Continuum modeling of the reverse Hall–Petch effect in nanocrystalline metals under uniaxial tension: how many grains in a finite element model?

Owing to their very high strength, nanocrystalline metals have been extensively studied over the recent years. The direct Hall–Petch law, empirically proportioning the material strength to the inverse square root of its grain size has been shown to break down below a grain size of the order of tenths of nanometers. This phenomenon has been widely rationalized as a gradual switch from intragrain mediated deformation mechanisms to grain boundary mediated deformation mechanisms. This transition has been observed in many finite element simulations, despite the intrinsic restriction of necessarily limiting the nanocrystalline representative assembly to only a few grains. Such a limitation is generally overlooked, and its influence on an uniaxial tension test – when compared to a complete sample of millions of grains – ignored. We propose here to quantify the approximation done by considering a finite number of grains by means of a simple analytical model based on the early work of Stevens [R.N. Stevens, Philos. Mag. 23 (1971) p. 265]. The finite element approximation is demonstrated to be relatively good, even down to only three grains in width, and a method to “correct” the stress-strain curves of small representative volumes is proposed.     

Revisions and Regret: The Cost of Changing your Mind

Decision reversals often imply improved decisions. Yet, people show a strong resistance against changing their minds. These are well‐established findings, which suggest that changed decisions carry a subjective cost, perhaps by being more strongly regretted. Three studies were conducted to explore participants' regret when making reversible decisions and to test the hypothesis that changing one's mind will increase post‐outcome regret. The first two studies employed the Ultimatum game and the Trust game. The third study used a variant of the Monty Hall problem. All games were conducted by individual participants playing interactively against a computer. The outcomes were designed to capture a common characteristic of real‐life decisions: they varied from rather negative to fairly positive, and for every outcome, it was possible to imagine both more and less profitable outcomes. In all experiments, those who changed their minds reported much stronger post‐outcome regret than those who did not change, even if the final outcomes were equally good (Experiments 2 and 3) or better (Experiment 1).This finding was not because of individual differences with respect to gender, tendency to regret, or tendency to maximize. Previous studies have found that those who change from a correct to wrong option regret more than those who select a wrong option directly. This study indicates that this finding is a special case of a more general phenomenon: changing one's mind seems to come with a cost, even when one ends up with favorable outcomes. Copyright © 2011 John Wiley & Sons, Ltd.     

A randomised Monty Hall experiment: The positive effect of conditional frequency feedback

The Monty Hall dilemma (MHD) is a notorious probability problem with a counterintuitive solution. There is a strong tendency to stay with the initial choice, despite the fact that switching doubles the probability of winning. The current randomised experiment investigates whether feedback in a series of trials improves behavioural performance on the MHD and increases the level of understanding of the problem. Feedback was either conditional or non-conditional, and was given either in frequency format or in percentage format. Results show that people learn to switch most when receiving conditional feedback in frequency format. However, problem understanding does not improve as a consequence of receiving feedback. Our study confirms the dissociation between behavioural performance on the MHD, on one hand, and actual understanding of the MHD, on the other. We discuss how this dissociation can be understood.     

Describing organizations as reinforcer systems: A new use for job satisfaction and employee attitude surveys

Job satisfaction data on managerial personnel were used to illustrate how organizations can be differentiated and described as reinforcer systems. Twenty-seven specific satisfaction scales were regressed on overall job satisfaction, separately for each of five groups of managers from five organizations. For all groups, overall satisfaction was found to be determined mainly by scales concerning challenge of the job and prospects of one's chosen career. Application of decremental stepwise multiple regression procedures to obtain minimum-variable-set equations resulted in different, though overlapping, sets of variables in the equations for the different organizations. These results suggest a way of describing organizations as reinforcer systems, in terms of the specific determinants of overall satisfaction for the organization.     

