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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Structural optimization 18 (1999), S. 12-23 
    ISSN: 0934-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The numerical treatment of shape optimization problems requires sophisticated software tools such as Computer Aided Design (CAD), the Finite Element Method (FEM) and a suitable Mathematical Programming (MP) algorithm. Efficiency of the overall procedure is guaranteed if these tools interact optimally. The theoretical and numerical effort for sensitivity analysis reflect the complexity of this engineering problem. In this paper we outline a general modelling concept for shape optimization problems. Hierarchical design models within Computer Aided Geometrical Design (CAGD) and the interaction of geometry and FEM lead to an efficient overall optimization procedure. Our concept has been derived, implemented and tested for shell structures but it is seen to be generally applicable. After a short introduction containing the state of the art we give an overview of the numerical tools used and outline the interaction of CAGD and FEM within the overall optimization procedure. The paper is mainly devoted to the hierarchical design space based on a hierarchical geometrical modelling. The major part of computational effort is consumed by sensitivity analysis related to the number of design variables. Therefore, this number should be limited and only few powerful design variables corresponding to the special interests of the considered problem should be defined. This procedure may lead to a considerable limitation of the design space. Based on a hierarchy in the geometrical model different types of design variables are introduced: design variables with global, regional and local influence. The new method is based on successive activation of these types of design variables. This procedure leads to a considerable reduction of computational time for the sensitivity analysis without loss of geometrical flexibility. A new method of geometrical refinement and a successive adaptively driven expansion and reduction of the design space is described. It is based on the degree elevation or degree reduction of parametric curves and surfaces, respectively. A numerical example illustrates the new method and the efficiency of the overall optimization procedure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 83-87 (Jan. 1992), p. 823-828 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0168-9452
    Keywords: Brassica napus ; Northern blot ; RNA slotblot ; amino acid sequence ; cDNA sequence ; myrosinase
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 82 (1959), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 230 (1989), S. 119-123 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 274 (1996), S. 218-226 
    ISSN: 1435-1536
    Keywords: Microemulsion ; ABA-triblock copolymer ; polymer network ; elastomer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract ABA-triblock copolymers bearing polymerizable methacrylate end-groups are covalently crosslinked in the droplet phase of W/O- and O/W-microemulsions. The resulting microemulsion elastomers combine the structure and the phase behavior of microemulsions with solid state properties such as elasticity or stability of shape. These new materials are characterized with the help of conductivity, dynamic-mechanical and dynamic light-scattering investigations. The influence of the chemical crosslinking process on the phase behavior and the dynamics of the underlying microemulsion is discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Structural and multidisciplinary optimization 18 (1999), S. 12-23 
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The numerical treatment of shape optimization problems requires sophisticated software tools such as Computer Aided Design (CAD), the Finite Element Method (FEM) and a suitable Mathematical Programming (MP) algorithm. Efficiency of the overall procedure is guaranteed if these tools interact optimally. The theoretical and numerical effort for sensitivity analysis reflect the complexity of this engineering problem. In this paper we outline a general modelling concept for shape optimization problems. Hierarchical design models within Computer Aided Geometrical Design (CAGD) and the interaction of geometry and FEM lead to an efficient overall optimization procedure. Our concept has been derived, implemented and tested for shell structures but it is seen to be generally applicable. After a short introduction containing the state of the art we give an overview of the numerical tools used and outline the interaction of