Yield vertices for {123}〈111〉 multiple slip

The single-crystal yield surfaces of bcc crystals for slip on {123}〈111〉 systems have been analyzed systematically and derived based on the Taylor/Bishop-Hill theory. It is found that there are 338 stress states altogether. All the stress states are classified according to the crystal symmetry. The results demonstrated that there are 14 groups of yield vertices, which activate five, six, or eight slip systems, depending on the crystallographically none quivalent groups. In addition, the four groups of yield vertices that Chin and Wonsiewicz^[15] did not consider have been obtained (there are 126 stress states). Among all these vertices, the fraction of vertices for which there is slip ambiguity (more than five active slip systems) is reduced considerably to 146/338 (≈43 pct). By means of the stress states obtained by Chin et al. and by the present authors, respectively, the plastic flow for axially symmetric deformation and three-axial deformation have been analyzed. In the case of axially symmetric deformation, the results are the same using the two different kinds of stress states. The obtained new stress states are necessary in order to analyze the three-axial deformation.     

Capillary instabilities in thin films: A model of thermal pitting at grain boundary vertices

The equation describing surface topographic evolution by surface diffusion is adapted to describe the thermal pitting of a surface in the vicinity of a grain boundary vertex (triple junction of three boundaries) in order to model experimental observations of hole formation in thin films; isotropy of surface properties is assumed. An analytic solution for the evolution of an initially flat surface is obtained for a sector between two intersecting boundaries (of a triple junction) with an included angle ϕ=90°, and numerical solutions are calculated for several other values of ϕ. The results show that the surface shape is time-independent with linear dimensions that are proportional to $\text{t}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$. For a given angle at the root of the groove, the calculations show that the rate of pit deepening increases as ϕ decreases and show that, typically, pitting is appreciably faster than thermal grooving.     

具有给定悬挂点数目的树的Hosoya指标极值

具有r个悬挂点的树称为r叶树.研究了具有n个顶点的4叶和5叶树的Hosoya 指标值,刻画了具有最大和最小Hosoya指标的5叶树和最小Hosoya指标的4叶树.     

Grouping and detecting vertices in 2-D, 3-D, and quasi-3-D objects.

In 2 experiments, observers (n?=?17) searched for a misaligned vertex in displays depicting 1 or more two-dimensional (2-D), three-dimensional (3-D), and quasi-3-D objects that were drawn with unconnected vertices. Serial search functions were obtained for all 3 conditions, even after much practice. In addition, search among the 2-D objects was more efficient than search among either 3-D or quasi-3-D objects, which did not differ after practice. This finding suggests that differences in depicted dimensionality cannot explain the difference in performance between the 2-D and 3-D conditions, but differences in stimulus complexity can. Further, after practice with the 2-D displays, observers could detect a misaligned vertex as rapidly among 2 objects as they could with 1-object displays. These findings have implications for models of object recognition that assign a critical role to vertices in early vision, as well as the notion that mechanisms underlying preattentive processing may differ from those underlying the automaticity of processing that develops with practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)