Residual stress measurements in irradiated solution-annealed type 304 stainless steel tubing

Immersion density and residual stress measurements were made on solution-annealed type 304 stainless steel capsule tubing irradiated up to fluence levels of 9 × 10²² n/cm² (E > 0.1 MeV). The measured residual stress is dependent on the competition between differential swelling which builds up differential stresses, and irradiation creep which relaxes these stresses. The measurements were analyzed using a bilinear swelling equation formulated with swelling data from the same heat of material. The temperatures and fluence levels of the swelling and slit tube data were each calculated with the same computer code. At high fluence, when swelling was in the steady-state region, the effective irradiation creep rate increased by a factor of about three. Further analysis was made assuming that stress-enhanced swelling and swelling-enhanced irradiation creep were the enhanced relaxation mechanisms.     

Modern Teaching and Training in Metallurgical Engineering

This contribution deals with advanced educational technologies needed to equip customers from higher education institutions, research and industry with efficient tools supporting their work and operating new skills‐training methods. The challenges are reducing the training costs, improving quality and increasing the number of graduates in engineering departments. The concept of a Virtual Lab based on the combination of various teaching methods and tools is presented. Principles of mathematisation in metallurgical education and training are discussed. An example of online course designed in the form of Virtual Lab is demonstrated.     

Three isoflurane preparations from various manufacturers. A comparison of isoflurane concentrations in fresh gas after vaporization with a Drager vaporizer type 19.3

OBJECTIVES: The purpose of this study was to check the precision of the Dr?ger vaporizer model 19.3 when filled with three different preparations of isoflurane. METHODS: Six Dr?ger vaporizers model 19.3 calibrated with forene were filled with forene (Abbott), isoflurane (Lilly) and isoflurane (Pharmacia); gas output was measured by infrared absorption (Irina, Dr?ger) at vaporizer settings of 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 and 5.0 vol%, starting with a fresh gas flow of 2 1/min followed by 4, 6 and 12 1/min. Thus each of the three isoflurane preparations was checked in six different vaporizers and with four different fresh gas flows. RESULTS: Within the concentration range used in clinical practice there was no significant difference in the delivery of the three isoflurane preparations. Each of the six vaporizers produced a controllable and predictable concentration of the three preparations. CONCLUSION: Vaporizers of Dr?ger type 19.n calibrated with forene deliver the same predictable concentration of the volatile anaesthetic when filled with isoflurane from Lilly or isoflurane from Pharmacia instead of forene and may be used without impairment in patient safety. In addition, no specific calibration with one of the new isoflurane preparations is required.     

Extensions to an authentication technique proposed for the globalmobility network

We present three attacks on the authentication protocol that has been proposed for the so-called global mobility network in the October 1997 issue of the IEEE Journal on Selected Areas in Communications. We show that the attacks are feasible and propose corrections that make the protocol more robust and resistant against two of the presented attacks. The aim is to highlight some basic design principles for cryptographic protocols, the adherence to which would have prevented these attacks     

Untersuchungen des Zeitstandverhaltens von Schweißverbindungen der Werkstoffe X 20 CrMoV 12 1 und GS-17 CrMoV 5 11

Untersucht wird das Zeitstandverhalten gleichartiger Schweißverbindungen des Werkstoffs X 20 CrMoV 12 1 sowie ungleichartiger Verbindungen zwischen diesem und dem Werkstoff GS-17 CrMoV 5 11. Bei quer entnommenen Kleinproben zeigt sich ein Abfall der Zeitstandfestigkeit gegenüber dem Grundwerkstoff. Große Querproben aus einer ungleichartigen Verbindung weisen eine höhere Zeitstandfestigkeit auf als entsprechende Kleinproben. Zur Klärung der in den Schweißverbindungen auftretenden Spannungs- und Dehnungsumlagerungen wurden inelastische Finite-Elemente-(FE-)Berechnungen durchgeführt. Dabei wurde das Zeitdehnverhalten von Grundwerkstoffen, Schweißgut und thermisch simulierten Gefügen der Wärmeeinflußzone berücksichtigt. Die Anwendung spannungsbezogener Kriterien zur Bestimmung der Anrißdauer der Proben auf die FE-Ergebnisse läßt eine Voraussage des Versagensorts sowie eine sichere Abschätzung der Versagenszeit zu.     

Computation of plate columns for NOx absorption by a new stage-to-stage method

A new stage-to-stage method has been developed for the calculation of NX_x absorption columns. Each stage of the absorption column is simulated as a combination of a bubble column reactor (absorption) and an adiabatic plug for reactor (oxidation). The bubble column reactor is modelled as two single stirred tank reactors, one as a gas-phase and one as a liquid-phase reactor, both coupled by mass and heat transfer. In this hydrodynamic model, a dynamic approach is adopted, in which the gas-phase transport of N₂O₄ is the limiting step for the absorption. A gas-phasepseudo-enhancement for factor for N₂O₄ is therefore introduced. The balance equations for a single phase of the bubble column are solved with a Newton-Raphson algorithm. The entire column calculation is divided into a gas and a liquid side. On both sides, the stage-to-stage method is applied in such way that the overall calculation is performed as a loop process. The direction of the loop calculation follows that of the flow: gas-side upwards and liquid-side downwards.     

Interfacial chemistry of cobalt(II) during sol–gel synthesis of cobalt-containing mesoporous materials

Co-MCM-41 and Co-MCM-48 with cobalt amounts from about 3 wt.% to 9 wt.% have been synthesized under various conditions, and the samples were characterized by XRF, XRD and N₂-sorption. EXAFS least-squares curve fitting detected only oxygen and silicon backscattering shells, which verified the incorporation of cobalt into the silica framework both for as-synthesized and calcined samples. XANES profiles showed that the oxidation state of cobalt in the samples is unaltered during synthesis. It has been shown that the cobalt is precipitated as cobalt hydroxide during synthesis, and this hydroxide is in equilibrium with aqueous cobalt ions in the synthesis gel. The precipitated cobalt hydroxide precursors are incorporated into the mesoporous silica framework, while the aqueous cobalt ions remain dissolved in the aqueous phase. The cobalt amount in the final samples is therefore pH dependent. This equilibrium is also important in the formation of the mesoporous structure. Addition of increasing amounts of cobalt salt to a MCM-48 synthesis gel causes a change in the mesoporous structure from cubic Ia3d to hexagonal, which is suggested to be a consequence of the charge density matching process. The increased amounts of the divalent cobalt(II) ions in the gel screen the negatively charged silica precursors, which decreases the total surface charge density of the silica, and thus causes the surfactants to self-assemble into the hexagonal structure.