A multivariate investigation of the reinforcer structure of occupations

Earlier research based on 81 Occupational Reinforcer Patterns (ORPs) suggested a nine-category classification of occupations. The present research, based on 148 ORPs, investigated the ability of that classificatory system to assimilate new information. Cluster analysis of the 148 ORPs yielded an eight-category classification of occupations in which five of the original occupational clusters appeared virtually unchanged; the other four original clusters were combined into two occupational clusters. One new cluster was identified. Principal factors analysis was employed to study the factor structure of the occupational reinforcers and to highlight the essential nature of the classificatory system. Five reinforcer factors were identified.     

Personality correlates of Holland's occupational types: A cross cultural study

Recent studies have investigated the personality traits of persons in Holland's six occupational categories. In the present study the generalizability of Holland's characterizations of adults within the occupational categories was investigated in a group of 402 Mexican-Americans. Occupational Scale scores on the Kuder Occupational Interest Survey were used to classify subjects into Holland's occupational types. Multiple discriminant analysis of groups' Guilford-Zimmerman Temperament Survey scale scores resulted in significant overall groups differentiation and two significant discriminant functions for males but no significant results for females. The personality characteristics of the male groups provide strong support for the generalizability of Holland's characterizations to Mexican-American males.     

The effect of career education on career maturity

According to Hoyt (1974), career education efforts are underway in almost one-third of all school districts in the United States. Indications are that this trend will continue. However, the question of the effects of career education programs remains essentially unanswered. This study was designed to assess the effects of a career education program on students' career maturity as measured by the Career Maturity Inventory (CMI). A pretest/ posttest design was used. The sample consisted of 480 sixth and eighth grade students, one-half of whom participated in a career education program (experimental), with the remaining one-half in a regular school program (control). The career education students consistently displayed higher posttest career maturity levels, four scores being significantly higher. Significant differences were found in occupational knowledge of sixth graders, occupational planning for both the sixth and eighth graders and in the attitude scale score for the eighth graders. It was concluded that the career education program had a positive effect in increasing students' levels of career maturity.     

Multidimensional scaling study of visual memory of 5-year olds and adults.

Nonmetric multidimensional scaling is expounded as a methodology for investigating memory development. Judgements of similarities between complex objects were obtained from 5-year-olds and adults under two conditions: (1) when objects were simultaneously present at the time of comparison, and (2) when the objects were not simultaneously present and had to be compared on the basis of short-term memory. Scaling solutions for similarity judgments by each age group in the two conditions were obtained. Comparison within each age group of the configurations from the memory condition with the simultaneous condition indicated that the internal representations of both children and adults contained much of the information the subjects extracted from the stimuli during “direct” perception. The scaling techniques, which could be widely applied in developmental studies of memory and perception, are explained and critically discussed.     

Supervisor estimation of abilities required in jobs

The Minnesota Job Requirements Questionnaire (MJRQ) was developed and administered to supervisors of 11 selected jobs who rated the ability requirements of the job they supervised. The MJRQ represented each of nine GATB aptitudes by five items in a Likert-type format. MJRQ ratings were compared with expert ratings in the Dictionary of Occupational Titles (DOT) and Occupational Ability Patterns (OAPs) derived from administration of the General Aptitude Test Battery (GATB). Reliability of MJRQ ratings was shown by high Hoyt reliability coefficients. Comparison of mean ratings and variabilities of ratings by supervisors in a job showed construct validity for the MJRQ approach, as did intercorrelations of MJRQ ratings. OAPs derived from the MJRQ compared favorably with those derived from the GATB and DOT, showing promise for the parsimonious MJRQ approach to the development of OAPs.     

Classroom behavior inventory: Factor verification

Sixty-nine second grade suburban children were rated by three teachers using a classroom behavior inventory. Factor analysis was performed to test the a priori structure of the instrument. The 18-item inventory was analyzed on three factors: Task-Oriented vs Distractibility, Extroversion vs Introversion, and Considerateness vs Hostility. The three factors loaded perfectly according to the a priori design. The need for further investigations concerning the reliability and a comparison of the rating scale with objective observations is indicated.