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International Review of
Aerospace Engineering - Papers
 Airline Choices for the Future: From Alliances to Mergers
by K. Iatrou, K. Mason
Abstract
- The Air France-KLM merger, followed suit by the Lufthansa-Swiss merger announcement and the agreement of a new transatlantic air transport accord, has changed the landscape of air transport and set the foundation stone towards air transport consolidation. Once considered a remote eventuality, cross-border mergers and the potential they represent have become a concrete possible source of competitive advantage in the search of efficiencies and synergies in a highly competitive and volatile air transport arena. The present paper attempts to assess how the members of the three strategic alliances (Star Alliance, oneworld and SkyTeam) perceive alliance evolution and merger prospects under the impact of these developments. Through a questionnaire survey the paper analyzes how airlines themselves view mergers, what benefits mergers can offer as well as the obstacles they might encounter and in which areas these benefits and/or problems could arise. It further to assess how fast consolidation will move, what role alliances will play in the emerging restructured air transport industry and how alliances and mergers will interact. As it is the very first survey to focus on and analyze cross-border mergers from the industry’s point of view, its findings will be of interest not only to the industry itself but to governments, competition authorities, academics and to all those directly or indirectly involved in and/or influenced by developments in air transport.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Airline alliances, cross-border mergers, questionnaire, consolidation.
The Strategy of Asia-Pacific Low Cost Carriers Expansion
by C. H. Chang, S. Bond, C. W. Cheung
Abstract
- This paper describes how some Low Cost Carriers (LCCs) in the Asia-Pacific region have circumvented the restrictions of air freedoms by way of establishing a new company in another country in order to expand their network service. Faced with stiff competition from successfully established LCCs, some Full Service Carriers (FSCs) also formed fully own subsidiary LCCs and adopted this approach as a foreign expansion strategy. The advantage of investing a new company in another country makes good use of the opportunity of sixth air freedom of the third-party country, optimises fleet utilisation and improves luggage check-in service. The strategy provides a solution for business expansion to those countries without direct flight agreement due to political problems, such as China and Taiwan.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Low Cost Carriers, Open Skies, Expansion.
Space Shuttle Hypersonic Atmospheric Re-Entry: Aerodynamics and Thermodynamics Simulation Analysis
by E. E. Panagiotopoulos, D. P. Margaris, D. G. Papanikas
Abstract
- A full-synthesized aerothermodynamics trajectory simulation analysis is developed for atmospheric hypersonic re-entry flight missions. Modified finite wing span Newtonian Flow model is applied for Space Shuttle hypervelocity aerodynamic coefficients. Engineering correlations for stagnation heat flux and wall temperature are derived based on real gas effects depending on suitable modifications of the full classical Fay-Riddell theory.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Finite Wing Span Newtonian Flow, High Thermal Loads, Hypersonic Aerodynamic Coefficients, Real Gas Effects, Re-entry Trajectory, Wall Temperature Analysis.
Modification of Kohonen Rule for Vehicle Path Planning
by R. R. Kulić, S. Bauks, D. P. Margaris
Abstract
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The problem of path generation for the autonomous vehicle in environments with the infinite number obstacles is considered. Generally, the problem is known in the literature as the path planning. In this paper the algorithm, named MKBC, is based on the Kohonen rule. Kohonen rule connected with the weighting coefficients. The MKBC algorithm does not use the weighting values as values from the previous time, but permanentlly uses the training values as weighting values. This enables an intelligent system to learn from the examples (operator’s demonstrations) to control a vehicle in avoiding obstacles, like the human operator does, which is known as behavioral cloning. Following the given context the problem narrow passage avoiding and the goal position reaching fundamentally is treated. Namely, defining if – then rule according to the problem the previously is observed as destroying of the consistency of the reached methodology. At the end, the autonomous vehicle mathematical model is used by nonlinear equations describing a 12 state dynamical system and in that case the exposed methodology is applied successfully. The advantage of this approach lies in the fact that a complete path can be defined off-line, without using sophisticated symbolical models of obstacles. The very important characteristic of the MKBC algorithm is symplicity. In the next phase it is expected to confirm results in on-line simulation process.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Behavioral cloning, Kohonen rule, obstacle avoiding, neural network, vehicle path planning.
