Simulation of an Austenite-Twinned-Martensite Interface

Developing numerical methods for predicting microstructure in materials is a large and important research area. Two examples of material microstructures are Austenite and Martensite. Austenite is a microscopic phase with simple crystallographic structure while Martensite is one with a more complex structure. One important task in materials science is the development of numerical procedures which accurately predict microstructures in Martensite. In this paper we present a method for simulating material microstructure close to an Austenite-Martensite interface. The method combines a quasi-Newton optimization algorithm and a nonconforming finite element scheme that successfully minimizes an approximation to the total stored energy near the interface of interest. Preliminary results suggest that the minimizers of this energy functional located by the developed numerical algorithm appear to display the desired characteristics.     

Interaction between synesthetically corresponding dimensions.

This article presents findings of cross-sensory dimensional interaction for the visual dimension of vertical position and the auditory dimension of pitch. Subjects were simultaneously presented with attributes from both dimensions and performed speeded classification of one dimension. There were four task conditions. The irrelevant dimension was varied orthogonally or held constant, and attributes were always synesthetically congruent or always synesthetically incongruent. Subjects displayed reaction time (RT) interference when the second dimension varied orthogonally (a failure of selective attention). In addition, redundancy gain was asymmetric. Reaction time facilitation was only present when attributes were synesthetically congruent. Negatively correlated redundancy (incongruence) yielded neither facilitation nor interference. Interaction was unaffected by changes in the spatial origin of signals (Experiment 3) and was still evident when signals were temporally separated (Experiment 4). Several explanations for these results are considered. It is argued that these results may represent a new form of dimensional interaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similarity relations among synesthetic stimuli and their attributes.

Four experiments examined the similarity relations that exist among bimodal attributes that correspond synesthetically (e.g., white color and high pitch) and among stimuli formed by combining these attributes either congruently (e.g., white/high, black/low) or incongruently (e.g., white/low, black/high). Previous research suggests two hypotheses: (a) Synesthetic stimuli are compared as wholes on the basis of their overall similarity, and (b) nonidentical congruent stimuli are more dissimilar than nonidentical incongruent stimuli. Similarity among either individual attributes (Experiments 1 and 4) or bimodal stimuli (Experiments 2 and 3) was measured by either ratings or response latencies; similarity judgments were scaled with an individual differences scaling procedure (SINDSCAL). Stimulus comparisons were fit well by a Euclidean but not a city-block metric, supporting the overall similarity hypothesis. However, there was little evidence that subjects perceived congruity/incongruity among stimulus wholes, even though subjects were sensitive to correspondence/noncorrespondence among attributes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Driven by information: A tectonic theory of Stroop effects.

The goal of avoiding distraction (e.g., ignoring words when naming their print colors in a Stroop task) is opposed intrinsically by the penchant to process conspicuous and correlated characteristics of the environment (e.g., noticing trial-to-trial associations between the colors and the words). To reconcile these opposing forces, the authors propose a tectonic theory of selective attention in which 2 memory-based structures--dimensional imbalance and dimensional uncertainty--drive selection by processing salient, surprising, and/or correlated information contained within and across stimulus dimensions. Each structure modulates the buildup of excitation to targets and the buildup of inhibition to distractors and to memories of previous stimuli. Tectonic theory is implemented to simulate the impact of 4 types of context on the presence, magnitude, and direction of congruity effects and task effects in the Stroop paradigm. The tectonic model is shown to surpass other formal models in explaining the range and diversity of Stroop effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A confluence of contexts: Asymmetric versus global failures of selective attention to Stroop dimensions.

In 6 experiments probing selective attention through Stroop classification, 4 factors of context were manipulated: (a) psychophysical context, the distinctiveness of values along the color and word dimensions; (b) set size context, the number of stimulus values tested; (c) production context the mode used to respond; and (d) covariate context, the correlation between the dimensions. The psychophysical and production contexts mainly caused an asymmetry in selective attention failure between colors and words, whereas the set size and covariate contexts contributed primarily to the average or global magnitudes of attentional disruption across dimensions. The results suggest that (a) Stroop dimensions are perceptually separable, (b) J. R. Stroop's (1935) classic findings arose from his particular combination of contexts, and (c) stimulus uncertainty and dimensional imbalance are the primary sources of task and congruity effects in the Stroop paradigm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early-holistic processing or dimensional similarity?

