Showing papers by "Technical University of Berlin published in 1975"

On turbulence and noise of an axisymmetric shear flow

Abstract: The noise produced by mean flow-turbulence interaction of a circular subsonic jet is investigated theoretically, and expanded in azimuthal constituents of the turbulent pressure fluctuations. It is found that the low-order azimuthal constituents are the most efficient sound sources. On the basis of pressure correlation measurements, the azimuthal constituents are determined in a low Mach number jet. It is found that, in a range of Strouhal numbers between 0·2 and 1, the first three to four azimuthal constituents clearly dominate over the rest of the turbulent source quantity. A strictly axisymmetric ring vortex model for the coherent structure of the turbulence is, however, shown to be inappropriate.

13C-NMR-Spektren von Monoterpenen

Abstract: Die 13C-NMR-Spektren von fast 100 Monoterpenen zeigen, das sie zur Charakterisierung derartiger Verbindungen sehr brauchbar sind. Besonders wertvoll ist diese Methode zur Klarung stereochemischer Probleme. Bis auf wenige Falle folgen die beobachteten chemischen Verschiebungen den allgemeinen Regeln. Die Probleme der Messungen mit Verschiebungsreagenzien werden diskutiert. The 13C NMR spectra of nearly 100 monoterpenes show that they are very useful for the characterisation of these compounds. This method is especially valuable for the elucidation of stereochemical problems. With the exception of a few cases the observed chemical shifts follow the common rules. The problems with measurements using shift reagents are discussed.

Lupinen‐Alkaloide, XLI. 13C‐NMR‐Spektren von Lupinen‐Alkaloiden

Abstract: Die Analyse der 3C-NMR-Spektren von 47 Chinolizidinen und Piperidinen sowie einiger deuterierter Derivate gibt die Moglichkeit, die gefundenen Signale der Spektren mehrerer Lupinen-Alkaloide zuzuordnen. Die beobachteten chemischen Verschiebungen folgen im allgemeinen den ubliche Regeln. Jedoch werden besondere Effekte beobachtet, die vor allem auf spezielle sterische Situationen zuruckzufuhren sind. Die Brauchbarkeit der 13C-NMR-Spektroskopie fur Lupinen-Alkaloide wird gezeigt. Lupin-Alkaloids, XLI. 13C-N.M.R.-Spectra of Lupin-Alkaloids The analysis of the 13C-n.m.r.spectra of 47 quinolizidines and piperidines as well as some deuterated derivatives give the possibility to coordinate the found signals of the spectra of several lupin-alkaloids. The observed chemical shifts follow in general the common rules. However several particular effects can be recognized mainly due to special steric situations. The usefullness of 13C-n.m.r. spectroscopy for lupin-alkaloids has been shown.

Fluiddynamik bei quer angeströmten Zylindern

Abstract: Die vorliegende Untersuchung befa\t sich mit der stationAren Umstromung eines einzelnen Kreiszylinders. Die vollstAndige Navier-Stokessche Gleichung wurde fur den Bereich der Reynolds-Zahl von Re=10−4 bis Re=1,2·102 numerisch intergriert. — Die das Stromungsfeld kennzeichnenden Merkmale sind der Stromungswiderstand, die Gro\en fur die Ablosung der Stromung sowie die kritische Reynolds-Zahl. Sie sind abhAngig von der Ausdehnung des umgebenden Fluids. Zur Berechnung dieser Gro\en werden Gleichungen mit praktisch bedeutsamen Gultigkeitsbereich mitgeteilt. Diese Berechnungsgleichungen sind durch theoretisch-numerische Daten sowie durch zahlreiche Me\daten gestutzt. — Insbesondere wird ein Widerstandsgesetz erortert, dessen Gultigkeit im Bereich der Reynolds-Zahl von Re=10−4 bis zur kritischen Reynolds-Zahl theoretisch und experimentell einwandfrei gesichert ist. Es ist das bisher umfassendste Widerstandsgesetz fur Kreiszylinder. Fur kleinere Werte der Reynolds-Zahl als Re=10−4 wird ein analytisches NAherungsgesetz fur den Widerstandsbeiwert mitgeteilt.

