Thermal expansion of cementite and thermoelastic stresses in white cast iron

With X-ray diffraction the three microscopic differential thermal expansion coefficients of pure cementite were determined with high precision in the temperature range 30–320 °C. These data were used to calculate the average three-axial thermoelastic stresses in white cast iron with differently shaped and oriented cementite inclusions. Between 30 and 300 °C the orientation distribution of the (211) interplanar spacing of the ferrite phase in white cast iron was determined. An evaluation of these data according to the formalism of conventional X-ray stress analysis, however, yields completely wrong results because this formalism is based on the assumption that only biaxial average stresses parallel to the surface exist in the thin surface layer which is penetrated by the X-rays. It is demonstrated that what were observed in reality were the three-axial average phase-specific stresses from the interior of the specimen, which are complicated because of the preferred orientation of the cementite plates. The average phase-specific stress component σ₃₃ perpendicular to the irradiated surface drops to zero only in a sub-micrometre range below the surface. Because of the equilibrium conditions it is exactly zero at the external surface.     

19F and 31P NMR spectroscopy of calcium apatites

Glass ceramics that include apatite crystals are used as implant materials. Because most of these glass ceramics are comprised of fluoride-containing glass compositions, the included apatites could be hydroxyapatite, fluorapatite or fluoride-substituted hydroxyapatite. However, these apatites differ in regard to their solubility and thermal stability. The purpose of the current study was to determine the possibilities of distinguishing between these apatities. High resolution solid-state ¹⁹F and ³¹P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of two fluorapatites, a hydroxyapatite and a fluoridated hydroxyapatite have been obtained. Using ³¹P NMR investigations it is possible to distinguish between calcium apatites and other calcium phosphates, but the distinction between fluoride-containing apatite and hydroxyapatite is not possible. However, ¹⁹F high-resolution solid-state NMR investigations permit the distinction between these various apatites. The results of the NMR investigations could be used for the characterization of glass ceramics. The application of those results was demonstrated using a newly developed apatite-containing glass ceramic.     

Novel systemically active antagonists of the glycine site of the N-methyl-D-aspartate receptor: electrophysiological, biochemical and behavioral characterization

A series of novel tricyclic pyrido-phthalazine-dione derivatives was tested for antagonistic effects at the strychnine-insensitive modulatory site of the N-methyl-D-aspartate (NMDA) receptor (glycineB). All compounds displaced [3H]MDL-105,519 binding to rat cortical membranes with IC50 values of between 90 nM and 3.6 microM. In patch-clamp experiments, steady-state inward current responses of cultured hippocampal neurons to NMDA (200 microM, glycine 1 microM) were antagonized by these same compounds with IC50 values of 0.14 to 13.8 microM. The antagonism observed was typical for glycineB antagonists, i.e., they induced desensitization and their effects were not use or voltage dependent. Moreover, increasing concentrations of glycine were able to decrease their apparent potency. Much higher concentrations (>100 microM) were required to antagonize alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced currents. They were potent, systemically active NMDA receptor antagonists in vivo against responses of single neurons in the rat spinal cord to microelectrophoretic application of NMDA with ID50 values in the low milligram per kilogram i.v. range. They also inhibited pentylenetetrazol-, NMDA- and maximal electroshock-induced convulsions in mice with ED50 values ranging from 8 to 100 mg/kg i.p. The duration of anticonvulsive action was rather short but was prolonged by the organic acid transport inhibitor probenecid (200 mg/kg). The agents tested represent a novel class of systemically active glycineB antagonists with greatly improved bioavailability.     

Axiomatisations of functional dependencies in the presence of records,lists, sets and multisets

We investigate functional dependencies in databases that support complex values such as records, lists, sets and multisets. Therefore, an abstract algebraic framework is proposed that classifies data models according to the underlying types they support. This allows to emphasise the impact of the data types rather than the specifics of a particular data model.     

An IMPOC-1BM pulsed magnetic production-line monitor

An IMPOC-1BM setup for the nondestructive testing of the mechanical properties of rolled steel sheets no thicker than 3 mm on a production line is described. The setup operates at a velocity of a moving sheet of up to 10 m/s and with a 2-m distance between the test points. The results of its laboratory and production tests are presented.     

制革生态学(续六)

4 Finishing The purpose of finishing leather is to improve its serviceability by protecting it from damage by water, soil and mechanical action. Finishing modifies the shade, gloss and handle of the leather, improves its physical properties such as its lightfasthess and rubfastness, and hides any defects and     

The direct boundary element method in plate bending

The direct boundary element method based on the Rayleigh-Green identity is employed for the static analysis of Kirchhoff plates. The starting point is a slightly modified version of Stern's equations. The focus is on the implementation of the method for linear elements and a Hermitian interpolation for the deflection w. The concept of element matrices is developed and the Cauchy principal values of the singular integrals are given in detail. The treatment of domain integrals, the handling of internal supports, the properties of the solution and the effect of singularities are discused. Numerical examples illustrate the various techniques. In the appendix the influence functions for the second and third derivatives of the deflection w are given.     

Experimental validation of high-order time integration for non-linear heat transfer problems

An accurate prediction of the temperature distribution in space and time plays an important role in many industrial applications, in particular when phase transformations are involved. In this article the thermo-physical properties of steel 51CrV4 (SAE 6150) are determined and used in numerical simulations. For the simulation of the temperature field a semi-discrete approach is used, consisting of a finite element approximation in space and a high order Runge– Kutta integration in time. Several adaptive high-order time integration method (stiffly accurate diagonally implicit Runge–Kutta methods) are applied and their computational efficiency is investigated. The theoretical rates of convergence are achieved for all problems, including the non-linear case. Whereas the second order accurate method of Ellsiepen with time adaptive step-size control proves to be most efficient. Further, the influence of the material model on the simulation results is studied and the numerical results are verified by experiments. The best correlation of the simulation and experimental data is achieved using temperature-dependent parameters.