Numerical Simulation of Water Circulation In Marinas of Complex Geometry By A Multi-block Technique

International audienceThis paper presents a finite-volume method for solving the Shallow-Water Equations (SWE) in a curvilinear coordinate system on an arbitrary overlapping composite grids. A multi-block technique is implemented. The academic tests are also presented to validate the proposed technique. A typical application of this technique is the simulation of water circulation in marinas and harbor

Accelerated Data-Flow Analysis

Acceleration in symbolic verification consists in computing the exact effect of some control-flow loops in order to speed up the iterative fix-point computation of reachable states. Even if no termination guarantee is provided in theory, successful results were obtained in practice by different tools implementing this framework. In this paper, the acceleration framework is extended to data-flow analysis. Compared to a classical widening/narrowing-based abstract interpretation, the loss of precision is controlled here by the choice of the abstract domain and does not depend on the way the abstract value is computed. Our approach is geared towards precision, but we don't loose efficiency on the way. Indeed, we provide a cubic-time acceleration-based algorithm for solving interval constraints with full multiplication

Applications of Polyhedral Computations to the Analysis and Verification of Hardware and Software Systems

Convex polyhedra are the basis for several abstractions used in static analysis and computer-aided verification of complex and sometimes mission critical systems. For such applications, the identification of an appropriate complexity-precision trade-off is a particularly acute problem, so that the availability of a wide spectrum of alternative solutions is mandatory. We survey the range of applications of polyhedral computations in this area; give an overview of the different classes of polyhedra that may be adopted; outline the main polyhedral operations required by automatic analyzers and verifiers; and look at some possible combinations of polyhedra with other numerical abstractions that have the potential to improve the precision of the analysis. Areas where further theoretical investigations can result in important contributions are highlighted.Comment: 51 pages, 11 figure

FORMULAE AND ASYMPTOTICS FOR COEFFICIENTS OF ALGEBRAIC FUNCTIONS

International audienc

Research reports: 1987 NASA/ASEE Summer Faculty Fellowship Program

For the 23rd consecutive year, a NASA/ASEE Summer Faculty Fellowship Program was conducted at the Marshall Space Flight Center (MSFC). The program was conducted by the University of Alabama in Huntsville and MSFC during the period 1 June to 7 August 1987. Operated under the auspices of the American Society for Engineering Education, the MSFC program, as well as those at other NASA Centers, was sponsored by the Office of University Affairs, NASA Headquarters, Washington, D.C. The basic objectives of the program are: (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of the participant's institutions; and (4) to contribute to the research objectives of the NASA Centers. This document is a compilation of Fellow's reports on their research during the Summer of 1987

A steady-state model of ecological hierarchy

A generalized mathematical model of ecosystems is developed. The model begins with the general class of systems known as state-determined systems, in which the time-derivative of each state variable is a function of some subset of the set of all system state variables and .environmental parameters. A formal basis is presented for considering the steady-state behavior of such systems in terms of isoclines, drawing upon the fields of graph theory, linear algebra, and differential equations. The simplifying capabilities of hierarchy theory are invoked to mitigate the adverse effects of model complexity. Like the theory of isocline analysis, the particular formulation of hierarchy theory presented is phrased in graph-theoretic terms, enabling the model to be developed as a technique for analyzing the steady-state behavior of hierarchical systems. The role of inter-level time scale heterogeneity in hierarchical organization is discussed. As an illustration of its ability to portray the behavior of spatially-nested hierarchies, the model is used to provide a perspective on data from the climax vegetation of the Great Smoky Mountains. The effects of time scale heterogeneity are also illustrated by using the model to organize data sets from several vegetation/avian communities across the United States. The vegetation is taken to behave with a lower characteristic frequency than the relatively rapidly-developing avian subcommunity, thus constraining the latter in a hierarchical fashion. In order to understand in a more general way the role such a model might play in advancing ecological understanding, a broad framework is presented for analyzing the role of conceptual structures in science and the place of models in these structures. A view of models as scientific metaphors is advanced as an alternative to the pictorial/realist interpretation of models. Given this understanding of models in general, the proposed model and its underlying assumptions are compared and contrasted with a set of four partial conceptual structures drawn from the fields of systems ecology, plant ecology, natural resource economics, and organismic systems theory

Bowdoin Orient v.134, no.1-24 (2004-2005)

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