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  • Chemistry  (4)
  • 25.70.Jj  (2)
  • 61.16.Ch  (1)
  • 1
    ISSN: 1434-601X
    Keywords: 25.70.Cd ; 25.70.Jj ; 25.70.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mass and charge distributions for binary reaction channels have been measured for the reactions86Kr with76Ge,104Ru and130Te at the Coulomb barrier using chemical separations andγ-ray spectroscopy. These systems span the region where dynamical hindrance to complete fusion sets in. The binary reactions can be subdivided into two components associated withi) reflection from the outer potential barrier (quasielastic), andii) reseparation after passing the barrier (complex reactions). The sum of complex-reaction channels and evaporation residues from complete fusion can be reproduced by a barrier passing calculation. The fraction of the barrier passing flux leading to reseparation increases from 26±10% for the lightest system to more than 90% for the heaviest system. The data indicate that fusion hindrance is primarily caused by reseparation shortly after passage of the barrier before Swiatecki's conditional saddlepoint is overcome, resulting in partitions close to the entrance channel configuration. In addition, for the heaviest system, a quasifission component representing somewhat less than 20% of the barrier-passing flux was observed. From the missing masses of fragment pairs we can deduce that the reseparating complex-reaction products have kinetic energies well below the fusion barrier and share the excitation energy in a way similar to the sawtooth-like curve known from low-energy fission. The quasielastic, predominantly one- and two-nucleon transfer channels, have strongly varying cross sections for the three systems despite similar effectiveQ-values. A systematics of one-neutron transfer cross sections at the Coulomb barrier is established and shown to differ considerably from the smooth behaviour observed at energies 20–30% above the barrier. The connection to nuclear polarization phenomena and orbit matching is pointed out.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6036
    Keywords: 61.16.Ch ; 61.80.Jh ; 74.60.Ge ; 74.70.Ad
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We observe vortex pinning in 2.2 GeV Au-ion irradiated NbSe2 by scanning tunneling microscopy (STM) at 3K. The ion irradiation generates columnar defects which act as pinning sites. At various external magnetic fields the vortex arrangement is clearly resolved but shows strong distortion. The location of individual defects is extracted from STM data and compared to the vortex arrangement.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 107-107 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 13 (1982), S. 221-227 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 10 (1979), S. 49-57 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Einfluß eines Temperaturgradienten senkrecht zur Faserachse auf das Gefüge einer gerichtet erstarrten eutektischen 73C-LegierungDie thermische Stabilität einer gerichtet erstarrten eutektischen CoCrCAl-Legierung in einem Temperaturgradienten wird mit dem Verhalten unter isothermen Bedingungen verglichen.Zur Prüfung von gerichtet erstarrten Eutektika in hohem Temperaturgradienten und bei Temperaturen oberhalb 1300 K wurde eine Versuchseinrichtung entwickelt, die Experimente in unterschiedlicher Atmosphäre und im Vakuum ermöglicht. Die Versuche in diesem Gradienten-Ofen ergaben eine Vergröberung der Karbidfasern, die in dieser Legierung die Verstärkungsphase bilden. Durch die Umwandlung von Karbiden wird die Gefügestabilität beeinträchtigt.Diese Effekte werden in bezug auf isotherme Bedingungen diskutiert und ihre Auswirkungen auf die Anwendbarkeit dieser Legierung als Material für Hochtemperatur-Gas-Turbinen überprüft.
    Notes: The thermal stability of a directionally solidified (d. s.) eutectic CoCrCAl-alloy in a thermal gradient is compared to isothermal conditions.A device has been designed and constructed for examination of d. s. eutectics in high temperature gradients at temperatures above 1300 K in different atmospheres and vacuum.Experiments in this gradient furnace show coarsening of the carbide fibres forming the aligned strengthening phase. A microstructural instability resulting from the transformation of carbide fibres has been observed.These effects are discussed in relation to isothermal conditions and their implications on the applicability of the alloy as high temperature gas turbine blade material.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 18 (1987), S. 241-250 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Aspects of the Powder Metallurgy of High-Strength Light Metal Alloys on Aluminium and Titanium BaseAdvantages expected from powder metallurgy  -  cost reduction, improvement of properties and development of new alloys not producible by conventional ingot metallurgy  -  were tried likewise to be applied to high-strength light weight alloys for more than ten years. State of the art and problems still to be solved are reviewed with respect to the particular objectives, and future trends of development are pointed out. For aluminium alloys, the main objective is the improvement of properties, e. g. higher elevated temperature strength by rapid solidification and mechanical alloying, whereas in the case of titanium alloys first of all the reduction of production costs was aspired. Meanwhile, improved properties could be achieved by rapid solidification for titanium alloys as well. But, the improvement of economy still remains an important task to be solved for both types of alloys.
    Notes: Die von der Pulvermetallurgie erwarteten Vorteile  -  Kostensenkung, Verbesserung der Eigenschaften und Entwicklung neuer Werkstoffe, die über den Schmelzweg nicht herstellbar sind  -  hat man seit über zehn Jahren auch für hochfeste Leichtmetallegierungen zu nutzen versucht. Der jetzige Stand und die noch zu lösenden Probleme werden im Licht der jeweiligen Zielsetzungen umrissen und Entwicklungstrends aufgezeigt. Während bei Aluminiumlegierungen Eigenschaftsverbesserungen wie z. B. größere Warmfestigkeit durch schnelle Erstarrung und mechanisches Legieren im Vordergrund stehen, wurde bei Titanlegierungen zunächst eine Kostensenkung angestrebt. Verbesserte Eigenschaften konnten aber z. B. durch schnelle Erstarrung auch an Titanlegierungen erzielt werden. Die Erhöhung der Wirtschaftlichkeit ist für beide Legierungsarten eine noch zu lösende, wichtige Aufgabe.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 326 (1987), S. 313-326 
    ISSN: 1434-601X
    Keywords: 25.70.Jj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Fission-fragment angular distributions were measured in the reaction of40Ar with208Pb near the fusion barrier. For nearly symmetric mass-/charge splits we find angular distributions symmetric around θ=90 degrees, however, with unusually large anisotropies. These develop gradually into forward-backward asymmetric distributions as one moves away from mass-/charge symmetry. This indicates that non-compound fission (‘quasi-fission’) competes with true fusion-fission. The relative contribution of quasi-fission to the total fission cross section is somewhere between 51 and 85%. In the framework of the extra-push model this is equivalent to an extra-extra push energy for compound-nucleus formation inside the true fission saddle point of 4〈E xx 〈9 MeV in agreement with a recent empirical parametrization of fusion-barrier shifts based on fusion-fission cross sections. On the basis of cross sections for fusion-evaporation residues it had previously been concluded that fusion of40Ar with Pb isotopes occurs unhindered. Possible reasons for this apparent discrepancy are discussed.
    Type of Medium: Electronic Resource
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