Untersuchungen zur transkristallinen und interkristallinen Spannungsrißkorrosion austenitischer Chrom-Nickel-Stähle in heißen Magnesiumchlorid-Lösungen

Investigations Into transgranular and intergranular stress corrosion cracking of austenitic stainless steels In hot magnesium chloride solutions The stress corrosion cracking (SCC) of austenitic stainless steels in hot magnesium chloride solutions is known to be transgranular. Therefore the slip-step-dissolution model is most favourable when explaining the failure mechanism. Constant load and constant extension rate tests (CERT) show that both methodes are almost equivalent. Moreover constant extension rate tests in more concentrated magnesium chloride solutions at 135°C reveal a small potential range of intergranular stress corrosion cracking more negative than the range of transgranular SCC. Observations of crack nucleation and crack propagation make plain that crack nucleation is a localized corrosion process. Pitting produces crack nucleis in the elastic range whereas cracks start along slip lines after plastic deformation. Fractography of specimens which failed by intergranular and transgranular SCC show macroscopically brittle fracture surfaces. Therefore a model is proposed which explains crack propagation by hydrogen-induced intermitted cracking at high-stressed sites at the crack tip.     

Forward osmosis extractors

Osmosis occurs when two solutions of differing osmolar concentrations are separated by a membrane permeable to the solvent but not (or nearly not) to the solutes. The paper derives the relationship between the kinetics and design parameters of systems designed for the purpose of applying this process to problems such as agricultural water reclamation, dehydration of solutions and the production of potable nutrient solutions from sea water. Three mathematical models that include increasingly complex fundamental process assumptions are presented. In all cases the fundamental mechanical device is assumed to be a continuous flow extractor that incorporates a semipermeable membrane.     

New fabrication techniques for components

This paper presents the high quality level of nuclear technology in the Federal Republic of Germany, which has been achieved by the consistent application of advanced manufacturing techniques. Therefore the synchronous development and sophistication of manufacturing process coupled with the utilization of optimized materials is demonstrated by two typical examples. The forged prechamber of the residual heat exchangers as well as the inductive bending of thick-walled pipes show that the use of complex forgings and of L- and Z-shaped piping may guarantee perfectly satisfactory fabrication and testing conditions while at the same time a reduction in the fabrication and testing costs may be achieved.     

Coded 64-CAP ADSL in an impulse-noise environment-modeling ofimpulse noise and first simulation results

This paper presents the performance of various coding schemes for the asymmetrical digital subscriber line (ADSL) in an impulse-noise environment. Impulse noise is considered to be one of the most damaging impairments in the ADSL, in which compressed video signals are delivered to residential customers. The impulse noise used in this study was measured and collected in German telephone networks. Based on this measurement and the corresponding statistical modeling, a simulation model for impulse noise is proposed and its properties are outlined. The coding schemes considered here utilize burst-error correcting Reed-Solomon codes and/or random error correcting trellis codes as well as symbol interleaving between the two codes. It has been found through computer simulations that a proper concatenation of the two codes could increase the immunity against impulse noise compared to an uncoded scheme. Specifically, a concatenated code, using a 2-dimensional 8-state trellis code and a 4-error-correcting Reed-Solomon code with an interleaving depth of 18 symbols, was able to eliminate all the errors caused by the impulse noise used in the study. It has also been found that the trellis codes are not very effective against impulse noise, unless they are used in conjunction with Reed-Solomon codes and a proper symbol interleaving. Performance results of other coding configurations using Reed-Solomon codes with different error-correcting capabilities are also presented. In addition, we also show the performance results when simple array codes are used instead of the Reed-Solomon codes     

Berechnung der Läufererwärmung von Turbogeneratoren mittels der Methode der äquivalenten Wärmequellennetze

Zusammenfassung Aus dem angeführten Beispiel ist ersichtlich, daß trotz äußerst einfachen Formeln, die sich aus der Benutzung der Methode der äquivalenten Wärmequellennetzes ergeben, ein Ergebnis erhalten wird, daß dem mittels eindimensionaler Wärmeströmung errechnetem, gleichwertig ist. Dabei ist der gesamte Rechenaufwand bedeutend geringer und einfacher¹.Die Resultate sind sehr instruktiv und durchsichtig, denn das Wärmequellennetz-Schema gibt ein gutes Bild der thermischen Verhältnisse und der thermischen Belastung des Läufers. So ist z. B. ohne weiteres zu ersehen, in welchem Verhältnis der Einfluß der einzelnen Größen d _L , ₂ und ₃ usf. auf die Wärmeabfuhr ist, oder daß z. B. bei relativ geringer Verbesserung des Wärmeüberganges im Ventilationsspalt, der Temperaturanstieg bei verringerter Nutzahl bedeutend geringer sein wird, usf. Es sei allerdings bemerkt, daß natürlich die richtige Zusammenstellung des Netzschemas und die richtigen Formeln zur Wertbestimmung der Widerstände äußerst wichtig sind².Mit 8 Textabbildungen     

Angioimmunoblastic lymphadenopathy: a case study

The case of a 57-year-old man with lymphadenopathy fever, splenomegaly, and polyclonal gammopathy is described. The difficult clinical course, the short lived response to cytotoxic treatment, the frequent infections, the immunologic abnormality, and the histologic findings in lymph node biopsy and postmortem material justified our diagnosis of angioimmunoblastic lymphadenopathy with dysproteinemia, a new entity described recently.     

Renal arteriovenous fistulas

Sinusoidal variations of CO2 were applied to anesthetized White Leghorn cockerels enclosed in a body plethysmograph. Waveforms were 2.5% mean plus 2.5% peak sine wave CO2 in air, at frequencies of 0.011 to 0.467 rad/s. Reflex variation in tidal volume and respiratory interval in response to the inputs of sinusoidally varying fractional content of inhaled CO2 for nine points within the above range of driving frequencies were recorded breath-by-breath. A least squares best-fit procedure was used to estimate mathematical input-output relationships (transfer functions) between the outputs, tidal volume (VT) and respiratory interval (1/f), and the single input, inspired CO2 fraction. For VT, a three time constant model most closely fitted the data. Two time constants, 80 s and 3.9 s, were associated with negligible delay; the third, 14 s, has a 0.35 s time delay. Dynamics of VT and interval reflex responses differed significantly suggesting that they are regulated by separate mechanisms.     

Approximation des zeitveränderlichen Temperaturverlaufs in elektrischen Maschinen mittels äquivalenter Wärmequellennetze

Übersicht Es wird der Versuch unternommen nachzuweisen, daß es ganz allgemein möglich ist, den zeitveränderlichen Temperaturverlauf der elektrischen Maschine (eines beliebigen Körpersystems) mittels äquivalenter Wärmequellennetze beliebig genau zu approximieren.Die Methode der äquivalenten Wärmequellennetze wurde zur Berechnung der Erwärmung clektrischer Maschinen entwickelt, in einigen Fällen aber auch auf andere Probleme angewandt. Im Prinzip ist sie wohl für die Berechnung der mittleren Temperaturen in beliebigen Körpersystemen geeignet, müßte aber natürlich den spezifischen Bedingungen des jeweiligen Problems angepaßt werden.