Asymptotically exact a posteriori error estimator for biquadratic elements

This paper addresses the finite element method with a posteriori error estimation for elements of degree p = 1 and p = 2. It gives the formulae for the error indicators and error estimators. Basic mathematical characterizations of the estimators are given and it is shown that the estimators for p = 1 and p = 2 have different structures. Numerical examples show the effectivity of the approach and the high quality of the estimator.     

The μ-dependence of the effective weak Hamiltonian andK→2π amplitudes in chiral-bag model

This paper studies the μ-dependence of the operator matrix elements. Although the μ-dependence must in principle cancel as illustrated in the paper by using a simple pedagogical model, in practice the choice of μ markedly influences the theoretical predictions forK→2π decays.     

Spannungsdoppelbrechung an Hydrogelen des Mineralreichs

Ohne Zusammenfassung     

A formal apparatus for modeling trust in computing environments

Recent research in computer systems security has evolved into trust issues, which are now becoming an important topic. The majority of approaches for trust modeling addressed trust by actually focusing on security, and some of them addressed also trust as such. This paper presents a formal apparatus that concentrates on trust as such. It is flexible enough to accommodate the driving factors behind trust and consequently different trust-focused methodologies and technologies. The basic goal of the work presented in this paper is the definition of qualitative trust modeling methodology for trust management in contemporary computing environments that efficiently complements existing quantitative methodologies. Further, an open conceptual model for trust management is presented that accommodates various qualitative and quantitative trust management methodologies. This model has also been implemented in the web services environment, and this is discussed in this paper as well.     

An acceleration of Erlenkotter-Körkel’s algorithms for the uncapacitated facility location problem

This contribution is focused on an acceleration of branch and bound algorithms for the uncapacitated facility location problem. Our approach is based on the well-known Erlenkotters’ procedures and Körkels’ multi-ascent and multi-adjustment algorithms, which have proved to be the efficient tools for solving the large-sized instances of the uncapacitated facility location problem. These two original approaches were examined and a thorough analysis of their performance revealed how each particular procedure contributes to the computational time of the whole algorithms. These analyses helped us to focus our effort on the most frequent procedures. The unique contribution of this paper is a new dual ascent procedure. This procedure leads to considerable acceleration of the lower bound computation process and reduces the resulting computational time. To demonstrate more efficient performance of amended algorithms we present the results of extensive numerical experiments.     

Characterization of surface-active substances during a semi-field experiment on a phytoplankton bloom

The determination of surface-active substances (SAS) during the evolution of a phytoplankton bloom in a model plankton ecosystem was done by electrochemical methods. The separation and characterization of the organic material present were also done on XAD-8 resin columns. It was found that large amounts of the SAS, predominantly of the humic (fulvic) type, were present from the beginning of the experiment and partly masked the effects of organic substances released by phytoplankton. Although the transformation of the organic matter (consumption and/or excretion) was obvious, no general trend in the amount or type of surface-active matter was observed during the experiment.