Entschwefelung von gerührtem und ungerührtem Roheisen mit kalkreicher Schlacke unter oxidierender Gasatmosphäre

Aus Betriebsergebnissen bei der Pfannenentschwefelung ist ein negativer Einfluß oxidierender Gasphasen bekannt. Daher war es das Ziel der eigenen Untersuchungen in einer geeigneten Apparatur die Wirkung oxidierender Bedingungen in der Gasphase sowohl auf den Verlauf des Schwefelabbaues in der Schlacke als auch des Schwefeltransportes aus dem Roheisen in die Schlacke zu untersuchen. Oxidierende Gasphasen erwirken bei der Pfannenentschwefelung an der Phasengrenze Schlacke/Gas eine Oxidation des Schwefels aus der Schlacke, ohne jedoch bei ruhender Schlackenschicht ein Oxidationspotential in der Schlacke aufzubauen, das bis zur Phasengrenze Roheisen/Schlacke durchgreift und dort die Entschwefelung des Roheisens durch die Siliciumgehalte stört. Sowohl die Entschwefelung des Roheisens als auch die Oxidation des Schwefels aus der Schlacke werden durch höhere Temperaturen und durch eine Rührwirkung gefördert. Der Schwefeltransport wird bei den ungerührten wie bei den gerührten Schmelzen durch Diffusionsvorgänge gesteuert und auch hier durch steigende Temperaturen und rührende Kräfte begünstigt.     

Synthesis of Aminopyridazines from Aminocyclopropenylium Salts and Diazomethyl Compounds [1]

Amino-substituted cyclopropenylium salts ( 11a,b ) react with diazomethyl compounds ( 12a-i ) in dichloromethane or acetonitrile in the presence of a base (ethyldiisopropylamine, 1,5-diazabicyclo[4.3.0] non-5-ene) to form 4-aminopyridazines ( 13a-i ) specifically. The reaction is interpreted in terms of an initial electrophilic diazoalkane substitution to give diazomethylcyclopropenes ( 11 + 12 → 14 ) which undergo a [1.5]-cyclisation to form the betaines 16 which, in turn, isomerise with opening of the bridging bond to give the aminopyridazines 13 . In a similar manner, the tris[amino] cyclopropenylium salts 8a,b and 10a-c are converted to the 3,4,5-tris[amino]-pyridazines ( 21a-k ) by treatment with diazomethyl compounds ( 12a, c-f ).     

Elastic constants of face-centered cubic and L1<Subscript>2</Subscript> Ni-Si alloys: Composition and temperature dependence

The adiabatic elastic stiffness constants C _ij of Ni-Si single-crystal solid-solution alloys of two slightly different compositions, 10.78 and 11.17 at. pct Si, were measured over the temperature range from 20 °C to 900 °C using the rectangular parallelepiped resonance method. The isotropic elastic constants of the polycrystalline ordered intermetallic compound Ni₃Si containing 23 at. pct Si were also measured over this temperature range. Values of the C _ij for Ni₃Si were estimated from the data on the polycrystalline alloy, as well as from published data in the literature on isomorphous ternary ordered intermetallic compounds containing different amounts of Si. Using measured values and previously published data, the stiffness constants of Ni₃Ti were estimated; these are the only available data on this alloy. The estimated single-crystal elastic constants of Ni₃Si, as well as the experimentally measured bulk modulus, are considerably smaller than published values calculated from first-principles methods. The same is true for the C _ij of Ni₃Ti, but the discrepancies are smaller.     

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Verbessertes Widerstandsgesetz für Stufendiffusoren

Zusammenfassung Es wird ein allgemeines Widerstandsgesetz für Stufendiffusoren hergeleitet, bei dem die Widerstandszahl den Zusatzverlust gegenüber den Verlusten der bis zum Kontursprung reichenden fiktiven Kanal- bzw. Rohrstr?mungen in der Zu- und Abstr?mung beschreibt. Unter vereinfachenden Annahmen reduziert sich dieses Gesetz auf die bekannte Carnot-Formel. Insbesondere wird dabei der Anteil des Zusatzverlustes, der vom Unterdruck an der Stufe und von der Wandschubspannungs?nderung unmittelbar hinter der Stufe herrührt, vernachl?ssigt. Die Berücksichtigung dieses Anteils führt zu einem gegenüber der Carnot-Formel verbesserten Widerstandsgesetz. Herrn Prof. Dr.-Ing. Martin Fiebig zum 60. Geburtstag     

Automated model generation for performance engineering of building automation networks

Large technical systems need to be designed both reliable and efficient. Specialized design tools offer therefore a simplified, abstract design and extend details autonomously in the background. Analytic and simulation based models could improve the quality by testing and dimensioning the design before implementation, but setting up the necessary models is time-consuming and expensive. Therefore many developers ask for analysis tools which are able to create their models from the available information in the design tools. This paper presents such an automated modeling approach basing on an existing design database at the example of a network analysis for building automation fieldbuses. The process of automated modeling is unfolded, and the potentials and limitations are discussed.     

Planning considerations for domestic replacement satellites

Several domestic satellite systems have been more than 10 years in operation. During this time, the world has experienced a dramatic growth in communication. While the demand for more telephony and data circuits and television channels is still on the rise, new methods of signal transmission and circuit compression have been developed which may balance or reduce the need for more satellite trunk capacity. And while whole national networks are converting to digital transmission, new transmission media like optical fibre, are finding application, and may take over some of the heavy traffic routes previously carried by satellite. On the other side, business data communication between roof-top terminals, thin route traffic to remote users, television distribution by direct satellite broadcasting are becoming more popular and satellite land mobile communication may soon be a reality. Thus the domestic satellite's role appears to be slowly changing towards thin route and mobile traffic and DBS-type distribution and perhaps even radio position determination. System planners are adapting to the new trends in satellite communication and are trying to accommodate the various service payloads on a single satellite. This article discusses some aspects of the emerging multi-purpose domestic satellite, which carries fixed and mobile services, TV direct broadcasting and radio position determination, in view of network digitalization, network expansion, circuit compression, synchronization. The discussion centres on transponder supply and demand, satellite replenishment, K_u-band vs. C-band for TV direct satellite broadcasting, choice of modulation/multiple access for mobile communication, and expected accuracy in radio position determination.