Marr's Model Research Articles

Microstructure study and constitutive modeling of Ti–6Al–4V alloy at elevated temperatures

A reliable and accurate prediction of flow behavior of metals in industrial forming process considering the coupled effects of strain, strain rate and temperature is crucial in understanding the workability of the metal and optimizing parameters for hot forming process. In this study, the tensile fracture behavior of the Ti–6Al–4V alloy is examined with scanning electron microscope (SEM) over the range of magnifications. SEM study revealed that microvoids and shallow dimples are observed at the fracture surface which indicates the fracture is predominately ductile in nature. Also, an investigation on flow behavior of Ti–6Al–4V alloy is done using constitutive models. Four constitutive models; modified Johnson-Cook (m-JC), modified Arrhenius type equations (m-Arr), modified Zerilli–Armstrong (m-ZA) and Rusinek–Klepaczko (RK) models are developed to predict the flow stress. The predictions of these constitutive models are compared with each other using statistical measures like correlation coefficient, average absolute error and its standard deviation. Comparing the statistical measures, m-Arr model is a better model for predicting the flow stress, but considering the fact that m-ZA model is a physical based model, m-ZA model is preferred over the m-Arr model.

Development of constitutive models for dynamic strain aging regime in Austenitic stainless steel 304

The experimental stress–strain data from isothermal tensile tests over a wide range of temperatures (623–923K at an interval of 50K), strains (0.02–0.30 at an interval of 0.02) and strain rates (0.0001, 0.001, 0.01, 0.1s−1) were employed to determine the Dynamic Strain Aging (DSA) regime and to formulate a suitable constitutive model to predict the elevated-temperature deformation behavior in DSA regime of Austenitic Stainless Steel (ASS) 304. Four models, namely, Johnson Cook (JC) model, modified Zerilli–Armstrong (m-ZA) model, modified Arrhenius type equations (m-Arr) and Artificial Neural Networks (ANNs), were investigated. Suitability of these models was evaluated by comparing the correlation coefficient, average absolute error and its standard deviation. It was observed that JC, m-ZA and m-Arr model could not effectively predict flow stress behavior of ASS304 in DSA regime, while the predictions by ANN model are found to be in good agreement with the experimental data.

David Marr's theory of cerebellar learning: 40 years later

David Marr's theory of cerebellar learning: 40 years later

The Development of Visual Object Recognition in School-Age Children

This study documents the age-dependent development of visual object recognition abilities in 115 children aged 6 to 11 years, using a battery of neuropsychological tests based on Marr's model (Efron test, Warrington's Figure-Ground Test, Street Completion Test, Poppelreuter-Ghent Test, a selection of stimuli from the Birmingham Object Recognition Battery, a series of color photographs of objects presented from unusual perspectives or illuminated in unusual ways). The results suggest a maturation of complex visual perceptual abilities, possibly related to the development of the cerebral processes involved in object recognition, and could be the starting point for future investigations of these skills in impaired populations.

Surveying the seen: 100 years of British vision

Perceptual phenomena and their interpretations have fashioned the course of psychology. This article surveys how theories of visual perception and methodologies have developed during the lifetime of the British Psychological Society. The experimental study of vision was instigated by British natural philosophers in the early nineteenth century but this impetus was not maintained thereafter. Not until the 1930s and 1940s did research on perception resume in earnest within British universities. The adoption of concepts (such as schema) potentially grounded in neural organization, particularly by Bartlett and Craik, accelerated experimental, theoretical and applied vision research. From mid-century the influence of information processing models of perception became increasingly dominant, and they were often integrated with the rapidly expanding understanding of neurophysiological underpinnings. The epitome of these developments was Marr's model of vision which, in our view, marked the start of the modern era of vision research. Computers have transformed the nature of stimulus control and response measurement in perceptual experiments. More naturalistic stimuli can be presented and manipulated, and complex behavioural responses, such as patterns of eye movements, fractionated. Non-invasive recording of brain activity to visual stimulation has similarly been transformed with a variety of methods for imaging brain activity. Neuroimaging has been applied to localizing perceptual and cognitive functions and in studying patients with known deficits in visual recognition. However, the eagerness with which the computer has been adopted by perceptual psychologists is likely to be tempered by a growing awareness of the differences between viewing scenes and simulations of them.

Cognitive Processing of Drawing Abilities

This critical review examines constructional apraxia from a cognitive neuropsychological perspective. To our knowledge, van Sommers (1989) is the only researcher to present a global cognitive model of drawing abilities. He organizes it into two hierarchical systems: Marr's model of visual perception and a graphic production system. The latter comprises four hierarchically organized components: depiction decisions, production strategy, contingent planning, and articulatory and economic constraints. Van Sommers' model will be discussed in light of other models and on the basis of empirical neuropsychological studies (Farah, 1984; Kosslyn & Koenig, 1992; Roncato, Sartori, Masterson, & Rumiati, 1987; van Sommers, 1989). We find that: (1) the Kosslyn and Koenig visual perception model describes more accurately the perceptual components underlying copying than the visual perception system of van Sommers' drawing model, (2) Van Sommers' arguments in favor of a depiction processing as opposed to visual imagery are not convincing, (3) Van Sommers' assumption that a production strategy is a component is unclear, and (4) articulatory and economic constraints are not cognitive components, but constraints imposed during action programming. This literature review leads to a discussion of future research topics and the specificity of constructional apraxia.

