Cette étude traite de la simulation numérique desécoulements à haute enthalpie en non-équilibrethermochimique. La résolution des équations2D-axisymétrique de Navier-Stokes permet de prévoirnumériquement la structure d'un écoulement réactif,partiellement ionisé. La méthode numérique repose surune formulation de type volume fini couplée à l'approcheMUSCL-TVD et est associée à un solveur de Riemann.L'intérêt est porté sur la contribution desdifférents phénomènes de non-équilibre sur le fluxde chaleur et les paramètres thermodynamiques.L'écoulement est externe et s'effectue autour du nez d'unsphère-cylindre se déplaçant avec des nombres de Machcompris entre 15 et 18. Les résultats obtenus sont en bonaccord avec lesvaleurs prédites par d'autres simulations et les données expérimentales.

Computer programming is ideal for the identification of ticks. This is due to the ability of computers to make rapid, repeated and complete searches of a large database of features in answer to a series of questions which lead to a single species. The program can allow the search to start in any order and to avoid difficult questions. It enables illustrations to be displayed when a question is asked. In contrast, classical dichotomous keys need to be used in a fixed sequence in which it is difficult to avoid questions, and often use vaguely defined characters and obscure language. To program an electronic key a character state matrix is constructed of rows of precisely defined characters with the two or more states in which they may occur and of columns in which the species are placed. Each state is recorded as being positive or negative. This corresponds to the binary system needed for computing and this need enforces a discipline on the identification method that has to define in illustrations and precise standardized language the characters and their states. These concepts are illustrated by the development of ‘Multikey’ program for the identification of ticks of domestic animals in Africa. The advantages of Multikey are its ease of use, its compatibility with comprehensive tick guides on compact discs and the ability to expand it with more information. The disadvantages are the requirement for a computer next to the laboratory microscope and the difficulty in browsing the contents. These disadvantages can be overcome by a printed version and there is use for both the printed and the electronic versions of such guides.

There is still fierce debate in the international community regarding the use and standards of electronic chart data and equipment. Whilst the standards for ecdis are now virtually complete and type-approved equipment will be entering the market during 1998, there is currently no IMO/IHO compliant enc data service from any national hydrographic office. It is expected that it will be 1 to 2 years before there is any appreciable quantity of enc data supported by a proper update service. It will be many more years before enc data becomes available to match the present coverage of paper charts, but we can expect that most major routes and the port entries of the majority of the world's trading nations will be available within a few years. This situation is examined, together with the ideas that IMO is considering to improve the availability of official electronic chart data. In addition, the distribution of electronic charts is discussed and the future trends in navigation that will occur with the availability of ecdis equipment and related data are explored.