Strive for accuracy—improvement of predictions

Finite-difference approximations to the governing equations of fluid motinos are discussed for viscous three-dimensional flows for Reynolds numbers of several hundred, for three-dimensional incompressible and compressible boundary layers and for inviscid near-sonic supersonic flows. It is shown how the boundary conditions of the problems chosen influence the solutions. If certain conditions to be discussed in the following are not met, neither convergence nor uniqueness of the solution can be guaranteed. Comparison of the predictions described herein with experimental data of the recent literature asserts the validity of the solutions given. The examples chosen include: Viscous flows through biological vessels with bends and bifurcations, formation of Taylor-Görtler vortices in spherical gaps, three-dimensional viscous displacement effect on wings in transonic flow and front and embedded shocks in flow fields with Mach numbers slightly above one.     

TAS-Verfahren zur schnellen Abtrennung von Pesticiden und Konservierungsstoffen

Zusammenfassung Einleitend werden die Grundzüge des neuen Thermomikro-Abtrenn- und Auftrageverfahrens sowie die Funktion des TAS-Ofens geschildert und bewährte Arbeitstechniken zusammengestellt. Anhand von Modellgemischen und Handelsproben sind dann die Möglichkeiten zum schnellen Nachweis von Konservierungsstoffen, z. B. von Diphenylderivaten, PHB-Estern, Sorbin- und anderen Säuren aufgezeigt. Aus dem Gebiet der Pesticide wurden einige Insecticide, u. a. Pyrethrine, DDT,-HCH, sowie einige der herbicid wirkenden aromatischen Säuren herausgegriffen und die Abtrenn- und DC-Bedingungen ermittelt.Zahlreiche weitere Anwendungsmöglichkeiten auf dem Gebiet der Analytik von Lebens-, Genußmitteln und Gebrauchsgegenständen sind abschließend zusammengestellt, nachdem zuvor im Vergleich mit der Gaschromatographie auf die Vor- und Nachteile der TAS-Methode eingegangen wurde.

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The TAS-Method for rapid seperation of pesticides and preservatives

Summary The principles of the new thermomicroseperation method, the function of the TAS-stove and the techniques applied are described. Using modell-mixtures and commercial samples, the possibilities for rapid detection of preservatives, e.g. diphenylderivates, PHB-esters, sorbic and other acids, are demonstrated. From the pesticides some insecticides, e.g. pyrethrine, DDT,-HCH and some aromatic acids effective as herbicides are taken and analyzed. By a comparison with gaschromatography the advantages and disadvantages of the new method are discussed by the author together with additional possibilities of application in the field of food science and technology.

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Herrn J.Fuchs danke ich für die sorgfältige experimentelle Durchführung der Versuche.     

The Importance of Micromechanical Phenomena in Energetic Materials

Micromechanical phenomena are the key to the understanding of the mechanical behavior of energetic materials. Not only their mechanical behavior is influenced by micromechanics, but also their sensitivity to mechanical impacts. This paper describes today's knowledge about micromechanical phenomena in energetic materials and their influence on the macroscopic observable mechanical behavior, the measurement technique and a modern approach to the analytics and the design of energetic materials with the help of computational methods.     

Characterization of the grinding process by acoustic emission

The properties of a ground surface can be estimated on-line during manufacturing based on the analysis of acoustic signals emitted by the grinding process. This possibility is demonstrated using an experimental system comprising an external grinding machine, a data acquisition unit and an artificial neural network. In the initial phase of system application, an empirical model of the grinding process is formed in the memory of the neural network by self-organized learning driven by empirical data consisting of the acoustic emission spectrum and a surface roughness correlation function. After learning, the system applies the model to estimate the correlation function of the surface profile from the input acoustic emission spectrum. For this purpose, non-parametric regression, based on the conditional average estimator, is utilized. Experiments were done on the grinding of hardened steel workpieces by a corundum wheel. During formation of the model, the surface profile and its correlation function were determined off-line, while in testing system performance the surface correlation function was estimated on-line from the acoustic emission spectrum. With respect to the estimation error, three characteristic periods of the process were observed corresponding to grinding with a newly dressed, slightly worn, and worn out wheel. The best estimation is obtained during grinding by a slightly worn wheel.     

Intelligent modular design with holonic fuzzy agents

Presently,modular designs use various technologies accompanied by multiple models.Although no integral solution is known,a plethora of approaches is used to res...     

Δ16-20-Ketosteroide durch C2-Verlängerung aus Δ16-17-substituierten Steroiden

Δ¹⁶-20-Ketosteroids by C₂-Elongation from Δ¹⁶-17-Substituted Steroids Reactions of corticoid precursor steroids with a Δ¹⁶-double bond and iodine, trimethylsilyl, tributylstannyl or trifluoromethanesulfonyloxy groups in 17-position were studied with the aim of introducing an acyl substituent in 17-position. Starting with the 17-trimethylsilyl compounds, using acyl chlorides and AlCl₃ as a catalyst, a mixture of chlorinated compounds were obtained, among others. Better results gave palladium-catalyzed reactions, such as the cross-coupling of 17-tributylstannyl compounds with acyl chlorides or the substitution of the 17-iodides or the 17-triflates by vinyl ethers. In the reaction of the 17-iodides, different protecting groups are tolerated; thus this method is of general use. No Δ¹⁶-17-triflates were obtained by the reaction of androsta-4-ene-3, 17-dione or androsta-1,4-diene-3, 17-dione with trifluoromethanesulfonyl anhydride. This is a limitation of the triflate method, which in the other cases gives the best yields (>80%).     

Aza-Enamine. IX. UV/VIS- und NMR-spektroskopische Interpretation der Elektronenstruktur in Aldehydhydrazonen und daraus hergestellten Aza-Trimethinen

Aza-Enamines. IX. UV/VIS and N.M.R. Spectroscopic Interpretation of the Electron Structure in Aldehyde-N,N-dialkylhydrazones and in Aza-trimethines Prepared from These The n.m.r. and u.v./vis spectroscopic data of the compounds 2 , 3 and 4 – synthesized by electrophilic substitution at the azomethine carbon atom of the aldehyde hydrazones 1 according to the aza-enamine-concept – are reported. Compared to the respective C-atom of the starting hydrazones 1 the azomethine-C-atom of the compounds 2 – 4 exhibits a ¹³C-n.m.r. shift not corresponding to usual substituent effects. Our interpretation for this and for the u.v./vis spectroscopic data, too, is a simultaneous existence of both an aza-trimethine structural unit and an aromatic structure in the compounds 2 – 4 .