Transport of Heat Across a Plane Turbulent Mixing Layer

Abstract: Publisher Summary A well-known characteristic of turbulent shear flows is that the spread of scalar quantities—that is, heat or matter, is faster than the spread of momentum This chapter describes a model for the transport mechanism of a scalar quantity in typical turbulent shear flows In the present state of the investigation, measurements of the temperature field alone have been obtained and the temperature field is mathematically represented by four equations; the equation of motion, the continuity equation for the mean velocities, the heat-transfer equation, and the equation of the balance of temperature fluctuations The chapter provides some important observations, such as based on the shape of the temperature fluctuations as well as the mean quantity distributions it can be assumed that the transport mechanism is largely due to a large scale vortical motion, the mean temperature distribution in the turbulent domain is largely homogeneous, the temperature across a single vortex is linear in the mean, and the temperature fluctuation variance in the turbulent domain is approximately constant

Die arc sin √P-Transformation — ein einfaches Verfahren zur grafischen und rechnerischen Auswertung geplanter Wöhlerversuche

Abstract: Einleitend wird auf die Notwendigkeit hingewiesen, den Werkstoffkennwert „Dauerfestigkeit” in Zukunft scharfer zu definieren und dieser Definition sowohl hinsichtlich des Versuchsaufwandes als auch bezuglich der Auswertmethodik hinreichend Rechnung zu tragen, da nur so Hoffnung besteht, die „Sprachverwirrung” innerhalb des grosen Forschungsgebietes Werkstoffermudung zu mindern. Sodann wird eine Auswertmethode fur Dauerschwingergebnisse, die sog. arc sin √P-Transformation, in „benutzerfreundlicher” Darlegung vermittelt. Die arc sin √P-Transformation durfte das derzeit am eingehendsten experimentell uberprufte Auswertverfahren fur Wohlerversuche darstellen und demzufolge das Adjektiv „ausgetestet” am ehesten verdienen. Die bisher mit diesem Verfahren gesammelten Erfahrungen legen seine Anwendung auf breiter Ebene nahe. Arc Sine √P-Transformation — an effective tool for graphical and numerical evaluation of planned Wohler-Experiments. Some critical remarks are made about the fact, that the very important terms of fatigue testing, i.e. fatigue strength and minimum life, often are interpreted ambiguously. To avoid this, introduction of compulsory definitions of these terms with regard to statistical methods of planning tests and analyzing their results seems to be urgent. The arc sine √P-transformation proved to be a technically appropriate model law for estimating fatigue strength and likewise minimum life. Hitherto, this evaluation method worked so satisfactory at the field of fatigue data analysis, that its application on a broad level can be recommended now. The course of evaluation is presented in this paper in a step-by-step way.

Motion sequence criteria and design proposals for restraint devices in order to avoid unfavorable biomechanic conditions and submarining

Abstract: Our aim is to show that today's safety standards (FMVSS 208, EC-Proposals) are inadequate in the present state to ensure optimum protection for belted passengers. These standards do not take into account motion sequence during impact. The postulated tolerance limits - HIC, SI, forward displacements etc.-cannot describe the dynamic behavior adequately. We emphasize the importance of motion sequence to ensure optimum biomechanic conditions, because motion sequence is the necessary prerequisite for any discussion about biomechanical tolerance limits. First results of our current belt-accident-investigations indicate that this is an important problem. By applying experience from crash tests and accident investigations, we try to define simple and well controllable criteria for motion sequence. These criteria should not only guarantee favorable biomechanical loads for the belt-restrained passenger, but also give the possibility of simplifying data registration and calculation of results. Our final aim is to reduce belt-specific injuries, since they are avoidable by using current technical capability. The solution of these problems can be achieved by modifications of safety standards using defined motion sequence criteria. This would lead to further developments of the system comprising a 3-point-belt and the seat. In this paper we introduce one possible development. Results of a number of crash tests show its efficiency.

Conversion of linoleic acid hydroperoxide by soybean lipoxygenase in the presence of guaiacol: Identification of the reaction products

Abstract: Linoleic acid hydroperoxide formed by soybean lipoxygenase was metabolized by the same enzyme in the presence of guaiacol. The products of this reaction included trihydroxyoctadecenoic acids, hydroperoxydihydroxyoctadecenoic acids, hydroxyepoxyoctadecenoic acids, dihydroxyoctadecenoic acids, hydroxyoctadecadienoic acids, and oxooctadecadienoic acids.

