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.     

Structural controllability of multi-agent networks: Robustness against simultaneous failures

In this paper, structural controllability of a leader–follower multi-agent system with multiple leaders is studied from a graph-theoretic point of view. The problem of preservation of structural controllability under simultaneous failures in both the communication links and the agents is investigated. The effects of the loss of agents and communication links on the controllability of an information flow graph are previously studied. In this work, the corresponding results are exploited to introduce some useful indices and importance measures that help characterize and quantify the role of individual links and agents in the controllability of the overall network. Existing results are then extended by considering the effects of losses in both links and agents at the same time. To this end, the concepts of joint (r,s)$(r,s)$-controllability and joint t$t$-controllability are introduced as quantitative measures of reliability for a multi-agent system, and their important properties are investigated. Lastly, the class of jointly critical digraphs is introduced, and it is stated that if a digraph is jointly critical, then joint t$t$-controllability is a necessary and sufficient condition for remaining controllable following the failure of any set of links and agents, with cardinality less than t$t$. Various examples are exploited throughout the paper to elaborate on the analytical findings.     

GEL FORMATION IN VACUUM GAS OIL. I. ROLE OF COMPOSITION

The compositional analysis of aromatics, saturates and urea non adductables obtained from vacuum gas oil (VGO) distillate (370-550°C) and its seven sub-fractions: (1) 370-400, (2) 400-425, (3) 425-450, (4) 450-475, (5) 475-500, (6) 500-525 and (7) 525-550°C, derived from both paraffinic and aromatic base crude oils have been done using thin layer chromatography/flame ionisation detection technique. The physico- chemical characteristics are measured using the ASTM/ standard test procedures and an attempt has been made to correlate the physico-chemical properties with the composition. The phenomenon of gel formation at low temperatures and the characteristics of the gel in these VGO sub-fractions have been studied by X-ray diffractometry and photomicrography. It is found that at low temperatures the gel formation takes place due to the development of a three dimensional network by the crystallizing n-paraffins, as well as by the agglomeration of molecules due to very high viscosity. Both processes proceed simultaneously and the concentration and composition of n-paraffins have been found to determine the dominance or otherwise of the crystallization process.     

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)     

A model of homeless migration: homeless men in Skid Row,Los Angeles

"In this paper a conceptual model of homeless migration is developed that links migration behavior with the coping status of homeless individuals. The model is evaluated by using data drawn from a recent random probability sample of men surveyed in Skid Row, Los Angeles, [California]. Results indicate that homeless migrants tended to be young, never married, white, mentally disabled, and either newly or cyclically homeless individuals. Long-term residents, in contrast, were apt to be older, physically disabled or suffering from a health-related problem, and had been homeless for some time. The dominant reason given for moving was to find a job...." Coping strategies and migration behaviors are also described.     

Asymmetric Dynamic Green’s Functions in a Two-Layered Transversely Isotropic Half-Space

By virtue of a complete representation using two displacement potentials, an analytical derivation of the elastodynamic Green’s functions for a transversely isotropic layer underlain by a transversely isotropic half-space is presented. Three-dimensional point-load and patch-load Green’s functions for stresses and displacements are given in the complex-plane line-integral representations. The formulation includes a complete set of transformed stress-potential and displacement-potential relations in the framework of Fourier expansions and Hankel integral transforms, that is useful in a variety of elastodynamic as well as elastostatic problems. For the numerical computation of the integrals, a robust and effective methodology is laid out. Comparisons with the existing numerical solutions for a two-layered transversely isotropic half-space under static surface load, and a homogeneous transversely isotropic half-space subjected to buried time-harmonic load are made to confirm the accuracy of the present solutions. Selected numerical results for displacement and stress Green’s functions are presented to portray the dependence of the response of the two-layered half-space on the frequency of excitation and the role of the upper layer.