5,454 research outputs found
An assembly oriented design framework for product structure engineering and assembly sequence planning
The paper describes a novel framework for an assembly-oriented design (AOD) approach as a new functional product lifecycle management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently. Integration issues of product life cycle into the product development process have received much attention over the last two decades, especially at the detailed design stage. The main objective of the research is to define assembly sequence into preliminary design stages by introducing and applying assembly process knowledge in order to provide an assembly context knowledge to support life-oriented product development process, particularly for product structuring. The proposed framework highlights a novel algorithm based on a mathematical model integrating boundary conditions related to DFA rules, engineering decisions for assembly sequence and the product structure definition. This framework has been implemented in a new system called PEGASUS considered as an AOD module for a PLM system. A case study of applying the framework to a catalytic-converter and diesel particulate filter sub-system, belonging to an exhaust system from an industrial automotive supplier, is introduced to illustrate the efficiency of the proposed AOD methodology
On Role Logic
We present role logic, a notation for describing properties of relational
structures in shape analysis, databases, and knowledge bases. We construct role
logic using the ideas of de Bruijn's notation for lambda calculus, an encoding
of first-order logic in lambda calculus, and a simple rule for implicit
arguments of unary and binary predicates. The unrestricted version of role
logic has the expressive power of first-order logic with transitive closure.
Using a syntactic restriction on role logic formulas, we identify a natural
fragment RL^2 of role logic. We show that the RL^2 fragment has the same
expressive power as two-variable logic with counting C^2 and is therefore
decidable. We present a translation of an imperative language into the
decidable fragment RL^2, which allows compositional verification of programs
that manipulate relational structures. In addition, we show how RL^2 encodes
boolean shape analysis constraints and an expressive description logic.Comment: 20 pages. Our later SAS 2004 result builds on this wor
New approach to nonrelativistic ideal magnetohydrodynamics
We provide a novel action principle for nonrelativistic ideal
magnetohydrodynamics in the Eulerian scheme exploiting a Clebsch-type
parametrisation. Both Lagrangian and Hamiltonian formulations have been
considered. Within the Hamiltonian framework, two complementary approaches have
been discussed using Dirac's constraint analysis. In one case the Hamiltonian
is canonical involving only physical variables but the brackets have a
noncanonical structure, while the other retains the canonical structure of
brackets by enlarging the phase space. The special case of incompressible
magnetohydrodynamics is also considered where, again, both the approaches are
discussed in the Hamiltonian framework. The conservation of the stress tensor
reveals interesting aspects of the theory.Comment: 20 pages, LaTeX, a new section on incompressible MHD included,
published in Eur. Phys. J.
- …