We consider the relation between mixed global gauge gravitational anomalies and boundary conformal field theory in WZW models for simple Lie groups. The discrete symmetries of consideration are the centers of the simple Lie groups. These mixed anomalies prevent gauging them i.e, taking the orbifold by the center. The absence of anomalies impose conditions on the levels of WZW models. Next, we study the conformal boundary conditions for the original theories. We consider the existence of a conformal boundary state invariant under the action of the center. This also gives conditions on the levels of WZW models. By considering the combined action of the center and charge conjugation on boundary states, we reproduce the condition obtained in the orbifold analysis.

The effects of load and time on the Vickers indentation responses of a graded zirconium phosphate (ZP)–filled epoxy resin are described. The hardness of this material is dependent on the concentration of ZP dispersed within the epoxy matrix. In the region poor in ZP, the hardness response is independent of load. In contrast, the hardness response in the region rich in ZP is profoundly load‐dependent as a combined result of particle agglomeration and an indentation‐size effect. When compared with the ZP‐rich‐epoxy, the ZP‐poor epoxy exhibits a larger creep and a more pronounced elastic recovery in the Vickers impression. The nature and degree of deformation in the vicinity of Vickers contacts are also studied. During indentation the ZP‐rich epoxy exhibits no contact‐induced cracks but displays microscale plasticity, which can be associated with intergrain sliding, debonding, and grain push‐out. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 931–935, 2001

ABSTRACT:The effects of load and time on the Vickers indentation responses of a graded zirconium phosphate (ZP)-filled epoxy resin are described. The hardness of this material is dependent on the concentration of ZP dispersed within the epoxy matrix. In the region poor in ZP, the hardness response is independent of load. In contrast, the hardness response in the region rich in ZP is profoundly load-dependent as a combined result of particle agglomeration and an indentation-size effect. When compared with the ZP-rich-epoxy, the ZP-poor epoxy exhibits a larger creep and a more pronounced elastic recovery in the Vickers impression. The nature and degree of deformation in the vicinity of Vickers contacts are also studied. During indentation the ZP-rich epoxy exhibits no contact-induced cracks but displays microscale plasticity, which can be associated with intergrain sliding, debonding, and grain push-out.