Nucleation of recrystallization in fine-grained materials: an extension of the Bailey–Hirsch criterion

Abstract

A new criterion for nucleation in the case of dynamic recrystallization is proposed in order to include the contribution of the grain boundary energy stored in the microstructure in the energy balance. Due to the nucleation events, the total surface area of pre-existing grain boundaries decreases, leading to a nucleus size smaller than expected by conventional nucleation criteria. The new model provides a better prediction of the nucleus size during recrystallization of pure copper compared with the conventional nucleation criterion.     

Influenceability of Sex Differences under Conditions of Risk Taking

In an experiment on the effect of intensity accents on the perception of time intervals between tones. H. G. Tekman (2001) found that the regular placement of deviant time intervals in short sequences of tones reduced detection, especially if intensity accents marked the deviant time intervals. That was the opposite of what one wòuld have expected on the basis of the dynamic attending theory of M. R. Jones (1976). The effect might have occurred because temporally deviant tones create cumulative onset shifts that affect all the subsequent tones. If the deviations were randomly placed, then they could follow each other in close succession and change the local tempo. In the present study, the changes of local tempo, which might have acted as a cue for the detection of temporal deviations in the random sequences, were eliminated by compensating for deviant time intervals with equal deviations in the opposite direction in the interval that followed. That change in the stimuli eliminated the negative main effect of regularity, and the accenting interacted with regularity in favor of detection in the regular sequences. However, a simple advantage of regular over random sequences was not observed. The author discusses possible reasons for the lack of a facilitatory effect of regularity.     

An Empirical Comparison of Audition,Vision, and Touch in the Discrimination of Temporal Patterns and Ability to Reproduce them

Two conditional reasoning tests were administered to 34 students (17 males and 17 females) at each of four grade levels (i.e., 5th, 6th, 7th, and 8th). Both tests contained conditional reasoning arguments which assessed students' comprehension of five basic principles of inference. However, they varied systematically according to the sex typing of the content (i.e., masculine or feminine). The results indicated that there were no significant sex differences according to grade level, type of content, or principle of inference. On the other hand, at each grade level, there were consistent differences among the mean scores for the five principles, and valid principles were significantly easier than invalid principles. The implications of these findings for future research were discussed.     

Moral Motivation Based on Multiple Developmental Structures: An Exploration of Cognitive and Emotional Dynamics

Intrapersonal variability and multiplicity in the complexity of moral motivation were examined from Dynamic Systems and Self-Determination Theory perspectives. L. Kohlberg's (1969) stages of moral development are reconceptualized as soft-assembled and dynamically transformable process structures of motivation that may operate simultaneously within person in different degrees. Moral motivation is conceptualized as the real-time process of self-organization of cognitive and emotional dynamics out of which moral judgment and action emerge. A detailed inquiry into intrapersonal variation in moral motivation is carried out based on the differential operation of multiple motivational structures. A total of 74 high school students and 97 college students participated in the study by completing a new questionnaire, involving 3 different hypothetical moral judgments. As hypothesized, findings revealed significant multiplicity in the within-person operation of developmental stage structures, and intrapersonal variability in the degrees to which stages were used. Developmental patterns were found in terms of different distributions of multiple stages between high school and college samples, as well as the association between age and overall motivation scores. Differential relations of specific emotions to moral motivation revealed and confirmed the value of differentiating multiple emotions. Implications of the present theoretical perspective and the findings for understanding the complexity of moral judgment and motivation are discussed.     

Interlimb Coordination: Real Constraints and False Dichotomies

Despite the recent advances in the field of coordination dynamics addressing the interplay of constraints of different natures in the emergence of human coordination, F. Mechsner (2004) invites us to revive hierarchical and dichotomous thinking by offering again his exclusive position that coordinated movements are (purely) perceptual-cognitive/psychological in nature. In this comment, the authors address a number of theoretical and methodological issues that might potentially puzzle the readers of Mechsner's article. They contend that the dichotomy proposed by Mechsner (i.e., perceptual-cognitive vs. motor) constitutes a restrictive framework for understanding human coordination.     

