Mechanical-milling-induced amorphization of Se: A crystallite destabilization model

Complete solid-state amorphization has been realized in elemental Se by means of mechanical milling of crystalline Se powder. Quantitative X-ray diffraction and thermal analyses were employed to characterize the amorphization process and indicated that the amorphization onset corresponds to a critical crystallite size and a drop in microstrain. During the major amorphization process, the remaining crystallite size remains unchanged with a constant lattice expansion. A new kinetics model of crystallite destabilization is proposed for the solid-state amorphization which satisfactorily explains the experimental observations.     

On the dislocation mechanism of amorphization of Si by indentation

The formation of an amorphous phase underneath a Vickers indentation produced on a Si(001) surface at room temperature has been observed by cross-sectional transmission electron microscopy. Two types of location are observed for the amorphous phase. One is formed just underneath the image of the indentation and the other is parallel to the slip planes of Si. It is concluded that the latter type, at least, is formed as a result of activation of dislocations which is induced by an external shear stress combined with a hydrostatic pressure.     

Stacking fault and dislocation glide on the basal plane of graphite

Generalized stacking-fault energies for the basal plane of graphite are calculated from first principles for slip along two high-symmetry directions. The rhombohedral fault energy compares well with experiment and the anisotropy in behaviour is consistent with observed dislocation network geometry. Utilizing these calculated fault energies within a modified Peierls-Nabarro model, we estimate the barrier for basal dislocation motion based on lattice friction. This is found to be extremely small, from which we conclude that dislocation network interaction and pinning, rather than the Peierls barrier, must determine the practical shear strength of graphite. However, at low dislocation densities or over small crystallite regions, the shear strength should tend to this lower limit. We discuss the relevance of this to the mechanism of lubrication.     

A model for evidence accumulation in the lexical decision task

We present a new model for lexical decision, REM-LD, that is based on REM theory (e.g., ). REM-LD uses a principled (i.e., Bayes' rule) decision process that simultaneously considers the diagnosticity of the evidence for the 'WORD' response and the 'NONWORD' response. The model calculates the odds ratio that the presented stimulus is a word or a nonword by averaging likelihood ratios for lexical entries from a small neighborhood of similar words. We report two experiments that used a signal-to-respond paradigm to obtain information about the time course of lexical processing. Experiment 1 verified the prediction of the model that the frequency of the word stimuli affects performance for nonword stimuli. Experiment 2 was done to study the effects of nonword lexicality, word frequency, and repetition priming and to demonstrate how REM-LD can account for the observed results. We discuss how REM-LD could be extended to account for effects of phonology such as the pseudohomophone effect, and how REM-LD can predict response times in the traditional 'respond-when-ready' paradigm.     

Work engagement accumulation of task, social, personal resources: A three-wave structural equation model

Drawing on Conservation of Resources Theory and previous research on work engagement, the present study investigates gain spirals between employees' engagement and their task, social, and personal resources. It focuses on the key resources of job control, positive work relationships, and active coping behavior. In a three-wave design, work engagement (T2) is suggested to function both as an outcome and antecedent of these resources, so that engagement mediates indirect longitudinal effects of initial (T1) on subsequent (T3) resources. Item-level structural equation modeling supported our hypotheses in a three-wave panel (N = 416) of hospital physicians with measurement intervals of 14 and 19 months. Connections between engagement research and other evolving perspectives in organizational research are highlighted. Unique contributions of the present study and their implications for further research and practice are discussed.     

The simplest complete model of choice response time: linear ballistic accumulation

We propose a linear ballistic accumulator (LBA) model of decision making and reaction time. The LBA is simpler than other models of choice response time, with independent accumulators that race towards a common response threshold. Activity in the accumulators increases in a linear and deterministic manner. The simplicity of the model allows complete analytic solutions for choices between any number of alternatives. These solutions (and freely-available computer code) make the model easy to apply to both binary and multiple choice situations. Using data from five previously published experiments, we demonstrate that the LBA model successfully accommodates empirical phenomena from binary and multiple choice tasks that have proven difficult for other theoretical accounts. Our results are encouraging in a field beset by the tradeoff between complexity and completeness.     

An evidential support accumulation model of subjective probability

A model of cue-based probability judgment is developed within the framework of support theory. Cue diagnosticity is evaluated from experience as represented by error-free frequency counts. When presented with a pattern of cues, the diagnostic implications of each cue are assessed independently and then summed to arrive at an assessment of the support for a hypothesis, with greater weight placed on present than on absent cues. The model can also accommodate adjustment of support in light of the baserate or prior probability of a hypothesis. Support for alternatives packed together in a "residual" hypothesis is discounted; fewer cues are consulted in assessing support for alternatives as support for the focal hypothesis increases. Results of fitting this and several alternative models to data from four new multiple-cue probability learning experiments are reported.     

Dislocation multiplication in bcc molybdenum: A dislocation dynamics simulation

Plastic deformation of Mo single crystals is examined by direct simulation of dislocation dynamics under stress. Initial dislocation populations are made to mimic real dislocation microstructures observed in transmission electron microscopy cross-sections of pure annealed Mo single crystals. No a priori sources for dislocation multiplication are introduced, and yet multiplication takes place through a sequence involving aggregation of grown-in superjogs, bowing of screw dislocation segments and fast lateral motion of edge segments, producing a large number of elongated loops and a characteristic cross-grid pattern of screw dislocations.     

