Zusammenhang zwischen dem Oxidationsgrad der Eisenoxide und den Verteilungswerten des Schwefels beim Gleichgewicht zwischen Eisenschmelzen und MgO-gesättigten Stahlwerksschlacken

Die Oxidationsgrade der Eisenoxide in MgO-gesättigten Stahlwerksschlacken beim Gleichgewicht mit flüssigem Eisen wurden durch Auswertung zahlreicher im Schrifttum mitgeteilter Versuchsergebnisse bestimmt und ihre Abhängigkeit von der Schlak-kenzusammensetzung dargestellt. Desgleichen wurde das Entschwefelungsvermögen MgO-gesättigter Stahlwerksschlacken anhand der Gleichgewichtsverteilungswerte beschrieben. Es wird festgestellt, daß optimale Ergebnisse nur bei gleichzeitiger Kalksättigung zu erzielen sind. Ein Zusammenhang zwischen der Schwefelverteilung und dem dreiwertigen Eisengehalt der Schlacke konnte aufgezeigt und durch Bildung von auf dem dreiwertigen Eisenoxid basierenden Oxisulfiden gedeutet werden.     

Einfluß der Fe2O3-Gehalte in Frischschlacken auf die MgO-Löslichkeit bei verschiedenen Sauerstoffpartialdrücken des Schlacke-Gas-Gleichgewichtes

Untersuchungen an isothermen Sättigungsschmelzen komplexer Stahlwerksschlacken bei 1600°C sollten Aussagen zum Verschleißangriff von Frischschlacken auf MgO-haltiges Feuerfestmaterial ermöglichen. Dabei wurde besonders der Einfluß von erhöhten Sauerstoffpartialdrücken des Gas-Schlacke-Gleichgewichtes (ρ_o2 von 10° bis 10^?8 bar) berücksichtigt, die über eine Zunahme der 3wertigen Eisenanteile in der Schlacke wirksam werden. Durch Sättigungsschmelzen sind experimentell die bisher nur unzulänglich erforschten MgO-Sättigungsgehalte in Schlacken bei höheren, durch Ar/O₂- bzw. CO/CO₂-Gasgemische festgelegten Sauerstoffdrücken untersucht worden. Die MgO-Löslichkeit steigt im reinen System FeO—Fe₂O₃—MgO zunächst, ausgehend von einem Grundwert, den die Schlackenzusammensetzung beim Gleichgewicht mit flüssigem Eisen vorgibt, mit steigenden Fe₂O₃-Gehalten, solange ein Magnesiowüstit-Mischkristall die sättigende Phase darstellt. Bei Sauerstoffdrücken ab etwa 10^?3 bar aufwärts findet entlang der dann herrschenden Magnesioferrit(MF)-Sättigung ein Abfall im MgO-Sättigungsgehalt statt, der aber zum Gleichgewicht mit reinem Sauerstoff hin (ρ_O2 = 1 bar) wieder leicht ansteigt. Der Magnesioferrit-Sättigungsbereich wird bei Anwesenheit weiterer Oxide, wie SiO₂ und CaO, zurückgedrängt und konnte bereits im System FeO—Fe₂O₃—MgO—CaO—SiO₂ nicht mehr eindeutig nachgewiesen werden. Die erhöhten Löslichkeiten für MgO in stark aufoxidierten Schlacken müssen bei der Beurteilung des Schlackenangriffs auf das Feuerfestmaterial zusätzlich zu den Sättigungsgehalten beim Gleichgewicht mit einer Eisenschmelze in Rechnung gestellt werden.     

Die kombinierten Desoxidationsgleichgewichte mit Mangan,Aluminium und Silicium sowie ihre Bedeutung für die Einschlußbildung

Thermodynamische Berechnung des Zustandsschaubildes MnO–Al₂O₃. Polytherme Darstellung des Schlackensystems FeO_n–MnO–Al₂O₃. Entwicklung der kombinierten Desoxidationsgleichgewichte mit Mangan und Aluminium sowie Einschluß-bildung während der Auflösung von Aluminium in einer manganhaltigen Stahlschmelze. Entwicklung der kombinierten Desoxidationsgleichgewichte mit Aluminium und Silicium. Einfluß von Mangan auf die kombinierten Desoxidationsgleichgewichte mit Aluminium und Silicium.     

Effect of bottom stirring and post stirring on the oxygen distribution between metal and slag at the end of the LD process

Studies concerning the effect of stirring and post-stirring on the oxygen distribution at the end of the LD process show that a post-stirring phase following the end of the blow establishes an oxygen distribution close to equilibrium. The sub-lance tests performed at 90% of the oxygen throughput show in comparison with the post-stirring phase a distinct oxygen deficiency, while the blow end-point measurements show an excess of oxygen.     

Liquid equilibria in the Fe–Ni–Mn system

New literature results on the liquid equilibria in the three edge binary systems make necessary a reconsideration and correction of liquidus surfaces of the γ and δ solid solutions hitherto outlined in the literature. Therefore, with respect to the critically reinterpreted edge binary systems, the shape of the stable liquidus surface of the γ and δ solid solutions has been newly outlined.     