Wind-tunnel simulation of the atmospheric boundary layer: a report on Euromech 50

Abstract: The 50th Euromech Colloquium, on wind-tunnel simulation of the atmospheric boundary layer, was held in Berlin from 23–25 September 1974. Thirty-eight participants from eleven countries were present. Papers were presented describing and analysing different methods of simulation of neutral, stable and unstable atmospheric conditions in various types of wind tunnel. Numerous applications of wind-tunnel simulations were described or mentioned in the papers and the discussion sessions. Some conclusions about the validity, the techniques, the limitations and future developments of wind-tunnel simulations were reached in discussion. Tables are presented in appendix A listing the institutes in Europe and the U.S.A. of actual or invited participants where wind tunnels are used for simulation work; also listed are the characteristics of the wind tunnels and relevant measurements of the simulated atmospheric boundary layers, to enable comparisons to be made between different techniques.

Diskrete Approximation von Eigenwertproblemen

Abstract: 1. Einleitung Die Existenz asymptotischer Entwicklungen kann bei vieIen numerischen Verfahren sehr vorteilhaft ausgenutzt werden. Die auf [16, 4] zurfickgehende Idee hat z.B. mit der Romberg-Integration (s. L9, t0]) und mit dem Verfahren von Gragg-Bulirsch-Stoer [2, 3] bei gew6hnlichen Anfangswertaufgaben zur Aufstellung ~uBerst wirkungsvoller numerischer Prozeduren geftihrt. Ftir eine Ubersicht vgl. die Arbeiten [t0, t9]. Die vorliegende Arbeit besch~ftigt sich in einem allgemeinen Rahmen mit der Existenz asymptotischer Entwicklungen ftir die Eigenwerte und Hauptvektoren bei der n~herungsweisen L/~sung des Eigenwertproblems

Natürlich vorkommende Cumarin-Derivate, XI. Über die Inhaltsstoffe von Gerbera piloselloides Cass

Abstract: Die Wurzeln von Gerbera piloselloides Cass. enthalten den neuen Cumarin-Typ 1. Weiterhin konnten die Strukturen mehrerer p-Hydroxyacetophenon-Derivate (6–8, 10, 11), die auch aus den Wurzeln isoliert wurden, geklart werden. Naturally Occuring Coumarin Derivatives, XI. on the Constituents of Gerbera piloselloides Cass The roots of Gerbera piloselloides Cass. contain the new coumarin type 1. Furtheron the structures of several p-hydroxyacetophenone derivatives (6–8, 10, 11) also isolated from the roots could be established.

Natürlich vorkommende Terpen‐Derivate, XLVIII. Über neue Inhaltsstoffe der Gattung Anthemis

Abstract: Die Untersuchung mehrerer turkischer Arten der Gattung Anthemis ergibt neben bereits bekannten Acetylenen neue Sesquiterpen-Derivate (5, 6, 16 und 19), deren Strukturen durch spektroskopische Methoden und einige chemische Reaktionen geklart werden. Es ergeben sich keine charakteristischen Unterschiede zwischen diesen Arten und den europaischen. Naturally Occurring Terpene Derivatives, XLVIII. On New constituents of the Genus Anthemis The investigation of several Turkish species of the genus Anthemis yields, besides already known acetylenes, new sesquiterpene derivatives (5, 6, 16 and 19), their structures being elucidated by spectroscopic methods and some chemical reactions. There are, however, no characteristic differences between these species and the European ones.

Darstellung und Eigenschaften von 1-Chlor-2-phenylcyclopropenen

Abstract: Die Cyclopropene 5–8 werden aus den Dichlorcyclopropanen 1–4 mit Kalium-tert-butylat in THF dargestellt. 5–7 werden zu den Cyclopropanen 9–11 hydriert. 5 und 6 ergeben mit Cyclopentadien die Addukte 12 und 13. Synthesis and Properties of 1-Chloro-2-phenylcyclopropenes The cyclopropenes 5–8 are prepared from the dichlorocyclopropanes 1–4 with potassium tert-butoxide in THF. 5–7 are hydrogenated to the cyclopropanes 9–11. 5 and 6 yield with cyclopentadiene the adducts 12 and 13.