The Rikitake Two-Disk Dynamo System and Domains with Periodic Orbits

The Rikitake two-disk dynamo system is a simplemodel to describe the earth's magnetic field. We derivethe conditions to find periodic orbits of this systemusing an ellipsoid bounding condition. We prove that the conditions cannot besatisfied.     

Soft boundary layers in polymeric films

Application of a polymer on a substrate, e. g. a metal sheet, generates a boundary layer in the polymer. In this boundary layer the properties of the polymer differ from the bulk properties. In the present contribution a mechanical theory based on a structural parameter is presented that allows for the existence of such interphases and, therefore, leads to effective material properties depending on the thickness of the layer. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Lorentz invariance of wave equations and galilean invariance of diffusion equations

The Lorentz invariance of a certain class of wave equations and on the other hand the galilean invariance of a certain class of diffusion equations is discussed.     

Relativistic classical mechanics and canonical formalism

The analysis of interacting relativistic many-particle systems provides a theoretical basis for further work in many diverse fields of physics. After a discussion of the nonrelativisticN-particle systems we describe two approaches for obtaining the canonical equations of the corresponding relativistic forms. A further aspect of our approach is the consideration of the constants of the motion.     

A non-destructive internal nuclear forensic investigation at Argonne: discovery of a Pu planchet from 1948

A plutonium alpha standard dating from 1948 was discovered at Argonne National Laboratory and characterized using a number of non-destructive analytical techniques. The principle radioactive isotope was found to be ²³⁹Pu and unique ring structures were found across the surface of the deposition area. Due to chronological constraints on possible sources and its high isotopic purity, the plutonium in the sample was likely produced by the Oak Ridge National Lab X-10 Reactor. It is proposed that the rings are resultant through a combination of polishing and electrodeposition, though the hypothesis fails to address a few key features of the ring structures.

     

Analysis and modeling of the hydro-mechanics of deformable fractures

In the present contribution, we investigate and model the flow of a viscous fluid into a single deformable fracture and the associated elastic deformation of the surrounding porous rock. Due to the coupled nature of the problem, conceptually and technically different strategies can be applied to model and solve the resulting hydro-mechanical system. Therefore, two different modeling approaches are analyzed. On the one hand, we derive the governing equations from the conservation of mass avoiding any of the frequently used approximations or simplifications. On the other hand, we describe the physics based on Biot's quasi-static poroelastic equations. We compare and critically discuss the results obtained with the presented different solution approaches. The results show that both models are able to capture the same physical effects, also those caused by the fracture deformation. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On response functions in linear thermoelastic models of shape memory polymers

This paper is concerned with the broad class of Liner Thermoelastic (LTE) models for Shape Memory Polymers (SMPs) which unifies numerous constitutive theories proposed in the literature for this kind of smart material. It is shown that the response functions for the general model of this class may be determined directly from experimental data measured in standard thermomechanical cyclic tests. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microscopical investigation of wave propagation phenomena in residual saturated porous media

Wave propagation is used in many fields for measurement and characterization. Corresponding multiphase models usually use a continuous approach. Nevertheless, systems like wetted rocks may be saturated residually in certain situations. In such cases, one fluid is distributed as clusters, each different in size and shape. One single, continuous phase cannot account for a variety of fluid clusters, either disconnected from each other or connected only about thin liquid films. Therefore, we present a model that considers a heterogeneous distribution of disconnected fluid clusters in the form of harmonic oscillators. These oscillators are described and distinguished by their mass, damping and eigenfrequency. Hence, the model allows to characterize different clusters and includes an additional damping mechanism due to oscillations of the fluid clusters. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microseparations of cesium and barium in glass

A chemical micro-separation of Cs and Ba in complex glass with a high lanthanide content is presented. High purity silica, with and without Cs and Ba fortification, was subjected to identical dissolution, microseparation, and analysis as a control glass matrix. Dissolution was performed with hot concentrated nitric and hydrofluoric acids followed by fluoride complexation with boric acid, evolution of excess boric acid as methyl borate, and finally conversion to soluble nitrate species in 3 M nitric acid. Separation was performed with a miniature gas pressurized extraction chromatography system using a column packed with Eichrom Sr resin^™. High purity 3 M nitric acid was used to rinse Cs through the column and high purity 1% acetic acid was used to strip Ba from the resin. Quantitative recovery of both Cs (99.5 ± 0.7%) and Ba (99.1 ± 2.0%) was achieved in the lanthanide glass matrix and no statistically significant difference was observed in Cs or Ba recovery in the control high purity silica.