Sound transmission through the walls of light aircraft: An investigation of structure-borne noise in a Handley Page 137 Jetstream 3 aircraft

This study indicates that the structureborne noise due to wing/vortex interation for the Handley Page-137 Jetstream may be significant at frequencies above 500 Hz. It was found that by preventing such interaction, noise reductions between 1 to 3 dB were attainable. However, this study did not show any significant contribution due to this phenomena at the first blade passage tone. It is suspected that the wing/vortex interaction effect varies from plane to plane

A preliminary evaluation of the B2000 nonlinear shell element Q8N.SM

Aerospace Engineerin

A preliminary evaluation of the B2000 nonlinear shell element Q8N.SM

Over the past ten years, there has been a growing interest within the mechanics community towards the application of group theoretic methods to aid in the global buckling analysis of symmetric-free structures. Within the context of a numerical arclength continuation procedure, group theory helps one systematically find an "optimal" set of basic vectors which reflect the symmetry of a given problem. The immediate payoff in formulating the numerical procedure with respect to the symmetry-adapted basis is a global de-coupling of the equilibrium equations which in turn leads to: (1) a dimensional reduction in the problem size; (2) improved numerical conditioning while computing solutions in the vicinity of singular points; (3) a systematic method for detecting and diagnosing for symmetry-breaking bifurcations. In this book, a new group theoretic nonlinear continuation algorithm, written for the modular finite element package B2000, will be discussed. The focus of the work was to provide a general computational environment in which a wide range of symmetric problems for structural mechanics could be formulated and solved. A group theoretic approach allows the computation of equilibrium solutions for perfect structures which might otherwise be numerically intracebie. Furthermore, understanding the global behaviour of the perfect structure can be crucial to understanding the behavior of the imperfect structure. Numerical examples to be presented include results from the buckling analysis of a flat plate and an axially compressed cylindrical shell.Aerospace Engineerin

RapidSched: Static scheduling and analysis for real-time CORBA

This paper presents a real-time CORBA Scheduling Service called RapidSched. RapidSched uses a global, distributed deadline monotonic priority assignment, enforcement of priorities by commercial real-time operating systems, and distributed priority ceiling resource management. RapidSched is integrated with an enhanced version of the PERTS real-time analysis tool

Expressing and Enforcing Timing Constraints in a Dynamic Real-Time CORBA System

Distributed real-time applications have presented the need to extend the Object Management Group's Common Object Request Broker Architecture (CORBA) standard to support real-time. This paper describes a Dynamic Real-Time CORBA system, which supports the expression and enforcement of end-to-end timing constraints as an extension to a commercial CORBA system. The paper also describes performance tests that demonstrate the system's ability to enforce expressed timing constraints