Wechselwirkung zwischen Blei(II)-Ionen und hydratisiertem γ-Al2O3

Ohne Zusammenfassung     

Ab initio molecular dynamics — Applications to the molecular and solid state physics of phosphorus

Summary We review combined molecular dynamics (MD) and density functional (DF) simulations and their applicability in chemistry and physics. This method (also termedab initio MD, first principles MD or Car-Parrinello method) exhibits characteristic strengths and weaknesses, and we demonstrate both in a set of typical example applications from molecular physics (phosphorus clusters) and solid state physics/chemistry (liquid phosphorus). Dynamical, finite temperature, simulations deriving interatomic forces from state-of-the-art density functional calculations represent a substantial advance over both (i) traditional pointwise total energy and electronic band structure calculations and (ii) classical MD simulations with empirical or semi-empirical forces, and have already yielded qualitatively new insights in several fields.     

The vibrational behaviour of bladed disks with multiple coupling devices

In turbomachinery applications turbine blades are subjected to high static and dynamic loads. Static loads are due to centrifugal stresses and thermal strains. Especially the dynamic excitation caused by fluctuating gas forces results in high vibration amplitudes which can lead to high cycle fatigue failures (HCF). Therefore, in practical applications, coupling devices like underplatform dampers, lacing wires and tip shrouds are installed to the structure. In case of blade vibrations the relative displacements between these coupling devices and the blades generate friction forces. The resulting energy dissipation provides additional damping to the structure. Furthermore, coupling devices, in particular tip shrouds, snubbers and lacing wires, increase the stiffness of the structure. Hence, they lead to a shift of the resonance frequencies. So far, only effects of single coupling devices and the influencing properties have been examined. Within this paper the effect of multiple couplings is determined and compared with single couplings. The forced response of turbine bladings with multiple couplings is calculated under consideration of geometrical and mechanical parameters of the blading and contacts, respectively. The results are compared with the single coupled blading. Furthermore, a multiple coupled device with under-platform damper and connecting pin is compared with respect to his effectiveness. Especially the influence on the resonance frequency and the achievable damping is analysed. The results of the simulation are verified by measurements at a two-blade non-rotating test rig with an underplatform damper and connecting pin. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Die Herstellung von Reinstsiliciumscheiben: Mehr Chemie als man glaubt

Monocrystalline semiconductor wafers made of silicon represent the base material for microelectronic devices. The transfer of the precursor material quartz into a 300 mm wafer deposited with an epitaxial layer requires a multitude of process steps, part of which are determined by chemical reactions. This article has introduced into the manufacturing of semiconductor silicon and the processes etching, polishing, cleaning and epitaxy. This technology branch, though, is distinguished by extreme requirements regarding surface perfection and cleanliness, which may be expressed in atomic layers (surface roughness of the wafers) and ppt (contamination of chemicals)     

Military terrain vehicles

The author gives a survey of the historical background, current developments and future aspects of the most important wheeled and tracked military terrain vehicle systems focusing, in particular, on their automotive technological performance as well as on their tactical features. Weapon systems, radio and other military equipment are not part of this survey.This paper does not cover niche products such as over-snow and amphibious vehicles which are also used for military purposes. However, hybrid propulsion systems are included.     

X-ray Raman scattering at the Si LII,III-edge of bulk amorphous SiO

X-ray Raman spectra of bulk amorphous SiO have been measured at energy losses around the Si L_II,III-edges for different momentum transfers at beamline ID16 of ESRF. The spectra are compared with measurements of the L_II,III-edges of Si powder and with results of first-principles calculations for Si and α-quartz SiO₂. Indications of sub-oxidic contributions to the L_II,III-edges are found in the experiment and discussed with respect to the model of interface clusters mixture in bulk amorphous SiO.     

Bioactivity-Based Analysis of Sunscreens Using the Luminescent Bacteria Vibrio fischeri

JPC – Journal of Planar Chromatography – Modern TLC - Sunscreen products are meant to protect people from damaging UVA and UVB radiation. However, in some formulations the UV filters...