Forming limit stresses predicted by phenomenological plasticity theories with anisotropic work-hardening behavior

Forming limit stresses of sheet metals subjected to linear and combined stress paths are analyzed using the M-K model in conjunction with two anisotropic work-hardening models: a work-hardening model which is capable of describing Bauschinger and cross-hardening effects, and a work-hardening model which cannot predict the cross-hardening effect. It is found that the forming limit stress is path-independent when the stress–strain curves for the linear and combined stress paths agree well with each other. On the other hand, the forming limit stress for the combined stress path depends on the strain path when the prestrain changes the subsequent stress–strain relation. We conclude that the stress-based forming limit criterion is efficient only for a material with a work-hardening behavior that is not affected by strain path change. The influence of the work-hardening behavior on the forming limit stress is discussed in detail.     

Resin-supported acid- and base-catalyzed one-pot sequential reaction including an enantioselective step

One-pot sequential acidic deacetalization and basic enantioselective aldol reaction were realized using Amberlite IR-120 (H⁺-form) and a resin-supported peptide catalyst, and the reusability of the catalysts was demonstrated.     

Elastic scattering for the system 11Be + 209Bi at Coulomb barrier energies

The elastic scattering process for ¹¹Be ions impinging on a ²⁰⁹Bi target was studied in the energy range around the Coulomb barrier. The angular distributions of the ¹¹Be scattered particles were analyzed within the optical model framework in order to evaluate the reaction cross section, which turned out to be much larger than the fusion one, especially in the sub-barrier region. The comparison with the system ⁹Be + ²⁰⁹Bi showed that the reaction cross section is larger for the reaction ¹¹Be + ²⁰⁹Bi in the energy range around the Coulomb barrier, while they are rather similar at higher bombarding energies. This result suggests that direct processes related to the ¹¹Be halo structure and lower binding energy are more relevant at near-barrier energies.     

Raman studies of lattice dynamics in 1T-TiSe2

Raman scattering measurements were carried out on 1T-TiSe₂ above and below the phase transition temperature. Below _c many new lines appear, which are the Γ-point phonon modes folded from the original zone boundary points L, M and A due to the formation of the 2a₀ × 2a₀ × 2c₀ superlattice. Among them the strong A_1g line at 119 cm^?1 and the E_g line at 78 cm^?1 at 11 K show softening, as the temperature approaches to T_c, but the modes become overdamped before the energies go to zero.     

Generation of upper-hybrid solitons in a weak magnetic field

A simple model is presented which describes the space—time evolution of upper-hybrid (UH) waves excited in the mode-conversion conversion process. The model predicts oscillatory UH waves due to the ion inertia effect in the weakly nonlinear regime, and an UH soliton in the strongly nonlinear regime.     

A simple purely infinite <Emphasis Type="Italic">C</Emphasis>*-algebra associated with a lambda-graph system of the Motzkin shift

The Motzkin shift is a nonsofic subshift consisting of the four brackets (,[,),] with standard bracket rule and one additional symbol, the unit 1. We show that the C*-algebra associated with a -graph system that presents the Motzkin shift is simple and purely infinite. It is generated by two partial isometries and three isometries, and is a universal unique C*-algebra subject to some operator relations among the generators. The K₀-group of the C*-algebra is computed to be the abelian group of all -valued continuous functions on the Cantor set. The K₁-group is trivial. Hence it is not stably isomorphic to any Cuntz-Krieger algebra and to any Cuntz-algebra.Mathematics Subject Classification (2000): 46L80, 46L55, 37B10in final form: 6 October 2003     

Bowen–Franks Groups for Subshifts and Ext-Groups for C*-Algebras

We generalize the Bowen–Franks groups for topological Markov shifts to general subshifts as the Ext-groups for the associated C ^*-algebras. The generalized Bowen–Franks groups for subshifts are shown to be invariant under flow equivalence and, hence, invariant under topological conjugacy. They are regarded as the indices of Fredholm operators related to extensions of the associated C ^*-algebras so that they are described in terms of symbolic dynamical systems. In particular, the group for a sofic subshift is determined by the adjacency matrix of its left Krieger cover graph. The Bowen–Franks groups for some non sofic subshifts are calculated, proving that certain subshifts with the same topological entropy are not flow equivalent.