Verformungsvorgänge bei erosiver Beanspruchung und ihre Beeinflussung durch korrosive Medien

Deformation processes by erosive treatment and influences of corrosive media As a result of our solid impact experiments on steel increased wear was established, if aqueous media are added to the particle stream. Because of the absence of any corrosion mark on the worn surfaces in SEM topography changed deformation behaviour was supposed as the cause of the enhanced material loss. This paper deals with a survey of the deformation mechanisms of the erosive surface damage. Environmental influences of deformation processes are discussed by experimental results and by a literature review.     

Functionalized polyisobutenes by SH-en addition

Low molecular weight polyisobutenes can be transformed into macromonomers by means of SH-en addition, provided that the thiols contain an additional hydroxy group. The product structures formed by free-radical or electrophilic addition reactions can be determined on model compounds as well as on the polymers by ¹H- and ¹³C-NMR spectroscopy.     

Mobility of the growth promoters trenbolone and melengestrol acetate in agricultural soil: column studies

There is growing concern about environmentally released man-made chemicals suspected to be responsible for a number of adverse effects on endocrine function in wildlife species and possibly also in humans. Sex hormones are of particular interest due to their regulatory role in developmental processes such as sexual differentiation. Endogenous hormones of human or animal origin as well as exogenous sex steroids used for contraception or as anabolics for farm animals are excreted and reach the environment. We investigated the transport of the synthetic growth promoters trenbolone (TbOH) and melengestrol acetate (MGA) in agricultural soil by means of column experiments with aggregated soil materials (Ap and Bt horizons of a Luvisol). Column effluent concentrations and depth profiles of TbOH and MGA were determined with sensitive enzyme immunoassay systems and HPLC (RP-18), respectively. All procedures were confirmed by liquid chromatography-mass spectrometry. Small amounts of TbOH and MGA passed the columns very quickly. However, both hormones exhibited a high affinity to the organic matter of both horizons leading to a high retardation within the upper layers of the soil columns. Although we cannot deduce whether hormones of animal origin reach the ground water under field conditions, our model experiments show that their transition can be presumed.     

Light deflection from ferroelectric domain structures in congruent lithium tantalate crystals

Congruently grown lithium tantalate crystals containing ferroelectric domain structures have been illuminated with ultraviolet light along the crystallographic c axis with simultaneous application of an external electric field. This gives rise to a star-shaped light diffraction pattern in the transmitted beam. The characteristics of this phenomenon are investigated and compared with those observed in lithium niobate crystals.     

Curvature analysis and visualization for functions defined on Euclidean spaces or surfaces

Visualization of a scalar-valued function ƒ defined on Euclidean n-space ⁿ is often based on its graph-hypersurface . Particularly for curvature interrogation, it is natural to equip ^n-1 with a so-called isotropic metric and use isotropic measures of the graph instead of Euclidean invariants. The ideas are extended to functions defined on surfaces in ³. We present the central formulae for a curvature analysis of functions defined on surfaces. It is shown how to use them for visualization purposes and as a mathematical basis for the construction of interpolating or approximating functions on surfaces.     

Fixed bed reactor kalman filtering and optimal control—II Experimental investigation of discrete time case with stochastic disturbances

Discrete time linear quadraticoptimal control is investigated experimentally on a catalytic fixed-bed reactor with stochastic upstream disturbances. It is demonstrated that the discrete time variance evaluated with time intervals equal to the control intervals oscillates along the reactor axis due to the time discretization of the control action. However, if the variance is evaluated with much shorter time intervals than used for control, the oscillations are not present. The control system behaviour is demonstrated with both Gaussian and step disturbances.     

Application of a new automatic lattice orientation measurement technique to polycrystalline aluminum

The power of a fully automatic system for measuring lattice orientation in the scanning electron microscope is demonstrated. The system couples automatic analysis of electron backscattering diffraction patterns with precise movement of a computer-controlled stage. Over 100 000 lattice orientations were measured on 40% channel-die compressed aluminum. The texture calculated from these measurements closely matched the expected rolling texture. The value of this technique for exploring the relationships between lattice orientation and morphology in polycrystalline microstructures is demonstrated by reconstructing grain boundary maps from the measurements and using color to visualize particular orientations. It is also shown that the average grain shape for a particular orientation can be recovered from the measurements using statistical measures of spatial orientation correlation.     

Industrielle aspekte der suspensionspolymerisation

Suspension polymerization is one of the most important processes for the production of high polymers. Great demands are made on the technical applicability of the polymers. In order to meet these requirements the distribution of the particle sizes and the morphology of the particles are of great importance. The size and the structure of the particles depend in a complicated interaction on factors such as the chemical structure of the suspending agent, the concentration of the suspending agent and on the agitation conditions. The interdependence of these factors have been and still are explained differently. Important mechanistic and process engineering aspects of the suspension polymerization are demonstrated by the polymerization of vinylchloride and styrene.     

Ventilation of passenger car cabins: comparison of experimental data and numerical calculations

The complex flow in the interior of a passenger car cabin is measured and calculated in a Reynolds number range of practical importance. It turns out that the mean flow field compares quite well, even in minor details. But, experiments and calculations deviate considerably as far as turbulent quantities are concerned. The situation is analysed by a closer look to the physics of the flow field. From this, conclusions are drawn why the k−ɛ model applied here might be inappropriate for the flow field under consideration.