Aerodynamic Optimization of a Transonic Wing using Grid Computing
by B. H. Dennis, I. N. Egorov
Abstract
- A methodology for aerodynamic design optimization using grid computing is presented. Current design optimization methodologies require substantial computer resources when the analysis code is based on computational fluid dynamics (CFD) analysis. The wall time to complete the optimization can be reduced by employing parallel computer resources. This route requires a numerical optimization algorithm that can effectively distribute the work load in the form of simultaneous design analyses. However, when the optimization problem involves 3-D viscous flow simulation, a single parallel computer cluster may require a week or more to complete the design. The present approach makes use of distributed parallel computing resources, connected to the Internet, or “grid”, to solve a single design optimization problem. Our approach couples a powerful parallel optimization algorithm based on response surfaces, a CFD analysis code, shape generation, and a new software library developed specifically to enable design optimization on computing grids. The methodology is used to optimize the shape of a transonic wing to minimize the drag while maintaining a specified lift and wing volume.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Grid computing, aerodynamic shape optimization, transonic wing, parallel computing.
The Effect of Angular Velocity on Inter-Satellite Links in LEO Satellite Networks
by K. Sidibeh, T. Vladimirova
Abstract
- This paper describes the impact of orbit dynamics on the antenna angular rate required to maintain inter-satellite links (ISL) in Low Earth Orbit (LEO). The main factor affecting ISLs in LEO constellations is the time variant position of the satellites. In order to establish ISLs, it is necessary to determine antenna-pointing requirements such as the azimuth and elevation angles, by calculating the exact positions of the satellites with respect to each other as they move in their orbits. To enable an efficient inter-satellite connectivity between satellites the variation of the orbital characteristics on the inter-satellite link length and antenna design on board LEO satellites must be investigated. The analysis in this paper shows that the angular variation between satellites depends upon constellation design parameters such as the number of planes, the number of satellites per plane and the choice of the crosslink pattern. The selection of the optimal value of the off-viewing angle between satellites in different orbital planes can have a significant impact on the maximum delay, delay variation and antenna angular rate. The rate of change of the angular variation between satellites in different planes increases as the satellites approach the poles causing a surge in the ISL length change rate and a sudden drop in the signal-to-noise ratio. The values of these design parameters should be taken into account in antenna design in order to minimize the ISL length change rate with angular velocities.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
LEO satellite networks, inter-satellite links, angular velocity, antenna design.
by S. Chintalapati, D. R. Kirk
Abstract
- A current problem that severely affects the performance of spacecraft is related to slosh dynamics in liquid propellant tanks under microgravity conditions. Accurate prediction of the slosh dynamics is critical for successful mission planning and may impact vehicle control and positioning during rendezvous, docking, and reorientation maneuvers. The purpose of this work is to assess the performance of various slosh-mitigating baffle designs and configurations using computational fluid dynamics. This work develops metrics, including wall wetting, peak slosh amplitude, and bulk fluid motion, to assess the relevance of a particular baffle geometry and placement within the tank for a prescribed bulk fluid motion over a range of acceleration levels. The two- and three-dimensional studies are used to assess the slosh model’s sensitivity to grid resolution, laminar versus turbulent flow models, and Bond number scaling. The results are used to develop a foundation on which to build a full six-degree-of-freedom dynamic mesh model, allowing for fluid-force interaction with a propellant tank, which will be benchmarked against low-gravity slosh flight data.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Liquid Propellant Rockets, Slosh, Slosh Baffles, CFD, Volume of Fluid Methods.
Effect of Rib on Suddenly Expanded Supersonic Flow
by K. Vijayaraja, S. Elangovan, E. Rathakrishnan
Abstract
- Effect of annular rib on the base pressure and wall pressure field in a suddenly expanded flow in a circular duct has been experimentally studied at Mach 1.6. Both the base pressure and the wall pressure distribution in the enlarged duct are significantly influenced by the location of the rib and the expansion level of the nozzle.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Sudden expansion, base flow, ribs, supersonic flows.
