Semi‐Markovian modelling and performance analysis of variable rate traffic in ATM networks

Semi‐Markovian processes (SMP) serve as a versatile means to model various traffic types generated by sources or superposed from links in ATM networks. An efficient discrete time analysis method is proposed for SMP/G/1 queueing systems to evaluate ATM switches with non‐renewal input. Some basic results are derived for the autocorrelation function of semi‐Markovian processes and for the effect of state space reduction on autocorrelation, which show how to represent correlated traffic with given characteristic by an adequate SMP model of limited size. This revised version was published online in June 2006 with corrections to the Cover Date.     

A polynomial factorization approach to the discrete time GI/G/1/(N) queue size distribution

The queue of a single server is considered with independent and identically distributed interarrivai and service times and an infinite (GI/G/1) or finite (GI/G/1/N) waiting room. The queue discipline is non-preemptive and independent of the service times.

A discrete time version of the system is analyzed, using a two-component state model at the arrival and departure instants of customers. The equilibrium equations are solved by a polynomial factorization method. The steady state distribution of the queue size is then represented as a linear combination of geometrical series, whose parameters are evaluated by closed formulae depending on the roots of a characteristic polynomial.

Considering modified boundary constraints, systems with finite waiting room or with an exceptional first service in each busy period are included.     

Quantitative phase evaluation of converter slags

The slags formed in the LD vessel during the refining process turn out with different chemical compositions, mineralogical structures and physical properties, in dependence on the charging and processing conditions. Electron probe microanalysis (EPMA) combined with a data processing method for mineralogical analysis was used to characterize the mineralogical phases in LD slags and moreover to determine their volume fractions. By this method some correlations between the phase contents and the chemical composition of LD slags were established. The diagrams gained from this work have proven to be a valuable aid for understanding the interrelationships between the chemical composition, the mineralogical structure and some physical properties of LD slags.     

Steel Desulphurisation and Sulphur Bonding in Solidified Ladle Slags

It was investigated in which form sulphur is bonded in ladle slags. For this purpose, the mineralogical phases of the ladle slags were qualitatively and quantitatively evaluated by means of a microprobe. This slag characterisation allowed reconstructing the bonding of sulphur into the phases of the ladle slag. Moreover, the reaction process with regard to the ionic theory as well as the structural formula for the mechanism of sulphur bonding were discussed. The bonding of sulphur into calcium aluminate slags is determined by the sulphide ion content in the slag as well as by the ratio of (CaO)/(Al₂O₃). Calcium sulphide separates only if the slag contains a large number of sulphide ions. When Ca₁₂Al₁₄O₃₃ is separated the sulphide ion is successively integrated into the lattice. The crystal lattice of Ca₁₂Al₁₄O₃₃ is characterised by an open, three‐dimensional anionic network composed of aluminium‐oxygen tetrahedrons linking the edges. In this network, large interstitial spaces are formed, which may be filled with calcium ions on the one hand and statistically with a free oxygen or sulphide ion on the other hand.     

Norican Steel ‐ An Assessment of the Archaeological Finds at the Magdalensberg Site,Carinthia, Compared to the “Celtic Trove” of Gründberg Hill,Linz

The analysis of Celtic steel products from depots found in the area north of the Danube has shown that their excellent properties are due to the choice of unalloyed or alloyed steel bars that were shaped by fire‐forging. Phosphorus was used as an alloying element, while carbon was added through carburizing of the workpiece. Was this forging technique also known to regions in the very heart of the Alps? Our analysis set out to find an answer to this question. The Celtic smiths in the inner Alpine regions used shaft furnaces to produce steel loops with numerous slag inclusions but very low contents of trace elements in the steel matrix. In a series of process steps in the smithy ‐ trimming the steel loop, forging into bars, “sheafing”, carburizing, hardening ‐ the steel properties demanded by the customers were achieved. Phosphorus was not deliberately employed as an alloying metal in the valleys of the Central Alps. The fact that the forging technique was tailored to the actual product appears to underlie the high quality of “Norican steel”.     

Identification of process parameters for efficient poling of PZT ceramics for mass production

Advanced, cost–effective and series compatible manufacturing of active structural components demands for short production times and complex multi-material designs. Highest efficiency is achieved when integrating the poling process of the piezoceramic that activates the piezoelectric effect into the manufacturing chain. The present paper reports on first results of the systematic evaluation of parameters governing the poling regime of commercial lead zirconate titanate (PZT) ceramics. It aims to find the conditions for efficient poling of the active material as an integrated technology step in mass production. In the present investigation, the influence of poling field strength and temperature on the obtained remanent polarization is considered by varying the temperature from ?175 °C to 150 °C and the electric poling field strength from 1.0 to 2.0 kV/mm. Six commercially available piezoceramic materials, primarily used in actuator applications, were investigated. From the findings, it was possible to deduce technological parameters for an efficient poling process.