Pharmacokinetics of the PDGF-antagonist trapidil in patients with and without renal impairment

BACKGROUND: From July 1989 to February 1996, 130 patients underwent stereotactic radiosurgery. We report the results of the first 50 patients eligible for a minimum of three years of follow-up. METHODS: Twenty women and 30 men, (mean age: 37.5 years) were treated by dynamic rotation on a 6 MV linear accelerator. Prior treatment was embolization in seventeen, surgery in three and embolization and surgery in six. All had DSA and enhanced CT scanning, while some had MRI. Forty-seven treatments used a single isodose. Restricting eloquent normal tissue to 15 Gy, margin doses (at 50-90% isodose) were 12 Gy (one patient); 15 Gy (sixteen patients); 20 Gy (31 patients); 25 Gy (two patients). Maximum diameters were: < 1.5 cm (12 patients); < 2.0 cm (nine patients); < 2.5 cm (twelve patients); < 3.0 cm (thirteen patients; 3.0 cm (four patients). RESULTS: Forty-five patients were evaluable at three years, with thirty-nine having angiography. Twenty-five had angiographically confirmed obliterations; two had parenchymal AVMs obliterated but with residual dural components; four had MRI evidence of obliteration (refused angiography). One patient acutely had a seizure; one patient (with hemorrhages, resection, and embolizations preceding two applications of radiosurgery, separated by 3.5 years) had worsening of memory. CONCLUSIONS: Our uncorrected (five patients unevaluable at three years) and corrected angiographically confirmed obliteration rates are 54% and 60% respectively. Our follow-up (98% accounting of cohort; 78% angiographic rate) and explicit derivation of denominators help delineate the efficacy of radiosurgery at these doses.     

Clean-sheared and rectangular edges through counter-shaving

A various number of products exist which require a clean-sheared edge due to function or surface feel. Traditionally, these parts are produced on fine blanking presses with three separate and distinct movements. Shaving, in particular counter-shaving is a shearing operation to improve the edge quality of a blanked part or punched hole. This paper introduces a progressive die tool to realize the counter-shaving process on a single acting press. Advancing the chip flow through choosing a cutter angle can achieve up to a 85% clean-sheared edge and rectangular edge. Thereby, a sharp-edged transition—without any rollover depth—between the upper surface of the sheet metal and the sheared-edge are formed. The end of the clean-sheared edge is followed by a tear which shapes a burr in the form of a triangular lappet, which can be deburred in a subsequent vibratory grinding process. Experimental results of different process parameters for two sheet metal materials at three thicknesses are discussed and compared to finite element calculations. The presented research work was supported by the German Research Foundation (DFG).     

Optische Konstanten von Substraten im NIR/MIR‐Spektralbereich

Determination of the Optical Constants of Common Substrate Materials in the NIR/MIR‐Spectral Regions An approach is reported for determining the optical constants of substrates and single layer coatings in the near and mid‐infrared spectral regions. A combination of the algorithm from Nichelatti and a multi‐oscillator model has been used to determine the optical constants of the substrates. Thus, the approach even works when the sample transmittance is vanishing. We demonstrate the application of the approach to the evaluation of transmission and reflection spectra of common substrates (CaF₂, Q1, Sapphire) measured by a Fourier‐Transform‐Infrared spectrophotometer. The comparison of the calculated optical constants with values reported in literature confirms the validity of the used approach. We also demonstrate the IR characterisation of a tantalum oxide single layer deposited onto a Q1 substrate by means of the multi‐oscillator‐model. The results are again in good agreement with literature data.     

Using the continuous price as control variate for discretely monitored options

Variance reduction is of highest importance in financial simulation. In this study, we present a new and simple variance reduction technique for pricing discretely monitored lookback and barrier options. It is based on using the corresponding continuously monitored option as external control variate. To obtain the value of the continuously monitored price both, conditional simulation and conditional expectation can be utilized. From numerical experiments we can conclude that the efficiency gains obtained by our new method are significant.     

Extended defect related energy loss in CVD diamond revealed by spectrum imaging in a dedicated STEM

This article aims at investigations of the low EEL region in the wide band gap system diamond. The advent of the UHV Enfina electron energy loss spectrometer combined with Digital Micrograph acquisition and processing software has made reliable detection of absorption losses below 10 eV possible. Incorporated into a dedicated STEM this instrumentation allows the acquisition of spectral information via spectrum maps (spectrum imaging) of sample areas hundreds of nanometers across, with nanometers pixel sizes, adequate spectrum statistics and 0.3 eV energy resolution, in direct correlation with microstructural features in the mapping area. We aim at discerning defect related losses at band gap energies, and discuss different routes to simultaneously process and analyse the spectra in a map. This involves extracting the zero loss peak from each spectrum and constructing ratio maps from the intensities in two energy windows, one defect related and one at a higher, crystal bandstructure dominated energy. This was applied to the residual spectrum maps and their first derivatives. Secondly, guided by theoretical EEL spectra calculations, the low loss spectra were fitted by a series of gaussian distributions. Pixel maps were constructed from amplitude ratios of gaussians, situated in the defect and the unaffected energy regime. The results demonstrate the existence of sp2-bonded carbon in the vicinity of stacking faults and partial dislocations in CVD diamond as well as additional states below conduction band, tailing deep into the band gap, at a node in a perfect dislocation. Calculated EEL spectra of shuffle dislocations give similar absorption features at 5-8 eV, and it is thought that this common feature is due to sp2-type bonding.