Physical properties in the temperature range from –180 to 400°C of nickel alloy steels for low-temperature applications

Nickel, which is the second neighbour to iron in the periodic table of elements, has a significant effect on most of the physical properties of the steels studied here, with the nickel content of the steels varying between 3 and 9%. Density and coercive force increase as the nickel content in the steel increases. By contrast, thermal expansion, modulus of elasticity and shear modulus decrease with increasing nickel content. Because of large scatter in the data, it is not possible to notice any significant influence of nickel content on Poisson's ratio and bulk modulus. Specific heat is also found not to vary with the nickel content of the steel. Electrical resistivity and thermal resistivity values increase, as expected, with increasing nickel content. The results of thermal conductivity measurements on 12 Ni 19 and X 8 Ni 9 have led to the development of modified Smith-Palmer relationships, which allow the calculation of the thermal conductivity values for the present set of steels and other steels with similar compositions.     

Analysis of guarana seeds II. Studies on the composition of the tannin fraction

Summary The content of the total tannins, proanthocyanidins and prototannins in the seeds of guarana, Paullinia cupana var. sorbilis HKB (Sapindaceae) was studied. A total tannin content of 12.1% dry matter was found in air dried samples. Reversed-phase high-performance liquid chromatography (RP-HPLC) analysis resulted in 6.0% (+)-catechin and 3.8% (–)-epicatechin on an average. Hydrolysable tannins were not detectable. The results for one of two analyzed ground samples from the Brazilian market were substantially lowered. It is concluded that this product was adulterated with another no tannin containing material.

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Zur Analytik von Guarana. II. Zusammensetzung der Gerbstoffe

Zusammenfassung Der Gehalt an Gesamtgerbstoffen, Proanthocyanidinen und Prototanninen im Samen von Guarana,Paullinia cupana var.sorbilis HKB (Sapindaceae), wurde untersucht. In lufttrockenen Samen wurde ein Gesamttanningehalt von 12,1% i. T. gefunden, die Proanthocyanidin-Bestimmung ergab einen Gehalt von 10,7%; mittels RP-HPLC-Analyse wurden 6,0% an (+)-Catechin und 3,8% (–)-Epicatechin gefunden. Hydrolysierbare Tannine waren nicht nachweisbar. Bei einer von zwei untersuchten gemahlenen Proben des brasilianischen Handels waren alle Analysenwerte erheblich erniedrigt, was auf eine Streckung des Produkts mit nicht gerbstoffhaltigem Material schließen läßt.

     

Anomalien in der Wärmeausdehnung austenitischer Cr—Ni-Stähle

An folgenden sieben austenitischen Cr—Ni-Stählen wurden zwischen 20 und rd. 900°C der differentielle und der mittlere lineare Wärmeausdehnungskoeffizient bestimmt: X 5 NiCrMoCuTi 20 18, X 10 NiCrMoTiB 15 15, X 2 CrNiMo 25 22 2, X 3 CrNiMoN 17 13, X 2 CrNiMo 18 12, X 6 CrNi 18 11 und X 5 CrNi 18 9. Im Verlauf des differentiellen linearen Ausdehnungskoeffizienten ergeben sich im Temperaturbereich um 200°C sowie um 600 bis 700°C ausgeprägte Maxima. Diese erweisen sich als streng reversibel und können weder Ausscheidungen noch Nahordnungsvorgängen oder magnetischen Ordnungseinstellungen zugeordnet werden. Durch Anpassung der Grundkurve an einen nach der Grüneisen-Theorie berechneten Verlauf verbleibt ein zusätzlicher Beitrag, ein sogenannter Ausdehnungsexzeß. Dieser läßt sich wie bei einer früheren Untersuchung zur spezifischen Wärmekapazität auf thermisch induzierte Elektronenübergänge, basierend auf der γ₁ – γ₂-Hypothese von R. J. Weiss, zurückführen.     

