0000000000684086
AUTHOR
David Thompson
Eulerian models of the rotating flexible wheelset for high frequency railway dynamics
Abstract In this paper three formulations based on an Eulerian approach are presented to obtain the dynamic response of an elastic solid of revolution, which rotates around its main axis at constant angular velocity. The formulations are especially suitable for the study of the interaction of a solid with a non-rotating structure, such as occurs in the coupled dynamics of a railway wheelset with the track. With respect to previous publications that may adopt similar hypotheses, this paper proposes more compact formulations and eliminates certain numerical problems associated with the presence of second-order derivatives with respect to the spatial coordinates. Three different models are dev…
Atomic layer deposition of Ru films from bis(2,5-dimethylpyrrolyl)ruthenium and oxygen
Abstract Ru thin films were grown on hydrogen terminated Si, SiO 2 , Al 2 O 3 , HfO 2 , and TiO 2 surfaces by atomic layer deposition from bis(2,5-dimethylpyrrolyl)ruthenium precursor and oxygen. The 4–20 nm thick films on these surfaces consisted of nanocrystalline hexagonal metallic ruthenium, regardless of the deposition temperature. At the lowest temperatures examined, 250–255 °C, the growth of the Ru films was favored on silicon, compared to the growth on Al 2 O 3 , TiO 2 and HfO 2 . At higher temperatures the nucleation and growth of Ru became enhanced in particular on HfO 2 , compared to the process on silicon. At 320–325 °C, no growth occurred on Si–H and SiO 2 -covered silicon. Res…
The current planetary crisis: a missing dimension in science education
The origin of our research has been the intuition that, in spite of some dramatic calls of United Nations experts, the attention paid by science education research to the study of citizens’ awareness of the state of the world and of the danger of an irreversible degradation of life in our Planet, has been very poor. Our work intends to clarify to what extent this essential issue in the education of future decision-making citizens is adequately dealt with in science education research. With this purpose, we have posed open questions to several hundreds of science teachers in training and in service about “problems and challenges that humanity has to face” and we have analysed the content of …