Iterative Stokes Solvers in the Harmonic Velte Subspace

We explore the prospects of utilizing the decomposition of the function space (H ¹ ₀) ⁿ (where n=2,3) into three orthogonal subspaces (as introduced by Velte) for the iterative solution of the Stokes problem. It is shown that Uzawa and Arrow-Hurwitz iterations – after at most two initial steps – can proceed fully in the third, smallest subspace. For both methods, we also compute optimal iteration parameters. Here, for two-dimensional problems, the lower estimate of the inf-sup constant by Horgan and Payne proves useful and provides an inclusion of the spectrum of the Schur complement operator of the Stokes problem. We further consider the conjugate gradient method in the third Velte subspace and derive a corresponding convergence estimate. Computational results show the effectiveness of this approach for discretizations which admit a discrete Velte decomposition. Received June 11, 1999; revised October 27, 2000     

Statistical reconstruction of random point patterns

A general reconstruction method is described which simulates point patterns possessing prescribed summary characteristics, which are free of explicit model conditions. The characteristics are for instance the intensity, the L-function, the spherical contact distribution function and the kth nearest neighbour distance distributions. The use of the statistical reconstruction method is demonstrated on both a theoretical and practical example.     

Force distribution analysis in loaded planar disc systems by means of FEM

This paper presents results of mechanical analyses of force distributions in three geometrically different loaded planar disc systems. For the calculations the disc systems are replaced by mechanically equivalent beam systems, and FEM then yields the contact forces in a simple way. There is a big influence of the geometrical arrangement of discs on force transmission and of disc diameters on the magnitudes of contact forces. The statistical analyses lead to a new probability distribution for the contact forces, namely the distribution of the absolute value of a Gaussian random variable. Received: 13 December 2001     

Variable distance absolute reflectometry

In many interferometric applications the variation of the reflected light intensity due to the separation distance change between two optical systems is the raw signal from which some unknown parameters must be determined. We consider the general situation in which the signal offset and amplification, the initial separation, and the optical properties of one of the systems are unknown. Using some major results from the complex analysis we derive closed-form expressions that give the exact solution of the above inverse problem in terms of the signal's Fourier coefficients. It is shown that the absolute reflectivity can be found unambiguously, while the initial separation and the reflectance phase are mutually correlated and one of these parameters can be found only if the other one is known.     

Verification of the VVER-440 pressure vessel neutron fluence calculation by activity measurement

To qualify the calculation methodology, measurements of neutron flux responses of a VVER-440/230 reactor pressure vessel have been carried out.The activity of shavings sampled out from the inner pressure vessel wall of Unit 1 of Kozloduy NPP after the 14th cycle has been measured. Calculation of the expected activity at the shaving positions has been carried out, taking into account the local power distribution. Comparison of calculated and measured activity values has indicated that the computed value for the fast neutron fluence is underestimated by up to 20%.     

Optimization of 3D Objects Layout into a Multiply Connected Domain with Account for Shortest Distances

The layout of 3D objects into a multiply connected domain formed by a circular cylinder and right rectangular prisms is optimized. Constraints are imposed on the shortest distances between objects. In order to construct a mathematical model, the Φ-function technique is employed. A special approach is proposed to construct different starting points. The approach is based on solving an auxiliary problem with an increased dimension of the solution space. The numerical examples are given.     

Neural Networks to model the innovativeness perception of co-creative firms

Value co-creation is an emerging business, marketing and innovation paradigm describing the firms aptitude to adopt practices enabling their customers to become active participants in the design and development of personalised products, services and experiences. The main objective of our contribution is to make a quantitative analysis in order to assess the relationship between value co-creation and innovation in technology-driven firms: we are using Artificial Neural Network (ANN) to investigate the relationship between value co-creation and innovativeness, and Self Organising Map (SOM) models to cluster firms in terms of their degree of involvement in co-creation and innovativeness. Results from the ANN show that a strong relationship exists between value co-creation and innovativeness; furthermore, SOM are well performing in identifying cluster of firms that are more involved in co-creation values. Our work makes a methodological contribution by adopting and validating a combination of techniques that is able to address complexity and emergence in value co-creation systems.