Conversion of ethanol over zeolite H-ZSM-5

The conversion of ethanol over H-ZSM-5 was studied as a function of ethanol partial pressure, reaction temperature, weight hourly space velocity and Si/Al ratio. The results obtained were in qualitative agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temperature programmed reaction measurements of ethanol, diethyl ether and ethene were performed. The formation of ethene from ethanol via direct elimination or from diethyl ether as intermediate could be confirmed. In the conversion of ethanol/water mixtures, the product distribution did not change significantly up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of aromatics was observed. When several reaction mixtures from syngas conversion to ethanol were converted over H-ZSM-5, the coking rate depended on the product distribution in the feed. Product mixtures from processes with higher amounts of compounds having an unfavourable C/H ratio led to rapid deactivation of the zeolite.     

Über den thermischen Abbau von Polyamiden der Nylon-Reihe

Several aliphatic polyamides (nylon-7, nylon-12, nylon-4, nylon-6,6, nylon-6,10, nylon-4,10, nylon-11,6, nylon-12,12) have been investigated in a mass spectrometer. Cyclic oligomers, which evaporate in the high vacuum of the ion source at temperatures below 200°C can be detected without previous isolation. The start of a thermal decomposition can be observed via the total ion current at temperatures above 350°C. Under those conditions polyactams are degraded by ring-chain equilibration into cyclic oligomers, whereas the favoured decomposition of polyamides of dicarboxylic acids and diamines is a cis elimination and the cleavage of the amide bond. With an increasing content of methylene groups these mechanisms also occur in polylactams. Mass spectra recorded of each polyamide at 170°C and ca. 400°C are characteristic and can be used for a fast identification and differentiation.     

Gaschromatographisch-massenspektrometrische Untersuchungen zur Kinetik der Redoxreaktionen vonl-Ascorbinsäure undl-Dehydroascorbinsäure in Weizenmehlteigen

European Food Research and Technology - A gaschromatographic/mass spectrometric method for separation and determination ofl-ascorbic acid (l-AA) and the different isomeric forms ofl-dehydro...     

Spherical Visibility Sampling

Many 3D scenes (e.g. generated from CAD data) are composed of a multitude of objects that are nested in each other. A showroom, for instance, may contain multiple cars and every car has a gearbox with many gearwheels located inside. Because the objects occlude each other, only few are visible from outside. We present a new technique, Spherical Visibility Sampling (SVS), for real‐time 3D rendering of such – possibly highly complex – scenes. SVS exploits the occlusion and annotates hierarchically structured objects with directional visibility information in a preprocessing step. For different directions, the directional visibility encodes which objects of a scene's region are visible from the outside of the regions' enclosing bounding sphere. Since there is no need to store a separate view space subdivision as in most techniques based on preprocessed visibility, a small memory footprint is achieved. Using the directional visibility information for an interactive walkthrough, the potentially visible objects can be retrieved very efficiently without the need for further visibility tests. Our evaluation shows that using SVS allows to preprocess complex 3D scenes fast and to visualize them in real time (e.g. a Power Plant model and five animated Boeing 777 models with billions of triangles). Because SVS does not require hardware support for occlusion culling during rendering, it is even applicable for rendering large scenes on mobile devices.     

Evaluation of presentation of information for process control operations

In an experimental process control simulation study two operators performed monitoring and control operations including safety critical tasks that required parallel processing of information distributed over different functional mimic displays. The assignment of mimic displays to Visual Display Units (VDUs) was experimentally varied by allowing one or two VDUs for mimic presentation. The study revealed no evidence for differences in task performance during normal process control operations. During abnormal operations, however, detrimental effects both on performance and work load were observed. Having only one VDU available for mimic display revealed either a lower level of performance (time for fault management) and/or a higher level of emotional work strain. It is concluded that decisions on the number of VDUs necessary for effective and efficient process control must refer to the tasks to be performed and the presentation of information necessary for a safe, effective and efficient task performance under critical, but not only normal conditions.