A generic tool for cost estimating in aircraft design

A methodology to estimate the cost implications of design decisions by integrating cost as a design parameter at an early design stage is presented. The model is developed on a hierarchical basis, the manufacturing cost of aircraft fuselage panels being analysed in this paper. The manufacturing cost modelling is original and relies on a genetic-causal method where the drivers of each element of cost are identified relative to the process capability. The cost model is then extended to life cycle costing by computing the Direct Operating Cost as a function of acquisition cost and fuel burn, and coupled with a semi-empirical numerical analysis using Engineering Sciences Data Unit reference data to model the structural integrity of the fuselage shell with regard to material failure and various modes of buckling. The main finding of the paper is that the traditional minimum weight condition is a dated and sub-optimal approach to airframe structural design.

Chitosan nanoparticle as protein delivery carrier - Systematic examination of fabrication conditions for efficient loading and release

Chitosan nanoparticles fabricated via different preparation protocols have been in recent years widely studied as carriers for therapeutic proteins and genes with varying degree of effectiveness and drawbacks. This work seeks to further explore the polyionic coacervation fabrication process, and associated processing conditions under which protein encapsulation and subsequent release can be systematically and predictably manipulated so as to obtain desired effectiveness. BSA was used as a model protein which was encapsulated by either incorporation or incubation method, using the polyanion tripolyphosphate (TPP) as the coacervation crosslink agent to form chitosan-BSA-TPP nanoparticles. The BSA-loaded chitosan-TPP nanoparticles were characterized for particle size, morphology, zeta potential, BSA encapsulation efficiency, and subsequent release kinetics, which were found predominantly dependent on the factors of chitosan molecular weight, chitosan concentration, BSA loading concentration, and chitosan/TPP mass ratio. The BSA loaded nanoparticles prepared under varying conditions were in the size range of 200-580 nm, and exhibit a high positive zeta potential. Detailed sequential time frame TEM imaging of morphological change of the BSA loaded particles showed a swelling and particle degradation process. Initial burst released due to surface protein desorption and diffusion from sublayers did not relate directly to change of particle size and shape, which was eminently apparent only after 6 h. It is also notable that later stage particle degradation and disintegration did not yield a substantial follow-on release, as the remaining protein molecules, with adaptable 3-D conformation, could be tightly bound and entangled with the cationic chitosan chains. In general, this study demonstrated that the polyionic coacervation process for fabricating protein loaded chitosan nanoparticles offers simple preparation conditions and a clear processing window for manipulation of physiochemical properties of the nanoparticles (e.g., size and surface charge), which can be conditioned to exert control over protein encapsulation efficiency and subsequent release profile. The weakness of the chitosan nanoparticle system lies typically with difficulties in controlling initial burst effect in releasing large quantities of protein molecules. (C) 2007 Elsevier B.V. All rights reserved.

HBrowse: a GRACE tool for browsing R-matrix H-files

An H-file is used to convey information from the inner-region to the outer-region in R-matrix computations. HBrowse is a workstation tool for displaying a graphical abstraction of a local or remote R-matrix H-file. While it is published as a stand-alone tool for post-processing the output from R-matrix inner-region computations it also forms part of the Graphical R-matrix Atomic Collision Environment (GRACE), HBrowse is written in C and OSF/Motif for the UNIX operating system. (C) 2000 Elsevier Science B.V. All rights reserved.