Axialer Verlauf der Geschwindigkeit in Luft-Freistrahlen

Zusammenfassung Die bisher bekannten Beziehungen zur Berechnung des axialen Geschwindigkeitsverlaufs in isothermen Luft-Freistrahlen gelten nur für das Strahlende etwa im Gebiet von x/d>50, in dem die Reynoldszahl keinen Einflu? mehr auf den Geschwindigkeits-oder Impulsabfall hat. In dem Gebiet4<x/d<50 nimmt das Verh?ltnis mit wachsender Reynoldszahl bis zu einer Grenz-Reynoldszahl zu. Durch Definition einer axialen Halbwertl?nge x_0,5 (x_0,5=x bei ) wurde eine Beziehung gefunden, die den Einflu? der Reynoldszahl am Strahlanfang berücksichtigt. Mitteilung aus dem Engler-Bunte-Institut, Bereich Feuerungstechnik, der Universit?t Karlsruhe (TH), Direktor des Instituts: Prof. Dr.-Ing. R. Günther.     

Multiple models and mental illnesses: A rejoinder to "Failure of a moral enterprise: Attitudes of the public toward mental illness" by T. R. Sarbin and J. C. Mancuso.

Critically analyzes the T. R. Sarbin and J. D. Mancuso (see record 1971-04081-001) report. Data are presented indicating that the public is (a) generally accepting of the medical model of mental illness; (b) optimistic about prognosis; and (c) able to identify the simple schizophrenic, the alcoholic, and the juvenile character disorder as mentally ill and in need of medical care. The public does not place a sizable social distance between themselves and those labeled mentally ill. These data contradict the claims advanced for a unitary social deviancy model. It is argued that the medical model is neither rejected by the public nor discredited by current research. The need is not for the abandonment of medical and psychological models which have already demonstrated formidable heuristic value; what is needed is recognition that there are many different kinds of mental illnesses and that multiple models may consequently have value. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Turbulenz in isothermen Freistrahlen

Zusammenfassung Die Str?mungsvorg?nge in turbulenten Strahlen wurden theoretisch und experimentell untersucht. Ausgehend von den Ans?tzen nach H. Reichardt und L. Prandtl lieferte die Theorie für den Fall eines isothermen, homogenen Freistrahls die ?rtlichen Werte der Schwankungsgeschwindigkeit, der scheinbaren kinematischen Viskosit?t und der turbulenten Schubspannung. Die berechneten Verteilungen stimmen mit den in isothermen Luftstrahlen gemessenen Werten und mit den aus dem Schrifttum bekannten Beziehungen befriedigend überein. Mitteilung aus dem Institut für Gastechnik, Feuerungstechnik und Wasserchemie der Universit?t Karlsruhe (TH); Auszug aus der von der Fakult?t für Maschinenbau und Verfahrenstechnik der Universit?t Karlsruhe (TH) genehmigten Dissertation des Verfassers.     

Konzentrationsfelder in isothermen Luft-Freistrahlen

Zusammenfassung Der turbulente Vermischungsproze? in einem Freistrahl, in dem eine Düsenstr?mung sich in einem ruhenden Umgebungsmedium ausbreitet, kann durch experimentelle Ermittlung der lokalen Stoffverteilung besser begründet werden. In isothermen Luft-Freistrahlen wurden unter Verwendung der Laser-Streulichtmethode Mittel-und Schwankungswerte der Konzentration gemessen und daraus die ?rtlichen Turbulenzintensit?ten ermittelt. Durch Vergleich mit Geschwindigkeitsmessungen wurde eine Abh?ngigkeit der turbulenten Schmidtzahl von der Reynoldszahl gefunden. Dr.-Ing.I. Ebrahimi war bei Abfassung des Beitrags Alexander-von-Humboldt-Stipendiat an diesem Institut. Die Verfasser danken Herrn Prof. Dr.-Ing.R. Günther für die Unterstützung dieser Arbeit. Weiterer Dank gilt der Deutschen Forschungsgemeinschaft für die Bereitstellung von Me?ger?ten, die diese Untersuchungen erm?glichten. Au?erdem sei der Alexandervon-Humboldt-Stiftung für die Gew?hrung eines Dozentenstipendiums herzlich gedankt.     

Operation Homecoming.

Describes the military's "Operation Homecoming" for Vietnam war veterans and argues that the military's effort to be helpful (delaying reentry into society and discouraging fanfare) was unnecessary and harmful. The hero's welcome provides a means of relief from guilt felt over killing, destruction, and activities not normally tolerated by society. (0 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Different finite element techniques to predict welding residual stresses in aluminum alloy plates

This study is a 3D thermomechanical finite element (FE) analysis of a single-pass and butt-welded work-hardened aluminum (Al) 5456 plates. It aims to validate the use of FE welding simulations to predict residual stress states in assessing the integrity of welded components. The predicted final residual stresses in the plate from the FE simulations are verified through comparison with experimental measurements. Three techniques are used to simulate the welding process. In the first two approaches, welding deposition is applied by using element birth and interaction techniques. In the third approach, the entire weld zone is simultaneously deposited. Results show a value at approximately the yield strength for longitudinal residual stresses of the welded center of the butt-welded Al alloy plates with a thickness of 2 mm. Considering the application of a comprehensive heat source, along with heat loss modeling and the temperature-dependent properties of the material, the approach without deposition predicts a reasonable distribution of residual stresses. However, the element birth and interaction techniques, compared with the no-deposit technique, provide more accurate results in calculating residual stresses. Furthermore, the element interaction technique, compared with the element birth technique, exhibits higher efficiency and flexibility in modeling the deposition of welded metals as well as less modeling cost.     

Crack shape developments for LBB applications

The flaw shape during sub-critical crack propagation (fatigue or stress corrosion) is important in order to estimate the crack opening area and leak rate at breakthrough and for the leaking crack. The ability to detect this leak rate is one of the cornerstones in the leak before break philosophy. In this study, the crack shape development is analysed and predicted using modern FEM techniques. The predictions are benchmarked against available fatigue experiments. Recommendations are given for crack shapes for both surface cracks and through-wall cracks in pipes and plates, and for sub-critical crack propagation as well as ductile tearing loading.     

Effect of flexibility on the dynamic stability of a four-bar mechanism

Dynamic behavior of flexible components of mechanisms is prone to instabilities which create resonant speed barriers. By considering small deformations superimposed on the steady dynamic state, equations governing evolution of disturbances can be obtained. For the case of mechanisms driven by periodic inputs these equations reduce to a system of coupled Mathieu-Hill equations for the amplitudes of modes of vibrations. Application of the Floquet theory determines the critical conditions of speed, geometry and material properties causing dynamic instability.     

THE COLLOIDAL STABILITY OF CRUDE OILS AND CRUDE OIL RESIDUES

A crude oil and three residues of the crude oil processing were investigated by determination of flocculation points of both the product solutions and the original products. Diverse analytical methods were used for characterizing products and their fractions. The evaluation of results was performed by the theory of regular solutions and its extension by Hansen. It was found, that the colloidal disperse phase shows a behaviour similar to that of polymer solutions. The conditions of the destabilization of the colloids can be defined by the critical Flory-Huggins interaction parameter. The solvation and the low soluble part of the asphaltenes have the greatest influence on the colloidal stability. The lowest stability is found for the visbreaking residue. The influence of the crude oil distillation on the colloidal stability is not significant.