center cracked plate with wide uncracked ligaments in tension.

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Résumé On présente la définition de l'intégrale J cyclique et sa signification physique dans le cas d'une croissance de fissure de fatigue est discutée en utilisant le modèle de Dugdale et l'hypothèse que la fermeture de la fissure, la déformation de fluage liée au cycle, et l'extension de la fissure au cours du cycle peuvent être négligées. On montre que l'intégraleJ cyclique est, dans le cas d'écoulement plastique à faible échelle, équivalente à l'intégraleJ utilisée pour les fissures élastiques linéaires indépendamment des processus de mise en charge, tandis que la valeur de déformation plastique macroscopique varie avec le processus de mise en charge. Cependant, dans les 2 cas, l'intégraleJ cyclique demeure constante au cours du renversement de charge appliquée à tension constante si l'on exclut le premier stade de mise en charge monotone. Dans cette situation, l'intégraleJ cyclique peut être appliquée comme critère de la croissance d'une fissure de fatigue puisqu'elle représente une forme généralisée de force, un effort sur les dislocations à mouvoir ou à l'écoulement d'énergie dissipée en chaleur par les mouvements de dislocation dans un élément immédiatement solidaire de l'extrémité de la fissure de fatigue, au cours d'un cycle de mise en charge. On suggère que les données expérimentales disponibles sur différents matériaux pour la croissance d'une fissure de fatigue puissent être généralisées à une formulation unifiée, sur base d'un critère d'énergie. On déduit également que le seuil J correspondant à K _th devrait être plus grand que 4, où est l'énergie de surface du matériau. Finalement, la définition opérationnelle de l'intégraleJ cyclique sous simple charge en fonction des courbes de déplacement est fournie dans le cas d'une plaque comportant une fissure centrale et de larges ligaments non fissurés, soumises à traction.

     

Chemical potential of a metal as a criterion of corrosion-mechanical fracture

Odessa Technological Institute of the Food Industry, Odessa. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 1, pp. 124–125, January–February, 1994.     

Surround modulation in visual cortex can predict border-ownership selectivity: psychophysical study of border-ownership-dependent tilt aftereffect

Recent physiological studies revealed that neurons in the macaque visual cortex encode the direction of a figure along a contour (border ownership, BO). Although their cortical mechanisms have not been clarified, a computational model for BO has suggested that surround modulation in early vision can play an important role. Here we examined psychophysically how the strength of BO-dependent tilt aftereffect (BO-TAE) is modulated by a stimulus outside the adapted location in relation to the strength of surround modulation reported in physiological experiments. The results showed systematic change of the strength of BO-TAE, depending on the difference in orientation and spatial frequency between the bars placed outside and at the adapted location, indicating a crucial role of surround modulation in the neural mechanism underlying BO selectivity.     

TiO2 pure phase brookite with preferred orientation,synthesized as a spin-coated film

An oriented titania (brookite) film containing neither anatase nor rutile was synthesized by a new modified sol–gel method. The precursor was TiCl₄ with cellulose and oxalic acid as complexing agent. The XRD results show oriented pure brookite titania thin film. The SEM micrograph shows square particles on the crack free continuous film. A diffusion of sodium from the substrate was detected by XPS. It was found that the nature of complexation, the concentration of the precursors, the polymer additive, solution media (low pH, solvent-EG) and the substrate were significant of the oriented brookite TiO₂ films obtained.     

Role of the normal elasticity modulus as a connecting criterion in selecting structural materials

Leningrad. Translated from Problemy Prochnosti, No. 2, pp. 36–39, February, 1988.     

On weak differential uniformity of vectorial Boolean functions as a cryptographic criterion

We study the relation among some security parameters for vectorial Boolean functions which prevent attacks on the related block cipher. We focus our study on a recently-introduced security criterion, called weak differential uniformity, which prevents the existence of an undetectable trapdoor based on imprimitive group action. We present some properties of functions with low weak differential uniformity, especially for the case of power functions and 4-bit S-Boxes.     

Ultimate exhaustion of local plasticity as a criterion of fatigue crack initiation

The calculation model for assessing the life of cyclically hardening materials earlier proposed by the authors is extended to strain-softening materials. The conditions for evaluating the model parameters are justified. The presented calculated dependences of elastic strains on the number of loading cycles are compared with the experimental ones.     

Understanding knee points in bicriteria problems and their implications as preferred solution principles

A knee point is almost always a preferred trade-off solution, if it exists in a bicriteria optimization problem. In this article, an attempt is made to improve understanding of a knee point and investigate the properties of a bicriteria problem that may exhibit a knee on its Pareto-optimal front. Past studies are reviewed and a couple of new definitions are suggested. Additionally, a knee region is defined for problems in which, instead of one, a set of knee-like solutions exists. Edge-knee solutions, which behave like knee solutions but lie near one of the extremes on the Pareto-optimal front, are also introduced. It is interesting that in many problem-solving tasks, despite the existence of a number of solution methodologies, only one or a few of them are commonly used. Here, it is argued that often such common solution principles are knee solutions to a bicriteria problem formed with two conflicting goals of the underlying problem-solving task. The argument is illustrated on a number of tasks, such as regression, sorting, clustering and a number of engineering designs.