Considers current evidence for the theory that multidimensional stimuli are initially processed as unanalyzed wholes. The theory appears unable to explain observers' behavior in various speeded and unspeeded tasks: (1) Perceivers can differentiate tiny changes made between confusable dimensions; (2) the fits of distance metrics to rating data appear to be largely under the control of optional processes; and (3) direct predictions from early-holistic models, as instantiated in the Euclidean hypothesis, are disconfirmed in tests using the rotation paradigm. In contrast, evidence has mounted to support the view that perception relies on a set of primary dimensions, processed within context-bound constraints. D. G. Kemler Nelson (see record 1994-08234-001) has been critical of the authors' approach; they respond to each of her objections. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dimensional interactions in language processing: Investigating directions and levels of crosstalk.

In this article we evaluate current models of language processing by testing speeded classification of stimuli comprising one linguistic and one nonlinguistic dimension. Garner interference obtains if subjects are slower to classify attributes on one dimension when an irrelevant dimension is varied orthogonally than when the irrelevant dimension is held constant. With certain linguistic–nonlinguistic pairings (e.g., Experiment 1: the words high and low spoken either loudly or softly), significant Garner interference obtained when either dimension was classified; this indicated two-directional crosstalk. With other pairings (e.g., Experiment 3: spoken vowels and loudness), only the nonlinguistic dimension (e.g., loudness) displayed interference, suggesting unidirectional crosstalk downstream from a phonemic/graphemic level of analysis. Collectively, these results indicate the interaction can occur either within or across levels of information processing, being directed toward either more advanced or more primitive processes. Although poorly explained by all current models of language processing, our results are strikingly inconsistent with models that posit autonomy among levels of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dimensional interaction between color and pitch.

In three experiments I investigated the nature of cross–modal dimensional interaction by testing speeded classification of the synesthetically corresponding dimensions of color (white–black) and pitch (high–low). Experiment 1 showed significant Garner interference when these dimensions were varied orthogonally—redundancy gain for positively correlated dimensions and redundancy loss for negatively correlated dimensions. Attributes from synesthetically congruent stimuli were classified faster than attributes from incongruent stimuli (a congruity effect). Experiment 2 tested a perceptual explanation of this interaction (i.e., that color and pitch are configural dimensions) by using Pomerantz's (1986) diagnostic (comparison of selective and divided attention performance). The configurality hypothesis received little support. Experiment 3 examined the effect of optional processes on color and pitch classification. The results suggest that partly strategic and partly mandatory components may constitute overall performance. Three alternative explanations of the color–pitch interaction—perceptual, semantic, and response based—are evaluated in the context of the present results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classification of color dimensions in multiple contexts.

Hue, saturation, and brightness were tested in pairs, with one dimension creating a classification context and the other serving as the basis of a set of speeded classification tasks. In Experiment 1, performance suffered when the context-setting dimension varied within a response category (intraclass context) and benefited when this variation occurred between response categories (redundant context). In Experiment 2, participants showed no interference from irrelevant variation in tasks that combined intraclass context with redundant context. Experiment 3 opened the interpretative window by varying 5 levels of intraclass context factorially with 5 levels of redundant context. The dimensions were found to differ in hardness—the degree of resistance to intraclass context across levels—with hue showing the greatest resistance and brightness the least. Hardness may reflect the efficacy of a dimension for distinguishing real-world categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The duality of selection: Excitatory and inhibitory processes in auditory selective attention.

Behavioral and event-related potential (ERP) measurements were made in an auditory selective-attention paradigm, both before and after a series of inhibition or discrimination training sessions. The presence of distractors caused poor perceptual sensitivity, weak P3 responses, conservative responding, and slow reaction times relative to baseline. Distraction prompted a frontal enhancement of ERP components occurring 100-250 ms after the onset of attended signals (N1, P2, and N2). Training ameliorated behavioral interference from distraction. Participants receiving inhibition training acquired improved inhibitory processing of distractors, an effect that peaked 200 ms after distractor onset, In a proposed model, distinct excitatory and inhibitory mechanisms work interactively to maintain sensitivity to environmental change in the fare of disruption from the contextual integration of irrelevant events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)