Analytic model for the line tension of a bowing dislocation segment

The resistance of a dislocation to bowing under stress governs the strength of the gamut of metallic material systems. This resistance is commonly referred to as the dislocation line tension (Γ) and is employed ubiquitously within continuum scale models of metal plasticity. Despite its significance, a unifying model for the line tension of a bowing dislocation segment, which has been analytically derived and independently reproduces simulation results, remains lacking. Here, we report a model for Γ of a curved, semicircular bowing dislocation segment. Upon applying our model to the operative stress of a Frank–Read dislocation source, we predict a prelogarithmic scaling of the Frank–Read source strength in agreement with existing simulation results. Moreover, in the limit of infinitesimal bowout we predict a prelogarithmic line tension factor which also agrees with theoretical analyses. Our model provides insight into the evolution of an arbitrarily oriented, stressed dislocation segment without resorting to numerical methods.     

A moving screw dislocation in transversely isotropic magnetoelectroelastic materials

The study of dislocations is of great interest for understanding the strengthening and hardening mechanisms in materials. A magnetoelectroelastic material containing a moving screw dislocation is considered using an extended version of the Stroth formalism. A complex-variable method is applied to obtain closed-form solutions. The present solutions, which contain previously known results as special cases, may be of great help in analyzing the reliability of devices made from these advanced materials.     

A systems model of leadership: WICS

This article reviews a systems model of leadership. According to the model, effective leadership is a synthesis of wisdom, creativity, and intelligence (WICS). It is in large part a decision about how to marshal and deploy these resources. One needs creativity to generate ideas, academic (analytical) intelligence to evaluate whether the ideas are good, practical intelligence to implement the ideas and persuade others of their worth, and wisdom to balance the interests of all stakeholders and to ensure that the actions of the leader seek a common good. The article relates the current model to other extant models of leadership.     

Atomistic study of structural fluctuations during radiation-induced amorphization in the ordered intermetallic compound NiTi

We have carried out an atomistic study of electron-induced amorphization of an ordered intermetallic compound NiTi by means of in-situ high-resolution high-voltage electron microscopy observations and molecular dynamics simulations. Both theoretical and experimental results show that metastable nanometre-size atomic clusters form and disappear during irradiation, so that a spatiotemporal fluctuation under amorphization is induced. Mean-lifetime measurements of these clusters demonstrate that high-energy particle irradiation provides a useful tool to study dynamic fluctuations of the local atomic structure in the non-equilibrium open systems.     

Playing hard-to-get: A two-determinant model

Walster, Walster, Piliavin, and Schmidt (Journal of Personality and Social Psychology, 1973, 26, 113–121) found that a hard-to-get woman was liked only if she was hard-to-get for other men but easy-to-get for the subject. They suggested that the subjects liked this type of woman because of the socially desirable personality characteristics they attributed to her. A second determinant of liking is proposed in the present study. It concerns the effect of a person's evaluation of a subject on the subject's self-esteem. It was predicted that there would be a positive relationship between changes in the subject's self-esteem and liking for the evaluator. The results demonstrated that this determinant, as well as the one that Walster et al. suggested, is important in understanding the type of opposite-sex person that men and women find most attractive. These results, and the differences between the Walster et al. and the present studies, were discussed in terms of the relative impact of the two determinants in laboratory and real-life situations.     

Critical thinking: A Socratic model

A concept of critical thinking is developed based on the Socratic method and called accordingly a Socratic model. First the features of critical thinking stressed in this model are stated and illustrated. The Socratic method is presented and interpreted, then taken to yield a model of critical thinking. The process of internalization by which the Socratic model helps us to become critical thinkers is described. Argument analysis is considered as a widely used instructional strategy adaptable for teaching critical thinking on the Socratic model. This Socratic model is advanced as one helpful way of organizing our ideas about critical thinking, helpful in unifying disparate factors and anchoring them in the humanist tradition.     

Reconstructive memory: A computer model

This study presents a process model of very long-term episodic memory. The process presented is a reconstructive process. The process involves application of three kinds of reconstructive strategies—component-to-context instantiation strategies, component-instantiation strategies, and context-to-context instantiation strategies. The first is used to direct search to appropriate conceptual categories in memory. The other two are used to direct search within the chosen conceptual category. A fourth type of strategy, called executive search strategies, guide search for concepts related to the one targeted for retrieval. A conceptual memory organization implied by human reconstructive memory is presented along with examples which motivate it. A basic retrieval algorithm is presented for traversing that stucture. Retrieval strategies arise from failures in that algorithm. The memory organization and retrieval processes are implemented in a computer program called CYRUS which stores events in the lives of former Secretaries of State Cyrus Vance and Edmund Muskie and answers questions posed in English concerning that information. Examples which motivate the process model are drawn from protocols of human memory search. Examples of CYRUS's behavior demonstrate the implemented process model. Conclusions are drawn concerning retrieval failures and the relationship of episodic and semantic memory.     

English palindromes: A distributional model

A list of English palindromes that approaches comprehensiveness is given. A stochastic model for the distribution of palindromes within the language is proposed. The model relates frequencies of palindromes and of heteropalindromes (Jones, 1980) as a function of word length, and it is shown to predict accurately the actual numbers of palindromes that occur.     

A non-linear model of dynamics: A case of panic

This is a case report of a patient with panic who is on the edge of relapse into alcoholism. It is a case of general theoretical interest, because of the separate phases of containment of his desperation, involving psychopharmacology, sociotherapy, and psychotherapy. It extends the dynamic model into non-linear dynamics, an extension that allows the patient to come to face his amazement at the sudden eruption of unconscious forces, and that allows the psychotherapist to see the therapeutic path of backing up from walking forward, unwittingly, into catastrophe.     

A humanistic developmental model of counselling: A psycho-educational approach

A developmental model of counselling, based on humanistic principals of psychological functioning, is proposed. A psycho-educational approach, in which counsellors are seen as helping clients develop skills rather than solve problems, is discussed. The counselling model involves three stages: exploration, intervention and empowering. The intervention stage includes techniques focused on affect, behaviour or cognition, as suggested by the ABC model of personal change described in the paper.