Abstract The compressive and tensile behaviors in a Ti nanopillar with a biphasic hexagonal close-packed (HCP) /face-centered cubic (FCC) phase boundary are theoretically researched using classic molecular dynamic simulation. The results indicate that the HCP/FCC interface and free surface of the nanopillar are the sources of dislocation nucleation. The plastic deformation is mainly concentrated in the metastable FCC phase of the biphasic nanopillar. Under compressive loading, a reverse phase transformation of FCC to the HCP phase is induced by the dislocation glide of multiple Shockley partial dislocations 1 2 < 1 ¯ 21 >under compressive loading. However, for tensile loading a large number of Lomer-Cottrell sessile dislocations and stacking fault nets are formed when the partial dislocations react, which leads to an increase in stress. The formation mechanism of a Lomer-Cottrell sessile dislocation is also studied in detail. Shockley partial dislocations are the dominant mode of plastic deformation behaviors in the metastable FCC phase of the biphasic nanopillar.

Because of the apparent slowdown in the growth of crop yield potential, the increasing share of farmers already using modern crop varieties, and the accelerating flow of knowledge on agricultural technology, one would expect to find gradual convergence in observed crop yields. Instead, using a new, sub-national yield database, we find a divergence. We illustrate how technology generation has been biased towards more-favored production systems, leaving persistent pockets of low yields in more marginal lands. Rainfall patterns appear to have changed in ways that exacerbate yield divergence. Cross-border barriers to technology spillover appear larger among than within countries

La aparente disminución del crecimiento en el potencial del rendimiento de los cultivos, la creciente proporción de agricultores que utilizan variedades de alto rendimiento (HYV), y el flujo de conocimiento sobre tecnología agropecuaria sugieren convergencia en los rendimientos de los cultivos. En cambio, utilizando una base de datos nueva sobre rendimiento de cultivos a nivel subnacional, vemos una divergencia. La generación de tecnología ha estado sesgada hacia sistemas de producción más favorecida, dejando atrás nichos de baja producción persistentes en las tierras marginales. Los patrones de pluviosidad cambiaron en formas que exacerban la divergencia de rendimiento. Los obstáculos al flujo de conocimiento y tecnología parecen mayores entre diferentes países que dentro de ellos mismos