Thermal Conductivity and Thermal Expansion Coefficients of the Lanthanum Rare-Earth-Element Zirconate System

To enhance the insulating properties of a thermal barrier coating, one has to focus on new materials with lower intrinsic thermal conductivity than established yttria-stabilized zirconia. Substances with pyrochlore structure were investigated. Starting from lanthanum zirconate, substitutions of the lanthanum by other trivalent rare-earth elements were made, and the thermal conductivity and the thermal expansion coefficient of the manufactured materials were measured. A complete substitution of the lanthanum led to increased thermal expansion coefficients, whereas the partial substitution did not show an appreciable effect. The thermal conductivities of the modified materials were lower than that of the pure lanthanum zirconate for temperatures <1000°C for all amounts and elements of substitution. A comparison of the observed values with calculated values of the thermal conductivities showed a relatively good agreement.     

Infrared Reflection Spectroscopy of Polycyanurate Thin Films on Solids-State of the Interphase

FTIR reflection spectroscopy was used to characterize thin films of a cyanurate prepolymer on evaporated aluminium and on silicon single crystal wafers. Both substrates are covered by their native oxides. The optical function of the prepolymer is derived from ATR measurements. The measured thin film reflectance spectra have to be interpreted in comparison with the corresponding bulk spectra obtained by simulation. All samples re-produce the bulk composition. The cyanate groups of the prepolymer are not involved in specific intermolecular interactions or in preferential orientation. This is also found for the triazine rings on Si. On Al, however, a considerable excess of triazine rings are oriented parallel to the interface. The vibration frequencies of the triazine groupings that are perpendicular to the Al substrate show a red shift to some 2-8 c^-1. This special interaction effect does not occur on Si. Both the preferential orientation and the specific inter-molecular interaction act at least 100 nm into the prepolymer layer.     

Einführung in Informationssicherheitsmanagementsysteme (IV): Vereinfachte IT-Risikoanalyse

Zusammenfassung  Zum Abschluss unserer Serie wollen wir an einem praktischen Beispiel zeigen, welche grundlegenden Arbeitsschritte bei der Einführung eines ISMS bzw. seiner jeweiligen Teile zu absolvieren sind. Dipl.-Ing. Detlef Kilian ist Senior Consultant bei der Controlware AG in Hannover.     

Numerical analysis of dissolution processes in cementitious materials using discontinuous and continuous Galerkin time integration schemes

The present paper is concerned with the numerical integration of non‐linear reaction–diffusion problems by means of discontinuous and continuous Galerkin methods. The first‐order semidiscrete initial value problem of calcium leaching of cementitious materials, based on a phenomenological dissolution model, an electrolyte diffusion model and the spatial p‐finite element discretization, is used as a highly non‐linear model problem. A p‐finite element method is used for the spatial discretization. In the context of discontinuous Galerkin methods the semidiscrete mass balance and the continuity of the primary variables are weakly formulated within time steps and between time steps, respectively. Continuous Galerkin methods are obtained by the strong enforcement of the continuity condition as special cases. The introduction of a natural time co‐ordinate allows for the application of standard higher order temporal shape functions of the p‐Lagrange type and the well‐known Gauss–Legendre quadrature of associated time integrals. It is shown, that arbitrary order accurate integration schemes can be developed within the framework of the proposed temporal p‐Galerkin methods. Selected benchmark analyses of calcium dissolution demonstrate the robustness of these methods with respect to pronounced changes of the reaction term and non‐smooth changes of Dirichlet boundary conditions. Copyright © 2006 John Wiley & Sons, Ltd.     

Binary decision diagrams in theory and practice

Decision diagrams (DDs) are the state-of-the-art data structure in VLSI CAD and have been successfully applied in many other fields. DDs are widely used and are also integrated in commercial tools. This special section comprises six contributed articles on various aspects of the theory and application of DDs. As preparation for these contributions, the present article reviews the basic definitions of binary decision diagrams (BDDs). We provide a brief overview and study theoretical and practical aspects. Basic properties of BDDs are discussed and manipulation algorithms are described. Extensions of BDDs are investigated and by this we give a deeper insight into the basic data structure. Finally we outline several applications of BDDs and their extensions and suggest a number of articles and books for those who wish to pursue the topic in more depth. Published online: 15 May 2001     

Sichere Internet-Zahlungsdienste durch starke Kundenauthentifizierung?

Die europäischen Aufsichtsbehörden haben dem Betrug im Internet-Zahlungsverkehr den Kampf angesagt. Aufsichtsrelevante Sicherheitsvorgaben sollen in Europa für ein einheitlich hohes Schutzniveau sorgen. Eine zentrale Sicherheitsanforderung besteht darin, dass die sogenannte starke Kundenauthentifizierung verpflichtend wird. Doch können dadurch wirklich Schäden nachhaltig reduziert und das Vertrauen in Internet-Zahlungsdienste gesteigert werden?