Air transport in Africa: toward sustainable business models for African airlines

Although there is a vast amount of literature on airline business models and their evolution in changing global landscapes, there is a general lack of research into the applicability of those models, traditionally defined in European and North American contexts, to the African scene. Implicit in this study is the hypothesis that the African environment is unique enough to warrant its own host of strategies, which may be distinctive enough to form part of a new strategic template, or business model. Initially, a review of existing literature is undertaken to profile the African aviation environment and evaluate existing airline business models and their evolution, both globally and in Africa. The methodology consists firstly of a cluster exercise, whereby 57 African airlines are analysed in terms of their network and size, to yield a number of heterogeneous groups which serve to identify the current business models of airlines on the continent. Following this, eight airlines (representative of the groups outlined in the cluster analysis) were subsequently selected for analysis in terms of the Product and Organisational Architecture framework. While it was evident that the traditional models are followed in Africa, in some instances variations were apparent. Full-service network carriers and regional carriers were concluded as being the most prominent and stable in the African market. The applicability of the low-cost carrier model in Africa was also examined at length, with mixed results. The analysis also raised network density and connectivity as essential components of business models for delivering profits in an African context

Description of GADEL

This article describes the first implementation of the GADEL system : a Genetic Algorithm for Default Logic. The goal of GADEL is to compute extensions in Reiter's default logic. It accepts every kind of finite propositional default theories and is based on evolutionary principles of Genetic Algorithms. Its first experimental results on certain instances of the problem show that this new approach of the problem can be successful.Comment: System Descriptions and Demonstrations at Nonmonotonic Reasoning Workshop, 2000 6 pages, 2 figures, 5 table

Vertical Structure and Strategic Environmental Trade Policy

The idea that environmental trade policy may be used to achieve competitive advantage in international markets has important implications for the way we conceive tree-trade. This paper reconsiders the issue of strategic environmental policy in a model that makes explicit the vertical structure that supports production of the traded good. We find these intranational vertical relationships to have a substantial qualitative effect on the optimal strategic environmental trade policy. We show that under both quantity and price competition in the international market, the optimal policy to levy on the polluting input when vertical contracts are allowed is a Pigouvian tax.strategic trade, vertical contracts, environmental policy

Ramanujan sums as supercharacters

The theory of supercharacters, recently developed by Diaconis-Isaacs and Andre, can be used to derive the fundamental algebraic properties of Ramanujan sums. This machinery frequently yields one-line proofs of difficult identities and provides many novel formulas. In addition to exhibiting a new application of supercharacter theory, this article also serves as a blueprint for future work since some of the abstract results we develop are applicable in much greater generality.Comment: 32 pages. Comments welcom

Behavioural Interventions for Obese Adults with Additional Risk Factors for Morbidity : Systematic Review of Effects on Behaviour, Weight and Disease Risk Factors

Peer reviewedPostprin

Macroeconomic Uncertainty and Firm Leverage

This paper investigates the link between the optimal level of nonfinancial firms' leverage and macroeconomic uncertainty. We develop a structural model of a firm's value maximization problem that predicts that as macroeconomic un-certainty increases the firm will decrease its optimal level of borrowing. We test this proposition using a panel of non{financial US firms drawn from the COM-PUSTAT quarterly database covering the period 1991{2001. The estimates confirm that as macroeconomic uncertainty increases, firms decrease their levels of leverage. Furthermore, we demonstrate that our results are robust with respect to the inclusion of the index of leading indicators.Leverage; Uncertainty; Non-financial firms; Panel data

Optimal control of electromagnetic field using metallic nanoclusters

The dielectric properties of metallic nanoclusters in the presence of an applied electromagnetic field are investigated using non-local linear response theory. In the quantum limit we find a non-trivial dependence of the induced field and charge distribution on the spatial separation between the clusters and on the frequency of the driving field. Using a genetic algorithm, these quantum functionalities are exploited to custom-design sub-wavelength lenses with a frequency controlled switching capability.Comment: accepted for publication in New Journal of Physic