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  • Articles: DFG German National Licenses  (12)
  • 1990-1994  (12)
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  • Articles: DFG German National Licenses  (12)
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Year
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The band structure and magnetic properties are studied for RFe11TiNx (R=Y, Nd, Sm; x=0,1) rare-earth iron intermetallic compounds using the linear muffin tin orbital with the atomic sphere approximation (LMTO-ASA) method. In order to elucidate the role played by the rare-earth atoms in these compounds, a full electron calculation is performed using a semirelativistic spin-polarized LMTO-ASA method in the local spin density approximation (LSDA) regime. The 4f electrons of the rare-earth atoms are considered to be valence electrons in the self-consistent calculations. For NdFe11TiN, a calculation in which the 4f electrons are treated as core-frozen states is also performed, and is compared with the full electron calculation. The effects of N atoms in these compounds are also discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present studies on both the electronic and magnetic properties of LaCo13 and La(FexAl1−x)13 intermetallic compounds by cluster model calculations within the scheme of density-functional theory. The equilibrium structures of the isolated and embedded clusters, obtained by minimizing the total binding energy, are in good agreement with available experimental data and other theoretical results. The relative stability and formation of LaCo13 and La(FexAl1−x)13 phases have been successfully explained. Interesting changes of magnetic properties in an Al doped Fe13 cluster have been obtained. The possible effect of Al on the magnetic phase diagram of La(FexAl1−x)13 is discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 4496-4500 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 1650-1655 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archive of applied mechanics 62 (1992), S. 530-543 
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Übersicht Im Hinblick auf Materialsymmetrien kann man für den praktischen Einsatz transversal-isotrope, orthotrope, tetratrope, hexatrope oder auch oktotrope faserverstärkte Verbundwerkstoffe unterscheiden. Für Anwendungen im Ingenieurbereich sind sie von größter Bedeutung. Die Darstellungstheorie tensorwertiger Funktionen bildet die Grundlage zur Formulierung von Stoffgleichungen anisotroper Stoffe, zu denen auch die oben erwähnten Verbundwerkstoffe gehören. Tensorfunktionen speziell für transversal-isotrope und orthotrope Stoffe sind hinreichend bekannt. Hingegen fehlen entsprechende Untersuchungen zum tetratropen und hexatropen Verhalten. Daher sollen im folgenden vollständige und irreduzible Darstellungen für derartige Materialorientierungen entwickelt werden. Dazu müssen vektor- und tensorwertige Funktionen mit unterschiedlichen Tensor- und Vektorargumenten in Betracht gezogen werden. Eine weiterführende Untersuchung (Teil II), in der u. a. auch anisotrope Werkstoffschädigungen berücksichtigt werden, ist in Vorbereitung.
    Notes: Summary From the continuum mechanical point of view, most of practical fibre-reinforced composites may be considered to be transversely isotropic, orthotropic, tetratropic, hexatropic, or octotropic according to material symmetries. Engineering applications of fibre-reinforced materials have already been well established. Based on tensor function representations, the formulation of constitutive equations for fibre-reinforced composites constitutes a consistent mathematical basis for modelling the mechanical behaviour of these oriented materials. Although we have good knowledge of transversely isotropic and orthotropic tensor function representations, only integrity bases for tetratropic and hexatropic polynomials could be learnt up to now in very limited cases. In this paper, we present the complete and irreducible representations for tetratropic, hexatropic and octotropic scalr-, symmetric tensor-, skew-symmetric tensor- and vector-valued functions (not only polynomials) of any finite number of symmetric tensors, skew-symmetric tensors and vectors in plane problems; a generalization of these results is also given. By use of these representations we shall perform the formulation of constitutive equations of fibre-reinforced composites in plane problems of elasticity, heat conduction, asymmetric elasticity, plasticity and continuum damage mechanics in a continued paper (Part II).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 26 (1991), S. 323-330 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Für den Parameterbereich konventioneller Dampferzeuger wurde an einer Hochdruckversuchsanlage der Druckverlust in glatten und innenberippten Verdampferrohren gemessen. Basierend auf diesen Experimenten und Meßwerten aus der Literatur wurden Verfahren entwickelt, mit denen der Reibungsdruckverlust in diesen Rohren mit guter Genauigkeit berechnet werden kann. Um die diesen Verfahren zugrundeliegenden Modellvorstellungen zu überprüfen, wurde die Staudruckverteilung bei einund zweiphasiger Durchströmung in glatten und innenberippten Rohren bestimmt. Durch Vergleichsmessungen, die bei horizontaler und vertikaler Rohrlage durchgeführt wurden, konnte außerdem die sogenannte Gravitationsdichte, der der geodätische Druckabfall proportional ist, für innenberippte Rohre ermittelt werden.
