Stability of certain one-dimensional unsteady gas motions

This paper studies the stability of the adiabatic unsteady motions of a perfect gas for which the velocity is proportional to the distance to the center of symmetry. The solutions of the gas dynamic equations of such a form and their physical interpretation are considered in [1]. The stability of one of the solutions, which corresponds to the pulsations of uniform gravitating spheres, was studied in paper [2]. The stability of the other solutions (gas motions in the absence of Newtonian gravitation, nonperiodic motions of gravitating gas) has not previously been investigated. The stability of such solutions is investigated in this paper and it is shown that the motions in which gas compression occurs are, as a rule, unstable.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 120–127, November–December, 1985.     

Limit analysis of circular and annular plates

Summary The problem of the plastic collapse load of circular and annular plates is dealt with. For simply supported and built-in edge plates, different loading conditions are considered and the annular plates are studied for varying geometries. The solutions obtained according to both Tresca's and Mises' yield conditions are exact in the sense of limit analysis.

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Zur Grenztragfähigkeits-Theorie bei Kreis- und Kreisringplatten

Übersicht Es werden Traglasten von Kreis- bzw. Kreisringplatten ermittelt. Dabei werden gelenkig gelagerte sowie eingespannte Kreisplatten bei verschiedener Belastung und Kreisringplatten bei verschiedener Geometrie betrachtet. Die mit Hilfe der Fließbedingungen nach Tresca bzw. v. Mises erhaltenen Lösungen sind exakt im Sinne der Grenztragfähigkeits-Theorie.

     

An iterative method of evaluation of elastic-plastic deflections of hyperstatic framed structures

Summary The concept of substitutive concentrated elastic-plastic rotations, replacing actual elasticplastic zones is used, together with an iterative method of determination of the bending moment distribution to simplify the evaluation of elastic-plastic deflections of hyperstatic beams and frames.

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Eine iterative Methode der Auswertung von elastisch-plastischen Verschiebungen für statisch unbestimmte Rahmen

Übersicht Die Idee von fiktiven Ersatzrotationen, welche die tatsächlichen elastisch-plastischen Zonen modelliert, wird mit einer iterativen Methode kombiniert, um eine relativ einfache Bestimmung von Biegemomentenfeldern in statisch unbestimmten Balken und Rahmen zu ermöglichen. Die resultierenden Verschiebungen, ergeben sich mit ausreichender Genauigkeit.

     

Experimental investigation of superconductivity in 2H-NbSe2 single crystal

The basic quantities characterizing the superconducting behaviour of pure 2H-NbSe₂ single crystals have been determined from specific heat measurements, performed between 0.3 and 10 K in magnetic fields up to 55 KG. When Ti impurities are added, changes are observed both in the superconducting parameters and in the onset of charge density waves, strengthening the idea that a connection exists between the two phenomena.     

Inner-shell ionization ofZ=25–32 elements by 5-48 MeV32S ions

TheK-shell ionization cross sections of Mn, Ni, Cu, Zn and Ge under³²S bombardment have been measured in the energy range from 5 to 48 MeV. The cross sections are compared with available theories based on a direct Coulomb ionization mechanism and with the predictions of theK-vacancy sharing process. This last process can reasonably account for the measured cross sections at high bombarding energies. The energy shifts of theK - andK -lines and theK /K -intensity ratios have also been measured. This information is used to deduce the defect configuration of the atoms. The mechanisms responsible for the multiple vacancy production are discussed.     

Cross-sections for deuteron photo-disintegration from 139 to 832 MeV

The cross-sections for deuteron photo-disintegration have been measured at nine c.m. angles from 37 to 143 degrees. The minimum and maximum photon energies have been 139 and 832 MeV respectively. The results are in agreement with earlier data above 300 MeV, but are significantly larger below 200 MeV, the discrepancies being up to 50% at the lowest energies measured.     

Etude d'impulsions lumineuses breves par interferometrie a deux ondes

We have studied the evolution of the light transmitted through matter in which an optical breakdown is taking place. With a two-waves interferometer made a birefringent plate between polarizers we get informations about the time correlation function of the fields. With an interferometer made of two identical harmonic generating plates separated by a dispersion medium, we learn about the correlation function of the square of the fields. Both systems act as spectral filters with a notch cosine-shaped centered at the incident frequency. We have also observed a transient angular spreading of the beam not previously emphasized which brings a further complication in the picture.     

Search for anomalous interaction mean free paths of charge, 2≦Z≦18 projectile fragments in emulsions exposed to 1.8 A GeV40Ar ions

⁴⁰Ar-emulsion interactions are studied, to investigate the question of anomalons, in twoG- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect,N _h dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level.