Extended Conventional Finite Element Method vs. Differential Quadrature Method Comparison in Two-dimensional Heat Transfer Problem
by Md. Moslemuddin Fakir, S. Basri, R. Varatharajoo, A. A. Jaafar, A. S. Mohd. Rafie, D. L. A. Majid
Abstract
- Presently there are many numerical solution techniques for solving initial and boundary value problems. Finite element method (FEM) and differential quadrature method (DQM) are two important of those techniques. In this paper, these two methods are applied for the solution of two-dimensional heat transfer problem in a rectangular thin fin and the results are compared. It is found that the results agree very well, moreover FEM sometimes exhibit more accurate results than DQM.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Finite element method, Differential quadrature method, Heat transfer problem.
The Calculation of Axisymmetric Duct Geometries with Hagen-Poiseuille Flow for an Incompressible Fluid
by V. Pavlika
Abstract
-
In this paper a numerical algorithm is described for solving the boundary value
problem associated with axisymmetric, inviscid, incompressible, rotational (and
irrotational) flow in order to obtain duct wall shapes from prescribed wall
velocity distributions. The governing equations are formulated in terms of the
stream function
Ψ(x,y) and the velocity potential function for irrotational flow only φ(x,y) as independent variables where for irrotational flow
φ(x,y)
can be recognized as the velocity potential function, for
rotational flow
φ(x,y)
ceases being the velocity potential function but does remain
orthogonal to the stream lines. A numerical method based on finite differences
using an integral formula on a uniform mesh is employed. The technique described
is capable of tackling the so-called inverse problem where the velocity wall
distributions are prescribed from which the duct wall shape is calculated, as
well as the direct problem where the velocity distribution on the duct walls are
calculated from prescribed duct wall
shapes. The two different cases as outlined in this paper are in fact boundary
value problems with Neumann and Dirichlet boundary conditions respectively. Even
though both approaches are discussed, only numerical results for the case of the
Dirichlet boundary conditions are given. A downstream condition is prescribed
such that cylindrical flow, that is flow which is independent of the axial
coordinate, exists.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Incompressible, Hagen-Poiseuille flow, Upstream conditions and Downstream Cylindrical flow condition, Adjoint equation, Green’s function and Integral Formula.
The Effects of Thermally Induced Residual Stress on the Fatigue Behaviour of Fibre Metal Laminates
by P. P. Krimbalis, C. Poon, Z. Fawaz, K. Behdinan
Abstract
- The focus of this study is the examination and modification of existing analytical models for the calculation of effective stress intensity factor range and prediction of fatigue crack growth rates in GLass REinforced (GLARE) fibre metal laminates (FMLs). The effects of tensile residual stress have been largely unconsidered by existing models and therefore a modified model for calculating effective stress intensity factor range as well as crack propagation rate has been proposed. This modification includes the detrimental tensile residual stresses induced in the aluminum layers as a result of the laminate curing process. A previous model developed with the implementation of the fibre bridging mechanism has also been modified to include residual stress. The results of the analysis agree well with the trends and magnitudes found in the literature, though due to a lack of available experimental data, a direct evaluation of the proposed modifications was not possible.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Fatigue, Fibre Metal Laminates, GLARE, Residual Stress, Stress Intensity Factor.
Steady State Nonlinear Dynamic Response of a Composite Rotor Blade Using Implicit Integration of Intrinsic Equations of a Beam
by M. Ghorashi, F. Nitzsche
Abstract
- An algorithm has been developed for the calculation of the steady state behavior of a rotor blade by solving the nonlinear intrinsic differential equations of motion of a beam. In the process, the steady state form of the intrinsic equations is obtained in the form of a boundary value problem. This problem is then converted into a series of initial value problems where the unknown initial conditions are calculated through an iterative process using the Newton-Raphson method. These correspond to the proper boundary conditions of the original boundary value problem. Having obtained the correct initial and boundary conditions, the steady-state solution, including steady state internal forces and moments, as well as velocities and angular velocities along the blade have been calculated. It is shown that this solution compares very well with the other steady-state solution which has been obtained by an explicit integration algorithm for analyzing the transient form of the nonlinear intrinsic differential equations of motion of a beam.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Implicit integration, intrinsic equations of a beam, Newton-Raphson method, steady state solution, variational asymptotic method.
