Abstract Phase stability of the intermetallic compound Al3Nb is investigated as a function of nickel additions by band structure calculations based on an extended Hueckel tight-binding method. With this method, the electronic structure and total energies of the Al6-n-NinNb2 compounds (where n is an integer from 0 to 6) are calculated for both D022 and L12 structures under the assumption that nickel substitutes for aluminium. The electronic total energies obtained from integration of the energy states of all electrons considered have shown that the D022 structure is stable in the binary Al3Nb compound as compared with the L12 structure; conversely, the L12 structure is stable for compounds with n values greater than 1. These calculations are in good agreement with X-ray diffraction results reported by Schubert and co-workers. Differences in the electronic total energy per atom between D022 and L12 are - 0·79 eV and 0·56 eV for n equal to 0 and 2, respectively. 相似文献
In this cross-cultural study, 115 Hong Kong Chinese and 117 Brazilian college students described a childhood peak-experience
(occurring before the age of 14) and provided a self-rating on its enduring impact. Among various categories of peak-experiences,
both Hong Kong Chinese and Brazilians reported interpersonal joy most frequently; the second most frequently reported category
was external achievement for the Hong Kong sample and developmental landmark for the Brazilian sample. Compared with Brazilians’
narratives, those of Hong Kong Chinese were more social-focused, involving greater number of other people, but less specific.
These characteristics of autobiographical memory, i.e., memory focus (self vs. social), memory specificity (specific vs. general),
and the number of other people involved, significantly mediated the relation between culture and interpersonal joy. The present
findings have extended research on peak-experiences to cross-cultural contexts and incorporated measures of autobiographical
memory to unpack cultural variations in these two collectivist societies. 相似文献
Representing spatial information is one of our most foundational abilities. Yet in the present work we find that even the simplest possible spatial tasks reveal surprising, systematic misrepresentations of space—such as biases wherein objects are perceived and remembered as being nearer to the centers of their surrounding quadrants. We employed both a placement task (in which observers see two differently sized shapes, one of which has a dot in it, and then must place a second dot in the other shape so that their relative locations are equated) and a matching task (in which observers see two dots, each inside a separate shape, and must simply report whether their relative locations are matched). Some of the resulting biases were shape specific. For example, when dots appeared in a triangle during the placement task, the dots placed by observers were biased away from certain parts of the symmetry axes. But other systematic biases were not shape specific, and seemed instead to reflect differences in the grain of resolution for different regions of space. For example, with both a circle and even a shapeless configuration (with only a central landmark) in the matching task, observers were better at discriminating angular differences (when a dot changed positions around the circle, as opposed to inward/outward changes) in cardinal versus oblique sectors. These data reveal a powerful angular spatial bias, and highlight how the resolution of spatial representation differs for different regions and dimensions of space itself.
The purpose of this experiment was to examine the combined effects of self-control and frequency of model presentation on learning a complex motor skill, i.e., ballet passé relevé. Before practice started self-control participants were asked to choose two viewings or six viewings (before practice and then every five trials) and the externally controlled groups were yoked to their self-control counterparts. All participants completed 15 acquisition trials followed by 5 trials for the immediate and 5 trials for the delayed retention tests 48 hours later. Dependent variables included cognitive representation scores, physical reproduction rankings, and balance time. Statistical analyses indicated that under limited physical practice conditions self-control and higher frequency of model presentation facilitated the development of cognitive representation and did not produce further benefits in movement reproductions and balance time. The results were discussed with respect to the social cognitive theory. 相似文献