    Notes: Abstract The pressure drop in smooth and rifled evaporator tubes was measured on a high pressure test facility for the range of parameters of a conventional steam generator. Based on these experiments and results from literature, methods were developed by which the frictional pressure loss in these tubes may be calculated with a good degree of accuracy. To verify the assumptions on which these models are based, the stagnation pressure distribution in single-phase and two-phase flow in smooth and rifled tubes was determined. By comparing measurements taken on tubes in horizontal and vertical orientation, the so called liquid hold-up, which is a measure for the hydrostatic pressure drop, could be determined for rifled tubes.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 102 (1994), S. 73-89 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary We reconsider the definitions of both material symmetries and physical symmetries which are described in terms of point groups, i.e. subgroups of the full orthogonal group, because these two concepts are often confused and the classical descriptions of physical symmetry for inelastic behaviour of materials are impracticable. All two- and three-dimensional point groups are classified into two types: compact and non-compact. The reality of every compact point group in the description of a material or a physical symmetry is justified in four aspects, that is: (i) point groups characterized by a finite set of tensors, (ii) Hilbert's theorem for integrity bases, (iii) correlation between integrity bases and function bases (generalization of Wineman and Pipkin's theorem), and (iv) physical reality. The unreality of any non-compact point group in the description of a material or a physical symmetry is proposed as a new principle of continuum physics. As applications, the complete sets of all classes of two-and three-dimensional point groups which describe physical symmetries for linear physical properties (such as thermal expansion, piezoelectricity, elasticity, etc.) and for more general mechanical constitutive laws are given.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 91 (1992), S. 97-105 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Most of the practical materials may be regarded as Noll's simple materials and their constitutive laws are, in general, determined through some arotational constitutive experiments. The perfixa — in the term “arotational” from Greek denotes “without”. In this paper we give an equivalence theorem between the objectivity axiom and the formulation of the generalized constitutive laws from their arotational forms for simple materials. Finally, an example of simple shearing is given.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Living cationic copolymerization of 11-[(4-cyano-4′-biphenyl)oxy]undecanyl vinyl ether (6–11) with 11-vinyloxyundecanyloxy methacrylate (16-11) leads to copolymers poly[(6–11)-co(16-11)]X/Y (where X/Y is the mol ratio between the two monomers in copolymer) containing methacryloyl side groups. All copolymers are crosslinked upon annealing via the thermal induced polymerization of their methacryloyl side groups. The copolymers with X/Y=6/4 to 9/1 lead after crosslinking to liquid crystalline networks exhibiting a SA mesophase.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Living cationic copolymerization of (2S, 3S)-(+)-2-chloro-3-methylpentyl 4′-(8-vinyloxyoctyloxy)biphenyl-4-carboxylate (15-8) with 2-vinyloxyethyloxy methacrylate (16-2) leads to reactive copolymers poly[(15-8)-co-(16-2)]X/Y (where X/Y is the mol ratio between the two monomers in the copolymer) containing methacryloyl side groups. The thermally crosslinked copolymers with X/Y=5/5 to 9/1 display an enantiotropic chiral smectic C (S C * ) mesophase.
    Type of Medium: Electronic Resource
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