The velocity field of a system of unsteady cycloidal vorticies

An essential difference between two-dimensional and three-dimensional models of cycloidal rotors, the presence of unsteady trailing cycloidal vorticies in the wake, was studied. The velocity induced by these vorticies is the primary mechanism producing flow retardation for low span/radius ratio, finite blade number rotors. Results of using idealized rigid wake model of finite blade cycloidal rotors to investigate some cycloidal rotor problems are presented

Self-dual quiver moduli and orientifold Donaldson-Thomas invariants

Motivated by the counting of BPS states in string theory with orientifolds, we study moduli spaces of self-dual representations of a quiver with contravariant involution. We develop Hall module techniques to compute the number of points over finite fields of moduli stacks of semistable self-dual representations. Wall-crossing formulas relating these counts for different choices of stability parameters recover the wall-crossing of orientifold BPS/Donaldson-Thomas invariants predicted in the physics literature. In finite type examples the wall-crossing formulas can be reformulated in terms of identities for quantum dilogarithms acting in representations of quantum tori.Comment: 24 pages. The factorization used to define orientifold DT invariants has been slightly revise

New Lessons: The Power of Educating Adolescent Girls

Offers data and analysis on the impact of education on adolescent girls' lives and highlights promising approaches. Calls for evaluating girl-friendly education programs, compiling data on non-formal schools, and improving curricula, access, and supports

Experimental and numerical studies of ferritic stainless steel tubular cross sections under combined compression and bending

An experimental and numerical study of ferritic stainless steel tubular cross sections under combined loading is presented in this paper. Two square hollow section (SHS) sizes—SHS 40×40×240×40×2 and SHS 50×50×250×50×2 made of Grade EN 1.4509 (AISI 441) stainless steel—were considered in the experimental program, which included 2 concentrically loaded stub column tests, 2 four-point bending tests, and 14 eccentrically loaded stub column tests. In parallel with the experimental investigation, a finite-element (FE) study was also conducted. Following validation of the FE models against the test results, parametric analyses were carried out to generate further structural performance data. The experimental and numerical results were analyzed and compared with the design strengths predicted by the current European stainless steel design code EN 1993-1-4 and American stainless steel design specification SEI/ASCE-8. The comparisons revealed that the codified capacity predictions for ferritic stainless steel cross sections under combined loading are unduly conservative. The deformation-based continuous strength method (CSM) has been extended to cover the case of combined loading. The applicability of CSM to the design of ferritic stainless steel cross sections under combined loading was also evaluated. The CSM was shown to offer substantial improvements in design efficiency over existing codified methods. Finally, the reliability of the proposals was confirmed by means of statistical analyses according to both the SEI/ASCE-8 requirements and those of EN 1990