Consolidation of graphite thermoplastic textile preforms for primary aircraft structure

The use of innovative cost effective material forms and processes is being considered for fabrication of future primary aircraft structures. Processes that have been identified as meeting these goals are textile preforms that use resin transfer molding (RTM) and consolidation forming. The Novel Composites for Wing and Fuselage Applications (NCWFA) program has as its objective the integration of innovative design concepts with cost effective fabrication processes to develop damage-tolerant structures that can perform at a design ultimate strain level of 6000 micro-inch/inch. In this on-going effort, design trade studies were conducted to arrive at advanced wing designs that integrate new material forms with innovative structural concepts and cost effective fabrication methods. The focus has been on minimizing part count (mechanical fasteners, clips, number of stiffeners, etc.), by using cost effective textile reinforcement concepts that provide improved damage tolerance and out-of-plane load capability, low-cost resin transfer molding processing, and thermoplastic forming concepts. The fabrication of representative Y spars by consolidation methods will be described. The Y spars were fabricated using AS4 (6K)/PEEK 150g commingled angle interlock 0/90-degree woven preforms with +45-degree commingled plies stitched using high strength Toray carbon thread and processed by autoclave consolidation

The Procyclical Effects of Bank Capital Regulation

We assess the procyclical effects of bank capital regulation in a dynamic equilibrium model of relationship lending in which banks are unable to access the equity markets every period. Banks anticipate that shocks to their earnings as well as the cyclical position of the economy can impair their capacity to lend in the future and, as a precaution, hold capital buffers. We find that under cyclically-varying risk-based capital requirements (e.g. Basel II) banks hold larger buffers in expansions than in recessions. Yet, these buffers are insufficient to prevent a significant contraction in the supply of credit at the arrival of a recession. We show that cyclical adjustments in the confidence level underlying Basel II can reduce its procyclical effects on the supply of credit without compromising banks’ long-run solvency targets.Banking regulation;Basel II;Business cycles;Capital requirements;Credit crunch;Loan defaults;Relationship banking

The role of rotation on Petersen Diagrams. The Pi1/0(Omega) Pi_{1/0}(Omega) period ratios

The present work explores the theoretical effects of rotation in calculating the period ratios of double-mode radial pulsating stars with special emphasis on high-amplitude delta Scuti stars (HADS). Diagrams showing these period ratios vs. periods of the fundamental radial mode have been employed as a good tracer of non-solar metallicities and are known as Petersen diagrams (PD).In this paper we consider the effect of moderate rotation on both evolutionary models and oscillation frequencies and we show that such effects cannot be completely neglected as it has been done until now. In particular it is found that even for low-to-moderate rotational velocities (15-50 km/s), differences in period ratios of some hundredths can be found. The main consequence is therefore the confusion scenario generated when trying to fit the metallicity of a given star using this diagram without a previous knowledge of its rotational velocity.Comment: A&A in pres

Implementation of the barotropic vorticity equation on the MPP

A finite difference version of the equations governing two-dimensional, non-divergent flow on a sphere is implemented and integrated on the Massively Parallel Processor (MPP). The MPP's performance is then compared with the Cyber's. The feasibility of using a massively parallel architecture to solve the hydrodynamic equations as they are used in numerical weather prediction (NWP) are described