A Dynamic Finite Element for Coupled Extensional-Torsional Vibration of Uniform Composite Thin-Walled Beams
by S. M. Hashemi, A. Roach
Abstract
- A Dynamic Finite Element (DFE) formulation for the free vibration analysis of extension-torsion coupled uniform composite thin-walled beams is presented. Employing the exact solutions of the differential equations governing the uncoupled vibrations of a uniform beam element, the analytical expressions for extensional and torsional dynamic trigonometric shape functions are derived. By exploiting the principle of virtual work and the frequency-dependent shape functions, the element dynamic stiffness matrix is developed. The application of the theory is demonstrated by a Circumferentially Uniform Stiffness (CUS) composite circular tube for which the influence of ply fibre-angle on the natural frequencies is studied. A variety of CUS configurations are studied and the correctness of the theory and the superiority of the proposed DFE over the conventional FEM methods are confirmed by numerical checks and the published results.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Composite Beam, Extension-Torsion Couplings, Dynamic Finite Element (DFE), Dynamic Stiffness Matrix (DSM), Finite Element Method (FEM), Materially coupled vibrations.
Resonant Frequency of a Rectangular Patch Antenna Using the Asymptotic Entire Domain and Chebychev Polynomial Basis Functions
by A. Boufrioua, A. Benghalia
Abstract
- The moment method technique has been developed to examine the scattering properties of a perfectly conducting microstrip patch which is printed on isotropic or uniaxial anisotropic substrate. The choice of the asymptotic basis functions defined over the patch is illustrated to model the unknown currents. The resonant frequency of a rectangular microstrip patch antenna using these different asymptotic basis functions is investigated. Also the CPU-time for the resonant frequency of a uniaxial anisotropy substrate is presented for these asymptotic currents. Comparisons are made, and show that the utilization of the asymptotic Chebychev basis function provides a significant improvement in the computation time over the sinusoid entire domain forms in the evaluation of the resonant frequency of a microstrip patch antenna. Convergent solutions are in good agreement with the exact sinusoid basis function without edge condition and with those obtained from literature.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Asymptotic, Chebyshev polynomial, Entire domain, Patch antenna.
A Single Amplifier Third Order Butterworth Filter for Aerospace Measurement Applications
by S. A. Whitmore, S. D. Eilers
Abstract
- Design, analysis, and testing of a third order active low-pass Butterworth filter is presented. The design uses a single operational amplifier with an accompanying resistor-capacitor network. Previously, a minimum of two operational amplifiers was required for third order Butterworth response. Idealized filter frequency response is derived and decoupled into first and second order components. Using the decoupled transfer function, a criterion for constructing Butterworth-filter response is derived. Multiple hardware realizations of the filter are constructed, tested, and evaluated. Filters were built using a 741-operational amplifier with standard laboratory-grade resistor-capacitor elements selected at random from a pool of components. When response latency of the operational amplifier is accounted for, the measured filter responses agree well with the idealized response. Monte-Carlo simulations are performed to determine sensitivity of the filter to uncertainties in resistor-capacitor network components. Variations in laboratory results are compared with statistical error predictions and Monte-Carlo simulation results. The filter is demonstrated to have excellent robustness with respect to uncertainties in the resistor-capacitor filter components. Flat pass-band frequency response, construction simplicity, and robustness to component uncertainties, make this filter ideally suited for measurement anti-aliasing applications where multiple channels must be simultaneously filtered prior to sampling.
Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Butterworth Filter, Operational Amplifier, Anti-aliasing.
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