Value-Driven Design Framework for Competitive Aviation Markets

Determining the “best” aircraft design for a given market segment is a challenging proposition. In this paper, a value-driven design framework is created to illustrate how economic theory can be used to assess business strategies and engineering solutions within the civil aviation industry. The framework addresses a number of assumptions inherent within the surplus value theory and compares them through a commercial aviation case study, for which the potential market size is highly uncertain. The case study demonstrated that, without addressing these assumptions, a potential 380% difference in program surplus value was calculated. More specifically, the manufacturer value of the aircraft program can be calculated incorrectly by up to 900%. This was determined by creating a multistage, noncooperative game to characterize the behavior of the commercial aviation industry to capture the effects of design parameters on the program value against different levels of competition from direct and adjacent markets

Coupled Personalisation of Electrophysiology Models for Simulation of Induced Ischemic Ventricular Tachycardia

International audienceDespite recent efforts in cardiac electrophysiology modelling, there is still a strong need to make macroscopic models usable in planning and assistance of the clinical procedures. This requires model personalisation i.e. estimation of patient-specific model parameters and computations compatible with clinical constraints. Fast macroscopic models allow a quick estimation of the tissue conductivity, but are often unreliable in prediction of arrhythmias. On the other side, complex biophysical models are quite expensive for the tissue conductivity estimation, but are well suited for arrhythmia predictions. Here we present a coupled personalisation framework, which combines the benefits of the two models. A fast Eikonal (EK) model is used to estimate the conductivity parameters, which are then used to set the parameters of a biophysical model, the Mitchell-Schaeffer (MS) model. Additional parameters related to Action Potential Duration (APD) and APD restitution curves for the tissue are estimated for the MS model. This framework is applied to a clinical dataset provided with an hybrid X-Ray/MR imaging on an ischemic patient. This personalised MS Model is then used for in silico simulation of clinical Ventricular Tachycardia (VT) stimulation protocol to predict the induction of VT. This proof of concept opens up possibilities of using VT induction modelling directly in the intervention room, in order to plan the radio-frequency ablation lines

A subject-specific technique for respiratory motion correction in image-guided cardiac catheterisation procedures

We describe a system for respiratory motion correction of MRI-derived roadmaps for use in X-ray guided cardiac catheterisation procedures. The technique uses a subject-specific affine motion model that is quickly constructed from a short pre-procedure MRI scan. We test a dynamic MRI sequence that acquires a small number of high resolution slices, rather than a single low resolution volume. Additionally, we use prior knowledge of the nature of cardiac respiratory motion by constraining the model to use only the dominant modes of motion. During the procedure the motion of the diaphragm is tracked in X-ray fluoroscopy images, allowing the roadmap to be updated using the motion model. X-ray image acquisition is cardiac gated. Validation is performed on four volunteer datasets and three patient datasets. The accuracy of the model in 3D was within 5 mm in 97.6% of volunteer validations. For the patients, 2D accuracy was improved from 5 to 13 mm before applying the model to 2–4 mm afterwards. For the dynamic MRI sequence comparison, the highest errors were found when using the low resolution volume sequence with an unconstrained model

Radial basis function based meshless methods for fluid flow problems

This thesis is concerned with the development of meshless methods using radial basis functions for solving fluid flow problems. The advantage of meshless methods over traditional mesh-based methods is that they make use of a scattered set of collocation points in the physical domain and no connectivity information is required. An important objective of the present research is to develop novel meshless methods for unsteady flow problems. Symmetric/unsymmetric radial basis function collocation schemes are proposed for solving an unsteady convection-diffusion equation for various Peclet numbers. Both global and compactly supported radial basis functions are used and the convergence behaviours of various radial basis functions are studied. The performance of the presented schemes is shown by using both uniform as well as scattered distribution of points. Numerical results suggestthat these schemes are capable of obtaining accurate results for low and medium Peclet numbers. Next, two directions have been explored in this thesis for using radial basis functions to solve large scale problems encountered in fluid flow problems. They are namely, domain decomposition schemesand radial basis functions in finite difference mode. These schemes are shown to be computationally efficient and also aid in circumventing the ill-conditioning problem. The performance of both schemes are evaluated by solving the unsteady convection-diffusion problem. The last part of this thesis isconcerned with the solution of the 2D Navier-Stokes equations. Meshless methods based on radial basis collocation and scattered node finite difference schemes are formulated for solving steady and unsteady incompressible Navier-Stokes equations. A novel ghost node strategy is proposed for incor-porating the no-slip boundary conditions. Optimisation strategies based on residual error objective and leave-one-out statistical criterion are proposed to evaluate the optimal shape parameter value in case of the multiquadric RBF for collocation and scattered finite difference approaches respectively.Standard benchmark problems like the driven cavity flows in square and rectangular domains and backward facing step flow problem are solved to study the performance of the developed schemes. Finally, a higher order radial basis function based scattered node finite difference method is proposed for solving the incompressible Navier-Stokes equations

Global and compact meshless schemes for the unsteady convection-diffusion equation

The numerical solution of convection-diffusion equation has been a long standing problem and many numerical schemes which attempt to find stable and accurate solutions for convection dominated cases have to resort to artificial dissipation to stabilize the numerical solution. In this paper, we investigate the application of global and compact meshless collocation techniques with radial basis functions for solving the unsteady convection-diffusion equation. We employ the method of lines approach to discretize the governing operator equation. The stability of both explicit and implicit time stepping schemes are analyzed. Numerical results are presented for one-dimensional and two-dimensional problems using various globally supported radial basis functions such as multiquadric (MQ), inverse multiquadric (IMQ), Gaussian, thin plate splines (TPS) and quintics. Numerical studies suggest the global MQ, IMQ and Guassian (when the shape parameter is prperly tuned) have very high convergence rate than TPS and appears that the global meshless collocation techniques require a very dense set of collocation points in order to achieve accurate results for high Peclet numbers. For the compact supported RBFs, it is found that as the support parameter is increased, the sparsity decreases resulting in a better accuracy but at additional computational cost

Unsymmetric and symmetric meshless schemes for the unsteady convection–diffusion equation

In this paper we investigate the application of unsymmetric and symmetric meshless collocation techniques with radial basis functions for solving the unsteady convection–diffusion equation. We employ the method of lines approach to discretize the governing operator equation. The stability of both explicit and implicit time-stepping schemes are analyzed. Numerical results are presented for 1D and 2D problems to compare the performance of the unsymmetric and symmetric collocation techniques. We compare the performance of various globally supported radial basis functions such as multiquadric, inverse multiquadric, Gaussian, thin plate splines and quintics. Numerical studies suggest that symmetric collocation is only marginally better than the unsymmetric approach. Further, it appears that both collocation techniques require a very dense set of collocation points in order to achieve accurate results for high Pe´clet numbers

Combined Life-Cycle Including Carbon Footprint for Composite Materials

Cost estimation for a composite material part requires cost driver information from various activities just like any other material part. Every process involved to convert the product from raw material to finished state requires the consumption of certain cost value. The activities that are responsible for these cost changes are termed as cost drivers. Process cycle or life-cycle is a way to represent the processes necessary in a products complete journey. It is important to map different phases in a processes and include them in the life-cycle for proper analysis and management. The present work reviews the importance of different phases in a processes and quantifies the contribution of various processes in the composite material part overall cost. This contribution is represented in a tabular form and then compared to conventional method of life-cycle. The importance of including carbon footprint in the life-cycle is also reviewed and finally a generic process/ project life-cycle for composite material part is defined. This contain processes that are contributing the most to the overall cost of the product and form a basis for process/project analysis, optimization and management