The Emergence of Emotions

Emotion is conscious experience. It is the affective aspect of consciousness. Emotion arises from sensory stimulation and is typically accompanied by physiological and behavioral changes in the body. Hence an emotion is a complex reaction pattern consisting of three components: a physiological component, a behavioral component, and an experiential (conscious) component. The reactions making up an emotion determine what the emotion will be recognized as. Three processes are involved in generating an emotion: (1) identification of the emotional significance of a sensory stimulus, (2) production of an affective state (emotion), and (3) regulation of the affective state. Two opposing systems in the brain (the reward and punishment systems) establish an affective value or valence (stimulus-reinforcement association) for sensory stimulation. This is process (1), the first step in the generation of an emotion. Development of stimulus-reinforcement associations (affective valence) serves as the basis for emotion expression (process 2), conditioned emotion learning acquisition and expression, memory consolidation, reinforcement-expectations, decision-making, coping responses, and social behavior. The amygdala is critical for the representation of stimulus-reinforcement associations (both reward and punishment-based) for these functions. Three distinct and separate architectural and functional areas of the prefrontal cortex (dorsolateral prefrontal cortex, orbitofrontal cortex, anterior cingulate cortex) are involved in the regulation of emotion (process 3). The regulation of emotion by the prefrontal cortex consists of a positive feedback interaction between the prefrontal cortex and the inferior parietal cortex resulting in the nonlinear emergence of emotion. This positive feedback and nonlinear emergence represents a type of working memory (focal attention) by which perception is reorganized and rerepresented, becoming explicit, functional, and conscious. The explicit emotion states arising may be involved in the production of voluntary new or novel intentional (adaptive) behavior, especially social behavior

HIGHER-ORDER SHEAR DEFORMABLE THEORIES FOR FLEXURE OF SANDWICH PLATES - FINITE-ELEMENT EVALUATIONS

A simple isoparametric finite element formulation based on a higher-order displacement model for flexure analysis of multilayer symmetric sandwich plates is presented. The assumed displacement model accounts for non-linear variation of inplane displacements and constant variation of transverse displacement through the plate thickness. Further, the present formulation does not require the fictitious shear correction coefficient(s) generally associated with the first-order shear deformable theories. Two sandwich plate theories are developed: one in which the free shear stress conditions on the top and bottom bounding planes are imposed and another, in which such conditions are not imposed. The validity of the present development(s) is established through, numerical evaluations for deflections/stresses/stress-resultants and their comparisons with the available three-dimensional analyses/closed-form/other finite element solutions. Comparison of results from thin plate. Mindlin and present analyses with the exact three-dimensional analyses yields some important conclusions regarding the effects of the assumptions made in the CPT and Mindlin type theories. The comparative study further establishes the necessity of a higher-order shear deformable theory incorporating warping of the cross-section particularly for sandwich plates

FINITE-ELEMENT ANALYSIS OF LAMINATED COMPOSITE PLATES USING A HIGHER-ORDER DISPLACEMENT MODEL

A C° continuous displacement finite element formulation of a higher-order theory for flexure of thick arbitrary laminated composite plates under transverse loads is presented. The displacement model accounts for non-linear and constant variation of in-plane and transverse displacement model eliminates the use of shear correction coefficients. The discrete element chosen is a nine-noded quadrilateral with nine degrees-of-freedom per node. Results for plate deformations, internal stress-resultants and stresses for selected examples are shown to compare well with the closed-form, the theory of elasticity and the finite element solutions with another higher-order displacement model by the same authors. A computer program has been developed which incorporates the realistic prediction of interlaminar stresses from equilibrium equations

A SIMPLE FINITE-ELEMENT FORMULATION OF A HIGHER-ORDER THEORY FOR UNSYMMETRICALLY LAMINATED COMPOSITE PLATES

A higher-order theory which satisfies zero transverse shear stress conditions on the bounding planes of a generally laminated fibre-reinforced composite plate subjected to transverse loads is developed. The displacement model accounts for non-linear distribution of inplane displacement components through the plate thickness and the theory requires no shear correction coefficients. A C0 continuous displacement finite element formulation is presented and the coupled membrane-flexure behaviour of laminated plates is investigated. The nodal unknowns are the three displacements, two rotations and two higher-order functions as the generalized degrees of freedom. The simple isoparametric formulation developed here is capable of evaluating transverse shears and transverse normal stress accurately by using the equilibrium equations. The accuracy of the nine-noded Lagrangian quadrilateral element is then established by comparing the present results with the closed-form, three-dimensional elasticity and other finite element available solutions

A consistent refined theory for flexure of a symmetric laminate

Any two-dimensional plate theory is an approximation of the real three-dimen- sional elasticity problem. The classical laminated plate theory is based on the Kirchhoff hypothesis and ignores the effects of transverse shear deforma- tion, normal stress, normal strain and nonlinear in-plane normal strain dis- tribution through the plate thickness [ 1,2]. Two types of composite plates are generally identified in practice: (i) 'fibre reinforced laminates' in which layers of composite materials with high ratios of Young's-to-shear modulii are bonded together and (2) 'sandwiches' in which layers of isotropic materials with some layers having significantly lower elastic modulii than others, are bonded together. The effects of shear deformation are signific- ant in these situations and thus the classical theory is inadequate. Exact elasticity solutions for flexure of some standard composite and sandwich plate problems have been obtained by Pagano [ 3] and Pagano and Hatfield [4]. Whitney [5] and Mau [6] have presented first-order laminate theories in which transverse shear strain is assumed constant through the thickness. This re- quired, however, use of a transverse shear correction factor which generally varied with the lamination scheme.© Elsevie

A REFINED HIGHER-ORDER GENERALLY ORTHOTROPIC C0 PLATE BENDING ELEMENT

A finite element formulation for flexure of a generally orthotropic plate based on a higher-order displacement model and a three-dimensional state of stress and strain is presented here. This higher-order theory incorporates linear variation of transverse normal strain/stress and parabolic variation of transverse shear strains through the thickness of the plate. The nine-noded quadrilateral from the family of two-dimensional C0 continuous isoparametric Lagrangian elements is then developed as a generally orthotropic higher-order element. The performance of this element is evaluated on square plates with different support conditions and under uniformly distributed and central point loads. The numerical results of the present formulation are compared with thin plate, elasticity and Mindlin/Reissner solutions. The effect of degree of orthotropy on the maximum bending moment location is examined for different loading and boundary conditions. The effect of directional orthotropy on the location of the maximum values for the various stress-resultants is also studied

A refined higher-order generally orthotropic C° plate bending element

A finite element formulation for flexure of a generally orthotropic plate based on a higher-order displacement model and a three-dimensional state of stress and strain is presented here. This higher-order theory incorporates linear variation of transverse normal strain/stress and parabolic variation of transverse shear strains through the thickness of the plate. The nine-noded quadrilateral from the family of two-dimensional C° continuous isoparametric Lagrangian elements is then developed as a generally orthotropic higher-order element. The performance of this element is evaluated on square plates with different support conditions and under uniformly distributed and central point loads. The numerical results of the present formulation are compared with thin plate, elasticity and Mindlin/Reissner solutions. The effect of degree of orthotropy on the maximum bending moment location is examined for different loading and boundary conditions. The effect of directional orthotropy on the location of the maximum values for the various stress-resultants is also studied.© Elsevie