CAGD and FEM within the overall optimization procedure. The paper is mainly devoted to the hierarchical design space based on a hierarchical geometrical modelling. The major part of computational effort is consumed by sensitivity analysis related to the number of design variables. Therefore, this number should be limited and only few powerful design variables corresponding to the special interests of the considered problem should be defined. This procedure may lead to a considerable limitation of the design space. Based on a hierarchy in the geometrical model different types of design variables are introduced: design variables with global, regional and local influence. The new method is based on successive activation of these types of design variables. This procedure leads to a considerable reduction of computational time for the sensitivity analysis without loss of geometrical flexibility. A new method of geometrical refinement and a successive adaptively driven expansion and reduction of the design space is described. It is based on the degree elevation or degree reduction of parametric curves and surfaces, respectively. A numerical example illustrates the new method and the efficiency of the overall optimization procedure.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of economics 65 (1997), S. 311-327 
    ISSN: 1617-7134
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Structural and multidisciplinary optimization 9 (1995), S. 46-51 
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The numerical solution of shape optimization problems is considered. The algorithm of successive optimization based on finite element techniques and design sensitivity analysis is applied. Mesh refinement is used to improve the quality of finite element analysis and the computed numerical solution. The norm of the variation of the Lagrange augmented functional with respect to boundary variation (residuals in necessary optimality conditions) is taken as an a posteriori error estimator for optimality conditions and the Zienkiewicz—Zhu error estimator is used to improve the quality of structural analysis. The examples presented show meaningful effects obtained by means of mesh refinement with a new error estimator.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0044-2313
    Keywords: Silver(I) complexes, phosphazane ligands ; X-ray structure ; vibrational and NMR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry of Polyfunctional Molecules. 124. Silver(I) Complexes Containing the Ligands Bis(diphenylphosphanyl)amine, -amide and Tris(diphenylphosphanyl)amineBis(diphenylphosphanyl)amine HN(PPh2)2 (1) reacts with AgCl to the complex HN(PPh2AgCl)2 (5) for which in the solid state the cluster structure Ag4Cl4[HN(PPh2)2]2 is assumed. Reaction of 5 with LiN(PPh2)2 (2) gives the known [N(PPh2AgPh2P)2N] (8) and the new complex [Ag(μ - Ph2PNPPh2)2(μ - Ph2PNHPPh2)Ag] · dioxane (7 · dioxane). The compound 7 · dioxane has been characterized by X-ray diffraction. The molecules are found to contain a bicyclo[3.3.3]undecane-type structure with trigonal planar coordinated silver atoms, which are separated by 281,6(1) pm. The dioxane is bound via H-bridge bond to the NH group of the coordinated HN(PPh2)2. Treatment of 8 with ClPPh2 yields N(PPh2AgCl)3 (12), which has also been obtained by the reaction of N(PPh2)3 (3) with silver chloride. All the compounds have been characterized, so far as possible, by IR, Raman, 1H NMR, 31P{1H} NMR, 13C{1H} NMR and mass spectroscopy.
    Notes: Bis(diphenylphosphanyl)amin, HN(PPh2)2 (1), reagiert mit AgCl zu dem Komplex HN(PPh2AgCl)2 (5), für den aufgrund spektroskopischer Daten im Festzustand die dimere Clusterstruktur Ag4Cl4[HN(PPh2)2]2 angenommen wird. Die Umsetzung von 5 mit LiN(PPh2)2 (2) in Dioxan liefert die bereits bekannte Verbindung [N(PPh2AgPh2P)2N] (8) und den neuen, gelb-grünen Komplex [Ag(μ-Ph2PNPPh2)2(μ-Ph2PNHPPh2)Ag] · Dioxan (7 · Dioxan), von dem eine Kristallstrukturanalyse angefertigt wurde. Sie zeigt, daß 7 · Dioxan eine Bicyclo[3.3.3]undecan-Struktur besitzt, in der die Silberatome die seltene trigonal-planare Koordination einnehmen. Der (AgAg)-Abstand beträgt 281,6(1) pm und deutet auf eine Wechselwirkung zwischen den Silberatomen hin. Das Dioxan ist über eine Wasserstoffbrückenbindung an die NH-Gruppe des koordinierten HN(PPh2)2 gebunden. Mit ClPPh2 bildet 8 N(PPh2AgCl)3 (12), welches auch durch direkte Reaktion von N(PPh2)3 (3) mit Silber(I)-chlorid erhältlich ist. Alle Verbindungen wurden, soweit möglich, durch IR-, Raman-, 1H-NMR-, 31P{1H}-NMR-, 13C{1H}-NMR- und Massenspektren charakterisiert.
    Additional Material: 4 Ill.
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