Mathematical conditions for adaptive control in Marr's model of the sensorimotor system

Conditions of stability have been investigated for a certain class of functions representing the closed loop in the sensorimotor system. Since learning exists in the closed loop system constituted by the cerebellar cortex and the limb premotor network, the dynamics of the cerebellar cortex subsystem has to be stable for this class of functions. Two complementary problems of adaptive control have been solved: (i) the conditions of stability for the dynamics in the cerebellar neural network considered as an open-loop system, about the steady state, here called the “resting state” because the system is not in the learning phase: an internal dynamics results from these conditions; (ii) the conditions of stability for the dynamics of learning in the closed-loop system, i.e., a problem of optimization between the calculated output and the required output, which corresponds to the ability of the system to reach a target fixed in advance during the learning phase: the dynamics resulting from the variations in time of the synaptic efficacy between parallel fibres and Purkinje cell, is added to the internal dynamics in the steady state. Although the structure of the loop is imposed by the mathematical functions that make the global system stable, it is sufficiently general to be readily identified with global sensorimotor models.

Apparatus for manufacturing a glass and organic composite strand, including blowing device

This critical review examines constructional apraxia from a cognitive neuropsychological perspective. To our knowledge, van Sommers (1989) is the only researcher to present a global cognitive model of drawing abilities. He organizes it into two hierarchical systems: Marr's model of visual perception and a graphic production system. The latter comprises four hierarchically organized components: depiction decisions, production strategy, contingent planning, and articulatory and economic constraints. Van Sommers' model will be discussed in light of other models and on the basis of empirical neuropsychological studies (Farah, 1984; Kosslyn & Koenig, 1992; Roncato, Sartori, Masterson, & Rumiati, 1987; van Sommers, 1989). We find that: (1) the Kosslyn and Koenig visual perception model describes more accurately the perceptual components underlying copying than the visual perception system of van Sommers' drawing model, (2) Van Sommers' arguments in favor of a depiction processing as opposed to visual imagery are not convincing, (3) Van Sommers' assumption that a production strategy is a component is unclear, and (4) articulatory and economic constraints are not cognitive components, but constraints imposed during action programming. This literature review leads to a discussion of future research topics and the specificity of constructional apraxia.

Simplicity, Cognition and Adaptation: Some Remarks on Marr's Theory of Vision

David Marr's theory of vision has been a source of both fascination and confusion for many in cognitive science. There has, of course, been substantial technical interest in the particulars of Marr's model. But beyond this we have seen his work cited in debates about the nature of mental representation and computation, the structure of cognition, the role of theoretical knowledge in perception, how and indeed whether one ought to apply results from cognitive science to antecedent questions in epistemology. Marr's theory is cited in such debates because it is widely seen as a successful, rigorous account of a large scale cognitive/perceptual process (if not as the successful such account). But it has been suggested that Marr's theory might be mistaken as a whole; that Marr might have been wrong not just about one or several of the sub-mechanisms of vision, and not just in offering an incomplete account, but wrong in his basic approach to the study of vision.

Image gathering and processing: information and fidelity.

In this paper we formulate and use information and fidelity criteria to assess image gathering and processing, combining optical design with image-forming and edge-detection algorithms. The optical design of the image-gathering system revolves around the relationship among sampling passband, spatial response, and signal-to-noise ratio (SNR). Our formulations of information, fidelity, and optimal (Wiener) restoration account for the insufficient sampling (i.e., aliasing) common in image gathering as well as for the blurring and noise that conventional formulations account for. Performance analyses and simulations for ordinary optical-design constraints and random scenes indicate that (1) different image-forming algorithms prefer different optical designs; (2) informationally optimized designs maximize the robustness of optimal image restorations and lead to the highest-spatial-frequency channel (relative to the sampling passband) for which edge detection is reliable (if the SNR is sufficiently high); and (3) combining the informationally optimized design with a 3 by 3 lateral-inhibitory image-plane-processing algorithm leads to a spatial-response shape that approximates the optimal edge-detection response of (Marr's model of) human vision and thus reduces the data preprocessing and transmission required for machine vision.

Reliability of pattern separation by the cerebellar mossy fiber--granule cell system.

As a simple example of a neuronal network in which synaptic connectivity among neurons is probabilistic, Marr's model for the granular layer of cat cerebellar cortex is examined. The mean and variance are computed for the fraction of granule cells activated, and for the extent of pattern separation by granule cells, for various mossy fiber inputs and various values of connectivity and electrical parameters of the network structure. Results suggest different functions for the network, and different optimal ranges for its parameters, depending on whether Golgi cells are present or absent. The model network does not perform the functions originally prescribed for it with high reliability.