13,780 research outputs found
A Static Analyzer for Large Safety-Critical Software
We show that abstract interpretation-based static program analysis can be
made efficient and precise enough to formally verify a class of properties for
a family of large programs with few or no false alarms. This is achieved by
refinement of a general purpose static analyzer and later adaptation to
particular programs of the family by the end-user through parametrization. This
is applied to the proof of soundness of data manipulation operations at the
machine level for periodic synchronous safety critical embedded software. The
main novelties are the design principle of static analyzers by refinement and
adaptation through parametrization, the symbolic manipulation of expressions to
improve the precision of abstract transfer functions, the octagon, ellipsoid,
and decision tree abstract domains, all with sound handling of rounding errors
in floating point computations, widening strategies (with thresholds, delayed)
and the automatic determination of the parameters (parametrized packing)
Automating the design of scientific computing software
SINAPSE is a domain-specific software design system that generates code from specifications of equations and algorithm methods. This paper describes the system's design techniques (planning in a space of knowledge-based refinement and optimization rules), user interaction style (user has option to control decision making), and representation of knowledge (rules and objects). It also summarizes how the system knowledge has evolved over time and suggests some issues in building software design systems to facilitate reuse
The CIAO multiparadigm compiler and system: A progress report
Abstract is not available
Computational aerodynamics and artificial intelligence
The general principles of artificial intelligence are reviewed and speculations are made concerning how knowledge based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use expert systems, and how expert systems may speed the design and development process. In addition, the anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements for using artificial intelligence in computational fluid dynamics and aerodynamics are examined. Three main conclusions are presented. First, there are two related aspects of computational aerodynamics: reasoning and calculating. Second, a substantial portion of reasoning can be achieved with artificial intelligence. It offers the opportunity of using computers as reasoning machines to set the stage for efficient calculating. Third, expert systems are likely to be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics
Fourier analysis of finite element preconditioned collocation schemes
The spectrum of the iteration operator of some finite element preconditioned Fourier collocation schemes is investigated. The first part of the paper analyses one-dimensional elliptic and hyperbolic model problems and the advection-diffusion equation. Analytical expressions of the eigenvalues are obtained with use of symbolic computation. The second part of the paper considers the set of one-dimensional differential equations resulting from Fourier analysis (in the tranverse direction) of the 2-D Stokes problem. All results agree with previous conclusions on the numerical efficiency of finite element preconditioning schemes
Concurrent Image Processing Executive (CIPE). Volume 1: Design overview
The design and implementation of a Concurrent Image Processing Executive (CIPE), which is intended to become the support system software for a prototype high performance science analysis workstation are described. The target machine for this software is a JPL/Caltech Mark 3fp Hypercube hosted by either a MASSCOMP 5600 or a Sun-3, Sun-4 workstation; however, the design will accommodate other concurrent machines of similar architecture, i.e., local memory, multiple-instruction-multiple-data (MIMD) machines. The CIPE system provides both a multimode user interface and an applications programmer interface, and has been designed around four loosely coupled modules: user interface, host-resident executive, hypercube-resident executive, and application functions. The loose coupling between modules allows modification of a particular module without significantly affecting the other modules in the system. In order to enhance hypercube memory utilization and to allow expansion of image processing capabilities, a specialized program management method, incremental loading, was devised. To minimize data transfer between host and hypercube, a data management method which distributes, redistributes, and tracks data set information was implemented. The data management also allows data sharing among application programs. The CIPE software architecture provides a flexible environment for scientific analysis of complex remote sensing image data, such as planetary data and imaging spectrometry, utilizing state-of-the-art concurrent computation capabilities
Transformation Acoustics in Generic Elastic Media
In this work a transformation acoustics scheme for generic elastic media is
developed. Our approach starts form the decomposition of the elasticity tensor
in terms of its eigentensors, an idea previously used by Norris. While Norris'
transformation acoustics is restricted to the special class of so-called
pentamode materials, we show that a similar scheme can be defined for the most
general elasticity tensor. As in case of Norris' model (and in sharp contrast
to transformation optics), the compatibility equations of the transformation
medium are not purely algebraic and it is not guaranteed that solutions to
these equations exist for any choice of material parameters and coordinate
transformation. Nonetheless, it is shown that our scheme yields new cloaking
solutions for certain classes of materials. In particular, we present the first
application of a transformation based device for a non-scalar wave equation
outside of the field of electromagnetics.Comment: 14 pages, LaTe
Finite element analysis of a deployable space structure
To assess the dynamic characteristics of a deployable space truss, a finite element model of the Scientific Applications Space Platform (SASP) truss has been formulated. The model incorporates all additional degrees of freedom associated with the pin-jointed members. Comparison of results with SPAR models of the truss show that the joints of the deployable truss significantly affect the vibrational modes of the structure only if the truss is relatively short
Fusion in conformal field theory as the tensor product of the symmetry algebra
Following a recent proposal of Richard Borcherds to regard fusion as the
ring-like tensor product of modules of a {\em quantum ring}, a generalization
of rings and vertex operators, we define fusion as a certain quotient of the
(vector space) tensor product of representations of the symmetry algebra . We prove that this tensor product is associative and symmetric up to
equivalence. We also determine explicitly the action of on it, under
which the central extension is preserved. \\ Having given a precise meaning to
fusion, determining the fusion rules is now a well-posed algebraic problem,
namely to decompose the tensor product into irreducible representations. We
demonstrate how to solve it for the case of the WZW- and the minimal models and
recover thereby the well-known fusion rules. \\ The action of the symmetry
algebra on the tensor product is given in terms of a comultiplication. We
calculate the -matrix of this comultiplication and find that it is
triangular. This seems to shed some new light on the possible r\^{o}le of the
quantum group in conformal field theory.Comment: 21 pages, Latex, DAMTP-93-3
- …