Introduction to the Meta-Structures Project: Prospective Applications

This research project proposes the modeling of collective behaviors such as flocks, industrial districts, and markets. Unlike many other approaches, the aim is to identify ways to recognize, change, and maintain the coherence of collective behaviors, as well as inducing their emergence in configurations of elements that only interact without acquiring properties. The basic assumption is that currently collective behavior is not adequately modeled for the purpose described above when intended as given by sequences of states adopted by the same system over time. Here the sequence of states of a collective behavior in time is considered as corresponding to sequences of different states adopted by systems made up of the same elements interacting with different structures. Sequences of structures are considered to establish meta-structures and their properties correspond to the coherence acquired. The project is based on the use of mesoscopic variables to represent such structural dynamics considered in turn to represent the continuous emergence of coherent collective behavior. Mesoscopic variables are specified and their properties considered as meta-structural properties (properties of sequences of structures). The purpose of this research project is to search for meta-structural properties within processes of computational emergence (computer simulated). I discuss the problem of prescribing meta-structural properties to non-coherent, disordered collective behaviors. I introduce possible approaches for applications to social systems.     

The development of a brief group intervention (Dynamic Interpersonal Therapy) for patients with medically unexplained somatic symptoms: a pilot study

The primary aim of this equivalence study was to compare the outcome of a brief group therapeutic intervention, based on the principles of dynamic interpersonal therapy (DIT) with an intervention based on cognitive behavioural therapy (CBT) in patients suffering from medically unexplained somatic symptoms (MUSS). Participants were 89 patients (aged 18 to 62) who were offered 20 sessions of either DIT or CBT, as central part of a treatment package, consisting of art therapy, psychomotor therapy, social therapy and physical therapy. Measurements were conducted at baseline, 10 weeks and 20 weeks, using self-rating scales measuring the level of anxiety and depression, the severity of medically unexplained symptoms and quality of life. Results showed that CBT and DIT were comparable. The conclusion was that it is recommended to design a larger scale randomised controlled trial to further elaborate the short-term and long-term effects of this novel psychodynamic group therapy for MUSS patients.     

Design strategy for microalloyed ultra-ductile magnesium alloys

This article describes a design strategy deployed in developing ultra-ductile Mg alloys based on a microalloying concept, which aims to restrict grain growth considerably during alloy casting and forming. We discuss the efficiency of the design approach, and evaluate the resulting microstructural and mechanical properties. After processing, the so-designed alloys ZQCa3 (Mg–3Zn–0.5Ag–0.25Ca–0.15Mn, in wt.%) and ZKQCa3 (Mg–3Zn–0.5Zr–0.5Ag–0.25Ca–0.15Mn, in wt.%) reveal very fine grains (<10 µm), high ductility (elongation to fracture of up to 30%) at moderate strength or high strength (ultimate tensile strength of up to 350 MPa) at reasonable ductility. These properties are explained based on thermodynamic modelling, microstructure analysis including transmission electron microscopy studies, and microstructural and mechanical testing after annealing, and are compared to a related commercial alloy (ZK31).     

Crystal growth velocity in deeply undercooled Ni–Si alloys

The crystal growth velocity of Ni₉₅Si₅ and Ni₉₀Si₁₀ alloys as a function of undercooling is investigated using molecular dynamics simulations. The modified imbedded atom method potential yields the equilibrium liquidus temperatures T _L?≈?1505 and 1387?K for Ni₉₅Si₅ and Ni₉₀Si₁₀ alloys, respectively. From the liquidus temperatures down to the deeply undercooled region, the crystal growth velocities of both the alloys rise to the maximum with increasing undercooling and then drop slowly, whereas the athermal growth process presented in elemental Ni is not observed in Ni–Si alloys. Instead, the undercooling dependence of the growth velocity can be well-described by the diffusion-limited model, furthermore, the activation energy associated with the diffusion from melt to interface increases as the concentration increases from 5 to 10?at.% Si, resulting in the remarkable decrease of growth velocity.